JP2002324910A - Optical semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical semiconductor device whose output has no sensitivity in an infrared region and which has the spectral sensitivity characteristics controlled more precisely. SOLUTION: The optical semiconductor device comprises a photodiode formed on a semiconductor substrate of a first conductivity, and a photodetector provided with an amplifying and processing circuit which amplifies and processes a signal from the photodiode. The photodetector comprises a rap and block layer of a second conductivity for trapping and blocking the carriers, which is formed in at least one place out of a region in contact with a scribe end face, a lower layer of an n base layer, and a lower layer of the photodiode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical semiconductor device, and more particularly to an optical semiconductor device used for an illuminance detection sensor for detecting ambient brightness.

[0002]

2. Description of the Related Art In recent years, in response to the need for energy saving in home electric appliances and the like, for example, televisions, liquid crystal monitors and the like detect the illuminance of the use environment and automatically control the screen brightness. Also, in air conditioners, etc., nighttime is detected,
Products that reduce power consumption by automatically setting a power saving mode have been commercialized.

In an optical semiconductor device used for an illuminance detection sensor or the like of a product of such an energy-saving design,
Until now, for example, a photodiode (hereinafter referred to as PD) and P
A circuit for amplifying the optical signal from D and performing arithmetic processing is integrated into a single chip, and a filter for performing visibility correction on the light receiving surface of the chip (light receiving element), that is, a filter that reflects infrared light and transmits visible light. A transmitting filter is applied. FIG.
FIG. 1A shows a specific structure of such a light receiving element. The light receiving element 8 is a molded package type element, which is mounted on a lead frame (not shown), and after bonding wiring, a transparent epoxy resin is used. Molded at 25. FIG. 11 (b) is a view showing a structure of a substrate mounting type. The structure is mounted on a printed circuit board 26, bonded, electrically connected, and molded with a transparent epoxy resin.
It is separated into individual elements. These are connected to external elements at the outer lead portion 27 and the metallized portion 28 of the lead frame, respectively.

[0004]

However, in such an optical semiconductor device, as described above, a filter that reflects infrared light and transmits visible light is attached to the light receiving surface. However, there is a problem that the sensitivity is provided in an infrared region which does not need to be sensed. As a result of investigating this factor, the present inventors have found that light including an infrared region that does not pass through a filter enters from a scribe line portion of the light receiving element. FIG. 12 is a cross-sectional view of a part of the light receiving element. Carrier 22 is generated by light including an infrared region incident from the scribe end face 10 and the scribe line 21 of the light receiving element. Has been found to affect

As another factor, it has been found that, depending on the incident angle of light, the filter cannot reflect the infrared light and is received by the PD, thereby having a sensitivity in the infrared region.

As described above, in the conventional optical semiconductor device, there has been a problem that the incidence of infrared light is unavoidable and the output has a sensitivity in the infrared region.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an optical semiconductor device in which the spectral sensitivity characteristics are controlled with higher accuracy by eliminating such disadvantages of the conventional optical semiconductor device.

[0008]

According to the present invention, there is provided an optical semiconductor device comprising: a photodiode formed on a semiconductor substrate of a first conductivity type; and an amplifying / arithmetic circuit for amplifying and arithmetically processing a signal from the photodiode. Formed in the first conductivity type semiconductor substrate around at least one of the transistor element or the photodiode constituting the amplification / arithmetic circuit, and a reverse bias potential is applied between the first conductivity type semiconductor substrate and the first conductivity type semiconductor substrate. And an island-shaped high-concentration layer of the second conductivity type provided.

Further, in the optical semiconductor device of the present invention,
The island-type high concentration layer of the second conductivity type is formed at least at a position in contact with a scribe end face of the semiconductor substrate of the first conductivity type.

Further, in the optical semiconductor device according to the present invention, the high-concentration island-shaped layer of the second conductivity type may be a transistor element or a photo-element that constitutes the amplification / arithmetic circuit from the surface of the semiconductor substrate of the first conductivity type. It is formed at a depth corresponding to the bottom of the element formation region where the diode is formed, and is connected to a bias terminal formed on the surface of the semiconductor substrate.

Further, in the optical semiconductor device according to the present invention, the first conductive type high concentration layer formed between the island-like high concentration layer and the transistor element or one of the photodiodes is provided on the substrate. Wherein a bias potential is applied through a sub-extraction layer.

Further, in the optical semiconductor device of the present invention, the photodiode is formed in the first conductivity type semiconductor substrate from the substrate surface to the inside thereof, and the first and second photodiodes having different wavelength sensitivities are provided. It is characterized by being constituted by a photodiode.

Further, in the optical semiconductor device of the present invention, of the first and second photodiodes, the first photodiode formed on the surface of the first conductive type semiconductor substrate has a wavelength in a visible light region. Having sensitivity, the first
The second photodiode formed inside the conductive semiconductor substrate has a wavelength sensitivity in an infrared light region.

Further, in the optical semiconductor device according to the present invention, a filter that transmits the visible light and reflects the infrared light is provided on an upper surface of the first photodiode. Is what you do.

Further, in the optical semiconductor device according to the present invention, the filter is characterized by comprising a multilayer film in which high refractive index thin films and low refractive index thin films are alternately laminated.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below.
This will be described with reference to the drawings. FIG. 1 is a sectional view showing the element structure of two sensors PDa1 and PDb2 used in the optical semiconductor device of the present invention, and FIG. 2 is a circuit diagram of an amplifying / arithmetic circuit used in the optical semiconductor device of the present invention. FIG.
FIG. 4 is a diagram showing spectral sensitivity characteristics of the PDa and PDb.

The sensor PDa1 is formed by a PN junction in an N well formed on the surface of the p-type silicon substrate 9, and the PDb2 is formed by a PN junction at a boundary between the substrate and the N well at a portion deeper than the PN junction. Have been. The amplifier / arithmetic circuit to which the outputs of these sensors PDa and PDb are supplied is supplied with the outputs of the two sensors PDa and PDb and computes the difference between the two outputs, as shown in FIG. It is a circuit that amplifies. As shown in the block diagram of FIG. 2B, the amplifying / arithmetic circuit converts light signals into electric signals by PDa and PDb, which are light-receiving units, and converts them into a first-stage amplifier circuit 4, a differential circuit 5, and an arithmetic circuit. 6. Output through the amplifier circuit 7. The spectral sensitivity characteristics of PDa and PDb both have sensitivity in the infrared region as shown in FIG.

FIG. 4 is a cross-sectional view of a semiconductor integrated circuit device on which the optical semiconductor device having such a configuration is formed. A high-concentration layer (N +)
Are formed, and are connected to the contact 17 via the n-layer 16. This N episode 11
In the vicinity of the substrate 9, the p-type high concentration layer (P +) su
The b-out layer 12 is formed, and the sub-out layer 12 is connected to the contact 20 on the surface of the substrate 9 via the high-concentration layer (P +). The ground potential VSS and the power supply potential VCC are supplied to these contacts 17 and 20, respectively, and the N epi islands 11 and s formed in the substrate 9 are respectively provided.
A reverse bias potential is applied between the ub extraction layers 12, and a depletion layer 23 is formed in the vicinity of the reverse bias potential.

The sub removal layer 12 is formed so as to surround the periphery of the NPN transistor 13 which is disposed horizontally inside the scribe end face 10 of the substrate 9. This NPN transistor 13 is one of the elements included in the amplifier circuit constituting the optical semiconductor device. Further, a portion of the substrate 9 further inside the scribe end face 10 in the horizontal direction includes a lateral PNP transistor (hereinafter referred to as PNP-Tr) 13 ′, which is also one of the elements included in the amplifier circuit, and a p-type transistor. A sub-sublayer 14 is arranged, and an N-epi island 15 which is a high-concentration layer (N +) is arranged outside the sub-out layer 14. The N epi-island 15 is connected to the contact 17 via the n-layer 16, and the sub-out layer 14 is a high-concentration layer (P +).
Is connected to a contact 20 on the surface of the substrate 9. The ground potential VSS and the power supply potential VCC are supplied to these contacts 17 and 20, respectively, and the N epi island 15 and the sub removal layer 1 formed in the substrate 9 are provided.
A reverse bias potential is applied between the four, and a depletion layer 23 is formed in the vicinity of the reverse bias potential. Note that an N epi-island 18 serving as a base region is formed below the PNP-Tr 13 '.

FIG. 5 is a sectional view of another portion of the semiconductor integrated circuit device on which the optical semiconductor device is formed. That is, this cross-sectional view shows the PD unit 19 serving as a light receiving unit. Under the PD portion 19, an N epi-island 18 serving as a high concentration layer (N +) is formed.

An operation of the optical semiconductor device thus configured for preventing the influence of infrared light will be described.

Some of the minority carriers 22 composed of electrons, for example, generated by the infrared light incident from the scribe end face 10 and the scribe line 21 reach the depletion layer 23 between the N epi island 11 and the sub removal layer 12 as a diffusion current. Then, the contact layer 20 is absorbed by the
From the substrate 9 to the substrate 9 and the NPN transistor 1
No. 3 is not affected by the diffusion current.

When infrared light having a wavelength of 1000 nm is applied to the silicon substrate from the scribe end face 10 or the scribe line 21, 90% of the light is absorbed as shown in the light absorption characteristic diagram of silicon in FIG. Requires a distance of about 50 μm from the irradiation surface, almost 100%
A distance of about 100 μm is required to be absorbed. However, since the diffusion current reaches deeper than this, it is difficult in design to form a transistor or a PD element constituting the amplification / arithmetic circuit at a distance where the diffusion current from the scribe end face 10 does not reach. Therefore, if this distance is not sufficient, the diffusion current flows into, for example, the N-epi island 18 'serving as the collector region of the NPN-Tr 13 or the N-epi island 18 serving as the base region of the lateral PNP-Tr 13' in FIG. It affects the operation of each circuit. In particular, in the latter case, the current becomes the base current of Tr13 'and is amplified, so that the influence on the circuit operation is remarkable.

In order to absorb this diffusion current, NPN-
A p-type sub removal layer 12 is formed around Tr 13, and an N epi-island 15, which is a high concentration (N +) layer, is further formed therearound. The N epi-island 15 is connected to the ground potential VSS via the n-base layer 16 and the contact 17, and
The p-type sub removal layer 12 is connected to the power supply potential VCC via the contact 20. As a result, a depletion layer 23 is formed in the substrate 9 between the N epi island 15 and the p-type sub removal layer 12. Similarly, a p-type sub-sublayer 14 is formed around the lateral PNP-Tr 13 ′, and an N epi-island 15, which is a high concentration (N +) layer, is formed therearound. And N
The epi-island 15 is connected to the ground potential VSS via the n-base layer 16 and the contact 17, and the p-type sub removal layer 14 is connected to the power supply potential VCC. As a result, a depletion layer 23 is formed in the substrate 9 between the N epi island 15 and the p-type sub removal layer 14.

Therefore, the minority carriers 22 that have reached a deep position in the substrate 9 from the scribe end face 10 are subjected to the electric field generated in the depletion layer 23 so that the p-type sub removal layer 12,
14, is consumed as a current flowing into the substrate 9 from the contact 20, and the influence on the PNP-Tr 13 or the lateral PNP-Tr 13 ′ is prevented.

The above configuration and operation are the same in the circuit portion including the PD section 19 shown in FIG.
Around the PD portion 19, a p-type sub-cutting layer 14 is formed, and further around the PD portion 19, an N epi island 15 which is a high concentration (N +) layer is formed. The N epi island 15 is formed on the n base layer 1.
6. While being connected to the ground potential VSS via the contact 17, the p-type sub removal layer 14 is connected to the power supply potential VCC via the contact 20. As a result, a depletion layer 23 is formed in the substrate 9 between the N epi island 15 and the p-type sub removal layer 14. Therefore, the minority carriers that reach this portion are similarly absorbed by the sub-extraction layer 14, and
It is consumed as a current flowing from the contact 20 into the substrate 9.

The optical semiconductor device thus formed on the semiconductor substrate is diced, mounted and bonded to a lead frame in the same manner as in the prior art, and then molded with a transparent epoxy resin. Implemented directly in FIG. 7 shows the spectral sensitivity characteristics of the optical semiconductor device thus formed. It can be seen that, although some sensitivity remains in the infrared region, good spectral sensitivity characteristics are obtained in the visible light region.

FIG. 8 shows the light receiving sections PDa1, PDa1 shown in FIG.
FIG. 9 is a sectional view showing an embodiment in which an infrared filter 24 is formed on the surface of b2, and FIG. 9 is a view showing spectral sensitivity characteristics of these PDa and PDb.

As shown in FIG. 8, a filter 24 that transmits light in a predetermined wavelength range and reflects light in a wavelength range outside the predetermined wavelength is formed on a PD serving as a light receiving unit. Filter is 0.2 for each
A 75 μm thick titanium dioxide thin film 24H and a silicon dioxide thin film 24L each having a thickness of 4 μm are alternately stacked. FIG. 9 shows the spectral sensitivity characteristics of each of PDa and PDb when such a filter is used. It can be seen that light in the infrared region is cut by the filter.

FIG. 10 shows the spectral sensitivity characteristics of an optical semiconductor device using the light receiving element configured as described above and using the amplification / arithmetic circuit formed as described above. As shown in the figure, it can be seen that good spectral sensitivity characteristics are obtained.

The filter used in the present embodiment is a multilayer filter in which a high-refractive-index thin film titanium dioxide film and a low-refractive-index thin film silicon dioxide film, which are directly deposited on a PD, are alternately laminated. With such a multilayer film, a filter characteristic independent of the incident angle of light can be obtained. In this case, since the interface between the two films has a filter function, the number of layers must be equal. The spectral sensitivity characteristic depends on the number of layers, each film thickness, and its composition. For example, Al2O3, In2O3, Ta2
By using a material having an appropriate difference in refractive index such as O3 and a mixture thereof, predetermined characteristics can be obtained.

In the two embodiments, PDs having two different wavelength sensitivity characteristics are used. However, depending on the wavelength region required for sensing, a single PD or three or more PDs may be used.
D may be used. In addition, the N epi-island for trapping and blocking carriers is located in the region in contact with the scribe end face, PN
Although provided below the P-Tr, the NPN-Tr, and the PD, the effect of trapping and blocking can be obtained at any one of the locations.

The mounting method is not particularly limited. As in the first and second embodiments, the semiconductor device is mounted on a lead frame shown in FIG. 11A, bonded, and then molded with a transparent epoxy resin 25. Other, for example, FIG.
As shown in (b), the through holes in which a large number of light receiving elements 8 are arranged and a linear pattern are mounted on a printed circuit board 26 formed in a predetermined arrangement, bonded, and electrically connected, and a transparent epoxy resin 27 is used. After molding,
One obtained by separating into individual elements by dicing or the like may be used. At this time, the printed circuit board is preferably made of BT resin or the like, and is made of black, gray, or other light-reflecting color or material.

Further, the spectral sensitivity characteristic is controlled over the entire visible light range in order to be used as an illuminance detection sensor. In addition, the spectral sensitivity characteristic is controlled over a monochromatic light range such as blue, green, and red of a predetermined object. Thereby, it can also be used as an object detection sensor.

Although no particular mention is made of the arrangement of the circuits in the light-receiving element, the first-stage amplifier circuit, which is particularly susceptible to the influence of carriers, is formed within 100 μm or more where most of the light is absorbed from the scribe end face. Is preferably performed.

[0036]

According to the present invention, it is possible to provide an optical semiconductor device whose spectral sensitivity characteristics are controlled with higher precision without having sensitivity in the infrared region.

[Brief description of the drawings]

FIG. 1 is a sectional view showing PDa and PDb used in a first embodiment.

FIG. 2 is a circuit diagram of a light receiving element.

FIG. 3 is a diagram showing spectral sensitivity characteristics of PDa and PDb in the first embodiment.

FIG. 4 is a sectional view showing a part of the light receiving element according to the first and second embodiments.

FIG. 5 is a sectional view showing a part of the light receiving element according to the first and second embodiments.

FIG. 6 is a graph showing light absorption characteristics of silicon.

FIG. 7 is a diagram illustrating spectral sensitivity characteristics of the optical semiconductor device according to the first embodiment.

FIG. 8 is a sectional view showing PDa and PDb used in the second embodiment.

FIG. 9 is a diagram showing spectral sensitivity characteristics of PDa and PDb in the second embodiment.

FIG. 10 is a diagram illustrating spectral sensitivity characteristics of the optical semiconductor device according to the second embodiment.

FIG. 11 is a diagram showing a structure of an optical semiconductor device.

FIG. 12 is a cross-sectional view showing a part of a conventional light receiving element.

[Explanation of symbols]

 Reference Signs List 1 PDa 2 PDb 3 Amplification / arithmetic circuit 4 First stage amplifying circuit 5 Differential circuit 6 Arithmetic circuit 7 Amplifying circuit 8 Light receiving element 9 P-type silicon substrate (substrate) 10 Scribe end face 11, 15, 18, 18 ′ N epi island 12, Reference Signs List 14 p-type sub removal layer 13 NPN transistor 13 ′ lateral PNP transistor 16 n base layer 17, 20 contact 19 PD section 21 scribe line 22 carrier 23 depletion layer 24 filter 24 H titanium dioxide thin film 24 L silicon dioxide thin film 25 transparent epoxy resin 26 printed board 27 Outer lead part of lead frame 28 Metallized part

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroshi Suzunaga 1F, Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa F-term in Toshiba Microelectronics Center Co., Ltd. 2G065 AA03 AB04 BA09 BB27 BC03 BC13 CA08 DA20 4M118 AA10 AB10 BA02 CA03 CA40 GC11 5F049 MA02 NA05 NA10 NB10 PA17 RA06 SS03 SZ07 SZ08 UA13 UA17 UA20 WA03 5F082 AA08 AA24 BA02 BA12 BC04 BC11 BC20

Claims (8)

[Claims] 1. A photodiode formed on a semiconductor substrate of a first conductivity type, an amplifying / arithmetic circuit for amplifying / arithmetic processing a signal from the photodiode, and a transistor element constituting the amplifying / arithmetic circuit. A second conductive island high concentration layer formed in the first conductive semiconductor substrate around at least one of the photodiodes and having a reverse bias potential applied to the first conductive semiconductor substrate. An optical semiconductor device comprising: 2. The optical semiconductor according to claim 1, wherein the island-type high-concentration layer of the second conductivity type is formed at least at a position in contact with a scribe end face of the semiconductor substrate of the first conductivity type. apparatus. 3. The high-concentration island-type layer of the second conductivity type is formed from a surface of the semiconductor substrate of the first conductivity type to an element formation region where a transistor element or the photodiode constituting the amplification / operation circuit is formed. 3. The optical semiconductor device according to claim 2, wherein the optical semiconductor device is formed at a depth corresponding to a bottom of the semiconductor substrate, and is connected to a bias terminal formed on a surface of the semiconductor substrate. 4. A bias is provided on the substrate via a sub-extraction layer which is a first conductivity type high concentration layer formed between the island-like high concentration layer and one of the transistor element or the photodiode. The optical semiconductor device according to claim 3, wherein a potential is applied. 5. The semiconductor device according to claim 1, wherein the photodiode is formed by laminating the first conductivity type semiconductor substrate from the substrate surface toward the inside, and includes first and second photodiodes having different wavelength sensitivities. The optical semiconductor device according to claim 1, wherein: 6. The first photodiode of the first and second photodiodes, which is formed on the surface of the first conductivity type semiconductor substrate and has a wavelength sensitivity in a visible light region, and has a first conductivity type. Formed on the inner side of the mold semiconductor substrate
6. The optical semiconductor device according to claim 5, wherein said photodiode has a wavelength sensitivity in an infrared light region. 7. The optical semiconductor device according to claim 6, wherein a filter that transmits the visible light and reflects the infrared light is attached to an upper surface of the first photodiode. . 8. The optical semiconductor device according to claim 7, wherein said filter comprises a multilayer film in which high-refractive-index thin films and low-refractive-index thin films are alternately laminated.