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High Efficiency Thermal Atomic Source

IP.com Disclosure Number: IPCOM000039549D
Original Publication Date: 1987-Jun-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 54K

Publishing Venue

IBM

Related People

Demuth, JE: AUTHOR [+2]

Abstract

A high efficiency thermal atomic (HETA) source is described which is an inexpensive, clean and efficient means for generating high flux rates of thermal atomic species in a high vacuum or ultra-high vacuum environment. It can be used for defect passivation, doping or compound formation during conventional or new low temperature VLSI processing of Si. More importantly, it can be utilized for these same functions in situ during the growth processes used in molecular beam epitaxy (MBE). For MBE processing this seeding of atomic species in situ can allow the tailoring of device characteristics on a layer-by-layer basis during growth, and provides for passivation or doping, as well as the formation of new compound layers (i.e., in situ oxidation or nitridation for isolation or as a diffusion barrier layer.

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High Efficiency Thermal Atomic Source

A high efficiency thermal atomic (HETA) source is described which is an inexpensive, clean and efficient means for generating high flux rates of thermal atomic species in a high vacuum or ultra-high vacuum environment. It can be used for defect passivation, doping or compound formation during conventional or new low temperature VLSI processing of Si. More importantly, it can be utilized for these same functions in situ during the growth processes used in molecular beam epitaxy (MBE). For MBE processing this seeding of atomic species in situ can allow the tailoring of device characteristics on a layer-by-layer basis during growth, and provides for passivation or doping, as well as the formation of new compound layers (i.e., in situ oxidation or nitridation for isolation or as a diffusion barrier layer. Unlike conventional processing where samples are removed from one chamber to be processed in another, the more stringent cleanliness and growth conditions for MBE or GaAs processing in almost all cases precludes such conventional processing steps, and demands clean, in-situ methods. For example, Fig. 1 schematically shows a MBE set-up to form a passivated and doped heterojunction structure, such as that of Fig. 2. The MBE sources A and B are sources for semiconductors A and B, respectively, while HETA sources C, D, E are sources of atomic hydrogen (H) boron (B), and oxygen (O), respectively. The timing pattern for the various phases of the deposition and doping are shown in Fig. 2. The high reactivity of atomic species will also generally lower the required process temperatures, while in-situ passivation at specific stages can remove defects or trap states formed during lower temperature growth steps. The same HETA sources can be used to produce a variety of thermal atomic species produced from parent gases (i.e., H from H2, O from O2, N from N2 , etc.) as well as mixed atomic species (B and N from BN, P and Ha from PH3, etc.). For certain species the filament material choice and filament operating temperature in the HETA source can be selected to optimize the operating conditions for each species desired. The HETA source consists of a 1/4" dia. x 0.020 thick molybdenum tube 10, containing a coaxial tungsten filament, which is brazed onto a vacuum flange, as shown in Fig. 4. Molecular hydrogen is fed into the tube, into the vacuum chamber 12 through a leak valve behind a...