JPH1065134A - Photosemiconductor integrated circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable working the application of polyimide resin and also avoiding the mis-operation due to the light coming through the vent holes by a method, wherein dummy islands are arranged adjacent to the main bodies of photodiodes while arranging vent holes in the dummy islands. SOLUTION: Dumny islands 27 are arranged adjacent to photodiodes 23, 24, 25. Further, the upper part of a semiconductor chip is covered with a light barrier film 22. On the other hand, the flare stopping film 22 on the upper part of these photodiodes 23, 24, 25 as well as the upper part of the dummy islands 27 are respectively arranged with photosignal incoming spertures and the gas vent holes 27. In such a constitution, the dummy islands 27 are reverse biased to be dummy photodiodes, while the photocurent generated by the light coming through the gas vent holes 28 is absorbed by arranging the gas vent holes adjacent to the contacts 29 so as not to reach the inner circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical integrated circuit with a built-in photodiode, comprising a photodiode for receiving an optical signal and a circuit element for signal processing, and using a polyimide resin as an interlayer insulating film. It is.

[0002]

2. Description of the Related Art On a 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 receiving light is integrated with its peripheral circuit has been used. Was.
An IC-based device has the advantages that cost reduction can be expected as compared with a device that is hybridized with individual components, and that it is more resistant to noise due to an external electromagnetic field.

The above-described semiconductor device with a built-in photodiode includes:
Since the photodiode and the NPN transistor coexist, it is necessary to block a region other than the photodiode portion from the incident light so as not to generate an extra photocurrent due to light incident on the peripheral circuit. 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. 3 shows an example of the integrated circuit. In FIG. 3, 1 is a semiconductor chip, 2 is a light shielding film, 3 is an electrode pad, 4 is a photodiode, and 5 is a circuit element. The upper part of the circuit element 5 is covered with the light shielding film 2, and the photodiode 4 is opened for light incidence. Electrode pads for external connection are arranged in the electrode pads 3 so as to alternately overlap with each other so as not to short-circuit with the light shielding film 3.

FIG. 4 shows a partial sectional view. In FIG.
Reference numeral 6 denotes a P-type semiconductor substrate, 7 denotes an N-type island region formed by separating an epitaxial layer by a P + isolation region 8, 9 denotes an NPN transistor formed as one of the island regions 7 as a circuit element, and 10 denotes an insulating film. It is. The photodiode 4 uses the island region 7 as a cathode, the substrate 6 and the isolation region 8 as anodes, and has an N + type cathode contact region 11 on the surface of the island region 7. This integrated circuit employs a two-layer multilayer wiring structure as a whole, and the light-shielding film 2 is composed of a second aluminum wiring layer. The wiring for electrical connection of each element of the circuit element 5 is formed. The NPN transistor 9 has a P-type base region 13 and an N + -type emitter region 14 formed on the surface of an island region 7 serving as a collector. Fifteen
Is an N + type collector contact region, and 16 is an N + buried layer.

[0006]

However, light incident from the outside enters the substrate not only vertically but also obliquely. In addition, light not only passes through the silicon surface but also reflects at portions having different reflectivities (such as an interface between silicon and a silicon oxide film).
Therefore, as shown in FIG. 5, the obliquely incident light 17 is reflected on the back surface side of the light shielding film 2 and the silicon surface, and this is repeated a plurality of times (referred to as multiple reflection) to enter a region other than the photodiode. There is. If the penetrating light reaches the inside of the silicon, an undesired photocurrent is generated, which has a disadvantage that the circuit element 5 malfunctions.

There is also a demand for using an inexpensive polyimide resin as an interlayer insulating film of a multilayer wiring. However, when the surface of the polyimide resin is covered with aluminum having a certain area or more, there is a phenomenon that aluminum is swollen by gas generated from the resin when heated. Therefore, when the aluminum electrode covers a large area, it is necessary to arrange holes for degassing every fixed area,
Since light leaks from this hole, there is a disadvantage that it cannot be used as an interlayer insulating film.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and requires a contact hole in which an N or I type dummy island is reverse-biased. If a gas venting hole is provided near this contact hole when viewed in plan, carriers generated by light leaking from the gas venting hole,
Since it is generated in the vicinity of the contact portion, it is instantaneously absorbed from the contact portion and the influence on the outside can be suppressed.

Another object of the present invention is to provide a structure in which a polyimide resin can be used as an interlayer insulating film without increasing an occupied area by arranging a vent hole of the polyimide insulating film on the dummy island.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view showing an optical integrated circuit of the present invention. Referring to FIG. 1, reference numeral 21 denotes a semiconductor chip, and 22 denotes a light-shielding film covering almost the entire surface of the semiconductor chip 21. Since the light-shielding film does not appear in the drawing if it is entirely covered on the drawing, a gas vent hole is formed. Only the part is shown. 2
3, 24, 25 are photodiodes, 26 is an isolation region surrounding the photodiodes 22, 24, 25, 2
Reference numeral 7 denotes a dummy island further surrounding the isolation region surrounding the periphery of the photodiodes 22, 24, 25; 28, a gas vent hole formed in the light shielding film 22 above the dummy island 27; 29, a reverse bias between the dummy island 27 and the adjacent isolation region. Is a contact hole. Reference numeral 30 denotes a first-layer cathode electrode that contacts the cathode regions of the photodiodes 23 and 25, and reference numeral 31 denotes a cathode electrode of the photodiode 24. Although not shown, the circuit elements are arranged outside the isolation region 32 around the dummy island 27.

The center photodiode 24 detects a positional shift due to irradiation with a beam spot, and the photodiodes 23 and 25 on both sides are used for tracking. Although not shown here, the photodiode 2
Portions of the light-shielding film 22 corresponding to the light-receiving portions 3, 24, and 25 are open.

FIG. 2 is a sectional view taken along line AA of FIG. 41
Reference numeral denotes a P-type semiconductor substrate, and reference numeral denotes a P + -type isolation region formed by separating an N-type epitaxial layer formed on the substrate by an epitaxial growth method into a plurality of island regions 43 to. The photodiodes 23 and 25 have island regions 44 and 4 respectively.
7 is configured as a cathode, and the substrate 41 and the isolation region 42 are configured as an anode. On the surface of the island region, an N + type cathode contact region (indicated by a cross in FIG. 1) is formed, and the cathode electrode 30 is arranged on the surface of the cathode contact region. The cathode electrode 30 is connected to the signal input terminal of the internal circuit. Have been.

An anode electrode 49 is disposed on the surface of the isolation region 42 for partitioning the island region, and a ground potential (GN) is applied to the anode.
D) is applied. Similarly, in the photodiode 24, an N + type cathode contact region is formed in a portion indicated by X, and the cathode electrode 31 extends from the N + type cathode contact region. Passive elements and active elements are formed as circuit elements in the island region different from the photodiode. An example is N
A PN transistor and the like are formed. A dummy island 27 is arranged between a circuit element such as an NPN transistor and the photodiodes 23 and 25. The dummy island 27 is a region where the epitaxial layer is separated by the separation region 42 like the island region for element formation. Then, a cathode region 50 is formed on the surface of the dummy island 27, and a power supply potential (VCC) that is a reverse bias such as +5 V is applied to the cathode electrode 51 of the cathode region 50,
A dummy photodiode is formed using the dummy island 27 as a cathode and the substrate 41 and the isolation region 42 as anodes.

The surface of the epitaxial layer has a silicon oxide film 5
2 and an aluminum electrode extends on the surface to electrically connect each circuit element to form an integrated circuit network. In this example, a two-layer wiring structure is employed. 2
In the layer wiring structure, the upper (second) electrode layer covers almost the entire surface of the oxide film to form the light shielding film 52. The first-layer electrode wiring and the second-layer electrode wiring (light-shielding film 22) are interlayer-insulated by an interlayer insulating film 53 made of a polyimide resin. In the light-shielding film 22, the upper part of the photodiode is opened with a size substantially equal to the size of the island region constituting the photodiode for the incidence of an optical signal. Further, the light shielding film 2
4 μm × 4 μm above the dummy island 27
A hole 28 for degassing a polyimide resin used as an interlayer insulating film, which is of a small size, is formed.

In FIG. 2, only a portion of the light shielding film 22 is shown in a perspective view so that it can be seen that the light shielding film 22 is arranged. That is, it can be seen that a portion corresponding to the photodiode portion is opened, and a gas vent hole is also opened. The feature of the present invention resides in that the gas vent hole 28 provided in the light shielding film is provided near the contact 29.

For example, if light enters the dummy island 27, the light is captured as a photocurrent of a dummy photodiode formed by the dummy island and becomes a photocurrent between the anode electrode 49 and the cathode electrode 51. It does not flow into the circuit. The same can be said for the light that enters the dummy island through the gas vent hole, but a problem occurs depending on the position of the gas vent hole. For example, consider what kind of difference occurs in the generated photocurrent between the case where the vent hole is provided at the position indicated by the point B in FIG. 1 and the case where the vent hole is provided at reference numeral 28. Naturally, the size of the vent holes is the same.

As the dummy island 27, an N-type is used as an example. Since a part of the photocurrent generated from B, that is, the electron, is negative, it repels the P + type isolation region fixed to GND or the P + type semiconductor substrate fixed to GND, and the contact portion is VCC. , It moves toward the right contact 29 or the contact in the lower direction with respect to the paper surface.
However, since the path between them is long, some of them affect the elements constituting the photodiode and the outside arithmetic circuit.

Therefore, in the vicinity of the contact 29,
The so-called resistance component is reduced, and even if electrons are generated in the island corresponding to the gas vent hole 28 and in the vicinity thereof, the electrons are instantaneously absorbed without fluttering. Holes generated together with electrons are recombined or absorbed by an adjacent separation region or substrate. In FIG. 2, the cathode electrode 51 is provided, and this cathode electrode is in contact with the light shielding film 52 (22). However, the light shielding film may directly contact the dummy island. Therefore, the contact 29 shown in FIG. 1 is also a contact of the cathode electrode or a contact of the light shielding film.

[0019]

As described above, by arranging the vent holes of the polyimide insulating film on the dummy islands, the polyimide resin can be used as the interlayer insulating film without increasing the occupied area. In addition, a contact hole is required to reverse bias the dummy island. If a gas vent hole is provided near this contact hole in a plan view, a photocurrent generated by light leaking from the gas vent hole (here, Since the electrons are generated in the vicinity of the contact portion, the electrons are instantaneously absorbed from the contact portion and the influence on the outside can be suppressed.

[Brief description of the drawings]

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

FIG. 2 is a schematic cross-sectional view taken along the line AA of FIG.

FIG. 3 is a plan view of an optical semiconductor integrated circuit illustrating a conventional optical element.

FIG. 4 is a sectional view of FIG. 3;

FIG. 5 is an enlarged sectional view for explaining a conventional example.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Osamu Joma 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (2)

[Claims] 1. A photodiode formed on a part of a semiconductor chip, a circuit element formed on another part of the semiconductor chip, and a dummy island formed between the circuit element and adjacent to the photodiode. An electrode wiring layer for connecting the circuit elements to each other, a polyimide-based interlayer insulating film covering the electrode wiring layer, and a surface of the interlayer insulating film above the circuit element and the dummy island on the surface. An optical semiconductor integrated circuit, comprising: a light-shielding film covering the light-shielding film; an opening of the light-shielding film for light incidence formed on the photodiode; and a gas vent hole of the light-shielding film formed on the dummy island. A contact hole for applying a predetermined voltage to the dummy island so that the dummy island and an adjacent isolation region are reverse-biased; , Gas release openings of the shielding film, an optical semiconductor integrated circuit, characterized in that provided in close proximity with the contact holes in plan view. 2. A photodiode formed on a part of a semiconductor chip, a circuit element formed on another part of the semiconductor chip, and a dummy island formed between the circuit element and adjacent to the photodiode. An electrode wiring layer for connecting the circuit elements to each other, a polyimide-based interlayer insulating film covering the electrode wiring layer, and a surface of the interlayer insulating film above the circuit element and the dummy island on the surface. An optical semiconductor integrated circuit, comprising: a light-shielding film covering the light-shielding film; an opening of the light-shielding film for light incidence formed on the photodiode; and a gas vent hole of the light-shielding film formed on the dummy island. A contact electrode which is in contact with the dummy island and is formed in the same layer as the electrode wiring layer, and which is in contact with the light shielding film via the interlayer insulating film; An isolation region adjacent to the dummy island is reverse-biased, and a gas vent hole of the light-shielding film is provided in proximity to a contact hole of the contact electrode in plan view. .