DE1245500B - Method for non-blocking contacting of a semiconductor body - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY.

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

Hell

German KL: 21 g - 11/02 '

Number: 1245500

File number: T 22744 VIII c / 21 g

Filing date: September 15, 1962

Opened on: July 27, 1967

The invention relates to a method for non-blocking contacting one surface side of a on the opposite surface side having alloy electrodes by means of semiconductor body a collector plate coated with an aluminum or an aluminum semiconductor metal layer is plated by alloying by heating to a temperature above the eutectic temperature of the aluminum semiconductor material. . Such semiconductor bodies have already become known with the so-called mesa transistors or the so-called planar transistors. A mesa transistor often consists of a p-conducting base body as a collector, on one surface of which a thin η-conductive base layer is applied. A so-called Mesaberg generated, which consists essentially of the η-conductive base layer. On the free The surface of this base layer is a non-blocking base electrode and a blocking emitter electrode applied, which consists for example of a thin alloyed layer of aluminum.

A planar transistor almost always consists of an η-conducting Sihzium base body as a collector, which is oxidized on all sides. The oxide layer is applied to a surface using a photoresist process partially removed and one after the other a base zone by diffusing in p-type impurity material and creating an emitter region by alloying and diffusing η-conductive impurity material. The planar transistors very often aluminum is used. However, pnp planar transistors with an aluminum emitter can also be used Manufacture in which the collector is advantageously contacted with aluminum.

The electrodes and the collector of these semiconductor components described above must now electrical contact can be made without blocking. For this purpose, fine electrodes are very often used on the emitter and base electrodes Gold wires. attached by thermo-compression at temperatures of around 300 ° C and the collector body on a metal sheet, for example made of an iron-nickel compound with the interposition a layer made of a material that produces the same conductivity type as the collector body owns, alloyed.

When choosing this conductive material, which is also solder, there are very important things to consider Difficulties arise, as they are to be shown in the following example of the Mesa transistor. As an impurity material with p-conductivity, methods for non-blocking contacting are available Semiconductor body

Applicant:

Telefunken

Patent management company m. B. H., Ulm / Danube, Elisabethenstr. 3

ίο named as inventor:

Dipl.-Ing. Elmar Müller, Ulm / Danube

Gallium, Indium, Boron and Aluminum are known. Of these materials, boron is unsuitable as a solder, because it does not bond with the semiconductor material. Gallium and indium are so low Melting point that they are at the subsequent

ao thermo-compression of the contact wires on the base and emitter electrodes become fluid again. and thus the semiconductor body can shift on the contact plate, which very easily results in failures. The attempt was made to avoid this difficulty by combining these substances with one material admitted that with · the. Semiconductor material has a eutectic temperature that is above the temperature of 300 ° C required for thermo-compression.

For this case in which the semiconductor body consists of p-conducting germanium, for example a gold-gallium alloy or a gold-indium alloy is used as solder, since the Eutek-

. _t tikum temperature is of gold-germanium at 350 ° C, ie above the temperature which occurs during the thermal compression process. It has now been shown, however, that semiconductor arrangements whose collector contact is made by means of one of the above -.-. given gold solders were attached, have the undesirable so-called thyratron effect when a certain collector current is exceeded, which results from the fact that from this current value on additional charge carriers from the collector contact

v3 to be injected. By adding tiny amounts of copper to one of the gold solders given above, a reduction in this undesirable thyratron effect can be achieved, but it cannot be completely eliminated.

If you now use aluminum as an intermediate.

layer-metal, the effect described above is eliminated, but the following difficulty arises on: . . ..

709 618/432

Claims (2)

The soldering temperature must now be above 426 ° C, since the eutectic temperature of germanium-aluminum is only at this temperature. However, as already described above, the emitter or base electrodes of the semiconductor arrangements have very often been produced by alloying and diffusing aluminum, so that the aluminum continues to alloy at this temperature and the semiconductor component is thus unusable. It must therefore be avoided that the electrodes opposite the contacting surface reach such a high temperature. Recently, a method has become known which is used for blocking-free contacting of the collector of germanium transistors which have electrodes made of aluminum on the surface opposite the contacting surface. In this known method, an aluminum-plated collector plate is heated above the eutectic temperature of germanium-aluminum, then the collector plate is subjected to strong cooling when this temperature is reached and at the same time the transistor arrangement with its collector body is placed on the plated surface of the collector plate. However, this known method has the major disadvantage that it is very difficult to actually always place the collector body on the heated collector plate at the right time, and it also requires a relatively complicated manufacturing device. So it becomes too difficult and expensive to use in high volume production. The manufacturing method according to the invention now avoids these disadvantages of the known methods described above, aluminum or aluminum-germanium-plated sheet metal also being used for contacting semiconductor components. According to the invention it is proposed that the semiconductor body is placed with the alloy electrodes facing down in a suitably shaped recording device with high heat capacity, that the -plated contacting sheet is then placed on the surface of the semiconductor body to be contacted and with a pressure piece which is placed on the semiconductor body Leaves part of the sheet uncovered, is weighted and that finally the uncovered part of the sheet lying on the semiconductor body is heated very quickly to an alloy temperature above the eutectic temperature of the corresponding aluminum semiconductor material by thermal radiation. This ensures that the clad sheet is quickly brought to the soldering temperature, for example 440 ° C, due to its low heat capacity due to the radiant heat, while the emitter side of the semiconductor device is kept at a temperature below the eutectic temperature by good thermal contact with the holding device with high heat capacity will. If a germanium body is to be contacted with the aid of the method according to the invention, a soldering temperature above 426 ° C. should be selected. For the contacting of silicon bodies must. on the other hand, they are above 577 ° C. It is expedient to heat the plated sheet on the semiconductor body under protective gas, e.g. B. nitrogen or hydrogen. In the following, the invention is based on the in F i g. 1 and 2 illustrated devices explained in more detail. F i g. 1 shows, in section, a device for carrying out the method according to the invention. The semiconductor body 1 is placed together with an aluminum-clad sheet metal 4 with the electrodes 4 facing down in the recess of a receiving device 3. The receiving device 3 consists of a material with a high thermal capacity, for example graphite or V 2-A steel. From above, a pressure piece 5 presses on the clad sheet metal 2 to be soldered, which is shaped in such a way that the part of the clad sheet metal 2 resting on the semiconductor body remains uncovered. For this purpose, the pressure piece, as shown in FIG. 2 is shown, a recess at the corresponding point. This pressure piece 5 can either itself be so heavy that its weight is sufficient for the desired purpose of thermal contact between the semiconductor arrangement and the receiving device, but it can also be weighed down by an additional weight 6, as shown in FIG. A heat radiation body, as symbolized by 7, then heats the arrangement from above. A further development of the invention is when a large number of depressions are made in the receiving device 3 which are suitable for receiving a plurality of semiconductor bodies. The associated pressure piece must then have corresponding recesses. If necessary, it is very useful to vibrate the arrangement during the alloying, for example by means of ultrasound, so that the formation of an oxide skin on the aluminum is prevented and a uniform alloying is achieved. Patent claims: 1. Method for non-blocking contacting of one surface side of one on the opposite Surface side having alloy electrodes by means of a semiconductor body Collector sheet plated with an aluminum or an aluminum semiconductor metal layer is, by alloying by heating to a 'temperature above the eutectic temperature of the aluminum semiconductor material, characterized in that the semiconductor body with the alloy electrodes facing down into a suitably shaped receptacle high heat capacity is placed, which is then on the surface to be contacted Semiconductor body placed the plated contact sheet and with a pressure piece, which leaves the part of the sheet metal resting on the semiconductor body uncovered, is weighted and that finally the uncovered part of the on the semiconductor body by thermal radiation lying sheet very quickly an alloy temperature above the eutectic temperature of the corresponding aluminum semiconductor material is heated. 2. The method according to claim 1, characterized in that the arrangement during the The heating process is set in vibration by an ultrasonic treatment.