U.S. Philips Corporation

Jan T Bosiers

Agnes C Kleimann

Edwin Roks

Bartholomeus G Dillen

In charge-coupled imaging devices it is generally necessary to provide zones (12) in the matrix with a contact. These zones may form part, for example, of a mechanism for draining charge, for example as a protection against overexposure. In the case of imaging devices with a horizontal readout register on one side of the matrix, these contacts can be provided on the opposite side. However, it is often desirable or even necessary, as in the case of imaging devices with four-quadrant readout, to provide such contacts on the same side as the horizontal readout register. To this end, a dummy line (14'-17') is provided in accordance with the invention between the matrix and the horizontal readout register (6), said dummy line having an electrode structure which leaves room for contact windows (22) to the zones (12).

Charge-coupled imaging device having electrical connections on the

It is known to reduce the leakage current or dark current in charge-coupled devices with buried channels such as, for example, charge-coupled imaging devices by bringing the surface to the inverted state. In such a device, however, it is not possible to empty the channel completely locally in usual manner in that the charge is drained off through the substrate by means of a voltage pulse applied to the gates (charge reset). To be able to carry out charge reset nevertheless, the voltage pulse is applied between the substrate and the intermediate zone interposed between the substrate and the CCD channel. Since this voltage pulse is active over the entire range of the device, the device also prevents charge from being removed in locations where this is not desired when the pulse is applied. It is possible in this manner to carry out charge reset, for example, in the imaging section only, in imaging devices without removing the information which is simultaneously in store in the memory section and/or in the read-out register.

Charge-coupled device having charge reset

It is known to bring the surface into the inverted state in CCD imaging devices with buried channels during the integration period in order to keep the dark current low (All Gates Pinning). The desired potential profile, with wells in which the charge is integrated bounded by potential beers, is obtained through the use of a two-phase structure with a doping profile in the channel or with a gate oxide having thickness differences. Owing to limiting conditions which hold for the clock voltages used for charge transport, serious limitations are imposed on the depth of the potential wells and thus also on the charge storage capacity of the pixels. This disadvantage is counteracted by the operation of the device not as a two-phase but, for example, as a four-phase CCD according to the invention, whereby a d.c. shift is present between the clock voltages for compensating the built-in, comparatively great potential differences described above. An imaging device is obtained thereby with a low dark current, a great charge storage capacity per pixel, and a high transport efficiency.

Buried channel charge coupled device

A charge-coupled device includes a parallel section of parallel channels which are situated next to one another and are mutually separated by limitation zones, and a single readout register coupled thereto. The readout register is provided with clock electrodes in a multi-layer wiring system, the electrodes of the upper layer belonging to a common phase and being constructed as a continuous track which extends over the other electrodes. In the bottom wiring layer, electrodes are formed which are each associated with a limitation zone between the parallel channels and which have a length which is at most equal to the width of the limitation zones, and which also belong to a common phase, so that narrow-channel effects are avoided. The invention is of particular importance for CCD image sensors.

Growing community of inventors

Eindhoven, Netherlands

Jan T Bosiers