JP2000200892A - Semiconductor device with built-in photodiode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device equipped with a built-in photodiode and a circuit element coated with a light blocking film, where the light blocking film and cross wirings are made to coexist without increasing multilayered wirings in the number of layers. SOLUTION: A semiconductor chip is equipped with a photodiode and a circuit element, and the semiconductor chip is covered with a light blocking film 12 formed of an aluminum wiring layer excluding the photodiode. An opening is provided to a part of the light blocking film 12 deposited on the circuit element to serve as a cross wiring section 16, a cross electrode 18 is formed of a wiring layer at the same level with the light blocking film 12, and a cross wiring consisting of first electrode wirings 17a and 17c and an electrode wiring 17b can be realized by an interlayer connection. A dummy photodiode is arranged under the cross wiring section to absorb an excess incident light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a multi-layer wiring structure of a semiconductor device having a built-in photodiode for receiving an optical signal and having a light shielding film for shielding unnecessary light.

[0002]

2. Description of the Related Art On the receiving side of an optical signal transmitting means using infrared rays or the like or an optical signal reading device of an optical pickup device, a semiconductor device in which a photodiode for light reception is integrated together with its peripheral circuit has been used. . I
The C-type device has the advantages that cost reduction can be expected as compared with a device hybridized with individual components, and that it is more resistant to noise due to an external electromagnetic field.

In the above-described semiconductor device with a built-in photodiode, since a photodiode and an NPN transistor coexist, it is necessary to block a region other than the photodiode portion from incident light so that an extra photocurrent due to light incident on a peripheral circuit does not occur. is there. As such a light shielding means, the method of covering the peripheral circuit portion with the uppermost aluminum wiring by using a multilayer wiring technology of a semiconductor integrated circuit is the simplest (for example, Japanese Patent Application No. 4-287584).

FIG. 5 shows the semiconductor device. In the figure, 1 is a semiconductor chip, 2 is a light shielding film, 3 is an electrode pad portion, 4 is a photodiode portion, and 5 is a circuit element portion. The entire circuit element section 5 is covered with the light shielding film 2, and the photodiode section 4 is opened for light incidence. Electrode pads for external connection are arranged in the electrode pad portion 3 so as to alternately overlap with each other so as not to short-circuit with the light shielding film 3. The light-shielding film 2 is formed of the uppermost wiring layer of the multilayer wiring structure. Under the light-shielding film, each element of the circuit element portion 5 is electrically connected by a wiring layer below the light-shielding film.

[0005]

However, since the light-shielding film 2 occupies the uppermost layer of the multilayer wiring structure, the number of wiring layers available for electrode wiring decreases. A prominent example is a two-layer wiring structure, and consuming the second layer for forming the light-shielding film 2 means that element-to-element connection must be performed only with the first wiring layer. Then, the cross connection peculiar to the multilayer wiring cannot be performed, and there is a disadvantage that the pattern design becomes difficult.

The problem can be solved by simply increasing the number of wiring layers to three or four. However, there is a number of wiring layers corresponding to the number of built-in elements and the chip size. Increasing the number has the disadvantage of being more costly. Although a certain degree of cross wiring is possible by using a diffusion region with a high impurity concentration as a part of the wiring,
There is a limit due to high wiring resistance.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has an intersection wiring portion having a light shielding film formed in a part of a circuit element portion. A cross-wiring is performed using the same wiring layer, and unnecessary light incident through the opening is absorbed by a dummy photodiode provided below the cross-wiring portion, thereby eliminating adverse effects on other circuit elements. It is.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an enlarged plan view showing a part of a chip of a semiconductor device of the present invention, and FIG.
FIG. 3 is a plan view showing the entire semiconductor chip. First, referring to FIG. 3, reference numeral 11 denotes a semiconductor chip integrating a photodiode element and other peripheral circuit elements;
Is a light-shielding film formed of aluminum electrode wiring, 13 is an electrode pad portion, 14 is a photodiode portion, and 15 is a circuit element portion. The light-shielding film 12 covers substantially the entire circuit element portion 15 and extends to the vicinity of the scribe line on the outermost periphery of the semiconductor chip 11, and the photodiode portion 4 is opened for light incidence. Although the electrode pad section 13 is not shown in detail,
Bonding pads for external connection are provided therein by aluminum electrode wiring, and their ends overlap with each other using a multilayer wiring structure so that the bonding pads and the light-shielding film are not short-circuited and the surface of the semiconductor chip 11 is not exposed. It has become.

An NPN transistor,
Many active elements and passive elements such as resistors are formed,
Under the light-shielding film 12, electrical connection between each element is formed by a wiring layer below the light-shielding film 12 (or by a first wiring layer if the light-shielding film is the second layer). Is going. Then, the light shielding film 12 covering the circuit element portion 15
Are formed to form a cross wiring portion 16.

FIG. 1 is an enlarged plan view of the cross wiring portion 16. Referring to FIG. 1, electrode wirings 17a and 17b formed in the first wiring layer by opening light-shielding film 12 are provided.
17c is exposed, and the cross electrode 18 formed of the second wiring layer like the light shielding film 12 is interlayer-connected to the electrode wirings 17a and 17c via through holes formed in the interlayer insulating film. Then, the crossing electrode 18 crosses the electrode wiring 17b via the interlayer insulating film, thereby forming the electrode wiring 17b.
Cross wiring between the electrodes 17a and 17b and the electrode wiring 17b is performed. Each of the electrode wirings 17a, 17b, 17c extends on the insulating film and is connected to a desired circuit element.

A dummy photodiode D-PD having a larger area is arranged below the intersection wiring portion 16. FIG. 2 is a sectional view taken along line AA of FIG. Referring to FIG. 2, reference numeral 21 denotes a P-type silicon semiconductor substrate;
Is a P + type isolation region penetrating an N type epitaxial layer formed by vapor phase growth on the substrate, and 23 is an island region formed by the isolation region. Dummy photodiode DP
D is a P-type silicon semiconductor substrate 21 and a P + isolation region 2
2 as an anode, an N-type layer (N + buried layer 2
7) as a cathode. An anode electrode 24 is disposed on the surface of the isolation region 22 to supply a ground potential GND, and a power supply potential V such as +5 V is supplied to the island region 23 by a cathode electrode 26 via an N + contact region 25.
Apply CC. The application of this potential reverse biases the dummy photodiode D-PD to generate a depletion layer.
Here, 27 is an N + buried layer, 28a is an insulating film such as a silicon oxide film, 28b is an interlayer insulating film such as a silicon oxide film and a silicon nitride film, and 28c is a passivation film such as a silicon oxide film and a silicon nitride film. The light-shielding film 12 and the cross electrode 18 are formed in the second wiring layer, and the cross electrode 18 connects the electrode wirings 17a and 17c via through holes in the interlayer insulating film and crosses the electrode wiring 17b. . Each of the insulating films 28a, 28b, 28c is translucent, and the semiconductor chip 11 is molded with a translucent resin. The light-shielding film 12 made of aluminum is light-shielding.

Light that cannot be shielded by providing the light-shielding film 12 with the opening called the cross wiring portion 16 is incident on the island region 23 below the light-shielding film. The incident light is converted into a photocurrent by a depletion layer formed by the dummy photodiode D-PD, or an N-type or P-type semiconductor layer on both sides of the depletion layer, and the photocurrent is diffused to the anode electrode 24 or the cathode electrode 2.
Collected in 6. Therefore, malfunction and latch-up due to the photocurrent flowing into another circuit element can be prevented.

Since the light-shielding film 12 is grounded, the light-shielding film 12 may be connected to the anode electrode 24 in some cases. The anode electrode 24 extends as much as possible along the isolation region 24 around the island region 23. At this time, if the light is extended while being connected to the light-shielding film 12 between the layers, it is possible to shield the multi-reflected light, which is repeatedly reflected on the silicon surface and the back surface of the light-shielding film 12, from the intersection wiring portion 16. However, the extension of the first-layer electrode wiring 17 is not prevented. The light-shielding film 12 extends from the end of the isolation region 22 to the inside of the island region 23 forming the dummy photodiode so that the isolation region 22 is not exposed.

FIG. 4 is a cross-sectional view showing the structure of an NPN transistor as a representative of a circuit element and a photodiode element PD formed in the photodiode section 14. In the figure, reference numeral 30 denotes a P-type base region formed on the surface of the island region 23, 31 denotes an N + type emitter region formed on the surface of the base region 30, and 32 denotes an N + type formed on the surface of the island region 23.
Mold collector contact area. The same parts as those in FIG. Photodiode P
Only the light-shielding film 12 above D is opened, and the light-shielding film 12 extends over the circuit element. Under the light-shielding film 12, a first-layer electrode wiring 17 performs inter-element connection. Photodiode P
The structure of D is basically exactly the same as that of the dummy photodiode PD.

According to the semiconductor device of the present invention described above, the same level of the aluminum wiring layer as the light-shielding film 12 is used as the crossing electrode 18, so that the first-layer electrode wiring 17 can be cross-connected. it can. Therefore, wiring pattern design becomes easy. Further, since the number of layers of the multilayer wiring does not need to be increased, the cost can be reduced. By arranging the dummy photodiode D-PD below the cross wiring section 16, the incident light passing through the cross wiring section 16 is collected, and is prevented from flowing to other circuit elements, thereby preventing a malfunction of the circuit element. To prevent.

The structures of the photodiode PD and the dummy photodiode D-PD are not limited to those of the above-described embodiment. For example, a P-type anode region is formed by diffusion on the surface of the island region 23 in the same manner as the base region 30. A configuration in which a PN junction between the region and the island region 23 is a photodiode may be used.

[0017]

As described above, according to the present invention, a wiring layer at the same level as the light-shielding film 12 is used for the crossing electrode 18, so that it is not necessary to add one wiring layer for cross wiring. Has advantages. Therefore, there is an advantage that the pattern design of the electrode wiring becomes easy and the cost is not increased.

Further, by arranging the dummy photodiode D-PD below the intersection wiring portion 16, there is an advantage that a photocurrent due to extra incident light can be collected and malfunction of other circuit elements can be prevented.

[Brief description of the drawings]

FIG. 1 is a plan view for explaining the present invention.

FIG. 2 is a cross-sectional view for explaining the present invention.

FIG. 3 is a plan view for explaining the present invention.

FIG. 4 is a cross-sectional view for explaining the present invention.

FIG. 5 is a plan view for explaining a conventional example.

Claims (2)

[Claims] A photodiode portion formed in a part of the semiconductor chip; a circuit element portion formed in another portion of the semiconductor chip; a multilayer wiring layer connecting each element of the circuit element portion; A light-shielding film covering the surface of the semiconductor chip so as to remove the portion; an intersection wiring portion formed by removing the light-shielding film on a part of the light-shielding film; A semiconductor device with a built-in photodiode, comprising: an electrode wiring to be formed; and a dummy photodiode provided below the intersection wiring portion. 2. The semiconductor device with a built-in photodiode according to claim 1, wherein said multilayer wiring has a two-layer structure, and said light-shielding film is formed by a second wiring layer.