US-12625009-B2 - Optical sensor

US12625009B2US 12625009 B2US12625009 B2US 12625009B2US-12625009-B2

Abstract

An optical sensor includes a support layer, a thermoelectric-conversion material section disposed on the support layer and including strip-shaped p-type material layers configured to convert thermal energy into electric energy and strip-shaped n-type material lavers configured to convert thermal energy into electric energy, a heat sink, a light absorbing film, and an insulating film disposed between the thermoelectric-conversion material section and the light absorbing film. Each of the p-type material layers includes a first region overlapping the heat sink and a second region overlapping the light absorbing film. Each of the n-type material layers includes a third region overlapping the heat sink and a fourth region overlapping the light absorbing film. The p-type material layers and the n-type material layers are alternately disposed in series. The light absorbing film includes 60 mass % to 95 mass % of carbon and 5 mass % to 40 mass % of a resin.

Inventors

Kyohei KAKUYAMA
Kotaro HIROSE
Masahiro Adachi

Assignees

SUMITOMO ELECTRIC INDUSTRIES, LTD.

Dates

Publication Date: 20260512
Application Date: 20231010
Priority Date: 20221011

Claims (11)

1 . An optical sensor comprising: a support layer having a first main surface and a second main surface located opposite the first main surface in a thickness direction; a thermoelectric-conversion material section including a plurality of p-type material layers and a plurality of n-type material layers, each of the plurality of p-type material layers having a strip shape, being formed of SiGe having p-type conductivity, and being configured to convert thermal energy into electric energy, each of the plurality of n-type material layers having a strip shape, being formed of SiGe having n-type conductivity, and being configured to convert thermal energy into electric energy, the thermoelectric-conversion material section being disposed on the first main surface; a heat sink disposed on the second main surface and having a recess on an inner side as viewed in a direction perpendicular to the first main surface; a light absorbing film disposed so as to overlap the recess as viewed in the direction perpendicular to the first main surface; and an insulating film disposed between the thermoelectric-conversion material section and the light absorbing film, wherein each of the plurality of p-type material layers includes a first region overlapping the heat sink and a second region overlapping the light absorbing film as viewed in the direction perpendicular to the first main surface, each of the plurality of n-type material layers includes a third region overlapping the heat sink and a fourth region overlapping the light absorbing film as viewed in the direction perpendicular to the first main surface, the plurality of p-type material layers and the plurality of n-type material layers are alternately disposed in series such that the first regions are electrically connected to the third regions and the second regions are electrically connected to the fourth regions, and the light absorbing film includes 60 mass % to 95 mass % of carbon, and 5 mass % to 40 mass % of a resin.
2 . The optical sensor according to claim 1 , wherein the light absorbing film has a thermal conductivity of 1 W/mK or less.
3 . The optical sensor according to claim 1 , wherein the resin includes an epoxy resin.
4 . The optical sensor according to claim 1 , wherein the light absorbing film has a thickness of 2 μm to 7 μm.
5 . The optical sensor according to claim 1 , wherein the light absorbing film has a circular outer shape as viewed in the direction perpendicular to the first main surface, and the plurality of p-type material layers and the plurality of n-type material layers are radially disposed.
6 . The optical sensor according to claim 5 , wherein the second regions and the fourth regions are located in a region of 30% or more and 80% or less of a radius of the light absorbing film from a center of the light absorbing film in a radial direction.
7 . The optical sensor according to claim 1 , wherein the light absorbing film has a rectangular outer shape as viewed in the direction perpendicular to the first main surface, and the plurality of p-type material layers and the plurality of n-type material layers are disposed such that longitudinal directions thereof are parallel to a direction in which a side of the light absorbing film extends or to a direction perpendicular to the direction in which the side of the light absorbing film extends.
8 . The optical sensor according to claim 1 , wherein the first regions are electrically connected to the third regions through first connection portions having conductivity, and the second regions are electrically connected to the fourth regions through second connection portions having conductivity.
9 . The optical sensor according to claim 1 , wherein the first regions of the plurality of p-type material layers and the third regions of the plurality of n-type material layers overlap each other as viewed in the direction perpendicular to the first main surface and are connected in ohmic contact with each other, and the second regions of the plurality of p-type material layers and the fourth regions of the plurality of n-type material layers overlap each other as viewed in the direction perpendicular to the first main surface and are connected in ohmic contact with each other.
10 . The optical sensor according to claim 1 , wherein the plurality of p-type material layers, the plurality of n-type material layers, or both the plurality of p-type material layers and the plurality of n-type material layers include SiGe having at least one of a nanocrystal structure having a grain size of 3 nm to 200 nm or an amorphous structure.
11 . The optical sensor according to claim 1 , wherein the SiGe is a polycrystal.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims priority based on Japanese Patent Application No. 2022-163187, filed on Oct. 11, 2022, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to an optical sensor. BACKGROUND A technique related to a thermopile-type infrared sensor using a thermoelectric conversion material for converting a temperature difference (thermal energy) into electric energy is known (see, for example, Japanese Patent Application Laid-Open No. 2000-340848). The infrared sensor includes a light receiving portion (light absorbing film) that is configured to convert optical energy into thermal energy and a thermoelectric conversion section (thermopile) that is configured to convert a temperature difference (thermal energy) into electric energy. In the thermoelectric conversion section, a thermocouple is used, which a p-type thermoelectric conversion material and an n-type thermoelectric conversion material are connected to each other to form. A plurality of the p-type thermoelectric conversion materials and a plurality of the n-type thermoelectric conversion materials are alternately connected in series to each other to increase an output. SUMMARY An optical sensor according to the present disclosure includes a support layer having a first main surface and a second main surface located opposite the first main surface in a thickness direction; a thermoelectric-conversion material section disposed on the first main surface and including a plurality of p-type material layers and a plurality of n-type material layers; a heat sink disposed on the second main surface and having a recess on an inner side as viewed in a direction perpendicular to the first main surface; a light absorbing film disposed so as to overlap the recess as viewed in the direction perpendicular to the first main surface; and an insulating film disposed between the thermoelectric-conversion material section and the light absorbing film. Each of the plurality of p-type material layers has a strip shape, is formed of SiGe having p-type conductivity, and is configured to convert thermal energy into electric energy. Each of the plurality of n-type material layers has a strip shape, is formed of SiGe having n-type conductivity, and is configured to convert thermal energy into electric energy. Each of the plurality of p-type material layers includes a first region overlapping the heat sink and a second region overlapping the light absorbing film as viewed in the direction perpendicular to the first main surface. Each of the plurality of n-type material layers includes a third region overlapping the heat sink and a fourth region overlapping the light absorbing film as viewed in the direction perpendicular to the first main surface. The plurality of p-type material layers and the plurality of n-type material layers are alternately disposed in series such that the first regions are electrically connected to the third regions and the second regions are electrically connected to the fourth regions. The light absorbing film includes of 60 mass % to 95 mass % of carbon and 5 mass % to 40 mass % of a resin. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic plan view of an appearance of an optical sensor according to a first embodiment. FIG. 2 is a schematic cross-sectional view of the optical sensor according to the first embodiment showing a cross-section taken along line II-II in FIG. 1. FIG. 3 is a schematic cross-sectional view of a portion of the optical sensor showing a cross-section taken along line II-III in the optical sensor according to the first embodiment shown in FIG. 1. FIG. 4 is a graph showing a relationship between a temperature and a distance from a center in the optical sensor according to the first embodiment and in an optical sensor using only carbon as an infrared absorbing film. FIG. 5 is a graph showing a comparison between a sensitivity of the optical sensor according to the first embodiment and a sensitivity of an optical sensor using only carbon as an infrared absorbing film. FIG. 6 is a schematic plan view of an appearance of an optical sensor according to a second embodiment of the present disclosure. FIG. 7 is a schematic cross-sectional view of the optical sensor according to the second embodiment showing a cross-section taken along line VII-VII in FIG. 6. FIG. 8 is a schematic plan view of an appearance of an optical sensor according to a third embodiment of the present disclosure. DETAILED DESCRIPTION In an optical sensor, a temperature difference is formed depending on light received by a light absorbing film, and this temperature difference (thermal energy) is converted into electric energy. The optical sensor is required to have an improved sensitivity. Therefore, an object of the present disclosure is to provide an optical sensor having an improved sensitivity. First, embodiments of the present disclosure will be listed