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 includes a plasma electrode 30 that is rotatably provided and generates plasma and irradiates the surface of the work-piece W to be processed. The plasma electrode 30 is divided into a plurality of divided electrodes 32 in the circumferential direction, and a slit portion 36 provided between adjacent divided electrodes is configured as a plasma generation space, and a processing pad 40 is provided on the bottom surface of each divided electrode 32.SELECTED DRAWING: Figure 1

Description

Technical Field

[0005]

[0001] The present invention relates to a workpiece processing apparatus, and more particularly to a workpiece processing apparatus that performs surface processing by bringing a processing head into sliding contact with a workpiece held on a holding plate.

Background Art

[0002] In manufacturing semiconductor power devices, surface processing of a substrate (workpiece) exemplified by a wafer is essential. In particular, wide-bandgap semiconductor substrates typified by silicon carbide (SiC), gallium nitride (GaN), and diamond are hard and brittle, and thus there is a problem that high-efficiency processing is difficult with conventional mechanical processing. Note that "processing" in the present application widely includes processing for removing the surface, such as grinding for shaving the surface, polishing for reducing surface roughness, and planarization for enhancing flatness.

[0003] When processing the above-described substrate, it is conceivable to use a processing method called P-CVM (Plasma Chemical Vaporization Machining). This method is a chemical processing method using plasma in an atmospheric pressure atmosphere, and high-efficiency processing is possible due to its high radical density. However, since it is a processing method that performs isotropic etching and processes not only surface protrusions but also surface recesses, it is not suitable for the purpose of planarization.

[0004] Therefore, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2015-159257), Patent Document 2 (Japanese Patent Application Laid-Open No. 2015-179830), etc., methods and apparatuses for processing difficult-to-machine materials such as silicon carbide (SiC), gallium nitride (GaN), and diamond with high efficiency and high precision by combining plasma treatment and mechanical processing are disclosed.

Prior Art Documents

Patent Documents

[0006] However, in conventional workpiece processing equipment as exemplified in Patent Document 1, the mechanism for performing CMP (Chemical Mechanical Polishing) and the mechanism for performing plasma processing are arranged separately, and the workpiece processing is repeated alternately in each mechanism. As a result, the cycle time becomes long, and production efficiency decreases.

[0007] On the other hand, in the conventional workpiece processing apparatus exemplified in Patent Document 2, the plasma processing mechanism is incorporated into the surface platen, which leads to problems such as slurry solidification at the incorporation 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 view of the above circumstances, and aims to provide a workpiece processing apparatus that can achieve a high processing rate and perform stable processing in a short time for workpieces formed using difficult-to-process materials.

[0009] The present invention solves the above-mentioned problem by a solution described below as one embodiment.

[0010] The workpiece processing apparatus according to the present invention is a workpiece processing apparatus that processes the surface of a workpiece by sliding a processing head against a workpiece held on the upper surface of a holding plate, wherein the processing head is rotatably mounted and has a plasma electrode that generates plasma and irradiates the surface of the workpiece to be processed, the plasma electrode is configured to be divided into a plurality of divided electrodes in the circumferential direction, and a slit portion provided between adjacent divided electrodes is configured as a plasma generation space, and a processing pad is provided on the bottom surface of each of the divided electrodes. [Effects of the Invention]

[0011] According to the present invention, even workpieces formed using difficult-to-process materials can be processed while modifying or etching the workpiece 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, improving production efficiency. [Brief explanation of the drawing]

[0012] [Figure 1] This is a front cross-sectional view showing an example of a workpiece processing apparatus according to the first embodiment of the present invention. [Figure 2] This is a cross-sectional view taken along line II-II in Figure 1. [Figure 3] This is an enlarged view showing an example of a machining head in a workpiece processing machine, as shown in Figure 1. [Figure 4] This is a cross-sectional view showing another example of a machining head in a workpiece processing machine, as shown in Figure 1. [Figure 5] Figure 1 is a perspective view showing an example of a plasma electrode on a machining head in a workpiece processing apparatus. [Figure 6] Figure 1 shows a perspective view illustrating another example of a plasma electrode on the machining head of a workpiece processing apparatus. [Figure 7] Figure 1 shows a perspective view illustrating another example of a plasma electrode on the machining head of a workpiece processing apparatus. [Figure 8]It is a perspective view showing another example of the plasma electrode of the processing head in the workpiece processing apparatus of FIG. 1. [Figure 9] It is a cross-sectional view showing another example of the plasma electrode of the processing head in the workpiece processing apparatus of FIG. 1. [Figure 10] It is a front cross-sectional view showing an example of a workpiece processing apparatus according to a second embodiment of the present invention. [Figure 11] It is a cross-sectional view taken along line XI-XI in FIG. 10. [Figure 12] It is a cross-sectional view showing another example of the processing head in the workpiece processing apparatus of FIG. 10. [Figure 13] It is a cross-sectional view showing another example of the processing head in the workpiece processing apparatus of FIG. 10. [Figure 14] It is a cross-sectional view showing another example of the processing head in the workpiece processing apparatus of FIG. 10. [Figure 15] It is an enlarged view of part XV in FIG. 9. [Figure 16] It is a diagram visualizing the generation intensity of plasma in the sample shown in Table 1. [Figure 17] It is a cross-sectional view showing another example of the plasma electrode of the processing head in the workpiece processing apparatus of FIG. 1.

Mode for Carrying Out the Invention

[0013] (First Embodiment) Hereinafter, the first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a front cross-sectional view (schematic view) showing an example of a workpiece processing apparatus 1 according to the present embodiment. Further, FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1 (schematic view). Further, FIG. 3 is an enlarged view (schematic view) of a processing head 14 in the workpiece processing apparatus 1 of FIG. 1. In all the drawings for explaining each embodiment, members having the same function are denoted by the same reference numerals, and repeated explanations may be omitted.

[0014] The workpiece processing apparatus 1 according to this embodiment is a device that performs processing (surface processing) by sliding a processing head 14 against a workpiece W on a holding plate 20 fixed to the upper surface of a rotating disk 12 while pressing it against the workpiece.

[0015] On the other hand, the workpiece W to be processed is a substrate (for example, a disc-shaped wafer) formed using so-called difficult-to-process materials such as silicon carbide (SiC), gallium nitride (GaN), and diamond, 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 micrometers to several millimeters).

[0016] Furthermore, in this embodiment, the holding plate 20 holds (attaches) one or more workpieces W to its holding surface (upper surface), and functions to bring the workpiece W's workpiece surface (upper surface) 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 attached to the holding surface (upper surface) of the holding plate 20 by a known peelable adhesive, but this is not the only method, and methods such as vacuum suction or fitting by forming a recess may also be used. The holding plate 20 is required to be made of a material that has high flatness accuracy and is resistant to deformation, and is generally made of glass or ceramics.

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

[0018] Here, the carrier 22 is meshed between the sun gear 16 and the internal gear 18, which are positioned so as to align with the central axis of the turntable 12, and is driven to rotate (in the direction of arrow C) and revolve (in the direction of arrow D) by the rotation of the turntable 12. This rotation of the carrier 22 causes the holding plate 20 to rotate (in the direction of arrow C) and revolve (in the direction of arrow D). In this embodiment, four carriers 22 are arranged between the sun gear 16 and the internal gear 18, but the configuration is not limited to this.

[0019] Next, the machining head 14 according to this embodiment is supported above the rotary disk 12 so as to be able to move up and down, and is configured to be rotatable by a drive device (not shown) consisting of an electric motor or the like which is disposed on the support frame 10 (direction of arrow B). For example, it is configured by a known mechanism equipped with a spline or the like. Furthermore, the lower surface is configured as a workpiece machining surface for machining the workpiece W, and it is further configured to be equipped with a plasma electrode 30 which generates plasma and irradiates the workpiece W to be machined.

[0020] In this embodiment, the plasma electrode 30 is composed of a plurality of divided electrodes 32, and the slit portion 36 provided between adjacent divided electrodes 32 is configured as a plasma generation space (details will be described later). Furthermore, a processing pad 40 is provided on the bottom surface of each divided electrode 32.

[0021] Plasma can be generated by supplying a base gas (a rare gas such as He) and a reaction gas from each storage section (not shown) to the slit section 36 through piping 46, while applying a predetermined voltage between adjacent electrodes constituting the slit section 36. Specific examples of reaction gases include fluorine-based gas and oxygen gas when the workpiece is SiC, 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 the turntable 12, the holding plate 20 can be rotated and revolved via the carrier 22. At the same time, the processing head 14 can be rotated and brought into sliding contact with the workpiece W held on the holding plate 20 while pressing it against it. At this time, plasma can be generated by the rotating plasma electrode 30 and irradiated onto the workpiece W's work surface. Therefore, processing can be performed on the workpiece W's work surface while modifying or etching (either both or one depending on the material of the workpiece W and the type of reaction gas) by irradiating it with plasma, thereby improving the processing rate. Compared to an apparatus that alternately performs a plasma processing step and a processing step using separately arranged mechanisms, as exemplified in Patent Document 1, according to this embodiment, these steps can be performed simultaneously, that is, without the need to rearrange the workpiece W, and through continuous processing, thus enabling processing in a short time and improving production efficiency.

[0023] The workpiece processing apparatus 1 according to this embodiment is configured such that multiple processing heads 14 (for example, two) are arranged with an outer diameter and arrangement that allows the slit portion 36 to pass through and the processing pad 40 to slide against the entire area of ​​the workpiece surface of all workpieces W whose relative positions change due to the movement (rotation) of each mechanism. This improves the processing rate and enables processing in a short time. However, the number of processing heads 14 is not limited to the above, and as a modification, a configuration with three or more (not shown) may be used.

[0024] As another variation, the device may be configured with a single processing head 14, as shown in Figure 4 (a cross-sectional view of the position corresponding to Figure 2). In this case, the device may be simplified by having the holding plate 20 rotate only on its own axis and not revolve (not shown).

[0025] Furthermore, the workpiece processing apparatus 1 according to this embodiment is configured to include a slurry supply device (not shown) for supplying slurry. With this configuration, the supply (including non-supply) of slurry during the processing step can be appropriately set according to the material of the workpiece W and the processing conditions.

[0026] Next, an embodiment of the plasma electrode 30 provided on the processing head 14 will be described in detail. The plasma electrode 30 according to this embodiment is formed in a circular shape when viewed from the bottom and is divided into a plurality of segmented electrodes 32 (two or more, with no particular upper limit, but approximately 20 or less as an example) that are point-symmetric with respect to the axis point S. As mentioned above, the slit portion 36, which is the space provided between the segmented electrodes, is configured as the plasma generation space. Therefore, it is usually configured in an even number such that the polarity of adjacent segmented electrodes is different. The constituent material of the segmented electrodes 32 is not particularly limited, but it is formed using a conductive material.

[0027] As a specific example of configuration, regarding a plasma electrode 30 having multiple divided electrodes 32 that are point-symmetric with respect to the axis point S, Figure 5 shows the case with 2 divided electrodes 32, Figure 6 shows the case with 4 divided electrodes 32, and Figure 7 shows the case with 8 divided electrodes 32. However, the number is not limited to these. Incidentally, these examples can also be said to be configurations that are evenly divided in the circumferential direction. Furthermore, Figures 9 to 14 below illustrate using the configuration in Figure 6.

[0028] With this configuration, plasma can be generated in the slit portion 36 provided between the divided electrodes, and the plasma can be irradiated onto the workpiece surface W. Therefore, the more circumferential slit portions 36 are set, the more plasma can be generated (irradiated) per rotation of the processing head 14, thereby enhancing the modification and etching effects on the workpiece surface W, and further improving the processing rate and production efficiency.

[0029] On the other hand, regardless of the number of divided electrodes 32, the processing pad 40 provided on its bottom surface preferably has an extension portion 40a that extends outward (in the direction intersecting with the side surface) for a predetermined length relative to the outer peripheral surface (in this case, the side surface) of the plasma electrode 30 (more specifically, the divided electrode 32) and inclined upward, as shown in Figure 3. With this configuration, when the bottom surface of the rotating processing head 14 slides against the workpiece W in a pressing state, the edge of the workpiece W is forced to slide under the extension portion 40a, thereby preventing the processing pad 40 from coming into contact with the edge and peeling off.

[0030] Next, a modified example of the plasma electrode 30 will be described. Specifically, as shown in Figure 8, an additional plate-shaped or block-shaped electrode 34 is provided in the slit portion 36, parallel to the electrode surface of the divided electrode 32. That is, in a plan view, the slit portion 36 is divided in the circumferential direction by the additional electrode 34, 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.

[0031] With this configuration, the number of slit portions 36, i.e., the plasma generation space, can be increased in the processing head 14 without increasing the number of divided electrodes 32. This allows for an increase in the number of plasma generation cycles (irradiation amount) per rotation of the processing head 14, thereby enhancing the surface modification and etching effects on the workpiece W, and further improving the processing rate and production efficiency.

[0032] Another modification of the plasma electrode 30 will be described. Specifically, as shown in Figure 9 (a cross-sectional view of the position corresponding to Figure 3), a protrusion 38 is provided at the lower end of at least one of the two opposing sides 32a and 32b (Figure 9 is an example of a configuration where it is provided on both sides) that protrudes in a direction that reduces the separation dimension (circumferential dimension) of the slit portion 36.

[0033] With this configuration, plasma can be concentrated at the position of the protrusion 38 on the plasma electrode 30, that is, at the lower end position closer to the workpiece W. Therefore, the amount of plasma irradiation acting on the workpiece W can be increased, thereby enhancing the surface modification and etching effects on the workpiece W, and further improving the processing rate and production efficiency.

[0034] Here, the inventors further researched the configuration of the protrusion 38 in order to generate plasma that can further enhance the above effects. As an example, Table 1 and Figure 16 show the experimental results obtained using samples (1) to (5) with different configurations of the protrusion 38 (see Figure 15, however, the processing pad 40 is not shown for simplification of the figure). Table 1 shows the measurement results of the power [W] required to stably generate plasma. On the other hand, Figure 16 visualizes the plasma generation intensity at a predetermined distance (for example, set to 2 mm) from the lower surface of the plasma electrode 30 using a plasma indicator (registered trademark) manufactured by Sakura Color Products Corporation (darker areas indicate higher (stronger) intensity).

[0035] [Table 1]

[0036] As shown in Table 1, the configurations having the protrusion 38 (samples (2) to (5)) were found to reduce the power required to stably generate plasma compared to the configuration without the protrusion 38 (sample (1)), thus enabling energy saving.

[0037] Furthermore, as shown in Figures 16A to 16E, the configuration in which the protrusions 38 are provided on both sides 32a and 32b of the plasma electrode 30 with the same radial dimension (including approximately the same dimension) (samples (4) and (5)) can generate a higher (stronger) plasma intensity than the configuration in which they are provided on only one side (samples (2) and (3)), meaning that the amount of plasma irradiation acting on the workpiece W can be increased. In addition, it was confirmed that configuring the radial spacing c between the two sides 32a and 32b to be five times or more the radial spacing a between the two protrusions 38A and 38B is preferable in order to reliably obtain the above effect.

[0038] Furthermore, another modification of the plasma electrode 30 will be described. Specifically, as shown in Figure 17 (a cross-sectional view of the position corresponding to Figure 3), the two opposing sides 32a and 32b, separated by the slit portion 36, have a configuration in which a region without the protrusion 38 (in this case, the axial region) is formed using an insulating material. This suppresses discharge to the region without the protrusion 38, allowing for more concentrated plasma generation between the two protrusions 38A and 38B. Therefore, the amount of plasma irradiation acting on the workpiece W can be increased.

[0039] Examples of insulating materials used include ceramics, heat-resistant glass, quartz, and resins. When the plasma irradiation time is set to a relatively short duration, suitable resins include POM (polyacetal resin), PVC (polyvinyl chloride resin), ultra-high molecular weight polyethylene resin, and phenolic resin. When the plasma irradiation time is set to a relatively short duration, heat resistance is required, and suitable resins include epoxy resin, PTFE (polytetrafluoroethylene resin), PEEK (polyetheretherketone resin), and PPS (polyphenylene sulfide resin). When selecting materials and setting radial thickness, dimensional stability under processing conditions, chemical resistance, etc., should be considered.

[0040] (Second Embodiment) Next, a workpiece processing apparatus 1 according to a second embodiment of the present invention will be described. Here, Figure 10 is a front cross-sectional view (schematic diagram) showing an example of the workpiece processing apparatus 1 according to this embodiment. Figure 11 is a cross-sectional view (schematic diagram) taken along line XI-XI in Figure 10.

[0041] The workpiece processing apparatus 1 according to this embodiment has the same basic configuration as the first embodiment described above, but has differences, particularly in the mechanism for rotating the holding plate 20. The following description will focus on these differences. The modified examples shown in Figures 8 and 9 described above can also be applied to this embodiment in the same way.

[0042] Specifically, in this embodiment, the holding plate 20 is held (fixed) on the rotating disk 12 without a carrier, with its axis aligned with the central axis of the rotating disk 12. That is, the holding plate 20 rotates (rotates) as the rotating disk 12 rotates (direction of arrow A) (direction of arrow C). The machining head 14 rotates (rotates) in the same manner as in the first embodiment (direction of arrow B).

[0043] Compared to the first embodiment described above, since there is only one holding plate 20 held on the rotating disc 12, the number of workpieces W that can be processed simultaneously decreases, but it becomes possible to significantly miniaturize the device.

[0044] On the other hand, the machining head 14 is configured to have multiple units (for example, two units). However, it is not limited to this configuration, and as a variation, a configuration (not shown) in which three or more machining heads 14 are installed is also possible.

[0045] As another variation, as shown in Figure 12 (a cross-sectional view of the position corresponding to Figure 11), a single machining head 14 may be positioned so that its axis aligns with that of the rotary disk 12. In this configuration, when machining is performed by rotating the machining head 14, the rotary disk 12 can be set to a low-speed state or a stopped state. In particular, if only workpieces W that can be machined with the rotary disk 12 stopped are targeted, a simple device configuration without a rotating mechanism can be used, thus reducing the device cost.

[0046] As another variation, as shown in Figures 13 and 14 (both cross-sectional views of the position corresponding to Figure 11), a single machining head 14 may be positioned with its axis eccentric to that of the rotating disc 12. Figure 13 is an example where multiple workpieces W, each with a diameter smaller than the radius of the holding plate 20, are held (attached) to the holding surface (upper surface) of the holding plate 20 for machining. On the other hand, Figure 14 is an example where one workpiece W, each with a diameter larger than the radius of the holding plate 20, is held (attached) to the holding surface (upper surface) of the holding plate 20 for machining. In either case, this configuration makes it possible to machine the entire surface of the workpiece W with only one machining head 14. Therefore, compared to the case where multiple machining heads 14 are provided, a simpler device configuration can be achieved, thus reducing the device cost.

[0047] Furthermore, since the other effects and benefits are the same as those of the first embodiment described above, a repeated explanation will be omitted.

[0048] As explained above, according to the present invention, even workpieces formed using difficult-to-process materials can be processed while modifying or etching the workpiece surface, thereby increasing the processing rate. Furthermore, since the plasma treatment process and the processing process can be performed simultaneously, that is, in a continuous process without rearranging the workpiece between mechanisms, processing can be completed in a short time, improving production efficiency.

[0049] It should be noted that the present invention is not limited to the embodiments described above, and various embodiments are conceivable. Specifically, the rotation mechanism of the holding plate can be configured to rotate only, revolve only, rotate and revolve, or not rotate, and the rotation mechanism of the machining head can be configured to rotate only, revolve only, rotate and revolve, or not rotate, and as many configuration examples as there are combinations of these configurations are conceivable (except for combinations in which the holding plate and the machining head do not rotate). The same effects as described above can be obtained with these configuration examples as well.

[0050] Incidentally, the first embodiment described above corresponds to a configuration in which the rotation mechanism of the holding plate rotates on its own axis and revolves around an orbit, and the rotation mechanism of the machining head rotates on its own axis. Similarly, the second embodiment described above corresponds to a configuration in which the rotation mechanism of the holding plate rotates on its own axis, and the rotation mechanism of the machining head rotates on its own axis. In particular, these embodiments are highly effective in improving the machining rate and production efficiency.

[0051] Furthermore, although the explanation used a disc-shaped wafer as an example of the workpiece to be processed, the method is not limited to this and can be similarly applied to other flat (especially disc-shaped) workpieces. [Explanation of Symbols]

[0052] 1. Workpiece processing equipment 12-turn disc 14 Machining heads 20 Retaining plate 22 Carriers 30 Plasma electrodes 32, 32A~32H split electrode 34, 34A~34D additional electrode 36 Slit section 38 Protrusion 40 Machining Pads 40a Extension Double job

Claims

1. A workpiece processing apparatus that processes the surface of a workpiece by sliding a processing head against a workpiece held on the upper surface of a holding plate, The processing head is rotatably mounted and has a plasma electrode that generates plasma and irradiates the workpiece surface with it. The plasma electrode is configured to be divided into a plurality of segmented electrodes in the circumferential direction, and the slit portion provided between adjacent segmented electrodes is configured as a plasma generation space, and a processing pad is provided on the bottom surface of each segmented electrode. A workpiece processing device characterized by the following.

2. The plasma electrode is formed in a circular shape when viewed from the bottom and is divided into two or more segmented electrodes that are point-symmetric with respect to the axis. A workpiece processing apparatus according to claim 1, characterized by the following:

3. The plasma electrode further has plate-shaped or block-shaped additional electrodes in the slit portion, and in a plan view, the slit portion becomes a space divided by the additional electrodes, and each of the spaces is configured as a plasma generation space. A workpiece processing apparatus according to claim 1 or claim 2, characterized by the above.

4. The machining heads are provided one or more times, with an outer diameter and arrangement such that the slit portion can pass through and the machining pad can slide against the entire area of ​​the workpiece surface where the relative positions change. A workpiece processing apparatus according to any one of claims 1 to 3, characterized by the above.

5. The processing pad has an extension that extends outward for a predetermined length relative to the side surface of the plasma electrode and is inclined upward. A workpiece processing apparatus according to any one of claims 1 to 4, characterized by the above.

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