U.S. patent application number 14/183630 was filed with the patent office on 2014-07-10 for composition for forming a developable bottom antireflective coating.
This patent application is currently assigned to AZ ELECTRONIC MATERIALS USA CORP.. The applicant listed for this patent is Srinivasan CHAKRAPANI, Shinji MIYAZAKI, Shigemasa NAKASUGI, Munirathna PADMANABAN, Kazuma YAMAMOTO. Invention is credited to Srinivasan CHAKRAPANI, Shinji MIYAZAKI, Shigemasa NAKASUGI, Munirathna PADMANABAN, Kazuma YAMAMOTO.
Application Number | 20140193753 14/183630 |
Document ID | / |
Family ID | 48610456 |
Filed Date | 2014-07-10 |
United States Patent
Application |
20140193753 |
Kind Code |
A1 |
NAKASUGI; Shigemasa ; et
al. |
July 10, 2014 |
COMPOSITION FOR FORMING A DEVELOPABLE BOTTOM ANTIREFLECTIVE
COATING
Abstract
The present invention provides a composition for forming a
bottom anti-reflective coating, and also provides a photoresist
pattern formation method employing that composition. The
composition gives a bottom anti-reflective coating used in a
lithographic process for manufacturing semiconductor devices, and
the coating can be developed with a developing solution for
photoresist. The composition contains a solvent, a polymer having a
condensed polycyclic aromatic group, and a compound having a
maleimide derivative or a maleic anhydride derivative. The
composition may further contain a photo acid generator or a
crosslinking agent.
Inventors: |
NAKASUGI; Shigemasa;
(Kakegawa-shi,, JP) ; YAMAMOTO; Kazuma;
(Kakegawa-shi, JP) ; MIYAZAKI; Shinji;
(Kakegawa-shi, JP) ; PADMANABAN; Munirathna;
(Bridgewater, NJ) ; CHAKRAPANI; Srinivasan;
(Bridgewater, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NAKASUGI; Shigemasa
YAMAMOTO; Kazuma
MIYAZAKI; Shinji
PADMANABAN; Munirathna
CHAKRAPANI; Srinivasan |
Kakegawa-shi,
Kakegawa-shi
Kakegawa-shi
Bridgewater
Bridgewater |
NJ
NJ |
JP
JP
JP
US
US |
|
|
Assignee: |
AZ ELECTRONIC MATERIALS USA
CORP.
SOMERVILLE
NJ
|
Family ID: |
48610456 |
Appl. No.: |
14/183630 |
Filed: |
February 19, 2014 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13327030 |
Dec 15, 2011 |
8697336 |
|
|
14183630 |
|
|
|
|
Current U.S.
Class: |
430/283.1 ;
430/325 |
Current CPC
Class: |
C08K 5/1535 20130101;
C09D 135/00 20130101; G03F 7/095 20130101; G03F 7/091 20130101;
G03C 1/73 20130101; G03F 7/0392 20130101; C08K 5/3415 20130101;
G03F 7/20 20130101 |
Class at
Publication: |
430/283.1 ;
430/325 |
International
Class: |
G03F 7/20 20060101
G03F007/20; G03C 1/73 20060101 G03C001/73 |
Claims
1. A composition for forming a bottom anti-reflective coating,
comprising a solvent, a polymer represented by the following
formula (1): -A.sub.m-B.sub.n- (1) in which A and B are repeating
units represented by the following formulas (A) and (B),
respectively: ##STR00010## wherein each of R.sup.11 and R.sup.12 is
independently hydrogen or an alkyl group; L.sup.11 is a single
bond, COO or a straight- or branched chain alkylene containing one
or more carbon atoms; Y is a condensed polycyclic aromatic group
containing two or more benzene rings; and Z is a group selected
from the group consisting of R.sup.3COOR.sup.4 and R.sup.3OR.sup.4,
provided that R.sup.3 is a single bond, oxygen or a straight- or
branched chain alkylene which may have a fluorine atom and which
contains one or more carbon atoms and also provided that R.sup.4 is
hydrogen or a substituted or non-substituted hydrocarbon group;
each of m and n is a number indicating the polymerization degree
provided that m is not less than 10 and n is not less than 0; and,
a compound comprising an anhydride represented where the compound
is represented by any of the following formulas (2) to (4): is
represented by any of the following formulas (2) to (4):
##STR00011## in which each of R.sup.21, R.sup.22 and R.sup.23 is
independently a group selected from the group consisting of
hydrogen, alkyl, aryl, halogen atom, alkoxy, nitro, aldehyde,
cyano, amido, dialkylamino, sulfonamide, imido, carboxylic acid,
carboxylic acid ester, sulfonic acid, sulfonic acid ester,
alkylamino, and arylamino; ##STR00012## in which each of R.sup.41
and R.sup.42 is independently a group selected from the group
consisting of hydrogen, alkyl, aryl, halogen atom, alkoxy, nitro,
aldehyde, cyano, amido, dialkylamino, sulfonamide, imido,
carboxylic acid, carboxylic acid ester, sulfonic acid, sulfonic
acid ester, alkylamine, and arylamino.
2. The composition according to claim 1, where Y is a condensed
polycyclic aromatic group containing two or more benzene rings
provided that one of the benzene rings is replaced with a quinone
ring and that the condensed polycyclic aromatic group may
optionally have a substituent selected from the group consisting of
alkyl, aryl, halogen, alkoxy, nitro, aldehyde, cyano, amido,
dialkylamino, sulfonamido, imido, carboxy, carboxylic acid ester,
sulfo, sulfonic acid ester, alkylamino, and arylamino.
3. The composition according to claim 1, where the compound is
represented by formula (2)
4. The composition according to claim 1, comprising the compound
represented by the formula (4).
5. The composition according to claim 1, further comprising a photo
acid generator.
6. The composition according to claim 1, further comprising a
crosslinking agent.
7. The composition according to claim 1, wherein each of R.sup.11
and R.sup.12 is independently hydrogen or methyl, L.sup.11 is COO,
and Z is R.sup.3COOR.sup.4, provided that R.sup.3 is a single bond
or a straight chain alkylene group having 1 to 6 carbon atoms and
that R.sup.4 is hydrogen or a branched chain alkyl group having 1
to 10 carbon atoms.
8. A bottom anti-reflective coating formed on a substrate the
composition of claim 2 and then heating for forming a bottom
anti-reflective coating.
9. The bottom anti-reflective coating according to claim 8, formed
by a heat-induced Diels-Alder reaction between the polymer
represented by the formula (1) and the compound represented by
formula (2).
10. The bottom anti-reflective coating according to claim 8, formed
by a heat-induced Diels-Alder reaction between the polymer
represented by the formula (1) and the compound represented by
formula (4).
11. A pattern formation method comprising the steps of: spreading
the composition according to claim 1 for forming a bottom
anti-reflective coating on a semiconductor substrate and then
baking, to form a bottom anti-reflective coating; forming a
photoresist layer on the bottom anti-reflective coating; exposing
to light the semiconductor substrate covered with the bottom
anti-reflective coating and the photoresist layer; and after the
exposure, developing them by use of a developing solution selected
from the group consisting of alkaline developing solution and
organic solvent, thereby forming a pattern in the photoresist and
the antireflective coating.
12. The pattern formation method according to claim 11, wherein the
photoresist layer is a positive-working photoresist, R.sup.4 is
hydrogen, and the developing solution is an alkaline aqueous
solution.
13. The pattern formation method according to claim 11, wherein the
photoresist layer is made of a positive-working photoresist,
R.sup.4 is a substituted or non-substituted hydrocarbon group, and
the developing solution is an alkaline aqueous solution.
14. The pattern formation method according to claim 13, wherein the
composition for forming a bottom anti-reflective coating further
contains a photo acid generator.
15. The pattern formation method according to claim 11, wherein the
photoresist layer is a negative-working photoresist, R.sup.4 is
hydrogen, and the developing solution is an alkaline aqueous
solution.
16. The pattern formation method according to claim 15, wherein the
composition for forming a bottom anti-reflective coating further
contains a photo acid generator.
17. The pattern formation method according to claim 15, wherein the
composition for forming a bottom anti-reflective coating further
contains a crosslinking agent.
18. The pattern formation method according to claim 11, wherein the
photoresist layer is a positive-working photoresist, R.sup.4 is a
substituted or non-substituted hydrocarbon group, and the
developing solution is an organic solvent.
19. The pattern formation method according to claim 18, wherein the
composition for forming a bottom anti-reflective coating further
contains a photo acid generator.
20. The pattern formation method according to claim 10, wherein the
exposure is carried out by use of light in the wavelength range of
13.5 to 248 nm.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional application of Ser. No.
13/327,030 filed Dec. 15, 2011 the content of which are hereby
incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to a composition for forming a
bottom anti-reflective coating employed in lithographic pattern
formation using photoresist, and also to a bottom anti-reflective
coating formation method employing that composition. In addition,
the present invention further relates to a bottom anti-reflective
coating formed from the composition.
BACKGROUND ART
[0003] In production of semiconductor devices, micro-fabrication is
generally carried out according to lithographic techniques by use
of photoresist. The process of micro-fabrication comprises the
steps of: forming a thin photoresist layer on a semiconductor
substrate such as a silicon wafer; covering the layer with a mask
pattern corresponding to the aimed device pattern; exposing the
layer to active light such as UV light through the mask pattern;
developing the exposed layer to obtain a photoresist pattern; and
etching the substrate by use of the photoresist pattern as a
protective film, to form a fine relief corresponding to the above
pattern. Since integration degree of semiconductor devices has been
increased recently, the step of exposure tends to be carried out by
use of light of very short wavelength, such as KrF excimer laser
light (wavelength: 248 nm), ArF excimer laser light (wave-length:
193 nm) or extreme UV light (wavelength: 13.5 nm). The above
photolithographic process, however, often suffers from a problem of
dimension precision degradation of the photoresist pattern. The
dimension precision degradation is caused by a standing wave of
light reflected from the substrate and/or by diffused reflection of
the exposure light due to roughness of the substrate. Further, the
resist layer may be adversely effected by gases given off from the
substrate placed thereunder if the exposure is performed by use of
light of very short wavelength, such as extreme UV light. To cope
with those problems, many researchers are studying about a bottom
anti-reflective coating provided between the photoresist layer and
the substrate. The bottom anti-reflective coating is required to
have various properties. For example, it is preferred for the
bottom anti-reflective coating to largely absorb radiation used for
exposure of the photoresist, to prevent diffuse reflection and the
like so that the exposed and developed photoresist can have a cross
section perpendicular to the substrate surface, and to be insoluble
in solvents contained in the photoresist composition (namely, not
to cause intermixing). The intermixing is particularly serious
because it often gives adverse effects to the interface between the
photoresist layer and the bottom anti-reflective coating.
Accordingly, the intermixing is liable to make it difficult to
control the pattern or shape of the photoresist.
[0004] The bottom anti-reflective coating is often formed from a
thermo-crosslinkable composition, so as to prevent intermixing with
the photoresist applied thereon. Consequently, the formed coating
is generally insoluble in an alkaline developing solution used for
development of the photoresist. Accordingly, in general, the
anti-reflective coating must be removed by dry-etching before
fabrication of the semiconductor substrate (see, for example,
Patent document 1).
[0005] However, when the coating is removed by dry-etching, the
photoresist tends to be partly removed together with the coating.
This makes it difficult to keep enough thickness of the photoresist
to fabricate the substrate.
[0006] In view of this, it is desired to develop a bottom
anti-reflective coating which is sufficiently soluble in an
alkaline developing solution used for development of the
photoresist and hence which can be developed and removed together
with the photoresist. In order to meet this desire, researchers
have studied the bottom anti-reflective coating developable and
removable together with the photoresist, wherein the pattern is
formed in the photoresist and the bottom anti-reflective
coating.
[0007] For example, methods are proposed in which reactions between
dienes and dienophiles are made to form bottom anti-reflective
coatings developable and removable together with the photoresist
(Patent documents 2 to 4). However, if those methods are adopted,
it is often the case that the coating is still not crosslinked when
the photoresist composition is spread thereon and, as a result, the
coating is liable to intermix with the photoresist layer. In order
to avoid the intermixing, the solvent of the photoresist
composition must be selected not to dissolve the bottom
anti-reflection coating. Accordingly, since usable photoresists are
restricted depending on the selected solvent, there is a problem of
lacking versatility.
PRIOR ART DOCUMENTS
[0008] [Patent document 1] U.S. Pat. No. 6,156,479 [0009] [Patent
document 2] Japanese Patent Laid-Open No. 2011-53652 [0010] [Patent
document 3] Japanese Patent Laid-Open No. 2010-256859 [0011]
[Patent document 4] Japanese Patent Laid-Open No. 2010-250280
[0012] [Patent document 5] Japanese Patent Laid-Open No.
2004-102203
DETAILED DESCRIPTION
Problem to be Solved by the Invention
[0013] In consideration of the above problems, it is an object of
the present invention to provide a bottom anti-reflective coating
which does not intermix with the resist layer and which is
optionally soluble in an alkaline developing solution used for
development of the photoresist, and also provides good lithographic
performance. Further, it is also an object of the present invention
to provide a composition for forming that bottom anti-reflective
coating.
SUMMARY OF INVENTION
[0014] The present invention relates to a composition for forming a
bottom anti-reflective coating, comprising [0015] a solvent, [0016]
a polymer comprising the following formula (1):
[0016] -A.sub.m-B.sub.n- (1) [0017] in which [0018] A and B are
repeating units represented by the following formulas (A) and (B),
respectively:
[0018] ##STR00001## [0019] wherein [0020] each of R.sup.11 and
R.sup.12 is independently hydrogen or an alkyl group; [0021]
L.sup.11 is a single bond, COO or a straight- or branched chain
alkylene containing one or more carbon atoms; [0022] Y is a
condensed polycyclic aromatic group containing two or more benzene
rings, and, [0023] Z is a group selected from the group consisting
of R.sup.3COOR.sup.4 and R.sup.3OR.sup.4, provided that R.sup.3 is
a single bond, oxygen or a straight- or branched chain alkylene
which may optionally have a fluorine atom and which contains one or
more carbon atoms and also provided that R.sup.4 is hydrogen or a
substituted or non-substituted hydro-carbon group; [0024] A and B
may be combined either randomly or in blocks; [0025] each of A and
B may be a combination of two or more repeating units having
different structures; and [0026] each of m and n is a number
indicating the polymerization degree provided that m is not less
than 10 and n is not less than 0; [0027] and [0028] a compound
comprising a maleimide or a maleic anhydride. Further the compound
may be represented by any of the following formulas (2) to (4):
[0028] ##STR00002## [0029] in which each of R.sup.21, R.sup.22 and
R.sup.23 is independently a group selected from the group
consisting of hydrogen, alkyl, aryl, halogen atom, alkoxy, nitro,
aldehyde, cyano, amido, dialkylamino, sulfonamido, imido,
carboxylic acid, carboxylic acid ester, sulfonic acid, sulfonic
acid ester, alkylamino, and arylamino;
[0029] ##STR00003## [0030] in which each of R.sup.31 to R.sup.36 is
independently a group selected from the group consisting of
hydrogen, alkyl, aryl, halogen, alkoxy, nitro, aldehyde, cyano,
amido, dialkylamino, sulfonamido, imido, carboxylic acid,
carboxylic acid ester, sulfonic acid, sulfonic acid ester,
alkylamino, and arylamino; and L.sup.31 is an alkylene or an
arylene; [0031] and
[0031] ##STR00004## [0032] in which each of R.sup.41 and R.sup.42
is independently a group selected from the group consisting of
hydrogen, alkyl, aryl, halogen atom, alkoxy, nitro, aldehyde,
cyano, amido, dialkylamino, sulfonamido, imido, carboxylic acid,
carboxylic acid ester, sulfonic acid, sulfonic acid ester,
alkylamino, and arylamino.
[0033] The present invention further relates to a bottom
anti-reflective coating formed by spreading on a substrate and then
heating the above composition for forming a bottom anti-reflective
coating.
[0034] The present invention also relates to a pattern formation
method comprising the steps of:
[0035] spreading the above composition for forming a bottom
anti-reflective coating on a semiconductor substrate and then
baking it, to form a bottom anti-reflective coating;
[0036] forming a photoresist layer on the bottom anti-reflective
coating;
[0037] exposing to radiation the semiconductor substrate covered
with the bottom anti-reflective coating and the photoresist layer;
and after the exposure,
[0038] developing by use of a developing solution selected from the
group consisting of alkaline developing solutions and organic
solvents.
Effect of the Invention
[0039] The composition according to the present invention enables
to prevent intermixing with a photoresist composition layer and
thereby to form a photoresist pattern having a cross section near
perpendicular to the substrate surface. In one embodiment, by use
of the composition of the present invention for forming a bottom
anti-reflective coating, it becomes possible to form a bottom
anti-reflective coating which can be readily dissolved after
hardened in an alkaline developing solution used for development of
the photoresist and accordingly which can be developed and removed
together with the photoresist to form a pattern. In another
embodiment, by use of the composition of the present invention for
forming a bottom anti-reflective coating, it becomes possible to
form a bottom anti-reflective coating which is not soluble in
developer of the photoresist.
BEST MODE FOR CARRYING OUT THE INVENTION
[0040] Embodiments of the present invention are described below in
detail.
[0041] The composition of the present invention for forming a
bottom anti-reflective coating contains a polymer having an
aromatic ring; a maleimide derivative or a maleic anhydride
derivative; and a solvent, and further, if needed, a crosslinking
agent or a photo acid generator. Those components of the
composition are explained below in order.
(Polymer Having an Aromatic Ring)
[0042] The composition of the present invention for forming a
bottom anti-reflective coating is hardened by a particular
reaction. However, if the polymer used in the composition is
properly selected, the coating formed from the composition can be
made either removable by development or durable against a
developing solution. The polymer for each type of the coating is
described below.
[0043] The polymer used in the composition according to the present
invention is represented by the formula (1):
-A.sub.m-B.sub.n- (1).
[0044] In the formula (1), A and B are repeating units represented
by the following formulas (A) and (B), respectively:
##STR00005##
[0045] In the formulas (a) and (b), [0046] each of R.sup.11 and
R.sup.12 is independently hydrogen or an alkyl group, preferably
hydrogen or methyl; [0047] L.sup.11 is a single bond, COO or a
straight- or branched chain alkylene containing one or more carbon
atoms, preferably COO; [0048] Y is a condensed polycyclic aromatic
group containing two or more benzene rings. The aromatic ring may
be where one of the benzene rings may be replaced with a quinone
ring and that the condensed polycyclic aromatic group may
optionally have a substituent selected from the group consisting of
alkyl, aryl, halogen, alkoxy, nitro, aldehyde, cyano, amido,
dialkylamino, sulfonamido, imido, carboxy, carboxylic acid ester,
sulfa, sulfonic acid ester, alkylamino, and arylamino; and [0049] Z
is a group selected from the group consisting of R.sup.3COOR.sup.4
and R.sup.3OR.sup.4, provided that R.sup.3 is a single bond, oxygen
or a straight- or branched chain alkylene which may optionally have
a fluorine and which contains one or more, preferably 1 to 6 carbon
atoms and also provided that R.sup.4 is hydrogen or a substituted
or non-substituted hydrocarbon group. The hydrocarbon group can be
aromatic (such as phenyl, benzyl) or nonaromatic
[0050] The repeating units A and B may be combined either randomly
or in blocks; [0051] each of A and B may be a combination of two or
more repeating units having different structures; and [0052] each
of m and n is a number indicating the polymerization degree
provided that m is not less than 10 and n is not less than 0.
[0053] The above polymer can be obtained by polymerizing monomers
corresponding to the repeating units (A) and (B) in the formula
(1).
[0054] The polymer represented by the formula (1) has a substituent
Y, which is a condensed polycyclic aromatic group containing two or
more benzene rings. This substituent enhances absorbance of light
in particular wavelength, and thereby gives optical effects when
contained in the bottom anti-reflective coating. Further, the
substituent participates in a Diels-Alder reaction described later,
and thereby enables to form the coating soluble in an alkaline
developing solution. There is no particular restriction on the
number of benzene rings contained in the polycyclic aromatic group,
but the polycyclic aromatic group preferably contains five or less
benzene rings. The polycyclic aromatic group may contain a five- or
seven-membered hydrocarbon ring, but in one embodiment it does not
contain that ring.
[0055] Examples of the condensed polycyclic aromatic rings
containing the substituent Y include rings of naphthalene,
anthracene, phenanthrene, tetracene, chrysene,
benzo[c]-phenanthrene, triphenylene, pentacene, picene, and
benzo[c]chrysene. The polycyclic aromatic ring may have a
substituent selected from the group consisting of alkyl, aryl,
halogen atom, alkoxy, nitro, aldehyde, cyano, amido, dialkylamino,
sulfonamido, imido, carboxy, carboxylic acid ester, sulfo, sulfonic
acid ester, alkylamino, and arylamino. Further, one of the benzene
rings contained in the condensed polycyclic aromatic ring may be
replaced with a quinone ring. Examples of the quinone ring include
rings of anthraquinone, 5,12-naphthacenequinone (tetracenequinone),
5,6-chrysenequinone, [0056] 6,12-chrysenequinone, and
6,13-pentacenequinone.
[0057] Since greatly contributing to light-absorption of the
polymer, the substituent Y is preferably selected according to
wavelength of light used for exposure. For example, if KrF laser
(wavelength: 248 nm) is used as the exposure light source, the
substituent Y preferably contains an anthracene ring or the like,
which has high absorbance at that wavelength.
[0058] Examples of the monomer corresponding to the repeating unit
(A) include naphthalene methacrylate 9-anthracenemethyl acrylate,
9-tetracenemethyl acrylate, 9-pentacenemethyl acrylate,
9-anthracenemethyl methacrylate, 9-tetracenemethyl methacrylate,
and 9-pentacenemethyl methacrylate. In view of availability,
9-anthracenemethyl methacrylate is preferred. It is possible to use
a combination of two or more monomers corresponding to the
repeating unit (A). There is no particular restriction on how to
obtain the monomer, and hence commercially available monomers may
be used or otherwise monomers to use may be synthesized.
[0059] Meanwhile, the structure and polymerization ratio of the
repeating unit (B) can be selected according to whether the coating
formed from the composition of the present invention is made
developable or insoluble in a developing solution. In the following
description, for the sake of convenience, the composition for
forming a bottom anti-reflective coating developable or insoluble
in a developing solution is referred to as a "first" or "second"
composition, respectively.
[0060] Further, with respect to the first composition for forming a
bottom anti-reflective coating, the structure of its repeating unit
(B) is selected also according to whether the coating formed from
the composition is made photosensitive or not.
[0061] If R.sup.4 at the terminal of the group Z is hydrogen, that
is, if the group Z is R.sup.3COOH or R.sup.3OH, particularly if the
group Z is R.sup.3COOH, the polymer is readily soluble in an
alkaline developing solution and hence the composition can form a
non-photosensitive bottom anti-reflective coating whether or not
the exposure is carried out. On the other hand, if the group Z is
R.sup.3COOR.sup.4 or R.sup.3OR.sup.4, particularly if the group Z
is R.sup.3COOR.sup.4 (in which R.sup.4 is a substituted or
non-substituted hydrocarbon group, for example, t-butyl), the group
Z as a whole is neither an acid radical nor a polar group and hence
the polymer is hard to dissolve in an alkaline developing solution
and the like. However, when the coating is exposed to light, acid
is generated to release the alkyl group and thereby to increase
solubility in an alkaline developing solution. As a result, the
bottom anti-reflective coating becomes photosensitive. In
consideration of this, it is preferred to select the structure of
the repeating unit (B) suitably for the use of the bottom
anti-reflective coating. Specifically, if the composition for
forming a bottom anti-reflective coating needs to be
non-photosensitive, R.sup.4 is preferred to be hydrogen. If the
composition needs to be photosensitive, R.sup.4 is preferred to be
a substituted or non-substituted hydrocarbon group. This
hydrocarbon group may be a straight chain, branched chain or cyclic
alkyl group, and may contain an oxygen or nitrogen atom replacing a
carbon atom. Examples of the hydrocarbon group include straight
chain alkyl, branched chain alkyl, cycloalkyl, cyclic lactone,
benzyl, tetrahydrofuranyl, methyladamantyl, ethyladamantyl,
oxathianyl, ethylcyclopentyl, menthyl, tetrahydropyranyl, and
mevalonolactone. Preferred is a branched chain alkyl group having 1
to 10 carbon atoms.
[0062] In the group Z, R.sup.3 serves as a linking group and is a
single bond, an oxygen or a straight- or branched chain alkylene
having 1 or more carbon atoms. The straight- or branched chain
alkylene may have a fluorine atom, and preferably contains 1 to 6
carbon atoms. Examples of the linking group R.sup.3 include a
single bond, --O--, --CH.sub.2--, --CH.sub.2--CH.sub.2--,
--C(CF.sub.3).sub.2-- and --C(CF.sub.3).sub.2O--. Among them,
particularly preferred are a single bond and a straight-chain
alkylene having 1 to 6 carbon atoms.
[0063] In view of controlling solubility of the bottom
anti-reflective coating in an alkaline developing solution, the
group Z is preferably R.sup.3COOR.sup.4 or R.sup.3OR.sup.4, more
preferably R.sup.3COOR.sup.4.
[0064] Examples of the monomer corresponding to the repeating unit
(B) include acrylic acid, 3-butenoic acid, 4-pentenoic acid,
5-hexenoic acid, 6-heptenoic acid, 7-octenoic acid, 8-nonenoic
acid, methacrylic acid, 2-methyl-3-butenoic acid,
2-methyl-4-pentenoic acid, 2-methyl-5-hexenoic acid,
2-methyl-6-heptenoic acid, 2-methyl-7-octenoic acid,
2-methyl-8-nonenoic acid, 4-vinylbenzoic acid, tert-butyl acrylate,
tert-butyl methacrylate, 9-hydroxynaphtyl methacrylate,
9-hydroxynaphthyl acrylate, 4-hydroxyphenyl methacrylate,
4-hydroxyphenyl acrylate, and 4-hydroxyl styrene. In view of
availability, preferred are acrylic acid, methacrylic acid,
tert-butyl acrylate, and tert-butyl methacrylate. There is no
particular restriction on how to obtain the monomer, and hence
commercially available monomers may be used or otherwise monomers
to use may be synthesized. It is possible to use a combination of
two or more monomers corresponding to the repeating unit (B). For
example, acrylic acid or methacrylic acid can be used in
combination of tert-butyl acrylate or tert-butyl methacrylate.
[0065] The bottom anti-reflective coating formed from the first
composition is required to change its solubility in a developing
solution between before and after the radiation exposure. In order
to change the solubility, the repeating unit (B) is indispensable.
Accordingly, the polymerization degree n needs to be not less than
1. Specifically, the polymerization ratio of the repeating unit (A)
is preferably 30 to 60 mol %, more preferably 40 to 50 mol % based
on all the repeating units constituting the polymer. That is
because the polymer preferably contains the repeating unit (A) more
than a particular amount so that the resultant bottom
anti-reflective coating can have sufficient light-absorption and
also because the polymer preferably contains the repeating unit (B)
more than a particular amount so as to ensure solubility in a
developing solution. The polymerization ratio of the repeating unit
(B) is preferably 40 to 70 mol %. The polymer may contain other
repeating units unless they impair the effect of the present
invention; in one case, polymerization ratio is generally 10 mol %
or less of the polymer.
[0066] In contrast, the bottom anti-reflective coating formed from
the second composition is insoluble in the developing solution.
Here, the term "insoluble" does not mean that the developing
solution cannot dissolve the bottom anti-reflective coating at all,
but it means that the coating becomes thinner by 1% or less in the
step of development. In the second composition, it is unnecessary
for the polymer to contain R.sup.3COOH, R.sup.3OH or the precursors
thereof (i.e., R.sup.3COOR.sup.4, R.sup.3OR.sup.4). The repeating
unit (B) is, therefore, dispensable for the polymer used in the
second composition for forming a bottom anti-reflective coating.
Accordingly, as for the second composition, the polymerization
degree n in the formula (1) is a number of 0 or more and hence the
polymer may be a homo-polymer consisting of only the repeating unit
(A).
[0067] However, as long as the effect of the present invention can
be obtained, the second composition for forming a bottom
anti-reflective coating may contain the repeating unit (B)
including R.sup.3COOH or R.sup.3OH. In the second composition, the
polymerization ratio of the repeating unit (B) including
R.sup.3COOH or R.sup.3OH is preferably not more than 5 mol % or not
more than 70 mol %, respectively. Examples of the monomer
preferably used in this case include acrylic acid, 3-butenoic acid,
4-pentenoic acid, 5-hexenoic acid, 6-heptenoic acid, 7-octenoic
acid, 8-nonenoic acid, methacrylic acid, 2-methyl-3-butenoic acid,
2-methyl-4-pentenoic acid, 2-methyl-5-hexenoic acid,
2-methyl-6-heptenoic acid, 2-methyl-7-octenoic acid,
2-methyl-8-nonenoicacid, 4-vinylbezoic acid, 9-hydroxynaphtyl
methacrylate, 9-hydroxynaphthyl acrylate, 4-hydroxyphenyl
methacrylate, 4-hydroxyphenyl acrylate, and 4-hydroxyl styrene.
[0068] On the other hand, the repeating unit (B) including
R.sup.3COOR.sup.4 or R.sup.3OR.sup.4 (in which R.sup.4 is a
substituted or non-substituted hydrocarbon group) gives small
effect on the solubility of the bottom anti-reflective coating, and
hence it may be contained in the polymer in a relatively large
amount. In that case, the polymerization ratio of the repeating
unit (B) including R.sup.3COOR.sup.4 or R.sup.3OR.sup.4 is
preferably not more than 75 mol %. Examples of the monomer
preferably used in this case include tert-butyl acrylate,
tert-butyl methacrylate, 9-hydroxynaphtyl methacrylate,
9-hydroxynaphthyl acrylate, 4-hydroxyphenyl methacrylate,
4-hydroxyphenyl acrylate, and 4-hydroxyl styrene.
[0069] In contrast, the polymerization ratio of the repeating unit
(A) is preferably not less than 20 mol % based on the whole
polymer, so as to ensure sufficient light-absorption.
[0070] The polymer represented by the formula (1) can be obtained
from the above monomers in a proper solvent by use of a radical or
ionic polymerization initiator. In the present invention, the
polymer of the formula (1) may be any type of copolymers such as
random copolymers or block copolymers, and accordingly the
polymerization conditions can be selected according to the type of
the polymer.
[0071] Examples of the polymerization initiator include
2,2'-azobis(isobutyronitrile) (AIBN),
2,2'-azobis-dimethyl-1-(2-methylpropionate),
2,2'-azobis-(4-methoxy-2,4-dimethylvaleronitrile),
2,2'-azobis-(2-cyclopropylpropionitrile),
2,2'-azobis(2,4-di-methylvaleronitrile),
2,2'-azobis(2,4-dimethylpentane-nitrile),
1,1'-azobis(cyclohexanecarbonitrile), benzoyl peroxide, t-butyl
peroxide benzoate, di-t-butyldiperoxy phthalate,
t-butylperoxy-2-ethylhexanoate, t-butylperoxy pivalate,
t-amylperoxypivalate, and butyllithium. In view of safety and
availability, 2,2'-azobis-dimethyl-1-(2-methylpropionate) is
preferred. The amount thereof is preferably 1 to 10 wt % based on
the total weight of all the monomers.
[0072] Examples of the solvents preferably used for the
polymerization reaction include toluene, tetrahydrofuran, benzene,
methyl amyl ketone, dimethylformamide, dimethyl sulfoxide, ethyl
lactate, and propyleneglycol monomethyl ether acetate (PGMEA).
Those solvents may be used singly or in combination of two or more.
The amount thereof is preferably 1 to 10 times as large as the
total weight of all the monomers.
[0073] The polymerization reaction is conducted at a temperature of
normally 50 to 200.degree. C., preferably 60 to 150.degree. C.,
more preferably 80 to 120.degree. C.
[0074] In the present invention, there is no particular restriction
on the molecular weight of the polymer represented by the formula
(1). However, when measured in terms of standard polystyrene by gel
permeation chromatography (GPC), the weight average molecular
weight thereof is preferably in the range of 2000 to 5000000 Da.
Further, in consideration of film formability, solubility and heat
stability, it is more preferred for the polymer of the formula (1)
to have a weight average molecular weight of 3000 to 100000 Da. The
molecular weight of the polymer, which is obtained by the
polymerization reaction, can be controlled by various
polymerization conditions such as polymerization time and
temperature, concentrations of the monomers and the initiator used
in the reaction, and the reaction solvent. If ionic polymerization
is selected as the polymerization reaction, the polymer having a
narrow molecular weight distribution can be obtained.
[0075] After the polymerization reaction is completed, the polymer
can be separated and purified from the reaction solution by use of
techniques adopted in normal polymer syntheses. For example,
n-hexane or n-heptane, which is a poor solvent of the polymer but
has good miscibility with the solvent of the polymerization is
poured into the reaction solution so as to separate the polymer.
However, without separating or purifying the polymer, the mixture
solution obtained by the polymerization reaction may be directly
used as a material of the composition for forming a bottom
anti-reflective coating.
[0076] As long as all the components are homogeneously dissolved in
the composition of the present invention for forming a bottom
anti-reflective coating, there is no particular restriction on the
concentration of the above polymer. However, in view of controlling
the thickness, the concentration thereof is preferably 1 to 50 wt
%, more preferably 1 to 2 wt % based on the total weight of the
composition.
(Maleimide Derivative and Maleic Anhydride Derivative)
[0077] The composition of the present invention for forming a
bottom anti-reflective coating contains a compound which is a
maleimide derivative or a maleic anhydride derivative. The compound
may be represented by any of the following formulas (2) to (4):
##STR00006##
in which each of R.sup.21, R.sup.22 and R.sup.23 is independently a
group selected from the group consisting of hydrogen, alkyl, aryl,
halogen atom, alkoxy, nitro, aldehyde, cyano, amido, dialkylamino,
sulfonamido, imido, carboxylic acid, carboxylic acid ester,
sulfonic acid, sulfonic acid ester, alkylamino, and arylamino;
##STR00007##
in which each of R.sup.31 to R.sup.36 is independently a group
selected from the group consisting of hydrogen, alkyl, aryl,
halogen, alkoxy, nitro, aldehyde, cyano, amido, dialkylamino,
sulfonamido, imido, carboxylic acid, carboxylic acid ester,
sulfonic acid, sulfonic acid ester, alkylamino, and arylamino; and
L.sup.31 is an alkylene or an arylene; and
##STR00008##
in which each of R.sup.41 and R.sup.42 is independently a group
selected from the group consisting of hydrogen, alkyl, aryl,
halogen, alkoxy, nitro, aldehyde, cyano, amido, dialkylamino,
sulfonamido, imido, carboxylic acid, carboxylic acid ester,
sulfonic acid, sulfonic acid ester, alkylamino, and arylamino.
Among them, the compound of the formula (2) or (3) is a maleimide
derivative while that of the formula (4) is a maleic anhydride
derivative.
[0078] Examples of the compound represented by the formula (2)
include maleimide, N-alkylmaleimide, N-aromatic maleimide, and
N-sulfonic maleimide. Those compounds may be substituted with
alkyl, aryl, halogen, alkoxy, nitro, aldehyde, cyano, amido,
dialkylamino, sulfon-amido, imido, carboxy, carboxylic acid ester,
sulfo, sulfonic acid ester, alkylamino, or arylamino.
[0079] Examples of the compound represented by the formula (3)
include N,N'-alkylbismaleimide, N,N'-aromatic bismaleimide, and
N,N'-sulfonic bismaleimide. Those compounds may be substituted with
alkyl, aryl, halogen atom, alkoxy, nitro, aldehyde, cyano, amido,
dialkylamino, sulfonamido, imido, carboxy, carboxylic acid ester,
sulfo, sulfonic acid ester, alkylamino, or arylamino. In formula
(3), L.sup.31 may be C.sub.1-C.sub.20 alkyl.
[0080] Examples of the compound represented by the formula (4)
include maleic anhydride, which may be substituted with alkyl,
aryl, halogen, alkoxy, nitro, aldehyde, cyano, amido, dialkylamino,
sulfonamido, imido, carboxy, carboxylic acid ester, sulfo, sulfonic
acid ester, alkylamino, or arylamino.
[0081] In one embodiment the compound represented by any of the
formulas (2) to (4) causes a Diels-Alder reaction with the polymer
of the formula (1). As a result of the reaction, the polymer forms
a coating soluble in a developing solution of the photoresist.
Thus, the effect of the first invention is obtained.
[0082] Examples of the compound represented by the formula (2)
include 1,2-bismaleimide ethane, 1,4-bis-maleimide butane, and
1,6-bismaleimide hexane.
[0083] Examples of the compound represented by the formula (3)
include N,N'-1,4-phenylenedimaleinnide,
N,N'-1,3-phenylenedinnaleimide, N,N'-4,4'-bismaleimide
diphenylmethane, and
bis(3-ethyl-5-methyl-4-maleimidephenyl)methane.
[0084] Examples of the compound represented by the formula (4)
include maleic anhydride, methylmaleic anhydride, and
dimethylmaleic anhydride.
[0085] There is no particular restriction on how to obtain those
compounds, and hence commercially available compounds may be used
or otherwise compounds to use may be synthesized. The compounds of
the formulas (2) to (4) may be used in combination of two or more.
The amount of the compound represented by any of the formulas (2)
to (4) is preferably 0.1 to 1 mole, or 0.2 to 1 mole based on 1
mole of the aromatic group, such as naphthalene, anthracene,
tetracene or pentacene, contained in the substituent Y in the above
polymer. Accordingly, the compound causes a Diels-Alder reaction to
combine with a part of the substituent Y in the above polymer.
Since the substituent Y contributes to light-absorption of the
bottom anti-reflective coating, the effect of the present invention
cannot be obtained if all the substituents Y are reacted.
Accordingly, the substituents Y are preferably left unreacted in an
amount of 20% or more based on the number of the substituents Y
contained before the reaction in the above polymer.
[0086] In the Diels-Alder reaction, the maleimide derivative or the
like serves as a dienophile to react with a diene structure
contained in the condensed polycyclic aromatic skeleton of the
substituent Y, so that pi-bonds in the skeleton are rearranged and
a new C--C bond and a new pi-bond are formed. By way of example,
the reaction between an anthracene skeleton and a maleimide
derivative is shown below.
##STR00009##
[0087] The above reaction enhances polarity of the polymer to lower
solubility in a solvent, such as propylene glycol monomethylether
acetate (PGMA), used for the photoresist. If a compound having two
maleimide structures, such as a compound of the formula (3), is
adopted, each maleimide reacts with the group Y in the polymer to
form a crosslinking structure and hence to further lower the
solubility in an organic solvent. This means that the compound of
the formula (3) also functions as a crosslinking agent.
Accordingly, it is preferred to use the compound represented by the
formula (3).
[0088] In the first composition for forming a bottom
anti-reflective coating, the polymer after the Diels-Alder reaction
contains the group Z shown in the formula (1). The group Z includes
carboxyl, hydroxyl or a group in which hydrogen of carboxyl or
hydroxyl is substituted with an alkyl or the like. This substituted
group is converted into carboxyl or hydroxyl by acid generated from
the photo acid generator after exposed to light, and thereby the
polymer becomes highly soluble in an alkaline developing solution
containing a base such as strongly basic tetramethylammonium
hydroxide (hereinafter, referred to as "TMAH").
[0089] As long as all the components are homogeneously dissolved in
the composition of the present invention for forming a bottom
anti-reflective coating, there is no particular restriction on the
concentration of the compound represented by any of the formulas
(2) to (4). However, as described above, the light-absorption and
the solubility vary depending on the progression of the Diels-Alder
reaction. Accordingly, the composition contains the compound of the
formula (2), (3) or (4) in an amount of preferably 0.15 to 0.75 wt
%, more preferably 0.2 to 0.4 wt %, based the total weight of the
composition.
(Photo Acid Generator)
[0090] If necessary, the composition of the present invention for
forming a bottom anti-reflective coating contains a photo acid
generator. As the photo acid generator, any compound can be used as
long as it generates acid when exposed to light of KrF excimer
laser (wavelength: 248 nm), ArF excimer laser (wavelength: 193 nm)
or the like.
[0091] The photo acid generator can be freely selected from
conventionally known ones. Examples of the photo acid generator
include onium salt compounds, sulfone maleimide derivatives, and
disulfonyl diazomethane compounds.
[0092] Examples of the onium salt compounds include: iodonium salt
compounds, such as diphenyliodonium hexafluorophosphate,
diphenyliodonium trifluoro-methanesulfonate, diphenyliodonium
nonafluoro-n-butane-sulfonate, diphenyliodonium
perfluoro-n-octanesulfonate, diphenyliodonium camphorsulfonate,
bis(4-tert-butylphenyl)iodonium camphorsulfonate, and
bis(4-tert-butylphenyl)iodonium trifluoro-methanesulfonate; and
sulfonium salt compounds, such as triphenylsulfonium
hexafluoroantimonate, triphenyl-sulfonium
nonafluoro-n-butanesulfonate, triphenyl-sulfonium camphorsulfonate,
and triphenylsulfonium trifluoromethanesulfonate.
[0093] Examples of the sulfone maleimide derivatives include
N-(trifluoromethanesulfonyloxy)succinimide,
N-(fluoro-n-butanesulfonyloxy)succinimide,
N-(camphor-sulfonyloxy)succinimide, and
N-(trifluoromethanesulfonyl-oxy)naphthalimide.
[0094] Examples of the disulfonyl diazomethane compounds include
bis(trifluoromethylsulfonyl)diazomethane,
bis(cyclohexylsulfonyl)diazomethane,
bis(phenylsulfonyl)diazomethane,
bis(p-toluenesulfonyl)-diazomethane,
bis(2,4-dimethylbenzenesulfonyl)diazo-methane, and
methylsulfonyl-p-toluenesulfonyldiazo-methane.
[0095] The composition of the present invention for forming a
bottom anti-reflective coating can contain those photo acid
generators in combination of two or more. The amount of the photo
acid generator is in the range of preferably 0.01 to 20 weight
parts, more preferably 0.02 to 5 weight parts, based on 100 weight
parts of the polymer represented by the formula (1). The photo acid
generator can be also used for the purpose of controlling the shape
of photoresist pattern. The mechanism of that is not completely
known, but is presumed that the photo acid generator works to
balance the acidity of the bottom anti-reflective coating. The
photo acid generator thus enables to form a photoresist pattern in
a preferred rectangular shape.
(Crosslinking Agent)
[0096] The composition of the present invention for forming a
bottom anti-reflective coating contains a crosslinking agent, if
necessary. As described above, if containing the compound of the
formula (3), the composition forms a crosslinking structure when
heated to lower the solubility in a solvent for photoresist.
However, if containing the compound of the formula (2) or (4), the
solubility of the polymer depends on how the substituents are
changed by the Dields-Alder reaction. In that case, the
crosslinking agent makes it possible to control the solubility by
increasing the molecular weight. Even in the case where the
composition contains the compound of the formula (3), the
crosslinking agent is preferably incorporated therein if the amount
of the compound is small.
[0097] As the crosslinking agent, any compound can be used as long
as it is made to crosslink the polymer of the formula (1) by the
generated acid when exposed to light of KrF excimer laser
(wavelength: 248 nm), ArF excimer laser (wavelength: 193 nm) or the
like.
[0098] Examples of the crosslinking agent include
hexa-methylmelamine, hexamethoxymethylmelamine,
1,2-dihydroxy-N,N'-methoxymethylsuccinimide,
1,2-di-methoxy-N,N'-methoxymethylsuccinimide,
tetramethoxy-methylglycoluril, and N,N'-methoxymethylurea.
[0099] The amount of the crosslinking agent is preferably 10 to 50
weight parts, more preferably 15 to 30 weight parts, based on 100
weight parts of the polymer represented by the formula (1).
(Solvent)
[0100] Any solvent can be used in the (first or second) composition
of the present invention for forming a bottom anti-reflective
coating, as long as it can dissolve all the components. Examples of
the solvent include ethyleneglycol monomethyl ether, ethyleneglycol
monoethyl ether, methyl cellosolve acetate, ethyl cellosolve
acetate, diethyleneglycol monomethyl ether, diethyleneglycol
monoethyl ether, propylene glycol, propyleneglycol monomethyl
ether, propyleneglycol monomethyl ether acetate, propyleneglycol
propyl ether acetate, toluene, xylene, methyl ethyl ketone,
cyclopentanone, cyclohexanone, ethyl 2-hydroxypropionate, ethyl
2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl
hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate, methyl
3-methoxypropionate, ethyl 3-methoxypropionate, ethyl
3-ethoxypropionate, methyl 3-ethoxypropionate, methyl pyruvate,
ethyl pyruvate, ethyl acetate, butyl acetate, ethyl lactate, butyl
lactate, N,N-dimethylformamide, N,N-dimethylacetamide, and
N-methylpyrrolidone. Those solvents can be used singly or in
combination of two or more. Further, they may be used in
combination with high boiling point solvents such as
propyleneglycol monobutyl ether and propyleneglycol monobutyl ether
acetate.
(Composition for Forming a Bottom Anti-Reflective Coating from the
First Composition for Forming a Bottom Anti-Reflective Coating)
[0101] The composition of the present invention for forming a
bottom anti-reflective coating can be prepared by mixing and
dissolving the above components homogeneously.
[0102] In the preparation, the polymer of the formula (1) or the
combination of other additives can be selected according to the use
of the composition. If the bottom anti-reflective coating to
produce is wanted to be both developable and photosensitive, the
group Z of the polymer represented by the formula (1) is preferably
R.sup.3COOR.sup.4 in which R.sup.4 is a substituted or
non-substituted hydrocarbon group. Further, in that case, the
composition preferably contains a photo acid generator to assist
elimination of R.sup.4 caused by exposure. On the other hand, if
the anti-reflective coating to produce is wanted to be
non-photosensitive, the group Z is preferably R.sup.3COOH.
[0103] If the bottom anti-reflective coating is designed to use
with a positive-working photoresist layer, the composition
basically consisting of the above combination can work
satisfyingly. However, if the coating is designed to combine with a
negative-working photoresist layer, the composition preferably
further contains a crosslinking agent.
[0104] According to the present invention, even if the bottom
anti-reflective coating is combined with a positive-working
photoresist layer, it can be made possible to produce a
negative-working resist pattern by changing the developing
conditions (as described later in detail),
[0105] Further, if necessary, the composition of the present
invention for forming a bottom anti-reflective coating can contain
other additives, such as, thickening agents, surfactants, slipping
agents, or colorants such as dyes.
[0106] The composition obtained by mixing the components is
preferably used after filteration through a 0.2 to 0.05 .mu.m
porous size filter. The composition thus prepared is excellent in
storage stability at room temperature for a long time.
(Formation Method of a Bottom Anti-Reflective Coating)
[0107] The below described is a bottom anti-reflective coating
formation method employing the composition according to the present
invention. In the following description, the pattern formation
method is categorized into (a) to (e) and explained based on the
kind of photoresist and the components contained in the composition
for forming a bottom anti-reflective coating.
Pattern Formation Method (a)
[0108] First, in the case where the composition of the present
invention is non-photosensitive and combined with a
positive-working photoresist, the pattern formation method is
described below.
[0109] The composition of the present invention for forming a
bottom anti-reflective coating is spread by proper means, such as a
spinner or a coater, on a semiconductor substrate (e.g.,
silicon/silicon dioxide-coated substrate, silicon nitride
substrate, silicon wafer substrate, glass substrate, ITO
substrate). In this method, the composition contains, at least, a
polymer represented by the formula (1), a compound represented by
any of the formulas (2) to (4), and a solvent. In the polymer of
the formula (1), the group Z is preferably R.sup.3COOH or
R.sup.3OH, more preferably R.sup.3COOH so that the polymer can keep
high solubility in an alkaline developing solution. The spread
composition is then baked to form a bottom anti-reflective coating.
The baking conditions are properly determined. For example, the
baking temperature is generally 80 to 250.degree. C., preferably
100 to 250.degree. C.; and the baking time is generally 0.3 to 5
minutes, preferably 0.5 to 2 minutes. This baking drives a
Diels-Alder reaction in the composition layer, and accordingly a
hardening reaction proceeds to form a bottom anti-reflective
coating.
[0110] On the bottom anti-reflective coating thus formed, a
positive-working photoresist composition is applied. Here, the
"positive-working photoresist" means a substance that causes a
reaction under exposure to light and thereby increases solubility
in an alkaline developing solution. There is no particular
restriction on the photoresist, and any positive-working
photoresist can be adopted as long as it is sensitive to light of
exposure for pattern formation.
[0111] Thereafter, the step of exposure is carried out by use of a
predetermined mask. There is no particular restriction on the
wavelength of light used for exposure, but it is preferred to use
light of 115 to 248 nm. Examples of the light include KrF excimer
laser light (wavelength: 248 nm), ArF excimer laser light
(wavelength: 193 nm) and extreme UV light (wavelength: 13.5 nm). If
the exposure is performed by use of light of very short wavelength,
such as extreme UV light, the light intensity is generally so weak
that the bottom anti-reflective coating is not always very
effective in preventing light-reflection, but the coating may
function to inhibit adverse effects of gases given off from the
substrate placed thereunder. After the exposure, post-exposure bake
can be carried out. The temperature of post-exposure bake is 80 to
150.degree. C., preferably 100 to 140.degree. C.; and the time
thereof is 0.3 to 5 minutes, preferably 0.5 to 2 minutes.
[0112] Successively, the step of development is carried out by use
of an alkaline developing solution. Thereby, in the area exposed to
light, the photoresist layer and the bottom anti-reflective coating
placed thereunder are developed and removed to form a photoresist
pattern, thereby forming a pattern in the photoresist and the
antireflective coating.
Pattern Formation Method (b)
[0113] In the case where the composition of the present invention
is non-photosensitive and combined with a negative-working
photoresist, the pattern formation method (a) is repeated only
except that the photoresist composition is changed. Here, the
"negative-working photoresist" means a substance that causes a
reaction under exposure to light and thereby decreases solubility
in an alkaline developing solution. As a result of the exposure,
the photoresist in the area exposed to light becomes to have low
solubility and hence that in the area not exposed to light becomes
to have relatively high solubility. Accordingly, when developed
with the alkaline developing solution after the exposure, the
photoresist is brought into contact with the alkaline developing
solution and consequently the photoresist in the area not exposed
to light is removed to leave that in the area exposed to light.
Further, in the area where the photoresist is removed, the bared
bottom anti-reflective coating is also dissolved and removed. Thus,
in the area not exposed to light, the photoresist layer and the
bottom anti-reflective coating placed thereunder are developed and
removed to form a photoresist pattern.
Pattern Formation Method (c)
[0114] In the case where the composition of the present invention
is photosensitive and combined with a positive-working photoresist,
the polymer of the formula (1) preferably has a particular
structure. That is, the group Z in the polymer is preferably
R.sup.3COOR.sup.4 or R.sup.3OR.sup.4 (in which R.sup.4 is a
substituted or non-substituted hydrocarbon group) so that the
solubility of the polymer can be changed by exposure. The polymer
having that structure in itself has low solubility in an alkaline
developing solution. However, when the composition is exposed to
light, acid is generated and releases R.sup.4 to enhance the
solubility in an alkaline developing solution. The acid generated
by exposure may be given either from a photo acid generator
contained in the photoresist layer or from a photo acid generator
added, as necessary, in the bottom anti-reflective coating.
[0115] The procedure of this method is the same as that of the
pattern formation method (a). However, this pattern formation
method is characterized in that the bottom anti-reflective coating
before the exposure has low solubility in an alkaline solution but
that the solubility is enhanced by exposure. Thus the pattern is
formed in the photoresist and the antireflective coating.
Pattern Formation Method (d)
[0116] In the case where the composition of the present invention
is photosensitive and combined with a negative-working photoresist,
the polymer of the formula (1) preferably has a particular
structure. That is, the group Z in the polymer is preferably
R.sup.3COOH or R.sup.3OH. The polymer having that structure in
itself has high solubility in an alkaline developing solution.
However, when the composition is exposed to light, the polymer of
the formula (1) reacts with a crosslinking agent to lower the
solubility in an alkaline developing solution. The acid generated
by exposure may be given either from a photo acid generator
contained in the photoresist layer or from a photo acid generator
added, as necessary, in the bottom anti-reflective coating. The
crosslinking agent is preferably contained in the bottom
anti-reflective coating so that the coating in itself can be also
crosslinked by the acid to lower the solubility in an alkaline
developing solution.
Pattern Formation Method (e)
[0117] The above pattern formation methods (a) to (d) make use of
the solubility of the bottom anti-reflective coating in an alkaline
developing solution. However, it is also possible to utilize
solubility thereof in an organic solvent for forming the pattern.
Specifically, in the case where the composition of the present
invention is photosensitive and combined with a positive-working
photoresist as described above in the pattern formation method (c),
the R.sup.4 groups are released by exposure and accordingly polar
groups such as COOH are thickly formed in the area exposed to
light. Consequently, the coating in the exposed area becomes to
have low solubility in an organic solvent, and hence that in the
area not exposed to light becomes to have relatively high
solubility. Accordingly, development can be carried out after
exposure by use of an organic solvent, and thereby the photoresist
and the bottom anti-reflective coating in the area not exposed to
light can be removed to form a negative-type pattern. This pattern
formation method is characterized in that a negative-type pattern
can be obtained by use of a positive-working photoresist.
(Formation Method of a Bottom Anti-Reflective Coating from the
Second Composition for Forming a Bottom Anti-Reflective
Coating)
[0118] A bottom anti-reflective coating insoluble in a developing
solution is formed from the second composition of the present
invention for forming a bottom anti-reflective coating. The below
described is a bottom anti-reflective coating formation method
employing the second composition according to the present
invention. In the following description, the pattern formation
method is categorized into (f) to (h) and explained based on the
kind of photoresist and the components contained in the composition
for forming a bottom anti-reflective coating.
[0119] Pattern Formation Method (f)
[0120] The composition of the present invention for forming a
bottom anti-reflective coating is spread by proper means, such as a
spinner or a coater, on a semiconductor substrate (e.g.,
silicon/silicon dioxide-coated substrate, silicon nitride
substrate, silicon wafer substrate, glass substrate, ITO
substrate). In this method, the composition contains, at least, a
polymer represented by the formula (1), a compound represented by
any of the formulas (2) to (4), and a solvent, as described
previously. The spread composition is then baked to form a bottom
anti-reflective coating. The baking conditions are properly
determined. For example, the baking temperature is generally 80 to
250.degree. C., preferably 100 to 250.degree. C.; and the baking
time is generally 0.3 to 5 minutes, preferably 0.5 to 2 minutes.
This baking drives a Diels-Alder reaction in the composition layer,
and accordingly a hardening reaction proceeds to form a bottom
anti-reflective coating.
[0121] On the bottom anti-reflective coating thus formed, a
positive-working photoresist composition is applied in the same
manner as in the above pattern formation method (a), and then
exposed to light and developed to form a photoresist pattern,
without forming a pattern in the antireflective coating.
Pattern Formation Method (g)
[0122] In the case where the composition for forming a bottom
anti-reflective coating is combined with a negative-working
photoresist, the pattern formation method (f) is repeated only
except that the photoresist composition is changed. By use of this
method, a negative-working photoresist pattern can be formed.
Pattern Formation Method (h)
[0123] The above pattern formation methods (f) and (g) make use of
the insolubility of the bottom anti-reflective coating in an
alkaline developing solution. However, in the same manner as in the
pattern formation method (e), it is also possible to utilize
insolubility thereof in an organic solvent for forming the pattern.
Specifically, the composition for forming a bottom anti-reflective
coating is combined with a positive-working photoresist, and then
exposed to light. After the exposure, development is carried out by
use of an organic solvent, so that a negative-type pattern can be
obtained in the photoresist only.
[0124] Examples of the alkaline developing solution used in the
pattern formation methods (a) to (d), (f) and (g) include: an
aqueous solution of alkali metal hydroxide, such as potassium
hydroxide or sodium hydroxide; an aqueous solution of tertiary
ammonium hydroxide, such as tetra-methylammonium hydroxide,
tetraethylammonium hydroxide or choline; and an aqueous solution of
amine, such as ethanolamine, propylamine or ethylenediamine.
Particularly preferred is a 2.38 wt % TMAH aqueous solution, which
is commonly used as an alkaline developing solution.
[0125] Those developing solutions enable to dissolve and remove the
bottom anti-reflective coating readily at room temperature. The
developing solutions may contain surfactants and the like. Examples
of the organic solvent used as a developing solution in the pattern
formation methods (e) and (h) include (1) ketones, (2) esters, (3)
alcohols, (4) amides, (5) ethers and (6) hydrocarbons. Examples of
(1) ketones include 1-octanone, 2-octanone, 1-nonanone, 2-nonanone,
acetone, 2-heptanone (methyl amyl ketone), 4-heptanone, 1-hexanone,
2-hexanone, diisobutyl ketone, cyclohexanone, methyl cyclohexanone,
phenylacetone, methyl ethyl ketone, methyl isobutyl ketone,
acetylacetone, acetonylacetone, ionone, diacetonyl alcohol,
acetylcarbinol, acetophenone, methyl naphthyl ketone, isophorone
and propylene carbonate. Example of (2) esters include methyl
acetate, ethyl acetate, isopropyl acetate, n-butyl acetate, amyl
acetate, propyleneglycol monomethylether acetate, ethyleneglycol
monoethylether acetate, diethyleneglycol monobutylether acetate,
diethyleneglycol monoethylether acetate, ethyl-3-ethoxypropionate,
3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, methyl
formate, ethyl formate, butyl formate, propyl formate, ethyl
lactate, butyl lactate and propyl lactate. Example of (3) alcohols
include (3a) alcohols, such as methyl alcohol, ethyl alcohol,
n-propyl alcohol, iso-propyl alcohol, n-butyl alcohol, sec-butyl
alcohol, tert-butyl alcohol, iso-butyl alcohol, n-hexyl alcohol,
n-heptyl alcohol, n-octyl alcohol, n-decanol and methoxy methyl
butanol; (3b) glycols, such as ethylene glycol, diethylene glycol
and triethylene glycol; and (3c) glycol ethers, such as
ethyleneglycol monomethyl ether, propyleneglycol monomethyl ether,
ethyleneglycol mono-ethyl ether, propyleneglycol monoethyl ether,
diethyleneglycol monomethyl ether and triethyleneglycol monomethyl
ether. Example of (4) amides include N-methyl-2-pyrrolidone,
N,N-dimethylacetamide, N,N-dimethylformamide, hexamethylphosphoric
triamide and 1,3-dimethyl-2-imidazolidinone. Examples of (5) ethers
include glycol ethers of (3c), dioxane and tetrahydrofuran.
Examples of (6) hydrocarbons include aromatic hydrocarbon solvents
such as toluene and xylene, pentane, hexane, octane and decane.
[0126] The temperature of the developing solution is generally 5 to
50.degree. C., preferably 25 to 40.degree. C.; and the developing
time is generally 10 to 300 seconds, preferably 30 to 60
seconds.
[0127] The present invention is further explained by use of the
following examples, but they by no means restrict embodiments of
the present invention. In the description of the examples, "parts"
and "%" mean "weight parts" and "wt %", respectively, unless
otherwise noted.
Example 1
Synthesis of AMMA/TBMA/MAA (40/20/40) terpolymer
[0128] In a reaction vessel equipped with a stirrer, a condenser, a
heater and a thermostat, N,N'-dimethyl-formamide (500 parts) and
methyl amyl ketone (500 parts) were placed. The solvent was purged
with nitrogen gas for 30 minutes, and then heated to 90.degree.
C.
[0129] Independently, 9-anthracene-methyl methacrylate (AMMA, 1735
parts), tert-butyl methacrylate (TBMA, 447 parts), methacrylic acid
(MAA, 542 parts), dimethyl 2,2'-azobis(2-methylisobutylate)
(radical polymerization initiator, 273 parts),
N,N'-dimethylformamide (3000 parts) and methyl amyl ketone (3000
parts) were placed in a sample container and then stirred. The
obtained mixture solution was purged with nitrogen gas for 30
minutes.
[0130] The mixture solution was then introduced into the reaction
vessel over a period of 2 hours by means of a peristaltic pump.
After the introduction was completed, the reaction mixture was kept
at 90.degree. C. for 4 hours.
[0131] After cooled to room temperature, the mixture was poured
into n-heptane (50000 parts). The top clear portion was removed and
the left reaction mixture was dissolved in tetrahydrofuran (7000
parts). The obtained solution was poured into water (50000 parts)
to form white precipitates. The precipitates were isolated by
filtration under reduced pressure, and dried overnight in a vacuum
oven at 50.degree. C.
[0132] As a result of drying, AMMA/TBMA/MAA (40/20/40) terpolymer
in an amount of 2537 parts (yield: 93%) was obtained in the form of
white powder. The molecular weight of the product was measured by
means of GPC (THF), to find that the product had a weight average
molecular weight Mw of 6182 Da, a number average molecular weight
Mn of 3373 Da and a polydispersity index PDI of 1.83.
(Preparation of Composition [A] for Forming a Bottom
Anti-Reflective Coating)
[0133] To the polymer of Example 1 (90 parts),
N,N'-1,3-phenylenedimaleimide (14 parts), triphenyl-sulfonium salt
(2 parts), propyleneglycol monomethyl ether acetate (1713 parts),
propyleneglycol monomethyl ether (2936 parts) and
.gamma.-butyrolactone (245 parts) were added.
[0134] The mixture was stirred for 30 minutes at room temperature,
to prepare a composition [A] for forming a bottom anti-reflective
coating.
(Evaluation of Composition [A] for Forming a Bottom Anti-Reflective
Coating)
[0135] The composition [A] for forming a bottom anti-reflective
coating was spread by spin-coating on a silicon microchip wafer,
and crosslinked by heating at 180.degree. C. for 60 seconds on a
vacuum hot-plate to obtain a bottom anti-reflective coating. The
obtained coating was measured by means of ellipsometer, and it was
found that the refractive index (n value) and the extinction
coefficient (k value) at 248 nm were 1.59 and 0.35, respectively.
The refractive index (n value) and the extinction coefficient (k
value) at 193 nm were also found to be 1.67 and 0.34,
respectively.
[0136] Independently, the above procedure was repeated and the
composition was baked at 180.degree. C. to form a bottom
anti-reflective coating. It was verified that the formed coating
was insoluble in any of ethyl lactate, propyleneglycol monomethyl
ether acetate and propyleneglycol monomethyl ether.
[0137] Successively, on the obtained bottom anti-reflective
coating, a commercially available 248 nm positive-working
photoresist was spin-coated. The formed resist layer was soft-baked
on a vacuum hot-plate at 120.degree. C. for 60 seconds, and then
imagewise exposed to radiation of 248 nm through a photomask. After
subjected to post-exposure baking at 130.degree. C. for 60 seconds,
the resist layer was developed with a 2.38 wt % TMAH aqueous
solution. As a result of this development, both of the photoresist
layer and the bottom anti-reflective coating were removed in the
area demarcated by the photomask. In the area exposed to radiation,
the anti-reflective coating was dissolved together with the
photoresist and any residue of the coating was not observed. The
formed pattern had a cross section in which both of the photoresist
and the bottom anti-reflective coating showed rectangular
side-faces perpendicular to the substrate surface.
Example 2
Synthesis of AMMA/MAA (40/60) Copolymer
[0138] In a reaction vessel equipped with a stirrer, a condenser, a
heater and a thermostat, N,N'-dimethyl-formamide (150 parts) and
methyl amyl ketone (150 parts) were placed. The solvent was purged
with nitrogen gas for 30 minutes, and then heated to 120.degree.
C.
[0139] Independently, 9-anthracene-methyl methacrylate (AMMA, 558
parts), methacrylic acid (MAA, 267 parts), dimethyl
2,2'-azobis(2-methylisobutylate) (radical polymerization initiator,
83 parts), N,N'-dimethylformamide (900 parts) and methyl amyl
ketone (900 parts) were placed in a sample container and then
stirred. The obtained mixture solution was purged with nitrogen gas
for 30 minutes.
[0140] The mixture solution was then introduced into the reaction
vessel for 2 hours by means of a peristaltic pump. After the
introduction was completed, the reaction mixture was kept at
120.degree. C. for 4 hours.
[0141] After the mixture was cooled to room temperature, n-heptane
(15000 parts) was added and then the top clear portion was removed.
The left reaction mixture was dissolved in tetrahydrofuran (2000
parts): To the obtained solution, water (15000 parts) was added to
form white precipitates. The precipitates were isolated by
filtration under reduced pressure, and dried overnight in a vacuum
oven at 50.degree. C.
[0142] As a result of drying, AMMA/MAA (40/60) copolymer in an
amount of 780 parts (yield: 96%) was obtained in the form of white
powder. The molecular weight of the product was measured by means
of GPC (THF), to find that the product had a weight average
molecular weight Mw of 6389 Da, a number average molecular weight
Mn of 2159 Da and a polydispersity index PDI of 2.96.
(Preparation of Composition [B] for Forming a Bottom
Anti-Reflective Coating)
[0143] To the polymer of Example 2 (90 parts),
N,N'-1,3-phenylenedimaleimide (14 parts), propyleneglycol
monomethyl ether acetate (1713 parts), propyleneglycol monomethyl
ether (2936 parts) and .gamma.-butyrolactone (245 parts) were
added. The mixture was stirred for 30 minutes at room temperature,
to prepare a composition [B] for forming a bottom anti-reflective
coating.
(Evaluation of Composition [B] for Forming a Bottom Anti-Reflective
Coating)
[0144] The composition [B] for forming a bottom anti-reflective
coating was spread by spin-coating on a silicon microchip wafer,
and crosslinked by heating at 180.degree. C. for 60 seconds on a
vacuum hot-plate to obtain a bottom anti-reflective coating. The
obtained coating was measured by means of ellipsometer, and it was
found that the refractive index (n value) and the extinction
coefficient (k value) at 248 nm were 1.60 and 0.34, respectively.
The refractive index (n value) and the extinction coefficient (k
value) at 193 nm were also found to be 1.65 and 0.36,
respectively.
[0145] Independently, the above procedure was repeated and the
composition was baked at 180.degree. C. to form a bottom
anti-reflective coating. It was verified that the formed coating
was insoluble in any of ethyl lactate, propyleneglycol monomethyl
ether acetate and propyleneglycol monomethyl ether.
[0146] Successively, on the obtained bottom anti-reflective
coating, a commercially available 248 nm positive-working
photoresist was spin-coated. The formed resist layer was soft-baked
on a vacuum hot-plate at 120.degree. C. for 60 seconds, and then
imagewise exposed to radiation of 248 nm through a photomask. After
subjected to post-exposure baking at 130.degree. C. for 60 seconds,
the resist layer was developed with a 2.38 wt % TMAH aqueous
solution. As a result of this development, both of the photoresist
layer and the bottom anti-reflective coating were removed in the
area demarcated by the photomask. In the area exposed to radiation,
the anti-reflective coating was dissolved together with the
photoresist and any residue of the coating was not observed. The
formed pattern had a cross section in which both of the photoresist
and the bottom anti-reflective coating showed rectangular
side-faces perpendicular to the substrate surface.
Example 3
Preparation of Composition [C] for Forming a Bottom Anti-Reflective
Coating
[0147] To the polymer of Example 2 (90 parts),
N,N'-1,3-phenylenedimaleimide (14 parts), triphenyl-sulfonium salt
(2 parts), a crosslinking agent for electronics material
(methylated urea resin MX-270 [trademark], manufactured by Sanwa
Chemical Co., Ltd.) (14 parts), propyleneglycol monomethyl ether
acetate (1713 parts), propyleneglycol monomethyl ether (2936 parts)
and .gamma.-butyrolactone (245 parts) were added. The mixture was
stirred for 30 minutes at room temperature, to prepare a
composition [C] for forming a bottom anti-reflective coating.
(Evaluation of Composition [C] for Forming a Bottom Anti-Reflective
Coating)
[0148] The composition [C] for forming a bottom anti-reflective
coating was spread by spin-coating on a silicon microchip wafer,
and crosslinked by heating at 180.degree. C. for 60 seconds on a
vacuum hot-plate to obtain a bottom anti-reflective coating. The
obtained coating was measured by means of ellipsometer, and it was
found that the refractive index (n value) and the extinction
coefficient (k value) at 248 nm were 1.60 and 0.34, respectively.
The refractive index (n value) and the extinction coefficient (k
value) at 193 nm were also found to be 1.65 and 0.36,
respectively.
[0149] Independently, the above procedure was repeated and the
composition was baked at 180.degree. C. to form a bottom
anti-reflective coating. It was verified that the formed coating
was insoluble in any of ethyl lactate, propyleneglycol monomethyl
ether acetate and propyleneglycol monomethyl ether.
[0150] Successively, on the obtained bottom anti-reflective
coating, a commercially available 248 nm negative-working
photoresist was spin-coated. The formed resist layer was soft-baked
on a vacuum hot-plate at 120.degree. C. for 60 seconds, and then
imagewise exposed to radiation of 248 nm through a photomask. After
subjected to post-exposure baking at 130.degree. C. for 60 seconds,
the resist layer was developed with a 2.38 wt % TMAH aqueous
solution. As a result of this development, both of the photoresist
layer and the bottom anti-reflective coating were removed in the
area not demarcated by the photomask. In the area not exposed to
radiation, the anti-reflective coating was dissolved together with
the photoresist and any residue of the coating was not observed.
The formed pattern had a cross section in which both of the
photoresist and the bottom anti-reflective coating showed
rectangular side-faces perpendicular to the substrate surface.
Example 4
Preparation of Composition [D] for Forming a Bottom Anti-Reflective
Coating
[0151] To the polymer of Example 2 (90 parts),
N,N'-1,3-phenylenedimaleimide (14 parts), propyleneglycol
monomethyl ether acetate (1713 parts), propyleneglycol monomethyl
ether (2936 parts) and .gamma.-butyrolactone (245 parts) were
added. The mixture was stirred for 30 minutes at room temperature,
to prepare a composition [D] for forming a bottom anti-reflective
coating.
(Evaluation of Composition [D] for Forming a Bottom Anti-Reflective
Coating)
[0152] The composition [D] for forming a bottom anti-reflective
coating was spread by spin-coating on a silicon microchip wafer,
and crosslinked by heating at 180.degree. C. for 60 seconds on a
vacuum hot-plate to obtain a bottom anti-reflective coating. The
obtained coating was measured by means of ellipsometer, and it was
found that the refractive index (n value) and the extinction
coefficient (k value) at 248 nm were 1.60 and 0.34, respectively.
The refractive index (n value) and the extinction coefficient (k
value) at 193 nm were also found to be 1.65 and 0.36,
respectively.
[0153] Independently, the above procedure was repeated and the
composition was baked at 180.degree. C. to form a bottom
anti-reflective coating. It was verified that the formed coating
was insoluble in any of ethyl lactate, propyleneglycol monomethyl
ether acetate and propyleneglycol monomethyl ether.
[0154] Successively, on the obtained bottom anti-reflective
coating, a commercially available 248 nm negative-working
photoresist was spin-coated. The formed resist layer was soft-baked
on a vacuum hot-plate at 120.degree. C. for 60 seconds, and then
imagewise exposed to radiation of 248 nm through a photomask. After
subjected to post-exposure baking at 130.degree. C. for 60 seconds,
the resist layer was developed with a 2.38 wt % TMAH aqueous
solution. As a result of this development, both of the photoresist
layer and the bottom anti-reflective coating were removed in the
area not demarcated by the photomask. In the area not exposed to
radiation, the anti-reflective coating was dissolved together with
the photoresist and any residue of the coating was not observed.
The formed pattern had a cross section in which both of the
photoresist and the bottom anti-reflective coating showed
rectangular side-faces perpendicular to the substrate surface.
Example 5
Preparation of Composition [E] for Forming a Bottom Anti-Reflective
Coating
[0155] To the polymer of Example 1 (90 parts),
N,N'-1,3-phenylenedimaleimide (14 parts), triphenyl-sulfonium salt
(2 parts), propyleneglycol monomethyl ether acetate (1713 parts),
propyleneglycol monomethyl ether (2936 parts) and
.gamma.-butyrolactone (245 parts) were added. The mixture was
stirred for 30 minutes at room temperature, to prepare a
composition [E] for forming a bottom anti-reflective coating.
(Evaluation of Composition [E] for Forming a Bottom Anti-Reflective
Coating)
[0156] The composition [E] for forming a bottom anti-reflective
coating was spread by spin-coating on a silicon microchip wafer,
and crosslinked by heating at 180.degree. C. for 60 seconds on a
vacuum hot-plate to obtain a bottom anti-reflective coating. The
obtained coating was measured by means of ellipsometer, and it was
found that the refractive index (n value) and the extinction
coefficient (k value) at 248 nm were 1.59 and 0.35, respectively.
The refractive index (n value) and the extinction coefficient (k
value) at 193 nm were also found to be 1.67 and 0.34,
respectively.
[0157] Independently, the above procedure was repeated and the
composition was baked at 180.degree. C. to form a bottom
anti-reflective coating. It was verified that the formed coating
was soluble in methyl amyl ketone but insoluble in any of ethyl
lactate, propyleneglycol monomethyl ether acetate and
propyleneglycol monomethyl ether.
[0158] Successively, on the obtained bottom anti-reflective
coating, a commercially available 248 nm positive-working
photoresist was spin-coated. The formed resist layer was soft-baked
on a vacuum hot-plate at 120.degree. C. for 60 seconds, and then
imagewise exposed to radiation of 248 nm through a photomask. After
subjected to post-exposure baking at 130.degree. C. for 60 seconds,
the resist layer was developed with methyl amyl ketone. As a result
of this development, both of the photoresist layer and the bottom
anti-reflective coating were removed in the area not demarcated by
the photomask. In the area not exposed to radiation, the
anti-reflective coating was dissolved together with the photoresist
and any residue of the coating was not observed. The formed pattern
had a cross section in which both of the photoresist and the bottom
anti-reflective coating showed rectangular side-faces perpendicular
to the substrate surface.
Example 6
Preparation of Composition [F] for Forming a Bottom Anti-Reflective
Coating
[0159] To the polymer of Example 1 (90 parts), N-phenyl-maleimide
(28 parts), triphenylsulfonium salt (2 parts), propyleneglycol
monomethyl ether acetate (1713 parts), propyleneglycol monomethyl
ether (2936 parts) and .gamma.-butyrolactone (245 parts) were
added. The mixture was stirred for 30 minutes at room temperature,
to prepare a composition [F] for forming a bottom anti-reflective
coating.
(Evaluation of Composition [F] for Forming a Bottom Anti-Reflective
Coating)
[0160] The composition [F] for forming a bottom anti-reflective
coating was spread by spin-coating on a silicon microchip wafer,
and crosslinked by heating at 180.degree. C. for 60 seconds on a
vacuum hot-plate to obtain a bottom anti-reflective coating. The
obtained coating was measured by means of ellipsometer, and it was
found that the refractive index (n value) and the extinction
coefficient (k value) at 248 nm were 1.55 and 0.36, respectively.
The refractive index (n value) and the extinction coefficient (k
value) at 193 nm were also found to be 1.67 and 0.34,
respectively.
[0161] Independently, the above procedure was repeated and the
composition was baked at 180.degree. C. to form a bottom
anti-reflective coating. It was verified that the formed coating
was soluble only slightly enough to use practically in any of ethyl
lactate, propyleneglycol monomethyl ether acetate and
propyleneglycol monomethyl ether.
[0162] Successively, on the obtained bottom anti-reflective
coating, a commercially available 248 nm positive-working
photoresist was spin-coated. The formed resist layer was soft-baked
on a vacuum hot-plate at 120.degree. C. for 60 seconds, and then
imagewise exposed to radiation of 248 nm through a photomask. After
subjected to post-exposure baking at 130.degree. C. for 60 seconds,
the resist layer was developed with a 2.38 wt % TMAH aqueous
solution. As a result of this development, both of the photoresist
layer and the bottom anti-reflective coating were removed in the
area demarcated by the photomask. In the area exposed to radiation,
the anti-reflective coating was dissolved together with the
photoresist and any residue of the coating was not observed. The
formed pattern had a cross section in which the photoresist and the
bottom anti-reflective coating showed side-faces in such slightly
undercut and fitting shapes, respectively, as were practically
usable without any troubles.
Example 7
Preparation of Composition [G] for Forming a Bottom Anti-Reflective
Coating
[0163] To the polymer of Example 1 (90 parts), maleic anhydride (28
parts), triphenylsulfonium salt (2 parts), propyleneglycol
monomethyl ether acetate (1713 parts), propyleneglycol monomethyl
ether (2936 parts) and .gamma.-butyrolactone (245 parts) were
added. The mixture was stirred for 30 minutes at room temperature,
to prepare a composition [G] for forming a bottom anti-reflective
coating.
(Evaluation of Composition [G] for Forming a Bottom Anti-Reflective
Coating)
[0164] The composition [G] for forming a bottom anti-reflective
coating was spread by spin-coating on a silicon microchip wafer,
and crosslinked by heating at 180.degree. C. for 60 seconds on a
vacuum hot-plate to obtain a bottom anti-reflective coating. The
obtained coating was measured by means of ellipsometer, and it was
found that the refractive index (n value) and the extinction
coefficient (k value) at 248 nm were 1.52 and 0.38, respectively.
The refractive index (n value) and the extinction coefficient (k
value) at 193 nm were also found to be 1.67 and 0.34,
respectively.
[0165] Independently, the above procedure was repeated and the
composition was baked at 180.degree. C. to form a bottom
anti-reflective coating. It was verified that the formed coating
was soluble only slightly enough to use practically in any of ethyl
lactate, propyleneglycol monomethyl ether acetate and
propyleneglycol monomethyl ether.
[0166] Successively, on the obtained bottom anti-reflective
coating, a commercially available 248 nm positive-working
photoresist was spin-coated. The formed resist layer was soft-baked
on a vacuum hot-plate at 120.degree. C. for 60 seconds, and then
imagewise exposed to radiation of 248 nm through a photomask. After
subjected to post-exposure baking at 130.degree. C. for 60 seconds,
the resist layer was developed with a 2.38 wt % TMAH aqueous
solution. As a result of this development, both of the photoresist
layer and the bottom anti-reflective coating were removed in the
area demarcated by the photomask. In the area exposed to radiation,
the anti-reflective coating was dissolved together with the
photoresist and any residue of the coating was not observed. The
formed pattern had a cross section in which the photoresist and the
bottom anti-reflective coating showed side-faces in such slightly
undercut and fitting shapes, respectively, as were practically
usable without any troubles.
Example 8
Preparation of Composition [H] for Forming a Bottom Anti-Reflective
Coating
[0167] To the polymer of Example 1 (90 parts),
N,N'-1,3-phenylenedimaleimide (14 parts), propyleneglycol
monomethyl ether acetate (1713 parts), propyleneglycol monomethyl
ether (2936 parts) and .gamma.-butyrolactone (245 parts) were
added. The mixture was stirred for 30 minutes at room temperature,
to prepare a composition [H] for forming a bottom anti-reflective
coating.
(Evaluation of Composition [H] for Forming a Bottom Anti-Reflective
Coating)
[0168] The composition [H] for forming a bottom anti-reflective
coating was spread by spin-coating on a silicon microchip wafer,
and crosslinked by heating at 180.degree. C. for 60 seconds on a
vacuum hot-plate to obtain a bottom anti-reflective coating. The
obtained coating was measured by means of ellipsometer, and it was
found that the refractive index (n value) and the extinction
coefficient (k value) at 248 nm were 1.59 and 0.35, respectively.
The refractive index (n value) and the extinction coefficient (k
value) at 193 nm were also found to be 1.67 and 0.34,
respectively.
[0169] Independently, the above procedure was repeated and the
composition was baked at 180.degree. C. to form a bottom
anti-reflective coating. It was verified that the formed coating
was insoluble in any of ethyl lactate, propyleneglycol monomethyl
ether acetate and propyleneglycol monomethyl ether.
[0170] Successively, on the obtained bottom anti-reflective
coating, a commercially available 248 nm positive-working
photoresist was spin-coated. The formed resist layer was soft-baked
on a vacuum hot-plate at 120.degree. C. for 60 seconds, and then
imagewise exposed to radiation of 248 nm through a photomask. After
subjected to post-exposure baking at 130.degree. C. for 60 seconds,
the resist layer was developed with a 2.38 wt % TMAH aqueous
solution. As a result of this developnient, both of the photoresist
layer and the bottom anti-reflective coating were removed in the
area demarcated by the photomask. In the area exposed to radiation,
the anti-reflective coating was dissolved together with the
photoresist and any residue of the coating was not observed. The
formed pattern had a cross section in which both of the photoresist
and the bottom anti-reflective coating showed rectangular
side-faces perpendicular to the substrate surface.
Example 9
Preparation of Composition [I] for Forming a Bottom Anti-Reflective
Coating
[0171] To the polymer of Example 2 (90 parts),
N,N'-1,3-phenylenedimaleimide (14 parts), a crosslinking agent for
electronics material (methylated urea resin MX-270 [trademark],
manufactured by Sanwa Chemical Co., Ltd.) (14 parts),
propyleneglycol monomethyl ether acetate (1713 parts),
propyleneglycol monomethyl ether (2936 parts) and
.gamma.-butyrolactone (245 parts) were added. The mixture was
stirred for 30 minutes at room temperature, to prepare a
composition [I] for forming a bottom anti-reflective coating.
(Evaluation of Composition [I] for Forming a Bottom Anti-Reflective
Coating)
[0172] The composition [I] for forming a bottom anti-reflective
coating was spread by spin-coating on a silicon microchip wafer,
and crosslinked by heating at 180.degree. C. for 60 seconds on a
vacuum hot-plate to obtain a bottom anti-reflective coating. The
obtained coating was measured by means of ellipsometer, and it was
found that the refractive index (n value) and the extinction
coefficient (k value) at 248 nm were 1.60 and 0.34, respectively.
The refractive index (n value) and the extinction coefficient (k
value) at 193 nm were also found to be 1.65 and 0.36,
respectively.
[0173] Independently, the above procedure was repeated and the
composition was baked at 180.degree. C. to form a bottom
anti-reflective coating. It was verified that the formed coating
was insoluble in any of ethyl lactate, propyleneglycol monomethyl
ether acetate and propyleneglycol monomethyl ether.
[0174] Successively, on the obtained bottom anti-reflective
coating, a commercially available 248 nm negative-working
photoresist was spin-coated. The formed resist layer was soft-baked
on a vacuum hot-plate at 120.degree. C. for 60 seconds, and then
imagewise exposed to radiation of 248 nm through a photomask. After
subjected to post-exposure baking at 130.degree. C. for 60 seconds,
the resist layer was developed with a 2.38 wt % TMAH aqueous
solution. As a result of this development, both of the photoresist
layer and the bottom anti-reflective coating were removed in the
area not demarcated by the photomask. In the area not exposed to
radiation, the anti-reflective coating was dissolved together with
the photoresist and any residue of the coating was not observed.
The formed pattern had a cross section in which both of the
photoresist and the bottom anti-reflective coating showed
rectangular side-faces perpendicular to the substrate surface.
Example 10
Preparation of Composition [J] for Forming a Bottom Anti-Reflective
Coating
[0175] To the polymer of Example 1 (90 parts),
N,N'-1,3-phenylenedimaleimide (14 parts), propyleneglycol
monomethyl ether acetate (1713 parts), propyleneglycol monomethyl
ether (2936 parts) and .gamma.-butyrolactone (245 parts) were
added. The mixture was stirred for 30 minutes at room temperature,
to prepare a composition [3] for forming a bottom anti-reflective
coating.
(Evaluation of Composition [3] for Forming a Bottom Anti-Reflective
Coating)
[0176] The composition [3] for forming a bottom anti-reflective
coating was spread by spin-coating on a silicon microchip wafer,
and crosslinked by heating at 180.degree. C. for 60 seconds on a
vacuum hot-plate to obtain a bottom anti-reflective coating. The
obtained coating was measured by means of ellipsometer, and it was
found that the refractive index (n value) and the extinction
coefficient (k value) at 248 nm were L59 and 0.35, respectively.
The refractive index (n value) and the extinction coefficient (k
value) at 193 nm were also found to be 1.67 and 0.34,
respectively.
[0177] Independently, the above procedure was repeated and the
composition was baked at 180.degree. C. to form a bottom
anti-reflective coating. It was verified that the formed coating
was soluble in methyl amyl ketone but insoluble in any of ethyl
lactate, propyleneglycol monomethyl ether acetate and
propyleneglycol monomethyl ether.
[0178] Successively, on the obtained bottom anti-reflective
coating, a commercially available 248 nm positive-working
photoresist was spin-coated. The formed resist layer was soft-baked
on a vacuum hot-plate at 120.degree. C. for 60 seconds, and then
imagewise exposed to radiation of 248 nm through a photomask. After
subjected to post-exposure baking at 130.degree. C. for 60 seconds,
the resist layer was developed with methyl amyl ketone. As a result
of this development, both of the photoresist layer and the bottom
anti-reflective coating were removed in the area not demarcated by
the photomask. In the area not exposed to radiation, the
anti-reflective coating was dissolved together with the photoresist
and any residue of the coating was not observed. The formed pattern
had a cross section in which both of the photoresist and the bottom
anti-reflective coating showed rectangular side-faces perpendicular
to the substrate surface.
Example 11
Synthesis of AMMA/TBMA/MI (36/50/14) Terpolymer
[0179] In a reaction vessel equipped with a stirrer, a condenser, a
heater and a thermostat, N,N'-dimethyl-formamide (500 parts) and
methyl amyl ketone (500 parts) were placed. The solvent was purged
with nitrogen gas for 30 minutes, and then heated to 90.degree.
C.
[0180] Independently, 9-anthracene-methyl methacrylate (AMMA, 1543
parts), tert-butyl methacrylate (TBMA, 1103 parts), maleimide (MI,
211 parts), dimethyl 2,2'-azobis(2-methylisobutylate) (radical
polymerization initiator, 143 parts), N,N'-dimethylformamide (3000
parts) and methyl amyl ketone (3000 parts) were placed in a sample
container and then stirred. The obtained mixture solution was
purged with nitrogen gas for 30 minutes.
[0181] The mixture solution was then introduced into the reaction
vessel for 2 hours by means of a peristaltic pump.
[0182] After the introduction was completed, the reaction mixture
was kept at 90.degree. C. for 4 hours.
[0183] After the mixture was cooled to room temperature, n-heptane
(50000 parts) was added and then the top clear portion was removed.
The left reaction mixture was dissolved in tetrahydrofuran (7000
parts). To the obtained solution, water (50000 parts) was added to
form white precipitates. The precipitates were isolated by
filtration under reduced pressure, and dried overnight in a vacuum
oven at 50.degree. C.
[0184] As a result of drying, AMMA/TBMA/MI (36/50/14) terpolymer in
an amount of 2540 parts (yield: 93%) was obtained in the form of
white powder. The molecular weight of the product was measured by
means of GPC (THF), to find that the product had a weight average
molecular weight Mw of 6232 Da, a number average molecular weight
Mn of 3373 Da and a polydispersity index PDI of 1.91.
(Preparation of Composition [K] for Forming a Bottom
Anti-Reflective Coating)
[0185] To the polymer of Example 11 (180 parts),
triphenyl-sulfonium salt (2 parts), propyleneglycol monomethyl
ether acetate (4891 parts) and propyleneglycol monomethyl ether
(4891 parts) were added. The mixture was stirred for 30 minutes at
room temperature, to prepare a composition [K] for forming a bottom
anti-reflective coating.
(Evaluation of Composition [K] for Forming a Bottom Anti-Reflective
Coating)
[0186] The composition [K] for forming a bottom anti-reflective
coating was spread by spin-coating on a silicon microchip wafer,
and crosslinked by heating at 180.degree. C. for 60 seconds on a
vacuum hot-plate to obtain a bottom anti-reflective coating. The
obtained coating was measured by means of ellipsometer, and it was
found that the refractive index (n value) and the extinction
coefficient (k value) at 248 nm were 1.49 and 0.61, respectively.
The refractive index (n value) and the extinction coefficient (k
value) at 193 nm were also found to be 1.68 and 0.28,
respectively.
[0187] Independently, the above procedure was repeated and the
composition was baked at 180.degree. C. to form a bottom
anti-reflective coating. It was verified that the formed coating
was slightly soluble in any of ethyl lactate, propyleneglycol
monomethyl ether acetate and propyleneglycol monomethyl ether.
[0188] Successively, on the obtained bottom anti-reflective
coating, a commercially available 248 nm positive-working
photoresist was spin-coated. The formed resist layer was soft-baked
on a vacuum hot-plate at 120.degree. C. for 60 seconds, and then
imagewise exposed to radiation of 248 nm through a photomask. After
subjected to post-exposure baking at 130.degree. C. for 60 seconds,
the resist layer was developed with a 2.38 wt % TMAH aqueous
solution. As a result of this development, both of the photoresist
layer and the bottom anti-reflective coating were removed in the
area demarcated by the photomask. In the area exposed to radiation,
the anti-reflective coating was dissolved together with the
photoresist and any residue of the coating was not observed. The
formed pattern had a cross section in which the photoresist and the
bottom anti-reflective coating showed side-faces in slightly
undercut and fitting shapes, respectively. Further, the side-faces
were not perpendicular to the substrate surface.
Comparative Example 1
[0189] According to the method described in Patent document 2, a
polymer and a composition for forming a bottom anti-reflective
coating were produced.
(Synthesis of MI/AMMA/HNMA-2/TBA (34.3/31.5/25.0/9.2)
Tetrapolymer)
[0190] In a round-bottom flask equipped with a mechanical stirrer,
a condenser, a heater and a thermostat, dioxane (215 parts) was
placed. The solvent was purged with nitrogen gas for 15 minutes,
and then heated to 85.degree. C.
[0191] Independently, in an Erlenmeyer flask equipped with a
stirring rod, maleimide (MI, 53.10 parts), 9-anthracene-methyl
methacrylate (AMMA, 138.7 parts), 2-hydroxynaphthalene-methyl
methacrylate monomer (HNMA-2, 96.53 parts), t-butyl acrylate (TBA,
18.80 parts) and dioxane (423.5 parts) were placed. The mixture
solution was stirred for 30 minutes at room temperature, and then
purged with nitrogen gas for 15 minutes to prepare a monomer
solution.
[0192] Further separately from the above, in a 500-mL vessel,
2,2-azobis(2,4-dimethylvaleronitrile) (11.89 parts) and dioxane
(78.0 parts) were placed and mixed to prepare an initiator
solution.
[0193] The monomer solution was then introduced into the
round-bottom flask at the rate of 8.5 g/minute for 1.5 hours by
means of a peristaltic pump. At the same time, the initiator
solution was also introduced into the round-bottom flask at the
rate of 1.1 g/minute for 90 minutes by means of a peristaltic
pump.
[0194] After the introduction of the monomer and initiator
solutions was completed, a mixture of
2,2-azobis(2,4-di-methylvaleronitrile) (7.93 parts) and dioxane
(151 parts) was introduced into the round-bottom flask at the rate
of 8.0 g/minute for 20 minutes by means of a peristaltic pump.
Thereafter, the reaction mixture was kept at 85.degree. C. for 1.5
hours.
[0195] After the mixture was cooled to room temperature, 15.0 L of
methanol was added to precipitate a white product. The white
precipitates were isolated by filtration under reduced pressure,
washed with 3.0 parts of methanol, and then dried overnight in a
vacuum oven at 50.degree. C. As a result, the titled polymer in the
form of white powder was obtained in the yield of 64%. The
molecular weight of the product was measured by means of GPC (THF),
to find that the product had a weight average molecular weight Mw
of 9300 Da, a number average molecular weight Mn of 6500 Da and a
polydispersity index PDI of 1.5.
(Preparation of Composition [L] for Forming a Bottom
Anti-Reflective Coating)
[0196] The polymer of Comparative Example 1 (90 parts),
triphenylsulfonium salt (2 parts) and ethyl lactate (4894 parts)
were mixed and stirred for 30 minutes at room temperature, to
prepare a composition [L] for forming a bottom anti-reflective
coating.
(Evaluation of Composition [L] for Forming a Bottom Anti-Reflective
Coating)
[0197] The composition [L] for forming a bottom anti-reflective
coating was spread by spin-coating on a silicon microchip wafer,
and hardened by heating at 180.degree. C. and 210.degree. C. for 60
seconds each on a vacuum hot-plate to obtain a bottom
anti-reflective coating.
[0198] It was verified that the obtained bottom anti-reflective
coating was very soluble in any of ethyl lactate, propyleneglycol
monomethyl ether acetate and propyleneglycol monomethyl ether, as
compared with the coatings of Examples 1 to 11. Further, a
photoresist layer was formed on the obtained coating and then
developed. However, the bottom anti-reflective coating was
dissolved in a developing solution so readily that the resist layer
peeled off from the substrate, and consequently it was impossible
to form a pattern.
Example 12
Synthesis of AMMA Homo-Polymer
[0199] In a reaction vessel equipped with a stirrer, a condenser, a
heater and a thermostat, propyleneglycol monomethyl ether acetate
(1000 parts) was placed. The solvent was purged with nitrogen gas
for 30 minutes, and then heated to 90.degree. C.
[0200] Independently, 9-anthracene-methyl methacrylate (AMMA, 2727
parts), dimethyl 2,2'-azobis(2-methyl-isobutylate) (radical
polymerization initiator, 273 parts), and propyleneglycol
monomethyl ether acetate (6000 parts) were placed in a sample
container and then stirred. The obtained monomer solution was
purged with nitrogen gas for 30 minutes.
[0201] The monomer solution was then introduced into the reaction
vessel over a period of 2 hours by means of a peristaltic pump.
After the introduction was completed, the reaction mixture was kept
at 90.degree. C. for 4 hours.
[0202] After cooled to room temperature, the mixture was poured
into n-heptane (50000 parts). The top clear portion was removed and
the left reaction mixture was dissolved in tetrahydrofuran (7000
parts). The obtained solution was poured into water (50000 parts)
to form white precipitates. The precipitates were isolated by
filtration under reduced pressure, and dried overnight in a vacuum
oven at 50.degree. C.
[0203] As a result of drying, AMMA homo-polymer in an amount of
2537 parts (yield: 93%) was obtained in the form of white powder.
The molecular weight of the product was measured by means of GPC
(THF), to find that the product had a weight average molecular
weight Mw of 4230 Da, a number average molecular weight Mn of 2350
Da and a polydispersity index PDI of 1.80.
(Preparation of Composition [M] for Forming a Bottom
Anti-Reflective Coating)
[0204] To the polymer of Example 1 (90 parts),
N,N'-1,3-phenylenedimaleimide (30 parts), propyleneglycol
monomethyl ether acetate (1713 parts), propyleneglycol monomethyl
ether (2936 parts) and .gamma.-butyrolactone (245 parts) were
added. The mixture was stirred for 30 minutes at room temperature,
to prepare a composition [M] for forming a bottom anti-reflective
coating.
(Evaluation of Composition [M] for Forming a Bottom Anti-Reflective
Coating)
[0205] The composition [M] for forming a bottom anti-reflective
coating was cast by spin-coating on a silicon microchip wafer, and
crosslinked by heating at 180.degree. C. for 60 seconds on a vacuum
hot-plate to obtain a bottom anti-reflective coating. The obtained
coating was measured by means of ellipsometer, and it was found
that the refractive index (n value) and the extinction coefficient
(k value) at 248 nm were 1.58 and 0.35, respectively. The
refractive index (n value) and the extinction coefficient (k value)
at 193 nm were also found to be 1.67 and 0.32, respectively.
[0206] Independently, the above procedure was repeated and the
composition was baked at 180.degree. C. to form a bottom
anti-reflective coating. It was verified that the formed coating
was insoluble in any of ethyl lactate, propyleneglycol monomethyl
ether acetate and propyleneglycol monomethyl ether.
[0207] Successively, on the obtained bottom anti-reflective
coating, a commercially available 248 nm positive-working
photoresist was spin-coated. The formed resist layer was soft-baked
on a vacuum hot-plate at 120.degree. C. for 60 seconds, and then
imagewise exposed to radiation of 248 nm through a photomask. After
subjected to post-exposure baking at 130.degree. C. for 60 seconds,
the resist layer was developed with a 2.38 wt % TMAH aqueous
solution. As a result of this development, the photoresist layer
was removed in the area demarcated by the photomask. The formed
pattern had a rectangular cross section perpendicular to the
substrate surface.
Example 13
Preparation of Composition [N] for Forming a Bottom Anti-Reflective
Coating
[0208] To the polymer of Example 12 (90 parts),
N,N'-1,3-phenylenedimaleimide (30 parts), propyleneglycol
monomethyl ether acetate (1713 parts), propyleneglycol monomethyl
ether (2936 parts) and .gamma.-butyrolactone (245 parts) were
added. The mixture was stirred for 30 minutes at room temperature,
to prepare a composition [N] for forming a bottom anti-reflective
coating.
(Evaluation of Composition [N] for Forming a Bottom Anti-Reflective
Coating)
[0209] The composition [N] for forming a bottom anti-reflective
coating was cast by spin-coating on a silicon microchip wafer, and
crosslinked by heating at 180.degree. C. for 60 seconds on a vacuum
hot-plate to obtain a bottom anti-reflective coating. The obtained
coating was measured by means of ellipsometer, and it was found
that the refractive index (n value) and the extinction coefficient
(k value) at 248 nm were 1.60 and 0.34, respectively. The
refractive index (n value) and the extinction coefficient (k value)
at 193 nm were also found to be 1.65 and 0.36, respectively.
[0210] Independently, the above procedure was repeated and the
composition was baked at 180.degree. C. to form a bottom
anti-reflective coating. It was verified that the formed coating
was insoluble in any of ethyl lactate, propyleneglycol monomethyl
ether acetate and propyleneglycol monomethyl ether.
[0211] Successively, on the obtained bottom anti-reflective
coating, a commercially available 248 nm negative-working
photoresist was spin-coated. The formed resist layer was soft-baked
on a vacuum hot-plate at 120.degree. C. for 60 seconds, and then
imagewise exposed to radiation of 248 nm through a photomask. After
subjected to post-exposure baking at 130.degree. C. for 60 seconds,
the resist layer was developed with a 2.38 wt % TMAH aqueous
solution. As a result of this development, the photoresist layer
was removed in the area not demarcated by the photomask. The formed
pattern had a cross section in which the photoresist showed a
rectangular side-face perpendicular to the substrate surface.
Example 14
Preparation of Composition [0] for Forming a Bottom Anti-Reflective
Coating
[0212] To the polymer of Example 12 (90 parts),
N,N'-1,3-phenylenedimaleimide (14 parts), propyleneglycol
monomethyl ether acetate (1713 parts), propyleneglycol monomethyl
ether (2936 parts) and .gamma.-butyrolactone (245 parts) were
added. The mixture was stirred for 30 minutes at room temperature,
to prepare a composition [0] for forming a bottom anti-reflective
coating.
(Evaluation of Composition [0] for Forming a Bottom Anti-Reflective
Coating)
[0213] The composition [0] for forming a bottom anti-reflective
coating was cast by spin-coating on a silicon microchip wafer, and
crosslinked by heating at 180.degree. C. for 60 seconds on a vacuum
hot-plate, to obtain a bottom anti-reflective coating. The obtained
coating was measured by means of ellipsometer, and it was found
that the refractive index (n value) and the extinction coefficient
(k value) at 248 nm were 1.58 and 0.35, respectively. The
refractive index (n value) and the extinction coefficient (k value)
at 193 nm were also found to be 1.63 and 0.35, respectively.
[0214] Independently, the above procedure was repeated and the
composition was baked at 180.degree. C. to form a bottom
anti-reflective coating. It was verified that the formed coating
was insoluble in any of ethyl lactate, propyleneglycol monomethyl
ether acetate, propyleneglycol monomethyl ether and methyl amyl
ketone.
[0215] Successively, on the obtained bottom anti-reflective
coating, a commercially available 248 nm positive-working
photoresist was spin-coated. The formed resist layer was soft-baked
on a vacuum hot-plate at 120.degree. C. for 60 seconds, and then
imagewise exposed to radiation of 248 nm through a photomask. After
subjected to post-exposure baking at 130.degree. C. for 60 seconds,
the resist layer was developed with methyl amyl ketone. As a result
of this development, the photoresist layer was removed in the area
not demarcated by the photomask. The formed pattern had a cross
section in which the photoresist showed a rectangular side-face
perpendicular to the substrate surface.
Comparative Example 2
[0216] According to the method described in Patent document 5, a
polymer and a composition for forming a bottom anti-reflective
coating were produced.
(Synthesis of TFEM/HEM Co-Polymer)
[0217] After 15 g of 2,2,2-trifluoroethyl methacrylate (TFEM) and
15 g of 2-hydroxyethyl methacrylate (HEM) were dissolved in 120 g
of ethyl lactate, the solution was heated at 70.degree. C. and, at
the same time, bubbled with nitrogen gas. Successively, 0.6 g of
azobis(isobutyronitrile) was added as a polymerization initiator.
The solution was stirred for 24 hours under nitrogen atmosphere,
and then 0.01 g of 4-methoxyphenol was added as a polymerization
terminator. Thereafter, the solution was poured into diethyl ether,
to precipitate a resin compound. The molecular weight of the resin
compound was measured by means of GPC, to find that the product had
a weight average molecular weight of 20200 in terms of standard
polystyrene.
(Preparation of Composition [P] for Forming a Bottom
Anti-Reflective Coating)
[0218] After 18.42 g of 60% xylene/butanol solution of tetrabutoxy
methyl urea oligomer composition (polymerization degree: 5) UFR300
([trademark], manufactured by Mitsui Cytec Ltd.), 1.22 g of the
above TFEM/HEM co-polymer and 0.33 g of p-toluenesulfonic acid were
mixed, 186.9 g of ethyl lactate was poured therein. The obtained
mixture was filtrated through a 0.10 .mu.m porous size
polyethylene-made micro-filter and further filtrated through a 0.05
.mu.m porous size polyethylene-made micro-filter, to prepare a
composition for forming a bottom anti-reflective coating.
(Evaluation of Composition [P] for Forming a Bottom Anti-Reflective
Coating)
[0219] The composition for forming a bottom anti-reflective coating
was cast by spin-coating on a silicon microchip wafer, and
crosslinked by heating at 180.degree. C. for 60 seconds and further
at 205.degree. C. for 60 seconds on a vacuum hot-plate, to obtain a
dry bottom anti-reflective coating.
[0220] It was verified that the formed coating was slightly
soluble, as compared with the coatings of Examples, in any of ethyl
lactate, propyleneglycol monomethyl ether acetate and
propyleneglycol monomethyl. Successively, on the obtained bottom
anti-reflective coating, a commercially available positive-working
photoresist was spin-coated. The formed resist layer was soft-baked
on a vacuum hot-plate at 120.degree. C. for 60 seconds, and then
imagewise exposed to radiation through a photomask. After subjected
to post-exposure baking at 115.degree. C. or 130.degree. C. for 60
seconds, the resist layer was developed with a 2.38 wt % TMAH
aqueous solution. As a result of this development, the photoresist
layer was removed in the area demarcated by the photomask. The
formed pattern had a cross section in which the photoresist showed
a slightly fitting and not perpendicular side-face.
Example 15
Synthesis of HNMA/AMMA/OTMA (60/25/15) Terpolymer
[0221] In a 250 mL round-bottom flask equipped with a magnetic
stirrer, a condenser, a nitrogen inlet and a thermostat, 135 g of
propyleneglycol monomethyl ether acetate (PGMEA) solvent was
placed. The solvent was purged with nitrogen gas for 30 minutes,
and then heated at 80.degree. C. by means of a heating mantle.
Independently, 16.7 g of 9-hydroxynaphthyl methacrylate (HNMA), 3.4
g of oxathianyl methacrylate (OTMA), 8.43 g of 9-anthracenemethyl
methacrylate (AMMA), 1.44 g of azobis(isobutyronitrile) (AIBN)
initiator and 135 g of PGMEA were mixed and purged with nitrogen
gas for 30 minutes, to prepare a deaerated PGMEA solution. The
obtained PGMEA solution was dropwise added over a period of 3 hours
into the above heated solvent from a pressure equalizing dropping
funnel. The reaction mixture was further kept heated at 80.degree.
C. for 3 hours, to promote the polymerization. Thereafter, the
reaction mixture was cooled to room temperature under nitrogen
atmosphere. When the temperature of the mixture reached down to
30.degree. C., 4.5 g of methanol was added so as to terminate the
reaction. The obtained PGMEA solution was poured into twice volumes
of hexane, to precipitate the polymer. The precipitated polymer was
collected and washed three times with a mixture of water and
methanol, and then dried in a vacuum oven at 40.degree. C. for 48
hours.
[0222] As a result of the above procedure, 21.24 g of the polymer
was obtained (yield: 74.3%). The molecular weight of the product
was measured, to find that the product had a weight average
molecular weight Mw of 8661 Da, a number average molecular weight
Mn of 4597 Da and a polydispersity index PDI of 1.88.
(Preparation of Composition [Q] for Forming a Bottom
Anti-Reflective Coating)
[0223] To the polymer of Example 15 (1.667 parts),
N,N'-1,3-phenylenedimaleimide (0.433 part), propyleneglycol
monomethyl ether (PGME, 138.2 parts), cyclohexanone (8.221 parts)
and .gamma.-valerolactone (1.479 parts) were added. The mixture was
stirred for 30 minutes at room temperature, to prepare a
composition [Q] for forming a bottom anti-reflective coating.
(Evaluation of Composition [Q] for Forming a Bottom Anti-Reflective
Coating)
[0224] The composition [Q] for forming a bottom anti-reflective
coating was cast by spin-coating on a silicon microchip wafer, and
crosslinked by heating at 190.degree. C. for 60 seconds on a vacuum
hot-plate, to obtain a bottom anti-reflective coating. The obtained
coating was measured by means of ellipsometer, and it was found
that the refractive index (n value) and the extinction coefficient
(k value) at 248 nm were 1.9288 and 0.1629, respectively. The
refractive index (n value) and the extinction coefficient (k value)
at 193 nm were also found to be 1.5531 and 0.4113,
respectively.
[0225] Independently, the above procedure was repeated and the
composition was baked at 190.degree. C. to form a bottom
anti-reflective coating. It was verified that the formed coating
was insoluble in either of ethyl lactate and a mixture of
propyleneglycol monomethyl ether acetate (30) and propyleneglycol
monomethyl ether (70).
[0226] Successively, on the obtained bottom anti-reflective
coating, a commercially available 193 nm positive-working
photoresist was spin-coated. The formed resist layer was soft-baked
on a vacuum hot-plate_under recommended conditions, and then
imagewise exposed to radiation of 193 nm through a photomask. After
subjected to post-exposure baking at a recommended temperature, the
resist layer was developed with a 2.38 wt % TMAH aqueous solution.
As a result of this development, the photoresist layer was removed
in the area demarcated by the photomask. In the area exposed to
radiation, the photoresist was dissolved away to leave the
anti-reflective coating in tact. The formed pattern had a cross
section in which the photoresist showed a rectangular side-face
perpendicular to the substrate surface.
Example 16
Synthesis of PQMA/AMMA/EtCpMA (66/22.5/11.5) Terpolymer
[0227] In a 250 round-bottom flask equipped with a mechanical
stirrer, a condenser, a nitrogen inlet and a thermostat, 384 g of
propyleneglycol monomethyl ether acetate (PGMEA) solvent, 6.24 g of
2-ethylcyclopentyl methacrylate (EtCpMA), 34.99 g of
4-hydroxyphenyl methacrylate (PQMA), 18.50 g of 9-anthracenemethyl
methacrylate (AMMA) and 5.97 g of azobis(isobutyronitrile) (AIBN)
initiator were mixed and purged with nitrogen gas for 30 minutes.
The deaerated reaction mixture was heated by means of a heating
mantle at 70.degree. C. for 5 hours, to promote the polymerization.
Thereafter, the reaction mixture was cooled to room temperature
under nitrogen atmosphere. When the temperature of the mixture
reached down to 30.degree. C., 9 g of methanol was added so as to
terminate the reaction. The obtained PGMEA solution was poured into
twice volumes of hexane, to precipitate the polymer. The
precipitated polymer was collected and washed three times with a
mixture of water and methanol, and then dried at 40.degree. C. for
48 hours.
[0228] As a result of the above procedure, 56.66 g of the polymer
was obtained (yield: 94.9%). The molecular weight of the product
was measured, to find that the product had a weight average
molecular weight Mw of 21910 Da, a number average molecular weight
Mn of 8572 Da and a polydispersity index PDI of 2.56.
(Preparation of Composition [R] for Forming a Bottom
Anti-Reflective Coating)
[0229] To the polymer of Example 16 (1.904 parts),
N,N'-1,3-phenylenedimaleimide (3.916 parts), propyleneglycol
monomethyl ether (PGME, 125.6 parts), cyclohexanone (3.721 parts)
and .gamma.-valerolactone (1.479 parts) were added. The mixture was
stirred for 30 minutes at room temperature, to prepare a
composition [R] for forming a bottom anti-reflective coating.
(Evaluation of Composition [R] for Forming a Bottom Anti-Reflective
Coating)
[0230] The composition [R] for forming a bottom anti-reflective
coating was cast by spin-coating on a silicon microchip wafer, and
crosslinked by heating at 190.degree. C. for 60 seconds on a vacuum
hot-plate, to obtain a bottom anti-reflective coating. The obtained
coating was measured by means of ellipsometer, and it was found
that the refractive index (n value) and the extinction coefficient
(k value) at 248 nm were 1.6905 and 0.1959, respectively. The
refractive index (n value) and the extinction coefficient (k value)
at 193 nm were also found to be 1.7552 and 0.5782,
respectively.
[0231] Independently, the above procedure was repeated and the
composition was baked at 190.degree. C. to form a bottom
anti-reflective coating. It was verified that the formed coating
was insoluble in either of ethyl lactate and a mixture of
propyleneglycol monomethyl ether acetate (30) and propyleneglycol
monomethyl ether (70).
[0232] Successively, on the obtained bottom anti-reflective
coating, a commercially available 193 nm positive-working
photoresist was spin-coated. The formed resist layer was soft-baked
on a vacuum hot-plate under recommended conditions, and then
imagewise exposed to radiation of 193 nm through a photomask. After
subjected to post-exposure baking at a recommended temperature, the
resist layer was developed with a 2.38 wt % TMAH aqueous solution.
As a result of this development, the photoresist layer was removed
in the area demarcated by the photomask. In the area exposed to
radiation, the photoresist was dissolved away to leave the
anti-reflective coating in tact. The formed pattern was able to
resolve nicely up to 110 nm feature size by use of a mask with a
line-and-space pattern having a pitch of 1:1 and line width 140
nm.
Example 17
Synthesis of PQMA/AMMA/EdMA/MAA (54/29/12/5) Tetrapolymer
[0233] In a 250 mL round-bottom flask equipped with a mechanical
stirrer, a condenser, a nitrogen inlet and a thermostat, 31 g of
methyl amyl ketone (MAK) was placed and purged with nitrogen gas
for 30 minutes. The deaerorated solvent was then heated at
80.degree. C. Independently, 3.95 g of 2-ethyladamantyl
methacrylate
[0234] (EAdMA), 12.98 g of 4-hydroxyphenyl methacrylate (PQMA),
10.25 g of 9-anthracenemethyl methacrylate (AM MA), 0.57 g of
methacrylic acid (MAA) and 1.11 g of azobis(iso-butyronitrile)
(AIBN) initiator were dissolved in 70 g of MAK, and then purged
with nitrogen gas for 30 minutes. The obtained deaerated mixture
was added over a perid of 3 hours into the above pre-heated solvent
in the flask by means of a syringe pump. The reaction mixture was
further kept heated at 80.degree. C. for 3 hours, to promote the
polymerization. Thereafter, the reaction mixture was cooled to room
temperature under nitrogen atmosphere. When the temperature of the
mixture reached down to 30.degree. C., 4 g of methanol was added so
as to terminate the reaction. The obtained MAK solution was poured
into twice volumes of hexane, to precipitate the polymer. The
precipitated polymer was collected and washed three times with a
mixture of water and methanol, and then dried at 40.degree. C. for
48 hours.
[0235] As a result of the above procedure, 26.90 g of the polymer
was obtained (yield: 93.2%). The molecular weight of the product
was measured, to find that the product had a weight average
molecular weight Mw of 10701 Da, a number average molecular weight
Mn of 5515 Da and a polydispersity index PDI of 1.94.
(Preparation of Composition [S] for Forming a Bottom
Anti-Reflective Coating)
[0236] To the polymer of Example 17 (1.872 parts),
N,N'-1,3-phenylenedimaleimide (0.228 part), propyleneglycol
monomethyl ether (PGME, 142.1 parts), cyclohexanone (4.335 parts)
and .gamma.-valerolactone (1.479 parts) were added. The mixture was
stirred for 30 minutes at room temperature, to prepare a
composition [S] for forming a bottom anti-reflective coating.
(Evaluation of Composition [S] for Forming a Bottom Anti-Reflective
Coating)
[0237] The composition [S] for forming a bottom anti-reflective
coating was cast by spin-coating on a silicon microchip wafer, and
crosslinked by heating at 190.degree. C. for 60 seconds on a vacuum
hot-plate, to obtain a bottom anti-reflective coating. The obtained
coating was measured by means of ellipsometer, and it was found
that the refractive index (n value) and the extinction coefficient
(k value) at 248 nm were 1.6808 and 0.2124, respectively. The
refractive index (n value) and the extinction coefficient (k value)
at 193 nm were also found to be 1.741 and 0.5520, respectively.
[0238] Independently, the above procedure was repeated and the
composition was baked at 190.degree. C. to form a bottom
anti-reflective coating. It was verified that the formed coating
was insoluble in either of ethyl lactate and a mixture of
propyleneglycol monomethyl ether acetate (30) and propyleneglycol
monomethyl ether (70).
[0239] Successively, on the obtained bottom anti-reflective
coating, a commercially available 193 nm positive-working
photoresist was spin-coated. The formed resist layer was soft-baked
on a vacuum hot-plate under recommended conditions, and then
imagewise exposed to radiation of 193 nm through a photomask. After
subjected to post-exposure baking at a recommended temperature, the
resist layer was developed with a 2.38 wt % TMAH aqueous solution.
As a result of this development, the photoresist layer was removed
in the area demarcated by the photomask. In the area exposed to
radiation, the photoresist was dissolved away to leave the
anti-reflective coating in tact. The formed pattern was able to
resolve nicely up to 145 nm feature size by use of a mask with a
line-and-space pattern having a pitch of 1:1 and line width 140
nm.
* * * * *