Single Wafer Silicon Nitride Etching with Soluble Silica Complexes
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Solution Overview
Problem
The wet etching process for semiconductor substrates, particularly in removing silicon nitride layers, faces challenges such as particle accumulation and cross-contamination in batch processes, leading to reduced etching performance and increased manufacturing costs, while single wafer processes suffer from low throughput due to compromised selectivity and etch rate.
Innovation Solution
A single wafer etching process using a mixture of phosphoric acid and a silicon-containing material, such as organosilane or colloidal silica, is employed, which is delivered to the wafer surface at controlled temperatures to maintain high selectivity and prevent silica precipitate formation, thereby enhancing etch rate and throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a batch wet etching process using hot phosphoric acid is used to remove silicon nitride, then the etching capability is sufficient, but silica precipitates accumulate in the bath reducing etching performance and bath age
Solution Approach 1:
The patent extracts the harmful silica precipitates from the etching system by introducing a silicon-containing material that reacts with phosphoric acid to form soluble silicon-phosphorus complexes, preventing precipitate formation and accumulation in the bath
Solution Approach 2:
The silicon-containing material acts as an intermediary substance that mediates between phosphoric acid and silicon nitride, forming soluble intermediates that prevent silica precipitation while maintaining etching effectiveness
2Productivity
If a batch wet etching process is used to remove silicon nitride, then etching can be performed, but cross-contamination occurs among semiconductor substrates requiring post-cleaning
Solution Approach 1:
The patent employs a single-wafer processing approach where each wafer is processed individually with fresh etching solution, effectively making the processing environment disposable for each wafer to prevent cross-contamination, though this reduces batch processing efficiency
3Speed
If the temperature of phosphoric acid is increased to improve etch rate, then etching speed increases, but selectivity between silicon nitride and silicon oxide decreases
Solution Approach 1:
The patent changes the chemical composition parameters of the etching solution by adding silicon-containing materials, which modifies the etching chemistry to achieve high selectivity at elevated temperatures, decoupling the trade-off between etch rate and selectivity
4Reliability
If a single wafer etching process is used to prevent particle accumulation, then particle contamination is reduced, but throughput decreases due to compromised selectivity and etch rate
Solution Approach 1:
The patent modifies the etching solution composition by adding silicon-containing materials, enabling single-wafer processing to achieve both high particle contamination control and maintained throughput through enhanced etching performance
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
The process achieves selectivity greater than or equal to 100:1 and maintains a satisfactory etch rate of silicon nitride, addressing the issues of particle accumulation and low throughput, while eliminating the need for post-cleaning processes and reducing manufacturing costs.
Implementation Method 1
a wet etching process is utilized to etch material from target locations on a semiconductor substrate
Implementation Method 2
particles such as silica precipitates may be generated and then accumulated in the bath
Data Source
AI summary
A method of selectively removing silicon nitride is provided. The method includes: providing a wafer having silicon nitride on a surface of the wafer; providing a mixture of phosphoric acid and a silicon-containing material; and delivering the mixture to the surface of the wafer to remove the silicon nitride. Single wafer etching apparatuses of selectively removing silicon nitride are also provided.