JPH06151792A - Ccd image sensing device - Google Patents

Abstract

PURPOSE:To eliminate a smear component, which is generated by the effect of a waveguide, as well as to contrive a miniaturization of a CCD image sensing device by a method wherein a light-shielding electrode is electrically connected with the surface of a photodiode. CONSTITUTION:A light-shielding electrode 12 is electrically connected to the end part of the surface 6 of a P-type region of a photodiode 3. This constitution of a CCD image sensing device is manufactured by forming a contact at the end part of the photodiode, for example, by a prescribed masking process. Or it is also possible to form the constitution in a self-alignment manner to a polysilicon electrode 10 by a process using a nitride film. For example, the constitution of a CCD image sensing device can be formed in a self-alignment manner by a method, wherein a polysilicon electrode 10 is oxidized by a prescribed film thickness by using an ONO film for a gate insulating film 9 and after that, the film 9 is etched to the surface of a photodiode 3 with low damage by using anisotropic dry etching and wet etching processes and a light-shielding electrode 12 is deposited on the surface of the photodiode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device, particularly a CC.
The present invention relates to a D-type solid-state imaging device.

[0002]

2. Description of the Related Art In recent years, solid-state imaging devices are
Due to excellent features such as long life, low afterimage, and low power consumption,
It has become widely used in video movies and surveillance cameras.

A conventional solid-state image pickup device will be described below with reference to the drawings. FIG. 2 is a structural sectional view showing an example of a pixel portion of a conventional CCD type image pickup device. In the figure, 1 is an n-type substrate forming a pixel portion of a CCD image pickup device,
2 is a P-type well, 3 is a photodiode of an n-type region, 4
Is a P-type well for forming the vertical BCCD portion, and a well having a higher concentration than the P-type well 2 is usually used. Reference numeral 5 is an n-type region forming a vertical BCCD, 6 is a P-type region for reducing a dark current generated from an interface state, that is, the surface of a photodiode, and 7 is a vertical direction of the optical signal charge from the photodiode 3. A P-type region of the gate for reading out to the BCCD, and 8 is a P-type region for separating the photodiode and the vertical BCCD.

Reference numeral 9 denotes a vertical BCCD gate insulating film,
Reference numeral 10 is a polysilicon electrode that also serves as a read gate and vertical BCCD, 11 is an interlayer insulating film, and 12 is a light-shielding electrode for shielding light, and an aluminum alloy or a refractory metal material is used. Reference numeral 13 is a protective film.

[0005]

The following problems occur in the CCD type solid-state image pickup device including the above components. That is, the optical signal incident on the photodiode 3 generates electron-hole pairs in the photodiode 3 section, and while the electrons are accumulated in the photodiode 3 and read out, the electron generated by the optical signal entering the deep portion of the substrate. Or
Electrons generated in the vicinity of the vertical BCCD portion are directly leaked into the vertical BCCD by the optical signal, a part of which passes through the light shielding electrode 12, and become a so-called smear signal. In addition to these, incident light is repeatedly reflected between the surface 6 of the photodiode 3 and the light-shielding electrode 12 to generate a waveguide effect, and an optical signal leaks into the vertical BCCD to become a smear signal. These smear signals generate upper and lower bands on the image when strong light is incident, which is a major factor of image quality deterioration.

Of the smear signal, the smear component due to the electrons generated in the deep portion of the substrate is the P-type well 4 having a high concentration.
Thus, the potential barrier can be greatly reduced.

Further, the light component transmitted through the light-shielding electrode 12 can be reduced to a level below the practical level by providing the antireflection film on the upper layer or the lower layer of the aluminum metal film. Further, although this cross-sectional view shows an example in which the light-shielding electrode 12 has a single layer, a refractory metal film is provided as a lower layer and an aluminum alloy film is provided as an upper layer via a planarization film to significantly reduce transmitted light. You can also

However, for the component generated by the waveguide effect, a method of reducing the film thickness of the interlayer insulating film 11 is adopted, but it is 10 from the ability of the present process technology.
The film can only be thinned to about 00Å to 500Å. Therefore, as the CCD solid-state imaging device becomes smaller, the smear component due to the waveguide effect becomes a main component of the smear component, which becomes a major impediment to the miniaturization of the device.

The present invention has been made in consideration of the above conventional problems, and an object of the present invention is to provide a CCD type solid-state image pickup device which can eliminate the smear component caused by the waveguide effect and can be miniaturized without trouble.

[0010]

In order to achieve the above object, a CCD type solid-state image pickup device of the present invention has a structure in which a light-shielding electrode is electrically connected to an end portion of the surface of a photodiode.

[0011]

With this configuration, the smear component generated by the waveguide effect can be set to 0 in principle, and CC
The performance of the D-type solid-state imaging device can be dramatically improved, and the size can be further reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows C showing an embodiment of the present invention.
It is sectional drawing of the pixel figure of a CD type solid-state imaging device. Reference numbers 1 to
The function of each component indicated by 13 is the same as that of the conventional example, and the description thereof is omitted. The characteristic structure of this embodiment is that the light-shielding electrode 12 is electrically connected at the end of the surface 6 of the P-type region of the photodiode 3.

In order to realize this structure, for example, it can be manufactured by forming a contact at an end portion of the photodiode 3 by a predetermined mask process. Alternatively, the polysilicon electrode 10 can be formed in a self-aligned manner by a process using a nitride film. For example, by using an ONO film as the gate insulating film 9, the polysilicon electrode 10 is oxidized by a predetermined film thickness, and then,
By using the anisotropic dry etching and the wet etching process, the surface 6 of the photodiode diode 3 can be etched with low damage, and the light shielding electrode 12 can be deposited to be self-aligned.

[0014]

As is clear from the description of the above embodiment,
In the CCD type solid-state imaging device of the present invention, since the light-shielding electrode is electrically connected to the surface of the photodiode, the smear component generated by the waveguide effect can be reduced to 0, the performance is high, and the size is small. Can be realized.

[Brief description of drawings]

FIG. 1 is a sectional view of a pixel portion of a CCD type solid-state imaging device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a pixel portion of a conventional CCD solid-state imaging device.

[Explanation of Codes] 1 n-type substrate 2 P-type well 3 n-type photodiode 4 P-type well of vertical BCCD 5 n-type region of vertical BCCD 6 surface of P-type region of photodiode 7 From photodiode to vertical BCCD P-type region of gate for reading 8 Separation P-type region of photodiode and vertical BCCD 9 Gate insulating film of vertical BCCD 10 Polysilicon electrode of vertical BCCD 11 Interlayer insulating film 12 Light-shielding electrode 13 Protective film

Claims (3)

[Claims] 1. A CCD type solid-state imaging device in which a light shielding electrode and a photodiode surface are electrically connected. 2. The CCD type solid-state image pickup device according to claim 1, wherein the light-shielding electrode is formed of a multi-layer film in which an aluminum alloy and a high melting point silicide film are combined or a high melting point polycide film. 3. The CCD type solid-state image pickup device according to claim 1, wherein the light-shielding electrode and the photodiode section are electrically connected to each other in a self-aligned manner with respect to the polysilicon electrode.