Polyimide patterning

Polyamic acid methacrylate esters are the first self-patternable, pure organic polyimide precursors to be described. They are the polymer basis of the first technically applied resist to produce polyimide patterns in a direct process. They are synthesized simply by the addition of hydroxyethylmethacrylate to aromatic acid dianhydride, and subsequent polycondensation of the intermediate tetracarboxylic acid diester with aromatic diamines. These polyimide precursors give rise to a number of special photoresist properties which lead to important applications, such as photolithographically produced protection layer against a-radiation on memory... 

Figure 1. Chemical principle and processing steps for direct production of polyimide patterns...

With regard to thermal conversion to polyimide, we evaluated the suitable reaction conditions for thermal conversion of the photo-crosslinked patterns into completely polyimide patterns and found, that the crosslinked bridges are split off and depolymerization takes place. More than 95 % of the volatile product is the monomer hydroxyethylmethacrylate. 

Fig. 14 SEM photographs of polyimide patterns with CVD tetravinylsilane film as an etch barrier (a) a stencil mask used, (b) (b),(c) polyimide patterns of (PMDA-ODA) vapor deposited.

H. Itatani, S. Matsumoto, T. Itatani, T. Sakamoto, S. Gorwadkar, and M. Ko-muro. Method for forming polyimide pattern using photosensitive polyimide and composition for use therein. US Patent 6777 159, assigned to PI... 

Figure 8. TEM and optical absorption of the sample implanted with 5 x 10 Au /cm (a) TEM cross-sectional micrograph (dashed lines represent the free surface and film-substrate interface) (b) nanoparticles size distribution (c) simulated optical spectra (1) Au cluster in a non-absorbing medium with n = 1.6 (2) Au cluster in polyimide (absorbing) (3) Au(core)-C(shell) cluster in a nonabsorbing medium with n = 1.6 (4) the experimental spectrum of Au-implanted polyimide sample, (d) X-ray diffraction patterns as a function of the implantation fiuence.

Manufacture of Printed Wiring Boards. Printed wiring boards, or printed circuit boards, are usually thin flat panels than contain one or multiple layers of thin copper patterns that interconnect the various electronic components (e.g. integrated circuit chips, connectors, resistors) that are attached to the boards. These panels are present in almost every consumer electronic product and automobile sold today. The various photopolymer products used to manufacture the printed wiring boards include film resists, electroless plating resists (23), liquid resists, electrodeposited resists (24), solder masks (25), laser exposed photoresists (26), flexible photoimageable permanent coatings (27) and polyimide interlayer insulator films (28). Another new use of photopolymer chemistry is the selective formation of conductive patterns in polymers (29). 

Schematic of the Si-nMEA fabrication process (a) sputter Au layer on double-side polished wafer (b) pattern Au layer with liftoff process (c) spincoat and cure a polyimide layer (d) perform the double-sided photolithography to pattern etch pits (e) etch Si in ICP-DRIE to form Au/Si electrode (f) dice the wafer into a single die (g) RIE etch the polyimide layer with a shadow mask to expose current collecting region (h) electroplate Pt black on Au layer (i) sandwich both electrodes with Nafion 112 in a hot-press bonder. (Reprinted from J. Yeom et al. Sensors Actuators B107 (2005) 882-891. With permission from Elsevier.)...

As insulation between the coil and the magnetic core, a hard-cured (to 200°C) photoresist insulator is patterned. It is a novolak polymer or polyimide about 5 fim thick, which is popular for its high insulator and photolithographic properties. This provides electrical insulation as well as a planar surface for subsequent deposition of copper cods. 

The present work is a report of the properties of polyimide which define functionality as an interlevel dielectric/passivant. Thus, the planarizing and patterning characteristics and electrical characteristics of current vs voltage, dissipation, breakdown field strength, dielectric constant, charge and crossover isolation are discussed in addition to the reliability-related passivation properties. 

I would like to express thanks to Kathleen Ginn for excellent technical assistance In preparing patterned polyimide films. 

A 3/8 inch diameter aluminum or titanium-tungsten dot pattern WLs fabricated on top of the cured polyimide film to make electrical leakage to substrate measurements for pinhole density estimation. An etch decoration technique was used to visually determine pinhole densities in polyimide films. The polyimide film was cast on substrates comprised of a layer of 200 nm thick alumimmi on blue colored field oxide with a grid pattern for area computation. Replicate holes were etched in the aluminum by a hot phosphoric acid solution. With the polyimide film removed, a good visual contrast was achieved for pinhole density counting. 

X-ray powder diffraction was recorded using a conventional x-ray powder diffractometer with Cu-Ka radiation. Polyimide film on which sample particles are deposited is glued on a glass sample holder with vacuum grease. Figure 1.6.9 shows the recorded diffraction pattern. An analysis of the pattern is made by comparing the lattice parameters and diffraction intensities of the particles and those of known iron compounds, and shows that the particles are Fe304. 

Fluorinated polyimide (PMDA/TFDB) and nonfluorinated polyimide (PMDA/DMDB) films prepared on a silicone substrate were introduced into an electron beam lithography system and subsequently exposed for square patterns (4x4 mm). The electron beam energy was 25 keV the beam current was 10 nA, and the beam dose was 300-1500 pC/cm. The 4x4 mm square was written by a 0.1-pm-wide electron beam. 

The structural anisotropy in crystalline or structurally ordered BPDA-PFMB films was studied in this laboratory with wide-angle X-ray diffraction (WAXD) methods. In brief, WAXD experiments were designed to examine both the reflection and transmission modes of thin-fihn samples. In addition, uniaxially oriented polyimide fiber WAXD patterns were obtained to aid in the identification of the film structure. The film WAXD pattern obtained from the reflection mode corresponded well to the fiber pattern scanned along the equatorial direction (Figure 16.3), " which indicates that the reflection mode pattern represents the (hkQ) diffractions. On the other hand, as shown in Figure 16.4, the (001) diffractions were predominant in the film WAXD pattern obtained via the transmission mode. This pattern corresponded to the fiber pattern scanned along the meridian direction. These experimental observations clearly indicate that the c-axes of the crystals are preferentially oriented parallel to the film surface however, within the film, they are randomly oriented. 4.2 5 j( should be pointed out that the WAXD experiments are only sensitive to crystalline or ordered structures in polyimide films. They do not provide any information on the amorphous regions. 

As a radical photoinitiator, we used 2-hydroxyisopropyl phenyl ketone (DAROCUR 1173 Ciba-Geigy), taken in an amount of 3 wt% based on polyimide (Scheme 5.13). The pattern of an exotherm obtained for the 1% solution of the polyimide (-X- = -O-), the high value of polymerisation enthalpy (352.4 J/g) and the short times of attaining the maximum peak (4.4 s) and the induction time (2.4 s) allow us to consider that this polyimide to be rather reactive from the point of view of polymerisation and formation of a crosslinked structure. 

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