Chemistry: electrical and wave energy – Apparatus – Electrolytic
Reexamination Certificate
1999-04-27
2001-03-13
Bell, Bruce F. (Department: 1741)
Chemistry: electrical and wave energy
Apparatus
Electrolytic
C204S240000, C204S276000
Reexamination Certificate
active
06200436
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application contains subject matter related to a concurrently filed U.S. Patent Application by Christy M. Woo entitled “Consistent Plating System for Electroplating”. The related application is also assigned to Advanced Micro Devices, Inc. and is identified by 09/300,811.
TECHNICAL FIELD
The present invention relates generally to plating and more particularly to electro-chemical plating for semiconductor devices.
BACKGROUND ART
In the process of manufacturing integrated circuits, after the individual devices such as the transistors have been fabricated on the silicon substrate, they must be connected together to perform the desired circuit functions. This connection process is called “metalization” and is performed using a number of different photolithographic and deposition techniques. As the technology has been developing, electro-chemical deposition or electroplating has become the preferred metalization process to deposit the bulk amount of conductive metal and metal alloys for interconnecting semiconductor devices.
Typically, the chemical bath used in the electroplating process is the most difficult parameter to control. To achieve successful deposition of metal into smaller and smaller, high aspect ratio features, such as semiconductor trenches or vias where the width is small compared to a large depth, different fluid additives must be added to and mixed in the plating bath to enhance the electroplating filling capability. Each plating bath is used to process in excess of 1,500 wafers per batch of plating solution. The useful life of a batch of plating solution is determined by how quickly the additives are consumed during the plating process, how quickly the additives are destroyed by oxidation during processing, or how quickly detrimental by-products from the plating process accumulate. All these factors create unstable and changing formulations of the plating bath. At the end of the useful life of the batch of plating solution, it must be disposed of and a new batch of plating solution formulated.
In the past, the plating bath control method employed by the semiconductor industry was to monitor important components on an analysis bench outside the plating equipment. For example, for copper plating, the important components for an acid copper plating bath included analysis for copper ion, sulfuric acid, hydrochloric acid, other additives, and carbon by-product level. After analysis, the desired component concentration was maintained by adding a required amount of the individual components in a predetermined amount so as to maintain the bath in a predetermined, but relatively wide, range.
The analysis of particulate and carbon by-products generally determined when the plating bath solution needed to be disposed of and a new batch formulated since there was no method of removing the carbon by-products without also removing some of the other additives. This generally resulted in the need to dispose of large volumes of environmentally unsafe fluid.
As the semiconductor industry moves into higher and higher volume production, it has become more pressing that a solution be found to provide a more environmentally friendly way of handling waste materials in semiconductor manufacturing. Further, copper is becoming more commonly used and copper is much more toxic than the aluminum which it is replacing.
DISCLOSURE OF THE INVENTION
The present invention provides an automated system for recycling the waste fluids of a semiconductor plating system in which additives to the plating solution can be controlled down to the single wafer level. The basic plating solution and all its additives are mixed in a plating solution reservoir immediately prior plating and recirculated for one semiconductor wafer. After plating, the depleted plating solution is filtered and analyzed for the amount of additive filtered out so the amount can be replenished during mixing for the next wafer.
The present invention provides a plating system where there is no variation in the plating between successive plated products. A basic plating solution and its non-degradable additives are premixed and then mixed with degradable additives in a plating solution reservoir immediately prior plating and recirculated for one semiconductor wafer. After plating, the depleted plating solution is filtered and analyzed for immediate replenishment of the non-degradable additives.
The present invention further provides a consistent and extremely tight control of component composition during plating. A basic plating solution and its non-degradable additives are premixed at a remote site. The premixed plating solution and degradable additives are mixed in a plating solution reservoir immediately prior plating and recirculated for one semiconductor wafer. After plating, the depleted plating solution is filtered and analyzed for later replenishment of the non-degradable additives at the remote site.
The present invention further eliminates the accumulation of detrimental plating by-products in a plating bath.
The above and additional advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description when taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 3649509 (1972-03-01), Morawetz et al.
patent: 5344491 (1994-09-01), Katou
patent: 5391285 (1995-02-01), Lytle et al.
patent: 6024856 (2000-02-01), Haydu et al.
Advanced Micro Devices , Inc.
Bell Bruce F.
Ishimaru Mikio
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