Investigation of the Hydrogen Content of Silicon in an Integrated Rapid Thermal Processing Reactor
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Investigation of the Hydrogen Content of Silicon in an Integrated Rapid Thermal Processing Reactor M. A. George, Dept. ofChemical Engineering,Lehigh University, Bethlehem, PA.; S. E. Beck and D.A. Bohling, Air Products and Chemicals Inc, Allentown, PA.; G.A. Hames and J.J. Wortman, Dept. ofElectricalEngineering, North CarolinaState University, Raleigh, NC.; and J. A. Melzak, Dept. of Electrical Engineering, Case Western Reserve University, Cleveland, OH. Abstract
The effects of H2 and H atoms on electronic properties of crystalline silicon is of great interest to many scientists and technologists involved in developing and manufacturing of microelectronic devices. Hydrogen is of interest because of its ability to interact with defects and impurities in single crystal silicon, its abundance in many processing steps, and its effect on electronic structure of the interface between Si and SiO 2 . Here we present results of experiments examining the gas phase concentration of impurities during thermal oxidation and annealing of p(100) silicon. These experiments reveal that a significant quantity of hydrogen is contained in virgin wafers, which may have significant impact on thermal processing. A brief review of studies done on hydrogen diffusion in p-type silicon is provided with a perspective to the process investigated here.
Introduction
Fabrication of sub-micron devices utilizing thin gate oxide structures requires stringent control of the properties of the Si/SiO2 interface. Gate dielectrics having thicknesses below 100 A will be required for future generations of sub-micron MOS devices. The interfacial chemistry of these thin oxides, in particular with respect to hydrogen contamination, can control gate oxide properties. Hydrogen in silicon and silicon dioxide can arise from processing steps such as polysilicon deposition, forming gas (e.g. 5 %H2/95 %N2) annealing, ion implantation, nitridation, oxidation and dopant diffusion. Particular emphasis has recently been pointed to acceptor passivation by H impurities in p-type silicon n-channel MOS devices Ill and the effect of H, in the form of H,O, on thermally grown oxide 121.
Mat. Res. Soc. Symp. Proc. Vol. 282. D1993 Materials Research Society
482
Thermal Oxidation of Silicon The motivation for our experimental work is the concern of hydrogen introduced to the oxidizing atmosphere during thermal oxidation of silicon. As stated above silicon dioxide (Si0 2 ) gates having thicknesses below 100 A will be required for future generations of sub-micron MOS devices. Hydrogen and hydroxyl groups incorporated in this SiO2 can potentially affect device performance by passivating interface traps at the Si/SiO2 interface [31,141 and by passivating holes in p-type silicon, as a result'of hot electron injection 151. In order to investigate the role of H20 as a source for hydrogen and hydroxyl groups in the growing oxide we have utilized a Rapid Thermal Processor (RTP) equipped with in-situ gas analysis 16] and doping. This reactor operates in a pressure regime between I at
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