Evaluation of mask repair strategies via focused electron, helium, and neon beam induced processing for EUV applications

Abstract

One critical area for EUV lithography is the development of appropriate mask repair strategies. To this end, we have explored etching repair strategies for nickel absorber layers and focused electron beam induced deposition of ruthenium capping layers. Nickel has higher EUV absorption than the standard TaN absorber layer and thus thinner films and improved optical quality can be realized. A thin (2.5 nm) ruthenium film is commonly used as a protective capping layer on the Mo-Si EUV multi-layer mirror which mechanically and chemically protects the multi-layers during standard mask-making procedures. The gas field ion (GFIS) microscope was used to investigate helium and neon ion beam induced etching (IBIE) of nickel as a candidate technique for EUV lithography mask editing. No discernable nickel etching was observed for helium, however transmission electron microscopy (TEM) revealed subsurface damage to the underlying Mo-Si multilayers. Subsequently, neon beam induced etching at 30 keV was investigated and successfully removed the 50 nm nickel absorber film. TEM imaging also revealed subsurface damage in the underlying Mo-Si multilayer. Two damage regimes were apparent, namely: 1) beam induced mixing of the Mo-Si layers and 2) nanobubble formation. Monte Carlo simulations were performed and the observed damage regimes were correlated to: 1) the nuclear energy loss and 2) a critical implant concentration. Electron beam induced deposition (EBID) was explored to deposit ruthenium capping/protective layers. Several ruthenium precursors were screened and so far liquid bis(ethylcyclopentyldienyl)ruthenium(II) was successful. The purity of the as-deposited nanodeposits was estimated to be 10% Ru and 90% C. We demonstrate a new chemically assisted electron beam purification process to remove carbon by-products and show that high-fidelity nanoscale ruthenium repairs can be realized.

Ultra-fast direct growth of metallic micro- and nano-structures by focused ion beam irradiation

“…Similarly, Cryo-FIBID holds great potential for mask repair in optical lithography. Nowadays, FIBID competes with FEBID for growth of restoring materials during mask repair 17,18 . The main disadvantage of FIBID for this application, which is the ion damage that changes the mask optical properties, could be avoided by means of Cryo-FIBID given the very low ion dose needed.…”

“…In the so-called Focused Electron Beam Induced Deposition (FEBID) and Focused Ion Beam Induced Deposition (FIBID) techniques, the attained lateral resolution of the deposits is regularly within a few tens of nm, but proof-of-concept experiments have shown resolution as good as 3 nm for the growth of Pt-based dots by FEBID 13 , and 10 nm for the growth of cobalt lines by He + -FIBID 14 . FEBID/FIBID techniques have found applications for the local growth of metal lines used to establish electrical connection between different parts of microelectronic circuits during circuit edit 15,16 , for the restoration of material continuity when repairing defects found in optical masks 17,18 , and, more recently, for the growth of functional materials in the fields of magnetism 19,20 , superconductivity 21 , nano-devices 22 , nano-optics and plasmonics 23,24 , and sensing 25 . In these applications, FEBID and FIBID bring in a high lateral resolution, the capability for three-dimensional growth, the functionality of the deposited material, the tunability of the deposit composition during growth or by post-processing, and the freedom in the choice of substrate.…”

Comparison between Focused Electron/Ion Beam-Induced Deposition at Room Temperature and under Cryogenic Conditions

“…In Figure 1, various applications of FEBID and FIBID are sketched: the growth of in-plane and three-dimensional nanostructures on flat substrates [25], as well as on unconventional substrates such as cantilevers/tips [26], and flexible [27], insulating [28] or origami substrates [28], etc. Materials grown by FEBID/FIBID are currently used for circuit edit and mask repair in the semiconductor industry [24,[29][30][31], lamellae preparation [7], the placement of electrical contacts to micro-and nano-structures [32,33], for producing sensors [34,35] and magnetic tips [36][37][38], plasmonic [39][40][41][42] and nano-optical elements [43], superconducting films [44] and nanowires [45], etc. Although FEBID/FIBID is an active field of research and development, a wider impact is hampered by the limited process speed.…”

Comparative study of extreme ultraviolet absorber materials using lensless actinic imaging

“…4,16 However, obtaining thin, smooth, and defect-free Ni layers on ML stacks without damaging the ML is extremely difficult. 17,18 Also, in the case of HSQ, the index of refraction depends on the development parameters after electron beam exposure, as density and composition may vary. 19 The given range corresponds to a density between 1.57 and 2.17 g∕cm 3 .…”