Experimental Measurement of Photoresist Modulation Curves

An approach to measurement of resist CD response to image modulation and dose is presented. An empirical model with just three terms is used to describe this response, allowing for direct calculation of photoresist modulation curves. A thresholded latent image response model has been tested to describe CD response for both 90 nm and 45 nm geometry. An assumption of a linear optical image to photoresist latent image correlation is shown as adequate for the 90 nm case, while the 45 nm case demonstrates significant non-linear behavior. This failure indicates the inadequacy of a “resist blur” as a complete descriptive function and uncovers the need for an additional spread function in OPE-style resist models

Resist Process Window Characterization for the 45-nm Node Using an Interferometric Immersion microstepper

Projection and interference imaging modalities for application to IC microlithography were compared at the 90 nm imaging node. The basis for comparison included simulated two-dimensional image in resist, simulated resist linesize, as well as experimental resist linesize response through a wide range of dose and focus values. Using resist CD as the main response (both in simulation and experimental comparisons), the two imaging modes were found nearly equivalent, as long as a suitable Focus-Modulation conversion is used. A Focus-Modulation lookup table was generated for the 45 nm imaging node, and experimental resist response was measured using an interferometric tool. A process window was constructed to match a hypothetical projection tool, with an estimated error of prediction of 0.6 nm. A demodulated interferometric imaging technique was determined to be a viable method for experimental measurement of process window data. As long as accurate assumptions can be made about the optical performance of such projection tools, the response of photoresist to the delivered image can be studied experimentally using the demodulated interferometric imaging approach

Film quantum yields of EUV & ultra-high PAG photoresists

Base titration methods are used to determine C-parameters for three industrial EUV photoresist platforms (EUV-2D, MET-2D, XP5496) and twenty academic EUV photoresist platforms. X-ray reflectometry is used to measure the density of these resists, and leads to the determination of absorbance and film quantum yields (FQY). Ultrahigh levels ofPAG show divergent mechanisms for production of photo acids beyond PAG concentrations of 0.35 moles/liter. The FQY of sulfonium PAGs level off, whereas resists prepared with iodonium PAG show FQY s that increase beyond PAG concentrations of 0.35 moles/liter, reaching record highs of 8-13 acids generatedlEUV photons absorbed

High index 193 nm immersion lithography: The beginning or the end of the road

For several years, SEMATECH has invested significant effort into extending 193 nm immersion lithography by developing a set of high index materials. For high index immersion lithography (HIL) to enable 1.70NA imaging, a high index lens element with an absorbance = 1.80, and a resist with an index >1.9 are needed. This paper reviews the success or failure of various HIL components and presents the top final material prospects and properties in each category. Since this abstract was submitted, the industry has decided to cease any effort in HIL, not because of fundamental showstoppers but because of timing. This choice was made even though the only currently available technology the can enable 32 nm and 22 nm manufacturing is double patterning. This may represent a paradigm shift for the semiconductor industry and lithography. It may very well be that using lithography as the main driver for scaling is now past. Due to economic forces in the industry, opportunity costs will force performance scaling using alternative technology