KR20070113607A - Cmos image sensor pixel and method for sensing signal thereof - Google Patents

Abstract

A pixel of a CMOS image sensor and a method for sensing a signal thereof are provided to increase the voltage of an N-type diffusion area of a charge amount sensing node under a condition of low driving voltage required in a CMOS image sensor. A photodiode includes the second conductive type first diffusion area formed in the first conductive type first semiconductor area. The photodiode absorbs light to generate charged particles and stores the charged particles in the first diffusion area. A floating diffusion sensing node includes the second conductive type second diffusion area formed on the first conductive type second semiconductor area. The floating diffusion sensing node stores the charged particles in the second diffusion area. A transfer gate(44) transfers the charged particles stored in the first diffusion area into the second diffusion area. A reset switch(53) is connected between a reset voltage source and the second diffusion area to reset the voltage of the second diffusion area. A coupling capacitor is connected to the second diffusion area and the first electrode, and connects the second electrode to an input terminal of a signal amplifier. A signal amplifier(55) is connected to the second electrode and the input terminal to deliver a voltage signal of the second electrode to a pixel array signal line. A multi-functional switch(54) has the first terminal connected to the second electrode and the input terminal of the signal amplifier and the second terminal connected to a variable voltage source. The multi-functional switch(54) applies the voltage of the variable voltage source to the second electrode and the input terminal of the signal amplifier.

Description

CMOS image sensor pixel and method for sensing signal

1 is a view showing the structure of a conventional image sensor pixel.

2 is a cross-sectional view and a circuit diagram of one embodiment of the image sensor pixel of FIG.

3 illustrates the structure of an image sensor pixel according to the present invention;

4 is a cross-sectional view and a circuit diagram of one embodiment of the image sensor pixel of FIG.

5 is another embodiment of an image sensor pixel in accordance with the present invention.

FIG. 6 is an enlarged cross-sectional view and a circuit diagram of a portion of the signal charge sensing node in FIG. 5; FIG.

7 is another embodiment of an image sensor pixel in accordance with the present invention.

8 is yet another embodiment of an image sensor pixel in accordance with the present invention.

Explanation of symbols on the main parts of the drawings

PPD: Pinned Photodiode

21,26,41,47: P-well

22,42 n-type diffusion region

23,43: p + region

24,44: Transfer Gate

25,45: multi-function charge detector

27: Floating Diffusion Sensing Node Capacitor

28: Floating Diffusion Sensing Node

29,53: reset switch

CC: Coupling Capacitor

31: first electrode

32: second electrode

33,54: Multifunction Switch

35,55: signal amplifier

46: CCFLFD detection node (Capacitor Combined Floating Layer Floating Diffusion Sensing Node)

48: n-type diffusion region

50: floating p layer (first electrode)

51: second electrode

52,52a, 52b: insulation layer

70: Source Follower Amplifier

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a complementary metal-oxide semiconductor (CMOS) image sensor pixel and a signal sensing method thereof, and more particularly, to a structure, a function, and an operation method of a signal charge amount sensing unit having multifunction in a CMOS image sensor pixel.

In general, an image sensor is a device that converts an external optical image signal into an electrical image signal. In particular, CMOS image sensors are image sensors fabricated using CMOS fabrication techniques. In the CMOS image sensor, each pixel uses a photodiode to convert the light signal radiated from the corresponding part of the object into an electron, stores the converted light signal, and converts the accumulated charge amount into a voltage signal and outputs the converted voltage signal.

In the conventional CMOS image sensor pixel, a floating diffusion detection node (FD) is used as a charge sensing node in order to sense a signal charge amount. A charge sensing part is configured by combining a reset switch and a reset voltage source for resetting the floating diffusion sensing node with the floating diffusion sensing node.

1 is a diagram illustrating a pixel structure of such a conventional CMOS image sensor.

The conventional CMOS image sensor includes a photodiode 1, a transfer gate 5, a charge amount sensing unit 6, and a signal amplifier 12. Here, the charge amount sensing unit 6 includes a floating diffusion sensing node 9, a reset switch 10, and a reset voltage source VR.

In FIG. 1, the capacitor 8 is the sum of the junction capacitor and the peripheral parasitic capacitor in the floating diffusion sensing node 9. The signal voltage of the capacitor 8 is transmitted to the input terminal of the signal amplifier 12 through a conductive line that is ohmic contacted to the n-type diffusion region of the floating diffusion detection node 9.

2 is a cross-sectional view and a circuit diagram of one embodiment of the image sensor pixel of FIG. 1.

The conventional CMOS image sensor shown in FIG. 2 is implemented using a pinned photodiode PPD and an n-channel MOSFET. In the pinned photodiode PPD, an n-type diffusion region 3 is formed in a p-type epitaxial layer P-EPI, a p + region 4 is formed in an n-type diffusion region 3, and an n-type diffusion region. P-wells 2 are formed by sidewalls of (3) and p + regions (4). In addition, the charge detection unit 6 includes a P-well 7 formed in the p-type epitaxial layer P-EPI, and a floating n-type diffusion region 9 formed inside the P-well 7. do.

Referring to the operation of the conventional CMOS image sensor pixel having such a configuration is as follows.

First, in a state where the transfer gate 5 is turned off, the photodiode PPD converts a light signal into an electron and stores it in its n-type diffusion region 3. Accordingly, the photodiode PPD absorbs light and converts it into electrons for the charge accumulation time (Integration Time) before the transfer gate 5 is turned on again.

Subsequently, the voltage of the n-type diffusion region of the floating diffusion sensing node 9 is reset to a voltage higher than the voltage of the n-type diffusion region 3 of the photodiode PPD using the reset switch 10 and the reset voltage source VR.

Thereafter, the transfer gate 5 is turned on to accumulate in the n-type diffusion region 3 of the photodiode PPD by using a voltage difference between the photodiode PPD and the n-type diffusion region of the floating diffusion sensing node 9. The signal electrons are moved to the n-type diffusion region of the floating diffusion sensing node 9. That is, as the signal electrons move from the photodiode PPD to the floating diffusion sensing node 9 during the charge transfer time, the voltage of the n-type diffusion region of the floating diffusion sensing node 9 changes.

The change in voltage is transmitted to the input terminal of the signal amplifier 12 through a conducting wire in ohmic contact with the n-type diffusion region of the floating diffusion sensing node 9.

Here, the output signal of the signal amplifier 12 is directly connected to a signal line of a pixel array or through an addressing switch having a function of turning on / off the output signal of the signal amplifier 12. It is connected to the signal line. Here, the structure directly connected without the addressing switch is used when the on / off state of the signal amplifier 12 itself can be adjusted in the pixel operating method.

After the electron transfer from the photodiode PPD to the floating diffusion sensing node 9, the photodiode PPD is completely depleted. Subsequently, the transfer gate 5 is turned off again, and the photodiode PPD starts converting the light signal into an electron and storing it in its n-type diffusion region 3. Then, the operation of the unit pixel is repeated to read all the image signals of the entire subject.

However, conventional CMOS image sensor pixels have four problems as follows.

First, a CMOS image sensor uses a low pixel driving voltage unlike a CCD (Charge Coupled Device) image sensor. Accordingly, when moving electrons from the photodiode PPD to the floating diffusion sensing node 9, there is a lack of voltage difference between the n-type diffusion region 3 of the photodiode PPD and the n-type diffusion region of the floating diffusion sensing node 9. This makes it difficult to completely move the electrons to the floating diffusion sensing node 9. Therefore, in order to completely move the electrons from the n-type diffusion region 3 of the photodiode PPD to the n-type diffusion region of the floating diffusion sensing node 9, the floating diffusion sensing node 9 may be operated even under the condition of low driving voltage. It should be possible to make the voltage of the n-type diffusion region as high as possible.

Second, in the conventional CMOS image sensor pixel, the floating diffusion sensing node 9 and the input terminal of the signal amplifier 12 are connected by ohmic contact. In order to directly contact ohmic contact with the diffusion region of the floating diffusion detection node 9, the doping concentration of the diffusion region should be made high. However, due to material defects occurring in the process, a very large dark current is generated in the floating diffusion sensing node 9. Accordingly, in the case of using the floating diffusion sensing node 9 using the ohmic contact, when the signal electrons are stored in the floating diffusion sensing node 9 for a long time, a large dark current of the floating diffusion sensing node 9 causes a serious problem. Let's do it. Therefore, it is required to devise a sensing node with a significantly lower dark current than the floating diffusion sensing node 9 using ohmic contact.

Here, an example of the case in which it is necessary to store the signal electrons in the floating diffusion sensing node 9 for a long time is a global shuttering operation of the image sensor.

Third, in the conventional CMOS image sensor pixel, the floating diffusion sensing node 9 and the signal amplifier 12 are directly connected by conductors. When the voltage of the input terminal of the signal amplifier 12 is intentionally changed from the outside, the amount of the signal charge stored in the floating diffusion sensing node 9 is changed accordingly, and the stored information is lost. That is, in the structure of the conventional CMOS image sensor pixel, the next operation of the pixel cannot be executed by changing the voltage of the input terminal of the signal amplifier 12 while keeping the amount of signal charge stored in the floating diffusion sensing node 9 as it is.

Fourth, light incident to the floating diffusion sensing node 9 should be blocked because it causes errors in the operation of the pixel. Accordingly, there is a need to provide a charge amount sensing unit having a structure that effectively blocks light incident to the charge amount sensing node as much as possible.

The present invention has been made to solve the above problems, and has the following object.

First, the signal electrons can be completely moved from the n-type diffusion region of the photodiode to the n-type diffusion region of the charge sensing node by boosting the voltage of the n-type diffusion region of the charge sensing node even under the condition of a low pixel driving voltage. In addition, the maximum amount of charge stored in the charge sensing node is increased.

Second, by using the coupling capacitor formed without forming an ohmic contact in the n-type diffusion region of the charge sensing node, the signal voltage of the charge sensing node is transmitted to the input terminal of the signal amplifier, thereby making it possible to detect the existing sensing node using ohmic contact. It is more to reduce the dark current of the sensing node.

Third, by coupling the signal voltage delivered to the signal amplifier with the coupling capacitor, it is possible to operate the pixel by changing the voltage of the input terminal of the signal amplifier while preserving the signal charge amount stored in the charge sensing node. .

Fourth, the purpose of the present invention is to effectively block light incident on the charge detection node by using an electrode of the coupling capacitor, which is a component of the charge detection unit, as a light blocking mask.

The CMOS image sensor pixel of the present invention for achieving the above object includes a first diffusion region of the second conductive type formed in the first semiconductor region of the first conductive type, and absorbs incident light to generate charged particles. A photodiode for storing in the first diffusion region; A floating diffusion sensing node comprising a floating second diffusion region of a second conductivity type formed in the second semiconductor region of the first conductivity type, and storing charged particles transferred from the first diffusion region of the photodiode in a second diffusion region; A transfer gate transferring the charged particles stored in the first diffusion region to the second diffusion region; A reset switch connected between the reset voltage source and the second diffusion region to reset the voltage of the second diffusion region; A coupling capacitor connected to the second diffusion region and the first electrode and connected to the input terminal of the signal amplifier; A signal amplifier connected to the second electrode and the input terminal to transfer a voltage signal corresponding to the voltage of the second electrode to the signal line of the pixel array; And a multifunction switch in which one terminal is commonly connected to the input terminal of the second electrode and the signal amplifier, and the other terminal is connected to the variable voltage source to apply the voltage of the variable voltage source to the input terminal of the second electrode and the signal amplifier. It is characterized by.

In addition, the CMOS image sensor pixel of the present invention includes a floating first diffusion region of the second conductivity type formed in the first semiconductor region of the first conductivity type, and stores the charged particles transferred from the outside in the first diffusion region. Floating diffusion sensing node; A reset switch connected between the reset voltage source and the first diffusion region to reset the voltage of the first diffusion region; A coupling capacitor connected to the first diffusion region and the first electrode and to the multifunction switch and the second electrode; One terminal is connected to the second electrode, the variable voltage source and the other terminal is connected, it characterized in that it comprises a multifunction switch for applying the voltage of the variable voltage source to the second electrode.

In addition, the CMOS image sensor pixel of the present invention includes a first diffusion region of the second conductivity type formed in the first semiconductor region of the first conductivity type, and absorbs incident light to generate charged particles to generate a first diffusion region. Photodiodes stored in the; The second diffusion region of the second conductivity type formed in the second semiconductor region of the first conductivity type, the floating third diffusion region of the first conductivity type formed in the second diffusion region, and the third diffusion region are the first electrodes. Capacitor Combined Floating Layer Floating Diffusion (CCFLFD) sensing node including a coupling capacitor having an electrode formed on the upper side of the third diffusion region as a second electrode, and storing charged particles transferred from the first diffusion region in the second diffusion region. ; A transfer gate transferring the charged particles stored in the first diffusion region to the second diffusion region; A reset switch connected between the reset voltage source and the second diffusion region to reset the voltage of the second diffusion region; A signal amplifier connected to the second electrode and the input terminal to transfer a voltage signal corresponding to the voltage of the second electrode to the signal line of the pixel array; And a multifunction switch in which one terminal is commonly connected to the input terminal of the second electrode and the signal amplifier, and the other terminal is connected to the variable voltage source to apply the voltage of the variable voltage source to the input terminal of the second electrode and the signal amplifier. It is characterized by.

In addition, the CMOS image sensor pixel of the present invention includes a first diffusion region of the second conductivity type formed in the first semiconductor region of the first conductivity type, a floating second diffusion region of the first conductivity type formed in the first diffusion region, And a coupling capacitor having the second diffusion region as the first electrode and the electrode formed on the upper side of the second diffusion region as the second electrode, and storing charged particles transferred from the outside in the first diffusion region. Combined Floating Layer Floating Diffusion) detection node; A reset switch connected between the reset voltage source and the first diffusion region to reset the voltage of the first diffusion region; And a multifunction switch connected to one terminal of the second electrode and the other terminal of the variable voltage source to apply the voltage of the variable voltage source to the second electrode.

In addition, the signal sensing method of the CMOS image sensor pixel of the present invention, a floating diffusion sensing node for storing the electrons transferred from the first diffusion region of the photodiode in the second diffusion region, the second diffusion region and the first electrode are connected. And a coupling capacitor having a second electrode connected to the signal amplifier input terminal, a reset switch connected between the reset voltage source and the second diffusion region, a signal amplifier connected to the second electrode and the input terminal, and between the variable voltage source and the second electrode. A signal sensing method of a CMOS image sensor pixel including a connected multifunction switch, comprising: a first step of turning on a multifunction switch to apply a voltage of a variable voltage source to a second electrode to fix the second electrode to a first voltage; A second step of turning on the reset switch, applying a voltage of the reset voltage source to the second diffusion region to reset the second diffusion region, and then turning off the reset switch; Changing the voltage of the variable voltage source raises the voltage of the second electrode to a second voltage higher than the first voltage to boost the voltage of the second diffusion region, sets the input terminal of the signal amplifier to the second voltage, and outputs the signal amplifier. Reading a third step; A fourth step of turning off the multifunction switch and turning on the transfer gate to move and store electrons stored in the first diffusion region to the second diffusion region and then turn off the transfer gate; And a fifth step of detecting an amount of change in which the value of the output voltage of the signal amplifier falls from the value of the output voltage read in the third step.

In addition, the signal sensing method of the CMOS image sensor pixel of the present invention, a floating diffusion sensing node for storing the electrons transferred from the first diffusion region of the photodiode in the second diffusion region, the second diffusion region and the first electrode are connected. And a coupling capacitor having a second electrode connected to the signal amplifier input terminal, a reset switch connected between the reset voltage source and the second diffusion region, a signal amplifier connected to the second electrode and the input terminal, and between the variable voltage source and the second electrode. A signal sensing method of a CMOS image sensor pixel including a connected multifunction switch, the method comprising: turning off a reset switch and turning on a transfer gate to move and store electrons stored in a first diffusion region to a second diffusion region, and then turning off a transfer gate First step; A second step of turning on the multifunction switch and setting the voltage of the input terminal of the signal amplifier to the first voltage using the variable voltage source and reading the output of the signal amplifier; Turning off the multifunction switch and turning on the reset switch to discharge electrons in the second diffusion region; And a fourth step of detecting an amount of change in which the value of the output voltage of the signal amplifier rises from the value of the output voltage in the second step.

In the CMOS image sensor pixel signal sensing method, a sensing node for storing electrons transferred from a first diffusion region of a photodiode in a second diffusion region, a second diffusion region and a first electrode are connected, and a second A coupling capacitor having an electrode connected to the signal amplifier input terminal, a reset switch connected between the reset voltage source and the second diffusion region, a signal amplifier connected to the second electrode and the input terminal, and a multifunction switch connected between the variable voltage source and the second electrode. A signal sensing method of a CMOS image sensor pixel comprising: a first reading of an output of a signal amplifier by setting a voltage of an input terminal of a signal amplifier to a first voltage using a multifunction switch and a variable voltage source with a reset switch turned off; step; Turning off the multifunction switch and turning on the transfer gate to move and store electrons from the first diffusion region to the second diffusion region and then to turn off the transfer gate; A third step of sensing an amount of change in the value of the output voltage of the signal amplifier from the output voltage value read in the first step; And a fourth step of repeatedly performing the first to third steps while the reset switch is turned off.

A signal sensing method of a CMOS image sensor pixel of the present invention includes: a photodiode that absorbs light and converts it into electrons and stores the same in a first diffusion region; A coupling capacitor having a second diffusion region, a floating third diffusion region formed in the second diffusion region, and a third diffusion region as a first electrode and an electrode formed above the third diffusion region as a second electrode; A CCFLFD (Capacitor Combined Floating Layer Floating Diffusion) sensing node for storing electrons transferred from the first diffusion region of the photodiode in the second diffusion region; A reset switch connected between the reset voltage source and the second diffusion region; A signal amplifier connected to the second electrode and the input terminal; And a multifunction switch for applying a voltage of the variable voltage source to an input terminal of the second electrode and the signal amplifier, wherein the multifunction switch is turned on to apply a voltage of the variable voltage source to the second electrode. A first step of fixing the second electrode to the first voltage; A second step of turning on the reset switch, applying a voltage of the reset voltage source to the second diffusion region to reset the second diffusion region, and then turning off the reset switch; Changing the voltage of the variable voltage source raises the voltage of the second electrode to a second voltage higher than the first voltage to boost the voltage of the second diffusion region, sets the input terminal of the signal amplifier to the second voltage, and outputs the signal amplifier. Reading a third step; A fourth step of turning off the multifunction switch and turning on the transfer gate to move and store electrons stored in the first diffusion region to the second diffusion region and then turn off the transfer gate; And a fifth step of detecting an amount of change in which the value of the output voltage of the signal amplifier falls from the value of the output voltage read in the third step.

A signal sensing method of a CMOS image sensor pixel of the present invention includes: a photodiode that absorbs light and converts it into electrons and stores the same in a first diffusion region; A coupling capacitor having a second diffusion region, a floating third diffusion region formed in the second diffusion region, and a third diffusion region as a first electrode and an electrode formed above the third diffusion region as a second electrode; A CCFLFD (Capacitor Combined Floating Layer Floating Diffusion) sensing node for storing electrons transferred from the first diffusion region of the photodiode in the second diffusion region; A reset switch connected between the reset voltage source and the second diffusion region; A signal amplifier connected to the second electrode and the input terminal; And a multifunction switch for applying a voltage of a variable voltage source to an input terminal of a second electrode and a signal amplifier, the method of sensing a pixel of a CMOS image sensor pixel, wherein the reset switch is turned off and the transfer gate is turned on to be stored in the first diffusion region. A first step of moving the electrons to the second diffusion region and storing the electrons and then turning off the transfer gate; A second step of turning on the multifunction switch and setting the voltage of the input terminal of the signal amplifier to the first voltage using the variable voltage source and reading the output voltage of the signal amplifier; Turning off the multifunction switch and turning on the reset switch to discharge electrons in the second diffusion region; And a fourth step of detecting an amount of change in which the value of the output voltage of the signal amplifier rises from the value of the output voltage read in the second step.

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention. Like numbers refer to like elements throughout the specification.

3 is a diagram illustrating a pixel structure of an image sensor according to the present invention.

The present invention includes a pinned photodiode PPD, a transfer gate 24, a charge sensing part 25, and a signal amplifier 35. Here, the charge amount detection unit 25 includes a floating diffusion sensing node 28, a reset switch 29, a reset voltage source VR, and a coupling capacitor. CC, Multi-Functional Switch (33), Variable Voltage Source (Variable Voltage Source) VC.

In FIG. 3, the capacitor 27 is the sum of the junction capacitor and the peripheral parasitic capacitor of the floating diffusion sensing node 28. The signal voltage of the capacitor 27 is transmitted to the input terminal of the signal amplifier 35 through the coupling capacitor CC.

4 is a cross-sectional view of one embodiment of the image sensor pixel of FIG. 3.

The present invention is implemented using a pinned photodiode PPD and an n-channel MOSFET (MOS Field Effect Transistor).

In the pinned photodiode PPD, an n-type diffusion region 22 is formed in a p-type epitaxial layer (P-EPI), a p + region 23 is formed in an n-type diffusion region 22, and an n-type diffusion region 22 is formed. ) And the sidewalls of p + region 23 to form P-well 21. Here, the present invention has been described in the embodiment that the n-type diffusion region 22 is formed in the p-type epitaxial layer (P-EPI), the present invention is not limited to this, but the p-type epitaxial layer (P-) Instead of EPI, a p-type substrate P-SUB may be formed.

In addition, the charge detection unit 25 is formed such that the P-well 26 is formed in the p-type epitaxial layer (P-EPI) and is surrounded by the P-well 26 in the P-well 26. n-type diffusion region 28 is included.

In addition, an insulating layer 34 is formed on the P-well 26. The transfer gate 24 is formed on the insulating layer 34 to connect the n-type diffusion region 22 of the pinned photodiode PPD and the n-type diffusion region of the floating diffusion sensing node 28. The n-type diffusion region of the floating diffusion sensing node 28 is connected to the first electrode 31 of the coupling capacitor CC, and the second electrode 32 of the coupling capacitor CC is connected to the input terminal of the signal amplifier 35. do. The multifunction switch 33 is connected between the second electrode 32 of the coupling capacitor CC and the variable voltage source VC.

In the present invention having such a configuration will be described in more detail the function and connection of each component as follows.

First, the pinned photodiode PPD converts incident light into electrons and stores them in its n-type diffusion region 22. The transfer gate 24 moves electrons stored in the n-type diffusion region 22 of the pinned photodiode PPD to the floating diffusion detection node 28 of the charge detection unit 25. The floating diffusion sensing node 28 stores the electrons received through the transfer gate 24 in its n-type diffusion region.

The reset switch 29 is formed on the insulating layer 34 so that one terminal is connected to the n-type diffusion region of the floating diffusion sensing node 28 and the other terminal is connected to the reset voltage source VR. And discharges the electric charge stored in the n-type diffusion region of (28). Here, the reset switch 29 may be formed of a field effect transistor (FET) or a transfer gate structure. The coupling capacitor CC has a first electrode 31 connected to the n-type diffusion region of the floating diffusion sensing node 28, and the second electrode 32 is connected to the input terminals of the multifunction switch 33 and the signal amplifier 35. Connected.

In the multifunction switch 33, one terminal is commonly connected to the input terminal of the second electrode 32 and the signal amplifier 35 of the coupling capacitor CC, and the other terminal is connected to the variable voltage source VC. The multifunction switch 33 may be formed of a field effect transistor (FET).

In addition, the reset voltage source VR and the variable voltage source VC are located outside the pixel, and are connected to the corresponding point of each pixel by a conductive line. The signal voltage of the floating diffusion sensing node 28 is transmitted to the input terminal of the signal amplifier 35 connected to the second electrode 32 of the coupling capacitor CC through the coupling capacitor CC.

Here, the output signal of the signal amplifier 35 is directly connected to the signal line of the pixel array, or is connected to the signal line through a switch of a function of turning on / off the output signal of the signal amplifier 35. . Here, the structure directly connected without the switch is used when the on / off state of the signal amplifier 35 itself can be adjusted in the pixel operating method.

In addition, the charge detection unit 25 included in the unit pixel of the present invention may be shared by the photodiode PPD or the signal amplifier 35 of another pixel.

Referring to the operation of the present invention having such a configuration as follows.

First, while the transfer gate 24 is off, the pinned photodiode PPD converts light signals into electrons and stores them in its n-type diffusion region 22. Accordingly, the pinned photodiode PPD absorbs and converts light into electrons during charge integration time until the transfer gate 24 is turned on again.

The voltage of the n-type diffusion region of the floating diffusion sensing node 28 is reset to a voltage higher than the voltage of the n-type diffusion region 22 of the pinned photodiode PPD while the transfer gate 24 is turned off. That is, the variable voltage source VC is kept at the voltage level VCL, and the multifunction switch 33 is turned on to fix the second electrode 32 of the coupling capacitor CC to the voltage level VCL. Here, the embodiment describes setting the voltage level VCL to the ground voltage level.

In this state, the reset switch 29 is turned on to make the voltage of the n-type diffusion region of the floating diffusion sensing node 28, that is, the voltage of the capacitor 27 of the floating diffusion sensing node 28, become the reset voltage VRN. Here, the reset voltage VRN is a value determined by the reset voltage source VR and the characteristics of the reset.

Thereafter, the reset switch 29 is turned off, and the variable voltage source VC is raised from the voltage level VCL to the voltage level VCH. Here, the embodiment describes setting the voltage level VCH to the pixel driving power supply voltage level. At this time, the capacitor 27 of the floating diffusion sensing node 28 is charged through the coupling capacitor CC, thereby increasing the voltage of the capacitor 27 from the reset voltage VRN to VRN + α × (VCH-VCL). Where α is a positive constant of 1 or less. That is, the voltage of the n-type diffusion region of the floating diffusion sensing node 28 is boosted by α × (VCH-VCL). This effect of voltage boosting facilitates the complete migration of electrons stored in the pinned photodiode PPD to the floating diffusion sensing node 28. Further, the maximum amount of charge that can be stored in the n-type diffusion region of the floating diffusion sensing node 28 is increased. After this boosting operation, the multifunction switch 33 is turned off.

Subsequently, the transfer gate 24 is turned on to take advantage of the voltage difference between the n-type diffusion region 22 of the pinned photodiode PPD and the n-type diffusion region of the floating diffusion sensing node 28 to n of the pinned photodiode PPD. The signal electrons accumulated in the type diffusion region 22 are moved to the n type diffusion region of the floating diffusion detection node 28. At this time, the pinned photodiode PPD is completely depleted. As signal electrons move from the pinned photodiode PPD to the floating diffusion sensing node 28, the voltage of the n-type diffusion region of the floating diffusion sensing node 28 changes.

The voltage change of the n-type diffusion region of the floating diffusion sensing node 28, that is, the voltage change of the capacitor 27 of the floating diffusion sensing node 28 is transmitted to the input terminal of the signal amplifier 35 through the coupling capacitor. Subsequently, the transfer gate 24 is turned off again, and the pinned photodiode PPD converts the light signal into an electron and stores it in its n-type diffusion region 22. Then, the operation of the unit pixel is repeated to read all the image signals of the entire subject.

One of the important features of the charge sensing unit 25 having such an operation process is to transfer the voltage change of the n-type diffusion region of the floating diffusion sensing node 28 to the input terminal of the signal amplifier 35 through the coupling capacitor CC. will be. Therefore, even if the voltage of the input terminal of the second electrode 32 or the signal amplifier 35 of the coupling capacitor CC is changed to a desired value using the multifunction switch 33 and the variable voltage source VC, the floating diffusion sensing node 28 ), The number of signal electrons stored in the n-type diffusion region, that is, the amount of charge in the n-type diffusion region is preserved.

The present invention uses the multifunction switch 33 of the pixel and the variable voltage source VC to preserve the signal charge stored in the floating diffusion sensing node 28 by using the characteristics of the charge detection unit 25. For operation, the voltage of the input terminal of the signal amplifier 35 may be changed.

For example, in the CMOS image sensor of the present invention, unlike the signal detection method of a general CMOS image sensor, a signal may be detected by the following method.

First, the electrons of the n-type diffusion region 22 of the pinned photodiode PPD are moved and stored in the n-type diffusion region of the floating diffusion sensing node 28 in the same manner as the operation method of the CMOS image sensor.

Subsequently, the voltage of the input terminal of the signal amplifier 35 is set to a voltage level VL larger than the input threshold voltage of the signal amplifier 35 by using the multifunction switch 33 and the variable voltage source VC.

Then, the multifunction switch 33 is turned off, and the reset switch 29 is turned on to flow out signal electrons stored in the n-type diffusion region of the floating diffusion detection node 28. Accordingly, the voltage of the second electrode 32 of the coupling capacitor CC or the voltage of the input terminal of the signal amplifier 35 is higher than the voltage VL so as to flow out of the n-type diffusion region of the floating diffusion sensing node 28. The amount of charge of the signal electrons is measured.

In addition, without performing a reset operation using the reset switch 29, the multifunction switch 33 is turned on while the electrons are stored in the n-type diffusion region of the floating diffusion sensing node 28. And the voltage of the input terminal of the signal amplifier 35 is set using the variable voltage source VC. Subsequently, there is a method of combining the electrons transferred from the pinned photodiode PPD by turning on the transfer gate 24 with the electrons previously stored in the n-type diffusion region of the floating diffusion sensing node 28.

The function of the coupling capacitor CC in the charge detection unit 25 used in the pixel of the present invention is summarized as follows.

First, the voltage of the n-type diffusion region of the floating diffusion sensing node 28 is boosted and raised through the link operation with the reset switch 29, the reset voltage source VR, the multifunction switch 33, and the variable voltage source VC.

Second, the signal voltage of the n-type diffusion region of the floating diffusion sensing node 28 is transmitted to the input terminal of the signal amplifier 35.

In addition, the functions of the multifunction switch 33 and the variable voltage source VC in the charge detection unit 25 used in the pixel of the present invention are summarized as follows.

First, a discharging path is provided in the floating structure of the input terminal of the second electrode 32 and the signal amplifier 35 of the coupling capacitor CC to discharge unwanted charges, thereby preventing an operation error of the devices.

Second, the voltage of the n-type diffusion region of the floating diffusion sensing node 28 is boosted and raised through the link operation with the reset switch 29, the reset voltage source VR, and the coupling capacitor CC.

Third, a function of setting an initial reference voltage of an input terminal of the signal amplifier 35 is performed. This enables the signal charge detection of the various methods presented above. In addition, when the signal amplifier 35 has a source follower structure, the on / off of the signal amplifier 35 may be controlled.

In addition to the operation of the charge amount sensing unit 25 of the present invention, the operation of the entire pixel is the same as that of a well-known pixel, and thus its detailed description will be omitted.

5 is another embodiment of an image sensor pixel according to the present invention.

5 includes a pinned photodiode PPD, a transfer gate 44, a charge amount sensing unit 45, and a signal amplifier 55. Here, the charge amount sensing unit 45 includes a CCFLFD sensing layer (Capacitor Combined Floating Layer Floating Diffusion Sensing Node) 46, a reset switch 53, a reset voltage source VR, a multifunction switch 54, and a variable voltage source VC.

6 is an enlarged cross-sectional view and a circuit diagram of the structure of the CCFLFD sensing node 46 of the charge amount detecting unit 45.

In the pinned photodiode PPD, an n-type diffusion region 42 is formed in a P-type epitaxial layer (P-EPI), a p + region 43 is formed in an n-type diffusion region 42, and an n-type diffusion region 42 ) And the sidewalls of the p + region 43.

The CCFLFD sensing node 46 has a P-well 47 or a p-type diffusion region formed in the P-type epitaxial layer (P-EPI), and is formed by the P-well 47 inside the P-well 47. And a floating n-type diffusion region 48 formed to be wrapped. A floating p layer 50 formed to be surrounded by the n type diffusion region 48 is formed inside the n type diffusion region 48, and the second electrode 51 and the floating p layer 50 of the coupling capacitor CC are formed. An insulating layer 52 that is an oxide is formed therebetween.

In this case, the floating p layer 50 is configured not to contact the p-well 47 or the p-type diffusion region surrounding the n-type diffusion region 48. That is, the floating p layer 50 is formed to be surrounded by the n-type diffusion region 48, and only the upper region is exposed to be connected to the insulating layer 52.

The floating p layer 50 formed as described above serves as a first electrode of the coupling capacitor CC. The second electrode 51 of the coupling capacitor CC is formed on the insulating layer 52. That is, the coupling capacitor CC forms the floating p layer 50 as the first electrode with the insulating layer 52 interposed therebetween, and forms a second electrode 51 provided separately on the insulating layer 52. . Accordingly, the coupling capacitor CC is formed by forming the second electrode 51 of the coupling capacitor CC on the floating p layer 50 without allocating a separate space to form the second electrode 51. In order to reduce the area of the pixel required additionally.

Since the thickness of the insulating layer 52 of the coupling capacitor CC is very thin, the second electrode 51 of the coupling capacitor CC may serve as a light blocking mask that effectively blocks light incident to the CCFLFD sensing node 46. Can be.

In addition, the floating p-layer 50 serves as a coupling for the coupling capacitor CC to the n-type diffusion region 48 without ohmic contact at the CCFLFD sensing node 46. Thus, the physical defects that occur to form ohmic contacts are reduced and thus the dark current is reduced. In addition, it suppresses the generation of electrons generated in the semiconductor surface region, thereby significantly reducing the dark current and noise of the CCFLFD sensing node 46. This is similar to the role of the p + region 43 in the pinned photodiode PPD.

Here, the junction capacitor of the pn junction J1 between the floating p layer 50 and the n-type diffusion region 48 is referred to as CFP. At this time, the coupling capacitor CC and the junction capacitor CFP are connected in series in a circuit.

In addition, the n-type diffusion region 48 is a portion for storing signal electrons. The junction capacitor of the np junction J2 between the n-type diffusion region 48 and the p-well 47 or the p-type diffusion region and the surrounding parasitic capacitors are collectively referred to as capacitor CFD. Accordingly, whenever electrons flow into or out of the n-type diffusion region 48, the voltage of the n-type diffusion region 48 changes, and the change of the voltage is transmitted to the outside through the junction capacitor CFP and the coupling capacitor CC. .

In addition, an insulating layer 52a is formed on the P-well 47. The transfer gate 44 is formed on the insulating layer 52a and serves as a switch connecting the n-type diffusion region 42 of the pinned photodiode PPD and the n-type diffusion region 48 of the CCFLFD sensing node 46. .

In the embodiment of Figures 5 and 6 having such a configuration will be described in more detail the function and connection of each component as follows.

First, the pinned photodiode PPD converts incident light into electrons and stores it in its n-type diffusion region 42. The transfer gate 44 moves electrons stored in the photodiode PPD to the CCFLFD sensing node 46 of the charge amount sensing unit 45. The CCFLFD sensing node 46 stores the electrons received from the pinned photodiode PPD through the transfer gate 44 in its n-type diffusion region 48.

In addition, an insulating layer 52b is formed on the P-well 47. The reset switch 53 is formed on the insulating layer 52b so that one terminal is connected to the n-type diffusion region 48 of the CCFLFD sensing node 46 and the other terminal is connected to the reset voltage source VR. The reset switch 53 discharges charge stored in the n-type diffusion region 48 of the CCFLFD sensing node 46 and resets the voltage of the region. In the multifunction switch 54, one terminal is connected together to the second electrode 51 of the coupling capacitor CC and the input terminal of the signal amplifier 55, and the other terminal is connected to the variable voltage source VC. This multifunction switch 54 transfers the voltage of the variable voltage source VC to the second electrode 51 of the coupling capacitor CC.

In addition, the reset voltage source VR and the variable voltage source VC are located outside the pixel, and are connected to the corresponding point of each pixel by a conductive line. The output voltage of the CCFLFD sensing node 46 is transmitted to the input terminal of the signal amplifier 55 connected to the second electrode 51 of the coupling capacitor CC through the coupling capacitor CC.

Here, the input terminal of the signal amplifier 55 is connected to the second electrode 51 of the coupling capacitor CC and one terminal of the multifunction switch 54. The output terminal of the signal amplifier 55 is directly connected to a signal line of a pixel array, or is connected to a signal line through a switch having a function of turning on / off an output signal of the signal amplifier 55. . Here, the structure directly connected without a switch is used when the on / off state of the signal amplifier 55 itself can be adjusted in the pixel operating method.

Referring to the operation of the present invention having such a configuration as follows.

First, while the transfer gate 44 is off, the pinned photodiode PPD converts a light signal into an electron and stores it in its n-type diffusion region 42. Accordingly, the pinned photodiode PPD absorbs light for charge accumulation time until the transfer gate 44 is turned on again, converts it into electrons, and accumulates it.

Then, the voltage of the n-type diffusion region 48 of the CCFLFD sensing node 46 is reset to a voltage higher than the voltage of the n-type diffusion region 42 of the pinned photodiode PPD while the transfer gate 44 is turned off. That is, the variable voltage source VC is maintained at the voltage level VCL, and the multifunction switch 54 is turned on to fix the voltage at the voltage level VCL to the second electrode 51 of the coupling capacitor CC.

When the reset switch 53 is turned on in this state, the voltage of the n-type diffusion region 48 of the CCFLFD sensing node 46 is reset to the reset voltage VRN by the reset voltage VR. Here, the reset voltage VRN to be reset is a value determined by the reset voltage VR and the characteristics of the reset.

Thereafter, the reset switch 53 is turned off, and the variable voltage source VC is raised from the voltage level VCL to the voltage level VCH. At this time, the junction capacitor CFD of the J2 junction is charged through the coupling capacitor CC and the junction capacitor CFP of the J1 junction, which are connected in series, so that the voltage of the n-type diffusion region 48 of the CCFLFD sensing node 46 is reset voltage VRN. VRN + alpha x (VCH-VCL) becomes high. Where α is a constant of 1 or less. In other words, the voltage of the n-type diffusion region 48 of the CCFLFD sensing node 46 is boosted by α × (VCH-VCL) from the reset voltage VRN to VRN + α × (VCH-VCL).

As such, the voltage of the n-type diffusion region 48 of the CCFLFD sensing node 46 is raised to a high level so that signal electrons stored in the pinned photodiode PPD can be easily moved to the CCFLFD sensing node 46. Then, the maximum amount of charge that can be stored in the n-type diffusion region 48 increases. Following this boosting operation the multifunction switch 54 is turned off.

The pinned photodiode PPD is then made using the voltage difference between the n-type diffusion region 42 of the pinned photodiode PPD and the n-type diffusion region 48 of the CCFLFD sensing node 46 with the transfer gate 44 on. The signal electrons accumulated in the n-type diffusion region 42 of the N-type diffusion region are moved to the n-type diffusion region 48 of the CCFLFD sensing node 46. That is, as the signal electrons move from the pinned photodiode PPD to the CCFLFD sensing node 46 during the charge transfer period, the voltage of the n-type diffusion region 48 of the CCFLFD sensing node 46 changes.

The change in the voltage of the n-type diffusion region 48 is transmitted to the input terminal of the signal amplifier 55 through the coupling capacitor CC.

At this time, the pinned photodiode PPD is completely depleted. Then, the transfer gate 44 is turned off again, and the pinned photodiode PPD converts the light signal into an electron and stores it in its n-type diffusion region 42. Then, the operation of the unit pixel is repeated to read all the image signals of the entire subject.

One of the important features of the charge detection unit 45 having such an operation process is that the voltage variation of the n-type diffusion region 48 of the CCFLFD detection node 46 is transferred to the input terminal of the signal amplifier 55 through the coupling capacitor CC. To convey. Therefore, even when the voltage of the input terminal of the second electrode 51 of the coupling capacitor CC or the signal amplifier 55 is changed to a desired value using the multifunction switch 54 and the variable voltage source VC, the CCFLFD sensing node 46 The number of signal electrons stored in the n-type diffusion region 48 of is preserved.

When the configuration of the charge amount sensing unit 45 according to the present invention is formed by using the CCFLFD sensing node 46, the present invention has the following advantages.

First, by forming the floating p layer 50 and using it as the first electrode of the coupling capacitor CC, there is no need to form an ohmic contact to connect the coupling capacitor CC and the CCFLFD sensing node 46 with a conductor. . Therefore, the doping concentration of the n-type diffusion region 48 of the CCFLFD sensing node 46 can be greatly reduced than the doping concentration for ohmic contact. Accordingly, it is possible to reduce the defect of the material generated in the process, it is possible to significantly reduce the dark current generated in the sensing node.

Second, by forming the floating p layer 50 in the interface region of the n-type diffusion region 48, the dark current caused by electrons generated in the interface region with the oxide insulating layer 52 can be greatly reduced.

Third, by forming the coupling capacitor CC directly above the floating diffusion structure, an area of an additional pixel required for forming the coupling capacitor CC may be reduced.

Fourth, the sensing electrode is formed by forming a second electrode 51 of the coupling capacitor CC formed on the CCFLFD sensing node 46 with an extremely thin (~ nm) oxide insulating layer 52 therebetween as an opaque material. It can block the incident light. Here, the opaque material may be formed of a metal electrode such as copper or aluminum, or a poly silicide electrode.

In this case, the second electrode 51 covering the CCFLFD sensing node 46 at an extremely close distance also serves as an optical blocking mask function that effectively blocks light incident to the CCFLFD sensing node 46. do.

7 is yet another embodiment of an image sensor pixel according to the present invention.

The embodiment of FIG. 7 differs from the embodiment of FIG. 5 in that the lower region of the transfer gate 44 between the pinned photodiode PPD and the P-well 47 is formed as a p-type diffusion region 60. Since the other configuration and operation process are the same as the embodiment of FIG. 5, the detailed description of the configuration and operation process will be omitted. Here, the p-type region 60 has a different doping concentration from the P-well 47, and is formed between the pinned photodiode PPD and the P-well 47 to increase the transfer efficiency of the transfer gate 44. will be.

8 is another embodiment of an image sensor pixel according to the present invention.

The embodiment of FIG. 8 is an embodiment in which the signal amplifier 55 is implemented as a source follower (SF) amplifier 70 in a pixel using the multi-function charge detector 45 shown in FIG. 5.

The source follower amplifier 70 includes an active transistor 71 and a constant current source 72 connected through a signal line SL. Further, without the reset voltage source VR, one terminal of the reset switch 53 is tied together with the drain of the source follower transistor 71 to use the pixel driving voltage source VDD as the reset voltage source.

As described above, the present invention provides the following effects.

First, it is easy to completely move the signal electrons of the photodiode to the charge sensing node by increasing the voltage of the n-type diffusion region of the charge sensing node even under the low driving voltage required in the CMOS image sensor. In addition, the maximum amount of charge that the charge detection node can store increases.

Second, without forming an ohmic contact in the n-type diffusion region of the charge sensing node, the signal voltage of the charge sensing node is transmitted to the input terminal of the signal amplifier through the coupling capacitor, thereby making the existing charge sensing node using the ohmic contact. Compared with that, the dark current of the sensing node can be significantly reduced.

Third, by using a method of transferring the voltage change of the charge sensing node to the input terminal by the coupling capacitor, to perform the next pixel operation while preserving the signal charge stored in the charge sensing node. The voltage can be changed to any value externally.

Fourth, the electrode of the coupling capacitor serves as an optical blocking mask that is very close to the charge sensing node, thereby providing an effect of blocking the light incident to the charge sensing node very efficiently.

In addition, a preferred embodiment of the present invention is for the purpose of illustration, those skilled in the art will be able to various modifications, changes, substitutions and additions through the spirit and scope of the appended claims, such modifications and changes are the following claims It should be seen as belonging to a range.

Claims (47)

A photodiode comprising a first diffusion region of a second conductivity type formed in the first semiconductor region of the first conductivity type, the photodiode absorbing incident light to generate charged particles and storing the charged particles in the first diffusion region; A floating second diffusion region of a second conductive type formed in a second semiconductor region of the first conductive type, and storing the charged particles transferred from the first diffusion region of the photodiode in the second diffusion region A diffusion sensing node; A transfer gate transferring the charged particles stored in the first diffusion region to the second diffusion region; A reset switch connected between a reset voltage source and the second diffusion region to reset a voltage of the second diffusion region; A coupling capacitor connected to the second diffusion region and the first electrode and having a second electrode connected to an input terminal of a signal amplifier; The signal amplifier connected to the second electrode and the input terminal to transfer a voltage signal corresponding to the voltage of the second electrode to a signal line of a pixel array; And One terminal is commonly connected to the input terminal of the second electrode and the signal amplifier, and the other terminal is connected to a variable voltage source, and multi-function for applying the voltage of the variable voltage source to the input terminal of the second electrode and the signal amplifier. CMOS image sensor pixel comprising a switch. The CMOS image sensor pixel of claim 1, wherein the first conductive type and the second conductive type have polarities opposite to each other. The CMOS image sensor pixel of claim 1, wherein the first semiconductor region is formed of any one of a first conductive epitaxial layer and a first conductive substrate. The CMOS image sensor pixel of claim 1, wherein the second semiconductor region is a first conductive diffusion region formed in the first semiconductor region. The CMOS image sensor pixel of claim 1, wherein the photodiode is a pinned photodiode further comprising a diffusion region of a first conductivity type in the first diffusion region. 2. The CMOS image sensor pixel of claim 1, wherein said multifunction switch is comprised of a FET. 2. The CMOS image sensor pixel of claim 1, wherein said reset switch comprises one of a FET and a transfer gate structure. 2. The CMOS image sensor pixel of claim 1, wherein the multifunction switch forms a discharge passage to prevent an electrical floating structure between the second electrode of the coupling capacitor and the input terminal of the signal amplifier. . 2. The CMOS image sensor pixel of claim 1, wherein the multifunction switch sets the voltage of the input terminal of the second electrode and the signal amplifier of the coupling capacitor using a variable voltage source to a specific voltage value. The pixel of claim 1, wherein the signal amplifier further comprises a switch connected between an output terminal and a signal line of the pixel array. The CMOS image sensor pixel of claim 1, wherein the signal amplifier is an amplifier of a source follower structure. 12. The CMOS image sensor pixel according to claim 1 or 11, wherein a driving voltage source of said signal amplifier is used as said reset voltage source. The CMOS image sensor pixel of claim 1, wherein the signal amplifier is adjusted in an on / off state by the multifunction switch and the variable voltage source. The pixel of claim 1, wherein at least one of the floating diffusion sensing node, the reset switch, the coupling capacitor, the multifunction switch, and the signal amplifier is shared by at least two pixels. . A floating diffusion sensing node including a floating first diffusion region of a second conductivity type formed in a first semiconductor region of a first conductivity type, and storing charged particles transferred from the outside into the first diffusion region; A reset switch connected between a reset voltage source and the first diffusion region to reset a voltage of the first diffusion region; A coupling capacitor connected to the first diffusion region and the first electrode and to a multifunction switch and a second electrode; And And a multifunction switch connected to the second electrode at one terminal, and connected to a variable voltage source and the other terminal to apply a voltage of the variable voltage source to the second electrode. The pixel of claim 15, wherein the first conductive type and the second conductive type have polarities opposite to each other. A photodiode comprising a first diffusion region of a second conductivity type formed in the first semiconductor region of the first conductivity type, absorbing incident light to generate charged particles, and storing the charged particles in the first diffusion region; The first electrode includes a second diffusion region of the second conductivity type formed in the second semiconductor region of the first conductivity type, a floating third diffusion region of the first conductivity type formed in the second diffusion region, and the third diffusion region. A coupling capacitor having an electrode formed on the upper side of the third diffusion region as a second electrode, and storing the charged particles transferred from the first diffusion region in the second diffusion region. Layer Floating Diffusion Sensing Node; A transfer gate transferring the charged particles stored in the first diffusion region to the second diffusion region; A reset switch connected between a reset voltage source and the second diffusion region to reset a voltage of the second diffusion region; The signal amplifier connected to the second electrode and an input terminal to transfer a voltage signal corresponding to the voltage of the second electrode to a signal line of a pixel array; And One terminal is commonly connected to the second electrode and the input terminal of the signal amplifier, and the other terminal is connected to a variable voltage source to apply a voltage of the variable voltage source to the input terminal of the second electrode and the signal amplifier. A CMOS image sensor pixel comprising a multifunction switch. 18. The pixel of claim 17, wherein the first conductivity type and the second conductivity type have opposite polarities. 18. The pixel of claim 17, wherein the first semiconductor region comprises one of a first conductive epitaxial layer and a first conductive substrate. 18. The pixel of claim 17, wherein the second semiconductor region is a first conductive diffusion region formed in the first semiconductor region. 18. The pixel of claim 17, wherein the photodiode is a pinned photodiode further comprising a diffusion region of a first conductivity type in the first diffusion region. 18. The method of claim 17, wherein the coupling capacitor The first electrode formed as the third diffusion region; An insulating layer formed on the first electrode; And And the second electrode formed on the insulating layer. 18. The pixel of claim 17, wherein the third diffusion region is floated in the second diffusion region without contacting the second semiconductor region of the first conductivity type. 18. The pixel of claim 17, wherein a doping concentration of the second diffusion region and the third diffusion region is set lower than a doping concentration for ohmic contact. 18. The pixel of claim 17, wherein said multifunction switch comprises an FET. 18. The pixel of claim 17, wherein said reset switch comprises one of a FET and a transfer gate structure. 18. The pixel of claim 17, wherein the multifunction switch forms a discharge passage to prevent the second electrode of the coupling capacitor and the input terminal of the signal amplifier from electrically floating. . 18. The pixel of claim 17, wherein the multifunction switch sets the voltage of the input terminal of the second electrode and the signal amplifier of the coupling capacitor using a variable voltage source to a specific voltage value. 18. The pixel of claim 17, wherein said signal amplifier further comprises a switch coupled between an output terminal and a signal line of said pixel array. 18. The CMOS image sensor pixel of claim 17, wherein said signal amplifier is a source follower structure amplifier. 31. The CMOS image sensor pixel of claim 17 or 30, wherein a driving voltage source of said signal amplifier is used as said reset voltage source. 18. The pixel of claim 17, wherein the signal amplifier is adjusted in an on / off state by the multifunction switch and the variable voltage source. 18. The pixel of claim 17, wherein at least one of the CCFLFD sensing node, the reset switch, the multifunction switch, and the signal amplifier is shared by at least two pixels. 18. The pixel of claim 17, wherein the second electrode is formed of an opaque material to act as a light blocking mask to block light incident to the second diffusion region. A first diffusion region of the second conductivity type formed in the first semiconductor region of the first conductivity type, a floating second diffusion region of the first conductivity type formed in the first diffusion region, and the second diffusion region of the first electrode And a coupling capacitor having an electrode formed on the upper side of the second diffusion region as a second electrode, and storing the charged particles transferred from the outside in the first diffusion region, CCFLFD (Capacitor Combined Floating Layer Floating Diffusion). Sensing node; A reset switch connected between a reset voltage source and the first diffusion region to reset a voltage of the first diffusion region; And And a multifunction switch connected to one terminal of the second electrode and the other terminal of the variable voltage source to apply the voltage of the variable voltage source to the second electrode. 36. The pixel of claim 35, wherein the first conductive type and the second conductive type have polarities opposite to each other. A floating diffusion sensing node for storing electrons transferred from the first diffusion region of the photodiode in a second diffusion region, a coupling of a first electrode connected to the second diffusion region and a second electrode connected to an input terminal of the signal amplifier CMOS image sensor comprising a capacitor, a reset switch connected between a reset voltage source and the second diffusion region, the signal amplifier connected with the second electrode and the input terminal, and a multifunction switch connected between a variable voltage source and the second electrode. In the signal detection method of the pixel, A first step of applying the voltage of the variable voltage source to the second electrode by turning on the multifunction switch to fix the second electrode to the first voltage; A second step of applying the voltage of the reset voltage source to the second diffusion region by turning on the reset switch to reset the second diffusion region and then turning off the reset switch; Changing the voltage of the variable voltage source to raise the voltage of the second electrode to a second voltage higher than the first voltage to boost the voltage of the second diffusion region, and the input terminal of the signal amplifier to the second voltage. Setting and reading the output of the signal amplifier; Turning off the multifunction switch and turning on a transfer gate to move and store electrons stored in the first diffusion region to the second diffusion region and then to turn off the transfer gate; And And a fifth step of detecting a change amount in which the value of the output voltage of the signal amplifier falls from the value of the output voltage read in the third step. 38. The method of claim 37, wherein the voltage of the second diffusion region is boosted by α × (second voltage-first voltage) by the first voltage and the second voltage, where α is a constant of 1 or less. And a signal sensing method of the CMOS image sensor pixel. 38. The method of claim 37, wherein the first voltage is a ground voltage level and the second voltage is a pixel driving power supply voltage level. A floating diffusion sensing node for storing electrons transferred from the first diffusion region of the photodiode in a second diffusion region, a coupling of a first electrode connected to the second diffusion region and a second electrode connected to an input terminal of the signal amplifier CMOS image sensor comprising a capacitor, a reset switch connected between a reset voltage source and the second diffusion region, the signal amplifier connected with the second electrode and the input terminal, and a multifunction switch connected between a variable voltage source and the second electrode. In the signal detection method of the pixel, Turning off the reset switch and turning on a transfer gate to move and store electrons stored in the first diffusion region to the second diffusion region and to turn off the transfer gate; A second step of turning on the multifunction switch and setting the voltage of the input terminal of the signal amplifier to the first voltage using the variable voltage source and reading the output of the signal amplifier; Turning off the multifunction switch and turning on the reset switch to discharge electrons in the second diffusion region; And And detecting a change amount of the output voltage of the signal amplifier rising from the value of the output voltage read in the second step. 41. The method of claim 40, wherein the first voltage is set to a value higher than an input threshold voltage of the signal amplifier. A sensing node for storing electrons transferred from the first diffusion region of the photodiode in a second diffusion region, a coupling capacitor having a first electrode connected to the second diffusion region and a second electrode connected to an input terminal of the signal amplifier; And a reset switch connected between a reset voltage source and the second diffusion region, the signal amplifier connected with the second electrode and the input terminal, and a multifunction switch connected between a variable voltage source and the second electrode. In the signal detection method, A first step of setting a voltage of an input terminal of the signal amplifier as a first voltage using the multifunction switch and the variable voltage source in a state in which the reset switch is turned off, and reading an output of the signal amplifier; Turning off the multifunction switch and turning on a transfer gate to move and store electrons from the first diffusion region to the second diffusion region and then to turn off the transfer gate; A third step of sensing an amount of change in the value of the output voltage of the signal amplifier from the value of the output voltage read in the first step; And And a fourth step of repeating the third step from the first step while the reset switch is turned off. A photodiode that absorbs light and converts it into electrons and stores the light in a first diffusion region; A coupling capacitor having a second diffusion region, a floating third diffusion region formed in the second diffusion region, and the third diffusion region as a first electrode, and an electrode formed above the third diffusion region as a second electrode. A capacitor coupled floating layer floating diffusion (CCFLFD) sensing node configured to store electrons transferred from the first diffusion region of the photodiode in the second diffusion region; A reset switch connected between a reset voltage source and the second diffusion region; A signal amplifier connected to the second electrode and an input terminal; And a multifunction switch configured to apply a voltage of a variable voltage source to the second electrode and an input terminal of the signal amplifier. A first step of applying the voltage of the variable voltage source to the second electrode of the coupling capacitor by turning on the multifunction switch to fix the second electrode to the first voltage; A second step of applying the voltage of the reset voltage source to the second diffusion region by turning on the reset switch to reset the second diffusion region and then turning off the reset switch; Changing the voltage of the variable voltage source to raise the voltage of the second electrode to a second voltage higher than the first voltage to boost the voltage of the second diffusion region, and the input terminal of the signal amplifier to the second voltage. Setting and reading the output of the signal amplifier; Turning off the multifunction switch and turning on a transfer gate to move and store electrons stored in the first diffusion region to the second diffusion region and then to turn off the transfer gate; And And a fifth step of detecting a change amount in which the value of the output voltage of the signal amplifier falls from the value of the output voltage read in the third step. 45. The method of claim 44, wherein the voltage of the second diffusion region is boosted by α × (second voltage-first voltage) by the first voltage and the second voltage, where α is a positive constant of 1 or less. And a method for detecting a signal of a CMOS image sensor pixel. 45. The method of claim 44, wherein the first voltage is a ground voltage level and the second voltage is a pixel driving power supply voltage level. A photodiode that absorbs light and converts it into electrons and stores the light in a first diffusion region; A coupling capacitor having a second diffusion region, a floating third diffusion region formed in the second diffusion region, and the third diffusion region as a first electrode, and an electrode formed above the third diffusion region as a second electrode. A capacitor coupled floating layer floating diffusion (CCFLFD) sensing node configured to store electrons transferred from the first diffusion region of the photodiode in the second diffusion region; A reset switch connected between a reset voltage source and the second diffusion region; A signal amplifier connected to the second electrode and an input terminal; And a multifunction switch configured to apply a voltage of a variable voltage source to the second electrode and an input terminal of the signal amplifier. Turning off the reset switch and turning on a transfer gate to move and store electrons stored in the first diffusion region to the second diffusion region and to turn off the transfer gate; A second step of turning on the multifunction switch and setting the voltage of the input terminal of the signal amplifier to the first voltage using the variable voltage source and reading the output of the signal amplifier; Turning off the multifunction switch and turning on the reset switch to discharge electrons in the second diffusion region; And And detecting a change amount of the output voltage of the signal amplifier rising from the value of the output voltage read in the second step. 47. The method of claim 46, wherein the first voltage is set to a value higher than an input threshold voltage of the signal amplifier.

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