US-20260129997-A1 - LIGHT DETECTION ELEMENT

US20260129997A1US 20260129997 A1US20260129997 A1US 20260129997A1US-20260129997-A1

Abstract

A light detection element includes a first semiconductor layer having a first main surface and a second main surface, a layer structure, metal wiring located inside of the layer structure, and a plurality of quenching elements. The first semiconductor layer includes a plurality of first semiconductor regions, a plurality of second semiconductor regions, and a plurality of third semiconductor regions. The thickness of the metal wiring is larger than the distance from the first surface of the metal wiring on a side opposite to the first main surface to the surface of the layer structure on a side opposite to the first main surface, and is larger than the distance from the second surface of the metal wiring on the first main surface side to the surface of the layer structure on the first main surface side.

Inventors

Masanori Okada
Yuta TSUJI
Ryutaro Tsuchiya
Shinya IWASHINA

Assignees

HAMAMATSU PHOTONICS K.K.

Dates

Publication Date: 20260507
Application Date: 20251030
Priority Date: 20241105

Claims (9)

1 . A light detection element comprising: a first semiconductor layer having a first main surface as a light incident surface and a second main surface opposite to the first main surface; a layer structure formed on the first main surface; metal wiring formed on the first main surface and at least partially located inside the layer structure; and a plurality of quenching elements located on the second main surface side with respect to the first semiconductor layer, wherein the first semiconductor layer includes a plurality of first semiconductor regions of a first conductivity type, a plurality of second semiconductor regions of a second conductivity type located closer to the second main surface than the plurality of first semiconductor regions and constituting a plurality of avalanche photodiodes together with the plurality of first semiconductor regions, and a plurality of third semiconductor regions of the first conductivity type located closer to the first main surface than the plurality of first semiconductor regions and having an impurity concentration higher than an impurity concentration of the plurality of first semiconductor regions, each of the plurality of quenching elements is electrically connected to a corresponding second semiconductor region among the plurality of second semiconductor regions, a trench extending so as to separate the plurality of third semiconductor regions from each other is formed in the first semiconductor layer, the metal wiring is formed on the first main surface so as to extend along the trench, and electrically connects the plurality of third semiconductor regions to each other, and a thickness of the metal wiring is larger than a distance from a first surface of the metal wiring on a side opposite to the first main surface to a surface of the layer structure on a side opposite to the first main surface, and is larger than a distance from a second surface of the metal wiring on a side of the first main surface to a surface of the layer structure on a side of the first main surface.
2 . The light detection element according to claim 1 , wherein the layer structure includes a first insulating layer formed on the first main surface and a second insulating layer formed on the first insulating layer, and the metal wiring is located inside the first insulating layer and the second insulating layer.
3 . The light detection element according to claim 2 , wherein a side surface of the metal wiring is in contact with the first insulating layer and the second insulating layer.
4 . The light detection element according to claim 1 , wherein the layer structure is a single insulating layer.
5 . The light detection element according to claim 1 , further comprising a lens portion disposed on the layer structure.
6 . The light detection element according to claim 5 , wherein a thickness of the metal wiring is larger than a distance from a surface of the lens portion on a side of the first main surface to the first surface.
7 . The light detection element according to claim 5 , further comprising a plurality of lens portions each configured to be the lens portion, wherein each of the plurality of lens portions is disposed so as to overlap a corresponding avalanche photodiode among the plurality of avalanche photodiodes in a direction perpendicular to the first main surface, and an outer edge of each of the plurality of lens portions overlaps the trench when viewed from the direction perpendicular to the first main surface.
8 . The light detection element according to claim 1 , wherein the metal wiring is formed so as to cover the entire trench when viewed from a direction perpendicular to the first main surface, and each of the plurality of avalanche photodiodes is surrounded by the metal wiring when viewed from the direction perpendicular to the first main surface.
9 . A light detection element comprising: a first semiconductor layer having a first main surface as a light incident surface and a second main surface opposite to the first main surface; a layer structure having a first insulating layer formed on the first main surface, and a second insulating layer formed on the first insulating layer; metal wiring formed on the first main surface, at least a part of which is located inside the layer structure; and a plurality of quenching elements located on the second main surface side with respect to the first semiconductor layer, wherein the first semiconductor layer includes a plurality of first semiconductor regions of a first conductivity type, a plurality of second semiconductor regions of a second conductivity type located closer to the second main surface than the plurality of first semiconductor regions and constituting a plurality of avalanche photodiodes together with the plurality of first semiconductor regions, and a plurality of third semiconductor regions of the first conductivity type located closer to the first main surface than the plurality of first semiconductor regions and having an impurity concentration higher than an impurity concentration of the plurality of first semiconductor regions, each of the plurality of quenching elements is electrically connected to a corresponding second semiconductor region among the plurality of second semiconductor regions, a trench extending so as to separate the plurality of third semiconductor regions from each other is formed in the first semiconductor layer, the metal wiring is formed on the first main surface so as to extend along the trench, and electrically connects the plurality of third semiconductor regions to each other, and a surface of the metal wiring on a side opposite to the first main surface is located farther from the first main surface than a surface of the first insulating layer on a side opposite to the first semiconductor layer in a direction perpendicular to the first main surface.

Description

TECHNICAL FIELD One aspect of the present disclosure relates to a light detection element. BACKGROUND WO 2018/174090 A discloses, as an example of a light detection element, an imaging device including a first semiconductor layer formed on a semiconductor substrate, a second semiconductor layer formed on the first semiconductor layer and having a conductivity type opposite to that of the first semiconductor layer, a third semiconductor layer formed on the second semiconductor layer and having the same conductivity type as that of the second semiconductor layer, a pixel isolation portion defining a pixel region including the first semiconductor layer and the second semiconductor layer, a first electrode connected to the first semiconductor layer, and a second electrode connected to the second semiconductor layer. In such a light detection element, light incident on each pixel region is photoelectrically converted and detected as a current signal. For example, in the imaging device described in WO 2018/174090 A, charge carriers are generated (photoelectrically converted) in the third semiconductor layer by incidence of light, and then the charge carriers are multiplied in the first semiconductor layer and the second semiconductor layer to which voltage is applied via the first electrode and the second electrode. The multiplied charge carriers are detected as current signals. SUMMARY In the light detection element as described above, an avalanche photodiode is formed in each pixel, and charge carriers generated in the semiconductor layer by incidence of light are multiplied and detected by the avalanche photodiode. However, the charge carriers multiplied by the avalanche photodiode may recombine to generate secondary photons. The secondary photons can cause crosstalk. Specifically, there is a possibility that the secondary photons are incident on other pixels to generate new charge carriers. Such crosstalk reduces detection accuracy in the light detection element. An object of one aspect of the present disclosure is to provide a light detection element capable of suppressing a decrease in detection accuracy. A light detection element according to one aspect of the present disclosure is [1] “a light detection element including: a first semiconductor layer having a first main surface as a light incident surface and a second main surface opposite to the first main surface; a layer structure formed on the first main surface; metal wiring formed on the first main surface and at least partially located inside the layer structure; and a plurality of quenching elements located on the second main surface side with respect to the first semiconductor layer, in which the first semiconductor layer includes: a plurality of first semiconductor regions of a first conductivity type; a plurality of second semiconductor regions of a second conductivity type located closer to the second main surface than the plurality of first semiconductor regions and constituting a plurality of avalanche photodiodes together with the plurality of first semiconductor regions; and a plurality of third semiconductor regions of the first conductivity type located closer to the first main surface than the plurality of first semiconductor regions and having an impurity concentration higher than an impurity concentration of the plurality of first semiconductor regions, each of the plurality of quenching elements is electrically connected to a corresponding second semiconductor region among the plurality of second semiconductor regions, a trench extending so as to separate the plurality of third semiconductor regions from each other is formed in the first semiconductor layer, the metal wiring is formed on the first main surface so as to extend along the trench, and electrically connects the plurality of third semiconductor regions to each other, and a thickness of the metal wiring is larger than a distance from a first surface of the metal wiring on a side opposite to the first main surface to a surface of the layer structure on a side opposite to the first main surface, and is larger than a distance from a second surface of the metal wiring on a side of the first main surface to a surface of the layer structure on a side of the first main surface.” In the light detection element, a trench extending so as to separate the plurality of third semiconductor regions from each other is formed in the first semiconductor layer. As a result, the secondary photons of the charge carriers multiplied in the avalanche photodiode can be prevented by the trench from being incident on the adjacent avalanche photodiodes through the third semiconductor region. In addition, the light detection element includes metal wiring formed on the first main surface so as to extend along the trench and at least partially located inside the layer structure, and a thickness of the metal wiring is larger than a distance from a first surface of the metal wiring on a side opposite to the