CN115074821A

CN115074821A - Thermal field structure and method for growing silicon carbide by graphite resistance heating

Info

Publication number: CN115074821A
Application number: CN202210467250.0A
Authority: CN
Inventors: 胡动力; 张永伟; 王人松; 刘海; 黎志欣
Original assignee: Linton Kayex Technology Co Ltd
Current assignee: Linton Kayex Technology Co Ltd
Priority date: 2022-04-29
Filing date: 2022-04-29
Publication date: 2022-09-20

Abstract

The invention discloses a thermal field structure and a method for growing silicon carbide by graphite resistance heating, which relate to the technical field of silicon carbide single crystal growth; an upper heat insulation layer, a side heat insulation layer and a lower heat insulation layer are fixedly arranged on the outer side of the protection barrel, the support shaft penetrates through the lower heat insulation layer and is fixedly connected with a support plate positioned in an inner cavity of the protection barrel, a crucible is clamped and mounted on the support plate, the top of the crucible is hermetically connected with a crucible cover bonded with seed crystals, powder is contained in the inner cavity of the crucible, heaters are mounted on the outer sides of the crucibles, and the baffle is movably mounted above the crucible; the invention has adjustable radial and axial temperature gradients, can provide uniform radial temperature gradients which are less than 1 ℃/cm for the growth area and the powder area, and is more beneficial to the growth of thick crystals with large size and low defects.

Description

Thermal field structure and method for growing silicon carbide by graphite resistance heating

Technical Field

The invention belongs to the technical field of silicon carbide single crystal growth, and particularly relates to a thermal field structure and a method for growing silicon carbide through graphite resistance heating.

Background

The silicon carbide single crystal is one of the most important third-generation semiconductor materials, has the characteristics of large forbidden band width, high thermal conductivity, high saturated electron mobility, high breakdown electric field and the like, and has unique advantages in the fields of smart power grids, electric traction, electric automobiles, microwave radio frequency and the like.

The mainstream technology for growing silicon carbide single crystal is Physical Vapor Transport (PVT), and commercialization has been achieved. The method is characterized in that powder filled at the bottom of a closed crucible is sublimated by heating, and generated gas-phase components are conveyed to a seed crystal under the action of a temperature gradient and are recrystallized. The heat insulation material around the crucible is generally made of carbon fiber, and under a high-temperature environment, the heat insulation material is uneven in heat insulation due to graphitization and corrosion of silicon component gas. In addition, the uneven heating of the crucible caused by the uneven material of the crucible and the axial symmetry deviation of the installation, and finally the uneven distribution of radial temperature fields of the growth cavity and the powder area. The mainstream heating mode of the commercial equipment is coil induction heating, the radial temperature gradient of the heating mode is large, powder close to the crucible wall in the crucible is sublimated in a large amount at first due to the fact that the temperature is obviously higher than the middle position, a foam-shaped carbon shell layer is formed on the periphery, the heat conductivity of the foam-shaped carbon is low, heat is prevented from being transmitted to the center, the radial temperature difference is further increased, and then the axial temperature gradient is reduced. In addition, due to electromagnetic induction, coupling phenomenon exists between axial temperature and radial temperature in the induction heating, the growth rate can be reduced when the axial temperature gradient is reduced, and the radial temperature distribution of a growth area is changed due to the coupling phenomenon, so that the concave-convex degree of a growth interface is changed, the stress is increased, and further the crystal defects are increased.

Although some patents have relieved the temperature non-uniformity through the rotation of the crucible or the insulating layer, the problems of large radial temperature gradients of the growth area and the powder area and insufficient gas phase components caused by the temperature gradient of the powder area are still not fundamentally solved, which is very disadvantageous for growing thick-size, high-quality 6-inch and 8-inch crystals.

Disclosure of Invention

In order to solve the defects and the insufficient problems of the prior art, the invention aims to provide a thermal field structure and a method for growing silicon carbide by graphite resistance heating; the invention has adjustable radial and axial temperature gradients, can provide uniform radial temperature gradients which are less than 1 ℃/cm for the growth area and the powder area, and is more beneficial to the growth of thick crystals with large size and low defects.

In order to achieve the purpose, the invention adopts the technical scheme that: the device comprises an upper heat-insulating layer, a baffle, a side heat-insulating layer, a protective barrel, a heater, a crucible, a supporting disk, powder, seed crystals, a crucible cover, a supporting shaft and a lower heat-insulating layer; the utility model discloses a crucible, including protection bucket, supporting shaft, supporting disk, heater, baffle movable mounting, protection bucket's the outside fixed mounting have last heat preservation, side heat preservation and heat preservation down, the supporting shaft passes down the heat preservation and keeps fixed connection with the supporting disk that is located the protection bucket inner chamber, the crucible is installed to the joint on the supporting disk, the top of crucible keeps sealing connection with the crucible lid that bonds the seed crystal, and the inner chamber splendid attire of crucible has the powder, the heater is all installed in the outside of crucible, baffle movable mounting is in the oblique top of crucible.

Preferably, the heater includes a side heater, a lower heater, and an upper heater; the upper heater, the lower heater and the side heater are respectively positioned above, below and at the side part of the crucible, the side heater is integrated or divided into an upper section of the side heater and a lower section of the side heater, each heater can be independently controlled and is made of graphite; the heater can be fully or partially turned on during growth, so as to control the temperature uniformity and axial temperature gradient of the powder region at the same time.

Preferably, the baffle is positioned above the side heater, the baffle is made of carbon, graphite, carbon felt or any combination of the carbon, the graphite and the carbon felt, the baffle is adjustable in axial and radial positions and 10-150mm in thickness, the inner surface (close to one side of the crucible) of the baffle is in a shape of a cylindrical surface, a conical surface, an arc surface or any combination of the three, and the outer end surface of the baffle can be in contact with the protective barrel, the upper heat-insulating layer and the crucible and can also be provided with a certain gap; the function is to control the heat radiation and the heat distribution by changing the shape, the thickness and the size of the material, thereby playing the role of adjusting the axial and radial temperature gradients.

Preferably, the protection barrel is made of carbon or graphite, the protection barrel is positioned between the side heater and the side heat-insulating layer, and the outer diameter surface of the protection barrel is in close contact with the side heat-insulating layer; aims to reduce uneven corrosion of the heater and high-temperature silicon component gas to the side heat preservation felt and enhance the heat preservation and temperature uniformity of the side part.

Preferably, the supporting disk is made of carbon or graphite and has a clamping groove or clamping ring structure with a positioning function; the purpose is to position the crucible in the center of the rotating shaft, so that the radial temperature gradient in the crucible is uniform.

Preferably, the support shaft is made of carbon or graphite and has lifting and rotating functions; the axial temperature distribution is adjusted, so that the radial heat radiation of the crucible is more uniform.

Preferably, a through hole is formed in the middle of the upper heat-insulating layer; the purpose firstly builds the low temperature point, forms controllable temperature gradient to promote crystal shaping efficiency, the temperature measurement of being convenient for, real time monitoring thermal field temperature, the technology debugging of being convenient for.

A thermal field structure and a method for growing silicon carbide by graphite resistance heating comprise the following steps:

s1: placing the crucible with the seed crystal and the powder assembled in a supporting disc clamping ring or a clamping groove, and adjusting the axial position, the thickness and the radial position of a baffle;

s2: after the heat-insulating layer is arranged, the furnace is closed and vacuumized to<10 ^-2 Pa, charging protective gas to 20-60KPa for a period of time, the protective gas being pure Ar gas or Ar/H ₂ 、Ar/N ₂ Mixing gas;

s3: vacuum is again pumped to 10 ^-1 Pa, filling protective gas to 20-60 KPa.

S4: adjusting the power ratio of the heater, and raising the temperature to 1800-2400 ℃ at a certain rate.

S5: reducing the pressure to 100-2000Pa at a certain rate, maintaining the temperature, moving the crucible at a certain speed, and growing for 50-200 h;

s6: and (5) turning off the heating power supply, cooling to room temperature, and taking out the crystal.

Compared with the prior art, the invention has the beneficial effects that:

firstly, an independently controlled graphite heater is adopted to heat the crucible in a heat radiation mode, and the working position of the heater can be selected from one or more of the upper part, the lower part and the side part, so that the temperature distribution in the crucible is easier to control;

secondly, a baffle is arranged at the upper part of the side heat-insulating layer, and the axial and radial positions of the baffle and the thickness of the heat-insulating layer at the upper part of the baffle can be adjusted to achieve the effect of controlling the temperature distribution in the crucible;

thirdly, the crucible can rotate and lift, so that radial uniform heating and axial temperature adjustment are facilitated;

and a protective barrel is arranged on the inner side of the side heat-insulating layer, so that the uneven erosion of the heater and high-temperature silicon component gas to the side heat-insulating layer felt can be reduced, the uniformity of side heat insulation is enhanced, and the service life of the side heat-insulating layer felt is prolonged.

Drawings

For ease of illustration, the invention is described in detail by the following detailed description and the accompanying drawings.

FIG. 1 is a schematic structural view of the present invention;

fig. 2 is a schematic structural view of the heater 5 of the present invention.

In the figure: the device comprises an upper heat insulation layer 1, a baffle plate 2, a side heat insulation layer 3, a protective barrel 4, a heater 5, a crucible 6, a supporting plate 7, powder 8, seed crystals 9, a crucible cover 10, a supporting shaft 11, a lower heat insulation layer 12, a side heater upper 51, a side heater lower 52, a lower heater 53 and an upper heater 54.

Detailed Description

In order that the objects, aspects and advantages of the invention will become more apparent, the invention will be described by way of example only, and in connection with the accompanying drawings. It is to be understood that such description is merely illustrative and not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.

It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps that are closely related to the solution according to the present invention are shown in the drawings, and other details that are not so relevant to the present invention are omitted.

As shown in fig. 1, the following technical solutions are adopted in the present embodiment: the device comprises an upper heat-insulating layer 1, a baffle 2, a side heat-insulating layer 3, a protective barrel 4, a heater 5, a crucible 6, a supporting disk 7, powder 8, seed crystals 9, a crucible cover 10, a supporting shaft 11 and a lower heat-insulating layer 12; the utility model discloses a crucible furnace, including protection bucket 4, supporting shaft 11, supporting disk cover 10, heater 5, baffle 2, heat preservation 1, side heat preservation 3 and lower heat preservation 12 are installed to the outside fixed mounting of protection bucket 4, supporting shaft 11 passes heat preservation 12 down and keeps fixed connection with the supporting disk 7 that is located protection bucket 4 inner chamber, crucible 6 is installed to the joint on the supporting disk 7, the top of crucible 6 keeps sealing connection with the crucible cover 10 that bonds seed crystal 9, and the inner chamber splendid attire of crucible 6 has the powder 8, heater 5 is all installed in the outside of crucible 6, 2 movable mounting of baffle are in the oblique top of crucible 6.

As shown in fig. 2, further, the heater 5 includes a side heater, a lower heater 53, and an upper heater 54; the upper heater 54, the lower heater 53 and the side heater are respectively positioned above, below and at the side part of the crucible 6, the side heater is integrated or divided into an upper section 51 of the side heater and a lower section 52 of the side heater, each heater 5 can be independently controlled and is made of graphite; the heater can be fully or partially turned on during growth, so as to control the temperature uniformity and axial temperature gradient of the powder region at the same time.

Furthermore, the baffle 2 is positioned above the side heater, the baffle 2 is made of carbon, graphite, carbon felt or any combination of the carbon, the graphite and the carbon felt, the baffle 2 is adjustable in axial and radial positions and 10-150mm in thickness, the inner surface (close to one side of the crucible) of the baffle 2 is in a shape of a cylindrical surface, a conical surface, an arc surface or any combination of the three, and the outer end surface of the baffle can be in contact with the protective barrel 4, the upper heat-insulating layer 1 and the crucible 6 and can also be provided with a certain gap; the function is to control the heat radiation and the heat distribution by changing the shape, the thickness and the size of the material, thereby playing the role of adjusting the axial and radial temperature gradients.

Further, the protection barrel 4 is made of carbon or graphite, the protection barrel 4 is located between the side heater and the side heat-insulating layer 3, and the outer diameter surface of the protection barrel 4 is in close contact with the side heat-insulating layer 3; aims to reduce uneven corrosion of the heater and high-temperature silicon component gas to the side heat-insulating felt and enhance the heat insulation of the side part and the temperature uniformity.

Furthermore, the supporting disk 7 is made of carbon or graphite and has a clamping groove or clamping ring structure with a positioning function; the purpose is to position the crucible in the center of the rotating shaft, so that the radial temperature gradient in the crucible is uniform.

Furthermore, the supporting shaft 11 is made of carbon or graphite and has lifting and rotating functions; the axial temperature distribution is adjusted, so that the radial heat radiation of the crucible is more uniform.

Furthermore, a through hole is formed in the middle of the upper heat-insulating layer 1; the purpose firstly builds the low temperature point, forms controllable temperature gradient to promote crystal shaping efficiency, the temperature measurement of being convenient for, real time monitoring thermal field temperature, the technology debugging of being convenient for.

s3: vacuum is again pumped to 10 ^-1 Pa, filling protective gas to 20-60 KPa.

Examples

The side heater is selected to be started for heating, the side heater is divided into an upper section and a lower section which are independently controlled, and the ratio of the power of the upper section heater to the power of the lower section heater is set as 3: 1. the baffle is made of a carbon-carbon and graphite fiber combined material, the upper part of the baffle is 50mm of a carbon fiber material and is connected with the upper heat insulation part, the lower part of the baffle is 70mm of a carbon material, and the inner surface of the carbon material part adopts a combination mode of a cylindrical surface and a conical surface; the protective barrel is made of carbon materials, and the outer diameter of the protective barrel is in heat-preservation contact with the side; the support plate is made of carbon materials, a protruding clamping ring structure is arranged on the support plate and used for fixing the crucible and ensuring axial symmetry of the crucible, and the support shaft is made of carbon materials. A through hole with the diameter of 40mm is formed in the top heat preservation center, and the structural schematic diagram of the thermal field is shown in figures 1 and 2.

3kg of high-purity powder is filled into the bottom of the crucible, matched and screwed with a crucible cover for bonding seed crystals, and then is filled into a tray snap ring for fixing. The position of the baffle is adjusted until the upper end surface of the baffle is 30mm above the crucible and has a clearance of 15mm with the crucible wall, and the upper part of the baffle is connected with the upper heat preservation part.

The furnace is closed and vacuumized to 10 ^-2 Pa, charging pure Ar gas to 50Kpa and keeping for 1 h; vacuum is again pumped to 10 ^-1 Pa, filling protective gas to 30 KPa. The rotation is started, and the rotating speed is 0.3 r/min. Adjusting the power of the upper heater and the lower heater to be 18Kw and 6Kw, gradually increasing the temperature to 2150 ℃ within 7h, keeping the temperature unchanged, and reducing the pressure to 500Pa within 2 h. The temperature was maintained and the crucible was moved at a speed of 0.2mm/h to grow for 100 h. The heater is closed, Ar is injected to 30KPa, and the crucible and the crystal are taken out after the temperature is cooled to the room temperature.

The obtained crystal has smooth surface and single crystal form, the thickness reaches 31mm, and the density of the microtubes detected by a polished wafer after slicing is 0.5/cm ² ，TSD：121/cm ² ；TED：4842/cm ² ；BPD：456/cm ² The radial temperature and the axial temperature of the temperature field are proper, the temperature field is suitable for large-size and thick crystal growth, and the thermal stress in the crystal is low.

The invention has adjustable radial and axial temperature gradients, can provide uniform radial temperature gradients which are less than 1 ℃/cm for the growth area and the powder area, and is more beneficial to the growth of thick crystals with large size and low defects.

The invention has the beneficial effects that: the graphite heater which is controlled independently is adopted to heat the crucible in a heat radiation mode, and the working position of the heater can be selected from one or more of the upper part, the lower part and the side part, so that the temperature distribution in the crucible is controlled more easily; the upper part of the side heat-insulating layer is provided with a baffle, and the axial and radial positions of the baffle and the thickness of the heat-insulating layer at the upper part of the baffle can be adjusted to achieve the effect of controlling the temperature distribution in the crucible; the crucible can rotate and lift, which is more beneficial to radial heating uniformity and axial temperature adjustment; the inner side of the side heat-insulating layer is provided with the protective barrel, so that the uneven erosion of the heater and high-temperature silicon component gas to the side heat-insulating layer felt can be reduced, the uniformity of side heat insulation is enhanced, and the service life of the side heat-insulating layer felt is prolonged.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art will be able to make the description as a whole, and the embodiments may be appropriately combined to form other embodiments as will be apparent to those skilled in the art.

Claims

1. A thermal field structure for growing silicon carbide by graphite resistance heating is characterized in that: the crucible comprises an upper heat-insulating layer (1), a baffle (2), a side heat-insulating layer (3), a protective barrel (4), a heater (5), a crucible (6), a supporting disk (7), powder (8), seed crystals (9), a crucible cover (10), a supporting shaft (11) and a lower heat-insulating layer (12); the utility model discloses a crucible, including protection bucket (4), supporting shaft (7), support disc (6), heat preservation (1), side heat preservation (3) and lower heat preservation (12) are gone up to the outside fixed mounting of protection bucket (4), support shaft (11) pass down heat preservation (12) and are kept fixed connection with supporting disc (7) that are located protection bucket (4) inner chamber, crucible (6) are installed to the joint on supporting disc (7), the top of crucible (6) keeps sealing connection with crucible lid (10) that bonds seed crystal (9), and the inner chamber splendid attire of crucible (6) has powder (8), heater (5) are all installed in the outside of crucible (6), baffle (2) movable mounting is in the oblique top of crucible (6).

2. The thermal field structure of graphite resistance heating growth silicon carbide of claim 1, characterized in that: the heater (5) comprises a side heater, a lower heater (53) and an upper heater (54); the upper heater (54), the lower heater (53) and the side heater are respectively positioned above, below and at the side part of the crucible (6), the side heater is integrated or divided into an upper side heater (51) and a lower side heater (52) which are divided into an upper section and a lower section, each heater (5) can be independently controlled, and the material is graphite.

3. The thermal field structure for growing silicon carbide by graphite resistance heating according to claim 2, wherein: the baffle (2) is positioned above the side heater, the baffle (2) is made of carbon, graphite, carbon felt or any combination of the carbon, the graphite and the carbon felt, the baffle (2) is adjustable in axial and radial positions, the thickness is 10-150mm, the inner surface of the baffle (2) is in a cylindrical surface shape, a conical surface shape, an arc surface shape or any combination of the cylindrical surface shape, the conical surface shape and the arc surface shape, the outer end surface of the baffle can be in contact with the protective barrel (4), the upper heat insulation layer (1) and the crucible (6), and a certain gap can be reserved.

4. The thermal field structure for growing silicon carbide by graphite resistance heating according to claim 2, wherein: the material of protection bucket (4) is carbon or graphite, and protection bucket (4) are located between side heater and side heat preservation (3), the external diameter face and the side heat preservation (3) in close contact with of protection bucket (4).

5. The thermal field structure of graphite resistance heating growth silicon carbide of claim 1, characterized in that: the supporting disk (7) is made of carbon or graphite and has a clamping groove or clamping ring structure with a positioning function.

6. The thermal field structure of graphite resistance heating growth silicon carbide of claim 1, characterized in that: the supporting shaft (11) is made of carbon or graphite and has lifting and rotating functions.

7. The thermal field structure of graphite resistance heating growth silicon carbide of claim 1, characterized in that: the middle part of the upper heat-insulating layer (1) is provided with a through hole.

8. A thermal field structure and a method for growing silicon carbide by graphite resistance heating comprise the following steps:

s2: after the heat-insulating layer is installed, the furnace is closed and the vacuum is pumped to<10 ^-2 Pa, charging protective gas to 20-60KPa for a period of time, the protective gas being pure Ar gas or Ar/H ₂ 、Ar/N ₂ Mixing gas;

s3: vacuum is again pumped to 10 ^-1 Pa, filling protective gas to 20-60 KPa.