Double-Side Silicon Wafer Polishing Agent Transition
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Solution Overview
Problem
The existing double-side polishing method for silicon wafers often results in micro scratches due to oscillation of the carrier plate during the switching of polishing agents, caused by increased frictional resistance without abrasive grains, leading to defects on the wafer surfaces.
Innovation Solution
A method involving a double-side polishing apparatus where the first and second polishing agents are mixed during the transition period, with the upper and lower plates continuously rotated, and surface pressure reduced in the second polishing step to prevent oscillation and micro scratches, using an alkaline aqueous solution with abrasive grains for the first step and a water-soluble polymer solution without abrasive grains for the second step.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the polishing agent is switched from a solution with abrasive grains to a solution without abrasive grains, then the surface roughness is improved, but the carrier plate oscillates due to increased frictional resistance causing micro scratches
Solution Approach 1:
The patent applies preliminary action by gradually reducing the concentration of abrasive grains in the polishing agent before complete removal. The polishing process transitions through multiple stages where the abrasive grain concentration is progressively decreased (e.g., from 100% to 50%, then to 25%, and finally to 0%), allowing the system to adapt to changing friction conditions and prevent sudden oscillations that would cause micro scratches on the wafer surface.
2Ease of operation
If the rotation of upper and lower plates is stopped during polishing agent switching, then the switching can be performed, but the carrier plate oscillates when rotation resumes causing micro scratches
Solution Approach 1:
The patent maintains continuous rotation of the upper and lower plates throughout the polishing agent switching process. By keeping the rotation continuous and gradually changing the polishing agent composition rather than stopping and restarting, the system avoids sudden changes in frictional resistance that would cause carrier plate oscillation and subsequent micro scratches.
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 prevents the formation of micro scratches on the silicon wafer surfaces during polishing, ensuring high productivity and surface quality by maintaining continuous rotation and controlled pressure during the agent switching process.
Implementation Method 1
a first polishing step of performing double-side polishing while supplying a first polishing agent that is an alkaline aqueous solution containing abrasive grains
Implementation Method 2
a first polishing step of performing double-side polishing while supplying a first polishing agent that is an alkaline aqueous solution containing abrasive grains
Implementation Method 3
a second polishing step of performing double-side polishing while supplying a second polishing agent that is an alkaline aqueous solution containing a water-soluble polymer with no abrasive grains
Data Source
AI summary
Provided is a method of double-side polishing a silicon wafer using a double-side polishing apparatus, the method including in succession: a first polishing step of performing double-side polishing while supplying a first polishing agent that is an alkaline aqueous solution containing abrasive grains to the polishing cloths; a polishing agent switching step of stopping the supply of the first polishing agent and starting the supply of a second polishing agent that is an alkaline aqueous solution containing a water-soluble polymer with no abrasive grains, with the polishing cloths of the upper plate and the lower plate being in contact with the front surface and the back surface of the silicon wafer, respectively and with the upper plate and the lower plate being continuously rotated; and a second polishing step of performing double-side polishing while supplying the second polishing agent to the polishing cloths.