A semiconductor neutron detector and a method of manufacturing the same

Abstract

This invention provides a semiconductor neutron detector and its manufacturing method. A semiconductor neutron detector includes: a semiconductor substrate; a trench array formed on the surface of the semiconductor substrate, the trench array defining a semiconductor mesa region isolated from the trench bottom region on the surface of the semiconductor substrate; a neutron conversion material layer filled within the trench array; a back ohmic contact layer disposed on the back side of the semiconductor substrate; and a front ohmic contact layer disposed on the surface of the semiconductor mesa region; wherein the trench array is formed by a plurality of cross-shaped unit trenches arranged in a close-packed tessellation manner, thereby defining the semiconductor mesa region as a continuous two-dimensional interconnected mesh structure. This invention improves the mechanical stability of the semiconductor mesa region, effectively preventing collapse, breakage, or fracture during manufacturing or application, and achieves a synergistic improvement in device reliability and performance.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor neutron detection technology, specifically relating to a semiconductor neutron detector and its manufacturing method. Background Technology

[0002] A semiconductor neutron detector consists of a neutron conversion material and a semiconductor diode. Since neutrons are electrically neutral, they do not ionize when passing through the semiconductor material. However, neutrons undergo nuclear reactions with the conversion material, producing secondary charged particles. These secondary charged particles ionize into numerous electron-hole pairs when passing through the semiconductor diode. Collecting these electron-hole pairs using external electrodes allows for indirect neutron detection.

[0003] Planar semiconductor neutron detectors suffer from neutron detection efficiencies that rarely exceed 5% due to the self-absorption effect of the neutron conversion material. Microstructured semiconductor neutron detectors, however, can significantly improve neutron detection efficiency by increasing the amount of neutron conversion material and the probability of secondary particles entering the detector. Traditional microstructured semiconductor neutron detectors primarily employ three structures: cylindrical, aperture-type, and trench-type. A typical trench-type structure is a long, straight trench semiconductor neutron detector, where a series of parallel, long, straight trenches are etched into a semiconductor substrate and filled with neutron conversion material.

[0004] In this traditional long, straight trench structure, after the trenches are etched, the remaining semiconductor region forms multiple independent, slender fins or wall structures. These structures have a very large aspect ratio, resulting in poor structural mechanical stability. In subsequent processing steps, especially during the centrifugal backfilling of neutron conversion material powder, the enormous centrifugal force easily causes these fragile semiconductor fins to collapse, break, or fracture. Furthermore, physical bombardment during dry etching and stress caused by thermal expansion mismatch during high-temperature passivation or high-temperature applications can also damage the fin structure. This structural instability not only severely affects device manufacturing yield but also reduces the detector's performance reliability in complex or extreme environments. Summary of the Invention

[0005] Based on the above background, the purpose of this invention is to provide a semiconductor neutron detector and its manufacturing method, which solves the technical problems of existing long straight strip trench detectors being prone to collapse and breakage during manufacturing and having low reliability in application due to the poor mechanical stability of semiconductor fins.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A semiconductor neutron detector, comprising:

[0008] Semiconductor substrate layer;

[0009] A trench array formed on the surface of the semiconductor substrate layer, the trench array defining a semiconductor mesa region on the surface of the semiconductor substrate layer that is isolated from the trench bottom region of the trench array;

[0010] A neutron conversion material layer filled within the trench array;

[0011] A back-side ohmic contact layer disposed on the back side of the semiconductor substrate; and,

[0012] An ohmic contact layer is provided on the surface of the semiconductor mesa region;

[0013] The trench array is formed by a plurality of cross-shaped unit trenches arranged in a close-packed tessellation manner, thereby defining the semiconductor mesa region as a continuous two-dimensional interconnection grid structure; each cross-shaped unit trench is composed of two mutually perpendicular intersecting trench segments, and the width Tw of each trench segment, the length L of each trench segment, and the spacing Tg between adjacent trench segments separated by the semiconductor mesa region satisfy the following relationship: L=3Tw+2Tg.

[0014] Preferably, each of the cross-shaped unit grooves is vertically and horizontally symmetrical with respect to its own geometric center.

[0015] High symmetry helps to achieve uniform stress distribution during device manufacturing and operation.

[0016] Preferably, the material of the semiconductor substrate is selected from silicon, germanium, silicon carbide or gallium nitride.

[0017] Silicon and germanium are conventional semiconductor materials, while silicon carbide and gallium nitride, as wide bandgap semiconductor materials, have excellent high temperature resistance and radiation resistance.

[0018] Preferably, the material of the neutron conversion material layer is selected from the following: 10 B or 6 LiF.

[0019] 10 B and 6 Both LiF and LiF materials have extremely large thermal neutron trapping cross sections, enabling them to efficiently convert incident neutrons into charged particles that can be detected by semiconductors.

[0020] Preferably, each of the cross-shaped unit trenches consists of two mutually perpendicular intersecting trench segments, when the material of the neutron conversion material layer is... 10At time B, the width Tw of the trench segment is 1.5 μm, and the spacing Tg between adjacent trench segments separated by the semiconductor mesa region is 0.5 μm; when the material of the neutron conversion material layer is 6 In LiF, the width Tw of the trench segment is 15 μm, and the spacing Tg between adjacent trench segments separated by the semiconductor mesa region is 5 μm.

[0021] The specific dimensions given above are optimized values ​​based on the characteristics of different neutron conversion materials, which can achieve the best balance between detection efficiency, charge collection efficiency and process feasibility.

[0022] A method for manufacturing a semiconductor neutron detector as described in any of the above descriptions, the method comprising the following steps:

[0023] Prepare the semiconductor substrate layer;

[0024] Etching is performed on the semiconductor substrate to form a trench array consisting of multiple cross-shaped unit trenches arranged in a close-packed mortise and tenon configuration, thereby defining a corresponding semiconductor mesa region with a continuous two-dimensional interconnect mesh structure.

[0025] A back ohmic contact layer is formed on the back side of the semiconductor substrate, and a front ohmic contact layer is formed on the surface of the semiconductor mesa region;

[0026] Neutron conversion material is backfilled into the trench array.

[0027] Preferably, a dry etching process is used to etch the semiconductor substrate.

[0028] Dry etching enables the fabrication of microstructures with high aspect ratios and high precision, while the robust two-dimensional interconnected mesh structure can withstand the physical bombardment during the dry etching process, ensuring the quality of the microstructure fabrication.

[0029] Preferably, the step of backfilling the neutron conversion material is carried out using the centrifugal backfilling method.

[0030] Centrifugal backfilling can efficiently and densely fill powder materials into micron-sized trenches, while the robust two-dimensional interconnected mesh structure can effectively resist the centrifugal force.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] The present invention discloses a semiconductor neutron detector, which transforms the mechanically fragile and independent long straight fins in the traditional scheme into a robust two-dimensional interconnected grid structure by using a trench array composed of densely packed cross-shaped unit trenches. This effectively disperses stress, improves the mechanical stability of the semiconductor mesa region, and effectively prevents it from collapsing, breaking or fractured during manufacturing or application.

[0033] The present invention discloses a method for manufacturing a semiconductor neutron detector, which is based on a robust two-dimensional interconnect mesh structure. In subsequent process steps with large mechanical or thermal stress, such as dry etching and centrifugal backfilling, the integrity of the structure is maintained, significantly improving the manufacturing yield of the device and the reliability of the process.

[0034] The structural improvement of this invention is achieved while keeping key geometric parameters that affect detection efficiency, such as trench width and trench spacing, unchanged. Therefore, while significantly improving structural stability, the detector's neutron detection efficiency is not sacrificed, thus achieving a synergistic improvement in device reliability and performance. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0036] Figure 1 This is a top view of a long, straight strip-shaped trench semiconductor neutron detector after trench etching in the existing technology;

[0037] Figure 2 This is a cross-sectional view of a long, straight strip-shaped trench semiconductor neutron detector in the prior art after trench etching.

[0038] Figure 3 This is a top view of the semiconductor neutron detector of the present invention after trench etching;

[0039] Figure 4 This is a cross-sectional view of the semiconductor neutron detector of the present invention after trench etching;

[0040] Figure 5 This is a top view of a long, straight, trench-type semiconductor neutron detector in the existing technology after metallization on both sides;

[0041] Figure 6 This is a cross-sectional view of a long, straight strip-shaped trench semiconductor neutron detector after metallization on both sides in the existing technology;

[0042] Figure 7 This is a top view of the semiconductor neutron detector of the present invention after metallization on both sides;

[0043] Figure 8 This is a cross-sectional view of the semiconductor neutron detector of the present invention after metallization on both sides;

[0044] Figure 9 This is a top view of a long, straight, trench-type semiconductor neutron detector in the existing technology after powder backfilling;

[0045] Figure 10 This is a cross-sectional view of a long, straight strip-shaped trench semiconductor neutron detector in the prior art after powder backfilling;

[0046] Figure 11 This is a top view of the semiconductor neutron detector of the present invention after powder backfilling;

[0047] Figure 12 This is a cross-sectional view of the semiconductor neutron detector of the present invention after powder backfilling;

[0048] In the figure: 1. Semiconductor substrate layer; 2. Trench array; 3. Back ohmic contact layer; 4. Front ohmic contact layer; 5. Neutron conversion material layer. Detailed Implementation

[0049] The technical solution of the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the implementation of the present invention is not limited to the following embodiments, and any modifications and / or alterations made to the present invention will fall within the protection scope of the present invention.

[0050] In this invention, unless otherwise specified, all parts and percentages are by weight, and the equipment and raw materials used are commercially available or commonly used in the art. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art. Unless otherwise specified, the components or equipment in the following embodiments are general standard parts or components known to those skilled in the art, and their structures and principles can be learned by those skilled in the art through technical manuals or conventional experimental methods.

[0051] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In this detailed description, numerous specific details are set forth to facilitate explanation and provide a thorough understanding of the embodiments of the present invention. However, one or more embodiments may be practiced by those skilled in the art without these specific details.

[0052] like Figure 1 and Figure 2As shown, in the prior art, the long straight strip trench type semiconductor neutron detector only requires etching a simple long straight strip trench array pattern on the semiconductor substrate layer. However, its mechanical stability is poor, which leads to easy collapse and breakage during the manufacturing process and low reliability in application.

[0053] like Figure 3 and Figure 4 As shown, an embodiment of the present invention discloses a semiconductor neutron detector, including a semiconductor substrate layer, a trench array with a specific pattern formed on the surface of the semiconductor substrate layer, a neutron conversion material layer filled in the trench array, and a back ohmic contact layer and a front ohmic contact layer respectively provided on the back side of the semiconductor substrate layer and on the surface of the patterned semiconductor mesa region.

[0054] Unlike existing technologies that use parallel, long, straight trenches, the trench array of this invention is composed of multiple cross-shaped unit trenches arranged in a close-packed, interlocking pattern. Each cross-shaped unit trench is centrally symmetrical, exhibiting both vertical and horizontal symmetry relative to its geometric center. This specific geometry and arrangement ensures that the remaining semiconductor mesa regions separated by the trench array are no longer the elongated, isolated fins of traditional solutions, but rather form a continuous two-dimensional interconnected mesh structure. Each node in this mesh structure is interconnected with surrounding nodes, forming an integrated mechanical system with higher rigidity and strength.

[0055] To achieve this ideal close-packed tiling, the geometry of the cross-shaped cell trenches must satisfy specific relationships. In a preferred embodiment, each cross-shaped cell trench is formed by two trench segments of length L and width Tw intersecting each other perpendicularly. For these cell trenches to be seamlessly joined into a continuous trench array, the length L, width Tw, and the spacing Tg between adjacent trench segments separated by the semiconductor mesa region must satisfy the geometric relationship L = 3Tw + 2Tg.

[0056] The semiconductor substrate can be made of conventional semiconductor materials such as silicon or germanium, or wide-bandgap semiconductor materials such as silicon carbide or gallium nitride, to withstand extreme application environments such as high temperature and strong radiation. The neutron conversion material layer filling the trench array can be selected from materials with a large neutron trapping cross-section. 10 B or 6 LiF material is used to ensure high neutron detection efficiency.

[0057] When the neutron conversion material layer is 10 At time B, an optimized parameter combination is: the trench width Tw is 1.5 μm, and the spacing Tg between adjacent trench segments separated by the semiconductor mesa region is 0.5 μm. The material of the neutron conversion material layer is... 6For LiF, due to its different characteristics, an optimized parameter combination could be: a trench width Tw of 15 μm and a spacing Tg of 5 μm between adjacent trench segments separated by semiconductor mesa regions. Of course, the trench width and the spacing between adjacent trench segments separated by semiconductor mesa regions can be finely adjusted according to actual process conditions.

[0058] Embodiments of the present invention also disclose a method for manufacturing a semiconductor neutron detector, the method comprising the following steps.

[0059] First, a semiconductor substrate is prepared. Then, a trench array consisting of cross-shaped cell trenches is formed on the semiconductor substrate using photolithography and etching processes. This etching step employs a dry etching process to obtain steep and precise trench sidewalls. After this step, the semiconductor mesa region of a two-dimensional interconnect mesh structure is formed.

[0060] Subsequently, a back ohmic contact layer is formed on the back side of the semiconductor substrate through processes such as evaporation or sputtering, and a front ohmic contact layer is formed on the surface of the semiconductor mesa region of the two-dimensional interconnect grid structure. Figure 5 and Figure 6 This diagram illustrates the front and back metallization of a long, straight trench-type semiconductor neutron detector in the prior art. Figure 7 and Figure 8 A schematic diagram of a cross-shaped trench semiconductor neutron detector after front and back metallization according to the method of this embodiment is shown.

[0061] Finally, the powdered neutron conversion material is backfilled into the trench array. Centrifugal backfilling is preferred for this step. Since the semiconductor mesa region at this point is already a two-dimensional interconnect mesh structure with excellent mechanical properties, it can fully withstand the enormous mechanical stress generated during centrifugal backfilling, effectively avoiding the collapse and breakage problems that often occur in traditional long straight fin structures during this step, greatly improving manufacturing yield. Figure 9 and Figure 10 This diagram illustrates the powder backfilling process for a long, straight trench-type semiconductor neutron detector in the prior art. Figure 11 and Figure 12 A schematic diagram of a cross-shaped trench semiconductor neutron detector according to the method of this embodiment after powder backfilling is shown.

[0062] As described above, compared to traditional long, straight trench semiconductor neutron detectors, the cross-shaped trench semiconductor neutron detector proposed in this embodiment does not require changes to structural parameters such as trench width Tw and trench spacing Tg. It simply converts the long, straight trenches into cross-shaped trenches and arranges them in a close-packed configuration, without affecting detection efficiency or increasing manufacturing difficulty. The centrally symmetrical cross-shaped trench pattern can be inlaid into a close-packed form, resulting in a detector die with less stress mismatch. Furthermore, the etched semiconductor mesa region will have greater mechanical stability, exhibiting less thermal expansion stress mismatch during dry etching and high-temperature passivation processes, effectively preventing wafer surface cracking and warping. The centrally symmetrical cross-shaped trenches are more robust and possess superior mechanical stability, especially during the powder centrifugal backfilling process, preventing collapse, breakage, and fracture of the semiconductor fin region.

[0063] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A semiconductor neutron detector, characterized in that: The semiconductor neutron detector includes: Semiconductor substrate layer; A trench array formed on the surface of the semiconductor substrate layer, the trench array defining a semiconductor mesa region on the surface of the semiconductor substrate layer that is isolated from the trench bottom region of the trench array; A neutron conversion material layer filled within the trench array; A back-side ohmic contact layer disposed on the back side of the semiconductor substrate; and, An ohmic contact layer is provided on the surface of the semiconductor mesa region; The trench array is formed by a plurality of cross-shaped unit trenches arranged in a close-packed tessellation manner, thereby defining the semiconductor mesa region as a continuous two-dimensional interconnection grid structure; each cross-shaped unit trench is composed of two mutually perpendicular intersecting trench segments, and the width Tw of each trench segment, the length L of each trench segment, and the spacing Tg between adjacent trench segments separated by the semiconductor mesa region satisfy the following relationship: L=3Tw+2Tg.

2. A semiconductor neutron detector according to claim 1, characterized in that: Each of the cross-shaped unit grooves is vertically and horizontally symmetrical with respect to its own geometric center.

3. A semiconductor neutron detector according to claim 1, characterized in that: The material of the semiconductor substrate is selected from silicon, germanium, silicon carbide or gallium nitride.

4. A semiconductor neutron detector according to claim 1, characterized in that: The material of the neutron conversion material layer is selected from the following: 10 B or 6 LiF.

5. A semiconductor neutron detector according to claim 4, characterized in that: Each of the aforementioned cross-shaped unit trenches consists of two mutually perpendicular intersecting trench segments, when the material of the neutron conversion material layer is... 10 At time B, the width Tw of the trench segment is 1.5 μm, and the spacing Tg between adjacent trench segments separated by the semiconductor mesa region is 0.5 μm; when the material of the neutron conversion material layer is 6 In LiF, the width Tw of the trench segment is 15 μm, and the spacing Tg between adjacent trench segments separated by the semiconductor mesa region is 5 μm.

6. A method for manufacturing a semiconductor neutron detector as described in any one of claims 1-5, characterized in that: The method includes the following steps: Prepare the semiconductor substrate layer; Etching is performed on the semiconductor substrate to form a trench array consisting of multiple cross-shaped unit trenches arranged in a close-packed mortise and tenon configuration, thereby defining a corresponding semiconductor mesa region with a continuous two-dimensional interconnect mesh structure. A back ohmic contact layer is formed on the back side of the semiconductor substrate, and a front ohmic contact layer is formed on the surface of the semiconductor mesa region; Neutron conversion material is backfilled into the trench array.

7. A method for manufacturing a semiconductor neutron detector according to claim 6, characterized in that: The semiconductor substrate layer is etched using a dry etching process.

8. A method for manufacturing a semiconductor neutron detector according to claim 6, characterized in that: The step of backfilling the neutron conversion material adopts the centrifugal backfilling method.

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