Limited Reaction Processing
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LIMITED REACTION PROCESSING
JAMES F. GIBBONS*, C. M. GRONET*, J. C. STURM**, C. KING*, K. WILLIAMS*, S. WILSON+, S. REYNOLDS*, D. VOOK*, M. SCOTT, R. HULL, C. NAUKA, J. TURNER, S. LADERMAN, and G. REID++. *Stanford Electronics Laboratories, Stanford, CA 94305 **Princeton University, EE Department, Princeton, NJ 08544 +Charles Evans & Associates, San Mateo, CA 94402 ++Hewlett-Packard Materials Characterization Laboratory, Palo Alto, CA 94304
ABSTRACT Limited reaction processing (LRP), a new technique which provides precise control of thermally driven surface reactions, was used to grow multilayer structures composed of semiconductors and insulators. Results are presented for group IV-based materials including epitaxial Si, SiGe alloys, Si0 2 , and polysilicon. III-V materials such as GaAs, AlGaAs, and InGaAs have also been successfully grown. A number of diagnostic techniques were used to define the advantages and capabilities of LRP, including TEM, SIMS and AES. In addition, some preliminary device results are presented.
INTRODUCTION The fabrication of thin, high quality layers of semiconductor and insulator films is critical to the future of semiconductor processing. It is also of potentially great importance to be able to fabricate several films sequentially without removing the substrate from the processing chamber. This latter feature is important to minimize chemical and particulate contamination. Regarding the layers themselves, we want to maintain interfaces between layers that are as abrupt as possible, which generally argues for a minimum high-temperature exposure; and we want good intra-layer material quality and low defect interfaces, which argues for high temperature processing in many cases. The Limited Reaction Processing (LRP) technique was developed in an attempt to meet these objectives [1-4].
The Basic Process It is convenient to think of the Limited Reaction Process as a technique that uses temperature rather than gas flow as a reaction switch. Conceptually, what we have is a CVD reactor of small volume that is driven by a source of high intensity, incoherent radiation that can be switched on and off quickly. The wafer being processed rests on three quartz pins and represents most of the thermal mass in the system, similar to a conventional RTA apparatus. Details of the chamber and related equipment are given in Ref. [11. In a typical process sequence we first purge the chamber, then establish a carrier flow of inert gas and appropriate flows of reactive gases with the substrate at low temperature (unilluminated). We then raise the wafer temperature quickly (>300°C/sec) to the desired processing temperature, normally in the range of 1000'C, leave it there for the time required to achieve the desired layer growth, and then switch the light source off again. After the wafer has cooled, we switch off the reactive gases and purge the chamber again to set up the next cycle.
Mat. Res. Soc. Symp. Proc. Vol. 74. 91987 Materials Research Society
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The potential of such a system for semiconductor
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