JPS6034015A - Pattern formation - Google Patents

Abstract

PURPOSE:To obtain a high quality deposited film pattern by a method wherein, when a resist pattern is obtained by exposing and developing a positive type resist layer laminated on a substrate, another positive type resist layer is laminated after the exposure and the exposure is performed in such a manner that the exposed area is gradually reduced while the exposed part of the pattern is overlapped. CONSTITUTION:A positive type resist layer 2 is laminated on an insulating substrate 1 and exposed through a pattern mask 3 by irradiation of ultraviolet rays, far ultraviolet rays, X-rays, electron beams and the like. Then, without developing, another positive type resist layer 2' of the same material is laminated on the exposed layer 2. After that a mask 3' which has smaller apertures than the mask 3 is formed on the layer 3' and the layers in the smaller apertures are exposed and developed to leave the resist layer 4' with trapezoidal sections. Then a deposited layer 5 is formed over the whole surface in such a manner that the layer 5 on the substrate 1 exposed in the apertures and the layer 5' on the layer 4' are separated. The required layer 5 is obtained on the substrate 1 by removing the layer 4' with the layer 5' on it.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photolithography technique used for microfabrication, and more particularly to a method for forming a photoresist pattern on a substrate such as a circuit board, a glass plate, or a solid-state image sensor.

Conventionally, a pattern forming method called a lift-off method (or reverse etching method) has been known as a method for manufacturing fine patterns for large-scale integrated circuits, fine color filters, and the like. In this method, a patterned mask (hereinafter referred to as an undermask) made of photoresist is formed in advance on a variety of substrates, a vapor deposited layer of metal, dye, etc. is laminated on top of the mask, and a direct action is applied to the vapor deposited layer. In this method, by removing the lower undermask from the substrate without causing any damage, the unnecessary vapor deposited layer above it is physically removed, and a desired pattern of the vapor deposited layer or the like is formed on the substrate.

Below, the steps of this lift-off method are explained in Figures 1 to 7.
This will be explained more specifically using figures.

First, as shown in Figure 1, a positive resist 2 (a negative resist is sometimes used, but a positive resist is often used because it is easier to dissolve and remove later) is applied on the substrate l. (a positive resist is used) is laminated by means such as coating, and exposed through a pattern mask 3.
As shown in the figure, development is performed with a positive resist developer to form an undermask 4 on the substrate. In this case, the cross-sectional shape of the undermask 4 is often trapezoidal or rectangular due to the nature of the photodecomposition reaction of the photoresist. Next, as shown in FIG. 3, a deposited layer 5 of a material desired to form a pattern is provided on the entire surface of the substrate and undermask by vacuum evaporation or the like. Thereafter, as shown in 41.DELTA., when the undermask is dissolved and removed, the pre-deposited layer 5 on the undermask is also removed at the same time, and the deposited layer 5 having a pattern of a desired shape can be obtained on the substrate.

However, according to this method, the cross section of the undermask 4 has a trapezoidal or rectangular shape as described above, and as shown in FIG. 5, which is an enlarged view of section A in FIG.
Since the deposition layer 5 formed on the substrate and the undermask has good step coverage (the ability to continuously cover steps), even if the undermask 4 is melted, the coating layer 5 can be covered as shown in B in FIG. 6. Defects such as a portion of the vapor deposited layer 5 that should be removed remain on the substrate, or defects such as a portion of the vapor deposited layer 5 that should be removed remain in the form of whiskers, such as the portion shown by C in FIG. Easy to occur. That is, such defects in fine patterns cause short circuits in the case of circuit patterns, and cause color mixture in the case of multicolor fine color filters. In this way, in the lift-off method,
Since it has the disadvantage that it is difficult to form a perfect vapor deposition pattern, it is difficult to introduce it into an actual production process.

As a result of intensive study on a method for forming a resist pattern in the lift-off method that solves the above-mentioned drawbacks, the inventors of the present invention conducted the process of laminating a positive resist layer and performing pattern exposure multiple times, and then It has been discovered that by developing the resist, the cross-sectional shape of the resist pattern can be formed into a T-shape or an inverted trapezoidal shape, and by this, it is possible to suppress the occurrence of deposition pattern defects due to good step coverage. I found out what is possible.

The purpose of the present invention is to solve the disadvantages of forming a pattern of a deposited film on a substrate by a lift-off method using a positive photoresist, that is, the above-mentioned disadvantages caused by the undermask having a trapezoidal or rectangular cross-sectional shape. It is an object of the present invention to provide a novel method for forming a resist pattern that can solve the above problems and form a high-quality deposited film pattern.

That is, the pattern forming method of the present invention is a method for forming a resist pattern on a substrate by laminating a positive resist layer on a substrate, performing pattern exposure, and developing. After laminating the resist layer and performing pattern exposure, a positive resist layer is further laminated on the exposed resist layer, and the pattern exposed portion overlaps with the pattern exposed portion of the resist layer, and the pattern exposed portion gradually becomes smaller. The method is characterized in that the process of performing pattern exposure as described above is performed at least once, and then the resist layer is developed.

The following five pattern forming methods according to the present invention will be explained based on the drawings.

First, as shown in FIG. 8, a positive resist 2 is laminated on a substrate 1 and exposed through a pattern mask 3 to ultraviolet light, deep ultraviolet light, X-rays, electron beams, or the like. As the substrate used in the method of the present invention, various substrates can be used depending on the purpose of use, and although not particularly limited, specifically, the following substrates can be used. For example, when manufacturing integrated circuits, paper-phenolic resin laminates, glass-
Films or plates made of various insulating materials conventionally used as circuit boards, such as epoxy resin laminates, can be used to manufacture fine color filters, such as glass plates; optical resin plates; gelatin, polyvinyl alcohol, Examples include resin films such as hydroxyl ethyl cellulose, methyl methacrylate, polyester, polybutyral, and polyamide. In addition, it is possible to form the substrate integrally with the color filter to which it is applied, and examples of the substrate in this case include CCD, BBD, CID, etc.
Examples include solid-state imaging devices such as, cathode ray tube display surfaces, image pickup tube light receiving surfaces, liquid crystal display surfaces, color electrophotographic photoreceptors, and the like. On the other hand, the positive resist 2 may be a liquid type or a dry film type.

Next, as shown in FIG. 9, a positive resist, preferably the same as the positive resist, is laminated on the exposed resist layer 2, and the previously used pattern mask 3 is laminated.
A pattern mask 3 that has the same pattern as the pattern mask 3 and has a smaller exposed area than when exposed with the pattern mask 3.
′, the exposed portion of the lower resist layer is exposed so that the exposed portion of the upper resist layer overlaps. If necessary, the process shown in FIG. 9 may be repeated multiple times.

Next, as shown in FIG. 1O, the exposed positive resist is selectively dissolved in the exposed portion using a resist developing chamber to obtain an under mask 4'. The cross-sectional shape of the undermask 4' thus obtained exhibits an overhang structure such as a T-shape or an inverted trapezoidal shape.

When a resist pattern is formed by the method of the present invention, the film thickness of the first layer of positive resist 2 is not particularly limited, but is generally 1 mm thicker than the film thickness of the substance to be patterned on the substrate. It is preferable to set it to about .2 to 1.5 times. Further, the thickness of the second and subsequent resist layers 2' is preferably the same as or less than the thickness of the first resist layer 2. Generally speaking, the length of the overhang part of the surface layer resist is 172 mm, which is the difference between the line width of the surface layer resist pattern and the line width of the first layer resist pattern in contact with the substrate. ) is the line width of the final pattern to be formed on the substrate.
~115, preferably 1/10~115.

In addition, when forming a resist pattern by the method of the present invention, in the previous example, when exposing the positive resist from the second layer onwards, the exposed area is smaller than when exposing with the pattern mask 3 of the first layer. Pattern mask 3
Although the exposure was carried out using a pattern mask 3', this is an example of a preferable method;
There is no necessity to use it. In other words, pattern exposure in which the pattern exposure area gradually becomes smaller as used in the present invention means, for example, using the same pattern mask 3 used in the exposure of the first layer, and changing the exposure time for the second and subsequent layers. This also includes a method in which the length is adjusted to be shorter, and it is also possible to form a resist pattern having an overhanov cross-sectional structure using such a method.

In order to manufacture large-scale integrated circuits, fine color filters, etc. using the undermask 4' thus formed, as shown in FIG. Substrate l and undermask b. Undermask 4' formed by the method of the present invention
has the above-mentioned overhang structure, so the vapor deposited layer 5 on the substrate and the vapor deposited layer 5' of the undermask 4'' are formed intermittently (discontinuously).

Next, as shown in FIG. 12, when the undermask is removed by means such as melting, the unnecessary vapor deposited layer 5' on the under mask is also removed at the same time, leaving a vapor deposited layer 5 having a desired pattern on the substrate. can be obtained.

According to the pattern forming method of the present invention, an undermask having an overhanging structure such as a T-shape or an inverted trapezoidal cross section is formed on the substrate, so that the undermask can be removed after the patterning material is deposited. When removed, it is possible to accurately form a desired base pattern on the substrate without causing defects as shown in FIGS. 6 and 7. Furthermore, when removing the undermask with a resist solution, the immersion time of the substrate in the resist solution can be significantly shortened, especially when the patterning material on the substrate is an organic substance such as a dye. It is possible to minimize the influence of the resist solution on these patterning substances, and it is possible to form a high-quality deposited film pattern.

Hereinafter, the pattern forming method of the present invention will be explained based on Examples.

Example I On a wafer on which a 5i02 layer was formed on a Si base substrate, a positive type film AZ1350 (trade name, manufactured by Shipley Far East) was applied to a film thickness of 7000 Å using a spinner. This resist film was dried and prebaked at 90±5° C. for 20 minutes, and then exposed to ultraviolet light for 3 seconds and 1131 seconds using a mask with a line width of 2 scales in the exposed area.

Next, the same positive resist as described above was coated on this exposed resist film 2 to a thickness of 3000 mm using a spinner. This resist film was also dried and pre-baked in the same way, and then exposed to ultraviolet light for 3 seconds using a mask that had the same pattern as the mask used previously and had a line width of 1.8 scales in the exposed area. exposure was performed. The alignment of the first layer resist and the second layer resist during exposure was performed using alignment marks on the wafer and the mask.

Immediately, the wafer on which this exposed resist was laminated was immersed in an aqueous solution prepared by diluting AZ Developer (developer for the above resist) twice with water, and the resist was developed and further rinsed with pure water. Through the above two steps, an undermask having a T-shaped cross section could be formed on the wafer.

Next, set this wafer in a vacuum evaporator and
After evacuation to 6Toor, the 6-evaporation wafer, in which A1 was deposited to a thickness of 500 (IA) on the wafer by electron beam, was taken out from the vacuum evaporator and placed in dimethylformamide for 10 seconds to remove the undermask (lift-off). immersed while applying ultrasound, then immersed in isopropyl alcohol for 10 seconds while applying ultrasound,
Lift-off was performed.

When the Al circuit pattern on the wafer thus manufactured was observed under a microscope, it was found that the circuit pattern had no defects such as pattern breakage or short circuits.

Comparative Example 1 An undermask was formed in the same manner as in Example 1, except that only one layer of positive resist was applied to a thickness of 8000 on a wafer, and exposure 1 and development were performed.
Vapor deposition of I and lift-off were performed.

When the Al circuit pattern manufactured in this manner was observed under a microscope, several short-circuited locations were found.

Example 2 Positive molding on a cleaned glass substrate) FPM-21
0 (product name, manufactured by Taigo Kogyo ■) with a spinner.
It was applied to a film thickness of 0OA. Dry this resist film,
After prebaking at 180° C. for 30 minutes, exposure was performed for 210 seconds in deep ultraviolet light using a mask with a line width of 5 − in the exposed area. Next, on this exposed resist film, the same positive resist as above was applied using a spinner to a thickness of 2000 mm. This resist film was also dried and blistered in the same way, and then exposed to deep ultraviolet light for 21 seconds using a mask with the same pattern as the mask used previously and a line width of 41iIfi in the exposed area. exposure was performed. Note that the alignment of the first layer resist and the second layer resist during exposure was performed using alignment marks on a glass substrate and a mask. Next, the glass substrate laminated with this exposed resist was coated with a developer (FPM).
-2100, trade name, manufactured by Daikin Industries, Ltd.),
The resist was developed to form an undermask having a T-shaped cross section.

Thereafter, the entire surface of the glass substrate was exposed to deep ultraviolet light for 6 minutes, and the undermask was treated so that it could be dissolved by the resist developer in the lift-off process.

Next, this glass substrate is set in a vacuum evaporation device, and 1
After evacuating to 0'Toor, a Ha hoard containing copper phthalocyanine, which had been placed in a vacuum evaporation apparatus in advance, was heated to 500 to 600°C, and copper phthalocyanine was evaporated to a thickness of 300 OA on the glass substrate. The vapor-deposited glass substrate was taken out from the vacuum vapor deposition apparatus and immersed in the above-mentioned agitated resist developer for 2 minutes to remove the undermask. Next, this glass substrate was washed with a rinsing liquid (FPM-
Rinse with 21OR1 product name (manufactured by Daikin Industries),
Dry with nitrogen gas.

In this way, a line width of 5 and a pitch of ++5- are printed on the glass substrate.
It was possible to form a monochromatic color stripe filter. When this was observed under a microscope, there were no defects in the pattern.

Comparative Example 2 An undermask was formed on a glass substrate in the same manner as in Example 1, except that the second layer of positive resist was not applied and exposure was not performed, and copper phthalocyanine was deposited and lifted off. carried out.

B [1] When removing the undermask, it took 5 minutes or more to immerse it in the developer. When the dye pattern produced in this manner was observed under a microscope, several defects were found, including areas where vapor-deposited dye remained in areas that should have been removed, and areas where vapor-deposited dye was missing in areas where it should remain.

[Brief explanation of drawings]

1 to 4 are process diagrams showing a pattern forming method using a conventional lift-off method. FIG. 5 is a partially enlarged view of FIG. 3, and FIGS. 6 and 7 are diagrams showing pattern defects that occur when using the conventional lift-off method. 8th
12 are process diagrams showing a pattern forming method according to the present invention. 1 Substrate 2.2'Ni-resist layer 3.3': Pattern mask 4.4' Near-resist mask 5.5': Adhesion layer A/undermask step generation part B Defects caused due to good stamp coverage Whisker-like defects in C vapor deposited layer Fig. 4 Fig. 12 ri! J

Claims (1)

[Claims] In a method of forming a resist pattern on a substrate by laminating a positive resist layer on a substrate, performing pattern exposure, and developing, a positive resist layer is laminated on the substrate and pattern exposure is performed. Afterwards, a positive resist layer is further laminated on the exposed resist layer, and pattern exposure is performed such that the pattern exposure portion overlaps with the pattern exposure portion of the resist layer and the pattern exposure portion becomes gradually smaller. A pattern forming method characterized in that the pattern forming method is carried out at least once, and then the resist layer is developed.