CN108389931B - Bio-neural chip integrating photoelectrode and microelectrode and preparation method thereof - Google Patents

Abstract

The invention relates to the technical field of semiconductor devices, in particular to a biological nerve chip integrating a photoelectrode and a microelectrode and a preparation method thereof. The specific structure of the chip comprises a photoelectrode part and a microelectrode part, wherein the photoelectrode part utilizes a light-emitting diode to emit light of 470nm to stimulate nerve cells to generate nerve current signals, and the microelectrode part near the photoelectrode is used for receiving the potential change of the nerve signals, so that the influence of the external signals on the nerve cells is detected, and the biological behavior is further studied. The photoelectrode part comprises a gallium nitride-based light emitting diode, a metal electrode, a transparent conducting layer, a temperature sensor, a metal circuit and a PAD electrode; the microelectrode part comprises a transparent film electrode or a metal electrode, a metal line and a PAD electrode. The invention integrates the photoelectrode and the microelectrode, has the characteristics of small size, high test precision, high conversion efficiency, easy implantation into organisms and the like, and realizes the measurement of nerve potential while carrying out optical stimulation on nerve cells.

Description

Bio-neural chip integrating photoelectrode and microelectrode and preparation method thereof

Technical Field

The present invention relates to the technical field of semiconductor devices, and more specifically, to a biological neural chip integrating photoelectrodes and microelectrodes and a preparation method thereof.

Background technique

Since the 20th century, human research on biological cells has developed rapidly. Research in electrophysiology has greatly promoted research on the functional activities of individual single nerve cells, the physiological and physical properties of neuronal membranes, and the location and role of individual neurons in neuronal circuits. People's understanding of the nervous system has been continuously improved, and they have begun to treat neurological diseases through the electrical activity of nerves. Traditional electrophysiological experiments require electrical stimulation of neurons. The disadvantage of electrical stimulation is that its intensity is too high and it is easy to cause the temperature of local nerve tissue to be too high, causing damage to the nervous system; in addition, electrical stimulation generally has a large range of action and its accuracy is difficult to control. Therefore, people try to find other alternative technologies.

Optogenetics is a rapidly developing multidisciplinary biotechnology that uses light to stimulate photosensitive genes to write external information, and uses photoelectrode array technology to read electrophysiological information under specific behaviors, thereby analyzing the functional characteristics of a certain neural region and its relationship with biological behavior. The light stimulation used in optogenetics can effectively act on specific individual neurons, and the speed of light pulses can reach sub-milliseconds, which is similar to electrical pulses.

Optogenetics mainly achieves control by stimulating two photosensitive proteins, channelrhodopsin (ChR2) and halorhodopsin (NpHR). Among them, channelrhodopsin (ChR2) is most sensitive to light stimulation at 470nm and can cause neural excitation; halorhodopsin (NpHR) is most sensitive to light stimulation at 580nm and can inhibit neural excitation. The present invention mainly controls channelrhodopsin, that is, we use a blue light device near 470nm.

At present, most semiconductor neural chips developed under the background of optogenetics can only realize the recording function, and most of their light stimulation is provided by optical fiber transmission near the recording location. The light stimulation transmission efficiency of this method is low, and the accuracy of the action position is insufficient.

Summary of the invention

In order to overcome at least one of the defects of the prior art described above, the present invention provides a biological neural chip integrating photoelectrodes and microelectrodes and a preparation method thereof, which combines the luminous signal required in the optogenetic technology with the received electrical signal.

The technical solution of the present invention is: a bio-neural chip integrating photoelectrodes and microelectrodes, wherein the photoelectrode part and the microelectrode part are included. The photoelectrode part uses a light emitting diode to emit 470nm light to stimulate nerve cells to generate neural current signals, and then the microelectrode part near the photoelectrode receives the change in the potential of the neural signal, thereby detecting the influence of the external signal on the nerve cells, and then studying biological behavior. The photoelectrode part includes a gallium nitride-based light emitting diode, a metal electrode, a transparent conductive layer, a temperature sensor, a metal circuit and a PAD electrode; the microelectrode part includes a transparent film electrode or a metal electrode, a metal circuit and a PAD electrode.

Furthermore, the epitaxial stack used in the photoelectrode can be made of gallium nitride, indium aluminum gallium nitride and other materials, which are suitable for emitting 470nm light signals; the transparent thin film conductive layer on the epitaxial stack can be any light-transmitting conductive material such as indium tin oxide, indium gallium zinc oxide, zinc oxide, iridium oxide, thin Ni/Au, etc.; the n-pole and p-pole metal electrodes used in the photoelectrode can be alloys such as Ni/Au, Ti/Au, Ti/Al/Ni/Au, etc.

Furthermore, the material used for the microelectrode can be transparent or opaque according to its relative position to the photoelectrode; the metal material used for the transparent microelectrode can be transparent materials such as ITO, IGZO, ZnO, IrO, thin Ni/Au, etc.; the metal material used for the opaque microelectrode can be thick Ni/Au, Ti/Au, Cr/Au, etc. The growth method thereof is electron beam evaporation, metal organic chemical vapor deposition, magnetron sputtering, etc.;

Furthermore, the microelectrode and photoelectrode parts are isolated by a transparent dielectric layer to avoid interference of neural current on photoelectrode current and noise generated by photoelectrode light signal on microelectrode receiving neural current signal; the dielectric layer can be a transparent non-conductive layer such as silicon dioxide and silicon nitride.

Furthermore, the position of the microelectrode can be the same position as the light-emitting transparent conductive layer of the photoelectrode part, in different isolated layers; it can also be near the light-emitting position of the photoelectrode part; the arrangement of the microelectrodes can be either linear or rectangular dot.

Furthermore, the material of the temperature sensor can be any metal whose resistivity changes stably with temperature, such as platinum, copper, etc., which is suitable for working at different temperatures.

In the present invention, the chip is small in size and thin in thickness, easy to implant in a living body, with little damage to tissues, and can be reused. The photoelectrode and the microelectrode are combined in the same position, which can accurately record neural potentials with high resolution while light stimulating the light-sensitive channel protein. Unlike traditional light stimulation conducted through optical fibers, the photoelectrode uses micro-light-emitting diodes. The miniaturization of the size allows the experimental mice to move freely and more biological reactions can be observed. In order to achieve the integration of the photoelectrode and the microelectrode in the same position of the chip,

The method for preparing a biological neural chip integrating a photoelectrode and a microelectrode comprises the following steps:

S1. Etching a P-type platform on the epitaxial stack of the grown GaN light-emitting layer using a plasma etching method;

S2. Then, an ITO transparent conductive film is deposited on the entire surface, and wet etching is performed to leave only the ITO conductive layer on the p-type platform with a p-type window;

S3. Depositing a mask dielectric layer using PECVD, and then etching p-type and n-type windows on the dielectric layer;

S4. A p-type electrode, an n-type electrode, a microelectrode, a metal line, a PAD electrode portion, and a temperature sensor are obtained on the dielectric layer by photolithography, full-surface metal deposition, stripping, or etching;

S5. PECVD is used again to deposit a mask dielectric layer, and a PAD window and a microelectrode window are etched on the dielectric layer.

Preferably, the present invention uses a gallium nitride-based sapphire substrate; the n-pole metals are preferably Ti/Al/Ni/Au and Ni/Au respectively; the transparent conductive layer is preferably ITO; the microelectrode material is preferably ITO; the circuit and PAD parts are preferably Ni/Au and Ti/Au; the temperature sensor is preferably Pt metal; the dielectric layer material is preferably silicon dioxide (SiO ₂ ). The size of the entire device is preferably length*width=1.0cm*0.30mm; the p-type electrode and the n-type electrode are preferably rectangular, the transparent conductive layer is preferably rectangular, and the microelectrode is preferably circular. After the front process is completed, the substrate can be appropriately thinned to reduce damage when implanted into biological neural tissue.

Compared with the prior art, the present invention has the following beneficial effects: the present invention integrates the photoelectrode and the microelectrode in the same position, which not only has the effect of simulating nerve stimulation, but also can simultaneously record the changes in nerve potential generated during stimulation. The photoelectrode and the microelectrode are close in height, which can also improve the accuracy of the stimulation signal. In addition, the chip has the characteristics of small size, high conversion efficiency, and easy implantation in the body, and will have broad prospects for future research in optogenetics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective structural diagram of Example 1.

FIG. 2 is a top view of the structure of Example 1.

FIG. 3 is a schematic diagram of a local device of the detection position portion implanted in a living body in Example 1. FIG.

FIG. 4 is a first schematic diagram of a local device of the detection position portion implanted in a living body in Example 2. FIG.

FIG. 5 is a second schematic diagram of a local device implanted in a biological body for detecting a position in the embodiment 2. FIG.

FIG6 is a cross-sectional view of the device of Example 1 at the tip where the photoelectrode and the microelectrode are integrated.

FIG. 7 is a schematic diagram of the window opening position of the encapsulation layer in Example 1 (the dotted line portion in the figure is the opening).

FIG8 is a top view of the front photoelectrode of Example 3.

FIG9 is a cross-sectional view of Example 3 along the vertical direction of the photoelectrode-microelectrode.

Detailed ways

The drawings are only for illustrative purposes and cannot be construed as limiting the present invention. To better illustrate the present embodiment, some parts of the drawings may be omitted, enlarged, or reduced, and do not represent the size of the actual product. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the drawings. The positional relationships described in the drawings are only for illustrative purposes and cannot be construed as limiting the present invention.

Embodiment 1

As shown in Figures 1, 2, 3, 6, and 7, this example integrates the microelectrode and the photoelectrode at the same position at the tip of the probe chip. The photoelectrode part is a buffer layer, an n-GaN layer, a quantum well light-emitting layer, and a p-GaN layer grown in sequence on a sapphire substrate. After the original film is cleaned, it is photolithographically developed, and a p-type platform is formed by plasma etching to a certain depth. Then, an ITO conductive film is deposited on the entire surface, and the part other than the p-type platform is etched away, and a p-type window is exposed on the p-type platform. Then, a mask layer is deposited and etched to expose the n and p-pole windows, and n and p electrodes, metal lines and PAD electrode metals are evaporated in sequence. At this point, the photoelectrode is completed. On the basis of the above, it is continued to be made into the electrode part. First, in order to prevent the microelectrode part from being disturbed by the current of the photoelectrode line, it is necessary to deposit a dielectric layer on the device to play a protective isolation role, and then open a window at one end of the metal line connecting the microelectrode on the transparent conductive layer. Then, an ITO transparent conductive film is deposited on the entire surface, and a round tip is etched out. At this point, the microelectrode part is completed. Finally, the entire device is packaged, leaving only the microelectrode and PAD electrode windows exposed, as shown in the shaded areas of FIG. 7 .

Embodiment 2

As shown in Figures 4 and 5, the device structure is similar to that of the first embodiment, except that the arrangement of the microelectrodes is changed, and metal materials are used as microelectrodes, that is, the microelectrodes themselves are opaque. Since the optical power of the photoelectrodes used in the present invention is large enough, even if the microelectrodes themselves are not on the photoelectrode part, they can receive the neural potential signals from the neuronal cells stimulated by the light emitted by the photoelectrodes. Since the microelectrodes can be made of the same metal material as the metal circuit, the process steps can be saved. At the same time, the microelectrodes are arranged outside the light-emitting area to avoid the switching potential changes caused by direct light irradiation.

Embodiment 3

As shown in Figures 8 and 9, this device adds a Pt temperature sensor to monitor the heating condition of the photoelectrode, and the microelectrode part is placed on the back of the substrate. The device uses a sapphire transparent substrate, and the light emitted by the photoelectrode can pass through the substrate to illuminate the neuron cells where the microelectrode is located, and the microelectrode receives the change in neural potential. At the same time, the shape of the photoelectrode n and p electrodes can be a ring electrode and a rectangular electrode as shown in Figure 6.

Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims (7)

1. The biological nerve chip integrating the photoelectrode and the microelectrode is characterized by comprising a photoelectrode unit and a microelectrode unit, wherein the photoelectrode unit comprises a gallium nitride luminous layer, a p-type electrode, an n-type electrode, a transparent conducting layer, a temperature sensor, a metal circuit and a PAD electrode; the microelectrode unit comprises four microelectrodes, four metal lines and four PAD electrodes; the microelectrode is a transparent film electrode or a metal electrode;

The photoelectric electrode unit and the microelectrode unit are positioned on the same side of the substrate, in the photoelectric electrode unit, a gallium nitride light-emitting layer is connected with a PAD electrode through a p-type electrode, an n-type electrode and a metal circuit, a transparent conductive layer covers part of the gallium nitride light-emitting layer, a mask medium layer covers the top of the gallium nitride light-emitting layer and the top of the transparent conductive layer, a transparent medium layer covers the top of the mask medium layer, and the p-type electrode, the n-type electrode, the microelectrode, the metal circuit, the PAD electrode part and the temperature sensor are respectively obtained on the mask medium layer by photoetching, whole-surface metal evaporation, stripping or corrosion methods;

The microelectrode unit is positioned on the upper layer which is mutually isolated from the photoelectrode unit and the temperature sensor, wherein the four microelectrodes are respectively connected with the four PAD electrodes through four metal lines;

the microelectrode is positioned at the same position as the transparent conducting layer of the photoelectrode unit and is in different layers isolated from each other;

The microelectrode and the photoelectrode unit are isolated by a transparent dielectric layer.

2. The photoelectrode and microelectrode integrated biochip according to claim 1, wherein: the material of the epitaxial lamination used by the photoelectrode unit is gallium nitride, and the epitaxial lamination is suitable for emitting 470nm optical signals; the transparent conductive layer on the epitaxial lamination is made of transparent conductive material and comprises indium tin oxide, indium gallium zinc oxide, iridium oxide or thin nickel-gold alloy; the n-pole and p-pole metal electrodes adopted by the photoelectrode unit comprise nickel-gold alloy, titanium-gold alloy or titanium-aluminum-nickel-gold alloy.

3. The photoelectrode and microelectrode integrated biochip according to claim 1, wherein: the microelectrode is made of transparent or opaque materials according to the relative positions of the microelectrode and the gallium nitride light-emitting layer; materials adopted by the transparent microelectrode comprise ITO, IGZO, znO, irO or thin nickel-gold alloy; materials used for the opaque microelectrode include thick nickel-gold alloy, titanium-gold alloy or chrome-gold alloy.

4. The photoelectrode and microelectrode integrated biochip according to claim 1, wherein: the transparent dielectric layer is a transparent non-conductive layer comprising silicon dioxide or silicon nitride.

5. The photoelectrode and microelectrode integrated biochip according to claim 1, wherein: the microelectrodes are arranged in a linear array or in a rectangular mesh.

6. The photoelectrode and microelectrode integrated biochip according to claim 1, wherein: the material of the temperature sensor is metal with stable resistivity along with temperature change.

7. The method for manufacturing a photoelectrode and microelectrode integrated biological neural chip according to claim 1, comprising the steps of:

s1, etching a P-type platform on an epitaxial lamination layer on which a gallium nitride luminescent layer is grown by using a plasma etching method;

S2, depositing an ITO transparent conductive film on the whole surface, and carrying out wet etching to only leave the ITO transparent conductive film on the p-type platform to form a transparent conductive layer with a p-type window;

S3, depositing a mask dielectric layer by utilizing PECVD, and etching p-type and n-type windows on the mask dielectric layer;

s4, respectively obtaining a p-type electrode, an n-type electrode, a microelectrode, a metal circuit, a PAD electrode part and a temperature sensor on the mask dielectric layer by photoetching, whole-surface vapor plating metal, stripping or corrosion;

S5, depositing a mask dielectric layer by PECVD, and etching a PAD window and a microelectrode window on the mask dielectric layer.