Shoaib Hasan Zaidi

FTIR based nondestructive method for metrology of depths in poly silicon-filled trenches

A method that uses Fourier Transform Infrared (FTIR) Reflectance spectroscopy to determine the depths of poly silicon filled trenches is described. These trenches, which form the cells for trench DRAM, are arranged in arrays that are periodic in both directions. The method is non-contact and non-destructive. Large number of points per wafer can be easily measured to determine etch uniformity performance. Unlike cross section SEM based metrology, the wafer does not need to be cleaved, and thereby destroyed. The technique is thus suited for in-line metrology of product wafers. The FTIR technique was found t be very robust and provided excellent correlations with SEMs have been observed for 110 nm trenches and are reported in the paper. The method is a viable manufacturing solution for inline, non-destructive, rapid metrology on product wafers.