New Metrology for Process Optimization and Water and Energy Savings during Surface Preparation of Patterned Wafers.

Dhane, Kedar; Han, Jeongnam, Yan, Jun; Shadman, Farhang, Vermeire, Bert
(University of Arizona, Tucson, AZ)

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New Metrology for Process Optimization and Water and Energy Savings during Surface Preparation of Patterned Wafers. 1Kedar Dhane, 2Jeongnam Han, 1Jun Yan, 3Bert Vermeire, 1Farhang Shadman 1 University of Arizona, 2 Samsung Electronics Co. Ltd., 3 Arizona State University. Abstract: Surface preparation of patterned wafers by batch processing becomes a major challenge as semiconductor fabrication moves deeper in submicron technology nodes. Many fabs already employ single-wafer immersion and single wafer spinning tools. The main drawback of single-wafer tools is their lower throughput. This disadvantage is eased by introduction of multi chamber tools. To reduce cycle time and resource utilization during rinse and dry processes without sacrificing surface cleanliness and throughput, in-situ metrology is desirable. Electrochemical Residue Sensor (ECRS), metrology was used to compare typical single wafer spinning tools with immersion tools for rinsing of the patterned wafers. This novel metrology technology combines hardware for an in-situ measurement with software for process data analysis. Successful incorporation of this metrology improves visibility of what is happening inside micro-features during surface preparation and will reduce dependency on external analyzing techniques such as ICPMS, SEM, and TEM and will lead to fast response time. In this study the ECRS was incorporated into a lab scale single-wafer spinning and a single- wafer immersion tool. A special contact pad was designed and fabricated for the single wafer spinning tool. It was mounted below the chuck to electronically connect the ECRS to the LCR meter. This modified single-wafer spinning clean/rinse/dry tool setup can provide real-time data on the amount of contaminant or water left inside micro- and nano-structures during rinsing and drying. The ECRS was used to monitor the dynamics of rinsing after various cleans such as SC-1, SC-2 and Piranha. It was observed that different cleaning chemicals impact the subsequent rinse not only through adsorption and desorption of the cleaning chemical but also through surface charge. The surface charge depends on the concentration and the temperature of the cleaning chemicals. The results are analyzed by using the comprehensive process model which takes into account various transport mechanisms such as adsorption, desorption, diffusion, convection and surface charge. This allows the concentration of contaminant on the surface to be extracted from the measurements. By using this in-situ and real time metrology it is possible optimize any rinsing or drying process that will lead to savings of water and energy usage. This novel metrology can be used at very low impurity concentration with very high accuracy.

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