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P-N Junction Doping Profile Extraction via Inverse Modelling
Student: Tong Lee Too
Supervisor: Y Yeow
Category: Engineering Thesis Project - Electrical
With the increase complexity of device fabrication process and downsizing of semiconductor devices, there is an increasing importance to measure the doping profile of the final device. Knowledge of doping profiles of semiconductors devices allows the determination of electrical characteristics of the devices. Extracted doping profiles can also act as an indicator of the fabrication process of the devices.
Over the years, many methods have been developed by researchers to extract doping profiles of semiconductor devices. The conventional analysis of capacitance-voltage (C-V) measurement is widely used for doping profile extraction due to its simplicity. However, this analysis provides only an approximate value of the actual doping profile of the device. It could only extract doping profile of the less highly doped side of P-N junctions and the extracted profile is limited.
In this thesis, a more accurate method of doping profile extraction for P-N junction is presented. The conventional method is extended via an inverse modelling approach in hope to overcome existing limitations. The inverse modelling process is done in device simulator ATLAS. An initial estimate of the doping profile is treated as input and then simulated to obtain a C-V curve in ATLAS. The parameters in ATLAS are adjusted until the C-V curve obtained in the simulation best fits the C-V curve obtained from the experiment. The doping profile that produces the C-V curve that best fits the measured C-V curve is deemed to possess the profile of the actual device.
As an introduction, this thesis surveys the literature of P-N junction device physics and conventional C-V technique. Next, the method adopted in this thesis will be presented with experimental verification via measurements on an actual device. Doping profile for the lightly doped side of the P-N junction has been extracted with the method purposed and results matched with the expected result thus, proving the validity of the proposed method.