Growth chamber and method for crystal growth by sublimation

Abstract

The present disclosure relates to a method for growing a crystal in a growth chamber, the method (300) comprises providing (310) a seed crystal (180) into an internal volume (110) of said growth chamber (100), wherein the growth chamber (100) is arranged to grown said crystal at said seed crystal (180); providing (320) a source material (120) comprising material for growing said crystal at said seed crystal (180) into said internal volume (110); flowing (340) carrier gas (130) to the source material (120) and thereafter to the seed crystal (180); and applying (350) EM-radiation on a region (120') of the source material (120), thereby releasing material from the source material (120) and allowing the carrier gas flow (130) to transport said released material to the seed crystal (180), whereby the crystal is grown at the seed crystal (180).

Description

[0001] Growth chamber and method for crystal growth by sublimation

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to single-crystal growth, crystal growth by sublimation, SiC and AIN crystal growth, laser sublimation, growth chambers for crystal growth, and mass transport by carrier gas.

[0004] BACKGROUND ART

[0005] Silicon carbide (SiC) is a compound that can be grown as a single crystal and has various applications. The common techniques for growing silicon carbide single crystals are based on vapor growth or solution growth. Existing solutions for producing bulk SiC include physical vapor transport, PVT, high temperature chemical vapor deposition, HTCVD, modified physical vapor transport, M-PVT, closed-field physical vapor transport, CF-PVT, halide chemical vapor deposition H-CVD, and solution growth.

[0006] Vapor growth methods involve sublimation of raw materials, mass transport, and surface crystallization on a seed crystal. The most widely used vapor growth method is PVT which typically uses an induction furnace to heat the source material and the seed crystal. PVT can produce large-size SiC boules, but it has challenges such as low growth rate, high defect density, and non-uniform doping. Crystal cracking may be caused by built in stress during growth, which is normally caused by thermal gradients. Existing methods show significant issues when attempting to produce SiC crystals with diameters of 8” or larger. Typically, traditional methods use inductive heating utilizing a copper coil which encircles a quartz tube containing the heated graphite crucible surrounded by a thick insulating layer of graphite felt heated by the coil. The static design of such crucible heating solutions makes it difficult to adapt the thermal gradients required for crystal growth. At high temperature Si diffuses out through the graphite crucible and condenses in the insulating felt which now becomes conductive, coupling to the inductive heating which leads to drift in the system. The Si may also cause etching of the graphite and degradation of the insulation.

[0007] Solution growth methods involve dissolving the source material in a molten solvent and crystallizing it on the seed crystal, such as liquid phase epitaxy, LPE . The most widely used solution growth method is top-seeded solution growth, TSSG, which uses a crucible with a concave bottom to hold the solvent and the seed crystal. TSSG can achieve high growth rate, low defect density, and uniform doping, but it has challenges such as high temperature, high pressure, and complex fluid dynamics.

[0008] There is a need for new solutions to grow larger crystals with improved quality and crystal growth rates.

[0009] SUMMARY OF THE INVENTION

[0010] Existing solutions to grow crystals have large costs associated with operating growth chambers, such as high energy demands, high source material consumption, and slow growth rates.

[0011] One object of the invention is to provide a growth chamber for producing silicon carbide crystals with a diameter of at least 300 mm.

[0012] This has in accordance with the present disclosure been achieved by means of a method for growing a crystal in a growth chamber. The method comprises

[0013] - providing a seed crystal into an internal volume of said growth chamber, wherein the growth chamber is arranged to grow said crystal at said seed crystal;

[0014] - providing a source material comprising material for growing said crystal at said seed crystal into said internal volume;

[0015] - flowing carrier gas to the source material and thereafter to the seed crystal; and

[0016] - applying electromagnetic, EM, radiation on a region of the source material, thereby releasing material from the source material and allowing the carrier gas flow to transport said released material to the seed crystal, whereby the crystal is grown at the seed crystal.

[0017] This has the advantage of allowing crystal growth driven by applying EM-radiation on a region of the source material combined with a carrier gas transport, thus allowing crystal growth when the bulk the source material and the seed crystal are substantially the same temperature. This further allows the crystal growth to be performed at higher pressure than traditional physical vapor transport methods, thus increasing the potential crystal growth rate.

[0018] In some embodiments, the method further comprises heating the internal volume to at least 1000°C utilizing a heating device comprised in said growth chamber.

[0019] This has the advantage of allowing the source material to be heated to a temperature close to the temperature of sublimation, thus reducing the amount of heat required from EM-radiation to cause sublimation of the source material. In some embodiments, the step of flowing carrier gas to the source material and thereafter to the seed crystal comprises flowing carrier gas through the source material.

[0020] This has the advantage of efficiently transporting sublimated source material away from the surface of the source material by flowing carrier gas through the source material so as to exit at the surface where sublimation occurs.

[0021] In some embodiments, the crystal to be grown at the seed crystal is a crystal of silicon carbide, SiC, aluminium nitride, AIN, gallium nitride, GaN, gallium oxide, Ga2Os, and / or zinc oxide, ZnO, and the source material comprises SiC, AIN, GaN, Ga2Os, and / or ZnO.

[0022] In some embodiments, wherein applying EM-radiation on a region of the source material comprises causing at least some material of the source material to undergo sublimation.

[0023] In some embodiments, the method further comprises the step of providing a curtain gas flow through the internal volume, wherein the curtain gas flow is arranged to provide a gas curtain for the flow of carrier gas exiting through the source material.

[0024] This has the advantage of providing improved control of the carrier gas flow inside the growth chamber by directing the carrier gas movement with one or more curtain gas flows.

[0025] The present disclosure further relates to a growth chamber for growing a crystal. The growth chamber comprises an internal volume, a seed crystal holder arranged to hold a seed crystal in said internal volume, an EM-radiation source, and a heating device arranged to heat the internal volume to at least 1000°C. The growth chamber is arranged to receive the seed crystal at the seed crystal holder, and to receive, in said internal volume, a source material comprising material for growing said crystal, and to provide a flow of carrier gas to the source material and thereafter to the seed crystal. The EM-radiation source is arranged to provide EM-radiation to a region of the source material, thereby releasing material from the source material and allowing the carrier gas flow to transport said released material to the seed crystal, whereby the crystal is grown at the seed crystal.

[0026] In some examples, the growth chamber is arranged to maintain a gas pressure in the range of 20 to 150 kPa inside the internal volume 110 during crystal growth.

[0027] In some embodiments, the chamber is arranged to provide a curtain gas flow through the internal volume, wherein the curtain gas flow is arranged to provide a gas curtain for the flow of carrier gas exiting through the source material. In some embodiments, the growth chamber comprises a computer arranged to control the EM- radiation source, the seed crystal holder, the flow of carrier gas, the flow of curtain gas and / or the heating device.

[0028] The present disclosure further relates to a system for growing a crystal. The system comprises said growth chamber, a computer, and a set of gas flow control devices. The computer is connected to the growth chamber and the set of gas flow control devices. The computer is arranged to control the set of gas flow control devices to control the carrier gas flow through the growth chamber, and control the EM-radiation source to radiate the source material.

[0029] BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Fig. 1 shows a cross section of a growth chamber for crystal growth

[0031] Fig. 2 shows a cross section of a growth chamber for crystal growth utilizing gas curtains

[0032] Fig. 3 illustrates gas flow in growth chamber with gas curtains

[0033] Fig. 4 shows a system comprising a growth chamber for crystal growth

[0034] Fig. 5 shows a method for growing a crystal with a growth chamber

[0035] DETAILED DESCRIPTION

[0036] Throughout the figures, same reference numerals refer to same parts, concepts, and / or elements. Consequently, what will be said regarding a reference numeral in one figure applies equally well to the same reference numeral in other figures unless explicitly stated otherwise.

[0037] Terms and expressions

[0038] The term seed crystal relates to a crystal from which crystal growth in the growth chamber starts. It is to be understood that expressions describing transporting material to the seed crystal, or crystal growth occurring at the seed crystal, relates to both the seed crystal and any crystal that has been grown on the seed crystal.

[0039] The term source material relates to material from which the crystal is grown. Typically, the source material is a sintered source material or a powder source material.

[0040] The expression “material released by sublimation of the source material” relates to source material and derivatives thereof that have been released from the source material due. The term carrier gas flow relates to a gas arranged to transport sublimated species from the source material to the region of crystal growth. In some examples, the carrier gas main component is an atom or a molecule with high mass and low diffusivity, such as argon.

[0041] The term curtain gas flow relates to gas arranged to guide the carrier gas. Typically, curtain gas comprises heavy species arranged to push into the carrier gas, thus reducing the probability of species in the carrier gas moving out of the flow of carrier gas.

[0042] The expression “a heating device comprised in the growth chamber” relates to being arranged at the exterior of the growth chamber, at the internal volume of the growth chamber, or within the walls of the growth chamber that separate the internal volume and the environment.

[0043] Fig. 1 shows a cross section of an example growth chamber 100 for crystal growth. The growth chamber 100 comprises an internal volume 110 surrounded by a first layer comprising heating device 150 and a second layer comprising insulation 160. The heating device comprised in the first layer 150 are arranged to heat the internal volume 110 to a temperature within a first temperature range.

[0044] The growth chamber 100 comprises a seed crystal holder 170 in said internal volume 110, wherein the seed crystal holder 170 is arranged to hold a seed crystal 180 for growing a crystal (not shown). Typically, the seed crystal holder 170 is arranged to move the seed crystal 180, such as rotating the seed crystal 180. The growth chamber 100 is arranged to hold a source material 120 comprising material to be grown at the seed crystal 180, wherein the source material 120 is arranged to allow a flow of carrier gas 130 pass through said source material 120. The growth chamber 100 further comprises an electromagnetic radiation source 140 arranged to radiate the source material 120 so as to sublimate at least some material to be grown at the seed crystal 180.

[0045] In some examples, the seed crystal holder 170 is arranged to move the seed crystal 180. In some of these examples, the seed crystal holder 170 is arranged to rotate and / or lift the seed crystal 180. Rotating the seed crystal 180 may allow for a more uniform crystal growth, and upon the thickness of the grown crystal increasing, the surface of the crystal may be kept in substantially the same plane by lifting the grown crystal, which may allow flow conditions to be maintained during crystal growth.

[0046] In some examples, the growth chamber 100 is arranged to transport carrier gas 130 to the source material 120 and thereafter to the seed crystal 180, whereby material transported by said carrier gas 130 from the source material 120 is arranged to grow crystal at the seed crystal 180. In some examples, the growth chamber 100 is arranged to transport carrier gas 130 through the source material 120 and thereafter to the seed crystal 180. In the example in fig. 1 , the carrier gas 130 enters into the lower section of the internal volume 110, passes through the source material 120, passes the seed crystal 180, and exits the internal volume 110 at the upper section of the internal volume 110. It is to be understood that the geometry of the internal volume 110 and / or the geometry of the path of the carrier gas 130 in relation to the source material 120 or the seed crystal 180 may be designed in other ways than shown in the examples.

[0047] In the example in fig. 1 , the seed crystal 180 is a silicon carbide seed crystal, and the source material 120 comprises sintered silicon carbide. The heating device 150 comprised in the first layer comprises a resistive heater arranged to heat the internal volume 110 to 1500°C to 2200°C. The example electromagnetic radiation source 140 is a 2 kW continuous wave laser arranged to radiate the source material 120 on a side facing the seed crystal 180, thus locally raising the temperature of the source material 120. Carrier gas comprising argon and hydrogen is transported through the source material 120 and thereafter to the seed crystal 180, thereby transporting any silicon carbide sublimated from the source material 120 by the continuous wave laser to the seed crystal 180.

[0048] In some examples, wherein SiC crystal is being grown, the target spot temperature upon applying electromagnetic radiation is 2200 to 3000°C. Preferably the spot temperature is around 2600°C for which the sublimation is expected to be stoichiometric. An advantage of a stoichiometric reaction is a reduced need for hydrogen in the carrier gas 130 to remove carbon from the source material 120.

[0049] Preferably, the carrier gas 130 comprises gases with high mass and low diffusivity, such as Ar. Preferably the gas has a low thermal conductivity, which allows the gas cloud created by the electromagnetic radiation device to maintain temperature until it is transported by the carrier to the seed crystal and cooled by the "contact" with the crystal surface. If the temperature is not maintained then homogeneous nucleation may occur, homogeneous nucleation here relating to growth in the gas phase where the sublimed species will start recombining to form microcrystals.

[0050] In some examples, the growth chamber 100 comprises a computer (not shown) arranged to control the electromagnetic radiation source 140 and / or the seed crystal holder 170. In some examples, said computer is comprised in a programmable logic controller and / or a hardware controller for automation of the growth chamber 100. In some examples, the growth chamber 100 is arranged to utilize the electromagnetic radiation source 140 to sweep radiation across the source material 120. For example, radiating in an approximately 10 mm diameter spot and sweeping said spot of radiation such that is moves at 100 mm per second across the surface of the source material surface.

[0051] It is to be understood that the sweep pattern and the time spend radiating each part of the source is also important, as this will ensure that the temperature in the radiated part(s) reaches a desired value. The sweep pattern is also important in order to consume the source evenly and may have an impact on the growth of the crystal being grown. Typically, the location of the part of the source being radiated has an impact on where the created gas cloud of sublimated source material comes into contact with the crystal being grown. For example, the purpose of sweeping radiation across the source material 120 may be to sequentially heat the whole surface of the source material 120 to a desired temperature in which case a relatively large spot is used, such as 10 mm; or to locally heat a small region to create a high amount of sublimed species in which case a relatively small spot is used, such as like 4 mm, and scanning is done relatively rapidly.

[0052] In some examples, the internal volume 110 comprises a region that is substantially cylinder shaped. In some examples, the source material 120 is arranged opposite to the crystal holder 170.

[0053] The growth chamber 100 may be arranged to grow crystals of SiC, aluminium nitride AIN, gallium nitride, GaN, gallium oxide, Ga2Os, and / or zinc oxide, ZnO.

[0054] It is to be understood that pressure range, temperature range, carrier gases and several additional parameters for performing crystal growth with the growth chamber 100 are dependent on the type of crystal being grown. Examples herein predominantly describe growing SiC crystals, however, the growth chamber, system and method are not limited to SiC crystal growth, and the examples also relate to corresponding examples for other types of crystals.

[0055] In some examples, the growth chamber 100 is arranged to grow crystals with a diameter of at least 200 mm, or at least 300 mm. In some of these examples, the growth chamber 100 is arranged to grow silicon carbide crystals with a diameter of at least 200 mm, or at least 300 mm.

[0056] In some examples, the source material 120 comprises SiC, AIN, gallium nitride, GaN, gallium oxide, Ga2Os, and / or zinc oxide, ZnO. In some examples, the source material 120 comprises at least 50 wt% of SiC, AIN, gallium nitride, GaN, gallium oxide, Ga2Os, and / or zinc oxide, ZnO.

[0057] In some examples, the source material 120 comprises vanadium, wherein vanadium is arranged to dope the grown crystal.

[0058] In some examples, the source material 120 comprises sintered source material and / or a plurality of particles.

[0059] It is to be understood that the level of sintering or the particle size of the source material 120 is important. A compact sintered source will have a fairly decent thermal conductivity which will impact the way the EM radiation heating spreads in the source. Typically, the best efficiency is achieved when the thermal conductivity of the source is low as it will allow the spot temperature to significantly increase without significant amounts of heat spreading through the source.

[0060] In some examples, the source material 120 comprises a plurality of particles with an average diameter of 10-400 pm. In some of these examples, the average diameter is 20-200 pm, or 40- 100 pm.

[0061] In some examples, the source material 120 comprises sintered source material formed by a plurality of particles with an average diameter of 10-4000 pm. In some of these examples, the average diameter is 20-2000 pm, 40-1000 pm, 100-600 pm, or 200-400 pm.

[0062] In some examples, the growth chamber 100 comprises a holder (not shown) for said source material 120. In some of these examples, the growth chamber 100 and holder upon receiving a corresponding source material 120 creates two volumes separated by the source material 120, such that the flow paths for carrier gas 130 has to pass through the source material 120 to move between said two volumes. Typically, the two volumes compartments relate to a first volume where the carrier gas 130 enters and a second volume between the source material 120 and the seed crystal 180.

[0063] In some examples, the growth chamber 100 comprises the holder for said source material 120, wherein the carrier gas 130 flows at, and / or through, the source material 120 comprised in said holder.

[0064] In some examples, the growth chamber 100 comprises the holder for said source material 120, wherein electromagnetic, EM, radiation is applied to the source material 120 comprised in said holder. It is to be understood that, even though the seed crystal 180 and the source material 120 are needed for crystal growth, the growth chamber 100 is typically not manufactured or sold with the seed crystal 180 or the source material 120 installed. Instead, the seed crystal 180 and the source material 120 may be considered consumables that will be replaced multiple times over the lifespan of a growth chamber, much like paper and ink cartridges for a printer. Typically, the seed crystal 180 and the source material 120 are replaced each crystal growth run.

[0065] It is to be understood that “sublimating the source material 120” releases and forms a plurality of species, such as Si, Si2C and SiC2, by providing heat to the source material 120. The electromagnetic radiation source 140 is preferably a high power laser that is either CW or pulsed with low energy levels, that is to say an electromagnetic radiation source 140 that does not utilize very short pulses. These types of lasers are commonly used in pulsed laser deposition, PLD, to sputter off chunks of material that are sprayed onto the receiving surface. PLD is an entirely different process carried out in high vacuum.

[0066] In some examples, the flow of carrier gas 130 comprises at least one inert gas and hydrogen. If the source material is SiC then the sublimation is typically not stoichiometric and carbon is left behind in the source material, this may be mitigated by introducing hydrogen in the carrier gas. Hydrogen may readily react with excess carbon to form hydrocarbons, which keeps the source clean and also increases the growth rate which normally is carbon limited, this benefit does not occur in Si-limited CVD.

[0067] In some examples, the flow of carrier gas 130 comprises and / or consists of argon and hydrogen. In some of examples, the flow of carrier gas 130 comprises 0.5-10 SLM argon and 0-10 SLM hydrogen. In some of these examples, the flow of carrier gas 130 comprises 1-6 SLM, or 2-4 SLM argon. In some of these examples, the flow of carrier gas 130 comprises 0.5- 6 SLM, or 1-4 SLM hydrogen.

[0068] In some examples, the growth chamber 100 is arranged to have a flow of carrier gas 130 corresponding to a volumetric exchange rate in the internal volume 110 in a range of 0.1 min-1to 2 min-1. In some of these examples, the volumetric exchange rate in the internal volume 110 is in the range of 0.2 min-1to 1 min-1, or 0.4 min-1to 0.8 min-1.

[0069] In some examples, the flow of carrier gas 130 has a flow rate in the range of 0.1 to 10 m / s in the internal volume 110 in the growth chamber 100 at the source material 120 where carrier gas 130 exits the source material 120. In some of these examples, the flow of carrier gas 130 has a flow rate in the range of 0.2 to 5 m / s, 0.4 to 2 m / s, or 0.6 to 1 m / s.

[0070] It is to be understood that said flow rate of carrier gas 130 relates to an average gas flow. In some examples, the flow of carrier gas 130 comprises argon and hydrogen in an Ar:H2 ratio within the range of 5-95%. In some of these examples, the flow of carrier gas 130 comprises argon and hydrogen in an Ar:H2 ratio within the range of 10-90%, 15-80%, 25-75%, or 30-60%.

[0071] For an example scenario, the internal volume 110 is evacuated prior to starting the growth process, and thereafter Ar gas is introduced and the pressure controlled to between 20 kPa to 150 kPa absolute. Several other parameters for performing the crystal growth are typically determined based on the pressure, such as the velocity of the gas, gas density, the etch rate at the seed crystal, the spread of the “cloud” of sublimed species from the source material, the homogeneous nucleation, and the temperature of the spot for a given electromagnetic radiation. Thus, pressure regulation is important for reliable performance of the crystal growth. Typically, there is no pressure difference or a minor pressure difference between the inlet and outlet. The average flow through the growth chamber is quite small and slow, so no major pressure differences are required. The pressure in the internal volume 110 and the pressure difference between inlet and outlet may be selected based on the expected partial pressure of the sublimed species due to electromagnetic radiation, to make sure that the whole gas “cloud” of released source material is guided in a controlled manner. Precise pressure control may be utilized to control the growth front of the crystal and to reduce homogeneous nucleation at high rates.

[0072] In some examples, wherein a SiC crystal is being grown, the source material 120 comprises SiC particles mixed with a plastic, whereby the stoichiometry of the source material 120 is tuned towards having more carbon.

[0073] In some examples, the growth chamber 100 is arrange to, during crystal growth, consume source material at a higher rate at the side of the source material 120 furthest from the crystal holder 170 compared to the rate at the side of the source material 120 closest from the crystal holder 170. In some of these examples, the growth chamber 100 comprises an external port (not shown) arranged to allow source material to be added to the side of the source material 120 closest from the crystal holder 170. In some of these examples, the source material 120 is added as a powder.

[0074] In some examples, the carrier gas comprises one or more dopants, or precursors thereof, for the crystal being grown.

[0075] In some examples, the carrier gas comprises nitrogen. N2 is a n-type dopant at least for SiC and it is essential in order to produce crystals for power devices, such as power electronics used in electric vehicles and charging stations. In some examples, the carrier gas comprises vapours of Tri-Methyl-Aluminium, TMA, vanadozine, and / or vanadium chloride. The aluminium comprised in TMA is a p-type dopant at least for SiC.

[0076] It is to be understood that for growing doped crystals the carrier gas and / or the source material may comprise dopants or precursors thereof.

[0077] In some examples, wherein an AIN crystal is being grown, the carrier gas comprises nitrogen.

[0078] In some examples, wherein a GaN crystal is being grown, the carrier gas comprises chlorine and / or HCI. These species may be useful due to the low vapor pressure of gallium.

[0079] In some examples, wherein a ZnO crystal is being grown, the carrier gas comprises oxygen. In some of these examples, the seed crystal holder 170 comprises quartz, or another high temperature oxide with low vapor pressure. In some of these examples, the crystal growth chamber 100 comprising at least one heating device comprising Molybdenum disilicide, MoSi2.

[0080] In some examples, the electromagnetic radiation source 140 is arranged to radiate a region 120’ of the source material 120. In some examples the electromagnetic radiation source 140 is arranged to simultaneously radiate two or more different regions of the source material 120. In some of these examples, the electromagnetic radiation source 140 is connected to a computer and is arranged to be controlled to aim at different regions of the source material 120 by said computer.

[0081] It is to be understood that a region 120’ of the source material 120, typically, is a true subregion of the source material 120 that is directly exposed and / or heated by the EM-radiation.

[0082] In some examples, the electromagnetic radiation source 140 is arranged to radiate a region 120’ of the source material 120 in a pattern across the source material 120. It is to be understood that raising the temperature of at least part of the source material 120 may be performed in many ways, either according to a predetermined pattern or based on some sensor data relating to the source material or the crystal being grown. It is further to be understood that the position on the source material being heated may impact the distribution of crystal growth at the seed crystal, such as increased crystal growth at a position of the seed crystal that is closest to the position being heated.

[0083] In some examples, the growth chamber 100 is arranged to control the electromagnetic radiation source 140 to radiate a position on the source material 120 based on sensor data of the crystal being grown, wherein heating the position on the source material 120 causes an uneven crystal growth at the crystal being grown. In some examples, the heating device 150 comprises a resistive heater and / or an induction heater.

[0084] In some examples, the growth chamber 100 comprises insulation. In some of these examples, the insulation is arranged outside the first layer comprising the heater device 150. Adding insulation to the outside of the growth chamber 100 saves a lot of energy which is a major cost in crystal growth.

[0085] In some examples, the growth chamber 100 is arranged to heat the seed crystal 180 and / or the source material 120 to a temperature in the range of 1000-2500°C. In some of these examples, the growth chamber 100 is arranged to heat the seed crystal 180 and / or the source material 120 to a temperature in the range of 1200-2400°C, 1400-2300°C, 1600-2200°C, 1800- 2100°C, or 1900-2000°C.

[0086] In some examples, the growth chamber 100 is arranged to heat the seed crystal 180 and the source material 120 to substantially the same temperature. In some of these examples, the temperature difference between the seed crystal 180 and the source material 120 is at most 200°C. In some of these examples, said temperature difference is at most 150°C, at most 100°C, at most 70°C, at most 50°C, at most 40°C, at most 30°C, at most 20°C, or at most 10°C.

[0087] The expression “the growth chamber 100 is arranged to heat the source material 120 to a temperature” relates to heating the source material 120 as a whole and the temperature values typically relate to temperature values achieved prior to applying EM-radiation from the electromagnetic radiation source 140.

[0088] In some examples, the growth chamber 100 comprises a resistive heater and / or an induction heater arranged to heat the seed crystal 180 and / or the source material 120.

[0089] It is to be understood that for some embodiments of the invention it may be possible to grow the crystal while maintaining the seed crystal 180 at a higher temperature than the source material 120 as a whole, as the EM-radiation from the electromagnetic radiation source 140 may create a large temperature difference between the radiated region 120’ of the source material 120 and the seed crystal 180.

[0090] In some examples, the growth chamber 100 is arranged to produce semi insulating SiC that is grown using extremely high purity, wherein the carrier gas is purified to remove nitrogen, and wherein the source material is generated through a gas fed process utilizing silane and ethylene. For example, this may be performed in-situ by allowing said gases to react on a grid or a plurality of short cylinders of graphite and then sublime the SiC from the cylinder walls or grid.

[0091] In some examples, the seed crystal holder 170 is arranged to rotate the seed crystal 180 and / or lift the seed crystal 180. In some of these examples, the seed crystal holder 170 is in communication with a computer (not shown) arranged to control the movement of said seed crystal 180.

[0092] In some examples, the growth chamber 100 comprises a set of sensors (not shown) arranged to measure and / or capture an image of at least one of

[0093] - temperature in the internal volume 110,

[0094] - pressure in the internal volume 110,

[0095] - temperature of the source material 120,

[0096] - temperature of the crystal holder 170 and / or the crystal being grown,

[0097] - temperature of carrier gas 130 entering and / or exiting the internal volume 110,

[0098] - the surface of the crystal holder 170 and / or the crystal being grown,

[0099] - the surface of the source material 120, and

[0100] - composition of carrier gas 130 entering and / or exiting the internal volume 110.

[0101] It is to be understood that the composition of the carrier gas 130 exiting the internal volume 110 relates to both the carrier gas 130 and any species transported out of the internal volume 110, such as silicon dicarbide, SiC2.

[0102] In some examples, the growth chamber 100 comprises at least one optical port (not shown) arranged to allow, from outside the internal volume 110, detection of electromagnetic radiation from within the internal volume 110 of the growth chamber 100, and allow transmission of electromagnetic radiation into the internal volume 110, such as radiation from an electromagnetic radiation source 140 arranged outside the internal volume 110. In some of these examples, at least one of the set of sensors is arranged to measure a value and / or capture an image through said at least one optical port.

[0103] In some examples, the electromagnetic radiation source 140 is arranged outside the internal volume 110 and irradiates the region 120’ of the source material 120 through at least one optical port.

[0104] In some examples, the growth chamber 100 comprises said set of sensors and a computer,

[0105] - wherein the computer controls the set of sensors to measure the temperature of the crystal holder 170 and / or the crystal being grown, measures a value and / or captures an image of the surface of the crystal holder 170 and / or the crystal being grown, or measures a value and / or captures an image of the source material 120; and - wherein the computer is arranged to control the at least one heating device 150, the crystal holder 170, the EM radiation source 140, and / or control flows based on said measurement by the set of sensors. In some of these examples, the growth chamber comprises at least one actuator arranged to control gas flow, and wherein the computer is arranged to control gas flow by controlling said at least one actuator.

[0106] In some of these examples, the computer is arranged to measure the temperature of the crystal holder 170 and / or the crystal being grown, compare measured values with a target temperature, and control the temperature of the crystal holder 170 and / or the crystal being grown utilizing a heater based on said comparison.

[0107] In some examples, the computer is arranged to measure the crystal being grown, determine a growth rate of the crystal, compare the determined growth rate with a target growth rate, and control the EM-radiation source 140, flow of carrier gas and / or curtain gas flow based on said comparison.

[0108] In some examples, the computer is arranged to measure the gas composition in the internal volume 110 the growth chamber 100, compare the measured composition values with a target composition, and control the EM-radiation source 140, flow of carrier gas and / or the hydrogen content of the carrier gas based on said comparison.

[0109] In some examples, the growth chamber 100 comprises said set of sensors and a computer,

[0110] - wherein the set of sensors measures the temperature of the crystal holder 170 and / or the crystal being grown, or measures a value and / or captures an image of the surface of the crystal holder 170 and / or the crystal being grown, and

[0111] - wherein the computer is arranged to determine crystal growth rate, defects, polytypes, and / or facet development based on said measurement.

[0112] In some examples, the growth chamber 100 comprises a set of sensors and a computer,

[0113] - wherein the set of sensors measures the composition of carrier gas 130 exiting the internal volume 110, and

[0114] - wherein the computer is arranged to determine the ratio of hydrocarbons based on said measurement.

[0115] It is to be understood that the expression “measures the composition of carrier gas 130” may relate to performing a measurement such that the measured data is indicative of the composition.

[0116] In some examples, the growth chamber 100 is arranged to adjust the hydrogen content of the carrier gas 130, and the set of sensors is arranged to measure hydrocarbons in the internal volume 110 of the growth chamber 100, wherein the computer is arranged to

[0117] - measure hydrocarbons in the internal volume 110 the growth chamber 100,

[0118] - compare the measured values with a target value for hydrocarbons, and

[0119] - control the EM-radiation source 140, the hydrogen content of the carrier gas 130 and / or the flow rate of the carrier gas 130 based on said comparison.

[0120] In some examples, the set of sensors comprise a Fourier transform infrared, FTIR, sensor. It is to be understood that measurement values from an FTIR sensor arrange to measure the gas in the internal volume 110 may be utilized to determine molecules in gas inside the internal volume 110. In some of these examples, the computer is arranged to compare the chemical composition in the gas against a predetermined set of criteria, and present a warning and / or perform control the growth chamber 100 based on said comparison. In some of these examples, the computer is arranged to control the EM-radiation source 140, the hydrogen content of the carrier gas 130 and / or the flow rate of the carrier gas 130 based on said comparison.

[0121] In some examples, the set of sensors comprise an optical sensor arranged to detect the optical spectrum emitted from the source material 120 and / or the crystal being grown. In some of these examples, the computer is arranged to determine the chemical composition and / or structural properties of the source material 120 and / or the crystal being grown. In some of these examples, the computer is arranged to compare the chemical composition and / or structural properties of the source material 120 and / or the crystal being grown against a predetermined set of criteria, and present a warning and / or perform control the growth chamber 100 based on said comparison. In some of these examples, the computer is arranged to control the EM-radiation source 140, the hydrogen content of the carrier gas 130 and / or the flow rate of the carrier gas 130 based on said comparison.

[0122] In some examples, the set of sensors comprise an optical sensor arranged to measure in the infrared, visible, and / or UV spectral ranges inside the internal volume 110 of the growth chamber. It is to be understood that, at least for measurements, “inside the internal volume 110” includes the source material 120, the crystal being grown and other parts inside or in contact with the internal volume 110.

[0123] In some examples, the set of sensors comprises a weighing scale arranged to measure the weight of the source material 120 and / or the weight of the holder of said source material. In some of these examples, the computer is arranged to determine the depletion of the source material 120 based on the measured weight. In some of these examples, the computer is arranged to control the EM-radiation source 140, the hydrogen content of the carrier gas 130 and / or the flow rate of the carrier gas 130 based on said determined depletion of the source material 120.

[0124] In some examples, the set of sensors comprises a Michelson interferometer arranged to measure the surface of the crystal being grown. In some of these examples, the computer is arranged to determine the growth rate of the crystal based on the measurement. In some of these examples, the computer is arranged to measure and determine the growth rate for two or more positions on the surface of the crystal being grown.

[0125] In some examples, the set of sensors comprises an emissometer arranged to measure the emissivity of the surface of the crystal being grown. In some of these examples, the computer is arranged to determine the surface geometry of the crystal being grown based on the measured emissivity. In some of these examples, the computer is arranged to control the EM- radiation source 140, the hydrogen content of the carrier gas 130 and / or the flow rate of the carrier gas 130 based on said determined surface geometry of the crystal being grown.

[0126] In some examples, the set of sensors comprises an emissometer arranged to measure the emissivity of the surface of the crystal being grown, and the set of sensors comprises a temperature measuring device arranged to determine the temperature of the surface of the crystal being grown. In some of these examples, the computer is arranged to determine the surface geometry of the crystal being grown based on the measured emissivity and the measured temperature.

[0127] In some examples, the growth chamber comprises at least one actuator arranged to adjust the curtain gas flow in the internal volume. In some of these examples, the computer is arranged to control the at least one actuator based on determine crystal growth rate, defects, polytypes, facet development, and / or the ratio of hydrocarbons; or determine crystal growth rate, defects, polytypes, facet development, and / or the ratio of hydrocarbons.

[0128] In some of these examples, the growth chamber 100 is arranged to adjust a first and / or a second curtain gas flow in the internal volume 110, and the set of sensors is arranged to measure crystal growth rate, wherein the computer is arranged to

[0129] - measure the crystal being grown,

[0130] - determine a growth rate of the crystal,

[0131] - compare the determined growth rate with a target growth rate, and

[0132] - control said curtain gas flow(s) in the internal volume 110 based on said comparison.

[0133] It is to be understood that the computer may be arranged to control the EM-radiation source 140, carrier gas flow 130 and / or curtain gas flow based on any combination of the determined properties in the previous examples. Fig. 2 shows a cross section of an example growth chamber for crystal growth utilizing gas curtains. The growth chamber 100 may be a growth chamber as described in fig. 1 further arranged to provide a curtain gas flow 131 comprising argon through the internal volume 110. The curtain gas flow 131 is arranged to provide a gas curtain for the flow of carrier gas 130 exiting through the source material 120. Typically, the curtain gas flow 131 is configured to force the flow of carrier gas 130 exiting the source material 120 along a flow path towards the seed crystal 180, such that more of the material carried from the source material 120 by the carrier gas 130 is brought into proximity of the seed crystal 180. This further reduces parasitic deposition on the walls. In some examples, the curtain gas flow 131 comprises argon, krypton, xenon, helium, and / or neon. It is to be understood that the impact of utilizing curtain gas flow 120 is significantly amplified by operating the growth chamber 100 under relatively high pressures compared to typical physical vapor transport, PVT, systems.

[0134] It is to be understood that the expression “brought into proximity" relates to material carried from the source material 120 by the carrier gas to the vicinity of the seed crystal surface, close enough for diffusion to act as the main gas transport mechanism. Typically, the carrier gas 130 will not bring the carried material into direct contact with the seed crystal surface, as the likely scenario is that there is a stagnant layer of non-descript gas that exists closest to the surface and the incoming specie diffuse through this onto the surface of the crystal being grown. Diffusion is quick at the operating temperatures and pressures used so a good measure of the stagnant layer thickness relates to the diffusion length and forced convection velocity parallel to the surface of the crystal being grown. For a likelihood of a molecule reaching the surface being 50%, the efficiency of transport is 50%.

[0135] In fig. 2 the curtain gas flow 131 is depicted as travelling in parallel with the flow of carrier gas 130 passing through the source material 120, such that in an example with a cylinder symmetric internal volume 110, the flow of carrier gas 130 passing through the source material 120 forms a cylinder that is surrounded by a tube of curtain gas flow 131 pushing the flow of carrier gas 130 transporting material from the source material 120 towards the centreline and towards the seed crystal 180. It is to be understood that the curtain gas flow 131 may enter the internal volume 110 in other ways than depicted in fig. 2, such as being entering at or slightly downstream of the side of the source material 120 where the flow of carrier gas 130 exits.

[0136] In some examples, growth chamber 100 is arranged to generate at least two curtain gas flows. In some of these examples, an inner curtain gas flow is parallel to the carrier gas flow and forms a "tube" surrounding the carrier gas flow, and a second curtain gas flow, typically called the focus flow, comes in at an angle and is arranged to further push the carrier gas flow towards its centre line. It is to be understood that these curtain gas flows may be adapted to obtain different flow profiles for growing a crystal. The example growth chamber 100 shown in fig. 2 and fig. 3 has a rotationally symmetric disc shaped source material 120 and the curtain gas flow 131 enters the internal volume 110 via the ring-shaped gap between the source material 120 and the inner wall of the growth chamber 100 formed by the heating device 150.

[0137] Fig. 3 illustrates gas flow in an example growth chamber with gas curtains. The growth chamber 100 may be a growth chamber as described in fig. 2. Fig. 3 shows an example schematic gas boundary 135 between regions predominantly containing carrier gas and curtain gas. The depicted gas boundary 135 aims to illustrate how the curtain gas 131 may impact the flow of carrier gas 130, and the shape of the example gas boundary 135 may differ from real world measurements.

[0138] It is to be understood that the flow of gases through the internal volume 110 may be altered by the flow of the carrier gas 130 passing through the source material 120, the flow of the curtain gas flow 131 , and / or the composition of the curtain gas flow 131. Typically, the purpose of utilizing curtain gas flow 131 is to improve control over the carrier gas 130 after passing through the source material 120, so as to obtain an increased growth rate and / or a higher quality crystal growth.

[0139] In some examples, at least one curtain gas flow 131 is angled towards a centreline of the flow of carrier gas 130, thereby concentrating the flow of carrier gas 130 to said centreline.

[0140] In the example shown in fig. 2 and fig. 3 the curtain gas flow 131 is depicted as entering the internal volume 110 at the edges of the source material 120. In some examples, the curtain gas flow 131 is introduced into the internal 110 volume via one or more channel, each with an outlet (not shown) arranged inside the internal volume 110.

[0141] In some examples, the curtain gas flow 131 is introduced into the internal volume 110 in a rotationally symmetric fashion. In some of these examples, the curtain gas flow 131 is released into the internal volume 110 from a continuous outlet arranged in the rotationally symmetric fashion, such as depicted in fig. 2 and fig. 3.

[0142] In some examples, at least one curtain gas flow 131 comprises and / or consists of 0.5-10 SLM argon. In some of these examples, at least one curtain gas flow 131 comprises and / or consists of 1-6 SLM, or 2-4 SLM argon.

[0143] Fig. 4 shows an example system for crystal growth, the system 200 comprises a growth chamber 100 for crystal growth, a computer 210, and a set of gas flow control devices 221 ,222. The growth chamber 100 may be a growth chamber according to any of the growth chambers 100 described in relation to fig. 1 and fig. 2. The computer 210 is connected to the growth chamber and the set of gas flow control devices 221,222, and is arranged to control the set of flow control devices to control the carrier gas flow through the growth chamber 100, and control the EM-radiation source to radiate the source material.

[0144] In some examples, the set of gas flow control devices 221,222 comprises an inlet mass flow controller and an outlet gas pump. In some examples, the set of gas flow control devices 221,222 comprise a mass flow controller and / or a gas pump.

[0145] It is to be understood that the set of gas flow control devices 221 ,222 in fig. 4 may be a set of valves controlling the flow of high pressure gases. Typically, utilizing a pump or compressor makes it easier to reclaim the exhaust gases from the growth chamber 100. In some examples, gas flow control device(s) 221 at the inlet is arranged to control the ratio of H2 to Ar, or other heavy carrier gas. In some examples, the gas flow control device(s) at the inlet is arranged to remove any hydrocarbons.

[0146] In some examples, the set of gas flow control devices 221 ,222 comprises a gas inlet valve and an outlet valve.

[0147] It is to be understood that the set of gas flow control devices 221 ,222 and the connections between themselves and the growth chamber 100 may comprise one or more of the plurality of standard components comprised in a pipeline, and are not limited to pumps, valves and mass flow controllers.

[0148] In some examples, the computer 210 is connected to the heater device and / or the seed crystal holder comprised in the growth chamber 100, and is arranged to control the heater device and / or the seed crystal holder.

[0149] In some examples, the system 200 further comprises a gas recovery device 230 arranged to purify and / or recover the carrier gas and / or material transported by said carrier gas that has exited the growth chamber 100. In some of these examples, the gas recovery device 230 is connected to the gas inlet pump 221 by a gas tube 227, whereby recovered gas may be fed back into the growth chamber 100.

[0150] In some examples, if the spot temperatures of the electromagnetic radiation device 140 is above 2600°C, carrier gas without hydrogen may be utilized, thus making the recycling of exhaust gas from the growth chamber simpler by the gas recovery device 230.

[0151] In some examples, the set of gas flow control devices are arranged to control the carrier gas, the curtain gas, the exhaust gases from the growth chamber 100, and / or the recovered gas. In some examples, the system 200 comprises an EM radiation source 240 separate from the growth chamber 100, wherein the EM radiation source 240 is arranged to radiate the source material 120 so as to sublimate at least some material to be grown at the seed crystal. In some of these examples, the EM radiation source 240 is connected to the computer and is arranged to be controlled by the computer 210. In some examples, the EM radiation source 240 is a radiations source corresponding to the EM radiation source 140 described in fig. 1 and 2.

[0152] For example, sublimation of SiC occurs at approximately 1800°C in an inert and low pressure environment. By combining an ambient temperature below 1800°C and EM radiate from the EM radiation source 240 a region of the source material 120 may be heated to a temperature where significant amounts of sublimation occurs. Heating by EM radiation removes the strict temperature gradient requirements of the growth chambers found in traditional physical vapor transport, PVT, methods. Furthermore, compared to PVT methods the transport of the growth species is not thermal gradient based but gas-flow based.

[0153] In some examples, the EM radiation source 240 is arranged to elevate the temperature in a region of the source material 120 to at least 200°C above the average temperature of the remaining regions of the source material 120. It is to be understood that heating from the EM radiation source is a very local heating process and the energy is used for the phase change, such as sublimation, of the source material and at least some heat may thereby be removed from the source material which limits the rise of the bulk temperature of the source material as a whole.

[0154] In some examples, the system 200 comprises a memory storage 211 comprised in the computer 210 and / or is connected to the computer 210, wherein the memory storage 211 is arranged to comprise a computer program arranged to, upon execution on the computer, control the system to grow crystals.

[0155] In some examples, the system 200 comprise a set of analytical equipment (not shown) comprising at least one pyrometer, thickness measurement device, camera, thermal imaging camera, optical spectrometer; or a device for quantitative mineral analysis, Fourier transform infrared spectroscopy, X-ray diffraction, or emissivity measurement.

[0156] Fig. 4 depicts the parts of the system 200 as separate parts connected by communication or gas tubes 225,226, however, any of said parts may be arranged at or comprised in the growth chamber 100. It is to be understood that the growth chamber 100 may comprise any or all of the parts of the system 200. In some examples, the system 200 is comprised in one unit.

[0157] In some examples, the system 200 is arranged to maintain a gas pressure in the range of 20 to 150 kPa inside the internal volume of the growth chamber 100 during crystal growth. In some of these examples, the system 200 is arranged to maintain a gas pressure in the range of 25 to 200 kPa, 15 to 400 kPa, or 10 to 1000 kPa.

[0158] Fig. 5 shows a method for growing a crystal with a growth chamber. The method comprises the steps of

[0159] - providing 310 a seed crystal into an internal volume of said growth chamber, wherein the growth chamber is arranged to grow said crystal at said seed crystal;

[0160] - providing 320 a source material comprising material for growing said crystal at said seed crystal into said internal volume;

[0161] - flowing 340 carrier gas to the source material and thereafter to the seed crystal; and

[0162] - applying 350 EM-radiation on a region of the source material, thereby releasing material from the source material and allowing the carrier gas flow to transport said released material to the seed crystal, whereby the crystal is grown at the seed crystal.

[0163] In some examples, the method comprises heating 330 the internal volume to at least 1000°C, or at least 1400°C utilizing a heating device comprised in said growth chamber.

[0164] In some examples, flowing 340 carrier gas to the source material and thereafter to the seed crystal comprises flowing 340 carrier gas through the source material.

[0165] In some examples, heating 330 the internal volume to at least 1000°C, or at least 1400°C utilizing a heating device comprised at and / or outside said growth chamber. For example, the growth chamber may comprise a quartz tube style reactor with a coil for inductive heating on the outside.

[0166] In some examples, heating 330 the internal volume comprises heating the seed crystal and / or the source material to a temperature in the range of 1000-2500°C. In some of these examples, the growth chamber is arranged to heat the seed crystal and / or the source material to a temperature in the range of 1200-2400°C, 1400-2300°C, 1600-2200°C, 1800-2100°C, or 1900- 2000°C.

[0167] In some examples, heating 330 the internal volume comprises heating the seed crystal and the source material to substantially the same temperature. It is to be understood that said heating typically relates to the temperature of the source material prior to applying EM-radiation on a region of the source material. In some of these examples, the temperature difference between the seed crystal and the source material is at most 200°C. In some of these examples, said temperature difference is at most 150°C, at most 100°C, at most 70°C, at most 50°C, at most 40°C, at most 30°C, at most 20°C, or at most 10°C. In some examples, heating 330 the internal volume, comprises generating a temperature gradient within the source material, wherein the temperature of the side of the source material facing the seed crystal is higher than the side opposite side. Said side facing the seed crystal corresponds to the surface where the carrier gas exits the source material, and said opposite side relates to the surface where the carrier gas enters the source material. Preferably, the side of the source material facing the seed crystal is kept at high enough temperature to keep crystal growth at a minimum. The purpose of said gradient is to reduce crystal formation inside the source material by providing an increasing temperature for any released material as it is transported through the source material by the carrier gas.

[0168] In some examples, providing 320 a source material comprising material for growing said crystal comprises providing said source material in a holder for source material; and

[0169] - flowing 340 carrier gas to the source material comprises flowing 340 carrier gas to, and / or through, said source material comprised in said holder for source material; and / or

[0170] - applying 350 EM-radiation on a region of the source material comprises applying EM- radiation to source material comprised in said holder for source material.

[0171] It is to be understood that typically, the source material is held in place by a holder, as in a structure keeping the bulk of the source material in place, allowing carrier gas to flow at or through the source material in the holder, and allowing the EM-radiation to radiate the source material at or in the holder.

[0172] In some examples, applying 350 EM-radiation on a region of the source material comprises radiating a spot on the source material. Preferably applying 350 EM-radiation on a region of the source material is performed in a large spot and small heating depth, around 0.5 mm or less. The spot is preferably scanned over the surface quite fast, such as irradiating with 2kW a spot with a spot diameter of 10 mm for 10 ms, or sweeping the spot over the surface at 1 m / s. This may give a growth rate of 0.7 mm / h on a 200 mm diameter substrate for a SiC growth setup. If the spot lingers significantly longer on the same spot, such as 1 s on the same spot, the heat will go deeper, such as 1 mm, and the growth rate may increase to 2 mm / h. Hence growth rate may be controlled by the spot size, hold time, or sweeping speed. A system with reasonable directionality of carrier gas may tailor the shape of crystal growth by tuning the spot hold time, spot size and radiation intensity.

[0173] In some examples, the method comprises maintaining a gas pressure in the range of 20 to 150 kPa inside the internal volume while applying 350 EM-radiation on a region of the source material. In some of these examples, the method comprises maintaining a gas pressure in the range of 25 to 200 kPa, 15 to 400 kPa, or 10 to 1000 kPa.

[0174] In some examples, the method further comprises measuring 360 growth chamber state utilizing a set of sensors. In some of these examples, measuring 360 growth chamber state comprises optical measurements of the crystal being grown, optical measurements of the source material, and / or measuring composition of carrier gas exiting the growth chamber.

[0175] In some examples, the method further comprises controlling 370 the EM-radiation during crystal growth based on measured growth chamber state, wherein controlling 370 the EM- radiation comprises aiming the position of radiation on the source material and / or controlling the radiation intensity based on the measured growth chamber state, thus impacting the crystal growth of the crystal being grown.

[0176] In some examples, controlling 370 the EM-radiation during crystal growth based on measured growth chamber state comprises controlling heating and / or gas flow in the growth chamber.

[0177] Returning to fig. 2 and fig. 3 an example scenario of utilizing the growth chamber for SiC single crystal growth will be described.

[0178] The source material is weighed and poured into a cup with small holes in the bottom to allow the carrier gas to flow through the cup. The size of the holes are smaller than the SiC particles that are loaded. The size of the particles that are loaded match the desired porosity and hence thermal conductivity after the optional in-situ pre-sintering. Pre-sintering of the source powder can be done externally as well. The growth chamber is loaded with the cup containing the source material and the lower chamber hatch is closed. The source distance to the top edge of the chamber is checked and adjusted with the lifting mechanism. A seed crystal is prepared with an optional backside coating. The seed is attached or otherwise fixed to the seed holder which is attached to the upper hatch via a graphite rod. The height of the seed is checked to the bottom of the hatch and adjusted if necessary with the lifting mechanism. The source to seed distance is preferably between 50 - 200 mm. The upper hatch is closed and rotation of the source and seed are started. The chamber is carefully evacuated down to a vacuum below 1 mbar. With the pump still running, the throttle valve set to control mode maintaining the desired growth pressure (normally between 400 - 800 mbar), and a small flow of Ar is introduced into the chamber. The flows are gradually increased until the desired flow is reached. A flow of 1 - 5 SLM is normally enough to achieve a growth rate of more than 1 mm / h. The flow may be blended with 0.5 - 2 SLM of hydrogen depending on the spot temperature. Heating may be started while the flows and pressure is ramping up. The heating should not be too fast, and the entire temperature ramp up to 2000 °C should take around 30 - 60 minutes. A typical growth temperature is around 2000 °C. The heating should also ensure that the seed temperature is uniform and at the same temperature as the source or slightly lower. This can be achieved by controlling the heaters individually around the source and seed. The final temperature of the source should be somewhere between 1600 - 2200 °C.

[0179] Once the source temperature has reached its steady state temperature, e.g. 1800 °C, the laser is started at low power and a spot size of 10 mm in diameter and it is scanned over the source surface. The temperature of the source surface is checked as well as the spot temperature which should be 50 - 100 °C higher than the seed temperature. The growth rate should be checked so that there is not a too high growth rate during this final ramp up. When the final temperature, e.g. 2000 °C, is reached, the laser power is increased, and the spot diameter is reduced such that the spot temperature reaches 2400 or more. At a growth pressure of 600 mbar, a carrier gas flow of 5 SLM, and source temperature of 1600 °C, and using a spot size of 6 mm in diameter and a net laser power of 1.2 kW, a growth rate of 1 mm / h is achieved on a 230 mm diameter crystal. The spot temperature in this example is about 2500 °C.

[0180] An alternative way to start the run is to continue heating the source up to the growth temperature and let the source lead the seed temperature with a few degrees. Once at the growth temperature e.g. 2000 °C, the laser can be ramped up to power until the desired growth rate and / or quality is obtained. Once the laser is started, the source temperature can be lowered so that the surface temperature of the source does not become too high.

Claims

CLAIMS1. A method for growing a crystal in a growth chamber, the method (300) comprises- providing (310) a seed crystal (180) into an internal volume (110) of said growth chamber (100), wherein the growth chamber is arranged to grow said crystal at said seed crystal (180);- providing (320) a source material (120) comprising material for growing said crystal at said seed crystal (180) into said internal volume (110);- flowing (340) carrier gas (130) to the source material (120) and thereafter to the seed crystal (180); and- applying (350) electromagnetic, EM, radiation on a region (120') of the source material (120), thereby releasing material from the source material (120) and allowing the carrier gas flow (130) to transport said released material to the seed crystal (180), whereby the crystal is grown at the seed crystal (180).

2. The method according to claim 1, further comprising heating (330) the internal volume (110) to at least 1000°C utilizing a heating device (150) comprised in said growth chamber (100).

3. The method according to claim 1 or 2, wherein flowing (340) carrier gas (130) to the source material (120) and thereafter to the seed crystal (180) comprises flowing (340) carrier gas (130) through the source material (120).

4. The method according to any preceding claim, wherein the crystal to be grown at the seed crystal (180) is a crystal of silicon carbide, SiC, aluminium nitride, AIN, gallium nitride, GaN, gallium oxide, GajOs, and / or zinc oxide, ZnO, and wherein the source material (120) comprises SiC, AIN, GaN, GajOs, and / or ZnO.

5. The method according to any preceding claim, wherein applying (350) EM-radiation on a region (120') of the source material (120) comprises causing at least some material of the source material (120) to undergo sublimation.

6. The method according to any preceding claim, wherein the seed crystal (180) and the source material (120) are heated to the range of 1000-2500°C.

7. The method according to any preceding claim, wherein heating the seed crystal (180) and the source material (120) is performed utilizing a resistive heater and / or an induction heater.

8. The method according to any preceding claim, wherein applying EM-radiation on a part of the source material (120) comprises applying EM-radiation utilizing a continuous wave laser and / or a pulsed laser arranged to pulse for at least 1 ms.

9. The method according to any preceding claim, further comprising the step of providing a curtain gas flow (131) through the internal volume (110), wherein the curtain gas flow (131) is arranged to provide a gas curtain for the flow of carrier gas (130) exiting through the source material (120).

10. The method according to any preceding claim, wherein the carrier gas comprises argon and / or hydrogen.

11. The method according to any preceding claim, wherein crystal growth is performed with a gas pressure in the range of 20 to 150 kPa.

12. A growth chamber for growing a crystal, the growth chamber (100) comprises an internal volume (110), a seed crystal holder (170) arranged to hold a seed crystal (180) in said internal volume (110), an EM-radiation source (140), and a heating device (150) arranged to heat the internal volume (110) to at least 1000°C; wherein the growth chamber (100) is arranged to receive the seed crystal (180) at the seed crystal holder (170), and to receive, in said internal volume (110), a source material (120) comprising material for growing said crystal, and to provide a flow of carrier gas (130) to the source material (120) and thereafter to the seed crystal (180); and wherein the EM-radiation source (140) is arranged to provide EM-radiation to a region (120') of the source material (120), thereby releasing material from the source material (120) and allowing the carrier gas flow (130) to transport said released material to the seed crystal (180), whereby the crystal is grown at the seed crystal (180).

13. The growth chamber according to claim 12, wherein the chamber is arranged to provide a curtain gas flow (131) through the internal volume (110), wherein the curtain gas flow (131) is arranged to provide a gas curtain for the flow of carrier gas (130) exiting through the source material (120).

14. The growth chamber according to claim 12 or 13, wherein the growth chamber comprises a computer arranged to control the EM-radiation source (140), the seed crystal holder (170), the flow of carrier gas (130), the flow of curtain gas (131) and / or the heating device (150).

15. A system for growing a crystal, the system (200) comprises a growth chamber (100) according to any of claims 12 to 14, a computer (210), and a set of gas flow control devices (221,222), wherein the computer (210) is connected to the growth chamber (100) and the set of gas flow control devices (221,222), and wherein the computer (210) is arranged to control the set gas flow control devices (221,222) to control the carrier gas flow through the growthchamber (100), and control the EM-radiation source (140) to radiate the source material (120).

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