Wafer Tester Preheating Control Based on Lot-Change Idle Time
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Solution Overview
Problem
Wafer testing devices experience unstable device temperatures when idle for long periods, leading to inaccurate measurements and increased measuring time due to unnecessary preheating upon each wafer lot change, thereby reducing productivity.
Innovation Solution
A preheating control system with a timing circuit and controlling circuit that calculates lot-changing time and determines whether to perform device preheating based on this time compared to a standard, allowing preheating only when the lot-changing time exceeds a preset threshold, thereby optimizing preheating operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If device preheating is performed whenever a wafer lot is inserted, then temperature stability is improved, but total measuring time increases and productivity decreases
Solution Approach 1:
The system changes the parameter of preheating execution by evaluating the idle time parameter. When idle time exceeds a threshold, preheating is performed; when it is below the threshold, preheating is skipped. This dynamic parameter-based decision resolves the contradiction by adapting preheating behavior to actual temperature stability needs.
Solution Approach 2:
The system implements feedback by calculating idle time between wafer lot removal and insertion, comparing it against a threshold, and using this feedback to决定是否 perform preheating. This closed-loop control ensures preheating is only performed when temperature stability requires it, avoiding unnecessary preheating that would reduce productivity.
2Measurement precision
If device preheating is performed upon each wafer lot change, then measurement accuracy is improved, but time loss increases
Solution Approach 1:
The system dynamically changes the preheating execution parameter based on the idle time parameter. When idle time is sufficient, preheating is performed to ensure measurement accuracy; when idle time is insufficient, preheating is skipped to avoid time loss. This resolves the contradiction between measurement precision and time efficiency.
3Stability of the object's composition
If preheating system is always active, then device temperature stability is maintained, but energy consumption increases and productivity decreases
Solution Approach 1:
The system changes the preheating activation parameter based on idle time evaluation. Instead of keeping the preheating system always active, it activates preheating only when idle time exceeds a threshold, thereby maintaining temperature stability when needed while reducing energy consumption when preheating is unnecessary.
Data Source
AI summary
A preheating control system comprising a testing device and a processor is provided in present disclosure. The testing device is configured to perform a wafer testing on a wafer lot and perform a device preheating on the testing device. The processor is coupled to the testing device and comprises a timing circuit and a controlling circuit. The timing circuit is configured to calculate a lot-changing time, wherein the lot-changing time is a difference between a time corresponding to removal of a previous wafer lot from the testing device and a time corresponding to insertion of the wafer lot into the testing device. The controlling circuit is configured to control the testing device to perform the wafer testing, and configured to control the testing device to perform the device preheating according to the lot-changing time and a standard lot-changing time.