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Method for removing and preventing metal redeposition during CMP

IP.com Disclosure Number: IPCOM000020729D
Publication Date: 2003-Dec-10
Document File: 4 page(s) / 528K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for removing and preventing metal redeposition during chemical mechanical planarization (CMP). Benefits include improved functionality and improved performance.

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Method for removing and preventing metal redeposition during CMP

Disclosed is a method for removing and preventing metal redeposition during chemical mechanical planarization (CMP). Benefits include improved functionality and improved performance.

Background

Metal must be removed and not redeposited during metal CMP. The conventional practice is a post-CMP rinse, using deionized water (DI) or a conventional chemical solution. However, metal redeposition cannot be removed completely. For example, Cu can be redeposited on an oxide surface (see Figure 1). Redeposited Cu causes line-to-line leakage (pico- to micro-amp range) and metal comb structure failure.

         During the metal CMP process, metallic redeposition on the wafer surface can occur at high enough rates to cause metal-to-metal leakage. Metal redeposition can cause metal comb leakage failures (see Figure 2). An improved cleaning solution is required to enhance metal removal and prevent metal redeposition.

General description

         The disclosed method is a procedure and chemistry for enhancing metal removal and preventing metal redeposition during CMP. Metals include aluminum (Al), copper (Cu), and tungsten (W) etc. The chemistry can be used in addition to the slurry used for polishing the barrier layer or the post-CMP cleaning solution.

         The key elements of the method include:

•         Etchant to undercut metallic residue from the oxide surface

•         Cationic surfactant to modify the wafer surface charge and repel positively charged metallic ions from the wafer surface

•         Chelating agent to prevent metallic redeposition

Advantages

         The disclosed method provides advantages, including:

•         Improved functionality due to preventing redeposition during post-CMP processing and eliminate metal-to-metal leakage

•         Improved performance due to improving metal removal during CMP processing

Detailed description

         The disclosed method includes a chemical solution comprised of a combination of an undercut etchant, cationic surfactant, and/or chelating agent. Undercut etchant...