KR20040002002A - Method of manufacturing a image device - Google Patents

Abstract

PURPOSE: A method for manufacturing an image device is provided to be capable of carrying out a self-alignment between a gate electrode and an ion implantation mask by using low reflectivity of a lower BARC(Bottom Anti-Reflective Coating). CONSTITUTION: A semiconductor substrate(110) is defined with a photo diode region(A) and a gate electrode region(Z). A tunnel oxide layer(113), a polysilicon layer(114), and a BARC(118) are sequentially formed at the upper portion of the semiconductor substrate. A plurality of gate electrodes(116) are formed at the gate electrode region by carrying out a gate patterning process at the resultant structure. After depositing a photoresist layer on the entire surface of the resultant structure, an ion implantation mask(126) is formed by carrying out a lithography process using an exposure mask for opening the photo diode region. A predetermined ion implantation is carried out at the resultant structure.

Description

Method of manufacturing a image device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure mask and a method of forming a photoresist pattern using the same. The present invention relates to an exposure mask for implanting ions with a high implantation amount during a manufacturing process of an image sensor, which is a semiconductor device, and a photoresist pattern using the same.

In the manufacturing process of a conventional image sensor, a gate electrode is formed, and then a high implantation amount of N-type ion implantation is performed in a region where a photodiode is to be formed. However, after the gate electrode patterning, the alignment of the photoresist pattern for ion implantation is not accurate, which causes many problems.

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

Referring to FIG. 1A, a device isolation layer 12 is formed on a semiconductor substrate 10 in which a photodiode region A is defined to separate devices. Polysilicon 14 is deposited on top of the entire structure and then planarized. The first photoresist layer pattern 20 is formed by coating a photoresist layer on the polysilicon 14 and then performing a patterning process. In the first photoresist layer pattern 20, the photoresist layer is positioned on the region where the gate electrode is to be formed and exposes the polysilicon 14 in a region excluding the gate electrode.

Referring to FIG. 1B, an etching process using the first photoresist pattern 20 as an etching mask is performed to form the gate electrode 16. The second photoresist layer pattern 22 is formed by depositing a photoresist layer over the entire structure and then performing exposure and development processes using an exposure mask 50 for implanting a high implantation amount of N-type ion. The second photoresist layer pattern 22 exposes the photodiode region A. FIG. A high capacity N-type ion implantation using the second photosensitive film pattern 22 as an ion implantation mask is performed.

At this time, in the exposure process performed when the second photoresist pattern 22 is formed, a portion of the first photoresist pattern 20 on the gate electrode 16 is exposed without being accurately aligned on the gate electrode 16 (FIG. 1B). See M). That is, an ion implantation mask formed of the first photoresist pattern 20 is formed on the gate electrode 16 adjacent to the photodiode region A, and an ion implantation mask composed of the second photoresist pattern 20 having a sufficient thickness in the remaining region. Is formed. As a result, when the N-type ion implantation having a high capacitance is formed, an unwanted ion layer is formed under the gate electrode 16, which causes channeling under the gate electrode 16, resulting in deterioration of device reliability. Will bring. This is because the limitation of the exposure mask 50 and the exposure equipment for forming the second photoresist pattern 22 accurately corrects the second photoresist pattern 22 on the gate electrode 16 on which the first photoresist pattern 16 remains. This is because they cannot overlap (see T ₁ and T _{2 in} FIG. 1B). In order to solve this problem, manufacturing cost increases due to the use of expensive DUV process equipment.

Accordingly, the present invention forms an exposure mask using a semi-transmissive film in order to solve the above problems, and low reflectivity of the bottom anti-reflection coating (hereinafter referred to as BARC) on the gate electrode It is an object of the present invention to provide a method of manufacturing an image device capable of self-aligning between a gate electrode and an ion implantation mask formed of a photosensitive film by using a.

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

2A to 2D are cross-sectional views illustrating a method of manufacturing an image device according to the present invention.

3A to 3C are cross-sectional views illustrating a method of manufacturing an exposure mask according to the present invention.

<Explanation of symbols for the main parts of the drawings>

10, 110: semiconductor substrate 12, 112: device isolation film

14, 114: polysilicon layer 16, 116: gate electrode

50, 150: exposure mask 113: gate oxide film

118: BARC layer 120, 124: photosensitive film

126: ion implantation mask 152: transparent substrate

154: transflective film 156: light shielding film

20, 22, 122, 160, 162: photosensitive film pattern

According to an aspect of the present invention, a tunnel oxide film, a polysilicon layer, and a BARC layer are formed on a semiconductor substrate on which a photodiode region and a gate electrode region are defined, and a gate patterning process is performed to perform the gate electrode region. Forming a gate electrode on the substrate, and depositing a photoresist on the entire structure, and then performing a lithography process using an exposure mask having an exposure film, a light shielding film, and a transflective film to form an ion implantation mask that opens the photodiode region. And providing a high capacity N type ion implantation on the entire structure.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention in more detail. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention, and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you. Like numbers refer to like elements in the figures.

2A to 2D are cross-sectional views illustrating a method of manufacturing an image device according to the present invention.

Referring to FIG. 2A, an isolation layer 112 is formed on the semiconductor substrate 110 in which the photodiode region A and the gate electrode region Z are defined to separate the elements. The gate oxide film 114 and the polysilicon layer 114 are deposited on the entire structure and then planarized. A BARC layer 118 having a low reflectance is formed on the polysilicon layer 114, and then the first photoresist layer 120 is coated.

Referring to FIG. 2B, the first photoresist layer 120 is patterned to form a first photoresist pattern 122 for forming the gate electrode 116. That is, in the first photoresist pattern 122, the first photoresist layer 120 remains on the BARC layer 118 where the gate electrode 116 is to be formed, and the first photoresist layer 120 in the remaining region is removed.

An etching process using the first photoresist pattern 122 as an etching mask is performed to sequentially form the gate electrode 116 by etching the BARC layer 118, the polysilicon layer 114, and the gate oxide layer 113. The diode region A is exposed.

2C and 2D, a second photosensitive film 124 to be used as a high capacity N type ion implantation mask is coated on the entire structure. At this time, the second photosensitive film 124 is coated with a thickness of 8000 to 10000 ??, which is a thickness that can prevent the ion implantation in the remaining region except for the photodiode region A when the N-type ion implantation of a high capacity.

An ion implantation mask 126 is formed by patterning the second photosensitive film 124 by performing exposure and development using the exposure mask 150. In the present invention, the interface between the exposure area M and the light blocking area N is formed on the lower semiconductor substrate 110 having the BARC layer 118 formed on the gate electrode 116 (that is, the photodiode region of the lower semiconductor substrate 110). The exposure process is performed using the exposure mask 150 in which the semi-transmissive film region L is located on the interface (A) and the region Z on which the gate electrode is formed, whereby the semi-transmissive film and the semiconductor of the exposure mask 150 are formed. Due to the BARC layer 118 having the low reflectance of the substrate 110, exposure of the second photosensitive layer 124 to distinguish the photodiode region A and the gate electrode region Z may be performed by self alignment. The semi-permeable membrane region L refers to a region made of a material such as molybdenum (Mo) having a light transmittance of 40 to 60%.

Specifically, the symbols in the drawings will be described by way of example. In order to form an ion implantation mask 126 formed of a photoresist film on the semiconductor substrate 110, an exposure mask 150 divided into an exposure area M, a light blocking area N, and a transflective film area L is used. An exposure process is performed. The semi-transmissive layer region L of the exposure mask 150 is positioned at the interface between the gate electrode region Z and the photodiode region A of the semiconductor substrate 110, but the gate electrode region in the light blocking region direction N. It can extend to the range which does not exceed the width | variety (refer to H of FIG. 2C) of the gate electrode 116 formed in the boundary surface of (Z) and the photodiode area | region A, and extends to a range sufficient in the exposure area M direction. (See K of FIG. 2C). Preferably, in the light blocking region direction N, the semi-transmissive layer region L is formed to the center of the gate electrode 116 formed at the interface between the gate electrode region Z and the photodiode region A (H / 2 in FIG. 2C). ) Is positioned in the exposure area (N) direction as much as the range (the center of the gate electrode 116) extended from the boundary surface of the photodiode area (A) toward the light shielding area (N).

When the exposure process using the above-described exposure mask 150 is performed, four phenomena appear in four regions according to the light passing through the exposure mask 150 in the second photosensitive film 124. The light is transmitted through the semi-transmissive layer region L of the fully transmissive developing portion (region B of FIG. 2C), which is completely developed by the light passing through the exposure region M of the exposure mask 150, and the exposure mask 150. A semi-transmissive developing portion (C region of FIG. 2C), which is fully developed by the light reflected from the bottom, light passing through the semi-transmissive layer region L of the exposure mask 150 and BARC formed on the lower gate electrode 116. A semi-transmissive non-developed portion that is not developed by the layer 118 (D region of FIG. 2C) and an impermeable non-developed portion that cannot be developed because light cannot pass through the light shielding region N of the exposure mask 150 (FIG. E region of 2c). According to the above-described principle, the phenomenon of the second photosensitive film 124 can be accurately corrected based on the gate electrode 116 formed on the interface between the photodiode region A and the gate electrode region Z. FIG. As a result, the ion implantation mask 126 to be used for the high-capacity N-type ion implantation can be formed by a self-aligning method.

The manufacturing method of the exposure mask 150 divided into the above-described exposure area M, light blocking area N, and semi-transmissive film area L will be briefly described.

3A to 3C are cross-sectional views illustrating a method of manufacturing an exposure mask according to the present invention.

Referring to FIG. 3A, a transflective film 154, a light shielding film 156, and a photoresist film are coated on the transparent substrate 152 on which the exposure area M, the light blocking area N, and the transflective film area L are defined. do. The writing process is performed to form a first photoresist layer pattern 160 through which the light blocking layer 156 formed on the exposure region M and the transflective region L is exposed. The above-described 'shielding region' generally refers to a region in which light does not transmit on the exposure mask 150, such as a chromium film. 'Exposure area' refers to all areas through which light passes on an exposure mask, such as a transparent substrate or a phase reversal film. The semi-permeable membrane region refers to a region in which the semi-permeable membrane 154 is formed of a material such as molybdenum (Mo) having a light transmittance of 40 to 60%.

3B and 3C, an etching process using the first photoresist layer pattern 160 as an etching mask is performed to remove the light blocking layer 156 over the exposure region M and the semi-transmissive layer region L, thereby removing the semi-transmissive layer. Expose (154). After removing the first photoresist pattern 160, a photoresist is applied over the entire structure, and a writing process is performed to form a second photoresist pattern 162 exposing the transflective layer 154 formed on the exposure area M. do. An etching process using the second photoresist layer pattern 162 as an etching mask is performed to remove the semi-transmissive layer 154 over the exposure area M to expose the transparent substrate 152. By removing the second photoresist pattern 162, the exposure area M on which the transparent substrate 152 is positioned, the semi-transmission film area L on which the transflective film 154 is located, and the light shielding area N on which the light blocking film 156 is located ) To form an exposure mask 150 is formed.

As described above, the present invention forms a BARC layer over the gate electrode and an exposure mask defined as an exposure area, a semi-transmissive film area and a light shielding area, thereby self-aligning the semi-transmissive film of the exposure mask and the BARC layer of the semiconductor substrate. By using the method, an ion implantation mask using a photosensitive film capable of opening only a photodiode region can be formed on a semiconductor substrate.

In addition, it is possible to prevent the channeling phenomenon occurring in the lower portion of the gate electrode located at the interface between the photodiode region and the gate electrode formation region due to misalignment of the ion implantation mask, and to secure a process margin for forming an ion implantation mask using a photosensitive film. .

In addition, an ion implantation mask can be formed using an inexpensive exposure apparatus, whereby productivity can be improved.

Claims (5)

Forming a tunnel oxide film, a polysilicon layer, and a BARC layer on a semiconductor substrate on which a photodiode region and a gate electrode region are defined; Performing a gate patterning process to form a gate electrode in the gate electrode region; Depositing a photoresist on the entire structure, and then performing a lithography process using an exposure mask on which an exposure film, a light shielding film, and a transflective film are formed to form an ion implantation mask that opens the photodiode region; And A method of manufacturing an image device comprising the step of performing a high capacity N-type ion implantation on the entire structure. The method of claim 1, The transflective layer of the exposure mask is positioned at an interface between the gate electrode region and the photodiode region of the semiconductor substrate, and the width of the gate electrode is formed at an interface between the gate electrode region and the photodiode region in the light blocking film direction. It extends to the range which does not exceed, and can extend to the whole range of an exposure area in the said exposure film direction, The manufacturing method of the image element characterized by the above-mentioned. The method of claim 1, The transflective layer of the exposure mask is positioned at an interface between the gate electrode region and the photodiode region of the semiconductor substrate, and is formed in the positive direction of the gate electrode formed on the interface between the gate electrode region and the photodiode region in the light blocking film direction. And a position extending in the exposure film direction by a range extending from the boundary surface of the photodiode region to the light shielding film direction. The method of claim 1, And the semi-transmissive layer of the exposure mask is made of a material such as molybdenum having a light transmittance of 40 to 60%. The method of claim 1, wherein the gate patterning process, Applying a photoresist film on the BARC layer and then performing a lithography process to form a first photoresist pattern; And Performing an etching process using the first photoresist pattern as an etching mask to remove the BARC layer, the polysilicon layer, and the gate oxide layer to form the gate electrode, wherein the first electrode is used as an etching mask on the gate electrode The method of manufacturing an image device comprising the step of removing the photosensitive film pattern.