Method and pyrometer for measuring the temperature of a semiconductor substrate

Abstract

The invention relates to a method and a pyrometer for measuring the temperature of a semiconductor substrate during lamp-based thermal treatment of same. In the method, the following steps are provided: directing radiation in a wavelength range of 6 to 20 µm emitted by the semiconductor substrate onto a sensor; capturing radiation at the sensor, the radiation having a first radiation portion originating from the semiconductor substrate that is to be measured and a second radiation portion originating from components located in the sensor's field of view; identifying the second radiation portion taking into account a temperature of the components; outputting a temperature of the semiconductor substrate on the basis of the captured radiation. The pyrometer has an optical sensor, means for directing radiation in a wavelength range of 6 to 20 µm onto the sensor, at least one first housing surrounding the sensor, and means for ascertaining the temperature of the sensor and / or of components of the pyrometer which are located in the sensor's field of view.

Description

[0001] Method and pyrometer for measuring the temperature of a semiconductor substrate

[0002] The present invention relates to a method and a pyrometer for measuring the temperature of a semiconductor substrate, in particular a semiconductor substrate with a wide band gap (band gap > 1.2 eV), during a lamp-based thermal treatment thereof. The invention also relates to an apparatus for thermally treating a semiconductor substrate, which comprises the aforementioned pyrometer.

[0003] In semiconductor technology, it is common practice for semiconductor substrates to undergo multiple thermal treatments during manufacturing, whereby the temperatures during the thermal treatment must be precisely controlled to achieve the desired process results. During the thermal treatment, the semiconductor substrates are exposed to a specific gas atmosphere, which is usually exchanged and / or changed intermittently and / or continuously during the thermal treatment.

[0004] Lamp-based heating systems are frequently used for thermal treatment, particularly those based on halogen lamps. These systems are typically separated from the process chamber containing the semiconductor substrates and the gas atmosphere by quartz elements. However, the larger the substrate's band gap, the less the lamp radiation couples into the substrate, particularly at low substrate temperatures. At the same time, emissions are greatly reduced due to band transitions in the low temperature range and for substrates with a wide band gap, so that heating is often carried out using power-controlled, open-loop heating until an emissivity signal is measured in the pyrometer. On the other hand, intermediate elements made of graphite or silicon carbide were often inserted between the heating lamps and the wide-bandgap semiconductor substrate.These intermediate elements absorb the lamp radiation better, are heated, and then emit thermal radiation of a different wavelength, which couples more effectively into the semiconductor substrates. It is also known to accommodate the semiconductor substrates in a box consisting of a base and a lid in order to achieve corresponding indirect heating (convective heating) of the semiconductor substrates with lamp radiation. The material of the boxes is usually graphite, pyrolytically coated graphite, or SiC-coated graphite, or SiC. The boxes can be equipped with or without access openings for gas purging and, if necessary, holes for independently lifting the wafer and lid. The access openings make it possible, for example, to set a special gas atmosphere for processing, thus avoiding outgassing from the substrate (e.g., in the case of GaAs substrates).

[0005] However, such elements, which are provided, for example, as plates or boxes for holding the semiconductor substrates, can impair and, in particular, slow down the temperature control of the semiconductor substrates contained therein. Furthermore, the temperature of the semiconductor substrate cannot be measured directly in such a setup and is therefore only known approximately. Furthermore, such elements can also impair gas exchange on the surface of the substrate, i.e., within the box, which is important for the process results.

[0006] For temperature measurement and control, both for direct measurement of the semiconductor substrate and for indirect measurement via a box or plate, contactless measurement methods are generally used. Pyrometers with a measurement wavelength range of 2.3 or 2.7 pm are frequently used. The measurement wavelength range is usually determined by a filter element of the pyrometer, which essentially only transmits the measurement wavelength or a measurement wavelength range. Direct measurement of the substrate temperature in the lower temperature range (< 600 °C) is not possible, as the emissivity in this measurement wavelength range depends heavily on the semiconductor substrate itself, but also on the coating of the semiconductor substrate. Uncoated semiconductor substrates, in particular, have low emissivity in this measurement wavelength range, making them practically transparent.Although emissivity increases with increasing temperature, even at high temperatures, emissivity can still be quite low. Due to the large band gap in wide-bandgap semiconductor substrates, intrinsic conduction, or electron excitation, is very low across the entire temperature range of typical applications, and thus no free electrons are available for absorption or emission. This problem is exacerbated for semiconductor substrates with a wide bandgap. Therefore, temperature measurements in this measurement wavelength range require considerable effort and often require more than one pyrometer to determine a substrate temperature from the measured pyrometer signals.

[0007] The invention is therefore based on the object of providing a simplified contactless, direct temperature measurement of semiconductor substrates, in particular semiconductor substrates with a large band gap and also of element semiconductor substrates, during thermal treatment, with a lamp-based heating system, in particular from almost room temperature.

[0008] According to the invention, a method and a pyrometer are provided according to claim 1 and claim 9, respectively. A device for thermal treatment is also provided according to claim 23. Further embodiments of the invention are set forth, inter alia, in the subclaims.

[0009] In particular, a method for measuring the temperature of a semiconductor substrate during a lamp-based thermal treatment thereof is provided, comprising the following steps: directing radiation emanating from the semiconductor substrate in a wavelength range of 6 to 20 pm onto a sensor, detecting radiation at the sensor which has a first radiation component originating from the semiconductor substrate to be measured and a second radiation component originating from components located in the field of view of the sensor, determining the second radiation component taking into account a temperature of the components, outputting a temperature of the semiconductor substrate based on the detected radiation.

[0010] Such a method is particularly suitable for contactless, direct temperature measurement of semiconductor substrates with a wide band gap (>1.2 eV). In the specified wavelength range, the semiconductor substrates, especially semiconductor substrates with a wide band gap, have a relatively high emissivity even at low temperatures. For example, silicon carbide semiconductor substrates can achieve an emissivity of approximately 0.7 even at room temperature. This is probably due, among other things, to the fact that the emissivity here is not based on free electrons but on phonon absorption or emission. The second radiation component detected by the sensor, which originates from components in the sensor's field of view, can be easily determined by taking into account the temperature of the components and subtracted from the total sensor signal in order to directly output the temperature of the semiconductor substrate based on the detected radiation.Although a wider range of wavelengths, especially towards longer wavelengths, is possible, the specified range is considered sufficient for most applications. The specified range should therefore be interpreted to mean that at least wavelengths from this range are used in the method.

[0011] Preferably, radiation in a wavelength range of 7 to 15 pm, especially 8 to 14 pm, is directed onto the sensor, since the semiconductor substrate typically has increased emissivity in this range. To achieve improved independence from coatings on the semiconductor substrate, which can significantly influence emissivity at individual wavelengths, the wavelength range should preferably have a width of at least 4 pm.

[0012] To ensure good separation of the first and second radiation components, the radiation from the semiconductor substrate is advantageously guided to the sensor via an elongated viewing channel. The elongated viewing channel defines the sensor's field of view, such that essentially only light from the sensor's immediate surroundings (from a housing surrounding the sensor and / or the viewing channel) and from the semiconductor substrate to be measured falls on the sensor. The sensor's immediate surroundings are known and constant, so the second radiation component can be easily determined based on its temperature.

[0013] The method preferably comprises tempering the sensor, components that lie in the field of view of the sensor, in particular components that surround the sensor, and / or a body that defines the field of view to a predetermined temperature. By tempering the environment of the sensor, the sensor is essentially in an isothermal environment, which means that the second radiation component remains within a fluctuation range (caused by fluctuations in the tempering temperature) and can be easily compensated. It should be noted that a corresponding sensor not only receives radiation from a semiconductor substrate to be measured, but also radiation from the immediate environment and outputs a corresponding signal. Therefore, particularly at low temperatures of the semiconductor substrate, small fluctuations in the temperature of the sensor environment can lead to corresponding measurement inaccuracies.The means for controlling the temperature of the sensor and its immediate surroundings can counteract this accordingly. The sensor used is preferably a thermopile-based sensor, which collects radiation from the entire space surrounding the sensor. Such a sensor has the advantage of being able to measure broadband at least across the entire wavelength range mentioned. The predetermined temperature during the temperature control is preferably regulated or controlled with an accuracy of ± 0.5°C, preferably ± 0.1°C, since, particularly at low temperatures of the semiconductor substrate, slight fluctuations in the temperature of the sensor's surroundings could lead to corresponding measurement inaccuracies.

[0014] Alternatively or additionally, the method preferably comprises sensing the temperature of the sensor, components surrounding the sensor, and / or a body defining the viewing channel, wherein the sensed temperature is taken into account for determining the second radiation component. This, particularly in combination with temperature control, can increase the accuracy of the temperature reading for the semiconductor substrate.

[0015] The method is particularly suitable for measuring the temperature of a semiconductor substrate with a band gap of > 1.2 eV, but also for semiconductors, in particular element semiconductors with a smaller band gap.

[0016] The pyrometer for measuring the temperature of a semiconductor substrate comprises, in particular, an optical sensor, means for directing radiation in a wavelength range of 6 to 20 pm onto the sensor, at least one first housing surrounding the sensor, and means for determining the temperature of the sensor and / or components of the pyrometer located in the field of view of the sensor. Such a pyrometer enables an environment and the provision of signals that enable the implementation of the above-mentioned method with the corresponding advantages.

[0017] In particular, the means for guiding radiation can be configured to guide radiation in a wavelength range of 7 to 15 pm, in particular from 8 to 14 pm, and preferably with a wavelength range width of at least 4 pm, to the sensor. Preferably, the means for guiding radiation in a specific wavelength range comprise a bandpass filter in the beam path of the pyrometer (between the object to be measured and the sensor).

[0018] The means for determining the temperature preferably comprise means for tempering the sensor and / or components of the pyrometer that are in the field of view of the sensor to a predetermined temperature. In this case, the means for tempering should preferably be suitable for tempering the corresponding components with an accuracy of ± 0.5°C, preferably ± 0.1°C. In one embodiment, the pyrometer further comprises an elongated viewing channel that delimits a field of view of the sensor in the direction of the semiconductor substrate. This makes it possible to define a specific measuring spot on the semiconductor substrate, on the one hand, and the environment of the sensor from which radiation is recorded, on the other hand. In particular, in combination with a lens unit, the measuring spot (orits size) essentially independent of the distance to the semiconductor substrate, so that the substrate can be moved towards and away from the pyrometer within a process chamber, for example, without affecting the measurement result.

[0019] To increase the accuracy of the pyrometer, the means for determining the temperature, in addition to or alternatively to the means for temperature control, comprise a temperature sensor for measuring a temperature of the sensor and / or of components of the pyrometer that are within the sensor's field of view, in particular of the first housing and / or a body forming the viewing channel. Preferably, the pyrometer also comprises a compensation unit that compensates for influences on the sensor signal caused by the temperature of the sensor, the housing, and / or a body forming the viewing channel.

[0020] In one embodiment, the first housing is formed by a housing part having a receptacle and a diaphragm with a radiation opening, both to define a known environment and to provide a corresponding beam path toward the semiconductor substrate. To further define and limit the beam path, an elongated viewing channel is preferably provided, extending behind the radiation opening of the diaphragm in a viewing direction of the sensor.

[0021] In order to prevent radiation from outside the pyrometer (with the exception of direct radiation from a semiconductor substrate to be measured) from falling onto the sensor, the inner walls of the first housing and / or the viewing channel have a surface which substantially suppresses internal reflection of light entering at the radiation opening and / or at the free end of the viewing channel in the direction of the sensor. For this purpose, the surface can at least partially have a black coating which absorbs at least 90%, in particular at least 95% and preferably at least 99% of the light. The inner walls of the viewing channel can also be at least partially structured and preferably have a thread structure, in particular a fine thread structure or a structure in which the inner edges of the thread (towards the beam path) are not flattened.

[0022] The pyrometer preferably has a second housing that accommodates the first housing with the sensor accommodated therein and, if present, the body forming the viewing channel. The second housing has at least one flow channel for a fluid that is connectable to a source of temperature-controlled fluid. The pyrometer can have the source of temperature-controlled fluid, wherein the source of temperature-controlled fluid is preferably configured to provide fluid at a predetermined temperature with an accuracy of ± 0.5°C, preferably ± 0.1°C or less.

[0023] The device for thermally treating a semiconductor substrate comprises a process chamber with a receiving area for a semiconductor substrate, at least one heating unit suitable for heating a semiconductor substrate received in the receiving area, and a pyrometer of the type described above. The pyrometer is oriented such that, in addition to components of the pyrometer itself, only a surface of a semiconductor substrate received in the receiving area lies in the field of view of the sensor. The pyrometer is preferably directed substantially perpendicularly to the surface of a semiconductor substrate received in the receiving area.

[0024] In one embodiment, the at least one heating unit comprises at least one lamp, in particular a halogen lamp with a quartz jacket. The quartz jacket acts as a first filter for radiation from the halogen lamps above approximately 5 pm. Preferably, the at least one lamp is located on a side of the receiving area facing the pyrometer, and at least one further lamp or at least one plasma source is provided on the other side of the receiving area.

[0025] The invention will now be explained in more detail with reference to the drawing. The drawing shows:

[0026] Fig. 1 is a schematic sectional view of an apparatus for thermally treating substrates with a pyrometer;

[0027] Fig. 2 is a schematic sectional view of a pyrometer according to the invention;

[0028] Fig. 3 is an enlarged detailed view of part of the pyrometer according to Fig. 2;

[0029] Fig. 4 is a graph showing emissivity variations for silicon substrates with different coatings for different wavelengths and temperatures;

[0030] Fig. 5 is a graph showing an example of temperature control for a bare silicon carbide wafer in a direct heating mode; and

[0031] Fig. 6 is a graph showing an output signal of a pyrometer sensor with and without compensation.

[0032] Location terms used in the following description, such as above, below, etc., refer to the representation in the figures and are not to be seen as restrictive unless explicitly stated. However, they can indicate a preferred orientation. The term "essentially" is intended to include deviations of ± 10%, preferably ± 5%, with respect to a specified value. When specifying angles, the wording "essentially" is intended to include ± 10°, preferably ± 5°. Fig. 1 shows an apparatus 1 for the thermal treatment of substrates 2, in particular semiconductor substrates, and here preferably semiconductor substrates with a wide band gap, ie a band gap of > 1.2 eV.

[0033] The device 1 comprises a process chamber 4, heating units 6, 7, a substrate holding unit 9, and a pyrometer 10. The process chamber 4 is formed by a process chamber housing 12, which has a loading / unloading opening 14 in a side wall, which can be closed by a door element 15.

[0034] Although not shown, a lock unit may be provided in this area. A gas inlet 17 is provided on the side of the process chamber housing 12 opposite the loading / unloading opening 14, and an exhaust 18 is provided in the bottom of the process chamber housing 12. The gas inlet 17 and the exhaust 18 are shown only schematically and can easily be designed differently.

[0035] The heating unit 6 is arranged within the process chamber 4, specifically adjacent to a floor thereof. The heating unit 6 essentially consists of a plurality of rod-shaped lamps, for example halogen lamps, 20, each surrounded by a quartz tube 21. The lamps 20 extend perpendicular to the plane of the page according to Fig. 1 through the process chamber 4, as is known in the art. Instead of halogen lamps, other lamps can also be used. The lamps can also be separated from the actual process area of ​​the process chamber 4 by a quartz plate instead of individual quartz tubes.

[0036] The lamps 20 are arranged symmetrically with respect to a center plane of the process chamber 4. However, a symmetrical arrangement is not absolutely necessary.

[0037] The heating unit 7 is essentially constructed in the same way as the heating unit 6, with lamps 20, each surrounded by a quartz tube 21. The heating unit 7 is also arranged within the process chamber 4, but adjacent to an upper side thereof. Furthermore, the lamps 20 of the upper heating unit 7 are arranged rotated by 90° with respect to the lamps 20 of the lower heating unit 6. Both the number of lamps and their rotated arrangement are only examples, and an actual arrangement in a process chamber can be constructed differently. The respective lamps can be arranged such that the lamps in the fields are arranged parallel or perpendicular to one another as single-filament or double-filament lamps.

[0038] Furthermore, depending on the application, the upper heating unit 7 can be omitted and replaced, for example, by a plasma unit. Such a plasma unit can be constructed, for example, from elongated plasma rods housed in quartz tubes, as is known, for example, from EP 231 1066 A1.

[0039] The quartz tubes 21 are essentially transparent to the radiation of the lamps 20, but absorb radiation above 5 pm wavelength or may also contain water absorption bands (OH bands) and therefore additionally filter out radiation around 2.7 pm.

[0040] The substrate holding unit 9 essentially consists of a shaft 24 extending vertically through the floor of the process chamber housing 12, cantilevers 25 extending vertically thereto, and supports 26 extending vertically to the cantilevers 25. The shaft can be rotated about its own axis via a corresponding drive (not shown) and can optionally be moved up and down. Preferably, three cantilevers 25, each with a corresponding support 26, are provided. The shaft 24, the cantilever 25, and the supports 26 are preferably made of quartz glass and are thus essentially transparent to the radiation from the lamps 20. However, the substrate holding unit 9 can also be constructed differently, as is known in the art.

[0041] The substrate holding unit 9 defines a substrate receiving plane spanned by the respective upper sides of the supports 26. This plane is preferably aligned such that it extends substantially parallel to the floor of the process chamber housing 12. Thus, a horizontal alignment is preferably specified when a substrate 2 is placed on the supports 26. It is assumed that the substrate has a substantially flat shape.

[0042] The pyrometer 10 is arranged below the process chamber housing 12 here, but can also be arranged above it, in such a way that it looks into the process chamber 4 through a viewing window 28. The pyrometer 10 with the viewing window 28 is provided in such a way that it preferably looks through the center between two adjacent lamps 20 of the lower heating unit 6 onto the underside of a substrate 2 when the substrate 2 is placed on the supports 26. The viewing window 28 can be cooled or not cooled and is designed such that the radiation passes through and is not absorbed. In particular, the pyrometer 10 looks essentially perpendicularly onto the underside of the substrate 2. If the pyrometer is mounted on top, the directional information changes accordingly.

[0043] The pyrometer 10 is shown in greater detail in Figures 2 and 3, wherein Figure 2 shows a schematic sectional view of the pyrometer 10 and Figure 3 shows an enlarged detailed view of a measuring unit 30 of the pyrometer 10.

[0044] The pyrometer 10 has the measuring unit 30, a first housing 32 for receiving the measuring unit 30 and a second housing 34 for receiving control electronics for the measuring unit 30.

[0045] The measuring unit 30 is shown enlarged in Figure 3. It comprises a housing part 36, which, together with a diaphragm 37, forms a substantially closed receiving space for a sensor 38, as well as a body part 39, which forms a viewing channel 40.

[0046] The housing part 36 has a round rod shape that tapers several times along the outer circumference to form shoulders 42, 43, and 44. Between the shoulders 43 and 44, the outer circumference has an external thread. At one end, the end with the smallest outer circumference, a centered receptacle 46 is formed, which, as will be explained in more detail below, serves to accommodate the sensor 38.

[0047] From the receptacle 46, a through opening 48 also extends to the other end of the housing part 36, which, as will be explained in more detail below, is provided for the passage of cables.

[0048] The shoulder 42 of the housing part 36 serves as a fastening stop for the measuring unit 30 in the first housing 32, as explained in more detail below. The second shoulder 43 serves as a stop for the body part 39 forming the viewing channel.

[0049] As previously mentioned, the sensor 38 is received in the receptacle 46 of the housing part 36. The aperture 37 is also received, at least partially together with the sensor 38, in the receptacle 46 of the body part 39. The aperture 37, like the housing part 36, has a substantially round shape. Starting from a first end, the aperture 37 initially has a uniform outer circumference in a first section 50. The outer circumference then widens at a step on an outer circumference that approximately corresponds to the outer circumference of the housing part 36 at its narrowest point. This forms a bearing shoulder 51 on the aperture 37. From there, the outer circumference of the aperture 37 tapers via a second section 52 and a third section 53 in the direction of a longitudinal center plane of the aperture 37. A taper angle of the second section 52 with respect to the longitudinal center axis of the aperture 37 is smaller than a taper angle of the section 53.In both sections 52 and 53 the taper is essentially linear.

[0050] The outer circumference of the aperture 37 in the first section 50 substantially corresponds to the inner circumference of the receptacle 46 of the housing part 36 such that the aperture 37 can be snugly received therein. The length of the first section 50 of the aperture 37 substantially corresponds to the depth of the receptacle 46, so that when the first section 50 of the aperture 37 is inserted into the receptacle 46, the abutment shoulder 51 engages one end of the housing part 36.

[0051] The aperture 37 has a centered receptacle 55 with a round cross-section. The receptacle 55 extends from the first end, i.e. the end that is to be inserted into the receptacle 46 of the housing part 36, towards the second end. At the first end, the inner circumference of the receptacle 55 has a widening shoulder 57. At the second end of the aperture 37, the receptacle 55 tapers corresponding to the taper of the outer circumference in the third section 53. A central through-opening 58 is also formed in the second end. The inner surface of the aperture is preferably designed such that it does not reflect radiation entering through the through-opening and for this purpose preferably has a black coating that absorbs at least 95%, preferably at least 99%, of radiation in a wavelength range from 6 pm to 20 pm.

[0052] The sensor 38 has its own sensor housing 60, in which a holder 62 for a sensor element 64 and a lens 66 are provided. The sensor housing 60 is essentially tubular and has an outer circumference that essentially corresponds to the inner circumference of the receptacle 55 of the aperture 37—in the non-tapered part. Thus, the sensor housing 60 can be inserted snugly into the receptacle 55 of the aperture 37. At one end, a rear side, the sensor housing 60 has a flange 68 that is dimensioned to cooperate with the shoulder 57 of the aperture to limit the insertion depth of the sensor 38 into the receptacle 55.

[0053] The holder 62 is inserted tightly into the sensor housing 60 and, for example, firmly glued to it. The holder 62 holds the actual sensor element 64 in a centered manner such that an active surface of the sensor element points toward the lens 66. The lens 66 is located in front of the sensor element and, when the sensor 38 is installed, serves to direct light passing through the through-opening 58 of the aperture 37 onto the active surface of the sensor element 64, as shown in Figure 3.

[0054] The sensor element 64 has signal lines 69 that can be led out of the receptacle 46 via the through-opening 48 in the housing part 36. A temperature sensor (not shown in detail) is also provided in or on the holder 62, which is positioned such that it can measure the temperature of the holder or the sensor element. A corresponding signal line of the temperature sensor can also be led out of the receptacle 46 of the housing part 36 via the through-opening 48.

[0055] The body part 39 of the measuring unit 30, in turn, essentially has a tubular shape with an outer circumference that is essentially constant in a first section 70, which tapers at a first angle in a second section 71, tapers further in a third section 72 at a second angle that is smaller than the first angle of section 71, and tapers further in a fourth section at an angle that is greater than that of the second section toward a through-opening 75. The through-opening 75 is provided centrally. The through-opening 75 defines a front end of the body part 39.

[0056] Starting from the opposite rear end, the body part 39 has an inner circumference which initially forms an internally threaded section into which the external thread on the housing part can be screwed until the rear end of the body part engages the stop 43. At the end of the threaded section, the inner circumference is initially essentially constant up to the end of the first section 70. In the second section 71, the inner circumference tapers in line with the outer circumference in this section. In the third section 72, the inner circumference remains essentially constant, and in the fourth section 74, the inner circumference tapers in line with the taper of the outer circumference in the direction of the through opening 75. The body part 39 forms the viewing channel 40 in sections 72, 73, whereby the front taper in the fourth section 73, in combination with the through opening 75, forms a diaphragm.The inner walls of the body part 39 are designed, at least in the region of the third and fourth sections, i.e., in the region of the viewing channel, such that internal reflection of radiation entering through the through-opening 75 in the direction of the aperture 37, in particular the through-opening 58 of the aperture 37, is substantially suppressed. In particular, the surface here can also be black and, in the region of the third section 72, can have a structure, in particular a thread structure and preferably a fine thread structure, which ensures that internal reflection does not occur in the direction of the aperture 37 and thus in the direction of the sensor 38.

[0057] The body part 39 is dimensioned to at least partially accommodate the housing part 36 with the aperture and sensor accommodated therein, as shown in Figure 3. In particular, the body part 39 is dimensioned such that the end opposite the through-opening 75 can bear against the shoulder 43 of the housing part 36 when the external thread on the housing part 36 is screwed into the internal thread on the housing part 39. The housing part 36 is dimensioned such that it preferably only contacts the body part 39 in the threaded area. The taper of the body part 39 in the second section 71 is, in the assembled state, essentially at the same height as the taper in section 52 of the aperture 37.

[0058] The overall design of the measuring unit 30 is such that, as external radiation, only radiation entering essentially parallel to a longitudinal center axis of the sensor element can impinge on the active surface of the sensor element 64. With appropriate alignment of the measuring unit 30 or the pyrometer 10, it can thus be ensured that, as external radiation, essentially only radiation from the semiconductor substrate to be measured impinges on the sensor element 64. In addition, however, radiation generated by the intrinsic temperature of the components of the measuring unit 30, in particular from the area of ​​the aperture 37 or the viewing channel 40 in the body part 39, also impinges on the sensor element.

[0059] The measuring unit 30 is housed in the first housing 32 of the pyrometer 10. The housing 32 has a substantially cuboid-shaped body 82 with end faces 83, 84, which form a front and a rear side of the housing, respectively. A through-opening 86 extends through the first housing 32 between the front side 83 and the rear side 84.

[0060] The through-opening 86 has a substantially circular cross-section. Starting from the rear side 84, the through-opening 86 has a first inner diameter, which then tapers in a step-like manner to form a bearing shoulder 88, which serves as a bearing surface for the bearing shoulder 42 of the housing part 36 of the measuring unit 30 or a centering ring (not shown), as can be seen in Figure 2. Further along, the through-opening 86 has a linear taper, which corresponds to the taper in section 71 of the body part 39. This taper is in turn followed by a straight section, and adjacent to the front end 83, the through-opening 86 then has a step-like widening, forming a bearing shoulder 89 facing the front side 83. The measuring unit 30 can be inserted into the through opening 86 from the rear side 84, wherein means for centering the measuring unit 30 (not shown in detail) can be provided.The measuring unit 30 is accommodated in the through opening 86 in such a way that a thermal coupling between the two is not essential.

[0061] In the enlarged section of the through-opening 86 adjacent to the front side 83, a lens package 90 is provided, which has one or more lenses and filters. The lens package 90 is dimensioned such that it fits tightly into the enlarged section of the through-opening 86 or is screwed into it and rests against the contact shoulder 89, as shown in Figure 2. The lens package is designed such that a purge gas can flow around the lenses and in particular filters in order to dissipate absorbed thermal energy. The lens package 90 generates a confocal beam path in order to always measure the same radiation intensity, regardless of movement of the semiconductor substrate in the chamber (and thus varying distance between sensor and semiconductor substrate).The filters in the lens package are designed as bandpass filters that preferentially transmit only radiation in the wavelength range from 6 pm to 20 pm, preferably from 7 pm to 15 pm, and especially from 8 pm to 14 pm. The filter thus defines the actual measurement wavelength of the pyrometer, since the actual sensor, such as a thermopile sensor, could measure over a much broader range.

[0062] In the extended section adjacent to the rear side 84, a heat sink 91 can also be inserted into the through-opening 86 in order to close the through-opening from this side and to provide cooling / temperature control.

[0063] The body 82 of the first housing 32 further has internal lines 94 for a temperature control fluid. The internal lines 94 can be connected to a source of temperature control fluid via connections 95. The lines 94 extend at least partially parallel to the longitudinal axis of the through-opening 86, with cross connections also being provided to allow circulation of a temperature control fluid through the lines 94. The body 82, and thus the elements accommodated therein, can be kept essentially at a predetermined temperature via the temperature control fluid. In particular, it is possible to keep the components of the measuring unit 30 at a predetermined temperature, wherein a predetermined temperature, for example 25°C as room temperature, can preferably be set via the temperature control unit with an accuracy of ± 0.5°C, preferably ± 0.1°C.

[0064] Furthermore, a recess or bore 97 is provided in the body 82, which serves to accommodate a temperature sensor 98. The recess 97 extends laterally into the body 82 in such a way that a measuring head of the temperature sensor 98 is located near the through-opening 86, approximately at the level of the body part 39 forming the viewing channel 40.

[0065] The body 82 further has a through-opening 99, which connects the through-opening 86 adjacent to the rear side 84 to a side of the body 82. The through-opening 99 extends from the side of the body 82 in which the recess for the temperature sensor 98 is also provided.

[0066] The second housing 34 is attached to the side of the body 82 to which the through-opening 99 extends. The second housing 34 is essentially hollow and serves as a receptacle for an electrical component 100, which serves to receive and, if necessary, process signals from the measuring unit 30 and the temperature sensor 98. These signals can be conducted to the component 100 via the through-opening 99. The temperature sensor 98 is also partially accommodated in the second housing 34 and extends through an opening therein into the recess 97 in the body 82. The component 100 is connected via corresponding lines to the temperature sensor 98 and the sensor element 64 of the measuring unit 30, as well as to the temperature sensor adjacent to the sensor element 64 of the measuring unit 30. The component 100 can be connected to an external control unit via a connector.

[0067] As can be seen from the above description, the sensor element 64 of the measuring unit 30 is embedded in an isothermal environment that essentially encompasses the viewing angle of the sensor element. There is only a very small entrance opening for external radiation in the front area of ​​the aperture 37 and the front opening in the body part 39. Possible environmental effects on the radiation measurement are structurally compensated by this isothermal environment. The only external radiation reaching the sensor is direct radiation from the semiconductor substrate, which is achieved, among other things, by the viewing channel 40 in the body part 39. The structuring and the black color of the viewing channel prevent scattered radiation from reaching the sensor. The sensor element generates an output signal from the radiation from the isothermal environment as well as the radiation originating from the semiconductor substrate.Since the temperature of the isothermal environment is known, the corresponding portion of the radiation can be removed from the signal, so that the output signal of the sensor element can be used for a direct temperature measurement of the semiconductor substrate. In order to detect any small temperature fluctuations in the immediate vicinity of the sensor element, the temperature sensor is provided on the sensor element 64 and the temperature sensor 98 is provided in the body 82 of the first housing. Should these temperature sensors indicate deviations from a predetermined temperature, it is possible to electronically compensate for such deviations, which lead to corresponding deviations in the signal of the sensor element. Short fluctuations can be corrected, for example, using a low-pass filter. Such compensation using a low-pass filter is shown, for example, in Fig.6, where the X-axis represents the signal amplitude of a sensor signal and the Y-axis represents a time axis. Curve A shows a compensated signal, and curve B shows an uncompensated signal from the sensor.

[0068] In the following, a thermal treatment of a substrate 2 of the figures will be explained in more detail.

[0069] After a substrate 2 has been loaded into the process chamber 4, a desired process gas atmosphere (reactive, inert, oxidizing, reducing, etc.) can be set in the process chamber 4. The lamps of the lower and / or upper heating units 6, 7 are then controlled to heat the substrate. In this case, a certain temperature profile is usually specified for the semiconductor substrate that is to be achieved. Such a temperature profile is shown, for example, in Fig. 5, where the solid line specifies a temperature setpoint, i.e. a target temperature for the substrate during the process. Fig. 5 also shows a dotted line which represents a temperature detected by the pyrometer 10. The dashed line indicates the heating power of the lamps of the lower and upper heating units 6, 7, which is controlled based on the pyrometer signal.

[0070] For semiconductor substrates, particularly those with a wide band gap, such as silicon carbide (SiC), gallium arsenide (GaAs), gallium nitride (GaN), indium phosphide (InP) and others, or also silicon (Si), germanium (Ge), it is known that visible and infrared light from halogen lamps essentially passes through the substrate, especially at low temperatures. Only short-wave lamp light is absorbed sufficiently to achieve heating. With appropriate heating power, however, this proportion of short-wave light plus the long-wave portion absorbed by phonons is sufficient to heat semiconductor substrates with a wide band gap sufficiently quickly. High ramp rates can be achieved because the semiconductor wafer is heated directly, i.e. without intermediate elements such as plates or boxes made of graphite or SiC.Furthermore, direct temperature measurement (emissivity measurement) allows for good control of both the ramp rate and the semiconductor substrate temperature. Since additional elements in the chamber are eliminated, this not only minimizes the thermal mass that needs to be heated and cooled, but also allows for improved control of the process gas atmosphere. An additional element that could be provided in addition to the semiconductor substrate is a ring made of the same or a similar semiconductor material, formed in one piece or from multiple segments, that surrounds the substrate to be processed in the plane to compensate for edge effects during heating / cooling.

[0071] As previously mentioned, quartz essentially absorbs wavelengths of halogen lamp radiation above 5 pm, so that at measurement wavelengths from 6 to 20 pm, especially from 7 to 15 pm, and preferably from 8 to 14 pm, direct lamp radiation cannot interfere with the measurement. This leads to significantly reduced background radiation compared to other measurement wavelengths. The thin coatings used in semiconductor technology on the surface of semiconductor substrates influence the emissivity of the substrates, partly through the thickness of the dielectric layers, and partly through different doping concentrations or electrical conductivities.Due to the broad wavelength range, including the preferred wavelength range of 8-14 pm for the measurement, the usually much thinner layers in the measurement range used have a significantly reduced influence on the emissivity compared to narrower-band and shorter-wavelength measurements. Furthermore, since phonon interactions are significant at the measurement wavelength used, the different doping concentrations of conductive layers, which essentially influence free electron absorption, also have a significantly smaller contribution to the emissivity compared to shorter measurement wavelengths. Therefore, the width of the wavelength range for the measurement (also called the measurement wavelength) should be at least 4 pm or more.

[0072] Fig. 4 shows an example of an emissivity variation that can occur with different wafers and different coatings on the wafers at different temperatures for different measurement wavelengths. Si wafers with a SiO2 layer and different layer thicknesses of a SiAlSk layer were used as a basis. The figure shows that, for example, at a temperature of 400°C, the emissivity of the wafer - in the range of a measurement wavelength of 2.3 pm - can change between 0.1 and approximately 0.95 depending on the coating. At a measurement wavelength of 8 to 14 pm, a corresponding change only occurs between 0.7 and 0.95. Thus, at a measurement wavelength of 8 to 14 pm, the emissivity dependence is significantly lower. The range of variation becomes smaller at higher temperatures, although it is also clearly visible here that a measurement wavelength of 8 to 14 pm leads to smaller variations.

[0073] Furthermore, the use of a measurement wavelength of 8 to 14 pm has the advantage that the actual wafer temperature is recorded, whereas at conventional measurement wavelengths the temperature of the layers is recorded. The use of a pyrometer as described above enables direct heating using lamp radiation with direct temperature measurement, particularly for semiconductor substrates with a wide band gap. Intermediate elements (plate / box) can thus be omitted, which simplifies movement of the semiconductor substrate in the process chamber (up / down / rotation). The adjustment of a process gas ambient is also facilitated and improved. Direct temperature measurement allows rapid direct control of the lamp power. In the embodiment shown in Figure 1 with a bottom heating unit and temperature measurement from below, the upper heating unit can also be replaced with a plasma unit.This enables plasma processing of the front surface for processes such as side-wall smoothing, oxidation, nitridation, or other processes. The substrate temperature can be varied to make the plasma processes on the front surface more effective.

[0074] The invention has been explained in more detail with reference to the figures without being limited to the exact embodiment.

Claims

Patent claims 1 . A method for measuring the temperature of a semiconductor substrate during a lamp-based thermal treatment thereof, the method comprising: Directing radiation emanating from the semiconductor substrate in a wavelength range of 6 to 20 pm to a sensor; Detecting radiation at the sensor which has a first radiation component originating from the semiconductor substrate to be measured and a second radiation component originating from components located in the field of view of the sensor; Determining the second radiation component taking into account the temperature of the components; Outputting a temperature of the semiconductor substrate based on the detected radiation.

2. A method for measuring the temperature of a semiconductor substrate according to claim 1, wherein directing radiation emanating from the semiconductor substrate to a sensor comprises directing radiation in a wavelength range from 7 to 15 pm, in particular from 8 to 14 pm.

3. A method for measuring the temperature of a semiconductor substrate according to claim 1 or 2, wherein the wavelength range has a width of at least 4 pm.

4. A method for measuring the temperature of a semiconductor substrate according to any one of the preceding claims, wherein the radiation is directed from the semiconductor substrate to the sensor via an elongated viewing channel.

5. A method for measuring the temperature of a semiconductor substrate according to any one of the preceding claims, further comprising tempering of the sensor, of components that are in the field of view of the sensor, in particular of components that surround the sensor, and / or of a body that defines the field of view to a predetermined temperature.

6. A method for measuring the temperature of a semiconductor substrate according to claim 5, wherein the predetermined temperature is controlled during tempering with an accuracy of ± 0.5°C, preferably ± 0.1°C.

7. A method for measuring the temperature of a semiconductor substrate according to any one of the preceding claims, further comprising sensing the temperature of the sensor, components surrounding the sensor, and / or a body defining the viewing channel, wherein the sensed temperature is taken into account for determining the second radiation component.

8. A method for measuring the temperature of a semiconductor substrate according to any one of the preceding claims, wherein the semiconductor substrate is a semiconductor with a band gap of > 1.2 eV.

9. Pyrometer for measuring the temperature of a semiconductor substrate, in particular during a lamp-based thermal treatment thereof, comprising: an optical sensor; Means for conducting radiation in a wavelength range from 6 to 20 pm on the sensor; at least one first housing surrounding the sensor; and Means for determining the temperature of the sensor and / or components of the pyrometer that are in the field of view of the sensor.

10. Pyrometer according to claim 9, wherein the means for directing radiation are configured to direct radiation in a wavelength range from 7 to 15 pm, in particular from 8 to 14 pm, onto the sensor.

11. Pyrometer according to claim 9 or 10, wherein the means for directing radiation comprises a band-pass filter in the beam path of the pyrometer.

12. Pyrometer according to one of claims 9 to 11, wherein the means for determining the temperature comprise means for tempering the sensor and / or components of the pyrometer which are in the field of view of the sensor to a predetermined temperature.

13. A pyrometer according to any one of claims 9 to 12, further comprising an elongated viewing channel defining a field of view of the sensor.

14. Pyrometer according to one of claims 9 to 13, further comprising at least one temperature sensor for measuring a temperature of the sensor and / or components of the pyrometer which are in the field of view of the sensor, in particular the housing and / or a body forming the viewing channel.

15. Pyrometer according to one of claims 9 to 14, further comprising a compensation unit which compensates for influences on the signal of the sensor by the temperature of the sensor, the housing and / or a body forming the viewing channel.

16. Pyrometer according to one of claims 9 to 15, wherein the first housing surrounding the sensor is formed by a housing part having a receptacle and a diaphragm with a radiation opening.

17. Pyrometer according to claim 13 and 16, wherein the elongated viewing channel extends in a viewing direction of the sensor behind the radiation opening of the aperture. TI 18. Pyrometer according to one of claims 9 to 17, wherein inner walls of the first housing and / or the viewing channel have a surface which substantially suppresses internal reflection of light entering at the radiation opening and / or at the free end of the viewing channel in the direction of the sensor.

19. A pyrometer according to claim 18, wherein the surface has at least a partial black coating.

20. Pyrometer according to claim 18 or wherein the inner walls of the viewing channel are at least partially structured and preferably have a thread structure, in particular a fine thread structure.

21. Pyrometer according to one of claims 9 to 20, comprising a second housing that accommodates the first housing with the sensor accommodated therein and, if present, the body forming the viewing channel, wherein the second housing has at least one flow channel for a fluid that is connectable to a source of temperature-controlled fluid.

22. Pyrometer according to claim 21, comprising the source of tempered fluid, wherein the source of tempered fluid is suitable for providing fluid at a predetermined temperature with an accuracy of ± 0.5°C, preferably ± 0.1°C or less.

23. A device for thermally treating a semiconductor substrate, comprising: a process chamber with a receiving area for a semiconductor substrate; at least one heating unit adapted to heat a semiconductor substrate received in the receiving area; a pyrometer according to one of claims 9 to 22, wherein the pyrometer is aligned such that, in addition to components of the pyrometer itself, only a surface of a semiconductor substrate received in the receiving area lies in the field of view of the sensor.

24. The apparatus of claim 23, wherein the pyrometer is directed substantially perpendicularly to the surface of a semiconductor substrate received in the receiving region.

25. Device according to claim 23 or 24, wherein the at least one heating unit comprises at least one lamp, in particular a halogen lamp with a quartz jacket.

26. Device according to one of claims 23 to 25, wherein the at least one heating lamp is located on a side of the receiving area facing the pyrometer and at least one further heating lamp or at least one plasma source is provided on the other side of the receiving area.

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