Hiroyuki Hiraoka

Non-linear photochemistry of polymer films: laser ablation of poly (n-vinylcarbazole)

Abstract Irradiation of some poly(N-vinylcarbazole) films with a 248 nm excimer laser resulted in their ablation, giving an etched hole with a submicrometer depth. A characteristic periodic pattern and small particles with diameter of the order of submicrometers were formed in the etched area. This ablation behavior was affected by doping excitation energy and electron acceptors, discussed from a photophysical viewpoint.

Resist image enhancement by UV-, soft vacuum pulsed electron beams and organometallic compounds

Abstract UV-hardening/photostabilization process is used for preventing thermal flow of resist images at high temperatures.[1] Because of high temperature stability and highly crosslinked nature of resist surfaces, UV-hardening is used for resist enhancement for reactive ion etchings of metals, high temperature sputtering, lift-off and others.[2] We like to present here multilayer resist applications using highly crosslinked resist surfaces. Because of large deep UV absorption coefficients, application of UV-hardening to thick films is limited. For thick resist films, resist stabilization by pulsed electron beams operating in soft vacuum [3] is far more efficient because of deeper penetration of electron beams of 25 KeV energy. The present technique has an advantage over a conventional CW electron source with a larger diameter, cold cathode of an ordinary metal operating in a soft vacuum with high efficiency. Exposures of resist images to organometallic compounds either in vapor phase or in solutions provide them specific RIE resistances and thermal flow resistance.

Acid hardenable, spin-coatable silicon ladder polymer systems as a resist materials

Abstract Poly(phenylsisesquioxane) (PSQ) is known for its high RIE resistance , particularly in oxygen RIE condition, because of its ladder-type polymer structure with a high silicon content. Except chlorinated and vinyl substituted ones, the lithographic sensitivity is low. Low resist sensitivities of PSQ in both photo and electron beam lithography have been improved as reported here by a chemical amplification of crosslinking of hexamethoxymethylmelamine (HMMM) to the ladder-type silicon polymer, catalyzed by a photo-acid generator like triphenylsulfonium hexafluroantimonate (TPHA) onium salt. Spectroscopic and GPC data indicates HMMM acting as a crosslinking agent to give higher molecular weight resin despite no electrophilic sites available in the resin.

Pulsed electron beam lithography in soft vacuum

Large‐area (cm2 ) proximity patterning of selected microelectronic polymers using soft vacuum (0.05 Torr) pulsed electron beams is described using polymers with widely differing electron sensitivities (2–80 μC/cm2 at 20 keV). The short duration (∼100 ns) electron beams are produced in the pulsed mode (25–28 keV electrons, 2–3 J/pulse). These electrons impinge upon thin polymer films in the presence of an ambient gas to produce electron initiated bulk polymer chemical reactions including partial self‐development. In soft vacuum, pulsed electron beams are shown to be capable of transferring submicron (∼0.5 μm) features from an electron transmitting stencil mask onto poly(methylmethacrylate) (∼3 μm thick) films. Wide‐area exposure (field size ∼20 mm) is also demonstrated for micron feature sizes. Soft vacuum lithography appears well suited to microelectronics packaging lithography where resist thickness is substantial, linewidths are 1–10 microns, areas to be processed are large (100 cm2 ), and where registr...

Lithographic processing of polymers using plasma-generated electron beams

Pattern definition in polymer films is achieved using electron beams generated in soft vacuum (0.05-0.50 torr) glow discharges either on a continuous or a pulsed (20-100 ns) basis. With the continuous-mode electron beam, 7- mu m transmission mask features are replicated in both polymethyl methacrylate (PMMA) and polyimide resists. Using a pulsed electron-beam submicron ( approximately 0.5 mu m) features are transferred from an electron-transmitting stencil mask into the PMMA. The soft-vacuum pulsed electron beam is also eminently suited for polymer stabilization. Pulsed electron-beam hardening of 0.05-3.5 mu -thick AZ-type and MacDermid resist patterns is also demonstrated with hardened resist patterns stable to temperatures between 200 degrees and 350 degrees C. The demonstrated replication and pattern stabilization technique may be applicable in microelectronics packaging lithography where the resist thickness is substantial, linewidths are 1-10 mu m, and registration requirements are less stringent. >

Soft vacuum, pulsed electron-beam hardening of lithographic polymers

A 25 kV pulsed electron beam was used to harden 0.5--3.0 ..mu..m thick AZ-type, MacDermid, and polyamic acid (PMDA+ODA) resist patterns. The resist profiles are stable against high-temperature treatment that ranges between 200--350 /sup 0/C. The short pulse approx.100 ns, electron beams employed in resist hardening are produced from a cold cathode in 30--50 mTorr air by discharging energy stored in a 7.5 nF capacitor producing a dose/pulse approx.1 ..mu..C/cm/sup 2/ at the processed surface. Comparisons with conventional hardening methods using ultraviolet emission from a high-pressure mercury lamp, a windowless, vacuum ultraviolet (VUV) lamp, and low-energy electron emission from a cw source are also made.

High‐resolution polymer replication of surface topography

A few micron wide and thick polymer lines are formed from a monomer, methacrylic anhydride, according to a metal pattern of a mask under high‐energy radiation, such as γ rays. The resolution is limited only by the mask configuration; with our present mask configuration it is better than ∼2000 A. The polymerization is initiated by electrons ejected from metal lines.

SIMPLE METAL-ON-PLASTICS PATTERNING BY PULSED ELECTRON BEAM IN SOFT VACUUM

Direct patterning of polyimide images with a built-on-metal layer can be accomplished by electron beam exposures of doped polyamic acid films, followed by wet development in NMP and subsequent heating and curing to polyimide films. During curing at 300°C the metal salts converted to metal and migrated to the top surface of polyimide films. Additional electron beam exposures of images assisted metal film formation. Auger electron and Rutherfold backscattering spectroscopic analyses were carried out to confirm metal migration to the surface. Silver nitrate, gold mercaptide and cupric chloride were used as dopants in polyamic acid films.

Soft Vacuum Pulsed Electron Beam Processing Of Tenon And Teflon-Like Films

Poly(tetrafluoroethylene), Teflon, is an excellent engineering material with a low dielectric constant, chemical. inertness in hazardous environments, and thermal stability. However, it has many shortcomings such as poor adhesion to substrates, difficulty in micron-sized via hole fabrication, and almost zero solubility in common solvents. We found that Teflon self-developed very efficiently under pulsed electron beam (25 KV to 30 KV) exposure in soft vacuum. Teflon images were obtained by performing the electron exposure through a mask. its etching rate is the highest among the polymer films studied including radiation-sensitive poly(2-butene sulfone). A possible mechanism for this high self-development rate is proposed.

A Simple Metal Pn Polymer Process Using Pulsed Electron Beams In Soft Vacuum

We describe the proximity patterning using 28 kV, soft vacuum exposing electrons of silver, copper and gold containing metal-polymer composite films. The cross-linking of the metal doped polyamic acid, resulting in reduced solubility of exposed regions, leads to successful patterning following conventional wet development. The patterned films were found to contain the metal content redistributed, preferentially enriching the surface during the imidization cure, as supported by a variety of surface analysis methods.