Alois Gutmann

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.

Process window simulation study with immersion lithography for 45-nm technology node

As the potentials of experimental studies are still limited, a predictive resist image simulation of Immersion lithography is very important for a better understanding of the technology. One of the most critical issues in Immersion lithography is the description of the influence of immersion which is the presence of a uniform liquid layer between the last objective lens and the photo resist, on optical lithography. It enables the real part of the index of refraction in the image space, and the numerical aperture of the projection lens, to be greater than unity. Therefore, it is virtually involves Maxwell vector solution approach, including polarization effects and arbitrary thin film multi-layers. This paper discusses the improvement in process window afforded by immersion under a variety of conditions, including 193nm and 157nm, Off-axis illumination, Attenuated Phase Shift Mask for 65nm and 45nm technology node. Comparisons with dry and liquid lithography simulations are used to evaluate the availability and the performance of the proposed approach. The implemented resist simulation approach is examined the impact to the process window of variations in liquid refractive index as well.