JPH02116170A - Solid state image sensing device - Google Patents

Abstract

PURPOSE:To prevent transfer efficiency from being lowered by applying to a first output gate electrode a voltage higher than that of a second output gate electrode. CONSTITUTION:There are independently connected to a voltage application terminals 14, 15 a first output gate electrode 2 comprising a first layer polycrystalline silicon film adjoining to a floating diffusion layer 1 provided on a silicon semiconductor substrate and a second output gate electrode 3 comprising a second layer polycrystalline silicon adjoining to said electrode 2. In such a construction, provided a higher voltage is applied to the electrode 2 than the third electrode 3, all electric charges existent under a transfer electrode flow into the floating diffusion layer through an output gate voltage to eliminate any remaining charges not transferred under the output gate electrode. Thus, those electric charges can securely be transferred to the diffusion layer 1 to prevent any lowering of transfer efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid-state imaging device, and particularly to a CCD solid-state imaging device.

[Conventional technology]

A conventional solid-state imaging device using a charge-coupled device has a photosensitive part that accumulates charge according to the amount of incident light, a transfer register that transfers the charge accumulated in this photosensitive part, and a charge detection device that detects the transferred charge. It consists of parts. The configuration near the charge detection section includes a floating diffusion layer that receives transferred charges, an output gate electrode adjacent to the floating diffusion layer on the transfer register side, and a reset electrode on the opposite side.

[Problem to be solved by the invention]

As shown in FIG. 4, the charge detection section of this solid-state imaging device consists of a floating diffusion layer 1 that receives transferred charges, an output gate electrode (2, 3>) on one side adjacent to the floating diffusion layer 1, and an output gate electrode (2, 3> on the other side). It is composed of a reset electrode 12 that resets charges transferred to the side for each photosensitive part.Then, this floating diffusion layer 1
It is necessary to make the size small from the viewpoint of sensitivity. This requires precise processing, and the electrodes on both sides of the floating diffusion layer 1 are usually constructed from the first layer electrodes.

In addition, since the last electrode of the transfer electrode whose output is adjacent to the gate electrode usually ends in the first layer, the output gate electrode has two layers and one layer of electrodes, and these two electrodes (the second output gate electrode 3 and the first output The gate electrode 2) is connected by wiring and connected to a DC bias voltage application terminal 15. Therefore, depending on the diffusion process, the potential below the second layer of the output gate electrode (second output gate 3) may become higher.

In this case, the charge corresponding to the potential difference between the first layer and the second layer is left behind under the output gate electrode, resulting in a disadvantage that the transfer efficiency deteriorates.

An object of the present invention is to provide a solid-state imaging device that can prevent deterioration in transfer efficiency that may occur due to the diffusion process and provide a stable yield.

[Means to solve the problem]

The solid-state imaging device of the present invention includes a transfer register that receives and transfers charges from a photosensitive portion provided on one main surface of a semiconductor substrate, and a transfer register that is sequentially arranged adjacent to a transfer electrode at the final stage of the transfer register. A solid-state imaging device having two output gate electrodes, a first output gate electrode, and a floating diffusion layer for charge detection, comprising means for applying a higher voltage to the first output gate electrode than to the second output gate electrode. That is what it is.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1(a) is a schematic plan view showing one embodiment of the present invention, and FIG. 1(b) is a sectional view taken along the line AA' in FIG. 1(a).

A first output gate electrode 2 made of a first layer of polycrystalline silicon is adjacent to a floating diffusion layer 1 provided on a silicon semiconductor substrate, and a second output gate electrode made of a second layer of polycrystalline silicon is adjacent to this first output gate electrode. Two output gate electrodes 3 are each independently connected to voltage application terminals 14 and 15. The operation here is as follows. FIG. 2 is a signal waveform diagram of transfer electrode drive pulses 1 and 2, and FIG. 3 is a potential distribution transition diagram for explaining a charge transfer grid. At the current timing 1, there is a charge (indicated by diagonal lines in FIG. 3) transferred below the transfer electrode 4 at the final stage of the transfer register, and in order for this charge to flow into the floating diffusion layer 1, the transfer electrode 4 ( When the voltage applied to the first layer (consisting of a polycrystalline silicon film) falls to a low level (timing t2), the potential becomes shallow and charges flow into the floating diffusion layer through the output gate electrode.At this time, the first output If a higher voltage (about IV) is applied to the gate electrode 2 than to the second output gate electrode 3, all the charges under the transfer electrode will flow into the floating diffusion layer through under the output gate electrode. Therefore, no residual transfer occurs under the output gate electrode.

In this way, since the second output gate electrode and the first output gate electrode are connected to different terminals, applying a slightly higher voltage to the first output gate electrode ensures that the charge is floatingly diffused. transfer efficiency can be prevented from deteriorating.

〔Effect of the invention〕

As explained above, the present invention provides the first structure adjacent to the floating diffusion layer.
．． connecting the second output gate electrode to separate voltage application terminals;
By applying a high voltage to the side adjacent to the floating diffusion layer (first output gate electrode), problems due to residual charge transfer under the output gate electrode are eliminated, and a stable yield of solid-state imaging devices can be achieved. There is.

[Brief explanation of drawings]

FIG. 1(a) is a schematic plan view of the vicinity of a charge detection section showing an embodiment of the present invention, and FIG. 1(b) is a plane view taken along line AA' in FIG.
A schematic diagram of a line cross section, Fig. 2 is a signal waveform diagram of a transfer electrode drive pulse, Fig. 3 is a potential distribution transition diagram to explain the state of charge transfer, and Fig. 4 is a plane near the charge detection section showing a conventional example. It is a schematic diagram. 1... Floating diffusion layer, 2... First output gate electrode, 3
... second output gate electrode, 4 to 11 ... transfer electrode,
12... Reset electrode, 13... Reset drain, 14... First output gate electrode voltage application terminal, 15.
...Second output gate electrode voltage application terminal, 16...Silicon oxide film.

Claims (1)

[Claims] A transfer register that receives and transfers charge from a photosensitive portion provided on one principal surface of a semiconductor substrate, a second output gate electrode, and a first output, which are sequentially arranged adjacent to a final stage transfer electrode of the transfer register. A solid-state imaging device having a gate electrode and a floating diffusion layer for charge detection, characterized in that the solid-state imaging device includes means for applying a higher voltage to the first output gate electrode than to the second output gate electrode. .