JPH07120764B2 - Solid-state image sensor - Google Patents

Description

The present invention relates to a solid-state image sensor.

[Conventional technology]

 An example of a conventional solid-state image sensor is shown in FIG.

In FIG. 3, 1 is a p-type semiconductor substrate and 2 is an n ⁻ -type first substrate.
Region 3, 3 is a first charge transfer gate, 4 is a charge storage gate, 5 is a second charge transfer gate, 6 is an n ⁺ -type second region,
Reference numeral 7 is an output amplifier. The n ⁻ type region 2 and the p type semiconductor substrate 1 form a photodiode.

Next, the operation of the solid-state image sensor of FIG. 3 will be described with reference to FIGS. 4 (a) to 4 (c), symbols φ _{1 to} φ ₄ are the n ⁻ -type first regions 2 in FIG.
Shows the potential in the p-type semiconductor substrate 1 of the second region 6 of ~n ⁺ -type.

First, as shown in FIG. 4 (a), electrons photogenerated by a photodiode composed of the n ⁻ -type first region 2 and the p-type semiconductor substrate 1 are accumulated up to the potential φ ₁ . The electrons accumulated at the potential φ ₁ or more pass over the potential φ ₁ under the first charge transfer gate and are accumulated under the charge storage gate 4, that is, at the potential φ ₂ . Next, as shown in FIG. 4B, by applying an appropriate voltage to the second charge transfer gate 5, the potential φ ₃
Is raised to the potential φ _{5, the} electrons accumulated under the charge storage gate 4 are transferred and accumulated in the n ⁺ -type second region 6, that is, the potential φ ₄ . Next, as shown in FIG. 4C, the voltage of the second charge transfer gate 5 is cut off, and the potential φ ₅ is returned to the potential φ ₃ . At this time, the potential φ ₄ of the n ⁺ -type second region 6 is equal to the potential φ _4.
Go down to ₆ . Finally, the potential difference φ ₄ −φ ₆ in the n ⁺ type second region 6 is amplified by the output amplifier 7 and output. Therefore, the magnitude of the output signal is proportional to the amount of electrons, that is, the amount of light.

[Problems to be solved by the invention]

The conventional solid-state image sensor shown in FIG. 3 has a serious drawback. It will be described with reference to FIG.

Now, when noise is applied to the first charge transfer gate 3, the potential φ ₁ rises to the potential φ ₇ . As a result, the electrons accumulated in the n ⁻ -type first region 2 are transferred to and accumulated in the charge accumulation gate 4. As a result, the output signal has a magnitude as if the light were irradiated onto the n ⁻ -type first region 2,
A read malfunction occurs.

It is an object of the present invention to provide a solid-state image sensor having a structure capable of preventing read malfunction due to noise.

[Means for solving problems]

A solid-state imaging device according to the present invention includes a photodiode formed of a first region of opposite conductivity type selectively formed on a semiconductor substrate of one conductivity type, a charge storage / transfer means for transferring charges, and the first storage device.
In a solid-state imaging device having a charge transfer gate provided on the semiconductor substrate via an insulating film between a region and the charge storage / transfer means, even if noise is applied to the charge transfer gate, the charge transfer gate is based on the noise. The charge transfer gate extends over the first region such that the photogenerated carriers in the first region can be prevented from being transferred to the charge storage and transfer means by changing the potential of the first region. It is characterized in that an extending portion is provided.

〔Example〕

 Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of an embodiment of the present invention.

In this embodiment, a photodiode composed of a p-type semiconductor substrate 1 and an n-type first region 2 provided on the semiconductor substrate, and an n-type second region 6 provided on the p-type semiconductor substrate.
And a charge storage gate 4 provided between the first region 2 and the second region 6 and a photo-generated carrier of a photodiode provided above the first region 2 and transferred below the charge storage gate 4. The first charge transfer gate 8 and the second charge transfer gate 5 that transfers the charges accumulated under the charge storage gate 4 to the second region 6 are included. The first charge transfer gate 8 and the first region 2 are capacitively coupled.

Next, the operation of this embodiment will be described.

FIG. 2 is a potential distribution diagram for explaining the operation of the embodiment shown in FIG.

Now, when noise is applied to the first charge transfer gate 8, the potential φ ₁ of the region immediately below the semiconductor substrate ₁ is transiently changed to the potential φ 1.
It will be ₈ . At this time, the first region 2 has the first charge transfer gate 8
Since it is capacitively coupled with
φ = φ ₈ −φ ₁ rises, and therefore electrons cannot cross the potential φ ₈ under the first charge transfer gate. Therefore, read malfunction due to noise can be prevented.

In this embodiment, the case where a constant voltage is applied to the first charge transfer gate 8 has been described, but the present invention can also be applied when a pulse is applied to read electrons from the first region 2. At that time, when a charge read pulse is applied to the first charge transfer gate 8, the potential of the first region 2 changes at first with the potential below the first charge transfer gate, but noise is applied during the period during which the charge read pulse is applied. Since it is much longer than that, the capacitance between the first charge transfer gate 8 and the first region 2 is charged, the potential of the first region 2 finally becomes shallower than the potential under the first charge transfer gate, and the electrons are It will be read.

With the above-described configuration, the present invention can be applied regardless of the case where there is no charge storage gate and the means for transferring the charge to the output amplifier.

〔The invention's effect〕

As described above, according to the present invention, even when noise is applied to the charge transfer gate, it is possible to obtain the solid-state imaging device capable of preventing the occurrence of the read malfunction due to the noise.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, FIG. 2 is a potential distribution diagram for explaining the operation of the embodiment shown in FIG. 1, and FIG. 3 is a sectional view of an example of a conventional solid-state image sensor. 4 Figures (a) to (c)
And FIG. 5 is a potential distribution diagram for explaining the operation of the solid-state imaging device shown in FIG. 1 ... p-type semiconductor substrate, 2 ... first region (n ^- type), 3 ...
… First charge transfer gate, 4 …… Charge storage gate, 5 ……
Second charge storage gate, 6 ... Second region (n ⁺ type), 7 ...
Output amplifier, 8 ... First charge transfer gate.

Claims (1)

[Claims] 1. A photodiode comprising a first region of opposite conductivity type selectively formed on a semiconductor substrate of one conductivity type, a charge storage / transfer device for transferring charges, the first region and the charge storage / transfer device. In the solid-state imaging device having a charge transfer gate provided on the semiconductor substrate via an insulating film between and, even if noise is applied to the charge transfer gate, the potential of the first region is changed based on the noise. The charge transfer gate is provided with an extending portion extending above the first region so that the photo-generated carriers in the first region can be prevented from being transferred to the charge storage and transfer means by changing the number. A solid-state image sensor characterized by the above.