JP2006142438A - Polishing pad and polishing method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad having very high flatness and capable of preventing the surface of a wafer from being damaged in surface planarization machining for a semiconductor device wafer. <P>SOLUTION: The polishing pad has a polishing molding as a constituent element. The tensile storage elastic modulus E'<SB>30</SB>at 30°C of the polishing molding is ≥3×10<SP>9</SP>dyn/cm<SP>2</SP>. A ratio (E'<SB>30</SB>/E'<SB>60</SB>) of the E'<SB>30</SB>at 30°C to E'<SB>60</SB>at 60°C of the polishing molding is 2-7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a material used for polishing semiconductors and various memory hard disk substrates, and more particularly to a polishing pad suitable for surface planarization processing of a semiconductor device wafer, such as an interlayer insulating film and metal wiring.

An example of a chemical mechanical polishing method (CMP), which is a typical process used for surface planarization of a semiconductor device wafer, is shown in FIG. While rotating the surface plate (2) and the sample holder (5) and supplying the polishing slurry (4) through the slurry supply pipe (10), the semiconductor device wafer (1) is molded to polish the polishing pad (12). (6) By pressing against the surface, the device surface is polished and flattened with high accuracy.
Conventionally, for example, a polyurethane foam has been typically used as a polishing pad for a polishing pad, but a tool (3) generally called a dresser is usually rotated before or during polishing. On the other hand, the bubbles contained in the abrasive compact were opened by pressing the surface against the surface of the abrasive compact (6) and performing a sharpening treatment.
In addition to the polishing conditions, the surface hardness and compression rate of the polishing pad, and when the polishing molding is a foam, the size and density of the bubbles contained in the polishing molding are determined by the workpiece after polishing. It has a great influence on the finish.
Conventionally, as a polishing molded body of a polishing pad used for polishing, for example, an interlayer insulating film or a metal wiring, a slurry is used due to dressing before use, dressing during use, and abrasion of the surface of the polishing pad accompanying the progress of polishing. For example, a member containing a hole or the like that expresses the function of holding has been used.
As a typical polishing molded body, there is a polishing molded body in which hollow polymer microelements are dispersed in a matrix resin, represented by IC1000 manufactured by Rodel (see, for example, Patent Document 1). As the matrix resin, for example, a thermosetting polyurethane resin that is hard and has a low compressibility has been used.
Recent advances in the electronics industry have evolved into transistors, ICs, LSIs, and super LSIs. As the degree of integration of circuits in these semiconductor elements increases rapidly, the design rules of semiconductor devices are becoming finer year by year, the depth of focus in the device manufacturing process becomes shallower, and the level of flatness required for the pattern formation surface is It has become increasingly severe. At the same time, the diameter of the wafer has increased, and how to suppress variations in flatness within the device wafer surface to be processed, that is, how to improve the uniformity within the wafer surface and between wafers has been a major issue.
As an approach for achieving both flatness and uniformity, a so-called two-layer polishing pad in which a conventional hard abrasive compact is bonded to a soft support layer having cushioning properties has been used so far. However, there was a drawback that the flatness was not sufficient.

Patent No. 3013105 JP-A-6-21028

  It is an object of the present invention to provide a polishing pad that has very high flatness and does not cause scratches on the wafer surface in the surface flattening process of a semiconductor device wafer.

In view of the above-mentioned conventional problems, the present inventors have made extensive studies and have completed the present invention by the following means. That is, the present invention
(1) A polishing pad comprising a polishing molded body as a constituent element, the tensile storage elastic modulus E ′ ₃₀ at 30 ° C. of the polishing molded body being 3 × 10 ⁹ dyn / cm ² or more and polishing molding. A polishing pad, wherein the ratio of E ′ _{30 at} 30 ° C. to E ′ _{60 at} 60 ° C. (E ′ ₃₀ / E ′ ₆₀ ) of the body is 2 to 7;
(2) The polishing pad according to (1), wherein the polishing pad further comprises a support layer made of a thermoplastic elastomer,
(3) The polishing pad according to (1) or (2), which has a groove,
(4) A polishing method in which the polishing pad according to any one of (1) to (3) is attached to a polishing machine to flatten the surface of a workpiece,
It is.

  The polishing pad obtained by the present invention and the polishing method using the same can be suitably used for polishing for surface flattening of a semiconductor device wafer.

In the present invention, a polishing pad is mounted on a polishing machine to flatten the surface of a workpiece. A polishing pad comprising a polishing molded body as a constituent, the tensile storage elastic modulus E ′ ₃₀ at 30 ° C. of the polishing molded body being 3 × 10 ⁹ dyn / cm ² or more, and 30 ° C. of the polishing molded body. does not cause damage to the very high has flatness and wafer surface for E _'30 and 60 ° C. of E' ₆₀ ratio of _{(E '30 / E' 60} ) are the abrasive pad is 2-7 Therefore, it is very preferable.

  The polishing pad of the present invention includes a molded article for polishing as an essential component, and may include, for example, a member for mounting the molded article for polishing as another component. For example, it shall include an abrasive compact that does not have a laminated structure, or an abrasive laminate in which an abrasive compact and a support layer are laminated, and a cushioning double-sided tape or the like is pasted on a surface plate of a polishing machine in advance. When the abrasive compact is directly attached to this, only the abrasive compact is defined as a polishing pad.

Since the polishing pad of the present invention has very high flatness, it must be highly elastic. Specifically, the molded article for polishing has a tensile storage elastic modulus E ′ ₃₀ at 30 ° C. of 3 × 10 ⁹ dyn / cm ² or more, and heat is generated by friction during polishing. More specifically, the ratio of E ′ _{30 at} 30 ° C. to E ′ _{60 at} 60 ° C. (E ′ ₃₀ / E ′ ₆₀ ) of the molded article for polishing is 2 to 7, preferably 4-7.

The tensile storage modulus can be obtained with a general dynamic viscoelasticity measuring apparatus. As a specific example, a sample having a thickness of 1.5 mm, a width of 6 mm, and a length of 30 mm is set using DMS200 of Seiko Instruments Inc., and a tensile storage elastic modulus E ′ at 30 ° C. and 60 ° C. at 2 ° C./min and 10 Hz. ₃₀ and E ′ ₆₀ can be obtained.

  The thickness of the molded body for polishing immediately before the start of polishing is not particularly limited, but is preferably 2 mm or less.

  The molded article for polishing of the present invention is not particularly limited, but it is more preferable that air bubbles are included when a polishing slurry is held or a surface state suitable for polishing is formed by a dressing process using a dresser or the like. When enclosing bubbles, the average diameter of the bubbles is not particularly limited, but is preferably 0.1 to 100 μm, more preferably 0.1 to 50 μm, and most preferably 0.1 to 30 μm.

  When the average diameter of the bubbles is less than 0.1 μm, polishing scraps generated as the polishing progresses, for example, when abrasive grains are contained in the polishing slurry, aggregates of the abrasive grains, etc. There is a possibility that the air holes are clogged because they are not easily discharged from the open air holes. As a result, it is not preferable because variations in polishing performance are likely to occur, and further, fluctuations in polishing performance with time may increase. On the other hand, when the thickness exceeds 100 μm, for example, the surface roughness after dressing with a dresser becomes rough. In other words, since the unevenness of the polishing surface becomes large, the holding performance of the polishing slurry becomes less variable in the polishing surface, and as a result, the variation in polishing performance may increase, which is not preferable.

Although the main raw material of the molded article for polishing of the present invention is not particularly limited, it is preferable to use a thermoplastic elastomer, for example, a urethane-based or olefin-based thermoplastic elastomer is suitable.
In addition to the above components, additives such as fillers may be added.

The material of the support layer used in the present invention is not particularly limited. Depending on the desired polishing performance, for example, a flexible substrate such as plastic, thermoplastic elastomer, or rubber can be used as appropriate. These may contain bubbles or may not contain bubbles. Further, it may be reinforced with glass fiber, carbon fiber, synthetic fiber, or a woven or nonwoven fabric thereof. Furthermore, a flexible metal thin plate represented by stainless steel can also be used. Specifically, non-foamed substrates such as epoxy resins, polyurethane resins including thermoplastic polyurethane, polyethylene terephthalate, polybutylene terephthalate, polycarbonate and the like and those reinforced with glass fibers are preferably used. . Preferably, a thermoplastic polyurethane elastomer and a thermoplastic polyester elastomer are mixed.
Or you may use various adhesive agents, for example, the highly transparent double-sided tape etc. which apply | coated the acrylic adhesive to both surfaces of PET base material, etc. as a support layer.

  In the present invention, the method for laminating the molded body for polishing and the support layer is not particularly limited. A medium such as an adhesive or a double-sided tape may or may not be used. However, for example, a medium such as an adhesive or a double-sided tape is not used in terms of suppressing the cost and particularly the factor of quality variation. The structure laminated | stacked on is preferable. Specifically, a coextrusion method, a method in which a support layer in a molten state is bonded to a polishing molded body by a method usually called thermal lamination, and the like are preferable.

When polishing a device wafer using the polishing pad of the present invention, the polishing slurry is held as necessary to obtain a surface state suitable for polishing and / or a groove serving as a flow path for the polishing slurry. May be. The shape of the groove is not particularly limited, but can be selected as needed, for example, parallel, lattice, concentric, or spiral. Alternatively, a large number of cylindrical through holes can be provided.
By providing the grooves, the polishing slurry is more widely spread and cheaper over the entire polishing surface, which is preferable in terms of ensuring uniformity, polishing performance variation, and time-dependent fluctuations in the polishing performance.
Further, the groove size, that is, the groove width, the interval between adjacent grooves, and the groove depth are not particularly limited. In FIG. 2, the groove width indicates the distance A, the distance between adjacent grooves indicates the distance B, and the groove depth indicates C.
In the groove of the present invention, a desired size can be selected. In particular, with respect to the groove depth, a groove may be provided partway through the abrasive compact, or it may penetrate through the abrasive compact and reach the surface of the support layer. Furthermore, a groove may be provided through the support layer and partway through the support layer, or a groove may be provided only in the support layer.

The groove processing method is not particularly limited, but from a practical viewpoint in consideration of processing cost, processing accuracy, etc., machining by a lathe, a milling machine, a laser, or the like is preferable.
Note that FIG. 2 shows a polishing laminate in which a polishing compact (30) and a support layer (31) are directly bonded together by a thermal lamination method, and is fixed to a surface plate (34) of a polishing machine using a double-sided tape (35). Shows the state.
FIG. 3 shows a polishing laminate in which a polishing compact (50) and a support layer (51) are bonded via a double-sided tape (54), and a polishing platen (55) using a double-sided tape (56). A fixed state is shown.
FIG. 4 shows a state in which the molded body for polishing (60) is fixed to the surface plate (34) of the polishing machine through the thick coating layer (61).
FIG. 5 shows a state in which the molded article for polishing (70) is fixed to the surface plate (76) of the polishing machine via a double-sided tape (77). When the double-sided tape (77) is divided in more detail, it can be divided into a base material (71) and adhesive layers (74), (75). First, the double-sided tape (77) is applied to the abrasive compact (70). When sticking, a double-sided tape base material (71) corresponds to the support layer of this invention. Conversely, when the double-sided tape (77) is first applied to the surface plate (76), the molded article for polishing (70) corresponds to the polishing pad of the present invention.
2 and 3 show a case where a polishing laminate prepared by previously bonding a molded body for polishing and a support layer is pasted on a surface plate, so that both can be grooved to a depth reaching the support layer. It is.
On the other hand, FIG. 4 and FIG. 5 show the case where the abrasive compact is directly attached to the surface plate via a medium such as an adhesive or double-sided tape, and in this case, the groove is in the middle of the abrasive compact. It stops at.
The polishing laminate of the present invention can have a desired size and a desired shape, for example, a disk shape, a belt shape, and other various shapes.

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.
Example 1
<Production of polishing laminate>
FIG. 6 shows an outline of a production facility for a molded article for polishing used in the examples of the present invention. Tandem type extruder in which a first extruder (101) having a barrel diameter of 50 mm and L / D = 32 and a second extruder (108) having a barrel diameter of 65 mm and L / D = 36 are connected by a hollow single pipe (107). A die (109) having a lip width of 300 mm was attached to the tip of the plate.
100 parts by weight of thermoplastic polyurethane elastomer (trade name: Resamine P-4230) manufactured by Dainichi Seikagaku Co., Ltd., which is the main raw material, and 3.5 parts by weight of its cross-linking agent (trade name: Crossnate EM-30) Premixed raw materials were used.
After taking out from the cylinder (106), carbon dioxide pressurized by the gas booster pump (105) was injected through an injection port (104) attached to the center front side of the first extruder (101). The pressure immediately before and after the injection port (104) was measured by a pressure sensor attached to the barrel of the first extruder (101), and they were 24 MPa and 21 MPa, respectively.
Immediately after the extrusion, pinching with a pinch roll (111) was carried out and cooled in a water tank (110) almost at the same time to obtain a foam molded article.
The obtained foam was cut into a width of 210 mm and a length of 630 mm to produce a molded article for polishing. When a predetermined size was cut out from the molded article for polishing and the tensile storage elastic modulus E ′ ₃₀ and E ′ ₃₀ / E ′ ₆₀ at 30 ° C. were determined, they were 7.8 × 10 ⁹ dyn / cm ² and 5.6, respectively. there were.
Table 1 shows the molding conditions.

An outline of the stacking equipment used in the examples of the present invention is shown in FIG.
A die (202) having a lip width of 800 mm was attached to the tip of an extruder (201) having a barrel diameter of 50 mm and L / D = 32. A support plate (205) was installed on the roller conveyor (203). A veneer plate having a thickness of 5 mm was used as the support plate.
Three abrasive compacts (206) having a width of 210 mm and a length of 630 mm were placed on the support plate so that the polishing surface was in contact with the support plate and each joint was tightly fitted, and the joints were temporarily fixed with staples. .

100 parts by weight of a thermoplastic polyurethane elastomer (trade name: Resamine P-4250) manufactured by Dainichi Seika Kogyo Co., Ltd. 3.5 parts by weight of the cross-linking agent (trade name: Crossnate EM-30) as a raw material hopper (208) And pushed out from the mold (202).
Under the mold (202), a support plate (205) on which a molded article for polishing is placed is passed while sliding on a roller conveyor (203), and the molten resin extruded from the mold (202) is polished. Immediately after being laminated on the molded article for use (206), a pinch roll (204) was passed, and the molded article for polishing and the support layer were pressure bonded.
After the support layer had cooled sufficiently, the staples were removed.
Then, the polishing surface side of the obtained 630 mm square laminate was polished with a belt sander (trade name: MNW-610-C2) manufactured by Marugen Steel Works, and the non-foamed layer near the surface of the polishing molded body was removed. Thus, a polishing laminate was obtained.

<Groove processing>
Using a crosswise saw manufactured by Shoda Techtron Co., Ltd., a groove having a width of 2 mm was applied in a lattice pattern over the entire polished surface so that the distance between adjacent grooves was 13 mm.
At the time of grooving, the groove interval is set so that grooves are always inserted at the joints between adjacent molded bodies for polishing, and the groove is formed so as to reach the support layer (31) through the molded body for polishing (30). The depth was set programmatically.
A highly transparent PET base double-sided tape having a thickness of 75 μm was attached to the support layer side of the obtained laminate for polishing, and then cut into a disk shape having a diameter of 610 mmφ to obtain a polishing pad.

(Example 2)
<Production of polishing laminate>
Example using 100 parts by weight of a thermoplastic polyurethane elastomer (trade name: Resamine P-4250) manufactured by Dainichi Seika Kogyo Co., Ltd. and 3.5 parts by weight of the cross-linking agent (trade name: Crossnate EM-30) A polishing compact was produced in the same manner as in Example 1. A predetermined size was cut out from the molded body for polishing, and the tensile storage elastic modulus E ′ ₃₀ and E ′ ₃₀ / E ′ ₆₀ at 30 ° C. were determined to be 5.0 × 10 ⁹ dyn / cm ² and 6.8, respectively. there were.
Using the same laminating equipment as used in Example 1, the support layer was extruded and the abrasive compact and the support layer were pressed in the same manner as in Example 1. The support layer had the same composition as that used for the molded article for polishing.
Then, the polishing surface side of the obtained 630 mm square laminate was polished with a belt sander (trade name: MNW-610-C2) manufactured by Marugen Steel Works, and the non-foamed layer near the surface of the polishing molded body was removed. Thus, a polishing laminate was obtained.
Groove processing similar to that in Example 1 was performed to obtain a polishing pad.

(Comparative example)
A laminated pad (trade name: IC1000 / SUBA400) manufactured by Rodel with a diameter of 610 mm was used as a comparative example. A predetermined size was cut out from the molded body for polishing, and the tensile storage elastic modulus E ′ ₃₀ and E ′ ₃₀ / E ′ ₆₀ at 30 ° C. were determined to be 6.2 × 10 ⁹ dyn / cm ² and 1.5, respectively. there were.
Note that the entire polishing surface of the laminated pad of this comparative example is provided with a grid-like groove having a width of 2 mm and a gap of 13 mm between adjacent grooves, as in the example.

<Polishing performance evaluation>
As an object to be polished, a 10,000-inch Cu film was prepared by electrolytic plating on a 3-inch silicon wafer.
A single-side polishing machine with a platen diameter of 200 mm was used for polishing. A polishing pad is affixed to the surface plate of the polishing machine with double-sided tape, and a dressing disk electrodeposited with diamond is polished for 2 hours under conditions of a load of 10 kPa, a surface plate rotation speed of 60 rpm, and a dressing disk holder rotation speed of 50 rpm. After dressing the pad surface, a polishing slurry (product name: iCue5003) manufactured by Cabot was passed to polish the Cu film for 1 minute.
As polishing conditions, the load applied to the wafer was 350 g / cm ² , the rotation speed of the surface plate was 70 rpm, the rotation speed of the wafer was 70 rpm, and the flow rate of the polishing slurry was 200 ml / min.
After cleaning and drying the polished wafer, the Cu film thickness was measured using a sheet resistance measuring machine, and the average polishing rate, the polishing rate variation in the wafer surface, and the flatness were compared with the conventional pad.

<Evaluation results>
In (Example 1) and (Example 2), the polishing rate variation in the wafer surface was reduced and the flatness was improved as compared with (Comparative Example). Also, the surface of the wafer after polishing in (Comparative Example) was scratched, but the surface of the wafer after polishing in (Example 1) and (Example 2) was scratched. Did not exist.

  The polishing pad obtained by the present invention can be suitably used for polishing a surface flattening process of a semiconductor device wafer.

It is an example of a standard process of chemical mechanical polishing (CMP). It is sectional drawing which shows an example of the state which affixed the polishing pad on the surface plate of this invention. It is sectional drawing which shows an example of the other state which affixed the polishing pad on the surface plate of this invention. It is sectional drawing which shows an example of the other state which affixed the polishing pad on the surface plate of this invention. It is sectional drawing which shows an example of the other state which affixed the polishing pad on the surface plate of this invention. It is the schematic of the molded object manufacturing apparatus for grinding | polishing used in the Example. It is the schematic of the lamination equipment used in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor wafer 2 Surface plate 3 Dresser 4 Polishing slurry 5 Sample holder 6 Polishing molded object 7 Rotating shaft 8 Wafer fixing jig 9 Backing material 10 Slurry supply piping 11 Support layer 12 Polishing pads 30, 50, 60, 70 Polishing Molded body 31, 51 Support layer 61 Adhesive layer 71 Double-sided tape base material 32, 52, 62, 72 Polished surface 33, 53, 63, 73 Groove 35, 54, 56, 74, 75 Adhesive layer 34, 55, 64, 76 Surface plate 77 Double-sided tape 101 First extruder 102 Raw material hopper 103 Pressure regulating valve 104 Foaming agent injection part 105 Gas booster pump 106 Cylinder 107 Hollow single pipe 108 Second extruder 109 Mold 110 Water tank 111 Pinch roll 112 Water absorption Roll 113 Molded body for polishing 201 Single screw extruder 202 Mold 203 Roller conveyor
204 Pinch roll 205 Support plate 206 Laminated laminate 207 Support layer

Claims (4)

A polishing pad having a polishing compact as a constituent element, wherein the polishing compact has a tensile storage elastic modulus E ′ ₃₀ at 30 ° C. of 3 × 10 ⁹ dyn / cm ² or more, and 30 of the polishing compact. A polishing pad, wherein the ratio of E ′ ₃₀ at 60 ° C. to E ′ _{60 at} 60 ° C. (E ′ ₃₀ / E ′ ₆₀ ) is 2 to 7. The polishing pad according to claim 1, wherein the polishing pad further comprises a support layer made of a thermoplastic elastomer. The polishing pad according to claim 1, wherein the polishing pad has a groove. A polishing method for mounting a polishing pad according to any one of claims 1 to 3 on a polishing machine to flatten the surface of a workpiece.

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