US-20260129992-A1 - LIGHT DETECTION ELEMENT AND METHOD FOR MANUFACTURING LIGHT DETECTION ELEMENT

US20260129992A1US 20260129992 A1US20260129992 A1US 20260129992A1US-20260129992-A1

Abstract

A light detection element includes a first semiconductor layer having a first main surface and a second main surface, an insulating layer, a second semiconductor layer, and a quenching element located on the second main surface side. The first semiconductor layer includes a first semiconductor region of a first conductivity type, a second semiconductor region of a second conductivity type constituting an avalanche photodiode together with the first semiconductor region, and a third semiconductor region of the first conductivity type located closer to the first main surface than the first semiconductor region and having an impurity concentration higher than an impurity concentration of the first semiconductor region. The quenching element is electrically connected to the second semiconductor region. A texture structure having an uneven shape is formed on a surface of the second semiconductor layer.

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 (10)

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; an insulating layer formed on the first main surface; a second semiconductor layer formed on the first main surface with the insulating layer interposed therebetween; and a quenching element located on the second main surface side with respect to the first semiconductor layer, wherein the first semiconductor layer includes a first semiconductor region of a first conductivity type, a second semiconductor region of a second conductivity type located closer to the second main surface than the first semiconductor region and constituting an avalanche photodiode together with the first semiconductor region, and a third semiconductor region of the first conductivity type located closer to the first main surface than the first semiconductor region and having an impurity concentration higher than an impurity concentration of the first semiconductor region, the quenching element is electrically connected to the second semiconductor region, and a texture structure having an uneven shape is formed on a surface of the second semiconductor layer.
2 . The light detection element according to claim 1 , wherein the texture structure is formed on a surface of the second semiconductor layer opposite to the insulating layer.
3 . The light detection element according to claim 2 , further comprising: a resin layer formed on the second semiconductor layer so as to cover the texture structure; and a lens portion disposed on the texture structure with the resin layer interposed therebetween.
4 . The light detection element according to claim 1 , wherein the first semiconductor layer includes a plurality of first semiconductor regions each configured to be the first semiconductor region, and a plurality of second semiconductor regions each configured to be the second semiconductor region, the plurality of first semiconductor regions and the plurality of second semiconductor regions constitute a plurality of avalanche photodiodes each configured to be the avalanche photodiode, a trench extending so as to separate the plurality of avalanche photodiodes from each other when viewed from a direction perpendicular to the first main surface is formed in the first semiconductor layer, and the trench is formed to extend from the first main surface to the second main surface.
5 . The light detection element according to claim 4 , further comprising a plurality of lens portions disposed on the second semiconductor layer, 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 the 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.
6 . The light detection element according to claim 4 , further comprising metal wiring disposed on the first main surface so as to extend along the trench, wherein a side surface of the metal wiring is in contact with the insulating layer and the second semiconductor layer.
7 . The light detection element according to claim 6 , further comprising a resin layer formed on the second semiconductor layer, wherein a surface of the metal wiring opposite to the first main surface is in contact with the resin layer.
8 . The light detection element according to claim 6 , wherein the metal wiring is formed so as to cover the entire trench when viewed from the 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 method for manufacturing a light detection element, the method being a method for manufacturing the light detection element according to claim 1 , comprising the steps of: forming the second semiconductor layer by polishing and thinning a layer corresponding to the second semiconductor layer formed on the insulating layer; and forming the texture structure on a surface of the second semiconductor layer.
10 . The method for manufacturing a light detection element according to claim 9 , wherein in the step of forming the texture structure, the texture structure is formed by etching a surface of the second semiconductor layer opposite to the insulating layer.

Description

TECHNICAL FIELD One aspect of the present disclosure relates to a light detection element and a method for manufacturing the 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, even if light is incident on the semiconductor layer, generation of charge carriers in the semiconductor layer may be insufficient, and as a result, in some cases, light incident on the light detection element is not detected with desired accuracy. An object of one aspect of the present disclosure is to provide a light detection element capable of improving detection accuracy, and a method for manufacturing such a light detection element. 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; an insulating layer formed on the first main surface; a second semiconductor layer formed on the first main surface with the insulating layer interposed therebetween; and a quenching element located on the second main surface side with respect to the first semiconductor layer, in which the first semiconductor layer includes: a first semiconductor region of a first conductivity type; a second semiconductor region of a second conductivity type that is located closer to the second main surface than the first semiconductor region and constitutes an avalanche photodiode together with the first semiconductor region; a third semiconductor region of the first conductivity type located closer to the first main surface than the first semiconductor region and having an impurity concentration higher than an impurity concentration of the first semiconductor region, and the quenching element is electrically connected to the second semiconductor region, and a texture structure having an uneven shape is formed on a surface of the second semiconductor layer.” In the light detection element, the first semiconductor layer has the first main surface that is a light incident surface, and the texture structure having an uneven shape is formed on a surface of the second semiconductor layer formed on the first main surface with the insulating layer interposed therebetween. As a result, the optical path of the light incident on the first semiconductor layer is changed so as to be oblique with respect to the direction perpendicular to the first main surface due to the uneven shape of the texture structure. As a result, the optical path length of light passing through the first semiconductor region becomes long, and more charge carriers are generated in the first semiconductor region. The generated charge carriers are further multiplied in an avalanche photodiode including the first semiconductor region and the second semiconductor region, and are detected as a current signal. Therefore, the sensitivity (PDE: photon detection efficiency) of the light detection element is improved. In a case where the texture structure is formed in the third semiconductor region, the first semiconductor layer may be damaged, and the detection accuracy may be deteriorated by a noise signal caused by the damage. In addition, in a case where a texture structure is formed in the insulating layer, crosstalk with the insulating layer may occur, and detection accuracy may be deteriorated. On the other hand, in the light detection element, since the texture structure is formed on the surface of the second semiconductor layer, it is possible to suppress a decrease in detection accuracy due to such damage and crosstalk. In the light detection element, the first semiconductor layer