In the paper given by these authors this spring at Photomask Japan, investigations into the advances in the CATS tool that combine hierarchical fracturing and distributed processing were begun. In addition to the beneficial reduction in processing times, various shortcomings of the software were detailed.
For this study, the next version of the CATS software tool has been made available and those shortcomings are remedied. Difficult model OPC (MOPC) fractures and complicated de-slivering fractures for variable shaped beam machines are analyzed. Timing results, exclusive-OR operations, and the implications of Amdahl’s Law are also considered. Further intricacies of Linux cluster computing are also addressed.
In previous papers, [BACUS 2000 4186-13 and BACUS 2001 4562-20], developments in hierarchical fracturing and in distributed processing in the CATSTM tool were studied. This study investigates the advances in the CATSTM tool that combine hierarchical fracturing and distributed processing. Time-consuming processes such as PSM, OPC and de-slivering logic for shaped beam machines are addressed. The attendant hierarchical fracturing commands are reviewed and commands associated with distributed processing are introduced. Hierarchical and flat data fracture times are compared, as well as threaded fracture and distributed fracture times. The resulting benefits are tabulated.
New reticle designs frequently contain mask features the inspection tools find objectionable. Typically these illegal features are handled in one of two ways. They are removed from the database with “do not inspect” regions, or the sensitivity is compromised to a level sufficient to reduce these nuisance defects to a tolerable level. Using the inspection machine to find these areas is both costly and inefficient. This paper presents a survey of the Manufacturing Rules Check option available from Transcription Enterprises to screen the database for these features before the reticle goes to inspection.
Historically the transcription of design data, in preparation for mask manufacture, has been to produce flat exposure tool data. Recent developments in hierarchical fracturing in the CATSTM tool are reviewed and explained. Current design data, especially memory products or even microprocessors containing cache, benefit immensely from these developments. The pertinent CATSTM commands are reviewed. Records of typical data fractures are presented and reviewed, showing the overall decrease in CPU usage with the hierarchal methods. The concomitant decrease in file sizes is also shown.
We have explored two-level, or `twin' masks as a mask-based means of increasing depth of focus. Simulations have shown that the technique offers substantial gains for a variety of pattern types. To verify this experimentally, we have fabricated a test mask containing two- level as well as conventional mask patterns. We have performed through-focus series of photoresist exposures and demonstrated the expected improvement in focus latitude.
Transmission defects are localized variations in the nominal transmission value of a photomask or reticle. Experience has shown that random transmission defects on reticles and photomasks have caused both device failures and reliability problems. In order to characterize the nature of transmission defects and the ability to detect them, the fabrication and evaluation of a programmed transmission defect test mask was undertaken. Using the programmed transmission test mask, quantitative data was obtained regarding the detectability of transmission errors on contact geometry.
Communication and verification of information has historically been an important and significant part of mask order entry. Although SEMI defined and adopted a specification for a mask order entry data base, it has met numerous practical obstacles and has not yet been widely accepted or implemented. Concise and clear communication of information between designer and mask vendor, between departments within the mask vendor's organization and ultimately to the wafer fab continues to be an error-prone, paper-based system.
The project undertaken here addresses, through software tools, the specification and communication of "specific points of interest". These points may be, but are not limited to, critical dimension marks, registration marks, specific geometries or areas in question. Data markers may be added into the binary data file at any point in the process from design to mask data preparation to mask manufacturing and inspection to wafer fab. Several marker types are available and may be defined and utilized at the users' discretion. Each marker may have an associated comment and may be instantly called up and displayed graphically.
Once these markers are defined and stored they are then communicated through the binary data file or job deck file. A designer may place markers indicating critical dimensions to be measured, along with their intended data and mask dimensions, store them into the design library and communicate them to the mask vendor through that library. The defined markers are passed from design data base into E-beam or optical lithography format as the data is fractured. Markers specifying critical dimensions may be automatically verified by the software or manually by the operator. Similarly, these critical dimension or registration markers may be used to generate run control files for automated CD and/or registration measurement equipment.