JPH0212870A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To enhance a light-shielding effect by light-shielding films and to improve the reliability of the photoelectric conversion characteristics of the title device by a method wherein the light-shielding films are formed of a pure Al film and wiring parts connected to the source and drain regions of a MOS transistor are each formed into a two-layer structure consisting of an Al layer and a poly Si layer or are formed of an Al layer containing Si. CONSTITUTION:In a solid-state image sensing device wherein light-shielding films 8 provided at a photoelectric conversion part constituted of photodiodes 2 and wiring parts 9 connected to source and drain regions 4 of a MOS transistor which is used as a peripheral circuit are each constituted of an Al film, said films 8 are formed of a pure Al film and said wiring parts 9 are respectively formed into a two-layer structure consisting of an Al layer 11 and a poly Si layer 10 or are formed of an Al layer containing Si. Thereby, as no pinhole exists in the films 8, a light-shielding effect is enhanced and the deterioration of photo characteristics can be prevented. Moreover, as the Al layers of the wiring parts 9 are never transformed into an eutectic with the source and drain regions, the breakdown of the junction between the source and drain regions is prevented and the deterioration of the characteristics of the MOS transistor can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a solid-state imaging device, and particularly to a solid-state imaging device that ensures reliability against strong light.

[Conventional technology]

Conventionally, in this type of solid-state imaging device, in order to prevent light from entering parts other than the photodiode that performs photoelectric conversion,
A light shielding film made of aluminum or the like is provided on the top surface of the device. Usually, this light shielding film is
It is formed using a portion of aluminum wiring for electrically connecting OS transistors and other elements.

・[Problem to be solved by the invention] In the conventional solid-state imaging device described above, in order to reduce the capacity and reduce the capacity of the MOS (MOS) run lister, the source
There is a tendency for drain junctions to be made shallow, but when aluminum is directly connected to these sources and drains,
Sinking at 400 to 500°C tends to cause alloy spikes in which aluminum becomes eutectic with silicon and breaks through the bond. To prevent this, a polycrystalline silicon layer is usually interposed between the source/drain and the aluminum.
Alternatively, attempts have been made to prevent bond breakdown by incorporating approximately 1 to 2% silicon into aluminum.

However, according to the inventor's study, such two
It was discovered that there are many small pinholes in the layered structure and aluminum containing silicon. for example,
In the case of a two-layer structure of 500 polycrystalline silicon and 1 μm aluminum, approximately 300
In the case of 1 μm aluminum containing 1% silicon, approximately 7000 pinholes/cm” were observed in the same sink.

Therefore, when such aluminum is used in the light shielding film of the solid-state imaging device described above, light passes through small pinholes, reducing the light shielding effect. In particular, when strong light is irradiated, the light that passes through the pinhole operates the photodiode and generates an electrical signal.

An object of the present invention is to provide a solid-state imaging device in which the light shielding effect of a light shielding film is enhanced and the reliability of photoelectric conversion characteristics is improved.

[Means for Solving the Problems] The solid-state imaging device of the present invention includes a light shielding film provided on a photoelectric conversion section consisting of a photodiode made of pure aluminum,
(MOS as a peripheral circuit) The wiring connected to the source/drain region of the run lister has a two-layer structure of aluminum and polycrystalline silicon, or is made of aluminum containing silicon.

[Effect]

In the above-described structure, the aluminum connected to the source/drain regions is made of polycrystalline silicon or contains silicon to prevent junction breakdown. Furthermore, since the light shielding film of the photoelectric conversion section is made of pure aluminum, there are no pinholes, which improves the light shielding effect.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view of an embodiment of the present invention. In the figure, reference numeral 1 denotes a P-type semiconductor substrate, on the main surface of which two arrays of N' layers separated by channel stoppers consisting of 29 layers 3 are formed to constitute a photodiode as a photoelectric conversion section. Further, an N-type source/drain region 4 is formed adjacent to the photoelectric conversion section, and a gate electrode 6 made of polycrystalline silicon is formed on the gate insulating film 5 to constitute a MOS transistor constituting a peripheral circuit. There is.

Then, an insulating film 7 is formed on the photodiode (MOS) transistor, and a light shielding film 8 is formed on the insulating film 7 to cover areas other than the photodiode in the photoelectric conversion section. Furthermore, in the MOS (MOS) run lister, a contact hole is formed in the insulating film 7, and a wiring 9 connected to the source/drain region 4 is formed therein.

Here, the light shielding film 8 is formed of a pure aluminum film containing no silicon or the like. On the other hand, the wiring 9 is made up of a lower layer polycrystalline silicon film 10 and an upper layer aluminum film 11.
It is structured in layers.

According to this configuration, in the MOS (MOS) run lister, since the polycrystalline silicon film 10 is interposed between the aluminum film 11 and the source/drain region 4, even when sinking is performed, the aluminum does not overlap with the silicon of the semiconductor substrate 1. There is no eutectic formation and no breakdown of the junction between the source and drain regions.On the other hand, in the photoelectric conversion section, since the light shielding film 8 is made of pure aluminum, there are no pinholes. Even when strong light is irradiated, it reliably prevents light transmission and prevents deterioration of optical characteristics.

FIG. 2 is a sectional view of another embodiment of the present invention, and the same parts as in FIG. 1 are given the same reference numerals.

This embodiment is the same as the previous embodiment in that the light shielding film 8 in the photoelectric conversion section is made of pure aluminum, and M
OS') The difference is that an aluminum film 11A containing silicon is used for the wiring 9 of the run lister.

In this configuration, since the aluminum film 11A connected to the source/drain region 4 contains silicon, the aluminum is eutecticized with the silicon contained by the sink, so that the junction between the source/drain regions is not destroyed. There isn't.

Further, since there are no pinholes in the light shielding film 8, the light shielding effect can be enhanced and deterioration of optical characteristics can be prevented.

〔Effect of the invention〕

As described above, in the present invention, since the light shielding film provided in the photoelectric conversion section of the solid-state imaging device is made of pure aluminum, there are no pinholes in the light shielding film, and the light shielding effect is improved. In addition, since the wiring connected to the source/drain regions of MOS transistors as peripheral circuits is constructed with a two-layer structure of aluminum and polycrystalline silicon or aluminum containing silicon, aluminum connects the source/drain regions with eutectic This prevents junction breakdown in the source/drain regions. Thereby, it is possible to prevent deterioration of the optical characteristics and also to prevent deterioration of the characteristics of the MOS transistor.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the invention, and FIG. 2 is a sectional view of another embodiment of the invention. DESCRIPTION OF SYMBOLS 1... P-type semiconductor substrate, 2... N'' layer (photodiode), 3... P+ layer (channel stopper), 4...
... Source/drain region, 5... Gate insulating film, 6
. . . Gate electrode, 7. Insulating film, 8. Light shielding film, 9. Wiring, 10. Polycrystalline silicon film, 11.
IIA...aluminum film.

Claims (1)

[Claims] 1. In a solid-state imaging device in which a light shielding film provided on a photoelectric conversion section composed of a photodiode and wiring connected to the source/drain region of a MOS transistor as a peripheral circuit are each composed of aluminum, A solid-state imaging device, characterized in that the shielding film is formed of pure aluminum, and the wiring is formed of a two-layer structure of aluminum and polycrystalline silicon or of aluminum containing silicon.