JP2006055944A - Cmp pad conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pad conditioner for a CMP (chemical mechanical polishing) device for use in machining a semiconductor substrate, which carries out stable and uniform pad removal while ensuring the flatness of a pad. <P>SOLUTION: The pad conditioner for the CMP device is formed by bonding a single layer of diamond grains having a mean grain size of 5 to 1,000 μm, to a surface of a metal base, by nickel plating or a binder containing a brazing material as a main component. Specifically the pad conditioner is divided into a plurality of regions which are different in pad removing ability from each other, and super-abrasive grains are arranged at each intersection of straight lines constituting regular triangular mesh. Thus the number of abrasive grains is adjusted by varying the size of the mesh, i.e. the length of a side of a regular triangle, depending on the required pad removing ability of the conditioner. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a pad conditioner, and more particularly to a pad conditioner of a polishing pad for CMP (Chemical Mechanical Polishing) used for processing a semiconductor substrate.

CMP is a method of planarizing a silicon wafer and a multilayer wiring portion on the wafer without a work-affected layer. In CMP, a slurry in which fine particles such as silica are turbid in an acidic or alkaline aqueous solution and a polishing pad made of foamed polyurethane, polyester nonwoven fabric or the like is used. As the silicon wafer is polished, the polishing pad may become clogged or the flatness will decrease. Therefore, the polishing pad is always or periodically dressed to maintain the accuracy of flatness and eliminate clogging. Need arises. The dressing tool used here has a single layer of diamond abrasive grains or superabrasive grains such as CBN abrasive grains fixed on the surface of a disk-shaped or ring-shaped metal base metal, and is called a pad conditioner. Yes.

In conventional pad conditioners, superabrasive grains are usually fixed randomly. In some cases, assuming a parallelogram or rectangular mesh, superabrasive grains are arranged and fixed at each intersection. May be used. However, when dressing a polishing pad using these pad conditioners, the superabrasive grains fixed to the pad conditioner are not evenly spaced with respect to the rotation direction of the pad conditioner. There was a problem that it was difficult to maintain the intended pad removal ability. Furthermore, when multiple areas with different pad removal capabilities are provided, it is necessary to accurately design the pad removal capability of each area. Therefore, in addition to regularity in the surface, regularity with respect to the rotation direction of the pad conditioner. Is required.

In the conventional CMP pad dresser, superabrasive grains are fixed to the annular region of the outer peripheral portion, and the superabrasive particles are also fixed to the island-shaped protrusions provided in the central region from the inner periphery of the annular region. Has been. Furthermore, the abrasive density in the region where the superabrasive grains provided on the island-shaped protrusions are fixed is lower than the abrasive density in the annular region. (For example, see Patent Document 1)

In the invention of the above publication, superabrasive grains are arrayed and fixed at each intersection assuming a parallelogram mesh. In this case, since the grindstone has a cylindrical shape, the cutting direction is also ruled. Is secured. However, when this method is used to fix superabrasive grains to a disk-shaped base metal, regularity in the rotational direction is lost, causing superabrasive grains to wear unevenly, shortening the life of the pad conditioner, and flatness of the pad. Reduce.
JP 2001-71271 A

The present invention has been made to solve the above problems. That is, it is an object of the present invention to provide a pad conditioner that has a long lifetime and stable dressing performance from the beginning, and can maintain a high degree of flatness of the pad during that time.

A pad conditioner having a superabrasive grain layer in which a superabrasive grain is fixed to the surface of a disk-shaped base metal, wherein the disk-shaped base metal is provided with a plurality of regions having different pad removal capabilities, An equilateral triangle mesh is assumed on the entire surface, superabrasive grains are arranged and fixed at each intersection, and the assumed equilateral triangle mesh size, that is, the length of one side of the equilateral triangle is 0.2 mm or more and 10 mm or less. Pad conditioner characterized by.

Here, the reason why the abrasive grains are arranged at each intersection assuming a regular triangular mesh will be described. When the dresser is rotated on the rotating polishing pad, the distance that the superabrasive grains on the dresser pass on the pad has a distribution of axial objects in the pad surface. Since the distribution may be considered to have a correlation with the speed of removing the pad, it can be said that the flatness of the pad has a correlation with the distribution. Here, the rotational axis of the dresser is different from the rotational center position of the polishing pad and exists on the polishing pad. When the uniform abrasive layer is formed on the entire dresser, the distribution is such that the passing distance is maximized in the vicinity of the pad radius position where the dresser rotation shaft is installed. On the other hand, when a single annular superabrasive grain layer is formed, the distribution is such that the passing distance is minimized in the vicinity of the pad radius position where the dresser rotation shaft is installed. When both pad dressers are used, when a single annular superabrasive grain layer is formed, the pad shape is convex between the outer diameter and inner diameter of the pad, and the entire surface is superabrasive. It is known that when a grain layer is formed, the pad is recessed between the outer diameter and inner diameter of the pad. (For example, see Patent Document 2)
JP 2004-17207 A

From these facts, the pad shape is actually a shape obtained by transferring the passage distance distribution. Therefore, in order to make these passing distances uniform, it is necessary to provide a plurality of regions having different pad removal capabilities, and to provide each region with the required pad removal capability accurately and continuously. The present invention divides the surface on which the abrasive grain layer of the pad conditioner is formed into a plurality of regions having different pad removal capabilities in order to provide the pad removal capability accurately and continuously, and each region is divided into each region. Assuming an equilateral triangular mesh, superabrasive grains were arranged and fixed at each intersection. In order to adjust the removal capability of the pad, the assumed equilateral triangle mesh size, that is, the length of one side of the equilateral triangle was changed. Furthermore, the mesh was arranged so that the center of the triangle that overlapped the center of the disk-shaped base metal overlapped the center of the disk-shaped base metal, and the meshes at the boundary of the region were matched with the least common multiple of the mesh size. The area of the superabrasive layer was monotonously decreased or made equal from the outer peripheral side toward the inner peripheral side. The pad conditioner obtained by the present invention has a high removal rate while maintaining a high level of flatness of the pad, and the removal rate is stable and has a long life.

Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 (1) is a layout diagram of the mesh on the surface to which the superabrasive grains of the substrate orthogonal to the rotation axis of the pad conditioner are fixed, and shows that it consists of a high-density abrasive layer and a low-density abrasive layer. Yes. In addition, the high-density abrasive grain layer is an outer peripheral annular region, and the low-density abrasive layer is an inner peripheral annular region.

D represents the outer diameter of the disk-shaped base metal, WH represents the superabrasive layer width of the high-density layer, and WL represents the superabrasive layer width of the low-density layer. FIG. 1 (2) is an enlarged view of part A, and shows that the mesh is arranged so that the center of gravity of the equilateral triangle coincides with the center of the disk-shaped base metal. If abrasive grains are present in the center of the disk-shaped base metal, there is a problem of cutting on a specific radius of the pad, but there is no such problem as shown in FIG. FIG. 1 (3) is an enlarged view of part B, and shows that the meshes are matched at the least common multiple interval of the mesh size at the region boundary.

Next, a method for dressing the polishing pad will be described. FIG. 2 is a conceptual diagram of dressing the polishing pad 9 with the pad conditioner P. When the pad conditioner P is placed on the polishing pad 4 and both are rotated at a predetermined rotational speed, the superabrasive grains fixed to the pad conditioner P draw a locus depending on the rotational speed and the positional relationship between the rotational axes. . At this time, if the passing distance through which the superabrasive grains fixed to the pad conditioner pass at an arbitrary point of the pad 4 is accumulated within the dressing time, the passing distance on the pad 4 forms a distribution of axial objects. In the case of having a single annular abrasive layer, the distribution forms a minimum distribution between the inner peripheral edge and the outer peripheral edge of the pad. On the other hand, when the super-abrasive layer is provided on the entire surface of the pad conditioner, a distribution that is maximum between the inner peripheral end and the outer peripheral end of the pad is formed. Therefore, if dressing is performed using both a pad conditioner having a single annular superabrasive layer and a pad conditioner having a superabrasive layer on the entire surface, the passing distance on the pad formed by each pad conditioner can be reduced. Distribution is offset. In this case, if the dressing time when using a pad conditioner with a single annular abrasive layer and the dressing time when using a pad conditioner with a superabrasive layer over the entire surface are optimally adjusted, The distribution of the passing distance formed in the above is made more uniform.

Therefore, in order to obtain the same effect as using both the pad conditioners by using one pad conditioner, the number of superabrasive grains fixed to the pad conditioner is adjusted. In this case, the region where a large number of superabrasive grains are fixed has an effect of increasing the number of superabrasive grains passing on the pad, and conversely increasing the passing distance when viewed from any point on the pad. That is, in the region where a large amount of superabrasive grains are fixed, the amount of pad removal is larger than the region where there are few superabrasive grains. When designing a pad conditioner based on these ideas, for example, a plurality of concentric annular regions can be provided from the inner peripheral side to the outer peripheral side of the pad conditioner, and the arrangement density of superabrasive grains in each region can be adjusted. The pad can be removed uniformly. Specifically, within each region, assuming an equilateral triangle mesh, superabrasive grains are arranged at each intersection, and the mesh size, that is, the length of one side of the equilateral triangle, is set according to the required abrasive grain arrangement density. Change the pad removal ability.

When the width between the inner peripheral edge and the outer peripheral edge of the pad is smaller than the outer diameter of the pad conditioner, the above tendency is particularly remarkable. The inner and outer diameters of each annular region may be set by performing computer simulation in advance and actually dressing the polishing pad. In this case, compared to the conventional conditioner having a single annular superabrasive grain layer and the conditioner having a superabrasive grain layer on the entire surface, the flatness of the pad is improved, while maintaining the flatness, The amount of pad removal was high and stable. When the length of one side of the equilateral triangle was smaller than 0.2 mm, the number of abrasive grains increased and it was difficult to produce. On the other hand, if it is larger than 10 mm, the pad removing ability in the set region is lowered, so that the pad removing ability necessary for the pad conditioner cannot be obtained. In addition, the length of one side of the regular triangle is preferably 0.5 mm or more and 5 mm or less, and most preferably 0.8 mm or more and 2.5 mm or less.

In this invention, the average particle size of the superabrasive grains is desirably 5 μm or more and 1000 μm or less. When the average particle size is less than 5 μm, the dressing ability for the pad is extremely lowered, which is not practical. On the other hand, if the average particle size exceeds 1000 μm, the dressing ability is increased, but the pad surface becomes rough, the processing quality of the wafer surface is lowered, and the quality is not practical. The average particle size of the superabrasive grains is preferably 10 μm or more and 500 μm or less, and most preferably 30 μm or more and 300 μm or less.

Moreover, in this invention, it is desirable that the average protrusion amount of the superabrasive grains is 3% or more and 70% or less of the average particle diameter. In order to measure the protruding amount of superabrasive grains, a method using a dial gauge or the like has been proposed, but zygo (three-dimensional) is most accurately used to measure the level difference from the protruding end of superabrasive grains to the binder. It is appropriate to use a surface structure analysis microscope.

For example, the average protrusion amount is determined by measuring the protrusion amount of 100 superabrasive grains arbitrarily selected, and multiplying the average value by the average grain diameter of the superabrasive grain by multiplying by 100. Defined. Since several tens of thousands to several hundreds of thousands of superabrasive grains are fixed to the superabrasive grain layer, it takes a lot of labor to measure the protruding amount of all superabrasive grains. For this purpose, it is practical to employ an average value of about 100 abrasive grains.

If the average protrusion is less than 3%, the sharpness of the pad conditioner will not be sufficient, causing a reduction in processing efficiency. If it exceeds 70%, the holding power of the diamond abrasive grains will be reduced, causing dropout. is there. In order to increase the holding power of the diamond abrasive grains to prevent dropping and to obtain sufficient processing efficiency, the average protrusion amount is more preferably 10% or more and 45% or less, and more preferably 10% or more and 40% or less. Most preferred.

The binding material used for the pad conditioner of the present invention is not particularly limited as long as it is a binding material capable of firmly fixing superabrasive grains to a disk-shaped base metal. The demagnetized superabrasive grains adhere to the polishing pad and remain even when the wafer is polished with the polishing pad, causing scratches on the workpiece. Accordingly, since a stronger abrasive grain holding force is required as the bonding material, a plated metal or brazing material is suitable.

A brazing material is most preferred as the binder. The method of fixing superabrasive grains to a disk-shaped base metal with a brazing material is as follows: (1) Superabrasive retention is superior to other binders; (2) Superabrasive protrusion is large and Features such as smooth powder discharge and excellent sharpness. In particular, an Ag-Cu-Ti-based activated brazing material that is excellent in wettability with diamond and that provides a high adhesive force is optimal. In addition, a Ni—Cr brazing material or a Co—Ni—Cr brazing material is also applicable.

In order to fix the superabrasive grains with the brazing material, it is appropriate to use a pasty brazing material. Here, the paste-like brazing material is generally a brazing material powder kneaded with a binder, and has an appropriate viscosity, so that the operation is easy. In actual work, first, a paste-like brazing material is applied to the fixed surface of the superabrasive grains of the base metal, and the superabrasive grains are regularly arranged thereon. When the brazing material is dried and no longer flows, it is placed in a furnace and heated to melt the brazing material. Thereafter, the superabrasive grains are fixed by cooling in a furnace.

Nickel plating can be used as another binder. The nickel plating used in the present invention is excellent in that the abrasive density can be increased and the base metal can be reused.

In the present invention, the pad conditioner is used for dressing a polishing pad for CMP.

As described above, according to the present invention, since the distribution of the passing distance of the abrasive grains acting on the pad can be made uniform, the flatness of the pad after dressing is good, the dressing rate for the pad is high and stable. A pad conditioner is obtained.

The best mode will be described in detail in the following example section.

First, as shown in FIG. 3 (1), a disk-shaped base metal having an outer diameter D of 100 mm and a height T of 20 mm was prepared. The material of the disk-shaped base metal is stainless steel SUS304. The region where the superabrasive layer is fixed is provided with two concentric annular regions on the outer peripheral side and the inner peripheral side, the outer diameter of the outer annular region is 100 mm, the inner diameter is 80 mm, and the outer annular region is outside the inner annular region. The diameter was 80 mm and the inner diameter was 10 mm. The abrasive grain arrangement density for fixing the superabrasive grain layer to each of the outer peripheral side and the inner peripheral side was set so that the area on the outer peripheral side was four times that of the inner peripheral side. This ratio was expressed as a triangular mesh size assumed in a region where superabrasive grains are fixed in each annular region, that is, a general length. That is, in FIG. 1, 2ΔH = ΔL, where ΔH = 1 mm. FIG. 3B is a cross-sectional view when the abrasive grains are arranged.

Next, the disk-shaped base metal 3 is coated with an Ag-Cu-Ti-based activated brazing material on a paste, and an extra jig is used so that the brazing material has a constant thickness. The brazing material was removed.

Thereafter, diamond abrasive grains having an average particle diameter of 150 μm were regularly arranged on the brazing material and sintered at 850 ° C. in a vacuum atmosphere to complete the pad conditioner of the example of the present invention.

The effect of the present invention was confirmed by the method shown in FIG. 2 under the conditions shown in Table 1. That is, the pad conditioner P to which dressing pressure was applied was placed on the polishing pad 4 and polished while rotating each in the direction of the arrow. The rate of decrease of the dress rate (pad processing speed), which is an index of the life and performance stability of the pad conditioner P, and the flatness of the pad were measured and listed in Table 2. The comparative example is a case where only the high-density abrasive layer in FIG. 1 is used, and the results of the comparative example are also shown in Table 2.

FIG. 4 is an explanatory diagram of a method for measuring the dressing rate. FIG. 4 shows a state where the polishing pad is polished by the method shown in FIG. 2 and a measuring instrument is attached. Table 2 shows the change of the dial gauge read from the jig 9 for attaching the conditioner P to the rotating shaft 8 of the conditioner via the dial gauge contact 10 and the measured value divided by the dressing time. In the example of the product of the present invention, the rate of decrease of the dress rate after 10 hours was 6%. However, in the comparative example, the rate of decrease of the dress rate after 10 hours was 19%. Further, the flatness of the pad was measured with a micrometer at a regular interval along the radius of the pad after 10 hours of dressing, and the difference between the maximum value and the minimum value was defined as the flatness. In the case of the example, it was 1.3 μm, but in the case of the comparative example, it was 3.2 μm.

FIG. 1 (1) is a superabrasive grain arrangement diagram of the pad conditioner of the present invention, FIG. 1 (2) is an enlarged view of part A of FIG. 1 (1), and FIG. 1 (3) is an enlarged view of part B. is there. It is a conceptual diagram which dresses a polishing pad with a pad conditioner. FIG. 3A is a cross-sectional view of the base metal. FIG. 3B is a cross-sectional view when the abrasive grains are fixed to the base metal. It is a conceptual diagram of the system which measures a dressing rate.

Explanation of symbols

1 Base metal 2 Superabrasive layer (high density side)
3 Super abrasive layer (low density side)
4 Polishing pad 5 Point A locus 6 Point B locus 7 Super abrasive grain 8 Rotating shaft 9 Jig 10 Dial gauge contact O Base metal center D Pad conditioner outer diameter WH Super abrasive grain layer (high density side) Width WL Superabrasive layer (low density side) width ΔH Superabrasive layer (high density side) mesh size ΔL Superabrasive layer (low density side) mesh size

Claims (8)

A pad conditioner having a superabrasive grain layer in which a superabrasive grain is fixed to the surface of a disk-shaped base metal, wherein the superabrasive grain layer is provided with a plurality of regions, and an equilateral triangular mesh is formed on the entire surface of each of the regions. The superabrasive grains are arranged and fixed at each intersection, and the assumed equilateral triangle mesh size, that is, the length of one side of the equilateral triangle (ΔH, ΔL) is 0.2 mm or more and 10 mm or less. Features pad conditioner. The mesh size is constant in individual regions having different pad removal capabilities, and a ratio (ΔH / ΔL) of a large mesh (ΔH) to a small mesh (ΔL) between adjacent regions is greater than 1 and 20 or less. The pad conditioner according to claim 1, wherein the pad conditioner is provided. The length (ΔH, ΔL) of one side of the equilateral triangle is smaller in the region on the outer peripheral side of the disc-shaped base metal than in the region on the central axis side of the disc-shaped base metal. The pad conditioner according to claim 1 or 2. Of the equilateral triangles of the mesh, a center of gravity of the equilateral triangle that overlaps the center of the base metal and the center of the base metal are matched, and the mesh is matched at the least common multiple interval of the mesh size in the region boundary portion. The pad conditioner according to any one of claims 1 to 3. The pad conditioner according to any one of claims 1 to 4, wherein the average grain size of the superabrasive grains is 5 µm or more and 1000 µm or less. The pad conditioner according to any one of claims 1 to 5, wherein an average protrusion amount of the superabrasive grains is 3% or more and 70% or less of the average particle diameter. The pad conditioner according to any one of claims 1 to 6, wherein the bonding material for fixing the superabrasive grains is metal plating or brazing material. The pad conditioner according to any one of claims 1 to 7, wherein the pad conditioner is used for dressing a polishing pad for CMP.

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