INFICON MDC-370 Thin Film Deposition Controller - Manual (Page 50)

MDC-370 DEPOSITION CONTROLLER
bulk material can be used and can be obtained from The Handbook of Physics or
other source of acoustic data. The shear wave impedance should be used. The
shear wave acoustic impedance can be calculated from the shear modulus or the
shear wave velocity and the density by using the following equation:
Where:
AI= Acoustic Impedance
ρ
= Density (gm/cm
3
)
C= Transverse (shear) wave velocity (cm/sec)
G= Shear Modulus (dynes/cm
2
).
A list of the acoustic impedance and density of the more commonly deposited
materials is presented in Table 10-1 and a technique for empirically determining
this parameter is presented in Section 10.6.3.
In many cases and particularly if the sensor crystal is not heavily loaded,
sufficient accuracy can be achieved by using the acoustic impedance of quartz
which is 8.83 X 10
5
gm/cm
2
sec.
6. Tooling Factor (10.0 to 499.9%)
This parameter is the tooling factor for the average rate and thickness
measurements. Typically this parameter is left at the default setting of 100%
because each sensor has a tooling factor that is used to compensate for geometric
factors in the deposition system which result in a difference between the
deposition rate on the substrates and the rate on the sensing crystal. However, this
parameter might be used to compensate for any changes in the system that affects
all sensor heads equally.
Empirical calibration of the tooling factor is described in Section 10.6.2.
7. Proportional Gain (0 to 9999)
This parameter is the proportional gain factor for the source power control loop.
Control loop tuning is covered in Section 6-1.
8. Integral Time constant (0 to 99.9 sec)
This parameter is the system time constant. Control loop tuning is covered in
Section 6-1.
9. Derivative Time constant (0 to 99.9 sec)
This parameter is the system dead time. Control loop tuning is covered in Section
6-1.
10. Rise To Soak Time (0 to 9:59:59)
AI C G
= ⋅ = ⋅ ρ ρ
PROGRAMMING AND CONTROLLER SETUP 4-18