Walter Scott, Jr. College of Engineering

Graduate Exam Abstract

Ovidiu Stan
Ph.D. Final
Feb 22, 2007, 9AM
Hammond Auditorium Engineering 120
Novel Techniques of RF High Power Measurement

RF diagnostic systems provide essential parameters for both statistical process control (SPC) and automated process control (APC). To achieve process repeatability and process control of RF plasma processes such as plasma-enhanced chemical vapor deposition (PECVD) and plasma etching (PE), it is necessary to accurately monitor and control the actual plasma impedance and RF power delivered to the plasma. The metrology of the RF system can determine the accuracy of SPC control limits and will dictate the accuracy and repeatability of the APC RF control points.
The actual trend into RF process is to go to extremes: High Frequency and High Power (large area flat panels/solar panels) or very Low Power. Industry requirements are up to 50kW at 13.56 MHz and up to 200 MHz in frequency. There are isolated applications reported at higher frequency (microwave).
Todays state of the art instruments can measure RF power with 1% accuracy at its best; typical accuracy is around 3%. Usually the accuracy is degrading with the increase in Voltage Standing Wave Ratio (VSWR). There are a lot of efforts to improve the RF sensors and measurement techniques. My research proved that using the proper digital correction a better then 1% RF power accuracy can be obtained. A novel power measurement technique for adapted lines is presented along with the test results. For RF power measurements into complex impedances (non adapted lines) I researched a direct sampling method.
Absolute accuracy of the RF metrology is compounded from errors introduced by the measurement system, calibration method and power references. RF high power standards are not traceable directly to primary metrology references. In order to improve the accuracy I focused my research not only on measurement techniques but also I examined the errors involved in the calibration methods.
Adviser: George Collins
Non-ECE Member: Hiroshi Sakurai, Department of Mechanical Engineering
Member 3: Thomas W. Chen, Department of Electrical and Computer Engineering
Addional Members:
Program of Study: