Maintenance Efficacy Evaluation via Cumulative Sum Chart
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Solution Overview
Problem
Current methods for evaluating the efficacy of prevention maintenance for semiconductor tools do not effectively assess whether maintenance activities improve wafer production yield, as they rely on fixed intervals rather than actual production parameter stability.
Innovation Solution
A method that involves selecting a tool, choosing a productive parameter, collecting and analyzing data before and after maintenance using a moving average and Cumulative Sum chart to determine stability and efficacy of maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If prevention maintenance is executed at fixed intervals, then the tool is assumed to be adjusted to a good state and manufacturing capacity meets demands, but it cannot ensure that the maintenance is actually helpful to wafer production and yield may still be reduced
Solution Approach 1:
The patent implements a feedback mechanism by collecting productive parameter data before and after maintenance, transforming it into Cumulative Sum charts, and using the stability of parameter variations to evaluate whether maintenance actually improved tool performance. This feedback loop replaces fixed-schedule maintenance with performance-based maintenance decisions.
Solution Approach 2:
The system enables self-service by automatically collecting productive parameter data from the tool, processing it through moving average and Cumulative Sum transformations, and generating maintenance efficacy evaluations without requiring external intervention. The tool's own operational data serves as the basis for maintenance decisions.
2Reliability
If prevention maintenance is executed too early, then the tool availability is maintained, but recourse costs of basic consumables are wasted and usage rate of the lapping tool decreases
Solution Approach 1:
The patent changes the parameter used for maintenance scheduling from fixed time intervals to dynamic evaluation based on productive parameter stability. By monitoring parameters such as lapping pressure, speed, and temperature, and evaluating their variation stability through Cumulative Sum charts, the system determines the optimal maintenance timing based on actual tool performance rather than predetermined schedules.
3Productivity
If prevention maintenance is executed too late, then the usage rate of the lapping tool is maximized, but the demand of size precision of products cannot be achieved which reduces yield
Solution Approach 1:
The system continuously monitors productive parameters and provides feedback on tool performance degradation trends. By analyzing the stability of parameter variations using Cumulative Sum charts, the system detects when precision is beginning to deteriorate and triggers maintenance at the optimal moment, preventing precision loss while maximizing tool usage.
Data Source
AI summary
A method for evaluating efficacy of prevention maintenance for a tool includes the steps of: choosing a tool which has been maintained preventively and choosing a productive parameter of the tool; collecting values of the productive parameter generated from the tool during a time range for building a varying curve of the productive parameter versus time, modifying the varying curve with a moving average method; transforming the varying curve into a Cumulative Sum chart; and judging whether the values of the productive parameter generated from the tool after the prevention maintenance are more stable, compared with the values of the productive parameter generated from the tool before the prevention maintenance, according to the Cumulative Sum chart. Thereby, if the varying of the values of the productive parameter after the prevention maintenance isn't stable, then the efficacy of this prevention maintenance for the tool is judged not good.