Johannes Bihr

Electron-beam-based photomask repair

High-resolution electron-beam-assisted deposition and etching is an enabling technology for current and future generation photomask repair. NaWoTec in collaboration with Carl Zeiss NTS (formerly LEO Electron Microscopy) has developed a mask repair tool capable of processing a wide variety of mask types, such as quartz binary masks, phase shift masks, extreme ultraviolet masks, and e-beam projection stencil masks. Specifications currently meet the 65nm device node requirements, and tool performance is extendible to 45nm and below. The tool combines LEO’s ultra-high-resolution Supra scanning electron microscope platform with NaWoTec’s proprietary e-beam deposition and etching technology, gas delivery system, and mask repair software. In this article, we focus on tool performance results; that is, the reproducibility and accuracy of repair of clear and opaque programmed defects on Cr binary and MoSi phase shift masks. These masks have in the past been difficult to repair due to beam position instability caus...

A novel electron-beam-based photomask repair tool

High-resolution electron-beam assisted deposition and etching is an enabling technology for current and future generation photo mask repair. NaWoTec in collaboration with LEO Electron Microscopy has developed a mask repair beta tool capable of processing a wide variety of mask types, such as quartz binary masks, phase shift masks, EUV masks, and e-beam projection stencil masks. Specifications currently meet the 65 nm device node requirements, and tool performance is extendible to 45 nm and below. The tool combines LEOs ultra-high resolution Supra SEM platform with NaWoTecs e-beam deposition and etching technology, gas supply and pattern generation hardware, and repair software. It is expected to ship to the first customer in October this year. In this paper, we present the tool platform, its work flow oriented repair software, and associated deposition and etch processes. Unique features are automatic drift compensation, critical edge detection, and arbitrary pattern copy with automatic placement. Repair of clear and opaque programmed defects on Cr, TaN, and MoSi quartz masks, as well as on SiC and Si stencil masks is demonstrated. We show our development roadmap towards a production tool, which will be available by the end of this year.

Electron-beam Induced Processes and their Applicability to Mask Repair

The applicability of electron-beam induced chemical reactions to mask repair is investigated. To achieve deposition and chemical etching with a focused electron-beam system, it is required to disperse chemicals in a molecular beam to the area of interest with a well-defined amount of molecules and monolayers per second. For repair of opaque defects the precursor gas reacts with the absorber material of the mask and forms a volatile reaction product, which leaves the surface. In this way the surface atoms are removed layer by layer. For clear defect repair, additional material, which is light absorbing in the UV, is deposited onto the defect area. This material is rendered as a nanocrystalline deposit from metal containing precursors. An experimental electron-beam mask repair system is developed and used to perform exploratory work applicable to photo mask, EUV mask, EPL and LEEPL stencil mask repair. The tool is described and specific repair actions are demonstrated. Platinum deposited features with lateral dimensions down to 20 nm demonstrate the high resolution obtainable with electron beam induced processes, while AFM and AIMS measurements indicate, that specifications for mask repair at the 70 nm device node can be met. In addition, examples of etching quartz and TaN are given.

Application of electron-beam-induced processes to mask repair

An electron beam technology for repair of Next Generation Lithography masks is described. Deposition of missing material in clear defects is shown with different material characteristics. Etching of opaque defects is demonstrated. The superiority of the electron beam technology to the well established and widely used focused ion beam techniques is discussed. Electron beam repair avoids the unacceptable transmission loss which is generated by focus ion beam techniques especially for 193 nm and 157 nm lithography by Ga-ion implantation. Shrinking dimensions of printable defects require higher resolution than ion beams allow, which is, however, obtained routinely with electron beam systems. Specially designed lenses having low aberrations provide outstanding better signal to noise ratio than ion beam systems. Results on deposition and etching of NGL mask relevant materials like TaN, SiC, Mo/Si, and silicon dioxide is demonstrated. In general 1 keV electrons and a low electron current were used for the etching processes.

Electron beam mask repair with induced reactions

Electron-beam induced chemical reactions and their applicability to mask repair are investigated. For deposition and chemical etching with a focused electron-beam system, it is required to disperse chemicals in a molecular beam to the area of interest with a well-defined amount of molecules and monolayers per second. For repair of opaque defects the precursor gas reacts with the absorber material of the mask and forms a volatile reaction product, which leaves the surface. In this way the surface atoms are removed layer by layer. For clear defect repair, additional material, which is light absorbing in the UV, is deposited onto the defect area. This material is rendered as a nanocrystalline deposit from metal containing precursors. An experimental electron-beam mask repair system is developed and used to perform exploratory work applicable to photo mask, EUV mask, EPL and LEEPL stencil mask repair. The tool is described and specific repair actions are demonstrated. Platinum deposited features with lateral dimensions down to 20 nm demonstrate the high resolution obtainable with electron beam induced processes, while AFM and AIMS measurements indicate, that specifications for mask repair at the 70 nm device node can be met. In addition, examples of etching quartz, TaN, and silicon carbide stencil masks are given.