JPS63296221A - Formation of resist pattern - Google Patents

Abstract

PURPOSE:To obtain the sufficient thermal resistance by using UV curing device of a low-output light source without a need for a long-hour process and for an investment in plant and equipment by a method wherein a groove whose depth is less than a thickness of a resist pattern is formed inside the resist pattern. CONSTITUTION:A positive-type photoresist film 2 is formed on a substrate 1 to be processed. Then, an exposure operation is executed via a mask to which a vacant pattern 4 whose size is less than a limit of resolution of the resist film 2 is attached. Then, after a development operation, UV curing operation is executed by irradiation with UV rays 6 while the substrate is being heattreated 7 and a resist pattern having a groove whose depth is less than a thickness of the pattern is formed inside the resist pattern. By this setup, an area of a resist-hardening layer 2d on the surface is expanded after the UV process and the layer becomes strong structurally against internal stress. Accordingly, it is possible to obtain the sufficient thermal resistance by using a UV curing device of a low-output light source and to achieve the desired purpose.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application J This invention relates to a method for forming a resist pattern.

[Prior Art J] FIG. 5 is a cross-sectional view of a resist pattern along line a in the steps after development processing in a resist/four-turn forming method using a positive photoresist.

FIG. 5(a) shows a cross-sectional view of a resist pattern obtained by applying a positive resist onto a substrate 1 to be processed, prebaking, selectively exposing a predetermined pattern, and performing a development process. FIG. 5(b) shows UV curing treatment, showing 6Fi ultraviolet light and 7I/i substrate heating. still,
Substrate heating in step 7 may not be used together. 2d indicates a hardened portion of the resist that has undergone a photo-crosslinking reaction and hardened due to UV curing treatment, and 2c indicates a fully cured portion. Figure 5 (
c) Fi indicates post-bake treatment, 9 indicates heating.

Heating is done using an oven or hot plate.

UV curing treatment is generally performed for the purpose of improving the heat resistance and 1IiFt plasma etching properties of positive photoresists. The VU cure process is shown in Figure 5 (
As shown in b), the above objective is usually achieved by irradiating the resist with UV light while heating the substrate to cause a photocrosslinking reaction in the resist and harden the resist. The hardened portion of the resist by UV curing progresses from the resist surface to the inside. If the progress of the hardened portion is insufficient, the pattern shape may not be maintained due to internal stress due to heat during post-baking processing or plasma etching processing, and the pattern may become deformed, as shown in Figure 5 (Q). It ends up. Deformation of the resist pattern causes dimensional changes in the etched pattern after plasma etching, and also reduces dimensional controllability. As the resolution of resists progresses, resin molecules tend to have lower molecular weights, and as a result, the rate at which cured areas are formed by UV curing is reduced, making it difficult to form cured areas.

Therefore, it becomes necessary to take a longer time for UV curing treatment and to increase the output of the light source, which makes it inevitable to reduce geographic capacity and require capital investment.

On the other hand, as the hardened portion of the resist grows, it becomes difficult to remove the resist. Therefore, if the UV curing process is performed excessively, the removal process will take a long time, leading to problems such as increased damage to the underlying substrate.

[Problem to be Solved by the Invention 1] As described above, in the conventional example, if the hardened portion of the positive photoresist formed by UV curing treatment is insufficiently grown, post-bake treatment or plasma etching is performed. 6. At the time of processing, the resist pattern is deformed and dimensional controllability is reduced.9. In order to improve the above-mentioned problems, it is inevitable to reduce the processing capacity due to the longer UV curing process or to invest in equipment due to the increase in the output of the light source. On the other hand, if the UV curing treatment is performed excessively, the removal treatment becomes difficult.

This invention solves the above-mentioned problems, and uses a UV curing device with a low-power light source to obtain sufficient #thermal properties without requiring long processing times or equipment investment, and also solves the difficulty of resist removal processing. The object of the present invention is to obtain a resist pattern forming method that does not cause oxidation.

[Means for solving problems]

In this invention, by adding an empty pattern on the substrate to be processed inside each pattern of the mask that transfers the pattern to the resist, the size is equal to or smaller than the resolution limit dimension of the positive resist used. In this method, grooves having a depth equal to or less than the thickness of the pattern are formed in the resist pattern to achieve the above object.

[Effect]

FIG. 4 shows cross-sectional defects of a conventional resist pattern and a pattern in which grooves are formed in the resist pattern after UV curing treatment. FIG. 4(a) shows a conventional pattern, and FIG. 4(b) shows a pattern in which a groove is inserted into the pattern. 2
d#-t hardened part of resist, 2a is uncured part, (8
) indicates internal stress. If the thickness of the cured S portion, r, and the thickness of the resist pattern are (a)% (b) both the same,
(b), which has grooves in the pattern, has a larger volume of the hardened part even though the internal volume of the pattern is smaller, so it is structurally more resistant to internal stress than the conventional pattern (a). It can be said that it is strong. If the internal stress becomes larger than the force that maintains the pattern shape, the internal S stress is eliminated by deforming the pattern. (See FIG. 5(0)) Therefore, when UV curing is performed with the same irradiation energy, the pattern (b) having grooves inside the pattern has higher heat resistance.

FIG. 3 shows examples of mask patterns in the conventional case and in the case of forming grooves in the resist pattern.

FIG. 3(a) shows examples of conventional mask patterns in the case of a line shape and a circular shape, which are chromium portions that are normally used as a 3Fi mask material.

The axis in FIG. 3 shows an example of a mask pattern that can be used when forming grooves in a resist pattern. 3 indicates a chrome portion, and 4 indicates an empty pattern portion added inside the pattern. FIG. 2 shows the exposure state of a positive photoresist during iris photolithography when a conventional mask is used and when a mask having an empty pattern inside the mask pattern is used. Figure 2 (,) shows the case where a conventional mask is used, and Figure 2 (b) //
A case is shown in which a mask having an empty pattern in the same area as the i-mask pattern is used. In the figure, 2a indicates the exposed portion of the resist, 2b indicates the unexposed portion, and indicates the sensitive wavelength light of the 5#-i resist. Also, it is the same as 3.4Vi Fig. 3. Second
As shown in figure (b), there is an empty hole 4 inside the mask pattern.
If the dimension is narrower than the resolution limit dimension of the positive type 7 photoresist used, the exposed area of the resist will not reach the bottom of the resist and will be incomplete.

When the resist in this state is developed, the resist is removed by the amount of exposure S, so that a resist pattern having grooves with a depth equal to or less than the thickness of the pattern can be formed.

[Example J FIG. 1 shows an example of the present invention, and is a cross-sectional view of each step from the resist coating process to the UV curing process. 1, 1 to 7 are from Figures 2 to 5.
Same as the figure.

FIG. 1(a) shows a state in which a film 2 of positive type 7 photoresist is formed on a substrate 1 to be processed by a coating process. FIG. 1(b) shows the exposure process performed through a mask to which an empty pattern smaller than the resolution limit dimension of the resist 2 used in the mask pattern is added. In the figure, 3 indicates chrome S+ of the mask pattern, and 4 indicates an empty pattern added within the mask pattern. Also, the exposed portion of the 2aFi resist is shown, and the unexposed portion of the 2bI-i resist is shown. 4
FIG. 1(e) shows the cross-sectional shape of the resist pattern after the development process.

Figure 1(d) I/'i, shows UV curing treatment in which the substrate is heated 7 and then irradiated with ultraviolet light 6, as in the prior art (see Figure 5(b)), and the substrate is formed by 2diz treatment. %2+ indicates the cured portion of the resist, and %2+ indicates the uncured portion.

By the above method, a resist pattern having grooves less than the thickness of the pattern is formed in the resist pattern, and then a post bake process is performed.As a matter of fact, no deformation of the resist pattern was observed. It was confirmed that the thermal properties were clearly improved compared to the above. Furthermore, the deformation of the resist pattern by plasma treatment,
No abnormalities such as an increase in the number of resist film plates 9 were observed, and no abnormalities were observed in the resist removal process using oxygen plasma.

In Fig. 1 above, a same-magnification projection exposure device is used as the JI optical device, but if a reduction projection exposure device is used, the pattern size of the mask can be enlarged by the reduction magnification.
It becomes easy to create a chamber pattern to be added within the pattern.

Further, in FIG. 1, only one groove is provided in the resist pattern, but the above effect can be further improved by providing a plurality of grooves.

Furthermore, in FIG. 1 above, the grooves are formed in the same direction with respect to the pattern, but considering the interval between the grooves, the grooves may be in any direction with respect to the pattern, for example, vertically or diagonally. Young fruits similar to those described above can be obtained either in the direction or in combination.

[Effects of the Invention] As described above, according to the present invention, in a method for forming a predetermined positive resist pattern on a substrate to be processed, a solution of the positive resist to be used is formed on the substrate to be processed inside the pattern of the mask. By adding a drag pattern that is less than the image limit dimension, we have created a groove that is less than the thickness of the pattern in the resist pattern after development, making it possible to prevent UV rays.
Cure J1. The area of the surface hardened layer of the resist that occupies the cross-sectional area of the resist pattern is increased compared to the pattern from the RT pattern, and the resist pattern becomes structurally strong against internal stress.

Therefore, in UV curing treatment, the high output of the light source and
It is possible to improve the heat resistance and plasma etching resistance of the resist without requiring a long processing time, which would otherwise lead to a reduction in equipment investment and equipment processing capacity.

[Brief explanation of the drawing]

FIG. 1 is a step-by-step cross-sectional view of a pattern forming method for a positive type 7-otonist showing an embodiment of the present invention, FIG. Figure 3 shows the difference between this invention and the conventional mask pattern in Figure 11rl11], and Figure 4 shows the difference between the mask pattern and the conventional one.
A cross-sectional view of a phase filter according to the present invention and a conventional method in the cross-sectional structure of a resist pattern after curing treatment is shown, and FIG. 5 is a step-by-step cross-sectional view of a conventional positive photoresist pattern forming method. In the figure, 1 processed group & 2 positive type photoresist films, 2a the exposed part of #-1 resist, 2b the unexposed part of the Vi resist, 2c the uncured part of the resist, 2d
3 is the chrome pattern part of the mask pattern, 4 is the empty pattern part in the mask pattern, 5 is the photosensitive light of the resist, 6 is ultraviolet light, 7 is substrate heating, 8#: l: heat 9 is heating. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] (1) A resist pattern forming method for forming a predetermined positive resist pattern on a substrate to be processed, the method comprising forming a groove in the resist pattern with a depth equal to or less than the thickness of the resist pattern. (2) A resist pattern forming method according to claim 1, characterized in that an empty pattern is added inside each pattern of the mask to which the groove formation is to be transferred.