FOROB II

BAVARIAN JOINT RESEARCH PROGRAM FOR SURFACE TECHNOLOGY

II.2 Chemical vapour deposition of thin films with high relative permittivity instanced by barium-strontium-titanate

Field of work:

On account of its changeable permanent polarisation, its high relative permittivity and its cycle-stability, the high-k as well as ferro-electric material barium-strontium-titanate (BST) has a high potential of implementation for very large scale integrated circuits, such as dynamic and non-volatile random access memory (DRAM, FRAM). This was shown by investigations of BST thin films, which were generated for example by sol-gel processes. However, production methods are required for the generation of very thin layers upon 3D-structured surfaces for storage application. Only low pressure chemical vapour deposition (LPCVD) meets this requirement.

Deposition processes for generating the ferro-electrical layer systems BST by LPCVD are conducted by use of suitable metal-organic precursors, which will be specificaly developed over the course of the project. The materials are vapourized and deposited through thermal decomposition. A horizontal cold-wall reactor for single-disc processes is at disposal and will be modified for the intended application. The investigation of the layer-properties comprises an extensive characterisation of the layers in interaction with optimisation of the deposition process. The essential characteristic of the prcursor includes a sufficiently high vapour pressure along with a high thermal stability, which allows the decomposition of the substance to take place at the surface of the substrate. Additionally the deposition of carbon must be reduced to a minimum.