JPS6390165A - Optical semiconductor element - Google Patents

Abstract

PURPOSE:To shield a leakage light without reducing a sensitivity due to an aluminum film by determining the hole of a photodiode by a wiring aluminum film and shielding the aluminum film by a pure aluminum film of upper layer so as not to extend from the aluminum film. CONSTITUTION:The periphery of a drain 4 is shielded by aluminum wirings connected to the drain 4 in a picture element of an MOS solid state image sensing device so that a light is not incident directly to the drain 4. A pure aluminum film 21 is so provided on a wiring aluminum film 7 as not extend therefrom. Thus, a leakage light through the film 7 is shielded without deteriorating the hole of a photodiode 3 to reduce a smear phenomenon.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an optical semiconductor device, and particularly to a solid-state imaging device suitable for suppressing a smear phenomenon.

[Conventional technology]

A two-dimensional solid-state image sensor will be described as an example of a conventional solid-state image sensor.

FIG. 2H shows a cross-sectional view of a pixel of a conventional MO8 type solid-state imaging device disclosed in the TV Society Zenkin Convention, p. 37 (1979). In the figure, 1 is an n-type 3i substrate, 2 is a p-type well layer, 3 is an n-type layer that becomes a photodiode, 4 is an n-type layer that becomes a drain, 5 is a gate electrode made of polycrystalline Si, and 6
7 is an oxide film for isolation, 7 is an At film for wiring which also serves as a light shield so that light does not enter the drain 4, and 8 is an oxide film for isolation between elements.

In this way, in the conventional device, the area around the train 4 is shielded by the At wire 7 tangential to the drain 4 so that light does not directly enter the drain 4 . This At wiring 7i
In order to prevent an alloying reaction between At and 3i in the drain region (an alloying reaction would cause problems such as a reduction in the junction breakdown voltage), it was formed of At containing 2 to 3% Si. As a result, there is light leakage that passes through the At wiring through the Si in the At wiring, which poses a major problem in reducing the smear phenomenon.

Note that since the At film 7 containing Si allows light to pass through, an insulating film is formed on the At wiring 7, and a pure A4 film that does not contain Si is further formed on the At wiring for light shielding. 7 is also covered. However, in this case, as shown in FIG. 3, there is light scattering due to diffraction 22 and multiple reflection 23 at 5, so even if you try to use the pure A/2 film 9 to block light wider than the At film 7, the aperture of the photodiode 3 will be blocked. There was a problem that the effect was small even though it reduced the number of people.

[Problem that the invention seeks to solve]

In the above conventional technology, light passes through the Si in the At wiring.
No consideration is given to the existence of leaked light that passes through the wiring, and the conventional light shielding methods that have been used as a countermeasure for this problem have had the problem of degrading sensitivity and having little light shielding effect.

An object of the present invention is to block the leaked light without causing a decrease in sensitivity due to pure AtIIX.

[Means for solving problems]

The above purpose is to allow the opening of the photodiode to be determined by the At film for interconnection, and to make the opening of the photodiode to be determined by the At film for interconnection.

This is achieved by shielding the At film for wiring from light so that it does not protrude.

[Effect]

The pure At film is provided so as not to protrude beyond the wiring At film. As a result, the At film for wiring can be sufficiently shielded from light and the smear phenomenon can be reduced without deteriorating the aperture of the photodiode.In addition, with the above-mentioned configuration, the incident light can be reflected outside the element, resulting in multiple reflections. Therefore, it is possible to effectively prevent light from entering the drain portion.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

The difference between this embodiment and the conventional example shown in Fig. 3 is that the wiring A/
, the structure is such that the pure At film 21 does not protrude from the film 7. This makes it possible to block leakage light through the wiring At film and reduce the smear phenomenon without deteriorating the aperture of the photodiode 3.

In addition to the MO8 type solid-state image sensor shown in FIG.
Of course, the present invention can also be applied to a CD-type solid-state image sensor. An example of its configuration is shown in FIG. Here, 11 ken n type 8i
A substrate, 10 is a p-type layer, 12 is an n-type layer constituting a photodiode, 13 is a p-type layer for channel stop, 14
is a vertical COD channel n-type layer for charge transfer, 15 is a vertical C
16.17 is an interlayer oxide film, 18 is a single-layer Atg film, and 19 is a two-layer line At film. The same applies when 15 is formed from silicide or a metal gate and is used as a light shielding film.

It goes without saying that the present invention is not limited to the above embodiments. That is, in the above embodiment, the pixel or memory section was formed in an N-type well on a P-type substrate, but
Of course, the effects of the present invention do not change even when pixels are formed in a p-type well on an n-type substrate. Moreover, although metal is mainly used as the light-shielding film here, the effects of the present invention will of course remain the same even if a light-shielding film other than metal is used. In the above embodiments, a two-dimensional solid-state image sensor has been described, but it goes without saying that the present invention can also be implemented in a -dimensional solid-state image sensor. Furthermore, the photodiode is M
It can also be applied to optical semiconductor devices having O8 capacitance and other optical semiconductor devices.

〔Effect of the invention〕

According to the present invention, since the upper At film does not protrude from the lower At film, light can be blocked without reducing the aperture ratio, and deterioration of the smear phenomenon caused by light transmitted through the lower At layer can be suppressed. .

[Brief explanation of the drawing]

FIG. 1 is a device cross-sectional view showing an example in which the present invention is applied to an MO8 type solid-state image sensor, and FIGS. 2 and 3 are a conventional example of r4.
FIG. 4 is a cross-sectional view showing the configuration of an OS type solid-state image sensing device. FIG. 4 is a device cross-sectional view showing an embodiment in which the present invention is applied to a CCD type solid-state image sensing device. 1.11...n-type Si substrate, 2,10...p-type well layer, 3.12...photodiode, 4...drain. 5.15...gate electrode, 6,16,17.20...
・Interlayer oxide film, 7.18...-layer At film, 9,19°21...Pure A/, film, 8.13...Element isolation, 14
... Vertical CCD channel layer, 22 ... Diffracted light, 23
...Multiple reflected light. Vines 1 Figure 1z diagram

Claims (1)

[Claims] 1. In an optical semiconductor element comprising a photosensitive part consisting of a photoelectric conversion element and a light shielding part having two or more layers of light shielding films consisting of a charge readout mechanism including a switch element, the upper layer of the light shielding film is the lowermost layer of the light shielding film. An optical semiconductor element characterized in that the width is no wider than the light-shielding film.