Patent Application
20250041985
Embodiments of the present invention generally relate to chemical mechanical polishing (CMP), and more specifically to a multiple disk pad conditioner for use in chemical mechanical polishing.
Integrated circuits are typically formed on substrates, particularly silicon wafers, by sequential deposition of conductive, semiconductive or insulative layers. After each layer is deposited, the layer is etched to create circuitry features. As a series of layers are sequentially deposited and etched, the outer or uppermost surface of the substrate, i.e., the exposed surface of the substrate, becomes successively less planar. A non-planar surface can prevent proper focusing of a photolithography apparatus used in subsequent processing operations. Therefore, there is a need to periodically planarize the substrate surface to provide a planar surface.
Chemical mechanical polishing (CMP) may be used as a method of planarization. CMP typically requires that the substrate be mounted on a carrier or polishing head, with the surface of the substrate to be polished exposed. The substrate is then placed against a rotating polishing pad. The carrier head may also rotate or oscillate to provide additional motion between the substrate and polishing surface. Further, a polishing liquid, which may include an abrasive and at least one chemically reactive agent, may be spread on the polishing pad.
During polishing, the pad is subject to compression, shear, and friction which produces heat and wear. Slurry and abraded material from the substrate and pad are pressed into the pores of the pad material and the material itself becomes matted and even partially fused. These effects, sometimes referred to as “glazing,” reduce the pad's roughness and ability to apply and retain fresh slurry on the pad surface. It is, therefore, desirable to condition the pad by removing trapped slurry, and unmatting, then re-expanding or re-roughening the pad material. The pad can be conditioned after each substrate is polished, or after a number of substrates are polished, which is often referred to as ex-situ pad conditioning. The pad can also be conditioned at the same time substrates are polished, which is often referred to as in-situ pad conditioning.
Accordingly, there is a need for a method and device that can reliably and uniformly condition a polishing pad.
Embodiments herein are generally directed to chemical mechanical polishing (CMP), and more specifically to a pad conditioner for use in chemical mechanical polishing.
In an embodiment, a pad conditioning assembly is provided. The pad conditioning assembly includes a base, an arm coupled to the base, a conditioning head coupled to the arm, a gimbal control assembly including at least one electromagnet coupled to the conditioning head, a gimbal flexure configured to couple to a pad conditioning disk, and a gimbal control feature coupled to the gimbal flexure, and a controller configured to control operation of the pad conditioning assembly.
In another embodiment, a gimbal control assembly is provided. The gimbal control assembly includes at least one electromagnet coupled to a conditioning head of a pad conditioner, a gimbal flexure configured to couple to a pad conditioning disk of the pad conditioner, and a gimbal control feature coupled to the gimbal flexure.
In yet another embodiment, a method of conditioning a pad for chemical mechanical polishing is provided. The method includes initiating, using a controller, conditioning of a pad on a platen using a pad conditioning assembly, receiving a distance data stream using at least one sensor of the pad conditioning assembly, determining, using the controller, if the distance data stream exceeds a predetermined threshold, and upon determining that the distance data stream exceeds the predetermined threshold, biasing a pad conditioning disk of the pad conditioning assembly.
So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, 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 exemplary embodiments of the disclosure and are therefore not to be considered limiting of its scope, as the disclosure may admit to other equally effective embodiments.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
Embodiments herein are generally directed to chemical mechanical polishing (CMP), and more specifically to a pad conditioner for use in chemical mechanical polishing.
In CMP, the pad conditioner plays a critical role in ensuring removal of material from the substrate surface. It is known, however, that gimbal bias of the pad conditioner can cause variations in pad conditioning, especially with pivoting arms. As a result the diamond disk of the conditioner has sparse contact with the pad, which reduces its effective cut-rate. Therefore, additional bias is necessary to improve cutting efficiency and compliance with the pad. Gimbal tilt and bias control can achieve this and minimize platen-to-platen differences. Currently, pad conditioners can be shimmed to bias the disk, but this is only a global control. In other words, existing methods of biasing the gimbal require the pad conditioner arm to be biased as a whole, which may not be optimal. The present disclosure provides improved methods and systems that enable localized biasing of the gimbal to provide more effective conditioning of the pad, improving CMP performance.
Further, creating a uniform contact surface between the pad conditioning disk and the polishing pad while they are rotating in the same direction, e.g., clockwise or counterclockwise, results in a faster diamond cut velocity on the side of the pad conditioning disk closest to the center of the polishing pad, referred to herein as the out-of-phase cut rate, since the pad movement and pad conditioner diamonds are moving in an opposing direction. The diamond cut velocity on the side of the pad conditioning disk closest to the edge of the polishing pad is slower than the diamond cut velocity at the center of the polishing pad and is referred to herein as the in-phase cut rate.
The present disclosure provides a pad conditioning assembly including at least one electromagnet coupled to a pad conditioner head to control gimbal tilt of the pad conditioning disk based on a magnetic attraction force, magnetic repulsion force, or a combination thereof. In particular, magnets or ferromagnetic material on the pad conditioning disk gimbal may interact with the electromagnet on the pad conditioning head. This allows for compensation of gimbal bias over the lifetime of the pad due to the decreasing thickness of the pad. Additionally, the at least one electromagnet may amplify or reduce gimbaling to maximize out-of-phase cut rate of the pad conditioning disk.
The gimbal of the pad conditioner of the present disclosure is compliant and rotating, allowing the pad conditioning disk to couple with the polishing pad in an unconstrained manner. The gimbal of the pad conditioning disk can be locally tilted without requiring a slip ring or control in the rotating mechanism. The present disclosure maximizes the contact area of the diamonds on the pad, facilitating more effective conditioning. The compliance of the gimbal enables the pad conditioner to conform to the pad surface, resulting in improved contact and more uniform material removal across the substrate surface.
The gimbal control assembly 140 may include at least one electromagnet 142 coupled to the conditioning head 130 and a pad conditioner gimbal flexure 144. The electromagnet 142 may be configured to tilt or compensate the pad conditioning disk 150 and gimbal flexure 144 such that the contact between the pad conditioning disk 150 and the polishing pad 114 is parallel or otherwise substantially flat. Alternatively, the pad conditioning disk 150 may be tilted to amplify the biased downforce on the polishing pad 114 to maximize the cut rate of the pad conditioning assembly 100.
The above-described pad conditioning assembly 100 is controlled by a processor based system controller, such as a controller 160, which may be coupled to a user interface 168. For example, the controller 160 is configured to control cutting pressure, rotation speed of the platen 112 and the pad conditioning disk 150, the movement of the arm 120, and the biasing of the electromagnets 142. The controller 160 includes a programmable central processing unit (CPU) 162 that is operable with a memory 164, support circuits 166, a mass storage device, an input control unit, and a display unit (not shown), such as power supplies, clocks, cache, input/output (I/O) circuits, and the like, coupled to the various components of the pad conditioning assembly 100 to facilitate control of the substrate processing. The controller 160 also includes hardware for monitoring substrate processing through sensors in the pad conditioning assembly 100.
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Creating a uniform contact surface between the pad conditioning disk 150 and the polishing pad 114 results in a faster diamond cut velocity on the side of the pad conditioning disk 150 closest to the center of the polishing pad 114 since the pad movement and pad conditioner diamonds are moving in an opposing direction. Doing so creates a uniform cutting pressure. However, the pad conditioning disk 150 may be biased in instances where non-uniform contact is desired, such as when either the edge or the center of the polishing pad 114 require additional cutting pressure.
In block 404, the controller 160 may receive a distance data stream from the at least one sensor 420. In block 406, the controller 160 may determine that the pad conditioning disk 150 requires biasing. For example, the controller 160 may determine that the distance between the platen 112 and the arm 120 falls below (or exceeds) a predetermined threshold, for example, by 10% or less, or by 5% or less.
The controller 160 may then, in block 408, actuate the electromagnets 142 to bias an outside edge of the pad conditioning disk 150 closest to the outside edge of the platen 112. The electromagnets 142 may be biased a predetermined amount based on user input or, alternatively, the electromagnets 142 may be biased based on the distance data stream from the at least one sensor 420. For example, the electromagnets 142 may be biased by a percentage correlating to a percentage of the predetermined threshold. For example, if the distance between the platen 112 and the arm 120 falls below the predetermined threshold by 10%, the electromagnets 142 are biased 10% toward the outside edge of the platen 112. Biasing of the pad conditioning disk 150 may be continuously monitored by returning back to block 404 until the pad conditioning process is ended. Alternatively, the biasing of the pad conditioning disk 150 may be discretely monitored by limiting the iterations of blocks 404 through 408.
By biasing the pad conditioning disk 150 towards the edge of the platen 112, the out-of-phase areas of the platen 112 (e.g., the center of the platen 112) have less cutting pressure while the in-phase areas of the platen 112 (e.g., the edge of the platen 112) have more surface contact with the pad conditioning disk 150 for pad cutting.
In block 504, the controller 160 may receive a distance data stream from the at least one sensor 520. In block 506, the controller 160 may determine that the pad conditioning disk 150 requires biasing. For example, the controller 160 may determine that the distance between the platen 112 and the arm 120 falls below (or above) a predetermined threshold, for example, by 10% or less, or by 5% or less.
The controller 160 may then, in block 508, actuate the electromagnets 142 to bias an inner edge of the pad conditioning disk 150 closest to the center of the platen 112. The electromagnets 142 may be biased a predetermined amount based on user input or, alternatively, the electromagnets 142 may be biased based on the distance data stream from the at least one sensor 520. For example, the electromagnets 142 may be biased by a percentage correlating to a percentage of the predetermined threshold. For example, if the distance between the platen 112 and the arm 120 falls below the predetermined threshold by 10%, the electromagnets 142 is biased 10% toward the outside edge of the platen 112. Biasing of the pad conditioning disk 150 may be continuously monitored by returning back to block 504 until the pad conditioning process is ended. Alternatively, the biasing of the pad conditioning disk 150 may be discretely monitored by limiting the iterations of blocks 504 through 508.
By biasing the pad conditioning disk 150 towards the center of the platen 112, the out-of-phase areas of the platen 112 (e.g., the center of the platen 112) with the highest linear velocity will have increased cutting pressure bias.
The present disclosure provides a pad conditioning assembly with gimbal control for a pad conditioner. The compliance of the gimbal of the present disclosure allows the pad conditioning disk to couple with the polishing pad in an unconstrained manner to conform to the pad surface, maximizing the contact area of the diamonds on the disk to facilitate more effective conditioning and more uniform planarization.
When introducing elements of the present disclosure or exemplary aspects or embodiment(s) thereof, the articles “a,” “an,” “the” and “said” are intended to mean that there are one or more of the elements.
The terms “comprising,” “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
The term “coupled” is used herein to refer to the direct or indirect coupling between two objects. For example, if object A physically touches object B and object B touches object C, the objects A and C may still be considered coupled to one another-even if objects A and C do not directly physically touch each other. For instance, a first object may be coupled to a second object even though the first object is never directly in physical contact with the second object.
While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
