3.1.1 History of Oxidation Simulators

Several numerical techniques for the visualization and modeling of silicon oxidation have been published and implemented in commercial and educational simulation tools. The Institute of Microelectronics at TU Wien is no exception, with several works on silicon oxidation being published [80], [178]. Both works implement simulations using the FEM and follow the Deal-Grove concept, with [80] using the FEDOS simulation tool, developed at the Institute of Microelectronics. The advantage of using the Deal-Grove concept, with two rate constants and two moving boundaries is the existence of the calibrated rate constant for a variety of oxidation conditions.

A tool developed at Stanford University's Department of Electrical Engineering for process simulations is SUPREM-IV [195]. This tool is a pioneer in TCAD simulations, with its roots as a one-dimensional processing tool. SUPREM-IV now has a compress and a viscous mechanical model for the oxidation of silicon and gallium arsenide (GaAs) [196]. The compress model treats the oxide as a compressible liquid, while the viscous model treats it as an incompressible viscous liquid. Its predecessor SUPREM-III is the basis for two commercial tools, TSUPREM-IV and ATHENA.

TSUPREM-IV is an enhanced version of SUPREM-IV, which was commercialized by Technology Modeling Associates Inc. (TMA), a company which was founded at Stanford University and introduced the commercial TCAD business. TMA was acquired by Avant! Corp. in 1998 and by 2002, TSUPREM-IV grew to offer oxidation simulations for compress, viscous, and visco-elastic modeling. In 2002, Avant! was purchased by Synopsys and is still offering TSUPREM-IV.

The Integrated Systems Laboratories at ETH Zurich developed a two-dimensional process simulator DIOS and a one-dimensional simulator TESIM in 1992. Later, the company Integrated Systems Engineering AG (ISE) was formed, distributing DIOS as a commercial simulation tool. By 2004, DIOS had viscous, elastic, or visco-elastic models for the mechanical oxidation problem, at which time it was purchased by Synopsys.

At approximately the same time, TMA developed a three-dimensional process and device simulator Taurus, which was only released after acquisition by Avant!. The mechanics of oxidation were described with a visco-elastic model, but many problems with the moving boundary in three dimensions existed and Taurus was not able to become a complete process simulator until Avant!'s acquisition by Synopsis. Currently, Synopsis has combined the TSUPREM-IV tool with the Taurus tool and it is being offered commercially as Taurus TSUPREM-IV [205].

Around 1994, the first version of the Florida Object Oriented Process Simulator (FLOOPS) was released. Already in 1996, the FLOOPS interface was extended to include three-dimensional models. FLOOPS was commercialized by ISE in 2002 and with additional development from ISE, a new tool FLOOPS-ISE became a stable three-dimensional oxidation simulator. FLOOPS-ISE contained the same mechanical models as ISE's other software, DIOS, but extended to three-dimensional structures. As mentioned previously, ISE along with its software package was sold to Synopsys in 2004. The combination of DIOS and Taurus TSUPREM-IV, released in the FLOOPS-ISE platform was released as a three-dimensional tool, Sentaurus Process [204] by Synopsys.

The company Synopsys, Inc was founded in 1986. After it acquired Avant! and ISE, it became the largest company in the TCAD industry. It now has nearly an 80% share in the TCAD market with Silvaco its sole competitor.

ATHENA is the commercial version of SUPREM-IV from Silvaco Inc., which still distributes ATHENA [188]. While ATHENA has not modified much and is still a two-dimensional simulation tool, Silvaco offers VICTORY Process [189], a three-dimensional process simulator which has empirical models based on the Deal-Grove and Massoud models in addition to physical models which include the reaction at the Si-SiO$_2$ interface, viscous flow, material deformation, and stress formation. A more detailed look into the oxidation tool offered by Silvaco, which uses a LS environment is described in Section 3.1.3.

Other non-commercialized tools still exist. One process simulator PROPHET was created around 1994 at Bell labs which later became Agere and then, after merging with LSI Logic Corporation, LSI Corporation. Besides these simulators, there are numerous other university and commercial simulators such as PROMIS [91], a two-dimensional process simulator developed at the Institute for Microelectronics, TU Wien.