JPH07176726A - Charge transfer device - Google Patents

Abstract

PURPOSE:To obtain a charge transfer device which can isolate a floating gate from a gate in a charge transfer part, enhance the charge-to-voltage conversion efficiency of the floating gate, enhance the sensitivity of a solid-state image pick up device and enhance an S/N. CONSTITUTION:Individual electrodes for a first output gate OG1 and a second output gate OG2 are formed between a charge transfer stage and a charge storage part, the electrode for the first output gate OG1 is driven by a constant voltage, and the output of a charge detection part 3 is fed back to the electrode for the second output gate OG2 on the side of the charge storage part via a feedback passage. Thereby, the electrode for the second output gate OG2 is driven by an image-sensing signal S whose phase is identical to that of a voltage change DELTAV in the charge storage part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge transfer device used as a charge transfer stage including an output part of a solid-state image pickup device having a charge detection part by a floating gate amplifier.

[0002]

2. Description of the Related Art Generally, a charge transfer device used as a charge transfer stage including an output part of a solid-state image pickup device comprises a charge transfer part for sequentially transferring signal charges and a floating diffusion amplifier or a floating gate amplifier. And an electric charge detection unit.

In particular, the charge detection section using the floating gate amplifier can nondestructively detect the signal charge transferred from the charge transfer section by using the floating gate, and the density can be easily increased. The characteristics are that the parasitic capacitance is small, the sensitivity is high, and the noise is small.

As shown in FIG. 7, a conventional charge transfer device has a charge transfer section 31 for sequentially transferring signal charges, using a P-type silicon substrate as a base, and the charge transfer section 31.
And a charge detection unit 32 that detects the signal charge that is transferred.

The charge transfer section 31 has a so-called two-phase drive transfer system configuration in which signal charges are sequentially transferred by applying, for example, two-phase drive pulses φ1 and φ2 of opposite phases to each other. ing.

The charge detection unit 32 is composed of a floating gate amplifier which nondestructively detects the signal charges transferred from the charge transfer unit 31. This floating gate amplifier includes an output gate OG formed adjacent to the final stage of the charge transfer unit 31 and a floating gate F.
G, a discharge element 33 composed of a precharge gate PG and a drain region D, and a source follower circuit 34 composed of an output element Q1 and a load resistance element Q2 in the subsequent stage of the floating gate amplifier. There is.

The output gate OG has its gate electrode supplied with the DC voltage Vog, and the precharge gate PG has its gate electrode supplied with a control pulse φpg.
Is supplied. As a result, the floating gate FG is transferred from the charge transfer unit 31 via the output gate OG.
The signal charge accumulated in the drain region D is swept out.

The gate electrode of the floating gate FG is connected to a switching transistor Tr to which a reset pulse Pr is supplied and a drain terminal thereof is supplied with a power supply voltage Vr for resetting. By supplying the reset pulse Pr to the gate electrode of the switching transistor Tr, the potential under the floating gate electrode is fixed to the Vr level. Further, by supplying the voltage change ΔV to the source follower circuit 34 in the subsequent stage by the signal charge transferred / accumulated under the floating gate electrode, the source follower circuit 34
Is output as an output voltage (imaging signal) S from the output terminal φout.

[0009]

However, in the above charge transfer device, since the voltage Vog applied to the output gate OG is a fixed potential, the charge-voltage is caused by the parasitic capacitance between the floating gate FG and the output gate OG. It is an obstacle to improving the conversion efficiency.

The present invention has been made in view of the above-mentioned problems, and includes a floating gate FG and an output gate O.
The parasitic capacitance between the Gs can be reduced, the floating gate FG and the gate of the charge transfer unit 31 can be separated, and the charge-voltage conversion efficiency in the floating gate FG can be improved, which improves the sensitivity of the solid-state imaging device. And S / N
An object of the present invention is to provide a charge transfer device capable of improving the ratio.

[0011]

A charge transfer device according to the present invention is a charge transfer device comprising a charge detection part for detecting charges accumulated in a charge storage part, wherein a charge transfer stage is provided between the charge transfer stage and the charge storage part. And a means for supplying a DC voltage to the first output gate electrode of the charge transfer stage, and an output of the charge detection unit on the side of the charge storage unit. It is characterized by having a return path for returning to the second output gate electrode.

The charge transfer device according to the present invention is a charge transfer device comprising a charge detection part for detecting charges accumulated in a charge storage part, wherein an output gate provided between the charge transfer stage and the charge storage part. The output gate electrode has an extension portion extending along both side edges of the charge storage portion.

Further, in the charge transfer device according to the present invention, a floating gate electrode is arranged on the charge storage portion via an insulating film, and the floating gate electrode is
It is characterized in that it has respective facing portions facing the respective extension portions of the output gate electrode.

Furthermore, the charge transfer device according to the present invention is characterized in that the capacitance between each extension of the output gate electrode and the opposing portion of the floating gate electrode is smaller than the capacitance between the floating capacitance / gate electrode and the substrate. And

[0015]

In the charge transfer device according to the present invention, the first and second output gate electrodes are provided between the charge transfer stage and the charge storage section, and the first output gate electrode is driven at a constant voltage. The output of the charge detection unit is fed back to the second output gate electrode on the charge storage unit side via the feedback path. This allows
The second output gate electrode is connected to the charge storage unit by a voltage change Δ
It drives with the imaging signal S of the same phase as V.

In the solid-state imaging device according to the present invention, an output gate electrode is provided between the charge transfer stage and the charge storage part, and the output gate electrode is extended along both side edges of the charge storage part. It has an extension.

Further, in the solid-state image pickup device according to the present invention, a floating gate electrode is arranged on the charge storage portion via an insulator, and the floating gate electrode is
It has a facing portion facing the output gate and surrounds the floating gate electrode with the output gate. .

Further, in the solid-state image sensor according to the present invention,
The floating gate of each extension of the output gate electrode
The distance between the facing part of the gate electrode and the floating capacitance
The gap is smaller than the gap between the gate electrode and the substrate.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of a charge transfer device according to the present invention will be described below with reference to the drawings.

First, a charge transfer device according to the first embodiment of the present invention will be described.

The output section 1 of the charge transfer device according to the first embodiment of the present invention shown in FIG. 1 is, for example, a P-type silicon substrate as a substrate, and a charge transfer section 2 for sequentially transferring signal charges.
The charge transfer unit 2 includes a charge detection unit 3 that detects signal charges transferred from the charge transfer unit 2.

The charge transfer section 2 is formed, for example, with a horizontal register 8 formed of an N type impurity diffusion region band on the surface of a P type silicon substrate 7, and an insulating film 9 on the horizontal register 8. It has first and second horizontal transfer electrodes 10 and 11 (of the first and second polycrystal silicon layers), and these two horizontal transfer electrodes 10 and 11 are respectively set as one set. It is formed by sequentially arranging and forming in the horizontal direction. Then, two-phase drive pulses φ that are in opposite phases to each other
By applying 1 and φ2 for each set, the signal charges are sequentially transferred to the output section 1 side.

The charge detection section 3 has a floating gate amplifier 4 for nondestructively detecting the signal charge transferred from the charge transfer section 2.

The floating gate amplifier 4 has first and second floating gate amplifiers 4 formed adjacent to the final stage of the charge transfer section 2.
Output gates OG1 and OG2, a floating gate FG, a discharge element 5 including a precharge gate PG and a drain region D, and a source including an output element Q1 and a load resistance element Q2 at a stage subsequent to the discharge element. The follower circuit 6 is provided. The output element Q1 and the load resistance element Q2 are, for example, N-channel type MOS.
It is composed of a FET (MOS field effect transistor).

A DC voltage Vog1 is supplied to the gate electrode 21 of the first output gate OG1, and a control pulse φpg is supplied to the gate electrode 24 of the precharge gate PG. As a result, the signal charges transferred from the charge transfer unit 2 via the first and second output gates OG1 and OG2 and accumulated in the floating gate FG are swept out to the drain region D.

Further, the gate electrode 23 of the floating gate FG is connected to a switching transistor Tr to which a reset pulse Pr is supplied and a drain terminal thereof is supplied with a reset power supply voltage Vr. By supplying the reset pulse Pr to the gate electrode of the switching transistor Tr, floating
The potential below the gate electrode 23 of the gate FG is fixed at the Vr level. In addition, floating gate FG
By supplying the voltage change ΔV due to the signal charges transferred / stored under the gate electrode 23 of the source follower circuit 6 to the output terminal φout of the source follower circuit 6.
Is output as an output voltage (imaging signal) S from the.

The output timings of the two-phase drive pulses φ1 and φ2 and the reset pulse φpg are shown in FIG.

Therefore, the voltage change ΔV taken out from the gate electrode 23 of the floating gate FG becomes a signal containing a signal component based on the precharge drain voltage Vdd and the accumulated charge amount as shown by the waveform 1 in FIG. . Further, regarding the output signal from the source follower circuit 6, when the gain of the source follower circuit 6 is G (0.7 <G ≦ 1),
As shown in waveform 2, the floating gate FG
The signal becomes a signal obtained by multiplying the voltage change ΔV extracted from the gate electrode 23 by G times, and the relationship of each signal (voltage change ΔV and output signal S) is in phase.

At this time, in the output signal S from the source follower circuit 6, the voltage corresponding to the precharge drain voltage Vdd in the voltage change ΔV taken out from the gate electrode 23 of the floating gate FG is Vo.
And the magnitude relation is the gain G of the source follower circuit 6.
From the relationship, Vo <Vdd.

Therefore, in this example, the feedback path 15 connecting the output side of the source follower circuit 6 and the gate electrode 22 of the second output gate OG2 is provided, and the output signal ( The image pickup signal S is fed back to the gate electrode 22 of the second output gate OG2. In this case, since the signal in phase with the voltage change ΔV extracted from the gate electrode 23 of the floating gate FG is supplied to the gate electrode 22 of the second output gate OG2,
Floating gate FG and second output gate OG2
The parasitic capacitance between them is reduced.

In reality, when the gain of the source follower circuit 6 is G, the parasitic capacitance between the floating gate FG and the second output gate OG2 can be reduced by (1-G) times. Therefore, ideally, by changing the bias potential Vgg applied to the gate of the load resistance element Q2 of the source follower circuit 6, the gain G of the source follower circuit 6 is brought close to 1 and the floating gate FG is reduced. Of the output signal S from the source follower circuit 6 and the voltage change ΔV taken out from the gate electrode of the second gate FG2 are close to 0, the parasitic capacitance between the floating gate FG and the second output gate OG2.
Can be equivalently zero.

As described above, according to the present example, the output (image pickup signal S) from the source follower circuit 6 is fed back to the gate electrode 22 of the second output gate OG2, so that the floating The parasitic capacitance between the gate FG and the second output gate OG2 can be reduced.
Further, since the output gate has a two-stage structure, the floating gate FG and the gate of the charge transfer portion can be separated. That is, by biasing the direct current to the first output gate OG1, the second pulse of the drive pulse φ2
Can be prevented from coupling to the output gate OG2. From this, the charge-voltage conversion efficiency in the floating gate FG can be improved, and the sensitivity and S / N ratio of the solid-state imaging device can be improved.

Next, a charge transfer device according to the second embodiment of the present invention will be described.

In the above description of the first embodiment, the output of the source follower circuit 6 is fed back to the gate electrode 22 of the second output gate OG2 via the return path 15.
The solid-state image sensor according to the second embodiment is the same as the return path 1 described above.
5 is saved, and the second output gate OG2 provided adjacent to the first output gate OG1 is driven by a constant voltage by the configuration shown in FIG.

The parts showing the same operations as those of the first embodiment described above are designated by the same reference numerals, and the detailed description thereof will be omitted.

That is, in FIG. 4, the gate electrode 22 of the second output gate OG2 of the solid-state imaging device according to the second embodiment is extended along both side edges of the gate electrode 23 of the floating gate FG. Each extension 22a, 2
The gate electrode 23 of the floating gate FG has a facing portion 23a, 23b of the gate electrode 23 of the second output gate OG2 facing the extension portion 22a, 22b.
b. Specifically, as shown in FIG.
Each extension 22 of the gate electrode 22 of the output gate OG2 of
a, 22b is between t ₂ and substrate 7, are configured to have a smaller spacing than the spacing t ₁ between the facing portions 23a, 23b of the gate electrode 23 of the floating gate FG.

As a result, as shown in FIG. 6, the second output gate O is larger than the capacitance Ccs between the channel stop 25 and the gate electrode 23 of the floating gate FG.
The capacitance between the gate electrode 22 of G2 and the gate electrode 23 of the floating gate FG can be made much smaller. Further, since the output gate has a two-stage structure, the floating gate FG and the gate of the charge transfer portion can be separated. Therefore, it is possible to reduce the parasitic capacitance between the floating gate FG and the second output gate OG2, and to reduce the total capacitance related to the floating gate FG. From this, the charge-voltage conversion efficiency in the floating gate FG can be improved, and the sensitivity and S / N ratio of the solid-state imaging device can be improved.

In the above-mentioned second embodiment, the first and second output gates are provided between the charge transfer section and the charge storage section, but the first output gate is The same effect can be obtained by the omitted configuration, that is, the configuration in which only one output gate having the respective extension portions extended along both side edges of the charge storage portion is provided.

Next, a charge transfer device according to the third embodiment of the present invention will be described.

In the above description of the second embodiment, the second
It was decided to drive the output gate OG2 of
In the charge transfer device according to the third embodiment, the output of the source follower circuit 6 in the second embodiment is used as the second output.
A feedback path for returning to the gate electrode 22 of the output gate OG2 is provided.

With such a configuration, the second output gate OG2 is supplied with a signal in phase with the voltage change ΔV taken out from the gate electrode of the floating gate FG. Further, the capacitance between the gate electrode 22 of the second output gate OG2 and the gate electrode 23 of the floating gate FG is made much smaller than the capacitance Ccs between the channel stop 25 and the gate electrode 23 of the floating gate FG. Can also have 2 output gates
Because of the step structure, the floating gate FG and the gate of the charge transfer portion can be separated. Therefore,
Floating gate FG and second output gate OG2
The parasitic capacitance between them can be reduced, and the reduction of the total capacitance related to the floating gate FG can be realized. From this, the floating gate FG
Can improve the charge-voltage conversion efficiency in
It is possible to improve the sensitivity and the S / N ratio of the solid-state image sensor.

In the above description of the second embodiment, each extension 2 of the gate electrode 22 of the second output gate OG2 is described.
In 2a and 22b, the distance t2 from the substrate is set to be smaller than the distance t1 between the facing portions 23a and 23b of the gate 23 of the floating gate electrode FG (t1> t2), but in the third embodiment, For example, when the interval t1 and the interval t2 are the same (t1 = t2), or the interval t2 is the interval t.
The same effect can be obtained when the value is set to be larger than 1 (t1 <t2).

Further, the voltage change Δ taken out from the gate electrode 23 of each of the first to third floating gates FG.
An example in which V is applied to the output unit 1 that amplifies V in the source follower circuit 5 including the output element Q1 and the load resistance element Q2 has been shown. However, other than the source follower circuit 6, any voltage follower type amplifier can be used. All are applicable.

Further, the case where electrons are used as carriers to be treated as signal charges by using N-type as the impurity diffusion region forming the charge transfer section 2 has been described.
In addition, the present invention can be applied to the case where the impurity diffusion region forming the charge transfer unit 2 is P-type and the carriers handled as signal charges are holes.

The same effects can be obtained by applying the above invention to a floating diffusion amplifier.

[0046]

In the charge transfer device according to the present invention, the first and second output gate electrodes are provided between the charge transfer stage and the charge storage section, and the first output gate electrode is driven with a constant voltage. At the same time, the output of the charge detection unit is fed back to the second output gate electrode on the charge storage unit side via the feedback path. As a result, the second output gate electrode is driven by the imaging signal S in phase with the voltage change ΔV in the charge storage section. Therefore, since the floating gate and the gate of the charge transfer section can be separated from each other, the charge-voltage conversion efficiency in the floating gate can be improved, the sensitivity of the solid-state imaging device and the S / N ratio can be improved. Can be planned.

In the charge transfer device according to the present invention, an output gate electrode is provided between the charge transfer stage and the charge storage part, and the output gate electrode is extended along both side edges of the charge storage part. It has an extension. Because of this, floating
The parasitic capacitance between the gate and the output gate can be reduced, and the sensitivity of the solid-state image sensor and the S / N ratio can be improved.

Further, in the charge transfer device according to the present invention, a floating gate electrode is arranged on the charge storage portion via an insulator, and the floating gate electrode is
It has a facing portion facing the output gate and surrounds the floating gate electrode with the output gate. Therefore, since the floating gate and the gate of the charge transfer unit can be separated from each other, the charge-voltage conversion efficiency in the floating gate can be improved, the sensitivity of the solid-state imaging device can be improved, and the S-value can be improved.
It is possible to improve the / N ratio.

Further, in the charge transfer device according to the present invention, the distance between each extension of the output gate electrode and the facing portion of the floating gate electrode is smaller than the distance between the floating capacitor / gate electrode and the substrate. Therefore, the capacitance between the output gate electrode and the floating gate electrode can be made much smaller than the capacitance between the channel stop and the floating gate electrode. Therefore, since the floating gate and the gate of the charge transfer section can be separated, it is possible to further improve the charge-voltage conversion efficiency in the floating gate, improve the sensitivity of the solid-state imaging device, and improve the S / N ratio. It is possible to improve.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a main configuration of a charge transfer device according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram showing output timings of two-phase drive pulses and reset pulses in the first embodiment.

FIG. 3 is a waveform diagram showing the relationship between the voltage change from the floating gate and the output signal from the source follower circuit in the first embodiment.

FIG. 4 is a configuration diagram showing a configuration of a main part of a charge transfer device according to a second embodiment of the present invention.

5 is a sectional view taken along line II of the second output gate of the charge transfer device shown in FIG.

FIG. 6 is a diagram for explaining a capacitance between a channel stop and a floating gate in the second embodiment.

FIG. 7 is a configuration diagram showing a configuration of an output section of a conventional charge transfer device.

[Explanation of symbols]

1 Output unit 2 Charge transfer unit 3 Charge detection unit 4 Floating gate amplifier 5 Discharge device 6 Source follower circuit 7 Substrate 8 Horizontal register 9 Insulation film 22 ...... gate electrode of second output gate 22a, 22b ...... extension of gate electrode of second output gate 23 …… gate electrode of floating gate 23a, 23b …… opposite portion of gate electrode of floating gate 25 ...... Channel stop OG1 ...... First output gate OG2 ...... Second output gate FG ...... Floating gate PG ...... Reset gate D ...... Drain region

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] February 2, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

The output gate OG has its gate electrode supplied with the DC voltage Vog, and the precharge gate PG has its gate electrode supplied with a control pulse φpg.
Is supplied. As a result, the floating gate FG is transferred from the charge transfer unit 31 via the output gate OG.
The signal charge accumulated in the drain region is swept out to the drain region D.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

Further, in the solid-state image pickup device according to the present invention, a floating gate electrode is arranged on the charge storage portion via an insulator, and the floating gate electrode is
It has a facing portion facing the output gate and surrounds the floating gate electrode with the output gate.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

Further, in the solid-state image sensor according to the present invention,
The floating gate of each extension of the output gate electrode
The distance between the facing part of the gate electrode and the floating capacitance
The gap is larger than the gap between the gate electrode and the substrate.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0049

[Correction method] Change

[Correction content]

Further, in the charge transfer device according to the present invention, the distance between each extension of the output gate electrode and the facing portion of the floating gate electrode is larger than the distance between the floating capacitor / gate electrode and the substrate. Therefore, the capacitance between the output gate electrode and the floating gate electrode can be made much smaller than the capacitance between the channel stop and the floating gate electrode. Therefore, since the floating gate and the gate of the charge transfer section can be separated, it is possible to further improve the charge-voltage conversion efficiency in the floating gate, improve the sensitivity of the solid-state imaging device, and improve the S / N ratio. It is possible to improve.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahide Hirama 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation

Claims (4)

[Claims] 1. A charge transfer device including a charge detection unit for detecting charges accumulated in a charge accumulation unit, wherein first and second output gate electrodes provided between a charge transfer stage and the charge accumulation unit. A means for supplying a DC voltage to the first output gate electrode of the charge transfer stage, and a feedback path for returning the output of the charge detection unit to the second output gate electrode on the charge storage unit side. A charge transfer device characterized by: 2. A charge transfer device comprising a charge detection unit for detecting charges stored in a charge storage unit, comprising: an output gate electrode provided between the charge transfer stage and the charge storage unit; The charge transfer device according to claim 1, wherein the gate electrode has extension parts extending along both side edges of the charge storage part. 3. A floating gate electrode is disposed on the charge storage portion via an insulating film, and the floating gate electrode has respective facing portions facing the respective extension portions of the output gate electrode. The charge transfer device according to claim 2, which is characterized in that. 4. The charge transfer according to claim 3, wherein the capacitance between each extension of the output gate electrode and the opposing portion of the floating gate electrode is smaller than the capacitance between the floating capacitance / gate electrode and the substrate. apparatus.