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WO1998018049A1 - Formation de motifs submicroniques en utilisant la gravure optique - Google Patents

Formation de motifs submicroniques en utilisant la gravure optique Download PDF

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Publication number
WO1998018049A1
WO1998018049A1 PCT/US1997/019157 US9719157W WO9818049A1 WO 1998018049 A1 WO1998018049 A1 WO 1998018049A1 US 9719157 W US9719157 W US 9719157W WO 9818049 A1 WO9818049 A1 WO 9818049A1
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WO
WIPO (PCT)
Prior art keywords
fourier components
substrate
mask
fourier
pattern
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US1997/019157
Other languages
English (en)
Inventor
Andrew M. Hawryluk
Natale M. Ceglio
Daniel G. Stearns
Stephen P. Vernon
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
University of California Berkeley
University of California San Diego UCSD
Original Assignee
University of California Berkeley
University of California San Diego UCSD
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by University of California Berkeley, University of California San Diego UCSD filed Critical University of California Berkeley
Priority to AU49952/97A priority Critical patent/AU4995297A/en
Publication of WO1998018049A1 publication Critical patent/WO1998018049A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/70408—Interferometric lithography; Holographic lithography; Self-imaging lithography, e.g. utilizing the Talbot effect

Definitions

  • the present invention relates to optical lithography, particularly to patterning using optical lithography, and more particularly to sub-micron patterning using optical lithography for uses in applications such as giant magnetoresistive devices and devices using field emission tips, such as flat panel displays.
  • a mask pattern In traditional optical lithography, a mask pattern, sometimes called a reticle, is imaged onto a substrate, such as silicon or glass, using imaging optics, as shown in Figure 1.
  • the imaging process demagnifies the mask pattern onto the substrate, at anywhere from 1 to 10X demagnification, and the substrate is coated with a material sensitive to the imaging radiation, as shown in Figure 1. This material is often called photosensitive resist, or simply, resist.
  • the image that is projected onto the substrate is an identical copy of the pattern on the reticle, as illustrated in Figures 2A and 2B, wherein the minimum feature sizes (mfs) are the same.
  • the imaging system is assumed to have unity demagnification.
  • FIG. 3 illustrates an electric field pattern at the substrate for an imaging system with finite resolution.
  • the practical resolution of the imaging system is determined by the imaging wavelength, ⁇ , and the numerical aperture of the system.
  • the practical resolution of the imaging system i.e., the minimum feature size that can be recorded at the substrate
  • mfs 0.7 ⁇ /(na)
  • (na) is the numerical aperture of the imaging system.
  • a present-day state-of-the-art optical imaging system for lithography has a numerical aperture (na) of approximately 0.5 and utilizes a wavelength ( ⁇ ) of approximately 250nm. This results in a practical resolution limit of 350nm which is too large for certain devices, such as giant magnetoresistive (GMR) sensors for ultra-high density magnetic storage or field emission tips for flat panel displays, high speed electronics or microwave devices.
  • GMR giant magnetoresistive
  • phase shifting masks and/or modifications to the mask illumination by apodizing the condenser optics i.e., so called "off-axis illumination”
  • These techniques can improve the practical resolution by nearly a factor of approximately 1.5 for specific conditions.
  • the complexity of modern integrated circuits dictates that these techniques be applicable to a wide variety of pattern shapes and densities. This places severe restrictions on the fabrication techniques.
  • modern demagnifying optical lithographic tools and phase shifting masks often require monochromatic sources which are generally less intense than broadband sources. As a result, the actual improvement in resolution for the manufacture of complex integrated circuits is limited and the device throughput is reduced. For these reasons, these techniques have not been readily accepted by the manufacturing community.
  • Giant magnetoresistive (GMR) sensors for ultra-high density magnetic storage are very promising and offer advantages over traditional display and information storage technology.
  • various devices using field emission such as flat panel displays and random access memory (RAM) devices, such as a dynamic random access memory (DRAM), a static random access memory (SRAM), and a magnetic random access memory (MRAM) are being actively developed.
  • DRAM dynamic random access memory
  • SRAM static random access memory
  • MRAM magnetic random access memory
  • these device concepts may require the ability to fabricate periodic or quasi-periodic structures with sub-quarter micron features. While it is possible to fabricate these devices in a research environment to test these devices, traditional high resolution fabrication technologies, such as proximity print x-ray, EUV lithography, or electron and ion beam lithographies are immature technologies, are very slow or are too expensive for large scale, commercial manufacturing.
  • Laser interference lithography employs a laser beam and relies on the coherent properties of the laser to produce a sinusoidal pattern at the substrate.
  • the throughput of the laser interference lithography process is generally limited by the practical power limitations in the laser beam.
  • the electric field pattern produced at the substrate is a sinusoidal pattern on a constant ("DC") background when the power in the two laser beam arms is not identically balanced. This is illustrated in the electric field pattern of Figure 6B. This background exposure limits the latitude of this process.
  • the structure produced by laser interference lithography is periodic everywhere and it is difficult to produce an arbitrary pattern.
  • the light (or radiation) diffracted by the reticle is captured by the imaging optics and projected onto the substrate, previously shown in Figure 1.
  • the light diffracted by the reticle can be identified by its Fourier expansion:
  • E r (x) X Bn exp (iknx)
  • E r (x) is the electric field of the diffracted light from the reticle as a function of position
  • x Bn is the electric field amplitude of the n tn diffracted order
  • kn is the reciprocal wave vector, equal in magnitude to 2 ⁇ n / pr, where pr is the period of the pattern on the reticle.
  • n 2 in Figure 1.
  • the pattern that is recorded on the substrate is the linear combination of the Fourier components that are captured by the imaging optics and projected onto the substrate. To accurately copy the pattern of the mask onto the substrate, it is necessary to capture all of the Fourier components. However, by this invention, it is possible to fabricate a different pattern on the substrate by modifying or filtering the Fourier components and this process does not require a coherent laser source.
  • the present invention involves a process whereby traditional optical lithography generates the desired high resolution pattern required for GMR or field emission devices.
  • the advantages of this approach are that 1) it can be a high throughput process suitable for large scale manufacturing, and 2) it relies on technologies that have already been developed for the mature semi-conductor manufacturing industry.
  • the present invention is directed to a process involving sub-micron patterning using optical lithography.
  • Another object of the invention is to provide a process whereby very high resolution, periodic patterns can be fabricated using optical lithography by creating an electric pattern with the required Fourier components.
  • Another object of the invention is to provide a process which involves maximizing the energy in desired Fourier components while minimizing the amount of energy in undesired Fourier components.
  • Another object of the invention is to enable the creation of an electric field pattern by maximizing the energy in desired Fourier components while minimizing the energy in undesired components using optical lithography without the use of a laser.
  • the present invention is based on the recognition that the fabrication of periodic and quasi-periodic electric field patterns, such as for GMR and field emission devices, requires the existence of desired Fourier components in the electric field, and in some cases, the absence of undesired Fourier components.
  • This invention recognizes that very high resolution, periodic and quasi-periodic patterns can be fabricated using optical lithography by creating an electric field pattern with the required Fourier components.
  • the invention involves techniques that may be employed to maximize the energy in these desired Fourier components while minimizing the amount of energy in the undesired components.
  • the invention utilizes optical imaging for the fabrication of sub-micron structures for GMR and field emission devices, for example, and does not require a laser with monochromatic illumination and/or spatial coherence.
  • Advantages provided by the present invention include a high throughput process suitable for large scale manufacturing, and reliance on technologies that have already been developed for the mature semiconductor manufacturing industry.
  • the invention can be carried out using different techniques for generating the required Fourier components.
  • a first technique uses a reticle (mask) that is specifically fabricated to generate the desired Fourier components.
  • a second technique utilizes filters (apodizers) in the imaging system to adjust the amplitudes of the diffracted Fourier components so that when they recombine at the substrate they will produce the desired pattern.
  • a third technique involves producing the desired electronic field pattern at the substrate by combining the first and second above-described techniques, which may include using partially transparent filters or wave plates.
  • the present invention involves a process: using optical lithography for the fabrication of sub-quarter micron structures for field emission devices by: 1) using a specially fabricated reticle (with the appropriate phase shift and line to space ratio) to generate the necessary Fourier coefficients so as to generate a pattern at the substrate with a smaller spatial period; or 2) modifying the diffracted light from a reticle (through either modifications to the condenser illumination or by attenuating or shifting the relative phase of the Fourier components) to generate a pattern at the substrate with a smaller spatial period; or a combination of 1) and 2) above.
  • Figure 1 schematically illustrates a prior art optical lithography system generally used in semiconductor manufacturing.
  • Figures 2A and 2B illustrate an electron field pattern of mask and substrate under ideal (infinite resolution) imaging conditions.
  • Figure 3 illustrates a practical electron field pattern from a real (finite resolution) imaging system.
  • Figure 4 illustrates an embodiment of a GMR structure which can be produced using the process of the present invention.
  • Figure 5 illustrates an embodiment of a field emission device which can be produced using the process of this invention.
  • Figures 6A and 6B illustrate a laser interference lithography system and the electric field pattern of the system at the substrate.
  • the present invention is directed to sub-micron patterning using optical lithography and particularly to a process for sub-micron patterning for giant magnetoresistive (GMR) devices, such as sensors for ultra-high density magnetic storage, or for field emission tips for flat panel displays, DRAMs, SRAMs, and MRAMs.
  • GMR giant magnetoresistive
  • the pattern that is recorded on the substrate is the linear combination of the Fourier components that are captured by the imaging optics projected onto the substrate.
  • To accurately copy the pattern of the mask or reticle onto the substrate it is necessary to capture all of the Fourier components.
  • This invention sets forth and identifies the techniques for the fabrication of sub-quarter micron structures for GMR and field emission devices, for example, using optical imaging of larger structures and modifying the energy in the components of the Fourier expansion of the diffracted light.
  • the basis of the present invention is the recognition that the fabrication of periodic and quasi-periodic patterns (such as for GMR or field emission devices), requires the existence of specific (desired) Fourier components and, in some cases, the absence of other (undesired) Fourier components.
  • the present invention as described in detail hereinafter, involves:
  • the first step in the process of this invention is to determine which Fourier components are desired at the substrate. This is determined by analyzing the Fourier transform of the desired pattern at the substrate. Assuming that the desired pattern is periodic with a period, pd, then the Fourier expansion of the desired pattern is: n where Ed(x) is the electric field of the desired pattern as a function of position, x, An is the electric field amplitude of the nth diffracted order, and kn is the reciprocal wave vector, equal in magnitude to 2 ⁇ n / pd- Comparing this electric field pattern to the electric field pattern from the reticle:
  • Er( ⁇ ) Bn exp (iknx) n it is possible to fabricate the desired electric field pattern from the electric field pattern at the reticle provided the period at the reticle, pr, is an integer multiple of the desire pattern, pd, and the Fourier coefficients from the reticle, Bn, are made to match their corresponding Fourier coefficients for the desired pattern, An. Matching the Fourier coefficients can be accomplished by 1) modifying the phase and amplitude of the diffracted electric field pattern from the mask through modifications to the line-to-space ratio on the mask and the phase shift through the lines (relative to the spaces), and 2) by filtering (or attenuating) the diffracted electric field pattern in the imaging system through apodizers.
  • FIG. 7 shows an imaging system similar to that of Figure 1 and thus corresponding components have been given similar reference numerals.
  • the resulting electric field pattern at the substrate in Figure 7 is a period pattern with a period smaller than the original (mask) pattern.
  • an electric field pattern with half the period of the original pattern is generated; i.e., a new pattern with half the minimum feature size of the original pattern is generated at the substrate.
  • an integral divisor i.e., 2 times smaller, 3 times smaller, and 4 times smaller, etc.
  • a reticle mask
  • the second technique to fabricate these structures is to use filters (apodizers) in the imaging system.
  • filters apodizers
  • the purpose of these filters is to adjust the amplitudes of the diffracted Fourier components so that, when they combine at the substrate, they will produce the desired pattern.
  • Figure 7 illustrates a simple example of this technique.
  • Figure 7 illustrates a GMR structure wherein an array of rectangular members 20 are formed on a substrate 21.
  • the sub-micron array of members 20 are constructed of magnetic materials, or as illustrated, alternating layers 22 of magnetic materials and layers 23 of non-magnetic materials.
  • the array of members 20 may be constructed so that each pattern has, for example, a width, w, of 20-500nm and a length, 1, of 200-5000nm.
  • Figure 5 illustrates a flat panel display, for example, wherein an array of sub-micron field emission tips or pillars 30 are formed on a substrate 31.
  • the tips or pillars 30 typically have a dimension, d, of 10-500nm and are spaced every 200-2000nm, as indicated at s.
  • the present invention provides for sub-micron patterning using optical lithography, and is particularly applicable for sub-micron patterning for GMR and field emission devices, such as flat panel displays and RAM devices.
  • the process of this invention enables the use of traditional optical lithography to generate the desired high resolution pattern for GMR and field emission devices.
  • This approach can be used in a high throughput process suitable for large scale manufacturing, and it relies on technologies that have already been developed for the optical lithography industry.
  • the process simply involves the generation of required Fourier components, and this is accomplished using two techniques.
  • the first uses a mask that is specifically fabricated so as to generate the desired Fourier components
  • the second uses filters (apodizers) in the imaging system to adjust the amplitudes of the diffracted Fourier components or physically blocks undesired Fourier components. Also, these two techniques can be combined to produce a desired electric field pattern at the substrate.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
  • Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)

Abstract

La présente invention concerne un procédé d'utilisation de gravure optique classique permettant de générer un motif haute résolution dans une réserve (13) sur un substrat (12). Le processus reconnaît que la fabrication de motifs périodiques et quasi périodiques requiert des composants de Fourier spécifiques et, dans certains cas, l'absence desdits composés de Fourier non désirés. Le processus implique une détermination, des composants de Fourier désirés, une analyse de la transformée de Fourier du motif par comparaison du motif de champ électrique désiré avec le motif du champ électrique au niveau du masque. Des techniques variées peuvent être utilisées de façon à générer les composants de Fourier désirés, comportant l'utilisation d'un masque (10) ou de filtres (15) ou une combinaison des deux.
PCT/US1997/019157 1996-10-22 1997-10-21 Formation de motifs submicroniques en utilisant la gravure optique Ceased WO1998018049A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU49952/97A AU4995297A (en) 1996-10-22 1997-10-21 Sub-micron patterning using optical lithography

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US73482696A 1996-10-22 1996-10-22
US08/734,826 1996-10-22

Publications (1)

Publication Number Publication Date
WO1998018049A1 true WO1998018049A1 (fr) 1998-04-30

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7161684B2 (en) 2000-02-15 2007-01-09 Asml Holding, N.V. Apparatus for optical system coherence testing
US7242464B2 (en) 1999-06-24 2007-07-10 Asml Holdings N.V. Method for characterizing optical systems using holographic reticles
US7440078B2 (en) 2005-12-20 2008-10-21 Asml Netherlands B.V. Lithographic apparatus and device manufacturing method using interferometric and maskless exposure units
US7443514B2 (en) 2006-10-02 2008-10-28 Asml Holding N.V. Diffractive null corrector employing a spatial light modulator
US7561252B2 (en) 2005-12-29 2009-07-14 Asml Holding N.V. Interferometric lithography system and method used to generate equal path lengths of interfering beams
US7751030B2 (en) 2005-02-01 2010-07-06 Asml Holding N.V. Interferometric lithographic projection apparatus
US7952803B2 (en) 2006-05-15 2011-05-31 Asml Netherlands B.V. Lithographic apparatus and device manufacturing method
US8264667B2 (en) 2006-05-04 2012-09-11 Asml Netherlands B.V. Lithographic apparatus and device manufacturing method using interferometric and other exposure
US8934084B2 (en) 2006-05-31 2015-01-13 Asml Holding N.V. System and method for printing interference patterns having a pitch in a lithography system

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4947413A (en) * 1988-07-26 1990-08-07 At&T Bell Laboratories Resolution doubling lithography technique
US5343292A (en) * 1990-10-19 1994-08-30 University Of New Mexico Method and apparatus for alignment of submicron lithographic features
US5650632A (en) * 1994-12-28 1997-07-22 International Business Machines Corporation Focal plane phase-shifting lithography

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4947413A (en) * 1988-07-26 1990-08-07 At&T Bell Laboratories Resolution doubling lithography technique
US5343292A (en) * 1990-10-19 1994-08-30 University Of New Mexico Method and apparatus for alignment of submicron lithographic features
US5650632A (en) * 1994-12-28 1997-07-22 International Business Machines Corporation Focal plane phase-shifting lithography

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7242464B2 (en) 1999-06-24 2007-07-10 Asml Holdings N.V. Method for characterizing optical systems using holographic reticles
US7804601B2 (en) 1999-06-24 2010-09-28 Asml Holding N.V. Methods for making holographic reticles for characterizing optical systems
US7161684B2 (en) 2000-02-15 2007-01-09 Asml Holding, N.V. Apparatus for optical system coherence testing
US7751030B2 (en) 2005-02-01 2010-07-06 Asml Holding N.V. Interferometric lithographic projection apparatus
US7440078B2 (en) 2005-12-20 2008-10-21 Asml Netherlands B.V. Lithographic apparatus and device manufacturing method using interferometric and maskless exposure units
US7561252B2 (en) 2005-12-29 2009-07-14 Asml Holding N.V. Interferometric lithography system and method used to generate equal path lengths of interfering beams
US8264667B2 (en) 2006-05-04 2012-09-11 Asml Netherlands B.V. Lithographic apparatus and device manufacturing method using interferometric and other exposure
US7952803B2 (en) 2006-05-15 2011-05-31 Asml Netherlands B.V. Lithographic apparatus and device manufacturing method
US8934084B2 (en) 2006-05-31 2015-01-13 Asml Holding N.V. System and method for printing interference patterns having a pitch in a lithography system
US7443514B2 (en) 2006-10-02 2008-10-28 Asml Holding N.V. Diffractive null corrector employing a spatial light modulator

Also Published As

Publication number Publication date
AU4995297A (en) 1998-05-15

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