In single crystal growth of silicon, it is important to acquire correct knowledge about momentum, heat and mass transfers in the crystal growth furnace and then to control them, because the quality of crystals is closely related to the transport phenomena in the furnace. Numerical simulation is one of the methods to understand the phenomena in the furnace, and recently there has been much interest in the calculation of melt convection and global analysis of heat transfer in the furnace. Particularly, since the growth of larger single crystals generates turbulent melt convection, most of the studies focus on accurate modeling of turbulence in the melt to understand the melt convection in the real crystal growth process. Here, the recent studies on numerical simulations of silicon single crystal growth by the Czochralski and floatingzone methods are introduced, and also the values of thermophysical properties used in these numerical studies are investigated. Moreover, being based on the sensitivity analysis of the thermophysical properties by using the global model of the CZ furnace in addition to the survey of properties, the necessity of the standard data for thermophysical properties is discussed.
Thermophysical properties required for numerical simulation of silicon crystal growth processes have been investigated from Japanese silicon wafer producers. Results from the survey are presented for molten silicon, crystalline silicon and refractory materials. Thermal transport properties such as thermal conductivity of both melt and crystal are greatly important. Mechanical properties such as elastic constant of the crystal are required especially at high temperatures. Thermal transport properties of refractory materials are also essential for the global analysis of heat transfer in the furnace. However, refractory data have been kept confidential.
SOI (Si-on-insulator) substrate is one of the key materials to promote Si LSI performance in the "post-scaling era". Right after SOI devices were emerged in the market, many advanced SOI structures such as ultra-thin SOI, patterned-SOI, FinFET, and strained-SOI have been proposed. In this paper, we demonstrate our recent study on the evaluation of ultra-thin SOI and the formation of high-quality patterned-SOIs by Light Ion Implantation technique. We also describe recent progress in FioFET and strained-SOI, and discuss about the expectation for SOI substrates to realize them.
High quality SIMOX wafers, one of silicon-on-insulator (SOI) materials, are produced with combined two technologies, low-dose oxygen implantation and the internal thermal oxidation (ITOX) annealing. Basic features of low-dose ITOX-SIMOX technology, such as excellent layer thickness uniformity and improvement of buried oxide (BOX) quality by ITOX process, will be reviewed. Further quality improvement has been achieved by incorporating nitrogen doped (N-doped) Czochralski (Cz) silicon as a starting substrate for low-dose ITOX SIMOX process. Surface pits due to crystal originated particles (COPs), which are void defects existing in as-grown CZ, can be eliminated with N-doped CZ silicon. The impact on gate oxide integrity (GOI), which is one of important indicators of surface quality, has been also investigated for ITOX process and types of stating substrate. It is demonstrated that ITOX-SIMOX wafers with starting substrate of N-doped CZ silicon exhibit superior GOI.
The effect of L-methionine additive on the crystal growth of L-alanine crystal was investigated by atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS) and time of flight-secondary ion mass spectrometry (TOF-SIMS). The crystal was grown in the presence of L-methionine (5 mol % with respect to L-alanine concentration) at a supercooling ΔT=2K. The growth rate of (120) face was almost suppressed and that of (011) face was only relatively inhibited. The surface topography of each face was also observed by AFM and they showed to be different. From the XPS depth profile results, sulfur atoms were detected only outer surface of the (120) face, but in the case of (011) face, sulfur atoms were detected not only outer surface but also in side of the crystalline lattice. In addition, from the TOF-SIMS results, L-methionine molecule and L-alanine molecule were dotted each other on the surface of (011) face, but in the case of (120) face, L-methionine molecule was present only on local part of surface, on which L-alanine molecule won't. It was considered that L-methionine molecule which exist in outermost surface of (120) face hinder the growth of that face of L-alanine and that which exist in the surface of (011) face don't prevent the growth. The difference of growth suppression effect on each face by L-methionine additive was confirmed by XPS analysis and TOF-SIMS analysis.
Aspects of perfect crystal growth in semiconductors are reviewed. This article contains our successful results on vapor phase epitaxy including photo epitaxy and epitaxy in UHV (molecular layer epitaxy). It is shown that the chemical reaction and kinematical aspects are important for the achievement of perfect crystal growth. Stoichiometry control issues in compound semiconductors are also shown in bulk crystal growth and LPE.