JP2005231014A - Polishing pad, and polishing method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad which has excellent homogeneity and can be easily mounted on a polishing machine in the machining for flattening a surface of a wafer for a semiconductor device. <P>SOLUTION: The polishing pad 12 has a polishing forming element 6 having at least a polishing layer 6 as a composing element, and has a bending elastic modulus of at most 6.5 MPa. The polishing pad 12 may have further a polishing laminated element 6 laminated with a supporting layer 11 as a composing element. In addition, preferably, a main raw material of the polishing forming element 6 is a thermoplastic elastomer, and the polishing pad 12 has grooves. <P>COPYRIGHT: (C)2005,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 platen (2) and the sample holder (5) and supplying the polishing slurry (4) through the slurry supply pipe (10), the semiconductor device wafer (1) is polished on the polishing layer (6) of the polishing pad (12). ) 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 molded article for polishing having a polishing layer of a polishing pad, but a tool (3) generally called a dresser is generally used before or during polishing. ) Is rotated against the surface of the polishing layer (6) and subjected to a sharpening treatment to open the bubbles contained in the polishing layer.
In addition to the polishing conditions, the surface hardness and compressibility of the polishing pad, and if the polishing layer is a foam, the size and density of the bubbles contained in the polishing layer are large in the finished state of the workpiece after polishing. affect.
Conventionally, as a polishing layer of a polishing pad used for polishing, for example, an interlayer insulating film or a metal wiring, a slurry is retained by dressing before use or during use, and abrasion of the polishing pad surface accompanying polishing progress. For example, a member that contains a hole or the like that exhibits a function has been used.
As a molded article for polishing having a representative abrasive layer, a molded article for polishing in which hollow polymer microelements are dispersed in a matrix resin, represented by IC1000 manufactured by Rodel, can be mentioned (for example, Patent Document 1). reference.). 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.
The approach to achieve both flatness and uniformity is to use a so-called two-layer polishing pad in which a conventional hard polishing layer is bonded to a soft support layer with cushioning properties. (For example, see Patent Document 2). Specifically, the concept is that the polishing layer having a high surface hardness and a low compression rate maintains flatness and the soft support layer having a compression rate higher than that of the polishing layer maintains uniformity.
However, the conventional polishing pad has poor uniformity of device wafer processing, and when the polishing pad is mounted on a surface plate of a polishing machine, the polishing pad does not bend, so there are bubbles between the surface plate and the polishing pad. It was easy to enter. When bubbles enter, irregularities occur on the surface of the polishing pad. Since the unevenness deteriorates the uniformity, it must be fixed so that bubbles do not enter, and installation requires skill and a great number of man-hours.

Patent No. 3013105 JP-A-6-21028

  An object of the present invention is to provide a polishing pad having good uniformity and easy mounting on a polishing machine in surface planarization processing 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 at least a molded article for polishing having a polishing layer as a constituent element and having a flexural modulus of 6.5 MPa or less.
(2) The polishing pad according to (1), wherein the polishing pad further comprises a polishing laminate in which a support layer is laminated.
(3) The polishing pad according to (1) or (2), wherein the main raw material of the molded article for polishing is a thermoplastic elastomer.
(4) The polishing pad according to (1) to (3) having a groove.
(5) A polishing method in which the polishing pad of (1) to (3) is attached to a polishing machine to flatten the surface of the 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 having a flexural modulus of 6.5 MPa or less is attached to a polishing machine to flatten the surface of a workpiece. It is very preferable that the bending elastic modulus of the polishing pad is 6.5 MPa or less because the uniformity of device wafer processing is improved and a lot of man-hours and skill are not required for mounting on the surface plate of the polishing machine.

In the present invention, the molded article for polishing and the polishing layer are strictly distinguished. For example, when a foamed layer is involved in polishing in the molded body for polishing, only the foamed layer corresponds to the polishing layer. If there is a non-foamed layer in the vicinity of the surface of the molded body for polishing, and the non-foamed layer is removed by dressing or the like before entering the flattening process of the workpiece, the non-foamed layer is included in the polishing layer. Absent.
On the other hand, the polishing pad includes at least a molded article for polishing having a polishing layer as a constituent element and includes elements from the polishing layer to a member for mounting. For example, it shall include a polishing molded body having no laminated structure, and a polishing laminated body in which a polishing molded body having a polishing layer and a support layer are laminated, and a cushioning double-sided tape or the like is previously placed on a surface plate of a polishing machine, etc. When affixing and attaching an abrasive compact directly to this, it is defined that only the abrasive compact is a polishing pad.

  The bending elastic modulus of the polishing pad of the present invention is set to 6.5 MPa or less in order to improve the uniformity of device wafer processing and to make the resulting polishing pad more flexible. When the flexural modulus is small, the retention of the slurry is improved, so that the uniformity of device wafer processing of the resulting polishing pad is improved. In addition, when polishing the surface of a semiconductor device wafer, if the flexural modulus of the polishing pad exceeds 6.5 MPa, the polishing pad is difficult to bend, and when the polishing pad is fixed to the surface plate of the polishing machine, bubbles are separated from the polishing pad. It becomes easy to enter between the constants of the polishing machine. The operation of mounting so that bubbles do not enter is not preferable because it takes skill and a great number of man-hours.

The flexural modulus can be calculated by the following equation (1) using the first linear portion of the bending stress-deflection curve.
Flexural modulus = Stress difference between two points on the straight line part / Difference in strain between the same two points (1)

As test conditions, test piece dimensions are: length 30 mm, width 10 mm, thickness: 2 mm or less, distance between fulcrums: 22 mm, crosshead speed: 0.6 mm / min.

  Further, the thickness of the polishing layer immediately before the start of polishing is not particularly limited, but is preferably 2 mm or less.

  The polishing layer of the present invention is not particularly limited, but it is more preferable that air bubbles are included in forming a surface state suitable for holding a polishing slurry or polishing by dressing treatment 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.

  The main raw material of the polishing layer of the present invention is not particularly limited, but it is preferable to use a thermoplastic elastomer. For example, polyurethane, polystyrene, polyester, polypropylene, polyethylene, nylon, polyvinyl chloride, polyvinylidene chloride, polybutene, polyacetal, polyphenylene oxide, polyvinyl alcohol, polymethyl methacrylate, polycarbonate, polyarylate, aromatic polysulfone, polyamide, polyimide, Fluorine resin, ethylene-propylene resin, ethylene-ethyl acrylate resin, acrylic resin, norbornene resin, for example, vinyl polyisoprene-styrene copolymer, butadiene-styrene copolymer, acrylonitrile-styrene copolymer, acrylonitrile-butadiene- Styrene copolymers represented by styrene copolymers, etc., or polyurethane and polyolefin thermoplastic elastomers It may be exemplified natural rubbers, synthetic rubbers and the like. These may be used singly or may be mixed or copolymerized, but from the viewpoint that physical properties such as hardness and compressibility that greatly affect the polishing characteristics can be controlled relatively easily, for example, urethane-based and olefins. A thermoplastic elastomer of the type is preferred. Among them, a thermoplastic polyurethane elastomer is most preferable in that the abrasion resistance important for polishing can be controlled in a relatively wide range.

The material of the support layer of the present invention is not particularly limited as long as the resulting polishing pad has a flexural modulus of 6.5 MPa or less. 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, epoxy resins, polyurethane resins including thermoplastic polyurethane elastomers, non-foamed substrates such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, and those reinforced with glass fibers are preferably used. Absent.
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 article 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 reducing 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 have a surface state suitable for polishing and / or has 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 applying the grooves, the polishing slurry is more widely spread and cheaper over the entire polishing surface, or when bubbles are not included in the polishing layer, the polishing slurry can be held and a surface state suitable for polishing can be obtained. This is preferable in terms of ensuring the performance, variation in polishing performance, and variation in the polishing performance over time.
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 refers to the distance A, the distance between adjacent grooves refers to the distance B, and the groove depth refers to C.
In the groove of the present invention, a desired size can be selected. In particular, with respect to the groove depth, the groove may be partway in the polishing layer, or may penetrate the polishing layer 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.
A raw material obtained by previously mixing the main material, a thermoplastic polyurethane elastomer (trade name: Resamine P-4250) manufactured by Dainichi Seika Kogyo Co., Ltd. (trade name: Crossnate EM-30), was 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.
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) with 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 exactly fitted, and the joint was temporarily fixed with a staple. .

A thermoplastic polyurethane elastomer (trade name: Resamine P-4250) manufactured by Dainichi Seika Kogyo Co., Ltd. was charged into the raw material hopper (208) and extruded 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 (206), a pinch roll (204) was passed and the polishing layer 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.
(Example 2)
<Production of polishing laminate>
Extrusion was performed using the same molding equipment used in Example 1, using the molded article for polishing obtained in Example 1. Extrusion of the support layer and press-bonding of the polishing layer and the support layer were performed in the same manner as in Example 1 using a thermoplastic polyurethane elastomer (trade name: Resamine P-4038) manufactured by Dainichi Seika Kogyo Co., Ltd.
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.
When grooving, the groove interval is programmed so that grooves are always inserted at the joint between adjacent polishing layers, and the groove depth is programmed so that the grooves penetrate the polishing layer (20) and reach the support layer (21). Set in.
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.

(Comparative Example 1)
A laminated pad (trade name: IC1000 / SUBA400) manufactured by Rodel with a diameter of 610 mm was used as a comparative example.
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.

<Measurement of flexural modulus (abrasive laminate)>
A polishing laminate in which the polishing layer and the support layer before being polished by the belt sander were pressure-bonded was cut out to a size of 30 mm in length and 10 mm in width, and three test pieces were prepared by laminating the polishing layer and the support layer. The thickness of the test piece was 2.00 mm. The flexural modulus was measured using an autograph tester AG-2000D manufactured by Shimadzu Corporation. Measurement was performed at each n = 3, and an average value was obtained. The flexural modulus was calculated by the following equation (1) using the first linear portion of the bending stress-deflection curve.

Flexural modulus = Stress difference between two points in the straight line portion / Strain difference between the same two points (1).

The test temperature was 23 ° C. and the humidity was 50%.

<Measurement of polishing layer thickness and calculation of average bubble diameter (polishing layer)>
The cross section of the polishing layer was observed with a scanning electron microscope S-2400 manufactured by HITACHI, and the thickness of the foam layer was measured. Further, the diameter of each bubble included in the image with a magnification of 300 was measured, and the average value of the diameters of all the bubbles was calculated. For a bubble having a cross-sectional shape that is not a perfect circle, for example, an elliptical shape or an irregular polygonal shape, the equivalent circle diameter was calculated as the diameter of the bubble.

Table 2 summarizes the values of physical properties related to the present invention for each of Examples and Comparative Examples.

<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 the conditions of a load of 10 kPa, a rotation speed of the surface plate of 60 rpm, and a rotation speed of the dressing disk holder 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), as compared with (Comparative Example 1), the variation in the polishing rate in the wafer surface was reduced, and the flatness was improved. In addition, in comparison with (Comparative Example 1), in (Example 1) and (Example 2), when the polishing pad is fixed to the surface plate of the polishing machine, the polishing pad is folded without causing wrinkles on the polishing surface. Since it was possible to laminate easily, it was possible to work without man-hours.

  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 Molding body for polishing (polishing layer)
7 Rotating shaft 8 Wafer fixing jig 9 Backing material 10 Slurry supply pipe 11 Support layer 12 Polishing pads 30, 50, 60, 70 Polishing compact (polishing layer)
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 Polishing Molded body 201 Single screw extruder 202 Mold 203 Roller conveyor
204 Pinch roll 205 Support plate 206 Laminated laminate 207 Support layer

Claims (5)

A polishing pad comprising a polishing compact having at least a polishing layer as a constituent element, the polishing pad having a flexural modulus of 6.5 MPa or less. The polishing pad according to claim 1, wherein the polishing pad further comprises a polishing laminate in which a support layer is further laminated. The polishing pad according to claim 1 or 2, wherein a main raw material of the molded article for polishing is a thermoplastic elastomer. The polishing pad according to claim 1, further comprising 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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