Harnessing Light Optical Science and Engineering for the 21st Century (1998) / Chapter Skim
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5 Optics in Industrial Manufacturing
5 Optics in Industrial Manufacturing
Pages 195-234
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From page 195... ...
2. Controlling manufacturing: Optics is used to provide information about a manufacturing process, as in the chemical industry's use of optical sensors for in-line process control, or to inspect a manufactured C h a p t e r 5 195
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It endeavors instead to cover a representative sample, including those applications TABLE 5.1 Major Uses of Optics in industrial Manufacturing Automobiles Semi- Chemicals conductors Aircraft and Construction Aerospace Value of shipments 152.9 32.2 305.4 131.9 391.2 (billions of 1992 dollars) a Photolithography - Critical Laser materials processing Critical Major - Major Significant Rapid three-dimensional Emerging - - Emerging prototyping Metrology (location, position, dimension,and alignment)
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that is the workhorse of the integrated circuit (lC) industry and an optical material the light-sensitive photoresist used to transfer the desired pattern to the silicon substrate or thin film of interest (Figure 5.1~.
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projects the minimum feature anddepthoffocusofpho- sizes desired in the future and the technologies that must be developed tolithography systems drive to achieve them. increases in the speed and Exposure Tools performance of computers The workhorse of photolithography is the step-and-repeat camera.
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From page 199... ...
Mask alignment is also a critical issue. Subsequent masks must be precisely aligned with patterns on the silicon wafer with a precision far beyond that of the minimum feature dimensions.
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New photolithographic tools in general have low-brightness sources, and high-sensitivity resists are highly desirable. Additionally, the absorption of conventional pho toresists is too high to allow uniform imaging through practical resist film thicknesses, usually on the order of 1 ~m.
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From page 201... ...
Laser Materials Processing Laser materials processing offers many powerful advantages for manufacturing applications. Unlike competitor technologies such as resistance welding, plasma arc cutting, and flame hardening, lasers deliver energy to the workpiece without physical contact, provide high localized energy densities, and are remarkably versatile in their energy delivery.
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Box 5.1 notes the use of excimer lasers to clean ancient metal art objects. There are two areas in which the general field of laser materials processing could benefit from advances in optical technology.
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A growing application for laser materials processing is the welding of zinc-coated (galvanized) steel for car bodies.
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A recent publication describes one of the first uses of an Nd:YAG laser (instead of the CO2 laser) for cutting sheet metal (Industrial Laser Review, 1997~.
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Because the absorption of laser radiation in cold metals is low, laser surface hardening often requires energy-absorbing coatings on surfaces (Molian, 1 986~. Industrial Lasers Market Perspective A special class of lasers, known as "industrial lasers," has evolved to serve the needs of laser materials processing for manufacturing and exists as an industry in its own right.
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From page 206... ...
Between 1 970 and 1 985, however, there was a significant net outflow of laser technology from the United States, and in 1985, industrial laser activity in Europe and Japan began a period of rapid development in both technology scope of application and market TABLE 5.2 Annual Wor~cwice Market for industrial Lasers Year Market Increase ($ millions)
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From page 207... ...
U.S.-owned companies now enjoy a leadership position only in low-power sealed CO2 lasers; intermediatepower fast axial flow CO2 lasers; low-power, diode-pumped Nd:YAG lasers; and laser marking and coding systems (Belforte, 1995~. Industrial lasers must compete with many other materials processing technologies.
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From page 208... ...
Rapid Prototyping and Manufacturing Using Optics The pressure to bring new products to market on an ever-decreasing design-to-manufacture cycle time has driven the development of techniques to produce prototype parts in the early stages of development, FIGURE S.2 Technology developed by the Precision Laser Machining Consortium can cut com posite materials for airframes with 'polished edge" quality (left)
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The first use of rapid prototyping in commercial, industrial equipment was hood on nhotonolvmers sv~tems hood on this technio~e C h a p t e r 5 .
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manufacturing processes. Optical metrology techniques allow control of critical dimensions and layout or positioning; infrared imaging allows rapid determination of temperature profiles of semiconductor chips and preventive maintenance in many manufacturing scenarios.
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As shown in Figure 5.4, the optoelectronic sensing equipment market for industrial metrology applications is expected to double every 5 years. The usual optical metrology system consists of an i I rumination source, optics to focus the il rumination and direct it where needed, a detector to collect information about the part under inspection, and electron ic process)
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Optical inspection systems can be sensitive to a variety of parameters simultaneously, such as chemical composition, electronic state, mechanical stress, temperature, size, flaws, or texture. Many optical metrology systems are built using visible light, but specific applications may use wavelengths ranging from the vacuum ultraviolet (10 nm)
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One often-observed barrier to the introduction of optical metrology systems is the apparent need for custom solutions for each specific application. This customization has an impact on the selection of a particular optical configuration, the illumination system, and the processing algorithms.
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What has limited the further application of machine vision technology? By far the most important limiting factor is the poor performance of the image processing and pattern recognition algorithms.
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The potential for optics to lower automotive manufacturing costs is largely untapped in the United States, and fuller exploitation requires immediate changes in the optical engineering infrastructure. The use of high-power lasers for materials processing functions such as cutting and welding has now become routine in numerous automo _ _ _ _ _ _ _ _ _ _ .
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can automatically adapt to their changing environment, leading to the fixtureless manufacturing line. Although the use of tailored blanks and other such advanced laser materials processing technologies is not fully used in U.S.
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Microelectronics to control automobile functions; and 3. Rapid prototyping to reduce the time from design to production, now typically on the order of 4 years.
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The Semiconductor integrated Circuit industry The immense semiconductor integrated circuit manufacturing indus try is powered by optics, optical systems, and optical materials. A modern electronic integrated circuit is a complex three-dimensional structure of alternating patterned layers of conductors, dielectrics, and semiconductor films.
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Some of these inspections are automated, but many still require the image analysis powers of the human operator to accomplish because of the increasing complexity of the images as the wafers proceed through the processing line. Another area in which optics and optical systems contribute greatly to manufacturing process control is in noncontactfilm characterizationfor example, thickness measurements.
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to maintain the correct film thickness for the subsequent lot. Diagnostic uses for optical sensors in semiconductor manufacturing can be thought of as addressing three areas of manufacturing: contamination-free manufacturing, adaptive process control, or environmental safety and health.
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Off-line analytical laboratories were the primary users for applications such as quality control and trouble shooting. Today, optical techniques are used to provide information for process control in-line (within the process tool)
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The improved speed and sensitivity that have led to this expanded range of applications within the manufacturing line have been made possible principally by the advent of optical fibers, lasers, or other improved light sources, and new optical detectors, along with advances i n com puter tech no I ogy. In the chemical industry, optical techniques are critical parts of a multifaceted approach to chemical process issues to advance quality, quantity, customization, and reductions in waste while enhancing yield.
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The implementation of optical sensors has been found in some instances to double the production output of an existing chemical plant. In other instances, chemical processes could not operate at all without real-time optical sensors.
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Planes of light, generated by a rotating laser head, are used for airplane body joint and wing alignment and for the generation of airplane interior ref erence planes during cabin outfitting. Crossed-fan laser beams are used to align a reference mark on a workpiece with a drill during machining.
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Cost savings at Boeing are proprietary, but the installation of multiple units speaks to the success of the introduction of these optical techniques; active research and development on optical hole diameter measurements, surface profiling, wind tunnel instrumentation, and both cutting and welding indicate a considerable cost payoff in aircraft manufacturing. The Construction Industry New construction accounts for about 9% of the nation's gross domestic product each year.
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At the construction site, optical transducers are used for gathering engineering data and for geodesy (surveying) , including making dis tance measurements, measuring positions, and monitoring physical and chemical properties that can be detected from changes in optical prop erties.
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BOX 5.6 GROWTH OF MARKET FOR OPTICS IN PRINTING The printing industry is large and growing steadily.The market for optical techniques in printing is growing at an annual rate four times that of the industry overall.
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Current electroplating techniques offer faster processing speed, about 20 square inches per second, but the resolution is only 1,200 pixels per inch. For digital printing, desktop applications are anticipated to increase from 30 to 100 square inches per second within 1 0 years, with production applications increasing from 200 to 1,200 square inches per second.
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Many exciting advances are anticipated in the field of laser materials processing, where new laser sources will provide shorter wavelengths, higher beam intensity, and sharper focus. An exciting possibility is the use of adaptive optics to achieve true diffraction-limited resolution on arbitrarily shaped workpieces in environments with poor optical quality.
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Optical metrology should benefit from the development of smart sensors that incorporate data processing capability and from improved optical figure measurement techniques with 1 -n m accu racy. I mprovements in window and optical fiber materials will make it possible to use optical sensors to control manufactu ri ng processes i n i ncreasi ngly hosti le environments such as foundries.
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Compared to conventional techniques, laser materials processing tools operate without physical contact, provide high localized energy density, and are truly versatile in their energy delivery. The United States once dominated the production of specialized industrial lasers to perform materials processing functions but now has only a minority share of the market.
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A factor that has undoubtedly aided the more rapid acceptance of laser materials processing in the foreign automobile industry is the greater level of emphasis that European and Japanese uni versities place on training engineers to be familiar with laser manufactur ing techniques. The establishment of an application test facility in a service center setting in the United States would be particularly useful.
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The special need of the construction industry is for portable sensors that are rugged enough to survive field use. To preserve and enhance this critical technology base, coordinated government-industry-university activities are recommended in the following areas: A multiagency-supported application and test facility should be established in a service center setting using the DARPA-sponsored Precision Laser Machining Consortium as a model for extension of laser materials processing and other optically assisted manufacturing techniques.
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1995. Laser and light sources applications,Vol.
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