The present invention generally relates to methods and apparatuses for processing, such as electroplating or electro-polishing, a semiconductor wafer, and more specifically relates to a method and apparatus for achieving wafer contact in a process, such as an electroplating or electro-polishing process.
In many semiconductor fabrication process steps, such as electro-plating or electro-polishing (either of which are hereafter referred to as “electro-processing”), there is a need for good electrical contact to the front side of the semiconductor wafer. This contact is necessary for a complete electrical circuit to be made for the process, such as an electro-plating or electro-polishing process, to be effective. In other words, a front side contact (i.e., contact to the device side of the wafer) must be made to enable the process to function.
Contacting a semiconductor wafer on its front side in a process, such as in an electro-process, presents several problems. Currently, many different methods are in use to achieve front side contact to the conductive film. In fact, many different vendors have their own proprietary method for making contact. Generally, the methods which are widely practiced provide that the edge die (i.e., the die disposed proximate the edge of the wafer) are impacted. Depending on the tool set-up, a certain degree of wafer edge exclusion is created. Additionally, front side contact often presents an interference problem during processing, due to processing not be able to occur in the area of contact. Furthermore, a contact ring is often used to hold the wafer, and the edge of some of the die are often impacted by the contact ring. Process uniformity is also affected in the proximity of the contact ring.
An object of an embodiment of the present invention is to provide a method and apparatus which avoids having to make front side contact with a wafer during processing, such as electro-processing.
Another object of an embodiment of the present invention is to provide a method and apparatus which reduces defect density in electro-processing a semiconductor wafer.
Still another object of an embodiment of the present invention is to provide a method and apparatus which provides that no die are damaged on the front side of a semiconductor wafer during electro-processing.
Still yet another object of an embodiment of the present invention is to provide a method and apparatus which provides that a final edge clean step can be less encroaching due to reduced front side damage of a semiconductor wafer during electro-processing.
Briefly, and in accordance with at least one of the foregoing objects, an embodiment of the present invention provides a method and apparatus which uses a conductive type of seed or process film that covers the front side, the side, and at least a portion of the back side of a semiconductor wafer. The portion of the film which is on the back side of the wafer acts as contact for the electro-plating or electro-polishing process, thereby obviating the need for any front side contact. During the electro-process, the wafer can be positioned on a backing plate which supports the wafer as well as contacts (i.e., the part of the chuck or head that holds the wafer, making contact with the metal or conductive layer on the back side of the wafer). A wear ring may also be used to hold the wafer.
In depositing the conductive seed or process film, the wafer is positioned on a pedestal which has a diameter that is smaller than a diameter of the wafer. The pedestal may or may not utilize lift pin technology to load and unload the wafer. The difference in the pedestal and wafer diameters then becomes the area where the conductive seed or process film covers the back side of the wafer. Thereafter, this portion can be used as the contact area, thereby obviating the need for front side contact. The conductive film can be easily removed during subsequent processing steps.
The organization and manner of the structure and operation of the invention, together with further objects and advantages thereof, may best be understood by reference to the following description, taken in connection with the accompanying drawing, wherein:
While the invention may be susceptible to embodiment in different forms, there is shown in the drawings, and herein will be described in detail, a specific embodiment with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that as illustrated and described herein.
In contrast, the present invention avoids having to make front side contact with a wafer during processing, such as electro-processing, thereby reducing defect density, providing that no die are damaged, and providing that a final edge clean step can be less encroaching.
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The present invention obviates the need to contact the front side of a semiconductor wafer in an electro-process, thereby reducing defect density, as well as providing that no die are damaged and that a final edge clean step can be less encroaching. The present invention can be used in connection with electro-polishing, electroplating, scrubbing, CMP or any other process that would otherwise require front side wafer contact for processing to occur.
While an embodiment of the present invention is shown and described, it is envisioned that those skilled in the art may devise various modifications of the present invention without departing from the spirit and scope of the appended claims.