Lithography Tool Research Articles

Atomic Layer Deposition of Nanostructured Tunable Resistance Coatings: Growth, Characterization, and Electrical Properties

We have developed ALD method to synthesize nanocomposite coatings comprised of conducting, metallic nanoparticles embedded in an amorphous dielectric matrix. These films are nominally composed of M:Al2O3 where M= W or Mo, and are prepared using alternating exposures to trimethyl aluminum (TMA) and H2O for the Al2O3 ALD and alternating MF6/Si2H6 exposures for the metal ALD. By varying the ratio of ALD cycles for the metal and the Al2O3 components in the film, we can tune precisely the resistance of these coatings over a very broad range (e.g. 1011-104 Ohm-cm). These films exhibit Ohmic behavior and resist breakdown even at high electric fields of 107V/m. Moreover, the self-limiting nature of ALD allows us to grow these films inside of high aspect ratio substrates and on complex, 3D surfaces. To investigate the ALD growth mechanism for the nanostructure composite films we employed in-situ quartz crystal microbalance (QCM), quadrupole mass spectrometry, and Fourier transform infrared (FTIR) absorption spectroscopy studies. For M:Al2O3 films, QCM showed that the metal ALD inhibits the Al2O3 ALD and vice versa. Despite this inhibition, the relationship between metal content and metal ALD cycle percentage was close to expectations. Depth profiling X-ray photoelectron spectroscopy showed that the M:Al2O3 films are uniform in composition and contained Al, O, and metallic Mo or W as expected, but also presence of moderate F and C. Attempts were also made to investigate the TMA as reducing precursor for MF6 and resulted in similar kind of resistive coatings but very significant F and C which shows influence on microstructure of the layers. Cross-sectional transmission electron microscopy (XTEM) revealed the film microstructure to be metallic nanoparticles (~1-2 nm) embedded in an amorphous matrix. The transport properties of these M:Al2O3 were studied as function of ratio of metal to Al2O3ALD cycles.We have utilized these nanocomposite coatings to functionalize capillary glass array plates to fabricate large-area MCPs suitable for application in large-area photodetectors. In addition, we have applied these films to serve as charge drain coatings in MEMS devices for a prototype maskless electron beam lithography tool, permitting high resolution electron beam patterns without charging artifacts. Here we will discuss the ALD growth, characterizations, and applications of ALD tunable resistive coatings.

Additive nanomanufacturing – A review

Abstract

A Moiré-Based Four-Channel Focusing and Leveling Scheme for Projection Lithography

Focusing and leveling are two imperative processes to adjust the wafer onto the ideal focal plane of projection lithography tools. Based on moire fringes formed by particularly designed dual-grating marks, the four-channel focusing and leveling scheme is proposed and demonstrated. These relationships between the tilted amount of wafer, the vertical defocusing amount, and the phase distributions of moire fringes are deduced. A single-channel experimental setup is constructed to verify the performances of proposed method. Results indicate that the tilted amount and the vertical defocusing amount can be precisely detected with accuracy at 10(-4) rad and several nanometers level, respectively, and therefore meet the demand of the high-demanding focusing and leveling processes.

Annular nanoplasmonic void arrays as tunable surface enhanced Raman spectroscopy substrates

We report the use of annular nano-voids in a metallic thin-film as programmable molecular sensors for surface-enhanced Raman spectroscopy (SERS). To date, research into these structures has focused on the exploration of their extraordinary optical transmission attributes. We now show that by using advanced lithography and simulation tools, we can generate a porous SERS material for molecular interrogation. Using ultra-thin annular structures, rather than simple circular holes, allows us to reduce both the volume and cross-sectional area of the void, maximizing the electric-field confinement, while, importantly for SERS, producing resonant conditions in the visible region of the spectrum. By comparing our annular films with conventional circular films with the same resonant frequency, we show a significant improvement in the efficiency of Raman scatter, creating stronger signals that also contain more spectral information.

Free-standing subwavelength grid infrared cut filter of 90 mm diameter for LPP EUV light source

A subwavelength grid infrared (IR) cut filter as large as 90mm in diameter was fabricated and tested on a 6inch Si wafer for a laser-produced plasma (LPP) extreme ultraviolet (EUV) light source used in the next generation lithography tools. The IR cut filter is a grid type, which has higher thermal stability compared with a conventional multilayer metal membrane filter. The grid is a free-standing Molybdenum coated Si honeycomb structure with a thickness of 5μm, a wire width of only 0.35μm and a pitch of 4.5μm. Such a large-size free-standing microstructure was successfully fabricated by carefully balancing film stress at each process step. The fabricated IR cut filter demonstrated 99.7% rejection for 10.6μm IR light. The IR cut filter was finally installed in a LPP EUV light source.

Fabrication of chemical patterns from graphoepitaxially assembled block copolymer films by molecular transfer printing

Fabrication of chemical patterns by electron beam lithography or extreme ultraviolet interference lithography is either low-throughput or prohibitively expensive to practice at sub-50 nm feature dimension. Here we report a new high-throughput approach that combines the advantages of both graphoepitaxy and molecular transfer printing (MTP) to fabricating chemical patterns at low cost for directed assembly of block copolymers. In this new approach, a cylinder-forming block copolymer ternary blend film is directed to assemble on a topographic HSQ substrate with sub-Lo, where Lo is the natural period of the block copolymer, relief structures to increase the feature density by a factor of ∼20, the surface domain pattern is replicated using MTP to create 1:1 chemical pattern, and then a lamellae-forming block copolymer is directed to assemble on the chemical pattern to realize high-aspect ratio Manhattan type nanostructures. This combined strategy allows us to fabricate chemical patterns with feature dimension below the resolution limit of current lithographic tools.

Atomic Layer Deposition Assisted Pattern Multiplication of Block Copolymer Lithography for 5 nm Scale Nanopatterning

5‐nm‐scale line and hole patterning is demonstrated by synergistic integration of block copolymer (BCP) lithography with atomic layer deposition (ALD). While directed self‐assembly of BCPs generates highly ordered line array or hexagonal dot array with the pattern periodicity of 28 nm and the minimum feature size of 14 nm, pattern density multiplication employing ALD successfully reduces the pattern periodicity down to 14 nm and minimum feature size down to 5 nm. Self‐limiting ALD process enable the low temperature, conformal deposition of 5 nm thick spacer layer directly at the surface of organic BCP patterns. This ALD assisted pattern multiplication addresses the intrinsic thermodynamic limitations of low χ BCPs for sub‐10‐nm scale downscaling. Moreover, this approach offers a general strategy for scalable ultrafine nanopatterning without burden for multiple overlay control and high cost lithographic tools.

Aberration measurement technique based on an analytical linear model of a through-focus aerial image

We propose an in situ aberration measurement technique based on an analytical linear model of through-focus aerial images. The aberrations are retrieved from aerial images of six isolated space patterns, which have the same width but different orientations. The imaging formulas of the space patterns are investigated and simplified, and then an analytical linear relationship between the aerial image intensity distributions and the Zernike coefficients is established. The linear relationship is composed of linear fitting matrices and rotation matrices, which can be calculated numerically in advance and utilized to retrieve Zernike coefficients. Numerical simulations using the lithography simulators PROLITH and Dr.LiTHO demonstrate that the proposed method can measure wavefront aberrations up to Z(37). Experiments on a real lithography tool confirm that our method can monitor lens aberration offset with an accuracy of 0.7 nm.

Alignment verification for electron beam lithography

Alignment between lithography layers is essential for device fabrication. A minor defect in a single marker can lead to incorrect alignment and this can be the source of wafer reworks. In this paper we show that this can be prevented by using extra alignment markers to check the alignment during patterning, rather than inspecting vernier patterns after the exposure is completed. Accurate vernier patterns can often only be read after pattern transfer has been carried out. We also show that by using a Penrose tile as a marker it is possible to locate the marker to about 1nm without fully exposing the resist. This means that the marker can be reused with full accuracy, thus improving the layer to layer alignment accuracy. Lithography tool noise limits the process.

A variable-temperature nanostencil compatible with a low-temperature scanning tunneling microscope/atomic force microscope

We describe a nanostencil lithography tool capable of operating at variable temperatures down to 30 K. The setup is compatible with a combined low-temperature scanning tunneling microscope/atomic force microscope located within the same ultra-high-vacuum apparatus. The lateral movement capability of the mask allows the patterning of complex structures. To demonstrate operational functionality of the tool and estimate temperature drift and blurring, we fabricated LiF and NaCl nanostructures on Cu(111) at 77 K.

Classic, liquid, and matrix-assisted dip-pen nanolithography for materials research.

As a powerful atomic force microscopy-based nanotechnological tool, dip-pen nanolithography (DPN) has provided an ideal direct-write "constructive" lithographic tool that allows materials to be patterned from DPN tips onto a surface with high registration and sub-15 nm resolution. In the past few decades, DPN has been enormously developed for studying the patterning of inorganic, organic, and biological materials onto a variety of substrates. The focus of this review is on the development of three types of DPN: classic, liquid, and matrix-assisted DPN. Such development mainly includes the following aspects: the comparisons of three types of DPN, the effect factors and basic mechanisms of three types of DPN, and the application progress of three types of DPN.

A New Low Power Instrument for Impedance Measurements in Biomedicine Based on FFT. Application to Interleukin-10 Protein Detection

We describe a low power, easy to use and portable device for measuring the electrochemical impedance of different types of biosensors. The measurement technique is based on the direct synthesis of sinusoidal signals followed by a discrete time Fourier transform analysis, carried out by an integrated electronic stage that excites and collects the response from the sample. This kind of technique provides very good signal to noise ratio, high sensibility to small variations in the sensor impedance and high accuracy and reliability.The device was tested studying the sensor response at different frequencies of a gold microelectrode, fabricated through a combination of soft lithography tools, capable of monitoring the antibody-antigen concentration for the Interleukin 10 (IL-10). Our custom design makes possible extending the current range down to the pA, with accuracy better than 1%, and optimizing the power consumption to reach figures under 150μW per measurement.

Effect of Source Pupil Shape on Process Windows in EUV Lithography

According to the International Technology Roadmap for Semiconductors report, extreme ultraviolet (EUV) lithography is a key lithography tool for manufacturing devices at the 22-nm node and above. The current findings suggest that the lithographic image affects the critical dimensions (CDs) of wafers used in EUV lithography differently from those used in conventional lithography because of off-axis illumination and reflective optics design. The process windows of line/space (L/S) were explored, using a target CD of 22 nm and illuminating target contact hole (CH) features of a CD of 35 nm by using conventional, annular, dipole, and quasor source shapes. The diffraction amplitudes of the L/S and CH EUV masks and corresponding aerial images were calculated. The results indicate that the dipole is the favorable illumination source shape for printing the L/S features and the quasor is favorable for printing the CH features. In addition, the optimal dipole and quasor illumination settings are reported for the L/S and CH features, respectively. The exposure latitude was 4% and the depth of focus (DOF) was 100 nm to illuminate the L/S feature by using the dipole to print the target at a CD of 22. The exposure latitude was 24% and the DOF was 300 nm to illuminate the CH feature by using the quasor to print the target CD at 35 nm.

用于ArF光刻机偏振照明系统的沃拉斯顿棱镜的设计

用于ArF光刻机偏振照明系统的沃拉斯顿棱镜的设计

基于二次规划的光刻机光源优化方法

基于二次规划的光刻机光源优化方法

Novel gate-all-around polycrystalline silicon nanowire memory device with HfAlO charge-trapping layer

Gate-all-around (GAA) nanowire (NW) memory devices with a SiN- or Hf-based charge-trapping (CT) layer of the same thickness were studied in this work. The GAA NW devices were fabricated with planar thin-film transistors (TFTs) on the same substrate using a novel scheme without resorting to the use of advanced lithographic tools. Owing to their higher dielectric constant, the GAA NW devices with a HfO2 or HfAlO CT layer show greatly enhanced programming/erasing (P/E) efficiency as compared with those with a SiN CT layer. Furthermore, the incorporation of Al into the Hf-based dielectric increases the thermal stability of the CT layer, improving retention and endurance characteristics.

Monte Carlo Simulation of Electron Trajectory in Solid for Electron Beam Lithography

We have developed a GUI(Graphical User Interface)-based Monte Carlo simulation tool for electron beam lithography. Simulation was executed by changing initial energy, thickness of resist, and target material. We focused on penetration range, backscattering coefficient and spatial distribution of lost energy. Comparison with other theory indicates that our simulation is reliable in the 10-50keV range of the energy of the electron. It seems that backscattering coefficient is strongly affected by the kind of atoms in the target, not initial energy.

ChemInform Abstract: Chemical Routes to Top‐Down Nanofabrication

AbstractReview: 44 refs.

A novel method of partial coherence measuring for the illumination system and its defocus performance analysis

Partial coherence (generally represented by σ) is one of the important parameters of lithographic tool to assess the performance of pupil fill. In this paper, a novel method of partial coherence measurement for the illumination system is proposed. Statistical results of measured σ by the proposed method are analyzed. The dependence of partial coherence on the defocus, which is the distance from the measuring position to the best image plane, is also investigated. The simulation results prove the effectiveness of this method, and with the defocus increasing, the measured partial coherence decreases. Generally, if three times of the standard deviation is required to be 1×10−3, the amount of defocus should be less than 96μm.

Novel Hybrid Organic–Inorganic Spin‐on Resist for Electron‐ or Photon‐Based Nanolithography with Outstanding Resistance to Dry Etching

A new spin-on alumina-based resist exhibits excellent performance in terms of both achievable lateral resolution and etch resistance in fluorine-based non-cryo-cooled dry etching processes. The resist has selectivity greater than 100:1 with respect to the underlying silicon during the etching process, patternability with various lithographic tools (UV, X-rays, electron beam, and nanoimprint lithography), and positive and negative tone behavior depending only on the developer chemistry.