JPS61292361A - Charge-injected solid-state image pickup device - Google Patents

Abstract

PURPOSE:To make it possible to read a video signal with a simple element structure without necessity of large capacity at a high speed by forming a photosensitive region in reverse conductive type well structure to a semiconductor substrate, and composing to read out a signal current in an output circuit with minority carrier injected in a well when reading out a photocharge. CONSTITUTION:Each photosensitive cell 14 has a well 16 of rectangular P-type impurity diffused region formed on the main surface of an N-type substrate 12, and a rectangular N<-> type impurity diffused region 18 also formed in the well. The main surface of the substrate 12 is coated with a gate oxide film 20 of silicon dioxide, and a transparent electrode layer 22 is arranged above the region 18. A photodiode for generating and storing photocharge in response to an incident light is formed of the regions 16, 18. A hole 24 is formed at the portion of the film 20 in contact with the well 16, and a conductor electrode layer 26 is arranged. Since the potential of the well 16 to the electron becomes lower than the region 18, the photoelectron stored in the region 18 is injected as minority carrier to the well 16.

Description

[Detailed Description of the Invention] The present invention relates to a solid-state imaging device, particularly a charge injection type solid-state FF.
The present invention relates to an image device.

i-kengenki As is well known, charge injection is used in solid-state imaging devices.

A large number of photosensitive cells, such as photodiodes or phototransistors, are arranged in the row and column direction, and each cell is connected to a row selection line and a column selection line via two corresponding capacitors. Each photosensitive cell accumulates photocharges corresponding to incident light. When a particular row select line and column select line are biased with a predetermined voltage, this voltage is divided by two capacitors, and the accumulated charge of that photosensitive cell is selectively injected into the substrate.

This injected charge is read out as a signal from an output circuit connected to the substrate. By sequentially rask-scanning the photosensitive cells arranged in rows and columns in this manner, video signals are serially read out from the output.

In conventional charge injection type stationary imaging devices, the substrate area is quite large, resulting in a large capacitance of the readout circuit and, as a result, a large RC time constant. Therefore, it has been difficult to output video signals at high speed. Therefore, it has not been possible to realize a high resolution imaging device by integrating each imaging cell at a high density.

the purpose The present invention overcomes these drawbacks of the prior art.

It is an object of the present invention to provide a charge injection type solid-state imaging device that has a relatively simple configuration and can operate at high speed.

According to the present invention, a semiconductor substrate of one conductivity type, a well region of the other conductivity type formed in a matrix on the main surface of the semiconductor substrate, and a photosensitive region formed in this well region. a plurality of photosensitive cells including a plurality of photosensitive cells, an insulating layer covering the main surface of the semiconductor substrate, a transparent electrode layer commonly disposed on the insulating layer above the photosensitive region in the arrangement of the photosensitive cells in a first direction, and a first a conductor layer that commonly connects well regions for each array of photosensitive cells in a second direction substantially perpendicular to the direction, and photocharges generated in the photosensitive regions by incident light are injected into the well regions;
A charge injection type solid-state imaging device is provided in which a signal current is read out in a conductor layer.

According to another aspect of the invention, an island region is formed in the well region and has a conductivity type opposite to that of the well region, and the island region is connected to a conductor layer and together with the well region and the photosensitive region. A transistor is formed, and the signal current is amplified and read out by this transistor.

Next, embodiments of a charge injection solid-state imaging device according to the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, a charge injection in-place imaging device 10 according to a particular embodiment of the present invention includes a plurality of photosensitive cells 14 on one major surface of a semiconductor substrate 12 of, for example, n-type silicon.
are arranged in rows and columns to form a photosensitive cell array.

As can be seen from FIG. 2, each photosensitive cell 14 includes a well IB, which is a rectangular p-type impurity diffusion region formed on the main surface of the n-type substrate 12, and a rectangular well IB formed therein. n- impurity diffusion region 18. The main surface of the substrate 12 is covered with a gate oxide film 20 such as silicon dioxide, and a transparent electrode layer 22 is disposed above the n- diffusion region 18. These regions 16 and 18 form a photodiode that generates and accumulates photoelectric charges in response to incident light incident thereon.

Further, an opening 24 is provided in a portion of the oxide 820 in contact with the p-type well 1B, and a conductive electrode layer 2B' made of, for example, aluminum or polycrystalline silicon is provided thereon. In this way, the electrode layer 2G is electrically connected to the p-type well 1B. Other parts are covered with an insulating film 28 made of silicon dioxide, for example.

Returning to FIG. 1, a transparent electrode layer 22 is connected in common for each photosensitive cell 14 for each horizontal row, and is connected to each register stage of a vertical scanning shift register (VStR) 3G. is one photosensitive cell per vertical column.
4, vertical column selection IGFE↑32
connected to the source-drain path of the ICFET
32 and 34 are gated horizontal scanning shift registers (HS
R) 3B, and the source/drain path is commonly connected to the video signal input terminal 3B for each vertical column. Output terminal 38 is also connected to resistor 4 in this embodiment.
Grounded through 0. These constitute a signal readout circuit for each photosensitive cell 14. Although only four photosensitive cells 14 are not shown in the figure to avoid complicating the drawing, in reality, a large number of such photosensitive cells 14 are arranged in rows and columns to form an imaging cell array.

By the way, in the normal state, the p-type well I6 and the n-diffusion region of each cell 14! The transparent electrode 22 is connected to the photodiode from the vertical shift register 30 so that a potential gradient as shown in FIG.
biased towards. Therefore, a transparent electrode 22 is placed in this bonding area.
When incident light enters through, corresponding photoelectron-hole pairs are generated, and the electrons are accumulated in the n layer 18 of the junction region, as shown in FIG. 3B.

Therefore, by driving the horizontal shift register 3B and the vertical shift register 30 to sequentially select the horizontal rows, and while the horizontal row is selected, the horizontal shift register is shifted all the way to the final register stage.
The 32 gate electrodes 34 are sequentially energized, and the p-type cell I
Earth air is applied to the electrode 2B of B through the output resistor 40. As a result, the potential for electrons in the pN well 1B becomes lower than that in the n- region 18, so as shown in FIG. 3C, the photoelectrons accumulated in the n- region 18 are
They are injected into the type well 1B as minority carriers. A current corresponding to this charge flows through the resistor 40 and the source/drain path of the ICFET 32 to the pH well! flowing into 8,
As a result, the voltage generated across the resistor 40 is transferred to the output terminal 3.
The pixel signal of the photosensitive cell 14 is read out from the beginning.

Such an operation is sequentially performed for each cell 14 in the horizontal row as the horizontal shift register 3B scans horizontally. When such a read operation is performed up to the last cell I4 in the horizontal row, the vertical shift register 30 advances;
The next horizontal row is selected and a similar read operation is performed. In this way, the raster-scanned video signal is output in series from the output terminal 3B.

Referring to FIG. 4, in another embodiment of the present invention, an island-shaped n◆ impurity diffusion region 50 is formed at the connection portion of the p-type well 16 with the electrode 28. As shown in FIG. 5, this is formed in the p-type well 18 so as to be electrically connected to the electrode layer 26. As a result, in this embodiment, an npn (npn) is formed in which the n- region 18 is the emitter, the p-type well 1B is the base, and the n◆ region 50 is the collector.
A transistor 54 is formed. Returning to FIG. 4, the power supply 52 for driving the mpn transistor 54
is connected to the output resistor 40. Other configurations may be similar to the embodiment shown in FIG. 1. In these figures, the same components as in FIGS. 1 and 2 are designated by the same reference numerals to avoid redundant explanation.

As can be seen from the fact that such a transistor 54 is equivalently formed, when the ICFET 32 is opened and a positive voltage of the power supply 52 in the n◆ region is applied,
The minority carriers injected into the p-type well 16 from the n- region 18 flow into the n+ region 50 as a current with a current amplification factor hfe times the number of injected carriers. In other words, this transistor 54 has the effect of amplifying the generated photocurrent, and the thus amplified signal current is read out from the output terminal 38.

As described above, in the embodiment of the present invention, a photosensitive region is formed in the p-type well 16, and when the generated photocharges are read out, they are injected into the p-type well 1B as minority carriers and output as a signal current to the circuit. It is configured to be read out.

Therefore, since a large capacitance unlike the conventional charge injection type device is not required, high-speed reading of video signals is possible with an element structure as simple as MO3. In addition, each imaging cell is integrated with high density, and a high resolution video signal can be obtained.

Note that the embodiments described here are for explaining the present invention, and the present invention is not necessarily limited thereto, and modifications and variations that can be made by those skilled in the art without departing from the spirit of the present invention. Modifications are within the scope of this invention. For example, the conductivity type of the semiconductor of the solid-state imaging device in the example is merely an example, including its impurity concentration, and may be the opposite conductivity type to the illustrated conductivity type. The polarity is also switched.

As described above, according to the present invention, a photosensitive region is formed in the well structure of the conductivity type opposite to that of the semiconductor substrate, and when reading out the generated photocharges, these are injected into the well as minority carriers. The configuration is such that the signal current is read across the output circuit as a signal current. Therefore, since a large capacitance unlike the conventional charge injection type device is not required, high-speed reading of the video signal is possible with an element structure as simple as a MOS.

Further, if the portion including the photosensitive region and the well is formed into a transistor structure, the photocurrent is amplified and read out.

Therefore, a charge injection type stationary imaging device is provided which has a relatively simple configuration and can operate at high speed.

[Brief explanation of drawings]

FIG. 1 is a block diagram conceptually showing an embodiment of a charge injection solid-state imaging device according to the present invention, and FIG. 2 is a cross-sectional diagram schematically showing the cross-sectional structure of one imaging cell in the embodiment shown in FIG. Figures 3A to 3
Fig. C is an energy band diagram for explaining the principle operation of the embodiment shown in Fig. 1, and Fig. 4 is a configuration diagram similar to Fig. 1 showing another embodiment of the present invention. 5 is a sectional view similar to FIG. 2 schematically showing the sectional structure of one imaging cell in the embodiment shown in FIG. 4. FIG. Theory 12, Semiconductor substrate 14, Photosensitive cell 1B, P-type well 1B, N-diffusion region 22, Transparent electrode 2B, Metal electrode Patent applicant Fuji Photo Film Co., Ltd. Company Figure 2 Figure 5

Claims (1)

[Claims] 1. A semiconductor substrate of one conductivity type, well regions of the other conductivity type formed in a matrix on the main surface of the substrate, and a plurality of photosensitive regions formed in the well regions. a photosensitive cell; an insulating layer covering the main surface of the substrate; a transparent electrode layer commonly disposed on the insulating layer above the photosensitive region for the array of photosensitive cells in a first direction; and a conductor layer that commonly connects the well region for each array of photosensitive cells in a second direction substantially perpendicular to the conductor layer, wherein photocharges generated in the photosensitive region by incident light are injected into the well region. A charge injection type solid-state imaging device characterized in that the charge injection type solid-state imaging device is read out as a signal current to the conductor layer. 2. In the solid-state imaging device according to claim 1, a readout circuit is connected to the conductor layer for sequentially and selectively applying a predetermined potential to the conductor layer to read out the signal current. A charge injection solid-state imaging device characterized by: 3. In the solid-state imaging device according to claim 1, an island-like region having a conductivity type opposite to that of the well region is formed in the well region, and the island-like region is connected to the conductor layer. A charge injection type solid-state imaging device, wherein a transistor is formed together with the well region and the photosensitive region, and the signal current is amplified and read out by the transistor. 4. In the solid-state imaging device according to claim 3, a readout circuit is connected to the conductor layer to read out the signal current by sequentially and selectively applying power to the transistor from the conductor layer. A charge injection solid-state imaging device characterized by: