JPS5917971B2 - semiconductor equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device that makes it possible to simultaneously obtain both adhesion strength and resistance contact between a semiconductor substrate and a frame that is a conductive support plate.

In recent years, semiconductor devices have been required to be manufactured at low cost.

Therefore, conventionally, for bonding between the semiconductor substrate and the frame, gold or the like has been used, which easily forms a eutectic alloy with the semiconductor substrate at a relatively low temperature, and which can be easily attached to the frame by plating or the like. However, since gold is a precious metal and is expensive, solder, which is an alloy mainly composed of inexpensive lead and tin, has come to be used5. However, since solder does not directly adhere to the semiconductor substrate, conventionally, titanium, chromium, etc., which have strong adhesion to the semiconductor substrate, are attached to the semiconductor substrate in advance.On the other hand, titanium, chromium, etc. have poor adhesion with solder, As an intermediate metal, nickel, copper, etc., which have strong adhesion to solder, titanium, chromium, etc., are deposited on top of titanium, chromium, etc., thereby making the semiconductor substrate and frame adhere closely. .

15 However, when the impurity concentration of titanium and chromium in the semiconductor becomes low, they no longer form a resistive contact with the semiconductor substrate.

Moreover, various functional elements are formed on one side of the semiconductor substrate by thermal diffusion method, ion infrastructure method, etc.
Due to electrical characteristics, the impurity concentration of the 20 semiconductor substrate is often required to be such that the metals such as titanium and chromium mentioned above do not come into contact with each other, and this semiconductor substrate is often used with a reference potential. be. In such a case,
The frame bonded to the semiconductor substrate has an extremely low resistance, and the fact that the semiconductor substrate and the frame have resistive contact eliminates variations in the reference potential caused by the low impurity concentration and high resistivity of the semiconductor substrate. was used to reduce the amount. However, if the semiconductor substrate and the frame do not have resistive contact, the 30 reference potential will vary from place to place;
This causes the device characteristics to fluctuate or become defective. FIG. 1 is a longitudinal sectional view of an example of a conventional semiconductor substrate in close contact with a frame.

In this conventional example, gold or gold alloy 2 is placed between the semiconductor substrate 1 on which the functional area is formed and the gold 3 attached to the frame 4 by plating or the like, and is heated. It is joined to the frame 4. : Koo J In this conventional method, since gold, which is an expensive metal, is used, the price of semiconductor devices is not high, and the semiconductor substrate 1 and the frame 4 are bonded using gold or a gold alloy. Therefore, there is a problem that the heating temperature is as high as 300° C. or more, and the functional regions formed on the semiconductor substrate 1 are adversely affected.

In addition, in this conventional method, when bonding, it is necessary to remove a slight oxide film formed on the bonding surface of the semiconductor substrate 1, so there is a problem in that work such as mechanically rubbing the bonding surface is required. There is.

FIG. 2 is a longitudinal sectional view showing another conventional device that is an improvement over the conventional device shown in FIG.

In FIG. 2, titanium, which is a metal with strong adhesion to the semiconductor substrate 1, is deposited on the other main surface of the semiconductor substrate 1 with a functional region formed on one main surface by vacuum evaporation, sputtering, or the like. Attach 5.

Subsequently, nickel 6, which is a metal with strong adhesion to solder, is attached by vacuum evaporation or sputtering, and then solder 7 is placed between it and the frame 4 and heated.
It becomes possible to bond the semiconductor substrate 1 and the frame 4 together. Although the conventional device shown in FIG. 2 can eliminate the drawbacks of the conventional device shown in FIG. 1, the following new drawbacks occur in the conventional device shown in FIG.

Since the functional regions of the semiconductor substrate 1 are formed by introducing various impurities into the semiconductor substrate 1 by thermal diffusion, ion implantation, etc., the impurity concentration of the semiconductor substrate 1 is small. On the other hand, it is a well-known fact that titanium forms a shot contact with a semiconductor substrate having a low impurity concentration, and therefore the titanium 5 and the semiconductor substrate 1 are in non-resistance contact. For this reason, when operating the functional area with the semiconductor substrate 1 at a reference potential, the metal frame 4
Taking advantage of the fact that the electrical resistance of It becomes possible to maintain the substrate 1 at a constant reference potential.

However, when the frame 4 and the semiconductor substrate 1 are in non-resistance contact, the resistance of the semiconductor substrate 1 becomes high because the impurity concentration of the semiconductor substrate 1 is low, and therefore, due to the non-resistance contact, the current flows through the semiconductor substrate 1. A potential difference is generated by the flow in the substrate, and the semiconductor substrate is not at a reference potential due to uniform scratches, and due to fluctuations in the reference potential of the semiconductor substrate, the functional area does not operate normally.

The present invention has been made in order to solve the problems of the conventional devices as described above, and provides a semiconductor device in which a semiconductor substrate and a conductive support plate are bonded together at low cost using solder or the like. A first metal layer having resistive contact with the substrate is provided on the other main surface on which the functional region is not formed, and a semiconductor substrate is provided on the first metal layer and the other main surface of the substrate. providing a second metal layer with a high adhesion strength;
Further, by providing a third metal layer on the second metal layer, which is bonded to the conductive support frame via solder, the adhesion between the semiconductor substrate and the conductive support plate using solder is improved. It is an object of the present invention to provide a semiconductor device which is capable of forming a resistive contact between the semiconductor device and a conductive support plate.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a longitudinal sectional view showing a state in which a semiconductor substrate and a frame are bonded together according to an embodiment of the present invention. In FIG. 3, the same reference numerals as in FIGS. 1 and 2 indicate the same or corresponding parts, and in this embodiment, the semiconductor substrate 1 on which the functional area is formed and the frame 4 made of copper alloy or the like are , to bond with solder 7, which is an alloy such as tin? , first the semiconductor substrate 1
Gold 8 with a thickness of 10-400 angstroms (λ) is deposited in advance on the main surface opposite to the main surface on which the functional area is formed, that is, the surface to be bonded to the frame 4, by vacuum evaporation or sputtering, and then titanium 5 is deposited in the same vacuum. 100 to 5,000 people, preferably 300 to 1,000 λ, are deposited by vapor deposition or sputtering, and then 300 to 5 λ of nickel 6 is deposited by vacuum evaporation or sputtering.
00 people, preferably 500 to 1500 people. Next, solder 7 is sandwiched between the frame 4 and the semiconductor substrate 1 to which the gold 8, titanium 5, and nickel 6 have been adhered, and this is heated to 150 to 300°C. This makes it possible to bond the semiconductor substrate 1 to the frame 4. In this example, since the film thickness of gold 8 was set to 10 to 100λ,
It is a well-known fact that the film does not form a uniform film over the entire surface, but instead adheres in the form of islands.

Therefore, part of the titanium 5 is bonded to the semiconductor substrate 1, and the remaining part is bonded to the gold 8. Therefore, even if the impurity concentration of the semiconductor substrate 1 is low and a shot junction occurs with the titanium 5, the shot junction will not occur in the gold 8 part because the gold 8 exists between the semiconductor substrate 1 and the chinon 5. .

Therefore, the part where titanium 5 and semiconductor substrate 1 are bonded is
Even if the contact is non-resistance due to a shot bond, the portion where the gold 8 and the semiconductor substrate 1 are bonded becomes a resistance contact.
Further, it is a well-known fact that the adhesion of the part where the semiconductor substrate 1, gold 8 and titanium 5 are bonded in this order is weak, but the adhesion of the part where the semiconductor substrate 1 and titanium 5 are bonded in this order is extremely strong. As a result, in this example, the semiconductor substrate 1 and the titanium 5 have a resistive contact and strong adhesion since the gold 8 has a thickness of 10 to 100K. Also, lead,
Solder 7, which is an alloy such as tin, does not adhere to titanium 5, but
In this embodiment, since the nickel 6 that adheres to both the solder 7 and the titanium 5 is interposed, the semiconductor substrate 1 and the frame 4 can be bonded to each other with resistance contact and strong adhesion.

Further, since the solder 7 is used, the semiconductor substrate 1 and the frame 4 can be bonded together at a temperature of 150 to 300°C, and the semiconductor substrate 1
There is no negative impact on the functional areas above. In the above embodiment, the film thickness of gold 8 was set to 10 to 100 mm to make use of the fact that gold 8 was deposited in an island shape. However, in the present invention, after depositing gold 8 of 100K or more, photolithography was applied. Using a method, a part of the gold 8 is selectively removed to form islands, and then,
The same effect can be obtained even if titanium 6 is deposited by vapor deposition, sputtering, or the like.

Further, in the above embodiment, gold 8 is used as the first metal layer, but this first metal may be other metal, such as silver, which has a resistive contact with the semiconductor substrate 1. The same effects as in the embodiment are achieved.

Furthermore, in the above embodiment, titanium 5 is used as the second metal layer, but the second metal may be a metal that has strong adhesion to the semiconductor substrate 1, such as chromium. However, the same effect as in the above embodiment can be obtained. Further, by using the principles of the present invention, by controlling the amount of gold 8 deposited on the semiconductor substrate 1, it is possible to form an element with arbitrary characteristics between a shot junction and a resistive contact.

As described above, according to the semiconductor device of the present invention, the first metal layer having resistance contact with the semiconductor substrate is provided on the other main surface on which the functional region is not formed, and A second metal layer having a high adhesion strength to the semiconductor substrate is provided on the first metal layer and the other main surface of the substrate, and is further bonded onto the second metal layer via solder to a conductive support plate. By providing a third metal layer that adheres to the semiconductor substrate, it is possible to significantly improve the adhesion between the semiconductor substrate and the conductive support plate at a lower cost than before without making any major changes to the manufacturing method, and to obtain a resistive contact. It has the effect of

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing a conventional semiconductor device, FIG. 2 is a vertical cross-sectional view showing an improved conventional semiconductor device, and FIG. 3 is a vertical cross-sectional view of a semiconductor device according to an embodiment of the present invention. . The same symbols in the figures refer to the same items. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 4... Conductive support plate, (Frame 5... Second metal layer (titanium), 6... Third metal layer (nickel), 7... Solder, 8...First metal layer (to).

Claims (1)

[Scope of Claims] 1. A conductive support plate, a semiconductor substrate having a functional area formed on one main surface and bonded to the conductive support plate on the other main surface, and a semiconductor substrate on the other main surface of the semiconductor substrate. a first metal layer that is partially provided and has resistance contact with the semiconductor substrate; and a first metal layer that is provided on the other main surface of the semiconductor substrate and the first metal layer and has a high adhesion strength to the semiconductor substrate; A semiconductor device comprising: a second metal layer; and a third metal layer for bonding the second metal layer to the conductive support plate via solder. 2. The semiconductor device according to claim 1, wherein the first metal layer is gold or silver, and the second metal layer is titanium or chromium.