Wafer Level Processing of Silicon Arrays for Implantable Medical Devices

Micro system technology is well suited to batch fabricate multiple electrodes neural probes, intended for recording and stimulating neural tissue. Silicon neural probes have been produced using fixed lithographic mask sets, which is straightforward but costly for small production volumes. We demonstrate a novel method to fabricate high throughput, three dimensional microneedle arrays with a mask-less process. The wafer level etching enables not only low cost process but also it reduces lead time. The concept is based on the use of wet isotropic silicon etchant to define pen/fork-shaped electrodes. A custom made stirring system has been developed, in which the wafer is placed in a recessed Teflon holder over an O-ring, which completely seal the back-side of the wafer from the wet etchant. The wafer scale etching process has been optimized and the etching results have been analyzed and compared with the array etching. The results indicate that the etching process is repeatable and electrode geometry is highly uniform. The electrode arrays´ mechanical strength was analyzed by poking the array into a known Young´s modulus polydimethylsiloxane (PDMS) sample.