DE1276824B - Method for producing an ohmic contact on a semiconductor body - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

HOIl

German class: 21g-11/02

Number: 1276 824

File number: P 12 76 824.0-33 (St 21634)

Filing date: February 1, 1964

Open date: September 5, 1968

It is already known to make ohmic contacts by depositing metals from solutions to apply electrochemical or chemical reduction or according to German patent specification 966 906 by evaporation of metals in a vacuum or by cathode sputtering. Where contacts are great Area required to withstand relatively strong currents were, as from the German Auslegeschrift 1018 557 known, molybdenum or tungsten discs on the previously metallized semiconductor soldered on, which is usually made of silicon. The expansion coefficient of these metals is Sufficiently similar to that of silicon under most conditions. Difficulties arise with that Soldering process, however, the use of hard solder reduces the risk of alloys between the silicon surface and the solder, which have a lower melting point than the other components have. Such alloys can penetrate the silicon and the ao electrical properties of a subsequent

affect the pn layer or destroy it completely

disturb. Relatively soft solders have poor mechanical strength, especially after several Temperature grinding.

The use of soft solder also limits the operating conditions of the device to a temperature which is clearly below the melting point of the solder.

The invention is based on the object of reducing the problems occurring during soldering or eliminate it entirely.

From the German patent specification 865 160 and the Austrian patent specification 222702 it is known Semiconductor layers through thermal decomposition of a volatile compound of the semiconductor material precipitate from the vapor phase on a support body. From the Austrian patent specification is also known to produce ohmic contacts in the same way.

The invention relates to a method for producing an ohmic contact on a semiconductor body whose surface to be contacted is provided with a contacting metal layer by thermal decomposition of a gaseous compound of the contact metal and deposition thereof, as was known in principle from Austrian patent specification 222 702. An ohmic contact is produced according to the invention in that a metal layer with a thermal expansion coefficient corresponding to that of the semiconductor body by thermal decomposition of a volatile halogen process for producing an ohmic
Contact on a semiconductor body

Applicant:

German ITT Industries
Company with limited liability,
7800 Freiburg, Hans-Bunte-Str. 19th

Named as inventor:

Henley Frank Sterling,

Cyril Francis Drake, Harlow, Essex

(Great Britain)

Claimed priority:

Great Britain 8 February 1963 (5231) - -

Compound or a volatile carbonyl of the metals molybdenum, tungsten, tantalum and / or metals the platinum group is deposited from the vapor phase on the semiconductor surface.

From the German Auslegeschrift 1109 002 there is a method for producing metal layers known by thermal decomposition of a volatile carbonyl on the vapor phase. It but carbonyls of nickel and chromium are used and metallic objects made of aluminum and not made of a semiconductor material nickel-plated or chrome-plated.

In a preferred embodiment of the invention, which is described with reference to the drawing is to be, a metal layer 1 is brought into ohmic contact with a semiconductor body 2, for example with silicon. For this purpose, molybdenum or tungsten is produced from the vapor phase at one temperature precipitated below 1300 ° C. The molybdenum or tungsten forms a layer, for example 0.25 mm thick and which is intimately connected to the silicon grid, so that the aforementioned soldering problem disappears completely.

The molybdenum or tungsten is obtained from suitable compounds, such as. B. from molybdenum pentachloride or tungsten hexachloride, which are reduced with hydrogen, which also serve as a carrier gas can. Other halogen compounds of these metals or their carbonyls can also be used with suitable ones Temperature and pressure conditions used

■ "," - · '■■■ 809 599/426

to generate a precipitate from the gas phase.

An exact coefficient of thermal expansion Alloys of molybdenum and tungsten and / or similar metals can also be obtained get knocked down. Tantalum can also be precipitated from the gas phase to form a ohmic contact with a thermal expansion coefficient similar to that of silicon. Also alloys and metals of the platinum group, such as. B. osmium and iridium can be used.

The type of ohmic contact required can vary in type and structure, from simple ones flat areas on both sides of a wafer of semiconductor material with a pn junction up to complex arrangements of several interconnected metals or very small ones Areas for numerous individual elements. Any suitable masking of the surface of the semiconductor can be used to create the pattern you need.

When epitaxial deposition of semiconductor material from the gas phase, such as. B. with silicon, is Usually an induction preheater is used to heat the treated silicon wafer. A metal layer, For example, made of tungsten, which previously by the method described above on a Side of the disc that has been applied for later contact can be used to remove the Absorb energy to heat the silicon during the epitaxial growth process.

Claims (5)

Patent claims: 1. A method for producing an ohmic contact on a semiconductor body, whose to contacting surface through thermal decomposition of a gaseous compound of the contact metal and depositing the same is provided with a contacting metal layer, characterized in that a metal layer with a thermal expansion coefficient corresponding to that of the semiconductor body by thermal decomposition of a volatile Halogen compound or a volatile carbonyl of the metals molybdenum, tungsten, tantalum and / or metals of the platinum group deposited from the vapor phase on the semiconductor surface will. 2. The method according to claim 1, characterized in that the surface of the semiconductor body is partially covered with a mask. 3. The method according to claim 1 or 2, characterized in that a semiconductor body consists of Silicon is used. 4. The method according to claim 3, characterized in that the volatile chemical compound Molybdenum pentachloride or tungsten hexachloride is used. 5. The method according to claims 1 to 4, characterized in that the metal layer for Heating of the semiconductor body during an epitaxial growth process for inclusion the energy used by an induction preheater. Considered publications:
German Patent Nos. 865160, 966 906;
German explanatory documents No. 1018 557,
002;
Austrian patent specification No. 222702. 1 sheet of drawings 809 599/426 p. 68 © Bundesdruckerei Berlin