Magnet Coils - Watchdog Monitoring Circuit for Magnetic Coils - Power Circuits of Sputter Magnetron Cathodes
Original Publication Date: 1996-Feb-01
Included in the Prior Art Database: 2005-Mar-31
This article describes a "watchdog" monitoring circuit especially useful for sputter magnetron cathodes.
Magnet Coils - Watchdog Monitoring Circuit for Magnetic
Coils - Power
Circuits of Sputter Magnetron Cathodes
describes a "watchdog" monitoring circuit
especially useful for sputter magnetron cathodes.
magnet coils on each of the 16 magnetron sputter
cathodes are distributed over 20 power circuits. The coils are
located with the rear wall of the cathode in the same cooling water.
During operation, the cooling water, with a conductivity of 150 - 200
&mu.s has a sputter potential of 500 - 600 VDC (Umax. 1300 VDC when
insulation occurs on one or more of the 48
magnetic coils, the relevant magnet power circuit couples to the high
DC sputter voltage. This leads to undesirable voltage retardation
and to DC fault currents. The degree of coupling depends on the
extent of the insulation defect on the coil in question. Severe
coupling leads to inequality of the A-/B-sides of the chrome or
magnetic layers (active layer).
consequence is high numbers of rejects before the problem
is detected by "send ahead measurements".
The watchdog is structured as follows:
20 measured value pickups transmit an analogue signal of
0 to minus
10 V to an LED diode matrix. The most negative measurement input is
switched through and displayed. A connected trigger circuit
recognizes three conditions: Green LED, all coils are within limit.
Yellow LED, at least one circuit is coupling moderately. Red LED,