A multi-step electrochemical etching process for a three-dimensional micro probe array

Abstract

We present a simple, fast, and cost-effective process for three-dimensional (3D) micro probe array fabrication using multi-step electrochemical metal foil etching. Compared to the previous electroplating (add-on) process, the present electrochemical (subtractive) process results in well-controlled material properties of the metallic microstructures. In the experimental study, we describe the single-step and multi-step electrochemical aluminum foil etching processes. In the single-step process, the depth etch rate and the bias etch rate of an aluminum foil have been measured as 1.50 +/- 0.10 and 0.77 +/- 0.03 mu m min(-1), respectively. On the basis of the single-step process results, we have designed and performed the two-step electrochemical etching process for the 3D micro probe array fabrication. The fabricated 3D micro probe array shows the vertical and lateral fabrication errors of 15.5 +/- 5.8% and 3.3 +/- 0.9%, respectively, with the surface roughness of 37.4 +/- 9.6 nm. The contact force and the contact resistance of the 3D micro probe array have been measured to be 24.30 +/- 0.98 mN and 2.27 +/- 0.11 Omega, respectively, for an overdrive of 49.12 +/- 1.25 mu m.