Showing papers on "Photomask published in 1980"

Photo method of making tri-level density photomask

Abstract: A method of fabricating a photomask having at least three distinct zones of light transmissibility is disclosed. A first mask is made from a predetermined pattern, this mask having only two distinct zones of light transmissibility. A second mask, made by contact printing of a diazo film, is formed from a selected portion of one zone of the original pattern, which zone has the greater light transmissibility. The second mask, being a contact print, is the photographic opposite of the first. The two masks are then aligned with the selected portion of the second mask superimposed over its original location in the first mask and a composite latent image thereof is formed in a suitable emulsion. This composite image is then developed and fixed on an appropriate support to form a photomask having at least three density zones.

High resolution lithography system for microelectronic fabrication

Abstract: Master and working photomasks are made using a photoresist darkened on and bonded to respective quartz substrates. The working photomask is formed by deep ultraviolet light exposure through an electron beam patterned master mask. Deep ultraviolet light is also used to pattern a resist on a silicon slice through the working mask. The same resist is preferably used on the slice and both masks.

Manufacturing of photomask substrate

Abstract: PURPOSE:To minimize occurrence of pinholes on chamferred surface of mask substrate, by removing fine projections from the surface prior to formation of photomask. CONSTITUTION:When a photomask-making glass substrate is chamferred, numerous microcracks are caused to the surface bt fine glass projections and these microcracks become causes of occurrence of pinholes later. And therefore, after sharp corner is chamferred into round by using a grindstone is normal manner, feather-like glass projections produced on the chamferred surface are removed by polishing with a buff or leather. Or, by melting and curing these projections using etching liquid such as solution of HF, NaOH, etc., the microcracks are completely removed although the eroded surface may become rough noticeably. While the substrate surface is slightly etched, this is solved by polishing lightly with polyurethane, etc. Or, a flame may be run along the chamferred surface. And then, by preparing thin-film photomask of Cr, etc., pinhole-free mask of good quality can be obtained.

Base material for photomask

Abstract: PURPOSE:To obtain a base material for photomasks which withstands washing with a strong acid in repeated uses of the photomask, has good etchability and is suited for formation of fine patterns by providing one or more layers of imperfect oxide layers of the same metal directly or indirectly on a tranparent substrate. CONSTITUTION:In the production of a base material for photomasks for production of semiconductor devices etc., a higher oxide of a higher rate of 10 in a 90:10- 10:90 element ratio between metals and 0 and a lower oxide are provided on a transparent substrate 1. For example, an oxide of an 83:17 element ratio of Cr and O is provided to about 500Angstrom thickness to provide a lower oxide layer 2', on which a higher oxide layer 3' of 45:55 said ratio is provided to 250Angstrom thickness. In this way, the low reflection base material of thromium for photomasks of a considerably low rate of dissolution of hot concd. sulfuric acid and high etching performance is obtained. The higher yield in the production of masks and the longer life of masks are made possible by the use of this base materiral.

Negative for photomask

Abstract: PURPOSE:To obtain the title negative, which is not charged in production of a photomask, by covering both main faces of a light-transmissive substrate with light- transmissive electrically-conductive films electrically connected to each other and by attaching a pattern-forming opaque film to one main face. CONSTITUTION:Preheated light-transmissive substrate 1 is sprayed with a mixed solution of a tin chloride solution and an antimony chloride solution to form light- transmissive electrically-conductive film 6 all over the substrate 1 surface. Next, by vacuum-depositing or sputtering chromium or the like light-untransmissive metal film 2 is formed on one main face to obtain a negative (hard surface plate) for a photomask.

Method and apparatus for photoresist sensitizing process

Abstract: PURPOSE:To improve a precision of photoresist process by providing a precise thermostat on a portion where to mount photomask and wafer and also on a portion where to enclose unsensitized wafer. CONSTITUTION:There is provided a precise thermostat in an area A including a stage part 4 to mount a wafer for photoresist sensitizing process and a photomask 5 holding part and also in an area B to enclose a multitude of unsensitized wafers at a stage preceding to photoresist sensitizing process, and temperatures on those portions and room temperature are adjusted to coincide with a set temperature. A photoresist error to occur according to thermal expansion is minimized consequently to improve a pattern precision by photoresist process.

Application of Photolithography to Development of Photocathodes for Electron Optical Imaging Devices

Abstract: Photolithography was used for the replication of high resolution patterns from flat master masks to curved quartz substrates. Special Mylar photomasks were developed for contact printing of the patterns on the curved substrates, The contrast of the Chromium-Gold mask on Mylar was determined by micro-densitometry. This was followed by the deposition of thin films of gold on the patterned surface to obtain the photocathodes.This paper describes the methodology of the experimental techniques employed for such photocathode processing. The most important use of patterned gold photocathodes is in studying the electron-optical characteristics of high resolution electron devices like image tubes. A brief description of such studies carried out on an electron-optical bench is given.

Semiconductor wafer holding jig

Abstract: PURPOSE:To avoid airtrap phenomenon and sticking phenomenon, by providing absorbing part, flexible substance and blow off gate, on a jig which closely hold photomask to be used in photolighography for semiconductor integrated circuit and etc. CONSTITUTION:Hard mask (photomask) 1 is held with holder 2 by vacuum chuck 21, 22 which are air extracted by valve V2. Wafer 3 which is closely adhere with hard mask 1, is sucked by sucking hole 51, 52 and absorbed and fixed with second holder 5 and at the same time, is moved upward due to opening of valve 4 and blowing out of nitrogen gas, and is pressed against mask 1. Furthermore, from valve V1 air is blown into hollow part 6 and presses flexible rubber 4 and gives uniform adherence of wafer 3 with mask 1.

Macroelectronic Photolithography: I-The Optimization Of Photoresist Application By Roller Coating

Abstract: Macroelectronic photolithography is an extension of conventional photolithographic processes to produce high resolution patterning of thin film integrated circuits over large area substrates. Such patterns are needed in fabricating the addressing circuitry for flat panel liquid crystal displays. The first important step in macroelectronic photolithography involves the development of reliable large area coating processes for photoresist materials. This paper deals with the optimization of the roller coating process for Shipley AZ-1350 J positive photoresist to achieve a resolution of 4 μm line widths and spacings extended and distributed over 10 cm x 10 cm glass substrates. Resist viscosity, doctor bar pressure and roller/substrate interference level were investigated to achieve resist thickness uniformity of ±0.1 μm; this variation in resist thickness would cause a variation of ±0.6 μm in line width. Other problems associated with the photofabrication of thin film macrocircuits are discussed. These include mask preparation, inspection and etching processes. Anticipated solutions to these problems are briefly outlined.© (1980) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Photomask for preparation of semiconductor wafer

Abstract: PURPOSE:To enable a photomask used to be discriminated by sight when a wafer is observed, by forming a photomask so as to eneable element patterns as well as an information pattern to be transferred on the wafer. CONSTITUTION:A necessary number of element patterns connected to one another, for example, element patterns corresponding to chips 4 in the circumferential part of wafer 3 low in manufacture yield are selected from element patterns 2 drawn on the surface of photomask 1 to form indication (information) pattern 6 in place of them. Indication part 7 discriminable easily by sight is formed in addition to element pattern chips 4 on the wafer 3 printed using photomask 1 having element patterns 2 and indication pattern 6.

Double-etching technique for the fabrication of submicron channels on a GaAs wafer and its application to laser fabrication

Abstract: We demonstrate in this paper a simple, reproducible, uniform, and reliable double‐etching technique which enables us to make submicron channels on a GaAs wafer from a photomask of considerably larger dimension. Only conventional photolithographic process and preferential etching are required. The technique consists of stripping the photoresist after a first‐step preferential etching and then immersing the wafer back into the etchant to perform the second etching. As a first example, we have applied this technique to the fabrication of a channeled‐substrate planar laser using liquid‐phase epitaxy. The surface morphology of the LPE layers and the performance of the laser are shown to be of superior quality.

Inspection device for flaw of mask

Abstract: PURPOSE:To detect only such a flaw as is larger than desired by providing a scattering unit like ground glass on a main surface side in a device to detect luminous parts generated on the main surface of a photomask by irradiating a beam to the end of a light-transmissive substrate of the photomask. CONSTITUTION:A mask inspection device comprises a control box 1, a stage 3 to provide a photomask 2 thereon, a tubular cover 4 to prevent the ambient beam from coming onto the top of the photomask on the stage, and a lamp house 5 enclosing a lamp. A tungsten lamp 7 in the lamp house feeds a white beam to the photomask 2 through a projection port 16. There is arranged a ground glass 16 closely and in parallel over the stage 3. By arranging so, a luminous part relating to such a small flaw which to exerts no influence on the mask function is gradated by the ground glass, therefore only such luminous part which should be checked by the inspection can easily be observed through scattering and enlarging.

Optical flaw detection for photomasks - by angularly adjustable parallel light beam on side opposite to microscope

Abstract: Method for the optical check of photomasks, consisting of glass plates with one-sided opaque structures, by a microscope, is based on directing a parallel beam of light against the underside while the microscope is focussed on a major plane of the mask. The angle of the incident light beam is varied in the horizontal and vertical plane to prevent its perpendicular incidence on the edges of the opaque structures. These edges therefore have little brilliance under the microscope but any scratched or foreign particles adhering to the photomask after usage are clearly marked by a strong contrast. This is a low-cost method of finding and localising defects in photomasks.

Inspection for registration of photomask

Abstract: PURPOSE:To reduce the damage to master mask and to eliminate the error which takes a reference mask for other one by comparing the scale pattern of the reference mask and the pitch pattern of photomask and by measuring the deviation. CONSTITUTION:A chip pattern 4 which forms horizontal and vertical pitch purpose patterns 5, 6 of the same shaped pattern is formed in line on the surface of a photomask 2 to be measured. The same shaped pattern 7 as the patterns 5, 6 is lined up in the horizontal direction at about central line at regular intervals. And a scale pattern is formed. The following is inspection procedurse: Firstly, a pattern 7 is fixed to form a line in accordance with the transverse direction of a table 1. A pattern 5 is fixed in the same way. Secondly, a mask 2 is adjusted so that microscope images 5a' and 7a' may fall on. Thirdly, the table 1 moves by the number of (transverse pitch of a pattern 4)X(transverse pattern 4). Fourthly, the images 7b' and 5b' are superposed each other and the quantity of slight displacement is read. The same measurement is made by changing the direction of the mask 2 by 90 deg. for the table 1.

Microdensitometer Measurements Of Photomask Quality

Abstract: Summary of linewidth (b) and line separationmeasurement (a)Dimensions Measured Mean (pm) Standard Deviation (pm) a b 23.340 0.0376.005 0.033 Large scale mensurationIn an attempt to get data on the accuracy with which the LMD can make measurements over large distances,the following test was performed. In one direction, the photomask is composed of 14 individual dies. The corresponding feature (line edge) was located on each of the 14 dies. This was done by making 14 individual scans. Coordinate data recorded with each scan enabled the 14 scans to be related to an absolute coordinate system. Edge location was determined just as in the previous tests. These scans showed a mean separationbetween the dies of 6044.623 pm and a spread about the mean (standard deviation) of 0.272 pm.I have no independent data against which I could compare my results and the scans were only made once.Despite this, the results mentioned above are not inconsistent with the die to die registration required forthis particular photomask which has a minimum linewidth of -9 pm. In addition, while analyzing these data, itappeared that the photomask had moved as a result of the rapid acceleration and deceleration at the beginningand end of each scan. This only presented a problem when individual scans were referenced to an absolutecoordinate system, as in this test.This large scale mensurational capability is what is required in order to perform the registration scansreferred to earlier.112 / SPIE Vol 220 Optics in Metrology and Quality Assurance (1980)

Producing method of electron beam drawing photomask

Abstract: PURPOSE:To form a mask identification marking, a photomask coated with an electron beam resist is exposed to far ultraviolet beam through a mask having a specified pattern of the identification. CONSTITUTION:In an electron beam drawing unit, a pattern is baked on the drawing area 2 on the plate coated with an electron beam resist (chrome blank plate). An identification marking is written on the peripheral area 3 by the use of a character printer using far ultraviolet beam through a mask having a required pattern. When the plate is developed in normal procedure, both the electron beam drawing and the far ultraviolet exposed pattern are developed. This eliminates the need for consideration on the printer XY stage movement distances as is required in the use of only the electron beam drawing process. The electron beam resist used here has sensitivity to X ray and a far ultraviolet beam of 150nm-300nm wavelength and works as a positive type resist, thus allowing simultaneous development and providing simple mask identification marking.

Automatic Yield Prediction From Photomask Inspection Data

Abstract: Existing methods of predicting mask-limited device yield based on average defect density do not account for defect size or superposition of defective dice, since to do so would require a degree of computation which is not feasible with purely manual means. This paper proposes a new algorithm for computing predicted yield, and describes a system which automates the computation of this algorithm, in addition to permitting on-line collection and storage of inspection data from an automatic photomask inspection system. The use of yield predictions obtained thereby for optimizing device yield, or for apportioning the cause of actual degraded yield between the process and the masks, is also discussed.

Spray type photomask etching apparatus

Abstract: PURPOSE:To enhance etching accuracy by setting a light receiving device for receiving light transmitted through a photomask at a position away from the loci of an etching solution sprayed and detecting the etching end point according to the output of the light receiving device. CONSTITUTION:A photomask is placed on a supported rotary stand, and control section 14 is actuated to spray an etching solution from fan-shaped spray nozzle 4 as well as to rotate the stand. Light receiving device 6 is set which receives light transmitted through the mask at a position away from the loci of the solution sprayed. The output of light receiving device 6 is amplified 8 and converted into digital signals with A/D converter 9. Operation circuit 10 takes the difference between the former signal and the latter one to average the difference with a plurality of continuous dots. This output is converted into a binary code at a predetermined level, the time at which the binary code signal changes from 1 to 0 is considered as the etching end point, and the signal is sent to section 14. When section 14 receives the signal, it stops pressurizing pump 17 to stop spray of the etching solution from nozzle 4, and water is sprayed upon the mask from nozzle 22.

Photomask and its manufacture

Abstract: PURPOSE:To improve positional precision and work efficiency and facilitate to connect inspection and correction devices by providing a special pattern in addition to a semiconductor element pattern making this position as a reference origin. CONSTITUTION:When different pattern inspection and correction devices are used, under the influence of the method of fixing the photomask or the external dimensions of the photomask, deviations DELTAx, DELTAy assume different values and the position of virtual reference origin 13 is varied. For this reason, apart from semiconductor element pattern 4, origin reference pattern 8 is provided at the specified position of photomask 1, and by making it easy to detect this reference pattern 8, deviations DELTAx, DELTAy are corrected and set at the reference origin. Pattern 8 is placed at an easily detectable position on mask 1 as an origin with shape and size convenient for setting. By this structure, defective pattern 9 is detected and its position can be stored or recorded, so that the mask can be corrected easily and with high precision.

Alignment matching exposure apparatus

Abstract: PURPOSE:To obtain a high accuracy pattern preventing sticking of a photomask to a semiconductor substrate by placing the photomask on a support plate, which can deform the central part of the photomask to a convex form toward the semiconductor substrate. CONSTITUTION:A photomask supporting plate 2 is tapered at the portion contacting the photomask 1. The mask 1 supported therewith is deformed convex at the face facing the semiconductor substrate 4. Therefore, the pushed up substrate sticks to the mask 1 in the order from the center to the periphery, so that the gas left between the mask 1 and substrate 4 are driven away from the center to the periphery whereby the mask 1 and the substrate are entirely put together. With the adjustment of the thrusting pressure of a cylinder 6, they can be tightly sticked to each other. After the exposure, as the cylinder 6 is lowered, the mask is separated from the substrate in the order from the periphery. Thus, they are completely free from sticking.

Inspection device for defect of mask

Abstract: PURPOSE:To make clear a luminous part by irradiating a beam of different color from the beam irradiated to the end of a light-transmissive substrate of photomask from counter side of the mask main surface in a device to detect the luminous part on the mask main surface. CONSTITUTION:A mask inspection device comprises a control box 1, a stage 3 to provide a photomask 2 thereon, a tubular cover 4 to prevent the ambient beam from coming onto the top of the photomask on the stage, and a lamp house 5 enclosing a lamp. A tungsten lamp 7 in the lamp house feeds white beam to the photomask 2 through a projection port 16. There is provided a back lamp 10 emitting a blue or other color beam under the stage 3 consisting of ground glass, which irradiates the photomask from behind. The photomask portion other than a metallic film comes to look colored by this way of arrangement, therefore it can be discriminated clearly whether or not the metallic film is damaged internally.

Photomask substrate working method

Abstract: PURPOSE:To reduce occurrence of pinholes and enhance the yield by chamfering a photomask substrate and covering the chamfered surface having many fine protrusions with a covering material. CONSTITUTION:Glass substrate 1 for a photomask is chamfered 2 by grinding on a grindstone, and the whole chamfered surface is covered 3 with silicone or epoxy type resin or the like. Thus, the surface microcracked owing to many fine glass protrusions formed by the chamfering is covered to prevent occurrence of pinholes. On cover 3 chromium or chromium oxide film 4 is formed. Using this substrate a worked substrate applicable to manufacture a highly integrated semiconductor with a high accuracy pattern is obtd.

Mask base material

Abstract: PURPOSE:To provide high quality to a mask base material for a photomask used in manufacture of LSI, etc. by using an Si or Ge layer or an Si-Ge mixed layer, as the shielding layer of the material, to which a III or V group element in the periodic table has been added. CONSTITUTION:When transparent substrate 21 is covered with Si-Ge layer 22 as a shielding layer, hydride of a III or V group element such as B or Ga is fed together with silicon hydride and germanium hydride using H2 gas as carrier to form mask base material 22 on glass substrate 21. After coating layer 22 with resist film 24 made of polymethyl methacrylate or the like a pattern is drawn with electron beams and developed to form resist pattern 25. Exposed film 22 is then etched selectively by reactive sputtering technique to form mask pattern 26, thus manufacturing photomask 27. This pattern is of high accuracy and free from pattern deformation due to electric charging in the electron beam drawing.

Photomask for photoetching and manufacture thereof

Abstract: PURPOSE:To manufacture a high-accuracy photomask in a high yield by selectively applying radiation to a transparent substrate until the substrate screens ultraviolet and visible rays to correct or remove pinholes, etc. in a metal mask such as a photomask for an integrated circuit. CONSTITUTION:On glass substrate 1 transparent to ultraviolet and visible rays wiring or an element pattern is formed as thin layer 2 of a metal such as Cr or Ni or a metal oxide such as chromium oxide. When pinhole 3, dot 4, unsatisfactory form portion 5, etc. are present in the pattern, in order to correct pinhole 3 an area slightly larger than pinhole 3 is irradiated with radiation 7 such as gamma-Co rays while regulating the area with aperture 6 to change part 8 of transparent substrate 1 in quality so that it screens ultraviolet and visible rays. Aperture 6 is of radiation screening substance such as Au. A pattern face may directly be formed on substrate 1 by applying radiation 7 besides the correction. Thus, a high-accuracy photomask is easily manufactured in a high yield.

Photomask Mensuration With The Linear Microdensitometer

Abstract: Recent improvements to the Aerodyne Linear Microdensitometer have enabled the attainment of mensurational accuracies of 0.025- microns. This accuracy, coupled withoptical resolution capabilities of 0.5 to 1.0- microns, permits computerized photomaskinspection that allows submicron defect detection with outstanding mensurational accuracy. For photomask line widths on the order of 1- micron, mensurational accuracies of betterthan 5% of the line width are thus achieved.IntroductionThe continuing evolution of the integrated circuit is reflected in dramaticallyincreasing packing densities coupled with constantly improving cost /performance ratios.As the requirements for smaller and smaller geometries have become more demanding,increased demands have been placed on the microlithography industry to provide greater andgreater resolution. Reference 1 points toward a reduction in line widths from 5 micronsto under 1 micron in approximately a decade as the desired goal. At the same time, the

Mask positioning device

Abstract: PURPOSE:To ensure a good substrate contact and to facilitate separation of a wafer and a mask, a means is provided to perform pressure regulation of the enclosed spaces in the photomask container and in the substrate container in a mask positioning device CONSTITUTION:Mask holders 4, a photomask 2, and a transparent glass plate 3 define a space 10 The photomask 2, bases 5, and a wafer chuck 6 define a space 12 When a 3kg/cm nitrogen gas is introduced into the space 10 and the photomask 2 is convexly bent toward the semiconductor substrate 1, the substrate 1 and mask 2 become easy to separate, so positioning is very easy When the space 12 is made vacuum, the wafer chuck 6 is pushed by the atmospheric pressure, permitting the semiconductor substrate 1 to contact the photomask 2 This tends to bend the photomask 2 convexly, but regulating the pressure in the space 10 allows to provide the optimum contact condition