JPH0364968A - Solid-state image sensing device and manufacture thereof - Google Patents

Abstract

PURPOSE:To enable a flare to decrease to a detection limit or below without changing an image sensing device in other characteristics by a method wherein a TiN film is provided onto an aluminum or an aluminum alloy film which serves as an optical shielding film as coming into close contact with it and covering the whole of it. CONSTITUTION:A solid-state image sensing device is formed, where aluminum or aluminum alloy is evaporated to form an optical shielding film 1, in succession a TiN film 2 is evaporated thereon to form a two-layered film, and then the two-layered film is plasma-etched through a mixed gas of BCl3, Cl2, and N2 at the same time to form an optical shielding region. An anti-reflection film 2 of TiN is formed on the upside of the aluminum or the aluminum alloy film 1, whereby the reflected light at the surface of aluminum is decreased to 5% or below in a visible ray region and a flare is decreased to an observation limit or below.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a solid-state image sensor, and in particular, the present invention relates to a solid-state image sensor, in which incident light is reflected on the surface of the image sensor, and the reflected light is reflected again by a lens and enters other pixels of the image sensor. The present invention relates to a solid-state image sensor and a method for manufacturing the same, which reduce the flare phenomenon that degrades images.

Conventional Solid-state imaging devices using a photodiode and a CCD or MOS transistor are shielded from light using aluminum or an aluminum alloy, except for the photodiode portion that photoelectrically converts incident light. This aluminum or aluminum alloy is also used for wiring for CCDs, MOS transistors, and peripheral circuits.

FIG. 2 is a cross-sectional view showing the structure of a conventional solid-state image sensor. As shown in the figure, the entire area covered with the aluminum light-shielding film 1 except for the photodiode section 5 is C00.
The portion 6 is located below the aluminum light shield I11. In addition,
In the figure, 3 is a COD polysilicon gate, and 4 is a protective film.

Problems to be Solved by the Invention When a light-shielding film is formed using aluminum or an aluminum alloy, the light that enters the solid-state imaging device through the lens is totally reflected on the aluminum surface, and this reflected light is reflected again on the lens surface, causing the original The light enters a pixel section different from the one it should enter,
This causes image deterioration called flare. In order to prevent this flare, conventionally, the lens surface was coated with an anti-reflection film to reduce the reflectance, thereby suppressing re-reflection on the lens surface. However, the degree of reduction in reflection on the lens surface was not at all high.

Incidentally, in order to reduce flare, it is sufficient to reduce the amount of light reflected on the surface of the aluminum or aluminum alloy film. For example, a method of reducing the reflectance by growing grains on the surface of the aluminum or aluminum alloy can be used. However, if grains are grown after aluminum etching, abnormal growth of grains called hillock occurs, resulting in variations in the area of the opening of the photodiode section. On the other hand, if grain growth is performed before aluminum etching,
Aluminum etching becomes difficult. Therefore, the flare phenomenon still remains as one of the problems to be solved in order to improve images.

Means for Solving the Problems The present invention provides a structure of a solid-state image sensor capable of solving the above-mentioned problems and realizes this structure. It has a structure in which a TiN film is provided on top of the aluminum alloy film in close contact with the aluminum or aluminum alloy film and covering the entire area of the aluminum or aluminum alloy film.

In addition, when manufacturing solid-state image sensors, Ti
A method is employed in which a N film is vapor-deposited to form a two-layer film, and then the two-layer film is simultaneously plasma etched using a mixed gas system of BCl3, Cl2, and N2 to form a light-shielding region.

By forming an antireflection film made of functional TiN on the top surface of an aluminum or aluminum alloy film, the reflected light on the aluminum surface is reduced to 5% or less in the visible light region, and flare is below the observation limit.

Example The present invention will be explained in detail below.

In the present invention, flare is reduced by forming a film with low reflectance on the aluminum or aluminum alloy film, and this anti-reflection film needs to cover the aluminum area in just the right amount. open it. These conditions were taken into consideration, such as the need to etch this anti-reflective film at the same time as aluminum etching, and the fact that normal dielectric films cannot be processed at the same time as aluminum etch, so the anti-reflective film is limited. A structure is adopted in which a titanium nitride (T i N) film is formed on top of an aluminum or aluminum alloy film as a satisfactory film.

1yJ shows the cross-sectional structure of the pixel portion of the solid-state image sensor according to the present invention, which differs from the conventional solid-state image sensor in that the TiN film 2 is formed on the top surface of the aluminum light-shielding film 1 as shown in the figure. ing.

Incidentally, the TiN film has a thickness of about 100 OA and exhibits a brownish color, and not only does it have a high light absorption, but it can also be formed by reactive sputtering, and it tends to be formed using a gas such as BCl 3 used in plasma etching of aluminum. ．． Anisotropic etching can be performed using a mixed gas of Ce 2 and N 2 . For this reason, the formation of a TiN film can be easily achieved by vapor deposition subsequent to the vapor deposition of an aluminum light shielding film, and the two-layer film of an aluminum light shielding film and a TiN film formed in this way is
Can be patterned using gas plasma etching treatment for aluminum.

In the solid-state imaging device of the present invention formed in this way, the aperture area of the photodiode portion is completely unchanged compared to the conventional example shown in FIG. 2, and therefore the imaging characteristics other than flare remain unchanged.

Effects of the Invention According to the present invention, flare could be reduced to below the detection limit without causing any change in other imaging characteristics.

[Brief explanation of drawings]

FIG. 2 shows a schematic diagram of a cross-sectional structure of a pixel portion of a conventional CCD image sensor.

Claims (1)

[Claims] (1) In a solid-state image sensor that uses aluminum or an aluminum alloy to form a light-shielding film of aluminum or an aluminum alloy on an element area other than a photodiode that performs photoelectric conversion, the aluminum or aluminum alloy is coated on top of the aluminum or aluminum alloy. Alternatively, a solid-state imaging device characterized by having a structure in which TiN is provided in close contact with an aluminum alloy and covering the entire aluminum or aluminum alloy region. 2. Following the vapor deposition of aluminum or aluminum alloy that forms the light-shielding film, a TiN film is vapor-deposited to form a two-layer film,
A method for manufacturing a solid-state image sensor, characterized in that the two-layer film is then plasma-etched simultaneously with a mixed gas system of BCl_3, Cl_2, and N_2 to form a light-shielding region.