Method and apparatus for temperature measurement using thermal expansion

Claim 1

An apparatus for determining the temperature of a semiconductor wafer during processing comprising: a light source directing a beam of light at an edge of said semiconductor wafer: a chopper wheel mounted to rotate through a reflected beam of said beam of light off said semiconductor wafer; first and second photodetectors mounted to receive said reflected beam as chopped by said chopper wheel; processing means, coupled to said first and second photodetectors, for determining a phase difference between first and second electrical signals from said first and second photodetectors; means for moving said chopper wheel relative to said semiconductor wafer in a direction corresponding to the sign of said phase difference until said phase difference is eliminated; means for measuring a distance said chopper wheel is moved; processing means for applying said distance to a predetermined coefficient of thermal expansion for said semiconductor wafer to produce a signal indicating the temperature of said semiconductor wafer.

Claim 2

An apparatus for determining the temperature of a semiconductor wafer during processing comprising: a light source directing a beam of light at an edge of said semiconductor wafer: a chopper wheel mounted to rotate through a reflected beam of said beam of light off said semiconductor wafer; first and second photodetectors mounted to receive said reflected beam as chopped by said chopper wheel; processing means, coupled to said first and second photodetectors, for determining a phase difference between first and second electrical signals from said first and second photodetectors; means for moving said chopper wheel relative to said semiconductor wafer in a direction corresponding to the sign of said phase difference until said phase difference is eliminated; means for measuring a distance said chopper wheel is moved; processing means for applying said distance to a predetermined coefficient of thermal expansion for said semiconductor wafer to produce a signal indicating the temperature of said semiconductor wafer.

Claim 3

A method for determining the relative temperature of a semiconductor wafer during heat treatment comprising the steps of: measuring the physical change in a dimension of said semiconductor wafer by reflecting a light beam off an edge of said semiconductor wafer and detecting the focus position of a reflected beam, said detecting step including rotating a chopper wheel through said reflected beam, generating first and second electrical signals from two photodetectors receiving said reflected beam as chopped by said chopper wheel, determining a phase difference between said first and second electrical signals, moving said chopper wheel relative to said semiconductor wafer in a direction corresponding to the sign of said phase difference until said phase difference is eliminated, and measuring the movement of said chopper wheel; applying said measured physical change to a predetermined coefficient of thermal expansion for said semiconductor wafer.

Claim 4

A method for determining the relative temperature of a semiconductor wafer during heat treatment comprising the steps of: measuring the physical change in a dimension of said semiconductor wafer by reflecting a light beam off an edge of said semiconductor wafer and detecting the focus position of a reflected beam, said detecting step including rotating a chopper wheel through said reflected beam, generating first and second electrical signals from two photodetectors receiving said reflected beam as chopped by said chopper wheel, determining a phase difference between said first and second electrical signals, moving said chopper wheel relative to said semiconductor wafer in a direction corresponding to the sign of said phase difference until said phase difference is eliminated, and measuring the movement of said chopper wheel; applying said measured physical change to a predetermined coefficient of thermal expansion for said semiconductor wafer.