Irradiation resistance of intravolume shading elements embedded in photomasks used for CD uniformity control by local intra-field transmission attenuation

How to improve intra-field CDU of contact hole patterns in both X-Y directions with CDC technology

“…We calculate the ∆I% based on above theory, regarding of k (extinction coefficient) , since there is no change in the fused silica chemistry, it should stay unchanged, here we will not consider the absorption factor . The formula is as follows: (6) To describe the formula graphically, as shown in Fig. 5.4，we pilot the ∆I% versus incidence angle , and we can see that ∆I% grows up exponentially as increases.…”

“…In the current perception, the on-wafer CD is a linear function of dose in a certain latitude, so one potential solution for CDU correction could be controlling the local dose to compensate for CD deviation. Critical dimension correction (aka CDC) is a mask tuning system which uses a well-controlled ultra-short pulse laser technology to locally change the mask transmittance based on the intra-field CDU map and therefore can result in controlling local dose to improve CDU on wafer [4][5][6]. To achieve this, the printed on-wafer CD must have sensitivity to the mask transmittance changes, which is called "CDC ratio (aka CDCR)" and represents the on-wafer CD change by applying 1% attenuation (99% transmittance) using CDC process.…”