利用RELACS辅助技术制作"T"型栅

利用RELACS化学收缩辅助技术制作了i线三层胶结构的"T"型栅。首先利用水溶性的化学收缩试剂RELACS,涂在曝光完成的光刻图形上,然后借由混合烘焙让光刻胶中的光酸分子因受热而产生扩散运动并进入到RELACS试剂内,催化RELACS试剂,让RELACS试剂中的高分子与交链分子产生交链反应,使得光刻胶表面形成新的一层不溶于水的交链层而达到光刻图形收缩的目的。此方法增加了细栅光刻的宽容度,降低了细栅光刻制作的难度,极易将0.5μm的栅条收缩到0.3μm,甚至更小,不但有效地减小了栅长,而且提高了细栅光刻的成品率。RELACS技术可以应用于不同光刻胶类型的"T"型栅制作中。     

UV impact on the optical properties of thin films of positive tone chemically amplified resist

Chemically amplified photo resist are blend materials whose main compounds are a polymer matrix and an added photo acid generator. Lithography processes that allow imaging patterns in a CAR resist films consist in exposing at first the film to UV light and then to post-bake the film in order to initiate a chemical reaction that induces a local solubility switch of the resist. Sensitivity of the resist is measured by monitoring the UV dose needed to induce the proper solubility switch. For positive tone resist, the efficiency of the photolysis of the PAG to an acid and the deprotection kinetic during the post-exposure bake directly govern the resist sensitivity. This article deals with measurements of the PAG photolysis efficiency by real time spectroscopic ellipsometry. C Dill parameter of 193 nm photoresists is then measured for various film thicknesses and PAG loading.     

Bio‐Orthogonally Crosslinked,Engineered Protein Hydrogels with Tunable Mechanics and Biochemistry for Cell Encapsulation

Covalently‐crosslinked hydrogels are commonly used as 3D matrices for cell culture and transplantation. However, the crosslinking chemistries used to prepare these gels generally cross‐react with functional groups present on the cell surface, potentially leading to cytotoxicity and other undesired effects. Bio‐orthogonal chemistries have been developed that do not react with biologically relevant functional groups, thereby preventing these undesirable side reactions. However, previously developed biomaterials using these chemistries still possess less than ideal properties for cell encapsulation, such as slow gelation kinetics and limited tuning of matrix mechanics and biochemistry. Here, engineered elastin‐like proteins (ELPs) are developed that crosslink via strain‐promoted azide‐alkyne cycloaddition (SPAAC) or Staudinger ligation. The SPAAC‐crosslinked materials form gels within seconds and complete gelation within minutes. These hydrogels support the encapsulation and phenotypic maintenance of human mesenchymal stem cells, human umbilical vein endothelial cells, and murine neural progenitor cells. SPAAC‐ELP gels exhibit independent tuning of stiffness and cell adhesion, with significantly improved cell viability and spreading observed in materials containing a fibronectin‐derived arginine‐glycine‐aspartic acid (RGD) domain. The crosslinking chemistry used permits further material functionalization, even in the presence of cells and serum. These hydrogels are anticipated to be useful in a wide range of applications, including therapeutic cell delivery and bioprinting.     

Bioorthogonal Strategies for Engineering Extracellular Matrices

Hydrogels are commonly used as engineered extracellular matrix (ECM) mimics in applications ranging from tissue engineering to in vitro disease models. Ideal mechanisms used to crosslink ECM‐mimicking hydrogels do not interfere with the biology of the system. However, most common hydrogel crosslinking chemistries exhibit some form of crossreactivity. The field of bioorthogonal chemistry has arisen to address the need for highly specific and robust reactions in biological contexts. Accordingly, bioorthogonal crosslinking strategies are incorporated into hydrogel design, allowing for gentle and efficient encapsulation of cells in various hydrogel materials. Furthermore, the selective nature of bioorthogonal chemistries can permit dynamic modification of hydrogel materials in the presence of live cells and other biomolecules to alter matrix mechanical properties and biochemistry on demand. This review provides an overview of bioorthogonal strategies used to prepare cell‐encapsulating hydrogels and highlights the potential applications of bioorthogonal chemistries in the design of dynamic engineered ECMs.     

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.     

Suppression of pinhole defects in fullerene molecular electron beam resists

Molecular resists, such as fullerenes, are of significant interest for next generation lithographies. They utilize small carbon rich molecules, giving the potential for higher resolution and etch durability, together with lower line width roughness than conventional polymeric resists. The main problem with such materials has historically been low sensitivity, but with the successful implementation of chemical amplification schemes for several of the molecular resist families this is becoming less of a concern. Aside from sensitivity the other main obstacle has been the difficulty of preparing good quality thin films of non-polymeric materials. Here we present a study of pinhole defect density in fullerene films as a function of substrate cleanliness, post-application bake, and incorporation of chemical amplification components. Ultrathin (sub 30 nm) films of the previously studied fullerene resist MF03-01, and the polymeric resist PMMA were prepared on hydrogen terminated silicon by spin coating and the density of pinhole defects in the films was studied using atomic force microscopy. It was seen that pinhole density was strongly affected by the quality of the substrates, with the lowest densities found on films spun on freshly cleaned substrates. Aging of the film subsequent to spin coating was seen to have less effect than similar aging of the substrate prior to spin coating. Additionally, the use of a post-application bake significantly degraded the quality of the films. The addition of an epoxy crosslinker for chemical amplification was found to reduce defect density to very low levels.     

3D Printing of Bioinspired Alginate-Albumin Based Instant Gel Ink with Electroconductivity and Its Expansion to Direct Four-Axis Printing of Hollow Porous Tubular Constructs without Supporting Materials

A successful 3D printable hydrogel ink needs not only biofunctionalities but also minimal fabrication steps such as multiple crosslinking sites, high printability, cytocompatibility, high shape fidelity, stability, shear thinning, robust properties, and less time-consuming processing steps, by maximizing known material chemistries and functionalities. This work reports a novel bioinspired conjugate with polysaccharide (alginate)–tannic acid (TA)–protein (bovine serum albumin) to fabricate proteoglycan-like gels, which are 3D printable with multilayers, shear-thinning, elastic, electroconductive (with carbon nanotubes), controlled crosslinking/degradation through multiple crosslinking mechanisms (TA, Ca²⁺ ions, and NaIO₄ oxidation), and interactions with cytocompatible hydrogel system. The synthesis process is simple, and gelation (within 2 h) is ensured without any chemical crosslinking agents (at room temperature). While cell-adhesive albumin largely improves cytocompatibility, carbon nanotubes in the gel give electrical conductivity in the different four-axis 3D printed structures, including large hollow tubular constructs. This work demonstrates promising results of electroconductive proteoglycan-like gel ink to address the challenges in 3D/four-axis ink printing such as synthesis, printability, shape fidelity, electroconductivity, controlled fabrication and degradation, cytocompatibility, and multiple crosslinking abilities to maintain the dimensions of the diversely printed constructs.     

Protein Particles Formed by Protein Activation and Spontaneous Self‐Assembly

In this article, a non‐chemical crosslinking method is used to produce pure protein microparticles with an innovative approach, so‐called protein activation spontaneous and self‐assembly (PASS). The fabrication of protein microparticles is based on the idea of using the internal disulfide bridges within protein molecules as molecular linkers to assemble protein molecules into a microparticle form. The assembly process is triggered by an activating reagent–dithiothreitol (DTT), which only involved in the intermediate step without being incorporated into the resulting protein microparticles. Conventional protein microparticle fabrication methods usually involve emulsification process and chemical crosslink reactions using amine reactive reagents such as glutaraldehdye or EDC/NHS. The resulting protein microparticles are usually having various size distributions. Most importantly crosslinking reactions using amine reactive reagents will result in producing protein microparticles with undesired properties such as auto‐fluorescence and high toxicity. In contrast to the conventional methods, our technology provides a simple and robust method to produce highly homogeneous, stable and non‐fluorescence pure protein microparticles under mild conditions at physiological pH and temperature. The protein microparticles are found to be biodegradable, non‐toxic to MDCK cells and with preserved biological activities. Results on the cytotoxcity study and enzyme function demonstrate the potential applications of the protein microparticles in the area of pharmaceutics and analytical chemistry.     

Anomalous acid diffusion in a triphenylene molecular resist with melamine crosslinker

Next generation lithography will require next generation resists. Molecular resists, based on small non-polymeric molecules, promise improvements in line width roughness and resolution control for high resolution lithographic patterns. However, these materials are generally not sensitive enough for commercial application. We have investigated the application of a common chemical amplification scheme to molecular resists. The triphenylene derivative C5/C0 (symmetrical 2,6,11-trihydroxy-3,7,11-tris(pentyloxy)triphenylene), mixed with the crosslinker hexamethoxymethyl melamine and the photoacid generator triphenylsulfonium triflate shows a substantial sensitivity enhancement, requiring a dose of only 5 μC/cm² compared with the pure triphenylene sensitivity of 6500 μC/cm² at 20 keV. Previous work has indicated that the acid diffusion length of the photoacid generator used here is around 350 nm and that the diffusion length decreases with film thickness. However, in this molecular resist system anomalous levels of acid diffusion were observed, indicating that previous results for polymeric systems may not hold true for these new materials. Initial results indicate that the acid diffusion length in this system may be on the order of microns. Furthermore, there is some evidence that the excessive diffusion is occurring in the surface layers of the resist or at the air: resist interface itself.     

Investigation of physical and chemical property changes of ultra low-κ SiOCH in aspect of cleaning and chemical repair processes

The physical and chemical property changes of chemical vapor deposited ultra low-κ (ULK) SiOCH dielectric films due to different post ash treatments were studied by Auger electron spectroscopy, ellipsometric porosimetry and surface free energy evaluation. Structural changes in the ULK layer with respect to the carbon content were analyzed. Using a downstream and a reactive ion etch process for photo resist removal a reduction of carbon was observed. For different plasma gas chemistries the pore size reduction depends first on the process condition (downstream or reactive ion etch) and then on the gas. Differences in the pore size then also influence the amount of carbon depletion besides the influence of the gases used for photo resist processes. The damage at the surfaces was characterized by contact angle measurements providing both the polar and dispersive part of the surface free energy. The wettability of different solvents and repair chemicals was classified calculating their surface free energies and comparing those energies with the surface free energies of modified ULK surface. It is shown that especially reducing gases provide a surface free energy with a higher dispersive part compared to oxidative plasma treatments. Furthermore it was found that the wettability of repair chemicals and solvents strongly changes for reductive based strip processes with plasma exposure time, since a high variation of the surface free energy occur.     

Electron beam and X-ray resists

The optimisation of the lithographic performance of negative-working electron beam resists is developed through consideration of the radiation chemistry of crosslinking of representative materials, typically epoxy-functionalised polymers and polystyrene and its derivatives. Similarly, the lithographic behaviour of positive-working systems based on radiation-induced chain scission reactions is discussed with reference to acrylate and methacrylate polymers and polysulphones. The difficulties encountered in devising desirable working systems based on novolacs are considered and contrasted with the promise offered by recent developments arising from the extension of chemical amplification techniques to the electron beam lithographic domain.     

Injectability of Biosynthetic Hydrogels: Consideration for Minimally Invasive Surgical Procedures and 3D Bioprinting

Injectable hydrogels are often preferred when designing carriers for cell therapy or developing new bio-ink formulations. Biosynthetic hydrogels, which are a class of materials made with a hybrid design strategy, can be advantageous for endowing injectability while maintaining biological activity of the material. The chemical modification required to make these gels injectable by specific crosslinking pathways can be challenging and also make the hydrogels inhospitable to cells. Therefore, most efforts to functionalize biosynthetic hydrogel precursors toward injectability in the presence of cells try to balance between chemical and biological functionality, in order to preserve cell compatibility while addressing the injectability design challenges. Accordingly, hydrogel crosslinking strategies have evolved to include the use of photoinitiated “click” chemistry or bio-orthogonal reactions with rapid gelation kinetics and minimal cyto-toxicity required when working with cell-compatible hydrogel systems. With many new injectable biosynthetic materials emerging, their impact in cell-based regenerative medicine and bioprinting is also becoming more apparent. This review covers the main strategies that are used to endow biosynthetic polymers with injectability through rapid, cyto-compatible physical or covalent crosslinking and the main considerations for using the resulting injectable hydrogels in cell therapy, tissue regeneration, and bioprinting.     

Acid diffusion effects between resists in freezing processes used for contact hole patterning

Double patterning following an litho–litho-etch scheme is a possible option to create structure widths below the nominal resolution of optical light with current exposure technology. Interactions between the first and second resist layers may influence the final structure created. In this paper, we perform a model based investigation of the possible consequences of the diffusion of photo-generated acid from the second resist to the first one. As a consequence, less acid is available for the deprotection reaction, and we observe a tendency to an increase of the CD values of the primary structure. We attempt to explain observed footing effects in contact holes by this effect.     

Dual‐Tone Patterned Mesoporous Silicate Films Templated From Chemically Amplified Block Copolymers

Directly patterned mesoporous silicate films are prepared using positive‐ and negative‐tone strategies by performing phase selective silica condensation within lithographically exposed poly(styrene‐b‐tert‐butyl acrylate) (PS‐b‐PtbA) templates containing photoacid generators. The use of supercritical fluid as a process medium enables rapid diffusion of the silicate precursor within the prepatterned block copolymer template film without disrupting its morphology. Template exposure through the mask triggers area selective generation of acid, which in turn both deprotects the poly(tert‐butyl acrylate) block to yield a poly(acrylic acid) block and provides a catalyst for silica precursor condensation yielding pattern formation at the device level. Because the acid generated in the UV exposed field preferentially segregates into hydrophilic poly(acrylic acid) domains of the phase segregated, deprotected block copolymer, precursor condensation is simultaneously controlled at nanoscopic length scales via templating by the underlying block copolymer morphology. The ability of PS‐b‐PtbA to undergo chemical transformation in two stages, deprotection followed by crosslinking, enables precise replications of the photomask in positive and negative tones. Detemplating via calcination yields patterned mesoporous silicate films without etching. Template formulations are optimized using infrared spectroscopic studies and the silicate films are characterized using electron microscopy and scanning force microscopy.     

Enhancement or reduction of catalytic dissolution reaction inchemically amplified resists by substrate contaminants

Chemical interaction of resist and substrate at the interface, which modifies the dissolution reaction, has degraded sidewall profile of resist features. Depending on the nature of the residue on the substrate, the “bottom pinching” (BP) effect and footing are observed, especially for chemically amplified (CA) resists. The BP effect is observed for CA resist on top of organic bottom antireflection coating (BARC). The BP effect is attributed to the acid generated from the underlying organic BARC. With optimization on softbake temperature of BARC, the BP effect is eliminated. On a silicon nitride surface, new chemical information has been obtained which explains “footing” and BP effects in CA resists. X-ray photoelectron spectroscopy (XPS) measurements indicate that the residual alkaline molecules on the nitride surface play a major role in the formation of footing. It appears that the organic contaminants are not responsible for footing. Less severe footing is observed if the nitride surface is plasma-deposited with a thin oxide cap, which suppresses the surface basicity. However, extended plasma deposition causes resist BP. This is ascribed to the surface acidity of a newly formed oxide cap, which enhances the CA resist development process. Results show that the N (1 s) peak, after extended plasma treatment, has shifted to a higher binding state, which suggests that the nitride surface becomes acidic, causing BP     

General Photo‐Patterning of Polyelectrolyte Thin Films via Efficient Ionic Bis(Fluorinated Phenyl Azide) Photo‐Crosslinkers and their Post‐Deposition Modification

We have extended the well known bisfluorinated(phenyl azide) (bisFPA) methodology to develop an ionic bisFPA process suitable for photo‐crosslinking a wide variety of polyelectrolyte thin films. The crosslinking efficiencies (0.1–1.0 crosslink per photo‐reaction) are sufficiently high for the gel fraction to exceed 80 % for crosslinker concentrations of only a few weight %. This method is based on the photo‐induced formation of singlet nitrenes from FPAs and their insertion into unactivated C–H or other bonds, which thus general and not dependent on the presence of specific chemical functional groups. By derivatizing with ionic charge groups, we obtained ionic bisFPAs that can be properly dispersed into polyelectrolyte thin films. The sorbed moisture always present in these films however severely limits the photo‐crosslinking efficiency, apparently through nitrene protonation and intersystem crossing. This can be avoided by dehydration of the films, in some cases, to 130 °C for 10 min in nitrogen before photo‐exposure. We found that efficient photo‐crosslinking can then be achieved for polyelectrolytes even when they have nucleophilic groups. These include poly(styrenesulfonic acid) and their salts, poly(acrylic acid) and their salts, poly(dimethyldiallylammonium salts), as well as the electrically‐conducting poly(3,4‐ethylenedioxythiophene)‐poly(styrenesulfonic acid) complex (PEDT:PSSH). We further demonstrate using this ionic bisFPA methodology both photo‐patterning and post‐deposition chemical modifications of polyelectrolyte thin films. This opens broad new possibilities in membrane, sensor and actuator technologies, as well as for organic semiconductor plastic electronics (such as field‐effect transistors) and polyelectrolyte‐based devices.     

Formation Theory and Printability of Photocurable Hydrogel for 3D Bioprinting

Bio-ink has gradually transited from ionic-crosslinking to photocrosslinking due to photocurable bio-hydrogel having good formability and biocompatibility. It is very important to understand and quantify the crosslinking process of photocurable hydrogels, otherwise, bioprinting cannot be standardized and scalable. However, there are few studies on hydrogel formation process and its photocrosslinking behavior which cannot be accurately predicted. Herein, the photoinitiated radical polymerized bio-hydrogels are taken as an example to establish the formation theory. Three typical crosslinking reactions are first distinguished. It is further proposed that not all double-bonds consumed during crosslinking contributeequally to polymerization. Then the concept of effective double-bond conversion (EDBC) is elicited. Deriving from EDBC, several important formation indices are defined. According to theory, it is predicted that slow crosslinking can improve the crosslinking degree. Furthermore, based on the slow crosslinking effect, a new strategy of projection-based 3D printing (PBP) is proposed, which significantly improved printing quality and efficiency. Overall, this work will fill the gap in hydrogel's formation theory, making it possible to accurately quantify the formation process.     

Modeling of chemical-mechanical polishing considering thermal coupling effects

The removal of surface material in the conventional chemical-mechanical polishing (CMP) process is the result of synergetic effects of two dominant mechanisms: a mechanical process due to the abrasion of particles in the slurry, and a chemical process due to the reactions between the wafer and the chemicals in the slurry. In the overall material removal mechanism, in particular for metal layers, the mechanical and chemical effects are not independent, but are strongly coupled. Many models do not account for these coupling effects and cannot explain the non-Prestonian behavior that occurs when the material removal rate is a nonlinear function of the input areal power density. To address this deficiency and coupling effects, we propose a new integrated thermo-chemical-mechanical model that considers the synergistic effects of both the mechanical and chemical removal processes using the heat transfer mechanism as a bridge between them. In the modeling process, the material removal model is developed based on elastic and plastic contact mechanics and the dominant chemical reactions at the wafer surface. The temperature variation of the CMP system is treated as the coupling factor. The mechanical abrasion by the abrasive particles causes friction, which generates frictional heat on the contacting interfacial area. This heat plays a key role in accelerating the overall chemical reaction for the material removal. We performed a computer simulation with the proposed model using known parameters, and compared the results with other data to ensure its validity.     

Study on silicon surface oxidation of post-implant resist cleaning

Minimum substrate loss is required for resist strip of high dose, ultra shallow junction implant for source/drain extensions. Silicon surface oxidation of downstream plasma resist strip results in silicon recess of the source/drain extension regions. This paper reports the study of silicon surface oxidation for different resist strip plasma chemistries and the effect of plasma strip process parameters such as power, pressure and temperature on silicon surface oxidation. A good agreement was found between optical ellipsometry, XPS (X-ray photoelectron spectroscopy) and TEM (transmission electron spectroscopy) for thickness measurement of very thin (<20 Å) oxide grown on silicon surface due to plasma exposure. Selectivity of crust breakthrough and resist removal over silicon oxidation was also discussed in this paper along with dopant loss.     

High Sensitivity Graphene Field Effect Transistor‐Based Detection of DNA Amplification

Enzymatic DNA amplification‐based approaches involving intercalating DNA‐binding fluorescent dyes and expensive optical detectors are the gold standard for nucleic acid detection. As components of a simplified and miniaturized system, conventional silicon‐based ion sensitive field effect transistors (ISFETs) that measure a decrease in pH due to the generation of pyrophosphates during DNA amplification have been previously reported. In this article, Bst polymerase in a loop‐mediated isothermal amplification (LAMP) reaction combined with target‐specific primers and crumpled graphene field effect transistors (gFETs) to electrically detect amplification by sensing the reduction in primers is used. Graphene is known to adsorb single‐stranded DNA due to noncovalent π–π bonds, but not double‐stranded DNA. This approach does not require any surface functionalization and allows the detection of primer concentrations at the endpoint of reactions. As recently demonstrated, the crumpled gFET over the conventional flat gFET sensors due to their superior sensitivity is chosen. The endpoint of amplification reaction with starting concentrations down to 8 × 10^?21 m in 90 min including the time of amplification and detection is detected. With its high sensitivity and small footprint, this platform will help bring complex lab‐based diagnostic and genotyping amplification assays to the point‐of‐care.