Radial uniform-irradiation device and method for large-dimension monocrystalline silicon

Abstract

A radial uniform-irradiation device and method for large-dimension monocrystalline silicon. The radial uniform-irradiation device for large-dimension monocrystalline silicon comprises: a bucket body, in which silicon ingots to be irradiated can be placed; a neutron shielding layer, arranged on the outer side of the bucket body and used for preventing neutrons from entering the bucket body, the circumference of the neutron shielding layer being provided with gaps, and the gaps being used for enabling neutrons to enter the bucket body, so as to form neutron flux areas; a reflection block, arranged at ends of silicon ingots, neutrons entering the reflection block through the gaps, and after being scattered, irradiating the silicon ingots from the end surfaces of the reflection block; and a rotation driving mechanism, provided in the bucket body and used for driving the silicon ingots to rotate. Arranging the neutron shielding layer and the reflection block at the external position of monocrystalline silicon changes the position and direction of neutrons entering silicon ingots; and rotating the silicon ingots in cooperation during irradiation achieves radial uniformity of irradiation doping for large-dimension monocrystalline silicon.

Description

A radial uniform illumination device and method for large-size single crystal silicon

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202310929383.X filed on July 26, 2023, entitled “A radial uniform illumination device and method for large-size single crystal silicon”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the field of nuclear reactor engineering technology, and in particular to a radial uniform illumination device and method for large-size single crystal silicon. Background Art

[0004] Silicon is by far the most widely used semiconductor material. To improve product performance in its applications, doping techniques are used to add small amounts of impurities to high-purity single-crystal silicon. Neutron radiation doping (NTD) is a widely used method for doping single-crystal silicon in the industry. By placing a silicon ingot into a reactor's irradiation channel and irradiating it with neutrons generated by the reactor, some silicon atoms are converted into other nuclides, achieving the desired doping effect. Compared to other methods, NTD's greatest advantage lies in the uniformity and accuracy of doping. Silicon wafers produced using NTD can be used in high-end semiconductor products such as high-performance semiconductor energy devices and detectors. With the continuous development of the semiconductor industry, the size of silicon wafers has also continued to increase. Early silicon wafers were generally 2-inch and 3-inch in diameter, but now mainstream products have developed to 5-inch and 8-inch sizes, and are expected to be replaced by larger sizes such as 12-inch wafers in the near future.

[0005] Uniformity is a key performance metric for monocrystalline silicon products. For silicon ingots irradiated using the NTD method, uniformity is generally divided into radial (planar) and axial (longitudinal) uniformity, with users typically placing more stringent requirements on radial uniformity. Two main factors influence NTD radial uniformity: the gradient of the neutron flux within the irradiation channel itself, and the difference between the interior and exterior of the silicon ingot caused by the spatial self-screening effect. The latter factor is a major challenge for large-scale NTD irradiation.

[0006] The inventors discovered that when a silicon ingot is irradiated in a neutron field, some neutrons are absorbed at the periphery of the ingot, causing the neutrons that can penetrate into the ingot to attenuate. This is the spatial self-screening effect of neutron irradiation, which leads to uneven doping inside and outside the silicon ingot. When the silicon ingot size is small, this phenomenon is not obvious. Generally, 2-inch, 3-inch, and 5-inch products produced by the NTD method have good uniformity. However, as the size of the silicon ingot increases, the unevenness caused by the spatial self-screening effect will become more and more significant. Therefore, when using traditional NTD devices to irradiate 8-inch, 12-inch or larger products, the radial uniformity is difficult to meet the actual user requirements.

[0007] Summary of the Invention

[0008] In response to the shortcomings of the existing technology, the purpose of the present invention is to provide a radial uniform irradiation device and method for large-size single crystal silicon, which sets a neutron shielding layer and a reflective block to change the position and direction of neutrons entering the silicon ingot. During the irradiation process, the silicon ingot is driven to rotate by a rotating drive mechanism to achieve radial uniformity of irradiation doping of large-size single crystal silicon.

[0009] A first aspect of the present invention provides a radial uniform illumination device for large-size single crystal silicon, comprising:

[0010] a barrel body, wherein the silicon ingot for irradiation can be placed in the barrel body;

[0011] a neutron shielding layer, disposed on the outer side of the barrel body, for preventing neutrons from entering the barrel body, wherein gaps are formed in the circumference of the neutron shielding layer for allowing neutrons to enter the barrel body to form a neutron flux area;

[0012] a reflective block, disposed at the end of the silicon ingot, wherein neutrons enter the reflective block through the gap, are scattered, and irradiate the silicon ingot from the end surface of the emitting block;

[0013] The rotary drive mechanism is arranged in the barrel body and is used for driving the silicon ingot to rotate.

[0014] Preferably, a grid is provided in the barrel body, and the upper end of the grid is connected to the rotation drive mechanism.

[0015] Preferably, the gap is provided at a position corresponding to the reflective block.

[0016] Preferably, when a plurality of silicon ingots are placed in the barrel, the silicon ingots and the reflective blocks are stacked alternately, and the reflective blocks are arranged between two adjacent silicon ingots and coaxially with the silicon ingots.

[0017] Preferably, the neutron shielding layer is made of neutron absorbing material or neutron mirror material.

[0018] Preferably, the neutron shielding layer is made of boron, cadmium or titanium.

[0019] Preferably, the reflective block is made of neutron scattering material.

[0020] Preferably, the reflective block is made of beryllium, graphite or a deuterium compound.

[0021] Preferably, the lower end of the barrel is closed.

[0022] A second aspect of the present invention provides a radial uniform illumination method for large-size single-crystal silicon, using the radial uniform illumination device for large-size single-crystal silicon as described above, comprising the following steps:

[0023] S1: placing the barrel into the reactor irradiation channel, and placing the silicon ingot, the reflective block and the rotary drive mechanism in the barrel;

[0024] S2: Starting the rotary drive mechanism to drive the silicon ingot to rotate at a constant speed, the radially outer portion of the silicon ingot enters the neutron flux region, the neutrons enter the reflective block, and after scattering, irradiate the silicon ingot from the end surface of the emitting block.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention discloses a radial uniform irradiation device for large-size single crystal silicon. A neutron shielding layer is arranged on the outside of a barrel body for placing a silicon ingot, and a rotary drive mechanism and at least one reflective block are arranged inside the barrel body. The neutron shielding layer is provided with a gap in the circumferential direction. During irradiation, the rotary drive mechanism drives the silicon ingot in the barrel body to rotate continuously, and the radial outer part of the silicon ingot continuously and alternately enters neutron flux areas of different degrees. The reflective block is located at the end of the silicon ingot. Neutrons entering the reflective block are scattered and irradiate the silicon ingot from the end surface of the reflective block.

[0027] In the present invention, neutrons are injected into the interior of the barrel in a preset direction, forming neutron flux regions of varying degrees (high neutron flux regions and low neutron flux regions). The rotary drive mechanism drives the silicon ingot in the barrel to rotate continuously, and the radially outer portion of the silicon ingot continuously and alternately enters the high neutron flux region and the low neutron flux regions on both sides. In this way, the cumulative radiation amount is lower than that of radiation entirely within the high neutron flux region. Since the portion of the silicon ingot irradiated by neutrons is always within the high neutron flux region, its cumulative radiation amount does not change, which can offset the uneven neutron radiation inside and outside the silicon ingot caused by the spatial self-screening effect, thereby ensuring uniform irradiation of the silicon ingot in the circumferential direction. At the same time, the neutrons enter the reflective block, are scattered, and are uniformly irradiated on the silicon ingot from the end surface of the reflective block, thereby ensuring uniform irradiation on the radial plane of the silicon ingot.

[0028] The present invention places a neutron shielding layer and a reflective block outside the silicon ingot and opens a gap in the neutron shielding layer to change the position and direction of neutrons entering the silicon ingot. During the irradiation process, the silicon ingot is driven to rotate by a rotary drive mechanism, so that the silicon ingot is uniformly irradiated in the circumferential and radial directions, thereby achieving radial uniformity of radiation doping for large-size single crystal silicon.

[0029] It should be understood that the foregoing general description and the following detailed description are merely illustrative and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application.

[0031] FIG1 is a schematic structural diagram of a radial uniform illumination device for large-size single crystal silicon according to an embodiment of the present invention;

[0032] FIG2 is a diagram showing the working principle of the neutron shielding layer with gaps in an embodiment of the present invention;

[0033] FIG3 is a schematic diagram of the internal structure of a radial uniform illumination device for large-size single crystal silicon according to an embodiment of the present invention (without a barrel);

[0034] FIG4 is a cross-sectional view of the radial uniform illumination device for large-size single crystal silicon in FIG1 ;

[0035] FIG5 is a flow chart of a radial uniform illumination method for large-size single crystal silicon according to an embodiment of the present invention.

[0036] Reference numerals:

[0037] 1-barrel body;

[0038] 11- trellis;

[0039] 2- Neutron shielding layer;

[0040] 3-Gap;

[0041] 4-Rotation drive mechanism;

[0042] 5-Reflection block;

[0043] 6-Silicon ingot;

[0044] 7- Neutron flux region;

[0045] 71-high neutron flux region;

[0046] 72-low neutron flux region;

[0047] 8- Reactor core;

[0048] h1- axial height of neutron shielding layer;

[0049] h2- axial height of silicon ingot. DETAILED DESCRIPTION

[0050] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0051] When a silicon ingot is irradiated in a neutron field, some neutrons are absorbed at the periphery of the silicon ingot, causing the neutrons that can penetrate into the interior of the silicon ingot to attenuate. This is the spatial self-screening effect of neutron irradiation, which leads to uneven doping inside and outside the silicon ingot. When the silicon ingot size is small, this phenomenon is not obvious. Generally, 2-inch, 3-inch and 5-inch products produced by the NTD method have good uniformity; as the size of the silicon ingot increases, the unevenness caused by the spatial self-screening effect will become more and more significant. Therefore, when a traditional NTD device is used to irradiate 8-inch, 12-inch or larger products, the radial uniformity is difficult to meet the actual requirements of users; in response to the above problems, the present invention proposes a radial uniform irradiation device and method for large-size single crystal silicon, wherein large-size single crystal silicon refers to silicon ingot products that are larger in size than 2-inch, 3-inch and 5-inch products, such as single crystal silicon with a size greater than 2 inches.

[0052] FIG1 is a schematic structural diagram of a radial uniform illumination device for large-size single crystal silicon according to an embodiment of the present invention, and FIG2 is a schematic diagram of the working principle of a neutron shielding layer 2 with a gap 3 according to an embodiment of the present invention.

[0053] This embodiment provides a radial uniform irradiation device for large-sized single crystal silicon. As shown in FIG1 , the device comprises a barrel 1, with a neutron shielding layer 2 disposed on its exterior. Slits 3 are defined along the circumference of the neutron shielding layer 2. A rotary drive mechanism 4 is located within the barrel 1. Specifically, the barrel 1 can be made of reactor structural materials, such as aluminum, which have a small neutron cross-section. This minimizes the impact on the neutron flux distribution within the reactor while maintaining the structural integrity of the irradiation device. The lower end of the barrel 1 is sealed to prevent coolant from the water pool from flowing into the barrel 1 and affecting the irradiation effect. A neutron shielding layer 2 of a predetermined thickness is provided on the sidewalls of the barrel 1. The neutron shielding layer 2 can be secured to the sidewalls of the barrel 1 using fasteners or other conventional methods in the art. The neutron shielding layer 2 is made of a neutron absorbing material or a neutron mirror material, such as boron, cadmium, or titanium. Neutrons cannot penetrate the neutron shielding layer 2 and enter the barrel 1, providing directional neutron irradiation. Neutrons generated by the reactor core 8 cannot penetrate the neutron shielding layer 2 and enter the barrel 1. The thickness of the neutron shielding layer 2 is adjustable. As shown in FIG4 , the axial height of the neutron shielding layer 2 matches the axial height of the silicon ingot 6 placed in the barrel 1 , where h1 is the axial height of the neutron shielding layer and h2 is the axial height of the silicon ingot. The thickness can also be adjusted according to demand to control the amount of neutrons penetrating at different positions and in different directions.

[0054] Neutron shielding layer 2 is provided with strip-shaped slits 3 along its circumference. As shown in Figure 1, two slits 3 are provided in neutron shielding layer 2. Neutrons cannot penetrate neutron shielding layer 2 and can only enter barrel 1 through slits 3, thereby allowing neutrons to enter barrel 1 according to a predetermined direction. As shown in Figure 2, neutrons from reactor core 8 enter neutron shielding layer 2 according to a predetermined direction, forming neutron flux regions 7 of varying degrees. Neutron flux regions 7 include high neutron flux regions 71 and low neutron flux regions 72. High neutron flux region 71 has a higher neutron flux, while low neutron flux region 72 has a lower neutron flux than high neutron flux region 71. The position, number, and width of slits 3 can be adjusted to achieve uniformity according to different needs.

[0055] The rotary drive mechanism 4 is arranged inside the barrel body 1. During the radiation process, the silicon ingot 6 in the barrel body 1 is driven to rotate by the rotary drive mechanism 4. The rotation of the rotary drive mechanism 4 can be achieved by setting up a large motor or a large rotating mechanism. This belongs to the existing technology in this field and will not be described in detail here.

[0056] FIG3 is a schematic diagram of the internal structure of the radial uniform illumination device for large-size single-crystal silicon in an embodiment of the present invention (without the barrel 1 ); FIG4 is a cross-sectional view of the radial uniform illumination device for large-size single-crystal silicon in FIG1 .

[0057] A grid 11 is provided in the barrel body 1. As shown in FIG3 , the upper end of the grid 11 is connected to the rotary drive mechanism 4. Silicon ingots 6 to be irradiated and reflective blocks 5 are stacked alternately on the grid 11. Multiple sections of silicon ingots 6 can be arranged axially on the grid 11. Reflective blocks 5 are provided between two adjacent silicon ingots 6. The height of each section of silicon ingot 6 can be adjusted to achieve the goal of uniform doping of multiple sections of silicon ingots 6 in the axial direction.

[0058] As shown in FIG3 , the reflector block 5 is disposed between two adjacent silicon ingots 6 . The reflector block 5 and the silicon ingot 6 have similar shapes and are coaxially disposed. Both the radial and axial dimensions of the reflector block 5 can be adjusted as required, and neutron scattering materials such as beryllium, graphite, or deuterium compounds can be used.

[0059] As shown in Figures 2 and 4, when the rotary drive mechanism 4 rotates, it drives the silicon ingot 6 to rotate at a uniform speed through the grid 11, so that the radially outer portion of the silicon ingot 6 continuously and alternately enters the high neutron flux zone 71 and the low neutron flux zone 72. In this way, the cumulative radiation amount on the silicon ingot 6 is lower than when the silicon ingot 6 is entirely irradiated in the high neutron flux zone 71. The cumulative radiation amount of the portion of the silicon ingot 6 that has always been in the high neutron flux zone 71 does not change, which can offset the uneven neutron radiation inside and outside the silicon ingot 6 caused by the spatial self-screening effect, thereby ensuring that the silicon ingot 6 is uniformly irradiated in the circumferential direction.

[0060] The reflective block 5 is set at the position corresponding to the gap 3. The neutrons of the reactor core 8 pass through the gap 3 and enter the reflective block 5. After multiple scattering, they are evenly irradiated from the upper and lower end surfaces of the reflective block 5 to the silicon ingot 6, so that the silicon ingot 6 is evenly irradiated in the radial direction.

[0061] By placing a neutron shielding layer 2 and a reflective block 5 outside the silicon ingot 6 and providing a slit 3 on the neutron shielding layer 2, the position and direction of neutrons entering the silicon ingot 6 are changed. During the irradiation process, the silicon ingot 6 is rotated by the rotary drive mechanism 4, so that the silicon ingot 6 is uniformly irradiated in the circumferential and radial directions, thereby achieving radial uniformity of the irradiation doping of large-size single crystal silicon, and obtaining large-size silicon wafers with better uniformity to meet future market demand.

[0062] By adjusting the position, number and width of the gaps 3, adjusting the thickness of the neutron shielding layer 2, and adjusting the type and size of the reflector 5, uniform irradiation of single crystal silicon with various target requirements such as different sizes, different target resistivities and different uniformity targets can be achieved.

[0063] FIG5 is a flow chart of a radial uniform illumination method for large-size single crystal silicon according to an embodiment of the present invention.

[0064] As shown in FIG5 , a radial uniform illumination method for large-size single-crystal silicon employs the radial uniform illumination device for large-size single-crystal silicon as described above, and includes the following steps:

[0065] S1: Place the barrel 1 into the reactor irradiation channel, and place the silicon ingot 6, the reflective block 5 and the rotary drive mechanism 4 in the barrel 1;

[0066] S2: Start the rotary drive mechanism 4 to drive the silicon ingot 6 to rotate at a constant speed. The radial outer portion of the silicon ingot 6 enters the neutron flux region 7. Neutrons enter the reflective block 5 and are scattered to irradiate the silicon ingot 6 from the end surface of the emitting block 5.

[0067] During the irradiation process, the barrel 1 and the neutron shielding layer 2 remain fixed, and the rotary drive mechanism 4 drives the grid 11 to rotate at a constant speed along the longitudinal center axis, driving the silicon ingot 6 to rotate at a constant speed along the center axis, thereby adjusting the irradiation amount at different positions inside the silicon ingot 6.

[0068] Neutrons are injected into the barrel body 1 in a preset direction, forming neutron flux areas 7 of varying degrees (a high neutron flux area 71 and a low neutron flux area 72). The rotary drive mechanism 4 drives the silicon ingot 6 in the barrel body 1 to rotate continuously, and the radially outer portion of the silicon ingot 6 alternately enters the high neutron flux area 71 and the low neutron flux areas 72 on both sides. In this way, the cumulative radiation amount is lower than that of the entire silicon ingot 6 being irradiated in the high neutron flux area 71. Since the part of the silicon ingot 6 irradiated by neutrons is always in the high neutron flux area 71, its cumulative radiation amount does not change, which can offset the uneven neutron radiation inside and outside the silicon ingot 6 caused by the spatial self-screening effect, thereby ensuring that the silicon ingot 6 is uniformly irradiated in the circumferential direction. At the same time, the neutrons enter the reflective block 5, and after scattering, they are uniformly irradiated from the upper and lower end surfaces of the reflective block 5 to the silicon ingot 6, thereby ensuring that the radial plane of the silicon ingot 6 is uniformly irradiated.

[0069] The radial uniform irradiation method for large-sized single-crystal silicon in this embodiment can be used to irradiate and dope single-crystal silicon in neutron irradiation channels of various reactors. Large-sized silicon wafers with good uniformity can be produced using this method.

[0070] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A radial uniform illumination device for large-size single crystal silicon, characterized in that: include: A barrel body, in which a silicon ingot for irradiation can be placed; A neutron shielding layer is arranged on the outer side of the barrel body to prevent neutrons from entering the barrel body, and a gap is provided in the circumference of the neutron shielding layer to allow neutrons to enter the barrel body to form a neutron flux area; A reflective block is arranged at the end of the silicon ingot, and neutrons enter the reflective block through the gap, and after being scattered, irradiate the silicon ingot from the end surface of the emitting block; The rotary drive mechanism is arranged in the barrel body and is used for driving the silicon ingot to rotate.

2. The radial uniform illumination device for large-size single crystal silicon according to claim 1, characterized in that: A grid is provided in the barrel body, and the upper end of the grid is connected to the rotation drive mechanism.

3. The radial uniform illumination device for large-size single crystal silicon according to claim 1, characterized in that: The gap is arranged at a position corresponding to the reflection block.

4. The radial uniform illumination device for large-size single crystal silicon according to claim 1, characterized in that: When a plurality of silicon ingots are placed in the barrel, the silicon ingots and the reflective blocks are stacked alternately, and the reflective block is arranged between two adjacent silicon ingots and coaxially with the silicon ingots.

5. The radial uniform illumination device for large-size single crystal silicon according to claim 1, characterized in that: The neutron shielding layer is made of neutron absorption material or neutron mirror material.

6. The radial uniform illumination device for large-size single crystal silicon according to claim 5, characterized in that: The neutron shielding layer is made of boron, cadmium or titanium material.

7. The radial uniform illumination device for large-size single crystal silicon according to claim 1, characterized in that: The reflection block is made of neutron scattering material.

8. The radial uniform illumination device for large-size single crystal silicon according to claim 7, characterized in that: The reflective block is made of beryllium, graphite or deuterium compound.

9. The radial uniform illumination device for large-size single crystal silicon according to claim 1, characterized in that: The lower end of the barrel is closed.

10. A radial uniform illumination method for large-size single crystal silicon, characterized in that: The radial uniform illumination device for large-size single crystal silicon according to any one of claims 1 to 9 comprises the following steps: S1: placing the barrel into the reactor irradiation channel, and placing the silicon ingot, the reflective block and the rotary drive mechanism in the barrel; S2: starting the rotary drive mechanism to drive the silicon ingot to rotate at a constant speed, so that the radially outer portion of the silicon ingot enters the neutron flux region, and the neutrons enter the reflection block and, after being scattered, irradiate the silicon ingot from the end surface of the emission block.

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