KR19990054303A - Solid state imaging device and manufacturing method - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid state image pickup device and a method for manufacturing the same, wherein a light shielding layer is formed in a portion proximate to a substrate, whereby a photoelectric conversion region, a charge transport region, etc. are formed to prevent unwanted light from entering the VCCD. Preparing a semiconductor substrate; forming a gate insulating film covering an exposed entire surface of the semiconductor substrate; forming a first gate electrode on the gate insulating film of the charge transport region; Forming a surface oxide film covering an exposed surface, forming a polysilicon layer and a first insulating film continuously on the surface oxide film and the entire surface of the exposed substrate, and successively forming the first insulating film and a polysilicon layer below the first insulating film. Forming a second gate electrode on the first gate electrode by pattern etching and having an upper insulating layer thereon; Forming a second insulating film covering the exposed upper insulating film and the entire exposed substrate, forming a side insulating film on the side of the surface oxide film and the side of the second gate electrode by etching the second insulating film; The method may further include forming a light shielding layer covering the side insulating layer and the exposed upper insulating layer, thereby reducing leakage current and improving smear characteristics.

Description

Solid state imaging device and manufacturing method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid state image pickup device and a method of manufacturing the same. In particular, a light shielding layer covering a vertical charge transfer region (hereinafter referred to as VCCD) in a photo diode array unit is described. The present invention relates to a solid state image pickup device capable of maximizing light shielding ability of a light shielding layer by being formed close to a substrate, and a method of manufacturing the same.

The solid state image pickup device generates electrons by light, arranges charge coupled devices so as to have a directionality, and detects signal charges transmitted thereby. In other words, it is a device that transfers charges excited by light through a directional CCD array and then amplifies this signal to obtain a predetermined output signal. As such, the solid-state imaging device, which is an apparatus for converting an image signal into an electrical signal, includes an array unit arranged in unit cells composed of PD and VCCD, a horizontal charge coupled device, and a signal detection unit. The signal charges accumulated in the PD are sequentially transferred to the VCCD and the HCCD and output through the signal detection unit.

The operation of a general solid state image pickup device will be briefly described as follows. When the light focused through the microlens reaches the light receiving unit PD, the charge generated by the photoelectric effect accumulates in the potential well under the PD. The charge thus collected is transferred to the charge transfer path VCCD by the change of potential caused by the voltage across the transfer gate TG. The transmitted charge moves in sequence through the VCCD and then moves along a wider path called HCCD, which eventually collects on the floating gate. The charge collected in the floating gate is sensed by using the point that the potential of the floating gate changes up and down according to the amount of charge, and then is discharged to the drain.

1A to 1D are views for explaining a solid state image pickup device according to the related art, and show a manufacturing process for a partial cross-sectional structure of a PD array unit.

Referring to FIG. 1A, ONO (Oxide-Nitride-Oxide, Oxide-Nitride-Oxide, or ONO) on a substrate 100 in which VCCD and PD are formed at a predetermined position by a conventional process is referred to as " O " The gate insulating film 10 is deposited using an insulating material. Subsequently, a polysilicon layer is deposited on the entire surface, and the pattern is etched to form the first gate electrode 11, and then the first oxide layer 12 covering the exposed surface of the first gate electrode 11 is formed.

Referring to FIG. 1B, the polysilicon layer is again deposited on the exposed front surface and pattern-etched to form the second gate electrode 13, and then the second oxide layer 14 covering the exposed surface of the second gate electrode 13. ).

Referring to FIG. 1C, an interlayer insulating film 15 covering the entire surface exposed by the high temperature low pressure deposition (HLD) is deposited.

Referring to FIG. 1D, a metal layer is deposited on the exposed entire surface, and then pattern-etched to form a light shielding layer 16 covering the top of the VCCD. Accordingly, the light blocking layer 16 covering the upper portions of the gate electrodes 11 and 13 is positioned.

Thereafter, a subsequent process is performed to complete the manufacture of the solid state imaging device.

In the solid state image pickup device according to the related art, some of the light incident to the PD enters at an angle, enters the VCCD, causes unwanted light conversion to the VCCD, and generates smear charges. This is due to the large distance between the light shielding layer and the substrate in the prior art, as shown in the figure. That is, a thick insulating film is positioned between the PD and the light blocking layer due to the presence of the gate insulating film and the interlayer insulating film, so that the light blocking layer does not completely cover all parts except the PD, so that some of the light passing through the lens combs the light blocking layer. This is because it is incident. As a result, leakage currents and severe smears occur in the solid state image pickup device.

The present invention is intended to maximize the light blocking effect of the light blocking layer by narrowing the gap between the PD and the light blocking layer.

The present invention seeks to prevent unwanted light from entering the VCCD by forming the light shielding layer in a region proximate to the substrate.

The present invention provides a semiconductor substrate having a light conversion region and a charge transport region, a gate insulating film covering the semiconductor substrate, a gate electrode formed on the gate insulating film of the charge transport region, and an upper insulating film formed on the gate electrode. And a side insulating film formed on the side of the gate electrode, and a light shielding layer formed to cover the side insulating film and the upper insulating film.

The present invention provides a process of preparing a semiconductor substrate having a photoelectric conversion region and a charge transport region, forming a gate insulating film covering an exposed entire surface of the semiconductor substrate, and forming a first gate on the gate insulating film of the charge transport region. Forming an electrode; forming a surface oxide film covering an exposed surface of the first gate electrode; and successively forming a conductive layer and a first insulating film on the entire surface oxide film and the exposed substrate; Forming a second gate electrode on the first gate electrode by successively pattern-etching an insulating film and a polysilicon layer below the second insulating film; Forming a second insulating film covering the entire surface of the substrate; and etching the second insulating film so that the side surface of the surface oxide film and the second gate electrode A step of forming on the surface side insulating film, a method for manufacturing a solid-state image sensor comprising a step of forming a light shielding layer covering the exposed upper insulating film and the insulating film side.

1A to 1D are manufacturing process diagrams of a solid state image pickup device according to the related art.

2A to 2D are manufacturing process diagrams of the solid state image pickup device according to the present invention.

2A to 2D are views for explaining the solid state image pickup device according to the present invention, and show a manufacturing process for a partial cross-sectional structure of the PD array unit.

Referring to FIG. 2A, ONO (Oxide-Nitride-Oxide, Oxide-Nitride-Oxide, Oxide, hereinafter referred to as ONO) is formed on a semiconductor substrate 200 in which elements such as VCCD and PD are formed at predetermined positions by a conventional process. Alternatively, a gate insulating film 200 is deposited by depositing a conventional insulating material. ONO may proceed by depositing an oxide film and a nitride film continuously and forming an oxide film on the nitride film by oxidation. Subsequently, a conductive layer such as a polysilicon layer or a polysilicon layer doped with impurities is formed on the entire surface, and the pattern is etched to form the first gate electrode 21. Subsequently, the surface oxide film 22 is formed on the surface of the first gate electrode 21 by a normal oxidation process.

Referring to FIG. 2B, a conductive layer such as a polysilicon layer or a polysilicon layer doped with impurities is deposited on the entire surface of the substrate, and an insulating film by HLD is continuously deposited on the conductive layer. Subsequently, the insulating layer formed by the HLD and the conductive layer are successively patterned to form the second gate electrode 23 having the upper insulating layer 24 positioned on the upper portion of the VCCD region.

Referring to FIG. 2C, after an insulating film is deposited on the entire surface of the exposed substrate by HLD, anisotropic etching is performed to form the side surface of the surface oxide film 22 of the first gate electrode 21 and the second gate electrode 23. A side insulating film 25 is formed on the side. In this process, the gate insulating film 20 is exposed.

Referring to FIG. 2D, after forming the metal layer on the exposed substrate, the metal layer is pattern-etched to form the light shielding layer 26 covering the upper portion of the VCCD. As a result, the light shielding layer 26 can cover the VCCD with only the gate insulating film 20 interposed therebetween, thereby reducing the incidence of unwanted light into the VCCD as compared with the prior art. Therefore, the light shielding effect of the light shielding layer can be improved.

According to the present invention, by forming the light shielding layer in a position proximate to the substrate, unwanted light can be prevented from entering the VCCD. Therefore, the leakage current can be reduced, and the smear characteristics can be satisfactorily improved.

Claims (5)

A semiconductor substrate having a photoelectric conversion region and a charge transport region; A gate insulating film covering the semiconductor substrate; A gate electrode formed on the gate insulating film of the charge transport region; An upper insulating film formed on an upper end of the gate electrode; A side insulating film formed on the side of the gate electrode; And a light blocking layer formed to cover the side insulating film and the upper insulating film. The method according to claim 1, The gate electrode may include a first gate electrode formed on the insulating layer and having an exposed surface covered with a surface oxide film; And a second gate electrode disposed on the surface insulating film of the first gate electrode and having the upper insulating film on the top. Preparing a semiconductor substrate having a photoelectric conversion region and a charge transport region; Forming a gate insulating film covering an exposed entire surface of the semiconductor substrate; Forming a first gate electrode on the gate insulating film of the charge transport region; Forming a surface oxide film covering the exposed surface of the first gate electrode; Continuously forming a conductive layer and a first insulating film on the surface oxide film and the entire exposed substrate; Forming a second gate electrode on the first gate electrode by successively pattern-etching the first insulating layer and the polysilicon layer below the second insulating layer, the second insulating layer having an upper insulating layer thereon; Forming a second insulating film covering the exposed upper insulating film and the entire exposed substrate; Etching the second insulating film to form a side insulating film on a side surface of the surface oxide film and a side surface of the second gate electrode; And forming a light shielding layer covering the side insulating film and the exposed upper insulating film. The method according to claim 3, And the first and second insulating layers are deposited by HLD. The method according to claim 3, And etching the second insulating film in anisotropy.