Bulletin of the American Physical Society
38th Annual Meeting of the Division of Atomic, Molecular, and Optical Physics
Volume 52, Number 7
Tuesday–Saturday, June 5–9, 2007; Calgary, Alberta, Canada
Session C3: GEC Session: Nanoplasmas |
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Chair: R. Johnson, University of Pittsburgh Room: TELUS Convention Centre Glen 201-203 |
Wednesday, June 6, 2007 1:30PM - 2:06PM |
C3.00001: Experimental investigations of reactions in plasma etching of nanometer size structures Invited Speaker: As the size of features on semiconductor integrated circuits becomes ever smaller, patterning and pattern transfer processes must keep pace. Plasma etching is the only viable pattern transfer method today and it is likely to remain so in the foreseeable future. Selective etching of the silicon substrate or thin films results from the synergistic reactions of normal incidence positive ions and a non-directional flux of reactive neutrals. When considering the minimum feature size that can be replicated by plasma etching, unfortunately, several fundamental limitations appear to be looming. These include dimensions that do not scale with feature size: the depth of the disordered layers that form at the bottoms and sides of features, the thickness of protective layers that prevent the sides of features from eroding, and line edge roughness. In addition, an unprecedented control of the plasma etching process will be required, calling for a similar amount of control over the concentrations of plasma species, which in turn will require a high degree of control of the nature of the plasma reactor walls. This talk will review experimental studies from this and other laboratories that explore some of these issues in plasma-surface interactions at the substrate and at the chamber walls. [Preview Abstract] |
Wednesday, June 6, 2007 2:06PM - 2:42PM |
C3.00002: Plasma-particle interactions and their role in nanocyrstal formation in plasmas Invited Speaker: Nonthermal plasmas have recently been demonstrated to be capable sources of nanocrystals with some unique properties. The negative charge of particles acquired in a plasma strongly reduces particle agglomeration. Moreover, particles in plasmas are selectively heated by electron-ion and hydrogen recombination at the particle surface, heating the particles to temperatures that exceed the gas temperature by several hundreds of Kelvin. This property makes nonthermal plasmas uniquely suited for the synthesis of nanocrystals of covalently bonded materials, such as silicon, which require high temperatures for crystallization. Several plasma processes for the synthesis of silicon and germanium nanocrystals of different sizes and morphologies are discussed. The plasma properties are assessed with capacitive probes and emission spectroscopy. The particle density and size evolution in the plasma is studied via polarization-sensitive laser light scattering. Based on the experimentally determined plasma properties, the plasma-particle interactions are analyzed and their influence on the particle formation is discussed. Finally, several examples for the applications of plasma-synthesized nanocrystals are presented. [Preview Abstract] |
Wednesday, June 6, 2007 2:42PM - 3:18PM |
C3.00003: Plasma Etching of Nano-Scale Features Invited Speaker: As the technology moving to deep nanometer regime, patterning nano-scale semiconductor features with precision imposes many new challenges for plasma etching. Two of the challenges are evidently critical. One of the challenges is that as the sizes of nano-scale features shrinking down to the sub-10nm regime, plasma etching seems to approach to its `limits' in unprecedented ways. For instance, one may face the question of what is the smallest hole can be actually etched by plasmas. Another challenge is the precision controllability of nano-scale feature pattern transferring as the features sizes, masks materials and thickness being all shrinking down to the molecular cluster dimensions. In this paper, we summarize the recent results of studying plasma etching of true nano-scale features using variety of nano-scale patterns and masks, diblock copolymer (similar to resist) self assembled nano holes and lines and self-assembled organosilicate (similar to silicon oxide) nano patterns. Using samples patterned with arrays of nano hole or nano line dimensions in the range from 25nm down to sub-10nm, we studied plasma etching characteristics and challenges for transferring nano-scale patterns into different materials (silicon, and silicon dioxide) in different plasma chemistries and process conditions. By varying the dimensions and thickness of masks, the characteristics of aspect ratio dependence vs. `true' etching limits due to the sizes of sub-25nm nano-scale features were studied. The impacts and challenges of mask selectivity and line edge roughness (LER) to transfer sub-25nm patterns will be reviewed. A few proposed limiting factors of current etching tooling, underlying principles of different chemistries, and processing parameters and their advantage and drawback to etching nanometer scale features will also be discussed. [Preview Abstract] |
Wednesday, June 6, 2007 3:18PM - 3:54PM |
C3.00004: Nanoscale Challenges in Plasma-Surface Interactions Invited Speaker: Plasmas have been used for many years in various thin film processing technologies to transfer patterns via etching. Recent developments in semiconductor device manufacturing have increased plasma etch challenges. The historic shrink in critical dimension continues apace. New photoresist materials tend to etch faster and roughen more than previous resists. Important plasma etch goals includes controlling critical dimensions, maintaining high rates of etching, minimizing effects of local patterns, minimizing damage and contamination, and maintaining uniformity across 300 mm wafers. To achieve these goals, etch tool manufacturers often must explore a significant fraction of the enormous parameter space available in plasma etch tools, but with little guidance from fundamental understanding. In particular, a key problem is controlling feature shape with nanometer-scale precision. In this talk, I will describe results that focus on the principles of plasma-surface interactions, including the nature of the plasma-modified near-surface region, intrinsic nanoscale fluctuations during etching and the nature of plasma-induced surface roughness in organic polymers. [Preview Abstract] |
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