Direct Thermal Nitridation of Silicon Dioxide Films in Anhydrous Ammonia Gas

Abstract

It has been found that SiO2 can be converted directly to silicon nitride or oxynitride at the surface of SiO2 films by heating oxidized silicon wafers in anhydrous ammonia gas. At temperatures above 9O0~ nitrided SiO2 films have graded composites with respect to their nitrogen fraction. This analysis was performed by AES, infrared transmittance spectroscopy, and etch-rate profiles. Nitrided surface regions on SiO2 films, in which the nitride fraction ranged from 10% to 50%, showed remarkable masking effects against subsequent oxidation at high temperatures. * Electrochemical Society Active Member.

Selective Oxidation Using Ultrathin Nitrogen‐Rich Silicon Surface Layers Grown by Rapid Thermal Processing

“…For the low pressures used, typically 0.1-1.0 torr, diffusion coefficients are three to four orders of magnitude larger than at atmospheric pressure. The absence of a corresponding increase in growth rate eliminates some mass transport and depletion effects that are common to atmospheric systems (1)(2)(3)(4), and so allows high wafer density without compromising the uniformity of film growth. High wafer density is usually achieved by stacking the wafers coaxially in a wafer boat within a tubular reactor, shown in Fig.…”

“…When fur- nace is used for short periods of time (7 min in this case), the ratio of Eq. [3] may be as high as 38. However, it is not clear whether the complete elimination of the "bird's beak" effect (11) has occurred, but this inhibited oxide growth could be used in conjunction with photolithography to form sharp steps as demonstrated by this high step ratio.…”

Surface Chemical Studies of Oxides and Nitrides

“…One method utilizes a thermally-grown silica film on silicon; this thermal oxide is then nitrided at 900C -1200C in ammonia [17][18].…”

&#x2018;wet N<inf>2</inf>O oxidation&#x2019; process and interface state density characterization of nanoscale nitrided SiO<inf>2</inf> for flash memory application

“…Ammonia (NH 3 ) was historically used for the nitridation of tunnel oxides [10,11]. However the NH 3 nitridation introduces large amounts of hydrogen at the interface, giving rise to electron traps and hence the deterioration of the device performance [5,6,12].…”