Impact of inter-mask CD error on OPC accuracy for resolutions of 90 nm and below

An automatic system that combines actions in both the image domain as well as in the layout-database domain for accurate mask-defect analysis and application of design criticality will be presented. In this paper we will emphasize the qualification and calibration of the system and its various pieces of functionality with the use of programmed defect masks and low-voltage mask CD-SEM measurement data. Results on 1D and 2D programmed defects of various natures are reported in dense layout as well as in real memory design layout. The results show that the system can accurately extract mask CD-errors and defect sizes at a resolution far below that of the pixel-size of state-of-the-art mask-defect inspection tools at nanometer resolution.We will further demonstrate that mask-defect-inspection data can contain optical anomalies when defect or residual feature sizes are smaller than the inspection wavelength. Mask inspection images then no longer show the real defect. These anomalies can be analyzed with the system using advanced image actions.Finally, we will demonstrate the capability to calculate the effects that defects have on final wafer printability even without the need for input layout. Hence, model-based defect properties can be combined with rule-based defect properties as well as multi-layer, design-based criticality-region properties for utter flexibility in defect disposition capability.

Section: Introductionmentioning

confidence: 99%

DFM software for photomask production and qualification of its accuracy and functionality

Driessen¹,

Westra²,

Haens³

et al. 2008

“…Of course there has been manufacturability attention but that is usually only related to the single layer of the design that is used per mask such as the effects of the mask-error-enhancement-factor (MEEF) on printability (Ref. [2]). Such information is usually used to tighten the specifications of photomasks.…”

Section: Introductionmentioning

confidence: 99%

DFM for maskmaking: design-aware flexible mask-defect analysis

Driessen¹,

Westra²,

Scheffer³

et al. 2007

We present a novel software system that combines design intent as known by EDA designers with defect inspection results from the maskshop to analyze the severity of defects on photomasks. The software -named Takumi DesignDriven Defect Analyzer (TK-D3A)-analyzes defects by combining actions in the image domain with actions in the design domain and outputs amongst others flexible mask-repair decisions in production formats used by the maskshop. Furthermore, TK-D3A outputs clips of layout (GDS/OASIS) that can be viewed with its graphical user interface for easy review of the defects and associated repair decisions. As inputs the system uses reticle defect-inspection data (text and images) and the respective multi-layer design layouts with the definitions of criticalities.The system does not require confidential design data from IDM, Fabless Design House, or Foundry to be sent to the maskshop and it also has minimal impact on the maskshop's mode of operation. The output of TK-D3A is designed to realize value to the maskshop and its customers in the forms of: 1) improved yield, 2) reduction of delivery times of masks to customers, and 3) enhanced utilization of the maskshop's installed tool base.The system was qualified together with a major IDM on a large set of production reticles in the 90 and beyond-65 nm technology nodes of which results will be presented that show the benefits for maskmaking. The accuracy in detecting defects is extremely high. We show the system's capability to analyze defects well below the pixel resolution of all inspection tools used, as well as the capability to extract multiple types of transmission defects. All of these defects are analyzed design-criticality-aware by TK-D3A, resulting in a large fraction of defects that do not need to be repaired because they are located in non-critical or less-critical parts of the layout, or, more importantly, turn out to be repairable or negligible despite of originally being classified as unrepairable when no such criticality knowledge is used. Finally, we show that the runtimes of TK-D3A are relatively short, despite the fact that the system operates on full-chip designs.

“…Since, most of the time, the two-dimensional mask error information is not available, it usually is not taken into consideration when correlating GDS layout dimensions to real silicon measurement, during OPC model generation. Also, inter-mask CD error, which is the critical dimension difference between a test mask and a product mask, can also impact OPC accuracy (6) . Secondly, there are difficulties in accurately quantifying the twodimensional proximity effect on silicon, and usually a significant error is contributed from CD SEM measurement.…”

Section: Introductionmentioning

confidence: 99%

Line end optimization through optical proximity correction (OPC): a case study

Chou

McAllister

2006

Device performance is highly associated with the line end performance of critical layers. Poly line end shortening (LES) or bridging can result in leakage or short circuit. Model-based optical proximity correction (OPC) prioritized to fit onedimensional pitch structures can also improve two-dimensional line end performance. However, it may still fail without meeting the line end bridging margin or minimum line end length requirements. A leakage problem has been observed, when poly gate line end shortening occurs, following the use of an OPC recipe chosen to be a compromise for the line end bridging problem. In this paper, several approaches related to OPC are studied on poly layer, in terms of line end bridging margin and line end shortening, to optimize line end performance. The OPC minimum external constraint is optimized to meet both line end bridging and shortening requirements. Serif type line end provides the OPC model with more flexibility to pull back the center segment between line end serifs and improves the bridging margin by 2%, with negligible sacrifice on line end length under overexposure conditions. No effect is seen on the bridging margin with different segment lengths of center pull back at the serif line end. Bridging margin can be improved dramatically (6%) by adding SRAF, due to the increase of aerial image intensity in the line end space. Finally, the OPC model fitting for line end shortening is briefly described and a post-correction rule-based OPC is introduced to improve the line end shortening. Handcrafted OPC is also used for this case study for few structures that need extra correction to achieve enough line end length.