JP7804502B2 - Polishing pad and method for manufacturing polished workpiece - Google Patents

Description

The present invention relates to a polishing pad and a method for manufacturing a polished workpiece using the same.

In semiconductor manufacturing processes, chemical mechanical polishing (CMP) is used to planarize the surface after insulating film deposition and to form metal wiring. One of the important technologies required for chemical mechanical polishing is polishing endpoint detection, which determines whether the polishing process is complete. For example, over-polishing or under-polishing relative to the target polishing endpoint directly leads to product defects. For this reason, chemical mechanical polishing requires strict control of the amount of polishing by detecting the polishing endpoint.

Chemical mechanical polishing is a complex process, and the polishing speed (polishing rate) varies depending on the operating conditions of the polishing equipment, the quality of consumables (slurry, polishing pads, dressers, etc.), and variations in conditions over time during the polishing process. Furthermore, in recent years, the precision of remaining film thickness and in-plane uniformity required in semiconductor manufacturing processes have become increasingly strict. For these reasons, detecting the polishing endpoint with sufficient accuracy has become more difficult.

The main methods for detecting the polishing endpoint are optical endpoint detection, torque endpoint detection, and eddy current endpoint detection. With optical endpoint detection, the endpoint is detected by irradiating the wafer with light through a transparent window member installed on the polishing pad and monitoring the reflected light.

As an example of a polishing pad that uses this type of optical endpoint detection method, Patent Document 1 discloses a polishing pad that has a pad body and a transparent window member formed integrally with a part of the pad body, with the surface of the window member recessed from the surface of the pad body, with the aim of providing a polishing pad that can prevent slurry from accumulating in the grooves of the window member and thereby improve the accuracy of polishing rate detection.

Japanese Patent Application Laid-Open No. 2002-001647

One method for manufacturing a polishing pad with a window like the one described above involves filling a resin composition with a window member fixed in a mold, curing it, slicing the resulting cured product, and then performing a dressing process. Because the window member and the cured resin composition are made from different materials, their physical properties differ to some extent. For example, when slicing, there is a risk that the window portion may become dented or cracked. Furthermore, when performing a dressing process, there is a risk that the window portion may become dented due to the difference in the amount of wear between the window portion and the polishing layer.

When such depressions occur, slurry and polishing debris tend to accumulate there, potentially causing scratches and reducing the surface quality of the polished object. Furthermore, if the window portion is less worn, it is more likely to remain than the polishing layer as polishing progresses, which can result in the window portion becoming convex. Such convex window portions can also cause scratches and reduce the surface quality of the polished object.

The present invention was made in consideration of the above-mentioned problems, and aims to provide a polishing pad that exhibits excellent flatness during slicing and dressing processes, and a method for manufacturing a polished workpiece using the same.

The inventors conducted extensive research to resolve the above-mentioned problems. As a result, they discovered that the above-mentioned problems could be resolved by ensuring a specific relationship between the endpoint detection window and the polishing layer in pulsed NMR analysis, leading to the completion of the present invention.

That is, the present invention is as follows.
[1]
a polishing layer and an end point detection window provided in an opening in the polishing layer;
When the free induction decay curve of the spin-spin relaxation of 1H obtained by measuring with the solid echo method using pulsed NMR was separated into three curves derived from the three components of the crystalline phase, mesophase, and amorphous phase in order of shortest relaxation time,
the ratio (Lp20/Lw20) of the amorphous phase abundance ratio Lw20 in the endpoint detection window to the amorphous phase abundance ratio Lp20 in the polishing layer at 20°C is 0.8 to 1.2 ;
the ratio (Sp80/Sw80) of the abundance ratio Sw80 of the crystalline phase in the endpoint detection window to the abundance ratio Sp80 of the crystalline phase in the polishing layer at 80°C is 1.0 to 1.3 ;
Polishing pad.
[2]
the ratio (Mp20/Mw20) of the abundance ratio Mw20 of the mesophase in the endpoint detection window to the abundance ratio Mp20 of the mesophase in the polishing layer at 20°C is 0.7 to 1.5;
The polishing pad according to [1].
[3]
the ratio (Mp80/Mw80) of the abundance ratio Mw80 of the mesophase in the endpoint detection window to the abundance ratio Mp80 of the mesophase in the polishing layer at 80°C is 0.5 to 1.5;
The polishing pad according to [1] or [2].
[4]
The difference between the abundance ratio Lw20 and the abundance ratio Lp20 (|Lp20-Lw20|) is 10 or less;
The polishing pad according to any one of [1] to [3].
[5]
The difference between the abundance ratio Sw80 and the abundance ratio Sp 80 (|Sp80-Sw80|) is 15 or less;
[1] - [4] The polishing pad according to any one of the above.
[6]
the endpoint detection window contains a polyurethane resin WI,
The polyurethane resin WI contains a structural unit derived from an aliphatic isocyanate.
[1] - [5] The polishing pad according to any one of the above.
[7]
The polishing layer contains a polyurethane resin P,
The polyurethane resin P contains a structural unit derived from an aromatic isocyanate.
[1] - [6] The polishing pad according to any one of the above.
[8]
The polishing layer contains hollow fine particles dispersed therein.
[1] The polishing pad according to any one of [1] to [7].
[9]
In the presence of a polishing slurry, using the polishing pad according to any one of [1] to [8],
a polishing step of polishing an object to be polished to obtain a polished product;
an end point detection step of detecting an end point by an optical end point detection method during the polishing.
A method for manufacturing polished workpieces.

The present invention provides a polishing pad that exhibits excellent flatness during slicing and dressing processes, as well as a method for manufacturing a polished workpiece using the same.

1 is a schematic perspective view of a polishing pad according to an embodiment of the present invention. 3 is a schematic cross-sectional view of an end point detection window portion of the polishing pad of the present embodiment. FIG. 10 is a schematic cross-sectional view of another aspect of the end point detection window portion of the polishing pad of the present embodiment. FIG. FIG. 1 is a schematic diagram showing a film thickness control system installed in CMP. FIG. 10 is a diagram showing the surface state of the end point detection window portion of the polishing pad of Example 1 after slicing and before dressing. FIG. 10 is a diagram showing the surface state of the end point detection window portion of the polishing pad of Example 1 after slicing and before dressing. FIG. 10 is a diagram showing the surface state of the end point detection window portion of the polishing pad of Comparative Example 1 after slicing and before dressing. FIG. 10 is a diagram showing the surface state of the end point detection window portion of the polishing pad of Example 1 after dressing. FIG. 10 is a diagram showing the surface state of the end point detection window portion of the polishing pad of Example 2 after dressing. FIG. 10 is a diagram showing the surface state of the end point detection window portion of the polishing pad of Comparative Example 1 after dressing.

The following describes in detail an embodiment of the present invention (hereinafter referred to as "the present embodiment"), with reference to the drawings as necessary. However, the present invention is not limited to this, and various modifications are possible without departing from the spirit of the present invention. Note that identical elements throughout the drawings will be given the same reference numerals, and redundant explanations will be omitted. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios of the drawings are not limited to those shown.

1. Polishing Pad The polishing pad of this embodiment has a polishing layer and an end point detection window provided in an opening of the polishing layer, and when the free induction decay curve of 1H spin-spin relaxation obtained by measurement by the Solid Echo method using pulse NMR is waveform-separated into three curves derived from three components, namely, a crystalline phase, an intermediate phase, and an amorphous phase, in order of decreasing relaxation time, the ratio (Lp20/Lw20) of the abundance ratio Lw20 of the amorphous phase in the end point detection window to the abundance ratio Lp20 of the amorphous phase in the polishing layer at 20°C is 0.5 to 2.0, and the ratio (Sp80/Sw80) of the abundance ratio Sw80 of the crystalline phase in the end point detection window to the abundance ratio Sp80 of the crystalline phase in the polishing layer at 80°C is 0.5 to 2.0.

This improves flatness during the slicing process by making it less likely that protrusions will occur, and during the dressing process, it improves flatness by making it less likely that the endpoint detection window will be over-polished compared to the polishing layer. In this embodiment, these two types of flatness are collectively referred to simply as "flatness."

Figure 1 shows a schematic perspective view of the polishing pad of this embodiment. As shown in Figure 1, the polishing pad 10 of this embodiment has a polishing layer 11, which is a polyurethane sheet, and an endpoint detection window 12, and may optionally have a cushion layer 13 on the side opposite the polishing surface 11a.

Figures 2 and 3 show cross-sectional views of the area around the endpoint detection window 12 in Figure 1. As shown in Figures 2 and 3, an adhesive layer 14 may be provided between the polishing layer 11 and the cushion layer 13, and an adhesive layer 15 may be provided on the surface of the cushion layer 13 for bonding to the table 22 in Figure 4. The polishing surface 11a of the polishing pad of this embodiment may be flat as shown in Figure 2, or may be uneven with grooves 16 formed therein as shown in Figure 3. The grooves 16 may be formed in various shapes, such as multiple concentric circles, a grid pattern, or a radial pattern, either alone or in combination.

1.1. End Point Detection Window The end point detection window is a transparent member provided in an opening in the polyurethane sheet, and serves as a transmission path for light from the film thickness detection sensor in optical end point detection. In this embodiment, the end point detection window is circular, but it may be square, rectangular, polygonal, elliptical, or other shapes as needed.

In this embodiment, parameters related to the pulsed NMR of the endpoint detection window and the polishing layer are specified from the perspective of improving flatness by preventing the endpoint detection window from becoming recessed or cracked relative to the polishing layer when slicing is performed during the polishing pad manufacturing process, and preventing the endpoint detection window from becoming recessed or protruding relative to the polishing layer when a dressing process is performed.

1.1.1. Pulsed NMR
Pulsed NMR is a type of solid-state NMR that detects a response signal to a pulse and determines the ^1H nuclear magnetic relaxation time (an index of molecular mobility) of a sample. The response signal to the pulse is the free induction decay (FID) signal.

Pulse NMR is an analytical method for evaluating the mobility of polymer molecular chains as a whole system, and can be evaluated by measuring the relaxation time of a resin composition and the signal intensity at that time. Generally, the lower the mobility of the polymer chains, the shorter the relaxation time, so the signal intensity decays faster, and the relative signal intensity, when the initial signal intensity is taken as 100%, decreases over a short period of time. Furthermore, the higher the mobility of the polymer chains, the longer the relaxation time, so the signal intensity decays slower, and the relative signal intensity, when the initial signal intensity is taken as 100%, decreases gradually over a long period of time.

For example, when measuring a resin, the resulting FID is the sum of the FIDs of multiple components with different relaxation times, and by separating this using the least squares method, the relaxation time of each component can be detected. Approximating the free induction decay curve at a given temperature obtained by measurement using the solid echo method of pulsed NMR into three components allows the signal obtained by the measurement to be classified as originating from the component with the lowest mobility (crystalline phase), the component with intermediate mobility (intermediate phase), or the component with the highest mobility (amorphous phase) in the sample, and the abundance ratio of these components can be determined.

Specifically, by fitting a free induction decay curve measured by the solid echo method of pulsed NMR using the following formula (1), it is possible to approximate it to three components: a crystalline phase, an intermediate phase, and an amorphous phase, and the proportions of each component can be obtained by approximating it to these three components.
M(t)=αexp(-(1/2)(t/T _α ) ² ) sinbt/bt+βexp(-(1/Wa)(t/T _β ) ^Wa )+γexp(-t/T _γ )...(Formula 1)
α: composition ratio of crystalline phase _Tα : relaxation time of crystalline phase (unit: msec)
β: mesophase composition ratio _Tβ : mesophase relaxation time (unit: msec)
γ: composition ratio of amorphous phase _Tγ : relaxation time of amorphous phase (unit: msec)
t: Observation time (unit: msec)
Wa: Shape factor b: Shape factor

These pulse NMR measurement results allow us to evaluate the mobility of the polishing layer and the endpoint detection window. In this embodiment, pulse NMR is used to evaluate that the mobility of the polishing layer and the endpoint detection window is similar at a temperature of 20°C, which corresponds to the dressing temperature, and at a temperature of 80°C, which corresponds to the slicing temperature.

Specifically, at 20°C, the ratio (Lp20/Lw20) of the amorphous phase abundance ratio Lw20 in the endpoint detection window to the amorphous phase abundance ratio Lp20 in the polishing layer is 0.5 to 2.0, preferably 0.6 to 1.7, more preferably 0.7 to 1.5, and even more preferably 0.8 to 1.2. By keeping the ratio (Lp20/Lw20) within the above range, the mobilities of the materials constituting the polishing layer and the endpoint detection window are similar during dressing. This allows the polishing layer and endpoint detection window to be treated uniformly during the dressing process, further improving flatness after the dressing process.

Furthermore, the ratio (Sp80/Sw80) of the crystalline phase abundance ratio Sw80 of the endpoint detection window to the crystalline phase abundance ratio Sp80 of the polishing layer at 80°C is 0.5 to 2.0, preferably 0.6 to 1.7, more preferably 0.9 to 1.5, and even more preferably 1.0 to 1.3. By having the ratio (Sp80/Sw80) within the above range, the mobilities of the materials constituting the polishing layer and the endpoint detection window are similar during slicing. This allows the polishing layer and endpoint detection window to be processed uniformly during the slicing process, further improving flatness after the slicing process.

At 20°C, the ratio (Mp20/Mw20) of the mesophase abundance ratio Mw20 in the endpoint detection window to the mesophase abundance ratio Mp20 in the polishing layer is preferably 0.7 to 1.5, more preferably 0.7 to 1.3, and even more preferably 0.7 to 1.1. By keeping the ratio (Mp20/Mw20) within the above range, the polishing layer and endpoint detection window can be treated uniformly during the dressing process, which tends to further improve flatness after the dressing process.

At 80°C, the ratio (Mp80/Mw80) of the mesophase abundance ratio Mw80 in the endpoint detection window to the mesophase abundance ratio Mp80 in the polishing layer is preferably 0.5 to 1.5, more preferably 0.7 to 1.4, and even more preferably 0.8 to 1.3. By keeping the ratio (Mp80/Mw80) within the above range, the polishing layer and endpoint detection window can be processed uniformly during the slicing process, which tends to further improve flatness after the slicing process.

The difference between the abundance ratio Lw20 and the abundance ratio Lp20 (|Lp20 - Lw20|) is preferably 10 or less, more preferably 0 to 8.0, and even more preferably 0 to 5.0. By keeping the difference (|Lp20 - Lw20|) within the above range, the polishing layer and endpoint detection window can be treated uniformly during the dressing process, which tends to further improve flatness after the dressing process.

The difference (|Sp80-Sw80|) between the abundance ratio Sw80 and the abundance ratio Sp 80 is preferably 15 or less, more preferably 0 to 12, and even more preferably 0 to 8.0. When the difference (|Sp80-Sw80|) is within the above range, the polishing layer and the endpoint detection window can be uniformly processed in the slicing process, and the flatness after the slicing process tends to be further improved.

The crystalline phase abundance ratio Sw20 in the endpoint detection window at 20°C is preferably 30 to 65%, more preferably 35 to 60%, and even more preferably 40 to 55%.

The mesophase abundance ratio Mw20 in the endpoint detection window at 20°C is preferably 15 to 45%, more preferably 20 to 40%, and even more preferably 25 to 35%.

The amorphous phase abundance ratio Lw20 in the endpoint detection window at 20°C is preferably 10 to 40%, more preferably 15 to 35%, and even more preferably 20 to 30%.

By ensuring that the abundance ratio Sw20, abundance ratio Mw20, and abundance ratio Lw20 of the endpoint detection window at 20°C are each within the above ranges, the polishing layer and endpoint detection window can be treated uniformly during the dressing process, which tends to further improve flatness after the dressing process. The sum of the abundance ratio Sw20, abundance ratio Mw20, and abundance ratio Lw20 is 100%.

The crystalline phase abundance ratio Sw80 in the endpoint detection window at 80°C is preferably 15 to 50%, more preferably 20 to 45%, and even more preferably 25 to 40%.

The mesophase abundance ratio Mw80 in the endpoint detection window at 80°C is preferably 10 to 35%, more preferably 15 to 30%, and even more preferably 20 to 25%.

The amorphous phase abundance ratio Lw80 in the endpoint detection window at 80°C is preferably 30 to 60%, more preferably 35 to 55%, and even more preferably 40 to 50%.

By ensuring that the abundance ratio Sw80, abundance ratio Mw80, and abundance ratio Lw80 of the endpoint detection window at 80°C are each within the above ranges, the polishing layer and endpoint detection window can be processed uniformly during the slicing process, which tends to further improve flatness after the slicing process. The sum of the abundance ratio Sw80, abundance ratio Mw80, and abundance ratio Lw80 is 100%.

There are no particular limitations on the measurement conditions for pulsed NMR measurement, but measurements can be performed under the conditions described in the examples.

1.1.3. Constituent Material The material constituting the endpoint detection window is not particularly limited as long as it is a transparent member capable of functioning as a window, but examples thereof include polyurethane resin WI, polyvinyl chloride resin, polyvinylidene fluoride resin, polyethersulfone resin, polystyrene resin, polyethylene resin, and polytetrafluoroethylene resin. Among these, polyurethane resin WI is preferred. By using such a resin, it is easier to adjust the pulse NMR characteristics and transparency, and flatness can be further improved.

Polyurethane resin WI can be synthesized from polyisocyanate and polyol, and contains structural units derived from polyisocyanate and structural units derived from polyol.

1.1.3.1. Structural Units Derived from Polyisocyanates The structural units derived from polyisocyanates are not particularly limited, but examples include structural units derived from alicyclic isocyanates, structural units derived from aliphatic isocyanates, and structural units derived from aromatic isocyanates. Among these, the polyurethane resin WI preferably contains structural units derived from alicyclic isocyanates and/or aliphatic isocyanates, and more preferably contains structural units derived from aliphatic isocyanates. This makes it easier to adjust the pulse NMR values within the above ranges, further improving transparency and further improving flatness during dressing and slicing.

Alicyclic isocyanates are not particularly limited, but examples include 4,4'-methylene-bis(cyclohexyl isocyanate) (hydrogenated MDI), cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, and isophorone diisocyanate.

Aliphatic isocyanates are not particularly limited, but examples include hexamethylene diisocyanate (HDI), pentamethylene diisocyanate (PDI), tetramethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, trimethylene diisocyanate, and trimethylhexamethylene diisocyanate.

Aromatic isocyanates are not particularly limited, but examples include phenylene diisocyanate, 2,6-tolylene diisocyanate (2,6-TDI), 2,4-tolylene diisocyanate (2,4-TDI), xylylene diisocyanate, naphthalene diisocyanate, and diphenylmethane-4,4'-diisocyanate (MDI).

1.1.3.2. Structural Units Derived from Polyols Structural units derived from polyols are not particularly limited, but examples include low-molecular-weight polyols with a molecular weight of less than 300 and high-molecular-weight polyols with a molecular weight of 300 or more.

The low molecular weight polyol is not particularly limited, but examples include low molecular weight polyols having two hydroxyl groups such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexane glycol, 2,5-hexanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, tricyclodecane dimethanol, and 1,4-cyclohexane dimethanol; and low molecular weight polyols having three or more hydroxyl groups such as glycerin, hexanetriol, trimethylolpropane, isocyanuric acid, and erythritol. Low molecular weight polyols may be used alone or in combination of two or more.

Among these, low-molecular-weight polyols having three or more hydroxyl groups are preferred, with glycerin being more preferred. Using such low-molecular-weight polyols makes it easier to adjust the pulse NMR characteristics within the above range, adjusts the amount of abrasion, improves flatness, and also tends to improve transparency and yellowing resistance of the window.

The content of structural units derived from a low-molecular-weight polyol having three or more hydroxyl groups is preferably 8.0 to 30 parts by mass, more preferably 10 to 25 parts by mass, and even more preferably 12.5 to 20 parts by mass, per 100 parts by mass of structural units derived from polyisocyanate. By keeping the content of structural units derived from a low-molecular-weight polyol having three or more hydroxyl groups within the above range, it becomes easier to adjust the pulse NMR characteristics within the above range, which leads to improved flatness, improved transparency, and a tendency to further improve the yellowing resistance of the window.

The polymer polyol is not particularly limited, but examples include polyether polyols, polyester polyols, polycarbonate polyols, polyether polycarbonate polyols, polyurethane polyols, epoxy polyols, vegetable oil polyols, polyolefin polyols, acrylic polyols, and vinyl monomer-modified polyols. One type of polymer polyol may be used alone, or two or more types may be used in combination.

The number-average molecular weight of the polymer polyol is preferably 300 to 3,000, and more preferably 500 to 2,500. Using such a polymer polyol tends to make it easier to adjust the pulse NMR characteristics to within the above range.

Of these, polyether polyols are preferred, and poly(oxytetramethylene) glycol is more preferred. Using such polymer polyols makes it easier to adjust pulse NMR characteristics within the above range. Furthermore, flatness can be further improved, transparency is further improved, and the window's yellowing resistance tends to be further improved.

The content of the structural units derived from polyether polyol is preferably 60 to 130 parts by mass, preferably 65 to 120 parts by mass, and more preferably 70 to 110 parts by mass, per 100 parts by mass of the structural units derived from polyisocyanate. By having the content of the structural units derived from polyether polyol within this range, it becomes easier to adjust the pulse NMR characteristics within the above range, which can further improve flatness and transparency, and also tends to further improve the yellowing resistance of the window.

As the polyol, it is preferable to use a combination of a low-molecular-weight polyol and a high-molecular-weight polyol, and it is even more preferable to use a combination of a low-molecular-weight polyol having three or more hydroxyl groups and a polyether polyol. This makes it easier to adjust the pulse NMR characteristics to within the above range. It also tends to further improve flatness, transparency, and the window's resistance to yellowing.

From the above perspective, the content of polyether polyol is preferably 2.0 to 15.0 parts, more preferably 3.0 to 12.5 parts, and even more preferably 4.0 to 9.0 parts per part of low-molecular-weight polyol having three or more hydroxyl groups.

1.2 Polishing Layer The polishing layer of this embodiment has an opening in which an end-point detection window is embedded. The position of the opening is not particularly limited, but it is preferable to provide it at a radial position corresponding to the film thickness detection sensor 23 installed on the table 22. Furthermore, the number of openings is not particularly limited, but it is preferable to have multiple openings at similar radial positions so that the window passes over the film thickness detection sensor 23 multiple times during one rotation of the polishing pad 10 attached to the table 22.

The form of the polishing layer is not particularly limited, but examples include foamed resin molded bodies, non-foamed resin molded bodies, and resin-impregnated substrates in which a fibrous substrate is impregnated with resin.

Here, a resin foam molded product refers to a foam made from a specific resin without a fibrous base material. There are no particular restrictions on the foam shape, but examples include spherical cells, nearly spherical cells, teardrop-shaped cells, and open cells in which the individual cells are partially connected.

An unfoamed resin molded product refers to a non-foamed product made of a specific resin and does not have a fibrous substrate. A non-foamed product does not have the air bubbles described above. In the first embodiment, the term "unfoamed resin molded product" includes a product formed by applying a curable composition to a substrate such as a film and curing it. More specifically, the term "unfoamed resin molded product" includes cured resin products formed by methods such as the razor coater method, small-diameter gravure coater method, reverse roll coater method, transfer roll coater method, kiss coater method, die coater method, screen printing method, and spray coating method.

Furthermore, a resin-impregnated substrate refers to a material obtained by impregnating a fiber substrate with a resin. The fiber substrate is not particularly limited, but examples include woven fabric, nonwoven fabric, and knitted fabric.

1.2.1. Pulsed NMR
The abundance ratio Sp20 of the crystalline phase in the polishing layer is preferably 40 to 65%, more preferably 45 to 60%, and even more preferably 50 to 55%.

The proportion of the intermediate phase in the abrasive layer, Mp20, is preferably 10 to 40%, preferably 15 to 35%, and preferably 20 to 30%.

The amorphous phase content Lp20 of the polishing layer is preferably 10 to 35%, preferably 15 to 30%, and preferably 20 to 25%.

By ensuring that the abundance ratios Sp20, Mp20, and Lp20 of the endpoint detection window at 20°C are each within the above ranges, the polishing layer and endpoint detection window can be treated uniformly during the dressing process, which tends to further improve flatness after the dressing process. The sum of the abundance ratios Sp20, Mp20, and Lp20 is 100%.

The crystalline phase abundance ratio Sp80 of the polishing layer is preferably 25-50%, preferably 30-45%, and preferably 35-40%.

The proportion of the intermediate phase in the abrasive layer, Mp80, is preferably 10 to 40%, preferably 15 to 35%, and preferably 20 to 30%.

The amorphous phase content Lp80 of the polishing layer is preferably 25 to 50%, preferably 30 to 45%, and preferably 35 to 40%.

By ensuring that the abundance ratios Sp80, Mp80, and Lp80 of the endpoint detection window at 80°C are each within the above ranges, the polishing layer and endpoint detection window can be processed uniformly during the slicing process, which tends to further improve flatness after the slicing process. The sum of the abundance ratios Sp80, Mp80, and Lp80 is 100%.

There are no particular limitations on the measurement conditions for pulsed NMR measurements, but measurements can be performed under the conditions described in the examples.

1.2.2. Polyurethane Sheet In the following, a polyurethane sheet will be exemplified as an example of a polishing layer. The polyurethane resin P constituting the polyurethane sheet is not particularly limited, but examples thereof include polyester-based polyurethane resins, polyether-based polyurethane resins, and polycarbonate-based polyurethane resins. These may be used alone or in combination of two or more.

Such polyurethane resin P can be synthesized from a polyisocyanate and a polyol, and a reaction product of a urethane prepolymer and a curing agent is particularly preferred. Here, the urethane prepolymer can be synthesized from a polyisocyanate and a polyol. The polyisocyanate, polyol, and curing agent that make up the polyurethane resin P are described below.

1.2.2.1. Structural Units Derived from Polyisocyanates The structural units derived from polyisocyanates are not particularly limited, and examples thereof include structural units derived from alicyclic isocyanates, structural units derived from aliphatic isocyanates, and structural units derived from aromatic isocyanates. Among these, aromatic isocyanates are preferred, and 2,4-tolylene diisocyanate (2,4-TDI) is more preferred.

Examples of alicyclic isocyanates, aliphatic isocyanates, and aromatic isocyanates include those similar to those exemplified in the endpoint detection window above.

1.2.2.2. Structural units derived from polyols The structural units derived from polyols are not particularly limited, and examples include low-molecular-weight polyols having a molecular weight of less than 300 and high-molecular-weight polyols having a molecular weight of 300 or more. Among these, it is preferable to use at least a low-molecular-weight polyol, and it is also preferable to use a low-molecular-weight polyol and a high-molecular-weight polyol in combination.

Examples of low-molecular-weight polyols and high-molecular-weight polyols include those exemplified in the endpoint detection window above. Among these, low-molecular-weight polyols are preferably low-molecular-weight polyols having two hydroxyl groups, with diethylene glycol being more preferred. Furthermore, high-molecular-weight polyols are preferably polyether polyols, with poly(oxytetramethylene) glycol being more preferred.

The curing agent is not particularly limited, but examples thereof include polyamines and polyols. The curing agents may be used alone or in combination of two or more.

Polyamines are not particularly limited, but examples include aliphatic polyamines such as ethylenediamine, propylenediamine, and hexamethylenediamine; alicyclic polyamines such as isophoronediamine and dicyclohexylmethane-4,4'-diamine; and aromatic polyamines such as 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), 4-methyl-2,6-bis(methylthio)-1,3-benzenediamine, 2-methyl-4,6-bis(methylthio)-1,3-benzenediamine, and 2,2-bis(3-amino-4-hydroxyphenyl)propane.

Among these, aromatic polyamines are preferred, and it is more preferable to use 3'-dichloro-4,4'-diaminodiphenylmethane (MOCA).

Examples of polyols include those similar to those exemplified in the endpoint detection window above. Among these, polymer polyols are preferred, polyether polyols are more preferred, and polypropylene glycol is even more preferred.

1.2.2.4. Hollow Microparticles The polishing layer preferably contains hollow microparticles dispersed therein. Specifically, the polyurethane sheet is preferably a foamed polyurethane sheet containing polyurethane resin P and hollow microparticles dispersed therein. Such a polyurethane sheet has closed cells derived from the hollow microparticles, which tends to make it easier to adjust the pulse NMR characteristics within the above range.

The hollow microparticles may be commercially available or may be synthesized by conventional methods. The material of the outer shell of the hollow microparticles is not particularly limited, but examples include polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid, polyacrylamide, polyethylene glycol, polyhydroxyether acrylate, maleic acid copolymer, polyethylene oxide, polyurethane, acrylonitrile-vinylidene chloride copolymer, acrylonitrile-methyl methacrylate copolymer, and vinyl chloride-ethylene copolymer.

The shape of the hollow microparticles is not particularly limited and may be, for example, spherical or nearly spherical. Furthermore, if the hollow microparticles are expandable balloons, they may be used in either an unexpanded or expanded state.

The average particle size of the hollow microparticles contained in the polyurethane sheet is preferably 5 to 200 μm, more preferably 5 to 80 μm, even more preferably 5 to 50 μm, and especially preferably 5 to 35 μm. Having an average particle size within this range tends to make it easier to adjust the pulse NMR characteristics within the above range. The average particle size can be measured using a laser diffraction particle size analyzer (e.g., Mastersizer 2000, manufactured by Spectris Co., Ltd.).

1.3. Other The polishing pad of this embodiment may have a cushion layer on the side of the polishing layer opposite the polishing surface, or an adhesive layer between the polishing layer and the cushion layer, or on the side of the cushion layer opposite the polishing layer (the surface that is attached to the polishing machine). In this case, the cushion layer and the adhesive layer have openings in the same locations as the endpoint detection windows in the polishing layer.

2. Method for Manufacturing Polishing Pad The method for manufacturing the polishing pad of this embodiment is not particularly limited, but may include, for example, the steps of filling a resin composition constituting the polishing layer into a mold to which a window member that will become the endpoint detection window is fixed, and curing the resin composition to obtain a resin block in which the window member is embedded, and slicing the obtained resin block to obtain a polyurethane sheet having an endpoint detection window in its opening, and the polishing surface of the obtained polyurethane sheet may be dressed as necessary.

The temperature during slicing is preferably 70°C to 100°C. The temperature during dressing is preferably 20°C to 30°C. This tends to further improve flatness.

3. Manufacturing Method of Polished Product The manufacturing method of the polished product of this embodiment includes a polishing step of polishing a workpiece using the polishing pad in the presence of a polishing slurry to obtain a polished product, and an end point detection step of detecting the end point during the polishing by an optical end point detection method.

3.1 Polishing Process The polishing process may be primary lapping (rough lapping), secondary lapping (finish lapping), primary polishing (rough polishing), secondary polishing (finish polishing), or a process that combines these. Here, "lapping" refers to polishing at a relatively high rate using coarse abrasive grains, and "polishing" refers to polishing at a relatively low rate using fine abrasive grains to improve surface quality.

Of these, the polishing pad of this embodiment is preferably used for chemical mechanical polishing (CMP). Below, the method for manufacturing the polished product of this embodiment will be explained using chemical mechanical polishing as an example, but the method for manufacturing the polished product of this embodiment is not limited to the following.

The workpiece to be polished is not particularly limited, but examples include materials for semiconductor devices and electronic components, particularly thin substrates (workpieces to be polished) such as Si substrates (silicon wafers), SiC (silicon carbide) substrates, GaAs (gallium arsenide) substrates, glass, and substrates for hard disks and LCDs (liquid crystal displays). In particular, semiconductor devices with metal wiring such as W (tungsten) and Cu (copper) are included.

Any conventional polishing method can be used, and is not particularly limited. For example, first, the workpiece held on a holding platen positioned opposite the polishing pad is pressed against the polishing surface, and the polishing pad and/or holding platen are rotated while slurry is supplied from the outside. The polishing pad and holding platen may rotate in the same direction at different rotational speeds, or in opposite directions. Furthermore, the workpiece may be polished while moving (rotating) inside the frame during the polishing process.

The slurry may contain water, chemical components such as an oxidizing agent such as hydrogen peroxide, additives, abrasive grains (abrasive particles; for example, SiC, SiO ₂ , Al ₂ O ₃ , CeO ₂ ), etc. depending on the object to be polished and the polishing conditions.

3.2 End Point Detection Step The method for manufacturing a polished workpiece according to this embodiment includes an end point detection step in the polishing step, in which the end point is detected by an optical end point detection method. Specifically, a conventionally known method can be used as the end point detection method by the optical end point detection method.

Figure 4 shows a schematic diagram of an optical endpoint detection method. This diagram illustrates a chemical mechanical polishing process in which a wafer W held by a top ring 21 is pressed against a polishing pad 10 attached to a table 22 while a slurry 24 is flowing thereon, thereby polishing and flattening the uneven film on the surface of the wafer W. The polishing apparatus 20 is equipped with a film thickness detection sensor 23 on the table 22 that monitors the film thickness in order to accurately complete the process by simultaneously detecting the specified film thickness and planarizing the surface. The film thickness detection sensor 23 can detect the polishing endpoint by, for example, irradiating the polishing surface of the wafer W with light and measuring and analyzing the spectral intensity characteristics of the reflected light.

More specifically, the film thickness detection sensor 23 can detect changes in film thickness by irradiating light onto the surface of the wafer W through the endpoint detection window 12 and detecting the strength of the reflection intensity that arises from the phase difference between the light reflected by the film on the wafer W (wafer surface) and the light reflected at the interface between the film on the wafer W and the wafer substrate.

The present invention will be explained in more detail below using examples and comparative examples. The present invention is not limited in any way by the following examples. Note that "parts" refers to parts by mass.

[Production Example 1: End Point Detection Window 1]
A transparent member to become the end point detection window 4 was obtained by reacting 100 parts of 4,4' methylenebis(cyclohexyl isocyanate), 90.6 parts of poly(oxytetramethylene) glycol (PTMG) having a number average molecular weight of 1000, and 16.7 parts of glycerin.

[Production Example 2: End Point Detection Window 2]
A transparent member to become the end point detection window 2 was obtained by reacting 100 parts of 4,4' methylenebis(cyclohexyl isocyanate), 103.6 parts of poly(oxytetramethylene) glycol (PTMG) having a number average molecular weight of 1000, and 15.9 parts of glycerin.

[Production Example 3: End Point Detection Window 3]
A transparent member that would become the endpoint detection window 3 was obtained by reacting 100 parts of 4,4'methylenebis(cyclohexyl isocyanate), 78.6 parts of poly(oxytetramethylene) glycol (PTMG) having a number average molecular weight of 650, 4.5 parts of glycerin, and 10.5 parts of ethylene glycol.

Example 1
A urethane prepolymer mixture was obtained by adding and mixing 2.9 parts of unexpanded hollow fine particles (average particle size: 8.5 μm) whose shells consisted of acrylonitrile-vinylidene chloride copolymer to 100 parts of a urethane prepolymer having an NCO equivalent of 420, which was obtained by reacting 2,4-tolylene diisocyanate (2,4-TDI), poly(oxytetramethylene) glycol (PTMG) having a number average molecular weight of 650, poly(oxytetramethylene) glycol (PTMG) having a number average molecular weight of 1000, and diethylene glycol (DEG). The resulting urethane prepolymer mixture was charged into a first liquid tank and maintained at 60°C. Separately from the first liquid tank, 28.0 parts of 3,3'-dichloro-4,4'-diaminodiphenylmethane (methylenebis-o-chloroaniline) (MOCA) was placed in a second liquid tank as a curing agent, and the mixture was heated to melt at 120°C, mixed, and further degassed under reduced pressure to obtain a curing agent melt.

Next, the liquids from the first and second liquid tanks were poured into the two inlets of a mixer, and then stirred and mixed to obtain a mixed liquid.

The resulting mixture was then poured into a mold in which the endpoint detection window 1 obtained as described above had been previously installed, and subjected to primary curing at 80°C for 30 minutes. The resulting block-shaped molded product was removed from the mold and subjected to secondary curing in an oven at 120°C for 4 hours, yielding a urethane resin block. The resulting urethane resin block was then allowed to cool to 25°C.

Then, it was heated again in an oven at 120°C for 5 hours, then sliced. The sliced surfaces were ground (buffed) as needed to obtain foamed polyurethane sheets. Double-sided tape was attached to the back of the resulting polyurethane sheet, a cushion layer was attached, and then double-sided tape was attached to the surface of the cushion layer to obtain a polishing pad.

When evaluating the cross section around the end point detection window after the dressing treatment, the polishing pad obtained as described above was dressed under the following conditions.
(Dress requirements)
Polishing machine used: Speedfam, product name "FAM-12BS"
Platen rotation speed (polishing pad rotation speed): 50 rpm
Flow rate: 100 ml/min (pure water at 20°C was dropped from the center of rotation of the polishing pad.)
Dresser: 3M diamond dresser, model number "A188"
Dresser rotation speed: 100 rpm
Dressing pressure: 0.115 kg/cm
Dresser rotation direction: Rotates in the same direction as the polishing pad Test time: 60 minutes

Example 2
A polishing pad was obtained in the same manner as in Example 1, except that the end point detection window 2 of Production Example 3 was used.

Comparative Example 1
A polishing pad was obtained in the same manner as in Example 1, except that the end point detection window 3 of Production Example 3 was used.

[Pulse NMR]
Apparatus: Minispec MQ20 (manufactured by Bruker Biospin)
Nuclide: ^1H
Measurement: _T2
Measurement method: Solid echo method Number of integrations: 256 times Repetition time: 1.0 sec
Measurement temperature: 20°C, 80°C (measurement started 60 minutes after the device temperature reached the measurement temperature and the sample was set)
Using the above-mentioned apparatus and conditions, ten sample pellets each measuring 8 mm in diameter and weighing approximately 50 mg were prepared and packed into a sample tube, and pulse NMR measurement was carried out to obtain an attenuation curve.
The obtained decay curve was fitted and analyzed using the above formula (1) to obtain the relaxation times of the crystalline phase, mesophase, and amorphous phase in the polyurethane resin. The fitting and analysis were performed using the software attached to the measurement device.

[Cross-sectional evaluation]
For each pad obtained as described above, the area around the end point detection window after slicing but before dressing (the area surrounded by dashed line S in Figure 2) (Evaluation 1) and the cross section of the area around the end point detection window after dressing (the area surrounded by dashed line S in Figure 2) (Evaluation 2) were observed using a laser microscope (VK-X1000, manufactured by KEYENCE) in a range of approximately 14 mm x 1 mm relative to the surface of the diameter part of the end point detection window at 200 times magnification in the connected mode, and profile measurement of height information was performed based on the obtained laser images.

The results are shown in Figures 5A-C and 6A-C. Note that Figures 5A-C and 6A-C show the cross-sectional measurement results for two end-point detection windows, and show the results of cross-sectional measurements performed for each end-point detection window in the slice direction and in a direction perpendicular to the slice direction.

In Evaluation 1, if the endpoint detection window was within ±50 μm of the polished surface, it was marked as ○, and otherwise it was marked as ×. In Evaluation 2, if the cross-sectional image was flat (the height was the same from the edge to the center), it was marked as ○, and if it was convex (the height increased from the edge to the center), it was marked as ×.

The polishing pad of the present invention has industrial applicability as a pad suitable for polishing semiconductor wafers and the like.

10... Polishing pad, 11... Polishing layer, 11a... Polishing surface, 12... End point detection window, 13... Cushion layer, 14, 15... Adhesive layer, 16... Groove, 20... Polishing device, 21... Top ring, 22... Table, 23... Film thickness detection sensor, 24... Slurry, W... Wafer

Claims (9)

a polishing layer and an end point detection window provided in an opening in the polishing layer;
When the free induction decay curve of the spin-spin relaxation of 1H obtained by measuring with the solid echo method using pulsed NMR was separated into three curves derived from the three components of the crystalline phase, mesophase, and amorphous phase in order of shortest relaxation time,
the ratio (Lp20/Lw20) of the amorphous phase abundance ratio Lw20 in the endpoint detection window to the amorphous phase abundance ratio Lp20 in the polishing layer at 20°C is 0.8 to 1.2 ;
the ratio (Sp80/Sw80) of the abundance ratio Sw80 of the crystalline phase in the endpoint detection window to the abundance ratio Sp80 of the crystalline phase in the polishing layer at 80°C is 1.0 to 1.3 ;
Polishing pad. the ratio (Mp20/Mw20) of the abundance ratio Mw20 of the mesophase in the endpoint detection window to the abundance ratio Mp20 of the mesophase in the polishing layer at 20°C is 0.7 to 1.5;
The polishing pad of claim 1 . the ratio (Mp80/Mw80) of the abundance ratio Mw80 of the mesophase in the endpoint detection window to the abundance ratio Mp80 of the mesophase in the polishing layer at 80°C is 0.5 to 1.5;
The polishing pad according to claim 1 or 2. The difference between the abundance ratio Lw20 and the abundance ratio Lp20 (|Lp20-Lw20|) is 10 or less,
The polishing pad according to any one of claims 1 to 3. The difference between the abundance ratio Sw80 and the abundance ratio Sp 80 (|Sp80-Sw80|) is 15 or less;
The polishing pad according to any one of claims 1 to 4. the endpoint detection window contains a polyurethane resin WI,
The polyurethane resin WI contains a structural unit derived from an aliphatic isocyanate.
The polishing pad according to any one of claims 1 to 5. The polishing layer contains a polyurethane resin P,
The polyurethane resin P contains a structural unit derived from an aromatic isocyanate.
The polishing pad according to any one of claims 1 to 6. The polishing layer contains hollow fine particles dispersed therein.
The polishing pad according to any one of claims 1 to 7. a polishing step of polishing an object to be polished using the polishing pad according to any one of claims 1 to 8 in the presence of a polishing slurry to obtain a polished product;
an end point detection step of detecting an end point by an optical end point detection method during the polishing.
A method for manufacturing polished workpieces.