JPS617645A - Metal material for semiconductor device - Google Patents

Abstract

PURPOSE:To enable to obtain a state of film junction by a method wherein the surfaces of the sealing parts consisting of a metal material and glass are respectively formed with an amorphous metal layer. CONSTITUTION:The lead parts 38 of lead frames are placed on a low-melting point glass layer 36 encircling the recessed part 32 of a ceramic base 30. An amorphous metal layer 42 is formed on the surface of at least one side of glass sealing parts 40, which are located on the layer 36. Moreover, a recessed part 48 is formed in a ceramic cap 46, which is superposed on the base 30, corresponding to the recessed part 32 of the base 30, and a semiconductor chip 34 and Al wires 44 are housed in the space, which is defined by the recessed parts 32 and 48. The cap 46 is superposed on the base 30 in such a way as to hold the lead parts 38 between the cap 46 and the base 30 and a sealing treatment is performed. An amorphous metal layer provided on the surface of a metal material as mentioned above is larger in activity, as compared to a crystalline metal layer, and is easy to generate diffusion on a junction face with sealing glass. As a result, a highly reliable junction is obtained at the respective junction face and a highly reliable sealing can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a metal material that can be used for lead frames of semiconductor devices. The present invention relates to a metal material for semiconductor devices that can dramatically improve reliability.

BACKGROUND OF THE INVENTION The packaging methods for semiconductor integrated circuit devices currently in use can be broadly classified into resin sealing type, glass-ceramic sealing type, and laminated ceramic type. These packaging methods have advantages and disadvantages in terms of reliability and cost, and they are carefully weighed and used depending on the application. That is,
In terms of reliability, when comparing the best methods, the laminated ceramic type is the best, followed by the glass-ceramic sealing type, and then the resin sealing type. On the other hand, in terms of price, the opposite is true. Among these, the glass-ceramic sealed type is highly reliable and
It is a package that is in the middle of the price range and is highly desired for its combination of reliability and low cost.

FIG. 2 is a perspective view of the exploded parts arrangement of the glass-ceramic sealed package. However, some parts such as semiconductor devices and aluminum wires are omitted from illustration.

This glass-ceramic sealed package has a ceramic base 14, such as an aluminum alloy, with a recess 12 formed in the center in which a semiconductor chip is housed and bonded to the metallized bottom surface. A low melting point glass layer 16 such as lead glass is formed around the upper surface of the ceramic base 14 .

Leads 18 cut from a lead frame are placed so as to surround the recess 12 of the ceramic base 14, and each end of an aluminum wire is wire-bonded to the leads 18 and the semiconductor chip. Furthermore,
A ceramic cap 20 such as alumina is placed thereon. The ceramic cap 20 has a recess formed on the lower side surrounding the semiconductor chip and the aluminum wire, and further has a low melting point glass layer 22 such as lead glass formed around the lower surface.

Therefore, the ceramic base 14 and the ceramic cap 2
0 are stacked with the low melting point glass layers 16 and 22 with the lead 18 in between, and heated to form the low melting point glass layer 16.
and 22 are fused to each other while fixing the lead 18, thereby sealing the ceramic base 14 and the ceramic cap 22.

On the other hand, current trends in semiconductor integrated circuit devices call for miniaturization and multifunctionalization, and the above-mentioned glass-ceramic sealed package semiconductor integrated circuits are also affected by this trend. This means that as the semiconductor integrated circuit chip becomes more multifunctional, the size of the semiconductor integrated circuit chip itself increases, and the number of leads for connecting external terminals increases.
There are trends such as a shift from a 2-way external lead) to a Quad type (4-way external lead) and a decrease in the area of the glass-sealed part of the package due to an increase in the number of external terminal connection leads.

However, when the area of the glass sealing portion decreases in this way, the bonding force between the ceramic base and the ceramic cap provided by the glass particles decreases. There would be no problem if this decrease in bonding strength could be compensated for by the bonding force between the glass and the lead frame, but the bonding force between the currently used leads and low-melting glass is weaker than the bonding force between low-melting glasses. Quite low. Therefore, if the number of external terminal leads, that is, the leads 18 in the example of FIG. 2 increases,
Since the area of the bonded surface between the base and the cap where the lead is not sandwiched between them is reduced, the overall bonding force or airtightness is reduced.

Furthermore, in the current bonding between lead frames and glass, there is a problem in that the adhesiveness further deteriorates due to thermal cycles during the assembly process and use of the semiconductor device, leading to leakage.

Problems to be Solved by the Invention As mentioned above, conventionally used lead frames have low adhesion to glass, so as the number of leads increases, the sealing reliability of the package is not sufficient. It tends to disappear.

Therefore, the present invention aims to provide a metal material that has high adhesion to glass, is reliable, and can be used as a lead frame.

More specifically, even if the area of the glass sealing part in a semiconductor device package is reduced, the present invention can provide sufficient reliability to the hermeticity of the package, and can make it possible to create a closed frame. The aim is to provide a metal material that makes it possible.

Means for Solving the Problems The inventors of the present application conducted various studies on the sealing reliability between metal materials and glass, and as a result, confirmed the following fact.

(1) When sealing glass, the bonding ability between the amorphous surface of the metal material and the glass when the surface of the metal material is made amorphous is better than the bonding ability between the metal material and the glass. rise dramatically.

(2) A similar effect of improving glass bonding properties can be obtained not only when the surface of the metal material is made amorphous, but also when an amorphous metal film is attached to the surface of the metal material.

(3) If the thickness of these amorphous metal layers is at least 0.05 μm or more, it is effective in improving glass sealing properties.

Based on these confirmed facts, the present inventors conducted various studies aimed at improving the reliability of glass-ceramic sealed semiconductor integrated circuit devices, and as a result, they arrived at the present invention.

That is, according to the present invention, there is provided a metal material for a semiconductor device characterized in that an amorphous metal layer is provided on the surface of the sealing portion with glass.

By making at least the surface of the sealing portion of the metal material with glass an amorphous metal layer as described last month, the sealing performance with glass is improved. The reason is as follows.

In general, the important factors governing glass sealability are:
This depends on the wettability of glass to the metal material, and it is known that when the wettability is good, a diffusion layer is formed at the bonding interface and a strong bonded state is obtained.

By the way, in low melting point glass sealed packages, the glass and lead frame are bonded at a low temperature of 500°C or less in order to reduce the effect of heat on the semiconductor element, so such a diffusion layer is generally not formed. It was a target.

Therefore, in order to compensate for the decrease in the sealing portion and obtain high sealing reliability, it is necessary to facilitate diffusion bonding between the glass and the lead frame.

In the present invention, the amorphous metal layer provided on the surface of the metal material has significantly higher activity than the crystalline metal layer, and is more likely to diffuse at the bonding interface with the sealing glass.
It is believed that a highly reliable bond can be obtained and that extremely reliable sealing can be achieved compared to conventional sealing properties between metal and glass.

In addition, as a method of providing an amorphous metal layer on the surface of the glass sealing part of a metal material in this way, an amorphous metal layer is formed on the surface of the metal material by a coating method such as wet plating, PVD method, or CVD method. A coating method may be used, or a method of making the surface layer of the metal material amorphous by ion bombardment, electron beam bombardment, laser beam irradiation, or the like may be used.

In addition, from the viewpoint of the effects of the present invention, the thickness of the amorphous surface layer is 0.
, 05 μm or more is sufficient. On the other hand, making the amorphous layer thicker than necessary only increases the cost of forming the amorphous metal layer, which is not practical. Therefore, when considering both the effect of bonding reliability and the cost of forming an amorphous metal layer, the most effective range is 0.05 to 10 μm.

Note that when the metal material according to the present invention is used as a lead frame, the amorphous surface layer must be formed at least on the portion of the lead frame that is sealed with glass, but it may not be formed on other portions. Even if it were, it wouldn't be a problem.

Furthermore, when the metal material according to the present invention is used for a lead frame, an amorphous metal layer may be provided on the surface of the glass sealing part after punching into the shape of the lead frame, but It may be more practical to provide an amorphous metal layer on the surface of the required portion of the metal and then punch it into the shape of a lead frame.

Furthermore, when the metal material according to the present invention is used for a lead frame, it goes without saying that it is applicable to both DIP type and Quad type packages.

Example Next, the present invention will be explained by examples.

FIG. 1 is an exaggerated enlarged sectional view of a semiconductor device illustrating a case where a metal material according to the present invention is used as a lead frame.

The semiconductor device shown in FIG. 1 employs a DIP type glass-ceramic sealed package, and has a semiconductor chip 34 that is firmly bonded to a recess 32 of a ceramic base 30. A low melting point glass layer 36 is formed in the peripheral area surrounding the recess 32 of the ceramic base 30 .

Lead portions 38 of the lead frame are placed on a low melting point glass layer 36 surrounding such a recess 32 of the ceramic base 30.
is listed. An amorphous metal layer 42 is formed on at least one surface, for example, the top surface, of the glass sealing section 40 located on the low melting point glass layer 36 of the lead section 38 of the lead frame.

However, in order to improve sealing performance, amorphous metal layers may be provided on both sides of the glass sealing part 40 of the lead part 38.

In addition, the lead portion 38 of the lead frame and the semiconductor chip 3
4 and each end of an aluminum wire 44 is wire bonded.

Further, the ceramic cap 46 which is placed on the ceramic base 30 has a recess 48 which corresponds to the recess 32 of the ceramic base 30 and is larger than the recess 32 .
The semiconductor chip 34 is placed in the space defined by 2 and 48.
and an aluminum wire 44 are housed therein.

A low melting point glass layer 50 is also formed in the peripheral area surrounding the recess 48 of the ceramic cap 46 .

In this way, the ceramic cap 38 is placed on the ceramic base 30 so as to sandwich the lead portion 38 of the lead frame, and the ceramic cap 38 is sealed at a temperature of about 400° C. to 500° C., for example.

In the above configuration, 4 is used as the lead frame material.
Using a 2% Ni--Fe alloy, various materials were coated on the substrate and the glass sealability was investigated, and the results shown in Table 1 below were obtained.

Table 1 The glass sealability evaluation method used to create the data in Table 1 above is as follows.

Glass sealing was performed at a sealing temperature of 450°C using commonly used low melting point sealing glass, and then at -65°C to +1
After 100 heat cycles at 50° C., the presence or absence of fine leakage was measured using a He leak detector. Note that the minimum leak path (sealing length) of the DIP type glass-ceramic sealing package used was 0.7 mm.

From the above table, example 1 where no amorphous metal layer is provided on the surface
Examples 2 to 8 and 10 in which an amorphous metal layer was provided on the surface compared to
However, you can see that the leak test results are good.

Note that Example 9, in which an amorphous metal layer was not provided on the surface but a metallic aluminum coating was provided, is displayed as having a leak test result of △, similar to Example 2, but it is not ○ or △.
This was based on a three-level evaluation of , ×, and in reality, Example 2 was better than Example 9.

As is clear from the above results, the glass sealing performed through the amorphous metal layer formed on the surface of the lead frame according to the present invention is better than that of conventional lead frames (where the surface is made of crystalline metal). As a result, it has been demonstrated that the sealing reliability can be significantly improved, and that it can sufficiently respond to the trends of larger semiconductor devices and smaller packages.

In the above, the case where the metal material according to the present invention is applied to a lead frame has been described. However, as long as the metal material requires sealing reliability with glass, it can be used not only for lead frames but also for semiconductor devices. It is clear that it can also be applied.

As described in detail, the metal material according to the present invention can significantly improve sealing reliability with glass. Therefore, when used in lead frames, etc., even if the number of leads increases, the reliability of package sealing can be ensured sufficiently, and it can fully respond to the trend of larger semiconductor devices and smaller packages. .

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a semiconductor device package using a lead frame made of a metal material according to the present invention, and
FIG. 2 is a perspective view of the exploded parts arrangement of the glass-ceramic sealed package. [Main reference numbers] 14...Ceramic base, 16...Low melting point glass layer,
18...Lead cut from lead frame, 20...
・Ceramic cap, 22..Low melting point glass layer, 30..Ceramic base,
32... Concavity of ceramic base 30, 34... Semiconductor chip, 36... Low melting point glass layer, 38... Lead part of lead frame, 40... Glass sealing part of lead part 38, 42... Non-containing part. Crystalline metal layer, 44... Aluminum wire, 46... Ceramic cap, 48... Concave portion of ceramic cap 38, 50... Low melting point glass layer

Claims (5)

[Claims] (1) A metal material for a semiconductor device, characterized in that an amorphous metal layer is provided on the surface of a portion sealed with glass. (2) The metal material according to claim 1, wherein the amorphous metal layer is formed by making the surface of the metal material amorphous. (3) The metal material according to claim 2, wherein the amorphous metal layer is formed by irradiating the surface of the metal material with ion bombardment, electron beam bombardment, or laser beam irradiation. . (4) The metal material according to claim 1, wherein the amorphous metal layer is formed by coating the surface of the metal material with an amorphous metal layer. (5) A patent claim characterized in that the amorphous metal layer is formed by coating the surface of a metal material with an amorphous metal layer by wet plating, PVD, or CVD. The metal material according to item 4.