磁控溅射法制备ZnO薄膜的工艺与性能研究

PREPARATION OF ZnO THIN FILM BY MAGNETRON SPUTTERING

采用磁控溅射的方法,制备应用于Cu(In1-xGax)Se2(CIGS)太阳电池窗口层的本征ZnO薄膜。采用X射线衍射、扫描电子显微镜、透过率测试等方法研究和分析制备本征ZnO薄膜的工艺参数包括基底温度、氧分压等对薄膜性能的影响。结果表明:当基底温度较低时,薄膜的结晶状况较差,透过率较低,随着基底温度的升高,薄膜择优生长更明显,晶粒尺寸增大,缺陷密度降低,可见光透过率增加;当基底温度过高时,薄膜表面变粗糙,对光的散射增强,薄膜透过率减小;当氧分压较低时,薄膜中ZnO生长不充分,存在很多氧缺位。而当氧分压过高时,溅射过程中,薄膜表面吸附大量氧原子,阻碍ZnO晶粒的生长。优化后的ZnO薄膜制备工艺参数为:本底真空3.0×10-3Pa,基底温度200℃,溅射气压1.0Pa,氧分压2.0%,溅射功率0.5W/cm2,溅射时间30min。

ZnO thin films were deposited by magnetron sputtering, which could be used as window layer in CuInxGa1-xSe2 solar cell. XRD, SEM, transmissivity tests were used to research and analyze the microstructures, surface morphologies and transmissivities of the ZnO film. The effects of process parameters for depositing intrinsic ZnO films including substrate temperature, partial pressure of oxygen were systematically studied. The results show that the films have poor crystallization and low transmissivity when the substrate temperature is low. During the substrate temperature increases, the films have more obvious preferred orientation growth, larger grain size, less defects density and higher transmissivity. When the substrate temperature is too high, the film have rough surfaces, lower transmissivity because of the scattering of light. When oxygen partial pressure is low, films grow insufficiently because of the lack of oxygen. If oxygen partial pressure is high, the film surface adsorbs a lot of oxygen during sputtering, and this hinders the growth of ZnO grains. Optimized process parameters were obtained as follows of vacuum pressure of 3.0 × 10^-3Pa, sputtering pressure of 1.0Pa, substrate temperature of 200℃, partial pressure of oxygen of 2.0% , sputtering power of 0. 5W/cm^2 , sputtering time of 30min.