• If you DON’T measure it, you CAN’T control it.
  • If you CAN’T measure it, you CAN’T control it. And...
  • If you CAN’T measure it RELIABLY, you only think you're in control.

Why Measure?

  • Improve Process Capability
  • Reduce Process Variation
  • Reduce Production Cost
  • Associate Wafer Parametrics with Customer Applications

Critical Wafer Characteristics

  • Edge Exclusion
  • Particles and Defects
  • Surface Metals
  • Flatness
  • Nanotopography
  • Interstitial Oxygen
  • Shape / Bow / Warp
  • Oxidation Defects
  • Lifetime
  • Epi Layer Thickness
  • Epi Layer Resistivity
  • Dimensional Parameters
  • Bulk Resistivity
  • Bulk Iron


Particle and Defect Characterization – Principles of Operation

Figure 1

Laser Inspection Process Animation  (Quicktime Format -- Get the Free Player)

For certification requirements, wafers are 100 percent inspected using the latest particle detection tools. These tools use a scanning laser beam that sweeps the wafer's surface. Any particles present on the wafer surface will scatter the incident laser beam. By measuring the reflected light, it is possible to "map" the number, size and location of any particles.

Initial Oxygen Characterization

Interstitial oxygen content of a silicon wafer is an important material characteristic for most modern device technologies. Interstitial oxygen in silicon is typically measured by infrared absorption using either 2 mm thick slugs or thinner product wafers. The accuracy of these measurements is subject to error. These wafer measurements are time consuming and potentially introduce handling damage or contamination to the finished polished wafer. A new infrared approach allows the measurement of interstitial oxygen in single crystal silicon. Ground, large diameter, silicon crystals are profiled for interstitial oxygen using a Fourier transform infrared (FTIR) spectrometer transmitting through full diameter crystals. Measurement intervals and sample sizes may be defined prior to the wafering process, improving assurance of product quality and allowing rapid feedback to the crystal pulling floor. Wholerod FTIR (WRFTIR) measurements can increase the producer and consumer confidence in overall process control and product capability, efficiently generating oxygen profiles along the crystal.

Figure 2

Conventional FTIR

Whole Rod FTIR

Measurement of Interstitial Oxygen in Silicon Ingots (PDF Format, 82K)