US 20050145484 A1
Systems and methods to remove or lessen the size of metal particles that have formed on, and to limit the rate at which metal particles form or grow on, workpiece surface influencing devices used during electrodeposition are presented. According to an exemplary method, the workpiece surface influencing device is occasionally placed in contact with a conditioning substrate coated with an inert material, and the bias applied to the electrodeposition system is reversed. According to another exemplary method, the workpiece surface influencing device is conditioned using mechanical contact members, such as brushes, and conditioning of the workpiece surface influencing device occurs, for example, through physical brushing of the workpiece surface influencing device with the brushes. According to a further exemplary method, the workpiece surface influencing device is rotated in different direction during electrodeposition.
1. A processing apparatus for electrochemical mechanical processing of a workpiece using a solution comprising:
an electrochemical mechanical processing system adapted to operate on the workpiece, the system including an electrode, a holder adapted to hold the workpiece, a terminal adapted to make electrical contact with the workpiece, and a workpiece surface influencing device, wherein the electrochemical mechanical processing system is adapted to operate upon the workpiece using the solution, with the workpiece surface influencing device being disposed in proximity to the workpiece for a period of time during the electrochemical mechanical processing, the electrochemical mechanical processing also resulting in accumulation of particles onto the workpiece surface influencing device; and
a system adapted to operate on the workpiece surface influencing device and thereby result in one of the number of accumulated particles being reduced and the size of the accumulated particles being reduced.
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29. A system for processing a workpiece and removing particles on a workpiece surface influencing device, the workpiece surface influencing device being used in conjunction with a plating solution to process the workpiece, comprising:
a holder adapted to receive the workpiece and to move the workpiece proximate to the workpiece surface influencing device;
an apparatus adapted to deposit, via the plating solution, conductive material onto the workpiece using a first potential difference that is applied between an electrode and the workpiece with the workpiece surface influencing device in close proximity to the workpiece; and
a member having a conditioning conductor layer adapted to assist in removing at least a first portion of the particles that accumulate on the workpiece surface influencing device during the depositing of the conductive material using a second potential difference that is applied between the electrode and the conditioning conductor layer of the member, the second potential difference being of an opposite polarity to the first potential difference.
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32. A system for processing a workpiece and removing particles on a workpiece surface influencing device, the workpiece surface influencing device being used in conjunction with a plating solution to process the workpiece, comprising:
an apparatus adapted to deposit, via the plating solution and with the workpiece surface influencing device in close proximity to the workpiece, conductive material onto the workpiece in the presence of a first potential difference that is applied between an electrode and the workpiece;
a holder adapted to receive the workpiece, to move the workpiece in close proximity to the workpiece surface influencing device so that the depositing of the conductive material by the apparatus can take place, and to remove the workpiece from being in close proximity to the workpiece surface influencing device upon completion of the depositing by the apparatus; and
a member having at least one mechanical contact member and adapted to move against a top surface of the workpiece surface influencing device so that at least a portion of the particles that accumulate on the workpiece surface influencing device during the depositing of the conductive material are mechanically removed from the workpiece surface influencing device.
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35. A system for processing a workpiece and removing particles on a workpiece surface influencing device, the workpiece surface influencing device being used in conjunction with a plating solution to process the workpiece, comprising:
a deposition apparatus positioned in a lower chamber for depositing conductive material from the plating solution onto the workpiece with the workpiece surface influencing device in close proximity to the workpiece; and
a member adapted to be positioned in the lower chamber and to remove at least a portion of the particles that accumulate on the workpiece surface influencing device during the depositing of the conductive material by the deposition apparatus; and
a holder adapted to position the workpiece in the lower chamber while the deposition apparatus is being used.
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This is a divisional application of U.S. application Ser. No. 09/982,558 filed Oct. 17, 2001 entitled Method and Apparatus for Avoiding Particle Accumulation in Electrodeposition, which claims the benefit of priority to U.S. Provisional Application Ser. No. 60/280,524 filed Mar. 30, 2001.
1. Field of the Invention
The present invention relates to a method and apparatus for removing particles from surfaces, and avoiding particle accumulation on surfaces during, electrochemical mechanical processing.
2. Description of the Related Art
Conventional semiconductor devices generally include a semiconductor substrate, usually a silicon substrate, and a plurality of sequentially formed dielectric interlayers such as silicon dioxide and conductive paths or interconnects made of conductive materials. The interconnects are usually formed by filling a conductive material in trenches etched into the dielectric interlayers. In an integrated circuit, multiple levels of interconnect networks laterally extend with respect to the substrate surface. The interconnects formed in different layers can be electrically connected using vias or contacts. A conductive material filling process of such features, i.e., via openings, trenches, pads or contacts can be called out by depositing a conductive material over the substrate including such features.
Copper and copper alloys have recently received considerable attention as interconnect materials because of their superior electromigration and low resistivity characteristics. The preferred method of copper deposition is electrodeposition. During fabrication, copper is deposited on the substrate that has been previously coated with a barrier layer and then a seed layer. The barrier layer coats the vias and the trench as well as the surface of the dielectric layer to ensure good adhesion and acts as a barrier material to prevent diffusion of the copper into the semiconductor devices through the dielectric insulation layer. Typically, seed layer forms a conductive material base for copper film growth during the subsequent copper deposition. Typical barrier materials generally include tungsten, tantalum, titanium, their alloys, and their nitrides. The deposition process can be carried out using a variety of processes. After depositing copper into the features on the semiconductor wafer surface, an etching, an electropolishing (also called electroetching), an electrochemical mechanical etching (ECME) or a chemical mechanical polishing (CMP) step may be employed. These processes remove the conductive materials off the field regions of the surface, thereby leaving the conductive materials only within vias, trenches and other features.
In conventional electrodeposition techniques, copper is coated on the wafer surface in a conformal manner. As shown in
The importance of overcoming the various deficiencies of the conventional electrodeposition techniques is evidenced by technological developments directed to the deposition of planar copper layers. For example, U.S. Pat. No. 6,176,992, entitled “Method and Apparatus for Electrochemical Mechanical Deposition” and commonly owned by the assignee of the present invention, describes in one aspect an electro chemical mechanical deposition technique (ECMD) that achieves deposition of the conductive material into the cavities on the substrate surface while minimizing deposition on the field regions by polishing the field regions with a pad as the conductive material is deposited, thus yielding planar copper deposits. In another aspect, this application describes an electrochemical mechanical etching (ECME) or electroetching or electropolishing technique that removes conductive material from the surface of a workpiece.
U.S. Pat. No. 6,534,116 for “Plating Method and Apparatus that Creates a Differential Between Additive Disposed on a Top Surface and a Cavity Surface of a Workpiece Using an External Influence,” also assigned to the same assignee as the present invention, describes in one aspect another ECMD method and apparatus for plating a conductive material onto the substrate by creating an external influence, such as causing relative movement between a workpiece and a mask, to cause a differential in additives to exist for a period of time between a top surface and a cavity surface of a workpiece. While the differential is maintained, power is applied between an electrode (in this case anode) and the substrate to cause greater relative plating of the cavity surface than the top surface.
These ECMD methods can deposit metals in and over cavity sections on a workpiece in a planar manner. Some methods even have the capability to provide deposits with excess metal in and over the cavities. In such above-mentioned processes, a pad, a mask or a sweeper, hereinafter collectively referred to as a workpiece-surface-influencing device (WSID), can be used during at least a portion of the electrodeposition process when there may be physical contact between the workpiece surface and the WSID. The physical contact, polishing, or the external influence affects the growth of the metal by effectively reducing the growth rate on the top surface with respect to the features. During the process step that involves the WSID being in close proximity to, and typically in contact with, the metal surface, small particles of the metal may attach onto the WSID material. These particles may exist because of the fact that they may be just physically removed from the substrate surface or they may originate from the plating solution due to poor filtration of the plating solution. In any case once the conductive metal particles attach themselves to a location on the WSID, they may start growing in size because they become cathodic with respect to the electrode. Further, since they are conductive they receive coating and thus grow in size.
ECME methods also use a WSID, and during usage of these methods, the WSID is also in close proximity to, and typically in contact with, the metal surface of the workpiece. During ECME, the potential applied between the workpiece surface and the electrode is reversed rendering the workpiece surface anodic. Therefore, material is removed from the workpiece surface. If WSID is not used during this material removal step, i.e. if there is no mechanical action on the workpiece surface, the process is referred to as just electrochemical etching or polishing. It should be noted that in general both ECMD and ECME processes are referred to as electrochemical mechanical processing (ECMPR) hereinafter, since both involve electrochemical processes and mechanical action.
In addition to conductive particles, there are also non-conductive particles that may accumulate on the WSID material. The non-conductive particles may originate from other parts of the system, such as from the plating solution due to the poor filtration or from the WSID material itself due to the wear and tear during processing.
Presence of such particles on or in close proximity of the surface of the WSID is undesirable because if they become loose and find their way to the interface between the WSID and the workpiece surface, they can cause scratches, inclusions, or other defects on the workpiece surface or they can actually cause scratches on the surface of the WSID, especially if the WSID has a non-flat surface profile.
Therefore, elimination of such particles, or process steps to limit their growth, are very important to increase process yield and the lifetime of the WSID used in planar metal deposition techniques in which particles may come close to or touch the workpiece surface, and particularly when particles are disposed on a WSID that touches the workpiece surface.
It is an object of the invention to remove or reduce the size of particles that have formed on pads, masks, sweepers or WSIDs used during electrochemical mechanical processing (ECMPR).
It is another object of the invention to limit the rate at which conductive particles form or grow on WSID used during ECMPR.
It is yet another object of the invention to reduce defects on the workpiece.
Certain of the above objects of the invention, among others, either singly or in combination, are achieved in one embodiment by occasionally conditioning the WSID used during ECMPR.
In one embodiment, this involves placing the WSID in the presence of a conditioning substrate and applying a bias that will cause removal of, or reduction in the size of, conductive particles on the WSID.
In another embodiment, the WSID is conditioned using mechanical contact members, such as brushes, and conditioning occurs, for example, through physical brushing of the WSID with the brushes.
In another embodiment, conditioning occurs by rotating the WSIDs used during electrodeposition in different directions, or by rotating successive substrates or workpieces in different directions.
The above and other embodiments can also be combined, as described in further detail below.
These and other objects, features and advantages of the present invention are better understood by reading the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, in which:
One way of eliminating the growth of conductive, and typically metallic, or other particles on the workpiece surface influencing device (WSID) surface is to use a “particle elimination step” during electrochemical mechanical processing, either simultaneous with the electrochemical mechanical processing or when intermittently stopping the electrochemical mechanical processing. This step involves using a conditioning system, with a conditioning member that can assist in removing particles. As described hereinafter, this conditioning member can take the form of a conditioning substrate with a plurality of brushes that operates mechanically, a conductive conditioning substrate with conductive brushes that operates both mechanically and electrically, or a conditioning conductor layer that operates electrically. Of course, modifications of these embodiments can also exist. When operating electrically, as described hereinafter, the conductor used to coat is preferably an inert material that cannot be anodized or etched in the plating solution, under a bias, as will be described further hereinafter.
Reference will now be made to the drawings wherein like numerals refer to like parts throughout.
During an ECMD process, the front surface 108 of substrate 104 is brought into close proximity, or contact with, the top surface 112 of the WSID 106 for planar metal deposition. As a plating solution, depicted by arrows 124, is delivered to the channel 116, the substrate 104 is rotated about a rotation axis 126 while the front surface 108 contacts the top surface 112 of the WSID 106 or is in close proximity of the top surface 112. For the purpose of clarification, the rotation axis 126 may be the point at which the closed end 120 of the channel 116 is located, thereby ensuring that rotation of the substrate 104 will result in the entire front surface 108 of the substrate 104 having uniform contact with the channel 116. As the solution is delivered and fills the channel 116, it wets the front surface 108 of the substrate 104. Under an applied potential between the substrate and the electrode 102, in the presence of the solution 124 that fills the channel 116, the conductor or metal, such as copper, is plated on the front surface 108 of the substrate and the front surface 108 of the substrate 104 is also swept by the top surface 112 of the WSID 106. This sweeping of the top surface 112 of the WSID 106 assists in obtaining planar deposition of the metal. The solution 124, which is continuously delivered under pressure, will then flow through the channel 116 in the direction of the arrow 128 towards the open end 122 of the channel 116, and exits the WSID 106.
It is noted that the above description described rotation and movement of the substrate 104, assuming that the WSID 106 was stationary. It is understood that the system 100, as described above, will allow for either the substrate or the WSID to move, or for both of them to move, thereby creating the same relative effect. For ease of description, however, the invention was described and will continue to be described in terms of movement of the substrate. Furthermore, the shapes and forms of the channels may be different. When the system 100 is used for ECME, although the same plating solution that is used for the ECMD can still be used, it can be replaced with an electroetching solution or an electropolishing solution or an etching solution. In the ECME case, the WSID will typically contact the workpiece as described above, but the applied potential between the substrate and the electrode 102 will be opposite to that which is used for plating, and will be of the same polarity as that used when conditioning the WSID with a conditioning substrate that uses an applied potential, as discussed hereinafter.
It should be understood that ECMD, ECME, and other processes can occur in succession, and that any number of such processes can occur, with a conditioning step occurring thereafter, and then any number of such processes can occur again. For example, an ECMD process, followed by an ECME process, followed by an ECMD process is typical. It may then be desirable to perform conditioning of the WSID according to the present invention, and then resume with some number of processes, for instance another set of ECMD, ECME, and ECMD processes. Alternately, conditioning may be done after the ECMD process before the ECME process, etc.
As mentioned above, channels in a WSID may have different shapes and sizes.
In the above examples, channel and raised surface side-walls are described as the main particle growth or presence sites. However, such unwanted particle may be on other locations of a WSID for example on the top surface of a WSID.
Therefore, a cleaning process according to the teachings of the present invention not only cleans such fatigued portions 608 after they are broken off the surface but also removes them safely once they are weakly attached to the top surface before they are broken off.
To that effect, in one embodiment, a conditioning substrate 132, shown in
In another embodiment, a conditioning member may be used to mechanically dislodge particles of both natures, conductive or nonconductive. As shown in
Brushes 206 and the conditioning member 200 may be made of a conductive material or an insulator, depending upon whether conditioning that requires them to conduct is required, as explained herein. When the WSID needs to be cleaned, the conditioning member is placed on the wafer carrier, workpiece holder, or carrier head, and the conditioning member is lowered onto the WSID while being rotated or otherwise moved. As shown in
In the above embodiments, when a work piece is subsequently processed using the plating solution 124, particles do not present a threat to the integrity of the film because the surface of the WSID is substantially free of particles. If copper is being deposited, for example, without the use of the conditioning process, particles can grow to more than 10 microns in size after running more than 20-50 wafers with WSID touching, with the location of these particles being concentrated along the edges of the channels. Particle size and the growth rate may vary depending on the charge used per substrate and the duration of the process per wafer. In general, a conditioning process may be carried out after processing some number of wafers, such as 10 to 50 wafers, although it is understood that the number of wafers to be processed prior to using the conditioning system requires a balance between the desired throughput and the concentration of undesired particles that can be tolerated.
In another embodiment of the present invention, elimination of particle accumulation and growth, or at least a reduction in the formation and/or growth of such particles, along the channels of the WSID 106 is achieved by controlling the rotation direction of a substrate or a wafer in the process from run to run. As shown in
The embodiments described above can also be used together to further reduce the presence of undesired particles.
As previously mentioned, the WSID may have different channel configurations and shapes. As shown in
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While the present invention has been described herein with reference to particular embodiments thereof, a latitude of modification, various changes and substitutions are intended in the foregoing disclosure. It will thus be appreciated that in some instances some features of the invention will be employed without a corresponding use of other features without departing from the spirit and scope of the invention.