Photodetector and method of manufacturing the same

Abstract

This invention provides a photodetector and its fabrication method. The photodetector includes an intrinsic layer, a first electrode contact layer, an isolation layer, multiple second electrode contact layers, a lower electrode, an insulating layer, and an upper electrode. The first electrode contact layer is disposed on a first surface of the intrinsic layer; the isolation layer is disposed on a second surface of the intrinsic layer, dividing the second surface into multiple working areas; the multiple second electrode contact layers are each disposed within a working area. A groove is formed on the surface of the isolation layer, and a through-slot is formed on one side wall of the groove, connecting to one of the second electrode contact layers. The lower electrode is disposed along the groove and passes through the through-slot to be electrically connected to the second electrode contact layer; the insulating layer is disposed on the surface of the lower electrode; the upper electrode is disposed on the insulating layer and extends to be electrically connected to the second electrode contact layer on the other side. Compared with existing detectors, the photodetector of this invention significantly reduces the dead zone.

Description

Technical Field

[0001] This invention relates to the field of semiconductor testing equipment, and in particular to a photodetector and its fabrication method. Background Technology

[0002] Scanning electron microscopes (SEMs) are indispensable key equipment in 12-inch wafer fabs. As a "quality control officer," they precisely observe and analyze the surface structure of wafers by emitting high-energy electron beams and receiving secondary electron signals. PN junction detectors are widely used in scanning electron microscopes. Figure 1 This diagram illustrates the planar structure of a conventional twelve-segment detector. The detector surface is divided into four sector regions, each further subdivided into three sub-regions. The entire plane serves as the collection area, also known as the sensitive area, responsible for collecting returning secondary electrons and generating an electrical signal. The lines represent the signal conduction area, which does not participate in signal collection and is therefore also called the dead zone. Leads from the center along the lines to the edge of the sensitive area transmit the signal to the peripheral amplification circuit. The twelve-segment detector effectively improves the detector's response speed, reduces image acquisition time, and thus increases the equipment's throughput.

[0003] Figure 2 for Figure 1 The cross-sectional schematic diagram of the signal conduction region of the detector is shown in the figure. This region consists of two parallel metal leads responsible for transmitting the electrical signal to the external amplification circuit. Because the detector's dead zone cannot participate in signal collection, secondary electrons carrying sample surface topological information cannot be effectively detected in this region. This detection blind zone leads to significant unevenness in brightness and darkness in the final acquired image, and also presents dark lines corresponding to the shape of the detector's dead zone, significantly impacting image quality. Since the secondary electron signal cannot be effectively captured, the system's ability to extract defect features is significantly reduced, resulting in a substantial decrease in the success rate of scanning electron microscopy in detecting wafer defects. This phenomenon seriously affects production efficiency and product quality control. Summary of the Invention

[0004] One objective of this invention is to provide a photodetector with a smaller dead zone.

[0005] Another objective of this invention is to provide a method for fabricating a photodetector with a smaller dead zone.

[0006] According to one aspect of the present invention, a photodetector is provided, comprising an intrinsic layer, a first electrode contact layer, an isolation layer, a plurality of second electrode contact layers, a lower electrode, an insulating layer, and an upper electrode.

[0007] The first electrode contact layer is disposed on the first surface of the intrinsic layer; the isolation layer is disposed on the second surface of the intrinsic layer and divides the second surface into multiple working areas; multiple second electrode contact layers are disposed in one working area respectively.

[0008] Furthermore, a groove is formed on the surface of the insulating layer, and a through groove is formed on one side wall of the groove, connecting to a second electrode contact layer. The lower electrode is disposed along the groove, and the lower electrode passes through the through groove and is electrically connected to the second electrode contact layer; an insulating layer is disposed on the surface of the lower electrode; the upper electrode is disposed on the insulating layer, and the upper electrode extends to be electrically connected to the second electrode contact layer on the other side.

[0009] Optionally, the photodetector also includes a dielectric layer disposed on the surface of the groove.

[0010] Optionally, the dielectric layer is composed of an insulating material; or the dielectric layer is composed of one of the following materials: silicon oxide, hafnium oxide, or aluminum oxide.

[0011] Optionally, the thickness of the dielectric layer is 3 nm to 5 nm.

[0012] Optionally, the insulating layer is composed of insulating material; or the insulating layer is composed of one of the following materials: silicon oxide, silicon nitride, or aluminum oxide.

[0013] Optionally, the first electrode contact layer is an N-type heavily doped layer, and the second electrode contact layer is a P-type heavily doped layer.

[0014] According to another aspect of the present invention, the present invention provides a method for fabricating a photodetector, the method comprising: forming a groove on the surface of an isolation layer of a detector substrate; the detector substrate comprising an intrinsic layer, a first electrode contact layer disposed on a first surface of the intrinsic layer, an isolation layer disposed on a second surface of the intrinsic layer and dividing the second surface into multiple working areas, and multiple second electrode contact layers respectively disposed in a working area; forming a through groove communicating with a second electrode contact layer on one side wall of the groove; disposing a lower electrode along the groove and electrically connecting the lower electrode through the through groove to the second electrode contact layer; disposing an insulating layer on the surface of the lower electrode; disposing an upper electrode on the insulating layer and extending the upper electrode to electrically connect with the second electrode contact layer on the other side.

[0015] Optionally, before the step of forming a through groove on one side wall of the groove that connects to a second electrode contact layer, the preparation method further includes: setting a dielectric layer on the surface of the groove.

[0016] Alternatively, the insulating layer and the dielectric layer are formed by a deposition process.

[0017] Alternatively, the grooves and channels are formed by an etching process.

[0018] Compared with existing detectors, the photodetector of the present invention improves the electrode arrangement of the signal transmission region. By stacking the upper and lower electrodes one on the top and bottom, and using the groove formed on the isolation layer and the insulating layer formed between the upper and lower electrodes to hide and separate the upper and lower electrodes, the dead zone range is greatly reduced.

[0019] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of some specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0020] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a schematic top view of an existing twelve-segment detector; Figure 2 yes Figure 1 A schematic cross-sectional view of the signal conduction region of the detector shown. Figure 3 This is a schematic cross-sectional view of a photodetector according to an embodiment of the present invention; Figure 4 yes Figure 3 A partially enlarged schematic diagram of part A of the photodetector shown; Figure 5 This is a schematic flowchart of a method for fabricating a photodetector according to an embodiment of the present invention; Figure 6 This is a partial schematic diagram of the top surface formed after performing the steps of the preparation method in this application. Detailed Implementation

[0021] Figure 3 This is a schematic cross-sectional view of a photodetector 10 according to an embodiment of the present invention; Figure 4 yes Figure 3 A partially enlarged schematic diagram of part A of the photodetector 10 shown; Figure 6 This is a partial schematic diagram of the top surface formed after performing the steps of the preparation method in this application.

[0022] refer to Figure 3 and Figure 4As shown, this embodiment provides a photodetector 10. Obviously, the figure only schematically shows a partial cross-sectional view of the photodetector 10 at a signal conduction region 12. The photodetector 10 of this embodiment includes an intrinsic layer 21, a first electrode contact layer 22, an isolation layer 23, a plurality of second electrode contact layers 24, a lower electrode 31, an insulating layer 32, and an upper electrode 33.

[0023] The first electrode contact layer 22 is disposed on the first surface of the intrinsic layer 21; the isolation layer 23 is disposed on the second surface of the intrinsic layer 21 and divides the second surface into multiple working areas; and multiple second electrode contact layers 24 are disposed in one working area respectively.

[0024] Furthermore, a groove 231 is formed on the surface of the insulating layer 23, and a through groove 232 is formed on one side wall of the groove 231, which connects to a second electrode contact layer 24. The lower electrode 31 is disposed along the groove 231, and the lower electrode 31 passes through the through groove 232 and is electrically connected to the second electrode contact layer 24; an insulating layer 32 is disposed on the surface of the lower electrode 31; an upper electrode 33 is disposed on the insulating layer 32, and the upper electrode 33 extends to be electrically connected to the second electrode contact layer 24 on the other side.

[0025] In this embodiment, the intrinsic layer 21 can be a lightly doped semiconductor layer, such as intrinsic silicon. The first and second surfaces of the intrinsic layer 21 are the lower and upper surfaces of the intrinsic layer 21. The first electrode contact layer 22 is an N-type heavily doped layer, and the second electrode contact layer 24 is a P-type heavily doped layer. The first electrode contact layer 22 and the second electrode contact layer 24 form a PN junction for converting optical signals into electrical signals. That is, the photodetector 10 in this embodiment is a PN junction detector. Multiple working areas on the second surface can be referenced. Figure 1 As shown, its position corresponds to the collection area 11 of the photodetector 10 used to collect the returned secondary electrons, also known as the sensitive area. The second electrode contact layer 24 is disposed within the working area, and its surface forms the collection area 11 of the photodetector 10. The isolation layer 23 is used to isolate the second electrode contact layer 24 in different working areas, and can be made of pure silicon.

[0026] In this embodiment, the photodetector 10 has a groove 231 formed on the surface of the isolation layer 23 along the setting direction of the isolation layer 23. (Refer to...) Figure 6 As shown in Figure b, the groove 231 has sidewalls on both sides to separate the groove 231 from the second electrode contact layers 24 on both sides. (Reference) Figure 6As shown in Figure d, a through groove 232 is formed on one side wall of the groove 231, connecting to a second electrode contact layer 24. This allows the lower electrode 31, disposed within the groove 231, to pass through the through groove 232 and be electrically connected to the second electrode contact layer 24 on one side while simultaneously isolating it from the second electrode contact layer 24 on the other side. An upper electrode 33 is disposed above the lower electrode 31 and extends to be electrically connected to the second electrode contact layer 24 on the other side. An insulating layer 32 is disposed on the surface of the lower electrode 31 to isolate the lower electrode 31 from the upper electrode 33. In some optional embodiments, the insulating layer 32 is composed of an insulating material, specifically silicon oxide, silicon nitride, aluminum oxide, etc.

[0027] In addition, the photodetector 10 of this embodiment also includes a first electrode 34 disposed on the surface of the first electrode contact layer 22. That is, referring to Figure 3 As shown, the detector substrate 20 of the photodetector 10 in this embodiment sequentially includes: an isolation layer 23 and multiple second electrode contact layers 24 disposed on the same layer, an intrinsic layer 21, and a first electrode contact layer 22. A first electrode 34 electrically connected to the first electrode contact layer 22 is disposed on the surface of the first electrode contact layer 22. The second electrodes electrically connected to the multiple second electrode contact layers 24 are divided into an upper electrode 33 and a lower electrode 31 and disposed at the isolation layer 23. The first electrode 34, the upper electrode 33, and the lower electrode 31 are all made of metal, such as copper or aluminum.

[0028] The existing twelve-segment detector has the same arrangement as this application in the detector substrate 20, namely the intrinsic layer 21, the first electrode contact layer 22, the second electrode contact layer 24, and the isolation layer 23. However, because the existing detector places the two electrodes on the surface of the second electrode contact layer 24 on both sides of the isolation layer 23, the dead zone width is relatively large: not only can the isolation layer 23 area not participate in signal collection, but the electrode placement position cannot participate in signal collection either. This embodiment, without changing the arrangement of the detector substrate 20, creatively proposes a new electrode arrangement method. By dividing the second electrode into an upper electrode 33 and a lower electrode 31 and stacking them vertically, and using the groove 231 formed on the isolation layer 23 and the insulating layer 32 formed between the upper electrode 33 and the lower electrode 31 to hide and separate the upper electrode 33 and the lower electrode 31, the width occupied by the electrodes and the isolation layer 23 is greatly reduced, and the dead zone range is narrowed.

[0029] In some alternative embodiments, the photodetector 10 further includes a dielectric layer 25 disposed on the surface of the groove 231.

[0030] The dielectric layer 25 is used to reduce the surface states of the isolation layer 23 and improve the metal adhesion of the underlying electrode 31. Its composition is an insulating material, specifically silicon oxide, hafnium oxide, aluminum oxide, etc. In some optional embodiments, the thickness of the dielectric layer 25 is 3 nm to 5 nm.

[0031] It should be noted that the surfaces mentioned in this invention refer to the exposed surfaces. For example, the first and second surfaces of the intrinsic layer 21 refer to the upper and lower surfaces of the intrinsic layer 21 as shown in the illustration when the first electrode contact layer 22 and the second electrode contact layer 24 are not provided; the surface of the isolation layer 23 refers to the exposed upper surface of the isolation layer 23 as shown in the illustration (i.e., Figure 6 The surface shown in a); the surface of the groove 231 refers to the newly formed surface of the isolation layer 23 after the groove 231 is formed, including both the bottom surface and the sidewall surface of the groove 231; the surface of the lower electrode 31 refers to the surface of the lower electrode 31 exposed from the opening of the groove 231 after it is placed in the groove 231, and also includes the surface exposed from the opening of the through groove 232 (see reference). Figure 6 (as shown in e). In particular, insulating layer 32 can be as... Figure 6 As shown in f, it is only provided on the surface of the lower electrode 31 exposed from the opening of the groove 231, and can also further cover the surface of the lower electrode 31 exposed from the opening of the through groove 232.

[0032] Figure 5 This is a schematic flowchart of a method for fabricating a photodetector 10 according to an embodiment of the present invention.

[0033] This embodiment also provides a method for fabricating the photodetector 10. Figure 6 a to g sequentially illustrate partial top views of the photodetector 10 at a signal conduction region 12 after the fabrication method of this embodiment has been executed step by step. (Reference) Figure 5 and Figure 6 As shown, the preparation method includes the following steps: Step S502: A groove 231 is formed on the surface of the isolation layer 23 of the detector substrate 20; Step S504: A through groove 232 is formed on one side wall of the groove 231, which connects to a second electrode contact layer 24; Step S506: Set the lower electrode 31 along the groove 231 and make the lower electrode 31 pass through the through groove 232 and electrically connect with the second electrode contact layer 24; Step S508: An insulating layer 32 is formed on the surface of the lower electrode 31; Step S510: An upper electrode 33 is disposed on the insulating layer 32, and the upper electrode 33 extends to be electrically connected to the second electrode contact layer 24 on the other side.

[0034] The detector substrate 20 includes an intrinsic layer 21, a first electrode contact layer 22 disposed on a first surface of the intrinsic layer 21, an isolation layer 23 disposed on a second surface of the intrinsic layer 21 and dividing the second surface into multiple working areas, and multiple second electrode contact layers 24 disposed within a single working area. The fabrication method of the photodetector 10 in this embodiment is an improvement on the fabrication method for the detector substrate 20 of existing detectors, specifically addressing the placement of the second electrodes, without requiring a redesign of the manufacturing process of the detector substrate 20 itself. Therefore, the fabrication method of this embodiment can fully utilize the already mass-produced detector substrate 20 and its mature fabrication line, and can be directly applied to existing semiconductor production lines, greatly reducing the modification cost and technical barriers of upgrading from the original process to this solution.

[0035] Furthermore, the preparation method of this embodiment does not affect the setting of the first electrode 34. The setting step of the first electrode 34 can be placed in any preparation step of the photodetector 10. For example, the first electrode 34 can be set on the surface of the first electrode contact layer 22 before or after the setting step of the lower electrode 31 in step S506, or the first electrode 34 can be set on the surface of the first electrode contact layer 22 before or after the setting step of the upper electrode 33 in step S510, and so on.

[0036] In some alternative embodiments, the groove 231 and the through-slot 232 are formed by an etching process. The etching process is not limited to reactive ion etching (RIE) or the like.

[0037] In some alternative embodiments, prior to the step of forming a through groove 232 communicating with a second electrode contact layer 24 on one side wall of the groove 231, the preparation method further includes: providing a dielectric layer 25 on the surface of the groove 231.

[0038] In other words, in this embodiment, after etching the groove 231 on the isolation layer 23 and before etching the through groove 232, a dielectric layer 25 is first provided on the surface of the groove 231. The dielectric layer 25 can protect the groove 231 and prevent accidental over-etching of the groove 231 during the etching of the through groove 232, which would cause the groove 231 to become too deep and thus contact the intrinsic layer 21.

[0039] refer to Figure 6 As shown, among them Figure 6 a to Figure 6 b illustrates the changes on the surface of the isolation layer 23 of the detector substrate 20 before and after execution step S502, namely, the formation of grooves 231 on the surface of the isolation layer 23 that are spaced apart from the second electrode contact layers 24 on both sides. Figure 6 The vertical dashed line in b indicates the location of groove 231, rather than implying that its material is different from that of the two side walls. Figure 6c illustrates the change in the surface of the groove 231 after the step of setting the dielectric layer 25 on the surface of the groove 231 is performed, that is, the surface is covered by the dielectric layer 25. Figure 6 d illustrates the change of the isolation layer 23 on the side wall of the groove 231 after performing step S504, that is, the formation of a through groove 232 that connects to a second electrode contact layer 24. By controlling the etching range, this through groove 232 can extend into the second electrode contact layer 24 in order to increase the contact area between the lower electrode 31 and the second electrode contact layer 24. Figure 6 e illustrates the internal changes of the groove 231 and the through groove 232 after executing step S506, that is, the lower electrode 31 is provided in the groove 231, and the lower electrode 31 passes through the through groove 232 and is electrically connected to the second electrode contact layer 24. Figure 6 f illustrates the changes on the surface of the lower electrode 31 after executing step S508, namely, an insulating layer 32 is provided on the surface of the lower electrode 31. As previously mentioned, the insulating layer 32 can be used as... Figure 6 As shown in f, it is only provided on the surface of the lower electrode 31 exposed from the opening of the groove 231, and can also further cover the surface of the lower electrode 31 exposed from the opening of the through groove 232. Figure 6 g illustrates the change on the surface of the insulating layer 32 after step S510 is executed, namely, an upper electrode 33 is provided on the insulating layer 32, and the upper electrode 33 extends to be electrically connected to the second electrode contact layer 24 on the other side.

[0040] In some alternative embodiments, before performing step S510, a second electrode contact groove can be etched on the surface of the second electrode contact layer 24, which is not electrically connected to the lower electrode 31, so that the upper electrode 33 can... Figure 4 The second electrode contact groove is extended into the second electrode contact layer 24 to increase the contact area with the second electrode contact layer 24. In some optional embodiments, the step of etching the second electrode contact groove can be performed in step S504, that is, while etching the through groove 232 connecting one second electrode contact layer 24, the second electrode contact groove is also etched on the surface of the other second electrode contact layer 24. The etching position of the second electrode contact groove can be set to be close to the isolation layer 23.

[0041] In some alternative embodiments, the insulating layer 32 and the dielectric layer 25 are formed by a deposition process. The deposition process is not limited to thin film deposition processes, etc.

[0042] In some alternative embodiments, the lower electrode 31 and the upper electrode 33 are formed by metal deposition processes. The metal deposition processes are not limited to physical vapor deposition (PVD), chemical vapor deposition (CVD), thermal evaporation coating, etc.

[0043] In the description of this embodiment, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0044] The terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first," "second," etc., may explicitly or implicitly include at least one of that feature, that is, include one or more of that feature.

[0045] In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified. When a feature "includes or contains" one or more of the features it covers, unless otherwise specifically described, this indicates that other features are not excluded and may be further included.

[0046] Unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," and "coupling," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art should be able to understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0047] In the description of this invention, references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, apparatus, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, apparatus, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0048] Unless otherwise specified, all terms (including technical and scientific terms) used in the description of the embodiments of the present invention have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0049] Therefore, those skilled in the art should recognize that although numerous exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and construed as covering all such other variations or modifications.

Claims

1. A photodetector, comprising: Intrinsic layer; A first electrode contact layer is disposed on the first surface of the intrinsic layer; An isolation layer is disposed on the second surface of the intrinsic layer, and the second surface is divided into multiple working areas; Multiple second electrode contact layers are respectively disposed within one of the working areas; and The surface of the isolation layer has a groove, and a through groove connecting a second electrode contact layer is formed on one side wall of the groove. The photodetector also includes: A lower electrode is disposed along the groove, and the lower electrode passes through the through groove and is electrically connected to the second electrode contact layer; An insulating layer is disposed on the surface of the lower electrode; An upper electrode is disposed on the insulating layer, and the upper electrode extends to be electrically connected to the second electrode contact layer on the other side.

2. The photodetector according to claim 1, further comprising: A dielectric layer is disposed on the surface of the groove.

3. The photodetector according to claim 2, wherein... The dielectric layer is composed of insulating material; or The dielectric layer is composed of one of the following materials: silicon oxide, hafnium oxide, or aluminum oxide.

4. The photodetector according to claim 2, wherein The thickness of the dielectric layer is 3 nm to 5 nm.

5. The photodetector according to claim 1, wherein... The insulating layer is composed of insulating material; or The insulating layer is composed of one of the following materials: silicon oxide, silicon nitride, or aluminum oxide.

6. The photodetector according to claim 1, wherein... The first electrode contact layer is an N-type heavily doped layer, and the second electrode contact layer is a P-type heavily doped layer.

7. A method for fabricating a photodetector, comprising: A groove is formed on the surface of the isolation layer of the detector substrate; The detector substrate includes an intrinsic layer, a first electrode contact layer disposed on a first surface of the intrinsic layer, an isolation layer disposed on a second surface of the intrinsic layer and dividing the second surface into multiple working areas, and multiple second electrode contact layers disposed in one of the working areas; A through groove is formed on one side wall of the groove, connecting to a second electrode contact layer; A lower electrode is disposed along the groove, and the lower electrode passes through the through groove and is electrically connected to the second electrode contact layer; An insulating layer is provided on the surface of the lower electrode; An upper electrode is disposed on the insulating layer and extends to be electrically connected to the second electrode contact layer on the other side.

8. The method for fabricating a photodetector according to claim 7, wherein... Before the step of forming a through groove communicating with a second electrode contact layer on one side wall of the groove, the method further includes: A medium layer is provided on the surface of the groove.

9. The method for fabricating a photodetector according to claim 8, wherein... The insulating layer and the dielectric layer are formed by a deposition process.

10. The method for fabricating a photodetector according to claim 7, wherein... The grooves and through slots are formed by an etching process.

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