Enabling brighter, more efficient displays, and faster microprocessors.
Coherent delivers a broad range of laser technologies to service a wide array of applications within microelectronics fabrication, advanced packaging and flat panel display manufacture. Whether that laser technology is excimer, solid state, semiconductor or ultrafast, all Coherent lasers are designed and built to deliver superior processing results.
DPSS, ion and optically pumped semiconductor lasers enable front-end semiconductor manufacturing.
In front-end semiconductor manufacturing, lasers are mainly used in two applications: in lithography tools and in inspection. There are many different inspection steps in a modern semiconductor fab and Coherent lasers are used in most of them: mask inspection, bare and patterned wafer inspection. Coherent has many years of experience building lasers for these very demanding applications, which require ultra-high precision and no unscheduled down time.
Coherent lasers are used in a large number of advanced silicon wafer applications, both in high-volume production and in the development of tomorrow’s advanced chip architectures.
As silicon wafers get thinner and new material layers are added, lasers are playing a critical role in processing these wafers. As wafers get thinner, they become more difficult to process with traditional saws due to increased cracking and chipping. DPSS UV lasers like the AVIA can dice thin wafers with good throughput and edge quality. Similarly, the very brittle low-k materials that are so important in today’s advanced chips are best scribed by a DPSS UV laser. Lasers enable narrower street widths on the wafer further increasing overall yield.
Illuminating the semiconductor roadmap.
Laser technology’s role in semiconductor and microelectronics fabrication is growing exponentially as manufacturers seek to produce smaller, more powerful, reliable devices. More integrated components per area of silicon and reduced circuit geometries are the overriding benefits as lasers enable a complete range of semiconductor fabrication processes. As lasers trend towards shorter (UV) wavelengths, higher power and high reliability, they are expanding the bounds of semiconductor manufacturing.
Unparalleled Technology Depth
Coherent has the technology experience and diversity in all leading laser disciplines used in semiconductor and microelectronics manufacturing.
Like virtually every other branch of microelectronics, flex circuits are characterized by increasing miniaturization and the drive to decrease manufacturing costs. There is also increasing pressure to use greener fabrication methods. A new reel-to-reel process enabled by high power excimer lasers delivers tangible benefits in all three areas.
This direct patterning process takes advantage of the extremely high pulse energy of the LAMBDA SX laser. This is an industrial-grade excimer laser which can deliver 1050 mJ at 308 nm, at a repetition rate of 300 Hz. The high pulse energy is used to pattern circuits up to 400 mm2 in area with a single laser pulse. And at 300 pulses per second, this “single pulse” laser process can generate 18,000 circuits/minute.
The circuits are fabricated by vapor deposition of a uniform layer of metal (e.g., Au, Ag, Cu, Al) onto a flexible substrate such as PET, polyimide, PEN, or PMMA. The homogenized excimer beam is passed through a photomask, which is then re-imaged on this coated substrate. The high energy UV photons interact with the metal/substrate interface, directly removing the thin metal film in a pattern defined by the mask image. With a metal film thickness of 40 nanometers or less, a single laser pulse can perform a complete lift with clean edges and no breaks – even at linewidths of 10 microns or less.
The circuits can be fabricated using a reel-to-reel laser station with continuous motion of the web. The web motion appears “frozen” in the 30 nanosecond pulse duration. Or flying optics can be incorporated to enable roll-to-roll processing using stepped motion of the web. Some systems builders also incorporate a vacuum system which not only removes all the metal debris from the circuits, but also enables trapping and recycling of this valuable material.
This single-step dry process is now simplifying flex circuit fab and reducing overall fab costs by replacing traditional photochemical methods which involve seven (7) or eight (8) separate steps. Just as important, this laser-based method eliminates the need to use (and dispose of) wet chemicals. Furthermore, the various wet/dry cycles involved in traditional chemistry can cause shrinkage and deformation, limiting resolution and/or yields. This problem is no longer an issue with this new, single-step dry process.
Short and intense laser pulses provide unique benefits for many pulsed laser deposition applications.
Pulsed laser deposition (PLD) is a laser-based technique used to grow high quality thin films of complex materials on substrates like Silicon wafers. The material to be deposited (target) is vaporized by short and intense laser pulses and forms a plasma plume. Then, the vaporized target material from the plasma bombards the substrate and – under the right conditions – creates a thin homogenous layer on this substrate. For each laser shot, a layer of only a few nanometers of material is ablated to form the plasma plume in a process that typically last a few tens of picoseconds. To enable this process, nanosecond pulses with energies of tens or hundreds of millijoules are necessary and UV wavelengths are usually preferred. These requirements match well the performances of excimer lasers.
The first laser deposition experiments took place in the mid to late 1960s, but PLD gained tremendous interest after T. Venketesan in 1987 first applied this method to create high temperature superconductive (HTSC) films. Since then, many hundreds of lasers have been sold to drive research, process development and small-scale production of thin film devices, such as superconductive magnetic sensors (SQUIDs), thin film ferroelectrics and “high k” gate resistors, semiconductor alloys, carbon nano-tubes, and more.
Although visible or IR laser beams have been used for PLD applications, UV beams are now most commonly employed. Among UV pulsed lasers, excimer lasers provide a variety of short wavelengths combined with energy levels that fit perfectly most PLD applications. High laser pulse energy provides several benefits for pulsed laser deposition. First, it extends the range of possible target materials that can be used. Second, it enables a larger area on the target to be ablated with the desired fluence. In turn, this area enlargement increases the deposition rate and reduces the plume angle, resulting in higher deposition efficiency. Finally, higher pulse energy provides a larger process window, allowing a more consistent process.
Coherent’s COMPexPro and LPXpro laser series are designed for demanding high-pulse energy applications and are highly effective tools for pulsed laser deposition. They deliver the beam stability and energy stability performance required to achieve superior results in sophisticated thin film deposition experiments.
Since desktop inkjet printers are being produced with higher resolutions, there is a need for more and smaller holes in the nozzle array of the printing head.
The position of the holes, as well as the shape, must fulfill very tight tolerances (<1µm). While former products used electroforming for nozzle drilling, the excimer laser offers significantly better production yields and better control over the nozzle shape.
Coherent’s industrial excimer lasers are designed for high duty-cycle production with low maintenance downtime and low running-costs. State-of-the-art line beam optics are used for beam forming and homogenization. The results are up to 100 holes drilled simultaneously in patterns of up to 18 mm in length on the printer head that can be machined simultaneously with sub-micron accuracy.
The PCB industry is experiencing a tremendous increase in demand for multilayer boards (MLBs) and high-density interconnect structures (HDISs) driven by smart phones and tablets.
The extraordinary demand from smartphones and tablets, coupled with accelerating product cycles, has created a vigorous market for microvias and the equipment used to manufacture them in high volume.
There are four (4) microvia formation technologies: lasers, photovia, mechanical drilling, and plasma etching. Each technology has its inherent advantages and disadvantages.
The clear leader for blind microvias when considering cost per via, quality, size, and dynamic range and throughput is lasers. The following graph shows the dynamic range in hole sizes that the current laser technology offers
:As the leading supplier of lasers to the microvia industry, Coherent lasers are used to produce blind, buried or through microvias.
Coherent’s DIAMOND sealed CO2 lasers are used to drill >50 µm diameter vias in resin-coated copper (RCC), Fr4 and aramid-based dielectrics, as well as Cu-direct drilling processes.
The AVIA-series diode-pumped UV lasers are ideal for drilling <70 µm diameter vias in RCC and PTFE-based dielectrics and copper.
Excimer and fiber-based lasers enable industrial micromachining.
Ultraviolet (UV) laser light is an ideal tool for many micromachining applications. The short wavelength results in two major advantages: it allows the production of very small features and the effect on the surrounding material is minimal due to the non-thermal interaction.
There are two major technical breakthroughs that make UV lasers more and more useful in industrial applications. First is the dramatic maturation in excimer laser design. State-of-the-art excimer lasers using advanced technologies feature extended component lifetime, high reliability, low maintenance downtime and low running-costs. The second breakthrough is in the area of diode-pumped solid-state (DPSS) lasers. New generation lasers deliver high peak power, high repetition rates, and excellent beam quality (TEM00). They are also available with frequency conversion down to the fourth harmonic (266 nm).
Both advances make UV lasers more attractive to industrial users. As a result, they have been implemented in a wide range of micromachining applications. The following text outlines some important applications and specific laser requirements
.This photo shows excimer-micromachined script on a 120 micrometer diameter human hair. This is an example of high-resolution direct-ablation by mask imaging. This technique can produce resolved features down to a couple of microns.
Unique Application Examples for Excimer Laser Microstructuring
Images courtesy of Laser Laboratorium, Goettingen, Germany
MEMS combine mechanical and electrical functions on one chip, processed by traditional semiconductor techniques.
In the near future, gas sensors, chemical and biosensors, and actors like microvalves and microrelays will emerge. The field is now open for direct structuring of a wider range of materials and applications using UV lasers.
A very promising extension of 3D microstructuring has been explored by combining excimer laser ablation with the LIGA technique. Direct 3D microstructuring of the master by UV excimer light is much more flexible and economical than multi-step X-ray lithography.
DPSS and ion lasers enable laser lithography.
The Components of Lithography & Optics Testing
The rate of progress for optical lithography has been astounding. Twenty years ago, it was widely believed that optical technology for laser lithography would run out of steam at 0.75 mm. Progress in optical lens design, optical materials, optical manufacturing technology, and a steady reduction in the exposure wavelength, have resulted in the ability to print features of 0.18 mm in production today. Whenever the feature size is halved, the circuit density increases by four-fold. Smaller features, plus innovative circuit design and ever increasing chip sizes, has vastly increased the functionality per chip and has produced a bonanza of value and performance for the consumer. As long as the consumer has a sense of receiving more value for the computer dollar spent, consumers and corporations will continue to invest in upgrading their laser lithography systems.
Higher storage capacity of memory devices (DRAMs) and ever-faster clock speeds of microprocessors demand smaller circuit features, hence better resolution and smaller features in the lithography step. Larger optical field sizes are required for the more complex logic and storage devices and also provide higher throughput from the lithography equipment.
Laser Photolithography & Semiconductors
Laser photolithography requires UV both because it is easier to make UV sensitive resists and because deeper UV means better resolution.
There are two components to lithography:
Interferometric Optics Testing
Many applications use high-powered UV pulsed lasers for manufacturing operations. Some of these applications, such as semiconductor mask lithography, require extremely high pulse energies and demand UV optical components that are defect-free, low-absorption, and manufactured to within extremely tight tolerances.
Unfortunately, it is difficult to test these optical components with a pulsed laser system. The Innova 300 FreD provides a lower power CW UV source that can, without damaging the optical components, test these components before they are exposed to high power pulses. FreD’s 248 nm output line matches the wavelength of the KrF output of excimer lasers, and the 266 nm output from Azure matches that of the frequency-quadrupled output of a pulsed YAG laser.
The dramatic miniaturization of electrical and opto-electrical circuits and the growing need of high precision measurements of the shape of surfaces in industry are the driving force of the laser-based inspection market.
The laser is perfectly suited for high precision inspection, because of its high resolution and the various wavelengths available that can be selected according to the material under investigation.
What is Laser Inspection?
Laser inspection can be divided into two segments. One is the quality control of microscopically generated features and the determination of contamination in the semiconductor field. Microscopic laser inspection uses scattering, absorption and ultrasonic techniques to determine and locate a defect or a contamination of sizes in the range of the wavelength used. The Verdi series of CW solid-state lasers in the green and the Sapphire™ family in the blue cover scattering and absorption techniques, whereas the Vitesse family of femtosecond lasers serve ultrasonic applications.
Laser Inspection Equipment
The other segment in laser inspection is the determination of the quality of the macroscopic shape and its deviation to a reference. For this purpose, interferometry, shearography and holography using visible and deep UV wavelengths are widely used methods that achieve accuracy on the order of the wavelength employed. Coherent offers solutions to this ever-expanding marketplace with laser inspection equipment including the Verdi series (green - 532 nm), Sapphire (blue - 488 nm) and the Azure (deep UV - 266 nm). All of these lasers have the unique PermAlign™ technique for superior stability and lifetime. For the blue spectrum, Coherent offers the revolutionary Sapphire family at 460 and 488 nm.
Direct patterning of multiple layers plays a vital role in the Flat Panel Display (FPD) industry. The use of lasers helps meet the goal of lower manufacturing cost, high yields and environmentally friendly processing.
Direct laser patterning is achieved by various laser processes such as ablation, engraving, marking, or thermal treatment. Laser processing provides the advantage of being contact-free, flexible and highly reproducible. For most of these laser applications, the number of process steps is greatly reduced. Typical examples for laser direct patterning in the FPD industry include metal electrodes, contact holes, touch panel, and light guide plates.
To cover the large list of material mixes used in microelectronics and flat panel displays, Coherent offers a large product range of lasers. The range covers CO2 lasers for engraving, Direct Diode for thermal treatment, as well as DPSS and excimer lasers for ablation. Our lasers are perfectly matched to the direct patterning applications and provide the stability and robustness that is demanded by the industry. Global support and access to our fully equipped application centers are provided to ensure successful implementation.
Coherent lasers play a critical role in today’s advanced packaging and printed circuit board (PCB) applications, enabling smaller features, higher yield and higher throughput.
As feature sizes on PCBs continue to shrink, traditional printing methods are challenged to keep up with the precision requirements, particularly when it comes to multi-layer PCBs. Smaller features and more layers mean tighter and tighter tolerances on registration and control of the manufacturing process. Laser Direct Imaging (LDI), which uses a UV laser to directly write the desired pattern onto a photo-resist, solves or bypasses these problems and is becoming the manufacturing method of choice for the any layer boards now used in high-end smart phones. The Coherent Paladin family of lasers is the ideal source for LDI.
Laser crystallization drives faster, brighter displays with HD resolution. Excimer laser powers in excess of 1 kW and high precision UV optical systems are driving yield and productivity.
The trend towards mobile communications, smart phones, personal computing, and digital photo and video drives the market for advanced small and medium-sized displays with the highest resolution, high brightness and long battery life for a perfect user experience. For these displays, the LTPS (Low Temperature Poly Silicon) TFT backplane is inevitable to enable stable performance of AMLCD and AMOLED displays.
Coherent is the market leader for excimer lasers and UV optical systems that are the enabling components of the annealing system. Highest laser power of more than 1 kW and optimized line beams of up to 750 mm are used worldwide for the manufacturing of LTPS-based LCD and OLED displays.
Laser pulses can vary over a very wide range of duration (milliseconds to femtoseconds) and fluxes, and can be precisely controlled. This makes pulsed laser ablation very valuable for both research and industrial applications.
Laser Ablation is the process of removing material from a solid (or occasionally liquid) surface by irradiating it with a laser beam. At low laser flux, the material is heated by the absorbed laser energy and evaporates or sublimates. At high laser flux, the material is typically converted to a plasma. Usually, laser ablation refers to removing material with a pulsed laser, but it is possible to ablate material with a continuous wave (CW) laser if the laser intensity is high enough. The depth over which the laser energy is absorbed, and thus the amount of material removed by a single laser pulse, depends on the material’s optical properties and the laser wavelength.
Laser pulses can vary over a very wide range of duration (milliseconds to femtoseconds) and fluxes, and can be precisely controlled. This makes laser ablation very valuable for both research and industrial applications.
The 193 nm solid-sampling-system GeoLasPro is a self-contained laser ablation system for sample introduction in high-resolution LA-ICP MS (laser ablation inductively-coupled plasma mass spectrometry). GeoLasPro integrates the COMPexPro 193 nm ablation laser including beam homogenizing and shaping optics, a sample chamber, and unmatched microscopic sample observation capability. 193 nm sampling speed can be varied in a wide range from 1 Hz up to 100 Hz.
GeoLasPro includes several innovative features that enhance the performance of the overall LA-ICP-MS system. For example, the new sample observation microscope is made perfectly co-linear with the laser beam delivery optics through the use of an all-mirror microscope objective, which is free of chromatic aberration. This objective is also able to operate at higher laser power without the risk of coating damage that can occur when using lens-based objectives. These beam delivery optics can achieve a homogenized spot with a diameter as small as five (5) microns, which is ideal for sampling small fluid inclusions. The optics also include interchangeable circular and square beam shaping masks providing high sampling flexibility.
GeoLasPro is designed for geological and nuclear physics research and for quality control of materials and pharmaceutical samples. Examples include analysis of fluid inclusions in minerals, age determination of samples by isotope ratio analysis and analyzing high purity semiconductor materials
.Advantages of Laser Ablation
Solid-state lighting is a key element to achieve the global target for reduced energy consumption. Coherent lasers support this goal and drive new processes for advanced LED manufacturing.
The market for high-brightness light-emitting diodes (HB-LED) is poised for explosive growth over the next five years. Declining costs and improving performance have rendered HB-LEDs a viable competitor to conventional cold-cathode fluorescents (CCFLs) for backlighting flat screen televisions. Rapid adoption for LCD display backlighting is driving HB-LED market growth this time around.
The potential for HB-LEDs in general illumination such as retail display, outdoor, and residential lighting represents the largest overall market. Penetration into general lighting applications is expected to accelerate as manufacturing costs come down and device efficiency improves.
Novel laser-based manufacturing concepts such as laser-lift-off (LLO) processing with 193 nm and 248 nm excimer lasers enable vertical LED structures with increased light extraction efficiency.
Laser-based sapphire scribing, as well as wafer or substrate dicing with diode-pumped solid-state lasers at 266 nm and 355 nm or picosecond lasers, further reduce production costs and at the same time significantly enhance yield and efficiency of HB-LEDs.
The explosive growth within the electronics industry, driven primarily by telecommunications and portable devices, has resulted in an overwhelming demand for high-density flexible (HD flex) circuits.
Thanks to faster processing speeds, lower capital investment costs, higher quality processing, higher reliability, and the ability to process fine features, laser processing has proven to be an essential component for high-volume fabrication of HD flex. UV-DPSS and IR CO2 lasers offer the best overall solution to requirements set forth by flex manufacturers.
Laser technology can be used for a variety of applications within the HD flex industry: microvia drilling (blind and thru), excising, skiving, and coverlay processing. Coherent’s DIAMOND sealed CO2 lasers operating at 9.4 µm wavelength and AVIA-series diode-pumped UV lasers operating at 355 nm wavelength have become industry standards for laser flex processing.
Excimer lasers enable fiber bragg grating writing.
Photosensitivity is a non-linear optical phenomenon to describe a photorefractive effect in an optical fiber (i.e., a change in the value of the refractive index). A fiber irradiated by laser UV light will show a change in the transmission properties of the wave guides due to a permanent change of the refractive index.
Using an excimer UV laser to create an intense fringe pattern to irradiate the fiber, a permanent periodic modulation (spacing of the fringes) of the refractive index profile is photo induced giving rise to the periodic structure known as a Fiber Bragg Grating (FBG).
A Bragg Grating can produce a very precisely customised spectral profile allowing applications in filtering, wavelengths selections, Fabry-Perot etalon, and new types of sensors. The main use nowadays, however, is to allow a huge number of channels on fiber telecommunication and selecting the noise-free channels on wireless receivers of modern mobile phones.
Standard Optimization of the Excimer Laser aims for maximum Energy/Power, but is suboptimal with respect to Spatial Coherence
Optimization for spatial coherence achieves substantial improvements with little sacrifice in energy.
Sticking with a standard resonator design keeps alignment procedures easy for end users and is stable to temperature variation
Lasers are used to create periodic changes in the core refractive index of optical fiber.
UV lasers, including Coherent’s Innova Ion lasers, the LPXpro, COMPexPro and BraggStar series excimer lasers, are critical tools in the manufacture of high-performance fiber bragg gratings (FBG) for the Dense Wavelength Division Multiplexing (DWDM) marketplace. FBGs are used to perform a number of tasks in optical networks, including signal conditioning and routing. Ultraviolet (UV) lasers are used to imprint the gratings in the fiber.
The Innova Ion product line is a complete family of intracavity frequency-doubled argon lasers that produce high-power output in the deep-UV. The Innova Ion’s 244 nm wavelength is used to create periodic changes in the core refractive index of optical fiber. The resulting fiber gratings are used in DWDM technology, laser mirrors in fiber lasers, dispersion compensators, and gain-flattening amplifiers.
The Innova Ion lasers are used to produce a significant portion of high-performance FBGs.
The recent commercial boom in electronic devices and the trend toward miniaturization have caused ceramics fabricators to seek more efficient and precise manufacturing methods and tools.
Ceramic processing applications for lasers have increased since the development of several new industrial lasers. Lasers are now used to scribe, drill and profile, as well as for selective material removal and marking/serializing applications. They are also used to process fired substrates such as alumina (AL2O3 ), aluminum nitride (AIN) and beryllium oxide (BeO), and unfired (green) substrates.
Coherent’s DIAMOND sealed CO2 lasers, AVIA diode-pumped UV lasers and VECTOR diode-pumped solid-state lasers have become industry benchmarks for laser ceramics processing. These lasers are used for scribing, machining, marking and drilling of fired and unfired ceramic materials used as substrates in hybrid MCM and other microelectronics substrates.
Coherent supplies laser sources and tools for wire feed welding and brazing.
Coherent’s HighLight 4000L is a line source laser product, excellent for wire feed welding and brazing. The line spot of the 4000L makes feeding wire into the laser beam very easy. There is no need for expensive vision systems and precision alignment devices. The long beam which can only conduction mode weld “wets out” the weld. This produces excellent weld bead profiles.
Characteristics of conduction mode weld:
As with wire feed welding, the HighLight product line is an excellent heat source for Silicon Bronze brazing. For Body-n-White brazing, the HighLight 4000L is an excellent source for creating braze joints that do not need rework after brazing. The long beam wets out the weld.
Benefits of Laser Brazing
Direct from the computer to submicron dimensions using excimer lasers in the UV.
Excimer lasers can be used to shape a wide range of materials including polymers, metals, glass, ceramics and even diamonds. The direct-write approach using CAD/CAM software for laser machining in the dimensions of microns allows almost any shape to be generated on a surface.
The combination of compact excimer lasers and precision motion systems, video imaging and CAD/CAM software allows precision machining on scale-sizes in the 1 to 100 micron range.
Raster scanning on the work surface is one means of producing such three-dimensional structures. This technique forms the part by removing the material layer by layer.
Since the single-pulse ablation depth varies from a few nanometers to some tenths of a nanometer, it is possible to produce smooth, sloping surfaces with continuous height variation by excimer laser ablation.
Coherent has locations across the globe that are available to provide support for any product, service or inquiry.
5100 Patrick Henry Drive
Santa Clara, CA 95054 USA
Coherent has locations across the globe that are available to provide support for any product, service or inquiry.
Coherent has locations across the globe that are available to provide support for any product, service or inquiry.
Parc Technopolis 3, Avenue du Canada
91978 Courtaboeuf cedex
Room 1006 – 1009, Raycom Info Park Tower B, No. 2, Kexueyuan South Road Haidian District
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5100 Patrick Henry Drive
Santa Clara, CA 95054 USA
Toyo MK Building 7-2-14 Toyo, Koto-ku
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