Inficon TM-400 Thin Film Deposition Monitor Bedienungsanleitung PDF herunterladen (Seite 60)

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IPN 178800 Rev. B

TM-350/400 Operating Manual

9.3 Sensor Number (TM-400 Only)

The Sensor Number parameter defines the primary sensor for the film, meaning

the sensor that the film will start with. This parameter is included because it is

desirable to use one sensor/crystal for one material and the other sensor/crystal for

the second material in a multi layer application.

9.4 Density

The Density parameter provides the Monitor with the density of the material being

deposited so that it can calculate and display the physical film thickness. If the film

density is known, it should be used. A list of the more commonly used film densities

is presented in Table 9-2 on page 9-4. As a first approximation, bulk material

density can be used in programming this parameter. Empirical calibration of this

parameter is described in section 9.6.1 on page 9-3.

9.5 Acoustic Impedance

The shear wave acoustic impedance of the deposited film is required by the

monitor in order to accurately establish the sensor scale factor when the sensor

crystal is heavily loaded. If the acoustic impedance of the film material is known, it

can be entered directly in units of 100,000 gm/sq. cm sec. In most cases the

acoustic impedance of the bulk material can be used and can be obtained from the

Handbook of Physics or other source of acoustic data. 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:

[3]

where:

P = Density (gm/cm

C = Transverse (shear) wave velocity (cm/sec).

G = Shear modulus (dynes/cm

A list of the acoustic impedance and density of the more commonly deposited

materials is presented in Table 9-2 on page 9-4, and a technique for empirically

determining this parameter is presented in section 9.6.3 on page 9-4.

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:

8.83 X 100,000 gm/sq. cm sec. [4]

acoustic impedance PC PG==

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Inficon TM-400 Thin Film Deposition Monitor Bedienungsanleitung Seite 60