This invention relates generally to integrated circuit manufacturing equipments, and more particularly to equipments for chemical mechanical polish.
The chemical mechanical polish (CMP) is a common practice in the formation of integrated circuits. Typically, CMP is used for the planarization of semiconductor wafers. CMP takes advantage of the synergetic effect of both physical and chemical forces for the polishing of wafers. It is performed by applying a load force to the back of a wafer while the wafer rests on a polishing pad. A polishing pad is placed against the wafer. Both the polishing pad and the wafer are then counter-rotated while a slurry containing both abrasives and reactive chemicals is passed therebetween. CMP is an effective way to achieve global planarization of wafers.
A truly uniform polishing, however, is difficult to achieve due to various factors. For example, slurries are dispensed either from the top or bottom of the polishing pad. This will result in non-uniformity in polishing rate for different locations of the wafer. For example, if slurries are dispensed from the top, the edges of the wafers typically have higher CMP rates than the centers. Conversely, if slurries are dispensed from the bottom, the centers of the wafers typically have higher CMP rates than the edges. To reduce the non-uniformity in polishing rate, pressures applied on different locations of the wafers are adjusted. If the CMP rate in one region of a wafer is low, a higher pressure is applied to this location to compensate the low CMP rate. The increased pressure also serves the purpose of increasing the overall CMP rate, hence the increase in the throughput.
The method of compensating CMP rates through pressures, however, suffers limitations. Since pressures are typically applied through a single membrane, the increased pressure to one region of the wafer inevitably causes the increase in pressure to neighboring regions, and thus the compensation effect is reduced. Furthermore, high pressures applied to wafers may cause unwanted complexity to the wafers. A new CMP system is thus required to increase the CMP rate and/or improve the CMP uniformity without causing unwanted complexity to the wafers.
In accordance with one aspect of the present invention, a chemical mechanical polish (CMP) system for polishing a wafer includes a polishing head; an inner tube connected to the polishing head, wherein the inner tube is filled with a heat media; a media heater connected to the inner tube; and a pressure controller connected to the inner tube.
In accordance with another aspect of the present invention, a CMP system for polishing a wafer includes a polishing head; a plurality of inner tubes; a plurality of loading chambers in the polishing head and separated from each other, wherein each of the inner tubes is connected to one of the loading chambers; a membrane bordering the loading chambers; a plurality of media heaters, each being connected to one of the inner tubes; and a pressure controller connected to the inner tubes.
In accordance with yet another aspect of the present invention, a method of performing a CMP process to a wafer includes providing a CMP system comprising a polishing head; heating a pressure media in the polishing head; and attaching the wafer to the polishing head.
In accordance with yet another aspect of the present invention, a method of performing a CMP process to a wafer includes providing a CMP system comprising a polishing head; a plurality of inner tubes; a plurality of loading chambers in the polishing head, wherein each of the loading chambers is connected to one of the inner tubes; a membrane bordering the loading chambers, wherein the membrane is thermal conductive; and a pressure controller connected to the inner tubes. The method further includes connecting a plurality of media heaters each to one of the inner tubes; and heating a pressure media in the loading chambers during the CMP process.
The advantageous features of the present invention include increased polish rates and improved polish uniformity.
For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
The making and using of the presently preferred embodiments are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.
Polishing head 2 includes retaining ring 12, which is an annular ring secured at the outer edge of polishing head 2. During CMP processes, wafer 6 is confined by retaining ring 12 so that it moves with polishing head 2. Membrane 4 is a circular sheet formed of a flexible and elastic material, wherein an edge portion of membrane 4 extends along inner surface of retaining ring 12. Membrane 4 acts as the bottom of loading chamber 14, which is connected to inner tube 16.
The CMP system further includes pressure controller 18, which controls the pressure in loading chamber 14. During CMP operations, pressure controller 18 provides a pressure media, such as air, to loading chamber 14 through inner tube 16. Throughout the description, the pressure media is alternatively referred to as a heat media for its additional functions. Since membrane 4 is elastic, with air pressure in loading chamber 14, a downward force is applied to wafer 6 by membrane 4. When the polish is completed, air is pumped out of loading chamber 14, and thus membrane 4 moves upward. As a result, a vacuum is formed above wafer 6, providing an upward force to wafer 6, which counters the surface tension between wafer 6 and the slurries. Wafer 6 is thus lifted.
In the preferred embodiment, the pressure media is preheated before it is pumped into loading chamber 14. In a first embodiment, media heater 20 is connected to pressure controller 18. In a second embodiment, media heater 20 is integrated into pressure controller 18. In a third embodiment, media heater 20 is attached to inner tube 16. Advantageously, the heated air in loading chamber 14 heats membrane 4, which further heats wafer 6. As is known in the art, a CMP process includes chemical reactions and mechanical actions, and the speed of the chemical reactions is sensitive to temperature. Generally, a higher temperature will result in an increase in the chemical reaction speed, and hence an increase in CMP rate. By increasing the temperature of wafer 6, the throughput of the CMP process can be increased.
In order to effectively conduct heat to wafer 6, membrane 4 needs to have a high thermal conductivity. Preferably, the thermal conductivity of membrane 4 is greater than about 0.2 W/(m*K), and more preferably greater than about 20 W/(m*K). In an exemplary embodiment, membrane 4 is formed of CoolPoly® E-series (Cool Polymers Inc.) materials. The thermal conductivities of CoolPoly® materials may range between about 1.0 W/(m*K) and about 100 W/(m*K), which are comparable to the thermal conductivity of pure iron.
In alternative embodiments, as is illustrated in
In the embodiment shown in
Referring to
Air has a low thermal capacity, and thus the heat provided to wafer 6 is limited. In a variation of the present invention, materials having greater thermal capacities, such as water, oil, and the like, are advantageously used as the heat/pressure media in loading chambers 14.
The portions of inner tubes 16 between air-to-liquid pressure converters 26 and pressure controller 18 are filled with air, which is provided by pressure controller 18. Air-to-liquid pressure converters 26 pass the pressure applied by pressure controller 18 to the liquid.
It is appreciated that even though polishing head 2 has various designs, the concept of heating and controlling temperatures on wafers may still be applied.
The embodiments of the present invention provide a method for heating a wafer in order to expedite the polishing rate. Furthermore, being able to control the temperatures of different portions of the polished wafer, the present invention provides a means for adjusting the polishing rate chemically, as compared to mechanically, by applying different pressures to different portions of the wafer. With the means provided by the present invention, more uniform polishing can be achieved.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, and composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.
Number | Name | Date | Kind |
---|---|---|---|
5605488 | Ohashi et al. | Feb 1997 | A |
5797789 | Tanaka et al. | Aug 1998 | A |
5873769 | Chiou et al. | Feb 1999 | A |
6162116 | Zuniga et al. | Dec 2000 | A |
6306009 | Sandhu et al. | Oct 2001 | B1 |
6607425 | Kistler et al. | Aug 2003 | B1 |
6749484 | Yang et al. | Jun 2004 | B2 |
RE39471 | Nakashiba et al. | Jan 2007 | E |
20050239371 | Togawa | Oct 2005 | A1 |
20060205323 | Togawa et al. | Sep 2006 | A1 |