KR20010002502A - Chemical mechanical polishing apparatus - Google Patents

Abstract

PURPOSE: A chemical mechanical polishing(CMP) apparatus is provided to greatly improve a uniform surface profile between a central portion and an edge portion of a wafer in a polishing process, by making a central portion of a bladder have a protruded profile by using films having various kinds of width and thickness. CONSTITUTION: A chemical mechanical polishing(CMP) apparatus comprises an upper head(210), a lower head, a bladder(270), a film(300) and a plurality of polishing pads(290). The upper head includes a wafer chuck for absorbing a wafer through a plurality of holes and a retain ring for elastically holding a circumferential portion of the wafer while holding the wafer and being capable of revolving. The lower head is capable of revolving and sweeping regarding the upper head. The bladder is supplied to an upper portion of the lower head, capable of being transformed upward by pressure. The film is adhered to a central portion of an upper portion of the bladder, forming with the bladder a profile of which the central portion is protruded. The plurality of polishing pads are adhered to upper portions of the bladder and the film, and polish a bottom surface of the wafer by mechanical friction in a relative revolution and a sweep operation of the upper and lower heads.

Description

Chemical Mechanical Polishing Device {CHEMICAL MECHANICAL POLISHING APPARATUS}

FIELD OF THE INVENTION The present invention relates to a chemical mechanical polishing device (CMP device) of a wafer, and more particularly to a chemical mechanical polishing device for uniformizing the surface profile of a wafer through a polishing process.

Advances in electronic devices include the reduction in the size of components that make up integrated circuits, such as memory chips or logic devices. As circuit elements become smaller, the value of each unit area of the semiconductor wafer increases. In order to form integrated circuits that use more of the available wafer area, it is necessary to remove contaminant particles present on the wafer surface below a certain level. For example, oxygen or metal fine particles of 0.2 μm or less are unacceptable in most advanced circuit designs. This is because the particles can shorten two or more conducting lines.

In addition to the contaminant removal as described above, a CMP process is commonly used to planarize the material layer formed on the front or rear surface of the wafer. Usually, a CMP process is performed for the operation | work which grind | exposes a deposition excess after metal deposition, such as aluminum for wiring.

The CMP process presses the wafer held by the retaining ring and the wafer chuck onto the polishing pad while supplying a slurry to the interface between them to remove the surface of the wafer by a predetermined thickness by mechanical friction and chemical action. do.

U.S. Patent 5,868,896 discloses a CMP apparatus according to the prior art. Referring to FIG. 1, the CMP apparatus 10 includes a platen 20, a wafer carrier 30, and a polish pad portion 40. The slurry 44 is supplied to the upper portion of the polishing pad portion 40. The polish pad portion 40 is composed of a matrix material such as rubber or polyurethane, or abrasive particles fixedly distributed in a suspension medium. FIG. 2 shows a plan view and a side view of one polish pad 41 when a plurality of disc-shaped polish pads 41 are arranged in a matrix to form the polishing pad portion 40. The polishing pad 41 has an abrasive material such as rubber, and has a hole 41a formed in the center thereof to allow the supply of slurry through the polishing pad 41. On the other hand, the CMP apparatus 10 has an under pad 25 attached to the top surface of the platen 20 and the bottom surface of the polishing pad portion 40.

When driving the CMP device 10, the drive device 26 rotates and linearly moves the platen 20 so that the polishing pad 40 is moved together. The wafer 12 is attracted to the bottom of the wafer carrier 30 by vacuum application, and is rotated by the drive device 36. That is, at least one of the platen 20 or the wafer carrier 30 or together move relative to each other to cause the wafer 12 to rotate and linearly move relative to the flat surface 42. At this time, the wafer 12 is pressed toward the polishing pad 40, and the polishing pad 40 and the slurry 44 are rubbed with the wafer 12 to mechanically and chemically remove metal layers or foreign substances from the surface of the wafer 12. do.

On the other hand, since the surface of the polishing pad 41 is gradually smoothed by the repeated CMP process and its polishing function is gradually lost, the polishing pad 41 is periodically roughened by a device such as a pad conditioner so that the surface is polished as much as possible. It should be conditioned so that it can be ground uniformly.

3 shows the polishing amount profile of the bottom surface of the wafer when the wafer is polished using the conventional CMP apparatus. As shown in FIG. 3, the center portion of the wafer is relatively less polished than the edge portion, resulting in an uneven wafer surface profile. Therefore, it will adversely affect the subsequent semiconductor manufacturing process.

An object of the present invention is to attach a separate film to the center of the bladder to solve the polishing non-uniformity of the wafer, which is a problem of the prior art, or to make the shape of the bladder to be raised at the center thereof, the surface profile of the wafer during CMP It is to provide a CMP apparatus that can form a uniformly.

1 is a schematic diagram of a chemical mechanical polishing (CMP) device according to the prior art.

2 is a plan view and a side cross-sectional view of a polish pad according to the prior art.

3 is a graph showing the polishing amount of the bottom surface of the wafer polished by the CMP apparatus according to the prior art.

4 is a side cross-sectional view of a CMP apparatus in accordance with an embodiment of the present invention.

5 is a plan view and a side cross-sectional view of the polish pad shown in FIG. 4.

6 is a cross-sectional view of the bladder and film according to the present invention.

7 is a cross-sectional view of various types of film according to the present invention.

8 is a cross-sectional view of various types of bladder in accordance with the present invention.

FIG. 9 is a graph showing the amount of polishing of the bottom surface of a wafer when the films and bladder shown in FIGS. 7 and 8 are used.

<Description of the symbols for the main parts of the drawings>

200: CMP apparatus 210: upper head

220: wafer chuck 230: retaining ring

260: lower head 270: bladder

280: flexible metal panel 290: multiple polish pads

300: film

In order to achieve the above object of the present invention, the present invention provides an upper head rotatable while holding a wafer, a lower head rotatable and swept relative to the upper head, and provided on top of the lower head. A bladder deformable in a direction, a film attached to an approximately center portion of the upper portion of the bladder to form a profile having a raised shape with the bladder approximately in the center thereof, and attached to the bladder and the upper portion of the film And a plurality of polish pads which polish the bottom surface of the wafer by mechanical friction with the wafer during relative rotation and sweep movement of the upper and lower heads.

The upper head includes a wafer chuck that sucks the wafer by applying a vacuum to the upper surface of the wafer through a plurality of holes formed therethrough, and a retaining ring that elastically grips the outer peripheral portion of the wafer.

In this case, a first through hole is formed at an approximately center of the bladder, and a polishing liquid including a slurry is uniformly spread between the wafer and the polish pad through the through hole and the plurality of polish pads. Thereby polishing the bottom surface of the wafer by mechanical friction and chemical reaction with the wafer.

In addition, a second through hole is formed in a portion of the film corresponding to the first through hole of the bladder to allow passage of the polishing liquid. Preferably, the material of the bladder and the film is composed of a synthetic resin material containing abrasive rubber.

In another embodiment, the film may be integrally formed with the bladder.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

4 shows a CMP apparatus 200 according to a preferred embodiment of the present invention. Referring to FIG. 4, the CMP apparatus 200 includes a rotatable upper head 210 that holds the wafer 1 and a lower head 260 that is rotatable and sweepable relative to the upper head 210. The upper head 210 elastically applies a wafer chuck 220 that absorbs the wafer 1 by applying a vacuum to the upper surface of the wafer 1 through a plurality of holes 212 formed therethrough, and an outer circumferential portion of the wafer 1. It includes a retaining ring 230 to grip. The retaining ring 230 prevents the wafer 1 from sliding in the horizontal direction during polishing. The upper head 210 is attached to the cylindrical spindle (not shown) and rotated, and during the polishing process, the upper head 210 is swept horizontally from the edge of the lower head 260 by a predetermined distance in the center direction. Typically, the upper head 210 is rotated at approximately 20 RPM.

A plurality of holes 212 are formed in the wafer chuck 220. When a vacuum is applied to the holes 212, a plurality of holes 212 are shielded by the wafer 1 placed on the bottom surface of the wafer chuck 220, and atmospheric pressure acts on the bottom surface of the wafer 1 so that the wafer 1 is used. Is vacuum-adsorbed to the bottom of the wafer chuck 220.

The lower end of the lower head 260 has a driven pulley shape to which a driving belt (not shown) is coupled, and by rotation of the driving belt, the lower head 260 has a substantially circular track at a predetermined rotational speed, typically 320 RPM. Rotates along the phase. In addition, the driving belt is coupled with a driving device (not shown) composed of a driving pulley (not shown), a reduction gear (not shown), and a motor (not shown) to receive rotational force.

Above the lower head 260 is provided a bladder 270 that is deformable upwards by pressure. Preferably, the material of the bladder 270 is made of a synthetic resin material containing abrasive rubber. The film 300 is attached to an approximately center portion of the bladder 270 to form a profile having a shape in which a central portion thereof is raised with the bladder 270. 5 is a plan view and a cross-sectional view of the bladder 270 and the film 300 according to an embodiment of the present invention. The first through hole 272 is formed at approximately the center of the bladder 270. In addition, a second through hole 302 is formed in a portion of the film 300 corresponding to the first through hole 272 of the bladder 270. 6 illustrates a shape in which the bladder 270 is raised upward by compressed air. At this time, the film 300 is also made of the same material as the bladder 270, and raised together in accordance with the deformation of the bladder 270.

Meanwhile, referring back to FIG. 4, a plurality of polish pads 290 are attached to the bladder 270 and the film 300, so that the relative rotation and sweep of the upper and lower heads 210 and 260 may be applied during polishing. When the sweep motion is performed, the bottom surface of the wafer 1 is polished by mechanical friction with the wafer 1. At the same time, a polishing liquid including a slurry through the first and second through holes 272 and 302 formed in the bladder 270 and the film 300, and the plurality of polishing pads 290 is formed in the wafer ( It spreads uniformly between 1) and the polishing pad 290 to polish the bottom surface of the wafer 1 by mechanical friction and chemical reaction with the wafer 1. Meanwhile, the flexible metal panel 299 may be covered to cover the entire upper surface of the bladder 270 and the film 300 so that the plurality of polish pads 290 may be disposed to have a smooth surface profile.

According to another embodiment of the present invention, the film 300 may be integrally formed on the bladder 270. 7 and 8 illustrate a film 300 of various widths and thicknesses and a bladder 270 of various widths and thicknesses fabricated to have a raised shape at the center thereof. In polishing, a film 300 or an integrated bladder 270 suitable for the polishing amount of the wafer 1 may be attached to the lower head 260 according to the degree of variation in the polishing amount of the wafer 1.

Hereinafter, the polishing method according to the present invention will be described.

Typically, the diameter of the lower head 260 is at least twice the diameter of the wafer, and when the polishing process is performed, the position where the edge of the lower head 260 coincides with the edge of the upper head 210 is the starting position. The upper head 210 is moved slightly horizontally from this starting position toward the center to set the working position.

First, when the wafer 1 is loaded into a loading cup (not shown) through a wafer loading mechanism, the wafer chuck 220 is vacuum-adsorbed the wafer 1 loaded on the loading cup by the upper head 210. Hold in. The upper head 210 on which the wafer 1 is held is moved to the start position above the lower head 260. Subsequently, the upper head 210 is horizontally moved a predetermined distance in the direction of the center from the start position is disposed in the working position.

At this time, the vacuum acting on the hole 212 formed in the wafer chuck 220 is released. On the contrary, a downward pressure acts on the hole 212 to press the wafer 1 toward the polish pad 290. On the polishing pad 290, the slurry solution is supplied through the polishing liquid supply path 264 formed in the lower head 260, the driving belt (not shown) is rotated to rotate and revolve the lower head 260, and the spindle ( Not shown) is rotated to start the polishing operation by rotating the upper head (210). At the same time, compressed air is supplied through a plurality of compressed air supply paths 266 formed in the lower head 260 to raise the bladder 270 upward. Thus, in general, the central portion of the wafer 1 is subjected to more polishing. In Fig. 9, the wafer polishing amount after completion of polishing is shown graphically along its radial direction. As can be seen from FIG. 9, it can be seen that the polishing amount is remarkably uniform with respect to the wafer surface as compared with the conventional art.

When the processing surface of the wafer 1 is removed to a desired thickness by such a polishing process, the rotation of the upper and lower heads 210 and 260 is stopped, and the wafer 1 is vacuum-adsorbed to the wafer chuck 220 again.

Subsequently, the processed wafer 300 from the upper head 210 is unloaded. The wafer 1 unloaded with a load cap (not shown) is cleaned and provided to the next process.

As described above, by providing the central portion of the bladder with a raised profile using films of various widths and thicknesses, it is possible to remarkably improve the uneven surface profile between the central portion and the edge portion of the wafer during polishing. In addition, the same surface profile uniformity can be achieved by fabricating and using the shape of the bladder itself in a central raised form without a separate film.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims (3)

An upper head including a wafer chuck which is rotatable while holding a wafer, and a wafer chuck that applies a vacuum to the upper surface of the wafer through a plurality of holes formed therethrough and adsorbs the wafer; ; A lower head rotatable and swept relative to the upper head; A bladder provided above the lower head and deformable upward by pressure; A film attached to an approximately central portion of an upper portion of the bladder to form a profile of the shape of which the central portion is raised with the bladder; And And a plurality of polishing pads attached to the bladder and the upper film to polish the bottom surface of the wafer by mechanical friction with the wafer during relative rotation and sweep movement of the upper and lower heads. . The method of claim 1, wherein a first through hole is formed at an approximately center of the bladder, and a second through hole is formed at a portion of the film corresponding to the first through hole of the bladder. A polishing liquid including a slurry is uniformly spread between the wafer and the polishing pad through two through holes and the plurality of polishing pads, thereby mechanically rubbing and chemically reacting with the wafer. Polishing, and the material of the bladder and the film is composed of a synthetic resin material comprising abrasive rubber. The apparatus of claim 1, wherein the film is integrally formed with the bladder.