INFICON SQC-310 Thin Film Deposition Controller - Manual (Page 44)

Chapter 3 Menus
3-6
potentially unstable) loops. Try a value of 50, then gradually increase/decrease the
value to respond to step changes in rate setpoint.
I Term: The integral term controls the time constant of the loop response. A small I
term, say .5 to 1 seconds, will smooth the response of most loops.
D Term: The differential term causes the loop to respond quickly to changes. Use 0 or
a very small value to avoid oscillations.
Max Power: The maximum output power allowed for the selected output. The Scale
output voltage is a function of the deposition power supply input specifications, and is
set in the System Parameters menu. Max Power controls the maximum power that can
be used by this process layer.
Slew Rate: The maximum power change allowed on an output, per second. If power or
rate ramps exceed this value, an error will occur.
Material: Selects a material assigned to this film. As materials change, their density
and Z-Factor are updated.
Density: Sets the density for this material. Material density has a significant impact on
deposition calculations.
Z-Factor: Sets the Z-factor, an empirically determined measure of a material’s effect on
quartz crystal frequency change. Z-Factor is the ratio of the acoustic impedance of the
sensor to that of the deposited material. It is used to match the acoustic (oscillation)
properties of the material to the quartz sensor. If you know the “acoustic impedance” of
your material, divide it by 8.83 (the acoustic impedance of SiO
2
) to obtain the material’s
Z-Factor.
Ramp 1: During the deposition of a layer, it may be desirable to change the deposition
rate. For example, you may want to deposit slowly at first, then increase the rate once
an initial thickness is reached. Enabling rate ramps provides that capability. Once
enabled, these parameters are added to the list.
Start Thickness: The deposited thickness at which the new rate will begin.
Ramp Time: Time allowed for the rate to change from initial rate to new rate.
New Rate: The rate of deposition, which is reached at the end of Ramp 1.
Ramp 2: Two rate ramps are available for each layer. The start thickness for Ramp 2
should be greater than the start thickness for Ramp 1.