US20050164613A1

US20050164613A1 - Method of conditioning polishing pad for semiconductor wafer

Info

Publication number: US20050164613A1
Application number: US10/979,212
Authority: US
Inventors: Yoshiyuki Seike; Keiji Miyachi; Masahiko Amari; Ara Philipossian; Toshiro Doi
Original assignee: Asahi Sunac Corp
Current assignee: Asahi Sunac Corp
Priority date: 2004-01-28
Filing date: 2004-11-03
Publication date: 2005-07-28
Also published as: JP2005217037A

Abstract

Dressing is performed by spraying a cleaning liquid onto a polishing pad and after that abrasive slurry injected from a nozzle is supplied to the polishing pad. Provided is a method of conditioning a polishing pad for semiconductor wafer which is suitable for keeping the polishing performance of a polishing pad, provided with a polishing device for semiconductor wafer, in a stable condition for a long time.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a method of conditioning a polishing pad for semiconductor wafer and, more particularly, to a method of conditioning a polishing pad for semiconductor wafer which is suitable for keeping the polishing performance of a polishing pad of a semiconductor wafer polishing device in a stable condition for a long time.
2. Description of the Related Art
There is a chemical mechanical polishing (CMP) method as one of the polishing methods of semiconductor wafers. Under this polishing method, a polishing solution is prepared by causing abrasive grains formed from silica etc. to be suspended in an alkaline solution. The polishing solution is dripping onto a polishing pad, during a semiconductor wafer and the polishing pad are caused to perform relative movements while both are being pressed against each other. A reaction product is formed on the surface of the semiconductor wafer due to the actions of the polishing liquid and the abrasive grains, and the abrasive grains and the polishing pad scrape off the reaction product. As the use of the polishing pad is increased, the polishing pad is clogged by the above-described reaction product and polishing chips, so dressing is necessary.
As such dressing, it has been a general practice to adopt a method that involves causing a dresser embedded diamond abrasive grains on the surface, is performed movements relative to a polishing pad, being pressed against the polishing pad. However, this dressing method has the problems that the diamond abrasive grains fall off and may sometimes damage the work, and the like, the polishing pad is ground by the dresser so that the polishing pad is short lifetime.
On the other hand, various proposals which involve performing dressing by spraying high-pressure water onto a polishing pad have been made as techniques which replace such a dressing method as described above. Among others, for example, a proposal made by the present applicants specifies the size of mist particles of high-pressure water and the rate of high-pressure water to optimum ranges (Japanese Patent Application Publication No. 10-244459), and specific effects have been obtained.

SUMMARY OF THE INVENTION

However, dressing that involves spraying high-pressure water onto a polishing pad has the disadvantages that a polishing liquid (abrasive slurry) which remains on the polishing pad surface, and within the polishing pad is diluted, resulting in a decrease in the polishing rate. That is, abrasive slurry used in CMP is adjusted to alkalescency and hence its characteristic is such that the polishing rate decreases when pH decreases.
Therefore, a dressing method that involves spraying high-pressure water onto a polishing pad has not been able to make the most of its superiority because of the problems as already stated although it has better dressing performance than dressing methods using conventional pressers as described above.
The present invention was made in view of such a situation and has as its object the provision of a method of conditioning a polishing pad for semiconductor wafer which is suitable for keeping the polishing performance of a polishing pad of a semiconductor wafer polishing device in a stable condition for a long time.
To achieve the above-described object, the first aspect of the present invention provides a method of conditioning a polishing pad for semiconductor wafer, comprising dressing by spraying a cleaning liquid onto a polishing pad, and then supplying abrasive slurry injected from a nozzle to the polishing pad.
According to the first aspect of the present invention, after dressing that involves spraying a cleaning liquid onto a polishing pad was performed, an abrasive slurry is supplied by spraying to this polishing pad, thereby a decrease in the polishing rate due to a decrease in pH does not occur and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
The second aspect of the present invention provides a method of conditioning a polishing pad for semiconductor wafer, comprising dressing by causing relative movements while a polishing pad is being pressed against a dresser, and then supplying abrasive slurry injected from a nozzle to the polishing pad.
According to the second aspect of the present invention, after conventional dressing by a dresser was performed, abrasive slurry is supplied by injection to the polishing pad. Although the degree of dilution of abrasive slurry is small in the dressing by a dresser, the effect of supplying the abrasive slurry is obtained and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
The third aspect of the present invention provides a method of conditioning a polishing pad for semiconductor wafer, comprising dressing by spray of a cleaning liquid onto a polishing pad, and then supplying abrasive slurry to the polishing pad by adding dropwise.
According to the third aspect of the present invention, abrasive slurry is supplied to the polishing pad by being added dropwise. In addition, by such a supplying method like this, the permeation of the abrasive slurry into the polishing pad is ensured, and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
The fourth aspect of the present invention provides a method of conditioning a polishing pad for semiconductor wafer, comprising dressing by causing relative movements while a polishing pad is being pressed against a dresser, and then supplying abrasive slurry to the polishing pad by being added dropwise. According to the fourth aspect of the present invention, abrasive slurry is supplied to the polishing pad by being added dropwise. In addition, by such a supplying method like this, the permeation of the abrasive slurry into the polishing pad is ensured, and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
The fifth aspect of the present invention provides a method of conditioning a polishing pad for semiconductor wafer, comprising dressing by spraying a cleaning liquid onto a polishing pad, and then supplying abrasive slurry which does not contain abrasive grains to the polishing pad.
According to the fifth aspect of the present invention, abrasive slurry that does not contain abrasive grains is supplied to this polishing pad after dressing in that involves spraying a cleaning liquid onto a polishing pad. Because this liquid has almost the same pH as the abrasive slurry, a decrease in the polishing rate due to a decrease in pH does not occur, and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
Incidentally, abrasive slurry which does not contain abrasive grains may be abrasive slurry obtained by removing abrasive grains from abrasive slurry after preparation. Usually, however, it is a general practice to use abrasive slurry for which an adjustment is made by not adding abrasive grains alone in preparing the abrasive slurry.
The sixth aspect of the present invention provides a method of conditioning a polishing pad for semiconductor wafer, comprising dressing by causing relative movements while a polishing pad is being pressed against a dresser, and then supplying abrasive slurry which does not contain abrasive grains to the polishing pad.
According to the sixth aspect of the present invention, after conventional dressing by a dresser is performed, abrasive slurry, which does not contain abrasive grains, is supplied to the polishing pad. Although the degree of dilution of abrasive slurry is small in the dressing by a dresser, the effect of supplying this liquid is obtained, and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
The feature of the seventh aspect of the present invention is that the abrasive slurry which does not contain abrasive grains is supplied by injecting the liquid from a nozzle. According to the seventh aspect of the present invention, the liquid is supplied by being injected from a nozzle, so that the permeation of the liquid into the polishing pad is promoted, and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
The feature of the eighth aspect of the present invention is that the abrasive slurry which does not contain abrasive grains is supplied by adding the abrasive slurry dropwise the liquid is supplied to the polishing pad by being added dropwise. In addition, by such a supplying method like this, the permeation of the abrasive slurry into the polishing pad is ensured, and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
The ninth aspect of the present invention provides a method of conditioning a polishing pad for semiconductor wafer, comprising dressing by spraying a cleaning liquid onto a polishing pad, and then supplying a pH-adjusting liquid to the polishing pad.
According to the ninth aspect of the present invention, after dressing that involves spraying a cleaning liquid onto a polishing pad, a pH-adjusting liquid is supplied to this polishing pad. Owing to the adjustment of pH by this pH-adjusting liquid, a decrease in the polishing rate due to a decrease in pH does not occur, and so that the polishing performance of the polishing pad can be kept in a stable condition for a long time.
Incidentally, in this case, a pH-adjusting liquid is an alkaline adjusting liquid. Commercially available alkaline ion water and the like can be uses as such a pH-adjusting liquid.
The tenth aspect of the present invention provides a method of conditioning a polishing pad for semiconductor wafer, comprising dressing by causing relative movements while the polishing pad is being pressed against the dresser, and then supplying a pH-adjusting liquid to the polishing pad.
According to the tenth aspect of the present invention, a pH-adjusting liquid is supplied after the dressing by a conventional dresser. Although the degree of dilution of abrasive slurry is small in the dressing by a dresser, the effect of supplying the pH-adjusting liquid is obtained, and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
The feature of the eleventh aspect of the present invention is that the pH-adjusting liquid is supplied by being injected the pH-adjusting liquid from a nozzle. According to the eleventh aspect of the present invention, the pH-adjusting liquid is supplied by being injected from a nozzle, so that the permeation of the liquid into the polishing pad is promoted, and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
The feature of the twelfth aspect of the present invention is that the pH-adjusting liquid is supplied by being added dropwise. In addition, by such a supplying method like this, the permeation of the liquid into the polishing pad is ensured, and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
The feature of the thirteenth aspect of the present invention is that the cleaning liquid is pure water. According to the thirteenth aspect of the present invention, pure water is used as the cleaning liquid, so that the pollution of the polishing pad during dressing can be prevented.
The feature of the fourteenth aspect of the present invention is that the cleaning liquid is a pH-adjusting liquid. According to the fourteenth aspect of the present invention, the pH-adjusting liquid is used as the cleaning liquid, so that the pH of the polishing pad is optimized, and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
The feature of the fifteenth aspect of the present invention is that the cleaning liquid is abrasive slurry which does not contain abrasive grains. According to the fifteenth aspect of the present invention, abrasive slurry which does not contain abrasive grains is used as the cleaning liquid, so that the pH of the polishing pad is optimized, and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
The sixteenth aspect of the present invention provides a method of conditioning a polishing pad for semiconductor wafer, comprising dressing by spraying abrasive slurry onto a polishing pad.
According to the sixteenth aspect of the present invention, dressing that involves spraying abrasive slurry is performed in place of the dressing that involves spraying a cleaning liquid onto a polishing pad. Even by this method, a similar effect is obtained at the same time, therefore the pH of the polishing pad is optimized, and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
The seventeenth aspect of the present invention provides a method of conditioning a polishing pad for semiconductor wafer, comprising dressing by spraying abrasive slurry onto a polishing pad.
According to the seventeenth aspect of the present invention, dressing that involves spraying a pH-adjusting liquid is performed in place of the dressing that involves spraying a cleaning liquid onto a polishing pad. Even by this method, a similar effect is obtained at the same time, therefore the pH of the polishing pad is optimized, and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
The eighteenth aspect of the present invention provides a method of conditioning a polishing pad for semiconductor wafer, comprising spraying abrasive slurry which does not contain abrasive grains onto a polishing pad.
According to the eighteenth aspect of the present invention, dressing that involves spraying abrasive slurry that does not contain abrasive grains is performed in place of the dressing that involves spraying a cleaning liquid onto a polishing pad. Even by this method, a similar effect is obtained and at the same time, therefore the pH of the polishing pad is optimized, and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
The feature of the nineteenth aspect of the present invention is that polishing uses a dummy work after conditioning a polishing pad for semiconductor wafer by the method. According to the nineteenth aspect of the present invention, polishing using a dummy work is performed after the conditioning of the polishing pad, so that abrasive slurry is supplied to the polishing pad, with the result that the pH of the polishing pad is optimized, and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
The twentieth aspect of the present invention provides a method of conditioning a polishing pad for semiconductor wafer, comprising dressing by spray of pure water onto a polishing pad, and then polishing using a dummy work.
According to the twentieth aspect of the present invention, polishing using a dummy work is performed after the dressing of the polishing pad by spraying pure water, so that abrasive slurry is supplied to the polishing pad, with the result that the pH of the polishing pad is optimized, and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
As described above, according to the present invention, after the dressing of a polishing pad abrasive slurry is supplied to this polishing pad, a decrease in the polishing rate due to a decrease in pH does not occur, and the polishing performance of the polishing pad can be kept in a stable condition for a long time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial structural drawing of a conditioning device of a polishing pad for semiconductor wafer in the first embodiment of the present invention;
FIG. 2 is a partial structural drawing of a conditioning device of a polishing pad for semiconductor wafer in the second embodiment of the present invention;
FIG. 3 is a sectional view of a nozzle used in the embodiments of the present invention; and
FIG. 4 is a bottom view of the nozzle shown in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of a conditioning method of a pad for semiconductor wafer related to the present invention will be described in detail below with reference to the accompanying drawings. First, the first embodiment will be described.
FIG. 1 is a structural drawing of a conditioning device 10 of a polishing pad for semiconductor wafer to which a method of conditioning a polishing pad for semiconductor wafer related to the present invention is applied. This conditioning device 10 dresses a polishing pad 50 by spraying a cleaning liquid such as pure water from a nozzle 14 for spraying onto the polishing pad 50 on a surface 52 of a polishing device and, after dressing, conditions the polishing pad 50 on a surface plate 52 of a polishing device by spraying a chemical liquid such as abrasive slurry from a nozzle 74 for chemical liquid supply onto the polishing pad 50.
The nozzle 14 for dressing is connected to a pump 18 via a pipe 16, and this pump 18 is connected to a tank 22 via a flexible hose 20. A cleaning liquid stored in the tank 22 is pressurized by the pump 18, fed to the nozzle 14, and injected at the polishing pad 50.
The pump 18 is provided on a table 24. This table 24 can move freely in the direction of the arrow a on a rail 28 provided on a base 26, and an end portion of the table 24 is connected to an air cylinder 30 supported on the base 26 via a rod 32. Therefore, when the air cylinder 30 is actuated, the nozzle 14 moves in the direction of the arrow a via the table 24 etc.
The nozzle 74 for chemical liquid supply and the pipe 16 are arranged so that a chemical liquid such as abrasive slurry can be injected at the polishing pad 50. Because this arrangement is the same as the arrangement of the nozzle 14 for dressing, the pipe 16, etc., the diagrammatic representation and description of a flexible hose, a tank, a table, etc. used in this arrangement are omitted. Incidentally, the same arrangement is shown in FIG. 2 that explains the second embodiment, which will be described later.
In the arrangement of FIG. 1, the nozzle 74 for chemical liquid supply supplies a chemical liquid at a pressure of not less than 15 MPa but not more than 30 MPa in the same manner as the nozzle 14 for dressing, which will be described later. However, it is possible to adopt also a nozzle that simply adds a chemical liquid dropwise in place of this nozzle. Furthermore, it is possible to use a nozzle of the same pressure specification of not less than 15 MPa but not more than 30 MPa as the nozzle 14 for dressing and to adopt a method of use that involves adding a chemical liquid dropwise by setting the chemical liquid supply pressure at a level lower than the specification.
In FIG. 1, the nozzle 74 for chemical liquid supply and the pipe 16, and the nozzle 14 for dressing and the pipe 16 are arranged by shifting their positions in the vertical direction of the paper so that each set does not interfere with each other when moving in the lateral direction.
The surface plate 52 is connected to the motor 56 via a rotary shaft 54 and rotated in the direction of the arrow b. The polishing pad 50 is bonded to this surface plate 52.
Next, the operation of the conditioning device 10 constituted as described above will be described. When the dressing of the polishing pad 50 becomes necessary during polishing operation performed by the polishing pad 50, the nozzle 14 is positioned on the polishing pad 50 by actuating the air cylinder 30 and a cleaning liquid is injected from the nozzle 14 by actuating the pump 18. The cleaning liquid injected from the nozzle 14 collides against the polishing pad 50 in the form of mist particles, sputters and washes out polishing chips which have accumulated on the polishing pad 50.
Moreover, while the cleaning liquid is being injected from the nozzle 14, the polishing pad 50 is rotated by the motor 56 and the nozzle 14 is moved by the air cylinder 30. As a result of this, the whole surface of the polishing pad 50 can be dressed.
Incidentally, it is only necessary that the movements between the nozzle 14 and the polishing pad 50 are performed in a relative manner and, therefore, the movements are not limited to the above-described movement method. For example, with the polishing pad 50 fixed, the nozzle 14 may be moved back and forth and laterally to dress the whole surface of the polishing pad 50. Also, for example, the movement of the nozzle 14 may be performed by use of a screw feed device, or the nozzle 14 may be attached to a leading end of an arm so that be moved by rotating an arm.
It is necessary to adjust the size of mist particles and the collision speed of mist particles which are made to collide to the polishing pad 50 according to the material for the polishing pad 50. For example, when the polishing pad 50 is a hard porous polyurethane, the particle size of the mist particles of a cleaning liquid should be preferably not less than 1 mm but not more than 300 mm, and more preferably not less than 1 mm but not more than 100 mm. This is because in order for the mist particles of the cleaning liquid to enter the pores of the polishing pad 50 which are clogged with polishing chips and to wash the polishing chips out of the pores, it is necessary for the size of the mist particles to be more than of the same grade to the size of polishing chips but smaller than the pores of the polishing pad 50. More specifically, mist particles, which are too small compared to polishing chips, are weak in the force of washing out polishing chips. On the other hand, mist particles that are larger than the pores of the polishing pad 50 cannot enter the pores as they are, so the mist droplets cannot sputter the polishing chips out of the pores.
The speed at which the mist particles of a cleaning liquid corrode against the polishing pad 50 is preferably not less than 10 m/s but not more than 500 m/s, and more preferably more preferably not less than 30 m/s but not more than 150 m/s. If the collision speed of the mist particles is too low, the kinetic energy is insufficient for sputtering polishing chips. While, if the collision speed of the mist particles is too high, the polishing pad 50 may be damaged. In order to realize the above-described size and collision speed of the mist particles of the cleaning liquid, it is necessary to supply the cleaning liquid to the nozzle 14 at a pressure of not less than 15 MPa but not more than 30 MPa.
The size of the mist particles of the cleaning liquid and the speed of collision of the mist particles against the polishing pad 50 can be controlled by adjusting the nozzle diameter of the nozzle 14 and the supply pressure of the cleaning liquid to the nozzle 14 by the pump 18.
The distance between the tip of the nozzle 14 and the surface of the polishing pad 50 can be made into a proper value according to the nozzle diameter of the nozzle 14, the supply pressure of the cleaning liquid by the pump 18, the material for the polishing pad 50, the size of the polishing pad 50, etc., and for example, a value of 100 mm is adopted.
Pure water is generally used as the cleaning liquid. However, it is possible to use a pH-adjusting liquid and abrasive slurry, which does not contain abrasive grains, etc., can also be used in addition to this. As already described, an alkaline adjusting liquid, concretely, commercially available alkaline ion water, etc. can be used. As abrasive slurry which does not contain abrasive grains, as already described, it is possible to use abrasive slurry for which an adjustment is made by not adding abrasive grains alone in preparing the abrasive slurry.
After the completion of the dressing of the polishing pad 50, the nozzle 74 for chemical liquid supply injects a chemical liquid such as abrasive slurry to the polishing pad 50 on the surface plate 52 of the polishing device, so that the polishing pad 50 can be conditioned. This occasion, after an air cylinder 90 was actuated (hereinafter refer to FIG. 2) and the nozzle 74 was positioned on the polishing pad 50, a chemical liquid is injected from the nozzle 74 by actuating a pump 78. The chemical liquid injected from the nozzle 74 collides, in the form of mist particles, against the polishing pad 50 and penetrates into the polishing pad 50.
While the chemical liquid is being injected from the nozzle 74, the polishing pad 50 is rotated by the motor 56 (refer to FIG. 1) and the nozzle 74 is moved by the air cylinder 90. As a result of this, the whole surface of the polishing pad 50 can be conditioned.
Incidentally, it is necessary that the movements between the nozzle 74 and the polishing pad 50 are performed in a relative manner only and, therefore, the movements are not limited to the above-described movement method. For example, with the polishing pad 50 fixed, the nozzle 74 may be moved back and forth and laterally to condition the whole surface of the polishing pad 50. In addition, the movement of the nozzle 74 may be performed by use of a screw feed device, for example, or the nozzle 74 may be attached to a leading end of an arm and moved by rotating the arm.
Incidentally, as already described, conditioning that involves adding a chemical liquid dropwise may be adopted in place of the method that involves injecting a chemical liquid.
Abrasive slurry and the above-described pH-adjusting liquid and the abrasive slurry that does not contain abrasive grains, etc. can be used as a chemical liquid to be supplied such as abrasive slurry.
After the above-described conditioning of the polishing pad 50, it is also desirable to adopt a method by which polishing using a dummy work is performed before the polishing work of a product (or a semi-finished product). If polishing using such a dummy work is performed, abrasive slurry is supplied to the polishing pad and the pH of the polishing pad is optimized, with the result that the polishing performance of the polishing pad can be kept in a stable condition for a long time.
Next, the second embodiment of a method of conditioning a polishing pad for semiconductor wafer related to the present invention will be described on the basis of FIG. 2. Incidentally, the same members as in FIG. 1 or members similar to those of FIG. 1 are given like reference numerals and their descriptions are omitted.
FIG. 2 is a structural drawing of a conditioning device 10′ provided with a polishing pad for semiconductor wafer to which a method of conditioning a polishing pad for semiconductor wafer related to the present invention is applied. This conditioning device 10′ performs dressing by causing relative movements while pressing a pad dresser 60 against a polishing pad 50 and, after dressing, conditions the polishing pad 50 on a surface plate 52 of a polishing device by spraying a chemical liquid such as abrasive slurry from a nozzle 74 for chemical liquid supply onto the polishing pad 50.
A pad dresser electrodeposited with diamond abrasive grains 62 on the bottom surface or a pad dresser formed from a bonded layer (metal bond, vitrified bond or resin bond), which diamond abrasive grains 62 are dispersed, can be used as the pad dresser 60. The pad dresser 60 dresses the polishing pad 50 by being pressed by the force F against the polishing pad 50 on the polishing surface plate 52 while being rotated around a shaft 64.
The thickness of the pad dresser 60 is generally 10 to 30 mm or so and the outside diameter thereof is generally 100 to 250 mm (4 to 10 inches) or so. The seat of the pad dresser 60 is generally made of metal.
Incidentally, it is also possible to adopt an arrangement in which the pad dresser 60 and the shaft 64 are connected via a flexible joint (for example, a universal joint). By adopting this arrangement, the surface (bottom surface) of the pad dresser 60 and the surface of the polishing pad 50 are in contact with each other throughout the whole area, so that even during the dressing work, the surface of the pad dresser 60 can follow the surface of the polishing pad 50.
A nozzle 74 for chemical liquid supply is connected to a pump 78 via a pipe 76 and this pump 78 is connected to a tank 82 via a flexible hose 80. A cleaning liquid stored in the tank 82 is pressurized by the pump 78, fed to the nozzle 74, and injected at the polishing pad 50.
The pump 78 is provided on a table 84. This table 84 can move freely in the direction of the arrow c on a rail 88 provided on a base 86, and an end portion of the table 84 is connected to an air cylinder 90 supported on the base 86 via a rod 92. Therefore, when the air cylinder 90 is actuated, the nozzle 74 moves in the direction of the arrow c via the table 84 etc.
Next, the operation of the conditioning device 10′ constituted as described above will be described. When the dressing of the polishing pad 50 becomes necessary after the polishing operation is performed by the polishing pad 50, the pad dresser 60 is positioned on the surface of the polishing pad 50 and dressing is performed by causing relative movements while the pad dresser 60 is being pressed against the polishing pad 50. As a result of this, Polishing chips that have accumulated on the polishing pad 50 are removed and washed out by dressing water that is supplied.
More specifically, while the dressing water is being supplied from a nozzle for dressing water supply, which is not shown, or the nozzle 74, the polishing pad 50 is rotated by a motor 56, and the pad dresser 60 is rotated by the rotation of the polishing pad 50 in the direction of the arrow d. As a result of this, the whole surface of the polishing pad 50 can be dressed. Incidentally, in the case of an arrangement in which dressing water is supplied from the nozzle 74, a three-way valve is provided halfway in the pipe 76 to permit a switchover between pure water from a pure water supply source, which is not shown, and a chemical liquid from the pump 78.
After the completion of the dressing of the polishing pad 50, the polishing pad 50 is conditioned by injecting a chemical liquid such as abrasive slurry from the nozzle 74 for chemical liquid supply onto the polishing pad 50 on the surface plate 52 of the polishing device. This occasion, after the nozzle 74 is moved on the polishing pad 50 by actuating an air cylinder 90, a chemical liquid is injected from the nozzle 74 by actuating a pump 78. The chemical liquid injected from the nozzle 74 collides against the polishing pad 50, in form of the mist particles, and penetrates into the polishing pad 50.
In addition, while the chemical liquid is being injected from the nozzle 74, the polishing pad 50 is rotated by the motor 56 and the nozzle 74 is moved by the air cylinder 30. As a result of this, the whole surface of the polishing pad 50 can be conditioned.
As already described, conditioning that involves adding a chemical liquid dropwise may be performed in place of the method that involves injecting a chemical liquid.
Also in this embodiment, as with the first embodiment, abrasive slurry and, the above-described pH-adjusting liquid and, abrasive slurry that does not contain abrasive grains, etc. can be used as a chemical liquid to be supplied from the nozzle 74, such as abrasive slurry.
Similarly, After the above-described conditioning of the polishing pad 50, it is also desirable to adopt a method by which polishing using a dummy work is performed before the polishing work of a product (or a semi-finished product).
The embodiments of a method of conditioning polishing pads for semiconductor wafer related to the present work have been described above. However, the present invention is not limited to the above-described embodiments and it is possible to adopt various modes.
As this example, it is possible to adopt a method by which abrasive slurry is injected onto a polishing pad during the dressing of the polishing pad. That is, dressing that involves spraying abrasive slurry onto a polishing pad is performed in place of the dressing that involves spraying a cleaning liquid onto a polishing pad. However, also by this method, the same effect as with the above-described embodiments is obtained and, at the same time, the pH of the polishing pad is optimized, with the result that the polishing performance of the polishing pad can be kept in a stable condition for a long time.
In addition, it is possible to adopt a method that involves injecting a pH-adjusting liquid onto a polishing pad during the dressing of the polishing pad. That is, dressing that involves spraying a pH-adjusting liquid is performed in place of the dressing that involves spraying a cleaning liquid onto a polishing pad. However, also by this method, the same effect as with the above-described embodiments is obtained and, at the same time, the pH of the polishing pad is optimized, with the result that the polishing performance of the polishing pad can be kept in a stable condition for a long time.
In addition, it is possible to adopt a method by which abrasive slurry, which does not contain abrasive grains, is injected onto a polishing pad during the dressing of the polishing pad. That is, dressing that involves spraying abrasive slurry which does not contain abrasive grains is performed in place of the dressing that involves spraying a cleaning liquid onto a polishing pad. However, also by this method, the same effect as with the above-described embodiments is obtained and, at the same time, the pH of the polishing pad is optimized, with the result that the polishing performance of the polishing pad can be kept in a stable condition for a long time.
Furthermore, it is also possible to adopt a method by which dressing is performed by spraying pure water onto a polishing pad, and then the polishing using a dummy work is performed. That is, because polishing using a dummy work is performed after the dressing of the polishing pad by spraying pure water, abrasive slurry is supplied to the polishing pad, with the result that the pH of the polishing pad is optimized, and the polishing performance of the polishing pad can be kept in a stable condition for a long time.
An example of a method of conditioning a polishing pad for semiconductor wafer using the above-described conditioning device 10 provided with a polishing pad for semiconductor wafer will be described below.
FIGS. 3 and 4 show the construction of the nozzles 14, 74. The nozzles 14, 74 are each constituted by a nozzle tip 36 having an exhaust slot 34 and a nozzle case 38 into which this nozzle tip 36 is inserted. As shown in FIG. 4, the exhaust slot 34 is formed in the shape of a vertically long ellipse the middle portion of which is opened forward (downward in FIG. 3) and which has a minor axis of 200 mm and a major axis of 500 mm.
On the conditioning device 10, the distance between the nozzle 14 and the polishing pad 50 was set at 200 mm and water as a cleaning liquid was supplied to the nozzle 14 at a pressure of 25 MPa. The time of water supply from the nozzle 14 was 30 seconds. The polishing pad 50 used in the experiment was made of hard porous polyurethane and the diameter of pores was about 10 mm to 100 mm.
In this conditioning device 10, the water which discharged from the exhaust slot 34 as a film-like flow at an initial rate of about 350 m/s was dispersed by the resistance of the air in the shape of mist droplets having a particle size of 1 mm to 100 mm (the most frequent value being about 30 mm), and collided against the polishing pad 50 at an velocity of 30 m/s to 150 m/s.
As a result, polishing chips which had accumulated on the polishing pad 50 could be thoroughly removed from the surface layer of the polishing pad 50 to the deep layer thereof. Incidentally, the supply pressure and supply method of the cleaning liquid to the nozzle, the shape and size of the exhaust slot of the nozzle, and the distance between the nozzle and the polishing pad may be arbitrarily changed.
Next, on the conditioning device 10, the distance between the nozzle 74 and the polishing pad 50 was set at 200 mm, and abrasive slurry was supplied to the nozzle 74 at a pressure of 15 MPa. The time of supply of the abrasive slurry from the nozzle 74 was 10 seconds. Discharged abrasive slurry was dispersed by the resistance of the air in the form of mist droplets and collided against the polishing pad 50. As a result, the abrasive slurry thoroughly permeated into the polishing pad 50.
Immediately after the conditioning of this polishing pad, the polishing work of the work as a product was carried out and the measurement of the polishing rate and an evaluation of flaws on the polished surface of the work were performed. As a result, the polishing rate increased remarkably compared to the state immediately before the dressing and no flaw on the polished surface of the work was detected.

Claims

1. A method of conditioning a polishing pad for semiconductor wafer, comprising:

dressing by spraying a cleaning liquid onto a polishing pad; and then

supplying abrasive slurry injected from a nozzle to the polishing pad.

2. A method of conditioning a polishing pad for semiconductor wafer, comprising:

dressing by causing relative movements while a polishing pad is being pressed against a dresser; and then

supplying abrasive slurry injected from a nozzle to the polishing pad.

3. A method of conditioning a polishing pad for semiconductor wafer, comprising:

dressing by spray of a cleaning liquid onto a polishing pad; and then

supplying abrasive slurry to the polishing pad by adding dropwise.

4. A method of conditioning a polishing pad for semiconductor wafer, comprising:

supplying abrasive slurry to the polishing pad by being added dropwise.

5. A method of conditioning a polishing pad for semiconductor wafer, comprising:

dressing by spraying a cleaning liquid onto a polishing pad; and then

supplying abrasive slurry which does not contain abrasive grains to the polishing pad.

6. A method of conditioning a polishing pad for semiconductor wafer, comprising:

7. The method of conditioning a polishing pad according to claim 5, wherein the abrasive slurry which does not contain abrasive grains is supplied by being injected from a nozzle.

8. The method of conditioning a polishing pad according to claim 6, wherein the abrasive slurry which does not contain abrasive grains is supplied by adding dropwise.

9. A method of conditioning a polishing pad for semiconductor wafer, comprising:

dressing by spraying a cleaning liquid onto a polishing pad; and then

supplying a pH-adjusting liquid to the polishing pad.

10. A method of conditioning a polishing pad for semiconductor wafer, comprising:

dressing by causing relative movements while the polishing pad is being pressed against the dresser; and then

supplying a pH-adjusting liquid to the polishing pad.

11. The method of conditioning a polishing pad according to claim 9, wherein the pH-adjusting liquid is supplied by being injected the pH-adjusting liquid from a nozzle.

12. The method of conditioning a polishing pad according to claim 10, wherein the pH-adjusting liquid is supplied by being added dropwise.

13. The method of conditioning a polishing pad according to claim 1, wherein the cleaning liquid is pure water.

14. The method of conditioning a polishing pad according to claim 1, wherein the cleaning liquid is a pH-adjusting liquid.

15. The method of conditioning a polishing pad according to claim 1, wherein the cleaning liquid is abrasive slurry which does not contain abrasive grains.

16. A method of conditioning a polishing pad for semiconductor wafer, comprising dressing by spraying abrasive slurry onto a polishing pad.

17. A method of conditioning a polishing pad for semiconductor wafer, comprising spraying a pH-adjusting liquid onto a polishing pad.

18. A method of conditioning a polishing pad for semiconductor wafer, comprising spraying abrasive slurry which does not contain abrasive grains onto a polishing pad.

19. The method of conditioning a polishing pad for semiconductor wafer according to claim 1, wherein polishing uses a dummy work after conditioning a polishing pad for semiconductor wafer by the method of claim 1.

20. The method of conditioning a polishing pad for semiconductor wafer, comprising:

dressing by spray of pure water onto a polishing pad; and then

polishing using a dummy work.