US2887630A

US2887630A - Transistor

Info

Publication number: US2887630A
Application number: US640212A
Authority: US
Inventors: Nijland Louis Marius; Manintveld Jan Adrianus
Original assignee: US Philips Corp
Current assignee: US Philips Corp; North American Philips Co Inc
Priority date: 1956-02-29
Filing date: 1957-02-14
Publication date: 1959-05-19
Anticipated expiration: 1976-05-19
Also published as: NL205006A; BE555370A; GB831815A; CH351341A; NL94711C; DE1051984B; FR1167317A

Description

TRANSISTOR Filed Feb. 14, 1957 m luxlww INVENTOR s LOUIS MARIUS NIJLAND JAN ADRlAN US MANINTVELD BY 7 2 Z 2 I 4 AGENT United States Patent O TRANSISTOR Application February 14, 1957, Serial No. 640,212

Claims priority, application Netherlands February 29, 1956 9 Claims. (Cl. 317-234) The invention relates to a method of producing a semiconductive electrode system, more particularly a transistor, in which a semi-conductive body .of, for example, germanium or silicon is provided with at least one rectifying electrode and an ohmic connection, this structure being then etched and housed in an envelope.

The invention furthermore relates to a semi-conductive electrode system, more particularly a transistor, housed in an airtight'envelope.

The invention has been found to be of particular importance for transistors, for the purpose of increasing the current amplification factor ea which is defined by the equation:

wherein I and l designate the collector current and the base current respectively, measured at a constant collector voltage V It is already known that the current amplification factor of germanium transistors and particularly of silicon transistors can be enhanced by coating their semi-conductive surfaces with a layer of oxidizing material, for example, lead minium, zinc chromate or strontium chromate, and, furthermore, that organic compounds may be used for this purpose. By experiments it has been found, however, that the transistors thus manufactured are often not stable at higher temperatures.

The invention has for its object to provide inter alia a method by which a semi-conductive electrode system having a high current amplification factor and great stability can be manufactured. It has furthermore the advantage that, in a simple manner, the surface of the semiconductive body can be coated with very thin, effective layers even of molecular thickness.

In accordance with the invention the semi-conductive body with its electrode and ohmic connection is introduced, subsequent to the etching operation, into a milieu containing at least a nitrogen-oxygen compound.

Use is preferably made of a nitrogen-oxygen compound which contains molecules of N and N 0 the equilibrium shifting in the direction of the first-mentioned compound at higher temperatures. In order to increase the effect water vapour may also be added.

It is further noted that the results obtainable by the method according to the invention are in general not dependent upon the special etching solution'employed.

Although the invention is not restricted to a particular semi-conductive substance, it is particularly suitable for use with semi-conductive electrode systems, for example, alloy transistors, of which the semi-conductive body consists of silicon, since by the conventional means, which in the case of germanium yielded satisfactory values of the current amplification factor, unsatisfactory results are obtained in the case of silicon.

A particular embodiment of the invention consists in that the semi-conductive body with its electrode ,and ohmic connection is arranged in a vacuum-tight envelope 2,887,630 Patented May 19, 1959 containing at least one nitrogen-oxygen compound and, if desired, water vapour. With silicon transistors an additional effect is obtained, if the gaseous mixture in the envelope, before this envelope is finally closed, is pumped oif partly, preferably down to a pressure of less than 10- mm. Hg.

A particular embodiment of a semi-conductive electrode system, especially a transister according to the invention, contains in the vacuum-tight envelope at least one nitrogen-oxygen compound. There may furthermore be water vapour in the envelope.

It should be noted that the favourable effect of such a gaseous milieu or atmosphere is, of course, not restricted to transistors, but that similar effects will be obtained when the invention is applied to other semi-conductive electrode systems.

By way of example one embodiment of a semi-conduc tive electrode system according to the invention will now be described with reference to the sole figure in the accompanying drawing, which shows in cross-section, a transistor according to the invention.

Referring now-to the figure, the transistor comprises a thin semi-conductive disc 1 provided with an emitter electrode 2, a collector electrode 3 and an annular ohmic base connection 4. The electrodes 2 and 3 and the ohmic connection 4 are each connected to supply conductors 5, 6, 7 passing through a glass pinch 8, and are passed to the outside through the glass base 9, to which the glass bulb 10 is sealed. The envelope (9, 10) contains N0 (N 0,) vapour at a pressure of about 10-l mm. Hg.

The method according to the invention will now be described more fully with reference to a few examples.

Example 1 An alloy transistor device comprising a semi-conductive body consisting of p-type silicon provided with a base connection consisting of an alloy of by weight of indium and 10% by weight of copper, and further provided with an emitter electrode and a collector electrode both consisting of 75% by Weight of gold and 25% by weight of antimony was etched for about twenty seconds in a bath containing a mixture of a 52% aqueous solution of hydrofluoric acid and a 97% aqueous solution of nitric acid in the volume ratio 1:3 and subsequently washed in streaming distilled deionised water and dried. Subsequent to the etching treatment, the transistor was arranged in a glass envelope containing dry nitrogen dioxide (di-nitrogen-tetroxide). The current amplification factor a which amounted to 5 after the etching treatment, rose by this treatment almost immediately to a value 15. Then water vapour was introduced into the envelope to a quantity of less than 1% of the N0 content, which increased a further to the value 18. During the pumping out of this gaseous mixture a increased further to attain a maximum value of 22 at a pressure of about 10- mm. Hg, after which the glass envelope was sealed tight. In order to check the stability of the transistor, the structure was then heated, so that ar increased continuously until at C. a maximum value of 50 was attained. During the cooling to room temperature the same range of variations was reversed, which confirms the stability of the transistor.

Example 2 An alloy transistor comprising a semi-conductive body consisting of n-type germanium, provided with a base connection consisting of an alloy of 97% by weight of tin and 3% by weight of antimony, and further provided with an emitter electrode and a collector electrode both consisting of indium, was etched in a bath composed of 2 volume parts 52% aqueous solution of HF, 2 volume parts 97% aqueous solution of HN and volume parts H 0, and subsequently washed in distilled deionised water and dried. The transistor had a current amplification factor of 15.2 after this etching operation. The-transistor was subsequently arranged in an envelope containing dry nitrogen dioxide (di-nitrogen-tetroxide) at a pressure of about mm. Hg. Owing to this treatment u increased almost immediately to 32. By adding moist nitrogen dioxide (di-nitrogen-tetroxide) a increased further to the value 40 at a NO (N O pressure of about 10- mm. Hg and a water vapour pressure of about 10' mm. Hg. After sealing the transistor in a glass envelope the structure was heated to 65 C., at which temperature 06 attained the value 41.5; during cooling to room temperature about the same range of variations was reversed, and at room temperature ea had decreased to a value of about 40, which confirms the good stability of the transistor.

What is claimed is:

l. A method of manufacturing a semi-conductive device comprising a semi-conductive body and plural electrode connections to said body and possessing a current amplification factor whose value depends on the surrounding atmosphere, comprising the steps of etching the body, and thereafter introducing the body with its electrode connections into an atmosphere containing a nitrogenoxygen compound.

2. A method of manufacturing a semi-conductive device comprising a semi-conductive body selected from the group consisting of germanium and silicon and having ohmic and rectifying electrode connections to said body, comprising etching the body, and thereafter introducing the body with its electrode connections into an atmosphere containing a nitrogen-oxygen compound.

3. A method as set forth in claim 2 wherein the atmosphere also contains water vapor.

4. A method as set forth in claim 2 wherein the atmosphere is partly removed and then the body with its electrode connections sealed-off in a vacuum-tight envelope.

5. A semi-conductive device comprising an etched semi-conductive body with plural electrode connections to said body and possessing a current amplification factor whose value depends on the surrounding atmosphere, a sealed envelope enclosing the body with its connections, and an atmosphere in said envelope comprising a nitrogen-oxygen compound.

6. A semi-conductive device comprising an etched semi-conductive body selected from the group consisting of germanium and silicon, ohmic and rectifying electrode connections to said body, a vacuum-tight sealed envelope enclosing the body with its connections, and an atmosphere in said envelope comprising a nitrogen-oxygen compound.

7. A device as set forth in claim 6 wherein the nitrogen-oxygen compound is selected from the group consisting of nitrogen dioxide and di-nitrogen-tetroxide.

8. A device as set forth in claim 6 wherein the atmosphere includes Water vapor.

9. A device as set forth in claim 8 wherein the pressure of the atmosphere is below 10- mm. of mercury, and the semi-conductive body is silicon.

References Cited in the file of this patent UNITED STATES PATENTS 2,812,480 Ellis Nov. 5, 1957

Claims

1. A METHOD OF MANUFACTURING A SEMI-CONDUCTIVE DEVICE COMPRISING A SEMI-CONDUCTIVE BODY AND PLURAL ELECTRODE CONNECTIONS TO SAID BODY AND POSSESSING A CURRENT AMPLIFICATION FACTOR WHOSE VALUE DEPENDS ON THE SURROUNDING ATMOSPHERE, COMPRISING THE STEPS OF ETCHING THE BODY, AND THEREAFTER INTRODUCING THE BODY WITH ITS ELECTRODE CONNECTIONS INTO AN ATMOSPHERE CONTAINING A NITROGENOXYGEN COMPOUND.