KR100790210B1 - Image sensor and fabricating method of thesame - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image sensor, and in particular, by forming the P0 region for photodiodes in a ridge type protruding on a substrate, it is possible to fundamentally prevent the formation of a barrier on the charge transfer path, thereby increasing charge transfer efficiency, To provide an image sensor and a method of manufacturing the same that can increase the capacitance by increasing the surface area of the diode, the present invention comprises: a transfer gate provided on the main surface of the first conductive semiconductor substrate; A first impurity region for a photodiode of a second conductivity type provided under a main surface of one side of the transfer gate; And a second impurity region for a photodiode of a first conductivity type provided on the main surface of the semiconductor substrate on one side of the transfer gate.

In addition, the present invention includes a first step of selectively etching the first conductive substrate so that the region on which the photodiode of the substrate is to be formed to protrude to a predetermined thickness; Forming a transfer gate on a main surface of the substrate to be adjacent to the photodiode region; Performing a ion implantation to form a first impurity region for a photodiode of a second conductivity type in the substrate below the protruding photodiode formation region so as to be adjacent to the transfer gate; And a fourth step of performing ion implantation to form a second impurity region for a photodiode of a first conductivity type in the protruding substrate.

Ridge, potential barrier, photodiode, charge transport, transfer gate.

Description

Image sensor and its manufacturing method {Image sensor and fabricating method of thesame}             

1 is a cross-sectional view showing an image sensor according to an example in the prior art,

2 is a schematic diagram showing a potential distribution according to FIG. 1, FIG.

3A to 3C are cross-sectional views illustrating an image sensor manufacturing process according to an embodiment of the present invention;

4 is a schematic diagram showing the potential distribution in FIG. 3C.

Explanation of symbols on the main parts of the drawings

30: substrate

31: field insulating film

32: transfer gate

33: spacer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to semiconductor devices, and more particularly to an image sensor, and more particularly, to an image sensor having a shortest distance charge transport path and a manufacturing method thereof.

In general, an image sensor is a semiconductor device that converts an optical image into an electrical signal. In a double charge coupled device (CCD), individual metal-oxide-silicon (MOS) capacitors are very different from each other. A device in which charge carriers are stored and transmitted in a capacitor while being in close proximity, and a CMOS (Complementary MOS) image sensor is a CMOS technology that uses a control circuit and a signal processing circuit as peripheral circuits. Is a device that employs a switching method that creates MOS transistors by the number of pixels and sequentially detects the output using them.

In the manufacture of such various image sensors, efforts are being made to increase the photo sensitivity of the image sensor, one of which is a condensing technology. For example, a CMOS image sensor is composed of a photodiode for detecting light and a portion of a CMOS logic circuit for processing the detected light into an electrical signal to make data. To increase light sensitivity, the ratio of the photodiode to the total image sensor area is increased. Efforts have been made to increase (usually referred to as Fill Factor).

1 is a cross-sectional view showing an image sensor according to the prior art.

Referring to FIG. 1, a field insulating film 11 is locally formed on a P-type substrate 10. The field insulating film 11 has a structure such as STI or LOCOS (LOCal Oxidation of Silicon). The gate electrode 12, that is, a transfer gate, is formed in an area away from the photodiode, and serves to transport the photoelectrons from the photodiode to the floating sensing node (hereinafter referred to as FD).

An impurity region n− for photodiode in contact with the field insulating film 11 and the gate electrode 12 is formed in the substrate 10 to a predetermined depth, and is formed by using a high energy, for example, energy of 160 KeV to 180 KeV. It is lightly doped. An impurity region (P0 region) in contact with the top of the n− region and the surface of the substrate 10 is formed.

That is, the photodiode having a PNP structure has a high potential of n-region, and photons generated inside the substrate 10 by the incident light are collected in the n- region. In addition, an n + region in contact with the gate electrode 12 is formed on the other side of the photodiode region, which serves as a sensing node.

The conventional image sensor as described above has a PNP structure photodiode structure by forming a P-type impurity region 16 on the NP structure photodiode in order to increase charge capacity and increase photosensitivity to short wavelengths. Fully depletion of the n- region and serves to prevent electrons from the lattice defects on the silicon surface of the photodiode from collecting in the n- region, whereas the upper P0 region is the In the case where a potential barrier is formed in the charge transport passage from the n− region to the transfer gate 12 in the n-region by the process, the signal B is not processed for electrons B that do not cross the potential barrier. The problem of lowering the sensitivity of light occurs, and the charge transport passage itself does not take a straight path and has a long curved shape. Castle, so is the generation loss (Loss) of electrical charge corresponding to the recombination (Recombination) according to the longer the routine (Routine) itself.

FIG. 2 is a schematic diagram illustrating the potential distribution of FIG. 1. As shown in FIG. 2, as the P0 region acts as a barrier, electrons of 'A' are transmitted but electrons of 'B' are transmitted. This indicates that the P0 barrier prevents the transfer, thereby reducing the charge transport efficiency.

The present invention proposed to solve the above problems of the prior art, by forming the P0 region for the photodiode in the form of a ridge protruding on the substrate, thereby essentially preventing charge formation by forming a barrier on the charge transfer path An object of the present invention is to provide an image sensor and a method of manufacturing the same, which can increase efficiency and increase capacitance by increasing the surface area of a photodiode.

In order to achieve the above object, the present invention, a transfer gate provided on the main surface of the first conductive semiconductor substrate; A first impurity region for a photodiode of a second conductivity type provided under a main surface of one side of the transfer gate; And a second impurity region for a photodiode of a first conductivity type provided on the main surface of the semiconductor substrate on one side of the transfer gate.                     

In addition, in order to achieve the above object, the present invention, a first step of selectively etching the first conductive substrate so that the region in which the photodiode of the substrate is to be formed to protrude to a predetermined thickness; Forming a transfer gate on a main surface of the substrate to be adjacent to the photodiode region; Performing a ion implantation to form a first impurity region for a photodiode of a second conductivity type in the substrate below the protruding photodiode formation region so as to be adjacent to the transfer gate; And a fourth step of performing ion implantation to form a second impurity region for a photodiode of a first conductivity type in the protruding substrate.

Preferably, the protruding second impurity region of the present invention is characterized in that the thickness of 0.1㎛ to 0.2㎛, the first conductive type is characterized in that the P-type, the second conductive type is characterized in that the N-type.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. do.

3C is a cross-sectional view illustrating an image sensor according to an exemplary embodiment of the present invention.

Referring to FIG. 3C, an image sensor of the present invention is used for a transfer gate 32 provided on a main surface of a P-type semiconductor substrate 30 and an N-type photodiode provided under a main surface of one side of the transfer gate 32. The impurity region n− and the P-type photodiode impurity region P0 protruding from the main surface of the semiconductor substrate 30 on one side of the transfer gate 32 are provided.

With reference to the accompanying drawings, the image sensor of the present invention having the above configuration will be described in detail.

3A to 3C are cross-sectional views illustrating an image sensor manufacturing process according to an embodiment of the present invention.

First, as shown in FIG. 3A, the P-type semiconductor substrate 30 is selectively etched so that the region PD on which the photodiode of the substrate 30 is to be formed protrudes to a thickness of 0.1 μm to 0.2 μm.

That is, before the image sensor manufacturing process, the substrate 30 is etched by wet etching so that the region PD on which the photodiode is to be formed is protruded as described above, which is the region PD on which the protruding photodiode is to be formed. By increasing the surface area of the photodiode to increase the electrode capacity of the photodiode, it is possible to fundamentally eliminate the potential barrier along the P0 region in the charge transport path.

Next, as shown in FIG. 3B, the substrate 30 is formed to form a field insulating film 31 for device isolation and to be adjacent to the photodiode forming region PD using a gate insulating film (not shown), polysilicon, or the like. After the transfer gate 32 is formed on the main surface of the N-type impurity region for the photodiode so as to be adjacent to the transfer gate 32 in the substrate 30 under the protruding photodiode formation region PD by ion implantation. to form (n-).

Specifically, an n-region in contact with the field insulating film 31 is formed to a predetermined depth inside the substrate 30 by using an ion implantation mask (not shown), and then doped at a low concentration using high energy. An ion implantation mask (not shown) is removed through the PR strip.

Next, as illustrated in FIG. 3C, after depositing a nitride film or the like on the front surface, the spacer 33 is formed on the sidewalls of the transfer gate 32 through the front surface etching to form a high concentration of N-type impurities for forming a sensing node. After implantation to form an n + region, ion implantation is performed to form a P-type electrode P0 for photodiode in the protruding substrate 30, whereby a depletion region is formed by P / N / P junction, thereby forming a photodiode. Is formed and FD (n +) of the P / N junction is formed.

FIG. 4 illustrates smooth movement of electrons as the barrier of the P0 region is removed by FIG. 3C.

According to the present invention made as described above, in the initial stage of the image sensor manufacturing process, the portion of the P0 region of the photodiode forming region protrudes into a ridge, thereby forming the P0 region on the protruding portion, thereby increasing the electrode capacity. In addition, it was found that the charge transport efficiency can be improved by removing the potential barrier caused by the P0 region on the charge transport path.

Meanwhile, although an example of forming a floor-like structure through wet etching in the initial stage of manufacturing the image sensor of the present invention is shown, in addition to the above-described method, the selective epitaxial growth method and the deposition in the photodiode forming process By a mask pattern process can be used.                     

Although the technical idea of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

The present invention described above can increase the charge transport efficiency of the photodiode, increase the electrode capacity of the photodiode, and ultimately can expect an excellent effect that can greatly improve the performance and yield of the photodiode.

Claims (7)

A semiconductor substrate having protrusions protruding from the main surface in regions where photodiodes are to be formed; A transfer gate formed on a main surface of the semiconductor substrate toward one side of the protrusion; A first impurity region for a photodiode formed in the semiconductor substrate below the protrusion; And A second impurity region for a photodiode formed in a convex shape different from the first impurity region in the protruding portion with the main surface of the semiconductor substrate as a boundary; Image sensor comprising a. The method of claim 1, The protrusion is formed in the thickness of 0.1㎛ 0.2㎛ from the main surface of the semiconductor substrate. The method of claim 1, And the first impurity region is N-type and the second impurity region is P-type. Forming a protrusion in a region where a photodiode is to be formed on a main surface of the semiconductor substrate; Forming a transfer gate on a main surface of the semiconductor substrate spaced apart from one side of the protrusion; Forming a first impurity region for a photodiode in the semiconductor substrate below the protrusion; Forming spacers on both sidewalls of the transfer gate; And Forming a second impurity region for a photodiode in a convex shape different from the first impurity region in the protrusion part aligned with one side of the spacer and bordering a main surface of the semiconductor substrate; Image sensor manufacturing method comprising a. The method of claim 4, wherein The protrusion is an image sensor manufacturing method to form a thickness of 0.1㎛ to 0.2㎛. The method of claim 4, wherein And the first impurity region is N-type and the second impurity region is P-type. The method of claim 4, wherein Forming the protrusions, A method of manufacturing an image sensor formed by any one of a selective wet etching process, a selective epitaxial growth process, and a selective deposition process.

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