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  Polishing pad having edge surface treatmentUSPTO Application #: 20070015448Title: Polishing pad having edge surface treatment Abstract: A polishing pad has a sublayer and a polishing layer, wherein the surface of the outer peripheral edge of the sublayer can be at least partially treated to reduce the absorption or permeation of polishing fluid into the sublayer through the outer peripheral edge. The application of the surface treatment at least reduces the amount of polishing fluid absorbed by the sublayer of the polishing pad during the polishing process. The polishing pad of the present invention is useful in polishing microelectronic substrates and especially useful in chemical mechanical planarization of semiconductor wafers. (end of abstract) Agent: Deborah M. Altman Ppg Industries, Inc. - Pittsburgh, PA, US Inventors: Robert G. Swisher, Alan E. Wang USPTO Applicaton #: 20070015448 - Class: 451526000 (USPTO) Related Patent Categories: Abrading, Flexible-member Tool, Per Se The Patent Description & Claims data below is from USPTO Patent Application 20070015448. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATIONS [0001] This application is continuation-in-part of U.S. patent application Ser. No. 10/898,258 filed on Jul. 26, 2004 which is a conversion of U.S. Provisional Patent Application having Ser. No. 60/493,292, filed on Aug. 7, 2003. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention is directed to a polishing pad having a sublayer and a polishing layer that is constructed to reduce the absorption or permeation of polishing fluid into the sublayer through the outer peripheral edge. [0004] 2. Background Information [0005] It is typical to use polishing fluid, such as polishing slurry, in conjunction with a polishing pad to polish a microelectronic substrate. The polishing pad can comprise a stacked pad construction including a sublayer. During the polishing process, it is advantageous to at least reduce or minimize the adsorption of slurry into the sublayer. Absorption of slurry into the sublayer can alter or change the compressibility of the sublayer. For example, if the sublayer is made less compressible, the work surface of the pad construction may not adequately conform to the microelectronic substrate being polished, which can result in polishing performance which is not uniform across the substrate. Furthermore, if the sublayer compressibility decreases during the process of polishing a series of wafers, the wafer-to-wafer polish consistency can be compromised. [0006] It has been proposed to have a polishing pad having a liquid impermeable polishing layer and a liquid permeable sublayer wherein the sublayer has an outer peripheral edge that is completely sealed to prevent liquid permeation into the sublayer through the sealed outer peripheral edge. It has been proposed to emboss the outer peripheral edge to seal the edge, to heat seal the outer peripheral edge to seal the edge and to apply a continuous coating of a sealing material such as silicone rubber to completely coat and seal the edge. These solutions close the outer pores of the peripheral edge and can impact the desired characteristics of the sublayer, such as compressibility. [0007] There is a need in the art to develop a polishing pad that at least reduces the absorption of polishing fluid into the sublayer of the pad. It is still further contemplated that it would be desirable to develop such a polishing pad and means without significantly impacting the compressibility of the sublayer. SUMMARY OF THE INVENTION [0008] The present invention is directed to a polishing pad having a sublayer and a polishing layer. The surface of the outer peripheral edge of the sublayer can be at least partially treated to reduce the absorption or permeation of polishing fluid into the sublayer through the outer peripheral edge. The application of the surface treatment at least reduces the amount of polishing fluid absorbed by the sublayer of the polishing pad during the polishing process. The polishing pad of the present invention is useful in polishing microelectronic substrates and especially useful in chemical mechanical planarization of semiconductor wafers. [0009] It is noted that, as used in this specification, the singular forms "a,""an," and "the" include plural referents unless expressly and unequivocally limited to one referent. [0010] For the purposes of this specification, unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. [0011] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Numerical ranges are intended to include all subsets within that range whether expressly further defined or not. [0012] The present invention will be described in detail in the description of the preferred embodiments taken together with the drawings in which like reference numerals represent like elements throughout. The drawings are illustrative of the present invention, but are not intended to be restrictive thereof. BRIEF DESCRIPTION OF THE DRAWINGS [0013] FIG. 1 is a schematic side elevation view of a stacked polishing pad on a rotary platen in accordance with one aspect of the present invention; [0014] FIG. 2 is a schematic side elevation view of a stacked polishing pad on a rotary platen in accordance with one aspect of the present invention; [0015] FIG. 3 is a schematic side elevation view of a stacked polishing pad on a rotary platen in accordance with one aspect of the present invention; and [0016] FIG. 4 is a schematic side elevation view of stacked polishing pad on a rotary platen in accordance with one aspect of the present invention. DESCRIPTION OF THE PREFFERED EMBODIMENTS [0017] The present invention is directed to a polishing pad 10 for use in polishing a microelectronic substrate. Various pad constructions 10 suitable for use in the present invention are known in the art, representative examples of which are shown in FIGS. 1-4 and described below. The polishing pad 10 can include a polishing layer 12 and a sublayer 14. The polishing layer 12 can be at least partially connected to the sublayer 14 through a covered surface 20 of the sublayer 14. Surface 20 is a "covered surface" in that it is covered by the polishing layer 12 in the stacked pad 10. The sublayer 14 can have an outer peripheral edge 16. The phrase "outer peripheral edge" 16 when associated with the sublayer 14 of the pad 10 within the meaning of this application will reference that outer surface of the sublayer 14 of the assembled pad 10 that is visible, accessible for surface treatable (such as by wiping) and can be visually inspected after treatment. In other words, the "outer peripheral edge" 16 of the sublayer 14 is the exposed portion of the sublayer 14 in the stacked pad 10 configuration in use. At least a portion of the outer peripheral edge 16 can be surface treated with a material that reduces the ability of the outer peripheral edge 16 of the sublayer 14 to absorb polishing fluid, such that permeation of polishing liquid into the sublayer 14 is reduced. In a non-limiting embodiment, the material can be selected such that at least a portion of the surface of the outer peripheral edge 16 of the sublayer 14 is made substantially hydrophobic. In a further non-limiting embodiment, the material can be selected such that the wettability of at least a portion of the surface of the outer peripheral edge 16 of the sublayer 14 is at least reduced. [0018] A polishing pad 10 can generally comprise a stacked layer construction including at least a polishing layer 12 and a sublayer 14. The polishing layer 12 can function as the working surface 18 of the pad 10 such that the polishing layer 12 can at least partially interact with the microelectronic substrate to be polished and the polishing fluid. In alternate non-limiting embodiments, the material of the polishing layer 12 can be selected such that the polishing layer 12 is substantially impermeable to polishing fluid or substantially permeable to polishing fluid. In further non-limiting embodiments, the material of the polishing layer 12 can be selected such that the polishing layer 12 is substantially non-porous or substantially porous. [0019] The polishing layer 12 of the pad 10 can be at least partially connected to a sublayer 14 through surface 20 of sublayer 14. In non-limiting embodiments such as shown in FIGS. 1 and 2, the sublayer 12 of the pad 10 can function as the bottom layer of the pad 10 which can be attached through a bottom attaching surface 22 to the platen 24 of a polishing apparatus. Neither surface 20 nor 22 of the sublayer 14 can be considered "an outer peripheral edge" of the sublayer 14 as, in use, these surfaces are not visible, treatable or capable of being visually inspected (i.e. these surfaces are not exposed in the pad 10 in use). FIG. 2 illustrates a less conventional stacked pad 10 construction in which the polishing layer 12 is smaller than the sublayer 14, whereby the outer peripheral edge 16 is formed of a radial facing surface 16A and an annular surface 16B that is adjacent the covered surface 20. The material of the sublayer 14 can be selected such that the sublayer 14 is substantially permeable to polishing fluid. Further, the material of the sublayer 14 can be selected such that the sublayer 14 is substantially porous. Continue reading... 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