US-20260129986-A1 - LIGHT DETECTION ELEMENT

US20260129986A1US 20260129986 A1US20260129986 A1US 20260129986A1US-20260129986-A1

Abstract

The light detection element includes a first semiconductor layer having a first main surface and a second main surface. The first semiconductor layer includes a plurality of first semiconductor regions, a plurality of second semiconductor regions constituting a plurality of avalanche photodiodes together with the plurality of first semiconductor regions, and a frame region formed in a frame shape so as to surround the plurality of avalanche photodiodes. A trench is formed in the first semiconductor layer. The trench includes a plurality of frame portions that each extend to surround a corresponding avalanche photodiode. The impurity concentration of the frame region is higher than the impurity concentration of the plurality of first semiconductor regions. The width of the frame region is larger than the width of the region surrounded by the frame portion.

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 (6)

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; 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, 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, and a frame region of the first conductivity type formed in a frame shape so as to surround the plurality of avalanche photodiodes and electrically connected to the first semiconductor regions when viewed from a direction perpendicular to the first main surface, 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 avalanche photodiodes from each other is formed in the first semiconductor layer, the trench includes a plurality of frame portions each extending so as to surround a corresponding avalanche photodiode of the plurality of avalanche photodiodes when viewed from the direction perpendicular to the first main surface, an impurity concentration of the frame region is higher than an impurity concentration of the plurality of first semiconductor regions, and a width of the frame region is larger than a width of each of the plurality of regions surrounded by the plurality of frame portions in the first semiconductor layer when viewed from the direction perpendicular to the first main surface.
2 . The light detection element according to claim 1 , wherein when viewed from the direction perpendicular to the first main surface, a width of the frame region is twice or more a width of a region surrounded by each of the plurality of frame portions.
3 . The light detection element according to claim 1 , wherein when viewed from the direction perpendicular to the first main surface, a width of the frame region is larger than a width of a region located between the frame region and the plurality of frame portions.
4 . The light detection element according to claim 1 , further comprising metal wiring formed on the first main surface, wherein the trench is formed to separate the plurality of third semiconductor regions from each other and extend from the first main surface to the second main surface, and the metal wiring electrically connects the plurality of third semiconductor regions to each other.
5 . The light detection element according to claim 4 , wherein the first semiconductor layer further includes a fourth semiconductor region of the first conductivity type located closer to the first main surface than the frame region and having an impurity concentration higher than an impurity concentration of the plurality of first semiconductor regions, and the fourth semiconductor region is formed in a frame shape so as to surround the plurality of frame portions when viewed from the direction perpendicular to the first main surface, and the metal wiring electrically connects the fourth semiconductor region and the plurality of third semiconductor regions to each other.
6 . The light detection element according to claim 5 , wherein the frame region is formed to extend from the second main surface to the fourth semiconductor region in the 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, for example, a voltage is applied to the first electrode and the second electrode from a power supply circuit of a circuit layer formed on a semiconductor substrate. For example, in a case where the first electrode of the first electrode and the second electrode connected to the power supply circuit is disposed close to some pixels of the plurality of pixels and is disposed away from the other pixels, the voltage value applied to the pixel located away from the first electrode becomes relatively small, and a potential gradient occurs between the pixels. Such a potential gradient causes variation in current signals between pixels. In addition, when the voltage is applied from the power supply circuit to the first electrode and the second electrode via wiring, a voltage drop and heat generation due to the wiring resistance occur. Such a voltage drop and heat generation cause a decrease in the current signal generated in the pixel. The above-described variation and decrease in the current signal deteriorate detection accuracy. 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; 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; 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, and a frame region of the first conductivity type formed in a frame shape so as to surround the plurality of avalanche photodiodes and electrically connected to the first semiconductor regions when viewed from a direction perpendicular to the first main surface, 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 avalanche photodiodes from each other is formed in the first semiconductor layer, the trench includes a plurality of frame portions each extending so as to surround a corresponding avalanche photodiode of the plurality of avalanche photodiodes when viewed from a direction perpendicular to the first main surface, an impurity concentration of the frame region is higher than an impurity concentration of the plurality of first semiconductor regions, and a width of the frame region is larger than a width of each of the plurality of regions surrounded by the plurality of frame portions in the first semiconductor layer when viewed from the direction perpendicular to the first main surface.” In the light detection element, the frame region of the first conductivity type electrically con