WO2025136109A1

WO2025136109A1 - Cleaning method for removing parasitic grown silicon carbides and an interior part of an epitaxy process chamber and an epitaxy process system

Info

Publication number: WO2025136109A1
Application number: PCT/NL2024/050698
Authority: WO
Inventors: Guiming SONG; Bernd KOFER; Marc VAN MUNSTER
Original assignee: Schunk Kohlenstofftechnik GmbH; Schunk Xycarb Technology BV
Current assignee: Schunk Kohlenstofftechnik GmbH; Schunk Xycarb Technology BV
Priority date: 2023-12-22
Filing date: 2024-12-23
Publication date: 2025-06-26
Anticipated expiration: 2026-06-22
Also published as: WO2025136086A1

Abstract

A cleaning method for removing parasitic grown silicon carbides from an interior part of an epitaxy process chamber for epitaxial growth of silicon carbide, said interior part comprising a pyrolytic carbon coating, wherein said pyrolytic carbon coating (105) has a highly layered microstructure and comprises less than 5 ppm impurities, said method comprising the steps of: 1a) subjecting said interior part to a halogen-containing gas at a temperature of from 150 to 1700 °C to convert said parasitic grown silicon carbides present on said interior part into carbide-derived carbon (CDC) material, wherein said halogen-containing gas is chlorine, bromine, or a combination of two or more thereof, which may be mixed with nitrogen, argon, helium, or a combination thereof, or 1b) subjecting said interior part to an inert gas at a temperature of from 1000 to 2400 °C and at a pressure of from 1x10-10 to 500 mbar to convert said parasitic grown silicon carbides present on said interior part into said CDC material; 2) removing said CDC material from said interior part to obtain an outer surface of said interior part that is free or substantially free of said CDC material. An interior part of an epitaxy process chamber for epitaxial growth of silicon carbide suitable to be cleaned by the cleaning method and an epitaxy process system, comprising a controller and a epitaxy process chamber, wherein said epitaxy process chamber comprises at least one interior part, and wherein said controller is arranged for running said epitaxy process chamber in a cleaning mode, wherein parasitic grown silicon carbides on said at least one interior part in said epitaxy process chamber are removed in accordance with the cleaning method.

Description

TITLE Cleaning method for removing parasitic grown silicon carbides and an interior part of an epitaxy process chamber and an epitaxy process system

TECHNICAL FIELD

[0001] The present invention relates to a cleaning method for removing parasitic grown silicon carbides from an interior part of an epitaxy process chamber for epitaxial growth of silicon carbide, to an interior part of an epitaxy process chamber, and to a and epitaxy process system.

BACKGROUND

[0002] The silicon carbide epitaxy equipment market is experiencing rapid growth, primarily driven by the increasing electrification of the automotive industry. However, a challenge arises during the chemical vapor deposition (CVD) process of the silicon carbide epitaxy layer on silicon carbide wafers. The epitaxy layer tends to deposit on both the surfaces of the wafer carrier or susceptor and the interior parts inside the chamber, even though this simultaneous deposition is unnecessary.

[0003] The accumulation of these parasitic or unnecessary silicon carbide layers, also known as parasitic grown silicon carbides, leads to the emission of particles and disruption of the gas flow, significantly impacting the quality of the epitaxial layer. Furthermore, the parasitic grown silicon carbides may lead to dimensional issues as the layers of the parasitic grown silicon carbides can grow very thick thereby hindering movement and/or placement of parts. Consequently, it becomes imperative to periodically remove these parasitic silicon carbide layers from the surfaces of the parts. This removal process cannot be achieved easily through chemical methods, mechanical methods, or a combination of both, ensuring the repeatability and continued usability of the parts.

[0004] Unlike the epitaxy of silicon, where frequent etching of parasitic silicon deposits can be removed using HCI, with a minimal impact on the surfaces that are polycrystalline silicon carbide (SiC) coated graphite that in turn are used to protect the process chamber from otherwise exposed graphite.

[0005] The deterioration issue arises primarily due to the vulnerability of wafer susceptor or interior parts in the epitaxy chamber, such as graphite or silicon carbide- coated graphite, to etching and degradation in the high-temperature epitaxy environment containing hydrogen. During the epitaxy process, hydrogen gas is used in the etching or baking step prior to the silicon carbide deposition. This hydrogen gas attack can cause problems for uncoated porous graphite parts used in the epitaxy process chamber, resulting in carbon particle contamination within the chamber.

[0006] Moreover, uncoated graphite is porous and tends to trap and release impurities, thereby impacting the silicon carbide epitaxy's quality. In addition, when the temperature exceeds approximately 1450 °C, silicon atoms within the silicon carbide- coated graphite parts may escape from the silicon carbide coating surface and deposit onto the silicon carbide wafer surface, disrupting the silicon carbide epitaxy process.

[0007] To address these challenges, metallic carbide coatings, such as niobium carbide (NbC) and tantalum carbide (TaC), are utilized as a protective coating material. However, both NbC and TaC-coated graphite parts can be extremely expensive options. Moreover, these materials offer a better protection of the graphite as these do not sublime and leave TaC or NbC on the SiC wafer backside as SiC does when heated above 1600 °C.

[0008] To address the issue of cleaning parasitic grown silicon carbide layers or films from carbide-coated graphite parts or susceptors, a combination of chemical etch methods and mechanical methods is employed. In the US 11028474 B2 patent, a method is disclosed using a mixed gas containing fluorine gas and inert gas at temperatures ranging from 200 to 500 °C.

[0009] The thickness and distribution of the parasitic silicon carbide layer or particlelike layer on the graphite parts are often highly non-uniform. During the chemical cleaning process, incomplete removal of parasitic silicon carbide in one area may lead to the exposure of the graphite substrate to etching gases in another area. Both CIF3 and F2 gases can etch and degrade the graphite substrate.

[0010] To protect the graphite, pyrolytic carbon (PyC) can be used as a coating on the substrate. Nevertheless, CIF3 and F2 gases still have the potential to etch the pyrolytic carbon layer. While it is possible to tune the etch process and introduce additional steps, the overall cleaning process becomes complex, and a precise temperature control is crucial.

[0011] Mechanical polishing or grinding of the parasitic grown silicon carbides from coated graphite parts is an extremely challenging task, inevitably having a risk of causing extensive surface damage to the coated parts, including silicon carbide- coated graphite, tantalum carbide-coated graphite, niobium carbide-coated graphite, and pyrolytic carbon-coated graphite parts. The existing methods, whether chemical or mechanical, for removing parasitic silicon carbide, result in damage to the tantalum carbide coating, original silicon carbide coating, pyrolytic carbon coating, and graphite part, thus reducing the lifetime of these coatings. Especially, the mechanical grinding method used to remove parasitic silicon carbide layer from tantalum carbide coated graphite parts is being unacceptable now.

[0012] To protect the graphite parts used inside the chamber of silicon carbide epitaxy process, silicon carbide coating and tantalum carbide coating are deposited on the surfaces of the graphite parts, but the current cleaning work of the parasitic silicon carbide layer or particles on the protective coating surface with CIF3, NF3 or CI2, HCI etc. and even mechanical machining always damage both protective layers (silicon carbide and tantalum carbide layers), and therefore the lifetime of both silicon carbide coated graphite parts and tantalum carbide coated parts are short.

[0013] Therefore, there exists a need for a solution to remove parasitic grown silicon carbides from the surfaces of interior parts and/or the inside of the epitaxy process chamber that is used for epitaxial growth of silicon carbide that solves one or more of the above-mentioned problems. OBJECTIVE

[0014] It is therefore an object of the invention to provide for an improved cleaning method for removing parasitic grown silicon carbides from an interior part of an epitaxy process chamber.

[0015] It is a further object of the invention to provide for an improved cleaning method for removing parasitic grown silicon carbides from an interior part of an epitaxy process chamber, wherein the cleaning method enables in-situ cleaning of a silicon carbide (SiC) processing chamber by selective removal of parasitic grown silicon carbides from interior parts of said chamber.

SUMMARY

[0016] The foregoing object is achieved according to a first aspect of the present invention that relates to a cleaning method for removing parasitic grown silicon carbides from an interior part of an epitaxy process chamber for epitaxial growth of silicon carbide, said interior part comprising a pyrolytic carbon coating, wherein said pyrolytic carbon coating has a highly layered microstructure and comprises less than 5 ppm impurities, said method comprising the steps of:

1 a) subjecting said interior part to a halogen-containing gas at a temperature of from 150 to 1700 °C to convert said parasitic grown silicon carbides present on said interior part into carbide-derived carbon (CDC) material, wherein said halogencontaining gas is chlorine, bromine, or a combination of two or more thereof, which may be mixed with nitrogen, argon, helium, or a combination thereof, or

1 b) subjecting said interior part to an inert gas at a temperature of from 1000 to 2400 °C and at a pressure of from 1x1 O'¹⁰ to 500 mbar to convert said parasitic grown silicon carbides present on said interior part into said CDC material;

2) removing said CDC material from said interior part to obtain an outer surface of said interior part that is free or substantially free of said CDC material. [0017] A pyrolytic carbon (PyC) layer is used as a protective layer on the interior part. The PyC layer seals the porous surface of the interior part and reduces the likelihood of impurities becoming trapped and later released from the pores. Furthermore, the PyC layer shields the interior part from chemical attack during etching processes, thereby minimizing damage during the etch process of the silicon carbide wafer in which hydrogen gas is used.

[0018] Two variants of PyC layers, or PyC coatings, may exist. The first variant has a monolithic structure, meaning that the structure of the coating has a uniform, continuous, and seamless structure throughout its entirety. Hence, the coating does not contain distinct layers of carbon.

[0019] In the second variant of the PyC coating, which variant is used in the present invention, the PyC coating has a highly layered microstructure. With “highly layered microstructure” is meant that the PyC coating comprises multiple distinct layers arranged on top of each other in a systematic or repeated manner throughout the PyC coating's thickness, wherein there are clear differences present between two adjacent layers.

[0020] The PyC coating as used in the present invention comprises less than 5 ppm impurities, preferably less than 1 ppm impurities. The impurities may be anything other than carbon, such as metals, silicon, phosphorus, nitrogen, oxygen, and sulphur.

[0021] Having a PyC coating with a highly layered microstructure and less than 5 ppm impurities strongly reduces the susceptibility of the PyC layer to oxidation. In other words, the PyC coating is better resistant to oxidizing conditions such that the interior part, comprising the PyC coating, can be cleaned more efficient with a minimized risk of damaging the PyC coating, thereby extending the lifetime of the interior part.

[0022] Compared to depositing silicon carbide, niobium carbide, or tantalum carbide as a coating on graphite, it is less complex and more economical to deposit the PyC layer on the interior part. [0023] The cleaning method according to the present invention removes the parasitic grown silicon carbides from the interior part’s surface without damaging the pyrolytic carbon coating on the interior part. Therefore, the pyrolytic carbon coated interior part can be reused multiple times for the silicon carbide epitaxy process.

[0024] With the cleaning method according to the invention, a less complex method is provided that uses a halogen-containing gas, such as chlorine gas, to convert the parasitic silicon grown carbides deposited on the surface of the pyrolytic carbon coated interior parts to carbon. These so-called carbide-derived carbon (CDC) layers can be removed from the PyC-coated interior part’s surface at relatively easy and at relatively mild conditions without damaging the PyC coating.

[0025] Furthermore, the claimed method provides the possibility to apply a high temperature in the first step of the cleaning method. This has the benefit that the overall time needed for the cleaning process to complete can be strongly reduced compared to known cleaning processes, because a higher temperature in the first step results in faster conversion of the SiC to the CDC material and reduces the cooldown time between the SiC deposition in the CVD process and the first step of the claimed cleaning method.

[0026] As said, mechanical polishing or grinding of parasitic grown silicon carbides from coated graphite parts is an extremely challenging task, having the risk of causing extensive surface damage to the coated parts. However, the CDC material is a much softer material compared to the parasitic grown silicon carbides and this results in that mechanically - and also manually - removing the CDC material from the interior part strongly reduces the risk of damaging the interior parts. In other words, due to the cleaning method according to the invention, mechanical removing of the CDC material becomes a more attractive option.

[0027] There exist other methods to convert the parasitic grown SiC to the CDC material, like hydrothermal decomposition, but such methods might damage the PyC coating during the process due to the formation of SiC>2. It would be very complex to prevent this. [0028] The first step of the cleaning method, thus any of step 1a) and step 1b), not only enables mechanically/manually removing the CDC material, but it also enables removing the CDC chemically not damaging the coating by using a pyrolytic carbon coating instead of a conventional metal carbide coating, such as silicon carbide or tantalum carbide.

[0029] Preferably, the subjecting of the interior part to the halogen-containing gas in step 1a) is done at a temperature in a range from 390 to 700 °C, more preferably from 450 to 600 °C.

[0030] A benefit of step 1a) is that the resulting CDC material retains the original shape and crystalline surface morphology of silicon carbide (SiC), but with silicon atoms removed from the crystal structure, resulting in atomic vacancies. This unique crystalline structure of the CDC material exhibits different oxidation behaviour compared to the pyrolytic carbon coating on the interior part.

[0031] A benefit of step 1 b) is that there is no need for the epitaxy process system or parts thereof to be adapted for a halogen-containing gas, like CI2. Possibly, the system or parts thereof merely needs limited redesign for it to be withstand temperatures above 1600 °C.

[0032] Converting parasitic SiC grown on Pyrolytic carbon coated parts into CDC material is also known as selective etching, because the subjecting process conditions of step 1a) or step 1b) etch the parasitic SiC and leave the PyC coating intact.

[0033] Due to the specific properties of the pyrolytic carbon coating mentioned above, only the CDC material can be removed during step 2) of the claimed method.

[0034] The proposed method is also known as selective oxidation, because it can oxidize the CDC material efficiently and leaves the (underlying) PyC coating intact. A right oxidation temperature window is needed which allows a selective oxidation between CDC material and the substrate, like PyC coating. A high oxidation temperature not only oxidizes CDC material, but also oxidizes the substrate. A low oxidation temperature may oxidize CDC material not efficiently in order to avoid oxidizing the substrate material. The oxidation resistance of the substrate materials depends on how high the oxidation temperature is. Subjecting the CDC material to an oxygen-containing gas can oxidize the CDC material, but also may oxidize the substrate materials, like PyC coating or graphite or metallic carbide.

[0035] The oxidation onset temperature of the CDC material obtained in both step 1a) and step 1b) is significantly lower than that of graphite and pyrolytic carbon. Consequently, the CDC material can be effectively removed from the pyrolytic carbon coating surface, for example by oxidizing it using an oxygen-containing gas, while minimizing oxidation of the pyrolytic carbon and graphite. This not only enables the repeated use of a pyrolytic carbon-coated graphite part without significant surface damage to the interior part, but also enables in situ cleaning of the interior part.

[0036] The cleaning method allows the use of an interior part comprising a coating of pyrolytic carbon instead of a coating of, for example, silicon carbide or tantalum carbide. Depositing a protective pyrolytic carbon layer on the interior part strongly reduces the costs for producing interior parts, compared to the production of an interior part that includes depositing a silicon carbide or tantalum carbide layer on the interior part.

[0037] Furthermore, the PyC coated interior parts can be reused multiple times for silicon carbide epitaxy, enabling long lifetime. This makes the method particularly suitable as an in-situ cleaning method compared to the current state of the art. Unlike conventional cleaning methods, such as those based on CIF3, which attack carbon materials even at low temperatures and can damage uncoated graphite or insulation materials outside the hot reactor zone, the present method utilizes controlled oxidation temperatures that selectively oxidize the CDC material without attacking graphite or other carbon-based components. This ensures that uncoated materials outside the hot deposition zone remain unaffected, providing an additional advantage for in-situ cleaning applications. [0038] The cleaning method also provides the capability to tune the etching of parasitic SiC and the subsequent oxidation of the resulting CDC material. This tuning ensures that when the PyC coating is exposed during the cleaning process, the etching or oxidation proceeds evenly, minimizing localized damage to the PyC layer. The ability to control the timing of the etch/clean process enables precise removal of CDC material while preserving the structural integrity and performance of the PyC coating. This level of control provides an improvement over current methods, which lack such precision and may therefor result in uneven attack or damage to protective coatings.

[0039] A second aspect of the present invention relates to an interior part of an epitaxy process chamber for epitaxial growth of silicon carbide suitable to be cleaned by a cleaning method according to the first aspect of the present invention, said interior part comprising a pyrolytic carbon coating, wherein said pyrolytic carbon coating has a highly layered microstructure and comprises less than 5 ppm impurities, wherein said interior part is arranged to be subjected to said cleaning method, and/or wherein said interior part is cleaned according to said cleaning method.

[0040] A third aspect of the present invention relates to an interior part contaminated with parasitic grown silicon carbides arranged to be subjected to a cleaning method according to the first aspect of the present invention, said interior part comprising a pyrolytic carbon coating, wherein said pyrolytic carbon coating has a highly layered microstructure and comprises less than 5 ppm impurities. Said interior part may also comprise a diamond-like carbon layer or a glass carbon layer instead of said pyrolytic carbon layer, or a combination of the foregoing types of carbon layers.

[0041] A fourth aspect of the present invention relates to an epitaxy process system, comprising a controller and a epitaxy process chamber, wherein said epitaxy process chamber comprises at least one interior part according to the second or third aspect of the present invention, and wherein said controller is arranged for running said epitaxy process chamber in a cleaning mode, wherein parasitic grown silicon carbides on said at least one interior part in said epitaxy process chamber are removed in accordance with a cleaning method according to the first aspect of the present invention. [0042] In the present disclosure, with “interior” is meant the inner surfaces of the epitaxy process chamber for epitaxial growth of silicon carbide and the surfaces of the interior parts of said epitaxy process chamber that are inside said epitaxy process chamber.

[0043] Corresponding embodiments disclosed below for the first aspect are also applicable for the interior part of an epitaxy process chamber (second aspect), the interior part contaminated with parasitic grown silicon carbides (third aspect), and the device for cleaning of an interior of an epitaxy process chamber (fourth aspect) according to the present invention, unless stated otherwise.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] The present cleaning method is elucidated below with a detailed description.

[0045] In the present description, with “interior part” is meant a part, such as a carbonbased part or more in general, a carbon-based consumable part, inside an epitaxy process chamber that is exposed to a process of epitaxial silicon carbide deposition and as such susceptible to parasitic growth of silicon carbides.

[0046] In the present description, with “pyrolytic carbon” is meant a form of carbon that is produced through the process of pyrolysis, which involves heating a hydrocarbon to nearly its decomposition temperature and permitting the graphite to crystalize. This results in the formation of a material with a high degree of graphitic structure.

[0047] In the present description, with “carbide-derived carbon” (CDC) is meant any form of carbon material that is produced by selectively removing metal atoms, like Si or Ti, from a metal carbide, for example through a process called etching or extraction. Typically, metal carbides like silicon carbide (SiC) or Tantalum carbide (TaC) serve as precursors. The selective removal of metal leaves behind a carbon structure with a porous and high surface area. [0048] In an embodiment, the CDC material, or residuals or species, may be present as a layer or film. The formed CDC may even look like a crystal structure. In step 1a), besides the formation of CDC material, gaseous metal chlorides or fluorides may be formed as well. These are directly removed during the step 1a) of subjecting the interior part to the halogen-containing gas, e.g., the etching step.

[0049] In an embodiment, said step 2) is done by subjecting said CDC material to an oxygen-containing gas at a temperature of from 390 to 700 °C, preferably 450 to 600 °C. Step 2) may be conducted for 0.5 to 24 hours, preferably 3 to 12 hours, more preferably 5 to 10 hours. Furthermore, said step 2) may be conducted once every 1 or 2 weeks or as soon as the parasitic grown silicon carbide layer thickness exceeds a certain predefined thickness, such as 300 pm.

[0050] The use of an oxygen-containing gas with such conditions is normally not considered due to the high risk of oxidizing known PyC coatings. However, the specific PyC coating as used in the present invention, enables to combine the conditions of above-mentioned step 2) with the conditions of above-mentioned step 1a) or step 1 b) and has the effect that it enables to more effectively removing the parasitic SiC such that the PyC coating of the interior part remains intact, which substantially extends the lifetime of the interior part.

[0051] In the present disclosure, with "parasitic grown silicon carbide" is meant silicon carbide (SiC) deposited on surfaces in the reactor area not being the SiC wafer, thus on surfaces of the epitaxy process chamber or on surfaces of the interior parts. It may be present as a layer or (poly crystalline) film and once said layer or film becomes thicker - 1 few mm in thickness - it may have a shape like broccoli flower.

[0052] In an embodiment, said oxygen-containing gas may comprise an oxygen content up to 100 vol.%, such as from 15 to 50 vol.% or from 18 to 25 vol.%. Examples of the oxygen-containing gas are air, oxygen-enriched air, (pure) oxygen, oxygen mixed with one or more inert gases like argon, and nitrogen oxides, such as nitrous oxide (N2O), nitric oxide (NO), nitrogen dioxide (NO2), and dinitrogen tetroxide (N2O4). [0053] In an embodiment, in step 2), the CDC material may be removed by oxidizing the CDC material into carbon monoxide and carbon dioxide.

[0054] In an alternative embodiment, said step 2) may be done by subjecting said CDC material to a gas containing hydrogen and/or ammonia at a temperature of from 500 to 2300 °C, preferably 1000 to 1500 °C.

[0055] In another alternative embodiment, said step 2) may be done by mechanically removing, such as by mechanical polishing or grinding with metal or silicon carbide brushes, gas blowing/blasting, shock wave impulse cleaning, laser ablation, or plasma-assisted cleaning, said CDC material from said outer surface of said interior part.

[0056] In an embodiment, said interior part further comprises a graphite core and said pyrolytic carbon coating is deposited on said graphite core.

[0057] In an embodiment, said interior part is a wafer carrier, also known as a substrate carrier, susceptor, susceptor plate, teller, cover segment, half-moon, ring, upper or lower electrode, shower head, liner, wafer lift pin, pre-heat ring, planetary disc, spindle, spider, ceiling part, or cover segment.

[0058] In an embodiment, said step 1a) is conducted at a temperature of from 500 to 1450 °C, preferably 850 to 1200 °C.

[0059] Step 1a) or step 1b) may be conducted for 0.25 to 6 hours, preferably 1 to 4 hours. Furthermore, step 1a) or step 1 b) may be conducted once or twice per week or as soon as the parasitic grown silicon carbide layer thickness exceeds a certain predefined thickness, such as 300 pm.

[0060] In an embodiment, in step 1 b) argon is used as inert gas. [0061] In an embodiment, said step 1 b) is conducted at a temperature of from 1500 to 2200 °C, preferably 1800 to 2000 °C and/or at a pressure of from 0.0001 to 250 mbar, preferably 0.1 to 100 mbar.

[0062] In an embodiment, said step 1a) and/or step 2) is/are conducted at a pressure of from 100 to 1200 mbar, preferably 500 to 1100 mbar, more preferably 800 to 1050 mbar.

[0063] In an embodiment, said halogen-containing gas is chlorine, bromine, or a combination of two or more thereof, which may be mixed with nitrogen, argon, helium, or a combination thereof, preferably chlorine or chlorine mixed with nitrogen or argon.

[0064] In an embodiment, said step 1a), said step 1 b), and/or said step 2) is done in situ or ex situ.

[0065] The CDC material can be removed via multiple ways in step 2). Subjecting the CDC material to the oxygen-containing gas or to the gas containing hydrogen and/or ammonia to remove said CDC material can be done both in situ and ex situ. The removing in step 2) may be done ex situ by mechanically removing, such as by mechanical polishing or grinding with metal or silicon carbide brushes, gas blowing/blasting, shock wave impulse cleaning, laser ablation, or plasma-assisted cleaning, said CDC material from said outer surface of said interior part.

[0066] The CDC material may be removed from the outer surface of the interior part by milling, turning, grinding, and polishing with loose or bonded grit. Particle blasting, e.g., sand blasting, whereas instead of sand any material with a hardness in between graphite and CDC can be used, can also be used to remove the CDC material.

[0067] Alternatively, said step 2) may be done ex situ by dry chemically cleaning or wet cleaning, such as by cleaning with steam or chemicals, water jet, liquid blasting, or ultrasonic cleaning, or by laser pulsing, plasma cleaning, compressive gas blowing, and plasma enhanced oxidation, using an oxygen plasma. [0068] As another alternative, step 2) can be done in situ, for example by dry chemically removing the CDC material.

[0069] As the remaining CDC layer mainly keeps the same volume and topography as the original SiC, the density of the CDC layer is lower compared to the original SiC layer. This results in a relatively soft layer and therefore, making it relatively easy to remove the CDC layer manually, mechanically, or by blasting.

[0070] Said method may further comprise the step of:

3) washing and optionally drying of said interior part that is free or substantially free of said CDC material to obtain an interior part with reduced impurities and dust particles. Washing can be done with a liquid, such as demineralised or deionised water. Drying can be done in air under ambient conditions.

[0071] The interior part of the epitaxy process chamber for epitaxial growth of silicon carbide is specifically suitable for growing silicon carbide epitaxial layers on silicon carbide wafers, or silicon substrates, or graphite substrates.

[0072] Alumina (AI2O3) may also be a possible substrate material, but is a less suitable material to be used as a substrate, because chloride can etch the AI2O3 in the presence of carbon:

[0073] In an embodiment, said interior part comprises a graphite core that is selected from the group consisting of porous graphite, a graphite matrix, a carbon matrix containing other phases such as carbon fibres or particles.

[0074] In an embodiment, said pyrolytic carbon coating is deposited on said interior part using chemical vapor deposition (CVD) or physical vapor deposition (PVD).

[0075] In an embodiment, said pyrolytic carbon coating is deposited on said interior part using CVD and wherein a precursor gas containing a carbon source, such as methane or propane, is used, and/or a deposition temperature of from 900 to 2200 °C, preferably 1100 to 2000 °C, more preferably 1400 to 1900 °C.

[0076] In an embodiment, said pyrolytic carbon coating has a thickness of from 3 to 70 pm, preferably 5 to 50 pm, more preferably 5 to 25 pm, even more preferably 10 to 20 pm.

[0077] The presented method herein is a selective etching process using CI2, Br2, or a combination thereof, which is very fast (approximately 50-100 pm/hour) and does not etch the PyC coating. This method etches the parasitic SiC by removing Si atoms from the SiC crystalline lattice, leaving a nano-porous carbon matrix (carbide-derived carbon, CDC).

[0078] Especially when using a selective oxidation method, the porous carbon is oxidized without affecting the PyC coating by limiting the oxidation temperature to a specific range (390-700°C, preferably 450-600°C). Normally, the oxidation start temperature of the PyC coating ranges from 450-700°C, depending on the purity and microstructure of the PyC coating.

[0079] Therefore, oxidation methods for removing CDC from PyC coatings are not considered due to the risk of oxidizing the PyC. Our PyC coating has a special microstructure and high purity level (impurity <5 ppm, preferably <1 ppm), allowing selective oxidation to be well implemented, oxidizing only the CDC without affecting the PyC coating. This “selective etching” combined with “selective oxidation” is a new method to remove parasitic SiC from fragile PyC-coated graphite parts.

BRIEF DESCRIPTION OF THE DRAWINGS

[0080] The present invention is described hereinafter with reference to the accompanying drawings in which embodiments are shown and in which like reference numbers indicate the same or similar elements. The invention is in no manner whatsoever limited to the embodiments disclosed therein. Fig. 1 shows a cleaning method for removing parasitic grown silicon carbides from an interior part;

Fig. 2 shows an interior part comprising a pyrolytic carbon coating;

Fig. 3 shows a cross-sectional view of an interior part comprising a pyrolytic carbon coating;

Fig. 4 shows an interior part comprising a pyrolytic carbon coating on which a layer of silicon carbide is deposited;

Fig. 5 shows an interior part comprising a pyrolytic carbon coating that has undergone two cycles of repeated silicon carbide deposition, etching, and oxidation;

Fig. 6A shows a cross-sectional view of an interior part comprising a pyrolytic carbon coating according to the present invention (PyC-A);

Fig. 6B shows a cross-sectional view of an interior part comprising a pyrolytic carbon coating not according to the present invention (PyC-B);

Fig. 7 shows Raman spectra of the PyC-A coating and the PyC-B coating.

DETAILED DESCRIPTION OF THE DRAWINGS

[0081] Fig. 1 shows a flow chart of the cleaning method 1 for removing parasitic grown silicon carbides 101 from an interior part 103 of an epitaxy process chamber for epitaxial growth of silicon carbide. The cleaning method 1 may comprise a first step 1a) of subjecting 3a the interior part 103 to a halogen-containing gas, being chlorine, bromine, or a combination of two or more thereof, at a temperature of from 150 to 1700 °C, preferably from 390 to 700 °C, more preferably from 450 to 600 °C, to convert the parasitic grown silicon carbides 101 present on the interior part into carbide-derived carbon (CDC) material 107.

[0082] As an alternative to said step 1a), the cleaning method 1 may comprise a first step 1 b) of subjecting 3b the interior part 103 to an inert gas, such as argon, at a temperature of from 1200 to 2400 °C and at a pressure of from 1x1O'¹⁰ to 500 mbar to convert the parasitic grown silicon carbides 101 present on the interior part into the CDC material 107. [0083] A second step is removing 5 the CDC material 107, formed in the step of subjecting 3a, 3b, from the interior part 103 to obtain an outer surface 109 of the interior part 103 that is free of substantially free of the CDC material 107.

[0084] Fig. 2 shows an interior part 103 of an epitaxy process chamber for epitaxial growth of silicon carbide. The interior part 103 comprises a graphite plate 101 coated with a layer of pyrolytic carbon (PyC) 105. The PyC 105, which has a highly layered microstructure and comprises less than 5 ppm impurities, preferably less than 1 ppm impurities, is deposited onto the graphite substrate 101 through a high-temperature vapor deposition process. The interior part 103 is arranged to be subjected to silicon carbide (SiC) deposition.

[0085] Fig. 3 shows a cross-sectional view of an interior part 103 that comprises a graphite plate 111 and is coated with a layer of PyC 105. The PyC layer 105 on top of the graphite plate 111 , or graphite core, is clearly shown in the scanning electron microscopy (SEM) image and has an average thickness of approximately 7 to 8 pm. The outer surface 109 of the interior part 103 is free of CDC material 107. Furthermore, the highly layered microstructure of the PyC coating is clearly visible.

[0086] Fig. 4 shows an interior part 103 that comprises a graphite core 111 and a PyC coating 105. Parasitic grown silicon carbides 101 is present on the surface of the interior part 103 as a silicon carbide coating having a thickness of approximately 100 pm. The parasitic grown silicon carbide coating 101 is deposited onto the pyrolytic carbon-coated 105 graphite plate 111 using high-temperature chemical vapor deposition.

[0087] Fig. 5 shows an interior part 103, comprising a graphite plate 111 and a PyC coating 105. The interior part 103 has undergone two cycles of repeated SiC deposition, subjecting 3a the interior part 103 coated with deposited SiC 101 , being parasitic grown SiC, to a halogen-containing gas to convert the parasitic grown SiC 101 into CDC material 107, and removing 5 the CDC material 107 from the interior part 103 to obtain an interior part 103, being a PyC 105 coated graphite plate 111 , having an outer surface 109 that is substantially free of the CDC material 107. [0088] A comparison of the structure of the PyC coating 105 is shown in Figs. 6A and 6B. In Fig. 6A, a cross-sectional view of part of an interior part 103 (being a graphite substrate) comprising a pyrolytic carbon coating 105 according to the present invention (PyC-A) is shown. The highly layered microstructure of the PyC-A 105 is shown by the clearly visible individual layers that can be distinguished from each other in the SEM image. The highly layered microstructure is almost absent in PyC-B coating, provided on a graphite substrate, shown in Fig. 6B, which obviously has a more monolithic-like structure.

[0089] Raman spectra of the PyC-A coating 105 and of the PyC-B coating are shown in Fig. 7. Fig. 7 shows the peak intensities (I) in the wavenumber (A) range from 450 to 3500 cm^-1. G-band corresponds to the in-plane vibration of sp²-bonded carbon atoms and is associated with the stretching of C-C bond. It is a signature of graphitic materials and indicates the presence of ordered graphitic domains. A high intensity indicates a significant amount of graphitic (sp²) carbon present. A broader G band can indicate the presence of strain or defects within the graphitic structure. D-band is associated with the breathing modes of sp² carbon rings and requires a defect or edge to be active. D-band raises from a double resonance process involving intervalley scattering of phonons near the K point in the Brillouin zone. So, D-band is associated to the presence of defects and disorder in the carbon structure, and it is referred to as the “disorder” band. A higher intensity of D-band indicates that the material has more defects (structural imperfections, like disruptions in the sp² -bonded carbon network) and higher degree disorder. The positions of the peaks of the G-band and D-band for each PyC coating are provided in Table 1.

Table 1. Peak positions for coatings PyC-A and PyC-B.

[0090] The peak intensity ratio of G-band/D-band is an indication of the rate of ordering of in-plane of carbon atoms in the microstructure of the graphite (the substrate 111). As becomes clear from Fig. 7, the G-band/D-band ratio for PyC-A is much higher than for PyC-B, indicating a better ordering of in-plane of the carbon atoms in the microstructure of the graphite substrate of PyC-A.

[0091] Modifications and additions to the embodiments disclosed above are obvious to those skilled in the art and covered by the scope of the appended claims. Embodiments and examples of the first aspect of the present invention are also applicable to the second, third and fourth aspects of the present invention.

[0092] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope thereof. One or more of the objects of the invention are achieved by the appended claims.

EXAMPLES

[0093] Oxidation experiments have been executed to show the oxidation rates of different types of carbon materials. Table 2 gives the oxidation rates of two different PyC coatings, being the PyC-A and PyC-B as disclosed above, together with the oxidation rates of graphite and CDC material.

Table 2. Isothermal oxidation rate of different carbon materials in air.

The 55 pm CDC layer cracked and peel off from the graphite substrate after oxidized at 600 °C for 30 min.

** The oxidation of PyC-B coating was tested at 450 °C. *** The oxidation of PyC-B coating at 600 °C was not tested.

[0094] These results show that the PyC-A coating, having the highly layered microstructure, shows much better resistance against oxidation compared to the PyC- B coating, at least under oxidation conditions at which the CDC material is oxidized.

[0095] To efficiently remove the CDC material without damaging the PyC coating using a selective oxidation method, a high oxidation temperature is preferable. However, some PyC coatings, such as the PyC-B coating, will be definitely oxidized when the CDC carbon is oxidized. Therefore, the PyC-A coating is more suitable for this purpose compared to the PyC-B coating. In the present invention, a PyC coating with a highly layered microstructure, such as PyC-A as shown in Fig. 6A, is much more favourable for the purpose of cleaning an interior part with the cleaning method 1 according to the present invention. This enables us to remove the CDC material from the PyC-coated graphite part surface via a selective oxidation process within a temperature range of 390-700 °C, preferably 450-600°C.

[0096] Therefore, oxidation methods for removing CDC material from PyC coatings are not considered due to the risk of oxidizing the PyC. The PyC coating according to the present invention has a special highly layered microstructure and high purity level (impurity <5ppm, preferably <1 ppm), allowing selective oxidation to be well implemented, oxidizing only the CDC material without affecting the PyC coating. This “selective etching” combined with “selective oxidation” is a new method to remove parasitic SiC from fragile PyC-coated interior parts.

CLAUSES

1. A cleaning method for removing parasitic grown silicon carbides from an interior part of an epitaxy process chamber for epitaxial growth of silicon carbide, said interior part comprising a pyrolytic carbon coating, said method comprising the steps of:

1a) subjecting said interior part to a halogen-containing gas at a temperature of from 150 to 1700 °C to convert said parasitic grown silicon carbides present on said interior part into carbide-derived carbon (CDC) material, wherein said halogencontaining gas does not consist of or contain chlorine trifluoride or fluorine gas, or 1 b) subjecting said interior part to an inert gas at a temperature of from 1000 ( preferably 1200) to 2400 °C and at a pressure of from 1x10^-10 to 500 mbar to convert said parasitic grown silicon carbides present on said interior part into said CDC material;

2) removing said CDC material from said interior part to obtain an outer surface of said interior part that is free or substantially free of said CDC material.

2. Cleaning method according to clause 1 , wherein said step 2) is done by subjecting said CDC material to an oxygen-containing gas at a temperature of from 390 to 670 °C, preferably 450 to 600 °C.

3. Cleaning method according to clause 1 , wherein said step 2) is done by subjecting said CDC material to a gas containing hydrogen and/or ammonia at a temperature of from 500 to 2300 °C, preferably 1000 to 1500 °C.

4. Cleaning method according to clause 1 , wherein said step 2) is done by mechanically removing, such as by mechanical polishing or grinding with metal or silicon carbide brushes, gas blowing/blasting, shock wave impulse cleaning, laser ablation, or plasma-assisted cleaning, said CDC material from said outer surface of said interior part.

5. Cleaning method according to any of the preceding clauses, wherein said interior part further comprises a graphite core and said pyrolytic carbon coating is deposited on said graphite core.

6. Cleaning method according to any of the preceding clauses, wherein said interior part is a wafer carrier, also known as a substrate carrier, susceptor, susceptor plate, teller, cover segment, half-moon, ring, upper or lower electrode, shower head, liner, wafer lift pin, pre-heat ring, planetary disc, spindle, spider, ceiling part, or cover segment. 7. Cleaning method according to any of the preceding clauses, wherein said step 1a) is conducted at a temperature of from 500 to 1450 °C, preferably 850 to 1200 °C.

8. Cleaning method according to any of the preceding clauses, wherein said step 1 b) is conducted at a temperature of from 1500 to 2200 °C, preferably 1800 to 2000 °C, and/or at a pressure of from 0,001 to 250 mbar, preferably 0,1 to 100 mbar.

9. Cleaning method according to any of the preceding clauses, wherein said step 1a) and/or step 2) is/are conducted at a pressure of from 100 to 1200 mbar, preferably 500 to 1100 mbar, more preferably 800 to 1050 mbar.

10. Cleaning method according to any of the preceding clauses, wherein said halogen-containing gas is chlorine, bromine, or a combination of two or more thereof, which may be mixed with nitrogen, argon, helium, or a combination thereof, preferably chlorine or chlorine mixed with nitrogen or argon.

11. Cleaning method according to any of the preceding clauses, wherein said step 1a), said step 1 b), and/or said step 2) is done in situ or ex situ.

12. An interior part of an epitaxy process chamber for epitaxial growth of silicon carbide suitable to be cleaned by a cleaning method according to any of the preceding clauses, said interior part comprising a pyrolytic carbon coating, wherein said interior part is arranged to be subjected to said cleaning method, and/or wherein said interior part is cleaned according to said cleaning method, and/or an interior part contaminated with parasitic grown silicon carbides arranged to be subjected to said cleaning method.

13. Interior part according to clause 12, wherein said interior part comprises a graphite core that is selected from the group consisting of porous graphite, a graphite matrix, a carbon matrix containing other phases such as carbon fibres or particles.

14. Interior part according to clause 12 or 13, wherein said pyrolytic carbon coating is deposited on said interior part using chemical vapor deposition (CVD) or physical vapor deposition (PVD). 15. Interior part according to any of the clauses 12 to 14, wherein said pyrolytic carbon coating is deposited using CVD on said interior part and wherein a precursor gas containing a carbon source, such as methane or propane, is used, and/or a deposition temperature of from 900 to 2200 °C, preferably 1100 to 2000 °C, more preferably 1400 to 1900 °C.

16. Interior part according to any of the clauses 12 to 15, wherein said pyrolytic carbon coating has a thickness of from 3 to 70 pm, preferably 5 to 50 pm, more preferably 8 to 25 pm, more preferably 10 to 20 pm.

17. An epitaxy process system, comprising a controller and a epitaxy process chamber, wherein said epitaxy process chamber comprises at least one interior part according to any of the clauses 12 to 16, and wherein said controller is arranged for running said epitaxy process chamber in a cleaning mode, wherein parasitic grown silicon carbides on said at least one interior part in said epitaxy process chamber are removed in accordance with a cleaning method according to any of the clauses 1 to 11.

Claims

1. A cleaning method (1) for removing parasitic grown silicon carbides (101) from an interior part (103) of an epitaxy process chamber for epitaxial growth of silicon carbide, said interior part comprising a pyrolytic carbon coating (105), wherein said pyrolytic carbon coating (105) has a highly layered microstructure and comprises less than 5 ppm impurities, said method (1) comprising the steps of: la) subjecting (3a) said interior part to a halogen-containing gas at a temperature of from 150 to 1700 °C to convert said parasitic grown silicon carbides (101) present on said interior part (103) into carbide-derived carbon (CDC) material (107), wherein said halogen-containing gas is chlorine, bromine, or a combination of two or more thereof, which may be mixed with nitrogen, argon, helium, or a combination thereof, or l b) subjecting (3b) said interior part (103) to an inert gas at a temperature of from 1000 to 2400 °C and at a pressure of from 1x1 O'¹⁰ to 500 mbar to convert said parasitic grown silicon carbides (101) present on said interior part (103) into said CDC material (107);

2) removing (5) said CDC material (107) from said interior part (103) to obtain an outer surface (109) of said interior part (103) that is free or substantially free of said CDC material (107).

2. Cleaning method (1) according to claim 1 , wherein said step 2) is done by subjecting said CDC material (107) to an oxygen-containing gas at a temperature of from 390 to 700 °C, preferably 450 to 600 °C.

3. Cleaning method (1) according to claim 1 , wherein said step 2) is done by subjecting said CDC material (107) to a gas containing hydrogen and/or ammonia at a temperature of from 500 to 2300 °C, preferably 1000 to 1500 °C.

4. Cleaning method (1) according to claim 1 , wherein said step 2) is done by mechanically removing, such as by mechanical polishing or grinding with metal or silicon carbide brushes, gas blowing/blasting, shock wave impulse cleaning, laser ablation, or plasma-assisted cleaning, said CDC material (107) from said outer surface (109) of said interior part (103).

5. Cleaning method (1) according to any of the preceding claims, wherein said interior part (103) further comprises a graphite core (111) and said pyrolytic carbon coating (105) is deposited on said graphite core (111).

6. Cleaning method (1) according to any of the preceding claims, wherein said interior part (103) is a wafer carrier, also known as a substrate carrier, susceptor, susceptor plate, teller, cover segment, half-moon, ring, upper or lower electrode, shower head, liner, wafer lift pin, pre-heat ring, planetary disc, spindle, spider, ceiling part, or cover segment.

7. Cleaning method (1) according to any of the preceding claims, wherein said step 1a) is conducted at a temperature of from 500 to 1450 °C, preferably 850 to 1200 °C.

8. Cleaning method (1) according to any of the preceding claims, wherein said step 1 b) is conducted at a temperature of from 1500 to 2200 °C, preferably 1800 to 2000 °C, and/or at a pressure of from 0,001 to 250 mbar, preferably 0,1 to 100 mbar.

9. Cleaning method (1) according to any of the preceding claims, wherein said step 1a) and/or step 2) is/are conducted at a pressure of from 100 to 1200 mbar, preferably 500 to 1100 mbar, more preferably 800 to 1050 mbar.

10. Cleaning method (1) according to any of the preceding claims, wherein said halogen-containing gas is chlorine, bromine, or a combination of two or more thereof, which may be mixed with nitrogen, argon, helium, or a combination thereof, preferably chlorine or chlorine mixed with nitrogen or argon.

11. Cleaning method (1) according to any of the preceding claims, wherein said step 1a), said step 1 b), and/or said step 2) is done in situ or ex situ.

12. An interior part (103) of an epitaxy process chamber for epitaxial growth of silicon carbide (101) suitable to be cleaned by a cleaning method (1) according to any of the preceding claims, said interior part (103) comprising a pyrolytic carbon coating (105), wherein said pyrolytic carbon coating (105) has a highly layered microstructure and comprises less than 5 ppm impurities, wherein said interior part (103) is arranged to be subjected to said cleaning method (1), and/or wherein said interior part (103) is cleaned according to said cleaning method (1).

13. An interior part (103) contaminated with parasitic grown silicon carbides (101) arranged to be subjected to a cleaning method (1) according to any of the claims 1 to 11 , said interior part (103) comprising a pyrolytic carbon coating (105), wherein said pyrolytic carbon coating (105) has a highly layered microstructure and comprises less than 5 ppm impurities.

14. Interior part (103) according to claim 12 or 13, wherein said interior part (103) comprises a graphite core (111) that is selected from the group consisting of porous graphite, a graphite matrix, a carbon matrix containing other phases such as carbon fibres or particles.

15. Interior part (103) according to any of the claims 12 to 14, wherein said pyrolytic carbon coating (105) is deposited on said interior part (103) using chemical vapor deposition (CVD) or physical vapor deposition (PVD).

16. Interior part (103) according to any of the claims 12 to 15, wherein said pyrolytic carbon coating (105) is deposited using CVD on said interior part (103) and wherein a precursor gas containing a carbon source, such as methane or propane, is used, and/or a deposition temperature of from 900 to 2200 °C, preferably 1100 to 2000 °C, more preferably 1400 to 1900 °C.

17. Interior part (103) according to any of the claims 12 to 16, wherein said pyrolytic carbon coating (105) has a thickness of from 3 to 70 pm, preferably 5 to 50 pm, more preferably 8 to 25 pm, more preferably 10 to 20 pm.

18. An epitaxy process system, comprising a controller and a epitaxy process chamber, wherein said epitaxy process chamber comprises at least one interior part (103) according to any of the claims 12 to 17, and wherein said controller is arranged for running said epitaxy process chamber in a cleaning mode, wherein parasitic grown silicon carbides (101) on said at least one interior part (103) in said epitaxy process chamber are removed in accordance with a cleaning method (1) according to any of the claims 1 to 11 .