Charge coupled device used in an image sensor and a method of making the charge coupled device

A method of manufacturing a charge coupled device of the buried channel type with a semiconductor body in which are formed a first layer of a first conductivity type which adjoins a surface of the body and which forms a buried channel for storage and transport of electric charge, a second layer of the second conductivity type opposite to the first which lies below and adjoins the first layer and forms a barrier layer, and a third layer of the first conductivity type which lies below and adjoins the second layer and through which excess charge can be drained from the first layer, the surface being provided with a system of electrodes with a series of gate electrodes which are situated above the buried channel and which are connected to a voltage source for the at least temporary application of such a voltage to the gate electrodes that an inversion layer of the second conductivity type adjoining the surface may be formed below the gate electrodes, while means are provided for obtaining a built-in potential difference in the channel whereby potential wells in which charge can be stored alternating with potential barriers are formed in the channel upon the application of equal voltages to the gate electrodes, and while means are provided for charge reset said means comprising constrictions in the thickness or the doping concentration of the second layer below the channel that viewed in projection are lineshaped, characterized in that the line-shaped constrictions in the thickness or the doping concentration of the second layer are formed such that they run perpendicular to the length direction of the channel and parallel to the gate electrodes and in that at least one line shaped constriction is positioned below the series of gate electrodes.

A charge coupled device of the buried channel type with a semiconductor body comprising:

• a first layer of a first conductivity type which adjoins a surface of the semiconductor body and which forms a buried channel for storage and transport of electric charge;
• a second layer of a second conductivity type opposite to the first which lies below and adjoins the first layer, which form the buried layer of the channel and which forms a barrier layer;
• and
• a third layer of the first conductivity type which lies below and adjoins the second layer and through which excess charge can be drained from the first layer,
• wherein the surface is provided with a system of electrodes with a series of gate electrodes which are situated above the buried channel and which are connected to a voltage source for the at least temporary application of such a voltage to the gate electrodes that an inversion layer of the second conductivity type is formed adjoining the surface below the gate electrodes,
• while means are present for obtaining a built-in potential difference in the channel whereby potential wells in which charge can be stored alternating with potential barriers are formed in the channel upon the application of equal voltages to the gate electrodes,
• while means are present for charge reset through the barrier layer said means comprising regions of the second layer below the channel in which the thickness or the doping concentration of the second layer is smaller than outside said regions, said regions being further called constrictions, which constrictions viewed in projection are line-shaped, having a length larger than a width,
• wherein the line-shaped constrictions in the thickness or the doping concentration of the second layer run with their length perpendicular to the length direction of the channel and parallel to the gate electrodes, and
• wherein at least one line shaped constriction is positioned below the series of gate electrodes.