Investigation of the Role of Carbonylchemistry to Pattern Platinum Electrodes
- PDF / 411,635 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 11 Downloads / 202 Views
Investigation of the Role of Carbonylchemistry to Pattern Platinum Electrodes St. Schneider, H. Kohlstedt, and R. Waser Institut für Festkörperforschung, Forschungszentrum Jülich Jülich, 52425, Germany
ABSTRACT Noble metals like platinum or irdium are used as electrode materials in DRAM or FRAM devices. Their etch process is a challenge as conventional, sputter driven etch processes either result in redeposition problems (fences) or in a severe sloping (loss of dimension control) and are not acceptable for high density integration architectures. The high temperature etch regime offers a solution by increasing the chemical etch component and thus the volatility of the etch products. As previously reported, the platinum etch rate increases exponentially for a chlorine etch process with increasing wafer temperature. In this study we investigate the particular role of carbon monoxide in a Cl2/CO etch process. We find that carbon monoxide additions to a chlorine process boost the chemical component of the platinum etch rate very significantly, exceeding the effects in the chlorine only process regime by far. Additionally we compare these results with a Cl2/O2 and a Cl2/CO2 process chemistry, which are not found to be particularly beneficial. To better understand the etch process we use an energy dispersive quadrupole mass spectrometer for in situ monitoring, attached to the chamber at two different locations. We are able to position the probe orifice at the place of the wafer electrode, to record ion energy and ion mass spectra of species impinging on the wafer plane. A second off axis position allows for etch product monitoring.
INTRODUCTION Increasing the wafer temperature over 250°C in a platinum etch process is the most important way to add a chemical reaction channel to the etch process, which is sputter dominated at the conventional low temperature process regimes. Even though the platinum etch rate depends exponentially on the temperature, practical considerations like the temperature ramp rate of electrostatic chucks or the temperature control accuracy limit the maximum wafer temperature in conventional etch reactors to below 400°C and thus the maximal chemical etch component. Engineering the plasma chemistry offers a second process knob to boost the chemical etch component while simultaneously adjusting the selectivity to the mask. Going from a chlorine only process chemistry to mixtures of chlorine with oxygen, carbon monoxide, or carbon dioxide look the most promising. Using an energy dispersive quadrupole mass spectrometer to measure the mass spectrum of the ions impinging on the wafer surface as well as their ion energy distribution function helps to deepen the understanding of the etch process. In addition the etch products are monitored in a different set of experiments, too. C5.6.1
EXPERIMENTAL SETUP For our experiments we used an Ionfab 300plus from Oxford Plasma Technology, a reactive ion beam etch tool able to handle 6” wafers. The inductively coupled plasma (ICP) beam source is filament free and d
Data Loading...
