JP2012013475A - Composite detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an electromagnetic wave at high sensitivity by setting electromagnetic wave sensors of different wavelengths on the same semiconductor substrate.SOLUTION: A composite detector includes: a sensing section 20; a charge supply section 16 for supplying charges to the sensing section 20; a charge supply adjustment section ICG2 formed between the sensing section 20 and the charge supply section 16; a charge accumulating section 17 for accumulating charges from the sensing section 20; a charge transfer adjustment section TG1 formed between the sensing section 20 and the charge accumulating section 17; and an output section 21 corresponding to charges in the charge accumulating section 17. A first set and a second set are formed on the same semiconductor substrate. The sensing section 20 of the first set receives a first electromagnetic wave and generates charges corresponding to the intensity of the first electromagnetic wave. An electromagnetic wave sensing element for receiving a second electromagnetic wave of a wavelength different from that of the first electromagnetic wave, and outputting it according to the intensity of the second electromagnetic wave is mounted on a semiconductor substrate corresponding to the second set. The sensing section of the second set changes potential according to the power of the electromagnetic sensing element 130.

Description

  The present invention relates to a composite detection apparatus. More specifically, the present invention relates to a composite detection apparatus that can simultaneously detect a plurality of types of electromagnetic waves (for example, visible light and ultraviolet light) having different wavelengths.

In a fire sensor with imaging, the occurrence of a fire can be detected by taking the difference between the normal image and the fire occurrence image. In the event of a fire, a flame with ultraviolet rays may be generated, and an image of this flame cannot be obtained from a sensor that detects only visible light.
On the other hand, if a fire sensor is composed of only an ultraviolet sensor, it is difficult to form a normal image.
Therefore, it is desired to use a sensor capable of detecting ultraviolet rays in combination with a visible light sensor.
Various sensors including a CCD camera have been proposed as visible light sensors. As an ultraviolet sensor, a sensor using a wide gap semiconductor (photodiode) such as AlGaN, ZnO or diamond has been proposed. Non-Patent Document 1 discloses that a GaN-based ultraviolet array sensor is bonded to an existing CMOS readout circuit using a flip-chip technique.
See also Non-Patent Document 1 and Non-Patent Document 2 as documents disclosing techniques related to the present invention.

WO 2009/081890 A1

Opto-electronics Review 10 (4), 251-260 (2002) Abstract book of 2nd International Symposium on Advanced Plasma Science and its Application for Nitrides and Nanomaterials, p.108 (March 7-10, 2010, Nagoya) 10a-B06OB

Although there is a demand for miniaturization and weight reduction of fire sensors, there is no provision of a one-chip visible light sensor and ultraviolet sensor.
Since a small amount of ultraviolet rays is emitted from a fluorescent lamp as a lighting fixture, high sensitivity is required for the ultraviolet sensor from the viewpoint of eliminating the influence of the ultraviolet rays as the background.
In a system for detecting electromagnetic waves such as ultraviolet rays using a photodiode, the current generated by the photodiode receiving light is amplified and detected. Therefore, the problem of noise caused by current flow is included. In other words, detection with high sensitivity is difficult.
Of course, it is possible to improve the detection sensitivity by connecting a current amplifier to the outside, but this is not preferable from the viewpoint of manufacturing cost because the apparatus becomes large. In addition, the external current amplifier is a limitation in mounting the visible light sensor and the ultraviolet sensor on one chip.

  The inventor has conducted extensive studies to solve the above problems, and has found that noise is removed by using a so-called floating diffusion technique. Since detection of visible light using floating diffusion technology has been established (see Patent Document 1), if this visible light device structure can be used as it is for output detection of a photodiode for ultraviolet light, the apparatus can be simplified and compact. Satisfies the demand for conversion.

The first aspect of the present invention is based on the above findings of the present inventor and is defined as follows.
A sensing unit;
A charge supply unit for supplying charge to the sensing unit;
A charge supply control unit formed between the sensing unit and the charge supply unit;
A charge storage unit for storing the charge transferred from the sensing unit;
A charge transfer control unit formed between the sensing unit and the charge storage unit;
An output unit that generates an output corresponding to the charge stored in the charge storage unit, the first set and the second set are formed on the same semiconductor substrate,
The sensing unit of the first set receives a first electromagnetic wave and generates the electric charge according to the strength of the first electromagnetic wave,
An electromagnetic wave sensitive element that receives a second electromagnetic wave having a wavelength different from that of the first electromagnetic wave and generates an output corresponding to the intensity of the second electromagnetic wave is mounted on the semiconductor substrate corresponding to the second set. And the second set of sensing units changes its potential in accordance with the output from the electromagnetic wave sensing element.

In the composite detection device of the first aspect configured as described above, the first set is a light detection device using a so-called floating diffusion technology, and the visible light can be detected by covering the sensing portion with a transparent material, for example. It is.
The second set is a so-called physical / chemical phenomenon measuring device that converts the environmental change of the sensing unit into a charge amount and identifies the change. If the output generated by the electromagnetic wave sensitive element (the potential due to the electric charge generated corresponding to the intensity of the second electromagnetic wave) is used as the physical quantity to be detected, the output of the electromagnetic wave sensitive element is converted into a potential change of the sensing unit. Thus, by using the floating diffusion technology, the output of the electromagnetic wave sensitive element can be specified with high sensitivity without any current.
Here, by arranging the first set, the second set, and the electromagnetic wave sensitive element on the same semiconductor substrate, sensors of electromagnetic waves having different wavelengths can be integrated on one chip.
Furthermore, by making the configurations of the first set and the second set the same, simplification and compactness of the apparatus can be achieved.

The first electromagnetic wave and the second electromagnetic wave can be arbitrarily selected. However, since the first set directly measures the first electromagnetic wave, it depends on the characteristics of the semiconductor substrate constituting the sensing unit. When the substrate is formed of silicon, it is preferable to select a near infrared region from visible light as the first electromagnetic wave.
On the other hand, the electromagnetic wave sensitive element can cope with an electromagnetic wave having an arbitrary wavelength by adjusting the band gap.
When the composite detection device of the present invention is used as a fire sensor, it is preferable to employ visible light as the first electromagnetic wave and ultraviolet light as the second electromagnetic wave.

In the first set, the potential of the sensing unit is fixed, the charge well constituting the sensing unit is fully filled with charges, and the charge generated when receiving the first electromagnetic wave is charged from the sensing unit. The intensity of the first electromagnetic wave can be specified from the transferred charge amount. Alternatively, the charge in the charge well corresponding to the sensing unit may be emptied, and the charge accumulated when receiving the first electromagnetic wave may be read out.
On the other hand, in the second set, the potential of the sensing unit changes according to the output (charge amount) of the electromagnetic wave sensitive element applied to the sensing unit. When the output of the electromagnetic wave sensing element is zero (corresponding to the state where the second electromagnetic wave intensity is zero and the shutter of the electromagnetic wave sensing element is closed), the potential P0 and the electromagnetic wave sensing element have some output (first output, detection) The amount of charge transferred to the charge storage unit is specified from the difference from the potential P1 at the time of the first intensity of the second electromagnetic wave). The amount of charge stored in the charge storage unit is converted into a voltage by an arbitrary method, and the output of the electromagnetic wave sensitive element (that is, the intensity of the second electromagnetic wave) is specified.

In the second set of sensing units, there is a relationship shown in FIG. 1 between the change in output of the electromagnetic wave sensitive element and the change in charge transfer amount (change in the amount of charge accumulated in the sensing unit). In order to perform high-sensitivity measurement, it is necessary to use a region with a large slope in the relationship shown in FIG. It is preferable to set.
Since the characteristics of the sensing unit may change with time due to temperature or the like, the relationship between the output of the electromagnetic wave sensitive element and the potential of the sensing unit may also change. For example, when the position of the potential P0 when the electromagnetic wave sensitive element is in the shutter state becomes deeper than the set value, the amount of charge accumulated in the sensing unit increases. As a result, the upper part of the large inclined area in the relationship of FIG. 1 is used, which may lead to a reduction in sensitivity and a reduction in the measurement range.

  The amount of charge accumulated in the sensing unit is defined by the difference between the potential of the sensing unit and the potential of the charge transfer control unit. Therefore, in the second aspect of the present invention, by adjusting the potential of the charge transfer adjustment unit (that is, its potential), the amount of charge accumulated in the sensing unit is always suitable even if the potential of the sensing unit changes. It was decided to adjust to an appropriate amount. For example, when the position of the potential P0 in the shutter state of the electromagnetic wave sensitive element becomes deeper than a set value, the potential of the charge transfer adjustment unit is adjusted to lower the potential, thereby adjusting the amount of charge accumulated in the sensing unit, The amount is always located in the lower region of the large slope portion in the relationship of FIG.

It is a characteristic view which shows the relationship between the output of an electromagnetic wave sensitive element, and a charge amount. It is a schematic diagram which shows the structure of the composite detection apparatus of embodiment of this invention. The equivalent circuit of an ultraviolet-ray detection part is shown. It is a chart which shows the output characteristic of an ultraviolet detection part.

Embodiments of the present invention will be described below.
FIG. 2 is a schematic diagram illustrating a configuration of the composite detection device 1 according to the embodiment.
The composite detection apparatus 1 includes a visible light detection unit 10 and an ultraviolet detection unit 100. Reference numeral 3 in the figure denotes a silicon substrate, and a visible light detection unit 10 and an ultraviolet detection unit 100 are formed on the surface of the silicon substrate 3. Note that the visible light detection unit 10 and the ultraviolet detection unit 100 are charge readout devices (first set 11 and second set 111) using a following diffusion (hereinafter, may be abbreviated as “FD”) technology. Is provided. In both, the same elements are denoted by the same reference numerals, and the description thereof is omitted. By adopting the same element, it is possible to reduce the number of manufacturing steps and simplify the apparatus.
Reference numeral 5 in the figure denotes a lens.

(Visible light detector 10)
First, the visible light detection unit 10 will be described.
The visible light detection unit 10 includes a first set 11 as introduced in Patent Document 1 as a visible light measurement device.
The first set 11 has a MOS structure. A p-well 15 is formed on the surface of the silicon substrate 3, and n + regions 16, 17 and 18 are further formed in the p-well 15. In order to adjust the p-type and n-type conductivity types, respective impurities are doped into the substrate 3 by a general-purpose method.
The first n + region 16 is a charge supply unit, and the charge supply unit 16 is connected to the charge supply electrode ID1. The second n + region 17 is a charge storage unit, and the charge storage unit 17 is connected to the FD electrode FD 1, and the FD electrode FD 1 is connected to the output circuit 21. The output circuit 21 is formed in the n region of the substrate 3 and constitutes a CMOS structure together with the first set 11. The output circuit 21 converts a capacitance change accompanying a change in the amount of charge accumulated in the charge accumulation unit 17 into a voltage signal and outputs the voltage signal. The third n + region 18 is a drain portion, which transfers charges accumulated in the charge accumulation portion 17 via the reset gate RG1, and discharges the charges to the outside. A ground electrode for this purpose is also formed in the n region of the substrate 3.

An insulating film 21 made of silicon oxide is laminated on the surface of the sensing unit 20, and a light-transmitting protective film 23 made of silicon nitride is further laminated thereon. It is preferable to form an n-type thin buried channel region on the surface of the p-well constituting the sensing 20.
According to the visible light detection unit 10 configured as described above, charges (electrons) are generated in the sensing unit 20 according to the intensity of the visible light component in the light incident through the lens 5, and the charges are TG1. Then, it is transferred to the charge storage section 17 and read out to the output circuit 21 and output as a voltage signal.

(Ultraviolet detector 100)
The ultraviolet detection / detection unit 100 includes a second set 111 and an ultraviolet sensitive element 130.
The second set 111 has the same configuration as the first set 11 except for the sensing electrode 125. In the figure, the same elements are given the same reference numerals. Regarding the electrodes, ID1 and ID2, ICG1 and ICG2, TG1 and TG2, FD1 and FD2, and RG1 and RG2 have the same structure.
The sensing electrode 125 preferably covers the entire surface of the protective film 23 constituting the sensing unit 20 of the second set 111 so that visible light does not reach the sensing unit 20. The protective film 23 can be omitted.

A photodiode made of a group III nitride compound semiconductor was used for the ultraviolet sensitive element 130. The element 130 is mounted on the substrate 3 in a flip chip format as shown in FIG. That is, the n-type electrode of the element 130 is connected to the p-well 115 by the bump 131, and the p-type electrode is connected to the n region 116 by the bump 133. The n region 116 is connected to the sensing electrode 125 of the second set 111.
FIG. 3 shows an equivalent circuit of the ultraviolet detection unit 100.

The ultraviolet sensitive element 130 that has received light through the lens 5 generates a charge corresponding to the ultraviolet component contained in the received light, and a potential corresponding to the amount of the charge is generated in the sensing electrode 125 via the region 116.
Depending on the potential of the sensing electrode 125, the potential of the sensing unit 20 of the second set 111 changes. This potential change is converted into a charge amount stored in the charge storage unit 17 by the floating diffusion technique, and is further output as an output signal by the output circuit 21.
That is, in a state where the potential of the gate electrode TG2 is adjusted to prohibit the transfer of the charge from the sensing unit 20 to the charge storage unit 17, the potential of the charge supply adjusting unit ICG2 is adjusted and the charge is supplied from the charge supplying unit 16 to the sensing unit. Inject into 20. Thereafter, the charge supply from the charge supply unit 16 is stopped, and the electric potential of the charge supply adjustment unit ICG is lowered to wear out the charge of the sensing unit 20. Thus, charges corresponding to the potential depth are accumulated in the sensing unit 20. Next, the potential of the gate electrode TG <b> 2 is raised to transfer the charge stored in the sensing unit 20 to the charge storage unit 17, and the charge amount is read by the output circuit 21.

FIG. 4 shows the output result of the ultraviolet detection unit 100.
4A shows the output (Vsig) when blank (no UV irradiation), and FIG. 4B shows the output (Vsig) when UV (wavelength: 325 nm) is irradiated at an intensity of 510 μW / cm ³ .
From this result, it can be seen that ultraviolet rays can be detected by using the ultraviolet ray detection unit 100.

By arranging the visible light detection unit 10 and the ultraviolet detection unit 100 thus configured in a matrix on the silicon substrate 3, a visible light image and an ultraviolet light image can be simultaneously formed based on respective outputs. Is possible.
Since the output of the ultraviolet sensitive element 130 is a potential (not to detect current) in the ultraviolet detecting unit 100, it is not easily affected by noise and can be detected with high sensitivity.

  The present invention is not limited to the description of the embodiments and examples of the invention described above. Various modifications may be included in the present invention as long as those skilled in the art can easily conceive without departing from the description of the scope of claims.

DESCRIPTION OF SYMBOLS 1 Composite detection apparatus 3 Semiconductor substrate 10 Visible light detection part 11 1st set 16, ID1, ID2 Charge supply part ICG1, ICG2 Charge supply adjustment part 17, FD1, FD2 Charge storage part 20 Sensing part TG1, TG2 Charge transfer adjustment part 21 Output circuit 130 UV sensitive element

Claims (3)

A sensing unit;
A charge supply unit for supplying charge to the sensing unit;
A charge supply control unit formed between the sensing unit and the charge supply unit;
A charge storage unit for storing the charge transferred from the sensing unit;
A charge transfer control unit formed between the sensing unit and the charge storage unit;
An output unit that generates an output corresponding to the charge stored in the charge storage unit, the first set and the second set are formed on the same semiconductor substrate,
The sensing unit of the first set receives a first electromagnetic wave and generates the electric charge according to the strength of the first electromagnetic wave,
An electromagnetic wave sensitive element that receives a second electromagnetic wave having a wavelength different from that of the first electromagnetic wave and generates an output corresponding to the intensity of the second electromagnetic wave is mounted on the semiconductor substrate corresponding to the second set. And the second set of sensing units changes its potential in accordance with the output of the electromagnetic wave sensing element. A composite detection apparatus for detecting a plurality of electromagnetic waves.   Adjusting the electric potential of the charge supply adjusting unit in the second set, and adjusting the amount of charge transferred from the sensing unit to the charge storage unit to a predetermined amount when the output of the electromagnetic wave sensitive element is zero. The composite detection apparatus according to claim 1.   The composite detection apparatus according to claim 1, wherein the first electromagnetic wave is visible light, and the second electromagnetic wave is ultraviolet light.