Experimental validation of model for pulsed laser-induced subsurface modifications in Si

Wafers are traditionally diced with diamond saw blades. Saw dicing technology has a number of limitations, especially concerning the dicing of thin wafers. Moreover, the use of fluids and the gen-eration of debris can damage fragile components such as micro electro-mechanical systems. Laser ablation dicing is better suited for thin wafers, but is also not a clean process. An alternative dicing method is subsurface laser dicing. This technology is based on the production of laser-induced sub-surface modifications inside the wafer. These modifications weaken the material, such that the wafer separates along the planes with laser modifications when applying an external force. To find the right laser conditions to produce subsurface modifications in silicon, and to enhance the understand-ing of the underlying physics, a numerical model has previously been developed. To validate this model, the current work compares simulation results with experimental data obtained by focusing nano- and picosecond pulses inside silicon wafers. A fairly good agreement between experimental and numerical results was obtaine

Crystal structure of laser-induced subsurface modifications in Si

Laser-induced subsurface modification of dielectric materials is a well-known technology. Applications include the production of optical components and selective etching. In addition to dielectric materials, the subsurface modification technology can be applied to silicon, by employing near to mid-infrared radiation. An application of subsurface modifications in silicon is laser-induced subsurface separation, which is a method to separate wafers into individual dies. Other applications for which proofs of concept exist are the formation of waveguides and resistivity tuning. However, limited knowledge is available about the crystal structure of subsurface modifications in silicon. In this work, we investigate the geometry and crystal structure of laser-induced subsurface modifications in monocrystalline silicon wafers. In addition to the generation of lattice defects, we found that transformations to amorphous silicon and Si-iii/Si-xii occur as a result of the laser irradiatio

Toekomst Veenweide : klimaatadaptatie & maaivelddaling methode en toepassing in Midden-Delfland. Werkboek

Het Werkboek geeft een generiek stappenplan voor het identificeren van opgaven, maatregelen en strategieën voor polders. Er wordt hiertoe aanvullende informatie, een checklist en achtergronden aangereikt. Het project ‘Toekomst Veenweide’ is gericht op polders uit het Landschaps Ontwikkelingsperspectief (LOP) Midden-Delfland. De meeste polders hebben een landelijk karakte

Two-temperature model for pulsed-laser-induced subsurface modifications in Si

We investigated the laser-material interaction during the production of laser-induced subsurface modifications in silicon with a numerical model. Such modifications are of interest for subsurface wafer dicing. To predict the shape of these modifications, a two-temperature model and an optical model were combined. We compared the model results with experimental data obtained by focusing laser pulses in the bulk of silicon wafers using a microscope objective. This comparison revealed a good agreement between the simulations and the experimental results. A parameter study was performed to investigate the effect of the laser wavelength, pulse duration and pulse energy on the formation of subsurface modifications. We found that both single- and multi-photon absorption may be used to produce subsurface modifications in silicon. © 2013 Springer-Verlag Berlin Heidelberg

Two-photon–induced internal modification of silicon by erbium-doped fiber laser

Three-dimensional bulk modification of dielectric materials by multiphoton absorption of laser pulses is a well-established technology. The use of multiphoton absorption to machine bulk silicon has been investigated by a number of authors using femtosecond laser sources. However, no modifications confined in bulk silicon, induced by multiphoton absorption, have been reported so far. Based on results from numerical simulations, we employed an erbium-doped fiber laser operating at a relatively long pulse duration of 3.5 nanoseconds and a wavelength of 1549 nm for this process. We found that these laser parameters are suitable to produce modifications at various depths inside crystalline silico

Two-temperature model for pulsed-laser-induced subsurface modifications in Si

We investigated the laser–material interaction during the production of laser-induced subsurface modifications in silicon with a numerical model. Such modifications are of interest for subsurface wafer dicing. To predict the shape of these modifications, a two-temperature model and an optical model were combined. We compared the model results with experimental data obtained by focusing laser pulses in the bulk of silicon wafers using a microscope objective. This comparison revealed a good agreement between the simulations and the experimental results. A parameter study was performed to investigate the effect of the laser wavelength, pulse duration and pulse energy on the formation of subsurface modifications. We found that both single- and multi-photon absorption may be used to produce subsurface modifications in silico

Cost-effectiveness of nutritional intervention in elderly subjects after hip fracture: A randomized controlled trial

Hip fracture patients can benefit from nutritional supplementation during their recovery. Up to now, cost-effectiveness evaluation of nutritional intervention in these patients has not been performed. Costs of nutritional intervention are relatively low as compared with medical costs. Cost-effectiveness evaluation shows that nutritional intervention is likely to be cost-effective. Previous research on the effect of nutritional intervention on clinical outcome in hip fracture patients yielded contradictory results. Cost-effectiveness of nutritional intervention in these patients remains unknown. The aim of this study was to evaluate cost-effectiveness of nutritional intervention in elderly subjects after hip fracture from a societal perspective. Open-label, multi-centre randomized controlled trial investigating cost-effectiveness of intensive nutritional intervention comprising regular dietetic counseling and oral nutritional supplementation for 3 months postoperatively. Patients allocated to the control group received care as usual. Costs, weight and quality of life were measured at baseline and at 3 and 6 months postoperatively. Incremental cost-effectiveness ratios (ICERs) were calculated for weight at 3 months and quality adjusted life years (QALYs) at 6 months postoperatively. Of 152 patients enrolled, 73 were randomized to the intervention group and 79 to the control group. Mean costs of the nutritional intervention was 613 Euro. Total costs and subcategories of costs were not significantly different between both groups. Based on bootstrapping of ICERs, the nutritional intervention was likely to be cost-effective for weight as outcome over the 3-month intervention period, regardless of nutritional status at baseline. With QALYs as outcome, the probability for the nutritional intervention being cost-effective was relatively low, except in subjects aged below 75 years. Intensive nutritional intervention in elderly hip fracture patients is likely to be cost-effective for weight but not for QALYs. Future cost-effectiveness studies should incorporate outcome measures appropriate for elderly patients, such as functional limitations and other relevant outcome parameters for elderly

Toekomst Veenweide : klimaatadaptatie & maaivelddaling methode en toepassing in Midden-Delfland. Werkboek

Het Werkboek geeft een generiek stappenplan voor het identificeren van opgaven, maatregelen en strategieën voor polders. Er wordt hiertoe aanvullende informatie, een checklist en achtergronden aangereikt. Het project ‘Toekomst Veenweide’ is gericht op polders uit het Landschaps Ontwikkelingsperspectief (LOP) Midden-Delfland. De meeste polders hebben een landelijk karakte

Experimental validation of model for pulsed laser-induced subsurface modifications in Si

Wafers are traditionally diced with diamond saw blades. Saw dicing technology has a number of limitations, especially concerning the dicing of thin wafers. Moreover, the use of fluids and the gen-eration of debris can damage fragile components such as micro electro-mechanical systems. Laser ablation dicing is better suited for thin wafers, but is also not a clean process. An alternative dicing method is subsurface laser dicing. This technology is based on the production of laser-induced sub-surface modifications inside the wafer. These modifications weaken the material, such that the wafer separates along the planes with laser modifications when applying an external force. To find the right laser conditions to produce subsurface modifications in silicon, and to enhance the understand-ing of the underlying physics, a numerical model has previously been developed. To validate this model, the current work compares simulation results with experimental data obtained by focusing nano- and picosecond pulses inside silicon wafers. A fairly good agreement between experimental and numerical results was obtaine