ABSTRACT
After CNT growth, the dicing of the wafer removes the connection between the chips, leaving each chip with its own micro-hotplate and CNTs. As a proof of concept, they showed simultaneous growth of identical CNTs at adjacent chips (shown in Fig. 10.5). The on-chip growth of multiwall and single wall CNTs are shown in Figs. 10.6 and 10.7, respectively.
Figure 10.7 SEM image of the SWCNTs on micro-hotplate grown by the local growth technique. 10.4.3 Flame Spray PyrolysisLiquid feed-Flame pyrolysis is a one-step process by which a metal precursor(s), dissolved usually in an organic solvent, is sprayed with an oxidizing gas into a flame zone where the droplets are combusted and the precursor(s) converted into nano-sized metal or metal-oxides particles, depending on the metal and the operating conditions. Flame spray pyrolysis (FSP) is a very promising technique for nano-sensor material fabrication since it enables primary particle and crystal size control, which is important to tailor sensitivity, as well as the controlled in situ deposition of noble metal clusters. Another important feature is that FSP can be utilized for in situ direct deposition of porous sensitive layers onto diverse substrates. A typical FSP set-up described in [15] is shown in Fig. 10.8. The substrate wafer is clamped between the shadow mask and the chilled support plate and mounted upside down above the deposition flame. During deposition, the wafer temperature was held at 120°C. Kühne et al. have already reported wafer level post-CMOS FSP deposition of SnO2/Pt gas sensitive layers on microsensors, as shown in Fig. 10.9 [15].
