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Thermal stability and electrical characteristics of ultrathin hafnium oxide gate dielectric reoxidized with rapid thermal annealing Electrical and structural properties of poly-Si films grown by furnace and rapid thermal annealing of amorphous Si

Double-diffused shallow junctions have been formed by ion implantation of both phosphorus and arsenic ions into silicon substrates and rapid thermal annealing. Experimental results on defect removal, impurity activation and redistribution, effects of Si preamorphization, and electrical characteristics of Ti-silicided junctions are presented.

In this paper we report a systematic and comprehensive study of the effects of post-oxidation anneals on the electrical properties of thin polyoxide films. Thin (---20 nm) interpoly dielectrics have been grown on phosphorus implanted polysilicon by in situ multiple rapid thermal processing (RTP) including rapid thermal oxidation (RTO1), rapid thermal nitridation (RTN), and subsequent rapid thermal reoxidation (RTO2). In comparison with polyoxides grown in conventional furnace, RTO~ polyoxides exhibit a significantly reduced leakage current. In addition, both the dielectric breakdown strength and breakdown field distribution have been improved. It is found that RTN of RTO1 results in polyoxides with an unusual polarity asymmetry dependence of electrical conduction and trapping properties, i.e., a higher electrical conduction and electron trapping rate for electrons injected from the top poly-Si electrode than for electrons injected from the bottom poly-Si electrode. Subsequent RTO2 of nitrided polyoxides results in a reduction of both the leakage current and electron trapping rate. Longer RTO2, however, increases the leakage current due to the progressively deteriorated poly-Si/ polyoxide interracial texture.Oxide films grown on n+-poly-Si (i.e. polyoxides) are essential for the development of nonvolatile memory applications such as EPROM and E~'PROM devices. The scaling of device geometries makes thinner polyoxides necessary in order to keep a high gate coupling ratio. Device performance is determined by its data retentivity and programming efficiency, in terms of the leakage current and dielectric strength. However, polyoxides usually exhibit higher leakage current and inferior dielectric strength in comparison with oxides of comparable thickness grown on single crystalline-Si, due to the asperities and bumps at the polyoxide/poly-Si interface which lead to a localized field enhancement (1-7). The "roughness" is attributed to the different oxidation rates of randomly oriented poly-Si grains in low temperature ranges where the interfacial reaction rate controls the oxidation kinetics (8) and the irregular grain growth during the poly-Si doping process (8). It has been found that the quality of polyoxides depends upon the poly-Si preparation, oxidation condition, and post-oxidation annealing. It is known that the poly-Si oxidation and the electrical characteristics of resulting polyoxides strongly depend on the smoothness of the poly-Si surface prior to oxidation, as well as the doping conditions (8). For instance, a high temperature annealing of POCI~ doped poly-Si with an optimum level of 6 • 102o cm -s prior to oxidation was demonstrated to improve the dielectric strength (9) and reduce the leakage current (10). On the other hand, it has been proposed (8) and demonstrated (11, 12) that a smooth polyoxide/poly-Si interface could be achieved by a high temperature oxidation (e.g., 1050-1100~ which is predominantly diffusion-controlled. Furthermore, to improve the quality of polyoxide, furnace nitridation of polyox...

In the search of a high quality thin inter-polysilicon dielectric which has high breakdown voltage and low leakage current for high density non-volatile memory applications, thin (150±) inter-polysilicon reoxidized nitrided oxide capacitors were fabricated with multiple rapid thermal processing. While rapid thermal nitridation degraded the breakdown field if compared to the rapid thermal oxide capacitors, rapid thermal reoxidation greatly enhanced the dielectric strength of the rapid thermal nitrided samples. The short reoxidations increased the film thickness by less than 10 \. Breakdown field of optimized inter-polysilicon RTO/RTN/RTO capacitors up to 14 MV/cm has been measured.