Mask inspection tool with DUV laser source has been used for Photo-mask production in many years due to its high sensitivity, high throughput, and good CoO. Due to the advance of NGL technology such as EUVL and Nano-imprint lithography (NIL), there is a demand for extending inspection capability for DUV mask inspection tool for the minute pattern such as hp4xnm or less. But current DUV inspection tool has sensitivity constrain for the minute pattern since inspection optics has the resolution limit determined by the inspection wavelength and optics NA.
Based on the unresolved pattern inspection capability study using DUV mask inspection tool NPI-7000 for 14nm/10nm technology nodes, we developed a new optical imaging method and tested its inspection capability for the minute pattern smaller than the optical resolution. We confirmed the excellent defect detection capability and the expendability of DUV optics inspection using the new inspection method. Here, the inspection result of unresolved hp26/20nm pattern obtained by NPI-7000 with the new inspection method is descried.
A novel high-resolution mask inspection platform using DUV wavelength has been developed. This platform is designed to enable the defect inspection of high quality masks for 65nm node used in 193nm lithography. In this paper, newly developed optical system and its performance are reported. The system is operated at wavelength of 198.5nm, which wavelength is nearly equal to 193nm-ArF laser exposure tool. Some defect image data and defect inspection sensitivity due to simulation-base die-to-die (D/D) inspection are shown on standard programmed defect test mask. As an initial state D/D inspection performance, 20-60 nm defects are certified. System capabilities for 65nm node inspection and beyond are also discussed.
We have developed a new photomask inspection method which has capability for inspecting 65nm technology node reticles using 257nm wavelength light source. This new method meets the requirement for the current mask inspection system using KrF inspection light source to be employed even in the fabrication of photomasks for 65nm technology node by the appearance of immersion technology using ArF wavelength. This paper discusses the detection capability of the 257nm wavelength inspection system for the defects on the 6% ArF attenuated phase shifting masks for 65nm node, using DSM based test pattern mask.
The defect detection capability for a minute pinhole by a newly developed mask inspection system MC-3500 with DUV reflected light source is reported. The detection sensitivity of a minute pinhole less than 180 nm on a KrF phase shift mask (PSM) with transmitted light source is limited because the pinhole signal intensity is influenced by the diffraction light. The signal intensity of the pinhole both by the reflected light source and transmitted light source was calculated by an optical simulator, and the actual pinhole signal of the KrF PSM and that of the ArF PSM were measured using the MC-3500 with reflected light source. It was found that the 100 nm minute pinhole, which was not detected by the inspection with the transmitted light source, was detected by the inspection with the reflected light source. This shows the effectiveness of the reflective inspection, thus proved that the newly developed MC-3500 inspection system with reflective inspection capability has very high defect detection sensitivity for the advanced masks of 100-130 nm rule and below devices.
A new mask inspection system for 150nm and 130nm semiconductor devices which utilizes a DUV laser of 257nm wavelength for an inspection illumination has been developed. A newly developed optical phase shift disk cancels the speckle nose caused by the high coherency of a laser. The phase shift disk has micro pits with different depth disposed randomly over the entire plate surface. The speckle pattern changes randomly by rotating the plate, and averaging pattern image by TDI sensor cancels the speckle noise of the laser illumination. Using this method, inspection of masks was realized at DUV wavelength.
In order to perform mask inspection with the high reliability for 150 nm-rule and below devices, the inspection system with high resolution is indispensable. The phase shift masks like DUV HT masks must also be inspected with high sensitivity. A next generation mask inspection system MC-3000 which used DUV optics has been developed, in order to achieve these requirement. The wavelength of this optics is 257 nm that is shorter than that of current UV inspection systems, and is nearly equal to that of current DUV lithography systems. Short wavelength light and high NA optics obtain high resolution, so the defect detection of 130 nm or less is attained. The special issues for the DUV optics were solved by several new techniques. This paper reports the system configuration, basic characteristics for defect detection and inspection performances.
For mask defect inspection in 256 Mbit and 1 Gbit DRAMs, it is necessary to have high sensitivity of 0.2 - 0.1 micrometer. A new die-to-database mask inspection system MC-2000 for 256 Mbit and 1 Gbit DRAMs has been developed. This system has high resolution optics with i-line light and high NA lens, and high speed and high accuracy data processing circuit by new multilevel bit map pattern generator, so the system has both high detectability and high throughput. This paper describes system configuration which include optical system and mechanical system, the defect inspection method, and inspection performance including defect sensitivity.
This paper describes an image sensing method and defect detection algorithm applied for a newly developed mask inspection system, the MC-2000, for 256 Mbit and 1 Gbit DRAM masks. The MC-2000, which utilizes i-line wavelength optics, is designed for less than 0.2 micrometer defect detection capability. An image sensing system employing a TDI (time delay integration) CCD image sensor is used for i-line image acquisition with an 80 Mpixel/sec data rate. Defect detection is done by comparing sensor image data with CAD data. Here we utilized our original differential comparison method which has very high sensitivity for defect detection.
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