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Experimental data from the current 0.35pm deep-UV lithographic process was used in conjunction with simulations of future 0.25p.m lithography to provide a means of evaluating the possibility of meeting the National Lithography Roadmap goals for CD and overlay. This study found that the CD control issue has too many components to be captured by the single number listed in the Roadmap. The current magnitude of many of these components looks too large to justify their shrinking down to values consistent with the general 30% shrinks characteristic of our industry. For overlay the Roadmap value is clearly auainable for matched steppers in controlled tests, however unlikely for daily product results on random-matched steppers in a production environment. This study also examined the impact of pushing deep-UV technology to the 0.25tm regime on the process latitudes of dense/isolated lines and upon the poiy endcap.

DUV stepper technology has progressed to the point of practical implementation in the deep submicron lithography regime. A comparison of two sta.teof-.the-art DUV lenses, a GCA Thistie and an ASML 5500/90, will be presented. Lens performance parameters of interest to lithographers, eg., focus and exposure latitude, astigmatism, coma, focal plane deviation, dense to isolated bias, distortion and linewidth uniformity across lens, are reported. These lenses demonstrate the process latitude and resolution capability required for a production-worthy 0.35 pm process. In order to derive a meaningful assessment of lens performance, a rigorous lens analysis procedure is required. Using an automated metrology SEM, the Metrologix Metrostep 2002, and a statistical analysis software package, SAS, the components of variability in lens performance resulting from the specification, measurement and data analysis methods, along with the physical lens design and manufacture, are examined. For example, wafer non-flatness, can have a major impact on focal plane deviation and useable depth-of-field (UDOF). Lens specification can also greatly influence the perceived lens performance. Differences in the description of an acceptable resist profile contributed to a difference of O.6pm in UDOF values. Several external factors must be carefully considered when performing lens evaluations. The components of variability in lens performance have been identified and methods to account for these components are described.To enable sufficient process latitude with minimal changes to traditional lithography processing, many semiconductor companies are using DUV technology for O.35pm critical layers in production. The advantages and disadvantages of DUV exposure light have been discussed in previous papers1'2'3. Advancements in anti-reflective coatings, DUV resists and wavelength control for KrF excimer laser steppers have made DUV technology a practical choice for lithographers required to develop processes for O.35pm and below. DUV lenses have undergone improvements in focal plane deviation, distortion and other aberrations to the point that they can now be implemented in a production environment for critical layer imaging. Several lenses from two lens manufacturers, ASML and GCA, will be compared to demonstrate their current capability and the variability in design from vendor to vendor and within vendor. In addition, lens parameter measurement methodology and the sources of variation will be discussed. 2.0 Experimental 2.1 Processing GCA Lens Wafer Processing A virgin silicon wafer was coated with 830A of Brewer Science CD9 ARC and baked on a proximity hotplate at 250C for 60 seconds. The bake sequence was a two step process: 15 sec-678 ISPIE Vol. 2440 0-8194-1788-2/95/$6.00 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/26/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

The swing curve, more specifically the reflectance versus resist thickness, has been measured for APEX-E coated on 3 different film stacks for interconnects: Titanium nitride (TiN) capped aluminum, Brewer ARC CD9 coated aluminum, and CD9 coated on the TiN capped aluminum. The exposure and focus latitudes have been measured for each of the above film stacks along with pre-etch and post-etch cross section profiles. It appears that either the TiN or CD9 could be used as an ARL based on the swing curve alone, however, the TiN capped aluminum degrades the APEX-E profile to such an extent that TiN can not be used as an effective anti-reflective layer (ARL). Similar data, swing curves and process latitudes, were collected for the contact film stacks of silicon dioxide on aluminum, and CD9 coated silicon dioxide on aluminum. The swing curves showed erratic behavior, which is most likely due to oxide thickness variations across the wafer. Measurements of the across wafer contact size variation were taken to quantify the improvement in critical dimension control that results from the use of an ARL.