TWI821561B - Chemical-mechanical polishing pad with textured platen adhesive and an affixing method thereof - Google Patents

Abstract

A chemical-mechanical polishing pad comprising a removable platen adhesive comprising a textured surface. A method of using the polishing pad to eliminate or reduce the occurrence of spot balding on the surface of the polishing pad.

Description

Chemical mechanical polishing pad with textured plate adhesive and method of attaching same

The present invention relates to a chemical mechanical polishing pad and a method of attaching the chemical mechanical polishing pad to a flat surface.

Integrated circuits are typically formed on a substrate by sequentially depositing conductive, semiconductor, or insulating layers on a silicon wafer. Various manufacturing processes require planarization of layers on a substrate. For example, for some applications, such as grinding a metal layer to form vias, plugs, and lines in trenches of a patterned layer, the overlay is planarized until the top surface of the patterned layer is exposed. In other applications, such as planarizing dielectric layers for photolithography, the overlay is polished until the desired thickness is maintained above the underlying layer. Chemical mechanical polishing (CMP) is an acceptable planarization method. This planarization method usually requires mounting the substrate on a carrier head. Typically the exposed surface of the substrate is placed against a rotating polishing pad. The carrier head provides a controllable load on the substrate to push it toward the polishing pad. A polishing liquid, such as a slurry with polishing particles, is typically supplied to the surface of the polishing pad.

Polishing pads are typically made from extruded, molded, cast or sintered polyurethane materials. In the case of molding, one polishing pad can be produced at a time, for example by injection molding. In the case of casting, the liquid precursor is cast and solidified into a cake, which is then cut into individual gaskets. These gaskets can then be machined to final thickness. Grooves can be machined into the abrasive surface or can be formed as part of the injection molding process.

Polishing pads can be multi-layered or stacked pads. Multilayer pads may have an abrasive pad layer adhered to a rigid layer or directly adhered to an underlying layer or base layer. An adhesive, usually a permanent adhesive such as a hot melt adhesive, is used to bond the abrasive layer to the rigid layer or underlying layer. The rigid layer or underlying layer has a surface opposite the surface that adheres to the abrasive layer or stack, and this surface typically has an adhesive for adhering the pad to the flat plate of the abrasive tool. The plate adhesive is usually a temporary or removable adhesive relative to the surface of the plate and the surface of the underlying layer. The composition of the temporary adhesive is an important consideration because the adhesive must keep the polishing pad fixed to the plate during the polishing process where the chemicals in the polishing slurry and the heat generated may degrade the adhesive. The temporary adhesive must also allow easy removal of the wear pad after a certain number of grinding steps.

Adjust the polishing surface of the polishing pad during the polishing process. Adjustment or dressing is essential to maintain uniform grinding performance on a constant grinding surface. During the grinding process, the grinding surface of the grinding layer wears away, forming a glaze or an undesirably smooth surface lacking micro-texture. The conditioning step is typically accomplished by mechanically abrading the pad surface by dragging a conditioning disc across the pad's abrasive surface with downward pressure, thereby removing debris and creating microtexture. The dial typically has a surface made of embedded diamond particles that cut into the pad surface to create micro-protrusions and renew the abrasive texture. This conditioning process is necessary but shortens pad life by removing pad material from the surface. Since the adjustment process abrades the material from the grinding surface, and the pad material grinding is proportional to the downforce, the height difference of the pad relative to the flat surface will produce uneven grinding on the surface of the entire grinding layer. Therefore, uniformity of height or flatness is required to achieve uniform wear across the entire pad surface.

The rigid layer of a multi-layer polishing pad can be the middle layer or the lowest layer in the stacked pads. Alternatively, the underlying layer may be the bottom layer. In either case, the polishing pad design will vary and will be designed to address the polishing process needs. For example, the rigid layer or underlying layer may vary in compressibility and hardness depending on grinding requirements. Polishing pads having a softer polishing layer adhered to a hard rigid layer or an underlying layer are well known in the art. Additionally, polishing pads with softer, more compressible underlying layers are also known and may be advantageous for certain polishing procedures. The inventors have observed that softer, more compressible pads may have difficulty keeping the pad completely flat as it adheres to the flat surface. Therefore, there is a need to find an improved polishing pad with a softer, less compressible backing layer that will adhere easily to the flat surface and be flat.

The present invention provides a polishing pad including a removable flat adhesive, wherein the adhesive has a textured surface. The present invention also provides a chemical mechanical polishing pad including a polishing pad body having a polishing surface and a backside opposite the polishing surface, wherein a removable plate adhesive is secured to the backside, the plate adhesive having a textured surface.

The present invention further provides a polishing pad comprising a polishing layer attached to a backing layer, the polishing layer having a polishing surface, the backing layer having a surface opposite the polishing surface, and a plate adhesive fixed to the backing layer opposite the polishing surface Surface, where the flat adhesive has a textured surface.

The present invention further provides chemical mechanical polishing pads having a less rigid body that includes a textured plate adhesive affixed to the polishing pad surface.

The present invention further provides a method of attaching a chemical mechanical polishing pad to a flat surface, which includes: (a) fixing a flat adhesive with a textured surface to the polishing pad, (b) by texturing the flat adhesive The surface is pressed to the plate surface to adhere the polishing pad to the plate surface, where the textured surface of the plate adhesive allows air to escape without being trapped between the plate surface and the polishing pad.

The present invention further provides a method of attaching a chemical mechanical polishing pad with a less rigid body to a flat plate surface, which includes: (a) fixing a flat plate adhesive with a textured surface to the polishing pad, (b) by The polishing pad is attached to the plate surface by pressing the textured surface of the plate adhesive to the plate surface, where the textured surface of the plate adhesive allows air to escape without being trapped between the plate surface and the polishing pad.

The present invention provides a polishing pad with textured, removable plate adhesive. Textured slab adhesives can include grooves or microchannels to prevent bald spots and premature pad wear. The present invention also provides a method of preventing bald spots in the polishing pad and premature pad wear by using a polishing pad containing a removable textured plate adhesive.

The polishing pad of the present invention can be a solid pad or a multi-layer pad. When the polishing pad is a multi-layer pad, the pad may be composed of 2 or more layers bonded together with an adhesive. Pads with multiple layers can also have a monolithic construction, where the layers are covalently bonded to each other via an integral interface. In some embodiments, as disclosed herein, the pad is monolithic and therefore has an integral interface via which the layers are covalently bonded to each other.

The multi-layer polishing pad of the present invention may include a polishing layer adhered to a rigid backing layer and/or to an underlying layer. In some embodiments, the polishing pads of the present invention will include a polishing layer (also called a top sheet) adhered to a rigid backing (also called a base) layer, which is adhered to an underlying layer. In other embodiments, the abrasive layer adheres to the underlying layer. In yet other embodiments, the abrasive layer is adhered to the rigid backing layer without an underlying layer.

In other embodiments, a monolithic polishing pad as disclosed herein is defined as a polishing pad having a single layer of uniform material or homogeneous composition. In one embodiment, the homogeneous body is constructed from a thermoset closed cell polyurethane material. In the context of the present invention, the term "homogeneous" is used to indicate that the composition of the thermoset closed cell polyurethane material is constant throughout the composition of the body. For example, in one embodiment, the term "homogeneous" does not include a polishing pad body composed of, for example, impregnated felt or a composition (composite) of multiple layers of different materials.

Regardless of whether the polishing pad is a solid single-layer pad or a multi-layer pad, the polishing pad will consist of a polishing surface and a backside opposite the polishing surface. The backside opposite the grinding surface will contain the textured plate adhesive of the present invention, thereby securing (eg, adhering) the polishing pad to the surface of the plate of the grinding tool.

In one embodiment, the term "thermoset" is used to refer to polymeric materials that are irreversibly cured, such as by curing to irreversibly transform a material precursor into a refractory, insoluble polymer network. For example, in one embodiment, the term "thermoset" does not include polishing pads composed of materials such as "thermoplastics" or "thermoplastics," which are polymers that become liquid when heated and return to an extremely glassy state when sufficiently cooled. The materials out of which things are composed. It should be noted that polishing pads made from thermoset materials are usually made from low molecular weight precursors that react to form polymers in a chemical reaction, while pads made from thermoplastic materials are usually made by heating a pre-existing polymer to induce a phase change. and manufacturing, thereby forming the polishing pad in a physical process. Polyurethane thermoset polymers used to make the polishing pads described herein may be selected based on their stable thermal and mechanical properties, resistance to chemical environments, and tendency to resist abrasion.

The present invention may include an underpad as part of a polishing pad. Any suitable underlayment may be used, for example, the underlayment may include a polyurethane foam underlayment, an impregnated felt underlayment, a microporous polyurethane underlayment, and a sintered urethane underlayment. The underlying pad may optionally contain grooves, channels, hollows, windows, holes and the like. The underlying pad can be attached to the abrasive layer by any suitable means. For example, the abrasive layer and underlying pad may be attached via an adhesive or may be attached via welding or similar techniques.

The stiffness of the polishing pad can affect the pad's tendency to form bubbles caused by trapped air during pad installation. Thicker pads tend to be more rigid, but there are other factors as well, such as the materials used or the backing layer used. Rigid pads tend to trap fewer air bubbles and are therefore less prone to bald spots than less rigid pads. However, all polishing pads are capable of forming trapped air bubbles during installation. Less rigid pads tend to form trapped air bubbles easily and are therefore more prone to bald spots. As used herein, the stiffness of a polishing pad is the stiffness of the entire pad, whether it is a multi-layer pad or a uniform pad. The stiffness in the pad can be measured by any suitable method. For example, a universal stress strain tester can be used. The Universal Stress Strain Tester measures the force required to deflect a longer and larger pad sample (such as a 12" x 5" sample). Test pad samples may include top pads, bottom pads, adhesive layers, and release liners. Deflection is typically about 2 to 3 inches. Use these large dimensions to approximate the analog pad mounting process.

As used herein, a less stiff pad is defined as a pad that requires a lower force to deflect a pad sample compared to a control pad sample.

The polishing pad of the present invention includes a removable or temporary adhesive, such as a pressure-sensitive plate adhesive. A removable pressure-sensitive flat adhesive layer facilitates the installation of monolithic or multi-layer chemical mechanical polishing pads or pad stacks on polishing machines. The flat panel adhesive of the present invention can be any suitable material. The plate adhesive is preferably resistant to the heat and chemicals commonly used in chemical mechanical polishing processes. For example, the adhesive should maintain adhesive properties and not cause the polishing pad to detach from the plate surface during the chemical mechanical polishing process.

The present invention also provides various transfer tapes (also known as double-sided adhesive tapes), including flat adhesives and pad adhesives. Transfer tapes include one or more layers of adhesive on a carrier film and a liner, such as a release liner, for each adhesive side. In some embodiments, the transfer tape has a permanent adhesive on one side of the tape and a grooved flat adhesive on the opposite side. This embodiment is depicted in Figures 2 and 3. In other embodiments, the transfer tape can have the same adhesive on both sides, but only the flat side will have a grooved or textured surface.

The carrier film of the transfer tape can be any suitable material. For example, the carrier film may be polyethylene terephthalate (PET). Additionally, the carrier film can have any suitable thickness. For example, the thickness of the carrier film can be from about 0.5 mil to about 2.0 mil.

The release liner can be of any suitable material and thickness. For example, the release liner can be a polyester material and can have a thickness of about 2 mil to about 5 mil. In one embodiment of the invention, the release liner is textured or grooved so that the pattern on the release liner is imprinted on the adhesive, and the adhesive remains at least temporarily after the release liner is removed. The shape of the grooves or textures embossed by the release liner. In this embodiment, the release liner of the polishing pad is removed just before the pad is mounted on the plate.

The microchannels of the present invention can adopt various shapes or patterns. Microchannels are generally formed by structures in the adhesive that create a microstructured surface. Structures can be placed randomly around the adhesive surface or placed in regular textured patterns.

The textured pattern on the release liner can be any suitable pattern that prevents air from being trapped beneath the polishing pad during installation. For example, the pattern in the release liner can be a microchannel pattern consisting of an XY pattern. Alternatively, the pattern may be microchannels created by a series of connected honeycombs, diamond shapes, or other geometric designs. The size of the microchannels can be any suitable size, with the limitation that the microchannels allow air to escape during installation of the polishing pad. For example, channel depth may range from about 5 μm to about 250 μm. For example, the channel depth can be about 5 μm or greater, about 10 μm or greater, about 15 μm or greater, about 20 μm or greater, about 25 μm or greater, about 30 μm or greater, about 40 μm or larger. For example, the channel depth may be about 250 μm or less, such as about 200 μm or less, about 150 μm or less, about 100 μm or less, about 50 μm or less. Preferably, the channel depth ranges from about 20 μm to about 50 μm. The microchannels can have any suitable spacing. The distance between channels is related to the maximum size of the bubble that will not be trapped. The channel spacing may be about 0.1 mm or greater, such as 0.2 mm or greater, 0.5 mm or greater, 1.0 mm or greater, 5 mm or greater. The channel spacing may be about 10 mm or less, such as 8 mm or less, 7 mm or less, 6 mm or less. In one embodiment, the channel spacing is in the range of 1 mm to 5 mm.

The plate adhesive can be any suitable removable adhesive material that allows the polishing pad to be easily removed when worn but holds the polishing pad securely in place during the polishing operation. For example, the slab adhesive may be an acrylic resin adhesive, a rubber-based adhesive, a urethane resin adhesive, or a silicone resin adhesive. These adhesives are generally low-tack, removable adhesives.

Typically, the adhesive when incorporated into the transfer tape is in the form of a single uniform and continuous layer having a thickness of about 0.5 mil to about 20 mil, and more specifically about 1.0 mil to about 10 mil. The subject matter of the present invention also includes the use of patterned adhesives and multi-layer adhesives in transfer tapes.

Double coated tape can be used to apply slab adhesive to the polishing pad during the lamination step. Suitable double-coated tapes include 3M 456CR, 3M 442F and Avery 8603. The method of laminating double coated tape to the pad surface is well known. The dual-coated tape can be laminated to the polishing pad by using any suitable laminating machine, such as an AGL laminator (Advanced Greig Laminators, Inc., DeForest, Wisconsin) and following the supplier's recommended method.

Textured surfaces (eg, microchannels) can be formed by directly imprinting a pressure-sensitive adhesive layer with a structure. Alternatively, the liner or backing can be embossed first and then coated with a pressure-sensitive adhesive to impart structure to the adhesive. The film may be laminated or bonded to the side of the adhesive layer opposite the textured surface features.

One advantage of the present invention is to provide a flat adhesive-backed polishing pad with a textured surface such that paths suitable for air release are formed in the flat adhesive. Textures or microchannels define paths to the perimeter of the grind, which allow air to flow between the adhesive layer of the plate and the surface of the plate. In one embodiment, the microchannel path terminates very close to, but not at, the perimeter. In this embodiment, air is still allowed to escape and no air is trapped between the polishing pad and plate.

After final application of the polishing pad to the plate, the microchannels of the present invention at least partially disappear to provide the desired adhesion. The ability to at least partially disappear a microchannel depends on the shape of the microchannel and the rheology of the adhesive.

The ability of the microchannel plate adhesive to maintain the microchannels after the release liner has been removed is called channel life. For example, an adhesive with long channel life will maintain the microchannel structure for several minutes after the release liner is removed and possibly even after the polishing pad has been applied to the plate surface. The polishing pads of the present invention preferably have a channel life long enough to maintain the channel structure until the polishing pad is pressed against the flat surface during installation. Under these conditions, air will escape during pad placement, but after installation, there will be no open channels at the pad ends that could allow abrasive slurry or water to enter the underside of the pad.

The present invention provides a chemical mechanical polishing pad that avoids premature wear caused by bald spots. The polishing pad of the present invention includes a removable adhesive used to adhere the pad to a flat plate, and the adhesive has a textured surface so that the polishing pad can be installed without trapping air. The trapped air that occurs between the plate surface and the polishing pad during the installation process causes bulges in the polishing surface. The textured surface of the adhesive causes less or no air to be trapped.

The following examples further illustrate the invention, but of course should not be construed as limiting its scope in any way. Example 1

This example shows the difference in stiffness of polishing pads of different thicknesses and compositions.

Use the pad deflection test to test the stiffness of various polishing pad materials. The test uses a portion of the test pad cut into a rectangular shape with a length of 12.5 inches and a width of 5.5 inches. The test pad portion was mounted on a universal tester (Test Resources, Shakopee, MN) operating in stress-strain mode, which was capable of measuring the force required to bend the test pad sample 3 inches. Each test strip was tested 5 times and the results were averaged together.

The results of the deflection test are shown in Table 1. The results indicate that thicker pads and pads with a rigid underlay or backing layer have higher forces required to deflect three inches and are therefore considered stiffer. The difference between the thickness of the bottom pad and the thickness of the top pad minus the total thickness is the thickness of the adhesive layer between the bottom pad and the top pad. Table 1. Comparative stiffness measurements of various pads. pad sample lower pad Flat adhesive Top pad thickness(mil) Total pad thickness (mil) Average maximum force (lbf) 1 30 mil flat, removable 65 110 0.40 2 30 mil microchannel 65 110 0.45 3 30 mil Flat, low viscosity 65 110 0.35 4 30 mil, dense type flat, removable 65 110 0.40 5 15 mil flat, removable 65 105 0.22 6 15 mil flat, removable 65 105 0.22 7 15 mil flat, removable 65 105 0.26 8 30 mil flat, removable 100 145 1.02 9 without Flat, very low viscosity 130 135 0.67 10 Suba4, rigid, (IC1010) flat, removable 80 140 0.80 Example 2

This example demonstrates the effect of microchannel adhesive on pad wear under aggressive polishing conditions.

Comparing the same polishing pad using different plate adhesives. E6088 polishing pads (Cabot Microelectronics, Aurora IL) were laminated with microchannel adhesive (2B) or with flat adhesive (2A and 2C). The stiffness of E6088 pads in different configurations is demonstrated in Example 1. As a comparative example, commercially available polishing pad IC1010 (Rohm and Haas Electronic Materials) was used. The stiffness of IC1010 is shown in Example 1. IC1010 is the stiffest of the pad materials tested.

The polishing pads were tested under the following conditions using commercially available silica-based polishing slurry D9228 (Cabot Microelectronics) and TEOS blanket wafers. The grinding test used a CTS grinder model AP 300 (Creative Technology Solutions), which used a plate speed of 120 rpm, a grinding pressure of 4 psi, and a slurry feed rate of 250 ml/min. Condition the pads with commercially available CMP diamond conditioner at a pressure of 12 lbf. Each pad was used for grinding for 4 to 5 hours, followed by wear analysis. Visually inspect the pad for wear on the abrasive surface. Areas of excessive wear (eg, areas where no groove structure is visible) are counted as bald spots (bald spot count), and the number of pad bald spots is recorded. Figure 1 shows an example of visible pad wear that is considered a bald spot count.

Table 2 below shows the bald spot counts of the test pads. As evident from the table, the E6088 pad with microchannel adhesive has no bald spots, while the same pad with flat adhesive has a significantly increased number of these, with 6 bald spots. In addition, the E6088 pad with a rigid bottom pad also showed no bald spots. Table 2. Count of bald spots on various polishing pads. polishing pad describe bald spot count IC1010, commercially available pad Rigid pad, flat adhesive 0 2A Less rigid pad, 30 mil underpad, flat adhesive 6 2B Less rigid pad, 30 mil underpad, microchannel adhesive 0 2C Rigid pad, dense 30 mil underpad, flat adhesive 0

As is apparent from the data presented in this example, the less rigid polishing pad (2A) with flat adhesive has problems with bald spots. Use an adhesive with microchannels to prevent bald spot defects in less rigid polishing pads (2B). Example 3

This example illustrates the effect of microchannel adhesive on pad bald spots under simulated accelerated wear conditions.

Polishing pads that are less rigid as determined by deflection testing are laminated with non-textured removable plate adhesive or microchannel plate adhesive. In addition, rigid polishing pads are laminated with non-textured removable plate adhesive and microchannel plate adhesive. Rigid polishing pads are mounted on a flat plate that requires less attention than is normally used. Do this to increase the likelihood of air bubbles becoming trapped during installation. The cutting machine is a computer numerically controlled cutting machine (such as a Multicam CNC cutting machine) that removes a uniform depth of approximately 0.020" of the top layer of the pad. This test provides an accelerated wear test to identify bald areas caused by trapped air bubbling between the polishing pad and plate.

The results of the accelerated test were the same as those of the grinding test. Microchannel plate adhesive eliminates the problem of bald spots in less rigid pads or the problem of higher stiffness pads installed with less attention.

All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference was individually and specifically indicated to be incorporated by reference and in its entirety. Set forth in this article generally.

Unless otherwise indicated herein or otherwise clearly contradicted by context, use of the terms "a/an" and "the" and similar referents in the context of describing the invention (especially in the context of the following claims) shall It is understood to cover both the singular and the plurality. Unless otherwise indicated, the terms "includes," "has," "includes," and "contains" should be construed as open-ended terms (i.e., meaning "including, but not limited to"). Unless otherwise indicated, recitations of value ranges herein are intended only as a shorthand way of referring individually to each individual value falling within that range, and each individual value is incorporated into this specification as if individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (eg, "such as") provided herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention. Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. After reading the foregoing description, variations of the preferred embodiments will become apparent to those of ordinary skill in the art. The inventors expect those skilled in the art to employ such variations as appropriate, and the inventors intend the invention to be practiced otherwise than as specifically described herein. Accordingly, where permitted by applicable law, this invention is intended to include all modifications and equivalents of the subject matter recited in the claims appended hereto. Furthermore, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

101: Grinding layer/top pad 102: Adhesive layer 103: Lower pad 104:Permanent underlay adhesive 105: Adhesive backing layer 106:Removable tablet adhesive 107:Release liner 108: Release liner with textured surface

Figure 1 illustrates an example of spot balding on a groove grinding surface.

Figure 2 depicts one embodiment of the configuration of the polishing pad of the present invention.

Figure 3 depicts an exploded view of a flat panel adhesive layer showing the formation of microchannels in the flat panel adhesive formed by the textured surface of the release liner.

104:Permanent underlay adhesive

105: Adhesive backing layer

106:Removable tablet adhesive

108: Release liner with textured surface

Claims (10)

A chemical mechanical polishing pad, which includes: a polishing pad including a polishing surface, a backside opposite to the polishing surface, and a flat adhesive attached to the backside, wherein the flat adhesive has a textured surface and includes a removable adhesive agent, wherein the polishing pad is a multi-layer polishing pad, wherein the multi-layer polishing pad includes a polishing layer and a backing layer, wherein the multi-layer polishing pad optionally includes an underlying layer, and wherein the polishing pad is a pad with lower rigidity, defined as Use a 12" long x 5" wide sample strip with a load of 0.4 lbf or less at 3 inches of deflection. The polishing pad of claim 1, wherein the textured surface of the plate adhesive includes a microchannel texture. The polishing pad of claim 2, wherein the microchannel texture includes an XY pattern. The polishing pad of claim 2, wherein the microchannel texture is formed by geometric shapes. The polishing pad of any one of claims 1 to 4, wherein the polishing pad has an integral structure. Such as the polishing pad of claim 2, wherein the channel depth of the microchannels is 5 μm to 250 μm. The polishing pad of claim 6, wherein the channel depth is 20 μm to 50 μm. Such as the polishing pad of claim 2, wherein the channel spacing is 0.1mm to 10mm. Such as the polishing pad of claim 8, wherein the channel spacing is 1 mm to 5 mm. A method of attaching a chemical mechanical polishing pad to a flat surface, which includes: (a) fixing a flat adhesive layer with a textured surface to the polishing pad, (b) by attaching the textured surface of the flat adhesive to the polishing pad Pressing to the plate surface adheres the polishing pad to the plate surface, wherein the textured surface of the plate adhesive allows air to escape and not be trapped between the plate surface and the polishing pad, wherein the polishing pad is from Any one of claims 1 to 9.