热处理对磁控溅射法制备p-ITO(40 nm)薄膜特性的影响

为改善在实际生产中,p-ITO在膜厚较薄时所表现出的多种不良,如退火后膜质存在花斑不良、膜层易被刻蚀液腐蚀等,进行退火对p-ITO薄膜特性影响的研究。本实验利用磁控溅射法在玻璃基板上制备出40nm厚度的p-ITO膜,并在氮气环境中对膜层进行不同温度和时间的退火处理。分别采用XRD、AFM和SEM对p-ITO的结晶度和微观结构进行表征,并使用四探针(4-point probe,4P)和自动光学测试设备分别测试其方块电阻和光透射率。测试结果表明:pITO结晶温度相对于α-ITO存在严重滞后性;α-ITO(40nm)230℃已结晶充分,而p-ITO在230℃才开始结晶;p-ITO在230～250℃时结晶程度及均一性较差,导致多种特性的不稳定,比如膜质花斑状颜色差异(花斑不良),方块电阻、膜层厚度均一性差,膜层易受腐蚀等;退火温度提高到260～270℃时结晶基本完全,对薄膜的各种特性改善效果显著,如方块电阻降低、光透射率增加、花斑和腐蚀改善等。测试数据还反映出玻璃中部位置相对于边缘位置结晶程度差,可能原因为退火设备实际生产时玻璃中间位置热风阻力较边缘位置大,受热不充分导致。适当提高退火温度和时间,对pITO实际生产中遇到的多种不良有显著改善效果。

Effect of annealing treatment on the performances of 40 nm thick p-ITO films prepared by DC magnetron sputtering

The effect of annealing on the properties of p-ITO thin films was studied in order to improve many imperfections of p-ITO thin films in mass production, such as bad spots on the film after annealing and corrosion of the film by etching solvent. In this work, p-ITO of 40 nm thin films were deposited at room temperature by utilizing magnetron sputtering with DC power supply, and annealed in N₂ atmosphere under various annealing time and temperature. The crystallinity and microstructures of thin films were analyzed by XRD, AFM and SEM, and the square resistance and light transmittance were measured by four-point probe and automatic optics measuring system respectively. The results show that there is a serious hysteresis in the crystallization temperature of p-ITO compared with α-ITO. The crystallization temperature of p-ITO film is 230℃, at which α-ITO film has fully crystallized. It appears poor crystallinity and homogeneity of p-ITO at 230-250℃, resulting in instability of many characteristics, such as bad spots in film color, poor homogeneity of square resistance, easily to be corroded, etc. When annealing temperature is raised to 260-270℃, the crystallization is almost complete. It has a good effect on p-ITO films, such as the square resistance is lower, the transmittance is higher, and the bad spots of p-ITO thin films disappear. Research also shows that the crystallinity of the middle position of glass is worse than that of the edge at the same temperature, probably because the flow resistance of hot air is higher in the middle position and the heat is insufficient. The raising of the annealing temperature and time properly has a significant effect on the various defects encountered in the mass production of p-ITO.