We present a technique to produce isolated lines and trenches with arbitrary widths in the range of 12 nm to 500 nm, arbitrary heights and depths in the range of 100 nm to 2 μm, 90-degree sidewall angle, and top corner radii as small as 5 nm. These structures are ideal candidates as Critical Dimension (CD) absolute standards. The sidewall angle can further be varied to create an arbitrary sidewall angle that can be accurately measured.
An advanced control system providing modeling and predictive data simulation for pass-fail criteria of overlay production control has been used in 0.18 micrometer Design Rule production facilities for over a year. During this period overlay was measured on both product wafers and during periodic process qualification tests. The resulting raw data is modeled using exposure tool specific and layer-focused models. Modeled results, measured process statistics and tool signatures are combined in a real-time simulation to calculate the true overlay distribution over the entire wafer and lot. All results and raw data are automatically gathered and stored in a database for on-going analysis. In this manner, tool, product technology and process performance data are gathered for every overlay process-step. The data provides valuable insights into not only tool stability but also the process- step characteristic errors that contribute to the overlay spectrum of distortions. Data gathered in this manner is very stable and can be used to predict a feed-forward correction for all correctable coefficients. The technique must take into consideration algorithm modeled coefficient variations resulting from: (1) Reticle pattern-to-alignment mark design errors. (2) Process film variations. (3) Tool-to-tool static matching. (4) Tool-to-tool dynamic matching errors which are match-residual, process or time induced. This extensive database has resulted in a method of conducting Predictive Process Control (PPC) for overlay lithography within an advanced semiconductor line. Using PPC the wafer production facility experiences: (1) Improved Yield: Lots are always exposed with optimum setup. Optimized setups reduce rework levels and therefore wafer handling. (2) Capacity Improvement: Elimination of rework tacitly improves capacity in the facility. WIP is also simplified because lots do not have to wait for a dedicated exposure tool to become available. (3) Dynamic MatchingTM: Matching of multiple exposure tools is continuously monitored by the use of the feedback loop. Tool precision can be monitored as well as the setup systematic offsets. In this manner, the need to remove an exposure tool from production for match-maintenance can be predicted and scheduled. Residual matching errors can also be removed from the production cycle. The benefits of full production lot modeling and the contributors to production errors are presented. Process and Tool interactions as well as control- factor coefficient stability indicate the level of control to be well beyond manual methods. Calculations show that these contributors are predictable, stable and are a necessary tool for competitive sub-0.2 micron production. An analysis of the overlay error sources within two facilities results in consistent facility process response and a well-defined error budget derivation. From this analysis, the control added to semiconductor overlay is shown capable of extending mix-and- match exposure tool operations in production down to 0.12 micrometer design rules.
The use of programmed defect test reticles to characterize automatic defect inspection equipment has long been an established practice in the maskmaking industry. Measurement of the defect sizes on these programmed defect test masks is not necessary if one only desires to qualitatively investigate differences in system performance. However, more meaningful comparisons in inspection system performance require a calibrated programmed defect test mask. Historically, commercially available programmed defect test reticles have not had traceable or well-documented defect sizing methods nor was information regarding the precision of these measurements provided. This paper describes the methods used and results obtained from the work performed to address these issues. Using a low voltage scanning electron microscope as an image acquisition system, defect sizing is accomplished using automated pattern recognition software. The software reports defect size metrics such as maximum inscribed circle diameter and area. Measurement precision better than 30 nm has been demonstrated for the maximum inscribed circle method. The correlation of SEM based measurements to historical optical metrology measurements ia also discussed.
Programmed defect test reticles are required to characterize automatic defect inspection equipment. In order to perform meaningful, quantitative comparisons between inspection systems, a precise and accurate defect sizing methodology is required. Historically, commercially available programmed defect test reticles have not had traceable or well-documented defect sizing methods nor was information regarding the precision of these measurements provided. This paper describes the methods used and results obtained from the work performed to address these issues. Using a low voltage scanning electron microscope as an image acquisition system, defect sizing is accomplished using automated pattern recognition software. The software reports defect size metrics such as maximum inscribed circle diameter and area. Measurement precision better than 30 nm has been demonstrated for the maximum inscribed circle method. The correlation of SEM based measurements to historical optical metrology measurements is also discussed.
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