Fabrication of defect free EUV masks including their inspection is the most critical challenge for implementing EUV lithography into semiconductor high volume manufacturing (HVM) beyond 22nm half-pitch (HP) node. The contact to bit-line (CB) layers of NAND flash devices are the most likely the first lithography layers that EUV will be employed for manufacturing due to the aggressive scaling and the difficulty for making the pattern with the current ArF lithography.To assure the defect free EUV mask, we have evaluated electron beam inspection (EBI) system eXplore (TM) 5200 developed by Hermes Microvision, Inc. (HMI) [1]. As one knows, the main issue of EBI system is the low throughput. To solve this challenge, a function called Lightning Scan (TM) mode has been recently developed and installed in the system, which allows the system to only inspect the pattern areas while ignoring blanket areas, thus dramatically reduced the overhead time and enable us to inspect CB layers of NAND Flash device with much higher throughput.In this present work, we compared the Lightning scan mode with Normal scan mode on sensitivity and throughput. We found out the Lightning scan mode can improve throughput by a factor of 10 without any sacrifices of sensitivity. Furthermore, using the Lightning scan mode, we demonstrated the possibility to fabricate the defect free EUV masks with moderate inspection time.

Fabrication of defect free EUV mask is one of the most critical roadblocks for implementing EUV lithography into semiconductor high volume manufacturing for 22nm half-pitch (HP) node and beyond. At the same time, development of quality assurance process for the defect free EUV mask is also another critical challenge we need to address before the mass production. Inspection tools act important role in quality assurance process to ensure the defect free EUV mask. We are currently evaluating two types of inspection system: optical inspection (OPI) system and electron beam inspection (EBI) system [1, 2]. While OPI system is sophisticated technology and has an advantage in throughput, EBI system is superior in sensitivity and extendability to even small pattern.We evaluated sensitivity of EBI system and found it could detect 25 nm defects on 88nm L/S pattern which is as small as target defect size for 23 nm Flash HP pattern in 2013 in 2009 ITRS lithography roadmap [2, 3]. EBI system is effective inspection tool even at this moment to detect such small defects on 88nm HP pattern, though there are still some challenges such as the slow throughput and the reliability. Therefore, EBI system can be used as bridge tool to compensate insufficient sensitivity of current inspection tools and improve EUV mask fabrication process to achieve the defect free EUV mask. In this paper, we will present the results of native pattern defects founded on large field 88nm HP pattern using advance EBI system. We will also classify those defects and propose some ideas to mitigate them and realize the defect free EUV mask, demonstrating the capability of EBI as bridge tool.

In this study, a 3x-nm after development inspection (ADI) wafer with focus exposure matrix (FEM) was inspected with both an advanced optical system and an advanced electron beam inspection (EBI) system, and the inspection results were carefully examined. We found that EBI can capture much more defects than optical system and it also can provide more information about within reticle shot defect distribution. It has high capture rate of certain critical defects that are insensitive to optical system, such as nano-bridges. We also studied the critical dimension (CD) variations caused by the optical inspection and EBI.

Readiness of defect-free mask is one of the biggest challenges to insert extreme ultraviolet (EUV) lithography into semiconductor high volume manufacturing for 22nm half pitch (HP) node and beyond. According to ITRS roadmap updated in 2008, minimum size of defect needed to be removed is 25nm for 22nm HP node in 2013 [1]. It is necessary, therefore, to develop EUV mask pattern inspection tool being capable of detecting 25nm defect. Electron beam inspection (EBI) is one of promising tools which will be able to meet such a tight defect requirement. In this paper, we evaluated defect detection sensitivity of electron beam inspection (EBI) system developed by Hermes Microvision, Inc. (HMI) using 88nm half-pitch (HP) line-and-space (L/S) pattern and 128nm HP contact-hole (C/H) pattern EUV mask. We found the EBI system can detect 25nm defects. We, furthermore, fabricated 4 types of EUV mask structures: 1) w/ anti-reflective (AR) layer and w/ buffer layer, 2) w/ AR layer and w/o buffer layer, 3) w/o AR layer and w/ buffer layer, 4) w/o AR layer and w/o buffer layer. And the sensitivity and inspectability for the EBI were compared. It was observed that w/o AR layer structure introduce higher image contrast and lead to better inspectability, although there is no significant different in sensitivity.

We used electron beam (e-beam) inspection (EBI) systems to inspect nano imprint lithography (NIL) resist wafers with programmed defects. EBI with 10nm pixel sizes has been demonstrated and capability of capturing program defects sized as small as 4nm has been proven. Repeating defects have been captured by the EBI in multiple die inspections to identify the possible mask defects. This study demonstrated the feasibility of EBI as the NIL defect inspection solution of 32nm and beyond.

Nanoimprint lithography (NIL) is a candidate of alternative, low cost of ownership lithography solution for deep nano-meter device manufacturing12. For the NIL template pattern making, we have been developing the processes with 100keV SB EB writer and 50keV VSB EB writer to achieve the fine resolution of near 20nm1-7. However, inspection of nanoimprint template posed a big challenge to inspection system due to the small geometry, 1x comparing to 4x of Optical mask and EUV mask. Previous studies of nanoimprint template inspection were performed indirectly on a stamped wafer and/or on a round quartz wafer13. Electron beam inspection (EBI) systems have been widely used in semiconductor fabs in nanometer technology nodes. Most commonly EBI applications are electrical defects, or voltage contrast (VC) defects detection and monitoring8-11. In this study, we used a mask EBI system developed by Hermes Microvision, Inc. (HMI) to directly inspect a NIL template with line/space and hole patterns half pitched from 22nm to 90nm and with program defects sized from 4nm to 92nm. Capability of inspection with 10nm pixel size has been demonstrated and capability of capturing program defects sized 12nm and smaller has been shown. This study proved the feasibility of EBI as inspection solution of nanoimprint template for 22nmHP and beyond.