Silicon ingot diameter measurement

Optimizing wafer yield from a valuable and fragile silicon ingot is not an easy task. Step one is accurately sizing an irregular and glossy object. Choose an OD Precision distance sensor, set in differential/mirror mode. Surface variations don’t require time consuming recalibration.

Task

The finished ingots (multi or mono crystalline) are cut in blocks of the desired dimensions by a so called “squarer”. Then the blocks are combined on a glass carrier to be cut into thin wafers on a wire saw. Precise ingot and block measurement is key to quality and production yield.

Complexity of solution: The surface of an ingot is uneven. The optical properties are challenging. Along the ingot the surface vary between shiny and light absorbing.

Mechanical measurement is possible but delicate. The ingot is brittle. Mechanical stress on the surface can cause invisible micro-cracks. In addition, the measurement tools require regular calibration.

Implementation

OD Precision displacement sensors are used to profile the ingot to define the optimum cut.

Customer benefit

  • Waste reduction of expensive silicon material
  • Optimal usage of cross-sectional area allows greater production yield
  • Non-contact measurement creates no mechanical stress on the surface of the wafers
  • No regular calibration is requirement