Adoption of EUV lithography for high-volume production is accelerating. TNO has been involved in lifetime studies from the beginning of the EUV alpha demo tools. One of the facilities for these studies is the EUV Beam Line (EBL1) designed and installed at TNO, in close cooperation with Carl Zeiss. There was a desire to improve on the performance of EBL1 in terms of source power and intensity, and in handling of full size EUV photomasks. For this purpose TNO has invested in the realization of a second EUV Beam Line: EBL2. EBL2 makes use of a tin fueled (USHIO) source in order to have a similar pulse length, shape and spectrum as an EUV scanner of ASML. Samples can be exposed to various doses/intensities of EUV light. Various process gasses can be introduced in a broad range of partial pressures and also sample temperature can be controlled. In-situ ellipsometry and in-situ X-ray Photoelectric Spectroscopy (XPS) is available to track surface changes/modifications. In this presentation we will discuss the capabilities of this unique research facility which is open for external customers studying the influence of EUV radiation on mirrors, sensors, fiducials, pellicles and EUV photomasks. We will discuss in this presentation parts of the validation studies and the experience we gained over the past year by running the setup for external customers.
TNO has built EBL2, an EUV exposure facility equipped with an in vacuo X-ray photoelectron spectroscopy setup (XPS) and an in-situ ellipsometer. EBL2 enables lifetime testing of EUV optics, photomasks, pellicles and related components under development in relevant EUV scanner and source conditions, which was previously not available to industry. This lifetime testing can help the industry to prepare for high volume production using EUV lithography by bringing forward information about material behavior which facilitates the development cycle. This paper describes an EUV photomask lifetime test performed at EBL2. The mask was exposed to different EUV doses under a controlled gas and temperature environment. To investigate how EUV light interacts with the mask, various analysis techniques were applied before and after EUV exposure. In-situ XPS was used to investigate elemental compositions of the mask surface. An ex-situ critical dimension scanning electron microscope (CD-SEM) and an atomic force microscope (AFM) were used to explore the impact of EUV light on critical dimensions (CD) and feature profiles. In addition, EUV reflectometry (EUVR) was used to investigate the change of reflectivity after EUV exposures. The exposure conditions are reported, as well as an analysis of the effects observed.
We report on advanced defect classification using TNO’s RapidNano particle scanner. RapidNano was originally designed for defect detection on blank substrates. In detection-mode, the RapidNano signal from nine azimuth angles is added for sensitivity. In review-mode signals from individual angles are analyzed to derive additional defect properties. We define the Fourier coefficient parameter space that is useful to study the statistical variation in defect types on a sample. By selecting defects from each defect type for further review by SEM, information on all defects can be obtained efficiently.