Institute for Systems Research Technical Reports

This reactor is based on a novel segmented showerhead design in which gas precursor composition can be individually controlled in the gas fed to each segment. Because the exhaust gas is recirculated up through the showerhead though the individual segments, the gas flow pattern created eliminates convective mass transfer between the segment regions. The effect of this design is a CVD system in which across-wafer composition gradients can be accurately predicted and controlled.

This paper discusses the development of a simulator for a three-segment prototype that has recently been constructed as a modification to an Ulvac ERA1000 CVD cluster tool. A preliminary set of experiments has been performed to evaluate the performance of the prototype in depositing tungsten films for a range of wafer/showerhead spacing and segment gas compositions. We discuss the simulation approach taken to developing the simulator for this system focusing on a one-dimensional simulation of transport through the segments and exhaust mixing region, a model valid in the limit of close showerhead/wafer spacing. The use of simulation in the prototype system design, interpreting experimental data, and its ultimate use in controlling the CVD process to achieve true programmable CVD operation all will be discussed. Further information can be found at the project website, http://www.isr.umd.edu/Labs/CACSE/research/progrxr

The three-tier system architecture consists of a web-based GUI interface module, a business-handling module and a data services module. The user-friendly web-based GUI interface enables users to look up experimental results according to operating conditions, or to determine material and process gas physical properties using a physical property estimator, or to query and retrieve experimental data and run client-side simulations in the MATLAB environment.

Simulation results can be compared to experimental data to validate process models or used to optimize the operating conditions. The business-handling module interprets user's request to determine which information is required and how that information is extracted and synthesized from the back-end database. After this information is obtained, it is delivered to the users in an appropriate format (XML/HTML).

With process heating lamp power held constant, wafertemperature variations of up to 160 degrees K were observed by varying feed gasH_2/N_2 ratio. Heat transfer between the wafer and susceptor wasstudied by shifting the instrumented wafer off the susceptor axis,exposing a portion of the wafer backside to the chamber floor. Modelpredictions and experimental observations both demonstrated that the gasvelocity field had little influence on the observed wafer and predictedgas temperatures.