Wafer Re-cleaning Control for Semiconductor Yield
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Solution Overview
Problem
In substrate treatment systems for semiconductor manufacturing, wafers determined to be abnormal during inspection are often prematurely collected, leading to reduced yield due to incomplete cleaning, as existing systems do not effectively re-clean wafers that can become exposable after additional cleaning.
Innovation Solution
A substrate treatment system with a cleaning unit, inspection unit, and substrate transfer mechanism, where the substrate transfer control part re-routes wafers determined to be unexposable but potentially exposable after re-cleaning, allowing for continuous treatment and reducing the number of wafers collected prematurely.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wafers determined to be abnormal during inspection are collected immediately, then the inspection process is simplified and completed quickly, but the yield of substrate treatment is reduced due to premature collection of wafers that could be rescued by re-cleaning
Solution Approach 1:
The system performs preliminary classification of wafers into three categories (exposable, unexposable, and re-cleaning candidate) based on inspection results. Wafer information is stored and analyzed before final disposition decisions are made, allowing potential yield improvements through re-cleaning while maintaining process efficiency through pre-planned transfer routes.
Solution Approach 2:
The substrate transfer control part continuously monitors inspection results and dynamically adjusts transfer destinations based on wafer state. The system uses feedback from inspection data to determine whether to transfer wafers to cleaning units for re-cleaning or directly to collection, optimizing yield while adapting to real-time wafer conditions.
2Productivity
If all wafers determined to be unexposable are transferred to collection without re-cleaning, then the process flow is simplified and faster, but potential exposable wafers are lost reducing overall yield
Solution Approach 1:
The system performs preliminary assessment of wafer inspectability and stores wafer information before making final disposition decisions. This preliminary action allows the system to identify potential re-cleaning candidates without delaying the overall process flow, maintaining throughput while improving reliability of exposable state determination.
Solution Approach 2:
The system changes the parameter of wafer disposition from a binary decision (collect or process) to a three-state system (exposable, unexposable, re-cleaning candidate). This parameter change allows for more nuanced judgment of wafer quality and increases the accuracy of exposable state determination while maintaining efficient process flow.
Data Source
AI summary
An interface station of a coating and developing treatment system has: a cleaning unit cleaning at least a rear surface of a wafer before the wafer is transferred into an exposure apparatus; an inspection unit inspecting the rear surface of the cleaned wafer whether the wafer is exposable, before it is transferred into the exposure apparatus; wafer transfer mechanisms including arms transferring the wafer between the units and a wafer transfer control part controlling operations of the wafer transfer mechanisms. When it is determined that a state of the wafer becomes an exposable state by re-cleaning in the cleaning unit as a result of the inspection, the wafer transfer control part controls the wafer transfer mechanisms to transfer the wafer again to the cleaning unit.