JP2513018B2 - Semiconductor integrated circuit and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor integrated circuit including a photosensitive element sealed with a translucent resin so that light from the outside of the photosensitive element is incident, and a method for manufacturing the same. Regarding

[Conventional technology]

In order to package a semiconductor integrated circuit in which a light sensitive element and a circuit portion for processing the signal are formed on the same substrate, there is a method of using a container that allows light from the outside to enter the light sensitive element portion. Molding with a translucent resin makes it possible to reduce the cost.

[Problems to be Solved by the Invention]

When a semiconductor substrate containing a photosensitive element is molded into a translucent resin, it is not possible to maintain translucency by mixing additives such as adhesion enhancers into the resin, and wiring on the surface of the semiconductor substrate In addition, since there are irregularities, peeling and cracks are likely to occur in the mold resin, the optical characteristics of the photosensitive element fluctuate greatly, and the appearance defect rate is as low as about 50%. Further, during use, progressive defects due to the resin also occurred, and there was a problem in terms of reliability.

The object of the present invention is to prevent peeling and cracks at the interface between the semiconductor substrate and the mold resin, which are frequently generated in the prior art, to stabilize the optical characteristics of the photosensitive element included therein, and to prevent progressive defects. An object of the present invention is to provide a semiconductor integrated circuit having improved reliability and a method for manufacturing the same.

[Means for solving the problem]

To achieve the above object, a semiconductor integrated circuit according to the present invention has a film thickness of 2 μm or more in contact with the surface of a photosensitive element portion of a semiconductor substrate packaged with a transparent casting resin.
It is assumed that a light-transmissive resin having a range of 20 μm or less is applied, and a light-shielding resin is applied in contact with the surface of the semiconductor substrate other than the photosensitive element portion. Further, the method for manufacturing a semiconductor integrated circuit according to the present invention includes a step of applying a light-shielding polyimide resin to the surface of the semiconductor substrate when packaging the semiconductor integrated circuit substrate including a photosensitive element with a resin, and the light-shielding polyimide resin. Patterning to remove the light-shielding polyimide resin on the surface of the light-sensitive element, applying light-transmitting polyimide to flatten the surface, and molding a light-transmitting casting resin around the substrate. And a process.

[Action]

If the thickness of the translucent resin film as an inner coat applied on the light-sensitive element is 2 μm or less, the element surface is not sufficiently covered due to the variation in the film thickness, and the adhesion and the relaxation of strain are reduced. It is too thin and may cause peeling. When the thickness is 20 μm or more, the uniformity of the film quality after curing is insufficient, the reactions such as removal of internal solvent and water, and the polymerization reaction do not proceed sufficiently, and an increase in leakage current is observed. When a polyimide resin that is translucent at least on the surface of the photosensitive element is used as the resin to be applied, the polyimide resin has good adhesion to organic substances and inorganic substances, and therefore adheres well to the substrate surface. Furthermore, when a translucent resin such as an epoxy resin is molded thereon, the casting resin adheres well to the polyimide resin surface, and peeling or cracking does not occur.

〔Example〕

FIG. 1 is an enlarged view of an end portion of a semiconductor substrate according to a reference example of the present invention. The metal wiring 3 and the pad portion 4 are provided on the surface of the silicon substrate 1 on which the elements including the photosensitive element 2 are formed, and the portion other than the pad portion is covered with a CVD protective film 5 such as a nitride film. The substrate 1 is fixed on the mount portion 6 of the lead frame, and is connected to the pad portion 4 and the wire bonding portion of the lead frame (not shown in FIG. 1) by the conductor wire 7. Then, a transparent polyimide 10 having a concentration of 5% and using dimethylacetamide as a solvent is dripped on the periphery of the substrate 1 and on the substrate 1 in a total amount of 50 μl while scanning the nozzle 8 of the microdispenser. After the dropping, leave for 1 hour in a nitrogen stream and heat. Heating in the oven
By heating at 100 ° C. for 1 hour and at 200 ° C. for 1 hour, a translucent polyimide film 11 having a thickness of 2 μm or more and 20 μm or less and a refractive index of 1.7 is formed on the substrate. As a result, the wiring on the substrate 1
A film covering the wire bonding portion and extending on the frame 6 around the substrate is formed, and flattening on the substrate surface and mitigation of the step between the frame surface are achieved.

Further, the insulating film 12 is applied to the back surface of the frame mount portion 6 by using a roll coater and heated to form the insulating film 12. It is effective to perform heating at the same time as heating the polyimide film on the surface. The insulating film 12 is not limited to the polyimide film and does not need to have a light-transmitting property, but it is necessary to select a material having good adhesion to the metal and the casting resin. The silicon substrate mounted on the lead frame is then housed in a mold and molded with a translucent epoxy resin 13 having a refractive index of 1.55 as shown in FIG. Most of the wire bonding portion of the lead frame connected by the bonding wire 7 projects out of the resin 13 to form the metal terminal 14. In this packaging, the combination of the refractive indexes is 1.55 / 1.77, the loss due to reflection of external light until reaching the photosensitive element is small, and the substantial sensitivity of the element is improved.

FIG. 3 is an enlarged view of the edge portion of the semiconductor substrate according to the embodiment of the present invention. First, a light-shielding polyimide is applied on the surface of a substrate with a spin coater, patterned by a photo process, and cured by curing the casting resin for 30 minutes at 100 ° C., 200 ° C. and 350 ° C. to be cured to form a light-shielding polyimide film 15. At the time of patterning, a window is opened on the photosensitive element 2 and the pad portion 4 so that the light-shielding polyimide film 15 does not exist. A suitable thickness of this polyimide film 15 is about 2 μm. Next, use a spin coater to coat the entire surface with translucent polyimide, leave it in a nitrogen stream for 1 hour, and then in an oven.
Cure and cure at 100 ℃, 200 ℃, 350 ℃ for 30 minutes each 2
A coating 11 having a thickness of 20 μm is formed. Then, patterning having a window on the pad portion 4 is performed using a normal photoresist. Continuing on, the film 11 on the pad is removed from this window using hydrazine, and the photoresist film is removed using OMR stripper, trade name, manufactured by Tokyo Ohka Co., Ltd., and baked at 350 ° C for 30 minutes. . As a result, the CVD film 5 as the substrate surface protection film is not required, and the light-shielding and translucent polyimide films 15 and 11 also serve as the surface protection film. Further, the light-shielding polyimide film does not need to be shielded by the metal film in the portion other than the photosensitive element. The exposed pad portion 4 is connected to the wire bonding portion of the lead frame by the conductive wire 7. The insulating resin is applied to the back surface of the lead frame mount portion 6 by a roll coater, and the insulating film 12 is formed by heating at 100 ° C. for 30 minutes and 200 ° C. for 30 minutes, as in the case of FIG. After that, the same applies to resin molding as shown in FIG.

FIG. 4 shows a case where a translucent polyimide resin is applied to a thickness of 1 μm, the coating film is peeled off at the position A of the photosensitive element, there is no peeling at the portion B, and the sensitivity is at the peeled portion A. It is lower than that of the part B, indicating that a film thickness of 1 μm is too thin. Fig. 5 is a comparison of leakage current with respect to polyimide film thickness. The value (relative value) obtained by dividing the constant by the leakage current decreases when the film thickness exceeds 20 μm, and increases when the film thickness is too thick. I understand.

From the above results, it is clear that when a polyimide film is used as the translucent inner coat, the film thickness needs to be 2 to 20 μm, but a coating film of silicone resin or acrylic resin is used instead of the polyimide film. The same result is obtained when is used as the inner coat.

〔The invention's effect〕

According to the present invention, a coating film made of a light-transmissive resin, particularly a polyimide resin, is inner-coated on the light-sensitive element of a semiconductor substrate of a semiconductor integrated circuit that includes the light-sensitive element and is packaged by casting of a light-transmissive resin. By using as
Unlike the case of molding a translucent resin for casting, which can flatten the substrate surface and does not add an adhesion enhancer, and directly contact the semiconductor substrate, the adhesion of the inner coat film to organic and inorganic substances and the surface flatness Due to the effect of improvement, peeling and cracking of the casting resin can be prevented, yield can be improved, and reliability can be improved. Furthermore, these effects can be ensured by limiting the film thickness of the inner coat film.

In addition, since the polyimide film can also be used as the surface protective film and the light-shielding polyimide film can be replaced with the light-shielding film for the portion other than the light-sensitive element part, a great economic effect can be obtained in manufacturing a light-transmissive resin-molded light-sensitive semiconductor integrated circuit. Can be given.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of an edge portion of a semiconductor substrate in a reference example of the present invention, FIG. 2 is a sectional view of a semiconductor integrated circuit according to an embodiment of the present invention, and FIG. 3 is an edge portion of a semiconductor substrate in an embodiment of the present invention. FIG. 4 is an enlarged cross-sectional view of FIG. 4, and FIG. 4 is a relationship diagram between the position of the photosensitive element and the photoresponse time when the thickness of the polyimide film is thin.
The figure is a relationship diagram between the film thickness of the polyimide film and the magnitude of the leakage current. 1: Silicon substrate, 2: Photosensitive element, 3: Wiring, 4: Pad part,
11: translucent polyimide film, 13: cast translucent epoxy resin,
15: Light-shielding polyimide film.

Claims (2)

(57) [Claims] 1. A light-transmitting resin having a film thickness of 2 μm or more and 20 μm or less is applied in contact with the surface of a light-sensitive element portion of a semiconductor substrate packaged with a light-transmissive casting resin, except for the light-sensitive element portion. 2. A semiconductor integrated circuit, wherein a light-shielding resin is applied to the surface of the semiconductor substrate. 2. A step of applying a light-shielding polyimide resin to the surface of a semiconductor substrate when packaging a semiconductor integrated circuit substrate including a light-sensitive element with a resin, and patterning the light-shielding polyimide resin to form a light-sensitive element. Characterized in that it has a step of removing the light-shielding polyimide resin on the surface of the portion, a step of applying a transparent polyimide to flatten the surface, and a step of surrounding the substrate and molding a transparent casting resin. The method for manufacturing a semiconductor integrated circuit according to claim 1.