TWI411495B - Polishing pad - Google Patents

Abstract

The invention provides a polishing pad comprising a polishing layer having a polishing surface comprising plurality of grooves disposed into the polishing layer a measurable depth from the polishing surface, and a barrier region free of grooves, and a transparent window disposed in and surrounded by the barrier region.

Description

Polishing pad

The present invention provides a polishing pad.

Chemical mechanical polishing ("CMP") processes are used to fabricate microelectronic devices to form planes on semiconductor wafers, field emission displays, and most other microelectronic substrates. For example, the fabrication of semiconductor devices generally involves the formation of a plurality of processing layers, selectively removing or partially patterning the layers, and depositing other processing layers on the surface of the semiconducting substrate to form a semiconductor wafer. The processing layer can comprise, for example, an insulating layer, a gate oxide layer, a conductive layer, a metal or glass layer, and the like. Typically, the uppermost surface of the process layer in the particular step of the wafer process needs to be planar, such as planar, for deposition of subsequent layers. CMP is used to planarize the processing layer, wherein a deposition material, such as a conductive or insulating material, is polished to planarize the wafer for subsequent processing steps.

In a typical CMP process, the wafer is mounted upside down on a carrier within the CMP tool. Applying force pushes the carrier and presses the wafer down against the polishing pad. The carrier and the wafer are rotated on a rotating polishing pad on a polishing table of the CMP tool. A polishing composition (also referred to as a polishing slurry) is typically introduced between the rotating wafer and the rotating polishing pad during the polishing process. The polishing composition typically contains a compound that interacts with or dissolves a portion of the uppermost wafer layer and an abrasive material that physically removes a portion of the layer. The wafer and the polishing pad can be rotated in the same direction or in opposite directions, depending on which one is desirable for performing the particular polishing process. The carrier can also be swung across the polishing pad located on the polishing table.

When polishing the surface of the wafer, it is often advantageous to monitor the polishing process in situ. One method of monitoring the polishing process in situ involves the use of a polishing pad having a perforation or window. The perforation or window provides an inlet during the polishing process that allows light to pass through to allow inspection of the entrance to the wafer surface. Polishing pads with perforations and windows are known and have been used to polish substrates, such as the surface of semiconductor devices. For example, U.S. Patent No. 5,605,760 provides a pad having a transparent window formed of a solid, homogeneous polymer that does not have the inherent ability to absorb or transport the slurry. U.S. Patent No. 5,433,651 discloses a polishing pad in which a portion of the pad has been removed to provide a perforation through which light can pass. U.S. Patent Nos. 5,893,796 and 5,964,643 disclose the removal of a portion of the polishing pad to provide a perforation and a transparent polyurethane or quartz plug in the perforation to provide a transparent window or to remove a portion of the polishing pad to the back of the pad. Provide translucency. A polishing pad having a transparent region formed by curing a flowable material (e.g., polyurethane) at a rapid cooling rate is disclosed in U.S. Patent Nos. 6,171,181 and 6,387,312.

A problem often encountered during chemical mechanical polishing is the tendency of the polishing pad window to accumulate the polishing composition and the resulting polishing debris. The accumulated polishing composition and polishing debris can impede the transmission of light through the window to reduce the sensitivity of the optical endpoint detection method.

While several of the above polishing pads are suitable for their intended purpose, there is still a need for other polishing pads that provide effective planarization and effective optical endpoint detection methods, particularly in chemical mechanical polishing of a substrate. In addition, there is a need for polishing pads having satisfactory characteristics such as polishing efficiency, slurry flow over and remaining in the polishing pad, corrosion resistant etchant, and/or polishing uniformity. Finally, there is a need for polishing pads that can be manufactured using relatively low cost methods and require little adjustment prior to use.

The present invention provides a polishing pad comprising: (a) a polishing layer having a polishing surface, the polishing surface comprising: (1) a plurality of grooves disposed within the polishing layer having a measurable depth from the polishing surface, and (2) a barrier region having no such recess; and (b) a transparent window disposed within and surrounded by the barrier region. The invention further provides a method of polishing a substrate, the method comprising: (i) providing a workpiece to be polished, (ii) contacting the workpiece with the polishing pad of the present invention, and (iii) grinding the workpiece with the polishing system At least a portion of the surface to polish the workpiece.

The present invention relates to a chemical mechanical polishing pad comprising a polishing layer and a transparent window. The polishing layer has a polishing surface comprising (a) a plurality of grooves disposed in the polishing layer and (b) a barrier region having no such grooves. The transparent window system is disposed within and surrounded by the barrier region. While not wishing to be bound by any particular theory, it is believed that the presence of a barrier region substantially free of such grooves around the transparent window will reduce the amount of polishing composition remaining on or within the transparent window. .

The polishing pad can have any suitable size. Typically, the polishing pad may be rounded (e.g., for use in a rotary polishing tool) or fabricated as a looped tape (e.g., for use in a linear polishing tool). Preferably, the polishing pad is circular.

Figure 1 depicts a circular polishing pad of the present invention comprising a polishing layer (10) comprising a polishing surface (12), a continuous groove (40) and a discontinuous groove (50), and is disposed substantially free of A transparent window (15) in the barrier region (20) of the recess.

The grooves disposed within the polishing layer facilitate lateral transport of the polishing composition across the surface of the polishing pad. The grooves can be of any suitable pattern. For example, the grooves can be in the form of oblique grooves, circular grooves, concentric grooves, spiral grooves, radial grooves, or XY T-shaped patterns. The polishing pad can have two or more different groove patterns. For example, the polishing pad can have a combination of concentric grooves and radial grooves or a combination of concentric grooves and XY T-shaped patterns. Preferably, the grooves are concentric.

The grooves can be continuously connected across the surface of the polishing pad. Alternatively, the grooves may intermittently pass over the surface of the pad, wherein each of the interrupted grooves has a first end and a second end. In one embodiment, as depicted in FIG. 1, a portion of the grooves, for example, one or more of the grooves are continuous (40), and a portion of the grooves, for example, one or more of the grooves The groove is discontinuous (50).

As depicted in Figure 2, each groove has a measurable depth from the polishing surface. This depth can be any suitable depth. For example, the depth may be 1 mm or less, 0.8 mm or less, 0.6 mm or less, 0.5 mm or less, 0.4 mm or less, 0.3 mm or less, 0.2 mm or less, 0.1 Mm or smaller. The depths of the continuous and/or discontinuous grooves may be constant or may vary along the length or perimeter of the grooves. In one embodiment, as depicted in Figure 3, the depth of the discontinuous groove (50) transitions from a maximum depth to zero, i.e., the groove gradually taps toward the polishing surface (12) at at least one of the discontinuous grooves. reduce. Preferably, the depth transition is progressive, for example, longer than 0.5 mm or longer, 1 mm or longer, 2 mm or longer, 3 mm or longer, 4 mm or longer, or 5 mm or longer. In an embodiment, the depth is from a maximum depth to zero occurring adjacent to the barrier region.

The polishing pad further includes a barrier region that is substantially free of such grooves or desirably has only such grooves. In an embodiment, as shown in FIG. 1, the barrier region (20) is disposed between the first and second ends of the concentric, discontinuous recess (50).

The barrier region can have any suitable size and any suitable shape. The circumference of the barrier region (defined by the adjacent continuous and/or discontinuous grooves) can be any suitable shape (e.g., circular, elliptical, square, rectangular, triangular, etc.). When the shape of the barrier region is elliptical or rectangular, the barrier region generally has a long diameter axis or length of 2 cm or longer (eg, 3 cm or longer, 4 cm or longer, 5 cm or longer, 6 cm or Longer, 7cm or longer, 8cm or longer, 9cm or longer, 10cm or longer, 11cm or longer, or 12cm or longer) and a short diameter shaft or width of 1cm or longer (eg, 2cm) Or longer, 3 cm or longer, 4 cm or longer, 5 cm or longer, 6 cm or longer, 7 cm or longer, or 8 cm or longer). When the shape of the barrier region is circular or square, the circumference of the barrier region generally has a diameter or width of 2 cm or more (for example, 3 cm or longer, 4 cm or longer, 5 cm or longer, 6 cm or more). Length, 7 cm or longer, 8 cm or longer, 9 cm or longer, or 10 cm or longer).

As depicted in Figure 1, the transparent window (15) is disposed within and surrounded by the barrier region (20). The transparent window may be symmetrically or asymmetrically disposed within the barrier region.

The transparent window will have a circumference that defines a transparent window within the barrier region. Each point on the circumference of the transparent window will have the shortest distance from the continuous and/or discontinuous grooves to provide a series of shortest distances or intervals from the circumference of the transparent window to the grooves (eg, L ₁ , L ₂ , L ₃ ...). The minimum (L _min ) and maximum (L _max ) of the shortest distance of the series can be any suitable length. For example, L _min may be 0.5 cm or longer (eg, 1 cm or longer, 1.5 cm or longer, 2 cm or longer, 3 cm or longer, or 4 cm or longer). Further, alternatively, L _min may be 10 cm or less (for example, 8 cm or shorter, 7 cm or shorter, 6 cm or shorter, 5 cm or shorter, or 4 cm or shorter). L _max may independently be 0.5 cm or longer (for example, 1 cm or longer, 1.5 cm or longer, 2 cm or longer, 3 cm or longer, or 4 cm or longer). Further, alternatively, L _max may independently be 10 cm or shorter (for example, 8 cm or shorter, 7 cm or shorter, 6 cm or shorter, 5 cm or shorter, or 4 cm or shorter). L _min and L _max may be the same or different independently of the continuous grooves and the discontinuous grooves. Moreover, the series of shortest distances L ₁ , L ₂ , L _{3 ,} etc. need not be the same such that there is a uniform spacing between the transparent window and the grooves.

The transparent window can have any suitable dimensions (eg, length, width, diameter, and thickness) and any suitable shape (eg, circular, elliptical, square, rectangular, triangular, etc.). When the transparent window is elliptical or rectangular in shape, the transparent window generally has a long diameter axis or length of 1 cm or longer (for example, 2 cm or longer, 3 cm or longer, 4 cm or longer, 5 cm, 6 cm or Longer, 7cm or longer, or 8cm or longer) and a short diameter shaft or width of 0.5cm or longer (eg, 1cm or longer, 1.5cm or longer, 2cm or longer, 3cm or longer) , or 4cm or longer). When the transparent window is circular or square in shape, the transparent window generally has a diameter or width of 1 cm or more (for example, 2 cm or longer, 3 cm or longer, 4 cm or longer, or 5 cm or longer). .

The transparent window (15) includes an optically transmissive material. The presence of the transparent window allows the polishing pad to be used in situ with CMP process monitoring techniques. Typically, the optically transmissive material has an optical transmission rate of at least 10% or greater at one or more wavelengths (eg, 190 nm to 3500 nm, 200 nm to 1000 nm, or 200 nm to 780 nm) from 190 nm to 10,000 nm (eg, , 20% or more, 30% or more, or 40% or more). The optically transmissive material can be any suitable material, many of which are known in the art. The optically transmissive material may be the same or different from the material within the remainder of the polishing pad. For example, the optically transmissive material can be comprised of a glass or polymer-based plug that is inserted into the perforations of the polishing pad or can comprise the same polymeric material as used in the remainder of the polishing pad.

The transparent window can be secured to the polishing pad via any suitable mechanism. For example, the transparent window can be secured to the polishing pad via the use of an adhesive. Ideally, the transparent window is attached to the polishing pad without the use of an adhesive, for example by soldering. Similarly, the transparent window can have any suitable structure (e.g., crystallinity), density, and porosity. For example, the transparent window can be solid or porous (eg, micropores or nanopores having an average pore size of less than 1 micron). Preferably, the transparent window is solid or nearly solid (e.g., having a void capacity of 3% or less).

As depicted in Figure 2, the transparent window (15) can be immediately adjacent to the polishing surface (12) of the polishing layer, i.e., the highest window surface is substantially coplanar with the polishing surface. Alternatively, the window can be recessed from the polished surface of the polishing layer.

The polishing layer can be used alone or selectively as one of the layers of the multilayer stack polishing pad. For example, as shown in FIG. 4, including a polished surface (12), a barrier region substantially free of such recesses (20), a continuous recess (40) and a discontinuous recess (50), and a transparent window ( The polishing layer (10) of 15) can be used in combination with a sub-layer (30) that is substantially coextensive with the polishing layer. In some embodiments, the sub-layer (30) includes perforations (35) that are substantially aligned with the window (15) of the polishing layer.

The polishing layer, barrier region, transparent window, and sublayer of the polishing pad can comprise any suitable material that can be the same or different. Desirably, the polishing layer, the barrier region, the transparent window, and the sublayer of the polishing pad each independently comprise a polymer resin. The polymeric resin can be any suitable polymeric resin. Generally, the polymer resin is selected from the group consisting of thermoplastic elastomers, thermosetting polymers, polyurethanes (eg, thermoplastic polyurethanes), polyolefins (eg, thermoplastic polyolefins), polycarbonates, polyvinyl alcohols, nylons, elastomeric rubbers, Elastic material polyethylene, polytetrafluoroethylene, polyethylene terephthalate, polyimide, polyarylamine, polyarylene, polyacrylate, polystyrene, polymethyl methacrylate, etc. a group of copolymers, and mixtures thereof, etc. Preferably, the polymer resin is a polyurethane, more preferably a thermoplastic polyurethane. The polishing layer, barrier region, transparent window, and sublayer may comprise different polymeric resins. For example, the polishing layer can comprise a porous thermoset polyurethane, the secondary layer can comprise a closed cell polyurethane foam, and the transparent window can comprise a solid thermoplastic polyurethane.

The polishing layer and the sub-layer may have different chemistries (eg, polymer compositions) and/or physical properties (eg, porosity, compressibility, transparency, and stiffness). For example, the polishing layer and the sub-layer may independently be a closed cell (eg, a porous foam), an open cell (eg, a sintered material), or a solid (eg, cut from a solid polymer sheet) . Preferably, the polishing layer has less compressibility than the secondary layer. The polishing layer and the secondary layer can be formed by any suitable method, most of which are known in the art. Suitable methods include casting, cutting, reaction injection molding, injection blow molding, compression molding, sintering, thermoforming, and compression of the porous polymer into the desired polishing pad shape. Other polishing pad elements may also be added to the porous polymer before, during or after shaping the porous polymer, if desired. For example, the backing material can be coated, drilled, or provided with surface texture (eg, grooves, channels) via a variety of methods generally known in the art.

The polishing layer may further comprise organic or inorganic particles as the case may be. For example, the organic or inorganic particles may be selected from metal oxide particles (eg, cerium oxide particles, alumina particles, cerium oxide particles), diamond particles, glass fibers, carbon fibers, glass beads, aluminosilicates, A group consisting of a citrate (for example, mica particles), crosslinked polymer particles (for example, polystyrene particles), water-soluble particles, water-absorbing particles, hollow particles, a composition thereof, and the like. The particles can have any suitable size. For example, the particles can have an average particle diameter of 1 nm to 10 microns (eg, 20 nm to 50 microns). The amount of particles in the polishing pad body can be any suitable amount, for example, from 1 wt.% to 95 wt.%, based on the total weight of the polishing pad body.

The polishing pad of the present invention is particularly suitable for use with chemical mechanical polishing (CMP) devices. Typically, the apparatus includes: a platen that, when in use, is operative and has a rate of movement by rail, wire, or circular motion; the polishing pad of the present invention is in contact with the platen during operation And moving with the platen; and a carrier that maintains a workpiece that is polished via contact and movement relative to the surface of the polishing pad. The polishing of the workpiece occurs where the workpiece is in contact with the polishing pad and thereafter the polishing pad moves relative to the workpiece, typically having a polishing composition therebetween to abrade at least a portion of the workpiece to polish the workpiece. The polishing composition can be any suitable polishing composition. Polishing compositions typically include a liquid carrier (e.g., an aqueous carrier), a pH adjusting agent, and an abrasive. The polishing composition may further optionally include an oxidizing agent, an organic acid, a complexing agent, a pH buffering agent, a surfactant, a corrosion inhibitor, an anti-foaming agent, and the like, depending on the kind of the workpiece to be polished. The CMP device can be any suitable CMP device, many of which are known in the art. The polishing pad of the present invention can also be used with a linear polishing tool.

Desirably, the CMP apparatus further includes an in-situ polishing endpoint detection system, many of which are known in the art. Methods of inspecting and monitoring the polishing process by analyzing light or other radiation reflected from the surface of the workpiece are known in the art. Such methods are described in, for example, U.S. Patent No. 5, 196, 353, U.S. Patent No. 5, 433, 651, U.S. Patent No. 5, 609, 511, U.S. Patent No. 5,643,046, U.S. Patent No. 5,658,183, U.S. Patent No. 5,730,642, U.S. Patent No. 5,838,447, U.S. Patent No. 5,872,633, U.S. Patent No. 5,893,796, U.S. Patent No. 5,949,927, Patent No. 5,964,643. Ideally, the polishing process can be determined by examining or monitoring the polished workpiece, i.e., determining when the particular workpiece should terminate the polishing process.

The polishing pad of the present invention is suitable for use in a method of polishing a plurality of types of workpieces (e.g., substrates or wafers) and workpiece materials. For example, the polishing pad can be used to polish a workpiece, including a memory storage device, a glass substrate, a memory or a hard disk, a metal (eg, a precious metal), a magnetic read head, an interlayer dielectric (ILD) layer, a polymer film, and a low And high dielectric constant films, ferroelectrics, microelectromechanical systems (MEMS), semiconductor wafers, field emission displays, and other microelectronic substrates, especially including insulating layers (eg, metal oxides, tantalum nitride, or Low dielectric materials) and/or microelectronic substrates containing metal layers (eg, copper, tantalum, tungsten, aluminum, nickel, titanium, platinum, rhodium, ruthenium, iridium, alloys thereof, and the like). The term "memory or hard disk" means any disk, hard disk, hard disk, or memory disk used to retain electromagnetic form messages. A memory or hard disk typically has a surface comprising a nickel-phosphor, but the surface can comprise any other suitable material. Suitable metal oxide insulating layers include, for example, aluminum oxide, cerium oxide, titanium dioxide, cerium oxide, zirconium oxide, cerium oxide, magnesium oxide, and the like. Additionally, the workpiece can include, consist essentially of, or consist of any suitable metal composite. Suitable metal composites include, for example, metal nitrides (e.g., tantalum nitride, titanium nitride, and tungsten nitride), metal carbides (e.g., tantalum carbide and tungsten carbide), nickel-phosphorus, aluminum boron phthalic acid Salt, borosilicate glass, phosphonium silicate glass (PSG), borophosphoquinone glass (BPSG), tantalum/niobium alloy, and tantalum/niobium/carbon alloy. The workpiece can also comprise, consist essentially of, or consist of any suitable semiconductor based material. Suitable semiconductor base materials include single crystal germanium, polycrystalline germanium, amorphous germanium, germanium overlying insulating layers, and gallium arsenide.

10. . . Polishing layer

12. . . Polished surface

15. . . Transparent window

20. . . Barrier zone

30. . . Secondary layer

35. . . perforation

40. . . Continuous groove

50. . . Intermittent groove

1 is a schematic plan view of a polishing pad having a polishing layer (10) of the present invention, the polishing layer (10) comprising a polishing surface (12) having a continuous groove (40) and a discontinuous groove (50) and disposed in There is substantially no substantially transparent window (15) within the barrier region (20) of the grooves.

2 is a fragmentary, partial cross-sectional perspective view of a polishing pad having a polishing layer (10) of the present invention, the polishing layer (10) including a continuous configuration having a measurable depth from the polishing surface disposed within the polishing layer (10) The polishing surface (12) of the recess (40) and the discontinuous recess (50) and the substantially transparent window (15) disposed in the barrier region (20) having substantially no such recess.

3 is a partial cross-sectional perspective view of a polishing pad having a polishing layer (10) of the present invention, the polishing layer including a continuous groove (40) having a measurable depth disposed within the polishing layer from the polishing surface. The polishing surface (12) of the discontinuous groove (50) and the substantially transparent window (15) disposed in the barrier region (20) having substantially no such grooves, wherein the depth of the discontinuous groove is from a maximum The value transitions to zero adjacent to the barrier region (20).

4 is a fragmentary, partial cross-sectional perspective view of a polishing pad having a polishing layer (10) and a secondary layer (30) of the present invention, wherein the secondary layer has perforations substantially aligned with the transparent window (15) ( 35).

10. . . Polishing layer

12. . . Polished surface

15. . . Transparent window

20. . . Barrier zone

40. . . Continuous groove

50. . . Intermittent groove

Claims (16)

A polishing pad comprising: (a) a polishing layer having a polishing surface, wherein the polishing surface comprises: (1) a plurality of concentric grooves disposed within the polishing layer having a measurable depth from the polishing surface, and 2) a barrier region having no such recesses, and (b) a transparent window disposed within and surrounding the barrier region, wherein one or more of the equivalent recesses are discontinuous and have a first And a second end, wherein the barrier region is disposed between the first and second ends, and wherein the transparent window has a highest window surface that is substantially coplanar with the polishing surface. A polishing pad according to claim 1, wherein the depth transitions from a maximum value to zero adjacent to the barrier region. A polishing pad according to claim 2, wherein the depth is changed to progressive. A polishing pad according to claim 3, wherein the polishing pad is circular. A polishing pad according to claim 1, wherein the polishing layer comprises a polyurethane. A polishing pad according to claim 1, wherein the transparent window comprises a thermoplastic polyurethane. A polishing pad according to claim 1, wherein the polishing pad further comprises a sublayer. A method of polishing a substrate, comprising: (i) providing a workpiece to be polished, (ii) contacting a polishing pad as claimed in claim 1 with the workpiece, and (iii) grinding at least a portion of the surface of the workpiece with the polishing pad To polish the workpiece. The method of claim 8, wherein the method further comprises detecting the polishing endpoint in situ. The method of claim 8, wherein the workpiece is in contact with a chemical mechanical polishing composition located between the workpiece and the polishing pad. The method of claim 8, wherein the depth transitions from a maximum value to zero adjacent to the barrier region. The method of claim 11, wherein the depth is changed to progressive. The method of claim 12, wherein the polishing pad is circular. The method of claim 8, wherein the polishing layer comprises a polyurethane. The method of claim 8, wherein the transparent window comprises a thermoplastic polyurethane. The method of claim 8, wherein the polishing pad further comprises a sublayer.