JPS5949696B2 - Sealing method for semiconductor elements - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for sealing semiconductor elements.

Generally, photosensitive semiconductor devices such as solid-state image sensors are based on silicon MOS type integrated circuit technology.
In order to maintain this property, the container must be airtight.
In this case, the semiconductor element consists of a chip, a substrate on which the chip is attached, and a lid that covers the substrate, and the substrate and the lid form a so-called container. A part of the container is made of glass, and low-temperature sealing is required in consideration of the heat resistance of the chip in order to seal it with the ceramic that is the substrate material.Organic adhesive such as epoxy resin or low melting point solder glass is used. These seals require heating between 150°C and 400°C, but as the temperature rises, the pressure inside the container increases, and the internal gas partially escapes to push out the adhesive or sealant. This creates a gap, deteriorates the reliability of the seal, and in extreme cases leads to the formation of a complete leak bath. Although this drawback can be alleviated to some extent by improving the flatness of the bonding surface and increasing the bonding pressure, a decrease in yield is unavoidable and it becomes expensive. This invention solves the above-mentioned conventional drawbacks.
It is an object of the present invention to provide a method for sealing semiconductor elements in which the internal pressure of a container during sealing heating is kept equal to the external pressure.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

Generally speaking, in a semiconductor device such as a charge transfer device, which is a solid-state image sensor, as is clear from the figure, a chip (not shown in the figure) is attached to one surface of a substrate (stem) 1 made of ceramic, and a substrate 1 is attached to cover the chip. A lid part 2 made of glass is hermetically sealed on top with an adhesive 3 such as epoxy resin. The substrate 1 and the lid 2 form a so-called container. Now, when sealing the charge transfer device as described above, first, the chip is bonded to one side of the substrate 1, and then the lid part 2 coated with adhesive 3 is placed on the sealing surface side to a predetermined size. Apply a pressure of about 2 to 3 to 9/(-77f) using a suitable pressure jig.

Adjustment of this pressure is not critical. The simplest pressing jig is a spring or spring 4. Of course, if the heating temperature is high, it is necessary to use a heat-resistant elastic material for the spring 4. With the substrate 1 and the lid part 2 under pressure, sealing is finally performed.The simplest structure of the sealing jig used at this time is the flange type as shown in the figure. be.

That is, the container to be sealed, that is, the substrate 1 and the lid part 2 pressurized by the spring 4, are housed in the required quantity inside the two removable flanges 5 and 6, and between both sides of the flanges 5 and 6. Hold the copper packing T and tighten the bolts 8 around it, about 2
Maintain strength to withstand atmospheric pressure. This pressure needs to be adjusted depending on the heating temperature. Next, the sealing jig, that is, the flanges 5 and 6, is placed in a furnace heated and maintained at a predetermined temperature, and heated for a predetermined time.

During this time, it is desirable to measure the temperature of the flanges 5 and 6. After the heating process, it is taken out of the furnace and the flanges 5 and 6 are removed after it has cooled down to room temperature. In the above process, the pressure P1 inside the container and the pressure P inside the sealing jig are determined by PV-RT (P is pressure, V is volume, T is temperature, and R is a constant).
Since V is constant, P is proportional to the bottom, and P1 and P2
are always kept equal. Therefore, the gas inside the container will not escape to the outside. The sealing method of the present invention is constructed as described above and illustrated, and the internal pressure of the container during sealing heating is kept equal to the external pressure, so according to this method, flatness of the sealing surface is not necessary. The yield was 100%, and the problem with sealing was solved.

Further, the internal pressure of the container after sealing is 1 atm, and there is no risk of the internal pressure being reduced in the conventional method, and reliability is further improved. In the above example, the simplest sealing jig was explained, but the structure could be made even more complicated, such as by providing a pressure reducing valve (safety valve), or by using an easy-to-operate screw thread tightening method, or by modifying the shape. Various modifications can be considered, such as making it more attractive.

Also, the internal pressure after sealing is slightly higher than 1 atm.
Providing a pressure valve that can adjust the pressure inside the sealing jig, for example between 1 atm and 1.1 atm, is also effective as a means of increasing sealing reliability, since it is advantageous against moisture intrusion from outside the container. Therefore, the effects described in the above embodiments can be maintained in exactly the same way. Further, in the above embodiments, a charge transfer device was used as an example of a semiconductor device, but it goes without saying that the present invention is applicable not only to charge transfer devices but also to semiconductor devices in general. As explained above, according to the present invention, it is possible to provide a method for sealing semiconductor elements with great practical value.

[Brief explanation of the drawing]

The figure is a sectional view showing a method for sealing a semiconductor element according to an embodiment of the present invention. 1...Substrate, 2...One lid, 3...
...Adhesive, 4...Spring, 5,6...
・Flange, 1... Packing, 8...
··bolt.

Claims (1)

[Claims] 1. In a method for sealing a semiconductor element, the airtight container with a built-in semiconductor chip is constituted by a substrate on which a semiconductor chip is attached, and a lid part that covers the chip and is heat-sealed to the substrate with an adhesive. A lid is placed on the surface to be sealed via an adhesive, and the substrate and lid are pressed with a pressure jig, and then this is stored inside a sealing jig that can be sealed. Then, the sealing jig is placed in a heating furnace and heated to a predetermined temperature at which the substrate and lid are hermetically sealed with the adhesive, and then cooled to room temperature to embed the semiconductor chip. A method for sealing semiconductor elements, characterized by obtaining an airtight container.