DE1287405B - Etchant for semiconductor bodies made of silicon - Google Patents

Description

The invention relates to an etchant made from an acidic hydrofluoric acid polishing solution for lapped silicon semiconductor bodies.

In the known production of semiconductor devices, the disk-shaped silicon body after the shaping, mostly mechanical processing etched. By removing silicon from the surface of the silicon wafer are intended to eliminate crystallographic disturbances in the silicon surface layer and cleaning of the surface can be achieved.

The etched, then washed and dried silicon wafers become different by alloying or / and diffusion processes with zones or layers Conductivity type and provided with electrode connections. In order to receive a subsequent Etching to avoid erosion of the electrode material will be the usual Etching agent provided with an addition of orthophosphoric acid.

The well-known mixtures of nitric acid used for etching, Hydrofluoric acid and optionally glacial acetic acid are acidic etching solutions, although they are reflective Surface, but the silicon wafer is stronger at the edge than in the middle ablate. The silicon wafers treated with such etching solutions therefore have a non-planar, namely pillow-shaped cross-section perpendicular to the disc surface on. The lack of evenness of the pane surface is important for the dimensional accuracy of the Semiconductor arrangements to be produced for them are of considerable disadvantage.

The well-known etching of silicon wafers using hot potassium hydroxide solution results in a plane, but different because of the different crystal planes strong attack rough surfaces, which in the subsequent alloy or Diffusion processes to irregular or insufficiently controllable boundaries of the affected zones. Also, alkaline solutions can be extremely difficult to rinse off silicon wafers.

The invention is based on the object of an etchant for uniform To indicate removal of semi-conductor bodies made of silicon, in which the specified Disadvantages no longer occur.

This object is achieved according to the invention in that the solution an addition of hydrogen chloride (specific weight 1.19 g / cms) to 2 parts by volume Contains hydrofluoric acid (40 percent by weight).

Polishing etching solutions are etchants that are used in their application Treatment of lapped panes produces reflective surfaces. Such for Etching solutions suitable for polishing silicon wafers contain an oxidizing agent and a reducing component as well as the etching attack

Claims (2)

Claims: 1. Etchant made from an acidic hydrofluoric acid polishing solution for lapped silicon semiconductor bodies, d a d u r c h g e k e n n -z e i c h n e t that the solution contains an addition of hydrogen chloride (specific Weight 1.19 g / cm3) to 2 parts by volume of hydrofluoric acid (40 percent by weight). 2. Etchant according to claim 1, characterized in that the polishing solution from. 2 volume parts fuming nitric acid (specific weight> 1.52 g / cms), 1 part by volume of hydrofluoric acid (40 percent by weight) and 2 parts by volume of glacial acetic acid (98 percent by weight) and as an additive 1 part by volume of an aqueous solution of hydrogen chloride (specific gravity 1.1'9 g / cms). accelerating or retarding additives, with as reducing Hydrofluoric acid is used throughout. An additive that retards the etching attack is for example glacial acetic acid (highly concentrated acetic acid). The hydrochloric acid used is a aqueous solution of hydrogen chloride with a specific gravity of 1.19 g / cms and, as hydrofluoric acid, an aqueous solution of hydrogen fluoride at 40 percent by weight Called hydrogen fluoride. The etching according to the invention results in a removal in the case of silicon wafers, which both have a surface of low roughness as well as a surface with excellent flatness. For example, through an etching according to the invention of a circular disk-shaped silicon body of approx. 15 to 20 mm in diameter from the disk surfaces on both sides an approx. 100 #t thick silicon layer can be removed without reducing the thickness of the silicon wafer at the edge by more than 5 #t smaller than the thickness in the middle and the roughness the surface of the disc surface is greater than 1 1. In contrast, already results a bilateral removal of 50 to 60 1, with a silicon wafer of about 15 up to 20 mm in diameter by means of the well-known etchant CP-4 (5 parts by volume smoking Nitric acid, 3 parts by volume hydrofluoric acid; 3 parts by volume of glacial acetic acid and 0.06 parts by volume Bromine) a pillow-like shape of the silicon wafer, in which the thickness of the silicon wafer at the edge by 30 to 40 I. less than the strength in the middle. Is beneficial the use of an aqueous solution containing hydrogen chloride with 2 parts by volume Nitric acid, 1 part by volume hydrofluoric acid, 1 part by volume hydrochloric acid and 2 parts by volume glacial acetic acid, due to the good flatness of the etched surface as well as a short one Etching time is reached.