Abrasive tool and method of making the same

Abstract

An abrasive tool includes a substrate, a plurality of abrasive particle groups, and a bonding layer. The abrasive particle group consists of a plurality of abrasive particles grouped together. The abrasive particle groups are disposed in a regular pattern on the surface of the substrate and fixed on the surface by the bonding layer. To control the disposition of the abrasive particle groups, an abrasive particle template is used to form the required pattern. The size of the abrasive particle positioning holes on the template is used to adjust the number of particles in an abrasive particle group.

Description

BACKGROUND OF THE INVENTION

1. Field of Invention

The invention relates to an abrasive tool and the method of making the same. In particular, the invention relates to a diamond abrasive tool and the method of making the same.

2. Related Art

In the manufacturing process of deep sub-micro semiconductor devices, the planarization technique for the oxide layer and the metal layer on the surface of wafer becomes important along with the development in the wire miniaturization and the multiple metal connection technique. In order to have a dense circuit in a small area, the thickness and flatness in each layer of the wafer are strictly demanded.

The chemical mechanical polishing (CMP) technique employs slurry and polish pad, along with mechanical polishing, to planarize the oxide layer and the metal layer of a wafer. This method can remove limitations in the layout design, increase the pattern density, reduce the defect density, and promote the yield. In short, the required equipment of CMP includes a platen with a polish pad, and a carrier for holding a wafer and imposing a pressure thereon. The carrier sucks onto the back of the wafer by creating a vacuum in between. The part of the front surface of the wafer that requires planarization is pressed against the polish pad of the platen. The mechanical polishing is then performed by having a relative motion between the polish pad and the carrier. A polishing agent is added to create appropriate reactions for a higher polishing efficiency.

After polishing a certain time, the surface structure of the polish pad, such as its texture and roughness, will become smoother. Moreover, the debris getting off from the wafer and the slurry will deposit on the surface of the polish pad. Eventually, the polishing rate is lowered or even diminishing. Therefore, one usually has to use an abrasive tool to perform intermittent or continuous cleaning in order to remove the surface and debris of the polish pad, maintaining its roughness and elongating its lifetime.

As shown in FIG. 4, a conventional abrasive tool is formed by adhering abrasive particles 1 by a bonding layer 2 in a random way on the surface of a substrate 3. The abrasive particles used in this type of abrasive tool are highly rigid and abrasive. Since the diamond is one of the hardest industrial materials known to date, it is often used as the super-abrasive in abrasive tools.

In a CMP process, however, the abrasive particles fixed on the surface of the abrasive tool often cannot be held tightly on the surface of the metal substrate. Therefore, abrasive particles often get off from the abrasive tool. These lost particles are likely to damage precision and expensive wafers. In particular, since the abrasive particles are random disposed on the abrasive tool, their distribution may be non-uniform such that the abrasive particles are under different pressures. This is why the abrasive particles may fall off due to insufficient adhesive power and why the polishing effect is unstable. To further extend the lifetime of the abrasive tool and to improve its polishing effect, proposals are made to evenly and regularly distribute the abrasive particles 4 on the abrasive tool 5 (such as the matrix arrangement in FIG. 5) in place of the random disposition in the prior art. For example, U.S. Pat. Nos. 4,925,457 and 5,092,910, “Abrasive tool and method for making”, disclose an abrasive tool that uses a mesh to form a regularly disposed pattern of abrasive particles and the sintering process for making it.

The diamond particles in the abrasive tools for the manufacturing of wafers that have high precision and high added values have to be optimized in the following factors: pattern, pitch, particle size, protrusion height, homogeneity, and the crystal shape (i.e. the sharpness). To increase the cutting rate of the abrasive tool, one usually has to (a) increase the sharpness of the diamond particles or (b) increase the density of diamond particles. However, using highly sharp diamond particles may have the risk of breaking them because of their lower strength. Therefore, it is safer to make a CMP pad conditioner (or disk) with a high density of diamond particles to increase its cutting rate. One uses a template or a mesh with a previously designed pattern to position and dispose the abrasive particles in a uniform and regular way on the abrasive tool. Although this method can achieve the goal of evenly distribute the pressure to the abrasive particles, the diamond particles sizes are limited by the pitch of the template or mesh such that the density of abrasive particles cannot be increase. For a conditioner with regular diamond positioning used in a CMP process in an IC factory, the average size of the diamond particles for their primary conditioner products is between 100 μm and 220 μm. However, a mesh with a pitch as small as 250 μm to 350 μm has reached the limit of the template manufacturing for the conditioners with such diamond size. Therefore, it is difficult to further increase the density of diamond arrangement for the primary used conditioner products in IC factory.

SUMMARY OF THE INVENTION

In view of the foregoing, an object of the invention is to provide an abrasive tool and the method of making the same. It combines the features of regular and random abrasive particle dispositions. The surface of the abrasive tool is provided with a plurality of abrasive particle groups to increase the abrasive particle density and to maintain the uniform pressures on the abrasive particles. Therefore, the invention can increase the cutting rate and lifetime of the abrasive tool.

The structure of the disclosed abrasive tool includes: a substrate, a plurality of abrasive particle groups and a bonding layer. The abrasive particle group consists of a plurality of abrasive particles grouped together. The abrasive particle groups are disposed in a regular way on the surface of the substrate. The bonding layer fixes the abrasive particle groups onto the substrate.

The bonding layer can be a metal solder and/or polymer bonding layer to provide the necessary combining force for the abrasive particle. The bonding layer may use a low-temperature brazing material to avoid the problem of substrate deformation and diamond deterioration because of high-temperature brazing processes. A polymer bonding layer can completely free from the soldering process and problems derived from it.

The invention also discloses a method of making the abrasive tool, including the steps of: providing a substrate on which surface has a bonding layer; providing an abrasive particle disposition template with a plurality of abrasive particle positioning holes in a regular pattern; aligning the abrasive particle disposition template with the substrate surface; filling the abrasive particles into the positioning holes to form a plurality of abrasive particle groups, wherein the diameter of the abrasive particle positioning holes being 1.75 to 2.5 times that of the abrasive particles; and separating the abrasive particle disposition template from the substrate, leaving the abrasive particles fixed on the substrate surface by the bonding layer.

In particular, the abrasive positioning holes are designed to have an appropriate size so that a single hole can accommodate a plurality of abrasive particles to form an abrasive particle group. The abrasive positioning holes may have different patterns according to the abrasive tool that one wants to form. The abrasive positioning holes are preferably disposed in a shape of the donut type or the segment type. The pitch between the abrasive positioning holes is preferably to be greater than the diameter of the abrasive particle positioning holes by at least 75 μm. This is more practical in mass-producing the abrasive particle disposition template.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become more fully understood from the detailed description given hereinbelow illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 is a schematic cross-sectional view of the polish pad conditioner in an embodiment of the invention;

FIGS. 2A to 2E are schematic cross-sectional views of the steps for making the polish pad conditioner according to the embodiment of the invention;

FIG. 3 is a schematic view of a micro picture of the disclosed polish pad conditioner;

FIG. 4 is schematic view of randomly distributed abrasive particles in the prior art;

FIG. 5 is a schematic view of regularly distributed abrasive particles in the prior art; and

FIG. 6 is a flowchart of the steps for making the polish pad conditioner according to another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

As described above, the disclosed abrasive tool and the method of making the same can increase the cutting rate of the abrasive tool and solve the problem of falling abrasive particles due to non-uniform pressures. The disclosed abrasive tool thus has a better polishing homogeneity and longer lifetime. The invention is particularly of use for making the polish pad conditioner/dresser in high-precision CMP. Therefore, we explain the structure of the polish pad conditioner/dresser that utilizes the invention and the method of making the same. We use diamond particles as the abrasive particles.

With reference to FIG. 1, it is seen that the polish pad conditioner/dresser in this embodiment includes: a substrate 100, a plurality of diamond particle groups 200, and a bonding layer 110. Each diamond particle group 200 consists of several diamond particles 210 grouped together. The diamond particle groups 200 are disposed in a regular pattern on the surface of the substrate 100, separated by a fixed pitch. The bonding layer 110 on the surface of the substrate 100 fixes to the diamond particle groups 200 onto the substrate 100. Therefore, the cutting load can be evenly distributed to all the diamond particle groups 200. With the same amount of diamond particles, the invention has a higher diamond uniformity of distribution in the polishing region than the random distribution in the prior art because of the feature of regular diamond particle groups.

The bonding layer can be made of a polymer bonding agent, a metal electroplating layer, or a metal brazing material, or any other bonding agent with a sufficient combining force with the substrate. The polymer bonding agent is a room-temperature curable resin that naturally cures after a certain time. It can also be a resin that cures under heat or light so that it can be firmly fixed on the substrate after heating, baking or ultraviolet (UV) radiation. The metal electroplating layer is made by wrapping the bottom of the diamond particles on the substrate using electroplating nickel (or some other metal). The metal brazing material is melted using high-temperature vacuum furnace brazing method to fix the diamond particles on the metal substrate. Moreover, one may use metal powders as the bonding layer to fix the diamond particles by high-temperature sintering. One may also use ceramic materials in the bonding layer.

FIGS. 2A to 2E are schematic cross-sectional views of the steps for making the polish pad conditioner/dresser in the embodiment of the invention.

As shown in FIG. 2A, a substrate 100 coated with a polymer bonding layer 110 on its surface is provided.

As shown in FIG. 2B, an abrasive particle disposition template 300 with a plurality of abrasive particles positioning holes 310 disposed in a regular pattern is provided. The abrasive particle disposition template 300 is used to make the diamond particles 210 be disposed in the predetermined pattern and to limit the number and positions of them. Therefore, the pattern and diameter size of the abrasive positioning holes in the abrasive particle disposition template 300 are designed according to different needs. Limited by the feasibility of mass production, strength, and lifetime of the abrasive particle disposition template 300, the diameter of the abrasive particle disposition holes 310 is preferably smaller than their pitch by at least 75 μm. Therefore, there is enough space between the holes, making the hole drilling of the abrasive particle disposition template much easier. It is also unlikely to have the problem of broken holes in practical uses. In other words, the pitch of the abrasive particle positioning holes is preferably greater than the diameter of the abrasive particle positioning holes by 75 μm. Thus, it is more feasible from the viewpoints of mass production and technical details. For the diamond particles mostly used in a CMP polish pad conditioner/dresser with a regular distribution of diamond particles, their average particle size is mostly between 100 μm and 220 μm. For example, using the diamond particles US mesh #70/75 (average particle size ˜210 μm), #80/90 (average particle size ˜180 μm), #100/120 (average particle size ˜150 g m) #120/140 (average particle size ˜125 μg m), or #140/170 (average particle size ˜110 m), the pitch between the abrasive particle positioning holes 310 in a high density is preferably between 250 microns and 700 microns. However, the actual design of the pitch is determined by the size of the abrasive particles. If the pitch is too large, the effect of increasing the diamond density is diminishing. If the pitch is too small, then it will be very difficult to make he abrasive particle disposition template, and only small diamond particles can be used in this case.

As shown in FIG. 2C, the abrasive particle disposition template 300 is aligned and stacked on the surface of the substrate 100.

As shown in FIG. 2D, the diamond particles 210 are filled into the abrasive particle positioning holes 310 to form several diamond particle groups 200. An appropriate pressure can be imposed to embed the diamond particles 210 slightly more into the bonding layer 110. Generally speaking, to accommodate several diamond particles 210 in a single abrasive particle positioning hole 310, the diameter of the abrasive particle positioning holes 310 is preferably designed to be between 1.75 and 2.5 times of the diameter of the diamond particles 210 because the diamond crystals have different shapes and sizes. Using the design of different diamond size and diameter of the abrasive particle positioning holes, each diamond particle group preferably has an average number of 2 to 8. In particular, when the diamond particles 210 go through the abrasive particle positioning holes 310 to form a diamond particle group 200, the chances that the sharp ends of the diamond particles 210 point upward are increased; and so is the cutting rate. At the same time, the diamond particles in the diamond particle group can have a uniform distribution.

As shown in FIG. 2E, the abrasive particle disposition template 300 is separated and the bonding layer 110 is cured, so that the diamond particles 210 form a plurality of diamond particle groups in a regular pattern. They are fixed on the surface of the substrate by the bonding layer 110.

On the other hand, the disclosed polish pad conditioner/dresser can be manufactured by brazing. As shown in FIG. 6, a substrate of the kind mentioned above is provided (step 601). An adhesive or glue is used to combine a brazing material with the substrate (step 602). The brazing material can be a foil, powders, or a mixture of powders and organic binder from mixing and rolling, and is adhered on an area (or areas) on the substrate which diamond particles will be coated (or called diamond area) Afterwards, the abrasive particles are distributed regularly on the substrate in the form of abrasive particle groups (step 603). To fix the abrasive particles, the diamond area may be coated with a second adhesive or glue. This can be done before or after distributing the abrasive particles. Finally, the abrasive particles are permanently fixed on the substrate by brazing (step 604).

With reference to FIG. 3, each diamond particle group consists of a plurality of diamond particles grouped together. The diamond particle groups are disposed in a regular pattern with a fixed pitch on the surface of the substrate.

To illustrate that the invention can indeed increase the cutting rate, we compare the abrasive tool with single diamond particles disposed in a regular pattern as in the prior art and the disclosed conditioner formed with diamond particle groups disposed in a regular pattern. Here we use diamond particles of the same size and abrasive particle disposition template with abrasive particle positioning holes of the same pitch to make the conditioner. Average cutting rates are obtained after many times of experiments. The experimental parameters and measurement results are given in Table 1.

	TABLE 1
				No. of diamond
		Pitch of abrasive	Derived	particles in a single hole	Average
	Particle	particle positioning	diamond	(average no. of particles	cutting
	(us mesh)	holes on the template	pitch	in a diamond group)	rate
First Set
Multiple diamond	#80/90	400	147	2.73	369.5
particles in one hole
Single diamond in	#80/90	400	400	1	283.7
one hole
Second Set
Multiple diamond	#70/75	550	163	3.37	324.7
particles in one hole
Single diamond in	#70/75	550	550	1	65.8
one hole
Third Set
Multiple diamond	#70/75	450	134	3.37	523.8
particles in one hole
Single diamond in	#70/75	450	450	1	20.8
one hole

The derived diamond pitch is obtained from the pitch of the abrasive particle positioning holes on the template and the number of diamond particles in a single hole. From the results in Table 1, one sees that the cutting rate of the diamond particle group conditioner/dresser with multiple diamond particles in one hole is far larger than that of the diamond particle group conditioner/dresser with a single diamond in one hole.

Through the uniform distribution of the regular patterned abrasive particle groups in the abrasive tool, the invention can prevent the particles from falling due to inhomogeneous pressures. The abrasive particles can be evenly worn away, and the lifetime of the abrasive tool can be longer. The cut rate is also increased by increasing the abrasive particle density of distribution on the diamond area. The disclosed method can effectively control the disposition of the abrasive particle groups. The size of the abrasive particle positioning holes controls the number of particles in the hole, i.e. the number of particles in each abrasive particle group.

Certain variations would be apparent to those skilled in the art, which variations are considered within the spirit and scope of the claimed invention.

Claims

1. An abrasive tool, comprising:

a substrate;

a plurality of abrasive particle groups disposed in a regular pattern on a surface of the substrate, each of the abrasive particle groups consisting of a plurality of abrasive particles, the pitch of the abrasive particle groups being below 700 μm, each of the abrasive particle groups containing 2 to 8 abrasive particles; and

a bonding layer for fixing the abrasive particles on the substrate.

2. The abrasive tool of claim 1, wherein the abrasive particles are diamond particles.

3. The abrasive tool of claim 2, wherein the average particle size of the diamond particles is between 100 μm and 220 μm.

4. The abrasive tool of claim 2, wherein the size of the diamond particles is selected from the group consisting of US mesh #70/75 (average particle size ˜210 μm), #80/90 (average particle size ˜180 μg m), #100/120 (average particle size ˜150 μm), #120/140 (average particle size ˜125 μm), and #140/170 (average particle size ˜110 μm).

5. The abrasive tool of claim 1, wherein the bonding layer is selected from the group consisting of metal, ceramic, and polymer bonding agents.

6. The abrasive tool of claim 3, wherein the metal bonding layer is formed by brazing a Ni—Cr alloy material.

7. The abrasive tool of claim 3, wherein the polymer bonding layer is selected from the group consisting of a room-temperature curing resin, a thermal curing resin, and a photo-curing resin.

8. A method of making an abrasive tool, comprising the steps of:

providing a substrate on which surface has a bonding layer;

providing an abrasive particle disposition template with a plurality of abrasive particle positioning holes disposed in a regular pattern, the pitch of the abrasive particle positioning holes being below 700 microns;

aligning and stacking the abrasive particle disposition template on the surface of the substrate;

filling abrasive particles in the abrasive particle positioning holes to form a plurality of abrasive particle groups, the diameter of the abrasive particle positioning holes being between 1.75 and 2.5 times the average particle size of the abrasive particles;

separating the abrasive particle disposition template; and

fixing the plurality of abrasive particles on the surface of the substrate by the bonding layer.

9. The method of claim 8, wherein each of the abrasive particle groups contains 2 to 8 abrasive particles.

10. The method of claim 9, wherein the abrasive particles are diamond particles.

11. The method of claim 10, wherein the average particle size of the diamond particles is between 100 μm and 220 μm.

12. The method of claim 10, wherein the size of the diamond particles is selected from the group consisting of US mesh #70/75 (average particle size 210 μm), #80/90 (average particle size ˜180 μm), #100/120 (average particle size ˜150 μm), #120/140 (average particle size ˜125 μm), and #140/170 (average particle size ˜110 μm).

13. The method of claim 6, wherein the bonding layer is selected from the group consisting of a metal brazing material, a metal electroplating layer, a ceramic bonding agent, and a polymer bonding agent.

14. The method of claim 10, wherein the metal brazing material is a Ni—Cr alloy material.

15. The method of claim 10, wherein the polymer bonding layer is selected from the group consisting of a room-temperature curing resin, a thermal curing resin, and a photo-curing resin.

16. A method of making an abrasive tool, comprising the steps of:

providing a substrate;

forming a brazing material on a surface of the substrate;

distributing a plurality of abrasive particle groups on the brazing material in a regular pattern, the pitch between the abrasive particle groups being below 700 microns and each of the abrasive particle groups containing 2 to 8 abrasive particles; and

fixing the abrasive particles on the surface of the substrate by brazing.

17. The method of claim 16, wherein the abrasive particles are diamond particles.

18. The method of claim 17, wherein the average particle size of the diamond particles is between 100 μm and 220 μm.

19. The method of claim 18, wherein the size of the diamond particles is selected from the group consisting of US mesh #70/75 (average particle size ˜210 μm), #80/90 (average particle size ˜180 μm), #100/120 (average particle size ˜150 μm), #120/140 (average particle size ˜125 μm), and #140/170 (average particle size ˜110 μm).