Metal oxide-silicon capacitors

Sodium contamination and drift effects have traditionally been measured using static bias-temperature stress on metal-oxide-silicon (MOS) capacitors (7). This technique depends upon the perfection of the oxidized silicon interface to permit its use as a sensitive detector of charges induced in the silicon surface as a result of the density and distribution of mobile ions in the oxide above it. To measure the sodium ion barrier properties of another insulator by an analogous procedure, oxidized silicon samples would be coated with the film in question, a measured amount of sodium contamination would be placed on the surface, and a top electrode would be affixed to attempt to drift the sodium through the film with an applied dc bias voltage. Resulting inward motion of the sodium would be sensed by shifts in the MOS capacitance-voltage characteristic. 

Tan, J., et ah, Metal-Oxide-Semiconductor Capacitors Formed by Oxidation of Polycrystalline Silicon on SiC, Appl. Phys. Lett., Vol. 70, 1997, p. 2280. 

Thermal oxidation of the two most common forms of single-crystal silicon carbide with potential for semiconductor electronics applications is discussed 3C-SiC formed by heteroepitaxial growth by chemical vapour deposition on silicon, and 6H-SiC wafers grown in bulk by vacuum sublimation or the Lely method. SiC is also an important ceramic ana abrasive that exists in many different forms. Its oxidation has been studied under a wide variety of conditions. Thermal oxidation of SiC for semiconductor electronic applications is discussed in the following section. Insulating layers on SiC, other than thermal oxide, are discussed in Section C, and the electrical properties of the thermal oxide and metal-oxide-semiconductor capacitors formed on SiC are discussed in Section D. 

Liu, A., R. Jones, L. Liao, D. Smara-Rubio, D. Rubin, O. Cohen, R. Nicolaescu, and M. Paniccia. 2004. A high-speed silicon optical modulator based on a metal-oxide-semiconductor capacitor. Nature 427 615-618. 

An insnlating layer of Si02 is grown onto a crystalline silicon substrate, and thin conducting electrodes are placed on top of the silica layer to create metal-oxide-semiconductor (MOS) capacitors. The crystalline silicon has Si-Si bonds arranged in a 3D lattice. A bond can be broken by... 

The plates of the capacitors of integrated circuits (Fig. 2.50(b)) in most modem technologies (AUstot and Black, 1983) are formed by two heavily doped polysfiicon layers. The dielectric is usually a thin layer of silicon oxide. The whole capacitor is formed on a layer ofthick (field) oxide. The capacitors are temperature stable, their temperature coefficient is about 20 ppm/°C. A detailed comparative evaluation of the different metal oxide semiconductor (MOS) capacitor structures can be found in AUstot and Black (1983). 

MOSFETT s, and silicon oxide is deposited. The source/drain positions where electrical contact is to be made to the MOSFETs are defined, using the oxide-removal mask and an etch process. For shallow trench isolation, anisotropic silicon etch, thermal oxidation, oxide fill and chemical mechanical leveling are the processes employed. For shallow source/drains formation, ion implantation techniques are still be used. For raised source/drains (as shown in the above diagram) cobalt silicide is being used instead of Ti/TLN silicides. Cobalt metal is deposited and reacted by a rapid thermal treatment to form the silicide. Capacitors were made in 1997 from various oxides and nitrides. The use of tantalmn pentoxide in 1999 has proven superior. Platinum is used as the plate material. 

The SiC Schottky diodes and capacitors that have been processed by the authors were processed on either 6H or 4H substrates (n-type, about 1 x 10 cm ) with a 5-10- m n-type epilayer (2-6 x lO cm" ) [123, 124]. A thermal oxide was grown and holes were etched for the metal contacts. In the case of the Schottky sensors, the SiC surface was exposed to ozone for 10 minutes before deposition of the contact metal. This ozone treatment produces a native silicon dioxide of 10 1 A, as measured by ellipsometry [74, 75]. The MISiC-FET sensors (Figure 2.9) were processed on 4H-SiC, as previously described [125]. The catalytic metal contacts consisted of 10-nm TaSiyiOO-nm Pt, porous Pt, or porous Ir deposited by sputtering or by e-gun. 

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