KR20100030813A - Method of manufacturing a cmos image sensor - Google Patents

Method of manufacturing a cmos image sensor Download PDF

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Publication number
KR20100030813A
KR20100030813A KR1020080089712A KR20080089712A KR20100030813A KR 20100030813 A KR20100030813 A KR 20100030813A KR 1020080089712 A KR1020080089712 A KR 1020080089712A KR 20080089712 A KR20080089712 A KR 20080089712A KR 20100030813 A KR20100030813 A KR 20100030813A
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KR
South Korea
Prior art keywords
forming
film
gate
semiconductor substrate
sin film
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KR1020080089712A
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Korean (ko)
Inventor
김종만
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주식회사 동부하이텍
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Priority to KR1020080089712A priority Critical patent/KR20100030813A/en
Publication of KR20100030813A publication Critical patent/KR20100030813A/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/14609—Pixel-elements with integrated switching, control, storage or amplification elements
    • H01L27/14612—Pixel-elements with integrated switching, control, storage or amplification elements involving a transistor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14601—Structural or functional details thereof
    • H01L27/1462—Coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14683—Processes or apparatus peculiar to the manufacture or treatment of these devices or parts thereof
    • H01L27/14685—Process for coatings or optical elements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
    • H01L27/144—Devices controlled by radiation
    • H01L27/146—Imager structures
    • H01L27/14683—Processes or apparatus peculiar to the manufacture or treatment of these devices or parts thereof
    • H01L27/14689—MOS based technologies

Abstract

A method of manufacturing an image sensor is provided. The method of manufacturing the image sensor may include preparing a semiconductor substrate including a transfer gate, a photodiode region formed on one side of the transfer gate, and a floating diffusion region formed on the other side of the transfer gate, and forming a TEOS film on the semiconductor substrate. Forming a barrier layer on the TEOS layer, forming a photoresist pattern exposing a barrier layer corresponding to the photodiode region on the barrier layer, and exposing the barrier layer using the photoresist pattern. Removing by wet etching.

Description

Method of manufacturing a CMOS image sensor

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a CMOS image sensor that can improve the sensitivity.

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 photo diode for detecting light and a logic area for processing the detected light into an electrical signal to make data. That is, the image sensor may be referred to as an element that picks up an image of the light incident on the light receiving region with a photodiode and at least one transistor in each pixel unit.

1 illustrates a layout 100 of unit pixels of an image sensor having a general 4-TR structure. Referring to FIG. 1, the layout 100 of the unit pixel includes a photodiode region 10, a transfer transistor (Tx) 25, a floating diffusion region 25, and a reset transistor. A reset transistor (Rx) 30, a drive transistor Dx 40, and a select transistor Sx 50 are included.

2 is a cross-sectional view taken along the line AA ′ of the layout 100 of the unit pixel of the image sensor illustrated in FIG. 1. The unit pixel of the image sensor includes a transfer transistor 20, a photodiode 10, a floating diffusion region 25, a barrier layer 240, and an interlayer insulating layer 245.

The transfer transistor 20 includes a gate oxide film 215, a gate electrode 220, and a spacer 235 formed on the semiconductor substrate 210. The photodiode region 10 is formed on the semiconductor substrate 210 on one side of the gate electrode 220, and the floating diffusion region 25 is formed on the semiconductor substrate 210 on the other side of the gate electrode 220. Can be.

The barrier layer 240 is formed on the entire surface of the semiconductor substrate including the photodiode region 10 and the floating diffusion region, and a SiN film may be used.

When the BPSG layer 245 is used as an interlayer insulating film of the image sensor, the SiN film 240 is previously formed under the BPSG layer 245. In this case, the SiN film 240 prevents boron and phosphorus injected into the BPSG layer 245 from diffusing into the photodiode region 10 and the floating diffusion region 25. .

However, since the SiN film 240 does not have a good light transmittance, the SiN film 240 formed on the photodiode region 10 reduces the light absorption of the photodiode 10, which reduces the sensitivity of the CMOS image sensor. It can be bad.

The technical problem to be achieved by the present invention is to provide a method for manufacturing a CMOS image sensor that can improve the sensitivity characteristics, in particular low light characteristics of the image sensor.

According to an embodiment of the present disclosure, a method of manufacturing a CMOS image sensor may include a semiconductor including a transfer gate, a photodiode region formed at one side of the transfer gate, and a floating diffusion region formed at the other side of the transfer gate. Preparing a substrate, forming a TEOS film on the semiconductor substrate, forming a barrier layer on the TEOS film, and forming a photoresist pattern exposing a barrier layer corresponding to the photodiode region on the barrier layer. Forming and wet etching the exposed barrier layer using the photoresist pattern.

According to another aspect of the present invention, there is provided a method of manufacturing a CMOS image sensor, the method including forming a gate including a gate oxide layer and a gate electrode on a semiconductor substrate, and forming a photo on the semiconductor substrate at one side of the gate. Forming a diode region, forming a floating diffusion region in the semiconductor substrate on the other side of the gate, forming an insulating film on the entire surface of the semiconductor substrate so as to cover the gate, and etching back the insulating film to form a spacer on the gate sidewall Forming a TEOS film to cover the photodiode region, the floating diffusion region, the spacer, and an upper portion of the gate; forming a SiN film on the TEOS film; and wet etching the SiN film formed on the photodiode region. Removing using the same.

In the method of manufacturing a CMOS image sensor according to an embodiment of the present invention, the SiN film formed on the photodiode is removed using wet etching instead of reactive ion etching, and the SiN film and the photodiode region are secured to secure an etching margin. By forming a TEOS film therebetween, the low illuminance characteristic of the CMOS image sensor and the sensitivity of the CMOS image sensor can be improved.

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.

3A to 3F illustrate a method of manufacturing a complementary metal oxide semiconductor image sensor according to an exemplary embodiment of the present invention. First, as shown in FIG. 3A, a semiconductor substrate 210 (eg, a silicon substrate) in which an active region and an isolation region are defined is prepared. For example, the semiconductor substrate 210 may be a P-type silicon substrate, and may include a low concentration P-type epitaxial layer formed on the P-type silicon substrate.

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

Next, a gate of a transfer transistor including a gate oxide film 315 and a gate electrode 317 is formed in the active region (hereinafter referred to as “semiconductor substrate 310”).

For example, after the gate oxide film and the poly gate are sequentially formed on the semiconductor substrate 310, the gate oxide film and the poly gate are selectively etched by performing exposure, development, and etching processes using a photolithography process. The gate 320 of the transfer transistor including the gate oxide layer 315 and the gate electrode 317 may be formed.

The photodiode region 325 is formed on one side of the gate 320 of the transfer transistor. The photodiode region 325 may be formed by implanting impurity ions into the surface of the semiconductor substrate 310 on one side of the gate of the transfer transistor.

Although not shown in FIG. 3A, the photodiode region 325 may include a first conductivity type impurity ion implantation region (not shown) and a second conductivity type impurity ion implantation region (not shown) arranged at one side of a gate of the transfer transistor. ) May be formed in a stacked form. For example, the photodiode region 310 may have a structure in which an n-type ion implantation region and a P-type ion implantation region are sequentially stacked.

Subsequently, the floating diffusion region 330 is formed on the other side of the gate 320 of the transfer transistor. In this case, the floating diffusion region 330 may be formed first, and then the photodiode region 325 may be formed, and the floating diffusion region 330 and the photodiode region 325 may be simultaneously formed.

For example, a patterned ion implantation mask (not shown) is formed on the semiconductor substrate 310 and an impurity is selectively implanted into the semiconductor substrate 310 using the ion implantation mask to form the photodiode region 330 and The floating diffusion region 335 may be formed.

Next, as illustrated in FIG. 3B, spacers 335 and 340 are formed on sidewalls of the gate 320. The spacers 335 and 340 may include a spacer oxide layer 335 and a spacer nitride layer 340.

For example, an oxide film and a nitride film are coated on the semiconductor substrate 310 on which the gate 320 is formed. The coated nitride layer and the oxide layer may be etched back to form a spacer oxide layer 335 and a spacer nitride layer 340 in the gate 320. For example, etch back may be performed until the spacer oxide layer formed on the gate is removed, and the oxide layer formed on the photodiode region 325 and the floating diffusion region 330 may be partially etched back or all etched back. .

Next, as illustrated in FIG. 3C, after forming the spacers 335 and 340, a TEOS (Tetraethly orthosilicate, 345) film is formed on the entire surface of the semiconductor substrate 310. The TEOS 345 may be formed on the photodiode region 325 and the floating diffusion region 330 to have a thickness of 700 μs to 900 μs after etching back.

Next, as illustrated in FIG. 3D, a barrier layer, for example, an SiN film 350 is formed on the TEOS film 345, and the SiN film 350 may be formed to have a thickness of 300 μs to 400 μm.

In the SiN film 350, when a BPSG layer (Boro-Phospho Silicate Glass layer) is used as an interlayer insulating film of an image sensor, boron and phosphorus injected into the BPSG layer are formed in the photodiode region 325. And prevents diffusion into the floating diffusion region 330.

However, since the SiN film 350 does not have good light transmittance, the SiN film 350 formed on the photodiode region 325 reduces the light absorption of the photodiode 325.

As shown in FIG. 3E, the photoresist pattern 355 exposing the SiN film corresponding to the photodiode region 325 is exposed by performing an exposure and development process by a photolithography process on the SiN film 350. Form.

As shown in FIG. 3E, the photoresist pattern 335 is formed to expose a SiN film corresponding to a spacer adjacent to the photodiode region 325. However, unlike the photoresist pattern 335 shown in FIG. 3E, the SiN film corresponding to the photodiode region 325 is exposed, but the SiN film corresponding to the spacer adjacent to the photodiode region 325 is not patterned. Can be.

Subsequently, in order to improve light sensitivity of the photodiode region, the SiN film formed on the photodiode region 325 is removed using the photoresist pattern 335.

In the case of reactive ion etching (RIE) of the SiN film exposed by the photoresist pattern 335, damage may occur in the photodiode region 325 by plasma used during the reactive ion etching. Can be.

FIG. 4 shows damage occurring to the photodiode region when the SiN film shown in FIG. 3E is removed by reactive ion etching using plasma. The semiconductor substrate 410, the gate oxide film 415, the gate electrode 420, the photodiode region 430, the floating diffusion region 435, the spacer oxide film 425, the spacer nitride film 427 and SiN shown in FIG. The film 440 and the photoresist pattern 445 have only the subtitle numbers different from those shown in FIG. 3E, and the corresponding configurations are the same. In FIG. 4, the gate oxide layer is almost removed on the photodiode region 430 and the floating diffusion region 435 in the etch back process, and the formation of the TEOS layer to secure the etching margin is omitted.

Referring to FIG. 4, it can be seen that there is a loss in silicon (Si) of the photodiode region 430 when the SiN film is removed by reactive ion etching using plasma. The low light characteristic of the image sensor may be degraded due to the generation of unwanted electrons due to the silicon loss of the photodiode region 430.

In the method of manufacturing an image sensor according to the embodiment, the SiN film formed on the photodiode region 325 exposed by the photoresist pattern 355 is selectively removed using wet etching. At this time, HF solution may be used as an etching solution. Removal of the exposed SiN film by using wet etching is easy to remove the selective SiN because of the etch selectivity, and since the plasma is not used, the lower photodiode region 325 is not subjected to plasma damage. Therefore, since there is no loss of silicon in the photodiode region, the low light characteristic of the image sensor is not deteriorated, and since the SiN film having poor light transmittance formed on the photodiode is removed, the sensitivity of the image sensor can be improved.

In addition, in the present invention, before forming the SiN film 350, the TEOS film 345 may be formed to a thickness of 700 kPa to 900 kPa, thereby sufficiently securing the etching margin in the wet etching process.

Next, as shown in FIG. 3F, after the photoresist pattern 355 is removed using an ashing and strip process, the SiN film corresponding to the photodiode region 325 is selectively removed. The BPSG layer 360 is formed on the entire surface of the substrate 310.

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.

1 illustrates a layout of unit pixels of a CMOS image sensor having a general 4-TR structure.

FIG. 2 is a cross-sectional view taken along the line AA ′ of the layout of the unit pixel of the CMOS image sensor illustrated in FIG. 1.

3A to 3F illustrate a method of manufacturing a CMOS image sensor according to an exemplary embodiment of the present invention.

FIG. 4 shows damage occurring to the photodiode region when the SiN film shown in FIG. 3E is removed by reactive ion etching using plasma.

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

310: semiconductor substrate, 315: gate oxide film,

317: gate electrode, 320: gate,

325: photodiode region, 330: floating diffusion region,

335: spacer oxide film, 340: spacer nitride film

345: TEOS film, 350: SiN film,

355: photoresist pattern, 360: BPSG film.

Claims (12)

Preparing a semiconductor substrate including a transfer gate, a photodiode region formed on one side of the transfer gate, and a floating diffusion region formed on the other side of the transfer gate; Forming a TEOS film on the semiconductor substrate; Forming a barrier layer on the TEOS film; Forming a photoresist pattern on the barrier layer to expose a barrier layer corresponding to the photodiode region; And And wet-etching the exposed barrier layer by using the photoresist pattern to remove the barrier layer. The method of claim 1, wherein the forming of the barrier layer comprises: And forming a SiN film on the semiconductor substrate. The method of claim 2, wherein the manufacturing method of the image sensor comprises: And forming a BPSG layer on the entire surface of the semiconductor substrate from which the SiN film corresponding to the photodiode region is selectively removed after the photoresist pattern is removed. The method of claim 3, wherein the forming of the TEOS film, And forming the TEOS film on the photodiode region, the gate upper portion, and the floating diffusion region with a thickness of 700 kHz to 900 kHz. The method of claim 4, wherein The SiN film is a method of manufacturing a CMOS image sensor, characterized in that formed on the semiconductor substrate with a thickness of 300 ~ 400Å. The method of claim 1, wherein the wet etching of the barrier layer comprises: And wet etching the exposed barrier layer using an HF solution. Forming a gate including a gate oxide film and a gate electrode on the semiconductor substrate; Forming a photodiode region in the semiconductor substrate on one side of the gate and forming a floating diffusion region in the semiconductor substrate on the other side of the gate; Forming an insulating film on the entire surface of the semiconductor substrate to cover the gate; Etching back the insulating film to form a spacer on the gate sidewall; Forming a TEOS film to cover the photodiode region, the floating diffusion region, the spacer and the gate; Forming a SiN film on the TEOS film; And And removing the SiN film formed on the photodiode region by wet etching. The method of claim 7, wherein the manufacturing method of the image sensor,  And forming a BPSG layer on the entire surface of the semiconductor substrate from which the SiN film corresponding to the photodiode region is removed. The method of claim 8, wherein the forming of the insulating film, Forming a spacer oxide layer over the semiconductor substrate to cover the gate; And And forming a spacer nitride film on the oxide film. The method of claim 8, wherein forming the spacers, And forming the spacers by etching back the spacer nitride layer until the spacer oxide layer formed on the gate is exposed. The method of claim 9, wherein the removing of the SiN film by wet etching comprises: Forming a photoresist pattern on the SiN film to expose a SiN film corresponding to the photodiode region; And And wet-etching the SiN film exposed by using the photoresist pattern as an etch mask to remove the exposed SiN film by using an HF solution. The method of claim 11, wherein the forming of the photoresist pattern comprises: Exposing a SiN film corresponding to the photodiode region on the SiN film, wherein the SiN film corresponding to the spacer oxide film and the spacer nitride film adjacent to the photodiode region is patterned so as not to be exposed. .
KR1020080089712A 2008-09-11 2008-09-11 Method of manufacturing a cmos image sensor KR20100030813A (en)

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