ICMCTF2001 Session C6-2: Ellipsometry: Modeling, Measurement and Process Control

Tuesday, May 1, 2001 1:30 PM in Room Sunset

Tuesday Afternoon

Start	Invited?	Item
1:30 PM	Invited	C6-2-1 Real-Time In Situ Observation of Deep Submicron Topography Evolution Using Spectroscopic Ellipsometry and Reflectometry H.-T. Huang, B.S. Stutzman, W. Kong, P. Klimecky, F.L. Terry (University of Michigan) Fabrication of deep submicron structures for applications such as Si integrated circuits, optoelectronic devices, MEMS, and diffractive optics requires accurate control of topography on the nanometer scale. However, the great power of spectroscopic ellipsometry and related techniques has not been exploited in these applications due to the problems inherent in scattering from these patterns. Recently, our research group and others have shown that specular light measurements using spectroscopic ellipsometry (SE) and 2-channel spectroscopic reflectometry (2CSR) from grating test structures, combined with numerical vector diffraction modeling can be used to extract accurate topographic information from deep submicron lines.¹^,² In this talk, we will present in situ, real-time experimental data showing the applications of this technique to control the critical dimensions of reactively ion etched structures using both SE and 2CSR. In one experimental demonstration, photoresist lines were reduced using O₂ reactive ion etching from 325 to 250 nm bottom width with approximately 1 nm accuracy. Simulation results will be presented that demonstrate the power of this method for monitoring nanometer-scale feature evolution. Optimal measurement modes will be discussed, as will problems from systematic measurement errors sources. Methods for extracting topography data from limited-area test gratings surrounded by larger, more irregular structures will be presented. Extensions and possible applications of this type of topography measurement scheme to other areas will be briefly discussed. ¹ Lee, M. E., Galarza, C., Kong, W., Sun, W., and Terry, F. L., Jr., International Conference on Characterization and Metrology for ULSI Technology, Gaithersburg, MD, March 23-27, 1998, AIP Conference Proceedings 449, pp. 331-5 (1998) ² X. Niu, N. Jakatdar, J. Bao, C. J. Spanos, and S. Yedur Proc. SPIE, 3677, 159 (1999). .
2:10 PM		C6-2-3 Ellipsometric Studies of Oxygen Plasma Affects on Zinc selenide L. Yan, J.A. Woollam (University of Nebraska-Lincoln) Zinc selenide (ZnSe) is an attractive semiconductor material for optoelectronic devices, and is also of high interest for both coatings and substrates for high power CO₂ laser optics. To protect a newly developed infrared-active electrochromic thin film device ¹ from atomic oxygen (AO) erosion in Low earth orbit (LEO), an infrared transparent, anti-reflecting optical coating is indispensable. Among candidate materials for this application is zinc selenide. In this paper we present the optical constants of ZnSe at room temperature over a wide spectral range (140nm to 40 microns), before and after atomic oxygen exposure, using variable angle spectroscopic ellipsometry (VASE). Excellent fits were obtained, and comparisons are made to published results available in recent literature based on Adachi model ². To further investigate chemical changes upon radiation, X-Ray Energy-Dispersive Analysis (EDX) data were also taken on ZnSe sample films both before and after AO exposure. Dramatic changes were detected in both the visible and ultraviolet (UV) spectral range after AO exposure, while little was seen in the middle infrared (MIR), suggesting few chemical bonding changes upon AO irradiation. But, there is still a bit of mystery in the UV and the visible. This work is supported by NASA Glenn Research Center, Grant NAG3-2219, and the National Science Foundation Contact NSF II-9901510-EE-UNL. ¹E. B. Franke, C. L. Trimble, M. Schubert, J. A. Woollam. J. S. Hale, Appl. Phys. Lett. 77, 930 (2000). ²S. Adachi and T. Taguchi, Phys. Rev. B 43, 9569 (1991).