JPH0581060B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device that is used while being irradiated with light.

[Conventional technology]

In a conventional bipolar semiconductor device having a photoelectric conversion function, as shown in FIG. 6, an NPN transistor 1 and a PNP transistor 2 are shielded from light by a second metal layer 3. However, the chip peripheral area 4, the pad peripheral area 5, and the end face 6 of the semiconductor device
, the second metal layer 3 is not provided.
This is because, for example, regarding the chip peripheral part 4, during so-called dicing, in which the chip peripheral part 4 is cut into parts using a special rotary grindstone during the finishing of a semiconductor device, the rotary grindstone is clogged by the metal of the second metal layer 3. This is to avoid doing so. Also,
The reason for the bonding pad peripheral portion 5 is to avoid short-circuiting between the second metal layer 3 and the wire during wire bonding.

Therefore, light enters and is absorbed in these parts, and photoelectric conversion is performed. A portion of the minority carriers generated thereby move and enter the effective area 7 without being recombined. Most of the photocurrent due to the minority carriers is injected into the parasitic photodiode 10 formed at the junction between the N-type epitaxial layers 1a, 2a and the P-type substrate 8, which form elements such as the NPN transistor 1 and the PNP transistor 2. Ru.

The parasitic photodiode 10 is connected to the NPN transistor 1 and the PNP transistor 2 as shown in a and b of FIG. 7, respectively. For this reason, the photocurrent may induce malfunctions in each of the elements. At this time, the minority carriers are in the N-type epitaxial layer 1a,
The higher the impedance potential of 2a, the easier it is to be injected, and the more likely it is that each element will malfunction. Furthermore, in silicon, for example, light is attenuated exponentially and inversely proportional to the distance from the point of incidence, so elements closer to the position of light incidence are more susceptible to the effects of photocurrent.

Therefore, in conventional semiconductor devices, in order to avoid the influence of photocurrent caused by photoelectric conversion, the width of the chip peripheral area 4 is set to be sufficient, taking into consideration the position of the effective area 7 of each element and the attenuation distance of incident light. It is set to a spacious size. However, such a structure has the disadvantage that the chip size of the semiconductor device becomes large.

Therefore, in order to solve the above problems,
The semiconductor device shown in Figure 8 was first proposed (patent application 1983-
No. 248352). This semiconductor device has a dummy photodiode 9 electrically short-circuited around the chip periphery 4. That is, unnecessary photocurrent is canceled out by the function of the dummy photodiode 9 without ensuring a sufficient width of the chip peripheral area 4.

[Problem to be solved by the invention]

However, the above structure has a problem in that the structure of the chip peripheral portion 4 is complicated, which increases the number of manufacturing steps and increases costs.

[Means to solve the problem]

In order to solve the above problems, a semiconductor device according to the present invention uses a semiconductor as a substrate and forms a plurality of elements constituting a part of each element using an epitaxial semiconductor layer formed on the substrate. In a bipolar semiconductor device in which a light-shielding metal layer is formed on an element, the following measures are taken.

That is, an element for connecting the epitaxial semiconductor layer to a low impedance potential was formed around a portion where no light-shielding metal layer was formed and light could enter from the outside.

[Effect]

According to the above configuration, an element is formed in which an epitaxial semiconductor layer that is not affected by photocurrent due to incident light is connected to a low impedance potential around a region where a light-shielding metal layer cannot be formed due to device manufacturing. This eliminates the need to consider the attenuation distance of incident light and the need to provide a dummy photodiode, resulting in miniaturization of the device and simplification of the manufacturing process.

[Example] An example of the present invention will be described below based on FIG.

The bipolar semiconductor device according to this embodiment is
An N-type epitaxial layer 12 is formed within the P-type substrate 11, and further, this N-type epitaxial layer 12
A semiconductor laminated portion 14 has a structure in which an N ⁺ layer 13 is formed therein, and a part of the N type epitaxial layer 12 and the surface of the N ⁺ layer appear on the surface of the P type substrate 11.
have. On this semiconductor stack 14, an insulating oxide film 15, a first metal layer 16, a PIQ layer 1
7 and the second metal layer 18 are sequentially stacked to form an upper stacked body 22. With the above structure, the parasitic photodiode 19 and the oxide film capacitor 20 are formed.

Furthermore, a chip peripheral area 21 is formed between the end of the semiconductor device and the oxide film capacitor 20, and the second metal layer 18 covers the surface of the chip peripheral area 21 up to the middle.

Furthermore, the N-type epitaxial layer 12 of the oxide film capacitor 20 has, for example, a power supply voltage potential,
It has a structure in which it is connected to a low impedance potential such as a GND (ground) potential, a constant voltage circuit output voltage potential, or a potential with low output impedance in the circuit. The width of the chip peripheral portion 21 is not set to a wide dimension in consideration of the influence of photocurrent caused by incident light, but is set to a normally required dimension.

As described above, the oxide film capacitor 20 in the chip peripheral area 21 is selectively placed so that the N-type epitaxial layer 12 is connected to a low impedance potential.

In the above configuration, in this semiconductor device, the portions such as the oxide film capacitor 20 that are shielded from light by the second metal layer 18 are not directly affected by light. On the other hand, the chip peripheral area 21 and the semiconductor stacked area 1
Light is incident from a portion not shielded by the second metal layer 18, such as the end face of the semiconductor device 4, and photoelectric conversion is thereby performed. The minority carriers generated by this photoelectric conversion become photocurrent and are transferred to the parasitic photodiode 1.
Injected into 9. However, since the N-type epitaxial layer 12 has a low impedance potential,
The photocurrent does not affect the operation of the semiconductor device in any way.

Examples of other semiconductor devices having the same structure as the above semiconductor device and having a function of blocking the influence of incident light are shown in FIGS. 2 to 5. The semiconductor device shown in FIG. 2 includes an N-type epitaxial layer 12 and a P ⁺ layer 23 in a P-type substrate 11,
Semiconductor stack 1 in which an N-type epitaxial layer 12, P layers 24, 24, and implanted P region 25 are formed.
It has 4. On this semiconductor stack 14, an oxide film 15, a first metal layer 16..., a PIQ layer 17,
An upper laminate 22 is formed of the second metal layer 18 and the second metal layer 18. With such a structure, the diffused resistor 26 and the ion implanted resistor 27 are formed.

The semiconductor device shown in FIG.
type epitaxial layer 12, P ⁺ layer 23, N ⁺ layer 1
An upper stacked body 22 is formed on a semiconductor stacked section 14 made up of semiconductor stacked parts 3 and 13. This structure forms the NPN transistor 28.

The semiconductor device shown in FIG.
type epitaxial layer 12, P ⁺ layer 23, N ⁺ layer 1
An upper laminate 22 is formed on the semiconductor laminate 14 made up of 3 and 13, and a diode 29 is thereby formed.

Further, the semiconductor device shown in FIG. 5 has a P-type substrate 1
1. A structure in which an upper laminate 22 is formed on a semiconductor laminate 14 consisting of an N-type epitaxial layer 12, a P ⁺ layer 23, and an N ⁺ layer 13, and thereby a junction capacitor 30 is formed. It is something.

All of the semiconductor devices described above have their respective N
The influence of photocurrents is prevented by connecting the type epitaxial layer 12 to a low impedance potential.

The above elements are formed not only in the chip peripheral area 21 but also in areas where light can enter, such as the pad peripheral area, and each epitaxial layer thereof is connected to the low impedance potential of the circuit. This makes it possible to exhibit the above-mentioned protective function against photocurrent.

〔Effect of the invention〕

As described above, the semiconductor device according to the present invention includes an element that connects the epitaxial semiconductor layer to a low impedance potential around a portion where a light shielding metal layer is not formed and light can enter from the outside. This is the formed configuration.

This makes it possible to prevent adverse effects such as inducing malfunctions in each element due to photocurrent generated by light incident from the outside, and to stabilize the operation.

Furthermore, in consideration of the attenuation of incident light, there is no need to increase the distance between the end of the semiconductor device and the element, that is, the width of the chip periphery, so that the size of the semiconductor device does not increase. In addition, by providing a dummy photodiode near the light incident area such as the periphery of the chip, the structure is not complicated and can be manufactured in a small size and at low cost. .

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of main parts showing one embodiment of the present invention,
Figures 2 to 5 are explanatory diagrams of main parts showing other embodiments, Figure 6 is an explanatory diagram of main parts showing a conventional example, and Figures 7a and b are an NPN transistor and a photodiode, and a PNP transistor and a photodiode. FIG. 8 is a circuit diagram of a conventional example showing the connection with the conventional example, and FIG. 11 is a P-type substrate, 12 is an N-type epitaxial layer, 14 is a semiconductor stack, 20 is an oxide film capacitor, 21 is a chip peripheral area, 22 is an upper stack, 2
6 is a diffusion resistance, 27 is an ion implantation resistance, 28 is a
An NPN transistor, 29 a diode, and 30 a junction capacitor.

Claims (1)

[Scope of Claims] 1 A semiconductor substrate is formed with an epitaxial semiconductor layer formed on the substrate to form a plurality of elements constituting a part of each element, and a light-shielding metal layer is formed on these elements. In a bipolar semiconductor device consisting of a semiconductor device, an element for connecting the epitaxial semiconductor layer to a low impedance potential is formed around a portion where a light shielding metal layer is not formed and light can enter from the outside. Characteristic semiconductor devices.