Multilayer CMP Pad

Abstract

The polishing pad includes a textile layer, a compressible layer, and a water-impermeable layer disposed between the textile layer and the compressible layer, which reduces slurry usage by improving slurry transport and does not require diamond conditioning to maintain slurry transport.

Description

[Technical Field]

[0001] The present invention relates generally to the field of chemical mechanical planarization (CMP), and more specifically to CMP polishing pads used in CMP processes. [Background technology]

[0002] In modern integrated circuit (IC) manufacturing, layers of material are applied to pre-formed embedded structures on semiconductor wafers. Chemical mechanical planarization, also known as chemical mechanical polishing (CMP), is a polishing process used to remove these layers and polish the surface of the wafer flat to obtain the desired structures.

[0003] Multilayer CMP Pad CMP can be performed on both oxide and metal films and typically involves the use of a chemical slurry applied via a polishing pad that moves relative to the wafer (e.g., a pad that rotates in a circular motion relative to the wafer). The resulting smooth, flat surface is necessary to maintain the depth of focus for photolithography in subsequent steps and to prevent metal interconnects from deforming over contour steps. In damascene processes, CMP is required to remove metals such as tungsten or copper from the top surface of the dielectric to define the interconnect structure.

[0004] The planarization / polishing performance of a pad and slurry combination is determined, among other things, by its thermomechanical and chemical properties, as well as its ability to distribute the slurry uniformly. Typically, hard (i.e., rigid) pads provide good planarization but are associated with poorer within-wafer uniformity of film removal (WIWNU) and a higher tendency to cause microscratch defects. On the other hand, soft (i.e., compliant) pads provide good WIWNU polishing but poorer planarization. Therefore, in conventional CMP systems, harder pads are used for bulk film removal and feature planarization, while softer pads are used for finer polishing and removal of microscratch defects, as well as for substantial removal of slurry abrasive particles before rinsing with a CMP cleaner.

[0005] 1 shows a typical polishing system. A polishing pad 102 is secured to a polishing table 101 with a pressure-sensitive adhesive. A wafer 103 is held by a wafer holder 104 and pressed against the polishing pad 102 while both the polishing table 101 and the wafer holder 104 rotate about their respective axes and a slurry 106 is applied to the polishing pad.

[0006] Conventional polishing pads are typically made of polyurethane, filled with microporous elements in a cast form, or made from polyurethane-coated nonwoven felt. In addition to the above two processes, soft pads can be made by solution precipitation, in which a polymer is dissolved in a water-miscible solvent and precipitated by adding water as a non-solvent. This results in a porous pad surface with good polishing properties.

[0007] 2 shows a cross-sectional side view of a hard polishing pad 200. The polishing pad 200 consists of a urethane matrix 202, microelements 204, and grooves 206, much like those found in commercially available polishing pads such as the IC1000 available from DuPont Electronic Materials.

[0008] 3 shows a soft polishing pad 300. The polishing pad 300 comprises a urethane matrix 302 and vertically oriented pores 304. The pad surface may optionally be embossed to provide grooves to improve slurry distribution at the wafer-pad interface.

[0009] Polishing is performed by applying pressure and motion to the wafer, which causes deformation of the pad material. This deformation smooths the pad surface, which must be roughened to continue wafer polishing. The process of roughening the pad surface, known as pad conditioning, is performed by pressing a rotating disk covered with fine diamonds against the rotating pad. This restores the pad's roughness and enables localized slurry transport. Therefore, polishing pads require grooves, pores, and micro-roughness, which affect the uniform polishing process. Stable polishing performance requires optimization of grooves and porosity for macro-transport and diamond conditioning for localized slurry transport. Pads are supplied with excess slurry to ensure sufficient slurry is evenly distributed across the wafer-pad interface. Improving slurry transport can reduce slurry usage, and a pad that does not require diamond conditioning to maintain slurry transport would be advantageous. Summary of the Invention

[0010] According to one aspect of the present invention, there is provided a CMP polishing pad for use in CMP processing, which reduces slurry usage by improving slurry transport and does not require diamond conditioning to maintain slurry transport.

[0011] According to one embodiment of the present invention, a polishing pad may be configured to include a textile layer, a water-impermeable layer, and a compressible layer. A first side of the textile layer may form the polishing surface, while a second side may be attached to the first side of the impermeable layer. The second side of the impermeable layer may be attached to the first side of the compressible layer. The second side of the compressible layer may be secured to a polishing table by a pressure-sensitive adhesive.

[0012] In one embodiment, the base fabric of the textile layer forming the polishing surface may be woven to provide a controlled, structured surface. However, in another embodiment, the base fabric of the textile layer may be knitted. Several techniques may be used in weaving or knitting, allowing for the creation of precise patterns using a single yarn or multiple yarns. For example, rib or waffle patterns may be used to create 3D features. Terry weaving may create three-dimensional (3D) feature loops. Jacquard weaving may create specialized patterns using multiple yarns. These techniques, combined with yarn selection for a given pattern, allow for tailoring of local pad properties. For example, polyester yarns, nylon yarns, or Kevlar (poly(azanediyl-1,4-phenyleneazanediyl terephthaloyl) yarns may be selectively applied to create high and low modulus domains of desired size distributed within the pad. In another example, hydrophilic and hydrophobic yarns may be selectively applied to tailor slurry transport.

[0013] In one embodiment, the polishing pad comprises: a textile layer; a compressible layer; a water-impermeable layer disposed between the textile layer and the compressible layer.

[0014] The top surface of the textile layer may be configured to contact the wafer, and the bottom surface of the compressible layer may be configured to be secured to the polishing table.

[0015] The textile layer may have a top surface comprised at least in part of single-sided terry loops, the top surface of the textile layer being opposite its bottom surface, the bottom surface being adjacent to the top surface of the water-impermeable layer.

[0016] The textile layer may be made from multiple types of yarn constructions such as denier, twist, filament, and staple.

[0017] The terry loop may be 1.0 mm to 10 mm in height, preferably 2 mm to 6 mm in height.

[0018] The yarns of the textile layer may be made of one or more polymers including, but not limited to, polyvinyl alcohol (PVA), polyester, polyurethane, nylon, ultra-high molecular weight polyethylene (UHMWPE), polypropylene, acrylic, ethylene propylene diene monomer rubber (EPDM), polystyrene, acrylonitrile butadiene styrene (ABS), Kevlar, aramid, liquid crystal polymers such as Vectran, and liquid crystal polyoxazole (PBO), preferably polyurethane, nylon, UHMWPE, aramid, Kevlar, EPDM, and PVA, and more preferably polyurethane, nylon, UHMWPE, or Kevlar. Vectran is a manufactured fiber spun from a liquid crystal polymer available from Celanese, Inc.

[0019] The textile layer may have a yarn count of about 50 to about 500 warp yarns per inch and about 50 to about 500 weft yarns per inch.

[0020] The terry loop density may be from about 100 to about 10,000 per square inch.

[0021] The terry loops may be arranged in a pattern including linear, circumferential, spiral, arcuate, or other geometric arrangements.

[0022] The textile layer may comprise yarns of from about 50 to about 2500 denier, preferably from about 200 to about 1500 denier.

[0023] A textile layer may be made by interweaving two sets of yarns or threads at right angles to one another. The two sets of yarns or threads are referred to as warp (lengthwise) and weft (widthwise). A textile layer may have warp and weft yarns each comprising yarns made of a different material. Terry loops may be formed using yarns of additional materials using a weaving technique known as "terry cloth" or "terry toweling." This weaving technique involves adding at least one additional yarn and weaving it into the basic structure of the textile layer to form loops. The yarn(s) used to create the terry loops are sometimes referred to as pile yarns. The basic structure of a textile layer refers to a textile layer without terry loops and is sometimes referred to as the woven base fabric.

[0024] The water impermeable layer may be made from at least one of a thermoplastic polyurethane, an acrylic, or a polycarbonate polymer.

[0025] The water impermeable layer may be about 25 to about 250 microns thick.

[0026] In one embodiment, the water-impermeable layer may be thermally bonded to the textile layer. Thermal bonding involves heating the water-impermeable layer until the surface of the water-impermeable layer softens or melts before attaching the textile layer. The composite of the textile layer and the impermeable layer is then attached to the compressible layer. Heating the water-impermeable layer may be carried out by any suitable means, in a continuous or batch process. One such method is to use a heated press, which simultaneously applies heat and pressure to form a permanent bond between the textile layer and the impermeable layer.

[0027] In one embodiment, the water-impermeable layer may be bonded to the textile layer and the compressible layer using an adhesive, which may be a thermal adhesive.

[0028] The compressible layer may be a woven 3D fabric.

[0029] The compressible layer may be a closed cell foam.

[0030] The compressible layer may be a nonwoven textile.

[0031] The compressible layer may be from about 0.5 mm to about 2.5 mm thick.

[0032] The polishing pad is advantageous because, among other things, it can reduce slurry usage by improving slurry transport and can completely eliminate or reduce the need for diamond conditioning to maintain slurry transport.

[0033] These and other features of the present invention will be better understood by those skilled in the art from the following detailed description of embodiments of the invention taken in conjunction with some of the accompanying drawings. [Brief explanation of the drawings]

[0034] The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings. [Figure 1] FIG. 1 is a simplified schematic diagram showing a typical polishing setup. [Figure 2] FIG. 2 is a simplified schematic diagram showing a hard polishing pad. [Figure 3] FIG. 3 is a simplified schematic diagram showing a soft polishing pad. [Figure 4] FIG. 4 is a simplified schematic diagram illustrating a multi-layer polishing pad incorporating a textile layer according to one embodiment of the present invention. [Figure 5] FIG. 5 is a simplified schematic diagram illustrating a textile scrubbing layer and an impermeable layer according to one embodiment of the present invention. [Figure 6] FIG. 6 is a simplified schematic diagram illustrating a 3D cloth according to one embodiment of the present invention. Detailed Description

[0035] According to a first aspect of the present invention, a CMP pad is provided that reduces slurry consumption, reduces the need for reconditioning of the polishing surface, and is easily customizable to optimize the CMP process. The present invention also relates to methods for making the pad and methods of using the pad.

[0036] Thus, in one embodiment, a pad according to an embodiment of the present invention includes a textile layer, an impermeable layer, and a compressible layer. The textile layer may comprise a base fabric layer and a plurality of loops protruding from one side of the base fabric layer. A flat side of the base fabric layer opposite the side with the protruding loops may be attached to the water-impermeable layer, which may then be attached to the compressible layer.

[0037] Typically, cast urethane pads with Shore D hardness ranging from 55 to 75 are used for applications requiring planarization. One such hard pad, the IC1000 from DuPont Electronic Materials, has a Shore D hardness of 65. While such pads provide good planarization, their Wi-Fi noise performance may not be adequate for all planarization tasks. In an attempt to improve Wi-Fi noise performance, hard pads are typically stacked with a soft underpad, such as the SUBA IV™ pad, also from DuPont Electronic Materials. The soft underpad allows the upper hard pad to place a larger area of ​​its surface against the wafer. This results in an overall pad stack with lower stiffness than the hard pad alone. While this can improve Wi-Fi noise, it also results in reduced planarization performance. A typical polishing pad is 2 to 3 mm thick. The top or polishing layer is 1.5 to 2 mm thick, and the compressible soft pad underneath is 0.5 to 1.0 mm thick.

[0038] The present invention relates to a multi-layer CMP pad design that reduces slurry consumption and pad conditioning and provides a defect-free wafer surface. Figure 4 shows a pad 400 according to one embodiment of the present invention. The pad 400 is composed of textile layers 406, 408 having a base fabric 406, which may be a woven base fabric, and yarn loops 408. The yarn loops may be terry loops. The loops may be laid out in groups with spaces between them, or in a rectangular pattern with the spaces between them forming a perimeter. The loops may be arranged so that groups of high-modulus yarns interleave with low-modulus yarns in a predetermined pattern. The textile layers may be about 1 mm to about 3 mm thick. The woven textile layers 406, 408 may be attached to a water-impermeable layer 404, which may be a thermoplastic polyurethane or polyester and 25 microns to 250 microns thick. The water-impermeable layer 404 may be thermally bonded to the textile layers for a permanent bond. The opposite surface of the water-impermeable layer 404 may be attached to a compressible layer 402. The compressible layer 402 may be, for example, a closed-cell foam, an elastomeric solid sheet, a nonwoven fabric, or a 3D fabric. The thickness of the compressible layer 402 may be from about 0.5 mm to about 1.5 mm.

[0039] 5 shows textile layers 406, 408 and water-impermeable layer 404. The textile and impermeable layers are thermally bonded using a heat press by placing the textile and impermeable layers together and applying heat and pressure to press them together and heat them above the softening temperature of the impermeable layer.

[0040] 6 shows an example of a 3D fabric 402 that may be used as the compressible layer 402 of the pad 400, which includes an upper fabric 606 and a lower fabric 602 of the same or different weave construction, and a connecting yarn layer 604. The connecting yarn layer 604 may be independently varied to adjust the compressibility of the 3D fabric.

[0041] In one embodiment of the present invention, the textile layer may be constructed from engineered yarn (also referred to as thread or fiber) and a base fabric and textile technology to create woven loops that protrude perpendicularly from one side of the base fabric. This pad construction provides high performance, reduced slurry consumption, and reduced need for reconditioning of the pad's surface. Additionally, the manufacturing method for creating the pad is advantageous because it uses yarn loops to provide a controlled abrasive surface with a desired textured surface pattern.

[0042] The weaving process can be used to create a network of interconnected fibers / yarns in the XY direction, which may be varied to create features in the Z direction. However, the present invention is not limited to using weaving methods to create the base fabric and loops on the base fabric. Other suitable methods may be used.

[0043] For example, knitting is another process for creating textiles, which involves creating a series of interconnected loops to create a fabric. Knitting is similarly precise and can generate 3D features. Tufting is yet another method of weaving that lends itself to creating 3D features. Tufting is typically used to create carpets, where individual yarn loops are woven perpendicular to the base fabric. This approach has lower resolution than weaving or knitting and is used to create thicker substrates such as carpets, but it is highly versatile for applying specific yarns in specific locations. This technique can be used to create surfaces with highly controlled mechanical and fluid transport properties. For example, high and low modulus yarns may be employed to create islands of high modulus surrounded by low modulus, or vice versa. 3D features can be defined as features created on a surface by specifically applying one or more yarn weaves above and above adjacent surface yarns. Weave patterns, such as twill, rib, and waffle, are well known to those skilled in the art. In these weaving styles, the weave pattern places yarns in certain places preferentially over others, giving the fabric texture. Terry is another such process, where additional yarns are woven into the base fabric and extend out from the surface as loops.

[0044] In one embodiment, a "terry" weave process is employed, although other patterns may be employed. The terry process is well known for creating loop patterns on one or both sides of the fabric. The terry loops can be applied uniformly across the entire surface or arranged in any desired pattern. The terry can be single-sided or double-sided, with the loops extending to both sides of the fabric surface. For pads, single-sided terry in the desired pattern is preferred. Terry loops can significantly increase the surface area with the body due to the loop's flexural compliance. The present invention employs a terry weave process with specially modified fibers to provide a CMP pad with significantly improved texture and reduced slurry usage. Modified fiber materials and fiber diameters may be used to tailor the polishing response, and parameters such as loop size and surface density may be engineered to optimize polishing performance. Additionally, such surfaces allow for more efficient distribution of slurry and chemicals to the wafer surface. In addition to the weave pattern, several types of fibers may be combined to create the pad. For example, the loops may be woven with hydrophilic yarns such as polyurethane, polyester, nylon, etc., while the base fabric may be woven with a portion of hydrophobic yarns such as polypropylene or polyethylene. Such pads preferentially direct slurry to the polishing loop and efficiently remove debris and polishing by-products. Deniers between 100 and 2000 may be used to produce pads with suitable properties, although higher or lower denier may also be used. Generally, monofilament yarns are preferred over staple or staple yarns to minimize the possibility of fiber breakdown. However, staple yarns offer more flexibility in adjusting properties, so staple yarn pads may be desirable for certain applications. The yarns may be made from fibers containing abrasives such as silicon dioxide, ceria, alumina, silicon carbide, boron nitride, or other abrasives typically used in polishing suspensions. Nominal particle sizes similar to those of polishing suspensions (50 nm to 250 nm) may be used. Abrasives may be used at 20 to 50 volume percent. Abrasive-containing yarns may be used in combination with non-abrasive-containing yarns to produce pads.The pad may have multiple denier yarns; for example, the base fabric may be made of high-denier yarns and the terry loops may be constructed with low-denier yarns, or vice versa. Thus, terry is understood to be one method of creating surface texture through weaving or knitting. There are other weave / knit patterns that can be used to create 3D structures useful for applications. An advantage of the pad of the present invention is the reduction in slurry usage compared to existing CMP pads. Slurry usage is one of the highest single consumable costs in semiconductor manufacturing today. Yet another advantage is the potential elimination or minimization of diamond pad conditioning. Surface cleaning with a bristle cleaning brush may still be necessary.

[0045] In one example, the abrasive layer was fabricated from 300 denier polyester yarn with a loop height of approximately 3 mm and a total thickness of approximately 3.3 mm. The loops were arranged in 10 mm x 10 mm squares with a 2 mm gap between the squares. The abrasive layer was thermally bonded to a 100 micron thick polyurethane film (Covestro PT9200 film) using a heat press. The polyurethane-bonded textile layer was attached to a 0.062 inch thick closed-cell polyurethane foam (#4701-60-25062-04) from Rogers Corporation using Avery Dennison pressure-sensitive adhesive FT-1150. Another pressure-sensitive adhesive, FT-8305, was applied to the opposite side of the polyurethane foam to secure the pad to the polishing table.

[0046] In another example, an abrasive layer was fabricated from 300 denier nylon yarn and 300 denier polypropylene yarn with a loop height of approximately 2.5 mm and a total thickness of approximately 2.8 mm. The loops were arranged in alternating 10 mm x 10 mm squares with a 2 mm gap between the squares. The abrasive layer was thermally bonded to a 125 micron thick polyurethane film (Covestro PT7500 film) using a heat press. The polyurethane-bonded textile layer was attached to a 0.062 inch thick closed-cell polyurethane foam (#4701-60-25062-04) from Rogers Corporation using Avery Dennison pressure-sensitive adhesive FT-1150. Another pressure-sensitive adhesive, FT-8305, was applied to the opposite side of the polyurethane foam to secure the pad to the polishing table.

[0047] While the present invention has been described in terms of specific embodiments, it should be understood that those skilled in the art to which the present invention pertains may devise many other embodiments without departing from the scope, spirit, or technical concept of the present invention, as defined by the following claims.

Claims

1. A polishing pad comprising: a textile layer; a compressible layer; a water-impermeable layer; The polishing pad, wherein the water-impermeable layer is disposed between the textile layer and the compressible layer.

2. 2. The polishing pad of claim 1, wherein the textile layer has a top surface at least partially composed of single-sided yarn loops, the top surface of the textile layer being opposite a bottom surface of the textile layer, and the bottom surface of the textile layer being adjacent to the top surface of the water-impermeable layer.

3. 10. The polishing pad of claim 1, wherein the yarn loops are terry loops and the textile layer is a woven textile layer made from multiple types of yarn constructions, such as denier, twist, filament, and staple.

4. 4. The polishing pad of claim 3, wherein the terry loops are about 1.0 mm to about 10 mm in height.

5. 10. The polishing pad of claim 1, wherein the textile layer is made of yarns made of one or more polymers including polyvinyl alcohol (PVA), polyester, polyurethane, nylon, ultra-high molecular weight polyethylene (UHMWPE), polypropylene, acrylic, EPDM, polystyrene, ABS, Kevlar, aramid, liquid crystal polymers such as Vectran fibers, and liquid crystal polyoxazole.

6. 2. The polishing pad of claim 1, wherein the textile layer comprises a base fabric, the base fabric being a woven fabric having a warp count of about 50 to about 500 threads per inch and a weft count of about 50 to about 500 threads per inch.

7. the textile layer comprises a woven base fabric and a plurality of terry loops woven into the base fabric and protruding from an upper surface of the woven fabric; the base fabric has a warp thread count of about 50 to about 500 threads per inch and a weft thread count of about 50 to about 500 threads per inch; 10. The polishing pad of claim 1, wherein the Terry loop density is from about 100 to about 10,000 per square inch.

8. 8. The polishing pad of claim 7, wherein the terry loops are arranged in a pattern comprising a linear, circumferential, spiral, arcuate, or other geometric shape.

9. 10. The polishing pad of claim 1, wherein the textile layer comprises yarns of 50 to about 2500 denier.

10. 10. The polishing pad of claim 1, wherein the textile layer is a woven fabric having warp and weft yarns made of different materials, and the terry loops are formed from yarns of yet another material.

11. 10. The polishing pad of claim 1, wherein the water-impermeable layer is made of at least one of a thermoplastic polyurethane, an acrylic, or a polycarbonate polymer.

12. 10. The polishing pad of claim 1, wherein the water-impermeable layer is 25 to about 250 microns thick.

13. The polishing pad of claim 1 , wherein the water-impermeable layer is thermally bonded to the textile layer.

14. 10. The polishing pad of claim 1, wherein the water-impermeable layer is bonded to the compressible layer with an adhesive.

15. 10. The polishing pad of claim 1, wherein the compressible layer is a woven 3D fabric, or a closed-cell foam, or a nonwoven textile, and is about 0.5 mm to about 2.5 mm thick.

16. A method of using a polishing pad, comprising: Removably attaching the pad to a polishing table; attaching a wafer to a wafer holder; pressing a rotating wafer against the rotating polishing table with an appropriate pressure to remove a film on the wafer; A method comprising:

17. 17. The method of claim 16, wherein the textile layer comprises a woven base fabric and terry loops protruding from an upper surface of the base fabric.

18. The pad comprises a textile layer, a compressible layer, and a water-impermeable layer; the water-impermeable layer is disposed between the textile layer and the compressible layer; the textile layer includes a base fabric and a plurality of terry loops formed on a surface of the base foam facing the wafer; the terry loops have a height of about 1.0 mm to about 10 mm and a density of about 100 to about 10,000 per square inch; 17. The method of claim 16, wherein the woven base fabric has a warp thread count of about 50 to about 500 threads per inch and a weft thread count of about 50 to about 500 threads per inch.

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