Multi-layer cmp pad

Abstract

A polishing pad includes a fabric layer, a compressible layer, and a water impermeable layer disposed between the fabric layer and the compressible layer. The polishing pad reduces slurry usage by improving slurry delivery and does not require diamond finishing to maintain slurry delivery.

Description

Technical Field

[0001] The present invention relates generally to the field of chemical mechanical planarization (CMP), and more particularly to a CMP polishing pad for use in a CMP process. Background Art

[0002] In today's integrated circuit (IC) manufacturing, layers of material are applied to embedded structures previously formed on semiconductor wafers. Chemical mechanical planarization, also known as chemical mechanical polishing (hereinafter also referred to as CMP), is a polishing process used to remove these layers and polish the wafer surface flat to achieve the desired structure.

[0003] Multilayer CMP pad

[0004] CMP can be performed on both oxide and metal layers and generally involves the use of a chemical slurry that is applied via a polishing pad that moves relative to the wafer (e.g., the pad can rotate in a circle relative to the wafer). The resulting smooth, flat surface is required to maintain the depth of focus for photolithography in subsequent steps and to ensure that metal interconnects do not deform across profile steps. Damascene processing requires CMP to remove metal, such as tungsten or copper, from the top surface of the dielectric to define the interconnect structure.

[0005] The planarization / polishing performance of a pad / slurry combination is influenced by, among other factors, thermomechanical and chemical properties and the ability to distribute the slurry uniformly. Typically, hard (i.e., rigid) pads provide good planarization but are associated with poor removal of wafer-within-wafer non-uniformity (WIWNU) films and a greater susceptibility to micro-scratch defects. On the other hand, soft (i.e., flexible) pads provide good polishing of wafer-within-wafer non-uniformity but poor planarization. Therefore, in existing CMP systems, harder pads are used for bulk film removal and planarization features, while soft pads are used for finer polishing and removal of micro-scratch defects, as well as for substantial removal of slurry abrasive particles prior to cleaning in a post CMP cleaner.

[0006] Figure 1 A typical polishing system is shown. A polishing pad 102 is fixed to a polishing table 100 by a pressure sensitive adhesive. A wafer 106 is held by a wafer holder 104 and pressed against the polishing pad 102, while both the polishing table 100 and the wafer holder 104 rotate about their respective axes and a slurry 110 is applied to the polishing pad.

[0007] Existing polishing pads are usually made of urethane, either in cast form and filled with microporous pieces or from nonwoven felts coated with polyurethane. Soft pads can be made by the two processes mentioned above as well as by a dissolution precipitation method, where the polymer is dissolved in a water-miscible solvent and then precipitated by adding water as a non-solvent. This results in a highly porous pad surface with good polishing properties.

[0008] Figure 2 Shown is a side cross-sectional view of a hard polishing pad 200. The polishing pad 200 consists of a urethane matrix 202, trace elements 204, and grooves 206, very similar to those found in commercial polishing pads, such as IC1000 from Dupont Electronic Materials.

[0009] Figure 3 A soft polishing pad 300 is shown. The polishing pad 300 comprises a urethane matrix 302 and vertically oriented holes 304. The pad surface may be optionally embossed to provide channels for improved distribution of slurry at the wafer-pad interface.

[0010] Since polishing is accomplished by applying pressure and actuation to the wafer, the pad material undergoes deformation. This deformation results in smoothing of the pad surface, which must then be roughened to complete continued wafer polishing. Roughening of the pad surface, a process known as pad conditioning, is accomplished by pressing a rotating disk covered with fine diamonds against the rotating pad. This restores the roughness of the pad, enabling localized slurry delivery. Therefore, polishing pads require grooves, holes, and micro-roughness to affect uniform polishing. Consistent polishing performance requires optimization of grooves, porosity for macro-delivery, and diamond conditioning for localized slurry delivery. Excess slurry is supplied to the pad so that sufficient slurry is evenly distributed across the wafer-pad interface. It would be advantageous to have a pad that reduces slurry usage by improving slurry delivery without requiring diamond conditioning to maintain slurry delivery. Summary of the invention

[0011] According to one aspect of the present invention, a CMP polishing pad is provided, which can be used in a CMP process. The CMP polishing pad reduces slurry usage by improving slurry delivery and does not require diamond dressing for maintaining slurry delivery.

[0012] According to an embodiment of the present invention, the polishing pad may be configured to have a fabric layer, an impermeable layer and a compressible layer. The first side of the fabric layer may form a polishing surface, and the second surface 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 fixed to the polishing table by a pressure-sensitive adhesive.

[0013] In one embodiment, the base fabric of the fabric layer forming the polishing surface can be woven to provide a controlled structured surface. However, in another embodiment, the base fabric of the fabric layer can be knitted. Several techniques in weaving and knitting that can produce precise patterns with single or multiple yarns can be used. For example, a rib pattern or a waffle pattern can be used to produce three-dimensional features. Terry weave can produce coil three-dimensional (3D) features. Jacquard weaving can use multiple yarns to produce special patterns. For a given pattern, these techniques combined with the selection of yarns may modulate the properties of the local pad. For example, polyester yarn, nylon yarn or KEVLAR (poly(azanediyl-1,4-phenyleneazanediylterephthaloyl)) yarn can be selectively applied to produce high modulus domains and low modulus domains of desired sizes distributed in the mat. In another example, hydrophilic and hydrophobic yarns can be selectively applied to modulate the delivery of the slurry.

[0014] In one embodiment, the polishing pad comprises:

[0015] Fabric layer,

[0016] a compressible layer; and

[0017] The water-impermeable layer is disposed between the fabric layer and the compressible layer.

[0018] The top surface of the fabric layer can be configured to contact the wafer, and the bottom surface of the compressible layer can be configured to be secured to the polishing table.

[0019] The fabric layer may have at least a portion of a top surface comprising single terry knit loops, wherein the top surface of the fabric layer is opposite to the bottom surface, and the bottom surface is adjacent to the top surface of the impermeable layer.

[0020] The fabric layer may be made from more than one yarn construction, such as denier, twist, filament, staple.

[0021] The height of the terry loop may be 1.0 mm to 10 mm, preferably 2 mm to 6 mm.

[0022] The fabric layer yarns 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 (EPDM), polystyrene, acrylonitrile butadiene styrene (ABS), KEVLAR, aramid, liquid crystal polymer (liquid crystal polymer) such as VECTRAN (registered trademark) and liquid crystal polyoxazole (PBO), preferably polyurethane, nylon, ultra-high molecular weight polyethylene (UHMWPE), polyurethane, KEVLAR, ethylene propylene diene monomer (EPDM) and polyvinyl alcohol (PVA), and more preferably polyurethane, nylon, ultra-high molecular weight polyethylene (UHMWPE) or KEVLAR. VECTRAN is a man-made fiber that can be spun from a liquid crystal polymer available from Celanese Corporation.

[0023] The fabric layer has a yarn count of about 50 to about 500 per inch in the warp and a yarn count of about 50 to about 500 per inch in the weft.

[0024] The terry loop density may be from about 100 to about 10,000 loops per square inch.

[0025] The terry loops may be arranged in a pattern including lines, circles, spirals, arcs, or some other geometric configuration.

[0026] The fabric layer may include yarns of about 50 to about 2500 denier, and preferably about 200 to about 1500 denier.

[0027] The fabric layer can be made of two groups of yarns or threads interwoven at right angles. These two groups of yarns or threads are called warp knitting (longitudinal) and weft knitting (transverse). The fabric layer may include warp knitting and weft knitting, and each of the warp knitting and weft knitting contains yarns made of different materials. Terry loops can be formed by yarns of another material, using a weaving technique called "terry cloth" or "terry toweling", which includes adding at least one additional yarn woven into the basic structure of the fabric layer to form a loop. One or more yarns used to produce terry loops can be called pile yarns. According to the basic structure of the fabric layer, a fabric layer without terry loops is referred to herein, which can also be called a woven fabric base.

[0028] The water-impermeable layer may be made of at least one of thermoplastic polyurethane, acrylic or polycarbonate polymers.

[0029] The thickness of the water-impermeable layer may be from about 25 to about 250 microns.

[0030] In one embodiment, the impermeable layer can be thermally bonded to the fabric layer. Thermal bonding can include heating the impermeable layer until its surface softens or melts before the fabric layer is attached. The fabric layer-impermeable layer composite is then attached to the compressible layer. The heating of the impermeable layer can be performed in a continuous or batch process by any suitable means. One such method is to use a hot press to synchronously apply heat and pressure to permanently bond the fabric layer to the impermeable layer.

[0031] In one embodiment, the water-impermeable layer may be bonded to the fabric layer and the compressible layer using an adhesive. The adhesive may be a thermal adhesive.

[0032] The compressible layer may be a woven three-dimensional (3D) fabric.

[0033] The compressible layer may be a closed cell foam.

[0034] The compressible layer may be a non-woven textile.

[0035] The compressible layer may have a thickness of about 0.5 mm to about 2.5 mm.

[0036] The polishing pad is advantageous because slurry usage may be reduced, particularly by improving slurry delivery, and the need for diamond conditioning to maintain slurry delivery may also be completely eliminated or reduced.

[0037] These and other features of the present invention will be more clearly understood by those skilled in the art based on the following detailed description of embodiments of the present invention in conjunction with some drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention is illustrated by way of example and not limitation by the figures of the accompanying drawings in which:

[0039] Figure 1 is a simplified schematic diagram showing a typical polishing configuration;

[0040] Figure 2 is a simplified schematic diagram showing a hard polishing pad;

[0041] Figure 3 is a simplified schematic diagram showing a soft polishing pad;

[0042] Figure 4 is a simplified schematic diagram showing a multi-layer polishing pad incorporating a fabric layer according to an embodiment of the present invention;

[0043] Figure 5 is a simplified schematic diagram showing a textile polishing layer and an impermeable layer according to an embodiment of the present invention;

[0044] Figure 6 is a simplified schematic diagram illustrating a three-dimensional fabric according to an embodiment of the present invention. DETAILED DESCRIPTION

[0045] According to a first aspect of the present invention, a CMP pad is provided that reduces slurry consumption, reduces the need for polishing surface reconditioning, and can be easily customized to optimize the CMP process. The present invention also relates to a method for making the pad and a method of using the pad.

[0046] Accordingly, in one embodiment, a pad according to an embodiment of the present invention comprises a fabric layer, an impermeable layer and a compressible layer. The fabric layer may comprise a base fabric layer and a plurality of coils protruding from one side of the base fabric layer. The flat side of the base fabric layer opposite to the side having the protruding coils may be attached to the impermeable layer, which in turn may be attached to the compressible layer.

[0047] Typically, cast urethane pads with Shore D hardness in the range of 55 to 75 are used in applications that require planarization. One such hard pad, IC1000 made by DuPont Electronic Materials, has a Shore D hardness of 65. While this pad provides good planarization, its WIWNU performance may not be suitable for all planarization work. In an attempt to improve WIWNU performance, hard pads are often stacked with softer under-pads, such as: pads model SUBAIV.TM., also made by DuPont Electronic Materials. The soft under-pad enables the top hard pad to provide a global conformation of the pad surface against the wafer. The overall rigidity of the pad stack is therefore lower than that of a single hard pad. While this may help improve WIWNU, it can also result in reduced planarization performance. The thickness of a typical polishing pad is 2mm to 3mm. The top or polishing layer may be 1.5 to 2 mm thick; while the underlying compressible soft pad may be 0.5 mm to 1.0 mm thick.

[0048] The present invention relates to a multi-layer CMP pad design that can reduce slurry consumption and pad conditioning and provide a defect-free wafer surface. Figure 4 A pad 400 according to an embodiment of the present invention is shown. The pad 400 includes a fabric layer 406, 408 having a base fabric 406 and a yarn loop 408, the base fabric 406 can be a woven base fabric. The yarn loop can be a wool loop (Terryloops). The loops can be arranged in groups and have open spaces between the groups, or can be arranged in a rectangular pattern so that they form a periphery with open spaces between them. The loops can also be arranged so that the high modulus yarns in groups cross each other with the low modulus yarns in a predetermined pattern. The thickness of the fabric layer can be about 1mm to 3mm. The woven fabric layers 406, 408 are attached to an impermeable layer 404, which can be made of thermoplastic polyurethane or polyester and can have a thickness of 25 microns to 250 microns. The impermeable layer 404 can be permanently bonded to the fabric layer by heat bonding. The other side of the impermeable layer 404 can be attached to the compressible layer 402. The compressible layer 402 may be, for example, a closed-cell foam or an elastic solid sheet or a nonwoven fabric or a 3D fabric. The thickness of the compressible layer 402 may be about 0.5 mm to about 1.5 mm.

[0049] Figure 5 Shown are fabric layers 406, 408 and an impermeable layer 404. The fabric layer and the impermeable layer are thermally bonded using a heat press. Bonding can be accomplished by covering the fabric layer with the impermeable layer and applying heat and pressure in a press heated to above the softening temperature of the impermeable layer.

[0050] Figure 6An example of a 3D fabric 402 is shown that may be used as a compressible layer 402 of a pad 400 and includes a top fabric 606 and a bottom fabric 602 of the same or different weave structures, and a connecting yarn layer 604. The connecting yarn layer 604 may be varied individually to modulate the compressibility of the 3D fabric.

[0051] In an embodiment of the present invention, the fabric layer may include engineered yarns (also referred to as spun yarns or fibers) and textile techniques for producing a base fabric and woven loops protruding vertically from one side of the base fabric. This construction of the pad provides high efficiency, reduced slurry consumption, and reduced need for pad resurfacing. Additionally, the manufacturing method for making the pad is advantageous because it utilizes yarn loops to provide a controlled polished surface having a desired textured surface pattern.

[0052] The use of a weaving process allows the creation of an interconnected network of fibers / yarns in the XY direction, which can be altered to create features in the Z direction. However, the present invention may not be limited to using a weaving method to manufacture the base fabric and the loops on the base fabric. Other suitable methods may also be used.

[0053] For example, knitting is another process used to create textiles and involves creating a fabric by making a series of interconnected loops. Knitting is also precise and can create 3D features. Tufting is another weaving method that is useful for creating 3D features. In tufting, which is commonly used to make carpets, individual loops of yarn are woven in a vertical direction to form a base fabric. While this method has a lower resolution than weaving or knitting, it is used to make thicker substrates such as carpets, which are very elastic when special yarns are applied in special locations. Through this technology, surfaces with highly controlled mechanical and fluid transport properties can be created. For example, yarns with high modulus and low modulus can be applied to create high modulus islands surrounded by low modulus, and vice versa. 3D features can be defined as a feature created on a surface by specifically applying one or more yarns to and above the yarns adjacent to the surface. Weaving patterns, such as twill, rib, check, etc. are known to those skilled in the art. In these weaving styles, the fabric has texture because the weaving pattern preferentially places the yarns in certain locations rather than others. Terry is another such treatment in which additional yarns are woven into the base fabric and extend from the surface as loops.

[0054] According to one embodiment, a "terry" weave process is used, but other patterns may also be used. Terry processes for producing coil patterns on one or both sides of a fabric are well known. Terry coils may be distributed unevenly on a surface or arranged in any desired pattern. The terry may be single-sided or double-sided, with the coils extending on both sides of the fabric surface. For the pad, a single-sided terry with a desired pattern is preferred. Due to the flexing compliance of the coils, the terry coils can have a significantly higher surface area with the body. The terry weave process used in the present invention is used to provide significantly enhanced texture to the CMP pad and reduce slurry usage with specifically designed fibers. The designed fiber material and fiber diameter can be used to modulate the polishing response and design parameters, such as the size and surface density of the coils, to optimize polishing performance. In addition, this surface can also make the slurry and chemical distribution on the wafer surface more efficient. In addition to the weave pattern, several fibers can be combined to produce a pad. For example, the coils may be woven from hydrophilic yarns, such as polyurethane, polyester, nylon, etc., while the base fabric may be woven from a portion of all hydrophobic yarns, such as polypropylene or polyethylene. Such pads may preferably direct the slurry toward the polishing coils and also efficiently remove debris and polishing byproducts. 100 to 2000 deniers may be used to make pads with suitable characteristics. However, higher or lower denier numbers may also be used. In general, monofilament yarns are preferred over staple or short fiber yarns to minimize the possibility of fiber decomposition. However, staple yarns are more flexible in adjusting properties, so staple yarn pads may meet the needs of special applications. The yarns may be made of fibers containing abrasives, such as silica, ceria, aluminum oxide, silicon carbide, boron nitride, or other abrasives commonly used in emulsions for polishing. Nominal particle sizes may be used for abrasives similar to those in polishing emulsions (50nm to 250nm). 20 to 50 vol% abrasive may be used. Abrasive yarns may be used along with non-abrasive yarns to make pads. Pads may have yarns of more than one denier rating, for example: the base fabric may be made of high denier yarns, while the terry loops may be constructed of low denier yarns, or vice versa. Thus, it may be understood that terry is a method of creating surface textures by weaving or knitting. There are other weaving / knitting patterns that can be used to create 3D structures that are useful in applications. An advantage of the pad of the present invention is that it reduces slurry usage compared to existing CMP pads. Slurry usage is one of the highest single consumable costs in today's semiconductor manufacturing. Another advantage is the potential elimination or minimization of diamond pad dressing.A bristle cleaning brush is still required for surface cleaning.

[0055] In one example, the polishing layer can be made of 300 denier polyester yarn with a coil height of about 3 mm and an overall thickness of about 3.3 mm. The coils can be arranged in squares of 10 mm x 10 mm with a gap of 2 mm between the squares. The polishing layer can be thermally bonded with a polyurethane film about 100 microns thick, film PT 9200 from Covestro, using a heat press. The polyurethane bonded to the fabric layer is attached to a 0.062 inch thick closed cell polyurethane foam from Rogers Corporation (#4701-60-25062-04) using a pressure sensitive adhesive FT-1150 from Avery Dennison. Another pressure sensitive adhesive FT-8305 is applied to the opposite side of the polyurethane foam to secure the pad to the polishing table.

[0056] In another example, the polishing layer can be made of 300 denier nylon and 300 denier polypropylene yarns and have a coil height of about 2.5 mm and a total thickness of about 2.8 mm. The coils can be arranged in alternating 10 mm x 10 mm squares with a gap of 2 mm between the squares. The polishing layer can be thermally bonded with a 125 micron thick polyurethane film, film PT 7500 from Covestro, using a heat press. The polyurethane bonded to the fabric layer is attached to a 0.062 inch thick closed cell polyurethane foam (#4701-60-25062-04) from Rogers Corporation using a pressure sensitive adhesive FT-1150 from Avery Dennison. Another pressure sensitive adhesive FT-8305 is applied to the opposite side of the polyurethane foam to secure the pad to the polishing table.

[0057] Although the present invention has been described in terms of certain embodiments, it should be appreciated that those skilled in the art may conceive of various other embodiments without departing from the scope, spirit or technical concept of the invention as defined by the following claims.

Claims

1. A polishing pad comprising: fabric layer; Compressible layer; as well as A water-impermeable layer is disposed between the fabric layer and the compressible layer.

2. The polishing pad according to claim 1, wherein The fabric layer has at least a portion of its top surface comprising single jersey yarn loops, wherein the top surface of the fabric layer is opposite to a bottom surface of the fabric layer, and the bottom surface is adjacent to the top surface of the waterproof layer.

3. The polishing pad according to claim 1, wherein The yarn loops are terry loops, and wherein the fabric layer is a woven fabric layer made of more than one yarn construction, such as denier, twist, long staple, short staple.

4. The polishing pad according to claim 3, wherein: The height of the terry loops is about 1.0 mm to about 10 mm.

5. The polishing pad according to claim 1, wherein The fabric layer is made of yarn, and the yarn is made of one or more polymers, including: polyvinyl alcohol (PVA), polyester, polyurethane, nylon, ultra-high molecular weight polyethylene (UHMWPE), polypropylene, acrylic, ethylene propylene diene monomer (EPDM), polystyrene, acrylonitrile butadiene styrene (ABS), KEVLAR, polyaramid, liquid crystal polymer (liquid crystal polymer), such as VECTRAN fiber and liquid crystal polyoxazole.

6. The polishing pad according to claim 1, wherein The fabric layer includes a base fabric which is a woven fabric having a yarn count of about 50 to about 500 per inch in warp knitting and a yarn count of about 50 to about 500 per inch in weft knitting.

7. The polishing pad according to claim 1, in, The fabric layer includes a base fabric that is a woven fabric and a plurality of terry loops woven into the base fabric and protruding from a top surface of the woven fabric, wherein the base fabric has a yarn count of about 50 to about 500 per inch in warp knitting and a yarn count of about 50 to about 500 per inch in weft knitting, and The density of the pile loops is about 100 to about 10,000 per square inch.

8. The polishing pad according to claim 7, wherein: The terry loops are arranged in patterns including linear, circular, spiral, arc or other geometric shapes.

9. The polishing pad according to claim 1, wherein: The fabric layer includes yarns having a denier of 50 to about 2500.

10. The polishing pad according to claim 1, wherein The fabric layer is a woven fabric comprising warp knitted yarns and weft knitted yarns made of different materials, and wherein the terry loops are made of yarns of another material.

11. The polishing pad according to claim 1, wherein The water-impermeable layer is made of at least one of thermoplastic polyurethane, acrylic or polycarbonate polymers.

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

13. The polishing pad according to claim 1, wherein: The water-impermeable layer is thermally bonded to the fabric layer.

14. The polishing pad according to claim 1, wherein: The water-impermeable layer is bonded to the compressible layer using an adhesive.

15. The polishing pad according to claim 1, wherein The compressible layer is a woven three-dimensional fabric, or a closed-cell foam, or a nonwoven fabric, and has a thickness of about 0.5 mm to about 2.5 mm.

16. A method of using a polishing pad, comprising: The pad is removably attached to a polishing table, a wafer is applied to a wafer holder, and the rotating wafer is pressed against the rotating polishing table with a suitable pressure to remove the film on the wafer.

17. The method according to claim 16, wherein: The fabric layer includes a woven base fabric and terry loops protruding from a top surface of the base fabric.

18. The method according to claim 16, in, The pad comprises a fabric layer, a compressible layer and a water-impermeable layer, wherein the water-impermeable layer is disposed between the fabric layer and the compressible layer. The fabric layer includes a base fabric and a plurality of terry loops formed on a side of the base fabric facing the wafer. The height of the terry loops is about 1.0 mm to about 10 mm, and has a density of about 100 to about 10,000 per square inch, The woven base fabric has a yarn count of about 50 to about 500 per inch in the warp knitting and a yarn count of about 50 to about 500 per inch in the weft knitting.

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