A novel method for utilizing AIMS to evaluate mask repair and quantify over-repair or under-repair condition

Abstract

The ZEISS AIMS™ platform is well established as the industry standard for qualifying the printability of mask features based on the aerial image. Typically the critical dimension (CD) and intensity at a certain through-focus range are the parameters which are monitored in order to verify printability or to ensure a successful repair. This information is essential in determining if a feature will pass printability, but in the case that the feature does fail, other metrology is often required in order to isolate the reason why the failure occurred, e.g., quartz level deviates from nominal. Photronics-nanoFab, in collaboration with Carl Zeiss, demonstrate the ability to use AIMS™ to provide quantitative feedback on a given repair process; beyond simple pass/fail of the repair. This technique is used in lieu of Atomic Force Microscopy (AFM) to determine if failing post-repair regions are "under-repaired" (too little material removed) or "over-repaired" (too much material removed). Using the ZEISS MeRiT® E-beam repair tool as the test platform, the AIMS™ technique is used to characterize a series of opaque repairs with differing repair times for each. The AIMS™ technique provides a means to determine the etch depth based on through-focus response of the Bossung plot and further to predict the amount of MeRiT® recipe change required in order to bring out of spec repairs to a passing state.

Scanning coherent diffractive imaging methods for actinic EUV mask metrology

“…1 However, the key issue to solve, apart from the source power performance gap, still remains the reliable detection and repair of mask defects. 2,3 Actinic mask metrology, being regarded as an essential part of the EUV mask infrastructure, is a major challenge and methods beyond the state-of-the-art are needed. The established metrology tools such as scanning electron microscopy have the disadvantage of being non-actinic, i. e. their imaging response from the absorber, multilayer, and pellicle varies from that of the scanner due to the use of electrons and photons at wavelengths different from the EUV design wavelength.…”

Beam drift and partial probe coherence effects in EUV reflective-mode coherent diffractive imaging

“…Over the past decades, considerable effort has been spent on the development of extreme ultraviolet (EUV) lithography to make the transition from deep ultraviolet lithography in upcoming technology nodes [1] and it is now believed that the technology will be ready for the 7 nm node. In the meantime however, a method for the reliable detection of mask defects remains a challenge [2,3]. In this context, a defect is defined as any structure in the fabricated mask that will lead to a fault when copied to the wafer.…”

A two-step method for fast and reliable EUV mask metrology

“…1 One of the major challenges to be solved remains the reliable and high-throughput detection of mask defects. 2,3 Actinic mask metrology, being regarded as an essential part of the EUV mask infrastructure, is a major challenge and methods beyond the state-of-the-art are needed for patterned mask inspection. The established metrology tools such as electron microscopy or DUV scanning microscopy have the disadvantage of being non-actinic, i. e. their imaging response to the absorber, multilayer, and pellicle differs from that of the scanner due to the use of electrons and photons at wavelengths different from the EUV wavelength (13.5 nm).…”