In this work, a newly developed optical lens cementing technology is reported. A fluoride material is used as an optical cement that can reduce damage from deep-ultraviolet (DUV) radiation. The degradation of transmittance and the surface quality of the cemented optical elements, including adhesive used for cementing, are evaluated after prolonged DUV irradiation. It is shown that with a 248-nm wavelength, this cement works quite well, up to 1000 h of operation, and the change in transmittance is negligible where average irradiation power is within 27 to 37 mW/cm2. Hence for all practical purposes, the use of this cement in microscope objectives is quite acceptable for 248-nm applications, thus confirming that this cementing technology is satisfactory and meets the performance requirement of DUV inspection systems.
The most annoying problem accompanying production of high-fidelity pattern images in mask defect inspection
systems is the generation of virtual images in the imaging process. The focused image pattern on the image acquisition
sensor has two images, one true and one virtual. The virtual images are generated under Kohler's illumination using
an integrator. The theoretical cause of this virtual image is the periodicity of the integrator.
The improvement of image quality gives the mask defect inspection system higher defect detection sensitivity. To
reduce virtual images, the double integrator method is applied to the illumination optics. By adopting the double
integrator illumination method, virtual images disappear in the imaging field. Further, since this also lowers the power
density at bright spots, the interference of lenses in working environments at the aperture stop position between
objective imaging lenses is greatly reduced.
This paper reports a method by which the ill effects of image quality improvement in the mask defect inspection
system can be dramatically reduced. The simulation results when this method is applied to an advanced mask defect
inspection system are shown.
In this paper, a newly developed optical lens cementing technology is reported. Here, a fluoride material is used as an optical cement which can reduce damage from DUV radiation. The degradation of transmittance and the accuracy of surface of the cemented optical elements including adhesive used for cementing have been evaluated after prolonged DUV irradiation. It has been shown that with 248 nm wavelength this cement works quite well, and moreover, even with 193 nm wavelength, when used for 1000 hours, the change in transmittance was negligible where average irradiation power was kept within 300mW/cm2. Hence for all practical purpose the use of this cement in microscope objective is quite acceptable for 248 nm applications, thus confirming that this cementing technology is satisfactory and meets the performance requirement of DUV inspection systems.
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.
KEYWORDS: Objectives, 3D metrology, Image resolution, 3D image processing, Semiconductors, Reconstruction algorithms, 3D image reconstruction, Magnetism, Electron beams, Optical simulations
We report about three-dimensional measurement by CD-SEM. Last year, we reported that the new T-MOL (Tilting and Moving Objective Lens) electron optical system enabled the capture of tilt images without deterioration of the resolution and confirmed that the T-MOL system provides 4 nm resolution at tilting angle 5 degrees. In this year we developed and evaluated the new objective lens and the new octapole deflector for increase of tilting angle and improvement in resolution, and we confirmed that the new electron optical system provides 3.6 nm resolution at tilting angle 8 degrees. Moreover, we report the optimization of the stereo matching technique based on the tilting picture using the actual semiconductor device for measurement 3D analysis.
There is an increasing necessity for 3D measurement of formed patterns in the semiconductor manufacturing process, and the development of the 3D measurement technology is required even in CD-SEM. In order to obtain 3D images, it is necessary to acquire at least two tilted images from different directions. However, the procedure of tilting the specimen stage is disadvantageous from the throughput point of view. Therefore, we devised the T-MOL system, which enables the acquisition of tilt images without the deterioration of the resolution by tilting the primary electron beam. Moreover, the algorithm of the parallel projection for the 3D reconstruction was developed. Tests proved that new T-MOL electron optical system provides 4nm resolution tilting angle at 5 degrees and that 3D analysis based on T-MOL images is effective.
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.
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