A customer purchases services from a supplier to which VAT at the applicable rate is added but VAT was not actually due. Is the customer able to recover these payments by bringing an unjust enrichment claim against the Revenue and Customs Commissioners? “Yes”, answered the Court of Appeal, on the basis that as a matter of “economic reality” the Commissioners were enriched at the expense of the customers, and that such an enrichment was unjust because VAT was not actually due. Lord Reed, giving the unanimous judgment of the Supreme Court, reversed that decision: Investment Trust Companies (In Liquidation) v Revenue and Customs Commissioners [2017] UKSC 29; [2017] 2 W.L.R. 1200. The customers did not have an unjust enrichment claim against the Commissioners because their enrichment was not “at the expense of” the customers.

We report simultaneous measurements of time resolved reflection and transmission of low intensity 1.06 μm, 35 ps pulses subsequent to excitation of 50 KeV, 1016 cm−2 boron implanted silicon by 0.53 μm 35 ps pulses of varying energy densities. The samples are examined by optical and scanning electron microscopy in conjunction with defect etching. These data are discussed from the point of view of both the thermal melting model and plasma model.

We demonstrate, for the first time, a technique for the fabrication of polysilicon resistors with excellent control and temperature characteristics: a standard deviation of 2.5 Ω/□ and temperature variation of -5.6% from 25° to 125°C for 1.96kΩ/□, 4.5 × 1014 cm˗2 boron implanted polysilicon resistors. The technique is based on fabricating resistors in laser recrystallized polysilicon on SiO2. Resistor performance is compared to that of similar resistors fabricated in standard LPCVD polysilicon and in single crystal silicon.

We report an investigation of the effects of laser processing on the thermal oxides of polysilicon. LPCVD polysilicon, 500 nm thick, deposited on 500 nm thermal oxide of single crystal silicon was laser processed at various stages in the process sequence for device fabrication. Effects of CW Ar+ and pulsed 1.06 and 0.53 μm laser processing were investigated. Laser annealed polysilicon was oxidized in a steam ambient. Using a second level of polysilicon, guard ring diode and capacitors were fabricated. Electrical characterization revealed an improvement in breakdown field strengths of these oxides without deleterious effects on any of the associated interfaces.

The electrical effects associated with pulsed laser irradiation of thermal oxides of silicon were investigated. Three of the functions performed by thermal oxides are control of field effects, junction passivation and electrical isolation. Representative oxide thicknesses suitable for these applications were studied: ≈ 100 nm; ≈ 500 nm and ≥, 1.0 μm respectively. The oxides were irradiated by a repetitively Q-switched Nd 3+:YAG laser operated at the fundamental frequency. The key laser parameters of energy and power density were varied over a wide range, from no change to the onset of discernible change and irreversible damage. The range of energy densities over which the oxide was not electrically degraded was established for each thickness of the oxide. This range of energy densities is compared to the useful range of energy densities for annealing polysilicon and for activating an implant through an oxide. The electrical data was obtained using a mercury probe and through the analysis of a large number of MOS capacitors formed on the irradiated oxides. Parameters measured include: breakdown voltages, surface state charge densities and flat band voltages.

Large crystals of silicon were obtained via pulsed laser annealing of thinfilms of fine grain CVD polycrystalline silicon. These films were analyzed using a novel technique that provides rapid feedback of crystallographic and defect information. The technique uses very shallow angle metallurgical sections in conjunction with chemical decoration and scanning electron microscopy and results in excellent depth resolution (<10 nm) across large spatial distances (>100 μm). The technique was used to reveal conversion of very large areas (≈ 1 mm 2) of polysilicon films deposited on silicon into single crystal film, albeit with point defects, without requiring the melt depth to reach the polysilicon/silicon interface. A gradual transition from single crystal to increasingly polycrystalline material was observed going from top to bottom of the initially uniform polycrystalline film depending on the pulse energy used. Polysilicon on top of an oxide layer, on the other hand, transforms into large (≈ 10 μm) single crystals with grain boundaries penetrating the entire polysilicon film thickness. These experimental results shed new light on two very important questions: (1) Is laser annealing entirely an epitaxial process or is it strongly influenced by the thermal properties of the underlying substrate, and (2) Whether substantial regrowth of polysilicon requires equilibrium thermodynamics.