F. C. Schilling

Nuclear‐magnetic‐resonance characterization of doped SiO2 films used in integrated circuits

Phosphorus‐doped silicon dioxide dielectric films, prepared by plasma‐enhanced chemical‐vapor deposition at low temperature (400 °C), play a critical role in the reliability of very large scale integration devices. The phosphorus in the phosphosilicate glass (PSG) neutralizes the effect of mobile ion species and improves the glass flow, resulting in better gap filling and improved planarization. To extract the maximum contribution from this and other doped films (boron and germanium doped) in advanced sub‐0.5 μm complimentary metal‐oxide‐semiconductor technologies, it is necessary to understand dopant incorporation and the effects of variation in the exposure to water, dopant concentration, and high‐temperature annealing. An analysis of PSG by 1H, 29Si, and 31P solid‐state nuclear magnetic resonance establishes the chemistry of the phosphorus dopant incorporation and the effect of moisture on the glass structures. Exposure to water results in a depolymerization of the PSG structures and a concurrent decre...

Solid-state thermochromism and piezochromism in the polysilylenes

The polysilylenes exhibit complex solid-state structures and electronic properties. In this report the solid-state conformational structures of symmetrically substituted poly(di-n-alkylsilylenes) are described. Comparisons between the different structures and their respective UV absorption characteristics demonstrate that the relationship is complex and aspects of molecular geometry beyond chain conformation must be considered. The thermochromic and piezochromic behavior of several of these polysilylenes is discussed. The all-trans conformation of the silicon backbone is associated with both phenomena. The properties of several polysilylene copolymers have also been investigated. We find that some of the copolymers form a well-ordered structure and exhibit absorption characteristics similar to the crystalline phases of the corresponding homopolymers.

Comparison of structural and electronic absorption properties of poly(di-n-hexylsilane) and poly(di-n-butylsilane)

Abstract The Si-backbone in crystalline poly(di-n-hexylsilane) (PDHS) is known to be all-trans, whereas the chain conformation of poly(di-n-butylsilane) (PDBS) has been shown to form a 7/3-helix in the solid state. It is demonstrated here that all-trans PDBS can be produced by two methods: precipitation from dilute solution at low temperature, and by application of moderate pressure to the solid polymer. The absorption maximum of all-trans PDBS is red-shifted 40 nm from that of the 7/3-helical form. The effect of pressure on the solid-solid phase transitions in both PDBS and PDHS is presented.

RADIATION INDUCED MORPHOLOGICAL CHANGES IN A SEMI-CRYSTALLINE POLYMER: A 13C NMR STUDY

The structural and morphological changes occurring in poly(ethylene oxide) (PEO) when exposed to gamma-irradiation have been investigated by both solution and solid state 13C NMR techniques. The most striking change in the solid state CP/MAS 13C NMR spectrum is the growth of a resonance peak at 71.9 ppm as a function of radiation dose. This resonance peak is assigned to the crystalline carbons arising from the local rearrangements of polymer chains upon irradiation. The chemical shift separation of 1.4 ppm between the amorphous and crystalline resonances is attributed to differences in polymer chain conformations. Solution NMR data suggest the predominance of chain scission for samples irradiated in air, while vacuum-irradiated samples appear to be predominantly cross-linked.