CN115821395A - Annealing method of silicon carbide crystal and melt for annealing - Google Patents
Annealing method of silicon carbide crystal and melt for annealing Download PDFInfo
- Publication number
- CN115821395A CN115821395A CN202211635487.1A CN202211635487A CN115821395A CN 115821395 A CN115821395 A CN 115821395A CN 202211635487 A CN202211635487 A CN 202211635487A CN 115821395 A CN115821395 A CN 115821395A
- Authority
- CN
- China
- Prior art keywords
- silicon carbide
- annealing
- carbide crystal
- melt
- crystal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Landscapes
- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
The invention discloses an annealing method of a silicon carbide crystal, which comprises the step of placing the silicon carbide crystal to be treated in a melt containing elements Si and C for annealing. By controlling the annealing condition, the internal defects of the crystal move to the surface, the defects are repaired by using the Si and C in the melt and the specific metal or metal oxide, and meanwhile, the Si in the melt compensates the sublimation of the Si element on the surface of the crystal, so that the new defects generated on the surface of the silicon carbide crystal can be avoided.
Description
Technical Field
The invention relates to the field of semiconductor substrate and epitaxial processing. More particularly, the present invention relates to a method of annealing a silicon carbide crystal.
Background
The silicon carbide single crystal material belongs to the representative of a third generation wide band gap semiconductor material, and has the characteristics of wide forbidden band, high thermal conductivity, high breakdown electric field, high radiation resistance and the like, wherein N-type 4H silicon carbide can be used for manufacturing high-frequency devices such as MOSFET (metal-oxide-semiconductor field effect transistor), P-type silicon carbide can be used for manufacturing bipolar devices such as IGBT (insulated gate bipolar translator) and the like, and high-purity semi-insulating silicon carbide can be applied to the fields of mobile phone 5G communication, military radar radio frequency and the like.
However, the silicon carbide single crystal obtained by growth has internal stress therein, and the silicon carbide wafer obtained by single crystal processing has internal stress therein. Excessive internal stress can adversely affect further processing or epitaxial growth of the silicon carbide. The internal stress can be reduced to some extent by annealing the crystal or the substrate at 1000-2500 ℃ in an atmosphere. However, si in the silicon carbide crystal is easily sublimated at such a high temperature, and a new defect is caused.
In view of the above, it is desirable to provide an annealing method that can repair the defects of the silicon carbide crystal and reduce the defects newly generated during the annealing process while eliminating the internal stress.
Disclosure of Invention
In order to solve at least one or more of the above-mentioned technical problems, the present invention provides a method for annealing a silicon carbide crystal by placing the silicon carbide crystal to be treated in a melt containing elements Si and C for annealing.
By annealing in the melt, the elements in the melt repair the defects after the internal defects of the crystal have moved to the surface. Meanwhile, the silicon carbide crystal is soaked in the melt during annealing, so that the silicon carbide crystal is isolated from air, and the generation of secondary oxidation on the surface of the crystal is reduced. The Si element in the solution reduces new defects caused by S sublimation on the surface of the SiC crystal in the annealing process.
Drawings
The above and other objects, features and advantages of exemplary embodiments of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings. Several embodiments of the present invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar or corresponding parts and in which:
FIG. 1 is a schematic representation of the steps of a method of annealing a silicon carbide crystal according to an embodiment of the present invention;
FIG. 2 shows a schematic representation of the steps of a method of annealing a silicon carbide crystal including preparatory steps prior to annealing;
figure 3 shows a schematic diagram of an apparatus suitable for practicing the method of annealing a silicon carbide crystal according to embodiments of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
It should be understood that the terms "comprises" and/or "comprising," when used in this specification and claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It is also to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification and claims of this application, the singular form of "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should be further understood that the term "and/or" as used in the specification and claims of this specification refers to any and all possible combinations of one or more of the associated listed items and includes such combinations.
As used in this specification and claims, the term "if" may be interpreted contextually as "when", "upon" or "in response to a determination" or "in response to a detection". Similarly, the phrase "if it is determined" or "if a [ described condition or event ] is detected" may be interpreted contextually to mean "upon determining" or "in response to determining" or "upon detecting [ described condition or event ]" or "in response to detecting [ described condition or event ]".
The following detailed description of embodiments of the invention refers to the accompanying drawings.
FIG. 1 shows a schematic representation of the steps of a method of annealing a silicon carbide crystal according to an embodiment of the invention.
As shown in FIG. 1, a method for annealing a silicon carbide crystal includes, in step S300, placing the silicon carbide crystal to be treated in a melt containing the elements Si and C for annealing.
The silicon carbide crystal to be treated comprises a qualified silicon carbide single crystal grown according to the conventional technology or a wafer obtained after processing such as wire cutting. In the prior art, the physical vapor transport method, namely the PVT method, is relatively mature in the method for growing the silicon carbide crystal. In the process of growing SiC crystal by PVT method, the crucible material, temperature control precision, raw material, seed crystal and pressure are all required specifically, belonging to the category of the prior art, and the invention is not repeated. Crystals grown by the PVT method have more or less defects, such as: crystal defects within the wafer and surface defects at or near the wafer surface, including Basal Plane Dislocations (BPD), stacking Faults (SF), threading Edge Dislocations (TED), threading dislocations (TSD), micropipes, grain boundaries, and the like. In addition, temperature gradients in the crucible used for growing SiC crystals by the PVT method exist in both the longitudinal and radial directions, resulting in a difference in growth rate among the regions of the SiC crystal, and a large stress exists in the SiC crystal. The presence of these defects or stresses can affect the yield of SiC wafers, as well as the quality of epitaxial wafers with SiC as the substrate. To repair these defects or relieve stress, silicon carbide crystals are typically annealed. However, higher annealing temperatures in turn lead to sublimation of Si element on the surface of the silicon carbide crystal, resulting in new defects.
Therefore, the inventors protected the annealing treatment of the silicon carbide crystal with a melt containing a specific element, i.e., a melt containing elements Si and C. If the temperature of the melt is 1500-2500 ℃ in step S300, in the annealing process, the internal defects of the crystal are moved to the surface, and the defects are repaired with the aid of Si and C in the melt and the specific metal or metal oxide, and at the same time, the Si in the melt compensates the sublimation of the Si element on the surface of the crystal, thereby avoiding the new defects on the surface of the crystal.
Figure 2 shows a schematic step diagram of a method of annealing a silicon carbide crystal including preparatory steps prior to annealing.
As shown in fig. 2, the preparation step before annealing includes steps S100 and S200, and the melt passes through the preparation step S100, where the raw material of the melt is heated to a molten state, and the temperature in the molten state is controlled to be maintained at an appropriate annealing temperature.
The proportion of each element in the solution in step S100 may be set according to the proportion of the Si alloy solution in the process of producing SiC crystal by the liquid phase method. The basic principle of the liquid phase method for the crystal growth of the silicon carbide is that carbon is dissolved in high-temperature liquid consisting of silicon and a cosolvent, the carbon is separated out at a silicon carbide seed crystal due to supersaturation, and silicon atoms are carried out due to the action of a lattice coulomb field, so that the growth of the silicon carbide crystal is realized.
Methods for producing SiC crystals by the liquid phase method include, for example: graphite material is selected as a crucible, and simultaneously, the graphite material is used as a carbon source, and silicon melt is filled in the graphite crucible. And placing the SiC seed crystal on the top of the graphite crucible, just contacting the melt, and controlling the temperature of the seed crystal to be slightly lower than the temperature of the melt. The growth of the crystal is achieved using the temperature gradient as a growth driving force. Further examples are the Czochralski method (Czochralski): the purified feedstock is placed in a crucible, which is placed in a suitable thermal field. In the heating process, the raw materials are gradually melted in the crucible, the seed crystal placed in advance is pulled up, and the seed crystal rotates at a certain speed, so that the single crystal meeting the conditions is grown. However, the liquid phase method for producing SiC crystals has drawbacks such as slow growth rate, long cycle, and the like.
The inventors have found that, in annealing a silicon carbide crystal, both the compensation of internal defects and the compensation of new defects caused by sublimation of Si can be achieved by the growth process of SiC crystals. However, if the PVT method is still used, new surface defects may be caused due to an excessively high crystal growth rate. Therefore, in the annealing process of the silicon carbide crystal, the characteristics of slow growth speed and long period in the production of the SiC crystal by the liquid phase method are fully utilized by the inventor, the defects on the surface of the crystal are compensated, and the sublimation of Si is inhibited. The slow growth speed is matched with the promotion of the repair of local defects and the inhibition of the sublimation of Si, and the generation of new defects caused by high growth speed can be avoided.
According to an embodiment of the present invention, a cosolvent may be added to the melt, for example: the melt liquid contains elements Si, C and X, wherein X is a cosolvent and is selected from one or more of Al, ti, cr, Y, yb, pr, sn, la and Ce; in the melt, the molar ratio of Si, C and X is a: b: c, wherein a is more than or equal to 0.30 and less than or equal to 0.60, b is more than or equal to 0.30 and less than or equal to 0.40, c is more than or equal to 0.05 and less than or equal to 0.50, and a + b + c =1.
According to one embodiment of the invention, the annealing time is 1-72h, and the temperature of the molten liquid can be 1500-2000 ℃, 1800-2200 ℃, 1900-2100 ℃ or 1950-2050 ℃. In the temperature interval, the melt is kept in a stable molten state, the liquid crystal growth speed is influenced by controlling the temperature to be matched with the defect compensation, and the temperature is the annealing temperature suitable for the silicon carbide crystal. The inventors have found that, during annealing of a silicon carbide crystal, high temperatures tend to relax stresses within the silicon carbide crystal and move defects within the silicon carbide crystal toward the surface, but excessively high temperatures can cause damage to the surface of the silicon carbide crystal, resulting in the escape of a large amount of Si from the surface of the silicon carbide crystal, resulting in carbonization.
Based on this, the inventors have utilized the annealing method in the solution, and since the Si element is contained in the melt, si evolution on the surface of the silicon carbide crystal can be reduced, and thus, an appropriate high temperature can be adopted.
According to an embodiment of the present invention, preferably, in the annealing process of step S3, the temperature of the melt is 2000 ℃, and the annealing time is 5 hours. Similarly, the annealing time is a very important control condition, and the quality of the SiC wafer can be improved in a conventional manner under the protection of inert gas, and the annealing is usually carried out at 1450 ℃ for 1-2 hours. However, as the time for returning the silicon carbide crystal increases, for example, 3 hours or more, the quality of the silicon carbide crystal decreases to some extent, which means that the long-time annealing treatment rather deteriorates the crystal quality of the wafer, and this phenomenon can be explained by carbonization of the surface of the silicon carbide crystal. In fact, in the traditional high-temperature annealing treatment process, surface carbonization is inevitable, and the carbonization speed has a direct relation with the temperature. At higher temperatures, the carbonization proceeds very rapidly and can easily damage the surface. At lower temperatures, although the carbonization effect is not significant and the stress in the silicon carbide crystal can be released, the carbonization effect accumulates with the increase of the annealing time and the surface is damaged.
In the embodiment of the invention, the inventor adopts a higher temperature, preferably the temperature of the melt is 2000 ℃, the raw material of the melt is in a molten state, and simultaneously adopts a longer time, preferably 5 hours, so as to meet the annealing requirement of the silicon carbide and improve the quality of the silicon carbide crystal by utilizing the repairing function of the melt and the inhibiting function of the Si escape.
According to one embodiment of the invention, the silicon carbide crystal to be treated is rotated in the melt during annealing. In step S200, when the silicon carbide crystal to be processed is slowly placed in the melt, an obvious boundary can be formed between the silicon carbide crystal itself and the melt through slow rotation, and meanwhile, the defect on the surface of the silicon carbide crystal is compensated more uniformly by the melt, and each part of the silicon carbide crystal is heated uniformly.
The influence of the heating and cooling rates of the silicon carbide crystal in the hot pot city on the silicon carbide crystal is large, and if the heating or cooling rate is too high, the range can increase the residual stress in the silicon carbide crystal. For the process control of the temperature rise and the temperature drop of the silicon carbide crystal, a method of gradually raising the temperature and lowering the temperature can be adopted, for example, the temperature is changed at the speed of 200-300 ℃/h. For example: and putting the melt raw material and the silicon carbide crystal into an annealing device together, gradually heating to 2500 ℃, and then putting the silicon carbide crystal into the melt. When the silicon carbide crystal is immersed into the melt, the silicon carbide crystal is fixed on the rotary stirring rod and driven to rotate by the rotary stirring rod, and the rotating speed can be adjusted according to the size of the silicon carbide crystal and the annealing time.
According to one embodiment of the invention, the silicon carbide crystal to be treated is a 4-8 inch single crystal of N-type, P-type silicon carbide.
According to one embodiment of the invention, the melt is placed in a crucible, and is heated to 1500-2500 ℃ by a heating device; the silicon carbide crystals to be treated are placed at the tail end of the rotary stirring rod; the heating device uses a radio frequency induction heating furnace.
The material of the crucible is preferably a graphite crucible, and the erosion of the graphite crucible by the molten liquid can supplement the reduction of C in the molten liquid. And a platform for fixing the silicon carbide crystals is arranged at the tail end of the rotary stirring rod and is vertical to the rotating shaft of the rotary stirring rod. The silicon carbide crystal is fixed on a platform at the tail end of the rotary stirring rod, the rotary stirring rod is driven by external force to slowly descend and immerse the rotary stirring rod into the molten liquid, and meanwhile, the rotary stirring rod continuously rotates to form a limit between the silicon carbide crystal and the molten liquid and enable all parts of the silicon carbide crystal to be heated uniformly. The radio frequency induction heating furnace keeps the temperature of the melt constant and provides a stable environment for annealing the silicon carbide crystals.
According to one embodiment of the invention, the melt is made of Si, siC, ceO as raw materials 2 Melt forming, the molar ratio of Si: siC: ceO (CeO) 2 ＝1：1：1。
Si and SiC as Si and C sources, ceO 2 As a co-solvent to provide appropriate concentration control to limit the rate of SiC growth, as well as control the rate of erosion to the crucible, maintaining the ratio of Si and C sources to accommodate defect repair rather than rapid crystal growth.
According to one embodiment of the invention, the melt is made of Si, siC, ceO as raw materials 2 Cr is formed by melting, and the molar ratio of Si: siC: ceO (CeO) 2 : cr =1:1:1:1-1:0.4:1:2. CeO is added into the molten liquid 2 And Cr is added according to the proportion, so that the repair capability of the SiC crystal is greatly improved.
According to one embodiment of the invention, the pressure at which the silicon carbide crystal is annealed is 0.8-1.2bar, preferably 1bar.
According to another aspect of the invention, the melt for annealing the silicon carbide crystal is provided, and the temperature of the melt is 1500-2500 ℃; the molten liquid contains elements Si, C and X, wherein X is one or more of Al, ti, cr, Y, yb, pr, sn, la and Ce; in the molten liquid, the proportion of Si, C and X is a: b: c, wherein a is more than or equal to 0.30 and less than or equal to 0.60, b is more than or equal to 0.30 and less than or equal to 0.40, c is more than or equal to 0.05 and less than or equal to 0.50, and a + b + c =1.
According to one embodiment of the present invention, a melt preparation method comprises: placing a composition containing elements Si, C and an X element source in a crucible, and heating to a molten state to obtain a molten liquid, wherein the X element source is one or more of a simple substance of the X element and a compound of the X element.
Figure 3 shows a schematic diagram of an apparatus suitable for annealing a silicon carbide crystal according to an embodiment of the invention.
As shown in fig. 3, the silicon carbide crystal is fixedly arranged on a bearing platform at the tail end of a rotary stirring rod 2, a melt is contained in a crucible 1, the melt is heated to 1500-2500 ℃ depending on a heating device 3, the rotary stirring rod 2 is driven to descend to immerse the silicon carbide crystal into the melt, the rotary stirring rod 2 is driven to slowly rotate to anneal the silicon carbide crystal in the melt, and then the rotary stirring rod 2 is driven to ascend to obtain the annealed crystal.
While various embodiments of the present invention have been shown and described herein, it will be obvious to those skilled in the art that such embodiments are provided by way of example only. Numerous modifications, changes, and substitutions will occur to those skilled in the art without departing from the spirit and scope of the present invention. It should be understood that various alternatives to the embodiments of the invention described herein may be employed in practicing the invention. It is intended that the following claims define the scope of the invention and that equivalents or alternatives within the scope of these claims be covered thereby.
Claims (10)
1. A method of annealing a silicon carbide crystal, comprising:
putting the silicon carbide crystal to be treated into a melt containing elements Si and C for annealing;
the melt also comprises X;
and X is one or more of Al, ti, cr, Y, yb, pr, sn, la and Ce.
2. The method for annealing a silicon carbide crystal according to claim 1, wherein the silicon carbide crystal is annealed,
in the molten liquid, the molar ratio of Si, C and X is a: b: c, the number of the first and second groups is less than or equal to zero,
wherein the content of the first and second substances,
0.30≤a≤0.60，
0.30≤b≤0.40，
0.05≤c≤0.50，
a+b+c＝1。
3. the method for annealing a silicon carbide crystal according to claim 1, wherein the silicon carbide crystal is annealed,
the temperature of the melt is 1500-2500 ℃, and the annealing time is 1-72h.
4. The method for annealing a silicon carbide crystal according to claim 1, wherein the silicon carbide crystal is annealed,
and rotating the silicon carbide crystal to be treated in the molten liquid in the annealing process.
5. The method for annealing a silicon carbide crystal according to claim 1, wherein the silicon carbide crystal is annealed,
placing the raw materials of the melt in a crucible, and heating to 1500-2500 ℃ by a heating device to obtain the melt; the silicon carbide crystals to be treated are placed at the tail end of the rotary stirring rod;
the tail end of the rotary stirring rod is immersed in the molten liquid.
6. The method for annealing a silicon carbide crystal according to claim 1, wherein the silicon carbide crystal is annealed,
the molten solution is prepared from raw materials of Si, siC and CeO 2 Melt forming, the molar ratio of Si: siC: ceO (CeO) 2 ＝1：1：1。
7. The method for annealing a silicon carbide crystal according to claim 1, wherein the silicon carbide crystal is annealed,
the molten liquid is prepared from raw materials of Si, siC and CeO 2 Cr is formed by melting, and the molar ratio of Si: siC: ceO (CeO) 2 ：Cr＝1：1：1：1-1：0.4：1：2。
8. The method for annealing a silicon carbide crystal according to claim 1, wherein the silicon carbide crystal is annealed,
the pressure during annealing is 0.8-1.2bar.
9. A melt for annealing a silicon carbide crystal, characterized in that,
the temperature of the molten liquid is 1500-2500 ℃;
the melt liquid contains elements Si, C and X, wherein X is one or more of Al, ti, cr, Y, yb, pr, sn, la and Ce;
in the molten liquid, the molar ratio of Si, C and X is a: b: c, wherein,
0.30≤a≤0.60，
0.30≤b≤0.40，
0.05≤c≤0.50，
a+b+c＝1。
10. the melt for annealing a silicon carbide crystal according to claim 9, wherein the molar ratio of Si, C and X in the melt is a: b: c, the content of the first and second main body is controlled,
wherein the content of the first and second substances,
0.30≤a≤0.60，
0.30≤b≤0.40，
0.05≤c≤0.50，
a+b+c＝1。
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211635487.1A CN115821395A (en) | 2022-12-19 | 2022-12-19 | Annealing method of silicon carbide crystal and melt for annealing |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211635487.1A CN115821395A (en) | 2022-12-19 | 2022-12-19 | Annealing method of silicon carbide crystal and melt for annealing |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN115821395A true CN115821395A (en) | 2023-03-21 |
Family
ID=85516777
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211635487.1A Pending CN115821395A (en) | 2022-12-19 | 2022-12-19 | Annealing method of silicon carbide crystal and melt for annealing |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN115821395A (en) |
-
2022
- 2022-12-19 CN CN202211635487.1A patent/CN115821395A/en active Pending
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| KR101960209B1 (en) | Method for producing silicon carbide single crystal ingot and silicon carbide single crystal ingot | |
| EP2940196B1 (en) | Method for producing n-type sic single crystal | |
| EP2857562B1 (en) | Sic single-crystal ingot and production method for same | |
| JPS6046998A (en) | Pulling up of single crystal and its device | |
| JPH03122097A (en) | Preparation of single crystal ii-vi group or iii-v group compound and product made of it | |
| EP2455515A1 (en) | Process for producing sic single crystal | |
| SG189506A1 (en) | Method of manufacturing silicon single crystal, silicon single crystal, and wafer | |
| CN1016191B (en) | Production of high-oxygen-content silicon monocrystal substrate for semiconductor devices | |
| CN114606567A (en) | Method for producing n-type single-crystal silicon, ingot of n-type single-crystal silicon, silicon wafer, and epitaxial silicon wafer | |
| JP7321929B2 (en) | Manufacturing method of Zn-doped InP single crystal substrate | |
| TWI703242B (en) | Semi-insulating silicon carbide single crystal doped with a small amount of vanadium, substrate and preparation method | |
| CN110730831A (en) | Method for producing silicon single crystal, method for producing epitaxial silicon wafer, silicon single crystal, and epitaxial silicon wafer | |
| CN114438587A (en) | Method for producing n-type single crystal silicon, n-type single crystal silicon ingot, silicon wafer, and epitaxial silicon wafer | |
| US4637854A (en) | Method for producing GaAs single crystal | |
| JP4987784B2 (en) | Method for producing silicon carbide single crystal ingot | |
| CN115821395A (en) | Annealing method of silicon carbide crystal and melt for annealing | |
| JP5489064B2 (en) | Method for growing silicon single crystal | |
| JP6594148B2 (en) | Silicon carbide single crystal ingot | |
| JP4184622B2 (en) | Method for producing silicon carbide single crystal ingot | |
| KR102346307B1 (en) | Silicon single crystal manufacturing method and silicon single crystal wafer | |
| JP4080657B2 (en) | Method for producing silicon single crystal ingot | |
| JPH0367994B2 (en) | ||
| JP4200690B2 (en) | GaAs wafer manufacturing method | |
| JPH0474320B2 (en) | ||
| CN111962157B (en) | Healing method of silicon carbide crystal micropipe, silicon carbide product and application |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |