A thermal microprobe fabricated with wafer-stage processing

Abstract

A thermal microprobe has been designed and built for high resolution temperature sensing. The thermal sensor is a thin-film thermocouple junction at the tip of an atomic force microprobe ͑AFM͒ silicon probe needle. Only wafer-stage processing steps are used for the fabrication. For high resolution temperature sensing it is essential that the junction be confined to a short distance at the AFM tip. This confinement is achieved by a controlled photoresist coating process. Experiment prototypes have been made with an Au/Pd junction confined to within 0.5 m of the tip, with the two metals separated elsewhere by a thin insulating oxide layer. Processing begins with double-polished, n-type, 4 in. diameter, 300-m-thick silicon wafers. Atomically sharp probe tips are formed by a combination of dry and wet chemical etching, and oxidation sharpening. The metal layers are sputtering deposited and the cantilevers are released by a combination of KOH and dry etching. A resistively heated calibration device was made for temperature calibration of the thermal microprobe over the temperature range 25-110°C. Over this range the thermal outputs of two microprobes are 4.5 and 5.6 V/K and is linear. Thermal and topographical images are also obtained from a heated tungsten thin film fuse.

Recent Developments in Micro and Nanoscale Thermometry

“…Recently, several groups have attempted to batch-fabricate probes for scanning thermal microscopy [13][14][15]. Two groups fabricated thermal probes using only optical lithography and waferstage processing steps [13,14]. However, the probes were made of silicon, leading to the aforementioned inaccuracies and artifacts.…”

“…In addition, they were usually fabricated individually, making the process very time-consuming and irreproducible. Recently, several groups have attempted to batch-fabricate probes for scanning thermal microscopy [13][14][15]. Two groups fabricated thermal probes using only optical lithography and waferstage processing steps [13,14].…”

Local temperature surface measurement with intrinsic thermocouple

“…Optical techniques such as infrared thermometry [1,13] and surface reflectometry [2] are also state-of-the-art tools. Scanning Thermal Microscope (SThM) is a quite recent metrology technique based on a thermocouple or a thermoresistive probe mounted on an Atomic Force Microscope (AFM) [3][4][5][6][7][8][9]. It provides thermal and topographical images of sample surfaces with high spatial resolution.…”

Removal of a hydrogenated amorphous carbon film from the tip of a micropipette electrode using direct current corona discharge

“…When indurative resins, e.g., epoxy, are employed as insulators, their deformations due to surface tension, gravity, centrifugal force, and/or heat could be used to make the tip protrude. 12,13 Reference 14 explained how to dip and coat a needle tip with nail polish for masking. However, a spinning or dipping condition must be carefully adjusted with respect to the size and shape of each tip and the viscosity of the resin.…”