TWI622669B - Heat shielding assembly and thermal field structure of ingot drawing furnace - Google Patents

Abstract

The invention provides a heat shield assembly and a thermal field structure of a single crystal pulling furnace. The heat shield assembly includes a heat shield and an exhaust pipe located around the heat shield. The heat shield assembly of the present invention is provided with a set of exhaust pipes around the heat shield. When the heat shield assembly is used in a thermal field structure of a single crystal pulling furnace, the exhaust pipe can be used as an additional argon gas outlet. , Can change the flow path of argon in the thermal field structure, so that argon is not easy to form a vortex in the thermal field structure. At the same time, the silicon oxide (SiO) volatilized from the melt can be discharged in time to reduce the silicon oxide (SiO) in the argon gas flow into the melt and react with the high temperature graphite elements under the crucible, thereby extending the service life of each graphite element and reducing The oxygen content and carbon content in the crystal reduce the difficulty of cleaning the furnace after the growth of the crystal; at the same time, the heat shield assembly can also adjust the temperature gradient near the heat shield by changing the flow rate in the exhaust pipe.

Description

Thermal screen component and thermal field structure of single crystal pulling furnace

The invention belongs to the technical field of semiconductor equipment, and particularly relates to a heat shield assembly and a thermal field structure of a single crystal pulling furnace.

During the silicon single crystal preparation by the direct-drawing method, the quartz crucible is dissolved in a high temperature environment for a long time, and the generated oxygen will be transferred into the crystal through melt convection during the growth process and react with other defects in the crystal, which seriously affects The quality of silicon wafers and the performance of subsequent fabrication of semiconductor devices.

However, more than 99% of the oxygen dissolved in the quartz crucible into the silicon melt will be volatilized from the free surface of the melt in the form of silicon oxide (SiO), so argon will be introduced into the furnace and taken away from the furnace during the growth of silicon single crystal. Silicon oxide (SiO) in the bulk atmosphere to prevent oxygen from re-dissolving into the silicon melt. However, in the late growth period, the amount of melt in the quartz crucible is small, and argon will form vortexes in it, which will cause silicon oxide (SiO) not to be quickly discharged, which will increase the oxygen concentration in the tail of the silicon crystal.

The current thermal field structure of the single crystal silicon produced by the direct drawing method is shown in FIG. 1. As can be seen from FIG. 1, the thermal field structure directly pulls the melt 12 in the crucible 11 to form a crystal 13. Thermal screen 10; the arrows in Figure 1 indicate the flow path of argon gas in the thermal field structure. In the later stage of single crystal growth, as the melt 12 in the crucible 11 decreases, the volume occupied by the gas phase increases. When the argon gas sweeps across the surface of the melt 12, it will A vortex is formed above the melt 12, As shown in FIG. 2, that is, the arrow showing the flow path of the argon gas in FIG. 2 is vortex-shaped. Therefore, the SiO volatilized from the melt 12 cannot be taken away in time, so that the final oxygen concentration is relatively high. Moreover, SiO will react with the graphite component in the furnace at high temperature as follows: SiO + 2C = SiC + CO, and the generated CO will increase the carbon concentration in the crystal 13. The increase in the carbon concentration and the oxygen concentration in the crystal 13 will adversely affect the performance of the crystal 13.

In view of the shortcomings of the prior art described above, an object of the present invention is to provide a heat shield assembly and a single crystal pulling furnace thermal field structure, which are used to solve the problem that the single crystal pulling furnace thermal field structure in the prior art is in the late stage of single crystal growth. The melt in the crucible is reduced, and the volume occupied by the gas phase is increased. A vortex is formed above the melt in the crucible and cannot be eliminated in time, which causes the problem of increasing the oxygen concentration and carbon concentration in the growing crystal.

In order to achieve the above object and other related objects, the present invention provides a heat shield assembly suitable for a thermal field structure of a single crystal pulling furnace. The heat shield assembly includes a heat shield and an exhaust pipe located around the heat shield.

The invention also provides a thermal field structure of a single crystal pulling furnace. The thermal field structure of a single crystal silicon pulling furnace includes: a furnace body; a crucible located in the furnace body; and the heat shield assembly described in any one of the above schemes. Is located in the furnace body and above the crucible; the second section of the exhaust pipe extends to the outside of the furnace body.

As a preferred solution of the thermal field structure of the single crystal pulling furnace of the present invention, the thermal field structure of the single crystal silicon pulling furnace further includes: a heater located in the furnace body and located around the crucible; a graphite structure, Located in the furnace body, and located around the heater and the heat shield assembly; thermal insulation layer, located in the furnace body, and located around the graphite structure; graphite end cap, The second end of the exhaust pipe extends from the upper surface of the graphite end cover to the outside of the furnace body, and is located on the furnace body and on the top of the graphite structure and the heat insulation layer.

As described above, the heat shield assembly and the single crystal pulling furnace thermal field structure of the present invention have the following beneficial effects: The heat shield assembly of the present invention sets the heat shield assembly by setting a set of exhaust pipes around the heat shield. When used in the thermal field structure of a single crystal pulling furnace, the exhaust pipe can be used as an additional argon gas outlet, which can change the flow path of argon gas in the thermal field structure, making it difficult for argon to form vortices in the thermal field structure. Spin. At the same time, the silicon oxide (SiO) volatilized from the melt can be discharged in time to reduce the silicon oxide (SiO) in the argon gas flow into the melt and react with the high temperature graphite elements under the crucible, thereby extending the service life of each graphite element and reducing The oxygen content and carbon content in the crystal reduce the difficulty of cleaning the furnace after the growth of the crystal; at the same time, the heat shield assembly can also adjust the temperature gradient near the heat shield by changing the flow rate in the exhaust pipe.

10‧‧‧ hot screen

11‧‧‧ Crucible

12‧‧‧ Melt

13‧‧‧ Crystal

20‧‧‧Hot Screen Assembly

201‧‧‧ hot screen

202‧‧‧Exhaust pipe

203‧‧‧ Bezel

21‧‧‧furnace

22‧‧‧ Crucible

221‧‧‧graphite crucible

222‧‧‧Quartz Crucible

23‧‧‧heater

24‧‧‧ Graphite structure

25‧‧‧Insulation layer

26‧‧‧graphite end cap

27‧‧‧melt

28‧‧‧ Crystal

FIG. 1 is a structural schematic diagram of a thermal field structure of a single crystal pulling furnace in the conventional technology.

FIG. 2 is a schematic diagram showing the structure of a vortex formed by argon on the surface of a melt in a crucible in a thermal field structure of a single crystal pulling furnace in the conventional technology.

FIG. 3 is a schematic structural diagram of a heat screen assembly provided in Embodiment 1 of the present invention.

FIG. 4 is a schematic cross-sectional structure view taken along the AA ′ direction in FIG. 3.

FIG. 5 is a schematic diagram of a bottom view of a heat shield assembly provided in Embodiment 1 of the present invention.

FIG. 6 is a schematic structural diagram of a thermal field structure of a single crystal pulling furnace provided in Embodiment 2 of the present invention.

FIG. 7 is a schematic diagram of the flow direction of argon gas in the thermal field structure of the single crystal pulling furnace provided in the second embodiment of the present invention.

The following describes the embodiments of the present invention through specific specific examples. Those skilled in the art to which the present invention pertains can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

Please refer to FIG. 3 to FIG. 7. It should be noted that the diagram provided in this embodiment only illustrates the basic idea of the present invention in a schematic manner, although the diagram only shows the components related to the present invention instead of the actual ones. The number, shape, and size of the components during the implementation may be changed randomly, and the layout of the components may be more complicated.

Embodiment one:

Please refer to FIG. 3 to FIG. 4. The present invention provides a heat shield assembly 20, which is suitable for a thermal field structure of a single crystal pulling furnace. The heat shield assembly 20 includes a heat shield 201 and is located on the heat shield. The exhaust pipe 202 around 201 may also be said to be located on the back of the heat shield 201. By setting the exhaust pipe 202 around the heat shield 201, when the heat shield assembly 20 is used in the thermal field structure of a single crystal pulling furnace, the exhaust pipe 202 can be used as an additional argon outlet , The flow path of argon gas in the thermal field structure of the single crystal pulling furnace can be changed, so that argon gas is not easy to form a vortex in the thermal field structure of the single crystal pulling furnace. At the same time, the silicon oxide (SiO) volatilized from the melt can be discharged in time to reduce the SiO in the argon gas from entering the melt and reacting with the high temperature graphite elements below the crucible, thereby extending the service life of each graphite element and reducing the oxygen in the crystal. Content and carbon content, and reduce the difficulty of cleaning the furnace after the growth of the crystals; at the same time, the heat shield assembly 20 can also change the The flow velocity in the exhaust pipe 202 adjusts the temperature gradient near the heat shield.

As an example, the exhaust pipe 202 includes a first section and a second section; a first section of the exhaust pipe 202 is close to the back of the heat shield 201 and extends to the vicinity of the bottom of the heat shield 201; The second section of the gas pipe 202 is horizontally arranged. One end of the second section of the exhaust pipe 202 communicates with the interior of the first section of the exhaust pipe 202 and the other end extends to the single crystal pulling furnace. The outside of the field structure.

As an example, the bottom of the first section of the exhaust pipe 202 is bell-shaped, that is, the end of the exhaust pipe 202 near the bottom of the heat shield 201 is bell-shaped. Since the heat shield assembly 20 is used in the thermal field structure of the single crystal pulling furnace, the bottom of the heat shield 201 is close to the surface of the melt, and the first section of the exhaust pipe 202 is set to a bell mouth shape. It can prevent the air flow in the first stage of the exhaust pipe 202 from affecting the liquid surface of the melt, thereby avoiding adverse effects on the quality of the grown crystal.

As an example, the exhaust pipe 202 may be a molybdenum pipe but is not limited to a molybdenum pipe.

As an example, the shape of the radial section of the heat shield 201 may be circular but not limited to a circular ring, and the shape of the radial section of the exhaust pipe 202 may be a ring but not limited to a circular ring, as shown in FIG. 4 The radial section of the heat shield 201 and the exhaust pipe 202 is a section along the AA ′ direction in FIG. 3. Of course, in other examples, the shape of the radial section of the heat shield 201 and the shape of the radial section of the exhaust pipe 202 may also be rectangular, square, hexagonal, or the like.

As an example, the heat shield assembly 20 further includes a baffle 203 that is fixed to the bottom of the heat shield 201 and extends from the bottom of the heat shield 201 to the outside of the heat shield 201 to the heat shield 201. Under the exhaust pipe 202. Setting the baffle 203 on the bottom of the heat shield 201 can further prevent the air flow in the first section of the exhaust pipe 202 from affecting the liquid level of the melt.

As an example, the projection of the first section of the exhaust pipe 202 on the baffle 203 is located within the surface of the baffle 203, and the first end of the exhaust pipe 202 and the The upper surfaces are separated by a certain distance; that is, the baffle plate 203 completely shields the first end of the exhaust pipe 202 in a vertical direction to prevent the air flow at the first end of the exhaust pipe 202 from affecting the The liquid level of the melt has an effect.

As an example, the baffle 203 may be a molybdenum baffle but is not limited to a molybdenum baffle.

As an example, the shape of the radial section of the baffle 203 may be a circular ring shape, but is not limited to a circular ring shape, as shown in FIG. 5. Of course, in other examples, the shape of the radial section of the baffle 203 may also be rectangular, square, hexagonal, or the like.

It should be noted that the heat shield 201 and the exhaust pipe 202 are not visible in FIG. 5, but for convenience of illustration, the heat shield 201 and the exhaust pipe 202 are shown in FIG. 5.

Embodiment two:

Referring to FIG. 6, the present invention also provides a thermal field structure of a single crystal pulling furnace. The thermal field structure of a single crystal silicon pulling furnace includes: a furnace body 21; a crucible 22, and the crucible 22 is located in the furnace body 21. The heat shield assembly 20 as described in the first embodiment, which is located in the furnace body 21 and above the crucible 22; the exhaust pipe 202 in the heat shield assembly 20 The second section extends to the outside of the furnace body 21. For the specific structure of the heat shield assembly 20, refer to the first embodiment, which will not be described in detail here.

As an example, the crucible 22 includes a graphite crucible 221 and a quartz crucible 222, and the quartz crucible 222 is located in the graphite crucible 221.

As an example, the thermal field structure of the single crystal silicon pulling furnace further includes: a heater 23, which is located in the furnace body 21 and is located around the crucible 22; a graphite structure 24, The graphite structure 24 is located in the furnace body 21 and is located in the periphery of the heater 23 and the heat shield assembly 20; a heat insulation layer 25 is located in the furnace body 21 and is located in the furnace body 21; The periphery of the graphite structure 24; the thermal insulation layer 25 may be a graphite thermal insulation layer but not limited to the graphite thermal insulation layer; a graphite end cover 26, which is located in the furnace body 21 and is located in the graphite structure 24 And the top of the insulation layer 25; the second section of the exhaust pipe 202 extends from the upper surface of the graphite end cover 26 to the outside of the furnace body 21.

As shown in FIG. 7, the thermal field structure of the single crystal pulling furnace of the present invention is used in the heat shield assembly 20, and the exhaust pipe 202 can serve as a new argon outlet, which can change the The flow path in the field structure. The direction of the arrow in FIG. 7 is the flow path of argon. As can be seen from FIG. 7, during the late growth of the crystal 28, a part of the argon is eliminated along the original path, and another part of the argon passes through the exhaust gas. The tube 202 is discharged to the outside of the furnace body 21, so that argon gas is not easy to form a vortex above the melt 27 in the thermal field structure of the single crystal pulling furnace. At the same time, the SiO volatilized from the melt 27 can be discharged in time to reduce the SiO in the argon gas flow into the melt 27 and react with the high temperature graphite elements below the crucible 22, thereby extending the service life of each graphite element. Reduce the oxygen and carbon content in the crystal, and reduce the difficulty of cleaning the furnace after the growth of the crystal; at the same time, the temperature near the heat screen can be adjusted by changing the flow rate in the exhaust pipe 202 in the heat screen assembly 20 gradient.

In summary, the present invention provides a heat shield assembly and a thermal field structure of a single crystal pulling furnace. The heat shield assembly includes a heat shield and an exhaust pipe located around the heat shield. The heat shield assembly of the present invention is provided with a set of exhaust pipes around the heat shield. When the heat shield assembly is used in a thermal field structure of a single crystal pulling furnace, the exhaust pipe can be used as an additional argon gas outlet. , Can change the flow path of argon in the thermal field structure, so that argon is not easy to form a vortex in the thermal field structure. At the same time, the SiO volatilized from the melt can be discharged in time to reduce the SiO in the argon gas from entering the melt and the bottom of the crucible. The high temperature graphite element reacts, thereby prolonging the service life of each graphite element, reducing the oxygen content and carbon content in the crystal, and reducing the difficulty of cleaning the furnace after the growth of the crystal; at the same time, the heat shield component can also be changed by changing the The flow rate is adjusted to the temperature gradient near the hot screen.

The above-mentioned embodiments merely illustrate the principle of the present invention and its effects, but are not intended to limit the present invention. Anyone familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field to which they belong without departing from the spirit and technical ideas disclosed by the present invention should still be covered by the scope of patent application of the present invention.

Claims (10)

A heat shield assembly suitable for a thermal field structure of a single crystal pulling furnace, comprising: a heat shield; and an exhaust pipe located around the heat shield; a baffle, the baffle being fixed to the heat shield The bottom of the heat shield extends from the bottom of the heat shield to the outside of the heat shield to below the exhaust pipe. The heat shield assembly according to claim 1, wherein the exhaust pipe includes a first section and a second section; the first section of the exhaust pipe is closely attached to the back of the heat shield and extends to the Near the bottom of the heat shield; the second section of the exhaust pipe is horizontally arranged, one end of the second section of the exhaust pipe communicates with the interior of the first section of the exhaust pipe and the other end extends to the The exterior of the thermal field structure of a single crystal pulling furnace. The heat shield assembly according to claim 1, wherein the bottom of the first section of the exhaust pipe has a bell mouth shape. The heat shield assembly according to claim 1, wherein the exhaust pipe is a molybdenum pipe. The heat shield assembly according to claim 1, wherein a shape of a radial cross section of the heat shield and a shape of a radial cross section of the exhaust pipe are both circular rings. The heat shield assembly according to claim 1, wherein a projection of the first section of the exhaust pipe on the baffle is located within a surface of the baffle, and the first section of the exhaust pipe and the The upper surfaces of the baffles are separated by a certain distance. The heat shield assembly according to claim 1, wherein the baffle is a molybdenum baffle. The heat shield assembly according to claim 1, wherein a shape of a radial section of the baffle plate is a circular ring shape. A thermal field structure of a single crystal silicon pulling furnace includes: a furnace body; a crucible located in the furnace body; and the heat shield assembly according to any one of claims 1 to 8 located in the furnace. Inside the body and above the crucible; the second section of the exhaust pipe extends to the outside of the furnace body. The thermal field structure of the single crystal silicon pulling furnace according to claim 9, further comprising: a heater located in the furnace body and located around the crucible; a graphite structure located in the furnace body and located in A periphery of the heater and the heat shield assembly; a thermal insulation layer located in the furnace body and the periphery of the graphite structure; a graphite end cover located in the furnace body and located in the graphite structure and The top of the insulation layer; the second section of the exhaust pipe extends from the upper surface of the graphite end cover to the outside of the furnace body.