Selective Silicon Nitride Etching Preserving SiGe
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Solution Overview
Problem
Current methods for removing silicon nitride from semiconductor substrates during integrated circuit fabrication often result in the unintended removal of silicon-germanium alloys, necessitating the development of a selective etching process that distinguishes between silicon nitride and SiGex regions.
Innovation Solution
A method involving the use of an oxidizing agent, such as a mixture of sulfuric acid and hydrogen peroxide, followed by a silicon nitride etching agent like phosphoric acid and sulfuric acid, is applied as a liquid stream to selectively remove silicon nitride from substrates while preserving SiGex regions, utilizing a controlled temperature and steam to enhance etching efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used to remove silicon nitride, then silicon nitride removal is achieved, but silicon-germanium regions are also unintentionally removed
Solution Approach 1:
An oxidizing agent is applied to the substrate before the etching step to selectively oxidize the silicon-germanium regions, forming a protective oxide layer. This preliminary oxidation action prevents the subsequent etching agent from attacking the silicon-germanium material, thereby preserving it while allowing silicon nitride removal.
Solution Approach 2:
The oxidizing agent acts as an intermediary substance that modifies the surface chemistry of the silicon-germanium regions. By converting the silicon-germanium surface to an oxidized state, the intermediary creates a chemical barrier that selective etching agents cannot penetrate, thus protecting the underlying material during the etching process.
2Productivity
If high temperature processing is used to enhance etching rates, then etching efficiency is improved, but selectivity between materials decreases
Solution Approach 1:
The process utilizes temperature as a controllable parameter, operating at relatively low temperatures (below the damage threshold of silicon-germanium) to maintain material selectivity. By carefully controlling the temperature parameter, the process achieves adequate etching rates while preserving the selectivity between silicon nitride and silicon-germanium regions.
Solution Approach 2:
A strong oxidizing agent is employed to chemically activate and protect the silicon-germanium surfaces before etching. This chemical modification allows the etching process to proceed with high selectivity at lower temperatures, as the oxidized surface provides a protective barrier that prevents non-selective material removal.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach achieves selective etching of silicon nitride with improved selectivity over SiGex and silicon oxide, allowing for precise material removal at relatively low processing temperatures, with enhanced etching rates at temperatures above 180°C, thus addressing the challenge of preserving SiGex regions during silicon nitride removal.
Implementation Method 1
dispensing an oxidizing agent onto the surface of the substrate to oxidize the exposed SiGex
Implementation Method 2
dispensing a silicon nitride etching agent as a liquid stream onto the surface of the substrate to remove at least a portion of the silicon nitride
Implementation Method 3
utilizing a controlled temperature and steam to enhance etching efficiency
Implementation Method 4
enhanced etching rates at temperatures above 180°C
Data Source
AI summary
A method for selectively removing silicon nitride is described. In particular, the method includes providing a substrate having a surface with silicon nitride exposed on at least one portion of the surface and SiGex (x is greater than or equal to zero) exposed on at least another portion of the surface, and dispensing an oxidizing agent onto the surface of the substrate to oxidize the exposed SiGex. Thereafter, the method includes dispensing a silicon nitride etching agent as a liquid stream onto the surface of the substrate to remove at least a portion of the silicon nitride.