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.
InTlP — a proposed infrared detector material
In1−xTlxP is proposed as a promising material for infrared detectors. A number of key optical and structural properties are studied within local density‐functional theory. In1−xTlxP at x=0.67 and In1−xTlxAs at x=0.15 are estimated to have a gap of 0.1 eV. Their binding energies are larger than that of InSb, and they are found to form stable zinc‐blende alloys for all x. In1−xTlxP nearly lattice matches to InP, and offers the potential to integrate detector array and read‐out circuit.