Electroplating (often called “electrodeposition”) is a process for depositing an electrically conductive material onto an item. In the semiconductor industry, electroplating is often used to apply a layer of copper (or other highly conductive material) to a substrate (i.e., a wafer). Specifically, as shown in FIG. 1, the wafer 10 is placed in a container 12 which holds an electrolyte solution 14, and an electrical potential is applied (using a voltage source 16) between a conducting area on the wafer 10 and a counter electrode 18 (i.e., anode) in the liquid. This causes a chemical redox process to take place, resulting in the formation of a layer of copper on the wafer 10.
To facilitate the deposition process, the surface of the wafer 10 must have an electrically conducting coating before being immersed in the electrolyte bath 14, and electrical contact must be made with the wafer 10 (to complete the circuit) before deposition can take place. As shown in FIG. 1, to facilitate electrical contact with the wafer 10, a contact ring 20 is typically used, where the contact ring 20 includes a top portion 21 and a bottom portion 23, and the top portion includes electrical connectors or contacts 22. The wafer 10 is placed in the contact ring 20 and a backing plate (not specifically shown in FIG. 1) is used to apply pressure, causing the electrical contacts 22 of the top portion 21 of the contact ring 20 to electrically contact the electrically conducting coating on the wafer 10. Thereafter, an electrical potential is applied, resulting in the formation of a layer of copper (of desired thickness) on the wafer 10.
The fact that the wafer must be in electrical contact with the electrical contacts of the contact ring to enable deposition, leads to problems. The electrical contacts of the contact ring often develop a build up or wear which, in turn, causes localized high contact resistance between the wafer to be plated and the contact ring. When this occurs, a wafer non-uniformity during the deposition process can occur (i.e., copper will be deposited unevenly on the wafer).
A common, currently used solution to the problem is to painstakingly troubleshoot the hardware to determine the cause of the non-uniformity. This can be quite time-consuming. Additionally, it often results in unnecessary expense in that sometimes parts are replaced that are not the true cause of the problem. As an example, presently it is quite costly to replace a contact ring and anode in troubleshooting the problem. They have to replaced in pairs, so at a minimum, if this is the chosen course of action, it would be costly, and 16 to 24 man hours would be required. Furthermore, during the work, no wafers can be processed using the tool.
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