KR20110078869A

KR20110078869A - Method for manufacturing an image sensor

Info

Publication number: KR20110078869A
Application number: KR1020090135781A
Authority: KR
Inventors: 김정운
Original assignee: 주식회사 동부하이텍
Priority date: 2009-12-31
Filing date: 2009-12-31
Publication date: 2011-07-07

Abstract

PURPOSE: A method for manufacturing an image sensor is provided to prevent the pinch-off a connector region by making a deflection direction to the outside of a gate. CONSTITUTION: In a method for manufacturing an image sensor, a photo diode doped region(202) is formed in a semiconductor substrate(201). A connector region is formed by implanting impurities on the top side of the photo diode doped region A drain region is formed by implanting impurities on the surface of a semiconductor substrate. The first impurities are implanted on the surface of the semiconductor substrate. A gate electrode is formed on the semiconductor substrate.

Description

Method for manufacturing an image sensor

This embodiment discloses a method of manufacturing an image sensor.

Image sensors can be roughly divided into CCD and CMOS image sensors, and these two devices basically use an electron-hole pair generated by light of energy larger than the silicon bandgap. Or a hole) to estimate the amount of light emitted.

Since CMOS image sensors use photodiodes and transistors similarly to the general CMOS devices in each image pixel, and use the conventional CMOS semiconductor manufacturing process as they are, they must have an image signal processor on a separate chip. Compared to a CCD, an integrated circuit for image signal processing and detection can be integrated in an external pixel block, low voltage operation is possible, and manufacturing cost is low.

In general, a CMOS image sensor is divided into a four-transistor pixel structure and a three-transistor pixel structure by the number of transistors forming one pixel. Although the three-transistor pixel structure has advantages in terms of fill factor and manufacturing cost, it is highly responsive and sensitive to light by separating the light receiver from the detector and making the light receiver with silicon bulk excluding the surface. 4-transistor pixel structures that are resistant to dark current and noise are generally used.

1 and 2 are diagrams for explaining a problem that may occur in a conventional image sensor.

The transfer transistor includes a gate electrode 106, a substrate 101, and a photodiode region. The photodiode region includes a photodiode doped region 102, a surface doped region 104, and a photodiode doped region 102. And a connector region 103 into which impurities are injected to move the generated electrons to the drain region 105.

In order to produce a high quality image, electrons generated in the photodiode doped region 102 must be accurately moved without loss through the transfer gate. However, this requires an accurate photo process, so implementation is not easy.

And, as shown, in the case where the photodiode region has a three-layer stack structure, moving photo electrons buried under the silicon surface without loss is a large factor that determines the quality of an image.

However, as shown in FIG. 1, when the key hole A serving as the entrance and exit of the photo electrons is smaller than the expected area, a situation occurs in which electrons are not sufficiently delivered. On the other hand, as shown in FIG. 2, when the keyhole is larger than expected, electrons flow toward the silicon surface to form a leakage current, which adversely affects the image.

This phenomenon is an easy factor due to the process change occurring in the photo process.

Therefore, it is necessary to prevent electrons leaking to the silicon surface while stably securing the key hole area of the connector region.

This embodiment proposes a method of manufacturing an image sensor that can reduce the loss of electrons generated in the photodiode doped region and move the leakage current effectively.

In the present embodiment, a method of manufacturing an image sensor includes forming a photodiode doped region on a semiconductor substrate; Implanting impurities into the photodiode doped region to form a connector region; Implanting impurities into a surface of the semiconductor substrate to form a drain region; Forming a first photoresist pattern on the semiconductor substrate and performing a first impurity implantation process on a surface of the semiconductor substrate; Forming a gate electrode on the semiconductor substrate, and forming a second photoresist pattern on the gate electrode and on the drain region; And forming a surface doped region on the photodiode doped region by performing a second impurity implantation process using the second photoresist pattern as an ion implantation mask.

The forming of the second photoresist pattern may be patterned to expose a portion of the gate electrode.

In addition, the first impurity implantation process injects a small amount of impurities compared to the second impurity implantation process.

By the method of manufacturing an image sensor as proposed, it is possible to reduce the loss of electrons generated in the photodiode doped region, and to effectively block the path of leakage current.

Hereinafter, with reference to the accompanying drawings for the present embodiment will be described in detail. However, the scope of the idea of the present invention may be determined from the matters disclosed by the present embodiment, and the idea of the invention of the present embodiment may be performed by adding, deleting, or modifying components to the proposed embodiment. It will be said to include variations.

In the following description, the word 'comprising' does not exclude the presence of other elements or steps than those listed. In addition, in the accompanying drawings, the thickness thereof is enlarged in order to clearly express various layers and regions. In addition, the same reference numerals are used for similar parts throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only being another part "on top" but also having another part in the middle.

3 and 4 are views for explaining the manufacturing method of the image sensor according to the present embodiment.

First, referring to FIG. 3, a photodiode doped region 202 is formed by injecting a second conductive dopant into a semiconductor substrate 201 of a first conductivity type, and a second layer is formed on the photodiode doped region 202. The connector region 203 is formed by implanting conductive impurities.

Then, an impurity implantation process for forming the drain region 205 of the transfer transistor is performed.

A first photoresist pattern 310 is formed to cover the region where the gate electrode is to be formed and the drain region 205, and the first photoresist pattern 310 is formed as an ion implantation mask. Using the first impurity implantation process to form the surface doped region. In this case, the first impurity implantation process performed is smaller than the second impurity implantation process described later.

Next, referring to FIG. 4, the first photoresist pattern 310 is removed and a gate electrode 206 is formed on the substrate 201.

In addition, a second photoresist pattern 320 is formed on the gate electrode 206 and the drain region 205, and a second impurity implantation process using the second photoresist pattern 320 as an ion implantation mask is performed. To perform.

Here, the second photoresist pattern 320 is formed to expose a portion of the upper side of the gate electrode 206 by considering the variation width generated when the gate is formed. In this case, the impurity concentration of the lower right side of the gate electrode 206 may be formed smaller than the surface doped region 204. This is because impurities cannot be formed by the second impurity implantation process inside the region blocked by the second photoresist pattern 320. However, according to a modification of the embodiment, the second photoresist pattern 320 may be formed in the same manner as the first photoresist pattern 310.

By this method, the injection region of the first conductivity type impurity (for example, P-type ion) is kept out of the gate region, thereby blocking the path of leakage current, and together with the key hole B of the connector region 203. Even if the) region is formed small, the pinch-off phenomenon of the connector region 203 can be prevented by directing the deflation direction toward the gate outward direction (arrow direction shown).

1 and 2 are views for explaining a problem that may occur in the conventional image sensor.

Claims

Forming a photodiode doped region in the semiconductor substrate;

Implanting impurities into the photodiode doped region to form a connector region;

Implanting impurities into a surface of the semiconductor substrate to form a drain region;

Forming a first photoresist pattern on the semiconductor substrate and performing a first impurity implantation process on a surface of the semiconductor substrate;

Forming a gate electrode on the semiconductor substrate, and forming a second photoresist pattern on the gate electrode and on the drain region; And

And forming a surface doped region above the photodiode doped region by performing a second impurity implantation process using the second photoresist pattern as an ion implantation mask.

The method of claim 1,

The forming of the second photoresist pattern may include patterning such that a portion of the gate electrode is exposed.

The method of claim 1,

The method of claim 1, wherein the first impurity implantation process implants a small amount of impurities as compared to the second impurity implantation process.

The method of claim 1,

The first impurity implantation process and the second impurity implantation process is a method of manufacturing an image sensor to implant the P-type impurities.