Automatic CD-SEM offline recipe creation for OPC qualification and process monitoring in a DRAM pilot-fab environment

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For future technology nodes, highly accurate dimensional metrology will become more and more important. At this stage, measuring layer thickness in planar test structures or geometrical dimensions in simplified proxy structures may be not sufficient for accurate control of highly sophisticated process steps. Model-based dimensional metrology has the potential to provide critical parameters of interest for process control in high volume manufacturing, while during process and technology development the constrained flexibility of models and the required model-building efforts may be a serious limitation. On the other hand, model-free dimensional metrology may provide sufficient flexibility for process development, while in some cases it may not be production-worthy in high volume manufacturing. This article details advantages and disadvantages of the different methods during the lifetime of a product starting from early development to high-volume production.

Section: Methods For An Early Development Phasementioning

confidence: 99%

Model-free and model-based methods for dimensional metrology during the lifetime of a product

Weidner¹,

Kasic²,

Hingst³

et al. 2008

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“…The pattern recognition success rate is defined as the number of successfully recognized patterns divided by the total number of measurement sites in the recipes (3) . The objective is to understand OPC Check behavior for different pattern type, pattern surroundings, layer and process.…”

Section: A Pattern Recognition Success Ratementioning

confidence: 99%

“…Optical Proximity Correction (OPC) is widely used to compensate for image errors due to diffraction or some other process effects. One of the challenges now is the increasing number of measurements needed for OPC model calibration and verification with an increased complexity of the layers (3) .…”

Section: Introductionmentioning

confidence: 99%

Automatic setup of in-line critical dimension (CD) recipes during OPC qualification in a foundry environment

Yudhistira¹,

Fong²,

Sun³

et al. 2007

In this paper, we study the feasibility of using a new system to set up offline critical dimension scanning electron microscope (CDSEM) recipes for both litho and etch processes monitoring in a foundry environment before first silicon. We will automatically create CDSEM measurement recipes based on CAD design data (2) and litho illumination information. The main advantages of having recipes setup done through this method as compared to performing recipe creation on the CDSEM tool itself are the reduction in CD-SEM tool usage and more importantly, the availability of the recipes before the first wafer is being processed in lithography resulting in a faster of cycle time for new devices.To facilitate our objective, a new feature was implemented in the design to provide a universal global alignment (GA) feature under both optical and SEM view. The global alignment serves two functions: to minimize device-to-device and layer-to-layer optical variation. It synchronizes design (CAD) and wafer coordinate systems. With this universal alignment feature available across all production layers of interest, we can fully automate recipe creation process from design to production.

“…To cover a wide range of the 2D spatial room the measurements for an OPC model can easily exceed several 1000 measurements. All three trends above, more layers with OPC, more complex OPC models and the verification of OPC in production, lead to increased measurement efforts [3]. With increasing number of measurements the development cycles can increase.…”

Section: Introductionmentioning

confidence: 96%

CD-SEM contour-based process monitoring in DRAM production environment

Krämer¹,

Jackisch²,

Wildfeuer³

et al. 2008

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As design rules shrink, there is an increase in the complexity. OPC/RET have been facilitating unprecedented yield at k 1 factors, they increase the mask complexity and production cost, and can introduce yield-detracting errors. Currently OPC modeling techniques are based on extensive CD-SEM measurements which are limited to one dimensional structures or specific shape structures e.g. contact holes. As a result the measured information is not representing the whole spatial 2D change in the process. Therefore the most common errors are found in the OPC design itself and in the resulting patterning robustness across the process window. A new methodology for OPC model creation and verification is to extract contours from complex test structures which beside the CD values contain further information about e.g. various proximities.In this work we use 2D contour profiles extracted automatically by the CD-SEM over varying focus and exposure conditions. We will show that the measurement sensitivity and uncertainty of that algorithm through the whole process window fulfills the requirements of the ITRS with respect to CD-SEM metrology tools. This will be done on various test structures normally being used for OPC model generation and OPC stability monitoring. Furthermore a study on systematic influences on the quality of the extracted contours has been started. This study includes the evaluation of various parameters which are considered as possible contributors to the uncertainty of the edge contour extraction. As one of the parameters we identified the pixel size of the SEM images. Furthermore, a new metric for calculating repeatability and reproducibility determination for 2D contour extraction algorithms will be presented. By applying this contour extraction based methodology to different CD-SEM tool generations the influence of SEM beam resolution to the quality of the contours will be evaluated.