3 April 2008 Gap-fill type HSQ/ZEP520A bilayer resist process-(I): HSQ-coated ZEP520A CD shrinkage for 32-nm trench patterns
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The CD shrinkage by thermal reflow technique was frequently used for the formation of contact hole (C/H) of fine size. However, such technique is seldom used for line (trench)/space type patterns with complicate layout, like 6T-SRAM pattern. One of the reasons is the shape distortion of the designed layout after thermal reflow which results in the difficulty in CD control. In this study ultra-thin hydrogen silsesquioxane (HSQ)-coated ZEP520A trenchs are used to investigate the CD shrinkage effect and integrity of the shape after thermal reflow. 6T-SRAM transistor gate with various width/length (W/L) ratios is used as the test pattern. HSQ diluted by methyl-isobutyl ketone (MIBK) with 1:3 and 1:14 volume ratios was coated on ZEP520A trenchs. Post-applied baking (PAB) conditions of non-HSQ coated ZEP520A are split to find the optimal CD uniformity. The effects of thickness of HSQ, dilution ratio, spin speed of HSQ on the CD and shape after thermal reflow at various temperatures for HSQ-coated ZEP520A trench patterns are also studied. Multiple thermal reflows at 160oC-180oC are applied to obtain the best shrinkage results. It is found that the non-HSQ coated ZEP520A trench with all W/L ratios shrunk at 160oC. The smallest shrunk trench of 33.6 nm top-CD with 1/50 W/L ratio is obtained for HSQ (1:14)-coated ZEP520A for two thermal reflows at 160 oC/90 sec while 35.8 nm top-CD of the same W/L ratio is obtained after one 180oC/90sec reflow. Both sizes could meet the CD requirement of 32nm node and beyond. Above all, the HSQ-coated ZEP520A keeps the shape of trench pattern after one or multiple thermal reflows.
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Wei-Su Chen, Wei-Su Chen, Ming-Jer Kao, Ming-Jer Kao, Ming-Jinn Tsai, Ming-Jinn Tsai, } "Gap-fill type HSQ/ZEP520A bilayer resist process-(I): HSQ-coated ZEP520A CD shrinkage for 32-nm trench patterns", Proc. SPIE 6923, Advances in Resist Materials and Processing Technology XXV, 69232L (3 April 2008); doi: 10.1117/12.772496; https://doi.org/10.1117/12.772496

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