Detection of neutral products formed during excimer laser ablation of polyimide by UV and VUV laser photoionization/mass spectrometry

Some of the neutral species which are produced in the laser ablation of polyimide have been characterized using multiphoton ionization/time of flight mass spectrometry. Three different wavelengths (193 nm, 157 nm, and 118 nm) have been used in an attempt to effect soft ionization of the products formed during or after the initial laser ablation of the polymer. Neutral photo-ablation products detected using this scheme range from atomic to high molecular weight species which, depending on the probe wavelength, include pure carbon clusters as well as a broad distribution of heteroatom containing clusters. However, there is virtually no overlap in the mass spectra recorded at each probe wavelength. When probing with 193 nm, marked changes are observed in the mass spectra as a function of the probe flux used. At moderate fluxes, pure carbon clusters (fullerenes) are observed. The identification of a large distribution of species other than pure carbon clusters is in dramatic contrast to the recent observation [W.R. Creasy, J.T. Brenna: Chem. Phys. 126, 453 (1988)] of the positively charged ionic species produced, which are solely carbon clusters. These results suggest that the neutral and ionic products observed after ablation of the polymer are due to both condensation of the atomic and molecular fragments which form during the ablation laser pulse and nascent polymer fragments. Various implications of this result for the unambiguous determination of the true ablation product distribution are discussed.

[1]  Bodil Braren,et al.  Photochemical cleavage of a polymeric solid: details of the ultraviolet laser ablation of poly(methyl methacrylate) at 193 nm and 248 nm , 1986 .

[2]  R. F. Curl,et al.  Probing C60 , 1988, Science.

[3]  M. Stuke,et al.  Femtosecond uv excimer laser ablation , 1987 .

[4]  H. Philipp,et al.  Dependence of photoetching rates of polymers at 193 nm on optical absorption depth , 1986 .

[5]  S. Namba,et al.  Effective deep ultraviolet photoetching of polymethyl methacrylate by an excimer laser , 1982 .

[6]  R. Srinivasan,et al.  Laser ablation of organic polymers: Microscopic models for photochemical and thermal processes , 1985 .

[7]  J. Tarascon,et al.  Epitaxial ordering of oxide superconductor thin films on (100) SrTiO3 prepared by pulsed laser evaporation , 1987 .

[8]  R. Srinivasan,et al.  Dynamics of UV laser ablation of organic polymer surfaces , 1986 .

[9]  Roger Kelly,et al.  Reconsidering the mechanisms of laser sputtering with Knudsen-layer formation taken into account , 1988 .

[10]  Bodil Braren,et al.  Ablative photodecomposition of polymer films by pulsed far‐ultraviolet (193 nm) laser radiation: Dependence of etch depth on experimental conditions , 1984 .

[11]  M. Vries,et al.  Pulsed laser desorption near a jet orifice: Concentration profiles of entrained perylene vapor , 1988 .

[12]  R. Larciprete,et al.  Direct observation of excimer-laser photoablation products from polymers by picosecond-uv-laser mass spectroscopy , 1987 .

[13]  R. Srinivasan,et al.  Theory of etching of polymers by far-ultraviolet high-intensity pulsed laser- and long-term irradiation , 1984 .

[14]  Nicholas S. Nogar,et al.  Mass spectroscopic identification of wavelength dependent UV laser photoablation fragments from polymethylmethacrylate , 1986 .

[15]  R. Srinivasan,et al.  Self-developing photoetching of poly(ethylene terephthalate) films by far-ultraviolet excimer laser radiation , 1982 .

[16]  I. Mclaren,et al.  TIME-OF-FLIGHT MASS SPECTROMETER WITH IMPROVED RESOLUTION , 1955 .

[17]  P. Dyer,et al.  Excimer laser ablation and thermal coupling efficiency to polymer films , 1985 .

[18]  S. Namba,et al.  Deep uv submicron lithography by using a pulsed high‐power excimer laser , 1982 .

[19]  R. Srinivasan,et al.  Electrostatic collection of debris resulting from 193 nm laser etching of polyimide , 1987 .

[20]  L. Kiss,et al.  Statistical model for the UV laser ablation mechanism of polymers , 1988 .

[21]  Donald M. Cox,et al.  Production and characterization of supersonic carbon cluster beams , 1984 .

[22]  K. C. Reichmann,et al.  Carbon clusters revisited: The ‘‘special’’ behavior of C60 and large carbon clusters , 1988 .

[23]  James B. Anderson,et al.  Velocity Distributions in Molecular Beams from Nozzle Sources , 1965 .

[24]  R. Srinivasan,et al.  Ablative photodecomposition: action of far-ultraviolet (193 nm) laser radiation on poly(ethylene terephthalate) films , 1982 .

[25]  J. Brannon,et al.  Excimer laser etching of polyimide , 1985 .

[26]  S. C. O'brien,et al.  Lanthanum complexes of spheroidal carbon shells , 1985 .

[27]  R. Conzemius,et al.  A review of the applications to solids of the laser ion source in mass spectrometry , 1980 .

[28]  K. Reichmann,et al.  C60La: a deflated soccer ball? , 1986, Journal of the American Chemical Society.

[29]  N. S. Nogar,et al.  Summary Abstract: Mass spectral identification of ultraviolet‐laser photoablation products from polymers , 1987 .

[30]  D. Feldmann,et al.  Mass spectroscopic studies of the ArF-laser photoablation of polystyrene , 1987 .

[31]  Jean-Marie Tarascon,et al.  Low‐temperature preparation of high Tc superconducting thin films , 1988 .

[32]  P. H. Key,et al.  Direct etching of polymeric materials using a XeCl laser , 1983 .

[33]  G. Koren,et al.  Emission spectra, surface quality, and mechanism of excimer laser etching of polyimide films , 1984 .

[34]  R. Taylor,et al.  Effect of optical pulse duration on the XeCl laser ablation of polymers and biological tissue , 1987 .

[35]  M. Gower,et al.  Time resolved transmission studies of poly(methyl methacrylate) films during ultraviolet laser ablative photodecomposition , 1987 .

[36]  T. Venkatesan,et al.  Preparation of Y‐Ba‐Cu oxide superconductor thin films using pulsed laser evaporation from high Tc bulk material , 1987 .

[37]  W. R. Creasy,et al.  Large carbon cluster ion formation by laser ablation of polyimide and graphite , 1988 .

[38]  S. D. Jenkins,et al.  Novel method for measuring excimer laser ablation thresholds of polymers , 1988 .

[39]  Raghavan Srinivasan,et al.  Ultraviolet laser ablation of polyimide films , 1987 .

[40]  Donald L. Singleton,et al.  Excimer lasers in cardiovascular surgery: Ablation products and photoacoustic spectrum of the arterial wall , 1986 .

[41]  C. Fotakis,et al.  Spectroscopic studies of ArF laser photoablation of PMMA , 1985 .

[42]  T. Keyes,et al.  Theory of photoablation and its implications for laser phototherapy , 1985 .

[43]  D. Linde,et al.  Velocity distribution of molecular fragments from polymethylmethacrylate irradiated with UV laser pulses , 1986 .

[44]  G. Koren,et al.  Emission spectra and etching of polymers and graphite irradiated by excimer lasers , 1984 .

[45]  G. Mahan,et al.  Theory of polymer ablation , 1988 .

[46]  R. Linsker,et al.  Far‐ultraviolet laser ablation of atherosclerotic lesions , 1984, Lasers in surgery and medicine.

[47]  S. Babu,et al.  Excimer laser etching of polymers , 1986 .

[48]  Roger Kelly,et al.  On the effect of Knudsen-layer formation on studies of vaporization, sputtering, and desorption , 1988 .