Selective Etching of Silicon Oxide Films via Segmented Reactant Flow
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Solution Overview
Problem
Current methods for precleaning semiconductor substrates are inadequate in removing intervening materials like native oxides, which can lead to defects during material layer deposition, especially on substrates with high aspect ratio features, due to self-limiting chemistries and interaction with substrate topologies.
Innovation Solution
A method involving a semiconductor processing system that uses a halogen-containing reactant and a hydrogen-containing reactant to form preclean materials, specifically ammonium hexafluorosilicate and silicon fluoride, to effectively remove silicon oxide from substrate surfaces, with controlled etching ratios and minimal residual reactant influence, allowing for uniform cleaning and subsequent epitaxial deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional precleaning methods are used to remove silicon oxide, then some cleaning effect is achieved, but the cleaning is self-limiting and cannot thoroughly remove intervening materials, especially on substrates with high aspect ratio features
Solution Approach 1:
The precleaning process is divided into two distinct sequential steps: first forming a preclean material layer using halogen-containing reactant and hydrogen-containing reactant, then removing the silicon oxide using additional halogen-containing reactant. This segmentation allows each step to be optimized independently, achieving both thorough cleaning and defect prevention.
Solution Approach 2:
A preclean material layer is formed as an intermediate substance between the substrate and the final cleaning step. This intermediate layer facilitates controlled removal of silicon oxide and prevents direct harmful interactions, enabling uniform cleaning across complex substrate geometries.
2Productivity
If halogen-containing reactant and hydrogen-containing reactant are used together to form preclean material, then effective silicon oxide removal is achieved, but intermediate reaction products accumulate and limit further etching
Solution Approach 1:
The reactant introduction is segmented into phases: first introducing halogen-containing reactant and hydrogen-containing reactant together to form preclean material, then introducing only additional halogen-containing reactant to remove silicon oxide without forming more preclean material. This prevents intermediate product accumulation while maintaining high etching rates.
Solution Approach 2:
The process uses periodic introduction of different reactant combinations: an initial period with both halogen and hydrogen reactants to form preclean material, followed by a second period with only halogen reactant to remove silicon oxide. This periodic action maintains productivity while eliminating harmful intermediate accumulation.
3Device complexity
If conventional single-step precleaning is used, then process simplicity is maintained, but uniform cleaning on substrates with complex geometries and high aspect ratio features cannot be achieved
Solution Approach 1:
The precleaning process is segmented into two sequential steps with different reactant combinations, allowing each step to target specific cleaning requirements. This segmentation achieves uniform cleaning on complex geometries while keeping the overall process relatively simple and controlled.
Solution Approach 2:
The process changes chemical parameters by introducing different reactant combinations in sequence: first halogen-containing and hydrogen-containing reactants, then additional halogen-containing reactant. This parameter change enables adaptation to complex substrate geometries while maintaining process simplicity.
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 ensures thorough and uniform removal of silicon oxide, preventing defects and enabling high-quality epitaxial layer deposition on substrates with complex geometries by limiting the formation of intermediate reaction products and maintaining reaction sustainability without continuous catalyst supply.
Implementation Method 1
A halogen-containing reactant and a hydrogen-containing reactant are flowed into the reaction chamber. A first preclean material formed from the halogen-containing reactant, the hydrogen-containing reactant, and a first portion of the silicon oxide on the surface of the substrate. Additional halogen-containing reactant is flowed into the reaction chamber without flowing additional hydrogen-containing reactant into the reaction chamber and a second preclean material formed from the additional halogen-containing reactant and a second portion of the silicon oxide on the surface of the substrate.
Implementation Method 2
the method may include sublimating the first preclean material from the surface of the substrate subsequent to forming the second preclean material from the additional halogen-containing reactant and the silicon oxide on the surface of the substrate.
Data Source
AI summary
A method of precleaning a substrate includes supporting a substrate with silicon oxide on its surface within a reaction chamber of a semiconductor processing system and flowing a halogen-containing reactant and a hydrogen-containing reactant into the reaction chamber. A first preclean material is formed from the halogen-containing reactant, the hydrogen-containing reactant, and a first portion of the silicon oxide on the surface of the substrate. Additional halogen-containing reactant is flowed into the reaction chamber without flowing additional hydrogen-containing reactant into the reaction chamber, and a second preclean material is formed from the additional halogen-containing reactant and a second portion of the silicon oxide on the surface of the substrate. Methods of forming structures on substrates and semiconductor processing systems are also described.