Christopher Lee Pike

Lithography using ultrathin resist films

The industry trend toward higher numerical apertures and lower k1 factors is severely constraining the manufacturing process margin for current and future lithography technologies. Ultrathin resist (UTR) films and other thin layer imaging techniques offer the promise of improved process margin as compared to conventional single layer resist schemes. In this study, an UTR over hard mask process was used to pattern the transistor gates of a high performance microprocessor using 248 nm lithography while focusing on four key areas of concern for UTR films: resist film defectivity, response of thin resist to device topography, quality of pattern transfer on device wafers, and device yield comparable to a baseline process. The intrinsic defectivity of resist films as thin as 65 nm is found to be no greater than that of a >500 nm resist film on flat silicon wafers. No pinhole defects are observed during scanning electronic microscopy review of defects on as-coated UTR films. As expected, the UTR process is sensi...

Characterization of the manufacturability of ultrathin resist

A study was conducted to explore the manufacturability of ultrathin resist by focusing on two key issues, defects and etch resistance. Defects in ultrathin resist were characterized by optical inspection and scanning electron microscopy reviews. A number of representative defect types in the ultrathin resist/hardmask process were identified. With process optimization, defect density in ultrathin resist was reduced to levels that are comparable to that of a baseline 0.5 μm thick resist process on nontopographic wafers. Etch resistance sufficient for patterning metal–oxide–semiconductor transistor gate film stacks was demonstrated for a 100–150 nm thick resist layer.

Defects and metrology of ultrathin resist films

Defectivity in spin-coated, but unpatterned ultrathin resist (UTR) films (<EQ 1000 Angstrom) was studied in order to determine whether defectivity will present an issue in EUV (13.4-nm) and 157-nm lithographic technologies. These are the lithographic regimes where absorption issues mandate the use of ultrathin resists. Four resist samples formulated from the same Shipley UV6 polymer batch and having the same polymer molecular weight properties but different viscosities, were spin-coated at spin speeds ranging from 1000 to 5000 RPM on a production-grade track in a Class 1 pilot line facility. Defect inspection was carried out with KLA SP1/TBI tool, while defect review was carried out with JEOL 7515 SEM tool and KLA Ultrapointe Confocal Review Station (CRS) Microscope. The results obtained are related to the physical properties of the resist polymers, as well as to spin coating parameters. Also, the results of the defect inspection, review, characterization, and pareto are compared to those obtained on baseline thick resists (>= 3500 Angstrom) processed under similar condition as the ultra-thin resists. The results show that for a well-optimized coating process and within the thickness range explored (800 - 4200 Angstrom), there is no discernible dependence of defectivity on film thickness of the particular resists studied and on spin speed. Also assessed is the capability of the current metrology toolset for inspecting, reviewing, and classifying the various types of defects in UTR films.

Process-induced defects in sub-0.15-nm device patterning using 193-nm lithography

Process induced defects in sub-0.15 micrometer devices patterned on 193-nm photoresists have been studied and related to the physical and rheological properties of these polymers, as well as to the interaction of the photoresists with the two principal track-related unit operations: spin-coating and development. Studies on unpatterned wafers with these photoresists were conducted to elucidate the dependence of defectivity and defect types on spin coating parameters. Imaging was done on a full-field ASML 193 nm scanner and the resist processing was performed on a TEL MARK-8 track. Defect inspection was performed with a KLA 2132, KLA SP1 bright field inspection systems, and defect review was carried out with JEOL 7515 SEM tool. Results indicate that defectivity of an optimized 193-nm resist process is comparable to a well- optimized 248-nm baseline resist process. It was found that 193-nm resists suffer from the same residue problems as those of 248-nm. Yield data obtained on 193-nm and 248-nm resists processed under optimized conditions demonstrate that the 193- nm resist process is capable performance comparable to that of a baseline 248-nm resist process.