INFICON STC-2000A Thin Film Deposition Controller Operating Manual - Manual (Page 267)

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STC-2000A DEPOSITION CONTROLLER
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Thickness Reading Calibration
SECTION 7.1
Thickness
Instrument calibration is affected by three different parameters, material density, material
Z-Factor, and tooling. Tooling is a deposition system geometry correction (location of sensor relative to
substrates). Density and Z-Factor are material factors.
Density Determination
Use of the material bulk density value will normally provide sufficient film thickness accuracy. If
additional accuracy is required, the following procedure may be used:
Density
Using a new sensor crystal (this eliminates Z-Factor errors) place a substrate adjacent to the sensor
so that both sensor and substrate see the same evaporant stream. Set the instrument density to the bulk
value of the material (see the Material Reference Table in Section 7.2). Set the Z-Factor to 1.000 and the
Tooling Factor to 100%. Deposit approximately 5000 Angstroms of material on the sensor and substrate.
After deposition remove the substrate and measure the film thickness with a profilometer or multiple beam
interferometer. The correct density value may be determined by the formula:
Density
Gm
=
( Density Parameter) (Reading) ⎛
⎝⎜
⎞
⎠⎟
cc (Measured Thickness)
•
The calculated value may be checked by setting the STC-2000A density parameter to the
calculated value and observing that the STC-2000A thickness display shows the corrected reading. Minor
value adjustments can be made to make the measurements and calculations exactly equal.
Z-Factor Determination
A list of Z-Factor values may be found in the Material Reference Table in Section 7.2. For other
materials Z-Factor may be calculated by the following formula:
Z-Factor
Z - Factor =
D U
q q
1
2
•
•
⎡
⎢
⎤
⎥
D U
f f
⎣ ⎦
Dq = Density Of Quartz
Uq = Shear Modulus Of Quartz
Df = Density Of Film
Uf = Shear Modulus Of Film
The density and shear modulus values may be found in many material reference handbooks.
Z-Factor values are typically very close to bulk values. High stress materials seem to have values
slightly lower than expected.
For a more exact solution make a calibration deposition similar to the density method. Use the
calibrated density value, a Z-Factor of 1.000 and a tooling of 100%. Deposit a thick film using at least 50%
of the sensor crystal life. Measure the substrate and then adjust the STC-2000A Z-Factor parameter until
the correct thickness is displayed.
SECTION 7.XX page 267 of 292