The introduction of EUV photomasks has posed significant challenges in defect repair over the years. Defects within the unique multi-layer stack used for the reflective optics can easily lead to printing defects on the wafer. Although absorber compensation repair has been successfully demonstrated in high-volume manufacturing (HVM), it has been accompanied by several obstacles. Next-generation EUV lithography for high numerical aperture (NA) EUV photomasks is proving more difficult due to stringent requirements. The advanced scanner optics demand more precise edge control for photomask repairs, necessitating the incorporation of resist effects in the defect review process to better emulate wafer impact.
In the realm of next-generation EUV masks, several material candidates show promising absorber behaviors, ranging from binary to phase-shift types. However, the mask repair process presents challenges when managing wafer windows for repaired defects. Precious profile control, high repair-defect durability and clean reticle surface need to be sustained to ensure lithography processes window. In this paper, several materials’ opaque defect etching is evaluated by using ZEISS e-beam based MeRiT® neXT repair tools, which offer an optimal physico-chemical process with right precursor chemistry and an optimized scanning of the e-beam over the surface to ensure repair quality. Moreover, longer repair time for next generation masks also challenges post-repair clean yield due to poor wettability from etching byproduct redeposition on reticle surface. Thus, we control a plasma flushing vacuum chamber application to eliminate surface wettability degradation, ensuring high post-repair clean yield. Our comprehensive strategy not only addresses current challenges with better reticle quality and longer lifetime but also paves the way for the seamless integration of advanced EUV mask materials into the future of semiconductor lithography.
This conference presentation was prepared for Photomask Japan 2022: XXVIII Symposium on Photomask and Next-Generation Lithography Mask Technology, 2022.
Mask repair is an essential step in the mask manufacturing process as the extension of 193nm technology and the insertion of EUV are drivers for mask complexity and cost. The ability to repair all types of defects on all mask blank materials is crucial for the economic success of a mask shop operation. In the future mask repair is facing several challenges. The mask minimum features sizes are shrinking and require a higher resolution repair tool. At the same time mask blanks with different new mask materials are introduced to optimize optical performance and long term durability. For EUV masks new classes of defects like multilayer and phase defects are entering the stage. In order to achieve a high yield, mask repair has to cover etch and deposition capabilities and must not damage the mask. We will demonstrate in this paper that low energetic electron-beam (e-beam)-based mask repair is a commercially viable solution. Therefore we developed a new repair platform called MeRiT® neXT to address the technical challenges of this new technology. We will analyze the limits of the existing as well as lower energetic electron induced repair technologies theoretically and experimentally and show performance data on photomask reticles. Based on this data, we will give an outlook to future mask repair technology.
Mask repair is an essential step in the mask manufacturing process as the extension of 193nm technology and the
insertion of EUV are drivers for mask complexity and cost. The ability to repair all types of defects on all mask blank
materials is crucial for the economic success of a mask shop operation. In the future mask repair is facing several
challenges. The mask minimum features sizes are shrinking and require a higher resolution repair tool. At the same time
mask blanks with different new mask materials are introduced to optimize optical performance and long term durability.
For EUV masks new classes of defects like multilayer and phase defects are entering the stage. In order to achieve a high
yield, mask repair has to cover etch and deposition capabilities and must not damage the mask. These challenges require
sophisticated technologies to bring mask repair to the next level. For high end masks ion-beam based and e-based repair
technologies are the obvious choice when it comes to the repair of small features. Both technologies have their pro and
cons. The scope of this paper is to review and compare the performance of ion-beam based mask repair to e-beam based
mask repair. We will analyze the limits of both technologies theoretically and experimentally and show mask repair
related performance data. Based on this data, we will give an outlook to future mask repair tools.
In today's economic climate it is critical to improve mask yield as materials, processes and tools are more time and cost
involved than ever. One way to directly improve mask yield is by reducing the number of masks scrapped due to defects
which is one of the major mask yield reducing factors. The MeRiTTM MG 45, with the ability to repair both clear and
opaque defects on a variety of masks, is the most comprehensive and versatile repair tool in production today. The cost
of owning multiple repair tools can be reduced and time is saved when fast turnaround is required, especially when more
than one defect type is present on a single mask. This paper demonstrates the ability to correct repair errors due to
human mistakes and presents techniques to repair challenging production line defects with the goal of maximizing mask
repair yield and cycle time reduction.
UV nanoimprint lithography (UV-NIL) is a high-throughput and cost-effective patterning technique for complex nanoscale
features and is considered a candidate for CMOS manufacturing at the 22nm node and beyond. To achieve this
target a complete template fabrication infrastructure including inspection and repair is needed. Due to the 1X
magnification factor of imprint lithography the requirements for these steps are more challenging compared to those for
4X photomasks. E-beam repair is a very promising repair technology for high-resolution imprint templates. It combines
the advantages of precise beam placement using fine resolution images and damage free repair by electron beam induced
chemical reactions. In this work we performed template repair using a new test stand with improved beam and stage
stability. Repeatability of 3D pattern reconstruction with main focus on shrunk lateral repair dimensions and height
control was investigated. The evaluation was done on various features in a 40nm half pitch design. Additionally, the
resolution capability of the new hardware was examined on selected programmed defects in a 32nm half pitch design. A
first qualitative examination of the repaired template was done using top-view SEM images taken from the test stand
before and after repair. The repaired template was then imprinted on 300mm silicon wafers, and the imprinted repaired
defects were analyzed using a SEM Zeiss Ultra 60.
The cost and time associated with the production of photolithographic masks continues to grow, driven by the ever
decreasing feature size, advanced mask technologies and complex resolution enhancing techniques. Thus employment of
a high-resolution, comprehensive mask repair tool becomes a key element for a successful production line. The MeRiT®
utilizes electron beam induced chemistry to repair both clear and opaque defects on a variety of masks and materials with
the highest available resolution and edge placement precision. This paper describes the benefits of the electron beam
induced technique as employed by the MeRiT® system for a production environment.
With the continuing decrease of feature sizes on photomasks and the related rising costs for current and future masks
the importance of a reliable repair and repair assessment process has often been highlighted. The assessment, repair and
repair validation of these expensive masks has become a very substantial factor of the total mask production cost
The introduction of immersion lithography and the proposed introduction of double exposure strategies will further
amplify this trend. In this paper we have concentrated on masks with feature sizes relevant for the 45nm node and
defects with typical size and shape as they appear in production. Phase shifting masks with synthetic defects have been
manufactured and the printability of the defects is analyzed with an AIMSTM45-193i. For representative defects the
outline and three-dimensional shape as well as further characteristics have been visualized with the inherent electron
microscope capability of the electron beam based repair tool, prior to repairing them with the repair system. In addition
we will show the behaviour of the phase of the mask in a region of interest, that is in this case the repair area and its
immediate vicinity. This will be done by a special new tool, named Phame(R), developed for measuring the actual phase
of smallest mask features with a high spatial resolution.
The decreasing feature sizes as induced by the ITRS have a growing impact on the cost of current and future
photolithographic masks. The assessment, repair and repair validation of these expensive masks has become a very
substantial factor of the total mask production cost. The introduction of immersion lithography and the proposed
introduction of double exposure strategies will further amplify this trend. In order to make the whole procedure more
manageable in a production environment, with its constraints on timing and resource allocation, a seamless workflow of
the repair and validation procedure is sought. A proposed way to achieve this is the set up of a dedicated tool set with a
backbone infrastructure designed for this workflow as well as for the specific high resolution task. In this paper we
concentrate on masks with feature sizes relevant for the 45nm node and defects with typical size and shape as they
appear in production. Phase shifting masks with synthetic defects have been manufactured and the printability of the
defects is analyzed with an AIMSTM45-193i. In part the defect outline and three-dimensional shape as well as further
characteristics have been visualized with an electron microscope, prior to repairing them with an electron beam based
repair system. In addition we will show the behaviour of the phase of the mask in a region of interest, that is in this case
the repair area and its immediate vicinity. This will be done by a special new tool, named Phame®, developed for
measuring the actual phase of smallest mask features with a high spatial resolution.
In the conclusion we will give an outlook how the proposed workflow and the how the employed technologies will
influence the masks that are expected to emerge for the 32nm node.
Imprint lithography has been shown to be an effective method for replication of nanometer-scale structures from a
template mold. Step-and-Flash Imprint Lithography (S-FILTM) employs a UV-photocurable imprint liquid, which
enables imprint processing at ambient temperature and pressure. The use of a transparent fused silica template facilitates
precise overlay. With this combination of capabilities, NIL is a multi-node technique that is suitable for advanced
prototyping of processes and devices to meet the anticipated needs of the semiconductor industry. However, since the
technology is 1X, it is critical to address the infrastructure associated with the fabrication of templates. An essential part
of this infrastructure is the capability to identify and repair template defects. Fused silica imprint templates are typically
produced from photomask substrates, and it is straightforward to make use of the tools and processes that have been
developed to repair commercial photomasks. However, the optical properties of the repaired region are of secondary
importance because S-FIL patterning is based on direct transfer of topography (rather than indirect transfer of an optical
image). As in conventional photolithography, both additive and subtractive repairs are required to correct a variety of
defect types. Repair techniques that are based on electron-beam induced chemical reactions have demonstrated the
capability to perform both additive (deposition) and subtractive (etching) processes at high resolution. This work is a
demonstration that electron-beam directed additive repair is capable of repairing fused silica template structures with
sub-100 nm resolution.
With the continuing decrease of feature sizes in conjunction with both the enormous costs for current masks and
projections for future generations the area of mask repair has often been highlighted. Clearly, a viable repair
methodology going forward has the potential to significantly influence and reduce production costs for the complete
mask set. Carl Zeiss SMS had, in a concerted development effort with other Zeiss daughter companies, succeeded to
develop and deploy a novel mask repair tool capable of repairing specifically all types of advanced masks, such as quartz
binary masks, phase shift masks, EUV masks and S-FIL imprint templates. In addition to the pure technical capability of
the e-beam based approach a strong emphasis has been made towards the user friendliness and automation features of the
repair process as such.
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.
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.
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.
Klaus Edinger, Hans Becht, Rainer Becker, Volker Bert, Volker Boegli, Michael Budach, Susanne Göhde, Jochen Guyot, Thorsten Hofmann, Ottmar Hoinkis, Alexander Kaya, Hans Koops, Petra Spies, Bernd Weyrauch, Johannes Bihr
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 LEO's ultra-high resolution Supra SEM platform with NaWoTec's 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.
KEYWORDS: Photomasks, Etching, Electron beams, Ion beams, Lithography, Silicon carbide, Gemini Observatory, Magnetism, Signal attenuation, Electron beam lithography
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.
KEYWORDS: Photomasks, Electron beams, Etching, Platinum, Interferometers, Charged-particle lithography, Quartz, Silicon carbide, Scanning electron microscopy, Control systems
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.
Volker Boegli, Hans Koops, Michael Budach, Klaus Edinger, Ottmar Hoinkis, Bernd Weyrauch, Rainer Becker, Rudolf Schmidt, Alexander Kaya, Andreas Reinhardt, Stephan Braeuer, Heinz Honold, Johannes Bihr, Jens Greiser, Michael Eisenmann
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 a new thermal nano-probe based on the changes of electrical resistivity of a nanometer-sized filament with temperature has been presented for the thermal imaging of microwave power active devices. The filament is integrated into an atomic force scanning probe piezoresistive type cantilever. The novel thermal probe has a spatial resolution better than 80 nm and a thermal resolution of the order of 10-3 K. The measurements have been successfully performed on a 30 fingers GaAs-MESFET with a maximum power dissipation of 2.5 W. The microwave transistor has been implemented in a circuit in such a way to prevent the undesired microwave oscillations. In this case the power dissipation is equal to the dc power input. The near-field measurements have been compared with three-dimensional finite element simulations. A good agreement between simulations and measurements is achieved.
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