Showing papers on "Photomask published in 1969"

Inspection of integrated circuit photomasks with intensity spatial filters

Abstract: Spatial filtering is shown to be an effective method for integrated circuit photomask inspection Results show that errors of 02 mils can be detected using f/95 lenses and that the use of f/20 lenses detects errors of below 01 mil Contamination, missing and added features, and step and repeat errors are all displayed The method allows the observation of nonperiodic errors and can be used immediately for contamination inspection with very little increase in sensitivity The procedure only needs alignment of the mask in rotation, and means that the mask can be totally inspected by scanning it through a laser beam

Photomask inspection by spatial filtering

Abstract: This disclosure describes an optical spatial filtering technique for detecting hole-type defects and excess spot defects in photomasks used in making microcircuits. An approximate form factor intensity filter provides suppression of the regularly shaped mask features. For masks with features whose boundaries are along only the X-Y direction, this filter advantageously is a cross placed in the transform plane. With rectangular features suppressed, only nonrectangular defect data passes. Spots as small as 0.1 mil are detected and displayed on a TV monitor; or, using a photomultiplier tube, signals are stored on an oscilloscope or by a recorder for analysis, or counted with a pulse counter. Masks or circuits on opaque substrates are also inspected by this method.

Photomask inspection by optical spatial filtering

Abstract: An intensity-type optical spatial filtering system is arranged to form a composite visual image of all nonperiodic errors in a photomask or other two-dimensional pattern which contains an array of regularly spaced, normally identical elements. A coherent beam of light is diffracted by the pattern and focused onto a transparency having a second array of discrete opaque regions spaced by a distance inversely proportional to the element spacing on the pattern. The focused light, spatially modulated by the transparency, is reimaged and projected in enlarged form onto a display screen.

Method of generating high area-density periodic arrays by diffraction imaging

Abstract: High area-density arrays, such as diode array vidicon camera tube targets and electron tube electrode screens, are made by photolithographic printing utilizing a photomask diffraction image rather than a photomask shadow for exposing a photoresist masking layer. To form the masking layer, a relatively flat photoresist layer is exposed to a periodic array diffraction image from a photomask. The exposed portions of the layer are removed, leaving an array of unexposed portions. Alternatively, the unexposed portions of the layer may be removed, leaving an array of exposed portions. During the exposure, the layer is oscillated over a distance of essentially one-quarter the wavelength of the light and in a direction substantially perpendicular to the surface of the layer to avoid the appearance of interference fringe patterns after development.

Automatic holographic wafer positioning system and method

Abstract: System and method for automatic alignment of workpieces such as semiconductor wafers and a photomask for subsequent image exposure. Alignment is based on the transparency of the wafers to infrared light and the opaqueness thereto of alignment patterns fabricated in the wafer. A holographic optical system generates a Fourier transformed image of light transmitted through the wafer and cross-correlates the transformed image with a complex spatial filter to generate recognition spots of light having spot displacements corresponding to the waferfilter nonalignment. The spot displacements generate an error signal used to control the wafer position.

Photomask regeneration by intensity spatial filtering

Abstract: An intensity-type spatial filtering technique is employed to generate a corrected replica of a two-dimensional photomask or other pattern containing an array of regularly spaced elements which exhibit nonperiodic errors. A coherent beam of light is diffracted by the mask and focused onto a transparency containing an array of discrete transparent regions against an opaque background. The regions are spaced by a distance inversely proportional to the element spacing on the pattern. The focused light is spatially modulated by the transparency to suppress nonperiodic information contained in the focused light. The spatially modulated light transmitted by the filter is refocused on a photosensitive film which, when developed, defines an array of elements corresponding exactly to the array on the test pattern with the nonperiodic errors removed.

Step and repeat photomask and method of using same

Abstract: A method is described for exposing a layer of photoresist so as to eliminate the defects which would otherwise be caused by a defective photomask. The method utilizes a unique mask in which the repetitive opaque patterns are identical except that the patterns in alternate rows are slightly larger than the patterns in the other alternate rows. The photomask is aligned with the photoresist in the usual manner and the photoresist exposed. Then the photomask is indexed one row and the photoresist again exposed so that all areas of the photoresist are double exposed through different portions of the photomask, yet the edges of the unexposed areas are defined by a single exposure corresponding in size to the patterns in the rows which have the larger opaque areas.

Method of fabrication of photomasks

Abstract: A PHOTOMASK HAS MULTILAYER OPAQUE PLATTERNS ON A TRANSPARENT SUBSTRATE. EACH PATTERN INCLUDES A BOTTOM LAYER AND A TOP LAYER, EACH OF A MATERIAL CAPABLE OF BEING ETCHED BY A SUBSTANCE WHICH WILL NOT ETCH THE SUBSTRATE, AND AN INTERMEDIATE LAYER OF A MATERIAL CAPABLE OF BEING ETCHED BY A SUBSTANCE WHICH WILL NOT ETCH THE BOTTOM AND TOP LAYERS. THE SEVERAL LAYERS COMPENSATE FOR DEFECTS IN EACH LAYER. AN IMPROVED PHOTOMASK FABRICATION METHOD INCLUDES FORMING THE ABOVEMENTIONED PATTERNS BY SUCCESSIVELY DEPOSITING THE BOTTOM AND INTERMEDIATE LAYERS, PHOTOETCHING THE INTERMEDIATE LAYER INTO A DESIRED PATTERN, DEPOSITING THE TOP LAYER, AND THEN PHOTOETCHING THE TOP AND BOTTOM LAYERS INTO A DESIRED PATTERN.

Apparatus and method utilizable in forming metal grids

Abstract: Apparatus and method for forming metal grids The apparatus includes a support, carriage, photomask, photolamp, and interferometer A photographic plate is positioned on the support and the photomask is attached to the carriage which is translated to thereby carry the photomask across the photographic plate The interferometer allows repetitive exposure of the plate by the photolamp via the photomask by measuring the position of the carriage and by controlling a photolamp trigger circuit for flashing the photolamp when predetermined carriage positions are sensed by the interferometer The photomask contains a single slit through which light rays from the photolamp pass whereby the successive flashing of the photolamp is operative to form a pattern of parallel, closely spaced image patterns in the photographic plate The thus exposed photographic plate is developed and the resultant photographic master is replicated in a sequence of steps resulting in the formation of a metal grid on a target substrate Salient features of the apparatus and method contribute to the successful provision of metal grids characterized by substantially uniform spacing between parallel adjacent grid lines which increases the range of applications in which the grids can be utilized

Manu of thin film structures on substrates - and use of such structure, as photomasks

Abstract: First of all a layer of material which can easily be removed is deposited on the substrate. This is then partially removed in a desired pattern and a further layer of a strongly adhesive material is deposited on that part of the first layer that remains, both layers then being removed as one structure. The structure may be used as a photomask for integrated circuit manufacture or alternatively as an electrical conductor.

Method of making high area density array photomasks having matching registry

Abstract: The method comprises: PRINTING A MASTER PHOTOMASK HAVING AN ARRAY OF OPAQUE ELEMENTS ON A PHOTOGRAPHIC PHOTOSENSITIVE LAYER WITH OVEREXPOSURE; DEVELOPING THE OVEREXPOSED PHOTOSENSITIVE LAYER TO PRODUCE A SUBMASTER PHOTOMASK, THE SUBMASTER HAVING AN ARRAY OF SMALLER, OPAQUE ELEMENTS, AND REPEATING THE STEPS OF PRINTING BY OVEREXPOSING AND DEVELOPING A NUMBER OF TIMES, USING THE SUCCESSIVE SUBMASTERS IN PLACE OF THE MASTER TO PRODUCE A SUBSEQUENT SUBMASTER PHOTOMASK, THE SUBSEQUENT SUBMASTER HAVING OPAQUE ELEMENTS SUBSTANTIALLY SMALLER THAN THE ELEMENTS OF THE MASTER AND HAVING MATCHING REGISTRY WITH THE MASTER.