Showing papers on "Photomask published in 1991"

Simple CD measurement of periodic structures on photomasks

Abstract: For critical dimension (CD) metrology of photomasks, a laser scatterometer linewidth measurement tool provides noncontact rapid, and nondestructive measurement of linewidth. Calculation of the linewidth is based on a rigorous theoretical model, thus eliminating the need for calibrations. A chrome-on-glass diffraction grating is illuminated with a laser. A photodetector mounted behind the photomask measures the scattered power in each diffracted order. This provides data for the rigorous theoretical model which provides a relationship between the linewidth of the photomask grating and the fraction of total power diffracted into the transmitted zero-order. This scatterometer linewidth measurement technique provides a simple, rapid, nondestructive, and noncontact method of linewidth determination which takes into account the effect of the glass substrate on which the grating is placed. This technique is insensitive to variations in angle of incidence, spot size, position of the spot on the grating, polarization and wavelength.

Phase-shift mask pattern accuracy requirements and inspection technology

Abstract: Computer simulations and i-line phase shift lithography experiments with programmed 5X phase shift reticle defects were used to investigate the effect of opaque and phase-shift layer defects on sub-half-micron lines. Both the simulations and the experiments show that defects in the phase shift layer print larger than corresponding opaque defects, with 0.3-0.4 micrometers defects affecting sub-half-micron critical dimensions by more than the allowable 10%. Inspection of programmed phase shift defects with a prototype mask inspection system confirmed that the system finds the 0.3-0.4 micrometers phase shift defects critical to sub-half-micron lithography.

Phase-shifting photolithography applicable to real IC patterns

Abstract: A phase-shifting technique which simplifies mask fabrication and is applicable to actual IC patterns has been introduced into the i-line positive resist process. It combines edge-contrast enhancement and a chromeless mask. Although the effect of this technique on line and space patterns has turned out to be more restricted than that of the alternating mask technique, it can improve exposure and focus latitude in isolated hole patterning. The authors report on their estimation of the optimum shifter width which maximizes contrast enhancement on lines and spaces as well as on isolated hole patterns. Experimental data is presented to verify the improvements in photolithographic performance of isolated hole patterning due to this technique.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Investigation of self-aligned phase-shifting reticles by simulation techniques

Abstract: By means of simulation techniques using the SAMPLE and SPLAT programs the potential of self-aligned phase-shifting reticles for applications in microlithography is investigated and compared with conventional reticles and, to some extent, also with alternating and chromeless phase-shifter edge-line reticles. The analysis concentrates on partially coherent imaging ((sigma) equals0.5) of isolated spaces, line/space gratings and contact holes at k1 factors of 0.5 and 0.63, but wider and finer structures are also considered. The resist technique is found to have a considerable influence on the results. The work also includes a rough analysis of the necessary manufacturing tolerances of the phase reticles.

Method of preventing null formation in phase shifted photomasks

Abstract: A method of preventing null formation is performed on a phase shifted photomask including a clear quartz substrate, dark chrome feature features, and alternating clear phase shifters raised from the substrate. The phase shifter features are terminated in a transmissive, optically clear edge. To prevent null formation and consequent formation of stringers on the surface of the integrated circuit, the substantially vertical edge of the optically clear end of the phase shifter is tapered. The slope at any point along the tapered edge between the photomask substrate and the phase shifter is set to an angle, typically less than forty-five degrees, shallow enough that the point spread function does not produce an image. The point spread function of the imaging system spreads out the null, which is therefore not printed into the photoresist layer on the integrated circuit. The tapered edge of the phase shifter is created by either discrete or continuous etching methods. Both methods create the phase shifter and tapered edges simultaneously and are compatible with photomasks having either additive or subtractive type phase shifters.

Method of forming and etching titanium-tungsten interconnects

Abstract: A method of forming an interconnect, particularly a local interconnect, for a silicon substrate having integrated circuit devices between dielectric regions. Titanium disilicide is formed on electrode regions of the integrated circuit devices, whereafter titanium-tungsten is deposited across the silicon substrate. A photomask is formed and patterned to cover selected portions of the titanium-tungsten layer. The uncovered portions receive a preliminary etch of chlorine and carbon tetrafluoride to remove oxide. A second etch using trifluoromethane and oxygen removes the uncovered portions, leaving an electrically conductive interconnect extending from an electrode region onto a dielectric region leading to a second electrode region. The photomask is then removed.

Method and apparatus for measuring the dimensions of patterned features on a lithographic photomask

Abstract: A system for inspecting and measuring the dimensions of patterned features on lithographic photomasks includes a confocal scanning microscope beneath which is mounted the photomask to be inspected. The photomask is moved to permit the imaging beam from the microscope to record reflectivity information at closely spaced points along a scan line at the metal-substrate interface within the photomask, and the unpatterned side of the mask is positioned facing the microscope so that the imaging beam passes through the transparent substrate material of the mask to the desired measurement plane. An objective lens specially corrected for imaging through transparent materials is used in the optical system, and compensating glass plates may be selectively placed between the objective lens and the photomask when the substrate of the mask is thinner than the thickness of transparent material for which the objective lens was corrected.

Exploration of fabrication techniques for phase-shifting masks

Abstract: Techniques for fabrication and testing of phase-shifting masks have been explored. The masks were formed using quartz blanks with both directly etched-in phase-shifters as well as deposited SiO2 films and photoresist for the phase-shifting layer. The etched-in phase- shifters were fabricated by standard lithographic patterning and dry etching of the quartz mask surface. Phase-shifters consisting of photoresist were applied and important resist properties such as index of refraction and absorption were determined. A technique for precise control of the etched phase step using a self-terminated plasma etch into CVD SiO2 has also been explored. Printed patterns using the masks showed the expected benefits of phase-shifting. We also investigated the effect of fabrication tolerances. For example, misalignment of the auxiliary phase-shifters surrounding a contact hole has little impact on printed resist patterns. Phase-shifter parameters deviating from the optimum value were explored both experimentally and using the optical simulator SPLAT. Sloping side walls as well as absorption and interference in the phase-shifter show varying influence depending on the specific feature and the lens reduction. The tolerance in phase-shift magnitude has been examined in a number of cases, and is generally found to be in the neighborhood of 30 degree(s).

Film exposure apparatus and method of exposure using the same

Abstract: In a film exposure apparatus and method of exposure using the same which are disclosed herein, a plurality of frames arranged in a longitudinal direction of a belt-shaped film are exposed sequentially to light for transcript of an image onto each of the frames. The film exposure apparatus comprises an illumination system (10), a photomask (11) disposed at a location to which light from the illumination system is applied, a photomask position adjusting mechanism (M10), a projection lens (20) for projecting an image of the photomask irradiated, and a film feed mechanism (60) for step-feeding the film one frame by one frame. The belt-shaped film is provided with at least two or more film-side alignment marks (FM) on each frame, and the photomask is provided with a circuit pattern (MP) whose image is to be projected and transferred onto the film, and photomask-side alignment marks (MM) in correspondence to the film-side alignment marks.

Photomask blank and process for making a photomask blank using gradual compositional transition between strata

Abstract: A single pass, multiple target, continuous sputtering process for manufacturing photomask blanks comprising a single masking layer having plural strata of different composition and gradual compositional transitions between strata. Photomask blanks are useful in the process of integrated circuit manufacture.

Method for forming film of uniform thickness on semiconductor substrate having concave portion

Abstract: A photoresist of sufficient thickness to fill a scribe line is applied to an entire substrate. The photoresist is exposed through a photomask having a pattern corresponding to the scribe line and then developed. A photosensitized gelatin is applied by spincoating on the flat substrate obtained in this process, pattern and then dyed, to obtain a color filter array.

Photomask inspection device

Abstract: PURPOSE:To shorten the length of time that a pattern flaw is detected by detecting semitransparent foreign matter being present on an area which becomes a transparent pattern by distinguishing an opaque flaw from transparent flaw. CONSTITUTION:A laser beam from a laser head 11 is bisected. While the same position of the chip patterns 2A and 2B on the photomask 1 are irradiated, their entire areas are simultaneously scanned. Rays of light transmitted through the patterns are received by the corresponding photodetectors 12A and 12B. Their outputs are compared with each other by a signal processing circuit 13. According to the degree of the difference, semitransparent foreign matter 23 in a transparent pattern 22 is decided by distinguishing an opaque flaw 21X in the pattern 22 from an transparent flaw 22X in a light-shielding pattern 21. If the flaw 21X or the flaw 22X is found, the photomask is reprepared or partially corrected. If only the foreign matter 23 is found, it is rewashed.

Fabrication of grooved glass substrates by phase mask lithography

Abstract: A phase‐shifting mask without chrome opaque features can be used to print groove servo patterns for optical storage disks and provides improved contrast and resolution in printed photoresist images when used in a projection printer such as a Perkin‐Elmer MicralignTM‐500 mask aligner. Such a phase‐shifting photomask structure can be fabricated in the following way. Onto a conventional photoresist coated chrome on fused quartz photomask blank is written a pattern of concentric lines and spaces or a spiral pattern. The photoresist is developed and the exposed chrome etched in the conventional way to yield a transmission mask pattern of twice the pitch desired in the final groove pattern. The quartz is then etched, using the photoresist/chrome and/or chrome pattern as the resist, by either a wet or dry process, to a uniform depth. The chrome is then completely removed to form a ‘‘chromeless’’ phase‐shifting mask [K. K. H. Toh, G. Dao, R. Singh, H. Gaw, Proc. SPIE 1991 Symp. Microlithogr. 1463 (1991)] Phase‐sh...

Photomask with phase shifter and method of fabricating semiconductor device by using the same

Abstract: A photomask has a light shielding layer and a phase shifter based on a phase shift method, both of which are mounted on a mask substrate. The light shielding layer is shaped in a light shielding pattern, having light passing regions beside its opposite sides. The phase shifter is made by thinning the mask substrate at a portion associated with one of the light passing regions. An optical path through the phase shifter is shorter than the optical path of the other light passing region, thereby shifting the phase of light.

Process for producing a phase shift layer-containing photomask

Abstract: of EP0477035A photomask blank for preparing a reticle for use in the production of integrated circuits comprises a substrate 30, an electrically conductive layer 31, a light-shielding thin film 32 and an ionizing radiation resist 33 formed of a coated spin-on-glass layer. A pattern is directly formed on the layer 33 by electron beam exposure. After development with a solvent to give a resist pattern 35 (Fig 1c) exposed portions of the light-shielding layer 32 are etched by an etching glass plasma 36 (Fig 1d) to form a light-shielding pattern 37. The remaining resist 33 is incinerated by oxygen plasma 38 (Fig 1e) to form a photomask (Fig 1f). Next, a transparent film 39 is spin-coated over the pattern 37 (Fig 1g), and pattern-exposed to electron beam radiation 40 (Fig 1h), baked (Fig 1i) and developed to form a reticle bearing a phase shift pattern 41 (Fig 1j). The correction of defects in the phase shift layer is also disclosed.

Method of manufacturing a photomask for an optical memory

Abstract: A method of manufacturing a photomask for an optical memory, the photomask having two types of pattern where guide tracks and formatting pits are different in amount of optical transmissions, including the steps of (a) forming on a transparent substrate a thin film of which light transmission amount depends upon its thickness; (b) forming a photoresist film on the thin film; (c) exposing the photoresist film to light with different light intensities depending selectively on the guide tracks or formatting pits; (d) eliminating the photoresist film exposed to the more intense light by the development till the thin film becomes surface; (e) etching the thin film exposed to the more intense light and surfaced; (f) eliminating the photoresist film till the thin film exposed to the less intense light becomes surface; (g) etching away the thin film exposed to the more intense light and surfaced till the transparent substrate becomes surface; and (h) eliminating the remnant photoresist.

Reflection type photomask with phase shifter

Abstract: A reflection type photomask includes a substrate, and a reflecting surface formed on the substrate and including a first region and a second region which have a relative height difference Due to the concavo-convex structure of the reflecting surface, a light reflected from the first region and a light reflected from the second region have a predetermined phase difference which may be used effectively to form a pattern on a photoresist layer

Photomask and fabrication of the same

Abstract: A photomask for an ultraviolet light with a contrast of 10 or larger can be fabricated by generating a color center by irradiating a calcium fluoride crystal substrate with a KrF excimer laser (wavelength of 248 nm) with an energy of 10 J/cm 2 through an original photomask formed by a chromium film on a quartz substrate and forming a pattern by a color center corresponding to an original photomask pattern. In the same way, a similar photomask can be fabricated by irradiating a calcium fluoride crystal substrate with X-rays having a wavelength ranging from 0.5 to 1.0 nm through an original mask formed by a gold film on the silicon substrate.

Variable phase-shift mask for deep-submicron optical lithography

Abstract: A variable phase-shift mask for optical lithography, which gives several kinds of optical phase shifting to light transmitted through the mask apertures, is proposed, and image quality obtained with this mask is investigated. Clear regions with some optical phase shiftings between 0 degree(s) and 180 degree(s) are inserted between the two connected apertures, which are 180 degree(s) out of phase. The role of these inserted regions is to decrease the dip in intensity distribution, which is occasionally needed for producing complicated features. The advantages of this variable phase-shift mask and the effect of wave-front aberrations on imaging characteristics are investigated.

Novel toroidal mirror enhances x-ray lithography beamline at the Center for X-ray Lithography

Abstract: An unique lithography beamline is described that delivers x-rays using a flexible arrangement of two toroidal mirrors providing high spectral and spatial uniformity at the wafer plane. The image produced is a thin, scannable, horizontal line suitable for exposing a 25 nm X 50 nm field, compatible with submicron ULSI. The authors also present the current status of such a beamline currently under construction at CXrL for use with the Silicon Valley Group Lithography, Inc.'s 0.25 micron x-ray stepper.

Production of photomask having phase shift layer

Abstract: PURPOSE:To produce the photomask having many stages of phase shifter patterns having high accuracy with a fewer stages at a lower generation rate of defects. CONSTITUTION:After light shielding patterns 32 and phase shifter patterns 33 are formed on a transparent substrate 30, only the peripheral parts 35 of the phase shifter pattern 33 parts existing isolatedly from the light shielding patterns 32 on the transparent substrate are irradiated 34 with ions by using an ion milling method, by which the film thicknesses are decreased and phase differences are generated in the central parts in order to produce the photomask having the light shielding patterns 32 and the phase shifter patterns 33 on the transparent substrate 30 and having the phase shift layers smaller in the film thickness of the peripheral parts 35 of the phase shifter pattern parts existing isolatedly from the light shielding patterns on the transparent substrate 30 than the film thickness of the central parts.

Phase-shift mask technology: requirements for e-beam mask lithography

Abstract: Phase-shifted patterns (alternating, 90-degree, and chromeless) have been incorporated into a reticle layout, fabricated with a MEBESR III system, and evaluated experimentally at 365 nm using steppers with numerical aperture (NA) ranging from 0.4 to 0.48 and partial coherence ranging from 0.38 to 0.62. Test circuit layouts simulate actual circuit designs with critical dimensions ranging from 0.2 micrometers to 1.2 micrometers . These results, combined with experimental measurement of layer to layer registration and aerial image simulations, provide a first-order assessment of e-beam lithography requirements to support phase-shift mask technology.

Photomask cleaner, production for photomask and for semiconductor device

Abstract: PURPOSE: To provide a scrub cleaner for both side of photomask in which a particle sticking to a brush when removing the particle by rubbing the surface of the photomask with the brush does not stick to the surface of the photomask again. CONSTITUTION: A nozzle 9, to which a vibration plate 8 is adhered, is provided on an upper part of a scrub cleaning vessel 14. The vibration plate 8 gives vibration to pure water in the nozzle 9 by a ultrasonic oscillator and the particle falling down from the photomask 1 and sticking to the brush is easily removed by ejecting the pure water 10, to which ultrasonic vibration is given, from the nozzle 9 to the brush. COPYRIGHT: (C)1993,JPO&Japio

Method of manufacturing photomask

Abstract: A method of manufacturing a photomask, according to the present invention, comprises the step of entirely forming an intermediate shifter on a transparent substrate, light shielding layers and a phase shifter such that the thickness of the intermediate shifter successively varies. In edge portion of the phase shifter, thus, the phase of light is continuosly shifted from 0 to 180 degree. As in result, light intensity at the edge portion does not decrease to zero but has a relatively large value, preventing a bridge to be formed.

Fabrication of grooved-glass substrates by phase-mask lithography

Abstract: A phase-shifting mask can be used to print groove servo patterns for optical storage disks and provides improved contrast and resolution in printed photoresist images when used in a projection printer such as a Perkin-Elmer MicralignTM-500 mask aligner. Such a phase- shifting photomask structure can be fabricated in the following way. Onto a conventional photoresist coated chrome on fused quartz photomask blank is written a pattern of concentric lines and spaces or a spiral pattern. The photoresist is developed and the exposed chrome etched in the conventional way to yield a transmission mask pattern of twice the pitch desired in the final groove pattern. The quartz is then etched, using the photoresist/chrome and/or chrome pattern as the resist, by either a wet or dry process, to a uniform depth. The depth of quartz etch must be controlled as well as the width of the groove and land in the mask as well as the radius at the bottom of the etched groove walls. The chrome is then completely removed to form a 'chromeless' phase-shifting mask. Phase-shifting masks of this sort have been fabricated and used successfully to print photoresist images on glass disks yielding patterned photoresist structures of 1.5 micrometers pitch, 1.2 micrometers pitch, and 1.0 micrometers pitch. The resulting photoresist pattern could be transferred into the glass substrate by wet or dry (RIE) etch processes to generate the desired glass etch pattern after photoresist removal. Phase- shifting masks of this design require careful dimensional control in 3 dimensions. If the dimensions are not carefully controlled, the desired photoresist pattern is not obtained. For example, if the dimension of the mask groove is too large or if the bottom of the groove is rough, an alternating pattern of groove dimensions is obtained in the photoresist. Grooves etched from such a defective pattern would not be optimal for use as the servo pattern for an optical disk. One modification of the phase mask design described which simplifies the fabrication process is to alter the relative dimensions of the groove and land. If the land is made very small in relation to the groove, then the groove prints as though it were a clear feature in the transmission mask. Conversely, the land prints as though it were a chrome ('dark') feature. The contrast obtained in the image is much larger that can be obtained from a conventional transmission mask of similar dimensions. This 'darker than dark' phase- shifting mask phenomenon may prove valuable in the fabrication of complex patterns.

Phase-shift mask applications

Abstract: Phase-shifted masks (PSMs) promise significant performance benefits for conventional optical lithography. By simultaneously enhancing resolution and depth of focus (DOF), some PSM techniques offer lithography improvements equivalent to more than a 30% reduction of exposure wavelength. Existing wafer exposure equipment can be adapted to PSM use without extensive modification. However, widespread use of PSM technology must await the creation of a PSM infrastructure, including automated generation of PSM patterns, new mask-making materials, and production worthy PSM manufacturing equipment and methods. Modified CAD software, phase layer mask exposure, phase layer deposition, etch, inspection, repair, and other supporting equipment are still in research or development phases. The integration of PSM methodologies and processes to mask and wafer production facilities has not yet begun. In this paper PSM manufacturing and application issues will be examined, with emphasis on PSM reticle printing, PSM reticle requirements and PSM manufacturing alternatives. The authors report on the performance of a scanned laser mask lithography system optimized for printing multilayer phase-shift masks. This system leverages the sub-half micron printing performance of the ATEQ CORE-2500 combined with an optical alignment system. The use of 363.8 nm exposure wavelength offers significant advantages for making PSMs. Chrome alignment marks under dielectric phase and resist layers are accurately and nondestructively acquired with a nonactinic illumination system. The exposure wavelength, near i-line, does not cause or react to dielectric substrate charge. Optimum performance is achieved with common i-line resists which also provide ideal process performance for phase layer deposition and dry etching.

Photomask and its production and exposing method

Abstract: PURPOSE:To offer a proximity exposing method for resolving the micropattern of the resolution limit of the conventional proximity exposing method or below and photomask design production using it CONSTITUTION:The distribution of the amplitude and phase of photomask transmitting light is calculated so as to obtain a desired light intensity distribution on a substrate placed at a fine interval from a photomask A constitution that a micro light shielding pattern and a phase sifter are formed on the photomask, and the calculated distribution is actualized, is adopted The pattern transfer of high resolution is performed by using the conventional proximity exposing machine

Evaluation of a photoresist process for 0.75-micron g-line lithography

Abstract: A consistent 0.75 micron lithography process was developed for implementation in an existing technology environment. Prolith/2 modeling parameters were experimentally measured and photoresist simulations were performed to gain confidence in the modeling program. Experimental results fulfilled a proposed set of production process requirements, and a consistent three-quarter-micron, g-line process can be implemented in the manufacturing environment.

Method for producing photomasks

Abstract: A novel photomask structure and method of producing photomasks using a non-contacting spark-discharge recording apparatus. The recording constructions of the present invention comprise a conductive layer, a layer transparent to the radiation that will be used to expose the target photosensitive material and, optionally, a coating layer deposited over the metal layer.

Manufacture of photomask

Abstract: PURPOSE:To reduce the flaws of patterning caused by flaws of a photomask by forming accurately master patterns with the same pattern on both sides of a mask substrate. CONSTITUTION:On the surface of the substrate 1, a first master pattern 2' is formed. Next on the rear side of the substrate 1, a negative type photoresist 3 is applied in the predescribed film thickness and the surface side of the substrate 1 is irradiated with light, so that the photoresist 3 is selectively exposed by using the first mask pattern 2' as the mask and is developed and the photoresist 3 is removed selectively. On the substrate 1 on which the photoresist 3 is selectively formed, the film 4 of the mask material is formed and the photoresist 3 is removed, so that a second mask pattern 4' with the same pattern to the first mask pattern 2' is formed on the rear side of the substrate 1. Thus even when the flaws occur one either mask pattern 2' or 4', they are compensated with the other mask pattern 4' or 2' and the flaws of the patterning caused by the flaws of the photomask can be reduced.