JPS61102771A - solid state imaging device - Google Patents

Abstract

PURPOSE:To remove the occurrence of smearing charges, which are generated in a conventinoal solid-state image pickup sensor element, in principle or to decrease said occurrence to a large extent, by providing a photoelectric conver sion ele- ment part and vertical and horizontal transfer parts, and forming the vertical transfer part on a substrate having an SOI structure. CONSTITUTION:A drain 4 is formed on an SiO2 film 13, and a so-called an SOI structure is formed. In the drain part 4, which is formed on the SiO2 film 13, a depletion layer is not present in principle since N type impurities are diffused in the entire surface of the drain part 4. In the silicon and the drain part 4 beneath the gate electrode 14, however, some depletion layer is formed. In a conventional drain, which does not use the SOI structure, the depletion layer is inevitably formed. In the drain part 4 with this structure, the depletion layer can be completely eliminated, except some depletion layer between the gate electrode 14 and the drain part 4. The operation, in which smearing charges l<-> are not accumulated in principle, can be realised.

Description

[Detailed description of the invention] Fields of use in childcare The present invention relates to a solid-state imaging device.

Examples of conventional configurations and their problems Recently, development of solid-state imaging devices such as MaS type, CCD type, and CPD type has progressed, and devices comparable to image pickup tubes in terms of resolution, sensitivity, etc. have been put into practical use. . For example, regarding blooming, the photoelectric conversion part of the solid-state imaging device is formed in a well of the opposite conductivity type to the substrate, a predetermined voltage is applied to the substrate, and the generated blooming charge is discharged to the substrate. It has been reduced to a level that does not exist.

The well structures adopted in this case are the structures shown in Figures 1 (a) and (h) t (c) K for the MOS type, CCD type (IL-CCD type), and CPv type, respectively. .

In Figure 1, 1 is an n-type substrate, 2 is a P well, 3 is a photodiode, 4 is a drain, 6 is an aluminum light shielding film, 6 is a LOCO5 oxide film, 7 is an NSG cap, 8.9 is a channel stopper, and 1Q is a Aluminum signal line, 11 is vertical transfer CO
D, 12 is a vertical transmission line. In the MOS type (a), P
Well 2 uses a concentration that does not cause Vi depletion at a predetermined substrate voltage. In the ILo-CCD type shown in (b), the P well 2 under the photodiode 3 is depleted at a predetermined substrate voltage, but the well structure under the vertical transfer section 11 is not depleted. The CPD type shown in (C) employs a well concentration that is depleted at a predetermined substrate voltage. All of these structures are effective in reducing or eliminating blooming charges that occur above the saturation point. However, although the use of a well structure has a certain reduction effect on smear generated under saturated light, there is a limit due to the structure, and this is a practical problem.

In the MOS type shown in (a), the charge e- generated near the drain of the channel stopper 8 due to oblique light incidence and the charge e- generated deep in the substrate are not effectively applied to the substrate 1 because the well is not depleted. The charge cannot be discharged to the drain 4 and is diffused as shown by the arrow and accumulated in the depletion layer of the drain 4, eventually becoming a smear charge.

(Also in the case of the IL-CCD type (9), the charge e- generated by oblique light incidence and the charge e- generated in the substrate 1 diffuse as shown by the arrow and accumulate in the depletion layer of the vertical transfer section 11. In the case of the CPD type (C), as well as the MOS type (-), the charge e- generated by oblique light incidence and the charge e- generated deep in the substrate are As shown by the arrow, it diffuses and is trapped in the depletion layer of the drain 4, resulting in a smear.

As described above, in the conventional solid-state imaging device, it is impossible in principle to prevent the generation of smear charges.

OBJECTS OF THE INVENTION In view of the above drawbacks, the present invention provides a solid-state imaging device having a structure that can theoretically eliminate or significantly reduce the smear charge generated in conventional solid-state rRf quadrants. It is to be.

Structure of the Invention In order to achieve this object, the solid-state imaging device of the present invention has the following features:
It includes a photoelectric conversion element section arranged in a matrix, and vertical and horizontal transfer sections for reading out optical signal charges photoelectrically converted in the photoelectric conversion element section in time series, and the vertical transfer section has an SOI structure. The device is formed on a substrate having a structure.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings, taking a CPD type as an example. FIG. 2 shows a cross-sectional structure of an embodiment of the present invention. The case of n-channel will be described.

In FIG. 2, 1 is an n-type substrate, 2f'iP well, 3
is a photodiode formed on the P well, 4 is a drain, 5 is an aluminum light-shielding film, and 6 is LOCO3 for isolation between elements.
Thick film, 7 is NSG film, 12 is AI electrode of vertical transmission line, 1
3 is a SiO2 film, a poly7 silicon gate of a 14Vi vertical MOS transistor, and 16 is an SG film.

As can be seen from the figure, the drain 4 is formed on the Si○2 film 13, and is a so-called SOI (Semi-cond
A uctoron In5alator structure is formed. In this structure, first, the surface of an n-type silicon substrate 1 is oxidized, and then the generated 5iQ2 film is selectively etched to leave SiO2@13 in the form of islands. After polysilicon is deposited on the surface of the silicon substrate 1 from above the Si02 film 13, it is made into a single crystal by annealing.

Drain 4, fort diode 3, etc. in the single crystal layer? Form.

S 102 Since n-type impurities are diffused all over the drain region 4 formed on the film 13, a depletion layer of 1,000 is formed below the depletion layer.
Just do it. Therefore, while a depletion layer is inevitably formed in conventional drains that do not use SOI, the drain 4 of this structure has no depletion at all, except for a small amount of depletion between the gate electrode 14 and the drain 4. It is possible to eliminate the layer, and it is possible to realize an action in which smear charges e- are not accumulated in principle. In addition, the S102 film 13 under the drain 4 can completely remove the smear charge e- generated deep in the substrate 1 from the drain 4, thereby preventing it from moving in the direction of the arrow and reaching the drain 4. . In any case, the smear accumulation effect of the conventional drain structure can be virtually eliminated in principle, and smear, which is one of the biggest drawbacks of solid-state sensors, can be eliminated. Since the depletion layer in the drain section can be eliminated, the vertical transmission line for customers can also be greatly reduced, and at the same time, it is also possible to greatly reduce the noise generated from the vertical section.

Furthermore, in the IL-COD configuration, by forming the vertical COD on the S○ process, it is possible to completely eliminate smear charges that are accumulated in the vertical COD by diffusion from the deep part of the substrate. By applying it to a MOS type, it becomes possible to eliminate smear in principle.

As can be seen from the effects of the invention, the present invention makes it possible in principle to completely eliminate or greatly reduce smear, which is the biggest drawback in solid-state imaging devices, and has great practical effects. .

[Brief explanation of the drawing]

Figures 1(a), t(b), and (C) are cross-sectional structural diagrams showing the cross-sectional structures of conventional MOS type, CCD type, and CPD type solid-state imaging devices, respectively, and Figure 2 shows one embodiment of the present invention. This is a one-page structural diagram shown. 1...N type substrate, 2...P well, 3...
・Photodiode, 4... ・Drain, 5...
...Aluminum light shielding film, 6...LOCO3 oxide film, 7
・・・・・・NSG film, 12 ・・・AI of vertical transmission line
Electrode, 13... SiO3 model, 14...
Gate electrode of vertical MO3 transistor. Name of agent: Patent attorney Toshio Nakao and one other name
1 figure

Claims (1)

[Claims] A photoelectric conversion element section arranged in a matrix of m rows and n columns, and vertical and horizontal transfer sections for reading out optical signal charges photoelectrically converted in the photoelectric conversion element section in time series, the vertical transfer section comprising: A solid-state imaging device characterized by being formed on the surface of an insulating layer.