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Laser Processing of Materials: A New Strategy Toward Materials Design and Fabrication for Electronic Packaging
October 12, 2010 |Estimated reading time: 22 minutes
Abstract
PurposeMaterial formulation, structuring and modification are key to increasing the unit volume complexity and density of next generation electronic packaging products. Laser processing is finding an increasing number of applications in the fabrication of these advanced microelectronic devices. The purpose of this paper is to discuss the development of new laser-processing capabilities involving the synthesis and optimization of materials for tunable device applications.
Design/Methodology/Approach The paper focuses on the application of laser processing to two specific material areas, namely thin films and nanocomposite films. The examples include BaTiO3-based thin films and BaTiO3 polymer-based nanocomposites.
Findings A variety of new regular and random 3D surface patterns are highlighted. A frequency-tripled Nd:YAG laser operating at a wavelength of 355 nm is used for the micromachining study. The micromachining is used to make various patterned surface morphologies. Depending on the laser fluence used, one can form a "wavy," random 3D structure, or an array of regular 3D patterns. Furthermore, the laser was used to generate freestanding nano and micro particles from thin film surfaces. In the case of BaTiO3 polymer-based nanocomposites, micromachining is used to generate arrays of variable-thickness capacitors. The resultant thickness of the capacitors depends on the number of laser pulses applied. Micromachining is also used to make long, deep, multiple channels in capacitance layers. When these channels are filled with metal, the spacings between two metallized channels acted as individual vertical capacitors, and parallel connection eventually produce vertical multilayer capacitors. For a given volume of capacitor material, theoretical capacitance calculations are made for variable channel widths and spacings. For comparison, calculations are also made for a "normal" capacitor, that is, a horizontal capacitor having a single pair of electrodes.
Research Limitations/Implications This technique can be used to prepare capacitors of various thicknesses from the same capacitance layer, and ultimately can produce variable capacitance density, or a library of capacitors. The process is also capable of making vertical 3D multilayer embedded capacitors from a single capacitance layer. The capacitance benefit of the vertical multilayer capacitors is more pronounced for thicker capacitance layers. The application of a laser processing approach can greatly enhance the utility and optimization of new materials and the devices formed from them.
Originality/ValueLaser micromaching technology is developed to fabricate several new structures. It is possible to synthesize nano and micro particles from thin film surfaces. Laser micromachining can produce a variety of random, as well as regular, 3D patterns. As the demand grows for complex multifunctional embedded components for advanced organic packaging, laser micromachining will continue to provide unique opportunities.
1. Introduction
Material formulation, structuring, and modification are key to increasing the unit volume complexity and density of next generation electronic products (Markovich et al., 2007). Laser processing is finding an increasing number of applications in the fabrication of these advanced microelectronic devices (Bustillo et al., 1998). This is due, in part, to the ability to achieve highly localized treatment of materials with a spatial resolution of tens of microns. In addition, the process is data driven, that is, patterns can be generated without the need for masking materials. Laser processing parameters, such as fluence and wavelength, can be adjusted to suit a specific application, for example, micromachining (ablation) or annealing. Laser micromachining has been used for years as a means of microvia formation for electrical interconnection in microelectronic devices (Das et al., 2008). This method can be utilized to generate other new structures in nanocomposite materials without altering the dielectric properties of the nanocomposites. Conversely, laser annealing improves particle contact, or sintering, or crystalinity of the thin film, resulting in variation of dielectric properties (Stassinopoulos et al., 2005). As such, laser annealing can be used to control crystallinity, phase content, morphology, and dielectric properties of materials. Laser annealing also heals defects, and thus is a good approach for the repair of passives (Tsgarakis et al., 2006).
Several laser machining methods have been reported for advanced packaging applications. For example, Capineri et al. (2000) describe a laser ablation process on polyvinylidene fluoride film that provides a 150mm separation between active elements with negligible effects on the uniformity of the pyroelectric response. Willis and Dreier (2009) reported the effect of laser micromachining of indium tin oxide (ITO) films on polymer substrates. Gottmann et al. (2008) used femtosecond laser micromachining for the fabrication of green integrated lasers. Xu et al. (2006) mentioned the controlled micromachining of 100-nm thick ITO thin films on a glass substrate with a vacuum-ultraviolet (157 nm) F2 laser. Fu et al. (2006) investigated the laser micromachining of sputtered diamond-like carbon films with different thicknesses. However, no reports on laser micromachining of sol-gel thin films have been found in the literature. Kwon et al. (2006) reported an effective method of fabricating micro and sub-micro patterned zinc oxide nanorods using a micro molding technique. Micro moulding of a sol-gel-derived precursor resulted in the selective growth of the nanorods. Ng et al. (2009) reported a direct laser writing approach to deposit micro-patterned metal onto polymer. Here, a metal source is first doped into the substrate in the form of ions and a continuous wave HeCd laser was used for the reduction of metal ions allowing fine resolution of feature size. Zou et al. (2008) and coworkers patterned nanocrystalline La0.7Sr0.3MnO3 thin films. They transferred sol-gel precursor solution into the microchannels of a mould and then the mould and substrate were dried together.
Subsequently, the mould was removed to get the pattern. All these patterned processes are very lengthy and require a lot of chemicals and process restrictions.
The present study describes a novel process that uses a computer-controlled laser system to create multiple structures. Specifically, the focus is on the development of new multiple structures that can be generated from the same materials and layers, leading to multifunctional materials.
Laser-materials interactions have been investigated for a variety of sol-gel thin films using a computer-controlled laser system. Several micromachining technologies have been reported to remove materials selectively from any desired surface. But, there are no studies showing the effect of micromachining at laser fluences below the ablation threshold, that is, the minimum energy per unit area required for ablation. Here, we show several interesting surface phenomenon that occur in this regime. A combinatorial approach has been applied to determine the fluence necessary for ablation, and applied the desired laser fluence to generate/synthesize a variety of surface structures.
In addition, micromachining technology has been used to design and develop new vertical multilayer embedded capacitors for high-speed applications. High-speed packages require capacitors with high values of capacitance. This is typically achieved using thick dielectrics. Calculations show that multilayer vertical capacitors can be better than thick planner capacitors formed from a single layer. Typically, multilayer-embedded capacitors are fabricated by repeated deposition of capacitance layers. This is a lengthy process. As an alternative, we have deposited a single, thick capacitancelayer, and subsequent laser micromachining has been used to form multiple parallel channels of a controlled depth. Metal deposition in the channels results in a multilayer embedded capacitor structure. In addition, the laser micromachining technology has been extended to produce both variablethickness and discrete capacitors from a single sheet (layer) of capacitor material, such that both types of structures can be integrated into the same layer. As far as we know, this is the first time laser processing has been used to fabricate a materials library.
2. Experimental procedure
BaTiO3 sol-gel thin films were prepared by mixing 0.5 molar aqueous acetate solution of Ba(CH3COO)2 and Ti(OC2H5)4. The film was deposited on Si or glass substrates by spin coating, and dried successively at 150 and 4508C to remove all the organics. The film was then annealed at ,600-7008C in air to generate a crystalline phase.
A variety of BaTiO3 nano particles and their dispersion into epoxy resin were investigated in order to achieve a thin uniform film. In a typical procedure, BaTiO3 epoxy nanocomposites were prepared by mixing appropriate amounts of the BaTiO3 nano powders and epoxy resin in organic solvents. A thin film of this nanocomposite was then deposited on a copper substrate and cured.
Laser micromachining was performed on an ESI (Electro Scientific Industries Inc., Portland, Oregon) 5330 Laser Microvia Drill System. A pulsed (q-switched) frequencytripled Nd:YAG laser operating at a wavelength of 355nm was used. The pulse width of the laser was on the order of 50 to 100 ns. The beam was positioned relative to the surface of the work piece by coordinated motion of the stage on which the sample is mounted (y-axis), the optics (x-axis), and galvo mirrors (x- and y-axes). The position of the sample with respect to the focal plane of the laser beam (along the z-axis) can also be adjusted. The user has the option of micromachining using a beam with a Gaussian energy profile, or the spatial distribution of energy in the circular laser spot can be homogenized by use of ESI-supplied optics.
Adjustable parameters are defined as follows:
. Repetition rate is the number of laser pulses delivered to the workpiece per unit time.
. Power is the average power of the laser.
. Z-Offset is the relative position of the imaged beam with respect to surface of the substrate; a negative number indicates that the beam is imaged below the surface.
. Velocity is the speed at which the beam is traced along the programmed beam path.
. Repetitions is the number of times the system traces the programmed beam path.
. Bite size is the distance the system moves the beam relative to the workpiece between pulses, along the programmed beam path.
A XeCl excimer laser (l ¼ 308 nm) has been used to improve the surface morphology of barium titanate sol-gel thin films. We have used laser-annealed crystalline barium titanate films generated by laser annealing the films at around 300 mJ/cm2.
Additional post-thermal annealing (,6008C in air) was used to generate crystalline phases in the laser-annealed spots. Sol-gel thin film was micromachined using a variety of conditions to form various surface morphologies and capacitor arrays. Surface morphology and particle distributions of nanocomposite films were characterized by a LEO 1550 scanning electron microscope (SEM). The micromachining depths of the films were determined by optical microscope and SEM.
3. Results and discussion
Combinatorial synthesis is an approach that enables the creation of large compositional range "integrated materials chips" containing thousands, possibly millions, of different compounds/materials (Xiang, 1999). Technologies, such as thin film deposition, lithography, and high-resolution imaging, have enabled and sustained the revolutionary progress in the information industry based on integrated circuit chips. These same technologies are now being applied to revolutionize research in materials. Since the application of combinatorial synthesis to inorganic thin-film materials by a group at the Lawrence Berkeley National Laboratory (Xiang et al., 1995; Briceno et al., 1995), several investigators have focused on improving their processing, properties (electrical impedance, optical, and magnetic), and screening techniques.
The intent in all these investigation was to obtain a composition gradient in order to optimize a set of desired localized properties. Figure 1 shows the array of laserprocessed, surface-modified 50mm features on a sol-gel ferroelectric thin film deposited on a Si-wafer and annealed at 7008C for 1 h. The data show a continuous change in surface morphology with increasing laser fluence from 0.849 to 4.244 J/cm2. Spots micro machined at or above 3.4 J/cm2 show ablation. Similarly, Figure 2 shows an optical/SEM photograph, top view, of laser micromachined nanocomposite-based capacitor arrays. Fully micromachined capacitors can be consistently generated by using varying numbers of laser pulses. Optical and SEM micrographs are shown in Figure 2 for a series of arrays machined using varying numbers of laser pulses. The depth of microfabricated capacitors varies from 4 to 70mm, depending on the number of laser pulses. The thickness of the capacitors (remaining dielectric thickness below micromachined area) decreases with an increasing number of laser pulses. It is clear from Figure 2 that as the depth of the micromachined area is increased (thickness of the remaining dielectric reduced), the corresponding capacitance increases. Thus, micromachining can generate capacitor libraries (arrays) with variable capacitance density. Tuning the surface morphology/ thickness with proper laser fluence allows the fabrication of new tunable 3D devices.Figure 1: Optical photograph of 4 £ 10 array of 50mm spots. Figure 2: Optical photograph and SEM micrographs (inset) of laser micromachined capacitor arrays.
Laser micromachining is important for generating highresolution patterns. In contrast to many patterning techniques, this approach does not necessarily require toxic chemicals. Figure 3 shows a simple micromachined pattern composed of letters, lines, and a square grid. The vertical lines were positioned on a 200-mm pitch (left side) and a 100- mm pitch (right side). The length and width of the squares in the grid was 200mm. Line widths in all cases were 50mm.Figure 3: Optical micrograph of micro fabricated complex structures.
The laser can be used to machine small gaps for micro devices. For instance, small planar energy storage devices can be machined for remote sensors in security or defense applications.
The topography of the sol-gel thin film surfaces was examined by performing SEM, and optical imaging. Figure 4 shows different surface morphologies generated by variation of laser fluence. Laser processing of the as-deposited thin film leads to a noticeable conversion from a smooth surface to wavy cavity structure, as can be seen in the SEM and optical images (Figure 4(a)-(c)). This is apparently due to local melting of the top surface induced by the transient laser heating. Similar melting behaviour has been observed in pulsed laser deposition of ZnO films upon laser annealing at 193nm (Ozerov et al., 2004). The annealing substantially reduces the surface grain structure and generates a new porous channel-like network reminiscent of a labyrinth structure. Each channel has an average width of about 2-5mm and depth of about 0.1-0.5mm.Figure 4: SEM micrographs and optical photographs of laser micromachined sol-gel thin films.It is interesting to note that all the laser-annealed/ micromachined spots, irrespective of their location on the film (center or periphery), maintain almost the same kind of channel structure. Moreover, it can be created in selective locations. This kind of structure was shown to be critical for achieving laser-like action upon optical pumping as it favours efficient coupling of the pump light into the film material (Stassinopoulos et al., 2005).
Sufficiently strong laser pulses induce local melting and rapid cooling, leading to formation of an amorphous particle. Laser irradiation can be used to raise the temperature of the film above the crystallization temperature, but below the melting temperature, thus converting an amorphous region to a crystalline phase. Figure 4(d)-(f) shows typical examples of melting and solidification of particles. SEM clearly indicates free standing nano particles (Figure 4(f)). Some areas of the micrographs also exhibit individual micro-particles. Nano particles react with each other to produce highly agglomerated micro particles. Ablation was observed at very high-energy densities. Free standing ferroelectric nano particles are important for non-volatile random access memory (Aucillo et al., 1998). Several groups are developing selective growth of free standing ferroelectric particles. For example, Clemens and Schneller (2005) reported template-based top-down and bottom-up approaches to generate free standing nano structures. These processes require multiple chemical and photo process. In our study, laser micromachining was simply used for selective growth of free standing nano particles. Excess laser energy favours ablation. It can be seen that, at high laser energy, the film is ablated and the underlying silicon surface exposed (Figure 4(g) and (h)). With a gradual increase in energy, but still at high enough fluence values, the film will melt and subsequently decompose to gaseous components. Gas bubbles are formed under the surface as seen in the Figure 4(h). The gas bubble formation inside the film is attributed to the formation of gaseous components.
Moreover, an improved laser technique was developed to control the surface morphology and regular 3D patterning of sol-gel thin films. Surface morphological changes were monitored using optical microscopy. Figure 5 shows different surface morphologies, generated by variation of laser fluence, on laser-annealed sol-gel barium titanate thin film. Sufficiently strong laser pulses induce local melting and rapid cooling, leading to formation of 3D structures. Laser irradiation can be used to raise the temperature of the film above the melting temperature, but below the decomposition temperature, thus generating a 3D pattern. Ablation was observed at higher energy densities. With a gradual decrease in energy, but still at high enough fluence values, the central part of the area traced by the laser beam path completely melts, whereas the adjacent surrounding area appears to be a partially melted patterned surface. Figure 5(a) and (b) shows a variety of spiral patterns generated at a laser-annealed surface. Figure 5(b), spot 2, shows a laser ablated spiral pattern obtained at a fluence of 1.69 J/cm2, beam velocity of 100 mm/s, pulse repetition rate of 30 kHz, four repetitions, and radial pitch (distance between adjacent traces within the spiral) of 462.5mm. The laser selectively removed (ablated) film and generated a spiral pattern. Decreasing the radial pitch to 4.62mmat 30 kHz pulse repetition rate resulted in complete removal of the film (spot 1).Figure 5: Laser micromachining (regular 3D pattern) on laser-thermal and thermally annealed film deposited on Si-substrate.At lower fluence (0.679 J/cm2), with a radial pitch of 4.62mm, the film interacts with the laser, but the pattern was not uniform (spot 3). At this low fluence with higher radial pitch (46.25mm), a uniform 3D spiral pattern results (spot 4). These patterns are interacting with the visible light and show significantly different localized colour than the bulk film. The effect of laser fluence on laser-thermal annealed and thermally annealed surfaces was also investigated. Figure 5(c) and (d) shows 3D patterns on laser-thermal annealed and thermally annealed surface, respectively. Rastering at low laser fluence (0.679 J/cm2) with a 50mm spot size can generate a more uniformpattern at the laser-thermally annealed surface than on the thermally annealed surface.
BaTiO3-epoxy nanocomposites were used to fabricate vertical multilayer embedded capacitors. High temperature/ pressure lamination was used to embed capacitor dielectrics in multilayer printed circuit boards. The capacitor fabrication was based on a sequential build-up technology. First, channels were micromachined into the embedded capacitor material. After patterning of the channel, a conducting material (e.g. Cu, Ag, or Au) can be deposited within the channel. Conducting materials can be directly deposited either by sputtering or plating processes. BaTiO3-epoxy nanocomposite thin films with vertical multilayer embedded capacitors were used as the base substrate for subsequent build-up processing. Figure 6 shows a schematic process flow for making multilayer vertical embedded capacitors from a capacitor base substrate. The embedded capacitor can also act as a sub-composite and can be laminated with other sub-composites for making high layer count boards with embedded capacitors. Capacitance values are defined by the feature size, spacing, and dielectric constant of the polymer-ceramic compositions.
Figure 6: Processing of multilayer embedded capacitors (top and side view).Figure 7 shows top views of laser micromachined channels for vertical multilayer embedded capacitors. It is possible to make a wide variety of channels with different spacings. The spacing between two channels determines the capacitor thickness, and therefore, affects the capacitance value. For a given channel depth and dielectric constant, the smaller the spacing, the higher the capacitance. The desired spacing between two channels can be achieved by controlling the laser micromachining parameters. In the present process, spacings from about 5mm to about 50mm have been demonstrated.Figure 7: Optical (a-b) photographs and SEM (c-g) micrographs of laser micromachined channels for vertical multilayer embedded capacitors.Figure 7 shows a variety of samples with average spacing of 5, 10 and 25mm, as typical representative examples. It is also possible to control the channel width by controlling the laser beam width. Channel widths of 10-35mm are demonstrated here. Individual multilayer embedded capacitors are shown in Figure 7(a). The image of a 5-mm spacing is shown in top view in Figure 7(b). Laser micromachining can produce very small, in the range of 500-mm long, multilayer embedded capacitors, and it is possible to integrate these very close to the required circuits to reduce overall inductance.
As the spacing between the micromachined channels is decreased, the corresponding capacitance increases. In other words, micromachining can generate multilayer capacitors with variable capacitance density. Epoxy/BaTiO3 nanocomposite layers with dielectric constants around 30 have been fabricated. For a given volume of capacitor material, a theoretical capacitance calculation was made considering variable channel widths and spacings. For comparison, calculations were also made for a "normal" capacitor, that is, a horizontal capacitor having a single pair of electrodes. Table I shows capacitance (nF) calculations for a series of vertical 3D multilayer capacitors assuming a dielectric constant of 30, and a capacitor area of 1 in.2 for various capacitor thicknesses. Actual measurement of capacitance values for these variable spacing capacitor structures has not been performed. Decreasing the spacing and channel width can accommodate more capacitors per unit volume and results in a higher total capacitance within that volume. In this regard, calculations show that vertical 3D capacitors are better than normal thick capacitance layers.
For example, the capacitance of a 100-mm thick normal capacitor is 1.68 nF (total volume of 0.004 in.3 of capacitor material), whereas a 100-mm thick vertical 3D capacitor with 25-mm space and 25-mm wide channel results in a capacitance within the same volume of 13.48 nF, double that of the 25-mm thick normal parallel plate capacitor (6.74 nF). The benefit of the vertical multilayer capacitors is more pronounced for the thicker capacitance layers.
4. Conclusions
Initial demonstrations have shown the applicability of laser processing approaches to sol-gel thin films and nanocomposite films. This provides a powerful tool for both the synthesis of new materials and optimization of existing materials for tunable device applications. Laser micromaching technology was developed to fabricate several new structures. It is possible to synthesize nano and micro particles from thin film surfaces. Laser micromachining can produce a variety of random, as well as regular, 3D patterns. Laser micromachining performs better at laserthermal annealed surfaces than on surfaces that have only been thermally annealed.
This technique can be used to prepare capacitors of various thicknesses from the same capacitance layer, and ultimately can produce variable capacitance density, or a library of capacitors. The process is also capable of making vertical 3D multilayer embedded capacitors from a single capacitance layer. Vertical multilayer capacitors are particularly beneficial for thicker capacitor layers, as they could be used in high-speed applications where the thickness of the dielectric material in which the capacitors are embedded is, in general, greater.
As the demand grows for complex multifunctional embedded components for advanced organic packaging, laser micromachining will continue to provide unique opportunities. The strategy presented here may be extendedto other materials suitable for microelectronics packaging.
References
1. Aucillo, O., Scott, J.F. and Ramesh, R. (1998), "The physics of ferroelectric memories", Physics Today, Vol. 51 No. 7, pp. 22-7.2. Briceno,G.,Chang, H., Sun, X., Schultz, P.G. and Xiang, X.-D. (1995), "A class of cobalt oxide magnetoresistance materials discovered with combinatorial synthesis", Science, Vol. 270, pp. 273-5.3. Bustillo, J.M.,, Howe, R.T. and Muller, R.S. (1998), "Surface micromachining for microelectromechanical systems", Proc. IEEE, Vol. 86, pp. 1552-74.4. Capineri, L., Masotti, L., Mazzinghi, P. and Mazzoni, M. (2000), "Fabrication of pyroelectric PVDF linear arrays for diagnostic systems of high power CO2 laser beams", Proc. 5th Italian Conf. Sensors and Microsystems, pp. 411-15.5. Clemens, S. and Schneller, T. (2005), "Registered deposition nanoscale ferroelectric grains by template-controlled growth", Advanced Materials, Vol. 17, pp. 1357-61.6. Das, R.N., Egitto, F.D. and Markovich, V.R. (2008), "Nanoand micro-filled conducting adhesives for Z-axis interconnections: new direction for high-density, highspeed, organic microelectronics packaging", Circuit World, Vol. 34 No. 1, pp. 3-12.7. Fu, Y.Q., Luo, J.K., Flewitt, A.J., Ong, S.E., Zhang, S. and Milne, W.I. (2006), "Laser micromachining of sputtered DLC films", Applied Surface Science, Vol. 252, pp. 4914-18.8. Gottmann, J., Moiseev, L., Vasilief, I. and Wortmann, D. (2008), "Manufacturing of Er:ZBLAN ridge waveguides by pulsed laser deposition and ultrafast laser micromachining for green integrated lasers", Materials Science and Engineering B, Vol. 146, pp. 245-51.9. Kwon, S.J., Park, J.H. and Park, J.G. (2006), "Selective growth of ZnO nanorods by patterning of sol-gel-derived thin film", J. Electroceramics, Vol. 17 Nos 2-4, pp. 455-9.10. Markovich,V.R.,Egitto,F.D., Chan,B., Lauffer, J. andDas,R.N. (2007), "Anelectronic packaging roadmap", paper presented at the International Conference and Exhibition on Device Packaging, Scottsdale, AZ,March 19-22.11. Ng, J.H.-G.,Desmulliez,M.P.Y., Lamponi,M.andMoffat,B.G. (2009), "A direct-writing approach to the micro-patterning of copper onto polyimide", CircuitWorld, Vol. 35 No. 2, pp. 3-17.12. Ozerov, I., Arab, M., Safarov, V.I., Marine, W., Giorgio, S., Sentis, M. and Nanai, L. (2004), "Enhancement of exciton emission from ZnO nanocrystalline films by pulsed laser annealing", Appl. Surf. Sci., Vol. 226, p. 242.13. Stassinopoulos,A., Das,R.N., Giannelis, E.P.,Anastasiadis, S.H. and Anglos, D. (2005), "Random lasing fromsurface modified ZnO films of ZnO nanoparticles", Applied Surface Science, Vol. 247, pp. 18-24.14. Tsgarakis, E.D., Law, C., Thompson, M. and Giannelis, E.P. (2006), "Nanocrystalline barium titanate films on flexible plastic substrate", Applied Physics Letters, Vol. 89 No. 20, pp. 202910-13.15. Willis, D.A. and Dreier, A.L. (2009), "Laser micromachining of indium tin oxide films on polymer substrates by laserinduced delamination", J. Phys. D: Appl. Phys., Vol. 42, p. 8, 045306.16. Xiang, X.-D. (1999), "Combinatorial materials synthesis and screening: an integrated materials chip approach to discovery and optimization of functional materials", Annual Review of Materials Science, Vol. 29, pp. 149-71.17. Xiang, X.-D., Sun, X., Briceno, G., Lou, Y., Wang, K., Chang, H., Wallace-Freedman, W.G., Chen, S. and Schultz, P.G. (1995), "A combinatorial approach to materials discovery", Science, Vol. 268, pp. 1738-40.18. Xu, M.Y., Li, J., Lilge, L.D. and Herman, P.R. (2006), "F2-laser patterning of indium tin oxide (ITO) thin film on glass substrate", Appl. Phys. A, Vol. 85, pp. 7-10. 19. Zou, G., You, X. and He, P. (2008), "Patterning of nanocrystalline La0.7Sr0.3MnO3 thin films prepared by sol-gel process combined with soft lithography", Materials Letters, Vol. 62, pp. 1785-8.
About the authors
Rabindra N. Das is a Scientist at Endicott Interconnect Technologies. Prior to this, he was working as a Visiting Scientist in the Materials Science and Engineering Department at Cornell University. He holds an MS and a PhD in Chemistry from the Indian Institute of Technology, Kharagpur. His research work focuses in the area of nanotechnology and he has over 12-years experience in this area. He has developed number of advanced nanomaterials for applications ranging from interconnects to laser to embed passives. He has around 65 nano-based technical papers and several issued/filed patents. Rabindra N. Das is the corresponding author and can be contacted at: rabindra. das@eitny.com
Frank D. Egitto is Manager of Specialty Product Development at Endicott Interconnect Technologies, Inc. He holds BA and MA degrees in Physics from Binghamton University. He has 32 years of experience working in the electronics industry. Previously, he was a Senior Engineer for IBM Corporation in the design, process, materials, and assembly development group for organic laminate products. Earlier positions included development of plasma equipment and processes at Texas Instruments Inc. in Dallas, Texas, and Applied Materials Inc. in Santa Clara, California. He is co-author of six book chapters and over 50 technical papers, and holds 67 US patents. His areas of expertise include plasma interactions with materials, laser ablation, modification of polymers with ultraviolet radiation and advanced packaging. Voya R. Markovich is Senior VP and Chief Technology Officer at Endicott Interconnect Technologies. He was previously IBM Senior Technical Staff Member and Senior Manager of the WW materials, processes and assembly development group for organic laminate products. He was elected to the IBM Academy of Technology in 1997, and holds 212 US patents. His areas of current active interest are in the development of new processes and materials for integrated actives, passives, optical and RF for advanced systems integrated electronic packaging. He received his MS in Chemistry from The Polytechnic Institute of New York, 1980.