Formulations for chemical mechanical polishing pads and CMP pads made therewith

Abstract

A two component composition for making chemical mechanical polishing pad for polishing a semiconductor substrate is provided comprising a liquid aromatic isocyanate component having an unreacted isocyanate (NCO) concentration of from 15 to 40 wt. %, based on the total solids weight of the aromatic isocyanate component, such as methylene di(phenylisocyanate) (MDI), a liquid polyol component of a polyol having a polyether backbone and having from 5 to 7 hydroxyl groups per molecule, and a curative of one or more polyamine or diamine, wherein the reaction mixture comprises 50 to 65 wt. % of hard segment materials, based on the total weight of the reaction mixture. The composition when mixed cured to form a polyurethane reaction product. Also provided are CMP polishing pads made from the polyurethane reaction product by spraying the composition into a mold.

Claims

1. A polishing pad for polishing a substrate chosen from at least one of a magnetic substrate, an optical substrate and a semiconductor substrate, the polishing pad being formed from spraying a one shot formulation, the one shot formulation being a two component solvent free and substantially water free formulation comprising a liquid aromatic isocyanate component having an unreacted isocyanate (NCO) concentration of from 15 to 40 wt. %, based on the total solids weight of the aromatic isocyanate component, the isocyanate being a linear isocyanate-terminated urethane prepolymer of methylene diphenyl diisocyanate or a methylene diphenyl diisocyanate dimer, 35 to 50 wt. % of a liquid polyol component of a polyol having a polyether backbone and having from 5 to 7 hydroxyl groups per molecule and the liquid polyol forming soft segments, an isocyanate extender and a curative of one or more polyamine or diamine, wherein the reaction mixture comprises 50 to 65 wt. % of hard segment materials, based on the total weight of the reaction mixture, and, further wherein, the stoichiometric ratio of the sum of the total moles of amine (NH.sub.2) 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 and wherein the polishing pad has a matrix and the matrix has a tensile modulus of at least 240 MPa and an elongation at break of at least 130%.

2. The polishing pad as claimed in claim 1, wherein the liquid aromatic isocyanate component has an unreacted isocyanate (NCO) concentration of from 17.5 to 35 wt. %, based on the total solids weight of the aromatic isocyanate component.

3. The polishing pad as claimed in claim 1, wherein the liquid aromatic isocyanate component has a hard segment weight fraction of 84 to 100 wt. %.

4. The polishing pad as claimed in claim 1, wherein the liquid polyol component comprises a polyol having a polyether backbone and having 6 hydroxyl groups per molecule.

5. The polishing pad as claimed in claim 1, wherein the curative is one or more aromatic diamine.

6. The polishing pad as claimed in claim 1, wherein the liquid aromatic isocyanate component has a hard segment weight fraction of from 90 to 100 wt. %.

7. The polishing pad as claimed in claim 1, wherein the stoichiometric ratio of the sum of the total moles of amine (NH.sub.2) 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 0.85:1.0 to 1.1:1.0.

8. The polishing pad of claim 1 wherein the curative is dimethylthiotoluenediamine.

Description

EXAMPLES

(1) The present invention will now be described in detail in the following, non-limiting Examples:

(2) Unless otherwise stated all temperatures are room temperature (21-23 C.) and all pressures are atmospheric pressure (760 mm Hg or 101 kPa).

(3) Notwithstanding other raw materials disclosed below, the following raw materials were used in the Examples:

(4) Ethacure 300 curative: Dimethylthiotoluenediamine (DMTDA), an aromatic diamine (Albemarle, Charlotte, N.C.).

(5) Voranol V5055HH polyol: Multifunctional polyether polyol (OH Eq. wt 2000), high molecular weight ethylene oxide capped propylene oxide polyol with functionality=6 having a number average molecular weight, M.sub.N, of 12,000 (The Dow Chemical Company, Midland, Mich. (Dow)).

(6) MDI prepolymer: A linear isocyanate-terminated urethane prepolymer from MDI and the small molecules dipropylene glycol (DPG) and tripropylene glycol (TPG), with 23 wt. % NCO content and equivalent weight of 182. 100 wt. % of this MDI prepolymer is treated as hard segment.

(7) Niax L5345 surfactant: A non-ionic organosilicon surfactant (Momentive, Columbus, Ohio).

(8) DABCO 33 LV amine catalyst (Air Products, Allentown, Pa.) made from diazobicyclononane (triethylene diamine), DABCO 33 LV is a blend of 33 wt. % triethylene diamine and 67 wt. % dipropylene glycol.

(9) Unilink 4200 curative: N,N-dialkylamino-diphenylmethane (Dorf Ketal, Stafford, Tex.)

(10) PTMEG####: poly(THF) or polytetramethylene glycol, made via the ring-open polymerization of tetrahydrofuran (THF), and sold as PolyTHF polyol (BASF, Leverkusen, Del.). The number following PTMEG is the average molecular weight as reported by the manufacturer.

(11) 2-Component Air Spray System:

(12) An axial mixing device (a MicroLine 45 CSM, Hennecke GmbH, Sankt Augustin, Del.) having a (P) side liquid feed port, an (I) side liquid feed port and four tangential pressurized gas feed ports. The poly side (P) liquid component and the iso side (I) liquid component were fed to the axial mixing device through their respective feed ports with a (P) side charge pressure of 16,500-18,500 kPa, an (I) side charge pressure of 15,500-17,500 kPa. The flow ratio of (I)/(P) is defined in each example. The pressurized gas was fed through the tangential pressurized gas feed ports with a supply pressure of 830 kPa to give a combined liquid component to gas mass flow rate ratio through the axial mixing device of 3.7:1 to form a combination. The combination was discharged from the axial mixing device toward a mold to form a cake on the mold base.

(13) The following abbreviations appear in the Examples:

(14) PO: propylene oxide/glycol; EO: ethylene oxide/glycol; MDI: methylene diphenyl diisocyanate TDI: toluene diisocyanate (80% 2,4 isomer, 20% 2,6 isomer); DEG: diethylene glycol; DPG: dipropylene glycol; pbw: parts by weight.

Comparative Example 1

(15) In a mix cup, 97.91 g of a PTMEG with functionality=2, equiv wt=500 (BASF product PTMEG1000) was combined with 2.50 g Niax L5345 surfactant and 35.08 g Ethacure 300 curative and 3.39 g monoethylene glycol. To this mixed and degassed liquid, 121.27 g of MDI prepolymer with 23 wt. % NCO and equivalent weight of 182 was added. The cup contents were then mixed with a vortex mixer for 30 seconds and then poured into a mold to cast a plaque and cured at 100 C. for 16 hours. The formulation is described as having 62 wt. % hard-segment weight fraction, with a 0.95:1.0 stoichiometry, containing 13.5 wt. % Ethacure 300 curative. The hydroxyl content is 96.6 wt. % PTMEG1000. After curing, the plaque with density of 1.16 g/mL exhibited a 313 MPa tensile modulus, 49 MPa tensile strength, and 330% tensile elongation.

Comparative Example 2

(16) A 2-component air spray system was employed to spray a 1-shot polyurethane into an open mold. The polyurethane chemistry was identical to that reported in Comparative Example 1. The isocyanate component tank (iso side) was loaded with MDI prepolymer, while the polyol component tank was loaded with all other components (35.2 pbw PTMEG1000, 1.22 pbw monoethylene glycol, 0.90 pbw Niax L5345 surfactant, 12.63pbw Ethacure 300 curative, and 0.281 pbw DABCO 33LV catalyst) at the identical mass ratios as described in Comparative Example 1 with added tertiary amine catalyst to enhance kinetics of curing. The flow rates during spraying were 4.5 g/s for the polyol side and 3.92 g/s for the isocyanate side. The air injected into the nozzle was set to a nominal rate of 100 L/min. The sprayed polyurethane formulation was directed into a mold with groove topography. The sprayed pad was cured in a 100 C. oven for 10 min, then removed from the mold and cured in a 100 C. oven for 16 hours. The resulting pad contained both radial and concentric circular grooves. The resulting pad produced displayed a bulk density of 0.710 g/mL and displayed a bulk tensile modulus of 142 MPa and 228% tensile elongation. Pore size distribution for this pad was relatively narrow, and did not contain a significant quantity of pores over 100 microns.

Comparative Example 3

(17) In the same trial as reported in Comparative Example 2, the air injected into the nozzle was set to nominally 20 L/min. The sprayed polyurethane formulation was directed into a mold with groove features. The sprayed pad was cured in a 100 C. oven for 10 min, then removed from the mold and cured in a 100 C. oven for 16 hours. The resulting pad contained both radial and concentric circular grooves. The resulting pad produced displayed a bulk density of 0.920 g/mL and displayed a bulk tensile modulus of 217 MPa and 172% tensile elongation. Pore size distribution for this pad was broad, and contained significant quantity of pores over 100 microns.

Comparative Example 4

(18) A 2-component air spray system was employed to spray a 1-shot polyurethane into an open mold. The polyurethane chemistry consisted of the MDI prepolymer on the iso side. The polyol side consisted of a blend of 66.9 wt % PTMEG 2000, 31.4 wt % Ethacure 300 curative, and 1.7 wt % non-ionic surfactant NIAX L5345 surfactant. The flow rates during spraying were 4.57 g/s for the polyol side and 3.15 g/s for the iso side. The air injected into the nozzle was set to a nominal rate of 100 L/min. The sprayed polyurethane formulation was directed into a mold with groove features. The sprayed pad was cured in a 100 C. oven for 10 min, then removed from the mold and cured in a 100 C. oven for 16 hours. The resulting pad contained both radial and concentric circular grooves. The resulting pad produced displayed a bulk density of 0.790 g/mL and displayed a bulk tensile modulus of 151 MPa and 160% tensile elongation. Pore size distribution for this pad was relatively narrow, and did not contain a significant quantity of pores over 100 microns.

Example 5

(19) In a mix cup, 86.85 g of Voranol V5055HH polyol (equiv wt=1900) was combined with 2.50 g Niax L5345 surfactant and 39.70 g Ethacure 300 curative and 10.65 g DPG. To this mixed and degassed liquid, 110.30 g of MDI prepolymer was added. The cup was then mixed with a vortex mixer for 30 seconds and then poured into a mold to cast a plaque and cured at 100 C. for 16 hours. The formulation is described as having 60 wt. % hard-segment weight fraction, with a stoichiometry of 0.95:1.0, containing 15.88 wt. % curative. The hydroxyl content is 89.1% polyfunctional polyol and 10.9 wt. % DPG. After curing, the plaque with density of 1.16 g/mL showed 530 MPa tensile modulus, 39 MPa tensile strength, and 160% tensile elongation.

Example 6

(20) A 2-component air spray system was employed to spray 1-shot polyurethane into a mold. The polyurethane chemistry was identical to that reported in Comparative Example 5. The iso tank was loaded with MDI prepolymer, while the poly tank was loaded with all other components (49.69 pbw Voranol 5055HH, 6.09 pbw dipropylene glycol, 1.43 pbw Niax L5345 surfactant, 22.71 pbw Ethacure 300, 0.43 pbw DABCO 33LV) at the identical mass ratios as described in Example 4. The flow rates during spraying were 4.82 g/s for the polyol side and 3.78 g/s for the iso side. The air injected into the nozzle was set to a nominal rate of 100 L/min. The sprayed polyurethane formulation was directed into a mold with groove features. The sprayed pad was cured in a 100 C. oven for 10 min, then removed from the mold and cured in a 100 C. oven for 16 hours. The resulting pad contained both radial and concentric circular grooves. The resulting pad produced displayed a bulk density of 0.753 g/mL and displayed a bulk tensile modulus of 208 MPa, and 115% tensile elongation. Pore size distribution for this pad was relatively narrow, and did not contain a significant quantity of pores over 100 microns.

Example 7

(21) In the same trial as reported in Example 6, the air injected into the nozzle was decreased to nominally 20 L/min. The sprayed polyurethane formulation was directed into a mold with groove features. The sprayed pad was cured in a 100 C. oven for 10 min, then removed from the mold and cured in a 100 C. oven for 16 hours. The resulting pad contained both radial and concentric circular grooves. The resulting pad produced displayed a bulk density of 0.932 g/mL and displayed a bulk tensile modulus of 266 MPa and, and 86% tensile elongation. Pore size distribution for this pad was broad, and contained significant quantity of pores over 100 microns.

(22) The properties of the materials and pads in the Examples, above, are reported in Table 1, below. The pads made in the Examples, above, were tested as set forth in the test methods, below, and the results are reported in Table 2, below.

(23) TABLE-US-00001 TABLE 1 Properties of Pads and Plaques Nozzle Pore air Tensile Tensile Size flow Density Modulus Elongation Distri- Example Polyol (L/min) (g/mL) (MPa) (%) bution CE1 PTMEG1000 NA 1.16 310 330 NA.sup.1 CE2 PTMEG1000 100 0.710 142 228 good CE3 PTMEG1000 20 0.920 217 172 poor CE4 PTMEG2000 100 0.790 151 160 good 5 Voranol NA 1.16 530 160 NA.sup.1 5055HH 6 Voranol 100 0.753 208 115 good 5055HH 7 Voranol 20 0.932 267 86 poor 5055HH .sup.1Plaque or cast sheet

(24) Test Methods:

(25) Polishing experiments were conducted on the indicated tetraethoxysilicate (TEOS) wafer substrate with the pad produced in Comparative Example 4, the pad produced in Example 6, and a commercially available IC1000 polishing pad with K7 R32 groove pattern (Dow). The polishing pad as produced was first machined flat on a lathe to provide a polishing layer. The polishing layer was then stacked onto a SUBA IV subpad (Dow) via pressure sensitive adhesive. The final stacked pad was 508 mm in diameter wherein the polishing layer was nominally 2.0 mm thick and featured a mold-replicated groove pattern wherein the plurality of grooves featured a K7-R32 groove pattern with concentric circular grooves 0.50 mm wide, 0.76 mm deep, and at a 1.78 mm pitch, and with 32 radial grooves.

(26) The pad was mounted to the platen of an 200 mm Mirra polisher (Applied Materials, Santa Clara, Calif.). Polishing experiments were performed with a downforce of 0.010, 0.020, and 0.030 MPa, a slurry flow rate of 200 mL/min (ILD3225 fumed silica slurry, Nitta Haas, Japan), a table rotation speed of 93 rpm and a carrier rotation speed of 87 rpm. For polishing experiments with Examples 9, 10, 11 a Klebosol 1730 silica slurry (Dow) was employed. A Saesol AM02BSL8031C1 diamond pad conditioner (Saesol Diamond Ind. Co., Ltd., South Korea) was used to condition and texture the polishing pads. The polishing pads were each broken in with the conditioner and deionized (DI) water only using a down force of 31.1 N for 40 min. The polishing pads were further conditioned in situ during polishing at 10 sweeps/min from 43 to 233 mm from the center of the polishing pad with a down force of 31.1 N. The Removal Rates (RR) for the indicated pad were determined by measuring the film thickness of the indicated substrate before and after polishing using a FX200 metrology tool (KLA-Tencor, Milpitas, Calif.) using a 49 point spiral scan with a 3 mm edge exclusion. Removal rate was calculated by the change in thickness from a 49 point spiral scan across the wafer substrate, reported in Angstroms/min.

(27) Non-Uniformity Ratio (% NUR) was calculated by % standard deviation of the removal rates.

(28) Planarization efficiency (PE) was calculated from a polishing run with MIT-SKW7 patterned TEOS wafers (purchased from SKW Associates, Inc. of Santa Clara, Calif.) with downforce at 0.03 MPa. Wafers were periodically removed during the polishing run and analyzed using a SP2 wafer inspection tool (KLA-Tencor) to measure the wafer features. Planarization efficiency for a given feature step height is calculated by 1RR.sub.low/RR.sub.high and is desirably as high a percentage as possible. The planarization efficiency ratio was calculated by integrating under the curve of planarization efficiency vs. step height and dividing the result by the initial step height. % planarization efficiency is provided for the 80 nm pitch feature on the wafer substrate.

(29) Defectivity was determined using a SP2 XP and eDR5210 scanning electron microscope wafer defect review system (KLA-Tencor). Categorization of defect type was performed manually from a randomly selected set of 100 defects using Klarity Defect software. Defects were categorized, as follows:

(30) Aanything the computer sees; and,

(31) BChattermark scratches as identified by visual inspection by trained personnel.

(32) TABLE-US-00002 TABLE 2 Pad Performance Planariza- B- TEOS Non- tion A-Total Chatter- Removal Uniformity Efficiency Defect mark Rate Ratio (% at 80 nm Count Count Pad (/min) (% NUR) pitch) (N) (N) IC1000 1.5 psi 1439 7.2% 143 77 3.0 psi 2650 2.7% 173 38 4.5 psi 3869 2.9% 88.4% 102 50 C.E. 4 1.5 psi 1139 4.1% 3.0 psi 2298 1.9% 4.5 psi 3304 1.7% 74.7% Example 6 1.5 psi 1453 6.5% 105 40 3.0 psi 2870 3.0% 153 14 4.5 psi 4244 2.5% 84.0% 135 20

Example 8

(33) In a mix cup, 97.50 g of Voranol 5055HH polyol was combined with 2.50 g Niax L5345 surfactant and 38.68 g Ethacure 300 curative and 4.80 g monoethylene glycol. To this mixed and degassed liquid, 106.52 g of MDI prepolymer was added. The cup was then mixed with a vortex mixer for 30 seconds and then poured into a mold to cast a plaque and cured at 100 C. for 16 hours. The formulation is described as having 60 wt. % hard-segment weight fraction, with a stoichiometry of 0.95:1.0, containing 15.47 wt. % Ethacure 300 curative. The hydroxyl content is 95.3 wt. % Voranol V5055HH polyol. After curing, the plaque with density of 1.16 g/mL showed 579 MPa tensile modulus, 41 MPa tensile strength, and 175% tensile elongation.

Example 9

(34) A 2-component air spray system was employed to spray 1-shot polyurethane into a mold. The polyurethane chemistry was identical to that reported in Example 8. The iso tank was loaded MDI prepolymer, while the poly tank was loaded with all other components (33.80 pbw Voranol V5055HH polyol, 1.66 pbw monoethylene glycol, 0.867 pbw Niax L5345 surfactant, 13.409 pbw Ethacure 300 curative, 0.0 pbw DABCO 33LV catalyst) at the identical mass ratios as described in Example 8. The flow rates during spraying were 8.63 g/s for the polyol side and 6.37 g/s for the iso side. The air injected into the nozzle was set to a nominal rate of 100 L/min. The sprayed polyurethane formulation was directed into a mold with groove features. The sprayed pad was cured in a 100 C. oven for 15 min, then removed from the mold and cured in a 100 C. oven for 16 hours. The resulting pads contained both radial and concentric circular grooves. The resulting pads produced displayed an average density of 0.754 g/mL and displayed a bulk tensile modulus of 253 MPa, and 123% tensile elongation.

Example 10

(35) A 2-component air spray system was employed to spray 1-shot polyurethane into a mold. The polyurethane chemistry was identical to that reported in Example 8. The iso tank was loaded with MDI prepolymer, while the poly tank was loaded with all other components (33.80 pbw Voranol V5055HH polyol, 1.66 pbw monoethylene glycol, 0.867 pbw Niax L5345 surfactant, 13.409 pbw Ethacure 300 curative, 0.0 pbw DABCO 33LV catalyst) at the identical mass ratios as described in Example 8. The flow rates during spraying were 8.63 g/s for the polyol side and 6.37 g/s for the iso side. The air injected into the nozzle was set to a nominal rate of 40 L/min. The sprayed polyurethane formulation was directed into a mold with groove features. The sprayed pad was cured in a 100 C. oven for 15 min, then removed from the mold and cured in a 100 C. oven for 16 hours. The resulting pads contained both radial and concentric circular grooves. The resulting pads produced displayed an average density of 0.799 g/mL and displayed a bulk tensile modulus of 265 MPa, and 126% tensile elongation.

Example 11

(36) A 2-component air spray system was employed to spray 1-shot polyurethane into a mold. The polyurethane chemistry was identical to that reported in Example 8. The iso tank was loaded with MDI prepolymer, while the poly tank was loaded with all other components (33.80 pbw Voranol V5055HH polyol, 1.66 pbw monoethylene glycol, 0.867 pbw Niax L5345 surfactant, 13.409 pbw Ethacure 300 curative, 0.0 pbw DABCO 33LV catalyst) at the identical mass ratios as described in Example 8. The flow rates during spraying were 8.63 g/s for the polyol side and 6.37 g/s for the iso side. The air injected into the nozzle was set to a nominal rate of 20 L/min. The sprayed polyurethane formulation was directed into a mold with groove features. The sprayed pad was cured in a 100 C. oven for 15 min, then removed from the mold and cured in a 100 C. oven for 16 hours. The resulting pads contained both radial and concentric circular grooves. The resulting pads produced displayed an average density of 0.907 g/mL and displayed a bulk tensile modulus of 300 MPa and 80% tensile elongation.

Example 12

(37) In a mix cup, 95.90 g of Voranol V5055HH polyol was combined with 4.10 g polytetramethylene ether glycol (PTMEG) with molecular weight=650 g/mol and functionality=2 and 2.50 g Niax L5345 surfactant, 39.59 g Ethacure 300 curative and 3.82 g monoethylene glycol. To this mixed and degassed liquid, 106.59 g of MDI prepolymer. The cup was then mixed with a vortex mixer for 30 seconds and then poured into a mold to cast a plaque and cured at 100 C. for 16 hours. The formulation is described as having 60 wt. % hard-segment weight fraction, with a stoichiometry of 0.95:1.0, containing 15.84 wt. % Ethacure 300 curative. The hydroxyl content is 92.3 wt. % Voranol V5055HH polyol. The polyol content comprised 20 mol % PTMEG650. After curing, the plaque with density of 1.15 g/mL showed 471 MPa tensile modulus, 33.8 MPa tensile strength, and 163% tensile elongation.

(38) The properties of the materials and pads in the Examples 7 to 12, above, are reported in Table 3, below.

(39) TABLE-US-00003 TABLE 3 Pad Properties Nozzle Pore air Tensile Tensile Size flow Density Modulus Elongation Distri- Example Polyol (L/min) (g/mL) (MPa) (%) bution 9 Voranol 100 0.754 248 123 5055HH 10 Voranol 40 0.799 265 126 5055HH 11 Voranol 20 0.907 300 80 5055HH 12 Voranol 5055HH + NA 1.16 471 163 20 mol % PTMEG650