JP2012121129A - Polishing tool suitable for pad conditioning and polishing method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tool for use in conditioning, which is easy to control processes and also can improve a service life of the tool.SOLUTION: The polishing tool includes a rigid substrate having a planar circular surface, on which a group of cutting edges 31 with a flat top face of a limited area positioned within a certain level for the circular surface are arranged in a grid state comprising two intersecting sets of parallel lines 41 and 42. Each cutting edge 31 is made of sintered diamond having a rectangular cross section (horizontal cross section) vertical to an axis of the tool on the top and also having a longitudinal ridge extending in the axial direction. The cutting edge 31 is formed in a plurality of polishing islands with an area limited as a group. The polishing tool includes the plurality of polishing islands which are regularly disposed on concentric circles with respect to the rotation center of the tool at a constant spacing, and is suitable for dressing a CMP pad.

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 can be performed by using electrodeposited superabrasive grains, by polishing unit groups formed on a sintered diamond layer, or by padding at the tip (point) or apex of a pyramid of individual particles or polishing units. Based on the polishing action of scraping the surface. 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 a flattening process in which the pad surface is scraped off with the tip of an abrasive grain or polishing unit using a conventional dresser, the control of the material removal rate (cut rate) and the surface roughness are intricately intertwined. It was difficult to control the performance according to the purpose. Furthermore, in the electrodeposition type, as the grain size of the fixed abrasive grains (diamond, etc.) becomes finer, the proportion of abrasive grains that are exposed for processing decreases, and in this respect, the tool life is not always satisfactory. There wasn't.

  The present invention provides a tool for conditioning that solves the above-mentioned problems by making it easy to control the material removal rate and ensure surface flatness in conventional pad conditioning, and at the same time improve tool life. The main purpose is to do.

  The present inventor has obtained the following knowledge. That is, the surface of the rigid substrate having a planar circular surface has a flat top surface of a finite area located within a certain level with respect to the surface, and a longitudinal ridge line in the tool axis direction adjacent to the top surface at right angles. Using a polishing tool in which a plurality of cutting edges made of sintered diamond having a quadrilateral shape are arranged in a cross section perpendicular to the axial direction (horizontal cross section), the total area of the top surface of the entire tool is determined by the individual top surface and the cutting surface. The process can be easily controlled by adjusting the blade interval and the like, and the tool life can be improved. Based on this finding, the present invention has been completed.

  Accordingly, the present invention provides two sets of cutting blades having a flat top surface with a finite area located within a certain level with respect to the circular surface. A polishing tool arranged in a lattice pattern consisting of a group of parallel lines, each cutting edge having a quadrilateral cross section (horizontal cross section) perpendicular to the axis of the tool at the top and a longitudinal ridge line extending in the axial direction. The cutting blade is formed on a plurality of polishing islands having a limited area as a group, and a plurality of the polishing islands are regularly arranged on a concentric circle with respect to the rotation center of the tool at regular intervals. The gist of the present invention is a polishing tool suitable for dressing a CMP pad, characterized in that the polishing tool is arranged.

  In another aspect of the present invention, in a polishing method using such a tool, a flat top surface having a finite area located within a certain level with respect to the surface of the rigid substrate having a planar circular surface and the top surface are provided. By pressing the cutting edge of a polishing tool in which cutting edges of a quadrilateral cross section made of sintered diamond having a vertical ridge line adjacent to the surface at right angles are arranged in a plurality of parallel straight lines against the surface of the workpiece, By creating a displacement part displaced in the pressing direction on the surface of the workpiece, and further causing a relative movement in the horizontal direction with respect to the displacement part on the vertical ridge line of the cutting edge, the boundary between the displacement part around the ridge line and the remaining part The gist of the method is to scrape off the workpiece material.

  The polishing tool of the present invention has a small bite depth compared to a conventional tool having a sharp top edge, and unlike a conventional cutting mechanism with such a sharp tip, a cutting edge (especially a cutting edge (especially) The cutting proceeds by the vertical ridgeline of the top part and the side of the top part adjacent to the ridgeline. That is, when the workpiece surface is pressed, it is displaced according to the compression ratio of the material, but in this state, when performing relative movement between the cutting edge by rotating the tool (rotation), etc., the vertical ridgeline and adjacent side surface of the cutting edge As a result, the workpiece material around the boundary between the displaced portion and the remaining portion around the ridgeline is scraped off.

  In the present invention, the processing area of the workpiece is expanded by the rotation and revolution of the tool, but the processing is mainly due to the vertical ridgeline (edge) and the adjacent side surface, as in the case of plain (掛 け) hanging or only (鑿) punching. By performing with a planar blade, a surface with high flatness and less waviness is achieved.

Furthermore, especially in precision polishing of hard urethane, by adjusting the load receiving area by changing the area of the top edge of the cutting edge and the interval (pitch) of the cutting edge group, a high material removal rate (cut rate) per time, and / or Alternatively, it has the advantage that a small finished surface roughness (Rk, Rpk) can be achieved and this performance is maintained several times compared to similar conventional tools. The present invention will be described below with reference to the accompanying explanatory drawings.

It is a sketch showing the basic shape of the cutting edge in the polishing tool of the present invention. It is a sketch which shows another example of the cutting-blade shape in the polishing tool of this invention. It is an axial sectional view showing the reinforcing angle of the cutting edge in the polishing tool of the present invention. It is explanatory drawing which shows the example of cutting-edge arrangement | positioning in the polishing tool of this invention. It is explanatory drawing which shows another example of cutting-edge arrangement | positioning in the polishing tool of this invention. It is a more detailed plan view of another cutting edge arrangement example in the polishing tool of the present invention. It is a sketch showing the cutting edge shape (saw blade shape) in the polishing tool of the present invention. It is a sketch which shows the tool structural example in the polishing tool of this invention.

  As described above, the cutting edge for removing the workpiece in the polishing tool of the present invention includes the flat top surfaces 10 and 20 having the finite area, the vertical ridgelines 11, 12 and 13; 21, 22 and 23, and the side surface 15. 16; 25, 26 (FIGS. 1 and 2), and as such a cutting edge, the shape of the cutting edge in the cross section perpendicular to the height of the cutting edge or the tool axis (horizontal) is, for example, square, From the viewpoints of rectangles and parallelograms including rhombuses, particularly ease of processing and cutting edge strength, rectangles having a side length of 20 μm or more and parallelograms are suitable.

  The cutting edges are rectangular or long parallelograms, and the longitudinal direction is aligned with the tool radial direction, or they are aligned with a small inclination angle with respect to the radius. The larger the ratio of the short side to the long side of the quadrilateral, the more advantageous the area covered by the individual cutting edges when the tool rotates, but if it is too large, the cut rate tends to decrease. In these respects, the short side to long side ratio of the quadrilateral is effective from 1: 200 to 1, but practically from 1:50 to 10, particularly preferably 1:20 or less.

  The vertical ridgelines 11-13; 21-23, which act as edges in the cutting edge of the present invention, are constituted by the intersection of four side surfaces adjacent to the top surface of the flat quadrilateral. Each of these side surfaces may be parallel to the cutting edge or the axial direction of the tool. For example, as shown in FIG. 3 showing an axial sectional view passing through the center of the quadrilateral and parallel to the side, the side surface is parallel to the axial direction. It is particularly effective in a configuration in which the width of the cutting edge is small, in particular, to incline with respect to the reference line A at an inclination angle γ and to provide a reinforcing angle that increases the cross-sectional area toward the bottom of the cutting edge. The value of γ is 10 ° or less, particularly 7 to 8 °.

  The cutting edge of the present invention is a diamond sintered body, that is, diamond particles that are sized (classified) and a cemented carbide plate as a support material, and diamond is integrated in layers under thermodynamically stable pressure and temperature conditions. It is formed in the sintered diamond layer of the composite material that has been subjected to chemical sintering. Cutting blades 31, 32, 33 (representatively, only one is given a reference symbol) are formed on such composite material plates 34, 35, 36 pre-cut into a predetermined shape by wire cutting, EDM, etc. 4, straight lines in two directions intersecting at an intersecting angle α as shown in FIGS. 4, 5 and more detailed FIG. 6 (with one row as a representative of each direction). 41, 42; 43, 44; 45, 46, and a group of straight lines arranged in parallel to these groups. These techniques are used alone or in combination, and the use of a laser beam is particularly suitable for forming fine cutting edges such as 50 nm and 20 nm.

  The crossing angle α defines each vertex angle of the quadrilateral of the cutting edge, where α is 45 ° ≦ α <90 ° or 90 ° <α ≦ 135 °, preferably 60 ° ≦ α <90 ° or 90 °. <Α ≦ 150 ° can be used, and the cusp strength and performance of the cutting edge are optimized within these ranges. When α = 90 ° to α≈90 °, it is difficult to obtain a cut with a sharp apex, but the machining performance with a vertical ridge line is maintained.

  At this time, one parallel line group is inclined at an inclination angle β (clockwise) with respect to the rotation (tangential) direction R → of the tool, and the arrangement of the cutting edges in the long side direction is cut every pitch in the horizontal direction. When it is arranged without a gap in the rotation direction by shifting it by 1 / n of the blade length (for example, n: 4 to 6) (indicating a direction parallel to the rotation direction as the reference line L), one rotation of the tool (rotation) ), The surface roughness of the work piece can be more easily controlled. In the case of β = 0, a blank is generated in the machining area due to the rotation of the tool and the efficiency is lowered, but it is possible to ensure machining by the vertical ridge line in the present invention.

  On the other hand, when the ratio between the short side and the long side of the cutting edge is large, as illustrated in FIG. 7, one to a plurality of cuts 52 and 53 are provided on the top surface of the cutting edge 51 in parallel with the short side. If the contour is made into a saw blade shape, it is effective because the cutting powder and the polishing liquid can easily move and contribute to the improvement of work efficiency.

  The cutting blades having the shape and arrangement according to the present invention are formed, for example, in a plurality of diamond sintered bodies as polishing islands (chips) pre-cut into a rounded trapezoidal shape or a sector shape as shown in FIG. . Each of the polishing islands 55 (representatively, only one is given a reference symbol) is used in a uniform shape and regularly arranged on the tool substrate 56, for example, concentrically at regular intervals. At this time, in each polishing island, one of the two rows of cutting edge lattices, in particular a plurality of long sides, is aligned with the radial direction of the tool substrate, or aligned so that the inclination angle with respect to the radial direction is small. Let it fix. In this case, the other row (short-side direction) is inclined with an inclination angle β substantially with respect to the rotation direction.

  In the present invention, the machining performance such as the cut rate and the finished surface roughness is governed by the top area of the cutting edge or the horizontal cross-sectional area and the pitch (density) between the cutting edges. If a high cut rate is desired, the individual top surfaces are made smaller or / and the spacing between the cutting edges is made larger. On the other hand, when emphasizing the surface accuracy, it is effective to increase each top surface and / or reduce the distance between the cutting edges.

  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 cutting edge tips can be arranged in various shapes such as concentric circles, radial shapes, or combinations thereof on the outer peripheral portion of the tool substrate. At this time, various known techniques can be used for fixing to the substrate according to the material type.

  In the above, the cutting edge made of sintered diamond is formed into a sintered diamond layer on the surface of the composite material that is sintered under an ultra-high pressure and is firmly integrated through a diamond-diamond bond. There is an advantage that there are few troubles accompanying this.

  As shown in Fig. 8, 6 pieces of precut material pieces (width 20mm, height 14mm) made of diamond sintered body (PCD) sintered under ultra-high pressure and high temperature, with a cutting edge of 108mm in diameter SUS630 stainless steel circular substrate was fixed on the same circumference with an epoxy adhesive at equal intervals and used as a polishing island. The pre-cut material has a trapezoidal shape with rounded corners, the PCD layer is 1.0mm thick, is composed of diamond particles with a nominal particle size of 8-12μm, and is integrated with a cemented carbide (WC-8% Co) substrate by simultaneous sintering. It was converted.

  After flattening the surface of the sintered diamond layer by die discharge machining on this PCD piece, after cutting into the diamond layer surface in a cross-parallel line shape by wire-cut electric discharge machining, creating a lattice of cutting edges over the entire surface, A 200 μm-high cutting edge group having a flat top surface of 50 × 200 μm having a reinforcement angle of 7 ° was formed by laser beam processing. The lattice-shaped cutting edge had a crossing angle of 75 degrees in two directions, the pitch was 700 μm in the longitudinal direction, and the other was 600 μm.

  The tool was mounted on a lapping machine and subjected to a hard urethane polishing test simulating the condition of a polishing pad. The pressurizing load on the tool was a load of 3 kg for 20 minutes, and a cut rate of 10 μm / h and an Ra roughness of 2.3 μm were obtained.

  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.

DESCRIPTION OF SYMBOLS 10 Top surface 11-13 Longitudinal line 15, 16 Side surface 20 Top surface 21-23 Longitudinal line 25, 26 Side surface 31-33 Cutting edge 34-36 Material board 41-46 Parallel line group 51 Cutting edge 52, 53 Cutting 55 Polishing island 56 Tool substrate

Claims (16)

  The rigid substrate has a planar circular surface, and the substrate comprises two sets of parallel lines intersecting a set of cutting edges with a flat top surface of a finite area located within a certain level with respect to the circular surface. A polishing tool arranged in a grid, each cutting edge is a sintered diamond having a cross section perpendicular to the axis of the tool at the top (horizontal cross section) and a longitudinal ridge line extending in the axial direction. The cutting edge is formed into a plurality of polishing islands having a limited area as a group, and a plurality of the polishing islands are regularly arranged on a concentric circle with respect to the rotation center of the tool at regular intervals. A polishing tool suitable for dressing a CMP pad.   The polishing tool according to claim 1, wherein a horizontal section of the cutting edge is a parallelogram.   The polishing tool according to claim 1 or 2, wherein a horizontal section of the cutting edge is rectangular.   The polishing tool according to claim 1, wherein the ratio of the short side to the long side of the quadrilateral is a rectangle or parallelogram having a ratio of 1: 200 to 1.   The polishing tool according to claim 4, wherein the ratio of the short side to the long side of the quadrilateral is 1 to 50 to 10.   The polishing tool according to any one of claims 4 to 5, wherein a ratio of a short side to a long side of the quadrilateral is 1 to 20 or less.   The polishing tool according to claim 1, wherein one side of the quadrilateral is 20 μm or more.   The polishing tool according to any one of claims 1 to 6, wherein the cutting edge has one or a plurality of grooves crossing the top surface and has a sawtooth profile.   The polishing tool according to claim 1, wherein the cutting edge has a side surface extending downward with an inclination angle (γ) with respect to the cutting edge or the axis of the tool of 10 ° or less in an axial section.   The intersection angle (α) between the two sets of parallel line groups is α> 90 ° or α <90, and the direction of one parallel line group includes a direction perpendicular to the rotation direction. The polishing tool described.   The polishing tool according to claim 10, wherein an intersection angle (α) between the two sets of parallel line groups is α = 90 °.   2. The polishing tool according to claim 1, wherein, in at least one of the polishing islands, one set of parallel lines of the two sets includes a radial cutting edge row.   The polishing tool according to claim 1, wherein at least one of the polishing islands is inclined so that the cutting edge does not form a gap with respect to the rotation direction.   The polishing tool according to claim 1, wherein the cutting blade group is formed in a sintered diamond layer of a diamond sintered body in which diamond is integrated under a thermodynamically stable pressure and temperature condition.   A quadrilateral cross section comprising a flat surface of a rigid substrate having a planar circular surface, a flat top surface of a finite area located within a certain level with respect to the surface, and a sintered diamond having a longitudinal ridge line adjacent to the top surface at right angles By pressing the cutting blade of an abrasive tool with a plurality of cutting blades arranged in parallel straight lines onto the surface of the work piece, a displacement part displaced in the pressing direction is generated on the work surface, and further the cutting edge 2. A tool according to claim 1, wherein the workpiece material at the boundary between the displacement portion and the remaining portion around the ridge line is scraped off by causing the vertical ridge line to move horizontally relative to the displacement portion. Polishing method using The polishing method according to claim 15, wherein the workpiece is hard urethane.

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