Silicon oxide deposition procedure

A cross-sectional schematic of a monolithic gas sensor system featuring a microhotplate is shown in Fig. 2.2. Its fabrication relies on an industrial CMOS-process with subsequent micromachining steps. Diverse thin-film layers, which can be used for electrical insulation and passivation, are available in the CMOS-process. They are denoted dielectric layers and include several silicon-oxide layers such as the thermal field oxide, the contact oxide and the intermetal oxide as well as a silicon-nitride layer that serves as passivation. All these materials exhibit a characteristically low thermal conductivity, so that a membrane, which consists of only the dielectric layers, provides excellent thermal insulation between the bulk-silicon chip and a heated area. The heated area features a resistive heater, a temperature sensor, and the electrodes that contact the deposited sensitive metal oxide. An additional temperature sensor is integrated close to the circuitry on the bulk chip to monitor the overall chip temperature. The membrane is released by etching away the silicon underneath the dielectric layers. Depending on the micromachining procedure, it is possible to leave a silicon island underneath the heated area. Such an island can serve as a heat spreader and also mechanically stabihzes the membrane. The fabrication process will be explained in more detail in Chap 4. 

Microfabrication processes have been used successfully to form micro-fuel cells on silicon wafers. Aspects of the design, materials, and forming of a micro-fabricated methanol fuel cell have been presented. The processes yielded reproducible, controlled structures that performed well for liquid feed, direct methanol/Oj saturated solution (1.4 mW cm ) and direct methanol/H O systems (8 mA cm" ). In addition to optimizing micro-fuel cell operating performance, there are many system-level issues to be considered when developing a complete micro power system. These issues include electro-deposition procedure, catalyst loading, channel depth, oxidants supply, and system integration. The micro-fabrication processes that have... 

The SRPES results show that silicon oxide is formed during Pt deposition due to the scanning conditioning procedure (peak C2). The oxide thickness on H-terminated... 

Figure 11.6 Fabrication procedure of an IDA microelectrode. An oxidized silicon wafer (A) is coated with platinum (B). Carbon film is pyrolyzed on it (C). The substrate is coated with photoresist, which is exposed and developed (D) unnecessary portions are then removed by reactive ion etching (E). After removing the photoresist, an Si3N4 layer is deposited on the substrate (G). The substrate is coated with photoresist, which is exposed and developed (H) then the desired shape of the carbon electrode is exposed by reactive-ion etching (I). [Adapted from Ref. 36.]...

Another solution to reduce the loading effect was investigated by van Laarhoven et. al.61, (see figure 2.19). In their approach there was a 0.3 urn PECVD silicon nitride layer deposited atop the oxide prior to the contact opening. The normal procedure of adhesion layer (TiW), tungsten deposition and etch back was followed. Since the nitride etches with about the same rate as the tungsten (selectivity W SiN=0.8) both the loading is... 

This substitution procedure has been successful not just with a wide variety of neutral and charged carboxylic acids (to produce model systems for the deposition of polycationic [Mnn] units on oxide surfaces [54] or as precursors for the organisation of SMMs on silicon [55], or gold surfaces [56], for example), but also with other Ugands that can bond in a similar manner. Thus, nitrate (e.g. [Mni20i2(02CPh)i2(N03)4(H20)4], 4) [57],... 

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