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21 May 1996 Accurate overlay control for 0.30-um i-line lithography
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Errors induced by mask, stepper, process and measurement tool disturb the perfect registration. A new method to check the precision of the mask itself would be introduced. It could give more practical references for wafer processing. The amount of all other errors could be easily notified using the above method. It is shown that the thickness of mask is a quite important factor to decide the accuracy of pattern placement on mask. Thicker substrate has smaller distortion inherently, and is less deformed by the subsequent processes for the mask fabrication. Although the field size of the thicker one was almost twice than that of the thinner one, 250 mil quartz substrate had more accurately placed patterns than the 90 mil one. OAI is a kind of sources degrading registration accuracy, which can induce another lens aberration. This error should be compensated by magnification and rotation control of the chip. The misregistration was able to be suppressed less than 60 nm. The registration control of the contact hole is extremely important and difficult, especially when it has to be formed through multi-layers. A new method had been tried, which independently controls the overlays with respect to x and y direction, respectively. It was found to be a potential solution in this case.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
KeunYoung Kim, Ikboum Hur, Gook-Jin Jang, and Soo-Han Choi "Accurate overlay control for 0.30-um i-line lithography", Proc. SPIE 2725, Metrology, Inspection, and Process Control for Microlithography X, (21 May 1996); doi: 10.1117/12.240098;

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