JP2024166814A - Photoelectric conversion device and photoelectric conversion system - Google Patents

Abstract

To provide a technique advantageous in improving sensitivity to the infrared range in a photoelectric conversion apparatus including an avalanche photodiode.SOLUTION: A photoelectric conversion apparatus includes: a first semiconductor layer that has a first surface and a second surface; an avalanche photodiode that is arranged in the first semiconductor layer; an electrode layer that is arranged to contact the first surface such that a Schottky barrier diode is formed in a contact portion with the first semiconductor layer; and a first wiring structure that is arranged to contact the second surface. The avalanche photodiode is arranged between the second surface and the Schottky barrier diode. Light from outside enters the first semiconductor layer via the first wiring structure.SELECTED DRAWING: Figure 7

Description

The present invention relates to a photoelectric conversion device and a photoelectric conversion system.

Photodetectors that use avalanche photodiodes are known. Patent Document 1 shows a photodetector in which a sensor chip having an avalanche photodiode and a logic chip having a circuit for processing a signal output from the avalanche photodiode are stacked. The avalanche photodiode has an n-type semiconductor region and a p-type semiconductor region disposed below the n-type semiconductor region. The p-type semiconductor region has a multiplication region that avalanche-multiplies carriers generated by the incidence of light to be detected.

JP 2018-201005 A

With the photodetector described in Patent Document 1, it is difficult to improve sensitivity in the infrared range, for example, the shortwave infrared range.

The present invention aims to provide an advantageous technology for improving infrared sensitivity in a photoelectric conversion device having an avalanche photodiode.

One aspect of the present invention relates to a photoelectric conversion device, the photoelectric conversion device comprising a first semiconductor layer having a first surface and a second surface, an avalanche photodiode disposed in the first semiconductor layer, an electrode layer disposed in contact with the first surface to form a Schottky barrier diode at the contact portion with the first semiconductor layer, and a first wiring structure disposed in contact with the second surface, the avalanche photodiode being disposed between the second surface and the Schottky barrier diode, and external light being incident on the first semiconductor layer through the first wiring structure.

The present invention provides an advantageous technique for improving infrared sensitivity in a photoelectric conversion device having an avalanche photodiode.

FIG. 1 is a diagram showing an example of the configuration of a photoelectric conversion device according to an embodiment. FIG. 4 is a diagram showing an example of the configuration of a first substrate. FIG. 4 is a diagram showing an example of the configuration of a second substrate. FIG. 2 is a diagram showing an example of the configuration of a pixel and a signal processing unit. FIG. 4 is a diagram for explaining a photon detection operation. FIG. 2 is a plan view of a pixel according to the first embodiment. FIG. 2 is a cross-sectional view of a pixel according to the first embodiment. FIG. 11 is a cross-sectional view of a pixel according to a second embodiment. FIG. 13 is a cross-sectional view of a pixel according to a third embodiment. FIG. 13 is a cross-sectional view of a pixel according to a fourth embodiment. FIG. 13 is a cross-sectional view of a pixel according to a fifth embodiment. FIG. 1 is a diagram showing an example of the configuration of a photoelectric conversion system. FIG. 1 is a diagram showing an example of the configuration of a photoelectric conversion system. FIG. 1 is a diagram showing an example of the configuration of a photoelectric conversion system.

The following embodiments are described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe multiple features, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicate explanations are omitted.

FIG. 1 shows a schematic configuration example of a photoelectric conversion device 100 according to an embodiment of the present disclosure. The photoelectric conversion device 100 may have a structure in which a first substrate 11 and a second substrate 21 are stacked. The first substrate 11 may include a pixel array 12. The second substrate 21 may include a processing circuit 22 that processes signals output from the pixel array 12.

2 shows a schematic configuration example of the first substrate 11. The pixel array 12 of the first substrate 11 may include a plurality of pixels 101 arranged to form a plurality of rows and a plurality of columns. Each pixel 101 may have a photoelectric conversion unit 102. Each photoelectric conversion unit 102 includes an avalanche photodiode (hereinafter also referred to as an APD) and a Schottky barrier diode (hereinafter also referred to as an SBD) connected in series. A configuration including an APD and an SBD connected in series is advantageous for improving sensitivity in the infrared range, for example, the shortwave infrared range. In the following description, the photoelectric conversion device 100 is exemplarily described as an imaging device. However, the photoelectric conversion device 100 may be configured as another device. For example, the photoelectric conversion device 100 may be configured as a distance measuring device (for example, a focus detection device, a distance measuring device using TOF (Time Of Flight)), or a photometric device (for example, a device that measures the amount of incident light), etc. Note that the multiple pixels 101 may be arranged in a line, in which case the photoelectric conversion device 100 may constitute a line sensor. Hereinafter, the pixel 101 is defined as having a photoelectric conversion unit 102. Note that the pixel 101 may also be referred to as a unit cell, and the pixel array 12 may also be referred to as a unit cell array.

FIG. 3 shows a schematic configuration of the processing circuit 22 of the second substrate 21. The processing circuit 22 may include, for example, a plurality of signal processing units 103, a readout circuit 112, a control unit 115, a horizontal scanning circuit 111, a plurality of signal lines 113, a vertical scanning circuit 110, an output unit 114, and the like. Each signal processing unit 103 processes a signal output from a pixel 101. One signal processing unit 103 may be provided for one pixel 101, or one signal processing unit 103 may be provided for two or more pixels 101. In one example, one pixel 101 and one signal processing unit 103 may be electrically connected by a connection unit. The signal processing unit 103 may include, for example, a counter and a memory. The memory may hold the count value counted by the counter. Specific configurations of the connection unit include, for example, a structure in which conductor patterns such as copper are joined together, a structure using microbumps, and a structure in which a through electrode is provided.

The vertical scanning circuit 110 may, for example, sequentially select multiple rows of the pixel array 12 according to a control signal supplied from the control unit 115. The vertical scanning circuit 110 may supply control signals to the pixel array 12 via multiple control signal lines 116. The vertical scanning circuit 110 may, for example, include at least one of a shift register and an address decoder. The readout circuit 112 reads out signals output from the signal processing unit 103 via multiple signal lines 113 corresponding to the pixels 101 of the row selected by the vertical scanning circuit 110. The horizontal scanning circuit 111, for example, supplies one row's worth of signals read out by the readout circuit 112 to the output unit 114 in a predetermined order.

FIG. 4 shows an example of the configuration of the photoelectric conversion unit 102 and the signal processing unit 103. In the example shown in FIG. 4, one signal processing unit 103 is assigned to one photoelectric conversion unit 102. The photoelectric conversion unit 102 includes a series connection of an APD 201 and an SBD 221. As described above, the photoelectric conversion unit 102 is arranged on the first substrate 11, and the signal processing unit 103 is arranged on the second substrate 21. However, at least one of the multiple components of the signal processing unit 103 may be arranged on the first substrate 11. Alternatively, all of the multiple components of the signal processing unit 103 may be arranged on the first substrate. The solid line indicates the boundary between the first substrate 11 and the second substrate 21, and indicates the position of the joint. In this embodiment, one photoelectric conversion unit 102 and one signal processing unit 103 are paired.

A first potential VL may be applied to the anode of APD201, and a second potential VH may be applied to the cathode of APD201. The second potential VH is a potential higher than the first potential VL. That is, a potential difference between the first potential VL and the second potential VH is applied to APD201 (between the anode and cathode of APD201). This potential difference is a reverse bias voltage that causes APD201 to perform avalanche multiplication. The charge generated by the photons incident on APD201 causes avalanche multiplication, which generates an avalanche current. A third potential VSB may be applied to the anode of SBD221, and a first potential VL may be applied to the cathode of SBD221. A mode in which a voltage higher than the breakdown voltage of APD201 is applied between the anode and cathode of APD201 is called Geiger mode. A mode in which a voltage close to or less than the breakdown voltage is applied between the anode and cathode of the APD 201 is called a linear mode. An APD operating in Geiger mode may be called a SPAD (Single Photon Avalanche Diode). In one example, the first potential VL is -30 V, the second potential VH is 1 V, and the third potential VSB is -31 V.

The signal processing unit 103 may include a quench element 202 connected between a terminal to which the second potential VH is supplied and the cathode of the APD 201. The quench element 202 has a function of converting a change in avalanche current generated in the APD 201 into a voltage signal. The quench element 202 functions as a load circuit (quench circuit) during signal multiplication by avalanche multiplication, and has a function of suppressing avalanche multiplication by suppressing the voltage applied to the APD 201. This function is known as a quench operation.

The signal processing unit 103 may also include at least one of a waveform shaping unit 210, a counter circuit 211, and a selection circuit 212. The waveform shaping unit 210 may output a pulse signal by shaping the potential change of the cathode of the APD 201 when detecting a photon. The waveform shaping unit 210 may include, for example, an inverter circuit. In the example of FIG. 4, the waveform shaping unit 210 is composed of one inverter, but the waveform shaping unit 210 may be composed of multiple inverters connected in series, or may be composed of another circuit having a waveform shaping effect.

The counter circuit 211 can be configured to count the pulse signal output from the waveform shaping unit 210 and hold the count value obtained thereby. When an active level control pulse pRES is supplied from the vertical scanning circuit 110 via the drive line 213, the signal held in the counter circuit 211 can be reset. When an active level control pulse pSEL is supplied from the vertical scanning circuit 110 via the drive line 214, the selection circuit 212 can electrically connect the counter circuit 211 and the signal line 113. The selection circuit 212 can include, for example, a buffer circuit.

In this example, a counter circuit 211 is provided. However, the photoelectric conversion device 100 may be configured to acquire the pulse detection timing by providing a time-to-digital converter (TDC) instead of the counter circuit 211. In this case, the generation timing of the pulse signal output from the waveform shaping unit 210 may be converted into a digital signal by the TDC. To measure the timing of the pulse signal, a control pulse pREF (reference signal) may be supplied from the vertical scanning circuit 110 via a drive line to the TDC. The TDC may generate a digital signal corresponding to the generation timing of the pulse signal output from the waveform shaping unit 210 based on the control pulse pREF.

Figure 5 is a diagram explaining the photon detection operation in the photoelectric conversion device 100. Figure 5 (a) is a diagram in which the APD 201, SBD 221, quench element 202, and waveform shaping unit 210 are excerpted from Figure 4. Here, the input side of the waveform shaping unit 210 is node A, and the output side is node B. Figure 5 (b) shows the waveform of node A in Figure 5 (a), and Figure 5 (c) shows the waveform of node B in Figure 5 (a). Between time t0 and t1, a potential difference of VH-VSB is applied to the photoelectric conversion unit 102 consisting of the APD 201 and the SBD 221. Of these, a potential difference of VH-VL is applied to the APD 201, and a potential difference of VL-VSB is applied to the SBD 221. When a photon is incident at time t1, SBD221 generates a charge pair by photoelectric conversion, and avalanche multiplication occurs in APD201 in response to the charge pair. This causes avalanche multiplication current to flow through quench element 202, causing the voltage (electric potential) of nodeA to drop. When the amount of voltage drop increases and the electric potential difference applied to APD201 becomes smaller, avalanche multiplication in APD201 stops. After that, a current that compensates for the voltage drop from voltage VL flows through nodeA, and at time t3, nodeA settles to its original electric potential level. At this time, the portion of the output waveform at nodeA that exceeds a certain threshold is shaped by waveform shaping unit 210, and a pulse signal appears at nodeB.

Figures 6 and 7 show schematic diagrams of two pixels of the photoelectric conversion device 100 of the first embodiment. Here, Figure 6 is a plan view. Note that a plan view is synonymous with an orthogonal projection onto the first surface 303 or the second surface 304 described below, and is also referred to as a planar view. Figure 7 is a cross-sectional view taken along line A-A' in Figure 6. In Figures 6 and 7, the area surrounded by the dotted line is one pixel 101. In Figure 7, the area surrounded by the dotted line includes one pixel 101 and its corresponding signal processing unit 103.

The photoelectric conversion device 100 may include a first substrate 300. The first substrate 300 may include a first semiconductor layer (e.g., a silicon layer) 301 having a first surface 303 and a second surface 304, and a first wiring structure 302 having a second surface 304 and a fourth surface 306. The first wiring structure 302 may include at least one wiring layer each including a conductive pattern, and a plug electrically connected to the conductive pattern. The second surface 304 may be shared by the first semiconductor layer 301 and the first wiring structure 302. Alternatively, the second surface 304 may be an interface between the first semiconductor layer 301 and the first wiring structure 302.

The first substrate 300 may include an encapsulation structure 350 disposed on the side of the first surface 303 of the first semiconductor layer 301. The encapsulation structure 350 has a third surface 305. The first substrate 300 may include a support member 331 bonded to the encapsulation structure 350 directly or via another member. The support member 331 has a fifth surface 307. The support member 331 may be bonded to the third surface 305 of the encapsulation structure 350. The encapsulation structure 350 may include an encapsulation layer 327, a metal layer 328, and an encapsulation layer 329. The metal layer 328 may be disposed between the encapsulation layer 327 and the encapsulation layer 329.

The photoelectric conversion device 100 or the first substrate 300 may include an electrode film 324 arranged in contact with the first surface 303. The first semiconductor layer 301 may include a semiconductor region 309 constituting at least a part of the first surface 303. The electrode film 324 is arranged in contact with the first surface 303 so as to form a Schottky barrier diode 221 at the contact portion between the first semiconductor layer 301 and the semiconductor region 309. The electrode film 324 may be electrically connected to the metal layer 328 via the plug 325. A third potential VSB may be supplied to the electrode film 324 via the metal layer 328 and the plug 325.

The photoelectric conversion device 100 may further include a second substrate 320 disposed on the side of the fourth surface 306 of the first substrate 300. The second substrate 320 and the first substrate 300 may share the fourth surface 306. Alternatively, the fourth surface 306 may be an interface between the second substrate 320 and the first substrate 300. The fourth surface 306 may also be a bonding surface. The second substrate 320 has a sixth surface 308 on the opposite side of the fourth surface 306. The second substrate 320 may include a second semiconductor layer (e.g., a silicon layer) 321 and a second wiring structure 322. The second wiring structure 322 may be bonded to the first wiring structure 302 directly or via another member. In another respect, the first wiring structure 302 and the second wiring structure 322 may be disposed between the first semiconductor layer 301 and the second semiconductor layer 321. In addition, only the first wiring structure 302 or the second wiring structure 322 may be disposed between the first semiconductor layer 301 and the second semiconductor layer 321. The second wiring structure 322 may include at least one wiring layer each including a conductive pattern and a plug electrically connected to the conductive pattern. The second substrate 320 may include a surface protection layer 332 and a sealing layer 333 disposed between the second semiconductor layer 321 and the sixth surface 308. At least a part of the signal processing unit 103 that processes the signal output from the avalanche photodiode 201 (photoelectric conversion unit 102) may be disposed on the second substrate 320 (second semiconductor layer 321).

Light from outside the photoelectric conversion device 100 is incident on the first semiconductor layer 301 through the first wiring structure 302. In another aspect, light from outside the photoelectric conversion device 100 is incident on the first semiconductor layer 301 through the second substrate 320 and the first wiring structure 302. The photoelectric conversion device 100 may include a microlens 340. The microlens 340 may be arranged so that the first wiring structure 302 is located between the microlens 340 and the first semiconductor layer 301. In another aspect, the microlens 340 may be arranged so that the second substrate 320 and the first wiring structure 302 are located between the microlens 340 and the first semiconductor layer 301. The sealing layer 333 may include, for example, a color filter, a planarization film, a protective film made of an inorganic material, etc.

The avalanche photodiode (APD) 201 may be disposed between the second surface 304 and the Schottky barrier diode (SBD) 221. In an orthogonal projection onto the second surface 304, the avalanche photodiode 201 and the Schottky barrier diode 221 may overlap. A potential may be applied to the electrode film 324 such that a depletion region 326 is formed in the semiconductor region 309 of the first semiconductor layer 301. The avalanche photodiode 201 and the Schottky barrier diode 221 may be connected in series via the depletion region 326.

The avalanche photodiode 201 may include a first semiconductor region 311 of a first conductivity type and a second semiconductor region 312 of a second conductivity type. Furthermore, the avalanche photodiode 201 may include a third semiconductor region 313 of the first conductivity type arranged between the second surface 304 and the second semiconductor region 312. In one example, the first conductivity type is n-type and the second conductivity type is p-type, but the opposite may also be true. The third semiconductor region 313 may include a portion arranged between the first semiconductor region 311 and the second semiconductor region 312. The third semiconductor region 313 may also include a portion arranged between the second surface 304 and the second semiconductor region 312 so as to surround the side of the first semiconductor region 311. The semiconductor region 309, which is a part of the first semiconductor layer 301, may be a semiconductor region of the first conductivity type or a semiconductor region of the second conductivity type. It is preferable that the semiconductor region 309 has a lower second conductivity type impurity concentration (Net concentration) than the second semiconductor region 312 and the fourth semiconductor region 314.

The photoelectric conversion device 100 may further include a fourth semiconductor region 314 of the second conductivity type. The fourth semiconductor region 314 is electrically connected to the second semiconductor region 312 and extends between the first surface 393 and the second surface 394 in a direction perpendicular to the first surface 303. A potential may be applied to the second semiconductor region 312 through the fourth semiconductor region 314. The fourth semiconductor region 314 may be arranged so as to surround the first semiconductor region 311, the second semiconductor region 312, and the third semiconductor region 313. A fifth semiconductor region 315 of the second conductivity type may be arranged between the second surface 304 and the fourth semiconductor region 314. The impurity concentration of the second conductivity type in the fifth semiconductor region 315 may be higher than the impurity concentration of the second conductivity type in the fourth semiconductor region 314. An isolation trench 316 may be arranged between the fourth semiconductor region 314 of one pixel and the fourth semiconductor region 314 of the adjacent pixel. The isolation trench 316 is advantageous for reducing crosstalk between adjacent pixels. The isolation trench 316 may be a groove or a through hole provided in the semiconductor layer 301. Inside the isolation trench 316, a pinning layer, a gap, an insulating layer including a dielectric, a layer made of an opaque material for blocking light, etc. may be arranged. The third semiconductor region 313 of the first conductivity type is arranged to cover the corners of the first semiconductor region 311 of the first conductivity type, and may suppress the formation of a local high electric field region between the first semiconductor region 311 of the first conductivity type and the fifth semiconductor region 315 of the second conductivity type.

The photoelectric conversion device 100 may further include a pinning film 323 covering the first surface 303. The pinning film 323 may be an insulating film composed of at least one of hafnium oxide, zirconium oxide, aluminum oxide, titanium oxide, and tantalum oxide, for example. The pinning film 323 has an opening, and the electrode film 324 may be disposed in the opening of the pinning film 323. The pinning film 323 may include a portion disposed between the electrode film 324 and the first surface 303. The first surface 303 of the first semiconductor layer 301 may be sealed with the pinning film 323.

The electrode film 324 is made of a material that forms a Schottky junction between the semiconductor region 309 of the first semiconductor layer 301 and the electrode film 324. The electrode film 324 can be made of, for example, a metal, a metal silicide, or a metal oxide. A Schottky barrier is formed at the Schottky junction due to the difference in work function between the semiconductor region 309 and the electrode film 324. The height of the Schottky barrier is preferably 1/2 or less of the band gap of the semiconductor region 309 that constitutes the first semiconductor layer 301. When the Schottky junction of the Schottky barrier diode 221 is irradiated with infrared light (wavelength 0.8 to 30 um) that has energy exceeding the height of the Schottky barrier, electrons or holes overcome the Schottky barrier and reach the depletion region 326.

The electrode film 324 has a rectangular shape in a top view (orthogonal projection onto the first surface 303) and can be disposed on the first surface 303 of the first semiconductor layer 301. A plug 325 can be disposed in an appropriate position of the electrode film 324, for example, in the center. The electrode film 324 can be covered by a sealing layer 327, a metal layer 328 can be disposed so as to cover the sealing layer 327, and a sealing layer 329 can be disposed so as to cover the metal layer 328. The metal layer 328 can function as a light-shielding layer. The metal layer 328 can also function as a supply path that supplies the third potential VSB to the electrode film 324. A support member 331 can be bonded to the sealing layer 329. The support member 331 can be composed of, for example, an inorganic material such as silicon, glass, or metal, or an organic material such as resin. The dimensions of the electrode film 324 in the direction along the first surface 303 may be larger than the dimensions of the third semiconductor region 313 in the direction along the first surface 303. The area of the electrode film 324 in the direction along the first surface 303 may be larger than the area of the third semiconductor region 313 in the direction along the first surface 303. In this specification, the dimensions and area of the electrode film 324 are the dimensions and area of the portion where the electrode film 324 is in contact with the first surface 303.

The first semiconductor region 311 of the first conductivity type functions as a cathode of the APD 201 and is provided with a second potential VH. The fifth semiconductor region 315 of the second conductivity type functions as an anode of the APD 201 and is provided with a first potential VL. The first potential VL is provided to the second semiconductor region 312 of the second conductivity type through the fourth semiconductor region 314 of the second conductivity type. This forms an avalanche multiplication region in a region where the first semiconductor region 311 of the first conductivity type and the second semiconductor region 312 of the second conductivity type are adjacent to each other. Charges generated by the incident light (which may include charges generated in the SBD 221) cause avalanche multiplication in the avalanche region, generating an avalanche current. The fourth semiconductor region 314 of the second conductivity type may also function as an isolation region between adjacent pixels. The fifth semiconductor region 315 of the second conductivity type can function to reduce the contact resistance between the first semiconductor layer 301 and a conductive member (e.g., a plug) arranged in the first wiring structure 302. The fifth semiconductor region 315 has a higher impurity concentration of the second conductivity type than the fourth semiconductor region 314. The isolation trench 316 is advantageous for reducing crosstalk between adjacent pixels. The third semiconductor region 313 of the first conductivity type is arranged to cover the corners of the first semiconductor region 311 of the first conductivity type, and can suppress the formation of a local high electric field region between the first semiconductor region 311 of the first conductivity type and the fifth semiconductor region 315 of the second conductivity type.

The first wiring structure 302 includes a conductive path CP electrically connected to the first semiconductor region 311 as the cathode of the avalanche photodiode 201. The conductive path CP may include the above-mentioned node A. Here, the conductive path CP may include a conductive pattern WLP arranged in the wiring layer of the first wiring structure 302 and a plug PP that electrically connects the conductive pattern WLP and the first semiconductor region 311. The first wiring structure 302 is arranged between the microlens 340 and the second surface 304, and the conductive path CP may include a portion arranged between the microlens 340 and the second surface 304. A portion of the light incident on the first wiring structure 302 through the microlens 340 may be incident on a portion of the conductive path CP. A portion of the conductive path CP may be arranged in the second wiring structure 322.

The light incident on the microlens 340 is focused by the microlens 340, passes through the light guide region 343 of the second semiconductor layer 321, passes through the light guide region 342 of the second wiring structure 322, and passes through the light guide region 341 of the first wiring structure 302. The light that passes through the light guide region 341 may enter the first semiconductor layer 301 and reach the depletion region 326. The light that reaches the depletion region 326 may be photoelectrically converted to generate photocarriers. The photocarriers may diffuse through the first semiconductor layer 301 and reach the second semiconductor region 312 of the second conductivity type due to an electric field formed in the first semiconductor layer 301 by the third potential VSB applied to the electrode film 324.

The second embodiment of the present disclosure will be described below. Matters not mentioned as the second embodiment may follow the first embodiment. FIG. 8 shows a schematic configuration of two pixels of the photoelectric conversion device 100 of the second embodiment. FIG. 8 corresponds to the A-A' cross section of FIG. 6(a). In the second embodiment, at least a part of the signal processing unit 103 that processes the signal output from the avalanche photodiode 201 (photoelectric conversion unit 102) is arranged on the first substrate 300 (first semiconductor layer 301). The other part of the signal processing unit 103 may be arranged on the second substrate 320 (second semiconductor layer 321). According to the second embodiment, the components of the signal processing unit 103 are distributed and arranged on the first substrate 300 and the second substrate 320, thereby improving the degree of freedom of design.

The third embodiment of the present disclosure will be described below. Matters not mentioned as the third embodiment may follow the first embodiment. Figure 9 shows a schematic configuration for two pixels of the photoelectric conversion device 100 of the third embodiment. Figure 9 corresponds to the A-A' cross section of Figure 6(a). In the third embodiment, the photoelectric conversion device 100 is composed of one substrate 300. The signal processing unit 103 that processes the signal output from the avalanche photodiode 201 (photoelectric conversion unit 102) is disposed on the first substrate 300 (first semiconductor layer 301). Such a configuration is advantageous for reducing costs.

The fourth embodiment of the present disclosure will be described below. Matters not mentioned as the fourth embodiment may follow the first to third embodiments. FIG. 10 shows a schematic configuration of two pixels of the photoelectric conversion device 100 of the fourth embodiment. FIG. 10 corresponds to the A-A' cross section of FIG. 6(a). In the fourth embodiment, the dimension of the electrode film 324 in the direction along the first surface 303 is smaller than the dimension of the third semiconductor region 313 in the direction along the first surface 303. In addition, the area of the electrode film 324 in the direction along the first surface 303 is smaller than the area of the third semiconductor region 313 in the direction along the first surface 303. Such a configuration is advantageous for reducing dark current noise by reducing the area of the Schottky junction.

The fifth embodiment of the present disclosure will be described below. Matters not mentioned as the fifth embodiment may follow the first to fourth embodiments. FIG. 11 shows a schematic configuration of two pixels of the photoelectric conversion device 100 of the fifth embodiment. FIG. 11 corresponds to the A-A' cross section of FIG. 6(a). In the fifth embodiment, the electrode film 324 constituting the Schottky barrier diode 221 has a contact surface that contacts the first surface 303, and the contact surface has unevenness. An uneven structure is arranged on the first surface 303 of the first semiconductor layer 301. Such a configuration is advantageous for improving the photoelectric conversion efficiency by increasing the area of the Schottky junction. In addition, incident light may be reflected and diffracted at the interface between the electrode film 324 and the first semiconductor layer 301, and reflected at the second surface 304. This may improve the photoelectric conversion efficiency.

The following provides an exemplary explanation of a photoelectric conversion system incorporating the photoelectric conversion device described in each of the above embodiments. FIG. 12 shows an example of a photoelectric conversion system. The photoelectric conversion device described in each of the above embodiments is applicable to various photoelectric conversion systems. Examples of applicable photoelectric conversion systems include digital still cameras, digital camcorders, surveillance cameras, copiers, fax machines, mobile phones, vehicle-mounted cameras, and observation satellites. Additionally, camera modules equipped with an optical system such as a lens and an imaging device are also included in photoelectric conversion systems.

The photoelectric conversion system is configured as, for example, an imaging system SYS. The imaging system SYS is an information terminal having a camera or imaging function. The imaging apparatus IS may further include a package PKG that houses the photoelectric conversion apparatus 100 configured as an imaging device IC. The package PKG may include a base to which the imaging device IC is fixed, a lid body that faces the imaging device IC, and a connection member that connects a terminal provided on the base to a terminal provided on the imaging device IC. The imaging apparatus IS may also mount multiple imaging device ICs side by side in a common package PKG. The imaging apparatus IS may also mount an imaging device IC and other semiconductor device ICs stacked on top of each other in a common package PKG.

The imaging system SYS may include an optical system OU that forms an image on the imaging device IS. The imaging system SYS may also include at least one of a control device CU that controls the imaging device IS, a processing device PU that processes signals obtained from the imaging device IS, and a display device DU that displays images obtained from the imaging device IS. The imaging system SYS may also include a memory device MU that stores images obtained from the imaging device IS.

FIG. 13(a) illustrates an example of the configuration of a photoelectric conversion system applied to an in-vehicle camera. The photoelectric conversion system 2300 may have a photoelectric conversion device 100 configured as an imaging device 2310. The photoelectric conversion system 2300 has an image processing unit 2312 that performs image processing on a plurality of image data acquired by the imaging device 2310, and a parallax acquisition unit 2314 that calculates parallax (phase difference of parallax images) from a plurality of image data acquired by the photoelectric conversion system 2300. The photoelectric conversion system 2300 also has a distance acquisition unit 2316 that calculates a distance to an object based on the calculated parallax, and a collision determination unit 2318 that determines whether or not there is a possibility of a collision based on the calculated distance. Here, the parallax acquisition unit 2314 and the distance acquisition unit 2316 are examples of distance information acquisition means that acquire distance information to an object. That is, the distance information is information related to the parallax, the defocus amount, the distance to the object, and the like. The collision determination unit 2318 may determine the possibility of a collision using any of these distance information. The distance information acquisition means may be realized by dedicated hardware or a software module. It may also be realized by a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC), or a combination of these.

The photoelectric conversion system 2300 is connected to a vehicle information acquisition device 2320, and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. The photoelectric conversion system 2300 is also connected to a control ECU 2330, which is a control unit that outputs a control signal to generate a braking force for the vehicle based on the judgment result of the collision judgment unit 2318. The photoelectric conversion system 2300 is also connected to an alarm device 2340 that issues an alarm to the driver based on the judgment result of the collision judgment unit 2318. For example, if the judgment result of the collision judgment unit 2318 indicates that there is a high possibility of a collision, the control ECU 2330 performs vehicle control to avoid a collision and reduce damage by applying the brakes, releasing the accelerator, suppressing engine output, etc. The alarm device 2340 warns the user by sounding an alarm, displaying alarm information on a screen of a car navigation system, etc., or vibrating a seat belt or steering wheel. In this embodiment, the photoelectric conversion system 2300 captures an image of the surroundings of the vehicle, for example, the front or rear.

Figure 13 (b) shows a photoelectric conversion system configured to capture an image of the area in front of the vehicle (imaging range 2350). The vehicle information acquisition device 2320 sends instructions to the photoelectric conversion system 2300 or the imaging device 2310. This configuration can further improve the accuracy of distance measurement.

Although the above describes an example of control to prevent collisions with other vehicles, the system can also be applied to control of automatic driving to follow other vehicles, and control of automatic driving to avoid straying from lanes. Furthermore, the photoelectric conversion system is not limited to vehicles such as the vehicle itself, but can be applied to moving bodies (moving devices) such as ships, aircraft, and industrial robots. In addition, the system can be applied not only to moving bodies, but also to a wide range of equipment that uses object recognition, such as intelligent transport systems (ITS).

Figure 14 illustrates an example of the configuration of a photoelectric conversion system configured as a distance image sensor. The distance image sensor 400 is configured with an optical system 407, a photoelectric conversion device 408, an image processing circuit 404, a monitor 405, and a memory 406. The distance image sensor 400 can obtain a distance image according to the distance to the subject by receiving light (modulated light or pulsed light) that is projected from a light source device 409 toward the subject and reflected from the surface of the subject.

The optical system 407 is configured with one or more lenses, guides image light (incident light) from the subject to the photoelectric conversion device 408, and forms an image on the light receiving surface (sensor unit) of the photoelectric conversion device 408. The photoelectric conversion device of each of the above-mentioned embodiments is applied as the photoelectric conversion device 408, and a distance signal indicating the distance determined from the light receiving signal output from the photoelectric conversion device 408 is supplied to the image processing circuit 404.

The image processing circuit 404 performs image processing to construct a distance image based on the distance signal supplied from the photoelectric conversion device 408. The distance image (image data) obtained by this image processing is then supplied to the monitor 405 for display, or supplied to the memory 406 for storage (recording). In the distance image sensor 400 configured in this manner, by applying the above-mentioned photoelectric conversion device, it is possible to obtain, for example, a more accurate distance image as the pixel characteristics improve.

The present specification and drawings include the following disclosure.
(Document title) Claims
(Item 1)
a first semiconductor layer having a first surface and a second surface;
an avalanche photodiode disposed on the first semiconductor layer;
an electrode film disposed in contact with the first surface so as to form a Schottky barrier diode at a contact portion with the first semiconductor layer;
a first wiring structure disposed in contact with the second surface,
the avalanche photodiode is disposed between the second surface and the Schottky barrier diode;
external light is incident on the first semiconductor layer through the first wiring structure;
A photoelectric conversion device comprising:
(Item 2)
the avalanche photodiode includes a first semiconductor region of a first conductivity type and a second semiconductor region of a second conductivity type;
the first wiring structure includes a conductive path electrically connected to the first semiconductor region;
2. The photoelectric conversion device according to item 1,
(Item 3)
the avalanche photodiode further includes a third semiconductor region of the first conductivity type including a portion disposed between the first semiconductor region and the second semiconductor region;
3. The photoelectric conversion device according to item 2.
(Item 4)
the third semiconductor region further includes a portion disposed between the second surface and the second semiconductor region so as to surround a side surface of the first semiconductor region;
4. The photoelectric conversion device according to item 3,
(Item 5)
the conductive path includes a conductive pattern disposed in a wiring layer of the first wiring structure, and a plug electrically connecting the conductive pattern and the first semiconductor region;
5. The photoelectric conversion device according to item 4,
(Item 6)
Further comprising a microlens,
the first wiring structure is disposed between the microlens and the second surface,
the conductive path includes a portion disposed between the microlens and the second surface.
6. The photoelectric conversion device according to item 5,
(Item 7)
A part of the light incident on the first wiring structure through the microlens is incident on a part of the conductive path.
7. The photoelectric conversion device according to item 6,
(Item 8)
a fourth semiconductor region of the second conductivity type electrically connected to the second semiconductor region and extending between the first surface and the second surface in a direction perpendicular to the first surface,
A potential is applied to the second semiconductor region through the fourth semiconductor region.
8. The photoelectric conversion device according to any one of items 3 to 7.
(Item 9)
the fourth semiconductor region is disposed so as to surround the first semiconductor region, the second semiconductor region, and the third semiconductor region;
9. The photoelectric conversion device according to item 8,
(Item 10)
a fifth semiconductor region of the second conductivity type disposed between the second surface and the fourth semiconductor region,
10. The photoelectric conversion device according to item 9,
(Item 11)
a pinning film covering the first surface so as to surround the electrode film;
11. The photoelectric conversion device according to item 10,
(Item 12)
A support member;
a sealing structure disposed between the first surface and the support member;
12. The photoelectric conversion device according to any one of items 1 to 11, further comprising:
(Item 13)
the sealing structure includes a metal layer disposed between the electrode film and the support member;
13. The photoelectric conversion device according to item 12,
(Item 14)
Further comprising a second semiconductor layer,
the first wiring structure is disposed between the second semiconductor layer and the second surface;
14. The photoelectric conversion device according to any one of items 1 to 13.
(Item 15)
further comprising a second wiring structure disposed between the first wiring structure and the second semiconductor layer;
15. The photoelectric conversion device according to item 14,
(Item 16)
At least a part of a signal processing unit that processes a signal output from the avalanche photodiode is disposed in the second semiconductor layer.
16. The photoelectric conversion device according to item 15,
(Item 17)
At least a part of a signal processing unit that processes a signal output from the avalanche photodiode is disposed in the first semiconductor layer.
17. The photoelectric conversion device according to any one of items 1 to 16.
(Item 18)
a signal processing unit for processing a signal output from the avalanche photodiode is disposed in the first semiconductor layer and the second semiconductor layer in a distributed manner;
16. The photoelectric conversion device according to any one of items 1 to 15.
(Item 19)
a dimension of the electrode film in a direction along the first surface is larger than a dimension of the third semiconductor region in the direction along the first surface;
4. The photoelectric conversion device according to item 3,
(Item 20)
a dimension of the electrode film in a direction along the first surface is smaller than a dimension of the third semiconductor region in the direction along the first surface;
4. The photoelectric conversion device according to item 3,
(Item 21)
The electrode film has a contact surface in contact with the first surface, and the contact surface has projections and recesses.
21. The photoelectric conversion device according to any one of items 1 to 20,
(Item 22)
22. The photoelectric conversion device according to any one of items 1 to 21,
a signal processing unit that processes a signal output from the photoelectric conversion device;
A photoelectric conversion system comprising:

The invention is not limited to the above-described embodiment, and various modifications and variations are possible without departing from the spirit and scope of the invention. Therefore, the following claims are appended to disclose the scope of the invention.

201: avalanche photodiode, 221: Schottky barrier diode, 301: first semiconductor layer, 302: first wiring structure, 324: electrode film, 303: first surface, 304: second surface, 305: third surface, 306: fourth surface, 307: fifth surface, 308: sixth surface, 311: first semiconductor region of first conductivity type, 312: second semiconductor region of second conductivity type, 313: third semiconductor region of first conductivity type, 314: fourth semiconductor region of second conductivity type, 315: fifth semiconductor region of second conductivity type,

Claims (22)

a first semiconductor layer having a first surface and a second surface;
an avalanche photodiode disposed on the first semiconductor layer;
an electrode film disposed in contact with the first surface so as to form a Schottky barrier diode at a contact portion with the first semiconductor layer;
a first wiring structure disposed in contact with the second surface,
the avalanche photodiode is disposed between the second surface and the Schottky barrier diode;
external light is incident on the first semiconductor layer through the first wiring structure;
A photoelectric conversion device comprising: the avalanche photodiode includes a first semiconductor region of a first conductivity type and a second semiconductor region of a second conductivity type;
the first wiring structure includes a conductive path electrically connected to the first semiconductor region;
2. The photoelectric conversion device according to claim 1 . the avalanche photodiode further includes a third semiconductor region of the first conductivity type including a portion disposed between the first semiconductor region and the second semiconductor region;
3. The photoelectric conversion device according to claim 2. the third semiconductor region further includes a portion disposed between the second surface and the second semiconductor region so as to surround a side surface of the first semiconductor region;
4. The photoelectric conversion device according to claim 3. the conductive path includes a conductive pattern disposed in a wiring layer of the first wiring structure, and a plug electrically connecting the conductive pattern and the first semiconductor region;
5. The photoelectric conversion device according to claim 4. Further comprising a microlens,
the first wiring structure is disposed between the microlens and the second surface,
the conductive path includes a portion disposed between the microlens and the second surface.
6. The photoelectric conversion device according to claim 5. A part of the light incident on the first wiring structure through the microlens is incident on a part of the conductive path.
7. The photoelectric conversion device according to claim 6. a fourth semiconductor region of the second conductivity type electrically connected to the second semiconductor region and extending between the first surface and the second surface in a direction perpendicular to the first surface,
A potential is applied to the second semiconductor region through the fourth semiconductor region.
4. The photoelectric conversion device according to claim 3. the fourth semiconductor region is disposed so as to surround the first semiconductor region, the second semiconductor region, and the third semiconductor region;
9. The photoelectric conversion device according to claim 8. a fifth semiconductor region of the second conductivity type disposed between the second surface and the fourth semiconductor region,
10. The photoelectric conversion device according to claim 9. a pinning film covering the first surface so as to surround the electrode film;
The photoelectric conversion device according to claim 10 . A support member;
a sealing structure disposed between the first surface and the support member;
The photoelectric conversion device according to claim 1 , further comprising: the sealing structure includes a metal layer disposed between the electrode film and the support member;
13. The photoelectric conversion device according to claim 12. Further comprising a second semiconductor layer,
the first wiring structure is disposed between the second semiconductor layer and the second surface;
2. The photoelectric conversion device according to claim 1. further comprising a second wiring structure disposed between the first wiring structure and the second semiconductor layer;
15. The photoelectric conversion device according to claim 14. At least a part of a signal processing unit that processes a signal output from the avalanche photodiode is disposed in the second semiconductor layer.
16. The photoelectric conversion device according to claim 15. At least a part of a signal processing unit that processes a signal output from the avalanche photodiode is disposed in the first semiconductor layer.
2. The photoelectric conversion device according to claim 1. a signal processing unit for processing a signal output from the avalanche photodiode is disposed in the first semiconductor layer and the second semiconductor layer in a distributed manner;
2. The photoelectric conversion device according to claim 1. a dimension of the electrode film in a direction along the first surface is larger than a dimension of the third semiconductor region in the direction along the first surface;
4. The photoelectric conversion device according to claim 3. a dimension of the electrode film in a direction along the first surface is smaller than a dimension of the third semiconductor region in the direction along the first surface;
4. The photoelectric conversion device according to claim 3. The electrode film has a contact surface in contact with the first surface, and the contact surface has projections and recesses.
2. The photoelectric conversion device according to claim 1. The photoelectric conversion device according to any one of claims 1 to 21,
a signal processing unit that processes a signal output from the photoelectric conversion device;
A photoelectric conversion system comprising:

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