INFICON Cool Drawer Single Sensor - Manual (Page 49)

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Cool Drawer Single and Dual Sensors Operating Manual
4.3.5 Sputtering System Concerns
Cool Drawer sensors are suitable for Magnetron Sputtering and most other
sputtering systems where the plasma is controlled and constrained.
For radio frequency (RF) sputtering systems, the INFICON Sputtering sensor
(PN 750-618-G1) is recommended. Radio frequency (RF) sputtering systems
result in a flux of high-energy electrons which impinge on the sensor head and can
cause significant temperature related thickness errors if the change in the
temperature of the crystal during deposition is significant.
Standard precautions must be taken when installing the Cool Drawer sensor into a
RF sputtering system.
 The sensor must be water-cooled and receive a representative sample of the
deposited material (refer to
Chapter 2, Sensor Installation ).
 The installation of the sensor must not disrupt any electrical fields or otherwise
disturb the normal material deposition pattern.
The Cool Drawer sensor must be grounded. Therefore, the Cool Drawer sensor is
not suitable for use in bias sputtering where the sensor must be installed at some
RF potential above ground.
Because the sputtering process is very noisy electrically, it is important to ground
the monitor or controller, as well as the sensor, to the base plate or housing of the
sputtering chamber. Use a wide ground strap to obtain low impedance at radio
frequencies. Normal diameter wires have relatively high impedance at radio
frequencies and may allow a significant voltage to develop between the monitor or
controller and the system. This voltage is unlikely to cause any damage or shock
hazard, but may create an erratic thickness display.
4.3.6 Leaf Spring Maintenance
Leaf spring conditions should be observed as part of the routine maintenance
interval. Insufficient bends or deformities in the leaf spring contacts in the sensor
body are common causes of crystal problems.
See Figure 4-2 .
Figure 4-2 Shaping the retainer leaf spring
45°
Leaf
Spring
Avoid kinking
leaf spring