3 results
Employing Thin Film Failure Mechanisms to Form Templates for Nano-electronics
- Rainer Adelung, Mady Elbahri, Shiva Kumar Rudra, Abhijit Biswas, Seid Jebril, Rainer Kunz, Sebastian Wille, Michael Scharnberg
-
- Journal:
- MRS Online Proceedings Library Archive / Volume 863 / 2005
- Published online by Cambridge University Press:
- 01 February 2011, B7.3/O11.3
- Print publication:
- 2005
-
- Article
- Export citation
-
Recently, we showed that thin film stresses can be used to form well aligned and complex nanowire structures [1]. Within this approach we used stress to introduce cracks in a thin film. Subsequent vacuum deposition of metal leads to the formation of a metal layer on the thin film and of metal nanowires in the cracks of the film. Removal of the thin film together with the excess metal cover finishes the nanowire fabrication on the substrate. As stress can be intentionally introduced by choosing an appropriate thin film geometry that leads to a stress concentration, the cracks and consequently the nanowires can be well aligned. Meanwhile, we have demonstrated how to form thousands of parallel aligned nanowires, x-and y-junctions or nanowires with macroscopic contacts for sensor applications, simply by applying fracture mechanics in thin films. Christiansen and Gösele called this approach “constructive destruction” in a comment in Nature Materials [2]. This gives a hint how to overcome some problems of the approach, arising from the limits of thin film fracture. A generalization of the fracture approach by being “more destructive” can overcome this limitations. For example, it is difficult to form pairs of parallel wires with a nanometer distance of the pair, but a micrometer separation between the individual pairs. Structures like this are useful for many contact applications including sensor arrays or field effect transistors. As well as thin film fracture, thin film delamination can be well controlled by fracture mechanics. Our latest experiments show that the combination of both, fracture and delamination, forms an ideal shadow mask for vacuum deposition. Cracks with delaminated sides were used as templates for the deposition of pairs of parallel wires consisting out of different materials with only a few 10 nm separation. First, a metal was sputter deposited under an angle of approx. 45° through the delaminated crack, which was used as a shadow mask. Afterwards, a second deposition metal is deposited under the opposite 45° angle with respect to the sample normal, having the crack located in the middle between both deposition sources. The angle, the delamination height and the crack width determine the separation of the nanowire contacts. We present several examples which show how these mechanisms of mechanical failure of thin films can be turned into useful templates for various nanostructures. We will focus here on two thin film systems, that can be easily deposited in every lab. These are wet chemically deposited photo-resist and flash evaporated amorphous carbon. These examples are compared with finite element simulations of the thin film stress with the ANSYS program. Moreover, we show how the delamination cracks can be also used as masks for the removal of material. Channals with a width down to 20 nm produced by ion beam sputtering are shown.
Radiotracer Diffusion Measurements of Noble Metal Atoms in Semiconducting Organic Films.
- Michael Scharnberg, Jörn Kanzow, Klaus Rätzke, Rainer Adelung, Franz Faupel, Stephan Meyer, Jens Pflaum
-
- Journal:
- MRS Online Proceedings Library Archive / Volume 871 / 2005
- Published online by Cambridge University Press:
- 01 February 2011, I6.31
- Print publication:
- 2005
-
- Article
- Export citation
-
The application of organic field effect transistors (OFETs) for large scale low-cost electronic devices has lead to intense research. Diindenoperylene (DIP) thin films on SiO2 are a prominent system due to their high structural out-of-plane order. While bottom contact OFET structures can be realized easily, preparation of top contacts might cause diffusion of metal atoms (typically Ag or Au) deep into the organic film changing the injection properties at the interface. These properties are of great importance for device fabrication. Therefore, only by understanding the diffusion behaviour of metals into the organic layer, formation of well defined interfaces and control of their properties will become possible. For a better understanding of the diffusion of noble metal atoms into crystalline organic films, a radiotracer technique has been used to obtain diffusion profiles for Ag and Au diffusion in crystalline DIP films. For Ag diffusion in DIP, the decrease in Ag concentration of four orders of magnitude within the first few nanometers indicates that most of the metal atoms remain near the surface while small amounts can penetrate deep into the thin film and can even accumulate at the interface between organic film and the silicon substrate. A comparison with diffusion profiles obtained for polymers indicates that the interplay between diffusion and immobilization by aggregation also determine the diffusion behaviour of metals in organic crystalline materials. Latest experiments support this interpretation of the diffusion profiles. Single atoms are highly mobile in the organic crystalline material due to the weak interaction between the metal and the organic material. Therefore, most of the single atoms that penetrate into the material do so during the initial phase of the deposition. When more and more atoms arrive at the surface, cluster formation sets in. Due to the high cohesive energy of the metal the atoms can not leave the cluster and become immobilized. After deposition of a closed surface layer no further metal diffusion should be observed. With the knowledge about the diffusion processes gained by the radiotracer measurements control of process parameters and development of barrier layers in sub-monolayer range should be possible.
In-situ XPS Study of ALD Ta(N) Barrier Formation on Organosilicate Dielectric Surface
- Junjun Liu, Junjing Bao, Michael Scharnberg, Paul S. Ho
-
- Journal:
- MRS Online Proceedings Library Archive / Volume 812 / 2004
- Published online by Cambridge University Press:
- 17 March 2011, F2.6
- Print publication:
- 2004
-
- Article
- Export citation
-
Beams of nitrogen and hydrogen radicals were investigated as surface pre-treatment and process enhancement techniques for atomic layer deposition (ALD) of tantalum nitride barrier layer on a dense organosilicate (OSG) low k film. In-situ x-ray photoelectron spectroscopy (XPS) studies of the evolution of the low k surface chemistry revealed an initial transient growth region controlled mainly by the substrate surface chemistry. Pre-treatment of the low k surface with radical beams, particularly with nitrogen radicals, was found to enhance significantly the chemisorption of the TaCl5 precursor on the OSG surfaces. The enhancement was attributed to the dissociation of the weakly bonded methyl groups from the low k surface followed by nitridation with the nitrogen radicals. In the subsequent linear growth region, atomic hydrogen species was able to reduce the chlorine content under appropriate temperature and with sufficient purge. The role of the atomic hydrogen in this process enhancement is discussed.