Determination of acid diffusion and energy deposition parameters by point e-beam exposure in chemically amplified resists

A new method for the measurement of acid diffusion in chemically amplified resists is introduced. It is based on the measurement of the diameter of lithographic features (pillars for negative resists) obtained from single pixel e-beam exposures to determine the proximity function in a wide range of doses and PEB times. The method is applied in the measurement of the diffusion coefficients of two negative chemically amplified resists, the commercial resist SAL-601 (Shipley) and a prototype epoxy novolac based resist (EPR) developed at IMEL. The method directly provides proximity effect correction parameters for chemically amplified resists.     

Modelling of resist performance

Simulation of lithographic processes uksing novolac/diazonaphthoquinone resists has become widespread over the past 15 years. Several refinements to the original Dill model have been made to account for experimentally observed behavior. Models have also bee extended to cover other resist chemistry, including electron beam resists, chemically amplified resists and surface-imaging approaches. While these models are not yet mature, useful insight to the chemical mechanisms and processing can be gained through their use.     

紫外可见光谱法测量光刻胶的膜厚

在液晶显示器的制造过程中,光刻是极为重要的制造工艺过程之一。将厚的独立的负胶膜或者将光刻胶涂敷在二氧化硅衬底上以后,可以测量其膜厚,因为光刻胶膜厚决定其光刻工艺的工艺条件。能够快速地测量光刻胶的膜厚,是液晶显示器制造过程的先决性工作的一部分。文章提出了测量上述光刻胶膜厚的新方法,即利用紫外可见吸收光谱法中的Beer-Lambert定律来确定膜厚。在我们的研究中,采用acrylic负胶作为基质(resin) ,它分别具有50μm和100μm的膜厚。在350 nm时,50μm的薄膜的最大吸收为0 .728 ,而100μm的最大吸收为1 .468 5。而在正胶的研究中,采用novolac作为基质(resin)。它的膜厚通常是1 ～5μm。在紫外可见吸收光谱测膜厚的实验中,当重氮荼醌的吸收波长为403 .8 nm时,5 .93μm厚的薄膜的最大吸收为1 .757 4 ,其膜厚是由扫描电镜测得的。而另一个正胶薄膜在403 .8 nm的最大吸收为0 .982 3 ,其薄膜厚度计算得到为3 .31μm。利用这些数据,我们得到了这两种光刻胶薄膜的紫外可见吸收光强与其膜厚关系的两个校准曲线。     

Chemical Amplification of a Triphenylene Molecular Electron Beam Resist

Molecular resists, such as triphenylene derivatives, are small carbon rich molecules, and thus give the potential for higher lithographic resolution and etch durability, and lower line width roughness than traditional polymeric compounds. Their main limitation to date has been poor sensitivity. A new triphenylene derivative molecular resist, with pendant epoxy groups to aid chemically amplified crosslinking, was synthesized and characterized. The sensitivity of the negative tone, pure triphenylene derivative when exposed to an electron beam with energy 20 keV was ～ 6 × 10^–4 C cm^–2, which increased substantially to ～ 1.5 × 10^–5 C cm^–2 after chemical amplification (CA) using a cationic photoinitiator. This was further improved, by the addition of a second triphenylene derivative, to ～ 7 × 10^–6 C cm^–2. The chemically amplified resist demonstrated a high etch durability comparable with the novolac resist SAL 601. Patterns with a minimum feature size of ～ 40 nm were realized in the resist with a 30 keV electron beam.     

Ultrasonic sensor for photoresist process monitoring

An ultrasonic sensor has been developed to monitor photoresist processing in situ, during semiconductor manufacturing. Photoresist development, pre-exposure bake, and post-exposure bake were monitored for the Shipley 1800 series I-line resists, and the pre-exposure bake of Shipley APEX-E deep-uv (DUV) resist was monitored as well. Development monitoring was achieved by measuring thickness changes in the resist as it was removed. Data regarding dependence of development rate on exposure dose was obtained for the I-line resist with exposure doses varying from 20 to 68 mJ/cm². Measurements showed an increase in average development rate from 0.04 to 0.155 μm/s, with the rate leveling off at around 55 mJ/cm². Pre-exposure bake monitoring results demonstrated the ability of the sensor to measure the glass transition temperature of the resist film during prebake as well as the ability to invert out the elastic constants of the film using reflection theory. The glass transition temperature (T_g) is an important parameter in both the pre- and post-exposure bakes and therefore could be useful in monitoring these processes. Results of pre-exposure bake T_g measurements are presented for both-I-line and DUV resists. The glass transition temperature during prebake was found to be higher for the DUV resist than for the I-line series. The I-line resist post-exposure bake measurement of glass transition temperature confirmed the reported T_g of 118°C for the I-line novolac resin. The multiple uses of this sensor make it suitable for integration into a manufacturing setting     

阳极铝箔隧道孔的二次生长规律

将在酸性介质中产生了隧道孔的铝箔置于中性侵蚀液中继续成长。发现中性侵蚀液的组分对铝箔隧道孔形貌的影响规律:当溶液仅含Cl–时,会有新的隧道孔产生,铝箔表面隧道孔分布密度从3.63×107cm–2增加为3.72×107cm–2,隧道孔平均孔径从0.40μm扩展到0.75μm,但隧道孔长度没有明显变化;在含Cl–电解质中添加少量有机添加剂时,铝箔表面没有新的隧道孔产生,由于出现并孔现象,隧道孔分布密度反而从3.63×107cm–2降低至3.43×107cm–2,但隧道孔的孔径从0.40μm扩展到0.80μm,长度从24μm增加到37μm。     

Light-emitting diodes based on GaSb alloys for the 1.6–4.4 μm mid-infrared spectral range

The available publications concerned with fabrication and study of light-emitting diodes (LEDs) intended for operation in the 1.6–4.4 μm spectral range; based on GaSb substrates; and grown by liquid-phase epitaxy, which makes it possible to form fairly thick layers lattice-matched to GaSb, are reviewed. In these studies, the active region consists of the GaInAsSb compound in LEDs for the spectral ranges 1.8–2.4 and 3.4–4.4 μm and the AlGaAsSb compound for the spectral region 1.6–1.8 μm. The wide-gap AlGaAsSb confining layers contain up to 64% of Al, which is an unprecedentedly high content for liquid-phase epitaxy. Asymmetric (GaSb/GaInAsSb/AlGaAsSb) and symmetric (AlGaAsSb/GaInAsSb/AlGaAsSb) heterostructures have been fabricated and studied. Various types of designs that make it possible to improve the yield of radiation generated in the active region have been developed. The measured external quantum yield of emission is as high as 6.0% at 300 K for the LEDs operating at the wavelengths 1.9–2.2 μm. A pulsed optical-radiation power of 7 mW at a current of 300 mA with a duty factor of 0.5 and 190 mW at a current of 1.4 A with a duty factor of 0.005 have been obtained. The external quantum emission yield of ～1% has been obtained for LEDs that emit in the spectral range 3.4–4.4 μm; this yield exceeds that obtained for the known InAsSb/InAsSbP heterostructure grown on an InAs substrate by a factor of 3. The measured lifetime of minority charge carriers (5–0 ns) is close to the theoretical lifetime if only the radiative recombination and impact CHCC bulk recombination are taken into account. The impact recombination is prevalent at temperatures higher than 200 K for LEDs operating in the spectral range 3.4–4.4 μm and at temperatures higher than 300 K for LEDs operating in the spectral range 1.6–2.4 μm.     

High flowability monomer resists for thermal nanoimprint lithography

In this paper, we have been using polymer and thermally curable monomer resists in a full 8 in. wafer thermal nanoimprint lithography process. Using exactly the same imprinting conditions, we observed that a monomer solution provides a much larger resist redistribution than a polymer resist. Imprinting Fresnel zone plates, composed of micro- and nano-meter features, was possible only with the monomer resist. In order to reduce the shrinkage ratio of the monomer resists, acrylate–silsesquioxane materials were synthesised. With a simple diffusion-like model, we could extract a mean free path of 1.1 mm for the monomer resist, while a polymer flows only on distances below 10 μm in the same conditions.     

Effect of acid anion on the behavior of single component molecular resists incorporating ionic photoacid generators

A series of single component chemically amplified molecular resists were made using an onium salt cation core of tris(4-(tert-butoxycarbonyloxy)-3,5-dimethylphenyl)sulfonium (TAS) with five different acid anions: chloride (Cl), hexafluoroantimonate (SbF₆), triflate (Tf), nonaflate (Nf), and tosylate (Ts). The counter-ion had a large effect on both the performance and physical characteristics of the resists. TAS–SbF₆ and TAS–Tf imaged as positive tone resists with good LER, but suffered from acid diffusion problems which limited resolution. TAS–Ts and TAS–Cl had high water solubility that prevented their use as positive tone resists. TAS–Nf had poor wetting and adhesion that prevented it from being spin-coated into films. Using onium salts as single molecule resists places great restriction on the choice of anion used because of the large effect it has on the properties of the resist. Using extreme ultraviolet lithography, TAS–SbF₆, the best performing derivative, was able to resolve 50 nm 1:1 line/space patterns with LER (3σ) of 5.2 nm.     

Chemically amplified resists: Chemistry and processes

Continued advances in mocroelectronic device fabrication are trying the limits of conventional lithographic techniques. In particular, conventional photoresist materials are not appropriate for use with the new technologies that will be necessary for sub-0.5 μm lithography. One approach to the desing of new resist chemistries involves the concept of chemical amplification, where one photochemical event can lead to a cascade of subsequent reactions that effect a change in solubility of the parent material. The most well-known chemically amplified resists utilise photchemically generated acid to catalyse crosslinking or deprotection reactions. This paper reviews the acid generator, crosslinking, deprotection and depolymerisation chemistries that have been evaluated for chemical amplification resist processes. Additionaly, process characteristics and resist performance relative to the process environment are addressed.     

Advantages of solid-state photodetectors for a spectral interval of 1.4–1.7 μm in night-vision devices

Characteristics of external conditions are studied in spectral intervals of 0.4–0.9 and 1.4–1.7 μm. The advantages of photodetector arrays that are sensitive in a spectral interval of 1.4–1.7 μm are demonstrated for applications in night-vision devices.     

A General Approach to Semimetallic,Ultra‐High‐Resolution,Electron‐Beam Resists

Commercial electron‐beam resists are modified into semimetallic resists by doping with 1–3 nm metal nanoparticles, which improve the resolution, contrast, strength, dry‐etching resistance, and other properties of the resist. With the modified resists, fine resist nanopatterns from electron‐beam lithography are readily converted into 5–50 nm, high‐quality multilayers for metallic nanosensors or nanopatterns via ion‐beam etching. This method solves the problem of the fabrication of fine (<50 nm) metallic nanodevices via pattern transferring.     

Enhancement of the spectral sensitivity of photodiodes for the mid-IR spectral range

A new method is used to raise the spectral sensitivity of photodiodes based on GaSb/GaInAsSb/GaAlAsSb heterostructures for the spectral range 1.1–2.4 μm. It is shown that, with a profile formed as pits on the metal-free unilluminated rear surface area of the photodiode chip, it is possible to improve the spectral sensitivity of the photodiodes at wavelengths in the range 1.8–2.4 μm. The most pronounced increase of up to 53% at the sensitivity maximum, compared with the sensitivity of conventional photodiodes with a fully metallized rear surface of the chip, is observed for photodiodes with shallow pits 30 μm in radius on their rear surface. These devices can find wide application in systems measuring the amount of water in petroleum products and the moisture content of paper, soil and grain.     

Investigation of HgCdTe waveguide structures with quantum wells for long-wavelength stimulated emission

The photoluminescence and stimulated emission during interband transitions in quantum wells based on HgCdTe placed in an insulator waveguide based on a wide-gap CdHgTe alloy are studied. Heterostructures with quantum wells based on HgCdTe are of interest for the development of long-wavelength lasers in the range of 25–60 μm, which is currently unattainable for quantum-cascade lasers. Optimal designs of quantum wells for attainment of long-wavelength stimulated emission under optical pumping are discussed. It is shown that narrow quantum wells from pure HgTe appear to be more promising for long-wavelength lasers in comparison with wide (potential) wells from the alloy due to the suppression of Auger recombination. It is demonstrated that molecular-beam epitaxy makes it possible to obtain structures for the localization of radiation with a wavelength of up to 25 μm at a high growth rate. Stimulated emission is obtained for wavelengths of 14–6 μm with a threshold pump intensity in the range of 100–500 W/cm² at 20 K.     

Room-temperature lasing in microring cavities with an InAs/InGaAs quantum-dot active region

Microring cavities (diameter D = 2.7–7 μm) with an active region based on InAs/InGaAs quantum dots are fabricated and their characteristics are studied by the microphotoluminescence method and near-field optical microscopy. A value of 22 000 is obtained for the Q factor of a microring cavity with the diameter D = 6 μm. Lasing up to room temperature is obtained in an optically pumped ring microlaser with a diameter of D = 2.7 μm.     

Improvement in the quantum sensitivity of InAs/InAsSb/InAsSbP heterostructure photodiodes

InAs/InAs_0.88Sb_0.12/InAs_0.50Sb_0.20P_0.30 heterostructure photodiodes operating at room temperature in the spectral range 1–4.8 μm are developed. It is shown that the formation of a curvilinear reflecting surface constituted by a number of hemispheres on the rearside of the photodiode chip leads to an increase in the quantum sensitivity of the photodiodes by a factor of 1.5–1.7 at wavelengths in the range 2.2–4.8 μm. At an exposed photodiode area of 0.9 mm² and a p-n junction area of 0.15 mm², a zero-bias differential resistance of 30 Ω and a quantum sensitivity of 0.24 electron/photon at a wavelength of 3 μm are obtained. The operation of a photodiode with re-reflection of the photon flux in the crystal due to reflection from the curvilinear surface of the rearside of the photodiode chip is theoretically analyzed. The possibility of effective conversion of the re-reflected flux of photons into a photocurrent, with a simultaneous decrease in the p-n junction area, is demonstrated. An increase in the quantum sensitivity in the short-wavelength spectral range 1–2.2 μm by 35% relative to the calculated data is observed, which is probably due to impact ionization in the narrow-gap active region.     

A Nanoimprint Lithography Hybrid Photoresist Based on the Thiol–Ene System

A novel hybrid resist for UV nanoimprint lithography (UV‐NIL) based on the thiol–ene photopolymerization is presented. Our system comprises mercaptopropyl polyhedral oligomeric silsesquioxane and benzyl methacrylate, with trimethylolpropane trimethacrylate as the crosslinker. The obtained hybrid resists possess a variety of characteristics desirable for UV‐NIL, such as low viscosity (6.1–25 cP), low bulk‐volumetric shrinkage (5.3%), high Young's modulus (0.9–5.2 GPa), high thermal stability, and excellent dry‐etch resistance. Based on these performances, the optimized components are evaluated as UV‐NIL resists. The result is a high‐resolution pattern with feature sizes in the range of 100 nm to several microns. The double‐layer resist approach is used for pattern transfer into silicon substrates. The excellent oxygen‐etch resistance of the barrier material enables a final transfer pattern that is about three times higher than that of the original NIL mold.     

低维Bi_2Te_3热电材料的制备与性能研究

用溶剂热法制备了直径在100nm以内的一维针状及厚20～30nm、长几微米的二维花朵状Bi2Te3热电材料,分析了不同形貌产物的生长机理,并对其热电性能进行了比较。结果表明,添加剂的分子结构对产物形貌起决定性作用。不同形貌产物的热电性能随温度变化的机制不同,一维纳米结构Bi2Te3产物的功率因子随温度升高而增加,最大值为143.1μΩ·m–1K–2。而二维纳米结构的Bi2Te3产物虽然在室温附近有较大的Seebeck系数,约100μV/K,但由于其电导率较低,功率因子在较宽的温度范围内保持在23μΩ·m–1K–2左右。     

Nano Molecular‐Platform: A Protocol to Write Energy Transmission Program Inside a Molecule for Bio‐Inspired Supramolecular Engineering

In a coded self‐assembly, a simple code is written in the molecule, which self‐assembles the molecules into a fractal like structure, which acts as a seed for the next step. As the molecule turns into a complex seed, the code transforms into another form and several seeds self‐assemble into another structure, which acts as a seed for the next step. Until now, this technology was considered as a prerogative of nature. Here, a dendritic network is used to write a basic code by synthetically attaching 32 molecular rotors and doping two controller molecules in its cavity. The code live, which is an energy transmission path in the molecule, is imaged. When the energy transmission path or code is triggered, a series of products generate one after another spontaneously. Two examples are: i) dendritic seed (5–6 nm)→paired nanowire (≈12 nm)→nanowire (≈200 nm)→microwire (500 nm)→wire like rod (1–2 μm)→jelly→rectangular sheet (5 μm). ii) dendritic seed→nano‐sphere (20 nm)→micro‐sphere (500 nm)→large balls(1 μm)→oval shape rod (5–10 μm)→Y, L or T shaped rod assembly. The energy level interactions are tracked using spectroscopy how exactly a directed energy transfer code generates multi‐step synthesis from nano to the visible scale.     

纳米添加剂对永磁铁氧体微结构与性能的影响

通过高能球磨将添加剂纳米化,研究了其对永磁铁氧体(样品)磁性能和微观结构的影响。结果表明:添加剂的平均粒度从216.448μm减小到65nm时,有效降低了磁体的熔点,提高其致密化。1190℃烧结时磁体的Br和Hcj分别从404mT、366kA·m–1提高到418mT和402kA·m–1。SEM观察样品晶粒平均粒径在1~2μm,晶粒分布更加均匀。取向度从75.2%提高到84.0%。