Poly Etch Research Articles

Femtosecond fabricated surfaces for cell biology

Microfabrication using femtosecond pulse lasers is enabling access to a range of structures,surfaces and materials that was not previously available for scientific and engineeringapplications. The ability to produce micrometre sized features directly in polymer andmetal substrates is demonstrated with applications in cell biology. The size, shape andaspect ratio of the etched features can be precisely controlled through the manipulation ofthe fluence of the laser etching process with respect to the properties of the target material.Femtosecond laser etching of poly(methyl methacrylate) and aluminium substrates hasenabled the production of micrometre resolution moulds that can be accurately replicatedusing soft lithography. The moulded surfaces are used in the imaging of T cells anddemonstrate the improved ability to observe biological events over time periods greaterthan 10 h. These results indicate the great potential femtosecond pulse lasersmay have in the future manufacturing of microstructured surfaces and devices.

Improvement of Poly-Pimple-Induced Device Mismatch on 6T-SRAM at 65-nm CMOS Technology

An incremental poly etching method can improve the poly pimple defect-induced device mismatch on the static noise margin (SNM) of 65-nm-node low-power 6T-SRAM. The improvement on circuit level is examined by the yield of scan chain and memory built-in self-test (MBIST), which is known to correlate well to process-induced defects.

Electrokinetic study of etching latent tracks of accelerated heavy ions in poly(ethylene terephthalate) and polyimide

The etching of latent tracks and pore formation in track membranes are studied. It is shown that the incorporation of K+ and Ba2+ ions into alkaline solutions accelerates the etching of poly(ethylene terephthalate) (PET) and latent tracks in it. The etching is accelerated due to a decrease in the negative surface charge of PET surface and the pores in track membranes. Isoelectric points are determined for PET and polyimide track membranes and it is established that they depend on pore diameter. As the pore diameter is enlarged from 30 to 70 nm, the magnitude of the negative surface charge rises seemingly due to the increase in the concentration of carboxyl groups on the pore surface. It is assumed that this effect is due to either a high mobility of carboxyl groups in a gel, which is formed on pore walls as a result of etching latent tracks, or a displacement of the slipping plane caused by a decrease in the thickness of the gel layer.

Impact of Kr gas mixing in oxygen plasma etching of ferroelectric poly(vinylidene fluoride-trifluoroethylene) copolymer films

Oxygen plasma etching characteristics of ferroelectric poly(vinylidene fluoride-trifluoroethylene) copolymer films are investigated. It was found in MFM (M: metal; F: ferroelectric) capacitors that plasma damage effects to the ferroelectric properties were insignificant when Au metal masks were used. On the contrary, C-V (capacitance versus voltage) characteristics were significantly degraded in plasma-etched MFIS (I: insulator; S: semiconductor) diodes. The origin of this phenomenon is speculated to be degradation of the SiO2∕Si interface by energetic oxygen ions and then mixing of Kr gas to the oxygen plasma is attempted to decrease the plasma damage.

Pattern transfer fidelity in capillary force lithography with poly(ferrocenylsilane) plasma etch resists

The influence of processing conditions and polymer architecture on pattern transfer in capillary force lithography (CFL) using poly(ferrocenylsilane) etch resists is investigated. Zero-shear-rate viscosities measured at different temperatures and for polymers with different molar masses are related to the quality of CFL patterns, assessed based on atomic force microscopy experiments. An optimal range of viscosities corresponding to appropriate molar masses and processing temperatures is established. In this range, polymers possess enough mobility allowing for reasonably quick surface pattern formation. Yet, the polymers are not too mobile and preserve their shape when quenched to below T g prior to serving as etch resist masks.

Pretreatment of Poly(l-Lactide-co-Glycolide) Scaffolds with Sodium Hydroxide Enhances Osteoblastic Differentiation and Slows Proliferation of Mouse Preosteoblast Cells

Surface topography is important in the creation of a scaffold for tissue engineering. Chemical etching of poly(l-lactide-co-glycolide) with sodium hydroxide has been shown to enhance adhesion and function of numerous cell types. The authors investigated the effects of sodium hydroxide pretreatment of three-dimensional poly(l-lactide-co-glycolide) scaffolds on the adhesion, differentiation, and proliferation of MC3T3-E1 murine preosteoblasts. MC3T3-E1 cells were seeded onto three-dimensional poly(l-lactide-co-glycolide) scaffolds with and without 1 M sodium hydroxide pretreatment. Cells were then cultured in osteogenic medium and harvested at varying time points for RNA extraction. Quantitative real-time reverse-transcriptase polymerase chain reaction was performed to measure mRNA expression of several osteogenic marker genes. In addition, cell numbers were determined at varying time points during the culture period. All experiments were performed in triplicate. Pretreatment of three-dimensional poly(l-lactide-co-glycolide) scaffolds with sodium hydroxide resulted in statistically significant up-regulation of mRNA expression of alkaline phosphatase, bone sialoprotein, osteocalcin, and vascular endothelial growth factor during the first 10 days of culture. Histologic analysis demonstrated a striking increase in mineralized cell matrix deposition in the sodium hydroxide-treated group. Cell number was statistically higher in the sodium hydroxide-treated group immediately after cell seeding, suggesting improved adhesion. During the first 24 hours of culture, cells grew faster in the control group than in the sodium hydroxide-treated group. Chemical etching of poly(l-lactide-co-glycolide) scaffolds with sodium hydroxide strongly influences the behavior of MC3T3-E1 preosteoblasts in vitro by enhancing adhesion and differentiation and slowing proliferation. Sodium hydroxide treatment may represent a simple and inexpensive way of improving scaffolds for use in bone tissue engineering.

Ablation and water etching of poly(ethylene) modified by argon plasma

Ablation and water etching of high density polyethylene (PE) exposed to Ar plasma for 240 s at 8.3 W power were studied. Gravimetry was used to determine the ablated and etched layer thicknesses. The surface topography and roughness were observed via AFM. The chemical composition and structure of modified surface layer were studied by FTIR, XPS, RBS, and EPR techniques. It was found that under the experimental conditions ca. 30 nm thick layer is ablated, the surface topography changes dramatically and surface roughness increases. The cleavage of macromolecular chains is proved by the presence of surface free radicals. Oxygen containing groups known to enhance surface solubility are detected. Under present laboratory conditions ca. 20 nm thick surface layer is dissolved during 24 h. After water dissolution of the surface, the roughness increases.

THE EFFECT OF NAOH ON PROLIFERATION AND DIFFERENTIATION OF MC3T3-E1 PREOSTEOBLASTIC CELLS GROWN ON THREE-DIMENSIONAL POLY(L-LACTIDE-CO-GLYCOLIDE) SCAFFOLDS.

Background In creating a biosynthetic scaffold that promotes osteogenesis surface topography is an important variable. It has been demonstrated that chemical etching of poly(l-lactide-co-glycolide) (PLGA) with NaOH enhances adhesion and function of numerous cells types in two-dimensional systems (hepatocytes, endothelial cells, vascular and bladder smooth muscle cells) and three-dimensional (3-D) systems (chondrocytes). This study compares the biological behavior of osteoblasts grown on NaOH-treated PLGA scaffolds and conventional PLGA scaffolds by measuring osteoblast adhesion, differentiation, and proliferation of MC3T3-E1 cells cultured on NaOH-treated 3D PLGA scaffolds and untreated scaffolds. Methods MC3T3-E1 mouse preosteoblast cells were seeded onto 3-D PLGA scaffolds ± 1 M NaOH for 10 minutes. Quantitative real-time RT PCR was performed to measure mRNA expression of osteogenic marker genes. In addition, cell numbers were determined at varying time points. Results Pretreatment of 3D PLGA scaffolds with NaOH resulted in statistically significant up-regulation of mRNA expression of alkaline phosphatase (ALP), bone sialoprotein (BSP), osteocalcin (OCN), and vascular endothelial growth factor (VEGF). A striking increase in mineralized cell matrix deposition in the NaOH group was also observed. Cell number was statistically higher in the NaOH group immediately after cell seeding, suggesting improved adhesion. During the first 24 hours of culture, cell proliferative rates were higher in the control group than the NaOH group. Conclusion Chemical etching of PLGA scaffolds with NaOH enhances adhesion and differentiation and slows proliferation of preosteoblast cells. NaOH treatment may represent an inexpensive way to improve scaffolds for use in bone tissue engineering.

Comparative Study between Wet and Dry Etching of Poly(N‐vinylcarbazole)

AbstractThis work presents the study of two etching techniques, also applied in polymer. The chosen polymer was poly (N‐vinylcarbazole) (PVK), because of its easy processability and custom of process. The polymer was synthesized by “living” free radical polymerization process. Previous studies on the best technique for film preparation had been made. The photolithography process was done, then in sequence the etching process was applied in two separate steps: the wet etching with a polymer solvent and dry etching with argon and oxygen plasma. The comparison of the results shows a significant difference between the etching methods, which will be suitable for films preparation in aiming at novel electronic devices.

Etching of Poly(tetrafluoroethylene) Sheet by Synchrotron Radiation Exposure in Soft X-ray Region

The reaction mechanism for the direct photoetching of poly(tetrafluoroethylene) (PTFE) using synchrotron radiation (SR) in the soft X-ray region, which is important for the microfabrication of PTFE nanoparts, was investigated by varying the photon flux irradiated to a PTFE sheet by changing the electron current of the storage ring. The etching depth of the PTFE sheet by SR exposure at 100 mA·h was measured at room temperature, 120 and 200 °C. Etching depth increased with photon flux despite of setting the SR exposure on the same quantity at each substrate temperature. It was found that the etching of PTFE proceeds not only via the first-order reaction but also via the second-order reaction whether substrate temperature was higher than glass transition temperature.

Plasma modification of HEMA and EOEMA surface properties

Process of plasma etching of poly(2-hydroxyethylmethacrylate) (HEMA) and poly(2-ethyloxyethyl methacrylate) (EOEMA) in Ar atmosphere at room temperature was studied. Ablation of the samples exposed to the plasma was determined by gravimetry, surface wettability by goniometry, chemical structure by FTIR spectroscopy and surface morphology by Scanning Electron (SEM) microscopy. Adhesion and proliferation of 3T3 mouse fibroblasts was studied in vitro in order to determine biological activity of plasma-modified HEMA and EOEMA substrates. It was demonstrated that the plasma etching leads to oxidation of HEMA and to an increase of its wettability. More estheric structures are produced in EOEMA. For both polymers, a surface layer ∼2 μm thick is ablated after plasma etching for 400 s. The etching changes the sample surface morphology and its biological activity. The surface becomes smoother after etching. The results obtained after 3T3 cells cultivation show that the plasma etching decreases cell adhesion and increases cell proliferation in comparison with pristine polymers.

Surface roughness investigation of 157- and 193-nm polymer platforms using different etch conditions

A series of different fluorinated polymer platforms used for early and current 157-nm photoresists is investigated with regard to blanket etch properties and surface roughness. Besides methacrylic-based polymers applied for 193-nm lithography, fluorine containing norbornene homopolymers, fluorinated cycloolefines, and tetrafluoroethylene (TFE) norbornene copolymers are chosen. Etch rates in different plasmas used for several applications, such as poly, SiN mask open, and selective/nonselective SiO2 etch, are determined and compared to standard 193-nm platforms currently used for DRAM manufacturing. Looking at various base resins, significant differences can be found using HBr- or Cl2-based poly etch conditions and various fluorocarbon-based oxide etch chemistries. Up to 2.4 times higher etch rates in Cl2 and the different CxFy oxide etch recipes are observed for the highly fluorinated cycloolefines and the TFE norbornenes, showing a strong correlation between fluorine content and etch rate. After stress by different etch conditions, the polymer surfaces are characterized using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Surprisingly, the surface roughness of the methacrylic platforms and the norbornene base resin (determined by AFM) are found to be substantially higher than that of the highly fluorinated platforms. These results can directly be correlated to pictures obtained by optical methods (SEM).

A new method to extract gate coupling ratio and oxide trapped charge in flash memory cell

A new method to obtain the gate coupling ratio ( α g) and oxide trapped charge ( Q ox) as a result of cycling in flash memory cells is described here. Three cells with an equivalent physical structure but different erase characteristics are measured. The threshold changes versus erase times are fitted to the charge removal rate calculated based on Fowler–Nordheim (FN) tunneling and the capacitive relations among all nodes. The extracted α g is independent of technologies and this method is particular useful when the profile of the floating gate is not traditionally rectangular owing to advanced processes such as trapezoidal poly etch or a poly-spacer addition on the floating gate sidewall. The Q ox can also be determined once α g is extracted.

Making porous membranes by chemical etching of heavy-ion tracks in β-PVDF films

Production of porous membranes using heavy ion bombardment and subsequent chemical etching of poly(vinylidene difluoride) (PVDF) films has been reported several years ago. However, porous membranes with pore diameter in the nanometer scale requires a better understanding of the chemical etching mechanism. In this work PVDF foils irradiated with Sn ions (2.85MeV per nucleon) were exposed to several etching conditions which involved permanganate oxidation in different alkaline environments. The solution of KOH 9molL−1 and saturated in KMnO4 was the best etching reactant for PVDF. Functional groups created in the alkaline and oxidative attack by permanganate were studied by FT-IR and UV–vis spectroscopy. The spectroscopic data reveals that the formation of pores occurs by a two-step mechanism: (i) double bonds as a result of dehydrofluorination induced by alkaline media and (ii) oxidation of these double bonds in permanganate solution. The etching temperature and time can be attuned to prepare track-etched membrane with a desired pore diameter in the range of few hundred nanometers. Temperatures ranged between 55°C and 65°C were optimal to produce cylindrical pores. Temperatures higher than 85°C induce conical-shaped track-etched pores while temperatures lower than 50°C slow down the chemical attack. The addition of a phase-transfer agent enhances the chemical attack and allows the decrease of the etching temperature and/or time.

Nanoporous Polystyrene by Chemical Etching of Poly(ethylene oxide) from Ordered Block Copolymers

Nanoporous Polystyrene by Chemical Etching of Poly(ethylene oxide) from Ordered Block Copolymers

Silicon nanostructures from electroless electrochemical etching

Recent advances in the production of Si nanostructures from electroless etching are reviewed, including stain etching, metal-assisted etching and chemical vapour etching. A brief review of the explosion in applications of porous silicon over the past 18 months is also given. The stain film that results from the etching of (poly- or single-)crystalline Si is composed of a porous network of nanocrystalline silicon. Few mechanistic studies of electroless etching have been performed, but the more extensively studied anodic etching of silicon in fluoride solutions provides many clues as to how porous films are formed. Intriguing recent results have shown that control over the properties of the film can be obtained by exercising control over the composition of the etchant.

The impact of PMOST bias-temperature degradation on logic circuit reliability performance

This work investigated the impact of pMOST bias-temperature (BT) degradation on logic product's speed ( F max) and minimum allowed operating voltage ( V ccmin). BT degradation occurs during the product Burn-In and under the normal circuit operation. The interaction of device degradation and circuit performance is explained. Fluorine implants after poly etch and before hard-mask removal are utilized to separate out the BT instability effects from other reliability degradations. Physical mechanism and degradation models are proposed to explain the interaction of fluorine with device and circuit reliability. Process optimization, such as fluorine implant, can be used to reduce the pMOST BT impact on circuit degradation. Reliability guardband in F max and V ccmin is recommended, as part of the production testing to ensure reliable logic product performance and functionality during the product's lifetime. A guardband methodology is also discussed in the paper.

Sensibilization of Chemical Etching of Poly(ethylene terephthalate) Films Irradiated with Accelerated Xenon Ions

Processes of the sensibilization of alkaline etching are studied for poly(ethylene terephthalate) films irradiated with xenon ions with an energy of 1 MeV per nucleon. The photosensibilization of alkaline etching of latent tracks in poly(ethylene terephthalate) is shown to be due to photooxidation processes involving molecular oxygen dissolved in the polymer. Oxygen is assumed to form molecular complexes with aromatic rings of the macromolecules and polyester degradation products; these complexes absorb in the near ultraviolet spectral range (λmax ≈ 310 nm) and initiate photooxidative degradation in poly(ethylene terephthalate) and in the substance of latent tracks. Ozone is shown to be an efficient sensibilizer of the chemical etching of the tracks. The photosensibilization and ozone sensibilization effects are greater in films irradiated with xenon ions, indicating a high selectivity of sensibilization processes in the latent tracks.

Nanofibrillar Surfaces via Reactive Ion Etching

The reactive ion etching of poly(ethylene terephthalate) using various gas compositions was examined. A radio frequency power supply operating at 30 kHz was used to produce plasmas from the following gases and 50:50 gas mixtures: Ar, N 2 , O 2 , Ar-N 2 , Ar-O 2 , and N 2 -O 2 . Exposure times were typically 10, 20, and 30 min. The relatively inert gases and gas mixtures (Ar, N 2 , Ar-N 2 ) produced a polygonal pattern of protrusions surrounding shallow cavities. In contrast, the presence of oxygen or oxygen-containing plasmas invariably imposed a fibrillar structure on these polygons in which nanofibrils typically originated at the triple points of several neighboring polygons. The dimensions of these fibrils varied with the exposure time but were up to 300 nm in length and approximately 20 nm in diameter. Atomic force microscopy was used to quantify the surface roughness and show that the inert gas compositions (Ar, N 2 , Ar-N 2 ) produced statistically indistinguishable values of R a (14.1 ′ 1.7, 15 ′ 2.5, 14.2 ′ 2.9 nm) significantly larger than those of the as-received film. The pure oxygen-etched films have R a values approximately twice as large as those of the other gas compositions. Prior work by Nie et al. suggests that films consisting of etching-resistant, low-molecular-weight fragments can form under these conditions. We find that surface physics normally associated with thin polar films on apolar substrates adequately describes the origin of the observed nanofibrils. Prior surface deformation has an additional influence on fibril spacing and density.

An atomic force microscopy study of ozone etching of a polystyrene/polyisoprene block copolymer

The ozone etching of a commercial poly(styrene)/poly(isoprene) (PS/PI) block copolymer (Kraton D1117) was studied by atomic force microscopy. The copolymer contains 17% PS and forms a cylindrical phase in the melt. The copolymer dewetted when spin coated onto a silicon wafer but the film was stable on a grown silicon oxide layer. The structure of the stripe pattern formed was examined on substrates with different oxide layer thicknesses (surface energies). Finally etching by ozone was investigated. For low ozone doses, no degradation of polymer was observable. Extended ozone treatment resulted in more obvious degradation, but the etching was non-selective.