| 摘要 |
PURPOSE:To simplify the mounting of a chip by a method where in the need is eliminated for an insulating working of the surface and the rear of a wafer chip when an ion sensing FET is cut out of an Si wafer and a water proof construction is confined to an electric connection structure between a sensor and an external measuring circuit and each of the FETs is immersed into a measuring solution as intact. CONSTITUTION:A groove is cut into an Si wafer 1 of a bulk crystal by an anisotropic etching and the entire surface containing the groove is covered with an SiO2 to stack a multi-crystal Si layer 3 thereon. The, the work is turned upside down and cut from the side of the wafer 1 to leave the center of the wafer 1 in an island shape. Then, a diffusion layer of a source 5 and a drain 6 as components of an ion-selective FET is formed by an ion implantation through a gate oxide film 4. The entire surface containing the layer is covered with a highly water proofing Si3N47 and a portion corresponding to the diffusion layer is covered with a polyimide film 8 having an ion sensitive film 9 thereon. Thereafter, the wafer 1 is cut off the portion utilizing the groove to make FETs individually and each thereof is immersed into a measuring solution 10 to show the results on a display section 17. |
