US20070026769A1

US20070026769A1 - Chemical mechanical polishing apparatus and a method for planarizing/polishing a surface

Info

Publication number: US20070026769A1
Application number: US11/191,670
Authority: US
Inventors: Eugene Davis; Kyle Hunt; Daniel Caldwell
Original assignee: Texas Instruments Inc
Current assignee: Texas Instruments Inc
Priority date: 2005-07-28
Filing date: 2005-07-28
Publication date: 2007-02-01

Abstract

The present invention provides a method for planarizing/polishing a surface, a method for manufacturing an integrated circuit and a chemical mechanical polishing apparatus. The method for planarizing/polishing a surface, among other elements, includes providing a chemical mechanical polishing apparatus (200, 300, 400) having a polishing platen (210, 310, 410), a carrier head (220, 320, 420) positioned over the polishing platen (210, 310, 410), and a slurry delivery source (230, 330, 430) positioned over and off center the polishing platen (210, 310, 410), and rotating the polishing platen (210, 310, 410) in a direction (R_p2, R_p3, R_p4) such that slurry exiting the slurry delivery source (230, 330, 430) and contacting the polishing platen (210, 310, 410) must rotate an angle (θ₂, θ₃, θ₄) less than about 220 degrees before contacting a polishable surface maintained by the carrier head (220, 320, 420).

Description

TECHNICAL FIELD OF THE INVENTION

The present invention is directed, in general, to planarizing/polishing a surface and, more specifically, to a chemical mechanical polishing apparatus, a method for planarizing/polishing a surface, and a method for manufacturing an integrated circuit.

BACKGROUND OF THE INVENTION

Chemical mechanical planarizing/polishing (CMP) is an essential process in the manufacture of semiconductor chips today. Dielectric and metal layers used in chip fabrication must be made extremely flat and of precise thickness in order to pattern the sub-micron sized features that comprise a semiconductor device. During CMP, the combination of chemical etching and mechanical abrasion produces the required flat, precise surface for subsequent depositions.
Turning briefly to FIG. 1, illustrated is a schematic of a conventional CMP apparatus 100. The CMP apparatus 100 illustrated in FIG. 1 includes a polishing platen 110, the polishing platen 110 traditionally having a polishing pad located thereon. Positioned over the polishing platen 110 is a carrier head 120, the carrier head 120 configured to hold a polishable surface. The CMP apparatus 100 illustrated in FIG. 1 further includes a slurry delivery source 130 configured to provide slurry (e.g., silica-based slurry) to the polishing platen 110 while the polishable surface held by the carrier head 120 is being polished. The conventional CMP apparatus 100 further includes a polishing pad conditioner 140.
The CMP apparatus 100 illustrated in FIG. 1 typically operates by placing a polishable surface in the carrier head 120, then rotating the polishing platen 120 in a counter-clockwise direction (R_p1), rotating the carrier head 120 in a counter-clockwise direction (R_h1), providing slurry to the polishing platen 120 using the slurry delivery source 130, and then pressing the polishable surface held by the carrier head 120 against the polishing platen 110 using a predetermined set of conditions, including a predetermined down force. In many instances, as the polishable surface is being polished the polishing pad conditioner 140 is conditioning the polishing pad of the polishing platen 110. As is shown in FIG. 1, the polishing pad conditioner 140 both rotates in a counter-clockwise direction (R_c1) and oscillates across the polishing pad.
While CMP offers a practical approach for achieving the important advantage of global wafer planarity, CMP has certain disadvantages. One such disadvantage of CMP is the extreme cost associated therewith. For example, the cost associated with the CMP slurry itself can be significant.
Accordingly, what is needed in the art is a CMP process and a CMP apparatus that does not experience the drawbacks of the conventional CMP processes.

SUMMARY OF THE INVENTION

To address the above-discussed deficiencies of the prior art, the present invention provides a method for planarizing/polishing a surface, a method for manufacturing an integrated circuit and a chemical mechanical polishing apparatus. The method for planarizing/polishing a surface, among other elements, includes providing a chemical mechanical polishing apparatus having a polishing platen, a carrier head positioned over the polishing platen the polishing platen, and a slurry delivery source positioned over and off center the polishing platen, and rotating the polishing platen in a direction such that slurry exiting the slurry delivery source and contacting the polishing platen must rotate less than about 220 degrees before contacting a polishable surface maintained by the carrier head.
As briefly mentioned above, the present invention further provides a method for manufacturing an integrated circuit. The method for manufacturing the integrated circuit, without limitation, may include forming a polishable surface over a wafer substrate, and planarizing/polishing the polishable surface, the planarizing/polishing being conducted similar to that discussed in the paragraph directly above. For example, the planarizing/polishing could be conducted by placing the polishable surface in a carrier head positionable over a polishing platen of a chemical mechanical polishing apparatus, and rotating the polishing platen in a direction such that slurry exiting a slurry delivery source must rotate an angle (θ) less than about 220 degrees before contacting the polishable surface, the slurry delivery source positioned over and off center of the polishing platen.
Another aspect of the present invention provides a chemical mechanical polishing apparatus. In addition to other elements, the chemical mechanical polishing apparatus may include: 1) a polishing platen, 2) a carrier head positionable over the polishing platen, and 3) a slurry delivery source positionable over and off center the polishing platen, the polishing platen configured to rotate in a direction such that slurry exiting the slurry delivery source and contacting the polishing platen must rotate less than about 220 degrees before contacting a polishable surface maintained by the carrier head.
The foregoing has outlined preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed description when read with the accompanying FIGUREs. It is emphasized that in accordance with the standard practice in the semiconductor industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. Reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
Prior Art FIG. 1 illustrates a schematic of a conventional CMP apparatus;
FIG. 2 illustrates a plan view of a CMP apparatus manufactured and operated in accordance with the principles of the present invention;
FIG. 3 illustrates a plan view of an alternative embodiment of a CMP apparatus manufactured and operated in accordance with the principles of the present invention;
FIG. 4 illustrates a plan view of another alternative embodiment of a CMP apparatus manufactured and operated in accordance with the principles of the present invention; and
FIG. 5 illustrates an exemplary cross-sectional view of an integrated circuit (IC) manufacturing using a CMP apparatus constructed and/or operated in accordance with the principles of the present invention.

DETAILED DESCRIPTION

The present invention is based, at least in part, on the acknowledgment that the cost of slurry is a significant portion of the overall cost of manufacturing an integrated circuit, and moreover, that the conventional chemical mechanical polishing (CMP) apparatus, and the conventional techniques for planarizing/polishing surfaces using the conventional CMP apparatus, are responsible for a large portion of the cost. More specifically, the present invention has acknowledged that the conventional CMP apparatus, and the conventional techniques for planarizing/polishing surfaces using the conventional CMP apparatus, require that the slurry travel a significant distance on the polishing platen prior to encountering the polishable surface. It should be noted that for the purpose of the present invention, the terms planarizing and polishing are synonymous, and thus may be used interchangeably without limiting the present invention.
Referring briefly back to FIG. 1 and the design of the conventional CMP apparatus 100, it may be observed that the slurry must rotate an angle (θ₁) of at least about 240 degrees before encountering the polishable surface. This large angle (θ₁) translates into a significant distance for the slurry to travel before contacting the polishable surface. Often, the centrifugal force created by the rotation of the polishing platen 110 causes a significant amount of the slurry to exit the polishing platen 110 prior to encountering the polishable surface. Accordingly, the amount of slurry placed on the surface of the polishing platen 110 must be increased to compensate for the lost slurry, which may be a significant cost.
The present invention has further acknowledged that the design of the conventional CMP apparatus requires the slurry to encounter the polishing pad conditioner prior to encountering the polishable surface, as illustrated in FIG. 1. Unfortunately, the combination of the polishing pad conditioner 140 being located between the slurry delivery source 130 and the polishable surface, and the rotation and oscillation of the polishing pad conditioner 140, causes less than the original amount of slurry deposited on the polishing platen 130 to actually contact the polishable surface. Accordingly, the amount of slurry placed on the surface of the polishing platen 110 must further be increased to compensate for the lost slurry related to the interposed polishing pad conditioner 140.
Given the aforementioned acknowledgements, the present invention has uniquely recognized that placing the slurry delivery source closer to the polishable surface would significantly decrease the amount of slurry required to properly polish the polishable surface. Namely, by placing the slurry delivery source such that the slurry must rotate less than about 220 degrees before encountering the polishable surface, the amount of slurry used may be greatly reduced. The present invention has further uniquely recognized that placing the polishing pad conditioner such that the slurry must encounter the polishable surface before the polishing pad conditioner, would also significantly decrease the amount of slurry required to properly polish the polishable surface. By employing these two recognitions, it is believed that the amount of slurry traditionally used may be reduced by about 30-50 percent.
Regrettably, prior art CMP apparatuses are configured in such a way as to prevent accommodating the aforementioned acknowledgements. In other words, prior art CMP apparatuses during normal operation and without significant modifications may not accommodate the aforementioned acknowledgements. Namely, prior art CMP apparatuses are configured such that the slurry delivery source is substantially fixed with respect to the carrier head, and thus the polishable surface. As the slurry delivery source of the conventional CMP apparatuses is substantially fixed in a position that the slurry must rotate at least about 240 degrees before encountering the polishable substrate, conventional CMP apparatuses may not, without reconfiguration, accommodate the unique desire to have the slurry rotate less than about 220 degrees before encountering the polishable surface. While the rotation of the polishing platen could conceivably be changed to rotate in a clockwise direction, as compared to the counter-clockwise direction that the conventional CMP apparatuses require, the conventional CMP apparatuses are not, again without significant reconfiguration, capable of rotating in the clockwise direction. For example, attempting to rotate the conventional CMP apparatuses in a clockwise direction generates a collection of error messages in the software that operates the conventional CMP apparatuses. Because of the error messages, the conventional CMP apparatuses may not be configured to rotate in a direction such that the large degree of rotation may be reduced.
Additionally, the prior art CMP apparatuses are configured such that the location of the polishing pad conditioner is semi-fixed with respect to the carrier head, and thus the polishable surface. Accordingly, without a massive reconfiguration of the polishing pad conditioner, the conventional CMP apparatuses may not accommodate the unique desire to have the slurry encounter the polishable surface before contacting the polishing pad conditioner.
Turning now to FIG. 2, illustrated is a plan view of a CMP apparatus 200 manufactured and operated in accordance with the principles of the present invention. The CMP apparatus 200 illustrated in FIG. 2 includes a polishing platen 210. As is common in the industry, the polishing platen 210 has a conventional polishing pad located thereon or thereover. Positioned over the polishing platen 210 in the embodiment of FIG. 2 is a carrier head 220. The carrier head 220, as those skilled in the art appreciate, may be configured to maintain a polishable surface (e.g., such as a polishable surface located over a wafer substrate) therein or thereon. Any known or hereafter discovered polishable surface (e.g., interconnect material surface, shallow trench isolation material surface, etc.) might be used while staying within the purview of the present invention.
The CMP apparatus 200 illustrated in FIG. 2 further includes a slurry delivery source 230 positioned over and off center the polishing platen 210. Off center, as used herein, requires that the slurry delivery source 230 dispense the slurry outside a four-inch diameter ring around the center of the polishing platen 210. In an exemplary embodiment of the invention, the slurry delivery source 230 dispenses the slurry within boundaries of a path 235 created by the carrier head 220 on the polishing platen 210. The slurry delivery source 230 is configured to provide a desired (e.g., metered) amount of slurry to the polishing platen 210 during the polishing of the polishable surface. Any slurry, whether silica-based or not, may be used and remain within the scope of the present invention.
The CMP apparatus 200 additionally includes a polishing pad conditioner 240 positioned over the polishing platen 210. As those skilled in the art are generally aware, the polishing pad conditioner 240 is designed to condition or replenish the polishing pad on the polishing platen 210, thus extending its effective lifespan. The polishing pad conditioner 240 is configured to both rotate and oscillate about the polishing platen 210.
The CMP apparatus 200 illustrated in FIG. 2 is configured in such a way as to allow slurry deposited on the polishing platen 210 surface to rotate an angle (θ₂) of less than about 220 degrees before contacting the polishable surface maintained by the carrier head 220. In one advantageous embodiment, the CMP apparatus 200 is configured to allow the slurry to rotate an angle (θ₂) of less than about 180 degrees, and more advantageously, less than about 90 degrees before contacting the polishable surface. Moreover, in an exemplary embodiment of the present invention, the CMP apparatus 200 is configured to allow the slurry to rotate an angle (θ₂) of less than about 45 degrees before contacting the polishable surface.
In the embodiment of FIG. 2, the rotation of the polishing platen 210 has been significantly modified to allow the polishing platen 210 to rotate in a clockwise direction (R_p2) to accommodate the aforementioned requirement that the slurry rotate an angle (θ₂) of less than about 220 degrees. For example, a conventional CMP apparatus, such as the conventional CMP apparatus 100 illustrated in FIG. 1, may be significantly modified to cause the polishing platen 210 to rotate in the clockwise direction (R_p2), which is the opposite direction as it is designed and thus configured to operate.
The change of rotational direction of the polishing platen 210 may be accomplished a number of different ways. In one embodiment of the present invention, the motor connected to the polishing platen 210 of the conventional CMP apparatus 100 is replaced with a motor designed to rotate the polishing platen 210 in a clockwise direction. While this would be a significant modification to the conventional CMP apparatus, it might be the only modification that would need to be made to practice the novel aspects of the present invention, and thus a worthy modification.
Another embodiment might exist wherein the software that controls the conventional CMP apparatus 100 is rewritten to allow the original motor associated with the conventional CMP apparatus 100 to rotate in the opposite direction that it was initially designed to rotate (e.g., it was originally designed to rotate in a counter-clockwise direction). While this embodiment might require the hiring of a computer programmer and the introduction of the new software into the conventional CMP apparatus 100, it might be less costly than replacing the motor as described above.
Accordingly, in the embodiment of FIG. 2, the CMP apparatus might be operated as follows. Initially, the polishing platen 210 would begin rotating in the clockwise direction (R_p2), and the carrier head 220 would also begin rotating, advantageously in a clockwise direction (R_h2). The slurry would then be turned on, and thus exiting the slurry delivery source 230 onto the polishing platen 210. Thereafter, the polishing pad conditioner 240 might begin its operation, and thus in an advantageous embodiment, be rotating in the clockwise direction (R_p3) while moving laterally across a portion of the polishing platen 210. Thereafter, the carrier head 210, and thus the polishable surface maintained by the carrier head 210, would be pressed against the polishing pad on the polishing platen 210, thus beginning the polishing process.
The advantages of operating the CMP apparatus 200 in the aforementioned manner are significant. First and foremost, operating the CMP apparatus 200 in the aforementioned manner saves an exceptional amount of slurry. More specifically, operating the CMP apparatus 200 in the aforementioned manner may save at least about 30 percent, and more specifically from about 30-50 percent, of the slurry traditionally required. Moreover, the polishing process does not suffer at the expense of saving slurry, as might occur using other methods.
Turning now briefly to FIG. 3, illustrated is a plan view of an alternative embodiment of a CMP apparatus 300 manufactured in accordance with the principles of the present invention. The CMP apparatus 300, in contrast to the CMP apparatus 200, does not reverse the rotational direction of the polishing platen 310, but moves the slurry delivery source 330 to a position such that the slurry that exits the slurry delivery source 330 must rotate an angle (θ₃) less than about 220 degrees before encountering the polishable surface maintained by the carrier head 320. For example, this may be accomplished by placing the slurry delivery source 330 between the polishing pad conditioner 340 and the polishable surface (i.e., in the direction of movement of the polishing platen 310). Not only does this reduce the angle (θ₃), but it also causes the polishing pad conditioner 340 to not interpose the slurry delivery source 330 and the polishable surface.
It should be noted that the same idea might be accomplished by moving the carrier head 320 to a location wherein it interposed the slurry delivery source 330 and the polishing pad conditioner 340. Because the general idea is based upon the location of the slurry delivery source 330 to the carrier head 320, or vice verse, the movement of either to reduce the angle (θ₃) would suffice.
Turning to FIG. 4, illustrated is another alternative embodiment of a CMP apparatus 400 manufactured and operated in accordance with the principles of the present invention. The CMP apparatus 400 illustrated in FIG. 4 is substantially identical to the CMP apparatus 200 illustrated in FIG. 2 with the exception that the carrier head 420 is designed to maintain more than one wafer, each wafer having a polishable surface. Thus, while the CMP apparatus 400 is a single carrier head CMP apparatus, similar to those of FIGS. 2 and 3, the carrier head 420 of FIG. 4 maintains multiple wafers, each having a polishable surface.
Referring now to FIG. 5, illustrated is an exemplary cross-sectional view of an integrated circuit (IC) 500 manufactured using a CMP apparatus constructed and/or operated in accordance with the principles of the present invention. The IC 500 may include devices, such as transistors used to form CMOS devices, BiCMOS devices, Bipolar devices, as well as capacitors or other types of devices. The IC 500 may further include passive devices, such as inductors or resistors, or it may also include optical devices or optoelectronic devices. Those skilled in the art are familiar with these various types of devices and their manufacture. In the particular embodiment illustrated in FIG. 5, the IC 500 includes the semiconductor devices 510 having dielectric layers 520 located thereover. Additionally, interconnect structures 530 are located within the dielectric layers 520 to interconnect various devices, thus, forming the operational integrated circuit 500. The CMP apparatus or method of operation therefore may have been used to form a number of different features in the IC 500, including the interconnect structure 530.
Although the present invention has been described in detail, those skilled in the art should understand that they could make various changes, substitutions and alterations herein without departing from the spirit and scope of the invention in its broadest form.

Claims

1. A method for planarizing/polishing a surface, comprising:

providing a chemical mechanical polishing apparatus having a polishing platen, a carrier head positioned over the polishing platen, and a slurry delivery source positioned over and off center of the polishing platen; and

rotating the polishing platen in a direction such that slurry exiting the slurry delivery source and contacting the polishing platen must rotate an angle (θ) less than about 220 degrees before contacting a polishable surface maintained by the carrier head.

2. The method as recited in claim 1 wherein the polishing platen must rotate an angle (θ) less than about 180 degrees.

3. The method as recited in claim 1 wherein the polishing platen must rotate an angle (θ) less than about 90 degrees.

4. The method as recited in claim 1 wherein the polishing platen must rotate an angle (θ) less than about 45 degrees.

5. The method as recited in claim 1 wherein the polishing platen is rotated in a clockwise direction.

6. The method as recited in claim 5 wherein the carrier head is rotated in a clockwise direction.

7. The method as recited in claim 1 wherein the chemical mechanical polishing apparatus further includes a polishing pad conditioner, and wherein the polishing pad conditioner is positioned such that the slurry exiting the slurry delivery source contacts the polishable surface before the polishing pad conditioner.

8. The method as recited in claim 1 wherein the chemical mechanical polishing apparatus is a single carrier head chemical mechanical polishing apparatus.

9. The method as recited in claim 8 wherein the single carrier head chemical mechanical polishing apparatus maintains more than one wafer each having a polishable surface.

10. The method as recited in claim 1 wherein the slurry delivery source is positioned within boundaries of a path created by the carrier head on the polishing platen.

11. A method for manufacturing an integrated circuit, comprising:

forming a polishable surface over a wafer substrate; and

planarizing/polishing the polishable surface, the planarizing/polishing including;

placing the polishable surface in a carrier head positionable over a polishing platen of a chemical mechanical polishing apparatus; and

rotating the polishing platen in a direction such that slurry exiting a slurry delivery source must rotate an angle (θ) less than about 220 degrees before contacting the polishable surface, the slurry delivery source positioned over and off center of the polishing platen.

12. The method as recited in claim 11 wherein the polishing platen must rotate an angle (θ) less than about 180 degrees.

13. The method as recited in claim 11 wherein the polishing platen must rotate an angle (θ) less than about 90 degrees.

14. The method as recited in claim 11 wherein the polishing platen must rotate an angle (θ) less than about 45 degrees.

15. The method as recited in claim 11 wherein the polishing platen is rotated in a clockwise direction.

16. The method as recited in claim 11 wherein the chemical mechanical polishing apparatus further includes a polishing pad conditioner, and wherein the polishing pad conditioner is positioned such that the slurry exiting the slurry delivery source contacts the polishable surface before the polishing pad conditioner.

17. The method as recited in claim 11 wherein the chemical mechanical polishing apparatus is a single carrier head chemical mechanical polishing apparatus.

18. The method as recited in claim 11 wherein the polishable surface is an interconnect material.

19. The method as recited in claim 11 wherein the slurry delivery source is positioned within boundaries of a path created by the carrier head on the polishing platen.

20. A chemical mechanical polishing apparatus, comprising:

a polishing platen;

a carrier head positionable over the polishing platen; and

a slurry delivery source positionable over and off center the polishing platen, the polishing platen configured to rotate in a direction such that slurry exiting the slurry delivery source and contacting the polishing platen must rotate an angle (θ) less than about 220 degrees before contacting a polishable surface maintained by the carrier head.

21. A method for polishing a semiconductor wafer, comprising:

providing a semiconductor wafer; and

polishing the semiconductor wafer, the polishing including;

placing the semiconductor wafer in a carrier head positionable over a polishing platen of a chemical mechanical polishing apparatus; and