Pad for chemical-mechanical polishing

Abstract

Described are pads for chemical-mechanical polishing having a central area that is adapted to control pad temperature at the central area by controlling the amount of friction between the pad and a wafer substrate at the central area during chemical-mechanical processing, or by removing heat energy from the central area of the pad during chemical-mechanical polishing.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 738,463, filed Dec. 23, 2024, the entire disclosure of which is incorporated herein by reference for all purposes.FIELD

[0002] This disclosure relates to pads for use in chemical-mechanical polishing (also sometimes referred to as “chemical-mechanical planarization”), particularly to such pads that have a central area that is adapted to control the temperature of the pad at the central area by controlling the amount of friction between the pad and a wafer substrate at the central area during chemical-mechanical processing, or by removing heat energy from the central area of the pad during chemical-mechanical polishing, or both.BACKGROUND

[0003] Chemical-mechanical polishing (or “chemical-mechanical planarization” or “CMP”) is the process of selectively removing excess material that has been deposited onto an in-process microelectronic device substrate (i.e., a “wafer substrate”) to effect a leveling of the wafer substrate surface for subsequent processing at the surface. CMP uses the combined effects of physical (abrasive, mechanical) and chemical forces to remove material from a substrate surface. CMP is performed by applying pressure to the back of the wafer substrate while the substrate contacts a polishing pad and while a chemical-abrasive slurry (“CMP slurry”) is dispensed between the pad and wafer substrate. The pad is placed against the substrate with a desired amount of pressure and both the pad and the substrate are rotated while the slurry is presented therebetween.SUMMARY

[0004] CMP processes are used with different types of substrates to remove organic or inorganic materials from the substrate surface. Processes for particular types of substrates are carried out with specialized pads made of different polymer materials and having polishing surfaces with various highly refined patterns. Specialized CMP slurries are used with specific substrates and for removal of particular materials from the substrate. For removing different types or amounts of materials, selective amounts of pressure can be used, selected velocities can be used, and selective amounts of slurry can be used.

[0005] These factors affect the amount of friction and heat energy generated as well as the amount of heat energy retained at different locations of the pad surface and subsurface. Generally, a greater amount of heat may be generated at a central area of the pad because a higher relative velocity at the center of the pad generates a greater amount of friction, and also because of a higher contact time (the amount of time that the wafer substrate contacts the pad surface) at the central area of a pad. By some CMP processes, a center of a pad may be in contact with a retaining ring of a polishing head during most or all of the polishing time of the process.

[0006] Adding to the relatively greater generation of heat energy at the central area, heat energy generated at the central area may not readily dissipate from the central area. Firstly, the high contact time between the pad and the wafer at the central area prevents dissipation of heat from the central area. Additionally, the central area may not receive a regular or significant flow of CMP slurry, which can be effective to remove heat energy from the pad. The high contact time and lack of heat dissipation from the central area can cause a temperature increase at the central area, including below the pad surface at the pad interior or “subsurface.”

[0007] For many or perhaps most CMP processes, heat energy caused by friction does not increase the temperature of a pad to a level that impacts performance of the pad. For other CMP processes, including processes sometimes referred to as “high stress” CMP processes, the amount of heat energy generated by friction and retained in a pad, particularly a central area of a pad, can increase the pad temperature to a temperature that causes localized pad failure.

[0008] A high-stress CMP process is designed to achieve a relatively high rate of material removal. Certain types of materials are applied to wafer substrates at higher thicknesses than other materials. Examples include various organic materials and inorganic materials such as metals (e.g., copper, tungsten, molybdenum), metal oxides, silicon carbide, among others. To achieve desired processing throughput, a CMP process that removes a relatively greater amount of material may be designed to have a higher rate of removal by using a pressure at a high end of typical operating pressure ranges, a velocity between the pad and substrate that is at a high end of typical operating ranges, or both.

[0009] The higher pressure and velocity required to achieve the higher removal rate increase the amount of heat energy that is produced by friction, which increases the temperature of the pad. Prolonged exposure and retention of heat energy can lead to an excessive pad temperature, meaning a temperature that is capable of degrading or otherwise damaging the pad. With certain CMP processes and CMP pads, heat stress caused by an excessively high pad temperature at a central area of the pad has been found to produce acute defects within the pad such as bubbles within the pad subsurface. For the reasons described, the risk of heat-induced damage to a CMP pad is greatest at the central area of the pad, particularly in a CMP process that operates at a relatively high pressure and velocity between the pad and the wafer substrate. For such CMP processes there is a need to prevent a temperature increase of the pad, particularly at a center region of a pad, and particularly to avoid a temperature increase that would cause heat-induced damage such as bubbles being generated within the subsurface.

[0010] CMP pads, as described herein, include an upper surface that is adapted to process a wafer substrate by chemical-mechanical polishing. The upper surface includes a polishing area that is effective to remove material from all portions of a surface of a wafer substrate by a CMP process. The upper surface also includes a central area located at the center of the upper surface of the pad and extends from the center of the pad to a location on the pad referred to herein as a “central area radius.” An outer polishing area extends from the central area radius to an outer polishing area radius at or near an edge of the pad. The outer polishing area can include a pattern of polishing surfaces (“outer polishing surfaces”) and grooves (“outer grooves”) that may be arranged in any useful pattern and may have any useful shapes and dimensions.

[0011] The central area can include one or more of polishing surfaces, grooves, or non-polishing surfaces (for example grooves or another absence of a polishing surface) that control the temperature of the pad at the central area during a CMP process, specifically, that prevent an excessive increase in temperature of the pad at the central area and keep the temperature of the pad at the central area below a temperature that causes heat-induced damage to the pad. As described herein, certain arrangements of a non-polishing surface or a combination of polishing surfaces and non-polishing surfaces (e.g., grooves) at the central area can prevent an excessive temperature increase by controlling the amount of heat energy generated by friction at the central area, or by allowing or causing heat energy to be dissipated from the central area, or both.

[0012] To reduce or prevent heat energy from being generated at the central area, a central area can include a non-polishing surface or a combination of polishing surfaces and non-polishing surfaces (e.g., grooves) that controls the amount of friction between a wafer substrate and a pad at the central area during CMP processing. To dissipate heat energy away from the central area, the central area can include a non-polishing surface or a combination of polishing surfaces and non-polishing surfaces (e.g., grooves) that allows a CMP slurry to flow through the central area to remove the heat energy.

[0013] In short, heat stress-induced damage to a CMP pad may occur during CMP processing as heat energy accumulates within the pad, particularly within the pad subsurface at a central area. The heat energy is not readily dissipated from the central area of the pad, especially the subsurface, due to high contact time with the wafer substrate and a lack of CMP slurry contacting the central area. A high amount of heat generation and low heat dissipation lead to heat energy accumulation at the central area and an increase in temperature, which can cause acute damage to the pad and localized pad failure, particularly in high-stress CMP processes.

[0014] In one aspect, a chemical-mechanical polishing pad can include a central area extending from a center of the polishing pad to a central area radius and an outer polishing area that extends from the central area radius to an outer polishing area radius. The outer polishing area includes outer polishing surfaces and outer grooves having an outer groove depth. When a wafer substrate surface is placed in moving contact with the outer polishing area during chemical-mechanical polishing, an amount of polishing friction is produced between the outer polishing area and the wafer substrate surface. When the wafer substrate surface passes over the central area during the chemical-mechanical polishing, an amount of friction between the central area and the wafer substrate surface is less than the polishing friction.

[0015] In another aspect, a method of polishing a wafer substrate includes: providing a polishing pad that has an upper surface that includes a central area extending from a center of the polishing pad to a central area radius, an outer polishing area that extends from the central area radius to an outer polishing area radius, the outer polishing area having outer polishing surfaces and outer grooves; contacting a wafer substrate surface with the polishing pad upper surface with pressure and motion between the wafer substrate surface and the polishing pad upper surface; and applying abrasive slurry between the polishing pad upper surface and the wafer substrate surface. When the wafer substrate surface is in moving contact with the outer polishing area, an amount of polishing friction is produced between the outer polishing area and the wafer substrate. When the wafer substrate surface passes over the central area, an amount of friction is produced between the central area and the wafer substrate surface that is less than the polishing friction.

[0016] The preceding summary is provided to facilitate an understanding of some of the innovative features unique to the present disclosure and is not intended to be a full description. A full appreciation of the disclosure can be gained by taking the entire specification, claims, drawings, and abstract as a whole.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The disclosure may be more completely understood in consideration of the following description of various illustrative embodiments in connection with the accompanying drawings, in which:

[0018] FIG. 1 schematically shows a generic CMP apparatus and process including as described herein;

[0019] FIG. 2 schematically shows a generic CMP apparatus and process with wafer contact time and heat accumulation relative to the CMP pad; and

[0020] FIGS. 3, 4, and 5 show top views of example CMP pads as described herein.

[0021] While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit aspects of the disclosure to the particular illustrative embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.DETAILED DESCRIPTION

[0022] This disclosure relates to CMP pads that include an upper surface that is adapted to process a surface of a wafer substrate by chemical-mechanical polishing. The upper surface includes a central area that includes the center of the upper surface and that extends from the center of the upper surface to a central area radius. The central area includes a non-polishing surface or a combination of non-polishing surfaces and polishing surfaces that are adapted to control an amount of heat energy that is generated at the central area or that accumulates at the central area, to prevent an excess temperature increase of the pad at the central area during a CMP process. The upper surface also includes an outer polishing area that is effective to remove material from all portions of a wafer substrate surface (center, edge, and mid-radial ranges of the wafer substrate surface) during a CMP process.

[0023] A CMP pad as described can be used in a chemical-mechanical planarization process for processing a microelectronic device substrate (sometimes referred to herein as a “wafer substrate”) that contains in-process (partially completed) microelectronic device precursors at a surface of the substrate. A typical CMP process uses a platen to which the CMP pad is attached and a polishing head that holds the wafer substrate and presses the surface of the wafer substrate against the upper surface of the pad. The head and the platen both rotate in the same direction while an abrasive-chemical slurry (“CMP slurry”) is delivered between the upper surface of the pad and the surface of the wafer substrate in contact with the upper surface of the pad.

[0024] FIG. 1 shows a generalized, schematic view of an exemplary CMP apparatus 50 for performing an exemplary CMP process. In the exemplary process, using apparatus 50, slurry 52 is dispensed via slurry dispenser 54 onto an upper surface of CMP pad 56. Alternatively, slurry 52 may be delivered from the bottom of pad 56 to the upper surface of pad 56. Pad 56 is mounted on rotatable platen 58, from which a rotatable platen shaft 60 extends. Wafer substrate 66 is held by a substrate chuck (or “head”) 62 from which a substrate chuck shaft 64 extends. A down force is controllably applied to substrate head 62 via shaft 64 to provide controllable contact between pad 56 and wafer substrate 66.

[0025] FIG. 2 schematically shows a top view of apparatus 50 with CMP pad 56 and wafer substrate 66, including positions and movement of wafer substrate 66 relative to upper surface 70 of pad 56 during CMP processing. Upper surface 70 includes a pattern of polishing surfaces (not specifically shown) that are separated by grooves (not specifically shown) to form a polishing surface. As pad 56 is rotated (see the arrow R indicating the rotational direction), wafer substrate 66 also rotates while being moved laterally in an X-Y plane (see arrow X-Y) along the radius of pad 56 between the center (C) and outer edge of pad 56. Also included in FIG. 2, is a graphical representation showing the amount of time the upper surface 70 of pad 56 in in contact with the wafer substrate (contact time) relative to pad diameter and center C. As shown in the graphical representation of FIG. 2, the amount of time under wafer contact (contact time) of the wafer substrate 66 with the upper surface 70 of pad 56 is greatest at the middle region of pad 56, particularly at and near center C. The graphical representation in FIG. 2 also shows that the amount of heat that accumulates at different locations along the radius of pad 56, are greatest at the middle of pad 56 at and near center C.

[0026] Referring to FIG. 3, a top view of example CMP pad 100 is shown as having upper surface 110 that includes central area 112 that extends from center C to central area radius 114. Upper surface 110 also includes outer polishing area 116 that extends between central area radius 114 (dashed line) and outer polishing area radius 118 (dashed line) at the outer edge of upper surface 110. Outer polishing area 116 includes a pattern of polishing surfaces (not specifically shown) that are separated by grooves (not specifically shown). The combination of polishing surfaces and grooves at outer polishing area 116 may be of any useful pattern or dimensions.

[0027] Central area 112 can include a non-polishing surface alone, or a combination of polishing surfaces and non-polishing surfaces that may be grooves or another form of a non-polishing surface. (Polishing surfaces that are located in the central area may sometimes be referred to herein as “central polishing surfaces,” and grooves that are located in the central area may sometimes be referred to herein as “central grooves.”)

[0028] One example of central area 112 may include a single non-polishing surface over the entire area of central area 112 extending as a circular area from the pad center (C) to central area radius 114. Other examples of central area 112 may include a circular middle area (“sometimes referred to more simply herein as a “middle area”) that covers a circular portion of central area 112, including pad center C, and extends from pad center C to a middle area radius. A circular middle area may include a polishing surface only (i.e., over the entire middle area surface), or a non-polishing surface only (i.e., over the entire middle area surface) (see FIGS. 4 and 5, respectively). Alternately, a circular middle area of a central area 112 may include a combination of polishing surfaces and non-polishing surfaces, e.g., grooves. The annular area of central area 112 between the middle area radius 132 and the central area radius 114 may also contain polishing surfaces, non-polishing surfaces such as grooves, or both.

[0029] Still other examples of central area 112 may include polishing surfaces and grooves that have any other dimensions or pattern that is effective during CMP processing to control the temperature of the pad at central area 112 either by controlling an amount of friction and heat energy generated by friction between the pad surface and a wafer substrate surface, or by allowing or causing CMP slurry to pass through central area 112 (e.g., through grooves in central area 112) to carry heat energy from central area 112.

[0030] To reduce friction between a wafer substrate surface and central area 112 during a CMP process, example central areas 112 may have a total amount (by area) of central polishing surfaces that covers less than 85 percent of the total area of the central area (when viewed from above the central area as in FIGS. 3, 4, and 5). A central area as described that has no polishing surfaces as part of the central area is considered to have zero percent polishing surfaces based on total area of the central area. A central area 112 that has both polishing surfaces and non-polishing surfaces (grooves or another type of non-polishing surface) may have a total amount (area) of polishing surfaces that is less than 85, 80, 60, 50, 40, 30, or 20 percent of the total amount of area of the central area.

[0031] As used herein, a “polishing surface” (whether a polishing surface located at an outer polishing area or a polishing surface located in a central area) is a surface at an upper surface of a CMP pad that contacts a surface of a wafer substrate during a CMP process and, with relative motion and pressure between the wafer substrate surface and the pad surface, is effective to remove material from the wafer substrate surface by chemical-mechanical polishing mechanisms. Polishing surfaces are present at outer polishing areas of a CMP pad, and may optionally be present at a central area of a CMP pad. Polishing surfaces extend horizontally (in an x-direction and a y-direction) at the upper surface of a pad when the pad is viewed in cross-section. Polishing surfaces of a CMP pad, including outer polishing surfaces (located on an outer polishing area) and central polishing surfaces (located at a central area), are substantially coplanar, with the polishing surfaces being located substantially in a single plane, that plane sometimes being referred to herein as a “polishing plane.”

[0032] A “non-polishing” surface is a surface at the upper surface of the pad that does not contact a wafer substrate surface during a CMP process and does not engage the wafer substrate surface to remove material from the wafer substrate surface by chemical-mechanical polishing mechanisms. A non-polishing surface extends horizontally at a depth that is below the polishing plane (the depth is in a z-direction when the pad is viewed horizontally, from a side, as in FIG. 1), the depth being sufficiently large and the distance between the non-polishing surface and a polishing surface of the pad being sufficient to prevent a wafer substrate surface from contacting the non-polishing surface during a CMP process.

[0033] An example of a non-polishing surface is a groove (or open channel, or the like) that is formed in a pad upper surface between polishing surfaces. The groove includes an opening that originates at a level of a polishing surface, meaning at a polishing plane, and extends horizontally across the pad upper surface as well as vertically below the polishing surface. The depth of a groove (a bottom of a groove) below the polishing surface and polishing plane may sometimes be referred to herein as “groove depth.” Typically, a groove or similar structure at a pad upper surface can be an elongate, straight, or curved channel or channel-like open structure or open space that has a length that is significantly greater than its width and depth, and that is positioned between polishing surfaces. Example grooves may be radial grooves that extend linearly, continuously, or discontinuously, generally, or exactly along a line of a radius of the pad from the pad center to a pad edge. Other examples grooves may be curved or straight grooves that are arranged continuously or discontinuously in a concentric pattern around the pad center. Many or all of the grooves of a CMP pad can have a common groove depth, i.e., grooves of a CMP pad can have a groove depth that is coplanar, including among center grooves and outer grooves, with the groove depths of multiple grooves being coplanar in a plane that is parallel to the polishing plane.

[0034] In another embodiment, a non-polishing surface at a central area of a pad is circular and larger than a groove in horizontal dimensions of width and length, which are both significantly greater than a thickness dimension (a thickness in the z-direction) of the non-polishing surface. A non-polishing surface at a central area may extend over the entire central area from a pad center to a central area radius, or may extend over only a portion of a central area from a pad center to a middle area radius that is less than the central area radius (see FIG. 5). A non-polishing surface at a central area can have a depth that is coplanar with a groove depth of grooves of the outer polishing area (“outer grooves”) or may alternately have a depth that is greater than a groove depth of grooves of the outer polishing area, below a groove depth of grooves of the outer polishing surface.

[0035] A non-polishing surface or a combination of polishing surfaces and non-polishing surfaces at a central area can be effective to prevent an excessive increase in temperature at the central area to prevent the pad at the central area from reaching a temperature that becomes sufficiently high to cause heat-induced damage to the pad in the form of an acute defect (e.g., bubble formation) in the subsurface at the central area of the pad.

[0036] During a CMP process, friction exists due to moving contact between the surface of the wafer substrate and polishing surfaces of the CMP pad (this amount of friction may be referred to herein as an amount of “polishing friction”). With example CMP pads as described, a central area of a pad is adapted to produce an amount of polishing friction at the central area (“central polishing friction”) that is lower than an amount of polishing friction that is produced at an outer polishing area (“outer polishing friction”); i.e., during the CMP process, the amount of friction that exists between the surface of the wafer substrate and the central area is less than the amount of friction that exists between the surface of the wafer substrate and polishing surfaces at the outer polishing surface. The reduced amount of friction at the central area reduces the generation of heat energy at the central area to prevent an unwanted temperature increase of the pad at the central area.

[0037] The central area may also include a non-polishing surface that can maintain a presence or a flow of CMP slurry at the central area. The temperature of the pad at the central area may be further controlled by these non-polishing surfaces, which allow heat energy to be removed from the central area by the flow of CMP slurry.

[0038] An example design of polishing surfaces and non-polishing surfaces at a central area of a CMP pad is shown at FIG. 4. FIG. 4 is a top view of CMP pad 100 that includes upper surface 110 that includes central area 112 that extends from center C to central area radius 114. Upper surface 110 also includes outer polishing area 116 that extends between central area radius 114 and an outer polishing area radius (not shown) at the outer edge of upper surface 110. Outer polishing area 116 includes a pattern of geometrically-shaped (e.g., rectangular) outer polishing surfaces 120 arranged in a concentric pattern, interrupted by outer grooves 122 arranged in a radial and concentric pattern. The pattern of outer polishing surfaces 120 and outer grooves 122 may be of any useful design. Generally, with respect to any CMP pads described herein, central area radius 114 may be less than 10 percent of the outer polishing area radius. For example, for an outer polishing area having a radius is in a range from 30 to 40 cm and a central area radius is in a range from 1 to 3 cm.

[0039] Central area 112 includes a combination of polishing surfaces (sometimes referred to as “central polishing surfaces”) and grooves (sometimes referred to as “central grooves”). A circular middle area that extends from center C to middle area radius 132 includes middle polishing surface 130, which is coplanar with outer polishing surfaces 120. Additional central polishing surfaces 140 are arranged in a pattern of two concentric rings between middle area radius 132 and central area radius 114, each central polishing surface 140 being an elongate, curved (optionally straight) annular surface. Central grooves 142 (concentric) and 144 (radial) are located between middle area radius 132 and central area radius 114 to separate central polishing surfaces 140 and to allow flow of CMP slurry between central polishing surfaces 140, within central area 112, during a CMP process.

[0040] FIG. 5 is a top view of a different example CMP pad 100 that similarly includes upper surface 110 having central area 112 that extends from center C to central area radius 114. Other features of example CMP pad 100 of FIG. 5 are similar to example CMP pad 100 of FIG. 4, but with certain differences. The circular middle area of pad 100 of FIG. 5, between center C and middle area radius 132, does not include a middle polishing surface 130 as in FIG. 4 but instead includes non-polishing surface 134, which is a surface that is coplanar with or below (has a greater depth than) the depth of outer grooves 122 and central grooves 142 and 144.

[0041] The designs of polishing surfaces and non-polishing surfaces at central area 112 of CMP pad 100 shown in FIGS. 4 and 5 are exemplary. Those of skill in the art will recognize that other combinations of polishing surfaces and grooves may be used to achieve the same effect as those of FIGS. 4 and 5 to avoid an excessive temperature increase at a central area of a CMP pad.

[0042] A CMP pad as described herein can be used with any CMP process for removing a desired material from a wafer substrate surface. In specific applications, the CMP pad may be useful with CMP processes that produce and retain a significant amount of heat energy at a central area of a pad in a manner that would cause an excessive temperature increase in the pad and damage the polymer of the pad at the central area. These CMP processes include processes sometimes considered to be “high-stress” CMP processes that are designed to achieve a high removal rate of material from a wafer substrate surface by using relatively high pressure and relatively high velocity between a wafer substrate surface and a pad surface. Examples of materials that may be removed by such CMP processes include organic materials and inorganic materials such as metals (e.g., copper, tungsten, molybdenum), metal oxides, silicon carbide, among others.

[0043] The CMP pad may be made of any material and may have any dimensions. In certain applications, such pads include porous pads made of porous thermoset polyurethane. These porous polymeric pads may have a density of between 0.3 and 0.9 grams per cubic centimeter, e.g., from 0.5 to 0.8 grams per cubic centimeter. The porous polymeric pad may also be relatively flexible, having an elastic modulus at the pad surface that is a range from about 400 to about 1200 MPa.Aspects

[0044] Aspect 1. A chemical-mechanical polishing pad comprising a pad upper surface including a central area extending from a center of the polishing pad to a central area radius, and an outer polishing area that extends from the central area radius to an outer polishing area radius, the outer polishing area comprising outer polishing surfaces and outer grooves having an outer groove depth, wherein when a wafer substrate surface is placed in moving contact with the outer polishing area during chemical-mechanical polishing, an amount of polishing friction is produced between the outer polishing area and the wafer substrate surface, and when the wafer substrate surface passes over the central area during the chemical-mechanical polishing, an amount of friction between the central area and the wafer substrate surface is less than the polishing friction.

[0045] Aspect 2. A chemical-mechanical polishing pad comprising a pad upper surface including a central area extending from a center of the polishing pad to a central area radius, and an outer polishing area that extends from the central area radius to an outer polishing area radius, the outer polishing area comprising outer polishing surfaces and outer grooves having an outer groove depth, wherein when a wafer substrate surface is placed in moving contact with the outer polishing area during chemical-mechanical polishing, an amount of polishing friction is produced between the outer polishing area and the wafer substrate surface, and wherein a ratio of an area of the central polishing surfaces to an area of the central area is less than 85 percent.

[0046] Aspect 3. The chemical-mechanical polishing pad of aspect 1 or 2, wherein the central area comprises central polishing surfaces that are coplanar with the outer polishing surfaces, and central grooves having a depth of at least the outer groove depth.

[0047] Aspect 4. The chemical-mechanical polishing pad of aspect 3, wherein a ratio of an area of the central polishing surfaces to an area of the central area is less than 85 percent.

[0048] Aspect 5. The chemical-mechanical polishing pad of aspect 1 or 2, the central area comprising a circular middle area extending from the center of the polishing pad to a middle area radius, central polishing surfaces between the middle area radius and the central area radius, coplanar with the outer polishing surfaces, and central grooves between the middle area radius and the central area radius, having a depth of at least the outer groove depth.

[0049] Aspect 6. The chemical-mechanical polishing pad of aspect 5, wherein the circular middle area comprises a middle area polishing surface that extends between the center of the polishing pad to the middle area radius and is coplanar with the outer polishing surfaces.

[0050] Aspect 7. The chemical-mechanical polishing pad of aspect 6, wherein the circular middle area comprises the middle area polishing surface and grooves.

[0051] Aspect 8. The chemical-mechanical polishing pad of aspect 6, wherein the circular middle area comprises the middle area polishing surface with no grooves.

[0052] Aspect 9. The chemical-mechanical polishing pad of aspect 1, wherein the central area comprises a circular non-polishing surface extending from the center of the polishing pad to a middle area radius, having a depth that is coplanar with or below the outer groove depth.

[0053] Aspect 10. The chemical-mechanical polishing pad of aspect 1, wherein the central area consists entirely of a non-polishing surface.

[0054] Aspect 11. The chemical-mechanical polishing pad of any of aspects 1 through 10, wherein the central area radius is less than 10 percent of the outer polishing area radius.

[0055] Aspect 12. The chemical-mechanical polishing pad of any of aspects 1 through 11, wherein the central area radius is in a range from 1 to 3 cm and the outer polishing area radius is in a range from 30 to 40 cm.

[0056] Aspect 13. The chemical-mechanical polishing pad of any one of aspects 1 through 11, wherein the pad has a density in a range from 0.5 to 0.8 grams per cubic centimeter.

[0057] Aspect 14. A method of polishing a wafer substrate, the method comprising: providing a polishing pad comprising an upper surface that comprises a central area extending from a center of the polishing pad to a central area radius, and an outer polishing area that extends from the central area radius to an outer polishing area radius, the outer polishing area comprising outer polishing surfaces and outer grooves having an outer groove depth; contacting a wafer substrate surface with the polishing pad upper surface with pressure and motion between the wafer substrate surface and the polishing pad upper surface; and applying abrasive slurry between the polishing pad upper surface and the wafer substrate surface, wherein when the wafer substrate surface is in moving contact with the outer polishing area, an amount of polishing friction is produced between the outer polishing area and the wafer substrate, and when the wafer substrate surface passes over the central area, an amount of friction is produced between the central area and the wafer substrate surface that is less than the polishing friction.

[0058] Aspect 15. The method of aspect 14, wherein the central area comprises central polishing surfaces that are coplanar with the outer polishing surfaces, and central grooves having a depth of at least the outer groove depth.

[0059] Aspect 16. The method of aspect 15, wherein a ratio of an area of the central polishing surfaces to an area of the central area is less than 85 percent.

[0060] Aspect 17. The method of aspect 14 or 15, the central area comprising a circular middle area extending from the center of the polishing pad to a middle area radius, central polishing surfaces between the middle area radius and the central area radius, coplanar with the outer polishing surfaces, and central grooves between the middle area radius and the central area radius, having a depth of at least the outer groove depth.

[0061] Aspect 18. The method of any of aspects 14 through 17, wherein the central area radius is less than 10 percent of the outer polishing area radius.

[0062] Aspect 19. The method of any of aspects 14 through 18, wherein the central area radius is in a range from 1 to 3 cm and the outer polishing area radius is in a range from 30 to 40 cm.

[0063] Aspect 20. The method of any of aspects 14 through 19, wherein the pad is made of porous thermoset polymer.

[0064] Aspect 21. The method of any of aspects 14 through 20, wherein the pad is made of porous thermoset polyurethane.

[0065] Aspect 22. The method of claim 21, wherein the pad has a density in a range from 0.5 to 0.8 grams per cubic centimeter.

[0066] It will be understood, however, that this disclosure is, in many respect, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of parts without exceeding the scope of the disclosure. The disclosure's scope is, of course, defined in the language in which the appended claims are expressed.

Examples

Embodiment Construction

[0022]This disclosure relates to CMP pads that include an upper surface that is adapted to process a surface of a wafer substrate by chemical-mechanical polishing. The upper surface includes a central area that includes the center of the upper surface and that extends from the center of the upper surface to a central area radius. The central area includes a non-polishing surface or a combination of non-polishing surfaces and polishing surfaces that are adapted to control an amount of heat energy that is generated at the central area or that accumulates at the central area, to prevent an excess temperature increase of the pad at the central area during a CMP process. The upper surface also includes an outer polishing area that is effective to remove material from all portions of a wafer substrate surface (center, edge, and mid-radial ranges of the wafer substrate surface) during a CMP process.

[0023]A CMP pad as described can be used in a chemical-mechanical planarization process for ...

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 738,463, filed Dec. 23, 2024, the entire disclosure of which is incorporated herein by reference for all purposes.FIELD

[0002] This disclosure relates to pads for use in chemical-mechanical polishing (also sometimes referred to as “chemical-mechanical planarization”), particularly to such pads that have a central area that is adapted to control the temperature of the pad at the central area by controlling the amount of friction between the pad and a wafer substrate at the central area during chemical-mechanical processing, or by removing heat energy from the central area of the pad during chemical-mechanical polishing, or both.BACKGROUND

[0003] Chemical-mechanical polishing (or “chemical-mechanical planarization” or “CMP”) is the process of selectively removing excess material that has been deposited onto an in-process microelectronic device substrate (i.e., a “wafer substrate”) to effect a leveling of the wafer substrate surface for subsequent processing at the surface. CMP uses the combined effects of physical (abrasive, mechanical) and chemical forces to remove material from a substrate surface. CMP is performed by applying pressure to the back of the wafer substrate while the substrate contacts a polishing pad and while a chemical-abrasive slurry (“CMP slurry”) is dispensed between the pad and wafer substrate. The pad is placed against the substrate with a desired amount of pressure and both the pad and the substrate are rotated while the slurry is presented therebetween.SUMMARY

[0004] CMP processes are used with different types of substrates to remove organic or inorganic materials from the substrate surface. Processes for particular types of substrates are carried out with specialized pads made of different polymer materials and having polishing surfaces with various highly refined patterns. Specialized CMP slurries are used with specific substrates and for removal of particular materials from the substrate. For removing different types or amounts of materials, selective amounts of pressure can be used, selected velocities can be used, and selective amounts of slurry can be used.

[0005] These factors affect the amount of friction and heat energy generated as well as the amount of heat energy retained at different locations of the pad surface and subsurface. Generally, a greater amount of heat may be generated at a central area of the pad because a higher relative velocity at the center of the pad generates a greater amount of friction, and also because of a higher contact time (the amount of time that the wafer substrate contacts the pad surface) at the central area of a pad. By some CMP processes, a center of a pad may be in contact with a retaining ring of a polishing head during most or all of the polishing time of the process.

[0006] Adding to the relatively greater generation of heat energy at the central area, heat energy generated at the central area may not readily dissipate from the central area. Firstly, the high contact time between the pad and the wafer at the central area prevents dissipation of heat from the central area. Additionally, the central area may not receive a regular or significant flow of CMP slurry, which can be effective to remove heat energy from the pad. The high contact time and lack of heat dissipation from the central area can cause a temperature increase at the central area, including below the pad surface at the pad interior or “subsurface.”

[0007] For many or perhaps most CMP processes, heat energy caused by friction does not increase the temperature of a pad to a level that impacts performance of the pad. For other CMP processes, including processes sometimes referred to as “high stress” CMP processes, the amount of heat energy generated by friction and retained in a pad, particularly a central area of a pad, can increase the pad temperature to a temperature that causes localized pad failure.

[0008] A high-stress CMP process is designed to achieve a relatively high rate of material removal. Certain types of materials are applied to wafer substrates at higher thicknesses than other materials. Examples include various organic materials and inorganic materials such as metals (e.g., copper, tungsten, molybdenum), metal oxides, silicon carbide, among others. To achieve desired processing throughput, a CMP process that removes a relatively greater amount of material may be designed to have a higher rate of removal by using a pressure at a high end of typical operating pressure ranges, a velocity between the pad and substrate that is at a high end of typical operating ranges, or both.

[0009] The higher pressure and velocity required to achieve the higher removal rate increase the amount of heat energy that is produced by friction, which increases the temperature of the pad. Prolonged exposure and retention of heat energy can lead to an excessive pad temperature, meaning a temperature that is capable of degrading or otherwise damaging the pad. With certain CMP processes and CMP pads, heat stress caused by an excessively high pad temperature at a central area of the pad has been found to produce acute defects within the pad such as bubbles within the pad subsurface. For the reasons described, the risk of heat-induced damage to a CMP pad is greatest at the central area of the pad, particularly in a CMP process that operates at a relatively high pressure and velocity between the pad and the wafer substrate. For such CMP processes there is a need to prevent a temperature increase of the pad, particularly at a center region of a pad, and particularly to avoid a temperature increase that would cause heat-induced damage such as bubbles being generated within the subsurface.

[0010] CMP pads, as described herein, include an upper surface that is adapted to process a wafer substrate by chemical-mechanical polishing. The upper surface includes a polishing area that is effective to remove material from all portions of a surface of a wafer substrate by a CMP process. The upper surface also includes a central area located at the center of the upper surface of the pad and extends from the center of the pad to a location on the pad referred to herein as a “central area radius.” An outer polishing area extends from the central area radius to an outer polishing area radius at or near an edge of the pad. The outer polishing area can include a pattern of polishing surfaces (“outer polishing surfaces”) and grooves (“outer grooves”) that may be arranged in any useful pattern and may have any useful shapes and dimensions.

[0011] The central area can include one or more of polishing surfaces, grooves, or non-polishing surfaces (for example grooves or another absence of a polishing surface) that control the temperature of the pad at the central area during a CMP process, specifically, that prevent an excessive increase in temperature of the pad at the central area and keep the temperature of the pad at the central area below a temperature that causes heat-induced damage to the pad. As described herein, certain arrangements of a non-polishing surface or a combination of polishing surfaces and non-polishing surfaces (e.g., grooves) at the central area can prevent an excessive temperature increase by controlling the amount of heat energy generated by friction at the central area, or by allowing or causing heat energy to be dissipated from the central area, or both.

[0012] To reduce or prevent heat energy from being generated at the central area, a central area can include a non-polishing surface or a combination of polishing surfaces and non-polishing surfaces (e.g., grooves) that controls the amount of friction between a wafer substrate and a pad at the central area during CMP processing. To dissipate heat energy away from the central area, the central area can include a non-polishing surface or a combination of polishing surfaces and non-polishing surfaces (e.g., grooves) that allows a CMP slurry to flow through the central area to remove the heat energy.

[0013] In short, heat stress-induced damage to a CMP pad may occur during CMP processing as heat energy accumulates within the pad, particularly within the pad subsurface at a central area. The heat energy is not readily dissipated from the central area of the pad, especially the subsurface, due to high contact time with the wafer substrate and a lack of CMP slurry contacting the central area. A high amount of heat generation and low heat dissipation lead to heat energy accumulation at the central area and an increase in temperature, which can cause acute damage to the pad and localized pad failure, particularly in high-stress CMP processes.

[0014] In one aspect, a chemical-mechanical polishing pad can include a central area extending from a center of the polishing pad to a central area radius and an outer polishing area that extends from the central area radius to an outer polishing area radius. The outer polishing area includes outer polishing surfaces and outer grooves having an outer groove depth. When a wafer substrate surface is placed in moving contact with the outer polishing area during chemical-mechanical polishing, an amount of polishing friction is produced between the outer polishing area and the wafer substrate surface. When the wafer substrate surface passes over the central area during the chemical-mechanical polishing, an amount of friction between the central area and the wafer substrate surface is less than the polishing friction.

[0015] In another aspect, a method of polishing a wafer substrate includes: providing a polishing pad that has an upper surface that includes a central area extending from a center of the polishing pad to a central area radius, an outer polishing area that extends from the central area radius to an outer polishing area radius, the outer polishing area having outer polishing surfaces and outer grooves; contacting a wafer substrate surface with the polishing pad upper surface with pressure and motion between the wafer substrate surface and the polishing pad upper surface; and applying abrasive slurry between the polishing pad upper surface and the wafer substrate surface. When the wafer substrate surface is in moving contact with the outer polishing area, an amount of polishing friction is produced between the outer polishing area and the wafer substrate. When the wafer substrate surface passes over the central area, an amount of friction is produced between the central area and the wafer substrate surface that is less than the polishing friction.

[0016] The preceding summary is provided to facilitate an understanding of some of the innovative features unique to the present disclosure and is not intended to be a full description. A full appreciation of the disclosure can be gained by taking the entire specification, claims, drawings, and abstract as a whole.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The disclosure may be more completely understood in consideration of the following description of various illustrative embodiments in connection with the accompanying drawings, in which:

[0018] FIG. 1 schematically shows a generic CMP apparatus and process including as described herein;

[0019] FIG. 2 schematically shows a generic CMP apparatus and process with wafer contact time and heat accumulation relative to the CMP pad; and

[0020] FIGS. 3, 4, and 5 show top views of example CMP pads as described herein.

[0021] While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit aspects of the disclosure to the particular illustrative embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.DETAILED DESCRIPTION

[0022] This disclosure relates to CMP pads that include an upper surface that is adapted to process a surface of a wafer substrate by chemical-mechanical polishing. The upper surface includes a central area that includes the center of the upper surface and that extends from the center of the upper surface to a central area radius. The central area includes a non-polishing surface or a combination of non-polishing surfaces and polishing surfaces that are adapted to control an amount of heat energy that is generated at the central area or that accumulates at the central area, to prevent an excess temperature increase of the pad at the central area during a CMP process. The upper surface also includes an outer polishing area that is effective to remove material from all portions of a wafer substrate surface (center, edge, and mid-radial ranges of the wafer substrate surface) during a CMP process.

[0023] A CMP pad as described can be used in a chemical-mechanical planarization process for processing a microelectronic device substrate (sometimes referred to herein as a “wafer substrate”) that contains in-process (partially completed) microelectronic device precursors at a surface of the substrate. A typical CMP process uses a platen to which the CMP pad is attached and a polishing head that holds the wafer substrate and presses the surface of the wafer substrate against the upper surface of the pad. The head and the platen both rotate in the same direction while an abrasive-chemical slurry (“CMP slurry”) is delivered between the upper surface of the pad and the surface of the wafer substrate in contact with the upper surface of the pad.

[0024] FIG. 1 shows a generalized, schematic view of an exemplary CMP apparatus 50 for performing an exemplary CMP process. In the exemplary process, using apparatus 50, slurry 52 is dispensed via slurry dispenser 54 onto an upper surface of CMP pad 56. Alternatively, slurry 52 may be delivered from the bottom of pad 56 to the upper surface of pad 56. Pad 56 is mounted on rotatable platen 58, from which a rotatable platen shaft 60 extends. Wafer substrate 66 is held by a substrate chuck (or “head”) 62 from which a substrate chuck shaft 64 extends. A down force is controllably applied to substrate head 62 via shaft 64 to provide controllable contact between pad 56 and wafer substrate 66.

[0025] FIG. 2 schematically shows a top view of apparatus 50 with CMP pad 56 and wafer substrate 66, including positions and movement of wafer substrate 66 relative to upper surface 70 of pad 56 during CMP processing. Upper surface 70 includes a pattern of polishing surfaces (not specifically shown) that are separated by grooves (not specifically shown) to form a polishing surface. As pad 56 is rotated (see the arrow R indicating the rotational direction), wafer substrate 66 also rotates while being moved laterally in an X-Y plane (see arrow X-Y) along the radius of pad 56 between the center (C) and outer edge of pad 56. Also included in FIG. 2, is a graphical representation showing the amount of time the upper surface 70 of pad 56 in in contact with the wafer substrate (contact time) relative to pad diameter and center C. As shown in the graphical representation of FIG. 2, the amount of time under wafer contact (contact time) of the wafer substrate 66 with the upper surface 70 of pad 56 is greatest at the middle region of pad 56, particularly at and near center C. The graphical representation in FIG. 2 also shows that the amount of heat that accumulates at different locations along the radius of pad 56, are greatest at the middle of pad 56 at and near center C.

[0026] Referring to FIG. 3, a top view of example CMP pad 100 is shown as having upper surface 110 that includes central area 112 that extends from center C to central area radius 114. Upper surface 110 also includes outer polishing area 116 that extends between central area radius 114 (dashed line) and outer polishing area radius 118 (dashed line) at the outer edge of upper surface 110. Outer polishing area 116 includes a pattern of polishing surfaces (not specifically shown) that are separated by grooves (not specifically shown). The combination of polishing surfaces and grooves at outer polishing area 116 may be of any useful pattern or dimensions.

[0027] Central area 112 can include a non-polishing surface alone, or a combination of polishing surfaces and non-polishing surfaces that may be grooves or another form of a non-polishing surface. (Polishing surfaces that are located in the central area may sometimes be referred to herein as “central polishing surfaces,” and grooves that are located in the central area may sometimes be referred to herein as “central grooves.”)

[0028] One example of central area 112 may include a single non-polishing surface over the entire area of central area 112 extending as a circular area from the pad center (C) to central area radius 114. Other examples of central area 112 may include a circular middle area (“sometimes referred to more simply herein as a “middle area”) that covers a circular portion of central area 112, including pad center C, and extends from pad center C to a middle area radius. A circular middle area may include a polishing surface only (i.e., over the entire middle area surface), or a non-polishing surface only (i.e., over the entire middle area surface) (see FIGS. 4 and 5, respectively). Alternately, a circular middle area of a central area 112 may include a combination of polishing surfaces and non-polishing surfaces, e.g., grooves. The annular area of central area 112 between the middle area radius 132 and the central area radius 114 may also contain polishing surfaces, non-polishing surfaces such as grooves, or both.

[0029] Still other examples of central area 112 may include polishing surfaces and grooves that have any other dimensions or pattern that is effective during CMP processing to control the temperature of the pad at central area 112 either by controlling an amount of friction and heat energy generated by friction between the pad surface and a wafer substrate surface, or by allowing or causing CMP slurry to pass through central area 112 (e.g., through grooves in central area 112) to carry heat energy from central area 112.

[0030] To reduce friction between a wafer substrate surface and central area 112 during a CMP process, example central areas 112 may have a total amount (by area) of central polishing surfaces that covers less than 85 percent of the total area of the central area (when viewed from above the central area as in FIGS. 3, 4, and 5). A central area as described that has no polishing surfaces as part of the central area is considered to have zero percent polishing surfaces based on total area of the central area. A central area 112 that has both polishing surfaces and non-polishing surfaces (grooves or another type of non-polishing surface) may have a total amount (area) of polishing surfaces that is less than 85, 80, 60, 50, 40, 30, or 20 percent of the total amount of area of the central area.

[0031] As used herein, a “polishing surface” (whether a polishing surface located at an outer polishing area or a polishing surface located in a central area) is a surface at an upper surface of a CMP pad that contacts a surface of a wafer substrate during a CMP process and, with relative motion and pressure between the wafer substrate surface and the pad surface, is effective to remove material from the wafer substrate surface by chemical-mechanical polishing mechanisms. Polishing surfaces are present at outer polishing areas of a CMP pad, and may optionally be present at a central area of a CMP pad. Polishing surfaces extend horizontally (in an x-direction and a y-direction) at the upper surface of a pad when the pad is viewed in cross-section. Polishing surfaces of a CMP pad, including outer polishing surfaces (located on an outer polishing area) and central polishing surfaces (located at a central area), are substantially coplanar, with the polishing surfaces being located substantially in a single plane, that plane sometimes being referred to herein as a “polishing plane.”

[0032] A “non-polishing” surface is a surface at the upper surface of the pad that does not contact a wafer substrate surface during a CMP process and does not engage the wafer substrate surface to remove material from the wafer substrate surface by chemical-mechanical polishing mechanisms. A non-polishing surface extends horizontally at a depth that is below the polishing plane (the depth is in a z-direction when the pad is viewed horizontally, from a side, as in FIG. 1), the depth being sufficiently large and the distance between the non-polishing surface and a polishing surface of the pad being sufficient to prevent a wafer substrate surface from contacting the non-polishing surface during a CMP process.

[0033] An example of a non-polishing surface is a groove (or open channel, or the like) that is formed in a pad upper surface between polishing surfaces. The groove includes an opening that originates at a level of a polishing surface, meaning at a polishing plane, and extends horizontally across the pad upper surface as well as vertically below the polishing surface. The depth of a groove (a bottom of a groove) below the polishing surface and polishing plane may sometimes be referred to herein as “groove depth.” Typically, a groove or similar structure at a pad upper surface can be an elongate, straight, or curved channel or channel-like open structure or open space that has a length that is significantly greater than its width and depth, and that is positioned between polishing surfaces. Example grooves may be radial grooves that extend linearly, continuously, or discontinuously, generally, or exactly along a line of a radius of the pad from the pad center to a pad edge. Other examples grooves may be curved or straight grooves that are arranged continuously or discontinuously in a concentric pattern around the pad center. Many or all of the grooves of a CMP pad can have a common groove depth, i.e., grooves of a CMP pad can have a groove depth that is coplanar, including among center grooves and outer grooves, with the groove depths of multiple grooves being coplanar in a plane that is parallel to the polishing plane.

[0034] In another embodiment, a non-polishing surface at a central area of a pad is circular and larger than a groove in horizontal dimensions of width and length, which are both significantly greater than a thickness dimension (a thickness in the z-direction) of the non-polishing surface. A non-polishing surface at a central area may extend over the entire central area from a pad center to a central area radius, or may extend over only a portion of a central area from a pad center to a middle area radius that is less than the central area radius (see FIG. 5). A non-polishing surface at a central area can have a depth that is coplanar with a groove depth of grooves of the outer polishing area (“outer grooves”) or may alternately have a depth that is greater than a groove depth of grooves of the outer polishing area, below a groove depth of grooves of the outer polishing surface.

[0035] A non-polishing surface or a combination of polishing surfaces and non-polishing surfaces at a central area can be effective to prevent an excessive increase in temperature at the central area to prevent the pad at the central area from reaching a temperature that becomes sufficiently high to cause heat-induced damage to the pad in the form of an acute defect (e.g., bubble formation) in the subsurface at the central area of the pad.

[0036] During a CMP process, friction exists due to moving contact between the surface of the wafer substrate and polishing surfaces of the CMP pad (this amount of friction may be referred to herein as an amount of “polishing friction”). With example CMP pads as described, a central area of a pad is adapted to produce an amount of polishing friction at the central area (“central polishing friction”) that is lower than an amount of polishing friction that is produced at an outer polishing area (“outer polishing friction”); i.e., during the CMP process, the amount of friction that exists between the surface of the wafer substrate and the central area is less than the amount of friction that exists between the surface of the wafer substrate and polishing surfaces at the outer polishing surface. The reduced amount of friction at the central area reduces the generation of heat energy at the central area to prevent an unwanted temperature increase of the pad at the central area.

[0037] The central area may also include a non-polishing surface that can maintain a presence or a flow of CMP slurry at the central area. The temperature of the pad at the central area may be further controlled by these non-polishing surfaces, which allow heat energy to be removed from the central area by the flow of CMP slurry.

[0038] An example design of polishing surfaces and non-polishing surfaces at a central area of a CMP pad is shown at FIG. 4. FIG. 4 is a top view of CMP pad 100 that includes upper surface 110 that includes central area 112 that extends from center C to central area radius 114. Upper surface 110 also includes outer polishing area 116 that extends between central area radius 114 and an outer polishing area radius (not shown) at the outer edge of upper surface 110. Outer polishing area 116 includes a pattern of geometrically-shaped (e.g., rectangular) outer polishing surfaces 120 arranged in a concentric pattern, interrupted by outer grooves 122 arranged in a radial and concentric pattern. The pattern of outer polishing surfaces 120 and outer grooves 122 may be of any useful design. Generally, with respect to any CMP pads described herein, central area radius 114 may be less than 10 percent of the outer polishing area radius. For example, for an outer polishing area having a radius is in a range from 30 to 40 cm and a central area radius is in a range from 1 to 3 cm.

[0039] Central area 112 includes a combination of polishing surfaces (sometimes referred to as “central polishing surfaces”) and grooves (sometimes referred to as “central grooves”). A circular middle area that extends from center C to middle area radius 132 includes middle polishing surface 130, which is coplanar with outer polishing surfaces 120. Additional central polishing surfaces 140 are arranged in a pattern of two concentric rings between middle area radius 132 and central area radius 114, each central polishing surface 140 being an elongate, curved (optionally straight) annular surface. Central grooves 142 (concentric) and 144 (radial) are located between middle area radius 132 and central area radius 114 to separate central polishing surfaces 140 and to allow flow of CMP slurry between central polishing surfaces 140, within central area 112, during a CMP process.

[0040] FIG. 5 is a top view of a different example CMP pad 100 that similarly includes upper surface 110 having central area 112 that extends from center C to central area radius 114. Other features of example CMP pad 100 of FIG. 5 are similar to example CMP pad 100 of FIG. 4, but with certain differences. The circular middle area of pad 100 of FIG. 5, between center C and middle area radius 132, does not include a middle polishing surface 130 as in FIG. 4 but instead includes non-polishing surface 134, which is a surface that is coplanar with or below (has a greater depth than) the depth of outer grooves 122 and central grooves 142 and 144.

[0041] The designs of polishing surfaces and non-polishing surfaces at central area 112 of CMP pad 100 shown in FIGS. 4 and 5 are exemplary. Those of skill in the art will recognize that other combinations of polishing surfaces and grooves may be used to achieve the same effect as those of FIGS. 4 and 5 to avoid an excessive temperature increase at a central area of a CMP pad.

[0042] A CMP pad as described herein can be used with any CMP process for removing a desired material from a wafer substrate surface. In specific applications, the CMP pad may be useful with CMP processes that produce and retain a significant amount of heat energy at a central area of a pad in a manner that would cause an excessive temperature increase in the pad and damage the polymer of the pad at the central area. These CMP processes include processes sometimes considered to be “high-stress” CMP processes that are designed to achieve a high removal rate of material from a wafer substrate surface by using relatively high pressure and relatively high velocity between a wafer substrate surface and a pad surface. Examples of materials that may be removed by such CMP processes include organic materials and inorganic materials such as metals (e.g., copper, tungsten, molybdenum), metal oxides, silicon carbide, among others.

[0043] The CMP pad may be made of any material and may have any dimensions. In certain applications, such pads include porous pads made of porous thermoset polyurethane. These porous polymeric pads may have a density of between 0.3 and 0.9 grams per cubic centimeter, e.g., from 0.5 to 0.8 grams per cubic centimeter. The porous polymeric pad may also be relatively flexible, having an elastic modulus at the pad surface that is a range from about 400 to about 1200 MPa.Aspects

[0044] Aspect 1. A chemical-mechanical polishing pad comprising a pad upper surface including a central area extending from a center of the polishing pad to a central area radius, and an outer polishing area that extends from the central area radius to an outer polishing area radius, the outer polishing area comprising outer polishing surfaces and outer grooves having an outer groove depth, wherein when a wafer substrate surface is placed in moving contact with the outer polishing area during chemical-mechanical polishing, an amount of polishing friction is produced between the outer polishing area and the wafer substrate surface, and when the wafer substrate surface passes over the central area during the chemical-mechanical polishing, an amount of friction between the central area and the wafer substrate surface is less than the polishing friction.

[0045] Aspect 2. A chemical-mechanical polishing pad comprising a pad upper surface including a central area extending from a center of the polishing pad to a central area radius, and an outer polishing area that extends from the central area radius to an outer polishing area radius, the outer polishing area comprising outer polishing surfaces and outer grooves having an outer groove depth, wherein when a wafer substrate surface is placed in moving contact with the outer polishing area during chemical-mechanical polishing, an amount of polishing friction is produced between the outer polishing area and the wafer substrate surface, and wherein a ratio of an area of the central polishing surfaces to an area of the central area is less than 85 percent.

[0046] Aspect 3. The chemical-mechanical polishing pad of aspect 1 or 2, wherein the central area comprises central polishing surfaces that are coplanar with the outer polishing surfaces, and central grooves having a depth of at least the outer groove depth.

[0047] Aspect 4. The chemical-mechanical polishing pad of aspect 3, wherein a ratio of an area of the central polishing surfaces to an area of the central area is less than 85 percent.

[0048] Aspect 5. The chemical-mechanical polishing pad of aspect 1 or 2, the central area comprising a circular middle area extending from the center of the polishing pad to a middle area radius, central polishing surfaces between the middle area radius and the central area radius, coplanar with the outer polishing surfaces, and central grooves between the middle area radius and the central area radius, having a depth of at least the outer groove depth.

[0049] Aspect 6. The chemical-mechanical polishing pad of aspect 5, wherein the circular middle area comprises a middle area polishing surface that extends between the center of the polishing pad to the middle area radius and is coplanar with the outer polishing surfaces.

[0050] Aspect 7. The chemical-mechanical polishing pad of aspect 6, wherein the circular middle area comprises the middle area polishing surface and grooves.

[0051] Aspect 8. The chemical-mechanical polishing pad of aspect 6, wherein the circular middle area comprises the middle area polishing surface with no grooves.

[0052] Aspect 9. The chemical-mechanical polishing pad of aspect 1, wherein the central area comprises a circular non-polishing surface extending from the center of the polishing pad to a middle area radius, having a depth that is coplanar with or below the outer groove depth.

[0053] Aspect 10. The chemical-mechanical polishing pad of aspect 1, wherein the central area consists entirely of a non-polishing surface.

[0054] Aspect 11. The chemical-mechanical polishing pad of any of aspects 1 through 10, wherein the central area radius is less than 10 percent of the outer polishing area radius.

[0055] Aspect 12. The chemical-mechanical polishing pad of any of aspects 1 through 11, wherein the central area radius is in a range from 1 to 3 cm and the outer polishing area radius is in a range from 30 to 40 cm.

[0056] Aspect 13. The chemical-mechanical polishing pad of any one of aspects 1 through 11, wherein the pad has a density in a range from 0.5 to 0.8 grams per cubic centimeter.

[0057] Aspect 14. A method of polishing a wafer substrate, the method comprising: providing a polishing pad comprising an upper surface that comprises a central area extending from a center of the polishing pad to a central area radius, and an outer polishing area that extends from the central area radius to an outer polishing area radius, the outer polishing area comprising outer polishing surfaces and outer grooves having an outer groove depth; contacting a wafer substrate surface with the polishing pad upper surface with pressure and motion between the wafer substrate surface and the polishing pad upper surface; and applying abrasive slurry between the polishing pad upper surface and the wafer substrate surface, wherein when the wafer substrate surface is in moving contact with the outer polishing area, an amount of polishing friction is produced between the outer polishing area and the wafer substrate, and when the wafer substrate surface passes over the central area, an amount of friction is produced between the central area and the wafer substrate surface that is less than the polishing friction.

[0058] Aspect 15. The method of aspect 14, wherein the central area comprises central polishing surfaces that are coplanar with the outer polishing surfaces, and central grooves having a depth of at least the outer groove depth.

[0059] Aspect 16. The method of aspect 15, wherein a ratio of an area of the central polishing surfaces to an area of the central area is less than 85 percent.

[0060] Aspect 17. The method of aspect 14 or 15, the central area comprising a circular middle area extending from the center of the polishing pad to a middle area radius, central polishing surfaces between the middle area radius and the central area radius, coplanar with the outer polishing surfaces, and central grooves between the middle area radius and the central area radius, having a depth of at least the outer groove depth.

[0061] Aspect 18. The method of any of aspects 14 through 17, wherein the central area radius is less than 10 percent of the outer polishing area radius.

[0062] Aspect 19. The method of any of aspects 14 through 18, wherein the central area radius is in a range from 1 to 3 cm and the outer polishing area radius is in a range from 30 to 40 cm.

[0063] Aspect 20. The method of any of aspects 14 through 19, wherein the pad is made of porous thermoset polymer.

[0064] Aspect 21. The method of any of aspects 14 through 20, wherein the pad is made of porous thermoset polyurethane.

[0065] Aspect 22. The method of claim 21, wherein the pad has a density in a range from 0.5 to 0.8 grams per cubic centimeter.

[0066] It will be understood, however, that this disclosure is, in many respect, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of parts without exceeding the scope of the disclosure. The disclosure's scope is, of course, defined in the language in which the appended claims are expressed.

Examples

Embodiment Construction

[0022]This disclosure relates to CMP pads that include an upper surface that is adapted to process a surface of a wafer substrate by chemical-mechanical polishing. The upper surface includes a central area that includes the center of the upper surface and that extends from the center of the upper surface to a central area radius. The central area includes a non-polishing surface or a combination of non-polishing surfaces and polishing surfaces that are adapted to control an amount of heat energy that is generated at the central area or that accumulates at the central area, to prevent an excess temperature increase of the pad at the central area during a CMP process. The upper surface also includes an outer polishing area that is effective to remove material from all portions of a wafer substrate surface (center, edge, and mid-radial ranges of the wafer substrate surface) during a CMP process.

[0023]A CMP pad as described can be used in a chemical-mechanical planarization process for ...

Claims

1. A chemical-mechanical polishing pad comprising:a pad upper surface including:a central area extending from a center of the polishing pad to a central area radius,an outer polishing area that extends from the central area radius to an outer polishing area radius, the outer polishing area comprising outer polishing surfaces and outer grooves having an outer groove depth,wherein when a wafer substrate surface is placed in moving contact with the outer polishing area during chemical-mechanical polishing, an amount of polishing friction is produced between the outer polishing area and the wafer substrate surface, andwhen the wafer substrate surface passes over the central area during the chemical-mechanical polishing, an amount of friction between the central area and the wafer substrate surface is less than the polishing friction.

2. The chemical-mechanical polishing pad of claim 1, wherein the central area comprises:central polishing surfaces that are coplanar with the outer polishing surfaces, andcentral grooves having a depth of at least the outer groove depth.

3. The chemical-mechanical polishing pad of claim 2, wherein a ratio of an area of the central polishing surfaces to an area of the central area is less than 85 percent.

4. The chemical-mechanical polishing pad of claim 1, the central area comprising:a circular middle area extending from the center of the polishing pad to a middle area radius,central polishing surfaces between the middle area radius and the central area radius, coplanar with the outer polishing surfaces, andcentral grooves between the middle area radius and the central area radius, having a depth of at least the outer groove depth.

5. The chemical-mechanical polishing pad of claim 4, wherein the circular middle area comprises a middle area polishing surface that extends between the center of the polishing pad to the middle area radius and is coplanar with the outer polishing surfaces.

6. The chemical-mechanical polishing pad of claim 5, wherein the circular middle area comprises the middle area polishing surface and grooves.

7. The chemical-mechanical polishing pad of claim 5, wherein the circular middle area comprises the middle area polishing surface with no grooves.

8. The chemical-mechanical polishing pad of claim 1, wherein the central area comprises a circular non-polishing surface extending from the center of the polishing pad to a middle area radius, having a depth that coplanar with or below the outer groove depth.

9. The chemical-mechanical polishing pad of claim 1, wherein the central area consists entirely of a non-polishing surface.

10. The chemical-mechanical polishing pad of claim 1, wherein the central area radius is less than 10 percent of the outer polishing area radius.

11. The chemical-mechanical polishing pad of claim 1, wherein the pad has a density in a range from 0.5 to 0.8 grams per cubic centimeter.

12. A method of polishing a wafer substrate, the method comprising:providing a polishing pad comprising an upper surface that comprises:a central area extending from a center of the polishing pad to a central area radius,an outer polishing area that extends from the central area radius to an outer polishing area radius, the outer polishing area comprising outer polishing surfaces and outer grooves having an outer groove depth,contacting a wafer substrate surface with the polishing pad upper surface with pressure and motion between the wafer substrate surface and the polishing pad upper surface,applying abrasive slurry between the polishing pad upper surface and the wafer substrate surface,wherein when the wafer substrate surface is in moving contact with the outer polishing area, an amount of polishing friction is produced between the outer polishing area and the wafer substrate, andwhen the wafer substrate surface passes over the central area, an amount of friction is produced between the central area and the wafer substrate surface that is less than the polishing friction.

13. The method of claim 12, wherein the central area comprises:central polishing surfaces that are coplanar with the outer polishing surfaces, andcentral grooves having a depth of at least the outer groove depth.

14. The method of claim 13, wherein a ratio of an area of the central polishing surfaces to an area of the central area is less than 85 percent.

15. The method of claim 12, the central area comprising:a circular middle area extending from the center of the polishing pad to a middle area radius,central polishing surfaces between the middle area radius and the central area radius, coplanar with the outer polishing surfaces, andcentral grooves between the middle area radius and the central area radius, having a depth of at least the outer groove depth.

16. The method of claim 12, wherein the central area radius is less than 10 percent of the outer polishing area radius.

17. The method of claim 12, wherein the pad has a density in a range from 0.5 to 0.8 grams per cubic centimeter.

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