Ultracompliant, passively decoupled thermal probe arrays: large area mapping of non-planar surfaces without force feedback

This paper describes an 8-probe system for scanning thermal microscopy. The design of the probe array, along with the choice of polyimide as the structural material provides very large compliance that virtually eliminates the need for z-axis mechanical feedback both at the chip and probe level in contact mode scans. The high compliance accommodates significant variations in the sample surface, and also prevents damage to soft samples. In addition, since integrated actuators and accompanying circuitry are no longer required, the prospect of scaling to large numbers of probes for high speed, high resolution thermal mapping of large areas with simple detection circuitry is enhanced. Based on single probes fabricated in the same process, the estimated spatial resolution, thermal conductance resolution, and temperature resolution are 50 nm, 11 pW/K, and 1.2 mK respectively. Scalability and performance of the 8-probe prototype are evaluated, addressing issues of speed vs. resolution, thermal and mechanical decoupling. Results demonstrate that contact mode scans can provide better than 2 μm spatial resolution at speeds greater than 200 μm/sec with each probe.