MX 301
Wafer Thickness Gauge

Features:
  • Thickness measuring range user selectable, default setting 200 - 1000 µm
  • Dynamic range 800 µm
  • Wafer diameter range 20 to 200 mm
  • Simple and fast manual handlings
  • Two contactless distance sensors
  • Accuracy 0.5 µm
  • Resolution 0.1 µm
  • Five digit display directly in µm
  • Recalibration not necessary
  • Switch for high-ohm material (GaAs, GGG)
  • No limitations in case of electrical resistance (NTD silicon)
Description:
A capacitive distance measuring method is used for the non-contact measurement of wafer thicknesses. The capacitive distance sensors are located in a rigid holder above and below the object to be measured and are positioned at a specific distance from each other. The sum of the two distances to the wafer (front and back) will yield the wafer thickness.

The calculated value can be read off a five-digit numerical display or can be output via the instrument's built-in serial interface. The calibration can be checked with gauge blocks. The resistivity of silicon, up to 1,000,000 Ohmcm, does not affect the calibration.

The instrument can be set through a switch so that it is able to measure higher resistance material such as GaAs or GGG wafers. In the switch position 'GaAs', the sensors constitute a multi-layer capacitor with air and the high-resistance measuring object as dielectrics. A value of 11.3 is stored in the microprocessor EEPROM for the material constant (relative dielectric constant) used in the calculation. This value can be changed as needed by means of a utility.

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