JP2008079799A - Artificial retina and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an artificial retina conveniently manufactured and its manufacturing method. <P>SOLUTION: The manufacturing method is characterized by including a step (a) to prepare a substrate 10, a step (b) to form a first amorphous layer 12a on the upper part of the substrate 10, a step (c) to respectively infuse a first and second conductivity type impurities into a predetermined region of the first amorphous layer 12a for forming a photodiode 40, a step (d) to form the insulating layer 14 on the upper part of the first amorphous layer 12a, a step (e) to form a second amorphous layer 52a on an upper part of the insulating layer 14, a step (f) to crystallize the first amorphous layer 12a and the second amorphous layer 52a by irradiation wtih a laser learn with required characteristics and to form a first semiconductor layer 12 and a second semiconductor layer 52, and a step (g) to form an MIS transistor 50 on the second semiconductor layer 52. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an artificial retina and a manufacturing method thereof.

  Conventionally, development of an artificial retina (a type of artificial organ) that detects light signals instead of retinas damaged by diseases such as retinitis pigmentosa and macular degeneration and transmits information to the optic nerve has been studied. For example, since the retina is composed of cells with multiple functions (visual cells, horizontal cells, bipolar cells, ganglion cells) in a very thin part of the fundus, physiological studies of these cells, etc. It has been proposed that a new information processing system incorporating the mechanism clarified by the above will be realized by LSI chips by functions similar to cells, and artificial retinas will be manufactured by three-dimensionally stacking these LSI chips.

  However, in order to stack LSI chips three-dimensionally, formation of embedded wiring penetrating the silicon wafer, polishing for thinning the silicon wafer, formation of fine bumps for connection between stacked substrates, Various techniques are required, such as precise positioning in bonding and establishment of bonding technology that can withstand the manufacturing process.

Furthermore, in order to embed the artificial retina at the bottom of the eyeball, a technique for forming the artificial retina on a curved flexible material is required. However, it is difficult to form an artificial retina by applying a normal semiconductor process to a flexible material. Therefore, Patent Document 1 discloses a manufacturing method for manufacturing an artificial retina by sequentially laminating a plurality of thin film devices constituting an artificial retina on a curved flexible material while being peeled and transferred.
JP 2006-511164 A (published February 23, 2006)

  However, the manufacturing method disclosed in Patent Document 1 is a very complicated process and is difficult to realize easily. Specifically, it is difficult to ensure conduction between the upper and lower layers and to transfer a large area. Therefore, improvement of the manufacturing method of an artificial retina is desired so that it can be manufactured easily and a reduction in manufacturing cost can be realized.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an artificial retina in which an artificial retina in which semiconductor layers serving as active layers are three-dimensionally stacked can be manufactured by a simple method, and It is in providing the manufacturing method.

The method for producing an artificial retina according to the present invention includes:
(A) preparing a substrate;
(B) forming a first amorphous layer above the substrate;
(C) forming an insulating layer above the first amorphous layer;
(D) implanting first conductivity type and second conductivity type impurities into predetermined regions of the first amorphous layer in order to form a photodiode;
(E) forming a second amorphous layer above the insulating layer;
(F) crystallization of the first amorphous layer and the second amorphous layer by laser irradiation to form a first semiconductor layer and a second semiconductor layer;
(G) forming a MIS transistor in the second semiconductor layer,
The laser used in the step (f) is a laser having a wavelength that can pass through the second semiconductor layer and crystallize the first amorphous layer.

  In the method for manufacturing an artificial retina according to the present invention, a plurality of amorphous layers (amorphous semiconductor layers) are laminated via an insulating layer and then crystallized by one crystallization process. Thereby, a laminated structure of semiconductor layers on which various elements are formed can be obtained, and an artificial retina having a three-dimensional structure can be manufactured by a simple method. In order to realize a three-dimensional structure, the peeling transfer technique described in Patent Document 1 is disclosed, but this manufacturing method is actually applied as described in the section of the problem to be solved by the invention. There are many challenges. However, according to the manufacturing method according to the present invention, a three-dimensional structure can be easily realized by performing crystallization with a laser having a wavelength capable of exhibiting desired characteristics after laminating a plurality of amorphous layers. . In addition, since the second semiconductor layer formed by the method for manufacturing an artificial retina according to the present invention is a high-quality layer, a MIS (Metal Insulator Semiconductor) transistor having good characteristics can be formed. This MIS transistor plays a role of transmitting the electrical signal converted by the photodiode to the optic nerve while performing image processing also performed on the living body retina. Therefore, a high-performance artificial retina can be formed by forming a MIS transistor with good characteristics. Can be manufactured.

  In the present invention, “forming B above A” includes a case where B is formed directly on A and a case where B is formed on A via another layer.

  In the method for manufacturing an artificial retina according to the present invention, it is preferable to include patterning the first amorphous layer before the step (c). According to the above configuration, the size of the photodiode can be optimized by patterning the first amorphous layer.

The method for producing an artificial retina according to the present invention includes:
(A) preparing a substrate;
(B) forming a first amorphous layer above the substrate;
(C) injecting impurities of a first conductivity type and a second conductivity type into predetermined regions of the first amorphous layer, respectively, to form a photodiode;
(D) forming an insulating layer above the first amorphous layer;
(E) forming a second amorphous layer above the insulating layer;
(F) crystallization of the first amorphous layer and the second amorphous layer by laser irradiation to form a first semiconductor layer and a second semiconductor layer;
(G) forming a MIS transistor in the second semiconductor layer,
The laser used in the step (f) is a laser having a wavelength that can pass through the second semiconductor layer and crystallize the first amorphous layer.

In the method for producing an artificial retina according to the present invention,
Preferably, the method includes patterning the first amorphous layer before the step (c) or before the step (d).

  According to the method for manufacturing an artificial retina according to the present invention, it is possible to manufacture an artificial retina having the same effects as the above-described manufacturing method and having high performance.

  In the method for manufacturing an artificial retina according to the present invention, the wavelength of the laser is preferably 500 nm to 1600 nm. According to this configuration, the two amorphous layers can be crystallized satisfactorily.

  In the method for manufacturing an artificial retina according to the present invention, the laser is preferably a double wave of a YAG laser. According to this configuration, crystallization of the plurality of semiconductor layers stacked via the insulating layer can be performed more reliably.

  In the method for manufacturing an artificial retina according to the present invention, it is preferable that the step (f) includes activating impurities implanted into the first amorphous layer. According to this configuration, since the crystallization step includes an impurity activation step, it is not necessary to provide an activation step separately, and the time and cost required for manufacturing can be reduced.

  The artificial retina according to the present invention is manufactured by the above-described method for manufacturing an artificial retina of the present invention.

  According to the artificial retina according to the present invention, since it is manufactured by a simple manufacturing method, it is possible to provide an artificial retina whose cost is reduced. In addition, since the second semiconductor layer formed by the above manufacturing method is a high-quality layer, a MIS transistor (thin film transistor) with good characteristics can be formed. As a result, a high-performance artificial retina can be provided.

  According to the method for manufacturing an artificial retina according to the present invention, an artificial retina having a three-dimensional structure is obtained by crystallization with a laser having a wavelength capable of exhibiting desired characteristics after laminating a plurality of amorphous layers. It can be easily manufactured.

  Hereinafter, an embodiment of the present invention will be described.

1. Artificial Retina First, an artificial retina manufactured by an artificial retina manufacturing method according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is an exploded perspective view showing an artificial retina manufactured by the manufacturing method of the present embodiment. FIG. 2 is a cross-sectional view showing the artificial retina according to the present embodiment.

  As shown in FIG. 1, the artificial retina 100 of the present embodiment includes a first layer 100A on which a photodiode is formed and a second layer 100B on which a thin film transistor is formed. The second layer 100B is formed on the first layer 100A to realize a three-dimensional structure. The first layer 100A plays a role of converting received light into an electrical signal. The second layer 100B includes various elements and circuits composed of MIS transistors (hereinafter referred to as “thin film transistors”), and plays a role of transmitting the electrical signal converted in the first layer 100A to the optic nerve. Specifically, a pixel circuit (not shown) for driving a photodiode formed in the first layer 100A, and an electric signal photoelectrically converted by the photodiode is pulse-modulated to generate a pulse signal to the human optic nerve. A pulse modulation circuit (not shown) for supply is configured. Furthermore, an amplifying element (circuit) for amplifying the electric signal photoelectrically converted by the photodiode may be included.

  Next, the artificial retina 100 according to the present embodiment will be described in more detail with reference to FIG. As shown in FIG. 2, the artificial retina 100 includes a substrate 10, a first semiconductor layer 12 provided on the substrate 10, an insulating layer 14 provided on the first semiconductor layer 12, and an insulating layer 14. And a thin film transistor 50 provided on the substrate. The first semiconductor layer 12 can be, for example, a polycrystalline silicon film, and the insulating layer 14 can be silicon oxide. A PIN type photodiode 40 is formed in the first semiconductor layer 12. Specifically, it is composed of a first conductivity type region (P type region) 42, a second conductivity type region (N type region) 44, and an intrinsic region (I layer) 46. The intrinsic region 46 is provided between the first conductivity type region 42 and the second conductivity type region 44 so as to separate the first conductivity type region 42 and the second conductivity type region 44, and in the plane of the first semiconductor layer 12, as shown in FIG. 1. It has a comb pattern.

  The thin film transistor 50 includes a second semiconductor layer 52 formed on the insulating layer 14, a gate insulating layer 54 formed on the second semiconductor layer 52, and a gate electrode 56 formed on the gate insulating layer 54. And an impurity region 58 to be a source region or a drain region formed in the second semiconductor layer 52.

  An interlayer insulating layer 16 is provided above the substrate 10 so as to cover the thin film transistor 50 and the photodiode 40. In the present embodiment, a case where a plurality of layers are stacked as the interlayer insulating layer 16 is shown. Specifically, a first insulating layer 16a and a second insulating layer 16b are stacked. As the first insulating layer 16a and the second insulating layer, silicon oxide, silicon nitride, and various organic insulating materials can be used.

  The interlayer insulating layer 16 has a contact hole 60 formed on the impurity region 58 of the thin film transistor 50 and a contact hole 48 formed on the photodiode 40. In order to connect the contact hole 60 and the contact hole 48, the conductive layer 20 is formed. Further, the conductive layer 22 is formed so as to connect the contact holes 60 between the adjacent thin film transistors 50.

  Since the artificial retina 100 according to the present embodiment is manufactured by a simple manufacturing method, it is possible to provide the artificial retina 100 whose cost is reduced. Moreover, since the 2nd semiconductor layer 52 formed with the manufacturing method which concerns on this embodiment mentioned later is a high quality layer, the thin-film transistor 50 with a favorable characteristic can be formed. As a result, a high-performance artificial retina 100 can be provided.

2. Method for Producing Artificial Retina Hereinafter, an embodiment of a method for producing an artificial retina according to the present invention will be described with reference to FIG. FIG. 3A to FIG. 3D are diagrams showing a process for manufacturing an artificial retina according to the present embodiment.

  First, as shown in FIG. 3A, a substrate 10 is prepared. As the substrate 10, quartz glass, alkali-free glass, ordinary glass, plastic film or resin film, for example, polyimide (PI), polyethylene terephthalate (PET), polyethersulfone (PES), or the like is used. it can.

  Next, the first amorphous layer 12 a is formed on the entire surface of the substrate 10. Specifically, amorphous silicon can be formed. The first amorphous layer 12 a is crystallized by a crystallization process to be described later, and becomes the first semiconductor layer 12. Next, the insulating layer 14 is formed on the first amorphous layer 12a. As the insulating layer 14, for example, silicon oxide can be formed by a known CVD method. In addition, before forming the insulating layer 14, the first amorphous layer 12a may be patterned as necessary.

  Next, impurities are implanted to form the photodiode 40. Specifically, as shown in FIG. 3A, a mask M1 having openings of a predetermined pattern is formed on the insulating layer. At this time, the mask M1 covers a pattern in which the intrinsic region 46 and the second conductivity type region 44 are formed. Thereafter, a first conductivity type (P-type or N-type) impurity is implanted into the first amorphous layer 12a. As a result, a first conductivity type implantation region 13a is formed in a predetermined region of the first amorphous layer 12a.

  Next, as shown in FIG. 3B, the mask M1 is removed, and a mask M2 having openings of a predetermined pattern is formed. At this time, the mask M <b> 2 covers the intrinsic region 46 and the region that becomes the first conductivity type region 42. Thereafter, a second conductivity type (N-type or P-type) impurity is implanted into the first amorphous layer 12a. As a result, a second conductivity type implantation region 13b is formed in a predetermined region of the first amorphous layer 12a. The PIN type photodiode 40 is formed through an impurity activation process in a process described later.

  Next, as shown in FIG. 3C, the second amorphous layer 52 a is formed on the insulating layer 14. The second amorphous layer 52 a is a layer that is crystallized by a crystallization process to be described later and becomes the second semiconductor layer 52. As the second amorphous layer 52a, for example, amorphous silicon can be formed.

  Next, the first amorphous layer 12a and the second amorphous layer 52a are crystallized. The crystallization process is performed by laser irradiation. In the following, characteristics of a laser used as an example where the first amorphous layer 12a and the second amorphous layer 52a are amorphous silicon will be described. The laser wavelength is preferably 500 nm to 1600 nm. That is, the energy of the laser to be irradiated is not absorbed in the crystallization of the upper second amorphous layer 52a, but is absorbed in the lower first amorphous layer 12a. It is preferable. More specifically, a green laser that is a double wave (wavelength 532 nm) of an Nd: YAG laser (fundamental wavelength: 1064 nm) is preferably used as the laser.

  Since the green laser has a smaller light absorption coefficient with respect to polycrystalline silicon than the excimer laser, a part of the laser energy is transmitted. Therefore, it is possible to make the laser energy reach the first amorphous layer 12a, and crystallization can be performed using a silicon thin film substrate having a two-layer or multi-layer structure.

  Thus, by performing crystallization in a state where a plurality of amorphous layers are stacked, there is an advantage that a high-quality semiconductor layer can be obtained particularly as an upper semiconductor layer. The operation will be described below. During crystallization, heat is generated by the laser energy transmitted through the upper second semiconductor layer 52 being absorbed by the lower first amorphous layer 12a. Therefore, the lower layer functions as a heat bath, and a gentle annealing effect is generated on the upper second semiconductor layer 52 (polycrystalline silicon). Thereby, reduction of defects in the crystal grains of the second semiconductor layer 52 and improvement of the quality of crystal grain boundaries can be achieved. This also contributes to an improvement in characteristics of the thin film transistor formed in the second semiconductor layer 52.

  Further, this laser irradiation can also serve as an activation process for the impurities implanted into the first amorphous layer 12a. Therefore, it is not necessary to provide a separate process for activating impurities, and the manufacturing time and manufacturing cost can be reduced.

  By this step, as shown in FIG. 3D, the first semiconductor layer 12 and the second semiconductor layer 52 can be formed. When the first amorphous layer 12a and the second amorphous layer 52a are amorphous silicon, the second semiconductor layer 52 is polycrystalline silicon, and the first semiconductor layer 12 is microcrystalline silicon. At the same time, in the first conductivity type implantation region 13a and the second conductivity type implantation region 13b, the impurity is activated (enters into the lattice of the semiconductor layer), and the first conductivity type region 42 and the second conductivity type region 44 are formed. It is formed.

  Next, the second semiconductor layer 52 is patterned to form a second semiconductor layer 52 having a desired pattern as shown in FIG. Patterning can be performed by a known technique. A thin film transistor 50 is formed in the second semiconductor layer 52. The thin film transistor 50 can be formed according to a known formation method. Below, an example of the formation method of the thin-film transistor 50 is demonstrated.

  First, an insulating layer (not shown) made of silicon oxide or the like is formed on the second semiconductor layer 52. Next, a conductive layer (not shown) to be a gate electrode is formed on the insulating layer, and the conductive layer and the insulating layer are patterned. Thereby, as shown in FIG. 2, the gate insulating layer 54 and the gate electrode 56 can be formed on the second semiconductor layer 52. As the gate insulating layer 54 and the gate electrode 56, known materials can be used as appropriate.

  Next, an impurity region 58 to be a source region or a drain region is formed. In this step, a mask (not shown) that covers the region other than the region where the impurity region 58 is to be formed is formed, an impurity of a predetermined conductivity type is implanted, and heat treatment for activation is performed as necessary. The Through the above steps, the thin film transistor 50 can be formed.

  Next, as illustrated in FIG. 2, the interlayer insulating layer 16 is formed over the first semiconductor layer 12 so as to cover the thin film transistor 50. In the present embodiment, a case where a first insulating layer 16 a and a second insulating layer 16 b are stacked as the interlayer insulating layer 16 is illustrated. Next, a contact hole 48 and a contact hole 60 are formed. The contact hole 48 and the contact hole 60 can be formed by known lithography and etching techniques. Thereafter, conductive layers 20 and 22 are formed in the contact holes 48 and 60. Through the above steps, the artificial retina 100 according to the present embodiment can be formed.

  According to the method for manufacturing the artificial retina 100 according to the present embodiment, after laminating the first amorphous layer 12a and the second amorphous layer 52a with the insulating layer 14 interposed therebetween, a laser having a wavelength capable of exhibiting desired characteristics. Crystallization takes place. Thereby, the artificial retina 100 having a three-dimensional structure composed of a stacked structure of the first semiconductor layer 12 and the second semiconductor layer 52 on which the elements are formed can be manufactured by a simple method. In addition, the second semiconductor layer 52 formed by the method for manufacturing the artificial retina 100 according to the present embodiment is a high-quality layer and can form the thin film transistor 50 with good characteristics. Since the thin film transistor 50 plays a role of transmitting the electric signal converted by the photodiode 40 to the optic nerve, the high performance artificial retina 100 can be manufactured by forming the thin film transistor 50 with good characteristics.

  According to the method for manufacturing the artificial retina 100 according to the present embodiment, since a three-dimensional structure can be realized, the photodiode 40 can be formed in a wide area. Therefore, the photodiode can be formed in a wider area than in the case where the thin film transistor and the photodiode are formed in the same plane. As a result, the light absorption efficiency is improved, and the artificial retina 100 capable of transmitting more information to the optic nerve can be manufactured.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. That is, embodiments obtained by combining technical means appropriately changed within the scope of the claims are also included in the technical scope of the present invention.

  The present invention can be used for an artificial retina as a substitute for a retina damaged by various diseases.

It is a disassembled perspective view which shows the artificial retina manufactured by the manufacturing method which concerns on this embodiment. It is sectional drawing which shows the artificial retina manufactured by the manufacturing method which concerns on this embodiment. It is sectional drawing explaining the manufacturing method of the artificial retina which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Substrate 12 1st semiconductor layer 12a 1st amorphous layer 13a 1st conductivity type injection | pouring area | region 13b 2nd conductivity type injection | pouring area | region 14 Insulation layer 16 Interlayer insulation layer 40 Photodiode 42 1st conductivity type area | region 44 2nd conductivity type area | region 46 Intrinsic region 50 MIS transistor (thin film transistor)
52 Second semiconductor layer 52a Second amorphous layer 54 Gate insulating layer 56 Gate electrode 58 Impurity region 48, 60 Contact hole 100 Artificial retina 100A First layer 100B Second layer

Claims (8)

(A) preparing a substrate;
(B) forming a first amorphous layer above the substrate;
(C) forming an insulating layer above the first amorphous layer;
(D) implanting first conductivity type and second conductivity type impurities into predetermined regions of the first amorphous layer in order to form a photodiode;
(E) forming a second amorphous layer above the insulating layer;
(F) crystallization of the first amorphous layer and the second amorphous layer by laser irradiation to form a first semiconductor layer and a second semiconductor layer;
(G) forming a MIS transistor in the second semiconductor layer,
Producing an artificial retina, wherein the laser used in the step (f) is a laser having a wavelength that can pass through the second semiconductor layer and crystallize the first amorphous layer. Method.   The method for producing an artificial retina according to claim 1, comprising patterning the first amorphous layer before the step (c). (A) preparing a substrate;
(B) forming a first amorphous layer above the substrate;
(C) injecting impurities of a first conductivity type and a second conductivity type into predetermined regions of the first amorphous layer, respectively, to form a photodiode;
(D) forming an insulating layer above the first amorphous layer;
(E) forming a second amorphous layer above the insulating layer;
(F) crystallization of the first amorphous layer and the second amorphous layer by laser irradiation to form a first semiconductor layer and a second semiconductor layer;
(G) forming a MIS transistor in the second semiconductor layer,
Producing an artificial retina, wherein the laser used in the step (f) is a laser having a wavelength that can pass through the second semiconductor layer and crystallize the first amorphous layer. Method.   The method of manufacturing an artificial retina according to claim 3, comprising patterning the first amorphous layer before the step (c) or before the step (d).   The method of manufacturing an artificial retina according to any one of claims 1 to 4, wherein the laser has a wavelength of 500 nm to 1600 nm.   The method for manufacturing an artificial retina according to claim 1, wherein the laser is a double wave of a YAG laser.   The method of manufacturing an artificial retina according to any one of claims 1 to 6, wherein the step (f) includes activating impurities implanted into the first amorphous layer. .   An artificial retina manufactured by the manufacturing method according to claim 1.

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