Dopant and preparation method thereof, doped silicon wafer and manufacturing method thereof
By forming a deposition layer of dopant on the silicon wafer substrate, the problem of difficult control of the dopant amount in the prior art is solved, and the resistivity control and stability improvement of single crystal silicon is achieved.
Patent Information
- Application Number
- CN202211153844.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-09-21
- Publication Date
- 2024-12-24
- Estimated Expiration
- 2042-09-21
AI Technical Summary
The prior art is difficult to accurately control the amount of doped elements doped into single crystal silicon, resulting in the resistance of single crystal silicon being unable to be accurately controlled, and the resistivity consistency of different parts is poor, affecting usage and yield.
By contacting the raw material of the target doped element with the silicon wafer substrate, chemical deposition is used to form a deposition layer of a set thickness to form a dopant with precise parameters for forming silicon melt containing the target doped element in the melt The doped single crystal silicon rod is drawn by straight drawing to accurately control the content of doped elements.
The precise control of the resistivity of single crystal silicon is achieved, the stability and consistency of resistivity is improved, and the utilization and yield of single crystal silicon rods are improved.
Smart Images
Figure CN115710693B_ABST
Abstract
Description
Technical Field
[0001] The embodiments of the present invention relate to the field of semiconductor technology, and in particular to a dopant and a preparation method thereof, a doped silicon wafer and a manufacturing method thereof. Background Art
[0002] As electronic products continue to evolve towards miniaturization and high performance, more stringent requirements are placed on the operating voltage and energy consumption of related devices, especially standby power consumption. This trend has put forward higher requirements on the conductivity of crystal materials. In the prior art, in order to control the conductivity type and conductivity of crystal materials, specific impurities are added to molten silicon as dopants. At present, the main methods for doping single crystals are: direct doping method, master alloy doping method, and device doping method.
[0003] The direct doping method usually uses pure dopants with high evaporation rate and melting point. The method specifically includes: selecting a certain weight of dopant according to the target resistivity requirement, placing the dopant and polysilicon material into a quartz crucible at the same time, and the dopant and polysilicon material undergo a high-temperature melting stage at the same time. In this process, the melt is stirred to evenly distribute the dopant in the melt, and finally doped single crystal silicon is produced. The master alloy doping method uses a master alloy dopant and is usually used to produce single crystal silicon with less doping element content and higher target resistivity, wherein the master alloy dopant is obtained by making a master alloy of doping elements and polysilicon material. The master alloy doping method specifically includes: calculating the amount of master alloy dopant according to the content of doping elements in the master alloy dopant and the resistivity requirement, and placing the master alloy dopant and polysilicon material into a quartz crucible for melting at the same time, and finally producing doped single crystal silicon. The device doping method is usually suitable for special dopants that cannot be directly doped, such as dopants with strong volatility. Such dopants are, for example, loaded into a doping tool or a doping device in liquid state for doping.
[0004] For large-sized single crystal silicon pulled by the Czochralski method, during the crystal pulling process, it is necessary to control its conductivity type and resistivity according to the specifications of the single crystal silicon, application requirements, etc., wherein the conductivity type is determined by the number of outer electrons of the doped element, and the control of resistivity is achieved by controlling the concentration of the doping element contained in the silicon melt during the growth of the single crystal. At present, single crystal silicon rods can be divided into P-type single crystal silicon rods and N-type single crystal silicon rods according to the type of doping elements. According to the content of doping elements, P-type single crystal silicon rods can be divided into lightly doped P-type single crystal silicon rods and heavily doped P+ / P++ type single crystal silicon rods. In the process of preparing P-type silicon wafers by the Czochralski method, boron is usually selected as the dopant for controlling resistivity. At present, the manufacture of lightly doped single crystal silicon rods mainly uses master alloy dopants, and the manufacture of heavily doped single crystal silicon rods mainly uses pure dopants for direct doping.
[0005] However, whether using a master alloy dopant or a pure dopant, there is currently a problem that the amount of doping elements doped into the single crystal cannot be accurately controlled, which in turn results in an inability to accurately control the resistivity of the doped single crystal silicon. Summary of the invention
[0006] In view of this, the embodiments of the present invention hope to provide a dopant and a preparation method thereof, a doped silicon wafer and a manufacturing method thereof; and can improve the resistivity stability and consistency of the doped single crystal by precisely controlling the doping element content in the doped single crystal.
[0007] The technical solution of the embodiment of the present invention is achieved as follows:
[0008] In a first aspect, an embodiment of the present invention provides a method for preparing a dopant, the method comprising:
[0009] bringing a raw material containing a target doping element into contact with a silicon wafer substrate;
[0010] The raw material is deposited on the silicon wafer substrate by chemical deposition to form a deposition layer having a predetermined thickness, wherein the silicon wafer substrate having the deposition layer formed thereon can be used as a dopant.
[0011] In a second aspect, an embodiment of the present invention provides a dopant, wherein the dopant is prepared by the method according to the first aspect.
[0012] In a third aspect, an embodiment of the present invention provides a method for manufacturing a doped silicon wafer, the method comprising:
[0013] melting the dopant according to the second aspect and a polycrystalline silicon raw material to obtain a silicon melt containing a target doping element;
[0014] Using the silicon melt to pull a doped single crystal silicon rod by a Czochralski method;
[0015] The doped single crystal silicon rod is cut to obtain doped silicon wafers.
[0016] In a fourth aspect, an embodiment of the present invention provides a doped silicon wafer, wherein the doped silicon wafer is obtained by using the method according to the third aspect.
[0017] Embodiments of the present invention provide dopants and methods for preparing the same, doped silicon wafers and methods for manufacturing the same. According to the method for preparing the dopant provided by the embodiments of the present invention, the target doping element is formed on the surface of the silicon wafer substrate in the form of a deposition layer by chemical deposition and the silicon wafer substrate formed with the deposition layer is used as a dopant as a whole. Since the parameters of the deposition layer can be precisely controlled, the content of the doping element in the dopant finally obtained can be precisely controlled by controlling the parameters of the deposition layer. Furthermore, when the doping element obtained by the method provided by the embodiments of the present invention is used to produce doped single crystals, compared with existing dopants, the content of the doping element in the doped single crystals can be more precisely controlled, thereby improving the resistivity stability and consistency of the doped single crystals. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 A schematic flow chart of a method for preparing a dopant provided in an embodiment of the present invention;
[0019] Figure 2 A schematic diagram of a chemical deposition reaction device used in the method provided in an embodiment of the present invention;
[0020] Figure 3 A schematic flow chart of a method for manufacturing a doped silicon wafer provided in an embodiment of the present invention. DETAILED DESCRIPTION
[0021] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.
[0022] In the conventional method of manufacturing doped single crystal silicon wafers, the dopants usually used are pure dopants or master alloy dopants containing a certain concentration of doping elements. Among them, pure dopants are mainly suitable for preparing heavily doped silicon wafers with low resistivity, and master alloy dopants containing a certain concentration of doping elements are mainly suitable for preparing lightly doped silicon wafers with high resistivity. Taking boron as a dopant as an example, pure boron particles are mainly used to prepare P+ type silicon wafers or P++ type silicon wafers with low resistivity, and master alloys containing a certain concentration of boron elements are used to prepare P-type silicon wafers with high resistivity.
[0023] In conventional operation, when pure dopants are used, pure boron particles are usually added directly into the crucible to melt it together with polysilicon at high temperature. However, when the amount of pure dopant required is very small, for example, when the weight of the required pure dopant is less than 10 mg, if the required boron particles cannot be accurately weighed, the doping result will be far from the target value. In this case, master alloy dopants are usually used instead. When using a master alloy dopant, it is first necessary to test the resistivity of the master alloy dopant, and then calculate the content of the target doping element in the master alloy dopant based on the resistivity of the master alloy dopant, and weigh the required master alloy dopant according to the target product requirements and put it into a quartz crucible together with polycrystalline silicon, and undergo a high-temperature melting stage to distribute the doping element in the melt, so as to pull a crystal rod that meets the target resistivity. However, in the above operation, the doping element content calculated is only a theoretical value and there is a deviation from the actual value, so the added doping amount is often inaccurate, which ultimately makes it difficult to accurately control the resistivity of the doped single crystal, and for a single single crystal silicon rod, the resistivity consistency of different parts is poor. It is particularly noteworthy that due to the uncertainty of the dopant content, the head resistivity of the doped single crystal silicon rod often fluctuates, which also affects the resistivity distribution of the entire single crystal silicon rod, resulting in a reduced utilization rate of the entire single crystal silicon rod, thereby reducing the yield.
[0024] In order to more accurately and conveniently control the doping element content in the doped single crystal, thereby improving the resistivity stability and consistency of the doped single crystal, firstly, see Figure 1 , an embodiment of the present invention provides a method for preparing a dopant, the method comprising:
[0025] S101, bringing a raw material containing a target doping element into contact with a silicon wafer substrate;
[0026] S102, depositing the raw material on the silicon wafer substrate by chemical deposition to form a deposition layer with a set thickness, wherein the silicon wafer substrate formed with the deposition layer can be used as a dopant.
[0027] An embodiment of the present invention provides a method for preparing a dopant; according to the method for preparing a dopant provided by the embodiment of the present invention, a target doping element is formed on the surface of a silicon wafer substrate in the form of a deposition layer by chemical deposition and the silicon wafer substrate formed with the deposition layer is used as a dopant as a whole. Since the parameters of the deposition layer can be precisely controlled, the content of the doping element in the dopant finally obtained can be precisely controlled by controlling the parameters of the deposition layer. Furthermore, when the doping element obtained by the method provided by the embodiment of the present invention is used to produce a doped single crystal, compared with the existing dopants, the content of the doping element in the doped single crystal can be more accurately controlled, thereby improving the resistivity stability and consistency of the doped single crystal.
[0028] According to a preferred embodiment of the present invention, a silicon wafer substrate can be obtained as follows: only polycrystalline silicon is placed in a crucible and heated to form a melt, and the melt is grown into single crystal silicon by the Czochralski method, and then a polished wafer suitable for chemical deposition on its surface is made through processes such as slicing, grinding, polishing, and cleaning. This silicon wafer substrate itself does not contain the target doping element, but the dopant is formed on the surface of the silicon wafer substrate in the form of a deposition layer through chemical deposition. After chemical deposition, the silicon wafer substrate forms a doped silicon wafer, that is, a dopant as a whole. Since the parameters of the deposition layer, such as the thickness of the deposition layer, the concentration of the doping element in the deposition layer, etc., can be accurately controlled during the chemical deposition process, the amount of the doping element in the doped silicon wafer obtained after the chemical deposition can also be accurately controlled. When the doping silicon wafer is used for doping in the process of pulling a single crystal silicon rod, the doping element content in the doped single crystal silicon rod can also be accurately controlled. For example, if you want to obtain a single crystal silicon rod with a higher resistivity, you only need to add a small amount of dopant during the drawing process. In this case, the control of the dopant content is often required to be higher. As described above, it is difficult to obtain such a doped single crystal silicon rod by conventional pure dopants or conventional master alloy dopants. However, through the method provided by the present invention, the target doping element can be first formed on the silicon wafer substrate by chemical deposition to form a thin deposition layer, and a doped silicon wafer containing a small amount of doping elements can be obtained to be used as a dopant. The doped silicon wafer can be used to obtain a single crystal silicon rod with a low doping element content. Taking the manufacture of a single crystal silicon rod with a resistivity of 50 ohms as an example, it is only necessary to chemically deposit a chemical deposition layer with a thickness of about 8 microns on the silicon wafer substrate to form a doped silicon wafer, and use the doped silicon wafer as a dopant to be doped into the single crystal silicon rod during the drawing process.
[0029] According to another preferred embodiment of the present invention, if it is desired to obtain a single crystal silicon rod with a lower resistivity, a portion of the target doping element can be doped into the silicon wafer substrate during the manufacturing process to obtain a silicon wafer substrate with a certain content of the doping element in the body, and then chemical deposition is further performed on the surface of the silicon wafer substrate containing the doping element to form a deposition layer, thereby obtaining a doped silicon wafer with a higher content of the doping element for use as a dopant, and using this doped silicon wafer, a single crystal silicon rod with a higher content of the doping element can be obtained.
[0030] Considering that boron is currently usually selected as the doping element for controlling resistivity, preferably, the target doping element is boron.
[0031] The chemical deposition on the silicon wafer substrate needs to be carried out in a closed high-temperature environment. The figure shows a schematic diagram of a reaction device 100A for chemical deposition. The device 100A may include:
[0032] The bell jar 111A encloses the reaction chamber RC, wherein Figure 2 An upper bell housing 111A-1 and a lower bell housing 111A-2 are shown;
[0033] A disc-shaped susceptor 112A inside the reaction chamber RC, the susceptor 112A being configured to carry a silicon wafer substrate W;
[0034] A susceptor support frame 114A, the susceptor support frame 114A is used to support the susceptor 112A and drive the susceptor 112A to rotate around the central axis XA of the device 100A at a certain speed during chemical deposition. Since the wafer W is carried on the susceptor 112A, the wafer W rotates around the central axis XA together with the susceptor 112A;
[0035] The gas inlet 113A is configured to deliver reaction gas into the reaction chamber RC. Figure 1 As shown by the arrow at the air inlet 113A, wherein the air inlet 113A is located radially outside the base 112A and the base 112A is at a height flush with the air inlet 113A;
[0036] The exhaust port 115A is used to discharge the reaction tail gas out of the reaction chamber RC. Figure 2 As shown by the arrow at the exhaust port 115A;
[0037] A plurality of heating bulbs 116A are disposed at the periphery of the upper bell jar 111A-1 and the lower bell jar 111A-2 and are used to provide a high temperature environment in the reaction chamber RC through the upper bell jar 111A-1 and the lower bell jar 111A-2.
[0038] In a preferred embodiment of the present invention, the reaction temperature of the chemical deposition is between 1100°C and 1150°C.
[0039] Preferably, the chemical deposition may include introducing a mixed gas of H2 and B2H6 into a closed reaction chamber containing the silicon wafer substrate. Figure 3 During the chemical deposition process, a mixture of H2 and B2H6 is introduced into the reaction chamber RC through the gas inlet 113A as a reaction gas, wherein the ratio of H2 to the mixture of H2 and B2H6 may be, for example, 1:4.
[0040] As an example of the present invention, the flow rate of the H2 and B2H6 mixed gas may be no greater than 500 sccm.
[0041] According to an embodiment of the present invention, the thickness of the boron dopant layer is related to the required amount of dopant. Considering the objective requirements of the chemical deposition process and the actual required amount of dopant, preferably, the set thickness of the deposition layer is less than 30 microns.
[0042] In a second aspect, an embodiment of the present invention further provides a dopant, wherein the dopant is prepared by the method according to the first aspect.
[0043] Thirdly, see Figure 3 The embodiment of the present invention further provides a method for manufacturing a doped silicon wafer, the method comprising:
[0044] S201, melting the dopant according to the second aspect and the polycrystalline silicon raw material to obtain a silicon melt containing a target doping element;
[0045] S202, using the silicon melt to pull a doped single crystal silicon rod using a Czochralski method;
[0046] S203, cutting the doped single crystal silicon rod to obtain doped silicon wafers.
[0047] In a fourth aspect, an embodiment of the present invention provides a doped silicon wafer, wherein the doped silicon wafer is obtained by using the method according to the third aspect.
[0048] It should be noted that the technical solutions described in the embodiments of the present invention can be combined arbitrarily without conflict.
[0049] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.
Claims
1. A method for producing a doped silicon wafer, characterized in that: The method comprises: Melting a dopant and a polysilicon raw material to obtain a silicon melt containing a target doping element, using the silicon melt to pull a doped single crystal silicon rod by a Czochralski method, and cutting the doped single crystal silicon rod to obtain a doped silicon wafer; The dopant is obtained by contacting a raw material containing a target doping element with a silicon wafer substrate, and depositing the raw material on the silicon wafer substrate by chemical deposition to form a deposition layer with a set thickness.
2. The method according to claim 1, characterized in that The silicon wafer substrate is a polished silicon wafer that does not contain the target doping element.
3. The method according to claim 1, characterized in that The silicon wafer substrate is a polished silicon wafer containing a set amount of the target doping element.
4. The method according to claim 1, characterized in that The target doping element is boron.
5. The method according to claim 4, characterized in that The reaction temperature of the chemical deposition is between 1100°C and 1150°C.
6. The method according to claim 4, characterized in that The chemical deposition includes introducing a mixed gas of H2 and B2H6 into a closed reaction chamber containing the silicon wafer substrate.
7. The method according to claim 6, characterized in that The flow rate of the H2 and B2H6 mixed gas is not greater than 500sccm.
8. A doped silicon wafer, characterized in that: The doped silicon wafer is obtained by using the method according to any one of claims 1 to 7.