DE1127482B - Method for doping the emitter electrode of a semiconductor device with aluminum - Google Patents

Description

GERMAN

PATENT OFFICE

B 57723 Vfflc / 21g

REGISTRATION DATE: MAY 4, 1960

NOTICE THE REGISTRATION AND ISSUE OF EDITORIAL: APRIL 12, 1962

The invention relates to a method for doping the emitter electrode with a semiconductor arrangement Aluminum.

It has been found that to achieve optimal performance of a semiconductor device such. B. a pnp transistor, it is advantageous to form the alloyed emitter junction flat. A flat, alloyed emitter junction ensures an improved and uniform collector breakdown voltage V _ce for a certain base width, fewer emitter-collector short circuits during alloying and the possibility of alloying narrower base widths.

It was found by photomicrographs of cut transistors that the collector junction is smooth throughout, while the emitter junction is generally wavy Structure has. Experiments have shown that the ripple is due to the presence of gallium in the Emitter is based. Furthermore, emitters doped with aluminum gave more scattering results. in the In view of this, it was to be assumed that an emitter made of pure indium would produce the desired planar pn junction results. However, after the indium has penetrated into the germanium, it must be doped, to get the high performance you want.

Aluminum is advantageous for doping indium, but its rapid oxidation is one significant obstacle. Furthermore, it is necessary to delay the dissolution of the aluminum in the indium, in order to avoid ripples in the pn junction.

The invention is based on the object of a method for doping the emitter electrode of a To provide a semiconductor device with which the above difficulties are eliminated. According to the invention this is achieved by using a steel strip coated with aluminum, whose aluminum is freed of oxide and plated with nickel and which is then attached to the already alloyed Emitter electrode is melted from an indium alloy.

This not only prevents the aluminum from oxidizing, but also slows it down the dissolution of the aluminum in the molten indium-germanium alloy at the alloy temperatures.

The method according to the invention is described in detail in the following description in connection with FIG the drawings explained on the basis of a possible embodiment of the invention. It shows 1 shows a cross section through a according to the. ·· ■ ·.

Method for doping the emitter electrode of a semiconductor device with aluminum

Applicant:

The Bendix Corporation,
New York, NY (V. St. A.)

Representative: Dipl.-Ing. K.-A. Brose, patent attorney,
Pullach near Munich, Wiener Str. 2

Claimed priority:
V. St. v. America, May 27, 1959 (No. 816 233)

Thomas Hyde Strudwick, Sea Girt, N.J. (V. St. Α.), Has been named as the inventor

present invention made assembly prior to heating and

Figure 2 is a cross-section of the same arrangement after heating.

In the drawing, the same parts are assigned the same reference numerals in both figures. 5 is a Platelets made of semiconducting material, which can consist of germanium and with any the usual activators doped and treated in the usual way. Next is a collector 6 is present, which can consist of indium or another suitable material.

A disk made of an indium-lead alloy 7 is provided for the emitter, the lead being the The purpose is to be able to adjust the alloy depth and the alloy temperature. To the emitter also includes a central strip 8 made of steel strip, which on one side with nickel, on the other Side is clad with aluminum with a thickness ratio of 10: 80: 10 and under the Trade name "Alnifer" is sold. The strip is used to remove the alumina immersed in a hydrofluoric acid bath and then placed in a nickel bath to be chemically non-electrical create a thin nickel coating on the aluminum surface. The strips 8 are then punched out and consist of a layer 9 made of iron, furthermore a layer 10 made of aluminum as well the nickel-plated surface layers 11 and 12.

209 559/417

An electrode lead 13 can be attached to the surface layer 12 be attached.

The preceding parts come together with a base ring 14 heated in the usual way and result in the arrangement according to FIG. 2. The arrangement is etched and treated as usual after heating. After heating, part of the Collector material 6 penetrated into the plate 5 and forms a pn junction after solidification. A feed 15 can be attached to the collector 6. The indium-lead emitter 7 penetrates the Heating in the wafer 5, and at the same time the nickel plating by the indium in the The emitter alloy is dissolved and thus enables the exposed aluminum to also become in the indium to solve. With subsequent cooling, the recrystallization layer of the aluminum-germanium alloy forms with low resistance a relatively flat emitter junction with the desired electrical Properties. The collector can be treated in the same way as it is for the Emitter was set out.

Claims (1)

PATENT CLAIM: Method for doping the emitter electrode of a semiconductor device with aluminum, characterized by the use of an aluminum-coated steel strip, the aluminum of which is freed of oxide and plated with nickel and which is then melted onto the already-alloyed emitter electrode made of an indium alloy. Considered publications: German Auslegeschrift No. 1 005 646;
»Telecommunications Fachberichte ", Vol. 1, 1955, reprint 1957, p. 31/32;
"Gmelins Handbuch", 8th edition, Germanium - Supplementary volume, System No. 45, 1958, p. 366. 1 sheet of drawings ι 209 559/417 +.62