Silicon-Based Integrated Nano-Electro-Mechanical Probe Technology

To meet ultra-high density requirement of next-generation data storage, NEMS probe arrays consisting of piezoresistive-reading and electric-thermal writing functions have been investigated. The device is integrated with resistive heater and piezoresistor on an ultrathin microcantilever by using advanced silicon bulk mcromachining technologies. It differs from previous technologies either using two independent probes for piezoresistive-reading and electro-thermal writing or using one electric-thermal tip for both writing and reading. Besides rectangular shaped cantilevers with both piezoresistive sensor and electric heater, the "V" and "U" type cantilevers are also formed for electric-heating probes.An electric-heating theoretical model has been established. Based on theoretical analysis and simulation of Finite Element Method (FEM), the parameters of the device have been designed and optimized. Equisection cant: lever NEMS probes, V type cantilever NEMS probes and U type cantilever NEMS probes have been designed based on themodelling.During fabrication of the NEMS probes, KOH anisotropic etching technology has been developed for the formation of suitable silicon island with top size within 0.5 to 0.8m. Low-temperature oxidation-sharpening process have been explored for silicon nano-tips with tip radius within 30nm and 60nm and tip height between 2.0 and 3.0n. One set of boron diffusion technologies to form the heater have been developed, which is effective in preventing the invalidation of the perpendicular PN junction of the cantilever during tip heating, thereby avoiding electric current leakage. The integration technology of the heater and piezoresistor on one ultrathin cantilever has been finally completed.Testing technology for the electric heating performance, piezoresistive sensing performance and data storage performance of the device is studied. The static heating results agree well with the calculated ones, and the transient heating results are also ingood agreement with the ANSYS simulation. For equisection cantilever NEMS probes, under the 4V pulse power and 3 microseconds heating period, tip temperature of 463K, 6.2 microseconds cooling time constant of the heater and nearly one hundred KHz equivalent writing velocity have been realized. For V-type cantilever NEMS probes, under the 5V pulse power and 3 microseconds heating time, 465 K tip temperature, 7.5 microseconds cooling time constant of the heating resistor are experimentally obtained. Regarding to the U-type cantilever NEMS probes, even with 12.5V heating pulse and 15 microseconds heating period given, only 467 K tip temperature and nearly 90 microseconds cooling time constant can be obtained. The sensitivity of the piezoresistive sensor on the equisection cantilever under 2 10-7N force at cantilever-end is measured as 5.410-4 by R/R, which is enough for nano data reading. Finally, the data-writing performance with varied writing condition is studied. About 31.6Gb/in2 data-writing density is realized successfully on PMMA polymer thin film by using AFM equipment with optimized the thermal writing parameters.