Back to results
US 5,138,149 AGranted
Apparatus and method for monitoring radiant energy signals with variable signal gain and resolution enhancement
AssigneeXinix, Inc.
InventorsRaymond J. Cadet, Hung-Nan Chao, Sing-wing Hui, Eric Bogatin, Steven C. Leach
Life of this patent
Estimating the term…
Abstract
A sensor board for use with an endpoint controller which monitors light intensity is provided. The sensor board can provide a dynamic range of up to five million because a constant current driver and phase sensitive detector help eliminate noise from the detected signal. The sensor board can also subtract a DC voltage offset from the detected signal and amplify the difference to provide increased resolution of small changes in the detected signal.
Claims27
An apparatus comprising:
- a light source for providing light to be reflected from a substrate on which a chemical processing operation is performed;
- means for converting said light reflected from said substrate to an electrical signal;
- means for providing a plurality of gain settings for amplifying said electrical signal;
- means for choosing one of said plurality of gain settings for amplifying said electrical signal;
- means for amplifying said electrical signal to produce an amplified electrical signal within a predetermined range;
- and
- means for monitoring said amplified electrical signal so as to detect changes in the intensity of said reflected light.
4 more elements
A sensor board for processing electrical signals comprising:
- means for receiving an electrical current;
- means for converting said electrical current to a voltage;
- means for causing said electrical current to alternate between a high state and a low state such that said voltage alternates between a high state and a low state;
- means for subtracting said voltage in said low state from said voltage in said high state to produce a difference voltage;
- means for amplifying said difference voltage to produce an amplified difference voltage in a predetermined range;
- and
- means for monitoring said amplified difference voltage so as to detect changes in the magnitude of said electrical current.
4 more elements
A sensor board for processing electrical signals comprising:
- means for receiving an electrical current;
- means for converting said electrical current to a voltage, said converting means comprising an operational amplifier having a feedback loop, a plurality of resistors positioned in said feedback loop, each resistor having a different resistance value, and means for choosing one of said resistors such that said electrical current is converted to a voltage and amplified;
- means for causing said electrical current to alternate between a high state and a low state, such that said voltage alternates between a high state and a low state, comprising a light source for transmitting light to a surface which reflects some portion of said light, a means for generating said electrical current from said reflected light, and a means for switching said light source on and off at regular intervals such that said electrical current is in said high state when said light source is on and said electrical current is in said low state when said light source is off;
- means for subtracting said voltage in said low state from said voltage in said high state to produce a difference voltage comprising a multiplexer having a first input from said means for switching said light source and a second input from said operational amplifier, said multiplexer having a first output and a second output, said first output being a first input to a programmable gain difference amplifier and said second output being a second input to said programmable gain difference amplifier, said programmable gain difference amplifier having an amplifier output supplying the difference of said first input from said second input, said means for switching said light source causing said multiplexer to apply said voltage in said low state to said first output and said voltage in said high state to said second output such that said programmable gain difference amplifier subtracts said voltage in said low state from said voltage in said high state to produce said difference voltage;
- and
- means for amplifying said difference voltage to automatically produce an amplified difference voltage in a predetermined range.
3 more elements
A sensor board for processing electrical signals comprising:
- a light source for transmitting light to a surface which reflects some portion of said light;
- a first photodiode for generating a first electrical current from reflected light;
- a second photodiode for generating a second electrical current from reflected light;
- means for switching said light source on and off at regular intervals whereby said first and second electrical currents are in a high state when said light source is on and said first and second electrical currents are in a low state when said light source is off;
- means for converting said first electrical current to a first voltage whereby said first voltage alternates between a high state and a low state;
- means for converting said second electrical current to a second voltage whereby said second voltage alternates between a high state and a low state;
- means for subtracting said first voltage in said low state from said first voltage in said high state to produce a first difference voltage;
- means for amplifying said first difference voltage to produce a first amplified difference voltage in a first predetermined range;
- means for subtracting said second difference voltage in said low state from said second difference voltage in said high to produce a second difference voltage;
- means for amplifying said second difference voltage to produce a second amplified difference voltage;
- said first amplified difference voltage and said second amplified difference voltage being applied to a selector, said selector alternately outputting said first amplified difference voltage and said second amplified difference voltage;
- means for alternatively subtracting a voltage offset from said first and said second amplified difference voltages to produce a third and a fourth difference voltage;
- and
- means for amplifying said third and said fourth difference voltage to produce a third and a fourth amplified difference voltage.
11 more elements
A sensor board for processing electrical signals in an endpoint controller for detecting the endpoint of a chemical processing operation comprising:
- means for receiving an electrical current;
- means for converting said electrical current to a voltage;
- means for causing said electrical current to alternate between a high state and a low state such that said voltage alternates between a high state and a low state;
- means for subtracting said voltage in said low state from said voltage in said high state to produce a difference voltage;
- means for amplifying said difference voltage to automatically produce an amplified difference voltage in a predetermined range;
- means for subtracting a voltage offset from said amplified difference voltage to produce a second difference voltage;
- and
- means for amplifying said second difference voltage to produce a second amplified difference voltage in a second predetermined range.
5 more elements
A method for detecting the endpoint of a chemical processing operation on a substrate by monitoring changes in light intensity of light reflected from said substrate comprising the steps of:
- providing a light source, so that said light reflects from said substrate;
- converting said light reflected from said substrate to an electrical signal;
- providing a plurality of gain settings for amplifying said electrical signal;
- choosing one of said plurality of gain settings for amplifying said electrical signal;
- and
- amplifying said electrical signal to produce an amplified electrical signal within a predetermined range.
3 more elements
A method for processing electrical signals comprising the steps of:
- receiving an electrical current;
- converting said electrical current to a voltage;
- causing said electrical current to alternate between a high state and a low state such that said voltage alternates between a high state and a low state;
- subtracting said voltage in said low state from said voltage in said high state to produce a difference voltage;
- and
- amplifying said difference voltage to automatically produce an amplified difference voltage in a predetermined range.
3 more elements
A method for processing electrical signals comprising:
- transmitting a light source to a surface which reflects some portion of said light;
- generating from a first photodiode a first electrical current from reflected light;
- generating from a second photodiode a second electrical current from reflected light;
- switching said light source on and off at regular intervals such that said first and second electrical currents are in a high state when said light source is on and said first and second electrical currents are in a low state when said light source is off;
- converting said first electrical current to a first voltage such that said first voltage alternates between a high state and a low state;
- converting said second electrical current to a second voltage such that said second voltage alternates between a high state and a low state;
- subtracting said first voltage in said low state from said first voltage in said high state to produce a first difference voltage;
- amplifying said first difference voltage to produce a first amplified difference voltage in a first predetermined range;
- subtracting said second difference voltage in said low state from said second difference voltage in said high to produce a second difference voltage;
- amplifying said second difference voltage to produce a second amplified difference voltage;
- applying said first amplified difference voltage and said second amplified difference voltage to a selector, said selector alternately outputting said first amplified difference voltage and said second amplified difference voltage;
- alternatively subtracting a voltage offset from said first and said second amplified difference voltages to produce a third and a fourth difference voltage;
- and
- amplifying said third and said fourth difference voltage to produce a third and a fourth amplified difference voltage.
11 more elements
Dependencies are inferred from the claim text.