Silicon Wafer Single-Side Polishing Method for Defect Reduction
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Solution Overview
Problem
Conventional single-side polishing methods for silicon wafers struggle to achieve a completely flat surface, leading to high occurrences of stepped minute defects, which affect the quality and yield of polished silicon wafers.
Innovation Solution
A two-step single-side polishing method is introduced, where the first step focuses on removing the silicon oxide film with a higher polishing rate ratio, followed by a second step that polishes the bare silicon with a lower rate ratio, adjusting the applied pressure and relative speed to optimize the polishing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional single-side polishing method is used, then polishing process is simple, but stepped minute defects occur frequently
Solution Approach 1:
The polishing process is divided into three distinct steps: first polishing step (removing natural oxide film), second polishing step (intermediate polishing), and third polishing step (final polishing). Each step uses different polishing conditions including varying applied pressures and relative speeds, allowing systematic removal of defects while maintaining surface quality.
Solution Approach 2:
The first polishing step performs preliminary action by removing the natural oxide film before subsequent polishing steps. This preliminary removal of the oxide film prevents it from interfering with the polishing of bare silicon in later steps, thereby reducing stepped minute defects.
2Productivity
If polishing pressure is increased to improve polishing rate, then productivity increases, but polishing uniformity deteriorates
Solution Approach 1:
The polishing conditions are dynamically adjusted across different steps. The applied pressure and relative speed are varied systematically: the first step uses higher pressure for rapid oxide film removal, while subsequent steps use lower pressures for uniform polishing of bare silicon, optimizing both productivity and uniformity at different stages.
Solution Approach 2:
Polishing parameters including applied pressure and relative speed are changed between steps. The first polishing step uses different parameters compared to the second and third steps, allowing optimization of polishing rate in the first step while ensuring uniformity in subsequent steps.
3Productivity
If relative speed is increased to reduce polishing time, then productivity improves, but surface quality deteriorates
Solution Approach 1:
The relative speed between the polishing head and platen is dynamically adjusted across steps. Higher relative speeds are used in the first polishing step for rapid oxide film removal, while lower relative speeds are employed in the second and third steps to ensure high surface quality and reduce stepped minute defects.
Solution Approach 2:
The polishing process uses periodic action with distinct phases. Each polishing step has specific duration and parameter settings, with the first step focused on rapid material removal and subsequent steps focused on surface quality improvement, creating a periodic cycle of aggressive and gentle polishing.
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 significantly reduces the occurrence rate of stepped minute defects, improving the quality and yield of silicon wafers by ensuring a more uniform polishing process.
Implementation Method 1
performing chemical mechanical polishing on the polishing target surface of the semiconductor wafer
Implementation Method 2
a laser L (e.g. He—Ne laser) is split by a beam splitter S and applied to the surface of the semiconductor wafer W
Data Source
AI summary
A silicon wafer single-side polishing method that can significantly improve the stepped minute defect occurrence rate is provided. The silicon wafer single-side polishing method comprises: a first polishing step of performing polishing on one side of a silicon wafer under a first polishing condition; and a second polishing step of performing polishing on the silicon wafer under a second polishing condition in which at least one of an applied pressure and a relative speed in the first polishing condition is changed, after the first polishing step, wherein a polishing rate ratio according to the first polishing condition is higher than a polishing rate ratio according to the second polishing condition.