WO1997023909A1

WO1997023909A1 - Integrated circuit incorporating photodiode

Info

Publication number: WO1997023909A1
Application number: PCT/JP1996/003749
Authority: WO
Inventors: Osamu Shiroma
Original assignee: Sanyo Electric Co., Ltd.
Priority date: 1995-12-22
Filing date: 1996-12-20
Publication date: 1997-07-03

Abstract

Both light shielding film and cross-wiring of a semiconductor device which incorporates a photodiode and in which circuit elements are covered with the light shielding film are provided without increasing the number of layers of multilayered wiring. A polyimide interlayer insulating film is provided. The surface of a semiconductor chip (11) on which a photodiode section (14) and a circuit element section (15) are formed is covered except the photodiode section (14) with a light shielding film (12) composed of an aluminum wiring layer. Cross-wiring between first-layer electrode wirings (17a and 17c) and electrode wiring (17b) is realized by interlayer connection by forming a cross-wiring section (16) by opening part of the film (12) on the circuit element section (15) and a cross electrode (18) of a wiring layer at the same level as that of the light shielding film (12). A dummy photodiode D-PD is provided below the cross-wiring section (16) so as to absorb excessive incident light. The opening of the wiring section (46) also serves as a vent hole.

Description

Specification

Integrated circuit with integrated photodiode

The present invention relates to a multilayer 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. Background 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 integrated circuit in which a photodiode for light reception is integrated together with its peripheral circuits has been used. The IC-based device has the advantage that it can be expected to reduce costs compared to a device that is hybridized with individual components, and is more resistant to noise caused by external electromagnetic fields.

In the integrated circuit with built-in photodiode, since the photodiode and the NPN transistor coexist, the area other than the photodiode is shielded from the incident light so that extra photocurrent does not occur due to light entering the peripheral circuits. There is a need to.

The simplest way to shield light is to cover the peripheral circuit on the chip surface with aluminum wiring, utilizing the fact that the aluminum electrodes used to connect the elements of the semiconductor integrated circuit are light-shielding. (For example, Japanese Patent Application No. 4-12878782). Figure 8 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, the wiring layers below the light-shielding film electrically connect the respective elements of the circuit element section 5.

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-layer wiring layer. Then, a cross connection unique to multilayer wiring is created And the pattern design becomes difficult.

The problem can be solved simply by increasing the number of wiring layers to three or four.However, there are numbers of wiring layers that match the number of built-in elements and the chip size. An increase has the disadvantage of increasing costs.

In addition, by using a diffusion region with a high impurity concentration as a part of the wiring, it is possible to form a small amount of interconnects, but since the electrical resistance of the diffusion region is higher than that of aluminum material, the wiring resistance is limited. There is.

Further, as an interlayer insulating film for insulating the wiring layers from each other, there is a polyimide-based insulating film in addition to a PSG film, a BPSG film and the like. There is a strong demand for polyimide insulating films because they have excellent flatness and can be manufactured at low cost by spin-on coating. However, the polyimide insulating film generates gas due to various heat treatments after coating, and the generated scum pushes up the aluminum electrode covering the surface, so that aluminum over a large area of, for example, 200 mm x 200 mm Cannot be coated with electrodes. Therefore, there is a disadvantage that it cannot be used in the case where almost the entire surface of the chip is covered like the light shielding film 2. Also, if it is unavoidable to cover with a large area of aluminum electrode, it is necessary to intentionally provide a gas vent hole of about 5: X 5〃 for each fixed area, but the polyimide insulating film blocks light. Therefore, the gas vent hole cannot be formed in the light shielding film 2 described above.

Accordingly, the present invention provides an integrated circuit with a built-in photodiode which enables easy cross wiring by multi-layer wiring even when almost the entire surface of the semiconductor chip is covered with a light-shielding film made of aluminum electrodes.

Another object of the present invention is to provide an integrated circuit with a built-in photodiode, which can use a polyimide-based insulating film which is inexpensive and easy to manufacture as an interlayer insulating film. Disclosure of the invention

According to the present invention, a cross-wiring portion having a light-shielding film opened in a part of a circuit element portion is formed, and cross-wiring is performed in the cross-wiring portion using the same wiring layer as the light-shielding film. The incident unnecessary light is absorbed by a dummy photodiode provided below the intersection wiring portion, thereby eliminating adverse effects such as malfunction of other circuit elements. Furthermore, since it is necessary to provide an opening in the light-shielding film by providing the cross wiring portion, the chip size can be made more efficient by also using the opening as a gas vent for the polyimide-based insulating film. In addition, polyimide resin can be used as an interlayer insulating film. BRIEF DESCRIPTION OF THE FIGURES

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

FIG. 2 is an enlarged plan view of a main part of FIG.

FIG. 3 is a cross-sectional view taken along the line A A of FIG.

FIG. 4 is a cross-sectional view for explaining the first embodiment.

FIG. 5 is a plan view for explaining the second embodiment of the present invention.

FIG. 6 is a sectional view of a main part of FIG.

FIG. 7 is an enlarged plan view of a main part of FIG.

FIG. 8 is a plan view for explaining a conventional photodiode built-in integrated circuit. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a plan view showing an entire semiconductor chip of a photodiode-integrated integrated circuit according to a first embodiment of the present invention.

Referring to m1, 11 is a semiconductor chip in which a photodiode element and other peripheral circuit elements are integrated, 12 is a light-shielding film formed of aluminum electrode wiring, 13 is an electrode node, 1 Reference numeral 4 denotes a photodiode section, and 15 denotes a circuit element section. The light-shielding film 12 covers substantially the entire circuit element section 15 and extends to the vicinity of the outermost scribe line of the semiconductor chip 11, and the photodiode section 4 is opened for light incidence. Although not shown in detail, the electrode pad portion 13 is provided with a bonding pad for external connection by aluminum electrode wiring inside the electrode pad portion 13 so as not to short-circuit the bonding pad and the light shielding film, and To prevent the surface from being exposed, a multilayer wiring structure is used to make the ends overlap each other.

Numerous active and passive elements, such as NPN transistors and resistors, are formed in the circuit element section 15, and under the light-shielding film 12, a wiring layer below the light-shielding film 12 is used. (If the light-shielding film is the second layer, the first wiring layer is used.) Electrical connection between each element is made to configure the peripheral circuit. Then, a cross-wiring portion 16 is formed by opening a part of the light-shielding film 12 covering the circuit element portion 15.

FIG. 2 is an enlarged plan view of the cross wiring portion 16. Referring to FIG. 2, the opening of the light shielding film 12 reveals the electrode wirings 17a, 17b, and 17c formed in the first wiring layer. The cross electrode 18 formed by the second wiring layer is interlayer-connected to the electrode wirings 17a and 17c via through holes formed in the interlayer insulating film. Then, the cross electrode 18 crosses the electrode wiring 17b via the interlayer insulating film, whereby the cross wiring between the electrode wiring 17a, 17c and the electrode wiring 17b is performed. Each of the electrode wirings 17a, 17b, and 17c extends on the insulating film and is connected to a desired circuit element.

A dummy photodiode having a larger area is arranged below the crossed wiring portion 16.

FIG. 3 is a sectional view taken along line AA of FIG. Referring to FIG. 3, reference numeral 21 denotes a P-type silicon semiconductor substrate, and reference numeral 22 denotes a P + -type isolation region that penetrates N-type epitaxial dust formed on the substrate 21 by vapor phase growth. And 23 are bird regions formed by the separation regions. The dummy photodiode has a structure in which the P-type silicon semiconductor substrate 21 and the P + isolation region 22 are anodes, and the N-type layer (including the N + buried layer 27) in the island region 23 is a cathode. . The ground electrode GND is placed on the surface of the isolation region 22 with the anode electrode 24 placed by itself, and the island region 23 is connected to the +5 by the force source electrode 26 via the N + contact region 25. Apply a power supply potential VCC such as V. The application of this potential reverse biases the dummy photodiode D-PD to generate a depletion layer. 27 is an N + buried layer, 28 is an interlayer insulating film such as a silicon oxide film and a silicon nitride film, 29 a is an insulating film such as a silicon oxide film, and 29 b is a silicon oxide film and a silicon nitride film. And the like. 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 1 Ίa and 17 c via through holes in the interlayer insulating film. Crossed with wiring 17b. The insulating films 28 and 29 are translucent, and the semiconductor chip 11 is molded with a resin that transmits light of a specific wavelength. The aluminum light-shielding film 12 is light-shielding.

The light-shielding film cannot be shielded by providing an opening called a cross wiring part 16 in the light-shielding film The light is incident on the island region 23 under the light. The incident light is converted into a photocurrent by a depletion layer formed by a dummy photodiode or an N-type or P-type semiconductor layer on both sides of the depletion layer, and the photocurrent is diffused to an anode electrode 24 or a force source electrode 26. Will be collected at Therefore, it is possible to prevent a malfunction or a latch-up due to the photocurrent flowing into another circuit element.

Since the light-shielding film 12 is grounded, the light-shielding film 12 may be interlayer-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 interlayer-connected to the light-shielding film 12, it is possible to shield the multi-reflection 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, it does not hinder the extension of the first-layer electrode wiring 17. The light-shielding film 12 extends from the island region 23 forming the dummy photodiode to the inside of the end of the separation region 22 so that the separation 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 same figure, 30 is a P-type base region formed on the surface of the island region 23, 31 is an N + -type emitter region formed on the surface of the base region 30, and 32 is a region of the island region 23. This is the N + type collector contact area formed on the surface. The same parts as those in FIG. Only the light-shielding film 12 above the photodiode PD is opened, and the light-shielding film 12 extends over the circuit element. Under the light-shielding film 12, the first-layer electrode wiring 17 connects the elements. The structure of the photodiode PD and the structure of the dummy photodiode are basically exactly the same.

According to the semiconductor device of the present invention described above, since the aluminum wiring layer at the same level as the light shielding film 12 is used as the cross electrode 18, the cross connection of the first-layer electrode wiring 17 is performed. Can be. Therefore, wiring pattern design becomes easy. Also, since the number of layers in the multilayer wiring does not need to be increased, the cost can be reduced. By placing a dummy photodiode below the crossed wiring section 16, the incident light passing through the crossed wiring section 16 is collected, and is prevented from flowing to other circuit elements. To prevent.

The structures of the photodiode PD and the dummy photodiode are not limited to those in the above embodiment. For example, the P-type anode on the surface of the island region 23 as in the base region 30. The anode region and the island region 23 may be formed as a photodiode by diffusion forming the anode region and the island region 23.

According to the first embodiment of the present invention, a wiring layer at the same level as the light-shielding film 12 is used for the crossover 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 is facilitated and cost is not increased.

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

Hereinafter, a photodiode built-in integrated circuit according to a second embodiment of the present invention will be described.

FIG. 5 is a plan view showing an entire semiconductor chip of a photodiode built-in integrated circuit according to a second embodiment of the present invention.

Referring to FIG. 5, reference numeral 41 denotes a semiconductor chip in which a photodiode element and other peripheral circuit elements are integrated, 42 denotes a light-shielding film formed by aluminum electrode wiring, 43 denotes an electrode; Section, 44 is a photodiode section, and 45 is a circuit element section. The light-shielding film 42 covers the entire circuit element portion 45 and extends to the vicinity of the outermost scribe line of the semiconductor chip 41, and the photodiode portion 44 is opened for light incidence. Although not shown in detail, the electrode pad portion 43 is provided with a bonding pad for external connection by aluminum electrode wiring inside the electrode pad portion 43, so that the bonding pad and the light shielding film are not short, and To prevent the surface of the chip 41 from being exposed, the ends are overlapped by using a multilayer wiring structure.

In the circuit element section 45, a large number of active elements and passive elements such as NPN transistors and resistors are formed. These individual circuit elements are arranged below the light shielding film 42 by an aluminum wiring layer below the light shielding film 42 (or by a first wiring layer if the light shielding film is the second layer). Electrical connection between each element is made to configure. Then, a part of the light-shielding film 42 is opened with a size of about 3 O jxb 0 ° to form a cross wiring part 46. The cross-sectional structure of the integrated circuit shown in FIG. 5 is basically the same as the structure shown in FIG. That is, referring to FIG. 4, the photodiode 44 includes an island region 23 as a cathode, a substrate 21 and an isolation region 22 as anodes, and an N + type force on the bird region 23 surface. A contact region 25 is formed, a cathode electrode 26 is arranged on the surface of the cathode contact region 25, and an anode electrode 24 is arranged on the surface of the separation region 22. The photodiode PD is reverse biased by applying the ground potential GND to the anode electrode 24 and the power supply potential VCC such as +5 V to the force source electrode 26, and the optical signal enters the generated depletion layer. The photocurrent at the time of this is detected.

An NPN transistor as a circuit element is formed in an island region 23 different from the photodiode 44. The NPN transistor has an island region 23 as a collector, a P-type base region 30 formed on the surface of the island region 23, an N + type emitter region 31 formed on the surface of the base region 30, and an island region 2 It consists of an N + -type collector contact region 32 formed on three surfaces. 27 is an N + type buried layer. A base electrode, an emitter electrode, and a collector electrode, which are in omic contact, are formed in each region by the first-layer electrode wiring 17. The cathode electrode 26 and the anode electrode 24 are also formed of the first-layer electrode wiring. The surface of the epitaxial layer is covered with a silicon oxide film, and the first-layer electrode wiring extends on the silicon oxide film.

The upper part of the first-layer electrode wiring is covered with a polyimide-based interlayer insulating film 28 having a thickness of about 2.0 formed by a spin-on coating method, and the surface of the interlayer insulating film 28 is covered with a light-shielding film 42. (Indicated by reference numeral 12 in FIG. 4). Although not shown, the light-shielding film 42 (12) is covered with a polyimide-based passivation film, and FIG. 6 is a cross-sectional view showing the cross wiring portion 46. Referring to FIG. 6, an island region 23a having a larger area is formed below intersection wiring portion 46 to be a dummy island.

The dummy island 23a is connected to the ground potential GND on the surrounding P + isolation region 22 via the anode electrode 24a, and is connected to the island region 23a via the N + contact region 25a. By applying a power supply potential VCC such as +5 V through the electrode 26a, a dummy photodiode having the same structure as the photodiode PD in FIG. 4 is obtained.

In the opening of the cross wiring portion 46, a cross electrode 47 is formed in the second wiring layer, and the cross electrode 47 is connected to the first layer electrode wiring through a through hole of the interlayer insulating film 28. 48a, 48c are connected, and intersect with the electrode wiring 48b. The silicon oxide film and polyimide insulating film are all translucent, and the semiconductor chip 41 is capable of transmitting light of a specific wavelength. On the other hand, it is molded with a translucent resin. The aluminum light shielding film 42 has a light shielding property. FIG. 7 is an enlarged plan view of the cross wiring portion 46. By opening the light-shielding film 42, the electrode wirings 48a, 48b, 48c formed in the first wiring layer are exposed, and the same as the light-shielding film 42, in the second wiring layer. The formed cross electrode 47 is interlayer-connected to the electrode wirings 48 a and 48 c via through holes 50 formed in the interlayer insulating film 28. Then, since the cross electrode 47 is insulated by the electrode wiring 48b and the interlayer insulating film 28, cross wiring between the electrode wirings 48a and 48c and the electrode wiring 48b is performed. Each electrode wiring 48a, 48b, 48c extends on the insulating film and is connected to a desired circuit element.

The light that cannot be shielded due to the provision of the opening called the cross wiring portion 46 in the light-shielding film 42 is incident on the island region 23a under the light. The incident light is converted into a photocurrent by a photodiode depletion layer formed by a dummy island or an N-type or P-type semiconductor layer on both sides of the depletion layer, and the photocurrent is converted to an anode electrode 24 a or a cathode electrode 2. Recovered at 6a. Therefore, a malfunction due to the photocurrent flowing into another circuit element and a latch-up can be prevented.

Since the opening of the cross wiring portion 46 exposes the surface of the interlayer insulating film 28, it can serve as a gas vent hole of the polyimide insulating film as a material. The gas vent hole is used to prevent the aluminum that covers the surface from swelling with the gas due to the gas generated from the polyimide during the heat treatment after the polyimide is formed, for example, during the annealing treatment. In order to make a gas vent hole, a design is made such that one aluminum electrode is provided for every coating over a certain area (for example, 200 / X200). Naturally, it is necessary to protect the internal circuit from light entering through the opening, and it is difficult to arrange circuit elements below it. Therefore, by designing the opening for degassing and the opening for the cross wiring portion 46 in common, it is not necessary to provide an extra opening. Note that it is not necessary to form all the gas vent holes in the cross wiring portion 46, and if no cross wiring is required, they may be simply arranged as gas vent holes. In this case, the structure shown in FIG. 7 is used in which the crossing electrodes 47, 48a, 48b, and 48c are removed, or the same structure as the light-shielding film 42 is provided by the first-layer electrode. A film having a function may be formed, and the film may be disposed so as to close the opening of the gas vent hole. Further, as shown in FIG. 5, the area of the opening 51 can be smaller than that of the intersection 46 because the cross electrode 47 is unnecessary. According to the semiconductor device of the present invention described above, since the aluminum wiring layer at the same level as the light-shielding film 42 is used as the cross electrode 47, the first-layer electrode wiring can be cross-connected. . Therefore, wiring pattern design becomes easy. Also, since the number of layers of the multilayer wiring does not need to be increased, the cost can be reduced. Then, by placing a dummy photodiode below the cross wiring section 46, the incident light passing through the cross wiring section 46 is collected, and is prevented from flowing to other circuit elements, so that the Prevent malfunction.

Furthermore, since a polyimide-based insulating film is used as the interlayer insulating film 28, the device can be manufactured at low cost, and the manufacturing process can be simplified. By making the opening of the cross wiring part 16 and the opening of the gas vent hole common, the number of gas vent holes can be reduced, and the size of the tube can be reduced.

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

According to the second embodiment of the present invention, the same level of the aluminum wiring layer as the light-shielding film 42 is used as the cross electrode 47, so that the first-layer electrode wiring can be performed without increasing the number of wiring layers. Cross connection becomes possible. Therefore, the cost can be reduced, and the degree of freedom in pattern design increases, making it easier. Also, by using a polyimide insulating film as the interlayer insulating film 28, the manufacturing process can be simplified and the cost can be reduced. By forming a dummy photodiode below the intersection wiring portion 46, it is possible to prevent a circuit from malfunctioning due to unnecessary light incidence.

Furthermore, by designing the opening of the cross wiring portion 46 to also serve as a gas vent hole of the polyimide insulating film, the number of openings can be reduced, and unnecessary enlargement of the chip size can be prevented. Industrial applicability

As described above, the integrated circuit with a built-in photodiode according to the present invention is used as a signal reading device used for picking up a storage device using a laser such as a CD, as a device on the light receiving side of a remote control device using infrared rays. I like it. Also, on Each of the embodiments described above uses a BIP-type element as an example of a circuit element. However, the present invention can be applied to, for example, a MOS-type integrated circuit and a mixed-type BIP / MOS-type integrated circuit.

Claims

The scope of the claims

1. A photodiode formed in a part of the semiconductor chip,

A circuit element portion formed in another portion of the semiconductor chip,

A multilayer wiring layer for connecting each element of the circuit element section,

A light-shielding film that covers a surface of the semiconductor chip so as to remove the photodiode portion;

A cross-wiring portion formed by removing the light-blocking film on a part of the light-blocking film; and an electrode wiring crossing the multilayer wiring at the cross-wiring portion;

And a dummy photodiode provided below the intersection wiring portion.

2. The integrated circuit with a built-in photodiode according to claim 1, wherein the multi-layer wiring has a two-layer structure, and the light-shielding film is formed by a second-layer wiring layer.

3. The integrated circuit with built-in photodiode according to claim 1, wherein the multilayer wiring is interlayer-insulated by a polyimide insulating film.