JPH0521628A - Semiconductor device - Google Patents

Abstract

PURPOSE:To restrain the environmental deterioration in the insulation resistance when aluminum nitride (AlN) is used for a package for insulating the wiring between outer leads with AlN. CONSTITUTION:A YAG thin film 5 is provided on the AlN surface of a package 1 facing outside and located between outer leads 2. At this time, the environmental deterioration hardly occurs due to the chemical and electrical stability of the YAG thin film 5. This YAG thin film 5 covers the AlN surface to avoid the reaction the atmospheric water content and the AlN surface for precluding the possibility of making a path in lower volume resistivity on the surface so that stable insulation may be assured between outer leads 2 to avoid the miss-switching by any leakage current between the leads 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device which has a high insulation between outer leads and can be mounted on a semiconductor element operating at high speed without anxiety.

[0002]

2. Description of the Related Art Since aluminum nitride (hereinafter referred to as AlN) is a highly heat-conductive substance, it is being used in the field of semiconductor devices, especially packages for protecting semiconductor elements. Prior to that, ceramic packages were made of alumina, but because of their poor thermal conductivity, they were not suitable for mounting ICs, etc., which were fast and highly integrated. Therefore, for example, PGA (pin grid array) or C-QFP
A package in which the alumina part is replaced with AlN, such as (Squard Flat Package), has been developed.

A major feature of the alumina package is that it has a very high insulating property and is stable. Taking a typical PGA with a 2.54 mm pin pitch as an example, it is 10 ¹³ Ω
The insulation resistance of the pedestal shows little degradation after standard environmental testing. On the other hand, the AlN package has the following problems.

[0004]

The AlN package basically mimics the manufacturing process and structure of an alumina package, but it is inferior in moisture resistance to alumina, so that the following problems occur.

FIG. 2 shows an outline of PGA, and FIG.
The outer lead mounting surface side of the GA is partially enlarged. The internal structure of PGA is omitted or shown only schematically. A metallized layer 3 for joining the outer leads 2 is formed on the surface of the package 1, and a protective layer 4 is formed around the metallized layer 3 for the purpose of preventing the brazing material from spreading. This layer 4 is alumina in the case of an alumina package, and thus AlN in the case of AlN. The brazing material is not shown in each drawing.

However, AlN easily reacts with moisture in the air to produce low insulation resistance substances such as boehmite and aluminum hydroxide even in a room which is a general computer use environment. As a result, the environment of insulation resistance is high. Deterioration occurs. That is, if the product creates a path with a low volume resistance on the surface, the insulation resistance does not become large no matter how high the resistance of other parts is. The probability of misswitching increases especially when a high-speed operation semiconductor element is mounted due to a large leak current.

The problem taken up here occurs when the insulation resistance between the outer leads depends on the surface properties of AlN. That is, not the C-QFP or the like in which the outer leads are surrounded by a low-melting glass to insulate them,
The target is a PGA or a ceramic flat package in which the outer leads are insulated by AlN of the package.

[0008]

In order to solve the above problems, the present invention provides a thin film layer of YAG (yttrium aluminum garnet) on the surface of the aluminum nitride layer located between the outer leads and facing the outside. Set up.

If the YAG film is extremely thick, AlN
Since the effect of high thermal conductivity peculiar to the manufactured package is diminished, it is desirable to set the upper limit of the YAG film thickness on the surface to about 30 μm. Such a thin YAG film can be easily formed by the method described in the embodiment.

[0010]

Alumina is a chemically and electrically stable substance, and does not cause a reaction that reduces resistance at a temperature of approximately 120 ° C. or lower, which is the environment in which semiconductor devices are used. AlN
And alumina have a volume resistance of 10 ¹⁴ Ω · cm or more, but Al
The volume resistance of boehmite and aluminum hydroxide produced by the reaction of N with water is about 10 ⁵ to 10 ¹⁰ Ω · cm,
It is orders of magnitude smaller than AlN and alumina.

In the present invention, since the YAG thin film covers the surface of AlN and prevents the reaction with moisture on the surface of AlN, the volume resistance of the package surface between the outer leads does not extremely decrease.

[0012]

EXAMPLE FIG. 1 shows the structure of the outer lead mounting surface when PGA is applied. Here, made of AlN (A
1N and a conductor laminate) package 1 is used. Reference numeral 2 is an outer lead, and a flange at the root end of this lead is brazed to the metallized layer 3. Also,
A YAG thin film layer 5 characterizing the present invention is formed on the outer lead mounting surface side of the package 1. Although the YAG layer slightly overlaps the metallized layer in FIG. 1, it does not necessarily have to overlap. There may be an overlap or a gap between the flange and the flange.

FIG. 4 shows an example of a PGA manufacturing process having such a structure. In many cases, a plating process is also included between these processes. Screen-printed YAG on the outer lead mounting surface side of the package in the process of
And Y of the outermost surface by co-firing with printing metallization of each layer
Make an AG thin film. According to this method, the film thickness of the YAG thin film layer 5 is suppressed to about 20 μm at most, and therefore, the thermal conductivity of the AlN package is hardly reduced. Alternatively, the YAG thin film thickness 5 can be formed by the vapor phase synthesis method by omitting the step of FIG. 4 or adding the steps of resist coating / YAG coating / resist stripping after the step of. In this case, the film thickness of YAG can be reduced to several μm.

A more detailed embodiment will be described below. As sample A, the PGA of FIG. 2 was made based on the manufacturing process of FIG. Also, as sample B, YAG
A thin film formed by the above-mentioned vapor phase synthesis method was also prepared. Both of these are products of the present invention. Sample C is YA in FIG.
AlN printing is performed instead of G printing, and the protective layer 4 in FIG.
It is a conventional product made with 1N.

5 pieces of each of these samples were prepared, and 1
The insulation resistance at 00 VDC was examined. Also, after this, all samples were subjected to a 500-hour pressure cooker test (1
It was subjected to 21 ° C. and 100% RH), and then the insulation resistance was measured again.

The results are shown in Table 1. The sample of the conventional product is
After the test, the insulation resistance was reduced to 1/20 on the average, whereas the insulation resistance of the sample of the present invention was reduced by about A.
%, B remained at about 65%, demonstrating that the present invention has an excellent effect of maintaining insulation between outer leads.

[0017]

[Table 1]

[0018]

As described above, in the semiconductor device of the present invention, the surface of AlN is protected by the thin film layer of YAG to suppress the decrease in the volume resistance of the package surface between the outer leads, so that the high heat dissipation property is obtained. This has the effect of preventing mis-switching due to current leakage between leads when using an AlN package in order to provide it, and it is possible to provide a device with high operational reliability even when a high-speed IC is mounted. ..

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a waist of a semiconductor device according to an embodiment.

FIG. 2 is a diagram showing an outline of PGA.

FIG. 3 is a sectional view of an outer lead mounting surface side of a conventional PGA using an AlN package.

FIG. 4 is a flow chart showing an example of a manufacturing process of a semiconductor device of the present invention.

[Explanation of symbols]

 1 Package 2 Outer Lead 3 Metallization Layer 4 Protective Layer 5 YAG Thin Film Layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor ▲ Hiro ▼ Yoshiyuki Se 1-1-1 Kunyo Kita, Itami City Sumitomo Electric Industries Itami Works

Claims (1)

Claim: What is claimed is: 1. A semiconductor device in which outer leads are insulated from each other by aluminum nitride of a package, and YAG (on the surface of an aluminum nitride layer located between the outer leads and facing to the outside). A semiconductor device having a thin film layer of yttrium aluminum garnet).