Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-06-04
2001-09-25
Phan, James (Department: 2872)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S201100, C359S223100, C435S006120
Reexamination Certificate
active
06295153
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates in general to the field of optical chemistry, and more particularly, to an apparatus and method for conducting a light directed chemical synthesis or reaction on a substrate using a computer controlled digital light processing micromirror array.
BACKGROUND OF THE INVENTION
Without limiting the scope of the invention, its background is described in connection with the patterning of a photolithographic emulsion for the fabrication of electronic devices for use in large scale integration, as an example.
Heretofore, in this field, photolithographic patterning of integrated circuits has depended on the formation and images with visible or ultraviolet light in a photoresist. To achieve large scale integration of electronic circuit devices, photoresist is patterned is currently achieved using proximity or projection printing. Proximity or projection printing of photolithographic patterns on substrates such as single grain silicon, depend on the printing of a lithographic mask on, e.g., fused-silica.
One problem with photolithographic masks is the degradation of the mask with each exposure to high intensity light or other rays. For example, a fused-silica mask that is used to pattern a large, dense semiconductor chip can have a useful life as low as two hours. Furthermore, the formation of masks requires a separate process, akin to wafer fabrication, in which the masks are patterned on a ultraviolet transparent material, usually having a metallic overcoat into which the pattern is etched. The entire mask producing process is akin to wafer fabrication in that similar care must be taken to prevent contamination with particulate matter from processing reagents and the atmosphere in which the masks are created and handled. The mask process is also very costly, cost which is further accentuated by the difficulty in making reliable, long lasting masks. Also, the turnaround time for mask making makes rapid changes to designs somewhat prohibitive.
A number of problems are encountered using masks for a wide variety of applications. For example, U.S. Pat. No. 5,626,784, issued to Simons, discloses a method for improving the alignment of photolithographic masks using a frame having sides that are individually thermally expandable. The mask is fabricated to be undersized so that the distance between fiducials on the mask is less than a desired distance, which may be the distance between corresponding fiducials on the workpiece. The mask is mounted on the frame, and at least one side of the frame is heated to expand the side and stretch the mask to achieve the desired interfiducial distance. While alignment of a mask is improved using the method disclosed, masks for each of the steps requiring photoresist are still required. Also, with each step requiring a mask, the above method has to be repeated to accomplish the underlying photoresist patterning.
SUMMARY OF THE INVENTION
It has been found that present apparatus and methods fail to meet the demands for a low cost, efficient, customizable method of small scale patterning for use in the creation of arrays for read-out systems that are capable of overlapping, concurrent data acquisition and analysis. Present patterning techniques also require the creation of masks for each step that involves the patterning of a photoresist during the formation of integrated circuits.
In the area of semiconductor design and manufacturing, a significant problem of current systems is that during the formation of semiconductor chips a number of photolithographic masks must be custom designed and printed for steps that require photolithographic protection of portions of a substrate. Each steps that requires photolithographic masks to, e.g., protect portions of semiconductor layers during etching or blanket deposition of semiconductor device layers, must be fit with a unique mask. Furthermore, each mask must be closely aligned to achieve efficient formation of major semiconductor components. The cost of implementation of novel designs for semiconductor devices is greatly increased by the need to design, print and pattern each mask separately. What is needed to design, test and implement integrated circuit design changes, therefore, is a rapid, inexpensive apparatus and method for patterning a photoresist on a semiconductor substrate that uses existing technology.
Current biochip technology is based on principles not unlike the formation of integrated circuit devices on a semiconductor substrate or template. It is recognized, as disclosed herein, that current biochip fabrication technology is afflicted by the same inefficiencies intrinsic to the use of photolithography to pattern and protect light catalyzed chemical reactions on active and inactive substrates. The present invention is based on the recognition that photolithographic masks are incapable of being designed, printed and used, at a reasonable cost to achieve the needed diversity for arrays of, e.g., oligonucleotide, polypeptide arrays or small chemical molecules. During large scale resequencing, for example, the ability to create a system for determining nucleotide sequences having a large diversity based on data previously obtained from an automated sequencer.
More particularly, the present invention can be an apparatus for catalyzing a reaction on a substrate comprising a light source that is directed toward a micromirror positioned to redirect light from the light source toward a substrate. A computer is connected to, and controls, the micromirror and a substrate holder, such as a reaction chamber, that is placed in the path of light redirected by the micromirror, wherein light that is redirected by the micromirror catalyzes a chemical reaction proximate the substrate. By proximate it is meant that the light catalyzed reaction can occur on or about the surface of the substrate. A light source for use with the present invention is a lamp or laser, such as a UV light. In an alternative embodiment the light source can be, e.g., a xenon lamp, or a mercury lamp, or a laser or a combination thereof. The light produced by the light source can also be visible light. One advantage of catalyzing chemical reactions using UV light is that it provides photons having the required high energy for the reaction. UV light is also advantageous due to its wavelength providing high resolution. Lenses can be positioned between the light source and the micromirror, which can be a micromirror array, or between the micromirror and the substrate. An example of such a lens is a diffusion lens.
Light from the light source can interact with, e.g., a novolak resin proximate to the substrate to produce a negative or a positive pattern in photoresist. The light catalyzed synthesis or reaction can be, e.g., the addition a nucleotide base to the substrate or to a base or polynucleotide chain attached to the substrate. Likewise, the light redirected by the micromirror can catalyze a chemical reaction, e.g., an amino acid addition reaction or the addition, removal or crosslinking of organic or inorganic molecules or compounds, small or large. For example, during the addition of a nucleic or an amino acid residue, the light can deprotect protecting groups of, e.g., phosphoamidite containing compounds. Light can also be responsible for the crosslinking or mono-, bi-, or multi-functional binding groups or compounds to attach molecules such as, fluorochromes, antibodies, carbohydrates, lectins, lipids, and the like, to the substrate surface or to molecules previously or concurrently attached to the substrate.
The present invention can also be a method of patterning on a substrate comprising the steps of, generating a light beam, illuminating a micromirror with the light beam, redirecting the light beam with the micromirror onto a substrate and catalyzing a light sensitive reaction proximate to the surface of the substrate using the redirected light beam in a predetermined pattern. By using the method of the present invention as a series of cycles, a number of layers can be built on t
Board of Regents , The University of Texas System
Flores Edwin S.
Gardere Wynne & Sewell LLP
Phan James
Warren, Jr. Sanford E.
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