1. Field
Embodiments of the invention generally relate to devices and systems utilized in chemical mechanical polishing (CMP) processes. More specifically, embodiments disclosed herein are related to devices for localized control of CMP.
2. Description of the Related Art
Chemical-mechanical polishing (CMP), also known as chemical mechanical planarization, is a process used in the semiconductor fabrication industry to provide flat surfaces on integrated circuits devices. CMP involves pressing a rotating wafer against a rotating polishing pad, while applying polishing fluid or slurry to the pad to affect removal of films or other materials from a substrate. Such polishing is often used to planarize insulating layers, such as silicon oxide and/or metal layers, such as tungsten, aluminum, or copper, that have been previously deposited on the substrate.
CMP is reaching the limits of its capability using current state of the art hardware. One challenge for the process is incoming within-wafer-non-uniformity (WIWNU). The non-uniform stress on the wafer surface during CMP is a major reason for the non-uniform material removal rate which results in the WIWNU. Non-uniform stress can arise from a variety of sources, such as the pressure exerted by the polishing pad, shear stress due to the relative motion between the wafer and pad, from the film deposition or edge bead removal (EBR) non-uniformity. WIWNU can manifest as localized film thickness variation on regions, such as thickness variation between the substrate center and edge. Current CMP hardware is unable to address this localized material non-uniformity effectively.
The above challenges and requirements have led to the investigation of small pad CMP. The use of small pad CMP, though promising, presents significant challenges for process uniformity control due to the small size of the CMP pad (similar to wafer size). Therefore, there is a need for devices and methods to provide better control of local uniformity during CMP.
Embodiments described herein generally provide an apparatus employing magnetic-responsive composites for CMP. Magnetic-responsive composites, such as Magnetic-Polymer Composites (MPC), can achieve highly controlled local deformation of the pad and/or wafer surface during CMP. Controlled local deformation of the CMP polishing pad can provide process uniformity improvement which can help to minimize WIWNU.
In one embodiment, a polishing device can include a support with one or more magnetic field generators formed therein, wherein the magnetic field generators produce a magnetic field. A magnetic-responsive composite can be in connection with the magnetic field generators, wherein the magnetic-responsive composite changes shape in response to the magnetic field.
In another embodiment, a polishing device can include a polishing platen, a magnetic-responsive composite formed on the surface of the polishing platen, one or more magnetic field generators in magnetic connection with the magnetic-responsive composite, the magnetic field generators producing one or more magnetic fields, and a polishing pad formed in connection with the magnetic-responsive composite, the polishing pad changing shape with the magnetic-responsive composite.
In another embodiment, a polishing system can include a polishing pad configured to polish a substrate; a support comprising a plurality of magnetic field generators, the magnetic field generators configured to support a substrate or a polishing pad and produce one or more magnetic fields; and a magnetic-responsive composite in connection with the support, the magnetic-responsive composite configured to receive the one or more magnetic fields, change shape or position in response to the magnetic fields and apply a force to a polishing pad or a substrate in response to the change in shape.
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
To facilitate understanding, common words have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation.
The present invention relates to polishing articles and methods of manufacture thereof. Magnetic-responsive composites, such as MPCs, can be used to achieve highly controlled local deformation of the pad and/or wafer surface during CMP. An example of an MPC, useable with embodiments described herein, would consist of spherical iron particles embedded in a polysiloxane (silicone) matrix. MPCs, such as ferrogels, can achieve rapid, large and reversible deformation on application of a magnetic field. By controlling the rapid, large and reversible deformation of the MPC or other magnetic-responsive composites, the deformation of the polishing pad and/or wafer can be controlled during CMP.
In one embodiment, the magnetic-responsive composite can be positioned under the polishing pad. Magnetic field generators, such as electromagnets, can be positioned within a specific pattern or layout, such as concentric rings. In this embodiment, the magnetic field generators are embedded in the polishing platen. During the CMP process, a combination of specific magnetic field generators, such as the individual rings of the concentric ring layout, are activated to provide the necessary magnetic field distribution to deform the magnetic-responsive composite. The deformed magnetic-responsive composite will then deform the polishing pad respective to the position of the deformation on the magnetic-responsive composite.
In another embodiment, the magnetic-responsive composite is integrated into the polishing pad. As above, magnetic field generators, such as electromagnets, can be positioned with in a specific pattern or layout, such as concentric rings. In this embodiment, the magnetic field generators are embedded in the polishing platen. During the CMP process, a combination of specific magnetic field generators, such as the individual rings of the concentric ring layout, are activated to provide the necessary magnetic field distribution to deform the integrated magnetic-responsive composite/polishing pad at a desired location.
In another embodiment, the magnetic-responsive composite is integrated into the polishing head or wafer carrier. As above, magnetic field generators, such as electromagnets, can be positioned with in a specific pattern or layout, such as concentric rings. In this embodiment, the magnetic field generators are embedded in the polishing head above the magnetic-responsive composite. During the CMP process, a combination of individual rings is activated to provide the necessary magnetic field distribution to deform the magnetic-responsive composite. The deformed magnetic-responsive composite then pressurizes the wafer locally based on the location of the deformation in the magnetic-responsive composite. The benefits of this approach include enabling a simplified polishing head design with potentially faster zone control response and allowing for zone control in the main polish module and small pad buff step.
In this embodiment, a magnetic-responsive composite 110 can be positioned over the table 104. The magnetic-responsive composite 110 can be in direct contact with the magnetic field generators 108 or in magnetic communication with the magnetic field generators 108. The magnetic-responsive composite 110 is at least partially composed of a ferromagnetic material. Suitable ferromagnetic materials for use in the magnetic-responsive composite include but are not limited to cobalt, iron, nickel, composites thereof or combinations thereof. The magnetic-responsive composite 110 further includes a flexible matrix, thus allowing for the ferromagnetic material to respond to the magnetic field. In one example, the flexible matrix includes polysiloxane. The magnetic-responsive composite 110 has a first surface 112.
The magnetic-responsive composite 110 can be between about 1 and about 100 mils thick. The magnetic-responsive composite 110 can be disposed over at least a portion of the surface of the polishing platen 100, such as the first surface 106. The magnetic-responsive composite 110 can be of an unequal thickness or unequal composition such that one portion of the magnetic-responsive composite 110 is more or less responsive to a magnetic field than another portion of the magnetic-responsive composite 110. The magnetic-responsive composite 110 can include both magnetically responsive regions magnetically inert regions such that only portions of the magnetic-responsive composite 110 are responsive to a magnetic field. Further, the concentration of the ferromagnetic material disposed in the magnetic-responsive composite 110 may vary. In one example, where the magnetic-responsive composite 110 is separated into quadrants, the first quadrant can have a first amount of a ferromagnetic material disposed within the matrix, the second quadrant can then have a second amount of a ferromagnetic material, which is between 1% and 100% of the first amount, disposed with the matrix. The third and fourth quadrants can then have a third and fourth amount, each of the third and fourth amount being between 1% and 100% of the first amount, disposed with the matrix. The varying quantities are not necessarily separated into quadrants and can be any known shape. Further, the ferromagnetic material used need not be the same between across different regions of the magnetic-responsive composite 110. In one example, a first portion of the magnetic-responsive composite 110 uses cobalt, a second portion uses iron and a third portion uses CrO2.
A pad 118 can be positioned over the magnetic-responsive composite 110. Shown here, the pad 118 is positioned on the first surface 112 of the magnetic-responsive composite 110. The positioning of the pad 118 with respect to the magnetic-responsive composite 110 is not limiting, however. In another embodiment, the pad 118 and the magnetic-responsive composite 110 are the same structure, which is positioned on the first surface 106 of the table 104.
When the magnetic field generators 108 generate a magnetic field, the magnetic-responsive composite 122 will change shape in response to the magnetic field. The change of shape is translated to the overlying polishing pad 126 to increase force applied at one or more areas of the substrate during CMP processing.
The polishing pad described above, or elements thereof, are not depicted in
A magnetic-responsive composite 212 can be positioned on or in the polishing head 200. In one embodiment, the magnetic-responsive composite 212 is positioned on the first surface 208 of the platform 202. The magnetic-responsive composite 212 can be a magnetic-responsive composite as described with reference to
The magnetic field generators 210 are connected with a power source 214. The power source 214 provides power to the magnetic field generators 210. Further, the power source 214 is switchable, such that the magnetic field, produced by the magnetic field generators 210, can be turned on and off in a controllable fashion. The power source 214 is in connection with a controller 216. The controller 216 can be operated by a set of predesignated commands, by individual user control or combinations thereof to control the power source 214, the motor 116 and other components. Though described with reference to the polishing head 200, the power source 214 is equally applicable to other embodiments without further recitation.
Advantageously, the magnetic-responsive composite allows of localized control of the force applied between the substrate and the polishing pad during the CMP operation. This location specific control allows for more uniform polishing and avoidance of WIWNU.
Positioned opposite the polishing platen 310 is a polishing head 330. The polishing head 330 includes a platform 332 and a rod 336. The platform 332 has a first surface 333. Retained on the first surface 333 is a substrate 334. The substrate 334 can be held in position by a vacuum delivered through the first surface 333. In one embodiment, the vacuum is delivered through a membrane with a deflected shape. The rod 336 supports and rotates the platform 332 and the substrate 334.
In operation, the substrate 334 is positioned against the polishing pad 320. Both the polishing head 330 and the polishing platen 310 are rotated for the polishing process. During polishing, the substrate 334 is pressed against the polishing pad 320, while a slurry 322 is deposited in a continuous fashion on the polishing pad 320. The slurry 322 can comprise silica (and/or other abrasives) suspended in a mild etchant, such as potassium or ammonium hydroxide. The combination of chemical reaction from the slurry 322 and mechanical buffing from the polishing pad 320 removes vertical inconsistencies on the surface of the substrate, thereby forming an extremely flat surface.
At known points of non-uniformity, such as determined by scanning prior to positioning the substrate in the CMP system or as determined during processing by in-situ detection sensors, the magnetic field generators 316 can be activated to produce a magnetic field. As illustrated in
The magnetic-responsive composite 318 can be configured to apply localized force to different regions of the polishing pad 320. In the embodiment of
In further embodiments, the magnetic-responsive composite 318 can be separated into a plurality of responsive portions (shown with reference to
During normal operation, the force applied between the polishing pad 320 and the substrate 334 can include a first baseline force 354. The first baseline force 354 is the force that exists between the polishing pad 320 and the substrate 334 during normal polishing without a conformational shift at the magnetic-responsive composite 318. When the first group of magnetic field generators 316 receive power from a power source (shown with reference to
In an embodiment where the second group of magnetic field generators 316 are used, the force applied between the polishing pad 320 and the substrate 334 can include a second baseline force 360. The second baseline force is the force that exists between the polishing pad 320 and the substrate 334 during normal polishing without a conformational shift at the magnetic-responsive composite 318. When the second group of magnetic field generators 316 receive power from a power source (shown with reference to
A magnetic field can then be applied to at least a portion of the magnetic-responsive composite, at element 404. The polishing head, the polishing platen or both may have one or more magnetic field generators formed therein. The magnetic field generators generating one or more magnetic fields. The magnetic-responsive composite can then change shape in response to the magnetic fields. In an embodiment with the magnetic-responsive composite formed in contact with the polishing head, magnetic field will cause a change in shape of the magnetic-responsive composite. The magnetic-responsive composite then translates the change in shape to the substrate. In an embodiment with the magnetic-responsive composite formed in contact with the polishing platen, magnetic field will cause a change in shape of the magnetic-responsive composite. The magnetic-responsive composite then translates the change in shape to the polishing pad.
The substrate is then polished against the polishing pad, at element 406. In CMP processes, the surface layer is abraded using the pad and the applied slurry, as described above with reference to
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
This application claims benefit of U.S. Provisional Patent Application Ser. No. 61/886,633 (APPM/21121L), filed Oct. 3, 2013, which is herein incorporated by reference.
Number | Date | Country | |
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61886633 | Oct 2013 | US |