Patterning issues for the fabrication of sub-micron memory capacitors' electrodes
This paper describes some of the key issues associated with the patterning of metal electrodes of sub-micron (especially at the critical dimension (CD) of 0.15 μm) dynamic random access memory devices. Due to reactive ion etching lag, the Pt etch rate decreased drastically below the CD of 0.20 μm and thus K-th storage node electrode with the CD of 0.15 μm could not be fabricated using the Pt electrodes. Accordingly, we have proposed novel techniques to surmountly-the above difficulties. The Ru electrode cannot for the stack-type structure is introduced and alternative multischemes based on the introduction of the concave-type selfstructure upto using semi-Pt or Ru as an electrode material are outlined respectively.
Platinum Etching and Plasma Characteristics in RF Magnetron and Electron Cyclotron Resonance Plasmas
The properties of platinum etching were investigated using both rf magnetron and electron cyclotron resonance plasmas, together with measurement of the plasma parameters. Experiments were performed over a wide pressure range from 0.4 to 50 mTorr in Cl2 plasmas. In rf magnetron plasmas, the etch rate of Pt was constant at the substrate temperature from 20 to 160°C. The etch rate and the plasma electron density increased with decreasing gas pressure from 50 to 5 mTorr. In ECR plasmas for rf power of 300 W, the etch rate of Pt was almost constant (∼100 nm/min) with decreasing gas pressure from 5 to 0.4 mTorr, while the plasma electron density was gradually increased with decreasing gas pressure. These experimental results were discussed with respect to the relationship between the etch yield and ratio of neutral Cl flux and ion flux incident on the substrate. Submicron patterning (0.5 µm lines & spaces) of platinum masked with photoresist was demonstrated using Cl2 plasmas in ECR discharges. High accuracy was obtained with no undercutting.
Integrated Piezoelectric and Pyroelectric Devices from Thin Film Ferroelectrics
Thin PZT films 1-4 μm in thickness prepared by sputtering or sol gel methods allow PZT films to be integrated with silicon technology to achieve piezoelectric or pyroelectric structures having small size or mass. Design criteria, materials and processing techniques for such devices are discussed, and the implementation of small size devices on silicon substrates is demonstrated. Factors of importance are the piezoelectric and pyroelectric characteristics achievable in the films, mechanical strength and fatigue, and the stability and compatibility of the films and electrodes with device fabrication procedures and operating conditions.