JP4189963B2 - Polishing pad - Google Patents

Description

表１の結果より、別々に合成した疎水性プレポリマー（Ａ）と親水性プレポリマー（Ｂ）を併用することにより、平坦性、面内均一性、研磨速度が良好であり、研磨速度の変化が少なく、さらに寿命特性（寿命基準：研磨速度安定性の値が１０％以内）に優れる研磨パッドを製造することができる。上記２種のプレポリマーを併用しない場合には、上記いずれかの研磨特性が劣る。
【図面の簡単な説明】
【図１】ＣＭＰ研磨で使用する研磨装置の一例を示す概略構成図
【符号の説明】
１：研磨パッド（研磨層）
２：研磨定盤
３：研磨剤（スラリー）
４：被研磨材（半導体ウエハ）
５：支持台（ポリシングヘッド）
６、７：回転軸[0001]
BACKGROUND OF THE INVENTION
The present invention stabilizes flattening of optical materials such as lenses and reflecting mirrors, silicon wafers, glass substrates for hard disks, aluminum substrates, and materials that require high surface flatness such as general metal polishing, In addition, the present invention relates to a polishing pad that can be performed with high polishing efficiency. The polishing pad of the present invention is particularly suitable for a step of planarizing a silicon wafer and a device having an oxide layer, a metal layer, etc. formed thereon, before further laminating and forming these oxide layers and metal layers. Used for.
[0002]
[Prior art]
A typical material that requires high surface flatness is a single crystal silicon disk called a silicon wafer for manufacturing a semiconductor integrated circuit (IC, LSI). Silicon wafers have a highly accurate surface in each process of stacking and forming oxide layers and metal layers in order to form reliable semiconductor junctions of various thin films used for circuit formation in IC, LSI and other manufacturing processes. It is required to finish flat. In such a polishing finishing process, a polishing pad is generally fixed to a rotatable support disk called a platen, and a workpiece such as a semiconductor wafer is fixed to a polishing head. A polishing operation is performed by generating a relative speed between the platen and the polishing head by both movements, and continuously supplying a polishing slurry containing abrasive grains onto the polishing pad.
[0003]
The polishing characteristics of the polishing pad are required to be excellent in the flatness (planarity) and in-plane uniformity of the object to be polished and to have a high polishing rate. The flatness and in-plane uniformity of the object to be polished can be improved to some extent by increasing the elastic modulus of the polishing layer. The polishing rate can be improved by using a foam containing bubbles and increasing the amount of slurry retained.
[0004]
Examples of a method for increasing the amount of slurry retained include a method for making the polishing pad itself hydrophilic. Specifically, (1) a method for introducing a hydrophilic group such as a hydroxyl group into a matrix material, and (2) a matrix. The method of mixing a material and a hydrophilic substance is mentioned. For example, a polishing pad composition containing (A) a crosslinked elastomer and (B) a substance having a functional group such as a hydroxyl group is disclosed (Patent Document 1). Further, a polishing tool is disclosed in which a hydrophilic substance is further added to a material constituting the polishing tool or a hydrophilic group is added (modified) (Patent Document 2). Further, a polishing pad made of a thermosetting polymer matrix resin containing a sheet that is hydrophilic and substantially insoluble in water is disclosed (Patent Document 3). Furthermore, a polishing pad made of a polyurethane composition containing a urethane resin copolymerized with a compound having a hydrophilic group and containing a hydrophilic agent is disclosed (Patent Document 4).
[0005]
However, in the method (1), when the matrix material is polyurethane, a hydrophilic group containing active hydrogen such as a hydroxyl group reacts with an isocyanate group during the synthesis of the polyurethane, and as a result, an unreacted polyol component remains in the material. There is a fear. And since this residual polyol component brings about a plastic effect, it exists in the tendency for the physical property fall of a polishing pad to occur. Further, in the method (2), it is difficult to uniformly mix the hydrophilic substance into the matrix material, and a polishing pad having uniform physical properties cannot be obtained.
[0006]
On the other hand, if the polishing rate fluctuates immediately after use until the end of use, the polishing conditions must be adjusted, and there is a problem that the polishing efficiency is poor.
[0007]
For example, for the purpose of providing a non-foamed urethane abrasive capable of efficiently polishing a semiconductor wafer and having excellent flatness, it comprises an isocyanate-terminated urethane prepolymer and an active hydrogen-containing compound, and the isocyanate-terminated urethane prepolymer is a polyisocyanate. An abrasive comprising an abrasive composition obtained by using an aromatic diisocyanate as a low molecular polyol in a polyol component composed of a high molecular polyol and a low molecular polyol, using diethylene glycol, 1,3-butylene glycol, etc. It is disclosed (Patent Document 5).
[0008]
Further, for the purpose of imparting dressing properties to the polishing cloth itself and extending the polishing life, a polishing cloth is disclosed which is made of a polyurethane composition and has a wear amount of 150 to 350 mg according to a Taber abrasion test (Patent Document). 6).
[0009]
[Patent Document 1]
JP 2002-134445 A
[Patent Document 2]
JP 2003-11066 A
[Patent Document 3]
JP 2002-59358 A
[Patent Document 4]
JP 2003-128910 A
[Patent Document 5]
JP 2000-17252 A
[Patent Document 6]
JP 2001-277101 A
[Problems to be solved by the invention]
However, the abrasive described in Patent Document 5 is made of non-foamed urethane, and such a non-foamed abrasive has a low polishing rate, so that grooves are formed on the polished surface. It is very difficult to stabilize the polishing rate due to the local presence of. Further, the polishing cloth described in Patent Document 6 is easy to wear and has low hardness (because the bubbles are not uniform and the bubble diameter is large), so the flatness and in-plane uniformity are not sufficient, and the polishing rate changes. Is inevitable.
[0010]
An object of the present invention is to provide a polishing pad having good flatness, in-plane uniformity, and polishing rate, little change in polishing rate, and excellent life characteristics. Moreover, it aims at providing the manufacturing method of the semiconductor device using this polishing pad.
[0011]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by the polishing pad shown below, and have completed the present invention.
[0012]
  That is, the polishing pad of the present invention has a polishing layer made of a polyurethane resin foam having fine bubbles, the polyurethane resin foam,Selected from the group consisting of hydroxy-terminated polyester polyols, polycarbonate polyols, polyester polycarbonate polyols, polyether polyols, polyether polycarbonate polyols, polyester amides, phenol resin polyols, epoxy polyols, polybutadiene polyols, and polyisoprene polyols, and ethylene oxide units ( -CH ₂ CH ₂ Number average molecular weight of 500 or more without O-)Hydrophobic isocyanate-terminated prepolymer (A) comprising a hydrophobic high molecular weight polyol component and an isocyanate component as raw material components, an ethylene oxide unit (-CH₂CH₂O-)25% by weight or moreHaveNumber average molecular weight of 500 or moreIt comprises a hydrophilic isocyanate-terminated prepolymer (B) comprising a hydrophilic high molecular weight polyol component and an isocyanate component as raw material components, and a chain extender as raw material components.
[0013]
The polishing pad has good flatness, in-plane uniformity, polishing rate, little change in polishing rate, and excellent life characteristics. The reason why a polishing pad having excellent polishing characteristics can be obtained by adopting the production method is not clear, but is considered as follows.
[0014]
Usually, a polyurethane resin foam for a polishing pad is prepared by reacting all high-molecular-weight polyol components, low-molecular-weight polyol components, and isocyanate components at one time to synthesize one type of isocyanate-terminated prepolymer. It is synthesized by reacting a terminal prepolymer with a curing agent (chain extender).
[0015]
However, since each high molecular weight polyol and each low molecular weight polyol have different reactivity, it is not possible to synthesize an isocyanate-terminated prepolymer having a uniform structure, resulting in a heterogeneous structure. And it is thought that when a polyurethane resin foam is produced using an isocyanate-terminated prepolymer having a heterogeneous structure, polishing characteristics and polishing rate stability are lowered.
[0016]
In other words, since the reactivity of the hydrophilic high molecular weight polyol and the hydrophobic high molecular weight polyol having the same molecular weight is lower than that of the hydrophilic polyol, the isocyanate formed mainly by the reaction of the hydrophilic high molecular weight polyol. The terminal prepolymer has a low molecular weight and moves to the surface of the polishing pad (polishing layer) due to the bleed phenomenon. However, it is considered that when the surface of the polishing pad (polishing layer) is gradually scraped, the polishing rate decreases due to an increase in the hydrophobic component, and the polishing rate stability and the like decrease.
[0017]
On the other hand, the polishing pad of the present invention uses separately synthesized hydrophobic isocyanate-terminated prepolymer (A) and hydrophilic isocyanate-terminated prepolymer (B). The hydrophilic isocyanate-terminated prepolymer (B) has a sufficiently high molecular weight equivalent to the hydrophobic isocyanate-terminated prepolymer (A). By using both the prepolymers, it is considered that a hydrophilic portion and a hydrophobic portion can be suppressed from being generated in the polishing pad (polishing layer), thereby improving the polishing rate stability and the like.
[0018]
In the present invention, the polyurethane resin foam preferably contains a silicon-based nonionic surfactant having no hydroxyl group in an amount of 0.05 wt% to less than 5 wt%, more preferably 0.5 to 4 wt%. is there. When the amount of the silicon-based nonionic surfactant is less than 0.05% by weight, a fine-bubble foam tends to be not obtained. On the other hand, when the content is 5% by weight or more, the number of bubbles in the foam is too large, and it is difficult to obtain a polyurethane resin foam having high hardness.
[0019]
  In the present invention, the prepolymer (A) and / or (B) isLess than 500 molecular weightIt is preferable to contain a low molecular weight polyol component as a raw material component.
[0020]
Moreover, in this invention, the average hydroxyl value of all the polyol components which are the raw material components of the said prepolymers (A) and (B) is 560-580 (mgKOH / g), and the ethylene oxide unit in the said all polyol components (-CH₂ CH₂ The content of O-) is preferably 25 to 50% by weight.
[0021]
The average hydroxyl value is more preferably 565 to 575 (mg KOH / g). When the average hydroxyl value is less than 560, the physical properties of the polyurethane resin foam tend to decrease, and when it exceeds 580, the reactivity with the chain extender becomes too high and the moldability tends to deteriorate. . In addition, the detailed calculation method of an average hydroxyl value is based on description of an Example.
[0022]
Further, the content of ethylene oxide units in the total polyol component is more preferably 30 to 50% by weight. When the content of ethylene oxide units is less than 25% by weight, the polishing rate tends to decrease because the hydrophilicity of the polishing pad is not sufficient. On the other hand, when the content of the ethylene oxide unit exceeds 50% by weight, the hydrophilicity of the polishing pad becomes too high to absorb moisture, thereby reducing the elastic modulus, and the flatness and uniform in-plane of the object to be polished. Tend to decrease.
[0023]
In this invention, it is preferable that the isocyanate component which is a raw material component of the said prepolymer (A) and / or (B) is aromatic diisocyanate and alicyclic diisocyanate. The aromatic diisocyanate is preferably toluene diisocyanate, and the alicyclic diisocyanate is preferably dicyclohexylmethane diisocyanate. The polishing characteristics of the polishing pad can be improved by using the two kinds of diisocyanates as at least one isocyanate component of both prepolymers. Further, since the reaction rate with the chain extender can be controlled within a suitable range, it is preferable not only from the viewpoint of work but also from the viewpoint of moldability of the polyurethane resin foam. In particular, it is preferable to use both diisocyanates in a prepolymer having a higher mixing ratio of both prepolymers to be mixed in the production of a polishing pad. Thereby, the effect becomes remarkable.
[0024]
The present invention also relates to a semiconductor device manufacturing method including a step of polishing a surface of a semiconductor wafer using the polishing pad.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
The polishing pad of the present invention has a polishing layer made of a polyurethane resin foam having fine bubbles. The polyurethane resin foam serves as a polishing layer of a polishing pad. The polishing pad of the present invention may be a polishing layer alone or a laminate of a polishing layer and another layer (for example, a cushion layer).
[0026]
The polyurethane resin foam comprises a hydrophobic isocyanate-terminated prepolymer (A) (hereinafter referred to as a hydrophobic prepolymer) comprising a hydrophobic high molecular weight polyol component having no hydrophilic group other than a hydroxyl group and an isocyanate component as raw material components. (Also referred to as (A)), ethylene oxide unit (-CH₂ CH₂ Hydrophilic isocyanate-terminated prepolymer (B) (hereinafter, also referred to as hydrophilic prepolymer (B)) comprising a hydrophilic high molecular weight polyol component having an O-) and an isocyanate component as raw material components, and a chain extender As a raw material component.
[0027]
The hydrophobic prepolymer (A) and the hydrophilic prepolymer (B) are synthesized separately.
[0028]
Hydrophobic prepolymer (A) is manufactured from the raw material containing the hydrophobic high molecular weight polyol component and isocyanate component which do not have hydrophilic groups other than a hydroxyl group.
[0029]
The hydrophobic high molecular weight polyol component is not particularly limited as long as it is a high molecular weight (number average molecular weight of 500 or more) polyol that does not contain a hydrophilic group other than a hydroxyl group that reacts with an isocyanate group. The hydrophilic group other than the initial hydroxyl group is generally a functional group or salt containing an element such as oxygen, nitrogen, or sulfur.₂ , -CONH₂ , -NHCONH₂ , -SH, -SO_Three H, -OSO_Three H,-(CH₂ CH₂ O)_n -, -COOH and other functional groups, -SO_Three M (M: alkali metal), -OSO_Three M, -COOM, -NR_Three And salts such as X (R: alkyl group, X: halogen).
[0030]
Examples of such hydrophobic high molecular weight polyols include hydroxy-terminated polyester polyols, polycarbonate polyols, polyester polycarbonate polyols, polyether polyols, polyether polycarbonate polyols, polyester amides, phenol resin polyols, epoxy polyols, polybutadiene polyols, and polyisoprene polyols. Is mentioned.
[0031]
Examples of the polyester polyol include polypropylene adipate, polybutylene adipate, polyhexamethylene adipate, polycaprolactone polyol and the like.
[0032]
Examples of the polyether polyol include polyhexamethylene glycol (PHMG), polytetramethylene glycol (PTMG), and polypropylene glycol (PPG).
[0033]
Examples of the polyether polycarbonate polyol include diols such as 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, polypropylene glycol and / or polytetramethylene glycol, phosgene, and diallyl. Reaction products with carbonates (eg diphenyl carbonate) or cyclic carbonates (eg propylene carbonate) are mentioned.
[0034]
Examples of the polyester polycarbonate polyol include a reaction product of a polyester glycol such as polycaprolactone polyol and an alkylene carbonate, and an ethylene carbonate reacted with a polyvalent alcohol. Then, a product obtained by reacting the obtained reaction mixture with an organic dicarboxylic acid is exemplified.
[0035]
The said polyol may be used independently and may use 2 or more types together. If necessary, trifunctional or higher functional components may be used in combination.
[0036]
The number average molecular weight of the hydrophobic high molecular weight polyol component needs to be 500 or more from the viewpoint of the elastic characteristics of the obtained polyurethane resin foam. The number average molecular weight is preferably 500 to 5,000. When the number average molecular weight of the high molecular weight polyol component is less than 500, the polyurethane resin foam obtained by using the component does not have sufficient elastic properties and becomes brittle polymer and easily wears. From the point of view, it is not preferable.
[0037]
As the isocyanate component, a known compound in the field of polyurethane can be used without particular limitation. As the isocyanate component, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, Aromatic diisocyanates such as p-phenylene diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, etc. Aliphatic diisocyanates, 1,4-cyclohexane diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, isophor Diisocyanate, alicyclic diisocyanates such as norbornane diisocyanate and the like. These may be used alone or in combination of two or more.
[0038]
As the isocyanate component, a trifunctional or higher polyfunctional polyisocyanate compound can be used in addition to the diisocyanate compound. As a polyfunctional isocyanate compound, a series of diisocyanate adduct compounds are commercially available as Desmodur-N (manufactured by Bayer) or trade name Duranate (manufactured by Asahi Kasei Kogyo Co., Ltd.).
[0039]
Further, as a constituent of the hydrophobic prepolymer (A), in addition to the above-described hydrophobic high molecular weight polyol component, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis (2-hydroxyethoxy) benzene, tri Methylolpropane, glycerin, 1,2,6-hexanetriol, pentaerythritol, tetramethylolcyclohexane, methyl glucoside, sorbitol, mannitol, dulcitol, sucrose, 2,2,6,6-tetrakis (hydroxymethyl) cyclohex Nord, low molecular weight polyol component, such as triethanolamine, ethylenediamine, tolylenediamine, diphenylmethane diamine, can be used together low molecular weight polyamine component, such as diethylenetriamine, and the like. These low molecular weight polyols and low molecular weight polyamines may be used alone or in combination of two or more. The blending amount of the low molecular weight polyol or the low molecular weight polyamine is not particularly limited, and is appropriately determined depending on the properties required for the polishing pad (polishing layer) to be produced. The (number average) molecular weight of the low molecular weight polyol component or low molecular weight polyamine component is less than 500, preferably 250 or less.
[0040]
Also, ethylene oxide units (—CH₂ CH₂ When a compound having O-) (for example, ethylene glycol, diethylene glycol, etc.) is used, the ratio of ethylene oxide units in all polyol components constituting the hydrophobic prepolymer (A) is less than 25% by weight. The compound is preferably blended, more preferably the compound is blended so as to be less than 20% by weight.
[0041]
The hydrophobic prepolymer (A) uses the polyol component and the isocyanate component and the isocyanate group (NCO) and active hydrogen (H^* ) Equivalent ratio (NCO / H^* ) Is 1.2 to 5.0, preferably 1.6 to 2.6. If the ratio is less than 1.2, the prepolymer tends to be solidified or gelled with a high molecular weight during synthesis. On the other hand, when it exceeds 5.0, a large amount of unreacted isocyanate remains, so that the reaction with the chain extender is accelerated and the molding processability of the polyurethane resin foam tends to deteriorate.
[0042]
On the other hand, the hydrophilic prepolymer (B) is composed of ethylene oxide units (—CH₂ CH₂ It is produced from a raw material containing a hydrophilic high molecular weight polyol component having O-) and an isocyanate component.
[0043]
The hydrophilic high molecular weight polyol component is not particularly limited as long as it is a polyol having an ethylene oxide unit as a hydrophilic group and a high molecular weight (number average molecular weight of 500 or more). In addition, as another hydrophilic group, —NH₂ , -CONH₂ , -NHCONH₂ , -SH, -SO_Three H, -OSO_Three Functional groups such as H and -COOH, -SO_Three M (M: alkali metal), -OSO_Three M, -COOM, -NR_Three A salt such as X (R: alkyl group, X: halogen) may be contained.
[0044]
Examples of the hydrophilic high molecular weight polyol having an ethylene oxide unit include polyether polyol and polyether polycarbonate polyol.
[0045]
Examples of the polyether polyol include polyethylene glycol (PEG), polyols obtained by copolymerizing ethylene glycol or diethylene glycol and propylene oxide, butylene oxide, styrene oxide, or the like.
[0046]
Examples of the polyether polycarbonate polyol include reaction products of diols such as ethylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol with phosgene, diallyl carbonate (for example, diphenyl carbonate) or cyclic carbonate (for example, propylene carbonate). It is done.
[0047]
The said polyol may be used independently and may use 2 or more types together. If necessary, trifunctional or higher functional components may be used in combination.
[0048]
The number average molecular weight of the hydrophilic high molecular weight polyol component needs to be 500 or more for the same reason as described above. The number average molecular weight is preferably 500 to 5,000.
[0049]
As the isocyanate component, a known compound in the field of polyurethane can be used without particular limitation. Examples of the isocyanate component include those exemplified above.
[0050]
Moreover, as a structural component of a hydrophilic prepolymer (B), in addition to the hydrophilic high molecular weight polyol component mentioned above, the said low molecular weight polyol component, a low molecular weight polyamine component, etc. can be used together. These low molecular weight polyols and low molecular weight polyamines may be used alone or in combination of two or more. The blending amount of the low molecular weight polyol or the low molecular weight polyamine is not particularly limited, and is appropriately determined depending on the properties required for the polishing pad (polishing layer) to be produced.
[0051]
Moreover, it is preferable to adjust a polyol component so that the ratio of the ethylene oxide unit in all the polyol components which comprise a hydrophilic prepolymer (B) may be 25 to 100 weight%, More preferably, it is 40 to 100 weight%. is there.
[0052]
The hydrophilic prepolymer (B) uses the polyol component and the isocyanate component and the isocyanate group (NCO) and active hydrogen (H^* ) Equivalent ratio (NCO / H^* ) Is 1.2 to 5.0, preferably 1.6 to 2.6. If the ratio is less than 1.2, the prepolymer tends to be solidified or gelled with a high molecular weight during synthesis. On the other hand, when it exceeds 5.0, a large amount of unreacted isocyanate remains, so that the reaction with the chain extender is accelerated and the molding processability of the polyurethane resin foam tends to deteriorate.
[0053]
In the present invention, the average hydroxyl value of all polyol components constituting the prepolymers (A) and (B) is 560 to 580 (mg KOH / g), and the ethylene oxide units (—CH₂ CH₂ It is preferable to adjust the kind and blending ratio of the polyol component so that the content of O-) is 25 to 50% by weight.
[0054]
The polyurethane resin foam of the present invention is produced, for example, by mixing and curing a first component containing a hydrophobic prepolymer (A) and a hydrophilic prepolymer (B) and a second component containing a chain extender. can do.
[0055]
The chain extender is an organic compound having at least two active hydrogen groups and having a molecular weight of about 500 or less. Examples of the active hydrogen group include a hydroxyl group, a primary or secondary amino group, and a thiol group (SH). Specifically, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3- Aliphatic low molecular weight glycols and triols typified by methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, trimethylolpropane, etc., 1,4-bis (2-hydroxyethoxy) benzene, m-xylylene diene Aromatic diols represented by ol, etc., 4,4′-methylenebis (o-chloroaniline), 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, and other polyamines. These may be used alone or in combination of two or more.
[0056]
The blending ratio of the hydrophobic prepolymer (A) and the hydrophilic prepolymer (B) can be variously changed depending on the desired physical properties of the polishing pad to be produced, but is hydrophilic with respect to 100 parts by weight of the hydrophobic prepolymer (A). It is preferable to use 5 to 250 parts by weight of the prepolymer (B), more preferably 20 to 200 parts by weight, and particularly preferably 30 to 100 parts by weight. When the amount is less than 5 parts by weight, the polishing rate tends to decrease because the hydrophilicity of the polishing pad is not sufficient. On the other hand, when the amount exceeds 250 parts by weight, the hydrophilicity of the polishing pad becomes too high to absorb moisture, thereby lowering the elastic modulus and reducing the flatness and in-plane uniformity of the material to be polished. .
[0057]
The ratio of the prepolymer to the chain extender can be variously changed according to the molecular weight of each and the desired physical properties of the polishing pad produced therefrom. In order to obtain a polishing pad having desired polishing characteristics, the number of isocyanate groups of the prepolymer relative to the number of functional groups of the chain extender is preferably in the range of 0.95 to 1.20, more preferably 0.99 to 1.15. It is.
[0058]
Polyurethane resin can be manufactured by applying known urethanization technology such as melting method and solution method, but with regard to the polyurethane resin foam of the present invention, it is necessary to incorporate pores (bubbles) into the polyurethane resin. Further, it is preferable to manufacture by a melting method in consideration of cost, working environment and the like.
[0059]
Examples of the method for producing a polyurethane resin foam include a method of adding hollow beads, a mechanical foaming method, and a chemical foaming method.
[0060]
In particular, a mechanical foaming method using a silicone surfactant which is a copolymer of polyalkylsiloxane and polyether and does not have an active hydrogen group is preferable. As such a silicone-based surfactant, SH-192 (manufactured by Toray Dow Corning Silicon) is exemplified as a suitable compound.
[0061]
In addition, you may add stabilizers, such as antioxidant, a lubricant, a pigment, a filler, an antistatic agent, and another additive as needed.
[0062]
An example of a method for producing a fine cell type polyurethane resin foam constituting the polishing pad (polishing layer) will be described below. The manufacturing method of this polyurethane resin foam has the following processes.
[0063]
1) Foaming process for producing a cell dispersion of isocyanate-terminated prepolymer
Silicone surfactant is added to the mixture (first component) of the hydrophobic prepolymer (A) and the hydrophilic prepolymer (B), and the mixture is stirred in the presence of a non-reactive gas, and the non-reactive gas is made into fine bubbles. To obtain a cell dispersion. When the prepolymer is solid at normal temperature, it is preheated to an appropriate temperature and melted before use.
2) Curing agent (chain extender) mixing process
A chain extender (second component) is added to the above bubble dispersion, mixed and stirred to obtain a foaming reaction solution.
3) Casting process
The foaming reaction liquid is poured into a mold.
4) Curing process
The foaming reaction liquid poured into the mold is heated and reacted and cured.
[0064]
As the non-reactive gas used to form the fine bubbles, non-flammable gases are preferable, and specific examples include nitrogen, oxygen, carbon dioxide, rare gases such as helium and argon, and mixed gases thereof. In view of cost, it is most preferable to use air that has been dried to remove moisture.
[0065]
A known stirring device can be used without particular limitation as a stirring device for dispersing non-reactive gas in the form of fine bubbles and dispersed in the first component containing the silicone-based surfactant. Specifically, a homogenizer, a dissolver, 2 A shaft planetary mixer (planetary mixer) is exemplified. The shape of the stirring blade of the stirring device is not particularly limited, but it is preferable to use a whipper type stirring blade because fine bubbles can be obtained.
[0066]
In addition, it is also a preferable aspect to use a different stirring apparatus for the stirring which produces a cell dispersion in a foaming process, and the stirring which adds and mixes the chain extender in a mixing process. In particular, the stirring in the mixing step may not be stirring that forms bubbles, and it is preferable to use a stirring device that does not involve large bubbles. As such an agitator, a planetary mixer is suitable. There is no problem even if the same stirring device is used as the stirring device for the foaming step and the mixing step, and it is also preferable to adjust the stirring conditions such as adjusting the rotation speed of the stirring blade as necessary. .
[0067]
In the method for producing the polyurethane resin foam, heating and post-curing the foam reacted until the foaming reaction liquid is poured into the mold and no longer flows has the effect of improving the physical properties of the foam, Very suitable. The foam reaction solution may be poured into the mold and immediately put into a heating oven for post cure, and heat is not immediately transferred to the reaction components under such conditions, so the bubble size does not increase. . The curing reaction is preferably performed at normal pressure because the bubble shape is stable.
[0068]
In the polyurethane resin foam, a known catalyst that promotes polyurethane reaction such as tertiary amine may be used. The type and addition amount of the catalyst are selected in consideration of the flow time for pouring into a mold having a predetermined shape after the mixing step.
[0069]
Production of the polyurethane resin foam is a batch method in which each component is weighed and put into a container and stirred. Alternatively, each component and a non-reactive gas are continuously supplied to the stirring device and stirred. It may be a continuous production method in which a cell dispersion is sent out to produce a molded product.
[0070]
In addition, the prepolymer that is the raw material of the polyurethane resin foam is placed in a reaction vessel, and then a chain extender is added and stirred, and then poured into a casting mold of a predetermined size to produce a block, and the block is shaped like a bowl or a band saw. In the method of slicing using a slicer, or in the above-described casting step, a thin sheet may be used. Alternatively, the raw material resin may be dissolved and extruded from a T-die to directly obtain a sheet-like polyurethane resin foam.
[0071]
In this invention, it is preferable that the average cell diameter of the said polyurethane resin foam is 70 micrometers or less, More preferably, it is 30-60 micrometers. When deviating from this range, the planarity (flatness) of the polished material after polishing tends to decrease.
[0072]
The specific gravity of the polyurethane resin foam is 0.5 to 1.0 g / cm.^Three It is preferable that Specific gravity is 0.5g / cm^Three When the ratio is less than 1, the surface strength of the polishing layer is lowered, and the planarity of the material to be polished tends to be lowered. 1.0 g / cm^Three If it is larger, the number of bubbles on the surface of the polishing layer is reduced and the planarity is good, but the polishing rate tends to decrease.
[0073]
The hardness of the polyurethane resin foam is preferably 45 to 65 degrees as measured by an Asker D hardness meter. When the Asker D hardness is less than 45 degrees, the planarity of the material to be polished is lowered. When the Asker D hardness is more than 65 degrees, the planarity is good but the uniformity of the material to be polished is lowered. There is a tendency.
[0074]
The water absorption of the polyurethane resin (non-foamed material) produced from the raw material is preferably 1.1 to 3.5%, more preferably 1.2 to 3.0%. When the water absorption is less than 1.1%, the polishing rate tends to decrease because the hydrophilicity of the polishing pad is not sufficient. On the other hand, if the water absorption rate exceeds 3.5%, the hydrophilicity of the polishing pad becomes too high to absorb moisture, thereby lowering the elastic modulus and reducing the flatness and in-plane uniformity of the material to be polished. Tend to.
[0075]
The polishing surface of the polishing pad (polishing layer) of the present invention that is in contact with the material to be polished preferably has a surface shape that holds and renews the slurry. The polishing layer made of foam has many openings on the polishing surface and has the function of holding and renewing the slurry. However, in order to more efficiently retain the slurry and renew the slurry, the polishing layer is also polished. In order to prevent destruction of the material to be polished due to adsorption with the material, it is preferable that the polished surface has an uneven structure. The concavo-convex structure is not particularly limited as long as it is a shape that holds and renews the slurry. For example, an XY lattice groove, a concentric circular groove, a through hole, a non-penetrating hole, a polygonal column, a cylinder, a spiral groove, Examples include eccentric circular grooves, radial grooves, and combinations of these grooves. In addition, these uneven structures are generally regular, but in order to make the slurry retention and renewability desirable, the groove pitch, groove width, groove depth, etc. should be changed for each range. Is also possible.
[0076]
The method for producing the concavo-convex structure is not particularly limited. For example, a method of machine cutting using a jig such as a tool of a predetermined size, pouring a resin into a mold having a predetermined surface shape, and curing. Using a press plate having a predetermined surface shape, a method of producing a resin by pressing, a method of producing using photolithography, a method of producing using a printing technique, a carbon dioxide laser, etc. Examples include a manufacturing method using laser light.
[0077]
The thickness variation of the polishing layer is preferably 100 μm or less. When the thickness variation exceeds 100 μm, the polishing layer has a large waviness, and there are portions where the contact state with the material to be polished is different, which adversely affects the polishing characteristics. In order to eliminate the thickness variation of the polishing layer, in general, the surface of the polishing layer is dressed with a dresser in which diamond abrasive grains are electrodeposited and fused in the initial stage of polishing. As a result, the dressing time becomes longer and the production efficiency is lowered.
[0078]
Examples of a method for suppressing the variation in the thickness of the polishing layer include a method of buffing the surface of the polishing sheet sliced to a predetermined thickness. Moreover, when buffing, it is preferable to carry out stepwise with abrasives having different particle sizes.
[0079]
The polishing pad of the present invention may be a laminate of the polishing layer and a cushion sheet.
[0080]
The cushion sheet (cushion layer) supplements the characteristics of the polishing layer. The cushion sheet is necessary for achieving both planarity and uniformity in a trade-off relationship in CMP. Planarity refers to the flatness of a pattern portion when a material having fine irregularities generated during pattern formation is polished, and uniformity refers to the uniformity of the entire material to be polished. The planarity is improved by the characteristics of the polishing layer, and the uniformity is improved by the characteristics of the cushion sheet. In the polishing pad of the present invention, it is preferable to use a cushion sheet that is softer than the polishing layer.
[0081]
Examples of the cushion sheet include a fiber nonwoven fabric such as a polyester nonwoven fabric, a nylon nonwoven fabric, and an acrylic nonwoven fabric, a resin-impregnated nonwoven fabric such as a polyester nonwoven fabric impregnated with polyurethane, a polymer resin foam such as polyurethane foam and polyethylene foam, a butadiene rubber, Examples thereof include rubber resins such as isoprene rubber and photosensitive resins.
[0082]
Examples of means for attaching the polishing layer and the cushion sheet include a method of pressing the polishing layer and the cushion sheet with a double-sided tape.
[0083]
The double-sided tape has a general configuration in which adhesive layers are provided on both sides of a substrate such as a nonwoven fabric or a film. In consideration of preventing the penetration of the slurry into the cushion sheet, it is preferable to use a film for the substrate. Examples of the composition of the adhesive layer include rubber adhesives and acrylic adhesives. Considering the content of metal ions, an acrylic adhesive is preferable because the metal ion content is low. In addition, since the composition of the polishing layer and the cushion sheet may be different, the composition of each adhesive layer of the double-sided tape can be made different so that the adhesive force of each layer can be optimized.
[0084]
The polishing pad of the present invention may be provided with a double-sided tape on the surface to be bonded to the platen. As the double-sided tape, a tape having a general configuration in which an adhesive layer is provided on both surfaces of a base material can be used as described above. As a base material, a nonwoven fabric, a film, etc. are mentioned, for example. In consideration of peeling from the platen after use of the polishing pad, it is preferable to use a film for the substrate. Examples of the composition of the adhesive layer include rubber adhesives and acrylic adhesives. Considering the content of metal ions, an acrylic adhesive is preferable because the metal ion content is low.
[0085]
The semiconductor device is manufactured through a step of polishing the surface of the semiconductor wafer using the polishing pad. A semiconductor wafer is generally a laminate of a wiring metal and an oxide film on a silicon wafer. The method and apparatus for polishing the semiconductor wafer are not particularly limited. For example, as shown in FIG. 1, a polishing surface plate 2 that supports a polishing pad (polishing layer) 1 and a support table (polishing head) that supports the semiconductor wafer 4. 5 and a polishing apparatus equipped with a backing material for uniformly pressing the wafer and a supply mechanism of the abrasive 3. The polishing pad 1 is attached to the polishing surface plate 2 by attaching it with a double-sided tape, for example. The polishing surface plate 2 and the support base 5 are disposed so that the polishing pad 1 and the semiconductor wafer 4 supported on each of the polishing surface plate 2 and the support table 5 face each other, and are provided with rotating shafts 6 and 7 respectively. Further, a pressurizing mechanism for pressing the semiconductor wafer 4 against the polishing pad 1 is provided on the support base 5 side. In polishing, the semiconductor wafer 4 is pressed against the polishing pad 1 while rotating the polishing surface plate 2 and the support base 5, and polishing is performed while supplying slurry. The flow rate of the slurry, the polishing load, the polishing platen rotation speed, and the wafer rotation speed are not particularly limited and are appropriately adjusted.
[0086]
As a result, the protruding portion of the surface of the semiconductor wafer 4 is removed and polished flat. Thereafter, a semiconductor device is manufactured by dicing, bonding, packaging, or the like. The semiconductor device is used for an arithmetic processing device, a memory, and the like.
[0087]
【Example】
Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.
[0088]
[Measurement and evaluation methods]
(Measurement of number average molecular weight)
The number average molecular weight was measured by GPC (gel permeation chromatography) and converted by standard polystyrene.
GPC device: manufactured by Shimadzu Corporation, LC-10A
Column: Three columns (PLgel, 5 μm, 500 mm), (PLgel, 5 μm, 100 mm), and (PLgel, 5 μm, 50 mm) manufactured by Polymer Laboratories are used in combination.
Flow rate: 1.0 ml / min
Concentration: 1.0 g / l
Injection volume: 40 μl
Column temperature: 40 ° C
Eluent: Tetrahydrofuran
(Average hydroxyl value)
The average hydroxyl value (mgKOH / g) is calculated from the hydroxyl value of each polyol used and the molar ratio of each hydroxyl value to the polyol used.
[0089]
Hydroxyl value (mgKOH / g) = (f × [KOH] × 1000) / Mw
f: Number of hydroxyl groups
[KOH]: Molecular weight of KOH
Mw: Polyol molecular weight (number average molecular weight)
For example, the calculation method of the average hydroxyl value at the time of using 3 types of polyol (a, b, c) is shown.
[0090]
Average hydroxyl value (mgKOH / g) = (Va × Ma + Vb × Mb + Vc × Mc) / (Ma + Mb + Mc)
Va: hydroxyl value of polyol a
Vb: hydroxyl value of polyol b
Vc: hydroxyl value of polyol c
Ma: molar ratio of polyol a
Mb: molar ratio of polyol b
Mc: Mole ratio of polyol c
(Average bubble diameter measurement)
A sample obtained by cutting the produced polyurethane resin foam in parallel with a microtome cutter as thin as possible to a thickness of 1 mm or less was used as a sample for measuring the average cell diameter. The sample was fixed on a slide glass, and the total bubble diameter in an arbitrary 0.2 mm × 0.2 mm range was measured using an image processing apparatus (Image Analyzer V10, manufactured by Toyobo Co., Ltd.), and the average bubble diameter was calculated.
[0091]
(Specific gravity measurement)
This was performed according to JIS Z8807-1976. The produced polyurethane resin foam was cut into a 4 cm × 8.5 cm strip (thickness: arbitrary) and used as a sample for measuring specific gravity, and allowed to stand for 16 hours in an environment of temperature 23 ° C. ± 2 ° C. and humidity 50% ± 5%. I put it. The specific gravity was measured using a hydrometer (manufactured by Sartorius).
[0092]
(Hardness measurement)
This was performed in accordance with JIS K6253-1997. The produced polyurethane resin foam was cut into a size of 2 cm × 2 cm (thickness: arbitrary) and used as a sample for hardness measurement, and was allowed to stand for 16 hours in an environment of temperature 23 ° C. ± 2 ° C. and humidity 50% ± 5%. . At the time of measurement, the samples were overlapped to a thickness of 6 mm or more. The hardness was measured using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., Asker D type hardness meter).
[0093]
(Water absorption rate)
A non-foamed polyurethane block is produced using the materials described in Examples and Comparative Examples, and a sample having a thickness of 2 mm and 20 mm × 20 mm is cut out from the block. The sample was immersed in distilled water at 20 ° C. for 24 hours. The water absorption is calculated by the following formula.
[0094]
Water absorption (%) = [(weight after immersion) − (weight before immersion)] × 100 / (weight before immersion)
(Evaluation of polishing characteristics)
Using SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as a polishing apparatus, polishing characteristics were evaluated using the prepared polishing pad. The polishing rate was calculated from the time obtained by polishing about 0.5 μm of a 1-μm thermal oxide film formed on an 8-inch silicon wafer. An interference type film thickness measuring device (manufactured by Otsuka Electronics Co., Ltd.) was used for measuring the thickness of the oxide film. As the polishing conditions, silica slurry (SS12 Cabot) was added as a slurry at a flow rate of 150 ml / min during polishing. The polishing load was 350 g / cm 2, the polishing platen rotation number was 35 rpm, and the wafer rotation number was 30 rpm.
In the evaluation of the planarization characteristics, after depositing a thermal oxide film of 0.5 μm on an 8-inch silicon wafer and performing predetermined patterning, an oxide film of 1 μm is deposited by p-TEOS, and an initial step of 0.5 μm is formed. A wafer with a pattern was prepared, this wafer was polished under the above-mentioned conditions, and after polishing, each step was measured to evaluate the planarization characteristics.
[0095]
Two steps were measured as the flattening characteristics. One is a local step, which is a step in a pattern in which lines having a width of 270 μm are arranged in a space of 30 μm, and the step after one minute was measured. The other is the amount of scraping. In the pattern in which lines with a width of 270 μm are arranged in a space of 30 μm and the pattern in which lines with a width of 30 μm are arranged in a space of 270 μm, the level difference between the above two patterns is 2000 mm or less. The amount of scraping of the 270 μm space was measured. When the numerical value of the local step is low, it indicates that the flattening speed in a certain time is high with respect to the unevenness of the oxide film caused by the pattern dependence on the wafer. Further, when the amount of scraping of the space is small, the amount of shaving of the portion that is not desired to be shaved is small and the flatness is high.
[0096]
(Number of scratches)
Using a wafer surface inspection apparatus (WM2500) manufactured by Topcon Corporation, the number of streaks of 0.2 μm or more on the wafer was measured.
[0097]
(Polishing rate stability)
The polishing rate stability was determined by the following formula. The average polishing rate is obtained by performing polishing under the above-described polishing conditions using an 8 inch silicon wafer deposited with a thermal oxide film of 1 μm, and averaging the polishing rate from the first wafer to the 10th wafer polishing. Calculated. The maximum polishing rate is the maximum value of the polishing rate from the first wafer polishing start to the number of processed sheets (100, 300, 500, or 800), and the minimum polishing rate is 1 wafer starting polishing. It is the minimum value of the polishing rate from the eye to the same number of processed sheets.
Polishing rate stability (%) = {(maximum polishing rate−minimum polishing rate) / average polishing rate} × 100
Example 1
(Synthesis of hydrophobic isocyanate-terminated prepolymer (A))
In a separable flask, 412 parts by weight of polytetramethylene glycol (PTMG, manufactured by Mitsubishi Chemical Corporation, number average molecular weight 1018) and 40 parts by weight of diethylene glycol (DEG, manufactured by Mitsubishi Chemical Corporation) are added, and dehydration under reduced pressure for 1 to 2 hours with stirring. went. Next, nitrogen was introduced into the separable flask, and after nitrogen substitution, toluene diisocyanate (Mitsui Takeda Chemical Co., Ltd., 2,4-isomer / 2,6-isomer = 80/20 mixture: hereinafter referred to as TDI-80 and 237 parts by weight and 61 parts by weight of 4,4′-dicyclohexylmethane diisocyanate (hereinafter abbreviated as HMDI) were added. The reaction system was stirred until the reaction was completed while maintaining the temperature in the reaction system at about 70 ° C. The reaction was terminated when NCO% became almost constant (NCO% = 9.14). Thereafter, vacuum degassing was performed for about 2 hours to obtain a hydrophobic isocyanate-terminated prepolymer (A1). The content of ethylene oxide units in all polyol components was 7% by weight.
[0098]
(Synthesis of hydrophilic isocyanate-terminated prepolymer (B))
In a separable flask, 100 parts by weight of polyethylene glycol (PEG, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., number average molecular weight 1000), 32 parts by weight of polyethylene glycol (PEG, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., number average molecular weight 600), and 15 parts by weight of DEG were added. The mixture was stirred and dehydrated under reduced pressure for 1-2 hours. Next, nitrogen was introduced into the separable flask, and after nitrogen substitution, TDI-80 (103 parts by weight) was added. The reaction system was stirred until the reaction was completed while maintaining the temperature in the reaction system at about 70 ° C. The reaction was completed when NCO% became almost constant (NCO% = 9.94). Thereafter, vacuum degassing was performed for about 2 hours to obtain a hydrophilic isocyanate-terminated prepolymer (B1). The content of ethylene oxide units in all polyol components was 96% by weight.
[0099]
(Manufacture of polishing pad)
In the container, 750 parts by weight of the hydrophobic prepolymer (A1), 250 parts by weight of the hydrophilic prepolymer (B1), and 30 parts by weight of silicon-based nonionic surfactant SH-192 (2.3% by weight based on polyurethane) Were adjusted to 60 ° C. To this, 270 parts by weight of 4,4'-methylenebis (o-chloroaniline) (hereinafter abbreviated as MOCA), which had been melted at 120 ° C in advance, was vigorously stirred so as to take in bubbles. After stirring for about 1 minute, the mixed solution was put into a pan-type open mold and post-cured in an oven at 100 ° C. for 16 hours to obtain a polyurethane resin foam block. This polyurethane resin foam block had an average cell diameter of 48 μm. Moreover, the average hydroxyl value of all the polyol components which comprise a polyurethane resin foam was 569.2 (mgKOH / g), and the content rate of the EO unit in all the polyol components was 27 (wt%).
[0100]
A foam sheet is cut out from this polyurethane resin foam block using a slicer, a concentric groove is processed to produce a polishing layer, and a commercially available non-woven fabric is impregnated with polyurethane (cushion layer). A polishing pad was prepared by laminating.
[0101]
Example 2
(Synthesis of hydrophobic isocyanate-terminated prepolymer (A))
275 parts by weight of PTMG (number average molecular weight 1018) and 26 parts by weight of DEG were placed in a separable flask, and vacuum dehydration was performed for 1 to 2 hours while stirring. Next, nitrogen was introduced into the separable flask, and after nitrogen substitution, TDI-80 (158 parts by weight) and HMDI (41 parts by weight) were added. The reaction system was stirred until the reaction was completed while maintaining the temperature in the reaction system at about 70 ° C. The reaction was terminated when NCO% became almost constant (NCO% = 9.14). Thereafter, vacuum degassing was performed for about 2 hours to obtain a hydrophobic isocyanate-terminated prepolymer (A2). The content of ethylene oxide units in all polyol components was 7% by weight.
[0102]
(Synthesis of hydrophilic isocyanate-terminated prepolymer (B))
200 parts by weight of PEG (number average molecular weight 1000), 65 parts by weight of PEG (number average molecular weight 600), and 30 parts by weight of DEG were placed in a separable flask, and vacuum dehydration was performed for 1 to 2 hours with stirring. Next, nitrogen was introduced into the separable flask, and after nitrogen substitution, TDI-80 (206 parts by weight) was added. The reaction system was stirred until the reaction was completed while maintaining the temperature in the reaction system at about 70 ° C. The reaction was completed when NCO% became almost constant (NCO% = 9.94). Thereafter, vacuum degassing was performed for about 2 hours to obtain a hydrophilic isocyanate-terminated prepolymer (B2). The content of ethylene oxide units in all polyol components was 96% by weight.
[0103]
(Manufacture of polishing pad)
In a container, 500 parts by weight of the hydrophobic prepolymer (A2), 500 parts by weight of the hydrophilic prepolymer (B2), and 30 parts by weight of a silicon-based nonionic surfactant SH-192 (2.3% by weight based on polyurethane) Were adjusted to 60 ° C. To this, 276 parts by weight of MOCA previously melted at 120 ° C. was added with vigorous stirring so as to take in bubbles. After stirring for about 1 minute, the mixed solution was put into a pan-type open mold and post-cured in an oven at 100 ° C. for 16 hours to obtain a polyurethane resin foam block. This polyurethane resin foam block had an average cell diameter of 46 μm. Moreover, the average hydroxyl value of all the polyol components which comprise a polyurethane resin foam was 572.8 (mgKOH / g), and the content rate of the EO unit in all the polyol components was 48 (wt%).
[0104]
A foam sheet is cut out from this polyurethane resin foam block using a slicer, a concentric groove is processed to produce a polishing layer, and a commercially available non-woven fabric is impregnated with polyurethane (cushion layer). A polishing pad was prepared by laminating.
[0105]
Comparative Example 1
(Synthesis of isocyanate-terminated prepolymer)
In a separable flask, 412 parts by weight of PTMG (number average molecular weight 1018), 100 parts by weight of PEG (number average molecular weight 1000), 32 parts by weight of PEG (number average molecular weight 600), and 55 parts by weight of DEG are added. Performed for ~ 2 hours. Next, nitrogen was introduced into the separable flask, and after nitrogen substitution, TDI-80 (340 parts by weight) and HMDI (61 parts by weight) were added. The reaction system was stirred until the reaction was completed while maintaining the temperature in the reaction system at about 70 ° C. The reaction was completed when NCO% became almost constant (NCO% = 9.34). Thereafter, vacuum degassing was performed for about 2 hours to obtain an isocyanate-terminated prepolymer (1). The content of ethylene oxide units in all polyol components was 27% by weight.
[0106]
(Manufacture of polishing pad)
The container was mixed with 1000 parts by weight of the isocyanate-terminated prepolymer (1) and 30 parts by weight of silicon-based nonionic surfactant SH-192 (2.3% by weight based on polyurethane) and adjusted to 60 ° C. To this, 270 parts by weight of MOCA previously melted at 120 ° C. was added with vigorous stirring so as to take in bubbles. After stirring for about 1 minute, the mixed solution was put into a pan-type open mold and post-cured in an oven at 100 ° C. for 16 hours to obtain a polyurethane resin foam block. This polyurethane resin foam block had an average cell diameter of 49 μm. Moreover, the average hydroxyl value of all the polyol components which comprise a polyurethane resin foam was 569.2 (mgKOH / g), and the content rate of the EO unit in all the polyol components was 27 (wt%).
[0107]
A foam sheet is cut out from this polyurethane resin foam block using a slicer, a concentric groove is processed to produce a polishing layer, and a commercially available non-woven fabric is impregnated with polyurethane (cushion layer). A polishing pad was prepared by laminating.
[0108]
Comparative Example 2
(Synthesis of isocyanate-terminated prepolymer)
275 parts by weight of PTMG (number average molecular weight 1018), 200 parts by weight of PEG (number average molecular weight 1000), 65 parts by weight of PEG (number average molecular weight 600), and 56 parts by weight of DEG are placed in a separable flask. Performed for ~ 2 hours. Next, nitrogen was introduced into the separable flask, and after nitrogen substitution, TDI-80 (364 parts by weight) and HMDI (41 parts by weight) were added. The reaction system was stirred until the reaction was completed while maintaining the temperature in the reaction system at about 70 ° C. The reaction was terminated when NCO% became almost constant (NCO% = 9.54). Thereafter, vacuum degassing was performed for about 2 hours to obtain an isocyanate-terminated prepolymer (2). The content of ethylene oxide units in all polyol components was 48% by weight.
[0109]
(Manufacture of polishing pad)
The container was mixed with 1000 parts by weight of the isocyanate-terminated prepolymer (2) and 30 parts by weight of silicon-based nonionic surfactant SH-192 (2.3% by weight based on polyurethane) and adjusted to 60 ° C. To this, 276 parts by weight of MOCA previously melted at 120 ° C. was added with vigorous stirring so as to take in bubbles. After stirring for about 1 minute, the mixed solution was put into a pan-type open mold and post-cured in an oven at 100 ° C. for 16 hours to obtain a polyurethane resin foam block. This polyurethane resin foam block had an average cell diameter of 47 μm. Moreover, the average hydroxyl value of all the polyol components which comprise a polyurethane resin foam was 572.8 (mgKOH / g), and the content rate of the EO unit in all the polyol components was 48 (wt%).
[0110]
A foam sheet is cut out from this polyurethane resin foam block using a slicer, a concentric groove is processed to produce a polishing layer, and a commercially available non-woven fabric is impregnated with polyurethane (cushion layer). A polishing pad was prepared by laminating.
[0111]
Comparative Example 3
(Synthesis of isocyanate-terminated prepolymer)
550 parts by weight of PTMG (number average molecular weight 1018) and 53 parts by weight of DEG were placed in a separable flask, and vacuum dehydration was performed for 1 to 2 hours while stirring. Next, nitrogen was introduced into the separable flask, and after nitrogen substitution, TDI-80 (316 parts by weight) and HMDI (82 parts by weight) were added. The reaction system was stirred until the reaction was completed while maintaining the temperature in the reaction system at about 70 ° C. The reaction was terminated when NCO% became almost constant (NCO% = 9.14). Thereafter, vacuum degassing was performed for about 2 hours to obtain an isocyanate-terminated prepolymer (3). The content of ethylene oxide units in all polyol components was 7% by weight.
[0112]
(Manufacture of polishing pad)
In a container, 1000 parts by weight of the isocyanate-terminated prepolymer (3) and 30 parts by weight of silicon-based nonionic surfactant SH-192 (2.3% by weight with respect to polyurethane) were mixed and adjusted to 60 ° C. To this, 264 parts by weight of MOCA previously melted at 120 ° C. was added with vigorous stirring so as to take in bubbles. After stirring for about 1 minute, the mixed solution was put into a pan-type open mold and post-cured in an oven at 100 ° C. for 16 hours to obtain a polyurethane resin foam block. This polyurethane resin foam block had an average cell diameter of 52 μm. Moreover, the average hydroxyl value of all the polyol components which comprise a polyurethane resin foam was 565.5 (mgKOH / g), and the content rate of the EO unit in all the polyol components was 7 (wt%).
[0113]
A foam sheet is cut out from this polyurethane resin foam block using a slicer, a concentric groove is processed to produce a polishing layer, and a commercially available non-woven fabric is impregnated with polyurethane (cushion layer). A polishing pad was prepared by laminating.
[0114]
A polishing test was performed using the polishing pads obtained in Examples 1 and 2 and Comparative Examples 1 to 3, and polishing characteristics were evaluated. The results are shown in Table 1.
[0115]
[Table 1]

From the results shown in Table 1, by using the hydrophobic prepolymer (A) and the hydrophilic prepolymer (B) synthesized separately, the flatness, in-plane uniformity, and polishing rate are good, and the polishing rate changes. In addition, a polishing pad having a small life and excellent life characteristics (life criteria: polishing rate stability value within 10%) can be produced. When the two kinds of prepolymers are not used in combination, either of the above polishing properties is inferior.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an example of a polishing apparatus used in CMP polishing.
[Explanation of symbols]
1: Polishing pad (polishing layer)
2: Polishing surface plate
3: Abrasive (slurry)
4: Material to be polished (semiconductor wafer)
5: Support base (polishing head)
6, 7: Rotating shaft

Claims (7)

A polishing pad having a polishing layer comprising a polyurethane resin foam having fine bubbles, wherein the polyurethane resin foam comprises a hydroxy-terminated polyester polyol, a polycarbonate polyol, a polyester polycarbonate polyol, a polyether polyol, a polyether polycarbonate polyol, a polyester amide , A phenolic resin polyol, an epoxy polyol, a polybutadiene polyol, and a polyisoprene polyol, and a hydrophobic high molecular weight polyol having a number average molecular weight of 500 or more and having no ethylene oxide unit (—CH ₂ CH ₂ O—) comprising the component and the isocyanate component as raw material components hydrophobic isocyanate-terminated prepolymer (a), the ethylene oxide units (-CH ₂ H 2 _O-) a comprising a number average molecular weight of 500 or more hydrophilic high molecular weight polyol component and an isocyanate component having 25 wt% or more as a raw material component hydrophilic isocyanate-terminated prepolymer (B), and a chain extender A polishing pad comprising a raw material component.   The polishing pad according to claim 1, wherein the polyurethane resin foam contains 0.05 wt% or more and less than 5 wt% of a silicon-based nonionic surfactant having no hydroxyl group. The polishing pad according to claim 1 or 2, wherein the prepolymer (A) and / or (B) contains a low molecular weight polyol component having a molecular weight of less than 500 as a raw material component. The average hydroxyl value of all polyol components as raw material components of the prepolymers (A) and (B) is 560 to 580 (mg KOH / g), and ethylene oxide units (—CH ₂ CH ₂ in the all polyol components). The polishing pad according to any one of claims 1 to 3, wherein the content of O-) is 25 to 50% by weight.   The polishing pad according to any one of claims 1 to 4, wherein the isocyanate component which is a raw material component of the prepolymer (A) and / or (B) is an aromatic diisocyanate and an alicyclic diisocyanate.   The polishing pad according to claim 5, wherein the aromatic diisocyanate is toluene diisocyanate, and the alicyclic diisocyanate is dicyclohexylmethane diisocyanate.   A method for manufacturing a semiconductor device, comprising a step of polishing a surface of a semiconductor wafer using the polishing pad according to claim 1.

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