Design and Fabrication of Microheaters for Localized Carbon Nanotube Growth
This paper presents the design, fabrication and thermal imaging of three microheaters (Fig. 1) and the growth and characterization of single-walled carbon nanotubes (SWNTs) (Fig. 5) on these microstructures. SWNTs have many superior properties suitable for beyond-CMOS technology scaling and high-sensitivity chemical and biological sensors. For material synthesis, chemical vapor deposition (CVD) is a widely used method that produces high-quality SWNTs [1][2][3]. However, the high CVD growth temperature (typically 800-1000C) prevents their integration onto a mainstream CMOS platform. Although some low-temperature growth methods have recently been reported [4][5][6], compatibility with foundry CMOS processes still remains a challenge. Here we propose a post-CMOS compatible carbon nanotube growth method that bridges the gap between CVD and CMOS, in which microfabrication technology is used to create microheaters that can locally heat up for SWNT synthesis, leaving other areas remaining at low temperature.
The localized heating is realized by using dry etching processes to form a micro cavity to obtain thermal isolation. The fabrication process (shown in Fig. 2) starts from deposition of a 0.5 m thick SiO2. A 0.2 m thick Pt microheater layer is then sputtered and patterned using lift-off process. Another 0.5 m SiO2 layer is deposited and patterned as the mask to release microheater hotplates (or bridges) suspended over a micro cavity. The SiO2 over microheaters can be etched for direct contact between Pt and SWNTs. The first microheater design (Fig. 1a) is an 87×87 m² micro-hotplate with a meander Pt resistor embedded, which has the potential as gas sensors. The second microheater (Fig. 1b) has a curved shape that is designed to study E-field distribution and E-field enhancement of carbon nanotube alignment. The third microheater is further simplified into one straight line (5 m wide and 120 m long) (Fig. 1c) for studying temperature and SWNT density
The localized heating is realized by using dry etching processes to form a micro cavity to obtain thermal isolation. The fabrication process (shown in Fig. 2) starts from deposition of a 0.5 m thick SiO2. A 0.2 m thick Pt microheater layer is then sputtered and patterned using lift-off process. Another 0.5 m SiO2 layer is deposited and patterned as the mask to release microheater hotplates (or bridges) suspended over a micro cavity. The SiO2 over microheaters can be etched for direct contact between Pt and SWNTs. The first microheater design (Fig. 1a) is an 87×87 m² micro-hotplate with a meander Pt resistor embedded, which has the potential as gas sensors. The second microheater (Fig. 1b) has a curved shape that is designed to study E-field distribution and E-field enhancement of carbon nanotube alignment. The third microheater is further simplified into one straight line (5 m wide and 120 m long) (Fig. 1c) for studying temperature and SWNT density
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