ROTOR DISC, DOUBLE-SIDED MACHINE AND METHOD FOR MACHINING AT LEAST ONE WORKPIECE IN A DOUBLE-SIDED MACHINE - Patent application

Abstract

To provide a rotor disc, and a double-sided processing machine capable of: further optimizing the edge geometry of workpieces; and further reducing the wear of the rotor discs in particular.SOLUTION: A rotor disc 24 for guiding workpieces 28 in a double-sided processing machine, includes at least one workpiece opening for receiving at least one workpiece to be processed on both sides in the double-sided processing machine in a material-removing manner. The entire surface of the rotor disc includes a contact angle of a water drop of at least 70° and equal to or less than 75°.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a rotor disk for guiding a workpiece in a double-sided machining center, the rotor disk having at least one workpiece opening for receiving at least one workpiece to be machined on both sides in a material removing manner in the double-sided machining center. Additionally, the present invention relates to a double-sided machining center and a method for machining at least one workpiece in a double-sided machining center. [Background technology]

[0002] For processing, workpieces, such as wafers, are guided in a double-sided processing machine, for example a double-sided polishing machine, in a rotor disk. The rotor disk generally has a number of workpiece openings, in which the workpieces to be processed are received in a floating manner. In operation, the rotor disk is arranged between the working disks of the double-sided processing machine in a working gap formed by the working disks. In the course of the relative rotation between the working disks, the rotor disks rotate on the one hand along a circular path through the working gap and on the other hand around their own axis. As a result, the workpieces held in a floating manner in the rotor disks move along a cycloidal trajectory through the working gap. The purpose of this movement is to achieve a material removal process that is as uniform as possible and thus achieve a particularly high plane parallelism and flatness of the processed workpieces. For the material removal process, a processing fluid, in particular a so-called slurry, is generally introduced into the working gap. The processing fluid can contain an abrasive component.

[0003] Semiconductor wafers processed on such double-sided machines are used, among other things, to form integrated circuits (ICs). Since the structures of integrated circuits are becoming increasingly smaller, it is important that during the production of semiconductor wafers, e.g. made of silicon, various geometric parameters are monitored in the best possible way. In particular, the thickness variations across the workpiece must be minimized and the flatness at the workpiece edges must be maximized. In addition, wear on the rotor disks must be minimized.

[0004] The rotor disks and processing methods used so far lead to significant rounding of the workpiece at the edge or at the respective marginal area. In addition, typical rotor disks are subject to considerable wear. In DE102017221931A1, rotor disks with a diamond-like-carbon (DLC) coating and a hydrophilic surface with a water drop contact angle of less than 25° are proposed to increase the wear resistance and improve the edge profile. However, in practice, these measures have not led to a sufficient increase in the wear resistance and a sufficient improvement in the edge profile of the workpiece. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] DE 102017221931 A1 Summary of the Invention [Problem to be solved by the invention]

[0006] In view of the prior art described, it is therefore an object of the present invention to provide a rotor disk, a double-sided machining machine and a method of the type indicated above, which makes it possible to further optimize the edge shape of the workpiece and in particular to further reduce the wear of the rotor disk. [Means for solving the problem]

[0007] The present invention achieves this object by the subject matter of claims 1, 6 and 7. Advantageous configurations are set out in the dependent claims, the description and the drawings.

[0008] For rotor disks of the above kind, the present invention provides a method for manufacturing a rotor disk having a surface The entire angle is at least 70° and not more than 75°. The objective of having a water droplet contact angle of .about.100° is achieved.

[0009] In addition, the present invention achieves the object by a double-sided machining apparatus comprising a first working disk having a first working surface and a second working disk having a second working surface, the working surfaces defining a working gap between them, at least one of the working disks of the double-sided machining apparatus being capable of being driven in rotation, the double-sided machining apparatus further comprising a fluid supply for supplying a machining fluid to the working gap, and the double-sided machining apparatus comprising at least one rotor disk according to the present invention, by means of which at least one rotor disk at least one workpiece can be guided in the working gap for double-sided material removal machining.

[0010] Additionally, the present invention achieves the object by a method for machining at least one workpiece in a double-sided machining center according to the invention, in which at least one workpiece is received in at least one workpiece opening of at least one rotor disk and guided for machining in a working gap of the double-sided machining center, at least one of the working disks of the double-sided machining center is driven in rotation, and the working gap is supplied with a machining fluid during machining.

[0011] The double-sided processing machine can be, for example, a double-sided polishing machine. The rotor disk is typically equipped with a number of workpiece openings. As explained above, the workpieces, such as wafers, in particular semiconductor wafers, made of silicon for example, are held in a floating state in the workpiece openings of the rotor disk. During operation, the rotor disk is arranged in the working gap between the opposing working disks of the double-sided processing machine. The rotor disks generally have external teeth, which mesh with internal teeth provided on the inner edge of the working gap and external teeth provided on the outer edge of the double-sided processing machine working disk, for example of the lower working disk. In the course of the rotation, which occurs during the operation of at least one working disk, the rotor disk is consequently rotated on the one hand along a circular path through the working gap and on the other hand about its own axis. As a result, the workpieces received in the workpiece openings of the rotor disks are guided in a known manner along a cycloidal trajectory through the workpiece and processed in a material-removing manner. Likewise, a processing fluid, such as, for example, a so-called slurry, is introduced in a known manner into the working gap during processing. The processing fluid can contain abrasive elements.

[0012] According to the present invention, the surface of the rotor disk whole teeth, At least 70° The contact angle of the water droplet is .vinegarThat is to say, in contrast to the prior art described above, the surface is not hydrophilic. The inventors have noticed that in the prior art, a non-optimal distribution of the processing fluid on the surface of the rotor disk and thus on the processed workpiece leads to increased wear of the rotor disk and a non-optimal edge shape of the processed workpiece. In particular, the inventors have noticed that in the prior art, a non-uniform fluid film occurs between the processed workpiece and the surface of the working disk, for example the polishing cloth, which in particular leads to a reduction in the thickness of the fluid film from the edge to the center of the processed workpiece, which results in a non-uniform material removal and thus an unwanted intensification of edge rounding of the workpiece. This is remedied by the inventive surface design of the rotor disk. The inventive configuration of the rotor disk surface results in a more homogeneous fluid film on the rotor disk and thus also on the processed workpiece, compared to the prior art. In particular, the transport of the processing fluid, in particular the polishing fluid, to the center of the workpiece is significantly improved by the inventive configuration of the rotor disk surface. In this way, the undesirable rounding of the workpiece, which occurs in the prior art, is minimized. Thus, the geometry of the machined workpiece as a whole is improved. At the same time, the homogenization of the fluid film according to the invention minimizes wear of the rotor disk and increases its service life, with corresponding cost advantages. The inventors realized that, although this is proposed in DE102017221931A1, in practice no hydrophilic surfaces are suitable for this purpose, but rather non-hydrophilic or even hydrophobic surfaces, respectively, are suitable. The rotor disk according to the invention can be made of a metallic material, for example stainless steel, by way of example.

[0013] According to one configuration, the surface of the rotor disk is 、7 The water droplet has a contact angle of 5° or less. The inventors further noted that, particularly above 90°, an increase in sagging of the workpiece occurs again. That is, there exists an optimum window of contact angles where sagging is minimized.

[0014] According to a further configuration, the desired contact angle of the surface according to the invention can be obtained by roughening the surface of the rotor disk, i.e. the desired contact angle is mechanically adjusted, for example by a corresponding double-sided machining process on the rotor disk. The correspondingly roughened rotor disk can remain free of further coatings. In particular, the material of the rotor disk to be roughened can be a metallic material, for example stainless steel.

[0015] If necessary, it is also possible to obtain a surface with the desired contact angle by selecting a suitable rotor disk material without using additional coatings or roughening measures, for example a metallic material such as stainless steel is possible as the rotor disk material.

[0016] It is also possible to obtain the desired contact angle of the surface by suitable coating of the rotor disk substrate. For example, by suitable DLC coating, the contact angle according to the invention can be adjusted, and then no further processing such as roughening is required. By way of example, metals such as stainless steel can be used as substrates for rotor disks.

[0017] According to a further configuration, the rotor disk can comprise, in addition to the at least one workpiece opening, at least one auxiliary opening, in which the processing fluid, preferably an abrasive fluid such as a slurry, can collect during the processing of at least one workpiece in the double-sided processing machine. The rotor disk can in particular comprise a plurality of workpiece openings and / or a plurality of auxiliary openings. By providing one or more auxiliary openings in a targeted manner, the effect according to the invention of homogenizing the film of the processing fluid can be further strengthened. It has been shown that the processing fluid arranged in the auxiliary openings homogenizes the film of the fluid over the entire surface of the rotor disk and thus over the entire surface of the processed workpiece. On the one hand, since the processing fluid can escape relatively freely through the auxiliary openings, a more uniform fluid distribution is achieved on the upper and lower sides of the rotor disk through the auxiliary openings, where the workpiece to be processed is not received during operation. On the other hand, the fluid transport from the outer regions of the rotor disk, in particular the region of the external teeth, to the workpiece and the center of the rotor disk is improved by the auxiliary openings. In this way, the processing result can be further optimized and the wear of the rotor disk can be further minimized. The auxiliary openings can in particular be formed between the workpiece openings. For example, a number of auxiliary openings can be formed in each case between two adjacent workpiece openings, which further improves the distribution of the fluid.

[0018] Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. [Brief description of the drawings]

[0019] [Figure 1] 1 is a schematic cross-sectional view of a double-sided processing machine according to the present invention; [Diagram 2] 1 shows a schematic diagram of a rotor disk according to the invention in a top view according to a first exemplary embodiment; [Diagram 3] 1 shows a schematic top view of a rotor disk according to the invention, according to a further exemplary embodiment; [Figure 4] 1 shows a diagram with average workpiece thickness profiles of different workpieces machined on a double-sided machining center in a material removal mode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Unless otherwise stated, like reference numbers refer to like objects in the figures.

[0021] In Fig. 1, a double-sided processing machine, in particular a double-sided polishing machine, according to the invention is shown very diagrammatically. The double-sided processing machine comprises an upper carrier disk 10 and a lower carrier disk 12 arranged opposite it. The upper carrier disk 10 supports an upper working disk 14 and the lower carrier disk 12 supports a lower working disk 16. The working disks 14, 16 can be provided, by way of example, with polishing covers, in particular polishing pads. The carrier disks 10, 12 and therewith the working disks 14, 16 can be driven in rotation by drive shafts 18, 20 about their axes 26, which run longitudinally in Fig. 1, in particular in opposite directions during operation of the double-sided processing machine.

[0022] The working discs 14, 16 define a working gap 22 between them. A number of rotor discs 24 are arranged in the working gap. In FIG. 1, two rotor discs 24 are shown. Of course, more or less than two rotor discs can also be provided. A workpiece 28, for example made of silicon, for example a semiconductor wafer, is processed on both sides in a material removing manner and is held floating in the workpiece opening of the rotor disc 24 in the working gap 22. The rotor discs 24 usually have external teeth on their outer edge, which are not shown in more detail in FIG. 1, which mesh with internal teeth arranged on the inner edge of the working gap 22 and not shown in more detail in FIG. 1, and with external teeth arranged on the outer edge of the working gap 22 and also not shown in more detail in FIG. 1. As a result, the rotor disc 24 is rotated during operation along a circular path through the working gap 22 and also about the axis of the rotor disc 24, so that the workpiece 28 moves along a cycloidal orbit through the working gap 22. A processing fluid, in particular a polishing fluid (slurry), is supplied to the working gap 22 during operation by a fluid supply, shown diagrammatically in FIG. 1 with reference number 30. The surface of the rotor disc 24 has a water drop contact angle of at least 60°. For example, the surface of the rotor disc 24 can be mechanically roughened to obtain said contact angle. The surface of the rotor disc 24, which can be made of stainless steel by way of example, can also be mechanically roughened instead of roughened to obtain the desired contact angle. To, It is also possible for a coating, for example a DLC coating, to be provided.

[0023] In FIG. 2, a further rotor disk 124 according to the invention is shown, which can be used in the double-sided processing machine shown in FIG. 1. The rotor disk 124 has, in the example shown, three circular workpiece openings 132 in which the workpieces for processing can be received in a floating state. In addition, in the case of the rotor disk 124 in FIG. 2, external teeth 134 are visible. The rotor disk 124 shown in FIG. 2 also has a water drop contact angle of at least 60°. For example, the surface of the rotor disk 124 can be mechanically roughened to obtain said contact angle. The surface of the rotor disk 124, which can consist of stainless steel by way of example, can also be provided with a coating, for example a DLC coating, instead of or in addition to roughening, in order to obtain the desired contact angle.

[0024] FIG. 3 shows a further exemplary embodiment of a rotor disk 224 that can also be used in the double-sided machine shown in FIG. 1. The rotor disk 224 likewise has three circular workpiece openings 232 for receiving the workpiece to be processed in a floating state, and external teeth 234. Unlike the rotor disk 124 shown in FIG. 2, the rotor disk 224 shown in FIG. 3 has, in addition to the three workpiece openings 232, a number of auxiliary openings 236. The supplied processing fluid can collect in the auxiliary openings 236 during the processing of the workpiece in the working gap 22 of the double-sided machine. The auxiliary openings 236 act as a reservoir for the processing fluid and provide an optimal homogenization of the fluid film on the rotor disk 224, in fact on the upper and lower sides as well as on the individual sides, and therefore also on the workpiece received in the workpiece openings 232. The rotor disk 224 shown in FIG. 3 also has a contact angle of a water drop of at least 60°. For example, the surface of the rotor disk 224 can be mechanically roughened to obtain said contact angle. The surface of the rotor disk 224, which may be made of stainless steel for example, may also be provided with a coating, for example a DLC coating, instead of or in addition to roughening to obtain the desired contact angle.

[0025] All of the rotor disks 24, 124, 224 shown in FIGS. The part Preferably, the contact angle of the water droplet is 90° or less, more preferably 75° or less. The part , preferably at least 65°, more preferably at least 70°. All or part of the rotor disks 24, 124, 224 can be made of stainless steel, for example, or can include stainless steel as a substrate during subsequent coating. However, all or part of the rotor disks 24, 124, 224 can also be made of other materials. It is also conceivable that the rotor disks 24, 124, 224 are made of a material that already inherently has the desired contact angle, so that no subsequent coating or roughening is required. If the surfaces of the rotor disks 24, 124, 224 are roughened, or if the rotor disk material already inherently has the desired contact angle, these surfaces may not have any further coating.

[0026] In FIG. 4, the average workpiece thickness profile of a workpiece, in particular a silicon wafer, processed with three different rotor disks is shown. The outer workpiece region is shown from the workpiece radius of about 114 mm to the outer edge of the workpiece of about 149 mm. The base thickness, in particular in the region of the workpiece center, which can be seen for example at the workpiece radius of 114 mm in FIG. 4, is substantially equal or respectively standardized for all workpieces. In FIG. 4, the curves are shown on top of each other for the sake of illustration only. The average thickness profile of the workpiece was established by processing a number of workpieces, each with one of the three rotor disks, and subsequently averaging the thickness profiles. Processing was performed in the example shown on a double-sided polisher owned by the applicant, with a polishing fluid (slurry) being supplied to the working gap during processing.

[0027] The top curve in Figure 4 shows the average workpiece thickness profile when using a plain uncoated stainless steel rotor disk. The middle curve in Figure 4 shows the average workpiece thickness profile when using a stainless steel rotor disk with a conventional DLC coating. The bottom curve in Figure 4 shows the average workpiece thickness profile when using a rotor disk according to the present invention having a surface contact angle with a water droplet of at least 60°.

[0028] In Fig. 4, the sag heights of the workpiece thickness profile are indicated by the letters A, B and C, respectively. It can be clearly seen that sag A is the largest when using the stainless steel rotor disk, followed by sag B when using the rotor disk with a conventional DLC coating. In contrast, a significantly lower sag C is obtained with the rotor disk according to the invention. [Explanation of symbols]

[0029] 10 Upper Carrier Disk 12 Lower Carrier Disk 14 Upper working disc 16 Lower working disc 18 Drive shaft 20 Drive shaft 22 Working Gap 24 rotor disk 26 axis 28 Workpieces 30 Fluid supply section 124 rotor disk 132 Workpiece opening 134 Outer teeth 224 Rotor disk 232 Workpiece opening 234 Outer teeth 236 Auxiliary opening

Claims

1. A rotor disk for guiding a workpiece (28) in a double-sided processing machine, comprising: a rotor disk having at least one workpiece opening (132, 232) for receiving at least one workpiece (28) to be machined on both sides in a material removing manner in the double-sided machining machine, the entire surface of the rotor disk (24, 124, 224) having a water drop contact angle of at least 70° and no more than 75°; A rotor disk (24, 124, 224) characterized in that the entire surface of the rotor disk (24, 124, 224) is roughened to obtain the contact angle of the water droplet.

2. 2. The rotor disk of claim 1, wherein the entire surface of the rotor disk (24, 124, 224) is coated to obtain the contact angle of the water droplet.

3. 3. The rotor disk of claim 2, wherein said coating is a diamond-like carbon (DLC) coating.

4. A double-sided processing machine comprising a first working disc (14) having a first working surface and a second working disc (16) having a second working surface, the first working surface and the second working surface define a working gap (22) between the first working surface and the second working surface; At least one of the first working disk (14) and the second working disk (16) of the double-sided processing machine can be driven in rotation; The double-sided processing machine further comprises a fluid supply (30) for supplying a processing fluid to the working gap (22); The double-sided processing machine further comprises at least one rotor disk (24, 124, 224) according to any one of claims 1 to 3, A double-sided machining apparatus, wherein the at least one rotor disk (24, 124, 224) enables at least one workpiece (28) to be guided in the working gap (22) for double-sided material removal machining.

5. A method for machining at least one workpiece (28) on a double-sided machining center as claimed in claim 4, comprising the steps of: the at least one workpiece (28) is received in the at least one workpiece opening (32, 132, 232) of the at least one rotor disk (24, 124, 224) and guided for processing in the working gap (22) of the double-sided processing machine; At least one of the first working disc (14) and the second working disc (16) of the double-sided processing machine is driven in rotation and a processing fluid is supplied to the working gap (22) during the processing.

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