INFICON MDC-260 Thin Film Deposition Controller - Manual (Page 48)

MDC-260 DEPOSITION CONTROLLER
PROGRAMMING AND CONTROLLER SETUP 4-12
4.2.6.2 AUTOMATIC CRYSTAL SWITCHING
To enable automatic crystal switching upon failure, set the Backup Sensor,
Backup Crystal, and its Tooling Factor parameters to define which Sensor/Crystal
to switch to.
4.2.6.3 RATE ESTABLISH
The rate establish feature is used in critical processes where it is important to
establish the correct deposition rate prior to opening the source shutter and
depositing on the substrates.
NOTE: To use this feature, the sensor head must be mounted in such a way
that it is in the material vapor stream with the source shutter either opened or
closed.
To enable this feature you must set the Rate Estab. Time to a positive value, then
set the Rate Estab. Error parameter. The Rate Establish Time parameter sets the
maximum time that the controller will attempt to keep the rate error within the
Rate Estab. Error limit for a period of five seconds. If the rate error condition is
meet within the allotted time then the controller will enter the deposit state. If
not, then the process will be halted and a Rate Establish Error will be displayed.
4.2.6.4 RATE RAMPS
Rate ramping is typically used at the beginning of the deposition to ease the rate
up slowly to prevent material spitting. Rate ramping is also used towards the end
of the deposition to achieve a more accurate endpoint thickness. By slowing
down the rate, the thickness overshoot caused by the delay of the shutter closing
is diminished
The MDC-260 has two rate ramps available. A rate ramp is defined by a “Ramp
Start” and “Ramp Stop” thickness (expressed as % of total deposit) and the target
rate. For example, to setup the MDC-260 to deposit at 20Å/sec for 90% of the
layer, then ramp down to 5 Å/sec over the last 10%, you would enter the
following material parameters:
Deposit Rate #1 = 20Å/sec
Ramp #1 Start Thk = 90%
Ramp #1 Stop Thk = 100%
Deposit Rate #2 = 5Å/sec
The rate ramps are disabled by default with the Ramp Start and Ramp Stop
Thicknesses set to 100% since 100% represents the end of deposition for the
layer. The applicable parameters will become available for editing when the
start/stop thicknesses are changed from 100%.
4.2.6.5 RATE SAMPLE MODE
The Rate Sample feature is designed for large deposition thicknesses where
crystal life is a problem. By sampling the rate periodically to maintain rate
control, then closing the sensor shutter with the rate and power level constant, a
large deposition thickness can be achieved with one crystal.