Laser micromachining has been a part of the manufacturing process for semiconductors and microelectronics devices for several decades. More recent applications such as the drilling of microvia holes in high-density electronic packages... more
Laser micromachining has been a part of the manufacturing process for semiconductors and microelectronics devices for several decades. More recent applications such as the drilling of microvia holes in high-density electronic packages have recently entered broad industrial use for high-volume production. In such applications, process stability and throughput are key drivers of commercial success. Particularly in the UV, where solid-state laser power is growing rapidly but is still limited to less than 10 watts, innovations that permit the available laser power to be applied at the work surface more efficiently are of interest. Within the last two years, the use of beam shapers to create round laser spots with near-uniform irradiance at the work surface has been demonstrated. Shaping the irradiance profile has been shown to both increase process speed and improve the quality of the drilled holes, which range in diameter between 20 and 150 micrometers . This paper gives an historical overview of laser via drilling, presents the Gaussian-to-flattop beam shaping optics used in the microvia laser drills, and discusses the process results obtained.
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This paper presents a new CO2 laser technology for precision microfabrication applications. The laser produces short (microsecond) pulses at very high pulse repetition frequencies (PRFs). In contrast, most commercial CO2-laser... more
This paper presents a new CO2 laser technology for precision microfabrication applications. The laser produces short (microsecond) pulses at very high pulse repetition frequencies (PRFs). In contrast, most commercial CO2-laser micromachining applications employ one of two type of CO2 lasers: RF-excited with external pulse modulation, and TEA lasers. The laser technology presented here produces pulses sharing some of the characteristics
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ABSTRACT We report for the first time production-quality P2 and P3 scribes in CIGS based solar cells using a nanosecond-domain industrial pulsed laser We also show how the same laser can be used to produce the P1 scribe, and report what... more
ABSTRACT We report for the first time production-quality P2 and P3 scribes in CIGS based solar cells using a nanosecond-domain industrial pulsed laser We also show how the same laser can be used to produce the P1 scribe, and report what we believe to be the first all-laser-scribed monolithically-integrated CIGS solar cells in which all scribes were made using the same laser, at the same 1064nm wavelength. This paper reports the results of a collaborative effort involving two national laboratories and two private companies, and focuses on the laser scribing processes. A paper describing the design and characterization of the solar cells has been published elsewhere in this journal [1]. The new laser-based P2 and P3 processes rely on a "brittle fracture material removal" mechanism whose material removal characteristics are somewhat similar to those of mechanical scribing in that the material is ejected from the surface in fragments. However, unlike mechanical scribing, the laser process produces highly regular and deterministic edges. The first cells produced showed poor conversion efficiency, mostly attributed to high series resistance. These cells then had additional AZO deposited on them, and the results improved dramatically. Finally, we show results obtained using conventional mechanical scribing for the P2 and P3 processes on cells which are in other respects almost identical. Initial results are similar to the laser-scribed results.
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This paper describes the results from collaborative efforts in establishing an all-laser scribing technological capability for fabricating monolithically integrated CuInGaSe2 (CIGS) mini-modules. The scribing parameters required for each... more
This paper describes the results from collaborative efforts in establishing an all-laser scribing technological capability for fabricating monolithically integrated CuInGaSe2 (CIGS) mini-modules. The scribing parameters required for each of the three scribing steps (P1, P2, P3) were determined and optimized by using three specific samples fabricated at NREL. A fiber laser system using a single wavelength at 1064 nm was
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Abstract This paper reports the results of a study of the instantaneous spatial structure of a confined swirling flow after a sudden expansion. The flow chosen corresponds to the cold flow conditions of an axisymmetric laboratory-scale... more
Abstract This paper reports the results of a study of the instantaneous spatial structure of a confined swirling flow after a sudden expansion. The flow chosen corresponds to the cold flow conditions of an axisymmetric laboratory-scale research furnace. The swirl number of the flow is 0.7 at the inlet plane and the expansion diameter ratio is 6:1. The flow has a centre hub-to-throat diameter ratio of 1:4. Data are reported for the instantaneous spatial structure of the flow via transient planar elastic scattering imaging. This technique allows for unambiguous visualization of the spatial structure of the flow by slicing through it with a thin sheet (≅ 1.5 mm) of light at various locations in the axial/radial and radial/azimuthal planes. By varying the time delay between introduction of the seeding material and data acquisition, features of the flow that would ordinarily be inaccessible are revealed. Laser Doppler velocimetry is used to measure the time-averaged and root mean square velocity components in all three coordinate directions. Using these data, we construct a model of the flow from the viewpoint of the vorticity fed into the flow and its subsequent dynamics. This viewpoint suggests different reasons for the development of the observable features of the flow and shows promise for helping to deconvolve the apparent complexity of this flowfield.
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Recent years have witnessed the introduction of several new laser technologies for laser material processing. Particularly in micromachining processes, where excellent mode quality and high focusability are important for achieving small... more
Recent years have witnessed the introduction of several new laser technologies for laser material processing. Particularly in micromachining processes, where excellent mode quality and high focusability are important for achieving small feature sizes, these new lasers are enabling emerging commercial applications. Due to the various combinations of laser wave-length, pulse energy, pulsewidth, and pulse repetition frequency among these lasers, both gross and subtle differences occur in the complex laser/material interaction physics. Consequently, variations occur in the quality of the micromachined features and the speed of the process, and empirical data are still the best means of comparison of these industrially significant effects.In this study, we compare the drilling results obtained with six lasers of current industrial interest: frequency-tripled diode-pumped Nd:vanadate (355nm wavelength), frequency quadrupled diode pumped Nd:vanadate (266nm wavelength), KrF excimer (248nm) and three CO2-based laser technologies at wavelengths between 9.2 and 9.4 µm. We focus attention on drilling processes, where machining is often complicated by the material-ejection phenomena, particularly for deep holes. In a variety of materials, including ceramics and glasses, we examine the hole characteristics obtained and note the drilling speed possible with current commercially available lasers.Recent years have witnessed the introduction of several new laser technologies for laser material processing. Particularly in micromachining processes, where excellent mode quality and high focusability are important for achieving small feature sizes, these new lasers are enabling emerging commercial applications. Due to the various combinations of laser wave-length, pulse energy, pulsewidth, and pulse repetition frequency among these lasers, both gross and subtle differences occur in the complex laser/material interaction physics. Consequently, variations occur in the quality of the micromachined features and the speed of the process, and empirical data are still the best means of comparison of these industrially significant effects.In this study, we compare the drilling results obtained with six lasers of current industrial interest: frequency-tripled diode-pumped Nd:vanadate (355nm wavelength), frequency quadrupled diode pumped Nd:vanadate (266nm wavelength), KrF excimer (248nm) and three CO2-based las...
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Recent years have witnessed wider industrial implementation of high-speed laser micromachining processes. Often, commercial viability of such applications depends on achieving high beam placement accuracy as well as process throughput.... more
Recent years have witnessed wider industrial implementation of high-speed laser micromachining processes. Often, commercial viability of such applications depends on achieving high beam placement accuracy as well as process throughput. When available laser power is not the limiting factor, beam positioning systems that can move the beam at high speed and micron-scale accuracy are needed and represent the limiting factor. This paper reviews the state of the art of such positioning systems, with emphasis on the architectures used today for laser drilling of microvias for electronic packaging and interconnect. Beam placement requirements (speed and accuracy), drilling process techniques, historical progress since the mid- 1990s, and fundamental tradeoffs and limiting factors are discussed. Future directions are suggested.Recent years have witnessed wider industrial implementation of high-speed laser micromachining processes. Often, commercial viability of such applications depends on a...
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Within the last five years, laser drilling of microvia holes in high-density electronic packages has been widely adopted for high-volume production. In such micromachining applications, process stability and throughput are key drivers of... more
Within the last five years, laser drilling of microvia holes in high-density electronic packages has been widely adopted for high-volume production. In such micromachining applications, process stability and throughput are key drivers of commercial success. Particularly in the UV, where solid-state laser power is growing rapidly but is still limited, innovations that permit the available laser power to be applied at the work surface more efficiently are of interest. Within the last three years, the use of beam shapers to create round laser spots with near-uniform irradiance at the work surface has been demonstrated. Shaping the irradiance profile has been shown to both increase process speed and improve the quality of the drilled holes, which range in diameter between 20 and 150 µm. This paper gives a brief overview of laser via drilling and presents the Gaussian-to-flattop beam shaping optics used in UV laser via drills, along with the process results obtained.Within the last five ...
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recent article presented an overview of how lasers can play a key role in the development and production of solar devices, delivering twin benefits of lower fabrication costs and superior performance (see ILS, August 2007, p. 24). Laser... more
recent article presented an overview of how lasers can play a key role in the development and production of solar devices, delivering twin benefits of lower fabrication costs and superior performance (see ILS, August 2007, p. 24). Laser scribing is rapidly emerging as one of the most significant of all these processes as it is critically enabling high-volume production of next-generation thin-film devices, surpassing mechanical scribing methods in quality, speed, and reliability. These thin-film solar cells are important because they lend themselves to streamlined, high-volume manufacturing and greatly reduced silicon consumption. This results in dramatically lower fabrication costs per unit of power output compared to traditional silicon-wafer-based solar cells.
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Un laser solide (52)) a pompe diode de systeme a laser (50) delivre un faisceau de sortie gaussien ultraviolet (54) qui est converti par un element optique a diffraction (90) en faisceau de sortie mis en forme (94) presentant un profil... more
Un laser solide (52)) a pompe diode de systeme a laser (50) delivre un faisceau de sortie gaussien ultraviolet (54) qui est converti par un element optique a diffraction (90) en faisceau de sortie mis en forme (94) presentant un profil d'exposition energetique uniforme. Un pourcentage eleve de la sortie mise en forme (94) est focalise de maniere a passer par une ouverture d'un masque (98) et a delivrer en sortie un faisceau mis en forme (118) d'imagerie. Le systeme a laser (50) permet la mise en oeuvre d'un procede d'accroissement du rendement d'un processus de percage de trous d'interconnexion en comparaison de ce qu'il est possible d'obtenir avec un systeme a laser gaussien decoupe analogue. Ce procede est particulierement adapte au percage de trous d'interconnexion borgnes (20b) presentant de meilleures caracteristiques de bordures, de fond et de conicite que ceux produits au moyen d'un systeme a laser gaussien decoupe. Un autre systeme...
Cette invention concerne un actionneur a passe unique (70, 200), tel qu'un miroir deformable (70), qui modifie rapidement, de preference en moins d'une milliseconde, la mise au point et donc la taille ponctuelle d'impulsions... more
Cette invention concerne un actionneur a passe unique (70, 200), tel qu'un miroir deformable (70), qui modifie rapidement, de preference en moins d'une milliseconde, la mise au point et donc la taille ponctuelle d'impulsions laser dans l'ultraviolet ou de longueur d'onde visible. Il en resulte un changement de fluence de la sortie laser (66) au niveau de la surface de la piece entre au moins deux niveaux differents de fluence, ce qui facilite le traitement des couches metalliques superieures (264) a des fluences plus elevees et celui des couches dielectriques sous-jacentes a des fluences plus faibles, et donc protege les couches metalliques inferieures (268). Le changement de mise au point se fait sans deplacement de l'axe Z du systeme de positionnement du laser (62). Par ailleurs, la possibilite de modifier la taille pendant les operations de percage offre l'avantage d'attenuer la conicite des trous traversants, de reduire la formation de levres, d&#...
Photovoltaic energy conversion devices are on a rapidly accelerating growth path driven by increasing government and societal pressure to use renewable energy as part of an overall strategy to address global warming attributed to... more
Photovoltaic energy conversion devices are on a rapidly accelerating growth path driven by increasing government and societal pressure to use renewable energy as part of an overall strategy to address global warming attributed to greenhouse gas emissions. Initially supported in several countries by generous tax subsidies, solar cell manufacturers are relentlessly pushing the performance/cost ratio of these devices in a
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Semiconductor manufacturing, is dominated by the relentless demand for electronic products with greater performance, minimized dimensions, increased sophistication, and higher speed, all at reduced process cost. Logic device manufacturers... more
Semiconductor manufacturing, is dominated by the relentless demand for electronic products with greater performance, minimized dimensions, increased sophistication, and higher speed, all at reduced process cost. Logic device manufacturers need to satisfy this demand by producing integrated circuits that meet the predicted density increase encapsulated in Moore's law. This has led to the use of low-kappa dielectrics. For memory devices,
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A necessary step in the fabrication of many different flat panel display types is the selective removal of a thin layer of indium tin oxide (ITO) or other transparent conductor from the substrate to create circuit patterns. The... more
A necessary step in the fabrication of many different flat panel display types is the selective removal of a thin layer of indium tin oxide (ITO) or other transparent conductor from the substrate to create circuit patterns. The conventional method of performing this patterning utilizes photolithography. Specifically, an image of the desired pattern is projected on to a photoresist coated
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Laser drilling has emerged in the last five years as the most widely accepted method of creating microvias in high-density electronic interconnect and chip packaging devices. Most commercially available laser drilling tools are currently... more
Laser drilling has emerged in the last five years as the most widely accepted method of creating microvias in high-density electronic interconnect and chip packaging devices. Most commercially available laser drilling tools are currently based on one of two laser types: far-IR CO2 lasers and UV solid-state lasers at 355 nm. While CO2 lasers are recognized for their high average
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This paper presents a new CO2 laser technology for precision microfabrication applications. The laser produces short (microsecond) pulses at very high pulse repetition frequencies (PRFs). In contrast, most commercial CO2-laser... more
This paper presents a new CO2 laser technology for precision microfabrication applications. The laser produces short (microsecond) pulses at very high pulse repetition frequencies (PRFs). In contrast, most commercial CO2-laser micromachining applications employ one of two type of CO2 lasers: RF-excited with external pulse modulation, and TEA lasers. The laser technology presented here produces pulses sharing some of the characteristics
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Lasers continue to gain ground in materials processing applications for microelectronics manufacturing. Printed circuit boards, IC wafers, substrates for blue/green LEDs, and various components in flat panel displays are all being... more
Lasers continue to gain ground in materials processing applications for microelectronics manufacturing. Printed circuit boards, IC wafers, substrates for blue/green LEDs, and various components in flat panel displays are all being processed with lasers. Some of these operations, such as microvia drilling in high-density circuit boards, are well established; others are under evaluation or in early stages of development. This
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Photovoltaics has in the last five years enjoyed unprecedented growth and acceptance as part of the worldwide energy mix. Innovations in both wafered silicon and various thin-film PV technologies anticipated in the next 5-10 years promise... more
Photovoltaics has in the last five years enjoyed unprecedented growth and acceptance as part of the worldwide energy mix. Innovations in both wafered silicon and various thin-film PV technologies anticipated in the next 5-10 years promise to lower the cost of PV power to parity with that supplied by the grid. When that occurs, the growth of the industry will
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As the demand for semiconductor devices based upon ever-thinner silicon substrates continues to increase, mechanical techniques suitable for dicing wafers appear to be approaching their practical limits. Recent advances in power scaling... more
As the demand for semiconductor devices based upon ever-thinner silicon substrates continues to increase, mechanical techniques suitable for dicing wafers appear to be approaching their practical limits. Recent advances in power scaling have now enabled reliable ultraviolet-wavelength lasers to be considered to offer a flexible solution to this dilemma. This paper presents new data on the machining of thin silicon
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Laser processing of glass components is of significant commercial interest for the optoelectronics and telecommunications industries. In this paper, we present laser processing techniques using microsecond, nanosecond, and femtosecond... more
Laser processing of glass components is of significant commercial interest for the optoelectronics and telecommunications industries. In this paper, we present laser processing techniques using microsecond, nanosecond, and femtosecond lasers for machining of glass. Surface structures, mainly groove geometries, are generated with a diode-pumped solid-state nanosecond pulsed UV laser operating at 266 nm, a Q-switched CO2 laser operating at 9.25
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Laser micromachining in the microelectronics industry: a historical overview. [Proceedings of SPIE 4095, 118 (2000)]. Edward J. Swenson, Yunlong Sun, Corey M. Dunsky. Abstract. The use of lasers in microelectronics is production ...
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ABSTRACT
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As the demand for semiconductor devices based upon ever-thinner silicon substrates continues to increase, mechanical techniques suitable for dicing wafers appear to be approaching their practical limits. Recent advances in power scaling... more
As the demand for semiconductor devices based upon ever-thinner silicon substrates continues to increase, mechanical techniques suitable for dicing wafers appear to be approaching their practical limits. Recent advances in power scaling have now enabled reliable ultraviolet-wavelength lasers to be considered to offer a flexible solution to this dilemma. This paper presents new data on the machining of thin silicon wavers using a high average power 355-nm wavelength pulsed laser. In particular, the concept of pulse repetition-rate scaling of the effective cutting speeds was investigated to determine the preferred direction for further laser development efforts.