JP2003234283A - Forming method of pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of forming a pattern of polyimide or polybenzoxazole, which has a comparatively gentle inclination having an angle of inclination of less than 60° in the side of the pattern, on a semiconductor substrate. <P>SOLUTION: Exposure is effected by employing a mask having a boundary capable of changing the amount of exposure at the boundary between a light transmitting part and a light shielding part of the mask, whereby the angle of inclination at the end of the pattern can be gentled. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a polyimide or polybenzoxazole pattern on a semiconductor substrate.

[0002]

2. Description of the Related Art Conventionally, as a method for forming a pattern on a semiconductor substrate using a negative photosensitive polyimide precursor composition or a negative photosensitive polybenzoxazole precursor composition, 1) Step 2) coating and drying the photosensitive polyimide precursor composition or the photosensitive polybenzoxazole precursor composition 2) curing the exposed portion by irradiating it with ultraviolet rays through a photomask having a pattern consisting of a light transmitting portion and a light shielding portion Then, a process including a step 3) of making it insoluble in a developing solution and a step 4) of removing an uncured portion by treating with a developing solution and a heat treatment at a temperature of 250 ° C. or higher is performed.

However, when a pattern is formed by exposing a negative-type photosensitive polyimide precursor composition or a negative-type photosensitive polybenzoxazole precursor composition, the cured portion after exposure is exposed to a developer. Since it becomes almost insoluble, the inclination angle of the side surface of the pattern was relatively steep and nearly vertical (90 degrees). This has been one of the causes of problems such as disconnection of a corner portion when a rewiring layer or the like is provided on a polyimide or polybenzoxazole pattern.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a negative photosensitive polyimide resin precursor composition or a negative photosensitive polybenzoxazole precursor composition by coating, drying, exposing,
The purpose is to control the inclination angle of the side surface of the pattern obtained after development and heat treatment (the angle formed by the side surface of the resin pattern and the substrate surface in contact with the resin pattern). In particular, the present invention provides a method of forming a pattern of polyimide or polybenzoxazole having a comparatively gentle inclination with a side surface inclination angle of 60 degrees or less on a semiconductor substrate, As a result, it is an object of the present invention to provide a process by which a highly reliable semiconductor device can be easily obtained when a rewiring layer or the like is provided on a pattern.

[0005]

In order to solve the above-mentioned problems, the present inventor obtains after heat treatment by changing the exposure amount of a boundary portion of a pattern consisting of a light-transmitting portion and a light-shielding portion of a photomask at the time of exposure. It was found that the inclination angle of the side surface of the formed pattern had a comparatively gentle inclination, and the present invention was completed based on this finding.

That is, according to the present invention, 1) a step of applying a negative photosensitive polyimide precursor composition or a negative photosensitive polybenzoxazole precursor composition on a semiconductor substrate and drying it 2) a light transmitting portion and a light shielding portion A step of irradiating ultraviolet rays through a photomask having a pattern including a pattern, wherein a boundary portion between the light-transmitting portion and the light-shielding portion has a light transmittance lower than the value of the light-transmitting portion and higher than the value of the light-shielding portion. 3) A step of removing an uncured portion by treating with a developing solution 4) A pattern of polyimide or polybenzoxazole is formed on a semiconductor substrate, including a step of heat treatment at a temperature of 250 ° C. or higher. Provide a way.

Further, according to the present invention, the boundary portion of the photomask is constituted by providing a pattern of a plurality of minute light shielding areas in the light transmitting area, and the size of the minute light shielding areas is a negative type. The above pattern is formed, which is n / 5 or less of the minimum resolution dimension of the photosensitive polyimide precursor composition or the negative-type photosensitive polybenzoxazole precursor composition (n: mask magnification in a photomask). Provide a way to do.

Further, according to the present invention, the value of the light transmittance at the boundary portion of the photomask continuously changes from the value of the light transmitting portion to the value of the light shielding portion. Provide a way to do. The photomask referred to in the present invention includes a reticle for reducing and projecting a pattern in addition to a photomask which directly contacts a semiconductor substrate coated with a photosensitive resin.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. The negative photosensitive polyimide precursor composition or the negative photosensitive polybenzoxazole precursor composition used in the present invention is, for example, Japanese Patent No. 2826940, International Publication WO00 / 43439, JP 2002 -3602 and Japanese Patent Application Laid-Open No. 2002-12665, the "Paimel" (registered trademark) series manufactured by Asahi Kasei Corporation can be preferably used.

In the present invention, a photomask in which a boundary portion having a light transmittance lower than the value of the light transmitting portion and higher than the value of the light shielding portion is provided between the light transmitting portion and the light shielding portion which form the pattern. As one of practical methods for obtaining such a photomask, a known light-shielding silver salt method is used to form a partial light-shielding portion having a uniform optical density between the light-transmitting portion and the light-shielding portion as a light-transmitting portion. A method of forming it between the light shielding portions can be considered.

As another method, the minimum resolution dimension (about 1/2 of the coating film thickness) of the negative photosensitive polyimide resin precursor composition or the negative photosensitive polybenzoxazole precursor composition to be used is used. A pattern composed of a plurality of minute light-shielding regions having a size of n / 5 or less (n: mask magnification in a photomask) is arranged in a light-transmitting region at an arbitrary density, and apparently the light transmittance at the time of exposure at the boundary is A method of partially changing it can be considered. According to this method, since it is not necessary to form the halftone partial light-shielding portion, the photomask can be formed by the well-known electron beam drawing method, which is more preferable.

Further, the boundary of the photomask to be used is divided into two or more partial boundaries so that the change of the light transmittance from the light-shielding portion to the light-transmitting portion becomes a more gentle gradation. It is more preferable to reduce the unevenness on the side surface of the pattern. The gradation can be created by continuously increasing the density or size of the plurality of minute light-shielding regions drawn on the light-transmitting region in the boundary portion from the light-transmitting portion side to the light-shielding portion side.

In the present invention, a photomask having a pattern including a light-transmitting portion and a light-shielding portion, wherein the light transmittance between the light-transmitting portion and the light-shielding portion is lower than that of the light-transmitting portion and higher than that of the light-shielding portion. Regarding steps other than the step of irradiating ultraviolet rays through a photomask provided with a boundary portion, for example, the above-mentioned Japanese Patent No. 2826940, International Publication WO00 / 43439,
The methods described in JP-A-2002-3602 and JP-A-2002-12665 can be used.

Further, in the photomask used in the present invention, the existence of the boundary portion applies to the entire photomask,
It goes without saying that the application may be limited to the necessary part. The light-transmitting portion of the photomask used in the present invention,
It is impossible to obtain the light transmittances of the light-shielding portion and the boundary portion by directly measuring the photomask itself because the pattern is minute. Therefore, the light transmittance referred to in the present invention is a value obtained by measuring a test sample in which a light-transmitting portion, a light-shielding portion, and a boundary portion are formed over the entire area required for measuring the transmittance.

Next, the present invention will be described based on Reference Examples and Examples. [Reference Example] (Photomask making example 1) 40 μm by silver salt photography
The corner via hole is used as the light shield (light transmittance 0%),
(1) Translucent part around the via hole (light transmittance 95%)
Between the light shielding part and the light shielding part, a test pattern having a boundary part having a light transmittance of 50% of the light transmitting part and having a width of 4 μm, and (2) a test pattern having no boundary part between the light transmitting part and the light shielding part. Have P
An ET mask was created. This is called a photomask A.

(Photomask making example 2) A 200 μm square via hole was used as a light-shielding portion (light transmittance 0%) by an electron beam drawing method, and a surrounding light-transmitting portion (light transmittance 95%).
Between the light-shielding portion and the light-shielding portion, a test pattern provided with a boundary portion having a width of 25 μm and formed so that the change in light transmittance from the light-shielding portion to the light-transmitting portion has a gentle gradation A quartz reticle [mask magnification (n): 5] having and was prepared. This is called reticle B.

In the boundary portion, a rectangular small light-shielding area having a side of 0.5 μm square is drawn on the light-transmitting area. It is possible to obtain a desired light transmittance.

[0018]

[Example 1] "Paimel" (registered trademark) I-350A grade was coated on a silicon wafer, dried, and had a thickness of 10 µm.
A coating film of Using a PLA-501F type exposure machine, contact exposure was performed on this coating film by overlaying a photomask A, and after exposure, it was heated at 80 ° C. for 1 minute. This coating film was developed using a 2.38% TMAH (tetramethylammonium hydroxide) aqueous solution as a developing solution and water as a rinse solution, and heated in nitrogen at 350 ° C. for 1 hour to obtain a cured film pattern.

The inclination angle of the side face of the pattern of the 40 μm via hole obtained from the test pattern having the boundary was slightly uneven, but the average value was 40 degrees. On the other hand, the inclination angle of the pattern side surface of the via hole obtained from the test pattern having no boundary was 70 degrees.

[0020]

[Example 2] "Paimel" (registered trademark) I-8124C grade was applied on a silicon wafer, dried, and had a thickness of 8 µm.
A coating film of This coating film was subjected to 1/5 reduction exposure with reticle B using NSR-2005i8A type i-line stepper. The coating film was developed with a developer for exclusive use of A-515 "Pimel" and a rinse liquid for exclusive use of C-260 "Pimel", and heated in nitrogen at 350 ° C for 1 hour to obtain a pattern of a cured film.

The pattern side surface of the 40 μm via hole obtained from the test pattern having the boundary had very good smoothness, and the inclination angle of the side surface was 50 degrees. On the other hand, the inclination angle of the side surface of the via hole obtained from the test pattern having no boundary was 70 degrees.

[0022]

According to the method of the present invention, it is possible to form, on a semiconductor substrate, a pattern of polyimide or polybenzoxazole in which the side surface of the pattern has a comparatively inclined angle. As a result, as compared with the case where the inclination angle is close to vertical, the metal film can be evenly attached to the edge when the rewiring layer is provided, so that a more reliable semiconductor device can be obtained. Is.

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Claims (3)

[Claims] 1. A step of 1) applying a negative photosensitive polyimide precursor composition or a negative photosensitive polybenzoxazole precursor composition on a semiconductor substrate and drying it. 2) forming a pattern including a light transmitting portion and a light shielding portion. A step of irradiating ultraviolet rays through a photomask having a photomask having a boundary between the light-transmitting portion and the light-shielding portion, the light transmittance of which is lower than that of the light-transmitting portion and higher than that of the light-shielding portion 3) Developer The method for forming a pattern of polyimide or polybenzoxazole on a semiconductor substrate, which comprises the step 4) of removing the uncured portion by the treatment of 1.) and the step of heat treatment at a temperature of 250 ° C. or higher. 2. The boundary of the photomask is formed by providing a pattern of a plurality of minute light-shielding areas in a light-transmitting area, and the size of the minute light-shielding areas is a negative photosensitive polyimide precursor. 2. The pattern according to claim 1, which is n / 5 or less of the minimum resolution dimension of the body composition or the negative photosensitive polybenzoxazole precursor composition (n: mask magnification in a photomask). Method. 3. The value of the light transmittance at the boundary portion of the photomask continuously changes from the value of the light transmitting portion to the value of the light shielding portion, according to claim 1 or 2. A method of forming a pattern.