TABLE OF CONTENTS The discussion so far has concerned planar whole wafer SOI structures comprising a single continuous BOX, as shown in FIGURE 3.1. These substrates are most frequently used for advanced CMOS device applications; however, new uses are currently being investigated thanks to possibilities opened through a better understanding of the SIMOX process, improved processing equipment and the improving quality and lower unit cost of SOI wafers. For completeness novel SIMOX structures currently being researched will be briefly discussed below, although some structures and mechanisms are reviewed in greater detail in other chapters of this volume.
Separation by plasma implanted oxygen (SPIMOX) is the name given to SIMOX structures formed by plasma immersion ion implantation (PIII), in which the wafer is immersed in an oxygen plasma [86], as described in Section 3.5. A major advantage of PIII over conventional ion implantation is that it offers high dose rate implantation, hence shorter implantation times and lower processing costs, and is compatible with large area processing [72]. FIGURE 3.28 shows XTEM micrographs from an annealed SPIMOX structure formed by implantation of 2 10 17 O + cm ?2 at a bias voltage of 60 kV and annealed at 800 C for 1 hr followed by 1320 C for 2.5 hr. The BOX layer shows some non-uniformity although the Si/BOX interfaces are abrupt, as shown in the high resolution image [72].
