tailieunhanh - The Materials Science of Thin Films 2011 Part 5

Tham khảo tài liệu 'the materials science of thin films 2011 part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 178 Chemical Vapor Deposition SUSCEPTOR WAFERS .7- -TO VENT B2H6 mixtures generate BPSG. As noted in Section LPCVD processes have largely surpassed atmospheric CVD methods for depositing such films. - GAS FLOW RF HEATING o RADIANT HEATING Figure 4-13. Schematic diagrams of reactors employed in epitaxial Si deposition top horizontal lower left pancake lower right barrel. Reprinted with permission from John Wiley and Sons from s. M. Sze Semiconductor Devices Physics and Technology Copyright 1985 John Wiley and Sons . . High-Temperature Systems There is need to reduce semiconductor processing temperatures but the growth of high-quality epitaxial thin films can only be achieved by high-temperature CVD methods. This is true of Si as well as compound semiconductors. High-temperature atmospheric systems are also extensively employed in metallurgical coating operations. The reactors can be broadly divided into hot-wall and cold-wall types. Hot-wall reactors are usually tubular in form and heating is accomplished by surrounding the reactor with resistance elements. An example of such a reactor for the growth of single-crystal compound semiconductor films by the hydride process was given in Fig. 4-3. Higher temperatures are maintained in the source and reaction zones 800-850 C relative to the deposition zone 700 C . Prior to deposition the substrate is sometimes . CVD Processes and Systems 179 etched by raising its temperatures to 900 C. Provision for multiple temperature zones is essential for efficient transport of matrix as well as dopant atoms. By programming flow rates and temperatures the composition doping level and layer thickness can be controlled making it possible to grow complex multilayer structures for device applications. Cold-wall reactors are utilized extensively for the deposition of epitaxial Si films. Substrates are placed in good thermal contact with SiC-coated graphite susceptors which can be inductively heated while the .