Silicon on sapphire

Epitaxial Layers. Epitaxial deposition produces a single crystal layer on a substrate for device fabrication or a layer for multilevel conductive interconnects which may be of much higher quality than the substrate. The epitaxial layer may have a different dopant concentration as a result of introducing the dopant during the epitaxial growth process or may have a different composition than the substrate as in silicon on sapphire. Methods used for epitaxial growth include chemical vapor deposition (CVD), vapor phase epitaxy (VPE), liquid phase epitaxy (LPE), molecular beam epitaxy (MBE) and solid phase epitaxy (SPE). 

The lattice mismatch between silicon and mercury cadmium telluride makes it difficult to grow an epitaxial crystalline layer of mercury cadmium telluride on silicon. In EP-A-0343738 an imager is formed by growing mercury cadmium telluride on a sapphire substrate at openings formed in a silicon layer which has been grown on the sapphire substrate (silicon-on-sapphire, SOS) at an earlier stage. 

The electrical resistivity is as high as 1016 Q cm [17]. This is good for electrical isolation as it has been used for SOS (silicon on sapphire), but inhibits vertical current flow through sapphire. 

Two major improvements in the fabrication of an ion-sensitive FET that avoid most of the tedious polymer encapsulauon process have been reported. Matsuo and his coworkers (4, 37) fabricated a probe-type FET with a three-dimensional silicon nitride passivation layer around most of its surface, as shown in Fig. 2. The probe-type FET has one disadvantage Its fabrication requires a three-dimensional process that is uncommon for semiconductor construction facilities. An alternative approach utilizes a silicon-on-sapphire (SOS) wafer for FET fabrication (38, 39). The structure of a SOS-FET is depicted in Fig. 3. It has an island-like silicon layer on a sapphire substrate, in which an ion-sensitive FET is fabricated. The bare lateral sides do not need encapsulation because of the high insulation property of sapphire. 

The (0001) surface of sapphire (a-alumina, corundum) is one of the most widely used substrate for the growth of metal, semi-conductor or high-temperature superconductor thin films. It is also used as a substrate in silicon on sapphire (SOS) technology. Moreover, its initial state is known to play a role on the overlayer properties [50]. 

Miyahara et al. (1985) developed an integrated enzyme FET based on a silicon-on-sapphire (SOS) sensor for simultaneous determination of glucose and urea. Three ISFETs and two metal insulator semiconductor FETs (MISFETs) were integrated on a surface area of 2.5 mm x 2.5 mm (Fig. 54). One of the ISFETs served as reference sensor in order to compensate the signals caused by pH changes of the solution the two others were covered by GOD and urease, respectively. The MISFETs can be used as pH electrodes. For enzyme immobilization the chip was covered with a laminated photosensitive layer of 75 pm thickness and,... 

Molecular beam epitaxy. Epitaxial techniques are techniques of arranging atoms in single-crystal fashion on crystalline substrates so that the lattice of the newly grown film duplicates that of the substrate. If the film is of the same material as the substrate, the process is called homoepitaxy, epitaxy, or simply epi. The most important applications here are Si epi on Si substrates and GaAs epi on GaAs substrates. If the deposit is made on a substrate that is chemically different, the process is termed heteroepitaxy. An important application is the deposition of silicon on an insulator (SOI) e.g. with sapphire (AI2O3) as the insulator in the silicon on sapphire (SOS) process. 

R Laiwalla, K. Klemic, F.J. Sigworth, and E. Culurciello, "An integrated patch-clamp amplifier in silicon-on-sapphire CMOS," IEEE Trans. Circ. Syst. I Regular Papers, vol. 53, no. 11, pp. 2364-2370, Nov. 2006. 

Manasevit A process for making electronic devices by depositing thin films of elements or simple compounds, such as gallium arsenide, on flat substrates by CVD from volatile compounds such as trimethyl gallium and arsine. Harold Manasevit died in 2008. He was the first to demonstrate the epitaxial growth of silicon on sapphire, which is important in the production of microelectronic devices. 

Epitaxy, heteroepitaxy Oriented overgrowth on a substrate of a different material or the same material with a different crystalline structure. Example Silicon on sapphire. 

Heterogeneous nucleation (film formation) The nucleation of one material on a different material. Example Silicon on sapphire. See also Homogeneous nucleation. 

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