U.S. patent application number 10/964842 was filed with the patent office on 2005-05-12 for device and method for providing wavelength reduction with a photomask.
This patent application is currently assigned to Taiwan Semiconductor Manufacturing Company, Ltd.. Invention is credited to Chen, Chun-Kuang, Chen, Jeng Horng, Gau, Tsai-Sheng, Lin, Burn Jeng, Liu, Ru-Gun, Shih, Jen-Chieh.
Application Number | 20050100798 10/964842 |
Document ID | / |
Family ID | 35007632 |
Filed Date | 2005-05-12 |
United States Patent
Application |
20050100798 |
Kind Code |
A1 |
Lin, Burn Jeng ; et
al. |
May 12, 2005 |
Device and method for providing wavelength reduction with a
photomask
Abstract
Disclosed is a photomask having a wavelength-reducing material
that may be used during photolithographic processing. In one
example, the photomask includes a transparent substrate, an
absorption layer having at least one opening, and a layer of
wavelength-reducing material (WRM) placed into the opening. The
thickness of the WRM may range from approximately a thickness of
the absorption layer to approximately ten times the wavelength of
light used during the photolithographic processing. In another
example, the photomask includes at least one antireflection coating
(ARC) layer.
Inventors: |
Lin, Burn Jeng; (Hsin-Chu,
TW) ; Chen, Jeng Horng; (Hsin-Chu, TW) ; Chen,
Chun-Kuang; (Hsin-Chu, TW) ; Gau, Tsai-Sheng;
(Hsin-Chu, TW) ; Liu, Ru-Gun; (Hsin-Chu, TW)
; Shih, Jen-Chieh; (Hsin-Chu, TW) |
Correspondence
Address: |
HAYNES AND BOONE, LLP
901 MAIN STREET, SUITE 3100
DALLAS
TX
75202
US
|
Assignee: |
Taiwan Semiconductor Manufacturing
Company, Ltd.
Hsin-Chu
TW
|
Family ID: |
35007632 |
Appl. No.: |
10/964842 |
Filed: |
October 13, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60511503 |
Oct 15, 2003 |
|
|
|
Current U.S.
Class: |
430/5 ; 430/322;
430/323; 430/324 |
Current CPC
Class: |
G03F 1/50 20130101; G03F
1/46 20130101 |
Class at
Publication: |
430/005 ;
430/322; 430/323; 430/324 |
International
Class: |
G03F 009/00; G03C
005/00 |
Claims
What is claimed is:
1. A photomask for forming a pattern during photolithography when
illuminated with a predetermined wavelength of light, the photomask
comprising: a transparent substrate; an absorption layer proximate
to the substrate, wherein the absorption layer has at least one
opening formed therein; and a layer of wavelength-reducing material
disposed in the at least one opening, wherein the
wavelength-reducing material and the absorption layer form a
generally planar surface.
2. The photomask of claim 1 wherein a thickness of the
wavelength-reducing material is substantially equal to a thickness
of the absorption layer.
3. The photomask of claim 1 wherein the wavelength-reducing
material forms a generally planar surface beyond the absorption
layer.
4. The photomask of claim 1 wherein the wavelength-reducing
material thickness is less than or equal to about ten times the
predetermined wavelength of the light.
5. The photomask of claim 1 wherein the wavelength-reducing
material has a refractive index larger than 1 and a transmissivity
of more than 10%.
6. The photomask of claim 1 wherein the wavelength-reducing
material comprises a transparent polymer material.
7. The photomask of claim 1 wherein the wavelength-reducing
material comprises a photoresist material.
8. The photomask of claim 1 wherein the wavelength-reducing
material comprises a transparent dielectric material.
9. The photomask of claim 1 wherein the absorption layer has a
transmissivity of between 1% and 100% and is adapted to modify a
phase of light passing through the absorption layer, and wherein
the wavelength-reducing material has a refractive index larger than
1 and a transmissivity of more than 10%.
10. The photomask of claim 1 wherein wavelength-reducing material
has a refractive index different from that of the absorption
layer.
11. The photomask of claim 1 further comprising at least one
antireflection coating layer.
12. The photomask of claim 1 further comprising at least one
antireflection coating layer on the wavelength-reducing
material.
13. The photomask of claim 1 further comprising at least one
antireflection coating layer on the substrate.
14. The photomask of claim 1 further comprising at least one
antireflection coating layer between the absorption layer and the
wavelength-reducing material.
15. The photomask of claim 11 further comprising at least one
antireflection coating layer between the wavelength-reducing
material and the substrate.
16. The photomask of claim 1 further comprising at least one
antireflection coating layer between the absorption layer and the
substrate.
17. The photomask of claim 1 further comprising at least one
antireflection coating layer with a graded structure.
18. A method for fabricating a photomask on a transparent
substrate, the method compromising: forming an absorption layer
proximate to the substrate; patterning the absorption layer and
forming at least one opening in the absorption layer; and forming a
wavelength-reducing material in the at least one opening of the
absorption layer.
19. The method of claim 18 further comprising forming an
antireflection coating layer on a side of the substrate opposite
the wavelength-reducing material.
20. The method of claim 18 further comprising forming an
antireflection coating layer on the wavelength-reducing
material.
21. The method of claim 18 further comprising forming an
antireflection coating layer between the substrate and the
wavelength-reducing material.
22. The method of claim 18 further comprising forming an
antireflection coating layer between the substrate and the
absorption layer.
23. The method of claim 18 further comprising forming an
antireflection coating layer between the wavelength-reducing
material and the absorption layer.
24. The method of claim 18 wherein forming the wavelength-reducing
material comprises a spin coating process.
25. The method of claim 18 wherein forming the wavelength-reducing
material comprises a sputtering deposition process.
26. The method of claim 18 wherein forming the wavelength-reducing
material comprises a chemical vapor deposition process.
27. The method of claim 18 wherein forming the wavelength-reducing
material comprises an atomic layer deposition process.
28. The method of claim 18 wherein forming the wavelength-reducing
material comprises a physical vapor deposition process.
29. The method of claim 18 wherein forming the wavelength-reducing
material comprises limiting a thickness of the wavelength-reducing
material between about a thickness of the absorption layer to
approximately ten times a predefined wavelength of light.
30. The method of claim 18 wherein forming the wavelength-reducing
material comprises a planarizing process.
31. A photomask comprising: a substantially transparent substrate;
an absorption layer proximate to the substantially transparent
substrate and defining at least one opening therein; and a high
refractive index layer disposed in the at least one opening of the
absorption layer and operable to reduce a wavelength of light
passing therethrough during photolithography.
32. A photolithography method comprising: positioning a photomask
above a semiconductor formation, the photomask comprising: a
substantially transparent substrate; an absorption layer proximate
to the substantially transparent substrate and defining at least
one opening therein; and a high refractive index layer disposed in
the at least one opening of the absorption layer and operable to
reduce a wavelength of light passing therethrough during
photolithography; exposing the semiconductor formation and
photomask to light.
Description
BACKGROUND
[0001] This application claims benefit and priority from U.S.
Provisional Patent Application Ser. No. 60/511,503, filed on Oct.
15, 2003 and entitled "Device and Method for Providing Wavelength
Reduction with a Photomask".
[0002] The semiconductor integrated circuit (IC) industry has
experienced rapid growth. Technological advances in IC materials
and design have produced generations of ICs where each generation
has smaller and more complex circuits than the previous generation.
However, these advances have increased the complexity of processing
and manufacturing ICs and, for these advances to be realized,
similar developments in IC processing and manufacturing have been
needed.
[0003] For example, in the course of integrated circuit evolution,
functional density (i.e., the number of interconnected devices per
chip area) has generally increased while feature size (i.e., the
smallest component or line that can be created using a fabrication
process) has decreased. This scaling down process generally
provides benefits by increasing production efficiency and lowering
associated costs, but needs to be matched by improvements in the
fabrication process. For instance, many fabrication processes
utilize a photomask to form a pattern during photolithography. The
pattern may contain a pattern of designed circuits that will be
transferred onto a semiconductor wafer. However, because of the
increasingly small patterns that are to be used during
photolithography, photomasks have generally needed increasingly
high resolutions.
SUMMARY
[0004] In one embodiment, the present disclosure provides a
photomask for forming a pattern during photolithography when
illuminated with a predetermined wavelength of light. The photomask
comprises a transparent substrate; an absorption layer proximate to
the substrate, wherein the absorption layer has at least one
opening formed therein; and a layer of wavelength-reducing material
disposed in at least one opening, wherein a thickness of the
wavelength-reducing material and the absorption layer form a
generally planar surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 illustrates a cross-sectional view of one embodiment
of a photomask with a wavelength reducing medium.
[0006] FIG. 2 is a flow chart of an exemplary method for forming
the photomask of FIG. 1.
[0007] FIGS. 3a-3c illustrate various fabrication stages of the
photomask of FIG. 1 as it is formed using the method of FIG. 2.
[0008] FIG. 4 illustrates a cross-sectional view of another
embodiment of a photomask with a wavelength reducing medium.
[0009] FIG. 5 is a flow chart of an exemplary method for forming
the photomask of FIG. 4.
[0010] FIGS. 6a-6c illustrate various fabrication stages of the
photomask of FIG. 4 as it is formed using the method of FIG. 5.
[0011] FIG. 7 illustrates a cross-sectional view of yet another
embodiment of a photomask with a wavelength reducing medium.
[0012] FIG. 8 is a flow chart of an exemplary method for forming
the photomask of FIG. 7.
[0013] FIGS. 9a-9c illustrate various fabrication stages of the
photomask of FIG. 7 as it is formed using the method of FIG. 8.
DETAILED DESCRIPTION
[0014] The present disclosure relates generally to photolithography
and, more particularly, to using a wave-length reducing medium with
a photomask. It is understood, however, that the following
disclosure provides many different embodiments, or examples, for
implementing different features of the invention. Specific examples
of components and arrangements are described below to simplify the
present disclosure. These are, of course, merely examples and are
not intended to be limiting. In addition, the present disclosure
may repeat reference numerals and/or letters in the various
examples. This repetition is for the purpose of simplicity and
clarity and does not in itself dictate a relationship between the
various embodiments and/or configurations discussed.
[0015] Referring to FIG. 1, a cross-sectional view of one
embodiment of a photomask 100 is illustrated. The photomask 100
comprises a transparent substrate 102, an absorption layer 104, and
a wavelength-reducing material (WRM) 106. The transparent substrate
102 may use fused silica (SiO2) or a glass relatively free of
defects, such as borosilicate glass and soda-lime glass. Other
suitable materials may also be used.
[0016] The absorption layer 104 may be formed using a number of
different processes and materials, such as depositing of a metal
film made with Chromium (Cr) oxide and iron oxide, or an inorganic
film made with MoSi, ZrSiO, and SiN. The absorption layer 104 may
be patterned to have one or more openings 108 through which light
may travel without being absorbed by the absorption layer. In some
embodiments, the absorption layer 104 may have a multi-layer
structure, which may further include an antireflection (ARC) layer
and/or other layers. In addition, some of these layers may be
formed multiple times to achieve a desired composition of the
absorption layer 104.
[0017] The absorption layer 104 may be tuned to achieve a
predetermined transmittance and an amount of phase shifting,
enabling the absorption layer 104 to shift the phase of light
passing through the absorption layer, for improved imaging
resolution. For example, the transmittance of the absorption layer
104 may be tuned to between approximately three percent and thirty
percent, while the phase shift is tuned to approximately 180
degrees. This type of photomask is sometimes referred to as an
attenuated phase-shifting photomask. In another example, the
transmittance of the absorption layer 104 may be extremely high
(e.g., 95%), and the phase shift may be approximately 180 degrees.
This type of photomask is sometimes referred to as a chromeless
phase-shifting photomask.
[0018] The WRM 106 may be used to fill in the one or more openings
108 of the absorption layer 104. The surface of the WRM 106 may be
substantially co-planar with the surface of the absorption layer
104, but may be fine tuned to be slightly higher or lower with the
plane of the surface of the absorption layer 104. Both materials
may be planarized using known planarization techniques, such as
chemical-mechanical planarization (CMP) to form a planar surface.
The thickness of the WRM 106 may vary from less than to about the
thickness of the absorption layer 104 (e.g., if the surface of the
WRM is aligned with the surface of the absorber), to up to about
ten times the wavelength of light passing through the WRM 106
during photolithographic processing. The WRM material used for the
WRM 106 may be chosen based on a desired level of transparency and
a desired refractive index. The WRM 106 preferably has a refractive
index different from that of the absorption layer. In the present
example, the WRM material is selected to provide both a high level
of transparency and a high refractive index. Exemplary WRM
materials include photoresist materials, polymer materials, and
dielectric materials. For example, the material may include
polyimide, SiO2, indium tin oxide (ITO), polyvinyl alcohol (PVA),
or silicone.
[0019] During a photolithography process, the photomask 100 is
disposed above a semiconductor formation. Typically, the photomask
100 does not come into contact with the surface of the
semiconductor formation. Due to the relatively high refractive
index ("n") of the WRM 106, the wavelength of the light passing
through the WRM 106 during photolithography processing may be
reduced by a factor of n from the wavelength of the light in a
vacuum. Since the physical size of the opening 108 in the
absorption layer 104 remains the same, but the size of the opening
108 relative to the wavelength of the light is enlarged by the
factor of n, optical diffraction is reduced accordingly and the
resolution of imaging of the photomask 100 on a wafer may be
enhanced.
[0020] Referring now to FIG. 2 and with additional reference to
FIGS. 3a-3c, an exemplary method 150 may be used to form the
photomask 100 of FIG. 1. The method 150 begins in step 152 with the
formation of the absorption layer 104 above the transparent
substrate 102 as shown in FIG. 3a. It is understood that the
transparent substrate 102 may be cleaned or otherwise prepared
using processes not illustrated in the present example of method
100. The absorption layer 104 may be formed using a process such as
a physical vapor deposition (PVD) process, including evaporation
and sputtering, a plating process, including electroless plating or
electroplating, or a chemical vapor deposition (CVD) process,
including atmospheric pressure CVD (APCVD), low pressure CVD
(LPCVD), plasma enhanced CVD (PECVD), or high density plasma CVD
(HDP CVD). In the present example, a sputtering deposition may be
used to provide the absorption layer 104 with thickness uniformity,
relatively few defects, and a desired level of adhesion. As
previously described with respect to FIG. 1, the absorption layer
104 may include materials such as Chromium oxide, iron oxide, MoSi,
ZrSiO, and SiN.
[0021] In step 154 (FIG. 3b), the absorption layer 104 may be
patterned to have a predefined arrangement of openings 108 using
known processes such as a photolithography process or an electron
beam process. For example, the photolithography process may include
the following processing steps. A photoresist layer (not shown) may
undergo a process involving spin-on coating, baking, exposure to
illuminated light through a photomask, developing, and post baking.
This transfers the pattern from the photomask to the photoresist.
Next, a wet etching or dry etching may be used to etch an exposed
region of the absorption layer 104 to transfer the pattern from the
photoresist to the absorption layer. The photoresist may then be
stripped by wet stripping or plasma ashing. In the present example,
the patterned absorption layer has at least one opening, as shown
in FIG. 3b.
[0022] In step 156 and with additional reference to FIG. 3c, the
WRM 106 may be formed in the opening of the absorption layer 104
using a process such as a spin-on coating, CVD, atomic layer
deposition, or PVD. Depending on a desired thickness of the WRM or
upon a desired height of the WRM relative to the surface of the
absorption layer 104, the surface of the WRM is substantially
co-planar with the absorption layer, but may be fine-tuned to be
slightly higher or lower than the surface of the absorption layer
104. A planarizing process, such as CMP may be used to planarize
the WRM 106 and the absorption layer 104. In the present example,
the thickness of the WRM ranges from about the thickness of the
absorption layer 104 to approximately ten times the wavelength of
light passing through the WRM during photolithography processing.
The WRM may use a material of high transparency and high refractive
index, including photoresist materials, polymer materials, and
dielectric materials. Examples of WRM materials include polyimide,
SiO2, ITO, PVA, and silicone.
[0023] Referring now to FIG. 4, a cross-sectional view of another
embodiment of a photomask 200 is illustrated. The photomask 200
comprises a transparent substrate 202, an absorption layer 204, a
WRM 206, and a plurality of antireflection coating (ARC) layers. As
the transparent substrate 202, absorption layer 204, and WRM 206
are similar to those described with respect to FIG. 1, they will
not be described in detail in the present example.
[0024] For purposes of illustration, the ARC layers may include an
ARC layer 210 on an underside (relative to the absorption layer
204) of the substrate 202, an ARC layer 212 between the substrate
202 and the absorption layer 204, an ARC layer 214 between the
absorption layer 204 and the WRM 206, and/or an ARC layer 216 above
the WRM 206. It is understood that the ARC layer 214 may not cover
the sidewall of the patterned absorption layer 204, depending on a
particular processing sequence or processing method used to form
the photomask 100.
[0025] The ARC layers 210, 212, 214, 216 may be used at an
interface to reduce stray light introduced by the photomask. Such
interfaces may include an interface between the substrate 202 and
the absorption layer 204 (using the ARC layer 212), an interface
between the absorption layer 204 and the WRM 206 (using the ARC
layer 214), and an interface between the substrate 202 and the WRM
206 (using the ARC layer 212), even though these ARC layers may
function differently. For example, the ARC layer 214 on the
absorption layer 204 may eliminate stray light contributed by the
high reflectivity of the absorption layer. The ARC layer 216 on the
WRM 206 may reduce multiple reflections between the outer face of
the WRM 206 and the absorption layer 204. It may also reduce the
reflection between the WRM 206 and the space outside. The ARC layer
212 on the substrate may reduce flare back into an illumination
system used during photolithography and may provide a smooth
transition between the substrate 202 and the WRM 206 to eliminate
mismatch of the refractive index.
[0026] Each ARC layer may have multi-level structure that provides
each ARC layer with multiple layers having different refractive
indices. For example, the ARC layers may have a graded structure
where the refractive index of each ARC layer changes gradually to
match the refractive indexes of neighboring materials in the
photomask 100. The ARC layers may comprise an organic material
containing hydrogen, carbon, or oxygen; compound materials such as
Cr2O3, ITO, SiO2, SiN, TaO5, Al2O3, TiN, and ZrO; metal materials
such as Al, Ag, Au, and In; or combination thereof.
[0027] Referring now to FIG. 5 and with additional reference to
FIGS. 6a-6c, an exemplary method 250 may be used to form the
photomask 200 of FIG. 4. The method 250 begins in step 252 with the
formation of the ARC layer 210 on the substrate 202, the formation
of the ARC layer 212 on the other side of the substrate 202, the
formation of the absorption layer 204, and the formation of the ARC
layer 214 above the absorption layer 204.
[0028] As previously described, materials used for the absorption
layer 204 may include metal film such as Chromium (Cr) oxide and
iron oxide, or inorganic films such as MoSi, ZrSiO, and SiN. The
absorption layer 204 may be formed using CVD, plating, or PVD
processes. In the present example, sputtering deposition may be
preferred to provide the absorption layer 204 with thickness
uniformity, relatively few defects, and better adhesion.
[0029] The ARC layers may use an organic material containing
hydrogen, carbon, or oxygen; compound materials including Cr2O3,
ITO, SiO2, SiN, TaO5, Al2O3, TiN, and ZrO; metal materials such as
Al, Ag, Au, and In; or combination thereof. Methods used to form
the ARC layers include spin-on coating, CVD, plating, or PVD.
[0030] In step 254, the absorption layer 204 and the ARC layer 214
may be patterned to have a predefined arrangement of openings as
previously described with respect to the method 150 of FIG. 2. The
ARC layer 214 may be patterned using a processing sequence similar
to that used for the absorption layer 204, but may use a different
etchant. It is noted that the ARC layer 214 does not cover the
sidewalls of the absorption layer 204 (e.g., the walls of the
openings 208). In step 256, the WRM 206 may be formed and, in step
258, the ARC layer 216 may be formed using similar materials and
processing methods as those used in step 252.
[0031] Referring now to FIG. 7, a cross-sectional view of yet
another embodiment of a photomask 300 is illustrated. The photomask
300 comprises a transparent substrate 302, an absorption layer 304,
a WRM 306, and a plurality of antireflection coating (ARC) layers.
As the transparent substrate 302, absorption layer 304, and WRM 306
are similar to those described previously, they will not be
described in detail in the present example.
[0032] For purposes of illustration, the ARC layers may include an
ARC layer 310 on an underside (relative to the absorption layer
304) of the substrate 302, an ARC layer 312 between the substrate
302 and the absorption layer 304, an ARC layer 314 between the
absorption layer 304 and the WRM 306, and/or an ARC layer 316 above
the WRM 306. These ARC layers are similar to those described with
respect to FIG. 4, except that the ARC layer 214 covers the
sidewalls of the absorption layer 304 (e.g., the walls of the
openings 308).
[0033] Referring now to FIG. 8 and with additional reference to
FIGS. 9a-9c, an exemplary method 350 may be used to form the
photomask 300 of FIG. 7. The method 350 begins in step 352 with the
formation of the ARC layer 310 on the substrate 302, the formation
of the ARC layer 312 on the other side of the substrate 302, and
the formation of the absorption layer 304. Unlike the method 250
previously described, the ARC layer 314 is not formed during this
step.
[0034] In step 354, the absorption layer 304 may be patterned to
have a predefined arrangement of openings as previously described
and, in step 356, the ARC layer 314 is formed. Since the ARC layer
314 is formed after the absorption layer 304 is formed and
patterned, the ARC layer 314 conforms to the shape of the
absorption layer 304. This enables the ARC layer 314 to be formed
over the sidewalls of the absorption layer 304 (FIG. 8b). In step
358, the WRM 306 may be formed and, in step 360, the ARC layer 316
may be formed using similar materials and processing methods as
those used in step 352.
[0035] The present disclosure has been described relative to a
preferred embodiment. Improvements or modifications that become
apparent to persons of ordinary skill in the art only after reading
this disclosure are deemed within the spirit and scope of the
application. It is understood that several modifications, changes
and substitutions are intended in the foregoing disclosure and in
some instances some features of the invention will be employed
without a corresponding use of other features. For example, one or
more of the illustrated ARC layers may be excluded or additional
ARC layers may be used. Materials used for the transparent
substrate, absorption layer, wavelength reducing material, and ARC
layers may vary, as may the method by which the various layers are
formed. Accordingly, it is appropriate that the appended claims be
construed broadly and in a manner consistent with the scope of the
invention.
* * * * *