Bipolar technology

Autodopiag occurs whea dopants are unintentionally released from a substrate through diffusion and evaporation, and subsequently reiacorporated during the deposition layer. Epitaxial layers are typically doped at concentrations of lO " -10 atoms/cm. The higher levels of doping are used in bipolar technology where the epilayer forms the transistor base. The epitaxial layer can be up to several hundred micrometers, and as thin as 0.05—0.5 p.m. Uniformities of 5% are common. 

Multilevel structures consisting of alternating metal and dielectric layers are necessary to achieve Interconnection in high density or VLSI circuits using either MOS or bipolar technology. 

Bipolar Transistors. In bipolar devices, both electrons and holes participate in the conduction process, in contrast to MOSFETs, in which only one carrier type dominates. Bipolar technology has been used typically for high-speed-logic applications. 

Motorola Bipolar Technology Center, Mesa, AZ 85202 Semiconductor Research and Development Laboratory, Motorola SPS, Phoenix, AZ 85008... 

One of the yield limitations in an advanced bipolar technology is the collector-emitter leakage due to "pipes" which are associated with material defects (17), and generally the pipe density will increase with shallower junctions required for VLSI technologies. 

Advanced bipolar technologies include the seahng of blood vessels, fusion of tissue, tissue ablation, and bipolar cutting. Vessel sealing and tissue fusion uses special instruments and control algorithms to fuse the collagen within tissue. The most common use of this technology is to permanently seal blood vessels. 

Modem bipolar technologies were developed in the 1980s [12, 13]. Figure 2 shows a bipolar magnesium cell from a patent [12] where the electrodes are made from graphite which are coated by steel on the cathode side. Bipolar cells have shorter interelectrode distances, but the current efficiency is much lower due to bypass current, so the energy consumption is a little higher than that of the monopolar cells. 

FIGURE 31.24 SEM-micro aph of a Ni/Zn (Courtesy of Bipolar Technologies Corp.)... 

New Materials Technology. The unique chemical compatibihty of Si02 with sihcon and aluminum has been a significant factor in the dominance of siUcon-based semiconductor technology for MOSFETs in particular and integrated circuits in general. Two enhancements of conventional bipolar or MOS processes have been studied siUcon on insulator (SOI) and SiGe. An alternative material of importance is SiC. 

Fig. 1. Technological trends A, components per chip B, minimum feature length , metal oxide semiconductor (MOS) memory A, bipolar memory I MOS logic n, bipolar logic. The designations SSI, MSI, LSI, and VLSI stand for small-, medium-, large-, and very large-scale iategration, respectively.

A significant step for the commercialization of bipolar electrochemical promotion units has been made recently by Christensen, Larsen and coworkers at Dinex Filter Technology A/S in Denmark.18 20 The goal is the development of an efficient catalyst system for the aftertreatment of Diesel exhausts. This is one of the most challenging problems of current catalytic research. 

Bipolar plates for connecting fuel cells in a series. (Reproduced with permission from Wiley Kirk-Othmer Encyclopedia of Chemical Technology, Vol. 12, Wiley, New York, 2002.)... 

The process operates at current densities of about 1 kA/m2 and unit cell voltage of 1.5 V. The specific energy consumption is about 2 kWh/kg NaOH. Under the influence of the electric gradient the H + and OH ions emerge on opposite faces of the membrane. Bipolar membrane electrodialysis is being developed by several companies, e.g. WSI Technologies Inc. [270] and Aquatech Systems [129,275,276], Typical product specification ranges for the ICI electrodialysis process is summarized in Table 19. 

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