US20090036041A1

US20090036041A1 - Cmp pad dresser and cmp apparatus using the same

Info

Publication number: US20090036041A1
Application number: US12/181,591
Authority: US
Inventors: Toru Matsuzaki
Original assignee: Elpida Memory Inc
Current assignee: Micron Memory Japan Ltd
Priority date: 2007-07-30
Filing date: 2008-07-29
Publication date: 2009-02-05
Also published as: JP2009028874A

Abstract

A CMP pad dresser for dressing a polishing pad of a CMP apparatus is provided with a dressing pad having abrasive grains, a purified water supply unit provided to an external periphery of the dressing pad, and a drive mechanism for sliding the dressing pad in a radial direction of the polishing pad. The dressing pad is slidable to the outer side of the polishing pad. The purified water supply unit supply purified water at a prescribed pressure so that particles of abrasive grains that are dislodged from the dresser accumulate in the dressing pad.

Description

TECHNICAL FIELD

The present invention relates to a CMP (Chemical Mechanical Polishing) pad dresser and CMP apparatus using the CMP pad dresser, and more particularly relates to a CMP pad dresser that removes polishing pad clogs and foreign matter, rejuvenates the surface of the polishing pad, and restores polishing speed.

BACKGROUND OF THE INVENTION

CMP is an important technique in manufacturing semiconductor devices. Semiconductor integrated circuit chips are manufactured by forming conductive layers, insulating layers, or other thin film layers in a prescribed order on a wafer, patterning the layers depending on need by photolithography and etching, and cutting and separating each chip on the wafer after forming all layers. When there are convexities and concavities or steps in the substrate when a film is formed, the thickness of the film formed on the substrate will be thin in parts and step coverage will worsen, causing lower yield and other problems. Also, problems occur in that focus during exposure is not fixed and precise patterns cannot be transferred because convexities and concavities appear in upper layers due to the effect of the lower patterned layers. For this reason, the surface of the film material must be planarized, and CMP is used for such a purpose.
With CMP, a wafer is polished by bringing a polishing pad into contact with a wafer that has been set on a rotary surface plate, and mutually rotating the wafer and the polishing pad while a polishing fluid (slurry) is added. Since clogs occur when grinding dust from the polishing pad and slurry are caught in the micropores of the polishing pad, and polishing speed is reduced significantly when the polishing step extends over a long time, dressing (conditioning) of the polishing pad is performed using an apparatus referred to as a dresser. Generally, a CMP pad dresser is provided with a plurality of diamond abrasive grains and an anchoring layer (plating layer) for holding the diamond abrasive grains. Particles having a diameter of 0.2 to 0.3 mm are used as diamond abrasive grains and are embedded in the anchoring layer in a state in which only a distal end portion of the grain protrudes to the polishing pad side.
Nickel electrodeposition is used to anchor the diamond abrasive grains in the CMP pad dresser. Nickel electrodeposition is a method that resembles nickel electroplating, and diamond abrasive grains are held by filling the gaps between the diamond grains with nickel. However, the bonding strength is poor between the diamond abrasive grains and the nickel because there is substantially no wetting between the diamond abrasive grains and the nickel. Accordingly, the diamond abrasive grains occasionally dislodge from the surface in which the grains are embedded, and the dislodged diamond abrasive grains become the cause of scratches on the surface of the costly wafer.
A CMP pad dresser is proposed in Japanese Laid-open Patent Publication No. 2006-324310. According to this invention, SiC is used as a dressing pad; SiC pins, which are a substitute for diamond abrasive grains on the surface of the dressing pad, are formed by blasting; and an integral structure is thereby formed between the dressing pad and the abrasive grains.
However, there is a considerable need for a method that prevents wafer damage due to dislodged diamond abrasive grains in dressers that use diamond abrasive grains because CMP pad dressers using diamond abrasive grains are widely used and show exceptionally good polishing performance.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention is to provide a CMP pad dresser that does not scratch a wafer even if a diamond abrasive grain becomes dislodged, and to provide a CMP apparatus that uses the CMP pad dresser.
The above and other objects of-the present invention can be accomplished by a CMP pad dresser for dressing a polishing pad of a CMP apparatus, the dresser comprising: a dressing pad having abrasive grains; and a purified water supply unit provided to an external periphery of the dressing pad.
The above and other objects of the present invention can also be accomplished by a CMP apparatus that comprises a polishing pad; and, a CMP pad dresser for dressing the polishing pad, wherein the CMP pad dresser includes a dressing pad having abrasive grains and a purified water supply unit provided to the external periphery of the dressing pad, and the purified water supply unit for supplying purified water at a prescribed pressure so that particles of abrasive grains that have dislodged from the dresser accumulate in the dressing pad.
In the present invention, it is preferable that the purified water supply unit supplies purified water at a prescribed pressure so that particles of abrasive grains that are dislodged from the dresser accumulate in the dressing pad, and it is further preferable that the purified water supply unit includes a plurality of nozzles for spraying purified water perpendicularly to the surface of the polishing pad.
In the present invention, it is preferable that the CMP pad dresser further comprises a drive mechanism for sliding the dressing pad in a radial direction of the polishing pad, and that the dressing pad be able to slide to the outer side of the polishing pad.
According to the present invention, a purified water supply unit is thus provided to the external periphery of the dressing pad, and a wall of water pressure is provided so that particles of diamond abrasive grains accumulate inside the dressing pad, making it possible to provide a CMP pad dresser that does not scratch a wafer even when a diamond abrasive grain has become dislodged, and to provide a CMP apparatus using the dresser.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of this invention will become more apparent by reference to the following detailed description of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic view showing a configuration of a CMP apparatus according to a preferred embodiment of the present invention;

FIG. 2 is a schematic perspective view showing the configuration of the dresser;

FIG. 3 is a schematic side elevation view showing the configuration of the dresser;

FIG. 4 is a schematic plan view for explaining the action of the dresser; and

FIG. 5 is a schematic cross-sectional view for explaining the action of the dresser.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Preferred embodiments of the present invention will be described hereinafter with reference to the accompanying diagrams.
FIG. 1 is a schematic view showing a configuration of a CMP apparatus according to a preferred embodiment of the present invention.
As shown in FIG. 1, the CMP apparatus 100 is provided with a polishing head 12 for holding a wafer 11, a rotary surface plate 14 on which a polishing pad 13 is mounted, a slurry supply unit 15 for supplying a slurry that contains silica (SiO₂) microparticles or another abrasive, a pad probe 16 for measuring the state of a polishing pad 13, a dresser 17 for dressing the polishing pad 13, and a polishing control unit 19 that controls these components.
The polishing head 12 is provided with a spindle mechanism for rotating the wafer 11, and a pressing mechanism for pressing the wafer 11 against the polishing pad 13 using an optimal pressure. A guide ring 12 a is provided at the external periphery of the wafer 11 that is set in the polishing head 12, whereby the wafer 11 can be reliably held in place. The rotary surface plate 14 is also provided with a spindle mechanism for rotating the polishing pad 13. The wafer 11 and the polishing pad 13 can thereby be moved relative to each other, and uniform polishing can be efficiently performed.
The polishing pad 13 is bonded to the main surface of the rotary surface plate 14. The polishing pad 13 is composed of a two-layer structure of a cushion sheet and a polishing sheet having a microporous structure. Rigid polyurethane foam is used as the polishing sheet. The polishing pad 13 is a consumable article. The polishing surface of the polishing pad 13 is restored by performing periodic dressing using a dresser 17, but a polishing pad 13 that has been entirely worn is removed from the rotary surface plate 14 and replaced with a new polishing pad.
The pad probe 16 detects the service life of the polishing pad 13, the terminal point of the dressing, and processing abnormalities by monitoring the friction coefficient of the surface of the polishing pad 13. The pad probe 16 measures the surface of the polishing pad 13, and the polishing pad 13 is dressed when the friction coefficient is less than a prescribed threshold value.
The dresser 17 is used for dressing the polishing pad 13 when the friction coefficient has been reduced due to clogging and the like. The dresser 17 rotates while sliding in a radial direction of the polishing pad 13, and polishes the surface of the polishing pad 13. As will be described in detail later, a very small amount of diamond grains are embedded in a contact surface with the polishing pad 13, and the surface of the polishing pad 13 is cut by the diamond grains. Dressing in the present embodiment is performed as an independent step rather than simultaneously with wafer polishing, and the wafer polishing step is temporarily halted at this time.
The polishing control unit 19 controls the polishing head 12, the rotary surface plate 14, the slurry supply unit 15, and the like, and more specifically controls the position and rotating speed of the polishing head 12, the rotating speed of the rotary surface plate 14, the amount of slurry supplied from the slurry supply unit 15, and other parameters.
FIG. 2 is a schematic perspective view showing the configuration of the dresser 17. FIG. 3 is a schematic side elevation view showing the configuration of the dresser 17.
As shown in FIGS. 2 and 3, the dresser 17 is provided with a dressing pad 21, a plurality of diamond abrasive grains 22 disposed on the main surface of the dressing pad 21, a purified water supply unit 23 disposed on an external periphery of the dressing pad 21, and a dresser drive mechanism 24 for controlling the dressing pad 21 and the purified water supply unit 23.
The purified water supply unit 23 has numerous nozzles 23 a, and these nozzles 23 a are arrayed in equidistant intervals along the external periphery of the dressing pad 21. The direction of the purified water spray from the nozzles 23 a is preferably perpendicular to the polishing surface of the polishing pad 13. The nozzles 23 a may rotate together with the dressing pad 21 or may be secured in place. The high-pressure purified water sprayed from the nozzles 23 a in a perpendicular fashion to the polishing surface forms a wall 25 of water pressure. Particles of diamond abrasive grains 22 that are dislodged from the dressing pad 21 are therefore trapped inside the dressing pad 21, and diamond abrasive grains can be reliably prevented from reaching the wafer.
FIGS. 4 and 5 are schematic views for explaining the action of the dresser 17, wherein FIG. 4 is a schematic plan view, and FIG. 5 is a schematic cross-sectional view.
As shown in FIGS. 4 and 5, the dresser 17 cuts the polishing pad 13 while sliding in a radial direction of the polishing pad 13. A gap is formed in the underside of the dresser 17 when the dresser 17 moves in the external peripheral direction of the polishing pad 13 (in the direction P1 in FIG. 4) beyond the peripheral edge of the polishing pad 13. For this reason, the diamond abrasive grain particles 22 d that were trapped inside the dressing pad 21 are discharged by falling from the gap to the underside, as shown in FIG. 5. Accordingly, all the diamond abrasive grain particles 22 d that have accumulated inside the wall 25 of water pressure can be discharged.
As described above, according to the present embodiment, a situation can be prevented in which diamond abrasive grain particles 22 d that have dislodged from the dressing pad 21 reach the wafer 11 and scratch the surface of the wafer 11 because a purified water supply unit 23 is disposed on the external periphery of the dresser 17, and a wall 25 of water pressure is formed at the periphery of the dresser 17.
The present invention has thus been shown and described with reference to specific embodiments. However, it should be noted that the present invention is in no way limited to the details of the described arrangements but changes and modifications may be made without departing from the scope of the appended claims.
For example, in the above embodiment, the purified water supply unit 23 is composed of a plurality of nozzles for spraying purified water perpendicularly to the surface of the polishing pad, but the present invention is not limited to such a configuration, and various purified water supply mechanisms can be used to accumulate diamond abrasive grain particles inside the dressing pad.

Claims

1. A CMP pad dresser for dressing a polishing pad of a CMP apparatus, comprising:

a dressing pad having abrasive grains; and

a purified water supply unit provided to an external periphery of the dressing pad.

2. The CMP pad dresser as claimed in claim 1, wherein the purified water supply unit supplies purified water at a prescribed pressure so that particles of abrasive grains that are dislodged from the dresser accumulate in the dressing pad.

3. The CMP pad dresser as claimed in claim 1, further comprising a drive mechanism for sliding the dressing pad in a radial direction of the polishing pad, wherein the dressing pad is slidable to the outer side of the polishing pad.

4. The CMP pad dresser as claimed in claim 1, wherein the purified water supply unit includes a plurality of nozzles for spraying purified water perpendicularly to the surface of the polishing pad.

5. A CMP apparatus, comprising:

a polishing pad; and

a CMP pad dresser for dressing the polishing pad, wherein

the CMP pad dresser includes a dressing pad having abrasive grains and a purified water supply unit provided to the external periphery of the dressing pad, and

the purified water supply unit for supplying purified water at a prescribed pressure so that particles of abrasive grains that have dislodged from the dresser accumulate in the dressing pad.

6. The CMP apparatus as claimed in claim 5, wherein the CMP pad dresser further includes a drive mechanism for sliding the dressing pad in a radial direction of the polishing pad, and the dressing pad is slidable to the outer side of the polishing pad.

7. The CMP apparatus as claimed in claim 5, wherein the purified water supply unit includes a plurality of nozzles for spraying purified water perpendicularly to the surface of the polishing pad.