JP4470364B2 - Solid-state imaging device and camera device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides a solid-state imaging device such as a CMOS type image sensor for detecting and reading out photoelectric charges by providing a photoelectric conversion element, a floating diffusion (FD), and a pixel transistor for each of a plurality of pixels constituting the imaging region section, and The present invention relates to a camera device using the solid-state image sensor.
[0002]
[Prior art]
As a conventional CMOS type solid-state imaging device, those having various pixel configurations are known. For example, a photodiode (PD) that is a photoelectric conversion device that generates charges according to the amount of received light, and a PD of this PD A floating diffusion (FD) for detecting a signal charge, a transfer transistor (transfer gate) for transferring the signal charge of the PD to the FD, an amplifying transistor for detecting an electric potential change of the FD and outputting an electric signal, There is provided a transistor including a reset transistor that resets the potential to the power supply potential and a selection transistor that activates the amplification transistor and connects it to the output signal line.
[0003]
FIG. 5 is a cross-sectional view showing the structure of the periphery of the photodiode of such a conventional CMOS solid-state imaging device.
In this CMOS type solid-state imaging device, P well regions 42 and 44 as element forming regions are formed in an upper layer portion of a semiconductor substrate (N type silicon substrate) 40, and PD 46 and various gate elements are provided in the P well regions 42 and 44. Is formed. In the illustrated example, a PD 46, a transfer gate (MOS transistor) 48, and an FD 50 are formed in the P well region 42, and a MOS transistor 52 in the peripheral circuit portion is formed in the P well region 44.
[0004]
A polysilicon transfer electrode 56 for each gate is formed on the semiconductor substrate 40 via a gate insulating film 54, and multilayer wiring layers 60, 62, 64 are formed on the upper layer via an interlayer insulating film 58. Has been. The wiring film of the upper layer film 64 of this multilayer wiring layer is formed as a light shielding film.
Although omitted in FIG. 5, a contact is provided in the upper layer of the FD 50, and is connected to the gate of the amplification transistor (not shown in FIG. 5) via a multilayer wiring layer.
On the multilayer wiring layer, a color filter 72 and a microlens 74 are arranged via a protective film (SiN) 70.
[0005]
[Problems to be solved by the invention]
As described above, in the CMOS type solid-state imaging device, the pixels are also manufactured using the same CMOS process as that of the peripheral circuit. Therefore, compared to the case of the CCD type solid-state imaging device, the light-shielding film (wiring layer 64) is dropped closer to the PD 46. It is not possible to make a structure in which light is incident only on the PD 46.
Moreover, since there are many metal wiring layers, light is irregularly reflected in each layer. For this reason, as can be seen from FIG. 5, a large amount of light leaks into the FD 50, which hinders proper image detection.
In this case, light leakage may occur particularly in driving that stores signal charges in the FD for a long time, for example, non-destructive reading multiple times or simultaneous shutters in which all the pixels simultaneously transfer signal charges to the FD and read them one row at a time. The image quality is greatly degraded. Even when the signal charge is stored in the FD for a short time, when a high-luminance subject such as the sun enters, the potential of the FD fluctuates significantly during that time, and the signal is not normal.
[0006]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a solid-state imaging device and a camera device capable of effectively shielding FD and improving image quality when each pixel circuit of an imaging pixel unit is formed using a CMOS process. Is to provide.
[0007]
[Means for Solving the Problems]
In order to achieve the above-described object, the present invention provides a solid-state imaging device including an imaging region unit provided with a plurality of pixels and a processing circuit unit that processes an image signal output from the imaging region unit. A photoelectric conversion element that generates a signal charge according to the amount of received light, a floating diffusion unit that detects the amount of signal charge generated by the photoelectric conversion element, and a signal charge generated by the photoelectric conversion element to the floating diffusion unit A transfer transistor for transferring, an amplification transistor for outputting an electric signal corresponding to the potential of the floating diffusion portion, and a reset transistor for resetting a signal charge of the floating diffusion portion, and the imaging region portion and the processing circuit portion Multiple layers of gate electrode films of included transistors And forming gate electrodes of the transfer transistor and the reset transistor by using a gate electrode film on a lower layer side of the gate electrode of the multi-layer structure, and an upper layer of the gate electrode film of the multi-layer structure on the upper surface of the floating diffusion portion A light shielding film that also serves as a contact of the floating diffusion portion is formed using the side gate electrode film, the light shielding film is directly connected to the floating diffusion portion, and a part of the light shielding film extends to the amplification transistor side. It is characterized by being a gate electrode of an amplification transistor .
[0008]
According to the present invention, in the camera device that outputs an image picked up by a solid-state image pickup device, the solid-state image pickup device performs processing of an image pickup area section provided with a plurality of pixels and an image signal output from the image pickup area section. A processing circuit unit, and the pixel includes a photoelectric conversion element that generates a signal charge according to a received light amount, a floating diffusion unit that detects a signal charge amount generated by the photoelectric conversion element, and the photoelectric conversion element A transfer transistor that transfers the signal charge generated by the floating diffusion unit to the floating diffusion unit, an amplification transistor that outputs an electric signal corresponding to the potential of the floating diffusion unit, and a reset transistor that resets the signal charge of the floating diffusion unit. Having the imaging area section and the processing circuit section The gate electrode film of the transistor to be turned has a multi-layer structure, and the gate electrodes of the transfer transistor and the reset transistor are formed using a gate electrode film on the lower layer side of the gate electrode of the multi-layer structure, and is formed on the upper surface of the floating diffusion portion. Using the gate electrode film on the upper layer side of the multi-layered gate electrode film, a light shielding film that also serves as a contact of the floating diffusion portion is formed, and the light shielding film is directly connected to the floating diffusion portion, and the light shielding film Is partially extended to the amplification transistor side to serve as a gate electrode of the amplification transistor .
[0009]
In the solid-state imaging device and camera device of the present invention, the gate electrode films of the transistors included in the imaging region unit and the processing circuit unit have a multi-layer structure, and the gate electrodes of the transfer transistor and the reset transistor are on the lower layer side of the multi-layer gate electrode. Since the gate electrode film on the upper layer side of the gate electrode film having the multi-layer structure is formed on the upper surface of the floating diffusion portion, the light shielding film that also serves as the contact of the floating diffusion portion is formed. When each pixel circuit of the imaging pixel unit is formed using the CMOS process, the floating diffusion unit can be effectively shielded from light, and the image quality of the output layer can be improved.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a solid-state imaging device and a camera device according to the present invention will be described below.
In this embodiment, the gate electrode of each transistor of the CMOS solid-state imaging device has a two-layer structure, the gate electrode film of the transfer transistor or the reset transistor is formed using the lower gate electrode film, and the upper gate electrode film is used. By using this light shielding film as a gate electrode of the amplification transistor by extending this light shielding film to the amplification transistor side, it is possible to effectively shield the FD in a manufacturing process using a conventional CMOS process. The connection between the FD and the amplification transistor can be realized without using a contact or an upper layer wiring.
[0011]
FIG. 1 is a block diagram showing a configuration example of a camera system according to an embodiment of the present invention.
This camera system includes an imaging lens system 101, a solid-state imaging device 102, an analog circuit 103, an A / D converter 104, a camera signal processing circuit 105, a compression / decompression circuit 106, and a storage medium 107.
First, the light ray incident from the imaging lens system 101 forms an image on the two-dimensional pixel array of the solid-state imaging device 102. The solid-state image sensor 102 is an element such as a CMOS image sensor, and has an all-pixel simultaneous shutter function (reset / FD transfer) and a function of sequentially reading out rows from the FD, which are features of the present embodiment.
[0012]
The analog circuit 103 performs processing such as CDS (correlated double sampling) and AGC (auto gain control). The image signal processed by the analog circuit 103 is converted from analog data to digital data by the A / D converter 104 and output to the camera signal processing circuit 105.
The camera signal processing circuit 105 is a circuit that performs signal processing such as color signal processing, gain control processing, and white balance processing for converting the output data of the solid-state imaging device 102 into a video signal.
The compression / decompression circuit 106 is a circuit that compresses or decompresses the image data processed by the camera signal processing circuit 105 and converts the image into a format that can be stored in the storage medium 107. The storage medium 107 is, for example, a memory stick and is an example of a unit that outputs image data, but may be, for example, a display panel or various networks.
[0013]
FIG. 2 is a block diagram illustrating a configuration example of the solid-state imaging device 102 and the analog circuit 103 illustrated in FIG.
As shown in the figure, the solid-state imaging device of this example includes a pixel unit (imaging region unit) 210, a constant current unit 220, a column signal processing unit (column unit) 230, and a vertical (V) selection driving unit on a semiconductor element substrate 200. 240, a horizontal (H) selection unit 250, a horizontal signal line 260, an output processing unit 270, a timing generator (TG) 280, and the like.
The pixel unit 210 has a large number of pixels arranged in a two-dimensional matrix, and a pixel circuit as shown in FIG. 3 is provided for each pixel. The signal of each pixel from the pixel unit 210 is output to the column signal processing unit 230 through a vertical signal line (not shown in FIG. 2) for each pixel column.
In the constant current section 220, a constant current source (not shown in FIG. 2) for supplying a bias current to each pixel is arranged for each pixel column.
The V selection driving unit 240 selects each pixel of the pixel unit 210 one row at a time, and drives and controls the shutter operation and readout operation of each pixel.
[0014]
The column signal processing unit 230 receives the signal of each pixel obtained through the vertical signal line one row at a time, performs predetermined signal processing for each column, and temporarily holds the signal. For example, CDS (removing fixed pattern noise caused by variations in threshold values of pixel transistors) processing, AGC (auto gain control) processing, A / D conversion processing, and the like are appropriately performed.
The H selection unit 250 selects the signals of the column signal processing unit 230 one by one and guides them to the horizontal signal line 260.
The output processing unit 270 performs predetermined processing on the signal from the horizontal signal line 160 and outputs the signal to the outside, and has, for example, a gain control circuit and a color processing circuit. Instead of performing A / D conversion by the column signal processing unit 230, it may be performed by the output processing unit 270.
The timing generator 280 supplies various pulse signals necessary for the operation of each unit based on the reference clock.
[0015]
FIG. 3 is a circuit diagram showing a configuration example of a pixel circuit provided in each pixel of the solid-state imaging device shown in FIG.
In the configuration shown in the figure, a photodiode (PD) 219 and five pixel transistors (Tr) 211, 212, 213, 214, and 215 for transfer, amplification, selection, reset, and discharge are provided in each pixel.
The PD 219 accumulates electrons generated by photoelectric conversion, and transfers the electrons of the PD 219 to the floating diffusion (FD) 216 by turning on the transfer Tr 211. Since the FD 216 has a parasitic capacitance, photoelectrons are stored here.
[0016]
The amplifying Tr 212 has a gate connected to the FD 216 and converts a potential fluctuation of the FD 216 into an electric signal. The selection Tr 213 selects a pixel from which a signal is read out in units of rows. When the selection Tr 213 is turned on, the amplification Tr 212 and the constant current source 218 connected to the vertical signal line 217 outside the pixel form a source follower. Therefore, a voltage interlocked with the voltage of the FD 216 is output to the vertical signal line.
The reset Tr 214 resets the potential of the FD 216 to the wiring of Vdd.
The discharge Tr 215 directly resets the photoelectrons of the PD 219 to the wiring of the power supply Vdd. The wiring of the power supply Vdd is common to all pixels.
[0017]
Further, the wirings 211A, 213A, and 214A of the transfer Tr 211, the selection Tr 213, and the reset Tr 214 extend in the horizontal direction (horizontal = row direction), and simultaneously drive pixels included in the same row. Thereby, it is possible to cope with driving of the focal plane shutter.
Further, the wiring 215A of the discharge Tr 215 extends vertically, but is short-circuited at the upper and lower ends of the pixel portion, and is common to all the pixels.
[0018]
Next, as the PD 219, an embedded PD is used. For example, in the case of a photodiode in a P-well, the buried PD is a p-type region in the vicinity of the interface of the gate oxide film, and an n-type region is formed thereunder. Since the interface is covered with the p + region, dark current generated at the interface can be prevented.
In addition, if the design of the transfer Tr 211 and the PD 219 is appropriate, all the photoelectrons of the PD 219 can be transferred to the FD 216, which is a structure widely used in CCD sensors. For example, it is commercialized under the name HAD (Hole Accumulation Diode).
[0019]
Next, the maximum feature point in the present embodiment will be described.
That is, in this example, the gate wiring layer (electrode film) of each transistor formed by the CMOS process is made into two layers, and in the pixel Tr around the PD 219, the gate electrode film of the lower layer is used as the gate electrode of the transfer Tr 211 and the reset Tr 214. The upper gate electrode film is used as a light shielding film of the FD 216. Further, this light shielding film is extended and used as a gate electrode of the amplification Tr 212 to transmit the potential fluctuation of the FD 216 to the gate of the amplification Tr 212.
Note that at least the material of the upper gate wiring layer used as the light-shielding film needs to have light-shielding properties, and it is necessary to have heat resistance in the CMOS process. Specifically, a material having a high light-shielding property such as a refractory metal silicide such as tungsten silicide or cobalt silicide is used, and the entire upper surface or almost the entire surface of the FD is covered therewith.
The lower gate wiring layer is not particularly limited, and may be a polysilicon film or the like.
[0020]
FIG. 4 is a cross-sectional view showing the manufacturing process of the PD peripheral portion according to the present embodiment.
4A, in the P well region 310 provided in the silicon substrate 300, the p + region 219A and the n region 219B of the PD 219, the FD (n + region) 216, and the drain (n + region) of the reset Tr 214. ) 214C is formed.
On the silicon substrate 300, the gate electrode 211B of the transfer Tr 211 and the gate electrode 214B of the reset Tr 214 are formed via the gate insulating film 320, and the insulating film 330 is formed thereon. Here, the gate electrodes 2 11B, 214B is formed by a lower wiring layer of the two-layer gate interconnection layer described above.
[0021]
Next, in FIG. 4B, the gate insulating film 320 over the FD 216 is removed by etching or the like to form a contact opening 320A, and the upper surface region of the FD 216 is exposed.
Next, in FIG. 4C, a light shielding film 340 is formed over the FD 216. The light shielding film 340 is connected to the FD 216 through the opening 320A, and the peripheral part is formed in a state where it rides on the gate electrode 211 B of the transfer Tr 211 and the gate electrode 214 B of the reset Tr 214 via the insulating film 330. And formed so as to cover the FD 216.
By these, the light shielding film 340 can be formed in the area | region which FD216 adjoined, and can shield light effectively.
As a result, light illegally incident on the FD 216 after the reset can be prevented to the maximum even though it is a CMOS sensor.
Although not shown in the drawing, the second-layer gate wiring (light-shielding film) 340 connected to the FD 216 can be extended to the amplification Tr 212 side to be a gate electrode of the amplification Tr 212.
Further, if the gate electrode 211B of the transfer Tr 211 and the gate electrode 214B of the reset Tr 214 are the same material having high light shielding properties as the light shielding film 340, the light shielding effect is further enhanced, which is more preferable.
[0022]
In the above example, the gate wiring layer is made into two layers, but it may have a multilayer wiring layer. That is, in this example, “two layers” means at least two layers of a lower electrode film used for the gate electrodes of the transfer transistor and the reset transistor and an upper electrode film used for shielding and connecting the FD, and other wirings. The configuration of the layer (electrode film) is not particularly limited.
In the above description, the electrode film serving as a light shielding film for shielding the FD is formed as the gate electrode by extending to the amplification transistor side. However, such a wiring structure is not necessarily used. Alternatively, a contact plug or the like may be used for connection, and the connection may be appropriately selected based on the convenience of other element arrangements.
In addition, the element configuration of the solid-state imaging device and the configuration of the pixel circuit are not limited to the above-described examples, and can be widely applied to various forms.
Furthermore, although the above-described example is configured as a camera device, it is needless to say that the present invention can be configured as a single solid-state imaging device.
[0023]
【The invention's effect】
As described above, in the solid-state imaging device and camera device of the present invention, the gate electrode films of the transistors included in the imaging region unit and the processing circuit unit have a multi-layer structure, and the gate electrodes of the transfer transistor and the reset transistor have a multi-layer structure. Formed by using the gate electrode film on the lower layer side of the gate electrode, and using the gate electrode film on the upper layer side of the gate electrode film of the multi-layer structure on the upper surface of the floating diffusion portion, light shielding that also serves as a contact of the floating diffusion portion Since the film is formed , when each pixel circuit of the imaging pixel unit is formed using the CMOS process, the floating diffusion unit can be effectively shielded from light, and the image quality of the output image can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration example of a camera system according to an embodiment of the present invention.
2 is a block diagram illustrating a configuration example of a solid-state imaging device and an analog circuit of the camera system illustrated in FIG.
3 is a circuit diagram illustrating a configuration example of a pixel circuit provided in each pixel of the solid-state imaging device illustrated in FIG. 2;
4 is a cross-sectional view showing a manufacturing process of a PD peripheral portion of the solid-state imaging device shown in FIG. 2;
FIG. 5 is a cross-sectional view showing the structure of a conventional CMOS solid-state image sensor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Imaging lens system, 102 ... Solid-state image sensor, 103 ... Analog circuit, 104 ... A / D converter, 105 ... Camera signal processing circuit, 106 ... Compression / decompression circuit, 107 ... Storage medium, 200 ...... Semiconductor element substrate, 210 ...... Pixel part, 211 ...... Transfer Tr, 212 ...... Amplification Tr, 213 ...... Selection Tr, 214 ...... Reset Tr, 215 ...... Discharge Tr, 216 ...... FD, 219 ...... PD, 220 ... constant current section, 230 ... column signal processing section, 240 ... vertical (V) selection drive means, 250 ... horizontal (H) selection means, 260 ... horizontal signal line, 270 ... output processing Part, 280... Timing generator, 340.

Claims (4)

In a solid-state imaging device having an imaging region unit provided with a plurality of pixels, and a processing circuit unit that processes an image signal output from the imaging region unit,
The pixel includes a photoelectric conversion element that generates a signal charge according to a received light amount, a floating diffusion unit that detects a signal charge amount generated by the photoelectric conversion element, and a signal charge generated by the photoelectric conversion element. A transfer transistor that transfers to the floating diffusion portion, an amplification transistor that outputs an electrical signal corresponding to the potential of the floating diffusion portion, and a reset transistor that resets the signal charge of the floating diffusion portion,
A gate electrode film of a transistor included in the imaging region portion and the processing circuit portion has a multi-layer structure, and gate electrodes of the transfer transistor and the reset transistor are formed using a gate electrode film on a lower layer side of the multi-layer gate electrode. And
Using the gate electrode film on the upper layer side of the gate electrode film of the multi-layer structure on the upper surface of the floating diffusion part, forming a light shielding film that also serves as a contact of the floating diffusion part ,
Directly connecting the light-shielding film to the floating diffusion portion;
A part of the light shielding film extends to the amplification transistor side, and serves as a gate electrode of the amplification transistor
Solid-state imaging device. The light shielding film is formed of a refractory metal silicide.
Solid-state image pickup element 請 Motomeko 1 wherein. In a camera device that outputs an image captured by a solid-state image sensor,
The solid-state imaging device includes an imaging region unit provided with a plurality of pixels, and a processing circuit unit that processes an image signal output from the imaging region unit,
The pixel includes a photoelectric conversion element that generates a signal charge according to a received light amount, a floating diffusion unit that detects a signal charge amount generated by the photoelectric conversion element, and a signal charge generated by the photoelectric conversion element. A transfer transistor that transfers to the floating diffusion portion, an amplification transistor that outputs an electrical signal corresponding to the potential of the floating diffusion portion, and a reset transistor that resets the signal charge of the floating diffusion portion,
A gate electrode film of a transistor included in the imaging region portion and the processing circuit portion has a multi-layer structure, and gate electrodes of the transfer transistor and the reset transistor are formed using a gate electrode film on a lower layer side of the multi-layer gate electrode. And
Using the gate electrode film on the upper layer side of the gate electrode film of the multi-layer structure on the upper surface of the floating diffusion part, forming a light shielding film that also serves as a contact of the floating diffusion part,
Directly connecting the light-shielding film to the floating diffusion portion;
A part of the light shielding film extends to the amplification transistor side, and serves as a gate electrode of the amplification transistor
Camera device . The light shielding film is formed of a refractory metal silicide.
請 Motomeko 3 camera device as claimed.

Images