Photo-induced growth of dielectrics with excimer lamps

The underlying principles and properties of vacuum ultraviolet (VUV) and ul traviolet (UV) radiation (excimer lamps), generated by a dielectric barrier discharge in a rare-gas (Rg) or a mixture of Rg and halogen, are discussed . Compared with conventional sources, these excimer lamps offer narrow-band radiation at various wavelengths from 108-354 nm and over large areas with high efficiencies and high power densities. The variety of available wavel engths offers an enormous potential for new industrial applications in mate rials processing. Previously, photo-oxidation of silicon, germanium and sil icon-germanium and photo-deposition of single- and multi-layered films of s ilicon oxide, silicon nitride, and silicon oxynitride have been demonstrate d by using excimer lamps. This paper reviews the progress on excimer lamp-a ssisted growth of high dielectric constant (Ta2O5, TiO2 and PZT) and low di electric constant (polyimide and porous silica) thin films by photo-CVD and sol-gel processing, summarizes the properties of photoinduced growth of Ta 2O5 films and discusses the effect and mechanism of low temperature UV anne aling with 172 nm radiation. Metal oxide semiconductor capacitors based on the photo-induced Ta2O5 films grown directly on Si at low temperatures exhi bit excellent electrical properties. Leakage current densities as low as 5. 2 x 10(-7) A cm(-2) and 2.41 x 10(-7) A cm(-2) at 1 MV cm(-1) have been ach ieved for the as-grown Ta2O5 films deposited by photo-induced sol-gel proce ssing and photo-CVD, respectively-several orders of magnitude lower than fo r any other as-grown films prepared by any other technique, A subsequent lo w temperature (400 degreesC) UV annealing step improves these to 10(-8) A c m(-2). These values are comparable to those only previously achieved for fi lms annealed at high temperatures between 600 degreesC and 1000 degreesC. T hese properties make the photo-induced growth of Ta2O5 layers suitable alte rnative to SiO2 for high density DRAM application. (C) 2001 Elsevier Scienc e Ltd. All rights reserved.