铸造多晶硅少子寿命的热衰减研究

STUDY ON THERMAL DEGRADATION OF MINORITY CARRIER LIFETIME OF CAST MULTICRYSTALLINE SILICON

研究了加热温度与冷却速率对热处理铸造多晶硅少子寿命和间隙铁含量的影响。实验结果表明，铸造多晶硅在300～1050℃范围加热40min，以50℃／s的速率快冷至室温会提高硅片的间隙铁含量，降低硅片的少子寿命，加热温度越高，快冷后硅片的间隙铁含量越高，少子寿命越低；铸造多晶硅在900～1050℃的范围加热，以50℃／s的速率快冷至室温，高温下固溶于硅中的铁原子约有10％会形成间隙铁，约90％形成铁沉淀。铸造多晶硅片分别经800、900和1000℃加热40min后在0．017～50℃／s的速率范围冷却，硅片间隙铁含量随冷却速率增加而增加，少子寿命随冷却速率增加而降低，加热温度越高，间隙铁含量上升的幅度越大，而少子寿命下降的幅度越大。

The effects of heating temperature and cooling rate on the minority carrier lifetime and the interstitial iron concentration of cast multicrystalline silicon have been investigated. The results showed that the interstitial iron concentration is higher and the minority carrier lifetime is lower, than the original level when the mc-Si wafers are heated in 300-1050℃ for 40 minutes and cooled to room temperature at a rate as fast as 50℃/s; the interstitial iron concentration increases and the minority carrier lifetime decreases with increase of heating temperature. When the mc-Si wafers were heated in 900-1000℃ for 40 minutes and cooled to room temperature at a rate as fast as 50℃/s, 10% of th~ iron that dissolved at high temperature is kept in silicon as interstitial iron, while 90% of the iron form iron precipitates. When the mc-Si wafers were heated at 800℃, 900℃ or 1000℃ for 40 minutes, followed by cooling at different rates, the interstitial iron concentration increases and the minority carrier lifetime decreases, with increase of the cooling rate, from 0. 017-50℃/s.