JPS5950090B2 - Manufacturing method of semiconductor device - Google Patents

Description

[Detailed description of the invention] The present invention joins a semiconductor wafer and an electrode support plate.

The present invention relates to a method for manufacturing a semiconductor device having a structure. Conventional semiconductor devices improve reliability by housing a semiconductor element made of a semiconductor wafer such as Si in an airtight package made of ceramic or the like to stabilize the atmosphere of the semiconductor element, but recently the cost has increased. In order to reduce downtime, it is now possible to eliminate expensive airtight packages and use simple packages such as rubber rings, and even to apply boiling cooling methods in which semiconductor elements themselves are directly immersed in chemical refrigerants such as fluorocarbons. .

However, when such a simple package, boiling cooling method, etc. are applied, it is necessary to configure the electrodes of the semiconductor element to withstand the atmosphere in which it is used. To explain this with reference to the drawings, Fig. 1 shows an example of a conventional semiconductor element, in which 1 is a Si substrate having a PN junction, and 2 is an electrode support plate soldered to the Si substrate 1 with an Al brazing material S. 4 is an Al electrode deposited on the Si substrate 1 to obtain ohmic contact, 5 is the Si substrate 1
This is a surface treatment material that aims to stabilize the PN junction surface.

If a semiconductor element having such a structure is used as it is in the air, the surfaces of the Al electrode 4 and Mo plate 2 may be oxidized and the contact resistance with the external conductor pressed against these surfaces may increase. When this semiconductor element is used in a fluorocarbon refrigerant as described above, problems arise such as the Al electrode 4 being corroded by the acid produced by thermal decomposition of the fluorocarbon.

In order to solve these drawbacks, it is conceivable to use an Au film layer as a method to obtain a semiconductor element having excellent properties against oxidation and corrosion and to obtain an electrode with good conductivity.

However, as is known in the art, when direct ohmic contact is made with Au to the Si substrate 1, Au gradually diffuses into the Si substrate 1.
Adversely affects the electrical properties of semiconductor elements. It is also conceivable to further construct an Au electrode and an Au protective film by plating on the Al electrode 4 and the Mo plate 2 as an electrode support plate in a semiconductor element as shown in FIG. 5 is attacked by the plating solution, resulting in poor characteristics and poor yield.
The Au plated on the side of the plate 2 cannot jitter above the temperature limited by the melting point of the A1 brazing material 3 (a process in which after plating or vapor deposition, it is placed in a high-temperature atmosphere to increase the bonding strength of the plated vapor-deposited metal). Therefore, sufficient adhesion strength cannot be obtained and the Au plating effect cannot be obtained. Furthermore, Al electrode 4
The Au plated on top gradually forms a high-resistance alloy layer with the Al electrode 4 at the heat generation temperature when the semiconductor element is used, causing various problems such as an increase in electrical resistance. The present invention was made in order to eliminate the drawbacks of the conventional semiconductor element and its manufacturing method, and it provides the outermost electrode of the semiconductor element with extremely excellent properties against oxidation and corrosion without causing the above-mentioned disadvantages. It is an object of the present invention to provide a method for manufacturing a semiconductor device that can produce an Au electrode having an Au electrode and an electrode support plate on which an Au protective film is formed.

The method for manufacturing a semiconductor device according to the present invention includes sequentially forming an Al film layer, a Ni film layer, and an Au film layer on the electrode surface of a semiconductor wafer and the lower surface of an electrode support plate, and forming an electrode with these three layers. The present invention is characterized in that a semiconductor device with excellent characteristics, oxidation resistance, and corrosion resistance is obtained.

An embodiment of the present invention will be explained below with reference to the drawings. FIG. 2 is a flowchart showing an embodiment of the method for manufacturing a semiconductor device according to the present invention, and FIG. This shows the structure when manufactured.

The manufacturing process of the present invention will be explained in order based on these two figures. (a
) Alloy completed element A semiconductor wafer made of Si or the like having a predetermined PN junction and an electrode support plate such as an MO plate that supports it are joined by a well-known method via an A1 brazing material etc. to form a semiconductor element. be.

In FIG. 3, a Si wafer 1 and an MO plate 2 are soldered together using an Al brazing material 3. (b) Al Vapor Deposition: On both surfaces of the semiconductor element in (a) above, that is, on the semiconductor wafer electrode surface and the electrode support plate surface, an Al film layer is vacuum-deposited to a thickness of, for example, 10 μm.

The degree of vacuum in this case is, for example, 10-3T0rr. In FIG. 3, reference numeral 4 indicates this Al film layer. (c) Jitter The Al-deposited semiconductor element of (b) above is replaced with, for example, N
Jittering is performed for 30 minutes at 560° C. in two gases to form ohmic contact with the semiconductor wafer and increase the adhesion strength of the A1 vapor deposited layer on both surfaces of the semiconductor element.

(d) Ni plating On the Al film layer firmly attached to the semiconductor element in the step (c) above, Ni is plated to a thickness of, for example, 1μ.
Form a membrane layer.

This Ni plating layer functions as a barrier to prevent the formation of a high-resistance Al--Au alloy layer between the underlying Al film layer and the subsequently plated Au layer. Therefore, it is desirable that the thickness be kept at the minimum required level, and that it be formed by electroless plating from the viewpoint of density.
In FIG. 3, 6 indicates this Ni film layer. (e) Au plating On the semiconductor element plated with Ni in the above step (d), Au is plated to a thickness of, for example, 2 μm by electrolytic plating.

This Au plating layer is preferably relatively thick in order to obtain the effect of a protective film that prevents oxidation and corrosion of the electrode, and in this respect, it is easier to use electrolytic plating than electroless plating. In FIG. 3, 7 indicates this Au film layer. (f) For a semiconductor element for which electrode formation beyond pattern etching has been completed, if independent island-like electrodes are required on the electrode surface of the semiconductor wafer, separate electrodes with a three-layer structure of A1-Ni-Au- Pattern etching with appropriate chemicals.

For example, if the semiconductor element is a thyristor, the Si wafer side electrode is separated into a gate electrode and a cathode electrode. FIG. 3 shows the state in which this separation of the electrodes has taken place. It goes without saying that this step (f) is not necessary in the case of a diode. (g) Bevel processing In the semiconductor wafer periphery of the semiconductor element in which the A1-Ni-Au three-layer structure electrode has been completed in the above (f), the exposed surface of the PN junction is beveled and processed to reduce the surface electric field. .

The bevel processing method is performed by, for example, sandblasting, mechanical polishing, or the like. Slope 8 at the periphery of the Si wafer 1 in Fig. 3
is formed by this bevel processing. Wholesale Surface treatment Finally, after applying chemical etching to the beveled surface of the semiconductor element that has been beveled in step 1g) above,
For example, a surface treatment material such as varnish is applied to stabilize the exposed surface of the PN junction.

5 in FIG. 3 indicates this surface treated material. As shown in FIG. 3, the semiconductor device formed in the above manner is free from oxidation and If a suitable surface treatment material 5 that is resistant to corrosion is selected, it can be used as is in various atmospheres such as air or fluorocarbon.

Further, the Ni film layer 6 acts as a barrier between the Au film layer 7 and the Al film layer 4, and prevents the formation of a high resistance Al--Au alloy by both metals, thereby providing long-term reliability. Furthermore, M.O.
Since the Al electrode 4 has already been jittered, the Al--Ni--Au electrode on the plate 2 side has sufficient adhesion strength as a device used in a press-contact structure. In the above embodiment, an Al-Ni-Au three-layer structure electrode was formed not only on the electrode surface of the semiconductor element on the semiconductor wafer side but also on the surface of the electrode support plate (MO plate). , this MO board side,
In other words, the three-layer structure electrode is not formed on the surface of the electrode support plate, and A1-Ni-Au is formed only on the electrode surface of the semiconductor wafer.
It goes without saying that a three-layer structure may be formed.

As described above, according to the present invention, Al-Ni-
By forming an electrode with a three-layer structure of Au, a semiconductor device that is extremely resistant to oxidation and corrosion can be obtained. It is particularly suitable for use in manufacturing.

[Brief explanation of drawings]

Figure 1 is a sectional view showing a conventional semiconductor element, Figure 2 is a sectional view showing a conventional semiconductor element;
The figure is a flowchart showing an embodiment of the method for manufacturing a semiconductor device according to the present invention, and FIG. 3 is a sectional view showing an example of a semiconductor device obtained by the method for manufacturing a semiconductor device according to the present invention. 1... Semiconductor wafer, 2... Electrode support plate, 3... Al brazing material, 4...
All film layer, 6... Ni film layer, 7...
・Au film layer: In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A semiconductor element is formed by bonding an electrode supporting plate to a semiconductor wafer having a PN junction, and an Al film layer, a Ni film layer, and an Au film layer are sequentially laminated on the semiconductor wafer electrode surface of this semiconductor element to form a three-layer structure. A method for manufacturing a semiconductor device, comprising forming an electrode having a three-layer structure, and also forming a protective film having a three-layer structure on a surface of the electrode support plate.