Gas Source Si-MBE
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GAS SOURCE Si-MBE
Hiroyuki
HIRAYAMA*,
Masayuki HIROI*, Kazuhisa KOYAMA* AND Toru TATSUMI* Microelectronics Research Laboratories, NEC Corporation Miyazaki 4-1-1, Miyamae-ku, kawasaki 213, Japan
ABSTRACT Gas source Si molecular beam epitaxy (Si-MBE) apparatus has been devised. The growth mechanism was studied using reflection high energy electron diffraction (RHEED) intensity oscillation. Si epitaxial layers grew through a dissociative adsorption of Si 2 H 6 molecules on Si surfaces. This dissociative adsorption enables a selective epitaxial growth on SiO 2 patterned Si wafers. At low temperatures, the growth rate was limited by a desorption of hydrogen which terminates surface dangling bonds. Doping with B, Sb and P were also studied. B doping was achieved using HBO 2 Knudsen cell or B 2 H 6 gas dopant. Sb doping used an ionized doping cell. P doping was achieved using PH 3 gas dopant. The effect of B doping on the growth was studied using RHEED oscillation. A doped layer's selective epiataxial growth was possible by selective epitaxial growth under doping. This technique was applied to bipolar transistor fabrication. Moreover, using GeH 4 , SilxGex compound growth and its selective epitaxial growth was achieved. Using this Si 1 _xGex selectively grown layer, a Sil xGex base heterobipolar transistor (HBT) was also fabricated. An electron cyclotron resonance (ECR) gas source Si-MBE cell was used for a low temperature surface cleaning and a surface termination by atomic hydrogen.
INTRODUCTION A high speed large scale integrated (LSI) device requires a self-aligning epitaxial technique. Moreover, for LSI applications, the epitaxial film must have few surface defects. A low epitaxial temperature is also necessary to obtain a sharp doping profile. We have started the study on gas source Si molecular beam epitaxy (Si-MBE) to realize an epitaxial technique which satisfies above requirements. In respect of low temperature growth, a conventional e-gun evaporator type Si-MBE is well known to be superior [1,2]. Good crystal quality epitaxial films can be obtained at lower temperature than by conventional chemical vapor deposition (CVD). A sharp doping profile of B [3] and Sb [4) was also obtained. However, the grown film has many irregular-shaped surface defects, which are characteristic of e-gun evaporator type SiMBE. The irregular-shaped defect has its origin in the e-gun evaporator. [5) Hence, other Si sources than e-gun evaporator are necessary to solve the surface defect problem. We have chosen disilane gas as the Si source. Si-MBE in which a gas source Si-MBE machine, We devised The pressure molecu ar bgams. growth was achieved using disilane The high Torr. -10 the growth was designed to be 10 during electron energy high reflection of the use enables vacuum (QMS). (RHEED) and the quadrupole mass spectroscopy diffraction growth the of informations bring methods analysis These Mat. Res. Soc. Symp. Proc. Vol. 198. &1990 Materials Research Society
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mechanism. The characteristic growth mechanism of gas source SiMB
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