PRODUCTION OF 2D-ARRAYS

Abstract: A method for the production of an array of pixels arranged in a geometric pattern, which pixels have desired properties, such as electro-optical, magneto-optical or similar properties. Such pixels are connected by electrically conductive strips which allow one to connect at will one or more of the pixels with exterior recording means. Preferred are arrays of parallel pixels, arranged on parallel conductive stripes, on a transparent substrate which is an electrical insulator, with parallel conductive stripes at a perpendicular arrangement to the first stripes being in contact with the upper surface of the pixels. The pixels are generally in the micron or submicron size range, and a preferred material of these is bacteriorhodopsin (bR).

Description: Description PRODUCTION OF 2D-ARRAYS FIELD OF THE INVENTION The invention relates to a method for the production of any array of pixels of heat-sensitive material, with one of a wide variety of properties, such as electro-optical, magneto-optical etc. properties, defining an orderly geometric pattern, said pixels being connected by a pattern of electrically conductive transparent or opaque strips allowing for the connection of one or more of the pixels with external means of recording at any desired instant. BACKGROUND OF THE INVENTION Recently there have been several reports concerning the use in electrooptics of a unique biological, polymeric and other materials. One example of such a material is the membrane called purple membrane which contains the protein called bacteriorhodopsin (bR) . All of the applications of bR for producing devices demand a method that will be able to microfabricate this protein containing membrane without effecting the electooptical properties of bR. This is generally the case for many of the newly discovered materials that will be important in the future in electronic, optical and electrooptical device fabrication. Many of the most unique applications of such materials demand the generation of an array of electrodes sandwiched pixels (Figure 1) . In the case of bR for example, since it is a protein, it is not possible to use the generally used techniques of microelectronics that microfabricate silicon by methodolgies such as reactive ion etching etc., without destroying the required properties of the protein. In addition, any methodology designed for mi- cropatterning bR must be based on low temperature processes since the protein is sensitive to heat above 60 degrees C. Conventional techniques used with the usual materi¬ als in microelectronics, such as in the production of printed circuits and semi-conductor chips are not applicable with heat-sensitive substance which would be deactivated or even decomposed by the drastic conditions of conventional techniques, which employ corrosive substances, high vacuum, etc. The novel process of the invention overcomes these drawbacks and provides for the production of mico-arrays of inter-connectable pixels down to very small dimensions, in the micron size range. SUMMARY OF THE INVENTION The invention relates to arrays of pixels of heat- sensitive materials, defining an orderly geometric pattern, provided with electrode patterns enabling the connection at any one period of time of one or more of the pixels with current detection means external to such array. The pixels can be produced in any desired size, down to dimensions as small as less than a micron. The pixels are interconnected by a pattern of conductor stripes, where the stripes facing a source of suitable electromagnetic radiation, such as light, are essentially transparent to such radiation. The inven¬ tion further relates to a method for the production of such micro-arrays of pixels, which is characterised in that only such conditions are used which do not impair the activity of heat-sensitive substances, which are the main component of the said pixels. In general terms, the process of the invention comprises applying to a suitable substrate, such as glass, a thin transparent layer of an electrically conductive material, to which there is applied a thin layer of the active material, and on top of which there is positioned a suitable mask defining a pattern of parallel stripes. The thus created array is arradiated by a suitable energy source, such as an excimer laser, so as to remove the exposed material through a mask in a specified pattern both at the layer of the electrooptical material as well as the conductive layer, down to the substrate. If required, the array is cooled especially during the removal of the conductive material, so as not to damage the sensitive substance. After this patterning step the mask is removed and there is deposited on the entire area a thin film of conducting substance such as aluminum. This will be generally in the range of from about 10mm to about 100mm thick. On top of the thus produced electrically cond¬ uctive layer, there is applied a mask, perpendicular to the direction of the first pattern of parallel stripes. The array is again irradiated, and this time the exposure is such as to remove, according to the pattern defined by the grid, the aluminium and the sensitive material, down to the first electrically conductive layer, which is left intact. Thus there is created a pattern of geometrically arranged individual pixels, sandwiched between a pattern of criss-crossing electrically conductors, where the ones in a certain direction are beneath the pixels, and the others, perpendicular to the first ones, are on top and in contact with the said pixels. The array of cond¬ uctive stripes makes possible to connect one or more desired pixels with the outside of the pixel-array, and to disconnect these as well. The invention is illustrated with reference to the protein bacteriorhodopsin (bP) which is also termed "purple membrane", which is a well-known electrooptical active, yet heat-sensitive material. It is clear that this is by way of illustration only and that a variety of other proteins, polymers, compounds, complexes, etc. can be used as well. The invention is illustrated by way of example with reference to the enclosed schematical Figures, which are not according to scale and in which: Figure 1. A schematic of a pixel array of elec¬ trode sandwiching of an electrooptical material such as bacteriorhodopsin, essential for many computing and imaging electrooptical applications of new device materials such as bacteriorhodopsin. Figure 2 A schematic representation of the micropatterning procedure described in the text and used to create a large array of active electrode sandwiched bR pixels. Figure 3. Scanning electron micrograph of acti¬ ve electrode sandwiched bR pixels. Each pixel is 30mm x 30mm. Figure 4. The photocurrent response of micro- fabricated bR bar of 50 m x 800 m. This response is identical to that which is obtained from bR films that have not been exposed to the microfabrication process. As shown in Fig. 1 an array according to the present invention comprises a substrate 11, such as glass, on which there is deposited a pattern of parallel stripes 12 of transparent electrically conductive material, which support a pattern of pixels 13 of an electroactive or other substance, the area of which corresponds to the width of the stripes 12, below the pixels, and of the stripes 14, perpendicular to the direction of stripes 12 which are positioned on the pixels 13. Fig. la is a perspective view of the array and Fig. lb is a sectional side view of this pattern. As shown in the exploded view of Fig. 2, the materials used are a glass substrate 21, a conducting transparent or translucent film 22 and an oriented film of the active substance, in this case bR, 23 and grid 24. There is used an excimer laser for obtaining the stripe pattern 25, and after this there is evaporated on top a metal film 26, and after rotation of the mask (grid) 24 by 90 degrees, and laser ablation, there is obtained the pattern shown in 27, with 28 being a sectional side view of the finished pattern. The invention is further described with reference to the following example, which illustrates the production of micronrange size pixels in a structure according to the invention. As substrate there was chosen a glass plate of 5mm by 5mm of 1mm thickness. On this there was applied a transparent layer of tin oxide of uniform thickness of 500A. On top of this layer there was applied a suspension of bacteriorhodopsin (bR) of 100 1 with O.D. 15. This was dried by an electric field. A microscope grid (of an electron microscope) with a bar thickness of 30 m and with a distance of 30 m between bars was applied on top of this layer, and the bR between the bars was ablated using an Argon fluoride Excimer laser of MJ per pulse energy, using a beam site of 2 x 4 mm. About 40 pulses of 10 usec duration each were required to remove the bR layer between the bars and after this pulses of the same laser with the same power and pulse time to ablate also the tin oxide layer between the bars. During this process step the glass bar was cooled down to about 10 degrees C. After removal of the grid there was applied an aluminium layer of about 100A thickness on the entire surface of the glass substrate by conventional vapour deposition. The grid was again placed on the substrate, this time on top of the aluminium layer, with the bars perpendicular to the first direction. 40 pulses of the same excimer laser with the same power and pulse duration was used to ablate the aluminium layer and the bR layer, without damaging the tin oxide layer beneath these two. A pattern bR dB pixels of about 30 x 30 m was obtained, with strip-shaped transparent electrodes connecting these in one direction beneath the bR layer, and in a perpendicular to this on top of the bR layer.

Claims: CLAIMS : 1. An array of pixels of active material having desired properties, which pixels are arranged in an orderly geometric pattern, and which pixels are sandwiched and interconnected in different connections by a corresponding pattern of electrically conductive transparent strips, with stripes in one direction being in contact with the lower surface of the pixels, and stripes in another direction being in contact with the upper surface of the pixels, said stripes being connectable to with exterior recording means. 2. An array according to claim 1, where one array of parallel conductive stripes is deposited on a transparent insulating substrate, the pixels are above and in contact with these stripes, there being provided an array of parallel conductive stripes perpendicular with the first array, above and in contact with said pixels. 3. An array according to claim 1 or 2, where the pixels are in the micron or submicron size range. 4. An array according to any of claims 1 to 3, where the pixels consist of or contain bacteriorhodopsin (bR) . 5. An array according to any of claims 1 to 4, where the first array of parallel stripes consists of thin stripes of tin oxide on a glass substrate, and the second array, above the sensitive material, is a stripe pattern of vacuum deposited and patterned metal. 6. An array according to claim 5, where the active material is an oriented bR film. 7. A process for the production of an array of heat- sensitive material of desired electrooptical, magneto- optical or similar properties, which comprises applying to a transparent insulating substrate a transparent or translucent electrically conductive film, applying on top of this a layer of the heat-sensitive material, positioning on top of this layer a mask defining a pattern of parallel stripes, balating the layer of the heat sensitive material by a suitable beam of adequate energy, balating in a similar manner corresponding stripes of conductive material, applying by vapour deposition a thin metal layer on the entire surface, positioning a similar mask at 90 degrees to the first direction on this metal layer, balating both the metal layer and the layer of sensitive material according to the pattern of the mask, resulting in pixels of the sensitive substance arranged between and in contact with parallel conductive stripes below the pixels, and parallel stripes in a perpendicular direction on top of the sensitive material, means being provided to connect each of the stripes with external recording or detecting means. 8. A method according to claim 7, where the conductive layer is applied to a glass substrate, where the metal layer is applied by vapour deposition, and where the ablation steps are effected by Excimer lasers of mJ power with a plurality of pulses of tens of nanoseconds. 9. A process according to claims 7 or 8, where the conductive layer is one of tin oxide of some hundreds of A thickness, where the mask defines parallel stripes in the micron width and micron distance range, where the metal layer is one of aluminium, at a thickness in the 100 A range.

Inventors: HARONIAN DAN, LEWIS AARON, RAPAPORT ERICH, HARONIAN, DAN, LEWIS, AARON, RAPAPORT, ERICH
Applicants: AARON LEWIS, HADASIT MED RES SERVICE, HARONIAN DAN, RAPAPORT ERICH, YISSUM RES DEV CO, HADASIT MEDICAL RESEARCH SERVICES & DEVELOPMENT CO, RAPAPORT, ERICH, YISSUM RESEARCH DEVELOPMENT COMPANY OF THE HEBREW
Application year: 1993
Main classification: G03F7
IPC codes: B41M5, G03F7