KR20210004536A - Vertical nanowire based photodetector having double absorption layer and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a vertical nanowire photodetector with double absorption layer to form an hourglass-shaped vertical nanowire in an active area of a front surface of a semiconductor substrate and improve the performance of the photodetector by forming a rear absorption layer for improving the near-infrared absorption on the rear surface, and a manufacturing method thereof. According to the vertical nanowire photodetector with a double absorption layer according to the present invention, the vertical nanowire photodetector has the effect of improving the sensitivity in an infrared region and the external quantum efficiency of the photodetector. Since the vertical nanowire photodetector is manufactured using a silicon semiconductor process, the mass production is possible. The vertical nanowire photodetector has the advantage of excellent economic efficiency by using silicon with abundant reserves as main materials. In addition, the vertical nanowire photodetector has the advantage that vertical nanowire photodetector can be used in all fields of future industries such as autonomous vehicles, mobile health care systems, and security.

Description

Vertical nanowire based photodetector having double absorption layer and manufacturing method thereof {Vertical nanowire based photodetector having double absorption layer and manufacturing method thereof}

The present invention relates to a photodetector and a method of manufacturing the same, and more particularly, a photodetector by forming an hourglass-shaped vertical nanowire in the active area of the front surface of a semiconductor substrate and forming a rear absorbing layer for improving near-infrared absorption on the rear surface. It relates to a vertical nanowire photodetector having a double absorption layer with improved performance and a method of manufacturing the same.

A photodetector is an optical device for detecting the presence or absence of light or the intensity of a light source. It is a core device used throughout the modern industry, and various materials are used in sensor manufacturing according to the wavelength range to be detected.

In general, the detection wavelength of a material is determined by the band gap of the material. Ultraviolet (less than 400nm) photodetectors used for fire detection, medical UV calibration, and military submarine detection are manufactured based on compounds such as SiC, Al _x Ga _1-x N, and are for smartphones in the consumer electronics field. Visible light (400-700nm) photodetectors used in CMOS image sensors and digital camera CCDs are manufactured based on silicon materials.

Next, the infrared (0.7-hundred m) photodetectors used in military night vision, security surveillance cameras, and infrared diagnostic systems are various materials such as Ge, InGaAs, PbS, and HgCdTe, depending on the detection wavelength. . In particular, the near-infrared region (700-1,400nm) can be used in future industrial fields such as Nd:YAG medical laser system (1,064nm), optical communication (short-range 850nm, mid-range 1,310nm) and autonomous vehicles (905nm and 1,550nm). As a result, the demand is steadily increasing and the market size is growing rapidly.

Among the aforementioned materials, silicon has the advantage of excellent compatibility with existing CMOS semiconductor processes, enabling low-cost and mass production of photodetectors compared to other compound materials, and easy integration with signal processing circuits. However, the silicon material is suitable for detecting visible light due to the band gap of 1.12 eV, but it is difficult to detect near infrared rays having a wavelength larger than the band gap, and thus, it has not been utilized in the highly useful near infrared region.

If the near-infrared detection performance of the silicon photodetector is similar to or superior to the existing InGaAs photodetector, it is expected that it will have an advantage in economy and miniaturization and have a large ripple effect on the near-infrared photodetector market. Therefore, researches to improve the near-infrared detection performance of silicon photodetectors are being actively conducted worldwide. In particular, a silicon vertical nanowire array structure capable of improving the near-infrared detection characteristics of a silicon photodetector without a large change in manufacturing process has attracted great attention.

1 is a perspective view showing the basic structure of a conventional silicon vertical nanowire near-infrared photodetector.

Referring to FIG. 1, a conventional silicon vertical nanowire near-infrared photodetector 10 includes a p-type or n-type semiconductor substrate 11, and a cylindrical vertical silicon nanowire 12 in the form of an array formed on the semiconductor substrate 11. ), a first semiconductor layer 13 and a semiconductor substrate 11 in which a doping material of a type opposite to that of the semiconductor substrate 11 is injected at a high concentration to form a pn junction on the surface of the vertical silicon nanowire 12 Of the first electrode 14 and the semiconductor substrate 11 disposed at the edge of the first semiconductor layer 13 so that light is not in contact with the first semiconductor layer 13 and light is easily incident on the vertical nanowires 12. It includes a second electrode 15 formed on the rear surface.

In general, vertical nanowires and core-shell photodetectors with different doping types of the semiconductor layer surrounding the nanowires have an advantage of superior surface area-to-volume ratio compared to a flat plate structure, thereby increasing the electron-electron pair generated by light to provide excellent wavelength. It shows star sensitivity and quantum efficiency. In order to reduce the contact resistance between the semiconductor substrate 11 and the second electrode 15, the back layer of the semiconductor substrate 11 may be injected with a high concentration doping material of the same type as the semiconductor substrate 11.

In the vertical silicon nanowire array structure, light reflected or refracted from the nanowire surface is reabsorbed by the surrounding nanowires, thereby improving the detection performance of the near-infrared light source. As the aspect ratio of the vertical silicon nanowire structure increases, the absorption of near-infrared light with a deep light absorption depth increases. However, vertical nanowires with too high aspect ratio have poor structural stability and cannot be used for device fabrication, which limits the improvement of detection performance of near-infrared light with a deep light absorption depth.

Therefore, there is a need to develop a high-sensitivity silicon nanowire photodetector to effectively absorb a near-infrared light source with a deep light absorption depth while utilizing the existing semiconductor process.

The problem to be solved by the present invention is to improve the absorption of infrared light by forming hourglass-shaped vertical nanowires on the front surface of the substrate, and at the same time, forming a rear absorbing layer for infrared absorption on the rear surface of the substrate to improve the performance of the silicon nanowire infrared sensor. It is to provide a vertical nanowire photodetector having an improved double absorption layer.

Another problem to be solved by the present invention is to have a double absorption layer capable of manufacturing a silicon infrared sensor with high economical efficiency by making the vertical nanowire in the form of an hourglass on a silicon substrate and the rear absorption layer in an integrated manner using a semiconductor process capable of mass production. It is to provide a method for manufacturing a vertical nanowire photodetector.

In order to achieve the above object, a vertical nanowire photodetector having a double absorbing layer according to the present invention includes: a semiconductor substrate; Vertical nanowires formed in an array shape on the entire surface of the semiconductor substrate; A first semiconductor layer formed by doping a doping material on the vertical nanowires; A first electrode formed at an edge of an upper end of the first semiconductor layer; A rear absorption layer formed on the rear surface of the semiconductor substrate; And a second electrode formed under the rear absorption layer.

In order to achieve the above object, a method of manufacturing a vertical nanowire photodetector having a double absorbing layer according to the present invention comprises: forming a rear absorbing layer of forming an absorbing layer on a rear surface of a semiconductor substrate; Forming vertical nanowires in the form of an array by etching the surface of the semiconductor substrate; A first semiconductor layer forming step of forming a first semiconductor layer doped with a doping material of a type opposite to that of the semiconductor substrate on the surface of the vertical nanowires; And an electrode forming step of forming a first electrode positioned at an edge of the first semiconductor layer and a second electrode positioned below the rear absorbing layer.

According to the vertical nanowire photodetector having a double absorption layer according to the present invention, by forming a vertical nanowire in the form of an hourglass on the surface of a semiconductor substrate and forming a rear absorption layer on the rear surface of the substrate, the sensitivity of the infrared region and the external There is an advantage that can improve quantum efficiency.

In the inverted conical structure of the upper end of the vertical nanowire in the form of an hourglass, light resonance occurs and the infrared light source stays on the surface of the nanowire for a long time to improve light absorption. It reabsorbs the infrared wavelength light that leaks out of the route.

The rear absorbing layer on the back of the semiconductor substrate absorbs light in the infrared region that was not absorbed by the vertical nanowires in the form of an hourglass on the front, thereby improving the infrared detection characteristics of the silicon nanowire photodetector. At this time, the rear absorbing layer and the vertical nanowires absorb light reflected from the second electrode on the rear surface of the semiconductor substrate and emanate to the surface to further improve infrared detection characteristics. Light that is reflected from the back and reaches the vertical nanowires in the form of an hourglass regenerates light resonance, increasing the absorption of light. Accordingly, there is an advantage in that the sensitivity and quantum efficiency by near-infrared wavelength are more excellent than that of a flat-type double absorption layer silicon photodetector.

Since the vertical silicon nanowire photodetector having a double absorbing layer is manufactured using a silicon semiconductor process, mass production is possible, and since silicon having an abundant reserve is used as a main material, it has an advantage of excellent economical efficiency.

1 is a perspective view showing the basic structure of a conventional silicon vertical nanowire near-infrared photodetector.
2 is a perspective view showing the overall structure of a vertical nanowire photodetector having a double absorbing layer according to an embodiment of the present invention.
3 is a diagram showing sensitivity and external quantum efficiency (EQE) results for verifying the effects of the vertical nanowire and the rear absorbing layer of the vertical nanowire photodetector having a double absorbing layer according to an embodiment of the present invention.
4 is a diagram illustrating a principle of improving detection characteristics of a vertical nanowire photodetector having a double absorption layer according to an exemplary embodiment of the present invention.
5 is a flowchart of a method of manufacturing a vertical nanowire photodetector having a double absorbing layer according to an embodiment of the present invention.
6 is a plan view and a cross-sectional view illustrating a step of forming a rear absorption layer in the method of manufacturing a vertical nanowire photodetector having a double absorption layer according to FIG. 5.
7 is a plan view and a cross-sectional view illustrating a step of forming a vertical nanowire in the method of manufacturing a vertical nanowire photodetector having a double absorbing layer according to FIG. 5.
8 is a diagram showing various shapes of vertical nanowires formed according to FIG. 7.
9 is a plan view and a cross-sectional view illustrating a step of forming a first semiconductor layer in the method of manufacturing a vertical nanowire photodetector having a double absorbing layer according to FIG. 5.
10 is a plan view and a cross-sectional view illustrating a step of forming an electrode in the method of manufacturing a vertical nanowire photodetector having a double absorbing layer according to FIG. 5.

In the present invention, various modifications may be made and various forms may be applied, and specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific form disclosed, it should be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention.

In describing each drawing, similar reference numerals have been used for similar elements. In the present invention, in fabricating a vertical nanowire photodetector having a double absorbing layer, various processing equipment may be used, and in particular, the rear absorbing layer is not intended to be limited to a specific material, and it should be understood to include equivalents or substitutes.

In addition, the vertical silicon nanowire array is not intended to be limited to an hourglass shape, and it should be understood to include various structures (cylindrical, conical, and inverted conical types, etc.) that are manufactured based on a silicon etching process and can increase near-infrared light absorption. . Any one of the rear absorption layer and the hourglass-shaped vertical nanowire array is not applied to the photodetector alone, and the two structural layers are applied simultaneously and interact to obtain maximum near-infrared light absorption.

Unless otherwise defined, all terms used in the text, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and should not be interpreted as an ideal or excessively formal meaning unless explicitly defined in this application. Does not.

In this specification, directional expressions such as top, top (part), top, front, etc. may be understood as meanings of bottom, bottom (part), bottom, rear, etc. according to the criteria. In other words, the expression of a spatial direction should be understood as a relative direction and should not be construed limitedly to mean an absolute direction.

In the drawings, the thickness of layers and regions may be exaggerated or omitted for clarity. The same reference numbers throughout the specification denote the same elements.

Hereinafter, exemplary embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

2 is a perspective view showing the overall structure of a vertical nanowire photodetector having a double absorbing layer according to an embodiment of the present invention.

Referring to FIG. 2, a vertical nanowire photodetector 200 having a double absorption layer according to an embodiment of the present invention includes a p-type or n-type semiconductor substrate 210 in an array form on the front surface of the semiconductor substrate. The vertical nanowires 220 formed, the first semiconductor layer 230 formed by doping a doping material of a different type from the semiconductor substrate on the vertical nanowires 220, and the first semiconductor layer 230 are not in contact with the semiconductor substrate 210 A first electrode 240 formed at an upper edge of the first semiconductor layer 230 so that light is in contact only with the semiconductor layer 230 and light is easily incident on the vertical nanowire 220 in the form of an hourglass, and near-infrared rays having a long absorption depth In order to absorb light, a rear absorption layer 250 formed on the rear surface of the semiconductor substrate 210 and a second electrode 260 formed below the rear absorption layer 250 are included.

The vertical nanowire 220 in the form of an hourglass is composed of a combination of an inverted conical structure at the upper end and a conical structure at the lower end, and the doping concentration and doping type are the same as the semiconductor substrate 210. In an hourglass-shaped upper inverted cone structure, light resonance occurs at near-infrared wavelengths, and light stays on the upper nanowire surface for a long time, thereby improving light absorption. At the same time, the conical structure of the lower part has a smaller surface reflectivity than the cylindrical structure due to the slope of the surface, so it reabsorbs the light of the near-infrared wavelength that leaks from the optical resonance of the upper part of the adjacent hourglass. The vertical nanowire structure in the form of an hourglass has better light absorption than other cylindrical, conical, and inverted conical nanowire structures due to the interaction of the upper and lower parts.

A cylindrical, conical, or inverted conical nanowire structure may be used in place of the hourglass-shaped vertical nanowire 220.

A first semiconductor layer formed on the surface of the vertical nanowire 220 in the form of an hourglass and on the semiconductor substrate 210 to make the active area area of the photodetector constant and to electrically insulate the photodetectors on the semiconductor substrate 210 The first semiconductor layer 230 of the outer region of the circular or rectangular structure completely including the vertical nanowire 220 in the form of an hourglass is removed by etching.

An antireflection layer (not shown) may be additionally deposited on the first semiconductor layer 230 to reduce reflectivity of incident light. At this time, the antireflection film may be one of materials such as SiO ₂ , SiN _x , and Al ₂ O ₃ .

The rear absorption layer 250 is made of a material having a low resistance and having a band gap capable of absorbing light of a near-infrared or infrared wavelength. For example, it may be a semiconductor material such as Si _x Ge _1-x and Ge, but is not limited thereto. The rear absorption layer 250 is not absorbed by the vertical nanowires 220 in the form of an hourglass, but additionally absorbs near-infrared or infrared light reaching the rear surface of the semiconductor substrate 210 to improve the near-infrared or infrared detection characteristics of the photodetector.

The first electrode 240 is formed on the edge of the first semiconductor layer 230 formed by etching to form an electrical connection between the photodetector and allow light to enter the vertical nanowire 220 in the form of an hourglass. At this time, the first electrode 240 should contact the first semiconductor layer 230 and not the semiconductor substrate 210.

A second electrode 260 is formed under the rear absorbing layer 250 for electrical connection. The second electrode 260 is formed over the entire rear absorption layer 250 so that an even electric field can be applied to the front surface of the rear absorption layer 250. In addition, the rear absorbing layer 250 totally reflects the vertical nanowires 220 in the form of an hourglass and the near-infrared or infrared light having a long absorption depth that was not absorbed by the rear absorbing layer 250, so that the rear absorbing layer 250 and the vertical nanowires in the form of an hourglass are reflected. It is to be reabsorbed in the line 220 again.

The vertical nanowire photodetector having the double absorption layer improves absorption through the optical resonance effect and re-absorption of reflected light in the vertical nanowire structure in the form of an hourglass on the front surface, and is absorbed in the vertical nanowire 220 in the form of an hourglass. Near-infrared or infrared light having a long absorption depth that is not possible is reabsorbed in the rear absorption layer. In addition, the near-infrared or infrared light that has not been absorbed by the vertical nanowire 220 in the form of an hourglass and the rear absorbing layer 250 is totally reflected to the front surface of the semiconductor substrate 210 through the second electrode 260 to the rear absorbing layer 250. And by absorbing once again in the hourglass-shaped vertical nanowire 220 improves the photodetection characteristics (sensitivity and quantum efficiency).

Evaluation Example 1

3 is a diagram showing sensitivity and external quantum efficiency (EQE) results for verifying the effects of the vertical nanowire and the rear absorbing layer of the vertical nanowire photodetector having a double absorbing layer according to an embodiment of the present invention.

For performance comparison, the sensitivity and external quantum efficiency results of a cylindrical vertical nanowire and a flat plate photodetector with a rear absorption layer and a cylindrical vertical nanowire and a flat plate photodetector without a rear absorption layer are shown together. At this time, the rear absorption layer 250 is made of SiGe, and the first electrode 240 and the second electrode 260 are made of aluminum.

Sensitivity (R _λ, unit: A/W) is a characteristic index indicating how much the signal of the photodetector changes for a light source of the same intensity. Sensitivity is calculated as follows using the dark current and photocurrent of the photodetector appearing before and after irradiation of the light source of the monochromator.

In the equation, I _light is the current in the state where light is applied, I _dark is the current in the absence of light, dark current, P is the light intensity, and AA is the active area.

The external quantum efficiency ( EQE , unit: %) represents the rate at which charges generated by photons of incident light contribute to the photocurrent. The external quantum efficiency can be extracted using sensitivity, and the calculation formula is as follows.

In the above equation, h is the Planck constant (6.33x10 ^-34 m ² kg/s), c is the speed of light (3x10 ⁸ m/s), q is the amount of charge (1.6x10 ^-19 C), λ Represents the wavelength of light.

3A shows the sensitivity in the near-infrared wavelength region (700-1100 nm).

Referring to FIG. 3A, regardless of the presence or absence of the rear absorbing layer, it can be seen that the sensitivity is in the order of an hourglass-shaped vertical nanowire photodetector, a cylindrical vertical nanowire photodetector, and a flat plate photodetector. In the cylindrical vertical nanowire array structure, the nanowire has a large surface area and re-absorbs light reflected from adjacent nanowires, so it has better light absorption than a flat plate structure and shows high sensitivity.

The vertical nanowire array in the form of an hourglass generates light resonance in the upper inverted cone structure, so that light stays on the upper nanowire surface for a long time to improve light absorption. At the same time, the lower cone structure has a lower surface reflectivity than the cylindrical structure, so it is It absorbs more of the leaked near-infrared light than the cylinder. Therefore, the vertical nanowire array in the form of an hourglass has higher light absorption than that of cylindrical nanowires and flat plate structures and shows very excellent sensitivity.

In addition, it can be seen that the sensitivity of the vertical nanowire photodetector and the cylindrical nanowire photodetector having a rear absorption layer are improved compared to the case without the rear absorption layer. On the other hand, in the flat-panel photodetector, there is little difference in sensitivity depending on the presence or absence of the rear absorption layer. In the case of the flat plate structure, near-infrared light does not stay on the surface for a long time, but immediately reaches the rear absorption layer and is reflected by the rear second electrode to be absorbed again at the rear absorption layer and the surface. However, the amount of light reabsorbed from the rear absorbing layer and the surface after being reflected by the rear absorbing layer and the second electrode is small because the light of the near-infrared wavelength having a long absorption depth passes through the flat semiconductor substrate for a short time.

In contrast, vertical nanowires and cylindrical nanowires in the form of an hourglass have a longer time to stay in the nanowire structure, so the amount of light absorbed by the rear absorption layer is larger than that of the flat plate, and even after being reflected by the second electrode, the light remains on the surface. The structure is absorbed for a long time, so the sensitivity is high. In the case of the hourglass structure, since light stays longer than cylindrical nanowires due to optical resonance, the effect of improving the sensitivity is greater. The effect of improving the sensitivity of the double absorbing layer nanowire photodetector is large at long wavelengths (1,000 nm and 1,100 nm) with a light absorption depth of several hundred um or more, and light with a wavelength lower than the thickness of the substrate is in the form of a nanowire and the presence or absence of a rear absorbing layer Regardless of the sensitivity, there is no significant difference. This is because light of 700nm, 800nm and 900nm wavelength is difficult to reach the back side of the semiconductor substrate.

3B shows the external quantum efficiency in the near-infrared wavelength region (700-1100 nm).

Referring to (b) of FIG. 3, it can be seen that the external quantum efficiency has a similar tendency to the sensitivity. The photodetector having a rear absorbing layer shows high external quantum efficiency in the order of hourglass-shaped nanowires, cylindrical nanowires, and flat plate types. The external quantum efficiency of the photodetector is excellent when the front nanowire structure and the rear absorption layer are applied at the same time.

4 is a diagram illustrating a principle of improving detection characteristics of a vertical nanowire photodetector having a double absorbing layer according to an exemplary embodiment of the present invention.

4A is a diagram illustrating a process in which light is absorbed from the vertical nanowire in the form of an hourglass to the rear absorption layer in the vertical nanowire photodetector having a double absorption layer according to an embodiment of the present invention.

Light incident from the vertical nanowire 220 in the form of an hourglass is absorbed while staying on the surface for a long time because resonance occurs in an inverted cone structure at the top of the hourglass. At the same time, most of the light leaking from the surface of the inverted cone structure is absorbed by the conical structure at the bottom of the surrounding hourglass-shaped nanowire.

The conical structure increases in diameter from the top to the bottom, and the surface reflectivity is low, absorbing more light than the cylindrical structure. After that, the light not absorbed by the hourglass-shaped nanowires reaches the rear absorption layer and is absorbed. Light at wavelengths of 700 nm, 800 nm and 900 nm has no or very small amount reaching the back side of the semiconductor substrate because the light absorption depth is less than the thickness of the semiconductor substrate, and long wavelengths (1,000 nm and 1,100 nm) with a light absorption depth of several hundred micrometers (um) or more. ) Only light reaches the back of the substrate. Therefore, in order to absorb long wavelength light, a material having a small band gap is used as the rear absorption layer.

Additionally, light that cannot be absorbed by the vertical nanowire 220 in the form of an hourglass and the rear absorbing layer 250 is totally reflected by the second electrode 260 and goes back to the surface. It is reabsorbed in the line 220. Due to the interaction between the above-mentioned hourglass-shaped vertical nanowire 220 and the rear absorption layer 250, the amount of light absorption increases, and the detection characteristics of near-infrared or infrared wavelength light of the double-absorbing layer nanowire photodetector are improved. In the case of the flat plate structure, the near-infrared light does not stay on the surface for a long time and immediately reaches the rear absorption layer 250 and is reflected by the second electrode 260 on the rear surface to be absorbed again from the rear absorption layer 250 and the surface. Regardless of the presence or absence of the absorption layer 250, there is no significant change in the difference in the amount of absorbed light.

4B is a diagram depicting an energy band diagram for explaining a principle in which light is absorbed by a rear absorbing layer in a vertical nanowire photodetector having a double absorbing layer according to an embodiment of the present invention.

The energy band diagram shows when a reverse voltage is applied, and SiGe having a smaller band gap (<1.12eV) than that of a silicon material is used as the rear absorption layer 250. In the reverse voltage, the voltage drop inside the photodetector mostly occurs at the bonding surface between the first semiconductor layer 230 and the semiconductor substrate 210 and the bonding surface between the semiconductor substrate 210 and the rear absorbing layer 250. When near-infrared or infrared light is applied to the inside of the photodetector, electron-hole pairs are primarily generated by the light source at the junction surface of the first semiconductor layer 230 and the semiconductor substrate 210 on the front side, and the semiconductor substrate 210 and the rear side Electron-hole pairs are secondarily generated on the bonding surface of the rear absorption layer 250.

Thereafter, electron-hole pairs are thirdly generated at the junction surface of the semiconductor substrate 210 and the rear absorbing layer 250 by the light reflected from the second electrode 260, and finally, the first semiconductor layer 230 and the semiconductor substrate Electron-hole pairs are quaternarily generated at the junction of (210). At this time, the holes generated in the rear absorption layer 250 move to the second electrode 260 and contribute to the photocurrent. On the other hand, electrons generated in the rear absorption layer 250 pass through the semiconductor substrate 210 and move to the first electrode 240 to contribute to the photocurrent.

Electrons may be recombined and disappeared while moving the semiconductor substrate 210, and the amount of recombination is determined according to the concentration of the semiconductor substrate 210. Therefore, the double absorption layer nanowire photodetector is applied to holes generated on the bonding surface of the semiconductor substrate 210 and the rear absorption layer 250 and electrons generated on the bonding surface of the first semiconductor layer 230 and the semiconductor substrate 210. It can be seen that the photocurrent is determined by this.

5 is a flowchart illustrating a method of manufacturing a vertical nanowire photodetector having a double absorbing layer according to an embodiment of the present invention, and FIGS. 6 to 10 illustrate each step of the method of manufacturing a double absorbing layer nanowire photodetector according to FIG. 5. It is a cross-sectional view and a plan view for explanation.

A method of manufacturing a double absorbing layer nanowire photodetector according to an embodiment of the present invention will be described with reference to FIGS. 5 to 10.

As shown in FIG. 5, the method of manufacturing a vertical nanowire photodetector having a double absorbing layer according to an embodiment of the present invention includes forming a rear absorbing layer (S100), forming a vertical nanowire (S200), and forming a first semiconductor layer. (S300) and electrode formation step (S400).

In the step of forming the rear absorption layer (S100), the absorption layer 250 is formed on the rear surface of the semiconductor substrate 210.

In the vertical nanowire forming step (S200), the surface of the semiconductor substrate 210 is etched to form the vertical nanowire 220 in the form of an array.

In the first semiconductor layer forming step (S300 ), a first semiconductor layer 230 doped with a doping material of a type opposite to that of the semiconductor substrate 210 is formed on the surface of the vertical nanowire 220.

In the electrode formation step (S400), a first electrode 240 is formed at an edge of the first semiconductor layer 230 and a second electrode 260 is formed at a lower end of the rear absorbing layer 250.

Referring to FIGS. 6 to 10, the back absorbing layer forming step (S100), the vertical nanowire forming step (S200), the first semiconductor layer forming step (S300), and the electrode forming step (S400) will be described in detail.

6 is a plan view and a cross-sectional view illustrating a step of forming a rear absorption layer in the method of manufacturing a vertical nanowire photodetector having a double absorption layer according to FIG. 5.

Referring to FIG. 6, before forming the rear absorption layer 250, a natural oxide film removal step (S110) of removing the natural oxide film of the semiconductor substrate 210 using a wet etching process is performed. Thereafter, a rear absorption layer 250 is formed on the rear surface of the semiconductor substrate 210 to absorb near-infrared or infrared light. (S120) The semiconductor substrate 210 used at this time may be either a p-type or an n-type. The rear absorption layer 250 may be formed of any one of SiGe, Ge, InGaAs, and corresponding materials having a smaller band gap (1.12eV) than a silicon material. In addition, in order to lower the resistance of the rear absorption layer, an n-type or p-type impurity corresponding to the type of material (group IV, group III-V) may be implanted.

7 is a plan view and a cross-sectional view illustrating a step of forming a vertical nanowire in the method of manufacturing a vertical nanowire photodetector having a double absorbing layer according to FIG. 5.

Referring to FIG. 7, in the vertical nanowire formation step (S200), a mask layer and a photoresist layer deposition step (S210) of sequentially depositing a mask layer and a photoresist layer on the semiconductor substrate, forming a pattern on the photoresist layer. Pattern forming step (S220), vertical nanowire array forming step (S230) of forming an array of vertical nanowires by dry etching the mask layer and the semiconductor substrate exposed between the patterns in sequence (S230), and removing the photoresist layer and the mask layer And removing the photoresist layer and the mask layer (S240).

In the mask layer and photoresist layer deposition step (S210), a mask layer 280 to be used as an etching mask is deposited on the semiconductor substrate 210, and the photoresist layer 290 is sequentially applied. During the dry etching process, silicon and a material having a high etching selectivity are used as the mask layer 280 in order to manufacture the vertical nanowires 230 in the form of an hourglass having a high aspect ratio. The mask layer 280 used at this time may be one of an insulating material such as SiO ₂ and SiN, or a metal material such as Al, Cr, Ni, and Ti.

In the pattern formation step S220, the upper end pattern of the vertical nanowire 220 is formed on the photoresist 290 using a lithography process. Pattern formation is characterized by using any one of electron beam lithography, nanoimprint, ion beam lithography, X-ray lithography, extreme ultraviolet lithography, and photolithography (stepper, scanner, contact aligner, etc.). Since the surface reflectivity of light is also affected by the shape of the upper end of the vertical nanowire 220, patterns can be formed in various shapes such as a circle, a triangle, a square, a pentagon, and a hexagon, and the arrangement of the vertical nanowire 220 is also a triangle, a square, It can be formed in various shapes, such as pentagons and hexagons.

In the vertical nanowire array forming step (S230), the mask layer 280 is preferentially etched through dry etching to transfer the pattern of the photoresist to the mask layer 280. Thereafter, dry etching is performed on the semiconductor substrate 210 based on the mask layer 280 to which the pattern has been transferred, thereby forming the vertical nanowire 220 in the form of an hourglass. At this time, vertical nanowires 220 having an hourglass cross section are formed by adjusting the ratio, pressure, temperature, source power, and bias power of the etching gas used for dry etching. By adjusting the dry etching conditions, it is possible to form a cylindrical, conical, or inverted conical nanowire cross section. The cross-sections of the nanowires will be described in detail in FIG. 8 to be described later.

In the step of removing the photoresist layer and the mask layer (S240), after forming the vertical nanowire 220 in the form of an hourglass, the remaining mask layer 280 and the photoresist layer 290 are removed from SPM (H ₂ SO ₄ and H ₂ O ₂ mixture) solution and dHF (dilute hydrofluoric acid) solution are used to remove by wet etching process. Finally, the semiconductor substrate 210 on which the rear absorption layer 260 and the vertical nanowires 220 in the form of an hourglass are formed is fabricated.

After the dry etching process, a defect occurs on the surface of the vertical nanowire 220, which may reduce sensitivity and external quantum efficiency by recombining electron-hole pairs generated by light later. Therefore, in order to remove surface defects to improve the performance of the photodetector, an additional SiO ₂ formation oxidation process and a SiO ₂ removal wet etching process may be performed to further perform the surface defect removal step of the vertical nanowires to remove the surface defects of the vertical nanowires. .

8 is a diagram showing various types of vertical nanowires formed according to FIG. 7.

Referring to FIG. 8, in step S230 of the above-mentioned vertical nanowire formation step (S200), the gas ratio, pressure, temperature, source power, and bias power of dry etching are adjusted to form a cylindrical shape 320, a conical shape 420, and a reverse. A conical 520 vertical silicon nanowire can be manufactured. The cylindrical vertical nanowire 320 has a constant diameter from the upper end to the lower end, the conical vertical nanowire 420 is a structure having a larger lower end diameter than the upper end diameter, and the inverted conical vertical nanowire 520 has a diameter of the upper end at the lower end. It is a structure with a larger diameter.

In the conical vertical nanowire 420, an upper portion having a small diameter has a refractive index similar to that of air, and a lower portion having a large diameter has a refractive index similar to that of a silicon bulk material. Therefore, since the refractive index gradually increases from the upper end to the lower end, the surface reflectivity has a very small value, so that light absorption is better than that of the cylindrical vertical nanowire 320. In the inverted conical vertical nanowire 520, light of a specific wavelength is superimposed on a specific surface position of the nanowire due to a diameter decreasing from the upper part to the lower part, thereby generating a resonance called a whispering gallery mode. This resonance improves light absorption by making light stay on the nanowire surface for a long time.

Cylindrical, conical, and inverted conical nanowire structures have better light absorption characteristics than flat-panel structures, and when combined with the rear absorbing layer, the sensitivity and external quantum efficiency of the photodetector can be improved. Therefore, in the vertical nanowire photodetector having a double absorption layer, in addition to the vertical nanowire in the form of an hourglass, cylindrical, conical, and inverted conical nanowire structures can be used.

9 is a plan view and a cross-sectional view illustrating a step of forming a first semiconductor layer in the method of manufacturing a vertical nanowire photodetector having a double absorbing layer according to FIG. 5.

Referring to FIG. 9, in the step of forming a first semiconductor layer (S300), a first semiconductor layer deposition step of depositing a first semiconductor layer doped with a doping material of a type opposite to that of the semiconductor substrate on the surface of the vertical nanowire. (S310), a first semiconductor layer etching step (S320) of applying and selectively etching a photoresist layer on the first semiconductor layer, and a photoresist layer removing step (S330) of removing the photoresist layer.

In the first semiconductor layer deposition step (S310), a heavily doped first semiconductor layer 230 is deposited on the surfaces of the hourglass-shaped vertical nanowires 220 to form a pn junction core-shell structure. In this case, the first semiconductor layer 230 should be implanted with impurities of a type different from that of the vertical nanowire 220 in the form of an hourglass, and the doping concentration may be 10 ¹⁸ cm ^-3 to 10 ²¹ cm ^-3 . The first semiconductor layer 230 may be formed using a chemical vapor deposition (CVD) method to which an in-situ doping technique is applied, and the formed material may be one of a crystalline silicon layer, a polysilicon layer, or an amorphous silicon layer. When the first semiconductor layer 230 is formed in a p-type, at least one of B, Al, and Ga is implanted, and when formed in an n-type, at least one of P, As, and Sb is implanted. Can be.

In the first semiconductor layer etching step (S320 ), the first semiconductor layer 230 is selectively etched and removed to form electrical insulation between devices while defining an active region of the photodetector. To this end, a photoresist layer 290 is applied on the first semiconductor layer 230 and a pattern for etching the portion of the first semiconductor layer to be removed is formed using a photolithography (stepper, scanner, contact aligner, etc.) process. . During the etching process, the portion protected by the photoresist has a shape of a circle or a square including vertical nanowires 220 in the form of an hourglass.

In the photoresist layer removing step (S330), the first semiconductor layer 230 that is not protected by the photoresist layer 290 is completely etched and removed using a dry etching process. The photoresist layer 290 remaining after the etching process is removed through a wet cleaning process.

In order to reduce the reflectivity of incident light, an antireflection layer (not shown) may be additionally deposited on the surface of the first semiconductor layer 230 on the vertical nanowire 220 in the form of an hourglass. At this time, the antireflection layer may be one of materials such as SiO ₂ , SiNx, and Al ₂ O ₃ .

10 is a plan view and a cross-sectional view illustrating a step of forming an electrode in the method of manufacturing a vertical nanowire photodetector having a double absorbing layer according to FIG. 5.

Referring to FIG. 10, the electrode forming step (S400) includes a first electrode forming step (S410) of forming a first electrode on the first semiconductor layer, and a second electrode forming a second electrode under the rear absorbing layer. A forming step (S420) and a dicing step (S430) of dicing the photodetector fabricated on the semiconductor substrate into chips.

In the first electrode forming step (S410), the first electrode 240 is formed on the first semiconductor layer 230, and at this time, the first electrode 240 forms an electrical connection to the photodetector and incident near-infrared or infrared light It is formed only at the edge of the first semiconductor layer 230 so as to be incident on the vertical nanowire 220 in the form of an hourglass of the photodetector.

In this case, the first electrode 240 is formed in a structure such as a circle or a square according to the shape in which the first semiconductor layer 230 is etched. The first electrode 240 is formed in a desired shape at a desired position using a metal lift-off process. The first electrode 240 only makes contact with the first semiconductor layer 230 and does not make contact with the semiconductor substrate 210 and the antireflection layer (not shown).

The first electrode 240 may be a metal material of Al, Au, Ni, Ti, Pt, Ag, or a transparent electrode material such as ITO. When a transparent electrode material is used as the first electrode 240, a transparent electrode may be deposited over the entire first semiconductor layer 230.

In the second electrode forming step S420, the second electrode 260 is formed at the lower end of the rear absorbing layer 250 present on the rear surface of the semiconductor substrate 210. If the contact surface between the rear absorption layer 250 and the second electrode 260 is reduced to reduce contact defects, an insulating material may be deposited on the rear absorption layer 250 and then a contact hole may be formed and the second electrode 260 may be deposited. .

In the dicing step (S430), a dicing process is performed to make the unit photodetector fabricated on the semiconductor substrate 210 into chips. In this case, dicing is performed in an area larger than that of the first semiconductor layer 230 to protect the active region. As a dicing process, any one of a blade, laser, and plasma method may be used.

The technical effects of the present invention are not limited to those mentioned above, and other technical effects that are not mentioned will be clearly understood by those skilled in the art from the following description.

210: semiconductor substrate 220: vertical nanowires in the form of an hourglass
230: first semiconductor layer 240: first electrode
250: rear absorption layer 260: second electrode
280: mask layer 290: photoresist layer

Claims (21)

A semiconductor substrate;
Vertical nanowires formed in an array shape on the entire surface of the semiconductor substrate;
A first semiconductor layer formed by doping a doping material on the vertical nanowires;
A first electrode formed at an edge of an upper end of the first semiconductor layer;
A rear absorption layer formed on the rear surface of the semiconductor substrate; And
And a second electrode formed under the rear absorbing layer. The method of claim 1, wherein the vertical nanowire
A double absorbing layer nanowire photodetector, characterized in that it is in the form of an hourglass in which an inverted cone structure at the top and a cone structure at the bottom are combined. The method of claim 1, wherein the cross section of the upper end of the vertical nanowire is
Double absorption layer nanowire photodetector, characterized in that any one of circular, triangular, square, pentagonal and hexagonal. The method of claim 1, wherein the vertical nanowire
Double absorption layer nanowire photodetector, characterized in that any one of a cylindrical, conical, and inverted conical structure. The method of claim 1,
The vertical nanowire and the semiconductor substrate are doped with a first type of doping material, and the concentration of the doping material is in the range of 10 ¹² cm ^-3 to 10 ¹⁷ cm ^-3 . The method of claim 1, wherein the first semiconductor layer
Doped with a second type of doping material, and the concentration of the doping material is in the range of 10 ¹⁸ cm ^-3 to 10 ²¹ cm ^-3 . The method of claim 1, wherein the first semiconductor layer
Double absorption layer nanowire photodetector, characterized in that at least one from the group consisting of single crystal silicon, polycrystalline silicon and amorphous silicon. The method of claim 6, wherein the second type of doping material is
A double absorbing layer nanowire photodetector comprising phosphorus (P), arsenic (As) and antimony (Sb). The method of claim 6, wherein the second type of doping material is
B, BF ₂ , a double absorbing layer nanowire photodetector comprising Al or Ga. The method of claim 1, wherein the first semiconductor layer
Further comprising an anti-reflection film for preventing reflection of incident light,
The anti-reflection film is a double absorption layer nanowire photodetector, characterized in that made of any one of a silicon oxide film (SiO ₂ ) silicon nitride film (SiN _x ), or alumina (Al ₂ O ₃ ). The method of claim 1, wherein the rear absorption layer is
Si _x Ge _1-x , Ge, InGaAs, InGaAsP, InP, HgCdTe having a smaller band gap than silicon. The method of claim 1,
The first electrode is a double absorption layer nanowire photodetector, characterized in that made of any one of Al, Au, Ni, Ti, Pt, Ag, or ITO material. The method of claim 1, wherein the second electrode is
Double absorption layer nanowire photodetector, characterized in that made of any one of Al, Au, Ni, Ti, Pt or Ag. Forming a rear absorption layer of forming an absorption layer on the rear surface of the semiconductor substrate;
Forming vertical nanowires in the form of an array by etching the surface of the semiconductor substrate;
A first semiconductor layer forming step of forming a first semiconductor layer doped with a doping material of a type opposite to that of the semiconductor substrate on the surface of the vertical nanowires; And
And an electrode forming step of forming a first electrode positioned at an edge of the first semiconductor layer and a second electrode positioned below the rear absorbing layer. The method of claim 14,
Removing the natural oxide layer of the semiconductor substrate prior to the forming of the rear absorbing layer, the method of manufacturing a double absorbing layer nanowire photodetector further comprising. The method of claim 15, wherein the forming of the rear absorption layer comprises:
Injecting an n-type or p-type impurity to lower the resistance; a method for manufacturing a double absorption layer nanowire photodetector further comprising. The method of claim 14, wherein the forming of the vertical nanowire
A mask layer and a photoresist layer deposition step of sequentially depositing a mask layer and a photoresist layer on the semiconductor substrate;
A pattern forming step of forming a pattern on the photoresist layer;
Forming a vertical nanowire array by sequentially dry etching the mask layer and the semiconductor substrate exposed between the patterns to form an array of vertical nanowires; And
And a step of removing the photoresist layer and the mask layer for removing the photoresist layer and the mask layer. The method of claim 17,
After removing the photoresist layer and the mask layer, a vertical nanowire surface defect removing step of removing defects formed on the surface of the vertical nanowire; a method of manufacturing a double absorbing layer nanowire photodetector further comprising. The method of claim 18, wherein the step of removing surface defects of the vertical nanowires
A method of manufacturing a double absorption layer nanowire photodetector, characterized in that it proceeds through an oxidation process and a wet etching process. The method of claim 14, wherein the step of forming the first semiconductor layer
A first semiconductor layer deposition step of depositing a first semiconductor layer doped with a doping material of a type opposite to that of the semiconductor substrate on the surface of the vertical nanowire;
A first semiconductor layer etching step of coating and selectively etching a photoresist layer on the first semiconductor layer; And
A method of manufacturing a double absorbing layer nanowire photodetector comprising a; photoresist layer removing step of removing the photoresist layer. The method of claim 14, wherein the electrode forming step
A first electrode forming step of forming a first electrode on the first semiconductor layer;
A second electrode forming step of forming a second electrode under the rear absorber layer; And
And a dicing step of dicing the photodetector fabricated on the semiconductor substrate in a chip unit. 2. A method of manufacturing a double absorption layer nanowire photodetector comprising: a.

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