Etching silicon carbide films from reactor components

Abstract

The present invention relates to a method for etching silicon carbide deposits from one or more workpieces of a reaction chamber for depositing a silicon carbide layer on a substrate. The method comprises the steps of: (I) providing a silicon carbide deposit on one or more workpieces of a reaction chamber of a reactor for depositing silicon carbide; (II) performing at least one cycle of the etching process. The invention also relates to a reactor suitable for carrying out said process.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of epitaxial deposition of semiconductor accretions on substrates; in particular, to a method and a reactor suitable for performing a chemical etching of silicon carbide from reactor workpieces. BACKGROUND

[0002] During an epitaxial deposition process, one or more monocrystalline semiconductor layers are grown in a controlled manner on one or more rotating substrates. However, during the process, undesired semiconductor accretions can also grow simultaneously on other parts of the reaction chamber exposed to the process gases.

[0003] Indeed, during epitaxial deposition of monocrystalline silicon carbide on a substrate, for example during epitaxial deposition of 3C, 4H or 6H silicon carbide polytypes, the user typically observes uncontrolled silicon carbide accumulation on the structural and functional parts of the reaction chamber, hereinafter referred to as "workpieces". It should be noted that this undesired silicon carbide accumulation is very difficult to remove due to the hardness of the material, and that conventional techniques used in the silicon semiconductor industry are not suitable for removing silicon carbide parasitic deposits.

[0004] In contrast to the ordered monocrystalline layers deposited on the substrate, the silicon carbide accretions generally comprise silicon carbide in polycrystalline and / or amorphous form. Typically, the accretions are a mixture of polycrystalline and amorphous silicon carbide. The latter can represent up to 20-60% of the total, as can be observed in XRD measurements, although the relative proportions of the two forms can be subject to relevant local and average variations.

[0005] The above-mentioned parasitic phenomenon is particularly relevant in hot-wall reactors, where it generally affects the upstream end of the chamber, i.e. the point at which the precursor gases enter the reaction chamber, as well as the elements surrounding or in contact with the substrate.

[0006] It should be noted that the undesired SiC accumulation does not only occur on bare surfaces of the reaction chamber, but also on the workpieces which are coated preventively.

[0007] Indeed, reaction chamber parts made of graphite can be coated with a layer of TaC to protect the graphite surface during cleaning operations. Alternatively, a thin coating of SiC can be used to seal the exposed porous graphite surface to avoid contamination. In this case, the SiC coating used on the graphite workpieces is in polycrystalline form, with a smooth outer surface having a surface roughness much lower than 6.3 pm Ra, typically lower than 1 pm Ra.

[0008] It has been observed that the parasitic deposition of SiC accretions on the workpieces of the reaction chamber generally leads to the rapid growth of cauliflower-like, porous, dendritic structures, which ultimately affect the quality of the deposited layers on the semiconductor substrates. These parasitic accretions have a non-uniform appearance, with macroscopic corrugations.

[0009] To prevent the negative impact of parasitic deposits on the deposition process, the reaction chamber undergoes frequent preventative maintenance (PM) operations, such as after the growth of a total epitaxial layer of 100 μm to 2000 μm.

[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 operation negatively impacts reactor productivity, thus severely affecting the economics of the epitaxial deposition process. In fact, PM operation currently results in several hours of reactor downtime, and typically occurs 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 mechanically cleaned counterparts. Furthermore, in-situ etching processes can be performed without opening and entering the reactor's reaction chamber, advantageously reducing reactor downtime and simplifying operation.

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

[0014] It should be noted that in-situ etching typically uses chemicals that react with parasitic deposits, resulting in gaseous byproducts. In the case of silicon carbide, this process can lead to both gaseous and solid powdery byproducts.

[0015] The presence of powdery byproducts from the etching process in the reaction chamber can affect the quality of the epitaxial deposition process. However, without a significant extension of the etching time, they may be difficult to remove, potentially damaging the chamber components below and negatively impacting reactor downtime.

[0016] While methods for etching SiC have been disclosed in the art, these methods typically discuss the removal of several top layers of ordered SiC from a bulk SiC wafer, as described in US20140030892A1 and US20060001028A1. In these cases, the chemical etching of SiC occurs without the presence of an underlying workpiece (with a potentially different composition) that could be damaged during the process. These processes typically remove only a few micrometers of SiC to reduce warpage of the single-crystal SiC substrate and surface cracking of the SiC substrate holder, respectively. These methods do not address the removal of disordered parasitic SiC deposits without damaging the affected workpiece.

[0017] Therefore, it is desirable to provide a new method for etching polycrystalline-amorphous SiC parasitic deposits from the affected workpiece in the reaction chamber without damaging the workpiece.

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

[0019] Furthermore, it is desirable to provide a new reactor suitable for performing the above-described methods. Additionally, it is desirable to provide a reactor configured to perform the methods in an automated manner. Summary of the Invention

[0020] This summary is provided to present the chosen concepts in a simplified form. These concepts are further described in detail in the following detailed description of exemplary embodiments of this disclosure. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

[0021] The purpose of this invention is to overcome the shortcomings of the prior art.

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

[0023] Another object of the present invention is to provide a reactor that can be adapted to perform the new method, optionally in an automated manner.

[0024] The principal objective described above is achieved by the invention as set forth in the appended claims, which constitute the entirety of this specification.

[0025] It should be noted that the use of reference numerals (if any) in the claims does not limit their scope. The sole purpose of reference numerals is to make the claims easier to understand. Attached Figure Description

[0026] The illustrations presented herein are not intended to be actual views of any particular material, structure, or device, but are merely idealized representations used to describe embodiments of this disclosure.

[0027] Figure 1 A method according to the invention is shown according to one embodiment.

[0028] Figure 2 A method according to the invention is shown according to one embodiment.

[0029] Figure 3 A method according to the invention is shown according to one embodiment.

[0030] Figure 4 A method according to the invention is shown according to one embodiment.

[0031] Figure 5 A method according to the invention is shown according to one embodiment.

[0032] Figure 6 Detailed explanation based on Figure 5 The method routines of the embodiments shown are as follows.

[0033] Figure 7 A view in the transverse plane XY of a reaction chamber suitable for carrying out the method of the present invention according to one embodiment is shown.

[0034] Figure 8 It shows Figure 7 A side view of the reaction chamber in the longitudinal plane XZ.

[0035] Figure 9 A scheme for a reactor according to one embodiment is shown.

[0036] Figure 10 It is an image of a workpiece with silicon carbide deposits. Detailed Implementation

[0037] Although certain embodiments and examples are disclosed below, those skilled in the art will understand that the invention extends beyond the specific disclosed embodiments and / or uses of the invention and their obvious modifications and equivalents. Therefore, it is intended that the scope of the disclosed invention should not be limited to the specific disclosed embodiments described below.

[0038] Reference will now be made to the accompanying drawings, wherein the same reference numerals identify similar structural features or aspects disclosed in this subject matter.

[0039] exist Figures 1 to 6 In this context, optional steps and substeps are distinguished from basic steps and substeps by using dashed lines instead of solid lines.

[0040] exist Figure 9 In this diagram, all connections of digital signals are represented by dashed lines. Physical connections are indicated by solid lines.

[0041] It should be understood that the elements in the accompanying drawings are shown for simplicity and clarity. In particular, some elements or steps may have been omitted or may not be drawn to scale. For example, the dimensions of some elements in the drawings may be exaggerated relative to other elements to aid in understanding the embodiments illustrated in this disclosure.

[0042] In a first aspect, the present invention relates to a method 1 for etching a silicon carbide deposit 121 from one or more workpieces 120 of a reactor 1000 adapted to epitaxially deposit a single-crystal silicon carbide layer on a substrate.

[0043] "Etching" refers to chemical etching in the gas phase.

[0044] Method 1 includes the steps (I)-(II) listed below.

[0045] In step (I), SiC deposits are provided on one or more workpieces in the reaction chamber of the reactor used for depositing silicon carbide (box 10).

[0046] In step (II), at least one cycle of the etching process is performed. Figures 1 to 5 (Box 30). The etching process allows for chemical cleaning / removal of the SiC deposits provided in step (I).

[0047] The etching process includes the following consecutive steps or stages:

[0048] A. Raise the reaction chamber to the preset etching process conditions;

[0049] B. Etching silicon carbide deposits; and

[0050] C. Perform an optional cooling step.

[0051] Steps A, B, and C are described in boxes 40, 50, and 70, respectively.

[0052] Specifically, step A includes the following sub-steps:

[0053] A1. Set the temperature T of the reaction chamber. R Temperatures rise to 500-1450℃;

[0054] A2. Increase the pressure in the reaction chamber to 50-1000 mbar;

[0055] A3. Optionally, an inert gas can be introduced into the reaction chamber, which can help achieve and maintain the required temperature and pressure conditions.

[0056] All the above sub-steps A1-A3 (in respectively) Figure 2 (As described in boxes 41, 42 and 43), whether mandatory or optional, can be executed in any order, including simultaneous execution.

[0057] Step A is performed by gradually adjusting the pressure and temperature conditions from the initial values ​​to the desired process values, thereby protecting the reaction chamber from the undesirable effects of sudden changes that could lead to stress and damage to mechanical components and / or result in a lack of uniformity in process conditions inside the reaction chamber.

[0058] Once the reaction chamber has reached the desired temperature and pressure settings, the actual etching of the SiC parasitic deposits can proceed according to step B.

[0059] Step B includes the following sub-step B1:

[0060] B1. The first reactive composition is delivered into the reaction chamber (box 51).

[0061] 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.

[0062] The first reactive gas is a halogen or a halogen compound.

[0063] In one embodiment, if the first reactive gas is a halogen compound, then the compound is hydrogen halide.

[0064] In one embodiment, if the first reactive gas is a halogen compound, then the halogen compound is not a metal halide, interhalogen compound, organohalogen compound, or polyhalogen compound.

[0065] The first reactive composition also comprises a carrier gas; it is preferably an inert gas. For example, the inert gas may be nitrogen, helium, or argon to avoid contamination of the chamber. The carrier gas can be advantageously used to tailor and control the concentration and distribution of the reactive gas in the chamber.

[0066] Halogens or halogen compounds can be transported in the reaction chamber in molecular, radical, and / or ionized states (e.g., but not limited to plasma states).

[0067] In a non-limiting example, the free radicals and / or ions of the first reactive gas may be formed from molecular halogens or halogen compounds inside the reaction chamber by means of temperature and pressure conditions inside the chamber and / or under an RF alternating electric field.

[0068] Alternatively, under specific temperature, pressure, illuminance and / or electric field conditions, free radicals and / or ions of the first reactive gas can be formed immediately outside the reaction chamber.

[0069] The inventors have observed that the molar concentration of the first reactive gas entering the carrier gas should be equal to 15-40%. Surprisingly, by selecting this concentration, parasitic SiC deposits can be removed without damaging the associated coated / uncoated graphite components under the aforementioned temperature and pressure conditions. Removal of the parasitic SiC deposits does not necessarily proceed until 100% removal is achieved. Advantageously, the deposits can be removed to a degree suitable for reconstructing sufficient operating conditions within the reaction chamber, thereby extending the operating time between PM operations.

[0070] During a standard epitaxial deposition process, the SiC deposits mentioned above and below are obtained directly or can be obtained as parasitic deposition of silicon carbide on the reaction chamber component (workpiece), wherein the SiC layer is deposited on a rotating substrate inside the reaction chamber.

[0071] Therefore, SiC deposits are byproducts of one or more epitaxial deposition processes of single-crystal SiC layers on a rotating substrate, wherein the processes are performed in a reactor reaction chamber. The byproducts form on one or more workpieces within the reaction chamber, surrounding the substrate and exposed to process gases.

[0072] It should be noted that the technical properties of SiC deposits imparted by the parasitic deposition process can be fully defined only in terms of the parasitic process itself. While the latter certainly imparts identifiable features, such as the inhomogeneity and wrinkles of the deposits, characterizing SiC deposits based on these features would be overly restrictive.

[0073] These workpieces are typically not made of single-crystal SiC; therefore, the SiC deposits are not single-crystal but rather comprise polycrystalline and / or amorphous forms of silicon carbide. This method is not limited by the specific solid-state properties of the SiC deposits. The latter typically contain or consist of a mixture of polycrystalline and amorphous SiC, such as a mixture of polycrystalline SiC with 20-60% amorphous SiC. The amount of amorphous SiC in the deposit can undergo significant local and absolute variations.

[0074] The deposited SiC layers are typically single-crystal. They are usually, but not exclusively, 3C, 4H, or 6H polytypes.

[0075] Parasitic SiC deposits are a well-known undesirable byproduct of SiC layer deposition.

[0076] Parasitic SiC deposits occur on the surfaces of all components of the reaction chamber exposed to the gas flow of SiC precursors, particularly at the upstream end of the chamber (i.e., where the precursor gas enters the reaction chamber) and on components that are close to or in contact with the substrate.

[0077] In particular, the workpieces affected by parasitic deposition are the removable and stationary parts (covers, rings, walls) of the reaction chamber, whether stationary or rotating, due to their exposure to SiC precursor gases during the deposition process.

[0078] These workpieces are typically made of materials that are much less hard than SiC, such as coated or bare graphite.

[0079] Parasitic deposition of SiC is a unique but not exclusive phenomenon that affects hot-walled reaction chambers. The high temperatures of the reaction chamber walls and other parts favor parasitic accumulation.

[0080] Therefore, unless otherwise stated herein and below, the expression “SiC deposit” should be considered equivalent to “parasitic SiC film” or “SiC film” or “parasitic SiC deposit”, and will refer to SiC in polycrystalline and / or amorphous forms.

[0081] Furthermore, the term "accumulation" in expressions such as "SiC accumulation" or "silicon carbide accumulation" (and the term "film" in expressions such as "parasitic SiC film" or "SiC film") should not imply a two-dimensional, regular, and / or ordered geometry. Instead, it can refer to a non-uniform SiC coating formed on one or more surfaces of the impacted portion of the reaction chamber and can exhibit a three-dimensional structure, such as a rough, sandy surface, as seen from... Figure 10 It is obvious.

[0082] The terms “deposits” (or “films”) and “layers” are used here and below to distinguish, respectively, undesirable parasitic SiC deposits from desired controlled SiC layers deposited on a substrate.

[0083] Typically, parasitic SiC deposits exhibit uneven surfaces, such as pronounced wrinkles and variable thickness. Surface inhomogeneity, usually clearly visible to the naked eye, is often accompanied by, but not necessarily, cauliflower-like or fractal structures with visible macroscopic depressions and protrusions, possibly due to dendritic growth processes.

[0084] This phenomenon is particularly noticeable and affects the quality of the deposited layer when the reaction chamber is running total single-crystal SiC deposition of 100 μm to 2000 μm (on the same substrate or on multiple substrates processed in succession without PM cycling), for example when it is running total single-crystal SiC deposition of 200–800 μm.

[0085] In this case, the parasitic growth can be etched in a particularly satisfactory manner using this method.

[0086] This method can also be satisfactorily used for a wider range of total single-crystal SiC deposition, such as 10μm-2000μm, preferably 50μm-2000μm, preferably 100μm-2000μm, and even more preferably 100-800μm.

[0087] Figure 10 An image is shown of a parasitic SiC deposit 121 on a workpiece 120 positioned on the lower partition 115 of the reaction chamber 100. The workpiece 120, serving as an upstream cap, partially surrounds a receiving region 116 adapted to support a 6” substrate. The parasitic SiC deposit appears lighter in color in the grayscale image compared to the other visible portions of the reaction chamber, which is made of graphite. The deposit 121 is coated with a non-uniform, granular, and gravelly film onto the surface of the workpiece 120 exposed to the precursor gas.

[0088] The longer the reaction chamber workpiece is exposed to the precursor gas flow, the more pronounced the irregular features of the parasitic deposits become.

[0089] The silicon carbide deposits of the present invention can exhibit a surface roughness greater than 6.3 μm Ra.

[0090] In one embodiment, the optional cooling step C performed after step B includes the following sub-steps:

[0091] C1. Cool the reaction chamber to temperature T. c <T R And in any case T c <1000℃ (box 71), for example, Tc between 500-900℃; and

[0092] C2. Allow cooling gas to flow to achieve a pressure of 100-1000 mbar in the reaction chamber (box 72).

[0093] Sub-steps C1 and C2 can be performed in any order, but are preferably performed simultaneously.

[0094] Sub-step C1 can be carried out by turning off the heating source and cooling the reaction chamber (primarily via radiation). Sub-step C1 can be accelerated by running sub-step C2 simultaneously.

[0095] The cooling gas used in sub-step C2 is any gas suitable for cooling the accelerated chamber to idle temperature. Those skilled in the art can easily select the most suitable gas based on budget and time constraints. Non-limiting examples of cooling gases include helium, nitrogen, hydrogen, and combinations thereof.

[0096] Figure 2 This summarizes all steps A, B, and C, as well as their respective sub-steps, discussed above for step (II) and box 30.

[0097] In one embodiment, method 1 of the present invention may include performing steps after step (I) and Figure 3 The purging step (II0) of the reaction chamber is shown in box 20. The purging step is described in box 20 and includes performing a purging process of 1-20 cycles, which can clean the reaction chamber from residues of other operations / processes performed in the reaction chamber.

[0098] During the purging process, the following sub-steps are executed sequentially, starting from any of the following sub-steps (boxes 21 and 22):

[0099] - Adjust the pressure in the reaction chamber to ≤1 mbar; and

[0100] - Flow inert gas to achieve a pressure of 100-1000 mbar in the reaction chamber.

[0101] Step (II0) can be performed before step A.

[0102] Alternatively, it can be performed after step B, and before or after step C, if present. This can advantageously remove all traces of the reactive gases used, as well as any byproducts that may still be present in the chamber from the etching process.

[0103] Cooling step C can be advantageously used to establish favorable conditions for performing an optional purging process, and / or the latter can help to achieve the effects of cooling step C more effectively, depending on their execution order.

[0104] In summary, the optional purging process can be performed as follows: 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) once the etching process is complete, after both steps B and C.

[0105] In one embodiment, the flow rate of the first reactive gas is 0.5-2.3 mol / (s·m). 2 ).

[0106] In one embodiment, step (I) of the method according to the invention is performed by executing one or more epitaxial deposition cycles of a single-crystal SiC layer on the same or different substrates inside the reactor's reaction chamber until a predefined total thickness T of the single-crystal SiC layer deposited on one or more consecutive substrates is reached during the entire operating time of the chamber. z .

[0107] In this case, T z Preferably 10μm-2000μm, more preferably 50μm-2000μm, more preferably 100μm-2000μm, even more preferably 100-800μm, even more preferably 200-800μm, even more preferably 500-700μm.

[0108] During this step, parasitic SiC deposits of variable and non-uniform thickness are formed on one or more workpieces in the reaction chamber. The resulting SiC deposit is thus referred to as having an "equivalent thickness" T. z That is, the total cumulative thickness T of the deposits. z The thickness is obtained as a result of an ordered layer.

[0109] It should be noted that the local thickness of parasitic deposits can vary greatly and differs from the average thickness (T). z .

[0110] It should be noted that, due to the dendritic growth of the deposits, the peak value of parasitic deposits may be significantly higher than the thickness T. z .

[0111] In one embodiment, the etching process according to the method of the present invention has a predefined total thickness T per μm. z Execution time: 0.10-0.6 minutes.

[0112] In one embodiment, the predefined total thickness T per μm according to the method of the present invention z Execution time: 0.1-0.6 minutes.

[0113] In one embodiment, the predefined total thickness T per μm according to the method of the present invention z Execution time: 0.3-0.55 minutes.

[0114] As previously mentioned, in this art, the equivalent thickness of parasitic deposits is not their average or maximum thickness, as the latter may undergo significant local variations. The equivalent thickness of parasitic deposits corresponds to the thickness of the single-crystal layer deposited on one or more substrates during one or more consecutive deposition processes. As ordered single-crystal layers grow on the substrate, parasitic deposits grow on certain workpieces with variable heights within the reaction chamber. Therefore, it is more meaningful to refer to their equivalent thickness, which is a parameter set and controlled during reactor operation and can be readily measured on the actual substrate after the deposition process.

[0115] In one embodiment, the workpiece of the reaction chamber to be etched is made of graphite and optionally coated with single or polycrystalline silicon carbide, pyrolytic graphite, single or polycrystalline diamond, quartz and / or boron nitride with wrinkles <6.3 μm Ra.

[0116] The coatings described above help protect graphite workpieces during preventative maintenance operations and etching processes. They also prevent contamination of the reaction chamber during the deposition process.

[0117] It has been observed that graphite workpieces coated with single-crystal or polycrystalline diamond work particularly well in the implementation of the present invention, especially when the first reactive gas contains or is composed of fluorine atoms, molecules or free radicals.

[0118] It has been observed that graphite workpieces coated with pyrolytic graphite work particularly well in the implementation of the present invention, especially when the first reactive gas comprises or consists of chlorine atoms, molecules or free radicals.

[0119] In one embodiment, the first reactive gas may be selected from F2, ClF, ClF3, ClF5, Cl2, HCl, XeF2, XeF4, XeF6, XeO3, KrF2, Br2, I2 and HBr.

[0120] In one embodiment, the first reactive gas is F2, ClF, ClF3, or ClF5, and step A1 is performed at a temperature of 500-1000°C (T). R) to execute.

[0121] Alternatively, the first reactive gas is Cl2 or HCl, and:

[0122] - Step A1 at a temperature of 1000-1450℃ (T R The process is preferably carried out at a temperature of 1150-1350°C; and / or

[0123] - Step A2 is performed at a pressure of 50-700 mbar, preferably 150-700 mbar.

[0124] In one embodiment, in step A1, the temperature of the reaction chamber is adjusted to 1150-1350°C.

[0125] Surprisingly, within this temperature range, the ratio of Si and C etching via the free radicals of the first reactive gas is optimized relative to the overall etching process itself. Higher temperatures result in more prevalent Si etching, but at lower temperatures, the etching process is less efficient overall.

[0126] Advantageously, the above method can be used to etch SiC deposits in situ and ex-situ from one or more workpieces in the reaction chamber.

[0127] When the first reactive gas is a halogen, the latter is preferably selected to have a purity of 99.990% or greater, and even more preferably a purity of 99.998% or greater.

[0128] It should be noted that during the etching process, due to the pressure and temperature conditions inside the reaction chamber, halogen molecules form free radicals, which erode the SiC deposits, thus generating byproducts of the etching process. These byproducts are then discharged from the reaction chamber.

[0129] Under the process conditions listed in this disclosure, the method according to the invention allows for the appropriate removal of both carbon and Si from parasitic SiC deposits. This removal is sufficient to restore the deposition operation to its intended purpose, thereby extending the operational life of the reaction chamber between consecutive PMs.

[0130] For applications involving in-situ etching, the possibility of chemically cleaning the reaction chamber after parasitic buildup and setting it under appropriate operating conditions without (a) opening the reactor, (b) removing the reaction chamber, and (c) exposing its components to air for cleaning is a significant improvement over current mechanical cleaning techniques.

[0131] Surprisingly, despite the unique and challenging properties of SiC, it can effectively remove hard, disordered parasitic deposits up to hundreds of micrometers in size without damaging the components of the reaction chamber.

[0132] The above method meets the long-term industrial need of providing a method for in-situ cleaning of the reaction chamber of a SiC reactor to avoid parasitic deposits.

[0133] In one embodiment, the first reactive composition used in step B1 comprises a second reactive gas.

[0134] For example, the second reactive gas is an oxidizing agent or a reducing agent.

[0135] The second reactive gas can be delivered to the reaction chamber in molecular, free radical, and / or ionized states (such as, but not limited to, plasma states).

[0136] In a non-limiting example, the free radicals and / or ions of the second reactive gas may be formed from molecular halogens or halogen compounds inside the reaction chamber by means of temperature and pressure conditions inside the chamber and / or under an RF alternating electric field.

[0137] Alternatively, the free radicals and / or ions of the second reactive gas may be formed immediately under specific conditions of temperature, pressure, illuminance, and / or electric field before entering the reaction chamber.

[0138] A non-limiting example of a reducing agent is H2.

[0139] Oxidizing agents refer to oxygen compounds, oxygen molecules, or oxygen free radicals.

[0140] Examples of oxidants that have been observed to work particularly well in carrying out the present invention are: N2O, NO, N2O2, O2, O3 and H2O2.

[0141] Using a second reactive gas in the first reactive composition allows for targeting (or prevention of) undesirable byproducts from the reaction between the first reactive gas and the SiC deposit.

[0142] In one embodiment, the first reactive gas and the second reactive gas in the first reactive composition are selected from the following pairs: HCl and N2O, HCl and O3, HCl and H2O2, HCl and O2, Cl2 and O2, Cl2 and O3, Cl2 and H2O2, HCl and H2, and HCl and HF.

[0143] In one embodiment, the molar concentration of the second reactive gas entering the carrier gas is 0.1-20%.

[0144] In one embodiment, the molar concentration of the second reactive gas entering the carrier gas is 0.1-15%.

[0145] In one embodiment, the molar concentration of the second reactive gas entering the carrier gas is 1-10%.

[0146] It has been surprisingly observed that the use of halides and oxidants is particularly effective in removing unwanted byproducts without damaging the underlying workpiece and without producing solid powdery residues.

[0147] In one embodiment, the first reactive composition used in step B1 comprises a third reactive gas.

[0148] In one embodiment, step B further includes the following sub-steps:

[0149] B2. The second reactive composition is delivered into a reaction chamber; wherein the second reactive composition comprises one or more reactive gases and a carrier gas (box 52).

[0150] In this case, the carrier gas is an inert gas; and one or more reactive gases contain at least an oxidant.

[0151] It should be noted that sub-step B2 can be performed before or after sub-step B1.

[0152] If sub-step B2 is performed before sub-step B1, the oxidant may leave behind Si-rich byproducts suitable for removal by suction or by reaction with halogens or halogen compounds (especially fluorine-based molecules or fluorine compounds).

[0153] In one embodiment, sub-step B2 is performed after sub-step B1.

[0154] In one embodiment, the molar concentration of the oxidant entering the carrier gas is 0.1-20%.

[0155] In one embodiment, the molar concentration of the oxidant entering the carrier gas is 0.1-10%.

[0156] Under the above conditions, the oxidant can effectively remove any carbon-rich byproducts left by the first reactive composition.

[0157] The purging step can optionally be performed between sub-steps B1 and B2, or between sub-steps B2 and B1, depending on their order.

[0158] In one embodiment, step B1 includes the following sub-steps:

[0159] - Optionally, one or more reactive gases and / or carrier gases may be vented. "Ventilation" means bypassing the reaction chamber for a predetermined time period;

[0160] - Increase the flow rate of one or more reactive gases and carrier gases to the corresponding preset nominal flow rate;

[0161] - One or more reactive gases and a carrier gas are delivered to the reaction chamber at the preset nominal flow rate.

[0162] The above sub-steps may have different or the same start and / or duration for each of one or more reactive gases and the carrier gas.

[0163] For example, the first reactive gas may undergo a ramp time TR1 and a constant time TS1, and the inert gas may undergo a ramp time TR2 and a constant time TS2, and TR1, TS1, TR2, and TS2 may be different from each other. The ramp times for Cl2 and the inert gas may start differently, and they may undergo optional and different ventilation times.

[0164] Note that all parameters mentioned in this embodiment can be provided as user input or as predefined settings. Predefined settings can be calculated based on the calibration curve provided for a given reactor and the desired results. These can be obtained by those skilled in the art without undue burden and are adaptable to the specific reaction chamber design in use.

[0165] In one embodiment, the reaction chamber 100 includes at least one monitoring system 500 adapted to monitor etching parameters that indicate the end of the etching process.

[0166] In this case, process B according to the invention further includes a monitoring step (box 60) (see...) Figure 5 and Figure 6 It shows Figure 5 (Details of frame 31).

[0167] The monitoring step is performed at the end of step B (i.e., after step B1, and if applicable, after both step B1 and step B2).

[0168] The monitoring process includes the following sub-steps:

[0169] - Read the preset target value of the etching parameters (box 62), and optionally read the preset tolerance;

[0170] - Read the actual values ​​of the etching parameters (box 61);

[0171] - Check whether the actual value has reached the target value (decision block 63), optionally within the current tolerance;

[0172] - Repeat step B until the target value is reached (optionally within the current tolerance).

[0173] Once the target value is reached, the monitoring process ends.

[0174] The monitoring system can be a detector, such as a mass spectrometer, suitable for detecting the concentration of silicon and / or carbon in the byproduct gas produced after each cycle of etching step B.

[0175] Advantageously, this embodiment allows for monitoring of the progress of the method according to the invention.

[0176] In one embodiment, the method according to the invention is performed in situ to etch silicon carbide deposits from one or more workpieces in the reaction chamber, i.e., the method is performed while the reaction chamber is inside the reactor, without opening the reactor. For this purpose, the reaction chamber may be provided with at least one gas inlet port and at least one gas outlet port.

[0177] In this case, during step B, the first reactive composition is delivered into the reaction chamber through at least one gas inlet port, thereby forming byproducts of the etching process. These byproducts can then advantageously be discharged through at least one gas outlet port.

[0178] Any residual byproducts (if any) can be further etched with a second reactive composition.

[0179] Advantageously, in-situ cleaning of reaction chamber components allows for a significant reduction in PM time and limits operator exposure to the reaction chamber. Such exposure represents a safety concern, requiring complex and time-consuming safety procedures.

[0180] Preferably, but not exclusively, the reaction chamber in this embodiment is an epitaxial reaction chamber.

[0181] 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 single-crystal silicon carbide layer on a substrate, the method comprising the following steps:

[0182] (I) A silicon carbide deposit is provided on one or more portions of the reaction chamber of a reactor for depositing silicon carbide; wherein the reaction chamber is equipped with at least one gas inlet port and at least one gas outlet port;

[0183] (II) Perform at least one cycle of the etching process in the reaction chamber, the etching process comprising the following steps:

[0184] A. Raise the reaction chamber to the preset etching process conditions;

[0185] B. Etching silicon carbide deposits.

[0186] Step A includes the following sub-steps:

[0187] A1. Set the temperature T of the reaction chamber. R Adjust to 500-1450℃; and

[0188] A2. Adjust the pressure in the reaction chamber to 50-1000 mbar.

[0189] Step B includes the following sub-steps:

[0190] B1. A first reactive composition is delivered into a reaction chamber through a gas inlet port; wherein the first reactive composition comprises one or more reactive gases and a carrier gas.

[0191] The carrier gas is an inert gas.

[0192] One or more reactive gases include at least a first reactive gas, which is a halogen or a halogen compound, and the molar concentration of the first reactive gas in the carrier gas is 15-40%.

[0193] Advantageously, the method according to the invention allows for a concentration of 0.01-0.20 g / cm³ per hour. 2 The removal rate of silicon carbide deposits is achieved without affecting the workpiece below the reaction chamber. The removal rate can be measured during method calibration by weighing the affected workpiece before and after deposition, and before and after etching.

[0194] In one embodiment, the affected components include the upper and lower walls of the chamber, and / or the cover of said walls (upstream and / or downstream), and / or other components of the reaction chamber, and / or the substrate holder or components thereof (e.g., a ring).

[0195] This embodiment can be performed according to any other embodiment described above.

[0196] The method described above has been observed to work well with the reaction chamber used for silicon carbide deposition.

[0197] For example, but not limited to, the reaction chamber can be of the type disclosed in the following international patent applications: WO2004053187, WO2004053188, WO2007088420 and WO2015092525.

[0198] For example, but not limited to, the reaction chamber can be of the type described in U.S. Patent Application No. 18 / 953,993.

[0199] These designs are influenced by parasitic accumulations on graphite workpieces.

[0200] Parasitic accumulation occurs on graphite components that are crucial for preservation. Due to the specific process conditions disclosed herein, the method according to the invention effectively combats parasitic SiC accumulation without damaging the underlying graphite components.

[0201] Preferably, but not exclusively, the method according to the invention can be performed when the reaction chamber is of the hot-walled, epitaxial, horizontal, and / or cross-flow type.

[0202] In any case, the present invention is not limited to a specific reaction chamber design.

[0203] As an example, refer toFigure 7 and Figure 8 The reaction chamber 100 is configured for the epitaxial deposition of SiC and extends along the longitudinal direction X parallel to the process gas flow (the latter is formed by...). Figure 8 (Indicated by the arrows in the diagram). The chamber may include an inlet port 155 and an outlet port 150, which are adapted to inject and discharge process gases, purge gases, cooling gases, and reactive compositions into and out of the reaction chamber and above the receiving region 116. The latter is adapted to receive a substrate on a substrate holder.

[0204] The receiving region 116 may be a recess. It may be configured to allow positioning of the substrate holder.

[0205] The receiving area can be adapted to rotate the substrate holder during the SiC deposition process.

[0206] The chamber can be further equipped with suitable syringes, liners, nozzles, and spray heads to facilitate the entry and exit of any and all of the aforementioned gases.

[0207] 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 crescent-shaped and made of graphite. They are separated by two transverse partitions 117 made of polycrystalline SiC and having a surface roughness of 0.5-1 μm Ra.

[0208] The chamber may include other parts, such as workpiece 120, which in the illustrated embodiment is a cover for protecting the top surface of the lower separator 115 from SiC buildup.

[0209] The reaction chamber 100 may also include several heat insulation elements, of which only heat insulation element 180 is shown.

[0210] The reaction chamber 100 may also include a housing 170. The housing may be made of quartz, for example, it may consist of a double-walled quartz tube, which may optionally be cooled by a cooling fluid such as water.

[0211] The reaction chamber 100 may be surrounded by an induction coil 200 wound around a quartz housing 170. The coil may be configured to heat the top and lower partitions 110 and 115 of the reaction chamber.

[0212] Many other variations of the above-described reaction chamber design can be used to implement this invention.

[0213] 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 portions of a reaction chamber 100 according to any embodiment of the methods described above, wherein the silicon carbide deposits comprise silicon carbide in polycrystalline and / or amorphous forms.

[0214] The reactor 1000 includes at least one reaction chamber 100 for depositing a silicon carbide layer on a substrate, the reaction chamber being provided with at least one gas inlet port 155 and at least one gas outlet port 150.

[0215] In one embodiment, reactor 1000 includes 1 to 10 reaction chambers 100, for example, 1 to 4 reaction chambers.

[0216] exist Figure 9 An embodiment of reactor 1000 is schematically depicted in the figure.

[0217] According to one embodiment, reactor 1000 is connected to or may be connected to Si precursor source 1200 and C precursor source 1250. For example, the silicon precursor gas may be a chlorinated compound, preferably dichlorosilane, trichlorosilane, or tetrachlorosilane. The carbon precursor gas may be a hydrocarbon, particularly propane, ethylene, acetylene, or methane. Other types of precursors may be used.

[0218] Other sources (not shown), such as sources for n-doping and p-doping, may be connected to or can be connected to the reactor. For example, n-sources may be nitrogen, acetonitrile, pyrrole, ammonia, hydrazine, hydrogen cyanide, or methylamine.

[0219] The reactor can also be connected to or connected to a source of reactive composition via a gas inlet port 155, such that at least a first reactive composition is delivered into the reaction chamber through the inlet port 155.

[0220] The source of the first reactive composition may include a carrier gas (inert gas, preferably Ar or He) source 1100 and a first reactive gas source 1150. Other sources may be present, such as sources for other reactive compositions or other reactive gases, such as sources for oxidizing or reducing compositions.

[0221] The term "source" refers to a pipeline, cylinder, and / or container configured to contain a gas or liquid.

[0222] Reactor 1000 also includes a heating system 200 adapted to heat the reaction chamber to temperatures of 1450-1650°C or up to 1700°C, which is the typical upper limit of reaction chamber temperatures for silicon carbide deposition. Specifically, heating system 200 should be adapted to heat the reaction to a temperature equal to T as defined above. R The temperature is adjusted to allow for the etching process according to the method of the invention. It should be understood that the actual temperature inside the chamber can vary depending on the chamber design, the heating system, and the number of substrates being processed.

[0223] exist Figure 7 and Figure 8 In this case, the heating system is located outside the reaction chamber, but other configurations are also possible.

[0224] The reactor 1000 also includes a vacuum system 300 adapted to bring the reaction chamber to a pressure of ≤1000 mbar, for example in the range of 50-1000 mbar, or any other preferred range disclosed herein.

[0225] The vacuum system 300 may include at least one pump.

[0226] The pump is adapted to (a) depressurize the reaction chamber 100 and / or (b) allow exhaust gases (generated by the deposition and etching process and / or cooling steps) to flow out of the reaction chamber through the outlet port 150 and into the scrubber 400. The vacuum system may further include at least one valve, preferably a throttle valve upstream of the vacuum pump.

[0227] One or more gas outlets also allow byproducts of the etching process to be discharged into the scrubber 400.

[0228] Advantageously, the reactor described above is adapted to perform the method according to the invention, thereby providing a reduced PM time.

[0229] In one embodiment, reactor 1000 further includes processor 600, accessible memory, and in-situ etching procedure.

[0230] The in-situ etching program is stored as a sequence of machine language instructions in an accessible memory and is adapted to perform steps A and B of the etching process according to the method of the present invention.

[0231] The processor 600 is configured or can be configured to perform in-situ etching procedures, for example by actuating the controller 700 of the sources 1100 and 1150 of the reactive gas composition.

[0232] The controller 700 may include a valve system, such as a throttle valve, a pump, and circuitry capable of controlling the flow rate, timing, and absolute and relative quantities of a carrier gas and one or more reactive gases.

[0233] The gases used in the etching or SiC deposition process can be combined before entering the reaction chamber 100. They can enter the reaction chamber as a single stream. Alternatively, they can enter the reaction chamber as multiple streams with different concentrations and / or flow rates, depending on their injection point and direction. For this purpose, multiple inlets can be used. Alternatively, a single inlet attached to a liner with an isolation zone can be used to accommodate individual gas flow streams, as described in patent application WO2022053963.

[0234] The processor 600 can be configured or can be configured to control the vacuum system 300 via one or more valves (such as throttle valves) and circuitry.

[0235] The reactor 1000 may optionally include a human-machine interface 800 to allow the end user to start the etching process, adjust relevant parameters, and optionally follow its progress.

[0236] In one embodiment, the reaction chamber 100 of the reactor 1000 is of the hot-wall type and includes one or more sections made of graphite, optionally coated with pleated single-crystal or polycrystalline silicon carbide with a Ra less than 6.3 μm, or coated with pyrolytic graphite, diamond, quartz, and / or boron nitride. These optional coatings have been observed to work particularly well in carrying out the present invention.

[0237] The heating system 200 of the reactor 1000 can be an induction system.

[0238] The reactor may be equipped with a monitoring system 500, which is suitable for detecting / monitoring etching parameters that indicate the end of the etching process, and is located downstream of the reaction chamber 100 (after the gas outlet orifice 150) and between the scrubber 400 that treats the waste gas.

[0239] The processor 600 may be optionally configured to read and finely process one or more signals from the monitoring system 500 (if present).

[0240] The reactor according to the invention may include one or more detectors for detecting one or more reactive gases, wherein the detectors include means for triggering an alarm or stop signal to ensure user safety.

[0241] It should be understood that the reactor according to the invention may include all other elements necessary or desired in industry, such as cabinets, pipes, actuators, circuits, valves, pumps, power supply devices, etc.

[0242] The subject matter of this disclosure includes all novel and non-obvious combinations and sub-combinations of the various processes, systems and configurations disclosed herein, as well as any and all equivalents thereof.

Claims

1. A method for etching a silicon carbide deposit from one or more workpieces, the method comprising the steps of: (I) Providing a silicon carbide deposit on one or more workpieces in the reaction chamber of a reactor for depositing a silicon carbide layer on a substrate, the silicon carbide deposit comprising silicon carbide in polycrystalline and / or amorphous forms; (II) Perform at least one cycle of the etching process, including the following steps: A. Raise the reaction chamber to the preset etching process conditions; B. Etching silicon carbide deposits; Step A includes the following sub-steps: A1. Set the temperature T of the reaction chamber. R Temperatures rise to 500-1450℃; A2. Increase the pressure in the reaction chamber to 50-1000 mbar; Step B includes the following sub-steps: B1. A first reactive composition is delivered into a reaction chamber; the first reactive composition comprises one or more reactive gases and a carrier gas; The carrier gas is an inert gas; and Wherein, one or more reactive gases include at least a first reactive gas; Wherein, the first reactive gas is a halogen or a halogen compound; and The molar concentration of the first reactive gas entering the carrier gas is 15-40%.

2. The method according to claim 1, wherein, Step A includes another sub-step A3: allowing an inert gas to flow into the reaction chamber.

3. The method according to claim 1 or 2, wherein, The etching process further includes a cooling step C performed after step B; cooling step C includes the following sub-steps: C1. Adjust the temperature of the reaction chamber to value T. c <T R T c <1000℃; and C2. Allow the cooling gas to flow in the reaction chamber at a pressure of 100-1000 mbar.

4. The method according to any one of claims 1 to 3, further comprising the step (II0) of performing a purging process, wherein, The purging process includes the following sub-steps: - Adjust the pressure in the reaction chamber to ≤1 mbar; and - Flow inert gas to achieve a pressure of 100-1000 mbar in the reaction chamber; The purging process is performed 1-20 times before step A and / or after step B.

5. The method according to any one of the preceding claims, wherein, The carrier gas is selected from nitrogen, argon or helium.

6. The method according to any one of the preceding claims, wherein, The flow rate of the first reactive gas is 0.5-2.3 mol / (s·m). 2 ).

7. The method according to any one of the preceding claims, wherein, The silicon carbide deposit is obtained as a byproduct of one or more epitaxial deposition processes of a single-crystal silicon carbide layer on a rotating substrate performed in the reaction chamber of a reactor; the byproduct is formed on one or more workpieces in the reaction chamber.

8. The method according to any one of the preceding claims, wherein, Step (I) is performed by carrying out one or more epitaxial deposition cycles of a single-crystal silicon carbide layer on the same or different substrates inside the reactor's reaction chamber until a predefined total thickness T of the deposited single-crystal silicon carbide layer is reached. z T z The range is 10μm-2000μm.

9. The method according to claim 8, wherein, The etching process is performed for 0.10-0.6 minutes per μm of the predefined total thickness t. z The duration.

10. The method according to any one of the preceding claims, wherein, In step (I), the one or more workpieces are made of graphite, quartz, pyrolytic graphite, boron nitride and / or silicon carbide, optionally coated with diamond, wherein the silicon carbide has wrinkles with a Ra of ≤6.3 μm.

11. The method according to any one of claims 1 to 10, wherein, The first reactive gas is selected from F2, ClF, ClF3, ClF5, Cl2, HCl, XeF2, XeF4, XeF6, XeO3, KrF2, Br2, I2 and HBr.

12. The method according to claim 11, wherein, The first reactive gas is selected from F2, ClF, ClF3, and ClF5; and wherein, step A1 is performed at a temperature T of 500-1000℃. R Execute below.

13. The method according to claim 11, wherein, The first reactive gas is selected from Cl2 and HCl, and: - Step A1 at a temperature T of 1000-1450℃ R Execute below; and - Step A2 is performed at a pressure of 50-700 mbar.

14. The method of claim 13, wherein: - Step A1 at a temperature T of 1150-1350℃ R Execute below; and / or - Step A2 is performed at a pressure of 150-700 mbar.

15. The method according to any one of claims 11 to 14, wherein, The first reactive composition further comprises a second reactive gas, and preferably, the second reactive gas is an oxidizing agent or a reducing agent.

16. The method according to claim 15, wherein, The first reactive gas and the second reactive gas in the first reactive composition are selected from the following pairs: HCl and N2O, HCl and O3, HCl and H2O2, HCl and O2, Cl2 and O2, Cl2 and O3, Cl2 and H2O2, HCl and H2, and HCl and HF.

17. The method according to claim 16, wherein, The molar concentration of the oxidant entering the carrier gas is 0.1-20%.

18. The method according to any one of claims 11-15, wherein, Step B also includes the following sub-steps: B2. The second reactive composition is delivered into a reaction chamber; the second reactive composition comprises one or more reactive gases and a carrier gas; The carrier gas is an inert gas. Wherein, one or more reactive gases contain at least an oxidizing agent; and Sub-step B2 is performed before or after sub-step B1.

19. The method according to claim 18, wherein, Sub-step B2 is performed after sub-step B1, and the molar concentration of the oxidant entering the carrier gas is 0.1-20%.

20. The method according to any one of claims 15 or 18-19, wherein, The oxidant is selected from N2O, NO, N2O2, O2, O3 and H2O2.

21. The method according to any one of the preceding claims, wherein, The reaction chamber includes at least one monitoring system adapted to monitor etching parameters indicating the endpoint of the etching process; and The etching process also includes a monitoring step, which is performed at the end of step B and includes the following sub-steps: - Read the preset target value of the etching parameters; - Check the values ​​of the etching parameters against the target values; and - Repeat step B until the target value is reached.

22. The method according to any one of the preceding claims, wherein, When the reaction chamber is located inside the reactor, the method is performed to etch silicon carbide deposits from one or more workpieces within the reaction chamber. The reaction chamber is provided with at least one gas inlet port and at least one gas outlet port, and During step B, the first reactive composition is delivered into the reaction chamber through at least one gas inlet hole and forms a byproduct of the etching process, which is discharged through at least one gas outlet hole.

23. A reactor for depositing a silicon carbide layer on a substrate and configured to perform the method according to any one of the preceding claims, the reactor comprising: - At least one reaction chamber, the reaction chamber being provided with at least one gas inlet port and at least one gas outlet port; - A heating system suitable for heating the reaction chamber to temperatures up to 1700°C, and specifically to temperatures equal to T. R Temperature; - A vacuum system suitable for achieving a reaction chamber pressure of ≤1000 mbar; The at least one gas inlet port can be connected to a source of one or more reactive gases and carrier gases; The at least one gas outlet hole is configured to discharge byproducts of the etching process.

24. The reactor according to claim 23, further comprising: - Processor; - Accessible memory; - An in-situ etching program, which is stored as a sequence of machine language instructions in an accessible memory, the program being adapted to perform steps A and B of a method for etching silicon carbide deposits from one or more workpieces in a reaction chamber; The processor can be configured to execute an in-situ etching procedure.

Images