US-12622083-B2 - Light receiving element and distance measuring device

Abstract

To prevent leakage of incident light from pixels around a pixel region of a light receiving element. A light receiving element includes a pixel region and an adjacent pixel. In the pixel region, a plurality of pixels is arranged, the plurality of pixels including a photodiode formed on a semiconductor substrate in which a charge generated by photoelectric conversion of incident light is multiplied with a high reverse bias voltage, an on-chip lens that focuses the incident light on the photodiode, and a wiring region having a wiring layer connected to the photodiode and an insulating layer that insulates the wiring layer. The adjacent pixel is arranged adjacent to the pixel region and includes the photodiode, an on-chip lens having a curvature different from a curvature of the on-chip lens, and the wiring region.

Inventors

• Daisuke WASHIO
• Masahiko TSUJITA
• Hidenori Maeda

Assignees

• SONY SEMICONDUCTOR SOLUTIONS CORPORATION

Dates

Publication Date

20260505

Application Date

20240611

Priority Date

20191106

Claims (20)

1. 1 . A light receiving device, comprising: a first semiconductor substrate, including: a first plurality of pixels disposed in a pixel region, wherein each pixel of the first plurality of pixels includes: an avalanche photodiode disposed in the first semiconductor substrate, and an on-chip lens, wherein the on-chip lens is disposed on a first side of the first semiconductor substrate, a second plurality of pixels disposed in a region other than the pixel region, each pixel of the second plurality of pixels including: an avalanche photodiode disposed in the first semiconductor substrate, and a separation region disposed in the first semiconductor substrate; and a first wiring layer, wherein the first wiring layer is disposed on a second side of the first semiconductor substrate, and wherein the separation region is disposed at a boundary between the pixel region and the region other than the pixel region.
2. 2 . The light receiving device according to claim 1 , further comprising: a second wiring layer; and a second semiconductor substrate, wherein the first semiconductor substrate and the second semiconductor substrate are coupled to one another through the first and second wiring layers.
3. 3 . The light receiving device according to claim 1 , wherein the separation region includes a metal.
4. 4 . The light receiving device according to claim 1 , wherein the separation region is a light-blocking wall.
5. 5 . The light receiving device according to claim 4 , wherein the light-blocking wall extends from the first side of the first semiconductor substrate to the second side of the first semiconductor substrate.
6. 6 . The light receiving device according to claim 4 , further comprising: an insulating film, wherein the insulating film is disposed on a surface of the light-blocking wall.
7. 7 . The light receiving device according to claim 6 , wherein the insulating film is Silicon Oxide.
8. 8 . The light receiving device according to claim 4 , wherein in the second plurality of pixels, the light-blocking wall is not formed on a boundary different from the boundary between the pixel region and the region other than the pixel region.
9. 9 . The light receiving device according to claim 1 , wherein a first width of the separation region at the first side of the first semiconductor substrate is greater than a second width of the separation region at the second side of the first semiconductor substrate.
10. 10 . The light receiving device according to claim 1 , wherein each pixel of the second plurality of pixels includes an on-chip lens.
11. 11 . The light receiving device according to claim 10 , wherein a height of the on-chip lens of each pixel of the first plurality of pixels is greater than a height of the on-chip lens of each pixel of the second plurality of pixels.
12. 12 . The light receiving device according to claim 10 , wherein a height of the on-chip lens of each pixel of the first plurality of pixels is equal to a height of the on-chip lens of each pixel of the second plurality of pixels.
13. 13 . The light receiving device according to claim 10 , wherein the separation region is a light-blocking wall.
14. 14 . The light receiving device according to claim 13 , wherein the light-blocking wall extends from the first side of the first semiconductor substrate to the second side of the first semiconductor substrate.
15. 15 . The light receiving device according to claim 13 , wherein in the second plurality of pixels, the light-blocking wall is not formed on a boundary different from the boundary between the pixel region and the region other than the pixel region.
16. 16 . The light receiving device of claim 13 , wherein a first width of the separation region at first side of the first semiconductor substrate is greater than a second width of the separation region at the second side of the first semiconductor substrate.
17. 17 . The light receiving device according to claim 13 , further comprising: a second wiring layer; and a second semiconductor substrate, wherein the first semiconductor substrate and the second semiconductor substrate are coupled to one another through the first and second wiring layers.
18. 18 . The light receiving device according to claim 1 , wherein the pixel region includes a two-dimensional array of the first plurality of pixels, and wherein the region other than the pixel region surrounds the pixel region.
19. 19 . The light receiving device according to claim 18 , wherein the region other than the pixel region is disposed between the pixel region and end portion s of the first semiconductor substrate.
20. 20 . A distance measuring device, comprising: a light receiving device, including: a first semiconductor substrate, including: a first plurality of pixels disposed in a pixel region, wherein each pixel of the first plurality of pixels includes: an avalanche photodiode disposed in the first semiconductor substrate, and an on-chip lens, wherein the on-chip lens is disposed on a first side of the first semiconductor substrate, a second plurality of pixels disposed in a region other than the pixel region, each pixel of the second plurality of pixels including: an avalanche photodiode disposed in the first semiconductor substrate, and a separation region disposed in the first semiconductor substrate; and a first wiring layer, wherein the first wiring layer is disposed on a second side of the first semiconductor substrate, and wherein the separation region is disposed at a boundary between the pixel region and the region other than the pixel region.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation of U.S. patent application Ser. No. 17/773,154, filed Apr. 29, 2022, which is a national stage application under 35 U.S.C. 371 and claims the benefit of PCT Application No. PCT/JP2020/015477, having an international filing date of Apr. 6, 2020, which designated the United States, which PCT application claimed the benefit of Japanese Priority Patent Application JP 2019-201655, filed Nov. 6, 2019, the entire disclosures of each contents of which are incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to a light receiving element and a distance measuring device. More specifically, the present disclosure relates to a light receiving element including an avalanche photodiode and a distance measuring device that measures a distance to a target object using the light receiving element. BACKGROUND ART An imaging element and a light receiving element each configured by arranging a plurality of pixels having a photodiode for photoelectrically converting incident light formed on a semiconductor substrate have been used. By using such an image element, incident light can be detected for each pixel to generate an image signal, and a target object can be imaged. Furthermore, such an imaging element can be applied to a distance measuring device that measures a distance to a target object. In this distance measuring device, the distance can be measured by irradiating the target object with light, detecting reflection light reflected by the target object by a light receiving element, and measuring time from irradiation of the light to detection of the reflection light. By measuring the distance to the target object for each pixel, a three-dimensional shape of the target object can be obtained. As such an imaging element, for example, a solid-state imaging device that separates pixels by an element separation region configured by embedding an insulating film in a groove formed in a region of a semiconductor substrate between pixels is used (for example, see PTL 1). This solid-state imaging device is configured as a back-illuminated imaging element in which incident light is applied to a back surface of a semiconductor substrate, and an on-chip lens is arranged close to the semiconductor substrate. By arranging the separation region between pixels, it is possible to block the light that passes through the on-chip lens of the adjacent pixel arranged close to and obliquely enters, thereby preventing the occurrence of crosstalk and color mixing. A plurality of pixels of the solid-state imaging device is arranged in a two-dimensional array to form a pixel region, and is arranged at a central portion of the semiconductor substrate. CITATION LIST Patent Literature [PTL 1]JP 2017-191950A SUMMARY Technical Problem In the above-described related art, there is a problem that incident light from an end portion of the pixel region is mixed. In an imaging element, pixels that are not involved in generating an image signal are arranged between the pixel region and an end portion of the semiconductor substrate in order to ensure uniformity of each pixel in the pixel region. Such a pixel is called a dummy pixel, has the same configuration as a pixel in the pixel region, and is arranged adjacent to the pixel region. When the incident light that has passed through the dummy pixel is reflected by a wiring region or the like arranged on the front surface side of the semiconductor substrate and mixes with the pixel in the pixel region, noise such as flare occurs. For this reason, there is a problem that image quality is deteriorated. Furthermore, in the light receiving element used in a distance measuring device, an avalanche photodiode (APD) or a single photon avalanche diode (SPAD) is arranged in the pixel instead of the photodiode in order to improve the sensitivity. These are photodiodes whose sensitivity is increased by multiplying the charge generated by photoelectric conversion, and malfunction occurs due to leakage of incident light from dummy pixels. The present disclosure has been made in view of the above-described problem, and it is desirable to prevent leakage of incident light from pixels around a pixel region. Solution to Problem According to a first embodiment of the present disclosure, there is provided a light receiving element including: a pixel region in which a plurality of pixels is arranged, the plurality of pixels including a photodiode formed on a semiconductor substrate in which a charge generated by photoelectric conversion of incident light is multiplied with a high reverse bias voltage, an on-chip lens that focuses the incident light on the photodiode, and a wiring region having a wiring layer connected to the photodiode and an insulating layer that insulates the wiring layer; and an adjacent pixel arranged adjacent to the pixel region and including the photodiode, an on-chip lens having a curvature different from a