Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Reexamination Certificate
1999-01-15
2001-03-13
Rosasco, S. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
C355S053000
Reexamination Certificate
active
06200709
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an apparatus and method for the photolithographic manufacture of devices, and more particularly to an apparatus and method for using a photolithographic mask in the manufacture of devices.
BACKGROUND
Photolithography is a well known technique in the manufacture of many kinds of devices, and finds particular use in the semiconductor industry. Photolithography is very effectively employed in the mass production of semiconductor devices. However, it suffers from a drawback in the manufacture of devices which are required in very small numbers, and in the prototyping of devices. Photolithography is a method which uses masks. The cost of making many expensive masks may be prohibitively high if a product is to be manufactured in quantities of only a few units, or if a prototype has to be modified multiple times during development. Some of the methods which have been developed to try to avoid these difficulties include device modeling and direct write technology.
Device modeling generally uses a computer to calculate, or “model,” the behavior of a circuit or other device of interest. While modeling can provide important insights into the expected behavior of devices, and is generally faster and less expensive to perform than the actual fabrication of the modeled device, one obtains only a calculated result, and not an actual device of interest. Furthermore, modeling generally requires that simplifying assumptions be made to provide a tractable mathematical representation of the device under investigation. These simplifying assumptions generally cause the calculated answers to be approximations to the actual behavior of real devices.
Direct write technology generally employs a method of “writing” the patterns representing the various layers or levels of a device without a mask, by the direct illumination of a substrate with a very finely focused beam, such as an electron beam.
The patterns to be created or “written” are generally maintained in digital form in the memory of a digital computer, and are used to scan the electron beam over the surface of the substrate, and to turn the beam on and off as appropriate to generate the desired pattern. While the method can be used to produce devices, it typically suffers from the difficulties that the equipment required to carry out the process is generally more expensive than photolithography equipment, and that the process is generally slower than production using photolithography.
SUMMARY OF THE INVENTION
A photolithographic system is presented which uses a mask that carries a plurality of photolithographic images. In one aspect, the invention includes a photolithographic mask having a plurality of images which are suited to the manufacture of multiple device cells of more than one type. In one embodiment the cells may include such types as digital circuitry, analog circuitry, micromechanical devices, microelectromechanical devices, electrooptic devices, optoelectronic devices, and electronic sensor devices. In another embodiment, the mask includes a set of images for one cell that requires more than one layer for its manufacture.
In another aspect, the invention comprises a photolithographic system for employing photolithographic masks which have a plurality of images. The system includes a source of electromagnetic radiation, a substrate support, a mask positioner, and an adjustable aperture which can be moved and which is positioned between the source of electromagnetic radiation and the substrate support. An embodiment of this system includes an aperture which has a plurality of individually movable screens.
Still another aspect of the invention is a photolithographic process for the manufacture of a device. The process includes the steps of providing a source of electromagnetic radiation, supporting a substrate of material suitable for photolithographic processing, and positioning a photolithographic mask having a plurality of images in registry with the substrate. An aperture is positioned between the source of electromagnetic radiation and the substrate so as to permit a first image to be projected onto the substrate and the substrate is exposed to electromagnetic radiation through the aperture to imprint the first image upon the substrate. The photolithographic mask is then repositioned relative to the substrate so that a second of the images is in registry with the substrate. The aperture is then repositioned to permit the second image to be projected onto the substrate, and the substrate is reexposed to electromagnetic radiation through the aperture to imprint the second image upon the substrate. This process is repeated as many times as necessary to imprint the images required to manufacture the desired device, one layer at a time. In an embodiment of this invention, a processing step is interposed between the step of imprinting the first image and the step of imprinting the second image.
REFERENCES:
patent: 5932884 (1999-08-01), Aizaki
patent: 5994006 (1999-11-01), Nishi
patent: 5995200 (1999-11-01), Pierrat
Mitwalli Ahmed
Nuytkens Peter R.
Cohen Jerry
Custom One Design, Inc.
Erlich Jacob N.
Perkins Smith & Cohen LLP
Rosasco S.
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