WO2014200726A1

WO2014200726A1 - Low surface roughness polishing pad

Info

Publication number: WO2014200726A1
Application number: PCT/US2014/040226
Authority: WO
Inventors: Jayakrishnan NAIR
Original assignee: Cabot Microelectronics Corporation
Priority date: 2013-06-13
Filing date: 2014-05-30
Publication date: 2014-12-18
Also published as: CN105163907A; JP2016524549A; SG11201508452VA; TW201501865A; EP3007858A1; EP3007858A4; TWI542442B; CN105163907B; US20140370788A1; KR20160019465A

Abstract

The invention provides a polishing pad comprising a polishing pad body comprising a polishing surface, wherein the polishing body comprises pores, and wherein the polishing surface has a surface roughness of 0.1 µm to 10 µm.

Description

LOW SURFACE ROUGHNESS POLISHING PAD

FIELD OF THE INVENTION

[000! j The present invention relates to a polishing pad and a method of polishing a substrate; and in particular, the present invention relates io a polishing pad comprising a polishing pad body comprising a polishing suriace, wherein the polishing body comprises pores, and wherein the polishing surface has a surface roughness of 0. 1 ura to 10 am.

BACKGROUND OF THE INVENTION

j0002| Chemical-mechanical polishing ("C P") processes are used in the manufacturing of microelectronic devices to form flat surfaces on semiconductor wafers, field emission displays, and many other microelectronic substrates. For example, the maimfacture of semiconductor devices generally involves the formation of various process layers, selective removal or patterning of portions of those layers, and deposition of yet additional process layers above the surface of a semiconducting substrate to form a semiconductor wafer. The process layers can include, by way of example, insulation layers, gate oxide layers, conductive layers, and layers of metal or glass, etc. it is generally desirable in certain steps of the wafer process thai the uppermost surface of the process layers be planar, i.e., flat, for the deposition of subsequent .layers. CMP is used to planari/e process layers wherein a deposited material, such as a conductive or insulating material, is polished to planarize the wafer for subsequent process steps.

|O003j In a typical CMP process, a wafer is mounted upside down on a carrier in a CMP tool A force pushes the carrier and the wafer downward toward a polishing pad. The carrier and the wafer are rotated above the rotating polishing pad on the CMP tool's polishing table. A polishing composition (also referred to as a polishing slurry) generally is introduced between the rotating wafer and the rotating polishing pad during the polishing process. The polishing composition typically contains a chemical that interacts with or dissolves portions of the uppermost wafer layerfs) and an abrasive material that physically removes portions of the layeris). The wafer and the polishing pad can be rotated in the same direction or in opposite directions, whichever is desirable for the particular polishing process being carried out. The carrier also can oscillate across the polishing pad o the polishing table.

04J Polishi ng pads typically have an initial surface roughness of greater than 15 microns. During the polishing of several substrates with the same pad, normal wear on the pad surface results in a change in the surface roughness of the pad. As the surface roughness of the pad changes, contact between the pad surface and a substrate being pol ished changes, and thus the polishing rate can change. As a result, the amount of time required for polishing the substrates to achieve desired surface properties, such as pianarity, varies during a production run. Var iances from uniformity between substrates can therefore result.

[000S] Thus, there remains irt the art a need for improved pol ishing pads.

BRIEF SUMMARY OF THE INVENTION

[0006] The invention provides a polishing pad comprising a polishing pad bod comprising a polishing surface, wherein the polishing body comprises pores, and wherein th polishing surface has a surface roughness of 0.1 μηι to 10 urn.

10007] The invention also provides a method of polishing a substrate, which method comprises (i) providing a substrate to be polished, (ii) contactin the substrate with the aforesaid polishing pad and a polishing composition, and (iti) moving the substrate relative to the polishing pad with the polishing composition therebetween to abrade at least a portion of the substrate to polish the substrate.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0008] FIG. 1 is a scanning electron microscope image of the surface of polishing pad in accordance wi th an embodiment of the invention.

[0009} FIG. 2 is a scanning electron microscope image of the surface of a polishing pad in accordance with an embodiment of the invention.

[0010] FIG. 3 is a scanning electron microscope image of the surface of a conventional polishing pad.

JOOl l j FIG. 4 is a graphical representation of the silicon oxide removal rate versus the number of wafers polished using a polishing pad in accordance wi h an embodiment of the invention in comparison with a conventional polishing pad.

DEI AILED DESCRIPTION OF THE INVENTION

[0012] The invention provides a polishmg pad comprising a polishing pad body comprising a polishing surface, wherein the polishing pad body comprises pores, and wherein the polishing surface has a. surface roughness of 0.1 μηι to 1.0 pm.

[Θ013] The polishing pad bod can have an suitable dimensions. Typically, the polishing pad body is circular in shape (as is used in rotary polishing tools) or is produced as a looped linear belt (as is used in linear polishing tools). Preferably, the polishing pad body is circular. [0014] The polishing pad body can comprise, consist essentially of. or consist of any suitable material. Desirably, the polishing pad body comprises, consists essentially of, or consists of a polymer resin. The polymer resin can be any suitable polymer resin. Typically, the polymer resin is selected from the group consisting of thermoplastic elastomers, thermoset polymers, po yurethanes (e.g., thermoplastic polyorethanes), polyolefins (e.g., thermoplastic polyolefins}, polycarbonates, polyvinylaieoho!s, nylons, elastomeric rubbers, elastomeric polyethylenes, polyfetrafluoroethylenes, polyethyleneterephthalates, polyimides, polyaraniides, poiyaxylenes, polyacryiates, polystyrenes, polymemylmethacrylates, copolymers thereof and mixtures thereof. Preferably, th polymer resin i a po!yuretfiane, more preferably a thermoplastic polyurethane.

[001.51 The polishing pad body comprises pores. The pores can have an average pore diameter of 2 μηι or more, 3 pm or more, 4 pm or more, 5 μτη or more, 6 um or more, 7 pm or more, 8 pm or more, 9 pm or more, 10 pm or more, 3 5 pm or more, 20 pm or more, 25 μηι or more, 30 pm or more, 35 pm or more, 40 pin or more, 45 pra or more, or 50 pm or more. Alternatively, or in addition, the pores can have an average pore diameter of .150 pm or less, 125 pm or less, 100 pm or less, 90 μιη or less, 80 pro. or less, 70 pm or less, 60 pm or less, 50 μπι or less, 45 pro or less, 40 pm or less, 35 pro or less, 30 pra or less, 25 pm or less, 20 μΐϊ) or less, 15 pm or less, or 10 pm or less. Thus, the pores can have an average pore diameter bounded by any two of the endpoints recited for the average pore diameter . For example, the polishing pad body can have an average pore diameter of 2 pni to 1.50 pm, 3 um to 125 pm, 4 pm to 100 pm, 5 pm to 90 pm, 5 pm to 80 pm, 5 pm to 70 pm, 5 pm to 60 pm, 5 pm to 50 pm, 5 pm to 45 pm, 5 pm to 40 pm, 5 pm to 35 pm, 5 pm. to 30 pm, 5 pm to 25 pm, 5 um to 20 pm, 5 pm to 15 pm, 5 pm to 10 pm, 10 pro to 5 pm, 10 pm to 45 pm, 1 pm to 40 pm, 1 pm to 35 pm, 1.0 pm to 30 pm, 10 pm to 25 pm, or 1 pin to 20 pm.

[001.6) The polishing surface can have a surface roughness of 0.1 pm or more, 0.2 pm or more, 0.3 pm or more, 0.4 pm or more, 0.5 p.m or more, 0.6 um or more, 0.7 pm or more, 0.8 pm or more, 0.9 pm or more, or 1 pm or more. Alternatively, or in addition, the polishing surface ca ^'have a surface roughness of 4 pm or less, 3.8 pm or less, 3.6 pm or less, 3.5 pm or less, 3.4 pm or less, 3.2 pm or less, 3 pm or less, 2.8 pm or less, 2.6 pm or less, 2.5 pro or less, 2,4 pm or less, 2.2 pm or less, 2 pm or less, 1.8 pm or less, or 1 .6pm or less. Thus, the polishing surface can have a surface roughness bounded by any two of the endpoints recited for the surface roughness. For example, the polishing pad body can have a surface roughness of 0.1 pm to 4 p.m, 0.1 pm lo 3,8 pm, 0. i pm to 3.6 pm, 0. i pm to 3.4 pm, 0. 1 pm to 3.2 pm. 0.1 μι¾ to 3 η 0.1 μτο to 2.8 μηι, 0.1 μτη to 2.6 μηι, 0.1 μιη to 2.4 μι». 0.1 μιη to 2.2 μηι, 0.Ϊ μιη to 2 μιη, 0.1 pm to 1.8 μνη, 0.1 μιη to ί .6 μτη, 0.5 μιη to 4 urn, 0.5 μηι io 3.5 pm, 0.5 μιΐί to 3 μΐΏ, 0.5 μηι to 2.5 μηι, 0,5 μιη to 2 μιη, 1 μιη to 4 μν , 1 μηι to 3.6 μηι, 1 μιη to 3 μιη, ί μηι to 2.5 μηι, or ί μηι to 2 μην

[00 J 7] The surface roughness can be expressed as the average surface roughness as determined at several regions of the polishing surface. A. non-limiting example of a suitable method for determining the surface roughness of the polishing surface or of a region thereof is 18013565,

0018J The polishing pad body can be produced using any suitable technique, many of which are known in the art. For example, the pol ishing pad can be formed by methods such as casting and extrusion. The polymer resin may be a thermoplastic material which is heated to a temperature at which it will flow and is then formed into a desired shape by easting or extrusion. The polymer resi may provide a porous structure by its natural configuration. In other embodiments, the porous structure may be introduced through the use of various production techniques known in the art (e.g., foaming, blowing, and the like). Representative methods of providing a porous structure comprising closed-cell pores include foaming processes such as a mucell process, a phase inversion process, a spinodal or bimodal decomposition -process, or a pressurized gas injection process, all of which are well known in the art. A re resentative method providing a porous structure comprising open-cell pores comprises sintering particles of a thermoplastic polymer, such as a potyorethane, to provide an open-cell porous structure.

[0019] The polishing surface can be produced using any suitable method. In an embodiment, the polishing surface is produced by skiving the polishing pad body.

[0020] The polishing pad body can have a storage modulus of elasticity at 30° C of 5 MPa or more, 10 MPa or more, 20 MPa or more, 30 MPa or more, 40 MPa or more. 50 MPa or more, 60 MPa or more, 70 MPa or more, 80 MPa or more, 90 MPa or more, iOC) MPa or more, 200 MPa or more, 300 MPa or more, 400 MPa or more, or 500 MPa or more.

Aiteraniively, or in addition, the polishing pad body can have a storage modulus of elasticity at 30° C of 600 MPa or less, 550 MPa or less, 500 MPa or less, 450 MPa or less, 400 MPa or less, 350 M a or less, or 300 MPa or less. Thus, the polishing pad body can have a storage modulus of elasticity at W C bounded by any two of the eadpornis recited for the storage modulus of elasticity at 30° C . For example, the polishing pad body can have a storage modulus of elasticity at 30° C of 5 MPa to 600 MPa, 20 MPa to 600 MPa, 30 MPa to 600 MPa, 40 MP to 550 MPa, SO MPa to 500 MPa, 60 MPa to 450 MPa, 70 MPa to 400 MPa, 80 MPa to 350 MPa. 90 MPa to 300 MPa, 5 MPa to 500 MPa, 10 MPa to 500 MPa, 20 MPa to 400 MPa, or 20 MPa to 300 MPa.

[00211 A polishing pad in accordance with the invention can be used alone or optionally can be used as one layer of a multi -layer stacked polishing pad. For example, the inventive polishing pad can be used in combination with a subpad. The subpad can be any suitable subpad. Suitable subpads include poiyurethane foam subpads, impregnated felt subpads, microporous poiyurethane subpads, or sintered urethane subpads. The subpad typically is softer than the polishing pad of the invention and therefore is more compressible than the polishing pad. In some embodiments, the subpad is harder and is less compressible than, the polishing pad. The subpad optionall comprises grooves, channels, hollow sections, and the like. When the polishing pad of the invention is used in combination with, a subpad, typically there is an intermediate backing layer, such as a polyethy!eneterephthaiate film, coextensive with and between the polishing pad and the subpad.

|0022] In an embodiment, the polishing pad is prepared by sandwiching the polishing pad body between two layers of a backing material. The resulting sandwiched polishing pad body can then be skived to produce two polishing pads. In some embodiments, the sandwiched polishing pad body can be produced by curing a prepolymer, for example, a thermoplastic poiyurethane, between two backing layers. The backing material can be any suitable backing materia! and can comprise a polymeric sheet. In some embodiments, the backing material can comprise a subpad as described herein, in. these embodiments, the sandwiched polishing pad can be prepared in the form of an elongated sheet which is then skived and cut. into segments to form the polishing pad in a continuous process.

[0023 j As is illustrated in Figs, 1 and 2, the surface of the inventive polishing pad comprises open pores resulting from the formation of the polishing surface by skiving of the polishing pad body. The surface roughness of the pol ishing surface refers to the surface roughness of the polishing surface exclusive of the pores, FIG, 3 illustrates the surface of a con ventional polishing pad for purposes of comparison,

[0024] The surface roughness can be measured with. an. optica! type surface roughness tester, such as three-dimensional surface profiler, laser scanning microscope, electron beam surface profiler, a contact type surface roughness tester, such as a surface roughness tester with contaci stylus, and the like. Preferably, the surface roughness is determined according to ISO 13565. [0025] The invention further provides a method of polishing a substrate, which method comprises (i) providing a substrate to be polished, (ii) contacting the substrate with the inventive polishing pad described herein and a polishing composition, and (iii) moving the substrate relative to the polishing pad, with the polishing composition therebetween, to abrade at least a portion of the substrate to polish the substrate.

jO026| The polishing composition can be any suitable polishing composition. The polishing composition typically comprises an aqueous carrier, a pH adjuster, and optionally an abrasi ve. Depending on the type of substrate ( orkpiece) being polished, the pol ishing composition optionally can further comprise one or more oxidizing agents, organic acids, compSexing agent, pH buffers, surfactants, corrosion inhibitors, anti-foaming agents, biocides, and the like.

EXAMPLE

j0027J This example demonstrates the removal rate fo silicon oxide exhibited by the inventive polishing pad as a function of the number of substrates polished therewith.

|0028] Similar substrates comprising a blanket layer of silico oxi de derived from tetraethylorthosilicate were polished with polishing pad in accordance with an embodiment of the invention and with a conventional polishing pad in conjunction with a polishing composition. The inventive polishing pad was prepared using a thermoplastic polyurethane resi (the 8? A thermoplastic polyurethane resin from Lubrizol, Wickcliffe, OH) and had a Shore D hardness of 42D, an average pore diameter of 25-45 pm, an average surface roughness as measured by a confocal microscope of 1.4 pjm, and a storage modulus of elasticity (E\) as shown in the Table.

Table

(0029] The comparative polishing pad was a commercial thermoplastic polyurethane pad having a milled surface and an average surface roughness as measured by a confocal.

microscope of 5,6 pm.

[0O3O| Following polishin of the substrates, the removal rate was determined for each substrate, and the results are illustrated graphically in FIG, 4. [0031] As is apparent from the data shown in FIG. 4, the inventive polishing pad exhibited a silicon oxide removal rate that stabilized at approximately 530 A/min after polishing approximately 40 sisbstrates. The comparative polishing pad exhibited a silicon oxide removal rate that increased during polishing of successive substrates and approached approximatel 370 A/min after polishing over 200 substrates.

(0032] All .references, including publications, paten applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0033] The use of the terms "a" and "an" and "the" and "at. ieast one" and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term "at least one" followed by a list of one or more items (for example, "at least one of A and B") is to be construed to mean one item, selected from the listed items (A or B) or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context. The terras "comprising," "having," "including," and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to,") unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value jailing within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any sui table order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and ail examples, or e em lar)' language (e.g., "such as") provided herein., is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention, unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the pract ice of the i nvention.

[003 J Preferred embodiments of this i nvention are described herein, including the best mode known to the inventors for earning out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, ibis invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in ail possible variations thereof is encompassed by the invention uniess otherwise indicated herein or otherwise clearly contradicted by context.

Claims

CLAIMS):

1 . A polishing pad comprising a polishing pad body comprising a polishing surface, wherein the polishing body comprises pores, and wherein the polishing surface has a surface roughness of 0, 1 μιη to 4 μιη,

2. The polishing pad of claim I , wherein the polishing surface has a surface roughness of 0.5 μτη to 2 μνη.

3. The polishing pad of claim 1 , wherein the pores have an average pore diameter of 2 μ\ΐΐ to .150 μηι,

4. The polishing pad of claim 1 , wherein the polishing ad lias a storage modulus of elasticity at 30^c C of 5 MPa to 600 MPa.

5. The polishing pad of claim 1, whereto the polishing pad body comprises thermoplastic polynrethane.

6. The polishing pad of claim 1 , wherein the polishing pad further comprises a pad substrate.

7. The polishing pad of claim 6, wherein the polishing pad body has a non-polishing surface that is opposite to the polishing surface, and wherein the pad substrate is bonded to the non-polishing surface.

8. The polishing pad of claim I , wherein the polishing pad further comprises an optically trartsmissive region extending from the polishing surface to a surface opposite to the polishing surface.

9. A method of^■polishing a substrate, which method composes;

(i) providing a substrate to he polished,

(ii) contacting the substrate with a polishing pad of claim I and a polishing composition, and

(iii) moving the substrate relative to the polishing pad with the polishing composition therebetween to abrade at least a portion of the substrate to polish the substrate.