Showing papers on "Photomask published in 1996"

Exposure apparatus and method

Abstract: An exposure apparatus for reducing/projecting a plurality of patterns of a photomask, which are elongated in at least two different directions, onto a substrate through the photomask includes a polarized light source for illuminating the photomask, a polarization control unit for changing the direction of polarization of polarized light from the polarized light source, a slit filter arranged at a position where the polarized light is focused and having a slit-like opening portion elongated in a direction perpendicular to the direction of polarization of the polarized light, the slit filter transmitting polarized light, of the polarized light passing through the photomask, which has the direction of polarization, a unit for changing the direction of the opening portion of the slit filter in synchronism with a change in direction of polarization of polarized light which is made by the polarization control unit, and a unit for illuminating the photomask with the polarized light at each position where the direction of the pattern becomes parallel to the direction of polarization of the polarized light, thereby exposing a pattern, formed on the photomask, onto the substrate at the angle of a direction of polarization perpendicular to an incident plane of light incident on the substrate.

Process for detecting defects in photomasks through aerial image comparisons

Abstract: The present invention provides a process for performing automatic inspection of advanced design photomasks. In a preferred embodiment, an aerial image of a portion of a photomask is generated. A simulated image corresponding to original pattern data is also generated. The aerial image and simulated image are then compared and discrepancies are detected as possible defects.

Optical proximity correction halftone type phase shift photomask

Abstract: In a halftone type phase shift photomask, a patterned halftone layer is formed on a transparent substrate, and a light screen layer is formed on the halftone layer. A part of a mask pattern is changed from opaque to halftone, thus improving the resist pattern fidelity.

Photomask inspection method and inspection tape therefor

Abstract: A method of inspecting a photomask for use in photolithography which accounts for the rounding of corners of features that occurs during manufacture of the photomask. A data tape used in the preparation of the photomask is first provided. An inspection tape is then prepared by modifying the data on the data tape to account for rounding of the features during preparation of the photomask. Finally, an inspection device is used to compare features on the photomask to data on the inspection tape corresponding to such features.

Photo mask and method for manufacturing same

Abstract: A photo mask and method for manufacturing the same increase the capacitance of a capacitor by improving the proximity effect of a mask pattern. The photo mask includes a transparent substrate, an opaque mask pattern for defining an optical transmission area on the substrate, and an optical transmittance control film pattern for suppressing proximity effect in the optical transmission area. The proximity effect is suppressed by forming an optical transmittance control film pattern in the transmission area between the individual portions of the opaque mask pattern, so that the mask pattern shape can be exactly transferred onto a substrate.

Fidelity ratio corrected photomasks and methods of fabricating fidelity ratio corrected photomasks

Abstract: Methods of fabricating a photomask including a correction exposure utilizing a correction exposure mask. The methods include exposing a photoresist with an activating agent utilizing a predetermined exposure pattern with a first exposure dosage. The photoresist is also exposed with a correction exposure dosage of an activating agent using a correction exposure pattern. The correction exposure dosage is less than the first exposure dosage. The correction exposure pattern may include a portion of the predetermined exposure pattern having a low pattern fidelity ratio. Photomasks fabricated according to the methods of the present invention are also provided.

Method of phase shift mask fabrication comprising a tapered edge and phase conflict resolution

Abstract: A method for forming a phase shifting photomask is provided. The method includes forming a transparent substrate having a pattern of opaque features and determining areas of phase conflicts between the features. Phase shifters having a tapered edge are formed on selected portions of the features in the phase conflict areas while the remaining portion of the features remain unprotected. During a subsequent lithographic process using the photomask, the tapered edges of the phase shifters spread out the electric field so that an image corresponding to the tapered edges does not print at the target. This permits the phase shifters to be located without the constraints of an alternating aperture pattern. The phase shifters can be formed using an additive process in which a phase shift layer is deposited over the opaque features or using a subtractive process in which the substrate subjacent to the opaque features is etched.

Manufacture of semiconductor device

Abstract: PROBLEM TO BE SOLVED: To provide a manufacture for a semiconductor device, capable of accurately patterning a film to be etched according into a desired shape. SOLUTION: This method includes a step of forming a pattern 100 having an angle α in a film to be etched, a step of manufacturing a first photomask formed with a mask pattern 101 having a side β', and a second photomask formed with a mask pattern 102 having a side γ' so as to form an angle α', in response to an angle α by intersecting between the side β' and the side γ' when both the photomasks are overlaid each other, a step of patterning a silicon oxide film formed on the film to be etched by the use of the first photomask, a step of patterning the silicon oxide film by the use of the second photomask; and a step of etching the film to be etched by the use of the oxide film patterned as a mask.

Mask specifications for 193-nm lithography

Abstract: It is now generally accepted, that optical lithography will be the mainstream approach to manufacture the I Gbit DRAM device generation with minimum features between I 80 nm (first working samples) and I 50 nm (projected fabrication). This development demands a considerable tightening of mask specifications. The printing of 180 nm I 150 nm features on a 193 nm-, 0.6 NA- tool is a highly non-linear pattern transfer process (ki = 0.56 I 0.47). Therefore, mask irregularities (defects, linewidth variations) will print easier than at larger dimensions. This paper presents results of full lithography simulations for the printability of mask linewidth variations and mask defects. Assuming, that the wafer linewidth error budget is shared between the lithography process and the mask as it is currently done (75% for the process, 25% for the mask), the linewidth uniformity on a mask has to be better than 12 nm for 180 nm designrules and better than 8 nm for 150 nm designrules. Masks have to have no defects larger than 100 nm resp. 70 nm (all those numbers are given at the 4x mask!). These numbers are almost a factor of 2 tighter than assumed in published mask specification roadmaps. Besides tightening the current specifications, the mask roadmap has to include other important parameters: We show, that the butting error of the mask writing tool, corner rounding, and the quality of the mask repair have substantial impact on the linewidth error on the wafer. Since mask defects print proportional to the squareroot of their area, the definition of mask repair quality has to be revised. Current mask repair processes cannot provide adequate repair quality. Since masks with these specifications are - in our point of view - not easy to make, we propose to reevaluate carefully the sharing of the wafer Iinewidth error budget. In other words, 193 nm lithography must dedicate a significantly larger portion of its (actually not so large) process window to the mask. Keywords: Optical Lithography, Mask Specifications, Mask Defect Printability, Mask Repair, Linewidth Error Budget

Production of photomask

Abstract: PROBLEM TO BE SOLVED: To lessen the damage of light shielding film patterns by washing and to prevent the occurrence of mask defects by embedding the light shielding film patterns in the transparent substrate of a mask and flattening the mask surface. SOLUTION: A part of the transparent substrate 1 is selectively etched to form grooves 4. A light shielding film 5 is deposited over the entire surface of the transparent substrate formed with these grooves 4. The light shielding film 5 is polished until the surface of the light shielding film is flattened. The light shielding film is etched back until the transparent substrate surface is exposed to allow the light shielding film 5 to remain only within the grooves 4. As a result, the photomask surface may be flattened. The remaining of the foreign matter in the pattern edge parts of the light shielding film 5 is eliminated, the occurrence rate of the defect is lowered and the improvement in the capability to remove the foreign matter is simplified. The transmittance of the light shielding film 5 is made uniform by using a CMP and phase differences are made uniform as well in the case of a halftone mask. COPYRIGHT: (C)1998,JPO

Method for alignment mark regeneration

Abstract: The contact or via hole etch pattern photomask used in fabrication of integrated circuits is modified to provide a series of grooves or trenches to be etched in the silicon oxide layer simultaneously with the contact or via holes. These trenches, after deposition and planarization of tungsten metal layer, afford regenerated alignment marks with sharply-defined edges even after deposition of a second conductive layer.

Phase shift photomask and phase shift photomask dry etching method

Abstract: A phase shift photomask capable of being produced by dry etching with adequate in-plane uniformity of pattern dimension even if there is a large difference in exposed area ratio between different areas on the mask. In a phase shift photomask having an area provided with a phase shift layer which practically shifts the phase relative to another area, a dummy etching pattern (13) for dry etch rate correction is provided in an area other than a pattern exposure area (9 and 10), or a dummy etching pattern for dry etch rate correction having a size less than the limit of resolution attained by transfer is provided in the pattern exposure area, thereby reducing the etch rate nonuniformity due to the pattern density variation in the process of dry etching the phase shift photomask, and thus providing a phase shift photomask of high accuracy.

Phase shift layer-containing photomask, and its production and correction

Abstract: The present invention relates particularly to a process for producing phase shift layer-containing photomasks, which can produce phase shift photomasks through a reduced or limited number of steps to reduce or limit the incidence of phase shifter pattern deficiencies or other defects and at lower costs as well. For instance, a photomask blank of the structure that a substrate is provided thereon with an electrically conductive layer and a light-shielding thin film in this order is used to coat a starting material for spin-on-glass uniformly on a light-shielding pattern formed thereon. A pattern is directly drawn on the coaxed-spin-on-glass layer with energy beams emanating from electron beam exposure hardware, etc., and the substrate is developed with a solvent after pattern drawing with energy beams to wash off an excessive spin-on-glass portion other than the spin-on-glass layer irradiated with the ionizing radiations. Finally, the post-development substrate is baked to form a phase shifter pattern.

Photomask-pattern-shape evaluation method, photomask, photomask manufacturing method, photomask-pattern forming method, and exposure method

Abstract: A pattern-shape evaluation method for a photomask used in a photolithography process is provided in order to accurately evaluate pattern corrections performed against the optical proximity effect within mask-line-width latitude, exposure latitude, and the depth of focus. The pattern-shape evaluation method comprises the steps of: specifying a plurality of evaluation patterns to be formed on a photomask and specifying two of the three kinds of latitude; obtaining the transfer pattern corresponding to each of the evaluation patterns with a quantity related to the remaining latitude being changed as a changing quantity; obtaining the sizes of portions on the transfer pattern at the positions on the transfer pattern corresponding to a plurality of measurement points specified in advance on each of the evaluation patterns; and obtaining the minimum value of the changing quantity as the remaining latitude within the two kinds of latitude specified according to the obtained sizes of the transfer pattern and comparing the obtained latitude for each of the evaluation patterns.

One-step lithography for mass production of multilevel diffractive optical elements using high-energy beam sensitive (HEBS) gray-level mask

Abstract: Micro-optics such as diffractive optics and computer generated holograms are essential components for modern optical design To reduce their unit fabrication cost we describe a method of reproducing micro-optics in quantities A true gray-level mask was fabricated in High Energy Beam Sensitive (HEBS)-Glass by means of a single e-beam direct write step This gray-level mask was used in a optical contact aligner to print a multilevel Diffractive Optical Element (DOE) in a single optical exposure A chemically assisted ion beam etching process has been used to transfer the DOE structure from the resist into the substrate

Photomasks and a manufacturing method thereof

Abstract: A half-tone film, a light-shielding film and resist are formed on a transparent substrate in this order, and the resist is removed by adjusting the dosage of exposure for each area so that film-thickness differences are provided. A predetermined pattern is formed on the half-tone film and the light-shielding film by utilizing the film-thickness differences. This half-tone pattern is a pattern to be copied onto resist on a wafer. Further, the light-shielding film is formed between the inside edge of a scribe line that separates chips from each other and the peripheral edge of the photomask. Thus, it becomes possible to prevent multiple exposure that tends to be generated upon conducting exposure using the step-and-repeat system, and also to maintain high light contrast by using a half-tone film.

Method and apparatus for producing scanning data used to produce a photomask

Abstract: The invention provides a method for generating scanning data used to control a photomask production system for producing a photomask for use in semiconductor production so as to produce a photomask having a pattern corrected in terms of the optical proximity effects wherein it is possible to perform data processing and data conversion associated with the correction in terms of the optical proximity effects without introducing significant rounding errors, and it is possible to make correction in terms of the optical proximity effects without increasing the time required to produce the photomask, and furthermore it is possible to easily deal with a change in the process condition such as the resist exposure condition. In the method for generating scanning data used to control the pattern exposing operation of a pattern exposure apparatus of the raster scanning type or of the vector scanning type so as to form a pattern on a photomask, wherein the pattern formed according to the above scanning data is corrected so that when a pattern is formed in a resist by exposing the resist to exposure light via the above-described pattern formed on the photomask, the deformation of the resultant pattern formed in the resist is minimized, the scanning data is generated by the process including the steps of: generating scanning data on the basis of mask data received from the outside; and correcting the scanning data produced in the previous step according to a predefined correction method thereby generating the corrected scanning data.

Pattern transfer at k1=0.5: get 0.25-um lithography ready for manufacturing

Abstract: In pattern transfer, as in any other method of information transfer, the output is usually a nonlinear function of the input. Lithography at the limit of resolution is an excellent object to demonstrate this. Printing structures smaller than 300 nm with a 4 X 0.5NA tool, the derivative of the pattern transfer function, or the ratio of pattern size variations on the wafer over pattern size variations at the mask level, is not a 4:1, as one would expect from the demagnification of the step and scan tool. In other words, below 300 nm, mask linewidth variations (for example butting errors of the mask writing tool) print at about twice their expected size. In the concept of the pattern transfer function, a mask defect is viewed as a localized variation in the linewidth of the mask. The printing of a mask defect therefore depends strongly on the slope of the pattern transfer function. Defects smaller than 200 nm on the mask already cause a significant linewidth variation on the wafer, if those defects are in a regular array of 250 nm lines/300 nm spaces or in 300 nm contact holes. Lithogrpahy in a manufacturing environment means to deliver the designed pattern over large areas using real masks. We discuss our strategies of how we try to minimize the influence of mask irregularities in 0.25 micrometers lithography for the development of the 256M DRAM. Although certain improvements are possible, the nonlinearity of the pattern transfer function at low k obviously demands extremely tight mask specifications beyond the limits of current tools and processes.

Apparatus and method for identifying photomask pattern defects

Abstract: An apparatus and method for inspecting photomask pattern defects, discriminating true defects from false ones, efficiently detects only the true defects. The apparatus includes a light source; an irradiation section for transmitting light from the light source to a photomask; a light detecting section for detecting the light passing through transparent parts of the photomask; an image processing section for acquiring image data of the pattern according to signals from the light detecting section; a first condition setting section for setting a coordinate threshold that defines a misregistration defect in the pattern; a second condition setting section for setting an area threshold that defines an area defect of the pattern; a testing section that determines whether the coordinates of a pattern feature and the area of the pattern satisfy the thresholds upon comparison to a second pattern; and an output section for outputting a signal indicating a defect only when at least one of the thresholds is exceeded.

Photomask manufacturing process and semiconductor integrated circuit device manufacturing process using the photomask

Abstract: In order to improve the inspection efficiency of a photomask having a phase shifter pattern, the inspection of the photomask having the phase shifter pattern is divided into three steps, an anomaly extraction step, a first anomaly discrimination step and a second anomaly discrimination step. These inspection steps are performed at different inspection regions. An anomaly extraction station 7 for the anomaly extraction inspects the presence or absence of an anomaly for all the regions of the photomask 1. An anomaly discrimination station 8 for the anomaly discrimination classifies the content of the anomaly. A phase difference measurement station 9 for the anomaly discrimination measures the phase difference error.

Method of forming opaque border on semiconductor photomask

Abstract: The present invention provides a method of fabricating photomasks having a border region and a pattern region, which may be electrically isolated. The border region may include a nontransparent region, such as an opaque chrome layer. The pattern region may include a substantially nontransparent region, such as a leaky chrome layer. The methods of the present invention include placing the photomask in an electrochemical cell and electrically connecting a portion of the photomask to an electrode, and applying a potential, thereby electrochemically transferring a layer between the electrochemical cell and the photomask.

Photolithographic process for mask programming of read-only memory devices

Abstract: A photolithographic process which provides reduced line widths or reduced inter-element line spaces for the circuit elements on an IC chip, allowing the IC chip to have a higher degree of integration. The photolithographic process includes a double-exposure process on the same wafer defined by placing either the same photomask at two different positions or by using two photomasks. In the first exposure process, a first selected set of areas on the photoresist layer is exposed through the photomask. In the second exposure process, the photomask is shifted to predetermined positions interleaving or overlapping the positions where the first selected set of exposed areas are formed, or alternatively a second photomask replaces the first photomask. The second photomask has a plurality of patterns arranged in positions correspondingly interleaving or overlapping the positions where the first selected set of exposed areas is formed. The exposure light then illuminates the wafer again so as to expose a second selected set of areas on the photoresist layer. The first and second selected sets of exposed areas in combination constitute a layout for the circuit elements which are to be subsequently formed. Through the photolithographic process, the circuit elements are doubled in density compared with the corresponding patterns on the photomask and can be formed with a reduced line width or inter-element space.

Transfer method for non-critical photoresist patterns

Abstract: A method of direct transfer printing of a photoresist pattern layer onto the first pattern layer of a phase shift photomask reticle is described which allows completion of the photomask pattern at a much lower cost than the conventional multiple-pass photolithographic process. The direct transfer of the resist pattern from printing plate to mask surface by means of a platen is especially suitable for non-critical regions such as border regions, seal bands, identification marks, and the like.

Liquid crystal display device and a method of fabricating the device using transparent-electrodes as a photomask

Abstract: Disclosed is a liquid crystal display device which includes a pair of substrates interposing a display medium including a polymer and liquid crystal therebetween and transparent-electrode portions formed on at least one of the pair of substrates, the transparent-electrode portions not easily transmitting light within a certain wavelength range.

Method of checking alignment accuracy in photolithography

Abstract: In a photolithographic step in the fabrication of semiconductor integrated circuits, alignment of the photomask pattern with two patterns defined on the wafer in two previous steps is checked simultaneously. Each of the two patterns on the wafer is provided with an alignment check pattern consisting of a plurality of rectangular pattern elements arranged parallel to each other in a row at a first constant pitch. The pattern elements of one check pattern are respectively opposite to the pattern elements of the other check pattern. On the photomask there is an alignment check pattern consisting of a plurality of rectangular and relatively long pattern elements arranged parallel to each other in a row at a second constant pitch. In the composite layout of the three alignment check patterns, each pattern element of the check pattern on the photomask partly ovelaps a pattern element of each of the two check patterns on the wafer. Alignment accuracy is checked by examining which pattern element of the check pattern on the photomask is in accurate alignment with a pattern element of each check pattern on the wafer. Alignment of the photomask pattern with more than two patterns on the wafer can be checked in the same manner.

Process for fabricating multi-level read-only memory device

Abstract: A process for fabricating multi-level semiconductor ROM devices is disclosed. Each memory cell of the ROM device can be programmed to any of three possible conduction states including full-conduction, half-conduction and no-conduction. The fabrication process begins with a semiconductor silicon substrate. Buried bit and word lines are formed in the substrate. A photomask is then formed to correspond to code to be programmed into the ROM device. The photomask, when properly aligned over the ROM device, contains portions that fully cover the entire channel region of a cell to be programmed for full conduction, portions that partially cover the channel regions of cells that are to be programmed for half-conduction, and portions that do not cover at all the channel regions of cells to be programmed for no-conduction. Then ions are implanted with the photomask in place. The ions transform the regions not covered or partially covered by the photomask. In use, three levels of conduction current may then be sensed when the ROM device is accessed to represent three data levels.

Halftone phase shift photomask, halftone phase shift photomask blank, and method of producing the same comprising fluorine in phase shift layer

Abstract: A halftone phase shift photomask having a sufficiently high transmittance for light of short wavelength and usable for high-resolution lithography effected by exposure using deep-ultraviolet+radiation, e.g., krypton fluoride excimer laser light. The halftone phase shift photomask has on a transparent substrate a halftone phase shift layer which includes at least one layer composed mainly of a chromium compound. The chromium compound contains at least fluorine atoms in addition to chromium atoms. A transmittance higher than a predetermined level can be obtained even in exposure carried out at a relatively short wavelength. The photomask can be used for exposure using deep-ultraviolet+radiation, e.g., krypton fluoride excimer laser light (wavelength: 248 nm). Thus, high-resolution lithography can be realized. Since the photomask can be formed by approximately the same method as in the case of the conventional photomasks, it is possible to improve the yield and reduce the cost.

Frame-supported dustproof pellicle for photolithographic photomask

Abstract: Proposed is a frame-supported pellicle used for dustproof protection of a photomask in the photolithographic patterning work for the manufacture of electronic fine devices such as LSIs, VLSIs and the like by mounting thereon. The inventive frame-supported pellicle is characterized in that the pellicle frame, to which a pellicle membrane is adhesively bonded on one of the end surfaces, is partly subjected to smoothing treatment. The inventive frame-supported pellicle can solve the heretofore unavoidable problems of dust particle deposition on the photomask even under dustproof protection with a pellicle as well as the high cost of the preparation of the pellicle and the difficulty of finding of any dust particles deposited on the surface of the frame.

Method and apparatus for the fabrication of semiconductor photomask

Abstract: The present invention provides a method and apparatus of fabricating photomasks. The photomasks may be fabricated from a photomask blank structure having multiple layers. Upon patterning of these multiple layers by standard photolithographic processes, a photomask is created which is capable of phase-shifting incident light by various degrees, which may be 0°, 60°, 120°, and 180°.

Cylindrical photomask, its production and method for forming dynamic pressure generating groove using cylindrical photomask

Abstract: PROBLEM TO BE SOLVED: To remarkably shorten the exposure time and to form a minute and accurate pattern by obtaining a metallic cylindrical photomask by electroforming. SOLUTION: A photoresist layer is formed on the surface of a shaft base material and then exposed through a photomask having a desired dynamic pressure generating groove pattern to form the cured photoresist layer conforming to a desired dynamic pressure generating groove pattern on the base material surface. A metallic layer is then formed on the part other than the cured photoresist layer by electroforming, and the cured photoresist layer and the base material are removed to obtain a metallic cylindrical photomask 7. The photomask is engaged with a part 11 to be exposed with a photoresist layer 10 formed on the surface of the part 91 to be worked of a body 9 where a dynamic pressure generating groove is to be formed, exposure is conducted, the photomask 7 is detached, the photoresist layer is developed, and a dynamic pressure generating groove is formed on the body 9 by etching. COPYRIGHT: (C)1997,JPO