KR100531940B1 - Method of manufacturing image sensor - Google Patents

Abstract

The present invention provides a method of manufacturing an image sensor that can prevent ion channeling in a transfer gate, simplify the gate forming process, and improve charge transfer efficiency.

The present invention provides a method for forming a semiconductor device, comprising: forming a field oxide film on a first conductive semiconductor substrate having a photodiode region and a transfer transistor region defined therein; Forming a gate insulating film and a transfer gate over the substrate in the transfer transistor region; Forming a first conductivity type first impurity region on the substrate surface of the photodiode region; Forming an insulating film pattern surrounding the transfer gate on the substrate; Forming a second conductivity type impurity region in the portion of the photodiode region adjacent to the transfer gate using the insulating layer pattern, the second conductive type impurity region having a concentration profile in which a portion of the surface concentration is similar to the internal concentration; Etching the insulating film pattern to form a spacer on the gate sidewall; And forming a first conductivity type second impurity region on the substrate surface of the photodiode region.

Description

Manufacturing Method of Image Sensor {METHOD OF MANUFACTURING IMAGE SENSOR}

The present invention relates to a method of manufacturing an image sensor, and more particularly, to a method of manufacturing an image sensor having a photodiode having a PNP structure.

In general, an image sensor is a semiconductor device that converts an optical image into an electrical signal. The image sensor is composed of an optical sensing part that senses light and a logic circuit part that processes the sensed light into an electrical signal to make data. (Complementary Metal Oxide Semiconductor) In the case of image sensor, CMOS technology is used to make MOS transistors by the number of pixels, and the switching method is used to detect the output sequentially.

The unit pixel of the image sensor is composed of a photodiode, which is a light sensing part, and four NMOS transistors. The transfer transistor of the four NMOS transistors transports photocharges generated in the photodiode to a floating diffusion region. The reset transistor discharges the charge stored in the floating diffusion region for signal detection, the drive transistor serves as the source follower, and the selective transistor switches. ) And addressing.

A conventional method of manufacturing the image sensor will be described with reference to FIGS. 1A and 1B.

Referring to FIG. 1A, a field oxide film 11 is formed on a P ⁺ semiconductor substrate 10 in which photodiode and transfer transistor regions are defined and a P ⁻ epitaxial layer is formed. Next, the gate insulating layer 12 and the transfer gate 13 are formed on the substrate 10 in the transfer transistor region, and the lower gate channeling of the transfer gate 13 is performed on the subsequent deep N ⁻ ion implantation process on the transfer gate 13. In order to prevent this, a cap layer 14 made of a TEOS film having a thickness of about 1500 mm 3 is formed. Thereafter, a mask pattern 15 for opening the photodiode region is formed by a photolithography process, and a deep N ⁻ ion implantation process and a first P ⁰ ion implantation process are sequentially performed using the mask pattern 15. The deep N ⁻ region 16 and the first P ⁰ region 17a are formed.

Referring to FIG. 1B, the mask pattern 15 is removed by a known method, and the spacer 18 is formed on the side of the transfer gate 13. Thereafter, the second P ⁰ ion implantation process and the N ⁺ ion implantation process are sequentially performed to form a P ⁰ region 17 formed of the first and second P ⁰ regions in the photodiode region to form a photodiode having a PNP structure. And a floating diffusion region 19 consisting of N ⁺ regions is formed in the transfer transistor region.

However, as described above, in order to form the cap layer 14 on the transfer gate 13 to prevent channeling of the deep N ⁻ ions, the cap material may be formed using a gate mask (not shown) after deposition of the gate material and the cap material. Since the first step of etching and then again etching the gate material must be performed, not only the gate forming process is complicated but also it is difficult to set an etching target.

In addition, due to the concentration distribution of the deep N ⁻ region 16 formed by self-alignment in the transfer gate 16, impurities in the P ⁰ region 17 diffuse and float floating beyond the transfer gate in the photodiode. as well as to create a potential barrier to charge transport passage leading to the area to interfere with the charge transport, the relatively low dip ^N-in area ^16-deep N adjacent to the transfer gate (13) due to a surface concentration of the region 16 Depletion occurs earlier on the surface than in the interior, thereby degrading the fringing field development during the operation of the transfer gate 13, thereby interfering with the charge transport, thereby lowering the charge transport efficiency.

The present invention has been proposed to solve the above problems of the prior art, and provides a method of manufacturing an image sensor that can prevent ion channeling in a transfer gate, simplify the gate forming process, and at the same time improve charge transport efficiency. Its purpose is to.

According to an aspect of the present invention for achieving the above technical problem, an object of the present invention comprises the steps of forming a field oxide film on the first conductivity type semiconductor substrate defined photodiode region and transfer transistor region; Forming a gate insulating film and a transfer gate over the substrate in the transfer transistor region; Forming a first conductivity type first impurity region on the substrate surface of the photodiode region; Forming an insulating film pattern surrounding the transfer gate on the substrate; Forming a second conductivity type impurity region in the portion of the photodiode region adjacent to the transfer gate using the insulating layer pattern, the second conductive type impurity region having a concentration profile in which a portion of the surface concentration is similar to the internal concentration; Etching the insulating film pattern to form a spacer on the gate sidewall; And forming a first conductivity type second impurity region on the substrate surface of the photodiode region.

Preferably, the insulating film pattern is made of an oxide film having a thickness of about 1500 kPa.

Hereinafter, preferred embodiments of the present invention will be introduced in order to enable those skilled in the art to more easily carry out the present invention.

A method of manufacturing an image sensor according to an exemplary embodiment of the present invention will be described with reference to FIGS. 2A and 2B.

Referring to FIG. 2A, a field oxide film 21 is formed on a P ⁺ semiconductor substrate 20 in which photodiode and transfer transistor regions are defined and a P ⁻ epitaxial layer is formed. Next, the gate insulating film 22 and the gate material film are sequentially deposited on the substrate 20, and the gate material film is etched using a gate mask (not shown) to transfer the gate onto the substrate 20 in the transfer transistor region. 23). Thereafter, a first mask pattern (not shown) for opening the photodiode region is formed by a photolithography process, and a first P ⁰ ion implantation process is performed on the substrate surface of the photodiode region using the first mask pattern. After forming the first P ⁰ region 24a, the first mask pattern is removed by a known method.

Thereafter, an insulating film, preferably an oxide film, is deposited on the entire surface of the substrate at a thickness of about 1500 GPa, and after forming a second mask pattern 26 for opening the photodiode region on the substrate by a photolithography process, the second mask pattern is formed. The oxide layer is etched using (26) to form an oxide layer pattern 25 surrounding the transfer gate 23. Next, a deep N ⁻ ion implantation process is performed using the second mask pattern 26 and the oxide layer pattern 25 to form the deep N ⁻ region 27 in the substrate 20 of the photodiode region. At this time, not only the channeling of the deep N ⁻ ions in the transfer gate 23 is prevented by the oxide layer pattern 25, but the surface of the deep N ⁻ region 27 is adjacent to the transfer gate 23 as illustrated. The concentration will have a rounded stepped concentration profile similar to the internal concentration.

Referring to FIG. 2B, the second mask pattern 26 is removed by the known method, and the oxide layer pattern 25 is etched to form the spacer 28 on the side of the transfer gate 23. Thereafter, the second P ⁰ ion implantation process and the N ⁺ ion implantation process are sequentially performed to form a P ⁰ region 24 formed of the first and second P ⁰ regions 24a and 24b in the photodiode region. A photodiode having a PNP structure is formed, and a floating diffusion region 29 formed of an N ⁺ region is formed in the transfer transistor region.

According to the above embodiment, after the oxide film pattern is formed to surround the transfer gate, a deep N ^- ion implantation process is performed using the oxide film pattern, thereby preventing deep N ^- ion channeling at the transfer gate. In addition, since the surface concentration of the deep N ⁻ region in the region adjacent to the transfer gate has a concentration similar to that of the internal concentration, it is not only possible to prevent the generation of potential barriers due to diffusion of impurities in the P ⁰ region, but also to the fringing field during operation of the transfer gate. Since the development can be improved, the charge transport efficiency can be improved.

In addition, since only the gate material layer is etched without applying a separate gate cap material, the gate forming process may be simplified as well as the etching process may be simplified.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes are possible in the art without departing from the technical spirit of the present invention. It will be clear to those of ordinary knowledge.

The present invention can prevent ion channeling in the transfer gate and simplify the gate forming process.

In addition, the present invention can improve the charge transport efficiency, it is possible to improve the low light characteristics of the image sensor.

1A and 1B are cross-sectional views illustrating a method of manufacturing a conventional image sensor.

2A and 2B are cross-sectional views illustrating a method of manufacturing an image sensor according to an embodiment of the present invention.

※ Explanation of symbols for main parts of drawing

20: P ⁺ semiconductor substrate 21: field oxide film

22: gate insulating film 23: gate

24a, 24b: first and second P ⁰ regions

25: oxide film pattern 26: mask pattern

27: deep N ^- region 28: spacer

29: floating diffusion region

Claims (3)

Forming a field oxide film on the first conductivity type semiconductor substrate on which the photodiode region and the transfer transistor region are defined; Forming a gate insulating film and a transfer gate on the substrate in the transfer transistor region; Forming a first conductivity type first impurity region on a surface of the substrate of the photodiode region; Forming an insulating film pattern surrounding the transfer gate on the substrate; Forming a second conductivity type impurity region in the portion of the photodiode region adjacent to the transfer gate using the insulating layer pattern, the second conductivity type impurity region having a concentration profile with a partial surface concentration similar to an internal concentration; Etching the insulating layer pattern to form a spacer on the gate sidewall; And And forming a first conductivity type second impurity region on the substrate surface of the photodiode region. The method of claim 1, The insulating film pattern is a manufacturing method of an image sensor, characterized in that consisting of an oxide film. The method according to claim 1 or 2, And the insulating film pattern has a thickness of about 1500 mW.