JP5689891B2 - Apparatus and method for processing a flat workpiece on both sides - Google Patents

Description

  The present invention relates to an apparatus for processing a workpiece on both sides, the apparatus comprising an upper working disc and a lower working disc, both working discs working gaps for machining the workpiece between their working surfaces facing each other. And at least one of the working disks has a plurality of holes penetrating to the working surface for supplying the liquid working medium to the working gap. The invention also relates to a method of operating an apparatus for double-side machining a flat workpiece, the apparatus comprising an upper working disk and a lower working disk, both working disks machining the workpiece between their working surfaces facing each other. And at least one of the work disks has a plurality of holes that penetrate to the work surface for supplying the liquid work medium to the work gap.

  Such an apparatus and method is useful, for example, for double-side polishing of semiconductor wafers. When polishing, the polishing liquid is introduced into the work gap as a working means. For this purpose, a two-disc polishing machine is known from US Pat. The abrasive disc described herein has a series of axial parallel holes that are aligned with corresponding holes in the carrier disc that supports the abrasive disc and that are connected to a line that supplies abrasive means to the working surface of the abrasive disc. Have. These holes are provided in the upper working disk, and the polishing means is conveyed downward into the polishing gap by gravity. One problem here is that a uniform supply of the polishing means to the polishing gap cannot always be guaranteed. In particular, in the area of the abrasive disc where the workpiece frequently traverses during processing, the abrasive means can be depleted. This can affect the polishing result.

German Patent Application Publication No. 10007390 (A1)

  Against the background of the above prior art, an object of the present invention is to provide an apparatus and method of the above type in which a sufficient supply of working medium to the working space is guaranteed at any time.

  The above object is achieved according to the invention by the contents of independent claims 1 and 10. Advantageous embodiments are found in the dependent claims and in the following description and drawings.

  For an apparatus of the above type, the object of the present invention is to group the holes for supplying liquid into groups, connect each group to a separate pressurized supply line for the working means, and within the supply line This is achieved by providing at least one pressure control device capable of individually adjusting the pressure of the working means. For the above type of method, the object of the present invention is to group the holes into groups, supply pressure working means to each hole group, and individually apply the pressure of the working means supplied to each hole group. Achieved by adjusting.

  With the processing according to the invention, the material can be removed. The apparatus can be an apparatus that performs double-side polishing of a flat workpiece. The working fluid can accordingly be a polishing fluid. However, other processing methods are also conceivable, for example grinding or lapping. The workpiece on which processing according to the invention, for example coplanar processing, is performed can be, for example, a semiconductor wafer. The working disk can be annular, for example. The working gap can also be annular accordingly. A vertical drive shaft can be connected to one or both of the working disks. If the working disks are each supported by a carrier disk, this connection can be made by the carrier disk. At least one of these drive shafts can be driven and rotated by a suitable drive device, and the working disk connected to this drive shaft rotates accordingly. The workpiece is machined between working disks that rotate relative to each other. A hole is provided in at least one of the working disks, for example, the upper working disk. Of course, these holes can be provided in both working disks. A suitable pressure line, such as a pressure hose or pressure pipe, can transport the working means into the working cavity and penetrate the holes in the working disk (one or both).

  According to the invention, the provided holes are divided into several, for example two or more groups. A pressure supply line is associated with each group. Thus, in the example described above, a total of three or more pressurized supply lines may be deployed. By means of a group of holes, it is possible, for example, to supply working means to specific working gap zones. The pressure of the working means is the pressure in the supply line or hole filled with the working means. This pressure determines the flow rate of the working fluid flowing from the hole into the working cavity. According to the invention, the pressure of the working means, and thus the flow rate into the working gap of the working means, is adjusted individually for the individual supply lines to which the working means are supplied and thus for the individual groups of holes or each working zone. It becomes possible to do. This allows the supply of working means, for example polishing means, to be adapted to the process requirements in a flexible way. The flow rate of the working means can be adjusted, for example, according to the working parameters (guided by the working procedure). The division of the zones or the respective groups can be performed so that each hole of a zone is subjected to substantially uniform operating conditions during operation of the device.

  Thus, each hole in one working gap zone will be substantially traversed at a uniform frequency by the workpiece. Each hole in a group can be assigned, for example, to a specific radial region of the working gap. Thus, each group is formed from a hole in the annular zone. By commonly adjusting the pressure, and thus the flow rate through the holes, for each zone, an optimal supply of working fluid is ensured for that zone or each group. In particular, it is possible to adjust a certain preset pressure for each working means for each supply line. Thereby, holes in different zones are subjected to different operating conditions, but a constant polishing means can be supplied over the entire work gap. Of course, more than one adjusting device can be provided, for example for each supply line or for each group of holes. However, it is also conceivable to provide a common adjusting device for adjusting the pressure of the working means in all supply lines.

  Thereby, according to the invention, it is ensured that the working means is supplied uniformly and sufficiently to the working gap at any time. In addition to optimizing the work results, the work means can also be used more effectively to reduce the total demand of the work means. Scratching or similar processing damage is reliably avoided. Also, a relatively smooth polishing cloth can be used. If desired, the workpiece can be cleaned, for example through the upper working disk with holes, by rapidly increasing the pressure of the working means for a short period of time. This ensures that unnecessary adhesion of the workpiece is avoided when lifting the upper working disk at the end of the process. Further, for example, in order to cool a region where the processing temperature has risen, it is possible to intentionally change the amount of working means supplied to the working gap. This further optimizes the work results.

  According to one embodiment which is particularly suitable for implementation, the supply lines can each be connected to a common main pressure supply line and to each group of holes. The main supply line is connected to the storage tank of the working means and may have, for example, a pump for feeding working fluid from the main supply line to the individual supply lines. Furthermore, each supply line is provided with a pressure control unit which can adjust the pressure of the working means in each supply line independently of the other supply lines. It is also possible to provide a flow measuring device in the supply line, the measurement signal being connected to a corresponding flow control device that adjusts the flow rate of the liquid based on the measurement signal of the flow measuring device. The supply line according to the known method can be a plurality of feed lines that penetrate the holes in the working disk, for example a ring line or an annular channel connected to a feed tube. Such a pressure-resistant ring line serves to provide a plurality of lines communicating therewith in a particularly simple and reliable manner.

  A common main pressure supply line can then be guided through a vertical drive shaft assigned to at least one working disk with holes. The vertical drive shaft is driven by a drive device, such as a motor. As a result, the working disk connected to the drive shaft rotates. Thus, a pressure-resistant single channel rotary inlet is provided through the drive shaft to distribute the working means to the respective supply lines. In one advantageous method, only one main pressure supply line needs to be guided from the fixed device housing to the rotating parts. In this case, however, it is necessary to provide an electrical control device on the working disk in order to disperse the main pressure supply line into the individual supply lines. For some field applications, this is undesirable. Thus, as another example, a multi-channel rotary inlet is also possible, in which case the distribution to the individual supply lines has already taken place before the drive shaft and the corresponding lines are connected to the drive shaft. Guided through.

  According to another embodiment, the cross-section of the hole, or the cross-section of the liquid line guided in the hole, can be reduced at its end region that is open towards the work surface. The cross section can be reduced by more than 50%, for example. While the working means flows out, such a reduction in the cross section at the exit area to the working gap creates a back pressure, so that a minimum pressure is maintained in the supply line even when the working means is flowing freely. Guaranteed to be done. In particular, the pressure of the working means is not lost when the individual or several outlet openings are uncovered. Unlike the prior art, the polishing means can not only come out through a hole not covered by the workpiece, but in principle can also come out from a hole covered by the workpiece. In particular, if the supply line pressure is equal to or greater than the specific working pressure of the working cavity, the liquid will flow out. By maintaining a specific pressure level in the supply line, outflow from all outlet openings is guaranteed.

  Since the friction between the work coating on the work disk and the workpiece depends on the amount of liquid, a measuring device is further provided for measuring the torque applied by the rotational drive to at least one vertical shaft connected to at least one of the work disks. Can be deployed and the control device compares the torque measured by the measuring device with the reference torque or reference torque range, and if the measured torque deviates from the reference torque or reference torque range, the measured torque is again the reference torque Or the working means pressure in at least some of the supply lines is changed to be equal to or within the reference torque range. Furthermore, the control device may compare the measured torque with a preset limit torque. If the measured torque is less than the limit torque, the control device reduces the pressure of the working means in at least some of the supply lines so that the value of the measured torque again exceeds the limit torque.

  This design is based on the knowledge that when an excessive supply of working fluid occurs in the working gap, the torque applied by the drive to reach a predetermined rotational speed is drastically reduced in a manner similar to hydroplaning. is there. This unnecessarily impairs the machining of the workpiece. Therefore, in such a case, the supply of the working means is reduced by reducing the pressure in the supply line until the torque is again within a predetermined range. Of course, the pressure can be changed, especially in all supply lines, and can be reduced especially

  The holes can be grouped depending on the frequency with which they are covered by the workpiece to be machined during operation of the device. Based on this, the higher the frequency with which the holes of each group are covered by the workpiece to be machined during operation of the apparatus, the higher the pressure of the working means in the supply line of each group can be set. Thus, for different groups, there are various predetermined reference values for each supply line, and the reference pressure value is selected depending on the expected frequency with which the hole is covered by the workpiece to be processed.

  According to the invention, a carrier wheel with at least one, in particular a plurality of depressions, can be deployed in a known manner, in which the workpiece to be processed is held floating. The carrier wheel is driven to rotate in the working gap and the workpiece held in the wheel moves along the cycloid track in the working gap. This results in various dwell probabilities in the radial direction of the work gap during workpiece machining. Thus, the work well dwell probability at the edge region of the work gap, particularly the inner edge, can be higher than the probability at the center, for example. The above design takes this fact into account.

  Thus, the holes in a particular ring zone of the work gap can be grouped together and each ring zone is assigned a particular dwell probability for the workpiece. The higher the dwell probability for a ring zone or one of the respective groups, the greater the reference pressure of the working means for the supply lines assigned to this group. The control can be carried out so that the overall distribution of the working means in the entire working gap obtained as a result is as uniform as possible.

The method according to the invention can in particular be carried out with the device according to the invention. Likewise, the device is suitable for carrying out the method according to the invention.
Exemplary embodiments of the present invention are described in more detail below with reference to the drawings. The outline of the drawings is as follows.

Figure 2 is a vertical sectional view of a part of the device according to the invention. FIG. 3 is an enlarged view of a partial cross section of FIG. 1 according to another embodiment. It is an enlarged view of the cross section B of FIG. It is a circuit diagram which shows the control by this invention.

  Unless otherwise specified, the same reference numerals in the drawings denote the same object. FIG. 1 shows a cross-sectional view of an apparatus 10 according to the invention for double-side machining a flat workpiece. The illustrated apparatus is a double-side polishing machine that performs the same plane polishing of a semiconductor wafer. The exemplary device has three supply lines 36 extending from the polishing fluid reservoir, each guided through the vertical drive shaft 20 of the device via a connection 22 and a multi-channel rotary inlet 18. The polishing liquid can be conveyed from the liquid storage tank through the supply line 36 by a pump not shown in detail in FIG. The exemplary supply line 36 forms a ring line 36 with an outlet to each group of holes. The supply line 36 can be formed by a supply hose. Furthermore, pressure regulating devices not shown in detail can be provided, each designed to regulate the pressure of the working means in one of the supply lines 36. This will be described in detail later.

  The device 10 in a known manner additionally comprises annular upper and lower carrier disks and annular upper and lower working disks connected to the upper and lower carrier disks, respectively. FIG. 1 shows only the upper carrier disk 38 and the upper working disk 40 connected thereto. The upper carrier disk 38 is annular in design. Although not shown, the apparatus 10 has a lower carrier disk and a lower working disk that are almost symmetrical in design to the upper carrier disk 38 and the upper working disk 40. Both working disks define an annular working gap between the annular working surfaces facing each other. Of these working surfaces, the working surface of the upper working disk 40 is shown in FIG. The basic design of such a double-sided polishing machine with upper and lower working disks is known, for example, from US Pat.

  As further shown in FIG. 1, a plurality of axial holes 48 are provided through the working disk 40, each aligned with a corresponding hole 50 in the upper carrier disk 38. A pressure pipe 52 passes through each hole. FIG. 1 further shows that each annular supply line 36 is connected to the upper opening of the pressure pipe 52.

  The design of the holes 48 and 50 and the respective pressure pipes 52 will be described in more detail based on the enlarged views shown in FIGS. Unlike the exemplary embodiment of FIG. 1, in the exemplary embodiment of FIGS. 2 and 3, more supply lines 36, holes 48, 50, and pressure pipes 52 are provided. Otherwise, both exemplary embodiments are the same. 2 and 3 show that the pressure pipe 52 is connected to the ring line 36 via the connector 54 at the upper end. The pressure pipe 52 is, for example, plastic. A metal sleeve 58 is inserted into each of the holes 50 or 48 of the upper carrier disk 38 or the upper working disk 40. The pressure pipe 52 is sealed against the sleeve 58 in its end region that opens to the work surface 46. As further shown in FIG. 3, the pressure pipe 52 has a significantly reduced portion 62 at its lower end that exceeds 50% in cross section. Accordingly, the outlet opening 64 of the pressure pipe 52 is significantly smaller in diameter than the main region 66 of the pressure pipe 52.

  As shown in particular in FIGS. 1 and 2, the holes 48, 50 are arranged at various different radial distance positions in the working disc and the carrier disc. The upper working disk and the upper carrier disk that supports it have multiple annular rows of axial holes through the working disk 40 and the carrier disk 38 at various different radial distances from the center axis of rotation through the vertical drive shaft 20. . The holes of a certain radial distance are grouped together, and polishing means is supplied from the ring line 36.

  The function of the device according to the invention will be described again in more detail with reference to the schematic circuit diagram shown in FIG. The polishing means is conveyed from a storage tank of the polishing means (not shown) to the supply line 36 via a check valve 70 connected to the pump 68. From there, the polishing means is further conveyed to the pressure adjusting device 35. In addition, a two-way valve 72 is respectively arranged in the supply line 36 to turn on and off the supply circuit supplied through the supply line 36. The pressure of the polishing means in each of the ring lines 36 can be individually adjusted to a specific value using the pressure adjusting device 35. In addition, a flow meter 74 is disposed in each of the supply lines 36. Such adjustments, or flow control, respectively, are known to those skilled in the art and are therefore not described in greater detail herein.

The workpiece to be processed can be held in a carrier wheel in a known manner, for example to move along an annular track in the working gap. In the process, the work gap has a variety of different workpiece dwell probabilities. In particular, different radial hole groups of the upper working disk 40 are covered at different frequencies by the workpiece during operation. According to the present invention, taking this into account, the radial region of the hole that is expected to be covered more frequently, through the ring line 36 and the corresponding pressure regulator 35 assigned thereto, at a higher working pressure. Can be pressurized.

Claims (12)

An apparatus for processing a flat workpiece on both sides, comprising an upper working disk (40) and a lower working disk, the working disks (40) being placed between their working surfaces (46) facing each other. Forming a working cavity for machining a piece, wherein at least one of the working disks (40) passes through a plurality of holes (48) extending to the working surface (46) for supplying a liquid working medium to the working cavity; In a device having
The holes (48) are grouped into several groups depending on the frequency with which the holes (48) are covered by the workpiece to be machined during operation of the apparatus (10) for double-side processing the flat workpiece. , each group of holes (48) is connected to a separate pressurized feed line (36) for the working medium, at least the pressure of the working medium in said supply line (36) can be adjusted independently of each other Device, characterized in that one pressure control device (35) is provided.   The device according to claim 1, characterized in that each of the supply lines (36) can be connected to a common main pressure supply line and to each hole (48) of a group.   The common main pressure supply line is guided through a vertical drive shaft (20) assigned to the at least one working disk (40) with the hole (48). 2. The apparatus according to 2.   The feed line (36) is guided through a vertical drive shaft (20) assigned to the at least one working disk (40) with the hole (48). The device described in 1. The cross-section of the hole (48) or the cross-section of the liquid line (52) guided in the hole (48) is reduced at their end regions opened to the working surface (46). The apparatus according to claim 1 . The apparatus further comprises a measuring device for measuring torque applied by rotational drive to at least one vertical shaft (20) connected to at least one of the working disks, wherein the control device (35) is a torque measured by the measuring device. Is compared with the reference torque or the reference torque range, and if the measured torque deviates from the reference torque or the reference torque range, the supply line (36 6) The apparatus according to any one of claims 1-5 , characterized in that the pressure of the working means in at least some of the above is changed.   The control device (35) compares the measured torque with a predetermined limit torque, and if the measured torque falls below the limit torque, the control device (35) causes the measured torque to again exceed the limit torque. 7. Device according to claim 6, characterized in that the pressure of the working means in at least some of the supply lines (36) is reduced.   The control device (35) depends on the frequency with which each group of holes (48) is covered by the workpiece to be machined during operation of the device (10), in the supply line (36) of each group. 8. A device according to any one of the preceding claims, characterized in that the pressure of the working means is set.   A method of operating an apparatus for double-side processing a flat workpiece, said apparatus comprising an upper working disk (40) and a lower working disk, said working disks (40) being their working surfaces facing each other During (46), a working gap for machining the workpiece is formed, and at least one of the working disks (40) is provided with the working surface (46) for supplying a liquid working medium to the working gap. Having a plurality of holes (48) penetrating to
  The holes (48) are grouped into groups depending on the frequency with which the holes (48) are covered by the workpiece to be machined during operation of the device, and each group of holes (48) is pressurized by working means, and Method of adjusting the pressure of said working means supplied to each of the hole groups (48) individually with respect to each other.   Measuring torque applied by rotational drive to at least one vertical shaft (20) connected to at least one of the working disks, comparing the torque measured by the measuring device with a reference torque or a reference torque range, and measuring torque Is deviating from the reference torque or the reference torque range, the pressure of the working means in at least some of the supply lines is changed so that the measured torque is again equal to or within the reference torque range. The method according to claim 9, characterized by.   The measured torque is compared with a predetermined limit torque, and if the measured torque falls below the limit torque, the pressure of the working means supplied to at least some groups is reduced so that the measured torque again exceeds the limit torque The method of claim 10.   Depending on the frequency with which the holes (48) of each group are covered by the workpiece to be machined during operation of the device, the pressure of the working means supplied to each group is set. Item 12. The method according to Item 10 or 11.

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