JP2008211003A - Solid-state imaging device and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a picture quality by effectively supplying hydrogen in a solid-state imaging device and effectively suppressing noise generation. <P>SOLUTION: A hydrogen discharging film 160 for supplying hydrogen to a photodiode 110 and a pixel transistor 120 is formed on a silicon substrate 100 having the photodiode 110, the pixel transistor 120 and so on formed therein. A hydrogen shielding film 170 is formed on the film 160. Since the hydrogen discharging film 160 is located in the vicinity of the upper surface of the silicon substrate 100 and the hydrogen shielding film 170 is located on the film 160, the hydrogen of the hydrogen discharging film 160 can be shielded from being diffused in an upper layer direction, the hydrogen supply efficiency to the photodiode 110 or the transistor 120 can be increased, and noise suppression can be effectively attained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to various solid-state imaging devices such as a CCD image sensor and a CMOS image sensor, and more particularly to a solid-state imaging device capable of effectively reducing noise in an imaging signal and an imaging device using the same.

In recent years, solid-state imaging devices represented by CCD image sensors and CMOS image sensors have been actively developed, and are used in various camera devices and mobile phones.
For example, in a CCD image sensor, a plurality of pixels including photodiodes (photoelectric conversion units) are arranged in a two-dimensional direction on a semiconductor substrate, a CCD vertical transfer register is provided between each pixel row, and an output of each vertical transfer register is provided. A CCD horizontal transfer register is provided at the end.
A laminated film such as an insulating film, a transfer electrode film, and a light shielding film is sequentially formed on the semiconductor substrate, and a color filter, a microlens, and the like are further formed through a planarization film or the like.
In such a CCD image sensor, a driving pulse is supplied to a transfer electrode provided on a semiconductor substrate to drive each transfer register, and a signal charge generated by a photodiode of each pixel is transferred to a CCD vertical transfer register and a CCD horizontal transfer. The signal charges are sequentially transferred through the registers, and the signal charges are converted into voltage signals or current signals by a conversion unit provided at the output end of the CCD horizontal transfer register, and are output as pixel signals.

On the other hand, a CMOS image sensor is provided with an imaging region in which a plurality of pixels including photodiodes are arranged in a two-dimensional direction and a peripheral circuit region formed outside the imaging region on the same semiconductor substrate. .
In the imaging region, for each pixel, a readout transistor (transfer gate) that reads the signal charge of the photodiode to the FD (floating diffusion), an amplification transistor that generates a pixel signal corresponding to the potential of the FD, and a pixel signal Various pixel transistors such as a selection transistor for selecting a pixel to be output and a reset transistor for resetting the FD are provided, and signal charges detected by a photodiode of each pixel are converted into a pixel signal by driving each pixel transistor. Output from the provided signal line.
Further, in the peripheral circuit region, a drive control circuit that controls reading of pixel signals by supplying various control pulses to the pixel array unit, a signal processing circuit that performs various signal processing on the read pixel signals, A power supply control circuit for generating a drive power supply is provided.
A laminated film such as an insulating film, a transistor driving electrode film, a wiring film, and a light shielding film is sequentially formed on the semiconductor substrate, and a color filter, a microlens, and the like are further formed through a planarization film.
In such a CMOS image sensor, the signal charge accumulated in the photodiode of each pixel is converted into a pixel signal for each pixel by driving each pixel transistor, and this is output for each pixel column and is output to the signal processing circuit in the subsequent stage. Send, noise removal, signal processing, etc., and output.

By the way, in various solid-state imaging devices as described above, with the recent increase in the number of pixels, the area of the photodiode per pixel decreases, the amount of light reaching the photoelectric conversion unit also decreases, and the sensitivity decreases. ing.
For this reason, particularly at low illuminance, the influence of noise on image quality becomes large, and it is necessary to improve the S / N ratio.
Therefore, conventionally, it is known to suppress noise by supplying hydrogen to the photoelectric conversion unit and the transistor region.

FIG. 7 is a cross-sectional view showing a pixel structure of a CMOS image sensor according to a conventional example.
First, a photodiode (PD) 410 and a pixel transistor (Tr) 420 are formed in a region separated by the element isolation unit 401 in the upper layer portion of the silicon (Si) substrate 400. In addition, a lower layer laminated film 430 including a gate insulating film, a gate electrode film for driving a transistor, and the like is disposed on the surface of the silicon substrate 400, and a plurality of layers of wirings are formed thereon via various interlayer insulating films 440. A film 450 is formed.
In the conventional example, a hydrogen release film 460 containing hydrogen is formed on the interlayer insulating film 440, and a color filter 480 and an on-chip microlens 490 are formed thereon via a protective film 470 ( For example, see Patent Document 1).
JP 2002-231915 A

  However, in the above prior art, hydrogen from the hydrogen release film diffuses to regions other than the photodiode and the transistor, and accordingly, the amount of hydrogen supplied to the photodiode and the transistor is reduced, and effective noise removal is achieved. There was a problem that it could not be done.

  Accordingly, an object of the present invention is to provide a solid-state imaging device and an imaging device capable of effectively supplying hydrogen in the solid-state imaging device, effectively suppressing noise generation, and improving image quality. .

In order to achieve the above-described object, the solid-state imaging device of the present invention includes a semiconductor substrate on which a plurality of pixels each including a photoelectric conversion unit are formed, and a stacked film provided on the semiconductor substrate, The film includes a hydrogen release film that releases hydrogen, and a hydrogen barrier film disposed on an upper layer of the hydrogen release film.
Moreover, the imaging device of the present invention includes an imaging unit using a solid-state imaging device, a control unit that controls the imaging unit, and an operation unit that operates the imaging unit. A semiconductor substrate on which a plurality of pixels including a conversion unit are formed; and a stacked film provided on the semiconductor substrate, wherein the stacked film includes a hydrogen releasing film that releases hydrogen and an upper layer of the hydrogen releasing film And a hydrogen barrier film disposed on the substrate.

  According to the solid-state imaging device of the present invention, the hydrogen-releasing film is provided on the laminated film of the solid-state imaging device by providing the hydrogen-releasing film that releases hydrogen and the hydrogen-blocking film disposed above the hydrogen-releasing film. Without diffusing hydrogen released from unnecessary areas, it can be efficiently supplied to the photoelectric conversion part on the semiconductor substrate side, other transistors, transfer registers, etc., and a sufficient noise suppression effect can be realized by supplying sufficient hydrogen, The image quality in the solid-state imaging device can be improved.

  Further, according to the imaging device of the present invention, the stacked film of the solid-state imaging device used for the imaging unit is provided with a hydrogen releasing film that releases hydrogen and a hydrogen barrier film disposed on the upper layer of the hydrogen releasing film. Therefore, the hydrogen released from the hydrogen release film can be efficiently supplied to the photoelectric conversion unit on the semiconductor substrate side, other transistors, transfer registers, etc. without diffusing to unnecessary areas. The suppression effect can be realized, and the image quality in the imaging unit can be improved.

  FIG. 1 is a plan view showing a specific example of a solid-state imaging device in an embodiment of the present invention, and shows an example of a CMOS image sensor. FIG. 2 is a circuit diagram showing a circuit configuration in a pixel of the solid-state imaging device shown in FIG. Although the following embodiments will be described focusing on a CMOS image sensor, the present invention can be similarly applied to a CCD image sensor.

As shown in FIG. 1, the solid-state imaging device of the present embodiment includes a pixel array unit 20 that forms an imaging region by a plurality of pixels 16 arranged in a two-dimensional direction, and each pixel of the pixel array unit 20 is arranged in the vertical direction. A vertical scanning circuit 21 that scans and controls a pixel signal reading operation, a load MOS transistor circuit 24 that controls a vertical signal line 28 led from each pixel column of the pixel array unit 20, and a pixel array unit 20 A CDS circuit 26 that takes in pixel signals read from each pixel column and removes noise by correlated double sampling processing, a horizontal selection transistor circuit 26 that outputs pixel signals of the CDS circuit 26 to a horizontal signal line 27, A horizontal scanning circuit 22 for sequentially selecting the horizontal selection transistor circuit 26 in the horizontal direction and controlling the output of the pixel signal.
The pixel signal output to the horizontal signal line 27 is transmitted to the subsequent circuit through the buffer amplifier.

Further, as shown in FIG. 2, each pixel 16 includes a photodiode (PD) 1 that photoelectrically converts incident light, and a floating diffusion (FD) based on a transfer pulse (ΦTRG) of the photoelectrically converted electric signal. The transistor (TG) 12 transferred to the unit 3, the reset transistor (RST) 14 that resets the potential of the FD unit 3 to the power supply voltage VDD based on the reset pulse (ΦRST), and the potential fluctuation of the FD unit 3 as a voltage signal or current An amplification transistor (AMP) 13 that converts the signal into a signal and a selection transistor 15 that connects the output of the amplification transistor 13 to the vertical signal line 28 based on the selection signal (ΦSEL).
Therefore, in the vicinity of the pixel 16, a vertical signal line 28, a power supply line, and the like are wired in the vertical direction, and a readout line 17, a reset line 18, a selection line 19, and the like are wired in the horizontal direction.

FIG. 3 is a cross-sectional view showing the pixel structure of the CMOS image sensor according to this embodiment.
First, a photodiode (PD) 110, a pixel transistor (Tr) 120, and the like are formed in a region isolated by the element isolation unit 101 in the upper layer portion of the silicon (Si) substrate 100. Note that the pixel transistor 120 includes the above-described transistors such as transfer, amplification, and reset.
On the surface of the silicon substrate 100, a lower layer laminated film 130 including a gate insulating film, a gate electrode film for driving a transistor, and other functional films (for example, a CoBlock film) is disposed.

In this embodiment, a hydrogen release film 160 for supplying hydrogen to the photodiode 110 and the transistor 120 is formed on the lower laminated film 130, and a hydrogen barrier that prevents diffusion of hydrogen on the hydrogen release film 160 is formed. A film 170 is formed.
The hydrogen release film 160 contains hydrogen and is a film that stably releases hydrogen.
Further, the hydrogen blocking film 170 prevents the hydrogen released from the hydrogen releasing film 160 from diffusing upward and leads it toward the silicon substrate 100.
In this example, for example, UV-SiN is used for the hydrogen release film 160 and P-SiN is used for the hydrogen barrier film 170, for example. However, as long as it has the same function, it is needless to say that other films are used.
In some cases, among the films formed below the hydrogen release film 160 on the surface of the silicon substrate 100, a fine opening (not shown) is formed as necessary for a film with poor hydrogen permeability. The hydrogen supply into the silicon substrate 100 may be assisted.

A plurality of layers of wiring films 190 are formed on the hydrogen barrier film 170 via various interlayer insulating films 180, and a color filter 210 and an on-chip microlens 220 are formed thereon.
In such a configuration, by disposing the hydrogen release film 160 in the vicinity of the upper surface of the silicon substrate 100, sufficient hydrogen can be supplied to the underlying photodiode 110 and the transistor 120, and noise suppression can be effectively achieved. In addition, since the hydrogen blocking film 170 is disposed immediately above the hydrogen releasing film 160, hydrogen in the hydrogen releasing film 160 can be blocked from diffusing in the upper layer direction, and the efficiency of supplying hydrogen to the photodiode 110 and the transistor 120 can be improved. .

FIG. 4 is a cross-sectional view showing the manufacturing process of the embodiment shown in FIG.
First, in FIG. 4A, an element isolation portion 101, a photodiode 110, a pixel transistor 120, and the like are formed on a silicon substrate 100, and a gate insulating film, a gate electrode film, and other functional films are formed on the surface of the silicon substrate 100. A lower laminated film 130 containing is formed.
Therefore, in FIG. 4B, a predetermined pattern including the opening 131 is formed on these films using photolithography and etching. At this time, apart from a necessary pattern, a fine opening for facilitating supply of hydrogen to the silicon substrate 100 side is formed. Of course, this opening is formed in a shape that does not hinder the function of each film.
4C, a hydrogen release film 160 is formed thereon, and in FIG. 4D, a hydrogen barrier film 170 is formed on the hydrogen release film 160.
Thereafter, an upper layer film is sequentially formed in the same manner as in the conventional process, and a structure of a solid-state imaging device as shown in FIG.

In the solid-state imaging device of the present embodiment as described above, the hydrogen releasing film 160 and the hydrogen blocking film 170 are arranged in the laminated film laminated on the silicon substrate 100, so that photodiodes and transistors (other than the pixel region) are arranged. Sufficient hydrogen can be supplied to the transistor (including the transistor), and noise can be suppressed.
In addition, when there is a film that is difficult for hydrogen to pass under the hydrogen releasing film 160 (on the silicon substrate side), an opening is appropriately formed in the film, so that the hydrogen in the hydrogen releasing film 160 is effectively used as a photodiode. In addition, hydrogen can be supplied to the transistor, and a higher noise suppression effect can be obtained.

Next, another embodiment will be described.
FIG. 5 is a cross-sectional view showing the pixel structure of the CMOS image sensor according to this embodiment. In FIG. 5, the same components as those shown in FIG.
In the embodiment shown in FIG. 3, the hydrogen release film 160 is formed on the lower laminated film 130 having the opening 131 so that the hydrogen release film 160 and the silicon substrate 100 are in direct contact with each other. In the embodiment, a hydrogen passage film 230 is provided between the hydrogen release film 160 and the silicon substrate 100.
In FIG. 5, first, a photodiode (PD) 110, a pixel transistor (Tr) 120, and the like are formed in a region separated by the element isolation portion 101 in the upper layer portion of the silicon (Si) substrate 100.
Further, a lower layer laminated film 130 including a gate insulating film, a gate electrode film for driving a transistor, and other functional films is disposed on the surface of the silicon substrate 100.

In this lower layer laminated film 130, openings 131 corresponding to the pattern of the lower layer laminated film 130 and openings for assisting the supply of hydrogen into the silicon substrate 100 are formed. A hydrogen passage film 230 is formed in the corresponding lower layer region. The hydrogen passage film 230 is made of, for example, SiO ₂ . Then, a lower laminated film 130 is formed thereon, and a hydrogen release film 160 and a hydrogen blocking film 170 are further formed thereon.
By providing such a hydrogen passage film 230, direct contact between the silicon substrate 100 and the hydrogen release film 160 can be avoided, generation of the interface order can be suppressed, and signal characteristics can be stabilized.
The rest is the same as the embodiment shown in FIG.

The specific embodiments of the solid-state imaging device according to the present invention have been described above, but the present invention can be further modified in various ways. For example, in the above embodiment, the CMOS image sensor has been described as an example. However, the present invention is not limited to the CMOS image sensor, and can be applied to other solid-state imaging devices such as a CCD image sensor.
For example, in a CCD image sensor, a hydrogen release film and a hydrogen blocking film are provided on a transfer electrode film and a light shielding film on a silicon substrate. It is possible to suppress noise.

Further, the configuration of the pixel array unit is not necessarily limited to the two-dimensional array area sensor type solid-state imaging device, and can be applied to a one-dimensional array linear sensor type solid-state imaging device.
In addition, the position in the stack where the hydrogen releasing film and the hydrogen blocking film are provided can be changed as appropriate, and can be flexibly handled according to the stacked structure of the solid-state imaging device to be applied.
In addition, by forming a hydrogen passage film between the hydrogen release film and the hydrogen barrier film described above, the hydrogen release film and the hydrogen barrier film are not in direct contact with each other, and the structure is stabilized. It is also possible.
The hydrogen releasing film and the hydrogen blocking film can be formed on the entire surface of the semiconductor chip. However, the hydrogen releasing film and the hydrogen blocking film may be formed in a partial region where hydrogen supply is particularly desired to be controlled.

  The solid-state imaging device is not limited to an image sensor or the like configured on one chip, and may be a module in which an imaging unit, a signal processing unit, and an optical system are packaged together. Moreover, the apparatus utilized for a camera system or a mobile telephone device may be used. In the present invention, a configuration having a CMOS image sensor function alone is called a solid-state imaging device, and the solid-state imaging device and other elements (control circuit, operation unit, display unit, data storage function, communication function, etc.) An integrated configuration is referred to as an imaging device.

Hereinafter, a specific example of an imaging apparatus to which the present invention is applied will be described.
FIG. 6 is a block diagram showing a configuration example of a camera device using the CMOS image sensor of this example.
In FIG. 6, an imaging unit 310 performs imaging of a subject using, for example, the CMOS image sensor shown in FIG. 1, and outputs an imaging signal to a system control unit 320 mounted on the main board.
That is, the imaging unit 310 performs processing such as AGC (automatic gain control), OB (optical black) clamping, CDS (correlated double sampling), and A / D conversion on the output signal of the above-described CMOS image sensor, and performs digital processing. An imaging signal is generated and output.

In this example, an example in which an imaging signal is converted into a digital signal and output to the system control unit 320 in the imaging unit 310 is shown. However, an analog imaging signal is sent from the imaging unit 310 to the system control unit 320, and the system The control unit 320 may convert to a digital signal.
Various methods have been conventionally provided for specific control operations, signal processing, and the like in the imaging unit 310, and it is needless to say that the imaging device of the present invention is not particularly limited.

  The imaging optical system 300 includes a zoom lens 301 and an aperture mechanism 302 disposed in a lens barrel, and forms a subject image on the light receiving unit of the CMOS image sensor. Under the control of the drive control unit 330 based on this, each part is mechanically driven to perform control such as autofocus.

The system control unit 320 includes a CPU 321, a ROM 322, a RAM 323, a DSP 324, an external interface 325, and the like.
The CPU 321 uses the ROM 322 and the RAM 323 to send an instruction to each part of the camera apparatus to control the entire system.
The DSP 324 performs various kinds of signal processing on the imaging signal from the imaging unit 310, thereby generating a still image or moving image video signal (for example, a YUV signal) in a predetermined format.
The external interface 325 is provided with various encoders and D / A converters, and with external elements (in this example, the display 330, the memory medium 340, and the operation panel unit 350) connected to the system control unit 320. Various control signals and data are exchanged.

The display 330 is a small display such as a liquid crystal panel incorporated in the camera apparatus, and displays a captured image. In addition to the small display device incorporated in such a camera device, it is of course possible to transmit the image data to an external large display device for display.
The memory medium 340 can appropriately store images taken on various memory cards, for example, and the memory medium can be exchanged with the memory medium controller 341, for example. As the memory medium 340, in addition to various memory cards, a disk medium using magnetism or light can be used.
The operation panel unit 350 is provided with input keys for a user to give various instructions when performing a photographing operation with the camera device. The CPU 321 monitors an input signal from the operation panel unit 350, Various operation controls are executed based on the input contents.

  By applying the present invention to such a camera device, it is possible to provide a high-quality imaging device such as an improvement in image quality and a reduction in the size of the device. In the above configuration, unit devices and unit modules as system components, a combination method, a set size, and the like can be appropriately selected based on the actual state of commercialization and the like. The device shall include a wide variety of variations.

In the solid-state imaging device and imaging device of the present invention, the imaging target (subject) is not limited to a general image such as a person or a landscape, but a special fine image pattern such as a counterfeit bill detector or a fingerprint detector. It can also be applied to.
The apparatus configuration in this case is not the general camera apparatus shown in FIG. 5, but further includes a special imaging optical system and a signal processing system including pattern analysis. In this case as well, the operational effects of the present invention are included. This makes it possible to realize accurate image detection.
Furthermore, when configuring a remote system such as telemedicine, security monitoring, personal authentication, etc., it is also possible to configure the device configuration including a communication module connected to the network as described above, and a wide range of applications can be realized. It is.

It is a top view which shows the specific example of the solid-state imaging device in the Example of this invention. FIG. 2 is a circuit diagram showing a circuit configuration in a pixel of the solid-state imaging device shown in FIG. 1. 1 is a cross-sectional view illustrating a pixel structure of a CMOS image sensor according to an embodiment of the present invention. FIG. 4 is a cross-sectional view showing a manufacturing process of the CMOS image sensor shown in FIG. 3. It is sectional drawing which shows the pixel structure of the CMOS image sensor by the other Example of this invention. It is a block diagram which shows the structural example of the camera apparatus in the further another Example of this invention. It is sectional drawing which shows the pixel structure of the CMOS image sensor by a prior art example.

Explanation of symbols

  110... Photodiode, 120... Transistor, 131... Opening, 160... Hydrogen release film, 170. 220... On-chip microlens, hydrogen passage film 230.

Claims (10)

A semiconductor substrate on which a plurality of pixels each including a photoelectric conversion unit are formed, and a laminated film provided on the semiconductor substrate;
The stacked film includes a hydrogen releasing film that releases hydrogen, and a hydrogen barrier film disposed on an upper layer of the hydrogen releasing film,
A solid-state imaging device.   The solid-state imaging device according to claim 1, wherein an opening of a film that hardly allows hydrogen to pass between the semiconductor substrate and the hydrogen release film is provided.   The solid-state imaging device according to claim 1, wherein a hydrogen passage film is disposed between the semiconductor substrate and the hydrogen release film.   The solid-state imaging device according to claim 1, wherein a hydrogen passage film is disposed between the hydrogen release film and the hydrogen barrier film.   The stacked film includes a layer including an electrode film for driving the photoelectric conversion unit in a layer adjacent to the semiconductor substrate, and the hydrogen releasing film is formed on the layer including the electrode film. The solid-state imaging device according to claim 1. An imaging unit using a solid-state imaging device, a control unit that controls the imaging unit, and an operation unit that operates the imaging unit,
The solid-state imaging device
A semiconductor substrate on which a plurality of pixels each including a photoelectric conversion unit are formed, and a laminated film provided on the semiconductor substrate;
The stacked film includes a hydrogen releasing film that releases hydrogen, and a hydrogen barrier film disposed on an upper layer of the hydrogen releasing film,
An imaging apparatus characterized by that.   The imaging apparatus according to claim 6, wherein an opening of a film that hardly allows hydrogen to pass between the semiconductor substrate and the hydrogen release film is provided.   The imaging apparatus according to claim 6, wherein a hydrogen passage film is disposed between the semiconductor substrate and the hydrogen release film.   The imaging apparatus according to claim 6, wherein a hydrogen passage film is disposed between the hydrogen release film and the hydrogen barrier film.   The stacked film includes a layer including an electrode film for driving the photoelectric conversion unit in a layer adjacent to the semiconductor substrate, and the hydrogen releasing film is formed on the layer including the electrode film. The imaging device according to claim 6.

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