JP2003236764A - Foam sheet, and fixed abrasive grain foam for polishing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixed abrasive grain foam for polishing having small polishing performance dispersion and high polishing accuracy in a CMP process, easily enlarged in response to extended diameter of a wafer, and largely reducing dressing period. <P>SOLUTION: In the fixed abrasive grain foam for polishing, the cross section in the thickness direction of a foam sheet spirally wound and fixed via a bonding layer 13 having dispersed abrasive grains 15 is set as a polishing surface. An average diameter of air bubbles 14 contained in the foam sheet is not less than 0.1 μm and less than 300 μm, and main material constituting the foam sheet is thermoplastic polyuretane, and the bonding layer is a polyuretane based adhesive made of a curing agent having water solubility and/or water dispersibility. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing pad used for polishing semiconductors, substrates for various memory hard disks and the like, and in particular, surface flattening of a semiconductor device wafer such as an interlayer insulating film and metal wiring. The present invention relates to a polishing pad that is preferably used in.

[0002]

2. Description of the Related Art FIG. 1 shows an example of a chemical mechanical polishing (CMP) which is a typical process used for surface flattening of a semiconductor device wafer. While rotating the platen (2) and the sample holder (5) and dropping the polishing slurry (4) containing abrasive grains through the slurry supply pipe (10), the semiconductor wafer (1) is placed on the polishing pad (6) surface. The surface of the object to be polished is flattened with high precision by pressing it against. During polishing, the surface state of the polishing pad (6) is adjusted by pressing the dressing disc (3) against the surface of the polishing pad (6) while rotating the dressing disc holder (9). Not only the polishing conditions, but also the polishing pad (6), the dressing disk (3), the polishing slurry (4), the backing material (11), the wafer fixing jig (8), and other characteristics of each component are the polishing rate and the polishing. The polishing performance represented by the subsequent flatness and the in-plane uniformity of the semiconductor wafer is affected. Among them, the influence of the polishing pad (6) and the polishing slurry (4) and the abrasive grains contained in the polishing slurry is exerted. Is extremely large.

Conventionally, as the polishing pad, a single layer having only a polishing layer or a laminated structure having a polishing layer and a cushion layer bonded to each other has been used depending on the object to be polished and the required level of polishing accuracy. In the above structure, the polishing layer is roughly classified into, for example, an independent foamed body represented by IC1000 (trade name) manufactured by Rodel, or a fixed-abrasive molding in which abrasive grains are dispersed in the polishing layer in advance. It is used. In the conventional closed-cell foam, air bubbles are opened due to dressing before and during use, and abrasion of the polishing pad surface as the polishing progresses, so that the polishing slurry retaining ability is exhibited. It has been standardly used because of its relatively wide selection of polishing slurries and its high versatility. However, in the foam, there is a problem that the density varies due to, for example, the cross-linking density of the resin and the variation in the foam density. Since the density variation can exist not only in the polishing surface of the foam but also in the thickness direction, the conventional independent foam has the same foam surface within the same wafer or / and as the number of processing increases. There is a problem in that the polishing performance also varies due to abrasion and the polishing accuracy varies.

Further, in the conventional foam, it is necessary to dress the foam before use to open the cells. However, most of the matrix resins constituting the conventional closed foam are made of thermosetting polyurethane or the like. Since it is a resin having high wear resistance as typified by (1), dressing requires a long time, which causes a problem that throughput in the polishing step is reduced. On the other hand, in the fixed-abrasive molding, it is expected that the effect of suppressing the fluctuation of the polishing performance due to the density variation of the independent foam can be expected, for example, by mixing and dispersing the abrasive particles in the molding step and fixing them in advance. Has been done. When using a fixed-abrasive molded body as the polishing layer of the polishing pad, basically no slurry is used for that purpose, or a slurry called abrasive-less that does not contain abrasive particles is used. Compared with the case of using the polishing slurry of, for example, the absolute amount of abrasive grains is insufficient, the polishing rate is not, or due to the abrasive grains that have fallen off, problems such as micron-level scratches called scratches on the processed surface was there.

Due to the recent remarkable development of the electronics industry, it has evolved into transistors, ICs, LSIs and VLSIs. As the degree of integration of circuits in these semiconductor elements has rapidly increased, the design rules of semiconductor devices have become finer year by year, the depth of focus in the device manufacturing process has become shallower, and the flatness of the pattern formation surface has become more and more strict. Is coming. Along with that, CM in the future
It is inevitable that the polishing accuracy required for P will further increase, and the polishing performance level required for the polishing pad will also increase. In addition to improving the polishing performance level, it is also required to cope with the increase in wafer diameter from 200 mmφ to 300 mmφ, overcoming the problems of conventional pads,
There is a great demand for the appearance of a polishing pad that can realize highly accurate polishing and can also accommodate a larger diameter wafer.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to a conventional polishing pad using an independent foam, for example, a problem that the polishing performance varies, a long time is required for dressing before use, or a fixed abrasive molding. Of the polishing pad using, for example, to solve the problem that scratches are likely to occur due to the removal of abrasive grains, the purpose is to provide a stable polishing accuracy when used as the polishing layer of the polishing pad. And to provide a fixed abrasive foam for polishing which can cope with an increase in the diameter of a wafer.

[0007]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made extensive studies in view of the problems of the prior art, and as a result, have accomplished the present invention by the following means. That is, the present invention is
(1) A fixed abrasive grain foam for polishing, characterized in that a cross section in a thickness direction of a foamed sheet wound and fixed in a spiral shape via an adhesive layer in which abrasive grains are dispersed is a polishing surface.
(2) The average diameter of bubbles contained in the foam sheet is 0.1 μm.
As described above, the fixed abrasive grain foam for polishing according to item (1), which is less than 300 μm, and (3) the main raw material constituting the foam sheet,
Fixed abrasive grain foam for polishing according to item (1) or (2), which is a thermoplastic polyurethane, and (4) a polyurethane-based adhesive whose adhesive layer is made of a water-soluble and / or water-dispersible curing agent as a raw material. The fixed abrasive grain foam for polishing according to any one of items (1) to (3), wherein the fixed abrasive grain foam is for use in polishing.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the fixed abrasive grain foam for polishing of the present invention, the cross section in the thickness direction of the foamed sheet is the polishing surface.
Polishing surfacing is performed by, for example, slicing or cutting the foamed sheet. According to this method, the thickness can be strictly controlled, and at the stage where, for example, slicing or cutting is performed, bubbles are opened in the polishing surface. Therefore, with respect to the virgin product, the time required for dressing before polishing becomes short or completely unnecessary, so that the throughput in the polishing step can be significantly improved. Further, as a merit of winding the foamed sheet in a spiral shape, it is possible to manufacture a polishing pad of a desired size by adjusting the number of windings of the foamed sheet. In other words, the product can be increased in size without changing the quality according to the increase in the diameter of the semiconductor wafer.

In the fixed abrasive grain foam for polishing according to the present invention, the foamed sheet is fixed via the adhesive layer, and the abrasive grains are dispersed in the adhesive layer. Since air bubbles and abrasive grains coexist, both complement each other's defects. Specifically, the abrasive grains supplement the lack of retention and / or variation in retention of the slurry due to bubbles, and contribute to the development of stable polishing performance for a long time. Also, by adopting a polishing method using a polishing slurry, a so-called loose abrasive grain method,
The generation of fine scratches due to the removed abrasive grains can be suppressed.
The average diameter of the bubbles contained in the foamed sheet is not particularly limited, but is preferably 0.1 μm or more and less than 300 μm, more preferably 0.5 μm or more and less than 200 μm, and most preferably 1.0 μm or more and less than 100 μm. If the average diameter of the bubbles is less than 0.1 μm, for example, it is likely to be clogged with agglomerates of abrasive grains or polishing debris contained in the polishing slurry, and the polishing performance deteriorates in a short time, that is,
This is not preferable because the life of the product will be significantly shortened. On the other hand, when it is 300 μm or more, the strength of the product is remarkably reduced, which is not preferable.

The main raw material constituting the foamed sheet used for the fixed abrasive grain foam for polishing of the present invention is not particularly limited, but thermoplastic polyurethane, polystyrene, polyester, polypropylene, polyethylene, nylon, polyvinyl chloride, polyvinylidene chloride. , Polybutene, polyacetal, polyphenylene oxide, polyvinyl alcohol,
Polymethyl methacrylate, polycarbonate, polyarylate, aromatic polysulfone, polyamide, polyimide, fluororesin, ethylene-propylene resin, ethylene-ethyl acrylate resin, acrylic resin, norbornene-based resin, for example, vinyl polyisoprene-styrene copolymer, A styrene copolymer typified by a butadiene-styrene copolymer, an acrylonitrile-styrene copolymer, an acrylonitrile-butadiene-styrene copolymer, or a natural rubber or a synthetic rubber is preferable. These may be used alone, or may be mixed or copolymerized. In terms of abrasion resistance, hardness, compressibility, and other polishing suitability, it is preferable to use thermoplastic polyurethane as an essential component, that is, to use it as a main raw material because it is very well balanced.

The adhesive layer contained in the fixed abrasive grain foam for polishing of the present invention is not particularly limited, but it is environmentally friendly because it does not use an organic solvent. It is preferable that the adhesive layer is a polyurethane-based adhesive made of a water-soluble and / or water-dispersible curing agent as a raw material, in that the adhesive layer can be dispersed in a more homogeneous state. As a method of adding abrasive grains, for example, after stirring and mixing the main agent of the adhesive and the curing agent, an aqueous solution containing abrasive grains is added, and the water concentration is adjusted beforehand to an appropriate range by heating, etc., and stirred. However, a method of applying to the surface of the foamed sheet may be used.

The abrasive grains are not particularly limited, but can be arbitrarily selected depending on the processing target, required polishing accuracy, and the like. For example, silica-based (SiO ₂ ), ceria-based (CeO ₂ ), alumina-based (Al ₂ O ₃ ), zirconia-based (ZrO ₂ ), and manganese-based (MnO ₂ , Mn).
₂ O ₃ ), titanium oxide and the like, polymethyl methacrylate, copolymers of polymethyl methacrylate and divinylbenzene, and melamine formaldehyde condensates. These may be used alone or in combination of two or more. The combination, ratio, etc. are not particularly limited.

The method for producing the fixed abrasive grain foam for polishing according to the present invention is not particularly limited, but for example, a raw fabric produced by winding the foamed sheet surface while applying an adhesive with a knife coater or the like in a heating furnace. The method of slicing into a predetermined thickness after the adhesive is sufficiently cured, or after cutting the foamed sheet into a predetermined width, the sheet surface is wound while applying the adhesive, and then the heating furnace The method of fully curing the adhesive may be mentioned. These bonding and cutting steps may be incorporated after the sheet forming step, which is represented by, for example, extrusion molding, and may be continuously processed.
Alternatively, after forming the foamed sheet, a roll-to-roll method may be used by using a roll that is once wound on a roll. When the fixed abrasive foam for polishing of the present invention is used as a polishing pad, it may be used alone depending on the type of object to be polished, required polishing accuracy, or the like, or for example Rodel Co. It can also be used in the form of being attached to a soft sheet such as Suba 400.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the contents of the examples. <Evaluation of Polishing Performance> As an object to be polished, a 6-inch silicon wafer on which 10000 Å of Cu was formed by electrolytic plating was prepared. A one-side polishing machine having a platen diameter of 600 mm was used for polishing. A polishing pad was attached to the surface plate of the polishing machine with a double-sided tape, and while polishing the surface of the polishing pad with a diamond electrodeposition disk, polishing slurry (trade name: iCue5003) manufactured by Cabot Co. was flowed for 1 minute to form a Cu film. Polished.

As the polishing conditions, the load applied to the wafer is 350 g / cm ² , the rotation number of the surface plate is 70 rpm, the rotation number of the wafer is 70 rpm, and the flow rate of the polishing slurry is 200 ml.
/ Min. After cleaning and drying the wafer after polishing, the Cu film thickness was measured at 49 points on the wafer surface using a 4-probe sheet resistance measuring machine, and the average polishing rate was calculated as an index of polishing performance and the flatness was measured. Was compared with a conventional pad.

(Example) A foamed sheet obtained by extrusion molding using carbon dioxide as a foaming agent and made of thermoplastic polyurethane as a main raw material and having an average cell diameter of 35 μm was wound to prepare a raw fabric. The roll-to-roll method applies the urethane resin adhesive mixed with silica particles with a primary particle size of 0.05 μm to the surface of the foamed sheet and rolls it up into the dryer. After sufficiently curing, using a slicer, a thickness of 2.5 mm,
A fixed abrasive foam for polishing having a diameter of 600 mmφ was prepared.
The fixed abrasive grain foam for polishing was used alone as a polishing pad to polish a Cu film. (Comparative Example) As a polishing pad, an IC having a diameter of 600 mmφ
The Cu film was polished using 1000 (manufactured by Rodel).

<Evaluation Results> Comparing the polishing performances of (Example) and (Comparative Example), no significant difference in polishing rate was observed between the two, and both were at a level at which practical use was possible. For example, the flatness after polishing (comparative example)
Was better than. However, (Example) is a performance evaluation result of a virgin product without dressing before polishing. In (Comparative Example), in order to obtain a polishing rate equivalent to that of (Example), a load of 10 kPa,
Plate rotation speed 60 rpm, dressing head rotation speed 5
Two hours of dressing was required at 0 rpm.

[0018]

EFFECTS OF THE INVENTION The fixed abrasive grain foam for polishing in which abrasive grains are dispersed in the adhesive layer between the spirally wound foam sheets of the present invention is used as a polishing surface. With the polishing pad as a layer, variation in polishing performance was reduced and polishing accuracy was improved. Furthermore, the pad size can be arbitrarily adjusted without lowering the polishing performance, and the throughput is remarkably improved by shortening the dressing time for the virgin product or omitting the dressing step.

[Brief description of drawings]

FIG. 1 is an example of a standard process of chemical mechanical polishing (CMP).

FIG. 2 is an example of an overall image of a polishing surface (cross section in the thickness direction of a foamed sheet) of a polishing pad of the present invention.

FIG. 3 is an example of an enlarged image of a polishing surface of the polishing pad of the present invention.

[Explanation of symbols]

1 Semiconductor wafer 2 surface plate 3 dressing discs 4 Polishing slurry 5 Sample holder 6 polishing pad 7 rotation axis 8 Wafer fixing jig 9 Dressing disc holder 10 Slurry supply pipe 11 Backing material 12 Foam layer 13 Adhesive layer 14 bubbles 15 Abrasive grain

Claims (4)

[Claims] 1. A fixed abrasive foam for polishing, wherein a cross section in the thickness direction of a foamed sheet wound and fixed in a spiral shape through an adhesive layer in which abrasive particles are dispersed serves as a polishing surface. . 2. The fixed abrasive foam for polishing according to claim 1, wherein the average diameter of the bubbles contained in the foamed sheet is 0.1 μm or more and less than 300 μm. 3. The fixed abrasive foam for polishing according to claim 1, wherein the main raw material constituting the foamed sheet is thermoplastic polyurethane. 4. The adhesive layer is composed of a polyurethane adhesive made of a water-soluble and / or water-dispersible curing agent as a raw material. Fixed abrasive grain foam for polishing as described.