JP2011020182A - Polishing tool suitable for pad conditioning, and polishing method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tool for conditioning which is easy to control a process and capable of improving a tool service life. <P>SOLUTION: (1) A polishing tool includes a rigid substrate having a planar circular surface and a plurality of cutting edges 1 having a flat top face located within a constant level with respect to the circular surface fixedly disposed on the substrate. The top face 6 is surrounded by a plurality of linear ridges and is adjacent to a side face extending in a direction of a tool axis via the ridge, and at least the summit of the cutting edge is formed of sintered diamond. (2) A polishing method for removing a workpiece material using the polishing tool includes the steps of: pressing the cutting edge against the surface of the workpiece, thereby causing a deforming area displaced in the pressed direction on the surface of the workpiece; and removing the workpiece material at a border between the deforming area and a remaining area by further causing the linear ridge on the top of the cutting edge to relatively move from the deforming area. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polishing tool, in particular, a polishing tool that can efficiently condition a CMP pad made of hard urethane or the like.

  In the manufacturing process of memory chips and other LSI devices used in the electronics industry, it is indispensable to ultra-precision planarize the surface of silicon wafers and interlayer insulation films in multilayer structures. This is done by a system using a polishing pad. The polishing pad is generally made of rigid foamed polyurethane, but in order to maintain flatness and wafer polishing rate, the surface of the pad must be conditioned at all times or intermittently. There are known tools (conditioners, dressers) in which a pyramid-like row of protrusions is provided on a sintered diamond layer that is fixed to a substrate by electrodeposition or generally lined with a cemented carbide.

  As an electrodeposition type conditioning tool (conditioner, dresser), for example, the following rotary polishing tools are known.

A hollow area where no abrasive grains are arranged is provided at the center of the circular surface of the disk-shaped base, and a first abrasive grain area is provided outside the hollow area, and a second abrasive grain area is provided outside the hollow area. In the first abrasive layer region, a plurality of rows of small abrasive layer portions are provided at intervals, and each of the small abrasive layer portions is made of metal with superabrasive grains on the surface of a raised portion having a substantially spherical shape. It is fixed in the plating phase. The second abrasive layer region is configured by adhering superabrasive grains to a ring-shaped circumferential ridge with a metal plating phase.
JP 2002-337050 A

In place of the individual superabrasive particles fixed in the metal plating phase, a tool in which a row of pyramidal protrusions is formed of sintered diamond is described in, for example, the following publication. The projection group called is formed by cutting a sintered diamond layer lined with a cemented carbide with a wire cut. As the shape of the polishing unit, a pyramid type (square pyramid) or a quadrangular pyramid with an angle between faces of 90 °, a triangular pyramid, a triangular frustum, or the like is described. The polishing units are arranged along the intersecting linear groove group and separated by the groove group.
WO-A1-2007023249

  Conditioning according to the above-described prior art is based on the surface of the pad with the individual particles and the tips and protrusions (points) of the polishing unit, both by electrodeposited superabrasive grains and by the polishing unit group formed on the sintered diamond layer. Based on the polishing action to scrape off. Therefore, in order to ensure the flatness of the pad surface, a method of making the tip fine or increasing the density of the protrusions is employed.

  However, in the pad surface flattening mechanism by the conventional dresser that scrapes the pad surface at the point (point) of the polishing unit as described above, the flatness is ensured by making the polishing unit point finer and increasing the density of the polishing unit. That was not always easy.

  An object of the present invention is to solve the above-mentioned problems associated with conventional pad conditioning, and to provide a tool for conditioning that can be easily controlled and can also improve tool life.

  The present inventor has obtained the following knowledge. That is, the cutting edge of the pad dresser is made of a highly rigid material such as sintered diamond, and the top surface of the cutting edge tip in contact with the pad is flat, and the cutting process for the pad mainly surrounds the top surface of the cutting edge. When it is configured to be performed on the surface including the ridge line, especially on the side surface, the processing process to the pad is a cutting process in which a thin blade of the pad constituent material is scraped off with a flat blade like a planer (鉋) hook or chisel (鑿) strike. However, in this processing method, the process can be easily controlled by adjusting the load, and the tool life can be improved. Based on this knowledge, the present invention has been completed.

  The gist of the present invention is that the rigid substrate has a flat circular surface, and a plurality of cutting edges having a flat top surface located within a certain level with respect to the circular surface are fixedly arranged on the substrate. A tool, wherein the top surface is surrounded by a plurality of linear ridge lines and is adjacent to a side surface extending in the tool axis direction via the ridge lines, and at least the top portion of the cutting edge is made of sintered diamond. A polishing tool characterized by

  The polishing process using the polishing tool of the present invention is different from the conventional polishing mechanism mainly based on the load in the tool axial direction, and mainly under the load load in the side direction (radial direction) of the cutting edge. Based on cutting mechanism with adjacent top sides. That is, when the relative movement between the cutting edge and the cutting edge is performed in a state where the material is displaced according to the compression ratio by pressing the surface of the workpiece, the side surface of the cutting edge is a step of scraping the pad constituent material.

  Accordingly, in another aspect of the present invention, in a polishing method for removing workpiece material using such a polishing tool, the cutting edge is pressed against the surface of the workpiece, thereby being displaced in the pressing direction on the surface of the workpiece. A polishing method characterized by removing a workpiece material at a boundary between a deformed portion and a remaining portion by generating a deformed portion and further moving a linear ridge line of a cutting edge top portion relative to the deformed portion. Is also a summary.

The polishing tool of the present invention has a high material removal rate (cut rate) per hour and a sufficiently small roughness Ra of the finished surface, particularly in precision polishing of hard urethane. Moreover, this performance has the advantage that it is maintained several times as compared with the conventional similar tool.
The present invention will be described below with reference to the accompanying explanatory drawings.

It is a fragmentary sectional view of the cutting edge in the polishing tool of the present invention. It is explanatory drawing of the example of the cutting edge arrangement | positioning in the polishing tool of this invention. It is explanatory drawing of another example about cutting-edge arrangement | positioning in the grinding | polishing tool of this invention. It is explanatory drawing which shows another example about cutting-edge arrangement | positioning in the polishing tool of this invention. It is explanatory drawing of the fan-shaped raw material which consists of a diamond sintered compact used in Example 1. FIG. In Example 1, it is a fragmentary sectional view of the linear protrusion formed in the diamond layer surface. It is a graph which shows a test result (time-dependent change of a cut rate) about the polishing tool created in Example 1,2. It is explanatory drawing which shows an example of a cutting-blade structure in the polishing tool of this invention.

  In the method of the present invention, the cutting rate of the tool (the ability to reduce the workpiece (pad material) thickness within a certain time) is essentially determined by the load applied to the top surface of the cutting edge and the shape of the cutting edge surface, The smoothness of the workpiece (pad) varies depending on the magnitude of the load applied per unit area applied to the top surface of the cutting edge. That is, it is possible to control the working efficiency and the roughness of the finished surface by adjusting the load.

  Furthermore, the tool life varies depending on the ridge line length and the inclination angle of the side surface in the cutting edge configuration, and also depends on the peripheral length of the tip surface. Therefore, the tool life can be optimized by appropriately selecting the shape of the cutting edge. FIG. 1 is a partial sectional view of a cutting edge in a polishing tool of the present invention. In the present invention, the inclination of the side surface 2 of the cutting edge 1 is the axial direction with respect to an arbitrary reference plane 4 (referred to as a cutting edge axis surface) that includes the central axis of the tool and that is flat on the target side surface, and thus parallel to the surface. It is represented by an inclination angle (cutting edge axial surface angle) α in the (Z direction). Since the cutting edge 1 is usually formed by wire electric discharge machining, the base portion 5 may be rounded under the influence of the wire cross section, and the side surface of the cutting edge may exhibit a curved surface. In this case, the inclination angle of the side surface indicates the angle of the tangential surface.

  In the polishing tool (pad dresser) according to the present invention, each cutting edge is preferably formed in a quadrangular prism or quadrangular pyramid shape, or a triangular prism or triangular frustum shape. The inclination angle of each side surface adjacent to the top surface 6 of the cutting edge 1 is configured such that at least a portion adjacent to the top surface is perpendicular to the top surface, that is, a rectangular column having an inclination α = 0 ° with respect to the cutting blade axis surface. However, optimum results are obtained with respect to the cut rate and the finished surface roughness, and preferable results are obtained when the inclination angle is 60 ° or more, particularly 80 ° or more, or α is 30 ° or less, particularly 10 ° or less. It is done.

In the polishing tool of the present invention, the cutting edge 1 is arranged uniformly on the entire disk surface of the tool, for example, in a lattice shape as shown in FIG. 2, or partially at a specific portion, for example, FIG. As shown in FIG. 5, the substrate 7 is arranged at a uniform angle on one circumference or a plurality of concentric circumferences, or on a radius and arranged radially, or a combination thereof.
Further, as shown in FIG. 4, a configuration in which chips 8 formed with a plurality of cutting edges 1 (represented by individual squares) are radially fixed on the substrate 7 at an equal angle can be used. It is effective when forming a large number. In this case, the center line of the cutting edge or the tip is arranged so as to be parallel to the radius.

  In the present invention, only one of the many cutting edges provided for the purpose of simplifying and clarifying the drawings is provided with a reference symbol, but unless otherwise specified, other cutting edges of the formed cutting blade group are provided with reference numerals. It should be understood that the blades are equivalent in function and configuration, and that the description is applicable.

The number of cutting blades varies depending on the target cut rate, finished surface roughness, etc., but in the case of a tool having an outer diameter of about 100 mm, the total area of the top surface can be 220 mm ² or less. In addition, good performance can be obtained when the area ratio to the substrate cross section is 1000 to 0.5 / 10,000, particularly 160 to 1. However, the substrate cross-section of the present invention refers to a cross-sectional area limited by an outer peripheral circle in a circular tool substrate regardless of the presence or absence of the center hole.

  Several known techniques can be used to manufacture the polishing tool of the present invention. For example, the cutting edge is a single disk made of a diamond sintered body lined with cemented carbide, or a disk divided body (fan shape) combined in a disk shape, such as wire cutting into a sintered diamond layer. Cutting by electrical discharge machining or laser, or cutting from a diamond sintered body as a chip containing one cutting edge each, or as a block containing several to several tens of cutting edges, and placing and fixing on a substrate Can be formed.

  As the substrate, SUS stainless steel is preferable in terms of corrosion resistance, but other metal materials such as aluminum, synthetic resins such as bakelite, and metal-coated synthetic resins can be used depending on the use environment.

  The above-mentioned cutting edge chips and blocks are arranged in a concentric shape, a radial shape, or a combination of these on the outer peripheral portion of the tool substrate. Various known techniques can be used for fixing to the substrate depending on the material type. For example, holes and grooves of the shape and number corresponding to the chip or block are formed on the substrate and these are fitted, brazed or soldered, or bonded using an adhesive, super-hardness or quick-setting cement, or Furthermore, coating with acrylic or fluororesin prevents erosion due to contact with the slurry of the substrate and contamination by the eluted material.

  In each of the methods for forming the cutting edge, by cutting the sintered diamond layer of the diamond sintered body disk with a wire cut or the like, a square or triangular prism or a truncated pyramid shaped piece having a flat tip is formed. As for the method of forming the blade, the level of the tip surface of each cutting blade is uniform, so good flatness can be obtained, but on the other hand, the size of the tool (dresser) is limited to the size of the diamond sintered body that can be used Is done.

  A cutting blade material is produced from the diamond sintered body by cutting out a necessary number of prisms or pyramids as a single chip with a sintered diamond layer as a top, or a plurality of blocks included in a certain section as blocks for each section. A method is also available. In this case, although there is no restriction | limiting in the dimension of a tool, the grinding | polishing process for aligning a chip | tip surface and ensuring flatness as a finishing process is required.

  In the above, the cutting blade made of sintered diamond has an advantage that the blade is less likely to be broken and there are few troubles associated therewith. Further, the surface roughness Ra and the cut rate can be controlled by selecting the size of the diamond particles constituting the sintered diamond layer.

  As described above, in the tool of the present invention, the machining process for the pad is performed by the side surface of the tool cutting edge, and the pad is cut by the flat blade. Therefore, in addition to the above-described features, the tool of the present invention has the following advantages over the conventional method and tool.

(1) Since the area of the cutting edge is greatly increased compared to the prior art, the wear rate of the tool is small and the initial sharpness is sustained or the tool life is long. Further, a higher processing speed can be obtained.
(2) Since the contact of the cutting edge with the pad surface is not a point contact as in the conventional pyramid type, but a line contact by a ridgeline, the contact surface pressure is relatively small and the biting depth is small.
(3) Since the finished surface roughness Ra does not depend on the size of the cutting edge, it is possible to use chips and particles having a large size as the cutting edge. Next, the present invention will be described with reference to examples.

  Four fan-shaped materials 11 to 14 having a radius of 50 mm, an inner diameter of 60 mm, and a central angle of 90 ° were used as shown in FIG. A 1.0 mm thick PCD (sintered diamond) layer is composed of diamond particles with a nominal particle size of 8-12 μm and is integrated with a cemented carbide (WC-8% Co) substrate by simultaneous sintering. These fan-shaped materials were fixed on a SUS630 stainless steel circular substrate having a diameter of 108 mm with an epoxy-based adhesive to obtain a blank material.

First, the surface of the sintered diamond layer was flattened by die-discharge machining, and then the blank material was integrated with the cemented carbide substrate 15 as schematically shown in the sectional view in the axial direction (parallel axis plane) of FIG. By cutting vertically into the sintered diamond layer 16 by wire-cut electric discharge machining, linear protrusions 20 having a pair of opposing side surface portions 17 and 18 and a flat top surface portion 19 are formed in parallel to each other over the entire surface of the diamond layer. did.

  Next, this blank is rotated by 90 ° around the central axis and the above operation is repeated to form a total of four side surfaces, a square pyramid with a side of the top plane of 100 μm and a height of 150 μm with respect to the groove bottom. 2000 trapezoidal cutting edge groups were formed in an orthogonal lattice shape with a center-to-center distance (pitch) of 1500 μm.

  The operation of the above example was repeated. A fan-shaped material made of a diamond sintered body had a radius of 50 mm, an inner diameter of 30 mm, a center angle of 90 °, and was affixed to four similar substrates to form a blank material. This blank material is further operated in the same manner as in the above-described embodiment, and by wire-cut electric discharge machining, one side of the top plane is 200 μm, the height with respect to the groove bottom is 200 μm, and a portion parallel to the axial surface (square column shape) is formed. A group of 1500 pieces of square frustum-shaped cutting edges having an orthogonal lattice shape with a center-to-center distance (pitch) of 2000 μm was formed.

The composition of the tool created in each example is summarized and shown in the following table.

Comparative example

  A polishing tool with a square pyramid-shaped cutting edge was made for comparison purposes. A fan-shaped material of the same material and shape as in each of the above examples is fixed to a SUS316 circular substrate with an epoxy adhesive to form a blank material, and a rectangular pyramid-shaped cutting blade group is orthogonally crossed by wire-cut electric discharge machining as in the above example. It was formed in a lattice shape. The surface angle between the opposing sides of the quadrangular pyramid was 90 °, the height of the top with respect to the bottom between the cutting edges was 500 μm, and the distance (pitch) between the cutting edges was 1500 μm.

  The polishing tool prepared in each of Examples 1 and 2 and Comparative Example was subjected to a hard urethane polishing test simulating conditioning of a polishing pad. The pressure load on the tool was 2 kgf, and the test was continued for a maximum of 30 hours. The polishing was stopped several times along the way, and the thickness at six fixed points on the workpiece was measured to determine the amount of change. The amount of decrease per time is taken as the cut rate, and the change with time is shown in FIG. The finished surface roughness is shown in the following table.

  A tool 22 having a cutting edge 1 arrangement schematically shown in FIG. 8 was created. A diamond sintered body having a 0.5 mm thick sintered diamond layer (nominal grains: 8-16 μm) on a cemented carbide substrate having a thickness of 2.5 mm was used as a cutting blade material. This diamond sintered body is preliminarily secured by double-side polishing, and has a top part 23 of 800 μm × 800 μm sintered diamond by wire cutting from the sintered diamond surface. 24 24 were cut out.

  The cutting surfaces of these chips are polished with a diamond grindstone, and the cemented carbide side is the bottom, and each of the chips is placed on two concentric circles with a radius of 95 mm and 90 mm on a SUS630 substrate 25 via silver solder. Placed and fixed one by one. At this time, the tips were arranged using a template so that an equal interval was maintained between adjacent particles, and all the tips were heated in the axial direction from above.

  As a finishing process, a # 200 diamond grindstone was used, and surface grinding was performed until the step between the chips was not recognized, so that a dresser having a cutting edge made of a sintered prism in the form of a vertical square pillar was obtained. A polishing test was carried out under the same conditions, and after 10 hours, 24 μm / h and 3.0 μm were obtained as the cut rate and the finished surface roughness Ra, respectively.

  From the diamond sintered bodies of Examples 1 and 2, square and triangular prisms (tilt angle α = 0 °) with the dimensions shown in the table below were cut out by wire cutting. On the other hand, holes for fixing were carved in various patterns on the same type of substrate as in each of the above examples, and individual chips were placed and pressed in the axial direction from above to secure the fixedness and the top surface position uniformity.

  A polishing test was performed under the same polishing conditions as the hard urethane polishing test, and the following results were obtained.

  From the diamond sintered body of Example 1, a rectangular parallelepiped chip having 10 cutting edges was produced. The cutting edges formed on the sintered diamond layer are square columns with a height of 200 μm each having a top of 200 μm × 200 μm, arranged in 5 rows at a pitch of 1 mm in the radial direction and in 2 rows at a pitch of 1 mm in the circumferential direction. Has been. Twenty-four chips with the same configuration were prepared.

  24 grooves having a rectangular cross section were carved every 15 ° on the outer periphery of the substrate similar to that in Example 3, and each chip was placed, and after ensuring the level of the surface, it was press-fitted and fixed to obtain a tool.

  This tool was subjected to a hard urethane polishing test to obtain a cut rate of 180 μm / h and an Ra surface roughness of 4.9 μm.

  In the above description, the present invention has been described with reference to a diamond sintered body. However, a hard phase boron nitride (c-BN, w-BN) sintered body may be used instead.

  The tool of the present invention is particularly suitable for use as a pad conditioner, but it can also be used for precision finishing of hard materials.

1 Cutting Edge 2 Side 4 Reference Surface (Cutting Blade Shaft Surface)
6 Top surface 7 Substrate 8 Block chip 11-14 Fan-shaped material 15 Cemented carbide base 16 Sintered diamond layer 20 Linear protrusion 22 Tool 24 Composite material chip 25 Substrate

Claims (13)

  A polishing tool in which a rigid substrate has a flat circular surface, and a plurality of cutting edges having a flat top surface located within a certain level with respect to the circular surface are fixedly arranged on the substrate, Suitable for pad dressing, characterized in that it is surrounded by a plurality of linear ridgelines and adjacent to the side surface extending in the tool axis direction through the ridgelines, and at least the top of the cutting edge is made of sintered diamond Polishing tool.   The polishing tool according to claim 1, wherein the cutting edge has a quadrangular prism shape or a truncated pyramid shape.   The polishing tool according to claim 1, wherein the cutting edge has a triangular prism shape or a triangular frustum shape.   The polishing tool according to any one of claims 1 to 3, wherein a side edge angle of the side surface of the cutting edge is 30 ° or less.   The polishing tool according to claim 1, wherein the total area of the top surface of the cutting edge in the entire polishing tool is 10% or less and 0.005% or more (1000 / 10,000 or less and 0.5 or more) of the area in the substrate.   The polishing tool according to claim 1, wherein the cutting edges are arranged in a rectangular lattice at regular intervals.   The polishing tool according to claim 1, wherein the cutting edges are arranged concentrically at regular intervals.   The polishing tool according to claim 1 or 7, wherein a plurality of the cutting edges are disposed on the same radius.   The polishing tool according to claim 1, wherein the tool is a pad dresser having a diameter of 110 mm or less.   2. A polishing method for removing a workpiece material using the polishing tool according to claim 1, wherein a pressing portion is pressed against the surface of the workpiece to generate a displacement portion displaced in the pressing direction on the surface of the workpiece. A polishing method comprising: removing a workpiece material at a boundary between a deformed portion and a remaining portion by further moving a linear ridge line of the top of the cutting edge relative to the deformed portion.   The polishing method according to claim 10, wherein the workpiece is hard urethane.   The polishing method according to claim 10, wherein the cutting edge has a quadrangular prism shape or a truncated pyramid shape.   The polishing method according to claim 10, wherein the cutting edge has a triangular prism shape or a triangular frustum shape.

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