RF diagnostics and automatic control for a plasma etcher



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Texas Tech University


The microelectronics industry has undergone tremendous growth in the past few decades. The integrated circuits, IC's, that form the heart of microelectronics systems have become very complex. Due to improved manufacturing, the number of components on a chip has doubled every two years. At this rate, chips with more than one billion components will be available by the early twenty first century [1].

The integrated circuit manufacturing process involves many physical and chemical processing steps such as; oxidation, lithography, epitaxy, ion implantation, chemical vapor deposition, etching, and diffusion. To create an IC, these processes have to be repeated many times)^' Due to increasing complexity in the manufacturing process and escalating costs it is necessary to ensure that wafers are processed properly at each step. In many cases, it is impossible to measure the results of the process directly. Present practice is to measure some variables related to the process. However, the cumulative effect of the process is difficult to evaluate. This makes detection of equipment faults and changes in the process parameters causing wafer yield loss to go undetected until very late in the processing line [2]. Rejecting defective wafers early in the process helps in maintaining high yield. A key element in achieving the goal of high yield is to monitor and automate the processing equipment to ensure that the semiconductor wafers are processed properly at each step. Automation of semiconductor processing equipment can aid in maintaining tight control over the process parameters. The main emphasis of this work is to develop tight control over the process parameters. The main emphasis of this work is to develop an automatic monitoring and control system for a plasma etcher including RF diagnostic capabilities, and investigate the RF diagnostics as process parameters for plasma etching.

Chapter II gives some background on plasma etching. It describes the types of etching like isotropic and anisotropic etching, parameters that affect the etching process and the diagnostic techniques available. Chapter III describes the Autoload Single Slice Plasma Reactor (ASPR) system setup and describes the various sub systems of the plasma etcher including the magnitude and phase detector. Chapter IV describes the ASPR control system design with the interface boards and explains the control software developed. Chapter V explains the experimental setup for the phase and magnitude measurements, and the results are discussed. Chapter VI presents the conclusions drawn from the results and the fiiture work in the area that need to be done.