TW202132633A - Method for producing silicon single crystal - Google Patents

Abstract

Provided is a method for producing a silicon single crystal, the method being capable of producing a silicon single crystal having more uniform oxygen concentration distribution in the direction of the length of the silicone crystal. This method for producing a silicon single crystal comprises pulling a silicon single crystal from a silicon melt accommodated in a quartz glass crucible 3 using the Czochralski method and uses a quartz glass crucible for which the ratio t/T of the thickness t of the transparent inner layer to the thickness T of the side wall of the quartz glass crucible is adjusted from the top part to the bottom part of the side wall of the quartz glass crucible, wherein variation in the oxygen concentration in the crystal growth axis direction of the silicon single crystal pulled is within 20%.

Description

Method for manufacturing single crystal silicon

The present invention relates to a method for manufacturing single crystal silicon. It is a method for manufacturing single crystal silicon by the Czochralski method (also known as CZ method), which can produce a more uniform oxygen concentration in the long direction of the crystal. Single crystal silicon.

The incubation system of single crystal silicon by the CZ method is performed by the following method: a vitreous silica crucible 51 arranged in a chamber 50 as shown in FIG. After the heater 52 installed around 51 heats and melts the polysilicon as a silicon melt M, a seed crystal (seed) P installed in a seed chuck is immersed in the silicon melt M , The seed jig and the quartz glass crucible 51 are rotated in the same direction or the opposite direction and the seed jig is pulled up.

Generally speaking, before starting to pull up, if the temperature of the silicon melt M is stable, the seed crystal P is brought into contact with the silicon melt M and the front end of the seed crystal P is dissolved, and then necking is performed. The necking refers to an indispensable process for removing the dislocation of the single crystal silicon due to the thermal shock caused by the contact between the seed crystal P and the silicon melt M.

The neck P1 is formed by this necking. In addition, when the neck P1 is a crystal with a diameter of 300 mm, for example, the diameter is about 5 mm, and the length of the neck P1 needs to be 30 mm to 40 mm or more.

In addition, as a process after the start of pulling up, it is performed after the necking is completed: the forming process of the shoulder C1 is to expand the crystal to the diameter of the straight body; the forming process of the straight body C2 is to grow a single crystal into a product ; And the formation process of the tail portion (not shown) is to gradually reduce the diameter of the single crystal after the formation process of the straight body portion.

However, since the inner surface of the vitreous silica crucible 51 is in contact with the molten silicon M and dissolved, the oxygen contained in the vitreous silica crucible 51 is eluted into the molten silicon M and reacts with the molten silicon M to become SiOx. Most of this SiOx evaporates from the free surface of the molten liquid and is discharged together with the inert gas (Ar etc.) introduced into the single crystal pulling-up device.

Here, part of the SiOx system is taken into the growing single crystal, and the oxygen system taken into the single crystal silicon causes the absorption of heavy metals due to oxygen precipitates during the manufacturing process of the semiconductor device. (gettering), slip dislocation (slip dislocation) suppression effect.

However, there is a concern that if the aforementioned oxygen precipitates are present in the active layer during the manufacturing process of the semiconductor device, they may adversely affect the electrical characteristics. Therefore, it is required to manufacture wafers with proper and correct oxygen concentration according to the types of semiconductor devices.

In addition, since the upper part of the straight main body grown at the initial stage of the pull-up has a large amount of silicon melting in the quartz glass crucible and the contact area between the inner wall surface of the crucible and the silicon melt is large, the amount of oxygen eluted from the quartz glass crucible Many states pull down. As the single crystal is pulled up, since the amount of molten silicon in the crucible decreases, the contact area between the inner wall of the crucible and the molten silicon becomes smaller, and the amount of oxygen eluted from the quartz glass crucible to the molten silicon becomes smaller.

Therefore, the oxygen concentration in the silicon melt is unstable and the oxygen concentration distribution in the growth direction of the single crystal tends to be uneven (for example, the higher the upper part, the higher the oxygen concentration, the lower the lower the lower). In the single crystal growing process, in order to improve the yield, it is desirable to uniformly control the oxygen concentration in the crystal growing axis direction.

Regarding the aforementioned problem, Patent Document 1 (Japanese Patent Application Laid-Open No. 6-56571) discloses a method in which an inverted conical trapezoidal or cylindrical heat shielding mold is arranged above the silicon melt to adjust the level of the silicon melt and the aforementioned heat. Mask the gap between the lower ends of the mold, thereby controlling the oxygen concentration of the single crystal.

According to the method disclosed in Patent Document 1, the degree of cooling of the molten liquid surface caused by the inert gas supplied to the molten liquid surface from above the heat shielding mold and the shielding degree of the heat radiated from the crucible to the molten liquid surface can be accurately Control, as a result, the diffusion and evaporation of oxygen present in the melt is controlled, and the amount of oxygen supplied to the single crystal can be controlled.

In addition, Patent Document 2 (International Republication List WO2001/063027) discloses that the flow rate and pressure of the inert gas flowing in the furnace are controlled to control the oxygen concentration in accordance with the change in the pull-up amount.

According to the method disclosed in Patent Document 2, by changing the flow or pressure of the inert gas in the furnace, the amount of oxygen evaporated as oxide from the surface of the molten liquid near the crystal growth interface can be easily adjusted, and can be easily controlled. The amount of oxygen contained in the silicon melt.

However, although the methods disclosed in Patent Documents 1 and 2 can uniform the crystal oxygen concentration in the crystal growth axis direction, they have the following problems.

Specifically, the method disclosed in Patent Document 1 has the following problems: the temperature of the molten silicon surface changes due to the gap between the molten silicon surface and the heat shielding the mold, and the temperature distribution in the height direction of the crystal changes. Therefore, it affects the formation of crystal defects such as crystal originated particles (Crystal Originated Particle; also known as COP) and oxygen precipitates (Bulk Micro Defect; also known as BMD), and the distribution of crystal defects becomes uneven.

In addition, the method disclosed in Patent Document 2 adjusts the flow rate and pressure of the inert gas to adjust the evaporation amount of SiO gas from the molten liquid. There is the following problem: when the flow rate of the inert gas is large, the exhaust pump needs to be high The cost of a vacuum pump with high gas performance becomes higher. On the other hand, when the flow rate of the inert gas is small, there is a problem that the pollution in the furnace is not exhausted and the single crystalization rate is reduced.

The inventors have examined that it is not the method disclosed in Patent Document 1 that uses a heat shielding mold, nor does it use the method disclosed in Patent Document 2 to adjust the flow and pressure of an inert gas to evaporate the SiO gas from the melt. A new way of measuring.

As a result, it is known that the crystal growth of single crystal silicon can be controlled by adjusting the ratio t/T of the thickness t of the transparent inner layer to the thickness T of the wall of the vitreous silica crucible along the height direction of the vitreous silica crucible. The oxygen concentration in the axial direction, and thus completed the present invention.

The present invention is developed under the aforementioned general matters, and its purpose is to provide a method for manufacturing single crystal silicon by adjusting the ratio t/T of the thickness t of the transparent inner layer to the thickness T of the wall of the vitreous silica crucible. , And can produce single crystal silicon with a more uniform oxygen concentration distribution in the long direction of the silicon crystal.

The method for manufacturing single crystal silicon of the present invention developed to solve the aforementioned problems uses a quartz glass crucible with an opaque outer layer and a transparent inner layer. Liquid pull up single crystal silicon; use the following quartz glass crucible: the ratio t/T of the thickness t of the transparent inner layer to the thickness T of the side wall of the quartz glass crucible is adjusted from the upper part to the lower part of the side wall of the quartz glass crucible Over; The deviation of the oxygen concentration in the direction of the crystal growth axis of the pulled up single crystal silicon is within 20%.

Here, it is preferable that the vitreous silica crucible is divided into a plurality of regions from the upper portion to the lower portion of the side wall of the vitreous silica crucible, and the ratio t/T of the thickness t of the transparent inner layer to the thickness T of the side wall of the vitreous silica crucible Each of the above-mentioned plural areas is adjusted.

In addition, it is preferable that the ratio t/T of the thickness t of the transparent inner layer to the thickness T of the side wall of the vitreous silica crucible is greater than 0.05 to less than 0.8.

According to the single crystal silicon manufacturing method of the present invention, the ratio t/T of the thickness t of the transparent inner layer to the thickness T of the wall of the vitreous silica crucible is adjusted along the height direction of the vitreous vitreous crucible, and the pulling up is controlled. The oxygen concentration in the crystal growth axis direction of the single crystal silicon can suppress the deviation of the oxygen concentration in the crystal growth axis direction of the pulled-up single crystal silicon and make the oxygen concentration more uniform.

According to the present invention, a single crystal silicon manufacturing method can be obtained. By adjusting the ratio t/T of the thickness t of the transparent inner layer to the thickness T of the wall of the vitreous silica crucible, it can be manufactured in the long direction of the silicon crystal. Single crystal silicon with more uniform oxygen concentration distribution.

Hereinafter, the manufacturing method of the single crystal silicon of the present invention will be explained using drawings. Fig. 1 is a cross-sectional view of a single crystal pulling-up device for implementing the single crystal silicon manufacturing method of the present invention. Fig. 2 is a cross-sectional view of a quartz glass crucible included in the single crystal pulling-up device of Fig. 1.

The single crystal pull-up device 1 is provided with a furnace body 10 formed by overlapping a pull chamber 10b on a cylindrical main chamber 10a. The furnace body 10 is provided with a furnace body 10 capable of rotating around a vertical axis and capable of raising and lowering. A carbon susceptor (or graphite susceptor) 2 and a quartz glass crucible 3 held by the aforementioned carbon susceptor 2 (hereinafter, also referred to as crucible 3 for short). The crucible 3 can rotate around a vertical axis together with the rotation of the carbon base 2.

Here, the structure of the crucible 3 will be described in detail using FIGS. 2 and 3.

The crucible 3 has a bottom part 31 formed, for example, with a diameter of 800 mm and having a predetermined curvature; a corner part 32 formed around the bottom part 31 and having a predetermined curvature; and a straight body part 33 which extends upward from the corner part 32 extend. A crucible opening (upper end opening) is formed at the upper end of the straight main body portion 33.

As shown in FIG. 2, the crucible 3 has a two-layer structure of an opaque outer layer 3A (opaque layer) and a transparent inner layer 3B (transparent layer).

Among them, the opaque outer layer 3A is composed of natural raw material quartz glass, and the transparent inner layer 3B is composed of, for example, high-purity synthetic raw material quartz glass.

Here, opaque means that the quartz glass contains many bubbles (pores), and it is in a cloudy state when viewed. In addition, natural raw material quartz glass means silica glass produced by melting natural raw materials such as crystal; synthetic raw material quartz glass means to be synthesized by, for example, hydrolysis of silicon alkoxide. The synthetic raw materials are melted to manufacture silica glass.

Then, in this manufacturing method, the ratio t/T of the thickness t of the transparent inner layer to the thickness T of the wall of the vitreous vitreous crucible is adjusted (set) in the crucible height direction using a vitreous vitreous crucible.

As described above, in the process of pulling up the single crystal, there is a tendency that the oxygen concentration in the silicon melt is unstable and the oxygen concentration distribution in the growth direction of the single crystal is not uniform. The unevenness is not only affected by the change of the oxygen concentration in the molten liquid, but also by the magnetic field strength, the center position of the magnetic field, the flow rate of the inert gas, the furnace pressure, the rotation of the quartz glass crucible 3, the rotation of the single crystal, etc. Influence and decide.

Therefore, in the present invention, in a certain single crystal pulling device, the tendency of the pulled up single crystal to become a non-uniform oxygen concentration distribution (for example, the distribution of the oxygen concentration at the upper part of the crystal being higher than the lower part) is preliminarily grasped. Adjust the aforementioned ratio t/T for the basis.

In this embodiment, a case where the aforementioned oxygen concentration distribution tends to become a distribution in which the oxygen concentration in the upper part of the crystal is higher than the lower part is described as an example.

3, along the height direction of the straight body portion 33 of the crucible 3, for example, the upper portion 33A of the crucible, the middle portion 33B and the lower portion 33C of the crucible, the thickness t of the transparent inner layer 3B relative to the thickness of the wall of the crucible ( The ratio t/T of the total thickness of the opaque outer layer 3A and the opaque inner layer 3B) T is set to be between more than 0.05 and less than 0.8.

For example, the aforementioned ratio t/T is set from a small value to a large value from the upper portion 33A to the lower portion 33C. Specifically, for example, in the upper part 33A, the ratio t/T of the thickness t of the transparent inner layer 3B to the thickness T of the crucible wall is set to 0.10, the ratio t/T of the middle part 33B is set to 0.3, and the ratio t of the lower part 33C is set. /T is set to 0.6.

In addition, in the case where the aforementioned ratio t/T is 0.05 or less (when the thickness of the transparent inner layer 3B is too thin), there is a case where the transparent inner layer 3B is completely melted during crystal growth, and the opaque outer layer 3A containing bubbles is exposed to the silicon melt. There is a concern about the exfoliation of fine quartz particles on the liquid M side. In this case, there are doubts that particles reach the surface of the molten liquid and the dislocation rate increases, or bubbles are taken into the crystal to form an air pocket.

On the other hand, in the case where the aforementioned ratio t/T is 0.8 or more (in the case where the thickness of the transparent inner layer 3B is too thick), there is the following disadvantage: the uniform diffusion of heat due to the opaque outer layer 3A becomes insufficient And temperature control becomes difficult, or product prices become higher.

The predetermined ratio t/T as described above is due to the difference in heat transfer rate between the opaque outer layer 3A and the transparent inner layer 3B. Since the opaque outer layer 3A contains a large number of bubbles, it has a uniform temperature distribution that uniformly diffuses heat. On the other hand, the transparent inner layer 3B has high thermal conductivity and difficult temperature control.

Therefore, when the ratio t/T of the thickness T of the transparent inner layer 3B with respect to the wall of the crucible 3 is small, since the opaque outer layer 3A that uniformly diffuses heat becomes thicker, it is not necessary to heat the crucible 3 more than necessary. The temperature of the inner surface of the crucible becomes lower, so the dissolving amount of quartz into the silicon melt M becomes less.

On the other hand, when the ratio t/T of the thickness T of the transparent inner layer 3B to the wall of the crucible 3 is large, the temperature of the inner surface of the crucible becomes higher due to the large heat conduction, and the dissolved amount of quartz increases, and the quartz can be converted to silicon. The dissolved amount of melt M increases.

As crystal incubation progresses, the amount of molten silicon decreases, so the influence of oxygen concentration on the grown single crystal moves from the upper part 33A of the crucible at the position of the molten silicon level M1 to the middle part 33B and the lower part 33C.

In addition, as described above, the greater the amount of molten silicon in the vitreous silica crucible, the greater the amount of oxygen in the molten silicon at the initial stage of pulling up. Therefore, the higher the upper part of the single crystal, the higher the oxygen concentration tends to be.

Here, the embodiment of the present invention is configured as follows: the ratio t/T of the upper part 33A, the middle part 33B, and the lower part 33C of the crucible where the molten silicon level M1 that most influences the crystalline oxygen concentration moves sequentially is taken as an example. The upper part of the quartz glass crucible is individually set so that the lower part becomes larger, so that the oxygen concentration in the direction of the crystal growth axis becomes more uniform.

Next, returning to the description of FIG. 1, under the carbon base 2, there are provided: a rotating drive unit 14 such as a rotary motor to rotate the carbon base 2 around a vertical axis; and an up-and-down drive unit 15 to make the carbon The base 2 moves up and down.

In addition, a rotation drive control unit 14 a is connected to the rotation drive unit 14, and an elevation drive control unit 15 a is connected to the elevation drive unit 15.

In addition, the single crystal pulling-up device 1 is provided with: a side heater 4, which uses resistance heating to melt the semiconductor raw material (raw polysilicon) filled in the crucible 3 into a silicon melt M (hereinafter, also referred to as a melt M); And the pulling up mechanism 9 is to roll up the wire 6 to pull up the bred single crystal C. A seed crystal P is installed at the front end of the wire 6 of the aforementioned pulling mechanism 9.

In addition, the side heater 4 is connected to a heater drive control unit 4 a that controls the amount of power supplied, and the pull-up mechanism 9 is connected to a rotation drive control portion 9 a that controls the rotation of the pull-up mechanism 9.

In addition, in the single crystal pulling-up device 1, for example, an electromagnetic coil 8 for applying a magnetic field is provided on the outer side of the furnace body 2. If a predetermined current is applied to the electromagnetic coil 8 for applying a magnetic field, a horizontal magnetic field of predetermined strength is applied to the silicon melt M in the crucible 3. The electromagnetic coil 8 for magnetic field application is connected with the electromagnetic coil control part 8a which performs operation control of the electromagnetic coil 8 for magnetic field application.

That is, in this embodiment, the MCZ method (Magnetic field applied CZ method; Tchaikovsky method with magnetic field applied) is implemented in which a magnetic field is applied to the molten liquid M and the single crystal is grown, thereby controlling the silicon melt. The convection of liquid M seeks to stabilize the single crystal.

In addition, a radiation shield 7 surrounding the single crystal C is arranged above the molten liquid M formed in the crucible 3. The radiation shield 7 is formed with openings on the upper and lower portions, and shields the excess radiant heat from the side heater 4, the molten liquid M, etc. to the single crystal C being grown, and rectifies the gas flow in the furnace.

In addition, the gap between the lower end of the radiation shield 7 and the molten surface is controlled in such a way that a predetermined distance is maintained in accordance with the desired characteristics of the grown single crystal.

In addition, the single crystal pull-up device 1 includes a computer 11 having a memory device 11a and an arithmetic control device 11b; a rotation drive control unit 14a, a lift drive control unit 15a, an electromagnetic coil control unit 8a, and a rotation drive control unit 9a They are individually connected to the arithmetic control device 11b.

In the single crystal pulling-up device 1 configured in this way, in the case of growing a single crystal C having a diameter of, for example, 300 mm, the pulling-up is performed as follows. That is, the crucible 3 is initially filled with raw material polysilicon (for example, 350 kg), and the crystal growing process is started according to the program memorized in the memory device 11a of the computer 11.

First, the furnace body 10 is set to a predetermined ambient gas (mainly an inert gas such as argon gas), and the crucible 3 is loaded in the crucible while the crucible 3 is rotating at a predetermined rotation speed (rpm; revolution per minute) The raw material polysilicon in 3 is melted by heating by the side heater 4, and becomes molten M (step S1 in FIG. 4).

Next, a predetermined current is flowed through the electromagnetic coil 8 for magnetic field application, and the horizontal magnetic field is started to be applied in the molten liquid M with a magnetic flux density set in the range of 1000 Gauss (Gauss) to 4000 Gauss (for example, 2500 Gauss) (Fig. 4) Step S2).

In addition, the thread 6 descends and the seed crystal P is in contact with the molten liquid M, and after the front end of the seed crystal P is dissolved, the necking is performed, and the neck portion P1 is formed (step S3 in FIG. 4).

If the neck P1 is formed, the power supply to the side heater 4, the pulling-up speed, and the strength of the magnetic field application are used as parameters to adjust the pulling-up conditions, and the seed crystals are made at a predetermined rotation speed in the opposite direction to the direction of rotation of the crucible 3 P starts to rotate.

Then, the crystal diameter is gradually expanded to form a shoulder C1 (step S4 in FIG. 4), and it proceeds to the step of forming a straight body part C2 as a product part (step S5 in FIG. 4).

Here, the oxygen concentration in the single crystal grown from the silicon melt M in which oxygen eluted from the crucible 3 is introduced is determined by, for example, the strength of the magnetic field, the center position of the magnetic field, the flow rate of the inert gas and the pressure in the furnace, and the rotation of the quartz glass crucible 3. And the influence of parameters such as the rotation of the single crystal.

Although the oxygen concentration distribution in the direction of the crystal growth axis is affected by the above-mentioned parameters, it has been difficult to make the oxygen concentration in the direction of the crystal growth axis uniform only by controlling the above-mentioned parameters.

Here, in the embodiment of the present invention, not only by the above-mentioned parameter conditions but also by adjusting the ratio t/T of the thickness t of the transparent inner layer 3B in the height direction of the crucible 3 to the thickness T of the wall of the crucible Controls the crystal oxygen concentration in the direction of the crystal growth axis.

Specifically, the long axis direction of the single crystal C is pulled up by the above-mentioned parameters such as the magnetic field strength, the center position of the magnetic field, the flow rate of the inert gas, the furnace pressure, the rotation of the quartz glass crucible 3 as the base, and the rotation of the single crystal. The tendency of the oxygen concentration is recorded in the memory device 11a as data in advance, and the ratio t/T in the vitreous silica crucible 3 is determined in cooperation with this, and the crucible is manufactured and used accordingly.

As shown in (a) of Fig. 5, in the initial stage of incubation of the straight body portion C2, the molten silicon level M1 is located at the upper portion 33A of the crucible. The amount of oxygen taken into the single crystal C is most affected by the oxygen concentration in the silicon melt M near the silicon melt level M1.

Here, in the initial growth stage of the straight body part C2, the amount of silicon melt is large and the contact area with the inner surface of the crucible is large. Therefore, the oxygen concentration in the melt is high overall, but the upper part 33A of the crucible is in the transparent inner layer 3B. The ratio t/T of the thickness t to the thickness T of the wall of the crucible is set to be as small as 0.08, for example. That is, the thickness of the transparent inner layer 3B is formed to be thin, so the opaque outer layer 3A is thick, thereby diffusing and uniformizing heat. Thereby, the temperature of the inner surface of the crucible becomes lower, and the dissolution amount of quartz from the crucible 3 to the silicon melt M is suppressed.

As shown in Figure 5(b), the growth of the straight body part progresses. The molten silicon level M1 decreases and becomes the position of the middle part 33B of the crucible. Then the thickness t of the transparent inner layer 3B in the middle part 33B of the crucible is relative to that of the crucible. The ratio t/T of the wall thickness T is set to, for example, 0.3.

Here, the amount of silicon melt in the crucible decreases, so the oxygen concentration in the silicon melt tends to decrease. However, the thickness of the transparent inner layer 3B in the middle part 33B of the crucible where the silicon melt level M1 is located is thicker than the upper part 33A of the crucible. Therefore, the dissolution amount of quartz from crucible 3 to silicon melt M increases.

As shown in Fig. 5(c), further, the growth of the straight body part progresses, and the molten silicon level M1 becomes the position of the lower part 33C of the crucible, then the thickness t of the transparent inner layer 3B in the lower part 33C of the crucible is relative to the crucible’s The ratio t/T of the wall thickness T is set to be as high as 0.6, for example.

Here, the amount of silicon melt in the crucible is further reduced to a small amount. Therefore, although the oxygen concentration in the silicon melt is low, the thickness of the transparent inner layer 3B in the lower part 33C of the crucible is formed to be thick, so the thermal conductivity is high. As a result, the temperature of the inner surface of the crucible becomes higher, and the amount of dissolved quartz from the crucible 3 to the silicon melt increases.

By performing the cultivation of the straight main body portion C2 in this way, it is corrected so that the oxygen concentration in the long axis direction of the straight main body portion C2 becomes uniform.

Then, if the straight body portion C2 is formed to reach a predetermined length, it moves to the final tail process (step S6 in FIG. 2). In this tail process, the contact area between the lower end of the crystal and the melt M is gradually reduced, and the single crystal C and the melt M are cut away to produce single crystal silicon.

As described above, according to this embodiment, the ratio t/T of the thickness t of the transparent inner layer to the thickness T of the wall of the vitreous silica crucible is adjusted along the height direction of the vitreous silica crucible to control the single crystal that is pulled up. The oxygen concentration in the direction of the crystal growth axis of silicon can make the oxygen concentration in the direction of the crystal growth axis close to a desired value and uniform.

In addition, the conventional general single crystal pulling-up device only needs to adjust the thickness t of the transparent inner layer 3B with respect to the thickness T of the wall of the crucible 3, so that the cost can be suppressed.

In addition, since the temperature of the molten silicon surface can be controlled at a certain level, the distribution of crystal defects can be prevented from becoming uneven.

In addition, although the foregoing embodiment exemplifies the case where the ratio t/T of the thickness t of the transparent inner layer 3B to the thickness T of the crucible wall is set to 0.08, 0.3, or 0.6, by changing the magnetic field intensity and the magnetic field center The position, the flow rate of the inert gas, the pressure in the furnace, the rotation of the quartz glass crucible, the rotation of the single crystal and other parameters can be appropriately changed by the ratio t/T.

In addition, in the foregoing embodiment, although three regions (33A, 33B, 33C) are divided into three regions (33A, 33B, 33C) in the height direction of the vitreous silica crucible 3, and the ratio t/T is set in each region, the number of the foregoing regions in the present invention is not limited. It is limited and can be set appropriately.

In addition, instead of dividing into each area and setting a specific ratio t/T, the ratio t/T may be gradually changed in the height direction of the vitreous silica crucible 3.

In addition, although the quartz glass crucible 3 has a two-layer structure of an opaque outer layer 3A and a transparent inner layer 3B, the present invention is not limited to this structure, and the number of layers is not limited as long as the inner layer is a transparent layer.

Furthermore, when implementing the present invention, a method of using a heat shielding mold as disclosed in Patent Document 1 and a method of adjusting the flow rate and pressure of inert gas to SiO gas as disclosed in Patent Document 2 can also be used in combination. Method of evaporation of molten liquid.

[Example] The manufacturing method of the single crystal silicon of the present invention will be further described according to the embodiments.

[Experiment 1] In experiment 1, it was verified that the ratio t/T of the thickness t of the transparent inner layer to the thickness T of the crucible wall was changed in the direction of the crucible height to change the oxygen concentration in the pull-up direction of the pulled-up single crystal silicon How does the distribution affect.

In Experiment 1, in the single crystal pulling-up device constructed as shown in the above embodiment, 350 kg of raw polycrystalline silicon was put into the crucible, and the single crystal silicon with a diameter of 300 mm was pulled up. In order to suppress the natural convection of the silicon melt, the magnetic flux density of the horizontal magnetic field applied during pulling is set to 2500 Gauss.

In addition, the flow rate of the inert gas was set to 90 L/min, and the furnace internal pressure was set to 50 torr.

Furthermore, the rotation number of the crucible was set to 1 rpm, and the rotation number of the single crystal was set to 10 rpm (the rotation directions were set to be opposite to each other).

As shown in FIG. 3, the ratio t/T of the thickness t of the transparent inner layer 3B to the thickness T of the crucible wall was set as shown in Table 1 in Example 1, Example 2, and Comparative Example 1.

In Example 1, the ratio t/T of the quartz crucible was set under the conditions of the pull-up device which has a tendency that the oxygen concentration in the upper part of the pulled-up single crystal is higher than the oxygen concentration in the lower part.

In Example 2, the ratio t/T of the quartz crucible was set under the conditions of the pull-up device which has a tendency that the oxygen concentration in the upper part of the pulled-up single crystal is higher than the oxygen concentration in the lower part.

In addition, in Comparative Example 1, it was carried out without changing the ratio t/T of the quartz crucible under the conditions of the pull-up device which has a tendency that the oxygen concentration in the upper part of the pulled-up single crystal tends to be higher than the oxygen concentration in the lower part.

The results of Experiment 1 are shown in the line graph in FIG. 6. The vertical axis of the graph of Fig. 6 indicates the oxygen concentration (×10 ¹⁸ /cm ³ ), and the horizontal axis indicates the curing rate. In addition, Table 1 shows the deviation of the oxygen concentration in the axial direction of the single crystal pulled up under the conditions of Examples 1, 2 and Comparative Example 1.

[Table 1] The ratio of the thickness t of the transparent inner layer: t/T Deviation of oxygen concentration The upper part of the crucible Middle of crucible Crucible bottom Example 1 0.08 0.25 0.10 14% Example 2 0.25 0.72 0.66 13% Comparative example 1 0.23 0.25 0.11 30%

In Example 1 shown in the graph of FIG. 6, the oxygen concentration in the initial stage of crystal pulling up was suppressed, and a single crystal having a low oxygen concentration and a uniform oxygen concentration in the direction of the crystal growth axis was obtained. In addition, as shown in Table 1, the deviation of the oxygen concentration was suppressed to 14%.

In addition, the oxygen concentration in the late stage of crystal pulling up in Example 2 was increased, and a single crystal with a high oxygen concentration having a uniform oxygen concentration in the direction of the crystal growth axis was obtained. In addition, as shown in Table 1, the deviation of the oxygen concentration was suppressed to 13%.

In addition, in Comparative Example 1, a single crystal with a higher oxygen concentration as the upper part of the crystal is obtained. In addition, as shown in Table 1, the deviation of the oxygen concentration was as large as 30%.

It was confirmed from the results of Experiment 1 that according to the present invention, the oxygen concentration can be controlled more uniformly in the direction of the crystal growth axis and the deviation of the oxygen concentration can be suppressed within 20%.

[Experiment 2] In experiment 2, under the condition of a pulling device that has a tendency that the oxygen concentration in the upper part of the pulled up single crystal is lower than the oxygen concentration in the lower part, it was verified that the thickness t of the transparent inner layer is relative to the crucible of the quartz crucible The ratio t/T of the thickness T of the wall changes in the height direction of the crucible, and the deviation of the oxygen concentration in the height direction of the pulled-up single crystal. The conditions for pulling up the single crystal are the same as in Experiment 1.

The ratio t/T in the upper, middle, and lower crucibles in Examples 3 and 4 and Comparative Example 2 and the deviation of the oxygen concentration in the axial direction of the single crystal pulled up under these conditions are shown in Table 2.

In addition, the line in FIG. 7 shows the changes in the single crystal oxygen concentration in Examples 3 and 4 and Comparative Example 2. In the graph of Fig. 7, the vertical axis indicates the oxygen concentration (×10 ¹⁸ /cm ³ ), and the horizontal axis indicates the curing rate.

[Table 2] The ratio of the thickness t of the transparent inner layer: t/T Deviation of oxygen concentration The upper part of the crucible Middle of crucible Crucible bottom Example 3 0.75 0.64 0.25 6% Example 4 0.65 0.30 0.10 8% Comparative example 2 0.67 0.64 0.75 twenty two%

As shown in the graph of Figure 7 and Table 2, in Examples 3 and 4, the ratio t/T in the upper part of the crucible is set to be larger than the lower part of the crucible, so that the oxygen concentration in the pull-up axis direction of the single crystal is The deviation of the distribution is suppressed to be small (10% or less).

On the other hand, in Comparative Example 2, although the ratio t/T of the thickness of the transparent inner layer in the height direction of the crucible was set to be approximately constant, the oxygen concentration in the upper part of the single crystal that became pulled up was lower than that in the lower part ( Same as the base) and a large deviation of the oxygen concentration (22%).

[Experiment 3] In Experiment 3, the proper range of the ratio t/T of the thickness t of the transparent inner layer to the thickness T of the crucible wall was verified. The judgment of suitability is determined by the dislocation rate of the crystal and the amount of temperature fluctuation.

Table 3 shows the ratio t/T belonging to the conditions in Examples 5 to 7 and Comparative Examples 3 to 6, as well as the resulting crystal dislocation rate and the temperature variation amount of the melt. The ratio t/T was set in order to make the oxygen concentration distribution in the pull-up axis direction of the single crystals pulled up in Examples 5 to 7 and Comparative Examples 3 to 6 of Experiment 3 uniform. The other conditions are the same as experiment 1.

[table 3] The ratio of the thickness t of the transparent inner layer: t/T Misalignment rate Temperature variation Upper part Central Lower part Example 5 0.70 0.65 0.75 3% ±3℃ Example 6 0.10 0.25 0.25 5% ±1℃ Example 7 0.50 0.70 0.10 10% ±3℃ Comparative example 3 0.05 0.20 0.20 30% ±1℃ Comparative example 4 0.45 0.65 0.05 50% ±3℃ Comparative example 5 0.80 0.75 0.85 10% ±8℃ Comparative example 6 0.70 0.90 0.30 10% ±10℃

As shown in Table 3, in the ratio t/T set in Examples 5 to 7, good results were obtained in which the misalignment rate was 10% or less and the temperature fluctuation amount was ±3°C.

On the other hand, when there are places where the ratio t/T is 0.05 as low as in Comparative Examples 3 and 4, the bubbles of the opaque layer are exposed, fine quartz particles are generated, and the dislocation rate increases.

In addition, in the case where there is a portion with a ratio t/T of 0.80 or more as in Comparative Examples 5 and 6, the uniform diffusion of heat due to the opaque outer layer is insufficient, temperature control becomes difficult, and the temperature of the silicon melt changes. The amount becomes larger.

From this result, it was confirmed that the range of the ratio t/T of the thickness t of the transparent inner layer to the thickness T of the crucible wall is preferably greater than 0.05 to less than 0.80.

1: Single crystal pull-up device 2: Carbon base 3,51: Quartz glass crucible (crucible) 3A: Opaque outer layer (opaque layer) 3B: Transparent inner layer (transparent layer) 4: side heater 4a: Heater drive control unit 6: line 7: Radiation shielding 8: Electromagnetic coil for magnetic field application 8a: solenoid control unit 9: Pull up the mechanism 9a: Rotation drive control unit 10: Furnace 10a: Main chamber 10b: pull chamber 11: Computer 11a: Memory device 11b: Calculation control device 14: Rotary drive unit 14a: Rotation drive control unit 15: Lifting drive 15a: Lifting drive control unit 31: bottom 32: corner 33: Straight body part 33A: The upper part of the crucible 33B: The middle part of the crucible 33C: Lower part of the crucible 50: Chamber 52: heater C: Monocrystalline silicon C1: Shoulder C2: Straight carcass M: Silicon melt (melt) M1: Silicon melt surface P: Seed (seed) P1: neck T, t: thickness

[Fig. 1] is a cross-sectional view of a single crystal pulling-up device that implements the single crystal silicon manufacturing method of the present invention. [Fig. 2] is a cross-sectional view of the quartz glass crucible included in the single crystal pulling-up device of Fig. 1. [Fig. [Fig. 3] is an enlarged cross-sectional view of a part of the vitreous silica crucible in Fig. 2. [Fig. 4] is a flow chart showing the flow of the manufacturing method of single crystal silicon of the present invention. In [Fig. 5], (a), (b), and (c) are cross-sectional views showing the relationship between the amount of molten silicon and the crucible that changes with the pulling up of the crystal. [Fig. 6] A graph showing the results of Example (Experiment 1). [Fig. 7] A line graph showing the results of Example (Experiment 2). [Figure 8] is a cross-sectional view for explaining the process of pulling up the single crystal silicon by the Tchaikrasky method.

3A: Opaque outer layer (opaque layer)

3B: Transparent inner layer (transparent layer)

33A: The upper part of the crucible

33B: The middle part of the crucible

33C: Lower part of the crucible

T, t: thickness

Claims (3)

A method for manufacturing single crystal silicon uses a quartz glass crucible with an opaque outer layer and a transparent inner layer, and pulls up the single crystal silicon from the silicon melt contained in the aforementioned quartz glass crucible by the Tchaikovsky method; Use the following vitreous silica crucible: the ratio t/T of the thickness t of the transparent inner layer to the thickness T of the side wall of the vitreous vitreous crucible is adjusted from the upper part to the lower part of the side wall of the vitreous vitreous crucible; The deviation of the oxygen concentration in the direction of the crystal growth axis of the pulled up single crystal silicon is within 20%. The method for manufacturing single crystal silicon according to claim 1, wherein the vitreous silica crucible is divided into a plurality of regions from the upper portion to the lower portion of the side wall of the vitreous silica crucible, and the thickness t of the transparent inner layer is relative to the thickness t of the vitreous silica crucible. The ratio t/T of the thickness T of the side wall is adjusted for each of the aforementioned plural regions. The method for manufacturing single crystal silicon according to claim 1 or 2, wherein the ratio t/T of the thickness t of the transparent inner layer to the thickness T of the side wall of the vitreous silica crucible is greater than 0.05 to less than 0.8 .

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