KR20100079444A - Cmos image sensor and method of manufacturing the same - Google Patents

Cmos image sensor and method of manufacturing the same Download PDF

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Publication number
KR20100079444A
KR20100079444A KR1020080137937A KR20080137937A KR20100079444A KR 20100079444 A KR20100079444 A KR 20100079444A KR 1020080137937 A KR1020080137937 A KR 1020080137937A KR 20080137937 A KR20080137937 A KR 20080137937A KR 20100079444 A KR20100079444 A KR 20100079444A
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South Korea
Prior art keywords
photodiode
photodiodes
forming
image sensor
channel
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KR1020080137937A
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Korean (ko)
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이귀덕
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주식회사 동부하이텍
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Priority to KR1020080137937A priority Critical patent/KR20100079444A/en
Publication of KR20100079444A publication Critical patent/KR20100079444A/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
    • 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
    • H01L27/1461—Pixel-elements with integrated switching, control, storage or amplification elements characterised by the photosensitive area
    • 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
    • H01L27/14623—Optical shielding
    • 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

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Electromagnetism (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Solid State Image Pick-Up Elements (AREA)

Abstract

PURPOSE: A CMOS image sensor and a method of manufacturing the same are provided to extend an available dynamic area by increasing the potential well of a first photodiode. CONSTITUTION: A plurality of photo diodes(100, 200, 300) are formed on one pixel area which is defined in a semiconductor substrate. A metal layer shields photo diodes excluding one to receive an incident light. When an exposed photodiode receives and generates, a plurality of switches(150, 250, 350) forms a channel between photodiodes to store the charge in the photodiodes excluding the exposed photodiode.

Description

CMOS Image Sensor and Method of Manufacturing the same

An embodiment relates to a CMOS image sensor and a method of manufacturing the same.

Complementary Metal Oxide Silicon (CMOS) image sensor (CIS) is a semiconductor device that converts an optical image into an electrical signal.

The CMOS image sensor includes a pixel array in the form of a two-dimensional matrix, and is configured to output one image diode from each pixel by forming one photodiode in one pixel. Photodiodes generate charges according to the intensity of the received light energy. Thus, the CMOS image sensor may reproduce the optical image by restoring the received light energy using the charge generated in each pixel.

The CMOS image sensor enters a saturation state where the output voltage increases proportionally as the input illuminance increases, and when the output voltage reaches a certain level, the output voltage no longer increases. Accordingly, the illuminance section in which the input illuminance and the output voltage maintain a proportional relationship is called a dynamic range.

When a large increase rate of the output voltage with increasing input illuminance is designed, the light receiving sensitivity is improved, but the dynamic range is reduced by reaching saturation at low input illuminance. On the other hand, when the dynamic range is designed to be wide, the light receiving sensitivity is lowered, which reduces the quality of the reproduced image. In other words, if the sensitivity is lowered, the signal cannot be properly distinguished at low light. On the contrary, if the signal is well distinguished at low light, saturation can be reached quickly, and the signal cannot be distinguished at high light.

However, since the magnitude of the output voltage in saturation is determined by the magnitude of the potential well of the photodiode, it is impossible to produce a predetermined output voltage or more. Therefore, there is a limit to increasing sensitivity under constant saturation output voltage.

The embodiment provides a CMOS image sensor and a method of manufacturing the same, which can extend an operable dynamic range while maintaining sufficient light sensitivity in both low and high light conditions.

In an embodiment, the CMOS image sensor may include: a plurality of photodiodes formed in one pixel area defined in a semiconductor substrate; A metal layer shielding the remaining photodiodes so that only one of the plurality of photodiodes is exposed to receive incident light; When the exposed photodiode receives the incident light to generate charge, the photodiode includes a plurality of switches for forming a channel between the plurality of photodiodes such that the charge is accumulated in the remaining photodiodes.

According to an embodiment, there is provided a method of manufacturing a CMOS image sensor, including: forming a plurality of photodiodes by implanting ions at different N-type doping concentrations into one pixel region defined in a semiconductor substrate; Forming a plurality of switches for forming a channel such that mutual charges are transferred between the plurality of photodiodes; And forming a metal layer that shields the remaining photodiodes so that only the photodiodes having the highest N-type ion doping concentration among the plurality of photodiodes are exposed.

According to the CMOS image sensor and its manufacturing method of the embodiment, it is possible to expand the dynamic range operable while maintaining sufficient light receiving sensitivity in both low and high illumination conditions.

Hereinafter, a CMOS image sensor and a method of manufacturing the same according to an embodiment will be described in detail with reference to the accompanying drawings. However, in describing the embodiments, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

In addition, in describing the embodiments, each layer (film), region, pattern, or structure may be “on” or “under” a substrate, each layer (film), region, pad, or pattern. In the case of being described as being formed "in", "on" and "under" include both "directly" or "indirectly" formed. . Also, the criteria for top, bottom, or bottom of each layer will be described with reference to the drawings.

1 to 5 are cross-sectional views of a manufacturing process of the CMOS image sensor according to the embodiment.

First, as shown in FIG. 1, a shallow trench isolation (STI) 15 is formed in the semiconductor substrate 10 to set one pixel region, and a mask pattern for implanting ions into the upper surface of the substrate 10. To form 50a. When the first N-type ion implantation process is performed on the P-type substrate 10 using the mask pattern 50a, a first photodiode PD1 100 is formed as shown in FIG. 2. .

Next, as shown in FIG. 2, a mask pattern 50b exposing an adjacent region of the region where the first photodiode PD1 100 is formed is formed. A second N-type ion implantation process is performed on the substrate 10 by using the mask pattern 50b, and the second N-type ions implanted therein are implanted at a lower doping concentration than the first N-type ion. Thus, as shown in FIG. 3, the second photodiode PD2 200 is formed.

Next, as shown in FIG. 3, the mask pattern 50c exposing the adjacent region of the region where the second photodiode PD2 200 is formed is formed. A third N-type ion implantation process is performed on the substrate 10 by using the mask pattern 50c, and the third N-type ions to be implanted are implanted at a lower doping concentration than the second N-type ions. Thus, as shown in FIG. 4, a third photodiode PD3 300 is formed.

As such, in an embodiment, the N-type doping concentrations of the first photodiode (PD1) 100, the second photodiode (PD2) 200, and the third photodiode (PD3) 300 are PD1> PD2. > High in PD3 order. The higher the N-type doping, the higher the Fermi level, which results in the lowest balance and conduction bands of the first photodiode PD1 100 at equilibrium, and the third photodiode PD3 ( 300) can form the highest.

Next, as shown in FIG. 5, a floating diffusion (FD) 400 is formed to receive charges accumulated in each photodiode 100, 200, and 300 and transmit them to an external circuit.

First switch (T1) 150 for forming a channel between the first photodiode (PD1) 100 and the floating diffusion (FD) 400, the first photodiode (PD1) 100 and the second photo A channel between the second switch T2 250 and a second photodiode PD2 200 and a third photodiode PD3 300 for forming a channel between the diodes PD2 200. To form a third switch (T3) 350 to form a.

The metal layer 500 is formed to block light incident on the second photodiode PD2 200 and the third photodiode PD3 300.

As described above, the CMOS image sensor according to the embodiment forms a plurality of photodiodes in one pixel area. Therefore, when three photodiodes 100, 200, and 300 are formed, incident light is received only by the first photodiode PD1 100, and the second photodiode PD2 200 and the third photodiode PD3) 300 does not receive light. The first photodiode PD1 100 receives charge and generates charges, and the generated charge is connected to the first photodiode PD1 100 and the first photodiode PD1 100 through a channel. The second photodiode PD2 200 and the second photodiode PD2 200 may be stored in a third photodiode PD3 300 connected to a channel. That is, the charge is generated by one first photodiode (PD1) 100, and the generated charge is the first photodiode (PD1) 100, the second photodiode (PD2) 200, and the third photo It is stored in the diode (PD3) (300).

6 is a potential distribution diagram when detecting a low light signal of the CMOS image sensor of the embodiment.

The N-type doping concentrations of the first photodiode (PD1) 100, the second photodiode (PD2) 200, and the third photodiode (PD3) 300 are set in the order of PD1> PD2> PD3. The balance band and conduction band of the first photodiode PD1 100 are the lowest, and the third photodiode PD3 300 is formed the highest.

When the second switch T2 250 and the third switch T3 350 are maintained in the off state, no channel is formed between the photodiodes 100, 200, and 300.

When light of low illuminance is incident, electric charges generated by the first photodiode PD1 100 are accumulated in the first photodiode PD1 100.

7 is a potential distribution diagram when detecting a light intensity signal of the CMOS image sensor of the embodiment.

When the illumination intensity of the incident light increases, the second switch T2 250 and the third switch T3 350 are operated in a turned on state so that a channel is formed between each photodiode 100, 200, 300.

Accordingly, when light of medium intensity is incident and the amount of charge generated in the first photodiode PD1 100 increases, the generated charge is transferred to the second photodiode PD2 200 through a channel, thereby providing a first photodiode. The photodiode PD1 100 and the second photodiode PD2 200 are stored.

8 is a potential distribution diagram when detecting a high illuminance signal of the CMOS image sensor of the embodiment.

When a high intensity of light is incident and a large amount of charge is generated in the first photodiode PD1 100, the charge generated in the first photodiode PD1 100 is transferred through the channel to the second photodiode PD2. It is delivered to the 200 and the third photodiode (PD3) (300). Thus, the charge generated by the first photodiode PD1 100 is first photodiode PD1 100, second photodiode PD2 200, and third photodiode PD3 300. Are stored in.

Therefore, when light of high illumination enters, charges generated in the first photodiode PD1 100 are simultaneously distributed to the second photodiode PD2 200 and the third photodiode PD3 300. As a result, at high illumination, the size of the potential well of the first photodiode PD1 100 is increased.

9 is an operation graph of the CMOS image sensor according to the embodiment, in which the output voltage value of the conventional CMOS image sensor b and the CMOS image sensor a according to the embodiment are changed according to the change in the input illuminance. The change in output voltage is shown together.

 The conventional CMOS image sensor (b) generates and accumulates electric charges according to the received light using a single photodiode, so that the output value increases linearly until a certain illuminance, and the output value remains constant when the saturation state is reached. It shows form.

On the other hand, the CMOS image sensor a of the embodiment generates charges using one photodiode, but charges generated in three photodiodes are accumulated. Thus, in the low illumination period A, charges are accumulated only in the first photodiode PD1 100, thereby increasing the output value as in the conventional CMOS image sensor b.

In the light intensity section B, charges are accumulated in the first photodiode PD1 100 and the second photodiode PD2 200, so that the rate of increase of the output value is smaller than that of the conventional CMOS image sensor b. In addition, even when the conventional CMOS image sensor b enters an equilibrium state, an output value may be generated according to the received light.

In the high illuminance section C, the conventional CMOS image sensor b has already entered an equilibrium state and it is impossible to generate an output value. On the other hand, the CMOS image sensor (a) of the embodiment receives light due to accumulation of charges in the first photodiode (PD1) 100, the second photodiode (PD2) 200, and the third photodiode (PD3) 300. You can generate the output according to the light.

Thus, it can be seen that the dynamic range is increased compared to the conventional CMOS image sensor (b).

Although described above with reference to the embodiment is only an example and is not intended to limit the invention, those of ordinary skill in the art to which the present invention does not exemplify the above within the scope not departing from the essential characteristics of this embodiment It will be appreciated that many variations and applications are possible. For example, each component specifically shown in the embodiment can be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

1 to 5 are cross-sectional views of a manufacturing process of the CMOS image sensor according to the embodiment.

6 is a potential distribution diagram when detecting a low light signal of the CMOS image sensor of the embodiment;

7 is a potential distribution diagram when detecting a light intensity signal of the CMOS image sensor of the embodiment.

8 is a potential distribution diagram when detecting a high illuminance signal of the CMOS image sensor of the embodiment;

9 is an operation graph of the CMOS image sensor according to the embodiment.

Claims (9)

A plurality of photodiodes formed in one pixel region defined in the semiconductor substrate; A metal layer shielding the remaining photodiodes so that only one of the plurality of photodiodes is exposed to receive incident light; When the exposed photodiode receives the incident light to generate charge, the CMOS image sensor includes a plurality of switches for forming a channel between the plurality of photodiodes such that the charge is accumulated in the remaining photodiodes. . The method of claim 1, The plurality of photodiodes each CMOS image sensor having a different N-type doping concentration. The method of claim 2, The photodiode receiving the incident light has a highest N-type doping concentration than other photodiodes CMOS image sensor. The method of claim 1, And a floating diffusion that receives and accumulates charges accumulated in the plurality of photodiodes and transfers the accumulated charges to an external circuit. The method of claim 4, wherein And a floating switch forming a channel so that charges accumulated in the plurality of photodiodes are transferred to the floating diffusion. Forming a plurality of photodiodes by implanting ions at different N-type doping concentrations into one pixel region defined in the semiconductor substrate; Forming a plurality of switches for forming a channel such that mutual charges are transferred between the plurality of photodiodes; And forming a metal layer shielding the remaining photodiodes such that only the photodiodes having the highest N-type ion doping concentration are exposed among the plurality of photodiodes. The method of claim 6, Forming a plurality of photodiodes by implanting ions at different N-type doping concentrations in one pixel region defined in a semiconductor substrate, Forming a first photodiode on the semiconductor substrate by implanting ions at the highest N-type doping concentration to form a first photodiode; Forming a second mask pattern to implant ions into an adjacent region of the first photodiode at a next higher N-type doping concentration to form a first photodiode; And forming a third photodiode by forming a third mask pattern to inject ions into an adjacent region of the second photodiode at the lowest N-type doping concentration to form a third photodiode. The method of claim 7, wherein Forming a plurality of switches for forming a channel such that mutual charge is transferred between the plurality of photodiodes, Forming a second switch forming the channel between the first photodiode and the second photodiode; And forming a third switch for forming the channel between the second photodiode and the third photodiode. The method of claim 6, Forming a floating diffusion on the semiconductor substrate to receive and accumulate charges accumulated in the plurality of photodiodes; And forming a floating switch to form a channel such that charges accumulated in the plurality of photodiodes are transferred to the floating diffusion.
KR1020080137937A 2008-12-31 2008-12-31 Cmos image sensor and method of manufacturing the same KR20100079444A (en)

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