WO2010037469A1

WO2010037469A1 - Method for measuring the thickness of disc-shaped work pieces machined in a machine tool

Info

Publication number: WO2010037469A1
Application number: PCT/EP2009/006590
Authority: WO
Inventors: Ingo Grotkopp; Ulrich Ising; Hans-Peter Boller; Jörn KANZOW; Jörg Meyer
Original assignee: Peter Wolters Gmbh
Priority date: 2008-10-01
Filing date: 2009-09-11
Publication date: 2010-04-08
Also published as: DE102008049972A1

Abstract

The invention relates to a method for measuring the thickness of disc-shaped work pieces for integrated circuits machined in a machine tool, wherein the machine tool comprises an upper working disc driven in a rotating manner and having an annular working surface facing a lower working surface, and wherein the working surfaces form a working gap between them, in which a plurality of rotor discs are arranged which receive work pieces in recesses and which can be rotated by means of a rolling device, thereby causing the rotor discs and the tools received therein to move along a cycloid path. According to the invention, the thickness of at least one work piece present in the machine tool is measured using an optical measuring method. The invention further relates to a corresponding machine tool.

Description

Method for measuring the thickness of disc-shaped workpieces machined in a processing machine

The invention relates to a method for measuring the thickness of disc-shaped workpieces machined in a processing machine, which serve as a substrate for electronic components, wherein the processing machine has an upper rotatably driven working disk with an annular work surface facing a lower working surface, and wherein the work surfaces form a working gap between them, in which a plurality of carriers are arranged, which receive workpieces in recesses and are displaceable by means of a rolling device in rotation, whereby the carriers and thus the workpieces received in them move along a cycloidal trajectory.

The invention also relates to a processing machine with an upper rotating drivable working disk with an annular working surface which faces a lower working surface, wherein the working surfaces form a working gap between them, in which a plurality of carriers are arranged, which receive workpieces in recesses and by means of a rolling device in Rotation are displaceable, whereby the carriers and thus the workpieces received in them move along a cycloidal trajectory.

In working machines with upper and lower working disk one speaks of double-sided processing machines. With them, a plane-parallel machining of workpieces, such as semiconductor wafers (wafers). The machining may consist of grinding, lapping, polishing or the like. Depending on the machining process, the work surfaces on work coverings, which engage with the workpiece surfaces. Also, depending on the machining process, a cooling lubricant may be introduced into the working gap, which optionally contains polishing or lapping material. The geometry of the workpieces produced is of great importance for further use. Thus, the finished workpieces are often provided by optical imaging methods with integrated circuits. Unwanted thickness variations of the workpieces reduce the image sharpness and thus the quality of the integrated circuits.

At the end of the machining process, when the workpiece has reached a predetermined thickness, the machine is switched off. The so-called shutdown accuracy of double-side processing machines is subject to various influences, such as temperature drift, tool wear, contamination and mechanical compliance. Indirect measuring methods are known in order to estimate the thickness of workpieces during the machining process. However, these do not always provide sufficient accuracy. In addition, it has been proposed to measure the thickness of workpieces by mechanical, tactile measuring methods directly and during the machining process. However, the achievable in this way accuracies are also often not sufficient in practice. In addition, the mechanical measurement can lead to undesired effects on the workpiece.

Based on the explained prior art, the invention is therefore based on the object to provide a method and a processing machine of the type mentioned, with which a higher measurement accuracy is achieved without undesirable reaction to the workpiece.

The invention solves this problem by the subject matter of independent claims 1 and 14. Advantageous embodiments can be found in the dependent claims, the description and the figures. For a method of the type mentioned above, the invention solves the problem in that by means of an optical measuring method, the thickness of at least one workpiece located in the processing machine is measured. For the processing machine, the invention accordingly achieves the object by virtue of the fact that the processing machine has at least one optical measuring device with which the thickness of at least one workpiece located in the processing machine can be measured.

The invention is based on the idea of arranging an optical measuring device in or on the processing machine. The measuring device and in particular a corresponding measuring head are thus integrated into a region of the machine which temporarily allows a direct thickness measurement during processing. The mechanical workpiece thickness is determined. This can be done for example by means of a map, which was previously created as part of a calibration. By the direct optical measurement according to the invention a more accurate compared to the prior art thickness measurement is made possible during processing, so that for example the decisive in a material-removing workpiece machining shutdown of the machine can be determined more accurately. With the method according to the invention or the processing machine according to the invention, measuring accuracies of 1 μm and better are possible. Detrimental influences such as temperature drift, tool wear, contamination and mechanical compliance of the workpiece can be largely excluded according to the invention. In comparison with tactile measuring methods, according to the invention, there is no influence on the workpieces by the measurement.

The double side working machine may have upper and lower working disks and is for example used for grinding, lapping, polishing, or the like of the workpieces. The thin workpieces can have a thickness of have less than 1.5 mm. The workpieces can be semiconductor wafers, in particular silicon wafers, to which, for example, an integrated circuit can be applied. But there are also other workpieces conceivable, for example, sapphire disks ("Silicon On Insulator, SOI"), to which an integrated circuit or a single component, such as a diode can be applied. The workpieces can have a cylindrical or circular geometry. If necessary, a capacitive pre-measurement of the workpiece thickness at the machine input can take place.

According to the invention, a (partial) lateral, in particular radial, thickness profile can be created. The thickness measurement can therefore be carried out along different points distributed on a lateral line on the workpiece surface. Especially with double-side processing machines usually has the task of avoiding an undesirable concave or undesirable convex surface or thickness shape by the processing plate, such as polishing plate. Due to the prevailing in such processing machines rotating machining can be assumed that the workpieces are machined substantially rotationally symmetric, so that any deviations from the given geometry are rotationally symmetric. A lateral or radial thickness measurement thus provides sufficient accuracy.

During their cycloidal trajectory movement, the workpieces can pass through an area outside the working gap, for example during grinding or lapping operations. This is referred to as technical overflow. For example, it is located on the outside of the working gap. In the case of an annular working gap, however, the overflow can also be located on the inside of the working gap. According to one embodiment, it can therefore be provided that the optical thickness measurement takes place in the region outside the working gap, or that the Processing machine has at least one optical measuring device in the area outside the working gap, with which the thickness of at least one workpiece in the area outside the working gap is measurable. The overflow is easily accessible and is therefore particularly suitable for thickness measurement in this area.

According to an alternative embodiment, however, it can also be provided that the processing machine has at least one optical measuring device arranged in a working disk of the processing machine, with which the thickness measurement takes place or can take place. Double-side processing machines usually have an upper and a lower working disk. This embodiment is therefore based on the idea of arranging a measuring device in one of these working disks, preferably in the upper working disk, because of possible contamination, and in this way making it possible to measure the optical thickness during machining. This procedure is particularly suitable for polishing operations, in which an overflow may be undesirable.

According to a further embodiment, the thickness can be measured by means of an interferometric measurement method, that is to say the measuring device is an interferometric measuring device. In this case, for example, infrared interferometry can be used, in which infrared light is brought into interference. For this purpose, the workpieces, for example semiconductor wafers (silicon wafers or the like) may be partially transparent to infrared light. They are then also suitable for internal infrared interferometry. This allows a particularly accurate measurement.

According to a development of this embodiment of the method, the following steps can furthermore be provided:

Infrared radiation is directed to the workpiece top, wherein a first radiation component is reflected on the workpiece top and a second Radiation component penetrates the workpiece thickness, is reflected at the workpiece bottom and exits again on the workpiece top, the first and the second radiation component to form a

Interference pattern, based on the interference pattern, the optical workpiece thickness between the

Determined workpiece top and the workpiece base, from a measurement of the intensity of the reflected and / or transmitted from the workpiece infrared radiation is taking into account the optical

Workpiece thickness determines the mechanical workpiece thickness.

The processing machine according to the invention can be further characterized in that the measuring device has an infrared radiation source, with the infrared radiation can be directed to the workpiece top, so that a first radiation component is reflected on the workpiece top and a second radiation component penetrates the workpiece thickness, is reflected at the workpiece bottom and again on the workpiece top exits, and the first and the second radiation component to form an interference pattern interfere, the measuring device further comprises an evaluation, with the basis of the interference pattern, the optical workpiece thickness between the workpiece top and the workpiece bottom can be determined, the measuring device further comprises an intensity measuring device with which the intensity of the reflected and / or transmitted from the workpiece infrared radiation can be measured, wherein With the evaluation device from the measured intensity, taking into account the optical workpiece thickness, the mechanical workpiece thickness can be measured. In this embodiment, it has been recognized that, for example, due to material fluctuations (doping fluctuations), deviations of the refractive index and thereby falsification of the thickness measurement can occur. It has also been recognized that a change in the refractive index has an effect on the degree of reflection or absorption of the workpiece and, accordingly, with a changed refractive index, a corresponding change in the reflected or transmitted radiation intensity occurs. This effect is exploited to compensate for the refractive index fluctuations in the determination of the mechanical workpiece thickness from the determined optical workpiece thickness.

Depending on the particular material of the workpiece, in most cases an influence on the refractive index due to a changed absorption due to changed workpiece thickness can be neglected. This is especially true for infrared radiation only low-absorbing materials, such as silicon. With other materials it is possible that the absorption of the workpiece also changes with a change in thickness. The refractive index can then be determined by correcting the measured intensity by a scale factor determined during a calibration and indicating the changed absorption.

In the case of variations in the refractive index, for example due to doping fluctuations, this embodiment achieves a more accurate thickness measurement and thus improved properties for the application of integrated circuits or individual electronic components in comparison to the prior art.

With this embodiment, thin disk-shaped partially transparent workpieces are measured. The mechanical workpiece thickness can be calculated as the quotient of the optical workpiece thickness and the refractive index. The Determination of the optical workpiece thickness between the workpiece top side and the workpiece underside and an optional determination of the refractive index can be carried out in each case using suitable Kalibrationskenn- lines or appropriate calibration maps. The upper side of the workpiece is the side of the workpiece facing the incident radiation, while the side of the workpiece facing away from the incident radiation is referred to as the workpiece underside. Of course, this embodiment is independent of the orientation of the workpiece in space or of the direction of incidence of the infrared radiation. It can also be directed, for example, in a vertical direction from bottom to top on the workpiece.

In the case of the internal interferometry used in accordance with the invention, the second radiation component can, of course, repeatedly pass through the workpiece thickness and correspondingly be reflected several times on the lower and optionally inner surface of the upper side before it emerges from the workpiece again. The inclusion of the interference pattern is carried out in particular on the workpiece top side facing side. In this case, the infrared radiation can for example be coupled into a glass fiber and passed through it onto the workpiece, or the radiation coming from the workpiece can be picked up by the glass fiber and fed to a sensor and evaluation device. For the evaluation of the interference pattern, a suitable detector can be provided with a suitable evaluation electronics.

The disk-shaped workpiece may be part of a sandwich structure, in which case the workpiece underside forms the interface with the next underlying layer. Likewise, the workpiece top may be the interface to a next overlying layer. The interference pattern generated by the interference of the radiation components, for example, a diffraction pattern or a For example, be spectrally fanned out interference pattern analogous to white light interferometry. The type of interference is not important.

According to a further embodiment, an infrared radiation spectrum can be directed onto the workpiece top side, that is to say the infrared radiation source generates an infrared radiation spectrum. This spectrum can be directed in particular perpendicular to the workpiece top. It is then further possible to spectrally analyze the radiation resulting from the interference of the first and second radiation components by means of a spectrometer, for example a grating spectrometer. In this case, infrared radiation sources, in particular infrared lamps or infrared gas discharge lamps, can be used as infrared radiation sources. This leads to the interference of the two radiation components. In particular, for certain wavelengths of the spectrum, the path difference produced by the workpiece thickness is just such that destructive or constructive interference occurs. This interference pattern can then be spectrally analyzed and evaluated by means of a spectrometer. For example, from the distance between two maxima or minima, the optical workpiece thickness can be determined.

Of course, according to the invention, other interference methods are also conceivable, for example with radiation of high coherence length (for example laser radiation) and oblique radiation incidence.

According to a further embodiment, for measuring the intensity of the infrared radiation reflected and / or transmitted by the workpiece, the intensity of the radiation resulting from the interference of the first and second radiation components can be measured after their reflection at the workpiece top side or after their exit from the workpiece top side. The intensity measuring device is designed accordingly. In this embodiment, so the Intensity measurement on the same side on which the two interfering radiation components are received and evaluated. Thus, the same measuring arrangement can advantageously be used for the intensity measurement and the evaluation of the interference pattern. A particularly high accuracy can be achieved if an intensity difference between two defined points of the interference pattern, for example an interference maximum and an interference minimum, is determined for measuring the intensity. The minimum may in particular also have an intensity equal to zero.

According to an alternative embodiment, a third radiation component can emerge from the workpiece at the bottom of the workpiece and, for measuring the intensity of the reflected and / or transmitted infrared radiation, the intensity of the third radiation component can be measured after its exit from the workpiece. Again, the intensity measuring device is designed accordingly. In this embodiment, therefore, the intensity of the radiation radiating through the workpiece is recorded and deduced therefrom on the reflection or absorption degree. This embodiment lends itself, for example, when the underside of the workpiece is accessible from the outside and corresponding continuous radiation can be recorded.

According to a further embodiment, the refractive index of the workpiece can be determined, and the mechanical workpiece thickness can be determined taking into account the determined refractive index from the optical workpiece thickness. The refractive index can be determined, for example, from a characteristic curve representing the refractive index as a function of the intensity or the intensity difference of the infrared radiation reflected and / or transmitted by the workpiece. Such a characteristic can be part of a Calibration be created and stored, for example, in the evaluation. It is also conceivable to determine the mechanical workpiece thickness by means of a characteristic diagram. Such a characteristic map can represent, for example, the workpiece thickness as a function of the intensity or the intensity difference and the refractive index. Such a map is usually created as part of a calibration. The use of characteristic curves or characteristics leads to a particularly simple evaluation of the recorded radiation.

Alternatively, the workpiece thickness can also be measured by measuring the distances between the respective measuring device and the top or bottom of a workpiece passing through the region by means of at least two optical measuring devices arranged above and below the region outside the working gap, and measuring the workpiece thickness from the measured distances is determined by means of a differential measurement. It can be done in this embodiment, for example, a transit time measurement by means of two lasers, wherein a laser is disposed above the workpiece and a laser below. From the respective term of the laser radiation from the laser source to the workpiece and back can be closed to the distance.

According to a further embodiment, the processing machine in the area outside the working gap a along the traversed by a workpiece path before the measuring device arranged cleaning device, such as a rinsing device, with the located on the workpiece process medium, such as polishing or lapping, before a thickness measurement can be. In this way it is possible to remove interfering process medium from the workpiece for the optical thickness measurement before the measurement. To the workpiece after passing through the overflow again easily the other To be able to feed processing, it can further be provided that the processing machine in the area outside the working gap on the traversed by a workpiece path behind the measuring device means for (re-) application of process medium, such as polishing or lapping, to the workpiece having a thickness measurement. After carrying out the measurement, the process medium removed before the measurement can be applied to the workpiece again. Along the path of the workpieces through the overflow, a cleaning device, a measuring device and a device for re-applying process medium can thus be provided in succession.

Furthermore, the measuring device can have a measuring cleaning device with which at least part of the measuring device can be flushed with a cleaning medium, in particular a cleaning fluid (gas or liquid). In this case, flushing of an optical measuring head can take place in order to protect this contamination that falsifies the measurement result. The cleaning fluid is, for example, clean air or a corresponding aqueous fluid in question. The flushing of a measuring head can also be done with the process medium located on the workpiece.

According to a further embodiment, the carriers can be operated for the duration of the thickness measurement with a reduced rotational speed compared to the normal processing speed. Of course, the carriers can also be completely stopped for the measurement. The workpieces pass through the area used for the optical measurement, for example the overflow, so slower in this embodiment. In this way, a more accurate measurement of the thickness is possible. It may further be provided to adapt the position of the measuring device used for the thickness measurement as a function of wear of the processing machine, in particular of the working disks. The work disks or work coverings are used in operation. For example, the upper working disk is then correspondingly new delivered to the workpieces, so that again the desired pressure is exerted on the workpiece. Depending on the wear, the working gap can thus be shifted downwards, for example, overall. For example, if a distance measurement with lasers for thickness measurement, a shift of the working gap affects the measurement result. Therefore, it is provided in this embodiment, for example, that the measuring device according to the displacement of the working gap can also be moved. Such a tracking of the measuring device, the accuracy is maintained even at a wear of the machine at any time.

The processing machine can furthermore have a control device with which the processing parameters of the processing machine can be adapted in dependence on a determined workpiece thickness and / or a determined workpiece thickness profile. The control device can of course also be a control device. From a feedback of the workpiece thickness to the machine control system, a control and / or regulation of the machine parameters ("recipe recommendation / variation") can take place. Such an adaptation of the parameters of the machine may be, for example, a shutdown of the machine upon reaching a predetermined material removal, ie a predetermined workpiece thickness. Another example is the occurrence of undesirable convexity or concavity of a measured radial thickness profile of the workpieces. In this case, it can be assumed that the work disks or the work coverings correspondingly have an undesired concavity or convexity. To this, too correct, then can be influenced as machining parameters, the geometry of the working wheels, for example by applying mechanical pressure in the desired manner. Another example is so-called segmented work coverings, eg in polishing plates. In the case of such work coverings, it is possible, according to a measured geometry of the work piece, to exert targeted pressure on individual segments of the work cover so that a specific geometry adjustment is possible.

The processing machine according to the invention may be designed for carrying out the method according to the invention.

An embodiment of the invention will be explained in more detail with reference to a drawing. They show schematically:

1 shows a part of a processing machine according to the invention in a plan view,

2 shows a detail of the processing machine according to the invention in a plan view,

3 shows a detail of the processing machine according to the invention in a cross section,

Fig. 4 shows a structure of the measuring device according to the invention according to an exemplary embodiment, and

Fig. 5 is a sketch for illustrating the beam paths in the invention.

Unless otherwise indicated, like reference characters designate like items throughout the figures. In Fig. 1, a part of a double-side processing machine 10 according to the invention is shown in a plan view. To recognize the lower working disk 11 with a lower working surface 12, which together with a not shown working surface of an upper working disc limits a working gap. In the working gap a plurality of carriers 14 are arranged, each having a plurality of recesses 16 for not shown in Fig. 1 workpieces, for example, semiconductor wafers, such as silicon wafers have. In the example shown, each rotor disk 14 has four recesses 16. The rotor disks 14 are set in rotation by means of a rolling device, whereby they describe a cycloidal trajectory together with the workpieces received in their recesses 16.

In the course of the cycloidal trajectory, the recesses 16 and workpieces received therein pass partially through an area 18 outside the working gap bounded by the lower work surface 12 and upper work surface. This area 18 is also referred to as overflow 18. In the plan view in Fig. 2, this arranged on the outside of the annular working gap overflow 18 is shown enlarged. A second region 19 outside the annular working gap is located in Fig. 1 on the inside of the working gap. Although a thickness measurement at the overflow 18 on the outside of the gap is described below, such a thickness measurement would also be possible in an analogous manner in the overflow 19 on the inside of the gap.

In Fig. 2, a lapping disk 20 is also shown as the upper working disk 20 hi the example shown in Fig. 2, a workpiece passes through the overflow 18 along an illustrated by the arrow 22 track 22. Along this track 22 are in the overflow 18 in a row a cleaning device 24, in the illustrated example, a rinsing device 24, an optical measuring device 26 and a device 28 for applying process medium, in the example shown a lapping, arranged on the workpiece. With the flushing device 24, in the present case a water rinse, is located on the workpiece lapping before passing through the optical measuring device 26 from the workpiece. Subsequently, the thickness of the workpiece is measured directly with the optical measuring device 26 in the overflow 18. In order subsequently to be able to return the workpiece to the normal machining process, the previously removed lapping agent is applied to the workpiece again with the device 28. At least during the measuring process, the speed of the processing machine 10 and in particular of the rotor discs 14 can be reduced compared to the normal operation.

In Fig. 3, the measuring device 26 is shown in more detail. It can be seen how a recorded in a rotor 14 workpiece 30, in this case a silicon wafer 30, the overflow 18 passes. The wafer 30 is located between the lapping disk 20 and the lower working disk 11 and in particular in the working gap 31 delimited between the upper working surface 21 of the lapping disk 20 and the lower working surface 12 of the lower working disk 11. In the region of the overflow 18, the optical measuring device 26 , in the present case an infrared interferometric measuring device 26 is arranged. With the measuring device 26, an infrared radiation spectrum 32, that is to say infrared radiation of different wavelengths or frequencies, is directed onto the upper side 34 of the wafer 30. The measuring device 26 has a housing 36 which can be closed on its underside by a magnetically driven cover 38. The measuring device 26 further has a measuring cleaning device which, in the example shown, generates an air flow 40 for keeping the measuring head free of contaminants.

The infrared radiation 32 directed onto the workpiece upper side 34 by the measuring device 26 and in particular an infrared radiation source is reflected by a first radiation component on the workpiece upper side 34, while a second radiation component penetrates the workpiece thickness, on the underside of the workpiece is reflected and exits directly or after multiple reflections on the inside of the top 34 and the workpiece bottom 42 again on the workpiece top 34. The first and second radiation fractions coming back from the workpiece 30 reach a sensor and evaluation device 44 shown only schematically in FIG.

In Fig. 4, the construction of the measuring device 26 and in particular the sensor and evaluation device 44 is shown in more detail. In this case, the silicon wafer 30 is shown, whose mechanical thickness d is to be measured. An infrared radiation source 46, in the present case an infrared lamp 46, generates the infrared radiation 32. Through a beam splitter 48, for example a semitransparent mirror 48, the infrared radiation 32 focused by an optical system 50 reaches the upper side 34 of the wafer 30 under normal incidence.

The beam path when hitting the wafer 30 is shown in more detail in FIG. A first radiation component 52 is reflected on the workpiece upper side 34 and runs back perpendicular to the beam splitter 48. A further radiation component 53 penetrates the workpiece thickness d, is (partially) reflected on the workpiece underside 42, passes through the workpiece thickness d again from the bottom 42 to the top 34 and exits at least partially as a second radiation component 54 again on the workpiece top 34. The radiation 53 passing back through the workpiece thickness d from the workpiece underside 42 to the upper side 34 is in turn partially reflected at the upper side 34, so that a further radiation component 56 passes through the workpiece thickness d again from the upper side 34 to the workpiece lower side 42, and so on. These beam paths are known per se. Since the radiation 53 is only partially reflected on the underside of the workpiece 42, in the exemplary embodiment shown in FIG. 5, a third radiation component 58 emerges on the underside of the workpiece 42. The first and second radiation components 52, 54 (and possibly further reflected radiation components) strike the beam splitter 48 again after their reflection or after their re-emergence from the workpiece 30 and are deflected vertically by this and guided to a spectrometer 60. In the illustrated example, the spectrometer 60 is a grating spectrometer 60. By means of this spectrometer 60, the infrared radiation 32 striking the spectrometer 60 is spectrally fanned out, as shown schematically in FIG. 4 as the spectrum 62. In spectrum 62, for purposes of illustration only, the radiation intensity is plotted in arbitrary units versus wavelength.

The part of the infrared radiation 32 coming back from the wafer 30, in particular the first and second radiation parts 52, 54, interfere with each other in a manner also known per se. Depending on the path difference of the radiation components 52, 54 caused by the wafer thickness d, constructive or destructive interference occurs. A corresponding interference diagram is shown in a general and schematic manner in FIG. 4 at reference numeral 64. In the interference diagram 64, in turn, the intensity is plotted in arbitrary units over the wavelength. This results in an interference pattern 66. By evaluating the intensity signal in the interference diagram 64, the thickness d of the workpiece 30 is determined. For example, from the distance 68 of two interference maxima, the optical workpiece thickness L as a product of the mechanical workpiece thickness d and the refractive index of the wafer 30 can be determined in a manner known per se to the person skilled in the art. The intensity difference 70 between an interference maximum and an interference minimum contains information about the reflectivity of the wafer 30. Based on the measured intensity difference 70, the refractive index of the wafer 30 can be determined, for example, on the basis of a characteristic curve created during a calibration. On this basis, the mechanical workpiece thickness d are calculated as the quotient of the determined optical workpiece thickness L and the likewise determined refractive index n.

With the method according to the invention or the processing machine according to the invention, a thickness measurement which is more accurate than that of the prior art is possible online during the machining of a workpiece 30. In this case, at least the part of the workpiece 30 located in the overflow 18 can be measured radially, wherein the method for measuring the thickness is carried out successively along a radial surface line on the workpiece and thus a radial thickness profile is created.

On the basis of this thickness measurement conclusions can be made on the geometry of the workpiece 30 and in particular a comparison of the measured geometry with a predetermined geometry. On this basis, one or more parameters of the processing machine can be adjusted by a control and / or regulating device, not shown, in order to influence the workpiece geometry in the desired manner.

It should be noted that although in the exemplary embodiment illustrated in the figures, an optical measurement of the workpiece thickness is described in the traversed by the workpieces area outside the working gap, according to the invention in an analogous manner, a thickness measurement by means of one or more in the working wheels of the machine, for example the upper working disk, arranged optical measuring devices can be done.

Claims

Claims:

A method for measuring the thickness of disc-shaped workpieces (30) machined in a processing machine (10), which serve as a substrate for electronic components, wherein the processing machine (10) comprises an upper rotatably driven working disk (20) with an annular working surface which a lower work surface (12) facing, and wherein the work surfaces (12) between them form a working gap, in which a plurality of carriers (14) are arranged, the workpieces (30) receive in recesses (16) and by means of a rolling device in rotation whereby the carriers (14) and thus the workpieces (30) accommodated in them move along a cycloidal web (22), characterized in that the thickness of at least one workpiece (30) located in the processing machine is determined by means of an optical measuring method. is measured.

2. The method according to claim 1, characterized in that in the carriers (14) recorded workpieces (30) at least partially pass through a region (18) outside the working gap in their web movement, wherein the optical thickness measurement in the region (18) outside the working gap he follows.

3. The method according to claim 1, characterized in that the optical thickness measurement is carried out by means of at least one arranged in a working disk of the processing machine optical measuring device.

4. The method according to any one of the preceding claims, characterized in that the thickness is measured by means of an interferometric measuring method.

5. The method according to claim 4, characterized by the further steps:

Infrared radiation (32) is directed onto the workpiece upper side (34), wherein a first radiation component is reflected on the workpiece upper side (34) and a second radiation component penetrates the workpiece thickness (d), is reflected on the workpiece underside (42) and again on the workpiece upper side (34). 34), the first and second radiation portions interfere to form an interference pattern,

the optical workpiece thickness between the workpiece top side (34) and the workpiece bottom side (42) is determined on the basis of the interference pattern, from a measurement of the intensity of the infrared radiation (32) reflected and / or transmitted by the workpiece (30) taking into account the optical workpiece thickness ( L) determines the mechanical workpiece thickness (d).

6. The method according to claim 5, characterized in that an infrared radiation spectrum is directed to the workpiece top side (34).

7. The method of claim 2 or claim 2 and claim 4, characterized in that the workpiece thickness is measured by means of at least two above and below the area (18) outside the working gap arranged optical measuring devices, the distances between the respective measuring device and the top or bottom of a workpiece (30) passing through the region (18) are measured and the workpiece thickness is determined from the measured distances by means of a differential measurement.

8. The method according to any one of the preceding claims, characterized in that on the workpiece (30) befindliches process medium, in particular polishing or lapping, before the thickness measurement by means of a cleaning device (24), in particular a flushing device (24) is removed.

9. The method according to any one of the preceding claims, characterized in that after the thickness measurement process medium, in particular polishing or lapping, on the workpiece (30) is applied.

10. The method according to any one of the preceding claims, characterized in that a measuring device used for measuring thickness (26) at least partially with a cleaning medium (40), in particular a cleaning fluid (40), is washed around.

11. The method according to any one of the preceding claims, characterized in that the carriers (14) are operated for the duration of the thickness measurement at a reduced rotational speed.

12. The method according to any one of the preceding claims, characterized in that the position of a measuring device used for the thickness measurement (26) in dependence on wear of the processing machine (10), in particular the working disks (20) is adjusted.

13. The method according to any one of the preceding claims, characterized in that the machining parameters of the processing machine (10) are adjusted in dependence on the determined workpiece thickness.

14. Processing machine with an upper rotatably driven working disk (20) with an annular work surface, which faces a lower work surface (12), wherein the work surfaces (12) between them form a working gap in which a plurality of carriers (14) are arranged, the in recesses (16) receive workpieces (30) and are displaceable by means of a rolling device in rotation, whereby the carriers (14) and thus the workpieces (30) received in them move along a cycloidal path (22), characterized in that the processing machine (10) has at least one optical measuring device (26) with which the thickness of at least one workpiece (30) located in the processing machine can be measured.

15. Processing machine according to claim 14, characterized in that in the carriers (14) recorded workpieces (30) in their web movement at least partially through a region (18) outside the working gap, and that the processing machine at least one optical measuring device (26) in the area (18) outside the working gap, with which the thickness of at least one workpiece (30) in the region (18) outside the working gap is measurable.

16. Processing machine according to claim 14, characterized in that the processing machine has at least one arranged in a working disk of the processing machine optical measuring device with which the thickness measurement can take place.

17. Processing machine according to one of claims 14 to 16, characterized in that the measuring device (26) is an interferometric measuring device (26).

18. Processing machine according to claim 17, characterized in that: the measuring device (26) has an infrared radiation source, with the infrared radiation (32) on the workpiece top side (34) can be directed so that a first radiation component on the workpiece top side (34) is reflected and a second radiation portion penetrates the workpiece thickness (d), is reflected on the workpiece lower side (42) and exits again on the workpiece upper side (34), and the first and second radiation components interfere to form an interference pattern, the measuring device (26) further comprises an evaluation device with the aid of the interference pattern, the optical workpiece thickness between the workpiece top side (34) and the workpiece underside (42) can be determined, the measuring device (26) further comprises an intensity measuring device, with which the intensity of the workpiece (30) reflected and / or or transmitted infrared radiation (32) can be measured, wherein with the evaluation of the measured intensity taking into account the optical workpiece thickness (L), the mechanical workpiece thickness (d) can be determined.

19. Processing machine according to claim 18, characterized in that the infrared radiation source generates an infrared radiation spectrum (32).

20. Processing machine according to claim 15 or claim 15 and claim 17, characterized in that the measuring device has at least two above and below the area (18) outside the working gap arranged optical measuring devices with which the distances between the respective measuring device and the upper or underside of a workpiece passing through the area (30) are measurable and the measuring device further comprises an evaluation device, with which the workpiece thickness can be determined from the measured distances by means of a differential measurement.

21. Processing machine according to one of claims 14 to 20, characterized in that the processing machine (10) in the region (18) outside the working gap along the of a workpiece (30) traversed path (22) in front of the measuring device (26) arranged cleaning device (24), in particular a rinsing device (24), with which on the workpiece (30) located process medium, in particular polishing or lapping, before a thickness measurement can be removed.

22. Processing machine according to one of claims 14 to 21, characterized in that the processing machine (10) in the area outside the working gap along the of a workpiece (30) traversed path (22) behind the measuring device (26) arranged means (28) for applying process medium, in particular polishing or lapping, on the workpiece (30) after a thickness measurement.

23. Processing machine according to one of claims 14 to 22, characterized in that the measuring device (26) comprises a measuring cleaning device with which at least a part of the measuring device (26) with a Cleaning medium (42), in particular a cleaning fluid (42), can be washed around.

24. Processing machine according to one of claims 14 to 23, characterized in that the processing machine (10) has a control device, with which the processing parameters of the processing machine (10) can be adjusted in dependence on a determined workpiece thickness.