SPAD array and SPAD device
By designing an array structure of multiple microlens in the SPAD array, the problem of difficulty in making microlens in large-size SPAD is solved, the production of large-size SPAD is realized and the photon detection efficiency is improved.
Patent Information
- Application Number
- CN202420698150.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-07
- Publication Date
- 2025-04-11
- Estimated Expiration
- 2034-04-07
AI Technical Summary
The prior art is difficult to effectively produce the high micro lenses required in large-size SPADs, making it difficult to realize large-size SPADs.
A SPAD array is designed, wherein each SPAD unit comprises a PN junction, a metal grid, a dielectric layer and a microlens array, which comprises at least two microlenses, through which the height and difficulty of making the microlens are reduced.
By reducing the height and production difficulty of microlenses, the production of large-size SPADs is achieved, and the photon detection efficiency of SPAD units may be improved.
Smart Images
Figure CN222750788U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the semiconductor field, and in particular to a SPAD array and a SPAD device. Background Art
[0002] SPAD (Single Photon Avalanche Diode) is a photoelectric detection avalanche diode with single-photon detection capability. It has the advantages of high avalanche gain, fast response speed, low power consumption, low cost, and easy integration with CMOS (Complementary Metal Oxide Semiconductor) circuits.
[0003] SPAD is equipped with a microlens (ML), the size of which matches the size of SPAD. Microlens is usually made by photolithography. When the size of SPAD is large, the height of microlens is high, and it is difficult to expose and develop during production. Therefore, it is not easy to make a large-sized microlens, and it is not easy to obtain a large-sized SPAD.
[0004] Therefore, how to solve the above technical problems should be the focus of technical personnel in this field. Utility Model Content
[0005] The purpose of this application is to provide a SPAD array and a SPAD device to reduce the difficulty of manufacturing microlenses and obtain a large-sized SPAD array.
[0006] In order to solve the above technical problems, the present application provides a SPAD array, the SPAD array comprising a plurality of SPAD units, a PN junction is provided on the first surface of the light receiving region of each of the SPAD units, a metal grid is provided on the second surface between the plurality of SPAD units, a dielectric layer is provided above the metal grid and the light receiving region, and a microlens array is provided above the dielectric layer;
[0007] In each of the SPAD units, the microlens array includes at least two microlenses.
[0008] Optionally, in each of the SPAD units, the number of rows and the number of columns of the microlens array are equal, the number of rows and the number of columns of the microlens array are at least 2, and the microlenses are evenly distributed.
[0009] Optionally, the microlens includes a first microlens structure and a second microlens structure wrapping the first microlens structure, and a surface of the second microlens structure is a curved surface.
[0010] Optionally, the microlens is an integrated microlens located above the dielectric layer, and the surface of the microlens is a curved surface.
[0011] Optionally, the cross-sectional shape of the first microlens structure includes any one of a triangle, a rectangle, a trapezoid, and a cone, or any combination thereof.
[0012] Optionally, the material of the first microlens structure and the second microlens includes any one of silicon oxide, silicon nitride, and silicon oxynitride.
[0013] Optionally, the intersection of the edges of the adjacent microlens curved surfaces is located on the upper surface of the dielectric layer.
[0014] Optionally, the intersection of the edges of adjacent microlens curved surfaces is located above the upper surface of the dielectric layer.
[0015] Optionally, also include:
[0016] a passivation layer located on the upper surface of the dielectric layer;
[0017] Correspondingly, the microlens array is located on the upper surface of the passivation layer.
[0018] The present application also provides a SPAD device, which includes any one of the SPAD arrays described above.
[0019] The present application provides a SPAD array, which includes a plurality of SPAD units, wherein a PN junction is provided on the first surface of a light-receiving region of each of the SPAD units, a metal grid is provided on the second surface between the plurality of SPAD units, a dielectric layer is provided above the metal grid and the light-receiving region, and a microlens array is provided above the dielectric layer; in each of the SPAD units, the microlens array includes at least two microlenses.
[0020] It can be seen that the SPAD unit in the SPAD array of the present application includes a PN junction, a metal grid, a dielectric layer and a microlens array, and the microlens array includes more than two microlenses. That is, one SPAD unit in the present application corresponds to at least two microlenses. Compared with the microlenses in the SPAD unit of the related art, the curvature of the microlens in the present application becomes larger, the microlens focuses faster, and the height of the microlens is reduced, thereby reducing the difficulty of exposure and development when making the microlens, which is conducive to obtaining a large-sized SPAD unit. In addition, since one SPAD unit includes at least two microlenses, light can be focused to at least two positions, which may also improve the photon detection efficiency of the SPAD unit.
[0021] In addition, the present application also provides a SPAD device having the above advantages. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions of the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0023] Figure 1 A schematic diagram of the structure of a SPAD array provided in an embodiment of the present application Figure 1 ;
[0024] Figure 2 A schematic diagram of the structure of a SPAD array provided in an embodiment of the present application Figure 2 ;
[0025] Figures 3 to 9 A process flow chart of a SPAD array manufacturing method provided in an embodiment of the present application;
[0026] In the figure, 100, SPAD unit, 1, PN junction, 2, metal grid, 3, dielectric layer, 4, passivation layer, 5, microlens, 6, deep isolation trench structure, 7, first microlens material layer, 8, patterned photoresist layer, 9, first microlens structure. DETAILED DESCRIPTION
[0027] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.
[0028] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.
[0029] As described in the background technology section, a SPAD is provided with a microlens. When the size of the SPAD is large, the height of the microlens required is high, and the exposure and development are difficult during production. Therefore, it is not easy to produce a large-sized microlens, and thus it is not easy to obtain a large-sized SPAD.
[0030] In view of this, the present application provides a SPAD array, please refer to Figure 1The SPAD array includes a plurality of SPAD units 100, a PN junction 1 is provided on the first surface of the light receiving region of each of the SPAD units 100, a metal grid 2 is provided on the second surface between the plurality of SPAD units 100, a dielectric layer 3 is provided above the metal grid 2 and the light receiving region, and a microlens array is provided above the dielectric layer 3;
[0031] In each of the SPAD units 100 , the microlens array includes at least two microlenses 5 .
[0032] The first surface and the second surface are two opposite surfaces. For example, the first surface may be the front surface and the second surface may be the back surface. In this case, the SPAD unit 100 is back-illuminated. Alternatively, the first surface may be the back surface and the second surface may be the front surface. In this case, the SPAD unit 100 is front-illuminated.
[0033] The metal grid 2 includes but is not limited to an aluminum grid and a tungsten grid. When the metal grid 2 is a tungsten grid, the tungsten grid has a small reflection of light, which can reduce crosstalk and weaken the flash phenomenon.
[0034] The dielectric layer 3 may be a silicon oxide layer.
[0035] The SPAD array may further include a deep isolation trench structure 6 to prevent crosstalk between adjacent SPAD units 100 .
[0036] The metal grid 2 is located between adjacent single-photon avalanche diode units, that is, the metal grid 2 is located in the edge area of the single-photon avalanche diode unit, and the central area of the single-photon avalanche diode unit corresponds to the light receiving area.
[0037] In each SPAD unit 100, the number of micro lenses 5 can be set as needed, and is not limited in this application. The micro lenses 5 can be arranged regularly in the form of rows and columns, or in an irregular form.
[0038] As an implementation method, in each of the SPAD units 100 , the number of rows and columns of the microlens array is equal, the number of rows and columns of the microlens array is at least 2, and the microlenses 5 are evenly distributed.
[0039] In this embodiment, the microlenses 5 in the microlens array are arranged in an m×m array, where m is an integer greater than or equal to 2. For example, m can be 2, 3, 4, 5, etc., and the microlenses 5 are evenly distributed. At this time, each microlens 5 is hemispherical.
[0040] In order to improve the protection of the SPAD array, in one embodiment of the present application, it also includes:
[0041] A passivation layer 4 located on the upper surface of the dielectric layer 3;
[0042] Correspondingly, the microlens array is located on the upper surface of the passivation layer 4 .
[0043] It should be noted that the structure of the microlens 5 is not specifically limited in this embodiment and depends on the situation. Two different microlenses 5 are introduced below.
[0044] As an implementation method, the microlens 5 is an integrated microlens located above the dielectric layer 3 , and the surface of the microlens is a curved surface.
[0045] In this embodiment, the microlens 5 is an integrated structure, and the material of the first microlens structure includes but is not limited to any one of silicon oxide, silicon nitride, and silicon oxynitride.
[0046] As another possible implementation, the microlens 5 includes a first microlens structure and a second microlens structure encapsulating the first microlens structure, and the surface of the second microlens structure is a curved surface.
[0047] In this embodiment, the microlens 5 includes two parts, namely, a first microlens structure and a second microlens structure, wherein the materials of the first microlens structure and the second microlens 5 include any one of silicon oxide, silicon nitride, and silicon oxynitride. The materials of the first microlens structure and the second microlens structure may be the same or different. That is, the first microlens structure includes any one of a silicon oxide structure, a silicon nitride structure, and a silicon oxynitride structure; the second microlens structure includes any one of a silicon oxide structure, a silicon nitride structure, and a silicon oxynitride structure.
[0048] The cross-sectional shape of the first microlens structure includes but is not limited to any one or any combination of triangle, rectangle, trapezoid, cone. Correspondingly, the three-dimensional shape of the first microlens structure can be a trihedron, tetrahedron, polyhedron, polygonal trapezoid, rounded trapezoid, cone, etc.
[0049] In the prior art, taking a 10μm spad as an example, when making a microlens, the thickness of the first microlens material layer required is 3μm, and the thickness of the second microlens material is 3.5μm. Such a thick oxide requires a long deposition time and etching time. Moreover, the conventional oxide that manufacturers can produce now is 3μm, which increases the difficulty of production. In this application, taking a 10μm spad as an example, when making a microlens, the thickness of the first microlens material layer required is 2μm, and the thickness of the second microlens material layer is 1.65μm. The thickness of the first and second microlens material layers are greatly reduced, reducing the difficulty of production.
[0050] The microlens array of each SPAD unit 100 includes at least two microlenses 5 , and the curved edges of adjacent microlenses 5 intersect with each other. The position of the intersection of the curved edges of adjacent microlenses 5 is not limited in the present application.
[0051] As an implementation method, Figure 1 As shown, the intersection of the curved edges of adjacent microlenses 5 is located on the upper surface of the dielectric layer 3 .
[0052] As an implementation method, Figure 2 As shown, the intersection of the curved edges of adjacent microlenses 5 is located above the upper surface of the dielectric layer 3 , that is, the intersection of the curved edges of adjacent microlenses 5 is higher than the upper surface of the dielectric layer 3 .
[0053] The SPAD unit 100 in the SPAD array of this embodiment includes a PN junction 1, a metal grid 2, a dielectric layer 3 and a microlens array, and the microlens array includes more than two microlenses 5. That is, one SPAD unit 100 in the present application includes at least two microlenses 5. Compared with the microlenses 5 in the SPAD unit 100 of the related art, the curvature of the microlens 5 in the present application becomes larger, the microlens 5 focuses light faster, and the height of the microlens 5 is reduced, thereby reducing the difficulty of exposure and development when making the microlens 5, which is conducive to obtaining a large-sized SPAD unit 100. In addition, since one SPAD unit 100 includes at least two microlenses 5, light can be focused to at least two positions, which may also improve the photon detection efficiency of the SPAD unit 100.
[0054] The present application also provides a SPAD device, which includes the SPAD array described in any of the above embodiments.
[0055] The following is an introduction to the method for manufacturing the SPAD array in this application using a specific case.
[0056] Step S1: Figure 3 As shown, the first surface of the substrate is sequentially doped with N-type and P-type to form a PN junction 1; a SPAD unit includes a PN junction 1;
[0057] Step S2, manufacturing the deep isolation trench structure 6, the metal grid 2, etc. according to the conventional process flow, and depositing a dielectric layer 3 on the second surface, the material of which is silicon dioxide, and then chemically mechanically polishing the dielectric layer 3, such as Figure 4 As shown;
[0058] Step S3: Figure 5 As shown, a passivation layer 4 is deposited on the surface of the dielectric layer 3, and the material is silicon nitride;
[0059] Step S4: Figure 6As shown, a first microlens material layer 7 is deposited on the surface of the passivation layer 4; the thickness of the first microlens material layer 7 can be adjusted based on the size of the SPAD unit and the height of the microlens 5;
[0060] Step S5: Figure 7 As shown, a patterned photoresist layer 8 is formed on the first microlens material layer 7, the patterned photoresist layer 8 includes a plurality of photoresist columns, and each SPAD unit includes photoresist columns arranged in two rows and two columns;
[0061] Step S6: Figure 8 and Fig. 9 As shown, the first microlens material layer 7 is etched using the patterned photoresist layer 8 as a mask, and the patterned photoresist layer 8 is removed, so that four first microlens structures 9 are formed in each SPAD unit, and the first microlens structures 9 are arranged in two rows and two columns;
[0062] Step S7: Figure 2 As shown, a second microlens material is deposited to form a second microlens structure to obtain a microlens 5;
[0063] Step S8: When the optical path or the shape of the microlens 5 needs to be adjusted, the microlens 5 is etched back. Figure 1 shown.
[0064] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.
[0065] The SPAD array and SPAD device provided by the present application are introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the scheme and core ideas of the present application. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the present application.
Claims
1. A SPAD array, characterized in that: The SPAD array comprises a plurality of SPAD units, a PN junction is provided on the first surface of the light receiving region of each SPAD unit, a metal grid is provided on the second surface between the plurality of SPAD units, a dielectric layer is provided above the metal grid and the light receiving region, and a microlens array is provided above the dielectric layer; In each of the SPAD units, the microlens array includes at least two microlenses.
2. The SPAD array according to claim 1, characterized in that In each of the SPAD units, the number of rows and the number of columns of the microlens array are equal, the number of rows and the number of columns of the microlens array are at least 2, and the microlenses are evenly distributed.
3. The SPAD array according to claim 1, characterized in that The microlens comprises a first microlens structure and a second microlens structure that wraps the first microlens structure, and the surface of the second microlens structure is a curved surface.
4. The SPAD array according to claim 1, characterized in that: The microlens is an integrated microlens located above the dielectric layer, and the surface of the microlens is a curved surface.
5. The SPAD array according to claim 3, characterized in that: The cross-sectional shape of the first microlens structure includes any one of a triangle, a rectangle, a trapezoid, and a cone, or any combination thereof.
6. The SPAD array according to claim 3, characterized in that: The material of the first microlens structure and the second microlens includes any one of silicon oxide, silicon nitride and silicon oxynitride.
7. The SPAD array according to claim 1, characterized in that: The intersection points of the edges of the adjacent microlens curved surfaces are located on the upper surface of the dielectric layer.
8. The SPAD array according to claim 1, wherein: The intersection points of the edges of the adjacent microlens curved surfaces are located above the upper surface of the dielectric layer.
9. The SPAD array according to any one of claims 1 to 8, characterized in that: Also includes: a passivation layer located on the upper surface of the dielectric layer; Correspondingly, the microlens array is located on the upper surface of the passivation layer.
10. A SPAD device, characterized in that: The SPAD device comprises a SPAD array as claimed in any one of claims 1 to 9.