A Wafer-Scale Etching Technique for High Aspect Ratio Implantable MEMS Structures.

Microsystem technology is well suited to batch fabricate microelectrode arrays, such as the Utah electrode array (UEA), intended for recording and stimulating neural tissue. Fabrication of the UEA is primarily based on the use of dicing and wet etching to achieve high aspect ratio (15:1) penetrating electrodes. An important step in the array fabrication is the etching of electrodes to produce needle-shape electrodes with sharp tips. Traditional etching processes are performed on a single array, and the etching conditions are not optimized. As a result, the process leads to variable geometries of electrodes within an array. Furthermore, the process is not only time consuming but also labor-intensive. This report presents a wafer-scale etching method for the UEA. The method offers several advantages, such as substantial reduction in the processing time, higher throughput and lower cost. More importantly, the method increases the geometrical uniformity from electrode to electrode within an array (1.5 ± 0.5 % non-uniformity), and from array to array within a wafer (2 ± 0.3 % non-uniformity). Also, the etching rate of silicon columns, produced by dicing, are studied as a function of temperature, etching time and stirring rate in a nitric acid rich HF-HNO(3) solution. These parameters were found to be related to the etching rates over the ranges studied and more-importantly affect the uniformity of the etched silicon columns. An optimum etching condition was established to achieve uniform shape electrode arrays on wafer-scale.

[1]  Rajmohan Bhandari,et al.  Effect of sputtering pressure on pulsed-DC sputtered iridium oxide films , 2009 .

[2]  Klaus Wetzig,et al.  Experimental Studies on the Mechanism of Wet Chemical Etching of Silicon in HF ∕ HNO3 Mixtures , 2005 .

[3]  B. Schwartz,et al.  CHEMICAL ETCHING OF SILICON. IV. ETCHING TECHNOLOGY , 1977 .

[4]  K. Horch,et al.  A silicon-based, three-dimensional neural interface: manufacturing processes for an intracortical electrode array , 1991, IEEE Transactions on Biomedical Engineering.

[5]  A Novel Method of Fabricating Convoluted Shaped Electrode Arrays for Neural and Retinal Prosthesis , 2007 .

[6]  D. J. D'Stefan,et al.  Controlled Etching of Silicon in the HF ‐ HNO 3 System , 1962 .

[7]  R. Normann,et al.  A Novel Method of Fabricating Convoluted Shaped Electrode Arrays for Neural and Retinal Prosthesis , 2007, TRANSDUCERS 2007 - 2007 International Solid-State Sensors, Actuators and Microsystems Conference.

[8]  B. Schwartz,et al.  Chemical Etching of Silicon III . A Temperature Study in the Acid System , 1961 .

[9]  D. Edell,et al.  Factors influencing the biocompatibility of insertable silicon microshafts in cerebral cortex , 1992, IEEE Transactions on Biomedical Engineering.

[10]  Sandeep Negi,et al.  Wafer-scale fabrication of penetrating neural microelectrode arrays , 2010, Biomedical microdevices.

[11]  K. Najafi,et al.  A micromachined silicon sieve electrode for nerve regeneration applications , 1994, IEEE Transactions on Biomedical Engineering.

[12]  David J. Edell,et al.  A Peripheral Nerve Information Transducer for Amputees: Long-Term Multichannel Recordings from Rabbit Peripheral Nerves , 1986, IEEE Transactions on Biomedical Engineering.

[13]  R. Beard,et al.  Biocompatibility considerations at stimulating electrode interfaces , 2006, Annals of Biomedical Engineering.

[14]  K. E. Jones,et al.  A glass/silicon composite intracortical electrode array , 2006, Annals of Biomedical Engineering.

[15]  David J. Anderson,et al.  Solid-State Electrodes for Multichannel Multiplexed Intracortical Neuronal Recording , 1986, IEEE Transactions on Biomedical Engineering.

[16]  F. Solzbacher,et al.  In vitro comparison of sputtered iridium oxide and platinum-coated neural implantable microelectrode arrays , 2010, Biomedical materials.

[17]  Rajmohan Bhandari,et al.  A novel masking method for high aspect ratio penetrating microelectrode arrays , 2009 .

[18]  K. Wise,et al.  Performance of planar multisite microprobes in recording extracellular single-unit intracortical activity , 1988, IEEE Transactions on Biomedical Engineering.

[19]  H. K. Charles,et al.  Multisite microprobes for neural recordings , 1991, IEEE Transactions on Biomedical Engineering.

[20]  Bertram Schwartz,et al.  Chemical Etching of Silicon II . The System , , , and , 1960 .

[21]  Rajmohan Bhandari,et al.  Neural electrode degradation from continuous electrical stimulation: Comparison of sputtered and activated iridium oxide , 2010, Journal of Neuroscience Methods.