Eni Div. of Astec America, Inc.

Astec America, Inc.

Eni - a Division of Astec America, Inc.

Eni, a Div. of Astec America, Inc.

Anthony R Keane

Bart C Vandebroek

Steven E Hauer

An aliasing sampler probe for detecting plasma RF voltage and current employs a sampling signal with a sampling rate slower that the RF fundamental frequency selected to produce an aliasing waveform at an aliasing frequency that is several orders of magnitude below the RF fundamental frequency. In one embodiment, the RF power is applied at 13.56 MHz. and sampling pulses have a sampling rate of 2.732 MHz to produce replicas of the RF voltage and current waveforms at an aliasing frequency of about 100 KHz. The aliasing replicas preserve phase and harmonic information with an accuracy that is not available from other sampling techniques.

Aliasing sampler for plasma probe detection

A high-power radio-frequency amplifier acts on periodic pulses of RF energy. The bias is controlled for each of a bank of FETs or other amplifier devices that constitutes the main power stage. A sample of bias current is obtained during a blanking period on the front porch of the RF gating period. Quiescent drain current is measured, and stored on a sample/hold circuit. A digital signal processor provides bias values that are sent via a D/A converter to biasing circuits that add the bias levels to the input RF signal. If the bias current is above or below a desired level, the stored bias level is decreased or incremented respectively. A timing control circuit gates the sample/hold circuit and switches in advance of the biasing circuits. The timing control circuit also creates a blanking signal to apply to an attenuator to produce a null region during the first 100 microseconds of the gating signal. A thermal sensor is coupled to one or more amplifying devices for presetting the operating voltage when operation has been interrupted for a predetermined period of time.

Active bias for a pulsed power amplifier

A high-power radio-frequency amplifier act on periodic pulses of RF energy. The bias is controlled for each of a bank of FETs or other amplifier devices that constitutes the main power stage. A sample of bias current is obtained during a blanking period on the front porch of the RF gating period. Quiescent drain current is measured, and stored on a sample/hold circuit. A digital signal processor provides bias values that are sent via a D/A converter to biasing circuits that add the bias levels to the input RF signal. If the bias current is above or below a desired level, the stored bias level is decreased or incremented respectively. A timing control circuit gates the sample/hold circuit and switches in advance of the biasing circuits. The timing control circuit also creates a blanking signal to apply to an attenuator to produce a null region during the first 100 microseconds of the gating signal. A thermal sensor is coupled to one or more amplifying devices for presetting the operating voltage when operation has been interrupted for a predetermined period of time.

An RF generator has an analog feedback circuit in combination with a digital levelling assist circuit to compensate for non-linearities in the power metering circuit that measures the RF output energy. The digital leveling assist circuit has a digitizer with inputs coupled to receive the measured power voltage supplied from the power metering circuit and a power demand voltage. The digitizer has outputs that provide digital representations of the measured power voltage and the power demand voltage to a digital control element that derives a digital correction factor based on these digital representations. A d/a converter coupled to the digital control element provides a correction voltage corresponding to this digital correction factor, and this is furnished to a summing circuit that combines the correction voltage with the power demand voltage and with a control voltage that is supplied by the analog feedback circuit. The leveling assist circuit increases the accuracy of control of the RF output power with respect to the power demand voltage, without sacrificing the speed of the analog feedback circuit.

Digitally assisted power levelling circuit for rf power generator

The present invention relates to the protection of a semiconductor active device from thermal breakdown without actually measuring the temperature of the semiconductor active device. Instead, the present invention measures the magnitude of the forward electrical signal generated by the active device and the reflected electrical signal resulting from the interaction of the forward electrical signal and a load. The thermal energy generated by the active device is a function of these electrical signals. The generated thermal energy is transferred out of the active device at a predetermined rate. The temperature of the active device is calculated as a function of the thermal energy generated by the active device and the amount of thermal energy transferred out of the active device. When the calculated temperature is above a predetermined value, the active device is shut off, thereby preventing further generation of thermal energy.

Method and apparatus for maintaining an active device below a maximum

An automatic impedance matching apparatus for matching an RF-signal generator to a load, such as a plasma etching chamber, is disclosed. The matching apparatus comprises a matching network having two variable impedance devices, a tune detector for detecting the condition of the impedance match between the RF-signal and the load, and a controller for modifying the values of the variable impedance components in response to the measured tune condition. The present invention disclosed improve reset and convergence unit and eliminates the need for the 'dead-band' provided around the matching point found in prior art impedance matching controllers. Also disclosed is an improved adjustment unit for adjusting the variable impedance components which is faster and more stable than found in prior art controllers. Also disclosed is a normalization unit for normalizing the input detection siganls such that variations in turning performance due to variations in input power level from the source are substantially reduced.

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Webster, NY, United States of America

Anthony R Keane