A single crystal furnace for improving the uniformity of longitudinal oxygen content in crystal rods

Abstract

A single crystal furnace for improving the uniformity of longitudinal oxygen content of a crystal rod, comprising a furnace body and a crucible arranged in the furnace body, a heater is provided on the outer wall of the crucible, a support shaft for supporting the crucible is provided in the furnace body, a reflecting device is provided on the supporting shaft, which is located below the crucible and is used to reflect heat to the bottom of the crucible, the reflecting device comprises a reflecting disk and a mounting plate distributed along the height direction of the supporting shaft and coaxially arranged with the supporting shaft, and a thermal insulation felt is filled between the reflecting disk and the mounting plate. The utility model improves the uniformity of longitudinal oxygen content of the crystal rod.

Description

Technical Field

[0001] The utility model relates to the technical field of improving the uniformity of oxygen content in single crystal silicon, in particular to a single crystal furnace for improving the uniformity of oxygen content in the longitudinal direction of a crystal rod. Background Art

[0002] Semiconductor single crystal silicon is grown using the Czochralski method. Oxygen concentration is an important factor affecting the quality of silicon wafers. Interstitial oxygen mainly comes from the chemical reaction between the quartz crucible and the polycrystalline. The segregation coefficient of oxygen in silicon is about 1.25. According to the segregation mechanism and the formation mechanism of oxygen content, oxygen tends to gradually decrease from the head to the tail of the crystal rod.

[0003] The factors affecting the oxygen content in the crystal rod are mainly temperature, pressure in the furnace and the surface state of the quartz crucible. In the prior art, the oxygen content in the crystal rod is mostly controlled by adjusting the single crystal pulling process or by superconducting magnetic field pulling. However, adjusting the single crystal pulling process has a certain influence on the control of oxygen content, but the control range is small, and the oxygen content at the head and tail of the crystal rod is quite different, generally 6-8 ppma, that is, the oxygen content distribution in the longitudinal direction of the crystal rod is uneven, especially for large-sized ones. It is more difficult to control the oxygen content. Utility Model Content

[0004] In order to solve the problem of uneven distribution of oxygen content in the longitudinal direction of the crystal rod in the prior art, the utility model provides a single crystal furnace for improving the uniformity of oxygen content in the longitudinal direction of the crystal rod, thereby improving the uniformity of oxygen content in the longitudinal direction of the crystal rod.

[0005] In order to achieve the above-mentioned purpose, the specific scheme adopted by the utility model is: a single crystal furnace for improving the uniformity of the longitudinal oxygen content of the crystal rod, comprising a furnace body and a crucible arranged in the furnace body, the outer wall of the crucible is provided with a heater, and the furnace body is provided with a support shaft for supporting the crucible, and the support shaft is provided with a reflection device located below the crucible and used to reflect heat to the bottom of the crucible, the reflection device includes a reflection disk and a mounting plate distributed along the height direction of the support shaft and coaxially arranged with the support shaft, and the space between the reflection disk and the mounting plate is filled with thermal insulation felt.

[0006] As an optimization solution of the above-mentioned single crystal furnace for improving the uniformity of oxygen content in the longitudinal direction of the crystal rod: the material of the reflective disk is pyrolytic carbon.

[0007] As another optimization solution of the above-mentioned single crystal furnace for improving the uniformity of oxygen content in the longitudinal direction of the crystal rod: the reflection disk and the mounting plate are arc-shaped plate structures concave toward the bottom of the crucible.

[0008] As another optimization solution of the above-mentioned single crystal furnace for improving the uniformity of longitudinal oxygen content of the crystal rod: the edges of the reflection disk and the mounting plate are provided with a plurality of avoidance grooves corresponding to the electrodes in the furnace body.

[0009] As another optimization solution of the above-mentioned single crystal furnace for improving the uniformity of oxygen content in the longitudinal direction of the crystal rod: the thickness of the reflective disk is 10 mm.

[0010] As another optimization solution of the above-mentioned single crystal furnace for improving the uniformity of the longitudinal oxygen content of the crystal rod: the thickness of the thermal insulation felt is 30 mm.

[0011] As another optimization scheme for the above-mentioned single crystal furnace for improving the uniformity of longitudinal oxygen content of the crystal rod: the reflection device is suspended on the support shaft through a mounting piece, and a plurality of sockets distributed along the height of the support shaft are provided on the side wall of the support shaft, and the mounting piece can pass through the sockets and extend out of the sockets at both ends, and the mounting plate is suspended on the upper surface of the mounting piece.

[0012] As another optimization solution of the above-mentioned single crystal furnace for improving the uniformity of the longitudinal oxygen content of the crystal rod: a groove capable of accommodating the mounting part is provided on the side of the mounting plate away from the thermal insulation felt.

[0013] As another optimization solution of the above-mentioned single crystal furnace for improving the uniformity of longitudinal oxygen content of the crystal rod: the crucible includes a crucible support and three crucible blocks, and the three crucible blocks are fixed on the crucible support in pairs to enclose a circular crucible body.

[0014] As another optimization scheme for the above-mentioned single crystal furnace for improving the uniformity of longitudinal oxygen content of the crystal rod: the cross-section of the crucible support is a circular structure, an annular groove is provided on the upper end surface of the crucible support, a receiving groove is provided at the bottom of the annular groove near the bottom end, and a protrusion that can extend into the receiving groove is provided on the outer surface of the bottom of the crucible block.

[0015] Compared with the prior art, the utility model has the following beneficial effects:

[0016] 1. The utility model provides a single crystal furnace for improving the uniformity of longitudinal oxygen content of a crystal rod. A reflective plate is arranged below the crucible to reflect heat to the bottom of the crucible, thereby promoting natural convection and forced convection of oxygen in the melt in the crucible, and promoting more oxygen to enter the tail of the crystal rod in the middle and rear stages of crystal rod pulling, thereby improving the oxygen content at the tail of the crystal rod and further improving the uniformity of longitudinal oxygen content of the crystal rod.

[0017] 2. In the utility model, the reflecting device is suspended on the supporting shaft through the mounting part, and the distance between the reflecting plate and the crucible is adjusted by adjusting the position of the mounting part inserted into the insertion hole, thereby adjusting the heat reflected by the reflecting screen to the bottom of the crucible, that is, the utility model has wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the utility model;

[0019] Figure 2 is a schematic diagram of the structure of the reflection device;

[0020] Figure 3 is a schematic structural diagram of a reflection device in Example 2;

[0021] Figure 4 is a schematic structural diagram of a reflection device in Example 4;

[0022] Figure numerals: 1, furnace body, 2, heater, 3, crucible, 301, crucible support, 4, support shaft, 401, socket, 5, reflection plate, 6, thermal insulation felt, 7, mounting plate, 8, mounting part, 9, avoidance groove. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further elaborated in detail below in conjunction with specific embodiments. The parts of the present invention that are not described and disclosed in detail in the following embodiments should be understood as the prior art known or should be known to those skilled in the art, such as the structure of the crucible block, the structure of the crucible support 301, how the crucible block is installed on the crucible support 301, how the driving mechanism drives the support shaft 4 to rotate and move, etc.

[0024] Example 1

[0025] A single crystal furnace for improving the uniformity of longitudinal oxygen content of a crystal rod comprises a furnace body 1 and a crucible 3 arranged in the furnace body 1, the crucible 3 comprises a crucible support 301 and three crucible blocks, the three crucible blocks are fixed on the crucible support 301 in pairs and can enclose to form a circular crucible body, the crucible body opening is facing upward, the cross section of the crucible support 301 is a circular structure, the upper end surface of the crucible support 301 is provided with an annular groove, the bottom of the annular groove is provided with a receiving groove near the bottom end, and the outer surface of the bottom of the crucible block is provided with a protrusion that can extend into the receiving groove. The outer wall of the crucible 3 is sleeved with a heater 2, the heater 2 is a ring-shaped structure, and there is a gap between the outer wall of the crucible 3 and the inner wall of the heater 2. A support shaft 4 for supporting the crucible 3 is arranged in the furnace body 1, the top end of the support shaft 4 extends into the furnace body 1 and is located below the crucible 3, the crucible support 301 is installed on the top end of the support shaft 4, and the crucible 3 and the support shaft 4 are coaxially arranged; the bottom end of the support shaft 4 extends out of the furnace body 1 and is connected to an external driving mechanism, and the driving mechanism is used to drive the support shaft 4 to rotate around its axis and move along the axial extension direction.

[0026] The support shaft 4 is provided with a reflecting device located below the crucible 3 and used to reflect heat to the bottom of the crucible 3. The reflecting device reflects the heat of the heater 2 to the bottom of the crucible 3, promotes the natural convection and forced convection of oxygen in the melt in the crucible 3, and promotes more oxygen to enter the tail of the crystal rod in the middle and rear stages of the crystal rod drawing, thereby increasing the oxygen content at the tail of the crystal rod, and further improving the uniformity of the longitudinal oxygen content of the crystal rod. Specifically, the reflecting device includes a reflecting plate 5 and a mounting plate 7 distributed along the height direction of the support shaft 4 and coaxially arranged with the support shaft 4. The reflecting plate 5 can be a circular plate structure or a square plate structure. In this embodiment, the reflecting plate 5 is a circular plate structure; the reflecting plate 5 is made of pyrolytic carbon, which improves the ability of the reflecting plate 5 to reflect heat. The mounting plate 7 can be a circular plate structure or a square plate structure. In this embodiment, the mounting plate 7 is a circular plate structure. The reflective disk 5 and the mounting plate 7 have the same diameter, and there is a receiving space between the reflective disk 5 and the mounting plate 7. The reflective disk 5 and the mounting plate 7 are filled with a thermal insulation felt 6. In this embodiment, the receiving space is provided with a thermal insulation felt 6, that is, the reflective disk 5, the thermal insulation felt 6 and the mounting plate 7 are sequentially provided along the height direction of the support shaft 4. The thermal insulation felt 6 is a circular sheet structure, and the diameter of the thermal insulation felt 6 is the same as that of the reflective disk 5. The upper surface of the thermal insulation felt 6 is in close contact with the lower surface of the reflective disk 5, and the lower surface of the thermal insulation felt 6 is in close contact with the upper surface of the mounting plate 7. The provision of the thermal insulation felt 6 plays a role in heat preservation, avoids heat loss at the bottom of the crucible 3, and further promotes natural convection and forced convection of oxygen in the melt in the crucible 3, that is, further improves the uniformity of the longitudinal oxygen content.

[0027] The reflecting device is connected to the outer wall of the support shaft 4. Specifically, the center positions of the reflecting disk 5, the mounting plate 7 and the thermal insulation felt 6 are all provided with through holes with the same diameter as the support shaft 4. The support shaft 4 can pass through the through holes and the outer wall of the support shaft 4 is fixedly connected to the inner wall of the through hole on the mounting plate 7. The reflecting device can move with the up and down movement of the support shaft 4, ensuring that the distance between the reflecting disk 5 and the bottom of the crucible 3 does not change with the movement of the support shaft 4, thereby further improving the uniformity of the longitudinal oxygen content of the crystal rod.

[0028] The thinner the reflective disk is, the better. To ensure the flatness of the reflective disk, the thickness of the reflective disk is 10 mm. The thickness of the reflective disk 5 is 10 mm, the thickness of the thermal insulation felt 6 is 30 mm, and the thickness of the mounting plate 7 is 20 mm, to ensure the stability and safety of the reflective screen support.

[0029] In this embodiment, the diameter of the reflective plate 5 is equal to or larger than the outer diameter of the crucible 3 and smaller than the inner diameter of the heater 2 .

[0030] The above is a basic implementation method of the utility model, which can be further improved, optimized and limited on the basis of the above to obtain the following embodiments:

[0031] Example 2

[0032] This embodiment is a single crystal furnace improvement scheme for improving the uniformity of the longitudinal oxygen content of the crystal rod based on the embodiment 1. Its main structure is the same as that of the embodiment 1, and the improvement is as follows: Figure 3 As shown, the edges of the reflective disk 5 and the mounting plate 7 are provided with a plurality of avoidance grooves 9 corresponding to the electrodes in the furnace body 1. When the reflective device is located at the bottom of the furnace body 1, the electrodes are located in the avoidance grooves 9 to avoid collision between the reflective device and the electrodes.

[0033] Example 3

[0034] This embodiment is a single crystal furnace improvement scheme for improving the uniformity of the longitudinal oxygen content of the crystal rod based on the embodiment 1. Its main structure is the same as that of the embodiment 1, and the improvement is as follows: Figure 1 As shown, when pulling crystal rods of different diameters or different pulling processes, it is necessary to adjust the heat reflected by the reflecting device. In this embodiment, the heat reflected by the reflecting plate 5 is adjusted by adjusting the distance between the reflecting plate 5 and the crucible 3. Specifically, the reflecting device is suspended on the supporting shaft 4 through the mounting member 8. A plurality of sockets 401 distributed along the height thereof are provided on the side wall of the supporting shaft 4. The sockets 401 are long strip hole-like structures. The extending direction of the sockets 401 is perpendicular to the axial direction of the supporting shaft 4. Accordingly, the mounting member 8 is a sheet-like structure. The thickness of the mounting member 8 can reach the height of the socket 401. The width of the mounting member 8 is equal to the width of the socket 401. The length of the mounting member 8 is greater than the length of the socket 401, so that the mounting member 8 can pass through the socket 401 and both ends extend out of the socket 401. The mounting plate 7 is suspended on the upper surface of the mounting member 8.

[0035] In this embodiment, a groove capable of accommodating the mounting member 8 is formed on the side of the mounting plate 7 facing away from the thermal insulation felt 6 .

[0036] Example 4

[0037] This embodiment is a single crystal furnace improvement scheme for improving the uniformity of the longitudinal oxygen content of the crystal rod based on the embodiment 3. Its main structure is the same as that of the embodiment 3, and the improvement is as follows: Figure 4 As shown, the reflective plate 5 and the mounting plate 7 are arc-shaped plate structures concave toward the bottom of the crucible 3. The bottom of the crucible 3 is far from the inner wall of the heater 2. Therefore, the reflective plate 5 and the mounting plate 7 are arc-shaped plates, and the bottom of the reflective plate 5 and the mounting plate 7 are the center positions thereof. The curvature radius of the reflective plate 5 is 10 -3 , which can reflect heat to the center of the bottom of the crucible 3 and its surrounding area.

[0038] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A single crystal furnace for improving the uniformity of oxygen content in the longitudinal direction of a crystal rod, comprising a furnace body (1) and a crucible (3) arranged in the furnace body (1), a heater (2) being sleeved on the outer wall of the crucible (3), and a support shaft (4) for supporting the crucible (3) being arranged in the furnace body (1), characterized in that: The support shaft (4) is provided with a reflecting device located below the crucible (3) and used for reflecting heat to the bottom of the crucible (3), the reflecting device comprising a reflecting disk (5) and a mounting plate (7) distributed along the height direction of the support shaft (4) and arranged coaxially with the support shaft (4), and a heat-insulating felt (6) is filled between the reflecting disk (5) and the mounting plate (7).

2. A single crystal furnace for improving the uniformity of longitudinal oxygen content of a crystal rod according to claim 1, characterized in that: The material of the reflective disk (5) is pyrolytic carbon.

3. A single crystal furnace for improving the uniformity of longitudinal oxygen content of a crystal rod according to claim 1, characterized in that: The reflective disk (5) and the mounting plate (7) are arc-shaped plate structures concave toward the bottom of the crucible.

4. A single crystal furnace for improving the uniformity of longitudinal oxygen content of a crystal rod according to claim 1, characterized in that: The edges of the reflective disk (5) and the mounting plate (7) are provided with a plurality of avoidance grooves (9) corresponding to the electrodes in the furnace body (1).

5. A single crystal furnace for improving the uniformity of longitudinal oxygen content of a crystal rod as claimed in claim 1, characterized in that: The thickness of the reflective disk (5) is 10 mm.

6. A single crystal furnace for improving the uniformity of longitudinal oxygen content in a crystal rod according to claim 1, characterized in that: The thickness of the thermal insulation felt (6) is 30 mm.

7. A single crystal furnace for improving the uniformity of oxygen content in the longitudinal direction of a crystal rod as claimed in claim 1, characterized in that: The reflective device is suspended on the support shaft (4) via a mounting member (8); a plurality of insertion holes (401) distributed along the height of the support shaft (4) are provided on the side wall of the support shaft (4); the mounting member (8) can pass through the insertion holes (401) and both ends extend out of the insertion holes (401); and the mounting plate (7) is suspended on the upper surface of the mounting member (8).

8. A single crystal furnace for improving the uniformity of longitudinal oxygen content in a crystal rod according to claim 7, characterized in that: A groove capable of accommodating a mounting member (8) is provided on a side of the mounting plate (7) facing away from the thermal insulation felt (6).

9. A single crystal furnace for improving the uniformity of oxygen content in the longitudinal direction of a crystal rod according to claim 1, characterized in that: The crucible (3) comprises a crucible support (301) and three crucible blocks, wherein the three crucible blocks are fixed on the crucible support (301) in pairs and adjacent to each other to form a circular crucible body.

10. A single crystal furnace for improving the uniformity of oxygen content in the longitudinal direction of a crystal rod according to claim 9, characterized in that: The cross section of the crucible support (301) is a circular structure. The upper end surface of the crucible support (301) is provided with an annular groove, the bottom of the annular groove is provided with a receiving groove near the bottom end, and the outer surface of the bottom of the crucible block is provided with a protrusion that can extend into the receiving groove.

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