Light detector, light detection system, lidar device, and vehicle

According to one embodiment, a light detector includes a conductive layer, a first element, a second element, a first member, a first insulating part, and a second insulating part. The conductive layer includes a first conductive portion and a second conductive portion. The first element includes a first semiconductor layer and a second semiconductor layer. The second element includes a fourth semiconductor layer and a fifth semiconductor layer. The first member is provided between the first element and the second element and electrically connected to the conductive layer. The first member is conductive. The first insulating part is provided between the first element and the first member. The second insulating part is provided between the second element and the first member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-157217, filed on Aug. 29, 2019; the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a light detector, a light detection system, a lidar device, and a vehicle.

BACKGROUND

A light detector detects light incident on an element including a semiconductor. It is desirable to increase the performance of the light detector.

DETAILED DESCRIPTION

According to one embodiment, a light detector includes a conductive layer, a first element, a second element, a first member, a first insulating part, and a second insulating part. The conductive layer includes a first conductive portion and a second conductive portion. The first element includes a first semiconductor layer and a second semiconductor layer. The first semiconductor layer is of a first conductivity type. The second semiconductor layer is of a second conductivity type and is provided between the first conductive portion and the first semiconductor layer in a second direction crossing a first direction. The first direction is from the first conductive portion toward the second conductive portion. The second element includes a fourth semiconductor layer and a fifth semiconductor layer. The fourth semiconductor layer is of the first conductivity type. The fifth semiconductor layer is of the second conductivity type and is provided between the second conductive portion and the fourth semiconductor layer in the second direction. The first member is provided between the first element and the second element and electrically connected to the conductive layer. The first member is conductive. The first insulating part is provided between the first element and the first member. The second insulating part is provided between the second element and the first member.

The drawings are schematic or conceptual; and the relationships between the thicknesses and widths of portions, the proportions of sizes between portions, etc., are not necessarily the same as the actual values thereof. The dimensions and/or the proportions may be illustrated differently between the drawings, even in the case where the same portion is illustrated.

In the drawings and the specification of the application, components similar to those described thereinabove are marked with like reference numerals, and a detailed description is omitted as appropriate.

First Embodiment

FIG.1is a schematic plan view illustrating a light detector according to a first embodiment.

FIG.2AandFIG.2Bare schematic cross-sectional views illustrating the light detector according to the first embodiment.

As shown inFIG.1andFIG.2A, the light detector110according to the first embodiment includes a conductive layer10, a first element21, a second element22, a first insulating part31, a second insulating part32, and a conductor40. The first insulating part31surrounds the first element21. The second insulating part32surrounds the second element22. The conductor40surrounds the first insulating part31and the second insulating part32. The first element21, the second element22, the first insulating part31, the second insulating part32, and the conductor40are provided on the conductive layer10. Herein, the direction from the back toward the front in the page surface ofFIG.1is taken as “up”.

Carriers are generated in the first element21when light is incident on the first element21. Similarly, carriers are generated in the second element22when light is incident on the second element22. The light detector110detects the light incident on the elements as electrical signals.

The conductive layer10includes a first conductive portion11and a second conductive portion12. The direction from the first conductive portion11toward the second conductive portion12is taken as a first direction. For example, the first direction is along an X-direction shown inFIG.1. One direction perpendicular to the X-direction is taken as a Y-direction. A direction perpendicular to the X-direction and the Y-direction is taken as a Z-direction. A direction that crosses the first direction is taken as a second direction. For example, the second direction is along the Z-direction. A direction crossing a plane parallel to the first direction and the second direction is taken as a third direction. For example, the third direction is along the Y-direction. Hereinbelow, a case will be described where the first direction, the second direction, and the third direction are respectively along the X-direction, the Z-direction, and the Y-direction.

The first element21includes a first semiconductor layer21aof a first conductivity type, a second semiconductor layer21bof a second conductivity type, and a third semiconductor layer21cof the second conductivity type. The first semiconductor layer21a, the second semiconductor layer21b, and the third semiconductor layer21cspread along the X-direction and the Y-direction. The second semiconductor layer21band the third semiconductor layer21care provided between the first semiconductor layer21aand the first conductive portion11. The first semiconductor layer21ais separated from the first conductive portion11in the Z-direction. The second semiconductor layer21bis provided between the first conductive portion11and the first semiconductor layer21ain the Z-direction. The third semiconductor layer21cis provided between the first conductive portion11and the second semiconductor layer21bin the Z-direction and surrounds the first semiconductor layer21aand the second semiconductor layer21balong the X-Y plane. For example, the third semiconductor layer21ccontacts the first conductive portion11. The first semiconductor layer21a, the second semiconductor layer21b, and the third semiconductor layer21care electrically connected to the first conductive portion11.

The second element22includes a fourth semiconductor layer22dof the first conductivity type, a fifth semiconductor layer22eof the second conductivity type, and a sixth semiconductor layer22fof the second conductivity type. The fourth semiconductor layer22d, the fifth semiconductor layer22e, and the sixth semiconductor layer22fspread along the X-direction and the Y-direction. The fifth semiconductor layer22eand the sixth semiconductor layer22fare provided between the fourth semiconductor layer22dand the second conductive portion12in the Z-direction. The fourth semiconductor layer22dis separated from the second conductive portion12in the Z-direction. The fifth semiconductor layer22eis provided between the second conductive portion12and the fourth semiconductor layer22din the Z-direction. The sixth semiconductor layer22fis provided between the first conductive portion11and the fifth semiconductor layer22ein the Z-direction and surrounds the fourth semiconductor layer22dand the fifth semiconductor layer22ealong the X-Y plane. For example, the sixth semiconductor layer22fcontacts the second conductive portion12. The fourth semiconductor layer22d, the fifth semiconductor layer22e, and the sixth semiconductor layer22fare electrically connected to the second conductive portion12.

The conductive layer10spreads along the X-direction and the Y-direction and is arranged in the Z-direction with the first element21and the second element22. For example, the potential of the conductive layer10is controlled via the conductor40described below. Also, the potential of the second semiconductor layer21band the potential of the fifth semiconductor layer22ecan be controlled by controlling the potential of the conductive layer10. By controlling the potential of the second semiconductor layer21band the potential of the fifth semiconductor layer22e, voltages are applied between the first semiconductor layer21aand the second semiconductor layer21band between the fourth semiconductor layer22dand the fifth semiconductor layer22e. For example, the first element21and the second element22function as avalanche photodiodes.

For example, the first conductivity type is an n-type; and the second conductivity type is a p-type. The first conductivity type may be the p-type; and the second conductivity type may be the n-type. The impurity concentration of the second conductivity type in the third semiconductor layer21cis lower than the impurity concentration of the second conductivity type in the second semiconductor layer21b. Thereby, carriers that are generated in the third semiconductor layer21cmove into the second semiconductor layer21band undergo avalanche multiplication. The impurity concentration of the second conductivity type in the sixth semiconductor layer22fis lower than the impurity concentration of the second conductivity type in the fifth semiconductor layer22e. Thereby, carriers that are generated in the sixth semiconductor layer22fmove easily into the fifth semiconductor layer22e; and crosstalk can be reduced.

The direction from the first element21toward the second element22is along the X-direction. For example, the direction from the first semiconductor layer21atoward the fourth semiconductor layer22dis along the X-direction. The direction from the second semiconductor layer21btoward the fifth semiconductor layer22eis along the X-direction. The direction from the third semiconductor layer21ctoward the sixth semiconductor layer22fis along the X-direction.

The conductor40is provided around the first element21and the second element22along the X-Y plane. In other words, the conductor40surrounds the first element21and the second element22. In the example shown inFIG.1,FIG.2A, andFIG.2B, one unbroken conductor40is provided to be continuous around the first element21and the second element22. The configuration is not limited to the example; multiple conductors40may be arranged to be separated from each other around the first element21and the second element22; and the first element21and the second element22may be surrounded with the multiple conductors40. However, to reduce the crosstalk and reduce the resistance of the conductor40, it is favorable for the first element21and the second element22to be surrounded continuously with one conductor40.

Herein, “surround” includes not only the case where an unbroken component continuously surrounds another component, but also includes the case where multiple components are separated from each other and arranged around the other component. For example, the other component can be considered to be surrounded with the multiple components when the other component is positioned inside a path obtained by tracing along the multiple components.

It is favorable for the length in the Z-direction of the conductor40to be longer than the length in the Z-direction of the first element21and longer than the length in the Z-direction of the second element22. The length in the Z-direction of the conductor40is greater than the thicknesses in the Z-direction of the first semiconductor layer21a, the second semiconductor layer21b, and the third semiconductor layer21c. The conductor40contacts the conductive layer10. A portion of the conductor40may pierce the conductive layer10. The entire first element21and the entire second element22are covered with the conductor40in the X-direction and the Y-direction. In other words, the entire first element21and the entire second element22overlap the conductor40when viewed from the X-direction and from the Y-direction.

The conductor40includes a first member40apositioned between the first element21and the second element22in the X-direction. The first insulating part31is provided between the first element21and the first member40ain the X-direction. For example, the first insulating part31is provided around the first element21along the X-Y plane. In other words, the first insulating part31surrounds the first element21. Multiple first insulating parts31may be arranged around the first element21; and the first element21may be surrounded with the multiple first insulating parts31.

The second insulating part32is provided between the second element22and the first member40ain the X-direction. For example, the second insulating part32is provided around the second element22along the X-Y plane. In other words, the second insulating part32surrounds the second element22. Multiple second insulating parts32may be arranged around the second element22; and the second element22may be surrounded with the multiple second insulating parts32.

For example, the first insulating part31and the second insulating part32contact the conductive layer10. Because the first insulating part31and the second insulating part32contact the conductive layer10, it is possible to reduce the crosstalk and reduce the leakage current between the conductor40and the elements.

A semiconductor part25ais provided between the first insulating part31and the first member40ain the X-direction. A semiconductor part25bis provided between the second insulating part32and the first member40ain the X-direction. For example, the semiconductor parts25aand25bare of the second conductivity type.

The light detector110illustrated inFIG.1,FIG.2A, andFIG.2Bfurther includes a third element23, a fourth element24, a third insulating part33, a fourth insulating part34, first to fourth wiring parts51ato51d, a first connection wiring part52a, a second connection wiring part52b, first to fourth conductive parts53ato53d, a wiring part54, and first to third insulating regions61to63. The first to third insulating regions61to63are not illustrated inFIG.1. InFIG.1, the regions shown by broken lines show the regions where the first element21, the second element22, the third element23, the fourth element24, the conductor40, the first to fourth wiring parts51ato51d, the first connection wiring part52a, the second connection wiring part52b, the first to fourth conductive parts53ato53d, and the wiring part54contact each other.

As shown inFIG.2B, the conductive layer10further includes a third conductive portion13. The direction from the first conductive portion11toward the third conductive portion13is along the Y-direction.

The third element23includes a seventh semiconductor layer23gof the first conductivity type, an eighth semiconductor layer23hof the second conductivity type, and a ninth semiconductor layer23iof the second conductivity type. The seventh semiconductor layer23gis separated from the third conductive portion13in the Z-direction. The eighth semiconductor layer23his provided between the third conductive portion13and the seventh semiconductor layer23gin the Z-direction. The ninth semiconductor layer23iis provided between the third conductive portion13and the eighth semiconductor layer23hin the Z-direction and surrounds the seventh semiconductor layer23gand the eighth semiconductor layer23halong the X-Y plane. The impurity concentration of the second conductivity type in the ninth semiconductor layer23iis lower than the impurity concentration of the second conductivity type in the eighth semiconductor layer23h. For example, the third element23contacts the third conductive portion13.

The conductor40further includes a second member40bpositioned between the first element21and the third element23in the Y-direction. A portion of the first insulating part31is provided between the first element21and the second member40bin the Y-direction. The third insulating part33is provided between the third element23and the second member40bin the Y-direction. For example, the third insulating part33is provided around the third element23along the X-Y plane. For example, a portion of the third insulating part33is provided between the first conductive portion11and the third conductive portion13in the Y-direction.

The semiconductor part25ais provided between the first insulating part31and the second member40bin the Y-direction. A semiconductor part25cis provided between the third insulating part33and the second member40bin the Y-direction. For example, the semiconductor part25cis of the second conductivity type.

The direction from the second element22toward the fourth element24is along the Y-direction. The direction from the third element23toward the fourth element24is along the X-direction. The fourth insulating part34is provided around the fourth element24along the X-Y plane. The structure of the fourth element24is, for example, the same as the structure of the first element21.

The first wiring part51ais electrically connected to the first semiconductor layer21a. The second wiring part51bis electrically connected to the fourth semiconductor layer22d. The third wiring part51cis electrically connected to the seventh semiconductor layer23g. The fourth wiring part51dis electrically connected to the semiconductor layer of the first conductivity type of the fourth element24.

As shown inFIG.1andFIG.2A, in the Z-direction, the first element21and the first insulating part31are provided between the first conductive portion11and the first wiring part51a, between the first conductive portion11and the first insulating region61, and between the first conductive portion11and the first connection wiring part52a. In the Z-direction, the second element22and the second insulating part32are provided between the second conductive portion12and the second wiring part51b, between the second conductive portion12and the second insulating region62, and between the second conductive portion12and the second connection wiring part52b. As shown inFIG.1andFIG.2B, in the Z-direction, the third element23and the third insulating part33are provided between the third conductive portion13and the third wiring part51c, between the third conductive portion13and the third insulating region63, and between the third conductive portion13and the first connection wiring part52a.

The first conductive part53ais connected between the first connection wiring part52aand the first wiring part51a. The second conductive part53bis connected between the second connection wiring part52band the second wiring part51b. The third conductive part53cis connected between the first connection wiring part52aand the third wiring part51c. The fourth conductive part53dis connected between the second connection wiring part52band the fourth wiring part51d. The electrical resistances of the first to fourth conductive parts53ato53deach are higher than the electrical resistances of the wiring parts and higher than the electrical resistances of the connection wiring parts. For example, the first to fourth conductive parts53ato53dfunction as quenching resistances. For example, it is favorable for the electrical resistances of the first to fourth conductive parts53ato53deach to be not less than 50 kΩ and not more than 2 MΩ.

The first to fourth wiring parts51ato51d, the first connection wiring part52a, the second connection wiring part52b, and the first to fourth conductive parts53ato53dare electrically isolated from the conductor40. For example, as shown inFIG.2A, a portion of the first insulating region61is provided between the conductor40and the first connection wiring part52a.

The conductor40is electrically connected to the wiring part54. The position where the conductor40and the wiring part54are connected is arbitrary. The direction from the wiring part54toward one of the first to fourth wiring parts51ato51dis along a direction parallel to the X-Y plane.

Examples of the materials of the components are described below.

The first to fourth elements21to24include silicon. When the first to fourth elements21to24include silicon, at least one selected from the group consisting of arsenic, phosphorus, and antimony may be used as the impurity of the first conductivity type. Boron may be used as the impurity of the second conductivity type.

The semiconductor parts25a,25b, and25cinclude, for example, silicon and boron. The materials of the semiconductor parts25a,25b, and25cmay be the same or may be different from each other.

The impurity concentrations of the semiconductor layers are, for example, as follows.

The impurity concentration of the first conductivity type is not less than 1.0×1018atoms/cm3and not more than 1.0×1021atoms/cm3for the first semiconductor layer21a, the fourth semiconductor layer22d, and the seventh semiconductor layer23g. By setting this concentration range, the electrical resistances of the first semiconductor layer21a, the fourth semiconductor layer22d, and the seventh semiconductor layer23gcan be reduced; and the carrier loss in these semiconductor layers can be reduced.

The impurity concentration of the second conductivity type is not less than 1.0×1016atoms/cm3and not more than 1.0×1018atoms/cm3for the second semiconductor layer21b, the fifth semiconductor layer22e, and the eighth semiconductor layer23h. By setting this concentration range, the second semiconductor layer21b, the fifth semiconductor layer22e, and the eighth semiconductor layer23hcan have p-n junctions respectively with the first semiconductor layer21a, the fourth semiconductor layer22d, and the seventh semiconductor layer23g; and depletion layers can spread easily in the second semiconductor layer21b, the fifth semiconductor layer22e, and the eighth semiconductor layer23h.

The impurity concentration of the second conductivity type is not less than 1.0×1013atoms/cm3and not more than 1.0×1016atoms/cm3for the third semiconductor layer21c, the sixth semiconductor layer22f, and the ninth semiconductor layer23i. By setting this concentration range, depletion layers can spread sufficiently in the third semiconductor layer21c, the sixth semiconductor layer22f, and the ninth semiconductor layer23i; and the light detection efficiency or the light-receiving sensitivity can be increased.

The conductive layer10is a semiconductor layer of the second conductivity type. The impurity concentration of the second conductivity type in the conductive layer10is not less than 1.0×1017atoms/cm3and not more than 1.0×1021atoms/cm3. The conductive layer10may include a metal. For example, the conductive layer10includes at least one selected from the group consisting of aluminum, copper, titanium, gold, and nickel.

The first to fourth insulating parts31to34include at least one selected from the group consisting of silicon, oxygen, and nitrogen.

The first to fourth wiring parts51ato51d, the first connection wiring part52a, the second connection wiring part52b, and the wiring part54include at least one selected from the group consisting of aluminum and copper. The first to fourth wiring parts51ato51d, the first connection wiring part52a, the second connection wiring part52b, and the wiring part54may include an aluminum compound.

The first to fourth conductive parts53ato53dinclude polysilicon. The first to fourth conductive parts53ato53dmay further include an impurity of the first conductivity type or the second conductivity type.

The first to third insulating regions61to63include at least one selected from the group consisting of silicon, oxygen, and nitrogen. The first to third insulating regions61to63each may include multiple layers. For example, the first to third insulating regions61to63each include a layer including silicon oxide, a layer including silicon oxide, boron, and phosphorus, and a layer including silicon oxide.

The conductor40includes, for example, at least one selected from the group consisting of tungsten, polysilicon, aluminum, copper, nickel, titanium, and chrome. The conductor40can be provided with conductivity thereby. The conductor40may include an alloy including aluminum and copper.

Or, the conductor40includes at least one selected from the group consisting of tungsten, aluminum, copper, nickel, titanium, and chrome. Thereby, the light transmittance of the conductor40can be lower than the light transmittance of the third semiconductor layer21cand lower than the light transmittance of the sixth semiconductor layer22f.

Favorably, the conductor40includes at least one selected from the group consisting of tungsten, aluminum, and copper. Thereby, the conductor40can be provided with conductivity; and the light transmittance of the conductor40can be lower than the light transmittances of the semiconductor layers.

Examples of the lengths of the components will now be described.

The thicknesses in the Z-direction of the first semiconductor layer21a, the fourth semiconductor layer22d, and the seventh semiconductor layer23gare not less than 10 nm and not more than 2000 nm.

The second semiconductor layer21b, the fifth semiconductor layer22e, and the eighth semiconductor layer23hare positioned respectively at the lower portions of the first semiconductor layer21a, the fourth semiconductor layer22d, and the seventh semiconductor layer23g. The thicknesses in the Z-direction of the second semiconductor layer21b, the fifth semiconductor layer22e, and the eighth semiconductor layer23hare not less than 10 nm and not more than 5000 nm.

The thickness in the Z-direction of the third semiconductor layer21cis thicker than the total of the thickness in the Z-direction of the first semiconductor layer21aand the thickness in the Z-direction of the second semiconductor layer21band is 15 μm or less. The thickness in the Z-direction of the sixth semiconductor layer22fis thicker than the total of the thickness in the Z-direction of the fourth semiconductor layer22dand the thickness in the Z-direction of the fifth semiconductor layer22eand is 15 μm or less. The thickness in the Z-direction of the ninth semiconductor layer23iis thicker than the total of the thickness in the Z-direction of the seventh semiconductor layer23gand the thickness in the Z-direction of the eighth semiconductor layer23hand is 15 μm or less.

The length in the Z-direction of the first insulating part31is longer than the total of the thickness in the Z-direction of the first semiconductor layer21aand the thickness in the Z-direction of the second semiconductor layer21band is 20 μm or less.

The length in the Z-direction of the second insulating part32is longer than the total of the thickness in the Z-direction of the fourth semiconductor layer22dand the thickness in the Z-direction of the fifth semiconductor layer22eand is 20 μm or less.

The length in the Z-direction of the third insulating part33is longer than the total of the thickness in the Z-direction of the seventh semiconductor layer23gand the thickness in the Z-direction of the eighth semiconductor layer23hand is 20 μm or less.

For example, the thicknesses in the Z-direction of the first semiconductor layer21a, the fourth semiconductor layer22d, and the seventh semiconductor layer23geach are taken as T1. The thicknesses in the Z-direction of the second semiconductor layer21b, the fifth semiconductor layer22e, and the eighth semiconductor layer23heach are taken as T2. The thicknesses in the Z-direction of the third semiconductor layer21c, the sixth semiconductor layer22f, and the ninth semiconductor layer23ieach are taken as T3. The lengths in the Z-direction of the first insulating part31, the second insulating part32, and the third insulating part33each are taken as L1. In such a case, it is favorable for the relationships of the following Formula (1) and Formula (2) to be satisfied.
T1+1.1×T2<L1  (1)
L1<T1+T2+1.1×T3  (2)

By setting the length L1to satisfy Formula (1), the flow toward the conductor40of the carriers generated at each p-n junction surface can be suppressed sufficiently. By setting the length L1to satisfy Formula (2), the formation of the first to third insulating parts31to33is easy. Therefore, the yield of the light detector110can be increased.

However, when the thickness T2is greater than 10 times the thickness T3, it is favorable for the relationships of the following Formula (3) and Formula (4) to be satisfied.
T1+1.1×T2<L1  (3)
T1+T2+1.1×T3<L1  (4)

By setting the length L1to satisfy Formula (3) and Formula (4), the yield of the light detector110can be increased while suppressing the flow toward the conductor40of the carriers generated at each p-n junction surface.

It is favorable for the lengths in the Z-direction of the first member40aand the second member40beach to be greater than the thicknesses in the Z-direction of the third semiconductor layer21c, the sixth semiconductor layer22f, and the ninth semiconductor layer23i. The crosstalk can be reduced thereby. On the other hand, it is favorable for the lengths in the Z-direction of the first member40aand the second member40beach to be 20 μm or less to make the patterning of these members easy.

It is favorable for the distance in the X-direction between the first insulating part31and the second insulating part32to be 10 μm or less. Thereby, the surface area in the X-Y plane of the first element21and the second element22can be large; and the light detection efficiency can be increased. On the other hand, if the distance is too short, it is difficult to provide the first member40a. Therefore, it is favorable for the distance in the X-direction between the first insulating part31and the second insulating part32to be 0.5 μm or more.

It is favorable for the side surfaces of the first insulating part31, the second insulating part32, the first member40a, and the second member40beach to be oblique to the Z-direction. In other words, it is favorable for the widths of the first insulating part31, the second insulating part32, the first member40a, and the second member40bto decrease toward the conductive layer10. According to such configurations, it is easy to fill the insulating material or the conductive material when forming the first insulating part31, the second insulating part32, the first member40a, and the second member40b. Therefore, the yield of the light detector110can be increased.

FIG.3A,FIG.3B,FIG.4A, andFIG.4Bare schematic cross-sectional views illustrating manufacturing processes of the light detector according to the first embodiment.

A semiconductor layer20L of the second conductivity type is formed on a semiconductor layer10L of the second conductivity type. For example, the semiconductor layer20L is formed by epitaxial growth of silicon. Multiple trenches that pierce the semiconductor layer20L are formed. For example, the trenches are formed by reactive ion etching (RIE). Each of the trenches surrounds a portion of the semiconductor layer20L. Insulating layers are formed in the trenches. For example, the insulating layers are formed by chemical vapor deposition (CVD) using tetraethoxysilane. As shown inFIG.3A, an insulating layer31L and an insulating layer32L are formed thereby. Heat treatment of the semiconductor layer20L may be performed when forming the insulating layers. The defects of the semiconductor layer20L occurring when the trenches are formed can be repaired thereby.

A semiconductor layer of the first conductivity type and a semiconductor layer of the second conductivity type are formed in the portion of the semiconductor layer20L surrounded with the insulating layer by sequentially ion-implanting an impurity of the first conductivity type and an impurity of the second conductivity type. For example, a semiconductor layer21L of the first conductivity type and a semiconductor layer22L of the second conductivity type are formed inside the insulating layer31L. A semiconductor layer24L of the first conductivity type and a semiconductor layer25L of the second conductivity type are formed inside the insulating layer32L. An insulating layer61L which covers the semiconductor layer20L is formed by CVD. As shown inFIG.3B, an insulating layer62L is formed on the insulating layer61L. For example, the insulating layer61L includes silicon oxide. The insulating layer62L includes silicon oxide, boron, and phosphorus.

After melting the insulating layer62L, the melted insulating layer62L is caused to solidify. The flatness of the surface of the insulating layer62L improves thereby. A not-illustrated polysilicon layer is formed on the insulating layer62L; and the polysilicon layer is patterned. The conductive layers that correspond to the quenching resistances are formed thereby. As shown inFIG.4A, an insulating layer63L is formed by CVD on the insulating layer62L and the conductive layer. The insulating layer63L includes, for example, silicon oxide.

A trench is formed between the insulating layers piercing the semiconductor layer20L. The trench reaches the semiconductor layer10L. A metal layer40L is formed in the trench by CVD. The metal layer40L includes, for example, tungsten. Then, openings are formed by removing a portion of the insulating layer61L, a portion of the insulating layer62L, and a portion of the insulating layer63L by RIE. The semiconductor layers of the first conductivity type are exposed via the openings. A metal layer50L is formed on the insulating layer63L. The openings are filled with the metal layer50L. For example, the metal layer50L includes aluminum and is formed by sputtering. As shown inFIG.4B, multiple wiring parts are formed by patterning the metal layer50L. Thus, the light detector according to the first embodiment is manufactured.

According to the first embodiment, the performance of the light detector110can be improved as follows.

In the first embodiment, the conductor40is conductive and is electrically connected to the conductive layer10. For example, a portion of the first member40ais provided between the first conductive portion11and the second conductive portion12. Thereby, the potential of the conductive layer10can be controlled via the conductor40. The control of the potential of the conductive layer10is easy. Also, by providing the first insulating part31and the second insulating part32, the occurrence of the leakage current between the conductor40and the first element21and the occurrence of the leakage current between the conductor40and the second element22can be suppressed.

Or, in the first embodiment, the light transmittance of the first member40ais lower than the light transmittance of the third semiconductor layer21cand lower than the light transmittance of the sixth semiconductor layer22f. For example, the light transmittance of the first member40ais lower than the light transmittance of the first insulating part31and lower than the light transmittance of the second insulating part32. Thereby, secondary photons that are generated in one of the first element21or the second element22can be suppressed from entering the other of the first element21or the second element22. As a result, the crosstalk can be reduced.

The configurations described above may be combined. Namely, in the first embodiment, the conductor40is conductive; the first insulating part31and the second insulating part32are provided; and the light transmittance of the first member40ais lower than the light transmittance of the third semiconductor layer21cand lower than the light transmittance of the sixth semiconductor layer22f. Accordingly, the crosstalk can be reduced while making the control of the potential of the conductive layer10easy and suppressing the occurrence of the leakage current.

Second Embodiment

FIG.5AandFIG.5Bare schematic cross-sectional views illustrating a light detector according to a second embodiment.

In the light detector120according to the second embodiment shown inFIG.5AandFIG.5B, the first insulating part31and the second insulating part32contact the first member40aof the conductor40. The first insulating part31and the third insulating part33contact the second member40bof the conductor40.

Or, one of the semiconductor part25aor25bmay be provided between the first insulating part31and the first member40aor between the second insulating part32and the first member40a. One of the semiconductor part25aor25cmay be provided between the first insulating part31and the second member40bor between the third insulating part33and the second member40b.

In the light detector120, compared to the light detector110, the length in the X-direction of the first member40ais long; and the length in the Y-direction of the second member40bis long. According to the second embodiment, the following effects are obtained in addition to the effects of the first embodiment.

When the conductor40is conductive, the electrical resistance of the conductor40can be reduced. Thereby, the fluctuation of the potential of the conductive layer10can be suppressed when controlling the potential of the conductive layer10via the conductor40. Or, when the light transmittance of the conductor40is lower than the light transmittances of the semiconductor layers, the secondary photons do not pass through the conductor40easily. The crosstalk can be reduced thereby.

According to the second embodiment, compared to the first embodiment, the width of the trench formed between the insulating layers31L and32L can be wide when forming the metal layer40L shown inFIG.3BandFIG.4A. In other words, compared to the first embodiment, the ratio of the width of the trench to the depth of the trench is large. Thereby, it is easy to form the trench and the metal layer40L. As a result, for example, the yield of the light detector120can be increased.

Third Embodiment

FIG.6is a schematic plan view illustrating a light detector according to a third embodiment.

In the light detector130according to the third embodiment shown inFIG.6, the first connection wiring part52aand the second connection wiring part52bdo not overlap the conductor40in the Z-direction.

For example, multiple conductors40are provided in the X-direction. When viewed from the Z-direction, the first connection wiring part52ais positioned between one of the multiple conductors40and another one of the multiple conductors40in the X-direction. When viewed from the Z-direction, the second connection wiring part52bis positioned between the other one of the multiple conductors40and yet another one of the multiple conductors40in the X-direction.

According to the light detector130, the parasitic capacitance that occurs between the connection wiring part and the conductor40can be reduced. Therefore, according to the third embodiment, the following effects are obtained in addition to the effects of the first embodiment or the second embodiment. For example, the sensitivity when each element detects the light can be increased. Also, the effects on the time constant of the output pulse due to the parasitic capacitance can be reduced; and the crosstalk due to the parasitic capacitance can be suppressed.

Fourth Embodiment

FIG.7is a schematic plan view illustrating a light detector according to a fourth embodiment.

The light detector140according to the fourth embodiment shown inFIG.7includes a first member41and a second member42.

The first member41includes a first region41aprovided between the first element21and the second element22and between the third element23and the fourth element24in the X-direction. The first member41further includes multiple third regions41c. One end in the X-direction of each third region41cis connected to the first region41a.

The second member42includes a second region42bprovided between the first element21and the third element23in the Y-direction. The second region42bis positioned between the third regions41cin the Y-direction. The first element21is positioned between the second region42band one of the multiple third regions41c. The third element23is positioned between the second region42band another one of the multiple third regions41c.

The second member42further includes a fourth region42d. One end in the X-direction of the second region42bis connected to the fourth region42d. The first element21and the third element23are positioned between the first region41aand the fourth region42din the X-direction.

For example, the first member41and the second member42are conductive and are electrically connected to the conductive layer10. For example, the first member41and the second member42include tungsten.

The first member41and the second member42are separated from each other. Thereby, the semiconductor part25aand the semiconductor part25care linked between the first region41aand the other end of the second region42b. The multiple wiring parts54are electrically connected respectively to the first member41and the second member42.

The first connection wiring part52adoes not overlap the first member41or the second member42in the Z-direction. In other words, when viewed from the Z-direction, the position of the first connection wiring part52ais different from the position of the first member41and the position of the second member42. The position in the X-direction and the position in the Y-direction of each portion of the first connection wiring part52aare different from the position in the X-direction and the position in the Y-direction of the first member41. Also, the position in the X-direction and the position in the Y-direction of each portion of the first connection wiring part52aare different from the position in the X-direction and the position in the Y-direction of the second member42. For example, when viewed from the Z-direction, portions of the first connection wiring part52aare positioned between the fourth region42dand the third regions41c. When viewed from the Z-direction, another portion of the first connection wiring part52ais positioned between the first region41aand the second region42b. The parasitic capacitance between the first connection wiring part52aand the first member41and the parasitic capacitance between the first connection wiring part52aand the second member42can be reduced thereby.

For example, the light transmittances of the first member41and the second member42each are lower than the light transmittances of the third semiconductor layer21c, the sixth semiconductor layer22f, and the ninth semiconductor layer23i. As shown inFIG.7, the position in the X-direction of the gap between the first region41aand the second region42bis different from the position in the X-direction of the gap between the third region41cand the fourth region42d. According to the fourth embodiment, in addition to the effects of at least one of the first to third embodiments, the secondary photons that are generated in one element can be suppressed from entering an adjacent element. As a result, the crosstalk can be reduced further.

Fifth Embodiment

FIG.8is a schematic plan view illustrating a light detector according to a fifth embodiment.

FIG.9AandFIG.9Bare schematic cross-sectional views illustrating the light detector according to the fifth embodiment.

The light detector150shown inFIG.8,FIG.9A, andFIG.9Bincludes an insulating layer45and first to fourth connection parts55ato55d.

The conductor40is conductive in the light detector150according to the fifth embodiment. As shown inFIG.8, the first to fourth connection parts55ato55dare electrically connected to the conductor40. The first to fourth wiring parts51ato51dare electrically connected respectively to the first to fourth connection parts55ato55dvia the first to fourth conductive parts53ato53d.

As shown inFIG.9AandFIG.9B, the insulating layer45is provided between the conductor40and the conductive layer10. The conductor40is electrically isolated from the conductive layer10by the insulating layer45.

For example, the insulating layer45includes at least one selected from the group consisting of silicon, oxygen, and nitrogen. For example, the first to fourth connection parts55ato55dinclude at least one selected from the group consisting of aluminum, tungsten, copper, and titanium.

The conductor40is used as wiring in the light detector150. According to the fifth embodiment, in addition to the effects of at least one of the first to fourth embodiments, the amount of wiring provided on each element can be reduced. As a result, for example, the light detector can be downsized.

Sixth Embodiment

FIG.10AandFIG.10Bare schematic cross-sectional views illustrating a light detector according to a sixth embodiment.

In the light detector160according to the sixth embodiment shown inFIG.10AandFIG.10B, the first member40acontacts the first insulating part31and the second insulating part32. The second member40bcontacts the first insulating part31and the third insulating part33.

Or, a semiconductor part25may be provided between the first insulating part31and the first member40aor between the second insulating part32and the first member40a. The semiconductor part25may be provided between the first insulating part31and the second member40bor between the third insulating part33and the second member40b.

In the light detector160, compared to the light detector120, the length in the X-direction of the first member40ais long; and the length in the Y-direction of the second member40bis long. According to the sixth embodiment, the following effects are obtained in addition to the effects of at least one of the first to fifth embodiments.

When the conductor40is conductive, the electrical resistance of the conductor40can be reduced. Or, when the light transmittance of the conductor40is lower than the light transmittances of the semiconductor layers, the secondary photons do not pass through the conductor40easily. The crosstalk can be reduced thereby.

Seventh Embodiment

FIG.11AandFIG.11Bare schematic cross-sectional views illustrating a light detector according to a seventh embodiment.

In the light detector170according to the seventh embodiment shown inFIG.11AandFIG.11B, the first semiconductor layer21aand the second semiconductor layer21bcontact the first insulating part31. The fourth semiconductor layer22dand the fifth semiconductor layer22econtact the second insulating part32. The seventh semiconductor layer23gand the eighth semiconductor layer23hcontact the third insulating part33. Other than the points where the first to third insulating parts31to33contact the semiconductor layers, the configuration of the light detector170is, for example, similar to that of the light detector110.

According to the seventh embodiment, similarly to the first embodiment, the potential of the conductive layer10is controllable via the conductor40if the conductor40is conductive. Also, the occurrence of the leakage current between the conductor40and the first element21and the occurrence of the leakage current between the conductor40and the second element22can be suppressed by the first insulating part31and the second insulating part32. Or, the crosstalk can be reduced when the light transmittance of the first member40ais lower than the light transmittance of the third semiconductor layer21cand lower than the light transmittance of the sixth semiconductor layer22f.

The semiconductor layers similarly may contact the first to third insulating parts31to33in the light detectors according to any of the second to sixth embodiments.

Eighth Embodiment

FIG.12is a schematic view illustrating a lidar (Laser Imaging Detection and Ranging) device according to an eighth embodiment.

The embodiment is applicable to a long-distance subject detection system (LIDAR) or the like including a line light source and a lens. The lidar device5001includes a light projecting unit T projecting laser light toward an object411, and a light receiving unit R (also called a light detection system) receiving the laser light from the object411, measuring the time of the round trip of the laser light to and from the object411, and converting the time into a distance.

In the light projecting unit T, a laser light oscillator (also called a light source)404produces laser light. A drive circuit403drives the laser light oscillator404. An optical system405extracts a portion of the laser light as reference light, and irradiates the rest of the laser light on the object411via a mirror406. A mirror controller402projects the laser light onto the object411by controlling the mirror406. Herein, “project” means to cause the light to strike.

In the light receiving unit R, a reference light detector409detects the reference light extracted by the optical system405. A light detector410receives the reflected light from the object411. Based on the reference light detected by the reference light detector409and the reflected light detected by the light detector410, a distance measuring circuit408measures the distance to the object411. An image recognition system407recognizes the object411based on the results measured by the distance measuring circuit408.

The lidar device5001employs light time-of-flight ranging in which the time of the round trip of the laser light to and from the object411is measured and converted into a distance. The lidar device5001is applied to an automotive drive-assist system, remote sensing, etc. Good sensitivity is obtained particularly in the near-infrared region when the light detectors of the embodiments described above are used as the light detector410. Therefore, the lidar device5001is applicable to a light source of a wavelength band invisible to humans. For example, the lidar device5001can be used for obstacle detection in a vehicle.

FIG.13is a drawing for describing the detection of the detection object of the lidar device.

A light source3000emits light412toward an object600which is the detection object. A light detector3001detects light413which passes through the object600, is reflected by the object600, or is diffused by the object600.

For example, the light detector3001realizes a highly-sensitive detection when the light detector according to the embodiment described above is used. It is favorable to provide multiple sets of the light detector410and the light source404and to preset the arrangement relationship in the software (which is replaceable with a circuit). For example, it is favorable for the arrangement relationship of the sets of the light detector410and the light source404to be at uniform spacing. Thereby, an accurate three-dimensional image can be generated by the output signals of each light detector410supplementing each other.

FIG.14is a schematic top view of a vehicle including the lidar device according to the eighth embodiment.

A vehicle700according to the embodiment includes the lidar devices5001at four corners of a vehicle body710. Because the vehicle according to the embodiment includes the lidar devices at the four corners of the vehicle body, the environment in all directions of the vehicle can be detected by the lidar devices.

According to the embodiments described above, a light detector can be provided in which the performance is improved.

Hereinabove, embodiments of the invention are described with reference to specific examples. However, the invention is not limited to these specific examples. For example, one skilled in the art may similarly practice the invention by appropriately selecting specific configurations of components included in the light detector such as the conductive layer, the element, the insulating part, the first member, the wiring part, the connection wiring part, the conductive part, the connection part, the insulating region, etc., from known art; and such practice is within the scope of the invention to the extent that similar effects can be obtained.

Moreover, all light detector, all light detection systems, all lidar devices, and all vehicles practicable by an appropriate design modification by one skilled in the art based on the light detector, the light detection system, the lidar device, and the vehicle described above as embodiments of the invention also are within the scope of the invention to the extent that the spirit of the invention is included.