EUV substrate and blank inspection with confocal microscopy

One of the critical issues for extreme ultraviolet lithography masks is particle-free mask handling. We report that the number of particle adders on the front side of a mask in a dual pod can be reduced to less than 0.01 particles/cycle (>46-nm polystyrene latex) during the process of starting from the load port to placing an electrostatic chuck (ESC) in vacuum. In addition, we find that chucking the mask on the ESC causes serious issues. One of these issues is whether the masks will be electrically charged by chucking the ESC and whether some particles will be added on the front side. We measure the electric potential of the back and front sides of the mask and examine the particle adders. We find that when the mask is electrically floated, potential on the front side of the mask increases during ESC chucking; when the mask is released from the ESC, it is electrically charged. This electrification causes adhesion of the particles. Our experiments show that to protect the mask from particles, the mask must be grounded throughout the entire process. For electrification, we confirm that a dual-pod system is effective in protecting the mask from particles. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

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“…(9) into Eq. (8) and setting, we obtain F z = −χ · ε 0 · Q/ 4π · ε 0 · r 2 12 · dE /dr · (r 1 −r 2 ) · r 2 12 · 0 ≈ χ · ε 0 · E 12 · V · dE /dr.…”

Section: Discussionunclassified

“…7,8 The defect detection rate was greater than 95% for the 46-nm PSL on a quartz mask blank. The defect detection rate was greater than 90% for the 70-nm PSL on a CrN layer.…”

Section: Particle Inspection Toolmentioning

confidence: 99%

Study of electrification of extreme ultraviolet lithography mask and adhesion of particles during electrostatic chucking

Amemiya

Ota²,

Taguchi³

et al. 2011

J. Micro/Nanolith. MEMS MOEMS

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“…Multi-beam confocal inspection, a deep UV non-actinic method, has been the primary inspection method for substrates and blanks [104,105,[109][110][111]. However, the sensitivity of current non-actinic inspection may be not high enough, because actinic methods can diagnose multilayer defects [112][113][114] with better sensitivity [115,116] than the state-of-the-art non-actinic mask blank inspection system.…”

Section: Maskmentioning

confidence: 99%

Next-generation lithography for 22 and 16 nm technology nodes and beyond

2011

Sci. China Inf. Sci.

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In this paper, next-generation lithography (NGL) for the 22 and 16 nm technology nodes and beyond is reviewed. A broad range of topics, including history, technologies, critical challenges, and the most plausible candidates are discussed. The 22 and 16 nm technology nodes rely on NGL. NGLs have been extensively studied. Because of technological issues, the semiconductor industry has stopped pursuing several NGLs, such as X-ray proximity lithography, ion projection lithography, and scattering with angular limitation projection electron lithography. Currently, the primary candidate technologies are extreme ultraviolet lithography (EUVL), maskless lithography (ML2), and nanoimprint lithography (NIL), with EUVL being the leading candidate. Since EUVL was first proposed in 1988, many studies have been conducted. Currently, there is no "show stopper" for EUVL. Moreover, challenges are present in almost all aspects of EUVL technology. Almost all primary semiconductor manufacturing companies plan to implement commercial pre-production step-and-scan exposure tools in 2011. However, EUVL power at an intermediate focusing level has not yet met the volume manufacturing requirements. EUVL resists have been significantly improved recently, but there is still a critical need to meet requirements on resolution, line width roughness, and sensitivity. Creating a defect-free EUVL mask is another obstacle to the application of EUVL. ML2 and NIL, like EUVL, have also undergone significant progress recently, but throughput, defect control, and cost remain the critical impediments for practical application.

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“…Not only a 2nm-high multilayer defect at the surface of multilayer can be critical at 45nm node 2 , but very recently it is suggested by simulation of line CD variation for the 32 nm node logic that a multilayer bump lower than 1nm in height can be a critical defect with 90nm defocus in the worst case 3 . Lots of efforts are widely made for detecting such defects using visible light or UV and substantial progress is observed 4,5 . However, it is still unclear whether visible/UV inspection can detect all critical multilayer defects with clear disposition criteria because formation process of multilayer defects under manufacturing-compatible condition is not fully characterized.…”

Section: Introductionmentioning

confidence: 99%

Actinic detection and screening of multilayer defects on EUV mask blanks using dark-field imaging

et al. 2004

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MIRAI Project has developed a novel actinic (at-wavelength) inspection tool for detecting critical multilayer defects on EUV mask blanks using a dark-field imaging and a laser-produced plasma (LPP) light source. The first milestone of proof-of-concept was successfully achieved by demonstration of programmed defect detection accurate to 70nm in width and 2nm in height without any detection of false defects 1 . Characterization of this experimental actinic inspection tool is ongoing to define the detailed specification of a proto-type tool. One of the important factors that define the sensitivity of the inspection tool is the signal to noise ratio available from the inspection image. In this paper, characterization results of background fluctuation and through focus imaging are presented.The characterization of background fluctuation suggested that the pixel-to-pixel fluctuation by spatial fluctuation of roughness is smaller than originally assumed possibly because of the smoothing by the aberration of the imaging optics. The negative impact of the degradation of defect signal by the aberration at the best focus is relaxed due to the smoothed fluctuation of the background intensity.

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EUV substrate and blank inspection with confocal microscopy

Cited by 22 publications

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Study of electrification of extreme ultraviolet lithography mask and adhesion of particles during electrostatic chucking

Study of electrification of extreme ultraviolet lithography mask and adhesion of particles during electrostatic chucking

Next-generation lithography for 22 and 16 nm technology nodes and beyond

Actinic detection and screening of multilayer defects on EUV mask blanks using dark-field imaging

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