U.S. patent application number 10/053124 was filed with the patent office on 2002-05-30 for method of removing residual photoresist.
Invention is credited to Chou, Hsiao-Pang, Ku, Chi-Fa.
Application Number | 20020062838 10/053124 |
Document ID | / |
Family ID | 24053484 |
Filed Date | 2002-05-30 |
United States Patent
Application |
20020062838 |
Kind Code |
A1 |
Ku, Chi-Fa ; et al. |
May 30, 2002 |
Method of removing residual photoresist
Abstract
A method for removing residual color photoresist material from a
substrate after photoresist development. The method washes the
substrate with a high-pressure jet of de-ionized water that
contains an activated interface agent. A second method of removing
the residual photoresist material bombards the substrate with
oxygen plasma for a brief period so that the residual photoresist
material is polarized and then rinses the substrate with de-ionized
water.
Inventors: |
Ku, Chi-Fa; (Hsinchu Hsien,
TW) ; Chou, Hsiao-Pang; (Taipei Hsien, TW) |
Correspondence
Address: |
J.C. Patents
Suite 250
4 Venture
Irvine
CA
92618
US
|
Family ID: |
24053484 |
Appl. No.: |
10/053124 |
Filed: |
January 17, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10053124 |
Jan 17, 2002 |
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09515952 |
Feb 29, 2000 |
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Current U.S.
Class: |
134/1.2 ;
134/34 |
Current CPC
Class: |
G03F 7/30 20130101 |
Class at
Publication: |
134/1.2 ;
134/34 |
International
Class: |
B08B 003/02 |
Claims
What is claimed is:
1. A method for removing residual photoresist material on a
transistor substrate after development of a patterned color
photoresist layer, comprising the steps of: aiming a high-pressure
jet of de-ionized water that contains an activated interface agent
at the substrate.
2. The method of claim 1, wherein the activated interface agent
includes a sulfonate.
3. The method of claim 1, wherein the activated agent includes
Tergital.RTM..
4. The method of claim 1, wherein the activated agent includes
Teryitox.RTM..
5. A method for removing residual photoresist material on a
transistor substrate after the development of a patterned color
photoresist layer, comprising the steps of: bombarding the
substrate with oxygen plasma so that the residual photoresist
material is polarized; and removing the residual photoresist
material by washing the substrate with de-ionized water.
6. The method of claim 5, wherein the step of polarizing the
residual photoresist material includes forming C--OH bonds on a
surface of the residual photoresist.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method of removing any
residual photoresist that remains after photoresist development.
More particularly, the present invention relates to a method of
removing residual color photoresist from a developed color
photoresist layer often used as an image sensor.
[0003] 2. Description of the Related Art
[0004] A digital color image is normally formed by shining a beam
of light through a stack of color filter arrays (CFA) so that the
image is intercepted by a charge coupled device (CCD) or a CMOS
image sensor. In general, a CFA consists of three or more color
filtering channels alternately positioned such that each color
filter channel permits only a designated frequency bandwidth in the
visible light spectrum to pass to an image sensor. Hence, color
content of a photographic image is determined by various elements
in the CFA. Typical color elements used in a CFA includes red,
green, blue (RGB) or cyan, magenta, yellow (CMY) or some other
assembly of colors.
[0005] FIG. 1 is a schematic cross-sectional view showing a RGB
color photoresist layer 12 formed over a CMOS transistor substrate
10 in the process of forming the image sensor of a CFA. In general,
the photoresist layer is formed on a rough substrate surface. Since
the photoresist layer is neither smooth nor uniform in thickness,
diffused light is often produced in the process of transferring a
pattern to the photoresist layer, resulting in some residual
photoresist material 14 in the supposedly blank region20. Another
source that may contribute to the appearance of photoresist
material 14 inside the blank region 20 is an improper setting of
baking temperature or duration. The resulting residual photoresist
material is very difficult to remove by conventional cleaning
processes. However, if the residual photoresist is not removed from
the blank area 20, product quality is likely to be affected.
SUMMARY OF THE INVENTION
[0006] Accordingly, one object of the present invention is to
provide a method capable of removing residual color photoresist
without affecting the color photoresist pattern.
[0007] To achieve these and other advantages and in accordance with
the purpose of the invention, as embodied and broadly described
herein, the invention provides a method of removing any residual
color photoresist that remains on a substrate after a patterned
color photoresist layer is formed over the substrate. The method
includes aiming a high-pressure jet of de-ionized water that
contains an interface-activating agent at the substrate.
[0008] The invention also provides a second method of removing any
residual color photoresist that remains on a substrate after a
patterned color photoresist layer is formed over the substrate. The
method includes aiming oxygen plasma at the substrate so that the
residual photoresist material is polarized. The polarized residual
photoresist material is next removed by de-ionized water.
[0009] It is to be understood that both the foregoing general
description and the following detailed description are exemplary,
and are intended to provide further explanation of the invention as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The accompanying drawings are included to provide a further
understanding of the invention, and are incorporated in and
constitute a part of this specification. The drawings illustrate
embodiments of the invention and, together with the description,
serve to explain the principles of the invention. In the
drawings,
[0011] FIG. 1 is a schematic cross-sectional view showing a RGB
color photoresist layer formed over a CMOS transistor substrate in
the process of forming the image sensor of a CFA;
[0012] FIGS. 2A through 2C are schematic cross-sectional views
showing the steps for removing residual color photoresist from a
substrate according to a first preferred embodiment of this
invention; and
[0013] FIGS. 3A through 3D are schematic cross-sectional views
showing the steps for removing residual color photoresist from a
substrate according to a second preferred embodiment of this
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] Reference will now be made in detail to the present
preferred embodiments of the invention, examples of which are
illustrated in the accompanying drawings. Wherever possible, the
same reference numbers are used in the drawings and the description
to refer to the same or like parts.
[0015] The method of removing residual photoresist from the exposed
surface of a substrate is explained in two embodiments. In the
first embodiment of this invention, a high-pressure jet of
de-ionized water that contains an activated interface agent is
targeted at the substrate. In the second embodiment of this
invention, the residual photoresist material on the substrate is
first polarized through bombarding the substrate with oxygen
plasma, and then the polarized residual photoresist is washed away
by de-ionized water.
[0016] FIGS. 2A through 2C are schematic cross-sectional views
showing the steps for removing residual color photoresist from a
substrate according to a first preferred embodiment of this
invention. First, as shown in FIG. 2A, a substrate 100 is provided.
The substrate 100 already has CMOS transistors (not shown) formed
thereon from previous processing steps. A color photoresist layer
102 is formed over the substrate 100. The color photoresist layer
102 can be pigmented acrylate or dyed photoresist such as Novolac
resin or dyed polyimide, for example. In general, a negative
photoresist material is used to form the color photoresist layer
102.
[0017] Using conventional photolithographic techniques, the
photoresist layer 102 is first exposed to light followed by
chemical development of the exposed photoresist so that a pattern
is formed in the pattern region 202. Due to the presence of CMOS
transistors on the substrate 100, the upper surface is likely to be
uneven, leading to a local diffusion of light in photolithographic
operation. Hence, some residual photoresist material 110 may remain
on top of supposedly blank region 200 after chemical development of
the photoresist layer. In addition, the improper setting of baking
temperature and duration may also lead to the deposition of
residual photoresist material 110 in the blank region 200 of the
substrate 100.
[0018] Since color photoresist is a high-molecular weight polymer,
the residual photoresist 110 on the substrate 100 is composed of
high-molecular weight polymer, too. In general, high-molecular
weight polymer is normally non-polar and has alkyl radicals close
to the surface. Hence, the residual photoresist 110 can be
represented by a bulk material with many methyl functional groups
(--CH.sub.3) attached to the surface.
[0019] As shown in FIG. 2B, a jet of high-pressure de-ionized water
containing an activated interface agent is targeted at the
substrate 100. Activated interface agent includes sulfonate such as
Tergital or Teryitox.RTM.. In FIG. 2B, the activated interface
agent can be represented by a molecular formula R-SO.sub.3NH.sub.4.
Due to reaction between the non-polar end --R of the activated
interface agent R--SO.sub.3NH.sub.4 and the non-polar end at the
surface of the residual photoresist material 110, the photoresist
material 110 is enclosed and dissolved in small bits. Due to the
intrinsic polar property of de-ionized water and the erosive power
of the high-pressure water jet, the activated interface agent and
residual photoresist material 110 are pulled away as soon as they
react.
[0020] As shown in FIG. 2C, residual photoresist 110 is completely
removed from the blank region 200 through reaction with the
activated interface agent and pressure of the water jet.
Consequently, no other regions except the pattern region 202
contains the color photoresist layer 102.
[0021] FIGS. 3A through 3D are schematic cross-sectional views
showing the steps for removing residual color photoresist from a
substrate according to a second preferred embodiment of this
invention.
[0022] First, as shown in FIG. 3A, a substrate 100 is provided. The
substrate 100 already has CMOS transistors (not shown) formed
thereon in previous processing steps. A color photoresist layer 102
is formed over the substrate 100 in a manner similar to the process
described in the first embodiment.
[0023] Using conventional photolithographic techniques, the
photoresist layer 102 is first exposed to light followed by
chemical development of the exposed photoresist so that a pattern
is formed in the pattern region 202. Due to diffused light during
photolithographic operation or improper baking temperature or
duration, some residual photoresist material 110 is formed on top
of supposedly blank region 200 after chemical development of the
photoresist layer. The residual photoresist 110 on the substrate
100 is composed of high-molecular weight polymer. In general,
high-molecular weight polymer is normally non-polar having alkyl
radicals close to the surface. Hence, the residual photoresist 110
can be represented by a bulk material with many methyl functional
groups (--CH.sub.3) attached to the surface.
[0024] As shown in FIG. 3B, the residual photoresist material 110
is polarized by aiming oxygen plasma at the substrate 100 for a few
seconds. In the presence of oxygen plasma, the --CH.sub.3 bonds
near the surface of the residual photoresist material 110 are
transformed into C--OH bonds. Hence, the surface of the residual
photoresist material 110 is converted into a polar material 110a.
In other words, the hydrophobic residual photoresist material 110
is transformed into a hydrophilic substance 110a. Furthermore,
since oxygen plasma is applied to the substrate 100 only for a very
short period, the bulk of the color photoresist layer 102 is
unaffected.
[0025] As shown in FIG. 3C, the polarized residual photoresist
material 110a is removed by washing the substrate 100 with
de-ionized water. Since de-ionized water is slightly polar, the
polarized photoresist material 110a is able to dissolve and then be
washed away by the water.
[0026] As shown in FIG. 3D, residual photoresist 110 is completely
removed from the blank region 200 through reaction with the
activated interface agent and pressure of the water jet.
Consequently, only the pattern region 202 contains the color
photoresist layer 102.
[0027] In summary, this invention provides an effective method of
removing residual photoresist material on the blank region of a
substrate without damaging the color photoresist layer.
[0028] 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.
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