Research Of Patterned SOI Technology

In recent years, silicon-on-insulator (SOI) technology has started to be used as the mainstream technology in complementary metal-oxide-semiconductor (CMOS) ultra large-scale integrated circuit (ULSI) to maintain the performance gain according to the Moore's law. On the other hand, in order to manufacture more powerful and cheaper chips, it is desirable to integrate multiple functions, such as logic circuits and memories, which are previously implemented as multiple discrete chips, into a single chip to realize system-on-a-chip (SOC). However, there are some challenges in integration of RF circuits, imagers, DRAMs on a single SOI substrate due to their immature fabrication process. In addition, the presence of the buried oxide (BOX) layer in SOI substrate isolates the device electrically and thermally from the substrate, thereby resulting in severe floating-body and self-heating effects, which degrade the device performance and reliability.Patterned SOI technology is an attractive approach to solve the problems. In fact, the simplest and most economical method to suppress floating-body effect and self-heating effect in SOI devices is to create a silicon window in the BOX layer under the channel, thus forming DSOI (Drain and Source On Insulator) structure. Moreover, employing patterned SOI substrate comprising both SOI and bulk regions, we can integrate RF circuits, imagers and DRAMs, which are fabricated over bulk regions, together with high-performance logic circuits that built over SOI regions. Therefore, the use of patterned SOI substrates for implementing SOC will help reduce the constraint and widen the degree of freedom in design and fabrication.Separation by implantation of oxygen (SIMOX) technique is the first choice to fabricate patterned SOI materials because of its simplicity, maturity and compatibilityAbstractwith silicon process. However, it is very difficult to obtain high-quality patterned SOI materials due to the formation of local buried oxide (BOX) layers. Therefore, up to now, very few reports are available for high-quality patterned materials by SIMOX technology. Moreover, there is no report about the successful fabrication of the DSOI device.In the present work, patterned SOI technology including patterned SOI materials and patterned SOI (i.e. DSOI) devices was investigated systematically.Firstly, SIMOX technique was used to fabricate patterned SOI materials. In the experiment, we have studied the effect of process parameters, such as implant dose and energy on the quality of patterned SOI materials. The implant dose and energy range are 0.15-1.5><1018 cm"2 and 25-160 keV, respectively. For the high-dose case, the fabricated patterned SOI materials are inferior because of considerable amount of defect and very large step height between the bulk silicon and SOI regions, numerous silicon islands embedded in the whole BOX layer. We develop an optimized low-dose and low-energy SIMOX process to manufacture patterned SOI materials with improved quality. The patterned SOI materials prepared with this new SIMOX process exhibit high quality, which is indicated by the low defect transition of SOI and bulk silicon region, a high degree of surface planarity and a high-integrity BOX layer without detectable silicon islands. Furthermore, in order to realize DSOI device, the fabrication process of patterned BOX layers with different spacings was also investigated. The results indicated that excellent quality patterned BOX layers with deep submicron spacing could be were obtained by this new low-dose SIMOX technique. This paved the way for the realization of the novel DSOI device.Based on the above useful results, DSOI device was studied by device simulation and experimental analysis. The electrical and thermal characteristics of DSOI devices were analyzed using 2-D device simulation. The simulation results proved the advantages of the DSOI device. Then DSOI device was fabricated by combination of patterned SIMOX and conventional CMOS technologies. At theAbstractsame time, bulk and SOI de...