WO2023108441A1

WO2023108441A1 - Imaging device, electronic apparatus, and method for manufacturing an imaging device

Info

Publication number: WO2023108441A1
Application number: PCT/CN2021/138074
Authority: WO
Inventors: Seiji Takahashi; Dan GONG
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2021-12-14
Filing date: 2021-12-14
Publication date: 2023-06-22
Also published as: CN117242573A

Abstract

A imaging device (100) includes: a substrate comprising an photodiode (150); a floating diffusion (300) comprising a wiring connecting position; and a source follower device (600) being electrically connected to the floating diffusion (300), and comprising a gate (601), a source (603), a channel (604), and a drain (602); wherein the source (603) of the source follower device (600) comprises a wiring connecting position, and the drain (602) of the source follower device (600) comprises a wiring connecting position, and wherein at least one of the wiring connecting position of the source (603) and the wiring connecting position of the drain (602) is placed opposite side to the floating diffusion (300) with respect to the gate (601) of the source follower device (600) in planar view of the substrate.

Description

IMAGING DEVICE, ELECTRONIC APPARATUS, AND METHOD FOR MANUFACTURING AN IMAGING DEVICE

Technical Field

The present invention relates to animaging device, electronic apparatus and a methodfor manufacturing an imaging device.

Background

As imaging devices (image sensors) using photoelectric conversion elements detecting electromagnetic radiation and generating a charge, (charge coupled device, CCD) image sensors and (complementary metal oxide semiconductor, CMOS) image sensors have been put into practical use. CCD image sensors and CMOS image sensors have been widely applied as parts of digital cameras, video cameras, monitoring cameras, medical endoscopes, personal computers (PC) , mobile phones and other portable terminals (mobile devices) and other various types of electronic apparatuses.

Patent Document 1 discloses a rectangular image sensor array of pixel units fabricated by a CMOS technology, comprising: an array of quadrilinear photodiodes separated by upper and lower horizontal control device lanes and intersecting left and right vertical control device lanes whose layout further comprises: a transfer transistor located on a first corner of each photodiode for transferring image related potential levels to a floating drain node located within the right vertical control device lane nearest the transfer transistor; a reset transistor located within the right vertical control device lane nearest the floating drain with a source electrode connected to the floating drain by a doped Silicon pathway and with a drain electrode connected to a first power supply at its drain electrode; a source follower transistor located at intersection of the right vertical control device lane and the upper horizontal device control lane, wherein the gate electrode of the source follower transistor is spaced at the minimum distance from the floating drain as is allowed by the CMOS fabrication technology chosen to manufacture the image sensor array, and wherein a drain electrode of the source follower transistor is connected to a second power supply; anda row select transistor positioned within the upper horizontal device control lane and adjacent to the source follower transistor, wherein a drain electrode of the row select transistor is connected to a source electrode of the source follower transistor by a doped Silicon pathway and source electrode of the row select transistor is connected to a signal out node. Patent Document 1, United States Patent No. 10701298

Summary of the Invention

Problems to be Solved by the Invention

However, according toPatent Document 1, a source follower device is placed to FD as close as possible. Therefore, the image sensor disclosed in Patent Document 1 is hard to apply to sharing in-pixel devices architecture, or small pixel size.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention isto provide animaging device and electronic apparatus being able to have low read out noise, and a methodfor manufacturing an imaging device.

Means for Solving the Problem

The present invention has been made based on the above findings, and the gist is as follows.

[1] A imaging device including:

a substrate comprising an photodiode;

a floating diffusion comprising a wiring connecting position; and

a source follower device being electrically connected to the floating diffusion, and comprising a gate, a source, a channel, and a drain;

wherein the source of the source follower comprises a wiring connecting position, and the drain of the source follower comprises a wiring connecting position,

wherein at least one of the wiring connecting position of the source and the wiring connecting position of the drain is placed opposite side to the floating diffusion with respect to the gate of the source follower device in planar view of the substrate.

[2] The imaging device according to [1] , further comprising:

a first transfer gate and a second transfer gate,

wherein the source and the drain of the source follower device are placed between the first transfer gate and the second transfer gate in planar view of the substrate.

[3] The imaging device according to [1] or [2] ,

wherein the source follower comprises an active area, and the active area are U-shaped in planar view of the substrate.

[4] The imaging device according to [1] or [2] ,

wherein the source follower comprises an active area, and the active area is L-shaped in planar view of the substrate.

[5] The imaging device according to any one of [1] to [4] , wherein a shortest width of the channel of the source follower device is narrower than that of the source and the drain in planar view of the substrate.

[6] The imaging device according to any one of [1] to [4] , wherein a shortest width of the source of the source follower device is narrower than that of the channel and the drain in planar view of the substrate.

[7] The imaging device according to any one of [1] to [6] ,

wherein the drain of the source follower device comprises no LDD (lightly doped drain) implant.

[8] The imaging device according to any one of [1] to [7] ,

wherein the gate of the source follower device is a tri-gate structure.

[9] The imaging device according to any one of [1] to [8] ,

wherein the source, the channel, and the drain are placed within an area that is defined by a line running through the gate and being parallel to a direction where the gate of the source follower device and the floating diffusion line up in planar view of the substrate.

[10] The imaging device according to any one of [1] to [9] ,

wherein a width of the gate in the direction where the gate of the source follower device and the floating diffusion line up are wider than that of the shortest active areas in planar view of the substrate.

[11] The imaging device according to [2] ,

wherein each of the first transfer gate and the second transfer gate comprises a wiring connecting position, the wiring connecting position is placed at a farthest point from the floating diffusion in a direction perpendicular to a direction where the gate of the source follower device and the floating diffusion line up in planar view of the substrate.

[12] The imaging device according to any one of [1] to [11] ,

wherein at least two photodiodes share one floating diffusion.

[13] The imaging device according to any one of [1] to [12] ,

wherein at least two photodiodes share one source follower device.

[14] The imaging device according to any one of [1] to [13] ,

wherein a transfer gate comprises an embedded portion in the substrate.

[15] The imaging device according to any one of [1] to [14] , further comprising:

a dual conversion gain device and a reset device,

wherein a distance from an end of a gate of a dual conversion gain device to a wiring connecting position of the floating diffusion contact is far from a distance from an end of a gate of a reset device to a wiring connecting position of a drain of a reset device.

[16] The imaging device according to any one of [1] to [14] , further comprising:

a dual conversion gain device and a reset device,

wherein a distance from an end of a gate of a reset device to a wiring connecting position of the floating diffusion contact is far from a distance from an end of a gate of a dual conversion gain device to a wiring connecting position of a drain of a dual conversion gain device.

[17] The imaging device according to any one of [1] to [16] ,

wherein a height of the gate of the source follower device is less than that of the source and the drain in direction perpendicular to a surface of the substrate.

[18] The imaging device according to [15] or [16] ,

wherein a distance of a gate and an active area of a reset device against the floating diffusion is narrower than that of the drain of the reset device in the direction perpendicular to a direction where the gate of the source follower device and the floating diffusion line up in planar view of the substrate.

[19] The imaging device according to any one of [1] to [18] , further comprising:

a select device,

wherein an active area of a drain of the select device shares an active area of the source of the source follower device.

[20] The imaging device according to [15] or [16] ,

wherein an active area of the drain of a dual conversion gain device shares an active area of a source of areset device.

[21] The imaging device according [15] or [16] ,

wherein an additional capacitance on a node is placed between the dual conversion gain device and the reset device.

[22] The imaging device according to any one of [1] to [21] ,

wherein the gate of the source follower device and the floating diffusion can be electrically connected by a shared contact.

[23] The imaging device according to any one of [1] to [21] ,

wherein the gate of the source follower device and the floating diffusion can be electrically connected by metal-0 wiring.

[24] The imaging device according to any one of [1] to [22] , further comprising:

an isolation for separating devices,

wherein the isolation comprises STI or doping isolation.

[25] An electronic apparatus comprising:

animaging deviceaccording to any one of [1] to [24] .

[26] The method for manufacturing an imaging device according to Claims 1 to 24.

As described above, according to the present invention it is possible to provide animaging device and electronic apparatus being able to have low read out noise, and a methodfor manufacturing an imaging device.

Brief Description of the Figures

FIG. 1 is a top view of an example circuit layout according to the first embodiment of the present invention.

FIG. 2 is a block diagram of an imaging system according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram showing an example of a pixel according to the first embodiment of the present invention.

FIG. 4 is a top view of an example circuit layout according to the second embodiment of the present invention.

FIG. 5 is a top view of an example circuit layout according to the third embodiment of the present invention.

FIG. 6 is a top view of an example circuit layout according to the fourth embodiment of the present invention.

FIG. 7 is a top view of an example circuit layout according to the fifth embodiment of the present invention.

FIG. 8 is a top view of an example circuit layout according to the sixth embodiment of the present invention.

FIG. 9 is a top view of an example circuit layout according to the seventh embodiment of the present invention.

FIG. 10 is a top view of an example circuit layout, and cross-sectional views of an illustrative pixel according to the eighth embodiment of the present invention.

FIG. 11 is a cross-sectional view showing an example of the configuration of principal parts in a pixel according to the third embodiment of the present invention.

FIG. 12 isschematic diagrams illustrating the imaging device according to the embodiment of the present invention.

FIG. 13 is a block diagram of electronic apparatus according to the embodiment of the present invention.

FIG. 14 isexamples of technologies to which the image sensor of the present invention is applied.

FIG. 15 isexample of technologies to which the image sensor of the present invention is applied.

Embodiments

Hereinafter, an embodiment of the present invention will be described in detail with reference to the attached drawings. In addition, in this specification and the drawings, like constituent elements having substantially the same function and configuration are denoted by like reference numerals, and redundant description will be omitted.

Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The terms “coupled” and “connected” , which are utilized herein, are defined as follows. The term “connected” is used to describe a direct connection between two circuit elements, for example, by way of a metal line formed in accordance with normal integrated circuit fabrication techniques. In contrast, the term “coupled” is used to describe either a direct connection or an indirect connection between two circuit elements. For example, two coupled elements may be directly coupled by way of a metal line, or indirectly connected by way of an intervening circuit element (e.g., a capacitor, resistor, or by way of the source/drain terminals of a transistor) . The term “circuit” means either a single component or a multiplicity of components, either active or passive, that are coupled together to provide a desired function. The term “signal” means at least one current, voltage, or data signal. Should the invention involve a stacked chip arrangement, the front sides of two chips may be directly connected since the electrical interconnects on each chip will most commonly be formed on the front sides of each chip, or the front side of one chip may be directly connected to the backside of the second, which may employ through chip interconnects. Although circuit elements may be fabricated on the back side, when reference is made to certain circuit elements residing within or formed in a substrate, this is generally accepted to mean the circuits reside on the front side of the substrate.

<<<Imaging device>>>

First, animaging device 100 according toan embodiment of the present invention will be described in detail. Theimaging device 100 according to this embodiment of the present invention includes the following features: a substrate comprising an photodiode; a floating diffusion comprising a wiring connecting position; anda source follower device being electrically connected to the floating diffusion, and comprising a gate, a source, a channel, and a drain; wherein the source of the source follower comprises a wiring connecting position, and the drain of the source follower comprises a wiring connecting position, and wherein at least one of the wiring connecting position of the source and the wiring connecting position of the drain is placed opposite side to the floating diffusion with respect to the gate of the source follower device in planar view of the substrate. Theimaging device 100 may be solid-state imaging device.

<< First embodiment >>

FIG. 1 is a top view of an example circuit layout according to the first embodiment of the present invention. In the present embodiment, a top view means the pixel array of the imaging device is seen as a flat surface. As shown in FIG. 1, animaging device 100 according to the first embodiment of the present invention includes a first photodiode 1501, a second photodiode 1502, a third photodiode1503, a fourthphotodiode 1504, a first transfer device 4501, a second transfer device 4502, a third transfer device 4503, a fourth transfer device 4504, a floating diffusion 300, a dual conversion gain device 400, a reset device 500, a source follower device 600, and a select device 700. The dual conversion gain device 400 has a gate 401, a source 402, and a drain 403. The reset device 500 has a gate 501, a source 502, and a drain 503. The source follower device 600 has a gate 601, a drain 602, a source 603, and a channel 604. The select device 700 has a gate 701, a drain 702, and a source 703.

< Structure >

(Substrate)

Elements of the imaging device 100 can be arranged on a substrate (not shown in the FIGs. ) . The semiconductor substrate may consist of semiconductor material such as silicon or germanium. In some embodiments, the substrate may consist of at least one or more of other radiation sensitive materials, such as silicon germanium, silicon carbide, gallium arsenide, gallium phosphide, indium phosphide, indium arsenide, indium, antimonide, semiconductor on insulator or combinations thereof.

(Photodiode)

In the some embodiment, the imaging device 100 includes the photodiode 150. As shown in FIG. 1, the first photodiode 1501, the second photodiode 1502, the third photodiode 1503, and the fourth photodiode 1504 are shared the one floating diffusion 300. As shown in FIG. 1, an active area of the first photodiode 1501 makes contact with the second photodiode 1502. Both of the active areas of the first photodiode 1501 and the second photodiode 1502 make contact with the floating diffusion 300. An active area of the third photodiode 1503 makes contact with the fourth photodiode 1504. Both of the active areas of the third photodiode 1503 and the fourth photodiode 1504 make contact with the floating diffusion 300. On the other hand, the active areas of the first photodiode 1501 and the second photodiode 1502 does not make contact with the active areas of the third photodiode 1503 and the fourth photodiode 1504. That is, the active areas of the first photodiode 1501 and the second photodiode 1502 are placed apart from the active areas of the third photodiode 1503 and the fourth photodiode 1504.

(Transfer device)

In the some embodiment, the imaging device 100 includes the transfer device 450. The transfer device 450 is electrically connected to one part of the photodiode 150. As shown in FIG. 1, in the present embodiment, the imaging device 100 includes thefirst transfer device 4501, the second transfer device4502, the third transfer device4503, and the fourth transfer device4504. The first transfer device 4501transfer charges stored in the first photodiode1501 to the floating diffusion 300. The second transfer device 4502 transfer charges stored in the second photodiode 1502 to the floating diffusion 300. The third transfer device 4503 transfer charges stored in the third photodiode 1503 to the floating diffusion 300. The fourth transfer device 4504 transfer charges stored in the fourth photodiode 1504 to the floating diffusion 300. A channel of the first transfer device 4501 may share one active area with a channel of the second transfer device 4502. A channel of the third transfer device 4503 may share one active area with a channel of the fourth transfer device 4504. The floating diffusion 300 may share one active area with drains of the first transfer device 4501, the second transfer device 4502, the third transfer device 4503, and the fourth transfer device 4504.

The first transfer device 4501 has a transfer gate. The second transfer device 4502 has a transfer gate. The third transfer device 4503 has a transfer gate. The fourth transfer device 4504 has a transfer gate. Projection area of the gate 4511, the gate 4512, the gate 4513, and the gate 4514 are within the active areas of the first photodiode 1501, the second photodiode 1502, the third photodiode 1503, and the fourth photodiode 1504 in planar view of the substrate. The gate 4511, the gate 4512, the gate 4513, and the gate 4514 may be vertical transfer gate.

The imaging device 100 according to the present embodiment employs a configuration capable of reading out the charges stored in the photodiode 150 by the transfer device 450.

The transfer device 450 can be constituted by including an n layer forming a floating diffusion 300 to which the charges stored in the storage capacity parts formed in the sub-areas in the photoelectric conversion part 170 are transferred, a p type layer which is formed between the semiconductor layer 160 and the n layer forming the floating diffusion 300, and a gate electrode which is formed through an insulation film on at least the semiconductor layer 160.

The transfer device 450 is connected between the photodiode 150 and the floating diffusion 300. The transfer device 450 is controlled through a control signal TG. The transfer device 450 is selected in a period where the control signal TG is at a high level (H) and becomes a conductive state and transfers the charge (electrons) which is photoelectrically converted and stored in the photodiode 150 to the floating diffusion 300.

(Floating diffusion)

As shown in FIG. 1, the floating diffusion 300 is placed between the active areas of the first photodiode 1501 and the second photodiode 1502 and the active areas of the third photodiode 1503 and the fourth photodiode 1504. The floating diffusion 300 makes contact with a region where the first photodiode 1501 and the second photodiode 1502 are connected. The floating diffusion 300 also makes contact with a region where the third photodiode 1503 and the fourth photodiode 1504 are connected. That is, the smallest distance from the floating diffusion 300 to the active areas of the first photodiode 1501 is substantially the same as the smallest distance from the floating diffusion to the active areas of the second photodiode 1502, the smallest distance from the floating diffusion 300 to the active areas of the third photodiode 1503, and the smallest distance from the floating diffusion 300 to the active areas of the fourth photodiode 1504. A wiring makes contact with floating diffusion 300 at a wiring connectingposition where the smallest distancefrom the floating diffusion 300 tothe four active areasof photodiodesis the same.

The floating diffusion 300 function as a capacitance which temporary accumulates charges being transferred by transfer device 450.

(Dual conversion gain device)

As shown in FIG. 1, the dual conversion gain device 400 is placed between the active area of the third photodiode 1503 and the active area of the fourth photodiode 1504 in planar view of the substrate. The source 402 of the dual conversion gain device 400 makes contact with the active area of the floating diffusion 300. The dual conversion gain device 400 may share an active area with the floating diffusion 300. So, one active area can function as the floating diffusion 300 and the source 402 of the dual conversion gain device 400. The source 402 of the dual conversion gain device 400 is electrically connected to the drain 403 of the dual conversion gain device 400. A channel may be placed between the soured 402 of the dual conversion gain 400 and the drain 403 of the dual conversion gain device 400. The channel of the dual conversion gain device 400 may make contact with the source 402 and the drain 403 of the dual conversion gain device 400. The gate 401 of the dual conversion gain device 400 can switchelectrical connection between the source 402 and the drain 403 of the dual conversion gain 400 on and off.

As shown in FIG. 1, the dual conversion gain 400 is placed apart from the active area of the third photodiode 1503 and the active area of the fourth photodiode 1504 in planar view of the substrate. The smallest distance between the gate 401 of the dual conversion gain 400 and the active area of the third photodiode 1503 is the same as the smallest distance between the gate 401 of the dual conversion gain 400 and the active area of the fourth photodiode 1504.

The drain 403 of the dual conversion gain 400 makes contact with the source 502 of the reset device 500. The drain 403 of the dual conversion gain 400 may share an active area with the source of the reset device 500. That is, one active area function as the drain 403 of the dual conversion gain 400 and the source 502 of the reset device 500.

(Reset device)

As shown in FIG. 1, the reset device 500 is placed between the actives area of the second photodiode 1502 and the fourth photodiode 1504 in planar view of the substrate. The reset device is placed apart from the second photodiode 1502 and the fourth photodiode 1504 in planar view of the substrate. That is, the reset device 500 does not make contact with the actives area of the second photodiode 1502 and the fourth photodiode 1504. The source 502 of the reset device 500 makes contact with the drain 403 of the dual conversion gain device 400. The source 502 of the reset device 500 may share an active area with the drain 403 of the dual conversion gain device 400. That is, one active area functions as the source 502 of the reset device 500 and the drain 403 of the dual conversion gain device 400. The source 502 of the reset device 500 is electrically connected to the drain of the reset device 500. The reset device 500 may has a channel which makes connect with the source 502 and the drain 503 of the reset device 500. The channel of the reset device 500 may be placed between the source 502 and the drain 503 of the reset device 500 in planer view of the substrate. The drain 503 of the reset device 500 is electrically connected to AVDD (power supply voltage) . The gate 501 of the reset device 500 can switch electrical connection between the source 502 and the drain 503 of the dual conversion gain 400 on and off.

(Source follower device)

The source follower device 600is input charge signals from the floating diffusion 300. The source follower device 600 output electron signals. The source follower device 600 amplifies charge signals accumulated in the floating diffusion 300. As shown in FIG. 1, the source follower device 600 is placed between the active area of the first photodiode 1501 and the active area of the third photodiode 1503. In some embodiment, the source follower device 600 may be placed between the active area of the second photodiode 1501 and the active area of the fourth photodiode 1503. The source follower device 600 is placed apart from the active area of the first photodiode 1501, the active area of the third photodiode 1503, and the floating diffusion 300 in planer view of the substrate. In the present embodiment, at least one of the wiring connecting position of the drain 602 and the wiring connecting position of the source 603 is placed opposite side to the floating diffusion with respect to the gate 601 of the source follower device in planar view of the substrate. That is, in the present embodiment, all of the gate 601 is placed between the wiring position of the drain 602and the floating diffusion 300, or all of the gate 601 is placed between the wiring position of the source 603 and the floating diffusion 300. Thereby, the gate 601 of the source follower device 600 is able to be arranged closer to the floating diffusion 300. Thus, capacitance of capacitor formed by a wiring being made contact to the wiring connecting position of floating diffusion and a wiring being made contact to the wiring connecting position of the gate 601 of the source follower device 600 can be decreased. Therefore, a conversion gain of the imaging device 100 can be improved. It is preferable that both of the wiring connecting position of the drain 602 and the wiring connecting position of the source 603 are placed opposite side to the floating diffusion with respect to the gate 601 of the source follower device in planar view of the substrate. Therefore, a conversion gain of the imaging device 100 can be further improved.

In present embodiment, an active area is not placed between the gate 601 of the source follower device 600 and the floating diffusion 300. Thereby, the gate 601 of the source follower device 600 is able to be arranged further closer to the floating diffusion 300. Thus, capacitance of capacitor formed by a wiring being made contact to the wiring connecting position of floating diffusion and a wiring being made contact to the wiring connecting position of the gate 601 of the source follower device 600 can be further decreased. Therefore, a conversion gain of the imaging device 100 can be further improved.

In present embodiment, it is preferable that the gate 601 of the source follower device 600 is placed betweenthe active area of the drain 602and the floating diffusion 300 in planer view of the substrate. That is, all of the gate 601 of the source follower device 600 is placed between all of the active area of the drain 602 and the active area of the floating diffusion 300. Thereby, capacitance of capacitor formed by wiringscan be further decreased. Therefore, a conversion gain of the imaging device 100 can be further improved.

In present embodiment, it is preferable that the gate 601 of the source follower device 600 is placed between the active area of the source 603 and the floating diffusion 300 in planer view of the substrate. That is, all of the gate 601 of the source follower device 600 is placed between all of the active area of the source 603 and the active area of the floating diffusion 300. Thereby, capacitance of capacitor formed by wiringscan be further decreased. Therefore, a conversion gain of the imaging device 100 can be further improved. It is further preferable that the gate 601 of the source follower device 600 is placed between the active area of the source 603 and the floating diffusion 300, and the active area of the drain 602 and the floating diffusion 300 in planer view of the substrate.

In present embodiment, it is preferable that the channel 604 is not placed between the gate 601 of the source follower device 600 and the wiring position of the floating diffusion 300. The channel 604 can be semiconductor. A type of semiconductor of the channel 604 may be different from a type of semiconductor of the drain 602 and the source 603. In the present embodiment, the source follower may have an active area, and the active area may be U-shaped in planar view of the substrate. That is, active areas of the drain 602, the source 603, and the channel 604 may be form U-shape in planar view of the substrate.

In present embodiment, the drain 602 of the source follower device 600 is electrically connected to AVDD (power supply voltage) at a wiring connecting position. The source 603 of the source follower device 600 makes contact with the drain 702 of the select device 700. The source 603 of the source follower device 600 may share an active area with the drain 702 of the select device 700. That is, one active area functions as the source 603 of the source follower device 600 and the source of the select device 700. In the present embodiment, the drain 602, the source 603, and the channel 604 of the source follower device 600 is not electrically to active area of the floating diffusion 300 and the photodiodes.

(Select device)

As shown in FIG. 1, the select device 700 is placed between the active area of the first photodiode 1501 and the active area of the third photodiode. The drain 702 of the select device 700 makes contact with the source 603 of the source follower device 600. The drain 702 of the select device 700 may share an active area with the source 603 of the source follower device 600. That is, one active area functions as the drain 702 of the select device 700 and the source 603 of the source follower device 600. The source 703 of the select device 700 is electrically connected to the drain 702 of the select device 700. In some embodiment, a channel can be placed between the drain 702 and the source 703 of the select device 700. The channel of the select device 700 may make contact with the drain 702 and the source 703 of the select device 700. The source 703 of the select device is electrically connected to Vout (output voltage) . Active areas of the drain 702, the source 703, and the channel are not electrically connected to the active areas of the first photodiode 1501, the third photodiode 1503, and the floating diffusion 300.

High spatial resolution realized by pixel size scaling is highly demanded. As pixel size shrinks down, pixel noise degrades due to high source follower noise of its small dimensions. If much attention was paid for noise, large area consuming source follower device would be placed, it induces low fill factor, and full well capacity drops. Other approach other than increasing source follower device size is increasing conversion gain. The conversion gain is a function of capacitance of floating diffusion node. The lower the capacitance is, the higher conversion gain is. However, it is challenging to decrease the capacitance because parasitic capacitance, comprising of metal wiring is high especially in small pixel size due to high density of metal.

According to present embodiment, animaging devicehas in-pixel source follower amplifier device, and at least one of the wiring connecting position of the source and the wiring connecting position of the drain is placed opposite side to the floating diffusion with respect to the gate of the source follower device in planar view of the substrate. Thereby, the source follower can be placed close to floating diffusion. Capacitance of floating diffusion node drastically decreases because of low parasitic capacitance of metal wiring. Conversion gain would increase accordingly. As a result, read out noise can decrease a lot. Moreover, source follower width can be increased without sacrificing fill factor, then gm of source follower becomes high, which contributes to high speed readout. The high speed readout is critical for high pixel counts array with small pixel size.

In some embodiment, the source follower device has at least one active area of source-drain outside its gate in the direction of its channel, and the source follower placed close to floating diffusion region. As a result, read out noise can further decrease. Moreover, source follower width can be further increased without sacrificing fill factor, then gm of source follower becomes further high, which contributes to further high speed readout.

< Circuit >

FIG. 3 is a circuit diagram showing an example of a pixel according to the second embodiment of the present invention. As shown in FIG. 3, the pixel of the imaging device 100 according to the first embodiment of the present invention includes the photodiodes 1501 1502 1503 1504 1505 1506 1507 1508, the transfer device 4501 4502 4503 4504 4505 4506 4507 4508, a floating diffusion 300, a dual conversion gain device 400, a reset device 500, a source follower device 600, a select device 700 and a current source 800. The floating diffusion 300 is electrically connected to the transfer device 4501. As shown in FIG. 3, the floating diffusion 300 may be electrically connected to the transfer device 4502 4503 4504 4505 4506 4507 4508. In the present embodiment, two photodiodes may share one floating diffusion. Four photodiodes may share one floating diffusion. Eight photodiodes may share one floating diffusion.

The dual conversion gain device 400 is electrically connected to the floating diffusion 300. The reset device 500 is electrically connected to the floating diffusion 300 through the dual conversion gain device 400. The source follower device 600 is electrically connected to the floating diffusion 300. The select device 700 is electrically connected to the source follower device 600. Junction isolation or STI isolation can be used for dividing device elements of animaging device 100. The photodiode 1501 1502 1503 1504 1505 1506 1507 1508are electrically connected to AVSS1 (ground voltage 1) . Each source of the transfer devices 4501 4502 4503 4504 4505 4506 4507 4508is electrically connected to the photodiode 1501 1502 1503 1504 1505 1506 1507 1508. Each drain of the transfer devices 4501 4502 4503 4504 4505 4506 4507 4508 is electrically to the floating diffusion 300. In the present embodiment, the drain of transfer devices 4501 4502 4503 4504 4505 4506 4507 4508 may share active area with the floating diffusion 300. The floating diffusion 300 is electrically connected to the source 402 of the dual conversion gain 400, and the gate 601 of the source follower device 600. The drain 403 of the deal conversion gain 400 is electrically connected to the source 502 of the reset device 500. The drain 503 of the reset device 500 is electrically connected to AVDD (power supply voltage) . The drain 602 of the source follower device 600 is electrically connected to AVDD (power supply voltage) . The source 603 of the source follower device 600 is electrically connected to the drain 702 of the select device 700. The source 703 of the select device 700 is electrically connected to the current source 800, and Vout (output voltage) . The current source 800 is electrically connected to AVSS2 (ground voltage 2) .

In some embodiment, instead of reading out the data as a frame, an “event driven” type of an image sensor may be implemented by using the imaging device 100 according to the present invention. The event driven type of the image sensor may output data in an asynchronous way, in other words, at any time in response to changes in the intensity of electromagnetic radiation incident on one or more pixels. Specifically, for example, if pixel charges generated by electromagnetic radiation incident on one or more photodiodes (or one or more pixels) and stored in the one or more photodiodes exceed a predetermined threshold value, an event of an intensity of the electromagnetic radiation exceeding the threshold value or data representing the intensity of the electromagnetic radiation may be output along with coordinates of the one or more pixels (for example, x and y coordinates in the pixel array) and timing information.

(Photodiode)

The photodiode 1501 1502 1503 1504 1505 1506 1507 1508 generates and accumulates a signal charge (here, electrons) in an amount in accordance with the incident electromagnetic radiation quantity. Below, an explanation will be given of a case where the signal charge includes electrons and each transistor is an n-type transistor, but the signal charge can be holes and some of transistor may also be a p-type transistor. Further, the present embodiment is effective also in the case where each transistor is shared among a plurality of photodiodes and the case where a three-transistor (3Tr) pixel not having a selection transistor is employed.

As the photodiode 1501 1502 1503 1504 1505 1506 1507 1508, a pinned photodiode (PPD) may be used. On the substrate surface forming the photodiode 150, there is a surface level due to dangling bonds or other defects, therefore, a large charge (dark current) is generated by the heat energy, so a correct signal can no longer be read out. In a pinned photodiode (PPD) , a charge accumulation part of the photodiode 1501 1502 1503 1504 1505 1506 1507 1508are buried in the substrate, so it is possible to reduce entry of dark current into the signal.

(Transfer device)

In the present embodiment, the imaging device 100 includes the transfer device 4501 4502 4503 4504 4505 4506 4507 4508. The transfer device 4501 4502 4503 4504 4505 4506 4507 4508 have the transfer gate. The transfer device 4501 4502 4503 4504 4505 4506 4507 4508 transfer charge stored in the photoelectric conversion part 170 are connected to a floating diffusion 300. The transfer device 4501 4502 4503 4504 4505 4506 4507 4508 do not transfer charge which is stored in other pixels of the imaging device 100. The transfer device 4501 4502 4503 4504 4505 4506 4507 4508are electrically connected to one part of the photodiode 1501 1502 1503 1504 1505 1506 1507 1508. The transfer device 4501 4502 4503 4504 4505 4506 4507 4508 transfer charges which is passed through the photodiode 1501 1502 1503 1504 1505 1506 1507 1508. The transfer device 4501 4502 4503 4504 4505 4506 4507 4508 can have an embedded portion in the semiconductor layer 160. The charge transfer gate can be vertical transfer gate.

The imaging device 100 according to the present embodiment employs a configuration capable of reading out the charges stored in the photoelectric conversion part 170 by the transfer device 4501 4502 4503 4504 4505 4506 4507 4508.

The transfer device 4501 4502 4503 4504 4505 4506 4507 4508 can be constituted by including an n layer forming a floating diffusion 300 to which the charges stored in the storage capacity parts formed in the sub-areas in the photoelectric conversion part 170 are transferred, a p type layer which is formed between the semiconductor layer 160 and the n layer forming the floating diffusion 300, and a gate electrode which is formed through an insulation film on at least the semiconductor layer 160.

The transfer device 4501 4502 4503 4504 4505 4506 4507 4508are connected between the photodiode 1501 1502 1503 1504 1505 1506 1507 1508 and the floating diffusion 300. The transfer device 4501 4502 4503 4504 4505 4506 4507 4508are controlled through a control signal TG. The transfer device 4501 4502 4503 4504 4505 4506 4507 4508are selected in a period where the control signal TG is at a high level (H) and becomes a conductive state and transfers the charge (electrons) which is photoelectrically converted and stored in the photodiode 1501 1502 1503 1504 1505 1506 1507 1508 to the floating diffusion 300.

(Floating diffusion)

The floating diffusion 300 can be an n-type semiconductor. The floating diffusion 300 can be electrically connected to a variable capacity part which is connected to a floating diffusion 300 and can change the capacity of the floating diffusion 300 in response to a capacity changing signal.

(Dual conversion gain device)

A dual conversion gain device400 can be connected between a reset device 500 and the floating diffusion 300, in order to realize high dynamic range by combining two types of gains. The dual conversion gain device400 can be constituted by a MOS transistor. In some embodiment, dual conversion gain device 400 can be removed.

(Reset device)

A reset device 500 selectively resets an electrical charge accumulated in the FD. The reset device 500 can be constituted by a MOS transistor.

(Source follower device)

The source follower device 600 can be connected between the select device700 and the floating diffusion 300. The source follower device 600 can be constituted by a MOS transistor or a JFET.

(Select device)

The select device 700 can be connected between the source follower device 600 and the current source 800. The select device 700 can be constituted by a MOS transistor. Select device 700 may be row-select device.

(Current source)

The current source 800 can be connected between the select device700 and a ground. As the current source 800, a known current source 800 can be used.

< Imaging system >

Hereinafter, a second embodiment of the present invention will be described in detail with reference to the attached drawings. FIG. 2 is a block diagram of an imaging system 201 according to the second embodiment of the present invention. As shown in the FIG. 2, the imaging system 201 includes a control circuit 205, a pixel array 209, a readout circuit 210, and a signal processing circuit 206. The pixel array 209 is a two-dimensional array of pixels. Each pixel may be an imaging device as shown in FIG. 1. The pixels are arranged in rows (R1 to Ry) and columns (C1 to Cx) to obtain image data of a subject. The control circuit 205 controls the pixel array 209, for example, generates a shutter signal. The image data is readout by the readout circuit 210 via bit lines and sent to the signal processing circuit 206.

The base substrate may be composed of Si, SiGe, Ge, III-V semiconductor, semiconductor on insulator (SOI) , a semiconductor epitaxial layer, or any other photosensitive materials.

In the present embodiment, the imaging system 201 is, for example, constituted by a CMOS image sensor 201A. In the present embodiment, the imaging system 201 include the imaging device 100 according to the first embodiment. In addition, in the present embodiment, the imaging device 100 has the pixels arranged in a matrix in the pixel array 209 as photoelectric conversion elements. Photoelectric conversion elements are the photoelectric conversion part 170 in the present embodiment. Each of the pixels is formed by a photodiode 150. The photodiode is a pinned photodiode (PPD) in the present embodiment. The constitution of the photodiode 150 can be the same as that of the photodiode 150 in the first embodiment of the present invention.

For example, each pixel in the CMOS image sensor 201A can be constituted by including as active elements, for one photodiode, four elements of a transfer element including a transfer transistor, a reset element including a reset transistor, a source follower element (amplification element) including a source follower transistor, and a selection element including a selection transistor. Further, each pixel can be provided with an overflow gate (overflow transistor) for discharging an overflow charge overflowing from the photodiode in an accumulation period of the photodiode. In addition, each pixel can be provided with a dual conversion gain device400.

The transfer transistor can be connected between the photodiode and an output node including a floating diffusion 300. The transfer transistor can be held in a non-conductive state in the charge accumulation period of the photodiode. In the transfer period transferring the accumulated charges in the photodiode to the floating diffusion 300, a control signal is supplied to the gate whereby it is held in a conductive state and transfers the charges photoelectrically converted in the photodiode to the floating diffusion 300.

The reset transistor is connected between a power supply line and the floating diffusion 300. The reset transistor, when given a reset-use control signal at its gate, resets the potential of the floating diffusion 300 to the potential of the power supply line.

The floating diffusion 300 is connected to the gate of the source follower transistor. The source follower transistor is connected through the selection transistor to the vertical signal line and constitutes a source follower together with a constant current source 800 of a load circuit outside of the pixel part. Further, a control signal (address signal or select signal) is given to the gate of the selection transistor, whereby the selection transistor is turned on. When the selection transistor is turned on, the source follower transistor amplifies the potential of the floating diffusion 300 and outputs a voltage in accordance with that potential to the vertical signal line. Through the vertical signal line, voltages output from the pixels are output to a pixel signal readout circuit 210 constituted by a column-parallel processing part.

Further, in each pixel, as the photodiode 150, a pinned photodiode (PPD) is widely used. On the substrate surface forming the photodiode 150, there is a surface level due to dangling bonds or other defects, therefore a large charge (dark current) is generated by the heat energy, so a correct signal can no longer be read out. In a pinned photodiode (PPD) , a charge accumulation part of the photodiode 150 is buried in the substrate, so it is possible to reduce entry of dark current into the signal. Note that, the sensitivity of a photodiode 150 can be changed by, for example, changing the exposure time, etc.

The pinned photodiode (PPD) is, for example, constituted by forming an n-type semiconductor region and forming a shallow p-type semiconductor region which has a rich impurity concentration for suppressing dark current on the surface of this n-type semiconductor region, that is, in the vicinity of the interface with an insulation film.

<< Second embodiment >>

Hereinafter, animaging device 100A according to a second embodiment of the present invention will be described in detail with reference to the attached drawings. FIG. 4 is a top view of an example circuit layout according to the second embodiment of the present invention. As shown in FIG. 4, in the present embodiment, the source 603 of the source follower device 600 does not share an active area with the drain 702 of the select device 700. The source 603 of the source follower device 600 is electrically connected to the drain 702 of the select device 700 by a wiring. Different from the first embodiment, the select device 700 is not placed between the active area of the first photodiode 1501 and the active area of the third photodiode 1503in planar view of the substrate. The select device 700 is placed between the active area if the third photodiode 1053 and the active area of the fourth photodiode 1054 in planar view of the substrate. As shown in FIG. 4, the select device 700 is not electrically connected the active area of the third photodiode 1053 and the active area of the fourth photodiode 1054.

As shown in FIG. 4, the dual conversion gain is not provided in the present embodiment. The source 402 of the reset device 400 makes contact with the floating diffusion 300. The source 402 of the reset device 400 may share an active area with the floating diffusion 300. The drain 403 of the reset device 400 is electrically connected to AVDD (power supply voltage) . As shown in FIG. 4 the drain 403 of the reset device 400 is electrically connected to AVDD (power supply voltage) by a wiring.

In this configuration, source follower active area has an U-shaped, and contact locations of its source and drain are far from floating diffusion. Therefore capacitance of floating diffusion node drastically decreases, capacitance simulation results showed capacitance of this invention is only 0.29 fF compared with conventional of 1.62 fF in a 0.7 μm pixel size. Conversion gain would reach over 500 μV/e while conventional conversion gain is around 100 μV/e. Source follower width can be increased without sacrificing fill factor, then gm of source follower becomes high, which contributes to high speed readout. The high speed readout is critical for high pixel counts array with small pixel size. Although device isolation can be STI, doping isolation or combinations thereof, STI is better in terms of high conversion gain due to lower parasitic pn junction capacitance. The base substrate includes a semiconductor material such as silicon or germanium. In some embodiments, the substrate can include at least one or more of other photosensitive materials, such as silicon germanium, silicon carbide, gallium arsenide, gallium phosphide, indium gallium arsenide, indium phosphide, indium arsenide, indium antimonide, semiconductor on insulator or combinations thereof.

<< Third embodiment >>

Hereinafter,

animaging device

100B, 100C, 100D, 100E, 100F, according to a third embodiment of the present invention will be described in detail with reference to the attached drawings. FIG. 5 is a top view of an example circuit layout according to the third embodiment of the present invention. As shown in FIG. 5, in the present embodiment, the active areaof the source follower device 600 has a variation. FIG. 5A shows a L-shaped active area of source follower device, FIG. 5B shows source follower channel active area is narrower than that of S/D. FIG. 5C shows source follower source active area is narrower than that of drain. FIG. 5D shows no LDD (lightly doped drain) implant in drain region of source follower. FIG. 5E shows tri-gate source follower. These shows higher conversion gain and/or lower intrinsic source follower noise.

In FIG. 5A, an active area of the source follower device 600 is L-shaped in planar view of the substrate. An active area of the drain 602 of the source follower device 600extends in a direction where the gate of the source follower device and the floating diffusion line up in planar view of the substrate. The source 603 of the source follower device 600 extends in the direction perpendicular to where the gate of the source follower device and the floating diffusion line up in planar view of the substrate. As shown in FIG. 5A, the direction where the gate of the source follower device and the floating diffusion line up in planar view of the substrate is parallel to a direction where the first photodiode 1501 and the second photodiode 1502 line up in planar view of the substrate. In addition, the direction where the gate of the source follower device and the floating diffusion line up in planar view of the substrate is perpendicular to the direction where the first photodiode 1501 and the third photodiode 1503 line up in planar view of the substrate.

In FIG. 5B, a shortest width of the channel 604 of the source follower device 600 is narrower than that of the drain 602 and the source 603 in planar view of the substrate. In the present embodiment, the width of the channel 604 means a length of the channel 604 in direction where the gate of the source follower device and the floating diffusion line up in planar view of the substrate. As shown in FIG. 5B, the width of the channel 604 is smaller than that of the gate 601 of the source follower device 600 in planar view of the substrate. Thereby, conversion gain can be further increased. In the present embodiment, the width of the gate 601 means that a length of the gate 601 in direction where the first photodiode 1501 and the third photodiode 1503 line up in planar view of the substrate.

In FIG. 5C, a shortest width of the drain 602 of the source follower device 600 is narrower than that of the channel 604 and the source 603 in planar view of the substrate. The definition of the width of the drain 602, the width of the channel 604, and the width of the source 603 are the same as in FIG. 5B. In FIG. 5D, the drain 602 of the source follower device 600 has no LDD (lightly doped drain) implant. Thereby, overlap capacitances can be further decreased. Therefore, conversion gain can be further increased.

The right figure of FIG. 5E is a cross section A-A’ in the left figure of FIG. 5E. In FIG. 5E, the gate of the source follower device is a tri-gate structure. Thereby, area that the gate 601 and the channel 604 of the source follower device 600 is in contact. Therefore, lower intrinsic source follower noise can be further decreased.

<<Fourth embodiment >>

Hereinafter,

animaging device

100G, and 100H according to a fourth embodiment of the present invention will be described in detail with reference to the attached drawings. FIG. 6 is a top view of an example circuit layout according to the forth embodiment of the present invention. As shown in FIG. 6A, the source 603, the channel 604, and the drain 602 of the source follower device 600 are placed within an area that is defined by a line running through the gate 601 and being parallel to a direction where the gate 601 of the source follower device 600 and the floating diffusion line up in planar view of the substrate. In other word, the gate 601 ofthe source follower device 600 is wider than the shortest distance between the source 603 end and the drain 602 end. This can increase effective gate length. In addition, this can decrease random telegraph signal noise of the source follower device 600.

As shown in FIG. 6B, a width of the gate 601 in the direction where the gate 601 of the source follower device 600 and the floating diffusion 300 line up are wider than that of the shortest active area regions in planar view of the substrate. In other word, source follower gate is wider than the shortest distance between source and drain end. This can increase mutual inductance (gm) of the source follower device 600, which contributes to high speed readout. The high speed readout is critical for high pixel counts array with small pixel size.

<< Fifth embodiment >>

Hereinafter,

animaging device

100I, 100J, and 100K according to a fifth embodiment of the present invention will be described in detail with reference to the attached drawings. FIG. 7 is a top view of an example circuit layout according to the fifth embodiment of the present invention. As shown in FIG. 7A, each of the transfer gate of the first transfer device 4501 and the third transfer device 4503 has a wiring connecting position 4511 4513, the wiring connecting positions 4511 4513 are placed at a farthest point from the floating diffusion 300 in a direction perpendicular to a direction where the gate of the source follower device 600 and the floating diffusion 600 line up in planar view of the substrate. In addition, each of the transfer gate of the second transfer device 4502 and the fourth transfer device 4504 has a wiring connecting position 4512 4514, the wiring connecting positions 4512 4514 are placed at a farthest point from the floating diffusion 300 in a direction parallel to a direction where the gate of the source follower device 600 and the floating diffusion 600 line up in planar view of the substrate. In other word, the transfergates of the transfer devices contacts in the source follower device 600 side are placed at vertically farthest point from floating diffusion 300, and those in reset or the dual conversion gain 400 side are placed at horizontally farthest point from the floating diffusion 300. Thereby, parasitic capacitance can be further decreased. Therefore, the conversion gain can be further increased.

FIG. 7B shows configuration for two pixels sharing architecture. Left figure of FIG. 7C is a cross-sectional image of transfer gate device 4501, and shows the transfer gate of transfer gate device 4501 has an embedded portion in substrate. The transfer gates of transfer gate devices 4502 4503 4504 also have an embedded portion in substrate.

<< Sixth embodiment >>

Hereinafter,

animaging device

100L, and 100M according to a sixth embodiment of the present invention will be described in detail with reference to the attached drawings. FIG. 8 is a top view of an example circuit layout according to the sixth embodiment of the present invention. As shown in FIG. 8A, a distance from the gate 401 end of the reset device 500 or the gate 501 end of the dual conversion gain device400 to the wiring connecting position of the floating diffusion 300 is far from a distance from the gate 401 end of the reset device 500 or the gate 501 end of the dual conversion gain device400 tothe wiring connecting position of the drain 403 (or 503) . FIG. 8B shows the gate 401 and active area width of the dual conversion gain device400 against the floating diffusion 300 is narrower than that of the drain 403 of the dual conversion gain device 400. These embodiments can further reduce capacitance between floating diffusion and reset source. In FIG. 8B, the gate 501 and active area width of the reset device500 against the floating diffusion 300 may be narrower than that of the drain 503 of the dual conversion gain device 500.

<< Seventh embodiment >>

Hereinafter,

animaging device

100N, 100O, 100P, and 100Q according to a seventh embodiment of the present invention will be described in detail with reference to the attached drawings. FIG. 9 is a top view of an example circuit layout according to the seventh embodiment of the present invention. The seventh embodiment is shown in FIG. 9, in which a device active area shares different device active area. FIG. 9A shows an active area of the drain 702 of the select device 700 shares an active area of the source 603 of the source follower device 600. FIG. 9B shows the dual conversion gain 400 is added, and an active area of the drain 403 of the dual conversion gain 400 shares an active area of the source 502 of the reset device 500. FIG. 9C shows a combination of FIG. 9A and FIG. 9B configuration. FIG. 9D shows placing an additional capacitance on a node between the dual conversion gain 400 and the reset device 500, the additional capacitancecan be MOS capacitor, metal wiring capacitor, MIM or connecting the node to other node between the dual conversion gain 400 and the reset device 500. In the FIG. 9D, contact 901 and Vc 902 forms a capacitance 900. When the dual conversion gain 400 is placed, the reset device 500 is placed far away from the floating diffusion 300, and don’t influence the floating diffusion 300 capacitance. The benefits of these embodiments are increasing fill factor and/or dynamic range.

<< Eighth embodiment >>

Hereinafter, animaging device 100R according to an eighth embodiment of the present invention will be described in detail with reference to the attached drawings. FIG. 10 is a top view of an example circuit layout, and cross-sectional views of an illustrative pixel according to the eighth embodiment of the present invention. As shown in FIG. 10, some electrical connection between source follower gate and floating diffusion are shown. FIG. 10A shows shared contact. FIG. 10B shows metal-0 wiring. Some electrical connection has connection part 951, connection part 952, and connection part 953. Some electrical connection has shared contact 954. Some electrical connection has connection part 955 that is narrower than connection part 951, connection part 956 that is narrower than connection part 952, and connection part 957 that is narrower than connection part 953. These embodiments are effective to reduce parasitic metal capacitance of floating diffusion node.

<< Ninth embodiment >>

Hereinafter, animaging device 100S according to an eighth embodiment of the present invention will be described in detail with reference to the attached drawings. FIG. 11 is a cross-sectional view showing an example of the configuration of principal parts in a pixel according to the third embodiment of the present invention. FIG. 11 illustrates a cross-sectional view of some embodiments. This embodiment shows backside illuminated image sensor, but, it can be frontside illuminated image sensor. Moreover, its DTI depth can be less than radiation sensitive depth, equal to the radiation sensitive depth, or greater than radiation sensitive depth.

As shown in FIG. 11, animaging device 100S has, a semiconductor layer 160, a color filter layer 250, a micro lens 350, a floating diffusion 300, and a transfer transistor 450, anti-reflection 183, a metal grid 185, a deep trench isolation 173, a separation layer 180, an isolation 1732. The photoelectric conversion part 170 and the semiconductor layer 160 form a photodiode 150. The deep trench isolation 173 has a plate portion 1731. The separation layer 180 has a shallow p-well position 1801, and adeep p-well position 1802. The semiconductor layer 160 and the shallowp-well position 1801 are the active area in the other embodiments. Theimaging device 100S has second integrated circuit chip 850.

(Semiconductor layer)

As shown in FIG. 11, the semiconductor layer 160 is made of a second conductivity type semiconductor. The second conductivity type semiconductor can be p-type or n-type semiconductor. In FIG. 11, the semiconductor layer 160 is a p-type semiconductor in the present embodiment. The semiconductor layer 160 is joined with the photoelectric conversion part 170. The deep trench isolation 173 should be an insulator material, thus has no doping. The semiconductor layer 160 can be formed in contact with the photoelectric conversion part 170 at the second side.

(Photoelectric conversion part)

As shown in FIG. 11, the photoelectric conversion part 170 is made of the first conductivity type semiconductor. The photoelectric conversion part 170 can be p-type or n-type semiconductor. In FIG. 11, the photoelectric conversion part 170 is an n-type semiconductor in the present embodiment. The photoelectric conversion part 170 is joined with the semiconductor layer 160 to form the photodiode 150. The first conductivity type semiconductor is different from the second conductivity type semiconductor. The photoelectric conversion part 170 preferably has gradient of the doping concentration.

(The deep trench isolation)

As shown in FIG. 11, the deep trench isolation 173 is formed opposite the photoelectric conversion part 170 with respect to the epitaxial layer 180. In the present embodiment, the deep trench isolation 173 is formed in the portion of the photoelectric conversion part 170. The separation layer 173 covers the said portion of the photoelectric conversion part 170 so that the photoelectric conversion do not make contact with the other parts except for the deep trench isolation 173. The separation layer 173 is formed between two pixels.

A part of the deep trench isolation 173 can be formed in contact with the photoelectric conversion part 170 between the first plane (A) through the first side and the epitaxial layer 180. At least one end of the deep trench isolation 173 can be covered by the epitaxial layer 180. A depth of the deep trench isolation 173 can be equal to or larger than that of the photoelectric conversion part 170 in a direction perpendicular to a normal line of the first side.

As shown in FIG. 11, the deep trench isolation 173 portion is buried inside the separation layer 173 from a side of the second side 172 of a photoelectric conversion part 170. The deep trench isolation 173 portion can be a physical isolation portion. The deep trench isolation 173 portion overlaps the photoelectric conversion part 170 in a direction perpendicular to a normal line of the first side 171.

(Color filter layer)

As shown in FIG. 11, the color filter layer 250 is from on the separation layer 173. In the color filter layer 250, a plurality of color filters may be provided for each pixel, and the colors of the color filters may be arranged, for example, in a Bayer arrangement. The types of the color filter is not limited, and any known color filter can be used. The color filter 250 can include red filter, green filter and blue filter. As shown in FIG. 11, a grid 185 can be placed between the two color filter.

(Micro lens)

The types of the micro lens 350 is not limited, and any known micro lens 350 can be used.

The deep trench isolation 173 is buried inside the deep p-well portion of the separation layer 180. The deep trench isolation 173 does not penetrate the deepp-well position 1802 of the separation layer 180. There is the anti-reflection 183 part between the deepp-well position 1802 of the separation layer 180 and the deep trench isolation 173. The deep trench isolation 173 has a plate portion 1731 and a buried portion. The plate portion 1731 is placed on the second side 172 of the photoelectric conversion part 170. The plate portion 1731 covers pixels. There is the anti-reflection 183 part between the plate portion 1731 and the photoelectric conversion part 170.

FIG. 12 is schematic diagrams illustrating theimaging device 100T according to the embodiment of the present invention. First, a typicalimaging device 100T can be described with reference to A in FIG. 12. The typicalimaging device 100T includes a pixel array, a control circuit, and a logic circuit for signal processing, which are mounted on a single semiconductor chip. In general, an image sensor includes the pixel array and the control circuit. The pixel array can be frontside illuminations, and can be backside illuminations.

As shown in B in FIG. 12, on the other hand, animaging device 100T according to the embodiment of the present invention includes a pixel array and a control circuit (control region) mounted on a first semiconductor chip section and a logic circuit including a signal processing circuit for signal processing mounted on a second semiconductor chip section. The first semiconductor chip section and the second semiconductor chip section are electrically connected to each other, and can be to form a single semiconductor chip to provide theimaging device 100T.

As shown in C in FIG. 12, in theimaging device 100T according to embodiment of the present invention, the pixel array can be mounted on the first semiconductor chip section. Also, the control circuit and the logic circuit including signal processing circuit can be mounted on the second semiconductor chip section. The first semiconductor chip section and the second semiconductor chip section can be electrically connected to each other, and can be to form a single semiconductor chip to provide theimaging device 100T.

As shown in D in FIG. 12, in theimaging device 100T according to embodiment of the present invention, a pixel array can be is mounted on a first semiconductor chip section. Also, the memory circuit can be mounted on a second semiconductor chip section. Then, a control circuit and a logic circuit including signal processing circuit can be mounted on a third semiconductor chip section. The first semiconductor chip section and the second semiconductor chip section and the third semiconductor chip section can be electrically connected, and can be to form a single semiconductor chip or two semiconductor chips to provide the imaging device 100T.

As shown in E in FIG. 12, in theimaging device 100T according to embodiment of the present invention, a pixel array can be mounted on a first semiconductor chip section. Also, a pixel circuit can be mounted on a second semiconductor chip section. Then, a control circuit and a logic circuit including signal processing circuit can be mounted on a third semiconductor chip section. The first semiconductor chip section and the second semiconductor chip section and the third semiconductor chip section can be electrically connected, and can be to form a single semiconductor chip or two semiconductor chips to provide theimaging device 100T.

Theimaging device 100T according to the embodiment of the present invention can be applied to both of a frontside-illuminated type image sensor and backside-illuminated type image sensor.

Hereinafter, electronic apparatus according to an embodiment of the present invention will be described in detail with reference to the attached drawings.

<<Electronic apparatus>>

FIG. 13 is a block diagram of electronic apparatus according to the embodiment of the present invention. As shown in FIG. 13, the electronic apparatus 201A includes a lens 202A, a shutter203A, an imaging sensor209A, a signal processing circuit 206A, a monitor 207A, a memory 208A, and an control circuit 205A. Furthermore, in the electronic device 201A, the signal processingcircuit 206A, the monitor 207A, the memory 208A, a power source unit (not shown) , and the control circuit 205A are connected to each other via a bus line 209.

For example, the imaging sensor 209A corresponds to the imaging device 100. The signal processingcircuit 206A is a camera signal processing circuit for processing a signal supplied from the imaging sensor 209A. The signal processing circuit 206A outputs image data obtained by processing the signal from the imaging sensor 209A. The memory 208A temporarily holds the image data processed by the signal processing circuit 207A in memory. The monitor 207A includes, for example, a panel type display device such as a liquid crystal panel and an organic Electro Luminescence (EL) panel and displays a moving image or a still image imaged by the imaging sensor 209A. The memory 208A records the image data of the moving image or the still image imaged by the imaging sensor 209A to a recording medium such as a semiconductor memory or a hard disk. The control circuit 205A outputs an operation instruction regarding various functions of the electronic device 201A according to a user’s operation. The power source unit (not shown) appropriately supplies various power sources to be an operation power source of the signal processing circuit 206A, the memory 208A, the monitor 207A, the memory 208A, and the control circuit 205A to these components which are supply targets. FIG. 14 is examples of technologies to which the image sensor of the present invention is applied.

FIG. 14 is examples of technologies to which the image sensor of the present invention is applied. As shown in the FIG. 14, the imaging device 100 explained above can be applied as imaging device to an electronic apparatus such as a digital camera, video camera, portable terminal, or monitoring camera, camera for medical endoscope.

FIG. 15 is a block diagram of an exemplary schematic configuration of a vehicle control system 111. As shown in FIG. 15, a vehicle 12100 includes, as the image capturing sections 12031,

image capturing sections

12101, 12102, 12103, 12104, and 12105. The

image capturing sections

12101, 12102, 12103, 12104, and 12105 include the imaging device according to present invention. For example, the

image capturing sections

12101, 12102, 12103, 12104, and 12105 are provided at positions such as the front nose, the side-view mirrors, the rear bumper or the back door, and an upper part of the windshield in the cabin of the vehicle 12100. Each of the image capturing section 12101 on the front nose and the image capturing section 12105 on the upper part of the windshield in the cabin mainly obtains an image of an environment in front of the vehicle 12100. The image capturing sections 12102 and 12103 on the side-view mirrors mainly obtain an image of an environment on the side of the vehicle 12100. The image capturing section 12104 provided in the rear bumper or the back door mainly obtains an image of an environment behind the vehicle 12100. The images of the environment in front of the vehicle obtained by the

image capturing sections

12101 and 12105 are mainly used for detecting a preceding vehicle, a pedestrian, an obstacle, a traffic light, a traffic sign, a lane, or the like.

Note that FIG. 15 shows examples of photographing ranges of the image capturing sections 12101 to 12104.

At least one of the image capturing sections 12101 to 12104 may have a function of obtaining distance information. For example, at least one of the image capturing sections 12101 to 12104 may be a stereo camera including a plurality of imaging elements or an imaging element including pixels for phase difference detection.

For example, the microcomputer obtains the distance between the vehicle 12100 and each three-dimensional object in the imaging ranges 12111 to 12114 and the temporal change (relative speed to the vehicle 12100) of the distance on the basis of the distance information obtained from the image capturing sections 12101 to 12104, and may extract, as a preceding vehicle, especially a three-dimensional object which is the closest to the vehicle 12100 on the path on which the vehicle 12100 is traveling and which is traveling at a predetermined speed (e.g., 0 km/h or more) in the direction substantially the same as the traveling direction of the vehicle 12100. Further, the microcomputer may perform autobrake control (including follow-up stop control) , automatic acceleration control (including follow-up start-driving control) , and the like by presetting a distance to be secured between the vehicle 12100 and a preceding vehicle. In this way, it is possible to perform cooperative control intended to achieve autonomous driving without the need of drivers' operations, and the like.

For example, the microcomputer may sort three-dimensional object data of three-dimensional objects into motorcycles, standard-size vehicles, large-size vehicles, pedestrians, and the other three-dimensional objects such as utility poles on the basis of the distance information obtained from the image capturing sections 12101 to 12104, extract data, and use the data to automatically avoid obstacles. For example, the microcomputer sorts obstacles around the vehicle 12100 into obstacles that a driver of the vehicle 12100 can see and obstacles that it is difficult for the driver to see. Then, the microcomputer determines a collision risk, which indicates a hazard level of a collision with each obstacle. When the collision risk is equal to or higher than a preset value and thus there is a possibility of collision, the microcomputer may perform driving assistance to avoid a collision by outputting a warning to the driver via the audio speaker or the display section, or by forcibly reducing the speed or performing collision-avoidance steering via the drive system control unit 12010.

At least one of the image capturing sections 12101 to 12104 may be an infrared camera that detects infrared light. For example, the microcomputer may recognize a pedestrian by determining whether or not images captured by the image capturing sections 12101 to 12104 include the pedestrian. The method of recognizing a pedestrian includes, for example, a step of extracting feature points in the images captured by the image capturing sections 12101 to 12104 being infrared cameras, and a step of performing a pattern matching process with respect to a series of feature points indicating an outline of an object, to thereby determine whether or not the object is a pedestrian. When the microcomputer determines that the images captured by the image capturing sections 12101 to 12104 include a pedestrian and recognizes the pedestrian, the sound/image output section controls the display section such that a rectangular contour is displayed overlaid on the recognized pedestrian to emphasize the pedestrian. Further, the sound/image output section may control the display section such that an icon or the like indicating a pedestrian is displayed at a desired position.

An example of the vehicle control system to which the technology according to the present disclosure can be applied has been described above. The technology according to the present disclosure can be applied to the image capturing section and the like in the configuration described above.

<<Method for manufacturing animaging device>>

According to the present embodiment, known methods may be used for manufacturing an imaging device in present disclosure.

It should be noted that the embodiments of the present technology are not limited to the abovementioned embodiments, and various modifications can be made without departing from the gist of the present technology.

Reference throughout this specification to “one embodiment, ” “an embodiment, ” “one example, ” or “an example” means that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. Thus, the appearances of the phrases such as “in one embodiment” or “in one example” in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments or examples. Directional terminology such as “top” , “down” , “above” , “below” are used with reference to the orientation of the figure (s) being described.

Also, the terms “have, ” “include, ” “contain, ” and similar terms are defined to mean “comprising” unless specifically stated otherwise. Particular features, structures or characteristics may be included in an integrated circuit, an electronic circuit, a combinational logic circuit, or other suitable components that provide the described functionality. In addition, it is appreciated that the figures provided herewith are for explanation purposes to persons ordinarily skilled in the art and that the drawings are not necessarily drawn to scale.

Industrial Applicability

According to the present invention, it is possible to provide animaging device and electronic apparatus being able to have low read out noise, and a methodfor manufacturing an imaging device.

Designations

imaging device 100

semiconductor layer 160

photoelectric conversion part 170

color filter layer 250

micro lens 350

dual conversion gain device 400

reset device 500

source follower device 600

select device 700

current source 800

imaging system 201

control circuit 205

signal processing circuit 206

pixel array 209

readout circuit 210

floating diffusion 300

constant current source 800

Claims

Animaging device comprising:

a substrate comprising an photodiode;

a floating diffusion comprising a wiring connecting position; and

a source follower device being electrically connected to the floating diffusion, and comprising a gate, a source, a channel, and a drain;

wherein the source of the source follower comprises a wiring connecting position, and the drain of the source follower comprises a wiring connecting position, and

wherein at least one of the wiring connecting position of the source and the wiring connecting position of the drain is placed opposite side to the floating diffusion with respect to the gate of the source follower device in planar view of the substrate.
The imaging device according to Claim 1, further comprising:

a first transfer gate and a second transfer gate,

wherein the source and the drain of the source follower device are placed between the first transfer gate and the second transfer gate in planar view of the substrate.
The imaging device according to Claim 1 or 2,

wherein the source follower comprises an active area, and the active area are U-shaped in planar view of the substrate.
The imaging device according to Claim 1 or 2,

wherein the source follower comprises an active area, and the active area is L-shaped in planar view of the substrate.
The imaging device according to any one of Claims 1 to 4, wherein a shortest width of the channel of the source follower device is narrower than that of the source and the drain in planar view of the substrate.
The imaging device according to any one of Claims 1 to 4, wherein a shortest width of the source of the source follower device is narrower than that of the channel and the drain in planar view of the substrate.
The imaging device according to any one of Claims 1 to 6,

wherein the drain of the source follower device comprises no lightly doped drain implant.
The imaging device according to any one of Claims 1 to 7,

wherein the gate of the source follower device is a tri-gate structure.
The imaging device according to any one of Claims 1 to 8,

wherein the source, the channel, and the drain are placed within an area that is defined by a line running through the gate and being parallel to a direction where the gate of the source follower device and the floating diffusion line up in planar view of the substrate.
The imaging device according to any one of Claims 1 to 9,

wherein a width of the gate in the direction where the gate of the source follower device and the floating diffusion line up are wider than that of the shortest active areas in planar view of the substrate.
The imaging device according to Claim 2,

wherein each of the first transfer gate and the second transfer gate comprises a wiring connecting position, the wiring connecting position is placed at a farthest point from the floating diffusion in a direction perpendicular to a direction where the gate of the source follower device and the floating diffusion line up in planar view of the substrate.
The imaging device according to any one of Claims 1 to 11,

wherein at least two photodiodes share one floating diffusion.
The imaging device according to any one of Claims 1 to 12,

wherein at least two photodiodes share one source follower device.
The imaging device according to any one of Claims 1 to 13,

wherein a transfer gate comprises an embedded portion in the substrate.
The imaging device according to any one of Claims 1 to 14, further comprising:

a dual conversion gain device and a reset device,

wherein a distance from an end of a gate of a dual conversion gain device to a wiring connecting position of the floating diffusion contact is far from a distance from an end of a gate of a reset device to a wiring connecting position of a drain of a reset device.
The imaging device according to any one of Claims 1 to 14, further comprising:

a dual conversion gain device and a reset device,

wherein a distance from an end of a gate of a reset device to a wiring connecting position of the floating diffusion contact is far from a distance from an end of a gate of a dual conversion gain device to a wiring connecting position of a drain of a dual conversion gain device.
The imaging device according to any one of Claims 1 to 16,

wherein a height of the gate of the source follower device is less than that of the source and the drain in direction perpendicular to a surface of the substrate.
The imaging device according to Claim 15 or 16,

wherein a distance of a gate and an active area of a reset device against the floating diffusion is narrower than that of the drain of the reset device in the direction perpendicular to a direction where the gate of the source follower device and the floating diffusion line up in planar view of the substrate.
The imaging device according to any one of Claims 1 to 18, further comprising:

a select device,

wherein an active area of a drain of the select device shares an active area of the source of the source follower device.
The imaging device according to Claim 15 or 16,

wherein an active area of the drain of a dual conversion gain device shares an active area of a source of areset device.
The imaging device according Claim 15 or 16,

wherein an additional capacitance on a node is placed between the dual conversion gain device and the reset device.
The imaging device according to any one of Claims 1 to 21,

wherein the gate of the source follower device and the floating diffusion can be electrically connected by a shared contact.
The imaging device according to any one of Claims 1 to 21,

wherein the gate of the source follower device and the floating diffusion can be electrically connected by metal-0 wiring.
The imaging device according to any one of Claims 1 to 22, further comprising:

an isolation for separating devices,

wherein the isolation comprises STI or doping isolation.
An electronic apparatus comprising:

animaging deviceaccording to any one of Claims 1 to 24.