具体实施方式

下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本发明的一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。

需要说明，本发明实施例中所有方向性指示（诸如上、下、左、右、前、后……）仅用于解释在某一特定姿态（如附图所示）下各部件之间的相对位置关系、运动情况等，如果该特定姿态发生改变时，则该方向性指示也相应地随之改变。

另外，在本发明中如涉及“第一”、“第二”等的描述仅用于描述目的，而不能理解为指示或暗示其相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括至少一个该特征。在本发明的描述中，“多个”的含义是至少两个，例如两个，三个等，除非另有明确具体的限定。

在本发明中，除非另有明确的规定和限定，术语“连接”、“固定”等应做广义理解，例如，“固定”可以是固定连接，也可以是可拆卸连接，或成一体；可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通或两个元件的相互作用关系，除非另有明确的限定。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本发明中的具体含义。

另外，本发明各个实施例之间的技术方案可以相互结合，但是必须是以本领域普通技术人员能够实现为基础，当技术方案的结合出现相互矛盾或无法实现时应当认为这种技术方案的结合不存在，也不在本发明要求的保护范围之内。

本发明提供了一种光电探测器，所述光电探测器包括硅基层10、连接层20、第一陷光层30、第二陷光层40及光栅层50，所述硅基层10上相对的两面分别为入光面11和出光面12；所述连接层20设置在所述出光面12上；所述第一陷光层30设置在所述入光面11朝向所述出光面12的一侧；所述第二陷光层40设置在所述出光面12朝向所述入光面11的一侧；所述光栅层50设置在所述连接层20与所述出光面12之间。

本实施例中，所述硅基层10均采用背照式（Back Side Illumination，BSI）雪崩二极管（Single Photon Avalanche Diode，SPAD）结构，向所述硅基层10中注入离子，所述连接层20内用于安装SPAD与外部电源或设备电连接的电路。背照式工艺将做好电极和引线的SPAD直接翻转并与下方所述连接层20中的电路连接，然后把SPAD上方减薄至目标厚度，从而大幅提高SPAD的填充因子（Fill Factor），提高光电探测效率。

请参照图1，入射光从所述入光面11进入所述硅基层10中，透过所述硅基层10从底部的所述出光面12射出，部分光在所述连接层20的作用下被反射再次进入所述硅基层10中。

所述硅基层10内具有雪崩区90，也可以通过调整所述硅基层10中雪崩区90大小的方式来提高入射光的光程，入射光通常为近红外光。入射光在所述硅基层10中被吸收，并在迁移到雪崩区90引发雪崩。未被吸收的入射光从所述出光面12射出，最后被所述连接层20反射回所述硅基层10。

在所述连接层20的底部，也即所述连接层20背离所述硅基层10的一侧还可设置晶圆层。所述连接层20由二氧化硅制成，通过蚀刻、嵌入等方式在所述连接层20上制作形成金属连线。并与底部晶圆层中的晶圆体键合。近红外光透过所述硅基层10，并将检测的电信号通过线路发送至晶圆层。

其中二氧化硅对近红外光吸收为0。此外，所述连接层20也可以采用其他相同或相似性能材料进行制备。

为了提高近红外光的吸收效率，在所述入光面11的内侧，也即朝向所述出光面12的一侧设置了所述第一陷光层30；同时，在所述出光面12的内侧，也即朝向所述入光面11的一侧设置了所述第二陷光层40。在设置陷光层后，需对陷光层平坦化。

在所述入光面11的外侧还可以安装透镜80，透镜80可以采用凸透镜80，从而起到光线汇聚的效果，使更多的近红外光穿过所述入光面11进入到所述硅基层10中。

当近红外光通过所述入光面11进入所述硅基层10后，部分近红外光由于反射作用会被反射至所述入光面11，因此，在所述第一陷光层30作用下，近红外光通过所述第一陷光层30的表面再次反射，避免其射出所述入光面11，从而起到将近红外光限制在所述硅基层10中的作用，以提高所述硅基层10的光吸收率。

另外，通过调整所述第一陷光层30的表面形状，还能够使近红外光产生漫反射效果，进一步增加近红外光在所述硅基层10中的光程，从而提高对近红外光的吸收率。

作为一种实施例，可通过在所述入光面11上设置多个凸块形成所述第一陷光层30，实现改变表面形状的效果。具体的，所述第一陷光层30包括多个第一凸块31，多个所述第一凸块31均匀间隔设置在所述入光面11上。

所述第一凸块31可以采用四棱锥结构，请参照图1，所述第一凸块31的横截面呈三角形。多个所述第一凸块31间隔设置形成锯齿状结构，近红外光射入后在所述第一陷光层30的实现所述第一陷光层30的漫反射效果。

当近红外光透过所述硅基层10后，最终会射入到所述出光面12上。同理，在所述出光面12上设置多个所述第二凸块41来形成所述第二陷光层40。所述第二凸块41的形状与所述第一凸块31的形状相似。同样达到防止近红外光从所述硅基层10中射出，在所述第一陷光层30和所述第二陷光层40的相互配合下，实现将近红外光“锁”在所述硅基层10中的效果，提高所述硅基层10的光吸收率。

然而，需要说明的是，为了能使所述连接层20与底部的晶圆体电连接，需要在所述出光面12一侧设置电极。

因此，请参照图2，所述出光面12上具有第一电极区121、围合在所述第一电极区121的第一安装区123以及围合在所述第一安装区123周围的第二电极区122。

本实施例中使用Charge focusing（电荷聚焦）结构，所述出光面12一侧需要留出用于与电极连接的所述第一电极区121和所述第二电极区122。

所述第一电极区121可设置在所述出光面12的中心位置，所述第一安装区123则呈环形将所述第一电极区121包裹住，最后将所述出光面12上剩余的边缘部分作为所述第二电极区122。

其中，所述第一电极区121与SPAD阴极电连接，所述第二电极区122与SPAD阳极电连接，中间呈环形设置的所述第一安装区123则用于安装多个所述第二凸块41。

在上述方案中，针对不同方向的近红外光进行检测时，所述入光面11的安装方向可进行调整，例如向左或者向右等。

同时，在所述光栅层50的作用下，所述光栅层50与所述第二陷光层40相互配合，能够使得近红外光产生衍射效应，改变其光场分布。同时所述光栅层50与所述硅基层10之间也会产生等离子体激元效应，增加所述硅基层10的红外吸收率。

本实施例中，通过FDTD 光场仿真，请参照图4，当近红外光波长为850nm左右时，光吸收率为73%；当近红外光波长为905nm左右时，光吸收率为64%；当近红外光波长为940nm左右时，光吸收率为57%。得出结论，针对各个波长段的近红外光，光吸收率均有明显提升。

本发明技术方案分别在所述硅基层10的入光面11和出光面12上设置了陷光层，在所述第二陷光层40的作用下，改变了所述出光面12的表面结构，降低了光在进入所述出光面12时的反射率，配合所述光栅层50与硅形成等离子体激元效应，增强所述硅基层10的光吸收效率。在所述第一陷光层30的作用下，提高了光的反射率，防止光从所述入光面11射出，大大提高了所述硅基层10的光吸收率。

进一步地，所述光栅层50包括多个光栅条51，多个所述光栅条51间隔设置在所述连接层20与所述出光面12之间；其中，多个所述第二凸块41呈阵列分布，所述光栅条51与所述阵列的行方向或列方向平行。

为了保证所述光栅条51可以与所述硅基层10形成等离子体激元效应，增强所述硅基层10的光吸收率。所述光栅条51的位置应当与所述第二凸块41的位置相对应。因此，在所述连接层20朝向所述出光面12的一侧同样设置环形的所述第二安装区，在垂直所述出光面12的方向，所述第一安装区123与所述第二安装区的投影重叠。

本实施例中，多个所述第二凸块41之间阵列分布在所述第一安装区123内，在安装时，将所述光栅条51保持与所述第二凸块41阵列的行或者列方向平行，为了能够使每一条所述光栅条51能够覆盖住一行或一列所述第二凸块41，可对所述第二凸块41和所述光栅条51的尺寸进行控制和调整。

请参照图2，所述第二凸块41呈四棱锥体，所述第二凸块41在垂直所述出光面12方向上的投影呈正方向，所述光栅条51为长条状的四边形。所述第二凸块41的正方形投影的边长为600nm~800nm，任意相邻两个所述第二凸块41之间的间隔为50nm~200nm。请参照图3，所述光栅条51宽度为100nm~300nm，任意相邻两个所述光栅条51之间的间距为50nm~200nm。通过调整所述第二凸块41和所述光栅条51的尺寸，保证所述光栅条51能够覆盖在每一行或每一列所述第二凸块41上。

进一步地，所述光电探测器还包括反射板60，所述反射板60设置在所述连接层20内，所述反射板60的位置与所述光栅层50的位置相对应。近红外光在穿过所述硅基层10后，最终从所述出光面12射出。

所述反射板60靠近位于所述连接层20靠近所述硅基层10的一侧，采用金属材质制作，从而使得近红外光从所述出光面12射出后，射入到所述反射板60上，在所述反射板60的作用下近红外光被反射又重新从所述出光面12进入到所述硅基层10中，并被所述硅基层10重新吸收。进一步提高整体近红外光的吸收效率，提高检测精确度。

进一步地，所述光电探测器还包括隔离层70，所述隔离层70设置在所述硅基层10的侧壁上。

所述隔离层70设置在所述硅基层10的侧壁内侧，其中，所述硅基层10的侧壁是指连接所述出光面12与所述入光面11的连接壁。请参照图1，侧壁与所述出光面12和所述入光面11垂直连接，根据不同实验对光学特性的要求，可调整侧壁的形状或尺寸。

所述隔离层70将整个所述硅基层10的侧壁包裹住，用于光学串扰隔离。另外，在所述隔离层70的作用下，还能够能防止高电压击穿被包裹的所述硅基层10。提高整体的稳定性。

以上所述仅为本发明的优选实施例，并非因此限制本发明的专利范围，凡是在本发明的发明构思下，利用本发明说明书及附图内容所作的等效结构变换，或直接/间接运用在其他相关的技术领域均包括在本发明的专利保护范围内。

The specific embodiment

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only part of the embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without making creative labor belong to the scope of protection of the present invention.

It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, rear...... ) is only used to explain the relative position relationship between the parts under a specific attitude (as shown in the attached drawing), the movement, etc., and if the specific attitude changes, the directional indication will change accordingly.

In addition, descriptions such as "first", "second", etc., in the present invention are for descriptive purposes only and cannot be construed as indicating or implying their relative importance or implying the number of technical features indicated. Thus, defining the "first" and "second" features may explicitly or implicitly include at least one of those features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise expressly and specifically qualified.

In the present invention, unless otherwise expressly specified and qualified, the terms "connection", "fixed", etc., shall be construed broadly, for example, "fixed" may be a fixed connection, a detachable connection, or a whole, a mechanical connection, an electrical connection, a direct connection, or an indirect connection through an intermediate medium, or an internal connection of two elements or an interaction between two elements, unless otherwise expressly defined. For a person of ordinary skill in the art, the specific meaning of the above terms in the present invention may be understood according to the specific circumstances.

In addition, the technical solutions between the various embodiments of the present invention may be combined with each other, but must be based on those capable of being realized by a person skilled in the art, and when the combination of technical solutions contradicts each other or cannot be realized, it shall be considered that the combination of such technical solutions does not exist, and is not within the scope of protection claimed by the present invention.

The invention provides a photodetector, and the photodetector comprises a silicon base 10, a connecting layer 20, a first light trapping layer 30, the second light trapping layer 40 and the grating layer 50, the two opposite sides of the silicon base layer 10 are respectively the light entering surface 11 and the light outlet surface 12; the connecting layer 20 is arranged on the light outlet surface 12; the first light trapping layer 30 is arranged on one side of the light entering surface 11 towards the light outlet surface 12; the second light trapping layer 40 is arranged on one side of the light outlet surface 12 towards the light entering surface 11; and the grating layer 50 is arranged between the connecting layer 20 and the light outlet surface 12.

In this embodiment, the silicon base layer 10 adopts a back-side illumination (BSI) avalanche diode (Single Photon Avalanche Diode, SPAD) structure to inject ions into the silicon base layer 10, and the connecting layer 20 is used for installing a circuit for installing the SPAD and the electrical connection of the external power supply or equipment. The back-illuminated process directly flips the SPAD of the electrode and the lead wire and connects it with the circuit in the connection layer 20 below, and then thins the upper part of the SPAD to the target thickness, thereby greatly increasing the fill factor of the SPAD and improving the photoelectric detection efficiency.

Please refer to Fig. 1, the incident light enters the silicon base layer 10 from the light entering surface 11, and through the silicon base layer 10 it is emitted from the light surface 12 at the bottom, and part of the light is reflected and enters the silicon base layer 10 again under the effect of the connecting layer 20.

the silicon base layer 10 has an avalanche zone 90, and the light path of the incident light can also be increased by adjusting the size of the avalanche zone 90 in the silicon base layer 10, and the incident light is usually near-infrared light. The incident light is absorbed in the silicon base layer 10 and initiates an avalanche in the migration to the avalanche zone 90. The incident light that is not absorbed is emitted from the luminous surface 12 and is finally reflected back to the silicon base layer 10 by the connecting layer 20.

A wafer layer may also be arranged at the bottom of the connecting layer 20, that is, on one side where the connecting layer 20 deviates from the silicon base layer 10. the connecting layer 20 is made of silicon dioxide, and a metal connection is formed on the connecting layer 20 by etching, embedding, etc. and bonding to the wafer body in the bottom wafer layer. Near-infrared light passes through the silicon base layer 10, and the detected electrical signal is sent to the wafer layer through the line.

Among them, the absorption of near-infrared light by silica is 0. In addition, the connecting layer 20 can also be prepared by adopting other materials with the same or similar properties.

In order to improve the absorption efficiency of near-infrared light, a first light trap layer 30 is arranged on the inner side of the light entering surface 11, that is, on one side towards the light exit surface 12, and at the same time, a second light trapping layer 40 is arranged on the inner side of the light entering surface 12, that is, on one side facing the light entering surface 11. After setting the sinkhole, the sinkhole layer needs to be flattened.

A lens 80 can also be installed on the outer side of the light-entering surface 11, and the lens 80 may adopt a convex lens 80, so that the effect of light convergence is played, so that more near-infrared light passes through the light-entering surface 11 and enters the silicon base layer 10.

When near-infrared light enters the silicon base layer 10 through the light-entering surface 11, part of the near-infrared light will be reflected to the light-entering surface 11 due to the reflection effect, therefore, under the action of the first light-trapping layer 30, the near-infrared light is reflected again through the surface of the first light-trapping layer 30, so as to avoid it from emitting out of the light-entering surface 11, so as to play the role of near-infrared light being limited in the silicon base layer 10, so as to improve the light absorption rate of the silicon base layer 10.

In addition, by adjusting the surface shape of the first light trap layer 30, the near-infrared light can produce a diffuse reflection effect, and the optical path of the near-infrared light in the silicon base layer 10 is further increased, so that the absorption rate of the near-infrared light is improved.

As an embodiment, the effect of changing the surface shape is achieved by arranging a plurality of bumps on the glossy surface 11 to form the first light-trapping layer 30. Specifically, the first light trapping layer 30 comprises a plurality of first projections 31, and a plurality of first projections 31 are uniformly spaced on the light entering surface 11.

The first bump 31 can adopt a quadrangular pyramid structure, please refer to Figure 1, and the cross-section of the first bump 31 is triangular. a plurality of first bumps 31 are arranged at intervals to form a zigzag structure, and after near-infrared light is injected, the diffuse reflection effect of the first light trap layer 30 is realized in the first light trap layer 30.

When near-infrared light passes through the silicon base layer 10, it will eventually be emitted to the luminous surface 12. In the same way, a plurality of second projections 41 are arranged on the glossy surface 12 to form the second light-trapping layer 40. The shape of the second bump 41 is similar to that of the first bump 31. Similarly, to prevent near-infrared light from being emitted from the silicon base layer 10, under the mutual cooperation of the first light trap layer 30 and the second light trap layer 40, the effect of near-infrared light "locking" in the silicon base layer 10 is realized, and the light absorption rate of the silicon base layer 10 is improved.

However, it should be noted that, in order to electrically connect the connecting layer 20 with the wafer at the bottom, an electrode needs to be arranged on one side of the glossy surface 12.

Therefore, with reference to Fig. 2, the glossy surface 12 has a first electrode area 121, a first installation area 123 enclosed in the first electrode area 121, and a second electrode area 122 enclosed around the first installation area 123.

In this embodiment, a charge focusing (charge focusing) structure is used, and the first electrode region 121 and the second electrode region 122 for connecting with the electrode need to be reserved on one side of the glossy surface 12.

the first electrode area 121 may be arranged at the central position of the glossy surface 12, the first installation area 123 is wrapped in an annular shape around the first electrode area 121, and the remaining edge portion on the glossy surface 12 is finally used as the second electrode area 122.

Wherein, the first electrode area 121 is electrically connected with the SPAD cathode, the second electrode area 122 is electrically connected with the SPAD anode, and the first installation area 123 arranged in the middle in a ring shape is used for installing a plurality of second projections 41.

In the scheme, when detecting near-infrared light in different directions, the installation direction of the light entering surface 11 can be adjusted, such as to the left or to the right.

At the same time, under the effect of the grating layer 50, the grating layer 50 and the second light trap layer 40 cooperate with each other, so that the near-infrared light can produce a diffraction effect and change its light field distribution. At the same time, the plasma miciton effect is also produced between the grating layer 50 and the silicon base layer 10, and the infrared absorption rate of the silicon base layer 10 is increased.

In this embodiment, through the FDTD light field simulation, please refer to Figure 4, when the wavelength of near-infrared light is about 850 nm, the light absorption rate is 73%, when the wavelength of near-infrared light is about 905 nm, the light absorption rate is 64%, and when the wavelength of near-infrared light is about 940 nm, the light absorption rate is 57%. It is concluded that the light absorption rate of near-infrared light in all wavelength bands is significantly improved.

The technical scheme of the present invention is respectively provided with a light trap layer on the light entering surface 11 and the light outlet surface 12 of the silicon base layer 10, under the effect of the second light trapping layer 40, the surface structure of the light outlet surface 12 has been changed, the reflectivity of the light when entering the light outlet surface 12 has been reduced, and the grating layer 50 forms a plasmonic polarion effect with the silicon, and the light absorption efficiency of the silicon base layer 10 has been enhanced. Under the effect of the first light trap layer 30, the reflectivity of light is improved, the light is prevented from being emitted from the light entering surface 11, and the light absorption rate of the silicon base layer 10 is greatly improved.

Further, the grating layer 50 comprises a plurality of grating strips 51, and the grating strips 51 are arranged at intervals between the connecting layer 20 and the grating surface 12;

In order to ensure that the grating strip 51 can form a plasmon effect with the silicon base layer 10, and enhance the light absorption rate of the silicon base layer 10. The position of the grating strip 51 should correspond to the position of the second projection 41. Therefore, a ring-shaped second installation area is similarly arranged on one side of the connecting layer 20 toward the glossy surface 12, and the first installation area 123 overlaps with the projection of the second installation area in the direction of the perpendicular glossing surface 12.

In this embodiment, the arrays between the plurality of the second bumps 41 are distributed in the first installation area 123, and when installed, the grating strips 51 are kept parallel to the row or column directions of the second bumps 41 arrays, and the dimensions of the second bumps 41 and the grating bars 51 can be controlled and adjusted so that each grating bar 51 can cover a row or a column of the second bumps 41.

Please refer to Fig. 2, the second projection 41 is a quadrangular pyramid, the projection of the second projection 41 in the direction of the perpendicular surface 12 is in a positive direction, and the grating strip 51 is a quadrilateral in the shape of a long strip. The side length of the square projection of the second bump 41 is 600nm~800nm, and the interval between any two adjacent second bumps 41 is 50nm~200nm. Please refer to Figure 3, the width of the grating strip 51 is 100nm~300nm, and the spacing between any two adjacent grating strips 51 is 50nm~200nm. By adjusting the dimensions of the second bumper 41 and the grating bar 51, ensure that the grating bar 51 can cover the second bumper 41 in each row or column.

Further, the photodetector further comprises a reflector 60, the reflector 60 is arranged in the connecting layer 20, and the position of the reflector 60 corresponds to the position of the grating layer 50. After passing through the silicon base layer 10, near-infrared light is finally emitted from the glossing surface 12.

the reflector 60 is close to one side of the connecting layer 20 close to the silicon base 10, and is made of metal material, so that after the near-infrared light is emitted from the luminous surface 12, it is emitted into the reflector 60, and under the effect of the reflector 60, the near-infrared light is reflected and enters into the silicon base 10 again from the luminous surface 12, and is reabsorbed by the silicon base 10. Further improve the absorption efficiency of the overall near-infrared light and improve the detection accuracy.

Further, the photodetector further comprises an isolation layer 70, and the isolation layer 70 is arranged on the side wall of the silicon base layer 10.

the isolation layer 70 is arranged on the inner side of the side wall of the silicon base layer 10, wherein the side wall of the silicon base layer 10 refers to the connecting wall connecting the glossy surface 12 and the glossy surface 11. Please refer to Figure 1, the side wall is perpendicular to the light surface 12 and the light surface 11, and the shape or size of the side wall can be adjusted according to the requirements of different experiments for optical properties.

The isolation layer 70 wraps the side wall of the entire silicon base layer 10 for optical crosstalk isolation. In addition, under the effect of the isolation layer 70, it can also prevent the high voltage from penetrating the wrapped silicon base layer 10. Improves overall stability.

The above is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention, and all equivalent structural transformations made by using the contents of the description and drawings of the present invention under the invention conception, or directly or indirectly used in other related technical fields are included in the patent protection scope of the present invention.