Use of layout automation and design-based metrology for defect test mask design and verification
This paper studies the impact of shape and local environment (pattern layout) on the ability to detect defects on the reticle and the extent to which they affect the dimension of the printed image on the wafer. The authors have made extensive use of design information to perform a thorough evaluation. OPC software was used to generate mask data that was comparable to product mask data. Defects were placed on the post-OPC layout and OPC software was also used to simulate the dimension of the defective features as printed on the wafer. "Design Based Metrology" was used to create accurate metrology recipes to support wafer and mask metrology. Ultimately the procedures described in this paper allow a direct correlation to be made between reticle inspectability and the impact of the same defects on wafer CD. Data is presented for the case of the Contact Hole layer of a "65nm" Logic technology, though the methods described in the paper are applicable to all layers.
New energy flux method for inspection of contact layer reticles
With growing implementation of low k1 lithography on DUV scanners for wafer production, detecting and analyzing photomask critical dimension (CD) errors and semitransparent defects is vital for qualifying photomasks to enable high IC wafer yields for 130nm and 100nm nodes. Using the TeraStarTM pattern inspection system's image computer platform, a new algorithm, TeraFluxTM, has been implemented and tested for the inspection of small 'closed' features. The current algorithm is run in die-to-die mode and compares the energy flux differences on features between die for small closed features, such as, contacts, trenches, and cells on chrome and half-tone reticles. Tests show the new algorithm provides CD error detection to 5 percent energy flux variation with low false defect counts. The dispositioning of very small CD errors typically requires the precision and resolution of a CD-SEM. A new capability has been developed for review of very small CD errors for this application, which displays the energy flux difference between any corresponding closed features on different die. We have characterized the sensitivity and false defect performance of the new energy flux algorithm with production masks and programmed defect test masks. The program defect test mask contains two sets of contacts at 600nm and 800nm design sizes. At each design size there are six defect types in both dense and sparse geometry. The programmed defects are designed to have 1 percent energy increments for defect sizes from 1 percent to 10 percent, and 2 percent energy increments from 10 percent to 30 percent. A sampling of inspection results will be presented. SEM measurements were taken at programmed defect locations to develop a correlation between the energy flux difference and the measured CD.
Mississippian Barnett Shale: Lithofacies and depositional setting of a deep-water shale-gas succession in the Fort Worth Basin, Texas
The Mississippian Barnett Formation of the Fort Worth Basin is a classic shale-gas system in which the rock is the source, reservoir, and seal. Barnett strata were deposited in a deeper water foreland basin that had poor circulation with the open ocean. For most of the basin's history, bottom waters were euxinic, preserving organic matter and, thus, creating a rich source rock, along with abundant framboidal pyrite. The Barnett interval comprises a variety of facies but is dominated by fine-grained (clay- to silt-size) particles. Three general lithofacies are recognized on the basis of mineralogy, fabric, biota, and texture: (1) laminated siliceous mudstone; (2) laminated argillaceous lime mudstone (marl); and (3) skeletal, argillaceous lime packstone. Each facies contains abundant pyrite and phosphate (apatite), which are especially common at hardgrounds. Carbonate concretions, a product of early diagenesis, are also common. The entire Barnett biota is composed of debris transported to the basin from the shelf or upper oxygenated slope by hemipelagic mud plumes, dilute turbidites, and debris flows. Biogenic sediment was also sourced from the shallower, better oxygenated water column. Barnett deposition is estimated to have occurred over a 25-m.y. period, and despite the variations in sublithofacies, sedimentation style remained remarkably similar throughout this span of time.