Method for determining completion of cleaning process in process chamber of MOCVD reactor

Abstract

The present invention relates to a method for removing parasitic deposits on the surfaces of a process chamber (6) of a CVD reactor, particularly an MOCVD reactor. The CVD reactor's susceptor (2) is heated by a heating device (5), which adjusts the susceptor (2) to a predetermined temperature (T) or heats the susceptor (2) with a constant heat output. Simultaneously, an etching gas is supplied to the heated process chamber (6). The thermal response of at least one object is monitored, which is the temperature (T) of a major surface of a process chamber cover (7), which faces away from the process chamber (6). The parasitic deposits affect the emissivity of the surface of the process chamber cover (7), which in turn affects the temperature distribution in the region of the process chamber (6). The supply of the etching gas is stopped when the temperature reaches a comparative value (Tv), which varies based on the changing surface emissivity during the cleaning process.

Description

[Technical field]

[0001] The present invention relates to a method for removing parasitic deposits from surfaces of a process chamber of a CVD reactor having a susceptor that can be heated by a heating device, during which an etching gas is supplied into the process chamber heated to a high temperature, whereby a measurement value is obtained by monitoring the thermal response of at least one object in or near the process chamber, and the supply of the etching gas is terminated when the measurement value reaches a comparative value, whereby during the supply of the etching gas, a temperature regulator is adjusted to a pre-given temperature or heated with a constant heating power.

[0002] The invention further relates to an apparatus for carrying out the method, comprising a CVD reactor having a process chamber disposed within a housing of the CVD reactor, the process chamber having a susceptor with a plurality of storage locations for respectively storing at least one substrate, a heating device for heating the susceptor, a gas inlet member, one or more surfaces on which parasitic deposits are generated during a coating method in which at least one organometallic compound of main group II or III and at least one hydride of main group V or VI are supplied with a carrier gas through the gas inlet member into the process chamber, a measuring device for sensing a thermal response of at least one object in or near the process chamber, and a control device for controlling valves and mass flow controllers to generate a flow of etching gas through the process chamber and for stopping the flow of etching gas to the process chamber when a measured value obtained from the thermal response reaches a comparison value. [Background technology]

[0003] A CVD reactor, in particular an MOCVD reactor, is used to deposit a number of layers, in particular layers of III-V or II-IV materials, in successive deposition steps on a number of substrates which are simultaneously located on a susceptor in a process chamber of the reactor. For this purpose, a metal-organic reaction gas and a hydride are fed into the process chamber together with a carrier gas, for example hydrogen. The process chamber is heated to a process temperature. In so doing, not only the substrates but also the walls of the process chamber are brought to a temperature which forms a coating on the surface. The desired layer is formed on the substrate. Parasitic deposits are formed on the surface. This parasitic deposit must be removed periodically, in particular each time after removing the treated substrate from the process chamber. For this purpose, an etching gas, which contains or is chlorine, is fed into the process chamber, for example by means of a gas inlet member or a separate gas supply line. The prior art in particular provides for feeding into the process chamber a first etching gas, for example chlorine or HCl, for a given time in a number of successive phases or steps, followed by a second etching gas, for example ammonia, to remove the carbon residues. This etching step or phase is carried out for a predefined time or this etching cycle is carried out a predefined number of times.

[0004] US Patent No. 5,399,633 describes an apparatus and method for measuring luminescence at specific wavelengths during a dry etching process of a semiconductor wafer to determine when the etching process is completed, where a regression line is calculated from measurements made during the dry etching process.

[0005] US Patent No. 5,399,633 describes a method for plasma etching of a surface. During the etching process, the spectral emission rates of two or more luminescent reactive components are recorded.

[0006] US Patent No. 5,399,633 describes a cleaning process in which the thermal response of at least one object is monitored and a measured value is thereby obtained which is compared to a comparison value. The cleaning process is terminated when the measured value reaches the comparison value. A special sensor is used which has a sensor body which is maintained at a constant temperature.

[0007] Patent Document 4 describes a plasma coating apparatus equipped with a showerhead and a susceptor. A process chamber can be cleaned with the aid of plasma by supplying a cleaning gas. A temperature sensor measures the temperature in the process chamber and interrupts the cleaning process when a threshold value is reached.

[0008] Furthermore cleaning methods are known from US Pat. No. 5,993,621 or US Pat. No. 5,293,621. A CVD reactor is described, for example, in US Pat. No. 5,993,621. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] U.S. Patent No. 8,083,960 [Patent Document 2] U.S. Patent No. 6,919,279 [Patent Document 3] International Publication No. 2007 / 041454 [Patent Document 4] International Publication No. 2018 / 035418 [Patent Document 5] U.S. Patent No. 10,544,519 [Patent Document 6] DE 102012101438 A1 [Patent Document 7] DE 10043601 A1 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention is based on the problem of optimizing a method for removing parasitic deposits from the surfaces of a process chamber of a CVD reactor. A further object of the present invention is based on providing a means for ensuring that an etching step or etching cycle is long enough to remove the parasitic deposits to a sufficient extent, and that the etching cycle is performed without being too long, which not only increases the costs but also reduces the lifetime of the parts exposed to the etching gas. [Means for solving the problem]

[0011] This problem is solved by the invention defined in the claims, the dependent claims not only indicating advantageous further developments of the invention as defined in the subclaims, but also indicating independent solutions.

[0012] According to the invention, according to a first aspect of the invention, it is proposed to monitor the thermal response of an object in a process chamber or in its vicinity during a cleaning process. During the monitoring, at least one measurement value is obtained which changes as a result of a decrease in the thickness of a parasitic deposit on the surface of the process chamber. This measurement value is compared with a comparison value. If the measurement value reaches the comparison value, the cleaning process is terminated. The comparison value can be a reference value to which a tolerance limit is applied, for example a window of a temperature range or a limit temperature.

[0013] In particular, it is provided that during the supply of the etching body, the temperature regulating body is regulated to a pre-given temperature. According to the invention, the temperature regulating body is a susceptor which carries the substrate during the deposition process. It is heated by a heating device. A temperature sensor is provided which measures the temperature, for example, on the side of the susceptor facing the heating device, whereby this temperature is maintained at a constant value by the control device. During the supply of the etching gas, a thermal response of a surface of the process chamber or of a surface of another part is detected, from which a measurement value can be obtained. For example, the temperature of the other part which has a parasitic coating to be removed can be measured. According to a variant of the invention, the other part is the process chamber ceiling. The process chamber ceiling extends parallel to the susceptor, so that the process chamber is present between the susceptor and the process chamber ceiling.

[0014] It can be provided to measure the temperature on the rear side of the process chamber ceiling facing away from the process chamber. This can be done with a pyrometer or a thermocouple, etc. The surface whose temperature is measured can be free of parasitic deposits. However, the body whose temperature is measured may also have another surface with parasitic deposits. It is preferred to measure the temperature of a surface without a coating on the process chamber ceiling, which has on the other side a surface with a parasitic coating. The process chamber ceiling or another part whose thermal response is monitored is preferably located on the heat transport path between a heat source forming a heating device for a susceptor or a susceptor surface, and a heat sink formed by a housing wall or a process chamber wall, which is cooled by a cooling device with a constant cooling power or adjusted to a constant temperature by a control device and a cooling device.

[0015] Parasitic deposits affect the emissivity of the component whose thermal response is monitored. If the emissivity of the component changes, the heat flow between the heat source and the heat sink changes, and thus the temperature of the component. By continuously measuring the temperature of the component located on the heat transport path, it is possible to determine when the coating has been sufficiently removed. For this purpose, the measured value, in this case the temperature, is compared with a comparison value. The comparison value can be determined in a preliminary experiment, for example by operating a process chamber with the same process parameters set during the cleaning process and without parasitic deposits on the component, and measuring the temperature during this operation. The comparison temperature can be, for example, a temperature determined in such a preliminary experiment, which is subject to a tolerance. For example, the cleaning process can be carried out until the temperature measured during the process approaches the temperature determined in the preliminary experiment, for example by 5 K or 3 K. When this condition is reached, the cleaning step is terminated.

[0016] In a variant of the invention, it can be provided that the temperature of the part of the process chamber having the parasitic deposits to be removed, for example the process chamber ceiling, is maintained at a constant temperature during the cleaning step. This is done, for example, by supplying a temperature adjustment gas into the gap between the rear surface of the process chamber ceiling facing away from the process chamber and the cooled housing wall. The gas composition of the temperature adjustment gas can be varied by means of a mass flow controller. The temperature adjustment gas preferably consists of an adjustable mixture of a gas with a high thermal conductivity, for example hydrogen, and a gas with a low thermal conductivity, for example nitrogen. However, it is also possible to use two noble gases with different thermal conductivity properties. In this variant, the mixture proportion or mass flow rate of the temperature adjustment gas is monitored. In this variant, the comparison value is the mixture proportion or mass flow rate of the adjustment gas supplied to the gap in a preliminary experiment with the same process parameters but with clean parts. The process parameters in that case are in particular the susceptor temperature or the heating power for heating and keeping the susceptor constant, which is at least kept constant, the carrier gas flow through the process chamber, which is kept constant, and the total pressure in the process chamber, which is kept constant.

[0017] In one variant of the invention, it can be provided that the body to be cleaned, the thermal response of which is monitored, is a susceptor or a holding device arranged on the susceptor, a substrate holder carried by the susceptor, etc. (in particular a base module or a ring assembly). In particular, therefore, all of the areas formed by the susceptor or bodies carried by the susceptor can be taken into account. In the susceptor, the temperature of which is measured, for example, at the location, using a temperature measuring device, for example a pyrometer, a thermocouple or a light line, the temperature of the side facing the heating device is kept constant, while the temperature of the main surface of the susceptor facing the process chamber changes during etching due to the change in the emissivity of the surface. This temperature can be measured optically, for example, by a pyrometer.

[0018] In a variant, it can be provided that the comparison value is determined during the etching step. Prior to the removal of the parasitic deposits, one or more IV-IV, III-V or II-VI layers are deposited on a number of substrates arranged simultaneously in a susceptor containment by supplying at least one organometallic compound of an element of main group II, III or IV and at least one hydride of an element of main group IV, V or VI together with a carrier gas. A process gas formed by a reaction gas is supplied to the process chamber through a gas inlet member. The gas inlet member can be a central gas inlet member arranged in the center of the process chamber. However, the gas inlet member can also be a showerhead forming in a way the ceiling of the process chamber, which has a number of gas outlet holes facing the process chamber. The gas inlet member can have a first outlet hole through which a first reaction gas is supplied to the process chamber and a second outlet hole through which a second reaction gas is supplied to the process chamber, so that the two reaction gases come into contact with each other only in the process chamber. During this deposition process, the containment locations are in the shadow of the substrate and therefore no parasitic deposits are deposited. However, parasitic deposits are deposited on the intermediate area surfaces between the containment locations on the main surface of the susceptor facing the process chamber. During the cleaning step, the temperature is measured at the locations and the measured value can be treated as a comparison value. When the temperature of the coated intermediate area surface is sufficiently close to the comparison value, the etching step is terminated.

[0019] Not only the measured temperature can be used as the thermal response. The heating power of the heating device used to heat the susceptor to a predefined temperature can also be used. However, the temperature measured on the main surface of the susceptor facing the heating device when the susceptor is heated with a constant heating power can also be used as the thermal response. The optical properties of the surface, which change when the parasitic coating is removed, affect the heat flow from a heat source, e.g. a heating device that heats the susceptor, to a heat sink, e.g. a cooled process chamber wall. The change in heat flow causes a temperature change along the heat transport path.

[0020] The cleaning step may be a single cleaning step that is terminated when the measured value obtained by monitoring the thermal response reaches the comparison value. For safety reasons, it may be provided that the cleaning step continues for a pre-defined time after the measured value reaches the comparison value. If the comparison value is a temperature, it may be the temperature determined under clean conditions with otherwise identical process parameters, modified by a safety factor or margin of, for example, 3K or 5K.

[0021] In a variant of the invention, it is proposed that the cleaning step consists of a number of cycles, each cycle including an etching phase, which may have a predefined length, each cycle having at least one etching phase and a flushing phase, since between two etching phases the process chamber is flushed with a flushing gas.

[0022] However, it can also be provided that in a first etching phase, metals or metal-containing compounds are removed from the surface by an etching gas containing an element of main group VII, and, if necessary, after an intermediate phase in which a flushing gas is supplied to the process chamber, a second etching phase is carried out in which, for example, ammonia is supplied to the process chamber in order to remove carbon compounds from the surface of the part to be cleaned. These cycles comprising two or more phases are carried out in succession until the measurements representative of the thermal responses detected during them obtain the comparative values.

[0023] A further aspect of the invention can provide that the system is continuously learning and that using machine learning the comparison values ​​continuously adapt to changing environmental conditions due to drift etc., whereby for example process results of successive deposition processes are analysed and an analysis of these process results, e.g. properties of layers deposited on a substrate, can be used to determine whether a cleaning process has been performed with sufficient intensity.

[0024] However, instead of the temperature measurement, it can also be provided that another optical property, for example the emissivity of the surface to be cleaned, is continuously measured and that these measured values ​​are compared with a comparison value in order to terminate the supply of etching gas when they fall below or above a threshold value. The comparison value when measuring the temperature can be a reference temperature with a safety margin, whereas the comparison value when measuring the emissivity can be a measured value of a reference emissivity with a safety margin.

[0025] It is advantageous if measurements are taken on a surface of the body by an optical metrology device to determine when to terminate the supply of etching gas or to terminate an etching step or an etching cycle, and the measurements change because the body is located on a heat transfer path between a heat source that is hotter than the body and a heat sink that is colder than the body, and the substantial mechanism of heat transfer between the heat source and the body or between the body and the heat sink is thermal radiation, in which case at least one surface of the body has optical properties that change continuously during the etching step, and the body is a functional component of a process chamber.

[0026] With the above described device, variants of the method according to the further aspect of the invention can also be carried out. In that case, the comparison value changes during the supply of the etching gas. The comparison value is therefore a pre-given or variable comparison value. In one variant of the invention, it can be provided that the comparison value depends on the time-dependent change in the thermal response, for example the time-dependent change in temperature, of a nearby area of ​​the process chamber or of another object in the process chamber. It can be provided that the comparison value is a second temperature measured in the CVD reactor. It can further be provided that the second comparison value is a second temperature measured in the CVD reactor, which comprises an additional constant. To determine the comparison value, a second thermal response of the second object can be monitored during the etching step. This can be done with the above described means. In particular, a first means for monitoring the first thermal response and a second means for monitoring the second thermal response can be provided. In a preferred embodiment of the method or the program of the control device of the invention, a first thermal response is measured at the susceptor and a second thermal response is measured at the ceiling of the process chamber. In particular, an optically operating temperature measuring device can be used to measure the thermal response of an area of ​​the susceptor that is left uncoated during the coating process. In particular, a further optically operating second temperature measuring device can be used to measure the thermal response at a location on the ceiling of the process chamber, which can be a location that is left uncoated during the coating process. However, it can also be a location where a parasitic coating is formed during the coating process. The monitoring of the two thermal responses, preferably temperature measurements or radiation measurements, is performed continuously, quasi-continuously or periodically during the etching process.

[0027] In a variant of the invention, it can be provided that each of the two thermal responses is represented by a measurement value and that a relationship, for example a difference, is formed from the two measurements. In general, it can be assumed that there is a mathematical relationship between the measurements. In an exemplary embodiment, it can be provided that a relationship, for example a difference, is formed between the temperature measured at a location on the susceptor and the temperature measured at a location on the ceiling of the process chamber. This relationship, for example a difference, can be compared with a comparison value. When the relationship, for example a difference, between the two measurements falls within a set window around the comparison value, i.e. within a predefined distance value from the comparison value, the etching process, i.e. the supply of the etching gas, can be terminated. It is also possible to monitor the slope of a measurement curve obtained from the measurements during the etching process. Such a measurement curve can asymptotically approach a final value. It can further be provided that one of the measurement values ​​or the relationship between the two measurement values, for example the difference, or the absolute value of the time derivative of only one measurement value is monitored. A value which is a threshold for the time derivative can be specified. If the absolute value of the measurement value, or the relationship between the two measurement values, for example the difference, falls below the threshold, the supply of the etching gas is terminated. [Brief description of the drawings]

[0028] The invention will now be explained in more detail with reference to exemplary embodiments with reference to the accompanying drawings, in which:

[0029] [Figure 1] FIG. 1 is a schematic cross-sectional view of an MOCVD reactor. [Diagram 2] FIG. 2 shows the time course of the temperature measured at measuring point 20 on the process chamber ceiling 7 in the apparatus shown in FIG. 1 over time for a first exemplary embodiment. [Diagram 3] FIG. 3 is a view similar to FIG. 2 of a second exemplary embodiment. [Figure 4] FIG. 4 is a diagram similar to FIG. 3 of the time course of the change in temperature measurement. [Diagram 5] FIG. 5 is a view similar to FIG. 3 of a further exemplary embodiment, in which the measured temperature asymptotically approaches a final value during the etching step. [Figure 6] FIG. 6 is a diagram similar to FIG. 5 of a measurement curve of temperature asymptotically approaching a final value. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] FIG. 1 shows a schematic diagram of an MOCVD reactor with a housing 1. The MOCVD reactor closes the interior of the housing 1 in an airtight manner with respect to the housing periphery. Inside the housing 1 there is a susceptor 2 made of graphite, for example of coated graphite, which is formed by a circular disk-shaped disk. The susceptor 2 has a main surface facing downwards, the temperature of which can be measured by a temperature sensor 18 located on the main surface at the position indicated by reference number 18. The main surface 4 faces a heating device 5 capable of heating the susceptor 2. The heating device 5 can be an IR heater or an RF heater. The main surface 4 of the susceptor 2 is located opposite the main surface 3 facing the process chamber 6. On the main surface 3, one or more substrates 16 are placed, which may consist of III-V material, IV material, sapphire, etc. In the center of the process chamber 6 there is a gas inlet member 13 with two gas inlet channels, through which two different reactive gases can be fed separately into the process chamber 6. One reactive gas can be an organometallic compound of an element of main group III. The second reactive gas can be a hydride of a compound of an element of main group V. The surface of the substrate 16 is heated by means of a heating device 5 to a temperature such that layers are deposited on the surface of the substrate 16 by decomposition of the reaction gases and by reaction products with one another. The layers can be crystalline layers. They can also be amorphous. The layers can be III-V layers. Various deposition steps separated from one another by flushing steps, which can also change the temperature of the susceptor, are carried out, so that a number of layers with various layer compositions and layer thicknesses are deposited on the substrate 16. The gaseous reaction products can be sucked by a pump (not shown) through a gas exhaust member 15 that annularly surrounds the process chamber 6. To rotate the susceptor 2 relative to the process chamber ceiling 7, the susceptor 2 is carried by a rotatable shaft 17.

[0031] The process chamber 6 is adjacent at its lower end to the major surface 3 of the susceptor 2 and at its upper end to a major surface 9 of a process chamber ceiling 7 that extends parallel to the susceptor 2. The process chamber ceiling 7 is, in the exemplary embodiment, a thin, temperature-stable disk made of coated graphite, ceramic, quartz, or another suitable material. It has a major surface 8 that faces the gap 10. The major surface 8 is 9 and facing away from the process chamber 6 and facing the cooling device 11, thereby extending a gap 10 between the cooling device and the process chamber ceiling 7. The cooling device 11 has cooling channels 12 through which a coolant can flow.

[0032] A temperature measuring device 19, which may be a pyrometer, is arranged in the cooling device 11 or above a hole 21 in the wall formed by the cooling device 11. The measuring device 19 is used to measure the temperature of the process chamber ceiling 7 at a measuring point 20. A temperature adjustment gas supply line 22 opens into the gap 10, into which a temperature adjustment gas can be supplied by a temperature adjustment gas source 24. The temperature adjustment gas consists of two gases with different heat transfer properties, for example nitrogen and hydrogen or helium and argon. By changing the mixture ratio of the two gases, the heat transfer from the process chamber ceiling 7 to the process chamber wall formed by the cooling device 11 in the exemplary embodiment can be changed.

[0033] During the above-mentioned layer deposition on the surface of the substrate 16, the susceptor temperature, measured by the temperature sensor 18, is maintained at a constant value by means of a regulation device (not shown) of the control device 23. For this purpose, the heat flow to the susceptor 2, caused by the heating device 5, is varied. The temperature of the coolant flowing through the cooling channel 12 is also maintained at a pre-given coolant temperature. A temperature regulation gas, supplied to the gap 10, is provided by a temperature regulation gas source 24. The composition of the temperature regulation gas is varied in such a way that the temperature of the rear surface of the process chamber ceiling 7, measured at measurement point 20, remains at a constant value.

[0034] During the coating of the substrate 16, parasitic deposits accumulate on the main surface 9 of the process chamber ceiling 7 facing the process chamber 6 and on the areas of the main surface 3 of the susceptor 2 facing the process chamber 6 that are not covered by the substrate 16. These parasitic deposits must be removed after the deposition process. For this purpose, the invention presents several variants, some of which are explained in detail below.

[0035] An etching gas containing chlorine or a chlorine-containing compound is fed into the process chamber through the gas inlet member 13 or through a separate supply line, not shown. This is done together with an inert gas, for example nitrogen. The process chamber is heated to a temperature of more than 500, 600 or 700° C., at which temperature parasitic deposits, especially containing metals, are removed from the main surface 9 of the process chamber ceiling 7 facing the process chamber 6 by chemical reactions capable of forming chlorides.

[0036] Parasitic deposits on the main surface 9,3 result in a change in the optical properties of the main surface 9,3. Due to a temperature gradient between the main surface 3 and the main surface 9, a heat flow occurs from the susceptor 2 to the process chamber ceiling 7 during the etching process (but also during the growth process). The heat transport mechanism is on the one hand heat conduction via the gas supplied to the process chamber 6 at a pressure lower than atmospheric pressure, to some extent convection, but essentially thermal radiation from the susceptor 2 to the process chamber ceiling 7. The heat transferred by thermal radiation depends on the optical properties of the main surface 9,3, which are different when the main surface 9,3 is free of a coating, i.e. clean, and when it has a parasitic coating. As a result, the temperature measured at the main surface 3 of the susceptor 2 in the region between the substrates 16 or at the main surface 8 facing the gap 10 depends on the type and material thickness of the deposit on the main surface 3 or on the main surface 9 opposite the main surface 8 of the process chamber ceiling 7. In an exemplary embodiment, the measured temperature decreases as the deposits are removed from the main surface 3 or 9 and reaches a minimum value when the deposits are completely removed. If the reference temperatures of these main surfaces 3 or 8 are determined under the same process parameters under which the cleaning process is performed, and if a continuous change in these temperatures is observed during the cleaning process, it can be concluded that the cleaning can be terminated when the temperatures measured during the cleaning are sufficiently close to the reference temperatures.

[0037] The invention uses this effect to define an event whose occurrence triggers the termination of the etching step. In a preliminary experiment, certain process parameters, such as the temperature measured by the temperature sensor 18, the gas flow through the process chamber 6 and the temperature adjustment gas flow supplied to the gap 10, as well as the total pressure in the process chamber 6, the temperature of the main faces 3, 8, are set using a clean uncoated surface of the main faces 3, 9. With the process parameters thus set, reference temperatures are measured at selected points 20. From these reference temperatures, comparison values ​​are formed. These comparison values ​​are in particular comparison temperatures that differ from the reference temperature by a pre-given tolerance of about 3 K, 5 K, 6 K or 10 K. It can be provided that the comparison temperature is a temperature range in the form of a temperature window around the reference temperature.

[0038] During the etching step, the same process parameters are set and the etching gas is also supplied to the process chamber. The change at the measuring point 20 on the main surface 8 of the process chamber ceiling 7 is continuously measured. The measured temperature is compared with a comparison temperature derived from a reference value or with a temperature window around the reference temperature. If the measured temperature falls below or exceeds the reference temperature or falls within the temperature window, this is considered an event that terminates the etching step. The etching step can be terminated immediately by stopping the flow of the etching gas. However, it is also provided that after the occurrence of the event, the etching gas still flows further for a defined time.

[0039] According to a variant of the invention, instead of measuring the rear surface temperature of the process chamber ceiling 7, it is also possible to measure the temperature on the main surface 3 facing the process chamber 6. This temperature is also measured from the heating device 5 through the susceptor 2 to the wall located on the opposite side of the process chamber 6. to It changes because heat flow is always present.

[0040] According to a further variant, however, the temperature measured at measuring point 20 can also be kept constant by varying the composition of the temperature regulating gas supplied to gap 10 by means of temperature regulating gas supply line 22, and the cooling power of the coolant flowing through cooling channel 12 to the set temperature can be observed. If this cooling power is within a predefined range of a comparison value, the etching step can be stopped.

[0041] However, according to a variant of the invention, the heating power supplied to the heating device 5 can also be kept constant and the temperature sensor 18 can be used to measure the temperature of the susceptor which changes during the etching step, and the etching step can be stopped when this temperature falls within a comparison value range.

[0042] According to a further variant, however, it is also possible to measure the surface temperature of a containment location 25 on the main surface 3 of the susceptor 2 facing the process chamber 6, on which the substrate 25 was located during the preceding coating step, thus shielding the surface against the formation of parasitic deposits. This surface temperature can be compared with the surface temperature measured in an area adjacent to the containment location 25. When the two temperatures approach within a predetermined range, the etching step can be stopped.

[0043] 2 shows an exemplary embodiment, in which at the start of the cleaning process in the first cleaning step E1, the susceptor temperature is increased until it reaches a predefined value at time t1 and this value stabilizes. At time t1, a first etching gas, for example a chlorine-containing compound, is supplied to the process chamber. During this first cleaning phase, indicated by A, the temperature T measured at the measuring point 20 decreases continuously due to the change in emissivity of the main surface 3, 9 on which the parasitic deposits are present, accompanied by the action of the etching gas. The first cleaning phase A is carried out for a predefined time. At time t2, the etching gas is switched off and a flushing gas is supplied to the process chamber. During this flushing phase B, the susceptor temperature is increased. In a second cleaning phase C, which starts at time t3, another cleaning gas, for example ammonia, is fed into the process chamber. At time t4, the second cleaning gas is switched off and a flushing gas is fed into the process chamber. During this flushing phase D, the susceptor temperature decreases again and stabilizes until time t5. This is followed by a second washing step E2 which is essentially the same as the first washing step E1. 2 comprises a further first cleaning phase A followed by a flushing phase B, a second cleaning step C and a further flushing phase D. In this exemplary embodiment, several identical etching steps E1 and E2 of different phases are performed in succession. In the exemplary embodiment, only two etching steps E1 and E2 are shown. A number of etching steps can be performed in succession. The etching steps are performed in succession until the temperature measured at the measuring point 20 falls below the comparison temperature Tv. Then, either the entire cleaning process is stopped or a final etching step E+ is added.

[0044] 3 illustrates a simplified cleaning process in which a first etching step E1 begins at time t1 when etching gas is supplied to the process chamber. Temperature T is monitored at measurement point 20 throughout the etching process. In the exemplary embodiment, temperature T reaches a comparison temperature Tv at time t2, thereby triggering an event that terminates the cleaning process. A supplemental etching step E+ is performed for a time period until t3.

[0045] In a variant, it is provided that the comparison value Tv can vary with time. It can therefore be provided that the comparison value depends on further temperatures measured in the CVD reactor. The first temperature T1 can be, for example, a temperature measured on the susceptor, and in particular on an area that remains free of parasitic deposits during the deposition. The second temperature T2 can be, for example, a temperature measured on the process chamber ceiling. The second temperature can be a temperature measured on the side of the process chamber ceiling 7 facing the process chamber 6. In this case, the second temperature is measured at a position where the parasitic deposits are formed during the deposition process. The second temperature can also be a temperature measured on the side of the process chamber ceiling 7 facing away from the process chamber 6. In this case, the second temperature is measured at a position where the parasitic deposits are not deposited during the deposition process. The comparison value can be derived from the second temperature, for example by subtracting the measured second temperature by a constant value. Fig. 4 shows the time-dependent comparison value Tv, which is represented by the lower solid line in Fig. 4. The two dashed lines next to the solid line represent a window. As soon as the temperature measurement curve represented by the upper solid line enters the window, the supply of the etching gas is terminated. In the exemplary embodiment shown in Fig. 4, the etching process E1 starts at time t1 and ends at time t2.

[0046] FIG. 5 shows a variant in which the monitored temperature asymptotically approaches a constant value, represented in FIG. 5 by a horizontal line. Two dashed lines running parallel to it indicate a window. As soon as the measured temperature enters the window at time t2, the etching process is terminated. The horizontal line marked Tv can be a pre-given temperature. The temperature curve can be the curve of a single measured temperature, for example the temperature measured at the position of the susceptor. However, the temperature measurement curve can also be the relationship between two measured temperatures, for example the difference between the two temperatures, so that for example the first temperature can be the temperature measured on the susceptor 2 and the second temperature can be the temperature measured on the process chamber ceiling 7.

[0047] 6 shows a further variant, where the solid curve is a temperature measurement of a single temperature, e.g. the monitored temperature measured on the susceptor 2. However, the measurement curve can also be the relationship between two measured temperatures, e.g. the difference between a first temperature t1 measured on the susceptor 2 and a second temperature measured on the process chamber ceiling 7. For the location of the temperature measurements see the explanation above.

[0048] A calculation device is used to calculate a difference quotient representing the time derivative from the temperature measurement or from the relationship between a number of measured temperatures. This time derivative is compared with a predefined value Z. If the absolute value of the calculated time derivative is smaller than the predefined value Z, this is grounds for terminating the etching process. The curve shown in FIG. 6 can also asymptotically approach a final value.

[0049] The method has been described above using a single temperature measurement curve or two temperature relationship curves. The method according to the invention or the device according to the invention also includes exemplary embodiments in which more than two measured thermal responses are monitored to find the time to terminate the supply of etching gas. The thermal responses can be temperature measurements, emissivity measurements, or heating or cooling power.

[0050] The above description is intended to clarify all inventions contained in this application, each of which independently enhances the prior art with at least the following combinations of features, any two, more or all of which may be combined with each other:

[0051] The thermal response is 3 , 7, 8, 11, the temperature or emissivity of the surface without the coating.

[0052] The method, wherein the thermal response is a heating or cooling output to adjust the temperature T.

[0053] 1. A method according to claim 1, characterized in that, prior to the removal of parasitic deposits, one or more crystalline layers are simultaneously deposited on a number of substrates 16 arranged in a storage location 25 of a susceptor 2 adjacent to a process chamber 6 on one side thereof by supplying an organometallic compound of at least one element of main group II, III or IV and at least one hydride of an element of main group IV, V or VI together with a carrier gas, during which deposition the parasitic deposits to be removed are formed, and after the deposition of the layers the substrates 16 are removed from the process chamber 6, and the etching gas is or contains an element of main group VII.

[0054] A method characterized in that the monitored object is an area of ​​a surface 3, 8 of a body 2, 7 having a surface 3, 9 with parasitic deposits to be removed and / or the monitored object is a functional component of a process chamber.

[0055] The method, wherein the thermal response is measured by an optical metrology device (19).

[0056] The method, wherein the thermal response is a temperature T measured on a major surface 8 of a process chamber ceiling 7 adjacent to the process chamber 6 facing away from the process chamber 6 under process parameters that are otherwise held constant.

[0057] A method characterized in that the comparison value Tv is a temperature measured on a body 7 free of parasitic deposits in a preliminary experiment under the same parameters and / or the window is a temperature range around a reference temperature measured on a body 7 free of parasitic deposits in a preliminary experiment under the same parameters under the same process parameters.

[0058] Method, characterized in that the monitored object (2, 3, 7, 8, 11) belongs to a body (7) which receives heat from an actively heated susceptor (2) and emits heat to a heat sink (11).

[0059] A method characterized in that the object to be monitored is a heating device 5 and the thermal response is the heating output of the heating device to reach a pre-given temperature T of a functional component 2 of a process chamber 6.

[0060] A method characterized in that the object to be monitored is a cooling device (11) and the thermal response is the cooling output of the cooling device (11) to reach a predetermined temperature of a functional component (7) of a process chamber (6).

[0061] The comparison value Tv is a predetermined value and / or the comparison value Tv is a measured value. t and / or the comparison value Tv is constantly adjusted by machine learning.

[0062] The comparison value Tv is the temperature value of the surface of the storage location 25 of the substrate 16, and the measurement value t is a temperature value obtained on the surface 3 of the susceptor 6 other than at the storage location 25.

[0063] Measurements t is the composition or mass flow rate of the temperature regulating gas 24 in the gap 10 between the cooling body 11 and the body and / or process chamber ceiling 7 regulated to a pre-given temperature T.

[0064] The etching steps E1, E2 of the same or different duration may be performed several times in succession and / or the etching steps may be performed using a measurement t and / or the measured value is measured for a period of time until the comparison value Tv is reached or falls within a temperature window around the reference temperature. thas reached the comparison value Tv or is within the window, the last etching step E+ is performed for a predetermined time, and / or each etching step E1, E2, E+ or at least some of these etching steps E1, E2, E+ comprises a first cleaning phase A in which an etching gas is supplied into the process chamber 6, followed by a first flushing phase B, followed by a second cleaning phase C in which a cleaning gas is supplied to the process chamber, followed by a second flushing phase D.

[0065] A method, characterized in that the comparison value Tv is determined by monitoring a second thermal response of at least one second object 2, 3, 7, 8, 11 during the supply of the etching gas.

[0066] A method, characterized in that the comparison value Tv is the difference between a predetermined constant value and the thermal response detected on the second object 2, 3, 7, 8, 11.

[0067] A method comprising obtaining a measurement value t by monitoring a thermal response of at least one object 2, 3, 7, 8, 11 in a process chamber 6 or in a region adjacent thereto, and terminating the supply of etching gas when the absolute value of the time derivative of the change in the measurement value t falls below a predetermined value Z.

[0068] A method comprising the steps of: obtaining a first measurement value t1 by monitoring a first thermal response of at least one first object 2, 3, 7, 8, 11 in the process chamber 6 or in its vicinity; obtaining a second measurement value t2 by monitoring a second thermal response of at least one second object 2, 3, 7, 8, 11 in the process chamber 6 or in its vicinity; and terminating the supply of etching gas when the relationship between the two measurement values ​​t1, t2 falls within a window set around a comparison value tV or when the absolute value of the time derivative of the relationship between the two measurement values ​​t1, t2 falls below a predetermined value Z.

[0069] A method characterized in that the relationship between two measured values ​​t1, t2 is the difference between the two measured values ​​t1, t2.

[0070] An apparatus characterized in that, while supplying etching gas to the susceptor 2, the control device 23 is programmed to monitor the temporal change in a first temperature T of the first object 2, 3, 7, 8, 11 and / or the temporal change in a second temperature of the second object 2, 3, 7, 8, 11 by the method described in claims 1, 2, 3-6 or 14-18, or to monitor the temporal change in a measured value t of the output of the heating device 5 or the cooling device 11, the composition or the mass flow rate of the temperature regulating gas 4 by the method described in claims 11, 13 or 14.

[0071] All disclosed features are essential to the invention (both by themselves and in combination with one another). The disclosure of the present application includes in its entirety the disclosure content of the relevant / added priority documents (copies of the earlier application), also with a view to incorporating the features of these documents in the claims of the present application. The dependent claims are characterized by an independent, inventive further development of the prior art, even without the features of the cited claims, in particular in order to file a divisional application on the basis of these claims. The invention specified in each claim may additionally have one or more features specified in the preceding description, in particular those given reference signs and / or specified in the explanation of the signs. The present invention also relates in particular to design forms in which individual ones of the features mentioned in the preceding description are not implemented, insofar as they are obviously unnecessary for the respective intended use or can be replaced by other means having the same technical effect. [Explanation of symbols]

[0072] 1 Reactor housing 2 Susceptor 3. Main surface 4 Main Surface 5 Heating device 6 Process Chamber 7 Process chamber ceiling 8 Main Surface 9 Main Surface 10 gap 11 Cooling device 12 Cooling Channels 13 Gas inlet member 14 Gas outlet hole 15 Gas exhaust components 16 Substrate 17 Shaft 18 Temperature Sensor 19 Temperature measuring device 20 Measurement points 21 holes 22 Temperature control gas supply line 23 Control device 24 Temperature control gas source 25 Storage location Time t1 Time t2 Time t3 Time t4 At time t5 At t6 At time t7 At time t8 A. First cleaning phase B. First flushing phase C. Second cleaning phase D. Second flushing phase E1 Etching step E2 Etching step E+ Etching Step T temperature Tv comparison temperature Z Temporal sequence

Claims

1. A method for removing parasitic deposits from a surface of a process chamber (6) of a CVD reactor having a susceptor (2) that can be heated by a heating device (5), comprising the steps of: supplying an etching gas into the process chamber (6) heated to a high temperature during the removal; obtaining a measured value (t) by monitoring a thermal response of at least one object (2, 3, 7, 8) in the process chamber (6) or in a region adjacent thereto; and terminating the supply of the etching gas when the measured value (t) reaches a comparison value (Tv), when it falls within a window set around the comparison value (Tv), or when the absolute value of the time derivative of the change of the measured value (t) falls below a predefined value (Z); during the supply of the etching gas, a temperature regulator is adjusted to a predefined temperature (T) or heated with a constant heating power; and the thermal response is the temperature or emissivity of the surface of the component (2, 3, 7, 8), The method, wherein the components (2, 3, 7, 8) are arranged on a heat transport path between the heating device (5) and the cooling device (11) and the parasitic deposits affect the emissivity of the components (2, 3, 7, 8), the change in the emissivity changing the heat flow between the heating device (5) and the cooling device (11), 4. A method according to claim 3, wherein the surface of the component (2, 3, 7, 8) whose thermal response is monitored during removal of parasitic deposits is a surface free of parasitic deposits.

2. 2. A method according to claim 1, characterized in that, prior to the removal of parasitic deposits, one or more crystalline layers are deposited on a plurality of substrates (16) simultaneously arranged in a storage location (25) on a susceptor (2) adjacent to a process chamber (6) on one side by supplying at least one organometallic compound of an element of the II-, III- or IV- main group and at least one hydride of an element of the IV-, V- or VI- main group together with a carrier gas, during which deposition the parasitic deposits to be removed are formed, and after the deposition of the layers the substrates (16) are removed from the process chamber (6) and the etching gas is or contains an element of the VII- main group.

3. 3. The method according to claim 1 or 2, characterized in that the object to be monitored is an area of ​​a surface (3, 8) of a body (2, 7) having a surface (3, 9) with the parasitic deposits to be removed and / or the object to be monitored is a functional component of the process chamber.

4. The method according to any one of claims 1 to 3, characterized in that the thermal response is measured by an optical metrology device (19).

5. 5. The method according to any one of claims 1 to 4, characterized in that the thermal response is the temperature (T) measured on a main surface (8) of a process chamber ceiling (7) adjacent to the process chamber (6) facing away from the process chamber (6) under process parameters that are otherwise kept constant.

6. 6. The method according to claim 1, wherein the comparison value (Tv) is a temperature (T) measured on a body (7) free of parasitic deposits in a preliminary experiment under the same process parameters and / or the window is a temperature range around a reference temperature measured on a body (7) free of parasitic deposits in a preliminary experiment under the same process parameters.

7. 7. The method according to claim 1, characterized in that a functional component (2) of the process chamber (6) is brought to a pre-given temperature (T) by a heating output of the heating device (5) or a functional component (7) of the process chamber (6) is brought to a pre-given temperature (T) by a cooling output of the cooling device (11).

8. 8. The method according to claim 1, wherein the comparison value (Tv) is a predetermined value, and / or the comparison value (Tv) is obtained simultaneously with the measured value (t), and / or the comparison value (Tv) is constantly adjusted by machine learning.

9. 9. The method according to claim 1, wherein the comparison value (Tv) is a temperature value of the surface of a storage location (25) of a substrate (16) on the susceptor (2) and the measurement value (t) is a temperature value obtained on a surface (3) of the susceptor (2) other than the storage location (25).

10. 10. The method according to claim 1, wherein the measured value (t) is the composition or mass flow rate of a temperature-regulating gas (24) in a gap (10) between a cooling body (11) and a body and / or a process chamber ceiling (7) controlled to a pre-given temperature (T).

11. 11. The method according to any of the preceding claims, characterized in that several etching steps (E1, E2) of the same or different duration are performed in succession, and / or that the etching steps are performed until the measured value (t) reaches the comparison value (Tv) or falls within a temperature window around a reference temperature, and / or that a final etching step (E+) is performed for a predetermined time after the measured value (t) reaches the comparison value (Tv) or falls within the window, and / or that each of the etching steps (E1, E2, E+) or at least some of the etching steps (E1, E2, E+) comprises a first cleaning phase (A) supplying an etching gas to the process chamber (6), followed by a first flushing phase (B), followed by a second cleaning phase (C) supplying a cleaning gas to the process chamber (6), followed by a second flushing phase (D).

12. A method according to any one of the preceding claims, characterized in that said comparison value (Tv) is determined by monitoring the thermal response of at least one second object (2, 3, 7, 8, 11) during the supply of said etching gas.

13. 13. A method according to claim 12, characterized in that said comparison value (Tv) is the difference between a predetermined constant value and the thermal response detected in said second object (2, 3, 7, 8, 11).

14. 14. The method according to any one of the preceding claims, characterized in that the comparison value (Tv) is obtained by monitoring a second thermal response of at least one second object (2, 3, 7, 8, 11) in the process chamber (6) or in its vicinity.

15. An apparatus for carrying out the method according to any one of claims 1 to 14, comprising a CVD reactor having a process chamber (6) arranged in a CVD reactor housing (1), said process chamber (6) comprising a susceptor (2) with a number of storage locations (25) for storing at least one substrate (16) respectively, a heating device (5) for heating said susceptor (2) and a gas inlet member (13), one or more surfaces (3, 9) on which parasitic deposits form during a coating process in which at least one organometallic compound of an element of main group II, III or IV and at least one hydride of an element of main group IV, V or VI are fed together with a carrier gas through the gas inlet member (13) into the process chamber (16); a metrology device (19) for sensing a thermal response of at least one object (2, 3, 7, 8) within or near the process chamber (6); a control device (23) for controlling valves and mass flow controllers to generate a flow of etching gas through the process chamber (6) and for stopping the flow of etching gas in the process chamber (6) when a measured value (t) obtained from the thermal response reaches a comparison value (Tv); In the device, the components (2, 3, 7, 8) are arranged on a heat transport path between the heating device (5) and the cooling device (11), and the parasitic deposits affect the emissivity of the components (2, 3, 7, 8), the change in emissivity changing the heat flow between the heating device (5) and the cooling device (11), 15. Apparatus, characterized in that the control device (23) is programmed to terminate the supply of etching gas according to a method according to any one of the preceding claims.

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