Workpiece processing equipment

Abstract

To provide a work-piece processing device capable of realizing a high processing rate and stably processing a work-piece formed using a difficult-to-process material in a short time.SOLUTION: In a work-piece processing device 1 according to the present invention that performs processing by bringing a processing head 14 into sliding contact with a work-piece W held on the upper surface of a holding plate 20, the processing head 14 is arranged with a plasma electrode 30 that generates plasma and irradiates the surface of the work-piece W to be processed. The plasma electrode 30 has an annular or columnar central electrode 31 provided at the center in the radial direction and an annular peripheral electrode 32 provided radially outward with respect to the central electrode 31 at the boundary position via an annular slit portion 36, and the slit portion 36 is configured as a plasma generation space, and a processing pad 40 is provided on the bottom surfaces of the center electrode 31 and the peripheral electrode 32.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a workpiece machining device, and more particularly to a workpiece machining device that machines the surface of a workpiece held by a holding plate by sliding a machining head against the workpiece. [Background technology]

[0002] In the fabrication of semiconductor power devices, surface processing is essential for substrates (workpieces), such as wafers. Wide bandgap semiconductor substrates, such as silicon carbide (SiC), gallium nitride (GaN), and diamond, are particularly hard and brittle, making it difficult to process them efficiently using conventional mechanical processing. In this application, "processing" broadly includes processes that remove surface material, such as grinding to remove the surface, polishing to reduce surface roughness, and planarization to increase flatness.

[0003] When processing the above substrates, it is possible to use a processing method called P-CVM (Plasma Chemical Vaporization Machining). This method is a chemical processing method using plasma under atmospheric pressure, and its high radical density enables highly efficient processing. However, since it is a processing method that performs isotropic etching, it processes not only the convex parts of the surface but also the concave parts, making it unsuitable for planarization purposes.

[0004] Therefore, Patent Document 1 (JP 2015-159257 A) and Patent Document 2 (JP 2015-179830 A) disclose methods and devices for processing difficult-to-process materials such as silicon carbide (SiC), gallium nitride (GaN), and diamond with high efficiency and precision by combining plasma processing and mechanical processing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-159257 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-179830 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the conventional workpiece processing device exemplified in Patent Document 1, a mechanical unit that performs CMP (Chemical Mechanical Polishing) and a mechanical unit that performs plasma processing are arranged separately, and the workpieces are processed alternately in each mechanical unit, which results in a problem of a long takt time and reduced production efficiency.

[0007] On the other hand, in the conventional workpiece processing device exemplified in Patent Document 2, the mechanism for performing plasma processing is built into the base, which causes problems such as adhesion of the slurry at the built-in point and unstable plasma generation due to the influence of the slurry (wet environment). [Means for solving the problem]

[0008] The present invention has been made in consideration of the above circumstances, and aims to provide a workpiece processing device that can achieve a high processing rate for workpieces formed using difficult-to-process materials and perform processing stably in a short period of time.

[0009] The present invention solves the above problems by the solution means described below as one embodiment.

[0010] The workpiece processing device of the present invention is a workpiece processing device that processes the surface to be processed by sliding a processing head against the workpiece held on the upper surface of a holding plate, and the processing head is rotatably mounted and has a plasma electrode that generates plasma and irradiates the surface to be processed of the workpiece, and the plasma electrode comprises an annular or cylindrical central electrode located at the radial center and an annular outer electrode located radially outward from the central electrode, with an annular slit portion at the boundary position, and the slit portion is configured as a plasma generation space, and processing pads are provided on the bottom surfaces of the central electrode and the outer electrode. [Effects of the Invention]

[0011] According to the present invention, even for workpieces made of difficult-to-process materials, processing can be performed while modifying or etching the processing surface, thereby increasing the processing rate. Furthermore, since the plasma processing step and the processing step can be performed simultaneously, i.e., in a continuous process without rearranging the workpiece between mechanisms, processing can be completed in a short time, thereby improving production efficiency. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a front cross-sectional view showing an example of a workpiece machining device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] 2 is an enlarged view of a machining head in the workpiece machining device of FIG. 1. [Figure 4] 2 is a perspective view showing an example of a plasma electrode of a machining head in the workpiece machining apparatus of FIG. 1. FIG. [Figure 5] 1. FIG. 4 is a perspective view showing another example of the plasma electrode of the processing head in the workpiece processing apparatus of FIG. [Figure 6] 1. FIG. 4 is a cross-sectional view showing another example of the machining head in the workpiece machining apparatus of FIG. [Figure 7]1. FIG. 4 is a cross-sectional view showing another example of the plasma electrode of the machining head in the workpiece machining apparatus of FIG. [Figure 8] 1. FIG. 4 is a cross-sectional view showing another example of the plasma electrode of the machining head in the workpiece machining apparatus of FIG. [Figure 9] 1. FIG. 4 is a cross-sectional view showing another example of the plasma electrode of the machining head in the workpiece machining apparatus of FIG. [Figure 10] FIG. 10 is a front cross-sectional view showing an example of a workpiece machining device according to a second embodiment of the present invention. [Figure 11] 11 is a cross-sectional view taken along line XI-XI in FIG. [Figure 12] 11 is a cross-sectional view showing another example of the machining head in the workpiece machining apparatus of FIG. [Figure 13] 11 is a cross-sectional view showing another example of the machining head in the workpiece machining apparatus of FIG. [Figure 14] FIG. 10 is an enlarged view of a portion XIV in FIG. [Figure 15] FIG. 1 is a diagram visualizing the plasma generation intensity in the samples shown in Table 1. [Figure 16] 1. FIG. 4 is a cross-sectional view showing another example of the plasma electrode of the machining head in the workpiece machining apparatus of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] (First embodiment) A first embodiment of the present invention will be described in detail below with reference to the drawings. Fig. 1 is a front cross-sectional view (schematic diagram) showing an example of a workpiece machining apparatus 1 according to this embodiment. Fig. 2 is a cross-sectional view (schematic diagram) taken along line II-II in Fig. 1. Fig. 3 is an enlarged view (schematic diagram) of the machining head 14 in the workpiece machining apparatus 1 of Fig. 1. In all the drawings used to explain each embodiment, members having the same function are given the same reference numerals, and repeated explanations thereof may be omitted.

[0014] The workpiece machining device 1 according to this embodiment is a device that performs machining (surface machining) by pressing and sliding a machining head 14 against a workpiece W on a holding plate 20 fixed to the upper surface of a turntable 12.

[0015] On the other hand, the workpiece W to be processed is a substrate (for example, a disk-shaped wafer) formed using a so-called difficult-to-process material, such as silicon carbide (SiC), gallium nitride (GaN), diamond, etc., and its outer diameter and thickness are not particularly limited (for example, an outer diameter of several centimeters to several tens of centimeters, and a thickness of several μm to several mm).

[0016] Furthermore, the holding plate 20 according to this embodiment holds (attaches) one or more workpieces W on its holding surface (upper surface), and the workpiece W's processing surface (upper surface) is brought into contact with the workpiece processing surface (lower surface) of the processing head 14. In this embodiment, the lower surface of the workpiece W is adhered and affixed to the holding surface (upper surface) of the holding plate 20 using a known releasable adhesive, but this is not limiting, and methods such as vacuum suction or fitting by forming a recess may also be used. Note that the holding plate 20 is required to be made of a material that is highly flat and resistant to deformation, and is generally made of glass, ceramics, or the like.

[0017] Next, the turntable 12 according to this embodiment is formed of a metal material (such as a stainless steel alloy, for example) in a circular shape in a plan view, and is supported by bearings 44 and driven to rotate (in the direction of arrow A) by a drive device 42 (such as a drive mechanism equipped with an electric motor, for example). The holding plate 20 is held (fixed) at a predetermined position on the turntable 12 via a carrier 22. This carrier 22 is generally formed of a metal material (such as a stainless steel alloy, for example).

[0018] Here, the carrier 22 is sandwiched and meshed between the sun gear 16 and the internal gear 18, which are arranged so that their axes coincide with the central axis of the turntable 12, and is rotationally driven so as to rotate (in the direction of arrow C) and revolve (in the direction of arrow D) with the rotation of the turntable 12. The rotation of this carrier 22 causes the holding plate 20 to rotate (in the direction of arrow C) and revolve (in the direction of arrow D). Note that, in this embodiment, four carriers 22 are arranged between the sun gear 16 and the internal gear 18, but the present invention is not limited to this.

[0019] Next, the machining head 14 according to this embodiment is supported above the turntable 12 so as to be movable up and down, and is configured to be rotatable (in the direction of arrow B) by a drive device (not shown) consisting of an electric motor or the like disposed on the support frame 10. As an example, it is configured by a known mechanism including a spline or the like. In addition, the lower surface is configured as a workpiece machining surface for machining the workpiece W, and further configured with a plasma electrode 30 that generates plasma and irradiates the machining surface of the workpiece W with the plasma.

[0020] As shown in FIG. 4 (bottom perspective view), plasma electrode 30 according to this embodiment includes a cylindrical central electrode 31 located at the radial center and an annular outer electrode 32 located radially outward from center electrode 31, with an annular slit 36 ​​at the boundary between them. This slit 36 ​​serves as a plasma generation space (details will be described later). As a modification of plasma electrode 30, center electrode 31 may be configured to have an annular shape, as shown in FIG. 5 (bottom perspective view). While processing pads 40 are provided on the bottom surfaces of center electrode 31 and outer electrode 32 as shown in FIG. 3, processing pads 40 are not shown in FIGS. 4 and 5 to simplify the structure.

[0021] The plasma can be generated by supplying a base gas (a rare gas such as He) and a reactive gas from each reservoir (not shown) through piping 46 to the slit portion 36, while applying a predetermined voltage between adjacent electrodes constituting the slit portion 36. Specific examples of the reactive gas are fluorine-based gas and oxygen gas when the workpiece is SiC or the like, chlorine-based gas and oxygen gas when the workpiece is GaN, and fluorine-based gas, oxygen gas, or hydrogen gas when the workpiece is diamond.

[0022] According to the above configuration, by rotating (rotating) the turntable 12, the holding plate 20 can be rotated and revolved via the carrier 22. At the same time, the machining head 14 can be rotated (rotated) and pressed against and slidably contacted with the workpiece W held by the holding plate 20. At this time, the rotating plasma electrode 30 generates plasma and irradiates it onto the workpiece W's surface to be machined. Therefore, the workpiece W's surface to be machined can be machined while being modified or etched (either one or both depending on the material of the workpiece W and the type of reactive gas) by irradiating it with plasma, thereby improving the machining rate. Compared to the apparatus described in Patent Document 1, which alternates between the plasma treatment process and the machining process using separate mechanisms, this embodiment allows these processes to be performed simultaneously, i.e., continuously, without the need to rearrange the workpiece W. This enables machining to be completed in a short time and improves production efficiency.

[0023] The workpiece machining apparatus 1 according to this embodiment is configured such that multiple (for example, two) machining heads 14 are arranged with outer diameters and positions that allow the slits 36 to pass through and the machining pads 40 to slide over the entire area of ​​the machining surface of all workpieces W, whose positions change relative to one another as each mechanism moves (rotates). This improves the machining rate and enables machining to be completed in a short time. However, the number of machining heads 14 is not limited to the above, and may be three (or more) as shown in FIG. 6 (a cross-sectional view corresponding to FIG. 2), or may be one (not shown).

[0024] Furthermore, the workpiece machining apparatus 1 according to this embodiment is configured to include a slurry supply device (not shown) that supplies slurry. This allows the supply (or non-supply) of slurry in the machining process to be appropriately set according to the material and machining conditions of the workpiece W.

[0025] Next, an example of the plasma electrode 30 provided in the machining head 14 will be described in detail. The plasma electrode 30 according to this embodiment is circular in bottom view and includes an annular (cylindrical) or columnar center electrode 31 located at the radial center and an annular (cylindrical) outer electrode 32 located radially outward from the center electrode 31. As described above, a slit portion 36, which is a space provided at the boundary position, serves as a plasma generation space. Therefore, the polarities of adjacent electrodes across the slit portion 36 are different. As an example, as shown in the enlarged cross-sectional view of FIG. 3 and the perspective view of FIG. 4, one outer electrode 32 is provided for one center electrode 31. The materials of the center electrode 31 and the outer electrode 32 are not particularly limited, but they are formed using conductive materials.

[0026] As a modified example, as shown in FIG. 7 (a cross-sectional view corresponding to FIG. 3), a configuration may be adopted in which a plurality of (the number of) peripheral electrodes 32 (32A, 32B in the figure) (the number is not particularly limited, but FIG. 7 shows an example in which there are two) are provided for a central electrode 31. In this case, a slit portion 36 is provided at each boundary between adjacent peripheral electrodes 32. This allows for a larger number of slit portions 36 (36A, 36B in the figure), which increases the number of plasma generation times (irradiation amount) per rotation of the machining head 14, thereby enhancing the surface modification and etching effect of the workpiece W, and further improving the machining rate and production efficiency.

[0027] Regardless of the number of peripheral electrodes 32, it is preferable that machining pad 40 provided on the bottom surface thereof has extension portion 40a that extends a predetermined length outward (in a direction intersecting with the side surface) from the outer peripheral surface (here, the side surface) of plasma electrode 30 (more specifically, center electrode 31 and peripheral electrode 32) and slopes upward, as shown in Fig. 3. With this, when the bottom surface of rotating machining head 14 slides against workpiece W in a pressing state, the edge of workpiece W is caused to slip under extension portion 40a, thereby preventing machining pad 40 from coming into contact with the edge and being peeled off.

[0028] Next, a modified example of the plasma electrode 30 will be described. Specifically, as shown in Fig. 8 (a cross-sectional view at a position corresponding to Fig. 3), an annular (cylindrical) plate-shaped (or block-shaped) additional electrode 34 is provided in the slit portion 36, parallel to the electrode surface of the peripheral electrode 32. That is, in a plan view, the additional electrode 34 divides the slit portion 36 into spaces in the radial direction, and each space is configured as a plasma generation space. The material of the additional electrode 34 is not particularly limited, but it is formed using a conductive material.

[0029] With this configuration, the number of slit portions 36, i.e., the plasma generation space, can be increased in the machining head 14 without increasing the number of peripheral electrodes 32, thereby increasing the number of plasma generation times (irradiation amount) per rotation in the machining head 14, thereby enhancing the modification and etching effects on the machined surface of the workpiece W and further improving the machining rate and production efficiency.

[0030] Next, another modified example of the plasma electrode 30 will be described. Specifically, as shown in Fig. 9 (a cross-sectional view corresponding to Fig. 3), a protrusion 38 that protrudes in a direction that reduces the distance (radial dimension) between the slits 36 is provided at the lower end position of at least one of the two side surfaces 31a, 32a (Fig. 9 shows a configuration example in which a protrusion is provided on both sides) that face each other across the slits 36. Note that Fig. 9 shows a configuration example in which the center electrode 31 and the outer peripheral electrode 32 face each other, but the same configuration applies when a plurality of outer peripheral electrodes 32 are provided and the outer peripheral electrodes 32 face each other.

[0031] With this configuration, plasma can be generated intensively at the position of the protrusion 38 of the plasma electrode 30, i.e., at the lower end position closer to the workpiece W. This increases the amount of plasma irradiation acting on the workpiece W, thereby enhancing the modifying and etching effects on the workpiece W surface, and further improving the processing rate and production efficiency.

[0032] The inventors further studied the configuration of the protrusion 38 to generate plasma that can further enhance the above-mentioned effects. As an example, Table 1 and FIG. 15 show the results of experiments conducted using samples (1) to (5) with different configurations of the protrusion 38 (see FIG. 14, although the processing pad 40 is not shown for simplicity's sake). Table 1 shows the measurement results of the power [W] required to stably generate plasma. Meanwhile, FIG. 15 visualizes the intensity of plasma generation at a position a predetermined distance (set to 2 mm, for example) from the underside of the plasma electrode 30 using a Plasma Indicator (registered trademark) manufactured by Sakura Color Products Corporation (darker areas indicate higher (stronger) intensity).

[0033] [Table 1]

[0034] As shown in Table 1, the configurations having the protrusions 38 (samples (2) to (5)) require less power to stably generate plasma than the configuration not having the protrusions 38 (sample (1)), i.e., the results show that energy savings can be achieved.

[0035] 15A to 15E, a configuration in which the protrusions 38 are provided on both of the two side surfaces 31a, 32a of the plasma electrode 30 with the same radial dimension (including approximately the same dimension) (samples (4) and (5)) can generate a plasma with a higher (stronger) intensity than a configuration in which the protrusions 38 are provided on only one side (samples (2) and (3)). In other words, the plasma irradiation amount acting on the workpiece W can be increased. In addition, it was confirmed that in order to reliably obtain the above-mentioned effect, it is preferable to configure the radial spacing dimension c between the two side surfaces 31a, 32a to be five times or more the radial spacing dimension a between the two protrusions 38A, 38B.

[0036] Next, another modified example of the plasma electrode 30 will be described. Specifically, as shown in FIG. 16 (a cross-sectional view corresponding to FIG. 3), the two side surfaces 31a, 32a facing each other across the slit 36 ​​have a configuration in which the area where the protrusion 38 is not provided (in this case, the axial area) is formed using an insulating material. This makes it possible to suppress discharge to the area where the protrusion 38 is not provided, and therefore makes it possible to generate plasma more intensively between the two protrusions 38A, 38B. Therefore, the amount of plasma irradiation acting on the workpiece W can be increased.

[0037] Examples of the insulating material include ceramics, heat-resistant glass, quartz, and resin. When the plasma irradiation time is set to a relatively short time, examples of the resin that can be used include POM (polyacetal resin), PVC (polyvinyl chloride resin), ultra-high molecular weight polyethylene resin, and phenolic resin. On the other hand, when the plasma irradiation time is set to a relatively long time, long When the time is set to 100 seconds, heat resistance is required, and epoxy resin, PTFE (polytetrafluoroethylene resin), PEEK (polyether ether ketone resin), PPS (polyphenylene sulfide resin), etc. are preferably used. When selecting the material and setting the radial thickness, dimensional stability under processing conditions, chemical resistance, etc. are taken into consideration.

[0038] (Second embodiment) Next, a workpiece machining apparatus 1 according to a second embodiment of the present invention will be described. Here, Fig. 10 is a front cross-sectional view (schematic diagram) showing an example of the workpiece machining apparatus 1 according to this embodiment. Also, Fig. 11 is a cross-sectional view (schematic diagram) taken along line XI-XI in Fig. 10.

[0039] The workpiece machining apparatus 1 according to this embodiment has the same basic configuration as the first embodiment described above, but differs in particular in the mechanism for rotating the holding plate 20. This embodiment will be described below, focusing on these differences. Note that the modified examples shown in Figs. 7 to 9 described above can also be applied to this embodiment in the same way.

[0040] Specifically, in this embodiment, the holding plate 20 is held (fixed) on the turntable 12 with its axis aligned with the central axis of the turntable 12 without a carrier. That is, when the turntable 12 rotates (in the direction of arrow A), the holding plate 20 rotates (in the direction of arrow C). Note that the machining head 14 is also rotated (in the direction of arrow B) in the same manner as in the first embodiment.

[0041] Compared to the first embodiment described above, only one holding plate 20 is held on the turntable 12, so although the number of workpieces W that can be processed simultaneously is reduced, it is possible to significantly reduce the size of the device.

[0042] On the other hand, a configuration is adopted in which a plurality of (for example, two) processing heads 14 are arranged. However, this is not limited to this configuration, and as a modified example, a configuration in which three or more processing heads 14 are arranged (not shown) may also be adopted.

[0043] As yet another modified example, as shown in FIGS. 12 and 13 (both cross-sectional views corresponding to FIG. 11), a single machining head 14 may be disposed with its axis eccentric relative to the turntable 12. FIG. 12 shows an example in which multiple workpieces W, each with a diameter smaller than the radius of the holding plate 20, are held (attached) to the holding surface (top surface) of the holding plate 20 for machining. On the other hand, FIG. 13 shows an example in which a single workpiece W, with a diameter larger than the radius of the holding plate 20, is held (attached) to the holding surface (top surface) of the holding plate 20 for machining. In either case, this configuration allows the entire surface of the workpiece W to be machined using only one machining head 14. Therefore, compared to a case in which multiple machining heads 14 are provided, a simpler device configuration can be achieved, thereby reducing device costs.

[0044] The other effects are the same as those of the first embodiment, and therefore will not be described again.

[0045] As explained above, according to the present invention, even for workpieces made of difficult-to-process materials, it is possible to process them while modifying or etching the processed surface, thereby increasing the processing rate. Furthermore, since the plasma treatment process and the processing process can be performed simultaneously, i.e., in a continuous process without rearranging the workpiece between mechanisms, processing can be completed in a short time, thereby improving production efficiency.

[0046] The present invention is not limited to the above-described embodiment, and various other embodiments are possible. Specifically, the rotation mechanism of the holding plate may be configured to rotate only on its axis, revolve only, rotate and revolve, or non-rotate, and the rotation mechanism of the machining head may be configured to rotate only on its axis, revolve only, rotate and revolve, or non-rotate. As many configuration examples as there are combinations of these configurations are possible (excluding combinations in which the holding plate is non-rotating and the machining head is non-rotating). These configuration examples can also achieve the same effects as described above.

[0047] Incidentally, the first embodiment corresponds to a case where the rotation mechanism of the holding plate rotates and revolves around its axis, and the rotation mechanism of the machining head rotates around its axis. The second embodiment corresponds to a case where the rotation mechanism of the holding plate rotates around its axis, and the rotation mechanism of the machining head rotates around its axis. These embodiments are particularly effective in improving the machining rate and production efficiency.

[0048] Regarding the workpiece to be processed, a circular wafer has been used as an example, but this is not limited to this and can be similarly applied to other flat (especially circular) workpieces. [Explanation of symbols]

[0049] 1 Workpiece processing equipment 12 Turntable 14 Processing head 20 Retaining Plate 22 Career 30 Plasma electrode 31 Center electrode 32, 32A, 32B outer electrode 34 Additional electrodes 36, 36A, 36B slit section 38 Protrusion 40 Processing Pad 40a Extension double work

Claims

1. A workpiece processing device that processes a surface to be processed by sliding a processing head against a workpiece held on an upper surface of a holding plate, the processing head is rotatably provided and has a plasma electrode that generates plasma and irradiates the plasma onto the processing surface of the workpiece; The plasma electrode is comprised of a ring-shaped or cylindrical central electrode provided at the radial center and a ring-shaped outer electrode provided radially outward from the central electrode, with a ring-shaped slit at the boundary between them, the slit being configured as a plasma generation space, and processing pads being provided on the bottom surfaces of the central electrode and the outer electrode. A workpiece processing device characterized by the above.

2. A plurality of the peripheral electrodes are provided, and the slits are provided at the boundary positions of the electrodes.

2. The workpiece machining device according to claim 1, wherein:

3. The plasma electrode has a protrusion at a lower end position of at least one of the side surfaces facing each other across the slit portion, the protrusion protruding in a direction that reduces the distance between the slit portions.

3. The workpiece machining device according to claim 1 or 2, wherein:

4. The protruding portions are formed at the lower end positions of both of the two side surfaces so as to protrude with the same radial dimension.

4. The workpiece machining device according to claim 3, wherein:

5. The radial distance between the two side surfaces is configured to be five times or more the radial distance between the two protruding portions.

5. The workpiece machining device according to claim 4, wherein:

6. The side surface has an area where the protrusion is not provided, which is formed using an insulating material.

6. The workpiece machining device according to claim 4 or 5, wherein:

7. The plasma electrode has a ring-shaped additional electrode in the slit portion, and in a plan view, the slit portion is divided into spaces by the additional electrode, and each of the spaces is configured as a plasma generation space. The workpiece machining device according to any one of claims 1 to 6,

8. The processing head is provided with one or more heads with an outer diameter and arrangement that allows the slit portion to pass through and the processing pad to slide over the entire area of ​​the processed surface of all the workpieces whose positions change relatively. The workpiece machining device according to any one of claims 1 to 7,

9. The processing pad has an extension portion that extends outward from the side surface of the plasma electrode by a predetermined length and is inclined upward. The workpiece machining device according to any one of claims 1 to 8,

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