INFICON STC-2002 Thin Film Deposition Controller Operating Manual - Manual (Page 112)

p STC-2002 DEPOSITION CONTROLLER y
SECTION 3.XX e page 110 of 276 ^
Crystal Stability
The STC-2002 will display the crystal stability value detected during the deposition run on the 2 nd
STATUS screen (from the RunTime screen press the STATUS key twice). The data will appear below the
S (stability) header between the thickness column and the Life column. The display may read as follows:
Stability
indicates crystal stability
3 indicates that the 3 threshold setting was exceeded
9 indicates that the system was within 90% of exceeding the 4 Threshold
If these are typical run values, a setpoint value of 5 is a reasonable setting. If the readings are
much higher or lower, the setpoint should be scaled accordingly.
Control Quality
The control quality parameter sets a limit on the amount of sustained control loop deviation error.
Due to differing source and material characteristics optimum settings may need to be arrived at
experimentally. Control loop quality can be effected by EB gun or sputtering target arcs as well the PID
control loop parameters. These areas should be made to operate properly before attempting to set tight
switching threshold on control quality (press L/Q key area twice on RunTime screen).
The parameter values correspond to an allowable sustained deviation in the following manner.
Setpoint % Deviation Setpoint % Deviation
1 5 6 20
2 7.5
7 25
3 10 8 30
4 12.5 9 40
5 15 0 Off
The setpoint values detected and accumulated by these algorithms may be observed on the
RunTime display by pressing the L/Q key. The data will appear below the text label "loop" in the key
graphics area. After several deposition runs the typical values found here may be used for determining the
proper setpoint values. The display may read as follows:
Loop indicates control loop quality
2
indicates that the 2 threshold setting was exceeded
7 indicates that the system was within 70% of exceeding the 3 threshold
If these are typical run values a setpoint value of 4 is a reasonable setting. If the readings are much
higher or lower, the setpoint should be scaled accordingly.
Use for Multi Layer Depositions
Using Separate Crystals For Multi Layer Depositions
Where the ultimate in accuracy is required in a two material deposition, it is desirable to use
separate crystal sensors for each material. This would prevent any errors in Z-Factor correction due to the
layering of different materials to be reduced to the minimum. This mode of operation can be accomplished,
as described above, by programming the starting sensor parameters in the first film/map combination to
sensor 1, for example, and set the second film/map combination to start on sensor 2, for example. The CH x
backup parameter should be set to off in each layer or to a crystal channel other than 1 or 2 as in this
example. However, it may be set to ON even when using only 2 crystal channel sensors to allow for a
possible crystal failure recovery using the alternate crystal sensor. A recovery could possibly give a small
thickness error due to the mixing of materials but may be preferred over an aborted or time power
completed run. The tooling factors may also be optimized for differing source geometry's as each sensor
has its own tooling factor value in each map parameter program.