WO2023126761A1

WO2023126761A1 - Conditioning disk with microfeatures

Info

Publication number: WO2023126761A1
Application number: PCT/IB2022/062481
Authority: WO
Inventors: Junqing Xie; Matthew C. FRITZ; Uma Rames Krishna Laguda
Original assignee: 3M Innovative Properties Company
Priority date: 2021-12-31
Filing date: 2022-12-19
Publication date: 2023-07-06
Also published as: TW202339904A

Abstract

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

Description

CONDITIONING DISK WITH MICROFEATURES

Background

A certain class of pads are used for the chemical-mechanical polishing of semiconductor wafers to a high degree of flatness and smoothness. These pads (CMP pads) are rotated and contacted with a semiconductor surface in conjunction with a slurry to abrade material from the wafer and create a polished surface. Exposure to both the abrasive slurry and the wear of the abrasive process itself can cause the topography of the CMP pad to shift with use. In order to provide consistent, and desirable polishing performance, those CMP pads often undergo conditioning (either in-situ or ex-situ) with a conditioning disk. Use of a conditioning disk (which is also rotated and contacted to a surface, except in this case to the surface of the CMP pad) may be used to restore the working surface of the CMP pad to near its original surface geometry.

Summary

In one aspect, the present description 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, where the at least one microfeatures 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 a 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 a same length but shorter than the other edges, halfway in rotation between each of the two edges and extending from the base of the microfeature to the top. 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 a direction of instantaneous rotation of the pad conditioning disk.

In another aspect, the present description relates to a method of forming a pad conditioning disk. The method includes providing a carrier, and providing at least one discrete abrasive element. The at least one discrete element includes at least one microfeature having a base and atop, where the at least one microfeatures 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 a 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 a same length but shorter than the other edges, halfway in rotation between each of the two edges and extending from the base of the microfeature to the top. The method also includes 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. Brief Description of the Drawings

FIG. 1 is a schematic top plan view of a conditioning disk with microfeatures.

FIGS. 2A-2F are schematic top plan views of exemplary microfeature shapes.

Detailed Description

Chemical-mechanical polishing processes, conditioning processes, and related specifications vary among semiconductor fabricators. Therefore, different target surface profiles for these fabricators mean they may require different pad conditioner disk designs. For example, semiconductor fabricators may have different desired specifications for resultant pad wear rate (PWR) and surface roughness (Ra). For conventional, inorganic abrasive particle-based conditioning disks, this may mean changing the abrasive particle size, distribution, or composition in order to approach the desired specifications. For alternative, microfeature- (e.g., microreplicated abrasive features) based conditioning disks, this may mean changing the shape, size, and distribution of the microfeatures.

Described herein is a surprising approach to pad conditioning disks, where the shape of the microfeatures is selected such that performance can be adjusted through rotation of the microfeatures themselves, or by the rotation of an abrasive element having such microfeatures thereon. Accordingly, desired performance can be carefully calibrated without having to customize the entire manufacturing process.

Surprisingly, this also allows for hard to achieve combinations of Ra and PWR. 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 be increased or decreased together.

FIG. 1 is a schematic top plan view of a (CMP pad) conditioning disk. Conditioning disk 100 includes at least one discrete abrasive element 120 disposed on carrier 110, 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 a direction of instantaneous rotation of conditioning disk 100 is represented as angle 0.

Carrier 110 may be any suitable material, including metals or metal alloys, polymeric materials or blends, or other suitable substrates. 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.

Carrier 110 may include one or more mounting regions particularly adapted for disposing one or more discrete abrasive elements. These regions may be include raised or lowered regions of the carrier (machined, etched, or otherwise formed) or roughened areas to improve adhesion or attachment.

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 the use of a suitable adhesive. The adhesive may be selected for the appropriate compatibility of the adhesive with the carrier and the discrete abrasive element and other characteristics, such as the ability to provide a permanent or removable/repositionable adhesion, chemical resistance, adhesion under a range of normal use temperatures, and the like. While adhesives enable a significant class of mounting mechanisms for the at least one discrete abrasive element, the method of attachment 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.

The discrete abrasive element(s) includes a base including a working surface with at least one microfeature 122 or a plurality of microfeatures (for the ease of illustration, the size of at least one microfeature 122 is greatly exaggerated compared to atypical relationship between the at least one microfeature, the at least one discrete abrasive element, and the carrier). Being discrete, these abrasive elements do not form a continuous surface on the carrier of the pad conditioning disk. In some embodiments, these discrete abrasive elements may appear as a disc or a puck disposed on the carrier. In some embodiments, each of the discrete abrasive elements includes a working surface with 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 superabrasive grit in a metal matrix, ceramic bodies including ceramic material in an amount of at least 85% by weight, and ceramic bodies including a diamond coating. Example of superabrasive grit include cubic boron nitride (CBN) and chemical vapor disposition (CVD) diamond. Examples of other coatings and more details of the general properties and formation of precisely shaped microfeatures are described in U.S. Patent No. 10,710,211 (Lehuu et al.), which is hereby incorporated by reference.

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

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

In some embodiments, the orientation of the discrete abrasive element is such that the leading edge of the at least one microfeature forms an angle of at least 1 degree with a direction of instantaneous rotation of the pad conditioning disk. The direction (typically two directions) of instantaneous rotation is the direction which, for any given microfeature, the microfeature instantaneously travels when the conditioning disk is rotated clockwise or counterclockwise. While the direction of instantaneous rotation will vary infinitesimally in any direction, for the purposes of this description the direction of instantaneous rotation may be approximated by considering, for example, 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 affect the orientation of the discrete abrasive element and one or both may be suitable, depending on a user’s requirements. This direction is illustrated symbolically in FIG. 1 as the large arrows and the angle between this direction and the leading edge is shown as 0. In some embodiments, the orientation of the discrete abrasive element is such that the leading edge of the at least one microfeature forms an angle of at least 2 degrees with a direction of instantaneous rotation of the pad conditioning disk. In some embodiments, the orientation of the discrete abrasive element is 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. In some embodiments, the orientation of the discrete abrasive element is such that the leading edge of the at least one microfeature forms an angle of at least 10 degrees with a direction of instantaneous rotation of the pad conditioning disk. In some embodiments, the orientation of the discrete abrasive element is such that the leading edge of the at least one microfeature forms an angle of at least 20 degrees with a direction of instantaneous rotation of the pad conditioning disk. In some embodiments, the orientation of the discrete abrasive element is such that the leading edge of the at least one microfeature forms an angle of at least 30 degrees with a direction of instantaneous rotation of the pad conditioning disk. In some embodiments, the orientation of the discrete abrasive element is such that the leading edge of the at least one microfeature forms an angle of at least 45 degrees with a direction of instantaneous rotation of the pad conditioning disk. Surprisingly, precise alignment of the leading edge with the direction of instantaneous rotation does not typically result in a maximum or minimum of PWR or Ra. In some embodiments and applications, this may be because of the complicated motion of both sweep and rotation by the pad conditioning disk over the surface of the CMP pad.

The asymmetry of the at least one microfeature enables 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 in any desired angle, and the properties of the pad conditioning disk may likewise vary as this orientation is changed.

In some embodiments, the discrete abrasive element includes an array of microfeatures, where each of the microfeatures in the array has a shape having a base and a top, at least three faces with at least three edges, and a leading edge, as described for the at least one microfeature elsewhere in this description. 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 each have a leading edge oriented in the same direction. In some embodiments, one or more of the size, shape, or orientation may vary pseudorandomly or in a gradient along one or more in-plane directions.

The discrete abrasive elements may be spaced on the pad conditioning disk in an equal interval around the circumference of the carrier. In some embodiments, there are five discrete abrasive elements mounted on the carrier, and therefore are about 72 degrees (with reference to the center) apart 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 sixteen discrete abrasive elements.

In some embodiments, rotation of the at least one microfeature adjusts at least one of the resulting Ra (surface roughness) or PWR (pad wear rate: e.g., in micrometers per hour or angstroms per minute under typical use conditions, for example, 4-5 psi of pressure). Because of the asymmetry (e.g., the identifiability of a leading edge), it may be possible to determine, based on a given shape, a rotation necessary for adjusting (increasing or decreasing) a desired performance parameter. In some embodiments, after formation of discrete abrasive 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 with the aid of one or more fiducial marks, optical scanning, or any other precision alignment technology. In some embodiments, this may streamline the manufacturing process because the same components may be configured to provide a wide range of desired performance while only adjusting the orientation of the discrete abrasive elements. In some embodiments, including more than one discrete abrasive element, the orientation of these discrete abrasive elements may be different in order to achieve a blended performance between the two orientations while otherwise being formed in the same way. This concept is generalizable 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 may be determined or adjusted based on real-time or near real-time information on the actual shape of the manufactured discrete abrasive element, taking into account manufacturing errors and potential defects. For example, if variation in manufacturing produces a discrete abrasive element that would contribute to a lower PWR than desired, that discrete abrasive element may be rotated versus its original target orientation in order to compensate for that otherwise potentially out- of-spec performance. In some embodiments, the discrete abrasive elements are repositionably attached on the carrier of the conditioning disk and can be optionally removed, rotated, and optionally reattached to adjust the desired performance or to compensate for wear.

Examples

The present disclosure is more particularly described in the following examples that are intended as illustrations only, since numerous modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. CMP Tool Pad Wear Rate and Pad Surface Roughness Test Methods

Measurements were conducted on pads conditioned on an Applied Materials 200 mm REFLEXION polishing tool. The conditioning cycle was run using deionized water at 2.5 lbs (1.13 kg) of downforce with the 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 which had the following relative dwell times respectively: 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. The cycle time was 13 sweeps per minute. The pad used was a 30 inch Fujibo H800 pad. The pad wear rate was determined by using an eddy current gauge, comparing the thickness of the pad initially and after use. The difference in the final versus initial pad thickness averaged over 12 testing locations (0, 90, 180, and 270 degrees at each 3, 7, and 11 inch radii) divided by the test time was reported as the pad wear rate. To determine the surface roughness of the pad, NanoFocus confocal microscope was used to measure the Ra at 2 inch (5.1 cm), 5 inch (12.7 cm), 8 inch (20.3 cm), 11 inch (27.9 cm) and 14 inch (35.6 cm) distances from center of the recently conditioned pad. The Ra was reported as the average of these 5 locations.

Ten samples for exemplary pad conditioning disks were prepared. The abrasive elements were prepared as described in U.S. Pat. No. 9,965,664 (Lehuu et al.) — hereby incorporated by reference in its entirety — for Example 10, differing only in abrasive feature geometries as described in Table 1 and as follows: number of primary features per element: 944; primary feature height: 150 micrometers, offset height: 10 micrometers, truncation depth of primary microfeatures: 0 micrometers; aspect ratio: 0.50. The offset height between the primary and secondary abrasive features is defined as the height difference between the primary feature and secondary feature. 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 from which the theoretical peak would have been formed if the sides of the pyramid would have been allowed to converge to a point. The draft angle for these geometries is defined as the angle formed with the planes normal to the two base edges element (i.e., theoretical vertical sidewalls having a draft angle of zero) adjacent to the leading edge (which in these geometries is coincident with the shortest edge) of the abrasive features. The orientation is defined as the angle in degrees with respect to direction of instantaneous rotation (although two reference directions are possible the selected direction is based on actual direction of rotation as applied and tested). Each abrasive element had precisely shaped features having at least one primary feature height, which was higher and offset to either a secondary level of features or a flat base region between the features. Five abrasive elements were prepared for each Example and assembled into an abrasive article. The assembly process was developed such that the tallest, precisely shaped features on each element, all having the same design feature height, would become planar. A planar sapphire surface was used as an alignment plate. The elements were placed onto the alignment plate such that the major surfaces having precisely shaped features were in direct contact with the alignment plate (facing down) with their second flat, major surfaces facing upwards, rotating as necessary to align the orientation as desired. The abrasive elements were arranged in a circular pattern, such that their center points were positioned along the circumference of a circle with a radius of about 1.75 inch (44.5 mm) and spaced apart equally at about 72° around the circumference. A fastening element was then applied to the exposed surface of the abrasive elements in the center 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 inch (108 mm) and a thickness of 0.22 inch (5.64 mm) was then placed face down on top of the fastening element (the back side of the carrier is machined, such that, it may be attached to the carrier arm of a REFLEXION polisher). A 10 lb (4.54 kg) load was applied uniformly across the carrier's exposed surface and the adhesive was allowed to cure for about 4 hours at room temperature.

Table 1: Pad Conditioning Disk Abrasive Feature Geometries For The Examples.

Table 2: Ra And PWR For The Examples.

Claims

What is claimed is:

1. A pad conditioning disk, comprising: at least one discrete abrasive element, the at least one discrete abrasive element comprising at least one microfeature having a base and a top; wherein 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; wherein the at least three edges are not all a same length; and wherein the at least one microfeature has a leading edge, the leading edge being either

(i) coincident with the shortest edge from a top plan view of the at least three edges, or

(ii) if two edges of the at least three edges from a top plan view are a same length but shorter than the other edges, halfway in rotation between each of the two edges and extending from the base of the microfeature to the top; wherein 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 a direction of instantaneous rotation of the pad conditioning disk.

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 microfeatures 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. The pad conditioning disk of claim 1, wherein the at least one discrete element includes at least two discrete elements, and the at least two discrete elements each include at least one microfeature, with a same size and shape but have different orientations relative to a respective reference point.

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

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

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

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

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

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

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

15. The pad conditioning disk of claim 1, wherein the pad conditioning disk includes a carrier where the at least one discrete abrasive element is disposed.

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

17. A method of forming a pad conditioning disk, comprising: providing a carrier; providing at least one discrete abrasive element, wherein the at least one discrete element includes at least one microfeature having a base and a top, the microfeature including at least three facets with at least three edges, each edge being between an adjacent pair of facets and extending from the base, wherein the at least three edges are not all a same length, and wherein the at least one microfeature has a leading edge, the leading edge being 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 a same length but shorter than the other edges, halfway in rotation between each of the two edges and extending from the base of the microfeature to the top,

-9- 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.

18. The method of claim 17, wherein orienting and disposing the at least one discrete abrasive element includes 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 a different angle with a direction of instantaneous rotation of the pad conditioning disk.

19. The method of claim 17, wherein orienting and disposing the at least one discrete abrasive element includes 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 a 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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