U.S. patent application number 11/387425 was filed with the patent office on 2006-09-14 for electronic device manufacture.
This patent application is currently assigned to Shipley Company, L.L.C.. Invention is credited to Timothy G. Adams, Jeffrey M. Calvert, Michael K. Gallagher, Dana A. Gronbeck, Gregory P. Prokopowicz.
Application Number | 20060204742 11/387425 |
Document ID | / |
Family ID | 29550196 |
Filed Date | 2006-09-14 |
United States Patent
Application |
20060204742 |
Kind Code |
A1 |
Gronbeck; Dana A. ; et
al. |
September 14, 2006 |
Electronic device manufacture
Abstract
Methods for depositing uniform, pinhole-defect free organic
polysilica coatings are provided. These methods allow for the use
of these materials as spin-on cap layers in the manufacture of
integrated circuits.
Inventors: |
Gronbeck; Dana A.;
(Holliston, MA) ; Gallagher; Michael K.;
(Hopkinton, MA) ; Calvert; Jeffrey M.; (Acton,
MA) ; Prokopowicz; Gregory P.; (Lancaster, MA)
; Adams; Timothy G.; (Sudbury, MA) |
Correspondence
Address: |
S. Matthew Cairns;Rohm and Haas Electronic Material LLC
455 Forest Street
Marlborough
MA
01752
US
|
Assignee: |
Shipley Company, L.L.C.
Marlborough
MA
01752
|
Family ID: |
29550196 |
Appl. No.: |
11/387425 |
Filed: |
March 23, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10453337 |
Jun 3, 2003 |
7018678 |
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11387425 |
Mar 23, 2006 |
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60385369 |
Jun 3, 2002 |
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Current U.S.
Class: |
428/318.4 ;
257/E21.273; 427/384; 427/58 |
Current CPC
Class: |
H01L 21/02203 20130101;
H01L 21/02126 20130101; C09D 183/04 20130101; H01L 21/02282
20130101; H01L 21/31695 20130101; C09D 183/14 20130101; H01L
21/02216 20130101; Y10T 428/249987 20150401 |
Class at
Publication: |
428/318.4 ;
427/384; 427/058 |
International
Class: |
B05D 5/12 20060101
B05D005/12; B05D 3/02 20060101 B05D003/02; B32B 9/00 20060101
B32B009/00 |
Claims
1-10. (canceled)
11. A structure comprising a first layer of an organic polysilica
dielectric material and a second layer disposed on the first layer,
wherein the second layer is a composition comprising one or more
B-staged organic polysilica resins and one or more removable
porogens, wherein the removable porogens are present in an amount
sufficient to provide a pinhole-free second layer.
12. A structure comprising a layer of a dielectric material and
porous cap layer disposed on the dielectric material.
13. The structure of claim 12 wherein the cap layer comprises an
organic polysilica material.
14. The structure of claim 12 wherein the dielectric material is
porous.
15. The structure of claim 14 wherein the dielectric material
comprises an organic polysilica material.
16. The structure of claim 12 wherein the dielectric material has a
first etch selectivity and the porous cap layer disposed on the
dielectric material has a second etch selectivity, wherein the etch
selectivities have a difference of 10% or greater.
17. A structure comprising a dielectric layer having a dielectric
constant of .ltoreq.3 and an organic polysilica cap layer disposed
on the dielectric layer, wherein the organic polysilica cap layer
has a dielectric constant of .ltoreq.2.9.
18. The structure if claim 17 wherein the dielectric layer is
porous.
19. The structure of claim 17 wherein the organic polysilica cap
layer is porous.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates generally to the field of manufacture
of electronic devices. In particular, this invention relates to the
manufacture of integrated circuit devices containing low dielectric
constant material.
[0002] As electronic devices become smaller, there is a continuing
desire in the electronics industry to increase the circuit density
in electronic components, e.g., integrated circuits, circuit
boards, multichip modules, chip test devices, and the like without
degrading electrical performance, e.g., crosstalk or capacitive
coupling, and also to increase the speed of signal propagation in
these components. One method of accomplishing these goals is to
reduce the dielectric constant of the interlayer, or intermetal,
insulating material used in the components.
[0003] A variety of organic and inorganic porous dielectric
materials are known in the art in the manufacture of electronic
devices, particularly integrated circuits. Suitable inorganic
dielectric materials include silicon dioxide and organic
polysilicas. Suitable organic dielectric materials include
thermosets such as polyimides, polyarylene ethers, polyarylenes,
polycyanurates, polybenzazoles, benzocyclobutenes, fluorinated
materials such as poly(fluoroalkanes), and the like. Of the organic
polysilica dielectrics, the alkyl silsesquioxanes such as methyl
silsesquioxane are of increasing importance because of their low
dielectric constant.
[0004] A method for reducing the dielectric constant of interlayer,
or intermetal, insulating material is to incorporate within the
insulating film very small, uniformly dispersed pores or voids. In
general, such porous dielectric materials are prepared by first
incorporating a removable porogen into a B-staged dielectric
material, disposing the B-staged dielectric material containing the
removable porogen onto a substrate, curing the B-staged dielectric
material and then removing the porogen to form a porous dielectric
material. For example, U.S. Pat. No. 5,895,263 (Carter et al.) and
U.S. Pat. No. 6,271,273 (You et al.) disclose processes for forming
integrated circuits containing porous organic polysilica dielectric
material. In conventional processes, the dielectric material is
typically cured under a non-oxidizing atmosphere, such as nitrogen,
and optionally in the presence of an amine in the vapor phase to
catalyze the curing process.
[0005] After the porous dielectric material is formed, it is
subjected to conventional processing conditions of patterning,
etching apertures, optionally applying a barrier layer and/or seed
layer, metallizing or filling the apertures, planarizing the
metallized layer, and then applying a cap layer or etch stop. These
process steps may then be repeated to form another layer of the
device.
[0006] A disadvantage of certain dielectric materials, including
organic polysilica dielectric materials, is that they may not
provide sufficient resistance to planarization techniques, such as
chemical mechanical planarization ("CMP") used in subsequent
manufacturing steps or sufficient resistance to etching, such as
oxygen plasma, during photoresist removal from such dielectric
materials. One solution to this is to use a layer of a different
material atop the dielectric material (i.e. a cap layer) to provide
the desired characteristics. Cap layers are useful in both single
and dual damascene processes, particularly when porous dielectric
materials are used. These layers planarize the surface of the
dielectric by filling any surface defects, provide a denser matrix
than that of the dielectric so as to seal any porosity having
connectivity to the surface of the dielectric film (prevents
intrusion of any residues from subsequent processing into the
porous dielectric), improve the adhesion with subsequently applied
layers of material and provide a hardmask having sufficient
resistance to subsequent processing steps and etch differential
between it and the underlying porous dielectric layer to allow
sequential selective pattern transfers between successive layers of
photoimaged pattern, cap layer and dielectric. Suitable cap layer
compositions must be able to provide good coating uniformity in the
required thickness range (e.g., 100 to 600 .ANG.) and have a low
dielectric constant (k.ltoreq.3.5).
[0007] Although certain organic cap layers have recently been
recommended, such as poly(arylene ethers), typical cap layers are
based on silicon dioxide, silicon carbide, silicon nitride, silicon
oxynitride and the like. For example, a conventional poly(arylene
ether) dielectric material may have a non-porous methyl
silsesquioxane capping layer, or alternatively, a conventional
methyl silsesquioxane dielectric layer may have a non-porous
poly(arylene ether) capping layer. U.S. Patent Application No.
2001/0051447 A1 (Usami) discloses a methyl silsesquioxane
dielectric layer having a silicon oxide capping layer to improve
the etch resistance.
[0008] Chemical vapor deposition ("CVD") methods are conventionally
used to deposit cap layers on the underlying dielectric material.
The carrier gas used in the CVD methods can generate amines, which
in turn can lead to a poisoning of an overlaid photoresist layer,
necessitating the use of either an N.sub.2O ashing step of the
application of a barrier material between the cap layer and the
photoresist. This problem can be eliminated by a spin-on process
for the cap layer material. Spin-on methods for depositing cap
layers are not without drawbacks. The major problem is assuring a
uniform, defect-free coating of the cap layer material,
particularly when an inorganic or organic-inorganic material is
used as the cap layer. Organic polysilica materials, such as methyl
silsesquioxane, often suffer from poor coating uniformity, pinhole
defects, and crack formation during curing.
[0009] Thus, there is a need for methods for depositing cap layers,
particularly organic polysilica cap layers, on a dielectric
material that overcome the above problems.
SUMMARY OF THE INVENTION
[0010] It has been surprisingly found that cap layers containing
organic polysilica material, such as alkyl and/or aryl
silsesquioxane, can be prepared easily deposited on a dielectric
material by spin-coating. Uniform and pinhole defect-free coatings
of such cap layers have been achieved according to the present
invention.
[0011] The present invention provides a method for depositing an
organic polysilica cap layer on a dielectric material including the
steps of: a) disposing a cap layer composition on a dielectric
material, the cap layer composition including one or more B-staged
organic polysilica resins and one or more coating enhancers; and b)
at least partially curing the one or more B-staged organic
polysilica resins to form a cap layer; wherein the one or more
coating enhancers are present in an amount sufficient to provide a
pinhole-free cap layer. The coating enhancers may then be removed
prior to or during the step of completely curing the organic
polysilica cap layer resin.
[0012] In another aspect, the present invention provides a method
for manufacturing a device including the steps of: a) providing a
dielectric material; b) disposing a cap layer composition on a
dielectric material, the cap layer composition including one or
more B-staged organic polysilica resins and one or more coating
enhancers; and b) at least partially curing the one or more
B-staged organic polysilica resins to form a cap layer; wherein the
one or more coating enhancers are present in an amount sufficient
to provide a pinhole-free cap layer.
[0013] In a further aspect, the present invention provides a method
for manufacturing a device including the steps of: a) providing a
dielectric material; b) disposing a cap layer composition on a
dielectric material, the cap layer composition including one or
more B-staged organic polysilica resins and removable porogen; and
b) at least partially curing the one or more B-staged organic
polysilica resin to form a cap layer; wherein the removable porogen
is present in an amount sufficient to provide a pinhole-free cap
layer.
[0014] In yet another aspect, the present invention provides a
structure including a first layer of an organic polysilica
dielectric material and a second layer disposed on the first layer,
wherein the second layer is a composition including one or more
B-staged organic polysilica resins and removable porogen, wherein
the porogen is present in an amount sufficient to provide a
pinhole-free second layer. Also included are structures wherein the
second layer is at least partially cured.
[0015] Also provided by this invention is a structure including a
porous first layer of an organic polysilica dielectric material and
a porous cap layer disposed on the dielectric material. Preferably,
the cap layer includes an organic polysilica material.
[0016] Further, this invention provides a structure including a
layer of a dielectric material and porous cap layer disposed on the
dielectric material.
[0017] Structures including a porous first layer of an organic
polysilica dielectric material having a first etch selectivity and
a porous cap layer disposed on the dielectric material having a
second etch selectivity, wherein the difference in etch
selectivities is 10% or greater are also provided.
[0018] In a still further aspect, this invention provides a
structure including a dielectric layer having a dielectric constant
of <3 and an organic polysilica cap layer disposed on the
dielectric layer, wherein the organic polysilica cap layer has a
dielectric constant of .ltoreq.2.9.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a scanning electron micrograph ("SEM") of a
spin-coated organic polysilica cap layer having pinhole
defects.
[0020] FIG. 2 is a SEM of a spin-coated organic polysilica cap
layer prepared from a B-staged organic polysilica resin containing
3% by weight compatibilized porogen and having pinhole defects.
[0021] FIG. 3 is a SEM of a spin-coated organic polysilica cap
layer prepared from a B-staged organic polysilica resin containing
10% by weight compatibilized porogen and having no pinhole
defects.
DETAILED DESCRIPTION OF THE INVENTION
[0022] As used throughout this specification, the following
abbreviations shall have the following meanings, unless the context
clearly indicates otherwise: .degree. C.=degrees centigrade;
UV=ultraviolet; nm=nanometer; g=gram; wt %=weight percent; L=liter;
.mu.m=micron=micrometer; rpm=revolutions per minute; N=normal;
ca.=approximately; DI=deionized; and ppm=parts per million.
[0023] The term "alkyl" includes straight chain, branched and
cyclic alkyl groups. The term "porogen" refers to a pore forming
material, e.g. a polymeric material or particle dispersed in a
material that is subsequently removed to yield pores in the
material. Thus, the terms "removable porogen," "removable polymer"
and "removable particle" are used interchangeably throughout this
specification. "Porous" refers to a material that has been
intentionally made porous, such as by the use of a porogen. As used
herein, "dense" refers to material that has not been intentionally
made porous. "Cross-linker" and "crosslinking agent" are used
interchangeably throughout this specification. "Polymer" refers to
polymers and oligomers, and also includes homopolymers and
copolymers. The terms "oligomer" and "oligomeric" refer to dimers,
trimers, tetramers and the like. "Monomer" refers to any
ethylenically or acetylenically unsaturated compound capable of
being polymerized or other compound capable of being polymerized by
condensation. Such monomers may contain one or more double or
triple bonds or groups capable of being polymerized by
condensation.
[0024] The term "B-staged" refers to uncured organic polysilica
materials. By "uncured" is meant any material that can be
polymerized or cured to form higher molecular weight materials,
such as coatings or films. As used herein, "partially cured" refers
to a film or coating of organic polysilica resin or material that
has been sufficiently cured so that only 1% or less of the
thickness of the film is lost upon contact with a solvent suitable
for dissolving the B-staged organic polysilica resin. Such
partially cured films or coatings may undergo further curing during
subsequent processing steps. "Films" and "Layers" are used
interchangeably throughout this Specification. B-staged materials
may be monomeric, oligomeric or mixtures thereof. B-staged material
is further intended to include mixtures of polymeric material with
monomers, oligomers or a mixture of monomers and oligomers.
[0025] Unless otherwise noted, all amounts are percent by weight
and all ratios are by weight. All numerical ranges are inclusive
and combinable in any order, except where it is clear that such
numerical ranges are constrained to add up to 100%.
[0026] Organic polysilica cap layers can be deposited on a
dielectric material including the steps of: a) disposing a cap
layer composition on a dielectric material, the cap layer
composition including one or more B-staged organic polysilica
resins and one or more coating enhancers; and b) at least partially
curing the one or more B-staged organic polysilica resins to form a
cap layer; wherein the one or more coating enhancers are present in
an amount sufficient to provide a pinhole-free cap layer. The term
"cap layer" refers to any layer added to the top of a dielectric
material and which performs one or more of the following functions:
1) fills any surface defects of the dielectric material; 2)
provides a denser matrix than that of the dielectric so as to seal
any porosity having connectivity to the surface of the dielectric
film, which prevents intrusion of any residues from subsequent
processing into the porous dielectric; 3) improves the adhesion of
the dielectric layer with subsequently applied layers of material;
and 4) provides a hardmask having sufficient resistance to
subsequent processing steps and etch differential between it and
the underlying porous dielectric layer to allow sequential
selective pattern transfers between successive layers of
photoimaged pattern, cap layer and dielectric. "Cap layers", as the
term is generally used herein, include those layers functioning as
etch stops, CMP stops, hardmasks and the like and are typically
applied to a dielectric or insulating layer.
[0027] The present cap layer compositions include one or more
B-staged organic polysilica resins and one or more coating
enhancers. By "organic polysilica resin" (or organo siloxane) is
meant a compound including silicon, carbon, oxygen and hydrogen
atoms. Exemplary organic polysilica resins are hydrolyzates and
partial condensates of one or more silanes of formulae (I) or (II):
R.sub.aSiY.sub.4-a (I)
R.sup.1.sub.b(R.sup.2O).sub.3-bSi(R.sup.3).sub.cSi(OR.sup.4).sub.3-4R.sup-
.5.sub.d (II) wherein R is hydrogen, (C.sub.1-C.sub.8)alkyl,
(C.sub.7-C.sub.12)arylalkyl, substituted
(C.sub.7-C.sub.12)arylalkyl, aryl, and substituted aryl; Y is any
hydrolyzable group; a is an integer of 0 to 2; R.sup.1, R.sup.2,
R.sup.4 and R.sup.5 are independently selected from hydrogen,
(C.sub.1-C.sub.6)alkyl, (C.sub.7-C.sub.12)arylalkyl, substituted
(C.sub.7-C.sub.12)arylalkyl, aryl, and substituted aryl; R.sup.3 is
selected from (C.sub.1-C.sub.10)alkyl, --(CH.sub.2).sub.h--,
--(CH.sub.2).sub.h1-E.sub.k-(CH.sub.2).sub.h2--,
--(CH.sub.2).sub.h-Z, arylene, substituted arylene, and arylene
ether; E is selected from oxygen, NR.sup.6 and Z; Z is selected
from aryl and substituted aryl; R.sup.6 is selected from hydrogen,
(C.sub.1-C.sub.6)alkyl, aryl and substituted aryl; b and d are each
an integer of 0 to 2; c is an integer of 0 to 6; and h, h1, h2 and
k are independently an integer from 1 to 6; provided that at least
one of R, R.sup.1, R.sup.3 and R.sup.5 is not hydrogen.
"Substituted arylalkyl", "substituted aryl" and "substituted
arylene" refer to an arylalkyl, aryl or arylene group having one or
more of its hydrogens replaced by another substituent group, such
as cyano, hydroxy, mercapto, halo, (C.sub.1-C.sub.6)alkyl,
(C.sub.1-C.sub.6)alkoxy, and the like.
[0028] It is preferred that R is (C.sub.1-C.sub.4)alkyl, benzyl,
hydroxybenzyl, phenethyl or phenyl, and more preferably methyl,
ethyl, iso-butyl, tert-butyl or phenyl. Preferably, a is 1.
Suitable hydrolyzable groups for Y include, but are not limited to,
halo, (C.sub.1-C.sub.6)alkoxy, acyloxy and the like. Preferred
hydrolyzable groups are chloro and (C.sub.1-C.sub.2)alkoxy.
Suitable organosilanes of formula (I) include, but are not limited
to, methyl trimethoxysilane, methyl triethoxysilane, phenyl
trimethoxysilane, phenyl triethoxysilane, tolyl trimethoxysilane,
tolyl triethoxysilane, propyl tripropoxysilane, iso-propyl
triethoxysilane, iso-propyl tripropoxysilane, ethyl
trimethoxysilane, ethyl triethoxysilane, iso-butyl triethoxysilane,
iso-butyl trimethoxysilane, tert-butyl triethoxysilane, tert-butyl
trimethoxysilane, cyclohexyl trimethoxysilane, cyclohexyl
triethoxysilane, benzyl trimethoxysilane, benzyl triethoxysilane,
phenethyl trimethoxysilane, hydroxybenzyl trimethoxysilane,
hydroxyphenylethyl trimethoxysilane and hydroxyphenylethyl
triethoxysilane.
[0029] Organosilanes of formula (II) preferably include those
wherein R.sup.1 and R.sup.5 are independently
(C.sub.1-C.sub.4)alkyl, benzyl, hydroxybenzyl, phenethyl or phenyl.
Preferably R.sup.1 and R.sup.5 are methyl, ethyl, tert-butyl,
iso-butyl and phenyl. It is also preferred that b and d are
independently 1 or 2. Preferably R.sup.3 is
(C.sub.1-C.sub.10)alkyl, --(CH.sub.2).sub.h--, arylene, arylene
ether and --(CH.sub.2).sub.h1-E-(CH.sub.2).sub.h2. Suitable
compounds of formula (II) include, but are not limited to, those
wherein R.sup.3 is methylene, ethylene, propylene, butylene,
hexylene, norbornylene, cycloheylene, phenylene, phenylene ether,
naphthylene and --CH.sub.2--C.sub.6H.sub.4--CH.sub.2--. It is
further preferred that c is 1 to 4.
[0030] Suitable organosilanes of formula (II) include, but are not
limited to, bis(hexamethoxysilyl)methane,
bis(hexaethoxysilyl)methane, bis(hexaphenoxysilyl)methane,
bis(dimethoxymethylsilyl)methane, bis(diethoxymethyl-silyl)methane,
bis(dimethoxyphenylsilyl)methane, bis(diethoxyphenylsilyl)methane,
bis(methoxydimethylsilyl)methane, bis(ethoxydimethylsilyl)methane,
bis(methoxy-diphenylsilyl)methane, bis(ethoxydiphenylsilyl)methane,
bis(hexamethoxysilyl)ethane, bis(hexaethoxysilyl)ethane,
bis(hexaphenoxysilyl)ethane, bis(dimethoxymethylsilyl) ethane,
bis(diethoxymethylsilyl)ethane, bis(dimethoxyphenylsilyl)ethane,
bis(diethoxyphenyl-silyl)ethane, bis(methoxydimethylsilyl)ethane,
bis(ethoxydimethylsilyl)ethane, bis(methoxy-diphenylsilyl)ethane,
bis(ethoxydiphenylsilyl)ethane, 1,3-bis(hexamethoxysilyl))propane,
1,3-bis(hexaethoxysilyl)propane, 1,3-bis(hexaphenoxysilyl)propane,
1,3-bis(dimethoxy-methylsilyl)propane,
1,3-bis(diethoxymethylsilyl)propane,
1,3-bis(dimethoxyphenyl-silyl)propane,
1,3-bis(diethoxyphenylsilyl)propane,
1,3-bis(methoxydimehylsilyl)propane,
1,3-bis(ethoxydimethylsilyl)propane,
1,3-bis(methoxydiphenylsilyl)propane, and
1,3-bis(ethoxydiphenylsilyl)propane. Preferred of these are
hexamethoxydisilane, hexaethoxydisilane, hexaphenoxydisilane,
1,1,2,2-tetramethoxy-1,2-dimethyldisilane,
1,1,2,2-tetraethoxy-1,2-dimethyldisilane,
1,1,2,2-tetramethoxy-1,2-diphenyldisilane,
1,1,2,2-tetraethoxy-1,2-diphenyldisilane,
1,2-dimethoxy-1,1,2,2-tetramethyldisilane,
1,2-diethoxy-1,1,2,2-tetramethyldisilane,
1,2-dimethoxy-1,1,2,2-tetraphenyldisilane,
1,2-diethoxy-1,1,2,2-tetraphenyl-disilane,
bis(hexamethoxysilyl)methane, bis(hexaethoxysilyl)methane,
bis(dimethoxymethyl-silyl)methane, bis(diethoxymethylsilyl)methane,
bis(dimethoxyphenylsilyl)methane, bis(diethoxyphenylsilyl)methane,
bis(methoxydimethylsilyl)methane, bis(ethoxydimethyl-silyl)methane,
bis(methoxydiphenylsilyl)methane, and
bis(ethoxydiphenylsilyl)methane.
[0031] When the B-staged organic polysilica resins include one or
more of a hydrolyzate and partial condensate of organosilanes of
formula (II), c may be 0, provided that at least one of R.sup.1 and
R are not hydrogen. In an alternate embodiment, the B-staged
organic polysilica resins may include one or more of a
cohydrolyzate and partial cocondensate of organosilanes of both
formulae (I) and (II). In such cohydrolyzates and partial
cocondensates, c in formula (II) can be 0, provided that at least
one of R, R.sup.1 and R.sup.5 is not hydrogen. Suitable silanes of
formula (II) where c is 0 include, but are not limited to,
hexamethoxydisilane, hexaethoxydisilane, hexaphenoxydisilane,
1,1,1,2,2-pentamethoxy-2-methyldisilane,
1,1,1,2,2-pentaethoxy-2-methyldisilane,
1,1,1,2,2-pentamethoxy-2-phenyldisilane,
1,1,1,2,2-pentaethoxy-2-phenyldisilane,
1,1,2,2-tetramethoxy-1,2-dimethyldisilane,
1,1,2,2-tetraethoxy-1,2-dimethyldisilane,
1,1,2,2-tetramethoxy-1,2-diphenyldisilane,
1,1,2,2-tetraethoxy-1,2-diphenyldisilane,
1,1,2-trimethoxy-1,2,2-trimethyldisilane,
1,1,2-triethoxy-1,2,2-trimethyldisilane,
1,1,2-trimethoxy-1,2,2-triphenyldisilane,
1,1,2-triethoxy-1,2,2-triphenyldisilane,
1,2-dimethoxy-1,1,2,2-tetramethyldisilane,
1,2-diethoxy-1,1,2,2-tetramethyldisilane,
1,2-dimethoxy-1,1,2,2-tetraphenyldisilane, and
1,2-diethoxy-1,1,2,2-tetra-phenyldisilane.
[0032] In one embodiment, particularly suitable B-staged organic
polysilica resins are chosen from one or more of hydrolyzates and
partial condensates of compounds of formula (I). Such B-staged
organic polysilica resins have the formula (III):
((R.sup.7R.sup.8SiO).sub.c(R.sup.9SiO.sub.1.5).sub.f(R.sup.10SiO.sub.1.5)-
.sub.g(SiO.sub.2).sub.r).sub.n (III) wherein R.sup.7, R.sup.8,
R.sup.9 and R.sup.10 are independently selected from hydrogen,
(C.sub.1-C.sub.6)alkyl, (C.sub.7-C.sub.12)arylalkyl, substituted
(C.sub.7-C.sub.12)arylalkyl, aryl, and substituted aryl; e, g and r
are independently a number from 0 to 1; f is a number from 0.2 to
1; n is integer from 3 to 10,000; provided that e+f+g+r=1; and
provided that at least one of R.sup.7, R.sup.8 and R.sup.9 is not
hydrogen. In the above formula (III), e, f, g and r represent the
mole ratios of each component. Such mole ratios can be varied
between 0 and 1. It is preferred that e is from 0 to 0.8. It is
also preferred that g is from 0 to 0.8. It is further preferred
that r is from 0 to 0.8. In the above formula, n refers to the
number of repeat units in the B-staged material. Preferably, n is
an integer from 3 to 1000.
[0033] Suitable organic polysilica resins include, but are not
limited to, silsesquioxanes, partially condensed halosilanes or
alkoxysilanes such as partially condensed by controlled hydrolysis
tetraetboxysilane having number average molecular weight of 500 to
20,000, organically modified silicates having the composition
RSiO.sub.3, O.sub.3SiRSiO.sub.3, R.sub.2SiO.sub.2 and
O.sub.2SiR.sub.3SiO.sub.2 wherein R is an organic substituent, and
partially condensed orthosilicates having Si(OR).sub.4 as the
monomer unit. Silsesquioxanes are polymeric silicate materials of
the type RSiO.sub.1.5 where R is an organic substituent. Suitable
silsesquioxanes are alkyl silsesquioxanes such as methyl
silsesquioxane, ethyl silsesquioxane, propyl silsesquioxane, butyl
silsesquioxane and the like; aryl silsesquioxanes such as phenyl
silsesquioxane and tolyl silsesquioxane; alkyl/aryl silsesquioxane
mixtures such as a mixture of methyl silsesquioxane and phenyl
silsesquioxane; and mixtures of alkyl silsesquioxanes such as
methyl silsesquioxane and ethyl silsesquioxane. B-staged
silsesquioxane materials include homopolymers of silsesquioxanes,
copolymers of silsesquioxanes or mixtures thereof. Such materials
are generally commercially available or may be prepared by known
methods.
[0034] In an alternate embodiment, the organic polysilica resins
may contain a wide variety of other monomers in addition to the
silicon-containing monomers described above. For example, the
organic polysilica resins may further comprise cross-linking
agents, and carbosilane moieties. Such cross-linking agents may be
any of the cross-linking agents described elsewhere in this
specification, or any other known cross-linkers for
silicon-containing materials. It will be appreciated by those
skilled in the art that a combination of cross-linkers may be used.
Carbosilane moieties refer to moieties having a (Si--C), structure,
such as (Si-A).sub.x structures wherein A is a substituted or
unsubstituted alkylene or arylene, such as SiR.sub.3CH.sub.2--,
--SiR.sub.2CH.sub.2--, .dbd.SiRCH.sub.2--, and .ident.SiCH.sub.2--,
where R is usually hydrogen but may be any organic or inorganic
radical. Suitable inorganic radicals include organosilicon,
siloxyl, or silanyl moieties. These carbosilane moieties are
typically connected "head-to-tail", i.e. having Si--C--Si bonds, in
such a manner that a complex, branched structure results.
Particularly useful carbosilane moieties are those having the
repeat units (SiH.sub.xCH.sub.2) and
(SiH.sub.y-1(CH.dbd.CH.sub.2)CH.sub.2), where x=0 to 3 and y=1 to
3. These repeat units may be present in the organic polysilica
resins in any number from 1 to 100,000, and preferably from 1 to
10,000. Suitable carbosilane precursors are those disclosed in U.S.
Pat. No. 5,153,295 (Whitmarsh et al.) and U.S. Pat. No. 6,395,649
(Wu).
[0035] It is preferred that the B-staged organic polysilica resin
includes a silsesquioxane, and more preferably methyl
silsesquioxane, ethyl silsesquioxane, propyl silsesquioxane,
iso-butyl silsesquioxane, tert-butyl silsesquioxane, phenyl
silsesquioxane, tolyl silsesquioxane, benzyl silsesquioxane or
mixtures thereof. Methyl silsesquioxane, phenyl silsesquioxane and
mixtures thereof are particularly suitable. Other useful
silsesquioxane mixtures include mixtures of hydrido silsesquioxanes
with alkyl, aryl or alkyl/aryl silsesquioxanes. Typically, the
silsesquioxanes useful in the present invention are used as
oligomeric materials, generally having from 3 to 10,000 repeating
units.
[0036] Particularly suitable organic polysilica B-staged resins are
co-hydrolyzates and partial condensates of one or more
organosilanes of formulae (I) and/or (II) and one or more
tetrafunctional silanes having the formula SiY.sub.4, where Y is
any hydrolyzable group as defined above. Suitable hydrolyzable
groups include, but are not limited to, halo,
(C.sub.1-C.sub.6)alkoxy, acyloxy and the like. Preferred
hydrolyzable groups are chloro and (C.sub.1-C.sub.2)alkoxy.
Suitable tetrafunctional silanes of the formula SiY.sub.4 include,
but are not limited to, tetramethoxysilane, tetraethoxysilane,
tetrachlorosilane, and the like. Particularly suitable silane
mixtures for preparing the cohydrolyzates and partial cocondensates
include: methyl triethoxysilane and tetraethoxysilane; methyl
trimethoxysilane and tetramethoxysilane; phenyl triethoxysilane and
tetraethoxysilane; methyl triethoxysilane and phenyl
triethoxysilane and tetraethoxysilane; ethyl triethoxysilane and
tetramethoxysilane; and ethyl triethoxysilane and
tetraethoxysilane. The ratio of such organosilanes to
tetrafunctional silanes is typically from 99:1 to 1:99, preferably
from 95:5 to 5:95, more preferably from 90:10 to 10:90, and still
more preferably from 80:20 to 20:80.
[0037] In a particular embodiment, the B-staged organic polysilica
resin is chosen from one or more of a co-hydrolyzate and partial
co-condensate of one or more organosilanes of formula (I) and a
tetrafunctional silane of formula SiY.sub.4. In another embodiment,
the B-staged organic polysilica resin is chosen from one or more of
a co-hydrolyzate and partial co-condensate of one or more
organosilanes of formula (II) and a tetrafunctional silane of
formula SiY.sub.4. In still another embodiment, the B-staged
organic polysilica resin is chosen from one or more of a
co-hydrolyzate and partial co-condensate of one or more
organosilanes of formula (I), one or more silanes of formula (II)
and a tetrafunctional silane of formula SiY.sub.4. The B-staged
organic polysilica resins include one or more of a non-hydrolyzed
and non-condensed silane of one or more silanes of formulae (I) or
(II) with one or more of the hydrolyzate and partial condensate of
one or more silanes of formulae (I) or (II). In a further
embodiment, the B-staged organic polysilica resin includes a silane
of formula (II) and one or more of a hydrolyzate and partial
condensate of one or more organosilanes of formula (I), and
preferably one or more of a co-hydrolyzate and partial
co-condensate of one or more organosilanes of formula (I) with a
tetrafunctional silane of the formula SiY.sub.4 where Y is as
defined above. Perferably, such B-staged organic polysilica resin
includes a mixture of one or more silanes of formula (II) and one
or more of a co-hydrolyzate and partial co-condensate having the
formula (RSiO.sub.1.5) (SiO.sub.2) where R is as defined above.
[0038] When organosilanes of formula (I) are co-hydrolyzed or
co-condensed with a tetrafunctional silane, it is preferred that
the organosilane of formula (I) has the formula RSiY.sub.3, and
preferably is selected from methyl trimethoxysilane, methyl
triethoxysilane, ethyl trimethoxysilane, ethyl triethoxysilane,
phenyl trimethoxysilane, phenyl triethoxysilane and mixtures
thereof. It is also preferred that the tetrafunctional silane is
selected from tetramethoxysilane and tetraethoxysilane.
[0039] In another embodiment, particularly useful cap layer
compositions include one or more B-staged organic polysilica resins
having the formula ##STR1## wherein each R.sup.1 and R.sup.2 are
independently selected from hydroxyl, hydrogen,
(C.sub.1-C.sub.6)alkyl, (C.sub.2-C.sub.6)alkenyl, and
(C.sub.1-C.sub.6)alkylidine; x=0.3 to 0.7; and y+z=0.3 to 0.7;
wherein x and y+z=the mole fraction of the components. When x+y+z
does not equal 1, then it is understood that one or more other
monomer units are included in the resin. Such other monomer units
may be any which can co-condense with the monomer units of the
above formula, and preferably are one or more of the above
described silanes. In one embodiment, x+y+z=1. In another
embodiment, R.sup.1 and R.sup.2 are independently selected from
hydroxyl, hydrogen methyl, ethyl, vinyl, methylidine (--CH.sub.2--)
and ethylidine (--CH.sub.2CH.sub.2--). A particularly useful
composition of this formula is where R.sup.1 is methyl; R.sup.2 is
hydroxyl; x =0.5 to 0.6; and y+z=0.5 to 0.4. Such composition is
prepared by the co-hydrolysis or co-condensation of methyl
triethoxysilane and tetraethoxysilane. In general, resins having
the above formula have a molecular weight of from 4000 to
100,000.
[0040] Any compound that provides an organic polysilica cap layer
on a dielectric material wherein the cap layer is uniform and
pinhole defect-free may be used as the present coating enhancers.
As used herein, "pinhole" refers to a hole, such as from a few
angstroms to 10 nm in diameter, that communicates through the cap
layer from a top surface to a bottom surface and results from the
deposition of the cap layer. Such pinholes are typically channels
that are substantially circular in cross-section. The term
"pinhole" does not include rips, tears or other mechanical defects
and does not include intentionally formed pores such as by the use
of a porogen.
[0041] In general, the coating enhancers are substantially
non-aggregated or non-agglomerated in the B-staged material. Such
non-aggregation or non-agglomeration reduces or avoids the problem
of killer (very large) pore or channel formation in the cured or
partially cured resin material, and is achieved by making the
coating enhancer substantially compatible with the B-staged organic
polysilica resin. By "substantially compatible" is meant that a
composition of B-staged organic polysilica resin and coating
enhancer is slightly cloudy or slightly opaque. Preferably,
"substantially compatible" means at least one of a solution of the
B-staged resin and coating enhancer, and a film or layer including
a composition of B-staged resin and coating enhancer is slightly
cloudy or slightly opaque. To be compatible, the coating enhancer
must be soluble in or miscible in the B-staged resin, in the
solvent used to dissolve the B-staged resin or both. Preferably,
the coating enhancer must be soluble in or miscible in the B-staged
organic polysilica resin.
[0042] The coating enhancers are preferably removable, meaning that
they are sufficiently labile under certain conditions to be removed
from the resulting cap layer. In one embodiment, the coating
enhancers are removed and no pores are formed. In an alternate
embodiment, the coating enhancers are removed to provide pores in
the cap layer. As the purpose of a cap layer, inter alia, is to
provide a sealing layer over a porous dielectric layer, and to act
as a stop layer for certain processes such as CMP, the cap layer
typically needs to be dense only until the purpose of the cap layer
has been fulfilled. For example, when the cap layer is a CMP stop,
it needs to remain dense until the surface of the device has been
planarized. After such planarization, the cap layer may be made
porous.
[0043] Exemplary coating enhancers include, without limitation,
high boiling solvents, surfactants and removable polymers
(porogens). "High boiling solvents" refers to solvents having a
boiling point of .gtoreq.200.degree. C. at atmospheric pressure,
and preferably .gtoreq.250.degree. C. Useful surfactants are any
that contain poly(alkylene oxide) moieties or silicon-containing
moieties. Preferred poly(alkylene oxide)-containing surfactants are
ethylene oxide ("EO") or propylene oxide ("PO") polymers or
copolymers of EO/PO. Exemplary poly(alkylene oxide) surfactants are
polyethylene glycol and polypropylene glycol. Useful molecular
weight ranges for the poly(alkylene oxide) surfactants are 100 to
50,000, preferably 200 to 20,000 and more preferably 250 to 5000.
Particularly useful poly(alkylene oxide) surfactants are those sold
under the PLURONIC and TETRONIC brands by BASF, Ludwigshafen,
Germany. A wide variety of silicon-containing surfactants may be
used, such as those sold under the SILWET brand.
[0044] A wide variety of removable polymers (porogens) may be used
as the coating enhancers. The removable porogens may be polymers
(linear, branched or particles) or may be co-polymerized with an
organic polysilica dielectric monomer to form a block copolymer
having a labile (removable) component. Such polymers are preferably
compatible as described above. Suitable compatibilized porogens are
those disclosed in U.S. Pat. No. 6,271,273 (You et al.) and
European Patent Application EP Application No. 1 088 848 (Allen et
al.). In one embodiment, the compatibilized porogen is a polymer
that includes as polymerized units at least one compound selected
from silyl-containing monomers and poly(alkylene oxide) monomers.
The silyl containing monomers or poly(alkylene oxide) monomers may
be used to form the uncrosslinked polymer, used as the crosslinker,
or both. Other suitable removable particles are those disclosed in
U.S. Pat. No. 5,700,844.
[0045] Any monomer containing silicon may be useful as the
silyl-containing monomers. The silicon moiety in such silyl
containing monomers may be reactive or unreactive. Exemplary
"reactive" silyl containing monomers include those containing one
or more alkoxy or acetoxy groups, such as, but not limited to,
trimethoxysilyl containing monomers, triethoxysilyl containing
monomers, methyl dimethoxysilyl containing monomers, and the like.
Exemplary "unreactive" silyl containing monomers include those
containing alkyl groups, aryl groups, alkenyl groups or mixtures
thereof, such as but are not limited to, trimethylsilyl containing
monomers, triethylsilyl containing monomers, phenyldimethylsilyl
containing monomers, and the like. Polymeric porogens including
silyl containing monomers as polymerized units are intended to
include such porogens prepared by the polymerization of a monomer
containing a silyl moiety. It is not intended to include a linear
polymer that contains a silyl moiety only as end capping units.
[0046] Suitable silyl containing monomers include, but are not
limited to, vinyltrimethylsilane, vinyltriethylsilane,
vinyltrimethoxysilane, vinyltriethoxysilane,
y-trimethoxysilylpropyl (meth)acrylate, divinylsilane,
trivinylsilane, dimethyldivinylsilane, divinylmethylsilane,
methyltrivinylsilane, diphenyldivinylsilane, divinylphenylsilane,
trivinylphenylsilane, divinylmethylphenylsilane, tetravinylsilane,
dimethylvinyldisiloxane, poly(methylvinylsiloxane),
poly(vinylhydrosiloxane), poly(phenylvinylsiloxane),
allyloxy-tert-butyldimethylsilane, allyloxytrimethylsilane,
allyltriethoxysilane, allyltri-iso-propylsilane,
allyltrimethoxysilane, allyltrimethylsilane, allyltriphenylsilane,
diethoxy methylvinylsilane, diethyl methylvinylsilane, dimethyl
ethoxyvinylsilane, dimethyl phenylvinylsilane, ethoxy
diphenylvinylsilane, methyl bis(trimethylsilyloxy)vinylsilane,
triacetoxyvinylsilane, triethoxyvinylsilane, triethylvinylsilane,
triphenylvinylsilane, tris(trimethylsilyloxy)vinylsilane,
vinyloxytrimethylsilane and mixtures thereof.
[0047] The amount of silyl containing monomer useful to form the
porogens of the present invention is typically from 1 to 99 % wt,
based on the total weight of the monomers used. It is preferred
that the silyl containing monomers are present in an amount of from
1 to 80 % wt, and more preferably from 5 to 75 % wt.
[0048] Suitable poly(alkylene oxide) monomers include, but are not
limited to, poly(propylene oxide) monomers, poly(ethylene oxide)
monomers, poly(ethylene oxide/propylene oxide) monomers,
poly(propylene glycol) (meth)acrylates, poly(propylene glycol)
alkyl ether (meth)acrylates, poly(propylene glycol) phenyl ether
(meth)acrylates, poly(propylene glycol) 4-nonylphenol ether
(meth)acrylates, poly(ethylene glycol) (meth)acrylates,
poly(ethylene glycol) alkyl ether (meth)acrylates, poly(ethylene
glycol) phenyl ether (meth)acrylates, poly(propylene/ethylene
glycol) alkyl ether (meth)acrylates and mixtures thereof. Preferred
poly(alkylene oxide) monomers include trimethoylolpropane
ethoxylate tri(meth)acrylate, trimethoylolpropane propoxylate
tri(meth)acrylate, poly(propylene glycol) methyl ether acrylate,
and the like. Particularly suitable poly(propylene glycol) methyl
ether acrylate monomers are those having a molecular weight in the
range of from 200 to 2000. The poly(ethylene oxide/propylene oxide)
monomers useful in the present invention may be linear, block or
graft copolymers. Such monomers typically have a degree of
polymerization of from 1 to 50, and preferably from 2 to 50.
[0049] Typically, the amount of poly(alkylene oxide) monomers
useful in the porogens of the present invention is from I to 99 %
wt, based on the total weight of the monomers used. The amount of
poly(alkylene oxide) monomers is preferably from 2 to 90 % wt, and
more preferably from 5 to 80 % wt.
[0050] The silyl containing monomers and the poly(alkylene oxide)
monomers may be used either alone or in combination to form the
porogens of the present invention. In general, the amount of the
silyl containing monomers or the poly(alkylene oxide) monomers
needed to compatiblize the porogen with the dielectric matrix
depends upon the level of porogen loading desired in the matrix,
the particular composition of the organo polysilica dielectric
matrix, and the composition of the porogen polymer. When a
combination of silyl containing monomers and the poly(alkylene
oxide) monomers is used, the amount of one monomer may be decreased
as the amount of the other monomer is increased. Thus, as the
amount of the silyl containing monomer is increased in the
combination, the amount of the poly(alkylene oxide) monomer in the
combination may be decreased.
[0051] The polymers suitable for use as porogens in the present
invention are preferentially derived from one or more ethylenically
or acetylenically unsaturated monomers including as polymerized
units one or more compounds selected from silyl containing monomers
and poly(alkylene oxide) monomers and more preferable include one
or more cross-linking agents. Polymeric porogen particles contain
one or more cross-linking agents. Suitable monomers which may be
copolymerized with the one or more silyl containing monomers or one
or more poly(alkylene oxide) monomers or mixtures thereof include,
but are not limited to: (meth)acrylic acid, (meth)acrylamides,
alkyl (meth)acrylates, alkenyl (meth)acrylates, aromatic
(meth)acrylates, vinyl aromatic monomers, nitrogen-containing
compounds and their thio-analogs, and substituted ethylene
monomers.
[0052] Typically, the alkyl (meth)acrylates useful in the present
invention are (C.sub.1-C.sub.24) alkyl (meth)acrylates. Suitable
alkyl (meth)acrylates include, but are not limited to, "low cut"
alkyl (meth)acrylates, "mid cut" alkyl (meth)acrylates and "high
cut" alkyl (meth)acrylates.
[0053] "Low cut" alkyl (meth)acrylates are typically those where
the alkyl group contains from 1 to 6 carbon atoms. Suitable low cut
alkyl (meth)acrylates include, but are not limited to: methyl
methacrylate, methyl acrylate, ethyl acrylate, propyl methacrylate,
butyl methacrylate, butyl acrylate, isobutyl methacrylate, hexyl
methacrylate, cyclohexyl methacrylate, cyclohexyl acrylate and
mixtures thereof.
[0054] "Mid cut" alkyl (meth)acrylates are typically those where
the alkyl group contains from 7 to 15 carbon atoms. Suitable mid
cut alkyl (meth)acrylates include, but are not limited to:
2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, octyl
methacrylate, decyl methacrylate, isodecyl methacrylate, undecyl
methacrylate, dodecyl methacrylate (also known as lauryl
methacrylate), tridecyl methacrylate, tetradecyl methacrylate (also
known as myristyl methacrylate), pentadecyl methacrylate and
mixtures thereof. Particularly useful mixtures include
dodecyl-pentadecyl methacrylate, a mixture of linear and branched
isomers of dodecyl, tridecyl, tetradecyl and pentadecyl
methacrylates; and lauryl-myristyl methacrylate.
[0055] "High cut" alkyl (meth)acrylates are typically those where
the alkyl group contains from 16 to 24 carbon atoms. Suitable high
cut alkyl (meth)acrylates include, but are not limited to:
hexadecyl methacrylate, heptadecyl methacrylate, octadecyl
methacrylate, nonadecyl methacrylate, cosyl methacrylate, eicosyl
methacrylate and mixtures thereof. Particularly useful mixtures of
high cut alkyl (meth)acrylates include, but are not limited to:
cetyl-eicosyl methacrylate, which is a mixture of hexadecyl,
octadecyl, cosyl and eicosyl methacrylate; and cetyl-stearyl
methacrylate, which is a mixture of hexadecyl and octadecyl
methacrylate.
[0056] The mid-cut and high-cut alkyl (meth)acrylate monomers
described above are generally prepared by standard esterification
procedures using technical grades of long chain aliphatic alcohols,
and these commercially available alcohols are mixtures of alcohols
of varying chain lengths containing between 10 and 15 or 16 and 20
carbon atoms in the alkyl group. Examples of these alcohols are the
various Ziegler catalyzed ALFOL alcohols from Vista Chemical
company, i.e., ALFOL 1618 and ALFOL 1620, Ziegler catalyzed various
NEODOL alcohols from Shell Chemical Company, i.e. NEODOL 25L, and
naturally derived alcohols such as Proctor & Gamble's TA-1618
and CO-1270. Consequently, for the purposes of this invention,
alkyl (meth)acrylate is intended to include not only the individual
alkyl (meth)acrylate product named, but also to include mixtures of
the alkyl (meth)acrylates with a predominant amount of the
particular alkyl (meth)acrylate named.
[0057] The alkyl (meth)acrylate monomers useful in the present
invention may be a single monomer or a mixture having different
numbers of carbon atoms in the alkyl portion. Also, the
(meth)acrylamide and alkyl (meth)acrylate monomers may optionally
be substituted. Suitable optionally substituted (meth)acrylamide
and alkyl (meth)acrylate monomers include, but are not limited to:
hydroxy (C.sub.2-C.sub.6)alkyl (meth)acrylates,
dialkylamino(C.sub.2-C.sub.6)-alkyl (meth)acrylates,
dialkylamino(C.sub.2-C.sub.6)alkyl (meth)acrylamides.
[0058] Substituted alkyl (meth)acrylate monomers include those with
one or more hydroxyl groups in the alkyl radical, especially those
where the hydroxyl group is found at the P-position (2-position) in
the alkyl radical. Suitable hydroxyalkyl (meth)acrylate monomers
include those in which the substituted alkyl group is a
(C.sub.2-C.sub.6)alkyl, branched or unbranched. Exemplary
hydroxyalkyl (meth)acrylate monomers include, but are not limited
to: 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate,
2-hydroxypropyl methacrylate, 1-methyl-2-hydroxyethyl methacrylate,
2-hydroxy-propyl acrylate, 1-methyl-2-hydroxyethyl acrylate,
2-hydroxybutyl methacrylate, 2-hydroxybutyl acrylate and mixtures
thereof.
[0059] Other substituted (meth)acrylate and (meth)acrylamide
monomers include those with a dialkylamino group or
dialkylaminoalkyl group in the alkyl radical. Examples of such
substituted (meth)acrylates and (meth)acrylamides include, but are
not limited to: dimethylaminoethyl methacrylate, dimethylaminoethyl
acrylate, N,N-dimethylaminoethyl methacrylamide,
N,N-dimethyl-aminopropyl methacrylamide, N,N-dimethylaminobutyl
methacrylamide, N,N-di-ethylaminoethyl methacrylamide,
N,N-diethylaminopropyl methacrylamide, N,N-diethylaminobutyl
methacrylamide, N-(1,1-dimethyl-3-oxobutyl)acrylamide,
N-(1,3-diphenyl-1-ethyl-3-oxobutyl) acrylamide,
N-(1-methyl-1-phenyl-3-oxobutyl)methacrylamide, and 2-hydroxyethyl
acrylamide, N-methacrylamide of aminoethyl ethylene urea,
N-methacryloxy ethyl morpholine, N-maleimide of
dimethylaminopropylamine and mixtures thereof.
[0060] Other substituted (meth)acrylate monomers useful in the
present invention are silicon-containing monomers such as
.gamma.-propyl tri(C.sub.1-C.sub.6)alkoxysilyl (meth)acrylate,
.gamma.-propyl tri(C.sub.1-C.sub.6)alkylsilyl (meth)acrylate,
.gamma.-propyl di(C.sub.1-C.sub.6)alkoxy(C.sub.1-C.sub.6)alkylsilyl
(meth)acrylate, .gamma.-propyl
di(C.sub.1-C.sub.6)alkyl(C.sub.1-C.sub.6)alkoxysilyl
(meth)acrylate, vinyl tri(C.sub.1-C.sub.6)alkoxysilyl
(meth)acrylate, vinyl
di(C.sub.1-C.sub.6)alkoxy(C.sub.1-C.sub.6)alkylsilyl
(meth)acrylate, vinyl
(C.sub.1-C.sub.6)alkoxydi(C.sub.1-C.sub.6)alkylsilyl
(meth)acrylate, vinyl tri(C.sub.1-C.sub.6)alkylsilyl
(meth)acrylate, and mixtures thereof.
[0061] The vinylaromatic monomers useful as unsaturated monomers in
the present invention include, but are not limited to: styrene,
.alpha.-methylstyrene, vinyltoluene, p-methylstyrene,
ethylvinylbenzene, vinylnaphthalene, vinylxylenes, and mixtures
thereof. The vinylaromatic monomers also include their
corresponding substituted counterparts, such as halogenated
derivatives, i.e., containing one or more halogen groups, such as
fluorine, chlorine or bromine; and nitro, cyano,
(C.sub.1-C.sub.10)alkoxy, halo(C.sub.1-C.sub.10)alkyl,
carb(C.sub.1-C.sub.10)alkoxy, carboxy, amino,
(C.sub.1-C.sub.10)alkylamino derivatives and the like.
[0062] The nitrogen-containing compounds and their thio-analogs
useful as unsaturated monomers in the present invention include,
but are not limited to: vinylpyridines such as 2-vinylpyridine or
4-vinylpyridine; lower alkyl (C.sub.1-C.sub.8) substituted N-vinyl
pyridines such as 2-methyl-5-vinyl-pyridine,
2-ethyl-5-vinylpyridine, 3-methyl-5-vinylpyridine,
2,3-dimethyl-5-vinyl-pyridine, and
2-methyl-3-ethyl-5-vinylpyridine; methyl-substituted quinolines and
isoquinolines; N-vinylcaprolactam; N-vinylbutyrolactam;
N-vinylpyrrolidone; vinyl imidazole; N-vinyl carbazole;
N-vinyl-succinimide; (meth)acrylonitrile; o-, m-, or
p-aminostyrene; maleimide; N-vinyl-oxazolidone; N,N-dimethyl
aminoethyl-vinyl-ether; ethyl-2-cyano acrylate; vinyl acetonitrile;
N-vinylphthalimide; N-vinyl-pyrrolidones such as
N-vinyl-thio-pyrrolidone, 3 methyl-1-vinyl-pyrrolidone,
4-methyl-1-vinyl-pyrrolidone, 5-methyl-1-vinyl-pyrrolidone,
3-ethyl-1-vinyl-pyrrolidone, 3-butyl-1-vinyl-pyrrolidone,
3,3-dimethyl-1-vinyl-pyrrolidone, 4,5-dimethyl-1-vinyl-pyrrolidone,
5,5-dimethyl-1-vinyl-pyrrolidone,
3,3,5-trimethyl-1-vinyl-pyrrolidone, 4-ethyl-1-vinyl-pyrrolidone,
5-methyl-5-ethyl-1-vinyl-pyrrolidone and
3,4,5-trimethyl-1-vinyl-pyrrolidone; vinyl pyrroles; vinyl
anilines; and vinyl piperidines.
[0063] The substituted ethylene monomers useful as unsaturated
monomers is in the present invention include, but are not limited
to: vinyl acetate, vinyl formamide, vinyl chloride, vinyl fluoride,
vinyl bromide, vinylidene chloride, vinylidene fluoride and
vinylidene bromide.
[0064] The polymers useful as porogens in the present invention may
be prepared by a variety of polymerization techniques, such as
solution polymerization or emulsion polymerization, and preferably
by solution polymerization. It is preferred that the polymers of
the present invention are prepared using anionic polymerization or
free radical polymerization techniques. The solution polymers
useful in the present invention may be linear, branched or grafted
and may be copolymers or homopolymers. Particularly suitable
solution polymers include cross-linked copolymers. Typically, the
molecular weight of these polymers is in the range of 5,000 to
1,000,000. Exemplary molecular weight ranges are from 10,000 to
500,000, and from 10,000 to 100,000. The polydispersity of these
materials is in the range of 1 to 20, preferably 1.001 to 15, and
more preferably 1.001 to 10.
[0065] The solution polymers of the present invention are generally
prepared in a non-aqueous solvent. Suitable solvents for such
polymerizations are well known to those skilled in the art.
Examples of such solvents include, but are not limited to:
hydrocarbons, such as alkanes, fluorinated hydrocarbons, and
aromatic hydrocarbons, ethers, ketones, esters, alcohols and
mixtures thereof. Particularly suitable solvents include dodecane,
mesitylene, xylenes, diphenyl ether, gamma-butyrolactone, ethyl
lactate, propyleneglycol monomethyl ether acetate, caprolactone,
2-hepatanone, methylisobutyl ketone, diisobutylketone,
propyleneglycol monomethyl ether, decanol, and t-butanol.
[0066] The solution polymers of the present invention may be
prepared by a variety of methods, such as those disclosed in U.S.
Pat. No. 5,863,996 (Graham) and European Patent Application EP 1
088 848 (Allen et al.). The emulsion polymers useful in the present
invention are generally prepared the methods described in Allen et
al.
[0067] The polymer particle porogens of the present invention
include cross-linked polymer chains. Any amount of cross-linker is
suitable for use in the present invention. Typically, the porogens
of the present invention contain at least 1% by weight, based on
the weight of the porogen, of cross-linker. Up to and including
100% cross-linking agent, based on the weight of the porogen, may
be effectively used in the particles of the present invention. It
is preferred that the amount of cross-linker is from 1% to 80%, and
more preferably from 1% to 60%. It will be appreciated by those
skilled in the art that as the amount of cross-linker in the
porogen increases, the conditions for removal of the porogen from
the dielectric matrix may change.
[0068] Suitable cross-linkers useful in the present invention
include di-, tri-, tetra-, or higher multi-functional ethylenically
unsaturated monomers. Examples of cross-linkers useful in the
present invention include, but are not limited to: trivinylbenzene,
divinyltoluene, divinylpyridine, divinylnaphthalene and
divinylxylene; and such as ethyleneglycol diacrylate,
trimethylolpropane triacrylate, diethyleneglycol divinyl ether,
trivinylcyclohexane, allyl methacrylate, ethyleneglycol
dimethacrylate, diethyleneglycol dimethacrylate, propyleneglycol
dimethacrylate, propyleneglycol diacrylate, trimethylolpropane
trimethacrylate, divinyl benzene, glycidyl methacrylate,
2,2-dimethylpropane 1,3 diacrylate, 1,3-butylene glycol diacrylate,
1,3-butylene glycol dimethacrylate, 1,4-butanediol diacrylate,
diethylene glycol diacrylate, diethylene glycol dimethacrylate,
1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate,
tripropylene glycol diacrylate, triethylene glycol dimethacrylate,
tetraethylene glycol diacrylate, polyethylene glycol 200
diacrylate, tetraethylene glycol dimethacrylate, polyethylene
glycol dimethacrylate, ethoxylated bisphenol A diacrylate,
ethoxylated bisphenol A dimethacrylate, polyethylene glycol 600
dimethacrylate, poly(butanediol) diacrylate, pentaerythritol
triacrylate, trimethylolpropane triethoxy triacrylate, glyceryl
propoxy triacrylate, pentaerythritol tetraacrylate, pentaerythritol
tetramethacrylate, dipentaerythritol monohydroxypentaacrylate, and
mixtures thereof Silyl containing monomers that are capable of
undergoing cross-linking may also be used as cross-linkers, such
as, but not limited to, divinylsilane, trivinylsilane,
dimethyldivinylsilane, divinylmethylsilane, methyltrivinylsilane,
diphenyldivinylsilane, divinylphenylsilane, trivinylphenylsilane,
divinylmethylphenylsilane, tetravinylsilane,
dimethylvinyldisiloxane, poly(methylvinylsiloxane),
poly(vinylhydrosiloxane), poly(phenylvinylsiloxane),
tetraallylsilane, 1,3-dimethyl tetravinyldisiloxane, 1,3-divinyl
tetramethyldisiloxane and mixtures thereof.
[0069] Substantially compatibilized porogens, typically have a
molecular weight in the range of 5,000 to 1,000,000, such as from
10,000 to 500,000, and more typically 10,000 to 100,000. The
polydispersity of these materials is in the range of I to 20,
preferably 1.001 to 15, and more preferably 1.001 to 10. Typically,
the useful particle size range for the cross-linked polymeric
porogen particles described above is up to 1,000 nm, such as that
having a mean particle size in the range of 0.5 to 1000 nm. It is
preferred that the mean particle size is in the range of 0.5 to 200
nm, more preferably from 0.5 to 50 nm, and most preferably from 1
nm to 20 nm.
[0070] Suitable block copolymers having labile components are those
disclosed in U.S. Pat. Nos. 5,776,990 and 6,093,636. Such block
copolymers may be prepared, for example, by using as pore forming
material highly branched aliphatic esters that have functional
groups that are further functionalized with appropriate reactive
groups such that the functionalized aliphatic esters are
incorporated into, i.e. copolymerized with, the vitrifying polymer
matrix.
[0071] When the removable porogens are not components of a block
copolymer, they may be combined with the B-staged organic
polysilica resin by any methods known in the art. Typically, the
B-staged material is first dissolved in a suitable solvent, such as
methyl isobutyl ketone, diisobutyl ketone, 2-heptanone,
.gamma.-butyrolactone, .gamma.-caprolactone, ethyl lactate
propyleneglycol monomethyl ether acetate,
propyleneglycol-monomethyl ether, diphenyl ether, anisole, n-amyl
acetate, n-butyl acetate, cyclohexanone, N-methyl-2-pyrrolidone,
N,N'-dimethylpropyleneurea, mesitylene, xylenes, or mixtures
thereof to form a solution. The porogens are then dispersed or
dissolved within the solution. The resulting composition (e.g.
dispersion, suspension or solution) is then deposited on a
substrate by methods known in the art for depositing B-staged
dielectric materials.
[0072] The coating enhancers are typically added to the B-staged
organic polysilica resins in an amount sufficient to provide the
desired uniformity and pinhole defect-free cap layers. For example,
the coating enhancers may be added to the B-staged materials in any
amount of from 1 to 90 wt %, based on the weight of the B-staged
material, preferably from >3 wt %, more preferably .gtoreq.5 wt
%, and even more preferably from .gtoreq.10 wt %. There is no real
upper limit on the amount of coating enhancer that can be used. It
is preferred to use the lowest amount of coating enhancer that
provides the desired cap layer quality. For example, certain
coating enhancers may raise the dielectric constant of the cap
layer. As an overall low dielectric constant is desired for the
device, it is preferred to the least amount of such coating
enhancers required to provide the desired pinhole defect-free cap
layer, to avoid unnecessarily increasing the overall dielectric
constant of the dielectric layer-cap layer stack. Alternatively, it
may be desired to use a coating enhancer such as a removable
porogen which may provide a porous cap layer, thus reducing the
dielectric constant of the cap layer as well as the overall
dielectric constant of the dielectric layer-cap layer stack. When a
compatibilized polymeric porogen is used as the coating enhancer,
it is preferably used in an amount of >3 wt % to 25 wt %, more
preferably 5 to 20 wt % and still more preferably 8 to 15 wt %.
[0073] The cap layer compositions may further include one or more
organic solvents. A solvent is preferred. Any solvent that
dissolves, disperses, suspends or otherwise is capable of
delivering the B-staged organic polysilica resin and the coating
enhancer to the substrate is suitable. Such organic solvents are
well known in the art and include, but are not limited to, ketones
such as methyl isobutyl ketone, diisobutyl ketone, cyclohexanone,
and 2-heptanone, lactones such as .gamma.-butyrolactone and
.gamma.-caprolactone, esters such as ethyl lactate, propyleneglycol
monomethyl ether acetate, n-amyl acetate, n-butyl acetate, ethers
such as diphenyl ether and anisole, glycol ethers such as
propyleneglycol monomethyl ether, N-methyl-2-pyrrolidone,
N,N'-dimethylpropyleneurea, aromatic hydrocarbons such as
mesitylene, toluene, and xylenes, and mixtures of solvents.
Alternatively, solvents may consist of highly pressurized gases,
such as supercritical carbon dioxide, with one or more co-solvents
or additives to provide the desired solvency properties. It is
preferred that a composition including one or more B-staged organic
polysilica materials and one or more organic solvents is disposed
on a substrate. Once such a composition is disposed on the
substrate, the solvent may be removed prior to or during the step
of curing the B-staged organic polysilica material.
[0074] The cap layer compositions may further include one or more
additional components, such as inorganic compounds. Suitable
inorganic compounds include, but are not limited to silica,
alumina, ceria, zirconia, silicon carbide, silicon nitride and the
like, including mixtures thereof. Such inorganic particles may be
very fine (ultrafine) powders, sols, colloids, or in any other
suitable form. As an example, silica, alumina, and zirconia may be
synthesized by a fumed method in which oxygen and hydrogen are
reacted with silicon chloride, aluminum chloride or titanium
chloride in a gas phase. A sol-gel method may be also be used. In
this method, a metal alkoxide such as tetraethoxysilane or an
aluminum alkoxide is hydrolyzed and condensation is performed.
Colloidal silica is a dispersion of highly pure silicic anhydride
in a hydrophilic organic solvent, such as with a solids content in
the range of 10 to 40%, where the silica particles have an average
diameter of 5 to 30 nm and preferably 10 to 20 nm. Colloidal
silica, such as methanol silica sol or iso-propanol silica sol, and
colloidal alumina are generally commercially available, such as
from Nissan Chemical Industries, Ltd.
[0075] Alternatively, the inorganic compounds may be co-condensed
or co-hydrolyzed with any of the above described silicon-containing
monomers, oligomers or polymers. Metal alkoxides are typically used
as the inorganic compounds for use in such co-condensations or
co-hydrolyses. Cerium alkoxides, aluminum alkoxides and zirconium
alkoxides are the most useful metal alkoxides for this application.
Useful alkoxide moieties are (C.sub.1-C.sub.6)alkoxides and more
particularly (C.sub.1-C.sub.3)alkoxides.
[0076] One or more stabilizing compounds for the B-staged organic
polysilica resin may also be used in the cap layer compositions.
Such stabilizing compounds typically stabilize the organic
polysilica resin against premature condensation or polymerization.
Suitable stabilizing compounds include, but are not limited to,
organic acids having 2 carbons or more and having a pKa of 1 to 4,
and organic acids capable of functioning as a chelating agent. The
amount of such stabilizing compounds is in the range of I to 10,000
ppm and preferably 5 to 5000 ppm.
[0077] Other optional components that may be added to the present
cap layer compositions include, but are not limited to, copper
chelating agents, base curing agents, acid curing agents and the
like. Any useful copper chelating agent may be used, such as
hydroxylamine, hydroxylamine derivatives, benzotriazole, and the
like. Base curing agents include, bases, thermal base generators
and photobase generators. Complexes of bases with certain acids may
also be suitable base curing agents. Such base curing agents are
well known to those skilled in the art. Acid curing agents include
thermal acid generators and photoacid generators. The useful acid
curing agents are well-known to those skilled in the art. The
amount of such optional base and acid curing agents present in the
compositions is typically small, such as in catalytic quantities
and are well within the abilities of those in the art.
[0078] The cap layer compositions are disposed on a dielectric
substrate by any suitable means, such as, but not limited to, spin
coating, spray coating or doctor blading. Spin coating is
preferred. Such disposing means typically provide a film, layer or
coating of B-staged material. The dielectric substrate may be
partially cured or fully cured. The only concern being that the
dielectric substrate is sufficiently cured to prevent intermixing
with the cap layer composition.
[0079] Any dielectric material used in the manufacture of
electronic devices, such as integrated circuits, may benefit from
the cap layer of the present invention. Suitable dielectric
materials include, but are not limited to organic polysilica
materials, silicon dioxide, fluorinated silicon dioxide,
benzocyclobutenes, poly(arylene ethers), poly(aryl esters),
poly(ether ketones), polycarbonates, polyimides, fluorinated
polyimides, polynorbornenes, polyaromatic hydrocarbons such as
polynaphthalene, polyquinoxalines, poly(perfluorinated
hydrocarbons) such as poly(tetrafluoroethylene), and
polybenzoxazoles. Suitable organic polysilica dielectric materials
are any having the compositions described above. Preferably, the
dielectrics are porous. Porous organic polysilica dielectrics are
well known and are disclosed in U.S. Pat. No. 6,271,273 (You et
al.) and U.S. Pat. No. 5,895,263 (Carter et al.). In one
embodiment, the dielectric material is a thermally degradable
material, which can be subsequently selectively removed during
further processing of an electronic device, i.e. after curing of
any applied cap layer. Suitable thermally degradable polymers are
those disclosed in U.S. Pat. No. 6,165,890 (Kohl et al.).
[0080] Once the cap layer composition is applied to the dielectric
substrate, the solvent is removed such as by heating at a
temperature of 90.degree. to 150.degree. C. for 10 to 120 seconds.
The cap layer is then typically soft baked at a temperature of
150.degree. to 250.degree. for 10 to 360 seconds to at least
partially cure the cap layer.
[0081] Sufficient cap layer composition is typically applied to the
dielectric substrate to provide a cap layer having a desired
thickness. Typical thicknesses range from 100 to 1000 .ANG. and
preferably from 400 to 600 .ANG..
[0082] More than one cap layer may be used according to the present
invention. For example, a second cap layer may be applied to the
present cap layer to provide a dual cap layer structure. The second
cap layer may be any conventional cap layer such as organic
polysilica cap layer, silicon dioxide, silicon carbide, silicon
oxynitride, silicon nitride, silicon oxycarbide, polyarylene
ethers, and the like. Alternatively, the present organic polysilica
cap layers may be used as the second cap layer of a dual cap layer
structure (or the second or third cap layer of a three cap layer
structure, etc.) In such application, the present organic
polysilica cap layer composition is disposed on a cap layer which
is disposed on a dielectric layer. In one embodiment, where two
organic polysilica cap layers are used, it is preferred that the
first (or cap layer adjacent the dielectric layer) cap layer have a
higher silicon carbide content that the second (or upper) cap
layer.
[0083] To be useful as coating enhancers in the present invention,
such compounds, if they remain in the cap layer following final
cure, must not interfere with or adversely affect the properties of
the cap layer. Preferably, such coating enhancers are at least
partially removable under conditions which do not adversely affect
the organic polysilica material, preferably substantially
removable, and more preferably completely removable. The coating
enhancers may be removed prior, during or after complete or final
curing of the cap layer material. Preferably, the coating enhancers
are removed prior to or during the step of completely curing (final
cure) the organic polysilica cap layer material, and more
preferably during the final curing step. When the cap layer needs
to be dense to fulfill its function, the coating enhancers are
typically removed after such function has been fulfilled. By
"removable" is meant that the coating enhancer volatilizes,
depolymerizes or otherwise breaks down into volatile components or
fragments which are then removed from, or migrate out of, the
organic polysilica material. Any procedures or conditions which at
least partially remove the coating enhancer without substantially
degrading the organic polysilica material, that is, where less than
5% by weight of the dielectric material is lost, may be used. It is
preferred that the coating enhancer is substantially removed.
Suitable methods of removing the coating enhancers are those used
for the removal of porogens. Typical methods of removal include,
but are not limited to: exposure to heat, vacuum, pressure or
radiation such as, but not limited to, actinic, IR, microwave, UV,
x-ray, gamma ray, alpha particles, neutron beam or electron beam.
It will be appreciated that more than one method of removing the
coating enhancer may be used, such as a combination of heat and
actinic radiation. It is preferred that the organic polysilica
material is exposed to heat or UV light to remove the coating
enhancer. It will also be appreciated by those skilled in the art
that other methods of coating enhancer removal, such as by atom
abstraction, may be employed.
[0084] The coating enhancers can be thermally removed under vacuum,
nitrogen, argon, mixtures of nitrogen and hydrogen, such as forming
gas, or other inert or reducing atmosphere, air as well as under
oxidizing atmospheres. The coating enhancers may be removed at any
temperature that is higher than the thermal curing temperature and
lower than the thermal decomposition temperature of the organic
polysilica material. Typically, the polymeric porogen coating
enhancers may be removed at temperatures in the range of
150.degree. to 450.degree. C. and preferably in the range of
250.degree. to 425.degree. C. Under preferable thermal removal
conditions, the organic polysilica material is heated to a
temperature of 350.degree. to 400.degree. C. It will be recognized
by those skilled in the art that the particular removal temperature
of a coating enhancer will vary according to composition of the
coating enhancer. Such heating may be provided by means of an oven
or microwave. Typically, the coating enhancers of the present
invention are removed upon heating for a period of time in the
range of 1 to 120 minutes. After removal from the organic
polysilica material, 0 to 20% by weight of the coating enhancer
typically remains in the porous organic polysilica material. In
another embodiment, when a coating enhancer is removed by exposure
to radiation, the coating enhancer is typically exposed under an
inert atmosphere, such as nitrogen, to a radiation source, such as,
but not limited to, visible or ultraviolet light.
[0085] In one embodiment, the coating enhancers are removed from
the partially cured cap layer. In this process, the cap layer is
heated in a furnace to the desired curing temperature, e.g.
350.degree. to 500.degree. C. and preferably from 400.degree. to
475.degree. C., for a period of time sufficient to complete the
organic polysilica curing process. Such times are well known to
those skilled in the art. During such final cure step, the coating
enhancers may also be removed. In general, when such volatile
materials are moved from a fully cured dielectric material, pores
or voids remain. Accordingly, porous organic polysilica cap layers
are obtained.
[0086] The pores in such porous organic polysilica cap layers are
substantially the same size as that of the coating enhancer used,
particularly when the coating enhancer is a porogen particle. The
pore size of the pores in the porous organic polysilica material
made by a removable coating enhancer is from 0.5 to 1000 nm,
preferably from 0.5 to 200 nm, more preferably from 1 to 50 nm, and
still more preferably from 1 to 20 nm.
[0087] The present invention provides a structure comprising a
first layer of a dielectric material and a cap layer disposed on
the dielectric layer, wherein the cap layer is porous. Such cap
layer typically has a porosity substantially equal to the amount of
porogen used. The cap layer is preferably an organic polysilica cap
layer. It is also preferred that the dielectric layer is porous. It
is further preferred that the dielectric layer in such structure is
an organic polysilica dielectric material. Also provided by this
invention is a structure comprising a porous first layer of an
organic polysilica dielectric material and a porous cap layer
disposed on the dielectric material. Preferably, such cap layer
comprises an organic polysilica material.
[0088] In general, the porous cap layers of the present invention
have a reduced dielectric constant as compared to the same cap
layer that is non-porous. Useful organic polysilica cap layers are
those having a dielectric constant of .ltoreq.3, preferably
.ltoreq.2.9, more preferably .ltoreq.2.8 and still more preferably
in the range of 2.5 to 2.8.
[0089] The cap layers of the present invention are particularly
useful with low dielectric constant (k.ltoreq.3) dielectric
materials. Structures comprising a dielectric layer having a
dielectric constant of .ltoreq.3 and an organic polysilica cap
layer disposed on the dielectric layer, wherein the organic
polysilica cap layer has a dielectric constant of .ltoreq.2.9. Such
dielectric layers preferably include dielectric materials having a
dielectric constant of .ltoreq.2.8 and more preferably
.ltoreq.2.5.
[0090] In general, a cap layer has an etch selectivity of 3:1 to
10:1 or greater as compared to the dielectric material it is
disposed on. Preferably, the etch selectivity is 5:1 or greater.
The particular cap layer B-staged organic polysilica resin is
selected to provide such an etch differential with the dielectric
layer to which it is applied. When an organic polysilica cap layer
is used with an organic polysilica dielectric material such as
methyl silsesquioxane, the cap layer organic polysilica is selected
so as to have a higher silicon content to provide the requisite
etch differential.
[0091] The cap layers of the present invention are typically
selected such that the difference in etch selectivities between the
cap layer and the dielectric layer on which it is disposed is 10%
or greater, preferably 20% or greater and more preferably 40% or
greater. This is particularly the case when the dielectric layer is
a porous organic polysilica material. In a further embodiment, the
present invention provides a structure comprising a porous first
layer of an organic polysilica dielectric material having a first
etch selectivity and a porous cap layer disposed on the dielectric
material having a second etch selectivity, wherein the difference
in etch selectivities is 10% or greater. Also provided are
structures comprising a dielectric layer having a density of
.ltoreq.1 g/L and a cap layer disposed on the dielectric layer and
having a density of .gtoreq.1 g/L. Preferably such cap layers are
organic polysilica materials. Such organic polysilica cap layers
preferably have a density of .gtoreq.1.1, and more preferably
.gtoreq.1.2 g/L.
[0092] In a typical process, a dielectric composition, such as a
B-staged organic polysilica resin including a porogen (a plurality
of polymeric porogen particles), is disposed on a substrate. The
B-staged dielectric resin is then at least partially cured at a
temperature of up to 250.degree. C. to form the dielectric
substrate. A present cap later composition is then disposed, such
as by spin coating, on the partially cured organic polysilica
dielectric material to provide a two-layer stack or structure. The
stack is then set by either partially curing the cap layer or fully
curing the materials in the stack at high temperature
(.gtoreq.400.degree. C.). The polymeric porogen is removed from the
organic polysilica dielectric material during the final curing
step. Likewise, the cap layer coating enhancer is removed during
the final curing step. Preferably, the porogen used in the B-staged
organic polysilica dielectric material is the same as the coating
enhancer used in the cap layer composition. Such process has the
advantage of a reduced number of steps as compared to fully curing
each layer individually, as well as providing improved adhesion
between the organic polysilica dielectric material and the cap
layer material.
[0093] Alternatively, the dielectric material may be fully cured
prior to disposing the present cap layer compositions on the
dielectric substrate.
[0094] The present cap layers are useful in the manufacture of
electronic devices, particularly integrated circuits. In such
manufacturing process, a low dielectric constant dielectric
material is disposed on a substrate; the low dielectric constant
dielectric material is then at least partially cured to form a
dielectric material layer; a cap layer composition including a
B-staged organic polysilica resin and a coating enhancer is
disposed on the dielectric material layer, wherein the coating
enhancer is present in an amount sufficient to provide a
pinhole-free cap layer; the B-staged organic polysilica resin is at
least partially curing the to form a cap layer; the coating
enhancer is optionally removed; and the cap layer is the optionally
completely cured. Such cap layer may then have another cap layer
disposed on it, as described above. Alternatively, a pattern may be
formed in the cap layer. Such patterning typically involves (i)
coating the cap layer with a positive or negative photoresist, such
as those marketed by Shipley Company; (ii) imagewise exposing,
through a mask, the photoresist to radiation, such as light of
appropriate wavelength or e-beam; (iii) developing the image in the
resist, e.g., with a suitable developer; and (iv) transferring the
image through the cap layer to the substrate with a suitable
transfer technique such as reactive ion etching. Such etching
creates apertures in the cap layer and the dielectric material.
Optionally, an antireflective coating is disposed between the
photoresist layer and the cap layer. In the alternative, an
antireflective coating may be applied to the surface of the
photoresist. Such lithographic patterning techniques are well known
to those skilled in the art.
[0095] While the above description has been written exemplifying an
organic polysilica material as the cap layer material, it will be
appreciated by those skilled in the art that the present coating
enhancers may be used for other spin-on or liquid applied cap layer
materials, such as hydrogen silsesquioxane, spin-on glasses, i.e.
silicon dioxide precursors, poly(arylene ethers) and the like.
[0096] The following examples are presented to illustrate further
various aspects of the present invention, but are not intended to
limit the scope of the invention in any aspect.
EXAMPLE 1
[0097] Silicon wafers (8 inch or 20 cm diameter) were spin coated
with an organic polysilica composition containing 30% solids of
methyl silsesquioxane co-condensed with a tetraalkoxyorthosilicate
in an organic solvent using a commercially available coating track.
The organic polysilica composition contained 22.5% of a compatible
porogen by weight. The composition was spin coated on the wafers at
200 rpm and then a film was spread to a thickness of ca. 4000 .ANG.
at 3000 rpm. Excess material was removed from the back side of the
wafer using a conventional edge bead remover and back side rinse
agent. The films were then processed on a hot plate at 90.degree.
C. to partially remove the solvent, followed by heating at
230.degree. C. to partially cure the organic polysilica layer.
EXAMPLE 2 (COMPARATIVE)
[0098] An organic polysilica cap layer composition containing 3%
w/w of a copolymer of methyl silsesquioxane-tetraethylorthosilicate
(55:45 molar ratio, with a molecular weight of ca. 6500) in
propyleneglycol monomethyl ether acetate with 150 ppm of an acid
stabilizer was prepared. The cap layer film has an atom-weight
composition of 43% w/w silicon and 10% w/w carbon, which provided
an etch selectivity of 5x to lOx as compared to the organic
polysilica dielectric layer.
[0099] The cap layer composition was deposited on a wafer sample
from Example 1 by spin coating (2500 rpm) and had a thickness of
ca. 440-550 .ANG.. The sample was then cured in a furnace at
450.degree. C. The surface of the resulting cap layer was analyzed
by scanning electron microscopy for the presence of pinhole defects
using a KLA-Tencor instrument at 200,000 magnification. FIG. 1 is a
SEM of this cap layer which clearly shows the presence of pinhole
defects.
EXAMPLE 3
[0100] The procedure of Example 2 was repeated except that the cap
layer composition further included 3% by weight of a compatibilized
polymeric porogen as a coating enhancer. The porogen was a
copolymer of PPG260MA/trimethylene glycol dimethacrylate (90/10).
"PPG260MA" refers to a polypropyleneglycol ester of methacrylic
acid, where the polypropyleneglycol has an average molecular weight
of 260. Following furnace curing, the surface of the cap layer was
evaluated. FIG. 2 is a SEM of this cap layer which still shows the
presence of pinhole defects. The amount of the coating enhancer is
insufficient to provide a pinhole defect-free film.
EXAMPLE 4
[0101] The procedure of Example 2 was repeated except that 10% by
weight of the compatibilized polymeric porogen was used as the
coating enhancer. FIG. 3 is a SEM of this cap layer which still
shows the surface to be free of pinhole defects.
* * * * *