G. Haindl

Metal oxide/silicon oxide multilayer with smooth interfaces produced by in situ controlled plasma-enhanced MOCVD

Molybdenum oxide/silicon oxide and tungsten oxide/silicon oxide: multilayer with 24 periods and a period thickness of 9.2 nm were fabricated with plasma-enhanced MOCVD. The layer thickness was controlled by an in situ soft X-ray reflectivity measurement. For the deposition of the SiO2 layers, a new silicon organic precursor, pentamethylcyclopentadienyldisilane (Me5C5Si2H5) was used in an O-2 remote: plasma process. The high quality of multilayer interfaces was observed by cross-section transmission electron microscopy (TEM), the interface toughness was measured by hard X-ray reflectivity and diffuse scattering at grazing incidence experiments to be about 0.1 nm. Auger electron spectroscopy (AES) gives the information, that the silicon oxide is practically carbon free, and the carbon content of the metal oxides is low (<5%)

Effect of substrate heating and ion beam polishing on the interface quality in Mo/Si multilayers—X-ray comparative study

Three periodic Mo/Si multilayers were prepared by electron-beam evaporation at different conditions. An in situ polishing of amorphous Si layers with Ar+ ions of 800 eV energy and substrate heating to 170 degreesC were used for the two of them which were designed as multilayer mirrors optimized for 13 nm wavelength at normal incidence (30 periods of nominally 6.9 nm). A third multilayer was deposited at room temperature with reduced Mo layer thicknesses and number of periods to suppress interface roughness buildup. The goal was a comparison of ion beam polishing and substrate heating in terms of the interface quality and evaluation of the merit of more sophisticated depositions. The interfaces were studied by specular X-ray reflectivity and interface diffuse scattering measured at Cu K-alpha1 wavelength. The interface morphology parameters are very close on ion beam polishing and substrate heating indicating a similar relaxation mechanism of the growing surface. The main difference is a larger thickness of the Mo5Si3 interlayers with substrate heating, which has practical implications for peak reflectivities. On the other hand, a slightly worse interface replication here is appealing for the applications where a good imaging contrast is of primary importance. At room temperature deposition, the interface roughness is nearly doubled at 3 times smaller number of multilayer periods

Reactive ion etching with end point detection of microstructured Mo/Si multilayers by optical emission spectroscopy

Abstract Reactive Ion Etching (RIE) of Mo/Si multilayers (MLs) with double layer thicknesses of about 10 nm and total layer thicknesses between 80 nm and 300 nm prepared by electron beam deposition onto Si or oxidized Si substrates was investigated in a fluorine based plasma. Patterns with line widths in the range of 200 nm to several microns produced by e-beam- and UV-lithography were transferred into the MLs. For this application it is necessary to stop the etching process just after the ML is totally removed. For end point detection optical emission spectroscopy was used. The plasma was analyzed by optical emission spectroscopy and a significant drop of the atomic fluorine concentration at the multilayer/substrate interface was observed. An algorithm was developed to stop the etching process at the end point. AFM and TEM measurements show that the ML is totally removed and an over-etching of less than 6 nm occurs.

Thermal stability of W1−xSix/Si multilayers under rapid thermal annealing

W1−xSix/Si multilayers (MLs) (x⩽0.66) were deposited onto oxidized Si substrates, heat treated by rapid thermal (RTA) and standard furnace annealing up to 1000 °C for 30 s and 25 min, respectively, and analyzed by various x-ray techniques and Rutherford backscattering spectrometry. W1−xSix/Si MLs are more stable the higher the value of x because the driving force for interdiffusion is suppressed by the doping; the temperature for complete interdiffusion increases from 500 to 850 °C as x increases from 0 to 0.66. The as-deposited MLs were amorphous. Their thermal stability increases with increasing x. The interface roughness is independent of x but increases with increasing RTA temperature. The reflectivity of W1−xSix/Si MLs is lower than that of W/Si because of lower optical contrast.

W/Si multilayers deposited by hot-filament MOCVD

Abstract W/Si multilayers with eight double layers (double layer spacing d=20 nm) were deposited on Si [100] substrates using hot-filament (or hot-wire) metal organic chemical vapor deposition (MOCVD). The process was performed in a stainless steel reactor with a tungsten filament at a temperature of 1000°C and a substrate temperature of 190°C. The film thickness and growth was controlled by an in situ soft X-ray reflectivity measurement. The multilayers were characterized by cross-section transmission electron microscopy (XTEM) and sputter auger electron spectroscopy (AES). The results are compared to W/Si bilayers, which were deposited without a hot-filament at higher substrate temperatures (500–670°C).

Pentamethylcyclopentadienyl Disilane as a Novel Precursor for the CVD of Thin Silicon Films

There is a strong demand for alternative precursors for Si CVD that do not have the problems of highly pyrophoric silanes. Me5C5Si2H5 is an easy to handle liquid precursor that shows promise for CVD of Si-containing films. The fragmentation process (see Figure) has been studied by in-situ mass spectrometry and the pronounced leaving group character results in no carbon incorporation.

Metal/Silicon multilayers produced by low temperature MOCVD

W/Si and Mo/Si multilayers with 20 periods (doublelayer spacing d = 24nm) were deposited on silicon substrates using (remote-) plasma-enhanced MOCVD. The substrate temperature was below 200°C, which is necessary to avoid interdiffusion of the layers. The layer thickness and growth was controlled by an in situ soft x-ray reflectivity measurement. The characterisation of the multilayers showed an excellent growth of the silicon layers, while the metal layers are rough with embedded crystallites.