INFICON STC-2002 Thin Film Deposition Controller Operating Manual - Manual (Page 101)

p STC-2002 DEPOSITION CONTROLLER y
SECTION 3.XX e page 99 of 276 ^
SECTION 3.11 STC-2002 Shutter Delay
(Setting Up Shutter Delay Mode)
Shutter Delay Operation
Shutter delay operation is desirable when it is necessary to bring the deposition rate into good
control before exposing substrates to the evaporant stream. When this mode of operation is required it must
be enabled in the Review Film menu parameter list. This is not a global enable and will allow the
following associated film parameters of only this specific film to become active and programmable. These
parameters are:
Parameter 1
Shutter Delay Mode
(On/Off) This parameter enables the mode of operation for this specific film program and also
allows the following parameters to be accessed when ON.
Parameter 2
Shutter Delay Time Out
Time-Out (Accuracy) 1 To 99:59 M/S
This parameter determines how long the system will keep trying to obtain the control accuracy value before
giving up and aborting the run (process time).
When the desired control accuracy is maintained for a period of 3 seconds before the time-out
limit, the thickness display is set to zero and the substrate shutter relay is energized. All associated crystal
switch, crystal backup, or active sensor selections and operations remain valid in this mode. Proper control
loop P-I-D settings should be previously determined. This will insure minimum delay times and will also
optimize film consistency. Refer to the I/O programming in Section X5 of this manual for a guide on
selecting the logic for use as the substrate and sensor shutter controls.
Parameter 3
Shutter Delay Quality
Control Quality (Accuracy) 1 To 50% Of Setpoint
This parameter sets the desired accuracy of the control loop before the substrate shutter is opened. The
maximum accuracy available is 1% of the deposit rate setpoint or 1 angstrom per second; whichever is
greater. The control accuracy must be maintained for a period of 3 seconds.
Film Parameters (/menu): Sh u t te r Delay Mode OFF, ON
Sh u t te r D e l a y TIMEOUT 0:01-99:59 MM:SS
Sh u t te r D e l a y QUALITY 1-50%
SECTION 3.12 Deposition Source Control Loop Description
The STC-2002 instrument is designed to measure the rate of material deposition and compare this
measured value to a programmed rate setting, the difference between the actual and programmed rate is
used to generate a feedback control signal to the deposition source power supply. The power supply is then
adjusted by this control signal to achieve the programmed rate setpoint value. This method of control
allows the STC-2002 to compensate automatically for source condition changes.
Control Output Voltage
Since there are many different types of deposition power supplies and sources in use today, the
deposition control voltage provided by the STC-2002 has been made user configurable. This control
voltage can be wired to be either positive or negative from chassis ground and scaled for either 2.5, 5 ,or 10
volts full scale. Full scale corresponds to 100% on the LCD power digits. The control voltage has 12 bit
resolution and 10 milliampere source or sink capability. The sense of the control loop can also be set for
etching applications where it must operate in an inverted fashion. This configuration is done on the Review
Films parameter list menu (Etching Mode: Off/On).
P-I-D Control Loop
To accommodate the extremely wide range of control loop responses required for the diverse
deposition sources available today, a P-I-D type of control loop has been implemented. With this type of
control loop available to the user, it should be possible to achieve very good control of any deposition
source. The P or proportional gain term provides a fast response to any system rate control error and sets