DD206168B1 - AGENTS FOR POLYCRYSTALLINE SILICONE LAYERS - Google Patents

Description

Characteristic of the known technical solutions

For the etching of polycrystalline silicon layers in semiconductor fabrication according to DD-PS 123488 an etchant is known that from a mixture of acetic acid with 0.9 to 3% hydrofluoric acid, 2 to 8% nitric acid, 2 to 9% water and 2 10 ~ ³ ... is 8 × 10 ^"3% of silver nitrate. This etchant has the disadvantage that the etching rate varies greatly depending on the service life of the etchant and the etched therein number of semiconductor wafers. There are variations of the etching rate to to 40% from the initial value, so that the required dimensional accuracy of the etched structures in the polycrystalline silicon is not given in batch-to-batch batch processing.

Object of the invention

The object of the invention is to reduce the variations in the dimensional accuracy of the etched structures in the polycrystalline silicon during batch batch-batch processing.

Explanation of the essence of the invention

The object of the invention is to provide an etchant for polycrystalline silicon layers in semiconductor production, the etching rate of which is largely independent of the lifetime of the etchant and of the number of semiconductor wafers etched therein.

According to the invention, the object is an etchant for polycrystalline silicon layers, consisting of a mixture of acetic acid, 0.9 to 3% hydrofluoric acid, 2 to 8% nitric acid, 2 to 9% water and 2 x 10 ^-3 ... 8 10 " ³ % silver nitrate, achieved by the etchant containing a catalytic amount of nitrite ion.

It is desirable that the etchant contain from 0.03 to 1% of a water-soluble nitrite.

Finally, it is expedient for the etchant to contain 0.03 to 1% ammonium nitrite.

It has been found that the addition of a catalytic amount of nitrite ion has an extremely stabilizing effect on the etching rate.

The etchant according to the invention has the advantage that it has a practically constant etching rate until shortly before its exhaustion.

As a result, the variations in the dimensional accuracy of the etched structures in the polycrystalline silicon during batch-batch processing have been reduced such that the yield in structuring the polycrystalline silicon is substantially increased. In addition, the use of test disks for Ätzratenbestimmung is no longer necessary.

embodiment

The invention will be explained in more detail with reference to two embodiments.

example 1

To an etching solution of 300 ml hydrofluoric acid (37.5%), 300 ml nitric acid (65%), 18 ml 0.1 η silver nitrate solution and 5400 ml acetic acid (100%) are added 0.3 g ammonium nitrite.

Example 2

To an etching solution of 250 ml hydrofluoric acid (38.5%), 250 ml nitric acid (65%), 4500 ml acetic acid (100%) and 15 ml 0.1 η silver nitrate solution is added 5.3 g sodium nitrite or potassium nitrite.

It has been found that the polycrystalline silicon layers of up to 500 semiconductor wafers of 76 mm diameter can be patterned with these etching solutions, wherein the variation in the etching rate is only about 3... 6%. The etchants operate selectively and etch polycrystalline silicon about 100 times faster than silica.

Claims (3)

1. Etching agent for polycrystalline silicon layers, consisting of a mixture of acetic acid, 0.9 ... 3% hydrofluoric acid, 2 ... 8% nitric acid, 2 ... 9% water and 2 10 ~ ³ ... 8 · 10 ~ ³ % silver nitrate, characterized in that it contains a catalytic amount of nitrite ions. 2. etchant according to item 1, characterized in that it contains 0.03 ... 1% of a water-soluble nitrite. 3. etchant according to item 1 and 2, characterized in that it contains 0.03 ... 1% ammonium nitrite. Field of application of the invention The invention relates to an etchant for structuring polycrystalline silicon layers. It finds application in the manufacture of semiconductor devices.