Large-size high-resistance infrared silicon single crystal and preparation method thereof

Abstract

The invention relates to the technical field of infrared optical materials, and particularly discloses a large-size high-resistance infrared silicon single crystal and a preparation method thereof. The doping concentration of cobalt oxide in the large-size high-resistance infrared silicon single crystal is 10 ppm to 100 ppm, and the atomic concentration of phosphorus in the large-size high-resistance infrared silicon single crystal is 2 * 10 < 13 > / cm < 3 > to 6 * 10 < 13 > / cm < 3 >. The oxide of transition metal cobalt and phosphorus impurities are doped into the infrared silicon single crystal, carriers of cobalt and phosphorus and carriers of impurities such as boron and oxygen generate a recombination effect, so that the concentration of free carriers in the silicon single crystal is reduced, and the absorption coefficient of the doped silicon single crystal is relatively small; the infrared transmittance of the silicon single crystal in a medium wave band can be obviously increased, the resistivity can reach 600 omega.cm or above, and the use requirement of the infrared silicon single crystal in a high-performance infrared optical system can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of infrared optical materials, and in particular to a large-size high-resistance infrared silicon single crystal and a preparation method thereof. Background Art

[0002] Silicon is a common semiconductor material. Silicon single crystal is a diamond structure composed of covalent bonds. It has good electrical and mechanical properties and is mainly used as a substrate material for integrated circuit chips and solar cells. Silicon single crystal has good infrared optical properties. The band gap width of silicon is 1.12eV. It is opaque in the visible light range, but when infrared light enters the silicon material, its energy is not enough to excite the electrons in the silicon to jump from the valence band to the conduction band, so it will not be absorbed. The ideal transmission band of silicon single crystal is 2μm~6μm, and the theoretical transmittance in this band is 53.8%. In addition, it has the characteristics of high mechanical strength, low dispersion, and corrosion resistance, making it an ideal short- and medium-wave infrared optical material.

[0003] At present, the preparation methods of silicon single crystals mainly include the Czochralski method (Cz method) and the floating zone melting method (FZ method). The advantages of the Czochralski method are that the crystal stress is small, crystallization is easy, the single crystal integrity is good, the diameter and length can be large, and the growth rate is high; the disadvantage is that it is difficult to prepare single crystals with high purity and high resistivity due to the contact between the melt and the quartz crucible. The advantage of the floating zone melting method is that it can prepare high-purity, oxygen-free, high-resistance silicon because it does not contact any substance such as quartz; the disadvantage is that the maximum diameter of the silicon rod can only reach 8 inches, the growth rate is slow, and the production cost is high.

[0004] High-performance infrared optical systems used for long-distance detection in aerospace and other fields have higher requirements on the size, optical transmittance, absorption coefficient, etc. of silicon single crystals. Generally, large-aperture detection systems require infrared silicon lenses to be larger than 200 mm in size, with a transmittance of ≥52% in the 2μm~6μm band and an absorption coefficient of ≤0.05. At this time, the resistivity of silicon single crystals must reach above 500Ω·cm. However, although the resistivity of silicon single crystals prepared by the floating zone melting method can reach above 500Ω·cm, the diameter cannot reach above 200mm, and the production efficiency is low and the cost is high. For the preparation of high-resistance silicon single crystals by the direct-pull single crystal manufacturing method, whether it is P-type single crystal silicon or N-type single crystal silicon, the existing method can only prepare silicon single crystals within 300Ω·cm (resistivity cannot reach 500Ω·cm), and the method is complicated and requires multiple batches of doping and crystal pulling, etc. It cannot specifically solve the absorption problem of carriers in infrared silicon single crystals, and cannot meet the requirements of high-performance optical lenses for the use of high-resistance infrared silicon single crystals. Summary of the invention

[0005] In view of the above problems, the present invention provides a large-size high-resistance infrared silicon single crystal and a preparation method thereof. By controlling the doping material and its doping amount, the carriers of impurities such as boron and oxygen are compensated and recombine, thereby reducing the concentration of free carriers in the silicon single crystal, thereby improving the infrared optical performance of the silicon single crystal and greatly reducing the manufacturing cost.

[0006] In order to solve the above technical problems, the technical solution provided by the present invention is: In a first aspect, the present invention provides a large-sized high-resistance infrared silicon single crystal, wherein the doping concentration of cobalt oxide in the large-sized high-resistance infrared silicon single crystal is 10ppm~100ppm, and the atomic concentration of phosphorus in the large-sized high-resistance infrared silicon single crystal is 2×10 13 / cm 3 ~6×10 13 / cm 3 .

[0007] Compared with the prior art, the large-sized high-resistance infrared silicon single crystal provided by the present invention is doped with oxides of transition metal cobalt and phosphorus impurities into the infrared silicon single crystal, and the carriers of cobalt and phosphorus react with the carriers of impurities such as boron and oxygen to reduce the concentration of free carriers in the silicon single crystal. The absorption coefficient of the doped silicon single crystal is small, and the infrared transmittance of the silicon single crystal in the medium wave band can be significantly increased. The results of the embodiment show that the resistivity of the large-sized high-resistance infrared silicon single crystal provided by the present invention can reach more than 800Ω·cm, the average infrared transmittance in the range of 2μm~6μm is ≥52%, the absorption coefficient at 3μm is ≤0.01, and the diameter is ≥200mm, which can meet the use requirements of infrared silicon single crystals in high-performance infrared optical systems.

[0008] Preferably, the doping concentration of cobalt oxide in the large-size high-resistance infrared silicon single crystal is 10ppm~80ppm, and more preferably 20ppm~50ppm.

[0009] Preferably, the large-size high-resistance infrared silicon single crystal is produced by a Czochralski single crystal manufacturing method.

[0010] In a second aspect, the present invention provides a method for preparing the large-size high-resistance infrared silicon single crystal, comprising the following steps: Weigh the raw materials according to the designed ratio, put polycrystalline silicon, cobalt oxide and silicon-phosphorus alloy into a crucible, fuse the seed crystal under an inert atmosphere, and then pull the seed crystal to grow in equal diameter to obtain a large-sized high-resistance infrared silicon single crystal.

[0011] The method for preparing large-size high-resistance infrared silicon single crystals provided by the present invention has a simple process, high efficiency, low cost, and does not involve special processes. It is suitable for the preparation of large-diameter infrared silicon single crystals. It can not only improve the resistivity of the silicon single crystals, but also improve the infrared optical transmittance of the silicon single crystals. It has strong engineering applicability and is suitable for large-scale production.

[0012] Preferably, the atomic concentration of phosphorus in the silicon-phosphorus alloy is ≥10 18 / cm 3 , and more preferably 5×10 18 / cm 3 ~5×10 19 / cm 3 .

[0013] Preferably, the purity of the cobalt oxide is ≥99.9995%, and the purity of the polysilicon is ≥10N.

[0014] Preferably, the crucible is a quartz crucible with a purity of ≥99.99%.

[0015] Preferably, the inert atmosphere comprises an argon atmosphere with a purity of ≥99.9999%, and the flow rate of the argon is 100 L / min~130 L / min.

[0016] The present invention selects raw materials such as high-purity cobalt oxide, polycrystalline silicon, quartz crucible and argon gas, further reducing the generation of impurities in the preparation process and ensuring the stability of the preparation process of large-size high-resistance infrared silicon single crystals.

[0017] Preferably, the temperature of the fusion-bonded seed crystal is 1430° C. to 1450° C., and the pressure is 1 kPa to 2 kPa (more preferably 1 kPa to 1.5 kPa).

[0018] It should be noted that the welding of seed crystals of the present invention includes firstly melting the raw materials in the crucible into a melt, and then immersing one end of the seed crystal into the melt for subsequent equal-diameter growth to form a single crystal.

[0019] The present invention can further reduce the oxygen content and free carrier concentration in the silicon single crystal by limiting the temperature, pressure, argon gas flow rate and other parameters of the fusion seed crystal, thereby increasing both the resistivity of the infrared silicon single crystal and the infrared optical transmittance of the silicon single crystal.

[0020] For example, the pulling of the seed crystal includes necking, shouldering, equal diameter growth and tailing in sequence.

[0021] Preferably, during the isodiametric growth process, the rotation speed of the crucible is 4 r / min-6 r / min, and the rotation speed of the seed crystal is 6 r / min-9 r / min.

[0022] The present invention can ensure the stability of the solid-liquid interface during the single crystal growth process by limiting the conditions of equal diameter growth, thereby ensuring the quality of the finished infrared silicon single crystal. The present invention does not limit the necking, shouldering and other processes, and conventional operations in the art can be used.

[0023] For example, the finishing includes the following steps: after the equal-diameter growth is completed, the diameter and crucible heel ratio control programs are turned off, the temperature is raised to 1435℃~1460℃, and the pulling speed is manually adjusted to 1mm / min~5mm / min, so that the diameter of the single crystal gradually becomes smaller until the single crystal is separated from the liquid surface, thereby obtaining a large-size high-resistance infrared silicon single crystal. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a graph showing the infrared transmittance of the large-sized high-resistance infrared silicon single crystal in Example 2 of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] In the present invention, materials not otherwise specified are all commercially available products.

[0027] Example 1 This embodiment provides a large-sized high-resistance infrared silicon single crystal, in which the doping concentration of cobalt oxide is 10 ppm, and the atomic concentration of phosphorus in the large-sized high-resistance infrared silicon single crystal is 2×10 13 / cm 3 .

[0028] The method for preparing the large-size high-resistance infrared silicon single crystal comprises the following steps: Weigh the raw materials according to the designed ratio, and mix 100 kg of 10N pure polysilicon, 1 g of 99.9999% pure cobalt oxide, and 0.1 g of silicon-phosphorus alloy (the atomic concentration of phosphorus in the silicon-phosphorus alloy is 2×10 19 / cm 3 ) is placed in a quartz crucible with a purity of 99.99%, and then placed in a vertical single crystal furnace; high-purity argon gas with a purity of 99.9999% is introduced into the furnace, the flow rate of argon gas is 100L / min, the temperature is raised to 1430℃, the furnace pressure is 1kPa, and after the seed crystal is melted, the seed crystal is pulled in sequence for necking, shouldering, equal-diameter growth (the rotation speed of the quartz crucible is 4r / min, the rotation speed of the seed crystal is 6r / min) and finishing to obtain a large-size high-resistance infrared silicon single crystal.

[0029] Example 2 This embodiment provides a large-sized high-resistance infrared silicon single crystal, in which the doping concentration of cobalt oxide is 26.7 ppm, and the atomic concentration of phosphorus in the large-sized high-resistance infrared silicon single crystal is 4×10 13 / cm 3 .

[0030] The method for preparing the large-size high-resistance infrared silicon single crystal comprises the following steps: Weigh the raw materials according to the designed ratio, and mix 150 kg of 11N pure polysilicon, 4 g of 99.9999% pure cobalt oxide, and 0.3 g of silicon-phosphorus alloy (the atomic concentration of phosphorus in the silicon-phosphorus alloy is 4×10 19 / cm 3 ) is placed in a quartz crucible with a purity of 99.995%, and then placed in a vertical single crystal furnace; high-purity argon gas with a purity of 99.99995% is introduced into the furnace, the flow rate of argon gas is 120L / min, the temperature is raised to 1440℃, the furnace pressure is 1.25kPa, and after the seed crystal is melted, the seed crystal is pulled in sequence for necking, shouldering, equal-diameter growth (the rotation speed of the quartz crucible is 5r / min, the rotation speed of the seed crystal is 7r / min) and finishing to obtain a large-size high-resistance infrared silicon single crystal.

[0031] Example 3 This embodiment provides a large-sized high-resistance infrared silicon single crystal, in which the doping concentration of cobalt oxide is 90 ppm, and the atomic concentration of phosphorus in the large-sized high-resistance infrared silicon single crystal is 6×10 13 / cm 3 .

[0032] The method for preparing the large-size high-resistance infrared silicon single crystal comprises the following steps: Weigh the raw materials according to the designed ratio, and mix 200 kg of 10N pure polysilicon, 18 g of 99.9995% pure cobalt oxide and 0.3 g of silicon-phosphorus alloy (the atomic concentration of phosphorus in silicon-phosphorus alloy is 4×10 19 / cm 3 ) is placed in a quartz crucible with a purity of 99.99%, and then placed in a vertical single crystal furnace; high-purity argon with a purity of 99.9999% is introduced into the furnace, the flow rate of argon is 130L / min, the temperature is raised to 1450℃, the furnace pressure is 1.3kPa, and after the seed crystal is melted, the seed crystal is pulled in sequence for necking, shoulder release, equal diameter growth (the rotation speed of the quartz crucible is 6r / min, the rotation speed of the seed crystal is 9r / min) and finishing to obtain a large-size high-resistance infrared silicon single crystal.

[0033] Example 4 This embodiment provides a large-sized high-resistance infrared silicon single crystal, in which the doping concentration of cobalt oxide is 50 ppm, and the atomic concentration of phosphorus in the large-sized high-resistance infrared silicon single crystal is 2×1013 / cm 3 ~6×10 13 / cm 3 .

[0034] The method for preparing the large-size high-resistance infrared silicon single crystal comprises the following steps: Weigh the raw materials according to the designed ratio, and mix 100 kg of 11N pure polysilicon, 5 g of 99.9999% pure cobalt oxide and 0.12 g of silicon-phosphorus alloy (the atomic concentration of phosphorus in silicon-phosphorus alloy is 4×10 19 / cm 3 ) is placed in a quartz crucible with a purity of 99.995%, and then placed in a vertical single crystal furnace; high-purity argon gas with a purity of 99.99995% is introduced into the furnace, the flow rate of argon gas is 110L / min, the temperature is raised to 1445℃, the furnace pressure is 1.9kPa, and after the seed crystal is melted, the seed crystal is pulled in sequence for necking, shoulder release, equal diameter growth (the rotation speed of the quartz crucible is 5r / min, the rotation speed of the seed crystal is 8r / min) and finishing to obtain a large-size high-resistance infrared silicon single crystal.

[0035] Comparative Example 1 This comparative example provides an infrared silicon single crystal (not doped with cobalt oxide), the atomic concentration of phosphorus in the infrared silicon single crystal is 4×10 13 / cm 3 .

[0036] The method for preparing the infrared silicon single crystal is similar to that of Example 2, except that the addition of cobalt oxide to the raw materials is omitted. The remaining conditions are the same as those of Example 2 and will not be described in detail.

[0037] Comparative Example 2 This comparative example provides an infrared silicon single crystal (not doped with phosphorus), and the doping concentration of cobalt oxide in the infrared silicon single crystal is 26.7 ppm.

[0038] The method for preparing the infrared silicon single crystal is similar to that of Example 2, except that the silicon-phosphorus alloy is omitted from the raw materials. The remaining conditions are the same as those of Example 2 and will not be described in detail.

[0039] Comparative Example 3 This comparative example provides an infrared silicon single crystal, in which the doping concentration of cobalt oxide in the infrared silicon single crystal is 150ppm, and the atomic concentration of phosphorus in the infrared silicon single crystal is 4×10 13 / cm 3 .

[0040] The preparation method of the infrared silicon single crystal is similar to that of Example 2, except that the raw materials are 150 kg of polycrystalline silicon with a purity of 11N, 22.5 g of cobalt oxide with a purity of 99.9999%, and 0.3 g of silicon-phosphorus alloy. That is, except that the amount of cobalt oxide added is different from that of Example 2, the other conditions are the same as those of Example 2 and will not be repeated.

[0041] Comparative Example 4 This comparative example provides an infrared silicon single crystal, in which the doping concentration of cobalt oxide in the large-size high-resistance infrared silicon single crystal is 26.7ppm, and the atomic concentration of phosphorus in the infrared silicon single crystal is 2×10 14 / cm 3 .

[0042] The preparation method of the infrared silicon single crystal is similar to that of Example 2, except that the raw materials are 150 kg of polycrystalline silicon with a purity of 11N, 4 g of cobalt oxide with a purity of 99.9999%, and 1.5 g of silicon-phosphorus alloy. That is, except that the amount of silicon-phosphorus alloy added is different from that of Example 2, the other conditions are the same as those of Example 2 and will not be repeated.

[0043] Verification test The infrared optical performance tests were performed on the infrared silicon single crystals provided in Examples 1 to 4 and Comparative Examples 1 to 4, respectively, and the test results are shown in Table 1. The resistivity was tested using the GB / T 4326 standard using a Hall tester; the infrared transmittance was tested using the GJB2919A standard using an infrared spectrometer at a wavelength of 2 μm-6 μm; the absorption coefficient was tested using the GJB2919A standard using an infrared spectrometer at a wavelength of 3 μm, and the absorption coefficient was calculated according to Formula 1: Formula 1 Where ɑ represents the absorption coefficient, cm -1 ; d represents the sample thickness, cm; R represents the reflectance; T λ Indicates transmittance.

[0044] The reflectance R is calculated by formula 2: Formula 2 In the formula, R represents reflectance and n represents refractive index. At 3μm wavelength (@3μm), n=3.4320, and the sample thickness for the transmittance test is 2cm.

[0045] Table 1 Performance test results of infrared silicon single crystals of the embodiment and the comparative example

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A large-size high-resistance infrared silicon single crystal, characterized in that: The doping concentration of cobalt oxide in the large-sized high-resistance infrared silicon single crystal is 10ppm~100ppm, and the atomic concentration of phosphorus in the large-sized high-resistance infrared silicon single crystal is 2×10 13 / cm 3 ~6×10 13 / cm 3 .

2. The large-size high-resistance infrared silicon single crystal according to claim 1, characterized in that: The doping concentration of cobalt oxide in the large-size high-resistance infrared silicon single crystal is 10ppm-80ppm.

3. The large-size high-resistance infrared silicon single crystal according to claim 1, characterized in that: The large-size high-resistance infrared silicon single crystal is manufactured by adopting a Czochralski single crystal manufacturing method.

4. The method for preparing a large-size high-resistance infrared silicon single crystal according to any one of claims 1 to 3, characterized in that: The following steps are involved: Weigh the raw materials according to the designed ratio, put polycrystalline silicon, cobalt oxide and silicon-phosphorus alloy into a crucible, fuse the seed crystal under an inert atmosphere, and then pull the seed crystal to grow in equal diameter to obtain a large-sized high-resistance infrared silicon single crystal.

5. The method for preparing a large-size high-resistance infrared silicon single crystal according to claim 4, characterized in that: The atomic concentration of phosphorus in the silicon-phosphorus alloy is ≥10 18 / cm 3 .

6. The method for preparing a large-size high-resistance infrared silicon single crystal according to claim 4, characterized in that: The purity of the cobalt oxide is ≥99.9995%, the purity of the polysilicon is ≥10N, and the crucible is a quartz crucible with a purity of ≥99.99%.

7. The method for preparing a large-size high-resistance infrared silicon single crystal according to claim 4, characterized in that: The inert atmosphere includes an argon atmosphere with a purity of ≥99.9999%, and the flow rate of the argon is 100L / min~130L / min.

8. The method for preparing a large-size high-resistance infrared silicon single crystal according to claim 4, characterized in that: The temperature of the fusion seed crystal is 1430° C. to 1450° C., and the pressure is 1 kPa to 2 kPa.

9. The method for preparing a large-size high-resistance infrared silicon single crystal according to claim 4, characterized in that: The pulling of the seed crystal includes necking, shouldering, equal diameter growth and tailing in sequence.

10. The method for preparing a large-size high-resistance infrared silicon single crystal according to claim 4 or 9, characterized in that: During the isodiameter growth process, the rotation speed of the crucible is 4 r / min-6 r / min, and the rotation speed of the seed crystal is 6 r / min-9 r / min.

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