INFICON SQM-242 Thin Film Deposition Controller Card Software Operating Manual - Manual (Page 47)

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SQS-242 Operating Manual
Control Error: If the control loop cannot maintain the desired deposition rate (due
to loss of source material, excessively high rate ramps, or equipment malfunction)
a control error occurs. Control error % is the accuracy that must be exceeded for
the specified time (in seconds) to trigger a control error. Use shutter delay accuracy
to assure adequate process control before entering the deposition phase.
Crystal Fail: Establishes the number of bad readings (i.e., 0 Hz) from a sensor that
generates a Crystal Fail condition. If a crystal fails, the PID loop will send the
source supply to max power. Therefore, it is unlikely you will ever want to disable
this error.
Crystal Quality: Each time the rate deviation for this film exceeds the % value, a
counter is incremented. Each time the rate deviation is within the % value, the
counter is decremented (to zero minimum). If the counter exceeds the Counts
value during the entire layer deposition, an error occurs.
Crystal Stability: When material is being deposited, a crystal's frequency normally
drops. At the end of crystal life, sensor frequency may briefly "mode hop" to higher
frequencies. Single Hz is the largest single positive frequency shift allowed. Total
Hz is the sum of positive shifts allowed during a film's deposition.
On Error: When an error condition occurs, three actions are possible. Ignore the
error and let the PID loop attempt to maintain rate control. Stop the layer and allow
the user to fix or manually control deposition. The last choice, Timed Power, uses
the last good Rate/Power settings to "estimate" rate and thickness.
In Timed Power, the output is set to the power level that last yielded a rate reading
within the Control Error % deviation setting (10% deviation if Control Error is
disabled). The program then calculates the estimated thickness based on that rate
and the deposition elapsed time. When the calculated thickness reaches thickness
setpoint, deposition stops.
3.5.1.7 Analog Inputs
Normally the SQS-242 software uses SQM-242 card quartz sensor inputs to
measure or control rate and thickness. The SAM-242 Analog Input Card extends
this capability to allow measurement and control on DC voltage-based process
variables such as temperature transmitters, pressure/flow controllers.
Analog input based control is treated, for the most part, identically to quartz sensor
based control. Considerations for using an analog input are discussed below.
Layers Tab: In the Inputs dropdown, select one of the Analog inputs. In the Outputs
dropdown, select the output that is to be controlled. Enter the desired setpoint.
Normally this setpoint is in Volts, but can be converted to other units (e.g., degrees
or PSI) in the Edit, System, Analog dialog box.
Use Time Endpoint to stop the analog layer after a set time. Otherwise, a Sensor
input, programmed as a Codep layer, can control the layer endpoint. Final
Thickness and Thickness Endpoint settings have no effect for an analog input.