Giancarlo Meneghini

Highly sintered nickel oxide : surface morphology and FTIR investigation of CO adsorbed at low temperature

Abstract The monolayer of CO molecules adsorbed at low temperature on highly sintered nickel oxide, gives rise to a very symmetric IR absorption band at 2136 cm −1 ( θ max ) with a full-width at half-maximum (FWHM) of 3.7 cm −1 . This band shifts to higher frequenc upon decreasing the coverage, reaching the 2152 cm −1 value for θ→0. The observed shift is due to changes in the lateral interactions (dynamic and static) among the adsorbed molecules. The observed spectral simplicity implies that most of the adsorbed CO molecules occupy crystallographically identical sites with a similar environment. Moreover, the remarkably small half-width indicates that inhomogeneous broadening effects, due to surface defects, are very small and that NiO microcrystals behave as single crystals. The morphology of microcrystals has been studied by SEM, AFM and HRTEM techniques: it was concluded that the surface termination of the sample is mainly represented by the (100) and (111) faces.

Electron Beam Lithography Simulation on Homogeneous and Multilayer Substrates

A fast simulator for electron beam lithography, called SELID, is presented and applied in the case of homogeneous and multilayer substrates. For exposure simulation, an analytical solution based on the Boltzmann transport equation is used instead of the Monte Carlo. All important phenomena (forward scattering, backscattering, generation of secondary electrons) have been taken into account for a wide range of e-beam energies. The case of substrates consisting of more than one layer (multilayer) is considered in depth as it is of great importance in e-beam patterning. Results of simulation are compared with experimental ones in the case of single pixel exposures. Additionally, simulation results are compared with experimental ones for isolated and dense patterns in the sub-half-micron range, on conventional positive resist on homogeneous and multilayer substrates. By using SELID, forecast of resist profile with considerable accuracy for a wide range of resists, substrates and energies is possible. Additionally, proximity effect parameters are extracted easily for use in any proximity correction package.

Simulation of chemically amplified resist processes for 150 nm e-beam lithography

A fast simulator for e-beam lithography called SELID, is presented. For the exposure part, an analytical solution based on the Boltzmann transport equation is used instead of Monte Carlo. All-important phenomena (backscattering, generation of secondary electrons) are included in the calculation. The reaction/diffusion effects occurring during post exposure bake in the case of chemically amplified resists (CARs) are taken into account. The results obtained by the simulation are compared successfully with experimental ones for conventional and CARs. The case of substrates consisting of more than one layer is considered in depth as being of great importance in e-beam pattering. By using SELID, forecast of resist profile with considerable accuracy for a wide range of resists, substrates and energies is possible as long as the evaluation of proximity effect parameters.

Aqueous base developable epoxy resist for high sensitivity electron beam lithography

Aqueous base developable, chemically amplified negative resists, based on epoxy chemistry are introduced and evaluated for high resolution, high speed e-beam lithography. These resists are formulated using partially hydrogenated poly(hydroxy styrene) and epoxy novolac polymers and they do not suffer from thermal instability of unexposed regions during processing. Degree of hydrogenation controls the aqueous base solubility and micro phase separation phenomena. Reduction of edge roughness compared to the pure epoxy systems is observed whereas the absence of swelling phenomena allows lithography up to 100 nm regime.

Electron-beam lithography on multilayer substrates: experimental and theoretical study

A fast simulator for electron beam lithography called SELID, is presented. For the exposure part, an analytical solution based on the Boltzmann transport equation is used instead of Monte Carlo. This method has been proved much faster than Monte Carlo. All important phenomena are included in the calculation. Additionally, the reaction/diffusion effects occurring during post exposure bake in the case of chemically amplified resists are taken into account. The result obtained by the simulation are compared successfully with experimental and other simulation results for conventional and chemically amplified resists. The case of substrates consisting of more than one layer is considered in depth as being of great importance in electron beam patterning. By using SELID, it is possible to forecast the resist profile with considerable accuracy for a wide range of resists, substrates and energies. Additionally, proximity effect parameters are extracted easily for use in any proximity correction package.

Silylation and Dry Development of Chemically Amplified Resists SAL601*, AZPN114*1, and Epoxidised Resist (EPR*1) for High Resolution Electron-Beam Lithography

A comparative study of high resolution positive imaging obtained after liquid-phase silylation and dry development with two commercial and one experimental electron-beam chemically amplified resists (CARs), namely SAL601, AZPN114, and EPR (EPoxidised Resist) is presented. 150 nm lines and spaces are obtained for all resists, while 100 nm lines are achieved with AZPN114 and EPR at 50 kV exposures. The exposure doses for AZPN114 and SAL601 are 10 µC/cm2 and 20 µC/cm2, respectively, while EPR is considerably faster (1.5 µC/cm2). Chlorosilanes are used for EPR silylation, while SAL601 and AZPN114 are silylated with hexamethyl cyclo tri silazane (HMCTS) or bis (di methyl amino) di silane (B(DMA)DS). SAL601 shows less silylation selectivity between exposed and unexposed areas possibly due to insufficient crosslinking. Implications of the presented processes on low-energy electron-beam lithography are discussed.

CH4/H2 RIE of InGaAsP/InP materials: An application to DFB laser fabrication

Abstract In this paper we present the characterization and application of the CH4/H2 RIE technique for fabrication of optoelectronic devices on InGaAsP/InP materials. We obtained depth damage profile by Photoluminescence (PL) measurements and chemical etching. Using appropriate processing parameters a 15 nm deep damaged layer was measured on InGaAsP. Three CH4/H2 RIE process steps were successfully applied to the fabrication of emitting at 1.55 μm BRS-DFB lasers. The devices demonstrated cw operation at a threshold of 24 mA with a side mode suppression of about 30 dB.

Resolution limitation in EBL optical grating fabrication on InGaAsP/InP substrate

Abstract Monte Carlo (MC) simulation and experimental point exposure energy distribution on InP substrate are used to described the total energy response of 1 st and 2 nd order gratings for InP based solid state lasers. A good agreement between theoretical calculations and experimental obtained data is achieved. The triple gaussian approximation of the energy density profiles is suggested by an analysis of computed primary electron energy spectra. Examples of both dry and wet etched gratings in InP substrate and InGaAsP epitaxial layers, which fit with calculations are given.