JPS61210658A - Resin sealed type semiconductor memory device - Google Patents

Abstract

PURPOSE:To make a software error rate less than 75 fits, by performing direct sealing by using a sealing resin including a filler, in which the amount of inclusion of uranium and thorium is less than 0.2 p.p.b. CONSTITUTION:A semiconductor memory element having the integration degree of 16 K bits or more is directly sealed by a resin including a high purity filler. In the sealing resin, the amount of inclusion of uranium and thorium is less than 0.2 p.p.b. When the total amount of inclusion of uranium and thorium is made less than 0.2 p.p.b, the occurring rate of software errors can be reduced to less than 75 fits. Since the element is directly sealed, the forming work of a shielding film is not required. Therefore only the sealing work is enough and cracks are hard to occur in the sealing body even in heating cycles and the like. Thus, the highly reliable semiconductor memory element can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resin-sealed semiconductor memory device having an integration degree of 16 bits or more.

[Prior art]

1978, 16th Annual Proceedings, International Reliability Physics Symposium, April 18-20, 1978,
San Diego, U, S, A33-40 (16th A
nual Proceedings of 1978
International Reliabiljty
Physics Symposium.

April 18-20.1978. SanDieg
o, U, S, A+pp33-40')
New Physical Mechanism Huo Soft
Errors in Dynamic Memories (A Ne
wPhysical Mechanjsm for 5
of Errors in Dynan+icMem
According to the authors), when alpha rays are incident on a highly integrated semiconductor memory device, the transition from “1” to “0” or 11
Information reversal from 0” to “1”, so-called soft error (so
ft error) has been reported to occur. This alpha ray is produced by ceramics, which is the sealing material for semiconductor memory devices.
The main source of radiation is trace amounts of uranium and thorium contained in metals or molding resins. Therefore, if uranium and thorium are removed from this sealing material, the above-mentioned problem will be solved. In the above report, attempts were made to reduce the content of uranium and thorium by refining the sealing material, but it was reported that it was extremely difficult industrially to achieve a high degree of refining. There is.

He also stated, ``If you apply something 30 to 40 μm thick on the surface of a semiconductor chip, the alpha rays will stop.The candidate material for Co. 1 would be a polyimide-based organic polymer material.'' (Nikkei Electronics: NIKKEI
ELECTRONIC 3: August 6, 1979.

58-72). However, forming a coating film not only has the drawback of increasing the number of work steps, but also due to the compatibility between the coating film and the sealing resin on it and the difference in thermal expansion coefficient between the two.
The reliability of adhesion at the interface is an issue.

[Problem that the invention seeks to solve]

As mentioned above, solving the problem of software 1~ error by refining the sealing material itself was thought to be practically difficult.

However, while carrying out various studies on the purification of sealing materials, the present inventors discovered that when the content of uranium and thorium falls below a certain value, the soft error phenomenon caused by alpha rays rapidly decreases or does not occur. discovered.

The purpose of the present invention is to reduce soft errors caused by alpha rays.
Our goal is to provide a resin-sealed semiconductor memory device with a high degree of integration of 6 bits or more, especially for software 1 to 7 with an error rate of 7.
The goal is to provide items of 5 feet or less.

[Means for solving problems]

The present invention provides filler-containing sealing resin for sealing a semiconductor memory element having a high degree of integration that causes soft errors due to alpha rays, with a filler-containing sealing resin having a uranium and 1 to lium content of 0, 2 P, p.
, b or less is directly sealed in a semiconductor memory device.

As mentioned above, the content of uranium and thorium is 0,2
By directly sealing with resin below p, p, b,
It is possible to obtain a highly integrated semiconductor memory device in which the incidence of soft errors is reduced to 75 feet or less.

Errors in software 1 can be corrected by electrical circuit means, thereby ensuring the reliability of equipment such as computers.

However, as is generally said, the software error rate of the memory element itself exceeds 1000 feet.
In such cases, it becomes difficult to ensure the reliability of equipment using electric circuit means. Therefore, the software of the memory element itself
It is important to suppress the error rate to within 1/1000 fins. In particular, the present invention was made based on the discovery that by reducing the total amount of uranium and thorium to 0.2 p, p, b or less, the occurrence rate of software 1 errors could be reduced to 75 feet or less. .

Furthermore, since the present invention directly seals the element, there is no need to form a shielding film. Therefore, only the sealing work is required.''
There are advantages such as the fact that cracks do not easily occur in the sealed body even after a B1 cycle, etc., and a highly reliable semiconductor memory element can be obtained.

The resin referred to in the present invention is a polymer such as a synthetic resin, natural resin, synthetic rubber, or natural rubber. Polymers obtained by synthesis can be synthesized with high purity relatively easily by purifying monomers by distillation, recrystallization, etc., and then polymerizing them. Also.

Specific examples of resin materials used in the present invention include polyimide, polyamide, polyamideimide, engineered poxy resin,
Examples include phenol resins, diallylphthalene resins, fluororesins, polyester resins, silicone resins, and polysilicate resins. -1- Various fillers are blended into the resin. Of course, the filler must be highly purified so that the uranium and thorium contents satisfy the above-mentioned conditions. That is, when sealed, the content of uranium and thorium in the sealed body is 0.2P.
, p, b It is necessary to purify the filler so that it is below. Here, examples of high-purity fillers include organometallic compounds such as silicon compounds such as tetramethylsilane, dimethyldimethoxysilane, trichlorosilane, tetraethoxysilane, dimethyldichlorosilane, and diphenyldichlorosilane, aluminum triisopropylate, and monomers. -5ee-Butoxyaluminum diisopropylate, aluminum tributylate, ethyl acetoacetate aluminum diisopropylate, aluminum compounds such as aluminum tris (ethylacetoacetate), zirconium compounds such as zirconium tetrakis acetylacetate, zinc salicylate, octane Zinc compounds such as zinc oxide, lead compounds such as lead octoate and lead tetraphenyl, and tin compounds such as tin octoate and tin tetraphenyl are purified by distillation, recrystallization, etc., and then heated in air or oxygen. Oxides or nitrides subjected to oxidation or plasma oxidation are suitable. In addition, it is also advantageous in practice to hydrolyze or to hydrolyze and polymerize a different type of raw material before oxidizing the raw material. For example, there is an advantage that volatilization of raw materials during heating can be prevented. Metal oxides synthesized in this way are generally in powder form and can be used as fillers as they are, but
Depending on the case, it may be further pulverized before use.

These metal oxide fillers can easily be obtained with extremely low contents of uranium and thorium, compared to commonly used fillers made of finely powdered natural products.

Other fillers include heat-ring-closed polyimide powder,
Polymers that do not have the ability to form a sealant by themselves, such as polyimidazopyrrolone powder and silicone rubber, can also be used as fillers. The use of a sealing material containing a filler is effective in preventing shrinkage during curing or cracking due to P1 to cycle, and in improving thermal conductivity (heat dissipation) and reducing the coefficient of thermal expansion.

Furthermore, known silane coupling agents such as aminosilane, epoxysilane, mercap-1-silane, and vinylsilane, surfactants such as fluorocarbon, etc. may be added to the resin as necessary. Of course, these additives also have a uranium and thorium content of 0 when used as a sealed body.
, 2 p, p, b or less.

[Effect]

Needless to say, the effect of the present invention is that by reducing the number of α-ray sources in the sealed body, the occurrence of soft errors can be prevented.

In the case of bipolar semiconductor memory devices, this can be applied to devices with a high degree of integration that has a memory capacity of 1 bit or more, but especially for MIS type semiconductor memory devices including MOS type semiconductor memory devices with a memory capacity of -6K bits or more, especially 6K bits or more. Since software 1 errors are more likely to occur in the case of a memory element having a memory capacity of 4 or more bits or more, it is more effective to apply this method to a memory element with such a degree of integration.

In the present invention, uranium (U) and thorium (Th)
The content is a value determined by known activation analysis. In the present invention, a neutron activation analysis method using a nuclear reactor was used. That is, 2δOU and 288Gh produced from the (n,y) reaction of 2-8♂U and 282Tl
undergoes β-decay with a half-life of 23.5 minutes, and each
It decays into Op u and 288U, and the γ-rays emitted at this time are measured and compared with the γ-ray count rate of a standard sample irradiated under the same conditions to quantify U and Th. The measurement conditions are as follows.

'G o (L i ) ul' conductor detector, 4000ch
Wave height analyzer, counting bjHili 500-60,000
sec.

Examples are shown below. Note that parts below refer to parts by weight; l'X also refers to -1°.Example 1 Commercially available 3,4-epoxycyclohexylmethyl-3,4
- Evoxin chlorhexane lupoxylate i mn
Hg, 50 parts vacuum distilled at 155-158°C;
1 mn Hg, 50 parts of vinyl cyclohexane dioxide vacuum distilled at 65-67°C, IIrfIIHg
, 77 parts of methylnadic anhydride (curing agent) distilled at 1-1-3 to 1.15°C, 3. w+ Hg, 118~
66 parts of hexahydrophthalic anhydride (curing agent) distilled at 122°C, 168 parts of ethyl silicate as filler
370 parts of a powder produced by distillation purification at ~170°C, hydrolysis, and heating at an air width of about 500°C for 4 hours, 2 parts of tetraphenylphosphonium tel~roughenineborate (hardening accelerator), γ- A high purity resin composition was prepared by mixing 2 parts of glycidoxypropyltrimethoxysilane (coupling agent). Activation analysis of this composition revealed that the uranium content was 0.04 p, p, +b, and the thorium content was 0.05 p, p, b or less.

Next, using this composition, memory capacity], 6 bits M
OS-type and RAM-type memory elements were directly sealed to a thickness of 3 cm, and heated at 150° C. for 3 hours to cure them, thereby manufacturing resin-sealed semiconductor memory devices.

When we measured the soft error rate of this memory device, we found that
35 feet (1 fit is 1
09 hours).

Conventional Example A sealing material was manufactured by using the same epoxy resin composition as used in Example 1 above without purification, and using commercially available unrefined powdered silica as a filler. The uranium content of this sealing material is 18 p, p, b, the thorium is 11 p,
It was p, b. Using this sealing material, a memory element was directly sealed in the same manner as in Example 1 and cured to manufacture a memory device. The soft error rate of the memory device is 3
．． It was a 5 x 10' fit.

Example 2 100 parts of ethyl acetoacetate aluminum diisopropylate purified by distillation at 165 to 175°C and 3 mm Hg were dissolved in 500 parts of isopropanol, 10 parts of water was added, mixed, and left for 1 day. . After that, it was heated to 150°C in an air atmosphere.

1 hour, 200℃, 1 hour, 300℃, 1 hour, 400℃
℃, 1 hour, 500℃, 1 hour, 600℃.

After oxidizing by heating at 700° C. for 1 hour, the mixture was rubbed lightly with an agate pestle to obtain a fine powder.

On the other hand, 4,4'-diaminodiphenyl ether recrystallized from n-butanol and pyromellitic dianhydride, which was recrystallized from acetic anhydride and purified by sublimation, were mixed in N-methylpyrrolidone, which was dried over phosphorus pentoxide and purified by distillation. A high purity polyamic acid varnish was obtained by reacting at an equimolar ratio.

The fine powder was mixed with the high purity polyamic acid face to obtain a resin composition. The weight ratio of the polyimide obtained from this and the fine powder was 40:60. This composition was used to directly seal a memory element in the same manner as in Example 1 to produce a resin-sealed semiconductor memory device.

The uranium content in the above polyimide resin composition is 0,
07 p, p-b, thorium content is 0, 05 P,
It was below p and b.

The soft error rate for this memory device was 60 fits.

Experimental Example 1 Commercially available unpurified fine powder silica was added to silicone using α,ω-dihydroxypolydimethylsiloxane produced by hydrolyzing distilled purified dimethyldichlorosilane and distilled purified ethyl silicate as a crosslinking agent, in a weight ratio. A silicone resin composition mixed at a ratio of 60:40 and containing 0.2% by weight of dibutyltin dilaurate was coated on the same memory element as in Example 1 to a thickness of 50 to 60 μm, and after being left for a while, the silicone resin composition was heated at 150°C. It was cured at the above temperature to form a shielding layer.

Thereafter, it was sealed with an epoxy resin molding material containing about 70% by weight of quartz glass powder. The resulting memory device had a soft error rate of 9.5×10” fit.

The total content of uranium and thorium in the shielding layer was 1.5 p, p, b.

Example 3 Only fine powder silica was used, using silica powder synthesized from the same distilled and purified ethyl silicate as used in Example 1, and the rest using the silicone resin composition of Experimental Example 1, at a weight ratio of 60:40. The memory element of Example 1 was sealed with this mixture. The soft error rate of the obtained device is 4
It was 0 feet. The uranium content of the resin composition is 0.05 p, p, b, and the thorium content is 0.05.
p, p, b or less.

Example 4 4.4'-diaminodiphenyl ether recrystallized from n-butanol, 4.4' recrystallized from acetic anhydride.
, 3.3'-biphenyltetracarboxylic dianhydride was dried with phosphorous pentoxide and then purified by distillation. A resin composition was obtained in which the same fine powder of aluminum oxide was blended in a ratio of 40 parts of the former to 60 parts of the latter.

This composition is applied to a bit D-RAM memory element at 64.
Coated to a thickness of 150 μm (baking conditions are 1.
(heated at 5350°C for 1 hour) for 1 hour at 200°C. ”2, the uranium content in the polyimide resin is 0, 1
1 p, p, b, thorium content is 0, 09 p, p
, b. The soft error rate of this LSI was 75 feet.

The figure shows the relationship between the uranium and thorium contents and the soft error rate expressed by the Fit number in each example of the present invention.

Uranium and thorium content 0, 2 p, P, b
Below, the fit number will be 75 or less.

〔Effect of the invention〕

According to the present invention, the soft error rate of a semiconductor memory device having an integration density of 16 bits or more can be reduced to 75 feet or less.

Furthermore, since the objective can be achieved simply by directly sealing the semiconductor element, it is possible to provide a highly reliable semiconductor memory device that is less prone to cracking or peeling.

Furthermore, since no coating film forming work is required, it is also excellent in terms of workability.

[Brief explanation of drawings]

The figure shows the relationship between uranium and thorium content and Fitt number according to an embodiment of the invention.

Claims (1)

[Claims] A semiconductor memory element with an integration degree of 1.16K bits or more is directly encapsulated with a resin containing a high-purity filler, and the encapsulation resin has a uranium and thorium content of 0.2p.
．． p. 1. A resin-sealed semiconductor memory device characterized in that the temperature is less than or equal to b.