Effect of Electric ARC Plasma Jet Treatment on Mos Structure Reliability

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ABSTRACT The effect of electric arc plasma jet treatment (APJT) on MOS structure reliability has been investigated. Si/SiO 2 /Si*/AI structures have been studied using the technique of constant current charge to breakdown before and after APJT. The study showed that APJT can improve MOS structure reliability: constant current charge to breakdown Qbd increased to more than 5 C.cm-2 and breakdown field Ebd increased to more than 20 MV/cm. This result was attributed to a structural modification of SiO 2 and its interfaces as a result of APJT. Evidence for these structural changes is the appearance of additional SiO 2 IR absorption peak which was observed by us. INTRODUCTION Arc plasma jet treatment (APJT) of surface at atmospheric pressure is a new technology which meets the requirements of ultra clean processing [1]. APJT produces a hydrodynamically continuous high-enthalpy (> 104 J/g) low-temperature (< 2.104 K) plasma jet which impacts the surface for a short time (0.01-0. Is). The unique efficiency of APJT is provided by the high speed of the plasma jet (about 100 m/s) impacting the processed surface, along with the high densities of the heat flow (> 103 W.cm- 2) and the particles (1019 to 1021 cm- 2 s) on the plasma/surface of excited flows boundary. The surface temperature is controlled by the intersection velocity of wafer and plasma jet. The aim of this work was to investigate the effect of APJT on the reliability of thin MOS structures. EXPERIMENTAL The test Si/SiO 2 /Si*/Al structures were prepared using thermal gate oxidation of nSi(100) Cz wafers without H 2 post-annealing. The SiO 2 thickness was 27 nm. The Al electrodes on the chips were in the form of circles with diameter d = 0.1 to I mm. The treatment was carried out using Ar/air plasma jet in the mode which provided photoresist stripping at a rate of 10 ýtm/s. The total dose was determined by the number of arc plasma jet impacts (i = 2, 8, or 32). During APJT, the wafers were in rotary-reciprocating movement which provided for a high homogeneity of the surface treatment. The UV jet irradiation dose was nearly uniform across the wafer surface (from 1017 to 1018 plasma cm- 2 .s-l). The gate oxide integrity was estimated on the basis of the breakdown parameters (Ebd and Qbd) using the technique of constant current charge to breakdown (Qbd). Ebd 2 was measured until breakdown was reached. Qbd was measured on 0.0007 cm capacitors modes on other the effect of APJT We also analyzed during substrate electron injection. MOS physical parameters and IR absorption of SiO 2. IR spectra were measured using the 139

Mat. Res. Soc. Symp. Proc. Vol. 391 01995 Materials Research Society

differential technique. The measurements were carried out on 100 chips for every wafer, with one structure being analyzed using only one method to avoid interference of the measurement impacts on the structure parameters. The data were statistically processed and distributions of the parameters on the wafer surfaces were plotted. RESULTS The distributions of the initial parameters of