INFICON STC-2002 Thin Film Deposition Controller Operating Manual - Manual (Page 111)

p STC-2002 DEPOSITION CONTROLLER y
SECTION 3.XX e page 109 of 276 ^
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 twice. This will display the 2 nd STATUS screen.
On the 2 nd 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. (See section x.x) 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. Press MOR
E to view channels 5
through 8. 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. There can be as many backups as there are
installed and enabled supporting sensor cards (up to 7).
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 1-8 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[s]. 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-2002 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-2002 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.