KR100331851B1 - Solid state image sensor and for manufacturing the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device and a method of manufacturing the same, which improve charge transfer efficiency by rapidly moving charges when they are moved by a transfer gate bias voltage to floating diffusion of photoelectrically converted charges in a CMOS image receiving unit. A transfer gate formed through the gate insulating film, an insulating film sidewall formed on both sides of the transfer gate, a first photodiode region formed on the surface of the semiconductor substrate under the insulating film sidewall and having a conductivity opposite to that of the semiconductor substrate; A second photodiode region and a floating diffusion region formed at a higher concentration than the first photodiode region in the semiconductor substrate surfaces on both sides of the insulating film sidewall, and having different concentrations in the surface of the semiconductor substrate so as to contact the second photodiode region; 3rd, 4th Po And a second conductivity type impurity diffusion region formed on a surface of the todiode region and the second, third and fourth photodiode regions.

Description

Solid-state image sensor and its manufacturing method {SOLID STATE IMAGE SENSOR AND FOR MANUFACTURING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid state image pickup device, and more particularly, to a solid state image pickup device suitable for effectively transferring charges of a light receiving portion to a floating diffusion portion and a method of manufacturing the same.

In general, a solid-state imaging device refers to a device that photographs a subject using an photoelectric conversion device and a charge coupling device to output an electrical signal.

The charge coupling device is used to transfer the signal charge generated in the photoelectric conversion device (photodiode) through the color filter layer through the microlens in a specific direction by using the variation of the potential in the substrate.

The solid-state imaging device includes a plurality of photoelectric conversion regions PD, a vertical charge transfer region (VCCD: Vertical CCD) configured between the photoelectric conversion regions to transfer charges generated in the photoelectric conversion regions in a vertical direction; A horizontal charge transfer region (HCCD: Horizontal CCD) for transferring the charges transferred in the vertical direction by the vertical charge transfer region back to the horizontal direction, and a floating diffusion for sensing, amplifying, and outputting the horizontal transferred charges to a peripheral circuit. It is largely composed of areas.

Hereinafter, a conventional solid-state imaging device will be described with reference to the accompanying drawings.

1 is a structural cross-sectional view showing a conventional solid-state imaging device.

As shown in FIG. 1, a transfer gate 13 is formed on a p-type semiconductor substrate 11 via a gate insulating film 12, and within the surface of the semiconductor substrate 11 on one side of the transfer gate 13. A photodiode region consisting of a high concentration n-type impurity diffusion region 14 and a low concentration n-type impurity diffusion region 15 is formed.

A floating diffusion region 16 is formed in the surface of the semiconductor substrate 11 on the other side of the transfer gate 13, and is formed on the surfaces of the high concentration n-type impurity diffusion region 14 and the low concentration n-type impurity diffusion region 15. A high concentration p-type impurity diffusion region 17 is formed.

On the other hand, the low concentration n-type impurity diffusion region 15 is formed to extend to the lower portion of the high concentration n-type impurity diffusion region 14.

2 is a view showing a potential profile of a conventional solid-state imaging device.

As shown in FIG. 2, when a constant charge is accumulated in the photodiode region by the photoelectric effect, and then a high voltage is momentarily applied (or a low temperature) to the transfer gate 13, the charges accumulated in the photodiode region are Moving to the vertical charge transfer region (in the direction of the arrow in the drawing), the floating diffusion region 16 is well-filled, and the charged diffusion region 16 is charged through the floating diffusion region 16 due to the difference in voltage. Is output.

However, in the conventional solid-state imaging device as described above, there are the following problems.

That is, when the charges photoelectrically converted in the CMOS image receiver are moved to the floating diffusion region by the transfer gate bias voltage (5V), the charges are not completely moved, and thus a good image cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. The present invention provides a solid-state device for rapidly transferring charges when the photoelectrically converted charges are transferred to the floating diffusion in the CMOS image receiving unit by floating gate bias voltage to improve charge transfer efficiency. It is an object of the present invention to provide an image pickup device and a method of manufacturing the same.

1 is a structural cross-sectional view showing a conventional solid-state imaging device

2 shows a potential profile of a conventional solid-state imaging device.

3 is a structural sectional view showing a solid-state imaging device according to the present invention.

4 shows a potential profile of a solid-state imaging device according to the present invention.

5A to 5F are cross-sectional views illustrating a method of manufacturing a solid-state imaging device according to the present invention.

Explanation of symbols for main parts of the drawings

21 p-type semiconductor substrate 22 gate insulating film

23 transfer gate 24 first photoresist

25: first photodiode region 26: insulating film sidewall

27: second photoresist 28: second photodiode region

29: floating diffusion region 30: third photoresist

31: third photodiode region 32: fourth photodiode region

33: high concentration p-type impurity diffusion region

A solid-state imaging device according to the present invention for achieving the above object is a transfer gate formed on the semiconductor substrate via a gate insulating film, the insulating film sidewalls formed on both sides of the transfer gate, the semiconductor substrate under the insulating film sidewalls A first photodiode region formed on the surface of the semiconductor substrate opposite to the semiconductor substrate, a second photodiode region and a floating diffusion region formed at a higher concentration than the first photodiode region on the semiconductor substrate surfaces on both sides of the insulating film sidewall; Third and fourth photodiode regions formed at different concentrations in the surface of the semiconductor substrate so as to contact the second photodiode regions, and second conductive layers formed on the surfaces of the second, third and fourth photodiode regions. It is characterized in that it comprises a type impurity diffusion region.

In addition, a method of manufacturing a solid-state imaging device according to the present invention for achieving the above object is a step of forming a transfer gate on the first conductive semiconductor substrate via a gate insulating film, and the semiconductor substrate of both sides of the transfer gate; Forming a second conductive type first photodiode region in the surface, forming insulating film sidewalls on both sides of the transfer gate, and forming a second concentration higher than the first photodiode region in the semiconductor substrate surface on both sides of the insulating film sidewall. Forming a photodiode region and a floating diffusion region, forming a third photodiode region having a lower concentration than a second photodiode region in the semiconductor substrate surface on one side of the insulating film sidewall, and the second and third photodiode regions. And forming a first conductivity type impurity diffusion region on a surface of the substrate. It is characterized by.

Hereinafter, a solid-state imaging device and a method of manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.

3 is a structural sectional view showing a solid-state imaging device according to the present invention.

As shown in FIG. 3, the transfer gate 23 is formed on the p-type semiconductor substrate 21 via the gate insulating film 22, and the insulating film sidewall 26 is formed on both sides of the transfer gate 23. Formed.

Subsequently, a first photodiode region 25 formed of a low concentration n-type impurity diffusion region is formed in a surface of the semiconductor substrate 21 below the insulating film sidewall 26, and the semiconductor substrate 21 on both sides of the insulating film sidewall 26 is formed. A second photodiode region 28 and a floating diffusion region 29 each having a high concentration n + type impurity diffusion region are formed in the surface.

And a third photodiode region 32 and a fourth photo, each consisting of an n-type impurity diffusion region and a second low concentration n-type impurity diffusion region, respectively, in the surface of the semiconductor substrate 21 so as to contact the second photodiode region 28. Diode regions 33 are formed, respectively, and high concentration p-type impurity diffusion regions 33 are formed on the surfaces of the second, third and fourth photodiode regions 28, 31 and 32.

The high concentration p-type impurity diffusion region 33 not only prevents noise charges from entering the photodiode region through the surface of the semiconductor substrate, but also a silicon-silicon oxide layer (Si-SiO) that is a source of dark current. ₂ ) It plays a role in blocking the function as a cause of occurrence by trapping the interface in the non-depletion region.

Meanwhile, the third photodiode region 31 is formed deeper than the second photodiode region 28 and the first photodiode region 25, and the second photodiode region 28 is the first photodiode. It is formed deeper than the diode region 25.

In addition, the third photodiode region 31 is formed at the same impurity concentration as the first photodiode region 25 and has a lower impurity concentration than the fourth photodiode region 32.

That is, the fourth photodiode region 32 is formed by overlapping the third photodiode region 31 and the first photodiode region 25.

4 is a view showing the potential profile of the solid-state imaging device according to the present invention.

As shown in FIG. 4, the potential profile of the third photodiode region 31 and the first photodiode region 25 forms a stepped shape, thereby floating the photoelectric conversion charges in the CMOS image sensor receiver. ) By the transfer gate 23 bias voltage to complete the movement without leaving a charge when the movement to obtain a high-quality image.

5A to 5F are process cross-sectional views showing the manufacturing method of the solid-state imaging device according to the present invention.

As shown in FIG. 5A, a gate insulating film 22 is formed on the p-type semiconductor substrate 21, a polysilicon layer is formed on the gate insulating film 22, and then selectively patterned to transfer the gate 23. To form.

Here, the p-type semiconductor substrate 21 may be formed by implanting p-type impurity ions into the entire surface of the n-type semiconductor substrate to form a p-well region in the surface of the semiconductor substrate and then proceed with the subsequent process.

As shown in FIG. 5B, after applying the first photoresist 24 to the entire surface of the semiconductor substrate 21, the first photoresist 24 is patterned by exposure and development.

Subsequently, low concentration n-type impurity ions are implanted into the entire surface using the patterned first photoresist 24 and the transfer gate 23 as a mask to expose the surface of the exposed semiconductor substrate 21 on both sides of the transfer gate 23. The first photodiode region 25 is formed therein.

As shown in FIG. 5C, the first photoresist 24 is removed, an insulating film is formed on the entire surface of the semiconductor substrate 21 including the transfer gate 23, and an etch back process is performed to perform the transfer gate. An insulating film sidewall 26 is formed on both sides of the 23.

The cap insulating film may be formed on the transfer gate 23 before the insulating film sidewall 26 is formed.

As shown in FIG. 5D, the second photoresist 27 is coated on the entire surface of the semiconductor substrate 21, followed by an exposure and development process to pattern the second photoresist 27.

Subsequently, a high concentration of n-type impurity ions are implanted into the entire surface by using the patterned second photoresist 27 as a mask to form a second photodiode region in the surface of the exposed semiconductor substrate 21 on both sides of the insulating film sidewall 26. 28 and floating diffusion region 29 are formed, respectively.

As shown in FIG. 5E, the second photoresist 27 is removed, the third photoresist 30 is applied to the entire surface of the semiconductor substrate 21, and then exposed and developed to perform a third process. The photoresist 30 is patterned.

Subsequently, low concentration n-type impurity ions are implanted into the entire surface by using the patterned third photoresist 30 as a mask to form a third photodiode region 31 in the surface of the exposed semiconductor substrate 21.

Here, the portion where the third photodiode region 31 and the first photodiode region 25 overlap each other may have a higher concentration of the fourth photodiode region 31 than the third photodiode region 31 and the first photodiode region 25. 32) is formed.

The third photodiode region 31 is formed deeper than the first photodiode region 25.

In addition, a high concentration of p-type impurity ions is implanted into the entire surface by using the third photoresist 30 as a mask to diffuse the high concentration of p-type impurity onto the surfaces of the second, third, and fourth photodiode regions 28, 31, and 32. The region 33 is formed.

As shown in FIG. 5F, the process according to the present invention is completed by removing the third photoresist 30 and then proceeding.

As described above, the solid-state imaging device and its manufacturing method according to the present invention have the following effects.

First, the charges generated in the light receiving portion can be easily moved to the source portion of the transfer gate by the potential profile, thereby improving charge transfer efficiency.

Second, since the impurity diffusion regions formed on both sides of the transfer gate are formed in the LDD structure, noise due to hot carriers can be reduced.

Claims (6)

A transfer gate formed on the semiconductor substrate via a gate insulating film; An insulating film sidewall formed on both sides of the transfer gate; A first photodiode region formed in a surface of the semiconductor substrate below the sidewalls of the insulating film, the semiconductor substrate having a conductivity type opposite to that of the semiconductor substrate; A second photodiode region and a floating diffusion region formed at a higher concentration than the first photodiode region in the semiconductor substrate surfaces on both sides of the insulating film sidewall; Third and fourth photodiode regions formed at different concentrations in the surface of the semiconductor substrate so as to contact the second photodiode regions; And a second conductivity type impurity diffusion region formed on the surface of said second, third, and fourth photodiode regions. The solid-state imaging device as claimed in claim 1, wherein the third photodiode region is formed deeper than the second photodiode region and the first photodiode region. The solid-state imaging device as claimed in claim 1, wherein the second photodiode region is formed deeper than the first photodiode region. The solid-state imaging device as claimed in claim 1, wherein the third photodiode region is formed at the same impurity concentration as the first photodiode region, and has a lower impurity concentration than the fourth photodiode region. Forming a transfer gate on the first conductive semiconductor substrate via a gate insulating film; Forming a second conductivity type first photodiode region in a surface of the semiconductor substrate on both sides of the transfer gate; Forming sidewalls of an insulating film on both sides of the transfer gate; Forming a second photodiode region and a floating diffusion region having a higher concentration than the first photodiode region in the semiconductor substrate surfaces on both sides of the insulating film sidewall; Forming a third photodiode region having a lower concentration than a second photodiode region in a surface of the semiconductor substrate on one side of the insulating film sidewall; And forming a first conductivity type impurity diffusion region on the surfaces of the second and third photodiode regions. 6. The method of claim 5, wherein the fourth photodiode region having a higher concentration than the first and third photodiode regions and a lower concentration than the second photodiode region is formed in a portion where the first and third photodiode regions overlap. The manufacturing method of the solid-state image sensor.