Silicon Ingot Growth

Silicon ingot growth is the first stage of wafer production, where ultra-pure polysilicon feedstock is recrystallized into large single-crystal cylinders. The ingots form the raw substrate from which wafers are sliced, polished, and delivered to semiconductor fabs. Precision in this step is critical, as crystal defects, oxygen contamination, or dislocations will propagate through every downstream wafer and device.

Crystal Growth Methods

• Czochralski (CZ) Method:
  • Polysilicon chunks are melted in a quartz crucible.
  • A seed crystal is dipped and slowly pulled while rotating, forming a large cylindrical ingot.
  • Standard method for 200 mm and 300 mm wafers.
  • Oxygen incorporation from the crucible must be tightly controlled.
• Float Zone (FZ) Method:
  • A polysilicon rod is locally melted by a moving RF induction coil.
  • No crucible is required, eliminating oxygen contamination.
  • Produces higher-purity ingots, but limited to smaller diameters (100–200 mm).
  • Commonly used for power devices and high-resistivity wafers.

Ingot Growth Mapping

Key Considerations

• Crystal Quality: Defect density, dislocations, and oxygen incorporation directly affect wafer yield.
• Wafer Diameter: Larger ingots enable larger wafers, improving die count and throughput.
• Energy Demand: Both CZ and FZ are power-intensive, contributing to wafer production costs.
• Industry Trends: While CZ dominates, niche demand for FZ remains strong in power semiconductors and specialty markets.

FAQs

• Do fabs grow their own ingots? – Most purchase ingots or wafers from suppliers, though some IDMs remain vertically integrated.
• Why are ingot diameters limited? – Equipment, thermal stress, and defect control challenges increase with size.
• Is 450 mm wafer adoption likely? – Development exists, but cost and tool ecosystem challenges have delayed adoption.
• What’s the difference between CZ and FZ? – CZ is mainstream and scalable; FZ is smaller-scale but higher purity.