Silicon Wafer Surface Finishing Without Wet Etching
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Solution Overview
Problem
Conventional silicon wafer manufacturing methods using mixed-acid or alkali etching result in non-uniform etching, surface roughness deterioration, and deep pits, leading to reduced flatness and increased environmental and cost burdens due to chemical usage and wastewater treatment.
Innovation Solution
A silicon wafer manufacturing method involving a grinding step to achieve an arithmetic surface roughness of 10 nm or less, followed by isotropic whole-surface dry-etching with an etching removal of 1 μm or less, and a double-side polishing step with a stock removal of 3 μm or less, eliminating the need for wet etching and reducing chemical usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wet etching with mixed acid or alkali is performed, then mechanically damaged layer is removed, but productivity decreases due to large stock removal required in subsequent polishing
Solution Approach 1:
The patent performs preliminary mechanical polishing to remove the mechanically damaged layer before the final polishing step. This preliminary action removes the damaged layer with minimal stock removal, so that the subsequent final polishing step requires very little stock removal (0.5 μm or less per surface). This eliminates the need for large stock removal that would be required if wet etching were used first, thereby improving productivity.
2Ease of manufacture
If wet etching with mixed acid or alkali is performed, then mechanically damaged layer is removed, but environmental burden and cost increase due to chemical usage and wastewater treatment
Solution Approach 1:
The patent replaces the chemical wet etching process with a mechanical polishing process. This substitution eliminates the use of large amounts of chemicals (mixed acids or alkalis) and the associated wastewater treatment requirements. The mechanical polishing process uses minimal consumables and generates no harmful chemical waste, thereby eliminating environmental burden and treatment costs while maintaining process effectiveness.
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 method effectively removes mechanically damaged layers without deteriorating flatness, enhancing productivity and reducing environmental and cost burdens associated with chemical usage.
Implementation Method 1
a grinding step of grinding front and back surfaces of a raw wafer
Implementation Method 2
a dry-etching step of subjecting the wafer obtained in the grinding step to isotropic whole-surface dry-etching
Implementation Method 3
dry etching using plasma, dry etching, or vapor-phase etching
Implementation Method 4
a double-side polishing step of, after the dry-etching step, polishing both surfaces of the wafer
Data Source
AI summary
The present invention is a silicon wafer manufacturing method including a grinding step of grinding front and back surfaces of a raw wafer to obtain a wafer having an arithmetic surface roughness Sa per 2 μm2 of 10 nm or less; a dry-etching step of subjecting the wafer obtained in the grinding step to isotropic whole-surface dry-etching with an etching removal of 1 μm or less per surface to remove a mechanically damaged layer introduced into each of front and back surfaces of the wafer in the grinding step; and a double-side polishing step of, after the dry-etching step, polishing both surfaces of the wafer with a stock removal of 3 μm or less per surface. Thus, the silicon wafer manufacturing method that enables to manufacture a wafer having high flatness can be provided.