INFICON STC-2000A Thin Film Deposition Controller Operating Manual - Manual (Page 116)

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STC-2000A DEPOSITION CONTROLLER
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Forcing A Crystal Switch
Manual Crystal Switching can be accomplished from the front panel while in the RunTime
display by pressing in the fixed front panel STATUS key 3 times. This will display the 3
rd
STATUS screen.
On the 3
rd
STATUS screen, is the FORCE FAIL key. Crystal channel switching is accomplished by
manually failing the primary active channel and allowing its designated backup to automatically take
control. Pressing the FORCE FAIL key will change the key legend of the key to the far right to Fail
Channel 1. Subsequent presses will step through all of the installed and enabled channels ending with the
FAIL ALL selection. When the channel that needs to be failed appears, press the key on the far right to
accept. The FORCE FAIL key is the selector and the key to the far right accepts the selection. After FAIL
ALL, the selection returns to RE-VERIFY.
After the FAIL CH X is selected, the crystal designated as its backup is now displayed as the active crystal
number with its life values indicated on the appropriate channel line. Switching can also be done through
the remote hardware inputs or computer interfaces. To move back to the crystal sensor that was failed, use
FORCE FAIL to select RE-VERIFY and press to accept. If the crystal still has acceptable life, etc. it will
be reinstated as active and the other sensor channel will return to standby. The crystal sensor channel
designated as backup must be set to standby with the SS MAP parameter, CHx START MODE, as well as
the crystal sensor channel designated as primary being set to active with the SS MAP parameter, CHx
START MODE.
Once configured for serial multi sensor operation (one active at a time), Automatic crystal
switching for hard failures is enabled in the same way as it was for manual switching: by setting the
primary channel parameter CH x BACKUP LIST = [select desired 1-2 backup channel], the secondary
(backup) channel parameters to CH x START MODE = standby and CH x FAIL ACTION = none in the
individual ss map programs. A hard crystal failure of any kind will now automatically switch to the backup
sensor. Imminent failures predicted by the CRYSTAL STABILITY and CONTROL QUALITY algorithms
will also cause switching to the backup sensor. Setting a setpoint value other than zero for each type
enables the S&Q. Smaller numeric settings cause smaller errors to be tolerated and will typically cause
crystals to be switched sooner than large numbers. Initially these parameters should be set to a high value
or disabled (set to 0). For initial process evaluation a value of 6 is good for both parameters. These
parameters can be tightened as process history is obtained.
The
CRYSTAL STABILITY parameter sets a limit on the amount and magnitude of positive
frequency jumps allowed during a deposition control phase. The smaller the setpoint number the fewer
jumps allowed. Due to differing stress values exhibited by different film materials optimum settings are
material dependent and may require experimental derivation. A good starting point for most applications is
a value of 6.
Hardware Requirements
To utilize the Crystal Switch function, one of the following is required: either a dual sensor head
with shutter or two single sensor heads with shutters. Both primary and backup sensors are operational at
all times and are connected to the appropriate STC-2000A Sensor x BNC connectors through their
respective oscillator units. When a switch over is desired, one of the I/O relays provided within the STC-
2000A can be programmed to activate. These contacts should be utilized to operate an air type solenoid
valve that in turn activates the air operated shutter mechanism on the sensor heads. The primary crystal
then becomes shielded and the backup crystal is exposed to the deposition stream.
It should be noted that there are separate TOOLING FACTOR parameters for each sensor. This
parameter is designed for geometric position correction within the vacuum vessel and is set in the
individual film programs.
SECTION 3.XX page 116 of 292