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Method for monitoring metal-polishing slurries to maintain consistent polishing characteristics

IP.com Disclosure Number: IPCOM000012938D
Publication Date: 2003-Jun-11
Document File: 3 page(s) / 72K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for monitoring metal-polishing slurries to maintain consistent polishing characteristics. Benefits include improved performance and improved reliability.

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Method for monitoring metal-polishing slurries to maintain consistent polishing characteristics

Disclosed is a method for monitoring metal-polishing slurries to maintain consistent polishing characteristics. Benefits include improved performance and improved reliability.

Background

              Changes in slurry characteristics affect polishing parameters, such as the rate and uniformity. Conventionally, the chemical nature of the slurry is monitored by using Ph meters. The pH of the slurry is kept within tight control limits to try to keep the polish process consistent. Other slurry parameters that are monitored are specific gravity and particle counts.

              Metal polishing is achieved by the oxidation of the metal surface layer, which is then polished off with chemical mechanical polishing (CMP). The metal polishing slurries typically have an oxidizing component added to the slurry. The oxidation potential of the metal polishing slurry must be kept constant to achieve consistent removal rates.

              An oxidizing agent has the potential to acquire electrons and to become reduced. A reducing agent has the potential to donate electrons and to become oxidized. When electrons are transferred from one species to another in a chemical reaction, it is called an oxidation-reduction reaction. Oxidation and reduction reactions occur together, the electrons generated by a reduction reaction must be acquired by an oxidation reaction. The electron transfer between the two species continues until equilibrium is reached.

General description

              The disclosed method monitors and controls metal polishing slurries so that the polishing characteristics of the process remain consistent over time. Variation from tool to tool is minimized.

               The measurement of oxidation-reduction potential (ORP) of the slurry is one of the key parameters to be monitored. If the ORP changes, the addition of the correct component to bring the ORP to the correct value ensures that the polishing rate remains constant.

Advantages

              The disclosed method provides advantages, including:

•             Improved performance due to controlling the oxidation of the metal surface and the removal rate and uniformity

•             Improved reliability due to ensuring that the slurry chemistry and the polishing process remain consistent

             

Detailed description

              The disclosed method provides a direct measure of the efficiency of the oxidation potential of the slurry. It is the most important factor that controls the oxidation of the metal surface and the removal rate and uniformity. The slurry can be modified if the ORP moves outside the control limits, ensuring that the slurry chemistry and the polishing process remain consistent.

              ORP measures the ratio of the activities of the oxidizing and reducing species in a solution. This ratio indicates the solution’s electron activity, such as its ability to...