Abstract
Three important topics regarding the use of silicon crystals for applications in the electronics industry are reviewed in this paper. These are: (1) the perfection of silicon crystals required for ULSI device processing, (2) issues related specifically to large diameter crystal growth, and (3) the use of bonded wafers with SOI structures. There is no single silicon crystal specification that is ideal for all device processes. This is due to the facts that different processes have different thermal cycles and that contamination levels can vary from one facility to another. In Japan, lower oxygen concentrations are being chosen for specification of 200 mm silicon wafers compared to what is being used presently in 150mm specifications. This indicates that technology for cleaner device processing is considered more important than the use of internal gettering (IG) methods. It is believed that it is necessary to further reduce the concentrations of carbon and heavy metals in silicon crystals since they can serve as nucleation centers for harmful defects. In particular, control of point defects in large diameter crystals will be an important subject in the near future. After the 64M-bit DRAM generation of device processing, it is expected that an SOI structure may be used due to the high speed and high density requirements. A wafer-bonding process technology for such an SOI need is in-troduced. An understanding of the bonding mechanism is also described.
