Patent ID: 9685362
Date: 2017-06-20
CPC Classifications: G01B,G01S,H01L,Y10T

Claim:
1. An apparatus, comprising: a chuck in a process chamber, said chuck configured to removeably hold a substrate for processing; an array of three or more ultrasonic sensors in said process chamber, each sensor of said three or more ultrasonic sensors configured to emit and detect ultrasonic sound waves, each ultrasonic sensor of said three or more ultrasonic sensors equally spaced from each other and arranged about a center of said chuck and positioned relative to said chuck so as to send a respective ultrasonic sound wave to a respective preselected peripheral region of said substrate and receive a respective return ultrasonic sound wave from said preselected peripheral region of said substrate; a ceramic ring surrounding the chuck, wherein each ultrasonic sensor of the three or more ultrasonic sensors is notched into the ceramic ring, wherein a top surface of each ultrasonic sensor of the three or more ultrasonic sensors is coplanar with a top surface of the substrate, wherein a bottom surface of each ultrasonic sensor of the three or more ultrasonic sensors is coplanar with a bottom surface of the substrate, wherein a top surface of the ceramic ring is coplanar with a top surface of the chuck wherever on the ceramic ring there is a respective ultrasonic sensor of the three or more ultrasonic sensors, wherein the top surface of the ceramic ring is coplanar with the top surface of the substrate wherever on the ceramic ring there is no ultrasonic sensor of the three or more ultrasonic sensors, and wherein the bottom surface of the substrate is in direct physical contact with the top surface of the chuck; and a controller connected to said array of three or more ultrasonic sensors and configured to compare a measured position of said substrate on said chuck to a specified placement of said substrate on said chuck based on a measured elapsed time between sending said ultrasonic sound wave and receiving said return ultrasonic sound wave for each ultrasonic sensor of said array of three or more ultrasonic sensors.