JPS58125963A - Charge transfer image pickup device - Google Patents

Abstract

PURPOSE:To eliminate the lateral drift which is porduced when a subject of high luminance is photographed, by making a channel width at the junction part between a vertical shift register group and a horizontal shift register less than the channel width of the vertical shift register group. CONSTITUTION:The channel width WV' is reduced fro a region 61 close to a channel region 24 of a horizontal shift register in a channel region 60 of a vertical shift register. As a result, the channel potential phiV of a region 71 (61) is set slightly lower than the channel potential phiH of a region 71 (24). Therefore the width WV' is selected so that the channel potential difference phiV'-phiH between regions 70 and 71 is sufficiently higher than the level of the maximum signal charge of a charge transfer image pickup device. Thus the charge transfer of the horizontal shift register is carried out only at the region 71. Then a part of the signal charge never gets into the region 70. As a resutl, the lateral drift caused when a subject of high luminance is photographed is completely eliminated. At the same time, a part of the signal charge is never injected into a well 73 under a vertical charge transfer electrode 22. This eliminates the generation of a lateral linear pseudo signal.

Description

DETAILED DESCRIPTION OF THE INVENTION The invention relates to a solid-state imaging device using a charge transfer device. Solid-state imaging devices are small, lightweight, low power consumption,
In recent years, it has been characterized by high reliability and there is no worry about burn-in like in image pickup tubes.

Research and development is being carried out in many fields.

Figure @1 is a schematic diagram of one of the charge transfer imaging devices described above, which is called an yp-line transfer method. It consists of a group of charging conversion elements 11 arranged adjacent to each other, a horizontal shift register 12 electrically coupled to one end of each vertical shift register, and a charge detection section 13 provided at one end of the horizontal shift register 12. There is.

FIG. 2 is an enlarged view of the coupling region 14 between the vertical shift register group 10 and the horizontal shift register 12 in the charge transfer imaging device shown in FIG. and % Vertical transformer 71 gate electrode 2 that controls the transfer of signal charges from the vertical shift register 1G to the horizontal shift register 12
Covered by 3. Further, the channel region 24 of the horizontal shift register 12 has horizontal charge transfer voltages 1i25.26.27.
It is covered by 28.29. Furthermore, in the same figure, by covering the channel region 20t) with the terminal O region 30t and a part of the horizontal charge transfer electrode 27, the vertical shift register 1
G and the horizontal shift register 12 are electrically coupled. FIG. 3 schematically shows a cross section of the coupling region shown in FIG. 2 on the line 1--1. Principal surface W− of semiconductor substrate 31
is the vertical charge transfer electrode 21 mentioned above via the insulating layer 32'.
b 22s vertical transfer gate electrode 23° horizontal charge transfer electrode 27 is formed. Further, below the above and each electrode, a buried channel layer 33 having a conductivity type t opposite to that of the substrate semiconductor is formed, and outside the channel region, for example, an impurity t having a conductivity type opposite to that of the buried channel layer 33 is formed. A doped channel stop region 34 is formed. Further, the main surface of the semiconductor is shielded from light by, for example, a metal layer 35. In the figure, region 36 represents the region 30k of FIG. 2 that electrically couples the vertical shift register and the horizontal shift register, and region 37 represents the horizontal shift register O channel region - charge transfer imaging of such a structure. The operation of the device is shown in FIG. 1, in which signal charges are accumulated in the photoelectric conversion element group 11 according to the amount of incident light and the signal charges are accumulated in the photoelectric conversion element group 11 according to the image signal υ frame period.

Alternatively, after being read out to the corresponding vertical shift register group 10 for each field period, the signals are primarily transferred downward in parallel within the vertical shift register group 10 for each horizontal scanning period (IH) of the video signal.

The signal charge transferred at the end 1 of the vertical shift register group 10 is transferred to the horizontal shift register 12 every horizontal scanning period (IH) when the vertical transfer 1 gate electrode 23 is in the ON state.
Injected in parallel to ! 1. The signal charges sent to the horizontal shift register 12 are transferred to the vertical shift register group 1 in the next cycle.
Signal charges are transferred from 0 to 1,000 directions, and are taken out from the charge detection unit 13 as an image signal. In such conventional charge transfer imaging devices, high-brightness objects are imaged. In some cases, an undesirable phenomenon in terms of imaging operation has been observed, such as the image flowing in the horizontal direction or a horizontal line-like false signal appearing in front of the image. This phenomenon causes color shift and, in some cases, color shading when the charge transfer imaging device is applied to a single-chip color camera.

The above phenomenon is caused by the structure of the coupling region of the vertical shift register and horizontal shift register shown in FIG. 2 or 3. Figure 4 (at, (bl, (cl) [e
In order to explain the phenomenon, the potential distribution in each part of the cross-sectional view of the coupling region shown in FIG. 3 is schematically shown in FIG. When the transfer electrode 27 is on, the vertical transfer 1
The potential distribution at the time when the gate electrode @23 is in the OFF state is shown, and FIG. 4(c) shows the potential distribution at the time when only the horizontal charge transfer electrode 27 changes from the above state to the OFF state.

Further, FIG. 5 is a diagram showing the relationship between the channel potentials in the layer ξ of the channel region. Hereinafter, the above phenomenon will be explained using FIGS. 2, 3, 4, and 5.

First, in FIG. 4(a), the channel potential ψV of the region 36 shown in FIG. 3 is smaller than the channel potential ψ8 of the region 37 because the channel width Wv of the region 3Qv shown in FIG. 24, which is smaller than the width WH of the channel 51w1! The channel potential of the rv region is ψ□, but the channel potential ψV of the region shouldering the channel width Wvt becomes smaller than the channel potential ψM due to the narrow channel effect. Channel region 37χ The above two channel potential difference ψ
When signal charges with a small level of □-ψV are transferred, the signal charges do not enter the region 36, and efficient transfer is performed. However, as shown in FIG. 6(b), when the level of the signal charge increases to the extent that it exceeds the above potential difference ψ8−ψvt, a part of the signal charge enters the region 36, accumulating and deteriorating the transfer efficiency of the horizontal shift register. This is the tangential flow of the imager when photographing a high brightness object as described above.

It was the cause. Furthermore, when the horizontal charge transfer electrode 27 is turned off as shown in FIG.
The false signal charges injected into the well 41 are transferred to the horizontal shift register again at the timing when the vertical transfer gate electrode 23 is turned on. The injected signal charges are photographed as if they were real signal charges, which is the cause of the generation of false horizontal line signals when the high-intensity tactile object is imaged.

The object of the invention is to provide a high quality charge transfer device which eliminates the above-mentioned drawbacks.

According to the invention, a plurality of columns of vertical shift register groups ξ emitted from a charge transfer device formed on the same substrate, n photoelectric conversion element groups arranged corresponding to the vertical shift register groups, and the vertical shift register groups ξ a charge transfer horizontal shift register provided adjacent to one end of the group; and a charge transfer horizontal shift register provided by covering a channel region at the end of the vertical shift register group with a part of the horizontal charge transfer electrode of the horizontal shift register. A charge transfer imaging device comprising a coupling portion with a front horizontal shift register and a charge detection portion provided at one end of the horizontal shift register, wherein the channel potential of the coupling layer is set to the charge transfer imaging device. so that the maximum signal charge of the device is smaller than the channel potential under the horizontal charge transfer electrode when transferred to the horizontal shift register.

A charge transfer imaging device is obtained in which the channel width of the coupling portion is narrower than the channel width of the vertical shift register group.

Next, a non-inventive embodiment will be described with reference to the drawings.The basic configuration of the present invention is almost the same as that of the conventional example shown in FIG. FIG. 6 is an enlarged view of the combination of the vertical shift register group 10 and the horizontal shift register 12 shown in FIG. 1 in the charge transfer imaging device according to the present invention. This corresponds to FIG. 2 of the conventional example. Further, in this figure, the same numbers as in FIG. 2 indicate the same attached elements. In the figure, the channel region 60 of the vertical shift register is the vertical charge transfer electrode 2.
1° 22 and a vertical transfer gate electrode 23 that controls the transfer of signal charges from the aX shift register to the horizontal shift register 9, and a region of the channel region 60 that is close to the channel region 24 of the horizontal shift register. The channel width Wv of 61 is narrower than the channel width W7 of the conventional region 30 shown in FIG. Further, the channel region 24 of the horizontal shift register is covered with horizontal charge transfer electrodes 25°26.27, 28.29. Furthermore, in the same figure, the area 61 is the horizontal charge transfer electrode 27
A vertical shift register and a horizontal shift register are electrically connected to this part. 7th
The figure schematically shows a cross section on the line Vl and -Vl of the joint region shown in the sixth part, and thus corresponds to Figure @3 of the conventional example. The above-mentioned vertical charge transfer electrode 21%22% vertical transfer gate electrode 23. is formed on the main surface of the semiconductor substrate 31 with an insulating layer 32g interposed therebetween. A horizontal charge transfer 1i1ff127 is formed. Furthermore, under each of the above electrodes, for example, the substrate semiconductor ξ
A buried channel layer 33 having the opposite conductivity type t is formed.
Also, outside the channel region, a channel stop region 34 doped with, for example, an impurity of a conductivity type opposite to that of the buried channel layer 33 is formed. Further, the main surface of the semiconductor υ is shielded from light by, for example, a metal layer 35. In the figure, a region 70 shows the region 61'@- of FIG. 6 where the vertical shift register and the horizontal shift register 4vt are electrically connected, and a region 71 shows the channel region W of the horizontal shift register.

The operation of the charge transfer imaging device having such a structure is shown in FIGS. 1 and 2.
Figures and +ll! Since it is almost the same as the conventional example shown in Fig. 3, we will only use Fig. 8 to explain the charge transfer V pattern in the horizontal shift register. This diagram schematically shows the potential distribution in each part of the cross-sectional view, and shows the potential distribution when the vertical charge transfer electrodes 21 and 22 and the horizontal charge transfer electrode 27 are in the on state and the vertical transfer 1 gate electrode 23 is in the off state. The greatest feature of the present invention is that the channel potential 9 of region 70 shown in FIG. 8 is made sufficiently smaller than the channel potential ψHvc of region 710 shown in FIG. It is. In other words, in FIG.
The channel potential of the region 30 in the conventional example having ψV is ψV, but the channel potential of the region 61 according to the invention in which the total channel width W'V is narrowed by 1? Due to the narrow channel effect, the channel potential is further smaller than the channel potential ψ1. Therefore, in FIG. 8, the channel potential difference ψ between the region 70 and the region 71 is
+V-ψ□ becomes sufficiently large compared to the maximum signal charge level of the charge transfer imaging device according to the invention, I'l-
If the channel width W and i of the region 61 are selected, the charge transfer in the horizontal shift register (is performed only in one channel region 71), and part of the signal charge (h) does not enter the region 70. In the charge transfer imaging device according to the invention, the charge transfer in the horizontal shift register is efficiently performed, and the horizontal flow of the image when imaging a high-brightness object, which was conventionally required, is completely eliminated. Since a part of the injection field does not cross over the barrier 72 under the vertical transfer gate 23 and enter the well 73 under the vertical charge transfer electrode 22, the horizontal line-like false signal when imaging a high-brightness object, which is the case in the conventional example, is eliminated. It is possible to completely prevent the occurrence of 14 degrees or more (/, J), so the uninvented ML technique can realize a high quality charge transfer imaging device that does not generate false signals. Here, (1 uninvented t interline Charge transfer using transfer method!
Although the fl device lt'1I-7 has been described, it can be realized as one device using a frame transfer method.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an interline transfer type imaging device, and FIG. The figure is a cross-sectional view on the
), et al), (if cl, potential distribution model rS in Fig. 3
4. Figure 5 shows the channel width dependence of the channel potential. The structure according to the present invention is shown in an enlarged view of the coupling area of the vertical shift register and the horizontal shift register in Jv-4. FIG. 7 is a sectional view taken along the line ■-■ of FIG. 6, and FIG. This is a schematic diagram of potential distribution at
In the figure, there are 10 vertical shift registers, 11 light 1
Conversion element group, horizontal shift register 12. 13 is a charge detection section, 14 is a coupling region of the vertical shift register and horizontal shift register, 201160fl vertical shift register channel region, 21.22 is a vertical charge transfer electrode, 23 is a vertical transfer gate electrode 1i, 24.
37.71 is the channel area of the horizontal shift register, 25
~29 is horizontal charge transfer 1, 3Q, 36.61, 70
dHorizontal transfer' JL (1) -&Ii 6A* end of vertical shift register C11- region, 31 is semiconductor substrate, 32 is an insulating layer, 33 is a layer including J1, 34 is a channel stop region, 35 There is a gold tA layer. -3( 1st eye also 2 times

Claims (1)

[Claims] a plurality of vertical shift register groups formed on the same substrate and consisting of charge transfer devices; a photoelectric conversion element group disposed corresponding to the vertical shift register group; and a photoelectric conversion element group adjacent to one end of the vertical shift register group. a charge transfer horizontal shift register provided as a charge transfer horizontal shift register; A charge transfer imaging device comprising a coupling portion with a horizontal shift register and a charge detection portion provided at one end of the horizontal shift register, the channel potential of the coupling portion being such that the maximum signal charge of the charge transfer imaging device is The channel of the coupling portion is made narrower than the vertical shift register group O channel IIK so that the channel potential under the horizontal charge transfer electrode is lower than the channel potential under the horizontal charge transfer electrode when transferred to the horizontal shift register. Charge transfer imaging device