Etching Characteristics of Noble Metal Electrode
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Etching Characteristics of Noble Metal Electrode St. Schneider, H. Kohlstedt, and R. Waser Institut für Festkörperforschung, Forschungszentrum Jülich Jülich, 52425, Germany
ABSTRACT The objective of this work was to develop a process to pattern noble metal electrodes. To systematically investigate possible reactive etch process regions, characterized by volatile etch products, we used a reactive ion beam etching (RIBE) tool with a filament free ICP source. This configuration gives us exact control over the beam energy and the current density, and allows to use reactive gases. An energy dispersive quadrupole mass spectrometer is fitted to the chamber for in situ monitoring. We study the influence of the beam energy and the beam current impinging on the wafer surface as well as it's angular dependence. Several additives to the chlorinated process chemistry are investigated and characterized in terms of their role to help to increase the etch rate, maintain a vertical profile, or to enhance process selectivity. The main focus of the study is on Platinum. Blanket films were used to describe the influence of the material, and analysis were carried out to characterize the process in terms of etch rate, residues and selectivity. INTRODUCTION A reactive etch process to pattern noble metal electrodes is considered necessary for DRAM integration and desirable for FRAM application in near terms. However, few information has been released to the public literature so far [1]. A potential process has to meet the well known stringent requirements like a steep slope of the side wall, a minimal change in the feature size, no fences, and no residues on the wafer. Yield considerations from manufacturing impose totally different requirements like high mean time between clean (MTBC) to be able to cut down production costs. Due to the lack of a chemical etch rate one either ends up with quite steep side walls, to the cost of redeposition on the mask material (fences), or with fence free structures with very poor control over the feature size and an unacceptable slope [2-5]. Furthermore sputter etching offers only a very limited selectivity to the mask as well as the substrate. Beside those disadvantages a sputter process results in a coating of the inside walls of the etch chamber leading to particle problems as well as plasma instabilities, requiring often wet cleans of the tool. To understand the high temperature etch process of Platinum we systematically investigated different etch regimes and plasma chemistries. In order to separate the plasma physic from the surface chemistry, we choose a Reactive Ion Beam Etching (RIBE) tool, instead of a conventional plasma reactor. The main advantage of ion beam etching tools is the precise control over the beam energy as well as the beam current density in contrast to plasma reactors, where those plasma parameters are a result of the energy input from the generators and have to be measured for each process.
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EXPERIMENTAL SETUP Our Ionfab 300plus from Oxford Plasma Technology is able t
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