Ken-ichi Aketagawa

Selective epitaxial growth by UHV-CVD using Si2H6 and Cl2

The conditions under which selective epitaxial growth (SEG) is achieved in UHV-CVD with Si2H6 are determined by the amount of Si2H6 molecules being supplied, and there is a critical gas supply amount (Fc) beyond which SEG will break down and lose its selectivity. The value of Fc is itself determined by two factors, growth temperature and the material used for masking, i.e. SiO2, Si3N4. We found that this limiting factor of Fc was increased through the addition of a small amount of Cl2, and that after such addition, the resulting decrease in growth rate is minimal.

Limitations of selective epitaxial growth conditions in gas-source MBE using Si2H6

The limiting conditions of selective epitaxial growth (SEG) on SiO2 patterned Si(001) substrate were studied for Si gas-source molecular beam epitaxy (MBE) by use of 100% Si2H6. In the initial stage of growth, epitaxial Si was selectively grown on a Si surface in the temperature range of 500 to 850°C. On the other hand, polycrystalline Si nucleation on a SiO2 surface was intimately related to the impinging density of the Si2H6 molecules on SiO2, so that SEG was limited by the supply gas volume. Under optimum SEG conditions such as substrate temperature of 700°C and Si2H6 flow rate of 60 SCCM, a SEG layer could be deposited at a rate as high as 645 A/min.

Selective Epitaxial Growth of Si and Si1-xGex Films by Ultrahigh-Vacuum Chemical Vapor Deposition Using Si2H6 and GeH4

Aiming at the precise profile control of Si1-xGex, selective epitaxial growth (SEG) conditions and Si1-xGex growth were investigated by ultrahigh-vacuum chemical vapor deposition (UHV-CVD) using Si2H6 and GeH4. As long as the total amount of Si2H6 did not exceed the critical amount, Si- and Si1-xGex-SEG were both achieved independent of source gas flow rate and substrate temperature. The Ge fraction x of Si1-xGex could be decided by the flow rate ratio between Si2H6 and GeH4, independent of substrate temperature. Fast gas flow switching realized the formation of a Si(120 A)/Si1-xGex(69 A) strained layer superlattice at 587°C.

The influence of Cl2 on Si1 - xGex selective epitaxial growth and B-doping properties by UHV-CVD

Abstract We report the influence of a small quantity of Cl 2 , which enhanced the selectivity of silicon-selective epitaxial growth (Si-SEG) in UHV-CVD using Si 2 H 6 , on both the epitaxial growth rate and the B-doping properties for each Si and Si 1- x Ge x film. The small quantity of Cl 2 inhibited the Si, Ge and B incorporation, while the selectivity was enhanced. However, it was found, in the case of Si 1- x Ge x -SEG using Cl 2 , that the reduction ratio of both the growth rate and the B incorporation were smaller than those of Si-SEG with the selectivity still more enhanced.

SiGe/Si Heterostructures

2. EXPERIMENTAL Our UHV-CVD system included a stainless steel growth chamber, a water cool ed j acket, and separate nozzles for SiaHe and Clz. A 10001/s turbo-uolecular punp reduced background pressure on the growth chamber to 1.5x10-e Torr. 6-inch (100) Si wafers were nasked with 20004 patterns of either SiOa or SigNa. Wafers were precleaned with a chenical solution (NHa OH:He Oa:Ha O=l :6:20) to form a protective thin oxide layer before loading into the growth chamber. The thin oxide layer on the Si surface was evaporated by a thermal process, during which time the Sia He was supplied. The cl eaning temperature was 8000 C and SieHo was suppl ied at SSCCM wit h 10 sec wit hin t he overal I cl eaning process time of I min. Successful SEG condition was confirmed by RHEED in the growth chamber. The source Bas, pure SieHo, GeHa and Clz, first passed through a mass-flow cont roller and then into the growth chamber trough a nozzle without precracking. SiaHo and GeHl pressure in the growth chamber was 7xl0-a Torr, and Cla pressure was varied from 1xl0-6 to 1x10-5 Torr.

Si1-xGex Epitaxial Growth Using UHV-CVD and Its Device Applications

The condit ions under which sel ect ive epit axial gr owth (SEG) is achieved in UHV-CVD with SizHo and GeHl are determined by the amount of SiaHe molecules being supplied, and there is a critical gas supply amount (Fc ) beyoad which SEG wtl I br eak down and I ose it s sel ectivity. The val ue of Fc is itsel f determined by two factors, growth temperature and the material used for masking, i.e. SiOa, SisNl. We found that this liniting factor of Fc was increased through the addltion of a small amount of Cle, and that after such addition, the resulting decrease in growth rate is mininal. This techaique wa

Lattice Strain in Si1-xGex Alloy and Si/Si1-xGex Superlattice

applied to the self-aligned base fabricatioa of high speed bipolar t r ansist or s.

Thin film deposition method for wafer

Si1-xGex alloy and Si/Si1-xGex superlattice are coherently grown on Si substrates by UHV-CVD(Gas-Source MBE). Lattice strain is investigated by double crystal X-ray diffraction, Raman scattering and Photoluminescence experiments. By using the data of (004) and (113) diffraction lines, the c-axis of Si1-xGex alloy is evaluated to be expanded by 0.69% than the c-axis of Si substrate. For the case of Si/Si1-xGex superlattice the c-axis of Si1-xGex layer in superlattice is determined to have the same value with that of Si1-xGex alloy grown on Si substrate by the kinematical simulation of superlattice satellites, and the c-axis of Si layer in superlattice has the same value with that of Si substrate. The backscattering Raman spectra of two samples are identical with the frequencies of Si-Si, Si-Ge and Ge-Ge modes. In the 4.2 K-photoluminescence experiments, the same spectral features observed in the Si1-xGex alloy layer are appeared also in the Si/Si1-xGex superlattice, however the photon energy of luminescence is moved to lower by 10 meV. This indicates that the Si/Si1-xGex superlattice has the type II band line-up.