| With its unique structure, silicon-on-insulator (SOI) has benn found great potential in integrated circuits, where lower power consumption and high speed are required, as well as in radiation hardened circuits and high temprature devices. Separation-by-implanted-of-oxygen (SIMOX), in which a buried oxide (BOX) layer is formed in the Si substrate, is one of the most promising techniques for making SOI structures. Traditionally, SIMOX materials are fabricated by implanting high-dose high-energy oxygen ions. However, high-dose SIMOX wafers have the problems of a high threading dislocation density in the top silicon layer as well as a high production cost due to a long implantation time, which is the fatal obstacle for the commercial applications of SOI in the microelectronics industry. In recent years, there has been growing interest in low-dose SIMOX (dose <1.0 1018 ions/cm2) with a BOX layer thickness of 50-200 nm because of its potential technological and economic advantages (increase capacity up to 50-300%) over high-dose SIMOX. The other advantages include the drastically reduced threading dislocation density, thermal conductivity and improved device performance. However, for the best performance and reliability of circuits fabricated on such wafers, they should have a high-quality BOX with flat, sharp interfaces and the lowest density of pinhole and Si islands. Thus, the nature of the BOX microstructure is of significant concern in the technological development of low-dose SIMOX iraterials. Many efforts have been made over the past years for the fabrication of high-quality, low-dose SIMOXmaterials.In this paper, we reported formation of SIMOX-SOI materials with doses ranging from 1.8 to 5.5xl017/cm2 at acceleration energies of 45-160 keV, and subsequent annealing at temperature over 1310C in O2+Ar atmosphere for 5 hours.The materials were determined by XTEM, SIMS, AFM, and SE. These results showed high quality ultra-thin SOI materials, featured with integrity BOX, sharpinterface, and high thickness uniformity, have been fabricated. Especially, the sample implanted with 1.8 1017/cm2 at 45 keV had only 70 nm of the top silicon layer and 40 run of BOX layer, respectively.The further study on the process parameters, especially, implantation energy and dose, revealed that at each dose, there is an optimum energy range for the formation of the high quality SIMOX materials or vice versa. Moreover, the higher the implanted oxygen dose, the higher energy required for the formation of a BOX layer free from Si islands. An effort was made at understanding the growth mechanism of high-quality SIMOX materials fabricated at different optimum dose-energy match. The combination of dose-energy is attributed to the relationship of implanted oxygen concentration profile with implanted damage profile and its effect on the evolution of microstructure of SIMOX materials.In order to improve the quality of the BOX layer, we investigated the defectedinduced process. The results shows defect induced BOX (DIBOX) SIMOX samplewere featured with obvious expand BOX layer, the increase of thickness reaching tothe level of about 30%, after high temperature annealing with high oxygenconcentration in the atmosphere. In additional, the SIMOX sample withat 100 keV was carried with defected induced implantation at 45 keVwith . It was surprised to find an ultra-thin BOX layer had been formed atRp of 45 keV. The thickness of the continuous BOX layer with sharp interface isabout 10 nm. It is commonly known that dose at acceleration energy of45 keV cannot form continuous BOX layer. Thus, this phenomenon proved thedefect induced implantation and high oxygen concentration in the ambient could leadto the extend of the BOX layer.Effect of high temperature annealing on microstructure of low-dose SIMOX-SOI had been discussed. It is found that in single implanted samples, the thicker BOX layer and better quality SOI materials can be obtained by increasing oxygen concentration in the annealing atmosphere. I...
|
PDF Full Text Request