USHIO INC. Received the First Acceptance of the EUV Light Source for Mask Inspection to EUV Lithography Mass Production Process

Accelerating EUV Business by highly recognized performance in the R&D Equipment

USHIO INC. (Head office: Tokyo, Chief Executive Officer: Koji Naito) announced that the company has received the first acceptance of the EUV light source for mask inspection equipment*1 used in an EUV lithography mass-production process (hereinafter “EUV light source”)on July 2019.
EUV lithography technology is indispensable to the manufacturing process of more highly integrated next-generation semiconductor devices, and major device manufacturers are verifying the practical use of the technology. Meanwhile, the mask inspection with the EUV light source to detect defects in high-precision masks must be implemented in order to establish an EUV lithography mass-production technologies.
USHIO has been conducting research and development of the high-brightness EUV light source and has improved the performance and reliability by providing research and evaluation service using USHIO’s high-brightness laser-assisted discharge-produced plasma (Sn LDP) EUP light source*2  in the EUV exposure and analysis facility (“EBL2”) of the Netherlands Organization for Applied Scientific Research (“TNO”) from March 2017.
In addition to the activity in TNO, this acceptance had been made by the high performance achievement of the EUV sources previously delivered and currently operated for inspection tool development at an inspection equipment manufacturer. This high-brightness EUV light source enables “actinic” mask inspection for EUV lithography that is required for next-generation semiconductor mass-production process.
”We provide full lineup of lighting-edge solutions. In particular, the EUV light source is one of our core competences. The practical use of EUV lithography is one of the long-awaited necessary conditions to deliver tangible fruits of new generation technologies such as a new communication protocol and various applications using the communication technologies. As a light specialist company, it is our pleasure to contribute to the  realization of expected social infrastructure through the acceptance of EUV light source for inspection equipment for mass-production process. We will do our best to ensure the stable supply of products while keeping in mind our social responsibility for our future.” (Nobuhiro Inosako, Director in charge of EUV Business, USHIO INC.)
USHIO will continue to develop the EUV light source technologies for high-precision mask inspection and contribute to the progress of the cutting edge semiconductor manufacturing process.


*1 EUV light source for mask inspection equipment
EUV (Extreme ultraviolet) uses a reflective mirror instead of a lens as optics, since EUV hardly passes through a material. Mask blanks for reflective optics have a Mo/Si multilayer structure. If a defect exists, the pattern is deformed. Therefore, the inspection to check if there is a defect or not is necessary for the mass-production process. The EUV mask inspection is roughly divided into the following three types.

1-1. Actinic Blanks Inspection (ABI)
This inspection uses an EUV light source and is carried out for the quality control of EUV mask blanks. An EUV blank is made of a Mo/Si multilayer film. An actinic (EUV light) inspection is required to detect phase defects in a base low expansion substrate and in a multilayer film.
1-2. Actinic Pattern Inspection(API)
This inspection uses an EUV light source and is carried out for the quality control of EUV pattern masks. An actinic inspection is required to detect Mo/Si phase defects, in addition to absorber pattern defects on the surface. Inspection can also be carried out for a mask with a pellicle attached.
1-3. Systems for Aerial Image Measurement 
This system simulates exposure and determines the deterioration of optical contrast of a defect detected in the API inspection. It also inspects the optical contrast after fixing the defect to ensure the appropriateness of optical contrast.

*2 Laser-assisted discharge-produced plasma (SN LDP) EUV light source 
This method retrieves EUV light by evaporating the tin on the electrode with laser trigger and exciting the evaporated tin with the discharge-produced plasma. This method is characterized by higher intensity and more space saving compared to the LPP/Sn method, which retrieves EUV light by exciting the tin that produces plasma with laser, and the DPP method, which retrieves EUV light by exciting the xenon with the discharge-produced plasma.


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