研究目的
To study boron diffusion in n-type silicon from preform source for p+ emitter formation and investigate the influence of drive-in temperature, drive-in time, and temperature ramp-up time on the emitter's characteristics.
研究成果
The study successfully demonstrated the influence of drive-in temperature, drive-in time, and temperature ramp-up time on the characteristics of boron-doped emitters in n-type silicon. Higher drive-in temperatures and longer drive-in times resulted in lower sheet resistances and deeper junctions. The presence of a boron rich layer was confirmed for emitters formed at higher temperatures. The findings provide valuable insights for optimizing emitter formation in n-type silicon solar cells.
研究不足
The presence of boron rich layer (BRL) on the surface may degrade charge carrier lifetime and increase surface recombination velocity. The study also notes deviations in sheet resistance measurements between Hall Effect and four point probe techniques.
1:Experimental Design and Method Selection:
Boron diffusion was performed on both sides of planar n-type silicon wafers using a preform source in a quartz tube furnace. The study focused on varying drive-in temperature, drive-in time, and temperature ramp-up time.
2:Sample Selection and Data Sources:
N-type Cz-grown 300 μm thick silicon wafers with 1-3 Ω.cm resistivities were used. The wafers underwent saw damage etch in KOH and a standard RCA clean before diffusion.
3:List of Experimental Equipment and Materials:
Quartz tube furnace (Tempress system, Omega Junior 3, 1988), preform boron dopant source, KOH, HF solution, HNO3 solution, nitrogen and oxygen gases.
4:Experimental Procedures and Operational Workflow:
Diffusion processes included temperature ramp-up and drive-in steps under nitrogen ambient. After BSG removal, wafers were cleaned and sheet resistances were measured by four point probe method. Doping profiles were measured by ECV and SIMS.
5:Data Analysis Methods:
Sheet resistance mapping, ECV and SIMS for doping profiles, and Hall Effect for sheet resistance and charge carrier concentration measurements.
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