Amorphous Silicon by LPCVD

Polysilicon films are grown at 600-650 °C and amorphous silicon films (a-Si) are grown at 500-550 °C. Lower temperatures result in lower stress and smaller grain size. A post-growth anneal can be used to relieve film stress. Both large-grained and amorphous films have compressive stresses while smaller grains have tensile stresses. By alternating compressive and tensile layers, the overall stress can be kept low enough that a stress-relieving anneal is not required. Smaller grains have lower thermal conductivities and are etched faster by HF. Between 600 and 650 °C the film's orientation is predominantly (110), while at higher temperatures (100) dominates.

  • Typical Film Thickness: 0.1 to 2 µm
  • Batch Size: 50
  • Deposition rate: 1-3 nm/min. (10 - 30 Å/min.)
  • Deposition Temperature: 500 - 550 °C
  • Refractive index at 550nm
  • Uniformity: < 3% using 1 σ
  • Gases: Silane SiH4

Applications: thin-film transistors for LCDs, thin-film photovoltaic solar cells

LPCVD Processes