Inverse Explorer 


Inverse Explorer is a full feature, computational lithography platform used to develop lithography solutions for 32nm and below. Inverse Explorer streamlines the development process and dramatically reduces development time required for advanced technology node design rules and products.

Based on proprietary Inverse Lithography Technology (ILT), Inverse Explorer can inverse- or back-calculate what a mask design should be given the ideal target on the wafer. Combining ILT and its embedded RET engine, Inverse Explorer provides a full range capabilities to lithography and OPC professionals.

Inverse Explorer is used in several applications:

Source Mask Optimization (SMO)
Simultaneously optimize the mask and scanner illuminator designs to provide the best possible lithographic performance. Inverse Explorer uses its level set method and ILT to model both illumination and mask solutions. This highly efficient modeling technique enables simultaneous co-optimization. Solutions for both the mask and the illuminator can be free-form or can be approximated to account for manufacturability or cost.

Design Rule Development (DRD)
Determines and optimizes design rules based on lithography performance. For design rule development, Inverse Explorer develops the theoretical optimum OPC and SRAF treatments for each layout and for each candidate illumination condition. From these treatments, "Ideal" masks are generated. Subsequently, these masks "Manhattanized" in accordance with mask rules to ensure manufacturability. Either from the "idealized" or "Manhattanized" masks, Inverse Explorer can output the design rules for Luminescent's full-chip product, Inverse Synthesizer, or any other OPC program to use to apply to an entire mask layer.

Double Patterning Decomposition (DPD)
Decomposes complex pattern designs to 2 manufacturable mask designs. Double Patterning Decomposition provides both rule-based and model-based double patterning decomposition for both contact and metal/poly layers. The rule-based decomposition supports flexible rules that closely reflect litho performance. Polygon cutting, the process of decomposing metal or poly line structures to smaller structures, considers overlay robustness, balances pattern density between split layers, as well as other decomposition constraints. The model-based decomposition considers litho rules, such as contrast, DOF, and MEEF. In addition, detailed marker layers are produced for various types of unsolvable conflicts.

SRAF (Sub-Resolution Assist Feature) Rule Extraction (SRE)
Extracts the SRAF rules based on ILT and user specified lithography requirements. The input to this program is the complexity of SRAF requirements and lithography specs, such as DOF, EL, MEEF, PV bands, it then generates a SRAF table including all SRAF parameters, such as number of bands, location, size. Such table can be then used with the existing OPC with rule-based SRAF. SRE can also be used as an option of SMO when applying SMO results into customer's OPC.

Inverse Explorer also provides:
  • Optimization at nominal and throughout the process-window enables tradeoff analysis between CD uniformity and process window
  • Detailed, localized analysis using MEEF map and hotspot identification tools that reduces the amount of hotspot fixing required later in the design phase
  • Choice of optically-ideal or mask-rule-constrained output that enables assessment of theoretical limits of performance vs. real-world implementation

The Inverse Explorer product uses computational lithography to advance the state-of-the-art in wafer processing by allowing chip design rules (32nm and below) to continually shrink without requiring the use EUV, the next generation of stepper technology.

Similarly, Inverse Explorer can be used to enable current generation lithography hardware perform beyond its original capabilities. For example, a DRAM manufacturer has used Inverse Explorer to develop the lithography solution for the 4X node on a 193nm "dry" scanner. (4X refers to the CD in the 40-50nm range. Typically, this requires the use of a 193nm immersion scanner).

Inverse Explorer enables semiconductor companies to be more environmentally conscientious by:
  • Reducing lithography develop time
  • Developing larger lithography process windows for higher yields, and
  • Extending the applicability of the current 193nm immersion technology for another 2-3 generations=effectively putting off the need for EUV.