Detailed characterization of hydrogen silsesquioxane for e-beam applications in a dynamic random access memory pilot line environment

Abstract

Hydrogen silsesquioxane (HSQ) has interesting applications as an electron-beam resist and hardmask. In this work, HSQ was investigated with regard to the postcoat delay, isofocal dose for an optimum process window, e -beam proximity effect correction, and the molecular structure in order to better understand the processing. Several independent methods were set up and applied to characterize the structuring of HSQ with e-beam including contrast measurements, basedose-over-critical-dimension tests, the isofocal dose method, the doughnut test, and Fourier transform infrared analysis. HSQ was coated on 300mm bare silicon wafers and exposed with a 50kV variable shaped e-beam writer in the dynamic random access memory pilot line environment of Qimonda Dresden and Fraunhofer CNT. The postcoat delay showed no significant influence on the exposure results. A dose difference between the basedose and the isofocal dose was observed, which indicates a working point in a suboptimal process window related to the poor contrast. The FTIR analysis showed a molecular structure change up to 600μC∕cm2. Finally, a point-spread-function for HSQ has been generated for the first time. In summary, the results from this detailed characterization show promise for a manageable process.