U.S. patent application number 09/893532 was filed with the patent office on 2001-11-01 for photomask and pattern forming method employing the same.
This patent application is currently assigned to Hitachi, Ltd.. Invention is credited to Hasegawa, Norio, Hayano, Katsuya, Murai, Fumio.
Application Number | 20010036583 09/893532 |
Document ID | / |
Family ID | 18187754 |
Filed Date | 2001-11-01 |
United States Patent
Application |
20010036583 |
Kind Code |
A1 |
Hasegawa, Norio ; et
al. |
November 1, 2001 |
Photomask and pattern forming method employing the same
Abstract
A semitransparent phase shifting mask has, in the periphery of a
pattern element area, a light shielding portion which is formed by
a semitransparent phase shifting portion and a transparent portion
with the optimal size combination. A pattern is formed employing
the semitransparent phase shifting mask.
Inventors: |
Hasegawa, Norio; (Tokyo,
JP) ; Murai, Fumio; (Tokyo, JP) ; Hayano,
Katsuya; (Hachioji-shi, JP) |
Correspondence
Address: |
MATTINGLY, STANGER & MALUR, P.C.
Suite 370
1800 Diagonal Road
Alexandria
VA
22314
US
|
Assignee: |
Hitachi, Ltd.
|
Family ID: |
18187754 |
Appl. No.: |
09/893532 |
Filed: |
June 29, 2001 |
Related U.S. Patent Documents
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Application
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Filing Date |
Patent Number |
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09893532 |
Jun 29, 2001 |
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09577367 |
May 23, 2000 |
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6258513 |
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09577367 |
May 23, 2000 |
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09359732 |
Jul 23, 1999 |
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6087074 |
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09359732 |
Jul 23, 1999 |
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09188368 |
Nov 10, 1998 |
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6013398 |
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09188368 |
Nov 10, 1998 |
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08904754 |
Aug 1, 1997 |
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5851703 |
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08904754 |
Aug 1, 1997 |
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08699732 |
Aug 20, 1996 |
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5656400 |
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08699732 |
Aug 20, 1996 |
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08418402 |
Apr 7, 1995 |
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5578421 |
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08418402 |
Apr 7, 1995 |
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08162319 |
Dec 7, 1993 |
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5429896 |
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Current U.S.
Class: |
430/5 ; 430/311;
430/312; 430/313 |
Current CPC
Class: |
G03F 1/32 20130101; G03F
1/26 20130101; G03F 1/29 20130101; G03F 7/2022 20130101; G03F
7/70066 20130101 |
Class at
Publication: |
430/5 ; 430/311;
430/312; 430/313 |
International
Class: |
G03C 005/00; G03F
009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 7, 1992 |
JP |
04-326433 |
Claims
What is claimed is:
1. A photomask comprising: a semitransparent phase shifting area
which has a semitransparent area and a transparent area, which are
respectively transparent and semitransparent with respect to
exposure light beams, and in which light beams having passed
through said semitransparent area is substantially 180 degrees out
of phase with respect to light beams having passed through said
transparent area; and a pattern which is formed in said photomask
and in which a semitransparent phase shifting pattern and a
transparent pattern are arranged in a repeated pitch equal to or
smaller than the critical resolution of a projection exposure
optical system.
2. A photomask according to claim 1, wherein when the repeated
pitch represented by P is defined as:
P=.alpha..multidot..lambda./NA where NA represents a numerical
aperture of a projection lens, .lambda. represents a wavelength of
the exposure light beams, and .alpha..ltoreq.0.8.
3. A photomask according to claim 1, wherein when a size ratio
.alpha. of the size of said transparent pattern to the size of said
semitransparent phase shifting pattern is defined as:
.alpha.=.beta..multidot.{square root}{square root over (T)}where T
represents the transmittance of the semitransparent phase shifting
portion, and 0.5.ltoreq..beta..ltoreq.2.0.
4. A photomask according to claim 1, wherein when the repeated
pitch P is defined as: P=.alpha..multidot..lambda./NA where NA
represents a numerical aperture of a projection lens, .lambda.
represents a wavelength of the exposure light beams, and a
.ltoreq.0.8, and when a size ratio .alpha. of the size of said
transparent pattern to the size of said semitransparent phase
shifting pattern is defined as: .alpha.=.beta..multidot.{square
root}{square root over (T)}where T represents the transmittance of
the semitransparent phase shifting portion, and
0.5.ltoreq..beta..ltoreq.2.0.
5. A photomask according to claim 1, wherein an area, in which the
light intensity, on a projection surface, of the light beams passed
therethrough is one-half or lower than that, on the projection
surface, of the light beams having passed through said
semitransparent phase shifting area, includes a portion
corresponding to an area which is double-exposed with a projected
exposure surface thereof in the step and repeat exposure.
6. A method of forming a pattern, comprising the steps of: forming
a photoresist film on a substrate; placing said substrate having
said photoresist film on a sample stage of an aligner; exposing a
predetermined first area of said substrate by using a photomask
including a semitransparent phase shifting area which has a
semitransparent area and a transparent area, which are respectively
transparent and semitransparent with respect to exposure light
beams, and in which light beams having passed through said
semitransparent area is substantially 180 degrees out of phase with
respect to light beams having passed through said transparent area,
and a pattern which is formed in said photomask and in which a
semitransparent phase shifting pattern and a transparent pattern
are arranged in a repeated pitch equal to or smaller than the
critical resolution of a projection exposure optical system; moving
horizontally said substrate; and exposing a second area of said
substrate which is adjacent to said predetermined first area by
using said photomask.
7. A method according to claim 6, wherein said pattern in which
said semitransparent phase shifting pattern and said transparent
pattern are arranged at a repeated pitch equal to or smaller than
the critical resolution of said projection exposure optical system
is arranged in at least two sides which are perpendicular to each
other and are located in the periphery of a pattern element area of
said substrate in said photomask.
8. A method of manufacturing a semiconductor device, comprising the
steps of: forming diffusion layers in a surface of a semiconductor
substrate; forming an insulating film on said semiconductor
substrate having said diffusion layers; forming opening portions
through a photoresist film on said diffusion layers by a pattern
forming method, said pattern forming method including the steps of:
forming said photoresist film on said insulating film; placing said
substrate having said photoresist film on a sample stage of an
aligner; exposing a predetermined first area of said substrate by
using a photomask including a semitransparent phase shifting area
which has a semitransparent area and a transparent area, which are
respectively transparent and semitransparent with respect to
exposure light beams, and in which light beams having passed
through said semitransparent area is substantially 180 degrees out
of phase with light beams having passed through said transparent
area, and a pattern which is formed in said photomask and in which
a semitransparent phase shifting pattern and a transparent pattern
are arranged in a repeated pitch equal to or smaller than the
critical resolution of a projection exposure optical system; moving
horizontally said substrate; and exposing a second area of said
substrate which is adjacent to said predetermined first area by
using said photomask; etching selectively said insulating film with
said photoresist film having said opening portions as a mask to
expose said diffusion layers; and forming a wiring layer, which is
electrically connected to said diffusion layers, on said insulating
film.
9. A method of manufacturing a semiconductor device, comprising the
steps of: forming a first insulating film on a substrate; forming a
first wiring layer on said first insulating layer; forming a second
insulating film on said substrate having said first wiring layer;
forming opening portions through a photoresist film on said first
wiring layer by a pattern forming method, said pattern forming
method including the steps of: forming said photoresist film on
said second insulating film; placing said substrate having said
photoresist film on a sample stage of an aligner; exposing a
predetermined first area of said substrate by using a photomask
including a semitransparent phase shifting area which has a
semitransparent area and a transparent area, which are respectively
transparent and semitransparent with respect to exposure light
beams, and in which light beams having passed through said
semitransparent area is substantially 180 degrees out of phase with
respect to light beams having passed through said transparent area,
and a pattern which is formed in said photomask and in which a
semitransparent phase shifting pattern and a transparent pattern
are arranged in a repeated pitch equal to or smaller than the
critical resolution of a projection exposure optical system; moving
horizontally said substrate; and exposing a second area of said
substrate which is adjacent to said predetermined first area by
using said photomask; etching selectively said second insulating
film with said photoresist film having said opening portions as a
mask to expose said first wiring layer; and forming a second wiring
layer, which is electrically connected to said first wiring layer,
on said second insulating film.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
[0001] The present invention relates to a photomask which is used
to manufacture a semiconductor device and the like, and more
particularly to a photomask which has been subjected to a
processing of shifting a phase of exposure light beams and a
pattern forming method employing the same.
[0002] Along with an increase of the integration scale for
semiconductor devices, sizes of patterns for forming constituent
elements of the devices become fine, and size equal to or smaller
than the critical resolution of a projection aligner are required.
As a method of fulfilling such a request, in JP-B-62-50811
published on Oct. 27, 1987, and corresponding to JP-A-57-62052
(laid open on Apr. 14, 1982) for example, a photomask is employed
in which a transparent film for shifting a phase of exposure light
beams is provided on one of transparent portions on the opposite
sides sandwiching an opaque portion, and thus the resolution of a
pattern is exceptionally improved.
[0003] In the above-mentioned prior art, a phase shifter needs to
be arranged in one of the transparent portions adjacent to each
other, and for the arrangement of the phase shifter in the
complicated element pattern, high trial and error is necessarily
required. Thus, there is required considerable labor. In addition,
since the number of processes of manufacturing a photomask is
doubled as compared with the prior art, the reduction in yield and
the increase in cost become problems.
[0004] Those problems can be settled by employing a semitransparent
phase shifting mask in which a semitransparent portion and a
transparent portion are provided, and a little quantity of light
beams passed through the semitransparent portion is phase-inverted
with respect to light beams having passed through the transparent
portion. With respect to this point, the description will
hereinbelow be given with reference to the accompanying
drawings.
[0005] FIG. 1A is a cross sectional view showing a structure of an
example of a semitransparent phase shifting mask. In the figure,
reference numeral 1 designates a transparent substrate, and
reference numeral 2 designates a semitransparent film. A thickness
of the semitransparent film 2 is adjusted such that the light beams
having passed through the transparent portion 3 is phase-inverted
with respect to the light beams having passed through a
semitransparent portion 4. The semitransparent film 2 has a
transmittance such that a light beam having passed through the
transparent substrate 1 and the semitransparent film 2 has an
intensity high enough to cause an interference with a light beam
having passed through the transparent substrate 1. The transparent
film used in this specification means a film having the
above-mentioned transmittance. The light intensity distribution of
the projected light beams on a wafer becomes, as shown in FIG. 1B,
a sharp light intensity distribution. The reason such a sharp light
intensity distribution is obtained is that since the light beams
having passed through the transparent portion is phase-inverted
with respect to the light beams having passed through the
semitransparent portion, the former and the latter cancels each
other in a boundary portion of the pattern so that the light
intensity becomes approximately zero. In addition, since the
intensity of the light beams having passed through the
semitransparent portion is adjusted to the intensity equal to or
lower than the sensitivity of a photoresist, the intensity of the
light beams having passed through the semitransparent portion is
not an obstacle to the formation of the pattern. That is, in this
method, since the phase inversion effect between the pattern to be
transferred and the semitransparent portion therearound is
utilized, there is no need to take, as in the normal phase shifting
mask, the arrangement of the phase shifter into consideration. In
addition, in the prior art phase shift mask, the two lithography
processes are required for the formation of the mask. However, in
this method, one lithography process has only to be performed.
Thus, it is possible to form the mask very simply.
[0006] In this method, the light beams the intensity of which is
equal to or lower than the sensitivity of a photoresist, to which
the pattern of the mask is to be transferred are made to pass
through the semitransparent film so that the light beams which have
passed through the semitransparent film is phase-inverted with
respect to the light beams which have passed through the
transparent portion, and thus, the contrast of the pattern is
improved. As a result, it is possible to improve the resolution of
an aligner for transferring the mask pattern. The basic principle
of the semitransparent phase shifting mask is described in D. C.
Flanders et al.: "Spatial period division-A new technique for
exposing submicrometer-linewidth periodic and quasi-periodic
patterns" J. Vac. Sci. Technol., 16(6), Nov./Dec. pp 1949 to 1952
(1979), U.S. Pat. Nos. 4,360,586 and 4,890,309 and JP-A-4-136854
(laid open on May 11, 1992).
[0007] In the lithography process in which the above-mentioned
semitransparent phase shifting mask is employed, in the normal
exposed area, the good pattern formation can be performed. However,
it has been made clear by the investigations made by the present
inventors that since in the actual exposure of the wafer, the mask
pattern is repeatedly transferred by the step and repeat, the light
beams which have leaked from the semitransparent area, which is
located outside the periphery of the actual pattern element
corresponding to an active region of a substrate, leak out to the
adjacent exposed area, and thus this is an obstacle to the good
pattern formation.
[0008] It is therefore an object of the present invention to
provide a photomask by which a good pattern can be obtained even in
the case of an exposure, in which a mask pattern is repeatedly
transferred by the step and repeat, and a pattern forming method
employing the same.
[0009] According to one aspect of the present invention, the
above-mentioned object can be attained by effectively making a
light-shielding or opaque area of a semitransparent phase shift
mask which is located outside the periphery of a pattern element
formation area of the semitransparent phase shifting mask.
[0010] The light shielding portion in the semitransparent phase
shifting mask is formed by processing a semitransparent film to a
pattern having a width equal to or lower than the resolution. The
reason of adopting such a method is that if a light shielding film
is newly formed as the light shielding portion, this will result in
an increase of the number of processes of forming the mask.
Incidentally, by optimizing the area ratio of the semitransparent
portion to the transparent portion, it is possible to further
effectively form the light shielding portion.
[0011] These and other objects and many of the attendant advantages
of the invention will be readily appreciated as the same becomes
better understood by reference to the following detailed
description when considered in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIGS. 1A and 1B are respectively a cross-sectional view
showing a structure of a semitransparent phase shifting mask, and a
view showing the light intensity distribution of projected light
beams on a wafer when using the mask shown in FIG. 1A.
[0013] FIGS. 2A and 2B are respectively a plan view and a cross
sectional view each showing a structure of a photomask according to
the present invention.
[0014] FIG. 3A is a plan view showing a structure of a light
shielding portion of the photomask according to the present
invention.
[0015] FIG. 3B is a graphical representation showing the
relationship between the size of a transparent pattern of the
photomask according to the present invention and the intensity of
projected exposure light beams.
[0016] FIG. 4 is a plan view showing a structure of a mask for
forming contact holes of a 64 Mbits-DRAM according to the present
invention.
[0017] FIGS. 5A and 5B are respectively a plan view showing a
structure of a window pattern portion for aligning the position of
the mask according to the present invention, and a view showing the
light intensity distribution of the projected light beams on the
wafer when using the mask shown in FIG. 5A.
[0018] FIGS. 6A through 6D are cross sectional views showing steps
of a process of manufacturing a semiconductor device according to
the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] When both a semitransparent phase shifting pattern and a
transparent pattern are arranged with the same size and at a pitch
equal to or lower than the critical resolution, a pattern image can
be erased. But, in this case, the resulting uniform light intensity
does not become zero. This reason is that since there is a
difference between the quantity of light beams having passed
through the semitransparent phase shifting portion and that of
light beams having passed through the transparent portion, the
function of cancelling those light beams each other due to the
phase inversion effect is not efficiently performed.
[0020] Then, when the ratio of the area of the semitransparent
phase shifting portion to that of the transparent portion is
adjusted in accordance with a set transmittance of the
semitransparent phase shifting portion, it is made clear that the
light intensity can be zero. By using this pattern for an area of a
to-be-exposed water surface, which may be otherwise undesirably
double-exposed by the step and repeat by an aligner, it is possible
to prevent the double exposure on the wafer, and a pattern of
constituent elements as desired can be formed. Therefore, since the
present photomask is made up of only semitransparent phase shifting
portions and transparent portions, there is no need to newly form a
light shielding film for the formation of the light shielding
portion, and thus, the process of forming the photomask can be
simplified. Incidentally, the above-mentioned light shielding
portion is applicable to the formation of a light shielding portion
in a pattern element region of a substrate. In this case, since the
ratio of the transmittance of the transparent portion to that of
the light shielding portion can be made large, it is possible to
increase the tolerance for the variation of the quantity of light
beams required for the exposure.
[0021] As for the materials used for the formation of the
semitransparent phase shifting portion, a lamination film of a
semitransparent metal film (made of chromium, titanium or the like)
or a silicide film (e.g., a molybdenum silicide film) and a silicon
oxide film for the phase shift, or a single layer film such as a
metal oxide film (e.g., a chromium oxide film) or metal nitride
film (e.g., a chromium nitride film) may be employed. In the case
where a single layer film such as a chromium oxide film or a
chromium nitride film is employed, since the refractive index
thereof is larger than that of the silicon oxide film, the film can
be thinned. As a result, since the influence of the light
diffraction can be reduced, this single layer film is suitable for
the formation of a fine pattern.
[0022] Embodiment 1
[0023] A first embodiment of the present invention will hereinafter
be described in detail. FIGS. 2A and 2B are respectively a plan
view and a cross sectional view each showing the appearance of a
photomask employed in the present embodiment. In those figures,
reference numeral 1 designates a transparent substrate, and
reference numeral 5 designates an element pattern portion in which
both a semitransparent phase shifting portion and a transparent
portion are arranged. Moreover, reference numeral 6 designates a
portion acting, on a wafer, as a light shielding portion in which
semitransparent phase shifting patterns are arranged at a pitch
equal to or smaller than the resolution. Reference numeral 7
designates a masking blade for shielding, on the aligner side, the
exposure light beams. Since the masking blade 7 is poor in the
positional accuracy, it is positioned so as to shield the light
beams passing through the portion which is located outside the
intermediate position of the width of the area 6 acting as the
light shielding portion. The details of the area 6 acting as the
light shielding portion will hereinbelow be described with
reference to FIGS. 3A and 3B. FIG. 3A is a plan view showing a
structure of a pattern. In this connection, each transparent
pattern portion 10 is formed within a semitransparent phase
shifting portion 9. An arrangement pitch 11 of the transparent
patterns 10 is determined depending on the resolution
characteristics of the projection optical system employed. The
arrangement pitch P is expressed by the following expression:
P=.alpha..multidot..lambda./NA
[0024] where NA represents a numerical aperture of a projection
lens, .lambda. represents a wavelength of the exposure light beams,
and .alpha. represents a coefficient. In this connection, on the
basis of the experiments made by the present inventors, it is
desirable that the coefficient .alpha. is set to a value equal to
or larger than 0.8. However, the optimal value of .alpha. is not
limited thereto or thereby because the optimal value of .alpha.
depends on the characteristics of the illuminating system, the
pattern configuration and the like. A width 12 of the transparent
pattern 10 influences largely the formation of a dark portion. FIG.
3B shows the intensity of the projected light beams which is
obtained on the wafer when changing the width 12 of the transparent
pattern 10. Then, the intensity of the projected light beams shows
the intensity of the light beams which have passed through the
pattern along a line A-B of FIG. 3A. The pitch of the transparent
patterns 10 was determined to be 0.4 .mu.m by using .alpha.=0.1 in
the expression of the arrangement pitch. With respect to the three
kinds of transmittance 9%, 16% and 25% of the semitransparent phase
shifting portion, the change in the intensity of the projected
light beams were examined by changing the size of the transparent
pattern 10. The axis of abscissa of the graph represents the size
of the transparent pattern 10. From the graph of FIG. 3B, it can be
seen that a minimum value is present in the intensity of the
projected light beams depending on the size of the transparent
pattern, and this local minimum value is variable depending on the
transmittance of the semitransparent phase shifting portion. That
is, it can be seen that in accordance with the transmittance of the
semitransparent phase shifting portion 9, an optimal transparent
pattern size can be found. Denoting the size ratio of size 12 of
the transparent pattern to the size 13 of the semitransparent phase
shifting portion 13 by .alpha., an optimal value thereof for the
formation of the dark portion will be expressed by the following
expression:
.alpha.=.beta..multidot.{square root}{square root over (T)}
[0025] where T represents a transmittance of the semitransparent
phase shifting portion, and B represents a coefficient. The
allowable intensity of the projected light beams is variable
depending on intended purposes. In the case of preventing exposure
of a photoresist due to a double exposure, the allowable intensity
of the projected light beams may be set to an intensity which is
about one-half the intensity of light having passed through the
semitransparent phase shifting portion. However, in the case of
preventing a double exposure of a dark portion with a fine pattern
containing portion, the change in the size of the fine pattern
needs to be reduced as much as possible, and thus it is desirable
that the allowable intensity of the projected light beams is set to
a value equal to or lower than 0.05. The value of .beta. in this
case is in the range of about 0.5 to about 2.0. Then, the area 6 of
FIG. 2A was formed on the basis of the optimal conditions thus
obtained, and by actually using the projection aligner, the pattern
element 5 corresponding to the active region was exposed by the
step and repeat. As a result, the good pattern element
corresponding to the active region could be formed without
occurrence of the pattern destruction and the size shifting even in
the area in which the area 6 was doubled-exposed. As described
above, the semitransparent phase shifting portion and the
transparent portion were formed with the optimal size combination,
whereby the effective dark portion could be formed. Incidentally,
although in the present embodiment, the example is shown in which
the line transparent pattern is formed in the semitransparent phase
shifting area, the present invention is not limited thereto or
thereby. That is, for example, there is particularly no problem
even in the case of an island-like pattern and other patterns. In
such cases, if .alpha. in an expression of
.alpha.=.beta..multidot.{square root}{square root over (T)} is
replaced with the area ratio of the area of the transparent pattern
to the area of the semitransparent phase shifting portion, the
substantially same effects can be obtained. In addition, in the
present embodiment, the dark portion which is formed by the
combination of the semitransparent phase shifting pattern and the
transparent pattern is applied to the prevention of the double
exposure. However, the application of the dark portion of the
present invention is not limited thereto or thereby. It is, of
course, to be understood that the dark portion is applicable to the
necessary portions such as a window pattern for aligning the mask
position, a pattern for detecting the wafer position, and a
semitransparent phase shifting portion having a large area all of
which require a dark portion. Further, the above-mentioned
photomask having a dark portion is useful for the pattern formation
when manufacturing a semiconductor device.
[0026] Embodiment 2
[0027] A second embodiment of the present invention will
hereinafter be described with reference to FIG. 4. FIG. 4 is a plan
view showing a structure of a photomask which is used to form
contact holes of a 64 Mbits-dynamic random access memory (DRAM).
Two DRAM element areas 5 are arranged in a transparent substrate 1.
A scribing area 14 is provided between the two pattern element
areas 5. In addition, in a peripheral scribing area 15 on two sides
perpendicular to each other, a pattern for measuring the accuracy
of the mask alignment, a target pattern for the mask alignment, and
the like are arranged which becomes necessary for the process of
manufacturing a device. In the two sides opposite to the other
sides of the scribing area, a dark area 6 of the present invention
is arranged. The step and repeat in the projection aligner is
performed at a pitch 16 in the transverse direction and at a pitch
17 in the longitudinal direction. The peripheral portion which is
located outside a dotted line 18 as the setting center is
mechanically shielded from the light beams by a mechanical light
shielding plate of the aligner. In this connection, the dotted line
18 is set to the position at a distance equal to or longer than the
positional accuracy of the mechanical light shielding plate from
the scribing area such that the mechanical light shielding plate is
not shifted to the scribing area by mistake. In addition, the width
of the dark portion is set to a value equal to or larger than the
positional accuracy of the mechanical light shielding plate, and
the dotted line 18 is arranged in the about central portion of the
dark portion. Further, at least the three portions of the four
corner portions are made dark portions.
[0028] As a result of using this photomask in order to manufacture
the 64 Mbits-DRAM, the double exposure in the periphery of the chip
can be perfectly prevented, and thus the good device can be
manufactured. In addition, in the case where the pattern element
area 5 is formed by one chip, or the photomask having the dark
portion is applied to devices other than DRAM, the same effects can
be obtained.
[0029] Further, the description will hereinbelow be given with
respect to an example in which the dark portion of the present
invention is arranged in the periphery of a window pattern which is
used to align the mask position with reference to FIGS. 5A and 5B.
FIG. 5A is a plan view showing a structure of the window pattern
portion which is used to align the mask position. FIG. 5B shows the
distribution of the light intensity on the wafer corresponding to
the mask position. As shown in FIG. SA, a transparent portion 10
which has the size fulfilling the conditions for forming the dark
portion of FIG. 3B is formed around a window pattern 19. It can be
seen that in the distribution of the light intensity on the wafer
along a line A-B of the photomask of FIG. 5A at that time, the
light intensity in the periphery of the window pattern is, as shown
in FIG. 5B, zero, and thus signals representing the window pattern
are obtained in the high signal-to-noise (S/N) ratio and the
judgement of the position is performed with accuracy. In such a
way, the dark portion of the present invention is applicable to a
pattern utilizing light intensity signals each having a high S/N
ratio from a mask pattern and other patterns requiring the light
shielding portion as well as to the light shielding in the
periphery of a device chip.
[0030] Embodiment 3
[0031] Hereinbelow, an example will be shown in which a
semiconductor device is manufactured according to the present
invention. FIGS. 6A through 6D are cross sectional views showing
steps of a process of manufacturing a semiconductor device. By
using the conventional method, a P type well layer 21, a P type
layer 22, a field oxide film 23, a polycrystalline Si/SiO.sub.2
gate 24, a high impurity concentration P type diffusion layer 25, a
high impurity concentration N type diffusion layer 26, and the like
are formed in an N.sup.- type Si substrate 20. Next, by using the
conventional method, an insulating film 27 made of phosphor
silicate glass (PSG) is deposited thereon. Next, a photoresist 28
is applied thereto, and then a hole pattern 29 is formed by using
the semitransparent phase shifting mask of the present invention
(refer to FIG. 6B). Next, an insulating film 27 is selectively
etched by the dry etching technique with the resultant photoresist
as an etching mask, thereby to form contact holes 30 (refer to FIG.
6C). Next, by using the conventional method, a W/TiN electrode
wiring 31 is formed, and then an interlayer insulating film 32 is
formed. Next, a photoresist is applied thereto, and then by using
the conventional method, a hole pattern 33 is formed using the
semitransparent phase shifting mask of the present invention. Then,
a W plug is plugged in the hole pattern 33 to connect a second
level Al wiring 34 thereto (refer to FIG. 6D). In the following
passivation process, the conventional method is employed.
Incidentally, in the present embodiment, only the main
manufacturing processes have been described. In this connection,
the same processes as those of the conventional method are employed
except that the semitransparent phase shifting mask of the present
invention is used in the lithography process of forming the contact
hole. By the above-mentioned processes, CMOS LSI can be
manufactured at a high yield.
[0032] As set forth hereinabove, according to the present
invention, by forming the semitransparent phase shifting portion
and the transparent portion with the optimal size combination, even
if a light-shielding film is not newly formed, the effective dark
portion can be formed. In addition, without increasing in the
number of processes of forming the mask, the semitransparent phase
shifting mask which is useful in practical use can be produced.
Further, as a result of manufacturing the semiconductor device by
using the photomask of the present invention, it is possible to
form the pattern in which the effects inherent in the
semitransparent phase shifting mask are sufficiently utilized,
without any problem in the double exposure portion, and also it is
possible to realize the reduction of the device area.
[0033] It is further understood by those skilled in the art that
the foregoing description is a preferred embodiment of the
disclosed device and that various changed and modifications may be
made in the invention without departing from the spirit and scope
thereof.
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