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Method for polymer memory electrode ferroelectric performance enhancement

IP.com Disclosure Number: IPCOM000130476D
Publication Date: 2005-Oct-25
Document File: 4 page(s) / 366K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for polymer memory electrode ferroelectric performance enhancement. Benefits include improved functionality and improved power performance.

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Method for polymer memory electrode ferroelectric performance enhancement

Disclosed is a method for polymer memory electrode ferroelectric performance enhancement. Benefits include improved functionality and improved power performance.

Background

              Conventionally, the ferroelectric response of a memory cell is reduced to an unacceptable level before and during top electrode metal deposition due to energetic particle interaction. Several different techniques, such as physical vapor deposition (PVD) sputter and ion-beam deposition, have been used to address charging effects on the polymer surface. A relatively low-energy technique, such as e-beam evaporation, without optimization creates significant damage. Thermal evaporation is the least damaging technique for metals deposition but is not acceptable for high-volume manufacturing (HVM).

      The best-known conventional (process of record, POR) method for depositing metal directly onto polymer is noble-metal thermal evaporation. Noble-metal deposition ensures minimal chemical interaction. Evaporation achieves minimal physical bombardment due to low kinetic energy neutral particles. Thermal deposition limits charged particle interaction to low-energy thermionic emission. Because charged particles are minimal with thermal evaporation, the shaper mask location is optimized for film uniformity only. No magnets are required.

              Electron-beam (e-beam) evaporation is well established in metals deposition and is particularly important for deposition on sensitive substrates, such as compound semiconductors. In a polymer memory application, conventional deposition technology, PVD sputter, is too energetic for deposition directly onto the polymer substrate. E-beam evaporation has emerged as the leading method for metal deposition on polymer. E-beam evaporation uses relatively low energies and has a low flux of charged particles interacting with the exposed polymer while maintaining the capability required for an HVM tool. However, e-beam evaporation includes charged particles, such as the primary electron beam, backscattered electrons, and secondary electrons. Negatively charged particles directly affect the polymer's capability to hold its charge, electrically damaging the polymer.

               A primary electron beam is created using an electron gun. It contains focus bars, shunt bars, and electromagnet connections (see Figure 1).

              The focus bars (or pole pieces) focus the electrons into a tight beam. Without these pieces, the beam tends to diffuse due to the mutual repulsion of the like charges. Shunt bars reduce the strength of the permanent magnet and aid in beam centering prior to or in the absence of electromagnetic sweep control. Beam centering and sweep are controlled with the use of electromagnetic coils that counteract and/or aid the permanent magnet, defining the electron's path to the source. The use of beam sweeping, during rise and soak cycles prior to depos...