JPH0837142A - Method for applying polyimide precursor composition to semiconductor substrate - Google Patents

Abstract

PURPOSE:To provide a spin-coating method capable of forming a polyimide resin film having a uniform film thickness up to the end section of the surface of a semiconductor substrate. CONSTITUTION:On the occasion of spin-coating the surface of a semiconductor substrate with a polyimide precursor composition, a nitrogen gas is blown to the center part of the surface of the semiconductor substrate from a pipe 6, to the upside of the polyimide precursor composition 4 dripped to the center part, rotating the substrate. After the stop of the nitrogen gas blowing, the semiconductor substrate is moreover rotated and coated with the polyimide precursor composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for forming a polyimide resin film, and more particularly to a spin coating method of a resin having a high viscosity and forming a thick film. More specifically, a polyimide precursor composition is applied to the surface of a semiconductor substrate. The present invention relates to a method for applying a polyimide precursor composition onto a semiconductor substrate, which is suitable for applying the above composition in a uniform thickness when spin-coating the same.

[0002]

2. Description of the Related Art Conventionally, a polyimide resin film has been used as a surface protective film or an interlayer insulating film for various electronic parts such as semiconductors. The polyimide resin is PSG, SiO ₂ ,
For example, a flat film can be formed on a substrate having large irregularities as compared with an inorganic insulating film such as SiN, a thick film of 1 μm or more can be easily formed, and heat resistance is high compared to other organic materials. Because of its advantages, it has been adopted as an interlayer insulating film for bipolar ICs, and has recently been widely used as an α-ray shielding film and a buffer coat film for memory devices.

The above-mentioned polyimide resin film is formed by applying a polyimide precursor composition onto a semiconductor substrate such as a wafer by a spin method or the like and heating it. Further, patterns such as via holes are formed on the polyimide resin film. However, when the polyimide precursor composition is dropped onto the center of the semiconductor substrate surface and spin-coated, and then the semiconductor substrate is heat-treated on a hot plate, the thickness of the polyimide resin film at the center of the semiconductor substrate surface is reduced. Since a thin portion is generated, a photoresist used as a mask material for forming a pattern of a polyimide-based resin film is formed, and after exposure and etching treatment, the central portion of the semiconductor substrate surface can be etched in a predetermined time. In a portion where the thickness of the polyimide-based resin film from the central portion to the end portion is large, etching is insufficient and a good via hole cannot be formed. And
Due to this, it is necessary to remove the polyimide resin film on the wafer surface and regenerate the semiconductor substrate. This problem is more likely to occur as the thickness of the polyimide resin film to be formed becomes thicker and the low-speed spin coating is performed.

Therefore, recently, in order to form a more uniform polyimide resin film on the surface of a semiconductor substrate, a polar solvent such as N-methyl-2-pyrrolidone used in a polyimide precursor composition has low surface tension or low surface tension. A method of spin-coating a mixture of low-boiling solvents and a method of increasing the rotation speed during spin-coating (3000 rpm or more) have been proposed. However, in the above method, there is a possibility that the solubility and viscosity stability with the polyimide precursor composition may be adversely affected, and there is a limit, and in the above method, the viscosity of the polyimide precursor composition used and There are drawbacks such as the need to balance the film thickness of the polyimide resin to be formed.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and when a polyimide precursor composition is spin-coated on a semiconductor substrate or the like, a recess is formed in the center of the semiconductor substrate surface. First, the present invention provides a method for applying a polyimide precursor composition, which can form a more uniform thickness of a polyimide resin film on the surface of a semiconductor substrate.

[0006]

Means for Solving the Problems The present invention provides a method for applying a polyimide precursor composition onto a surface of a semiconductor substrate by a spin method, in which the polyimide precursor composition is dropped on the center of the semiconductor substrate surface. The present invention relates to a method for applying a polyimide precursor composition to a semiconductor substrate, characterized in that an inert gas is blown to the center of the substrate while the substrate is being rotated, and after the blowing of the inert gas is stopped, the semiconductor substrate is further rotated.

Examples of semiconductor substrates include wafers, ceramic substrates, glass substrates and the like. The polyimide precursor composition used in the present invention is, for example, N-methyl-2-
Pyrrolidone, N, N-dimethylacetamide, N, N-
A diamine component such as 4,4′-diaminodiphenyl ether is dissolved in an organic solvent such as dimethylformamide, and then an organic tetrabasic acid diamine such as 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride is dissolved. It is a composition obtained by adding an anhydride component and stirring and reacting at a temperature of 50 ° C. or lower, more preferably around room temperature or lower. Examples of commercially available polyimide precursor compositions include PIQ,
PIX (both are trade names manufactured by Hitachi Chemical Co., Ltd.) and the like.

A polyimide resin film is prepared by adding a solvent to the above polyimide precursor composition, stirring the mixture at a temperature of 50 to 80 ° C., adjusting the viscosity to a value suitable for use, and spin-coating on a semiconductor substrate to form a hot plate. 100 with a hot air dryer
It is obtained by heat-treating at a temperature in the range of to 350 ° C. for 3 hours or less and subjecting to dehydration ring closure.

The method of the present invention is performed, for example, as follows. First, the polyimide precursor composition is dropped by a dispensing method from the nozzle tip to the central portion of the semiconductor substrate surface and spin-coated. Slow spin of semiconductor substrate (20
˜2000 rpm; press pin), and at the same time, an inert gas is blown onto the polyimide precursor composition at the center of the semiconductor substrate surface from a pipe fixed to the nozzle. The inert gas is not particularly limited, but nitrogen gas is usually used.

When the inert gas is sprayed, the distance between the pipe and the surface of the polyimide precursor composition is 2 to 15 mm.
The range of 5 to 10 mm is more preferable. The rotation time varies depending on the film thickness of the polyimide resin film to be formed, etc., but is preferably within 15 seconds. The flow rate of spraying the inert gas is 0.2 to 6 Nl
/ Min is preferred. If the flow rate of the nitrogen gas is too high, the polyimide precursor composition will scatter during spin coating to cause pinholes, etc., and on the contrary, the uniformity of the thickness of the polyimide resin film in the surface of the semiconductor substrate tends to be poor. is there. Furthermore, after the spraying of the inert gas is completed, the substrate is rotated at a rotation speed and for a time period at which a predetermined film thickness is obtained, and spin coating is continuously performed.

The present invention will now be described in more detail with reference to the drawings. FIG. 1 is a process chart showing one embodiment of the method of the present invention. In FIG. 1, first, in the step (a), the polyimide precursor composition 4 is dropped from the dispensing nozzle 3 to the central portion of the surface of the semiconductor substrate 2 adsorbed by the spin head 1 in the coater cup 10.

Next, in the step (b), from the Teflon pipe 6 fixed to the dispensing nozzle 3,
Spin coating (press pin) is started by the rotation of the spin head 1 at the same time when the inert gas is started to be blown to the central portion of the dropped polyimide precursor composition 4, and the polyimide precursor composition 4 becomes the end portion of the surface of the semiconductor substrate 2. Flowed out in the direction.

After performing the inert gas spraying process for a predetermined time, this process is stopped, and in the step (c), the substrate is further continuously rotated. At this time, a part of the polyimide precursor composition 4 may sneak from the semiconductor substrate 2 to the back surface side of the semiconductor substrate 2, so that the cleaning liquid 2 sprayed from the back surface cleaning nozzle 5 (for example, N, N′-dimethylformamide). And a mixture of methanol). Thereby, the thickness of the polyimide precursor composition 4 on the surface of the semiconductor substrate 2 is made uniform.

Finally, in step (d), the semiconductor substrate 2 coated with the polyimide precursor composition 4 is heat-treated with a hot plate 8 to form a polyimide resin film 9.

[0015]

EXAMPLES The present invention will now be described in more detail by way of examples, which should not be construed as limiting the invention.

Example 1 54.05 g of 4,4'-diaminodiphenyl ether
(0.27 mol) and 1,3-bis (aminopropyl)
Tetramethyldisiloxane 7.45 g (0.03 mol)
Was thoroughly stirred and dissolved in 800 g of N-methyl-2-pyrrolidone, and then 48.33 g (0.15 mol) of 3,3 ', 4,4'-benzophenonetetracarboxylic acid dianhydride and pyromellitic acid were dissolved. 32.71 g of dianhydride (0.1
(5 mol) was gradually added and reacted at room temperature for 6 hours. Then, the mixture is stirred at 80 ° C. for 13 hours, and the viscosity is 80 poise (25
C.) and a resin content concentration of 18.6% by weight to obtain a polyimide precursor composition.

Then, the polyimide precursor composition was spin-coated as follows according to the process chart shown in FIG. 1 to form a polyimide resin film on the surface of a silicon wafer as a semiconductor substrate. First, the silicon wafer 2
[Wafer size: 15.24 cm (6 inches)] The dispensing nozzle 3 was moved to the center of the surface, and 5 g of the polyimide precursor composition 4 obtained above was dropped [(a) of FIG. 1]. Immediately after the dropping, nitrogen gas was started to be blown from the pipe 6 fixed to the dispense nozzle to the center of the polyimide precursor composition 4 at a flow rate of 2 Nl / min.
At the same time, spin coating (press pin) was performed by rotating at 1000 rpm for 10 seconds. During this time, the nitrogen gas is continuously blown to promote the volatility of the solvent contained in the polyimide precursor composition 4 [(b) of FIG. 1].

Next, after the blowing of nitrogen gas was completed, the coating was further spun by rotating at 3800 rpm for 30 seconds to spread the polyimide precursor composition on the entire surface of the silicon wafer 2. Next, by continuously rotating at 1500 rpm for 10 seconds and further rotating at 2300 rpm for 5 seconds, the composition wrapping around the back surface of the silicon wafer 2 is washed with a mixed solution of N, N′-dimethylformamide and methanol. After the removal, it was rotated at 3000 rpm for 1 second to complete the spin coating treatment of the polyimide precursor composition 4 [(c) of FIG. 1]. Then, the silicon wafer 2 coated with the polyimide precursor composition 4 is coated with a hot plate 8 13
A heat treatment (pre-baking) was performed at 0 ° C. for 90 seconds to form a 7.8 μm-thick polyimide resin film 9 [(d) of FIG. 1].

For the polyimide resin film 9 on the obtained semiconductor substrate 2, 17 points in radius of the silicon wafer 2 (using an interference film thickness meter (manufactured by Dainippon Screen Mfg. Co., Ltd., Lambda Ace, STM-602)) (5mm interval from the center of the board)
The thickness of the film was measured, but no extreme depression was found in the center of the silicon wafer 2, and the film thickness distribution was 0.1 μm in the range value.
Was a uniform film.

Further, a phenol novolac-based positive resist layer (manufactured by Tokyo Ohka Kogyo Co., Ltd., trade name OFPR-5000) was formed on the above polyimide resin film by spin coating, and then a g-line stepper (produced by Canon Inc., trade name). FP
A-1550) by a known photo-etching technique using an aqueous tetramethylammonium hydroxide solution NMD-3 (concentration: 2.38% by weight, manufactured by Tokyo Ohka Kogyo Co., Ltd.) at 23 ° C. By the paddle method for 90 seconds, the positive resist layer is developed and the polyimide resin film is etched at the same time.
By patterning m-square via holes and 80 μm scribe lines, all semiconductor devices (dimensions: 5.5 × 13.6)
(mm), a uniform polyimide resin film pattern could be formed.

Comparative Example 1 The same operation as in Example 1 was carried out except that the polyimide precursor composition 4 was not sprayed with nitrogen gas during spin coating. The obtained polyimide-based resin film on the silicon wafer had a thickness of 0.5 μm thin within a radius of 10 mm from the center of the silicon wafer and had a dent. Further, as a result of developing and etching in the same manner as in Example 1 and confirming the pattern shape, the via hole size is 110 in average in the area within 8 mm from the center of the silicon wafer.
The width was as wide as μm, overetching was observed, and variations in the pattern dimensions of the polyimide resin film within the surface of the silicon wafer were recognized.

Comparative Example 2 The same operation as in Example 1 was carried out except that nitrogen gas was continuously blown to the upper part of the polyimide precursor composition after the press pin treatment during spin coating. The polyimide-based resin film on the obtained silicon wafer had extremely concave and streak-like patterns near the center of the silicon wafer, and the film thickness on the surface of the silicon wafer was not uniform.

[0023]

By applying the polyimide precursor composition according to the method of the present invention, it is possible to form a polyimide resin film having a uniform thickness up to the end without a dent in the center of the semiconductor substrate, Since it is possible to form a pattern with uniform dimensions in the surface of the semiconductor substrate when manufacturing the pattern,
The yield of semiconductor elements can be significantly improved by patterning the polyimide resin film.

[Brief description of drawings]

FIG. 1 is a process drawing showing an embodiment of the present invention.

[Explanation of symbols]

 1 Spin Head 2 Semiconductor Substrate 3 Dispensing Nozzle 4 Polyimide Precursor Composition 5 Backside Cleaning Nozzle 6 Pipe 7 Cleaning Liquid 8 Hot Plate 9 Polyimide Resin Film 10 Coater Cup

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B05D 7/24 302 X 7415-4F G03F 7/16 502

Claims (3)

[Claims] 1. When a polyimide precursor composition is applied to the surface of a semiconductor substrate by a spin method, the polyimide precursor composition is dropped onto the center of the surface of the semiconductor substrate.
A method for applying a polyimide precursor composition to a semiconductor substrate, which comprises spraying an inert gas onto a central portion while rotating the substrate, stopping the spraying of the inert gas, and further rotating the semiconductor substrate. 2. The method for coating a polyimide precursor composition according to claim 1, wherein the inert gas is nitrogen gas. 3. An inert gas is blown at a distance of 2 to 15 mm from the surface of the polyimide precursor composition for 0.2 to 6 mm.
The method for applying a polyimide precursor composition to a semiconductor substrate according to claim 1 or 2, which is performed at a flow rate of Nl / min.