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Method for the prevention of oxygen build-up in chemical etch baths

IP.com Disclosure Number: IPCOM000022273D
Publication Date: 2004-Mar-03
Document File: 3 page(s) / 81K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for the prevention of the build up of oxygen in chemical etch baths. Benefits include improved functionality, improved performance, and improved yield.

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Method for the prevention of oxygen build-up in chemical etch baths

Disclosed is a method for the prevention of the build up of oxygen in chemical etch baths. Benefits include improved functionality, improved performance, and improved yield.

Background

         When exposed to ambient air, the oxygen level in a chemical-etch bath rises to the point where a thin layer of silicon dioxide can form on the surface of a wafer at a rate faster than or competitive with the etch rate. Because the silicon etch chemistries are selective to silicon, the presence of the oxide film prevents silicon etching. The constant introduction of oxygen causes the functional life of the bath chemistry to be approximately six hours (see Figure 1).

         The presence of oxygen poses the risk of an incomplete etch. If the formation of oxide interferes with the etching, either uniformly or non-uniformly across the wafer, the entire etch process must be restarted. As a result, damage can occur to substrate materials, yield is reduced, and costs are increased.

         Replenishment of the bath chemistry about every six hours as it becomes too oxygen enriched heavily impacts throughput time.

General description

The disclosed method prevents the introduction of oxygen into the bath chemistry and removes diffused oxygen. The method prevents the oxygen level from reaching the point where silicon dioxide forms on the wafer surface and interferes with silicon etching.

         The key elements of the method include:

•         Diffusion of inert gas into the bath chemistry during recirculation

•         Removal of oxygen from the chemistry during recirculation

•         Formation of a layer of inert gas on the surface of the bath chemistry

•         Sealing of the bath from ambient environment during and between processing

•         Presence of oxygen scavengers in the...