.0.13 ¦¬m In Stacked Dynamic Random Access Memory Lithography Process Optimization

The thesis introduce 0.13um stack DRAM process improvement and study photo many important parameters. The thesis has directive significance for stack DRAM process development.The thesis introduce 0.13um stack DRAM process flow simply. The special process structure is different with traditional trench DRAM. So it has more characteristics.The thesis summary and analyse some impact 0.13um stack DRAM yield problems in photo process. We designed the experiment and analysed theory to slove these problem.Below are the problems summary:1.Alignment process improvement. For the 0.13um stack DRAM special process structure, the layer to layer alignment need more exactness request. Customer request the production must run the alignment level poor machine. So it is difficult for the critical layer align accurately. The thesis study wafer alignment theory and improve the alignment exactness by change alignment mode and improve alignment mark quality.2. Bit line peeling issue improvement. For wafer center and edge CMP speed difference,the wafer center and edge flatness will be difference. The BL CD low and process window small will cause the wafer edge Bit line defocus and suffer peeling. The thesis solve this issue by process improve and qualify NA 850 machine to enlarge process window.3. CLD layer discolor issue improvement. Source and drain implant are very important for stack DRAM process. The 0.13um stack DRAM ploy line profile is roughness. So the CLD process often can not cover the ploy space completely. That will cause the un-implant area has implant. The thesis solve this issue by add TARC process and optimize process temperature.4.By column defocus issue improvement. The equipment engineer often clean lens when machine maintain. After the lens clean, the machine sometimes suffer exposure slit uniform shift cause by column defocus. But traditional monitor can not catch the slit uniform shift. The thesis apply a new monitor systerm Phase Shift Focus Monitor to catch this issue.5. The PSM mask haze prevent method. The mask has haze is very dangerous for critial mask, it can stop exposure light through the mask. The thesis found a new way to prevent the haze produce.