Impact of preanneal process on threshold voltage of MOS transistors for trench DRAM |
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Authors: | Yung-Hsien Wu Chih-Ming Chang Chun-Yao Wang Chien-Kang Kao Alex Ku |
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Affiliation: | a Department of Engineering and System Science, National Tsing-Hua University, 300 Hsinchu, Taiwan b Diffusion Department, ProMOS Technologies Inc., Science-Based Industrial Park, 300 Hsinchu, Taiwan c Strategic Process and JDP Department, ProMOS Technologies Inc., Science-Based Industrial Park, 300 Hsinchu, Taiwan |
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Abstract: | As the first step of DRAM manufacture, preanneal process plays an important role in determining the threshold voltage variation. It is found that the higher trans-1,2-dichloroethene flow in pad oxide growth and the higher nitrogen flow in high-temperature annealing step would respectively engender a lower boron segregation coefficient and higher nitridation of the oxide, both modify the boron distribution in the substrate and consequently the behavior of the threshold voltage. As the feature size of DRAM devices enter nanometer regime, besides gate oxidation, ion implantation and related thermal processes, the impact of preanneal process condition should be prudentially taken into consideration for rigorous control of the threshold voltage in the advanced DRAM production. |
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Keywords: | Threshold voltage control Preanneal process Boron segregation coefficient Nitridation by nitrogen Boron distribution Interstitial Si |
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