U.S. patent application number 11/133617 was filed with the patent office on 2005-11-24 for methods of patterning photoresist.
Invention is credited to Lee, Il Ho.
Application Number | 20050260527 11/133617 |
Document ID | / |
Family ID | 35375560 |
Filed Date | 2005-11-24 |
United States Patent
Application |
20050260527 |
Kind Code |
A1 |
Lee, Il Ho |
November 24, 2005 |
Methods of patterning photoresist
Abstract
Methods of patterning photoresist are disclosed. One example
method includes forming photoresist on a substrate having a lower
layer; performing a first exposure process to the photoresist in
state of positioning a mask on the photoresist; performing a first
development process to the photoresist; performing a second
entire-surface exposure process to the photoresist; and performing
a second development process to the photoresist.
Inventors: |
Lee, Il Ho; (Seoul,
KR) |
Correspondence
Address: |
HANLEY, FLIGHT & ZIMMERMAN, LLC
20 N. WACKER DRIVE
SUITE 4220
CHICAGO
IL
60606
US
|
Family ID: |
35375560 |
Appl. No.: |
11/133617 |
Filed: |
May 20, 2005 |
Current U.S.
Class: |
430/311 |
Current CPC
Class: |
G03F 7/2024 20130101;
G03F 7/40 20130101 |
Class at
Publication: |
430/311 |
International
Class: |
G03C 001/492 |
Foreign Application Data
Date |
Code |
Application Number |
May 20, 2004 |
KR |
P2004-0035850 |
Claims
What is claimed is:
1. A method of patterning a photoresist pattern comprising: forming
a photoresist on a substrate having a lower layer; performing a
first exposure process to the photoresist in state of positioning a
mask on the photoresist; performing a first development process to
the photoresist; performing a second entire-surface exposure
process to the photoresist; and performing a second development
process to the photoresist.
2. The method of claim 1, further comprising, performing an oxygen
plasma treatment to the lower layer, before forming the
photoresist.
3. The method of claim 1, further comprising, performing a
soft-baking process to the photoresist, to remove a solvent from
the photoresist, before performing the first exposure process.
4. The method of claim 1, wherein the soft-baking process is
performed at a temperature level not to pyrolyze components of the
photoresist.
5. The method of claim 1, further comprising, baking the exposed
photoresist, before performing the first development process.
6. The method of claim 1, wherein the lower layer is formed of a
silicon nitride layer or a silicon oxide layer.
7. The method of claim 1, wherein an exposure-energy level of the
exposure process is appropriate for decreasing a thickness of the
photoresist at 5% to 20%.
8. The method of claim 1, wherein the first and second exposure
processes use the same light source.
9. The method of claim 1, wherein the first and second exposure
processes use the light source of g-line of 436 nm, i-line of 365
nm, h-line of 405 nm, and a broad band of 240 nm to 440 nm, emitted
from a mercury or xenon Xe lamp.
10. The method of claim 1, wherein the first and second exposure
processes use the light source of KrF laser having a wavelength of
248 nm corresponding to a DUV (Deep Ultraviolet) region and ArF
laser having a wavelength of 193 nm.
11. The method of claim 1, wherein the second exposure process is
performed with the same mask used during the first exposure
process.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to semiconductor device
fabrication, and more particularly, to methods of patterning
photoresist.
BACKGROUND
[0002] With the recent development in information media such as
computers, technology for manufacturing semiconductor devices has
also developed rapidly. Accordingly, the semiconductor device has
been researched and studied to obtain a high integration, a minute
pattern, and a rapid operation speed. Thus, it is necessary to
develop a minute pattern technology, such as a lithography process,
for improving the integration of semiconductor device.
[0003] Lithography is a main technology for realizing minute
patterns and high integration. Using photolithography technology a
pattern of a mask is printed onto a substrate. Generally, the
photolithography process is performed using consecutive steps of
coating a photoresist, soft-baking the photoresist, and developing
the photoresist.
[0004] The photoresist having the etching-resistant characteristics
reacts to light when etching a lower layer, wherein the photoresist
can be classified into a positive photoresist and a negative
photoresist. In case of the positive photoresist, decomposition and
chain scission generate on portions exposed to the light, whereby
the solubility largely increases. Thus, the exposed portions of the
positive photoresist are removed during the development process.
That is, the positive photoresist has the etching-resistant
characteristics and high solubility, so that the positive
photoresist is generally used for the process of fabricating the
high-integration semiconductor device. In the meantime, in case of
the negative photoresist, bridge-construction generated on exposed
portions of the negative photoresist, whereby the molecular weight
largely increases. Thus, the exposed portions remain on the
development process.
[0005] Through the development process, the photoresist changed by
exposure is selectively removed, and a pattern of mask is printed
onto a substrate. In this case, a wet etching is generally used,
wherein the wet etching uses an alkali water solution as a
developer, the chief ingredients of which are TetraMethyl Ammonium
Hydroxide (hereinafter, referred to as TMAH).
[0006] To obtain the desired pattern, the development process is
performed using, for example, a puddle method, a spray method, or a
dipping method. In the puddle method, the developer is coated on
the substrate, and then the photoresist is developed in a
stationary state. In case of the spray method, the developer is
continuously sprayed onto the substrate, so that it is helpful to
the consecutive process. However, the spray method is
disadvantageous in that it uses the large amount of developer.
Also, in case of the dipping method, it is impossible to apply the
consecutive process. In addition, the dipping method uses the large
amount of developer. Thus, the dipping method is usually used for
testing performed during the process of research and
development.
[0007] After completing the development process, the photoresist
thinly remains between the patterns, thereby generating scum. Also,
on the development process, because residue of photoresist remains,
it also may cause the defects. Due to the scum and residue of
photoresist, when etching a lower layer, the lower layer may be
disturbed. Thus, a bridge is formed between lines, thereby
generating a short circuit defect on the device.
[0008] FIG. 1 is a cross sectional view of a portion of a
semiconductor device showing scum and residue after developing a
photoresist. Referring to FIG. 1, a photoresist 12 is coated on a
semiconductor substrate 10 having a lower layer 11, and then the
photoresist 12 is developed after alignment and exposure process,
thereby forming a photoresist pattern. If there are scum 12a and
residue 12b, formed by the remaining photoresist 12, when etching
the lower layer 11 by using the patterned photoresist 12 as a mask,
the lower layer 11 corresponding to the scum 12a and the residue
12b is not etched, thereby generating the defect on a semiconductor
device.
[0009] A pad open pattern process for etching a metal pad for
bonding with an external circuit to be exposed, uses a relatively
thick layer of photoresist and low exposure energy. Accordingly,
defects such as scum are generated due to nonuniformity in
thickness and exposure energy of the photoresist.
[0010] If the lower layer 11 is formed of a silicon oxide layer
SiO.sub.x or a silicon nitride layer SiN.sub.x, the photoresist 12
is coated on the semiconductor substrate 10, and then a baking
process is performed to the photoresist 12. Thus, PAG (Photo Acid
Generator), one component of the photoresist 12, reacts on the
silicon oxide layer SiO.sub.x or the silicon nitride layer
SiN.sub.x, so that a new material is produced. In this case,
because the reactivity between the new material and the developer
is low, the new material is not removed during the development
process. That is, the new material remains as the scum. Also, the
pad open pattern process may have more defects of scum because the
lower layer is generally formed of a silicon nitride layer.
[0011] A lithography process including the photoresist pattern
process according to the related art is described below with
respect to FIG. 2, which is a flowchart of a photolithography
process according to the related art.
[0012] First, a surface treatment is performed to a substrate, so
that it is possible to enhance an adhesive strength to a
photoresist. Then, the photoresist is coated on the substrate
(S100). At this time, in order to enhance the adhesive strength to
the photoresist, the substrate is treated with a material for
improving the resistance to moisture by making the surface of
substrate hydrophobic. The material may be, for example, HMDS (Hexa
Methyldisilazane) and a nitrogen gas that are together introduced
to a tank and vapor-coated on the substrate.
[0013] Next, after performing a soft-baking process, a mask is
aligned above the substrate, and then an exposure process is
performed thereto (S101). In this case, the soft-baking process is
performed to remove a solution from the photoresist, wherein it is
necessary to preset a temperature condition that does not pyrolyze
the components of photoresist.
[0014] After that, a Post-Exposure Baking (PEB) process is
performed to cure the photoresist, and then a development process
is performed thereto (S102). At this time, when light interference
generates at a corner of a light-shielding part in the mask, it is
impossible to precisely define a desired pattern onto the
substrate, thereby generating a standing wave. In order to solve
this problem, the PEB process is performed to improve uniformity on
width of line in the substrate.
[0015] Then, after obtaining the desired pattern by etching a lower
layer (S103), the photoresist is removed (S104). However, the
related art photoresist pattern process has the following
disadvantages.
[0016] In case of patterning the photoresist by exposure and
development, the defects such as scum and residue may generate. The
scum and residue disturb the etching of lower layer, whereby the
bridge generates between the lines, thereby causing the short
defect on the device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a cross sectional view of a portion of a
semiconductor device showing scum and residue of photoresist after
performing a development process to the photoresist.
[0018] FIG. 2 is a flowchart of a photolithography process
according to the related art.
[0019] FIG. 3 is a flowchart of one example disclosed
photolithography process.
[0020] FIG. 4 is a graph showing a relation between a thickness of
photoresist and threshold energy.
[0021] FIG. 5 is a graph of showing a relation between exposure
energy and a thickness of photoresist after performing a
development process to the photoresist.
DETAILED DESCRIPTION
[0022] Hereinafter, methods for patterning a photoresist are
described with reference to the accompanying drawings. The
disclosed methods for patterning photoresist improve the precision
of pattern formation and prevent defects such as scum
[0023] FIG. 3 is a flowchart of an example disclosed
photolithography process. According to one example of the disclosed
process, a lower layer is first formed on a substrate, and then a
surface treatment is performed to the lower layer of the substrate,
to enhance an adhesive strength when forming a photoresist on the
lower layer. Then, the photoresist is coated on the lower layer of
the substrate (S200). At this time, a material for the lower layer
is not limited. Also, according to one example, before coating the
photoresist an oxygen plasma treatment is performed to the lower
layer to improve the surface quality of the lower layer, so that it
is possible to prevent defects such as scum. Especially, in case
the lower layer is formed of a silicon oxide layer or a silicon
nitride layer the surface quality of the lower layer is improved by
the oxygen plasma treatment. During a pad open process of
generating the defects such as scum, the silicon nitride layer
generally remains on a metal layer for formation of pad. In this
case, it is possible to remove the cause of generating the scum by
performing the oxygen plasma treatment.
[0024] The oxygen plasma treatment changes the surface
characteristics of the lower layer, whereby a Si--N bonding
structure is changed to a Si--O bonding structure in the surface of
the lower layer. Accordingly, the surface of the lower layer has
the hydrophile property, so that it is possible to prevent the
reaction between the photoresist and the lower layer, thereby
preventing the defects such as scum.
[0025] Next, an exposure process is performed after aligning a mask
on the substrate (S201). Before aligning the mask and performing
the exposure process, it is necessary to perform a soft-baking
process. The soft-baking process is performed to remove a solvent
from the photoresist. Also, the soft-baking process is set to an
appropriate temperature level not to pyrolyze the photoresist.
According to one example, after the soft-baking process, various
steps are performed as follows: reading a position of alignment
mark remaining on the substrate with an alignment sensor; measuring
a position error by comparing the position of alignment mark
remaining on the substrate with other alignment mark previously set
in a job file; calculating translation, rotation and expansion data
of the substrate with the position error; measuring an exposure
position with the calculated data; and exposing the substrate.
[0026] The mask may be used as a general mask formed by
sequentially depositing chrome and oxide chrome on a quartz
substrate. In addition, the mask may be formed of a reflective mask
or a phase shift mask. Also, an eximer laser light source may be
used. For example, a KrF laser having a wavelength of 248
nanometers (nm) corresponding to a DUV (Deep Ultraviolet) region
and ArF laser having a wavelength of 193 nm, as well as g-line of
436 nm, i-line of 365 nm, h-line of 405 nm and a broad band of 240
nm to 440 nm, emitted from a mercury or xenon (Xe) lamp may be
used.
[0027] Next, a first development process is performed to the
photoresist (S202). Before performing the first development
process, according to an example, a PEB process is performed to
improve uniformity in line width of the substrate. Also, a wet
etching process of using an alkali water solution as a developer
may be used. In one example, the chief ingredients of the wet etch
process are TetraMethyl Ammonium Hydroxide (hereinafter, referred
to as TMAH). In this case, it is possible to remove the
considerable amount of scum and residue of the photoresist by
performing an oxygen plasma treatment to the lower layer. However,
after the completing the first development process, the scum and
residue of photoresist may remain. Thus, a second development
process is performed as follows, to completely remove the defects
such as scum and residue.
[0028] After that, an entire-surface exposure process is performed
(S203). When performing the entire-surface exposure process, it
uses the same light source as that of the aforementioned exposure
process (S201). Also, the step of aligning the mask on the
substrate is not required in case of using low exposure energy
suitable for selectively removing the scum and residue of
photoresist without any influence to the photoresist pattern. That
is, the exposure energy is set to an appropriate level not to
perform the exposure process including the substrate alignment
process.
[0029] As shown in FIG. 4, the exposure energy is controlled to an
appropriate level not to perform the exposure process for removing
the photoresist on the development process.
[0030] Referring to FIG. 4, there is a threshold energy value,
which is a minimum value for removing the photoresist on the
development process. Generally, there is the exposure energy, which
can selectively remove the scum and residue of photoresist without
any influence to the photoresist pattern since it has a higher
value as the photoresist becomes thicker, and it has a lower value
as the photoresist becomes thinner. Accordingly, as shown in FIG.
5, if the exposure energy is applied to the entire surface of the
substrate at a level for developing the thickness of photoresist
between 5% and 20%, advantageously, approx. 10%, it is possible to
selectively remove the scum and residue of photoresist.
[0031] Accordingly, as the entire-surface exposure process is
performed, it is possible to improve the precision in forming the
pattern, and to prevent the scum and residue of photoresist,
without the increase of the fabrication cost and time.
[0032] However, if the exposure process doesn't cause a bottle neck
in the entire fabrication process, it is possible to obtain the
more precise pattern by aligning the mask for patterning the
photoresist and performing the exposure process.
[0033] To remove the scum and residue of photoresist by performing
the entire-surface exposure process, a positive photoresist may be
used in which a portion exposed to the light is removed. For
example, the positive photoresist may be formed of a novolak type
composition, a chemical amplification composition, or a chain
scission composition.
[0034] Next, the scum and residue of photoresist are removed by
performing a second development process (S204). In one example, the
second development process uses the same developer as that in the
first development process.
[0035] Then, after etching the lower layer (S205), the photoresist
is removed (S206). In case of the pad open process, a metal pad for
bonding with an external circuit is exposed by etching the lower
layer.
[0036] The example disclosed methods for patterning the photoresist
by photolithography makes it possible to improve the precision in
forming the pattern, and to prevent the scum and residue of
photoresist, with the small fabrication cost and time.
[0037] The foregoing discloses example methods of patterning a
photoresist that substantially obviate one or more problems due to
limitations and disadvantages of the related art. In particular,
the disclosed example methods improve precision in pattern and
prevent defects such as scum, by additionally performing an
entire-surface exposure process and a development process after
firstly performing an exposure and development process to a
photoresist coated on a substrate.
[0038] As disclosed above, according to one example, a method for
patterning a photoresist pattern includes forming a photoresist on
a substrate having a lower layer; performing a first exposure
process to the photoresist in state of positioning a mask on the
photoresist; performing a first development process to the
photoresist; performing a second entire-surface exposure process to
the photoresist; and performing a second development process to the
photoresist.
[0039] This patent application makes reference to, incorporates the
same herein, and claims all benefits accruing under 35 U.S.C.
.sctn.119 from an application for METHOD FOR PATTERNING PHOTORESIST
filed in the Korean Industrial Property Office on May 20, 2004, and
there duly assigned Serial No. P2004-35850.
[0040] Although certain apparatus constructed in accordance with
the teachings of the invention have been described herein, the
scope of coverage of this patent is not limited thereto. On the
contrary, this patent covers every apparatus, method and article of
manufacture fairly falling within the scope of the appended claims
either literally or under the doctrine of equivalents.
* * * * *