INFICON MDC-260 Thin Film Deposition Controller - Manual (Page 54)

MDC-260 DEPOSITION CONTROLLER
PROGRAMMING AND CONTROLLER SETUP 4-18
G C AI ⋅ = ⋅ = ρ ρ
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 10.5.3.
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.
8. 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. To a first approximation the tooling factor can be
calculated using the following equation:
100 %
2
⋅ ⎟
⎠
⎞
⎜
⎝
⎛
=
ds
dc
Tooling
where:
dc = Distance from source to crystal.
ds = Distance from source to substrate.
The equation above assumes that the angle from normal between the source and
sensor and the source and substrate is zero. To account for the angle of the crystal
and the substrate, use the following equation:
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
⋅ ⋅ ⎟
⎠
⎞
⎜
⎝
⎛
=
c
s
ds
dc
Tooling
φ
φ
cos
cos
100 %
2
where:
dc= Distance from source to crystal.
ds = Distance from source to substrate.