Sundar Ramamurthy

Interaction of silicate liquid with a sapphire surface

Abstract The wetting behaviour of a calcium aluminosilicate liquid in contact with sapphire of four crystallographically different orientations has been investigated using scanning electron microscopy and atomic force microscopy. When continuous glass films are heat treated at 1600 and 1700°C, the glass dewets the surface to give islands of glass. The heat treatment also causes the alumina surfaces to facet which, in turn, influences the shape of the glass islands. The morphology of the islands with respect to the orientation of the facets is essential in understanding the liquid–solid interfacial energies and the importance of the orientation of the facets. This approach allows sequential study of the interaction between the facets and the silicate liquid. The equilibrium composition of the silicate changes as the temperature changes: solution, precipitation and evaporation processes may all affect the facet and step morphology. This study directly emphasizes the relevance of anisotropy in the α-Al2O3 crystal structure which may ultimately control some of the key issues of processing the materials.

Ni/sub 2/Si and NiSi formation by low temperature soak and spike RTPs

As the size of metal oxide semiconductor devices continues to be scaled down to sub-90 nm, novel materials must be integrated successfully in order to meet the technical demands. Nickel silicide (NiSi) is being considered as an alternative material to cobalt silicide (CoSi2) for the self-aligned silicide process, because it forms at lower temperatures with less silicon consumption and is compatible with SiGe. In order to prevent excessive silicidation in narrow gate lines and at the edges of source/drain regions, NiSi integration requires limiting silicidation kinetics via reduced thermal budgets followed by forming the low resistance phase. This paper focuses on the low temperature regime of the Ni-Si reaction through the use of soak RTP at 300degC and spike RTP at 300 ~ 400degC. In order to study the formation of Ni2Si and NiSi and the transformation from Ni2Si to NiSi, the silicide films are characterized by Rs sheet resistance measurements, XRD for phase identification, and TEM for microstructure. The intermediate phase of Ni2Si is formed at 270degC and its growth is observed with increasing anneal time. At temperatures above 300degC, the NiSi phase is found in addition to the Ni2Si phase, and the transformation from Ni2Si to NiSi is observed. The sequence of the Ni2Si-NiSi transformation involves the initial formation of NiSi and the change in the alignment of the crystal planes as the low resistance phase of NiSi forms. Two RTP schemes, soak RTP and spike RTP, follow parallel trends in the sequence of the Ni2Si-NiSi transformation with marked differences in the reaction kinetics

Enabling single-wafer low temperature radical oxidation

This paper reports the study of low temperature radical oxidation by using highly concentrated ozone gas in a single-wafer rapid thermal processor. As device structures continue to shrink in geometry, integration of new materials and the complexity of process flows demand growth of high quality oxides with reduced thermal budget. This requirement poses a major challenge for thermal oxidation since lowering the process temperature causes degradation of oxide film quality, in general. Based on the fact that RadOxtrade have already demonstrated unique advantages in a variety of applications for current devices, it is expected that enabling radical oxidation at lower temperature would be beneficial for advanced devices. Highly concentrated ozone gas was employed as the source of radicals. The ozonator used for this study is capable to produce a gas mixture up to 90 vol% ozone (in oxygen) safely by adsorption/desorption technique. Several design of experiments (DOE) were carried out for thickness and thickness non-uniformity study, and film properties were compared with baseline processes using non-contact electrical measurements

Ultra Low Temperature NiSi Processing

Manuscript not released forpublication due to legal issues.