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Thermal processing, oxide layers

Sihcon dioxide layers can be formed using any of several techniques, including thermal oxidation of siUcon, wet anodization, CVD, or plasma oxidation. Thermal oxidation is the dominant procedure used in IC fabrication. The oxidation process selected depends on the thickness and properties of the desired oxide layer. Thin oxides are formed in dry oxygen, whereas thick (>0.5 jim) oxide layers are formed in a water vapor atmosphere (13). [Pg.347]

In the oxidation process, a layer of dopant is apphed to the surface of sihcon and patterned sihcon dioxide for subsequent thermal diffusion into the sihcon. The masking property of the Si02 is based on differences in rates of diffusion. Diffusion of dopant into the oxide is much slower than the diffusion into the sihcon. Thus, the dopants reach only the sihcon substrate. Oxide masks are usually 0.5—0.7 p.m thick. [Pg.347]

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. [Pg.11]

Xie et al. [20] reported the fabrication chip for pumps and an electrospray nozzle. The process used to fabricate the electrochemical pump chips with electrospray nozzle is shown in Fig. 2.11. A 1.5 xm layer of Si02 was grown on the surface of a 4 inch silicon wafer by thermal oxidation. The front side oxide layer was patterned and removed with buffered FIF. XeF2 gaseous etching was used to roughen the silicon surface in order to promote the adhesion between subsequent layers and the substrate. The first 4.5 p,m parylene layer was deposited. [Pg.33]

In principle, the STM can work in air and liquid environments. However, most STM work has been done in ultra-high vacuum. This is because most sample surfaces in an air environment quickly develop an oxide layer. An ultra-high vacuum environment can prevent possible surface oxide formation and maintain a conductive sample surface. Also, low temperature is preferred because it reduces thermal drift and diffusion of atoms and helps to obtain a static surface image of atoms. However, an elevated temperature provides an environment for observing dynamic processes of atoms and molecules. [Pg.149]

In the first cycle the shape of the heating period (oxide formation) is different from the cooling period (thermal mismatch between layer and support). After the first cycle, the shape of the subsequent peaks are identical and all processes seem to be reversible. [Pg.291]

Literature presents numerous data on the syntheses by ML method of oxide layers of titanium, aluminum, chromium, phosphorus, tantalum and series of other elements on silica and alumina surfaces, when appropriate chloride and vapour of water are used as initial reagents [13,35,18,42]. The synthesis thus proceeds without the change of oxidation state of elements. But the stability of Si-O-M bonds in the process of gaseous treatment of element-chloride surface structures is of significant importance. Our researches have shown [44,68], that the strength of Si-O-M bonds is influenced by the thermal stability of element-oxide chloride groups, quantity of their bonds with surfaces (factor m) and series other ones. The reason for the destruction is the hydrogen chloride which educes in the process of vapour hydrolysis [68]. [Pg.226]

The sacrificial oxide layer is initially formed on top of the silicon substrate by thermal or plasma processing (Fig. 5.3.1a). If insulation of the functional layer from the silicon substrate is required, the sacrificial layer may be preceded by deposition of an insulating film, for example, silicon nitride. The thickness of the sacrificial oxide layer determines the height of the released cantilever above the silicon substrate. It is typically a few micrometers thick, depending on the specific requirements and application. [Pg.104]


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Oxidants layer

Oxide layer

Oxides layered

Processing layer

Thermal oxidation

Thermal oxidation process

Thermal oxides

Thermal processes

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