Measurement of line width roughness by using atomic force microscope

The analytical procedures are illustrated of the measurement of line width roughness (LWR) by using atomic force microscope (AFM). The relations are presented of line-width, line-width error vs. the height. With the increase of the height, the line width and its error become smaller. The trend of LWR and its error vs. height is the same as that of line-width vs. height. The four operators, i.e., Roberts, Sobel, Canny and Prewitt are respectively used to detect the edges on the top surface measured by using AFM with the carbon nanotube tip. Then the line width and LWR on the top-surface are calculated, which shows that different operators have almost no effect on the line width and LWR. A method to verify the nonlinear in z direction of the piezoelectric actuator of AFM is brought forward in terms of the processing technology on the top and bottom surface of the measured single crystal silicon step. In the method, the height of the scanning profile is equal to one another. LWR is compared with one another which are measured respectively by using AFM with the ordinary tip, the ultra-sharp tip and the carbon nanotube tip. There is no remarkable difference about the step in 1000 nm nominal line width. Thus the resolution of AFM must be improved in order to get more accurate topography of sidewall.