Aggressive line width control requirements for leading edge IC fabrication necessitate integration of novel techniques such as DoseMapper into the lithography process flow. DoseMapper is based on the simple concept that CD uniformity (CDU) can be improved through compensation of CD errors by using the scanner actuators. Specifically, the DoseMapper system allows for compensation of interfield and intrafield CD non-uniformity, based on the spatial distribution of in-line CD measurements or end-of-line electrical parameters for a stable process. This approach is supported by the fact that small variations of linewidth are correlated to exposure dose in a linear fashion. In this work we describe strategies for and results of the application of DoseMapper in a lithographic process for gate layer in a 65nm technology. We will highlight the potential strengths and weaknesses of various DoseMapper strategies to. For instance, we have learned that dose adjustments which are based on post-etch CD signature can lead to degradation of the lithography-based process window especially for 2 -dimensional features due to high MEEF. Therefore, it is asserted that application of DoseMapper in a high-volume manufacturing process requires consideration of such rational tradeoffs as mentioned above. Impact of Mask CD variation on DoseMapper effectiveness will also be discussed. This has the potential to have a significant impact on manufacturability of photo masks for the 65nm node and beyond
Microlithography applications such as advanced packaging, micromachining and thin film head (TFH) production frequently require the use of thick photoresists and large exposure doses for successful pattern transfer onto substrates. When thick negative acting photoresists are used, exposures as high as 5000mJ/cm2 may be required to maintain the pre-exposure photoresist thickness after develop. In this study, light transmission through photomasks with standard (OD3) and high-density (OD4) Cr films was measured through the ultraviolet spectrum to determine leakage thresholds and evaluate the risk of unwanted exposure with highly sensitive photoresists. Because the higher OD photomasks are the result of an increase in Cr film thickness, photomask process differences, resolution capability and Critical Dimension (CD) uniformity issues were also evaluated. The thicker Cr film could also affect pattern transfer to the wafer. Therefore, resolution and CD uniformity were compared on wafers patterned from both OD3 and OD4 Cr reticles.
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