Conditioning disk with microfeatures

Abstract

A conditioning disk having microfeatures is described. More specifically, the conditioning disk has at least one discrete abrasive element and at least one microfeature. The asymmetry of at least one microstructure can enable a wide range of pad polishing parameters, such as surface roughness and pad wear rate, based on the orientation.

Description

[Background technology]

[0001] A particular class of pads is used for chemical mechanical polishing of semiconductor wafers to a high degree of flatness and smoothness. These pads (CMP pads) are rotated and brought into contact with the semiconductor surface along with a slurry to polish material from the wafer and form a polished surface. Exposure to both the polishing slurry and the abrasion of the polishing process itself can cause the topography of the CMP pad to shift with use. To provide consistent and desirable polishing performance, these CMP pads are often conditioned (either in-situ or ex-situ) with a conditioning disk. The use of a conditioning disk (also rotated and brought into contact with the surface, but in this case the surface of the CMP pad) may be used to restore the working surface of the CMP pad to near its original surface shape. Summary of the Invention

[0002] In one aspect, the present disclosure relates to a pad conditioning disk. The pad conditioning disk includes at least one discrete abrasive element. The at least one discrete abrasive element includes at least one microfeature having a base and a top, the at least one microfeature having at least three facets with at least three edges, each edge being between an adjacent pair of facets and extending from the base. The at least three edges are not all the same length, and the at least one microfeature has a leading edge. The leading edge is either (i) coincident with the shortest edge of the at least three edges, or (ii) if two edges of the at least three edges are the same length but shorter than the other edge, it is midway between the rotation between each of the two edges and extends from the base to the top of the microfeature. The at least one discrete abrasive element is oriented and disposed on the pad conditioning disk such that the leading edge of the at least one microfeature forms an angle of at least 5 degrees with the direction of instantaneous rotation of the pad conditioning disk.

[0003] In another aspect, the present disclosure relates to a method of forming a pad conditioning disk, the method comprising: providing a carrier; and providing at least one discrete abrasive element. The at least one discrete element comprises at least one microfeature having a base and a top, the at least one microfeature having at least three facets with at least three edges, each edge being between an adjacent pair of the facets and extending from the base. The at least three edges are not all the same length, and the at least one microfeature has a leading edge. The leading edge is either (i) coincident with the shortest edge of the at least three edges, or (ii) if two edges of the at least three edges are the same length but shorter than the other edges, it is midway through the rotation between each of the two edges and extends from the base to the top of the microfeature. The method also comprises orienting and placing the at least one discrete abrasive element on the carrier such that the leading edge of the at least one microfeature forms an angle of at least 5 degrees with the direction of instantaneous rotation of the pad conditioning disk. [Brief description of the drawings]

[0004] [Figure 1] FIG. 2 is a schematic top view of a conditioning disk having microfeatures. [Figure 2A] 1A-1D are schematic top view illustrations of exemplary microfeature shapes. [Figure 2B] 1A-1D are schematic top view illustrations of exemplary microfeature shapes. [Figure 2C] 1A-1D are schematic top view illustrations of exemplary microfeature shapes. [Figure 2D] 1A-1D are schematic top view illustrations of exemplary microfeature shapes. [Figure 2E] 1A-1D are schematic top view illustrations of exemplary microfeature shapes. [Figure 2F] 1A-1D are schematic top view illustrations of exemplary microfeature shapes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0005] Chemical mechanical polishing processes, conditioning processes, and related specifications vary from semiconductor manufacturer to semiconductor manufacturer. Thus, the different target surface profiles of these manufacturers mean that they may require different pad conditioner disk designs. For example, semiconductor manufacturers may have different desired specifications for the resulting pad wear rate (PWR) and surface roughness (Ra). For traditional inorganic abrasive particle-based conditioning disks, this may mean changing the abrasive particle size, distribution, or composition to approach the desired specifications. For alternative microfeature (e.g., microreplicated abrasive feature)-based conditioning disks, this may mean changing the shape, size, and distribution of the microfeatures.

[0006] Described herein is a surprising approach to pad conditioning disks where the shape of microfeatures is selected such that performance can be tuned by rotation of the microfeatures themselves or by rotation of the abrasive elements having such microfeatures thereon, thus allowing for careful calibration of the desired performance without the need to customize the entire manufacturing process.

[0007] Surprisingly, this also makes the combination of Ra and PWR difficult to achieve. In some embodiments, high roughness and low pad wear rate, or conversely, low roughness and high pad wear rate, are achievable. Conventionally, these parameters were thought to increase or decrease together.

[0008] 1 is a schematic top view of a (CMP pad) conditioning disk. The conditioning disk 100 includes at least one discrete abrasive element 120 disposed on a carrier 110, the at least one discrete abrasive element 120 including at least one microfeature 122. The angle between the leading edge of the at least one microfeature 122 and the direction of instantaneous rotation of the conditioning disk 100 is represented as angle θ.

[0009] The carrier 110 may be any suitable material, including a metal or metal alloy, a polymeric material or blend, or other suitable substrate. For example, in some embodiments, the carrier may be or include stainless steel. In some embodiments, the carrier may be substantially rigid and inflexible under normal operating conditions. In some embodiments, the carrier may be flexible or conformable under normal operating conditions.

[0010] The carrier 110 may include one or more attachment areas specifically adapted for positioning one or more discrete abrasive elements. These areas may include raised or depressed areas of the carrier (machined, etched, or otherwise formed), or roughened areas to improve adhesion or attachment.

[0011] The at least one discrete abrasive element 120 is attached to or disposed on the carrier. In some embodiments, the at least one discrete abrasive element is attached by use of a suitable adhesive. The adhesive may be selected for suitable compatibility of the adhesive with the carrier and the discrete abrasive element, as well as other properties such as the ability to provide permanent or removable / repositionable adhesion, chemical resistance, adhesion under a range of normal use temperatures, etc. Adhesives allow an important class of attachment mechanisms for the at least one discrete abrasive element, but the attachment method is not limited. Other options such as welding (including ultrasonic welding), or mechanical attachment (such as hook and loop) are contemplated for attachment of the at least one discrete abrasive element.

[0012] The discrete abrasive element(s) include a base including a working surface having at least one microfeature 122 or a plurality of microfeatures (for ease of illustration, the size of the at least one microfeature 122 has been greatly exaggerated as compared to the typical relationship between the at least one microfeature, the at least one discrete abrasive element, and the carrier). Being discrete, the abrasive elements do not form a continuous surface on the carrier of the pad conditioning disk. In some embodiments, the discrete abrasive elements may be viewed as a disk or puck disposed on the carrier. In some embodiments, each of the discrete abrasive elements includes a working surface having a plurality of microfeatures. In some embodiments, the microfeatures are precisely shaped features. These microfeatures may be formed by a variety of suitable processes including micromachining, waterjet cutting, injection molding, extrusion, microreplication, or ceramic die pressing. In some embodiments, the discrete abrasive elements include a ceramic body including a superabrasive grit in a metal matrix, a ceramic body including a ceramic material in an amount of at least 85% by weight, and a diamond coating. Examples of superabrasive grits include cubic boron nitride (CBN) and chemical vapor disposition (CVD) diamond. Other examples of coatings, as well as general properties and further details of the formation of precisely shaped microfeatures, are described in U.S. Patent No. 10,710,211 (Lehuu et al.), which is incorporated herein by reference.

[0013] In some embodiments, the shape of the at least one microfeature 122 is rotationally asymmetric. The shape of the at least one microfeature 122 has a base and a top. Extending away from the base, the top includes one or more points furthest (distal) from the base along its z-direction. The top may be a point (as in the case of a pyramid), a line, or if truncated, a closed shape (i.e., 0-, 1-, or 2-dimensional). In this embodiment, the microfeature is at least three facets with at least three edges. Each edge is between an adjacent pair of facets and extends from the base to the top. In this embodiment, the at least three edges are not all the same length. In this embodiment, at least one microfeature has a leading edge that is either (i) coincident with the shortest edge from a top view of the at least three edges, or (ii) if two edges of the at least three edges are the same length but shorter than the other edge, is midway between each of the two shorter edges and extends from the base to the top of the microfeature.

[0014] 2A-2F show several potential embodiments of the microfeatures described herein. In each embodiment, the leading edges described herein are symbolically identified with dashed lines. FIG. 2A shows an example of a microfeature with a truncated top. FIG. 2B shows an example of a microfeature with a point as a top. FIG. 2C shows an example of a microfeature with an edge or line as a top. FIG. 2D shows an exemplary pyramidal microfeature with a triangular base versus a square base (as the specific shape of the base is not particularly limited), and FIG. 2E shows a microfeature with a pentagon as a base. FIG. 2F shows an example of a microfeature where there are two edges that are equal in length but longer than the other edge.

[0015] In some embodiments, the orientation of the discrete abrasive elements is such that the leading edge of at least one microfeature forms an angle of at least 1 degree with the direction of instantaneous rotation of the pad conditioning disk. The direction of instantaneous rotation (typically two directions) is the direction in which the microfeature instantaneously moves when the conditioning disk is rotated clockwise or counterclockwise for any given microfeature. The direction of instantaneous rotation varies infinitesimally in any direction, but for the purposes of this description, the direction of instantaneous rotation can be approximated, for example, by considering the center of the discrete abrasive element or the center of the microfeature as a reference point. In typical cases and applications, neither of these approximations significantly affects the orientation of the discrete abrasive elements, and one or both may be preferred depending on the user's requirements. This direction is symbolically shown in FIG. 1 as a large arrow, and the angle between this direction and the leading edge is shown as θ. In some embodiments, the orientation of the discrete abrasive elements is such that the leading edge of at least one microfeature forms an angle of at least 2 degrees with the direction of instantaneous rotation of the pad conditioning disk. In some embodiments, the orientation of the discrete abrasive elements is such that the leading edge of at least one microfeature forms an angle of at least 5 degrees with the direction of instantaneous rotation of the pad conditioning disk. In some embodiments, the orientation of the discrete abrasive elements is such that the leading edge of at least one microfeature forms an angle of at least 10 degrees with the direction of instantaneous rotation of the pad conditioning disk. In some embodiments, the orientation of the discrete abrasive elements is such that the leading edge of at least one microfeature forms an angle of at least 20 degrees with the direction of instantaneous rotation of the pad conditioning disk. In some embodiments, the orientation of the discrete abrasive elements is such that the leading edge of at least one microfeature forms an angle of at least 30 degrees with the direction of instantaneous rotation of the pad conditioning disk. In some embodiments, the orientation of the discrete abrasive elements is such that the leading edge of at least one microfeature forms an angle of at least 45 degrees with the direction of instantaneous rotation of the pad conditioning disk. Surprisingly, precise alignment of the leading edge with the direction of instantaneous rotation typically does not result in a maximum or minimum value for PWR or Ra.In some embodiments and applications, this may be due to the complex motion of both sweeping and rotating by the pad conditioning disk over the surface of the CMP pad.

[0016] The asymmetry of the at least one microfeature allows its leading edge to be positioned at different positions relative to the reference direction of instantaneous rotation. Depending on the application, this leading edge may be oriented at any desired angle, and the properties of the pad conditioning disk may similarly change as this orientation changes.

[0017] In some embodiments, the discrete abrasive elements include an array of microfeatures, each of which has a shape having a base and a top, at least three sides with at least three edges, and a leading edge, as described for at least one microfeature elsewhere herein. In some embodiments, each of the microfeatures in the array of microfeatures has the same shape. In some embodiments, each of the microfeatures in the array of microfeatures has the same size. In some embodiments, each of the microfeatures in the array of microfeatures may have respective leading edges oriented in the same direction. In some embodiments, one or more of the size, shape, or orientation may vary pseudo-randomly or with a gradient along one or more in-plane directions.

[0018] The discrete abrasive elements may be spaced on the pad conditioning disk at equal intervals around the circumference of the carrier. In some embodiments, there are five discrete abrasive elements mounted on the carrier, and thus spaced about 72 degrees (relative to the center) around the circumference. However, the number of discrete abrasive elements is not limited and can be adjusted based on the desired application and use. In some embodiments, there may be as few as one or as many as 16 discrete abrasive elements.

[0019] In some embodiments, the rotation of at least one microfeature adjusts at least one of the resulting Ra (surface roughness) or PWR (pad wear rate: e.g., in units of micrometers per hour or angstroms per minute under typical conditions of use, e.g., 4-5 psi pressure). For asymmetries (e.g., distinguishability of leading edges), it may be possible to determine the rotation required to adjust (increase or decrease) a desired performance parameter based on a given shape. In some embodiments, after formation of the discrete polishing elements, the rotation (i.e., orientation) on the carrier may be adjusted to achieve a desired or predicted performance. Any alignment, orientation, or rotation may be performed using one or more fiducial marks, optical scanning, or any other precision alignment technique. In some embodiments, this may streamline the manufacturing process since the same component may be configured to provide a wide range of desired performance while only adjusting the orientation of the discrete polishing elements. In some embodiments including two or more discrete polishing elements, the orientation of these discrete polishing elements may differ to achieve a blended performance between two orientations, but are otherwise formed in the same manner. This concept can be generalized to n discrete abrasive elements, with the orientation of the microfeatures of each discrete abrasive element contributing to the overall performance of the conditioning disk. In some embodiments, the orientation can be determined or adjusted based on real-time or near real-time information about the actual shape of the manufactured discrete abrasive elements, taking into account manufacturing errors and potential defects. For example, if a manufacturing variation produces a discrete abrasive element that contributes to a lower PWR than desired, the discrete abrasive element may be rotated relative to its original target orientation to compensate for an otherwise potentially out-of-specification performance. In some embodiments, the discrete abrasive elements are repositionably mounted on the carrier of the conditioning disk and can be optionally removed, rotated, and optionally remounted to adjust the desired performance or to compensate for wear. EXAMPLES

[0020] The present disclosure is now described in more detail in the following examples, which are for purposes of illustration only, since numerous changes and modifications within the scope of the disclosure will become apparent to those skilled in the art.

[0021] Test method for pad wear rate and pad surface roughness of CMP tools Measurements were performed on conditioned pads on an Applied Materials 200 mm REFLEXION polishing tool. The conditioning cycle was performed using deionized water with a down force of 2.5 lbs (1.13 kg) at a conditioner speed of 87 rpm and a pad speed of 93 rpm. The conditioner arm sweep recipe had a start position of 1.00 inch (2.5 cm) and an end position of 12.75 inch (32.4 cm). The sweep was divided into 13 zones with relative dwell times of 1.20, 1.10, 1.00, 1.00, 1.00, 1.00, 1.00, 1.00, 1.00, 1.00, 1.00, 1.20, and 1.55, respectively. The cycle time was 13 sweeps per minute. The pad used was a 30 inch Fujibo H800 pad. Pad wear rate was determined by comparing the initial and post-use pad thickness using an eddy current gauge. The difference in final pad thickness to initial pad thickness averaged over 12 test locations (0, 90, 180, and 270 degrees at 3, 7, and 11 inch radii, respectively) divided by the test time was reported as the pad wear rate. To determine the surface roughness of the pad, a NanoFocus confocal microscope was used to measure Ra at distances of 2 inches (5.1 cm), 5 inches (12.7 cm), 8 inches (20.3 cm), 11 inches (27.9 cm), and 14 inches (35.6 cm) from the center of the freshly conditioned pad. Ra was reported as the average of these five locations.

[0022] Ten samples were prepared for the exemplary pad conditioning disk. The abrasive elements were prepared as described in U.S. Patent No. 9,965,664 (Lehuu et al.), which is incorporated herein by reference in its entirety, for Example 10, except that the geometry of the abrasive features was different, as described in Table 1: Number of primary features per element: 944, Primary feature height: 150 micrometers, Offset height: 10 micrometers, Primary fine feature truncation depth: 0 micrometers, Aspect ratio: 0.50. The offset height between the primary and secondary abrasive features is defined as the difference in height between the primary and secondary features. The aspect ratio is defined as the feature height divided by its base width. The truncation depth of the primary feature is defined by the depth at which the theoretical apex would be formed if the sides of the pyramid were converged to a point. The draft angle of these geometries is defined as the angle formed with a plane perpendicular to the two base edge elements (i.e., theoretical vertical sidewalls with zero draft) adjacent to the leading edge of the abrasive feature (which in these geometries coincides with the shortest edge). The orientation is defined as the angle in degrees relative to the instantaneous direction of rotation (two reference directions are possible, but the direction selected is based on the actual rotation direction applied and tested). Each abrasive element had at least one precisely shaped feature with a primary feature height that was higher than and offset relative to either the secondary level features or the flat base area between the features. Five abrasive elements for each example were prepared and assembled into an abrasive article. An assembly process was developed so that the highest precisely shaped features on each element, all with the same feature design height, were planar. A planar sapphire surface was used as the alignment plate. The elements were placed on the alignment plate with their major surfaces having precisely molded features facing up and in direct contact with the alignment plate (facing down) with their second flat major surfaces facing up and rotated as necessary to align in the desired orientation. The abrasive elements were arranged in a circular pattern with their center points spaced equally circumferentially at approximately 72° intervals along the circumference of a circle with a radius of approximately 1.75 inches (44.5 mm).A fastening element was then applied to the exposed surface of the abrasive element in the central region. The fastening element was an epoxy adhesive available under the trade designation 3M SCOTCH-WELD EPOXY ADHESIVE DP420 from 3M Company, St. Paul, Minnesota. A circular stainless steel carrier having a diameter of 4.25 inches (108 mm) and a thickness of 0.22 inches (5.64 mm) was then placed face down on top of the fastening element (the back side of the carrier was machined so that it could be attached to the carrier arm of a REFLEXION abrasive). A load of 10 pounds (4.54 kg) was applied evenly across the exposed surface of the carrier, and the adhesive was allowed to cure at room temperature for approximately 4 hours. [Table 1] [Table 2]

Claims

1. 1. A pad conditioning disc comprising: at least one discrete abrasive element comprising at least one microfeature having a base and a top; the at least one microfeature has at least three facets with at least three edges, each edge being between an adjacent pair of facets and extending from the base; the at least three edges are not all the same length; The at least one microfeature has a leading edge, the leading edge comprising: (i) coincides with the shortest edge from a top view of the at least three edges; or (ii) if two of the at least three edges from a top view are the same length but shorter than the other edges, then midway between each of the two edges and extending from the base to the top of the microfeature; the at least one discrete abrasive element is disposed on the pad conditioning disk and oriented such that the leading edge of the at least one microfeature forms an angle of at least 5 degrees with a direction of instantaneous rotation of the pad conditioning disk; Pad conditioning disc.

2. The pad conditioning disk of claim 1 , wherein the at least one microfeature has a truncated top.

3. The pad conditioning disk of claim 1 , wherein the at least one microfeature has four edges.

4. The pad conditioning disk of claim 1 , wherein the at least one microfeature is an array of microfeatures.

5. The pad conditioning disk of claim 4 , wherein each microfeature in the array of microfeatures is the same shape, size, and orientation.

6. The pad conditioning disk of claim 4 , wherein the array of microfeatures varies by at least one of shape, size, or orientation.

7. 2. The pad conditioning disk of claim 1, wherein the at least one discrete element comprises at least two discrete elements, the at least two discrete elements each including at least one microfeature having the same size and shape but different orientations relative to a respective reference point.

8. The pad conditioning disc of claim 1 , wherein the at least one discrete element is attached to the pad conditioning disc by an adhesive.

9. The pad conditioning disk of claim 1 , wherein said at least one discrete element is repositionably attached to said pad conditioning disk.

10. The pad conditioning disc of claim 1 , wherein the at least one discrete abrasive element comprises at least five discrete abrasive elements.

11. The pad conditioning disc of claim 1 , wherein the at least one microfeature of the at least one discrete abrasive element comprises superabrasive grit.

12. 12. The pad conditioning disc of claim 11, wherein the at least one microfeature of the at least one discrete abrasive element comprises CVD diamond.

13. The pad conditioning disk of claim 1 , wherein the at least one microfeature of the at least one discrete abrasive element comprises a ceramic material.

14. The pad conditioning disk of claim 1 , wherein the at least one discrete abrasive element comprises a working surface on which the at least one microfeature is disposed and a carrier, the carrier comprising a metal substrate.

15. The pad conditioning disc of claim 1 , wherein the pad conditioning disc comprises a carrier on which the at least one discrete abrasive element is disposed.

16. 16. The pad conditioning disc of claim 15, wherein the carrier of the pad conditioning disc is stainless steel.

17. 1. A method of forming a pad conditioning disc, comprising: Preparing for a career and At least one discrete abrasive element, the at least one discrete element comprising at least one microfeature having a base and a top, the microfeature comprising at least three facets having at least three edges, each edge being between an adjacent pair of facets and extending from the base, the at least three edges not all being the same length, the at least one microfeature having a leading edge, the leading edge being: (i) coincident with the shortest edge of the at least three edges; or (ii) if two of the at least three edges are the same length but shorter than the other edge, then midway between each of the two edges and extending from the base to the top of the microfeature; Providing at least one discrete abrasive element; orienting and disposing the at least one discrete abrasive element on the carrier such that the leading edge of the at least one microfeature forms an angle of at least 5 degrees with a direction of instantaneous rotation of the pad conditioning disk; A method comprising:

18. 20. The method of claim 17, wherein orienting and disposing the at least one discrete abrasive element comprises orienting and disposing at least two discrete abrasive elements on the carrier, wherein a leading edge of at least one microfeature of each of the at least two discrete abrasive elements forms an angle different from a direction of instantaneous rotation of the pad conditioning disk.

19. 20. The method of claim 17, wherein orienting and disposing the at least one discrete abrasive element comprises orienting and disposing at least two discrete abrasive elements on the carrier, wherein a leading edge of at least one microfeature of each of the at least two discrete abrasive elements forms the same angle with a direction of instantaneous rotation of the pad conditioning disk.

20. The method of claim 17 further comprising repositioning at least one discrete abrasive element.

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