INFICON XTC/C Thin Film Deposition Controller - Manual (Page 119)

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XTC/C - XTC/2 Operating Manual
4.6.1 Q-Factor (Quality)
The Q-Factor is a measure of the quality of the rate control of the active
process. When the Q-Factor is activated the instrument senses the amount of
rate deviation from the desired programmed rate. Setting Q between 1 and 9
activates an algorithm which sets threshold limits on allowed rate deviation. If
the rate deviation relative to the programmed rate is greater than the
programmed threshold limit, the Q counter is incremented. If the rate deviation
is less than the programmed threshold, the Q counter is decremented. Q is not
allowed to have negative values. If the Q counter exceeds a value of 50, the
instrument will then automatically crystal switch, complete the process on
TIME-POWER or STOP the process. The quality limits (or band of allowed rate
deviation) are shown in
Table 4-3 . This deviation is computed on each
individual reading of the crystal during the deposit phase, i.e., every 250 ms.
.
Example
If the Programmed rate is: 45 Å/s and the actual rate is: 40 Å/s, then:
[2]
Table 4-3 Quality Limits
Q-Factor Threshold of Rate
Deviation (%)
0 Disabled
1 30.0
2 25.0
3 20.0
4 15.0
5 12.5
6 10.0
7 7.5
8 5.0
9 2.5
Deviation (%)
45 40 –
45
------------------- 100%
Ч
11.1% = =