Effects of various cleaning and annealing methods on the removal of the residue and physical damage remaining on the exposed silicon surface after the oxide overetching by C4F8 magnetized inductively coupled plasmas were studied. X-ray photoelectron spectroscopy, current–voltage characteristics of Au Schottky diodes, and high resolution transmission electron microscopy were used. The formation of Co silicide was also studied using x-ray diffraction, four-point probe, and Rutherford backscattering spectrometry to investigate the effectiveness of the cleaning and annealing methods on the residue and damage removal. Thicker than 65 Å of polymer and thicker than 40 Å of physical damage remained on the silicon surface etched by C4F8 magnetized inductively coupled plasmas. Among the investigated cleaning methods, SF6/O2 soft cleaning was the most effective in removing the residue. SF6/O2 soft cleaning was also the more effective method in removing the physical damage compared to the annealing methods used in the experiment. Stable Co silicide was formed on the silicon surface after O2 plasma cleaning followed by HF dipping or SF6/O2 soft cleaning. Sheet resistances measured on these silicides were close to those of the silicide formed on the clean control silicon surface. Surface residue not the physical damage appeared to affect the formation of Co silicides, and fluorine rich residue appears to prevent the formation of stable silicide more compared to carbon rich residue.
The multilayer desorption behavior of 2,5-diidothiophene and the dendritic aggregation of photochemical reaction products during the desorption of 2,5-diiodothiophene multilayers have been studied. Like many other aromatic compounds, 2,5-diiodothiophene shows a multilayer desorption behavior different from the typical zeroth-order kinetics, a metastable desorption peak growth at approximately 220 K followed by a thick multilayer peak growth at approximately 235 K. Traditionally, these desorption behaviors have been attributed to the formation of three-dimensional clusters. This paper provides the direct evidence of this clustering process by producing nondesorbing photoreaction products in the multilayer and by imaging their clusters after the multilayer desorption. Oligothiophene species are produced via photochemical reactions of 2,5-diiodothiophene during the multilayer deposition at approximately 180 K in ultrahigh vacuum (UHV). Upon heating the multilayer to room temperature, the oligothiophene species forms into fibrous aggregates with a fractal dimension varying from 1.37 to 1.81 depending on their surface concentration. Using a topographical alteration of the substrate with a repeating pattern, these oligothiophene fibers can be aligned to a certain direction. This may allow in-situ fabrication of aligned conjugated polymer fibers directly on a target substrate.
Effects of magnetic field on oxide etching characteristics in planar type radio frequency inductively coupled plasma J.Radiation damage and contamination on the silicon surfaces etched by magnetized inductively coupled C 4 F 8 plasmas were investigated. X-ray photoelectron spectroscopy ͑XPS͒, secondary ion mass spectrometry, spectroscopic ellipsometry, and transmission electron microscopy were used to characterize contamination and high resolution transmission electron microscopy, and I -V characteristics of Schottky diodes fabricated on the etched and/or annealed silicon surface were used to evaluate radiation damage. As the magnetic field applied to the inductively coupled plasmas increased from 0 to 12 G, the thickness of the residue layer formed on the silicon surface increased with the increase of SiO 2 etch rate and selectivity. XPS analysis showed that the composition of the residue layer changed from fluorine rich to carbon rich film by changing the carbon binding state from C-CF x to C-C. Dense defects distributed about 40 Å deep from the etched silicon surface were found for the 0 G condition and thicker but less dense defects were observed for higher magnetic field conditions. The electrical damage estimated from the I -V characteristics of Schottky diodes was reduced with increasing applied magnetic field strength.
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