Thermal nitridation, rapid

Gate oxide dielectrics are a cmcial element in the down-scaling of n- and -channel metal-oxide semiconductor field-effect transistors (MOSEETs) in CMOS technology. Ultrathin dielectric films are required, and the 12.0-nm thick layers are expected to shrink to 6.0 nm by the year 2000 (2). Gate dielectrics have been made by growing thermal oxides, whereas development has turned to the use of oxide/nitride/oxide (ONO) sandwich stmctures, or to oxynitrides, SiO N. Oxynitrides are formed by growing thermal oxides in the presence of a nitrogen source such as ammonia or nitrous oxide, N2O. Oxidation and nitridation are also performed in rapid thermal processors (RTP), which reduce the temperature exposure of a substrate. 

Tantalum Nitride as Diffusion Barrier. Tantalum nitride (TaN) produced by MOCVD has excellent potential as a barrier material, comparable to TiN. The resistivity of TaN thin films can be lowered by rapid thermal annealing in nitrogen. 

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. 

A. Ermolieff, S. Deleonibus, S. Marthon, B. Blanchard, and J. Piaguet, Study of Si02/Si Interface States in Mos Devices by Surface Charge Spectroscopy. Application to Rapid Thermal Nitridation of Silicon, J. Electron Spectros. Relat. Phenom. 67, 409-416 (1994). 

In general, several possible chemical reactions can occur in a CVD process, some of which are thermal decomposition (or pyrolysis), reduction, hydrolysis, oxidation, carburization, nitridization and polymerization. All of these can be activated by numerous methods such as thermal, plasma assisted, laser, photoassisted, rapid thermal processing assisted, and focussed ion or electron beams. Correspondingly, the CVD processes are termed, thermal CVD, plasma assisted CVD, laser CVD and so on. Among these, thermal and plasma assisted CVD techniques are widely used, although polymer CVD by other techniques has been reported. ... 

M.-J. Jeng and J.-G. Hwu, Enhanced nitrogen incorporation and improved breakdown endurance in nitrided gate oxides prepared by anodic oxidation followed by rapid thermal nitridation in N2O, Appl. Phys. Lett. 69(25), 3875, 1996. 

Recently, Kelner and co-workers [2] obtained a specific ohmic contact resistance of 3.5 x 10 6Qcm2 with a carrier concentration of 4x 10l8cm 3 to 6H-SiC. The contacts were resistively evaporated nickel that was rapidly thermally annealed at 1000°C, for 30 s, in a forming gas atmosphere. Crofton et al [3] recently reported a contact resistance as low as 10 5Qcm2 to p-type SiC. Another problem to be solved is the fabrication of low resistivity Au or Al overlays for device interconnects. These overlays have to be separated from contacts by a diffusion barrier layer (for example, W, Cr, Ti, or conducting nitrides). 

Thermal nrocessing- Difiusion furnaces are used not only for the anneal of implanted dopants but for growing high quality thermcd oxides, depositing polysilicon nitride films (SiN,) and for rapid thermcd processing of deposited films. 

There is the possibility to make substrates in various materials Alumina is an obvious possibility, but monoliths formed from alumina are particularly susceptible to thermal shock problems, and they readily crack during rapid temperature excursions. Silicon carbide and boron nitride are other possible materials having good properties, but they are expensive. 

Figure 5 shows the effects of filler content on thermal shock resistance at c/R - 0.2 for composites of silicon nitride, silicon carbide, silica, and alumina. The thermal shock resistance of resin filled with silicon nitride increases linearly with the volume fraction. The value of the thermal shock resistance is high, especially at higher volume fraction (Vf > 40%), that is, thermal shock resistance reaches 140 K (Figure 5a). The thermal shock resistance of composite filled with silicon carbide increases rapidly with the increase of filler content, and it reaches 135 K at Vf of 40%, which is similar to the case of silicon nitride (Figure 5b). In the case of silica-filled composites there is also an increase, but above a 30% volume fraction a plateau is reached (Figure 5c). Alumina-filled composites show a decrease in thermal shock resistance with filler content, then an almost constant value starting at Vf = 20% (Figure 5d).

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