JPS5838941B2 - Hand tie souchi - Google Patents

Description

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

Conventional devices that convert optical information into electrical signals include devices with a self-scanning function ("5elf-8
canned Image 5ansor “TEEE
ED-18NO11, 1971) and a charge transfer device (BBD or CCD).
etc.), there is a device that converts optical information into an electrical signal and reads it out using a charge transfer element.

Here, a photodiode, a phototransistor, or the like is used as the optical sensor.

There is also a method in which the charge transfer element is directly irradiated with light to perform the photoelectric conversion function and the readout function in the same element, but this method causes optical distortion because the transfer element is exposed to light even during charge transfer. This is a major problem and is not practiced much at present.

The present invention relates to the former device, which is composed of a part of the photosensor and a charge transfer part, and exchanges photoelectric conversion signals between the part of the photosensor and the charge transfer part not through a transistor, but by charge injection and charge transfer part. By using the capture method, it is possible to provide a high-density photoelectric conversion device in which a photoelectric conversion signal reading transistor and inter-channel isolation diffusion regions of a plurality of charge transfer elements are simultaneously exposed.

The details of the present invention will be explained below with reference to the drawings.

FIG. 1 shows a planar arrangement of elements according to an embodiment of the present invention.

Here, the charge transfer element is of the BBD type.

20 is a charge transfer element array formed on a semiconductor substrate, 15
16 is the source diffusion region of the MOS transistor that constitutes the charge transfer element, 16 is the drain diffusion region, 17.18.33
is the gate electrode of the same transistor, and clock pulses are alternately applied to these gate electrodes and the gate electrode 18 of the next stage to transfer the charges stored in the diffusion regions 15 and 16.

Numerals 13 and 14 are floating diffusion island regions having conductivity types opposite to that of the substrate, which are formed adjacent to the diffusion region 16 of the MOS transistor for charge transfer.

. Next, FIG. 2 shows a sectional view taken along the line I--I' of the device shown in FIG.

In FIG. 2, numeral 30 is a semiconductor substrate, and numeral 13 is an n-type diffusion island region having a conductivity type opposite to that of the semiconductor substrate 30. In FIG.

31 is an insulator layer. Reference numeral 15 denotes the n-type diffusion region of the MOS transistor constituting the charge transfer element, which corresponds to an intermediate stage of transfer.

33 is a gate electrode for charge transfer. Reference numeral 32 denotes an injection electrode capacitively coupled to the island region 13 via the insulator layer 31.

In order to explain the operating principle of FIGS. 1 and 2, FIG. 3 is a diagram showing the injection electrode 32, the floating island region 13, and the semiconductor substrate 30 as circuits.

C1 is the capacitance between the electrode 32 and the island region 13 via the insulating layer 31, C2 is the junction capacitance between the island region 13 and the substrate 30,
D indicates a diode formed by the island region 13 and the substrate 30, and G indicates an electrode 32.

Now, in FIG. 3a, when a negative pulse is applied to the G terminal as shown in the figure, a potential fluctuation at the D terminal is observed as shown in b.

Assuming that the potential of the island region 30 is zero in the initial state, that is, when VD is at O potential as shown in FIG. 3, when a partial negative pulse is applied, the terminal of vD becomes C1. Since there is capacitive coupling at C2, ①o momentarily becomes a negative potential of VD(-u2)-8, which is S·■.

However, in this state, since the diode D is unidirectionally biased, a quasi-directional current flows and VD immediately becomes the same potential as the substrate.

(Specifically, the potential is 20, SV negative from the substrate potential.

) When the pulse voltage is cut off in this state, the potential of vD is raised to approximately +(6)·■.

Now, if this voltage is VR, the diode D is reverse biased in this state, so the current path is blocked and the vR potential is maintained.

However, when diode potential light is irradiated in this state, a recombination current due to the light flows through the diode D, and the vR potential begins to fall toward zero potential in accordance with the amount of light irradiation.

That is, the charge stored in C1 will be discharged.

Therefore, when a negative pulse voltage = ■ is applied to the G terminal again in this state, the diode potential ■D is again changed to a negative potential and becomes -u1, the diode D becomes unidirectional, a quasi-directional current flows, and a small number of carrier (electron e in this case)
is injected into the semiconductor substrate 30.

The total amount of injected electrons e corresponds to the total amount of charges discharged by light irradiation.

Of course, if there is no light irradiation, electron injection will not occur due to the negative pulse application.

In this case, the leakage current due to heat is extremely small compared to the photocurrent and does not pose a problem.

The operation of injecting transformer conversion signal charges into the semiconductor substrate 30 has been described above.

Returning to FIG. 2 again, a charge transfer element consisting of a diffusion region 15 is formed adjacent to the injection diode D.

Assuming that the diffusion region 15 constituting the intermediate stage of the charge transfer element adjacent to the charge injection diode D is in a positive bias state due to an operation such as reading a positive potential from the charge transfer input stage, the semiconductor substrate Most of the photoelectric conversion signal charges (electrons e) injected into the substrate 30 are captured by the positively biased diffusion region by minority carrier diffusion, electric field effect, etc., and the other part is recombined with the substrate 30.

The fractional carriers captured in the diffusion region 15 in this way are photoelectric conversion signal charges, which are read into the charge transfer element and lower the signal potential in the middle of transfer depending on the injection amount (irradiation amount). The output of the charge transfer element can be extracted as a transfer signal by alternately applying clock pulses to the gates of the MOS transistors forming the charge transfer element.

In this way, the above device eliminates the need for a gate MOS transistor for reading photoelectric conversion signals, which has been commonly used in the past, and furthermore, it is possible to apply a negative pulse to an electrode capacitively coupled to a diode for photoelectric conversion. By doing this, it is possible to always obtain a stable photoelectric signal by always setting a constant potential, that is, by performing the refresh operation at the same time as the injection.

Another feature of the above-mentioned device is that it allows for higher density.

In particular, when constructing a two-dimensional transformer array using charge transfer elements, generally the transfer channel separation diffusion layer region is must be made.

However, according to the above-mentioned device, since the injection gate 32 serves as an electrical shielding effect for the charge transfer lock line, the separation diffusion region is unnecessary, and higher density is possible, which improves the resolution characteristics of the two-dimensional array. is significantly improved.

This will be explained below with reference to FIG.

FIG. 4a shows a planar structure of a two-dimensional optical sensor array constructed using the elements shown in FIGS. 1 and 2.

32, 32a are the aforementioned injection gate electrodes, 33.33a
, 33b, 33c are (gate electrodes) for charge transfer
This is the clock line.

FIG. 4 is a cross-sectional view taken along the line IV-I'V' of FIG.

31 is an insulating layer, 15.15a is a diffusion region of a MOS transistor constituting the charge transfer element, and the injection gate electrode 32 and clock line 33 cross over.

As mentioned above, the injection gate electrode is always exposed to O-
The parasitic MO8 effect does not occur because a voltage that does not cause parasitic MO8 is applied.

That is, since the electrode 32 is normally kept at the same potential as the substrate during charge transfer and a negative voltage is applied at other times, the parasitic MO8 effect between the two diffusion regions 15 and 15a is
2, it is electrically shielded and can be ignored.

In the present invention, the effect is exactly the same when the charge transfer element is constructed of a CCD type; in this case, the injected minority carriers are captured under the biased gate electrode of the CCD.

As described above, the present invention provides a simple high-density photoelectric conversion device by exchanging photoelectric conversion signals between a part of the photosensor and the charge transfer section using a charge injection and capture method.

Furthermore, since each gate electrode is formed separately without irregularities, it can be formed simultaneously by a method such as vapor deposition, which is advantageous in manufacturing.

[Brief explanation of the drawing]

FIG. 1 is a plan layout configuration diagram of a photoelectric conversion element according to an embodiment of the present invention, FIG. 2 is a cross-sectional structural diagram taken along the line I-P, and FIG. 3 a is an equivalent circuit diagram of the photoelectric conversion diamond section in FIG. 2. , the same is a waveform diagram of each part in a, FIG. 4 a is a plan layout configuration diagram of a two-dimensional optical sensor array using the elements in FIGS. FIG. 13.14...Floating diffusion island area, 15, 15a
16... Diffusion region, 20... Charge transfer element array, 30... P-type semiconductor substrate, 31...
... Insulator layer, 32 ... Injection gate electrode, 3
3...Gate electrode (clock line) for charge transfer.

Claims (1)

[Claims] 1. A charge transfer element comprising a first island region of one conductivity type formed on one principal surface of a semiconductor substrate of one conductivity type and a first electrode on the first island region; A plurality of electrically floating second island regions of the other conductivity type are formed at predetermined intervals from the region where the charge transfer element is formed on the main surface, and the second island region and the insulator are formed. a second electrode capacitively coupled through a film and formed at a predetermined distance from the first electrode; a means for driving the charge transfer element; applying a pulsed voltage between a second electrode capacitively coupled to the second island region and an electrode in resistive contact with the semiconductor substrate; By injecting minority carriers in an amount corresponding to the amount of light irradiated onto the second island region from the second island region into the semiconductor substrate, the first electrode of the charge transfer element is biased. A semiconductor device characterized in that the fractional carriers that have reached the lower or biased diffusion region are transferred by the charge transfer element driving means.