Two-step rapid thermal diffusion of boron into silicon using a boron nitride solid diffusion source |
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Authors: | Jeong-Gyoo Kim Choong-Ki Kim |
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Affiliation: | (1) Department of Electrical Engineering, Korea Advanced Institute of Science and Technology, Cheongryang, P.O. Box 150, Seoul, Korea |
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Abstract: | A two-step rapid thermal diffusion process of boron into silicon using a boron nitride solid diffusion source is described. During the first step, HBO2 glass is transferred onto the silicon wafer from the diffusion source by keeping the temperature of the silicon wafer at 750° C while the diffusion source is at about 900° C. Boron is, then, diffused into the silicon wafer from HBO2 glass at 1000° C or 1100° C in N2 during the second step. Extremely shallow junctions with junction depths of about 20 nanometers and sheet resistances of about 350 ohms/sq can be achieved with this method as well as relatively deep junctions with junction depths of about 175 nanometers and sheet re-sistances of about 55 ohms/sq. When the diffusion is performed at 1100° C, both the junction depth and electrically active boron concentration at the surface increase as the ambient gas is changed from N2 to O2 while the sheet resistance decreases. A boron rich layer which has high resistivity is not formed at the surface when the diffusion is performed at 1100° C in O2 ambient. This work was supported by Ministry of Science and Technology, Korea |
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Keywords: | Two-step rapid thermal diffusion boron nitride solid diffusion source effects of ambient gas |
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