As lithographic technology nodes advance beyond the 193 nm generation, the optical absorption of organic materials will require the use of thin layer imaging (TLI) techniques. Of the techniques under consideration, the use of ultra-thin resist (UTR) over a hardmask is the most desirable because of its simplicity and close similarity to standard single layer resist processes. Prior work has demonstrated that the UTR process is capable of pattern transfer to poly silicon device layers with as little as 1000 Angstrom of resist on flat wafers using 248 nm lithography. This was achieved with defect levels comparable to a conventional 5000 Angstrom resist process. In this work, we demonstrate 'proof of concept' by integrating the UTR process into the transistor gate module of a production device using 248 nm lithography. In doing so we focus on three key areas for manufacturability: inherent defectivity of UTR films, sensitivity of thin resist to topography, and quality of pattern transfer. We find that pinhole defects are of little concern in the UTR process after SEM review of defects on un-patterned UTR films. We show that the UTR process is sensitive to wafer topography, since it does not provide a completely planar surface over the underlying device features. Finally, we demonstrate that the UTR process is capable of reliable pattern transfer on a production device with defect levels comparable to the thicker baseline single layer resist process.
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.
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.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.