论文部分内容阅读
本文对于低压化学汽相沉淀方法沉积的多晶硅薄膜的电导性能进行了研究,并与大气压下沉积的薄膜的导电性能作了比较。低压薄膜在580℃和620℃下沉积成,然后用离子注入法掺入磷。在620℃下沉积的薄膜是多晶膜,而在580℃下沉积的薄膜最初是无定形膜,但经过热处理后,它就变成结晶膜。对于两种不同掺磷剂量的低压膜,研究了退火温度对电阻率的影响,发现电阻率随退火温度的升高而减小。580℃下沉淀的薄膜经退火后,它的电阻率总是比620℃下沉淀的薄膜的电阻率低,而且在退火温度较低的情况下,两者的差别最为显著。在第二组实验中,注入的磷量范围很宽,相当于平均掺杂浓度在2×10~(15)—2×10~(20)cm~(-3)之间。只有在浓度低于2×101~(15)cm~(-3)和高于2×10~(20)cm~(-3)的情况下,电阻率才是掺杂浓度的一个慢变化函数(Slowfunction);而浓度在2×10~(15)cm~(-3)和2×10~(20)cm~(-3)之间时,掺杂浓度稍有改变就会使电阻率发生很大的变化。如上所述,在580℃沉淀的薄膜,其电阻率总是最低,在掺杂浓度居于中间的情况下,这尤其显著。测量了霍尔迁移率,发现它在掺杂浓度近于6×10~(18)cm~(-3)时有一最大值,而且随掺杂浓度降低急速减小。可以预料,所观察到的霍尔迁移率的这种变化特性与薄膜是由含有大量载流子陷阱的晶粒间界环绕的微晶构成这一解释相一致。
In this paper, the conductivity of polycrystalline silicon films deposited by low pressure chemical vapor deposition was studied and compared with that of the films deposited at atmospheric pressure. Low-pressure films were deposited at 580 ° C and 620 ° C and then phosphorus was doped by ion implantation. The film deposited at 620 ° C is a polycrystalline film whereas the film deposited at 580 ° C is initially an amorphous film but after heat treatment it becomes a crystalline film. The effect of annealing temperature on the resistivity was studied for two different low-phosphorus films doped with phosphorus and found that the resistivity decreased with increasing annealing temperature. After annealing at 580 ° C, the resistivity of the film precipitated at 580 ° C is always lower than that of the film precipitated at 620 ° C, and the difference is most pronounced when the annealing temperature is low. In the second experiment, the amount of phosphorus implanted is very wide, corresponding to an average doping concentration of 2 × 10 ~ (15) -2 × 10 ~ (20) cm ~ (-3). The resistivity is a slowly varying function of the doping concentration only at concentrations below 2 × 10 ~ (15) cm ~ (-3) and above 2 × 10 ~ (20) cm ~ (-3) (Slowfunction). When the concentration is between 2 × 10 ~ (15) cm ~ (-3) and 2 × 10 ~ (20) cm ~ (-3), the resistivity will be slightly changed a big change. As mentioned above, the films precipitated at 580 ° C have the lowest resistivity, which is especially noticeable when the doping concentration is in the middle. The Hall mobility was measured and found to have a maximum at a doping concentration of approximately 6 × 10 ~ (18) cm ~ (-3), which decreases rapidly with decreasing doping concentration. It is expected that this observed change in Hall mobility is consistent with the explanation that thin films are composed of crystallites surrounded by a grain boundary containing a large number of carrier traps.