Institute for Systems Research Technical Reports

WaterSim simplifies the process of semiconductor manufacturing while teaching students engineering principles and the importance of recycling. The module was created to eliminate esoteric simulation codesand hard-to-understand models which have made it difficult to teachengineering principles to students.

As a participant in the Research Experiences for Undergraduates (REU)program, my role in the WaterSim project was a three-fold process. My firstrole was to create integrated html educational material for the simulator.

My second role was to learn about the simulation techniques that are being developed at ISR and integrate them with the Center for Environmentally-Benign Semiconductor Manufacturing (CEBSN) at the University of Arizona. This process involved creating simulation-basedlearning models with DELPHI and Vissim-based software.

My third role was to research the effects of recycling in ultra pure water (UPW)systems and its effects on a semiconductor manufacturing system. Theresults of this 8-week research include:

-- A beta version of an easy-to-use graphical user intervace called WaterSim

-- An integrated educational manual with written material

-- The formulation of web-based tutorials that exploit WaterSim's majorfeatures

-- An installation program specific to WaterSim that simplifies thedistribution of the product

-- Knowledge ofVissim and Delphi software to create simulations

To accomplish this an interface was designed via the DELPHI programminglanguage that can take inputs from a user as well as factory details froman Excel spreadsheet, run simulations, determine an optimal toolconfiguration, and output this data as easily as possible to the user.

The Interface will guide the Simulation as many times as needed to performits gradient analysis. After the program is complete, it determines a bestcase tool configuration that meets the user's throughput while maintainingto his budget. The interface will output how many of each tool to purchaseas well the best possible tool allocation (usage) for each tool.

Object-Oriented Programming techniques for solvingBVPs are introduced in this work. Object classes are created toencapsulate trial function sequences, discretized differential andquadrature operators, and other data structures used for spectraldiscretization and projection operations. Operator/functionoverloading subsequently is used to numerically implement theGalerkin projection method. Emphasis is placed on developingnumerical methods suitable for discretizing 2- and 3-dimensionalproblems, integrating the resulting ODE/AE systems in time, andreconstructing the solutions in the physical space. A detailed model of anisothermal carbon-carbon chemical vapor infiltration (CVI) systemwas studied as a true test of the ability of the numerical methods.

In this research, an ULVAC ERA-1000 selective tungsten chemical vapor deposition system located at the University of Maryland was studied where a temperature difference as large as 120 ^oC between the system wafer temperature reading and the thermocoupled instrumented wafer measurement was found during the manual processing mode.

The goal of this research was to develop a simplified, but accurate, three-dimensional transport model that is capable of describing the observed reactor behavior.

A hybrid approach combining experimental and simulation studies was used for model development. Several sets of experiments were conducted to investigate the effects of process parameters on wafer temperature.

A three-dimensional gas flow and temperature model was developed and used to compute the energy transferred across the gas/wafer interface. System dependent heat transfer parameters were formulated as a nonlinear parameter estimation problem and identified using experimental measurements.

Good agreement was found between the steady-state wafer temperature predictions and experimental data at various gas compositions, and the wafer temperature dynamics were successfully predicted using a temperature model considering the energy exchanges between the thermocouple, wafer, and showerhead.

To increase the utility of existing simulators, model reduction methods must be used to extract the dominant spatial characteristics of the discharge; numerically efficient spectral projection methods are then used to generated the reduced model. These practical needs motivated the development of a set of simulation tools that provide a framework for process simulation, model reduction, and analysis of simulator predictions.

The goals of this thesis were to build this framework by identifying the computationally common elements of semiconductor device manufacturing process simulation, model reduction, and analysis methods, and to test these tools on the difficult problem of RF plasma simulation. The simulation tools were developed as a library of MATLAB functions; the library and demonstration scripts have been distributed through the MWRtools project website.

Numericalexperiments on a queueing model with high-dimensional parameter vectorsdemonstrate orders of magnitude faster convergence using thesealgorithms over related $(N+1)$-Simulation finite difference analoguesand another two-simulation finite difference algorithm that updates incycles.

The overallobjective is to improve manufacturing effectiveness for epitaxial growth ofsilicon and silicon-germanium (Si-Ge) thin films on a silicon wafer. Growthtakes place in the ASM Epsilon-1 chemical vapor deposition (CVD) reactor, aproduction tool currently in use at ESSS. Phase II project results includedevelopment of a new comprehensive process-equipment model capable ofpredicting gas flow, heat transfer, species transport, and chemical mechanismsin the reactor under a variety of process conditions and equipment settings.

Applications of the model include prediction and control of deposition rate andthickness uniformity; studying sensitivity of deposition rate to processsettings such as temperature, pressure, and flow rates; and reducing the use ofconsumables via purge flow optimization. The implications of varioussimulation results are discussed in terms of how they can be used to reducecosts and improve product quality, e.g., thickness uniformity of thin films. We demonstrate that achieving deposition uniformity requires some degree oftemperature non-uniformity to compensate for the effects of other phenomenasuch as reactant depletion, gas heating and gas phase reactions, thermaldiffusion of species, and flow patterns.