Abstract:
A conditioner disk for use on a polish pad in chemical mechanical polishing process includes a base structure a plurality of curved blades supported by the base structure. The blades radiate outwardly from a center region of the base structure and curve in a common direction.

Description:
BACKGROUND 
   The present invention relates generally to chemical mechanical polishing of substrates, and more particularly to a conditioner disk for use in chemical mechanical polishing. 
   Integrated circuits are typically formed on substrates, particularly silicon wafers, by the sequential deposition of conductive, semiconductive or insulative layers. After each layer is deposited, the layer is etched to create circuitry features. As a series of layers are sequentially deposited and etched, the outer or uppermost surface of the substrate, i.e., the exposed surface of the substrate, becomes successively less planar. This non-planar outer surface presents a problem for the integrated circuit manufacturer as a non-planar surface can prevent proper focusing of the photolithography apparatus. Therefore, there is a need to periodically planarize the substrate surface to provide a planar surface. Planarization, in effect, polishes away a non-planar, outer surface, whether a conductive, semiconductive, or insulative layer, to form a relatively flat, smooth surface. 
   Chemical mechanical polishing is one accepted method of planarization. This planarization method typically requires that the substrate be mounted on a carrier or polishing head, with the surface of the substrate to be polished exposed. The substrate is then placed against a rotating polishing pad. The carrier head may also rotate and/or oscillate to provide additional motion between the substrate and polishing surface. Further, a polishing slurry, including an abrasive and at least one chemically reactive agent, may be spread on the polishing pad to provide an abrasive chemical solution at the interface between the pad and substrate. 
   Important factors in the chemical mechanical polishing process are: substrate surface planarity and uniformity, and the polishing rate. Inadequate planarity and uniformity can produce substrate defects. The polishing rate sets the time needed to polish a layer. Thus, it sets the maximum throughput of the polishing apparatus. 
   It is important to take appropriate steps to counteract any deterioration of the polishing pad which could present the possibility of either damaging the substrate (such as by scratches resulting from accumulated debris in the pad) or reducing polishing speed and efficiency (such as results from glazing of the pad surface after extensive use). The problems associated with scratching the substrate surface are self-evident. The more general pad deterioration problems both decrease polishing efficiency, which increases cost, and create difficulties in maintaining consistent operation from substrate to substrate as the pad decays. 
   The glazing phenomenon is a complex combination of contamination, thermal, chemical and mechanical damage to the pad material. When the polisher is in operation, the pad is subject to compression, shear and friction producing heat and wear. Slurry and abraded material from the wafer and pad are pressed into the pores of the pad material and the material itself becomes matted and even partially fused. These effects reduce the pad&#39;s roughness and its ability to apply fresh slurry to the substrate. 
   It is, therefore, desirable to continually condition the pad by removing trapped slurry, and unmatting, re-expanding or re-roughening the pad material. The pad can be conditioned after a number of substrates are polished. The pad can also be conditioned at the same time substrates are polished. 
   SUMMARY 
   In one aspect, the invention is directed to a conditioner for use on a polish pad in chemical mechanical polishing process. The conditioner includes a base structure having an axis of rotation and a plurality of curved blades supported by the base structure. The blades radiate outwardly from a center region of the base structure and curve in a common direction. 
   Implementations of the invention may include one or more of the following features. The base structure may be disk-shaped. The common direction may be counter-clockwise or clockwise as viewed from a side of the base structure with the blades. Adjacent the center region, each blade may be oriented parallel to a corresponding radius extending outwardly from the axis of rotation. At an outer circumference of the conditioner, each blade may be oriented such that the tangential of a surface of the blade forms an angle between about 0° and 60° with a corresponding radius extending outwardly from the axis of rotation. The blades may be distributed at equal angular intervals about the axis of rotation. Adjacent blades of the plurality of blades may form a channel that is narrower near the center region than at an edge of the conditioner. When the conditioner disk rotates in the common direction and the adjacent curved blades contact a surface of the polish pad, the channel between adjacent curved blades may capture slurry in an area near a periphery of the conditioner disk and direct the captured slurry to the center region. When the conditioner disk rotates opposite to the common direction and the adjacent curved blades contact a surface of the polish pad, the channel between adjacent curved blades may expel slurry from the center region and directs the expelled slurry to an area the periphery of the conditioner disk. Each blade may include a bottom surface, a back surface, and a front surface. At least one of the back surface and front surface is inclined. The front surface may incline forward and forms a forward inclination angle or incline backward and forms a backward inclination angle with a reference plane perpendicular to the bottom surface. At least one of the bottom surface, the back surface, and the front surface are coated with a hardening material, such as diamond. An edge between the bottom surface and one of the back surface and the front surface may be chamfered. At least one of the bottom surface, the back surface, and the front surface may be serrated or knurled. An insert tool holder may hold an insert that forms a portion of at least one of the blades. 
   In another aspect, the invention is directed to a method of conditioning. In the method, a plurality of curved blades supported by a base structure of a conditioner is brought into contact with a polishing surface, and the base structure rotates about an axis of rotation. The blades of the conditioner radiate outwardly from a center region of the base structure and curve in a common direction. 
   Implementations of the invention may include one or more of the following features. Rotating the base structure may include rotating in the common direction such that a channel between adjacent curved blades captures slurry in an area near a periphery of the conditioner and directs the captured slurry to the center region. Rotating the base structure may include rotating opposite to the common direction such that a channel between adjacent curved blades expels slurry from the center region and directs the expelled slurry to an area the periphery of the conditioner. 
   Additional advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention may be realized by means of the instrumentalities and combinations particularly pointed out in the claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be understood more fully from the detailed description and accompanying drawings of the invention set forth herein. However, the drawings are not to be construed as limiting the invention to the specific embodiments shown and described herein. Like reference numbers are designated in the various drawings to indicate like elements. 
       FIG. 1  shows a conditioner head placed on a polishing pad for conditioning the polishing pad with a conditioner disk. 
       FIG. 2  shows a conditioner disk that includes curved blades positioned at the bottom of the conditioner disk. 
       FIG. 3A  shows a bottom view of the conditioner disk of  FIG. 2 . 
       FIG. 3B  shows a side view of the conditioner disk of  FIG. 2  along line  3 B- 3 B from  FIG. 3A . 
       FIGS. 3C-3D  each show a side view of an implementation of the conditioner disk. 
       FIG. 4  shows an implementation of a conditioner disk having curved blades that include serrated edges. 
       FIGS. 5A-5C  show a conditioner disk that includes insert tool holders for holding insert tools. 
       FIG. 6  shows a conditioner disk that includes a passage for introducing cleaning fluids to areas near the center of the conditioner disk. 
   

   DETAILED DESCRIPTION 
   A substrate can be polished at a polishing station  25  of chemical mechanical polishing (CMP) apparatus. A description of a suitable CMP apparatus may be found in U.S. Pat. No. 5,738,574, the entire disclosure of which is incorporated herein by reference. Although unillustrated, the CMP apparatus can include multiple polishing stations. 
   As shown in  FIG. 1 , the polishing station  25  includes a rotatable platen  30 , which supports a polishing pad  32 , and a pad conditioner  40 . The rotatable platen  30  and the conditioner  40  are both mounted to a machine base of the CMP apparatus. Each pad conditioner  40  includes a conditioner head  46 , an unillustrated base, and an arm  42  connecting the conditioner head  46  to the base. The base can pivot to sweep the arm  42  and the conditioner head  46  across the polishing pad surface  36 . 
   Each polishing station  25  also includes a cleaning cup, which contains a cleaning liquid for rinsing or cleaning the conditioner head  46 . The arm  42  can move the conditioner head  46  out of the cleaning cup and place the conditioner head  46  atop the polishing pad  32 . 
   The conditioner head  46  includes a conditioner disk  200  that is brought into contact with the polishing pad. The conditioner disk  200 , which will be discussed in detail below, is generally positioned at a bottom of the conditioner head  46  and can rotate around an axis  41 . A bottom surface of the conditioner disk  200  can include conditioning formations, such as protrusions or cutting edges, that contact the surface of the polishing pad  32  during the conditioning process. During conditioning, both the polishing pad  32  and the conditioning disk  200  rotate, so that these protrusions or cutting edges move relative to the surface of the polishing pad  32 , thereby abrading and retexturizing the surface of the polishing pad  32 . 
   The conditioner head  46  includes mechanisms to attach the conditioner disk  200  to the conditioner head  46  (such as mechanical attachment systems, e.g., bolts or screws, or magnetic attachment systems) and mechanisms to rotate the conditioner disk  200  around the rotating axis  41  (such as drive belts through the arm or rotors inside the conditioner head). In addition, the conditioning system  40  can also include mechanisms to regulate the pressure between the conditioner disk  200  and the polishing pad  32  (such as pneumatic or mechanical actuators inside the conditioning head or the base). These mechanisms can have many possible implementations (and are not limited to those shown in  FIG. 1 ). Suitable implementations may be found in U.S. Pat. Nos. 6,200,199 and 6,217,429, the entire disclosures of which are incorporated herein by reference. 
   Referring to  FIG. 2 , the conditioner disk  200  includes a base structure  210  in the form of a generally planar disk, and multiple curved blades  220  projecting from the bottom of the base structure  210 . Each curved blade  220  extends generally in a radial direction and includes a bottom surface  222 , a front surface  224 , and a back surface  228 . Each curved blade  220  also includes a sharp leading edge  225 . All of the curved blades  220  can be identical in shape, or the blades  220  can have different shapes. 
   Each blade  220  can extend from a central region  240  (into which the blades do not extend) to the edge of the conditioner disk  200 . Adjacent the center region  240  of the conditioner disk, the blades  220  can be oriented generally parallel toward the center of rotation of the conditioning disk, whereas at the outer edge of the conditioner disk, the blades can oriented such that the tangential of the curved blade forms an angle of about 0° to 60° to the radial direction going through the disk center and the outer tangential point. 
   As shown in  FIG. 3A , each curved blade  220  can be designed such that the front surface  224  and the back surface  228  curve in the same tangential direction. In one implementation, all the curved blades  220  are positioned and aligned to curve generally in the same tangential direction, e.g., counterclockwise. Each pair of adjacent curved blades  220  can be positioned and aligned to curve generally in the same tangential direction to form a curved recess  230 . The recess  230  is wider at the periphery of the conditioner disk  200  (at the outer opening  231  of the recess) than near the center of the conditioner disk  200  (at the inner opening  232  of the recess). 
   During conditioning, the conditioning disk  200  is moved into contact with the polishing pad and rotated. Each pair of adjacent curved blades  220  contact the polishing pad  32  so that the curved recess provides a pumping channel for slurry distribution. If the conditioner disk  200  rotates in the same tangential direction  201  as the curved blades  220 , slurry  245  on the polishing pad at periphery of the conditioner disk  200  is captured and drawn inwardly to the center of the conditioner disk  200  though the pumping channels  230 . The decreasing cross-sectional area of the pumping channels act as a funnel to increase the pressure of the slurry as it enters the center region  240  of the conditioner disk  200 , causing the entrapped slurry near the center of the conditioner disk  200  to be driven into the open cell structures or grooves in the polishing pad  32  more effectively. Thus, the conditioning disk can aid in more uniform polishing slurry distribution. 
   In contrast, if the conditioner disk  200  rotates in a tangential direction  201  which is opposite to that of the curved blades  220 , the pumping channels  230  act to suction the slurry  245  out of the open cell structures in the polishing pad at the center region  240  of the conditioner disk  200  and expel the slurry toward the periphery of the conditioner disk  200  or out of the conditioner disk  200  entirely. Thus, the conditioning disk can aid in removing slurry from the polishing pad during a rinse cycle (in which a cleaning fluid such as DI water is supplied to the polishing pad to rinse off slurry), and thereby improve the cleanliness of the polishing pad and reduce defects. 
   Referring to  FIG. 3B , the curved blade  220  is positioned at the bottom of the conditioner disk  200  and supported by the base structure  210 . The bottom surface  222  of the curved blade  220  engages the top surface of the polishing pad  32 . In one implementation, shown in  FIG. 3B , the front surface  224  of the curved blade  220  is essentially perpendicular to the bottom surface  222  of the curved blade  220 . The leading edge  225  is defined between the front surface  224  and the bottom surface  222 . As the edge  225  contacts and moves against the polishing pad  32 , it abrades or gouges the polishing pad surface, thereby providing conditioning. 
   In another implementation, shown in  FIG. 3C , the front surface  224  inclines forward and forms a forward inclination angle φ with respect to a reference plane perpendicular to the bottom surface  222 , i.e., the angle between the front surface  224  and the bottom surface  222  that contacts the polishing pad surface  32  is an acute angle. As shown in the figure, when the front surface  224  inclines forward, the front surface  224  is in front of the edge  225  with respect to the direction of travel. 
   In another implementation, shown in  FIG. 3D , the front surface  224  inclines backward and forms a backward inclination angle φ with respect to a reference plane perpendicular to the bottom surface  222 , i.e., the angle between the front surface  224  and the bottom surface  222  that contacts the polishing pad surface  32  is an obtuse angle. As shown in the figure, when the front surface  224  inclines backward, the front surface  224  is behind the edge  225  with respect to the direction of travel. 
   In the implementations of  FIGS. 3B-3D , the edge  225  can be in the form of a right angle or sharp edge. The edge  225  can also be modified, e.g., chamfered, to make the edge  225  more compatible with the conditioning process required for a given type of polishing pad material, e.g., fixed abrasive, woven cloth, or cast polyurethane. 
   In the implementations of  FIGS. 3B-3D , the front surface  224  of the curved blade  220  can be planar. However, the front surface  224  can also be convex, concave, or have other shapes. In addition, the front surface  224  and/or the bottom surface  222  can be coated with a hardening material, such as diamond or a carbide, e.g., silicon carbide, titanium carbide or tungsten carbide. The front surface  224  and/or the bottom surface  222  can also include a serrated or knurled surface for forming multiple conditioning edge facets on the curved blade  220 .  FIG. 4  shows an implementation of the conditioner head in which the curved blades  220  include serrated edges on the front surfaces  224 . 
   In another implementation, shown in  FIGS. 5A-5C , the curved blade  220  can include an insert tool holder  229  for holding an insert tool  310  that provides the contact edges  311  for the conditioner disk. The insert tool  310  can be held on the conditioning disk by conventional mechanisms, such as screws, adhesive, or press fitting. The contact edge  311  can be in the same plane as the bottom surface  222  of the blade, or they can also extend beyond the bottom surface  222 . In addition, the distance that the contact edge  311  extends beyond the bottom surface  222  can be adjustable, e.g., with an adjustment screw. 
   In yet another implementation, shown in  FIG. 6 , the conditioner disk  200  can also include a passage  280  for introducing a cleaning fluids, such as deionized water, to areas near the center of the conditioner disk  200 . The passage  280  can be positioned at or near the center of the conditioner disk  200 , such as in the central region  240  into which the blades do not extend. The cleaning fluid introduced from the passage  280  will flow into channels  230  near the center of the conditioner disk  200 . When the conditioner disk  200  rotates in a tangential direction  203  opposite that of the blades  220 , the cleaning fluid  275  near the center of the conditioner disk  200  can be driven out of channels  230  from the peripheral area of the conditioner disk  200 . 
   Parts in the conditioner disk  200  can be constructed from stainless steel, a carbide, or some combination thereof. In addition, parts in the conditioner disk can also be constructed from a hard polymer, for example, a polyphenyl sulfide (PPS), a polyimide such as Meldin, a polybenzimidazole (PBI) such as Celazole, a polyetheretherketone (PEEK) such as Arlon, a polytetrafluoroethylene (PTFE) such as Teflon, a polycarbonate, an acetal such as Delrin, or an polyetherimide (PEI) such as Ultem. 
   The materials selected for constructing the conditioner disk  200  generally depend on the construction material of the polishing pad  32 . The preferred surface characteristics of the blades  220  generally also depend on the construction material of the polishing pad  32 . For example, when the construction material of the polishing pad  32  is polyurethane (e.g., materials provided by Rodel under trade name IC1000 or IC1010), all surfaces of the blades  220  that need to contact with the surface of the polishing pad  32  are preferably coated with diamond particles. The grit size of the diamond coating can be in the range from 60 to 120 grit. The diamond coating on the blades  220  can also be treated additionally to protect the diamond coating in low pH or corrosive environment. 
   The surface characteristics of the blades  220  can also be modified to make the blades  220  more effective during conditioning process. For example, the blades  220  on the conditioner disk  200  can be constructed and machined from silicon carbide, and the surfaces of the blades  220  can coated with or transformed into amorphous diamond surfaces using currently know surface treatment process. 
   The present invention has been described in terms of a number of embodiments. The invention, however, is not limited to the embodiments depicted and described. Rather, the scope of the invention is defined by the appended claims.