SiGe Selective Etching Uniformity via ClF3 and HF Gas Merging
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Solution Overview
Problem
The existing methods for selectively etching silicon germanium (SiGe) layers on semiconductor wafers face challenges in achieving uniform etching amounts due to non-uniform removal of natural oxide films, leading to inconsistent etching rates and film quality.
Innovation Solution
Simultaneously supplying a fluorine-containing gas and chlorine trifluoride (ClF3) gas in a vacuum atmosphere during the etching process, with hydrogen fluoride (HF) gas being used to uniformly adsorb and remove natural oxide films before ClF3 exposure, ensuring consistent etching rates across SiGe layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If only chlorine trifluoride gas is supplied for etching SiGe layers, then high etching selection ratio is achieved, but etching amount uniformity deteriorates
Solution Approach 1:
The patent combines chlorine trifluoride gas (for selective etching) and fluorine-containing gas (for oxide film removal) into a single etching process step. This merging of functions allows simultaneous achievement of high etching selection ratio and uniform etching amount without requiring separate processing steps, thus improving manufacturing precision without proportionally increasing device complexity.
Solution Approach 2:
The fluorine-containing gas performs preliminary removal of natural oxide films from SiGe layer surfaces before the chlorine trifluoride gas performs the main etching operation. This preliminary action ensures uniform exposure of the SiGe layers, which directly improves etching amount uniformity while maintaining the high selection ratio provided by chlorine trifluoride.
2Reliability
If natural oxide films are not uniformly removed, then etching selection ratio is maintained, but etching rate consistency deteriorates
Solution Approach 1:
The patent changes the chemical parameters by introducing fluorine-containing gas that specifically reacts with oxide films. This parameter change (adding fluorine chemistry to the etching process) enables uniform oxide removal and consistent etching rates across different SiGe layers, improving reliability while the overall process remains relatively simple to implement.
3Manufacturing precision
If fluorine-containing gas and chlorine trifluoride gas are simultaneously supplied, then etching amount uniformity is improved, but process complexity increases
Solution Approach 1:
The patent merges the functions of oxide removal (fluorine-containing gas) and selective etching (chlorine trifluoride gas) into a single simultaneous process step. This consolidation improves etching uniformity while minimizing the increase in gas supply system complexity, as both gases are supplied through the existing etching chamber infrastructure without requiring entirely new equipment.
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 results in uniform etching amounts and improved micro-loading of SiGe layers, enhancing the flatness of the surface and reproducibility of etching results, while maintaining high selectivity for SiGe layers over Si, SiO2, and SiN layers.
Implementation Method 1
hydrogen fluoride (HF) gas being used to uniformly adsorb and remove natural oxide films
Implementation Method 2
a method of performing etching by supplying chlorine trifluoride (ClF3) gas
Implementation Method 3
simultaneously supplying a fluorine-containing gas and a chlorine trifluoride gas to the substrate
Data Source
AI summary
A technique for making etching amounts uniform in selectively etching SiGe layers formed on a wafer with respect to at least one of an Si layer, an SiO2 layer, and an SiN layer is provided. In an etching process where SiGe layers in a wafer W in which the SiGe layers and Si layers are alternately stacked and exposed in a recess are removed by side etching, ClF3 gas and HF gas are simultaneously supplied to the wafer W. Accordingly, it is possible to make the etching rates for respective SiGe layers uniform, and it becomes possible to obtain a uniform etching amount for respective SiGe layers.