Co-Cr合金膜的X射线线形分析

X-RAY DIFFRACTION PROFILE ANALYSIS OF Co-Cr ALLOY THIN FILMS

利用近似函数法对Co－Cr合金薄膜的衍射线线形进行分析，并提出用“三线法”确定衍射线的函数类型及其积分宽度，由此可计算薄膜的晶粒尺寸和微观应变。理论计算和实验表明，“三线法”结合近似函数法在线形分析方面是简便、可靠的。通过分析Co－Cr膜在不同工艺条件下（膜厚、Ar工作气体压强和负偏压）的衍射线线形，发现衍射线的物理展宽（即有效晶粒尺寸的减小）与晶粒取向度的下降是相对应的。晶粒取向度的下降与结构缺陷密度的增大有关。负偏压溅射时由于Ar原子残留在膜内引起晶格膨胀，从而使微观应变有较大增加。

In this paper,the diffraction line profile of Co-Cr alloy thin films is analyzed with the method of approximate function,and the 'three-line' method is proposed to determine the type of function and its integral width,because the ratios of the chordwise widths at 1/4,1/2 and 3/4 peak heights are intrinsic. In this case,the crystallite size and the microstrain of the films can be calculated. In addition,the preferred orientation of crystallines is evaluated with the half width of rocking curve of HCP(0002)crystal planes. Theoretical calculations and experiments show that the 'three-line' method combined with the approximate function is convenient and reliable,and the accuracy is higher. Through analyzing the diffraction line profiles of Co-Cr films deposited by magnetron sputtering under different conditions(e. g.,film thickness,Ar working gas pressure and negative bias voltage),it is found that the broadening of diffraction profile(i. e.,the decreasing of effective crystallite size) corresponds to the deterioration of preferred orientation of crystallines. The degradation of the preferred orientation is related to the higher content of structural defects (e. g., voids, stacking faults, twinning and Cr segregation,etc. ). During the film growth process,the structural defects are eliminated progressively,and the microstrain relaxes gradually,so the preferred orientation with the HCP(0002) crystal planes parallel to the film surface is realized. When the films are deposited under negative bias voltage,the microstrain increases monotonically with the voltage due to the Ar^+ bombardment on the growing film surface.