The adsorption and reaction of tetraethoxysilane (TEOS) with hydroxylated SiO2 has been studied over the range of 100–450 K using transmission infrared spectroscopy. At 100 K, TEOS [Si(OC2H5)4] condenses on SiO2. Upon warming in vacuum, some of the condensed phase TEOS desorbs molecularly while a significant portion of the layer enters into a physisorption state. The physisorption state maximizes near 250 K, with strictly molecular desorption occurring upon warming to higher temperatures. When exposure occurs at 450 K, Si(OC2H5)4 reacts to form adsorbed siloxanes, thought to be a mixture of (SiO)2Si(OC2H5)2 and (SiO)Si(OC2H5)3. The adsorbed di- and triethoxysiloxanes decompose completely on heating in vacuum to 900 K. The chemistry of TEOS on SiO2 has been modeled using ethanol adsorption. Exposure of SiO2 to ethanol at 450 K leads to the formation of an adsorbed ethoxide species. Ethanol is shown to spectroscopically and chemically model the surface bound siloxanes produced upon reaction of Si(OC2H5)4 with hydroxylated SiO2 at 450 K. The vibrational spectrum of adsorbed ethoxide (SiOC2H5) is very similar to that of the adsorbed siloxanes produced from the adsorption of Si(OC2H5)4. The ethoxy modes are assigned through comparison of C2H5OH and CH3CD2OH adsorption. The temperature dependence of the decomposition of the adsorbed ethoxide is similar to that of the TEOS derived siloxanes. Decomposition of the adsorbed siloxanes is shown to evolve primarily ethylene.

The dissociative adsorption of tetraethoxysilane (TEOS) on SiO2 and the subsequent decomposition of the resulting siloxane species has been studied using Fourier transform infrared transmission spectroscopy. The adsorption and decomposition processes have been studied as a function of the initial surface hydroxyl concentration. The results are compared to previous, complementary studies of the surface chemistry of ethanol on SiO2 surfaces and the temperature programmed desorption of TEOS on Si(100).

No abstract

The reactive adsorption and decomposition of tetraethoxysilane is compared on Si(100) and SiO2 surfaces. The adsorption and decomposition behavior is compared to that observed for ethanol adsorption on both these surfaces. Tetraethoxysilane and ethanol both decompose to produce ethylene and hydrogen on Si(100). Ethylene desorption is also observed from decomposition of these molecules on SiO2. Ethanol adsorption on SiO2 is shown to model the chemistry of tetraethoxysilane on this surface. However, ethanol is significantly more reactive than tetraethoxysilane on the clean Si(100) surface. The decomposition is shown to be reaction limited, and distinct from that of adsorbed ethylene. The adsorbed species produced from adsorption of tetraethoxysilane on SiO2 at 450 K is shown to be a mixture of di- and triethoxysiloxanes.

Articles you may be interested inIn situ chemical sensing in Al Ga N ∕ Ga N high electron mobility transistor metalorganic chemical vapor deposition process for real-time prediction of product crystal quality and advanced process control J. Vac. Sci. Technol. B 23, 1386 (2005 10.1116/1.1993616 In situ mass spectrometry in a 10 Torr W chemical vapor deposition process for film thickness metrology and real-time advanced process control Real-time process sensing and metrology in amorphous and selective area silicon plasma enhanced chemical vapor deposition using in situ mass spectrometry Dynamic rate and thickness metrology during poly-Si rapid thermal chemical vapor deposition from SiH4 using real time in situ mass spectrometry Mass spectrometry has been exploited for rapid real-time sensing of both reactant and product species in single-wafer rapid thermal chemical vapor deposition ͑RTCVD͒ of polycrystalline Si from SiH 4 . Active mass spectrometric sampling at pressures to 5 Torr is achieved using two-stage differential pumping of a sampling aperture in the exhaust stream, leading to response times as short as ϳ3 sec to concentration and pressure changes in the reactor during a process carried out in ϳ30 sec. In addition to reactant species, gaseous reaction byproducts have been identified and differentiated from cracking fragments of the reactant through relative intensities of mass fragments as a function of wafer temperature ͑i.e., reaction rate͒. For RTCVD of poly-Si from SiH 4 , carried out in the range 450-800°C at 5 Torr in 10% SiH 4 /Ar, mass spectra reveal not only the time dependence of reactant ͑monitored by SiH 2 ϩ , 30 amu͒, but also-at higher temperatures-reactant depletion and product generation ͑from H 2 ϩ , 2 amu͒. These results demonstrate a basis for using mass spectrometry in real-time process diagnostics and control.