JPH0360073A - Optical semiconductor device - Google Patents

Abstract

PURPOSE:To improve a package density by covering at least one of analog circuit blocks including an amplifier for photoelectrically converting a photocurrent of a photodiode with a light shielding film made of a first metal wiring and a second metal wiring sequentially laminated in different laminating order by overlapping on the first wiring. CONSTITUTION:Photodetecting diodes PD1, PD2,... are arranged at the left side of a chip in a matrix state. Amplifiers A1, A2,... for amplifying photocurrents and other analog circuits B1, B2... (including a power source circuit) are standardized such that the top side is wired to GND and the other side is wired to VCC. The blocks are shielded by a first aluminum wiring (indicated by dense parallel oblique lines) and a second aluminum wiring (indicated by rough parallel oblique lines). Since the first and second wirings are horizontally overlapped at a boundary, it can prevent diffraction of a light, thereby completely shielding a light. Electrodes shielding the blocks against a light are used also as power source wirings, and can be efficiently wired.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to an optical semiconductor device, and in particular to an optical semiconductor device that integrates a photodetector diode, an amplifier circuit, and a logic circuit into one chip to achieve high-speed processing, high-density packaging, and cost reduction. The present invention relates to an optical semiconductor integrated circuit.

[Conventional technology]

Conventionally, in an auto-iris or auto-focus sensor section for a camera, photocurrent obtained from a light-receiving diode chip is supplied to an amplification and logic circuit IC through wiring patterned on a flexible substrate. The photodetector IC is molded with transparent resin to receive light and convert it into photocurrent. On the other hand, since the amplifier circuit amplifies a minute current of about 1oμA, it must receive the current at high impedance and is extremely sensitive to light. Therefore, conventionally, the chips that constitute this circuit have been sealed in black molding resin.

[Problem to be solved by the invention]

The two-chip sensor module described above does not have high packaging density or increases the number of photodiodes, resulting in an increase in the number of wires between the two chips and an increase in the area of the circuit board. There are also major drawbacks. Therefore, it is necessary to integrate the photodiode array, amplifier circuit, and logic circuit into one chip, but in this case, the photodiode must have as little light attenuation as possible within the required wavelength band. Therefore, it is necessary to completely shield the amplifier circuit and logic circuit from light irradiation. Conventionally, in order to shield a predetermined area from light, aluminum was deposited to a thickness of 1.0 to 2.0 μm to completely block light. In this case, it is possible to use the second layer of aluminum wiring exclusively for shielding and route the signal line and power supply line with only the first aluminum wiring, but the circuit scale becomes large and it is necessary to avoid crosstalk between circuit blocks. When the power supply is divided into multiple parts and the operating speed increases, wiring delays cannot be ignored, and it becomes necessary to use metal wiring to connect each block.

[Means to solve the problem]

The optical semiconductor device of the present invention is an optical semiconductor device in which a photodiode, an analog circuit block including an amplifier circuit for photoelectrically converting the photocurrent of the photodiode, and a logic circuit are configured on the same substrate. The surface of at least one of the analog circuit blocks is covered with a light shielding film consisting of a first metal wiring and a second metal wiring that overlaps the first metal wiring and has a different layered structure. It is said that

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 4 is a circuit block diagram showing a first embodiment of the present invention.

The photodiodes PDI to PD convert light into a photocurrent I.
eAl~A1, which converts into PI~IPa, is a MOS transistor high input impedance amplifier circuit, which logarithmically compresses the photocurrents IP,~IPa using diodes D, -D, and converts them into voltages. These voltages are multiplexed by MP
Analog-to-digital converter A/
Enter in D. The output of the analog-to-digital converter A/D is converted into serial data by the interface circuit IF and transferred to the CPU.The present invention relates to a surface wiring structure when everything from a photodiode to an interface circuit or CPU is integrated into one chip.

FIG. 1 is a schematic layout diagram showing a first embodiment of the present invention.

The light receiving diodes PDI, PD2, . . . are arranged in a matrix on the left side of the chip. Amplifier circuits Al, A2, etc. for charging current amplification and other analog circuits B 1
r B2 r... (including power supply circuit), top side is GN
D. The ground side is standardized to be wired to Vcc. Each block is shielded from light by the first aluminum wiring (indicated by dense parallel diagonal lines) and the second aluminum wiring (indicated by coarse parallel diagonal lines), and the first aluminum wiring and the second aluminum wiring are flat at the boundary. Since they overlap, it is possible to prevent light from going around, and it is possible to completely block light. Further, the electrodes that shield each block from light also serve as power supply wiring, which not only allows for efficient wiring, but also enables automatic layout because it is standardized. Since only the inner region of each block is sufficient as a light-shielding region, efficient inter-block interconnection can be performed in the outer region of the block using the first aluminum wiring and the second aluminum wiring. In addition, compared to the case where the entire surface is shielded with the second aluminum wiring, in the present invention, the area of the second aluminum wiring area is much smaller, so there is less yield loss due to pinholes etc. Wiring capacitance due to parasitic capacitance between the shield electrode and the shield electrode is also reduced, allowing high-speed signal transmission. A logic circuit section is arranged on the left side of the analog circuit section (indicated by a two-dot chain line), and a polycell system is adopted in this embodiment. The height of the polycell is usually smaller than the height of the analog circuit block, and for this reason several cell rows are grouped together and shielded from light by a second aluminum wiring. As a general rule, the wiring between blocks in the analog circuit section uses first aluminum wiring (indicated by solid lines) in the vertical direction and second aluminum wiring (indicated by broken lines) in the horizontal direction, but wiring between logic circuit blocks uses vertical wiring. Polysilicon wiring is used in the direction (shown by the wavy line), and first aluminum wiring is used in the horizontal direction.However, for signal lines that require high-speed data transfer, the first aluminum wiring and the second aluminum wiring are used instead of polysilicon wiring. Connect using aluminum wiring.

FIG. 2 is a cross-sectional view of a semiconductor chip showing the first embodiment, including a light receiving diode and an NPN transistor formed by the SL gate B1-CMOS process.

CM OS logic circuit section (P channel transistor.

Although the figure does not strictly correspond to Figure 1, it shows a PNP transistor (N-channel transistor).
Devices such as transistors, various resistors, and MOS capacitors are also formed on the same substrate. Also, the photodiode is N
Although a diode structure is shown in which boron ions are implanted into the epitaxial layer 3, a structure in which an N-type impurity such as arsenic is diffused into the P-well simultaneously with the NPN transistor may also be used.

FIG. 3(a) is a plan view of one block of the analog circuit section showing only the wiring structure of the first embodiment, and FIG. 3(b) is a plan view of one block of the analog circuit section showing only the wiring structure of the first embodiment.
FIG. 2 is a schematic cross-sectional view taken along line A-A in FIG.

23 is a first aluminum wiring which also serves as a Vcc wiring;
0 is an insulating film between the eyebrows that electrically separates the first aluminum wiring and the second aluminum wiring, 21 is the second aluminum wiring that also serves as the GND wiring, and the first aluminum wiring and the second aluminum wiring are connected to each other at the part 26. They overlap in a plane, and if the length of the overlap is made sufficiently large, it is possible to prevent light from seeping out in the lateral direction. In addition, in this example, the first aluminum distribution! It is possible for the second aluminum wiring 27 to pass over 23.

In this way, the analog circuit and the logic circuit can be shielded from light, the power supply for the circuit can be divided into a plurality of parts as necessary, and the second aluminum wiring layer can also be used for the wiring between blocks. Furthermore, since the analog circuit can be completely shielded from noise generated from the logic circuit, it is possible to perform highly accurate analog signal processing. Furthermore, since the photodiode array, amplifier circuit, analog-to-digital converter, and logic circuit are configured on the same chip, even if the number of photodiodes increases, there is no restriction on the board and it is possible to mount them at high density. be. Further, the wiring delay between the sensor section and the signal processing section can be reduced, and the overall processing speed of photoelectric conversion→A/D→digital signal processing can be increased.

FIG. 5 is a sectional view of a wiring structure showing a second embodiment of the present invention.

In this embodiment, the film thickness of the first aluminum wiring 23 is 1.0
μm, and the film thickness of the second aluminum wiring 21.210 is 2.
It is about 0 μm, so for the purpose of reducing the common impedance of the power supply line, it is better to use the second aluminum wiring as much as possible. 0 Normally analog circuits determine the bias using GND as the reference point, so for the purpose of reducing the impedance of the GND line. Although the second aluminum wiring is mainly used,
In this example, Vo. The line is also the first aluminum wiring 2
V as a two-story structure of 3 and the second aluminum wiring 21C
(H(The common impedance of the B line is reduced.

〔Effect of the invention〕

As described above, the present invention can significantly improve the packaging density by forming the light receiving diode, the amplifier circuit, and the logic circuit on the same substrate. In addition, since the sensor section, analog circuit section, and logic circuit section are formed on the same chip, the signal line from the photodiode matrix to the amplifier circuit section can be run using aluminum wiring inside the LSI, which allows for a large number of photodiodes. In this case, the present invention is extremely effective and can also be applied to high-speed processing.

The present invention uses the first aluminum wiring and the second aluminum wiring to efficiently shield the analog circuit section and the logic circuit section, excluding the light-receiving diode matrix section, so that it is possible to efficiently wire the power supply line. The second aspect of the present invention can prevent crosstalk caused by power lines between circuits, and can also prevent noise from entering analog circuits from digital circuits.
Since the light path by the aluminum wiring is limited to the minimum necessary area, the reduction in yield due to pinholes and the like is reduced compared to the case where a shield electrode is provided on the entire surface. Also, since the parasitic capacitance due to the shield electrode and the first aluminum signal line is reduced, there is less influence from wiring delays, and the second aluminum wiring can be used for part of each block and for inter-block wiring. Therefore, the degree of freedom in layout design is greatly increased, and not only can the chip size be reduced, but automatic layout is also possible, so it is possible to shorten the design TAT.
Although the above explanation has been made regarding the case where two-layer wiring is used, the present invention is not limited to only a two-layer structure, but can equally be applied to a case where three or more layers are used.

[Brief explanation of drawings]

FIG. 1 is a schematic layout diagram showing a first embodiment of the present invention, FIG. 2 is a cross-sectional view of a semiconductor chip showing the first embodiment, and FIG. 3(a) is a wiring diagram of the first embodiment. 3(b) is a schematic cross-sectional view taken along the line A-A in FIG. 3(a), FIG. 4 is a circuit block diagram of the first embodiment, and FIG. 5 is a schematic diagram of the second embodiment. FIG. 3 is a schematic cross-sectional view showing an example. 1...P type silicon substrate, 2...N+ type buried layer, 3
...N type epitaxial layer, 4...P well, 5.
...N well, 6...P type anode layer, 8...cathode electrode, 9...emitter electrode, 10...base electrode, 11...collector electrode, 12...N channel transistor Source electrode, 13... Drain electrode of N-channel transistor, 14... Gate electrode of N-channel transistor, 15... Train electrode of P-channel transistor, 16... Source electrode of P-channel transistor, 17...・Gate electrode of P channel transistor, 18...Field oxide film, 19...CV
Silicon oxide film by D method, 20... Interlayer insulating film, 2
1.21a, 21b, 21cm second aluminum wiring,
23.24...First aluminum wiring, 25...Silicon oxide film.

Claims (3)

[Claims] (1) In an optical semiconductor device in which a photodiode, an analog circuit block including an amplifier circuit for photoelectrically converting the photocurrent of the photodiode, and a logic circuit are configured on the same substrate, one of the analog circuit blocks At least one has a first metal wiring and a second metal wiring whose surface overlaps with the first metal wiring and has a different layer order.
An optical semiconductor device characterized by being covered with a light shielding film made of metal wiring. (2) Claim (1) wherein the first metal wiring also serves as a Vcc line and the second metal wiring also serves as a GND line.
). (3) The logic circuit section is made up of polycell rows, and at least a plurality of polycell rows are covered with a light shielding film made of the upper metal wiring of the first metal wiring and the second metal wiring. The optical semiconductor device according to item (1).