JP2002217448A - Semiconductor light illuminance sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light illuminance sensor which has infrared light components of a low sensitivity, even if light is incident from other device than a photodiode and which has stable operation in a circuit section. SOLUTION: An N-type region is formed around elements, which needs to be clear of the influence by scribe lines and an optical current. Carriers generated by irradiation of light and a diffusion current due to the optically excited carriers are absorbed by the N-type region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminance detecting element, and more particularly to a semiconductor light illuminance sensor having a photodiode and a circuit for calculating a signal from the photodiode.

[0002]

2. Description of the Related Art A semiconductor light illuminance sensor is required to have a wavelength sensitivity characteristic equivalent to the visibility characteristic as shown in FIG. Originally, the wavelength sensitivity characteristic of a silicon photodiode has sensitivity up to the infrared region as shown in FIG. 7, so that the semiconductor light illuminance sensor needs to have reduced sensitivity in the infrared region.

A conventional semiconductor light illuminance sensor uses an optical filter such as a multilayer interference filter or a dye filter that absorbs an infrared light component and transmits a visible light component on a photodiode in order to reduce sensitivity in an infrared region. In order to avoid the problem of cost increase when adding a step of mounting an optical filter, or depending on the required wavelength, there is no suitable dye that absorbs light other than that wavelength, As shown in FIG. 8, two photodiodes having wavelength sensitivity characteristics different from each other are arranged, and a method of lowering the sensitivity in the infrared region by calculating optical signals from the two photodiodes is implemented.

FIG. 9 shows an upper surface of a conventional semiconductor light illuminance sensor formed on a semiconductor substrate. Reference numeral 1 denotes a photodiode section (PD section) composed of a photodiode, and 2 denotes an optical signal from the photodiode section 1. Processing circuit part, 4
Is a bonding pad for input / output of the semiconductor light illuminance sensor. A scribe line 3 is formed so as to surround the photodiode unit 1, the circuit unit 2, and the bonding pad 4.

As described above, in this semiconductor light illuminance sensor, a method of forming an optical filter on the photodiode section 1 or forming two photodiodes having wavelength sensitivity characteristics different from each other and calculating an optical signal thereof. Is effective to reduce the sensitivity of the incident light from the upper surface of the photodiode to the infrared light component. In this case, in order to obtain a desired wavelength characteristic, it is necessary to cover a region other than the region where the photodiode is formed with a metal wiring layer serving as a light-shielding film so as to suppress generation of an unnecessary photocurrent.

However, it is very difficult to selectively form a light-shielding film on the outermost peripheral portion of the scribe line 3 or on the side surface of the semiconductor substrate due to the method of manufacturing the semiconductor light illuminance sensor. It is merely covered with a transparent package, in which case light also penetrates through the scribe line 3 and the side of the semiconductor substrate, thereby generating extra photocurrent due to carriers generated in the semiconductor substrate. Since the reflected light from the substrate on which the semiconductor light illuminance sensor is mounted also enters the side surface of the semiconductor substrate, the excess photocurrent becomes larger than expected. Therefore, not only the effect of the operation of the two photodiodes is not obtained, but also the extra photocurrent affects the operation of the circuit unit 1. In addition, scribe line 3
Light containing a large amount of infrared light component that has not passed through the optical filter penetrates into the cross section of the semiconductor substrate and generates an extra photocurrent corresponding to the infrared light component. In addition, an infrared light component having a peak at 1050 nm was detected.

[0007]

As described above, the conventional semiconductor light illuminance sensor is sensitive to infrared light components due to the generation of an extra photocurrent, and the circuit section 1 is affected by the extra photocurrent. Had an effect on the operation.

The present invention has been made in view of the above problems, and has low sensitivity to infrared light components even when light is incident from a source other than a photodiode, and the infrared light components affect the operation of a circuit section. It is an object of the present invention to provide a semiconductor light illuminance sensor which does not cause the problem.

[0009]

According to the present invention, there is provided a semiconductor light illuminance sensor having a first conductive semiconductor substrate and a circuit formed on a main surface of the semiconductor substrate. A second conductive region is provided at an end of the main surface of the substrate, and a bonding surface is formed at a boundary between the second conductive region and the semiconductor substrate.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

<First Embodiment> In a semiconductor light illuminance sensor according to a first embodiment, an N-type region is formed on a predetermined surface of a semiconductor substrate having P-type conductivity as a scribe line, and a scribe line is formed by the N-type region. A PN junction surface is formed in the semiconductor substrate below the line. Of the carriers generated by light incident on the scribe line or the scribe cross section (side surface of the semiconductor substrate), the carriers generated relatively on the surface and the carriers flowing as a diffusion current are N-type when reaching the PN junction surface. Therefore, the influence on the photodiodes and circuit elements due to the excess photocurrent can be reduced.

FIG. 1 shows the state of the upper surface of a semiconductor light illuminance sensor formed on a semiconductor substrate having P-type conductivity. Reference numeral 5 denotes a photodiode portion (PD portion) comprising a photodiode, and 6 denotes a photodiode. A circuit unit for processing an optical signal from the unit 1, a circuit element 9 for eliminating the influence of the photocurrent, and a bonding pad 10 for input / output. Reference numeral 7 denotes a scribe line formed of an exposed surface of the semiconductor substrate, and is formed so as to surround the photodiode unit 5, the circuit unit 6, the circuit element 9, and the bonding pad 10. The scribe line 7 is also an exposed surface of an N-type region 8 having N-type conductivity formed on the surface of the semiconductor substrate. Further, a side surface of the semiconductor substrate is exposed as a side surface of the semiconductor light illuminance sensor. When the semiconductor light illuminance sensor is irradiated with light, not only the photodiode portion 5 but also the N-type region 8 of the scribe line 7 and the side surface of the semiconductor substrate are irradiated. At this time, the light enters the inside of the semiconductor substrate, An extra photocurrent is generated.

FIG. 2 is a sectional view showing a part of a portion indicated by AA in FIG. In the figure, reference numeral 15 denotes a scribe line, 24 denotes a region having N-type conductivity formed by epitaxial growth, and the scribe line 15 is also an exposed surface of the N-type epitaxial layer 24. Reference numeral 16 denotes a scribe section, in which the side surface of the semiconductor substrate is exposed. 21, 22
Denotes two photodiodes having mutually different wavelength sensitivity characteristics, and 23 denotes an NPN bipolar transistor constituting a circuit unit.

An N-type epitaxial layer 24 serving as a scribe line 15 and an N + type N-type
Diffusion is formed, and these N-type epitaxial layers 2
4 and the N + diffusion are N-type regions 18. An isolation region 19 having P-type conductivity is formed between the N-type region 18 and the photodiodes 21 and 22, and the isolation region 19 is formed by diffusion into a P-type silicon substrate having P-type conductivity. The N-type region 18 is connected to the isolation region 19 by a contact portion 17. In this case, the N-type region 18 and the P-type silicon substrate 2
Although no bias voltage is applied between 0 and 0, there is a concentration gradient near the junction surface and a small depletion layer spreads, so that carriers generated near this junction surface due to light penetration and diffusion current to this junction surface The carriers that have arrived as are absorbed by the N-type region 18 and consumed as a current flowing to the P-type silicon substrate 20. Therefore, the photodiodes 21 and 22 and the NPN bipolar transistor 23 are hardly affected by this current, and this current is irrelevant to the current consumption of the semiconductor light illuminance sensor.

As described above, in the semiconductor light illuminance sensor according to the first embodiment, even if a carrier is generated in the semiconductor substrate by the incidence of light having an infrared light component from the scribe line 15 and the scribe section 16, extra light due to the carrier is generated. Since the unnecessary photocurrent is absorbed from the N-type region 18 and is consumed as a current flowing to the silicon substrate 20, the photodiodes 21 and 22 and the NPN bipolar transistor 23 forming the circuit section are affected by the extra photocurrent. The sensitivity of the infrared light component can be reduced without using a light-shielding film. <Second Embodiment> A second embodiment surrounds a predetermined circuit element whose influence is to be reduced in order to further reduce the influence on carriers caused by carriers generated inside the semiconductor substrate or carriers moved as a diffusion current. As described above, the N-type region is formed. With this structure, carriers generated in the semiconductor substrate and carriers flowing as a diffusion current can be absorbed in the N-type region.
The effect on the circuit elements surrounded by the mold region can be further reduced.

Such a structure is required for the following reasons. That is, when infrared light having a wavelength of 1000 nm is incident on silicon, a distance of about 170 μm is required from the incident surface in order to absorb 90% of the light.
A distance of 300 μm or more is required to absorb almost 100% of light. In addition, since the diffusion current due to the photoexcited carriers generated by the light reaches further than this distance, it is difficult to completely eliminate the effect even if the distance from the incident surface (scribed section of the semiconductor chip) is large. It is.

FIG. 3 is an enlarged view of the circuit element 9, and this circuit element 9 is a circuit element in which it is desired to eliminate the influence of extra photocurrent due to incident light in the present embodiment. Circuit element 14
Are formed around the electrode wiring 13, and the electrode wiring 12 is formed around the electrode wiring 13. Further, the electrode wiring 13
An isolation region (not shown) is formed in the lower layer, and an N region 11 is formed in the lower layer of the electrode wiring 12.

FIG. 4 shows a partial section taken along line BB of FIG.

In FIG. 4, reference numeral 26 denotes a lateral PNP bipolar transistor. In the lateral PNP bipolar transistor 26, the N-type region 28 having N-type conductivity serves as a base region. Therefore, when a diffusion current due to carriers flows into this region, the base current of the transistor becomes the base current of the transistor and the current amplification factor of the transistor. Multiplied and affects the circuit operation. In order to avoid this, in the present embodiment, as shown in FIG. 4, a P-type isolation region 27 having a P-type conductivity is provided around a lateral PNP bipolar transistor 26, and the P-type isolation region 27 is formed through diffusion. The N-type region 25 and the P-type isolation region 27 by connecting the N-type region 25 to the high potential. Further, a depletion layer is generated between the N-type region 25 and the P-type silicon substrate 20 to generate an electric field.
Due to this electric field, the minority carriers and the diffusion current generated in the P-type silicon substrate 20 are absorbed by the N-type region 25 and consumed as the current flowing into the P-type silicon substrate 20, so that the lateral current due to the extra photocurrent is generated. The effect on the PNP transistor 26 can be reduced.

<Third Embodiment> The characteristics can be further improved by combining the structures shown in the first embodiment and the second embodiment. The first embodiment is characterized in that the photodiode section 5 and the circuit section 6 are surrounded by an N-type region. However, the circuit elements 9 are individually surrounded by the photodiode section 5 and the circuit section 6 as well. By forming the N-type region, spectral sensitivity characteristics can be improved. According to the third embodiment, what has conventionally sensed infrared light having a peak at 1050 nm, as shown in the spectral sensitivity characteristics of FIG. 5, the luminosity factor having no sensitivity near the wavelength. Can be obtained.

In addition to the photodiodes 21 and 22 shown in FIG.
Semiconductor illuminance sensor that has a photodiode composed of a junction surface between a type epitaxial layer and a diffusion layer formed on the surface, and an optical filter that absorbs infrared light and transmits only visible light components on the photodiode. In this case, similar effects can be obtained by applying the first embodiment and the second embodiment.

[0022]

As described above, according to the present invention, the carrier generated by the incident light from the region other than the photodiode is absorbed by the N-type conductive region formed on the semiconductor substrate, and the current flowing through the semiconductor substrate is reduced. To be consumed as
A semiconductor light illuminance sensor having low sensitivity to infrared light components without a light-shielding film can be provided.

[Brief description of the drawings]

FIG. 1 is a top view of a semiconductor light illuminance sensor according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG. 1 according to the first embodiment of the present invention.

FIG. 3 is a circuit top view of a semiconductor light illuminance sensor according to a second embodiment of the present invention.

FIG. 4 is a sectional view taken along line BB of FIG. 3 according to a second embodiment of the present invention.

FIG. 5 is a wavelength sensitivity characteristic diagram of the semiconductor light illuminance sensor of the present invention.

FIG. 6 is a luminosity characteristic diagram.

FIG. 7 is a wavelength sensitivity characteristic diagram of silicon.

FIG. 8 is a wavelength sensitivity characteristic diagram of two photodiodes.

FIG. 9 is a top view of a conventional semiconductor light illuminance sensor.

FIG. 10 is a wavelength sensitivity characteristic diagram of a conventional semiconductor light illuminance sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Photodiode part 2 ... Circuit part 3 ... Scribe line 4 ... Bonding pad 5 ... Photodiode part 6 ... Circuit part 7 ... Scribe line 8 ... N type Area 9 9 Circuit element 10 Bonding pad 11 N-type area 12 Electrode wiring of N-type area 11 13 Electrode wiring of isolation area 14 Influence of photocurrent 15 scribe line 16 scribe section 17 contact part of N-type region 18 N-type region 19 separation region 20 P-type silicon substrate DESCRIPTION OF SYMBOLS 21 ... Photodiode 22 ... Photodiode 23 ... NPN bipolar transistor 24 ... N-type epitaxial layer 25 ... N-type area 26 ... Lateral PNP Bipolar transistor 27 ... isolation region 28 ... N-type region

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) H01L 27/14 F term (Reference) 2G065 AA03 AB04 BA09 BC03 CA08 4M118 BA02 CA03 FC09 GC11 5F049 MA02 MB03 NA04 NA17 NB07 QA01 QA11 RA06 UA13 5F082 AA00 AA36 BA02 BA47 BC01 BC04 BC11 BC20 GA02

Claims (6)

[Claims] 1. A semiconductor light illuminance sensor having a first conductive semiconductor substrate and a circuit formed on a main surface of the semiconductor substrate, comprising a second conductive region at an end of the main surface of the semiconductor substrate. A bonding surface is formed at a boundary between the second conductive region and the semiconductor substrate. 2. The semiconductor light illuminance sensor according to claim 1, wherein said second conductive region is formed so as to surround a main surface of said semiconductor substrate. 3. The semiconductor device according to claim 1, wherein said semiconductor substrate and said second conductive region are electrically short-circuited.
And a semiconductor light illuminance sensor according to claim 2. 4. The semiconductor device according to claim 1, wherein the junction surface is a PN junction surface, and the potential on the N-type semiconductor is higher than that on the P-type semiconductor. Semiconductor light intensity sensor. 5. The semiconductor illuminance sensor according to claim 1, wherein said semiconductor substrate has a scribe line, and said second conductive region is formed in said scribe line. 6. The semiconductor light illuminance sensor according to claim 1, further comprising a photodiode on a main surface of said semiconductor substrate.