Study on the Effect of Crucible-to-Crystal Ratio on Dislocation Density During the Growth of Large Size Cz Silicon

Abstract

The Czochralski (Cz) method, while being the predominant technique for monocrystalline silicon production, suffers from exponential dislocation density escalation (>1013 m-2) due to solid-liquid (S-L) interface instability, leading to crystalline structure degradation and low yield rates. To address the melt replenishment hysteresis effect inherent to CZ growth, this work introduces a pioneering interfacial stabilization strategy through dynamic crucible-to-crystal ratio (CCR) modulation. A multi-scale coupled modeling framework—integrating Alexander-Haasen dislocation dynamics with 2D transient thermo-mechanical finite element simulations—was developed to unravel the dual dependency of dislocation proliferation on pulling rate variations (governing S-L interface transitions from m-type to n-type morphologies) and CCR adjustments. Experimental validation demonstrated that implementing the optimized CCR protocol, coupled with reduced pulling rate fluctuations (±3% vs. baseline ±12%), achieved a 20.7% reduction in dislocation density at the head and 5.9% at the tail of 300 mm-diameter monocrystalline ingots, while extending defect-free constant-diameter growth lengths to 3500 mm. Mechanistic analysis revealed that CCR-driven stabilization of melt replenishment suppressed thermoelastic strain oscillations at the S-L interface, thereby inhibiting dislocation nucleation. These findings establish both theoretical principles and practical methodologies for high-efficiency manufacturing of photovoltaic-grade large-diameter monocrystalline silicon, bridging critical gaps between interfacial dynamics control and industrial-scale crystal quality optimization.

Keywords: Czochralski method, Photovoltaic monocrystalline silicon, Solid-liquid interface, Crucible-to-crystal ratio, Dislocation density.