|||||||||||||||| US00556943A United States Patent (19) 11 Patent Number: 5,156,943 Whitney (45) Date of Patent: Oct
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|||||||||||||||| US00556943A United States Patent (19) 11 Patent Number: 5,156,943 Whitney (45) Date of Patent: Oct. 20, 1992 (54) HIGH RESOLUTION IMAGERY SYSTEMS 4,895,790 l/1990 Swanson et al. .................... 430/32 AND METHODS Primary Examiner-Marion E. McCamish (76) Inventor: Theodore R. Whitney, 5500 Fenwood Assistant Examiner-Janis L. Dote Ave., Woodland Hills, Calif. 91367 Attorney, Agent, or Firm-Merchant, Gould, Smith, (21) Appl. No.: 520,629 Edell, Welter & Schmidt 22 Filed: May 8, 1990 (57) ABSTRACT The current limits of resolution of multi-element optical Related U.S. Application Data systems are exceeded by reducing the number of ele ments while introducing at the critical aperture a blazed 62) Division of Ser. No. 108,435, Oct. 23, 1987, Pat. No. transmission grating having grating rings of low bend 4,936,665. ing power defined by multiple plateaus. By illuminating 51 Int. Cl’................................................ G03C5/00 the optical train with monochromatic light that consti (52) U.S. Cl. .................................... 430/321; 430/323; tutes a multiplicity of distributed sources having a sub 430/324; 430/329; 430/22 stantial temporal coherence but spatial incoherence and (58) Field of Search ................... 430/321, 329, 324, 1, by varying the slopes and widths of the grating rings, 430/2, 323, 22; 350/162.16, 162.2, 162.22; local phase delays are introduced that adjust aberrations 359/565, 569, 572 in the optical system, providing an aligned composite (56) References Cited wavefront. The system and method may be used for presenting an image, as for a wafer stepper, or for view U.S. PATENT DOCUMENTS ing an image, as in a microscope. 4,637,697 1/1987 Freeman ............................. 351/161 4,690,880 9/1987 Suzuki et al. ....................... 430/313 5 Claims, 8 Drawing Sheets Phose Phose 86 Tronsition se 7O 86 Transition Mso U.S. Patent Oct. 20, 1992 Sheet 1 of 8 5,156,943 PZT 38 Wolfer Actuator Alignment Control Systern : 34 PZT 24 (Actuatoya Winoging stepper Ya/21 Reloy 11 lens Reticle 22 Mosking Spotiot Assembly Coherence Y Rondonizer f N y its on as tas on 8 - - - - - - - - - - - - - CoherencePortio Photomask : MeasuringModulus Plane Device : Quasi-RandomFirst 42 : Phase Surfoce 3 - Beorn Shoping turninotor 6 And Exponding O Optics 1 ! LightBursts 4/ - - - - OE xposurelater SystemEssedp Control : 56 44 58 : 12 4. () is as as a . : S2 O 4. sov ----- ---------------------- wafer Pone S4 U.S. Patent Oct. 20, 1992 Sheet 2 of 8 5,156,943 Centering And Positioning Rings - ES Multi Plategy- 2ESSl Red Wavelength Rings Transmission Groting Multi Plot edu Rings 68 1. UV Wovelength 82 Transmission Groting Ti Phose Tronsitions ZZZZ2ZZZZZZZZZZZZZZZZZZZZ42ZZ Z 2ZZZZZZZZZZZZZZZZ42ZZ U.S. Patent Oct. 20, 1992 Sheet 3 of 8 5,156,943 68 7O 17 2 (12 6 4. 228 5 Bond in / Bond n + x 88 68 Tronsition7. Phose (ZezáEZFAA-li-la-ST) Outer Centering 8 Red Wovelength UV Wayelength inner Fiduciol Positioning Tronsmission Grating Transmission fiducio Rings Groting Rings Grating Rings F.G. 5 U.S. Patent Oct. 20, 1992 Sheet 4 of 8 5,156,943 Phgse T. Phose 86 Tronsition se 7O transition Second 29 Field Lens V \ | A. \ i? 24ON f f -242 94. a re- ? A. - innersedAspheric fl V \ 4. S Collimoting 58 lenses Innersed Aspheric G 9. E nder AlignmentFrom NE-NE 9 O Detector 52 ----------- U.S. Patent Oct. 20, 1992 Sheet 6 of 8 5,156,943 2O2N 7 O -First Mask SKS3S35S3-First Resist Lloyer 332ZZ44ZZZZZZ44 TSubstrote fi/ZZZZZZZZZZ-First2O6 o Plateau Aaaaaaaaaaaaaaaaaaaaa. Ocalat a vaaaaa Aaaaaaaara as - Second Mosk 06 Ex;x; Second Resist Loyer D ZZZZZZZZZZZZZZZZZZJ-Secps Pioteou 207 - (2X) ZYZZZZZZ224ZZZZZZY2YThirderry SNSSSSSSSSSSS Third ResistMosk Loyer F -Third Pioteou 2O4 (4X) FG. IO 2O A N7NSSSSSSSSy-first 6 5 4 3 2 -First ResistMask Loyer 2O4 2ZZZZZZZZZZZZZZZZZZZZZZZ Substrate B.22 ZZZZZZZZ2-xy Etch C 2222222222222 Second ResistMosk Loyer D 24 (ZZZZZZZZZZZ-2x- - - - - Etch Parra Para O array AAAAA re-Pa-Aaaaa rkeler-Third Mosk 2XSSYaYYYYYYN N A W ThirdA. ResistO Loyer ZZZZZZZZZZZ-1 Layer Etch U.S. Patent Oct. 20, 1992 Sheet 7 of 8 5,156,943 F.G. 2A 236 23O 2.P CollinnatedLight 232 T FIG. 2 B SO 23S 22-23s 252 2SO 248 Aris ce FIG. I2C 249 luminotor 27O FIG. 3 U.S. Patent Oct. 20, 1992 Sheet 8 of 8 5,156,943 5,156,943 1. 2 pattern on the wafer, an exposure is made through the HGH RESOLUTION MAGERY SYSTEMS AND photomask, with the optical system typically reducing METHODS the image a selected amount, usually five or ten times. Inherent requirements for this type of system are that This is a divisional of application Ser. No. 108,435, 5 the light energy be adequate for each exposure, that the filed Oct. 23, 1987 U.S. Pat. No. 4,936,665. exposed image be. uniform across the image, that the depth of field be sufficient and that the resolution meet BACKGROUND OF THE INVENTION the specifications of the design. These requirements are The use of high resolution optical imagery systems, as not easily met in combination, because the very small in photolithographic systems for the semiconductor 10 size of the images and the extreme precision that are industry and microscope systems for a wide variety of required greatly restrict the design alternatives that are applications, has continued to grow despite the avail available. Once the exposure is made at all positions in ability of other technologies, such as high resolution the matrix and the unfixed material is washed off, the systems based upon atomic particle matter typified by images can be checked for accuracy and uniformity of electron beams or X-rays. The greater cost and lower 15 reproduction. Optical microscopes are usually em operating convenience of these latter systems, as well as ployed for checking, on a statistical basis, the character the longer times required for the formation of images, istics of the various images. The inspection may com establish that the optical imagery systems will remain prise one or more of a combination of procedures in preferable for many applications for the foreseeable volving automatic or operator measurement of line future. However, constantly increasing requirements 20 widths or other characteristics, but all of these proce for more precise technology have taken the optical dures entail precise and high resolution magnification of imagery systems virtually to the limits of resolution the image. values which can be achieved with refractive optics. The problems of obtaining higher resolution optical For example, very large scale integrated circuits are imagery systems of practical application thus appear to constantly being reduced in size and made with higher 25 have approached a limit. Whether or not such limit component density, an objective measure of which is ultimately is found to be insurmountable with more the minimum linewidth specification. Whereas one mi complex multi-element lens systems remains to be seen. cron linewidths were suitable until recently, present Some substantially different approach appears to be objectives in the industry contemplate linewidths well needed, however, that would free optical imagery sys down into the submicron category, of less than 0.5 30 tens from the constraints on design and manufacture microns and even 0.3 microns. This requires a line reso that are inherently imposed in reconciling many higher lution for a refractive optical system of the order of order terms involved in optical design equations. Tenta several thousand lines per millimeter, which has not tive movements in this direction were made a number of heretofore been achievable with an optical imaging years ago in proposals that an aspherical element of a system of suitable aperture and depth of field. 35 special character be introduced into the lens system. In response to these problems the optical industry has These proposals are best evidenced in an article by devised progressively more sophisticated multi-element Kenro Miyamoto entitled "The Phase Fresnel Lens', lens systems using advanced lens design computer pro presented at the November 1960 meeting of the Optical grams. The advanced level of the state of the art is Society of America and subsequently published in the exemplified by the so-called "i-line' lens system, which Journal of the Optical Society of America, January 1961, utilizes a complex configuration of some twenty refrac pp. 17-20. In that article, Miyamoto also referenced tive elements of highest quality glasses. The best that earlier articles of philosophically similar nature. He this system can achieve, however, is in the range of 0.7 principally suggested that a "phase Fresnel lens' be micron linewidth resolution, because the multiple fac inserted in the pupil plane of an optical system to de tors involved in complex lens design (chromaticism, 45 form the wavefront surface passing therethrough so as coma, astigmatism, spherical aberration being in to compensate, for example, for spherical aberration. cluded), together with the problems of achieving suffi His proposals were general in nature with no consider cient uniformity and adequate wave energy at the tar ation being given to problems of achieving high trans get, establish ultimate limitations that are presently at mission efficiency, high resolution such as would ap about 0.7 micron linewidth. There are also inherent 50 proach the needs of the semiconductor industry, or limitations on manufacture when dealing with this order adequate depth of field. Miyamoto, in an example, sug of precision. For example, the best diamond turning gested the use of single layer thin film rings of a mini procedures still leave optical surfaces too rough for mum radial dimension of 0.63 mm. He did not address operation at short wavelengths (e.g. ultraviolet). the difficulties involved in fabricating a more precise The semiconductor industry, however, has devised 55 system, i.e.