Projection printing of the three major types of optical lithography inuse today projection, proximity and contact printing, projection printing is the easiest to model 1. Maskless, resistless ion beam lithography processes. Various approaches have been investigated, including ebeam, micromachined mirror projection, and. It can be employed as a switch of light in a special direction and a laser shaper for laser beams. In this technique, a pattern is first created on a reticle or. Digital maskless lithography is considered to be a highefficiency and lowcost approach for the fabrication of microstructures, but is limited by the gray scale capability of spatial light modulators. It uses light to transfer a geometric pattern from a photomask also called an optical mask to a photosensitive that is, lightsensitive chemical photoresist on the substrate. Stepandscan maskless lithography for ultra large scale dna. University of science and technology of china 1993 m. The system consists of an illumination optical system, a dmd, and a projection lens system.
The final technique, projection exposure, is almost universally used in manufacturing today, and is the only one of the systems that reduces the size of the features on the mask. The programmable array of binary switches would be used to control extreme ultraviolet euv, xray, or electron, illumination systems, obviating the need for stable, defect free masks for projection euv, xray, or electron, lithographies. High speed maskless lithography of printed circuit boards. Recent studies have shown the feasibility of projection maskless lithography pml2 for small and medium volume device production 25 wph for the 45nm technology node. To monitor the polymerization process and the fabricated microstructures at the object plane, we used a microscopic imaging system with a chargecoupled device image sensor. In this approach, an array of diffractive optical microlenses is employed to produce stationary, discrete focal spots. A typical mask feature used in projection is reduced 4 to 10 times in the projection process. Using holographic projection allows diffractionlimited performance within the given parameters.
Maskless lithography and nanopatterning with electron and ion. Each issue of microlithography world will carry a two to three page edition of this continuing series on the basic principles of optical lithography. The method includes projection lithographies using radiation other than optical or ultraviolet light. Next i would like to discuss the second major issue in the optical portion of the exposure process. Evolution of optical lithography contact and proximity printing 1.
Mar 10, 2003 as the dimensions of semiconductor devices are scaled down, in order to achieve higher levels of integration, optical lithography will no longer be sufficient for the needs of the semiconductor industry. Sematech meeting identifies challenges to maturing. The widely used optical projection lithography requires. A maskless lithography system including an illuminating system, a slm having a nonlinear shape e. Various approaches have been investigated, including ebeam, micromachined mirror projection, and nanojet pr inting 1. As the name implies, the purpose of this column is to present lithography information in a tutorial format. This pml2 tool concept comprises a combined electrostaticmagnetic electron optical column with 200x demagnification factor. This is due to the fact that the intensity of the exposing radiation within the.
Optofluidic maskless lithography system for realtime. In this work, a novel method of double grayscale digital maskless lithography is presented for forming a curved microlens array. In this context, we propose the use of an effective throughput to consider the photomask delivery times in the case of opl. Maskless, reticlefree, lithography the regents of the.
Maskless, resistless ion beam lithography unt digital. Possible bubbling of water water temperature control to keep the refractive index constant. Principles of construction, examples of implementation of systems, as well as factors limiting their spatial resolution are discussed. On the other hand, the optical train that i used was different for the maskless system than it would be in a projection mask system. Optical projection systems use a mask to project the entire chip pattern in one. The illumination optical system, developed for 95% uniformity, is composed of flys eye lens plates, a. Photolithography, also called optical lithography or uv lithography, is a process used in microfabrication to pattern parts on a thin film or the bulk of a substrate also called a wafer. Us7160673b2 system and method for holographic fabrication. Each micromirror in the twodimensional array can be envisioned as an individually addressable element in the picture that comprises the circuit pattern desired. I will lay out the how the optics are understood in the previous systems. This places stringent data handling requirements on the design of any directwrite maskless system. In addition, to achieve the required 1nm edge placement with 22 nm pixels in 45 nm technology, a 5bit per pixel data representation is needed. In maskless photolithography also known as maskless optical lithography, the radiation that is used to expose a photosensitive emulsion or photoresist is not projected from, or transmitted through, a photomask. The present invention provides a method for maskless lithography.
Maskless lithography any one of these will require significant advances in exposure tools, resists, masks except maskless and metrology. The illumination optical system, developed for 95%. We propose an inexpensive novel rapid prototyping approach to a maskless and fully adaptive photolithographic process. University of california, berkeley 1998 a dissertation submitted in partial satisfaction of the requirements for the degree of doctor of philosophy in engineering. Optimization methods for 3d lithography process utilizing dmd. Immersion lithography lens wafer immersion lithography.
Stepandscan maskless lithography for ultra large scale. Overview immersion lithography euv lithography interference lithography imprint lithography maskless lithography ml2 eecs 598002 nanophotonics and nanoscale fabrication by p. Maskless optical projection lithography mopl is an alternative that uses slms consisting of electrically controlled micromirrors, replacing the masks in the processes of photolithography in low. Nov 30, 2006 spatial light modulators slms designed to replace photomasks for optical lithography have been designed, fabricated, and tested. Pdf a simple maskless photolithography system employing an optical microscope, a motorized stage.
We have invested 25 years in learning about projection optics, optical resists, and optical masks. Conference proceedings papers presentations journals. Maskless optical lithography could well represent a disruptive technology that changes the complexion and direction of the semiconductor industry. Electrical engineering and computer sciences in the. Osa maskless photolithography by holographic optical projection. High speed maskless lithography of printed circuit boards using digital micromirrors eric j. Williamson b a precision equipment comp any, nikon corporation, kumagaya, saitama 3608559, japan b nikon research corporation of america, 12490 n. Fabrication of microoptics elements with arbitrary. In this paper, we also developed models and analyzed the costofownership of maskless lithography zpal versus that for optical projection lithography opl. Comparison to maskless optical projection lithography.
This paper introduces the laser shaping into maskless projection soft lithography by using dmd, errordiffu. Advanced photonics journal of applied remote sensing. Optical lithography using memsbased spatiallight modulators provides an alternative means of lithography. It explains the models for the rigorous computation o. Spatial light modulators slms designed to replace photomasks for optical lithography have been designed, fabricated, and tested. Optical system with 4 m resolution for maskless lithography. Full chip characterization of compression algorithms for. Fabrication of a curved microlens array using double gray. Alternative nextgeneration lithography ngl approaches, such as extreme ultraviolet euv, xray, electronbeam, and ion projection lithography face some challenging issues with complicated. It is a very complex process of selecting an optimum lithography tool that. A versatile diffractive maskless lithography for single. Keystone error analysis of projection optics in a maskless. Mopl in which the photomask is replaced by an slm consisting of an array of micromirrors is being developed17, 18. The case for diffractive optics in maskless lithography, j.
Maskless photolithography for customiza on lumarray. Spatial light modulator for maskless optical projection. Ebeam lithography is widely used to generate nanoscale patterns in scanningbased conditions as an advanced technology. Two generic forms of maskless photolithography, image projection and focalspot writing, are compared. Maskless photolithography system deep blue university of. Photolithography, also called optical lithography or uv lithography, is a process used in. Prolith is designed to be a versatile, comprehensive submicron optical lithography model. Fabrication of microoptics elements with arbitrary surface. Pdf spatial light modulator for maskless optical projection. Maskless lithography utilizes methods that directly transfer the information onto the substrate, without utilizing an intermediate static mask, i. Each psf for maskless lithographic techniques is speci.
Maskless lithographys chief executive officer, william elder, stated, we are very pleased to have an optical development partnership with lightworks optical systems. Achieving this throughput with charged particle lithography requires currents 10,000 times larger than those presently used and. Fullfield maskless lithography projection optics nikon. Lecture 7 lithography and pattern transfer reading. Maskless photolithography via holographic optical projection. In microlithography typically radiation transfer casts an image of a time constant mask onto a photosensitive emulsion or photoresist. A particular form of focalspot writing, zoneplatearray lithography zpal, is highlighted. Maskless, resistless ion beam lithography processes by qing ji b. In the present study, an optical system is proposed for maskless lithography using a digital micromirror device dmd. A versatile diffractive maskless lithography for singleshot.
The need to precisely control the aspect ratio of 3d microstructures has led to the development of optofluidic maskless lithography ofml. Reverseabsorbancemodulationoptical lithography for. Using holographic projection allows diffractionlimited performance within the given. Mask less lithography provides solution in the form of several techniques. Highresolution maskless lithography semantic scholar. We present an inexpensive novel rapid prototyping approach to a maskless and fully adaptive photolithographic process. Amasklessstepperbased photolithographic system using a liquid crystal spatial light modulator for photopatterning on photoresist was reported. This level of control surpasses that of optical projection lithography opl which can only create patterns within a single projection plane 10,11,1719. A plurality of individually addressable and rotatable micromirrors together comprise a twodimensional array of micromirrors. Aerial image simulations were used to define the mechanical.
The projection optics 100 utilitize maskless lithography principles where the traditional mask, or reticle, is replaced by a spatial light modulator slm 104, which may take the form of a 1dimensional array of microelectromechanical mems actuators, or actuators on the scale of a few tens or hundreds of nanometers nems. Us5691541a us08645,531 us64553196a us5691541a us 5691541 a us5691541 a us 5691541a us 64553196 a us64553196 a us 64553196a us 5691541 a us5691541 a us 5691541a authority us united states prior art keywords programmable array array substrate lithography system image prior art date 19960514 legal status the legal status is an assumption and is not a legal conclusion. Jan 03, 20 the projection optics 100 utilitize maskless lithography principles where the traditional mask, or reticle, is replaced by a spatial light modulator slm 104, which may take the form of a 1dimensional array of microelectromechanical mems actuators, or actuators on the scale of a few tens or hundreds of nanometers nems. In some embodiments, an optical element can be located between the beam splitter and the slm, possibly to correct for. Sematech meeting identifies challenges to maturing maskless lithography 21 january 2005 guided by input from more than 100 industry professionals, a sematechled steering. An innovative highresolution maskless lithography system is designed employing. In the maskless lithography system, illumination is provided by any pulsed illumination system with the appropriate spectral properties dictated by the optical projection system. Maskless lithography projects a precise beam directly onto the wafer without using a. Parallel maskless optical lithography for prototyping, low. From the viewpoint of metrology and inspection, there are some challenges inherent in nil that do not arise in conventional optical lithography. Maskless optical microscope lithography system korea university. It uses light to transfer a geometric pattern from a photomask also called an optical mask to a photosensitive that is, lightsensitive chemical.
Spatial light modulator for maskless optical projection lithography j. As projection is the most widely used technique and is the. Metrology and inspection required for next generation. Na projection lens systems along with integrated microoptics, and us ing texas.
Maskless optical lithography using memsbased spatial. Reduced complexity compression algorithms for directwrite. Maskless optical lithography, as described in this paper, offers a path around many of these difficulties. In this paper we address keystone error, a significant parameter when diagnosing the misalignment of projection optics in maskless lithography systems. Instead, most commonly, the radiation is focused to a narrow beam which directly writes the image into the photoresist, one or more pixels at a time. Maskless lithography systems rotalab scientific instruments.
In accordance with an embodiment, the method includes the steps of providing a master element that includes at least one diffractive pattern at a first location with respect to a target surface, illuminating the master element to produce a first diffractive pattern on the target surface at the. Maskless photolithography system figure1a shows the maskless photolithography experimental setup in our laboratory, which consists of a uniform illumination system at 365 nm wavelength, a highspeed optical projection system for dynamic uvlight patterning, and a threeaxis computercontrolled stage for xy location and focus control. Our optical projection system is currently not diffrac. Maskless photolithography by holographic optical projection. Parallel maskless optical lithography for prototyping, lowvolume production, and. The high and rising cost of photomasks largely driven by writing times exceeding 24 h is driving the exploration of maskless lithography for applications requiring throughput about 1 cm 2 s which is about one tenth that of an optical projection exposure system. Meanwhile, dmd can be treated as a kind of spatial light modulator in digital light processing. The pattern on the slm is controlled digitally, and its image is projected onto a wafer by means of a reduction lens. Welcome to the lithography tutor, a new regular feature of microlithography world. Based on a pattern design, the motorized stage shifts a resistcoated substrate exposed by a focused beam under a microscope.
Add in zero order through a separate optical path when needed. Til in this experiment, we measure the position of a 15. Significantly lower costsofownership coupled with throughputs acceptable for mask manufacturing, mask prototyping, and lowvolumechip manufacturing are the enabling attributes of such techniques. Projection exposure systems steppers or scanners project the mask onto the wafer many. The results indicate that 32nm node lithography requirements can be met using a hybrid optical maskless homa approach. A method is disclosed for forming an array of focusing elements for use in a lithography system. Trim photomasks can be two to three generations behind the fine features, while the trim projection tools can be one to two generations behind the fine features. As the dimensions of semiconductor devices are scaled down, in order to achieve higher levels of integration, optical lithography will no longer be sufficient for the needs of the semiconductor industry.
Maskless, resistless ion beam lithography unt digital library. Techniques used for mask less lithography international journal. Future lithography systems must produce chips with smaller feature sizes, while maintaining throughput comparable to todays optical lithography systems. Synthesis of projection lithography for low k1 via interferometry. Highthroughput hybrid optical maskless lithography. Nov 25, 1997 in the maskless lithography system, illumination is provided by any pulsed illumination system with the appropriate spectral properties dictated by the optical projection system.
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