Volker Boegli

Electron beam lithography digital pattern generator and electronics for generalized curvilinear structures

A vector scan pattern generator, optimized for smooth curvilinear as well as rectilinear primitive shapes, has been designed and constructed. The pattern generator uses high‐speed hardware to implement a set of second‐order, quadratic equations to drive digital to analog converters and high‐speed array processors to calculate the coefficients for these equations. The digital pattern generator package contains the high‐speed digital, analog, and high‐resolution analog electronics. The initial lithography results confirm the operation of the system and stepping rates of 40 MHz have been achieved.

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...

Spatial-phase-locked electron-beam lithography : initial test results

Earlier spatial‐phase‐locked e‐beam lithography (SPLEBL) was proposed as a means of eliminating the well‐known problem of feature placement precision in scanning electron‐beam lithography. In SPLEBL, a grid with long‐range spatial‐phase coherence is created on a substrate (or on top of its resist coating) and this grid is used to feedback information on beam location to the control system. In initial tests a standard deviation (σ) of 0.3 nm for phase‐locking precision in one dimension was demonstrated, which represents the finest field stitching ever obtained with any lithographic method. In two dimensions (2D), σx, σy=0.6, 0.4 nm was obtained. Moire spatial‐phase locking was also demonstrated in 2D. Two strategies for the global‐fiducial grid appear feasible: plating base modulation and a thin film of holographically exposed photoresist on thin‐film Al above the e‐beam resist. Either would permit spatial‐phase locking without exposure of resist.

Metrology of electron‐beam lithography systems using holographically produced reference samples

Metrology in an electron‐beam lithography system is typically carried out by a combination of beam scan and laser‐interferometer‐controlled sample motion. The high‐resolution technique presented in this paper avoids the stage motion by using a holographically produced grid, which is essentially a permanently recorded interference pattern. This grid can be at least as accurate as the interferometer, and no stage motion, with the potential for additional error sources, is required to map out the distortion in the deflection field. The quality of the grid is critical since it is the reference to which the distortion is compared. With careful control of the holographic exposure system, high‐quality low‐distortion orthogonal grids were fabricated. We have produced grids with a period of 200 nm and orthogonality of a few arc seconds using an UV laser holographic system. Once the grid is processed to produce a high‐contrast signal for either back‐scattered or transmitted electrons, both scanning and signal‐proce...

Application data of the electron beam based photomask repair tool MeRiT MG

With the ever decreasing feature sizes and increasing cost of current and future photolithographic masks the repair of these masks becomes a substantial factor of the total mask production cost. In collaboration NaWoTec GmbH, Carl Zeiss Nano Technology Systems Division and Carl Zeiss Semiconductor Metrology Systems Division have launched a mask repair 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. In this paper, besides a brief overview of the tool platform, we will present the automated repair of clear and opaque defects on Cr and MoSi quartz masks. Emphasis will be put onto the resolution and the speed of the repair procedure and the high grade of automation and integration achievable in the repair of highend photomasks. An outlook against the ITRS requirements and the extendibility of the presented solution to further technology nodes will be given in the summary.

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.

Demonstration of damage-free mask repair using electron beam-induced processes

In this paper, we present the test results obtained from the first commercial electron beam mask repair tool. Repaired defect sites on chrome-on-glass masks are characterized with 193nm AIMS to quantify the edge placement precision as well as optical transmission loss. The electron beam mask repair tool is essentially based on a scanning electron microscope (SEM), therefore, it can be used for in-situ CD and defect metrology. E-beam for EUV mask defect repair is also discussed. These early results are very encouraging and demonstrate the basic advantages of electron beam mask repair as well as highlight the key challenge of charge control.

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.

Performance results from the Zeiss/NaWoTec MeRit MG electron beam mask repair tool

With the ever decreasing feature sizes and increasing cost of current and future photolithographic masks the repair of these masks becomes a substantial factor of the total mask production cost. In a collaborative effort NaWoTec, Carl Zeiss Nano Technology Systems Division (NTS) and Carl Zeiss Semiconductor Metrology Systems Division (SMS) have built an electron beam based mask repair 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. In this paper, besides a brief overview of the tool platform, we will present the automated repair of clear and opaque defects on Cr and MoSi quartz masks. Emphasis will be put onto the resolution and the speed of the repair procedure and the high grade of automation and integration achievable in the repair of high-end photomasks. An outlook against the ITRS requirements and the extendibility of the presented solution to further technology nodes will be given in the summary.