WO1981003628A1 - Process for forming a defect-free photomask or repairing defects in an existing photomask and product thereof - Google Patents

Process for forming a defect-free photomask or repairing defects in an existing photomask and product thereof Download PDF

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Publication number
WO1981003628A1
WO1981003628A1 PCT/US1981/000825 US8100825W WO8103628A1 WO 1981003628 A1 WO1981003628 A1 WO 1981003628A1 US 8100825 W US8100825 W US 8100825W WO 8103628 A1 WO8103628 A1 WO 8103628A1
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WO
WIPO (PCT)
Prior art keywords
substrate
photomask
defect
radiant energy
coating material
Prior art date
Application number
PCT/US1981/000825
Other languages
English (en)
French (fr)
Inventor
J Campi
Original Assignee
Master Images Inc
J Campi
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 Master Images Inc, J Campi filed Critical Master Images Inc
Publication of WO1981003628A1 publication Critical patent/WO1981003628A1/en

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Classifications

    • 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
    • G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
    • G03F1/68—Preparation processes not covered by groups G03F1/20 - G03F1/50
    • G03F1/72—Repair or correction of mask defects

Definitions

  • This invention relates to a technique for producing and repairing reticles and photomasks useful in the fabrication of integrated circuits and related devices. More particularly, this invention in one embodiment relates to a technique for producing defect-free photomasks. Description of the Prior Art
  • Photosensitive resist materials play an important part in the production of monolithic circuits.
  • the use of such photoresist materials is based on their capability in permitting the "engraving" of circuit patterns of specific dimensions in a predetermined monolithic substrate material, as for instance silicon. This is effected by means of a photolithographic process where a two-dimensional pattern corresponding to the circuit design is first imaged on the photoresist coated substrate surface by employing a suitable exposure mask. Through a subsequent developing process, the desired resist patterns are obtained on the substrate surface. In this process, the photoresist serves as a protective system for those areas of the substrate surface that have not been bared by the preceding photolithographic process.
  • photoresist systems are classified into negative-working and positive-working systems.
  • a negative-working photoresist is one which after exposure is insoluble in a (developing) solvent,, whereas the unexposed resist areas are dissolved by the "developer.”
  • a positive-working resist th.e photoresist is altered under exposure in such a manner that it is subsequently soluble in the developer.
  • the exposed areas of the resist film are removed during developing, and the bared unprotected areas on the substrate surface correspond to the transparent areas on the photomask.
  • the quality of the mask is of vital importance.
  • the mask like a photographic negative, (or positive) will duplicate any flaw or defect onto the photosensitive resist film.
  • the first category is that of opaque defects. These defects obstruct the passage of light preventing the exposure of the photoresist.
  • One such process is to isolate the defect with the aid of a photoresist coating.
  • the resist film protects the adjacent geometries leaving the defect exposed.
  • the defect is then subjected to an etchant that removes it from the mask.
  • Another method employs a laser beam focused onto the defect area, striking the defect with sufficient energy to vaporize it from the substrate.
  • Another object of the invention is to provide a process for repairing transparent defects in the opaque portions of a photomask.
  • the objects of the invention are achieved by applying a coating that absorbs radiant energy onto a surface of a transparent substrate and then utilizing a laser beam or other source of intense radiant energy to fuse the coating and substrate surface in selected areas.
  • the laser beam provides a source of controlled, localized thermal energy which is passed through the substrate and onto the coating at the interface between the substrate and the coating.
  • the result is that the thermal energy applied to the coating produces a baking of the coating onto the substrate as well as a skin-melting of the substrate surface closest to the coating.
  • This baking action in effect, alters the glass surface from a smooth finish to an irregular one consisting of a mixture of the substrate material and coating material which is capable of interrupting the transmission of light. Skin-melting of metallic surfaces is described in detail in U.S. Patent No.
  • Figure I is an illustration of the visual appearance of three common types of clear defects in a chrome mask (lOx reticle);
  • Figure II shows a higher magnification of a clear intrusion into an opaque pattern seen in Figure I;
  • Figure III shows a higher magnification of a broken geometric pattern seen in Figure I;
  • Figure IV shows a higher magnification of a pinhole defect seen in Figure I;
  • Figure V is an illustration of. the visual appearance of the defect areas after repair process is completed
  • Figure VI shows the defect area in Figure II having a different surface character after the repair process is completed
  • Figure VII shows the defect area in Figure III having a different surface character after repair process is completed
  • Figure VIII shows the defect area in Figure IV haying a different surface character after repair process is completed
  • Figure IX is an illustration of the visual appearance demonstrating the opacity of the invention. Using the repaired lOx reticle shown in Figure V, a 1x photomask was produced without the defects in Figure I;
  • Figure X is a microphoto of treated area
  • Figure XI is a higher magnification of Figure X.
  • Figure XII is an illustration of the process of the present invention.
  • a process for forming a defect-free photomask overlying a substrate transparent to radiant energy which comprises applying to a photomask or reticle containing clear defects, a coating material which absorbs radiant energy, directing a beam of coherent or other intense radiant energy through the substrate onto the coating in the clear defect areas so as to fuse the coating and substrate at their interface and form an opaque mixture thereof in the irradiated areas, thereby eliminating the defect in the photomask, and then removing from the photomask surface any unfused coating material.
  • the coating applied to the defect-containing photomask may be any coating material that absorbs (does not substantially transmit) radiant energy. Its function is to trap and contain the radiant energy which is passed through the substrate material from the source and to convert that energy into heat.
  • This conversion desirably occurs at the interface of the coating and the substrate such that the heat trapped at this interface fuses the coating and the substrate surface.
  • the coating is essentially organic in nature, such fusion will, in fact, be more in the form of degradation and carbonation (of the coating) resulting in a highly carbonized residue on the substrate.
  • Inorganic coatings typically will also be fused (melted) but may be preliminarily unaffected if of sufficiently high melting point. In either case, i.e., organic or inorganic coating materials, the heat generated from the beam of radiant energy causes a surface (skin) melting of the substrate material and a concurrent mixing of the melted, degraded or unaffected coating.
  • a treated substrate surface results comprising, in the case of organic coatings and inorganic coatings subject to melting in the process, a melted or thermally degraded layer overlying a mixed layer of organic coating/substrat which in turn overlies the "skin-melted" substrate.
  • the inorganic coatings may be unaffected by the interface heat and, as such, the treated areas of the substrate will be substantially two layers, an inorganic coating/substrate mix overlying a skin-melted substrate layer.
  • the treated area (coating and substrate mixture) must be at least 400 ⁇ in thickness. Lesser treatment must be of sufficient opacity in the mask to be effective for the purpose intended. Any thickness in excess of 400 ⁇ is therefor satisfactory but economics, e.g., time of repair, etc., become increasingly important as treatment depths increase.
  • the depth, of treated area is
  • the coating material should be applied to the substrate in sufficient thickness to act as a barrier to the radiant energy beam supplied by the laser and, as such, can be of any thickness as long as the trapped energy is converted into heat sufficient to effect melting of the substrate surface.
  • satisfactory coating thicknesses have been found to be about 300 ⁇ to about 500 microns, preferably 800 ⁇ to 100 microns, most preferably 5 to 35 microns. While power outputs of greater intensity than disclosed herein are capable of producing the desired fused, opaque areas, the amount of thermal energy generated is of such character and intensity as to possibly disrupt adjacent photomask geometries.
  • a radiation-treated area that is more opaque than the untreated areas results.
  • the coating is applied to defect—containing areas in a photomask, such greater opacity does not materially affect the subsequent use of the photomask for imaging.
  • the photomask itself is created by the irradiating operation, as described below, a photomask of sharper image formation occurs.
  • the coatings found of particular use in the process of this invention include those generally known to those skilled in the art as laquers, paints and varnishes, and encompass both the organic and inorganic type coatings normally used for decorative finishing or protective purposes.
  • Such include, for example, enamels, glazes, intremescent coatings, mastics, polishes, waxes, stains, and dyes.
  • the coatings primarily of an organic nature useful herein are those based on styrene butadiene, latexes, starch polymers, cellulose ethers and esters, rosin and modified rosins and resins, urea and melamine resins, vinyl resins and vinyl emulsions.
  • the coatings primarily of an inorganic nature useful herein are those employing pigments of iron oxide, copper and copperous oxide, lead, lead oxide and salts thereof, zinc oxide and salts thereof, titanium dioxide, chrome, chromic oxide and salts, thereof, antimony and antimony oxide, aluminum and aluminum oxide, and diatomaceous earth.
  • Metals such as silver, silver oxide and salts thereof, nickel and nickel oxide and salts thereof, gold, gold oxide and salts thereof, mercury, mercury oxide and salts, magnesium, magnesium oxide and salts thereof, lithium, rubidum, cesium, gallium, indium, and thallium.
  • the inorganic coatings contain a form of granular cargon, e.g., lampblack, furnace black, carbon black, animal, vegetable and mineral blacks or graphite, most preferably chromic oxide.
  • a form of granular cargon e.g., lampblack, furnace black, carbon black, animal, vegetable and mineral blacks or graphite, most preferably chromic oxide.
  • the actual molecular composition of the opaque coatings herein are not critical as long as the coating functions to trap sufficient thermal energy so as to "melt" and fuse the coating/substrate interface as described above.
  • the substrates of use herein are typically those employed in the present semiconductor technology and include glass, quartz, silicon, germanium, sapphire, etc. The main criteria for such being only that it be transparent to the radiant energy utilized in the process.
  • a further embodiment of the present invention contemplates a process for forming a substantially defect-free photomask overlying a substrate transparent to radiant energy which comprises applying to the transparent substrate a coating which absorbs radiant energy; directing a beam of radiant energy through the substrate onto the absorbing coating in a predetermined photomask pattern; fusing the coating/substrate interface; and removing from the substrate surface the unfused coating material.
  • a photomask pattern is thereby provided on the substrate surface without requiring the use of the usual prior art techniques of first coating the substrate surface with a photoresist material, exposing such, photoresist through a mask, etc., to obtain a photomask on the surface of a substrate.
  • the radiant energy sources presently available are, of course, readily programmable so as to. move in a predetermined (computer-controlled) pattern to effect the desired layout of opaque areas on the substrate surface.
  • the radiant energy generating source is a Florod Manual Zapper I Model LMT. This equipment utilizes a xeonon laser tube which produces a beam that travels down through a microscope top objective. A variable aperture system, controls the beam size (1-25 microns) and produces the desired power levels.
  • a defective reticle (10x mask) was manufactured with a chromium film and a sodalime glass substrate (3"x3"x.060"), Figures I, II, III and IV.
  • the defective area was coated with, a fluid comprised of 50% isopropol alcohol and 50% titanium dioxide pigment.
  • the coating was applied by means of a cotton swab and allowed to dry. (Coating thickness varied between 35 microns, to 45 microns.)
  • Coherent radiation from the laser was applied to the defective portion of the mask, the laser beam size being 15 microns in diameter at 5 pulses a second with each pulse lasting for one microsecond, the power supply being set at 3,000 volts to generate approximately 40 electron volts in the laser tube.
  • the glass surface was then cleaned with acetone and examined under a microscope. The results shown in Figures V, VI, VII and VIII show that the glass surface and the coating material have fused and intermingled giving a highly opaque surface.
  • the reticle was next subjected to a cleaning process. It was subsequently submerged in chromic acid for 30 minutes at 45°C in an attempt to remove the residue. The adhesion of the material to the glass was found to be good through the cleaning processes. Using a film thickness analyzer (Tencore Alpha Step) the surface texture was examined. The resulting measurement determined that the laser burned valleys into the glass surface up to 5,000 ⁇ . It was also observed that the treated area formed a "coating" approximately 10,000 ⁇ thick on the substrate ( Figures XI and XII).
  • the reticle was then mounted into a David Mann/GCA 3095 Photorepeater. This equipment used a 10x reduction lens and a 350 watt Merc Arc Lamp to produce ultraviolet light at 436 nanometers. This optical system reduces the image on the reticle ten times, projecting it onto a photoresist coated substrate. It is used here to test the opacity of the treated area. An exposure matrix was performed to test this interaction under different exposures. An exposure series was started at one second, progressing to five seconds in half second intervals with a light intensity of 225 mw/cm 2 at the image plane.
  • Figure IX illustrates the results with a nominal exposure time of two seconds.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Preparing Plates And Mask In Photomechanical Process (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)
PCT/US1981/000825 1980-06-19 1981-06-18 Process for forming a defect-free photomask or repairing defects in an existing photomask and product thereof WO1981003628A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US16097880A 1980-06-19 1980-06-19
US160978 1980-06-19

Publications (1)

Publication Number Publication Date
WO1981003628A1 true WO1981003628A1 (en) 1981-12-24

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EP (1) EP0054068A1 (enrdf_load_stackoverflow)
JP (1) JPS57501747A (enrdf_load_stackoverflow)
WO (1) WO1981003628A1 (enrdf_load_stackoverflow)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4466992A (en) * 1982-05-28 1984-08-21 Phillips Petroleum Company Healing pinhole defects in amorphous silicon films
EP0095094A3 (en) * 1982-05-24 1984-10-03 Hitachi, Ltd. Photomask with corrected white defects
WO2004011258A3 (en) * 2002-07-31 2004-07-29 Motorola Inc Method of forming and repairing a lithographic template having a gap defect
WO2013185401A1 (zh) * 2012-06-15 2013-12-19 深圳市华星光电技术有限公司 一种光罩及其修正方法
US8741506B2 (en) 2012-06-15 2014-06-03 Shenzhen China Star Optoelectronics Technology Co., Ltd. Mask and repairing method therefor

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2803259B2 (ja) * 1989-12-12 1998-09-24 三菱電機株式会社 マスクのパターン欠け欠陥の修正方法

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
IBM Technical Disclosure Bulletin Volume 7, No. 3, issued August 1964 ROSHON et al, "Printing by Means of a Laser Beam" *
IBM Technical Disclosure Bulletin Volume 7, No. 3, issued August 1964 ROSHON et al. "Printing by Means of a Laser Beam" *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0095094A3 (en) * 1982-05-24 1984-10-03 Hitachi, Ltd. Photomask with corrected white defects
US4466992A (en) * 1982-05-28 1984-08-21 Phillips Petroleum Company Healing pinhole defects in amorphous silicon films
WO2004011258A3 (en) * 2002-07-31 2004-07-29 Motorola Inc Method of forming and repairing a lithographic template having a gap defect
US7063919B2 (en) 2002-07-31 2006-06-20 Mancini David P Lithographic template having a repaired gap defect method of repair and use
WO2013185401A1 (zh) * 2012-06-15 2013-12-19 深圳市华星光电技术有限公司 一种光罩及其修正方法
US8741506B2 (en) 2012-06-15 2014-06-03 Shenzhen China Star Optoelectronics Technology Co., Ltd. Mask and repairing method therefor

Also Published As

Publication number Publication date
EP0054068A1 (en) 1982-06-23
JPS57501747A (enrdf_load_stackoverflow) 1982-09-24

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