Insulating layers silicon dioxide

The uses of CVD silicon dioxide films are numerous and include insulation between conductive layers, diffusion masks, and ion-implantation masks for the diffusion of doped oxides, passivation against abrasion, scratches, and the penetration of impurities and moisture. Indeed, Si02 has been called the pivotal material of IC s.1 1 Several CVD reactions are presently used in the production of Si02 films, each having somewhat different characteristics. These reactions are described in Ch. 11. 

Figure 4.2 Schematic diagram of a charge-coupled device (CCD) imaging sensor. It consists of a semiconducting substrate (silicon), topped by a conducting material (doped polysilicon), separated by an insulating layer of silicon dioxide. By applying charge to the polysilicon electrodes, a localized potential well is formed, which traps the charge created by the incident light as it enters the silicon substrate.

One such device consists of two small islands of / -type semiconductor with and n-type silicon substrate. The islands are joined by a narrow / -type channel. The oxide portion of the MOSFET is an insulating layer of silicon dioxide that is formed by surface oxidation of the silicon. Gate, drain, and source connectors are attached. The MOSFET differs from the junction transistor in that a single type of charge carrier, either an electron or a hole, is utilized, instead of both. The conductivity of the channel... 

Silicon possesses an excellent oxide. Silicon dioxide (Si02) is a remarkably stable passivating layer, acts as a good electrical insulator, and forms an excellent interface... 

A simplified example will illustrate the process of microstructure fabrication. With reference to Fig. 1, an //-type region has been created by diffusion of a donor impurity into a surface of p-type silicon, forming a p — n junction diode. There is a metal contact to the /(-region, and the contact line is insulated from the p-type surface by a layer of silicon dioxide. The diameter of the diode is on the order of 10 micrometers. 

This condition is naturally also satisfied in the Kelvin probe measurement, where the selective layer is interfaced to the air-gap which is an insulator. However, now we see a subtle but important difference between the Kelvin probe and a MIS-type measurement in the Kelvin probe, it is the bulk and the surface of the selective layer that contributes the WF modulation and the Ceii In the MIS capacitor (such as in the IGFET), it is the bulk and interface between the solid insulator (e.g., silicon dioxide) and the selective layer that contributes to the overall signal. 

A silicon dioxide layer 3 is formed on an insulating CdTe substrate 1. A photo-resist coating 5 is formed over the silicon dioxide layer. The photo-resist layer is patterned and the silicon layer is partly etched away. The photo-resist layer is removed and a film of HgCdTe 9 of a first mercury to cadmium ratio is deposited by liquid phase epitaxial deposition over the entire surface of the substrate. The HgCdTe film is only formed at regions where the CdTe substrate is exposed and does not adhere to the silicon dioxide. Next, the silicon dioxide layer is removed. In order to increase the window of frequency response of the detectors, the process is repeated using a second mercury to cadmium ratio different from the first ratio. 

Anodic sulphide films 13 are provided at surface regions where junctions are made between a p-type HgCdTe substrate and an n-type region 2. An insulating layer of silicon dioxide is formed and the p-type substrate and the n-type region are contacted by electrodes 5 and 6. 

SIMOX [Separation by IMplanted OXygen] In the manufacture of semiconductor devices, a thin layer of insulating silicon dioxide is formed beneath the surface of a monocrystalline silicon substrate to form a buried dielectric layer. The layer is formed by implanting oxygen ions at 500 to 600°C and then annealing at > 1000°C. 

In this section, we focus on the problem of self-heating in silicon-on-insulator transistors. Fig. 8 shows a two-dimensional domain representing the silicon-on-insulator transistor, similar to that described in [43]. A thin silicon layer resides on top of a thicker insulating silicon dioxide (Si02) layer. The left, right, and bottom boundaries of the domain are maintained at 300K and serve as heat sinks, while the top silicon boundary is diffusely reflecting (adiabatic), as shown in Fig. 8. 

There are other insulating materials that can be used instead of silicon dioxide. Silicon nitride, alumina, and aluminum nitride are a few that are often used. The selection of a proper insulation layer is based on the specific needs and the properties of selected materials. 

---