U.S. patent application number 13/167737 was filed with the patent office on 2011-10-20 for stacked structure.
Invention is credited to Yi-Hsing Chen, Jiunn-Hsiung Liao, Chuan-Kai Wang, Meng-Jun Wang, Min-Chieh Yang.
Application Number | 20110254142 13/167737 |
Document ID | / |
Family ID | 39101884 |
Filed Date | 2011-10-20 |
United States Patent
Application |
20110254142 |
Kind Code |
A1 |
Wang; Meng-Jun ; et
al. |
October 20, 2011 |
STACKED STRUCTURE
Abstract
A stacked structure for patterning a material layer to form an
opening pattern with a predetermined opening width in the layer is
provided. The stacked structure includes an underlayer, a silicon
rich organic layer, and a photoresist layer. The underlayer is on
the material layer. The silicon rich organic layer is between the
underlayer and the photoresist layer. The thickness of the
photoresist layer is smaller than that of the underlayer and larger
than two times of the thickness of the silicon rich organic layer.
The thickness of the underlayer is smaller than three times of the
predetermined opening width.
Inventors: |
Wang; Meng-Jun; (Taichung
City, TW) ; Chen; Yi-Hsing; (Changhua County, TW)
; Liao; Jiunn-Hsiung; (Tainan City, TW) ; Yang;
Min-Chieh; (Kaohsiung City, TW) ; Wang;
Chuan-Kai; (Tainan City, TW) |
Family ID: |
39101884 |
Appl. No.: |
13/167737 |
Filed: |
June 24, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11464496 |
Aug 15, 2006 |
|
|
|
13167737 |
|
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Current U.S.
Class: |
257/642 ;
257/E29.002 |
Current CPC
Class: |
H01L 21/0271 20130101;
H01L 21/0332 20130101; H01L 21/32139 20130101; H01L 21/3081
20130101 |
Class at
Publication: |
257/642 ;
257/E29.002 |
International
Class: |
H01L 29/02 20060101
H01L029/02 |
Claims
1. A stacked structure for patterning a material layer to form an
opening pattern with a predetermined opening width in the material
layer, comprising: an underlayer, disposed on the material layer; a
silicon rich organic layer, disposed on the underlayer; and a
photoresist layer, disposed on the silicon rich organic layer, the
thickness of the photoresist layer being larger than two times of
the thickness of the silicon rich organic layer, but is smaller
than the thickness of the underlayer.
2. The stacked structure for patterning as claimed in claim 1,
wherein the thickness of the underlayer is smaller than three times
of the predetermined opening width.
3. The stacked structure for patterning as claimed in claim 1,
further comprising a hard mask layer disposed between the material
layer and the underlayer, the thickness of the hard mask layer
being slightly larger than the thickness of the silicon rich
organic layer.
4. The stacked structure for patterning as claimed in claim 3,
wherein the thickness of the underlayer is smaller than three times
of the predetermined opening width.
5. The stacked structure for patterning as claimed in claim 3,
wherein the material of the hard mask layer comprises silicon
oxide, silicon nitride, silicon oxynitride, silicon carbide,
silicon oxycarbide, and silicon carbonitride.
6. The stacked structure for patterning as claimed in claim 1,
wherein the underlayer comprises varnish resin.
7. The stacked structure for patterning as claimed in claim 6,
wherein the underlayer comprises the I-line photoresist layer.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a division of U.S. application Ser. No.
11/464,496, filed Aug. 15, 2006, and incorporated herein by
reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a semiconductor process.
More particularly, the present invention relates to a stacked
structure and a patterning method using the stacked structure.
[0004] 2. Description of the Prior Art
[0005] In a semiconductor process, usually the pattern is formed on
the photoresist layer in a process of lithography. Then, the
photoresist layer serves as the etching mask to perform the dry or
wet etching process so as to transfer the pattern in the
photoresist layer to the layer to be patterned beneath the
photoresist layer. Along with the high integration of semiconductor
devices, the manufacturing critical dimension (CD) of the
integrated circuit increasingly becomes small. Therefore, the
resolution required by lithography becomes high. In order to
satisfy the demands for high resolution, the thickness of the
photoresist layer is gradually reduced. However, if the thickness
of the photoresist layer is too thin, in the subsequent etching
process, it is possible that the photoresist layer serving as the
etching mask is completely etched before completely transferring
the pattern to the layer to be patterned beneath the photoresist
layer. Therefore, it is urgent to find a way to completely transfer
the pattern to the layer thereunder by the use of the thin
photoresist layer.
SUMMARY OF THE INVENTION
[0006] Accordingly, the objective of the present invention is to
provide a patterning method using the thin photoresist layer to
transfer the pattern.
[0007] Another objective of the present invention is to provide a
stacked structure applicable to the patterning process, for
patterning the material layer with a smaller line width.
[0008] The present invention provides a method for patterning a
material layer to form an opening pattern with a predetermined
opening width in the material layer. In the method, an underlayer,
a silicon rich organic layer, and a photoresist layer are
sequentially formed on the substrate formed with a material layer.
The thickness of the photoresist layer is larger than two times of
the thickness of the silicon rich organic layer, but is smaller
than the thickness of the underlayer. Then, the photoresist layer
is patterned to form the opening pattern in the photoresist layer.
Next, the silicon rich organic layer is etched with the photoresist
layer serving as a mask, so as to transfer the opening pattern to
the silicon rich organic layer. Thereafter, the underlayer is
etched with the silicon rich organic layer serving as the mask, so
as to transfer the opening pattern to the underlayer. When the
opening pattern is completely transferred to the underlayer, the
photoresist layer is completely etched. Then, the material layer is
etched with the underlayer serving as the mask, so as to transfer
the opening pattern to the material layer. When the opening pattern
is completely transferred to the material layer, the silicon rich
organic layer is completely etched.
[0009] According to an embodiment of the present invention, a hard
mask layer with the thickness slightly larger than the thickness of
the silicon rich organic layer is further provided between the
material layer and the underlayer. After etching the underlayer and
before etching the material layer, the method further comprises
etching the hard mask layer with the silicon rich organic layer and
the underlayer serving as the mask, so as to transfer the opening
pattern to the hard mask layer. When the opening pattern is
completely transferred to the hard mask layer, the silicon rich
organic layer is completely etched.
[0010] According to an embodiment of the present invention, the
thickness of the underlayer is smaller than three times of the
predetermined opening width.
[0011] According to an embodiment of the present invention, after
forming the opening pattern in the photoresist layer and before
transferring the opening pattern to the silicon rich organic layer,
and/or after etching the hard mask layer and before transferring
the opening pattern to the material layer, the method further
comprises a trimming step to change the width of the opening
pattern.
[0012] According to an embodiment of the present invention, the
material layer comprises a conductive layer, and the method further
comprises etching the conductive layer with the underlayer serving
as the mask, so as to transfer the opening pattern to the
conductive layer, and then removing the underlayer.
[0013] According to another embodiment of the present invention, a
conductive layer is further provided between the material layer and
the substrate, and the method further comprises removing the
underlayer, and then transferring the opening pattern to the
conductive layer with the hard mask layer serving as the mask.
[0014] According to an embodiment of the present invention, the
material of the hard mask layer comprises silicon oxide, silicon
nitride, silicon oxynitride, silicon carbide, silicon oxycarbide,
and silicon carbonitride.
[0015] According to an embodiment of the present invention, the
thickness of the photoresist layer is about 500 to 2000 .ANG., the
thickness of the silicon rich organic layer is about 250 to 500
.ANG., the thickness of the underlayer is about 1000 to 2500 .ANG.,
and the thickness of the mask layer is about 250 to 900 .ANG..
[0016] According to an embodiment of the present invention, the
thickness of the underlayer is smaller than three times of the
predetermined opening width.
[0017] According to an embodiment of the present invention, the
silicon containing organic layer is formed by spin-coating, and the
thickness is the minimum thickness formed by spin-coating.
[0018] According to an embodiment of the present invention, the
material of the silicon rich organic layer comprises the silicon
polymer with the silicon content of 5-30 wt. %.
[0019] According to an embodiment of the present invention, the
underlayer comprises varnish resin, for example, an I-line
photoresist layer.
[0020] According to an embodiment of the present invention, the
method for patterning the photoresist layer comprises exposing in a
process of immersion lithography, and the photoresist layer is a
waterproof photoresist layer, or a photoresist material layer
covered by a waterproof layer on the top thereof.
[0021] According to an embodiment of the present invention, after
forming the opening pattern in the photoresist layer and before
transferring the opening pattern to the silicon rich organic layer,
and/or after etching the underlayer and before transferring the
opening pattern to the material layer, the method further comprises
a trimming step to change the opening width of the opening
pattern.
[0022] The present invention further provides a stacked structure
for patterning a material layer to form an opening pattern with a
predetermined opening width in the material layer. The structure
comprises an underlayer, a silicon rich organic layer, and a
photoresist layer. The underlayer is disposed on the material
layer; the silicon rich organic layer is disposed between the
underlayer and the photoresist layer, and the thickness of the
photoresist layer is larger than two times of the thickness of the
silicon rich organic layer, but is smaller than the thickness of
the underlayer.
[0023] According to an embodiment of the present invention, the
thickness of the underlayer is smaller than three times of the
predetermined opening width.
[0024] According to an embodiment of the present invention, the
stacked structure further comprises a hard mask layer disposed
between the material layer and the underlayer, and the thickness of
the hard mask layer is slightly larger than the thickness of the
silicon rich organic layer.
[0025] According to an embodiment of the present invention, the
material of the hard mask layer comprises silicon oxide, silicon
nitride, silicon oxynitride, silicon carbide, silicon oxycarbide,
and silicon carbonitride.
[0026] According to an embodiment of the present invention, the
material of the underlayer comprises varnish resin, for example,
the I-line photoresist layer.
[0027] In the present invention, by carefully arranging the
configuration order and thickness of each layer in the stacked
structure, and by using the characteristic of difference in etching
selectivity of the layers, the quite thin photoresist layer can be
used to transfer the pattern. Therefore, it is quite suitable for
the process of semiconductor device with small line width.
[0028] In order to the make aforementioned and other objects,
features and advantages of the present invention comprehensible,
preferred embodiments accompanied with figures are described in
detail below.
[0029] These and other objectives of the present invention will no
doubt become obvious to those of ordinary skill in the art after
reading the following detailed description of the preferred
embodiment that is illustrated in the various figures and
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIGS. 1A to 1E are schematic cross-sectional views of a
patterning method using a stacked structure according to an
embodiment of the present invention.
[0031] FIGS. 2A to 2E are schematic cross-sectional views of a
method of patterning the gate conductive layer by using the stacked
structure according to an embodiment of the present invention.
[0032] FIGS. 3A to 3F are schematic cross-sectional views of a
patterning method using a stacked structure according to another
embodiment of the present invention.
[0033] FIGS. 4A to 4F are schematic cross-sectional views of a
method of forming the trench of the shallow trench isolation (STI)
by using the stacked structure according to another embodiment of
the present invention.
DETAILED DESCRIPTION
[0034] FIGS. 1A to 1E are schematic cross-sectional views of a
patterning method using a stacked structure according to an
embodiment of the present invention.
[0035] Referring to FIG. 1A, the present invention provides a
stacked structure 150 for patterning a material layer 102 to form
an opening pattern 112 in the material layer 102 on the substrate
100. The opening pattern 112 has a predetermined opening width W1.
The stacked structure comprises an underlayer 106, a silicon rich
organic layer 108, and a photoresist layer 110. The underlayer 106
is disposed on the material layer 102, and the silicon rich organic
layer 108 is disposed between the underlayer 106 and the
photoresist layer 110.
[0036] The photoresist layer 110 comprises a positive photoresist
or a negative photoresist, which is a photoresist material usually
used in a conventional lithography process, or a waterproof
photoresist layer used in an immersion lithography process, or a
photoresist material layer covered by a waterproof layer on the top
thereof. The thickness of the photoresist layer 110 is smaller than
the thickness of the underlayer 106, but is larger than two times
of the thickness of the silicon rich organic layer 108. The
material of the silicon rich organic layer 108 comprises an organic
silicon material for the bottom antireflective coating (BARC), for
example, a silicon polymer with the silicon content of 5-30 wt. %,
disclosed in U.S. Pat. No. 6,025,117, which is incorporated herein
by reference. The method of forming the silicon rich organic layer
108 is, for example, spin-coating. In an embodiment, the thickness
of the silicon rich organic layer 108 is the minimum thickness
formed by the spin-coating. The material of the underlayer 106
comprises varnish resin, for example, an I-line photoresist layer.
In an embodiment, the thickness of the underlayer 106 is smaller
than three times of the predetermined opening width W1.
[0037] Referring to FIG. 1B, when the stacked structure 150 is used
to pattern the material layer 102, the photoresist layer 110 is
patterned first, so as to form an opening pattern 114 in the
photoresist layer 110. The method of patterning the photoresist
layer 110 can adopt the conventional lithography process, or the
immersion lithography process to perform an exposure process and
then a development process, so as to form the opening pattern
114.
[0038] If it is inspected that the opening pattern 114 in the
photoresist layer 110 cannot form an opening with the same width W1
as that of the predetermined opening 112 in the subsequent process
after development, a trimming step for the opening width can be
performed before etching the silicon rich organic layer 108, so as
to satisfy the requirement for the width of the opening pattern
114.
[0039] Next, the silicon rich organic layer 108 is etched with the
photoresist layer 110 serving as the mask, so as to transfer the
opening pattern 114 to the silicon rich organic layer 108. The
etching method can be dry etching. During the etching process, the
photoresist layer 110 loses due to the etching. When the opening
pattern 114 is completely transferred to the silicon rich organic
layer 108, a small part of the photoresist layer 110 remains on the
silicon rich organic layer 108.
[0040] Then, referring to FIG. 1C, the underlayer 106 is etched
with the photoresist layer 110 and the silicon rich organic layer
108 serving as the mask, so as to transfer the opening pattern 114
to the underlayer 106. When the opening pattern 114 is completely
transferred to the underlayer 106, the photoresist layer 110 is
completely etched.
[0041] Then, referring to FIG. 1D, the material layer 102 is etched
with the silicon rich organic layer 108 serving as the mask, so as
to transfer the opening pattern 114 to the material layer 102. When
the opening pattern 114 is completely transferred to the material
layer 102, the silicon rich organic layer 108 is completely etched.
If the silicon rich organic layer 108 is completely etched during
the etching process, the underlayer 106 serves as the etching mask
to continue etching until the opening pattern 114 is completely
transferred to the material layer 102. The method of etching the
material layer 102 is, for example, dry etching, and the etching
gas varies in accordance with the material layer 102 to be
etched.
[0042] Then, referring to FIG. 1E, the underlayer 106 is removed.
The method of removing the underlayer 106 is dry removing or wet
removing.
[0043] In the stacked structure of the present invention, the
stacking sequence and the thickness of each layer are carefully
considered, and the details will be illustrated as follows.
[0044] The Photoresist Layer:
[0045] After the silicon rich organic layer 108 is patterned, when
the pattern is transferred to the underlayer 106 thereunder, the
etching selectivity ratio between the silicon rich organic layer
108 and the underlayer 106 is quite high, so the thickness of the
silicon rich organic layer is required to be quite thin, for
example the minimum thickness formed by spin-coating. Therefore,
the thickness of the photoresist layer on the silicon rich organic
layer is required to be sufficient to serve as the mask for etching
the silicon rich organic layer, so as to successfully transfer the
pattern to the silicon rich organic layer thereunder. Therefore,
the present invention can adopt the photoresist layer having a
quite thin thickness, and can adopt the exposing light source
having a relatively short wavelength to fabricate the device with
small line width.
[0046] The Silicon Rich Organic Layer:
[0047] After the pattern is transferred to the underlayer 106, when
the material layer 102 below the underlayer 106 is etched, the
thickness of the silicon rich organic layer 108 serving as the top
mask layer is quite thin, so before completely transferring the
pattern to the material layer 102, the silicon rich organic layer
108 is completely etched. Thus, after completely transferring the
pattern to the material layer 102, the silicon rich organic layer
108 does not remain on the underlayer 106. Therefore, subsequently,
the problems that the remaining silicon rich organic layer 108 is
difficult to be removed, or during removing, the etchant damages
the opening pattern of the material layer 102 or damages the
substrate do not exist.
[0048] The Underlayer:
[0049] After the pattern is transferred to the underlayer 106, when
the material layer 102 below the underlayer 106 is etched, even if
the silicon rich organic layer 108 is completely etched before the
pattern is completely transferred to the material layer 102,
because the underlayer 106 has the enough thickness, the pattern
can be successfully transferred to the material layer 102. In
another aspect, because the thickness of the underlayer 106 is not
larger than three times of the predetermined opening width, i.e.
when the material layer 102 is etched, the aspect ratio of the
opening formed in the underlayer 106 and the material layer 102 is
smaller than 3. Thus, the opening pattern 114 can be completely
transferred to the material layer 102, and the problem that the
opening cannot be formed due to the incomplete etching does not
exist.
[0050] The stacked structure and the patterning method can be
applied in the process of patterning the dielectric layer or the
conductive layer. The process method of the gate conductive layer
is taken as an example for illustration with reference to FIGS. 2A
to 2E in the following.
[0051] Referring to FIG. 2A, a substrate 200 is provided. The
substrate 200 has a gate dielectric layer 201 and a gate conductive
layer 202. A plurality of gaps 212 is predetermined to be formed in
the gate conductive layer 202, and the predetermined width of the
gap 212 is W2. The gate conductive layer 202 is, for example, a
doped polysilicon layer, or a polysilicon metal layer composed of
the doped polysilicon layer and the silicon metal layer. The
stacked structure 250 comprises an underlayer 206, a silicon rich
organic layer 208, and a photoresist layer 210. The photoresist
layer 210 can adopt the positive photoresist or the negative
photoresist, and the thickness thereof is about 500 to 2000 .ANG..
The silicon rich organic layer 208 can adopt the silicon polymer
with the silicon content of 5-30 wt. %, disclosed in U.S. Pat. No.
6,025,117, and the thickness thereof is about 250 to 500 .ANG.. The
material of the underlayer 206 is, for example, the I-line
photoresist layer, and the thickness thereof is about 2000 to 2500
.ANG..
[0052] In an embodiment, the width W2 of the gap 212 between the
patterned conductive layers to be formed is 65 nm. The thickness of
the silicon rich organic layer 208 is 300 .ANG.. The thickness of
the photoresist layer 210 is larger than 600 .ANG.. The thickness
of the underlayer 206 is smaller than 1950 .ANG.. In another
embodiment, the width W2 of the gap 212 between the patterned
conductive layers to be formed is 55 nm. The thickness of the
silicon rich organic layer 208 is 300 .ANG.. The thickness of the
photoresist layer 210 is larger than 600 .ANG.. The thickness of
the underlayer 206 is smaller than 1650 .ANG.. In still another
embodiment, the width W2 of the gap 212 between the patterned
conductive layers to be formed is 45 nm. The thickness of the
silicon rich organic layer 208 is 300 .ANG.. The thickness of the
photoresist layer 210 is larger than 600 .ANG.. The thickness of
the underlayer 206 is smaller than 1350 .ANG..
[0053] Referring to FIG. 2B, when the conductive layer 202 is
patterned by using the stacked structure 250, the photoresist layer
210 is patterned first, so as to form the opening pattern 214 in
the photoresist layer 210. The method of patterning the photoresist
layer 210 can adopt the conventional lithography process, or can
adopt the immersion lithography process to perform the exposure
process and then the development process to form the opening
pattern 214.
[0054] If it is inspected that the opening pattern 214 in the
photoresist layer 210 cannot form an gap with the same width W2 as
that of the predetermined gap 212 in the subsequent process after
development, a step of trimming the gap width can be performed
before etching the silicon rich organic layer 208, so as to satisfy
the requirement for the width of the opening pattern 214. In the
trimming step, CF.sub.4 and hydrogen bromide act as the reaction
gas to etch the photoresist layer 110.
[0055] Then, the silicon rich organic layer 208 is etched with the
photoresist layer 210 serving as the mask, so as to transfer the
opening pattern 214 to the silicon rich organic layer 208. The
etching method can adopt the dry etching by using, for example,
fluorine-containing gas, such as perfluorinated compound as the
etching gas.
[0056] Then, referring to FIG. 2C, the underlayer 206 is etched
with the photoresist layer 210 and the silicon rich organic layer
208 serving as the mask, so as to transfer the opening pattern 214
to the underlayer 206. The etching method can adopt the dry etching
by using, for example, gas containing oxygen, carbon monoxide,
chlorine, and argon as the etching gas. When the opening pattern
214 is completely transferred to the underlayer 206, the
photoresist layer 210 is completely etched.
[0057] Then, referring to FIG. 2D, the conductive layer 202 is
etched with the silicon rich organic layer 208 serving as the mask,
so as to transfer the opening pattern 214 to the conductive layer
202. When the opening pattern 214 is completely transferred to the
conductive layer 202, the silicon rich organic layer 208 is
completely etched. If the silicon rich organic layer 208 is
completely etched during the etching process, the underlayer 206
serves as the etching mask to continue etching until the opening
pattern 214 is completely transferred to the conductive layer 202.
The method of etching the material layer 202 is, for example, the
dry etching, and the etching gas is, for example, perfluorocarbon
or SF.sub.6.
[0058] Then, referring to FIG. 2E, the underlayer 206 is removed,
such that the patterned conductive layer 202 is exposed. The method
of removing the underlayer 206 can adopt the dry removing, for
example, O.sub.2 plasma ashing.
[0059] FIGS. 3A to 3F are schematic cross-sectional views of a
patterning method using a stacked structure according to another
embodiment of the present invention.
[0060] Referring to FIG. 3A, the present invention provides a
stacked structure 360 for patterning a material layer 302 to form a
predetermined opening pattern 312 in the material layer 302. The
opening pattern 312 has a predetermined opening width W3. The
stacked structure comprises a hard mask layer 304, an underlayer
306, a silicon rich organic layer 308, and a photoresist layer 310.
The hard mask layer 304 is disposed on the material layer 302. The
underlayer 306 is disposed on the hard mask layer 304. The silicon
rich organic layer 308 is disposed between the underlayer 306 and
the photoresist layer 310. The thickness of the hard mask layer 304
is slightly larger than the thickness of the silicon rich organic
layer 308. The thickness of the photoresist layer 310 is smaller
than the thickness of the underlayer 306, but is larger than two
times of the thickness of the silicon rich organic layer 308.
[0061] The photoresist layer 310 comprises the positive photoresist
or the negative photoresist, which is the photoresist material
usually used in the conventional lithography process, or the
waterproof photoresist layer used in the immersion lithography
process, or the photoresist material layer covered by a waterproof
layer on the top thereof. The material of the silicon rich organic
layer 308 comprises the silicon-containing organic hard mask
material for the bottom antireflective coating (BARC), for example,
the silicon polymer with the silicon content of 5-30 wt. %,
disclosed in U.S. Pat. No. 6,025,117, which is incorporated herein
by reference. The forming method is, for example, the spin-coating.
In an embodiment, the thickness of the silicon rich organic layer
308 is the minimum thickness formed by spin-coating. The material
of the underlayer 306 comprises the varnish resin, for example, the
I-line photoresist layer. In an embodiment, the thickness of the
underlayer 306 is smaller than three times of the predetermined
opening width W3. The material of the hard mask layer 304 is, for
example, silicon oxide, silicon nitride, silicon oxynitride,
silicon carbide, silicon oxycarbide, or silicon carbonitride. The
forming method can adopt chemical vapor deposition.
[0062] Referring to FIG. 3B, when the material layer 302 is
patterned by using the stacked structure 360, the photoresist layer
310 is patterned first, so as to form the opening pattern 314 in
the photoresist layer 310. The method of patterning the photoresist
layer 310 can adopt the conventional lithography process, or can
adopt the immersion lithography process to perform the exposure
process and the development process to form the opening pattern
314.
[0063] If it is inspected that the opening pattern 314 in the
photoresist layer 310 can not form an opening with the same width
W3 as that of the predetermined opening 312 in the subsequent
process after development, a step of trimming the opening width can
be carried out before etching the silicon rich organic layer 308,
so as to satisfy the requirement for the width of the opening
pattern 314.
[0064] Then, the silicon rich organic layer 308 is etched with the
photoresist layer 310 serving as the mask, so as to transfer the
opening pattern 314 to the silicon rich organic layer 308. The
etching method can adopt the dry etching by using, for example, the
fluorine-containing gas, such as the perfluorinated compound as the
etching gas. During the etching process, the photoresist layer 310
loses due to the etching. When the opening pattern 314 is
completely transferred to the silicon rich organic layer 308, a
small part of the photoresist layer 310 remains on the silicon rich
organic layer 308.
[0065] Then, referring to FIG. 3C, the underlayer 306 is etched
with the photoresist layer 310 and the silicon rich organic layer
308 as the mask, so as to transfer the opening pattern 314 to the
underlayer 306. The etching method of can adopt the dry etching.
When the opening pattern 314 is completely transferred to the
underlayer 306, the photoresist layer 310 is completely etched.
[0066] Then, referring to FIG. 3D, the hard mask layer 304 is
etched with the silicon rich organic layer 308 and the underlayer
306 as the mask, so as to transfer the opening pattern 314 to the
hard mask layer 304. When the opening pattern 314 is completely
transferred to the hard mask layer 304, the silicon rich organic
layer 308 is completely etched.
[0067] After the hard mask layer 304 is etched, when it is found
that the opening pattern 314 in the hard mask layer 304 cannot form
an opening with the same width W3 as that of the predetermined
opening 312 in the subsequent process, a step of trimming the
opening width can be performed before etching the material layer
302, so as to satisfy the requirement for the width of the opening
pattern 314. During the trimming step, the removing rates of the
underlayer 306 and the hard mask layer 304 must be approximately
the same, so as to assure the consistency of the opening patterns
314 of the two.
[0068] Then, referring to FIG. 3E, the underlayer 306 is removed.
The method of removing the underlayer 306 is dry removing or wet
removing. The dry removing can adopt the O.sub.2 plasma ashing.
Then, the material layer 302 is etched with the hard mask layer 304
serving as the mask, so as to transfer the opening pattern 314 to
the material layer 302, as shown in FIG. 3F.
[0069] Referring to FIG. 3EE, another method involves after the
opening pattern 314 is completely transferred to the hard mask
layer 304, etching the material layer 302 with the underlayer 306
serving as the mask, so as to transfer the pattern 314 to the
material layer 302. If the underlayer 306 is completely etched
during the etching process, the hard mask layer 304 serves as the
mask to continue etching until the opening pattern 314 is
completely transferred to the material layer 302. If the underlayer
306 is not completely etched during the etching process, after the
opening patter 314 is completely transferred to the material layer
302, the underlayer 306 is removed, as shown in FIG. 3F.
[0070] In the stacked structure of the present invention, the
stacking sequence and the thickness of each layer are carefully
considered, and the details will be illustrated as follows.
[0071] The Photoresist Layer:
[0072] After the silicon rich organic layer 308 is patterned, when
the pattern is transferred to the underlayer 306 thereunder, the
etching selectivity ratio between the silicon rich organic layer
308 and the underlayer 306 is quite high, so the thickness of the
silicon rich organic layer 308 is required to be quite thin, for
example, the minimum thickness formed by spin-coating. Therefore,
the thickness of the photoresist layer 310 on the silicon rich
organic layer 308 is required to be sufficient to serve as the mask
for etching the silicon rich organic layer 308, so as to
successfully transfer the pattern to the silicon rich organic layer
308 thereunder. Therefore, the photoresist layer has a quite thin
thickness, and the exposing light source having a relatively short
wavelength can be adopted to fabricate the device with small line
width.
[0073] The Silicon Rich Organic Layer:
[0074] After the pattern is transferred to the underlayer 306, when
the hard mask layer 304 is etched, the thickness of the silicon
rich organic layer 308 serving as the top mask layer is thinner
than the thickness of the hard mask layer. Therefore, if the
etchant having substantially the same etching rate for the two is
selected during the etching process, before the pattern is
completely transferred to the hard mask layer 304, the silicon rich
organic layer 308 is completely etched. Thus, after the pattern is
completely transferred to the hard mask layer 304, no silicon rich
organic layer remains on the underlayer 306. Therefore,
subsequently, the problems that the remaining silicon rich organic
layer is difficult to be removed, or during removing, the etchant
damages the opening pattern of the hard mask layer 304 do not
exist.
[0075] The Underlayer:
[0076] After the pattern is transferred to the underlayer 306, when
the hard mask layer below the underlayer 306 is etched, even if the
silicon rich organic layer 308 is completely etched before the
pattern is completely transferred to the hard mask layer 304,
because the underlayer 306 has enough thickness, the pattern can be
successfully transferred to the material layer 302. In another
aspect, because the thickness of the underlayer 306 is not larger
than three times of the predetermined width W3 of the opening 312,
i.e. when the hard mask layer 304 is etched, the aspect ratio of
the opening 314 formed in the underlayer 306 and the hard mask
layer 304 is smaller than 3. Thus, the opening pattern 314 can be
completely transferred to the hard mask layer 304, and the problem
that the opening cannot be formed due to the incomplete etching
does not exist.
[0077] The Hard Mask Layer:
[0078] In order to avoid the incomplete etching, preferably the
thickness of the underlayer 306 is not larger than three times of
the width W3 of the opening 312. However, if the hard mask layer
304 does not exist, and the depth of the opening 312 to be formed
in the material layer 302 is relatively deep, the underlayer 306
must have enough thickness to serve as the etching mask. Otherwise,
before the opening depth formed in the material layer 302 reaches
the required depth, the underlayer 306 is completely etched. The
advantage of adding a hard mask 304 on the underlayer 306 and the
material layer 302 is that even if the underlayer 306 is completely
etched during the process of etching the material layer 302, the
etching rate of the hard mask layer 304 smaller than that of the
material layer 302 and far smaller than that of the underlayer 306
such that the hard mask layer 304 can serve as the mask, and thus
the required opening may be successfully formed in the material
layer 302.
[0079] The stacked structure and the patterning method can be
applied in the gate conductive layer or the STI process, but it is
not limited herein. The method applied in the STI is illustrated in
detail with reference to FIGS. 4A to 4F as follows.
[0080] Referring to FIG. 4A, a substrate 402 is provided. A
plurality of trenches 412 is preformed in the substrate 402, and
the predetermined width of the trench 412 is W4. The substrate 402
is, for example, entirely a semiconductor substrate, such as
silicon, germanium, SiGe, SiC, or silicon on insulator (SOI). Then,
a pad oxide layer 403 and a stacked structure 460 are formed on the
substrate 402. The stacked structure 460 comprises a hard mask
layer 404, an underlayer 406, a silicon rich organic layer 408, and
a photoresist layer 410. The photoresist layer 410 can adopt the
positive photoresist or the negative photoresist, and the thickness
thereof is about 500 to 2000 .ANG.. The silicon rich organic layer
408 can adopt the silicon polymer with the silicon content of 5-30
wt. %, disclosed in U.S. Pat. No. 6,025,117, the thickness thereof
is about 250 to 500 .ANG.. The material of the underlayer 406 is,
for example, the I-line photoresist layer, and the thickness
thereof is about 1000 to 2500 .ANG.. The material of the hard mask
layer 404 is, for example, silicon nitride, and the forming method
can adopt the chemical vapor deposition, and the thickness thereof
is slightly larger than the thickness of the silicon rich organic
layer 408, and is for example, about 250 to 900 .ANG..
[0081] Referring to FIG. 4B, when the substrate 402 is patterned by
using the stacked structure 460, the photoresist layer 410 is
patterned first, so as to form the trench pattern 414 in the
photoresist layer 410. The method of patterning the photoresist
layer 410 can adopt the conventional lithography process, or can
adopt the immersion lithography process to perform the exposure
process and then the development process to form the trench pattern
414.
[0082] If it is inspected that the trench pattern 414 in the
photoresist layer 410 cannot form a trench with the predetermined
width W4 in the subsequent process after development, a step of
trimming the trench width can be performed before etching the
silicon rich organic layer 408, so as to satisfy the requirement
for the width of the trench pattern 414. The trimming step 120 can
use CF.sub.4 and hydrogen bromide as the reaction gas.
[0083] Then, the silicon rich organic layer 408 is etched with the
photoresist layer 410 serving as the mask, so as to transfer the
trench pattern 414 to the silicon rich organic layer 408. The
etching method can adopt the dry etching by using, for example, the
fluorine-containing gas, such as the perfluorinated compound as the
etching gas. During the etching process, the photoresist layer 410
loses due to the etching. Therefore, when the trench pattern 414 is
completely transferred to the silicon rich organic layer 408, a
small part of the photoresist layer 410 remains on the silicon rich
organic layer 408, or is completely etched.
[0084] Then, referring to FIG. 4C, the underlayer 406 is etched
with the silicon rich organic layer 408 as the mask, so as to
transfer the trench pattern 414 to the underlayer 406. The etching
method can adopt the dry etching, for example, the gas containing
oxygen, carbon monoxide, chlorine, and argon as the etching gas.
When the trench pattern 414 is completely transferred to the
underlayer 406, the photoresist layer 410 is completely etched.
[0085] Then, referring to FIG. 4D, the hard mask layer 404 is
etched with the silicon rich organic layer 408 and the underlayer
406 as the mask, so as to transfer the trench pattern 414 to the
hard mask layer 404. During etching, the etchant having
substantially the same etching rate for the silicon rich organic
layer 408 and the hard mask layer 404 is selected for etching.
Because the thickness of the silicon rich organic layer 408 is
smaller than the thickness of the hard mask layer 404, when the
trench pattern 414 is completely transferred to the hard mask layer
404, the silicon rich organic layer 408 is completely etched, and
no silicon rich organic layer 408 remains on the underlayer
406.
[0086] After the hard mask layer 404 is etched, it is found that
the trench pattern 414 in the hard mask layer 404 cannot form a
trench 412 with the predetermined width W4 in the subsequent
process, a step of trimming the trench width can be performed
before etching the silicon substrate 402, so as to satisfy the
requirement for the width of the trench pattern 414. During the
trimming step, the removing rates of the underlayer 406 and the
hard mask layer 404 must be substantially the same, so as to assure
the consistency of the trench pattern 414 of the two. The trimming
step can use CF.sub.4 and trifluoromethane as the reaction gas to
perform etching, thus complete trimming.
[0087] Then, referring to FIG. 4E, the underlayer 406 is removed.
The method of removing the underlayer 406 can adopt the dry
removing or the wet removing. The dry removing can adopt the
O.sub.2 plasma ashing. Then, the pad oxide layer 403 and the
substrate 402 are etched by using the hard mask layer 404 as the
mask, so as to transfer the trench pattern 414 to the substrate
402, as shown in FIG. 4F. The method of etching the substrate 402
can adopt the dry etching by using, for example, perfluorocarbon or
SF.sub.6 as the etching reaction gas.
[0088] Referring to FIG. 4EE, another method involves after the
trench pattern 414 is completely transferred to the hard mask layer
404, before removing the underlayer 406, etching the substrate 402
with the underlayer 406 serving as the mask, so as to transfer the
opening pattern 414 to the substrate 402 to form the trench. If the
underlayer 406 is completely etched during the etching process, the
hard mask layer 404 serves as the mask to continue etching until
the trench pattern 414 is completely transferred to the substrate
402. If the underlayer 406 is not completely etched during the
etching process, after the trench pattern 414 is completely
transferred to the substrate 402, the underlayer 406 is removed, as
shown in FIG. 4F.
[0089] It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the
present invention without departing from the scope or spirit of the
invention. In view of the foregoing, it is intended that the
present invention cover modifications and variations of this
invention provided they fall within the scope of the following
claims and their equivalents.
[0090] Those skilled in the art will readily observe that numerous
modifications and alterations of the device and method may be made
while retaining the teachings of the invention. Accordingly, the
above disclosure should be construed as limited only by the metes
and bounds of the appended claims.
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