| 摘要 |
1319462 Cathode-ray tubes; semi-conductor devices GENERAL ELECTRIC CO 27 July 1970 [28 July 1969] 36227/70 Headings H1D H1K A taget for a cathode-ray tube comprising an array of diodes formed by conductive material in the apertures of an insulating coating on a semi-conductor substrate, is characterized is that the conductive material extends through the insulating coating and overlies it to stop it from becoming charged by the scanning electron beam. In one arrangement, Fig. 1, the substrate 11 is N-type silicon of a 1, 0, 0 orientation coated with silicon dioxide or nitride 11 in which apertures are formed, and P-type silicon is epitaxially grown on the exposed portion to form pyramids 13. If the target is to be charged by a light image it may be provided with an anti-reflective coating 15 of zinc sulphide, but the target may alternatively be charged by another electron beam or by X-rays. In an alternative arrangement the conductive material is metal and the diodes are Schottky diodes. Electrode processing.-A silicon single crystal having a 1, 0, 0 orientation is cut into a disc shaped wafer, lapped, polished, etched to a thickness of 100 microns, and oxidized at 1150‹ C. for 10 hours in dry O 2 to grow a 6000 A‹ layer of SiO 2 . A pattern is formed on a photoresist and the oxide partly removed by etching in buffered hydrofluoric acid to form an array of 8 micron diameter holes on a 16 micron grid preferably oriented along a 1, 1, 0 direction. The photoresist is removed by washing in hot sulphuric acid after which the wafer is washed in water and etched in buffered hydrofluoric acid to remove a thin layer of surface oxide. After washing in water to remove surface impurities the wafer is inserted between two susceptor discs in a vacuum reactor chamber. The upper disc is maintained at 1100‹ C. and serves as a source of P-type silicon (boron doped) which is transported to the wafer by an iodine pressure of 1 mm., whilst the lower disc is maintained at 1000‹ C. The wafer is next diffused to drive a portion of the P-type impurities into the wafer to a depth of 1 micron, and a portion of the oxide covering the reverse side of the wafer is removed by etching. Contact to the wafer is made by an indium ring. This produces a target sensitive to infra-red radiation. Improved response to visible light may be obtained by diffusing a light N-type surface into the wafer and by thining the central portion to 20 microns, or by starting with an N<SP>+</SP>-type wafer having an N-type layer epitaxially grown thereon, the N<SP>+</SP> material then being removed in the active regions of the device. |
