JP2005142441A - Wafer polishing method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wafer polishing device and a wafer polishing method which can restrain the occurrence of fine scratches caused by polishing a conducting film in a CMP treatment process. <P>SOLUTION: In the wafer polishing device and the wafer polishing method for polishing a conducting film formed on an insulating film provided to a wafer, a conducting water supply means for supplying conducting water to a polishing surface is provided, and polishing is carried out while supplying conducting water to the polishing surface in polishing of a wafer. A conducting water supply means starts the supply of conducting water after detecting that an insulating film is exposed as the conducting film is polished. The conducting water is pure water which is formed by dissolving carbon dioxide and/or ammonia gas. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wafer polishing apparatus and a wafer polishing method.

  Recently, as a method of forming a fine conductive region on a wafer, an insulating film having a required opening formed on the upper surface is provided on the surface of the wafer, and the required conductive film is formed on the upper surface of the insulating film. A forming method is known in which a conductive region is formed by polishing a film using a wafer polishing apparatus such as a CMP (Chemical Mechanical Polishing) apparatus so that the conductive film remains only in the opening portion of the insulating film (for example, , See Patent Document 1).

In particular, when polishing the conductive film, the upper surface portion of the insulating film exposed as the conductive film is polished is detected, and after that, overpolishing is further performed for a predetermined time to ensure that the required insulating film is formed on the entire surface of the wafer. It was exposed.
JP 2003-243346 A

  However, when the conductive region is formed by polishing the conductive film with the wafer polishing apparatus as described above, there is a problem that scratches are generated on the wafer at a certain rate, which hinders the improvement of the manufacturing yield. .

  The cause of this scratch has not been known for a long time, but due to static electricity generated by friction between the insulating film exposed during overpolishing and the polishing cloth of the wafer polishing apparatus, it is caused by electrostatic breakdown at the boundary between the insulating film and the conductive film. It was found that minute scratches were generated, and the coating provided on the lower layer through these minute scratches was eroded by a chemical solution or the like in a subsequent process, resulting in detectable scratches.

  Therefore, the present inventor has conducted research and development to prevent the generation of minute scratches by suppressing the accumulation of static electricity that causes electrostatic breakdown during overpolishing, and has reached the present invention.

  In the wafer polishing apparatus of the present invention, in the wafer polishing apparatus for polishing the conductive film formed on the insulating film provided on the wafer, conductive water supply means for supplying conductive water to the surface to be polished is provided.

  Further, the conductive water supply means is characterized in that the supply of the conductive water is started after detecting that the insulating film is exposed as the conductive film is polished. The conductive water is carbon dioxide and / or ammonia. It is also characterized by pure water in which gas is dissolved.

  In the wafer polishing method of the present invention, in the wafer polishing method for polishing a conductive film formed on an insulating film provided on a wafer, polishing is performed while supplying conductive water to the surface to be polished during polishing.

  Further, the supply of the conductive water is characterized by starting with the exposure of the insulating film.

  According to the first aspect of the present invention, in the wafer polishing apparatus for polishing the conductive film formed on the insulating film provided on the wafer, the supply is provided by providing the conductive water supply means for supplying the conductive water to the surface to be polished. Since the accumulation of static electricity in the insulating film portion exposed by polishing can be eliminated by the conducted conductive water, the generation of fine scratches can be suppressed.

  According to the second aspect of the present invention, after detecting that the insulating film is exposed as the conductive film is polished, the conductive water supply means starts supplying the conductive water, thereby preventing the accumulation of static electricity. Waste of conductive water due to supplying conductive water to the surface to be polished at the time of polishing only the film can be suppressed.

  According to the third aspect of the present invention, since the conductive water is pure water in which carbon dioxide gas and / or ammonia gas is dissolved, the fluctuation of the polishing rate and the polishing rate are increased with the supply of the conductive water to the surface to be polished. There is no variation, and generation of static electricity can be suppressed without affecting the polishing of the surface to be polished.

  According to invention of Claim 4, in the wafer polishing method which grind | polishes the electrically conductive film formed on the insulating film provided in the wafer, it polishes, supplying electrically conductive water to a to-be-polished surface during grinding | polishing. Similarly to the first aspect of the invention, since the accumulation of static electricity on the insulating film exposed by polishing can be eliminated by the supplied conductive water, the generation of fine scratches can be suppressed.

  According to the fifth aspect of the present invention, the supply of the conductive water starts with the exposure of the insulating film, and as in the second aspect of the invention, during the polishing of only the conductive film that does not cause static electricity accumulation. It is possible to suppress waste of the conductive water due to supplying the conductive water to the surface to be polished.

  In the wafer polishing apparatus and wafer polishing method of the present invention, when polishing a conductive film formed on an insulating film provided on a wafer, conductive water is supplied to the surface to be polished.

  By supplying conductive water to the surface to be polished in this way, it is possible to prevent static electricity from accumulating in the exposed insulating film part due to polishing, and to suppress the generation of micro scratches due to this static electricity. Yield can be improved.

  In particular, when the supply of conductive water is started at the stage where the insulating film is exposed from the conductive film, the conductive water is wasted by not supplying the conductive water to the surface to be polished when polishing only the conductive film in which static electricity does not accumulate. Can be suppressed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram of a wafer polishing apparatus according to this embodiment.

  The wafer polishing apparatus includes a rotating base 13 having a polishing cloth 12 mounted on the upper surface, a rotating head 11 for mounting a wafer 10 to be brought into contact with the polishing cloth 12 of the rotating base 13, and a polishing agent on the polishing cloth 12. A slurry supply pipe 14 for supplying slurry and a conductive water supply pipe 15 for supplying conductive water to the polishing pad 12 are configured.

  In FIG. 1, 14a is a slurry tank that contains slurry, and 14b is a slurry supply control pump that controls the supply of slurry from the slurry tank 14a to the slurry supply pipe 14. 15a is a conductive water tank containing conductive water, and 15b is a supply control pump for conductive water that controls the supply of slurry from the conductive water tank 15a to the conductive water supply pipe 15. The conductive water supply means is constituted by 15a, the conductive water supply control pump 15b, and the conductive water supply pipe 15. Reference numeral 16 denotes a conditioner for keeping the polishing state of the polishing pad 12 constant.

  The rotating base 13 is provided with a flat surface-like polishing cloth application surface, and the polishing cloth 12 is attached to the polishing cloth application surface so as to rotate at a predetermined rotation speed.

  The wafer 10 is fixedly mounted on the rotary head 11 by appropriate fixing means (not shown), and is rotated as the rotary head 11 rotates.

  Then, while rotating the rotation base 13 and the rotation head 11 in a predetermined rotation direction at a predetermined rotation speed, the wafer 10 mounted on the rotation head 11 is pressed onto the polishing cloth 12, and the wafer 10 and the polishing cloth 12 During this time, the slurry is fed to polish the wafer 10.

  An insulating film is formed on the surface of the wafer 10 to be polished by the above-described wafer polishing apparatus, and necessary openings are formed in the formed insulating film. The opening of the insulating film formed here is for forming a conductive region.

  Then, a conductive film is formed on the upper surface of this insulating film, and this conductive film is polished by the above-described wafer polishing apparatus, whereby the conductive film is left in the opening of the insulating film to form a conductive region.

Here, the insulating film is mainly an oxide film such as an HDP film, a BPSG film, a PSiO film, or a Th-SiO ₂ film, and the conductive film is polysilicon formed mainly by a CVD process, a PVD process, or a Diff process. Or a metal film such as tungsten, titanium nitride, or copper.

  When the conductive film formed on the upper surface of the insulating film is removed by polishing as described above, it is necessary to control the polishing amount of the conductive film. This control of the polishing amount of the conductive film is accompanied by polishing of the conductive film. Then, it is detected by detecting that the surface of the insulating film, which is the lower layer of the conductive film, is exposed from the conductive film, and controlling the maintenance time of the overpolishing state in which polishing is continued even after the exposure of the insulating film is detected.

  Insulating film exposure detection uses a torque detection method that uses the rotational torque of the rotary head 11 that varies with the exposure of the insulating film, or the surface condition of the surface to be polished that varies with the exposure of the insulating film. Current detection by detecting the current flowing between the anode electrode and the cathode electrode as the insulating film is exposed by providing an anode electrode and a cathode electrode on the polishing cloth 12. In this embodiment, the wafer polishing apparatus is provided with necessary detection means so as to detect the exposure of the insulating film by the current detection method.

  When the wafer 10 is polished by the above-described wafer polishing apparatus, the following is performed.

  First, in the wafer polishing apparatus, the polishing pad 12 is mounted on the rotary base 13 and the required wafer 10 is mounted on the rotary head 11. Here, it is assumed that an insulating film and a conductive film are sequentially formed on the wafer 10.

  Next, while discharging the slurry from the slurry supply pipe 14, the rotary head 11 and the rotary base 13 are each rotated in the required rotation direction, and the rotary head 11 is further lowered to bring the wafer 10 into contact with the polishing pad 12. The conductive film is polished by pressing the polishing cloth 12 with a predetermined pressure.

  When it is detected that the insulating film is exposed from the conductive film along with the polishing of the conductive film, the wafer polishing apparatus operates the conductive water supply control pump 15b to discharge the conductive water from the conductive water supply pipe 15, Polishing is performed for a predetermined time while supplying conductive water to 10 surfaces to be polished.

  Then, after a predetermined time has elapsed from the exposure of the insulating film, the wafer 10 is separated from the polishing pad 12 and the polishing process is completed.

  In this way, when the insulating film portion is polished, the conductive water is supplied to the surface to be polished, thereby eliminating the accumulation of static electricity generated by the friction between the insulating film and the polishing pad 12 in the insulating film portion. And the generation of fine scratches can be suppressed.

  Conductive water may be supplied to the surface to be polished immediately after the start of polishing of the wafer 10 by the wafer polishing apparatus. However, since no accumulation of static electricity occurs during polishing of the conductive film portion, there is no effect due to the supply of conductive water and insulation. By starting the supply of conductive water as the film is exposed, waste of the conductive water can be suppressed.

  The conductive water has a required electrical conductivity by dissolving a predetermined amount of carbon dioxide gas or ammonia gas, or carbon dioxide gas and ammonia gas in pure water. In this embodiment, carbon dioxide gas is dissolved in ultrapure water so that the electrical resistance of pure water, which is conventionally about 18 MΩ · cm, is adjusted to 6 to 12 MΩ · cm.

  When the accumulation of static electricity is eliminated by using conductive water, there will be no fluctuations in the polishing rate or variations in polishing with the supply of conductive water, and static electricity will be generated without affecting the polishing of the surface to be polished. Can be suppressed. Specifically, while the average polishing rate within the wafer 10 surface under the conventional polishing conditions was 382.8 nm / min and the in-plane uniformity was 6.68%, the conductive water was supplied after the insulating film was exposed. When polishing, the average polishing rate is 375.0 nm / min, the in-plane uniformity is 7.09%, and it can be seen that the supply of conductive water has almost no effect on the polishing of the wafer 10.

  Furthermore, by adjusting the amount of conductive water supplied to the surface to be polished or the pH of the conductive water, it is possible to further reduce the influence of the supply of conductive water on the polishing rate.

It is a schematic diagram of a wafer polishing apparatus.

Explanation of symbols

10 wafers
11 Rotating head
12 Abrasive cloth
13 Rotating base
14 Slurry supply pipe
15 Conductive water supply pipe
14a Slurry tank
14b Slurry supply control pump
15a Conductive water tank
15b Conductive water supply control pump
16 Conditioner

Claims (5)

In a wafer polishing apparatus for polishing a conductive film formed on an insulating film provided on a wafer,
A wafer polishing apparatus comprising conductive water supply means for supplying conductive water to a surface to be polished.   2. The wafer polishing apparatus according to claim 1, wherein the conductive water supply means starts supplying the conductive water after detecting that the insulating film is exposed as the conductive film is polished.   3. The wafer polishing apparatus according to claim 1, wherein the conductive water is pure water in which carbon dioxide gas and / or ammonia gas is dissolved. In a wafer polishing method for polishing a conductive film formed on an insulating film provided on a wafer,
A wafer polishing method comprising polishing while supplying conductive water to a surface to be polished during polishing.   The wafer polishing method according to claim 4, wherein the supply of the conductive water starts with the exposure of the insulating film.

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