Mask inspection

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

Wavelength-specific reflections: A decade of EUV actinic mask inspection research

Abstract: Mask inspection is essential for the success of any pattern-transfer lithography technology, and EUV Lithography in particular faces unique challenges. EUV masks resonant-reflective multilayer coatings have a narrow, wavelength-specific response that dramatically affects the way that defects appear, or disappear, at various illuminating wavelengths. Furthermore, the ever-shrinking size of 'critical' defects limits the potential effectiveness of DUV inspection techniques over time. Researchers pursuing numerous ways of finding and characterizing defects on EUV masks and have met with varying degrees of success. Their lessons inform the current, urgent exploration to select the most effective techniques for high-volume manufacturing. Ranging from basic research and demonstration experiments to commercial inspection tool prototypes, we survey the recent history of work in this area, including sixteen projects in Europe, Asia, and America. Solutions range from scanning beams to microscopy, dark field imaging to pattern transfer.

Mask inspection apparatus and exposure method using the same

Abstract: PROBLEM TO BE SOLVED: To provide a mask inspection apparatus which carries out rapid and efficient mask inspection and an exposure method using the same. SOLUTION: The mask inspection apparatus 6 having a contamination detecting means for detecting the sizes, number of pieces and adhesion positions of the contamination 8 on the mask 7 and a discrimination circuit 12 for discriminating the usability or not of the mask 7 in accordance with the output of this contamination detecting means is provided with a foreign matter removing means 14 for removing the contamination 8 on the mask 7 in accordance with a controls signal from the discrimination circuit 12, by which the contamination removal processing within the exposure device is made possible, the rapid and efficient mask inspection processing is realized and the degradation in productivity is prevented. COPYRIGHT: (C)2002,JPO

Photomask, inspection method and method for manufacturing semiconductor device

Abstract: PROBLEM TO BE SOLVED: To provide a photomask for inspecting the birefringence of a projection lens. SOLUTION: The photomask is provided with: a transparent substrate 10; a pattern of a light shielding film 11 having a window part and formed on the surface of the transparent substrate 10; a first inspection pattern 13 disposed in the window part and polarizing illumination light into a first polarized state; and a second inspection pattern 14 disposed so as to be separated from the first inspection pattern 13 by a fixed distance in the window part and polarizing the illumination light into a second polarized state different from the first polarized state. COPYRIGHT: (C)2005,JPO&NCIPI

EUV photomask defects: what prints, what doesn't, and what is required for HVM

Abstract: As Extreme Ultraviolet (EUV) lithography has matured, numerous imposing technical challenges have been the focus of intense scrutiny, including the EUV radiation source, reflective optics, and fundamental mask fabrication. There has been a lurking question on the state of mask defectivity that has been almost unanswerable until the recent relative maturation of the rest of the infrastructure. Without readily available actinic blank or patterned inspection systems, EUV blank and mask manufacturers must continue to rely on relatively low resolution optical systems for blank characterization. Despite best efforts, detectable defects still exist; these can be classified into three types: small defects that can be avoided through pattern-shift, medium defects that can be repaired, and large defects which must be suppressed during manufacture. To successfully intercept high-volume-manufacturing (HVM) for the 7nm node, aggressive, continued industry focus is required to ensure that these three defect types are addressed. Without actinic mask inspection, an unknown element with EUV lithography continues to be the presence of nondetected printable defects – defects that print on wafer despite being undetected during mask or blank fabrication. Another risk is that until recently, focus has been on developing techniques to identify catastrophic defects, while past manufacturing experience tells us that much more subtle defects (<10% CD variation) can have significant impact on yield and performance. Using information from many characterization sources, including blank inspections, patterned inspection, atomic-force microscopy (AFM), scanning-electron microscopy (SEM), as well as 36nm and 32nm pitch wafer printing results, we will try to address what the real current state of mask defectivity is. We will discuss techniques to answer the key questions of: “What defects print, what defects do not, and what might our inspections methods be missing?” From this vantage point, we will analyze the current mask defectivity rates and sources, and assess the gap in capability to support full HVM support.

A novel run-time MEEF-driven defect disposition extending high resolution contamination inspection to next generation photomask

Abstract: The advent of device miniaturization necessitates sub-half-micron features delineated on reticles where photomask quality, more so than ever, exerts remarkable yield impact on 65 nm node and below. The introduction of advanced reticles considerably augments the mask error enhancement factor (MEEF) in the non-linear regime ensuing aggressive OPC features. The increased MEEF leads to tightened defect capture criteria, in which many of the previously insignificant defects become of interest and may have substantial yield impact. To provide desired sensitivity, a high resolution inspection is a must; it also effectively monitors mask reliability. However, the productivity of such inspection greatly depends on defect disposition efficacy in sorting out critical defects from the large population detected on contaminated masks [1-3]. Anchoring high resolution reticle inspection, wafer fabs are in a relentless pursuit of optimal defect disposition method to meet the throughput demand. In particular, progressive defects or haze, induced by repeated laser exposure, continue to be a source of reticle degradation threatening device yield. Early detection of these defects to circumvent the printability impact becomes vitally important yet challenging. In addition to its size, the defect criticality also largely depends upon defect optical transmittance, residing surface, its proximity to a printing pattern as well as lithography parameters such as NA and sigma [4-6]. A MEEF-driven lithographic detector named "Litho3" has been designed that can be used run-time during mask inspection to effectively group the critical defects into a single bin based on their potential yield impact. The coordinates of these critical defects, identified by the above Litho3 detector, can then be transferred from reticle to wafer and subsequently subject to printability validation, upon which defective sites can be analyzed thoroughly on reticle or wafer review tools. Such capability reduces inspection cycle time by improving defect disposition efficacy, also assists in determining lithography process window and a further comprehension of defect progression mechanism.