Ammonia as a precursor in electron-enhanced nitridation of Si(100)

Abstract

Electron beam‐enhanced nitridation of Si(100) using ammonia as a precursor at 110 K was studied with electron‐stimulated desorption, XPS, AES and high‐resolution electron energy‐loss spectroscopy (HREELS). Hydrogen ion kinetic energy distributions from adsorbed ammonia exhibited a component from NH3(a) at 7.8 eV, from NH2(a) at 5.4 eV and from H(a) at 4 eV. Formation of the nitride following electron beam irradiation of adsorbed ammonia was shown by both N 1s at 398 eV and Si 2p at 102 eV in XPS spectra. From HREELS spectra following electron beam irradiation, we are able to show that the electron beam is highly effective in removal of hydrogen from NHx(a) (x = 3,2) and from the silicon surface. Electron‐stimulated desorption of adsorbed hydrogen and dissociation of adsorbed NHx (x = 3,2) are believed to be responsible for enhanced nitridation. Nitride can also form on the surface by irradiating the surface in an ammonia environment at 110 K. A nitride growth rate of 1 Å min−1 was obtained from the bulk Si LVV AES signal intensity attenuation. Copyright © 2000 John Wiley & Sons, Ltd.

Role of surface strain in the subsurface migration of adsorbates on silicon

“…43 However, experimental results have shown that desorption of NH 3 is a minor channel of desorption. 16,46 This indicates that an alternative theoretical approach is needed in order to better describe insertion processes.…”

Cooperative nitrogen insertion processes: Thermal transformation ofNH3on a Si(100) surface

“…from ͑Si͒NH 2 structures as the surface is annealed. At present, it is known that there are three processes occurring during the thermal annealing of the NH 3 -saturated Si͑100͒ surface: ͑i͒ decomposition of ͑Si͒NH 2 to ͑Si͒ 2 NH and ͑Si͒ 3 N, which also leads to the formation of additional Si-H species; 3,6-8, [10][11][12][13]26,27 ͑ii͒ desorption of ammonia and of hydrogen that have been observed to occur at 650 and 780 K, respectively; 7,9,[13][14][15]23,47 and ͑iii͒ migration of N atoms, initially into the bulk of the Si lattice, 1,2,7,8,26,27,52 followed by their segregation back to the surface around 1000 K. 27 Widjaja and Musgrave considered two decomposition pathways, outlined in Fig. 2, and offered a detailed mechanistic picture of the possible decomposition processes.…”

“…However, if these predictions are applied to the thermal decomposition of a surface saturated with ammonia at lower temperatures, they would suggest that desorption processes have to take place in order to start the decomposition of ͑Si͒NH 2 and the migration of N atoms. Since desorption processes start at 650 K, 7,9,[13][14][15]23,47 these computational studies propose that ͑Si͒NH 2 species are mostly stable up to this temperature and that later the majority of these species recombines with hydrogen and desorbs as ammonia. 48 Interestingly, temperature-programed desorption ͑TPD͒ experiments have shown that the amount of ammonia that is desorbed is minimal, 7,9,13,23 and several experimental studies suggested that nitrogen insertion is possible before desorption processes occur.…”

“…Since desorption processes start at 650 K, 7,9,[13][14][15]23,47 these computational studies propose that ͑Si͒NH 2 species are mostly stable up to this temperature and that later the majority of these species recombines with hydrogen and desorbs as ammonia. 48 Interestingly, temperature-programed desorption ͑TPD͒ experiments have shown that the amount of ammonia that is desorbed is minimal, 7,9,13,23 and several experimental studies suggested that nitrogen insertion is possible before desorption processes occur. 1,2,6,8,26,27 Most experimental studies used x-ray photoelectron spectroscopy ͑XPS͒ as the main characterization technique, [1][2][3]6,10,12,16,[18][19][20]54 and the lack of high-resolution investigations was partially responsible for the controversy regarding the thermal decomposition of ammonia.…”

“…As can be noted from the description above, the majority of the experimental studies involving the system NH 3 /Si͑100͒ relies on XPS, [1][2][3]6,10,12,16,[18][19][20]26,27,54 TPD,1,7,9,13,14,23,47 STM,4,5,25,[28][29][30] or HREELS. 8,11,14,23 However, a powerful surface analysis technique such as infrared ͑IR͒ spectroscopy has rarely been used to investigate this system.…”