JP2005316096A - Method for manufacturing patterned polyimide precursor film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a patterned polyimide precursor film which is peelable, without producing a portion of a photoresist as residue or dissolving remainder and will not give rise to cracking. <P>SOLUTION: The method for manufacturing the patterned polyimide precursur film comprises subjecting the photoresist film on a polyimide pattern to a heat treatment for 30 seconds to 30 minutes at a temperature ranging from 40 to 100°C within 30 minutes, before a process of peeling the photoresist film with a peeling liquid after patterning the polyimide precursur film formed on a semiconductor wafer, having a difference in level of ≥2 microns with the photoresist. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a patterned polyimide precursor film that is suitably used in the field of electronic materials, and more specifically, it can be peeled off without causing a portion of the photoresist film as a residue or undissolved residue. The present invention relates to a method for producing a patterned polyimide precursor film in which cracks do not occur.

  Since polyimide has excellent heat resistance, electrical properties, and mechanical properties, it is widely used in applications such as semiconductor device and wiring surface protective films, interlayer insulating films of multilayer wiring boards, and stress buffer coatings. In the pattern forming method made of these polyimides, there is a step of patterning with a photoresist as a mask and then stripping the photoresist film on the polyimide with a stripping solution. And as a photoist, the photoresist which consists of a naphthoquinone diazide type photosensitizer and a novolak-type resin is marketed, and butyl acetate / xylene (refer patent document 1) and ethyl acetate (refer patent document 2) as the peeling liquid. Was commonly used. However, ethyl acetate and butyl acetate have high volatility and an irritating odor, and have low flash points of −4 ° C. and 22 ° C., respectively. Therefore, there is a problem that expensive explosion-proof equipment must be provided in a clean room. In addition, it has also been proposed to use ethylene glycol monoethyl ether acetate or diethylene glycol monoethyl ether (ethyl carbitol) as the stripping solution (see Patent Document 3), but these stripping solutions are problematic in terms of safety. There is. In addition, it has been proposed that the polyimide precursor can be patterned with a photoresist, and the substrate can be heated and then peeled off with butyl acetate, whereby the photoresist can be peeled off in a short time with high stability ( (See Patent Document 4).

However, when a polyimide precursor is patterned with a photoresist on a semiconductor wafer having a level difference of 2 microns or more and the photoresist is peeled off, there is a problem in that a good pattern cannot be formed due to cracks on the surface of the polyimide film.
JP 60-247603 A (page 6) JP 63-85602 A (page 5) JP 7-318725 A (4-5 pages) JP-A-6-275511 (page 4)

  Accordingly, an object of the present invention is to provide a method for producing a patterned polyimide precursor film in which cracks do not occur in the polyimide precursor film, and no photoresist residue or photoresist remains undissolved.

  That is, the method for producing a patterned polyimide precursor coating according to the present invention includes patterning a polyimide precursor coating formed on a semiconductor wafer having a level difference of 2 microns or more with a photoresist, Production of a patterned polyimide precursor film characterized by performing a heat treatment for 30 seconds to 30 minutes at a temperature in the range of 40 to 100 ° C. within 60 minutes before the step of stripping the resist film with a stripper. Is the method.

  In the method for producing a patterned polyimide precursor film of the present invention, the stripping solution is a stripping solution mainly composed of ethyl lactate, and the stripping solution is a stripping solution composed of 100% ethyl lactate, In addition, it is included as a preferred embodiment that the stripping solution is a stripping solution composed of ethyl lactate and propylene glycol monomethyl ether acetate and composed of 50% or more of ethyl lactate.

  According to the polyimide pattern forming method of the present invention, a good polyimide pattern free of cracks can be obtained with high productivity.

  The present invention is a method for producing a good non-photosensitive polyimide precursor film without cracks on the surface of a polyimide film by performing a predetermined heat treatment before peeling off the photoresist film formed on the polyimide pattern. . Hereinafter, the manufacturing method of the patterned polyimide precursor film of this invention is demonstrated in detail.

  The semiconductor wafer used in the present invention has a step of 2 microns or more, and a typical example is a semiconductor wafer. The upper limit of the step is not particularly limited, but is about 20 μm. Semiconductors used in motor and brake control and inverters are increasing in quantity as power semiconductors. In semiconductor wafers, the electrodes formed on the top of the wafer have increased in thickness and have a thickness of 2 microns or more in order to make the semiconductor wafer finer and withstand a high breakdown voltage and a high current. For this reason, the materials that protect the electrodes and the semiconductor, and the materials and processing processes that secure the contact portions between the electrodes and the signal lines also have more advanced characteristics in order to ensure sufficient reliability against this step. Desired.

  In the present invention, a level difference is a level difference in a base on which a polyimide precursor film is to be applied. Specifically, an electrode formed of a metal such as aluminum or copper provided on the base, a signal line The thickness and the thickness of the insulating layer made of an inorganic compound such as silicon oxide or silicon nitride cause the step.

  Examples of the material of the semiconductor wafer used in the present invention include, but are not limited to, a silicon wafer, metal, glass, a metal oxide insulating film, and silicon nitride.

  Examples of the semiconductor wafer used in the present invention include a disk-shaped plate obtained by slicing a cylinder (called an ingot) crystallized from silicon, germanium, gallium arsenide, or the like. Examples of raw materials include silicon wafers. The diameter is usually 5 inches, 8 inches, or 12 inches, and the thickness of the substrate used as a material such as an IC is usually 0.5 mm to 1.5 mm. After various processing such as exposure and etching of the circuit pattern is performed on this, IC chips are individually cut out.

  Examples of the polyimide precursor used in the present invention include pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetra. Tetracarboxylic dianhydrides such as carboxylic dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, and cyclobutane tetracarboxylic dianhydride; and 4,4'-diaminodiphenyl ether, 3, Reaction with diamines such as 3′-diaminodiphenylsulfone, 4,4′-diaminodiphenylmethane, bis (3-aminopropyl) tetramethyldisiloxane, metaphenylenediamine, and paraphenylenediamine in an aprotic polar solvent. Examples thereof include, but are not limited to, polyimide precursors obtained. As the aprotic polar solvent, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, γ-butyrolactone and the like are preferably used, but are not limited thereto. Typical reaction conditions are performed at temperatures from 25 ° C to 150 ° C.

  In the present invention, a positive photoresist is preferably used as the photoresist. In general, a naphthoquinone diazide-based photosensitizer and a novolac-based resin are the main components, and commercially available products include “OFPR” (registered trademark) series manufactured by Tokyo Ohka, “AZ” series manufactured by Hoechst, and the like.

  Further, the photoresist stripping solution used in the present invention is a stripping solution mainly composed of ethyl lactate. Ethyl lactate is generally used as a photoresist solvent, but has not been used as a stripping solution in the process of processing a polyimide because of its strong property of swelling a polyimide precursor. The present invention provides a process for obtaining a highly productive and crack-free polyimide pattern.

  In the present invention, the photoresist stripping solution may be a 100% ethyl lactate stripping solution, or a stripping solution obtained by adding 50% or less of propylene glycol monomethyl ether acetate or the like to ethyl lactate can be used. Even in this case, ethyl lactate is preferably 50% by weight or more. Thus, by adding propylene glycol monomethyl ether acetate to ethyl lactate, it becomes possible to accelerate the drying of the photoresist stripping solution.

  Next, the processing method in the manufacturing method of the patterned polyimide precursor film of this invention is demonstrated.

  First, a polyimide precursor (composition) is applied on a substrate such as a semiconductor wafer having a step of 2 μm or more. As a method for applying the polyimide precursor, means such as spin coating using a spinner, spray coating using a spray coater, and roll coating are possible, but the present invention is not limited to these. The coating thickness of the polyimide precursor can be adjusted by the coating means, the solid content concentration of the composition, the viscosity, and the like, but is usually applied in a range of 2 to 30 μm.

  Next, the substrate coated with the polyimide precursor is dried to obtain a polyimide precursor film. Drying is preferably performed at a temperature in the range of 50 to 180 ° C. for 1 minute to several hours using an oven, a hot plate, infrared rays, and the like.

  Next, a photoresist is applied on the polyimide precursor film and dried to form a photoresist film. As a method of applying the photoresist, means such as spin coating using a spinner, spray coating using a spray coater, and roll coating are possible, but the invention is not limited to these. Drying is preferably performed using an oven, a hot plate, or the like at a temperature in the range of 80 to 120 ° C. for 1 minute to several hours.

  The film thickness of the photoresist film is preferably 0.5 to 10 microns, and is usually applied in the range of 2 to 5 μm.

Next, exposure is performed using a mask having a desired pattern. Although the amount of exposure is not particularly defined, a range of ^{20 to} 500 mJ / cm ² is preferable. The exposure wavelength may be any as long as it has a sensitivity for photosensitivity, but g-line (436 nm), h-line (405 nm), i-line (365 nm), etc. of an ultrahigh pressure mercury lamp are generally used.

  After the exposure, the polyimide layer is dissolved together with the photoresist according to the mask pattern using a photoresist developer. As the developer used at this time, an appropriate developer can be selected in accordance with the structure of the polyimide precursor. However, an alkaline aqueous solution such as ammonia, tetramethylammonium hydroxide, and diethanolamine, or an additive such as alcohol can be used. What added to the aqueous alkali solution etc. can be used preferably.

  Next, heat treatment is performed before the photoresist is peeled off. The heat treatment is preferably performed using a hot plate or the like at a temperature in the range of 40 to 100 ° C. for 30 seconds to 30 minutes. In particular, it is preferably performed at a temperature in the range of 60 to 90 ° C. for 1 to 2 minutes. In the present invention, it is important that the heat treatment before peeling the photoresist film is performed within 60 minutes before the peeling step. In other words, the photoresist film is peeled off within 60 minutes after the heat treatment. When the photoresist film is peeled after 60 minutes after the heat treatment, cracks occur in the polyimide precursor film.

  Next, the photoresist film is preferably stripped with a stripper mainly composed of ethyl lactate. The peeling temperature is preferably in the range of 10 ° C to 50 ° C, more preferably in the range of 15 ° C to 35 ° C. When the peeling temperature is low, peeling takes time, and when the peeling temperature is high, the polyimide precursor film may be cracked or peeled off. The peeling method of the photoresist film is not particularly limited, and examples of the peeling method include dip peeling, spin peeling, spray peeling, curtain flow peeling, and the like. It is also possible to enhance the peeling effect by applying ultrasonic waves. Thereby, a patterned polyimide precursor film can be obtained. As described above, the present invention is characterized in that a predetermined heat treatment is performed immediately before peeling of the photoresist film, and in this case, it is preferable to use a stripping solution containing ethyl lactate as a main component as the stripping solution. .

  The pattern obtained by the above treatment is a polyimide precursor film, and becomes a heat resistant polyimide film by heat treatment. In this case, the heat treatment is preferably performed at a temperature of 250 ° C. to 450 ° C., and is usually performed while raising the temperature stepwise or continuously.

  It is preferable that the polyimide film after heat-treating the polyimide precursor film obtained in the present invention as described above has a generated gas derived from an organic substance of 1 ppm or less at 100 ° C. for 5 hours after the heat treatment. As a result, a heat-resistant polyimide film with good productivity and good characteristics can be obtained even on a substrate having a step.

  The patterned polyimide precursor coating obtained in the present invention is thus suitable as a heat-resistant polyimide film for applications such as surface protection films for semiconductor elements and wiring, interlayer insulating films for multilayer wiring boards, and stress buffer coatings. It is.

Example 1
Non-photosensitive polyimide comprising pyromellitic dianhydride, 3.3 ', 4.4'-benzophenone tetracarboxylic dianhydride, 4.4'-diaminodiphenyl ether, bis (3-aminopropyl) tetramethyldisiloxane A silicon substrate having a precursor solution (viscosity 17,000 mPa · s / 25 ° C., solid concentration 22.0 wt%) formed on the entire surface with linear aluminum wiring having a thickness of 2.5 μm and a line width of 1 mm at intervals of 1 mm In addition, spin coating was applied with SKW-636 manufactured by Dainippon Screen Co., Ltd. to a film thickness of 16 μm, and drying was performed at 95 ° C. × 2.5 minutes + 125 ° C. × 2.5 minutes on the hot plate of the same apparatus. It was. Next, a photoresist “OFPR (registered trademark) -800” manufactured by Tokyo Ohka Co., Ltd. is spin-coated with the above apparatus so as to have a photoresist film thickness of 2.5 μm, and 100 ° C. on a hot plate. × 2 minutes of drying was performed to form a photoresist film. Thereafter, exposure was performed using a mask aligner PLA-501F manufactured by Canon Inc. The exposure measured by i-line was 100 mJ / cm ² . After the exposure, the photoresist film was developed with an alkaline aqueous solution NMD-3 manufactured by Tokyo Ohka Co., Ltd., and at the same time, the polyimide precursor film was developed to form a pattern. Before removing the photoresist, heating was performed on a hot plate at 80 ° C. for 1 minute. 30 minutes after the heat treatment, the photoresist film was peeled off with 100% ethyl lactate. The photoresist film could be peeled off without any residue or undissolved photoresist film, and the obtained polyimide precursor film had a good pattern shape without cracks. Moreover, the polyimide film after heat-treating the polyimide precursor film of the present invention had a generated gas derived from organic matter of 1 ppm or less in the treatment at 100 ° C. for 5 hours after the heat treatment. The results are shown in Table 1.

Example 2
In Example 1, before removing the photoresist, a pattern was formed in exactly the same manner except that the heat treatment was performed on a hot plate at 50 ° C. for 1 minute. There was no residue or undissolved residue of the photoresist film, and the photoresist film could be peeled off. The resulting polyimide precursor film had a good pattern shape with no cracks. In the polyimide film after heat-treating the polyimide precursor film of the present invention, the generated gas derived from organic matter in the treatment at 100 ° C. for 5 hours after the heat treatment was 1 ppm or less. The results are shown in Table 1.

Example 3
In Example 1, the pattern was formed in exactly the same manner except that after the photoresist was peeled off, a heat treatment was performed at 80 ° C. for 1 minute on a hot plate and then peeled off after 50 minutes. There was no residue or undissolved residue of the photoresist film, and the photoresist film could be peeled off. The resulting polyimide precursor film had a good pattern shape with no cracks. In the polyimide film after heat-treating the polyimide precursor film of the present invention, the generated gas derived from organic matter in the treatment at 100 ° C. for 5 hours after the heat treatment was 1 ppm or less. The results are shown in Table 1.

Example 4
In Example 1, the pattern was formed in exactly the same manner except that, after the photoresist was peeled off, the heat treatment was performed at 80 ° C. for 1 minute on a hot plate and the peeling was carried out 3 minutes later. There was no residue or undissolved residue of the photoresist film, and the photoresist film could be peeled off. The resulting polyimide precursor film had a good pattern shape with no cracks. In the polyimide film after heat-treating the polyimide precursor film of the present invention, the generated gas derived from organic matter in the treatment at 100 ° C. for 5 hours after the heat treatment was 1 ppm or less. The results are shown in Table 1.

Example 5
In Example 1, a pattern was formed in exactly the same manner except that a solution in which 60% by weight of ethyl lactate and 40% by weight of propylene glycol monomethyl ether acetate were used instead of 100% ethyl lactate was used. There was no residue or undissolved residue of the photoresist film, and the photoresist film could be peeled off. The resulting polyimide precursor film had a good pattern shape with no cracks. In the polyimide film after heat-treating the polyimide precursor film of the present invention, the generated gas derived from organic matter in the treatment at 100 ° C. for 5 hours after the heat treatment was 1 ppm or less. The results are shown in Table 1.

Comparative Example 1
In Example 1, a pattern was formed in exactly the same manner except that the photoresist was peeled off with 100% ethyl lactate without heat treatment before peeling off the photoresist film. The obtained polyimide precursor film was cracked on the entire surface, and a good pattern shape could not be obtained. The results are shown in Table 1.

Comparative Example 2
In Example 1, a pattern was formed in exactly the same manner except that the photoresist was peeled off with 100% propylene glycol monomethyl ether acetate without heat treatment before peeling off the photoresist. In the obtained polyimide precursor film, a part of the photoresist film remained and good photoresist peeling could not be performed. The results are shown in Table 1.

Comparative Example 3
In Example 1, a pattern was formed in exactly the same manner except that the photoresist was stripped with 100% butyl acetate without heat treatment before stripping the photoresist. In the obtained polyimide precursor film, a part of the photoresist film remained and good photoresist peeling could not be performed. The results are shown in Table 1.

Comparative Example 4
In Example 1, a pattern was formed in exactly the same manner except that, after the photoresist was peeled off, a heat treatment was performed at 80 ° C. for 1 minute on a hot plate and then peeled off after 90 minutes. The obtained polyimide precursor film was cracked on the entire surface, and a good pattern shape could not be obtained. The results are shown in Table 1.

  The patterned polyimide precursor coating obtained by the present invention is suitable and useful for applications such as surface protection films for semiconductor devices and wiring, interlayer insulating films for multilayer wiring boards, and stress buffer coatings.

Claims (4)

After the polyimide precursor film formed on the semiconductor wafer having a step of 2 microns or more is patterned with a photoresist, within 40 minutes before the step of stripping the photoresist film on the polyimide pattern with a stripping solution, A method for producing a patterned polyimide precursor coating, comprising performing a heat treatment for 30 seconds to 30 minutes at a temperature in the range of 100 ° C. 2. The method for producing a patterned polyimide precursor film according to claim 1, wherein the stripping solution is a stripping solution containing ethyl lactate as a main component. The method for producing a patterned polyimide precursor film according to claim 1 or 2, wherein the stripper is a stripper composed of 100% ethyl lactate. The method for producing a patterned polyimide precursor film according to claim 1 or 2, wherein the stripping solution is a stripping solution composed of ethyl lactate and propylene glycol monomethyl ether acetate and comprising 50% or more of ethyl lactate.