NEURALPROBE AND METHODS FOR MANUFACTURING SAME

• US 20090318824A1
• Filed: 06/01/2006
• Published: 12/24/2009
• Est. Priority Date: 06/01/2005
• Status: Abandoned Application

• Current Assignee: University of Florida Research Foundation, Incorporated (State University System of Florida)
• Original Assignee: University of Florida Research Foundation, Incorporated (State University System of Florida)
• Inventors: Sanchez, Justin C., Nishida, Toshikazu, Xie, Huikai, Patrick, Erin E.
• Application Number:
  US11/915,987
• Publication Number:
  US 20090318824A1
• Time in Patent Office: Days
• US Class Current: 600/544
• CPC Class Codes: A61B 2562/028 Microscale sensors, e.g. electromechanical sensors [MEMS]
• CPC Class Codes: A61B 5/24 Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof

Abstract

A neural probe and method of fabricating same are provided. The probe comprises a plurality of frames connected to each other and to a substrate by respective bimorphs. A probe base is connected by another bimorph to the frames. A probe tip extends from the probe base. The probe can achieve a large vertical motion and out-of-plane curling. The probe can operate according to three modes. The first mode pertains to a large-signal motion for tuning in single-unit neuronal activity. The second pertains to a small-signal motion with lock-in amplifier that increases SNR. The third pertains to burst small-signal motion for clearing tissue responses. Fabrication of a neural probe begins with a processed CMOS chip. Post-CMOS processing incorporates self-aligned selective nickel plating and sacrifices two aluminum layers. The fabrication technique produces a neural probe in which the sensing elements are in close proximity to CMOS circuitry. The fabrication technique obviates the need for post-CMOS masks, alignment, or assembly.

Claims

1. A micro-electromechanical system (MEMS) probe for sensing neuronal activity, the probe comprising:

a probe base having at least one preamplifier embedded therein

a bimorph mechanically connected to the probe base, the bimorph being capable of flexing in a predetermined direction in response to an applied electrical signal;

a probe tip extending from the probe base, the probe tip containing at least one electrode embedded therein and connected to the at least one preamplifier; and

the probe having a first mode of operation for large-signal motion in sensing single-unit neural activity, a second mode of operation for small-signal motion to increase a signal-to-noise ratio, and a third mode of operation for burst-type small-signal motion for clearing tissue responses.

2. The probe of claim 1, wherein the probe further comprises a first probe frame and the bimorph comprises a first bimorph, and wherein the probe further comprises a second probe frame and a second bimorph that mechanically connects the second probe frame to the first probe frame.

3. The probe of claim 1, wherein the at least one electrode comprises a plurality of electrodes, and wherein the at least one preamplifier comprises a plurality of preamplifiers, each of the preamplifiers comprising an operational transconductance amplifier that is AC coupled to a unique one of the electrodes.

4. The probe of claim 3, wherein the probe base further comprises an analog multiplexer embedded therein and connected to the plurality of preamplifiers for time multiplexing analog signals received.

5. The probe of claim 4, further comprising a plurality of MOS-bipolar pseudoresistor elements connected to each of the plurality of preamplifiers to mitigate a DC offset of a neural signal.

6. The probe of claim 5, wherein each of the plurality of electrodes comprises the gate of a metal-oxide semiconductor field-effect transistor.

7. The probe of claim 5, wherein the probe tip further implements a chopper stabilization technique to further mitigate flicker noise.

8. The probe of claim 5, wherein each one of the plurality of electrodes is connected to a pMOS transistor.

9. The probe of claim 1, wherein further comprising a thermally conductive package encasing the probe base, bimorph, and probe tip.

10. A micro-electromechanical system (MEMS) probe for sensing neuronal activity, the probe comprising:

a first probe frame;

a first bimorph for mechanically connecting the first probe frame to a semiconductor substrate, the first bimorph being capable of flexing in a predetermined direction in response to an applied electrical signal;

a second probe frame;

a second bimorph mechanically connecting the second probe frame to the first probe frame, the second bimorph being capable of flexing in a predetermined direction in response to an applied electrical signal;

a probe base having at least one preamplifier embedded therein;

a third bimorph mechanically connecting the probe base to the second bimorph, the third bimorph being capable of flexing in a predetermined direction in response to an applied electrical signal; and

a probe tip extending from the probe base, the probe tip containing at least one electrode embedded therein and connected to the at least one preamplifier.

11. The probe of claim 10, wherein the first and second bimorphs comprise a pair of folded thermal actuators for forming a flat platform for effecting large vertical displacements of the probe tip in response to an electrical signal.

12. The probe of claim 11, wherein the third bimorph flexes approximately ninety degrees (90°

).

13. The probe of claim 12, further comprising an embedded polysilicon for compensating an offset from the approximately ninety degrees.

14. The probe of claim 10, wherein the at least one preamplifier comprises a plurality of operational transconductance amplifiers, and further comprising an analog multiplexer for time multiplexing signals received from the operational transconductance amplifiers.

15. A method of fabricating a neural probe, the method comprising:

(a) forming a silicon membrane by backside etching of a processed CMOS wafer or chip and performing a plasma enhanced chemical vapor deposition (PECVD) oxide passivation;

(b) forming shallow cavities for neural electrodes in the CMOS wafer or chip by performing an anisotropic oxide etch from the front side of the CMOS wafer or chip using a metal as an etching mask;

(c) applying a spin-on photoresist to protect some portions of the metal;

(d) removing the top metal layer except portions of the metal protected by the spin-on photoresist;

(e) removing the photoresist and selectively electroplating cavity regions in the CMOS wafer or chip;

(f) performing an anisotropic etch, deep silicon etching and another anisotropic oxide etch to etch through the backside oxide layer;

(g) performing an isotropic silicon etch to etch silicon beneath narrow beams; and

(h) coating the structure with a biocompatible layer.