Patent Application
20180085891
The present invention relates to an apparatus for use in providing pad surface microtexture in polishing pads, such as polymeric pads, used for chemical mechanical planarization (CMP) of substrates, such as a semiconductor substrate, a magnetic substrate, and an optical substrate as well as to methods for using the same. More particularly, the present invention relates to an apparatus for grinding the surface of a CMP polishing layer comprising a rotary grinder having a grinding surface of a porous abrasive material to form an interface of the surface of the CMP polishing layer and the porous abrasive material, as well as a flat bed platen for holding the CMP polishing layer in place.
The manufacture of polishing pads for use in chemical mechanical planarization is known to include the molding and curing of a foamed or porous polymer in a mold having the desired diameter of the final polishing pad, such as a polyurethane, followed by demolding and cutting the cured polymer in a direction parallel to the top surface of the mold to form a layer having desired thickness, for example, by skiving, and then by shaping the resulting layer, for example, by grinding, routing or embossing a final surface design into the top of a polishing pad. Previously, known methods of shaping such layers into polishing pads include injection molding the layers, extruding the layers, buffing the layers with a fixed abrasive belt and/or facing the layers to a desired thickness and flatness. These methods have limited capability to achieve a consistent pad surface microtexture required for low defectivity in polished substrates and uniform removal of material from substrates. In fact, the methods generally create a visible design, such as grooves of a given width and depth and a visible but inconsistent texture. For example, a skiving process is unreliable for pad surface shaping because the stiffness of the mold changes with mold thickness and the skiver blade continuously wears. Single point facing techniques have been unable to yield a consistent pad surface microtexture due to continuous tooling wear and lathe positioning accuracy. Pads made by injection molding processes lack uniformity owing to inconsistent material flow throughout the mold; further, the moldings tend to distort as the pad sets and cures because the curative and the remainder of the molded material can flow at different rates during injection into a confined area, especially at elevated temperatures.
Buffing methods have also been used to smooth chemical mechanical polishing pads having a harder surface. In one example of a buffing method, U.S. Pat. No. 7,118,461 to West et al. discloses smooth pads for chemical mechanical planarization and methods for making the pads, the methods comprising buffing or polishing the surface of the pads with an abrasive belt to remove material from the pad surface. Buffing was in one example followed by a successive buffing step using a smaller abrasive. The product of the methods exhibits improved planarization capability over the same pad product that was not smoothed. Unfortunately, while the methods of West et al. can smooth a pad, they do not provide a consistent pad surface microtexture and cannot be used to treat in a softer pad (Shore D hardness according to ASTM D2240-15 (2015) of pad or pad polymer matrix of 40 or less). Further, the West et al. methods remove so much material that the useful life of the resulting polishing pads may be adversely affected. It remains desirable to provide a chemical mechanical polishing pad with a consistent surface microtexture without limiting the useful life of the pad.
Conditioning of a chemical mechanical polishing pad is akin to buffing, wherein the pads are generally conditioned in use with a rotary abrasive wheel having a surface that resembles fine sandpaper. Such conditioning leads to improved planarization efficiency after a ‘break in’ period during which the pad is not used for polishing is done. It remains desirable to eliminate the break in period and provide a pre-conditioned pad that can be used for polishing right away.
The present inventors have endeavored to find apparati for making pre-conditioned CMP pads that have a consistent pad surface microtexture while retaining their original surface topography.
1. In accordance with the present invention, apparati to provide pre-conditioned polymeric, preferably, porous polymeric, polyurethane or polyurethane foam, chemical mechanical (CMP) polishing pads or layers with a pad surface microtexture effective for polishing comprise a rotary grinder assembly having a wheel or rotor with a grinding surface of a porous abrasive material, and a flat bed platen for holding the CMP polishing layer in place, such as by pressure sensitive adhesive or, preferably, by vacuum, the grinding surface of the rotary grinder disposed above and parallel to or substantially parallel to the surface of the flat bed platen to form an interface of the surface of the CMP polishing layer and the porous abrasive material.
2. In accordance with the apparati of the present invention as recited in item 1, above, wherein the CMP polishing layer has a radius extending from its center point to its outer periphery and the grinding surface of the wheel or rotor of the rotary grinder assembly has a diameter equal to or greater than the radius of the CMP polishing layer, preferably, equal to the radius of the CMP polishing layer.
3. In accordance with the apparati of the present invention as recited in item 2, above, wherein the wheel or rotor of the rotary grinder assembly is positioned so that the outer periphery of its grinding surface rests directly over the center of the CMP polishing layer during grinding.
4. In accordance with the apparati of the present invention as recited in any one of items 1, 2 or 3, above, wherein the wheel or rotor of the rotary grinder assembly and the CMP polishing layer and flat bed platen each rotate during the grinding of the CMP polishing layer. Preferably, the flat bed platen rotates in the opposite direction as the rotary grinder assembly.
5. In accordance with the apparati of the present invention as recited in item 4, above, wherein the wheel or rotor of the rotary grinder assembly rotates at a rate of from 50 to 500 rpm or, preferably, from 150 to 300 rpm and the flat bed platen rotates at a rate of from 6 to 45 rpm or, preferably, from 8 to 20 rpm.
6. In accordance with the apparati of the present invention as recited in any one of items 1, 2, 3, 4 or 5, above, wherein the wheel or rotor of the rotary grinder assembly is positioned above the CMP polishing layer and flat bed platen during the grinding, and the rotary grinder is fed downward from a point just above the CMP polishing layer surface at a rate of from 0.1 to 15 μm/revolution or, preferably, from 0.2 to 10 μm/revolution, i.e. to shrink the interface of the surface of the CMP polishing layer and the porous abrasive material.
7. In accordance with the apparati of the present invention as recited in any one of items 1, 2, 3, 4, 5, or 6, above, wherein the rotary grinder assembly comprises a drive housing including a motor or rotary actuator, such as an electric or servo motor, and a vertically disposed axle connecting with and driven by the motor or rotary actuator, such as via a gear or a drive belt, which extends into a drive housing and connects at its lower end via a mechanical linkage, such as a gear or a drive belt, to the wheel or rotor so that it spins at a desired rate of revolutions per minute (rpm).
8. In accordance with the apparati of the present invention as recited in item 7, above, wherein the in the drive housing, the vertically disposed axle comprises a ball screw or secondary servo motor located where the axle connects to the motor or rotary actuator, at the mechanical linkage of the axle to the wheel or rotor, or both locations, whereby the wheel or rotor of the rotary grinder assembly can be fed downward at a set, incremental rate.
9. In accordance with the apparati of the present invention as recited in item 8, above, wherein the wheel or rotor comprises one or more eccentrics, pneumatic actuators, such as a cylinders, electronic actuators, or motor actuators, such as servo motors, preferably, three to eight of such actuators arranged in a radial array around the wheel or rotor, whereby the wheel or rotor can be tilted so that its grinding surface is substantially parallel to the top surface of the flat bed platen, such as to enable the grinding to create center-thick or center-thin CMP polishing layers or pads.
10. In accordance with the apparati of the present invention, wherein the rotary grinder assembly has a wheel or rotor having the porous abrasive material grinding medium, preferably, carried on a single carrier ring, the grinding medium attached at the underside of its periphery, such as via a radial array of clips, fasteners, or a laterally spring loaded snap ring located on the underside of the rotary grinder assembly into which the periphery of a ring of the porous abrasive material fits snugly.
11. In accordance with the apparati of the present invention as recited in item 11, above, wherein the porous abrasive material grinding medium is arranged in a plurality segments extending around the underside of periphery of the rotary grinder assembly and having gaps between the segments.
12. In accordance with the apparati of the present invention as recited in any of items 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11, above, wherein the porous abrasive material is a composite of a porous continuous phase having dispersed within it finely divided non-porous abrasive particles, such as boron nitride or, preferably, diamond particles.
13. In accordance with the apparati of the present invention as recited in item 12, above, wherein the porous continuous phase of the porous abrasive material has an average pore diameter of from 3 to 240 μm or, preferably, from 10 to 80 μm.
14. In accordance with the apparati of the present invention as recited in any one of items 8 or 9, above, wherein the porous continuous phase of the porous abrasive material comprises a ceramic, preferably, a sintered ceramic, such as alumina or ceria.
15. In accordance with the apparati of the present invention as in any one of items 1 to 14, above, wherein the flat bed platen contains a plurality of small holes, for example, from 0.5 to 5 mm in diameter, through the platen which are connected to a vacuum. The holes can be arranged in any suitable manner to hold the CMP polishing layer substrate in place during grinding, such as, for example, along a series of spokes extending outward from the center point of the flat bed platen or in a series of concentric rings.
16. In accordance with the apparati of the present invention as recited in any one of items 1 to 15, above, further comprising a conduit, hose, nozzle or valve for blowing compressed inert gas or air intermittently or, preferably, continuously, and positioned to blow the inert gas or air into the interface of the surface of the CMP polishing layer material and the porous abrasive material so as to impinge upon the porous abrasive material during grinding, preferably, from a point adjacent the center point of the CMP polishing layer on the flat bed platen through the interface of the CMP polishing layer and the porous abrasive material or, more preferably, the conduit, hose, nozzle or valve positioned to blow the inert gas or air from a point adjacent the center point of the CMP polishing layer on the flat bed platen through the interface of the CMP polishing layer and the porous abrasive material so as to impinge upon the porous abrasive material and, separately, a second conduit, hose or valve for blowing compressed inert gas or air upward from a point just below the periphery of the rotary grinder assembly so as to impinge upon the porous abrasive material during grinding, for example, where the periphery of the CMP polishing layer and the periphery of the rotary grinder come together.
17. In accordance with the apparati of the present invention as recited in any one of items 1 to 16, above, the apparati further comprising a substrate holder located above and parallel to the top surface of the flat bed platen so as not to overlap with the area over which the rotary grinder assembly is disposed and to which a CMP substrate, such as a semiconductor substrate or wafer, a magnetic substrate, or an optical substrate is attached, for example, clamped, thereby creating a polishing interface between the surface of the substrate and the CMP polishing layer wherein the substrate holder rotates independently from the rotary grinder assembly and the flat bed platen, for example, at an individual speed of from 1 to 200 rpm or, preferably, from 10 to 100 rpm.
18. In accordance with the apparati of the present invention as recited in item 17, above, wherein the substrate holder has a diameter smaller than the radius of the CMP polishing layer or pad held on the flat bed platen and, further wherein, the substrate holder is mechanically linked to or mounted on a first actuator, such as a servo motor for rotating the grinder about a central axis; and a second actuator, such as a second servo motor or a Z-axis ball screw for pressing the substrate holder against the CMP polishing layer or pad.
19. In accordance with the apparati of the present invention as in any of items 1 to 18, above, wherein the entire apparatus is enclosed inside an airtight enclosure, such as one wherein the relative humidity (RH) may range from 5 to 100%, for example, from 5 to 50%.
Unless otherwise indicated, conditions of temperature and pressure are ambient temperature and standard pressure. All ranges recited are inclusive and combinable.
Unless otherwise indicated, any term containing parentheses refers, alternatively, to the whole term as if no parentheses were present and the term without them, and combinations of each alternative. Thus, the term “(poly)isocyanate” refers to isocyanate, polyisocyanate, or mixtures thereof.
All ranges are inclusive and combinable. For example, the term “a range of 50 to 3000 cPs, or 100 or more cPs” would include each of 50 to 100 cPs, 50 to 3000 cPs and 100 to 3000 cPs.
As used herein, the term “ASTM” refers to publications of ASTM International, West Conshohocken, Pa.
As used herein, the term “thickness variation” means the value determined by the maximum variation in CMP polishing pad thickness.
As used herein, the term “substantially parallel” refers to an angle formed by the grinding surface of the rotary grinder and the top surface of the CMP polishing layer or, more particularly, an angle of from 178° to 182°, or, preferably, from 179° to 181° which is defined by the intersection of a first line segment running parallel to the grinding surface of the rotary grinder and ending at a point above the center point of the CMP polishing layer and a second line segment running from the end of the first line segment and parallel to the top surface of the flat bed platen and ending at the outer periphery of the flat bed platen, wherein the first and second line segments are within a plane that is normal to the flat bed platen and that runs through the center point of the CMP polishing layer and the point on the periphery of the grinding surface of the rotary grinder located furthest from the center point of the CMP polishing layer.
As used herein the term “Sq.” when used to define surface roughness means the root mean square of an indicated number surface roughness values measured at indicated points on the surface of a given CMP polishing layer.
As used herein, the term “surface roughness” means the value determined by measuring the height of a surface relative to the best fitting plane that represents a horizontal surface parallel to and located at the top surface of a given CMP polishing layer at any given point on that top surface. An acceptable surface roughness ranges from 0.01 μm to 25 μm, Sq, or, preferably, from 1 μm to 15 μm, Sq.
As used herein, the term “wt. %” stands for weight percent.
In accordance with the present invention, grinding apparati improve the surface microtexture of CMP polishing layers, include the top surface of CMP polishing pads and polishing layers. The apparati create a consistent surface microtexture characterized by a series of intersecting arcs in the CMP polishing layer surface and having the same radius of curvature as a circle defined by the outer periphery of the grinding surface of the rotary grinder and by a surface roughness on the upper surface of the CMP polishing layer of from 0.01 to 25 μm, Sq. The present inventors have found that CMP polishing layers treated with the rotary grinder in accordance with the present invention perform well with little or no conditioning, i.e. they are pre-conditioned. Further, the pad surface microtexture of the rotary grinder treated CMP polishing layers provide enhanced polishing of substrates. The apparati of the present invention help to avoid irregularities in pad morphology caused by skiving, which can cause surface defects, such as gouges, in chemical mechanical polishing pads as well as bubbling of window materials which are softer than the remainder of the CMP polishing layer. Further, the apparati of the present invention help to minimize negative impacts caused by deformation of the polishing layer during pad stacking in which two or more pad layers are passed through nips set a fixed distance apart and linear waves result. This is especially important with soft and compressible CMP polishing layers. In addition, the apparati of the present invention and the treated pads they provide enable optimized surface microtexture, lower defectivity and improved uniform material removal across a substrate surface, for example, semiconductor or wafer surface.
The present inventors have discovered that grinding a CMP polishing layer with a porous abrasive material enables grinding without fouling the grinding media and without causing damage to the CMP polishing layer substrate. The pores in the porous abrasive material are large enough to store the particulates that are being removed from the CMP polishing layer substrate; and the porosity of the porous abrasive material is sufficient to store the bulk of the removed material during grinding. Preferably, blowing compressed air across the interface of the porous abrasive material and the CMP polishing layer substrate further aids in removal of grinds and prevents fouling of the grinding equipment.
In any method of using the apparatus of the present invention, the blowing of the compressed gas or air can also take place before or after the grinding.
The apparati of the present invention may comprise a rotary grinder and a flat bed platen. The rotary grinder is lowered at a set rate or feed rate onto a CMP polishing layer which rests on the flat bed platen.
As shown in
The apparati of the present invention may, preferably, comprise both a grinder/conditioner and a polishing apparatus in which a CMP polishing pad is mounted on the flat bed platen and both the rotary grinder assembly and, independently, a substrate holder are lowered onto the CMP polishing pad to form for each an interface between them and the top of the CMP polishing layer. The substrate holder is mechanically linked to or mounted on a first actuator, such as a servo motor for rotating the substrate holder about a central axis; and a second actuator, such as a second servo motor or a Z-axis ball screw for pressing the substrate holder against the CMP polishing pad.
As shown in
The grinding and polishing apparatus operates as follows: The substrate, for example, a semiconductor wafer, is held on the lower surface of the substrate holder, and pressed against the CMP polishing pad on the upper surface of the flat bed platen. The flat bed platen and the substrate holder are rotated relative to each other thereby bringing the lower surface of the substrate in sliding contact with the polishing pad. At this time, an abrasive liquid nozzle (not shown) supplies an abrasive liquid, such as an aqueous silica or abrasive oxide, carbide or nitride particle slurry to the polishing pad. The lower surface of the substrate is polished by a combination of a mechanical polishing action of abrasive grains in the abrasive liquid and of the surface of the CMP polishing layer.
The rotary grinder of the present invention comprises a round rotary grinder assembly or rotor having attached at its periphery a porous abrasive material, preferably one that is notched or comprises discontinuities or gaps around the periphery of the rotary grinder. The underside of the porous abrasive material is the grinding surface of the rotary grinder. The porous abrasive material may be in the form of a ring or ring segments that fit into or attach to the underside of the rotary grinder assembly. The porous abrasive material can comprise of radially array of downward facing segments, usually from 10 to 40 segments of the porous abrasive material having gaps between them or a perforated ring made of the porous abrasive material having periodic perforations in it. The gaps or perforations allow the blowing of compressed gas or air into the interface of the surface of the CMP polishing layer and the porous abrasive material to remove grinds and clean the porous abrasive material before, during or after grinding. In addition, the notches or gaps in the porous abrasive material help to cool the surfaces of the porous abrasive material and the CMP polishing layer substrate during grinding.
The apparati of the present invention can be positioned to compensate for undesirable CMP substrate wear profiles, such as where CMP processes result in inconsistent wear profiles, such as too little or too much removal at the edge of a substrate. This, in turn can extend pad life. In such positions, the grinding surface of the rotary grinder assembly can be adjusted so that it is substantially parallel but not exactly parallel to the top surface of the flat bed platen or CMP polishing layer. For example, the grinding surface of the rotary grinder can be adjusted to yield a center-thick (angle between rotary grinder and a flat bed platen radius in a plane that is normal to the flat bed platen and runs through the center point of the CMP polishing layer and the point on the periphery of the grinding surface of the rotary grinder that is located furthest from the center point of the CMP polishing layer is more than) 180° or center-thin (angle is less than 180°).
The apparati of the present invention can be used in a wet environment, such as in conjunction with water or an abrasive aqueous slurry, such as a silica or ceria slurry.
The apparati of the present invention are scalable to fit CMP polishing layers of various sizes, as the size of the rotary grinder element can be varied. In accordance with the apparati of the present invention, the flat bed platen should be larger than the CMP polishing layer or, preferably, of a size having a radius that is equal to or within 10 cm longer than the radius of the CMP polishing layer. The apparati thus are scalable to treat CMP polishing layers having a radius of from 100 mm to 610 mm.
Various rotary grinder assemblies can be used with the apparatus in accordance with the present invention, using one at a time. The rotary grinder assembly is selected so that its diameter matches or is slightly larger than the radius of the CMP polishing layer being ground. Alternatively, the rotary grinder assembly is adapted to allow a ring or disc, preferably, a single carrier ring, of porous abrasive material grinding medium of various diameters to attach at the underside of its periphery.
Various substrate holders can be used with the apparatus in accordance with the present invention, using one at a time. The substrate holder is selected so that its diameter is smaller than the radius of the CMP polishing layer being used for polishing and larger than the diameter of the substrate being polished.
The apparati of the present invention enable the provision of CMP polishing layers or pads that do not suffer from window bulges and defects caused by skiving. Thus, in accordance with a method of using the apparati of the present invention, a CMP polishing layer can be formed by molding a polymer to form a porous molding having a desired diameter or radius, which will be the size of pads made therefrom, then skiving the molding to a desired thickness, which will be the target thickness of a pad made in accordance with the present invention, followed by grinding the pad or CMP polishing layer to provide the desired pad surface microtexture on the pad polishing surface.
In the methods of using the apparati of the present invention, the grinding can be performed on single layer or solo pads, as well as on stacked pads having a subpad layer. Preferably, in the case of stacked pads the methods comprise grinding the CMP polishing layer after the pads are stacked so that grinding can help eliminate deformities in stacked pads.
Suitable CMP polishing pads can be formed by molding the polymer and skiving the molded polymer to form the CMP polishing layer for use as the pad, or, preferably, formed by molding the polymer and skiving the molded polymer to form the CMP polishing layer followed by stacking the CMP polishing layer on top of a subpad or subbing layer having the same diameter as the CMP polishing layer to form the CMP polishing pad.
In the methods of using the apparati of the present invention can comprise forming the CMP polishing pad, forming grooves in the pads, such as by lathing the pads, and then grinding the CMP polishing pads with the rotary grinder to form a pad surface microtexture, including a series of visibly intersecting arcs on the polishing surface and having a radius of curvature equal to or greater than, preferably, equal to the radius of the polishing layer while, simultaneously planarizing a substrate with the CMP polishing pads. In such methods, the CMP polishing pads are being conditioned and resurfaced while in use.
In the methods of using the apparati of the present invention can comprise forming the CMP polishing pad, grinding the CMP polishing pads with the rotary grinder to form a pad surface microtexture, including a series of visibly intersecting arcs on the polishing surface and having a radius of curvature equal to or greater than, preferably, equal to the radius of the polishing layer while, simultaneously planarizing a substrate with the CMP polishing pads and then forming grooves in the pads, such as by lathing the pads.
In addition, the apparati of the present invention can be used as a CMP polishing or planarizing tool, i.e. a grinding and polishing apparatus.
In another aspect, the present invention provides method of using the grinding and polishing apparatus of the present invention. In accordance with the methods of using the grinding and polishing apparatus of the present invention, a CMP polishing pad is attached to the upper surface of the flat bed platen and the substrate, such as a semiconductor wafer to be polished, is clamped to the substrate holder so that its underside can be lowered onto the CMP polishing pad that is on the flat bed platen, followed by rotating all of the flat bed platen, the rotary grinder assembly and the substrate holder.
In the method of using the grinding and polishing apparatus of the present invention, an abrasive liquid containing abrasive grains, such as silica, ceria or alumina or their mixtures, is supplied onto the polishing pad and retained thereon. During operation, the substrate holder exerts a desired down pressure of from 2 to 69 kPa, preferably, from 3 to 48 kPa on the flat bed platen, and the surface of the substrate held against the CMP polishing pad is therefore planarized while the substrate holder and the flat bed platen are rotating.
Preferably, in methods of polishing a substrate in accordance with the present invention, the substrate holder and the flat bed platen are rotated in the same direction.
Suitable CMP polishing layers for use in accordance with the methods of using the apparatus of the present invention comprise a polymer or, preferably, comprise a porous polymer, polymeric foam or filler containing porous polymer material that has a Shore D hardness according to ASTM D2240-15 (2015) of from 20 to 80, or, for example, 40 or less.
Preferably, the methods of the present invention can be carried out on any CMP polishing pad, including those made from relatively soft polymers and find particular use in treating soft pads having a Shore D hardness of 40 or less.
Suitable CMP polishing layers for use in accordance with the methods of using apparatus of the present invention may further comprise one or more, non-porous, clear window sections, such as those comprising a non-porous polyurethane having a glass transition temperature (DSC) of from 75 to 105° C., such as window sections not extending over the center point of the CMP polishing layer. In such CMP polishing layers, the one or more window sections has a top surface defined by a window thickness variation of 50 μm or less over the largest dimension of the window, such as the diameter of a round window, or the larger of the length or width of a rectangular window.
Further, suitable CMP polishing layers for use with the methods of using the apparatus of the present invention may comprise a plurality of pores or microelements, preferably, polymeric microspheres, having an average particle size of from 10 to 60 μm. Preferably, such a CMP polishing layer has annular bands of alternating higher density and lower density extending outward from the center point of the CMP polishing layer toward its outer periphery. For example, the higher density annular bands have a density of from 0.01 to 0.2 g/cm3 higher than the lower density annular bands.
Accordingly, the chemical mechanical (CMP) polishing pads produced in accordance with the methods of using the apparati of the present invention comprise a porous polymeric CMP polishing layer having a radius and having a surface roughness of at least 0.01 μm to 25 μm, Sq, or, preferably, from 1 μm to 15 μm, Sq, and having a series of visibly intersecting arcs on the polishing layer surface and having a radius of curvature equal to or greater than half, preferably, equal to half the radius of curvature of the polishing layer. Preferably, the series of visibly intersecting arcs extends all the way around the surface of the polishing layer in radial symmetry around the center point of the polishing layer.
The CMP polishing pads produced in accordance with the methods of using the apparatus of the present invention have a center point and a radius. Such polishing pads can have a thickness whereby the pads are sloped so the thickness becomes greater closer to their center point, or are sloped to become greater further away from their center point.
In the following examples, unless otherwise stated, all units of pressure are standard pressure (˜101 kPa) and all units of temperature are room temperature (21-23° C.).
Trials were Conducted with Two Versions of a VP5000™ CMP polishing layer or pad (Dow Chemical, Midland, Mich. (Dow)) having a 330 mm (13″) radius. The pads had no windows. In Example 1-1, the CMP polishing layer comprised a single porous polyurethane pad which was 2.03 mm (80 mil) thick, and wherein the polyurethane had a Shore D hardness of 64.9. In Example 1-2, the CMP polishing layer comprised a stacked pad having the same polyurethane pad of Example 1-1 stacked using a pressure sensitive adhesive onto a SUBA IV™ sub-pad made from polyester felt (Dow).
The Comparatives in Examples 1-A and 1-B were the same pads, respectively, as in Examples 1-1 and 1-2, but not treated in accordance with the methods of the present invention: The stacked pad had a SIV sub-pad.
All pads had 1010 grooves (a concentric circle groove pattern with 0.0768 cm (0.030″) deep×0.0511 cm (0.020″) wide×0.307 cm (0.120″) pitch), and no window.
The porous abrasive material was a vitrified, porous diamond abrasive, having an average abrasive size of 151 μm. To grind the substrate, the rotary grinder assembly was positioned parallel to the top of the flat bed platen and was rotated counterclockwise at 284 rpm and the aluminum flat bed platen was rotated clockwise at 8 rpm. Starting from a point at which the porous abrasive material just begins to touch the CMP polishing layer substrate, the rotary grinder assembly was fed down towards the flat bed platen at a rate of 5.8 μm (0.0002″) increments every 3 pad revolutions. During this time compressed dry air (CDA) was blown into the interface of the surface of the porous abrasive material and the CMP polishing layer from 2 nozzles, one located just above the center point of the CMP polishing layer and the other located at approximately 210 mm (8.25″) from the pad center on the trailing side of the porous abrasive material. The grinding was continued for approximately 5 min.
The resulting pads from Example 1 were evaluated in polishing tests for removal rate, non-uniformity and chattermarks (defectivity), as follows:
Removal Rate:
Was determined on a 200 mm size tetraethoxysilicate (TEOS) substrate by planarizing the substrates using the indicated pads and an ILD3225™ fumed silica aqueous slurry (Dow) at 200 ml/min flowrate. Polishing pressure was varied from 0.11, 0.21 and 0.32 kg/cm2 (1.5, 3.0, 4.5 psi) downforce at 93/87 platen/substrate carrier rpm, using a Mirra™ polishing tool (Applied Materials, Santa Clara, Calif.). Prior to testing all polishing pads were conditioned for 40 minutes at 3.2 kg (7 lbs) using as a conditioner a SAESOL™ 8031C1 disk (braised diamond dust surface, 10.16 cm in diameter, Saesol Diamond Ind. Co., Ltd., Korea). During testing, the same conditioning of the pads was continued. A total of 18 wafers were tested per pad and the averages obtained.
Non-Uniformity:
Was determined on the same TEOS substrate planarized in removal rate testing and in the manner disclosed in removal rate testing, except that the data were obtained by observing within-wafer thickness variation. A total of 18 wafers were tested per pad and the averages obtained.
Chattermarks or Defect Count:
Was determined on the same TEOS substrate planarized in removal rate testing and in the manner disclosed in removal rate testing, except that the data were obtained by observing the total number of CMP defects. A total of 18 wafers were tested per pad and the averages obtained.
The resulting pads had a pad surface microtexture comprising intersecting arcs having a radius of curvature equal to that of the periphery of the rotary grinder assembly. Also, as shown in Table 1, below, the inventive pads of Example 1-1 and 1-2 gave the same planarization rates on a substrate as the Comparative pads of Examples 1-A (solo) and 1-B (stacked); meanwhile, the inventive pads of Example 1-1 and 1-2 produced significantly lowered defectivity and dramatically fewer chatter marks in the substrate than the pads of Comparative Examples 1-A and 1-B which were not subject to the grinding methods of the present invention.
Trials were conducted with a large 419 mm (16.5″) radius IC1000™ single layer polyurethane pads (Dow) having a Shore D hardness at 61.0, with the Example 2 pad treated in the manner as in Example 1 above, except that the rotary grinder assembly was fed down towards the flat bed platen at a rate of 20.3 μm (0.0007″) increments every 8 pad revolutions and grinding was continued for 5.5 min. The Comparative Example 2-A pad was the same pad as in Example 2 not treated in accordance with the methods of the present invention.
Trials were run on 14 pads and average results are reported for thickness variation, which was tested, as follows:
Thickness Variation:
Was determined using a coordinate-measurement machine across the surface of the polishing pads. A total of 9 discrete measurement locations from pad center to edge were collected per pad. Thickness variation was calculated by subtracting the thinnest measurement from the thickest measurement. Results are shown in Table 2, below.
The resulting inventive pads had the characteristic pad surface microtexture. The inventive pads of Example 2 have less average thickness variation and so are more consistent in their shape than the comparative Example 2-A pad.
Surface roughness was measured on the pads of Example 2, above, in comparison to commercially available IC1000™ pads (Dow). The Comparative Example 2 pad was the same pad as in Example 2-A but was not treated in accordance with the methods of the present invention.
Surface roughness was measured on at 5 evenly spaced points from pad center to edge on each of 2 pads and the average results are reported for surface roughness in Table 3, below.
As shown in Table 3, above, the CMP polishing layers of the present invention in Example 3 have a defined pad surface microtexture and a definite surface roughness characterized by a reduced valley depth.
