Mask inspection

About: Mask inspection is a research topic. Over the lifetime, 1072 publications have been published within this topic receiving 8696 citations.

Optimization of MDP, mask writing, and mask inspection for mask manufacturing cost reduction

Abstract: As the feature sizes of LSI become smaller, the increase in mask manufacturing time (TAT) and cost is becoming critical and posing challenges to the mask industry and device manufacturers. In May 2006, ASET Mask D2I launched a 4-year program for the reduction in mask manufacturing TAT and cost, and the program was completed in March 2010. The focus of the program was on the design and implementation of a synergetic strategy involving concurrent optimization of MDP, mask writing, and mask inspection. The strategy was based upon four key elements: a) common data format, b) pattern prioritization based on design intent, c) an improved approach in the use of repeating patterns, and d) parallel processing. In the program, various software and hardware tools were developed to realize the concurrent optimization. After evaluating the effectiveness of each item, we estimated the reduction in mask manufacturing TAT and cost by the application of results obtained from the Mask D2I programs. We found that mask manufacturing TAT and cost can be reduced to 50% (or less) and to about 60% respectively.

EUV pattern defect detection sensitivity based on aerial image linewidth measurements

Abstract: As the quality of EUV-wavelength mask inspection microscopes improves over time, the image properties and intensity profiles of reflected light can be evaluated in ever-greater detail. The SEMATECH Berkeley Actinic Inspection Tool (AIT) is one such microscope, featuring mask resolution values that match or exceed those available through lithographic printing in current photoresists. In order to evaluate the defect detection sensitivity of the AIT for dense line patterns on typical masks, the authors study the linewidth roughness (LWR) on two masks, as measured in the EUV images. They report the through-focus and pitch dependence of contrast, image log slope, linewidth, and LWR. The AIT currently reaches LWR 3σ values close to 9nm for 175nm half-pitch lines. This value is below 10% linewidth for nearly all lines routinely measured in the AIT. Evidence suggests that this lower level may arise from the mask’s inherent pattern roughness. While the sensitivity limit of the AIT has not yet been established, it ...

Superimposed common carrier mask inspection system

Abstract: A SYSTEM IN WHICH THE POSITION OF THE OPAQUE AREAS ON THE SURFACE OF A FIRST TRANSPARENT PHOTOGRAPHIC MASK ARE COMPARED TO THE POSITIONS OF THE OPAQUE AREAS ON THE SURFACE OF A SECOND TRANSPARENT PHOTOGRAPHIC MASK. THE TWO MASK SURFACE ARE PLACED FACE TO FACE AND SEPARATED BY A LAYER OF MATERIAL POSSESSING THE CHARACTERISTICS OF A "ONE-WAY" MIRROR. A SINGLE TELEVISION CAMERA, FOCUSED ON THE ADJACENT MASK SURFACES, VIEWS THE TWO MASKS WHICH ARE ALTERNATELY ILLUMINATED FROM ABOVE AND BELOW. WHEN ILLUMINATED FROM BELOW, LIGHT IS TRANSMITTED THROUGH BOTH MASKS AND THE "MIRROR", THE IMAGES OF THE OPAQUE AREAS ON BOTH MASKS APPEAR ON A MONITOR. WHEN ILLUMINATED FROM ABOVE, THE "MIRROR" REFLECTS LIGHT AND ONLY THE IMAGE OF THE OPAQUE AREAS ON THE UPPER MASK APPEARS ON THE MONITOR. A "FLECKER EFFECT," OR OTHER VISUAL DIFFERENTIAL DETECTION SYSTEM, INDICATES THE DEGREE OF DEVIATION OF THE POSITIONS OF THE OPAQUE AREAS ON THE FIRST MASK FROM THE SECOND MASK.

Development of coherent EUV scatterometry microscope with high-order harmonic for EUV mask inspection

Abstract: We have developed the standalone, coherent scatterometry microscope (CSM) for the inspection of extreme ultraviolet (EUV) lithography mask. The low divergence, coherent high-order harmonic (HH) was generated as coherent light source for CSM at a wavelength of 13.5 nm using a commercial laser system. The HH enable us to obtain the high contrast diffraction image from the mask. The diffraction light from the 2-nm wide line-defect and tens-nm size point-defects in the mask has been observed successfully with the system.

Actinic Mask Inspection Using an EUV Microscope –Preparation of a Mirau Interferometer for Phase-Defect Detection–

Abstract: This paper describes a mask defect inspection system using 13.5 nm light for extreme ultraviolet lithography (EUVL). The Schwarzschild optics which is employed as a microscope optics has a numerical aperture (NA) of 0.3 and a magnification of 30. Furthermore, it has a potential of detecting defects as small as 22 nm on a mask. In order to inspect defects with the phase change induced by swelling of the multilayer, a Mirau interferometer is employed. It is developed that the performance of the optical system, the focal position detection mechanism for image detection while scanning, and the driving mechanism of the reference mirror for the Mirau interference. Since the accuracy of the driving mechanism of the reference was found to be 0.1 nm, enough performance of the ring-shaped piezo actuator for interference measurement was confirmed. Moreover, examples of the mask inspection by this system are shown.