We evaluated the capability of a commercially available DUV system equipped with
reflective inspection optics with the shortest inspection wavelength of 199nm in detecting
pattern defect on EUVL mask of hp45nm programmed defect pattern. The sensitivity of the
system for opaque extension defects for hp45nm node was quite acceptable but for clear
extension defects the sensitivity of the system was rather poor. In this paper, the influence of
base pattern size on inspection sensitivities for opaque and clear extension defects is discussed.
The lithography potential of an ArF (193nm) laser exposure tool with high numerical aperture (NA) will expand
its lithography potential to 65nm node production and even beyond. Consequently, a mask inspection system with a light
source, whose wavelength is nearly equal to 193nm, is required so as to detect defects of the masks using resolution
enhancement technology (RET). Wavelength consistency between exposure tool and mask inspection tool is strongly
required in the field of mask fabrication to obtain high defect inspection sensitivity. Therefore, a novel high-resolution
mask inspection platform using DUV wavelength has been developed, which works at 198.5nm. This system has
transmission and reflection inspection mode, and throughput using 70nm pixel size were designed within 2 hours per
mask. In this paper, transmitted and reflected light image acquisition system and high accuracy focus detection optics are
presented.
We have developed a mask inspection system using 199nm inspection light wavelength. This system performs
transmission and reflection inspection processes concurrently within two hours per plate. By the evaluation result of
mask images and inspection sensitivity, it is confirmed that the 199nm inspection system has the advantage over the
system using 257nm and has the possibility corresponding to next generation mask inspection. Furthermore, advanced
die-to-database (D-DB) inspection, which can generate high-fidelity of a reference image based on the CAD data for
alternating phase shift mask (PSM) or tri-tone, is required for next generation inspection system, too. Therefore, a
reference image generation method using two-layer CAD data has been developed. In this paper, the effectiveness of
this method is described.
The usage of ArF immersion lithography for hp 65nm node and beyond leads to the increase of mask error enhancement factor in the exposure process. Wavelength of inspection tool is required to consistent with wavelength of lithography tool. Wavelength consistency becomes more important by the introduction of phase shift mask such as Tri-tone mask and alternating phase shift mask. Therefore, mask inspection system, whose inspection light wavelength is 199nm, has been developed. This system has transmission and reflection inspection mode, and throughput, using 70 nm pixel size, were designed within 2hours per mask. The experimental results show expected advantages for Die-to-Die and Die-to-Database inspection compared with the system using 257nm inspection optics. Shorter wavelength effect makes transmission inspection sensitivity increase, and realizes 40nm size particle inspection. As for the phase shift mask, the difference of gray value between the area with phase defect and without phase defect was clear relatively. In this paper, specifications and design, experimental results are described.
As the ArF lithography technology is going to progress to 90nm node from 130nm node, it has been more difficult to inspect all types of mask defects, which influence wafer. Photomask for 90nm node, the aggressive OPC mask and Phase Shift Mask (PSM) might be inevitable in production devices due to the slow progresses in lithography equipment itself compared to shrinkage speed in device manufacturing.
Recently, due to the similiar effect such like MEEF (Mask Error Enhancement Factor) phenomenon many mask defects become to detect difficult even printable defects even the lots of improvements mask inspection equipments. In this paper, we will present the inspection capability of advanced DUV inspection tool LM7000 (NEC) with various programmed defect masks (e.g. aggressive OPC masks, half-tone PSM, tri-tone PSM) with, and discuss the relationship between inspection sensitivity and mask defect printability.
We have improved DUV laser reticle inspection system LM7000 for 90 nm technology node devices. To increase inspection sensitivity, we developed a reflected light inspection as a supplementary method to transmittance light inspection. We have also strengthened inspection algorithm to distinguish between real defects and very small features from optical proximity effect correction (OPC). Finally, we have improved reference image for die to database inspection. With the merit of short wavelength of LM7000 (266 nm), the inspection sensitivity of the high-transmittance half-tone phase shift mask (HTPSM) does not deteriorated so severely compared to that of binary mask. With the help of these series of improvements, LM7000 could shows inspection capability for OPC masks and HTPSM for ArF lithography. The inspection capability of LM7000 was proved with the programmed defect masks and printability experiment using ArF scanner.
Semiconductor industry still inspect reticle with the i-line wavelength and ITRS indicates only minimum defect size corresponds to 20 percent of the pattern size on mask in the same light. Currently defect definition, however, varies from the fixed minimum defect size to non-printable-maximum defect size due to increased reticle cost. This paper provides an investigation of requirements of current inspection system 193nm lithography. The lines and contact holes patterns were also investigated by both simulation and experiment. The printability of defects was observed under the various circumstances such as pitch variation and transmission of halftone film. From the defect printability study we found that defect printability behave non-linearly as the exposure condition varies and the size defect should be treated importantly as the ArF lithography extends till 70nm era. It is also understood that there is a possibility to miss the important meaning of the size defects from the simple definition of reticle defect. From the analysis of various types of defects and exposure conditions we suggested detail level of inspection sensitivity that new reticle inspection system should be ready.
The prompt progress of photomask pattern shrinking leads to the overlooking for significant defects. To improve the defect detection performance, patterns must be observed thoroughly at first. These observations are also important for a total diagnostic of the lithography process. Our developing reticle inspection machine LM5000 is very suitable for such analyses. With LM5000, users are able to point any positions on the reticle very easily, view the images, measure the lengths or widths of the patterns, and the intensity at each pixel. Users are also able to apply various image processing algorithms. To follow the growth of the semiconductor processes, inspection algorithms should be developed within very short terms. LM5000 adopts a special image processing core consisted of IMAP. It has strong processing power of a super computer class, and it is programmable even by a C-like language. Libraries for development include most of the standard image processing functions. Its flexibility helps us for reducing the development periods of the new algorithms. In this presentation, the functions of the user interface of LM5000 are displayed as a mask analyzing tool, and the effects of the IMAP processing is explained.
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