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Etching method and etching composition useful for the method

a technology of silicon nitride and composition, which is applied in the direction of surface treatment composition, decorative arts, chemistry apparatus and processes, etc., can solve the problems of difficult continuous use of such an etchant, no constant effect of its addition is available, and large damage to silicon oxide, etc., to achieve high selective etching efficiency and high productivity

Inactive Publication Date: 2008-08-28
TOSOH CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides an etching method for silicon nitride that reduces the frequency of replacing phosphoric acid etchant and prevents damage to silicon oxide and precipitation. The etching composition comprises a phosphorus compound and / or a fluoride thereof, a boron compound and / or a fluoride thereof, a silicon compound and / or a fluoride thereof, and water. This results in better protection of silicon oxide and allows for constant etching of silicon nitride over a long period of time.

Problems solved by technology

However, high purity phosphoric acid has had a problem that when it is used at a high temperature of at least 150° C., damage to silicon oxide tends to be substantial.
However, hexafluorosilicic acid is a volatile substance, and at the operation temperature of at least 150° C., hexafluorosilicic acid tends to be volatile, whereby no constant effect of its addition is obtainable, and continuous use of such an etchant has been difficult.
Further, in a case where hexafluorosilicic acid is added, precipitation of an insoluble silicon compound from the etchant tends to be accelerated, and it has been problematic to use it in an industrial operation.
However, there has been a problem that such a precipitated silicon compound tends to adhere to semiconductor wafers, etc., before being filtered off.
However, with an etching composition having both hydrofluoric acid and nitric acid added to phosphoric acid, the damage to silicon oxide as another semiconductor material tends to be large, and it is problematic to use such a method for a semiconductor process, and such an adverse effect has been more remarkable when it is used at a high temperature.
Thus, heretofore, there has been no etching composition which is capable of selectively etching silicon nitride at a high temperature constantly for a long period of time.

Method used

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  • Etching method and etching composition useful for the method
  • Etching method and etching composition useful for the method
  • Etching method and etching composition useful for the method

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0042]A silicon wafer (15 mm square) having SiN deposited in a thickness of 300 nm by a CVD method and a silicon wafer (15 mm square) having a thermally oxidized film formed in a thickness of 1,000 nm were immersed at 150° C. for 30 minutes in 100 g of an etching composition comprising 0.02% of fluoroboric acid, 0.002% of ammonia, 5% of water and the rest being phosphoric acid. The wafers were taken out, washed with water and dried, and then the film thicknesses of SiN and the thermally oxidized film were measured by an optical interferotype film thickness meter. This operation was regarded as 1 batch and was continuously repeated for 14 batches. In the 14th batch, the SiN etching rate was 6.10 nm / min, and the etching rate of the thermally oxidized film was 0.03 nm / min. Even in the 14th batch, no precipitation of silicon oxide was observed on the thermally oxidized film, and the thermally oxidized film was found to be slightly etched.

[0043]This etching composition initially started ...

example 2

[0044]Etching of silicon nitride was carried out under the same conditions as in Example 1 by using a composition having 0.03% of hexafluorosilicic acid further added to the composition in Example 1.

[0045]Even in the 14th batch, no precipitation of silicon oxide was observed.

[0046]The selectivity for silicon nitride to silicon oxide was 220 from the first batch and thus was high from the beginning.

example 3

[0047]Etching of silicon nitride was carried out under the same conditions as in Example 1 by using a composition wherein 0.02% of fluoroboric acid in the composition in Example 1 was changed to 0.02% of fluorophosphoric acid.

[0048]In the 14th batch, the SiN etching rate was 6.00 nm / min, and the etching rate of the thermally oxidized film was 0.06 nm / min. Even in the 14th batch, no precipitation of silicon oxide was observed on the thermally oxidized film, and the thermally oxidized film was found to be slightly etched.

[0049]This etching composition initially started in a state where it contained no soluble silicic acid, but immediately after the initiation of its use, the composition was in a state where it contained soluble silicic acid. The etching selectivity for silicon nitride to silicon oxide (silicon nitride / silicon oxide) in each batch was examined, whereby it was found to be 15 in the first batch but 100 in the 14th batch.

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Abstract

In etching of silicon nitride with a phosphorus type, if etching is carried for a long time, silicon oxide tends to precipitate, and it has been impossible to constantly carry out the etching for a long period of time.By an etching method for silicon nitride using a composition comprising a phosphorus compound, a boron compound, a silicon compound and / or their fluorides thereof, there will be no precipitation of silicon oxide even when the composition is used for a long time. It is particularly preferred to further add nitric acid and / or a nitrate, whereby stability of selectivity will be increased.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to an etching composition for silicon nitride. More particularly, it relates to a composition capable of etching silicon nitride to be used for an insulating film for e.g. semiconductor devices or flat panel displays.[0003]2. Discussion of Background[0004]Silicon nitride is a very important compound as a ceramic material or a material for semiconductors. In a process for producing semiconductors, there is a step wherein it is required to selectively etch only silicon nitride without presenting any damage to silicon oxide. At present, in this step, high purity phosphoric acid is mainly used. However, high purity phosphoric acid has had a problem that when it is used at a high temperature of at least 150° C., damage to silicon oxide tends to be substantial.[0005]As a means to suppress such damage to silicon oxide, high purity phosphoric acid having silicon dissolved therein or phosphoric acid...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C23F1/00C23F1/10
CPCH01L21/31111C09K13/08
Inventor HARA, YASUSHISHIMONO, AKINORITAKAHASHI, FUMIHARU
Owner TOSOH CORP
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