18 September 1995 Oxygen precipitation and denuded zone characterization with ELYMAT technique
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In modern DRAM processes one needs a well defined defect free range called denuded zone. In a depth of several micrometers, a range of precipitated oxygen is used to achieve internal gettering. The usual characterization of oxygen precipitation is done by counting the defects with an optical microscope after cleavage face etching. Therefore one only examines a fraction of the whole wafer. Investigating precipitated wafers after two-step anneals we found a good correlation between the bulk micro detects and the diffusion length using the electrolytical metal tracer (ELYMAT) technique. So we achieved a spatially resolved image of the precipitated bulk. In processed wafers the depth of the precipitate free zone is of great importance. Insufficient denuding decreases the yield of device fabrication drastically. We assumed a two region model (defect free-precipitated region) with two different diffusion lengths LD in a depth t. Solving the set of differential equations we calculated a 3D picture of denuded zone depth and diffusion length in the precipitated bulk of the wafer. This means for practical application, that it is now possible to detertmine insufficient denuding and to get more information of oxygen precipitation behavior of the whole wafer using an improved ELYMAT technique.
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Guenther Obermeier, Guenther Obermeier, Juergen Hage, Juergen Hage, Norbert Hilger, Norbert Hilger, Diethard Huber, Diethard Huber, "Oxygen precipitation and denuded zone characterization with ELYMAT technique", Proc. SPIE 2638, Optical Characterization Techniques for High-Performance Microelectronic Device Manufacturing II, (18 September 1995); doi: 10.1117/12.221215; https://doi.org/10.1117/12.221215

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