AIRLESS ATOMIZING METHODS FOR MAKING CHEMICAL MECHANICAL PLANARIZATION (CMP) POLISHING PADS
The present invention provides methods of making chemical mechanical planarization (CMP) polishing pads comprising introducing, separately, through a side liquid feed port into an internal chamber having a downstream open end a liquid polyol component stream comprising an amine curative at a temperature T1 of from 40 to 90° C. and a liquid isocyanate component stream at a temperature T2 of from 40 to 90° C., each of the two components under a set point pressure of from 13,000 to 24,000 kPa so that the two streams are pointed towards each other at 90 degrees to downstream flow, thereby impingement mixing the two components to form a reaction mixture, discharging a stream of the reaction mixture from the open end of the internal chamber under pressure through a narrow, preferably, round orifice and onto an open mold substrate having a urethane releasing surface, and curing the reaction mixture to form a porous polyurethane reaction product.
The present invention relates to methods for producing porous polyurethane (PU) elastomer articles and chemical mechanical planarization (CMP) polishing pads comprising impingement mixing a two component reaction mixture to form a porous polyurethane without injecting or adding any air or gas to the reaction mixture.
Known methods for producing porous CMP polishing pads include the addition of porous polymeric fillers, for example, into a molded polymeric matrix, mechanical frothing of a gas/polyurethane (PU) mixture that cures to trap gas bubbles; addition of blowing agents or using water to create pores from physically or chemically generated gas; and rapid decompression of polymers saturated with supercritical (SC) fluids (e.g. SC—CO2). In any such methods, however, introduction of significant volumes of gas into a pad forming mixture gives rise to the need to condition the gas prior to its inclusion, and increases ventilation and effluent treatment requirements during and after processing. Known methods to generate or introduce gas to create pores into a pad forming mixture may not create a uniform pore distribution or uniformly fill molds to make CMP polishing pads. Further, introducing air or gas into or generating gas in such a reaction mixture for making CMP polishing pads can cause two phase flow from a spray device, which can lack homogeneity, alternating between liquid flow and gas flow at the spray tip or nozzle, resulting in an inhomogeneous material discharge and striation in the resulting product.
U.S. patent application publication no. 2009/0094900 A1, to Swisher et al., discloses methods for making CMP polishing pads comprising impingement mixing a first reactant, isocyanate-terminated urethane prepolymer at above 60° C. and a second reactant, diamine at above 100° C. in a ratio of first to second reactant of from 3:1 to 6:1, casting the mixture of the first and second reactants and forming the resulting polyurea polyurethane elastomer into a chemical mechanical planarization (CMP) polishing pad. Swisher discloses injecting gas into the reaction mixture at [0030].
The present inventors have sought to solve the problem of providing application or spray methods for making chemical mechanical polishing pads that have improved uniformity.
STATEMENT OF THE INVENTION1. In accordance with the present invention, methods of making chemical mechanical planarization (CMP) polishing pads comprise introducing, separately, through a side liquid feed port into an internal chamber having a downstream open end, preferably, a cylindrical chamber, a liquid polyol component stream at a temperature T1 of from 40 to 90° C. and a liquid isocyanate component stream at a temperature T2 of from 40 to 90° C., each of the two components under a set point pressure of from 13,000 to 24,000 kPa (2000 to 3400 psi) or, preferably, from 20,000 to 24,000 kPa, so that the two streams are pointed towards each other at 90 degrees to downstream flow, thereby impingement mixing the two components to form a reaction mixture, the liquid polyol component comprising one or more polyol and an amine curative, preferably, an aromatic diamine such as dimethylthiotoluenediamine; and the liquid isocyanate component comprising one or more polyisocyanate or isocyanate-terminated urethane prepolymer, preferably, an aromatic polyisocyanate or aromatic isocyanate-terminated urethane prepolymer; at least one component, preferably, the liquid polyol component containing a sufficient amount of up to 2.0 wt. % or, preferably, from 0.1 to 1 wt. %, based on the total solids weight of the reaction mixture, of a nonionic surfactant, preferably, an organopolysiloxane-co-polyether surfactant to facilitate the stabilization of pores formed in the method, discharging a stream of the reaction mixture from the open end of the internal chamber under pressure, such as a spray gun, for example, an airless or air assisted spray gun, through a narrow orifice, preferably, a round orifice having diameter of from 0.4 to 2.0 mm, preferably, from 0.6 to 1.7 mm or, more preferably, 0.9 to 1.4 mm, such as with an airless spray gun, and onto an open mold substrate having a urethane releasing surface, such as polytetrafluoroethylene, preferably, a mold having a female topography that forms a desired groove pattern of a CMP polishing pad as the applied reaction mixture fills the mold, and curing the reaction mixture at from ambient temperature to 130° C. or, preferably, from ambient temperature to 100° C., to form a porous polyurethane reaction product having a density ranging from 0.6 gm/cc to 1 gm/cc or, preferably, from 0.75 gm/cc to 0.95 gm/cc.
2. In accordance with the methods of present invention for making CMP polishing pads as set forth in item 1, above, wherein the internal chamber is a closed end cylinder having a downstream open end, an axis of symmetry, at least two liquid feed ports that open into the internal cylindrical chamber, at least one liquid isocyanate component feed port that opens into the internal chamber and at least on liquid polyol component feed port that opens into the internal chamber, wherein the closed end and the open end are perpendicular to the axis of symmetry; and, wherein the at least one liquid polyol component feed port and the at least one liquid isocyanate component feed port are arranged along a circumference of the internal cylindrical chamber proximate the closed end.
3. In accordance with the methods of present invention for making CMP polishing pads as set forth in any one of items 1 or 2, above, wherein, the reaction mixture contains no added blowing agent, including no added chemical or physical blowing agents.
4. In accordance with the methods of present invention for making CMP polishing pads as set forth in any one of items 1, 2 or 3, above, wherein, the reaction mixture contains no added pressurized gas, such as pressurized air.
5. In accordance with the methods of present invention for making CMP polishing pads as set forth in any one of items 1, 2, 3 or 4, above, wherein the reaction mixture has a gel time of 2 to 300 seconds or, preferably, from 5 to 60 seconds or, preferably, from 5 to 45 seconds at the curing temperature.
5. In accordance with the methods of present invention for making CMP polishing pads as set forth in any of items 1, 2, 3, 4, or 5, above, wherein upon introducing each of the liquid polyol component at temperature T1 and the liquid isocyanate component at temperature T2 to the internal chamber, each has a viscosity of from 10 to 1000 cPs or, preferably, from 100 to 500 cPs.
6. In accordance with the methods of present invention for making CMP polishing pads as set forth in item 5, above, further wherein, each of the liquid polyol component and the liquid isocyanate component is separately preheated, respectively, to a temperature T1 and T2, of from 45 to 80° C. before introducing it to the internal chamber.
7. In accordance with the methods of present invention for making CMP polishing pads as set forth in any one of items 1, 2, 3, 4, 5 or 6, above, wherein the liquid polyol component further comprises up to 3000 ppm or, preferably, up to 1500 ppm of water to enhance pad porosity.
8. In accordance with the methods of the present invention for making CMP polishing pads as set forth in any one or items 1, 2, 3, 4, 5, 6 or 7, wherein the resulting CMP polishing pad has an average pore diameter of from 20 to 80 μm, or, preferably, 30 to 65 μm.
9. In accordance with the methods of present invention for making CMP polishing pads as set forth in any one of items 1, 2, 3, 4, 5, 6, 7 or 8, wherein the reaction mixture and each of the liquid isocyanate component and the liquid polyol component are solvent free and substantially water free.
10. In accordance with the methods of present invention for making CMP polishing pads as set forth in any previous items 1 to 9, above, wherein curing the reaction mixture comprises initially curing at from ambient temperature to 130° C. for a period of from 1 to 30 minutes, or, preferably, from 30 seconds to 5 minutes, removing the polyurethane reaction product from the mold, and then finally curing at a temperature from 60 to 130° C. for a period of 1 minute to 16 hours, or, preferably, from 30 min to 4 hours to form a porous article.
11. In accordance with the methods of the present invention as in item 10, above, wherein the forming of the polishing pad further comprises stacking a sub pad layer, such as a polymer impregnated non-woven, or porous or non-porous polymer sheet, onto bottom side of the porous article so that the molded surface of the porous article forms the top surface of a CMP polishing pad.
12. In accordance with the methods of the present invention as in any one of items 1 to 11, above, wherein the discharging a stream of the reaction mixture onto a mold comprises overspraying the mold, followed by the curing the thus applied reaction mixture to form a polyurethane reaction product, removing the polyurethane reaction product from the mold and then punching or cutting the perimeter of the polyurethane reaction product to the desired diameter of the CMP polishing pad.
13. In accordance with the methods of the present invention as in any one of items 1 to 12, above, wherein the discharging is via an airless spray gun held in place by a mechanical actuator that enables movement in a plane parallel to the surface of the open mold, such as, for example, a programmable electronic actuator having mechanical linkage enabling the programmed movement, preferably, a robot having a four axis arm capable of XY axial movement or a six axis arm capable of XYZ axial movement and rotational movement.
For purposes of this specification, the formulations are expressed in wt. %, unless specifically noted otherwise.
Unless otherwise indicated, conditions of temperature and pressure are ambient temperature and standard pressure.
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.
Unless otherwise indicated, as used herein, the term “average molecular weight” of a polymer refers to the result determined by gel permeation chromatography against the indicated or, if not indicated, known appropriate standards, such as poly(ethylene glycol)s for polyols.
As used herein, the term “gel time” means the result obtained by mixing a given reaction mixture at about 80° C., for example, in an VM-2500 vortex lab mixer (StateMix Ltd., Winnipeg, Canada) set at 1000 rpm for 30 s, setting a timer to zero and switching the timer on, pouring the mixture into an aluminum cup, placing the cup into a hot pot of a gel timer (Gardco Hot Pot™ gel timer, Paul N. Gardner Company, Inc., Pompano Beach, Fla.) set at 65° C., stirring the reaction mixture with a wire stirrer at 20 RPM and recording the gel time when the wire stirrer stops moving in the sample.
As used herein, the term “ASTM” refers to publications of ASTM International, West Conshohocken, Pa.
As used herein, the term “polyisocyanate” means any isocyanate group containing molecule containing two or more isocyanate groups.
As used herein, the term “polyurethanes” refers to polymerization products from difunctional or polyfunctional isocyanates, e.g. polyetherureas, polyisocyanurates, polyurethanes, polyureas, polyurethaneureas, copolymers thereof and mixtures thereof.
As used herein, the term “reaction mixture” includes any non-reactive additives, such as surfactants and additives to lower the hardness of a polyurethane reaction product in the CMP polishing pad as measured according to ASTM D2240-15 (2015).
As used herein, the term “stoichiometry” of a reaction mixture refers to the ratio of molar equivalents of (free OH+free NH2 groups) to free NCO groups in the reaction mixture.
As used herein, the term “SG” or “specific gravity” refers to the ratio of density of a polishing pad or layer made in accordance with the present invention to density of water at the same temperature.
As used herein, the term “solids” refers to any materials that remain in the polyurethane reaction product of the present invention; thus, solids include reactive and non-volatile additives that do not volatilize upon cure. Solids exclude water and volatile solvents.
As used herein, the term “substantially free of blowing agents” means that a given composition contains no added chemical or physical blowing agent. Blowing agents do not include water. The air flow through a blast cap is not considered a part of a given composition.
As used herein, unless otherwise indicated, the term “substantially water free” means that a given composition has less than 2,000 ppm of added water, or, preferably, no added water and that the materials going into the composition have less than 2000 ppm, or, preferably, no added water. A reaction mixture that is “substantially water free” can comprise water that is present in the raw materials, e.g. as a pore former, in the range of from 50 to 2000 ppm or, preferably, from 50 to 1000 ppm, or can comprise reaction water formed in a condensation reaction or vapor from ambient moisture where the reaction mixture is in use.
As used herein, unless otherwise indicated, the term “viscosity” refers to the viscosity of a given material in neat form (100%) at a given temperature as measured using a rheometer, set at a steady shear of 1 rad/sec in a 50 mm parallel plate geometry with a 100 μm gap.
As used herein, the term “wt. %” stands for weight percent.
The present invention enables a simple spray application method for making porous polyurethane CMP polishing pads from a two component reaction mixture, with no added blowing agent. The method of the present invention generates an aerosol without requiring gas injection into the application device. No air or gas is added. Mixing is achieved via high pressure impingement mixing inside the internal chamber, but the atomization is produced by discharging the reaction mixture, still under high pressure, through a narrow orifice; the high velocity of the fluid reaction mixture leaving the airless spray device creates pores from the ambient air through which the fluid droplets travel from the spray tip of the device to the substrate. The only gas used in the methods of the present invention is ambient air through which a discharged stream of the reaction mixture flows. Atomization of the reaction mixture is produced by ejecting it under high pressure, through a narrow orifice. The orifice size can be varied to maintain adequate discharge pressure at a desired flow rate to insure atomization and effective application of the reaction mixture. The present inventors discovered that the methods of the present invention produces bubbles or pores without air or gas injection, or the addition of chemical or physical blowing agents; further, it is expected that the methods of the present invention for atomizing the reaction mixture will increase process stability and reduce pad-to-pad manufacturing variation.
The methods of the present invention enable the manufacturing a CMP polishing pad suitable for planarizing at least one of semiconductor, optical and magnetic substrates.
The methods of the present invention also enable the formation of stacked CMP polishing pads wherein the reaction mixture is discharged from the open end of the internal cylindrical chamber and onto an already formed base surface of a chemical mechanical polishing layer, and allowing the reaction mixture to solidify on the base surface of the chemical mechanical polishing layer to form a subpad; wherein the subpad is integral with the chemical mechanical polishing layer and the subpad has a subpad porosity that is different from that of the chemical mechanical polishing layer; and, wherein the chemical mechanical polishing layer has a porosity of 10 vol. % and a polishing surface adapted for polishing a substrate.
In the methods of making a stacked pad in accordance with the present invention, the base surface of the CMP polishing layer can be formed by the same impingement mixing of the two component liquid polyol component and liquid isocyanate component in an internal chamber at the pressures of the present invention to form a polishing layer reaction mixture, followed by discharging that reaction mixture onto the surface of an open mold.
In the internal chamber of the present invention, the pressure at which each stream is injected, for example, 17,000 to 24,000 kPa (2500 to 3400 psi) is high enough to insure homogeneous mixing. The upper limit of the pressure is determined by the limits of the equipment.
The apparatus used in the methods of the present invention may comprise an airless spray gun having a spray nozzle with an orifice of the desired size and equipped with two leads via a pump such as a piston pump, one for the liquid isocyanate component and the other for the liquid polyol component. Examples of suitable equipment are a Graco Probler™ P2 two component spray gun (Graco, Minneapolis, Minn.), fed by a high pressure metering pump or other Graco Airless spray guns equipped with a spray head having an orifice of the desired diameter and connected to a pump or metering device that can deliver the two component reaction mixture to the spray gun at the desired pressure and ratio for making the CMP polishing pads of the present invention.
The two leads into the spray gun in the apparatus of the present invention can comprise meter or delivery systems, such as a pair of pneumatically driven positive displacement piston pumps or precision gear pumps, each for dispensing the liquid polyol component or liquid isocyanate component through a series of fittings and tubing at high pressure to the impingement mixer. An example of a suitable meter device is the Gusmer™ HV-20\35 meter dispense unit (Graco, Minneapolis, Minn.).
As shown in
The reaction mixtures of the present invention comprise no solvent, and no added water except that up to 2000 ppm of water can be added to the liquid polyol component to facilitate pore formation.
The mold of the present invention is made of or is lined with a non-stick material, such as polytetrafluoroethylene. Preferably, the mold is machined to form a female topography so that the resulting molded polyurethane reaction product has a desired groove configuration.
Preferably, the substrate in the methods of the present invention is a mold wherein the produced CMP polishing pad will have groove pattern directly incorporated. For example, the mold may have a female topography that forms the groove pattern of the pad as the applied reaction mixture fills the mold.
The liquid isocyanate component of the present invention may comprise any of a diisocyanate, triisocyanate, isocyanurate isocyanate-terminated urethane prepolymer, or mixtures thereof. Preferably, the liquid isocyanate component comprises aromatic polyisocyanates, such as an aromatic diisocyanate chosen from methylene diphenyl diisocyanate (MDI); toluene diisocyanate (TDI); napthalene diisocyanate (NDI); paraphenylene diisocyanate (PPDI); o-toluidine diisocyanate (TODD; a modified diphenylmethane diisocyanate, such as a carbodiimide-modified diphenylmethane diisocyanate, an allophanate-modified diphenylmethane diisocyanate, a biuret-modified diphenylmethane diisocyanate; an aromatic isocyanurate, such as the isocyanurate of MDI; a linear isocyanate-terminated urethane prepolymer, for example, a linear isocyanate-terminated urethane prepolymer of MDI or an MDI dimer with one or more isocyanate extenders.
Suitable isocyanate extenders are ethylene glycol; 1,2-propylene glycol; 1,3-propylene glycol; 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, neopentyl glycol; 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, diethylene glycol; dipropylene glycol; tripropylene glycol, and mixtures thereof.
The liquid isocyanate component of the present invention can have a very high unreacted isocyanate (NCO) concentration of from 10 to 40 wt. %, or, preferably, from 15 to 35 wt. %, based on the total solids weight of the aromatic isocyanate component.
Suitable isocyanate-terminated urethane prepolymers are low free isocyanate terminated urethane prepolymers having less than 0.1 wt % free toluene diisocyanate (TDI) monomer content.
The liquid polyol component of the present invention can be anyone or more diols or polyether polyols having terminal hydroxyl groups, such as diols, polyols, polyol diols, copolymers thereof and mixtures thereof. Preferably, one or more polyol is chosen from polyether polyols (e.g., poly(oxytetramethylene)glycol, poly(oxypropylene)glycol and mixtures thereof); polycarbonate polyols; polyester polyols; polycaprolactone polyols; mixtures thereof; and, mixtures thereof with one or more low molecular weight polyols selected from the group consisting of ethylene glycol; 1,2-propylene glycol; 1,3-propylene glycol; 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, neopentyl glycol; 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, diethylene glycol; dipropylene glycol; and, tripropylene glycol.
More preferably, the one or more polyol of the liquid polyol component of the present invention is chosen from polytetramethylene ether glycol (PTMEG); ester containing polyols (such as ethylene adipates, butylene adipates); polypropylene ether glycols (PPG); polycaprolactone polyols; copolymers thereof; and, mixtures thereof.
Suitable polyols can include a high molecular weight polyol having a number average molecular weight, MN, of 500 to 10,000. Preferably, the high molecular weight polyol used has a number average molecular weight, MN, of 500 to 6,000, or, more preferably 500 to 4,000; most preferably 1,000 to 2,000). Such a high molecular weight polyol preferably has an average of three to ten hydroxyl groups per molecule. More preferably, the high molecular weight polyol used has an average of four to eight, or, still more preferably five to seven, or, most preferably six hydroxyl groups per molecule. An example of a 6 hydroxyl group containing high molecular weight polyol is a polypropoxy-co-ethoxy sugar alcohol, such as sorbitol, having ethoxy hydroxyl groups.
The amine curative of the present invention is an amine or polyamine having one or more or, preferably, two or more amine groups, or, preferably, an aromatic polyamine, such as aromatic diamines and aromatic polyamines having three amine groups. More preferably, the amine curative is one or more aromatic diamines selected from the group consisting of dimethylthiotoluenediamine; trimethyleneglycol di-p-aminobenzoate; polytetramethyleneoxide di-p-aminobenzoate; polytetramethyleneoxide mono-p-aminobenzoate; polypropyleneoxide di-p-aminobenzoate; polypropyleneoxide mono-p-aminobenzoate; 1,2-bis(2-aminophenylthio)ethane, toluenediamines, such as diethyltoluenediamine, 5-tert-butyl-2,4-toluenediamine, 3-tert-butyl-2,6-toluenediamine, 5-tert-amyl-2,4-toluenediamine, 3-tert-amyl-2,6-toluenediamine, 5-tert-amyl-2,4-chlorotoluenediamine, and 3-tert-amyl-2,6-chlorotoluenediamine; methylene dianilines, such as 4,4′-methylene-bis-aniline; isophorone diamine; 1,2-diaminocyclohexane, bis(4-aminocyclohexyl)methane, 4,4′-diaminodiphenyl sulfone; m-phenylenediamine; xylene diamines; 1,3-bis(aminomethyl cyclohexane); and mixtures thereof, preferably, dimethylthiotoluenediamine.
Generally, the stoichiometric ratio of the sum of the total moles of amine (NH2) groups and the total moles of hydroxyl (OH) groups in the reaction mixture to the total moles of unreacted isocyanate (NCO) groups in the reaction mixture ranges from 0.8:1.0 to 1.1:1.0, or, preferably, from 0.95 to 1.05.
The chemical mechanical polishing pads made by the methods of the present invention can comprise just a polishing layer of the polyurethane reaction product or the polishing layer stacked on a subpad or sub layer. The polishing pad or, in the case of stacked pads, the polishing layer of the polishing pad of the present invention is useful in both porous and non-porous or unfilled configurations.
Preferably, the polishing layer used in the chemical mechanical polishing pad of the present invention has an average thickness of from 500 to 3750 microns (20 to 150 mils), or, more preferably, from 750 to 3150 microns (30 to 125 mils), or, still more preferably, from 1000 to 3000 microns (40 to 120 mils), or, most preferably, from 1250 to 2500 microns (50 to 100 mils).
The chemical mechanical polishing pad of the present invention optionally further comprises at least one additional layer interfaced with the polishing layer. Preferably, the chemical mechanical polishing pad optionally further comprises a compressible sub pad or base layer adhered to the polishing layer. The compressible base layer preferably improves conformance of the polishing layer to the surface of the substrate being polished.
The polishing layer of the chemical mechanical polishing pad of the present invention has a polishing surface adapted for polishing the substrate. Preferably, the polishing surface has macrotexture selected from at least one of perforations and grooves. Perforations can extend from the polishing surface part way or all the way through the thickness of the polishing layer.
Preferably, grooves are arranged on the polishing surface such that upon rotation of the chemical mechanical polishing pad during polishing, at least one groove sweeps over the surface of the substrate being polished.
Preferably, the polishing layer of the chemical mechanical polishing pad of the present invention has a polishing surface adapted for polishing the substrate, wherein the polishing surface has a macrotexture comprising a groove pattern formed therein and chosen from curved grooves, linear grooves, perforations and combinations thereof. Preferably, the groove pattern comprises a plurality of grooves. More preferably, the groove pattern is selected from a groove design, such as one selected from the group consisting of concentric grooves (which may be circular or spiral), curved grooves, cross hatch grooves (e.g., arranged as an X-Y grid across the pad surface), other regular designs (e.g., hexagons, triangles), tire tread type patterns, irregular designs (e.g., fractal patterns), and combinations thereof. More preferably, the groove design is selected from the group consisting of random grooves, concentric grooves, spiral grooves, cross-hatched grooves, X-Y grid grooves, hexagonal grooves, triangular grooves, fractal grooves and combinations thereof. Most preferably, the polishing surface has a spiral groove pattern formed therein. The groove profile is preferably selected from rectangular with straight side walls or the groove cross section may be “V” shaped, “U” shaped, saw-tooth, and combinations thereof.
In accordance with the methods of making polishing pads in accordance with the present invention, chemical mechanical polishing pads can be molded with a macrotexture or groove pattern in their polishing surface to promote slurry flow and to remove polishing debris from the pad-wafer interface. Such grooves may be formed in the polishing surface of the polishing pad from the shape of the mold surface, i.e. where the mold has a female topographic version of the macrotexture.
The chemical mechanical polishing pad of the present invention can be used for polishing a substrate selected from at least one of a magnetic substrate, an optical substrate and a semiconductor substrate.
The CMP polishing pads of the present invention are efficacious for interlayer dielectric (ILD) and inorganic oxide polishing.
Preferably, the method of polishing a substrate of the present invention, comprises: providing a substrate selected from at least one of a magnetic substrate, an optical substrate and a semiconductor substrate (preferably a semiconductor substrate, such as a semiconductor wafer); providing a chemical mechanical polishing pad according to the present invention; creating dynamic contact between a polishing surface of the polishing layer and the substrate to polish a surface of the substrate; and, conditioning of the polishing surface with an abrasive conditioner.
Conditioning the polishing pad comprises bringing a conditioning disk into contact with the polishing surface either during intermittent breaks in the CMP process when polishing is paused (“ex situ”), or while the CMP process is underway (“in situ”). The conditioning disk has a rough conditioning surface typically comprised of imbedded diamond points that cut microscopic furrows into the pad surface, both abrading and plowing the pad material and renewing the polishing texture. Typically the conditioning disk is rotated in a position that is fixed with respect to the axis of rotation of the polishing pad, and sweeps out an annular conditioning region as the polishing pad is rotated.
ExamplesA Probler™ P2 two component spray gun (Graco, Minneapolis, Minn.), fed by a high pressure metering pump was used to mix the indicated liquid polyol component at 60° C. and liquid isocyanate component at 60° C., as shown in Table 1, below. The liquid polyol component and the liquid isocyanate component were metered into the spray gun at the pressure indicated in Table 2, below. The resulting reaction mixture was sprayed onto an open mold substrate with a non-stick surface made of polytetrafluoroethylene. Amounts are in weight parts solids.
A variety of air spray nozzle settings were studied, including commercial nozzle tips corresponding to different mixing chamber size and nozzle orifice diameters (tip designations 00, 01, 04; orifice diameter 0.9 mm (0.042 mil), 1.07 mm, 1.7 mm, respectively), operating pressure set points (13.8, 20.0, 23.5 MPa), and spray height above mold (˜38 cm, ˜76 cm). Table 2, below, provides pore diameters and densities of the articles molded from the examples.
Test Methods:
The resulting molded articles were tested, as follows, as shown in Table 2, below:
Image Analysis:
Scanning electron micrographs (SEM) of the resulting moldings provided insight into the pore size averages. The images (not shown) used in the image analysis were a cross-section of the indicated molding from top to bottom (image 1=top, image 3=bottom). Analysis of the data show that the average pore size is consistent from top to bottom of the molding, within a range of a 6 to 8 μm difference in average pore size for each image from top to bottom.
Density was measured by an Archimedes method comparing the weight of a given molding vs. its weight when immersed in water.
Average pore size was measured by an manual image analysis of a selected number of pores (˜150 pores) to determine the diameter of each, which was then averaged.
Optimum conditions were achieved with the 00 and 01 spray tips, and medium to high pressure. Overall, the data evidence excellent control over and predictability of porosity. The articles of Examples 1 to 14, without polymeric microspheres, have a similar density, and pores only from entrapped air, evidencing the flexibility of the methods of the present invention.
Claims
1. A method of making chemical mechanical planarization (CMP) polishing pads comprise introducing, separately, through a side liquid feed port into an internal chamber having a downstream open end a liquid polyol component stream at a temperature T1 of from 40 to 90° C. and a liquid isocyanate component stream at a temperature T2 of from 40 to 90° C., each of the two components under a set point pressure of from 13,000 to 24,000 kPa (2000 to 3400 psi) so that the two streams are pointed towards each other at 90 degrees to downstream flow, thereby impingement mixing the two components to form a reaction mixture, the liquid polyol component comprising one or more polyol and an amine curative; and the liquid isocyanate component comprising one or more polyisocyanate or isocyanate-terminated urethane prepolymer; at least one component containing a sufficient amount of up to 2.0 wt. %, based on the total solids weight of the reaction mixture, of a nonionic surfactant to facilitate the stabilization of pores, discharging a stream of the reaction mixture from the open end of the internal chamber under pressure through a narrow orifice and onto an open mold substrate having a urethane releasing surface, and curing the reaction mixture at from ambient temperature to 130° C. to form a porous polyurethane reaction product having a density ranging from 0.6 gm/cc to 1 gm/cc.
2. The method as claimed in claim 1, wherein the liquid polyol component comprises as an amine curative an aromatic diamine.
3. The method as claimed in claim 1, wherein the liquid isocyanate component comprises an aromatic polyisocyanate or aromatic isocyanate-terminated urethane prepolymer.
4. The method as claimed in claim 1, wherein the reaction mixture contains no added blowing agents and no added pressurized gas.
5. The method as claimed in claim 1, wherein the reaction mixture has a gel time of 2 to 300 seconds at the curing temperature.
6. The method as claimed in claim 1, wherein the internal chamber is a closed end cylinder having a downstream open end, an axis of symmetry, at least two liquid feed ports that open into the internal cylindrical chamber, at least one liquid isocyanate component feed port that opens into the internal chamber and at least on liquid polyol component feed port that opens into the internal chamber, wherein the closed end and the open end are perpendicular to the axis of symmetry; and, wherein the at least one liquid polyol component feed port and the at least one liquid isocyanate component feed port are arranged along a circumference of the internal cylindrical chamber proximate the closed end.
7. The method as claimed in claim 1, wherein the substrate is an open mold having a female topography that forms a desired groove pattern of a CMP polishing pad as the applied reaction mixture fills the mold.
8. The method as claimed in claim 1, wherein upon introducing each of the liquid polyol component at temperature T1 and the liquid isocyanate component at temperature T2 to the internal chamber, each has a viscosity of from 10 to 1000 cPs.
9. The method as claimed in claim 1, wherein the resulting CMP polishing pad has an average pore diameter of from 20 to 80 μm.
10. The method as claimed in claim 1, wherein the reaction mixture and each of the liquid isocyanate component and the liquid polyol component are solvent free and substantially water free.
Type: Application
Filed: Nov 30, 2016
Publication Date: May 31, 2018
Inventors: Adam Broderick (Midland, MI), Douglas A. Brune (Midland, MI)
Application Number: 15/365,289
