Dr. Ashwin M Khambadkone

Associate Professor Ashwin M Khambadkone is presented with the Best Paper Award in IEEE Transactions on Industrial Electronics and the prize of US$1,000 cheque on 4 November 2003 at IECON'03 Roanoke, Virginia, USA.

The 2003 Best Paper Award for the IEEE Transactions on Industrial Electronics has been selected on the basis of the value of the contribution, subject matter, originality and composition among those papers published in the transactions during 2002.

Overmodulation scheme was originally proposed by Prof Holtz, Dr Lotzkat and Dr Khambadkone in 1992. However, it was an open loop scheme and could not be applied to closed loop vector control scheme. The award winning contribution makes it possible to used the scheme in closed loop vector control.

Compensated Synchronous PI Controller in Overmodulation Range and Six-Step Operation of Space-Vector-Modulation-Based Vector-Controlled Drives

Abstract >> Overmodulation enhances the power utilization of the installed capacity of a voltage source inverter. A space vector strategy is used for constant switching frequency inverters. In order to achieve the overmodulation a modified reference signal with non-uniform angular velocity is generated using a preprocessor.

Such a reference wave produces low frequency harmonics in currents. The presence of current harmonics restricts the bandwidth of the synchronous PI current controller in the overmodulation range. A compensating current control in synchronous coordinates during overmodulation and six-step. The proposed scheme allows for an easy upgrade of conventional vector control scheme to include overmodulation and thus reduce the design-to-market time.

Industrial Electronics, IEEE Transactions
Publication Date: June 2002
Volume: 49, Issue 3 on page(s): 574-580

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For further information, please contact:
Dr. Ashwin M Khambadkone
Email: eleamk@nus.edu.sg
Telephone: 6516 5157

Dr. Mehul Motani

SIMagine is a worldwide GSM & JavaCard Developer Contest run by Axalto in the association with Sun Microsystems, Samsung and operator sponsors China Unicom, Cingular, Telcel, Telefonica and TIM.

The team from NUS consisting of Assistant Professor Mehul Motani, Abraham Hidayat (B.Eng, 2003), Kam Chuan Liang (B.Eng, 2003), presented their idea called SIM Bluetooth Advertising (SIMbad) at the 3GSM Congress at Cannes, France in February 2003. They won the Telecom Italia Mobile (TIM) Operator Award and a cash prize of €5000 euros, placing first amongst all university entries and fourth overall amongst all entries.

Assistant Professor Mehul Motani, a Ph.D. candidate in the School of Electrical Engineering, has been awarded an Intel Graduate Fellowship. These grants are awarded to doctoral students at selected schools who are judged to be the very best advanced graduate students in fields of study related to Intel's technology research.

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For further information, please contact:
Dr. Mehul Motani
Email: elemm@nus.edu.sg
Telephone: 6516 6918

Dr. Ho Weng Khuen

Associate Professor Ho Weng Khuen and his collaborator from Stanford University, Dr Charles Schaper, receiving the award at the 2003 IEEE International Symposium on Semiconductor Manufacturing. This Best Paper was announced in the November 2003 TSM issue of the Transactions.

The paper has been selected because it showed that cross-wafer operating uniformity does not necessarily lead to cross-wafer product uniformity which has enormous implications for in-situ process monitoring. This was demonstrated experimentally on the photo-resist coating process in lithography. The improvement that can be obtained from the application of control and signal processing in semiconductor manufacturing was also clearly illustrated in the paper.

Real-time Predictive Control of Photoresist Film Thickness Uniformity

Abstract >> With the trends toward larger wafer size and the linewidth going below 100 nm, one of the challenges is to control the resist thickness and uniformity to a tight tolerance in order to minimize the thin-film interference effect on the critical dimension. In this paper, we propose a new approach to improve resist thickness control and uniformity through the softbake process. Using an array of thickness sensors, a multizone bakeplate, and advanced control strategy, the temperature distribution of the bakeplate is manipulated in real time to reduce resist thickness nonuniformity. The bake temperature is also constrained to prevent the decomposition of a photoactive compound in the resist. We have experimentally obtained a repeatable improvement in resist thickness uniformity from wafer-to-wafer and across individual wafers. Thickness nonuniformity of less than 10 Å has been obtained. On average, there is 10 × improvement in the thickness uniformity as compared to conventional softbake process.

IEEE Transactions on Semiconductor Manufacturing
Publication Date: Feb 2002
Volume: 15, Issue 1 on page(s): 51-59

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For further information, please contact:
Dr. Ho Weng Khuen
E-mail address:elehowk@nus.edu.sg
Telephone: 6516 6286