JPH0770696B2 - Semiconductor integrated circuit device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor integrated circuit device including a photosensitive element such as a photodetector in a part of a plurality of semiconductor elements integrated on the same semiconductor substrate.

[Conventional technology]

Conventionally, many devices applying photodetection elements have been put to practical use, and all of them had a photodetection section and a signal processing circuit housed in separate containers. Recently, however, the system has been made compact and signal processing has been performed. In order to improve the performance of the device such as an improvement in speed, it has been used as a semiconductor integrated circuit device in which a photodetector and a signal processing circuit are formed on the same substrate.

[Problems to be Solved by the Invention]

The problem with the semiconductor integrated circuit device as described above is that when light is incident on an integrated circuit constituent element other than the photo-sensing element, an originally unnecessary electron-hole pair is excited in the semiconductor, so that the element That is, an unfavorable phenomenon such as an increase in the leak current is generated. This phenomenon poses a serious problem in analog circuits and digital circuits that perform dynamic operations. As an example, when considering a dynamic type MOS shift register used for a scanning circuit or the like, the gate capacitance of a MOS transistor is used as temporary information storage, but when light enters this portion,
Leakage current flows due to unnecessary electron-hole pairs generated in the junction region, which significantly shortens the storage time. As a result, a malfunction occurs with a clock pulse operating at a lower frequency than the time constant determined by the leak current.

As a measure against the above-mentioned problem, for example, as disclosed in Japanese Patent Publication No. 52-26876, there is a method of providing a conductive material on a region including a semiconductor element other than a photodetection element via an insulating film. This method can solve problems such as leakage current due to unnecessary electron-hole pairs, and this method has the advantage that it can be formed in the same process as a normal IC process step. The following serious drawbacks occur. That is, when the conductive material is formed on the region including the semiconductor element, a parasitic capacitance is formed between the conductive material and the metal wiring in the lower layer, which may cause operation delay and malfunction. In particular, metal wiring such as aluminum has a low resistivity and a large insulating film thickness under the wiring, and thus has a small parasitic capacitance with the semiconductor substrate. The light incident prevention film forms parasitic capacitance in proportion to the wiring area. In addition, since the insulating film on the wiring aluminum is a protective film for the element, a silicon nitride film with high moisture resistance is often used, but this also has a high relative dielectric constant of 7.5, and this is also a parasitic factor. This is one of the reasons for increasing the capacity. As described above, when the metal wiring has a large parasitic capacitance, an operation delay occurs in a logic circuit or the like that requires high-speed operation, which causes a problem that a malfunction occurs and the element does not work normally.

Further, as another problem, when a conductive material is formed on a large area including a semiconductor element, a short circuit may occur between the semiconductor elements through the conductive material. This significantly reduces the manufacturing yield of semiconductor integrated circuit devices.

As a method of compensating for these parasitic capacitance and short circuit, the semiconductor integrated circuit device shown in FIG. 2 is described in the specification of Japanese Patent Application No. 62-211952 filed by the present applicant. In the figure,
A plurality of photodetecting elements 1 are formed in the same semiconductor substrate, an analog circuit and a dynamic type digital circuit 2 are surrounded by the photodetecting element 1, and a digital circuit 3 is integrated outside thereof. Then, only the regions of the analog circuit and the dynamic type digital circuit 2 which are easily affected by the leak current around the photodetection region where the photodetection element 1 exists are covered with the conductive light incident prevention film 4 via the insulating film. There is. According to this, there is no problem of leakage current due to unnecessary electron-hole pairs, there is no influence of parasitic capacitance, and the probability of a short circuit is apparent, as compared with the method disclosed in Japanese Patent Publication No. 52-26876. The size is reduced and the manufacturing yield is improved.

However, also in this case, the following problems newly occur. That is, when the light incident prevention film 4 is provided only around the light detection element 1 as shown in FIG. 2, electron-hole pairs generated by the light incident on the outside of the light incidence prevention film 4 reach the light detection portion. It means that the light diffuses and gets on the regular amount of light detected by the light detector as a background. The diffusion length of electron-hole pairs depends on the lifetime in the IC substrate, but it is about 10 to 500 μm, and in order to eliminate this effect at all, it is necessary to cover all regions except the detection part with a light incident prevention film. However, this is impossible, as mentioned above. This background causes variations in sensitivity among the detectors as noise. As a result, in the case of the line sensor in which the photo-sensing elements 1 are arranged in a row as shown in FIG. 3, the sensitivity of each sensor is affected by the background as shown in FIG. Variation occurs.

An object of the present invention is to solve the above problems and suppress the probability of short circuit between a light incident prevention film and a wiring portion for preventing malfunction of a semiconductor integrated circuit device including a photodetector due to light, and prevent light incident. It is an object of the present invention to provide a semiconductor integrated circuit device in which the influence of the background on the photo-detecting element due to electron-hole pairs generated by the light incident on the outside of the film is eliminated.

[Means for Solving the Problems]

In order to solve the above problems, the present invention provides a semiconductor integrated circuit device in which a part of a plurality of semiconductor elements integrated in the same substrate is a photosensitive element, and an area in which the photosensitive element is formed has an analog circuit portion. And an area including a digital circuit section that performs a dynamic operation is two-dimensionally surrounded, and a digital circuit section that does not have a uniform metal wiring density is two-dimensionally surrounded outside the analog circuit section and a digital circuit section that performs a dynamic operation. A digital circuit in which the conductive light incident prevention film covers the entire area including the area and a part of the peripheral digital circuit area through an insulating film and the area of the light incident prevention film is large in metal wiring density. It should be wide in the digital circuit area where the metal wiring density is smaller than in the partial area.

[Action]

The present invention covers the area of the analog circuit and the dynamic type digital circuit, which is easily affected by the leak current around the area where the photosensitive element is provided, and the digital circuit section in the peripheral area thereof with the light incident prevention film. By making the area of the light incident prevention film on the area where the metal wiring is sparse as compared to the area where the metal wiring is dense, the area where the metal wiring is Compensate for the large difference in electron / hole pairs generated compared to the area where metal wiring is dense, equalize the amount of electron / hole pairs to be carried as the background, and vary the sensitivity of each photo detector. It is intended to suppress.

Note that the light quantity dependency of the electron / hole pair that is used as the background is the same as the light quantity dependency of the regular electron / hole pair that is generated in the photodetector, so there is no problem if a small amount of light is uniformly distributed as the background. There is no.

〔Example〕

An embodiment of the present invention is shown in FIG. 1, and the same parts as those in FIGS. 2 and 3 are designated by the same reference numerals. The arrangement of the elements is the same as that shown in FIG. 3, and the analog circuit and the dynamic digital circuit 2 are provided in the semiconductor substrate region surrounding the photo-sensing element 1 forming the line sensor, and further the digital circuit is provided outside thereof. There is a digital circuit 31 having a high metal wiring density and a digital circuit 32 having a low metal wiring density. In a region other than the region of the light detecting element 1, the regions of the analog circuit portion and the dynamic type digital circuit portion 2 are covered with a conductive light incident prevention film 4 via an insulating film, and the light incident prevention film 4 is further surrounded by the conductive light incident prevention film 4. It extends to a part of the digital circuit parts 31, 32 of.
In this case, in the peripheral digital circuit area, the area of the light incident prevention film 4 hatched with diagonal lines is made larger on the area 32 having a lower metal wiring density than on the area 31 having a high density.

By doing this, light incident on the area not covered by the light incident prevention film forms electron-hole pairs, but in areas where the metal wiring density is high, light is generated inside the substrate where the light is blocked by the metal wiring. The frequency of generation of electron-hole pairs per unit area is smaller than that in the region where the metal wiring density is low. In addition, in regions where the metal wiring density is low, the frequency of generation of electron-hole pairs per unit area is high, but since the area not covered by the protective film is smaller than in the regions where density is high, this effect results in electron-positive pairs. The hole pairs are comparable and have a uniform background. As a result, the sensitivity of each sensor is improved in uniformity as shown in FIG.

The area ratio covered by this light incident prevention film is generally calculated by the reciprocal of the wiring density ratio, but in reality various patterns are prepared,
It is desirable to actually measure the sensitivity variation and find the best pattern.

The light incident prevention film 4 can be formed on a silicon nitride film or the like using aluminum, molybdenum, dangsten or the like used for circuit wiring or the like, and the same process as a normal IC process step can be used.

〔The invention's effect〕

As described above, according to the present invention, the light incident prevention film that can be easily formed by the normal process is provided on the area of the analog section and the dynamic type digital section which are easily affected by the leak current due to the electron-hole pair. It is provided on a part of the area of the digital circuit part around it, and at that time, the area of the light incident prevention film on the region of the digital circuit part where the metal wiring density is high is By making it smaller than the area, the influence of leakage current due to light, the influence of parasitic capacitance on the high-speed operation digital circuit, the probability of short-circuit accident, etc. are suppressed, and the background to the photo-sensitive element is made uniform and the sensitivity varies. Therefore, it is possible to put into practical use a high-performance semiconductor integrated circuit device that operates stably.

[Brief description of drawings]

FIG. 1 is a plan view of a semiconductor integrated circuit device according to an embodiment of the present invention, FIG. 2 is a plan view of a semiconductor integrated circuit device of an already-filed application, and FIG. 3 is an apparatus configuration of FIG. 2 applied to a line sensor. FIG. 4 is a plan view in the case of doing so, FIG. 4 is a sensitivity distribution diagram of each optical sensor of the apparatus of FIG. 3, and FIG. 5 is a sensitivity distribution diagram of each optical sensor of the embodiment of FIG. 1: Photodetector, 2: Analog circuit and dynamic digital circuit, 31: Digital circuit with dense metal wiring, 32: Digital circuit with sparse metal wiring, 4: Light incident prevention film.

Claims (1)

[Claims] 1. A device in which a part of a plurality of semiconductor elements integrated on the same substrate is a photosensitive element, an area in which the photosensitive element is formed includes an analog circuit section and a digital circuit section which performs a dynamic operation. Is surrounded in a two-dimensional manner, and the outside is surrounded by a digital circuit area in which the metal wiring density is not uniform, and the entire area including the analog circuit section and the digital circuit section that performs dynamic operation and its peripheral area are digital. A part of the circuit area is covered with a conductive light incident prevention film through an insulating film, and the area of the light incident prevention film has a large metal wiring density. Digital with a smaller metal wiring density on the digital circuit area. A semiconductor integrated circuit device having a large area on a circuit area.