US20140154956A1

US20140154956A1 - Pad Conditioning and Wafer Retaining Ring and Manufacturing Method Thereof

Info

Publication number: US20140154956A1
Application number: US14/093,164
Authority: US
Inventors: Seh Kwang Lee; Joo Han Lee; Kwan Hee PARK
Original assignee: Ehwa Diamond Industrial Co Ltd
Current assignee: Ehwa Diamond Industrial Co Ltd
Priority date: 2012-11-30
Filing date: 2013-11-29
Publication date: 2014-06-05
Also published as: KR101392401B1; JP6332592B2; JP2014110428A

Abstract

The present invention relates to a wafer retaining ring used in a chemical mechanical polishing process (CMP) for semiconductor device manufacturing, and in particular, to a pad conditioning and wafer retaining ring designed to prevent a wafer from slipping during the CMP process and, simultaneously condition a pad uniformly, and to a manufacturing method thereof.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to Korean Patent Application No. 10-2012-0137490, filed on Nov. 30, 2012, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference.

BACKGROUND

1. Field of the Invention
The present invention relates to a wafer retaining ring that is used in a chemical mechanical polishing process (CMP) for semiconductor device manufacturing, and more particularly to a pad conditioning and wafer retaining ring designed to prevent a wafer from slipping during a CMP process and, simultaneously condition a pad uniformly, and to a manufacturing method thereof
2. Description of the Prior Art
Chemical mechanical polishing (CMP) is a process that polarizes the surface of semiconductor wafers using a combination of mechanical and chemical actions.
In principle, CMP is a process in which a slurry made from a mixture of abrasive particles and a chemical solution is supplied between a polishing pad and a wafer while the polishing pad and the wafer are allowed to move relative to one another while they are pressed against each other. Herein, many pores in the polishing pad surface are made of a polyurethane material that functions by receiving fresh slurry to achieve a high polishing efficiency and uniformity for the polishing of the wafer surface.
A polishing head in a CMP system, according to the conventional art, will now be briefly described with reference to FIG. 1.
As shown in FIG. 1, a polishing head 10 in a CMP system has a wafer holder 22 for supporting a wafer 24 during the CMP process, a retainer ring 26 for preventing the wafer from slipping during polishing, and a head body 28 for supporting these parts and applying the polishing pressure. Because the polishing head 10 should be able to apply pressure and be rotatable, it generally has a rotating shaft 30 at the center thereof, and pressure is applied through the shaft. Herein, the retainer ring 26 functions to retain the wafer 24 via adsorption by surface tension or vacuum pressure. In addition, the retainer ring 26 also functions as a means for ensuring the uniformity of the polishing.
The CMP process will now be briefly described. The wafer 24 is held by the wafer holder 22, and the wafer 24 is brought into contact with the surface of the polishing pad. In this state, the wafer holder 22 is rotated via driving shaft 30, while slurry 34 is supplied to the polishing pad 32, and then supplied to the wafer 24 through the gap between the retainer ring 26 and the polishing pad, thereby enabling CMP.
As shown in FIG. 2, on the lower surface of the retainer ring 26, a plurality of grooves 36 having a predetermined width and depth are formed and spaced from each other and pass through the thickness of the retainer ring 26. The retainer ring 26 having grooves 36 functions to prevent the wafer 24, held by the wafer holder 22, from slipping during CMP of the wafer 24 and ensures uniform supply of the slurry 34 to the wafer 24 via its friction with the polishing pad 32. In addition, it functions to condition the surface of the polishing pad 32 to achieve uniform polishing of the wafer 24.
However, both pressure and relative velocity are applied during the polishing, and thus over time, the surface of the polishing pad becomes non-uniform and the pores in the surface of the polishing pad become clogged with polishing residue, diminishing the performance of the polishing pad. This makes it difficult to achieve planarization and uniformity of the entire surface of the wafer during CMP.
To overcome this non-uniform deformation of the CMP polishing pad and the clogging of the pores, a CMP conditioning process is carried out in which the surface of the polishing pad is finely polished with a CMP pad conditioner to create new micropores.
Thus, typical consumption articles that are used in the CMP process include the pad, the slurry, the retainer ring, the pad conditioner, etc. Among them, the retainer ring functions to retain the wafer during the CMP process and helps to improve wafer uniformity. In addition, the CMP pad conditioner functions to improve the flowability of the slurry that is supplied to the pad and abrades the pad little by little to maintain the pad in the same condition as in its initial state or as if it were new.
In the conventional CMP process as described above, the retainer ring is used to retain the wafer, and the CMP pad conditioner is used to condition the pad in order to maintain the initial condition of the pad.

SUMMARY

The present inventors have made extensive efforts towards, and as a result have developed, a part having a wafer retaining ring combined with a CMP pad conditioner, thereby completing the present invention.
The present invention provides a pad conditioning and wafer retaining ring that enables a polishing pad to be maintained in the same condition as the initial condition of the pad during the polishing of a wafer, thus increasing the removal rate of the wafer, and a manufacturing method thereof.
The present invention also provides a pad conditioning and wafer retaining ring that eliminates the need to use a CMP pad conditioner having poor chemical resistance, thus reducing wafer scratches and contamination, and a manufacturing method thereof.
The present invention yet further provides a pad conditioning and wafer retaining ring wherein the width of the grooves at the outer circumference of the wafer retaining ring are formed to be sufficiently wide so that slurry can be efficiently supplied to a wafer to minimize the amount of slurry that is unnecessarily consumed without being added to the wafer, thereby reducing the polishing costs, and a manufacturing method thereof.
The present invention yet further still provides a pad conditioning and wafer retaining ring that eliminates the need to use a CMP pad conditioner, thus reducing the costs for consumption materials, and a CMP system having the wafer retaining ring.
The present invention further provides a pad conditioning and wafer retaining ring that eliminates the need to use a device for deriving a CMP pad conditioner, this increases the usable space of a CMP system thereby making it possible to add a wafer polisher to the CMP system, resulting in an increase in polishing productivity, and a CMP system having the wafer retaining ring.
The present invention yet further provides a pad conditioning and wafer retaining ring that can reduce the price of a CMP system, resulting in an increase in the productivity of a CMP process and greatly decreases the costs of the CMP process, and a CMP system having the wafer retaining ring.
The present invention is not to be limited to the above-mentioned provisions, and other provisions of the present invention will be clearly understood by those skilled in the art from the following description.
To achieve the above provisions, the present invention enables a pad conditioning and wafer retaining ring for preventing a wafer from slipping during a chemical mechanical polishing (CMP) process, wherein a plurality of cutting tips, each having a protrusion, are formed and spaced at a predetermined distances from each other on the surface of the wafer retaining ring so that the surface is able to function as a pad conditioner.
In an embodiment, grooves having a predetermined width and depth are formed between the plurality of cutting tips formed on the surface of the wafer retaining ring so as to extend from the outer circumference to the inner circumference of the wafer retaining ring.
In an embodiment, the width of the grooves at the outer circumference is wider than that at the inner circumference.
In an embodiment, the wafer retaining ring is formed of any one of a reinforced polymer composite material, a super-hard alloy-based material, or a ceramic material.
In an embodiment, the wafer retaining ring further includes a diamond coating layer formed on the surface of the plurality of protrusions constituting the cutting tips.
In an embodiment, the side cross-sectional shape of the protrusions constituting the cutting tips is polygonal.
In an embodiment, the planar shape of the protrusions constituting the cutting tips is polygonal, circular, or oval.
In an embodiment, the cutting tips include a plurality of protrusions formed at a predetermined distance from the inner circumference of the wafer retaining ring.
The present invention provides a method for manufacturing a pad conditioning and wafer retaining ring, the method including the steps of: preparing a ring-shaped substrate having a determined thickness and width; forming on the surface of the ring-shaped substrate a plurality of grooves having a predetermined width and depth at a predetermined interval so as to extend from the outer circumference to the inner circumference of the ring-shaped substrate; and forming a plurality of spaced cutting tips on the surface between the plurality of grooves.
In an embodiment, the step of forming the grooves is performed such that the width of the grooves at the outer circumference is wider than that at the inner circumference.
In an embodiment, the step of forming the cutting tips is performed such that the side cross-sectional shape of the plurality of protrusions is polygonal.
In an embodiment, the step of forming the cutting tips is performed such that the planar shape of the plurality of cutting tips is polygonal, circular or oval.
In an embodiment, the step of forming the cutting tips is performed such that a plurality of protrusions are formed at a predetermined distance from the inner circumference of the ring-shaped substrate.
In an embodiment, the method further includes a step of forming a diamond coating layer on the surface of the plurality of protrusions constituting the cutting tips.
In yet still another aspect of the present invention, provided is a CMP system including the above-described pad conditioning and wafer retaining ring or a pad conditioning and wafer retaining ring manufactured by the above-described manufacturing method.
In an embodiment, the CMP system includes no separate conditioning means.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other provisions, features, and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 shows the configuration of a polishing head in a chemical mechanical polishing apparatus according to the conventional art;

FIG. 2 is an enlarged top view of the wafer retaining ring shown in FIG. 1;

FIG. 3 shows a top view of a pad conditioning and wafer retaining ring, according to an embodiment of the present invention, and an enlarged view of a portion of the wafer retaining ring;

FIGS. 4 a and 4 b are top views of portions of the pad conditioning and wafer retaining rings that show the shape of grooves on the retaining rings, according to some embodiments of the present invention;

FIGS. 5 a to 5 d are partial perspective views showing a plurality of protrusions having various shapes, which constitute cutting tips formed on the surface of the wafer retaining rings according to some embodiments of the present invention; and

FIGS. 6 a to 6 f are photographs showing the morphologies of polishing pads conditioned using the pad conditioning and wafer retaining rings according to some embodiments of the present invention and a polishing pad conditioned according to a conventional method.

DETAILED DESCRIPTION

General terms that are currently and widely used are used in the present disclosure. However, in some cases, terms arbitrarily selected by the present inventors, and the meanings of these terms, should be construed by taking into consideration not the only the simple names of the terms, but the meanings of the terms described or used in the detailed description herein.
Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.
The present invention is not limited to the embodiments described herein and may be embodied in other forms. Throughout the specification, like reference numerals indicate like elements.
The technical characteristic of the present invention is that cutting tips are formed on the surface of a wafer retaining ring so that the wafer retaining ring can also function as a pad conditioner.
FIG. 3 shows a pad conditioning and wafer retaining ring 100 that functions to prevent a wafer from slipping during a CMP process. As shown in FIG. 3, a plurality of cutting tips 110, each having a protrusion, are formed to be spaced from each other at predetermined distances on the surface of the wafer retaining ring, so that the surface of the wafer retaining ring can function as a pad conditioner.
The inventive wafer retaining ring 100 functioning as a pad conditioner is further characterized in that grooves 120 having a predetermined width and depth are provided between the plurality of cutting tips 110 so as to extend from an outer circumference 130 to an inner circumference 140 of the ring. In particular, as shown in FIGS. 4 a and 4 b, the width of the grooves 120 at the outer circumference 130 may be wider than that at the inner circumference 140. When the grooves 120 are configured as described above, the slurry can be efficiently supplied to a wafer to improve the uniformity of the polishing of the wafer and minimizes the amount of slurry that is unnecessarily consumed without being supplied to the wafer, thereby reducing the polishing costs.
The pad conditioning and wafer retaining ring according to the present invention may be made of a material having excellent chemical resistance. More specifically, it may be formed of any one of a reinforced polymer composite material, a super-hard alloy-based material, and a ceramic material. Herein, examples of the reinforced polymer composite material include, without limitation, known polymer materials having significantly increased strength, including without limitation, reinforced plastic materials. Examples of the super-hard alloy-based material include, without limitation, tungsten carbide (WC)-based super-hard alloys, including without limitation, tungsten carbide-cobalt (WC—Co), tungsten carbide-titanium carbide-cobalt (WC—TiC—Co), and tungsten carbide-titanium carbide-tantalum carbide-cobalt (WC—TiC—TaC—Co), as well as thermet (TiCN), boron carbide (B4C), titanium boride (TiB₂), and the like. Furthermore, examples of the ceramic material include, without limitation, silicon nitride (Si₃N₄), silicon (Si), aluminum oxide (Al₂O₃), aluminum nitride (AlN), titanium oxide (TiO₂), zirconium oxide (ZrO_x), silicon dioxide (SiO₂), silicon carbide (SiC), silicon oxynitride (SiOxNy), tungsten nitride (WNx), tungsten oxide (WOx), diamond like coating (DLC), boron nitride (BN), chromium oxide (Cr₂O₃), and the like.
In addition, a diamond coating layer may further be formed on the plurality of protrusions constituting the cutting tips 110 formed on the pad conditioning and wafer retaining ring 100 of the present invention in order to improve the polishing performance, chemical resistance, abrasion resistance, and durability of the wafer retaining ring.
Herein, the plurality of cutting tips 110 may include a plurality of protrusions designed corresponding to the pattern of the cutting tips. For example, as shown in FIGS. 3, 5 a, and 5 b, the cutting tips 110 may include a plurality of spaced protrusions having a rectangular cross-sectional shape. Alternatively, as shown in FIG. 5 c, the cutting tips 110 may include a plurality of protrusions having a triangular cross-sectional shape. Alternatively, the planar shape of the plurality of protrusions constituting the cutting tips 110 may be polygonal, circular, or oval. Although not shown in the Figures, it will be understood that the protrusions may have a polygonal conical shape, a polygonal pillar shape, a conical shape, an oval conical shape, a cylindrical shape, or an oval pillar shape, when viewed three-dimensionally.
As shown in FIG. 5 d, the plurality of cutting tips 110 may be configured such that a plurality of protrusions may also be formed at a predetermined distance from the inner circumference 140 of the wafer retaining ring 100. In this case, the cutting tips 110 can keep sludge from entering the wafer after pad conditioning, thereby reducing scratches on the wafer.
In another aspect, the present invention provides a method for manufacturing a pad conditioning and wafer retaining ring, the method including the steps of: preparing a ring-shaped substrate having a determined thickness and width; forming on the surface of the ring-shaped substrate a plurality of grooves having a predetermined width and depth at a predetermined interval so as to extend from the outer circumference to the inner circumference of the ring-shaped substrate; and forming a plurality of spaced cutting tips on the surface between the plurality of grooves, wherein the step of forming the groves and the step of forming the cutting tips may be performed using a machining method, a laser processing method, or an etching method. Herein, the depth of the grooves formed in the groove-forming step is deeper than the height of the protrusions constituting the cutting tips.
The method of the present invention may further include a step of forming a diamond coating layer on the surface of the protrusions constituting the cutting tips 110. The step of forming the diamond coating layer may be performed by chemical vapor deposition (CVD) in such a manner that the cutting tips 110 are completely coated or only the top of the protrusions constituting the cutting tips 110 are coated. Before the diamond coating layer is formed, the ring-shaped substrate having the cutting tips 110 formed thereon may be ultrasonically pretreated. In this ultrasonic pretreatment process, fine scratches are formed on the cutting tips 110 using fine diamond particles so that the diamond coating layer is firmly formed.

EXAMPLES

Example 1

The pad conditioning and wafer retaining ring 100 as shown in FIG. 3 was manufactured in the following manner so as to have the cutting tips shown in FIG. 5 a. More specifically, a ring-shaped substrate (inner diameter: 301 mm; outer diameter: 349 mm) having a thickness of 6 mm and a width of 24 mm was prepared, and grooves 120 having a depth of 3 mm and a width of 3 mm were formed on the substrate by grinding wheel machining. Then, cutting tips 110 including protrusions having a flat top, a size of 200 μm×200 μm, a height 1000 μm and a spaced interval of 2000 μm were formed on the substrate surface between the grooves by grinding wheel machining, thereby manufacturing the wafer retaining ring 1.

Example 2

A pad conditioning and wafer retaining ring 2 was manufactured in the same manner as described in Example 1, except that the cutting tips 110 were formed to have the shape shown in FIG. 5 b. The cutting tips 110 formed included protrusions having a flat top, a size of 100 μm×100 μm, a height of 1000 μm and a spaced interval of 1000 μm.

Example 3

Pad conditioning and wafer retaining ring 3 was manufactured in the same manner as described in Example 1, except that the cutting tips 110 were formed to have the shape shown in FIG. 5 c. The cutting tips 110 formed included protrusions having a pyramidal shape, a bottom size of 200 μm×200 μm, a height of 1000 μm and a spaced interval of 2000 μm.

Example 4

Pad conditioning and wafer retaining ring 4 was manufactured in the same manner as described in Example 1, except that the cutting tips 110 were formed to have the shape shown in FIG. 5 d. Herein, the cutting tips 110 were formed in the same manner as described in Example 1, except that they formed at a distance of 3 mm from the inner circumference 140 of the ring-shaped substrate.

Comparative Example

A conventional wafer retaining ring as shown in FIG. 2 was prepared.

Test Examples 1 to 6

A CMP process was performed using only the conventional wafer retaining ring prepared in Example 1, and then the morphology of the surface of the pad was observed. Also, a CMP process was performed using the conventional wafer retaining ring prepared in Example 1 together with a pad conditioning means, and then the morphology of the pad surface was observed. The results of the observation are shown in FIGS. 6 a and 6 b and Table 1 below (Test Examples 1 and 2). In addition, a CMP process was performed using each of the pad conditioning and wafer retaining rings obtained in Examples 1 to 4, and then the morphologies of the pad surfaces were observed. The results of the observation are shown in FIGS. 6 c to 6 f and Table 1 below (Test Examples 3 to 6). Herein, a 300 mm CMP tester and silica slurry were used.

TABLE 1

	Pad	Normalized
	abrasion rate	wafer
CMP process	(μm/hr)	scratches

Test Example 1	Using only conventional	0	100
	wafer retaining ring
Test Example 2	Using conventional wafer	15	6
	retaining ring and pad
	conditioner
Test Example 3	Using pad conditioning	8	4
	and wafer retaining ring 1
Test Example 4	Using pad conditioning	16	4
	and wafer retaining ring 2
Test Example 5	Using pad conditioning	42	6
	and wafer retaining ring 3
Test Example 6	Using pad conditioning	12	2
	and wafer retaining ring 4

As can be seen in Table 1 above, when the pad conditioning and wafer retaining rings obtained in Examples 1 to 4 are used, the pads were abraded evenly when the CMP process was performed without using a separate conditioning means. Also, as can be seen in FIGS. 6 c to 6 f, the morphologies of the pad surfaces are similar to that of the pad surface (as shown in FIG. 6 b) remaining after the CMP process was performed using the conventional wafer retaining ring together with the conventional diamond conditioner. However, as can be seen from the results in FIG. 6 a and Table 1, which show the results of Test Example 1 performed using only the conventional wafer retaining ring without using a separate conditioner, when only the conventional wafer retaining ring is used, no pad abrasion occurs, and thus many scratches occur, suggesting that the CMP process cannot be performed normally.
In the case of Test Example 6 in which the pad conditioning and wafer retaining ring 4 was used, wafer scratches were reduced because no cutting tips were formed on the inner circumference of the wafer retaining ring. This is believed to be the result of sludge remaining after pad conditioning was kept from entering the wafer.
The above test results suggest that, when the inventive wafer retaining ring having a pad conditioning function is used, the CMP process can be performed normally even when the CMP system has no CMP pad conditioning means.
Thus, when the pad conditioning and wafer retaining ring of the present invention is used, a CMP pad conditioner does not need to be used, and thus the CMP system can be simplified, resulting in many advantages over the existing art.
As described above, the present invention has the following excellent effects.
First, according to the present invention, a polishing pad that comes into contact with a wafer can be maintained in the same condition as its initial condition during the polishing of the wafer, and thus the removal rate of the wafer can be increased.
Furthermore, according to the present invention, a CMP pad conditioner having poor chemical resistance does not need to be used, and thus wafer scratches and contamination thereof can be reduced.
Moreover, according to the present invention, the width of the grooves at the outer circumference of the wafer retaining ring are formed to be sufficiently wide so that the slurry can be efficiently supplied to a wafer to minimize the amount of slurry that is unnecessarily consumed without being supplied to the wafer, thereby reducing the polishing costs.
Furthermore, according to the present invention, a CMP pad conditioner is not required, and thus the costs of consumption materials can be reduced.
Furthermore, according to the present invention, a device for deriving a CMP pad conditioner is not required so that the usable space of the CMP system can be increased thereby making it possible to add a wafer polisher to the CMP system, resulting in increases in polishing productivity.
In addition, according to the present invention, the price of the CMP system can be reduced, resulting in increases in the productivity of the CMP process and greatly decreases the costs of the CMP process.
Although the exemplary embodiments of the present invention have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions, and substitutions are possible, without departing from the scope and spirit of the present invention as disclosed in the accompanying claims.

Claims

What is claimed is:

1. A pad conditioning and wafer retaining ring for preventing a wafer from slipping during a chemical mechanical polishing (CMP) process, the pad conditioning and wafer retaining ring having a plurality of cutting tips, each cutting tip comprised of a plurality of protrusions, the plurality of cutting tips formed to be spaced at a predetermined distance from each other on the surface of the pad conditioning and wafer retaining ring to function as a pad conditioner.

2. The pad conditioning and wafer retaining ring of claim 1, wherein grooves having a predetermined width and depth are formed between the plurality of cutting tips formed on the surface of the pad conditioning and wafer retaining ring so as to extend from the outer circumference to the inner circumference of the pad conditioning and wafer retaining ring.

3. The pad conditioning and wafer retaining ring of claim 2, wherein the width of the grooves at the outer circumference is wider than that at the inner circumference.

4. The pad conditioning and wafer retaining ring of claim 1, wherein the pad conditioning and wafer retaining ring is formed of a reinforced polymer composite material, a super-hard alloy-based material, a ceramic material, or a combination thereof.

5. The pad conditioning and wafer retaining ring of claim 1, wherein the pad conditioning and wafer retaining ring further comprises a diamond coating layer formed on the surface of the plurality of protrusions.

6. The pad conditioning and wafer retaining ring of claim 1, wherein the side cross-sectional shape of the protrusions.

7. The pad conditioning and wafer retaining ring of claim 1, wherein the planar shape of the protrusions is polygonal, circular, or oval.

8. The pad conditioning and wafer retaining ring of claim 1, wherein the cutting tips comprise a plurality of protrusions formed at a predetermined distance from the inner circumference of the wafer retaining ring.

9. A method for manufacturing a pad conditioning and wafer retaining ring, the method comprising:

preparing a ring-shaped substrate having a determined thickness and width;

forming on the surface of the ring-shaped substrate a plurality of grooves having a predetermined width and depth at a predetermined interval so as to extend from the outer circumference to the inner circumference of the ring-shaped substrate; and

forming on the surface of the ring-shaped substrate between the plurality of grooves a plurality of cutting tips having a plurality of protrusions at a predetermined interval formed to be spaced at a predetermined distance from each other.

10. The method of claim 9, wherein the forming of the plurality of grooves is performed such that the width of the grooves at the outer circumference is wider than that at the inner circumference.

11. The method of claim 9, wherein the forming of the cutting tips is performed such that the side cross-sectional shape of the plurality of protrusions is polygonal.

12. The method of claim 9, wherein the forming of the cutting tips is performed such that the planar shape of the plurality of protrusions is polygonal, circular, or oval.

13. The method of claim 9, wherein the forming of the cutting tips is performed such that a plurality of protrusions is formed at a predetermined distance from the inner circumference of the ring-shaped substrate.

14. The method of claim 9, further comprising forming a diamond coating layer on the surface of the plurality of protrusions constituting the cutting tips.

15. A chemical mechanical polishing (CMP) system comprising the pad conditioning and wafer retaining ring of claim 1.

16. The CMP system of claim 15, wherein the CMP system has no separate conditioning means.

17. A CMP system comprising the pad conditioning and wafer retaining ring manufactured by the method of claim 9.

18. The CMP system of claim 17, wherein the CMP system further comprises no separate conditioning means.