Patent Application
20060073773
This invention relates to the field of integrated circuit fabrication. More particularly, this invention relates to conditioning the pads that are used to planarize integrated circuits.
As microelectronic devices get increasingly smaller, new problems with fabricating the devices appear. For example, integrated circuits are typically fabricated by a process where different layers that provide specialized functions are deposited, patterned, and etched, and then subsequent layers are deposited over the top of the resultant structure, and the process continues in this manner for several layers until the integrated circuit is completed.
Because the different deposited layers are patterned and etched, the upper surface of the integrated circuit is made very uneven. This roughness of the upper surface of the integrated circuit is enhanced as each successive layer is deposited over a previously patterned layer, and then it too is patterned and overlaid with subsequent layers.
At a time when integrated circuits occupied a relatively large surface area, this condition was not too much of a problem, as the various layers could be deposited to a thickness that was sufficient to overcome the size of the steps that were created during the patterning process. Alternately, the various structures could be formed at a distance from each other that was sufficiently far apart that the various steps of the structures did not interfere to too great an extent with each other.
However, as the surface area in which an integrated circuit is fabricated has been reduced, the steps caused by the successive layers have become more of a problem. One aspect of this problem is that it becomes increasingly difficult to adequately deposit successive layers within the deep crevices that tend to be formed between the successive patterned structures. Further, the rough topography of these resultant integrated circuits tends to induce stress points within the layers, which tend to reduce the integrated circuit's resistance to failure in certain operating conditions and environments.
To counteract these problems, integrated circuits are typically planarized to some extent and in some manner before successive layers are deposited on underlying layers. This is often accomplished with a process known as chemical mechanical polishing. In this process, the surface of the substrate on which the integrated circuits are formed is abraded mechanically against a polishing pad, typically with the application of a slurry that also chemically erodes the surface of the substrate. This controlled chemical mechanical polishing tends to wear away those points on the upper surface of the substrate that are higher than other points, and thereby planarizes the integrated circuit.
As material from the substrate is worn away against the polishing pad, the pad tends to become loaded with the eroded material. This loading tends to reduce the abrasive quality of the polishing pad, and generally reduce its effectiveness. Thus, a conditioning process is applied to the pad at some interval, and sometimes is applied continuously to the pad. The conditioning is intended to release the eroded material from the pad, allowing it to be washed away, and also to help restore the nap or surface roughness of the pad.
Typically, the conditioner that is used to condition the pad is a bar or disk that is pressed against the pad, and thus makes physical contact with the pad. The conditioner often is impregnated with some type of hard material that creates a rough surface on the conditioner, such as diamond. The rough surface of the conditioner abrades the polishing pad, and thus conditions the surface of the polishing pad.
Unfortunately, there are many problems associated with the current state of the art in pad conditioning. For example, particles of the material that is impregnated on the conditioner can break free and remain on the polishing pad surface, thus causing dramatic scratching problems with the substrates that are polished on the pad. However, less abrasive conditioners, such as brushes, do not have enough force to sufficiently condition the surface of the polishing pad.
What is needed, therefore, is a system for conditioning polishing pads that overcomes problems such as those described above, at least in part.
The above and other needs are met by an apparatus for conditioning a polishing pad. A turntable is mounted to a frame, where the turntable is adapted to receive and rotate the polishing pad. A conditioning head is also mounted to the frame, where the conditioning head is adapted to spray a liquid from the conditioning head against the polishing pad at a pressure that is sufficient to dislodge eroded material from the polishing pad.
In this manner, a sufficiently abrasive spray can be generated, which can release the loaded material from the polishing pad, and otherwise condition the polishing pad. The spray also enables the released material to be washed away from the pad. In addition, because the abrasive action is provided by the force of the spray, there are no abrasive particles that can break free from the conditioning head and disrupt the desired operation of the pad.
In various embodiments, the rotation of the polishing pad enables all desired portions of the polishing pad to be conditioned by the liquid spray. There is preferably a plurality of nozzles disposed on the conditioning head and from which the liquid is sprayed. In various embodiments the nozzles are selectively replaceable, and have different spray pattern and flow volume characteristics, or can be adjusted in regard to at least one of flow volume and spray pattern. The apparatus preferably includes a pressure adjustment means for adjusting the pressure of the liquid spray, a height adjustment means for adjusting a distance of the conditioning head from the polishing pad, an angle adjustment means for adjusting an angle of the conditioning head relative to an upper surface of the polishing pad, a flow adjustment means for adjusting a volume of flow of the liquid sprayed from the conditioning head to the polishing pad, and an oscillator for moving the conditioning head relative to the rotating conditioning pad. In a most preferred embodiment, the apparatus is part of a chemical mechanical polisher.
According to another aspect of the invention there is disclosed a method of conditioning a polishing pad. Relative movement is provided between the polishing pad and a conditioning head, and a liquid is sprayed from the conditioning head against the polishing pad at a pressure that is sufficient to dislodge eroded material from the polishing pad. The relative movement enables all desired portions of the polishing pad to be conditioned by the liquid spray.
Further advantages of the invention are apparent by reference to the detailed description when considered in conjunction with the figures, which are not to scale so as to more clearly show the details, wherein like reference numbers indicate like elements throughout the several views, and wherein:
With reference now to
The apparatus 10 includes a conditioning head 12 that is preferably disposed over the polishing pad. Most preferably, the conditioning head 12 includes a plurality of nozzles 14, which spray a liquid, such as water, down onto the polishing pad that is disposed below the conditioning head 12. An armature 16 is preferably connected to the conditioning head 12, which armature 16 enables the conditioning head 12 to be disposed over a polishing pad that has a radius that is larger than the size of the conditioning head 12. The armature 16 is preferably connected to a mount 18, that is designed to mount to a frame of the piece of equipment on which the apparatus 10 is used, such as a chemical mechanical polisher.
The apparatus 10 is preferably fabricated predominantly of a resilient material, such as stainless steel. However, as it is a purpose of the apparatus 10 to deliver a liquid to the nozzles 14 under a certain degree of pressure, it is understood that the apparatus 10 will also preferably include materials such as plastics, rubbers, and other thermoplastic resins, such as for gaskets, seals, and deformable fittings.
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The side view of the second embodiment of
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Of course, other combinations of spray characteristics 24 are also contemplated. For example, a nozzle 14 may have a narrow spray and large flow volume, or a wide spray and a small flow volume. Other nozzles 14 may be configured to provide a pulsed spray, or a dynamic spray pattern, such as a spiral or a swirl. In some embodiments, the nozzles 14 are each adjustable, such as in the same manner that the nozzle of a garden hose is adjustable as to flow volume and spray pattern, or in the manner that a bathroom shower head is adjustable as to different patterns and flows.
All of the adjustments as described above are preferably provided so as to provide a conditioning for the polishing pad that is as uniform as possible in one embodiment, or is as configurable as possible in another embodiment. For example, if it is desired to condition the polishing pad uniformly, then the nozzles 14 of the apparatus 10 would preferably be set up in a first configuration. However, if it is desired to condition the polishing pad in a non uniform manner, then the nozzles 14 of the apparatus 10 would preferably be set up in a second configuration.
In some embodiments the conditioning apparatus 10 is fitted with a means for producing motion in the apparatus 10, such as an oscillator 36 that sweeps the armature 16 and the conditioning head 12 across the surface of the pad 28. A flow valve 32 is preferably used to adjust the volume of flow through the conditioning head 12. A means 34 is preferably used to adjust the pressure of the liquid that is delivered to the conditioning head 12, which means may be a device such as a pump or a regulator.
In this manner, the various embodiments of the present invention enable the use of a liquid spray to release loaded materials from the pad 28, and to otherwise roughen and condition the pad 28. The apparatus 10 delivers the spray in a manner that is highly configurable as to height above the pad 28 and angle of spray delivery, and also flow volume, spray pattern, and spray pressure. Thus, the apparatus 10 can be set up to provide a very uniform and consistent conditioning for the pad 28, as desired. Further, because a liquid is used instead of hard particles, there is no residue from the conditioning apparatus 10 that can remain on the pad 28 and reduce the effectiveness of the substrate polishing process.
The foregoing description of preferred embodiments for this invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments are chosen and described in an effort to provide the best illustrations of the principles of the invention and its practical application, and to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.
