Physical Sputter Etching

Recently, Lin et al. [81] used focused ion beam (FIB] milling to pattern photonic crystals [PhCs] with lattice periods of 300 nm to 1 pm. The milled surface was smooth, indicating FIB can be an effective method for nanophotonic fabrication. However, the major question for this method is the scalability of the process for large-scale devices. 

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Uses. The chemical inertness, thermal stability, low toxicity, and nonflammability of PFCs coupled with their unusual physical properties suggest many useflil applications. However, the high cost of raw materials and manufacture has limited commercial production to a few, small-volume products. Carbon tetrafluoride and hexafluoroethane are used for plasma, ion-beam, or sputter etching of semiconductor devices (17) (see loN implantation). Hexafluoroethane and octafluoropropane have some applications as dielectric gases, and perfluorocyclobutane is used in minor amounts as a dielectric fluid. Perfluoro-1,3-dimethyl cyclohexane is used as an inert, immersion coolant for electronic equipment, and perfluoro-2-methyldecatin is used for... 

Figure 1(a) shows the etch rates of niobium oxide pillar and Si film, and the etch selectivity of Si to niobium oxide as a function of CI2 concentration. The etch condition was fixed at coil rf power of 500 W, dc-bias to substrate to 300 V and gas pressure of 5 mTorr. As the CI2 concentration increased, the etch rate of niobium oxide pillar gradually decreased while Si etch rate increased. It indicates that the etch mechanism of niobium oxide in Cl2/Ar gas is mainly physical sputtering. As a result, the etch selectivity of Si film to niobium oxide monotonously increased. The effect of coil rf power on the etch rate and etch selectivity was examined as shown in Fig. 1(b). As the coil rf power increased, the etch rates of niobium oxide and Si increased but the etch rate of niobium oxide showed greater increase than that of Si. It is attributed to the increase of ion density with increasing coil rf power. Figure 1 (c)... 

The positive ions therefore arrive at the cathode with increased kinetic energy and material is removed from its surface by competitive physical sputtering, in which momentum transfer to the surface is involved, as well as chemical plasma etching, through the formation of volatile species, which... 

The plasma parameters of f=5 cm mln (at STP), p=0.015 torr and w 100 watts are the same In all cases. The ESCA data Immediately affirm that both molybdenum and copper are Incorporated Into the polymer films although as previously noted the method of cathode erosion must be different In the two cases, (chemical plasma etching versus physical sputtering). Consideration of the relative signal Intensities, corrected for the total relative sensitivities of the core levels, derived from standard homogeneous samples, allows estimates of the empirical formulae to be written for these materials as follows [C3F4 oOo.6 °0.3ln... 

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