CMP apparatuses with polishing assemblies that provide for the passive removal of slurry

Chemical mechanical planarization apparatuses with polishing assemblies that provide for the passive removal of slurry are provided. In accordance with an embodiment, a work piece polishing assembly comprises a polishing pad comprising a polishing surface and an exhaust aperture that extends through the polishing pad from the polishing surface and is configured to receive a slurry from the polishing surface. An underlying member is disposed underlying the polishing pad and comprises a peripheral surface. The underlying member comprises a channel that is in fluid communication with the aperture and that opens at the peripheral surface of the underlying member.

FIELD OF THE INVENTION

The present invention relates generally to apparatuses for polishing a surface of a work piece. More particularly, the invention relates to chemical-mechanical planarization apparatuses with polishing assemblies that provide for the passive removal of slurry from a polishing surface.

BACKGROUND OF THE INVENTION

The manufacture of many types of work pieces requires the substantial planarization or polishing of at least one surface of the work piece. Examples of such work pieces that require a planar surface include semiconductor wafers, optical blanks, memory disks, and the like. One commonly used technique for planarizing the surface of a work piece is the chemical mechanical planarization (CMP) process. The terms “planarization” and “polishing,” or other forms of these words, although having different connotations, are often used interchangeably by those of skill in the art with the intended meaning conveyed by the context in which the term is used. For ease of description such common usage will be followed and the term “chemical mechanical planarization” will generally be used herein with that term and “CMP” conveying either “chemical mechanical planarization” or “chemical mechanical polishing.” The terms “planarize” and “polish” will also be used interchangeably.

The CMP method typically requires the work piece to be loaded into and mounted precisely on a carrier head in a manner such that the surface to be planarized is exposed. The exposed side of the work piece is then held against a polishing pad and relative motion is initiated between the work piece surface and the polishing pad in the presence of a polishing slurry. The mechanical abrasion of the surface caused by the relative motion of the work piece with respect to the polishing pad combined with the chemical interaction of the slurry with the material on the work piece surface ideally produces a planar surface.

The polishing slurry can be applied to the surface of the polishing pad by deposition of the slurry directly onto the polishing surface of the polishing pad or, alternatively, the slurry can be delivered from a manifold assembly underlying the polishing pad through supply apertures or “through-holes” within the polishing pad. Spent slurry, that is, slurry that has reacted with the work piece surface and contains by-products from the polishing process then is removed from the surface of the polishing pad so that it can be replaced by fresh slurry for uniform planarization.

As an alternative to traditional CMP, electrochemical mechanical planarization (ECMP) can be used for polishing the work piece. ECMP involves removal of material from the surface of the work piece through the action of an electrolyte solution, electricity, and relative motion between the work piece and the surface of the polishing pad. The ECMP slurry, or electrolyte, also needs to be removed from the surface of the polish pad as does traditional CMP slurry.

Various methods have been used to remove the spent slurry from the polishing pad. One method utilizes polishing pads having grooves within the surface of the polishing pad that permit the spent slurry to flow out from the center of the polishing pad to be exhausted from a peripheral edge of the pad. While wide grooves would permit the slurry to flow freely, the width of the grooves is limited because wider grooves result in less polishing pad available for contact with the work piece. Accordingly, with narrow grooves, the flow of the slurry may be restricted and the residence time of the spent slurry on the surface of the pad may be longer than desired. As a result, a pressure gradient forms across the polishing pad from the center to the peripheral edge. This slurry build-up also may cause the work piece to hydroplane on the polishing pad, decreasing the polishing rate. Moreover, as the polishing pad wears, the depth of the grooves becomes even smaller, thus further reducing the volume of slurry the grooves can carry and compounding the above problems.

Another method for removing slurry from the surface of a polishing pad includes exhaust ports that extend through the polishing pad and the underlying polishing assembly. The polishing assembly can include one or more polishing sub-pads, such as a backing pad, a platen that is configured to support the polishing pad, and a manifold assembly that distributes the slurry to the surface of the polishing pad. The exhaust ports may use the force of gravity to exhaust the slurry or may be connected to a pump that pumps the slurry from the polishing pad. Accordingly, the exhaust ports are configured to extend, not only through the polishing pad, but also any polishing sub-pads, the platen and the manifold assembly. Because the polishing sub-pads, platen, and manifold assembly are manufactured separately, the exit ports add a high degree of complexity to the designing and manufacturing of the polishing pad assemblies.

Accordingly, it is desirable to provide work piece polishing assemblies that provide for the efficient and passive removal of slurry from the surface of a polishing pad of a CMP apparatus. In addition, it is desirable to CMP apparatuses that utilize such work piece polishing assemblies. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.

BRIEF SUMMARY OF THE INVENTION

In accordance with an exemplary embodiment of the present invention, a work piece polishing assembly comprises a polishing pad comprising a polishing surface and an exhaust aperture that extends through the polishing pad from the polishing surface and is configured to receive a slurry from the polishing surface. An underlying member is disposed underlying the polishing pad and comprising a peripheral surface. The underlying member comprises a channel that is in fluid communication with the exhaust aperture and that opens at the peripheral surface of the underlying member.

In accordance with another exemplary embodiment of the present invention, a chemical mechanical planarization apparatus comprises a work piece carrier configured to hold a work piece horizontally and a polishing assembly. The polishing assembly comprises a polishing pad disposed parallel to the work piece and an underlying member underlying the polishing pad. The underlying member comprises a channel configured to receive a slurry from the polishing pad and to permit the slurry to be exhausted from a peripheral surface of the underlying member.

In accordance with a further exemplary embodiment of the present invention, a work piece polishing assembly comprises a polishing means for polishing a work piece during planarization using a slurry and an underlying member underlying the polishing means. The polishing means has an aperture that extends therethrough. The underlying means comprises a removal means for receiving slurry from the polishing means and permitting the slurry to be exhausted from a peripheral surface of the underlying member. The removal means comprises a portion that has a cross-sectional area perpendicular to the direction of slurry flow through the portion that is greater than a cross-sectional area of the aperture.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a side view of a CMP apparatus50in accordance with an exemplary embodiment of the present invention. CMP apparatus comprises a work piece carrier52and a polishing assembly54. The work piece carrier52holds in a substantially horizontal plane a work piece58during the process of polishing or planarizing the work piece. The work piece carrier52is configured to press the work piece against a polishing surface, described below, while relative motion between the work piece and the polishing surface is effected. In one embodiment, the wafer carrier52rotates work piece58about an axis66. In another embodiment, wafer carrier52moves the work piece58linearly or orbitally relative to a polishing surface. Polishing assembly54comprises a horizontal polishing pad56, the hardness and density of which depend on the material that is to be polished and the degree of precision required in the polishing process. Polishing pad56may be comprised of a top-pad configured to contact the surface of the work-piece as well as one or more sub-pads. The hardness and density of the top-pad and each sub-pad may differ from each other. Polishing pad56is supported by and attached to a platen60, which in turn overlies a manifold assembly64. Manifold assembly64may comprise one or more layers that are pressed together to form the assembly. Polishing assembly54is configured to rotate, orbit, and/or dither by a motor (not shown) that is coupled thereto.

During a polishing operation, the work piece58is pressed against a polishing surface62of the polishing pad56with a desired amount of “down force” such that the polishing surface62exerts a desired amount of pressure against the surface of the work piece. When the work piece58comprises a low dielectric constant material, it may be desirable to limit this pressure to a reduced pressure range, which typically includes the pressure range of from about 0.10 psi to about 3.0 psi. Relative lateral motion is induced between the carrier52and the polishing pad56to promote polishing. A slurry, which can be abrasive or non-abrasive, is applied to the polishing surface62of the polishing pad56. Spent slurry then is passively removed from the polishing surface62.

FIG. 2is an exploded isometric view andFIG. 3is a cross-sectional view of polishing assembly54, in accordance with an exemplary embodiment of the invention, that delivers fresh polishing slurry to polishing surface62of polishing pad56and allows for the removal of spent slurry from the polishing pad via a peripheral surface of the polishing assembly. Polishing assembly54comprises a distribution manifold68disposed within the manifold assembly64. A pump70forces the slurry through a fluid line72and through distribution manifold68to one or more supply conduits74formed within platen60. The slurry then may suitably flow from supply conduits74through one or more supply holes76within polishing pad56. Polishing assembly54is connected to a drive assembly78that is operative to move polishing assembly54in an orbital pattern. Alternatively, it will be appreciated that the drive assembly78may be operative to move polishing assembly54in a rotary, linear or oscillatory pattern or any combination of orbital, linear, oscillatory, and rotary patterns.

As illustrated inFIG. 3, polishing pad56has one or more grooves80that permit the slurry to flow from supply holes76over the polishing surface62. The grooves80may be molded into the polishing pad56when originally fabricated or may be machined into the pad after fabrication. In one exemplary embodiment, relative to a coordinate system130, the grooves may run in the “x” and “y” directions to form a grid with parallel x-direction grooves82and crossing perpendicular y-direction grooves84. In another exemplary embodiment, x-direction grooves80may comprise major x-direction grooves86and minor x-direction grooves88and y-direction grooves84may comprise major y-direction grooves90and minor y-direction grooves92. The major grooves have a larger cross-sectional area perpendicular to the direction of slurry flow than the minor grooves. The area perpendicular to the direction of slurry flow is defined as the width of the groove80or84in the x- or y-direction, respectively, multiplied by the depth of the groove in the z-direction. Minor x-direction grooves88and minor y-direction grooves92intersect at supply holes76, causing slurry to flow from supply holes76to major grooves86and90. The minor grooves88and92and the major grooves86and90assist in the distribution of the slurry across polishing pad56during planarization. While polishing pad56is illustrated with minor grooves and major grooves in a perpendicular relationship, it will be appreciated that grooves80can be of any cross-sectional size and can be configured in any suitable pattern that is configured to facilitate distribution of slurry. For example, polishing pad56may comprise only major grooves or may comprise only minor grooves. Alternatively, polishing pad56may comprise grooves of a uniform cross-sectional area that are in a hexagonal or other pattern.

Referring again toFIGS. 2 and 3, in addition to supply holes76for delivery of the slurry to the polishing surface62, polishing pad56also comprises one or more exhaust apertures94through which spent slurry may flow away from polishing surface62. Exhaust apertures94have an inlet end96through which spent slurry enters at polishing surface62and an exit end98. The apertures94are in fluid communication with channels of an underlying member110of the polishing assembly, such as, for example, a polishing sub-pad (not shown), or the manifold apparatus. In one exemplary embodiment, the underlying member110is platen60, which comprises one or more channels100that extend horizontally through platen60. In one embodiment, channels100are disposed and open at a surface102of platen60, as illustrated. In another embodiment, channels100are disposed wholly within platen60and are in fluid communication with exhaust apertures94via conduits (not shown) within the platen. The exit end98of each exhaust aperture94opens to one of the channels100. The channels have at least one end140that extends to a peripheral surface104of platen60. As used herein, the term “peripheral surface” refers to an outer surface of a structure that is substantially perpendicular to a horizontal surface of the structure. In one exemplary embodiment, the channels100have a cross-sectional area126perpendicular to the direction of flow that is greater than a cross sectional area124of the exhaust apertures94. In this embodiment, the term “cross-sectional area126” of channels100is the cross-sectional area of the channels100that is perpendicular to the direction of slurry flow and is defined as a width138of the channel100that is perpendicular to the direction of flow, multiplied by the depth142of the channel in the z-direction. As illustrated inFIG. 2, channels100may comprise channels200that extend in the x-direction and perpendicular channels202that extend in the y-direction. Thus, the cross-sectional area126of channels200is defined as a width of the channel in the y-direction multiplied by the depth142of the channel in the z-direction. Similarly, the cross-sectional area126of channels202is defined as a width of the channel in the x-direction multiplied by the depth142of the channel in the z-direction. In the vertical exhaust apertures94, the term “cross-sectional area124” of the exhaust apertures94is the cross-sectional area perpendicular to the direction of slurry flow and is defined as a width136in the x-direction multiplied by the width (not shown) in the y-direction. In this regard, because the channels open to atmospheric pressure at the peripheral surface of the platen, and because the channels have a cross-sectional area126that is greater than the cross-sectional area124of the exhaust apertures, the spent slurry within the exhaust apertures and the channels is at atmospheric pressure so that the slurry flows passively from the polishing surface62of polishing pad56through exhaust apertures94, as illustrated by arrows115, and is exhausted at the peripheral surface104of the platen. Accordingly, there is minimal or no backup of the slurry in the channels100or exhaust apertures94that may increase the likelihood of hydroplaning of the work piece on the polishing surface62. In addition, because the channels100are not in the polishing pad56, exhaust flow of the slurry is not affected by wear of the polishing pad.

In one exemplary embodiment of the invention, the channels100are not uniform in size, cross-sectional area or pattern. For example, the cross-sectional areas126of the channels may be greater near the periphery of the platen than at the center. In another embodiment, the cross-sectional area of the channels may vary based on the location of the exhaust apertures with which they are in fluid communication, as described in more detail below. In yet another example, the channels do not lie in an x-y perpendicular pattern but, rather, lie in any other pattern that permits exhausting of the spent slurry to the periphery of the platen.

In one exemplary embodiment of the present invention, the channels100are disposed underlying the grooves80of polishing pad56and the pattern of the channels100mimics at least a portion of the pattern of the grooves80in the polishing pad56. In this regard, regions of the polishing pad that contact the work piece (“land areas”)122are fully supported by the platen60so that the polishing pad56maintains sufficient contact with the work piece during planarization. In an exemplary embodiment, the width138of the channels is substantially equal to the width136of apertures94so that the “land areas”122of the polishing pad are fully supported by platen60. In another exemplary embodiment of the invention, the width138of the channels is greater than the width136of exhaust apertures94.

Referring toFIG. 4, in one embodiment of the invention, polishing pad56has a plurality of supply holes76and a plurality of exhaust apertures94, with at least one exhaust aperture disposed proximate to a supply hole76. For example, in an exemplary embodiment of the present invention for the polishing of 300 mm work pieces, an exhaust aperture94is within about 0.25 inches to about 1 inch of a supply hole76. In another exemplary embodiment, an exhaust aperture94is within 0.5 to about 0.7 inches of a supply hole76. However, it will be appreciated that the exhaust apertures94can be any suitable distance from the supply holes76so that the configuration of supply holes and exhaust apertures minimizes the residence time of the spent slurry at the polishing surface62. As fresh slurry flows from the supply holes76to the polishing surface62, it reacts with the work piece surface. Because the exhaust apertures94are close to the supply holes76, the spent slurry can immediately drain from the polishing surface62so that spent slurry does not significantly dilute fresh slurry across the polishing surface.

Referring toFIGS. 5 and 6, in accordance with another exemplary embodiment of the present invention, one or more channels100are disposed wholly within platen60and are configured as one or more reservoirs116that have a width, indicated by double-headed arrow132, that is greater than width136of the exhaust apertures94of polishing pad56. The reservoir116has at least one end128that is open to the peripheral surface104of platen60. In one embodiment, due to the width of reservoir116, one or more supply tubes108extend from a surface160of platen60through the reservoir116to supply conduits74within platen60, which are in axial alignment and fluid communication with supply tubes108. Supply tubes108may be formed of flexible material, such as a polymer, or a rigid material, such as a thermoset polymer, a ceramic, or a metal. Exhaust apertures94are coupled to the reservoir(s)116via exhaust conduits106that extend through a portion of platen60. Accordingly, during the planarization process, spent slurry can flow from the polishing surface62through exhaust apertures94and exhaust conduits106to reservoir(s)116, where it flows horizontally, as illustrated by arrows120, under atmospheric pressure, around supply tubes108to exhaust at peripheral surface104of platen60.

As noted above, the underlying member110of a polishing assembly also can be a polishing sub-pad. Referring toFIG. 7, a polishing assembly150in accordance with another exemplary embodiment of the present invention comprises polishing top-pad56having supply holes76and exhaust apertures94, platen60having supply conduits74, and manifold assembly64disposed thereunder. A polishing sub-pad152is interposed between the top-pad56and the platen60. Polishing sub-pad152may comprise a polishing pad backing layer, an insulating layer, a diaphragm, or the like. Polishing sub-pad152may comprise one or more channels100disposed horizontally on a surface154of polishing sub-pad152or within polishing sub-pad152. The exit end98of each exhaust aperture94opens to one of the channels100. The channels have at least one end140that extends to the peripheral surface104of polishing sub-pad152. As described above, in one exemplary embodiment, the channels100have a cross-sectional area126that is greater than a cross sectional area124of the apertures94. Accordingly, because the channels open to atmospheric pressure at the peripheral surface of the polishing sub-pad, and because the channels have a cross-sectional area that is greater than the cross-sectional area of the exhaust apertures, the spent slurry within the apertures and the channels is at atmospheric pressure so that the slurry flows passively from the polishing surface62of top-pad56through exhaust apertures94and then flows horizontally, as illustrated by arrows125, to be exhausted at the peripheral surface104of the polishing sub-pad.

It will be appreciated that, while the above embodiments describe a CMP apparatus with a polishing assembly that is configured for the supply delivery of slurry through the polishing assembly via a distribution manifold, any other suitable means can be used to deliver the slurry to the polishing surface62of the polishing pad56. For example, the slurry can be deposited directly onto the polishing surface62of the polishing pad. Accordingly, during planarization, the slurry will be distributed across the polishing pad by the motion of the work piece and the polishing assembly and, if present, via grooves80. The slurry can then be passively removed from polishing surface62through exhaust apertures94and channels100.