U.S. patent application number 11/067283 was filed with the patent office on 2006-08-31 for method for fabricating etch mask and patterning process using the same.
Invention is credited to Benjamin Szu-Min Lin.
Application Number | 20060191863 11/067283 |
Document ID | / |
Family ID | 36931091 |
Filed Date | 2006-08-31 |
United States Patent
Application |
20060191863 |
Kind Code |
A1 |
Lin; Benjamin Szu-Min |
August 31, 2006 |
Method for fabricating etch mask and patterning process using the
same
Abstract
A method for fabricating a mask is provided. A patterned
sacrificial layer is formed over a mask material layer, and the
patterned sacrificial layer has an etch selectivity different from
that of the mask material layer. An isotropic etch process is
performed to the mask material layer by using the patterned
sacrificial layer as an etch mask to form a mask layer, wherein the
dimension of the mask layer is smaller than that of the patterned
sacrificial layer.
Inventors: |
Lin; Benjamin Szu-Min;
(Hsinchu, TW) |
Correspondence
Address: |
J C PATENTS, INC.
4 VENTURE, SUITE 250
IRVINE
CA
92618
US
|
Family ID: |
36931091 |
Appl. No.: |
11/067283 |
Filed: |
February 25, 2005 |
Current U.S.
Class: |
216/41 ;
257/E21.038; 257/E21.039 |
Current CPC
Class: |
H01L 21/0337 20130101;
H01L 21/0338 20130101 |
Class at
Publication: |
216/041 |
International
Class: |
C23F 1/00 20060101
C23F001/00 |
Claims
1. A method for fabricating a mask, comprising: forming a patterned
sacrificial layer over a mask material layer, the patterned
sacrificial layer having an etch selectivity different from that of
the mask material layer; and performing an isotropic etch process
to the mask material layer to form a mask layer by using the
patterned sacrificial layer as an etch mask, a dimension of the
mask layer being smaller than a dimension of the patterned
sacrificial layer.
2. The method for fabricating a mask of claim 1, wherein a method
for forming the patterned sacrificial layer comprises: forming a
sacrificial layer over the mask material layer; forming a patterned
photoresist layer over the sacrificial layer; and etching the
sacrificial layer by using the patterned photoresist layer as an
etch mask.
3. The method for fabricating a mask of claim 2, wherein the
patterned photoresist layer has a critical dimension (CD), and the
dimension of the mask layer is smaller than a CD.
4. The method for fabricating a mask of claim 1, wherein the
isotropic etch process comprises a wet etch process.
5. The method for fabricating a mask of claim 1, wherein the mask
material layer comprises a material selected from the group
consisting of silicon oxide, silicon nitride, silicon oxynitride,
polysilicon, doped polysilicon and a metal material.
6. The method for fabricating a mask of claim 1, wherein the
patterned sacrificial layer comprises a material selected from the
group consisting of silicon oxide, silicon nitride, silicon
oxynitride, polysilicon, doped polysilicon and a metal
material.
7. A patterning process, comprising: forming a mask material layer
over a material layer, the mask material layer having an etch
selectivity different from that of the material layer; forming a
patterned sacrificial layer over the mask material layer, the
patterned sacrificial layer having an etch selectivity different
from that of the mask material layer, the patterned sacrificial
layer having an etch selectivity the same as, or different from,
that of the material layer; performing an isotropic etch process to
the mask material layer to form a mask layer by using the patterned
sacrificial layer as an etch mask, a dimension of the mask layer
being smaller than a dimension of the patterned sacrificial layer;
and etching the material layer by using the mask layer as an etch
mask.
8. The patterning process of claim 7, wherein a method for forming
the patterned sacrificial layer comprises: forming a sacrificial
layer over the mask material layer; forming a patterned photoresist
layer over the sacrificial layer; and etching the sacrificial layer
by using the patterned photoresist layer as an etch mask.
9. The patterning process of claim 8, wherein the patterned
photoresist layer has a critical dimension (CD), and the dimension
of the mask layer is smaller than the CD.
10. The patterning process of claim 7, wherein the isotropic etch
process comprises a wet etch process.
11. The patterning process of claim 7, wherein the mask material
layer comprises a material selected from the group consisting of
silicon oxide, silicon nitride, silicon oxynitride, polysilicon,
doped polysilicon and a metal material.
12. The patterning process of claim 7, wherein the patterned
sacrificial layer comprises a material selected from the group
consisting of silicon oxide, silicon nitride, silicon oxynitride,
polysilicon, doped polysilicon and a metal material.
13. The patterning process of claim 7, wherein the material layer
comprises a material selected from the group consisting of silicon
oxide, silicon nitride, silicon oxynitride, polysilicon, doped
polysilicon and a metal material.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a semiconductor process,
and more particularly to a method for fabricating a mask and a
patterning process using the mask.
[0003] 2. Description of the Related Art
[0004] As the integration of circuits continues to increase, the
dimensions of circuit devices must shrink to meet the requirement.
One of the most important processes in the semiconductor technology
is the photolithographic process. Patterns of different film layers
and areas with dopants of Metal-Oxide-Semiconductor (MOS) devices
are defined by the photolithographic process. In detail, dimensions
of a photoresist layer formed by the photolithographic process or
dimensions of a mask formed by using the patterned photoresist
layer are closely related to the photolithographic process. Whether
the device integration of the semiconductor technology can progress
to smaller dimensions is depended upon the development of the
photolithographic technology.
[0005] In order to shrink the dimensions of a device and improve
exposure resolution, various improved designs of masks or light
sources with shorter wavelengths have been used to obtain devices
with smaller dimensions. Regardless of the improvement methods, the
improvement of the device dimensions is restricted by the
limitation of the exposure equipment. For example, the exposure
equipment itself has an ultimate resolution. The dimension of the
defined photoresist layer can only be reduced to a specific
dimension, i.e., the critical dimension (CD), and cannot be further
reduced. Accordingly, to further decrease the dimension of a film
layer defined by using the photoresist layer is also limited.
[0006] The issue described above can be solved by treating the
patterned photoresist layer with the trim technology to reduce the
dimension of the patterned photoresist layer. However, the
dimension of a trimmed photoresist layer is so small that
photoresist layer may collapse because the trimmed photoresist
layer cannot withstand stand the stress induced in the subsequent
etch process. As a result, the accuracy of the dimension of the
film layer defined by the trimmed photoresist layer is
affected.
SUMMARY OF THE INVENTION
[0007] Accordingly, the present invention is directed to a method
for fabricating a mask with a dimension smaller than the critical
dimension (CD) of the photolithographic process.
[0008] The present invention is also directed to a patterning
process to overcome the restraint on size reduction of devices due
to the limitation of the traditional exposure equipment.
[0009] The present invention provides a method for fabricating a
mask. The method includes forming a patterned sacrificial layer
over a mask material layer. The patterned sacrificial layer has an
etch selectivity different from that of the mask material layer. An
isotropic etch process is performed to the mask material layer to
form a mask layer by using the patterned sacrificial layer as an
etch mask. A dimension of the mask layer is smaller than a
dimension of the patterned sacrificial layer.
[0010] The present invention provides a patterning process. The
process includes forming a mask material layer over a material
layer. The mask material layer has an etch selectivity different
from that of the material layer. A patterned sacrificial layer is
formed over the mask material layer. The patterned sacrificial
layer has an etch selectivity different from that of the mask
material layer. The patterned sacrificial layer has an etch
selectivity the same as, or different from, that of the material
layer. An isotropic etch process is performed to the mask material
layer to form a mask layer by using the patterned sacrificial layer
as an etch mask. A dimension of the mask layer is smaller than a
dimension of the patterned sacrificial layer. The material layer is
then etched by using the mask layer as an etch mask.
[0011] According to the method for fabricating a mask or the
patterning process of embodiments of the present invention, the
method for forming the patterned sacrificial layer forms a
sacrificial layer over the mask material layer. A patterned
photoresist layer is then formed over the sacrificial layer. The
sacrificial layer is etched by using the patterned photoresist
layer as an etch mask, wherein, the patterned photoresist layer has
a critical dimension (CD), and the dimension of the mask layer is
smaller than the CD.
[0012] According to the method for fabricating a mask or the
patterning process of embodiments of the present invention, the
isotropic etch process comprises a wet etch process, for
example.
[0013] According to the method for fabricating a mask or the
patterning process of the embodiments of the present invention, the
material of the mask material layer comprises, for example, silicon
oxide, silicon nitride, silicon oxynitride, polysilicon, doped
polysilicon or a metal material.
[0014] According to the method for fabricating a mask or the
patterning process of the embodiments of the present invention, the
material of the patterned sacrificial layer comprises, for example,
silicon oxide, silicon nitride, silicon oxynitride, polysilicon,
doped polysilicon or a metal material.
[0015] According to the patterning process of an embodiment of the
present invention, the material of the material layer comprises
silicon oxide, silicon nitride, silicon oxynitride, polysilicon,
doped polysilicon or a metal material.
[0016] The present invention uses the patterned sacrificial layer
to define the film as the actual mask. By using the isotropic etch
process, the dimension of the film can be further reduced.
Accordingly, the dimension of the mask layer is smaller than that
of the sacrificial layer. In other words, if the dimension of the
patterned sacrificial layer is the smallest dimension (critical
dimension) that can be produced by the photolithographic equipment,
the dimension of the mask layer is smaller than the critical
dimension. Accordingly, the mask layer can be used to fabricate
devices with smaller dimensions. The integration of devices is thus
improved.
[0017] The above and other features of the present invention will
be better understood from the following detailed description of the
preferred embodiments of the invention that is provided in
communication with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIGS. 1A-1D are schematic cross sectional views showing the
progression of a patterning process according to an embodiment of
the present invention.
DESCRIPTION OF SOME EMBODIMENTS
[0019] FIGS. 1A-1D are schematic cross sectional views showing the
progression of a patterning process according to an embodiment of
the present invention.
[0020] Referring to FIG. 1A, a mask material layer 104 is formed
over a material layer 102. The mask material layer 104 has an etch
selectivity different from that of the material layer 102, wherein,
the material layer 102 is formed over a substrate 100, for example.
The material of the material layer 102 can be, for example, silicon
oxide, silicon nitride, silicon oxynitride, polysilicon, doped
polysilicon or a metal material. If the material layer 102 serves
as a gate after subsequent patterning processes, a gate dielectric
layer 106 can further be formed between the material layer 102 and
the substrate 100. In addition, the material of the mask material
layer 104 can be, for example, silicon oxide, silicon nitride,
silicon oxynitride, polysilicon, doped polysilicon or a metal
material. The material of the mask material layer 104 is not
specific as long as the mask material layer 104 has an etch
selectivity different from that of the material layer 102.
[0021] A patterned sacrificial layer 108 is then formed over the
mask material layer 104. The patterned sacrificial layer 108 has an
etch selectivity different from that of the mask material layer
104. The patterned sacrificial layer 108 has an etch selectivity
the same as, or different from, that of the material layer 102,
wherein, the material of the patterned sacrificial layer 108 can
be, for example, silicon oxide, silicon nitride, silicon
oxynitride, polysilicon, doped polysilicon or a metal material.
SThe material of the patterned sacrificial layer 108 is not
specific, as long as the patterned sacrificial layer 108 has an
etch selectivity different from that of the mask material layer
104. In other words, the patterned sacrificial layer 108 and the
material layer 102 can be the same, or different, materials.
[0022] In addition, the method of forming the patterned sacrificial
layer 108, for example, includes forming a sacrificial material
layer (not shown) over the mask material layer 104. Then a
patterned photoresist layer 110 is formed over the sacrificial
material layer 108, in which an exposure process is performed to a
photoresist layer (not shown) by using the mask 112, and a
development process is performed to the photoresist layer to form
the patterned photoresist layer 110. By using the patterned
photoresist layer 110 as an etch mask, the sacrificial material
layer is etched to form the patterned sacrificial layer 108. In an
embodiment, the patterned photoresist layer 110 has a critical
dimension due to the limitation of the exposure equipment. The
patterned sacrificial layer 108 defined by using the patterned
photoresist layer 110 also has the same critical dimension.
[0023] Referring to FIG. 1B, by using the patterned sacrificial
layer 108 as an etch mask, an isotropic etch process is performed
to the mask material layer 104 to form the mask layer 104a. The
dimension of the mask layer 104a is smaller than that of the
patterned sacrificial layer 108. The isotropic etch process can be
a wet etch process, for example. Because the patterned sacrificial
layer 108 has an etch selectivity different from that of the
patterned material layer 104, the patterned sacrificial layer 108
can withstand the etch process. It should be noted that because the
etch process is an isotropic etch process, portions of the mask
material laeyr 104 are removed to form undercuts on the mask
material layer 104 under the patterned sacrificial layer 108. The
dimension of the mask layer 104a is smaller than that of the
patterned sacrificial layer 108. In addition, during the process of
etching the mask material layer 104, the patterned photoresist
layer 110 and the patterned sacrificial layer 108 serve as an etch
mask. In another embodiment, the patterned photoresist layer 110 is
removed first, and then the patterned sacrificial layer 108 serves
as an etch mask in the etch process for the mask material layer
104.
[0024] Referring to FIGS. 1C and 1D, the material layer 102 is
etched by using the mask layer 104a as an etch mask. FIG. 1C is a
cross sectional view of the structure during the etch process. FIG.
1D is a cross sectional view of the structure after the etch
process. In FIG. 1C, the patterned sacrificial layer 108 with a
larger dimension covers a portion of the material layer 102 at the
initial step of the etch process. If the patterned sacrificial
layer 108 serves as an etch mask, the extrusion portion 114 of the
defined material layer 102a is larger than the mask layer 104a.
However, when the etch process is performed for a period of time as
shown in FIG. 1D, the patterned sacrificial layer 108 is gradually
removed and the mask layer 104a is exposed. Then the mask layer
104a serves as the etch mask so that the dimension of the mask
layer 102b is equal to the dimension of the mask layer 104a. The
dimension of the material layer 102b is thus smaller than the
critical dimension.
[0025] In addition, the mask layer 104a has an etch selectivity
different from that of the material layer 102. The mask layer 104
effectively prevents the material layer 102 from being etched.
Accordingly, the dimension of the defined material layer 102b is
more accurate.
[0026] Accordingly, the present invention uses the patterned
sacrificial layer to define the film which is to be as the a mask.
By using the isotropic etch process, the dimension of the mask can
be further reduced. Accordingly, the dimension of the mask layer is
smaller than that of the sacrificial layer. In other words, if the
dimension of the patterned sacrificial layer is the smallest
dimension (critical dimension) which can be obtained by the
photolithographic equipment, the dimension of the mask layer is
smaller than the critical dimension. Accordingly, the mask layer
can be used to fabricate devices with smaller dimensions. The
integration of devices is thus improved.
[0027] In addition, the present invention uses the isotropic etch
process to reduce the dimension of the mask layer so that the
dimension of the photoresist layer used to define the sacrificial
layer need not be reduced. Accordingly, the collapse of the
photoresist layer as often occurs in the prior art technology is
prevneted. Further, the dimension of the defined layer is more
accurate.
[0028] In addition, the present invention uses the patterned
sacrificial layer, the mask material layer and the material layer
with different etch selectivity ratios during the etch process. The
film layer serving as an etch mask can thus effectively withstand
the etch process. Accordingly, the dimension of the defined layer
is more accurate.
[0029] In addition, though the etch process is performed by using
the mask layer formed according to the embodiment of the present,
the application of the present invention, however, is not limited
thereto. In short, the mask of the present invention can also be
used in an ion implantation process or other processes which
require the mask.
[0030] Although the present invention has been described in terms
of exemplary embodiments, it is not limited thereto. Rather, the
appended claims should be constructed broadly to include other
variants and embodiments of the invention which may be made by
those skilled in the field of this art without departing from the
scope and range of equivalents of the invention.
* * * * *