JP7502592B2 - Polishing Pad - Google Patents

Description

The present invention relates to a polishing pad, and more specifically, to a polishing pad equipped with an end point detection window for detecting the end point of processing when processing a workpiece.

Conventionally, polishing pads for polishing a wafer as an object to be polished have been known, and further, polishing pads having a transparent end point detection window that transmits inspection light in order to detect the end point when polishing a wafer have been known (for example, Patent Documents 1 to 3).
In such conventional polishing pads, a through hole is provided in the polishing layer which is the main body, and a transparent window member which serves as an end point detection window is attached thereto to prevent leakage of the polishing liquid (slurry) used in polishing. Specifically, in the polishing pad of Patent Document 1, the window member which serves as the end point detection window is fitted into the through hole of the polishing layer and bonded with a photocurable adhesive, and in the polishing pad of Patent Document 2, the window member which serves as the end point detection window is fitted into the through hole of the polishing layer without adhesive. Furthermore, in the polishing pad of Patent Document 3, a single recess is formed on the inner peripheral surface of the through hole of the polishing layer, while a protrusion which engages with the recess is formed on the outer peripheral surface of the window member which serves as the end point detection window.

JP 2004-343090 A JP 2004-134539 A JP 2006-110686 A

However, the above-mentioned conventional polishing pads have the following problems.
That is, in the polishing pad of Patent Document 1, the photocurable adhesive comes into contact with the polished surface of the wafer during polishing, causing scratches on the polished surface of the wafer and deteriorating the polishing performance. Also, in the polishing pad of Patent Document 2, the end point detection window (window member) is likely to be insufficiently fitted into the through hole of the polishing layer, and there is a risk that the end point detection window will fall off from the through hole of the polishing layer during polishing of the wafer.
Furthermore, in the polishing pad of Patent Document 3, as the polishing pad is used, the polishing layer and the end point detection window of the polishing pad wear away, causing the convex portion formed on the outer peripheral surface of the end point detection window to disappear, and there was a risk that the end point detection window would easily fall off from the through hole during subsequent polishing of the wafer.
SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a polishing pad which prevents deterioration of polishing performance and also prevents the end point detection window from falling off from the polishing layer.

In view of the above circumstances, the present invention provides a polishing pad comprising a polishing layer having a polishing surface for polishing an object to be polished, and an end point detection window provided in a through hole of the polishing layer and allowing an inspection light and a reflected light from the object to pass therethrough, the end point detection window comprising:
a plurality of protrusions are formed on the side of the end point detection window in a direction perpendicular to the polishing surface;
a plurality of recesses that engage with the protrusions of the end point detection window are formed on an inner peripheral surface of the through hole of the polishing layer;
The plurality of protrusions and recesses are engaged without gaps without using adhesive,
a groove for holding and/or discharging a slurry is formed on the polishing surface of the polishing layer, and at least one protrusion and a recess are provided in a state of engagement below the height of a bottom of the groove;
Furthermore, the pitch of the convex portions is 0.2 to 0.5 mm,
The height of the projections is 0.15 to 0.5 mm .

According to this configuration, the end point detection window is attached to the through hole with the multiple projections and recesses tightly engaged with each other without using adhesive, so that the surface to be polished is not adversely affected by the adhesive when the workpiece is polished, and since the multiple projections and recesses are engaged with each other, it is possible to prevent the end point detection window from falling off the through hole of the polishing layer while the workpiece is being polished.
Furthermore, since at least one convex portion and concave portion are arranged in an engaged state below the height of the bottom of the groove in the polishing surface, even when the polishing surface wears away and the groove disappears, making it necessary to replace the polishing layer, at least one convex portion and concave portion will remain, thereby reliably preventing the end point detection window from falling off from the through hole in the polishing layer.

1 is a schematic perspective view showing an embodiment of the present invention; FIG. 2 is a cross-sectional view of a main part taken along line II-II in FIG. FIG. 3 is an enlarged view of a main part of FIG. 2 . 4A to 4C are diagrams showing the manufacturing process of the polishing layer of the polishing pad shown in FIG. 3 . 5A and 5B are cross-sectional views of the main part of FIG. 2, in which FIG. 5A shows the polishing pad in a state before use and FIG. 5B shows the polishing pad in a state after use. 6A and 6B are cross-sectional views showing another embodiment of the present invention, in which FIG. 6A shows a polishing pad in a state before use, and FIG. 6B shows a state after use. 7A and 7B are cross-sectional views showing another embodiment of the present invention, in which FIG. 7A shows a polishing pad in a state before use, and FIG. 7B shows a state after use.

1 and 2, reference numeral 1 denotes a polishing apparatus which polishes a thin plate-like object to be polished 2 (e.g., a semiconductor wafer) with a polishing pad 3. When performing polishing of the object to be polished 2, the polishing apparatus 1 irradiates a polishing surface 2A of the object to be polished 2 with an inspection light L1 and receives the reflected light with a detection mechanism 7 (light receiving section 7B), thereby making it possible to detect the progress of the polishing process and the end point of the process.
The polishing apparatus 1 comprises a polishing platen 4 located on the lower side and having a polishing pad 3 fixed on its upper surface, a holding platen 5 located on the upper side and holding the workpiece 2 on its lower surface, a slurry supply mechanism 6 that supplies slurry between the workpiece 2 and the polishing pad 3, and a detection mechanism 7 that uses an inspection light L1 to detect the progress of polishing of the workpiece 2 and the end point of the processing.
The workpiece 2 to be polished by the polishing device 1 is an optical material, a silicon wafer, a glass substrate for liquid crystal, a semiconductor substrate, and a plate-like object such as glass, metal, ceramic, etc. As the slurry to be supplied by the slurry supply mechanism 6, a suitable conventionally known material can be used depending on the workpiece 2 to be polished and the required processing accuracy.
The polishing platen 4 and the holding platen 5 are each substantially disk-shaped and are adapted to rotate in the direction of the arrow by a drive mechanism (not shown). The holding platen 5 is also provided so as to be movable up and down.
When polishing the object to be polished 2, the holding platen 5 presses the polished surface (lower surface) 2A of the object to be polished 2 against the polishing surface 3A of the polishing pad 3 at a set pressure while they are rotated relative to one another, and slurry is supplied from a slurry supply mechanism 6 between the polished surface 2A of the object to be polished 2 and the polishing surface 3A of the polishing pad 3.

When polishing the workpiece 2, it is necessary to detect the progress of the polishing of the workpiece 2 and the end point of the polishing. Therefore, the polishing device 1 is provided with a detection mechanism 7 that irradiates an inspection light L1 from below toward above and detects the progress of the polishing and the end point of the polishing based on the light reflected from the polished surface 2A of the workpiece 2. In addition, a transparent end point detection window 3B is provided at a predetermined position of the polishing pad 3, which transmits the inspection light L1 and the light reflected from the polished surface 2A of the workpiece 2.
The polishing pad 3 includes a disk-shaped polishing layer 3C located on the upper side, and a disk-shaped support layer 3D bonded with an adhesive to the lower surface of the polishing layer 3C. A transparent end point detection window 3B is provided at a predetermined position of the polishing layer 3C, and a through hole 3Da is drilled at the position of the support layer 3D below the end point detection window 3B to allow the inspection light L1 and the reflected light from the workpiece 2 to pass therethrough.
The upper surface 3Bb of the end point detection window 3B and the polishing surface 3A, which is the upper surface of the polishing layer 3C, are flush with each other. The lower surface 3Bc of the end point detection window 3B and the lower surface of the polishing layer 3C are flush with each other, and the upper surface of the support layer 3D is bonded thereto with an adhesive. The polishing pad 3, which is made up of the polishing layer 3C and the support layer 3D integrated vertically, has its lower surface (the lower surface of the support layer 3D) fixed to the upper surface 4A of the polishing table 4 with double-sided tape, adhesive, or the like.

The polishing layer 3C is made of hard urethane. Hard urethane is produced by a prepolymer method in which a urethane prepolymer, which is a reaction intermediate between a polyol component and an isocyanate component, is used to harden the polyurethane polyurea resin obtained by adding and mixing a hardener (chain extender) such as a diamine or diol, a foaming agent, a catalyst, etc. Note that although the polishing layer and the end point detection window are described below as being made of polyurethane polyurea resin, polyurethane resin or polyurea resin may also be used.

The manufacturing method of the polishing layer 3C may include, for example, a preparation step of preparing at least a polyurethane bond-containing isocyanate compound as a prepolymer, a curing agent, and a hollow body; a mixing step of mixing at least the polyurethane bond-containing isocyanate compound and the curing agent to obtain a mixture for molding a molded body; a molded body molding step of molding a polyurethane polyurea resin molded body from the mixture for molding a molded body; and a polishing layer formation step of forming a polishing layer having the polishing surface from the polyurethane polyurea resin molded body.

In the preparation process, for example, a polyurethane bond-containing isocyanate compound, a curing agent, and a hollow body are used as raw materials for the polyurethane polyurea resin molded body in the manufacture of the polishing layer 3C. Furthermore, a polyol compound may be used together with the above components, and components other than the above may be used together as long as the effects of the present invention are not impaired.

The polyurethane bond-containing isocyanate compound prepared in the preparation step is a compound obtained by reacting the following polyisocyanate compound with a polyol compound under commonly used conditions, and contains a polyurethane bond and an isocyanate group in the molecule. In addition, other components may be contained in the polyurethane bond-containing isocyanate compound within the range that does not impair the effects of the present invention.
The polyurethane bond-containing isocyanate compound may be a commercially available product, or may be a product synthesized by reacting a polyisocyanate compound with a polyol compound. The reaction is not particularly limited, and addition polymerization may be performed using a method and conditions known in the art for producing polyurethane resins.
For example, the polyisocyanate compound heated to 50°C is added to a polyol compound heated to 40°C while stirring in a nitrogen atmosphere, and the mixture is heated to 80°C after 30 minutes and then reacted at 80°C for 60 minutes.

First, the polyisocyanate compound means a compound having two or more isocyanate groups in the molecule. The polyisocyanate compound is not particularly limited as long as it has two or more isocyanate groups in the molecule.
For example, diisocyanate compounds having two isocyanate groups in the molecule include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate (2,6-TDI), 2,4-tolylene diisocyanate (2,4-TDI), naphthalene-1,4-diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), 4,4'-methylene-bis(cyclohexyl isocyanate) (hydrogenated MDI), 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, 3,3'-dimethyl- Examples of the diisocyanate include diphenylmethane-4,4'-diisocyanate, xylylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, p-phenylene diisothiocyanate, xylylene-1,4-diisothiocyanate, and ethylidine diisothiocyanate.
Furthermore, as the polyisocyanate compound, a diisocyanate compound is preferable, among which 2,4-TDI, 2,6-TDI and MDI are more preferable, and 2,4-TDI and 2,6-TDI are particularly preferable.
These polyisocyanate compounds may be used alone, or a plurality of polyisocyanate compounds may be used in combination.

Next, the above-mentioned polyol compound means a compound having two or more alcoholic hydroxyl groups (OH) in the molecule.
Examples of the polyol compound used in the synthesis of the polyurethane bond-containing isocyanate compound include diol compounds, triol compounds, and the like, such as ethylene glycol, diethylene glycol (DEG), butylene glycol, and the like; polyether polyol compounds, such as poly(oxytetramethylene) glycol (or polytetramethylene ether glycol) (PTMG), and the like; polyester polyol compounds, such as a reaction product of ethylene glycol and adipic acid, or a reaction product of butylene glycol and adipic acid, and the like; polycarbonate polyol compounds, polycaprolactone polyol compounds, and the like.
Also usable is a trifunctional propylene glycol having ethylene oxide added thereto. Among these, PTMG or a combination of PTMG and DEG is preferred.
The above polyol compounds may be used alone or in combination of two or more polyol compounds.

Here, the NCO equivalent of the prepolymer, which indicates the molecular weight of the prepolymer per NCO group, is preferably 200-800, more preferably 300-700, and even more preferably 400-600.
Specifically, the NCO equivalent of the prepolymer can be determined as follows.
NCO equivalent of prepolymer=(parts by mass of polyisocyanate compound+parts by mass of polyol compound)/[(number of functional groups per molecule of polyisocyanate compound×parts by mass of polyisocyanate compound/molecular weight of polyisocyanate compound)−(number of functional groups per molecule of polyol compound×parts by mass of polyol compound/molecular weight of polyol compound)]

As the curing agent, for example, a polyamine compound and/or a polyol compound can be used.
The polyamine compound means a compound having two or more amino groups in the molecule, and an aliphatic or aromatic polyamine compound, particularly a diamine compound, can be used.
Examples of the compound include ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, 3,3'-dichloro-4,4'-diaminodiphenylmethane (methylenebis-o-chloroaniline) (hereinafter abbreviated as MOCA), and polyamine compounds having the same structure as MOCA.
Furthermore, the polyamine compound may have a hydroxyl group, and examples of such amine compounds include 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, and di-2-hydroxypropylethylenediamine.
As the polyamine compound, a diamine compound is preferable, MOCA, diaminodiphenylmethane, and diaminodiphenylsulfone are more preferable, and MOCA is particularly preferable.
The polyamine compound may be used alone or in combination of two or more polyamine compounds.
In order to facilitate mixing with other components and/or to improve the uniformity of the bubble diameter in the subsequent molding process, the polyamine compound is preferably degassed under reduced pressure while being heated as necessary. As a method for degassing under reduced pressure, any method known in the production of polyurethanes may be used, and for example, degassing can be performed using a vacuum pump at a vacuum degree of 0.1 MPa or less.
When a solid compound is used as the curing agent, it can be melted by heating and degassed under reduced pressure.

The polyol compound used as the curing agent is not particularly limited as long as it is a diol compound, a triol compound, etc. The polyol compound may be the same as or different from the polyol compound used to form the prepolymer.
Specific examples include low molecular weight diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol; and high molecular weight polyol compounds such as poly(oxytetramethylene) glycol, polyethylene glycol, and polypropylene glycol.
The above polyol compounds may be used alone or in combination of two or more polyol compounds.

Here, the components are mixed so that the R value, which is the equivalent ratio of the active hydrogen groups (amino groups and hydroxyl groups) present in the curing agent to the isocyanate groups present at the ends of the polyurethane bond-containing isocyanate compound, is 0.60 to 1.40. The R value is preferably 0.65 to 1.30, and more preferably 0.70 to 1.20.

The hollow body means a microsphere having a void. The microsphere includes a spherical shape, an elliptical shape, and shapes similar thereto. Examples of hollow bodies include unfoamed heat-expandable microspheres having an outer shell (polymer shell) made of a thermoplastic resin and a low-boiling point hydrocarbon contained in the outer shell, and bodies obtained by thermally expanding unfoamed heat-expandable microspheres.
As disclosed in JP-A-57-137323, etc., the polymer shell may be made of a thermoplastic resin such as an acrylonitrile-vinylidene chloride copolymer, an acrylonitrile-methyl methacrylate copolymer, or a vinyl chloride-ethylene copolymer. Similarly, the low-boiling point hydrocarbon encapsulated in the polymer shell may be, for example, isobutane, pentane, isopentane, petroleum ether, etc.
In addition to using the hollow bodies, bubbles may be formed by chemical foaming such as water foaming or foaming due to mechanical stirring, or these methods may be combined.

Next, the mixing step will be described. In the mixing step, the polyurethane bond-containing isocyanate compound as a prepolymer, the curing agent, and the hollow bodies prepared in the preparation step are fed into a mixer and stirred and mixed. The mixing step is performed in a state where the components are heated to a temperature at which the fluidity of each component can be ensured.
Although there is no particular restriction on the order of mixing, it is preferable to prepare a mixed liquid obtained by mixing a polyurethane bond-containing isocyanate compound and a hollow body, and a mixed liquid obtained by mixing a curing agent and other components as necessary, and to supply both mixed liquids into a mixer and mix and stir them. In this way, a mixed liquid for molding a molded body is prepared.

Next, in the molding process, the mixture prepared in the mixing process is poured into a mold at 50 to 100°C, and the prepolymer and hardener react to form a polyurethane polyurea resin, which hardens the mixture and forms a polyurethane polyurea resin molded body.

In the abrasive layer forming step, the polyurethane polyurea resin molded body obtained in the molded body molding step is sliced into sheets, and the sliced resin sheets are cut into a predetermined shape.
The resin sheet thus obtained is subjected to grinding treatment on the front and/or back surface. One surface becomes the polished surface, and by performing cutting processing or the like on the polished surface using a required cutter, grooves having a desired pitch, width, and depth can be formed, thereby obtaining the polishing layer 3C.

For the support layer 3D, a support base material such as a resin-impregnated nonwoven fabric, a foam such as polyethylene foam or polyurethane foam, or polyethylene terephthalate (PET) can be used.
When the impregnated nonwoven fabric is used as the support layer 3D, the manufacturing process of the support layer 3D includes at least a step of wet-coagulating the resin impregnated in the nonwoven fabric substrate and a step of buffing both sides of the wet-coagulated fiber assembly. The nonwoven fabric substrate of this embodiment is not particularly limited, and various known nonwoven fabrics can be used.
Examples of the nonwoven fabric substrate include nonwoven fabrics of polyolefin, polyamide, polyester, etc. The method of entangling fibers when obtaining the nonwoven fabric substrate is not particularly limited, and may be, for example, needle punching or hydroentanglement.
The nonwoven fabric substrate may be one of the above-mentioned types, or a combination of two or more types. The nonwoven fabric substrate has many gaps between the fibers and is highly water-absorbent, but by impregnating the nonwoven fabric substrate with resin, the gaps are filled with resin, decreasing the water-absorbency.

Resins to be impregnated into the nonwoven fabric substrate include polyurethane-based resins such as polyurethane and polyurethane polyurea, acrylic-based resins such as polyacrylate and polyacrylonitrile, vinyl-based resins such as polyvinyl chloride, polyvinyl acetate and polyvinylidene fluoride, polysulfone-based resins such as polysulfone and polyethersulfone, acylated cellulose-based resins such as acetylated cellulose and butyrylated cellulose, polyamide-based resins and polystyrene-based resins.

The density of the nonwoven fabric before resin impregnation (web state) is preferably 0.3 g/cm3 or less, more preferably 0.1 to 0.2 g/cm3. The density of the nonwoven fabric after resin impregnation is preferably 0.5 g/cm3 or less, more preferably 0.3 to 0.4 g/cm3. If the density of the nonwoven fabric is too high, the processing accuracy tends to deteriorate, and if it is too low, it tends to absorb water relatively easily.
The adhesion rate of the resin to the nonwoven fabric is expressed as the weight of the resin adhered to the weight of the nonwoven fabric, and is preferably 50% or more, and more preferably 75 to 200%. If the adhesion rate of the resin is too high, the support layer 3D tends not to exhibit the desired cushioning properties, and if it is too low, the support layer 3D absorbs water, which affects the polishing characteristics.

As an example of impregnating a nonwoven fabric substrate with a resin and wet coagulating it, a case where a polyurethane resin is used will be described. A polyurethane resin is mixed with a solvent capable of dissolving the polyurethane resin and which is miscible with the coagulation liquid described below, and other additives as necessary, and the mixture is degassed under reduced pressure as necessary to prepare a polyurethane resin solution. The solvent is not particularly limited, but examples include N,N-dimethylformamide (DMF), isopropyl alcohol (IPA), and N,N-dimethylacetamide. For example, the polyurethane resin may be dissolved in the solvent in a range of 5 to 25% by mass, more preferably 8 to 15% by mass, based on the total amount of the polyurethane resin solution. In the above range, it is possible to easily distribute the polyurethane resin throughout the nonwoven fabric substrate.

Next, the sheet-shaped nonwoven fabric is immersed in the polyurethane resin solution, and then the resin solution is squeezed out by using a mangle roller that can apply pressure between a pair of rollers to adjust the amount of resin solution to be applied, so that the nonwoven fabric base is impregnated with the resin solution approximately uniformly. Next, the nonwoven fabric base impregnated with the resin solution is immersed in a coagulation liquid mainly composed of a poor solvent for the resin, such as water, to coagulate and regenerate the polyurethane resin. In order to adjust the regeneration speed of the resin, an organic solvent such as a polar solvent other than the solvent in the resin solution may be added to the coagulation liquid. The temperature of the coagulation liquid is not particularly limited as long as it is a temperature at which the resin can be coagulated, and may be, for example, 15 to 60°C. Thereafter, if necessary, the solvent remaining in the nonwoven fabric impregnated with the resin is removed using a conventionally known cleaning liquid, and the cleaning liquid may be removed by using a mangle roller or drying. In this way, a fiber aggregate in which the resin has been wet-coagulated can be obtained. Then, both sides of the fiber aggregate are buffed to adjust the thickness of the fiber aggregate.

Through holes are formed in the fiber aggregate, whose thickness has been adjusted, in the thickness direction at predetermined positions. The through holes can be formed by a drilling process or the like. This results in the support layer 3D.

A transparent substrate made of, for example, polyethylene terephthalate (PET) can be used for the support layer 3D. The support layer 3D can be attached and fixed to the polishing layer 3C by using double-sided tape or adhesive on both sides of the polyethylene terephthalate substrate and applying pressure as necessary. There are no particular restrictions on the double-sided tape or adhesive used for adhesion to the polishing layer 3C, and any double-sided tape or adhesive known in the art can be selected and used. Note that if the substrate is transparent, the inspection light can pass through, so there is no need to provide a through hole.

The end point detection window 3B can be made of the same material as the polishing layer, for example, hard urethane. The hard urethane of the end point detection window 3B is manufactured by a prepolymer method in which a polyurethane polyurea resin obtained by adding and mixing a urethane prepolymer with a hardener (chain extender) such as diamines or diols, additives, catalysts, etc. is hardened.

The urethane prepolymer used in the end point detection window may be the same as that used in the polishing layer, for example, a polyurethane bond-containing isocyanate compound. The polyurethane bond-containing isocyanate compound may be a commercially available product, or may be a product synthesized by reacting a polyisocyanate compound with a polyol compound. There is no particular restriction on the reaction, and addition polymerization may be performed using a method and conditions known in the manufacture of polyurethane resins. In addition, other components may be contained in the polyurethane bond-containing isocyanate compound within a range that does not impair the effects of the present invention.
As the polyisocyanate compound, a diisocyanate compound is preferable, and the diisocyanate compound used in the polishing layer can be used. Among the diisocyanate compounds, 2,4-TDI, 2,6-TDI, and MDI are more preferable, and 2,4-TDI and 2,6-TDI are particularly preferable. These polyisocyanate compounds may be used alone, or multiple polyisocyanate compounds may be used in combination.

The polyol compound used in the synthesis of the polyurethane bond-containing isocyanate compound can also be the polyol compound used in the polishing layer. Among the polyol compounds, PTMG or a combination of PTMG and DEG is preferred. The polyol compounds may be used alone or in combination.

For the prepolymer used in the end point detection window, the NCO equivalent of the prepolymer, which indicates the molecular weight of the prepolymer per NCO group, is preferably 200 to 800, more preferably 300 to 700, and even more preferably 400 to 600.

As the curing agent, the same compound as that used in the polishing layer, for example, polyamine compound and/or polyol compound can be used.As the polyamine compound, diamine compound is preferable, MOCA, diaminodiphenylmethane, diaminodiphenylsulfone are more preferable, and MOCA is particularly preferable.The polyamine compound can be used alone, or a combination of multiple polyamine compounds can be used.
As in the case of the polishing layer, the polyamine compound used in the endpoint detection window is preferably degassed under reduced pressure, if necessary while being heated, in order to facilitate mixing with other components and/or to remove air bubbles.

The polyol compound used as the curing agent for the end point detection window can be any compound, such as a diol compound or a triol compound, without any particular restrictions. The polyol compound may be the same as or different from the polyol compound used to form the prepolymer used for the end point detection window. The polyol compound may be used alone or in combination with multiple polyol compounds.

Here, the components are mixed so that the R value, which is the equivalent ratio of the active hydrogen groups (amino groups and hydroxyl groups) present in the curing agent used in the end point detection window to the isocyanate groups present at the ends of the polyurethane bond-containing isocyanate compound used in the end point detection window, is 0.60 to 1.40. The R value is preferably 0.65 to 1.30, and more preferably 0.70 to 1.20.

The endpoint detection window can contain additives such as known antioxidants, ultraviolet absorbers, and light stabilizers. By using these additives, yellowing and deterioration of the endpoint detection window can be suppressed.

The polishing table 4 is provided, below the end point detection window 3B of the polishing pad 3 and the through hole 3Da of the support layer 3D, with a light-emitting unit 7A that irradiates inspection light L1 vertically upward and a light-receiving unit 7B that receives reflected light from the polished object 2. The inspection mechanism 7 includes the light-emitting unit 7A, the light-receiving unit 7B, and a control unit 7C that controls their operation and detects the progress of polishing and the end point at which polishing ends.
While the workpiece 2 is being polished, inspection light L1 is emitted upward from the light-emitting unit 7A of the inspection mechanism 7, and the inspection light L1 passes through the transparent end-point detection window 3B and is irradiated onto the polished surface 2A of the workpiece 2. The inspection light L1 is then reflected downward by the polished surface 2A of the workpiece 2, and the reflected light passes through the transparent end-point detection window 3 and is detected by the light-receiving unit 7B. The reflected light detected by the light-receiving unit 7B is transmitted to the control unit 7C.
As the polishing of the workpiece 2 progresses and the polished surface 2A of the workpiece 2 is gradually polished, the intensity of the reflected light detected by the light-receiving unit 7B changes. When the intensity of the reflected light detected by the light-receiving unit 7B reaches a preregistered intensity, the control unit 7C determines that the polished surface 2A has reached the end point of polishing, and stops the polishing. Then, the drive mechanism is stopped, so that the rotation of the polishing platen 4 and the holding platen 5 stops, and the supply of slurry from the slurry supply mechanism 6 is also stopped.
The detection mechanism 7 detects the end point of the polishing process when the workpiece 2 is polished in this manner. The configuration of the detection mechanism 7 using the inspection light L1 is publicly known from the above-mentioned Patent Documents 1 to 3.

The present embodiment is characterized in that the end point detection window 3B provided in the polishing layer 3C and its mounting location, etc., have been improved as described below, thereby preventing the end point detection window 3B from falling off the polishing layer 3C during processing.
As shown in FIG. 3, a through hole 3Ca is formed in a predetermined position of the polishing layer 3C in the vertical direction, and a substantially cylindrical end point detection window 3B is provided in the through hole with no gap therein.
The end point detection window 3B is formed in a short cylindrical shape with an axial dimension and an outer diameter that are approximately the same. On the outer periphery of the side surface of the end point detection window 3B, flange-like bulges 3Ba are formed at two locations with a predetermined distance in the axial direction. That is, in the direction perpendicular to the polishing surface 3A, the bulges 3Ba are formed as convex portions at two locations on the outer periphery of the end point detection window 3B. The end point detection window 3B is made by curing a mixture of urethane prepolymer and a curing agent, and is capable of transmitting light. Although the end point detection window 3B has been described as being cylindrical, it may be a prismatic shape such as a square prism.
The thickness (axial dimension) and outward bulging length of each bulging portion 3Ba are the same. The length (height) of the bulging portion is preferably 0.1 to 0.5 mm. By making the length of the bulging portion 0.1 to 0.5 mm, it is possible to obtain the effect of preventing the end point detection window from falling off while ensuring the strength of the bulging portion. In addition, the distance (pitch) between the upper and lower bulging portions 3Ba is approximately the same as their thickness. The pitch of the bulging portions 3Ba is preferably 0.2 to 0.5 mm. By making the pitch of the bulging portions 3Ba 0.2 to 0.5 mm, the resin solution that is the material of the polishing layer 3C can be easily spread, making it easier to form (process) multiple bulging portions, and ensuring the strength of the bulging portions.
The upper bulge 3Ba is located below the upper surface 3Bb, which is the same as the polishing surface 3A, by a distance shorter than the thickness of the bulge 3Ba, and the lower bulge 3Ba is located above the lower surface 3Bc by about half the thickness of the bulge 3Ba. In addition, in the case where the bulge 3Ba forms a screw thread (spiral), which will be described later as another embodiment of the present invention, the bulge 3B is located continuously from the upper surface 3Bb to the lower surface 3Bc.
On the other hand, the through hole 3Ca of the polishing layer 3C is formed so as to engage with the original outer peripheral surface 3Bd and the bulging portion 3Ba of the end point detection window 3B without any gap.
That is, the original outer peripheral surface 3Bd of the end point detection window 3B fits snugly into the original inner peripheral surface of the through hole 3Ca. In addition, two recesses 3Cb are formed in predetermined positions on the inner peripheral surface of the through hole 3Ca in accordance with the shapes and dimensions of the bulges 3Ba of the end point detection window 3B. The bulges 3Ba of the end point detection window 3B are engaged snugly with the corresponding recesses 3Cb of the through hole 3Ca.
In this manner, the end point detection window 3B in this embodiment has two bulging portions 3Ba formed on its outer periphery to prevent it from falling off, while the through hole 3Ca of the polishing layer 3C has two recesses 3Cb formed therein into which the bulging portions 3Ba engage without any gaps.
An upper surface 3Bd of the end-point detection window 3B is flush with the polishing surface 3A of the polishing layer 3C, and a lower surface 3Bc of the end-point detection window 3B is flush with a lower surface 3Cc of the polishing layer 3C.
The upper surface of the polishing layer 3C is the polishing surface 3A that slides against the polished surface 2A of the workpiece 2, and grooves 3Cd are formed at predetermined positions on the polishing surface 3A. The grooves 3Cd are formed in a lattice pattern, concentric circles, radial patterns, etc. on the polishing surface 3A. The depths of the grooves 3Cd are all the same. The depths of the grooves 3Cd are set to be deeper than the upper bulge 3Ba of the end point detection window 3B and shallower than the lower bulge 3Ba. The grooves 3Cd are adapted to hold or discharge the slurry. The polishing layer 3C and the end point detection window 3B in the polishing pad 3 of this embodiment are configured as described above.

Next, one embodiment of a method for manufacturing the polishing layer 3C of the polishing pad 3 configured as above will be described with reference to FIG.
That is, first, a columnar material 100 having a required outer diameter and axial length is produced. In the embodiment, a cylindrical columnar material is described, but a rectangular columnar material may also be used. This columnar material 100 becomes a window member that will later become the end point detection window 3B. In this embodiment, a urethane prepolymer and a hardener are prepared as the materials for the columnar material, and the mixture is poured into a window mold and hardened to produce the columnar material 100 (see FIG. 4(a)).
Next, a plurality of flange-shaped bulging portions 100A are formed at equal pitches in the axial direction on the outer periphery of the columnar material 100. In this embodiment, the outer periphery of the columnar material 100 is cut to form the bulging portions 100A having a predetermined width (vertical dimension) and depth (radial dimension) at a plurality of locations in the axial direction (see FIG. 4(b)). In other words, in this process, the bulging portions 100A are formed as a plurality of convex portions on the outer periphery of the columnar material 100.
Next, a rectangular box-shaped formwork 101 (not shown) is prepared, and the columnar material 100 having the above-mentioned multiple bulges 100A formed thereon is placed in a predetermined position within the formwork 101 so that it is oriented vertically.
Thereafter, a mixture of urethane prepolymer and a hardener, which are materials for the polishing layer 3C, is poured into the mold 101 and hardened. This produces a polyurethane-polyurea resin molded body 102 having the same shape as the internal space of the mold 101 with the columnar material 100 embedded therein (see FIG. 4(c)). This polyurethane-polyurea resin molded body 102 becomes part of the polishing layer 3C.
The mixture of urethane prepolymer and a hardener, which are the materials for the polishing layer 3C, is initially in liquid form, so that the mixture fills the outer peripheral surface of the columnar material 100 placed within the formwork 101 and the surfaces of the multiple bulges 100A without leaving any gaps, and then hardens.
Next, after removing the polyurethane-polyurea resin molded body 102 from the formwork 101, the portions of the polyurethane-polyurea resin molded body 102 where the columnar materials 100 are embedded are thinly cut along a horizontal plane at a predetermined thickness to cut out multiple sheet-like members 103 (see Figure 4 (d)).
The upper and lower surfaces of the sheet-like member 103 are then polished to be smooth. After this, double-sided tape or the like is attached to the lower surface of the polishing layer 3C on the side opposite the polishing surface 3A. Grooves for discharging and retaining the slurry are formed at required positions on the upper surface that will become the polishing surface 3A. This completes the polishing layer 3C of the polishing pad 3 of this embodiment shown in FIG. 3 (see FIG. 4(d)).
In this way, the polishing layer 3C of the polishing pad 3 is produced, and the portion of the polishing layer 3C where the columnar material 100 is located becomes the end point detection window 3B. At least two bulging portions 3Ba are maintained in the vertical direction (axial direction) on the outer periphery of the end point detection window 3B, and these are tightly engaged with the through holes 3Ca on the polishing layer 3C side at adjacent positions.
After the polishing layer 3C has been produced in this manner, a support layer 3D having through holes 3Da formed therein is attached to the lower surface of the polishing layer 3C, thereby completing the manufacture of the polishing pad 3 of this embodiment (FIG. 4(e)).
The polishing pad 3 thus manufactured has its lower surface (the lower surface of the support layer 3D) fixed to the upper surface of the polishing platen 4 by means of double-sided tape, adhesive or the like.
In addition, as a method for forming the bulging portion, an example of cutting the outer periphery of the columnar material has been described, but the present invention is not limited to this. As another example, the mixed material of the columnar material is poured into a window mold in which a recess corresponding to the bulging portion of the end point detection window is formed, and when the material of the columnar material hardens, the window mold is removed and the hardened columnar material is taken out. As yet another example, a polyurethane-polyurea resin molded body is produced without embedding a columnar material, and a through hole is formed at a predetermined position of the polyurethane-polyurea resin molded body and threaded to form a through hole with a recess. Then, a mixture of a urethane prepolymer and a curing agent is poured into the through hole with the recess and hardened, whereby a bulging portion can also be formed in the columnar material.

In this embodiment, the polishing layer 3C of the polishing pad 3 is produced as described above, and the support layer 3D is attached thereto with double-sided tape, adhesive or the like to produce the polishing pad 3.
The polishing layer 3C of the polishing pad 3 of this embodiment is attached without using adhesive, with the end point detection window 3B tightly engaged with the through hole 3Ca of the polishing layer 3C. Therefore, during the polishing process in which the polishing surface 3A of the polishing layer 3C slides against the polished surface 2A of the polished object 2, the adhesive does not get mixed into the polishing surface 2A, and adverse effects (such as scratches) on the polished object 2 caused by the adhesive can be prevented.
In this embodiment, at least two bulges 3Ba in the end point detection window 3B are fitted tightly into the recesses 3Cb in the through holes 3Ca in the polishing layer 3C, preventing the end point detection window 3B from falling off the through holes 3Ca in the polishing layer 3C during polishing of the workpiece 2.
Furthermore, as shown in Figures 5(a) and 5(b), as the polishing process on the workpiece 2 is repeated, the polishing surface 3A of the polishing layer 3C of the polishing pad 3 wears down from the initial state shown in Figure 5(a) to the limit at which it needs to be replaced as shown in Figure 5(b).
As the polishing surface 3A wears away, the depth of the groove 3Cd becomes relatively shallow, and when the depth of the groove 3Cd reaches a predetermined limit, it is time to replace the polishing layer 3C (the state shown in FIG. 5(b)). Even in this state, one bulge 3Ba below the bottom of the groove 3Cd remains without being worn away and engages with the recess 3Cb. In other words, even when the polishing layer 3C needs to be replaced, at least one bulge 3Ba remains in the end point detection window 3B. Therefore, according to this embodiment, it is possible to reliably prevent the end point detection window 3B from falling off from the through hole 3Ca of the polishing layer 3C during the polishing process of the workpiece 2.

Next, Fig. 6(a) shows a second embodiment of the polishing layer 3C of the polishing pad 3. In this second embodiment, a male thread 3Bf is formed on the outer peripheral surface of the end point detection window 3B, and a female thread 3Cf that fits snugly with the male thread 3Bf is formed on the inner peripheral surface of the through hole 3Ca of the polishing layer 3C. The manufacturing method of the polishing layer 3C of this second embodiment is the same as that of the first embodiment shown in Fig. 4.
The male thread 3Bf has three or more threads as convex portions in the axial direction (vertical direction), so that even if the groove 3Cd becomes shallow enough to be replaced, at least one thread remains. The other configurations are the same as those of the first embodiment shown in Fig. 3 and Fig. 5(a).
In this second embodiment, even when the polishing surface 3A of the polishing layer 3C is worn down from the initial state shown in FIG. 6(a) to the point where it needs to be replaced as shown in FIG. 6(b), multiple threads remain as convex portions of the male screw 3Bf.
Therefore, even with the polishing pad 3 having the polishing layer 3C of the second embodiment shown in FIG. 6(a), it is possible to obtain the same functions and effects as those of the first embodiment.

7A shows a third embodiment of the polishing layer 3C of the polishing pad 3. In this third embodiment, a square-threaded spiral protrusion 3Bg is formed on the outer peripheral surface of the end-point detection window 3B, and in conjunction with this, a spiral recess 3Cg is formed on the inner peripheral surface of the through hole 3Ca of the polishing layer 3C, and they are engaged with each other without any gap.
The convex portion formed by the helical protrusion 3Bg is formed at two or more places in the longitudinal section in the axial direction (vertical direction). In addition, at least one convex portion formed by the helical protrusion 3Bg is formed below the bottom of the groove 3Cd. The other configurations are the same as those of the first embodiment shown in Figures 3 and 5(a). The manufacturing method of the polishing layer 3C of this third embodiment is also the same as that of the first embodiment shown in Figure 4.
In this third embodiment, even when the polishing surface 3A of the polishing layer 3C is worn down from the initial state shown in Figure 7(a) to the point where it needs to be replaced as shown in Figure 7(b), multiple convex portions of the spiral projection 3Bg remain.
Therefore, even with the polishing pad 3 having the polishing layer 3C of the third embodiment shown in FIG. 7A, it is possible to obtain the same functions and effects as those of the above-mentioned embodiments.

In the first embodiment shown in FIG. 3, multiple bulges 3Ba are formed in the end point detection window 3B, and corresponding recesses 3Cb are formed in the inner circumferential surface of the through hole 3Ca in the polishing layer 3C, but the relationship between the protrusions and recesses may be reversed. In other words, multiple recesses may be formed in the outer circumferential portion of the end point detection window 3B, and corresponding bulges may be formed in the inner circumferential surface of the through hole 3Ca in the polishing layer 3C. This relationship is similar for each of the embodiments disclosed in FIG. 6 and FIG. 7 above.

Reference Signs List 1: Polishing device 2: Object to be polished 3: Polishing pad 3A: Polishing surface 3B: Window for detecting end point 3Ba: Bulging portion 3C: Polishing layer 3Ca: Through hole 3Cb: Recess L1: Inspection light

Claims (3)

A polishing pad comprising: a polishing layer having a polishing surface for polishing an object to be polished; and an end point detection window provided in a through hole of the polishing layer and allowing an inspection light and a reflected light from the object to pass therethrough,
a plurality of protrusions are formed on the side of the end point detection window in a direction perpendicular to the polishing surface;
a plurality of recesses that engage with the protrusions of the end point detection window are formed on an inner peripheral surface of the through hole of the polishing layer;
The plurality of protrusions and recesses are engaged without gaps without using adhesive,
a groove for holding and/or discharging a slurry is formed on the polishing surface of the polishing layer, and at least one protrusion and a recess are provided in a state of engagement below the height of a bottom of the groove;
Furthermore, the pitch of the convex portions is 0.2 to 0.5 mm,
The polishing pad is characterized in that the height of the convex portions is 0.15 to 0.5 mm . 2. The polishing pad according to claim 1, wherein the convex portion is a bulge formed on the side of the end point detection window, and the concave portion is a concave portion formed on the inner surface of the through hole of the polishing layer. 2. The polishing pad according to claim 1 , wherein the convex portion is a male thread and the concave portion is a female thread.

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