JPS6189632A - Formation of resist pattern - Google Patents

Abstract

PURPOSE:To stabilize the sensitivity of a resist film and to facilitate the selection of arbitrary conditions of sensitivity by a method wherein the resist film is heated up above a transition temperature by baking after it is exposed, and then the film is cooled down below the transition temperature at a prescribed speed prior to a developing process thereof. CONSTITUTION:Processes of application and prebaking of a resist film are the same with conventional ones, and the cooling of the resist film is conducted after prebaking. This cooling process may be conducted by natural cooling or any other method, and the thermal history thereof is ignored. Next, exposure of the resist film is conducted in the same way as in a conventional process. After the exposure, pre-development baking is applied, and this baking requires only a time taken until the resist film is heated up above a glass transition temperature Tg. After this pre-development baking is ended, cooling is conducted under a speed control. By controlling or selecting this speed of cooling, the sensitivity of the resist film can be controlled or selected. After this cooling process, processes of development, rinsing, etc. are performed in the same way as in a conventional method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a process for manufacturing a semiconductor device, and particularly to a method for forming a resist pattern.

[Technical background of the invention and its problems]

2. Description of the Related Art As the degree of integration of semiconductor devices such as VLSIs increases, there is a need for fine pattern forming techniques with high precision. For this reason, the permissible dimensional accuracy is extremely strict, and in the cutting-edge field, a dimensional accuracy of 3σ≦0.1 μm (where σ indicates the variation with respect to the average wafer dimension value) within a 6-inch mask or 5-inch wafer is required. is beginning to be demanded. In addition, in order to be used on a mass production line, dimensional variations between masks or wafers must be reduced to 3σ≦0.
．． It is necessary to suppress the thickness to 15 μm, and on the other hand, in order to increase the hanging effect, a highly sensitive resist is required, and the sensitivity of the resist film must be adjusted so that the sensitivity is compatible with the 6A exposure setting (energy irradiation device) used. Control is needed.

By the way, conventionally, when forming a resist pattern,
A method as shown in flow p-1- of FIG. 5 is adopted. First, rinses 1 to 1 are applied onto a plate to be processed (for example, a mask substrate) by a spin coating method or a dipping method (step 100). Next, the resist IlQ on the substrate is heated to a predetermined temperature (temperature b) using a heating means such as an oven or a hot plate to perform prebeta (step 101). Then, after prebaking for a predetermined period of time, a resist film was applied. ! The Ha plate is naturally cooled at room temperature and pressure for about 20 to 30 minutes to a temperature of V (step 102). Next, the resist film on the cooled substrate is exposed to light at a predetermined exposure amount depending on the resist (step 103), and is further subjected to predetermined development processing (step 104) and rinsing processing to form a resist pattern.

However, with the conventional method shown in Figure 5, it is difficult to obtain the desired dimensional accuracy because the high-sensitivity resist has poor resolution, and conversely, the high-resolution resist has low sensitivity, so it is difficult to obtain the desired dimensional accuracy. There was a problem in that the high throughput required for this process could not be obtained. In addition, since it is possible to adjust the sensitivity of the resist using the same rinse, it can only be used under conditions where the exposure conditions and process are restricted, and it is not possible to form a resist pattern under appropriate conditions. There wasn't. Further, there is a drawback that a difference occurs in the sensitivity of the resist film on the plate to be processed after prebaking, making it difficult to form a highly accurate resist pattern.

[Purpose of the invention]

The present invention was made in order to overcome the drawbacks of the prior art as described above, and it stabilizes the sensitivity of the resist film and makes it easy to select arbitrary sensitivity conditions, thereby reproducing highly accurate resist patterns. The present invention provides a method for forming a resist pattern that can be formed with high quality.

[Summary of the invention]

In order to achieve the above object, the present invention involves heating the resist film to above the transition temperature by baking after exposing the resist film, cooling the resist film at a predetermined rate to below the transition temperature, and then developing the resist film. The present invention provides a method for forming a resist pattern in which processing is performed.

The method of forming the rinse 1 pattern as described above according to the present invention is based on the following three findings.

The first finding is that in the conventional method shown in FIG. 5, the number of resist films coated with a resist film is naturally cooled after blubberation. Isotherms of different temperatures as shown in T2, T2. -r3
This means that (T1>T2>T3) occurs on the plate to be processed. Here, FIG. 6 shows the processing target (Jj during cooling 141
It shows the state at a certain time, and changes moment by moment as time J′1 passes. The resist on the plate to be processed with one line (such as shown in FIG. As a result of precise measurements of Rinse 1 to pattern dimensions A and B after exposure and development, it was found that there is a strong correlation between the size distribution and temperature distribution.

The second finding (well, when the above-mentioned plate to be treated is left to cool naturally, the cooling IA speed when the plate to be treated (ν) is placed vertically is the 7th
Cold moon 1 at a speed that follows the cold 141 curve as shown in r21
This means that the -1 part that is cooled and the lower part that is cooled at a rate that corresponds to the cooling U1 curve B are two-fold on the plate to be processed.

When the sensitivity of the resist film portion on the plate subjected to cold JJI was investigated using the curve Δ shown in FIG. 7, it was found that it exhibited sensitivity characteristics as shown by the curve A' shown in FIG.

Similarly, it has been found that the sensitivity of the resist film portion on the plate to be processed cooled by curve 1i1B shown in FIG. 7 exhibits a sensitivity characteristic 1 as shown by curve B' shown in FIG. As a result, there is a strong correlation between cooling rate and sensitivity characteristics.
It has been found that these are the causes of differences in pattern dimensions.

The third finding is that even if a resist film has undergone pre-baking and natural cooling in the conventional method shown in Fig. 5, it must be baked at a temperature exceeding the glass transition temperature TO of the resist film after exposure and before development. After that, the sensitivity can be changed significantly by changing the cooling rate. In addition, no matter what the thermal history of the resist film is during pre-baking, the sensitivity can be changed by baking at a temperature exceeding Tg as described above before development, and then changing the cooling acceleration. I found out that it was Setsuru.

From the above, the conventional technology shown in Figure 5 does not control the cooling rate during the cooling process, so the sensitivity fluctuates depending on the cooling conditions, which makes it difficult to form highly accurate resist patterns. It turned out to be.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail based on embodiments with reference to FIGS. 1 to 4 of the accompanying drawings. FIG. 1 is a flowchart illustrating a resist pattern forming method according to the present invention. The resist film coating and pre-baking steps are similar to the conventional steps shown in FIG. 5 (step 100).
．． 101>.

After prebaking, the resist film is cooled, and this cooling process may be performed by natural cooling or any other method, and its thermal history is not critical (step 201). Next, the resist film is exposed to light, and this step is also the fifth step.
This is the same as the conventional process shown in the figure (step 103).
□ After exposure, the first feature of the present invention, which is the pre-development buffing process, is performed (step 202). The time required for this baking is sufficient to exceed the glass transition temperature TO of the resist. For example, in the case of positive electron beam sensitive resists poly(methyl methacrylate) and poly(70 loethyl α-chloroacrylate), a baking time of 5 minutes was sufficient.

This pre-development bake is followed by rate-controlled cooling, which is the second feature of the present invention (step 203). By controlling or selecting this cooling rate, the sensitivity of the resist film can be controlled or selected. After this cooling step, development processing (step 104), rinsing processing, etc. are performed in the same manner as in the conventional method.

Next, with reference to FIGS. 2 and 3 of the accompanying drawings, an example of a heating and cooling apparatus for realizing the method of the present invention shown in FIG. 1 will be described.

FIG. 2 is a schematic diagram of a heating and cooling device used in the resist pattern forming process according to an embodiment of the present invention;
The figure is an enlarged sectional view of the main part of the device shown in the second factor. A thin glass plate 2 is provided at the bottom of a chamber 1 whose walls except the bottom are made of a heat insulating material. A flat hollow body 3 through which a cooling medium (for example, water) flows is horizontally arranged on the earthen wall of the chamber 1, and both ends of this hollow body 3 are connected to the cooling fluid through cooling pipes 4a and 4b. It is connected to the reservoir 5. A pump 6 is installed in the cooling pipe 4a on the inlet side. In addition, the lower surface of the hollow body 3 has an absorption rate of ~9'0%.
A heat receiving plate 7 made of aluminum oxide is provided horizontally. Furthermore, a leak pipe 9 with a valve 81 interposed therein is connected to the left side wall of the chamber 1, and a suction pipe 10 with a valve 8□ interposed on the right side wall of the chamber 1 has a weight of 3 g!
It is withered. The other end of this suction pipe 10 is a vacuum pump 1
1. A hot plate 12 is disposed on the glass plate 2 at the bottom of the chamber 1 and is movable up and down and in close contact with the glass plate 2.

Next, a method of forming a resist pattern using the heating and cooling apparatus shown in FIGS. 2 and 3 will be specifically described.

First, the glass transition temperature (T O'
) E8 resist (polymethyl methacrylate) at 100° C. is spin-coated to form a resist film with a thickness of 0.6 μm (resist coating). After that, it was heated to 180℃ for 1 hour and 1 hour.
80? Bake in an oven at 30 degrees and cool to room temperature. Note that after the exposure process, there is a pre-development buffing process and a cooling process with temperature control.
The J1 process may be performed in any manner as described above.

After that, a predetermined pattern is exposed to electron beam.

Next, the blank mask 13 is housed in a cassette 14 made of the same material as that of the blank mask 13 as shown in FIG. 2 and FIG. Sect horizontally so that Next, the valve 81 is closed, the valve 82 is opened, and the vacuum pump 11 is activated to exhaust the gas in the chamber 1 to create a vacuum!
5 to about 10-'torr, then pot plate 1
The resist film on the blank mask 13 is baked at 180° C. for 5 minutes by heating the heater No. 2 (pre-phenomenon baking).

Immediately after the pre-phenomenal baking is completed, hot plates 1 and 12 are moved downward and separated from glass plate 2! After ζ, the pump 6 is operated to circulate the water in the cooling fluid reservoir 5 through the cooling pipe 4a, the hollow body 3, and the cooling pipe 4b, thereby sufficiently cooling the heat receiving plate 7 on the lower surface of the hollow body 3. At this time, the rinses 1 to B9 on the blank mask 13 are uniformly cooled at a predetermined rate only by radiant heat transfer by the heat receiving plate 7 inside the chamber 1 (the IC is kept in a high vacuum state.Blank mask When the surface temperature of the resist film on the cassette 13 becomes lower than its TO, after turning on the valve 81 and supplying N2 gas through the leak pipe 9 for about 10 minutes, the cassette 14
At the same time, the blank mask 13 is taken out from the chamber 1.

Next, development was carried out for 13 minutes with MIBK developer (solution temperature 25°C) [30 minutes with AA rinse solution (P & temperature 25°C)].
A resist pattern is formed on the blank mask by performing a rinsing process for seconds. In the above-mentioned development process, the development conditions (developing solution CJ polishing, temperature, etc.) are selected according to the sensitivity of the resist pattern, which is controlled by the cooling rate in the cooling step after the pre-development bake.

In this way, when the above-mentioned heating and cooling device performs pre-development baking and uniform cooling on the drawing contact of the resist film, the desired high fi' Rinse 1-pattern can be formed. In addition, by controlling the cooling rate after the pre-development beta, it is possible to obtain a resist pattern with the desired sensitivity and to appropriately select the development conditions according to the sensitivity, thereby greatly shortening the development time. can.

In the above example, by using materials with different absorption rates as the heat receiving plate and uniformly cooling the resist film on the blank mask only by radiant heat transfer, the sensitivity was stabilized and the sensitivity of the resist film was increased to 8 μC/ cm~0.5
It can be varied in the range of μC/cm.

In the above embodiment, water is used as the cooling medium in the cold fJI fluid pool, but other cooling liquids, or cooled nitrogen gas, argon gas, or chlorofluorocarbon gas may be used instead.

Furthermore, the method of the present invention is not limited to the case where pre-development baking and speed-controlled uniform cooling are performed using the heating and cooling apparatus shown in FIGS. 2 and 3. For example, as shown in FIG. 4,
A flat chamber 1 with a conveyor belt 15 arranged at the bottom
The heat receiving plate 7 is arranged horizontally in the upper part of the chamber 1', and the blank mask 13 is set together with the cassette 1-14 in the chamber 1'.
The distance 11fltd between the resist film on the surface and the heat receiving plate 7 is 7 m.
A heating/cooling device having a structure that allows it to be placed in close proximity to the following may be used.

Using this J: UNA heating and cooling device, the resist film on the blank mask 13 of the cassette 14 is heated by the hot plate 12 to bake it before development, and after moving the hot plate 12 downward, water is made to flow inside the hollow body 3. When the heat receiving plate 7 is cooled, the prebaked blank mask 13 is
Since the upper resist film is placed extremely close to the heat receiving layer (less than 7 mm from f7), the resist film is cooled by radiation heat transfer only, similar to when the chamber is in a high vacuum state, and its As a result, uniform cooling u1 is achieved.Therefore,
The apparatus shown in FIG. 4 has the advantage that uniform cooling can be achieved without the need for a vacuum pump to create a high vacuum in the chamber 1'.

〔Effect of the invention〕

As described above, in the present invention, after the resist film is exposed, the resist film is heated to a temperature higher than the glass transition temperature by baking, and then the resist film is cooled uniformly at a predetermined rate to below the glass transition temperature, and then the resist film is developed. This process not only stabilizes the sensitivity of the resist film but also makes it easy to select arbitrary sensitivity conditions, thereby making it possible to form highly accurate resist patterns with good reproducibility. A forming method can be obtained.

In addition, in the present invention, cooling after baking before development! Since the sensitizing effect of the resist can be reduced by increasing the cooling rate in the Jl step, the development time can be significantly shortened and a decrease in throughput can be suppressed. Furthermore, in the present invention, by baking before development, the thermal history of the resist film can be ignored, so variations in sensitivity within the resist 1 plane due to cooling after prebaking, exposure, or environmental conditions are eliminated. Therefore, a highly accurate resist pattern can be formed.

[Brief explanation of drawings]

FIG. 1 is a flowchart explaining the steps of the method of the present invention;
FIG. 2 is a schematic diagram of an example of a heating and cooling device for realizing an embodiment of the present invention, FIG. 3 is an enlarged sectional view of the main part of the device shown in FIG. 2, and FIG. A cross-sectional view of the main parts of another example of a heating and cooling device for realizing one embodiment, FIG. 5 is a flowchart explaining the steps of the conventional method, and FIG. Figure 7 is an explanatory diagram of temperature isotropic lines when left to cool naturally. Figure 7 is a characteristic diagram showing the cooling process when the plate to be treated after pre-baking is placed vertically and left to cool naturally. Figure 8 is Figure 7. FIG. 6 is a characteristic diagram showing the relationship between the exposure ω and the a ratio of the film thickness remaining rate in the resist portions in the illustrated different cooling processes. 1.1'...ヂ↑! 3... Hollow body in the shape of a pot,
5... Cooling flow rate reliever, 7... Heat receiving unit, 11.
...Vacuum pump, 12...Hot plate, 13...
-Blank mask, 14...cassette, 15...transport belt. Applicant's agent Kiyoshi Inomata Figure 2, Figure 8 5 minutes (minutes) 'om',! lC12-

Claims (1)

[Claims] 1. A first step of coating and forming a resist film on a substrate and baking it, and exposing the resist film by selectively irradiating the resist film with electromagnetic waves in a predetermined wavelength range or particle beams with a predetermined energy. a second step of heating the resist film above the transition temperature by baking; a fourth step of cooling the resist film at a predetermined rate to a temperature below the transition temperature; and a fourth step of cooling the resist film to a temperature below the transition temperature. and a subsequent fifth step of developing the resist film. 2. The method of forming a resist pattern according to claim 1, wherein cooling of the resist film in the fourth step is performed by radiant heat transfer.