WO2023051702A1 - Device and method for manufacturing nitrogen-doped monocrystalline silicon - Google Patents

Abstract

A device and method for manufacturing nitrogen-doped monocrystalline silicon, where the device includes: an air pressure control apparatus, the air pressure control apparatus being used for reducing the pressure of a gas near the liquid surface of a nitrogen-doped silicon melt; a crystal pulling apparatus, the crystal pulling apparatus using a direct method for drawing a monocrystalline silicon rod from the nitrogen-doped silicon melt.

Description

A kind of equipment and method for manufacturing nitrogen-doped single crystal silicon

Cross References to Related Applications

This application claims priority to Chinese Patent Application No. 202111162536.X filed in China on September 30, 2021, the entire contents of which are hereby incorporated by reference.

technical field

This application relates to the field of semiconductor wafer manufacturing. In particular, it relates to a device and method for manufacturing nitrogen-doped single crystal silicon.

Background technique

Silicon wafers used to produce semiconductor electronic components such as integrated circuits are mainly manufactured by slicing single crystal silicon rods drawn by the Czochralski method. The Czochralski method involves melting polysilicon in a crucible made of quartz to obtain a silicon melt, immersing a single crystal seed in the silicon melt, and continuously lifting the seed to move away from the surface of the silicon melt, whereby during the movement A single crystal silicon rod grows at the phase interface.

In the above-mentioned production process, it is very advantageous to provide such a silicon wafer: the silicon wafer has a crystal defect-free region (Denuded Zone, DZ) extending from the front side to the body and a denuded zone adjacent to the DZ and further extending to the body. Bulk Micro Defect (BMD) area, where the front side refers to the surface of the silicon wafer that needs to form electronic components. The above-mentioned DZ is important because in order to form electronic components on a silicon wafer, it is required that there are no crystal defects in the formation area of the electronic components, otherwise it will cause failures such as circuit breaks, so that the electronic components are formed in the DZ The influence of crystal defects can be avoided; and the function of the above-mentioned BMD is that it can generate an intrinsic getter (Intrinsic Getter, IG) effect on metal impurities, so that the metal impurities in the silicon wafer can be kept away from the DZ, thereby avoiding the leakage caused by metal impurities Adverse effects such as increased current and decreased film quality of the gate oxide film.

In the process of producing the aforementioned silicon wafers with BMD regions, it is very beneficial to dope the silicon wafers with nitrogen. For example, when nitrogen is doped in a silicon wafer, it can promote the formation of BMD with nitrogen as the core, so that the BMD can reach a certain density, and the BMD can effectively function as a metal gettering source, and it can also It has a favorable effect on the density distribution of BMD, such as making the distribution of BMD density more uniform in the radial direction of the silicon wafer, such as making the density of BMD higher in the area near the DZ and gradually decreasing towards the silicon wafer.

As an implementation of doping silicon wafers with nitrogen, the silicon melt in the quartz crucible can be doped with nitrogen, and the single crystal silicon rods drawn from this and the silicon crystals cut from the single crystal silicon rods are The flakes are then doped with nitrogen.

The problem in the process of drawing nitrogen-doped single crystal silicon rods from nitrogen-doped silicon melt is that the segregation coefficient of nitrogen is less than 1, specifically 7×10 ^-4 , which leads to nitrogen tending to stay in the melt, while Instead of entering the single crystal silicon rod, as the crystal pulling process continues, the concentration of nitrogen in the melt will gradually increase, so the nitrogen concentration of the drawn single crystal silicon rod will appear lower at the head and higher at the tail. High situation, or nitrogen concentration is inhomogeneous in the longitudinal direction of single crystal silicon rod, utilizes the difference between the nitrogen concentration of the different silicon slices that cut out of such single crystal silicon rod, thus can't aim at said difference. The silicon wafer adopts a uniform method to obtain the desired density distribution of BMD or effectively control the density distribution of BMD.

Contents of the invention

In order to solve the above technical problems, the embodiment of the present application expects to provide a device and method for manufacturing nitrogen-doped single crystal silicon, which can improve the problem of non-uniform distribution of nitrogen concentration in the nitrogen-doped single crystal silicon rod along the longitudinal direction.

The technical scheme of the present application is realized like this:

In the first aspect, the embodiment of the present application provides a device for manufacturing nitrogen-doped single crystal silicon, the device comprising:

A gas pressure control device, the gas pressure control device is used to reduce the pressure of the gas near the liquid level of the nitrogen-doped silicon melt;

A crystal pulling device is used for pulling single crystal silicon rods by using the nitrogen-doped silicon melt by direct method.

In the second aspect, the embodiment of the present application provides a method for manufacturing nitrogen-doped single crystal silicon, the method comprising:

Reduce the pressure of the gas near the liquid level of the nitrogen-doped silicon melt;

A single crystal silicon rod is drawn by the direct method by using the nitrogen-doped silicon melt.

The embodiment of the present application provides a device and method for manufacturing nitrogen-doped silicon single crystal. Since the pressure of the gas near the liquid level of the nitrogen-doped silicon melt is reduced, the nitrogen in the nitrogen-doped silicon melt can be more The fastest rate volatilizes in the form of nitrogen, and the rate of nitrogen concentration declines faster, and the concentration increase caused by the segregation coefficient of less than 1 can be reduced more significantly, so that the nitrogen concentration at the head and tail of the entire silicon rod The difference is smaller, or the nitrogen concentration of the whole silicon rod along the longitudinal direction is more uniform.

Description of drawings

Fig. 1 is the schematic diagram of the volatilization rate of the nitrogen in the melt and the relation between the nitrogen concentration and the gas pressure in the silicon rod;

Fig. 2 is a schematic structural diagram of a device for manufacturing nitrogen-doped single crystal silicon provided by an embodiment of the present application;

Fig. 3 is a schematic flowchart of a method for manufacturing nitrogen-doped single crystal silicon provided by the embodiment of the present application.

Detailed ways

The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

For the nitrogen doped in the silicon melt, it will volatilize from the silicon melt in the form of nitrogen gas, thus resulting in a decrease of the nitrogen concentration in the melt. However, the inventors of the present application have found that the above-mentioned rate of nitrogen volatilization is related to the air pressure above the melt, specifically, as shown in Figure 1, when the air pressure above the melt is P1, the rate of nitrogen volatilization is relatively high. Slow, the rate of decrease of nitrogen concentration is also slow, the nitrogen concentration in the melt will decrease by ΔC1 from the beginning of crystal pulling to the end of crystal pulling, thus forming a single crystal silicon rod concentration as indicated by the dotted line above the initial concentration line in Figure 1 change curve, and when the pressure above the melt is P2 which is less than P1, the nitrogen volatilization rate is faster, and the nitrogen concentration drop rate is also faster, and the nitrogen concentration in the melt will drop by more than ΔC1 to ΔC2, thus forming the single crystal silicon rod concentration change curve represented by the dotted line above the initial concentration line in Fig. However, the increased nitrogen concentration can be reduced to a certain extent.

Based on the above situation, referring to FIG. 2, the embodiment of the present application provides a device 1 for manufacturing nitrogen-doped single crystal silicon. The device 1 may include:

The gas pressure control device 10, the gas pressure control device 10 is used to reduce the pressure of the gas near the liquid level L of the nitrogen-doped silicon melt M, wherein, when the nitrogen-doped silicon melt M is schematically shown in Figure 2 When in the furnace body 2, a specific implementation of the above-mentioned air pressure control device 10, as shown in Figure 2, the air pressure control device 10 can include a pipeline 11 leading into the furnace body 2 and a A vacuum pump 12, the vacuum pump 12 is used to suck out the gas inside the furnace body 2 by means of the pipeline 11, as shown schematically by the arrow in the pipeline 11 in FIG. The internal air pressure is reduced, thereby reducing the pressure of the gas near the liquid level L of the nitrogen-doped silicon melt M;

A crystal pulling device 20, the crystal pulling device 20 is used to use the nitrogen-doped silicon melt M to pull a single crystal silicon rod R by a direct method, wherein, for the crystal pulling device 20 schematically shown in FIG. 2 , the crystal pulling device 20 is located on the top of the furnace body 2, and the single crystal silicon rod R is moved along the direction shown by the hollow arrow in Figure 2, so that the single crystal silicon rod R is at the phase interface or at the liquid level L keep growing.

Since the pressure of the gas near the liquid level L of the nitrogen-doped silicon melt M is reduced, the nitrogen in the nitrogen-doped silicon melt M can be volatilized in the form of nitrogen gas at a faster rate, and the nitrogen concentration decreases faster, as Figure 2 takes the whole silicon rod as an example, the concentration increase caused by the segregation coefficient of less than 1 can be reduced more significantly, so that the difference in nitrogen concentration between the head and tail of the whole silicon rod is smaller, or Make the nitrogen concentration of the whole silicon rod more uniform along the longitudinal direction.

For the above-mentioned obtaining of nitrogen-doped silicon melt M, in the equipment 1 according to the embodiment of the present application, as shown in FIG. Silicon nitride and polycrystalline silicon are melted to obtain said nitrogen-doped silicon melt M, wherein, for the melting device 30 schematically shown in FIG. 2 , the melting device 30 comprises a crucible for containing silicon nitride and polycrystalline silicon 31 and is used to heat the crucible 31 to melt silicon nitride and polysilicon contained in the crucible 31 .

For the above-mentioned obtaining of the nitrogen-doped silicon melt M, in the equipment 1 according to another embodiment of the present application, referring still to FIG. Silicon nitride crucible 31 melts polysilicon to obtain the nitrogen-doped silicon melt M, that is to say, the difference between this embodiment and the previous embodiment is that the crucible in this embodiment is made of silicon nitride, and in this When the crucible is heated, a part of the inner wall will be melted so that nitrogen is doped into the silicon melt formed after the polysilicon is melted, and the crucible in the previous embodiment may be a nitrogen-free crucible such as a quartz crucible; in this embodiment The crucible in can contain only polysilicon without containing any nitrogen-containing dopants, while the crucible in the previous embodiment needs to contain nitrogen-containing dopants such as silicon nitride to dope nitrogen into the silicon melt formed after the polysilicon is melted. body.

In order to avoid undesired chemical reactions between the high-temperature nitrogen-doped silicon melt M and the gas in the surrounding environment such as oxidation in the atmosphere, it is necessary to keep the nitrogen-doped silicon melt M in a protective gas atmosphere. For this reason, see Figure 2 , the equipment 1 may also include a gas supply device 40, the gas supply device 40 is used to make the inert gas flow through the liquid level L of the nitrogen-doped silicon melt M, and the aforementioned gas near the liquid level L is the inert gas here, wherein, for the gas supply device 40 schematically shown in FIG. The gas is delivered to the interior of the furnace body 2, as schematically shown in FIG. 2 by the arrow in the draft tube 42, which is used to guide the inert gas to the liquid level L of the nitrogen-doped silicon melt M , as schematically shown by the arrow above the liquid level L in FIG. 2 .

Regarding the above-mentioned types of inert gas, in one example, the inert gas may be argon.

Referring to Figure 3, the embodiment of the present application also provides a method for manufacturing nitrogen-doped single crystal silicon, the method may include:

Reduce the pressure of the gas near the liquid level of the nitrogen-doped silicon melt;

A single crystal silicon rod is drawn by the direct method by using the nitrogen-doped silicon melt.

Regarding the above obtaining of the nitrogen-doped silicon melt, in the method according to the embodiment of the present application, the method may further include: melting silicon nitride and polysilicon to obtain the nitrogen-doped silicon melt.

Regarding the above obtaining of the nitrogen-doped silicon melt, in the method according to another embodiment of the present application, the method may further include: melting polysilicon in a silicon nitride crucible to obtain the nitrogen-doped silicon melt.

As mentioned above, in order to maintain the nitrogen-doped silicon melt in a protective gas atmosphere, the method may further include: flowing an inert gas through the liquid surface of the nitrogen-doped silicon melt, and the aforementioned liquid The gas near the surface is the inert gas here.

The inert gas involved in the above method can also be argon.

It should be noted that: the technical solutions described in the embodiments of the present application may be combined arbitrarily if there is no conflict.

The above is only a specific implementation of the application, but the scope of protection of the application is not limited thereto. Anyone familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the application. Should be covered within the protection scope of this application. Therefore, the protection scope of the present application should be determined by the protection scope of the claims.

Claims (10)

A device for manufacturing nitrogen-doped single crystal silicon, the device comprising: A gas pressure control device, the gas pressure control device is used to reduce the pressure of the gas near the liquid level of the nitrogen-doped silicon melt; A crystal pulling device is used for pulling single crystal silicon rods by using the nitrogen-doped silicon melt by direct method. The device of claim 1, further comprising: A melting device used for melting silicon nitride and polysilicon to obtain the nitrogen-doped silicon melt. The device of claim 1, further comprising: A melting device, the melting device uses a silicon nitride crucible to melt polysilicon to obtain the nitrogen-doped silicon melt. The device according to any one of claims 1 to 3, further comprising a gas supply device for making an inert gas flow through the liquid surface of the nitrogen-doped silicon melt, wherein the The gas near the liquid surface is the inert gas. The apparatus of claim 4, wherein the inert gas is argon. A method for manufacturing nitrogen-doped single crystal silicon, the method comprising: Reduce the pressure of the gas near the liquid level of the nitrogen-doped silicon melt; A single crystal silicon rod is drawn by the direct method by using the nitrogen-doped silicon melt. The method of claim 6, further comprising: Silicon nitride and polysilicon are melted to obtain the nitrogen-doped silicon melt. The method of claim 6, further comprising: Polysilicon is melted using a silicon nitride crucible to obtain the nitrogen-doped silicon melt. The method according to any one of claims 6 to 8, further comprising: Making an inert gas flow through the liquid surface of the nitrogen-doped silicon melt, wherein the gas near the liquid surface is the inert gas. The method of claim 9, wherein the inert gas is argon.

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