- effect transistors. Control of this step is crucial in maintaining optimum device performance, and since at endpoint this step involves exposure of the increasingly thin gate dielectric, concern about damage and reliability is considerable for this step.
- Silicon dioxide etching in fluorocarbon-containing gases mixed with gases such as O2, H2, CO, He, and Ar. In back-end-of-the-line (BEOL) processes, one is mainly concerned with making the metallic interconnects inside a silicon dioxide insulator. The number of interconnect levels is rising, and the number of steps that involve contact (to the active device regions) and vias (from one level of metalization to the next) will increase accordingly. Concern here is with anisotropy, selectivity, and uniformity, as well as with contamination. These gases are also used to clean chambers that have been coated with dielectric films (silicon dioxide and silicon nitride) from previous steps using chemical vapor deposition (CVD). In addition, since many of the gases that are used for dielectric etching are currently of environmental concern because they are greenhouse gases (e.g. C2F6), an opportunity exists to minimize their use, remediate them as effluents, or even to replace them outright, if effective models of dielectric etching can be developed.
- Silicon dioxide deposition through plasma-enhanced chemical vapor deposition (PECVD), using mixtures of SiH4, N2O, and O2 or SiH4, O2, Ar, and TEOS (tetraethoxysilane). For the same reasons that oxide etching will continue to play an important role in BEOL processing as the number of interconnect levels increases, deposition of the intermetal dielectric will be a key process.
- At least one data center should be established to archive, evaluate, and disseminate the existing and future database for models of plasma materials processing in integrated circuit manufacturing. The archived database should include kinetic pathways, mechanisms, and comparisons of models to the results of experiments. This structure would provide a framework for iterative improvement of the database. Full advantage should be taken of emerging electronic data acquisition technology exploiting rapid access through the Internet and the World Wide Web. Although individual companies will no doubt develop proprietary databases, the goal sought with the establishment of the data center is to serve the entire community interested in plasma modeling and diagnostics.
1. National Research Council, Plasma Processing of Materials: Scientific Opportunities and Technological Challenges (National Academy Press, Washington, D.C., 1991).
2. Semiconductor International, May 1996, p. 83.
3. National Research Council, Plasma Processing of Materials: Scientific Opportunities and Technological Challenges (National Academy Press, Washington, D.C., 1991).
4. Semiconductor Industry Association, The National Technology Roadmap for Semiconductors (SEMATECH, Austin, Tex., 1994).