Pattern formation method and surface treating agent

Details Pattern formation method and surface treating agent Pattern formation method and surface treating agent

1996-08-01

2001-07-10

Shaver, Paul F. (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Silicon containing

C556S413000, C556S442000, C106S287130, C106S287140, C106S287150, C106S013000, C427S515000, C427S058000, C427S384000, C427S387000

Reexamination Certificate

active

06258972

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a pattern formation method whereby a resist pattern is formed on a semiconductor substrate in the process of manufacturing semiconductor devices and to a surface treating agent for use in the process of forming the resist pattern.
As higher-density and higher-integration semiconductor devices have been implemented in recent years, there has been increasing demand for micro-fabrication technology.
As a first method of enabling micro-fabrication in a lithographic process, there has been developed a technique for forming a resist pattern from a chemically amplified resist which utilizes the generation of an acid in response to exposing radiation such as a DUV ray from the light source of an excimer laser or a ray of a shorter wavelength such as an electron beam or an x-ray.
Referring now to
FIGS. 12 and 13
, a pattern formation method using a chemically amplified resist will be described as a first conventional embodiment.
FIG. 12
shows the process flow of the pattern formation method according to the first conventional embodiment.
FIG. 13
shows a surface of a semiconductor substrate formed by the pattern formation method according to the first conventional embodiment.
First, hexamethyldisilazane (hereinafter referred to as HMDS) as a surface treating agent is supplied to the surface of the semiconductor substrate
1
made of silicon to render the surface of the semiconductor substrate
1
hydrophobic and thereby improve adhesion to the semiconductor substrate
1
. The process is performed by bubbling liquid HMDS with the use of a nitrogen gas and spraying HMDS to the surface of the semiconductor substrate
1
heated to 60° C. for 30 seconds, as shown in FIG.
13
(
a
). During the process, Si(CH
3
)
3
(trimethylsilyl group) is substituted for the hydrogen atom of an OH group on the surface of the semiconductor substrate
1
as shown in FIG.
13
(
b
), so that the surface of the semiconductor substrate
1
becomes hydrophobic and adhesion to the semiconductor substrate
1
is thereby improved, while NH
3
(ammonia) is generated.
Next, a resist film is formed by coating the surface of the semiconductor substrate with a chemically amplified resist. The resist film is then exposed to light using a desired mask and sequentially subjected to post-exposure bake (hereinafter referred to as PEB) and development, resulting in a resist pattern.
As a second method of enabling micro-fabrication in a lithographic process, there has been proposed a technique for improving the adhesion of a resist pattern to a semiconductor substrate, as disclosed in Japanese Laid-Open Patent Publication SHO 58-188132.
Below, a pattern formation method using a resist containing, e.g., a phenol-based resin will be described as a second conventional embodiment.
First, a surface treating agent containing a silane compound represented by the following general formula:
R
1
SiX
3−n
R
2
n
(wherein n represents 0, 1, or 2; X represents a halogen group or —OR′ group (R′ represents an alkyl group having 1 to 3 carbons); R
1
represents a group containing CH
2
═CH—, ZCH
2
— (Z represents a halogen group), or
and R
2
represents a hydrogen or an alkyl group having 1 to 3 carbons) is supplied to a surface of a semiconductor substrate made of silicon to render the surface of the semiconductor substrate hydrophobic and thereby improve adhesion to the semiconductor substrate.
Next, a resist containing, e.g., a phenol resin is applied to the surface of the semiconductor substrate to form a resist film, which is then exposed to light using a desired mask and sequentially subjected to PEB and development, resulting in a resist pattern.
FIGS. 14 and 15
show schematic cross-sectional configurations of a resist pattern
2
formed on the semiconductor substrate
1
made of silicon or on a semiconductor substrate
5
made of BPSG by the pattern formation method according to the first conventional embodiment. Specifically,
FIGS. 14 and 15
show the cross-sectional configurations of patterns with 0.25-&mgr;m lines and spaces obtained by coating the surface of the semiconductor substrate
1
made of silicon or the semiconductor substrate
5
made of BPSG with a positive chemically amplified resist (KRF K2G commercially available from Japan Synthetic Rubber Co., Ltd.) having a thickness of 0.7 &mgr;m, exposing the resist to light by a KrF excimer laser stepper having a numerical aperture of 0.5, performing PEB with respect to the resist at a temperature of 100° C. for 90 seconds, and developing the resist in a 2.38 wt % aqueous solution of tetramethylammonium hydroxide.
In the first conventional embodiment, an insoluble skin layer
3
is formed on the surface of the resist pattern
2
as shown in
FIG. 14
or a footing
4
is formed at the base of the resist pattern
2
as shown in FIG.
15
. The formation of the insoluble skin layer
3
on the surface of the resist pattern
2
or the formation of the footing
4
at the base of the resist pattern
2
may be attributed to different atmospheres or different states on the surface of the substrate in which the pattern is formed.
The insoluble skin layer
3
formed on the surface of the resist pattern
2
or the footing
4
formed at the base of the resist pattern
2
will adversely affect the subsequent process, resulting in a first problem of a reduction in the yield of semiconductor devices.
On the other hand, a second problem of unsatisfactory adhesion occurs in the case of performing micro-fabrication with respect to a single layer during the lithographic process, though the resist pattern formed on the semiconductor substrate by the pattern formation method according to the second conventional embodiment exhibits improved adhesion that has been previously unattainable to the semiconductor substrate since the surface of the semiconductor substrate has been treated with the above surface treating agent. As a result, peeling off may occur when a pattern with a line width of 0.30-&mgr;m or less is formed by exposure to an i line, when a pattern with a line width of 0.25-&mgr;m or less is formed by exposure to a KrF excimer laser, or when a pattern with a line width of 0.20-&mgr;m or less is formed by exposure to an ArF excimer laser.
SUMMARY OF THE INVENTION
In view of the foregoing, a first object of the present invention is to prevent the formation of an insoluble skin layer on the surface of a resist pattern. A second object of the present invention is to prevent the formation of a footing at the base of the resist pattern. A third object of the present invention is to further improve the adhesion of the resist pattern to the semiconductor substrate.
The present inventors have examined various factors which may cause the insoluble skin layer to be formed on the surface of the resist pattern and found that an alkaline component is the cause. Specifically, when an alkaline component is present on the surface of the resist pattern, an acid generated on exposure to light is deactivated, resulting in the formation of the insoluble skin layer on the surface of the resist pattern having a T-top configuration. The finding is also endorsed by a report on the case where a pattern is not formed because of an excessive amount of alkaline component (S. A. MacDonald et al., Proc. SPIE, vol. 1466, p.2, 1991).
To examine the cause of an ammonia component generated as the alkaline component adversely affecting a chemically amplified resist, impurities in the environment of a clean room were analyzed and it was found that the concentration of trimethylsilanol decomposed from HMDS in the environment is directly proportional to the concentration of ammonia in the environment. From the result of the analysis, it may be inferred that the alkaline component adversely affecting the configuration of a chemically amplified resist pattern results from HMDS used as the surface treating agent for the semiconductor substrate.
The present inventors have also examined various factors which may cause the footing to be formed at th

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