Method for calibrating a pyrometer arrangement of a CVD or PVD reactor

Abstract

Method for calibrating a pyrometer arrangement (11, 12, 12') for measuring the surface temperature of a substrate (9) resting on a susceptor (6) of a CVD / PVD reactor (1), wherein the pyrometer arrangement (11, 12, 12') comprises a first pyrometer (11) sensitive in a narrow spectral range with a bandwidth of less than 20 nm, pre-calibrated at the factory or in a pre-calibration step, and at least one second pyrometer (12) sensitive in a second, broadband spectral range with a bandwidth greater than 100 nm, wherein in a first step the first pyrometer (11) is calibrated and in a second step the susceptor (6) or a calibration element (17) is heated to a calibration temperature or successively to several different calibration temperatures (T1, T2, T3, T4) which is measured with the first pyrometer (11) and is used as Support point (S1, S2, S3,S4) is used to determine a characteristic curve of the second pyrometer (12).

Description

[0001] A device for depositing semiconductor layers, e.g., III-IV semiconductor layers, has a reactor housing, a susceptor arranged therein, e.g., made of graphite or coated graphite, a heating device arranged below the susceptor, e.g., an IR, RF, or lamp heating device, a gas inlet device arranged above the susceptor, with which process gases are introduced into the process chamber, and one or more temperature-sensitive sensors for determining the surface temperature of the substrates resting on the susceptor and feeding this temperature to a control device with which the heating can be controlled such that the surface temperature is maintained at a predetermined value. DE 10 2012 101 717 A1, for example, describes such a device.In conjunction with several sensors and a multi-zone heater, the control system can regulate the temperature distribution on the susceptor and thus on the substrates and from substrate to substrate.

[0002] DE 10 2004 007 984 A1 describes a CVD reactor with a process chamber arranged in a reactor housing. The floor of the process chamber is formed by a susceptor, which supports the substrates to be treated, in particular coated. The process chamber ceiling is formed by a gas inlet element, which has inlet openings through which the process gases can enter the process chamber. A heater is arranged below the susceptor to heat the susceptor to the treatment temperature. The surface temperature of the susceptor is measured using a plurality of temperature sensors. Furthermore, US Pat. No. 6,492,625 B1, EP 1 481 117 B1, and DE 10 2007 023 970 A1 are also part of the prior art.

[0003] The temperature of the substrate surfaces is typically measured using a pyrometer. The pyrometer must be calibrated before being used as a temperature measuring device. EP 2 251 658 B1 and EP 2 365 307 B1 describe a method for calibrating a pyrometer using a light source that simulates a "Planckian radiator." This is a light source that irradiates the pyrometer during calibration with a controlled reference radiation flux that is equivalent to blackbody radiation in a relatively limited spectral wavelength range and corresponds to a previously calibrated reference temperature in the pyrometer.

[0004] Such a device with multiple light sources is described in US 2013 / 0 294 476 A1.

[0005] The aforementioned documents each describe methods for calibrating a narrowband pyrometer. Such pyrometers are sensitive, for example, to a wavelength of 950 nm, with a bandwidth of < 10 nm. The intensity measured with such a narrowband pyrometer depends approximately on the temperature T as follows: I = A*exp (- B / T), where A and B are constants to be determined during the calibration process. The key is to determine parameter A, which depends on the quality of the light path from the measuring point to the sensor, i.e., in particular, on the transmittance of a window or the size of a critical aperture. Parameter B is usually set during production when the pyrometer is calibrated. This is done using a blackbody radiator.The parameter B is determined, especially in the case of a narrowband pyrometer, by the wavelength at which the pyrometer is sensitive and is often determined by the choice of the filter that determines the wavelength and wavelength bandwidth in the sensor.

[0006] The prior art also includes the following documents dealing with the calibration of pyrometers: US 6 398 406 B1, EP 0 490 290 B1, US 6 151 446 A, US 8 296 091 B2, US 6 963 816 B1, WO 2004 / 001 840 A1, US 6 379 038 B1, WO 00 / 54 017 A1, US 2002 / 0066859 A1, WO 99 / 13 304 A1, WO 98 / 04 892 A1, EP 0 801 292 B1, WO 97 / 11 340 A1, WO 98 / 53 286 A1, US 5 249 142 A, US 4 979 134 A, US 4 979 133 A, EP 0 317 653 B1, US 4 708 474 A and US 4 222 663 A.

[0007] Measuring the temperature of a substrate surface with a narrowband pyrometer, as is common practice in the state of the art, has the disadvantage that it does not allow for reliable control of the heating. The temperature measurement is influenced, for example, by the Fabry-Perot effect during film growth. Due to the low intensity, the measured values ​​of a narrowband pyrometer suffer from high signal noise. Filters are used in narrowband pyrometers to prevent sensor drift due to changing sensor temperatures. The occupancy of the window through which the optical path passes also influences the measurement result.

[0008] In addition to narrowband pyrometers (bandwidth < 20 nm, preferably < 10 nm), broadband pyrometers (bandwidth > 100 nm, preferably > 200 nm) are also used. Due to their wider bandwidth, these pyrometers receive a significantly stronger light signal from the surface being measured. They are less sensitive to temperature drift. In pyrometers with wider bandwidths, the temperature measurement is less sensitive to thin-film interference effects (Fabry-Perot effect) and less sensitive to wavelength-dependent scattering on structured substrates. However, significant temperature drift occurs due to the lack of filters.

[0009] The procedure described above for calibrating narrowband pyrometers is no longer possible for broadband pyrometers for several reasons. Firstly, the reference radiation sources described above with a defined radiation flux corresponding to a calibrated radiation temperature and exhibiting the spectral characteristics of a blackbody radiator are practically unavailable for larger bandwidths (e.g., > 10 nm). Secondly, the relation I = A*exp (- B / T) is not applicable over larger spectral ranges because the sensitivity of the photodetectors used is wavelength-dependent. The relation for the spectral radiation intensity, the Planck equation, is: I(λ,T)dλ=C1λ5(eC1 / λT−1)dλ≈C1⋅e−C2 / λTλ5dλ, where the constant C1 can be wavelength-dependent if the detector sensitivity is wavelength-dependent. As a result, the relationship I = A*exp (- B / T) no longer applies when integrated over the entire spectral range, but is non-linear in the plot log(I) versus 1 / T. Due to this non-linearity, it is no longer possible to represent the relationship between signal intensity in the detector and temperature of the measurement object using two calibration constants A and B. Therefore, it is often common practice to use blackbody radiation sources for the calibration of broad-band pyrometers. These are cavity radiation furnaces heated to the respective radiation temperature. These are common for initial factory calibration of pyrometers, but are too bulky and time-consuming for calibration or sporadic recalibration of pyrometers on the plant due to the long temperature stabilization times.

[0010] Several methods are known to describe or approximate the relationship sufficiently precisely for the measurement process, for example, by using a higher-order fitting function for the non-linear curve in the Log(I) versus 1 / T plot, or by piecewise linearization, so that the relationship I = A*exp (- B / T) exists for specific temperature ranges 1, 2, 3, ..., with calibration parameters A1, A2, A3, ..., B1, B2, B3, ..., or a combination of both, i.e., higher-order piecewise approximations. The starting point in each case is the availability of a sufficient number of support points along the Log(I) versus 1 / T plot of the pyrometer.

[0011] The amount of light reaching the pyrometer can depend on other geometric effects, such as the window's occupancy. If the window's occupancy affects the window's transmissivity differently for different wavelengths, multiple pyrometers sensitive to different wavelengths can be used. To determine the surface temperature, not only the absolute intensity value but also a ratio between the two intensity values ​​is used.

[0012] The amount of light reaching the pyrometer can depend on geometric effects, but also on the unknown emissivity of the hot measuring object, especially of the substrate coated during the process. Unknown or incorrectly known emissivity leads to errors in temperature determination by pyrometers, in which the amount of radiation arriving at the sensor is related to the temperature of the radiation-emitting object using Planck's radiation equation.The following known technical solutions exist for addressing this problem: a) Determining the emissivity during the temperature measurement process by measuring the reflection of a light signal at the same wavelength to which the pyrometer detector is sensitive; b) Using two or more detectors sensitive to different wavelengths in the pyrometer arrangement and determining the surface temperature of the object by the ratio of the two or more intensity values, a so-called ratio pyrometer. Technical solution a) has several disadvantages, e.g.Scattering of the reflection signal on structured substrates or on the surface of a rough susceptor instead of the substrate surface leads to an underestimation of the reflectivity and an overestimation of the emissivity (E = 1-R). For partially transparent substrates, such as sapphire, E = 1-R no longer applies, and the spectral distribution of the reflection signal must be adapted to the spectral distribution of the detector's sensitivity. In practice, this is only achievable for relatively narrow bandwidths (<50 nm, often only <20 nm); the advantages of broadband measurement outlined above are then incompatible with this type of emissivity correction. Technical solution b) circumvents these limitations of solution a) by eliminating the need for a reflection measurement and thus enabling the simple use of broadband detection of the radiation emitted by the measurement object (substrate, susceptor).With solution b), i.e., a broadband ratio pyrometer, the insensitivity to thin-film interference effects (Fabry-Perot effect) can be combined with the use on rough surfaces or structured substrates and with the use at low signal intensities, so that the signal-to-noise ratio is superior to that of narrowband detectors. A limiting requirement for accurate temperature determination by forming the ratio of the intensities at the different wavelengths is that the emissivity of the measurement object is approximately constant at the two wavelengths, within the desired temperature measurement accuracy. The emissivity then cancels out when forming the ratio. Sapphire and GaN, as well as the susceptor material graphite, fulfill this requirement relatively well in the wavelength range relevant for the measurement (again, within the desired accuracy of the method).Strongly wavelength-dependent influences on emissivity, such as the Fabry-Perot effect, are sufficiently attenuated by the broadband nature of the detection. A further advantage of using ratio pyrometers is that geometric changes along the optical path or changes in optical transmission, for example, due to opacity or blockage of optical windows along the beam path, cancel out the quotient in a similar way to the emissivity of the target during the quotient calculation, provided, however, that these changes affect the intensity at the detector location uniformly for the different wavelengths, and with broadband detectors, uniformly across the entire relevant spectral range.

[0013] However, certain technical challenges arise with solution b): The occlusion or clouding of an optical window in the optical path from the measurement object to the detector can change the transmission of the radiation in a wavelength-dependent manner. This leads to inaccurate temperature measurement results, resulting in a drift of the measured temperature compared to the actual temperature of the measurement object. For long-term use of the pyrometer arrangement, for example in semiconductor manufacturing, this requires recalibration of the detectors, for example, during normal maintenance cycles. A well-known calibration method is based on the use of blackbody radiation across the entire relevant spectral range, which is generated by furnaces with cavity radiation. However, these furnaces are practically unsuitable for recalibrating pyrometers installed on top of or in the process chamber due to their size and long temperature stabilization times.

[0014] This results in the overall task of finding a calibration method for the use of broadband pyrometers for temperature measurement in the described application in semiconductor processing plants, which does not have the disadvantages of the known calibration methods and the limitation to sufficiently narrow-band pyrometers,

[0015] The invention is based on the object of providing a method for calibrating a broadband pyrometer.

[0016] The problem is solved by the invention specified in the claims.

[0017] To enable the described calibration, a pyrometer arrangement is used, consisting of a first, narrowband pyrometer sensitive in a specific spectral range, and at least one second, broadband pyrometer with a different spectral range than the first pyrometer, which is larger than that of the first pyrometer. Both pyrometers are preferably directed at the same measuring location. They can have the same optical path, but can alternatively have different optical paths. Alternatively, in the case of a rotating susceptor, both pyrometers can be located at different locations on the same radius. The second pyrometer can also consist of a ratio pyrometer, in which two or more broadband pyrometers or detectors are used to determine the temperature from the intensity ratio.The actual temperature measurement is performed with the broadband pyrometer; the narrowband pyrometer has an auxiliary function for calibrating one or more broadband pyrometers. When measuring temperature during production on the system, the narrowband pyrometer is not used for temperature control at all.

[0018] The inventive calibration method essentially begins with the following preparatory steps: - Providing a pyrometer arrangement whose pyrometers have been individually factory calibrated using a blackbody furnace, so that the steps described below allow adaptation to the actual geometric conditions in the process chamber during assembly or to miscalibration due to long-term operation, window clouding, aging of the detectors or electronics. - Providing a CVD / or PVD reactor with a susceptor for holding a substrate, - Providing a first pyrometer which is sensitive in a first spectral range, in particular narrow-band to a first wavelength, - Providing a second pyrometer which is sensitive in a second spectral range, in particular broadband on a second wavelength.

[0019] The first step involves calibrating the first pyrometer. This is done using the calibration tools described in the literature mentioned above, for example, using a reference body that is heated to different temperatures. Since the first pyrometer is a narrowband pyrometer, an elevated temperature is generally sufficient to determine the position of the straight characteristic curve plotted as log(I) versus 1 / T. However, calibration can also be performed using a calibration tool, which is essentially a light source that simulates the light emission of a heated reference body in a specific, in practice relatively narrow, wavelength range, and where the radiant power of the light emission is assigned a fixed temperature by factory calibration.In a subsequent step, the susceptor, or a calibration block resting on the susceptor instead of a substrate, is brought to one or more different calibration temperatures. This is achieved in particular by heating the susceptor, which can be a calibration block, or a calibration block resting on the susceptor. The calibration temperatures are measured with the already calibrated first pyrometer. The measured values ​​resulting from the temperature measurements by the already calibrated narrowband pyrometer are used as support points for a characteristic curve of the second pyrometer. The characteristic curve of a pyrometer refers to the assignment of temperatures to signal intensities; it is often plotted in the form log(I) versus 1 / T.From the characteristic curve, calibration parameters for the associated pyrometer can be determined, which are stored on the pyrometer's control unit. These parameters are then used for subsequent measurements on targets of unknown temperature and / or unknown emissivity to assign the measured temperature to the corresponding measured signal intensity based on the spectral radiant power arriving at the pyrometer. The measured values ​​can also be used to determine the calibration parameters for a piecewise linear approximation or a piecewise higher-order approximation for broadband pyrometers, or for a higher-order approximation over the entire temperature range. The characteristic curve of the second, broadband pyrometer is generally not a straight line in an Arrhenius plot, but rather a curve whose shape depends on the difference between the sensor's sensitivity spectrum and the emission spectrum of the reference body.It is intended that both pyrometers measure the intensity of the light emitted from the same measuring point (infrared light). The optical path from the measuring point to the pyrometers preferably runs through a gas outlet opening of the gas inlet device and through a window arranged on the rear of the gas inlet device. The pyrometer arrangement can be located inside the reactor housing. However, it can also be located outside the reactor housing. In this case, the optical path passes through another window. A beam splitter can be provided to split the optical path into at least two partial paths, with each partial path leading to one of the two pyrometers. The narrowband pyrometer can be sensitive to a wavelength of 950 nm. The bandwidth is preferably below 50 nm, more preferably in the range of 20 nm, 10 nm or less. The broadband pyrometer can be sensitive to the same wavelength.The bandwidth is preferably greater than 100 nm. It can be greater than 200 nm. While one measurement point is generally sufficient to calibrate the narrowband pyrometer, at least three measurement points are preferably determined to calibrate the broadband pyrometer in a temperature range between 200 and 1,300°C. This results in two temperature ranges that define a basic characteristic curve consisting of two support points. The basic characteristic curve can be formed in a log(I) versus 1 / T representation of two straight lines or a smooth curve passing through the support points. Preferably, more than three support points are recorded at more than three different temperatures. A ceramic body can be used as the calibration body.In particular, it is intended to use a graphite body, a SiC-coated graphite body, a silicon substrate, a SiC body, or a substrate coated with SiO2 or Si3N4 as the calibration body. The calibration body can be an optically gray body. The emissivity of the calibration body must be known for the assignment of temperature and signal intensity. If the calibration body has a non-constant emissivity (i.e., a non-gray body), the dependence of the emissivity on temperature and wavelength must be known. In a further development of the invention, the pyrometer arrangement has a third broadband pyrometer, which essentially has the same task as the second broadband pyrometer, namely to measure the surface temperature of the susceptor or a substrate at a specific location during regular operation of the CVD / or PVD device.The two broadband pyrometers are sensitive to different spectral ranges. For example, one broadband pyrometer may be a Si PIN diode. This pyrometer is sensitive in a spectral range from 400 to 1,200 nm. The second broadband pyrometer may be an InGaAs detector. This pyrometer is sensitive in a range between 1,100 and 1,700 nm. Temperature determination during regular operation of the PVD / CVD system is performed using the measured values ​​of both broadband pyrometers, using not only the absolute measured value but also the ratio, i.e., the quotient, of the two measured values. The calibration of the third pyrometer, i.e., the second broadband pyrometer, is carried out analogously to the calibration of the first broadband pyrometer, i.e., in the second calibration step.The calibration of the two broadband pyrometers takes place simultaneously at the same calibration temperatures and using the same calibration element, which can be a calibration block or a special susceptor. The narrowband pyrometer is sensitive to a first wavelength λ1. The second pyrometer is sensitive to a second wavelength λ2. The third pyrometer is sensitive to a wavelength λ3. The first wavelength λ1, the second wavelength λ2, and the third wavelength λ3 can lie within a frequency band that corresponds to the bandwidth of one of the broadband pyrometers. The wavelengths λ3, λ2, and λ3 can be the same wavelength, but they can also be different. The bandwidths of the two broadband pyrometers can be different, but they can also be the same. They can be offset by a certain amount, whereby the bandwidths may or may not overlap.The broadband pyrometer is preferably a two-color pyrometer, which has a silicon detector sensitive primarily in a spectral range between 450 nm and 1,100 nm, and an InGaAs detector sensitive primarily in a specialized range between 1,000 and 1,700 nm. The measured value provided by this pyrometer is the quotient of the measured values ​​of the two detectors. The first pyrometer is a broadband pyrometer by design. However, it is preceded by a narrowband filter so that it only receives light in the wavelength range specified by the filter. A body whose temperature profile of the emissivity is known is used as the calibration element.

[0020] Embodiments of the invention are explained below with reference to the accompanying drawings. They show: Fig. 1 schematically shows, as a sectional view, the essential details of a process chamber of a CVD reactor with a pyrometer arrangement 11, 12, 12' of a first embodiment, Fig. 2 the representation according to Fig. 1 during calibration of the narrow-band first pyrometer 11, Fig. 3 a representation according to Fig. 1 when calibrating the two broadband pyrometers 12, 12', Fig. 4 a representation according to Fig. 1 of a second embodiment, Fig. 5 a representation of log(I) versus 1 / T of a characteristic curve of a narrow-band pyrometer 11, and Fig. 6 a representation of log(I) versus 1 / T of a characteristic curve of a broadband pyrometer, which is drawn through four support points S1, S2, S3, S4 measured at temperatures T1, T2, T3, T4.

[0021] The Fig. 1 or Fig. 4 show the interior of a CVD reactor 1. The reactor housing is not shown. Within the reactor housing is a showerhead-like gas inlet element 2 with a gas outlet surface, which has a plurality of gas outlet openings 3, 3' evenly distributed over the circular disk-shaped surface. Below the gas outlet surface of the gas inlet element 2 is a process chamber 8, the floor of which is formed by a susceptor 6 made of coated graphite. The substrates 9 to be coated rest on the upper side of the susceptor 6 facing the process chamber 8. In the Fig. For clarity, only one substrate 9 is shown in Figure 1. A heating device 7 is located below the susceptor 6. This may be an infrared heating source.

[0022] The rear side of the inlet element, i.e., the side facing away from the gas outlet surface, has a window 5, 5'. The window 5, 5' is located above a gas outlet opening 3. An optical path 13 originating from a measuring point 15 on the substrate 9 is split into two optical paths 13', 13" by a beam splitter 14. A first pyrometer 11 receives light emitted from the measuring point 15 via the optical path 13, 13' according to Planck's radiation law. A second pyrometer 12 receives the thermal radiation in the infrared range from the measuring point 15 via the optical path 13, 13".

[0023] An electronic control device 10 is provided which interacts with the two pyrometers 11 and 12 and is capable of controlling the heating device 7.

[0024] The first pyrometer 11 is a narrowband pyrometer sensitive to a wavelength of 950 + / - 5 nm. It may be a silicon photodiode preceded by a narrowband filter 18 that only transmits the aforementioned wavelength of 950 nm.

[0025] The second pyrometer 12 has a silicon photodiode. This silicon photodiode is not preceded by a bandpass filter. The second pyrometer 12 is part of a pyrometer arrangement consisting of two pyrometers 12, 12'. It is formed by a silicon photodiode. It is a broadband pyrometer that operates across the entire spectral range of a silicon photodiode. This pyrometer arrangement can include a third pyrometer 12', which is formed by an InGaAs diode. This broadband pyrometer 12' is sensitive to a correspondingly broad spectral range of an InGaAs diode. The narrowband pyrometer 11 and the two broadband pyrometers 12, 12' receive infrared light from the same measuring point 15 through the same gas outlet opening 3 and the same window 5. Instead of two broadband pyrometers 12, 12', it is also possible to use just one broadband pyrometer 12.

[0026] In the Fig. In the embodiment shown in Figure 4, two pyrometer arrangements are provided, each having an identical structure. The two broadband pyrometers 12, 12' are separated from each other and each receive their respective light via a beam splitter 14'. The two sensor arrangements measure the light emission at two different locations on the surface of the susceptor 6. The two locations 15, 15' differ primarily in their radial distance R1, R2 from a central axis A. The susceptor 6 can be rotated about this central axis A. Thus, the sensor arrangements can measure temperatures at different radial distances.

[0027] During operation of the CVD reactor, in which process gases are introduced into the process chamber 8 through a supply line 4, enter the process chamber 8 through the gas outlet openings 3, 3', and pyrolytically decompose there, forming a layer on the surface of the substrate 9, the temperature at the measuring point 15, 15' is measured with the second pyrometer 12, 12'. This temperature is fed to the control device 10, which is capable of controlling the heater 7 such that the temperature measured at the measuring point 15 is maintained at a constant value.

[0028] When using pyrometer arrangements with two broadband pyrometers 12, 12' each, not only the absolute values ​​of the two broadband pyrometers 12, 12' are evaluated for temperature control or to determine a temperature measurement. In addition, a quotient of the two absolute measured values ​​is calculated and this quotient is evaluated. This measured value evaluation allows for the occupancy of windows through which the light emitted from the measuring point passes to be taken into account.

[0029] In a variant not shown, additional pyrometer arrangements 11, 12, 12' are provided, each of which receives infrared light passing through different gas outlet openings 3' in order to determine the temperature on the susceptor surface at different measuring points. The pyrometer arrangements are arranged at additional radial positions.

[0030] Calibration of the broadband pyrometer 12 or the two broadband pyrometers 12, 12' is carried out in the following steps:

[0031] First, a calibration tool 16 is used, as described in the aforementioned EP 2 365 307 B1 and EP 2 251 658 B1. This tool 16, simulating a heat-radiating gray or black body, is located below the gas outlet opening 3. The light emitted by the calibration tool 16 strikes the sensor surface of the narrowband pyrometer. This can be a Si PIN diode with an optical filter defining the spectral range. The narrowband pyrometer 11 is pre-calibrated at the factory in such a way that the slope of the characteristic curve in a log(I) plot over 1 / T does not need to be changed. The calibration essentially only determines the vertical position of the characteristic curve. The calibration tool 16 is used to Fig. 4 and in particular its altitude (indicated by the double arrow and the dashed parallel lines).

[0032] Alternatively, a calibration element can be heated to a specified temperature within the process chamber. The first, narrow-band pyrometer 11 is then calibrated using the light from this heated calibration element.

[0033] The calibration tool 16 or a calibration element is then removed from the process chamber. A calibration body 17 is inserted into the process chamber 8. The calibration body can be a silicon or sapphire substrate, or a coated silicon substrate or a coated sapphire substrate. However, it can also be a silicon substrate or a sapphire substrate provided with GaN or another III-V layer. It can be the same body that is used as a calibration element when calibrating the first pyrometer. It can be a ceramic plate, a graphite plate, or a metal plate. The susceptor 6 is first heated to a calibration temperature of > 200°C by means of the heater 7. Once the surface temperature on the calibration body 17 has stabilized, a first temperature T1 is measured using the already calibrated narrowband pyrometer 11.The intensity measured at this temperature T1 by the second pyrometer 12 is shown as support point S1 in the diagram (. Fig. 5). The third pyrometer 12' is calibrated in the same way at the same temperature T1.

[0034] The temperature is then increased to, for example, 400°. This temperature T2 is measured with the first pyrometer 11. The intensity measured at this temperature T2 with the second pyrometer 12 is entered as support point S2 in the diagram according to Fig. 5. Corresponding measurements are taken at higher temperatures, for example at a temperature T3 of 800°C and a temperature T4 of 1,200°C. The corresponding intensities are entered as support points S3 and S4 in the Fig. 5. The third pyrometer 12' can also be calibrated in the same way.

[0035] A characteristic curve is then created for the second pyrometer 12 and / or the third pyrometer 12'. For this purpose, a polygonal line (dashed line in Fig. 5) drawn or a smooth spline is placed.

[0036] The result is a basic characteristic curve with which the broadband pyrometer 12 or 12' is capable of determining the temperature of a substrate with the optical properties of the calibration block. From the basic characteristic curve, other characteristic curves can be derived for substrates with other known optical properties. List of reference symbols 1 CVD reactor 2 Gas inlet organ 3 Gas outlet opening 4 supply line 5 windows 5' window 6 Susceptor 7 Heating 8 Process Chamber 9 Substrat 10 Control device 11 Pyrometer / arrangement 12 pyrometers / arrangements 12' pyrometer / array 13 Optical path 13' Optical Path 13" Optical Path 14 beam splitters 14' beam splitter 15 measuring points 16 Calibration tool 17 Calibration element 18 narrowband filters A center axis S1 support points S2 support points S3 support points S4 support points T1 temperature T2 temperature T3 temperature T4 temperature

Claims

[1] Method for calibrating a pyrometer arrangement (11, 12, 12') for measuring the surface temperature of a substrate (9) resting on a susceptor (6) of a CVD / or PVD reactor (1), wherein the pyrometer arrangement (11, 12, 12') comprises a first pyrometer (11) sensitive in a narrow spectral range with a bandwidth of less than 20 nm, pre-calibrated at the factory or in a pre-calibration step, and at least a second pyrometer (12) sensitive in a second, broadband spectral range with a bandwidth of greater than 100 nm, in which in a first step the first pyrometer (11) is calibrated and in a second step the susceptor (6) or a calibration element (17) is tempered to a calibration temperature or successively to several different calibration temperatures (T1, T2, T3, T4) which can be determined with the first pyrometer (11) is measured and used as a support point (S1, S2, S3,S4) is used to determine a characteristic curve of the second pyrometer (12)., [2] Method according to claim 1, characterized by that the bandwidth of the first pyrometer (11) is less than 10 nm and the bandwidth of the second pyrometer (12) is greater than 200 nm. [3] Method according to one of the preceding claims, characterized by a third pyrometer (12') sensitive in a third broadband spectral range, which is calibrated together with the second pyrometer (12) in the second step and which forms a ratio pyrometer with different spectral ranges with the second pyrometer (12). [4] Method according to one of the preceding claims, characterized by that the first pyrometer (11) is calibrated with the susceptor (6) or calibration element (17) arranged within the CVD / or PVD reactor (1). [5] Method according to one of claims 1 to 3, characterized bythat the calibration of the first pyrometer (11) is carried out by means of a light-emitting calibration tool (16) with a known temperature dependence of the emissivity, for example a tempered reference body or a light source. [6] Method according to one of claims 3 to 5, characterized by that the first pyrometer (11) and the second pyrometer (12) and / or the third pyrometer (12') evaluate the intensity of the light emitted from the same measuring point (15) during calibration. [7] Method according to one of the preceding claims, characterized by that the first pyrometer (11) and the second pyrometer (12) are directed at the same measuring point (15) and have the same optical path (13) at least over a partial distance. [8] Method according to claim 7, characterized bythat the optical path (13) from the measuring point (15) to the first pyrometer (11) and to the second pyrometer (12) or third pyrometer (12') passes through a gas outlet opening (3) arranged on the front side of a gas inlet element (2) and through a window (5) on the back side of the gas inlet element (2). [9] Method according to one of the preceding claims, characterized by that three or more support points (S1, S2, S3, S4) are determined at a different temperature (T1, T2, T3, T4), in particular in a temperature range between 200 and 1300° C. [10] Method according to one of claims 5 to 9, characterized by that the reference body or the calibration element (17) is a susceptor used only for calibration, a plate made of a ceramic material, graphite or a semiconductor material, which is arranged on the susceptor (6) instead of the substrate (9). [11] Method according to one of the preceding claims, characterized by that during the tempering of the susceptor (6) or the calibration element (17), second or third pyrometers (12, 12') of further pyrometer arrangements are calibrated, each of which evaluates the intensity of the light emitted from different measuring points. [12] Method according to one of the preceding claims, characterized by that the calibration element (17) consists of a material belonging to the following group of materials: SiC, Si coated with SiC, graphite, graphite coated with SiC, Si, Si with a coating of SiO2 or Si3N4.

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