JP2002028849A - Polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing pad that can suppress a reduction in polishing speed after repeated polishing without an operation of surface updating by a diamond grinding wheel and the like. SOLUTION: The polishing pad comprises a plurality of peelable thin layers and has uniform numbers, sizes and forms of recesses, through holes, grooves and the like for retention, discharge and the like of a water system dispersed material. The polishing pad 1 comprises the lamination of peelable layers 11 to 17. Each layer has recesses 11a, holes 11b and slits 11c. The polishing pad 1 formed from the lamination of the layers has a hole 1a where the holes 11b are formed so as not to pass from the obverse to the reverse of the pad 1, a through hole 1b where the holes 11b are formed so as to pass from the obverse to the reverse of the polishing pad 1, and a groove 1c. The polishing pad 1 may have a hollow passage 1d extending in a plane direction, and the hollow passage 1d may be in communication with some of the holes 1a and the through holes 1b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a polishing pad. More specifically, the present invention relates to a polishing pad that does not require a surface renewal using a diamond grindstone or the like and can suppress a decrease in polishing rate when polishing is repeated. The polishing pad of the present invention can be used for polishing a semiconductor wafer or the like.

[0002]

2. Description of the Related Art Conventionally, as a method for polishing a surface of a semiconductor wafer or the like, a chemical mechanical polishing method (Chemical M polishing method) has been used.
Technical Polishing) is known. In this polishing method, a surface to be polished such as a wafer is slid while being pressed against a disk-shaped polishing pad made of a polyurethane foam or the like, and a polishing slurry containing abrasive grains or the like is supplied onto the polishing pad. This is done by: The supplied slurry is held in concave portions on the surface of the polishing pad, for example, in the case of a polishing pad made of a polyurethane-based foam, air bubbles opened on the surface, and functions as an abrasive.

[0003]

However, in a pad made of a polyurethane-based foam which is frequently used at present, a residue of polishing slurry or polishing debris is deposited in a concave portion opened on the surface during repeated polishing. It tends to accumulate and cause clogging, and requires timely renewal of the surface with a diamond grindstone or the like. Further, it is not easy to sufficiently distribute the slurry flowing down from above the pad and supplied between the surface of the polishing pad and the surface to be polished such as a wafer pressed by the polishing pad. Actually, it is a part of the supplied aqueous dispersion that functions as an abrasive, and at present, most of them are discharged without functioning as an abrasive.

As described above, at present, (1) the number, size, shape, and the like of the concave portions for holding the aqueous dispersion are non-uniform, so that clogging is likely to occur. As a result, (2) the polishing of a semiconductor wafer or the like must be interrupted to renew the surface of the pad with a diamond grindstone or the like, and (3) most of the supplied aqueous dispersion is an abrasive. There is a problem that the waste gas is discharged without functioning at all.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a polishing pad which does not require a complicated surface updating operation using a diamond grindstone or the like. In addition, the number, size and shape of the recesses, through holes, grooves, etc. for holding and discharging the aqueous dispersion are uniform,
The supply of the aqueous dispersion between the surface of the pad and the surface to be polished such as a semiconductor wafer, and the discharge of the aqueous dispersion after being subjected to polishing can be performed easily and reliably, and the polishing is repeated. It is an object of the present invention to provide a polishing pad capable of suppressing a decrease in polishing rate when the polishing is performed.

[0006]

A polishing pad according to a first aspect of the present invention is characterized in that the polishing pad has a peelable layer. The “peelable layer” is a layer that can be easily peeled off at the interface with another layer when necessary without being peeled off in a normal polishing operation. This means that the joint is not so strong as to cause cohesive failure at the interface with another layer at the time of peeling.

The above-mentioned “polishing pad” is usually 10 to 10
A large number of peelable layers of 00 layers, especially 30 to 300 layers, are laminated and formed. Polishing pad may be formed by laminating a layer that can be peeled over its entire thickness,
A substrate having the same planar shape as the releasable layer and having a predetermined thickness made of resin or the like, and a releasable layer laminated on the substrate may be used. Although the thickness of the peelable layer is not particularly limited, it is 500 to 10 μm, particularly 200 to 30 μm.
μm, more preferably 100 to 50 μm,
The thickness of each layer may be substantially constant or may be different as appropriate.

When the polishing pad cannot be polished at a sufficient speed due to repeated polishing, the surface can be easily renewed by peeling a peelable layer as in the second invention. it can. The layer to be peeled off may be only one layer or two or more layers, and is not particularly limited, and an appropriate number of layers may be peeled off in consideration of the degree of reduction in polishing rate and the like.

[0009] The peelable layer may have holes,
It has at least one of a slit and a recess. Also, by forming holes or slits of substantially the same shape at the same position in the plane direction over an appropriate number of layers to be laminated, a hole or through-hole of a predetermined depth, and a groove of a predetermined depth Can be obtained. With these through holes or grooves, the polishing slurry can be supplied to the polishing surface or discharged out of the pad. Further, the slurry can be held by the concave portion or the hole.

By forming a slit so that at least one end in the longitudinal direction of the groove is open to the end face of the pad, in particular, by forming such a pad having such a groove over the entire surface of the polishing surface, Slurry containing polishing debris and the like can be quickly discharged out of the pad. Also, the groove can be formed on the back of the pad fixed to the surface plate,
This allows the slurry flowing down from the through hole to the back surface to be quickly discharged.

In addition to holes, through holes, and grooves, hollow paths can be formed in the polishing pad. The path of the hollow path in the pad is not particularly limited. In addition, the number, cross-sectional shape, cross-sectional dimension, and the like of the hollow paths can be appropriately set. By connecting these hollow paths to the through holes and the grooves, they can be used for supplying the slurry and discharging the slurry after polishing. Further, the through-hole may be not only an opening in the polishing surface but also an opening in a groove formed in the polishing surface and penetrating the back surface. With such a through hole, the slurry after polishing can be more easily discharged.

The opening diameter (the maximum length is defined as the opening diameter when the opening surface is not circular) on the polishing surface of the concave portion, the hole and the through-hole is not particularly limited, but can be 10 μm to 10 mm. Among these, the opening diameter of the concave portion and the hole for holding the slurry is 10 to 200 μm, especially 30 to 200 μm.
It is preferably 150 μm, more preferably 50 to 100 μm. With the opening diameter in this range, the slurry can be sufficiently held. In addition, the through holes and grooves used for supplying the slurry and discharging the slurry after polishing can be adjusted in the opening diameter by the supply amount and the discharge amount of the slurry, and are larger than the holes and the like for holding the slurry. , 20
The opening diameter can be from 10 μm to 10 mm, especially from 100 μm to 2 mm. The diameter of the opening on the back surface is not particularly limited.

FIG. 1 schematically shows a part of the cross section of the polishing pad of the first to third inventions having holes, through holes, grooves and the like.
In FIG. 1, the polishing pad 1 has peelable layers 11-1.
7 are laminated and formed (the actual polishing pad is
Usually, a larger number of layers are laminated and formed. ). A concave portion 11a, a hole 11b, and a slit 11c are formed in the peelable layer 11, and any one of a concave portion, a hole, and a slit is similarly formed in each of the peelable layers 12 to 17, respectively. . Then, these layers are stacked, and holes 1a, holes 11b, etc., formed without penetrating holes 11b and the like on the front and back surfaces of polishing pad 1, are formed through holes 1b formed on the front and back surfaces of polishing pad 1. , And a groove 1c composed of a slit 11c and the like.

Further, in this polishing pad, a hollow path 1d extending in a plane direction can be formed, and this hollow path may communicate with some of the holes and the through holes. With such a structure, the concave portion, the hole, the through-hole, the groove, and the hollow path each perform the same or different action required for the pad, and have excellent polishing performance as a whole pad, and Can be a polishing pad with a small decrease in polishing rate when the above is repeated. FIG. 1 shows that concave portions, holes, through holes and the like can be formed at arbitrary positions. However, in an actual pad, concave portions, holes, through holes and the like having the same shape and dimensions are regularly formed. Often formed.

The through hole for discharging the polished slurry is formed such that the opening diameter on the back surface is larger than the opening diameter on the polishing surface, and the opening diameter gradually increases from the polishing surface to the back surface. You can also. With such a through hole, clogging due to polishing debris or the like can be sufficiently prevented, and the slurry after polishing can be quickly discharged. Thereby, the use time of the pad until the peelable layer is peeled off for surface renewal can be lengthened.

The shape of the opening surface of the hole, the through hole, the groove, the hollow passage, and the sectional shape in the polishing pad are not particularly limited.
Various shapes such as a circle, an ellipse, a sector, an arc, a polygon, an L-shape, a T-shape, and a cross shape can be adopted. Further, in the case of the through hole, the angle with respect to the thickness direction of the pad is not particularly limited. For example, it may be a through hole inclined toward the peripheral edge from the polishing surface to the back surface of the polishing pad. With such a through hole, the slurry after polishing can be more efficiently discharged by centrifugal force. Can be. Further, the shape in the length direction of the groove and the hollow path may be linear or may be an appropriate curve.

The polishing pads of the first to third inventions can be formed by the additive manufacturing method as in the fourth invention.
According to this method, holes, through holes, grooves, and the like having a certain shape and dimensions can be formed regularly. The additive manufacturing method is a method of forming a specific structure by stacking layers having a thickness of 10 μm to 5 mm, and the specific forming method is not particularly limited. As the additive manufacturing method, there is a method in which a desired thickness of a polishing pad is laminated based on three-dimensional data of a polishing pad intended for a photo-curable resin or a thermosetting resin and cured to form a polishing pad having a predetermined shape. . In addition, a method in which a thin layer made of various resins or the like is cut out based on three-dimensional data of a target polishing pad, stacked, and joined to form a polishing pad having a predetermined shape can also be used.

According to this additive manufacturing method, the shapes and dimensions of holes, through holes, grooves, and the like, and the positions where they are formed can be controlled with extremely high precision. This makes it possible to provide a polishing pad that is less likely to be clogged by polishing debris and the like, has excellent polishing performance, and can suppress a decrease in polishing rate even when polishing is repeated.

As a polishing pad, a polishing pad made of a polyurethane foam having a large number of cells for holding a slurry has been widely used. In the fourth invention, various types of photocurable resins or thermosetting resins are used. The pad may be made of a curable resin, and the material resin is not limited. Therefore, a polishing pad having an appropriate hardness can be obtained by selecting a resin. Even if the polishing pad is considerably thinner or thicker than a conventional pad made of a polyurethane foam, sufficient rigidity and hardness can be obtained. And a polishing pad having excellent polishing performance.

The polishing pads of the first to fourth inventions can be used for chemical mechanical polishing of semiconductor wafers, magnetic disks and the like. The film to be polished using this pad includes a silicon oxide film, an amorphous silicon film, a polycrystalline silicon film, a single crystal silicon film, a silicon nitride film, a pure tungsten film, a pure aluminum film, a pure copper film, and the like. In addition, a film made of an alloy of tungsten, aluminum, copper, or the like and another metal may be used. Further, a film to be processed made of an oxide, a nitride, or the like of a metal such as tantalum or titanium may also be used.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail by way of examples. (1) Preparation of polishing pad Using an optical molding device (trade name "Solid Creation System" manufactured by D-MEC Co., Ltd.), a photo-curable resin (trade name "Desolite S" manufactured by JSR Corporation)
CR701 ”) was sequentially laminated in a thickness of 100 μm, and a total of 30 layers were laminated while curing to prepare a polishing pad. After laminating each layer, when curing, adjust the bonding strength between each layer by the amount of light irradiation,
With the force applied during wafer polishing, the layers do not peel off,
If necessary, the polishing pad could be separated between the layers without cohesive failure.

(2) Shape of Polishing Pad FIG. 2 is a plan view (a) showing an outline of a plan view of the polishing pad manufactured in (1), and a cross-sectional view schematically showing a state in which through holes are formed. (B). This polishing pad has a diameter of 300 mm and a thickness of 2 mm. Further, 100 [mu] m square cross-sectional shape and dimensions through hole of which opens to the shaded area in FIGS. 1 (a) is formed in 400 equivalents per 1 cm ² is polished surface. Furthermore, 300 μm from the back surface to the polished surface
A total of four hollow paths having a cross-sectional shape of 13 mm in width and 300 μm in height are formed from the center of the polishing pad to the periphery at a position m. A part of this hollow path is a groove opened to the back side. Also, a groove having a depth of 1 mm and a width of 2 mm is formed in a grid pattern on the entire surface of the polished surface (a region including portions other than the hatched portions in FIG. Is formed.

(3) Comparison of polishing pad performance A polishing pad having a peelable layer obtained in (1) and a polishing pad made of polyurethane foam for comparison (Rodel Nitta, product number "IC1000") ) Was affixed to a surface plate of a polishing device (model “Lapmaster LM-15” manufactured by Lappmaster SFT). Thereafter, polishing was performed on these polishing pads while supplying a polishing slurry (trade name “W-2000” manufactured by Cabot Corporation) at a flow rate of 50 cc / min. 4 × 4cm as the material to be polished
A tungsten film wafer cut into a corner was used, fixed on a wafer carrier, and polished for 3 minutes at a rotation speed of the platen of 66 rpm.

After polishing, the resistance value of the wafer surface is measured by a direct current four-probe method using a resistivity meter (model “Σ-5” manufactured by NSP). The polishing rate was calculated from the resistance value of the wafer surface that had been set.

The polishing is performed on the polishing pad of the present invention having the peelable layer as described above and on the polishing pad made of polyurethane foam (PUF) which has been frequently used in the past. 100% speed
In this case, the evaluation was made as the retention rate of the average polishing rate of 10 wafers after polishing a total of 20 wafers and after polishing a total of 30 wafers. In the case of a polishing pad having a peelable layer, one layer is peeled off every 10 polishing steps, and the surface layer is renewed.
A comparative evaluation was made with a case where polishing of 30 wafers was continued without peeling. Further, the polishing pad made of PUF was compared and evaluated when the surface was renewed every time 10 wafers were polished, and when the polishing was continued on 30 wafers without renewing the surface. Table 1 shows the results.

[0026]

[Table 1]

According to the results shown in Table 1, with the polishing pad of the present invention, the average value of the polishing rate becomes substantially constant when the surface is renewed by peeling one layer at a time every 10 wafers are polished, There is almost no decline. Also, it can be seen that the decrease in the average value of the polishing rate is very small even when the peeling and the surface renewal are not performed. On the other hand, with a pad made of PUF,
Even when the surface is renewed every time the wafer is polished, the average value of the polishing rate decreases considerably. When polishing is performed without renewing the surface of 30 wafers, the speed greatly decreases with the number of polished wafers. It can be seen that the average value of the subsequent polishing rate is reduced to 50% of the initial average value.

[0028]

According to the pads of the first to third aspects of the present invention, the surface can be easily renewed by an extremely simple operation of peeling off one or two or more surface layers. Can be polished. Further, according to the fourth invention, the polishing pad of the first to third inventions can be easily and accurately formed, and clogging or the like due to polishing debris and the like hardly occurs, and until the surface is renewed by peeling of the surface layer. Time can be lengthened.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a structure of a polishing pad of the present invention.

FIGS. 2A and 2B schematically show a polishing pad manufactured in an example, and FIG. 2B is a cross-sectional view.

[Explanation of symbols]

1; polishing pad 1, 11 to 17; peelable layer, 11
a; recess formed in peelable layer 11; 11b; hole formed in peelable layer 11; 11c; peelable layer 1
1 slit; 1a; hole; 1b; through hole;
c: groove, 1d: hollow path.

Claims (4)

[Claims] 1. A polishing pad comprising a peelable layer. 2. The polishing pad according to claim 1, wherein the surface can be renewed by peeling the layer. 3. The polishing pad according to claim 1, wherein the layer has at least one of a hole, a slit, and a recess. 4. The polishing pad according to claim 1, wherein the polishing pad is formed by an additive manufacturing method.