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A new high spatial resolution non-contact temperature measurement technique (thermal scanning electron microscopy, ThSEM) is demonstrated. It employs temperature dependent thermal diffuse scattering in electron backscatter diffraction (EBSD) in a scanning electron microscope (SEM). Unlike conventional scanning thermal microscopy, which uses contact probes, ThSEM is a non-contact method. In contrast to optical temperature mapping techniques, ThSEM does not have the spatial resolution limitation that arises from the optical wavelength and theoretically can reach a resolution of <10 nm. The hardware setup is very similar to the EBSD system in an SEM, which can make the integration of temperature mapping into an SEM relatively straightforward. Moreover, multiple signals or contrast mechanisms, such as temperature distributions, grain orientation maps, topographic images and elemental maps can be obtained from the same sample area depending on the specific SEM capability. This technique thus adds a new channel-the temperature signal-to the collection of existing SEM signals.

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α α′ α″ α‴ Poly-tetrafluoro-p-xylylene (PA-f ) has been evaluated as an interlayer dielectric for multichip modules and integrated circuits, and its properties are reported. It has a lower dielectric constant and higher thermal stability than parylene-n (PA-n). The as-deposited films have very low crystallinity. The crystallinity increases as the film is annealed. Thermogravimetric analysis has shown that these films lose weight at temperatures higher than 480 °C. A shrinkage in the films of ∼10% was observed when annealed in a vacuum at a temperature of 425 °C. The as-deposited film has a low dielectric constant of 2.38 and a volume resistivity of 1.3×1016 Ω cm. The refractive index at optical wavelengths was 1.3 for as-deposited samples and it increased with annealing temperature. The stress levels observed after annealing are also lower (20 MPa) than for PA-n (40 MPa). The hardness, as determined by a microindentor, of PA-f was 0.56 GPa in the bulk, but the surface hardness was ∼1.0 GPa. The conformal nature of these films permitted successful coating of micron-sized gaps having an aspect ratio of 1.5–2. Diffusion of Cu into PA-f is reported here and is contrasted with Cu/PMDA-ODA polyimide. Scanning electron microscopy of film cross sections shows microstructure changes above 350 °C. The low dielectric constant and high thermal stability of PA-f makes it a good insulator for high-speed interconnection applications.

Thermal scanning electron microscopy is a recently developed temperature mapping technique based on thermal diffuse scattering in electron backscatter diffraction in a scanning electron microscope. It provides nano-scale and non-contact temperature mapping capabilities. Due to the specific temperature sensitive mechanism inherent to this technique, the temperature resolution is highly material dependent. A thorough investigation of what material properties affect the temperature resolution is important for realizing the inherent temperature resolution limit for each material. In this paper, three material dependent parameters—the Debye-Waller B-factor temperature sensitivity, backscatter yield, and lattice constant—are shown to control the temperature resolution.

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A thermal preannealing technique for limiting diffusion of Cu into parylene-n (PA-n) in an interconnection application has been demonstrated. These thermal pretreatments enhance fabrication latitude for PA-n. The Cu was deposited by partially ionized beam technique and the PA-n was vapor deposited. Diffusion was investigated using the Rutherford backscattering (RBS) technique. Cu was found to diffuse into as-deposited PA-n at temperatures of about 623 K. It was also found that with certain thermal pretreatment of PA-n, this diffusion could be stopped for temperatures as high as 623 K. Pretreatment at temperatures of 523 and 623 K were successful in stopping diffusion. The microstructure has been investigated using scanning electron microscopy and RBS. The annealing causes formation of lengthy grainlike structures perpendicular to the surface. Under some preanneal conditions, the grain structure reaches the surface and diffusion is observed for these samples. The preannealing technique has been successful in reducing diffusion caused at soldering temperatures (623 K) in a Cu/PA-n interconnection scheme. It must be noted that pretreatments at temperatures of 573 K were generally not effective, except for one case where the temperature was ramped down over a 2 h period.

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