INFICON Cygnus Thin Film Deposition Controller - Manual (Page 75)

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Cygnus Operating Manual
CRUCIBLE. . . . . . . . . . . . . . . . . . . . 1 to the maximum number of crucibles
programmed. (default = 1)
This parameter identifies which crucible of a multiple pocket source to use
when the channel is started.
CRYSTAL QUALITY . . . . . . . . . . . . 0 to 9 (default = 0)
This parameter is used to ensure tight rate control by monitoring the information
obtained from the crystal. It can be used to effect a crystal fail when operating
in the single frequency mode. The “single frequency” mode is when the Z-Ratio
type is set for Material Z, “dual frequency” mode is when the Z-Ratio type is set
for Auto Z. See
Table 3-1 .
For each rate reading, the percent relative deviation from the sensor’s rolling
average rate is calculated. Each time this deviation is greater than the allowed
percent relative deviation, as determined by the Crystal Quality value, a counter
is incremented by one count. If the deviation is within tolerance, the counter will
count down. (The counter will not count below zero.) When the count reaches
100, a crystal fail will be initiated. In this manner only sustained erratic rate
readings will trigger a crystal fail and instantaneous noise will be ignored.
If Auto Z is in use, the crystal quality will trigger an Auto Z failure instead of a
crystal fail. This will change the instrument from dual frequency measurement
mode to single frequency measurement mode. For some materials, it is
possible to regain rate stability by this change. Once the switch to single
frequency has occurred and a waiting period has elapsed (four times the
Primary Time Constant plus the System Dead Time plus ten seconds), the
counter will again track the rate deviation. If the counter reaches 100 a second
time, a crystal fail will be triggered.
Table 3-1 Crystal Quality Number and Threshold of Rate Deviation
Crystal Quality
Number
Threshold of
Rate Deviation
9 2.5%
8 5.0%
7 7.5%
6 10.0%
5 12.5%
4 15.0%
3 20.0%
2 25.0%
1 30.0%
0 Disabled