JPH0287652A - Semiconductor storage device - Google Patents

Abstract

PURPOSE:To effectively prevent a soft error action to be caused by a radiation of alpha-rays without causing fluctuation in characteristics and a deterioration in quality of a memory cell by a method wherein an alpha-ray-absorbing layer is formed at an inner face of a ceramic package member surrounding a memory cell array pellet. CONSTITUTION:The following are contained: a ceramic package lower-part member 2 where a memory cell array pellet 1 is mounted inside a cavity at the surface; metal thin wires 3 which connect electrodes of the memory cell array pellet 1 to electrodes on the ceramic package lower-part member 2 individually; a ceramic package lid member 5 which is connected to the ceramic package lower-part member 2 via an adhesive material 4 and which airtightly seal the memory cell array pellet 1 together with the metal thin wires 3; organic films, e.g., polyimide layers 6, which have been applied individually to a sidewall of the cavity in the ceramic package lower-part member 2 surrounding the memory cell array pellet 1 and to an inner wall of the lid member 5. In this case, the polyimide films 6 are composed of a material manufactured so as not to contain uranium as far as possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device, and particularly to a ceramic package type semiconductor memory device mounting a large capacity memory.

[Conventional technology]

Conventionally, ceramic packaged semiconductor storage devices with large-capacity memory have a low uranium content on top of the pellet to prevent soft errors in memory cells caused by X-rays from radioactive substances such as uranium contained in the ceramic package. Polyimide or silicone with a concentration of 50μ to 200μ
Measures have been taken to apply the coating to a thickness of about μ.

[Problem to be solved by the invention]

However, the above-mentioned prior art has the following drawbacks because polyimide or silicone is directly coated onto the IC pellet.

(1) If polyimide or silicone is directly coated onto the pellet, stress is applied to the pellet surface, resulting in variations in memory characteristics.

(2) After coating polyimide or silicone directly onto the pellets, high-temperature treatment such as drying the solvent is required, and thermal stress is applied to the pellets, causing quality deterioration of the memory device.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a semiconductor memory device having a countermeasure against soft errors without causing characteristic fluctuations or quality deterioration of memory cells due to direct coating of an α-ray absorbing layer on a pellet. It is.

[Means to solve the problem]

According to the present invention, a semiconductor memory device includes a memory cell array pellet, a ceramic package lower member in which the memory cell array pellet is placed in a recess on an upper surface thereof, and a ceramic package lower member in which the memory cell array pellet is placed in a recess on the upper surface thereof. - a ceramic package lid member that hermetically seals the pellet; and a ceramic package lid member that surrounds the memory cell array pellet;
The package includes an α-ray absorbing layer made of an organic resin that coats the side wall of the recess of the package lower member and the inner wall surface of the lid member.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view of a ceramic package type semiconductor memory device showing one embodiment of the present invention. According to this embodiment, the semiconductor memory device of the present invention includes a memory cell array,
pellet 1 and this memory cell array pellet 1
a ceramic package lower member 2 that is placed in a recess on the upper surface, a thin metal wire 3 that connects the electrodes of the memory cell array pellet 1 and the electrodes on the ceramic package lower member 2, and an adhesive 4. A ceramic package lid member 5 which is bonded to the ceramic package lower member 2 through the ceramic package lid member 5 to hermetically seal the memory cell array pellet 1 together with the thin metal wire 3;
Ceramic package lower member 2 surrounding pellet 1
A polyimide film 6 having a thickness of 50 to 200 μm is deposited on the side wall of the recess and the inner wall of the lid member 5, respectively.

Here, the polyimide film 6 is made of a material made so as not to deplete uranium as much as possible, and is less than a few hundredths of the uranium concentration of 10 to 500 ppB (for example, 0.1 ~0.5ppB) is used.

In the case of such a package structure, since the α rays emitted from the ceramic package members 1 and 2 toward the pellet 1 reach a depth of at most 50 μm within the polyimide film 5, the softness of the memory cell due to the α rays is・
The occurrence of errors is effectively suppressed.

FIG. 2 is a sectional view of a ceramic package type semiconductor memory device showing another embodiment of the present invention.

According to this embodiment, the ceramic package lower member 2
A polyimide film 6 attached to the side walls of the recess is formed to have a height exceeding the depth of the recess. This results in
α rays from the side surface of the package lower member 2 can be absorbed even more effectively.

Although the case where polyimide is used as the α-ray absorbing material has been described above, it is also possible to use silicone or other organic resins.

〔Effect of the invention〕

As explained in detail above, according to the present invention, the memory
The 9-wire absorbing layer on the inner surface of the ceramic package surrounding the cell array pellet has the advantage of eliminating the conventional mechanical and thermal stresses on the pellet surface, thereby improving memory cell performance. Soft error operations of memory cells due to alpha radiation from uranium contained in ceramic package members can be effectively prevented without causing characteristic fluctuations or quality deterioration.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a ceramic package type semiconductor memory device showing one embodiment of the present invention, and FIG. 2 is a cross-sectional view of a ceramic package type semiconductor memory device showing another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Memory cell array pellet, 2...Ceramic package lower member, 3...Metal thin wire, 4
... Adhesive material, 5. Ceramic package lid member, 6. Polyide film.

Claims (1)

[Claims] A memory cell array pellet, a ceramic package lower member in which the memory cell array pellet is placed in a recess on a top surface, and a ceramic package lid that hermetically seals the memory cell array pellet. and an α-ray absorbing layer made of an organic resin that coats the side wall of the recess of the ceramic package lower member surrounding the memory cell array pellet and the inner wall surface of the lid member, respectively. Semiconductor storage device.