JP7653784B2 - Polishing Pad - Google Patents

Description

The present invention relates to a polishing pad.

In mirror polishing of workpieces such as silicon wafers used as semiconductor substrates, urethane-based polishing pads made of polyurethane resin foam are widely used.

In recent years, there has been a demand to improve the flatness of the workpiece to be polished in order to increase the yield of semiconductor chip products. In particular, there is an increasing demand for flatness in the outer periphery of the workpiece to be polished. In order to improve such flatness, it is believed that it is effective to use a harder urethane-based polishing pad.

In addition, in the past, in urethane-based polishing pads, in order to improve polishing quality such as the polishing rate, hydrophilicity was increased by introducing hydrophilic groups into the urethane prepolymer or by reacting the urethane prepolymer with a compound having a hydrophilic group, thereby improving compatibility with the slurry (for example, Patent Documents 1 to 4).

JP 2019-034385 A JP 2018-043342 A JP 2016-215368 A JP 2003-128910 A

However, simply increasing the hardness of the polishing pad will wear down the workpiece and prevent an appropriate surface condition from being obtained, making it impossible to improve the flatness of the outer periphery of the workpiece. Furthermore, when the polishing pad is made hydrophilic using conventional methods, the polishing pad becomes soft when it comes into contact with water, reducing its hardness, which may reduce the flatness of the workpiece.

In view of the current situation, the present invention aims to provide a polishing pad that has excellent hydrophilicity and can improve the peripheral flatness of the object being polished.

The polishing pad according to the present invention is a polishing pad having a polyurethane resin foam containing a polyurethane resin, and has a polishing surface, the polishing surface being composed of the surface of the polyurethane resin foam, and the polyurethane resin foam contains an aqueous phase solution dispersed in the polyurethane resin.

In this polishing pad, the polyurethane resin foam contains an aqueous phase solution dispersed in the polyurethane resin, which suppresses softening when it comes into contact with water while enhancing hydrophilicity. This improves the compatibility between the polishing pad and the slurry, improving the slurry retention on the pad surface. As a result, stress on the outer periphery of the workpiece to be polished can be alleviated, and the outer periphery flatness can be improved.

As described above, the present invention can provide a polishing pad that has excellent hydrophilicity and can increase the peripheral flatness of the object being polished.

One embodiment of the present invention is described below.

The polishing pad according to this embodiment is a polishing pad having a polyurethane resin foam containing a polyurethane resin. The polishing pad has a polishing surface, which is formed by the surface of the polyurethane resin foam.

The polyurethane resin foam contains an aqueous solution dispersed in the polyurethane resin. An aqueous solution is a liquid that does not gel, separate, or thicken when mixed with water in a 1:1 ratio. The aqueous solution is dispersed in the polyurethane resin in a form that does not react with the isocyanate compound or active hydrogen compound described below.

Examples of the aqueous phase solution include alcohol-based solutions such as diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, and polyethylene glycol with a molecular weight of 600 or less; and amine-based solutions such as ethylenediamine and 1,3-propanediamine. Among these, from the viewpoint of improving hydrophilicity, it is preferable that the aqueous phase solution is at least one selected from the group consisting of diethylene glycol, polyethylene glycol with a molecular weight of 600 or less, and ethylenediamine.

From the viewpoint of improving hydrophilicity, it is preferable that the polyurethane resin foam does not have an aqueous non-phase solution dispersed therein. An aqueous non-phase solution is a liquid that gels, separates, or thickens when mixed with water in a 1:1 ratio. Examples of aqueous non-phase solutions include foam stabilizers such as silicone surfactants, fluorine surfactants, and ionic surfactants; and antifoamers such as silicone surfactants and acetylene surfactants.

The polyurethane resin comprises a first constituent unit of a compound containing active hydrogen (hereinafter also referred to as an "active hydrogen compound") and a second constituent unit of a compound containing an isocyanate group (hereinafter also referred to as an "isocyanate compound").

The polyurethane resin has a structure in which an active hydrogen compound and an isocyanate compound are bonded together, and the first structural unit of the active hydrogen compound and the second structural unit of the isocyanate compound are bonded together through urethane bonds, repeating alternately.

The active hydrogen compound is an organic compound having an active hydrogen group in the molecule that can react with an isocyanate group. Specific examples of the active hydrogen group include functional groups such as a hydroxyl group, a primary amino group, a secondary amino group, and a thiol group. The active hydrogen compound may have only one type of functional group in the molecule, or may have multiple types of functional groups.

Examples of the active hydrogen compound include polyol compounds having multiple hydroxyl groups in the molecule, and polyamine compounds having multiple primary amino groups or secondary amino groups in the molecule.

Examples of the polyol compound include polyol monomers and polyol polymers.

Examples of the polyol monomer include linear aliphatic glycols such as 1,4-benzenedimethanol, 1,4-bis(2-hydroxyethoxy)benzene, ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, and 1,9-nonanediol; branched aliphatic glycols such as neopentyl glycol, 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, and 2-methyl-1,8-octanediol; alicyclic diols such as 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and water-added bisphenol A; and polyfunctional polyols such as glycerin, trimethylolpropane, tributyrolpropane, pentaerythritol, and sorbitol.

The polyol monomer is preferably ethylene glycol or diethylene glycol, from the viewpoints that it is likely to have higher strength during reaction, that it is likely to have higher rigidity in the polishing pad having the produced polyurethane resin foam, and that it is relatively inexpensive.

Examples of the polyol polymer include polyester polyol, polyester polycarbonate polyol, polyether polyol, polycarbonate polyol, etc. In addition, examples of the polyol polymer include multifunctional polyol polymers having three or more hydroxyl groups in the molecule.

Examples of the polyester polyol include polyethylene adipate glycol, polybutylene adipate glycol, polycaprolactone polyol, polyhexamethylene adipate glycol, etc.

The polyester polycarbonate polyol may be, for example, a reaction product of a polyester glycol, such as polycaprolactone polyol, with an alkylene carbonate. Also included is a reaction product obtained by reacting ethylene carbonate with a polyhydric alcohol, and then further reacting the resulting reaction mixture with an organic dicarboxylic acid.

Examples of the polyether polyol include polytetramethylene ether glycol (PTMG), polypropylene glycol (PPG), polyethylene glycol (PEG), and ethylene oxide-added polypropylene polyol.

The polycarbonate polyols include reaction products of diols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, or polytetramethylene ether glycol with phosgene, diallyl carbonate (e.g., diphenyl carbonate), or cyclic carbonate (e.g., propylene carbonate).

Other examples of the polyol compound include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, and polyethylene glycol with a molecular weight of 400 or less.

The polyamine compounds include 4,4'-methylenebis(2-chloroaniline) (MOCA), 4,4'-methylenedianiline, trimethylene Bis(4-aminobenzoate), 2-methyl 4,6-bis(methylthio)benzene-1,3-diamine, 2-methyl 4,6-bis(methylthio)-1,5-benzenediamine, 2,6-dichloro-p-phenylenediamine, 4,4'-methylenebis(2,3-dichloroaniline), 3,5-bis(methylthio)-2,4-toluenediamine, 3,5-bis(methylthio)-2,6-toluenediamine, 3,5-diethyltoluene-2,4-diamine, 3,5-diethyltoluene-2,6-diamine, trimethylene glycol-di-p-aminobenzoate, 1,2-bis(2-aminophenylthio)ethane, 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, etc.

Examples of the isocyanate compound include polyisocyanates and urethane prepolymers.

Examples of the polyisocyanate include aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates.

Examples of the aromatic diisocyanate include tolylene diisocyanate (TDI), 1,5-naphthalene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, and 1,4-phenylene diisocyanate. Examples of the aromatic diisocyanate include diphenylmethane diisocyanate (MDI) and modified products of diphenylmethane diisocyanate (MDI).

Examples of modified diphenylmethane diisocyanate (MDI) include carbodiimide modified, urethane modified, allophanate modified, urea modified, biuret modified, isocyanurate modified, and oxazolidone modified. Specific examples of such modified products include carbodiimide-modified diphenylmethane diisocyanate (carbodiimide-modified MDI).

Examples of the aliphatic diisocyanate include ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate (HDI).

Examples of the alicyclic diisocyanate include 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, norbornane diisocyanate, and methylenebis(4,1-cyclohexylene) diisocyanate.

The urethane prepolymer is a polymer formed by combining a polyol and a polyisocyanate, and has an isocyanate group as a terminal group.

From the viewpoint of increasing the peripheral flatness of the polished object, it is preferable that the isocyanate compound of the polyurethane resin does not contain a hydrophilic group, and it is also preferable that the isocyanate compound does not react with a compound having a hydrophilic group. Examples of hydrophilic groups include an ethylene oxide group, a propylene oxide group, and an ethylene propylene oxide group.

As one aspect of the polishing pad according to this embodiment, the polyurethane resin preferably comprises a first constituent unit of a polyamine compound and a second constituent unit of a urethane prepolymer. That is, the polyurethane resin foam is preferably a cured product obtained by curing a curable resin composition containing a urethane prepolymer and a polyamine compound. In this aspect, the aqueous solution is dispersed in the polyurethane resin in a form that does not react with the urethane prepolymer and the polyamine compound. In addition, the urethane prepolymer preferably does not contain a hydrophilic group from the viewpoint of increasing the peripheral flatness of the polished object.

In the above embodiment, the amount of the aqueous phase solution is preferably 0.1 to 10.0 parts by weight, more preferably 0.1 to 5.0 parts by weight, even more preferably 0.5 to 3.0 parts by weight, and particularly preferably 1.0 to 2.0 parts by weight, relative to 100 parts by weight of the urethane prepolymer.

The amount of the aqueous non-phase solution is preferably 1.0 part by weight or less, more preferably 0.5 part by weight or less, per 100 parts by weight of the urethane prepolymer, and even more preferably does not contain any aqueous non-phase solution.

The polishing pad according to this embodiment is configured as described above. Next, we will explain an example of a method for manufacturing the polishing pad according to this embodiment.

The polishing pad according to this embodiment can be manufactured, for example, by the prepolymer method. Specifically, a urethane prepolymer having an isocyanate group as a terminal group and water as a foaming agent are mixed to obtain a dispersion, and an active hydrogen compound as a curing agent, an aqueous phase solution, and a catalyst are added and mixed to the dispersion and polymerized to obtain a polishing pad with a polyurethane resin foam.

The R value in a state where the aqueous phase solution is not contained is preferably designed to be 1.0 or more, and more preferably 1.05 or more. The R value in a state where the aqueous phase solution is contained is preferably designed to be 1.05 or more, and more preferably 1.1 or more. The R value is a value represented by the following formula (1).
R value = (number of moles of NH2 _groups + number of moles of OH groups) / number of moles of NCO (1)

Examples of objects that can be polished with the polishing pad of this embodiment include silicon wafers, optical materials, semiconductor devices, hard disks, glass plates, etc.

The polishing pad according to this embodiment is configured as described above and has the following advantages:

That is, the polishing pad according to this embodiment is a polishing pad equipped with a polyurethane resin foam containing a polyurethane resin, and has a polishing surface, the polishing surface being composed of the surface of the polyurethane resin foam, and the polyurethane resin foam contains an aqueous phase solution dispersed in the polyurethane resin, thereby suppressing softening upon contact with water and enhancing hydrophilicity. This improves the compatibility between the polishing pad and the slurry, and improves the slurry retention on the pad surface. As a result, stress on the outer periphery of the workpiece to be polished can be alleviated, and the outer periphery flatness can be improved.

The polishing pad according to the present invention is not limited to the above embodiment. The polishing pad according to the present invention is also not limited by the above-mentioned effects. The polishing pad according to the present invention can be modified in various ways without departing from the gist of the present invention.

Next, the present invention will be explained in more detail with reference to examples and comparative examples.

(Examples 1 to 4)
The TDI-based urethane prepolymer and water as a foaming agent were mixed in a mixing tank at 100°C with an agitator blade to obtain a dispersion in which air was dispersed as bubbles.Then, the dispersion, MOCA as a curing agent, a tertiary amine catalyst as a catalyst, and an aqueous phase solution were mixed in the mixing tank with an agitator blade to polymerize the prepolymer, thereby obtaining a polishing pad as a polyurethane resin foam.The amount of each component was adjusted so that the R value shown in Table 1 was obtained.The amount of the aqueous phase solution to 100 parts by weight of the urethane prepolymer is shown in Table 1.

(Comparative Example 1)
A polishing pad was obtained in the same manner as in each of the Examples, except that the aqueous phase solution was not mixed and a foam stabilizer was added to the dispersion. The amount of foam stabilizer added per 100 parts by weight of the urethane prepolymer is shown in Table 1.

(Comparative Example 2)
A polishing pad was obtained in the same manner as in each of the Examples, except that the aqueous phase solution was not mixed.

Details of the components shown in Table 1 are given below.
Foam stabilizer: Silicone surfactant DEG: Diethylene glycol PEG600: Polyethylene glycol (molecular weight 600)

(Polishing test)
Using the polishing pads of each of the Examples and Comparative Examples, polishing of an object to be polished was carried out under the following polishing conditions.
Polished object: Etched wafer (thickness: about 790 μm)
Polishing machine: DMS 20B-5P-4D, manufactured by Speed FAM Slurry flow rate: 5 L/min
Slurry type: NP6610 diluted with water (NP6610:water = 1:30 (volume ratio))
Evaluation machine: Nanometro 300TT-A (Kuroda Precision Industries, Ltd.)

The peripheral flatness is measured using a Nanometro 300TT-A. Specifically, first the PV value of the average data string of the radial data strings in the specified range of the outer periphery is calculated. The PV value is calculated for the data string after best fitting within the analysis range of the target radial data string. After best fitting within the section, the farthest value between the distance from the reference line to the peak and the distance to the valley is used to calculate the peripheral flatness, with signs above the reference line designated as "+" and signs below as "-". The results are shown in Table 1.

The polishing rate was calculated by dividing the thickness reduction by the polishing time. The measurement results are shown in Table 1. The polishing rate is a relative value when the polishing rate of Comparative Example 1 is set to 1.0.

As can be seen from the results in Table 1, the polishing pads of the examples that satisfy all of the constituent requirements of the present invention can increase the peripheral flatness of the workpiece by containing an aqueous phase solution. In addition, since the polishing rate is good, it can be said that the polishing pads have excellent hydrophilicity.

On the other hand, the polishing pads of the comparative examples that do not contain an aqueous phase solution have a good polishing rate but are unable to improve the peripheral flatness of the workpiece.

Claims (3)

A polishing pad comprising a polyurethane resin foam containing a polyurethane resin,
having a polished surface,
the polishing surface is formed from the surface of the polyurethane resin foam,
The polyurethane resin foam includes an aqueous phase solution dispersed in the polyurethane resin,
A polishing pad, wherein the aqueous phase solution is at least one selected from the group consisting of diethylene glycol, polyethylene glycol having a molecular weight of 600 or less, and ethylenediamine . 2. The polishing pad according to claim 1 , wherein the polyurethane resin foam is a cured product obtained by curing a curable resin composition containing a urethane prepolymer and a polyamine compound. 3. The polishing pad according to claim 2 , wherein the amount of the aqueous solution is 0.1 to 10.0 parts by weight based on 100 parts by weight of the urethane prepolymer.