National Research Development Corporation

Ashbrook Simon-hartley, LP

Kathryn Elizabeth McKell

Gordon Charles Joyce

Peter Ian Baldwin

Donald Thomas James Hurle

Khai Tran

A method and apparatus for growing single crystal of GaAs, etc uses the Czochralski techniques. Control of crystal (,) diameter is by a closed loop (,) control of melt (,) temperature in response to crystal weight signals (,) W or dW/dt. The invention injects a test signal St (,) into the control loop and performs a signal processing (,), e.g. cross correlation, on St and crystal weight signal. Peak amplitude of correlation values is related to the growing crystal shape. This is used by comparison with reference values (,) to control the growing-out phase from seed diameter (,) to full diameter of the crystal (,).

Growth of semiconductor single crystals

A beltpress controller performs on-line measurements of output sludge cake thickness. A controller takes a product of the measured cake thickness with belt speed, moisture content and belt width to determine a rate of dry solid output per unit time. The calculated rate is compared with a desired rate and the sludge flow rate is adjusted by adjusting the speed of a sludge feed pump to obtain the desired dry solid output rate. In systems which mix polymer with the sludge to increase the dewatering efficiency, the sizing of a mixing orifice through which the sludge and polymer is provided is adjusted to maintain a substantially constant mixing energy. This prevents errors in the streaming current detector which measures the amount of excess polymer in the filtrate and the controller adjusts the speed of a polymer dosing pump accordingly.

Growing community of inventors

Stockport, United Kingdom

Kathryn Elizabeth McKell