Lubomir L. Jastrzebski

SOI by CVD: Epitaxial Lateral Overgrowth (ELO) process—Review

Abstract The ELO process (Epitaxial Lateral Overgrowth), based on the growth of silicon film over an SiO2 mask by the CVD technique, has been reviewed. The silicon film is locally seeded in openings of the SiO2 mask from which it overgrows the oxide. The key to success is selective deposition; growth conditions which give growth of silicon over exposed silicon surfaces and at the same time prevent nucleation of silicon over oxide. These conditions, together with growth and surface morphology of obtained ELO films, are discussed as a function of gas composition, growth temperature, growth procedure and type of reactor. Defect structure and electric properties of ELO films are also reviewed together with performance of devices made in these films. Data obtained so far showed that monocrystalline silicon films with smooth mirror-like surfaces and low defect density can be grown over 20 μm wide SiO2 islands by the optimized ELO process. The performance of devices made in these ELO films was similar to devices made in homoepitaxial layers. On the basis of these data it is believed that the ELO technique is a promising approach for the fabrication of SOI films.

Silicon on insulators: Different approaches - A review

Abstract Different methods used to obtain silicon-over-insulator (SOI) films are compared, based on the information available in the literature. All techniques are briefly outlined and their assets and liabilities are compared with special emphasis on application in different present and future processing technologies. The CVD approach is discussed more than the others since it has been a focal point of work on SOI by the author. It seems that at the present stage of development the “leader” cannot be clearly identified, and different technologies could favor different SOI appoaches.

Device characterization on monocrystalline silicon grown over SiO 2 by the ELO (epitaxial lateral overgrowth) process

MOS and lateral bipolar transistors have been fabricated on epitaxial silicon layers which have been laterally overgrown over SiO2. These device characteristics were than compared to those measured on devices fabricated on homoepitaxial silicon and bulk silicon. The measurements indicate essentially identical MOS device characteristics for all three materials with a typical hole field effect mobility of about 180 cm2/vs. Lifetime measurements using pulsed C-V techniques showed essentially the same values for ELO material and homoepitaxial material with the ELO value being about 20 µS for 1015cm-3doping level. These lifetime values correlate will with diode and bipolar transistor measurements.

The characterization of CVD single-crystal silicon on insulators: Heteroepitaxy and epitaxial lateral overgrowth

Abstract In the development of the heteroepitaxial silicon technology, progress had been impeled because of the labor and time involved in the evaluation of the crystalline quality of the deposits by transmission electron microscopy and device performance. Therefore an important part of our program has been directed toward the development of rapid and non-destructive methods for the characterization of the silicon crystallinity. It is essential that the results of such methods relate to device performance. In this paper, we update earlier reports on this effort. Emphasis has been placed on the use of UV reflectometry for probing the near-surface silicon quality, photovoltage spectroscopy for probing the “bulk” of the film, interference photovoltage spectroscopy for probing the near-substrate portion of the silicon, and infrared multiple reflectometry to assess the crystalline quality of the substrate surface. The silicon-on-insulator effort has recently been extended on the growth of dielectrically isolated silicon by CVD epitaxial lateral overgrowth. The evaluation of these deposits by transmission electron microscopy is described.

Relationship between crystallinity and electronic properties of silicon-on-sapphire

Abstract A comparative study of electronic properties (determined by photovoltage spectroscopy) and of the crystalline perfection (determined by UV reflection technique) was carried out on a series of silicon-on-sapphire wafers of different crystallinity. It was found that the improvement of crystallinity led to a significant reduction of the concentration of deep levels in the middle of the energy gap. Differences in the as-deposited crystalline quality can be related to differences in the electronic properties even after the deposits were ion implanted, oxidized and annealed. Recently discovered slight amorphization of silicon-on-sapphire was quantitatively analyzed in terms of the amorphization factor, η. It was found that η decreases with improvement of crystallinity and its value for SOS films was one to two orders of magnitude smaller than in a typical a-Si.