Quality Improvement in LPCVD Silicon Nitrides by Anodic and Rapid Thermal Oxidations

Abstract

Low-pressure chemical vapor deposition ͑LPCVD͒ Si 3 N 4 quality presents a dramatic improvement after oxidation. Both liquidphase anodic oxidation and rapid thermal oxidation were studied in this work. After oxidation, ''SiO 2 ''-like layers grown on the surface, and oxygen incorporated into the Si 3 N 4 layer were observed. The nonstoichiometric bonding, i.e., Si 2 vN, Si dangling bonds, and crystalline Si were oxidized into Si 2 vNuO or SiO 2 , and the stoichiometric Si 3 wN bonding maintained a higher-k property. In addition, more oxygen replacement of the imperfect Si-N bonds after anodic oxidation contributed to better improvement in suppressing gate leakage current.For the shrinkage of metal-oxide-semiconductor field-effect transistors ͑MOSFETs͒, device-grade ultrathin SiO 2 is necessary to meet the integrated circuit requirement. However, the increasing problems with boron penetration through ultrathin oxide and exponentially increased direct tunneling ͑DT͒ current dictate the replacement of the prospective dielectrics. 1 Alternative material with higher permittivity is therefore considered because of the greater physical thickness under the same capacitance. Among these high-k materials, silicon-based Si 3 N 4 has been studied extensively, because of its high permittivity (k ϭ 6 -8, depends on stoichiometry͒, high processes compatibility, and good capability for suppressing boron penetration. 2 To obtain a stoichiometric Si 3 N 4 film, the nitriderelated technologies such as chemical vapor deposition ͑CVD͒ nitride, 3 jet-vapor-deposited ͑JVD͒ nitride, 4 atomic-layer-deposition ͑ALD͒, 5 and nitrided-SiO 2 , i.e., oxynitride, 6 have been studied extensively.At the same time, Si 3 N 4 grown by low-pressure chemical vapor deposition ͑LPCVD͒ is used to mask the active region or store the memory charges. CVD nitride exhibits a high throughput merit in batch processes. However, interactions of SiCl 2 H 2 and NH 3 tend to form silicon-rich nitride films, a great amount of traps and unbounded dangling bonds are present. Also, the extended crystalline silicon would induce extra leaky gate current that is unfavorable for transistor gate insulator. From a previous report, oxidation of CVD nitride is significant in enhancing dielectric quality. 7 Reaction between oxidant and CVD nitride plays a major role to compensate the imperfect bonding and reduce the traps. In addition, due to the barrier height difference under migration, electrons and holes were reported to be the dominant conduction carriers in SiO 2 and Si 3 N 4 , respectively. 8 When oxide is grown on the surface or incorporated into the nitride, the hole-flow current may be suppressed by the oxide, because the holes face a much higher barrier of SiO 2 (⌽ Bh ϭ 4.4 eV͒ than Si 3 N 4 (⌽ Bh ϭ 1.8 eV͒. 9 Accordingly, the total gate leakage current would be quenched after oxidation.From our studies, anodic oxidation exhibits the merits of low thermal budget and better thickness uniformity than thermal oxidation. 10 In this work, liquid-phase anodic oxidation and ...

Metal∕Dielectric Liner Formation by a Simple Solution Process for through Silicon via Interconnection

“…On the other hand, the low-pressure CVD (LPCVD) method is used to form dielectric layers of highstep-coverage and low leakage current, but it requires a high process temperature. 8 Moreover, this method has difficulty in depositing thin dielectric layers uniformly in high ARs via holes because its process parameters must be controlled carefully.…”

“…[7][8][9] Moreover, the overall cost of the deposition process is * Electrochemical Society Active Member. z E-mail: domi@etri.re.kr; kwonkh@korea.ac.kr greatly increased when the high cost equipment is required for long processing.…”