Dicing Technique Research Articles

466 mW green light generation using annealed proton-exchanged periodically poled MgO: LiNbO_3 ridge waveguides

We report high-power efficient green light generation by frequency doubling from a periodically poled MgO doped LiNbO(3) ridge waveguide. The ridge waveguide is fabricated by the annealed proton-exchanging and precise diamond blade dicing techniques. The ridge structure exhibits a surface roughness of only 3.7 nm, and near-90° vertical sidewall. The total insertion loss of an 8.5 µm wide and 1.4 cm long uncoated waveguide is 3.0 dB under direct fiber coupling. 466 mW of continuous-wave green light with an optical-to-optical conversion efficiency of 69.7% is obtained. To the best of our knowledge, this is the highest green light output power reached to date using a ridge-type LiNbO(3) waveguide device. Phase-matching temperature shift, tuning curve distortion, and waveguide loss increase are observed under high power operation. Our analysis shows that the photorefractive effect and the green induced infrared absorption are responsible for the observed phenomena, which becomes prominent under several megawatt per square centimeter power density.

Extremely High Tunability of Low Dielectric Constant 1‐3 Type (Ba,Sr)TiO3/Resin Epoxy

A 1‐3 type (Ba,Sr)TiO3 (BST)/resin epoxy composites were prepared by dice and fill technique. The microstructure, dielectric, and tunable properties of columnar composites were investigated. An important feature of 1‐3 type composites is that the dc field is efficiently applied to the high‐permittivity ferroelectric phase. With the increase of resin epoxy content, the tunability of the composite remains nearly unchanged while the permittivity decreases much. The coefficient of dielectric nonlinearity β increases sharply with the increase of resin epoxy volume and β increases up to 2.8 × 1012 when the resin epoxy volume is 90%. These properties make 1‐3 type composites very promising for potential tunable device applications.

Dielectric Properties of 2–2 PMN-PT/Cement Composites

Dielectric properties of 2–2 connectivity lead magnesium niobate-lead titanate (PMN-PT)/Cement composites were investigated at 0.1–20 kHz. PMN-PT of 60–80% by volume was used. The composites were fabricated using a dice and fill technique and cured in 98%RH curing chamber for 7 days before measurements. Dielectric constant (ϵr) at 1 kHz increased with PMN-PT volume, having values of 1504, 1645 and 2390 respectively. Dielectric loss (tanδ) values are 0.382, 0.185 and 0.188 at 1 kHz. In addition, the dielectric constant was found to decrease with an increase in the frequency tested having value of 1692, 1504 and 1322 for 0.1, 1 and 20 kHz respectively. The dielectric loss was found to be less with increasing frequency at 0.702, 0.382 and 0.179 for 0.1, 1 and 20 kHz respectively.

Optimization of UV laser scribing process for light emitting diode sapphire wafers

Billions of light emitting diodes (LEDs) are used today in traffic control, automotive headlights, flat panel display technology, mobile devices, back lighting, projection, and general illumination applications. With the dramatic growth in LEDs, manufacturers are looking for technologies to increase production yield and decrease cost. Sapphire wafer singulation into miniature dies is one of the critical steps used in blue LED manufacturing. Typical dicing techniques used in wafer singulation process include laser dicing, laser scribing and breaking, mechanical scribing and breaking, and diamond blade sawing. In recent years, laser scribing and breaking has proven to be very efficient for volume LED manufacturing. In this paper, we have characterized the effect of 355 nm Q-switched diode-pumped solid-state (DPSS) laser parameters such as fluence, pulse width, and repetition rate on laser scribing process by measuring sapphire wafer cutting depth and scribe kerf width. Furthermore, we have also explored the techniques to increase process efficiency while maintaining quality of scribes using different laser sources.

Experimental Research on UV Laser and High-Pressure Water-Assisted YAG Laser Dicing SiC Wafer

In this paper, the comparative experimental research on DPSS UV laser (wavelength is 355nm) and high-pressure water-assisted YAG laser dicing SiC wafer was done. The results show that is strict with the performance of laser source and the dicing technique parameters in UV laser dicing the SiC wafer, and the dicing surface of good quality can be obtained only when the parameters of laser source and dicing technology vary in a narrow range. Contrarily, the SiC wafer dicing technology using high-pressure water-assisted YAG laser has a perfect flexibility with the laser source and dicing apparatus, and the good dicing surface can be obtained even if the process parameters vary in a wide range.

Dielectric tunability of Ba0.6Sr0.4TiO3/poly(methyl methocrylate) composites in 1-3-type structure

The Ba0.6Sr0.4TiO3 (BST)/poly(methyl methacrylate) (PMMA) tunable composites in 1-3-type structure consisting of BST rods in low-permittivity PMMA matrix are fabricated by dice and fill technique. For the composite containing 41.6vol% BST, the permittivity and the loss tangent of the composite are 1212 and 0.026 at 10kHz, respectively, while the dielectric tunability is about 36% under the 16kV∕cm dc bias flied. The theoretical tunability and permittivity are in agreement with the experimental data. The 1-3-type BST/PMMA composites can meet the device requirement for tunable dielectrics with high dielectric tunability and low permittivity.

Fabrication of micro-mold for glass embossing using focused ion beam, femto-second laser, eximer laser and dicing techniques

Abstract Various nano-/micro-structuring methods, including focused ion beam (FIB), femto-second laser, KrF eximer laser and dicing techniques, were used to fabricate glassy carbon (GC) micro-molds and were characterized in terms of the process rate, the roughness and the shape of machined structure. The combination of femto-second laser ablation with subsequent FIB milling provided a possibility for the rapid fabrication of high quality micro-structures on a wide surface area. Obtained molds were applied to the hot-emboss process of glasses to investigate process conditions needed for the replication of structures with various geometries and dimensions.

Microstructuring of glassy carbon mold for glass embossing – Comparison of focused ion beam, nano/femtosecond-pulsed laser and mechanical machining

Various methods, including focused ion beam (FIB), femto-second laser, KrF eximer laser and dicing techniques, were employed for preparing glassy carbon (GC) micro-molds, and those methods were characterized in terms of the process rate, the roughness and the shape of machined structure. FIB milling using a repetitive pass method produced nano/microstructures with flat channel bottom and nearly vertical sidewalls. Although FIB milling was slowest process, it provided the best quality of machined surface ( R a = 4–30 nm depended on milled depth). Femtosecond-pulsed laser machining also allowed fabricating flat bottom and nearly vertical sidewalls on an area of 1.2 × 1.2 mm 2 at a scanning speed of 20 mm/s, but lead to an increase of the surface roughness ( R a = 80 nm). Femto-second laser in combination with FIB milling provided a possibility for the rapid fabrication of high quality microstructures on wide surface area. The roughness of machined surface decreased to 45 nm by the subsequent FIB milling. Microstructuring with a nanosecond-pulsed KrF eximer laser at an irradiation wavelength of 248 nm with a fluence of 13.2 J/cm 2 also allowed the fast fabrication of master structure for micro-gear, resulted in slanted sidewalls and not ideally flat bottoms. The surface roughness ( R a) of the bottom and the side wall was about 45 and 70 nm, respectively. Dicing technique allowed machining micro-channels with a rectangular and pyramidal cross-section on an area of 15 × 15 mm 2 under the feed speed of 50 mm/min. By reducing the feeding speed from 100 mm/min to 50 mm/min, surface roughness ( R a) of the structure side wall decreased from 150 nm to 70 nm. Achieved glassy carbon molds were then applied to the hot-emboss process of Pyrex and quartz glasses to investigate embossing conditions (emboss temperature, pressure and hold time) needed for the replication of Pyrex and quartz glass structures with various geometries and dimensions in glass plates with thickness of 1 mm. Replication results showed good replication at the nanoscale, resulted in the almost the same dimensions and surface roughness with that of cavities. Thicker plate provided faster filling in the emboss process of glass.

Time-Resolving Image Analysis of Drilling of Thin Silicon Substrates with Femtosecond Laser Ablation

We have analyzed a drilling process with a femtosecond laser on a silicon surface in order to investigate the degree of the thermal effect during the dicing of a very thin silicon substrate (thickness: 50 µm). A femtosecond laser pulse (E=30–500 µJ/pulse, τ=200 fs, λ=780 nm, f=10 Hz) was focused on a thin silicon substrate using a lens with a focal length of 100 mm. An image-intensified charge-coupled device (CCD) camera with a high-speed gate of 200 ps was utilized to take images of a drilled hole during the drilling process. As a result, it was found that the smaller the pulse energy, the faster the formation of the hole. Therefore, we tried to estimate the degree of the thermal effect semi quantitatively by analyzing the rise time of the formation of the hole. By measuring the rise time in 8 kinds of metallic material, it was found that the rise time strongly correlates with the thermal conductivity in these materials. This knowledge is thought to be very important and useful for developing a dicing technique for thin silicon wafers using a femtosecond laser.

Development of dicing technique for thin semiconductor substrate using temporally shaped femtosecond laser

AbstractRecently, semiconductor substrates for integrated circuits (ICs) have been required to be as thin as 50 µm, because many electronic devices must be miniaturized and light in weight. Machining of such thin substrates with conventional dicing techniques is very difficult. Therefore, we have proposed processing them using femtosecond laser ablation. In this work, we investigate the influence of conditions of a double pulsed laser such as the delay time and fluence on the depth and diameter in order to develop a new dicing technique for very thin ICs. A double pulsed laser (λ = 780 nm, τ = 150 fs, f = 10 Hz, Δt = 0 to 100 ps, E1 + E2 = 100 µJ) was focused on the Si substrate with a plano‐convex lens having a nominal focal length of 100 mm. At a delay time of 10 ps, singularly shallow and flat‐bottomed holes were obtained. When the substrates were diced under these conditions, the bottom of the processing groove was flat and very smooth, whereas many microcracks starting from the bottom of the groove formed by the conventional method have been observed. From these results, we were able to identify femtosecond laser processing conditions that were applicable to dicing of thin Si substrates. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(3): 43–48, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20028

Two dimensional arrays for real time 3D intravascular ultrasound.

We have previously described 2D arrays operating at up to 10.0 MHz consisting of several thousand elements for transthoracic cardiac imaging and over a hundred elements for intracardiac imaging using 7 Fr to 12 Fr catheters. We have begun to explore forward viewing real time 3D phased array intravascular ultrasound, which may require imaging depths of a few centimeters to look down the axis of a vessel to view vulnerable atherosclerotic plaque. We used a noncoaxial based cable technology that allowed 100 signal wires to be placed inside a4.8 French IVUS lumen with an inner diameter of 1.3 mm. We pursued two different fabrication technologies for the building of the transducers. Each transducer was constructed in the forward viewing configuration to allow simultaneous real time B-scans, C-scans and volumetric rendering of vessels and vascular stents distal to the catheter tip. In order to obtain the desired penetration depth, each transducer was constructed to operate at 10.0 MHz. The first method included an ordered array of 11 x 11 = 121 elements. In order to conform to the round aperture of the IVUS lumen, the comers were cut off, resulting in a total of 97 signal channels. Real time images include a 4 mm diameter vessel in a tissue mimicking phantom, an expanded stent and a stent in an excised sheep aorta. The second method is based upon a laser dicing technique that cuts the individual elements in a random pattern. This resulted in 61 signal channels. Real time 3D images of the AIUM test object were made with this transducer.

Dicing Process for Thin Silicon Wafer by Using Femtosecond-laser

Thin semiconductor wafer is more required for portable devices due to its mechanical flexibility or space gain. In dicing process for this thin wafer, suppression of micro-cracks is indispensable, which result in starting point of substrate breakage. In this research, laser cutting was performed for thin silicon wafer as a new dicing technique to conventional diamond blade dicing. Nano-, pico- and femtosecond laser were used to cut substrates in order to investigate the dependence of the flexural strength on the pulse width and the irradiated laser energy. As a result of that, the average strength of the diced wafer with the femtosecond laser was about three times larger than that with the nanosecond laser. In the case using the femtosecond laser, moreover, the minimum strength was about three times as large as that of the conventional blade dicer.

Sealing of adhesive bonded devices on wafer level

Abstract In this paper, we present a low temperature wafer-level encapsulation technique to hermetically seal adhesive bonded microsystem structures by cladding the adhesive with an additional diffusion barrier. Two wafers containing cavities for MEMS devices were bonded together using benzocyclobutene (BCB). The devices were sealed by a combined dicing and self-aligning etching technique and by finally coating the structures with evaporated gold or PECVD silicon nitride. The sealing layer was inspected visually by SEM and helium leak tests were carried out. Devices sealed with silicon nitride and with known damage of the sealing layer showed a helium leak rate of about 7–14 times higher than the background level. Devices of the same size without damage in the sealing layer had a leak rate of only 1.5 times higher than the background level. Experiments with evaporated gold as cladding layer revealed leaking cracks in the film even up to a gold thickness of 5 μm. The sealing technique with silicon nitride shows a significant improvement of the hermeticity properties of adhesive bonded cavities, making this bonding technique suitable for applications with certain demands on gas-tightness.

時間波形制御したフェムト秒レーザによる<br>極薄半導体基板のダイシング技術の開発

Recently, the semiconductor substrates for integrated circuits (ICs) have been required to become as thin as 50 mm, because the many electronic devices are strongly demanded to be miniaturized and light-weighted. Machining of such thin substrates with conventional dicing techniques is very difficult. Therefore, we have proposed to process them using femtosecond laser ablation. In this work, we have investigated the influence of conditions of doubled pulse laser such as delay time and fluence on the depth and diameter in order to develop a new dicing technique for very thin ICs. Double pulse laser ( λ = 780 nm, τ = 150 fs, ƒ = 10 Hz, Δt = 0 ∼ 100 ps, E1+E2 = 100 μJ ) was focused on the Si substrate with a plano-convex lens with a nominal focal length of 100 mm. In the case of the delay time of 10 ps, the singularly shallow and flat-bottomed holes was obtained. When the substrates have been diced on this condition, the bottom of the processing groove was flat and very smooth, whereas many microcracks started from the bottom of the groove formed by conventional method have been observed. From these results, we were able to find out the some processing conditions using femtosecond laser applicable dicing of thin Si substrate.

Caterpillar-type piezoelectric d33 bimorph transducer

A piezoelectric bimorph transducer utilizing piezoelectric d33 coefficient was developed. This bimorph consists of piezoelectric segments bonded by a polymeric agent and was fabricated by a dicing and layering technique. The transducer has superior piezoelectric characteristics compared to standard piezoelectric d31 bimorphs. Piezoelectric coefficients, electrical admittance, mechanical compliance, and losses of the actuator were found to increase with increasing driving electric field.

A hybrid wafer-dicing process for GaAs MMIC production

A dicing process for GaAs MMIC (monolithic microwave integrated circuit) wafers using spin-on wax for wafer mounting and a hybrid process of wet chemical etching/mechanical sawing for chip dicing is described. This process minimizes ragged chip edges and reduces generation of microcracks in addition to the elimination of the plated gold burrs on the backside of the diced MMIC chips. This process gives a uniformity of -3 mu m across a 2-in wafer following the completion of the whole backside process. This GaAs chip dicing technique is amenable to production because it exhibits both a very high chip yield (>90%) and nearly flawless edges.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>