Calibration setup and corresponding calibration procedure

Description

[0001] The present invention relates to a calibration arrangement and a corresponding calibration method for calibrating an infrared camera device for detecting the temperature of a chuck for wafer substrates that can be heated by a temperature control device.

[0002] US Patent 2012 / 0201267 A1 describes a calibration arrangement for calibrating a pyrometer used to detect the temperature of a wafer substrate chuck heated by a temperature control device and located in a deposition chamber. The arrangement includes a probe wafer with a plurality of temperature probes. The deposition chamber is sealed by an upper and a lower cover plate, the upper cover plate being optically transparent to infrared radiation emitted by the probe wafer heated by the chuck and detected by the pyrometer. A temperature sensing device detects the respective temperatures of the temperature probes and transmits them to a calibration device for calibrating the pyrometer.

[0003] Similar devices are known from WO 2015 / 123057 A1 and US 2017 / 372928 A1.

[0004] DE 69 730 639 T2 describes a method and a device for calibrating an infrared pyrometer in a heat treatment plant.

[0005] Heated chucks (wafer substrate clamping devices) are typically calibrated before commissioning and at regular intervals during operation to achieve the temperature accuracy required for testing circuit elements on the wafer substrates. Furthermore, it is desirable to know the set temperature at virtually every point on the chuck and thus on the wafer substrates under test.

[0006] It is possible to use a so-called test wafer or probe wafer for calibration, which has a number of temperature probes, for example, platinum resistors. Such platinum resistors are available in precisely pre-calibrated form. However, such test wafers or probe wafers are very expensive.

[0007] It is also possible to use an infrared camera device to calibrate the chuck, but this device has large tolerances and is difficult to calibrate. The infrared camera device can, for example, be pre-calibrated using the test wafer or probe wafer described above.

[0008] However, it has been found that, particularly at higher temperatures, air currents or gas currents of a purge gas used distort a measured temperature profile on the surface of the probe wafer, resulting in the measurement not of the temperature distribution on the surface of the probe wafer, but of a temperature distribution of the prevailing flow there, for example a convection flow at higher temperatures, especially above 100°C, or the influence of this flow on the temperature distribution.

[0009] The present invention provides a calibration arrangement according to claim 1 and a corresponding calibration method according to claim 14.

[0010] Preferred training opportunities are subject to the respective dependent claims.

[0011] The underlying idea of ​​the present invention is that, during the calibration of an infrared camera device, a flow shielding plate is used between the probe wafer and the infrared camera device, which is held at a distance from the special wafer by a slit and is optically transparent to infrared radiation emitted by the probe wafer heated by the chuck and to be detected by the infrared camera device.

[0012] With a suitable selection of the flow shielding plate or its contours, as well as with a suitable gap spacing, the so-called thermos flask effect can be achieved between the probe wafer and the flow shielding plate, meaning that the flows in question cannot establish themselves above the surface of the probe wafer. Thus, the present invention enables precise calibration of the infrared camera device.

[0013] According to the invention, the gap spacing is in the range of 1 mm to 10 mm, in particular 4 mm to 6 mm. This allows the desired thermos flask effect to be achieved with particular stability.

[0014] According to another preferred embodiment, the flow shielding plate is held by a mounting device by which the gap spacing of the gap can be variably adjusted. This increases flexibility.

[0015] According to a further preferred embodiment, the flow shielding plate is held by a preferably thermally insulating spacer device, which has a plurality of support elements extending from the probe wafer to the flow shielding plate. This simplifies the design of the arrangement.

[0016] According to another preferred embodiment, the majority of support elements are integrated into the probe wafer and / or the flow shielding plate. This eliminates the need for a separate mounting.

[0017] According to another preferred embodiment, the calibration device is connected to the temperature control device and is designed such that it can calibrate the temperature control device based on the respective temperatures detected by the temperature probes. This allows two calibration procedures to be performed simultaneously.

[0018] According to another preferred embodiment, the probe wafer has a black surface and is in particular a black plastic wafer or a black semiconductor wafer. This prevents interfering reflections of IR radiation.

[0019] According to another preferred embodiment, the flow-shielding plate is a glass plate, a semiconductor plate, or a ceramic plate. Such flow-shielding plates can be easily optimized with respect to the desired IR transparency.

[0020] According to a further preferred embodiment, the infrared camera device has a storage device in which calibration values ​​based on the respective temperatures measured by the temperature probes can be stored by the calibration device. This allows for future recalibration if necessary.

[0021] According to another preferred embodiment, the temperature probes are integrated into the probe wafer. This allows the temperature profile to be acquired with particularly little interference.

[0022] According to another preferred embodiment, the temperature probes are Pt resistors, in particular Pt1000 or Pt100 resistors. Such resistors are available with high pre-calibration accuracy.

[0023] According to another preferred embodiment, the calibration device is designed such that it takes into account the optical refractive index of the flow shielding plate when calibrating the infrared camera device. This allows the IR pixels to be assigned to corresponding points on the chuck surface even more precisely.

[0024] According to another preferred embodiment, the optical refractive index of the flow shielding plate can be entered into the calibration device. This allows the use of flow shielding plates with different refractive indices.

[0025] According to a further preferred embodiment, the infrared camera device has a significantly smaller scanning grid than the temperature probes, wherein the calibration device is designed to determine calibration values ​​adjacent to the temperature probes according to a predetermined extrapolation and / or interpolation algorithm.

[0026] Exemplary embodiments of the invention are shown in the drawings and explained in more detail in the following description.

[0027] They show: Fig. 1 a calibration arrangement according to a first embodiment of the present invention; Fig. 2 a use of an infrared camera device calibrated with the calibration arrangement according to a first embodiment of the present invention for calibrating the temperature control device of the chuck; Fig. 3 a calibration arrangement according to a second embodiment of the present invention; and Fig. 4 a calibration method according to a third embodiment of the present invention.

[0028] In the figures, identical reference symbols denote identical or functionally equivalent components.

[0029] Fig. 1 shows a calibration arrangement according to a first embodiment of the present invention.

[0030] In Fig. 1 Reference numeral 10 denotes a chuck for wafer substrates that can be heated by a temperature control device 15. Naturally, the chuck 10 can also be cooled by a cooling device (not shown), whereby a temperature equilibrium can be easily achieved by simultaneous heating and cooling. Typically, such chucks can operate in a temperature range of -65°C to 400°C.

[0031] The temperature control device 15 has a storage device 15a in which the control parameters to be applied for the respective adjustable setpoint temperatures, e.g. heating currents, are stored.

[0032] A probe wafer 20, which has a plurality of temperature probes 20a, 20b, is arranged on the surface of the chuck 10. These probes are typically uniformly embedded within the probe wafer, for example in the form of Pt100 or Pt1000 resistors. The probe wafer 20 is advantageously a black wafer, in particular a black semiconductor wafer or a black plastic wafer, to avoid interfering IR reflections during calibration.

[0033] Reference numeral 50 designates an infrared camera device with an image resolution of typically 10,000 to 50,000 pixels, which is directed towards the top surface of the probe wafer 20. The infrared camera device 50 includes a storage device 50a in which respective temperature values ​​are stored, corresponding to the intensity values ​​of the infrared radiation I to be detected by the infrared camera device 50.

[0034] A flow shielding plate 30 is held between the probe wafer 20 and the infrared camera device 50 by a gap 25 spaced apart by a gap distance d. This plate is optically transparent to the infrared radiation I emitted by the probe wafer 20 heated by the chuck 10 and to be detected by the infrared camera device 50.

[0035] Such a flow-shielding plate 30 is, for example, a glass plate, a semiconductor plate, or a ceramic plate with appropriate infrared transmission properties. A mounting device 35 holds the flow-shielding plate 30 at the predetermined gap distance d to the surface of the probe wafer 20. Preferably, the gap distance d is variably adjustable by means of the mounting device 35. The decisive factor for selecting the gap distance d during calibration is the desired achievement of the thermos effect, so that no flow can form between the probe wafer 20 and the flow-shielding plate 30 that could distort the calibration result.

[0036] The gap d required to achieve the thermos effect can vary depending on the design of the contours of the flow shielding plate or its surroundings and, when using the flat flow shielding plate 3 shown, is in a range of 1 mm to 10 mm, in particular from 4 mm to 6 mm.

[0037] A temperature sensing device 40 is connected to the temperature probes 20a, 20b and can record their respective temperatures, for example using the two-wire or four-wire method.

[0038] The temperature detection device 40 is connected to a calibration device 100, to which the respective temperatures recorded by the temperature probes 20a, 20b can thus be supplied.

[0039] Based on the respective temperatures recorded by the temperature probes 20a, 20b, the calibration device 100 can calibrate the infrared camera device 50 by verifying or modifying the calibration values ​​stored in the storage device 50a for the respective temperatures or infrared radiation intensities.

[0040] Reference numeral 150 designates an optional display device by means of which the temperature profile on the probe wafer 20 can be displayed at the respective calibration temperatures.

[0041] In the first embodiment, the calibration device 100 is additionally connected to the temperature control device 15 and can calibrate the temperature control device 15 based on the respective temperatures measured by the temperature probes 20a and 20b. This is done, for example, by modifying the setpoints for the corresponding control parameters, e.g., heating currents, in the storage device 15a if there is a deviation between the setpoint temperature set in the temperature control device 20 and the actual measured temperature of the probe wafer 20. The average temperature of the temperature probes 20a and 20b can be used for this purpose.

[0042] Since the infrared camera device 50 typically has a significantly smaller scanning grid than the temperature probes 20a, 20b, the calibration device 100 can be designed to determine calibration values ​​that lie next to the temperature probes 20b, 20b according to a predetermined extrapolation and / or interpolation algorithm.

[0043] Furthermore, it is possible that the calibration device 100 contains an algorithm that takes into account an optical infrared refractive index of the flow shielding plate 30 when calibrating the infrared camera device 50.

[0044] Optionally, the optical infrared refractive index of the flow shielding plate 30 can be entered into the calibration device 100, which allows the use of flow shielding plates with different optical infrared refractive indices.

[0045] Fig. 2 shows a use of an infrared camera device calibrated with the calibration arrangement according to a first embodiment of the present invention for calibrating the temperature control device of the chuck.

[0046] Fig. 2 shows that a cover wafer 20', which has a black surface, in particular a black plastic wafer or a black semiconductor wafer, is placed on the chuck 10 of the first embodiment. The infrared camera device 50, which is arranged according to Fig. 1 has been calibrated and is connected to a control unit 100', which in turn is connected to the temperature control unit 15 of the chuck 10.

[0047] This setup, using the infrared camera device 50, allows the temperature control device 15 of the heated chuck 10 to be calibrated or recalibrated via the control unit 100' by modifying the control parameters stored in the memory device 15a, e.g., heating currents, when there are deviations between the setpoint temperature and the actual temperature detected by the infrared camera device 50, as described above. This can be carried out, for example, in an iterative process until the setpoint temperature set on the temperature control device 15 corresponds to the actual temperature detected by the infrared camera device 50 (e.g., average temperature).

[0048] Fig. 3 shows a calibration arrangement according to a second embodiment of the present invention.

[0049] The structure of the second embodiment is essentially the same as that of the first embodiment described above, except that the mounting device 35 is replaced by the following: Fig. 1 A preferably thermally insulating spacer device 35' is provided between the probe wafer 20 and the flow shielding plate 30, which holds the flow shielding plate 30. In the present example, the spacer device 35' has a plurality of support elements 35a, 35b, 35c that extend from the probe wafer 20 to the flow shielding plate 30.

[0050] In another embodiment (not shown), these support elements 35a, 35b, 35c can be integrated into the probe wafer 20 and / or into the flow shielding plate 30. This is particularly easy to implement if the probe wafer 20 is a black plastic wafer produced using a molding process.

[0051] Such an arrangement can be implemented in a particularly compact way.

[0052] Fig. 4 shows a calibration method according to a third embodiment of the present invention.

[0053] In Fig. 4 The process steps that can be fundamentally carried out using the calibration arrangement according to the first and second embodiments are specified. In a first step S1, the probe wafer 20 is arranged on the chuck 10, which has the majority of temperature probes 20A, 20B.

[0054] In step S2, the flow shielding plate 30 is held between the probe wafer 20 and the infrared camera device 50 by a gap 25 spaced d apart. As already explained, the flow shielding plate 30 is optically transparent to the infrared radiation emitted by the probe wafer 20, heated by the chuck 10, which is to be detected by the infrared camera device 50. In step S3, the respective temperatures are measured using the temperature probes 20a and 20b, based on the setpoints configured on the temperature control device 15.

[0055] Finally, in step S4, the infrared camera device 50 is calibrated based on the respective temperatures recorded by the temperature probes 20a, 20b. In further (not shown) embodiments of the calibration method according to the invention, all the functionalities of the calibration arrangement described above can of course be implemented in the form of corresponding process steps.

[0056] Although the present invention has been explained above with reference to preferred embodiments, it is not limited to these, but can be modified in many ways as long as it falls within the scope of the claims that define the invention.

Claims

1. Calibration assembly for calibrating an infrared camera device (50) for detecting a temperature of a chuck (10) that can be heated by a temperature control device (15) for testing wafer substrates having: the temperature control device (15); the chuck (10) that can be heated by the temperature control device (15) for wafer substrates; a probe wafer (20) which is arranged on the chuck (10) and has a plurality of temperature probes (20a, 20b); the infrared camera device (50), which is directed towards the upper side of the probe wafer (20); a flow shield plate (30) held at a distance between the probe wafer (20) and the infrared camera device (50), which is spaced apart from the probe wafer (20) by a gap (25) with a gap distance (d) and which is optically transparent to infrared radiation emitted by the probe wafer (20) heated by the chuck (10) and to be detected by the infrared camera device (50); a temperature detection device (40) for detecting the respective temperatures of the temperature probes (20a, 20b); and a calibration device (100), to which can be transmitted the detected respective temperatures of the temperature probes (20a, 20b), for calibrating the infrared camera device (50) based on the detected respective temperatures of the temperature probes (20a, 20b); wherein the gap distance (d) of the gap (25) is in the range of 1 mm to 10 mm, in particular 4 mm to 6 mm; and wherein the gap distance (d) and the contours of the flow shield plate (30) are selected in such a manner that no air flow or gas flow of a used purge gas can form between the probe wafer (20) and the flow shield plate (30).

2. Calibration assembly according to claim 1, wherein the flow shield plate (30) is held by a holding device (35), by means of which the gap distance (d) of the gap (25) can be variably adjusted.

3. Calibration assembly according to claim 1, wherein the flow shield plate (30) is held by a spacer device (35'), which is preferably thermally insulating, which has a plurality of support elements (35a, 35b, 35c), which extend from the probe wafer (20) to the flow shield plate (30).

4. Calibration assembly according to claim 4, wherein the plurality of support elements (35a, 35b, 35c) are integrated into the probe wafer (20) and / or into the flow shield plate (30).

5. Calibration assembly according to one of the preceding claims, wherein the calibration device (100) is connected to the temperature control device (15) and designed in such a way that, based on the detected respective temperatures of the temperature probes (20a, 20b), it can calibrate the temperature control device (15).

6. Calibration assembly according to one of the preceding claims, wherein the probe wafer (20) has a black surface, in particular is a black plastic wafer or a black semiconductor wafer.

7. Calibration assembly according to one of the preceding claims, wherein the flow shield plate (30) is a glas plate or a semiconductor plate or a ceramic plate.

8. Calibration assembly according to one of the preceding claims, wherein the infrared camera device (50) has a storage device (50a), in which calibration values based on the detected respective temperatures of the temperature probes (20a, 20b) can be stored by the calibration device (100).

9. Calibration assembly according to one of the preceding claims, wherein the temperature probes (20a, 20b) are integrated into the probe wafer (20).

10. Calibration assembly according to one of the preceding claims, wherein the temperature probes (20a, 20b) are Pt resistances, in particular Pt1000 or Pt100 resistances.

11. Calibration assembly according to one of the preceding claims, wherein the calibration device (100) is designed in such a manner that it takes into account an optical refractive index of the flow shield plate (30) when calibrating the infrared camera device (50).

12. Calibration assembly according to claim 11, wherein the optical refractive index of the flow shield plate (30) can be entered into the calibration device (100).

13. Calibration assembly according to one of the preceding claims, wherein the infrared camera device (50) has a substantially smaller sampling grid than the temperature probes (20a, 20b) and the calibration device (100) is designed in such a manner that it determines calibration values near the temperature probes (20a, 20b) according to a predetermined extrapolation and / or interpolation algorithm.

14. Calibration method for calibrating an infrared camera device (50) for detecting a temperature of a chuck (10) that can be heated by a temperature control device (15) for testing wafer substrates having the steps of: arranging (S1) a probe wafer (20) on the chuck (10), wherein the probe wafer (20) has a plurality of temperature probes (20a, 20b); providing the infrared camera device (50), which is directed towards the upper side of the probe wafer (20); holding (S2) a flow shield plate (30) between the probe wafer (20) and the infrared camera device (50) in such a way that it is spaced apart from the probe wafer (20) by a gap (25) with a gap distance (d) and which is optically transparent to infrared radiation emitted by the probe wafer (20) heated by the chuck (10) and to be detected by the infrared camera device (50); wherein the gap distance (d) of the gap (25) is in the range of 1 mm to 10 mm, in particular 4 mm to 6 mm and the gap distance (d) and the contours of the flow shield plate (30) are selected in such a manner that no air flow or gas flow of a used purge gas can form between the probe wafer (20) and the flow shield plate (30); detecting (S3) the respective temperatures of the temperature probes (20a, 20b); and calibrating (S4) the infrared camera device (50) based on the detected respective temperatures of the temperature probes (20a, 20b).

15. Calibration method according to claim 14, wherein, based on the detected respective temperatures of the temperature probes (20a, 20b), the temperature control device (15) is calibrated.

16. Calibration method according to claim 14 or 15, wherein an optical refractive index of the flow shield plate (30) is taken into account when calibrating the infrared camera device (50).

17. Calibration method according to claim 14, 15 or 16, wherein the infrared camera device (50) has a substantially smaller sampling grid than the temperature probes (20a, 20b) and calibration values near the temperature probes (20a, 20b) are determined according to a predetermined extrapolation and / or interpolation algorithm.