JP2502377B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention includes a light-receiving element, and at least a light-transmissive resin is cast on a light-incident surface of the light-receiving element via a light-transmissive polyimide intermediate coating film. The present invention relates to a method for manufacturing a semiconductor device.

[Prior Art] To seal a semiconductor substrate including a light receiving element with resin,
At least the region where the light receiving element is formed needs to cover the semiconductor substrate with a translucent resin, which is usually an epoxy resin, so that light is incident on the light receiving element. In that case, if the translucent resin and the substrate or the protective film on the substrate have poor adhesion and the resin is peeled off, such defects are seen through from the outside, resulting in poor appearance. In order to prevent such a defective appearance, a semiconductor substrate or element protection film and a translucent polyimide intermediate coating film having good adhesion to the casting resin are interposed.

[Problems to be Solved by the Invention]

After applying the polyimide intermediate coating film to the surface of the semiconductor substrate, the intermediate coating film is patterned to expose the pad portion and the like on the substrate. If patterning is performed by photolithography, then the photoresist film must be removed. Conventionally, isopropyl alcohol has been used for removing the resist. However, the removal of the resist with isopropyl alcohol takes a long time to remove, and the resist residue is likely to occur. There is plasma ashing as another technique, but in this method, the polyimide film itself is damaged during ashing, the surface is apt to be rough, and the optical characteristics of the light receiving element are deteriorated, or the appearance defect rate is lowered. was there.

An object of the present invention is to provide a method for manufacturing a semiconductor device, which removes a resist film used for patterning a polyimide intermediate coating film in a short time and does not damage the polyimide film.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention is directed to a semiconductor device including a light-receiving element, in which a light-transmissive resin is cast on at least a light-incident surface of the light-receiving element via a light-transmissive polyimide intermediate coating film. In the manufacturing method, the resist film used for patterning the intermediate coating film is removed before the resin casting by using a mixed solution of isopropyl alcohol and acetone having a volume ratio of isopropyl to acetone of 70:30 to 95: 5. I shall.

[Action]

Acetone has a high resist removing ability, but it also corrodes the polyimide and makes the polyimide film cloudy. By mixing it with isopropyl alcohol and acetone in a volume ratio of 95: 5 or more, the removal capacity is increased and the removal time is shortened.
The remaining resist does not occur. However, when the volume ratio of acetone to the isopropyl alcohol is 70:30 or more, the surface of the polyimide film is damaged, resulting in cloudiness and deterioration of optical characteristics.

〔Example〕

FIG. 1 is an enlarged view of an end portion of a silicon substrate according to an embodiment of the present invention. An element including a light receiving element 2 is formed on the silicon substrate 1, and a metal wiring 3 and a pad portion 4 connected to the element electrode are formed on the surface. And
Except for the pad portion, it is covered with a protective film 5 such as a nitride film formed by CVD. On the upper surface of the substrate 1, a light-transmitting polyimide having a concentration of 12% and using N-methylpyrrolidone as a solvent is formed.
Spin coating at 3000 rpm for 30 seconds to form a translucent polyimide film 6 having a thickness of 2.5 μm. Next, the temperature is gradually raised from 100 ° C, and half-cure is performed at 150 ° C for 10 minutes and 200 ° C for 30 minutes. Further, a film 7 of positive photoresist OFPR-800 manufactured by Tokyo Ohka Co., Ltd. is applied with a viscosity of 30 cp, and the pad portion 4
Only expose the top. After exposure Developer NM manufactured by Tokyo Ohka Co., Ltd.
D-3 (tetramethylammonium hydroxide
2.38%), the photoresist film 7 is developed and the polyimide film 6 is simultaneously etched by immersion for 30 ± 5 seconds. Next, after washing with water and drying, using a mixed solvent of isopropyl alcohol and acetone in a volume ratio of 80:20,
Immerse for 2 minutes in the solvent bath to which ultrasonic waves of 28 kHz, 200 W are applied, and further for 1 minute in the same solvent in another tank. Thereby, the resist film 7 is removed and then dried. Before and after the step of removing the resist film 7, the variation in the film thickness of the polyimide film 6 was within ± 300 Å. For the final cure, gradually raise the temperature from 200 ° C, and
Heat at 00 ° C for 1 hour.

FIG. 2 shows a semiconductor device after the silicon substrate 1 shown in FIG. 1 is resin-sealed. The substrate 1 is fixed on the mount portion 81 of the lead frame after the dicing, and the pad portion of the substrate and the wire bonding portion 82 of the lead frame are connected by the conductive wire 9. On the back surface of the lead frame mount portion 81, an insulating film 10 made of, for example, polyimide is applied by a dipping method and cured by heating at 100 ° C. and 200 ° C. for 30 minutes respectively. The insulating film 10 is not limited to a polyimide film and does not need to have a light-transmitting property, but it is necessary to select a film having good adhesion to a casting resin coated in a later step.
In this way, the silicon substrate 1 is housed in a mold of a lead frame and a translucent epoxy resin 11 having a refractive index of 1.56 is cast. Most of the wire bonding portion of the lead frame connected to the pad portion of the substrate 1 by the conductive wire 9 projects out of the casting resin 11 to form an external terminal. Since the refractive index of translucent polyimide is 1.687, which is close to the refractive index of 1.56 of epoxy resin, there is little loss due to external light being reflected by the casting resin 11 and the intermediate coating film 6 on the substrate 1, The substantial sensitivity of the light receiving element 2 is improved.

FIG. 3 shows changes in the resist removal time when the mixing ratio of isopropyl alcohol and acetone as a solvent for removing the positive photoresist film 7 was changed. It can be seen that the removal time becomes constant when the amount of acetone exceeds 10% by volume.

〔The invention's effect〕

According to the present invention, by adding 5% or more of the total volume of acetone to isopropyl alcohol as a solvent for removing the resist film when patterning the translucent polyimide intermediate coating film, the resist film removal time can be reduced. It was possible to prevent the polyimide film from being damaged by shortening the amount to 2.5 times or less, preventing the resist residue from occurring, and suppressing the acetone to 30% or less of the total volume. As a result, the appearance defect in the manufacturing process is significantly reduced, and a great economic effect can be exerted on the manufacturing of the semiconductor device including the light receiving element sealed with the translucent resin.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of a silicon substrate in a polyimide intermediate coating film patterning process according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view of the manufactured semiconductor device, and FIG. 3 is a relationship diagram between the acetone content in the resist removal solvent and the resist film removal time. 1: Silicon substrate, 2: Light receiving element, 4: Pad part, 5: Protective film,
6: Translucent polyimide film, 7: Photoresist film.

Claims (1)

(57) [Claims] 1. A method for manufacturing a semiconductor device, comprising a light receiving element, wherein a light transmitting resin is cast on at least a light incident surface of the light receiving element via a light transmitting polyimide intermediate coating film. The resist film used for the patterning of the intermediate coating film was made to have a volume ratio of isopropyl to acetone of 70 to 30.
To 95: 5 mixed solution of isopropyl alcohol and acetone to remove the semiconductor device.