U.S. patent application number 13/670728 was filed with the patent office on 2015-02-26 for phase shift mask blank and phase shift mask.
This patent application is currently assigned to HOYA CORPORATION. The applicant listed for this patent is HOYA CORPORATION. Invention is credited to Masahiro Hashimoto, Hiroyuki Iwashita, Atsushi Kominato, Hiroaki Shishido.
Application Number | 20150056539 13/670728 |
Document ID | / |
Family ID | 47830126 |
Filed Date | 2015-02-26 |
United States Patent
Application |
20150056539 |
Kind Code |
A9 |
Iwashita; Hiroyuki ; et
al. |
February 26, 2015 |
PHASE SHIFT MASK BLANK AND PHASE SHIFT MASK
Abstract
The present invention provides a photomask blank used for
producing a photomask to which an ArF excimer laser light is
applied, wherein: a light-shielding film is provided on a light
transmissive substrate; the light-shielding film has a laminated
structure in which a lower layer, an interlayer and an upper layer
are laminated in this order from the side close to the light
transmissive substrate; the thickness of the entire light-shielding
film is 60 nm or less; the lower layer is made of a film containing
a metal and has a first etching rate; the upper layer is made of a
film containing a metal and has a third etching rate; the
interlayer is made of a film containing the same metal as that
contained in the lower layer or the upper layer and has a second
etching rate that is lower than the first etching rate and the
third etching rate; and the thickness of the interlayer is 30% or
less of the thickness of the entire light-shielding film.
Inventors: |
Iwashita; Hiroyuki; (Tokyo,
JP) ; Shishido; Hiroaki; (Tokyo, JP) ;
Kominato; Atsushi; (Tokyo, JP) ; Hashimoto;
Masahiro; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HOYA CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
HOYA CORPORATION
Tokyo
JP
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20130065166 A1 |
March 14, 2013 |
|
|
Family ID: |
47830126 |
Appl. No.: |
13/670728 |
Filed: |
November 7, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13001365 |
Dec 23, 2010 |
8329364 |
|
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PCT/JP2009/061574 |
Jun 25, 2009 |
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13670728 |
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61075558 |
Jun 25, 2008 |
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Current U.S.
Class: |
430/5 |
Current CPC
Class: |
G03F 1/26 20130101; G03F
1/28 20130101; G03F 1/58 20130101 |
Class at
Publication: |
430/5 |
International
Class: |
G03F 1/26 20120101
G03F001/26 |
Claims
1. A phase shift mask blank, which is an original plate of a phase
shift mask exposed to an ArF excimer laser light, wherein: the
phase shift mask blank has a light transmissive substrate, a phase
shift film and a light-shielding film; the phase shift film is
provided between the light transmissive substrate and the
light-shielding film; the phase shift amount of the phase shift
film with respect to the ArF excimer laser light is 160.degree. to
200.degree. and the transmittance of the phase shift film is 2 to
40%; the light-shielding film has a laminated structure in which a
lower layer, an interlayer and un upper layer are laminated in this
order from the side close to the light transmissive substrate; the
thickness of the entire light-shielding film is 60 nm or less; the
lower layer is made of a film containing a metal and has a first
etching rate; the upper layer is made of a film containing a metal
and has a third etching rate; and the interlayer is made of a
metallic nitride film, which contains the same metal as that
contained in the lower layer or the upper layer and nitrogen, and
has a second etching rate that is lower than the first etching rate
and the third etching rate.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a Divisional of application Ser. No. 13/001,365
filed Dec. 23, 2010, claiming priority based on International
Application No. PCT/JP2009/061574 filed Jun. 25, 2009, which claims
priority from U.S. Provisional Patent Application No. 61/075,558
filed Jun. 25, 2008, the contents of all of which are incorporated
herein by reference in their entirety.
TECHNICAL FIELD
[0002] The present invention relates to a phase shift mask blank
and a phase shift mask.
BACKGROUND ART
[0003] In general, in the production processes of high-density
semiconductor integrated circuits such as LSI, color filters for
CCD (charge-coupled device) and LCD (liquid crystal display
device), magnetic heads, etc., microfabrication utilizing the
photolithographic technique using photomasks is performed.
[0004] In this microfabrication, a photomask, in which a
light-shielding film consisting of a metal thin film such as a
chromium film is generally formed on a light transmissive substrate
made of quartz glass, aluminosilicate glass or the like by means of
sputtering, vacuum deposition or the like to provide a photomask
blank, wherein the light-shielding film is formed to have a
predetermined pattern, is used.
[0005] A photomask is produced using such a photomask blank with
the following processes: an exposure process in which a desired
pattern exposure is applied to a resist film formed on the
photomask blank; a development process in which, after the desired
pattern exposure is applied to the resist film formed on the
photomask blank, a developing solution is supplied thereto to
dissolve portions of the resist film soluble in the developing
solution, thereby forming a resist pattern; a etching process in
which, using the obtained resist pattern as a mask, portions in
which a light-shielding film is exposed with the resist pattern not
formed are removed by etching, such as, wet etching using an
etching solution consisting of a mixed aqueous solution of ceric
ammonium nitrate and perchloric acid, and dry etching using
chlorine gas, thereby forming a predetermined mask pattern on a
light transmissive substrate; and a stripping/removing process in
which the remaining resist pattern is stripped and removed.
[0006] During patterning of the light-shielding film in the etching
process, the resist pattern formed on the light-shielding film must
remain with a sufficient film thickness. However, when the resist
film thickness is increased, the aspect ratio is increased, and
this causes the problem of pattern collapsing, etc., particularly
in the case where a fine pattern is to be formed. Therefore, in
order to miniaturize a mask pattern formed on a photomask, it is
required to decrease the thickness of a resist film formed on a
photomask blank.
[0007] Regarding this point, Japanese Laid-Open Patent Publication
No. 2007-33470 (Patent Document 1) discloses a photomask blank
comprising a light-shielding film having a thickness of 100 nm or
less, wherein the film has a structure in which the percentage of
the film thickness of a chromium-based compound having a high
etching rate is 70% or more to enable reduction in etching time,
thereby realizing miniaturization of the resist. Specifically,
Patent Document 1 discloses a photomask blank in which a
semitransparent film, a CrON film, a Cr film and a CrON film are
laminated on a light transmissive substrate, wherein the percentage
of the thickness of the CrON film is 70% or more.
[0008] However, regarding the above-described CrON film, it is just
that the optical density per unit film thickness at a wavelength of
450 nm is set, and regarding a wavelength of exposure light equal
to or less than wave length of an ArF excimer laser light, no
optimization has been made. In particular, in the case of hyper-NA
lithography, the angle of light incidence relative to a photomask
becomes shallower, and this causes the problem that a miniaturized
mask pattern itself shades a transfer image (shadowing). When a
light-shielding film is thick, reduction of the amount of light
(deterioration of contrast) due to shadowing is highly influential.
In addition, the cross-section shape is prone to vary, and this,
together with shadowing, causes reduction of transfer accuracy of
CD (Critical Dimension).
[0009] Further, in order to improve resolution performance by finer
processing of a photomask, a phase shift mask blank, in which, for
example, a phase shift film having the transmittance of several
percent to several tens percent with the phase of transmitted light
being shifted 180.degree. (e.g., a phase shift film made of a metal
silicide oxide film or a metal silicide oxide nitride film
described in the specification of Japanese Patent No. 2837803
(Patent Document 2), a metal silicide nitride film described in the
specification of Japanese Patent No. 2966369 (Patent Document 3) or
the like) and a light-shielding film such as a chromium film having
etching selectivity relative to the phase shift film are formed on
the above-described light transmissive substrate by means of
sputtering, vacuum deposition or the like, and a phase shift mask
in which these light-shielding film and phase shift film are formed
in a predetermined pattern are used.
[0010] Regarding the structure of the phase shift mask, a general
example in the case where the transmittance of the phase shift film
is 10% or more (e.g., 10% to 40%) is described in the specification
of Japanese Patent No. 3445329 (Patent Document 4; Example 1 and
FIG. 1), and this is a phase shift mask having a structure in which
a light-shielding film pattern is formed on a phase shift film
pattern formed within a pattern transfer region and a
light-shielding film with a width of a predetermined value or more
is formed in a non-pattern-transfer region. Further, a general
example in the case where the transmittance of the phase shift film
is less than 10% (e.g., 2 to less than 10%) is described in the
specification of Japanese Patent No. 3411613 (Patent Document 5;
Example 1 and FIG. 1), and this is a phase shift mask having a
structure in which no light-shielding film pattern is formed on a
phase shift film pattern formed within a pattern transfer region
and a light-shielding film with a width of a predetermined value or
more is formed in a non-pattern-transfer region.
[0011] As recited in claims 25 to 29 in International Publication
WO 2004/090635 pamphlet (Patent Document 6), a phase shift mask
blank may have a structure in which a film for etching mask made of
an inorganic material having resistance to dry etching of a
light-shielding film is laminated on the light-shielding film,
which is formed on a phase shift film and comprises chromium.
[0012] [Patent Document 1] Japanese Laid-Open Patent Publication
No. 2007-33470 [0013] [Patent Document 2] Japanese Patent No.
2837803 [0014] [Patent Document 3] Japanese Patent No. 2966369
[0015] [Patent Document 4] Japanese Patent No. 3445329 [0016]
[Patent Document 5] Japanese Patent No. 3411613 [0017] [Patent
Document 6] International Publication WO 2004/090635 pamphlet
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0018] Under the above-described circumstances, a photomask blank
by which a fine mask pattern can be formed (e.g., a phase shift
blank) is desired. In addition, a photomask blank, by which a thin
resist film can be formed on a light-shielding film, wherein
pattern collapsing does not easily occur and good transfer accuracy
is provided as a result, is desired. Specifically, it is desired to
provide a photomask having a resolution desired for a generation of
hp 45 nm, hp 32 nm or beyond by reducing the thickness of the
resist film and the aspect ratio of the resist pattern in order to
prevent collapsing of the resist pattern.
[0019] In order to reduce the thickness of a resist film in a
photomask blank, it is required to shorten the etching time (ET) of
the light-shielding film, that is, to change the structure of the
light-shielding film.
[0020] The etching time (ET) is determined by the etching rate
(ER), the thickness of the light-shielding film (d) and the
cross-section angle adjustment time (over etching time) (OET) of
the light-shielding film pattern. The relationship between them is
as follows:
ET = d / ER + OET = CET + OET ( 1 ) ##EQU00001##
[0021] In formula (1), "CET" means clear etching (just etching)
time, and is time required for etching of a monitor pattern
(generally a several-mm-square hole pattern) to reach a substrate
or a lower-layer film such as a phase shift film.
[0022] Accordingly, it is desired to provide a photomask blank
having a light-shielding film with short etching time (ET) by
promoting improvement of the etching rate (ER), reduction in the
thickness (d) of the light-shielding film, reduction in over
etching time (OET), etc.
[0023] In order to reduce over etching time (OET), it is required
to reduce variation of the cross-section shape due to loading.
However, when the etching rate (ER) is too high, an under-cut
occurs during over etching, whereas when the etching rate (ER) is
too low, etching time (ET) becomes longer. Therefore, it is desired
to provide a photomask blank in which the etching rate in the
longitudinal direction (etching rate of each layer) is controlled
to enable reduction in over etching time (OET) as a result.
[0024] In order to increase the etching rate (ER), it is usually
required to decrease the content of metals. However, when the
content of metals is kept at a low level, the optical density per
unit film thickness becomes lower, and as a result, the film
thickness required for the light-shielding film to obtain a
predetermined optical density is increased. Therefore, it is
desired to provide a photomask blank, wherein a high etching rate
(ER) is provided, and wherein a light-shielding film has a
relatively low film thickness by which a sufficient optical density
is provided.
[0025] Moreover, it is desired to provide a photomask blank,
wherein, for example, by preventing unintended etching (e.g., an
under-cut), etc., the cross section of the light-shielding film
formed after etching is perpendicular to a substrate regardless of
the pattern density, and wherein the cross section of the
light-shielding film after etching is smooth.
[0026] With respect to the characteristics of the light-shielding
film desired in the above-described photomask blank, the same
characteristics are desired regarding a light-shielding film on a
phase shift film formed in a halftone phase shift mask blank.
[0027] Furthermore, it is desired to provide a light-shielding film
which is optimized for a phase shift mask and a blank thereof,
wherein the thickness of a phase shift film is reduced, collapsing
of OPC (Optical Proximity Correction) pattern does not occur,
requirements for pattern accuracy can be satisfied, and control of
optical properties and pattern defect test can be carried out.
Means for Solving the Problems
[0028] The present inventor found a phase shift mask blank which
enables formation of a fine mask pattern, wherein a light-shielding
film consists of three or more layers and the etching rate of each
of the layers satisfies predetermined conditions. The present
invention provides a phase shift mask blank and a phase shift mask
as described below.
[1] A phase shift mask blank, which is an original plate of a phase
shift mask exposed to an ArF excimer laser light, wherein:
[0029] the phase shift mask blank has a light transmissive
substrate, a phase shift film and a light-shielding film;
[0030] the phase shift film is provided between the light
transmissive substrate and the light-shielding film;
[0031] the phase shift amount of the phase shift film with respect
to the ArF excimer laser light is 160.degree. to 200.degree. and
the transmittance of the phase shift film is 2 to 40%;
[0032] the light-shielding film has a laminated structure in which
a lower layer, an interlayer and un upper layer are laminated in
this order from the side close to the light transmissive
substrate;
[0033] the thickness of the entire light-shielding film is 60 nm or
less;
[0034] the lower layer is made of a film containing a metal and has
a first etching rate;
[0035] the upper layer is made of a film containing a metal and has
a third etching rate; and
[0036] the interlayer is made of a metallic nitride film, which
contains the same metal as that contained in the lower layer or the
upper layer and nitrogen, and has a second etching rate that is
lower than the first etching rate and the third etching rate.
[2] The phase shift mask blank according to item [1], wherein:
[0037] the phase shift amount of the phase shift film is less than
180.degree. and the transmittance of the phase shift film is 10% or
more; and
[0038] the thickness of the entire light-shielding film is 50 nm to
60 nm.
[3] The phase shift mask blank according to item [1] or [2],
wherein the phase shift film is made of a material comprising: at
least one substance selected from the group consisting of oxygen
and nitrogen; a metal; and silicon as the main components. [4] The
phase shift mask blank according to any one of items [1] to [3],
wherein the thickness of the interlayer is 30% or less of the
thickness of the entire light-shielding film. [5] The phase shift
mask blank according to any one of items [1] to [4], wherein the
thickness of the interlayer is 40% or less of the thickness of the
lower layer. [6] The phase shift mask blank according to any one of
items [1] to [5], wherein the thickness ratio of the interlayer to
the upper layer is 1.0:0.7 to 1.0:7.0. [7] The phase shift mask
blank according to any one of items [1] to [6], wherein: the
optical density per unit film thickness of the upper layer or the
lower layer is 0.04 nm.sup.-1 or less; and the optical density per
unit film thickness of the interlayer is 0.05 nm.sup.-1 or more.
[8] The phase shift mask blank according to any one of items [1] to
[7], wherein:
[0039] the optical density of the lower layer is 1.1 to 1.8;
[0040] the optical density of the interlayer is 0.1 to 0.35;
and
[0041] the optical density of the upper layer is 0.4 to 0.6.
[9] The phase shift mask blank according to any one of items [1] to
[8], wherein:
[0042] the sum of the content of N and the content of O in the
lower layer is 40 to 55 atomic %;
[0043] the sum of the content of N and the content of O in the
interlayer is 30 atomic % or less; and
[0044] the sum of the content of N and the content of O in the
upper layer is 45 to 65 atomic %.
[10] The phase shift mask blank according to any one of items [1]
to [9], wherein: the optical density per unit film thickness of the
lower layer is 0.03 to 0.04 nm.sup.-1; and the optical density per
unit film thickness of the interlayer is 0.05 to 0.06 nm.sup.-1.
[11] The phase shift mask blank according to any one of items [1]
to [10], wherein:
[0045] in the lower layer, the metal content is 25 to 50 atomic %,
the sum of the content of N and the content of O is 35 to 65 atomic
%, and the optical density is 1.1 to 1.8;
[0046] the interlayer comprises the metal and N, wherein the metal
content is 50 to 90 atomic %, the thickness is 2 to 7 nm, and the
optical density is 0.1 to 0.35; and
[0047] in the upper layer, the metal content is 25 to 50 atomic %,
the sum of the content of N and the content of O is 45 to 65 atomic
%, and the optical density is 0.4 to 0.6.
[12] The phase shift mask blank according to any one of items [1]
to [11], wherein:
[0048] in the lower layer, the content of Cr is 30 to 40 atomic %,
the sum of the content of N and the content of O is 40 to 55 atomic
%, and the optical density is 1.1 to 1.8;
[0049] in the interlayer, the content of Cr is 50 to 90 atomic %,
the content of N is 3 to 25 atomic %, and the optical density is
0.1 to 0.35; and
[0050] in the upper layer, the content of Cr is 30 to 40 atomic %,
the sum of the content of N and the content of O is 50 to 60 atomic
%, and the optical density is 0.4 to 0.6.
[13] The phase shift mask blank according to any one of items [1]
to [12], wherein the etching rates of the lower layer, the
interlayer and the upper layer have the following relationship:
Second etching rate<First etching rate.ltoreq.Third etching
rate.
[14] A phase shift mask, which is produced using the phase shift
mask blank according to any one of items [1] to [13].
Advantageous Effect of the Invention
[0051] It is possible to reduce the thickness of a light-shielding
film of a phase shift mask blank in a preferred embodiment of the
present invention, and this enables reduction in clear etching time
(CET), and in addition, over etching time (OET) is also reduced. In
particular, in a photomask blank in a preferred embodiment of the
present invention, it is possible to reduce the thickness of a
light-shielding film having a structure made of a plurality of
layers (particularly a three-layer structure) by providing a
light-shielding layer (absorption layer) having a high content of a
metal such as Cr, and this enables reduction in clear etching time
(CET) and over etching time (OET).
[0052] Moreover, in a phase shift mask blank in a preferred
embodiment of the present invention, over etching time (OET) can be
reduced by combining a film containing a metal (e.g., Cr) having a
high etching rate (ER) (antireflection layer) with a
metal-containing film having a low etching rate (ER) (absorption
layer), by providing a predetermined balance between the thickness
of the layer having the high etching rate (ER) and the thickness of
the layer having the low etching rate (ER), and by disposing the
layer having the low etching rate (ER) at a predetermined
position.
[0053] In a phase shift mask blank in a preferred embodiment of the
present invention, the thickness of a resist formed on a
light-shielding film can be reduced by reducing clear etching time
(CET), over etching time (OET) or both of them. As a result, in the
phase shift mask blank in the preferred embodiment of the present
invention, the problem of pattern collapsing, etc. is not easily
caused, and therefore, a fine mask pattern can be formed
thereby.
[0054] Moreover, in a preferred embodiment of the present
invention, by providing a structure in which a plurality of layers
having a different metal content with a predetermined thickness are
laminated, it is possible to provide a phase shift mask blank
comprising a light-shielding film having a predetermined thickness
by which a sufficient optical density can be provided, wherein the
etching rate (ER) of the entire light-shielding film is high.
BRIEF DESCRIPTION OF THE DRAWINGS
[0055] FIG. 1 shows a diagram of a phase shift mask blank produced
in Examples 1 to 4.
[0056] FIG. 2 shows a diagram of a binary mask blank produced in
Reference Example 1.
EXPLANATIONS OF LETTERS OR NUMERALS
[0057] 1 . . . upper layer [0058] 2 . . . interlayer [0059] 3 . . .
lower layer [0060] 5 . . . phase shift film [0061] 10 . . . light
transmissive substrate
BEST MODE FOR CARRYING OUT THE INVENTION
[0062] In this specification, the "photomask blank" includes a
so-called "binary photomask blank", a "phase shift mask blank" that
has a phase shift film and a light-shielding film, etc. Note that
the phase shift mask blank may be used as the phase shift mask so
that phase shift effects are exerted, or used as the binary
photomask blank (for example, a case where the light-shielding film
and the phase shift film are etched to have the same pattern to
allow the phase shift film to function as the light-shielding film)
so that phase shift effects are not exerted.
[0063] In addition, the photomask blank of the present invention
includes a photomask blank in which a resist film is formed and a
photomask blank in which no resist film is formed. Accordingly, the
phase shift mask blank of the present invention includes a phase
shift mask blank in which a resist film is formed and a phase shift
mask blank in which no resist film is formed.
1. First Embodiment
[0064] At the time of processing a light-shielding film formed on a
phase shift film, the present inventor found the following
matters:
(1) in the case of a two-layer structure made of a light-shielding
layer and a front-surface antireflection layer, when the
light-shielding layer that is a lower layer is formed with a
material having a low etching rate, longer over etching time is
required, and as a result, the total etching time is increased,
whereas when the lower layer is formed with a material having a
high etching rate, clear etching time is reduced, but there is a
case where over etching time is increased due to loading, and thus,
it is difficult to reduce etching time when using the two-layer
structure; and (2) in order to reduce over etching time, it is
preferred to employ a three-layer structure consisting of a lower
layer, an interlayer and an upper layer, wherein a material having
an etching rate higher than that of the interlayer is used for the
upper layer and the lower layer. Thus, the invention of the phase
shift mask blank of the first embodiment was achieved.
[0065] The phase shift mask blank of the first embodiment is as
follows:
the phase shift mask blank of the present invention, which is an
original plate of a phase shift mask exposed to an ArF excimer
laser light, wherein:
[0066] the phase shift mask blank has a light transmissive
substrate, a phase shift film and a light-shielding film;
[0067] the phase shift film is provided between the light
transmissive substrate and the light-shielding film;
[0068] the phase shift amount of the phase shift film with respect
to the ArF excimer laser light is 160.degree. to 200.degree. and
the transmittance of the phase shift film is 2 to 40%;
[0069] the light-shielding film has a laminated structure in which
a lower layer, an interlayer and un upper layer are laminated in
this order from the side close to the light transmissive
substrate;
[0070] the thickness of the entire light-shielding film is 60 nm or
less;
[0071] the lower layer is made of a film containing a metal and has
a first etching rate;
[0072] the upper layer is made of a film containing a metal and has
a third etching rate; and
[0073] the interlayer is made of a metallic nitride film, which
contains the same metal as that contained in the lower layer or the
upper layer and nitrogen, and has a second etching rate that is
lower than the first etching rate and the third etching rate.
1.1. Light Transmissive Substrate
[0074] The light transmissive substrate is not particularly limited
as long as it is a substrate that is light-transmissive. Examples
thereof include a quartz glass substrate, an aluminosilicate glass
substrate, a calcium fluoride substrate, and a magnesium fluoride
substrate. Among them, the quartz glass substrate is preferred,
because it has a high flatness level and a high smoothness level,
and because, when transferring a pattern to a semiconductor
substrate using a photomask, distortion of a transfer pattern does
not easily occur and it is possible to perform pattern transfer
with high accuracy.
1.2. Light-Shielding Film
[0075] Regarding the phase shift mask blank of the present
invention, the light-shielding film in the phase shift mask blank
of the first embodiment has a laminated structure in which a lower
layer, an interlayer and an upper layer are laminated in this order
from the side close to the light transmissive substrate. It is
sufficient when the light-shielding film has at least 3 layers,
i.e., the lower layer, the interlayer and the upper layer. Further,
the light-shielding film may have another layer or other
layers.
1.2.1. Constitution of Respective Layers
[0076] Among layers forming the light-shielding film, the lower
layer is a layer provided to the downside of the interlayer (the
side close to the light transmissive substrate). The lower layer
preferably has a constitution in which the light shielding property
and the etching property of the light-shielding film are controlled
and in addition, the antireflection function and adhesion to a
phase shift film, etc. are controlled.
[0077] When the lower layer has the antireflection function, it is
sufficient when the back-surface reflectance of the lower layer is
suppressed to a degree in which there is no influence on transfer
properties by reflecting an exposure light incident from the light
transmissive substrate opposite to the side on which the
light-shielding film is formed by the lower layer to the side of an
exposure light source. The back-surface reflectance with respect to
a wavelength of an ArF excimer laser light is 40% or less,
preferably 30% or less, and more preferably 20% or less.
[0078] Among the layers forming the light-shielding film, the
interlayer is a layer provided between the lower layer and the
upper layer. The interlayer controls the light shielding property
and the etching property of the light-shielding film. Further, the
interlayer preferably has the highest light-shielding effect among
the layers in the film.
[0079] Among the layers forming the light-shielding film, the upper
layer is a layer provided to the upside of the interlayer (the side
far from the light transmissive substrate). The upper layer
controls the light shielding property and the etching property of
the light-shielding film, and in addition, it preferably has a
constitution in which it controls chemical resistance with respect
to washing of a phase shift mask blank or phase shift mask.
Moreover, when using as a phase shift mask, the upper layer
preferably exerts the effect to prevent reduction of the pattern
accuracy caused because reflected light from a transferred product
such as a semiconductor substrate returns to the transferred
product. It is desired that the surface reflectance with respect to
a wavelength of an ArF excimer laser light is 30% or less,
preferably 25% or less, and more preferably 20% or less.
[0080] Regarding the light-shielding film of the phase shift mask
blank of the first embodiment, it may be impossible to obtain a
sufficient optical density from the entire light-shielding film or
the film thickness may increase in the following cases: in the
lower layer, the metal content is less than 25 atomic %, or the sum
of the content of N and the content of O is more than 65 atomic %;
in the interlayer, the metal content is less than 50 atomic %; or
in the upper layer, the metal content is less than 25 atomic %, or
the sum of the content of N and the content of O is more than 65
atomic %. Meanwhile, etching time of the light-shielding film may
increase in the following cases: in the lower layer, the metal
content is more than 50 atomic %, or the sum of the content of N
and the content of O is less than 35 atomic %; in the interlayer,
the metal content is more than 90 atomic %; or in the upper layer,
the metal content is more than 50 atomic %, or the sum of the
content of N and the content of O is less than 45 atomic %.
[0081] Further, in the upper layer, if the metal content is more
than 50 atomic % or the sum of the content of N and the content of
O is less than 45 atomic %, the surface reflectance becomes too
high. In this case, it may be impossible to obtain the surface
reflectance of about 20% or less which is required with respect to
an ArF excimer laser light. Meanwhile, in the upper layer, if the
metal content is less than 25 atomic % or the sum of the content of
N and the content of O is more than 65 atomic %, the quality may be
reduced.
[0082] Regarding the light-shielding film of the phase shift mask
blank of the first embodiment, it may be impossible to obtain a
sufficient optical density from the entire light-shielding film or
the film thickness may increase in the following cases: in the
lower layer, the content of Cr is less than 30 atomic %, or the sum
of the content of N and the content of O is more than 55 atomic %;
in the interlayer, the content of Cr is less than 50 atomic %, or
the content of N is more than 25 atomic %; or in the upper layer,
the content of Cr is less than 30 atomic %, or the sum of the
content of N and the content of O is more than 60 atomic %.
[0083] Meanwhile, etching time of the light-shielding film may
increase in the following cases: in the lower layer, the content of
Cr is more than 40 atomic %, or the sum of the content of N and the
content of O is less than 40 atomic %; in the interlayer, the
content of Cr is more than 90 atomic %, or the content of N is less
than 3%; or in the upper layer, the content of Cr is more than 40
atomic %, or the sum of the content of N and the content of O is
less than 50 atomic %.
[0084] Further, regarding the light-shielding film of the phase
shift mask blank of the first embodiment, the content of N in the
interlayer is preferably 3 to 25 atomic %, since a relatively high
optical density can be obtained by a certain film thickness.
[0085] Regarding the light-shielding film of the phase shift mask
blank of the first embodiment, in the lower layer, it is preferred
that the metal content is 25 to 50 atomic % and the sum of the
content of N and the content of O is 35 to 65 atomic %, and it is
more preferred that the content of Cr is 30 to 40 atomic % and the
sum of the content of N and the content of O is 40 to 55 atomic
%.
[0086] Further, in the interlayer, it is preferred that metal, N
and O are contained and the metal content is 50 to 90 atomic %, and
it is more preferred that the sum of the content of N and the
content of O is 30 atomic % or less and the content of Cr is 50 to
90 atomic %.
[0087] Further, in the upper layer, it is preferred that the metal
content is 25 to 50 atomic % and the sum of the content of N and
the content of O is 45 to 65 atomic %, and it is more preferred
that the content of Cr is 30 to 40 atomic % and the sum of the
content of N and the content of O is 50 to 60 atomic %.
1.2.2. Thickness of Each Layer
[0088] Regarding the light-shielding film of the phase shift mask
blank of the first embodiment, etching time of the entire
light-shielding film can be reduced since the thickness of the
interlayer, which has a lower etching rate, is 30% or less of the
entire thickness. If the thickness of the interlayer is more than
30% of the thickness of the entire light-shielding film, the
thickness of the light-shielding film can be reduced, but the ratio
of the lower layer or the upper layer, which has a higher etching
rate, is reduced, and as a result, etching time cannot be reduced.
Therefore, such a thickness is not preferred.
[0089] In addition, regarding the light-shielding film of the phase
shift mask blank of the first embodiment, since the thickness of
the interlayer is 30% or less of the thickness of the entire
light-shielding film, variation of the cross-section shape due to
loading caused on the upper layer is reduced during etching of the
interlayer. After this process, the lower layer is rapidly etched
at a first etching rate, and this suppresses further etching of a
portion of the upper layer or the like which is not intended to be
etched during etching of the lower layer. As a result, a good
cross-section shape of the pattern is provided. Moreover, a better
cross-section shape can be provided by optimizing the introduction
position of the interlayer.
[0090] Regarding the light-shielding film of the phase shift mask
blank of the first embodiment, the thickness of the interlayer is
preferably 20% or less, and more preferably 10% or less of the
thickness of the entire light-shielding film, since etching time is
further reduced and a better cross-section shape can be provided.
If the interlayer, which has a lower etching rate, is thick, its
etched shape is more tapered, and due to this, the etching area of
the lower layer is narrowed, and as a result, the total etching
time is increased. However, in the case of the light-shielding film
of the phase shift mask blank of the first embodiment, if the
interlayer is thin, its etched shape is less tapered, and it is
preferred since the development of etching of the lower layer is
not prevented.
[0091] Further, if the interlayer is thinned while the thickness of
the lower layer is increased, it becomes possible to form the angle
of the cross-sectional shape of a pattern to be more nearly
perpendicular. In other words, in the light-shielding film, by
controlling the position of the interlayer, which has a low etching
rate, a better cross-section shape can be obtained, and it becomes
possible to improve pattern reproducibility.
[0092] Therefore, in the light-shielding film of the phase shift
mask blank of the first embodiment, the thickness of the interlayer
is preferably 40% or less, and more preferably 15% or less of the
thickness of the lower layer.
[0093] If the value of the thickness ratio between the interlayer
and the upper layer exceeds 1.0/0.7, the upper layer becomes too
thin, and therefore there is a case where it becomes impossible to
provide a desired antireflection function. In addition, if the
value of the thickness ratio is less than 1.0/7.0, there is a case
where it becomes impossible to reduce over etching time.
[0094] Therefore, in the light-shielding film of the phase shift
mask blank of the first embodiment, the thickness ratio between the
interlayer and the upper layer is preferably 1.0:0.7 to 1.0:7.0,
and more preferably 1.0:2.0 to 1.0:7.0. When the thickness ratio is
within the above-described range, it is possible to suppress
further etching of a portion which is not intended to be etched,
and therefore a better cross-section shape is provided and pattern
reproducibility can be improved.
[0095] In the light-shielding film of the phase shift mask blank of
the first embodiment, the thickness of the interlayer is preferably
0.5% or more, and more preferably 3% or more of the thickness of
the entire light-shielding film. There is a difference of the
etching rate between a fine pattern and a relatively large pattern
(micro-loading). Therefore, when the interlayer is too thin, CD
linearity by micro-loading is reduced, but it can be prevented by
the above-described thickness.
1.3. Optical Density
[0096] In the present specification, the optical density (OD)
satisfies the following relationship:
OD(Entire light-shielding film)=OD(Upper
layer)+OD(Interlayer)+OD(Antireflection layer)
[0097] Further, in the present specification, "optical density per
unit film thickness" satisfies the following relationship:
OD per unit film thickness(nm.sup.-1)=OD of film(layer)/Thickness
of film(layer)
[0098] In the light-shielding film of the phase shift mask blank of
the first embodiment, when the optical density of the lower layer
is less than 1.1, the optical density is insufficient, and
therefore, the thickness of any of the layers must be increased.
Meanwhile, when the optical density exceeds 1.8, the etching rate
becomes lower, and therefore, it becomes difficult to reduce the
film thickness.
[0099] Further, when the optical density of the interlayer is less
than 0.1, the optical density of the entire light-shielding film is
insufficient, and therefore, the thickness of any of the layers
must be increased. In addition, since reflection by the interlayer
is reduced, it becomes impossible to obtain a sufficient
interferential effect. As a result, the surface reflectance is
increased, and a desired reflectance cannot be obtained. Further,
when the optical density of the interlayer exceeds 0.35, etching
time is increased, and as a result, it becomes difficult to reduce
the thickness of the resist film.
[0100] Moreover, when the optical density of the upper layer is
less than 0.4, the reflectance becomes too low and the entire film
thickness is increased. When the optical density exceeds 0.6, the
reflectance becomes too high.
[0101] Therefore, in the light-shielding film of the phase shift
mask blank of the first embodiment, the optical density of the
lower layer is set at 1.1 to 1.8, the optical density of the
interlayer is set at 0.1 to 0.35, and the optical density of the
upper layer is set at 0.4 to 0.6. As a result, it is possible to
easily obtain a light-shielding film having a desired film
thickness, etching rate and optical properties.
[0102] Specifically, photomask blanks according to three
embodiments having a light-shielding film with an optical density
of 1.9 ((1) a light-shielding film with a low optical density; (2)
a light-shielding film with a high optical density; and (3) a
light-shielding film having a three-layer structure in which a
layer with a high optical density is combined with a layer with a
low optical density), will be compared to each other below.
(1) Light-Shielding Film Consisting of a Single Layer with Low
Optical Density
[0103] When forming a single-layer light-shielding film with a high
ER and OD per unit film thickness=0.036 nm.sup.-1, the thickness of
the light-shielding film is 53 nm. In this case, clear etching time
becomes the shortest, but over etching time becomes longer, and
there is a case where it is impossible to obtain a perpendicular
form.
(2) Light-Shielding Film Consisting of a Single Layer with High
Optical Density
[0104] When forming a single-layer light-shielding film with a low
ER and OD per unit film thickness=0.05 nm.sup.-1, the thickness
thereof is 38 nm. In this case, clear etching time becomes the
longest, and over etching time also becomes longer, and there is a
case where it is impossible to obtain a perpendicular form.
(3) Light-Shielding Film Having a Three-Layer Structure in which a
Layer with a High Optical Density is Combined with a Layer with a
Low Optical Density
[0105] When forming a light-shielding film using the following
three layers: a layer with a low optical density (OD per unit film
thickness=0.039 nm.sup.-1); a layer with a high optical density (OD
per unit film thickness=0.05 nm.sup.-1); and a layer with a low
optical density (OD per unit film thickness=0.036 nm.sup.-1), it
can be realized by, for example, setting thicknesses of the layers
at 30 nm, 4 nm and 14 nm, respectively. In this case, its clear
etching time has a length that is approximately intermediate
between that of the light-shielding film of item (1) above and that
of the light-shielding film of item (2) above, and over etching
time is optimized.
[0106] In view of the above-described point, it is understood that
etching time can be reduced by an interlayer in which a layer with
a high optical density is combined with a layer with a low optical
density. This can realize reduction of the thickness of the resist
film, improvement of the cross-section shape and reduction of CD
variation due to loading.
1.4. Etching Rate
[0107] When oxygen is included in a metal-containing layer which
constitutes a light-shielding film, the etching rate is increased,
but the optical density per unit film thickness is decreased, and
as a result, the thickness of the interlayer is increased. Further,
in the case of a film having a single speed in which there is no
difference of etching rate in the longitudinal direction, variation
of the cross-section shape due to loading tends to easily
occur.
[0108] Further, in the case of a photomask exposed to an ArF
excimer laser light, it preferably has a structure having a lower
layer and an upper layer in order to prevent reduction of the
pattern accuracy caused because reflected light from a transferred
product such as a semiconductor substrate returns to the
transferred product. However, in the case where a light-shielding
film having such a laminated structure is designed with the
limitation in which the thickness of the film is limited to a
certain value (e.g., 60 nm or less), if the thickness of the
interlayer becomes thicker, it is required to decrease the
thickness of the lower layer or the upper layer, but optical
properties, such as light-shielding property and reflectance, of
the entire film cannot be retained only by such decrease of the
thickness of the layer.
[0109] Therefore, the light-shielding film of the phase shift mask
blank of the first embodiment has a second etching rate (etching
rate of the interlayer), which is lower than a first etching rate
(etching rate of the lower layer) and a third etching rate (etching
rate of the upper layer). The etching rate can be increased by, for
example, inclusion of nitrogen or oxygen in a metal film.
[0110] In the aforementioned light-shielding film, by using a
metallic nitride film having a low etching rate as the interlayer,
the thickness of the light-shielding film can be reduced with the
optical density being kept at a high level. This enables easy
design of a light-shielding film having a laminated structure and
desired optical properties with the entire film thickness being
limited to a certain value, and as a result, reduction of the
thickness of the resist film can be realized.
[0111] In addition, since the second etching rate of the metallic
nitride film is lower than the etching rates of the lower layer and
the upper layer, it can change etching in the longitudinal
direction. That is, during etching of the metallic nitride film
having the low etching rate, variation of the cross-section shape
due to loading that occurs on the upper layer having the high
etching rate is reduced. After the completion of etching of the
interlayer, the lower layer is rapidly etched at the first etching
rate. This suppresses further etching of a portion of the upper
layer or the like which is not intended to be etched during etching
of the lower layer. As a result, a good cross-section shape of the
pattern is provided.
[0112] In general, when a metal in the light-shielding film is
nitrided, change of a crystal structure or reduction of a film
density occurs. Therefore, in the case where the interlayer is a
metallic nitride film, when compared to the case of a pure metallic
film, the tensile stress can be more relaxed and the film stress
may be more easily controlled.
2. Second Embodiment
[0113] (1) The phase shift mask blank of the second embodiment is
as follows: the phase shift mask blank of the present invention,
which is an original plate of a phase shift mask exposed to an ArF
excimer laser light, wherein:
[0114] the phase shift mask blank has a light transmissive
substrate, a phase shift film and a light-shielding film;
[0115] the phase shift film is provided between the light
transmissive substrate and the light-shielding film;
[0116] the light-shielding film consists of a plurality of
layers;
[0117] the optical density of the entire light-shielding film is
1.8 to 2.6;
[0118] the ratio of the optical density of a layer A constituting
the plurality of layers to the sum of the optical densities of all
the layers other than the layer A is 1:5 to 1:19;
[0119] each of the layers constituting the light-shielding film
contains a metal; and
[0120] the layers other than the layer A consist of a film
comprising: the same metal as that contained in the layer A; N; and
O, and the sum of the content of N and the content of O is 40 to 65
atomic %.
[0121] In the light-shielding film of the phase shift mask blank of
the second embodiment, within the range of the optical density of
the entire light-shielding film of 1.8 to 2.6, the ratio of the
optical density of the layer A to the sum of the optical densities
of all the layers other than the layer A is set at 1:5 to 1:19,
thereby providing a constitution in which most of the optical
density of the entire light-shielding film is provided by all the
layers other than the layer A. The optical density depends on a
composition and a film thickness. However, since the sum of the
content of N and the content of O in the layers other than the
layer A is set at 40 to 65 atomic %, though the film becomes
relatively thick for obtaining a desired optical density, the
etching rate is high. Due to this, the ratio of the thickness of
the layer having a higher etching rate becomes higher, and
therefore, etching time can be reduced and as a result, the resist
film can be thinned.
[0122] In the light-shielding film of the phase shift mask blank of
the second embodiment, if a value of the ratio of the optical
density of the layers other than the layer A to the optical density
of the layer A exceeds 1/5, the etching rate of the layers other
than the layer A becomes lower. Meanwhile, if a value of the
above-described ratio is less than 1/19, the thickness of the
layers other than the layer A becomes too thick. Further, in the
light-shielding film of the second embodiment, if the sum of the
content of N and the content of O in the layers other than the
layer A exceeds 65 atomic %, the film becomes thicker. Meanwhile,
if the above-described sum is less than 40 atomic %, the etching
rate becomes lower.
(2) In the light-shielding film of the phase shift mask blank of
the second embodiment, it is preferred that the optical density per
unit film thickness of the layers other than the layer A is 0.04
nm.sup.-1 or less, and that the optical density per unit film
thickness of the layer A is 0.05 nm.sup.-1 or more.
[0123] The second embodiment includes an embodiment in which:
[0124] the light-shielding film has a laminated structure in which
a lower layer, an interlayer and an upper layer are laminated in
this order from the side close to a light transmissive
substrate;
[0125] the optical density of the lower layer is 1.1 to 1.8;
[0126] the optical density of the interlayer is 0.1 to 0.35;
and
[0127] the optical density of the upper layer is 0.4 to 0.6.
[0128] In the phase shift mask blank of this embodiment, when the
optical densities of the respective layers are within the
above-described ranges, it is possible to easily obtain a
light-shielding film having a desired thickness, etching rate and
optical properties.
[0129] In the light-shielding film of the phase shift mask blank of
the second embodiment, when the optical density of the lower layer
is less than 1.1, the optical density is insufficient, and
therefore, the thickness of any of the layers must be increased.
Meanwhile, when the optical density exceeds 1.8, the etching rate
becomes lower, and therefore, it becomes difficult to reduce the
film thickness.
[0130] Further, in the light-shielding film of the phase shift mask
blank of the second embodiment, when the optical density of the
interlayer is less than 0.1, the optical density of the entire
light-shielding film is insufficient, and therefore, the thickness
of any of the layers must be increased. In addition, since
reflection by the interlayer is reduced, it becomes impossible to
obtain a sufficient interferential effect. As a result, the surface
reflectance is increased, and a desired reflectance cannot be
obtained. Further, when the optical density of the interlayer
exceeds 0.35, etching time is increased, and as a result, it
becomes difficult to reduce the thickness of the resist film.
[0131] Moreover, in the light-shielding film of the phase shift
mask blank of the second embodiment, when the optical density of
the upper layer is less than 0.4, the reflectance becomes too low
(particularly when the upper layer has the antireflection function)
and the entire film thickness is increased. When the optical
density exceeds 0.6, the reflectance becomes too high (particularly
when the upper layer has the antireflection function).
(3) Regarding the light-shielding film of the phase shift mask
blank of the second embodiment, it is preferred that:
[0132] the sum of the content of N and the content of O in the
lower layer is 40 to 55 atomic %;
[0133] the sum of the content of N and the content of O in the
interlayer is 30 atomic % or less; and that
[0134] the sum of the content of N and the content of O in the
upper layer is 45 to 65 atomic %.
[0135] In the phase shift mask blank of this embodiment, when the
content of N and O in each of the layers is within the
predetermined range, it is possible to easily obtain a
light-shielding film having a desired film thickness, etching rate
and optical properties.
[0136] In the light-shielding film of the phase shift mask blank of
the second embodiment, when the sum of the content of N and the
content of O in the lower layer is less than 40 atomic %, the
etching rate becomes lower, and when the sum of the content of N
and the content of O exceeds 55 atomic %, the optical density
becomes lower (the film thickness is increased), and as a result,
it becomes difficult to reduce the film thickness.
[0137] Further, in the light-shielding film of the phase shift mask
blank of the second embodiment, when the sum of the content of N
and the content of O in the interlayer exceeds 30 atomic %, the
etching rate becomes lower, and as a result, it becomes difficult
to reduce the film thickness.
[0138] Moreover, in the light-shielding film of the phase shift
mask blank of the second embodiment, when the sum of the content of
N and the content of O in the upper layer is less than 45 atomic %,
the etching rate becomes lower, and when the sum of the content of
N and the content of O exceeds 65 atomic %, the optical density
becomes lower (the film thickness is increased), and as a result,
it becomes difficult to reduce the film thickness.
[0139] In the light-shielding film of the phase shift mask blank of
the second embodiment, it is preferred that the optical density per
unit film thickness of the lower layer is 0.03 to 0.04 nm.sup.-1,
and that the optical density per unit film thickness of the
interlayer is 0.05 to 0.06 nm.sup.-1.
[0140] Note that the light transmissive substrate in the phase
shift mask blank of the second embodiment is the same as that of
the first embodiment.
3. Third Embodiment
[0141] (1) The phase shift mask blank of the third embodiment is as
follows: the phase shift mask blank of the present invention, which
is an original plate of a phase shift mask exposed to an ArF
excimer laser light, wherein:
[0142] the phase shift mask blank has a light transmissive
substrate, a phase shift film and a light-shielding film;
[0143] the phase shift film is provided between the light
transmissive substrate and the light-shielding film;
[0144] the light-shielding film has a laminated structure in which
a lower layer, an interlayer and an upper layer are laminated in
this order from the side close to the light transmissive
substrate;
[0145] the lower layer is made of a CrOCN film, which is formed
using Cr as a target in a mixed gas atmosphere comprising 45 to 65
vol % of an inert gas, 30 to 50 vol % of CO.sub.2 gas and 1 to 15
vol % of N.sub.2 gas;
[0146] the interlayer is made of a CrN film, which is formed using
Cr as a target in a mixed gas atmosphere comprising 70 to 90 vol %
of an inert gas and 5 to 25 vol % of N.sub.2 gas; and
[0147] the upper layer is made of a CrOCN film, which is formed
using Cr as a target in a mixed gas atmosphere comprising 40 to 60
vol % of an inert gas, 25 to 45 vol % of CO.sub.2 gas and 5 to 20
vol % of N.sub.2 gas.
[0148] The light-shielding film of the phase shift mask blank of
the third embodiment has a laminated structure in which desired
optical properties are provided when the film thickness is 60 nm or
less.
[0149] In the light-shielding film of the phase shift mask blank of
the third embodiment, when forming an upper layer and a lower
layer, O.sub.2 gas or NO gas can be used. However, when a film
having a high oxidation degree is desired to be formed, it is
necessary to perform sputtering under a relatively high gas
pressure in order to stabilize plasma. Therefore, a film obtained
tends to be fragile, and such a film attached to the interior of a
chamber is stripped and then attached to a substrate on which a
film is being formed. As a result, the quality of an obtained
product is prone to be reduced.
[0150] On the other hand, when using CO.sub.2 gas, the oxidation
degree can be controlled under a relatively low gas pressure. As a
result, a film can be formed at a gas flow rate within a range in
which a film does not become fragile.
[0151] Therefore, from the viewpoint of improvement of the quality
of a product, in the light-shielding film of the phase shift mask
blank of the third embodiment, as an atmosphere gas to be used for
forming a layer constituting a light-shielding film, CO.sub.2 gas
is preferably used.
(2) Regarding the light-shielding film of the phase shift mask
blank of the third embodiment, it includes an embodiment in which
an inert gas for forming a lower layer consists of 10 to 30 vol %
of Ar gas and 20 to 40 vol % of He gas and an inert gas for forming
an upper layer consists of 10 to 30 vol % of Ar gas and 20 to 40
vol % of He gas.
[0152] Regarding the phase shift mask blank of the third
embodiment, when He gas is included in an atmosphere gas, the
compressive stress of an obtained layer in the case of a Cr-based
light-shielding film is increased, and as a result, the film stress
can be controlled. Further, He gas mainly acts only to control the
film stress, and therefore it is preferred since it becomes easy to
design the film stress.
[0153] Note that the light transmissive substrate in the phase
shift mask blank of the third embodiment is the same as that of the
first embodiment.
4. Fourth Embodiment
[0154] (1) The phase shift mask blank of the fourth embodiment is
as follows: the phase shift mask blank of the present invention,
which is an original plate of a phase shift mask exposed to an ArF
excimer laser light, wherein:
[0155] the phase shift mask blank has a light transmissive
substrate, a phase shift film and a light-shielding film;
[0156] the phase shift film is provided between the light
transmissive substrate and the light-shielding film;
[0157] the light-shielding film has a laminated structure in which
a lower layer, an interlayer and an upper layer are laminated in
this order from the side close to the light transmissive
substrate;
[0158] in the lower layer, the metal content is 25 to 50 atomic %,
the sum of the content of N and the content of O is 35 to 65 atomic
%, and the optical density is 1.1 to 1.8;
[0159] the interlayer comprises the metal and N, wherein the metal
content is 50 to 90 atomic %, the thickness is 2 to 6 nm, and the
optical density is 0.1 to 0.35; and
[0160] in the upper layer, the metal content is 25 to 50 atomic %,
the sum of the content of N and the content of O is 45 to 65 atomic
%, and the optical density is 0.4 to 0.6.
[0161] Regarding the light-shielding film of the phase shift mask
blank of the fourth embodiment, it may be impossible to obtain a
sufficient optical density from the entire light-shielding film in
the following cases: in the lower layer, the metal content is less
than 25 atomic %, or the sum of the content of N and the content of
O is more than 65 atomic %; in the interlayer, the metal content is
less than 50 atomic %; or in the upper layer, the metal content is
less than 25 atomic %, or the sum of the content of N and the
content of O is more than 65 atomic %. Meanwhile, etching time of
the light-shielding film may increase in the following cases: in
the lower layer, the metal content is more than 50 atomic %, or the
sum of the content of N and the content of O is less than 35 atomic
%; in the interlayer, the metal content is more than 90 atomic %;
or in the upper layer, the metal content is more than 50 atomic %,
or the sum of the content of N and the content of O is less than 45
atomic %.
[0162] Further, regarding the light-shielding film of the phase
shift mask blank of the fourth embodiment, the content of N in the
interlayer is preferably 3 to 25 atomic %, since a relatively high
optical density can be obtained by a certain film thickness.
[0163] In the interlayer of the light-shielding film of the phase
shift mask blank of the fourth embodiment, the content of N is
preferably 3 to 25 atomic %. Moreover, in the interlayer, the
optical density per unit film thickness is preferably 0.05 to 0.06
nm.sup.-1.
(2) Regarding the light-shielding film of the phase shift mask
blank of the fourth embodiment, it is preferred that:
[0164] in the lower layer, the content of Cr is 30 to 40 atomic %,
the sum of the content of N and the content of O is 40 to 55 atomic
%, and the optical density is 1.1 to 1.8;
[0165] in the interlayer, the content of Cr is 50 to 90 atomic %,
the content of N is 3 to 25 atomic %, and the optical density is
0.1 to 0.35; and that
[0166] in the upper layer, the content of Cr is 30 to 40 atomic %,
the sum of the content of N and the content of O is 50 to 60 atomic
%, and the optical density is 0.4 to 0.6.
[0167] Regarding the light-shielding film of the phase shift mask
blank of this embodiment, it may be impossible to obtain a
sufficient optical density from the entire light-shielding film in
the following cases: in the lower layer, the content of Cr is less
than 30 atomic %, or the sum of the content of N and the content of
O is more than 55 atomic %; in the interlayer, the content of Cr is
less than 50 atomic %, or the content of N is more than 25 atomic
%; or in the upper layer, the content of Cr is less than 30 atomic
%, or the sum of the content of N and the content of O is more than
60 atomic %. Meanwhile, etching time of the light-shielding film
may increase in the following cases: in the lower layer, the
content of Cr is more than 40 atomic %, or the sum of the content
of N and the content of O is less than 40 atomic %; in the
interlayer, the content of Cr is more than 90 atomic %, or the
content of N is less than 3 atomic %; or in the upper layer, the
content of Cr is more than 40 atomic %, or the sum of the content
of N and the content of O is less than 50 atomic %.
[0168] Note that the light transmissive substrate in the phase
shift mask blank of the fourth embodiment is the same as that of
the first embodiment.
5. Preferred Embodiments Regarding the Light-Shielding Films of the
First to Fourth Embodiments
5.1. Etching Rate
[0169] In the phase shift mask blanks of the first, third and
fourth embodiments and the phase shift mask blank of the second
embodiment in which the light-shielding film has a three-layer
structure, the relationship among the etching rates is preferably
"Second etching rate (etching rate of the interlayer)<First
etching rate (etching rate of the lower layer).ltoreq.Third etching
rate (etching rate of the upper layer)", since the angle of the
cross section of a pattern becomes close to be perpendicular.
Further, "First etching rate<Third etching rate" is more
preferred since the angle of the cross section of the pattern
further becomes close to be perpendicular.
[0170] Further, the ratio between the second etching rate and the
third etching rate is preferably 1.0:1.1 to 1.0:2.0. When the third
etching rate exceeds 2.0 times the second etching rate, it causes
unevenness between the sections of the upper and lower layers and
the section of the interlayer. In the case of less than 1.1 times,
it becomes impossible to reduce the entire etching time. Further,
it is preferred that the third etching rate is 0.67 nm/sec or more
and that the second etching rate is 0.44 nm/sec or less.
5.2. Composition of Light-Shielding Film
[0171] In the phase shift mask blanks of the first, third and
fourth embodiments and the phase shift mask blank of the second
embodiment in which the light-shielding film has a three-layer
structure, a metal to be contained in the lower layer, the upper
layer or the interlayer is preferably a transition metal such as
Cr, Mo, W and Ta. Particularly preferred is Cr because
chlorine-based and oxygen-based dry etching is performed and
therefore the selectivity with a glass substrate or halftone phase
shift film is high. In addition, Cr is more preferred when compared
to other metals because it enables not only dry etching but also
wet etching.
[0172] In the phase shift mask blanks of the first, third and
fourth embodiments and the phase shift mask blank of the second
embodiment in which the light-shielding film has a three-layer
structure, it is preferred that the lower layer or the upper layer
has the Cr content of 50 atomic % or less and comprises at least
one of O, C and N, and that the interlayer has the Cr content of 50
atomic % or more. By providing such a structure, a film having the
relationship of "Second etching rate<First etching rate or Third
etching rate" can be easily formed.
[0173] The lower layer or the upper layer preferably consists of
CrN, CrON, CrO, CrC, CrCO or CrOCN, and among them, CrOCN is
particularly preferred.
[0174] Further, the interlayer preferably consists of CrN, CrON,
CrO, CrC, CrCO or CrOCN, and more preferably consists of CrN or
CrON.
[0175] When the lower layer or the upper layer consists of CrOCN,
it is preferred to employ an embodiment in which a Cr--Cr binding
component and a CrO.sub.xN.sub.y component are mixed together.
Further, when the interlayer consists of CrN, it is preferred to
employ an embodiment in which a Cr--Cr binding component is the
main component and a CrO.sub.xN.sub.y component is in a small
amount. By providing a larger amount of the CrO.sub.xN.sub.y
component, the etching rate can be accelerated.
[0176] Moreover, the lower layer or the upper layer of this
embodiment preferably has a fine amorphous structure.
[0177] Further, regarding carbon, it is preferred to provide a
state in which chromium carbide (Cr--C) is the main component and
other components, C--C, C--O and C--N are mixed therewith.
[0178] Further, it is preferred that the lower layer and the upper
layer have the same composition but a different composition ratio
and film thickness. By providing such a structure, when forming the
lower layer and the upper layer, the same atmosphere gas can be
used, and as a result, the process of forming the light-shielding
film can be simplified. In this case, it is easy to adjust the
oxidation degree of the upper layer in order to improve the quality
and to adjust the optical density of the lower layer to be higher
and the reflectance thereof to be lower.
5.3. Optical Density of Light-Shielding Film
[0179] In the phase shift mask blanks of the first to fourth
embodiments, when the light-shielding film has an interlayer, the
optical density per unit film thickness of the interlayer with
respect to an ArF excimer laser light is preferably 0.05 nm.sup.-1
or more.
5.4. Amount of Change of Flatness
[0180] In the phase shift mask blanks of the first to fourth
embodiments, the amount of change of flatness before and after the
film-forming process is preferably 0.05 .mu.m or less.
5.5. Resist Film/Etching Mask Film
[0181] In the phase shift mask blanks of the first to fourth
embodiments, a resist film having the thickness of 200 nm or less,
and more preferably 150 nm or less can be provided on the
light-shielding film.
[0182] Further, in the phase shift mask blanks of the first to
fourth embodiments, an etching mask film may be provided on the
light-shielding film. When the light-shielding film contains Cr, in
a general dry etching process, chlorine and oxygen are used as an
etching gas to cause sublimation in the form of chromyl chloride.
However, since the main component of the resist is carbon, the
resist is very weak against oxygen plasma. By providing an etching
mask film, load on the resist film can be reduced, and therefore,
it is possible to reduce the thickness of the resist film to 100 nm
or less. When Cr is the main component in the light-shielding film,
it is preferred to form an etching mask film having a thickness of
5 to 20 nm using SiON, SiN, SiO.sub.2, MoSiON, MoSiN or the like,
which has a high selectivity. Further, an organic film containing
20% or more of Si having the thickness of 20 to 40 nm can also be
provided as an etching mask film.
[0183] In the phase shift mask blanks of the first to fourth
embodiments, by providing an etching mask film on the
light-shielding film, the thickness of a resist can be further
reduced. Specifically, when the thickness of the resist is 100 nm
or less, the pattern shape is significantly deteriorated, and LER
(Line Edge Roughness) at the time when a mask pattern is
transferred to the etching mask film is deteriorated. The present
inventor found that, therefore, it is necessary to reduce the
etching time of the etching mask film. Since the light-shielding
film of the above-described embodiment has short etching time, the
thickness of the etching mask film can be reduced, and therefore,
etching time of the etching mask film can be reduced.
[0184] Further, in the phase shift mask blanks of the first to
fourth embodiments, the upper layer or the lower layer in the
light-shielding film preferably has an amorphous structure, since
the surface roughness thereof is small and therefore the surface
roughness of the upper layer, the etching mask film can be reduced.
As a result, the cross-section shape and LER at the time when the
etching mask film is etched are improved. Therefore, when etching
the lower layer, the light-shielding film utilizing an etching mask
film pattern as a mask, it is possible to prevent deterioration of
the cross-section shape and LER of the light-shielding film.
5.6. Phase Shift Film
[0185] The phase shift mask blank of the present invention has a
halftone phase shift film between the light transmissive substrate
and the light-shielding film.
[0186] In general, the phase shift amount is set at 180.degree.,
but under exposure conditions of immersion lithography, the phase
shift amount is not necessarily required to be 180.degree.. Rather,
it is preferred to reduce the thickness of the phase shift film
with the phase shift amount being set at less than 180.degree.,
since the cross-section shape of an OPC pattern or circuit pattern
is improved.
[0187] Specifically, the phase shift amount is preferably
160.degree. to less than 180.degree. at which a good pattern can be
obtained by sufficiently improving resolution by phase shift
effects without being dug in the substrate.
[0188] Further, the transmittance of the phase shift film is
preferably 2 to 40%.
[0189] When the transmittance of the phase shift film is 2% to less
than 10%, in a laminated film of the phase shift film and the
light-shielding film, the thickness of the light-shielding film is
set at a value required to provide a predetermined optical density
(OD) (e.g., 2.8 or more, preferably 3.0 or more), and the thickness
of the entire light-shielding film can be set at less than 50
nm.
[0190] Further, when the transmittance of the phase shift film is
set to 10% to 40% (preferably 10% to 30%, more preferably 10% to
20%) in order to improve resolution of a transferred pattern, like
the above-described case, in a laminated film of the phase shift
film and the light-shielding film, the thickness of the
light-shielding film is set at a value required to provide a
predetermined optical density (OD) (e.g., 2.8 or more, preferably
3.0 or more), and the thickness of the entire light-shielding film
can be set to 50 nm to 60 nm.
[0191] Since the thickness of the light-shielding film is set at 60
nm or less, the cross-section shape of the light-shielding film
pattern is nearly a perpendicular shape, and fine pattern accuracy
can be easily obtained. Therefore, also in a phase shift film
pattern in which patterning is performed using this light-shielding
film pattern as a mask, it becomes easy to obtain fine pattern
accuracy.
[0192] Further, in the case where the optical density of the
laminated film of the phase shift film and the light-shielding film
is set at 3.1, when the transmittance of the phase shift film is
10%, 12%, 15% and 20%, the optical density required in the entire
light-shielding film is about 2.10, 2.18, 2.28 and 2.40,
respectively.
[0193] In this case, the range of the preferred optical density and
the range of the preferred thickness of each of the layers in the
light-shielding film are as described below.
[0194] When the transmittance of the phase shift film is 10% to
20%: in the lower layer, the optical density is 1.3 to 1.8 and the
thickness is 33 nm to 46 nm; in the interlayer, the optical density
is 0.1 to 0.35 and the thickness is 2 nm to 7 nm; and in the upper
layer, the optical density is 0.4 to 0.6 and the thickness is 11 nm
to 17 nm.
[0195] A general example in the case where the transmittance of the
phase shift film is 10% or more is described in the specification
of Japanese Patent No. 3445329 (Example 1 and FIG. 1), and this is
a phase shift mask having a structure in which a light-shielding
film pattern is formed on a phase shift film pattern formed within
a pattern transfer region and a light-shielding film with a width
of a predetermined value or more is formed in a
non-pattern-transfer region.
[0196] Further, a general example in the case where the
transmittance of the phase shift film is less than 10% (e.g., 2 to
less than 10%) is described in the specification of Japanese Patent
No. 3411613 (Example 1 and FIG. 1), and this is a phase shift mask
having a structure in which no light-shielding film pattern is
formed on a phase shift film pattern formed within a pattern
transfer region and a light-shielding film with a width of a
predetermined value or more is formed in a non-pattern-transfer
region.
[0197] For a phase shift film, a material consisting of MoSiN or
MoSiON is preferably used. By providing the above-described
light-shielding film on the phase shift film consisting of the
material, it becomes possible to improve LER of the phase shift
film pattern compared to the case of providing a conventional
Cr-based light-shielding film.
[0198] Specifically, a conventional Cr-based light-shielding film
has a porous columnar structure, and since LER of the Cr-based
light-shielding film pattern becomes high for this reason, even
though the phase shift film has an amorphous structure, at the time
of dry etching of the phase shift film, due to LER of the Cr-based
light-shielding film, LER of the phase shift film pattern is
deteriorated. However, in the preferred embodiment of the present
invention, since the upper layer or the lower layer in the
light-shielding film has an amorphous structure, it is possible to
reduce LER of the light-shielding film pattern at the time of dry
etching of the light-shielding film. As a result, at the time of
dry etching of the phase shift film utilizing the light-shielding
film pattern as a mask, LER of the phase shift film can be improved
without deterioration of LER of the phase shift film pattern.
7. Phase Shift Mask and Production Method Thereof
[0199] A phase shift mask obtained from the phase shift mask blank
of the present invention and a method for producing the same will
be described below.
[0200] Firstly, a resist is applied to a phase shift mask blank in
which a light-shielding film is formed, and it is dried to obtain a
resist film. It is required to select an appropriate resist
corresponding to a writing apparatus to be used. For EB writing
that is usually employed, a positive-type or negative-type resist
having an aromatic skeleton in a polymer is preferably used, and
for production of a phase shift mask for a fine pattern in which
the present invention is particularly effectively used, a
chemically-amplified resist is preferably used.
[0201] The thickness of the resist film must be within a range in
which a good pattern shape can be obtained and the film can
function as an etching mask. In particular, when forming a fine
pattern as a mask for ArF exposure, the film thickness is
preferably 200 nm or less, and more preferably 150 nm or less. Note
that when utilizing a two-layer resist method in which a resist
comprising a silicon-based resin is combined with a lower layer
comprising an aromatic resin, or a surface imaging method in which
a chemically-amplified aromatic resist is combined with a
silicon-based surface treatment agent, the film thickness can be
further reduced. Application conditions and a drying method are
suitably selected depending on the type of a resist to be used.
[0202] In order to reduce occurrence of stripping or collapsing of
a fine resist pattern, a resin layer may be formed on the surface
of a phase shift mask blank before application of a resist.
Further, instead of forming the resin layer, a surface treatment
for decreasing surface energy on the surface of the substrate
(phase shift mask blank) may be performed before application of the
resist. Examples of surface treatment methods include those in
which HMDS or another organosilicon-based surface treatment agent
that is commonly used in the semiconductor production processes is
used to alkylsilylate the surface.
[0203] Next, regarding the phase shift mask blank in which the
resist film is formed, writing to the resist can be carried out
using a method utilizing EB irradiation or a method utilizing light
irradiation. In general, the method utilizing EB irradiation is
preferably used to form a fine pattern. When using a
chemically-amplified resist, writing is usually carried out with
energy in a range of 3 to 40 .mu.C/cm.sup.2, and after writing,
heat treatment is applied thereto and then a resist film is
subjected to development treatment to obtain a resist pattern.
[0204] Using the resist pattern obtained above as an etching mask,
etching is applied to a light-shielding film or a light-shielding
film and other films (phase shift film, etc.). At the time of
etching, a publicly-known chlorine-based or fluorine-based dry
etching can be suitably used depending on the composition of the
light-shielding film (surface layer, interlayer, antireflection
layer, etc.) or other films.
[0205] After obtaining a light-shielding pattern by etching, the
resist is stripped using a predetermined stripping solution,
thereby obtaining a photomask in which the light-shielding film
pattern is formed.
8. Pattern Transfer
[0206] The phase shift mask of the present invention is especially
useful as a mask to be used in a pattern transfer method in which a
fine pattern with a DRAM half-pitch (hp) of 45 nm or less in a
semiconductor design rule is formed by using an exposure method
with a numerical aperture NA>1 and an exposure light wavelength
of equal to or less than 200 nm.
[0207] The phase shift mask blank of the present invention is
especially effective in a case where it is used for forming a
resist pattern with a line width of less than 100 nm on a phase
shift mask blank. A mask having an OPC structure is an example of
such a phase shift mask blank. In the OPC mask, the width of an
auxiliary pattern provided around the main pattern with the object
of increasing the resolution of the main pattern is the smallest.
Therefore, the phase shift mask blank of the present invention is
especially useful for pattern transfer using a phase shift mask
having these patterns.
EXAMPLES
[0208] Hereinafter, the present invention will be described in more
detail based on working examples, but the present invention is not
limited thereto.
Example 1
Production of Photomask Blank
[0209] In this working example, a halftone phase shift mask blank,
in which a phase shift film 5 and a light-shielding film consisting
of 3 layers are provided on a light transmissive substrate 10, was
produced (see FIG. 1).
[0210] Firstly, on the light transmissive substrate 10 made of
quartz glass having a size of 6-inch square and a thickness of 0.25
inch, a halftone phase shift film 5 for ArF excimer laser
(wavelength: 193 nm) constituted by a single layer comprising Mo,
Si and N as the main components was formed (thickness: 69 nm) using
a single-wafer sputtering apparatus.
[0211] As shown in Table 1, sputtering (DC sputtering) conditions
are as follows:
Sputtering target: a mixed target of Mo and Si (Mo:Si=8:92 mol %)
Sputtering gas: a mixed gas atmosphere of Ar gas, N.sub.2 gas and
He gas (Ar: 9 sccm, N.sub.2: 81 sccm, He: 76 sccm) Gas pressure
during discharge: 0.3 Pa Applied power: 2.8 kW
[0212] When the ArF excimer laser light (wavelength: 193 nm) was
applied, the transmittance of the obtained phase shift film 5 was
5.5% and the phase shift amount was about 180.degree..
[0213] Next, using the same sputtering apparatus as that by which
the phase shift film 5 was formed, a lower layer 3 consisting of
CrOCN was formed (thickness: 30 nm). Sputtering (DC sputtering)
conditions are shown in Table 1.
[0214] After that, using the same sputtering apparatus as that by
which the lower layer 3 was formed, an interlayer 2 consisting of
CrN was formed (thickness: 4 nm). Sputtering (DC sputtering)
conditions are shown in Table 1.
[0215] In addition, using the same sputtering apparatus as that by
which the interlayer 2 was formed, an upper layer 1 consisting of
CrOCN was formed (thickness: 14 nm). Sputtering (DC sputtering)
conditions are shown in Table 1.
[0216] The flow rate of the sputtering gas in Table 1 is converted
into volume percentage as follows:
Upper layer 1: Ar=21.0 vol %, CO.sub.2=36.8 vol %, N.sub.2=10.5 vol
%, He=31.6 vol %
Interlayer 2: Ar=83.3 vol %, N.sub.2=16.7 vol %
[0217] Lower layer 3: Ar=22.0 vol %, CO.sub.2=38.9 vol %,
N.sub.2=5.6 vol %, He=33.3 vol %
[0218] Thus, a photomask blank, in which the phase shift film 5,
the lower layer 3, the interlayer 2 and the upper layer 1 are
laminated in this order on the light transmissive substrate made of
quartz glass, was obtained. The optical density (OD) of the
light-shielding film consisting of the lower layer 3, the
interlayer 2 and the upper layer 1 with respect to light having a
wavelength of 193.4 nm was 1.9. Further, the optical densities of
the respective layers are as shown in Table 1.
[0219] Further, compositions and atom number densities of the upper
layer 1, the interlayer 2 and the lower layer 3 of the obtained
photomask blank were analyzed by RBS (Rutherford Backscattering
Spectrometry). RBS is a technique for analyzing a surface
composition relative to a surface density (atms/cm.sup.2) in the
depth direction. When the thickness of each layer is already-known,
the atom number densities (atms/cm.sup.3) can be calculated from
the following formula:
Atom Number Density=Surface Density/Thickness
[0220] The atom number density of the upper layer 1 was calculated
using the above-described technique.
[0221] As a result, the film composition of the upper layer 1
(thickness: 14 nm) was as follows: Cr: 34 atomic %, C: 11 atomic %,
O: 39 atomic %, and N: 16 atomic %. Further, the chromium ratio in
the upper layer 1 was as follows: C/Cr: 0.3, O/Cr: 1.2, and N/Cr:
0.5. Further, the atom number density of the upper layer 1 was
10.5.times.10.sup.22 atms/cm.sup.3.
[0222] Regarding the film composition of the interlayer 2
(thickness: 4 nm), Cr was at least 64 atomic % or more, and N was
at least 8 atomic % or more.
[0223] Further, the film composition of the lower layer 3
(thickness: 30 nm) was as follows: Cr: 36 atomic %, C: 15 atomic %,
O: 39 atomic %, and N: 9 atomic %. Further, the chromium ratio in
the lower layer 3 was as follows: C/Cr: 0.4, O/Cr: 1.1, and N/Cr:
0.3.
[0224] When the cross section of the obtained photomask blank was
observed using a TEM (transmission electron microscope) and an
X-ray diffractometer (XRD), the upper layer 1 had an amorphous
structure in which the grain size was 1 to 2 nm. When measuring the
surface roughness using an atomic force microscope (AFM), Ra=0.45
nm.
[0225] Ozone water having a concentration of 50 ppm was supplied
with a flow rate of 1.4 L/minute to the surface of the substrate of
the photomask blank obtained in this working example being shaken
by a swing arm for 60 minutes, and changes of the thickness,
surface reflectance and optical density of the light-shielding film
were measured to evaluate chemical resistance.
[0226] As a result, the thickness of the light-shielding film was
not changed by spraying of the ozone water. Further, change of the
surface reflectance was +0.82% when using light having a wavelength
of 193 nm. Change of the optical density of the light-shielding
film was -0.04.
[0227] In addition, the same layer as the upper layer 1 of this
working example was directly formed on a glass substrate by
sputtering, and ozone water having a concentration of 50 ppm was
sprayed on the upper layer 1 for 60 minutes to measure change of
the reflectance. Note that in the measurement of this working
example, using a spectrophotometer (Hitachi High-Technologies
Corporation; U-4100), a reflection spectrum was measured before and
after spraying of the ozone water, and change of the amount thereof
was calculated.
[0228] As a result, changes were as follows: light having a
wavelength of 193 nm: +0.7%, light having a wavelength of 257 nm:
+1.5%, light having a wavelength of 365 nm: +2.0%, and light having
a wavelength of 488 nm: +1.2%. As used herein, "+" represents
increase of reflectance, and "-" represents decrease of
reflectance.
[0229] Thus, it was confirmed that the light-shielding film of this
working example has high chemical resistance with respect to ozone
treatment.
(Preparation of Photomask)
[0230] On the obtained photomask blank, a chemically-amplified
positive resist for electron beam writing (exposure) (PRL009:
FUJIFILM Electronic Materials Co., Ltd.) was applied using a spin
coat method to provide the film thickness of 150 nm. On the formed
resist film, a desired pattern was wrote using an electron beam
writing device, and after that, it was subjected to the development
using a predetermined developer to form a resist pattern.
[0231] Next, the light-shielding film consisting of the lower layer
3, the interlayer 2 and the upper layer 1 was subjected to dry
etching along the above-described resist pattern to form a
light-shielding film pattern. As a dry etching gas, a mixed gas of
Cl.sub.2 and O.sub.2 (Cl.sub.2:O.sub.2=4:1) was used.
[0232] During dry etching of the above-described light-shielding
film, etching rates of the respective layers were as shown in Table
1. The clear etching time of the entire light-shielding film was
84.5 sec, and when compared to Comparative Example 1 described
below, reduction in time of about 8% was confirmed. Further, when
the light-shielding film pattern was subjected to cross-sectional
observation using a SEM (Scanning Electron Microscopy), it was in a
good state in which the angle of the cross section of the
light-shielding film was perpendicular to the substrate. In
addition, a perpendicular cross-section shape was obtained even
when the over etching time was reduced, and it was confirmed that
it is possible to provide reduction in total etching time of about
20% compared to Comparative Example 1.
[0233] Next, etching of a phase shift film was carried out using
the above-described resist pattern and light-shielding film pattern
as a mask to form a phase shift film pattern. Etching of the phase
shift film is affected by the above-described cross-section shape
of the light-shielding film pattern. Since the light-shielding film
pattern had the good cross-section shape, the phase shift film
pattern also had a good cross-section shape.
[0234] After that, the remaining resist pattern was stripped off,
and a resist film was applied again. Then pattern exposure was
carried out in order to remove an unnecessary light-shielding film
pattern in the transfer area. After that, the resist film was
developed to form a resist pattern. Next, wet etching was carried
out to remove the unnecessary light-shielding film pattern, and the
remaining resist pattern was stripped off, thereby obtaining a
photomask.
[0235] The obtained photomask was subjected to resolution
evaluation. The resist film had a good resolution, and the
resolution of the light-shielding film pattern was less than 60 nm
(corresponding to DRAM hp 32 nm).
[0236] In the phase shift mask blank produced in Example 1, when
the thickness of the interlayer was regarded as 1, the thickness
ratio of the upper layer was 3.5. Further, the thickness percentage
of the interlayer relative to the thickness of the entire
light-shielding film was 8%, and the thickness percentage of the
interlayer relative to the thickness of the lower layer was 13%
(see Table 2).
Reference Example 1
[0237] In order to examine the light-shielding film provided in the
phase shift mask of the present invention, in this reference
example, a binary mask blank, in which a light-shielding film
consisting of 3 layers is provided on a light transmissive
substrate 10, was produced (see FIG. 2).
[0238] That is, reactive sputtering was carried out under the same
conditions as those in Example 1 except that the conditions of
sputtering were set as shown in Table 1.
[0239] The flow rate of the sputtering gas in Table 1 is converted
into volume percentage as follows:
Upper layer 1: Ar=21.0 vol %, CO.sub.2=36.8 vol %, N.sub.2=10.5 vol
%, He=31.6 vol %
Interlayer 2: Ar=30.8 vol %, NO=23.1 vol %, He=46.2 vol %
[0240] Lower layer 3: Ar=23.5 vol %, CO.sub.2=29.4 vol %,
N.sub.2=11.8 vol %, He=35.3 vol %
[0241] Thus, a photomask blank as shown in FIG. 2, in which the
lower layer 3, the interlayer 2 and the upper layer 1 are laminated
in this order on the light transmissive substrate 10 made of quartz
glass, was obtained. The optical density (OD) of the
light-shielding film consisting of the lower layer 3, the
interlayer 2 and the upper layer 1 with respect to light having a
wavelength of 193.4 nm was 3. Further, the optical densities of the
respective layers are as shown in Table 1.
[0242] Next, in the same manner as that in Example 1, the
compositions of the upper layer 1, the interlayer 2 and the lower
layer 3 obtained and the atom number density of the upper layer 1
were analyzed by RBS.
[0243] As a result, the film composition of the upper layer 1
(thickness: 14 nm) was as follows: Cr: 32 atomic %, C: 16 atomic %,
O: 37 atomic %, and N: 16 atomic %. Further, the chromium ratio in
the upper layer 1 was as follows: C/Cr: 0.5, O/Cr: 1.2, and N/Cr:
0.5. Further, the atom number density of the upper layer 1 was
11.0.times.10.sup.22 atms/cm.sup.3.
[0244] Regarding the film composition of the interlayer 2
(thickness: 25 nm), Cr was 87 atomic %, O was 9 atomic % and N was
4 atomic %. Further, the chromium ratio in the interlayer 2 was as
follows: O/Cr: 0.1, and N/Cr: 0.05.
[0245] The film composition of the lower layer 3 (thickness: 25 nm)
was as follows: Cr: 49 atomic %, C: 11 atomic %, O: 26 atomic %,
and N: 14 atomic %. Further, the chromium ratio in the lower layer
3 was as follows: C/Cr: 0.2, O/Cr: 0.5, and N/Cr: 0.3.
[0246] When the cross section of the obtained photomask blank was
observed using a TEM (transmission electron microscope) and an
X-ray diffractometer (XRD), the upper layer 1 had an amorphous
structure in which the grain size was 1 to 2 nm. When measuring the
surface roughness using an atomic force microscope (AFM), Ra=0.28
nm.
[0247] Ozone water having a concentration of 50 ppm was supplied
with a flow rate of 1.4 L/minute to the surface of the substrate of
the photomask blank obtained in this reference example being shaken
by a swing arm for 60 minutes, and changes of the thickness,
surface reflectance and optical density of the light-shielding film
were measured to evaluate chemical resistance.
[0248] As a result, the thickness of the light-shielding film was
not changed by spraying of the ozone water. Further, change of the
surface reflectance was -0.02% when using light having a wavelength
of 193 nm. Change of the optical density of the light-shielding
film was -0.06.
[0249] In addition, the same layer as the upper layer 1 of this
reference example was directly formed on a glass substrate by
sputtering, and ozone water having a concentration of 50 ppm was
sprayed on the upper layer 1 for 60 minutes to measure change of
the reflectance in the same measurement method as that in Example
1.
[0250] As a result, changes were as follows: light having a
wavelength of 193 nm: +0.5%, light having a wavelength of 257 nm:
+2.1%, light having a wavelength of 365 nm: +5.3%, and light having
a wavelength of 488 nm: +4.6%.
[0251] Thus, it was confirmed that the light-shielding film of this
reference example has high chemical resistance with respect to
ozone treatment.
[0252] On the obtained photomask blank, a chemically-amplified
positive resist for electron beam writing (exposure) (PRL009:
FUJIFILM Electronic Materials Co., Ltd.) was applied using a spin
coat method to provide the film thickness of 200 nm. On the formed
resist film, a desired pattern was wrote using an electron beam
writing device, and after that, it was subjected to the development
using a predetermined developer to form a resist pattern.
[0253] Next, the light-shielding film consisting of the lower layer
3, the interlayer 2 and the upper layer 1 was subjected to dry
etching along the above-described resist pattern to form a
light-shielding film pattern. As a dry etching gas, a mixed gas of
Cl.sub.2 and O.sub.2 (Cl.sub.2:O.sub.2=4:1) was used. After that,
the remaining resist pattern was stripped off, thereby obtaining a
photomask.
[0254] During dry etching of the above-described light-shielding
film, etching rates of the respective layers were as shown in Table
1. Further, when observing the light-shielding film pattern in a
manner similar to that in Example 1, though being tapered to a
certain degree, it was in a good state in which the angle of the
cross section of the light-shielding film was perpendicular to the
substrate. In addition, a perpendicular cross-section shape was
obtained even when the over etching time was reduced, and it was
confirmed that it is possible to provide reduction in total etching
time of about 25% compared to Comparative Example 2.
[0255] The obtained photomask was subjected to resolution
evaluation. The resist film had a good resolution, and the
resolution of the light-shielding film pattern was less than 70 nm
(corresponding to DRAM hp 45 nm).
Reference Example 2
[0256] In order to examine the light-shielding film provided in the
phase shift mask of the present invention like Reference Example 1,
in this reference example, the same binary mask blank as that in
Reference Example 1 was produced, except that the layer-forming
conditions and thickness of the interlayer 2 and the thickness of
the lower layer were changed from those in Reference Example 1.
[0257] That is, reactive sputtering was carried out under the same
conditions as those in Example 2 except that the conditions of
sputtering were set as shown in Table 1.
[0258] The flow rate of the sputtering gas in Table 1 is converted
into volume percentage as follows:
Upper layer 1: Ar=21.0 vol %, CO.sub.2=36.8 vol %, N.sub.2=10.5 vol
%, He=31.6 vol %
Interlayer 2: Ar=27.2 vol %, NO=18.2 vol %, He=54.5 vol %
[0259] Lower layer 3: Ar=23.5 vol %, CO.sub.2=29.4 vol %,
N.sub.2=11.8 vol %, He=35.3 vol %
[0260] Thus, a photomask blank as shown in FIG. 2, in which the
lower layer 3, the interlayer 2 and the upper layer 1 are laminated
in this order on the light transmissive substrate 10 made of quartz
glass, was obtained. The optical density (OD) of the
light-shielding film consisting of the lower layer 3, the
interlayer 2 and the upper layer 1 with respect to light having a
wavelength of 193.4 nm was 3.1. Further, the optical densities of
the respective layers are as shown in Table 1.
[0261] When the cross section of the obtained photomask blank was
observed using a TEM (transmission electron microscope) and an
X-ray diffractometer (XRD), the upper layer 1 had an amorphous
structure in which the grain size was 1 to 2 nm. When measuring the
surface roughness using an atomic force microscope (AFM), Ra=0.28
nm.
[0262] In addition, changes of the thickness, surface reflectance
and optical density of the light-shielding film were measured to
evaluate chemical resistance of the photomask blank in a manner
similar to that in Reference Example 1.
[0263] As a result, the thickness of the light-shielding film was
not changed by spraying of the ozone water. Further, change of the
surface reflectance was -0.02% when using light having a wavelength
of 193 nm. Change of the optical density of the light-shielding
film was -0.06.
[0264] Thus, it was confirmed that the light-shielding film of this
reference example has high chemical resistance with respect to
ozone treatment.
[0265] After that, a photomask was obtained in a manner similar to
that in Reference Example 1.
[0266] During dry etching of the above-described light-shielding
film, etching rates of the respective layers were as shown in Table
1. Further, when observing the light-shielding film pattern in a
manner similar to that in Example 1, it was in a good state in
which the angle of the cross section of the light-shielding film
was perpendicular to the substrate. In addition, a perpendicular
cross-section shape was obtained even when the over etching time
was reduced, and it was confirmed that it is possible to provide
reduction in total etching time of about 25% compared to
conventional cases.
[0267] The obtained photomask was subjected to resolution
evaluation. The resist film had a good resolution, and the
resolution of the light-shielding film pattern was less than 70 nm
(corresponding to DRAM hp 45 nm).
TABLE-US-00001 TABLE 1 Film Sputtering gas Gas Applied Thick-
Etching Com- (sccm) Pressure Power ness rate Optical position
Target Ar CH.sub.4 CO.sub.2 NO N.sub.2 He (Pa) (kw) (nm) (nm/sec)
Density Example 1 Upper layer 1 CrOCN Cr 20 -- 35 -- 10 30 0.2 1.7
14 0.67 0.51 Interlayer 2 CrN Cr 25 -- -- -- 5 -- 0.1 1.7 4
<0.44 0.20 Lower layer 3 CrOCN Cr 20 -- 35 -- 5 30 0.2 1.5 30
0.44~0.67 1.17 Phase shift MoSiN Mo + Si 9 -- -- -- 81 76 0.3 2.8
69 -- -- film 5 Reference Upper layer 1 CrOCN Cr 20 -- 35 -- 10 30
0.2 1.8 14 0.67 0.51 Example 1 Interlayer 2 CrON Cr 20 -- -- 15 --
30 0.1 1.7 25 <0.44 1.33 Lower layer 3 CrOCN Cr 20 -- 25 -- 10
30 0.2 1.7 25 0.44 1.14 Reference Upper layer 1 CrOCN Cr 20 -- 35
-- 10 30 0.2 1.8 14 0.67 0.51 Example 2 Interlayer 2 CrON Cr 15 --
-- 10 -- 30 0.1 1.7 17 <0.44 0.85 Lower layer 3 CrOCN Cr 20 --
25 -- 10 30 0.2 1.7 39 0.44 1.71
Example 2
[0268] In Example 2, a phase shift mask blank was produced in a
manner similar to that in Example 1, except that the transmittance
of the phase shift film 5 was increased, the thickness of each of
the interlayer 2 and the lower layer 3 in the light-shielding film
was changed to be larger and the thickness of the entire
light-shielding film was changed to be larger compared to those in
Example 1.
[0269] The phase shift film 5 was formed under the following
conditions:
Sputtering target: a mixed target of Mo and Si (Mo:Si=10 mol %:90
mol %) Sputtering gas: a mixed gas atmosphere of Ar gas, O.sub.2
gas, N.sub.2 gas and He gas (Ar: 6 sccm, O.sub.2: 15 sccm, N.sub.2:
57 sccm, He: 51 sccm) Gas pressure during discharge: 0.25 Pa
Applied power: 2.8 kW
[0270] Under the above-described conditions, the halftone phase
shift film 5 for an ArF excimer laser light (wavelength: 193 nm),
which is constituted by a single layer comprising Mo, Si, O and N
as the main components (thickness: 93 nm), was directly formed on a
light transmissive substrate.
[0271] With respect to the ArF excimer laser light (wavelength: 193
nm), the transmittance of the obtained phase shift film 5 was 15%
and the phase shift amount was 178.degree..
[0272] Next, a light-shielding film having the entire thickness of
58 nm was formed on the phase shift film under the same conditions
as those in Example 1, except that in the light-shielding film, the
thickness of the interlayer 2 was set at 5 nm and the thickness of
the lower layer 3 was set at 39 nm. Thus, a phase shift mask blank
was produced.
[0273] The structure of the phase shift mask blank produced in
Example 2 and the resolution and the cross-section shape of the
obtained phase shift mask were as shown in Table 2.
[0274] Note that in Table 2, values in the column of thickness
ratio show, from top down, "the thickness ratio of the upper layer
when the thickness of the interlayer in the light-shielding film is
regarded as 1" (e.g., 2.8 in Example 2), "the thickness percentage
(%) of the interlayer relative to the thickness of the entire
light-shielding film" (e.g., 9% in Example 2), and "the thickness
percentage (%) of the interlayer relative to the thickness of the
lower layer" (e.g., 13% in Example 2).
Comparative Example 1
[0275] In this comparative example, a halftone phase shift mask
blank, which has a light-shielding film consisting of a
light-shielding layer and a front-surface antireflection layer, was
produced.
[0276] Specifically, using an in-line sputtering apparatus, a
light-shielding layer was formed on the same phase shift film as
that in Example 1. Sputtering (DC sputtering) conditions are as
follows:
Sputtering target: Cr Sputtering gas: a mixed gas atmosphere of Ar
gas, N.sub.2 gas and He gas (Ar: 30 sccm, N.sub.2: sccm, He: 40
sccm) Gas pressure during discharge: 0.2 Pa Applied power: 0.8
kW
[0277] After that, a front-surface antireflection layer was formed
on the light-shielding layer. Sputtering (DC sputtering) conditions
are as follows:
Sputtering target: chromium (Cr) Sputtering gas: a gas in which a
mixed gas of argon (Ar) and methane (CH.sub.4) (CH.sub.4: 3.5
volume %), NO and He are mixed together (Ar+CH.sub.4: 65 sccm, NO:
3 sccm, He: 40 sccm) Gas pressure during discharge: 0.3 Pa Applied
power: 0.3 kW
[0278] Thus, a photomask blank having a thickness of the
light-shielding film of 48 nm, in which the phase shift film, the
light-shielding layer and the front-surface antireflection layer
are laminated in this order on the light transmissive substrate
made of quartz glass, was obtained. The optical density (OD) of the
light-shielding film consisting of the light-shielding layer and
the front-surface antireflection layer with respect to light having
a wavelength of 193.4 nm was 1.9.
[0279] Next, in the same manner as that in Example 1, the
compositions of the front-surface antireflection layer and the
light-shielding layer obtained and the atom number density of the
front-surface antireflection layer were analyzed by RBS.
[0280] As a result, the film composition of the front-surface
antireflection layer (thickness: 24 nm) was as follows: Cr: 34
atomic %, O: 32 atomic % and N: 23 atomic %. Further, the chromium
ratio in the front-surface antireflection layer was as follows:
O/Cr: 0.9, and N/Cr: 0.7. Further, the atom number density of the
front-surface antireflection layer was 7.4.times.10.sup.22
atms/cm.sup.3.
[0281] The film composition of the light-shielding layer
(thickness: 24 nm) was as follows: Cr: 59 atomic %, and N: 39
atomic %. Further, the chromium ratio in the light-shielding layer
was as follows: N/Cr: 0.7.
[0282] Since the in-line sputtering apparatus was used, each of the
light-shielding layer and the front-surface antireflection layer
was a gradient film that is compositionally-graded in the thickness
direction. Therefore, the above-described film compositions are
averaged values.
[0283] When the cross section of the obtained photomask blank was
observed using a TEM (transmission electron microscope) and an
X-ray diffractometer (XRD), the front-surface antireflection layer
had a low-density porous columnar structure. When measuring the
surface roughness using an atomic force microscope (AFM), Ra=0.70
nm.
[0284] In addition, chemical resistance of the photomask blank
obtained in this comparative example was evaluated in a manner
similar to that in Example 1.
[0285] As a result, the thickness of the light-shielding film was
decreased by 5.8 nm by spraying of the ozone water. Further, change
of the surface reflectance was +2.72% when using light having a
wavelength of 193 nm. Change of the optical density of the
light-shielding film was -0.38.
[0286] In addition, the same layer as the front-surface
antireflection layer of this comparative example was directly
formed on a glass substrate by sputtering, and change of the amount
of the reflectance was measured using the same measurement method
as that in Example 1.
[0287] As a result, changes were as follows: light having a
wavelength of 193 nm: +2.5% (19.8%.fwdarw.22.3%), light having a
wavelength of 257 nm: +9.1% (16.4%.fwdarw.25.5%), light having a
wavelength of 365 nm: +13.9% (19.9%.fwdarw.33.8%), and light having
a wavelength of 488 nm: +11.0% (29.9%.fwdarw.40.9%).
[0288] Thus, it was confirmed that the light-shielding film of this
comparative example had lower chemical resistance with respect to
ozone treatment compared to Examples 1 and 2.
[0289] On the obtained photomask blank, a chemically-amplified
positive resist for electron beam writing (exposure) was applied to
provide the film thickness of 150 nm in a manner similar to that in
Example 1, and a photomask was obtained in a manner similar to that
in Example 1.
[0290] During dry etching of the above-described light-shielding
film, the etching rate was lower than that of Example 1. The clear
etching time of the entire light-shielding film was 92.0 sec.
Further, when observing the light-shielding film pattern in a
manner similar to that in Example 1, the angle of the cross section
of the light-shielding film was not formed to be perpendicular to
the substrate. For this reason, the phase shift film pattern did
not have a good cross-section shape.
[0291] The obtained photomask was subjected to resolution
evaluation. The resolution of the resist film was bad, and due to
etching defects, the resolution of the light-shielding film pattern
was 80 nm or more.
TABLE-US-00002 TABLE 2 Cr N + O Cross- content content Thickness
Thickness section (atm %) (atm %) (nm) ratio (%) OD Resolution
shape Example 1 TOTAL -- -- 48 1.88 (T = 5.5%) TAR CrOCN 34 55 14
3.5 0.51 ABS CrN not less not 4 8 0.20 than 64 greater than 8 BAR
CrOCN 36 48 30 13 1.17 Example 2 TOTAL -- -- 58 2.28 (T = 15%) TAR
CrOCN 34 55 14 2.8 0.51 ABS CrN not less not 5 9 0.25 than 64
greater than 8 BAR CrOCN 36 48 39 13 1.52
Example 3
[0292] In Example 3, a light-shielding film having the same
composition as that in Reference Example 2 was formed on a phase
shift film having the transmittance of 20%, wherein the thicknesses
of the upper layer, the interlayer and the lower layer were changed
as shown in Table 3, thereby producing a phase shift mask
blank.
[0293] The phase shift film 5 was formed under the following
conditions:
Sputtering target: a mixed target of Mo and Si (Mo:Si=4 mol %:96
mol %) Sputtering gas: a mixed gas atmosphere of Ar gas, O.sub.2
gas, N.sub.2 gas and He gas (Ar: 11.5 sccm, O.sub.2: 8.1 sccm,
N.sub.2: 50 sccm, He: 100 sccm)
[0294] Under the above-described conditions, the phase shift film
5, which is constituted by a single layer comprising Mo, Si, O and
N as the main components (thickness: 74 nm), was formed on a light
transmissive substrate.
[0295] With respect to an ArF excimer laser light (wavelength: 193
nm), the transmittance of the obtained phase shift film 5 was 20.0%
and the phase shift amount was 177.4.degree..
[0296] When the obtained phase shift film was analyzed by RBS, Mo
was 1.8 atomic %, Si was 37.2%, N was 48.1% and O was 12.7 atomic
%.
[0297] Next, a light-shielding film was formed on the phase shift
film under the same sputtering conditions as those in Reference
Example 2, wherein the thicknesses of the lower layer, the
interlayer and the upper layer were set at 36 nm, 5 nm and 14 nm,
respectively.
[0298] The structure of the phase shift mask blank produced in
Example 3 and the resolution and the cross-section shape of the
obtained phase shift mask were as shown in Table 3. Further, the
etching rates of the respective layers in the light-shielding film
were the same as those in Reference Example 2.
Example 4
[0299] In Example 4, a light-shielding film having the same
composition as that in Reference Example 2 was formed on a phase
shift film having the transmittance of 14.8%, wherein the
thicknesses of the upper layer, the interlayer and the lower layer
were changed as shown in Table 3, thereby producing a phase shift
mask blank.
[0300] The phase shift film 5 was formed under the following
conditions:
Sputtering target: a mixed target of Mo and Si (Mo:Si=4 mol %:96
mol %) Sputtering gas: a mixed gas atmosphere of Ar gas, O.sub.2
gas, N.sub.2 gas and He gas (Ar: 11 sccm, O.sub.2: 4.2 sccm,
N.sub.2: 50 sccm, He: 100 sccm)
[0301] Under the above-described conditions, the phase shift film
5, which is constituted by a single layer comprising Mo, Si, O and
N as the main components (thickness: 68 nm), was formed on a light
transmissive substrate.
[0302] With respect to an ArF excimer laser light (wavelength: 193
nm), the transmittance of the obtained phase shift film 5 was 14.8%
and the phase shift amount was 176.8.degree..
[0303] When the obtained phase shift film was analyzed by RBS, Mo
was 1.8 atomic %, Si was 38.0%, N was 52.5% and O was 7.5 atomic
%.
[0304] Next, a light-shielding film was formed on the phase shift
film under the same sputtering conditions as those in Reference
Example 2, wherein the thicknesses of the lower layer, the
interlayer and the upper layer were set at 33 nm, 5 nm and 14 nm,
respectively.
[0305] The structure of the phase shift mask blank produced in
Example 4 and the resolution and the cross-section shape of the
obtained phase shift mask were as shown in Table 3. Further, the
etching rates of the respective layers in the light-shielding film
were the same as those in Reference Example 2.
Example 5
[0306] In Example 5, a light-shielding film having the same
composition as that in Reference Example 2 was formed on a phase
shift film having the transmittance of 13.4%, wherein the
thicknesses of the upper layer, the interlayer and the lower layer
were changed as shown in Table 3, thereby producing a phase shift
mask blank.
[0307] The phase shift film 5 was formed under the following
conditions:
Sputtering target: a mixed target of Mo and Si (Mo:Si=4 mol %:96
mol %) Sputtering gas: a mixed gas atmosphere of Ar gas, O.sub.2
gas, N.sub.2 gas and He gas (Ar: 10.5 sccm, N.sub.2: 55 sccm, He:
100 sccm)
[0308] Under the above-described conditions, the phase shift film
5, which is constituted by a single layer comprising Mo, Si and N
as the main components (thickness: 58 nm), was formed on a light
transmissive substrate.
[0309] With respect to an ArF excimer laser light (wavelength: 193
nm), the transmittance of the obtained phase shift film 5 was 13.4%
and the phase shift amount was 160.0.degree..
[0310] When the obtained phase shift film was analyzed by RBS, Mo
was 1.8 atomic %, Si was 39.7% and N was 58.3%.
[0311] Next, a light-shielding film was formed on the phase shift
film under the same sputtering conditions as those in Reference
Example 2, wherein the thicknesses of the lower layer, the
interlayer and the upper layer were set at 32 nm, 4 nm and 14 nm,
respectively.
[0312] The structure of the phase shift mask blank produced in
Example 5 and the resolution and the cross-section shape of the
obtained phase shift mask were as shown in Table 3. Further, the
etching rates were the same as those in Reference Example 2.
TABLE-US-00003 TABLE 3 Cr N + O Cross- content content Thickness
Thickness section (atm %) (atm %) (nm) ratio (%) OD Resolution
shape Example 3 TOTAL -- -- 55 2.36 (T = 20.0%) TAR CrOCN 32 53 14
2.8 0.51 ABS CrON 87 13 5 9 0.27 BAR CrOCN 49 40 36 14 1.58 Example
4 TOTAL -- -- 52 2.23 (T = 14.8%) TAR CrOCN 32 53 14 2.8 0.51 ABS
CrON 87 13 5 10 0.27 BAR CrOCN 49 40 33 15 1.45 Example 5 TOTAL --
-- 50 2.13 (T = 13.4%) TAR CrOCN 32 53 14 3.5 0.51 ABS CrON 87 13 4
8 0.21 BAR CrOCN 49 40 32 13 1.41
[0313] In Examples 2-5, the resist film had a good resolution, and
the resolution of the light-shielding film pattern was less than 60
nm. In addition, the cross-section shape was perpendicular and
good.
INDUSTRIAL APPLICABILITY
[0314] The photomask blank of the preferred embodiment of the
present invention can suppress shadowing, and therefore can be used
for high-NA lithography and can also be used for lithography using
an exposure light having a short wavelength. Therefore, by using
the photomask blank of the preferred embodiment of the present
invention, a very fine mask pattern can be formed.
[0315] In addition, the photomask blank of the preferred embodiment
of the present invention can be applied to, for example, a
photomask blank of a generation of hp 45 nm, hp 32 nm or beyond in
hyper-NA-ArF lithography.
* * * * *