JPS58125961A - Driving method of charge transfer image pickup device - Google Patents

Abstract

PURPOSE:To eliminate a diaphragm mechanism which is applied to a camera, etc., by having two levels for the adverse bias voltage which form a p-n junction together with a semiconductor substrate, and applied between two p type regions different in depths of junctions. CONSTITUTION:The adverse bias voltage which is formed between a semiconductor substrate 16 and a p type region 22 forming a p-n junction at a time point t1 has a high level V0. During a period of this level V0, the electric charge which is produced after being made incident to a photoelectric converting region 24 is not turned into the signal charge since the regions 24 and 22 are set in forward directions. The adverse bias voltage is converted into the ordinary voltage VS at a time point t2, and the electric charge generated by the light made incident to the region 24 during this period is turned into the signal charge. The voltage is applied to a transfer gate 13 at a time point t3, and the signal charge stored in a region is transferred to a vertical shift register 11. The voltage V0 is applied again to the region 24 at a time point t3 before the register 11 starts the transfer of electric charge. Then a diaphragm mechanism is eliminated if a period from the time point t2 through t3 is controlled in response to the incident light volume.

Description

[Detailed Description of the Invention] As an imaging device using a charge transfer device, a method called a frame transfer method or an interline transfer method has been developed. 7 However, considering the benefits and disadvantages of imaging devices, the advantages of solid-state devices mentioned above cannot be ignored due to noise, residuals, burn-in, etc. Although it is better than a picture tube, it still has problems with blooming and smear phenomena.In addition, when used as a system such as a charge transfer camera, it has a mechanical structure, that is, an aperture 9, to adjust the amount of incident light. I need.

As shown in FIG. 1, a conventional interline transfer type KL charge transfer imaging device has a plurality of columns of vertical shift registers 11 driven by the same charge transfer electrode group.

A photoelectric conversion section 12 adjacent to one side of each vertical shift register and electrically isolated from each other, a transfer gate terminal 1i13 for controlling signal charge transfer between the vertical shift register and the photoelectric conversion section, and a A charge transfer horizontal shift register 14 is electrically coupled to one end, and a signal charge detection device 15 is provided at one end of the horizontal shift register.

In a charge transfer imaging device using such an interline transfer method, the photoelectric conversion unit 12 converts signal charges l according to the amount of incident light.
l-1 For example, through the transfer gate 13
Transfer to the vertical shift register 11 corresponding to 1 ・After transferring the signal charge to the vertical shift register, transfer 1
The gate is closed lrL.

The photoelectric conversion unit 11 accumulates the signal *frv of the next cycle.

The signal charges transferred to -10,000 vertical shift registers 11 are transferred vertically in parallel, and are transferred to one horizontal shift register 14 for each vertical shift register Iυ-horizontal row. The voltage sent to the horizontal shift register is taken out as a signal by the device 1atP which transfers the signal charge in the direction of water while the signal is transferred from the next vertical shift register and detects it. 1 is a schematic cross-sectional view of the charge transfer imaging device taken along line A--A shown in FIG. In FIG. 2, a PN junction is formed with the substrate semiconductor 16, and
Two P-type regions 22 and 23 with different junction depths are formed, and a KuN-type photoelectric conversion region 24 is formed on the P-type region 22 with a shallow junction, and a deep P-type region with a 9% junction is formed. An N-type buried channel vertical shift register 25 is formed on 23.

FIG. 3 shows a potential distribution diagram on B-B@ of the photoelectric conversion section in the jlR2 diagram, and the horizontal axis is the distance in the depth direction.

The vertical axis represents the potential. Now, the N-type photoelectric conversion region 24 is connected to the transfer gate 1 with the potential of the channel stop region 20 shown in FIG.
3 voltage "vTG" Transfer gate threshold voltage 'gt
When vT, a cell h-g is generated at a potential of vTo-vT.

In addition, the DC reverse bias voltage applied to the P-type region #, 22 and the substrate]6 varies from the low voltage shown by the curve 26 to the higher reverse bias voltage 1 [BEv8U,vc'TI3t curve 2
7 [PW region 22 is completely depleted. When the photoelectric conversion region 24 is irradiated with light and signal charges are accumulated, the potential of the photoelectric conversion region 24 decreases from curve 28 to curve @29, and eventually the photoelectric conversion region 24 decreases as shown by curve 300J. 9. The junction between the P-type groove 22 and the P-type groove 22 is in the forward direction.9. Any more charges generated in the photoelectric conversion region 24 flow into the substrate semiconductor 16 via the Pfj1 substrate region 22k.

In other words, the channel stop region 20 i! is directly below the transfer 1 gate region 13 shown in FIG. Although not shown in the figure, the surface potential of all the regions including the optical IE conversion region 24 and the Pfi region 22e) has a high junction potential between the substrate semiconductor and the P-type region. 22K [
By applying a reverse bias voltage τ of fi, the excess charge generated in the photoelectric conversion region 24 is completely swept to the substrate semiconductor 16, and a heavy electron ξ is created.This structure and operation rc can be used to completely suppress the pluming phenomenon. However, when such a charge transfer imaging device is used as a system such as a camera, the incident light 1li1! ″Mechanical mechanism,
In other words, the drawback that must be adjusted with the aperture 9 is 6.
An object of the present invention is to eliminate the above-mentioned drawbacks and to provide an attractive method for driving a charge transfer device capable of suppressing blooming. In the bonding area formed by forming a conductive ζ-type hair opposite to the substrate marked #, a first C/J area with a shallow bonding depth and a second area with a deep bonding depth are provided, and the slope of the a1 is A charge transfer device VC (
In tvc, the normal reverse /
The normal voltage required for the first region to be completely depleted after a period of V after a high voltage t is applied between the region 1 and the second region ξ of the semiconductor substrate. A method for driving a charge transfer imaging device is obtained, characterized in that a reverse bias voltage is applied to the first region, the second region, and the semiconductor substrate.

Next, embodiments of the present invention will be described using the drawings. Hereinafter, in the embodiments of the present invention, in order to simplify the explanation, N-channel (e) semiconductor devices will be described.

Figure 4 is a drive pulse waveform diagram for explaining the inventive example.The difference from the conventional example is that the P-N junction is fully formed with the semiconductor substrate shown in Figure 2, and the contact radius is Reverse bias voltage 9 applied between two P-type regions 22, 2B with different
□b or two levels @v - "v" t- S O Figure 5 tX Similarly to Figure 3, the depth direction on the B-B line of the charge transfer imaging device shown in Figure 2 This shows the potential of

At time 11 C1) in FIG. 4, the semiconductor substrate 16
In Fig. 5, the reverse bias voltage qsub applied between the P-type region 22 forming a P-N junction is 1'', and the reverse bias voltage ψ, ub@Ivo'' is applied to the N-type photoelectric conversion. It is often necessary that the region 24 and the P-type region 22 be in the forward direction. Figure 5 shows this reverse bias voltage ψsub”■o
During the period of the level of this reverse bias voltage ψsub"o" shown by the curve 11-31 of the potential distribution created by Since 22 is in the forward direction, the substrate semiconductor 161C is swept out, so at time t2, when it does not become a signal charge, the reverse bias voltage ψsubha''v
Since the curve changes from o''' to v'', the curve indicating the depth direction position of the photoelectric conversion section changes from 31 to curve 27. Reverse bias 8 voltage? During the aub power "■S" level period, charges generated by light incident on the N-type photoelectric conversion region 24 become signal charges, and are accumulated in the N-type photoelectric conversion region 24, depending on the amount of incident light. The potential of the photoelectric conversion region 24 becomes smaller from the curve 28.

W time t, the voltage is applied to the transfer 1 gate, TG
is applied, and the signal charge accumulated in the %N type light 'Nf conversion region 24 is transferred to the vertical shift register l. At this time, the N-type photoelectric conversion region 24 is set at a potential of vTG-■A.

Time t4 before the vertical shift register starts charge transfer i
The reverse bias voltage ψsub vo'' is again applied to the N-type photoelectric conversion region 24, and the operation of the primary Q field is repeated. It is a period T from time t! to time t!.

The period T depends on the amount of incident light, and is short when the amount of incident light is large.
When the amount of incident light is small, it can be lengthened to control No. 6 charge Jlf: Therefore, the diaphragm mechanism used in conventional cameras is unnecessary. Also, the reverse bias voltage ψsub"lVo"H@Vs"↓ The voltage should be higher than the voltage that creates the voltage between the N-type photoelectric conversion region and the P-type region 24 in the t-1 direction, but the voltage must not be so large as to deplete the P-type region #25 directly below the vertical shift register. .

Although the driving method of the embodiment of the present invention has been described above for the JrN channel, it goes without saying that it can be applied to a P channel semiconductor device by reversing the four voltage types of each region.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an imaging device using a conventional charge transfer device, and FIG. 2 is a schematic cross-sectional view on line A-Person 1 shown in FIG.
FIG. 3 shows the potential distribution on the broken line B-B' shown in FIG. FIG. 4 shows a driving pulse waveform for explaining the present invention in detail, and FIG. 5 shows the potential distribution on B-BIJI shown in FIG. 2 by the uninvented driving method. In the figure, 11...1 ■ft register, 12...
...Photoelectric conversion section, 13...Transf 1 gate. 14...Horizontal shift register, 15...Charge detection device e%16...Semiconductor substrate, 17...Insulating film, 18-...Vertical shift register electrode, 19...
Transfer 1 gate electrode. 20... Chiminer stopper% 21... Light shielding. 22.23...P type region, 24...N type photoelectric conversion region. 25...°N type vertical shift register, 26,2 f,2
8.29, 30.31...Curve showing potential distribution. Susumu Hara, Patent Attorney Attorney Figure 1 15/4 Figure 2

Claims (1)

[Claims] a first region having a shallow junction depth, the junction region having a conductivity type opposite to that of the substrate formed on the principal surface of the semiconductor substrate;
111. Second region with deep junction depth? a charge transfer imaging device, wherein a photoelectric conversion element f# is formed on the main surface of the first region, and a weight element device for reading signals from the photoelectric conversion element group is formed on the main surface of the second region. During the I field period, the first region and the photoelectric conversion element group are in the forward direction, and a voltage higher than a normal reverse bias voltage is applied to the cocoon Ie first region and second region and the photoelectric conversion element group. A normal reverse bias voltage Wr#1 is applied between the semiconductor substrates and is necessary for the first region to be completely depleted after a certain period of time between the first region, the second region and the semiconductor substrate. to apply r
*Characteristics of driving method of charge transfer imaging device-