Wafer Inspection Temperature Control via Mahalanobis Sensor Selection
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Solution Overview
Problem
Existing inspection apparatuses face challenges in accurately selecting the most suitable temperature sensor for temperature control of electronic devices on a wafer, especially when devices are arranged in uneven distributions, as the closest temperature sensor may not always be appropriate for effective temperature regulation.
Innovation Solution
An inspection apparatus that acquires coordinate information of electronic devices and temperature sensors, calculates the Mahalanobis distance between the average vector of device positions and sensor positions, and selects the sensor with the smallest Mahalanobis distance for temperature control, ensuring accurate temperature measurement and regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the temperature sensor positioned closest to the electronic device (based on physical distance) is selected for temperature control, then the selection process is simple, but the temperature control accuracy deteriorates when electronic devices are arranged in uneven distribution
Solution Approach 1:
The patent changes the parameter used for sensor selection from simple physical distance to Mahalanobis distance, which incorporates the covariance structure of device positions. This parameter transformation allows the selection criterion to adapt to different distribution patterns (even or uneven), resolving the contradiction between selection simplicity and control accuracy
Solution Approach 2:
The patent replaces the mechanical/geometric approach of selecting the closest sensor based on Euclidean distance with a statistical approach using Mahalanobis distance. This substitution transforms the selection mechanism from a purely spatial criterion to one that accounts for the statistical distribution characteristics of devices, thereby improving accuracy without significantly complicating the selection process
2Measurement precision
If multiple temperature sensors are used to accommodate uneven device distribution, then the temperature control accuracy is improved, but the device complexity increases
Solution Approach 1:
The patent performs preliminary calculation of the Mahalanobis distance matrix based on the known device positions before actual temperature control begins. This preliminary action prepares the optimal sensor selection criterion in advance, allowing accurate temperature control to be achieved without requiring complex real-time calculations or additional sensors, thus avoiding increased device complexity
Data Source
AI summary
An inspection apparatus includes: an acquisition part configured to acquire first coordinate information indicating a position of an inspection object on a stage and a plurality of pieces of second coordinate information indicating positions of a plurality of temperature sensors on the stage when performing an inspection of the inspection object; a calculation part configured to calculate a Mahalanobis distance between a position specified by an average vector of the first coordinate information and the positions of the plurality of temperature sensors; a selection part configured to select at least one temperature sensor including a temperature sensor having a smallest Mahalanobis distance, among the plurality of temperature sensors; and a controller configured to control a temperature of the inspection object using temperature data measured by the selected at least one temperature sensor.