KR20100060765A

KR20100060765A - Image sensor and a method of manufacturing the same

Info

Publication number: KR20100060765A
Application number: KR1020080119499A
Authority: KR
Inventors: 박지환
Original assignee: 주식회사 동부하이텍
Priority date: 2008-11-28
Filing date: 2008-11-28
Publication date: 2010-06-07

Abstract

PURPOSE: An image sensor and a method of manufacturing the same are provided to suppress a leakage current from a gate of a transfer transistor by forming P well around a floating area and separating a floating area from the photodiode. CONSTITUTION: A gate oxidation film(120) is formed on a semiconductor substrate(110). A gate electrode(125) is formed on the gate oxidation film. A first conductive impurity ion is implanted into a semiconductor substrate of one side of gate electrode to form a first conductive well(145). A second conductive impurity ion is implanted into the semiconductor substrate of the other side of the gate electrode to form a photo diode(160). The second conductive impurity ion is implanted into the semiconductor substrate of one side of the gate electrode to form a floating diffusion region(170).

Description

Image sensor and a method of manufacturing the same

The present invention relates to a semiconductor device, and more particularly, to an image sensor and a manufacturing method thereof.

An image sensor refers to a semiconductor device that converts an optical image into an electrical signal, and includes a CCD (Charge Coupled Device) device and a CMOS (Complementary Metal-Oxide-Silicon) device. The image sensor is composed of a light receiving area including a photodiode for detecting light and a logic area for processing the detected light into an electrical signal to make data. The unit pixel of the image sensor may be composed of a photodiode and one or more transistors.

In general, in the CMOS image sensor, ion implantation for well formation is not performed in order to minimize the influence of impurities caused by ion implantation in the pixel region. This is to prevent electrons generated in the photodiode by light from being dissipated by impurities by not performing ion implantation for well formation.

However, under such a structure, there is a difficulty in isolation between the photodiode and the floating region, and electrons generated in the photodiode form leakage current, which may be a factor that inhibits the electrical characteristics of the photodiode.

The technical problem to be achieved by the present invention is to suppress the leakage current of the gate of the transfer transistor of the image sensor to prevent the leakage of electrons generated in the photodiode to the floating diffusion region, etc. Image sensor and its manufacture To provide a method.

According to another aspect of the present invention, there is provided a method of manufacturing an image sensor, the method including forming a gate oxide film on a semiconductor substrate, forming a gate electrode on the gate oxide film, and forming a gate electrode on one side of the gate electrode. Implanting first conductivity type wells into the semiconductor substrate to form a first conductivity type well, implanting second conductivity type impurity ions into the semiconductor substrate on the other side of the gate electrode to form a photodiode, and the gate And implanting second conductivity type impurity ions into the semiconductor substrate on one side of the electrode to form a floating diffusion region.

The image sensor according to an embodiment of the present invention for achieving the above object is a gate oxide film formed on a semiconductor substrate, a gate electrode formed on the gate oxide film, a first formed in the semiconductor substrate on one side of the gate electrode A conductive well, a photodiode formed by implanting a second conductivity type impurity ion into the semiconductor substrate on the other side of the gate electrode, and a second conductivity type impurity ion is implanted into the first conductivity type well formed on one side of the gate electrode And a floating diffusion region formed, wherein the first conductivity type well extends to one region of the lower semiconductor substrate of the gate electrode.

An image sensor and a method of manufacturing the same according to an embodiment of the present invention have an effect of suppressing a leakage current of a gate of a transfer transistor by forming a P-type well around a floating diffusion region to isolate the floating diffusion region from a photodiode region. have.

Hereinafter, the technical objects and features of the present invention will be apparent from the description of the accompanying drawings and the embodiments. Looking at the present invention in detail.

1 to 4 are process diagrams illustrating a method of manufacturing an image sensor according to an exemplary embodiment of the present invention.

First, as shown in FIG. 1, an isolation layer 115 defining an isolation region and an active region is formed on the semiconductor substrate 110. For example, the semiconductor substrate 110 may be a P-type silicon substrate, and the P-type silicon substrate may include a low concentration P-type epi layer.

The device isolation layer 115 may be formed using a conventional recessed-local oxide of silicon (R-LOCOS) technique or a shallow trench isolation (STI) technique.

A gate oxide layer 120 is formed on the semiconductor substrate 110 on which the device isolation layer is formed. The gate electrode 125 of the transfer transistor is formed on the gate oxide layer.

For example, the gate oxide layer 120 and the polysilicon (not shown) are sequentially formed on the entire surface of the semiconductor substrate 110. Thereafter, a first photoresist pattern 130 is formed on the polysilicon using a photolithography process. The gate electrode 125 may be formed by dry etching the polysilicon using the first photoresist pattern 130 as a mask.

In order to simplify the process by reducing the process step, the photolithography process is performed without removing the first photoresist pattern 130 to cover the region where the photodiode is to be formed and to expose the region where the floating gate is to be formed. 2 photoresist pattern 135 is formed.

Subsequently, a P-type well 140 is formed by performing a first implant process in which impurity ions are vertically implanted into the semiconductor substrate 110 using the second photoresist pattern 135 as a mask.

The P-type well 140 suppresses leakage current of the transfer gate by isolating between a later-formed photodiode and a floating region to be formed later, and prevents electrons generated from the photodiode from leaking. It serves to improve the electrical characteristics of the photodiode, such as.

In this case, the first implant process may be performed as follows. The impurity ions may be P-type impurity ions such as boron, and impurity ions perpendicular to the semiconductor substrate 110 with an energy of 50 to 250 KeV and a dose of 1E13 to 5E13 atoms / cm 2. Can be injected.

Next, as illustrated in FIG. 3, the gate electrode 125 may be formed by performing a second implant process of obliquely implanting impurity ions into the semiconductor substrate 110 using the second photoresist pattern 135 as a mask. The P-type well 145 extended to one region of the lower semiconductor substrate 110 is formed.

In this case, the second implant process may be performed as follows. The impurity ions are BF ₂ + can be ions, and impurities in the energy and help switch (dose) of 5E12 ~ 2E13 atoms / ㎠ of 30 ~ 100KeV to tilt (tilt) of 20 ~ 45 ° with respect to the semiconductor substrate 110 Ions can be implanted.

The second implant process is to increase the isolation effect between the photodiode and the floating region to be formed later by forming a well up to a part of the channel region under the transfer gate.

Next, as shown in FIG. 4, spacers 150 are formed on sidewalls of the gate electrode 125. For example, an insulating film is formed on the semiconductor substrate 110 on which the gate electrode 125 and the extended P-type well 145 are formed, and the insulating film is etched back to form a spacer 150 on the sidewall of the gate electrode 125. Can be formed. In this case, the spacer 150 may include at least one of an oxide film and a nitride film.

Next, the photodiode 160 is formed by selectively implanting N-type impurity ions into the region where the photodiode is to be formed in the semiconductor substrate 110. N-type impurity ions are selectively implanted into the P-type well 145 to form a floating diffusion region 170.

As shown in FIG. 4, since the P-type well 145 is formed around the floating diffusion region 170, the floating diffusion region 170 may be isolated from the photodiode region to leak the gate of the transfer transistor. Current can be suppressed.

In addition, since the P-type well 145 is formed only around the floating expansion region, and the impurity ions are not implanted into the photodiode region to form the well, the photodiode is not affected by impurities.

The image sensor according to the exemplary embodiment of the present invention illustrated in FIG. 4 includes a gate oxide film 120 formed on the semiconductor substrate 110, a gate electrode 125 formed on the gate oxide film 120, and the gate electrode ( A photodiode formed by implanting a second conductivity type impurity ion into the first conductivity type well 145 formed in the semiconductor substrate 110 on one side of the semiconductor substrate 110 and the semiconductor substrate 110 on the other side of the gate electrode 125. And a floating diffusion region 170 formed by implanting second conductivity type impurity ions into the first conductivity type well 145 formed on one side of the gate electrode 125. 145 may extend to one region of the lower semiconductor substrate 110 of the gate electrode 125.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be evident to those who have knowledge of. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims

Forming a gate oxide film on the semiconductor substrate;

Forming a gate electrode on the gate oxide film;

Implanting first conductivity type impurity ions into a semiconductor substrate on one side of the gate electrode to form a first conductivity type well;

Implanting second conductivity type impurity ions into the semiconductor substrate on the other side of the gate electrode to form a photodiode; And

And implanting second conductivity type impurity ions into the semiconductor substrate on one side of the gate electrode to form a floating diffusion region.

The method of claim 1, wherein the forming of the gate electrode comprises:

Forming poly silicon on the gate oxide film;

Forming a first photoresist pattern on the polysilicon using a photolithography process; And

And dry etching the polysilicon using the first photoresist pattern as a mask to form the gate electrode.

The method of claim 1, wherein the forming of the first conductivity type well comprises:

A first well implant step of injecting boron perpendicularly to the semiconductor substrate; And

BF ₂ + ion the production method of the image sensor, characterized in that it comprises a second well implant step for implanting a tilt (tilt) of 20 ~ 45 ° with respect to the semiconductor substrate.

The method of claim 2, wherein the forming of the first conductivity type well comprises:

Performing a photolithography process without removing the first photoresist pattern to form a second photoresist pattern covering a region where a photodiode is to be formed and exposing a region where the floating gate is to be formed;

A first implant step of implanting impurity ions perpendicularly to the semiconductor substrate using the second photoresist pattern as a mask; And

And a second well implant step of implanting impurity ions into the semiconductor substrate at a tilt of 20 ° to 45 ° using the second photoresist pattern as a mask.

A gate oxide film formed on the semiconductor substrate;

A gate electrode formed on the gate oxide film;

A first conductivity type well formed in the semiconductor substrate on one side of the gate electrode;

A photodiode formed by implanting second conductivity type impurity ions into the semiconductor substrate on the other side of the gate electrode; And

A floating diffusion region formed by implanting second conductivity type impurity ions into a first conductivity type well formed on one side of the gate electrode,

And the first conductivity type well extends to a region of a lower semiconductor substrate of the gate electrode.