研究目的
Investigating the concentrations of Cr, Fe, Ni, and Cu in a cast-monocrystalline silicon ingot grown for solar cell applications and their gettering to silicon nitride films.
研究成果
SiNx gettering was effective in concentrating metal impurities from the wafer bulk into the SiNx films, with metals gettered to the SiNx/Si interface. The study provided insights into the total bulk concentrations and chemical state of metals in the as-grown ingot.
研究不足
The dissolution of precipitates may not be complete, indicating that the gettered concentration might only be a fraction of the total bulk concentration. The mechanism of metal aggregation at the SiNx/Si interface is not fully understood.
1：Experimental Design and Method Selection:
The study involved coating wafers from a cast-monocrystalline silicon ingot with silicon nitride films and annealing them to getter mobile impurities. Secondary ion mass spectrometry (SIMS) was used to measure the metal content in the films.
2：Sample Selection and Data Sources:
Wafers were taken from different positions along the ingot, with specific solidified fractions. The doping levels were determined by dark conductance measurements.
3：List of Experimental Equipment and Materials:
A laser cutter was used to prepare samples, and a Roth and Rau AK400 chamber was used for PECVD SiNx film deposition. A Sinton Instruments WCT-120 quasi-steady-state photoconductance lifetime tester was used for lifetime measurements.
4：Experimental Procedures and Operational Workflow:
The wafers were RCA-cleaned, passivated with SiNx films, annealed, and then analyzed using SIMS to determine metal concentrations.
5：Data Analysis Methods:
The SIMS depth profiles were integrated to obtain the metal concentration gettered to the interface, and bulk concentrations were calculated.
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