Implantation mask

Many different materials can be used to spatially mask an implant on the semiconductor surface. Such masks include photoresist, dielectrics, and metals. In order to be an effective implant mask the material should be thick enough to prevent the implant from penetrating the mask and entering the sample. A minimum thickness for stopping 99.99% of the ions in the masking material is + 3.72Ai p (168). 

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. 

A. Splinter, O. Bartels, and W. Benecke. Thick porous silicon formation using implanted mask technology . Sensors and Actuators B76 (2001), 354-360. 

The Dielectric. Depending on the substrate, various dielectrics are used as diffusion and ion implantation masks, field and... 

Figure 8.2. Selective tungsten using silicon implantation, a) Mo is used as an implant mask, b) after removal of the Mo mask, c) after selective tungsten deposition.

Dielectric materials are used for isolating conducting layers, to facilitate the diffusion of dopants from doped oxides, as diffusion and ion implantation masks, capping doped films to prevent loss of dopant, for gettering impurities, for protection against mois-... 

Figure 16.6 shows the process sequence executed in p-well formation. The lithographic masking step (involving mask 2) is the same as that for the u-well implant mask. It defines the area of the inverter to be implanted to form the p-wells for the nMOS transistors. A boron implantation is performed, followed by resist stripping and cleaning. Annealing is done in basically the same manner as described above for the u-well. 

Prior to the final trench filling, a trench implantation (boron for P-type substrates) is performed. This is to ensure that the P-type substrate does not invert during subsequent processing and cause device-to-device leakages. The implant is directed vertically into the trench. Under these conditions the trench sidewall oxide acts as an efficient mask, while the implant in the bottom can reach into the substrate and form a P+ region. The remaining SiC film, which served as the RIE mask, also acts as an implant mask at the wafer surface. The implant energy and dose are adjusted for the thermal oxide thickness. 

Spannhake J, Schulz O, Helwig A, Krenkow A, Muller G, DoU T (2006) High-temperature MEMS heater platforms long-term performance of metal and semiconductor heater materials. Sensors 6 405 19 Splinter A, Bartels O, Benecke W (2001) Thick porous sflicon formation using implanted mask technology. Sens Actuators B 76 354-360... 

Organic polymers have attracted much interest in electrical and electronic applications because of their electrical insulating nature. Polyimides have gained much attention because of their excellent thermal stability and low dielectric constant. Polyimides have found applications in matrix resins for circuit boards, encapsulants, adhesives, passivation coatings, alpha particle barriers, ion implant masks and interlayer dielectrics."10... 

The first work that utilized a bipolar transistor was that of Prins (52). Using a natural p-type diamond bulk crystal as a substrate, carbon ions are ion implanted to form n-type-like regions with 3.2-pm-diameter wire as a implant mask. The energy level and mechanism of the carbon implantation cannot be estimated however, bipolar transistor behavior was achieved. The I-V characteristics are shown in Fig. 9. Although the current gain of ftp = Ic/h is only 0.11, the impact on researchers in this field was not insignificant. This was followed by several research activities, such as work on npn bipolar transistors with As implanted n-type-like regions and a point contact bipolar-like transistor (53). 

Tripathi, S.K., Scanlan, D., O Hara, N., Nadzeyka, A., Bauerdick, S., Peto, L., Cross, G.L.W., Hara, N.O., May 2012. Resolution, masking capability and throughput for direct-write, ion implant mask patterning of diamond surfaces using ion beam lithography. J. Micromech, Microeng. 22,055005. 

AIN RS, RIBS, ARE, CVD, Photo CVD, Plasma CVD Implantation mask, heat sink, surface acoustic wave devices High strength and corrosion resistant coatings... 

BN RS, ARE, CVD, Plama CVD Implantation mask. X-ray lithography mask Corrosion resistant 2q>pl >cations, wear resistant coating, high temperature applications... 

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