Polymer Ablation Research Articles

Hydrodynamic regimes of UV laser ablation of polymers

The applicability of hydrodynamic models for the theoretical description of UV laser ablation of polymers is studied. The plume formation is considered as a first-order like phase transition. This phase transition occurs for strongly absorbing polymers as a surface evaporation and for weakly absorbing polymers as a bulk evaporation. The vapor plume is assumed to be transparent to laser radiation, and its expansion is described by the isoentropic hydrodynamic equations. New analytical expressions for ablation (etch) depths per pulse are obtained, which are in good agreement with the available experimental data. A stationary model for the absorbing plume is constructed.

Synthesis of Polysulfides Containing the Triazeno Group and Their Application as Photoresists in Excimer Laser Polymer Ablation

Two bifunctional unsaturated monomers containing the photosensitive triazene group were synthesized and reacted with dithiols. A radical polyaddition afforded polysulfides which carry the photosensitive chromophores in their backbone. The molar masses reach up to 10 400 g/mol and the glass transitions range between −2 and 39 °C. With respect to their application as dry photoresists for excimer laser ablation, thermo- and photolytical decomposition of monomers and polymers were investigated. TGA measurements revealed that the polymers were stable up to 255 °C, slightly below those of the monomers (270 °C). For photolysis in solution observed by UV/vis spectroscopy, the triazene absorption vanished on a time scale of seconds. Pulsed laser patterning was performed at 193 nm and with PMMA as a reference system. The sensitivity of the resists to irradiation was higher for PMMA and also the structural precision seemed to be slightly better for the standard, both probably owing to the applied wavelength. In cont...

Laser Processing of Polymer Materials: New Techniques to Prepare Advanced Materials by using Excimer Lasers.

Development of excimer lasers brought new phenomena for processing of polymer materials. Polymer ablation has already been utilized for micromachining in industry. In these years investigations on laser processing of polymer materials are extending to not only micromachining but also thin film preparation and surface modification. This paper reviews new techniques to prepare advanced polymer materials and discusses new directions of polymer processing.Interaction of excimer lasers with polymer materials has induced various phenomena which could not be opened by other traditional methods or physical techniques. Most distinctive characteristics of excimer lasers is a source of high-quality and high-intensity ultraviolet photons, which makes possible to excite high electronic levels by multiphoton excitation mechanism. We can design and expect new reactions through higher excited levels for various starting materials including polymers. These possibilities will give useful processing of polymer materials if we correspond to industrial needs and design the most suitable reaction fields.

Photophysical ablation of organic polymers: the influence of stresses

Non-stationary effects and the influence of mechanical stresses during ns and ps UV excimer laser ablation of organic polymers are discussed. Direct comparison of theoretical calculations with experimental data for laser ablation of polyimide at different wavelengths shows that the photophysical ablation model describes the kinetics of ns UV laser ablation reasonably well. Small gaseous fragments produced within the bulk polymer may be responsible for the mass losses observed near the ablation threshold. At higher fluences, stresses caused by these fragments may facilitate photophysical ablation. With ps laser pulses, acoustic waves related to transient thermal stresses lead to additional defect formation.

Laser induced microexplosions of a photosensitive polymer

Laser ablation of a photosensitive triazene polymer was studied in a micro region by means of a nanosecond imaging technique. The propagation of a blast wave, 100 ns after laser irradiation, sufficiently matched a planar blast wave model including the decomposed source mass which indicates characteristics of a microexplosion. The measured velocities of the fronts indicates two blast waves: an initially fast unsupported wave around the peak of the laser pulse, and a relatively slow supported wave involving the main component of the decomposition.

A thermal model for the ablation of polymers by lasers and high intensity ion pulses

The results for the ablation of polymers by High-Intensity Pulsed Ion Beams (HIPIB) as well as by laser pulses of different wavelengths and pulse widths are discussed. A thermal model is proposed that reproduces all available experimental data. An Arrhenius type relation is assumed for the ablation velocityw(T) =w0 exp (−T1/T). Once the two parametersw0 andT1 are known for a certain polymer the model allows one to predict the ablation rate as a function of laser wavelength, fluence, and pulse width and for HIPIB pulses.

The effect of pulse repetition rate on laser ablation of polyimide and polymethylmethacrylate-based polymers

The effect of pulse repetition rate on polymer ablation was studied experimentally and theoretically for polyimide and 8230 photoresist, a polymethylmethacrylate (PMMA)-based polymer. Both the experimental data and the theoretical model showed a distinct tendency for increased repetition rate to decrease the ablation threshold, without substantially altering the absorption coefficient. This was attributed to heating of the sample sequentially by the laser pulses and the magnitude of the effect is proportional to the square of the absorption coefficient. Polyimide, with an absorption coefficient of , is expected to exhibit the repetition rate effect in the range of tens to hundreds of kilohertz; hence the effect has not heretofore been observed. The PMMA-based photoresist, on the other hand, exhibits the effect at a much lower repetition rate, owing to the smaller effective absorption coefficient.

The role of excited species in ultraviolet-laser materials ablation III. Non-stationary ablation of organic polymers

The role of non-stationary effects in nano-second ultraviolet (UV) excimer-laser ablation of organic polymers is discussed. The model includes reversible changes in absorption related to darkening and bleaching effects. Comparison of calculations and experimental data for polyimide demonstrates that the photophysical model describes the ablation kinetics quite well.

The role of excited species in ultraviolet-laser materials ablation III. Non-stationary ablation of organic polymers

The role of excited species in ultraviolet-laser materials ablation III. Non-stationary ablation of organic polymers

Pulsed laser ablation and deposition of fluorocarbon polymers

Thin films of polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF) have been formed by the pulsed-laser deposition technique. The structure of the PTFE films depends upon the substrate temperature during deposition. At substrate temperatures from room temperature to 200°C the films were determined to be amorphous. Films formed at higher substrate temperatures contain both amorphous and crystalline components. Transmission IR spectroscopy indicates that the amorphous and the semi-crystalline variants of PTFE are chemically equivalent. The PVDF films were found to be amorphous for all substrate temperatures studied in the range 25°C to 200°C. For both materials it was found that the use of higher substrate temperatures results in the formation of smoother films.

Excimer laser ablation of low and high absorption index polymers

A comparative study of laser ablation of bulk samples of Upilex polyimide and low density polyethylene, which represent extremes in terms of absorption index at the ArF laser wavelength, is reported. High Speed Shadow Photography (HSSP), Probe Beam Deflection (PBD) and Time Resolved Interferometry (TRI) techniques have been used to provide information about the ablation process. It is shown that HSSP allows the laser generated shock wave and particulate products to be visualised as they expand away from the ablation site. PDB signals are seen to correlate well with the HSSP results and allow data to be obtained for an ablation regime in which no visible plume is observed. The TRI technique gives complementary, time-space resolved, information about the nature of the product expansion.

VUV ablation of polymers by emission from gas-puff Z-pinch plasmas

We have made experiments of the polymer ablation utilizing the gas-puff Z-pinch plasmas which provide a highly bright emission extending over a broad wavelength range from visible lights to X-rays. When the emission was irradiated through a mask onto a polytetrafluoroethylene (PTFE) film, the irradiated area was ablated and a pattern of the mask was copied on the surface of the film. A detail observation with an atomic force microscope showed that the irradiated area was precisely processed with no thermal damage. A chlorinated polyvinylchloride (Cl-PVC) pellet was also irradiated. The analysis of unirradiated and irradiated surface was performed by FTIR-ATR. The FTIR-ATR spectrum after irradiation shows an appearance of a new peak attributed to C5C bonds.

High sensitivity quadrupole mass spectrometry of neutrals sputtered by UV-laser ablation of polymers

Laser Ablation-Sputtered Neutrals Spectrometry is developed as a portable system which consists of a commercial gas analyser (quadrupole mass spectrometer with e-beam ionization) in ultrahigh vacuum. ArF and KrF ablation of 20 polymers yielded mass spectra (1–200), rich in information, and mass intensity versus etching time for depth profiling analysis. The sensitivity is very high (100 ng of polymer can be probed) and microablation can be recorded by LA-SNMS.

Excimer laser ablation of polymers and glasses for grating fabrication

In this paper we describe studies carried out related to grating formation for optoelectronics applications using 248 nm and 193 nm excimer lasers. These include basic studies of UV laser induced incubation and ablation of various glasses, and an evaluation of laser-induced-periodic-surface-structures (LIPSS) and UV holographic techniques based on a phase mask for forming gratings on polymers and in fibres. Modelling and experiments show that the use of excimer laser illuminated phase masks in a contact printing mode or Talbot reimaging arrangement provide a particularly effective approach to forming submicron period gratings.

A thermal model for the ablation of polymers by lasers and high intensity ion pulses

A thermal model for the ablation of polymers by lasers and high intensity ion pulses

Possibility of depositing magnetic iron oxide films by excimer laser ablation of an organometallic polymer

Magnetic iron oxide films were successfully deposited on heated fused-quartz substrates via the plume generated by the excimer laser ablation of poly(ferric methacrylate), an organometallic polymer, in an oxygen atmosphere. The investigation for the deposited films by means of x-ray photoelectron spectroscopy, Raman spectroscopy, x-ray diffraction, and scanning electron microscopy demonstrates that these films consist of iron-rich Fe3O4 and α-Fe2O3 phases that are made up of ball-like grains with nanometer-size structure. Magnetic hysteresis loop of the deposited film was also measured. The values of saturation magnetization, remanence magnetization, and coercivity are 35.6 emu/cm3, 6.13 emu/cm3, and 200 Oe, respectively.

Laser-induced ablation of polymers using a patterned dopant generated from a leuco-dye precursor via flood exposure: A ?portable conformable mask? approach to laser ablation of PMMA at 351 nm

A two-stage laser ablation process is described, which initially generates a laser-light absorbing image from a conventional photolithographic mask via a UV-flood exposure step. For this purpose a colorless precursor of a dye, i.e., itsleuco form, is imbedded into the polymer to be ablated as a dopant. For poly(methyl methacrylate) as such a polymer, triphenylmethanol, the leuco precursor for the corresponding triphenylmethyl dye represents a good choice for ablation with excimer lasers operating at the wavelength 351 nm. In this fashion conventional masks and exposure tools of UV-photolithography may be used in combination with laser ablation. The resulting images are characterized by a good contrast and reasonably sharp contours. The photochemical mechanism and additional aspects of this two-step process, which resembles the “portable conformal mask” approach of photolithography, are outlined.

Laser-induced ablation of polymers using a patterned dopant generated from a leuco-dye precursor via flood exposure: A ?portable conformable mask? approach to laser ablation of PMMA at 351 nm

Laser-induced ablation of polymers using a patterned dopant generated from a leuco-dye precursor via flood exposure: A ?portable conformable mask? approach to laser ablation of PMMA at 351 nm

Ablation and surface modification of polymers with ultraviolet laser radiation.

The recent progress of UV-laser photoablation is reviewed with the sake of clarifying the various regimes of irradiation which are of interest for new processes. Fast, and Pre- ablation regimes are evidenced by Laser Ablation-Sputtered Neutrals Spectrometry (LA-SNMS). Mass spectra of a series of polymers. have been obtained. Sub-micron periodic structures and examples of microfabrication (microlens arrays) are presented. The recent developments of photoablation of polymers with the UV radiation of excimer lasers is reviewed. LA-SNMS is shown to be a very promising detector for future work in the photoablation of polymer area. The gases emitted by the ablative interaction are measured in ultra high vacuum conditions. Some polymer spectra (Kapton, Upilex, PEN) are presented and interpreted. The work on formation of submicron periodic structures is entering into a new phase with the discovery of systems giving visible structures which are studied by visible light diffraction. Photoablation is seen as an attractive tool for future development of microfabrications. The example of microlens arrays is presented. For clarity we define three main regimes of irradiation which we call: Pre-ablation, Slow Ablation and Fast Ablation. It is important to note that each regime of irradiation has evidenced interesting processes for the applications.

Instabilities and Structure Formation in Laser Processing

ABSTRACTThis paper gives an overview on different types of instabilities and structure formation in various fields of laser processing. Among the examples discussed in detail are non-coherent structures observed in laser-induced chemical vapor deposition (LCVD), in laser-induced surface modifications, and in laser ablation of polymers.