Impact of new MoSi mask compositions on processing and repair

Abstract

The mask industry has recently witnessed an increasing number of new MoSi mask blank materials which are quickly replacing the older materials as the standard in high end mask shops. These new materials, including OMOG (opaque MoSi on glass) and high transmission (Hi-T) films, are driven foremost by the need to reduce feature size through resolution enhancement techniques (RET). The subject of this paper is a new low stress, Hi-T material which addresses the challenges presented by transitioning to smaller technology nodes including difficulties with pattern transfer, cleaning and repair. This material, based on currently employed MoSi films, eliminates process steps and utilizes a thinner overall substrate stack than currently used Hi-T schemes allowing an increase in critical dimension (CD) uniformity and feature resolution and more robustness due to a lower aspect ratio. While this new material is MoSi based the small compositional change requires, in some cases, a significant change in processing. Among the most impacted areas are the etch, clean and repair steps. Given the potential for defects to manifest on masks, repair is an invaluable step that can significantly impact the overall yield and lead to a reduction in cycle time 1 . The Carl Zeiss MeRiT ® electron beam mask repair line provides the most advanced repair capabilities allowing a wide range of repairs to be performed on a number of mask types 2 . In a joint effort between MP Mask Technology Center LLC and Carl Zeiss SMT, this paper focuses on the benefits of the new Hi-T mask blank and the challenges it presents to the repair community. The differences between the new low stress, Hi-T material and current Hi-T technologies are presented and on site compositional analysis is performed with x-ray photoelectron spectroscopy (XPS) to illuminate the compositional differences. The development of a repair process for the new material utilizing the on-site Carl Zeiss MeRiT ® MG 45 is presented along with several repairs and their AIMS™ results. KEYWORDSMeRiT ® MG45, AIMS™ 45-193i, mask repair, defect repair, new MoSi materials, Hi-T, high transmission INTRODUCTIONEmbedded attenuated phase shift mask (EAPSM) technology is one of the most utilized RETs in high end mask shops today. The use of MoSi films which allow a small amount of the incident light to be transmitted through the opaque material, commonly 6% at a 180 degree phase shift with respect to the clear regions, allows for higher contrast and the ability to pattern smaller, more complex features than binary masks 3 . However, as the limits of this technology are currently being pushed the need to further reduce feature size and improve the process window has sparked interest in a number of new MoSi based films in order to bridge the gap between current mask manufacturing capabilities and the next technology. The importance of extending MoSi based materials as far as possible can be understood when considering the industry infrastructure. All current tools, materials and processes such as ...

Atomic layer etching of chrome using ion beams

“…The photomask generally consists of quartz, chrome (Cr), and molybdenum silicide (MoSi). Depending on the type of photomask such as standard chrome on glass, opaque MoSi on glass, and phase-shifting mask, Cr is dry etched and used as a hard mask to fabricate the photomask owing to the low-etch selectivity between MoSi and quartz [17][18][19]. Thus, the dry etch process of Cr with a low surface damage and high-uniformity is important in determining the CD of the photomask.…”