US20100015895A1

US20100015895A1 - Chemical mechanical polishing pad having electrospun polishing layer

Info

Publication number: US20100015895A1
Application number: US12/173,403
Authority: US
Inventors: Jeffrey J. Hendron; Mary Jo Kulp; Craig Sungail; Fengii Yeh
Original assignee: Rohm and Haas Electronic Materials CMP Holdings Inc
Current assignee: Rohm and Haas Electronic Materials CMP Holdings Inc
Priority date: 2008-07-15
Filing date: 2008-07-15
Publication date: 2010-01-21

Abstract

Chemical mechanical polishing pads having an electrospun polishing layer are provided, wherein the electrospun polishing layer has a polishing surface that is adapted for polishing a semiconductor substrate. Also provided are methods of making such chemical mechanical polishing pads and for using them to polish semiconductor substrates.

Description

The present invention relates generally to the field of polishing pads for chemical mechanical polishing. In particular, the present invention is directed to chemical mechanical polishing pads having an electrospun polishing layer and to methods of making and using the same.
Chemical mechanical planarization, or chemical mechanical polishing (CMP), is a common technique used to planarize or polish workpieces such as semiconductor wafers. In conventional CMP, a wafer carrier, or polishing head, is mounted on a carrier assembly. The polishing head holds the wafer and positions the wafer in contact with a polishing layer of a polishing pad that is mounted on a table or platen within a CMP apparatus. The carrier assembly provides a controllable pressure between the wafer and polishing pad. Simultaneously, a polishing medium is optionally dispensed onto the polishing pad and is drawn into the gap between the wafer and polishing layer. To effect polishing, the polishing pad and wafer typically rotate relative to one another. As the polishing pad rotates beneath the wafer, the wafer sweeps out a typically annular polishing track, or polishing region, wherein the wafer's surface directly confronts the polishing layer. The wafer surface is polished and made planar by chemical and mechanical action of the polishing layer and polishing medium on the surface.
For conventional polishing pads, pad surface “conditioning” or “dressing” is critical to maintaining a consistent polishing surface for stable polishing performance. Over time the polishing surface of conventional polishing pads wears down, smoothing over the texture of the polishing surface—a phenomenon called “glazing”. The origin of glazing is plastic flow of the polymeric material due to frictional heating and shear at the points of contact between the pad and the workpiece. Additionally, debris from the CMP process can clog the surface voids as well as the channels through which polishing medium flows across the polishing surface. When this occurs, the polishing rate of the CMP process decreases, and this can result in non-uniform polishing between wafers or within a wafer. Conditioning creates a new texture on the polishing surface useful for maintaining the desired polishing rate and uniformity in the CMP process.
Conventional polishing pad conditioning is achieved by abrading the polishing surface mechanically with a conditioning disk. The conditioning disk has a rough conditioning surface typically comprised of imbedded diamond points. The conditioning disk is brought into contact with the polishing surface either during intermittent breaks in the CMP process when polishing is paused (“ex situ”), or while the CMP process is underway (“in situ”). Typically the conditioning disk is rotated in a position that is fixed with respect to the axis of rotation of the polishing pad, and sweeps out an annular conditioning region as the polishing pad is rotated. The conditioning process as described cuts microscopic furrows into the pad surface, both abrading and plowing the pad material and renewing the polishing texture.
Conventional polishing pads have less than optimal texture. For example, Reinhardt et al., in U.S. Pat. No. 5,578,362, discloses the use of polymeric spheres to introduce texture into a polyurethane polishing pad. The conditioning of such pads is typically not exactly reproducible. The diamonds on a conditioning disk become dulled with use such that the conditioner must be replaced after a period of time; during its life the effectiveness of the conditioner thus continually changes. Conditioning also contributes greatly to the wear rate of a CMP pad. It is common for about 95% of the wear of a pad to result from the abrasion of the diamond conditioner and only about 5% from contact with workpieces.
Accordingly, there is a continuing need for CMP polishing pads having a polishing surface that can be renewed with a minimum of abrasive conditioning (i.e., that are self renewing); and hence, exhibit an extended useful pad life.
In one aspect of the present invention, there is provided a chemical mechanical polishing pad for polishing semiconductor substrates, comprising: an electrospun polishing layer; wherein the electrospun polishing layer has a polishing surface that is adapted for polishing a semiconductor substrate.
In another aspect of the present invention, there is provided a method for producing a chemical mechanical polishing pad, comprising: electrostatically spinning at least one liquid spinning composition through at least one spinneret to form spun fibers and collecting the spun fibers on a target to provide an electrospun polishing layer having a polishing surface, wherein the polishing surface is adapted for polishing a semiconductor substrate.
In another aspect of the present invention, there is provided a method for producing a chemical mechanical polishing pad, comprising: providing an electrospun polishing layer having a polishing surface and a thickness of ≧10 mils prepared by electrostatically spinning at least one liquid spinning composition through at least one spinneret into spun fibers and collecting the spun fibers on a target, wherein the liquid spinning composition is an organic material; and, incorporating texture into the polishing surface.
In another aspect of the present invention, there is provided a method of polishing a semiconductor substrate, comprising: (a) providing a chemical mechanical polishing pad comprising an electrospun polishing layer, wherein the electrospun polishing layer has a thickness of ≧10 mils and wherein the electrospun polishing layer has a polishing surface; (b) providing a semiconductor substrate; and, (c) creating dynamic contact between the polishing surface and the semiconductor substrate to polish a surface of the semiconductor substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a multi-head, multi-spinneret apparatus used to produce an electrospun polishing layer.

FIG. 2 is a scanning electron micrograph of an electrospun polishing layer.

FIG. 3 is a scanning electron micrograph of an electrospun polishing layer.

FIG. 4 is a side perspective representation of a chemical mechanical polishing pad of one embodiment of the present invention.

FIG. 5 is a top plan view of a chemical mechanical polishing pad of one embodiment of the present invention with a groove pattern in the polishing surface.

FIG. 6 is a top plan view of a chemical mechanical polishing pad of one embodiment of the present invention with a groove pattern in the polishing surface, wherein the polishing pad exhibits a pad outer radius R_Oand a base radius R_B; and 8 curved grooves.

FIG. 7 is a top plan view of a chemical mechanical polishing pad of one embodiment of the present invention with a groove pattern in the polishing surface, wherein the polishing pad exhibits a pad outer radius R_O; a base radius R_B; and 8 curved grooves.

FIG. 8 is a top plan view of a chemical mechanical polishing pad of one embodiment of the present invention with a groove pattern in the polishing surface, wherein the polishing pad exhibits a pad outer radius R_Oand a base radius R_B.

FIG. 9 is a close-up view of a groove segment of groove 404 of FIG. 5.

DETAILED DESCRIPTION

The term “thickness” as used herein and in the appended claims in reference to an electrospun polishing layer having a polishing surface means the average actual thickness of the electrospun polishing layer measured in a direction normal to the polishing surface.
The term “polishing medium” as used herein and in the appended claims encompasses particle-containing polishing solutions and non-particle-containing solutions, such as abrasive-free and reactive-liquid polishing solutions.
The term “substantially circular cross section” as used herein and in the appended claims in reference to an electrospun polishing layer means that the longest radius, r, of the cross section from the central axis to the outer periphery of the electrospun polishing layer is ≦20% longer than the shortest radius, r, of the cross section from the central axis to the outer periphery of the electrospun polishing layer. (See FIG. 4).
The term “poly(urethane)” as used herein and in the appended claims encompasses (a) polyurethanes formed from the reaction of (i) polyisocyanates and (ii) polyols; and, (b) poly(urethane) formed from the reaction of (i) polyisocyanates with (ii) polyols and (iii) water, polyamines or a combination of water and polyamines.
The term “circumference fraction grooved” or “CF” as used herein and in the appended claims is defined by the following formula:
$CF = {\frac{(Portion of circumference at a given radius, R, that lies across any groove)}{(Full circumference at the given radius, R)}}$
Note that if CF is constant as a function of radius for an electrospun polishing layer of a given chemical mechanical polishing pad, then the fractional portion of the polishing surface of the electrospun polishing layer that is grooved (or ungrooved) at a given radius will also be constant as a function of radius.
In some embodiments of the present invention, the chemical mechanical polishing pad for polishing semiconductor substrates, comprises: an electrospun polishing layer, wherein the electrospun polishing layer has a polishing surface that is adapted for polishing a semiconductor substrate and wherein the polishing surface is self renewing. In some aspects of these embodiments, the chemical mechanical polishing pad does not require abrasive conditioning of the polishing surface to facilitate polishing of multiple semiconductor substrates. That is, the electrospun polishing layer having a polishing surface facilitates the successive polishing of multiple semiconductor substrates with similar polishing characteristics without the need to periodically condition the polishing surface using abrasive conditioning techniques. The self renewing aspect of the polishing surface of the electrospun polishing layer results in an extended pad life.
In some embodiments of the present invention, the electrospun polishing layer comprises electrostatically spun fibers. The chemical and physical properties of the electrospun polishing layer can be specifically engineered for particular chemical mechanical polishing operations through the selection of the liquid spinning composition or compositions used to prepare the spun fibers and through adaptations of the spinning process. In some aspects of these embodiments, the electrospun polishing layer comprises spun fibers having a single composition, wherein the composition comprises a mixture of one or more components combined to form a liquid spinning composition, wherein each component contributes a particular characteristic or group of characteristics to the electrospun polishing layer formed therefrom. In some aspects of these embodiments, the electrospun polishing layer comprises spun fibers having more than one composition. In some aspects of these embodiments, spun fibers having different compositions are simultaneously deposited to form the electrospun polishing layer, wherein the electrospun polishing layer comprises an intimately intermingled mass of spun fibers having different compositions. In some aspects of these embodiments, spun fibers having different compositions are deposited non-simultaneously to form the electrospun polishing layer, wherein the electrospun polishing layer comprises a multiplicity of layers of different spun fiber composition. In some aspects of these embodiments, spun fibers having different composition are deposited both simultaneously and non-simultaneously to form the electrospun polishing layer, wherein the electrospun polishing layer comprises a multiplicity of layers, wherein some of the layers comprise an intimately intermingled mass of spun fibers having different compositions and wherein some of the layers comprise spun fibers having a single composition.
In some embodiments of the present invention, the electrospun polishing layer comprises electrostatically spun fibers, wherein the spun fibers are formed from a liquid spinning composition. In some aspects of these embodiments, the liquid spinning composition comprises a polymer melt, a liquid monomer, a solution, a dispersion or a suspension. In some aspects of these embodiments, the liquid spinning composition comprises a fiber forming thermoplastic. In some aspects of these embodiments, the fiber forming thermoplastic is selected from poly(urethane), polyurea, polyamide, polyvinyl chloride, polyacrylonitrile, polyethylene oxide, polyolefin, poly(alkyl)acrylate, protein, polysaccharide, polylactate and combinations thereof. In some aspects of these embodiments, the liquid spinning composition comprises a poly(urethane), a polyvinyl chloride or a combination thereof. In some aspects of these embodiments, the liquid spinning composition comprises a combination of polyurethanes and polyvinyl chloride.
In some embodiments of the present invention, the electrospun polishing layer comprises electrostatically spun fibers, wherein the fibers have a diameter selected to provide the desired polishing properties to the electrospun polishing layer. In some aspects of these embodiments, the electrospun polishing layer comprises electrostatically spun fibers, wherein the fibers have a diameter of 10 to 2,000 nm, preferably 50 to 2,000 nm; more preferably 100 to 2,000 nm. In some aspects of these embodiments, the electrospun polishing layer comprises electrostatically spun organic fibers, wherein the fibers have a diameter of 10 to 2,000 nm; preferably 50 to 2,000 nm; more preferably 100 to 2,000 nm. In some embodiments of the present invention, the diameter of the electrostatically spun fibers is manipulated by varying at least one of the size or shape of a spinneret nozzle through which the fibers are spun, the distance between a spinneret and a target, and an applied electrostatic potential across a spinneret and a target.
In some embodiments of the present invention, the electrospun polishing layer comprises electrostatically spun fibers, wherein the fibers are multicomponent fibers exhibiting any type of cross-section, including, for example, sheath/core configurations, side by side configurations, pie wedge configurations, segmented ribbon configurations, segmented cross configurations, tipped trilobal configurations and conjugate configurations. In some aspects of these embodiments, the multicomponent fibers include components derived from different liquid spinning compositions.
In some embodiments of the present invention, the electrospun polishing layer has an average pore size of ≦5 μm. In some aspects of these embodiments, the electrospun polishing layer has an average pore size of ≦2 μm. In some embodiments of the present invention, the average pores size is manipulated by, for example, varying a spinneret to target distance, varying a relative speed of movement between a spinneret and a target in equidistant parallel planes, varying a relative direction of movement between a spinneret and a target in equidistant parallel planes, varying a nozzle size or nozzle shape of a spinneret, varying an electrostatic potential applied across a spinneret and a target, and combinations thereof.
In some embodiments of the present invention, the electrospun polishing layer exhibits a polishing surface and a thickness (measured in a direction normal to the polishing surface) of ≧5 mils; preferably ≧10 mils; more preferably ≧20 mils. In some aspects of these embodiments, the electrospun polishing layer exhibits a thickness selected from 5 to 300 mils; preferably 10 to 300 mils; more preferably 30 to 200 mils; still more preferably 30 to 150 mils; yet still more preferably 30 to 125 mils and most preferably 40 to 120 mils.
In some embodiments of the present invention, the electrospun polishing layer is subjected to post spinning treatment to fine tune its polishing properties. In some aspects of these embodiments, the electrospun polishing layer is treated to modify its hydrophobicity, tensile strength, compressibility, total void volume, thermal stability, chemical resistance, surface area, or chemical functionality (e.g., to enhance adhesion between adjacent layers in the chemical mechanical polishing pad; to affect interactions between the electrospun polishing layer and a semiconductor substrate being polished; to affect interactions between the electrospun polishing layer and a polishing medium used in combination therewith). In some aspects of these embodiments, the electrospun polishing layer is treated with a binder. In some aspects of these embodiments, the electrospun polishing layer is heated to facilitate point bonding of the spun fibers. In some aspects of these embodiments, the electrospun polishing layer is compressed and heated to simultaneously facilitate point bonding of the spun fibers and a reduction in the total void volume within the electrospun polishing layer. In some aspects of these embodiments, the total void volume within the formed electrospun polishing layer is tailored by modifying the degree of entanglement of the spun fibers.
In some embodiments of the present invention, the electrospun polishing layer exhibits voids within the electrospun polishing layer. In some aspects of these embodiments, the total void volume within the electrospun polishing layer comprises 0.2 to 80 vol % of the electrospun polishing layer. In some aspects of these embodiments, the total void volume comprises 0.3 to 80 vol % of the electrospun polishing layer. In some aspects of these embodiments, the total void volume comprises 0.55 to 70 vol % of the electrospun polishing layer. In some aspects of these embodiments, the total void volume comprises 0.6 to 60 vol % of the electrospun polishing layer.
In some embodiments of the present invention, the electrospun polishing layer comprises a filler material. In some aspects of these embodiments, the filler material is selected from inorganic electrolytes, organic electrolytes, water soluble inorganic substances, water soluble organic substances, water insoluble inorganic substances and water insoluble organic substances. In some aspects of these embodiments, the filler material comprises an organometallic. In some aspects of these embodiments, the filler material comprises at least one non-electrospun fiber. In some aspects of these embodiments, the non-electrospun fiber is selected from natural fibers, synthetic fibers, inorganic fibers, combinations and blends thereof. The at least one non-electrospun fiber may be of any denier; may be a multi- or mono-filaments; may be false twisted or twisted; may incorporate multiple denier filaments into a single yarn through twisting or melting; may be a multicomponent fiber exhibiting any type of cross-section, including, for example, sheath/core configurations, side by side configurations, pie wedge configurations, segmented ribbon configurations, segmented cross configurations, tipped trilobal configurations and conjugate configurations. In some aspects of these embodiments, the non-electrospun fiber is electrically conductive.
In some embodiments of the present invention, the electrospun polishing layer comprises non-electrospun regions. In some aspects of these embodiments, the electrospun polishing layer comprises an island or islands of randomly oriented spun fibers within a foam material, a film or a non-woven material. In some aspects of these embodiments, the electrospun polishing layer comprises a region or regions of randomly oriented spun fibers and regions of a foam material, a film or a non-woven material. In some aspects of these embodiments, the electrospun polishing layer is tailored to exhibit regions that promote more aggressive polishing and regions that promote buffing.
In some embodiments of the present invention, the chemical mechanical polishing pad comprises an electrospun polishing layer and a base layer. In some aspects of these embodiments, the base layer is selected from a foam material, a film and a textile non-woven material. In some aspects of these embodiments, the base layer is selected from an open cell foam material, a closed cell foam material and a foam material having a combined open cell and closed cell structure. In some aspects of these embodiments, the base layer is an electrospun material. In some aspects of these embodiments, the base layer is a film. In some aspects of these embodiments, the base layer is a water impermeable film.
In some embodiments of the present invention, the chemical mechanical polishing pad further comprises a base layer and at least one additional layer interposed between the base layer and the electrospun polishing layer. In some aspects of these embodiments, the base layer and the at least one additional layer are independently selected from a foam material, a film and a textile non-woven material. In some aspects of these embodiments, the base layer is selected from an open cell foam material, a closed cell foam material and a foam material having a combined open cell and closed cell structure. In some aspects of these embodiments, the at least one additional layer is selected from an open cell foam material, a closed cell foam material and a foam material having a combined open cell and closed cell structure. In some aspects of these embodiments, the at least one additional layer is a film. In some aspects of these embodiments, the at least one additional layer is a water impermeable film. In some aspects of these embodiments, the base layer is a textile non-woven material. In some aspects of these embodiments, the base layer is an electrospun material. In some aspects of these embodiments, the at least one additional layer is a textile non-woven material. In some aspects of these embodiments, the at least one additional layer is an electrospun material. In some aspects of these embodiments, the base layer and the at least one additional layer both comprise an electrospun material.
In some embodiments of the present invention, the chemical mechanical polishing pad comprises an electrospun polishing layer, a base layer and, optionally, at least one additional layer interposed between the electrospun polishing layer and the base layer. In some aspects of these embodiments, the chemical mechanical polishing pad includes at least one additional layer interposed between the electrospun polishing layer and the base layer. In some aspects of these embodiments, the various layers are interfaced together using an adhesive. In some aspects of these embodiments, the adhesive is selected from pressure sensitive adhesives, hot melt adhesives, contact adhesives and combinations thereof. In some aspects of these embodiments, the adhesive is a hot melt adhesive. In some aspects of these embodiments, the adhesive is a contact adhesive. In some aspects of these embodiments, the adhesive is a pressure sensitive adhesive.
In some embodiments of the present invention, the chemical mechanical polishing pad is adapted to be interfaced with a platen of a polishing machine. In some aspects of these embodiments, the chemical mechanical polishing pad is adapted to be affixed to the platen. In some aspects of these embodiments, the chemical mechanical polishing pad is adapted to be affixed to the platen using at least one of an adhesive and a vacuum. In some aspects of these embodiments, the chemical mechanical polishing pad is adapted to be affixed to the platen using at least one of a pressure sensitive adhesive and a vacuum.
In some embodiments of the present invention, the chemical mechanical polishing pad used has an electrospun polishing layer having a polishing surface exhibiting texture. In some aspects of these embodiments, the polishing surface of chemical mechanical polishing pads exhibit texture in the form of one or more grooves. There are several reasons for incorporating grooves in the polishing surface of a chemical mechanical polishing pad, including: (A) to prevent hydroplaning of the substrate being polished across the surface of the polishing pad—(if the pad is either ungrooved or unperforated, a continuous layer of polishing medium can exist between the substrate and the pad, preventing uniform intimate contact and significantly reducing removal rate); (B) to ensure that polishing medium is uniformly distributed across the pad surface and that sufficient polishing medium reaches the center of the substrate—(this is especially important when polishing reactive metals such as copper, in which the chemical component of the polishing is as critical as the mechanical; uniform polishing medium distribution across the substrate is required to achieve the same polishing rate at the center and edge of the substrate; however, the thickness of the polishing medium layer should not be so great as to prevent direct pad-substrate contact); (C) to control both the overall and localized stiffness of the polishing pad—(this controls polishing uniformity across the substrate surface and also the ability of the pad to level features of different heights to give a highly planar surface); (D) to act as channels for the removal of polishing debris from the pad surface—(a build-up of debris increases the likelihood of scratches and other defects); and (E) to act as a vacuum break to facilitate separation of the chemical mechanical polishing pad from a semiconductor substrate being polished therewith.
Note that one factor that determines the polishing pad life for grooved polishing pad is the depth of the grooves. That is, acceptable polishing performance is possible only until the polishing pad has worn to the point where the grooves have insufficient remaining depth to effectively distribute polishing medium, remove polishing wastes and prevent hydroplaning. Accordingly, it should be apparent that deeper grooves can correlate to a longer polishing pad life. It should also be apparent that an initial electrospun polishing layer thickness exceeding a minimum is desirable to provide a commercially useful pad life. Preferably, the initial electrospun polishing layer thickness is ≧10 mils.
In some embodiments of the present invention, the electrospun polishing layer has a polishing surface exhibiting texture. In some aspects of these embodiments, the texture is designed to alleviate at least one of hydroplaning; to influence polishing medium flow; to modify the stiffness of the polishing layer; to reduce edge effects; to facilitate the transfer of polishing debris away from the area between the polishing surface and the substrate; and to facilitate separation of the chemical mechanical polishing pad from a semiconductor substrate. In some aspects of these embodiments, the texture comprises at least one groove. In some aspects of these embodiments, the at least one groove has a groove depth of ≧20 mils. In some aspects of these embodiments, the at least one groove has a depth of 20 to 100 mils. In some aspects of these embodiments, the at least one groove has a groove depth of 20 to 60 mils. In some aspects of these embodiments, the at least one groove has a groove depth of 20 to 50 mils.
In some embodiments of the present invention, the electrospun polishing layer has a polishing surface exhibiting texture, wherein the texture comprises a groove pattern and wherein the groove pattern comprises at least two grooves. In some aspects of these embodiments, the electrospun polishing layer exhibits a texture comprising a groove pattern that comprises at least two grooves having a depth of ≧15 mils; a width of ≧10 mils and a pitch of ≧50 mils. In some aspects of these embodiments, the groove pattern comprises at least two grooves having a depth of ≧20 mils; a width of ≧15 mils and a pitch of ≧70 mils. In some aspects of these embodiments, the groove pattern comprises at least two grooves having a depth of ≧20 mils; a width of ≧15 mils and a pitch of ≧90 mils.
In some embodiments of the present invention, the electrospun polishing layer exhibits a texture comprising a groove pattern. In some aspects of these embodiments, the groove pattern comprises at least one groove. In some aspects of these embodiments, the groove pattern comprises a plurality of grooves. In some aspects of these embodiments, the at least one groove is selected from curved grooves, straight grooves and combinations thereof. In some aspects of these embodiments, the groove pattern is selected from a groove design including, for example, concentric grooves (which may be circular or spiral), curved grooves, cross-hatch grooves (e.g., arranged as an X-Y grid across the pad surface), other regular designs (e.g., hexagons, triangles), tire-tread type patterns, irregular designs (e.g., fractal patterns), and combinations thereof. In some aspects of these embodiments, the groove pattern is selected from random, concentric, spiral, cross-hatched, X-Y grid, hexagonal, triangular, fractal and combinations thereof. In some aspects of these embodiments, the groove profile is selected from rectangular with straight side-walls or the groove cross-section may be “V”-shaped, “U”-shaped, triangular, saw-tooth, and combinations thereof. In some aspects of these embodiments, the groove pattern is a groove design that changes across the polishing surface. In some aspects of these embodiments, the groove design is engineered for a specific application. In some aspects of these embodiments, the groove dimensions in a specific design may be varied across the pad surface to produce regions of different groove densities. In some aspects of these embodiments, at least one groove in the groove pattern has an initial groove depth of ≧20 mils. In some aspects of these embodiments, at least one groove in the groove pattern has an initial depth of 20 to 100 mils. In some aspects of these embodiments, at least one groove in the groove pattern has an initial groove depth of 20 to 60 mils. In some aspects of these embodiments, at least one groove in the groove pattern has an initial groove depth of 20 to 50 mils.
In some embodiments of the present invention, the electrospun polishing layer exhibits a texture comprising a groove pattern, wherein the groove pattern comprises at least one groove, wherein CF remains within 25%, preferably within 10%, more preferably within 5% of its average value as a function of an electrospun polishing layer radius, R, in an area extending from an outer radius, R_O, of a polishing surface of an electrospun polishing layer a majority distance to an origin, O, at a center of the polishing surface. In some aspects of these embodiments, CF remains within 25%, preferably within 10%, more preferably within 5% of its average value as a function of the electrospun polishing layer radius, R, in an area extending from a base radius, R_B, to an outer radius, R_O. (See, e.g., FIG. 5).
In some embodiments of the present invention, the chemical mechanical polishing pad comprises an electrospun polishing layer having a polishing surface exhibiting a texture selected from at least one of perforations and grooves. In some aspects of these embodiments, the perforations can extend from the polishing surface part way or all of the way through the thickness of the electrospun polishing layer.
In some embodiments of the present invention, the chemical mechanical polishing pad has at least one of perforations that extend therethrough; conductive-lined grooves; an incorporated conductor, such as, conductive fibers, conductive network, metal grid or metal wire; which can transform the chemical mechanical polishing pad into an eCMP (“electrochemical mechanical planarization”) polishing pad.
In some embodiments of the present invention, the chemical mechanical polishing pad has a central axis and is adapted for rotation about the central axis. (See FIG. 4). In some aspects of these embodiments, the electrospun polishing layer 210 of the chemical mechanical polishing pad is in a plane substantially perpendicular to the central axis 212. In some aspects of these embodiments, the electrospun polishing layer 210 is adapted for rotation in a plane that is at an angle, γ, of 80 to 100° to the central axis 212. In some aspects of these embodiments, the electrospun polishing layer 210 is adapted for rotation in a plane that is at an angle, γ, of 85 to 95° to the central axis 212. In some aspects of these embodiments, the electrospun polishing layer 210 is adapted for rotation in a plane that is at an angle, γ, of 89 to 91° to the central axis 212. In some aspects of these embodiments, the electrospun polishing layer 210 has a polishing surface 214 that has a substantially circular cross section perpendicular to the central axis 212. In some aspects of these embodiments, the radius, r, of the cross section of the polishing surface 214 perpendicular to the central axis 212 varies by ≦20% for the cross section. In some aspects of these embodiments, the radius, r, of the cross section of the polishing surface 214 perpendicular to the central axis 212 varies by ≦10% for the cross section.
FIG. 5 provides a top plan view of a chemical mechanical polishing pad 400 of some embodiments of the present invention, wherein the polishing pad 400 has a texture comprising a groove pattern that comprises at least one groove 404. The polishing pad 400 has an outer radius R_Oand a polishing surface 402 with at least one groove 404 formed therein. Although only a single groove 404 is depicted in FIG. 5, the groove pattern can comprise two or more grooves 404. (See, e.g., FIGS. 6-8). The polishing pad radius R is measured from an origin O at the center of the polishing surface 402. A circle C_R(dashed line) drawn at radius R with a circumference 2πR is also shown in FIG. 5. The outer radius of polishing pad 400 is R_O. Groove 404 extends from base radius R_Bto outer radius R_O, which defines the outer periphery 406 of polishing surface 402. In some aspects of these embodiments, the groove(s) 404 extend from base radius R_Bto outer periphery 406 (as depicted in FIGS. 5-8). In some aspects of these embodiments, the groove(s) 404 extend from a point between the origin O and the base radius R_Bto outer periphery 406. In some aspects of these embodiments, the groove(s) 404 extend from origin O to outer periphery 406. FIG. 9 depicts a close-up view of a groove segment of groove 404 of FIG. 5, showing a small differential segment 410 of groove 404. At a given radius R, groove 404 has a given width W and a central axis A that forms an angle θ (“groove angle”) with respect to a radial line L connecting the origin O to the given radius R. In some aspects of these embodiments, the chemical mechanical polishing pad has a texture comprising a groove pattern, wherein CF remains within 25%, preferably within 10%, more preferably within 5% of its average value as a function of the polishing pad radius R in an area extending from an outer radius R_Oof the polishing surface a majority distance to origin O. In some aspects of these embodiments, the chemical mechanical polishing pad has a texture comprising a groove pattern, wherein CF remains within 25%, preferably within 10%, more preferably within 5% of its average value as a function of polishing pad radius R in an area extending from base radius R_Bto outer radius R_O.
In some embodiments of the present invention, the method of producing a chemical mechanical polishing pad, comprises: electrostatically spinning at least one liquid spinning composition through at least one spinneret to form spun fibers and collecting the spun fibers on a target to provide an electrospun polishing layer having a polishing surface, wherein the polishing surface is adapted for polishing a semiconductor substrate. In some aspects of these embodiments, the method comprises collecting randomly oriented spun fibers on the target to provide the electrospun polishing layer. The process of electrostatically spinning comprises the introduction of a liquid spinning composition into an electric field, whereby the liquid spinning composition is caused to produce fibers which tend to be drawn to a target. While being drawn from the liquid spinning composition, the fibers typically harden, which may involve cooling (e.g., systems in which the liquid spinning composition is normally a solid at room temperature), chemical hardening (e.g., systems in which the spun fibers are treated with a vapor or gas that causes the spun fibers to harden), or evaporation of a solvent from the liquid spinning composition. The resultant spun fibers collected on the target are typically later removed from the target. In some aspects of these embodiments, the electrostatic field is generated by applying an electrostatic potential across the target and the at least one spinneret during the electrostatic spinning operation of 5 to 1,000 kV; preferably 5 to 100 kV; more preferably 10 to 50 kV. Any appropriate method of producing the desired electrostatic potential can be employed. In some aspects of these embodiments, the target is maintained at ground potential. In some aspects of these embodiments, the at least one spinneret is maintained at ground potential.
In some embodiments of the present invention, the method of producing a chemical mechanical polishing pad, comprises: providing an electrospun polishing layer having a polishing surface and a thickness (measured in a direction normal to the polishing surface) of ≧10 mils, wherein the electrospun polishing layer is prepared by electrostatically spinning at least one liquid spinning composition through at least one spinneret forming spun fibers and collecting the spun fibers randomly oriented on a target, wherein the at least one liquid spinning composition comprises an organic material; and, incorporating a texture into the electrospun polishing layer. In some aspects of these embodiments, texture is incorporated into the electrospun polishing layer using at least one of chemical etching, laser ablation and machining.
In some embodiments of the present invention, the step of incorporating a texture into the electrospun polishing layer comprises providing at least one of (i) at least one groove and (ii) a plurality of perforations into the electrospun polishing layer. In some aspects of these embodiments, the step of incorporating a texture into the electrospun polishing layer comprises incorporating at least one groove, a plurality of perforations or a combination of both into the electrospun polishing layer. In some aspects of these embodiments, the method comprises incorporating at least one groove, a plurality of perforations, or a combination of both into the electrospun polishing layer using at least one of embossing, chemical etching, laser ablating and machining. In some aspects of these embodiments, the machining is performed using a device capable of both drilling and routing.
In some embodiments of the present invention, the method of producing a chemical mechanical polishing pad, comprises: providing a target, wherein the target exhibits a textured surface; electrostatically spinning at least one liquid spinning composition through at least one spinneret to form spun fibers; and collecting the spun fibers in random orientation on the target to provide an electrospun polishing layer having a polishing surface; wherein the electrospun polishing layer exhibits a texture, which is a negative of the textured surface exhibited by the target. In some aspects of these embodiments, the textured surface exhibited by the target includes at least one of (i) at least one groove and (ii) a plurality of pillars. In some aspects of these embodiments, the texture exhibited by the electrospun polishing layer comprises at least one of (i) at least one groove and (ii) a plurality of pillars. In some aspects of these embodiments, the texture exhibited by the electrospun polishing layer comprises a groove pattern as described hereinabove. In some aspects of these embodiments, the electrospun polishing layer provided exhibits a polishing surface and a thickness (measured in a direction normal to the polishing surface) of ≧10 mils.
In some embodiments of the present invention, the method of producing a chemical mechanical polishing pad further comprises: exposing the electrospun polishing layer to a compressive force normal to the polishing surface, thereby compressing the polishing layer reducing the thickness of the electrospun polishing layer and reducing the total void space within the electrospun polishing layer. In some aspects of these embodiments, the method further comprises: heating at least a portion of the compressed electrospun polishing layer to a temperature above the glass transition temperature for at least one spun fiber composition within the electrospun polishing layer; then cooling the heated portion of the compressed electrospun polishing layer, locking the compressed electrospun polishing layer in the compressed state; and then removing the compressive force.
In some embodiments of the present invention, the method of producing a chemical mechanical polishing pad further comprises: dispersing a filler material in the void spaces within the electrospun polishing layer. In some aspects of these embodiments, the filler material at least partially fills the void spaces within the electrospun polishing layer. Filler materials suitable for use in these methods are as previously described hereinabove.
In some embodiments of the present invention, the method of producing a chemical mechanical polishing pad, comprises: electrostatically spinning at least one liquid spinning composition through at least one spinneret to form spun fibers and collecting the spun fibers randomly oriented on a target to provide an electrospun polishing layer having a polishing surface, wherein the target is a volume of a conductive liquid and wherein the polishing surface is adapted for polishing a semiconductor substrate. In some aspects of these embodiments, the method further comprises providing a volume of a conductive liquid to be used as the target, wherein the conductive liquid comprises at least one of an inorganic electrolyte, an organic electrolyte or a combination thereof. In some aspects of these embodiments, the conductive liquid is a polymer which is dissimilar from the liquid spinning composition from which the electrospun fibers are formed. In some aspects of these embodiments, the conductive liquid comprises a conductive material selected from inorganic and organic filler. In some aspects of these embodiments, the conductive liquid comprises a carbonaceous material. In some aspects of these embodiments, the conductive liquid comprises carbon nanotubes. In some aspects of these embodiments, the conductive liquid comprises a thermoset or thermoplastic material. In some aspects of these embodiments, the conductive liquid target is a curable composition. In some aspects of these embodiments the conductive liquid target is a curable composition selected from thermally curable compositions, evaporatively curable compositions, photolytically curable compositions, chemically curable compositions and combinations thereof. In some aspects of these embodiments, the conductive liquid target is cured following collection of the spun fibers.
In some embodiments of the present invention, the method of producing a chemical mechanical polishing pad, comprises: electrostatically spinning at least one liquid spinning composition through at least one spinneret to form at least one of spun fibers and beads of material; and collecting the spun fibers and beads of material on a target to provide an electrospun polishing layer having a polishing surface, wherein the polishing surface is adapted for polishing a semiconductor substrate. In some aspects of these embodiments, the electrospun polishing layer formed primarily comprises beads of material (i.e., beads of material comprise ≧95 wt %, preferably ≧99 wt %, of the electrospun polishing layer). In some aspects of these embodiments, the electrospun polishing layer formed primarily comprises spun fibers (i.e., spun fibers comprise ≧95 wt %, preferably ≧99 wt %, of the electrospun polishing layer). In some aspects of these embodiments, the electrospun polishing layer formed comprises beads of material formed amongst spun fibers. In some aspects of these embodiments, the electrospun polishing layer formed comprises beads of material formed along spun fibers to create a “necklace” like structure. In some aspects of these embodiments, the ratio of beads of material to spun fibers, the size of the beads and the degree to which the beads of material are formed amongst rather than along the spun fibers are selected to tailor the CMP performance properties of the electrospun polishing layer.
In some embodiments of the present invention, the method of producing a chemical mechanical polishing pad, comprises: electrostatically spinning at least one liquid spinning composition through at least one spinneret to form spun fibers; varying at least one of the spinneret to target distance, spinneret bore cross-sectional shape, and spinneret bore cross-sectional area during the electrostatic spinning; and collecting the spun fibers randomly oriented on a target to provide an electrospun polishing layer having a polishing surface; wherein the polishing surface is adapted for polishing a semiconductor substrate.
In some embodiments of the present invention, the method of producing a chemical mechanical polishing pad, comprises: electrostatically spinning at least one liquid spinning composition through at least one spinneret to form spun fibers; collecting the spun fibers on a target to provide an electrospun polishing layer having a polishing surface; and providing a gas flow between the at least one spinneret and the target; wherein the polishing surface is adapted for polishing a semiconductor substrate.
In some embodiments of the present invention, the method of polishing a semiconductor substrate, comprises: a) providing a chemical mechanical polishing pad comprising an electrospun polishing layer, wherein the electrospun polishing layer has a thickness of ≧10 mils and wherein the electrospun polishing layer has a polishing surface; b) providing a semiconductor substrate; and, c) creating dynamic contact between the polishing surface and the semiconductor substrate to polish a surface of the semiconductor substrate. In some aspects of these embodiments, the method further comprises: incorporating a texture into the electrospun polishing layer. In some aspects of these embodiments, the method further comprises: providing a polishing medium at an interface between the polishing surface and the surface of the substrate. In some aspects of these embodiments, the polishing surface exhibits a self renewing property such that steps (b) and (c) can be repeated multiple times without a need for abrasive conditioning of the polishing surface.
Some embodiments of the present invention will now be described in detail in the following Examples.
The polishing pads used in the Examples were prepared using the following procedures. A multihead electrospinning nozzle assembly as depicted in FIG. 1 was used to prepare the electrospun polishing layers. In particular, the apparatus depicted in FIG. 1 comprised a four line nozzle assembly 10. The four line nozzle assembly 10 had four parallel heads (a first head 40, a second head 50, a third head 60, a fourth head 70) with sixteen 19 gage single needle stainless steel dispensing tips 20 and twenty-four 21 gage single needle stainless steel dispensing tips 30 arranged thereon as depicted in FIG. 1. The second and third heads 50, 60 were supplied with a liquid spinning composition to facilitate electrospinning via a main feed line 80, which split into a second feed 55 to the second head 50 and a third feed 62 to the third head 60. The first head 40 was charged with liquid spinning composition via a first connection 45 between the first head 40 and the second head 50. The fourth head 70 was charged with liquid spinning composition via a second connection 65 between the third head 60 and the fourth head 70.
The target used to produce the electrospun polishing layers used in the Examples was a copper plate sprayed with a release agent. The target was set up to move in an elliptical motion having a 4″ major axis and a 2″ minor axis at a speed of 0.1 inch/minute. The distance between the target and the multihead electrospinning nozzle assembly was set at 25 cm and the potential difference between the spinnerets and the target was set at 32 kV. The liquid spinning composition used was a 14.5 wt % solids solution in N,N-dimethylformamide with 0.5 wt % polyethyleneglycol monoethyl ether. The solids comprised a mixture of 87 wt % polyurethane blend and 13 wt % polyvinyl chloride. The electrospinning operation proceeded for 6.125 days to prepare each electrospun polishing layer. The electrospun polishing layers formed comprised a nonwoven web of spun fibers in random orientation with diameters of 100 to 2,000 nm. The electrospun polishing layers had a thickness of 30 to 120 mils and a density of 0.44 g/cm³. FIG. 2 is a 5,000× magnification, scanning electron micrograph of a electrospun polishing layer so formed. FIG. 3 is a 1,000× magnification, scanning electron micrograph of an electrospun polishing layer so formed. The electrospun polishing layers were then laminated to an SP2150 porous subpad material (a polyurethane roll-good available from Rohm and Haas Electronic Materials CMP Inc.) using a pressure sensitive adhesive to provide stacked chemical mechanical polishing pads. The polishing surfaces of the electrospun polishing layers were grooved with concentric circular grooves having a 20 mil width, a 30 mil depth and a 120 mil pitch. The stacked, grooved chemical mechanical polishing pads were then die cut to provide a substantially circular chemical mechanical polishing pads having an average diameter of 20 inches, which pads were then used to perform the polishing tests described in the Examples 1-15.

EXAMPLES 1-15

The polishing tests were performed using 200 mm blanket wafers, specifically (A) TEOS dielectric wafers (Examples 1-6); (B) Coral® low-k dielectric, carbon-doped oxide film wafers (available from Novellus Systems, Inc.) (Examples 7-9); (C) tantalum nitride wafers (Examples 10-12); and (D) electroplated copper wafers (Examples 13-15). A Strasbaugh nSpire™ CMP system model 6EC rotary type polishing platform was used to polish all of the blanket wafers in the Examples. The polishing conditions used in all of the Examples included a platen speed of 93 rpm; a carrier speed of 87 rpm; with a polishing medium flow rate of 200 ml/min and a downforce of 1 or 1.5 psi (as indicated in Table 1). The polishing medium used in all of the Examples was ACuPlane LK393C4 (an advanced Barrier CMP Slurry available from RHEM). Removal rates for each of the polish experiments are provided in Table 1. Note that the removal rates were calculated from the before and after polish film thickness on the blanket wafers. Specifically, the removal rates for the Coral® wafers and the TEOS wafers were determined using a SpectraFX 200 optical thin-film metrology system available from KLA-Tencor. The removal rates for the electroplated copper wafers and the tantalum nitride wafers were determined using a ResMap model 168 four point probe resistivity mapping system from Creative Design Engineering, Inc.

TABLE 1

		TEOS	Coral ®
	Down	removal	removal	Tantalum Nitride	Copper
Ex.	Force	rate	rate	removal rate	removal rate
No.	(psi)	(Å/min)	(Å/min)	(Å/min)	(Å/min)

1	1	81
2	1	123
3	1	145
4	1	146
5	1.5	207
6	1.5	230
7	1		122
8	1.5		173
9	1.5		173
10	1			155
11	1.5			230
12	1.5			227
13	1				68
14	1.5				134
15	1.5				115

Claims

1. A chemical mechanical polishing pad for polishing semiconductor substrates, comprising:

an electrospun polishing layer;

wherein the electrospun polishing layer has a polishing surface that is adapted for polishing a semiconductor substrate.

2. The chemical mechanical polishing pad of claim 1, wherein the electrospun polishing layer has a thickness of ≧10 mils.

3. The chemical mechanical polishing pad of claim 1, wherein the electrospun polishing layer has an average pore size ≦5 μm.

4. The chemical mechanical polishing pad of claim 1, wherein the electrospun polishing layer is formed of electrostatically spun organic fibers, wherein the fibers have a diameter of 100 to 2,000 nm.

5. The chemical mechanical polishing pad of claim 1, wherein the polishing surface of the electrospun polishing layer exhibits a texture to facilitate polishing of the semiconductor substrate.

6. A method for producing a chemical mechanical polishing pad, comprising:

electrostatically spinning at least one liquid spinning composition through at least one spinneret to form spun fibers and collecting the spun fibers on a target to provide an electrospun polishing layer having a polishing surface, wherein the polishing surface is adapted for polishing a semiconductor substrate.

7. The method of claim 6, wherein the target is a volume of a conductive liquid.

8. A method of polishing a semiconductor substrate, comprising:

a) providing a chemical mechanical polishing pad comprising an electrospun polishing layer, wherein the electrospun polishing layer has a thickness of ≧10 mils and wherein the electrospun polishing layer has a polishing surface;

b) providing a semiconductor substrate; and,

c) creating dynamic contact between the polishing surface and the semiconductor substrate to polish a surface of the semiconductor substrate.

9. The method of claim 8, wherein the polishing surface is self renewing and steps (b) and (c) are repeated multiple times without a need for abrasive conditioning of the polishing surface.