U.S. patent application number 09/792570 was filed with the patent office on 2001-06-28 for method for removing photoresist layer.
Invention is credited to Chen, Tong-Yu, Huang, Michael W.C., Yang, Chan-Lon.
Application Number | 20010005638 09/792570 |
Document ID | / |
Family ID | 22792200 |
Filed Date | 2001-06-28 |
United States Patent
Application |
20010005638 |
Kind Code |
A1 |
Yang, Chan-Lon ; et
al. |
June 28, 2001 |
Method for removing photoresist layer
Abstract
A method described for removing a photoresist/polymers layer on
a substrate. The method comprises the steps of providing a wafer
having an oxide layer, a photoresist/polymers layer, an opening
penetrating through the photoresist/polymers layer and the oxide
layer, and the sidewall polymer on the surface of photoresist layer
and the oxide layer. An in-situ plasma-etching step using an
additional gas mixed with oxygen as source is performed to remove
the photoresist/polymers layer without residues, no damages to
substrate and oxide and no changes on the critical dimension of the
opening during etching step.
Inventors: |
Yang, Chan-Lon; (Taipei,
TW) ; Chen, Tong-Yu; (Hsinchu, TW) ; Huang,
Michael W.C.; (Taipei Hsien, TW) |
Correspondence
Address: |
J.C. Patents
Suite 114
1340 Reynolds, Ave.
Irvine
CA
92614
US
|
Family ID: |
22792200 |
Appl. No.: |
09/792570 |
Filed: |
February 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09792570 |
Feb 23, 2001 |
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09212727 |
Dec 15, 1998 |
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6218084 |
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Current U.S.
Class: |
438/710 ;
257/E21.252; 257/E21.256; 438/712 |
Current CPC
Class: |
H01L 21/31116 20130101;
H01L 21/31138 20130101; G03F 7/427 20130101 |
Class at
Publication: |
438/710 ;
438/712 |
International
Class: |
H01L 021/302 |
Claims
What is claimed is:
1. A method for removing photoresist on a wafer having an oxide
layer, a photoresist/polymers layer, an opening penetrating through
the photoresist/polymers layer and the oxide layer, the method
comprising the steps of: performing an in-situ plasma etching step
using an additional gas mixed with oxygen as a source to remove the
photoresist/polymers layer.
2. The method of claim 1, wherein the additional gas is selected
from the group consisting of N.sub.2, hydrogen( H.sub.2)-containing
gas and the combination thereof.
3. The method of claim 2, wherein when the additional gas is
N.sub.2, the ratio of N.sub.2 to the O.sub.2/N.sub.2 mixing gas is
about 1%-50%.
4. The method of claim 2, wherein when the additional gas is the
hydrogen-containing gas, the ratio of hydrogen-containing gas to
the O.sub.2/hydrogen-containing mixing gas is about 1%-30%.
5. The method of claim 4, wherein the hydrogen-containing gas is
selected from a group consisting of CH.sub.2F.sub.2, CH.sub.3F,
C.sub.2H.sub.2F.sub.4, C.sub.3H.sub.2F.sub.6 and the combinations
thereof.
6. The method of claim 2, wherein when the additional gas is the
combination of N.sub.2 and hydrogen-containing gas, the ratios of
hydrogen containing gases and N.sub.2to the
O.sub.2/N.sub.2/hydrogen-cont- aining mixing gas are respectively
about 1%-30% and 1%-50%.
7. The method of claim 6, wherein the hydrogen-containing gas is
selected from a group consisting of CH.sub.2F.sub.2, CH.sub.3F,
C.sub.2H.sub.2F.sub.4, C.sub.3H.sub.2F.sub.6 and the combinations
thereof.
8. The method of claim 1, wherein the step of removing the
photoresist/polymers layer is performed under the conditions of: a
flux of about 100-3000 sccm for the mixing gas; a pressure of about
20 millitorr to 1 torr for the mixing gas; a power of about 1000 to
3000 W for the in-situ plasma etching step; a bias power on a wafer
of about 0 to 300 W for the in-situ plasma etching step; a wafer
temperature of about -20 to 400 centigrade for removing the
photoresist/polymers layer; and a pressure of about 1 to 100 torr
for the helium background gas.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method for removing a
photoresist layer and polymers layer in the fabrication of a
semiconductor device. More particularly, the present invention
relates to a high-density plasma method using mixing gases as
source for removing a photoresist layer and polymers layer
generated during plasma etching process.
[0003] 2. Description of the Related Art
[0004] In the fabrication procedure of a metal oxide semiconductor
(MOS), photoresist layers are widely used in patterning processes.
However, after an etching step is performed, the photoresist layer
and the sidewall polymers generated during plasma etching step
needs to be removed for subsequent processes. When the
photoresist/polymers layer is not removed completely, the residue
affects subsequent processes and debases the quality of the device.
Accordingly, it is important to avoid leaving any
photoresist/polymers layer residue when the photoresist/polymers
layer is removed.
[0005] In the conventional photolithography method, integrated
circuit patterns transferred on wafers comprises steps of coating a
photoresist layer over the wafer. The photoresist layer is
sensitive to light and resistant to etching. The image of the
master mask is replicated on the photoresist layer by an exposure
system to form a patterned photoresist layer. An etching step is
performed to form the predetermined pattern on the wafer by using
the patterned photoresist layer as an etching mask layer. At
present, high-density plasma (HDP) is usually used to perform an
anisotropic etching step, and during the etching step, heavy
sidewall polymers are deposited to meet etching requirements (e.g.
etching selectivity to substrate and profile control etc.).
Following the oxide plasma etching, the patterned photoresist layer
and sidewall polymer layers are stripped away in-situ. However,
during high-density plasma etching, some undesirable residues are
generated and accumulated on the surface of the photoresist layer
and/or the sidewall of the opening formed by etching. The residues
cannot be removed easily by oxygen plasma and leave on the wafer to
affect the subsequent processes. The main residues include the
following:
[0006] 1. Cross-linking polymer generated by ultraviolet
irradiation is generated on the top surface of the photoresist
layer;
[0007] 2. Silicon-containing polymer is generated while performing
the etching step; and
[0008] 3. The polymers on the sidewall of the opening are generated
during etching from the gasses such as C.sub.4H.sub.8,
CH.sub.2F.sub.2, and C.sub.3H.sub.2F.sub.6.
[0009] The residues often cannot be cleaned by solvents and result
in contamination and defects in the following subsequent process.
Recently, in order to avoid photoresist residues as mentioned above
left on the wafer, a bias is applied to the wafer to enhance the
ion bombardment when the oxygen (O.sub.2) plasma is performed to
remove the photoresist layer.
[0010] FIG. 1A is schematic, cross-sectional view of the
conventional HDP oxide etcher for removing a photoresist/polymers
layer by plasma. FIGS. 1B through 1C are schematic, cross-sectional
views of the conventional plasma method for removing a photoresist
layer.
[0011] As shown in FIG. 1A, a bias is applied on a wafer 114 to
enhance the ion bombardment of plasma for removing a photoresist
layer 104 (as shown in FIG. 1B).
[0012] As shown in FIG. 1B, after an opening 108 is formed, an
in-situ oxygen plasma etching step is used to remove the
photoresist/polymers layer 104. As the residual polymers 106 are
generated on the top surface of the photoresist layer 104, it is
difficult to strip away the photoresist layer 104 completely.
[0013] As shown in FIG. 1C, since the ion bombardment of the oxygen
plasma is enhanced, the substrate 100 and an oxide layer 102
underneath the photoresist layer 104 are attacked by the plasma.
Accordingly, it is desirable to develop a new method to solve the
problems such as the loss of substrate and oxide and an inability
to control the critical dimension of the opening during in-situ
oxygen plasma etching step.
SUMMARY OF THE INVENTION
[0014] It is therefore an objective of the present invention to
provide a method for removing a photoresist layer and polymers on
the wafer surface without any photoresist residues left.
[0015] It is an another objective of the present invention to
provide a method for removing a photoresist layer as well as
controlling the critical dimension of the openings formed during
etching.
[0016] To achieve these and other advantages and in accordance with
the purpose of the present invention, as embodied and broadly
described herein, this invention provides a method for removing
photoresist/polymers layer without any residues by using an
additional gas mixed with oxygen as a source for in-situ plasma
etching. The present method comprises the steps of providing a
wafer having an oxide layer, a photoresist layer, an opening
penetrating through the photoresist layer and the oxide layer. An
in-situ plasma-etching step is performed by using a mixing gases
containing oxygen as a source of plasma to remove the photoresist
layer.
[0017] In a preferred embodiment of the present invention, the
gases for mixing with oxygen as a source for plasma etching is
selected from the group consisting of nitrogen, hydrogen-containing
gas, the combinations thereof and the likes.
[0018] 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
[0019] 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,
[0020] FIG. 1A is a schematic, cross-sectional view of a
conventional HDP oxide etcher for removing a photoresist layer by
plasma;
[0021] FIGS. 1B through 1C are schematic, cross-sectional views of
the conventional plasma method for removing a photoresist layer;
and
[0022] FIGS. 2A through 2B are schematic, cross-sectional views of
the plasma method using a mixed gas as source for removing the
photoresist/polymers layer in a preferred embodiment according to
the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] 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.
[0024] As shown in FIG. 2A, after the opening 208 is formed, an
in-situ plasma etching step using an additional gas mixed with
oxygen (O.sub.2/additional gas) are performed to strip away the
photoresist/polymers layer 204. Although the polymer 206 is formed
on the top surface of the photoresist/polymers layer 204 and the
sidewall of the opening 208, the plasma using the
O.sub.2/additional gas as source can efficiently strip away the
photoresist/polymers layer 204. The examples of O.sub.2/additional
gas include O.sub.2/N.sub.2, O.sub.2/hydrogen-containing gases or
O.sub.2/N.sub.2/hydrogen-containing gases. The preferred volume
ratio of gas N.sub.2 to O.sub.2/N.sub.2 is about 1%-50%. The
preferred volume ratio of hydrogen-containing gases to
O.sub.2/hydrogen-containing gases is about 1%-30%. The preferred
volume ratio of hydrogen-containing gases to
O.sub.2/N.sub.2/hydrogen-containing gases and that of N.sub.2 gas
to O.sub.2/N.sub.2/ hydrogen-containing gases are respectively
about 1%-30% and 1%-50%. The hydrogen-containing gas can be
CH.sub.2F.sub.2, CH.sub.3F, C.sub.2H.sub.2F.sub.4 and
C.sub.3H.sub.2F.sub.6, for example.
[0025] The condition for practicing the method in accordance with
the present invention can be varied to optimize for operation. In
the preferred embodiment, the conditions for stripping away the
photoresist/polymers layer 204 are such as a mixing gas flux of
about 100 to 3000 standard cubic centimeter per minute (sccm), a
mixing gas pressure of about 20 millitorr to 1 torr, an electrical
power for generating plasma of about 1000 to 3000 W, a bias power
on a wafer (not shown) of about 0 to 300 W, the wafer temperature
of about -20.degree.C. to 400.degree.C. and a pressure of helium
used as a background gas of about 1 to 100 torr.
[0026] As shown in FIG. 2B, the plasma using mixed gas as source
has a high ability to remove the photoresist/polymers layer 204,
and the bias power applied on the wafer can be reduced, and even
eliminated. Accordingly, the bombardment of the plasma to the
photoresist/polymers layer 204 is moderate, and the substrate 200
and oxide layer 202, which are in the opening 208, do not suffer
plasma damage. Therefore, the problems encountered in the
conventional method, such as loss of the substrate 200 and oxide
layer 202 and loss of control over the critical dimension of the
opening 208 can be overcome.
[0027] Altogether, the advantages and benefit achieved by the
present invention include the following:
[0028] 1. The present invention provides a method for stripping
away the photoresist/polymers layer without residues, and the bias
power applied on the wafer can be reduced or even eliminated. The
problems such as loss of the substrate and oxide layer and loss of
control over the critical dimension of the opening can be
overcome.
[0029] 2. The method of the present invention can be practiced on
the conventional devices, thus the present invention is ready to be
implemented on current plant lines.
[0030] 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.
* * * * *