DE1212819B - Method for etching a silicon body of a semiconductor arrangement containing a pn junction - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

C23f

German class: 48 dl - 1/02

Number: 1212 819

File number: L 38110 VI b / 48 dl

Filing date: February 3, 1961

Opened on: March 17, 1966

The invention relates to a method for etching a silicon body containing a pn junction a semiconductor device.

For the production of semiconductor rectifiers with a silicon wafer as the semiconductor body according to the In alloying processes, it is known to start from p-conductive silicon wafers. The silicon wafers are lapped after drilling, washed in an ultrasonic washing system with trichlorethylene and after drying in a mixture of hydrofluoric acid and nitric acid, optionally also under Addition of acetic acid, etched down to the required thickness. In a metal or In the form of carbon or a combination of both substances, a molybdenum • or tungsten discs, an aluminum or silumin foil, a p-conducting silicon wafer and finally a gold-antimony foil layered on top of one another. The whole thing is heated to about 750 ° C in an atmosphere, for example in hydrogen. After cooling down becomes the environment of the gold-antimony foil produced by alloying with the η-conduction in the silicon crystal formed pn junction in hydrofluoric acid and nitric acid for a few minutes, since the Semiconductor rectifiers still show insufficient reverse voltage values. After careful rinsing in deionized water and in an ultrasonic washing system, the semiconductor rectifiers are in petroleum ether stored and then heated to about 270 ° C in a stream of nitrogen.

According to this known alloying process, semiconductor rectifiers with a gold-antimony surface are produced with a diameter of 4 to 8 mm, the high reverse voltage values and low reverse currents exhibit. Semiconductor rectifier with a gold-antimony foil with a diameter of more than 10 mm and semiconductor rectifiers with a gold-antimony foil with a diameter of less than 3 mm in these alloying processes, however, with satisfactory electrical values only in low yield obtain.

An alloying process for the production of pn junctions in silicon wafers of certain Area size, the results of which are easily reproducible, is not in the same way suitable for the production of pn junctions with a larger or smaller area. Both with a modification of the Alloying process for the production of pn junctions with a larger area as well as a modification the alloying process for the production of pn junctions with a smaller area resulted in the Investigations on which the invention is based

ίο

Process for etching a pn junction
containing silicon body a
Semiconductor device

Applicant:

Licentia Patent-Verwaltungs-G. mb H.,
Frankfurt / M., Theodor-Stern-Kai 1

Named as inventor:
Richard Magner, Warstein

if a number of semiconductor rectifiers are manufactured with silicon wafers, a smaller number of semiconductor rectifiers that have useful electrical properties than when performing of the alloying process for the production of pn junctions of the area size, for their production it had been trained.

According to the invention, one or more of the elements iron, manganese, lead, molybdenum, Acidic aqueous etching solution containing rhenium and chromium to improve the electrical properties a semiconductor device with a in a p-type silicon body by alloying with a η-line in the silicon crystal-producing dopant formed pn-junction is used.

By using one or more of the elements iron, manganese, Lead, molybdenum, rhenium and chromium containing acidic aqueous solution for etching is the yield the semiconductor devices produced by the alloy process, e.g. B. Semiconductor rectifiers, with silicon wafers, the pn junctions of which have high reverse voltage values and low reverse currents, elevated. The after the procedure according to the

^ o Invention to achieve an increase in yield of the alloying process is of particular advantage for the production of semiconductor arrangements with at least one silicon wafer containing a pn junction with a diameter of less than 3 mm, there are additional measures to improve the electrical values of semiconductor devices Silicon wafers with diameters greater than 10 mm, e.g. B. by repeating the alloying process under certain conditions, in the case of conductor arrangements with silicon wafers of diameters smaller than 3 mm only minor improvements result.

.. -, v. ·. , 609 538/378

The reduction in the spread of the alloying process can be explained by the fact that during the slow cooling of the alloying process contaminating foreign atoms partly at the edge zone of the pn junction, the length of which is Silicon wafers of smaller diameter to the pn junction area have a ratio of larger numerical value than with silicon wafers of larger diameter, concentrate. By using ernes Etchant according to the invention can provide greater uniformity in terms of, particularly in the case of silicon wafers smaller diameter foreign atoms absorbed on the surface, the z. B. able to stabilize the blocking characteristic by blocking recombination centers, be achieved; _-. · ■ · ■ '. - ·

With particular advantage, the elements can each be added in an amount that is at most 100 times, preferably ten times, the amount in which the element in question is in an acid (p. a.) suitable for analysis is contained. The easiest way to shape the elements add salts.

The known etching solutions for the etching of semiconductor bodies containing pn junctions are because of the influencing of the current-voltage characteristics that can be achieved with them Semiconductor bodies built ■ semiconductor arrangements applied. The application of the etchant for Metal surfaces, on the other hand, are made because of the intended use by the person concerned corrosive metal dependent effect.

To give objects made of aluminum or aluminum alloy a shiny surface give, the use of an acid bath is known which, as a catalyst, a metal salt, z. B. a nickel salt, contains a cobalt salt, a copper salt, a zinc salt, a chromium salt or an aluminum salt.

The strength of an etchant's attack on copper in relation to the strength of its attack on nickel or precious metal with a simultaneous action of the etching solution on these metals, which at Plates with printed circuits are next to each other, can be done with the well-known etching solution Iron (in) nitrate at a concentration of 20 to grams per liter. Chromic acid of a Κοηζβ, η-tration from 75 to 125 grams per liter and sulfuric acid, - where the · ratio of 'chromic acid to sulfuric acid is about 4 to 1, can be increased.

For the treatment of metals such as copper, tin,

ίο aluminum, zinc or lead, nickel, iron, cobalt, Cadmium, chromium, magnesium or alloys of any of these metals is a ferric chloride etching bath known, in which the iron (m) chloride turns into iron (II) chloride during the etching process converts and the chloride of the metal to be etched. or the chlorides of the metals of the to be etched alloy arise.

Claims (3)

Claims: ' 1. Use of one or more of the elements iron, manganese, lead, molybdenum, Acid aqueous etching solution containing rhenium and chromium for improving the electrical properties of a semiconductor device with one in a p-conductive silicon body by alloying with an η-conduction in the silicon crystal generating dopant formed pn junction. 2. The method according to claim 1, characterized in that that the elements are added in an amount that is no more than a hundred times, is preferably ten times the amount in which the element concerned is contained in an acid suitable for analysis is 3. The method according to claim 1 or 2, characterized in that the elements are added in the form of salts. Considered publications:
French Patent No. 967 207;
U.S. Patent No. 2,872,302. 609 538/378 3.66 © Bundesdruckerei Berlin