Radiation imagery chemistry: process – composition – or product th – Stripping process or element – Forming nonplanar image
Reexamination Certificate
2000-05-31
2004-11-09
Thornton, Yvette C. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Stripping process or element
Forming nonplanar image
C430S259000, C430S261000, C430S271100, C430S273100, C430S320000, C430S322000, C430S328000, C430S329000, C430S350000
Reexamination Certificate
active
06815142
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for forming a resist pattern, an overlying layer material and a semiconductor device used in a method for forming a resist pattern. More specifically, the present invention relates to a method for forming a resist pattern, where a process with a high level of environmental resistance has been established, and using an improved overlying layer material for obtaining a pattern having uniform and accurate dimensions, and having a high resolution; and to such an overlying layer material, and to such a semiconductor device.
2. Description of Related Art
In the excimer resist process using an excimer laser for exposure, chemical amplification type resists have been developed and manufactured as the mainstream for both positive and negative resists. These chemical amplification type resists are classified into two types: the type containing an acid forming agent, and the type containing a photo base generator. Either type of resists generates an acid or a base by exposure, and a catalyzed reaction occurs by heat treatment after exposure (post-exposure baking, PEB).
The type recently being developed is the type containing an acid forming agent. Generally in this type containing an acid forming agent, a positive resist comprises a base resin in which the polar group of an alkali-soluble resin is protected by a dissolution inhibiting group, and an acid forming agent; and a negative resist comprises a base resin, a cross-linking agent, and an acid forming agent. This resist containing an acid forming agent undergoes a reaction catalyzed by the acid formed by exposure. In case of the positive resist, the polymer protective group of the base resin is decomposed to be alkali-soluble for the developing solution, and in case of the negative resist, the cross-linking agent reacts with the polymer to increase the molecular weight, becoming insoluble in the developing solution. As a result, a resist pattern is formed. As described above, since the reaction is catalyzed by an acid, the reaction efficiency becomes high, and high sensitivity can be achieved. On the other hand, because of the high environment dependency of the clean room, if the time between exposure and PEB is long, the acid is deactivated by the effect of basic components of the air in the clean room, such as ammonia, raising a problem of the formation of less soluble surface layer in the positive resist. In order to solve this problem, the development of resist materials little affected by basic components of the air has been studied by making applying, exposing, and developing processes in-line.
Concurrent with the above-described development, the process in which an acidic overlying layer material is applied has also been studied for preventing the diffusion of basic components in the resist. The purpose of applying the overlying layer material also includes the improvement of dimensional accuracy. Since the multiple reflection of light beams occurs in the resist film, the dimension of the resist is varied if the thickness of the resist film is uneven. If the underlying layer has steps, the thickness of the resist film is varied, resulting in a significant change in the dimension of the resist pattern. Therefore, the development of the overlying layer material that can inhibit the multiple interference of light beams in the resist film has become essential.
FIGS. 4A through 4E
show the process flow of resist pattern formation using a conventional overlying layer material. In
FIGS. 4A through 4E
, the numeral
10
is a substrate,
12
is a resist applied on the substrate
10
,
40
is light beams for exposure,
12
a
is an exposed part exposed by light beams
40
,
12
b
is an unexposed part not exposed by light beams
40
,
14
is an overlying layer material applied on the resist
12
,
20
is an acid A contained in the overlying layer material
14
,
16
is a mask, and
17
and
18
are film edges formed on the surface of the resist
12
.
Referring to
FIG. 4A
, a resist
12
is applied on a substrate
10
, and subjected to a pre-baking treatment. Next, as
FIG. 4B
shows, an overlying layer material
14
is applied on the resist
12
, and subjected to a re-baking treatment. As
FIG. 4C
shows, light beams
40
are radiated onto the resist
12
through a mask
16
, and as
FIG. 4D
shows, a heat treatment (PEB) after exposure is performed. Finally, by developing the resist
12
, resist patterns shown in the left of
FIG. 4E
are formed in case of the positive resist, and resist patterns shown in the right of
FIG. 4E
are formed in case of the negative resist.
In order to apply the above-described resist pattern forming process using the conventional overlying layer material to a presently mainstream chemical amplification type resist containing an acid forming agent, the basic components in the air must be trapped. Therefore, the overlying layer material is typically an acidic film. As a result, in case of a positive resist, acid A (
20
) in the overlying layer material
14
is diffused into the unexposed part
12
b
of the resist
12
during the PEB treatment after exposure, raising the problems of the formation of film edges
17
on the surface of the unexposed part
12
b
of the resist
12
caused by the polymer elimination reaction, and the deterioration of the resist patterns. In case of a negative resist, acid A (
20
) in the overlying layer material
14
is diffused into the unexposed part
12
b
of the resist
12
, a cross-linking reaction occurs also in the unexposed part
12
b
, and a surface layer difficult to dissolve is formed as shown by the film edges
18
, raising a problem that the desired resist pattern cannot be obtained. When this phenomenon is significant, there is a problem that the surface of the resist becomes entirely insoluble. Furthermore, in case of a negative resist, there is a problem that an acidic overlying layer material
14
containing an acid A (
20
) does not match with the resist
12
, and the pattern is degraded or is not resolved.
SUMMARY OF THE INVENTION
The object of the present invention is to solve the above problems, and to provide a method for forming resist patterns, an overlying layer material and a semiconductor device used in the method for forming resist patterns, which can inhibit the multiple interference of light beams within a resist film and the uniformity of the dimensions of the resist patterns can be improved, even if the underlying layer has steps and the thickness of the resist film is varied.
Another object of the present invention is to provide a method for forming resist patterns, an overlying layer material and a semiconductor device used in the method for forming resist patterns, which can avoid the effect of basic components such as ammonia in the air in a clean room or the like in applying, exposing, and developing processes, and can inhibit the diffusion of basic components into the resist and improve the environmental resistance of the resist.
A further object of the present invention is to provide a method for forming resist patterns, an overlying layer material and a semiconductor device used in the method for forming resist patterns, which can prevent the diffusion of acids in the overlying layer material into the resist and can obtain resist patterns having rectangular sectional shapes.
According to a first aspect of the present invention, there is provided a method for forming a resist pattern, comprising the steps of: pre-baking a semiconductor substrate on the surface of which a resist has been applied; re-baking the semiconductor substrate, forming a film on the resist using an overlying layer material containing a water-soluble acid substance and a water-soluble photo base generator; post-baking the semiconductor substrate after exposing the overlying layer material to light beams; and forming a resist pattern, developing the resist using a predetermined developing solution and peeling off the overlying layer material together with the developing solut
Ishibashi Takeo
Kimura Yoshika
McDermott Will & Emery LLP
Renesas Technology Corp.
Thornton Yvette C.
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