Semiconductor wafer temperature determination by optical measurement of wafer expansion in processing apparatus chamber

Claim 1

A method of determining the temperature of and thermally processing wafers, of a material having a known coefficient of thermal expansion, stacked in parallel planes on an axis in a vacuum processing chamber of a wafer processing apparatus, the method comprising the steps of: placing a wafer stack in the chamber at a reference temperature; passing a spaced pair of beams of parallel light from at least one light source and along respective paths such that at least a portion of the light from each light beam is interrupted by opposite edges of one wafer of the stack when at the reference temperature, the paths being inclined at an angle to the axis and the planes; sensing with at least one light sensor, the amount of uninterrupted light from the beams that arrives opposite the edge from the light source, and generating a reference signal, representative of the positions of the edges, in response to the sensed light; storing the reference signal; changing the temperature of the wafers of the stack to a processing temperature; further passing a spaced pair of beams of parallel light along the paths from the source and through the chamber such that at least a portion of the light from each light beam is interrupted by the opposite edges of the one wafer when at the processing temperature; sensing with the sensor the amount of uninterrupted light from the beams arriving opposite the edge from the light source, when at the processing temperature, and generating, in response to the sensed light, a measurement signal representative of the positions of the edges; generating, from the stored reference and the processing signals, a dimension change signal responsive to the difference between the dimensions of the one wafer at the reference temperature and at the processing temperature; and deriving the processing temperature from the known coefficient of expansion of the material and the dimension change signal.

Claim 2

A method of determining the temperature of and thermally processing wafers, of a material having a known coefficient of thermal expansion, stacked in parallel planes on an axis in a vacuum processing chamber of a wafer processing apparatus, the method comprising the steps of: placing a wafer stack in the chamber at a reference temperature; passing a spaced pair of beams of parallel light from at least one light source and along respective paths such that at least a portion of the light from each light beam is interrupted by opposite edges of one wafer of the stack when at the reference temperature, the paths being inclined at an angle to the axis and the planes; sensing with at least one light sensor, the amount of uninterrupted light from the beams that arrives opposite the edge from the light source, and generating a reference signal, representative of the positions of the edges, in response to the sensed light; storing the reference signal; changing the temperature of the wafers of the stack to a processing temperature; further passing a spaced pair of beams of parallel light along the paths from the source and through the chamber such that at least a portion of the light from each light beam is interrupted by the opposite edges of the one wafer when at the processing temperature; sensing with the sensor the amount of uninterrupted light from the beams arriving opposite the edge from the light source, when at the processing temperature, and generating, in response to the sensed light, a measurement signal representative of the positions of the edges; generating, from the stored reference and the processing signals, a dimension change signal responsive to the difference between the dimensions of the one wafer at the reference temperature and at the processing temperature; and deriving the processing temperature from the known coefficient of expansion of the material and the dimension change signal.

Claim 8

A method of determining the temperature of and thermally processing a thin flat article, of a material having a known coefficient of thermal expansion, lying in a plane in a processing chamber of a processing apparatus, the method comprising the steps of: supporting an article in the chamber at a known reference temperature; passing a spaced pair of beams of parallel light from a pair of light sources, positioned outside of the chamber, and along respective paths through the chamber such that a portion of the light from each light beam is interrupted by opposite edges of the article when at the reference temperature; sensing with a pair of light sensors, the amount of uninterrupted light from the beams arriving opposite the edge from the light sources, and generating an analog reference signal, having a magnitude representative of the positions of the edges, in response to the sensed light; storing a digital representation of the reference signal; changing the temperature of the article to a processing temperature; further passing a spaced pair of beams of parallel light along the paths from the sources and through the chamber such that a portion of the light from each light beam is interrupted by the opposite edges of the article when at the processing temperature; sensing with the sensors the amount of uninterrupted light from the beams arriving opposite the edge from the light sources, when at the processing temperature, and generating, in response to the sensed light, a measurement signal representative of the positions of the edges; generating, from the stored representation of the reference signal and the processing signal, a digital dimension change signal responsive to the difference between the magnitudes of the reference and measurement signals and representative of the difference between the dimensions of the article at the reference temperature and at the processing temperature; and digitally deriving the processing temperature from the known coefficient of expansion of the material and the dimension change signal.

Claim 9

A method of determining the temperature of and thermally processing a thin flat article, of a material having a known coefficient of thermal expansion, lying in a plane in a processing chamber of a processing apparatus, the method comprising the steps of: supporting an article in the chamber at a known reference temperature; passing a spaced pair of beams of parallel light from a pair of light sources, positioned outside of the chamber, and along respective paths through the chamber such that a portion of the light from each light beam is interrupted by opposite edges of the article when at the reference temperature; sensing with a pair of light sensors, the amount of uninterrupted light from the beams arriving opposite the edge from the light sources, and generating an analog reference signal, having a magnitude representative of the positions of the edges, in response to the sensed light; storing a digital representation of the reference signal; changing the temperature of the article to a processing temperature; further passing a spaced pair of beams of parallel light along the paths from the sources and through the chamber such that a portion of the light from each light beam is interrupted by the opposite edges of the article when at the processing temperature; sensing with the sensors the amount of uninterrupted light from the beams arriving opposite the edge from the light sources, when at the processing temperature, and generating, in response to the sensed light, a measurement signal representative of the positions of the edges; generating, from the stored representation of the reference signal and the processing signal, a digital dimension change signal responsive to the difference between the magnitudes of the reference and measurement signals and representative of the difference between the dimensions of the article at the reference temperature and at the processing temperature; and digitally deriving the processing temperature from the known coefficient of expansion of the material and the dimension change signal.

Claim 15

An apparatus for processing semiconductor wafers of a material having a known coefficient of thermal expansion, the apparatus having a chamber in which a wafer is maintained at a processing temperature to be monitored, the apparatus comprising: a wafer support for supporting a wafer, the temperature of which is to be monitored, in a plane within the chamber, the wafer having a pair of generally opposite edge sections lying in the plane when supported on the support; a light source spaced from the edge sections of the wafer and operable to direct a spaced pair of beams of parallel light therefrom and along respective paths fixed in relation to the support such that a portion of the light of each light beam is interrupted by the generally opposite edge sections of the wafer in an amount corresponding to the position of the edge sections transverse the path; at least one light sensor positioned opposite the edge sections of the wafer from the light source and operable the amount of uninterrupted light from the beams; a monitoring signal generator operable to generate a monitoring signal in response to the amount of uninterrupted light from the beams impinging on the sensor; an information storage medium for storing information in response to a monitoring signal generated with the wafer at a first temperature; a temperature control operative to change the temperature of the wafer on the support to a second temperature; and a circuit responsive to the stored information, the known coefficient of thermal expansion and a monitoring signal generated with the wafer at a second temperature for generating an output signal representative of the difference between the first temperature and the second temperature.

Claim 16

An apparatus for processing semiconductor wafers of a material having a known coefficient of thermal expansion, the apparatus having a chamber in which a wafer is maintained at a processing temperature to be monitored, the apparatus comprising: a wafer support for supporting a wafer, the temperature of which is to be monitored, in a plane within the chamber, the wafer having a pair of generally opposite edge sections lying in the plane when supported on the support; a light source spaced from the edge sections of the wafer and operable to direct a spaced pair of beams of parallel light therefrom and along respective paths fixed in relation to the support such that a portion of the light of each light beam is interrupted by the generally opposite edge sections of the wafer in an amount corresponding to the position of the edge sections transverse the path; at least one light sensor positioned opposite the edge sections of the wafer from the light source and operable the amount of uninterrupted light from the beams; a monitoring signal generator operable to generate a monitoring signal in response to the amount of uninterrupted light from the beams impinging on the sensor; an information storage medium for storing information in response to a monitoring signal generated with the wafer at a first temperature; a temperature control operative to change the temperature of the wafer on the support to a second temperature; and a circuit responsive to the stored information, the known coefficient of thermal expansion and a monitoring signal generated with the wafer at a second temperature for generating an output signal representative of the difference between the first temperature and the second temperature.