JPH05199463A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To execute non-destructive read-out, and also, to execute read-out at a high speed, and to obtain the information of a high picture quality. CONSTITUTION:This device is divided roughly into a diode array 11 of a photodetecting part for photodetecting infrared rays and fetching information (image) as an electric signal, an amplification type MOS image sensor (AMI) part 12 which is used as a scanning circuits and a metallic bump 13 for connecting them, and the AMI part is provided with an (n+p) type photodiode (b) of a photoelectric converting part, and an (n) channel MOSFET for selecting reset, amplification and the vertical. By applying a reverse bias to the (n+p) type photodiode (b), discharging optical charge generated by infrared rays by a diode structure, and accumulating/amplifying and fetching its charge, it does not occur that a noise is mixed in and a signal is attenuated, and an output of a high S/N ratio is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device using a two-dimensional amplification type solid-state image pickup element as a solid-state image pickup element of a hybrid type infrared area sensor.

[0002]

2. Description of the Related Art Generally, an infrared area sensor for detecting infrared rays is roughly classified into a quantum effect type device and a thermal effect type device according to the principle of detection means. Highly sensitive quantum effect devices are used.

This quantum effect device is classified into a Schottky device and a compound device depending on the difference in the structure (material) of the detecting portion. The wavelength of the received light is 3-5μ
For infrared detection of m, a Schottky type device having a Pt-P type Si structure is suitable. However, when the wavelength range to be detected is wide, for example, 1 to 20 μm, the material forming the detection section can be freely selected, and the compound type device having a numerical aperture relatively larger than that of the Schottky type device. Is preferred.

The compound type device is, for example, "HgC".
Improving Resolution of dTe IR CCD "Technical Report of Television Society Vol. 15, No. 51 (1991, 9, 1
6) and with reference to FIG. 7, this HgCd
The configuration of an infrared area sensor using Te as an infrared sensor will be described.

As shown in FIGS. 7 (a) and 7 (b), a compound type infrared area sensor is a Si scanning circuit section in which a diode array 1 for photoelectrically converting infrared rays into an electric signal and a signal reading section are arranged in a matrix. 2 and In connecting them
The metal bumps 3 are made of metal.

The diode array 1 comprises a support substrate 4 made of CdZnTe, which is a transparent film that transmits infrared rays, and a p-type HgCdTe layer 5 formed on one surface of the support substrate 4 by an epitaxial method or the like. p-type Hg
A plurality of n + diffusion layers 6 are formed on the surface of the CdTe layer 5. Each of the n + diffusion layers 6 and each of the signal reading portions are connected by the metal bumps 3.

The operation of this compound type infrared area sensor is as follows.
When infrared rays are incident from the other surface side of the support substrate 4, hole / electron pairs are generated at the interface with the p-type HgCdTe layer 5. Of these, the electrons are transferred to the Si scanning circuit unit 2 via the n + diffusion layer 6 and the metal bump 3 and accumulated therein, and after a desired accumulation time, read out as a photoelectric conversion signal indicating optical information. ..

FIG. 8 shows respective sensitivities D ^* when the mixing ratio of Hg and Cd in the p-type HgCdTe layer 5 shown in FIG. 7 is changed ^. It is a characteristic diagram showing the characteristics of. This Figure 8
Therefore, the composition ratio x of Hg _1-x Cd _x Te is 0.39 to 0.
When changed in the range of 19, the infrared wavelength is 1 to 15 μm
It can be read that a high-sensitivity infrared sensor having a sensitivity close to the theoretical sensitivity limit indicated by wavelength in the range of γ is achievable.

Usually, a CCD (Cha) is provided in the Si scanning circuit 2 of the conventional compound type infrared area sensor as shown in FIG.
A non-amplification type solid-state image pickup device represented by a large coupled device) is used.

[0010]

However, the Si scanning circuit 2 of the above-mentioned conventional compound type infrared area sensor has a CC
D, MOS, CID (Charge Injectio)
n Device) or other non-amplifying solid-state image sensor.

Generally, the infrared sensor is operated in a low temperature atmosphere of about 77K in order to reduce noise caused by dark current and the like. However, as the low-temperature atmosphere approaches 77K, the CCD is more likely to have a signal transfer failure, and when this transfer failure occurs, an afterimage or resolution deterioration due to inter-pixel mixing of signals occurs, which causes deterioration of the infrared image. There are drawbacks.

With the demand for higher image quality, the Si scanning circuit needs to have a large number of pixels of about 1000 × 1000 pixels. In the conventional CCD, the power consumption is significantly increased due to the increase in the number of pixels, and the infrared sensor is heated to increase the dark current, that is, the sensitivity is lowered. Also,
To increase the number of pixels in the detector, it is necessary to speed up the signal processing in order not to delay the response signal, which makes it easier for signal transfer failure to occur, and also to prevent the read noise caused by the read operation other than the light receiving section. Raises the problem that

Further, as a conventional effective method for reducing the noise of the Si scanning circuit described above, it has been proposed to reduce the read noise by reading the signal many times.
In the non-amplification type solid-state imaging device composed of OS, once the information is read, the stored information is destroyed, so it is impossible to read the information many times, and this method cannot be used. ..

For long-time exposure for detecting low-level infrared rays, it is convenient to have a function of monitoring the signal accumulation state during exposure. As described above, CCD, M
In the OS non-amplification type solid-state imaging device, if the stored information is read for confirmation, the stored information is destroyed, so that the on-chip monitoring function cannot be formed. Therefore, it is an object of the present invention to provide a solid-state imaging device capable of non-destructive reading, high-speed reading, and high image quality of information.

[0015]

In order to achieve the above object, the present invention receives infrared rays having information, photoelectrically converts the infrared rays, and extracts the image information as infrared rays. An image taken out from the infrared area sensor means, in which a plurality of internal amplification type solid-state image pickup elements for reading are arranged so as to correspond to the detection area means and the respective two-dimensionally arranged solid-state image pickup elements of the infrared detection area means. Each of the internal amplification type solid-state imaging devices stores image information for a predetermined time, amplifies and outputs image information reading means, and bump means for transmitting image information from the infrared area sensor means to the image information reading means. Provided is a solid-state imaging device. The internal amplification type solid-state imaging device is composed of an amplification type MOS image sensor (AMI), and the infrared detection area means is composed of a narrow band gap compound semiconductor layer or a semiconductor layer having a Schottky barrier region.

[0016]

In the solid-state image pickup device having the above-described structure, since the reset period is one horizontal scanning period, the photodiode is reset to the initial value Vrs, that is, the information to be stored and erased is surely erased. It In addition, since the Schottky barrier layer is bump-formed on the amplification type MOS image sensor, an infrared sensor having a higher aperture ratio can be used as compared with the conventional sensor having a structure in which the Schottky barrier is formed on the same silicon substrate as the signal reading section. Provided. That is, a high-quality and high-quality infrared sensor can be created. Further, the hybrid type image sensor or the laminated type image sensor is applied to various two-dimensional image sensors for detecting ions, X-rays, ultraviolet rays, proteins and the like.

[0017]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows the configuration of a first embodiment of a solid-state imaging device according to the present invention.

In this structure, the diode array 1 of the light receiving portion for receiving infrared rays and extracting information (image) as an electric signal.
1 and an amplification type MOS image sensor (A
It is roughly classified into an MI (Amplified MOS Imager) portion 12 and a metal bump 13 made of indium (In) for connecting them.

The diode array 11 has a laminated structure of a support substrate 14 made of CdZnTe, which is a transparent film that transmits infrared rays, and a p-type HgCdTe layer 15.
A plurality of n + diffusion layers 16 are formed on the surface of the HgCdTe layer 15.
Are formed so as to be arranged in a matrix, for example. Next, in the structure of the AMI portion 12, first, an n + diffusion layer 18 is formed at a desired position on the P-type semiconductor substrate 17,
The diode a is configured.

The contact portion 19 of the diode a is
It is coupled to the n + diffusion layer 16 via the first Al layer 20, the second Al layer 21, the third Al layer 22, and the metal bump 13. Each layer of these conductors is electrically separated by an interlayer insulating film 23 such as SiO ₂ .

For a detailed description of the AMI section 12, that is, the AMI sensor for visible light, see, for example, "Amplification-type solid-state image pickup device AMI" published by the present applicant, Technical Report V of the Television Society.
ol. 14, No. 16. PP 33-38 (1990).

Basically, the AMI section has a plurality of image sensor elements (pixels) arranged and formed in a matrix, and receives a plurality of optical information signals output from a photoelectric conversion section connected by metal bumps, Each pixel is amplified individually, and is sequentially read out through the vertical and horizontal scanning switch circuits to form an XY address type. FIG. 2 shows the structure of one pixel of the visible light type AMI, and FIG. 3 shows its equivalent circuit. Here, members equivalent to the constituent members shown in FIG. 1 are designated by the same reference numerals.

One pixel of the AMI portion is provided with an n + p type photodiode b as a photoelectric conversion portion and a reset (Tr
s), three n for amplification (Ta) and vertical selection (Ty)
It is composed of a channel MOSFET. The horizontal switch Tx is provided for each vertical signal line. In the infrared image sensor, n + p shown in FIGS.
Instead of the photodiode b, the diode a has a structure as shown in FIG. In principle, the above n + p
A reverse bias is applied to the photodiode b, the photodiode is discharged by the photocharge generated by infrared rays in the structure of the diode as shown in FIG. 1, and the potential thereof is current-amplified and taken out. Next, the operation of the visible light type AMI will be described with reference to FIG. The operation of the visible light type AMI is divided into a reset period, a storage period, and a read period.

First, in the reset period, the photodiode b passes through the reset transistor Trs.
The initial value Vrs (positive potential) is set. Next, in the accumulation period, the electrons excited by the irradiation of infrared light are accumulated in the capacitance C _{PD of the} photodiode b. Therefore, the potential of the photodiode b decreases corresponding to the time when the infrared light is incident. This potential is applied to the gate of the amplification transistor Ta, and the current amplified according to the potential of the photodiode b is read out through the vertical scanning switch Ty and the horizontal scanning switch Tx (reading period). Since the photoelectric conversion unit and the amplification unit are extremely close to each other in the AMI, there is no mixing of noise or attenuation of the signal, and the AMI can be ideally amplified, so that an output with a good S / N ratio can be obtained. Next, FIG. 4 shows a basic arrangement configuration when it is used as an area sensor, and FIG. 5 shows its drive waveforms for explanation.

In this area sensor, a plurality of detecting portions (pixels) are arranged in a matrix, and a transistor switch Tx-1, which serves as a scanning switch for each horizontal and vertical line,
, Ty-1, Ty, Ty + 1, ... Are provided so that specific pixels can be selected.

When information is stored in each pixel in this configuration, the vertical scanning circuit 24 selects the nth row during reading, and vertical scanning is performed during one horizontal scanning period (one horizontal scanning period). The switch Ty is turned on. Meanwhile, the horizontal scanning circuit 25 sequentially turns on the horizontal scanning switch Tx to sequentially read signals for one horizontal line.

Then, the reading of the nth row is completed, and the next nth row is read.
At the same time as shifting to the + 1th row, the reset transistor Trs (not shown) provided in the nth row is changed to the next n + 1th row.
While all signals for one horizontal line in a row are read out, that is, 1
It is turned on during the horizontal scanning period, and the potential of the photodiode b is reset to the initial value Vrs.

The reset transistor Trs is 1
Since the photodiode b is turned on during the horizontal scanning period, the photodiode b is reliably reset to the initial value Vrs, and the cause of the afterimage is solved. Further, when interlacing is performed, the vertical resolution is not deteriorated because the upper and lower two pixels are read out pixel by pixel without being mixed.

Next, as a second embodiment of the solid-state image pickup device according to the present invention, an amplification type image pickup element is used instead of the AMI sensor.
IT (Static Induction Trans)
It is also possible to use an internal amplification type image sensor using an i-stor) as a signal reading element.

Further, although the information (image) incident on the internal amplification type image sensor of the present invention is composed of infrared rays in the embodiment, it is not limited to this. For example, a two-dimensional ion sensor that detects and reacts with sugar or amino acid can be formed by forming a layer of a receiving protein on the surface of the light receiving portion shown in FIG. Also, by forming a thin film of PbO on the surface, a two-dimensional X-ray sensor that detects X-rays and the like can be formed.

As described above, the solid-state image pickup device of the present invention is
The invention is not limited to the infrared image sensor, and the hybrid type image sensor or the laminated type image sensor can be applied to various two-dimensional image sensors for detecting ions, X-rays, ultraviolet rays, proteins and the like. Further, as described above, as the infrared sensor, there is a Schottky sensor made of P-Si and metal. Since this Schottky sensor usually has a structure in which a Schottky barrier is formed on a silicon substrate, a high-quality infrared sensor can be manufactured. But,
Along with the integration, a Schottky diode serving as an infrared sensor and a signal reading unit are formed on the same substrate, which has a drawback that the aperture ratio becomes low.

Therefore, a Schottky barrier layer can be bump-formed on the AMI of the present invention to improve the aperture ratio. That is, the compound semiconductor layer of the light receiving portion shown in FIG. 1 may be replaced with the Schottky barrier layer. FIG. 6 shows and describes the structure of the light receiving portion in which this Schottky barrier layer is formed. Here, the case where the P type is used for the silicon substrate will be described.

First, P ^{+ is formed} on one main surface of the P-type silicon substrate 31. A silicon layer 32 is formed, and a transparent electrode 33 such as ITO that transmits infrared rays is formed on the upper layer so as to have ohmic contact characteristics. Further, on the other main surface of the silicon substrate 31, for example, matrix-shaped S
forming an insulating film 34 made of iO _2.

Next, Pt- is formed on the region divided by the insulating film 34 and the other main surface of the silicon substrate 31 is exposed.
The metal film 35 made of Si, Ir-Si, TiSi, or the like,
It is formed to have a Schottky barrier property with the silicon substrate 31. An insulating film 36 is formed in a matrix on the insulating film 34 by covering the metal films 35.

Next, on each of the metal films 35, metal bumps 3 for connecting to a Si scanning circuit (not shown) are formed.
7 are formed so as to have ohmic contact characteristics with the metal film 35.

In the light receiving portion of this structure, light having information is incident from the surface of the transparent electrode 33 and the silicon substrate 3
A hole-electron pair is generated at the interface between 1 and the metal film 35, and the electrons of that pair flow into the metal layer 35. By using the Schottky barrier layer in the light receiving portion as described above, it is possible to form a hybrid infrared sensor. As described above, it goes without saying that various modifications and applications can be made without departing from the scope of the invention.

[0037]

As described above in detail, according to the present invention, it is possible to provide a solid-state image pickup device capable of non-destructive reading, high-speed reading and high image quality of information.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of a solid-state imaging device as a first embodiment according to the present invention.

FIG. 2 is a diagram showing a structure of one pixel of the solid-state imaging device of the first embodiment as a visible light type AMI.

3 is a diagram showing an equivalent circuit of the visible light type AMI shown in FIG.

FIG. 4 is a diagram showing a basic arrangement configuration when the solid-state imaging device of the first embodiment is used as an area sensor.

5 is a diagram showing drive waveforms of the area sensor shown in FIG.

FIG. 6 is a diagram showing a structure of a light receiving portion on which a Schottky barrier layer is formed.

FIG. 7 (a) is a diagram showing a configuration of a conventional infrared area sensor, and FIG. 7 (b) is a sectional view thereof.

8 is a diagram showing respective sensitivity characteristics when the mixing ratio of Hg and Cd in the p-type HgCdTe layer shown in FIG. 7 is changed.

[Explanation of symbols]

1, 11 ... Diode array, 2 ... Si scanning circuit section,
3, 13, 37 ... Metal bumps, 4, 14 ... Support substrate,
5,15 ... p-type HgCdTe layer, 6,16,18 ... n +
Diffusion layer, 12 ... Amplification type MOS image sensor (AMI)
, 17, 31 ... P-type semiconductor substrate, 19 ... Contact part, 20 ... First Al layer, 21 ... Second Al layer, 22 ... Third
Al layer, 23 ... Interlayer insulating film, 24 ... Vertical scanning circuit, 25
... horizontal scanning circuit, 32 ... P ⁺ Silicon layer, 33 ... Transparent electrode, 34, 36 ... Insulating film, 35 ... Metal film, a ... Diode, b ... Photodiode, Tx ... Horizontal scan switch, Ty ... Vertical scan switch, Trs ... Reset transistor.

Claims (4)

[Claims] 1. An infrared detection area means comprising a plurality of two-dimensionally arranged solid-state image pickup elements for receiving infrared rays having information, photoelectrically converting the infrared rays, and taking out as image information, and two-dimensional arrangement of the infrared detection area means. A plurality of read-out internal amplification type solid-state image pickup elements are arranged so as to correspond to the respective solid-state image pickup elements, and each internal amplification type solid-state image pickup element accumulates image information taken out from the infrared area sensor means for a predetermined time, A solid-state imaging device comprising: an image information reading unit that amplifies and outputs the image information; and a bump unit that transmits the image information from the infrared area sensor unit to the image information reading unit. 2. The internal amplification type solid-state imaging device is an amplification type M.
OS image sensor (AMI; Amplified M)
The solid-state image pickup device according to claim 1, which is made of an OS Imager. 3. The solid-state imaging device according to claim 1, wherein the infrared detection area means is made of a narrow band gap compound semiconductor layer. 4. The solid-state imaging device according to claim 1, wherein the infrared detection area means is made of a semiconductor layer having a Schottky barrier region.