SYSTEM AND METHOD FOR CONDITIONING CHEMICAL MECHANICAL POLISHING APPARATUS USING MULTIPLE CONDITIONING DISKS

Abstract

A chemical mechanical polishing (CMP) apparatus provides for polishing semiconductor wafers and for conditioning the polishing pad of the CMP apparatus using multiple conditioning disks at the same time. The conditioning disks may be moved together or independently along the surface of polishing pad to condition the entire surface of the rotating polishing pad.

Description

FIELD OF THE INVENTION

The present invention relates, most generally, to semiconductor device manufacturing equipment. More particularly, the present invention relates to a chemical mechanical polishing (CMP) apparatus and methods for chemical mechanical polishing of semiconductor wafers and for conditioning the CMP apparatus.

BACKGROUND

In today's rapidly advancing semiconductor manufacturing industry, chemical mechanical polishing (CMP) is an advantageous and favored way of planarizing and polishing semiconductor substrates to remove excess materials from over a surface of the semiconductor substrate. In this manner, damascene techniques may be used to form conductive features within openings such as trenches, vias or contacts formed in insulating layers. In damascene processing, a bulk material such as a conductive material is formed over an insulating layer and within such openings formed within the insulating layer, then removed from over the top surface of the insulating layer using chemical mechanical polishing. The resulting structure includes the conductive materials filling the various openings and extending up to the top surface of the insulating layer after the excess conductive materials have been removed from over the top of the insulating layer.

Chemical mechanical polishing involves a polishing pad and includes mechanical and chemical components. The polishing pad rotates and the wafer surface desired to be polished is brought into contact with the rotating polishing pad at a wafer polishing location. The wafer, i.e. substrate, advantageously rotates to enhance polishing. A dispenser head dispenses a polishing slurry onto the polishing pad. The polishing pad is typically made of polyurethane and the pad surface is typically permeated with the polishing slurry that contains both submicron abrasives and chemicals. The quality and uniformity of the polishing pad surface is critical to providing a uniform polish to the wafers being polished. In particular, the surface roughness of the polishing pad must be maintained in the same condition as several wafers are successively polished using the apparatus.

A conditioning process is used to condition the polishing pad surface and to maintain it in a desired and uniform state. The conditioning rejuvenates the polishing pad surface, removes debris from the polishing pad and maintains a stable removal rate. The conditioning member is typically a disk with a diamond grit surface that is pressed up against the rotating polishing pad during conditioning. The conditioning operation may take place concurrently with the wafer polishing operation or before or after the wafer polishing operation.

Because the polishing pad is typically much larger than conventional conditioning disks, the conditioning disk is typically slid along the polishing pad surface while the polishing pad rotates so that the entire polishing pad surface can be conditioned by the comparatively small conventional conditioning disk that may be about 4 inches in diameter or less. Typically, a particular number of scans or sweeps across the radius of the polishing pad, are desired to be made in a given time frame to provide a desired level of conditioning. As the size of the polishing pad increases, the scan speed of the conditioning disk being swept across the polishing pad surface must increase in order to maintain a given number of sweeps per minute. As the speed of the conditioning disk sliding across the surface increases, however, the quality of the condition operation diminishes.

Conditioning the entire polishing pad surface becomes more challenging as semiconductor wafer sizes increase. The increase in semiconductor wafer sizes mandates a corresponding increase in the size of the polishing pad. For example, wafer sizes are now as large as 450 millimeters in diameter and such wafers are polished using polishing pads that may be as great as 1 meter to 45 inches in diameter. This increased size requires a greater surface area to be covered during the conditioning process, as above. Conditioning the entire polishing pad surface is particularly challenging due to the difficulty of manufacturing diamond grit surfaces of the conditioning disks at larger dimensions. It is difficult to maintain the uniformity and quality of diamond grit conditioning disks that are greater than about four inches in diameter because such disks must be substantially completely flat and any deviation from planarity will cause diamond grit to become disengaged from the surface, causing contamination and scratches on the polishing pad and on the wafer surface.

It is therefore important to provide a system and method for conditioning a CMP polishing pad as the size of the polishing pad increases. The present invention addresses these shortcomings and challenges.

SUMMARY OF THE INVENTION

To address these and other needs and in view of its purposes, the present invention provides, in one aspect, a method for performing chemical mechanical polishing (CMP) on a substrate. The method includes simultaneously polishing the substrate or a material formed over the substrate, on a polishing pad in a CMP apparatus and conditioning the polishing pad with more than one separately controllable conditioning member by urging a diamond grit surface of each of the conditioning members against the polishing pad.

According to another aspect, provided is a method for conditioning a polishing pad of a CMP apparatus comprising simultaneously urging more than one separately controllable conditioning surface of a conditioning member against a rotating polishing pad of the CMP apparatus.

According to yet another aspect, provided is a chemical mechanical polishing apparatus. The apparatus includes a polishing pad fixedly disposed on a rotatable platen. The apparatus further includes a carrier that secures a semiconductor wafer that is being polished, against the polishing pad. The chemical mechanical polishing apparatus further includes more than one discrete, separately controllable conditioning fixture, each including a conditioning disk in contact with the polishing pad.

BRIEF DESCRIPTION OF THE DRAWING

The present invention is best understood from the following detailed description when read in conjunction with the accompanying drawing. It is emphasized that, according to common practice, the various features of the drawing are not necessarily to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Like numerals denote like features throughout the specification and drawing.

FIG. 1 is a perspective view illustrating aspects of a chemical mechanical polishing apparatus according to the invention;

FIG. 2 is a perspective view illustrating other aspects of a multiple conditioning disk CMP apparatus according to the invention;

FIG. 3 is a top view illustrating an exemplary arrangement of multiple conditioning members according to an aspect of the invention; and

FIG. 4 is a top view illustrating another exemplary arrangement of multiple conditioning members according to an aspect of the invention.

DETAILED DESCRIPTION

The invention provides for using multiple conditioning disks to condition a polishing pad in a CMP apparatus at the same time. The conditioning may take place in-situ, i.e. at the same time as the wafer polishing operation is being carried out, or it may take place before or after the wafer polishing operation is carried out on a semiconductor wafer. The invention finds application for various sized polishing pads and for polishing semiconductor wafers of various sizes. The multiple conditioning disk arrangement and method may be used in conjunction with various orientations and arrangements of CMP apparatuses. The conditioning disks may be separately controllable.

FIG. 1 is a perspective view showing rotatable platen 1 with polishing pad 3 including surface 7, fixedly secured to platen 1. Platen 1 rotates along direction of rotation 5 and at any of various suitable speeds. Wafer carrier 9 positions wafer 11 (shown separately) on polishing pad 3 at the polishing location. Polishing pad 3 may be made of polyurethane or other suitable materials. Force F applied along force direction 15 urges wafer carrier 9 downward toward and against polishing pad 3. Although not visible in FIG. 1, wafer 11 will be disposed underneath wafer carrier 9 at interface 13 between wafer carrier 9 and polishing pad 3. Wafer carrier 9 advantageously rotates along direction 29. This rotation may take place at the same time that platen 1 rotates along rotation direction 5. Slurry dispenser 19 dispenses slurry 19 at dispense location 21. Due to rotation, fresh slurry 23 spreads beneath wafer carrier 9 and therefore wafer 11 and spent slurry 25 exits the polishing location.

Also illustrated in FIG. 1 are two conditioning members 31. Although not illustrated as being positioned on polishing pad 3 in the illustrated embodiment, it should be understood and will be subsequently illustrated that both of conditioning members 31 may be disposed on surface 7 of polishing pad 3 simultaneously and at various locations and disposed various distances from one another. Additional conditioning members 31, i.e. more than two, may also be disposed on surface 7 of polishing pad 3 simultaneously. Conditioning members 31 each include a conditioning disk 33 that forms the bottom portion thereof in the illustration of FIG. 1. Exposed conditioning surface 35 of conditioning disk 33 is preferably formed of a commonly known diamond grit material advantageously used to condition polishing pad 3. In other exemplary embodiments, conditioning surface 35 may be formed of other suitable materials such as scouring materials or it may include bristles such as a brush. Conditioning disk 33 may have a diameter of about 4 inches or 100 mm in one exemplary embodiment, but other sizes may be used in other exemplary embodiments. When pressed against polishing pad 3, conditioning disks 33 and conditioning members 31 may rotate about axis 37 along direction of rotation 39. In some exemplary embodiments, conditioning disks 33 may not rotate. Various conventional means may be used to urge conditioning disk 33 and conditioning surface 35 against surface 7 of polishing pad 3 and to effect the rotation.

When conditioning disk 33 is disposed against polishing pad 3, the associated conditioning member 31 may be moved, preferably slid, along polishing pad 3 such that the entire surface 7 of rotating polishing pad 3 is conditioned. The conditioning disks 33 and conditioning member 31 may be separately controllable and may rotate at the same or different speeds and may be translated separately or in unison along surface 7 of polishing pad 3.

FIG. 2 is a perspective view showing another aspect of the multiple conditioning disk CMP apparatus according to the invention showing a plurality (two) of conditioning disks 33 on polishing pad 3. Each conditioning disk 33 is retained by an associated conditioning member 31 not illustrated in FIG. 2. According to one exemplary embodiment, the entire surface 7 of polishing pad 3 can be conditioned as platen 1 and polishing pad 3 rotate along direction 5, by sliding, i.e. translating, either or both of conditioning disks 33 along the direction of exemplary radius 47. Either or both of conditioning disks 33 may be moved both proximally toward and distally away from center point 43 of polishing pad 3, i.e. back and forth along a radius of polishing pad 3. According to one exemplary embodiment, each conditioning disk 33 may move along a scan direction along radius 47. According to one particular exemplary embodiment, one conditioning disk 33 may slide forward and backward, or backward and forward, along segment 46 of radius 47 and a second conditioning disk 33 may slide forward and backward along segment 48 of radius 47. In this manner, the entire radius of polishing pad 3, and hence the entire rotating polishing pad 3, will be scanned by one of conditioning disks 33. Conditioning disks 33 may move in unison or with respect to each other. As the scan speed of a conditioning disk 33 being slid along surface 7 increases, the quality of conditioning degrades. As such, according to the multi-conditioning disk arrangement, a desired number of conditioning scans per minute can be achieved at essentially half the scan speed because each conditioning disk 33 only covers about half of the scan distance along radius 47 when two conditioning disks 33 are used. This is especially advantageous as polishing pad 3 sizes increase such as to 45 inches or greater. According to various exemplary embodiments, the respective conditioning disks 33 may move along the same or different, angularly spaced radius lines, to cover the entire polishing pad 3. According to other exemplary embodiments conditioning disks 33 may move in other directions to scan the entire rotating polishing pad 3.

Now turning to FIG. 3, conditioning members 31 disposed on polishing pad 3 are coupled to each other and conditioning arm 53 by way of mechanical coupling 55. Conditioning members 31 may be spaced apart by various suitable distances. Mechanical coupling 55 may be pivotable about conditioning arm 53 or it may be fixed with respect to conditioning arm 53. Mechanical coupling 55 may be rigid or dynamically expandable and retractable, allowing for relative motion between conditioning member 31. Conventional means are used to apply force downward, urging the conditioning disks disposed beneath conditioning members 31, against surface 7 of polishing pad 3. With conditioning members 31 disposed against polishing pad 3, conditioning arm 53 may effectuate movement of conditioning members 31 along any direction in the x-y plane of surface 7 of polishing pad 3, or rotationally as indicated by arrow 59. Conventional mechanical means may be used. According to this exemplary embodiment, the speed of rotation of the conditioning members 31 may be separately controllable.

FIG. 4 shows another exemplary arrangement in which conditioning members 31 are capable of independent movement. Each conditioning member 31 is coupled to a corresponding conditioning arm 61 and each conditioning arm 61 may be coupled to separate mechanical movement means that separately move conditioning arms 61 and corresponding conditioning members 31 in any direction along polishing pad 3 to carry out the conditioning operation. In FIGS. 3 and 4, it should understood that each conditioning member 31 may be rotatable about its axis and such rotation may take place during the translational movement in which conditioning members 31 are slid along surface 7 of polishing pad 3.

Dimensions of the features may vary according to various exemplary embodiments. According to one exemplary embodiment, the diameter of conditioning disks 33 may be about four inches or less to advantageously maintain a substantially flat and defect free diamond grit or other polishing surface 35. Wafer 11 may include various diameters ranging from 100 mm to 450 mm and polishing pad 3 may have a diameter of up to about 1 meter or 45 inches in various exemplary embodiments.

According to an exemplary method of the invention, conditioning of polishing pad 3 may take place during, before or after, the wafer polishing operation in which a wafer is retained within wafer carrier 9 and polished. Conditioning may involve simultaneous rotation of one or more of the conditioning members 31 and translation of conditioning members 31 along polishing pad 3 in any direction, straight or curved.

According to one exemplary embodiment, the conditioning arm 53 or conditioning arms 61 may be coupled to a programmable controller that controls the motion of the conditioning arm and hence the associated conditioning member or members 31, i.e. the rotational speed of conditioning member 31 and the location and translational speed of conditioning member 31 being slid along polishing pad 3. According to one exemplary embodiment, such a controller may be programmed to cause a first conditioning member 31 to slide along a first radial segment of polishing pad 3 and to also cause a second conditioning member 31 to slide along another radial segment of polishing pad 3 such that each conditioning member 31 moves radially inward and outward but each scans only about half the radial distance such that, together, the entire radius of the polishing pad is scanned and hence the entire rotating polishing pad conditioned. According to another exemplary embodiment, there may be greater than the two conditioning members used at the same time and they may be positioned at various locations on the polishing pad with respect to the wafer polishing location, i.e. proximate or distal to the polishing location. The programmable controller may control the conditioning members separately or collectively.

The preceding merely illustrates the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples and conditional language recited herein are principally intended expressly to be only for pedagogical purposes and to aid in understanding the principles of the invention and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents and equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.

This description of the exemplary embodiments is intended to be read in connection with the figures of the accompanying drawing, which are to be considered part of the entire written description. In the description, relative terms such as “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described and/or as shown in the drawing under discussion. These relative terms are for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Terms concerning attachments, coupling and the like, such as “connected” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise.

Although the invention has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly, to include other variants and embodiments of the invention, which may be made by those skilled in the art without departing from the scope and range of equivalents of the invention.

Claims

1. A method for performing chemical mechanical polishing (CMP) on a substrate, comprising:

simultaneously polishing said substrate or a material disposed over said substrate, on a polishing pad in a CMP apparatus and conditioning said polishing pad with more than one separately controllable conditioning member by urging a diamond grit surface of each said conditioning member against said polishing pad.

2. The method as in claim 1, further comprising rotating each said diamond grit surface of each said conditioning member.

3. The method as in claim 1, wherein each said conditioning member comprises a disk and wherein said diamond grit surface forms a surface of said disk.

4. The method as in claim 1, wherein said polishing pad is disposed on and in fixed relation with respect to a platen, and said polishing comprises rotating said platen.

5. The method as in claim 4, further comprising simultaneously sliding each said conditioning member along a radial direction of said polishing pad including sliding a first one of said conditioning members only along a first segment of a radius of said polishing pad and sliding a second one of said conditioning members along a further segment of said radius of said polishing pad such that all locations of said polishing pad are conditioned.

6. The method as in claim 1, further comprising translating each said conditioning member against a surface of said polishing pad, wherein said more than one conditioning member are coupled to one another.

7. The method as in claim 1, wherein said conditioning said polishing pad with more than one separately controllable conditioning member comprises translating said conditioning members with respect to each other and against a surface of said polishing pad.

8. A method for conditioning a polishing pad of a chemical mechanical polishing (CMP) apparatus comprising simultaneously urging more than one separately controllable conditioning member against a rotating polishing pad of said CMP apparatus, each said conditioning member including a conditioning surface contacting said rotating polishing pad.

9. The method as in claim 8, wherein each said conditioning surface comprises a diamond grit surface of a disk.

10. The method as in claim 8, wherein said simultaneously urging comprises independently translating each said conditioning surface along a surface of said rotating polishing pad.

11. The method as in claim 8, further comprising sliding each said conditioning surface against a surface of said polishing pad, wherein said conditioning members are coupled to one another.

12. The method as in claim 8, further comprising polishing a material formed over a substrate, on said rotating polishing pad at the same time as said simultaneously urging.

13. The method as in claim 8, further comprising simultaneously sliding a first one of said conditioning surfaces along a first segment of a radius of said rotating polishing pad and separately sliding a second one of said conditioning surfaces against a further segment of a radius of said rotating polishing pad such that said entire polishing pad is conditioned.

14. A chemical mechanical polishing (CMP) apparatus comprising:

a polishing pad fixedly disposed on a rotatable platen;

a carrier that secures a semiconductor wafer that is being polished, against said polishing pad; and

more than one discrete conditioning fixture, each being individually controllable and including a conditioning disk in contact with said polishing pad.

15. The CMP apparatus as in claim 14, wherein each said conditioning disk has a diamond grit surface and each said discrete conditioning fixture comprises movement means for causing each said associated conditioning disk to slide across said polishing pad.

16. The CMP apparatus as in claim 15, wherein said discrete conditioning fixtures are coupled to one another by an expandable and retractable member.

17. The CMP apparatus as in claim 15, wherein said discrete conditioning fixtures are capable of independent translational motion with respect to one another.

18. The CMP apparatus as in claim 14, further comprising means for exerting a force directing each said conditioning disk against said polishing pad.

19. The CMP apparatus as in claim 14, wherein each said conditioning disk includes one of bristles and a diamond grit surface and each said discrete conditioning fixture is rotatable.

20. The CMP apparatus as in claim 14, wherein said semiconductor wafer includes a diameter of about 450 mm and each said conditioning disk is a surface of a disk having a diameter of about 100 mm.