JPH05292242A - Charge transfer device - Google Patents

Abstract

(57) [Abstract] [Purpose] By correcting the DC step at the signal charge transfer stage, the circuit configuration of the signal processing circuit connected in the subsequent stage is simplified, and the cost of electronic equipment equipped with a CCD linear sensor is reduced. It promotes cost reduction and structure miniaturization. [Structure] Readout gates 2a and 2b commonly formed for each light receiving unit 4 are formed on both sides of a light receiving unit row 1 configured by arranging light receiving units 4 corresponding to respective pixels in one direction, In the CCD linear sensor A in which the horizontal shift registers 3a and 3b are formed on the opposite sides of the readout gates 2a and 2b from the light receiving section column 1, respectively, the ends of the horizontal shift registers 3a and 3b opposite to the output sections 5a and 5b. The charge injection parts 6a and 6b are connected to the respective parts. Then, the potential V applied to each of the charge injection units 6a and 6b is controlled by the variable resistors R1 and R2, respectively, to control the amount of charges injected from the charge injection units 6a and 6b into the horizontal shift registers 3a and 3b. ..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for use in a charge transfer device, particularly a CCD solid-state image pickup device having a plurality of charge transfer sections, a CCD delay line for signal processing, and the like.

[0002]

2. Description of the Related Art A CCD linear sensor, a CCD image sensor, a CCD delay line, and the like are examples of devices having a plurality of CCD charge transfer units.

Among them, for example, a CCD linear sensor is
Pixels arranged on a straight line are sequentially read out.
For example, there is a device as shown in FIG. This conventional C
As shown in the figure, the CD linear sensor has a light receiving section 21 separated for each pixel, and read gates 22a, 22b and horizontal shift registers 23a, 23b formed commonly for each light receiving section 21.

Then, in the charge accumulation period, the signal charges e corresponding to the optical information are accumulated in the respective light receiving portions 21, and in the next read period, the read pulse Pr is applied to the respective read gates 22a and 22b via the input terminal φr. By applying the signal charges e, for example, the signal charges e accumulated in the odd-numbered light receiving portions 21 are transferred to the one horizontal shift register 23a through the one read gate 22a and are accumulated in the even-numbered light receiving portions 21. The signal charge e stored therein is transferred to the other horizontal shift register 23b through the other read gate 22b.
Transfer to.

The signal charges e transferred to the horizontal shift registers 23a and 23b are supplied to two input terminals φ1 and φ2.
By the transfer driving by, for example, two-phase transfer pulses P1 and P2 supplied to the
They are transferred to the a and 24b sides, respectively. Then, in each of the signal output sections 24a and 24b, the signal charge e is converted into a voltage, and the image pickup signals S1 and S2 are output from the output terminals φa and φb.
Take out each as.

[0006]

By the way, the above-mentioned CCD
As the output signal waveform of the linear sensor, as shown in FIG. 7, the reset level component Vr of the reset pulse P supplied to each output section 24a and 24b via the input terminal φ and the signal component Vs corresponding to the signal charge amount. And exist. In this output signal waveform, the waveform in the period indicated by T1 shows the output signal waveform due to the idle feed of the horizontal shift registers 23a and 23b, and the waveform in the period indicated by T2 transfers the signal charges e in the horizontal shift registers 23a and 23b. 3 shows an output signal waveform by.

Here, when there is only one horizontal shift register, there is no problem because there is only one type of signal handled by the signal processing circuit (not shown) in the subsequent stage, but as shown in FIG. When there are two image pickup signals S1 and S2 output from the output units 5a and 5b, particularly in the idle feed portion where the black level Vb that is the reference of signal output is output, the image pickup signals S1 and S2 are output. Amplitudes A1 and A
2 has a variation (offset ΔA). This phenomenon is generally called a DC step. This DC step is CCD
This is caused by manufacturing variations in the linear sensor, for example, the arrangement of horizontal shift registers and the difference in the layout of wirings that electrically connect a drive circuit (not shown) and each horizontal shift register.

Therefore, in the prior art, the DC step is corrected in the subsequent signal processing circuit, but the circuit configuration of the signal processing circuit becomes complicated and the CCD
There has been a problem that it is difficult to reduce the cost of an electronic device equipped with the linear sensor and to reduce the size of the structure.

The present invention has been made in view of the above problems, and an object of the present invention is to correct a DC step in a signal charge transfer stage and to provide a signal processing circuit connected in a subsequent stage. An object of the present invention is to provide a charge transfer device capable of simplifying the circuit configuration and promoting cost reduction and size reduction of an electronic device equipped with a CCD linear sensor.

[0010]

The present invention has a plurality of charge transfer sections 3a and 3b and output sections 5a and 5b connected to the next stage of each charge transfer section 3a and 3b. In the charge transfer device A that sequentially converts the signal charges e sequentially transferred from 3a and 3b into the electric signals S1 and S2 at the output units 5a and 5b, the charge transfer units 3a and 3b.
In the preceding stage, the charge injection units 6a and 6b for equalizing the reference potential levels Vb of the charge transfer units 3a and 3b are connected.

As the charge injection portions 6a and 6b, the gate electrode 15 to which a predetermined precharge potential Vg is applied.
And the charge injection region 16 to which the variable control potential V is supplied, or the control electrode 15 to which the variable control potential Vg is applied and the charge to which a predetermined precharge potential V is supplied. It may be configured with the implantation region 16.

[0012]

According to the above-described configuration of the present invention, each charge transfer section 3
Charge injection parts 6a and 6b for aligning the reference potential levels Vb of the charge transfer parts 3a and 3b are provided in front of a and 3b.
Therefore, the necessary charge ei is injected from the charge injection units 6a and 6b, and the charge transfer units 3a and 6b are connected.
It is possible to make the reference potential levels of a and 3b, for example, the black level Vb of the CCD linear sensor A at the time of idling, uniform between the plurality of charge transfer units 3a and 3b.

Generally, the black level Vb differs between the plurality of charge transfer portions 3a and 3b due to manufacturing variations, but according to the charge transfer device of the present invention,
The variation (DC step) ΔA of the black level Vb between the plurality of charge transfer units 3a and 3b can be easily corrected in the transfer stage of the signal charge e, and the DC step ΔA of the signal processing circuit connected to the subsequent stage can be corrected. It is not necessary to form a circuit for correction. As a result, the circuit configuration of the signal processing circuit can be simplified, and the cost reduction and the size reduction of the electronic device equipped with the CCD linear sensor can be promoted.

[0014]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic configuration diagram showing a CCD linear sensor A according to this embodiment.

The CCD linear sensor A has, as shown in the figure, one light-receiving section array 1, two readout gates 2a and 2b, and two horizontal shift registers 3a and 3b.

The light-receiving section array 1 is composed of, for example, light-receiving sections 4 separated for each pixel arranged in one direction (horizontal direction). Each light receiving portion 4 is formed of a photodiode by a pn junction of, for example, a P type silicon substrate or well region (not shown) and an N type impurity diffusion region formed on the surface thereof.

The read gates 2a and 2b are formed in common on each side of the light receiving section array 1 for each light receiving section 4. The horizontal shift registers 3a and 3b are provided on the opposite side of the readout gates 2a and 2b from the light receiving section column 1.
It is formed in common for each light receiving unit 4.

Then, during the charge accumulation period, the signal charge e corresponding to the optical information is accumulated in each light receiving portion 4, and in the next read period, the read pulse Pr is applied to each of the read gates 2a and 2b via the input terminal φr. By applying
For example, the signal charge e accumulated in the odd-numbered light receiving portions 4
Is transferred to one horizontal shift register 3a via one read gate 2a, and the signal charge e accumulated in the even-numbered light receiving section 4 is transferred to the other horizontal shift register 3b via the other read gate 2b. Forward.

The signal charges e transferred to the horizontal shift registers 3a and 3b are output in the horizontal direction, that is, by the transfer driving by the transfer pulses P1 and P2 of two phases supplied to the two input terminals φ1 and φ2. Parts 5a and 5b
It is transferred to each side. Then, in each of the output sections 5a and 5b, the signal charge e is converted into a voltage, which is taken out from each of the output terminals φa and φb as image pickup signals S1 and S2, respectively.

In this embodiment, however, the horizontal shift registers 3a and 3b are connected to the charge injection parts 6a and 6b at the ends opposite to the output parts 5a and 5b, respectively. Each of the charge injection units 6a and 6b has a function of electrically injecting charges into the corresponding horizontal shift registers 3a and 3b. This is the read gates 2a and 2b.
It is possible to supply the charges independently of the signal charges e corresponding to the optical information read from, and it is also possible to control the amount of injected charges from the outside.

FIG. 2 shows an example of the charge injection part (for example, 6a). In this example, the horizontal shift register 2a is composed of an N-channel CCD formed on a P-type silicon substrate 11. Also, the horizontal shift register 2a
The transfer electrodes formed on the upper side are composed of a first transfer electrode 12a made of, for example, a polycrystalline silicon layer and a second transfer electrode 12b made of a second layer, for example, a polycrystalline silicon layer. First and second transfer electrodes 12a and 12
b as one set, and the transfer pulses P of two phases are alternately arranged in each set.
1 and P2 are provided. In addition, one set of transfer electrodes (12
a, 12b) corresponds to one light receiving unit 4. Further, in the figure, 13 is a gate insulating film made of SiO ₂ or the like.

In particular, a low-concentration P-type impurity diffusion region 14 is formed under the second transfer electrode 12b, and as shown in the potential diagram of FIG. 3, each set has a stepwise descending shape along the charge transfer direction. The potential of is formed. Regarding the transfer electrodes 12a and 12b in the first stage, when the supplied transfer pulse P2 is at a high level,
As shown by the solid line, the potential well gets deeper,
At low levels, the potential well becomes shallow, as shown by the dashed line.

The charge injection portion 6a is composed of a first-layer gate electrode 15 formed of, for example, a polycrystalline silicon layer formed in the lateral direction of the transfer electrodes 12a and 12b in the first stage, and an N-type charge injection region 16. To be done. A predetermined pre-charge potential Vg is applied to the gate electrode 15, and the potential under the gate electrode 15 is fixed to, for example, an approximately midpoint of the potential amplitude L under the transfer electrodes 12a and 12b, as shown in FIG. .. The charge injection region 16 is connected to the external terminal φe1 and the potential under the charge injection region 16 is determined by supplying the potential V from the external terminal φe1.

Next, referring to FIGS. 2 and 3, the operation of the charge injection section 6a will be described.
Due to the supply of the potential V, a large amount of charges (electrons in this case) ei are supplied. When the potential of the charge injection region 16 is deep, the amount of the charge ei supplied to the charge injection region 16 decreases, so that the potential of the supplied charge ei under the adjacent gate electrode 15 serves as a barrier. No inflow below the transfer electrode 12a occurs.

On the contrary, when the potential of the charge injection region 16 is shallow, the charge ei supplied below the charge injection region 16 is increased.
Therefore, the supplied electric charge ei flows into the potential well below the transfer electrode 12a beyond the potential barrier below the adjacent gate electrode 15.

That is, the external terminal φe1 of the charge injection region 16
The charge inflow amount can be controlled by the potential V supplied to the charge injection region 1 if the supply potential V is constant.
The amount of electric charge ei supplied to 6 also becomes constant. Therefore, by appropriately controlling the potential V supplied to the charge injection region 16, it is possible to control the amount of the charge ei flowing into the potential well below the transfer electrode 12a in the charge injection region 16.

To control the potential V supplied to the external terminal .phi.e1, as shown in FIG. 1, a variable resistor R1 is connected to the external terminal .phi.e1 of the charge injection section 6a, and the variable resistor R1 is connected.
By controlling 1, the potential V supplied to the external terminal φe1 can be controlled. The other charge injection part 6b
Similarly, by connecting the variable resistor R2 to the external terminal φe2 of the charge injection unit 6b and controlling the variable resistor R2, the potential V supplied to the external terminal φe2 can be controlled.

The output signal waveform of the CCD linear sensor according to this embodiment will be described below with reference to FIG.
Output signal waveforms output from the output units 5a and 5b are
There is a reset level component Vr of the reset pulse P and a signal component Vs corresponding to the amount of signal charge, which are supplied to the output units 5a and 5b via the input terminal φ. The reset pulse P supplied from the input terminal φ is supplied to the output parts 5a and 5b.
It is for resetting the signal charge e whose voltage is converted in.

In this output signal waveform, the waveform in the period indicated by T1 shows the output signal waveform of the horizontal shift registers 3a and 3b in the idle feed, and the waveform in the period indicated by T2 shows in the horizontal shift registers 3a and 3b. The output signal waveform by transfer of the signal charge e is shown.

When a plurality of horizontal shift registers 3a and 3b are provided, normally, the black level Vb which is a reference of signal output is output among the image pickup signals S1 and S2 output from the output units 5a and 5b. In the idle feed portion, the amplitudes A1 and A2 of the image pickup signals S1 and S2 vary (DC step). This DC step is CCD
Manufacturing variations of the linear sensor A, for example, the arrangement of the horizontal shift registers 3a and 3b, a drive circuit (not shown)
And the horizontal shift registers 3a and 3b are electrically connected to each other.

The DC step appears as a difference (offset amount ΔA) between the amplitudes A1 and A2 of the image pickup signals S1 and S2 in the idling period T1. Therefore, when the DC step is corrected, the amplitude corresponding to the offset amount ΔA may be supplemented.

Therefore, in this example, the charge injecting section 6a or 6b corresponding to the output section 5a or 5b having the higher black level Vb is controlled to generate the charge ei corresponding to the offset amount ΔA. It is injected into the corresponding horizontal shift register 2a or 2b.

Specifically, first, the charge injection parts 6a and 6a.
The electric potentials supplied to the charge injection regions 16 of b are the same, and the electric charges ei are applied to the horizontal shift registers 2a and 2b.
Is set to a potential V that does not inject.

Then, for example, in an inspection step after the device is assembled, the black level Vb of the image pickup signals S1 and S2 output from the output sections 5a and 5b is detected by performing idle feeding. After that, the electric potential V of the charge injection unit 6a or 6b corresponding to the higher output unit 5a or 5b of the two black levels Vb is moved. For example, when the output signal waveform shown in FIG. 4 appears, the charge injection region 1 related to the charge injection portion 6a.
The potential V supplied to 6 is controlled by the variable resistor R1.

By controlling the potential V of the charge injection unit 6a, the charges ei are injected from the charge injection unit 6a into the horizontal shift register 2a, and the black level Vb output from the output unit 5a is lowered. Then, the black level Vb of the output unit 5a
Until it becomes the same as the black level Vb of the other output section 5b,
The potential V is controlled by the variable resistor R1.

That is, when adjusting the output of the CCD linear sensor A, DC is adjusted by adjusting the variable resistors R1 and R2 so that the idle feed potentials (black level Vb) from the output sections 5a and 5b become the same value. It is possible to suppress the occurrence of a step (offset ΔA).

In this case, the external terminals φe1 and φe2 of the charge injection units 6a and 6b are connected to the horizontal shift registers 2a.
And 2b, the variable resistor R1
The control of the potential V at R2 and R2 can be performed independently of the charge transfer operation at the horizontal shift registers 2a and 2b.
Therefore, the correction of the black level Vb is possible in any situation.

Next, FIG. 5 shows another example of the charge injection part (for example, 6a). Components corresponding to those in FIG. 2 are designated by the same reference numerals. In this example, the potential V supplied to the charge injection region 16 is
Is fixed and the potential Vg supplied to the gate electrode 15 is made variable. In this case, the charge injection region 16 is controlled by controlling the potential Vg supplied to the gate electrode 15 to control the level of the potential under the gate electrode 15.
It is possible to control the inflow amount of the electric charge ei supplied to the horizontal shift register 2a. This gate electrode 15
The control of the potential Vg supplied to the variable resistor can be performed by the variable resistor as in the case of FIG.

As described above, according to this example, the output units 5a and 5 are provided in the preceding stages of the horizontal shift registers 2a and 2b.
Since the charge injection parts 6a and 6b for equalizing the black level Vb output from b are connected, the necessary charge ei is injected from the charge injection parts 6a and 6b,
The black level Vb in each output section 5a and 5b can be made uniform among the plurality of horizontal shift registers 2a and 2b.

In general, the black level Vb is a plurality of horizontal shift registers 2a and 2b due to manufacturing variations.
Although the level is different between b, according to the CCD linear sensor A of the present embodiment, the horizontal shift registers 2a are
Of the black level Vb between 2 and 2b (DC step ΔA)
Can be easily corrected at the transfer stage of the signal charge e,
It is not necessary to install a circuit for correcting the DC step in the signal processing circuit connected to the subsequent stage. As a result, the circuit configuration of the signal processing circuit can be simplified, and the cost reduction and the size reduction of the electronic device equipped with the CCD linear sensor A can be promoted.

In the configuration of the above embodiment, the DC level difference is corrected in, for example, the inspection process after the device is assembled. However, for each output of the image pickup signals S1 and S2, the offset amount ΔA of the black level Vb in the idle feed is obtained. Is also possible, and the potential V (or Vg) of the charge injection parts 6a and 6b is adjusted by using the detection result.

In the above example, the CCD linear sensor A for sequentially reading out the signal charges in the pixels arranged in a straight line.
However, the present invention can also be applied to a CCD image sensor in which pixels are arranged in a matrix in a horizontal direction and a vertical direction and a plurality of horizontal shift registers are provided. It can also be applied to a CCD delay line having a plurality of charge transfer elements.

[0043]

According to the charge transfer device of the present invention, it is possible to correct a DC step at the signal charge transfer stage, and to simplify the circuit configuration of the signal processing circuit connected to the subsequent stage. The cost reduction and the structure miniaturization of the electronic device equipped with the transfer device can be promoted.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a CCD linear sensor according to an embodiment.

FIG. 2 is a configuration diagram showing an example of a charge injection unit according to the present embodiment.

FIG. 3 is a potential diagram of a charge injection unit according to the present embodiment.

FIG. 4 is a waveform diagram showing an output signal waveform of the CCD linear sensor according to the present embodiment.

FIG. 5 is a configuration diagram showing another example of the charge injection unit according to the present embodiment.

FIG. 6 is a schematic configuration diagram showing a CCD linear sensor according to a conventional example.

FIG. 7 is a waveform diagram showing an output signal waveform of a CCD linear sensor according to a conventional example.

[Explanation of symbols]

 1 Photoreceptive Array 2a, 2b Readout Gate 3a, 3b Horizontal Shift Register 4 Photoreceptive Section 5a, 5b Output Section 6a, 6b Charge Injection Section R1, R2 Variable Resistor 15 Gate Electrode 16 Charge Injection Area

Claims (3)

[Claims] 1. A plurality of charge transfer sections and an output section connected to the next stage of each charge transfer section, wherein signal charges sequentially transferred from each of the charge transfer sections are sequentially output as electric signals at the output section. A charge transfer device for converting into a charge transfer device according to claim 1, wherein a charge injection unit for adjusting the reference potential level of each charge transfer unit is connected to the preceding stage of each charge transfer unit. 2. The charge injection part comprises a gate electrode to which a predetermined precharge potential is applied and a charge injection region to which a variable control potential is supplied. Charge transfer device. 3. The charge injection part comprises a control electrode to which a variable control potential is applied and a charge injection region to which a predetermined precharge potential is supplied. Charge transfer device.