JPH04316362A - Semiconductor device - Google Patents

Abstract

PURPOSE:To prevent leak current due to flow of optical current to a parasitic photo transistor due to external light by forming a light-screening film at an upper portion of an active region of a semiconductor where an electronic circuit consisting of an element such as transistor is formed. CONSTITUTION:A light-screening film 5 is formed on an active region 6. Thus, an external light enters an element such as a transistor at a surface portion of a semiconductor substrate 1 and a photo current flows to a parasitic photo transistor, thus preventing leak current. Also, the light-screening film 5 is formed by a conductive metal such as aluminum and is connected to an electrode pad for supplying ground potential 8a. Then, by giving the ground potential to an electronic circuit through the light-screening film 5, a resistance at a ground line can be reduced greatly and fluctuation of a power supply potential can be reduced. Further, the light-screening film 5 covers an active region 6 and is grounded, thus preventing noise from entering the active region 6 from outside.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a semiconductor device in which an electronic circuit consisting of elements such as transistors is formed on the surface of a semiconductor substrate.

0002

2. Description of the Related Art Semiconductor devices generally include electronic circuits made of elements such as transistors formed on the surface of a semiconductor substrate. Furthermore, conventional semiconductor devices do not have any means for preventing light from entering the active region.

0003

By the way, it has been found that a non-negligible leakage current may flow in a conventional semiconductor device due to a photocurrent caused by external light. When we investigated the cause, we found the following. That is,
Since resin-sealed semiconductor devices are required to be thinner, the thickness of the resin package used to seal them tends to become thinner. When the resin package becomes thinner, external light passes through the thin resin package and enters the electronic circuit formed on the surface of the semiconductor substrate. This blocking of light from entering the electronic circuit can cause leakage current.

[0004] This is because an element such as a transistor or a junction becomes a phototransistor or a photodiode depending on the relationship of applied potentials, and when light is incident thereon, a photocurrent flows. For example, a pn junction that is reverse biased can be considered a parasitic transistor by itself, and when light enters there, a photocurrent may flow there. This photocurrent then becomes a leakage current. Therefore, when the semiconductor device is, for example, a static RAM, a problem arises in that the data retention voltage must be increased.

[0005] Furthermore, as semiconductor devices become larger in area and faster in speed, the potential changes depending on the location of the power supply line to an extent that cannot be ignored. Therefore, there are problems such as the need to increase the number of power supply pads and the tight noise margin against fluctuations in power supply voltage.

The present invention has been made to solve these problems, and one purpose is to prevent leakage current from flowing into an electronic circuit formed of a semiconductor due to external light. , Another purpose is to reduce fluctuations in power supply voltage depending on the location of the power supply line.

[Means for Solving the Problems] The semiconductor device of the present invention is characterized in that a light shielding film is formed above an active region.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The semiconductor device of the present invention will be explained in detail below according to the illustrated embodiments. 1 and 2 show one embodiment of the present invention, with FIG. 1 being a plan view and FIG. 2 being a sectional view.

In the drawings, 1 is a semiconductor substrate, 2 is an MO
S transistor, 3 is an interlayer insulating film, 4 is a wiring film made of aluminum, for example, 4a is a wiring film electrically connected to a ground electrode (ground potential electrode pad) of a power source, and 4b is a through hole.

Reference numeral 5 denotes a light-shielding film located above the wiring film 4, and is made of aluminum, for example.
formed on top. 7 is a final insulating film formed on the light shielding film 5.

Reference numerals 8, 8, . . . are electrode pads, and 8a is an electrode pad for supplying a ground potential among the electrode pads 8, 8, . The ground potential is applied from the pad 8a to elements such as the transistor 2 via the light shielding film 5, the through hole 4b, and the wiring film 4a.

This semiconductor device has a light shielding film 5 on the active region 6.
is formed, the light shielding film 5 can prevent external light from entering the active region 6. Therefore, it is possible to completely prevent external light from being incident on elements such as transistors on the surface of the semiconductor substrate 1, causing photocurrent to flow through the parasitic phototransistor and parasitic photodiode, resulting in leakage current.

Furthermore, a wide-area light-shielding film 5 covering the active region 6 is formed of a highly conductive metal such as aluminum, and is connected to an electrode pad 8a for supplying a ground potential, and is connected to an electronic circuit via the light-shielding film 5. Since the ground potential is applied to the ground line, the resistance of the ground line can be made extremely small, eliminating the possibility that the power supply potential will fluctuate depending on the location, and contributing to speeding up of electronic circuits.

Since the light shielding film 5 covers the active region 6 and is grounded, it has an electrostatic shielding effect and can prevent noise from entering the active region 6 from outside. can. In the above embodiment, the entire area of the active region 6 is covered with the light shielding film 5, but the portions of the active region 6 where there is no risk of leakage current or where there would be no problem even if leakage current occurs are not necessarily covered. It is not necessary to cover with the light shielding film 5. That is, there may be an embodiment in which a part of the active region 6 is covered with the light shielding film 5.

[0014]

The semiconductor device of the present invention is characterized in that a light shielding film is formed above an active region of a semiconductor in which an electronic circuit consisting of elements such as transistors is formed. Therefore, according to the semiconductor device of the present invention, the light-shielding film blocks external light from entering the active region, thereby preventing photocurrent from flowing through the parasitic phototransistor and parasitic photodiode due to external light and becoming a leakage current. can. Furthermore, since the light-shielding film has an extension that covers all or part of the active region, when used as a wiring film, the wiring resistance can be reduced. Therefore, by using a light-shielding film as a power supply line, the resistance of the power supply path can be reduced.
Furthermore, variations in power supply voltage depending on location can be eliminated. Further, since the active region can be electrostatically shielded by the light shielding film, noise resistance can be improved.

[Brief explanation of drawings]

FIG. 1 is a plan view of one embodiment of a semiconductor device of the present invention.

FIG. 2 is a sectional view of the above embodiment of the semiconductor device of the present invention.

[Explanation of symbols]

1 Semiconductor 2 Transistor 5. Light shielding film 6 Active area

Claims (1)

[Claims] 1. A semiconductor device characterized in that a light shielding film is formed above an active region of a semiconductor in which an electronic circuit consisting of elements such as transistors is formed.