News Column

Researchers Submit Patent Application, "Adjustable Current Shield for Electroplating Processes", for Approval

September 10, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors Sandmann, Gunther Wilhelm (Dresden, DE); Siury, Kerstin (Dresden, DE); Schroiff, Christian (Dresden, DE), filed on February 18, 2013, was made available online on August 28, 2014.

The patent's assignee is Globalfoundries Inc.

News editors obtained the following quote from the background information supplied by the inventors: "Generally, the present disclosure relates to the manufacture of sophisticated semiconductor devices, and, more specifically, to an adjustable current shield that may be employed in electroplating processes that are performed to form a conductive metal material.

"The manufacture of semiconductor devices often requires the formation of electrical conductors on semiconductor wafers. For example, electrically conductive leads on the wafer are often formed by electroplating (depositing) an electrically conductive layer, such as copper, on the wafer and into patterned trenches. There are two general types of electroplating equipment: fountain plating equipment and vertical plating equipment. Both have relative advantages in some applications. Although the orientation of the surface of the wafer to be plated is different in the two different processes--horizontal in fountain plating equipment and vertical in vertical plating equipment--the process operations are very similar.

"In general, electroplating involves making electrical contact with a so-called conductive 'seed' layer that is formed on the wafer surface upon which the electrically conductive layer, e.g., copper, is to be deposited. Current is then passed through a plating solution (i.e., a solution containing ions of the element being deposited, for example, a solution containing Cu.sup.++) between an anode and the conductive seed layer on the wafer plating surface that acts as a cathode. The seed layer carries the electrical plating current from the edge of the wafer, where electrical contact is made, to the center of the wafer, including through embedded structures, trenches and vias. This causes an electrochemical reaction on the wafer plating surface which results in the deposition of the electrically conductive layer. Ideally, the final layer of material that is electrodeposited on the seed layer should completely fill the embedded structures, and it should have a specific thickness profile across the surface of the wafer. Generally, in electroplating processes, the thickness profile of the deposited metal should be controlled as much as possible.

"In an attempt to minimize variations in the deposited material, it is important that the electrically conductive seed layer have a uniform thickness over the wafer plating surface. However, even with highly uniform seed layers, conventional electroplating processes produce a non-uniform deposition due to the so-called 'edge effect' associated with such plating processes. In general, the edge effect refers to the tendency of the deposited electrically conductive layer to be thicker near the wafer edge than at the wafer center, i.e., an 'edge-thick' profile. This edge-thick profile in the final layer is caused by, among other things, a decrease in current flow through the seed layer in the middle region of the wafer as compared to the current flowing near the edge region of the wafer. That is, since the conductive seed layer is contacted at the periphery of the wafer and the magnitude of the current flowing through the seed layer drops as one moves from the edge of the wafer toward the center of the wafer, there is less conductive material, e.g., copper, plated at the center of the wafer as compared to the edge region of the wafer.

"The formation of such edge-thick layers of material makes subsequent processing more difficult. For example, such edge-thick layers of material make subsequent chemical mechanical polishing operations more difficult to perform, i.e., it makes it more difficult to obtain a substantially planar surface after the polishing process has been performed. As another example, various processing parameters of the electroplating process may be adjusted in an attempt to combat this tendency to produce conductive material layers with an edge-thick profile. However, such processing changes may result in producing a conductive layer that is too thin in the middle area of the wafer, thereby leading to the formation of defective wiring features that are not as thick as intended by the design process. Such defective wiring features may reduce the useful life of an integrated circuit product and, in a worst-case scenario, may lead to complete device failure.

"One technique that has been employed in an effort to avoid or reduce the magnitude of the production of such edge-thick conductive layers involves the use of so-called current shields. Current shields are typically positioned between the anode and the wafer and they act to reduce the electrical field at the edge region of the wafer, which reduces the amount of the conductive material formed on the edge region of the wafer. The current shields may be made of a variety of materials, such as non-conductive, inert materials, like plastic. The current shields may be fixed or adjustable in terms of their area that is positioned between the anode and the wafer. In one example, a fixed current shield has a radial width of about 20-30 mm and a thickness on the order of about 2-3 mm. Such fixed current shields are typically sized and configured for a particular process flow and/or device by a trial and error process. Once acceptable results are achieved, the specifically designed current shield is used in production operations. Unfortunately, when there is a change in the design of the wafer or the process conditions, the existing current shield may not produce acceptable results. In that case, a new design of a current shield may need to be determined (by trial and error) and then put into production service. Alternatively, processing engineers may try to 'make-do' with the less than desirable original current shield, which may lead to the production of conductive layers that do not have the desired or target thickness profile and the problems associated with such layers as discussed above.

"The present disclosure is directed to a novel adjustable current shield that may solve or reduce one or more of the problems identified above."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an exhaustive overview of the invention. It is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.

"Generally, the present disclosure is directed to a plating tool that includes an adjustable current shield that may be employed in electroplating process operations. One illustrative plating apparatus disclosed herein includes a substrate holder that is adapted to receive a substrate, an anode and an adjustable current shield positioned between the substrate holder and the anode. In this illustrative embodiment, the adjustable current shield includes a stationary member, a moveable member that is adapted to be moved relative to the stationary member and a plurality of current shield members that are operatively coupled to either the stationary member or the moveable member, wherein each of the current shield members is rotatably pinned to either the stationary member or the moveable member and wherein each of the current shield members is adapted to rotate when there is relative movement between the moveable member and the stationary member.

"Another illustrative plating apparatus disclosed herein includes a substrate holder that is adapted to receive a substrate, an anode and an adjustable current shield positioned between the substrate holder and the anode. In this illustrative embodiment, the adjustable current shield includes a stationary ring, a moveable ring that is adapted to be moved relative to the stationary ring and a plurality of current shield members operatively coupled to the stationary ring and the moveable ring, wherein each of the plurality of current shield members is rotatably pinned to either the stationary ring or the moveable ring and wherein each of the current shield members is adapted to rotate when there is relative movement between the moveable ring and the stationary ring, thereby moving a portion of each of the current shield members radially inward or outward depending upon the direction of the relative movement.

"Yet another illustrative plating apparatus disclosed herein includes a substrate holder that is adapted to receive a substrate, an anode and an adjustable current shield positioned between the substrate holder and the anode, wherein the adjustable current shield includes a plurality of segmented shielding members that may be moved so as to effectively change a size of an opening of the adjustable current shield.

BRIEF DESCRIPTION OF THE DRAWINGS

"The disclosure may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which:

"FIGS. 1 and 1A are simplistic and schematic views of various illustrative embodiments of an electroplating apparatus having an adjustable current shield as disclosed herein;

"FIGS. 2A-2E depict various illustrative aspects of one illustrative embodiment of an adjustable current shield as disclosed herein; and

"FIGS. 3A-3B depict one illustrative embodiment of a plurality of current shielding members that may be employed in the illustrative adjustable current shield disclosed herein.

"While the subject matter disclosed herein is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims."

For additional information on this patent application, see: Sandmann, Gunther Wilhelm; Siury, Kerstin; Schroiff, Christian. Adjustable Current Shield for Electroplating Processes. Filed February 18, 2013 and posted August 28, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=6450&p=129&f=G&l=50&d=PG01&S1=20140821.PD.&OS=PD/20140821&RS=PD/20140821

Keywords for this news article include: Electronics, Globalfoundries Inc., Semiconductor.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


For more stories covering the world of technology, please see HispanicBusiness' Tech Channel



Source: Electronics Newsweekly


Story Tools






HispanicBusiness.com Facebook Linkedin Twitter RSS Feed Email Alerts & Newsletters