Method for controlling oxygen content of small-size crystal bar through magnetic field

Abstract

The invention provides a method for controlling the oxygen content of a small-size crystal bar through a magnetic field, and relates to the technical field of a single crystal oxygen content control method.Under the condition that a thermal field structure and crystal pulling parameters are the same, along with reduction of MCZ magnetic field intensity, the oxygen content of the crystal bar is reduced by 1.5 ppma-2. 5ppma every time the MCZ magnetic field intensity is reduced by 500GS, so that the oxygen content of the crystal bar is reduced by 1.5 ppma-2. 5ppma according to requirements; and applying different MCZ magnetic field intensities, and drawing the crystal bar to obtain the oxygen content crystal bar meeting the requirements of customers.

Description

Technical Field

[0001] The present invention belongs to the technical field of single crystal oxygen content control methods, and in particular relates to a method for controlling the oxygen content of a small-sized crystal rod through a magnetic field. Background Art

[0002] When pulling single crystal silicon, the Czochralski method is usually adopted, which is the process of growing single crystal silicon from liquid molten silicon. In the Czochralski method, it is difficult to pull products with an oxygen content lower than 11ppma for small-sized single crystals, and some products with low oxygen content requirements cannot be met by the Czochralski method. Therefore, in order to reduce the oxygen content, a strong magnetic field (MCZ) is usually applied to the outside of the single crystal furnace to suppress the thermal convection of the silicon melt to reduce the oxygen content in the crystal. However, due to different customer needs, the oxygen content of the required crystal is different, so it is necessary to study a method to control the oxygen content of the crystal rod to obtain crystal rods with different oxygen contents according to different needs. Summary of the invention

[0003] In view of this, the present invention provides a method for controlling the oxygen content of a small-sized crystal rod by a magnetic field to obtain crystal rods with different oxygen contents.

[0004] The technical solution adopted by the present invention to solve the technical problem is: A method for controlling the oxygen content of a small-sized crystal rod by a magnetic field. Under the condition that the thermal field structure and crystal pulling parameters are the same, as the MCZ magnetic field intensity decreases, the oxygen content of the crystal rod decreases. For every 500GS decrease in the MCZ magnetic field intensity, the oxygen content of the crystal rod decreases by 1.5ppma~2.5ppma.

[0005] Preferably, the position of the MCZ magnetic field is -50 mm to 50 mm.

[0006] Preferably, the upper limit of the MCZ magnetic field strength is 3000 GS, and the lower limit of the MCZ magnetic field strength is 1000 GS.

[0007] Preferably, within the upper and lower limits of the MCZ magnetic field strength, the oxygen content of the crystal rod is in the range of 7 ppma to 17 ppma.

[0008] Preferably, as the MCZ magnetic field strength decreases, the radial oxygen content ORG does not change significantly.

[0009] Preferably, the position where the oxygen content of the crystal rod decreases by 1.5 ppma to 2.5 ppma is when the length of the crystal rod is 200 mm to 1400 mm.

[0010] Preferably, when the thermal field structure and crystal pulling parameters are the same, When the MCZ magnetic field position is -50 mm, the radial oxygen content ORG of the crystal rod is 2.3%~3.3%; When the MCZ magnetic field position is 0 mm, the radial oxygen content ORG of the crystal rod is 1%~1.5%; When the MCZ magnetic field position is 50 mm, the radial oxygen content ORG of the crystal rod is 1.6%~2.3%.

[0011] Preferably, the radial oxygen content ORG of the crystal rod refers to a position between 600 and 1400 mm of the crystal rod.

[0012] Preferably, applying the MCZ magnetic field can reduce the radial oxygen content ORG of the crystal rod, and the radial oxygen content ORG of the crystal rod does not change significantly with the change of the MCZ magnetic field intensity.

[0013] Preferably, the magnetic field strength is 1000GS~2500GS.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for controlling the oxygen content of a small-sized crystal rod by a magnetic field. Under the condition that the thermal field structure and crystal pulling parameters are the same, as the MCZ magnetic field intensity decreases, the oxygen content of the crystal rod decreases. For every 500GS decrease in the MCZ magnetic field intensity, the oxygen content of the crystal rod decreases by 1.5ppma-2.5ppma. According to the required oxygen content of the crystal rod, different MCZ magnetic field intensities are applied to pull the crystal rod to obtain a crystal rod with an oxygen content that meets the customer's requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a graph showing the oxygen content of the crystal rods of Examples 1-3.

[0016] Figure 2 This is the ORG detection diagram of the crystal rod of Example 1-3.

[0017] Figure 3 This is the ORG detection diagram of the crystal rod of Example 4-6.

[0018] Figure 4 This is a graph showing the oxygen content of the crystal rods of Examples 4-6.

[0019] Figure 5 This is the ORG detection diagram of the crystal rod of Comparative Example 1. DETAILED DESCRIPTION

[0020] The technical solutions and technical effects of the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings of the present invention.

[0021] A method for controlling the oxygen content of a small-sized crystal rod by a magnetic field. Under the condition that the thermal field structure and crystal pulling parameters are the same, as the MCZ magnetic field intensity decreases, the oxygen content of the crystal rod decreases. For every 500GS decrease in the MCZ magnetic field intensity, the oxygen content of the crystal rod decreases by 1.5ppma~2.5ppma.

[0022] Specifically, the small size refers to a crystal rod with a size of less than 8 inches.

[0023] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for controlling the oxygen content of a small-sized crystal rod by a magnetic field. Under the condition that the thermal field structure and crystal pulling parameters are the same, as the MCZ magnetic field intensity decreases, the oxygen content of the crystal rod decreases. For every 500GS decrease in the MCZ magnetic field intensity, the oxygen content of the crystal rod decreases by 1.5ppma-2.5ppma. According to the required oxygen content of the crystal rod, different MCZ magnetic field intensities are applied to pull the crystal rod to obtain a crystal rod with an oxygen content that meets the customer's requirements.

[0024] Furthermore, the position of the MCZ magnetic field is -50mm~50mm.

[0025] Specifically, the position of the MCZ magnetic field refers to the distance between the center of the magnetic field and the surface of the silicon solution, wherein -50 mm means that the center of the magnetic field is located 50 mm below the silicon solution.

[0026] Furthermore, the upper limit of the MCZ magnetic field strength is 3000GS, and the lower limit of the MCZ magnetic field strength is 1000GS; on the one hand, the oxygen content is controlled within the upper and lower limits of the MCZ magnetic field strength to prevent excessive temperature differences in the furnace due to excessive fluctuations in the magnetic field strength, thereby affecting the crystal formation of the crystal rod; on the other hand, after falling below the lower limit of the MCZ magnetic field strength, the oxygen content no longer changes.

[0027] Furthermore, within the upper and lower limits of the MCZ magnetic field intensity, the oxygen content of the crystal rod is in the range of 7ppma to 17ppma.

[0028] Furthermore, as the MCZ magnetic field intensity decreases, the radial oxygen content ORG does not change significantly.

[0029] Furthermore, the position where the oxygen content of the crystal rod decreases by 1.5 ppma to 2.5 ppma is when the length of the crystal rod is 200 mm to 1400 mm.

[0030] Furthermore, under the same thermal field structure and crystal pulling parameters, When the MCZ magnetic field position is -50 mm, the radial oxygen content ORG of the crystal rod is 2.3%~3.3%; When the MCZ magnetic field position is 0 mm, the radial oxygen content ORG of the crystal rod is 1%~1.5%; When the MCZ magnetic field position is 50 mm, the radial oxygen content ORG of the crystal rod is 1.6%~2.3%, and the radial oxygen content ORG of the crystal rod is adjusted by the position of the magnetic field.

[0031] Furthermore, the radial oxygen content ORG of the crystal rod refers to the position of 600 to 1400 mm of the crystal rod.

[0032] Furthermore, applying the MCZ magnetic field can reduce the radial oxygen content ORG of the crystal rod, and the radial oxygen content ORG of the crystal rod has no significant change with the change of the MCZ magnetic field intensity.

[0033] Furthermore, the magnetic field strength is 1000GS~2500GS so as not to affect the crystallization of the crystal rod.

[0034] The use of the present invention is described by the following examples.

[0035] Embodiment 1-3: Using a 28-inch hot field, COPFree process was used to pull an 8-inch lightly boron-doped single crystal. The MCZ magnetic field position was 0mm. The required pulled crystal rods had oxygen contents of 7ppma-8ppma, 12ppma-13ppma, and 14ppma-15ppma. The MCZ magnetic field strengths were 1000GS, 1500GS, and 2500GS, respectively. The oxygen content results of the pulled crystal rods are shown in the figure below. Figure 1 shown.

[0036] Depend on Figure 1 It can be seen that according to the required oxygen content, reducing the MCZ magnetic field strength can meet the oxygen content requirement, and meet the control method of reducing the crystal rod oxygen content by 1.5ppma~2.5ppma for every 500GS reduction in the MCZ magnetic field strength.

[0037] Silicon wafers are made at each position of the crystal rod, and the radial oxygen content of the silicon wafers is tested. The ORG% of silicon wafers at different positions is as follows: Figure 2 shown.

[0038] Wherein ORG% = (average value of central oxygen - average value of edge oxygen) ÷ average value of central oxygen × 100; Depend on Figure 2 It can be seen that adjusting the MCZ magnetic field intensity does not significantly change the radial oxygen content ORG.

[0039] Embodiment 4-6: Using a 28-inch hot field, COPFree process was used to pull an 8-inch lightly boron-doped single crystal. The MCZ magnetic field strength was 2000GS. The radial oxygen content ORG of the pulled crystal rod was 2.3%~3.3%, 1%~1.5%, and 1.6%~2.3%. The MCZ magnetic field positions were -50mm, 0mm, and 50mm respectively. The crystal rod was pulled, and silicon wafers were made at each position of the crystal rod. The radial oxygen content of the silicon wafers was tested. The ORG% of the silicon wafers at different positions was as follows: Figure 3 shown.

[0040] Depend on Figure 3It can be seen that the requirement can be met by adjusting the magnetic field position according to the required radial oxygen content ORG.

[0041] The oxygen content of the crystal rod is tested as follows Figure 4 shown.

[0042] Depend on Figure 4 It can be seen that the oxygen content of the crystal rod does not change significantly when the MCZ magnetic field intensity is adjusted.

[0043] Comparative Example 1: Using a 28-inch hot field, the COPFree process was used to pull an 8-inch lightly boron-doped single crystal without adding a magnetic field; a crystal rod was pulled, and silicon wafers were made at each position of the crystal rod. The radial oxygen content of the silicon wafers was tested, and the ORG% of the silicon wafers at different positions was as follows: Figure 5 shown.

[0044] Depend on Figure 5 , Figure 2 and Figure 3 It can be seen that applying a magnetic field can reduce ORG and make its distribution more uniform, but adjusting the magnetic field strength does not significantly change ORG.

[0045] What is disclosed above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. A person skilled in the art can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for controlling the oxygen content of a small-sized crystal rod by a magnetic field, characterized in that: Under the same thermal field structure and crystal pulling parameters, as the MCZ magnetic field intensity decreases, the oxygen content of the crystal rod decreases. For every 500GS decrease in the MCZ magnetic field intensity, the oxygen content of the crystal rod decreases by 1.5ppma~2.5ppma.

2. The method for controlling the oxygen content of a small-sized crystal rod by a magnetic field according to claim 1, characterized in that: The position of the MCZ magnetic field is -50mm~50mm.

3. The method for controlling the oxygen content of a small-sized crystal rod by a magnetic field according to claim 2, characterized in that: The upper limit of the MCZ magnetic field strength is 3000GS, and the lower limit of the MCZ magnetic field strength is 1000GS.

4. The method for controlling the oxygen content of a small-sized crystal rod by a magnetic field according to claim 3, characterized in that: Within the upper and lower limits of the MCZ magnetic field strength, the oxygen content of the crystal rod is in the range of 7ppma to 17ppma.

5. The method for controlling the oxygen content of a small-sized crystal rod by a magnetic field according to claim 3, characterized in that: As the magnetic field intensity of the MCZ decreases, the radial oxygen content ORG does not change significantly.

6. The method for controlling the oxygen content of a small-sized crystal rod by a magnetic field according to claim 3, characterized in that: The position where the oxygen content of the crystal rod decreases by 1.5 ppma to 2.5 ppma is when the length of the crystal rod is 200 mm to 1400 mm.

7. The method for controlling the oxygen content of a small-sized crystal rod by a magnetic field according to claim 1, characterized in that: Under the same thermal field structure and crystal pulling parameters, When the MCZ magnetic field position is -50 mm, the radial oxygen content ORG of the crystal rod is 2.3%~3.3%; When the MCZ magnetic field position is 0 mm, the radial oxygen content ORG of the crystal rod is 1%~1.5%; When the MCZ magnetic field position is 50 mm, the radial oxygen content ORG of the crystal rod is 1.6%~2.3%.

8. The method for controlling the oxygen content of a small-sized crystal rod by a magnetic field according to claim 7, characterized in that: The radial oxygen content ORG of the crystal rod refers to the position of 600 to 1400 mm of the crystal rod.

9. The method for controlling the oxygen content of a small-sized crystal rod by a magnetic field according to claim 8, characterized in that: Applying MCZ magnetic field can reduce the radial oxygen content ORG of the crystal rod. The change of MCZ magnetic field intensity has no significant change on the radial oxygen content ORG of the crystal rod.

10. The method for controlling the oxygen content of a small-sized crystal rod by a magnetic field according to claim 8, characterized in that: The magnetic field strength is 1000GS~2500GS.

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