Etching of silicon carbide films from reactor components

Abstract

To provide etching of a silicon carbide film from a reactor component.SOLUTION: The present invention relates to a method for etching silicon carbide deposits from one or more workpieces in a reaction chamber to deposit a silicon carbide layer on a substrate. The method includes (I) providing a deposit of silicon carbide on one or more workpieces in a reaction chamber of a reactor for deposition of silicon carbide, and (II) performing at least one cycle of an etching process. The invention further relates to a reactor adapted to carry out said method.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the field of epitaxial deposition of semiconductor deposits on substrates, and in particular to a method and reactor adapted to perform chemical etching of silicon carbide from a reactor workpiece. [Background technology]

[0002] During an epitaxial deposition process, one or more single-crystalline semiconductor layers are grown in a controlled manner on one or more rotating substrates. However, during this process, unwanted semiconductor deposits may also grow simultaneously on other parts of the reaction chamber exposed to the process gases.

[0003] In fact, during epitaxial deposition of single crystal silicon carbide onto a substrate, for example, epitaxial deposition of 3C, 4H, or 6H silicon carbide polytypes, users often find uncontrolled silicon carbide buildup on structural and functional parts of the reaction chamber, hereinafter referred to as the "workpiece." Note that this undesired silicon carbide buildup is very difficult to remove due to the hardness of the material, and conventional techniques used in the silicon semiconductor industry are not suitable for removing silicon carbide parasitic deposits.

[0004] In contrast to an ordered, monocrystalline layer deposited on a substrate, silicon carbide deposits generally contain polycrystalline and / or amorphous forms of silicon carbide. Typically, the deposits are a mixture of both polycrystalline and amorphous silicon carbide. The latter may constitute up to 20-60% of the total, as can be observed in XRD measurements, although the relative ratios of the two forms may be subject to relevant local and average variations.

[0005] The above parasitic phenomena are particularly relevant to hot-wall reactors and primarily affect the upstream end of the chamber (i.e., where the precursor gases enter the reaction chamber), as well as elements surrounding and in contact with the substrate.

[0006] It should be noted that unwanted SiC buildup occurs not only on bare surfaces of the reaction chamber, but also on preventatively coated workpieces.

[0007] In fact, graphite reaction chamber parts may be coated with a TaC layer to protect the graphite surface during cleaning operations. Alternatively, a thin coating of SiC may be used to seal exposed porous graphite surfaces to prevent contamination. In this case, the SiC coating used on the graphite workpiece is in polycrystalline form and has a smooth outer surface with a surface roughness well below 6.3 μm Ra, and typically well below 1 μm Ra.

[0008] It has been observed that parasitic deposition of SiC deposits on workpieces in reaction chambers often results in the rapid growth of cauliflower-like porous dendritic structures, which ultimately affect the quality of the deposited layer on the semiconductor substrate. These parasitic deposits have a rough appearance with macroscopic wrinkles.

[0009] To prevent the adverse effects of parasitic deposition on the deposition process, the reaction chamber undergoes frequent preventative maintenance (PM) procedures, for example, every 100 μm to 2000 μm of total epitaxial layer growth.

[0010] During PM, the machine is cooled and purged, and some or all of the affected workpieces are manually removed from the chamber for mechanical cleaning, disposal, and / or replacement.

[0011] PM operations negatively impact reactor productivity and significantly affect the economics of epitaxial deposition processes. In fact, PM operations currently cause several hours of reactor downtime and are typically performed at least once or twice a week.

[0012] In silicon reactors, in-situ or ex-situ chemical etching processes are used to remove unwanted Si parasitic deposits. These methods allow for more reproducible results than their mechanical cleaning counterparts. Furthermore, in-situ etching processes can be performed without the need to open and access the reactor's reaction chamber, which can advantageously reduce reactor downtime and streamline operations.

[0013] However, silicon carbide exhibits very different chemical and physical properties compared to silicon. It is a much harder material and is difficult to attack via chemical means without ultimately damaging the associated reactor workpieces, which are typically made of graphite, and / or introducing potential contaminants into the chamber.

[0014] It should be noted that in-situ etching is typically performed using chemicals that react with parasitic deposits, resulting in gas-phase by-products. In the case of silicon carbide, this process can result in both gas-phase and solid powder-like by-products.

[0015] The presence of powder-like by-products of the etching process in the reaction chamber can affect the quality of the epitaxial deposition process, but can be difficult to remove without significantly extending the etching time, which can damage underlying chamber parts and adversely affect reactor downtime.

[0016] Although methods for etching SiC have been disclosed in the art, these methods typically address the removal of several top layers of well-ordered SiC from a bulk SiC piece, such as those described in U.S. Patent Application Publications US20140030892A1 and US20060001028A1. The chemical etching of SiC in these cases is performed in the absence of an underlying workpiece (potentially of a different composition) that could be damaged in the process. These processes typically remove only a few microns of SiC to reduce bowing of the single-crystal SiC substrate and surface cracking of the SiC substrate holder, respectively. These methods cannot address the removal of uncontrolled parasitic SiC deposits without damaging the affected workpiece.

[0017] It is therefore desirable to provide a new method for etching polycrystalline amorphous SiC parasitic buildup from affected workpieces in a reaction chamber without damaging said workpieces.

[0018] It is also desirable to provide a method for etching polycrystalline / amorphous SiC parasitic buildup that can be performed in-situ, i.e., directly in the reaction chamber, without opening the reactor chamber and / or removing the reactor chamber from the reactor.

[0019] It would further be desirable to provide a novel reactor adapted to carry out the above-described method. It would further be desirable to provide a reactor configured to carry out said method automatically. Summary of the Invention

[0020] This summary is provided to introduce some concepts in a simplified form that are described in more detail below in the detailed description of exemplary embodiments of this disclosure. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0021] The object of the present invention is to overcome the drawbacks of the prior art.

[0022] In particular, it is an object of the present invention to provide a method capable of etching polycrystalline / amorphous SiC deposits from an affected workpiece in a reaction chamber without damaging said workpiece. It is a further object of the present invention to provide a new method capable of etching polycrystalline / amorphous SiC deposits that can be performed in situ.

[0023] It is a further object of the present invention to provide a reactor that can be adapted to carry out the aforementioned new method, optionally in an automated manner.

[0024] The above-mentioned main object is achieved by the invention as defined in the appended claims, which form the main workpiece of this specification.

[0025] It should be noted that the use of reference signs in the claims does not limit the scope of the claims, but their sole purpose is to make the claims easier to understand.

[0026] BRIEF DESCRIPTION OF THE DRAWINGS The examples presented in this disclosure are not meant to be actual representations of any particular materials, structures, or devices, but are merely idealized representations used to describe embodiments of the present disclosure. [Brief explanation of the drawings]

[0027] [Figure 1] 1 illustrates a method according to the present invention, according to one embodiment. [Figure 2] 1 illustrates a method according to the present invention, according to one embodiment. [Figure 3] 1 illustrates a method according to the present invention, according to one embodiment. [Figure 4] 1 illustrates a method according to the present invention, according to one embodiment. [Figure 5] 1 illustrates a method according to the present invention, according to one embodiment. [Figure 6] 6A and 6B detail a routine of the method according to the embodiment illustrated in FIG. 5. [Figure 7] 1 is a cross-sectional XY view of a reaction chamber adapted to carry out the method of the present invention according to one embodiment. [Figure 8] 8 is a lateral view of the reaction chamber of FIG. 7 in the longitudinal plane XZ. [Figure 9] FIG. 1 shows a reactor scheme, according to one embodiment. [Figure 10] 1 is a photograph of a workpiece having silicon carbide deposits. DETAILED DESCRIPTION OF THE INVENTION

[0028] DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS While certain specific embodiments and examples are disclosed below, it will be understood by those skilled in the art that the scope of the invention extends beyond the specifically disclosed embodiments and / or uses of the invention, and obvious variations and equivalents thereof. It is therefore not intended that the scope of the disclosed invention should be limited by the specific disclosed embodiments described below.

[0029] Reference will now be made to the drawings in which like reference numbers identify similar structural features or aspects of the present disclosure.

[0030] In Figures 1-6, optional steps and sub-steps are distinguished from essential steps and sub-steps by using dashed lines instead of solid lines.

[0031] In Figure 9, all digital signal connections are shown with dashed lines, while physical connections are shown with solid lines.

[0032] It will be understood that elements in the figures are illustrated for simplicity and clarity. In particular, some elements or steps may be omitted or may not necessarily be drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of the illustrated embodiments of the present disclosure.

[0033] In a first aspect, the present invention relates to a method 1 for etching silicon carbide deposits 121 from one or more workpieces 120 in a reactor 1000 suitable for epitaxial deposition of monocrystalline silicon carbide layers on substrates.

[0034] "Etching" means chemical etching in the gas phase.

[0035] Method 1 includes the following steps (I) to (II): In step (I), a SiC deposit is present on one or more workpieces in a reaction chamber of a reactor for silicon carbide deposition (block 10). In step (II), at least one cycle of an etching process is performed (block 30, FIGS. 1-5). The etching process allows chemical cleaning / removal of the SiC deposit provided in step (I).

[0036] The etching process includes the following successive steps or phases: A. ramping the reaction chamber to preset etching process conditions; B. Etching the silicon carbide deposit; C. Performing an optional cooling step.

[0037] Steps A, B, and C are set forth in blocks 40, 50, and 70, respectively.

[0038] Specifically, step A includes the following substeps: A1. Temperature of the reaction chamber TR and increasing the temperature to 500 to 1450°C. A2. Increasing the pressure of the reaction chamber to 50-1000 mbar; A3. Optionally flowing an inert gas into the reaction chamber to help reach and maintain the desired temperature and pressure conditions.

[0039] All of the above sub-steps A1-A3 (respectively described in blocks 41, 42, and 43 of FIG. 2), whether required or optional, may be performed in any order, including simultaneously.

[0040] Step A. is performed by gradually adjusting the pressure and temperature conditions from starting values ​​to the desired process values, thereby protecting the reaction chamber from the undesirable effects of sudden changes that may cause stress and damage to mechanical parts and / or cause a lack of uniformity in the process conditions inside the reaction chamber.

[0041] Once the reaction chamber has reached the desired temperature and pressure settings, the actual etching of the SiC parasitic deposits can be performed according to step B.

[0042] Step B includes the following sub-step B1. B1. Delivering a first reactive composition into the reaction chamber (Block 51).

[0043] The first reactive composition comprises one or more reactive gases, i.e., gases suitable for reacting with Si and / or C for etching purposes. In particular, the reactive composition comprises at least a first reactive gas.

[0044] The first reactive gas is a halogen or a halogen compound.

[0045] In one embodiment, when the first reactive gas is a halogen compound, the compound is a hydrogen halide.

[0046] In one embodiment, when the first reactive gas is a halogen compound, the halogen compound is not a metal halide, an interhalogen compound, an organic halogen compound, or a polyhalogen compound.

[0047] The first reactive composition also contains a carrier gas, which is preferably an inert gas. For example, the inert gas may be nitrogen, helium, or argon to avoid contamination of the chamber. Advantageously, the carrier gas may be used to adjust and control the concentration and distribution of the reactive gas in the chamber.

[0048] Although not limited thereto, the halogen or halogen compound may be delivered into the reaction chamber in a molecular, radical, and / or ionized state, such as in a plasma state.

[0049] In a non-limiting example, radicals and / or ions of the first reactive gas may be formed from molecular halogens or halogen compounds inside the reaction chamber due to the temperature and pressure conditions inside the chamber and / or under an RF alternating field.

[0050] Alternatively, the radicals and / or ions of the first reactive gas may be formed just outside the reaction chamber under specific conditions of temperature, pressure, irradiation, and / or electric field.

[0051] The inventors have observed that the molar concentration of the first reactive gas to the carrier gas should be equal to 15-40%. Surprisingly, by selecting this concentration, it is possible to remove parasitic SiC deposits under the temperature and pressure conditions described above without damaging the associated coated or uncoated graphite components. Removal of parasitic SiC deposits does not necessarily have to be performed until 100% removal is achieved. Advantageously, deposits can be removed to a degree suitable for regenerating proper operating conditions inside the reaction chamber, thereby extending the operating time between PM operations.

[0052] The SiC deposits referred to above and below are obtained or can be obtained directly as parasitic deposits of silicon carbide on reaction chamber parts (workpieces) during standard epitaxial deposition processes, in which a SiC layer is deposited on a rotating substrate within the reaction chamber.

[0053] Thus, the SiC deposits are by-products of one or more epitaxial deposition processes of single-crystal SiC layers on rotating substrates, said processes being carried out in a reaction chamber of a reactor, where the by-products form on one or more workpieces in the reaction chamber, surround the substrate, and are exposed to process gases.

[0054] It should be noted that the technical properties of SiC deposits imparted by parasitic accumulation processes are properly defined only in terms of the parasitic processes themselves. While the latter impart recognizable characteristics, such as bumps and wrinkles to the deposit, characterizing SiC deposits in terms of said properties would be unduly limiting.

[0055] These workpieces are typically not fabricated from monocrystalline SiC, and as a result, the SiC deposit is not monocrystalline but contains polycrystalline and / or amorphous forms of silicon carbide. The method is not limited by the specific solid-state properties of the SiC deposit. The latter typically contains or consists of a mixture of both polycrystalline and amorphous SiC, e.g., a mixture of polycrystalline SiC with 20-60% amorphous SiC. The amount of amorphous SiC in the deposit may be subject to significant local and absolute variations.

[0056] The deposited SiC layers are typically single crystalline, generally of, but not limited to, the 3C, 4H, or 6H polytype.

[0057] Parasitic SiC deposits are a well-known undesirable by-product of SiC layer deposition.

[0058] Parasitic SiC deposits occur on surfaces in all parts of the reaction chamber exposed to the SiC precursor gas flow, particularly at the upstream end of the chamber (i.e., where the precursor gas enters the reaction chamber), as well as on elements in close proximity to or in contact with the substrate.

[0059] In particular, workpieces affected by parasitic deposition are removable and fixed parts of the reaction chamber (cover, ring, walls), whether stationary or rotating, as a result of exposure to SiC precursor gases during the deposition process.

[0060] These workpieces are often made from materials that have a much lower hardness compared to SiC, such as coated graphite or bare graphite.

[0061] Parasitic deposition of SiC is a phenomenon that particularly, but not exclusively, affects hot-wall reaction chambers, where the high temperatures of the walls and other parts of the reaction chamber tend to cause parasitic buildup.

[0062] Therefore, in this disclosure and below, the expression "SiC deposit" is considered equivalent to "parasitic SiC film" or "SiC film" or "parasitic SiC deposit" unless otherwise specified, and refers to SiC in polycrystalline and / or amorphous form.

[0063] Furthermore, the term "deposit" in the phrase "SiC deposit" or "silicon carbide deposit" (and the term "film" in the phrase "parasitic SiC film" or "SiC film") does not imply a two-dimensional regular and / or ordered geometric shape. On the contrary, it may refer to an uneven SiC coating formed on one or more surfaces of the affected portion of the reaction chamber, which may exhibit a three-dimensional structure, such as a rough, textured surface, as clearly shown in FIG. 10.

[0064] In this disclosure and below, the terms "deposit" (or "film") and "layer" are used to distinguish undesired parasitic SiC deposits from the desired, controlled SiC layer deposited on a substrate, respectively.

[0065] Parasitic SiC deposits typically exhibit an uneven surface, for example, with a wrinkled appearance and uneven thickness. The surface unevenness is often clearly visible to the naked eye, but is usually, but not always, accompanied by a kalifloral or fractal-like structure, with visible macroscopic depressions and protrusions, possibly resulting from a dendritic-like growth process.

[0066] This phenomenon is particularly visible and affects the quality of the deposited layer when the reaction chamber is run for a total monocrystalline SiC deposition of 100 μm to 2000 μm (on one and the same substrate or on several successively processed substrates without PM cycles in between), e.g., for a total monocrystalline SiC deposition of 200 to 800 μm.

[0067] In this case, the parasitic growth can be etched in a particularly satisfactory manner using the present method.

[0068] The present method can also be satisfactorily used for all single crystal SiC deposition in a wider range, such as 10 μm to 2000 μm, preferably 50 μm to 2000 μm, preferably 100 μm to 2000 μm, and even more preferably 100 to 800 μm.

[0069] FIG. 10 shows a photograph of parasitic SiC deposits 121 on a workpiece 120 positioned on the lower partition 115 of the reaction chamber 100. The workpiece 120, an upstream cover, partially surrounds a receiving area 116 adapted to support a 6-inch substrate. The parasitic SiC deposits appear lighter in color in the grayscale photograph compared to other visible parts of the reaction chamber made of graphite. The deposits 121 coat the surface of the workpiece 120 exposed to the precursor gas with an uneven, granular, and rough film.

[0070] The irregular shape of the parasitic deposits becomes more pronounced the longer the reaction chamber workpiece is exposed to the precursor gas flow.

[0071] Silicon carbide deposits of the present invention may exhibit a surface roughness of greater than 6.3 μm Ra.

[0072] In one embodiment, the optional cooling step C performed after step B comprises the following substeps: C1. The reaction chamber is heated to temperature T c <T R In either case, the temperature is cooled to T c <1000°C (block 71), e.g., T c is 500 to 900 ° C, and cooling; C2. Flowing cooling gas to reach a pressure of 100-1000 mbar inside the reaction chamber (block 72).

[0073] Sub-steps C1 and C2 may be performed in any order, preferably simultaneously.

[0074] Substep C1 may be performed by turning off the heating source and allowing the reaction chamber to cool primarily via radiation. Substep C1 may be sped up by simultaneously performing substep C2.

[0075] The cooling gas used in step C2 can be any gas suitable for accelerating the cooling process of the chamber to the idle temperature. Those skilled in the art can easily select the most appropriate gas depending on budget and time constraints. Non-limiting examples of cooling gases include helium, nitrogen, hydrogen, and combinations thereof.

[0076] FIG. 2 summarizes all steps A, B, and C described above for block 30, step (II), along with their respective substeps.

[0077] In one embodiment, method 1 of the present invention may include a step (II0) of purging the reaction chamber, which is performed after step (I) and is illustrated in Figure 3. The purging step is described in block 20 and may involve performing 1 to 20 cycles of a purging process to clean the reaction chamber and remove residues of other operations / processes performed therein.

[0078] During the purge process, the following substeps (blocks 21 and 22) are executed in sequence, starting with any of the following substeps: - adjusting the pressure of the reaction chamber to ≦1 mbar; - Flowing an inert gas to reach a pressure of 100-1000 mbar inside the reaction chamber.

[0079] Step (II0) may be carried out before step A.

[0080] Alternatively, it can be performed after step B and, if present, before or after step C. This may beneficially remove all traces of the reactive gases used, as well as any by-products of the etching process that may still be present in the chamber.

[0081] Depending on the order in which they are performed, cooling step C may advantageously be utilized to set favorable conditions for carrying out any purging process and / or said optional purging process may help to achieve the effects of cooling step C more efficiently.

[0082] In conclusion, an optional purge process may be performed: 1) before step A, 2) after step B, 3) after step B and before step C as an additional step in the etching process, or 4) after both steps B and C, after the etching process has finished.

[0083] In one embodiment, the flow rate of the first reactive gas is 0.5 to 2.3 mol / (s m2 )

[0084] In one embodiment, step (I) of the method according to the invention comprises performing one or more epitaxial deposition cycles of monocrystalline SiC layers on the same or different substrates in a reaction chamber of a reactor to a predetermined total thickness T of the monocrystalline SiC layers deposited on the one or more successive substrates during the total operating time of the chamber. z This is done by running the program until it reaches

[0085] In this case, T z is preferably 10 μm to 2000 μm, preferably 50 μm to 2000 μm, preferably 100 μm to 2000 μm, even more preferably 100 to 800 μm, even more preferably 200 to 800 μm, and even more preferably 500 to 700 μm.

[0086] During this step, a parasitic SiC deposit of variable and non-uniform thickness is formed on one or more workpieces in the reaction chamber. The resulting SiC deposit has an "equivalent thickness" T z , i.e., the total cumulative thickness T z The thickness is said to be the result of depositing an ordered layer of

[0087] The local thickness of the parasitic deposit is T z It may be significantly different from, and on average,

[0088] Note that the peak of the parasitic deposits is thicker than the thickness T due to the dendritic growth of the deposits. z can be significantly higher than

[0089] In one embodiment, the etching process of the method according to the present invention comprises etching a predetermined total thickness T z The process is performed for 0.10 to 0.6 minutes per 1 μm.

[0090] In one embodiment, the method according to the present invention comprises: z The treatment is carried out for 0.1 to 0.6 minutes per μm.

[0091] In one embodiment, the method according to the present invention comprises: z The treatment is carried out for 0.3 to 0.55 minutes per μm.

[0092] As previously mentioned, in the art, the equivalent thickness of a parasitic deposit is not its average or maximum thickness, since the latter may be subject to significant local variations. The equivalent thickness of a parasitic deposit is equivalent to the thickness of a monocrystalline layer deposited on one or more substrates during one or more successive deposition processes. As the monocrystalline layer grows orderly on the substrate, the parasitic deposit grows at various elevations on a particular workpiece in the reaction chamber. Therefore, it is more meaningful to refer to its equivalent thickness, which is a parameter that is set and controlled during reactor operation and can be easily measured on the actual substrate after the deposition process.

[0093] In one embodiment, the reaction chamber workpiece to be etched is made of graphite (optionally coated with single or polycrystalline silicon carbide having wrinkles with an Ra (surface roughness) of <6.3 μm), pyrolytic graphite, single or polycrystalline diamond, quartz, and / or boron nitride.

[0094] The above-described coatings can help preserve graphite workpieces during preventative maintenance operations and etching processes. They can also prevent contamination of reaction chambers during deposition processes.

[0095] Graphite workpieces coated with single or polycrystalline diamond have been observed to work particularly well in the practice of the present invention, especially when the first reactive gas comprises or consists of fluorine atoms, molecules, or radicals.

[0096] Graphite workpieces coated with pyrolytic graphite have been observed to work particularly well in the practice of the present invention, especially when the first reactive gas comprises or consists of chlorine atoms, molecules, or radicals.

[0097] In one embodiment, the first reactive gas may be selected from the group consisting of F2, ClF, ClF3, ClF5, Cl2, HCl, XeF2, XeF4, XeF6, XeO3, KrF2, Br2, I2, and HBr.

[0098] In one embodiment, the first reactive gas is F2, ClF, ClF3, or ClF5, and step A1 is performed at a temperature of 500 to 1000°C (T R ) is executed.

[0099] Alternatively, the first reactive gas is Cl or HCl; - Step A1 is performed at a temperature of 1000 to 1450°C (T R ), preferably carried out at a temperature of 1150-1350°C, and / or Step A2 is carried out at a pressure of between 50 and 700 mbar, preferably between 150 and 700 mbar.

[0100] In one embodiment, in step A1, the temperature of the reaction chamber is adjusted to 1150 to 1350°C.

[0101] Surprisingly, in this temperature range, the ratio of Si and C etching by the radicals of the first reactive gas is optimized for the overall etching process itself: at higher temperatures, Si etching becomes more prevalent, while at lower temperatures, the etching process becomes less effective overall.

[0102] Of great advantage, the above-described method can be used for in-situ and ex-situ etching of SiC deposits from one or more workpieces in a reaction chamber.

[0103] When the first reactive gas is a halogen, the halogen is preferably selected to be 99.990% or greater in purity, and even more preferably 99.998% or greater in purity.

[0104] During the etching process, due to the pressure and temperature conditions in the reaction chamber, the halogen molecules form radicals that attack the SiC deposits, thereby generating by-products of the etching process, which are then exhausted from the reaction chamber.

[0105] Under the process conditions described in this disclosure, the method according to the present invention allows for adequate removal of both the carbon and Si of the parasitic SiC deposits, suitable for the purpose of resuming the deposition operation, thereby extending the operational life of the reaction chamber between successive PMs.

[0106] For in-situ etching applications, the possibility to chemically clean the reaction chamber after parasitic buildup and set it in a suitable working condition without the need to (a) open the reactor, (b) remove the reaction chamber, and (c) expose its parts to air for cleaning is a considerable improvement over conventional mechanical cleaning techniques.

[0107] Surprisingly, despite the inherent and challenging properties of SiC, it is possible to effectively remove hard and damaging parasitic deposits up to several hundred microns thick without damaging any part of the reaction chamber.

[0108] The above method addresses a long felt need in the industry to provide a method for in-situ cleaning of the reaction chamber of a SiC reactor from parasitic deposits.

[0109] In one embodiment, the first reactive composition used in step B1 includes a second reactive gas.

[0110] For example, the second reactive gas is an oxidizing agent or a reducing agent.

[0111] The second reactive gas may be delivered into the reaction chamber in a molecular, radical, and / or ionized state, such as, but not limited to, a plasma state.

[0112] In a non-limiting example, radicals and / or ions of the second reactive gas may be formed from molecular halogens or halogen compounds inside the reaction chamber due to the temperature and pressure conditions inside the chamber and / or under an RF alternating field.

[0113] Alternatively, radicals and / or ions of the second reactive gas may be formed immediately prior to entering the reaction chamber under specific conditions of temperature, pressure, irradiation, and / or electric field.

[0114] A non-limiting example of a reducing agent is H2.

[0115] By oxidant is meant oxygen compounds, oxygen molecules, or oxygen radicals.

[0116] Examples of oxidizing agents that have been observed to work particularly well in the practice of this invention include: NO, NO, NO, O 2、 O3, and H2O 2。

[0117] The use of a second reactive gas in the first reactive composition may allow for targeting (or preventing the formation of) undesirable by-products of the reaction from the first reactive gas and the SiC deposit.

[0118] In one embodiment, the first reactive gas and the second reactive gas in the first reactive composition are each selected from the group consisting of the following pairs: HCl and N2O, HCl and O3, HCl and H2O2, HCl and O 2、 Cl2 and O2, Cl2 and O3, Cl2 and H2O2, HCl and H2, and HCl and HF.

[0119] In one embodiment, the molar concentration of the second reactive gas in the carrier gas is 0.1 to 20%.

[0120] In one embodiment, the molar concentration of the second reactive gas to the carrier gas is 0.1 to 15%.

[0121] In one embodiment, the molar concentration of the second reactive gas to the carrier gas is 1-10%.

[0122] Surprisingly, it has been observed that the use of halides with oxidizing agents is particularly effective in removing undesirable by-products without harming the underlying workpiece and without producing a solid, powder-like residue.

[0123] In one embodiment, the first reactive composition used in step B1 includes a third reactive gas.

[0124] In one embodiment, step B further comprises the following substeps: B2. Delivering a second reactive composition into the reaction chamber, the second reactive composition comprising one or more reactive gases and a carrier gas (Block 52).

[0125] In this case, the carrier gas is an inert gas and the one or more reactive gases include at least an oxidizer.

[0126] It should be noted that sub-step B2 may be performed before or after sub-step B1.

[0127] If sub-step B2 is performed before sub-step B1, the oxidizing agent may leave behind Si-rich by-products suitable for removal via suction or by reacting with a halogen or halogen compound, in particular a fluorine-based molecule or compound.

[0128] In one embodiment, sub-step B2 is performed after sub-step B1.

[0129] In one embodiment, the molar concentration of the oxidant in the carrier gas is 0.1 to 20%.

[0130] In one embodiment, the molar concentration of the oxidant in the carrier gas is 0.1 to 10%.

[0131] Under the conditions described above, the oxidizing agent can effectively remove any carbon-rich by-products left behind by the first reactive composition.

[0132] A purge step may optionally be performed between sub-steps B1 and B2 or between sub-steps B2 and B1, depending on their order.

[0133] In one embodiment, step B1 includes the following substeps: - optionally venting said one or more reactive gases and / or said carrier gas, by "venting" it is meant bypassing the reaction chamber for a preset period of time. - ramping up the one or more reactive gases and the carrier gas to their respective pre-set nominal flow rates; - delivering the one or more reactive gases and the carrier gas into the reaction chamber at the predetermined nominal flow rates.

[0134] The above sub-steps may be configured with different or the same start times and / or durations for each of the one or more reactive gases and the carrier gas.

[0135] For example, the first reactive gas may have a ramp time TR1 and a constant time TS1, and the inert gas may have a ramp time TR2 and a constant time TS2, where TR1, TS1, TR2, and TS2 may be different from one another. The ramp times for Cl2 and the inert gas may start at different times, and they may be configured to have optional and different vent times.

[0136] It should be noted that all parameters mentioned in this embodiment may be provided as input from a user or may be predetermined settings. The predetermined settings may be calculated based on a calibration curve provided for a given reactor and based on the results achieved. These may be obtained by a person skilled in the art without undue burden and adapted to a particular reaction chamber design at the time of use.

[0137] In one embodiment, the reaction chamber 100 includes at least one monitoring system 500 adapted to monitor an etching parameter indicative of an endpoint of the etching process.

[0138] In this case, the process B according to the invention further comprises a monitoring step (block 60) (see Figures 5 and 6, which show details of block 31 of Figure 5).

[0139] The monitoring step is performed at the end of step B (ie after step B1 and after both step B1 and step B2, if present).

[0140] The monitoring step includes the following substeps: - reading preset target values ​​and, optionally, preset tolerances of said etching parameters (block 62); - reading the actual values ​​of the etching parameters (block 61); - checking whether the actual value has reached the target value, and optionally whether the actual value is within the current tolerance (decision block 63); - repeating step B until said target value (optionally within said current tolerance) is reached.

[0141] Once the target value is achieved, the monitoring step terminates.

[0142] The monitoring system may be a detector suitable for detecting the concentration of silicon and / or carbon in the by-product gases produced after each cycle of the etching step B, such as a mass spectrometer.

[0143] Advantageously, this embodiment has the effect of making it possible to monitor the progress of the method according to the invention.

[0144] In one embodiment, the method according to the invention is carried out in situ to etch silicon carbide deposits from one or more workpieces in a reaction chamber, i.e., the method is carried out when the reaction chamber is located inside a reactor without opening the latter, which may be configured to have at least one gas inlet and at least one gas outlet opening.

[0145] In this case, during step B, the first reactive composition is delivered into the reaction chamber through at least one gas inlet opening, thereby forming by-products of the etching process, which may then advantageously be exhausted through at least one gas outlet opening.

[0146] If present, any residual by-products can be further etched with a second reactive composition.

[0147] Advantageously, in-situ cleaning of reaction chamber parts can dramatically reduce PM time and limit worker exposure to the reaction chamber, which represents a safety concern requiring complex and time-consuming safety procedures.

[0148] Preferably, but not exclusively, the reaction chamber of this embodiment is an epitaxial reaction chamber.

[0149] According to the above embodiments, the present invention relates to a method for in-situ etching of SiC deposits from one or more workpieces in a reaction chamber for depositing a monocrystalline silicon carbide layer on a substrate, the method comprising: (I) providing a silicon carbide deposit in one or more portions of a reaction chamber of a reactor for depositing silicon carbide, the reaction chamber comprising at least one gas inlet opening and at least one gas outlet opening; (II) performing at least one cycle of an etching process within the reaction chamber, the etching process comprising: A. ramping the reaction chamber to preset etching process conditions; B. Etching said silicon carbide deposit.

[0150] Step A is A1. Temperature of the reaction chamber T R a sub-step of adjusting the temperature to 500 to 1450°C; A2. Adjusting the pressure of the reaction chamber to 50 to 1000 mbar.

[0151] Step B. B1. Delivering a first reactive composition into the reaction chamber through the gas inlet opening, the first reactive composition comprising one or more reactive gases and a carrier gas.

[0152] The carrier gas is an inert gas.

[0153] The one or more reactive gases include at least a first reactive gas that is a halogen or halogen compound, and the molar concentration of the first reactive gas in the carrier gas is 15-40%.

[0154] Advantageously, the method according to the present invention achieves a deposition rate of 0.01 to 0.20 g / cm per hour without affecting the workpiece below the reaction chamber. 2 This has the effect of enabling silicon carbide deposit removal rates of up to 1000 .mu.m / s, which can be measured during calibration of the method by weighing the affected workpiece before and after deposition and before and after etching.

[0155] In one embodiment, the affected workpiece comprises the upper and lower walls of the chamber, and / or covers (upstream and / or downstream) of said walls, and / or other elements of the reaction chamber, and / or a substrate holder or elements thereof (such as a ring).

[0156] This embodiment may be implemented according to any other embodiment described above.

[0157] The above described method has been observed to work well with reaction chambers for the deposition of silicon carbide.

[0158] For example, but not by way of limitation, the reaction chamber may be of the type described in the following published international patent applications: WO2004053187, WO2004053188, WO2007088420, and WO2015092525.

[0159] For example, but not by way of limitation, the reaction chamber may be of the type described in US patent application Ser. No. 18 / 953,993.

[0160] These designs are affected by parasitic buildup on the graphite workpiece.

[0161] Parasitic buildup occurs on storage-critical graphite components, and the method according to the present invention is effective against parasitic SiC buildup without damaging the underlying graphite components, thanks to the specific process conditions disclosed herein.

[0162] Preferably, but not exclusively, the method according to the present invention can be carried out when the reaction chamber is of the hot-wall, epitaxial, horizontal and / or cross-flow type.

[0163] In any case, the present invention is not limited to any particular reaction chamber design.

[0164] 7 and 8, as an example, reaction chamber 100 is configured for epitaxial deposition of SiC and extends along a longitudinal direction X parallel to the flow of process gases (the flow of process gases is indicated by arrows in FIG. 8). The chamber may include an inlet opening 155 and an outlet opening 150 adapted to inject and exhaust process gases, purge gases, cooling gases, and reactive compositions into and out of the reaction chamber and onto a receiving area 116. The receiving area 116 is adapted to receive a substrate on a substrate holder.

[0165] The receiving area 116 may be a recess, which may be configured to allow for positioning of a substrate holder.

[0166] The receiving area may be adapted to rotate the substrate holder during the SiC deposition process.

[0167] The chamber may further be configured with appropriate injectors, liners, nozzles, and showerheads to facilitate the entry and evacuation of any and all of the gases described above.

[0168] The reaction chamber 100 may have a circular or elliptical cross section in a transverse plane yz perpendicular to the longitudinal direction x. The chamber may include an upper partition 110 and a lower partition 115. Both partitions are half-moon shaped and made of graphite. They are separated by two lateral partitions 117 made of polycrystalline SiC and having a surface roughness Ra of 0.5-1 μm.

[0169] The chamber may be configured to include other components such as a workpiece 120, and in the illustrated embodiment, the other component is a cover used to protect the top surface of the lower partition 115 from SiC buildup.

[0170] The reaction chamber 100 may be configured with several additional insulating elements, of which only insulating element 180 is shown.

[0171] The reaction chamber 100 may further comprise an enclosure 170. The enclosure may be made of quartz and may consist of a double-walled quartz tube, optionally cooled with a cooling fluid such as water.

[0172] The reaction chamber 100 may be surrounded by an induction coil 200 wrapped around a quartz enclosure 170. The coil may be configured to heat the upper and lower partitions 110, 115 of the reaction chamber.

[0173] Many other variations of the reaction chamber designs described above can be used in the practice of the present invention.

[0174] In a second aspect, the present invention relates to a SiC reactor 1000 adapted to perform in situ etching of silicon carbide deposits deposited on one or more components of the reaction chamber 100 according to any embodiment of the method described above, wherein the silicon carbide deposits comprise silicon carbide in polycrystalline and / or amorphous form.

[0175] The reactor 1000 comprises at least one reaction chamber 100 for depositing a silicon carbide layer on a substrate, said reaction chamber comprising at least one gas inlet opening 155 and at least one gas outlet opening 150.

[0176] In one embodiment, the reactor 1000 comprises 1 to 10 reaction chambers 100, for example 1 to 4 reaction chambers.

[0177] One embodiment of a reactor 1000 is shown schematically in FIG.

[0178] According to one embodiment, the reactor 1000 is connected or connectable to a source 1200 of Si precursor and a source 1250 of C precursor. For example, the silicon precursor gas may be a chlorinated compound, preferably dichlorosilane, trichlorosilane, or tetrachlorosilane. The carbon precursor gas may be a hydrocarbon, in particular propane, ethylene, acetylene, or methane. Other types of precursors may also be used.

[0179] Other sources (not shown), such as sources for n-doping and p-doping, may be connected or connectable to the reactor. For example, the n-source may be nitrogen, acetonitrile, pyrrole, ammonia, hydrazine, hydrogen cyanide, methylamine.

[0180] The reactor is also connectable or connected to a source of reactive composition through gas inlet opening 155 so that at least a first reactive composition is delivered into the reaction chamber through inlet opening 155.

[0181] The source of the first reactive composition may include a source 1100 of a carrier gas (an inert gas, preferably Ar or He) and a source of a first reactive gas 1150. Other sources of reactive compositions or gases may also be present, such as a source of an oxidizing composition or a reducing composition.

[0182] The term "source" refers to a gas or liquid line, a cylinder and / or a vessel configured to contain such gas or liquid.

[0183] The reactor 1000 further comprises a heating system 200 adapted to heat the reaction chamber to a temperature of 1450-1650°C, or up to 1700°C, which is the typical upper limit of the reaction chamber temperature for silicon carbide deposition. Specifically, the heating system 200 is adapted to heat the reaction chamber to a temperature of 1450-1650°C, or up to 1700°C, as defined above, for carrying out the etching process of the method according to the present invention. R It will be appreciated that the actual temperature inside the chamber may vary depending on the chamber design, heating system, and number of substrates being processed.

[0184] In Figures 7 and 8, the heating system is located outside the reaction chamber, although other configurations are possible.

[0185] The reactor 1000 further comprises a vacuum system 300 adapted to bring the reaction chamber to a pressure ≦1000 mbar, such as in the range of 50-1000 mbar, or any other preferred range disclosed herein.

[0186] The vacuum system 300 may include at least one pump.

[0187] The pump is suitable for (a) depressurizing the reaction chamber 100 and / or (b) forcing exhaust gases (resulting from the deposition and etching processes and / or the cooling step) out of the reaction chamber through the outlet opening 150 and into the scrubber 400. The vacuum system may further comprise at least one valve, preferably a throttle valve, upstream of the vacuum pump.

[0188] One or more gas outlets also allow by-products of the etching process to be exhausted into the scrubber 400 .

[0189] Advantageously, the reactor described above is adapted to carry out the method according to the invention, thereby providing a reduction in PM time.

[0190] In one embodiment, the reactor 1000 further comprises a processor 600, an accessible memory, and an in-situ etching program.

[0191] The in-situ etching program is stored in an accessible memory as a sequence of machine language instructions and is adapted to carry out steps A and B of the etching process of the method according to the invention.

[0192] The processor 600 is configured or configurable to execute an in-situ etching program, for example, by operating a control unit 700 that operates the sources 1100 and 1150 of reactive gas compositions.

[0193] The control unit 700 may be configured to include a system of valves, such as throttle valves, pumps, and circuits, that can control the flow rates, timing, and absolute and relative amounts of the carrier gas and one or more reactive gases.

[0194] The gases used in the etching or SiC deposition process may be mixed before entering the reaction chamber 100. The mixed gases may enter the reaction chamber as a single stream. Alternatively, the gases may enter the reaction chamber in multiple streams with different concentrations and / or flow rates depending on the injection point and direction. Multiple inlets can be used to this effect. Alternatively, a single inlet can be used that is attached to a liner with separate regions to accommodate the separate gas streams, as described in patent application WO2022053963.

[0195] The processor 600 may be configured or configurable to control the vacuum system 300 via one or more valves, eg, throttle valves, and circuits.

[0196] The reactor 1000 may optionally be equipped with a human machine interface 800 to allow an end user to initiate the etching process, adjust associated parameters, and optionally track its progress.

[0197] In one embodiment, the reaction chamber 100 of the reactor 1000 is of the hot-wall type and includes one or more components made of graphite, optionally coated with monocrystalline or polycrystalline silicon carbide having a wrinkled surface of less than 6.3 μm Ra, or with pyrolytic graphite, diamond, quartz, and / or boron nitride. These optional coatings have been observed to work particularly well in the practice of the present invention.

[0198] The heating system 200 of the reactor 1000 may be an induction system.

[0199] The reactor may be configured with a monitoring system 500 adapted to detect / monitor etching parameters indicative of the endpoint of the etching process and positioned between the downstream end of the reaction chamber 100 (after the gas outlet opening 150) and the scrubber 400 where the exhaust gases are treated.

[0200] Processor 600, if present, may optionally be configured or configurable to read and refine one or more signals from monitoring system 500.

[0201] A reactor according to the present invention may be equipped with one or more detectors for detecting one or more reactive gases, said detectors including means for triggering an alarm or stop signal to ensure user safety.

[0202] It will be understood that a reactor according to the present invention may also include any other elements required or desirable in the industry, such as cabinets, piping, actuators, circuits, valves, pumps, power supply means, etc.

[0203] The subject matter of the present disclosure includes all novel and non-obvious combinations and subcombinations of the various processes, systems, and configurations, and other features, functions, acts and / or properties disclosed herein, as well as any and all equivalents thereof. [Explanation of symbols]

[0204] 100 reaction chambers 116 Receptive Area 120 workpieces 121 Silicon carbide deposits 150 gas outlet opening 155 Gas inlet opening 170 Enclosure 180 Insulation Elements 200 Heating System 300 Vacuum System 400 Scrubber 500 Surveillance System 600 processors 700 control section 800 Human Machine Interface 1000 reactors 1100 Source 1150 Source 1200 Source 1250 Source

Claims

1. 1. A method for etching silicon carbide deposits from one or more workpieces, the method comprising: (I) providing a silicon carbide deposit on one or more workpieces in a reaction chamber of a reactor for depositing a silicon carbide layer on a substrate, the silicon carbide deposit comprising a polycrystalline form and / or an amorphous form of silicon carbide; (II) performing at least one cycle of an etching process, the performing comprising: A. ramping the reaction chamber to preset etching process conditions; B. Etching the silicon carbide deposit; Step A is A1. The temperature T of the reaction chamber Ｒ a sub-step of increasing the temperature to 500-1450°C; A2. The substep of increasing the pressure of the reaction chamber to 50-1000 mbar; Step B is B1. Delivering a first reactive composition into the reaction chamber, the first reactive composition comprising one or more reactive gases and a carrier gas; the carrier gas is an inert gas, the one or more reactive gases include at least a first reactive gas; the first reactive gas is a halogen or a halogen compound; The method wherein the molar concentration of the first reactive gas to the carrier gas is 15 to 40%.

2. 10. The method of claim 1, wherein step A comprises the further sub-step A3 of flowing an inert gas into the reaction chamber.

3. The etching process further comprises a cooling step C performed after step B, wherein the cooling step C comprises: C1. The temperature of the reaction chamber is T ｃ <T Ｒ The value of T ｃ a sub-step of conditioning at <1000°C; C2. The method of claim 1, further comprising the substep of flowing a cooling gas in the reaction chamber at a pressure of 100 to 1000 mbar.

4. The method further comprises the step (II0) of carrying out a purging process, wherein the purging process comprises: - adjusting the pressure of the reaction chamber to ≦1 mbar; - flowing an inert gas to reach a pressure of 100 to 1000 mbar in said reaction chamber, 2. The method of claim 1, wherein the purging process is performed before step A and / or after step B 1 to 20 times.

5. The method of claim 1 , wherein the carrier gas is selected from the group consisting of nitrogen, argon, or helium.

6. The flow rate of the first reactive gas is 0.5 to 2.3 mol / (s·m ２ 2. The method of claim 1 , wherein

7. 10. The method of claim 1, wherein the silicon carbide deposits are obtained as a by-product of one or more epitaxial deposition processes of single crystal silicon carbide layers on rotating substrates carried out in the reaction chamber of a reactor, the by-products being formed on one or more workpieces in the reaction chamber.

8. Step (I) is to deposit a monocrystalline silicon carbide layer to a predetermined total thickness T ｚ is carried out by performing one or more epitaxial deposition cycles of single crystal silicon carbide layers on the same or different substrates in a reaction chamber of the reactor until T ｚ The method of claim 1, wherein is 10 μm to 2000 μm.

9. The etching process is performed to obtain the predetermined total thickness T ｚ 9. The method of claim 8, wherein the method is carried out for a period of 0.10 to 0.6 minutes per μm of

10. 2. The method of claim 1, wherein in step (I), the one or more workpieces are made of bare graphite or graphite coated with diamond, quartz, pyrolytic graphite, boron nitride, and / or silicon carbide, the silicon carbide having wrinkles with an Ra of <6.3 μm.

11. The first reactive gas is F ２ , ClF, ClF ３ , ClF ５ , Cl ２ , HCl, XeF ２ , XeF ４ , XeF ６ , XeO ３ , KrF ２ ,Br ２ , I ２ 2. The method of claim 1, wherein the HCl is selected from the group consisting of:

12. The first reactive gas is F ２ , ClF, ClF ３ , and ClF ５ and sub-step A1 is selected from the group consisting of a temperature T Ｒ The method of claim 11 , wherein the method is performed by

13. The first reactive gas is Cl ２ and HCl; Substep A1 is performed at a temperature T between 1000 and 1450°C Ｒ It is executed with The method according to claim 11, wherein substep A2 is carried out at a pressure of between 50 and 700 mbar.

14. Substep A1 is performed at a temperature T between 1150 and 1350°C Ｒ and / or substep A2 is carried out at a pressure of between 150 and 700 mbar; The method of claim 13.

15. The method of claim 11 , wherein the first reactive composition further comprises a second reactive gas.

16. The method of claim 15 , wherein the second reactive gas is an oxidizing agent or a reducing agent.

17. The first reactive gas and the second reactive gas in the first reactive composition are HCl and N, respectively. ２ O, HCl and O ３ , HCl and H ２ O ２ , HCl and O ２、 Cl ２ and O ２ , Cl ２ and O ３ , Cl ２ and H ２ O ２ , HCl and H ２ 17. The method of claim 16, wherein the HCl and HF pair is selected from the group consisting of:

18. 18. The method of claim 17, wherein the molar concentration of the oxidant in the carrier gas is 0.1 to 20%.

19. Step B is B2. further comprising the substep of delivering a second reactive composition into the reaction chamber, the second reactive composition comprising one or more reactive gases and a carrier gas; the carrier gas is an inert gas, the one or more reactive gases include at least an oxidizer; The method of claim 11 , wherein sub-step B2 is performed before or after sub-step B1 .

20. 20. The method of claim 19, wherein sub-step B2 is performed after sub-step B1, and the molar concentration of the oxidant in the carrier gas is 0.1 to 20%.

21. The oxidizing agent is N ２ O, NO, N ２ O ２ , O ２ , O ３ , and H ２ O ２ 21. The method of any one of claims 16, 19 and 20, selected from the group consisting of:

22. the reaction chamber comprising at least one monitoring system adapted to monitor an etching parameter indicative of an endpoint of the etching process; The etching process further comprises a monitoring step performed upon completion of step B, the monitoring step comprising: - reading preset target values ​​of said etching parameters; - checking the values ​​of said etching parameters against said target values; - repeating step B until said target value is reached.

23. the method is carried out to etch the silicon carbide deposits from one or more workpieces in the reaction chamber when the reaction chamber is disposed inside the reactor; the reaction chamber is provided with at least one gas inlet opening and at least one gas outlet opening; 10. The method of claim 1, wherein during step B, the first reactive composition is delivered into the reaction chamber through the at least one gas inlet opening and forms by-products of the etching process, and the by-products are exhausted through the at least one gas outlet opening.

24. 10. A reactor for depositing a silicon carbide layer on a substrate, configured to carry out the method of claim 1, said reactor comprising: at least one reaction chamber, said reaction chamber being equipped with at least one gas inlet opening and at least one gas outlet opening; a heating system adapted to heat the reaction chamber to a temperature of up to 1700°C; a vacuum system adapted to bring the reaction chamber to a pressure of ≦1000 mbar, the at least one gas inlet opening is connectable to a source of the one or more reactive gases and the carrier gas; The reactor, wherein the at least one gas outlet opening is configured to exhaust by-products of the etching process.

25. a processor; an accessible memory; an in-situ etching program stored as a sequence of machine language instructions in said accessible memory, said in-situ etching program adapted to perform steps A and B of said method for etching silicon carbide deposits from one or more workpieces in a reaction chamber; the processor is configurable to execute the in-situ etching program; 25. The reactor of claim 24.

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