Next Generation Lithography Research Articles

Litho-only double patterning approaches: positive–negative versus positive–positive tone

Double patterning is considered the most viable option for 32- and 22-nm complementary metal-oxide semiconductor (CMOS) node development and has seen a surge of interest due to the remaining challenges of next-generation lithography systems. Most double patterning approaches previously described require intermediate processing steps (e.g., hard mask etching, resist freezing, spacer material deposition, etc.). These additional steps can add significantly to the cost of producing the double pattern. Alternative litho-only double patterning processes are investigated to achieve a composite image without the need for intermediate processing steps. A comparative study between positive–negative (TArF-P6239+N3007) and positive–positive tone (TArF-P6239+PP002) imaging is described. In brief, the positive–positive tone approach is found to be a superior solution due to a variety of considerations.

Principles of hydrocarbon detection in ultra high vacuum: Optimizing sensitivity and selectivity towards harmful species

The performance in regard to sensitivity and selectivity of a simple, reproducible hydrocarbon sensor based on a platinum film interfaced with yttria-stabilized zirconia has been characterized with respect to a range of hydrocarbons under high vacuum conditions that are pertinent to the intended application. Sensing and in situ X-ray photoelectron spectroscopy (XPS) data acquired under open circuit conditions permitted identification of the active oxygen species present at the sensing electrode as a function of sensor temperature. This fundamental information provides the basis for a plausible hypothesis for the mode of sensing action under conditions that are directly relevant to the intended application and remote from those under which YSZ-based sensors are normally operated. For unsaturates, which are damaging species, sensitivity is a strong function of the C:H ratio of the impinging molecule, increasing as this quantity increases, and a plausible explanation for this effect is proposed. Additionally, we show that the relative sensitivity (selectivity) towards different analytes may be strongly altered by choice of operating temperature, thus providing a means of tuning device performance. The device requires no power supply and is therefore well suited to large-scale application involving multiple locations, for example within next-generation extreme ultra-violet lithography (EUV) semiconductor chip fabrication plants.

Extreme-ultraviolet microexposure tool at 05 NA for sub-16 nm lithography

The resolution limit of present 0.3 NA 13.5 nm wavelength microexposure tools is compared to next-generation lithography research requirements. Findings suggest that a successor design is needed for patterning starting at the 16 nm semiconductor process technology node. A two-mirror 0.5 NA optical design is presented, and performance expectations are established from detailed optical and lithographic simulation. We report on the results from a SEMATECH program to fabricate a projection optic with an ultimate resolution limit of approximately 11 nm.

Feasibility Study on Immersion System Using High-Index Materials

ArF water immersion systems with a numerical aperture (NA) of more than 1.3 have already been introduced for the node up to 45-nm half-pitch production. For next-generation lithography, we focus on ArF immersion lithography using high-index materials. At present, LuAG (n=2.14) is the most promising candidate as a high-index lens material. Second-generation fluids (n=1.64) have the sufficient performance as a high-index immersion fluid. The combination of LuAG and a second-generation fluid can enhance the NA up to 1.55 and the exposure system would be available for the 34-nm half-pitch node when k1 is 0.27. Although high-index immersion lithography is attractive because it is effective in improving the resolution, there are some issues not encountered in a water immersion system. The issues associated with LuAG are its availability and intrinsic birefringence. Fluid degradation induced by dissolved oxygen or laser irradiation, lens contamination, and residual fluid on a wafer are the specific issues associated with second-generation fluids. In this article, we describe the current status of the above issues and discuss the feasibility of an ArF immersion system using high-index materials.

Evaluation of fast EUV scintillator using 13.9 nm x-ray laser

The nickel-like silver x-ray laser with the wavelength of 13.9 nm is used as a high power EUV excitation source to evaluate a scintillator for EUV lithography. The time resolved spectrum of zinc oxide exciton emission at around 380 nm was observed. The determined fluorescence lifetime of 1.1 ns is sufficiently short for characterizing EUV lithography light sources having a few nanoseconds duration. It is also shown that the x-ray laser is an excellent tool for spectroscopic characterization of materials intended for next-generation lithography applications.

The innovator's non‐dilemma: the case of next‐generation lithography

AbstractPrevious studies have analyzed how incumbents may falter when they focus too narrowly on satisfying the needs of current customers at the expense of pursuing innovations that will ensure future market leadership. This paper examines this ‘dilemma’ faced by incumbents and considers cases where incumbents do spearhead innovation on the technology frontier thus enabling future product generations. In particular, we examine the case of the semiconductor industry confronting a technological discontinuity in the production of chips. In anticipation of a discontinuity in the lithography production module, leading firms in the semiconductor industry have initiated next‐generation lithography (NGL) projects. These projects have exhibited an unprecedented level of horizontal and vertical cooperation. Our research analyzes how such cooperative research and development (R&D) programs allow incumbent innovators to mitigate four areas of uncertainty—leadership, preemption, performance, and industry adoption. We adapt a Hotelling location model to demonstrate the tension between mitigating these uncertainties through interfirm cooperation and the possibility of increased downstream competition. Such tensions have influenced cooperation within and across the R&D consortia pursuing NGL led by IBM, Intel, and Bell Labs. Copyright © 2008 John Wiley & Sons, Ltd.

Eight Technical Meetings in Fort Collins During 2007

SSCS DLs Fischette, Allstot and Nguyen Speak SSCS-Denver hosted eight seminars in 2007, including three sponsored by the Society's Distinguished Lecturer Series. The topics, spanning cutting-edge microprocessors, design techniques for high-speed serial links, and forefront technologies such as next-generation lithography were presented by SSCS DLs Dennis Fischette, David Allstot and Clark Nguyen and by Robin Porter, Troy Beukema, Shawn Searles, Gu-Yeon Wei and David Brooks, and Hugh Grinolds.

Next-Generation Lithography (B): Betting on New Production Technology in the Semiconductor Industry

Next-Generation Lithography (B): Betting on New Production Technology in the Semiconductor Industry

Line edge roughness after development in a positive-tone chemically amplified resist ofpost-optical lithography investigated by Monte Carlo simulation and a dissolutionmodel

Line edge roughness (LER) of patterned features in chemically amplified (CA) resists isformed in the acid generation stage and expected to be moderated by the acid diffusion anddevelopment process. It is essential to obtain information on the limit of LER in order torealize next-generation lithographies such as electron beam or extreme ultraviolet. Here,we report for the first time a process simulator based on physical and chemicalreaction mechanisms. The LER of a positive-tone CA resist after development isinvestigated by Monte Carlo simulation and Mack’s dissolution model. We foundthat the LER (high frequency) of less than 1.2 nm is achievable, although theprocess conditions and material design for achieving such a small LER are strict.

Fabrication of 3D-photonic crystals via UV-nanoimprint lithography

Optical lithography will reach its limits due to the diffraction effects encountered and the necessity for using complex resolution enhancement techniques like optical proximity correction, phase shift masks, and off-axis illumination [L. W. Liebmann et al., in Advanced Semiconductor Lithography (2001), Vol. 45]. The restrictions on wavelength, in combination with high process and equipment costs, make low-cost, simple imprinting techniques competitive with next-generation lithography methods. There are several nanoimprint lithography (NIL) techniques which can be categorized depending on the process parameters and the imprinting method—either step and repeat or full wafer single-step imprinting. A variety of potential applications has been demonstrated using NIL (e.g., surface acoustic wave devices, vias and contact layers with dual damascene imprinting process, Bragg structures, patterned media) [M. D. Stewart et al., Proc. SPIE 5751, 210 (2005); P. Dorsey et al., in Discrete Track Recording (DTR) Media Fabricated using Nanoimprint Lithography, NNT 1–3 December (2004)]. In this work UV-NIL has been selected for the fabrication process of 3D-photonic crystals.

Lithography potentials of UV-nanoimprint

Abstract In the past decade nanoimprint has been developed to a serious alternative for next generation lithography (NGL). In this work, the most recent developments of UV-nanoimprint Lithography (UV-NIL) with special emphasis to the work accomplished at AMO and the IHT-RWTH Aachen are reviewed and functional applications demonstrated. Further the potentials of various UV-NIL concepts are evaluated and possible interests in certain application areas are discussed.

Next-Generation Lithography

Next-Generation Lithography

저 에너지 초소형 전자칼럼 리소그래피를 이용한 SiO2박막의 Pattern 제작에 관한 연구

반도체의 고 집적회로를 형성하기 위하여 주로 이용하고 있는 광 리소그래피 기술을 대신하여 사용할 수 있는 차세대 리소그래피 기술로 전자빔 리소그래피 기술에 대한 연구가 진행되고 있다. 본 연구에서는 초소형 전자칼럼을 이용하여 전자빔 에너지와 조사농도에 따른 pattern 두께의 의존성을 조사하였으며 두께가 100nm인 <TEX>$SiO_2$</TEX> 박막의 patterning을 통하여 <TEX>$SiO_2$</TEX> 박막에 대한 저 에너지 전자빔 리소그래피 공정의 가능성을 입증하였다. Electron beam lithography has been studied as a next-generation lithography technology instead of photo lithography for ULSI semiconductor devices. In this work, we have made a low-energy electron beam lithography system based on the microcolumn and investigated the dependence of the pattern thickness on the energies and dose concentration of the electron beam. We have also demonstrated the potential of low-energy lithography by achieving 100 nm-<TEX>$SiO_2$</TEX> thin film patterning.

Long-term stability of Ru-based protection layers in extreme ultraviolet lithography: A surface science approach

Extreme ultraviolet lithography (EUVL) is a leading candidate for next-generation lithography for the semiconductor industry. This technology uses EUV light with a wavelength of 13.5nm (92.5eV) to be able to produce features as small as 20nm in size. The short wavelength of EUV means that reflective optics is needed for lithography in the form of Si–Mo multilayer stacks. However, surface contamination by water and hydrocarbons together with EUV light reduces unacceptably the mirror reflectivity with time. In this article, the authors review the material properties of two promising capping layer materials, Ru and RuO2, for protecting the EUVL mirrors against oxidation, carbon uptake, and the permeation of hydrogen and oxygen. Special emphasis is put on the surface properties of these potential cap layer systems. For both materials the microstructure, the morphology, and the stability under oxidizing and reducing environments are reviewed to promote the search for a successful candidate for a capping layer material of EUV optics.

Dielectronic Recombination processes of Xe10+ions

EUV light sources from compact plasmas are now intensively studied for the next generation of lithography. The multicharged Xe ions emit EUV emission and are now investigated extensively. However we do not know the detailed atomic processes for there Xe ions. We have calculated the energy levels, radiative transition probabilities (Ar), autoionization rates (Aa), and radiative recombination cross section for Xe10+ions using the FAC code. The dielectronic recombination rate coefficient (αLDR) from the Xe10+ions and the related dielectronic satellitie lines are obtained. The dielectronic recombination processes for the 4d8+ e → 4d74f1nl → 4d8nl+ hvand 4d8+ e → 4d75p1nl → 4d8nl+ hvbecome important at low plasma temperature Te ≈ 10eVfor line intensities.

Nanolayer Patterning Based on Surface Modification with Extreme Ultraviolet Light

As predicted by Moore’s Law, [1] the feature size of semiconductor devices reached the 90 nm node in 2004. [2] Presently, research is focused on reaching 32 nm. [3] Unfortunately, standard UV lithography cannot be used at this scale. [3] Thus, several next-generation lithographic techniques have been proposed. [4–7] Work combining scanning probe lithography and self-assembly [8] has demonstrated that a hybridization of topdown and bottom-up techniques may be effective. [9] As photolithography using shorter-wavelength light, such as extreme UV or soft X-rays, is considered to be a leading next-generation lithography technology, a hybrid approach combining extreme UV lithography (EUVL) with bottom-up assembly could be used in the industrial production of microelectronic devices. Polymers have typically been used as templates for this type of hybrid patterning, [10,11] but thinner layers are required to continue to reduce feature sizes via EUVL. Nanolayers of small molecules on silicon consist of only a few atomic layers. As these systems are structurally simple and well ordered, a number of surface science studies have been performed to probe the behavior of these materials during the last several decades. [12] Therefore, they are well understood and are an excellent choice for studying EUV-induced surface modification at the atomic scale. EUV is normally used in the identification of chemical structures or the analysis of chemical environments, but an EUV-induced surface modification is clearly observed for a molecular nanolayer of Cl2 in this work. We report that EUV-induced surface modification can be used to pattern surfaces, resulting in a variety of possible functionalities. As surface modification originates from secondary electrons produced by EUV, it can also occur from primary electrons or photons with shorter wavelengths, suggesting that our concept could be extended to electron-beam (e-beam) and proximity X-ray lithographies.

Nanotopography produced by using a vacuum pin chuck and the flattening ability around its periphery

In next-generation lithography, the problems of nanotopography and peripheral flatness deterioration caused by the flattening of a wafer with a current vacuum pin chuck must be solved. This paper describes the factors contributing to nanotopography and flatness deterioration, and determines the flattening ability around the periphery using a current pin chuck. It is shown that the nanotopography induced by clamping is very small after polishing of the chuck surface, but may increase above 10 nm due to pin wear. Since the ring seal used to prevent the leakage is 20–40 nm higher than the pins, the peripheral flatness of the wafer deteriorates. In addition, it is found that flattening a heavily warped wafer up to the wafer edge is difficult. As such, the current ring-seal-type chuck should be replaced with a static-pressure-seal-type chuck.

Nanoimprint lithography technology with automatic alignment

Nanoimprint lithography (NIL) is recognized as one of the most promising candidates for the next generation lithography (NGL) to obtain sub-100 nm patterns because of its simplicity, high-throughput and low-cost. While substantial effort has been expending on NIL for producing smaller and smaller feature sizes, considerably less effort has been devoted to the equally important issue—alignment between template and substrate. A homemade prototype nanoimprint lithography tool with a high precision automatic alignment system based on Moire signals is presented. Coarse and fine pitch gratings are adopted to produce Moire signals to control macro and micro actuators and enable the substrate to move towards the desired position automatically. Linear motors with 300 mm travel range and 1 μm step resolution are used as macro actuators, and piezoelectric translators with 50 μm travel range and 1 nm step resolution are used as micro actuators. In addition, the prototype provides one translation (z displacement) and two tilting motion(α and β ) to automatically bring uniform intact contact between the template and substrate surfaces by using a flexure stage. As a result, 10 μm coarse alignment accuracy and 20 nm fine alignment accuracy can be achieved. Finally, some results of nanostructures and micro devices such as nanoscale trenches and holes, gratings and microlens array fabricated using the prototype tool are presented, and hot embossing lithography, one typical NIL technology, are depicted by taking nanoscale gratings fabrication as an example.

Characterization of collector optic material samples exposed to a discharge-produced plasma extreme ultraviolet light source

Extreme ultraviolet (EUV) light sources with efficient emission at 13.5 nm are needed for next-generation lithography. A critical consideration in the development of such a source is the lifetime of collector optics. These experiments expose optics to a large flux of energetic particles coming from the expansion of the pulsed-plasma EUV source to investigate mirror damage due to erosion, layer mixing, and ion implantation. The debris ion spectra are analyzed using a spherical sector energy analyzer (ESA) showing ion energies of 2 to 13 keV, including Xe+-Xe+4, Ar+, W+, Mo+, Fe+, Ni+, and Si+. Microanalysis is performed on samples exposed to 10 million pulses, including atomic force microscopy (AFM), showing increased roughness for most exposed samples. Notably, a Mo-Au Gibbsean segregated alloy showed surface smoothing over this time frame, suggesting that the segregation worked in situ. TRIM predictions for ion implantation are consistent with ion debris measurements from the ESA. Finally, time exposures of samples from 2, 20, and 40 million pulses show an initial roughening with smoothing of the exposed samples at longer time frames. Constant erosion is demonstrated with the SEM. These analyses give an experimental account of the effects of the ion debris field on optic samples exposed to the EUV source.

Progress in the fabrication of low-defect density mask blanks for extreme ultraviolet lithography

Extreme ultraviolet lithography (EUVL) is the leading next-generation lithography (NGL) technology to succeed optical lithography at the 32-nm node and beyond. The technology uses a multilayer-based reflective optical system, and the development of suitable, defect-free mask blanks is the greatest challenge facing the commercialization of EUVL. We describe recent progress toward the development of a commercial tool and process for the production of EUVL mask blanks. Using the resources at Mask Blank Development Center at SEMATECH-North in Albany, New York, we are able to decrease the mean multilayer-coating-added defect density on 6-in. square quartz substrates by almost an order of magnitude, from ~0.5 defects/cm2 to ~0.055 defects/cm2 for particles 80 nm in size (polystyrene latex equivalent). We also obtain a "champion" mask blank with an added defect density of only ~0.005 defects/cm2. This advance is due primarily to a compositional analysis of the particles using focused ion beam and energy dispersive analysis of x-rays (EDX) followed by tool and procedural upgrades based on best engineering practices and judgment. Another important specification for masks blanks is the coating uniformity, and we have simultaneously achieved a centroid wavelength uniformity of 0.4% and a coating-added defect density of 0.06 def/cm2.