JPS5811751B2 - Hand tie souchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device, and more particularly to a device for obtaining one-dimensional or two-dimensional optical information as an electrical signal via a semiconductor device.

For example, conventional devices that convert optical information into electrical signals include:
An example of a device having a self-scanning function is a device that converts optical information into an electrical signal and reads it out using a combination of an optical sensor and a charge transfer device (BBD, CCD).

In this case, the optical sensor includes, for example, a photodiode.

There is also a device that performs photoelectric conversion and readout functions in the same device by directly irradiating the charge transfer device with light, but this method suffers from large optical distortion due to the constant exposure to light during signal charge transfer, and is currently not widely used. It won't happen.

The present invention relates to the former device, in which a special gate circuit (switch circuit) is used to connect a part of the optical sensor and a charge transfer part.
By applying a control pulse to the clock signal line for transfer, the information of the optical sensor can be loaded into the charge transfer stage and read out without adding a 2D optical sensor. This significantly improves the performance of the information reading device.

First, FIG. 1 shows a planar arrangement of a conventional optical sensor constructed on a semiconductor substrate, and FIG. 2 shows its circuit.

Areas 1, 2, 3, 4, 5, 6, indicated by numbers in FIG.
7 is 10, 20, 30, 4 respectively on the second equal circuit
It corresponds to 0°50.60.70.

Terminals 1 and 10 in FIGS. 1 and 2 are power supply terminals for setting the photodiodes 3 and 30 to a constant potential, 2 and 20 are gate terminals that control them, and 4 and 40 are power supply terminals for setting the photodiodes 3 and 30 to a constant potential. Signal transfer transistor Tr2
5.50 is the drain terminal of the transfer transistor, 6.60 is the source terminal, 7.71 is the gate terminal for applying the clock signal for transfer, Trl
Tr2 is a MOS transistor for setting the photodiode to a constant potential, Tr2 is a read gate MOS transistor, Tr3. Tr4 is a transfer transistor.

According to this method, when these are arranged in two dimensions, the terminals for controlling part of the photosensor are 10 and 20, the terminal for reading control is 40, and a total of three control lines are connected to the clock line. A line other than 70.degree. 80.degree. is required, and this control line occupies a necessary area and becomes an obstacle to increasing the density of pixels (one set of a sensor and a transfer stage).

The present invention provides the same functionality without using any such control lines.
The object of the present invention is to provide a device that solves the above-mentioned disadvantages by using only a different clock line.

FIG. 3 shows the arrangement of an element according to the invention on a semiconductor substrate in the same manner as in FIG. 1.

In FIG. 3, 13 is an MO for performing charge transfer.
The source diffusion region of the S transistor, 14 is the drain diffusion region of the same transistor, and 15 is the gate electrode of the same transistor. Clock pulses are alternately applied to the gate electrode 16 adjacent to this to perform charge transfer.

A photodiode 17 is formed by a floating diffusion region having a conductivity type opposite to that of the substrate, which is formed adjacent to the drain region of the MOS transistor for signal charge transfer.

The operating principle of the present invention will be explained below using this configuration as an example.

FIG. 4 shows a cross section taken along the dashed-dotted line ■--■' in FIG. 3, and parts corresponding to those in FIG. 3 are given the same numbers.

First, when a +V pulse voltage is applied to the gate terminal G of the gate electrode 15, the gate electrode 15 and the n+ type drain region 1
4 overlap with each other via a dielectric oxide film (not shown) and are capacitively coupled, so that a depletion region 100 is formed in the P-type semiconductor substrate 200 under the drain region 15 as shown in FIG. 4a. spread to

However, since the semiconductor substrate 200 and the n-type floating diffusion region 17 of the common conductivity type are formed adjacent to each other,
During this time, dielectric breakdown occurs (generally called punch-through breakdown), and the electrons e in the floating diffusion region 17 flow into the drain region 14, which has a higher potential, and as a result, the potential of the floating diffusion region 17 as shown in FIG. is in a raised state.

Further, when the pulse voltage is removed, the depletion layer state shown in c is obtained.

Furthermore, as shown by d, when the floating diffusion region 17 (photodiode) is irradiated with light, the floating diffusion region 11
The potential of is lowered after a certain period of discharge into the substrate as a result of hole and electron recombination at the p-n junction.

This amount is generally proportional to the intensity of the light.

Then, when the above-mentioned pulse voltage +V is applied to the gate terminal G again as shown in e, the same state as in a occurs, and dielectric breakdown occurs again, and electrons flow into the drain region 14 from the photodiode.

In this case, the amount of electrons flowing in is proportional to the charge discharged by the light irradiation for a certain period of time.

After the electrons flow into a stable state as shown in f, when the clock pulse is removed from the gate terminal G, a signal corresponding to the intensity of light is read into the drain region 14 by light irradiation for a certain period of time as shown in g. It will be done.

In this way, the signals read into the drain region 14 can be sequentially transferred by ordinary charge transfer means (here, a packet frigate method is shown) and read out via the output circuit.

As described above, according to the device of the present invention, the voltage of the photodiode that detects optical information is set at the same time as reading, and the reading function is performed simply by applying a photodiode reading control pulse to the gate of the charge transfer element. Therefore, it is possible to obtain a photoelectric conversion device suitable for rational high density, which is not found in the conventional devices described above.

According to the present invention, a two-dimensional array can be easily realized by using a plurality of the above structures.

[Brief explanation of drawings]

FIG. 1 is a partial arrangement diagram of a photoelectric conversion element that combines a photosensor and a charge transfer element on a semiconductor substrate, FIG. FIG. 4 is a schematic cross-sectional view taken along the line IV-IV' in FIG. 3, and FIGS. 4 a to 4 g show its operation mode. This shows that. 14...Drain region of MOS transistor,
15.16...Gate electrode, 17...
Floating diffusion region, 100... Depletion region, 200.
...Semiconductor substrate.

Claims (1)

[Claims] 1 Arranging a plurality of element arrays consisting of series-coupled MOS transistors in which source and drain regions of opposite conductivity type formed in a semiconductor substrate of one conductivity type and gate electrodes are capacitively coupled, and adjacent to the drain region. A floating diffusion region of the same conductivity type as the drain region is formed in the semiconductor substrate, and a gate voltage is applied to the gate electrode to cause dielectric breakdown between the drain terminal and the floating diffusion region. , the gate voltage is removed and the floating diffusion region is irradiated with light to discharge the charges accumulated in the floating diffusion region for a certain period of time, and the gate voltage is applied again to flow from the drain region to the floating diffusion region. A semiconductor device characterized in that a charge corresponding to the discharged charge is supplied, and the charge remaining in the drain region is sequentially transferred by the gate voltage to read optical information.