DD154410A1 - PROCESS FOR USE OF PN SUPPLIES - Google Patents

Abstract

The process for etching pn transitions on silicon devices aims at the ablation of crystallographic surface defects at barrier layers. The addition of alcohol to HF / HNO deep-containing 3 etchants after initiation of the etching process, a mixing is achieved with the reaction and at larger erosion a compensatory etching effect.

Description

22 5 A 5 U -4-

Stahnsdorf, 17. 11. 1980

Ing. Wolfgang Hirsch 1530 Teltow, Ernst-Thälmann-Str. 93 d

Ing. Hans Friedrich 1530 Teltow, Ernst-Thälmann-Str. 89 a

Dipl.-Chem. Monika Wanka 1502 Potsdam, Otto-Hahn-Ring

Dipl.-Chem. Arnfried Abraham 1532 Kleinmachnow, Langendreesch

Registered Agent:

VEB Gleichrichterwerk Stahnsdorf in the VEB Kombinat Mikroelektronik 1533 Stahnsdorf, Ruhlsdorfer Weg Central Patent Department

Method for etching pn junctions Field of application of the invention

The method for etching pn junctions relates to the chemical treatment of the barrier layers of silicon components, for example * power transistors in mesa technology, in which disturbed near-surface crystal regions are to be removed and the surface to be cleaned.

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Characteristic of the known technical solutions

In the production of high-barrier components is known to etch the pn junctions in mixtures of strong acids to achieve a homogeneous surface structure. The most common etching solutions contain the components HF and HNOo. It is also known that erosion becomes larger or the etching time becomes smaller with a larger proportion of HF. Good electrical properties are preferably achieved but with low efficiency etchants high HNOo ₁ moiety at a low ablation ,, which may apply only when the surface has low mechanical disturbances. The separation of the semiconductor components causes deep mechanical disturbances. They have to be removed more strongly and, when effective mixtures are used, lead to inhomogeneous etching structures and to re-deposits.

Object of the invention

It is the object of the invention to avoid inhomogeneous surface structures, which lead to electrical breakdowns in pn junctions and reduce the blocking voltage.

Explanation of the essence of the invention

The task of the method is to achieve homogeneous etching structures with sufficient removal in short times. Disturbed crystal areas are to be removed and the surface structures induced by them to be degraded. According to the invention, this object is achieved in that after introduction of the etching process with a HF / HNO "mixture, an addition of methyl or ethyl alcohol takes place. As a result, the etching reaction is slowed down continuously - probably due to the acetic acid formed by oxidation in the course of the etching reactions. The compensatory effect of this

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Even with a low level of HNO "content, it leads to a trouble-free surface at high erosion because the etching attack during the etching time decreases continuously as a result of this addition.

embodiment

An example should clarify the process.

Magazine pre-cleaned silicon chips with surface pn junctions are etched in an etchant of HF: HNO-, = 1: 4. After an etching time of 20 to 60 s, 1 to 10 % of ethyl alcohol is added to the etching solution.

o causes the oxidation of silicon to SiO ₂ , which goes into solution by the hydrofluoric acid. By adding alcohol, HNO ₂ is presumably additionally formed and the SiO ₂ -BiI-tion significantly enhanced, thereby causing acetic acid causes the process to end up slowed down. The reaction itself favors the mixing of the etching solution.

After approx. 6 minutes, a displacement rinse occurs. · Subsequent HNOx oxidation with triple methanol rinsing sets an optimal surface coverage.

Claims (2)

..- «- 225454 Erfindungsansprüch .. 1. A method for etching pn junctions on silicon devices with HF and HNCL-containing etchants, characterized in that the etchant after initiation of the etching, at the latest after one minute etching time, 1 to 10 % ethanol or methanol are added 2. Method according to item 1, characterized in that the etching process is followed by an oxidation process with nitric acid to which 1 to 10 % of ethanol or methanol are added.