KR100734407B1 - Ultraviolet rays sensor - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device for detecting ultraviolet rays, wherein an In _x Ga _1-x N (0 ≦ _x ≦ 0.5) layer formed on a substrate is formed of a light absorbing layer, or an In _y having a smaller In composition than the light absorbing layer and having a very thin In _y In a structure in which a Ga _{1 - y} N (0 ≦ _y ≦ _x ) layer is formed as a capping layer, a transparent Schottky bonding layer is formed thereon, and an ohmic bonding layer is formed on the light absorbing layer, the capping layer, or on the high temperature buffer layer. Thus, the cut-off wavelength at the longer wavelength side has a wavelength longer than 375 nm.

UV, Semiconductor, Device, Ohmic Bonding Layer, Cut-Off Wavelength, Light Absorption Layer

Description

Ultraviolet Ray Detection Semiconductor Device {Ultraviolet rays sensor}

1 is a cross-sectional view of a conventional ultraviolet sensing semiconductor device,

2 is a plan view of the device shown in FIG.

3 is a cross-sectional view of a conventional ultraviolet sensing semiconductor device,

4 is a plan view of the device shown in FIG.

5 is a graph illustrating a detection area of a conventional semiconductor device;

6 is a graph showing a sensing region of a semiconductor device according to the present invention;

7 is a cross-sectional view of a semiconductor device according to an embodiment of the present disclosure;

8 is a plan view of the semiconductor device illustrated in FIG. 7;

9 is a sectional view of a semiconductor device according to a second embodiment of the present invention;

10 is a plan view of the semiconductor device illustrated in FIG. 9;

11 is a sectional view of a semiconductor device according to a third embodiment of the present disclosure;

12 is a plan view of the semiconductor device illustrated in FIG. 11;

13 is a sectional view of a semiconductor device according to a fourth embodiment of the present invention;

14 is a plan view of the semiconductor device illustrated in FIG. 13.

* Explanation of symbols for main parts of the drawings

10 substrate 11 low temperature buffer layer

12 high temperature buffer layer 13 light absorbing layer

14: Schottky bonding layer 15: Schottky pad layer

16: ohmic bonding layer 17: capping layer

The present invention detects the ultraviolet light absorption particularly it relates to a semiconductor device _{In x Ga 1 -x N (0≤x≤0.5} ) layer to or above the low In composition is very thinner than the light absorption for the In _y Ga _{1 - y} By using the N (0≤y≤x) layer as a capping layer and forming a Schottky bonding layer thereon, the cut-off of the longer wavelength side than the detector using the conventional AlGaN, GaN material as the light absorption layer The present invention relates to an ultraviolet sensing semiconductor element adapted to be suitable for detecting a large wavelength, that is, longer than 375 nm.

Ultraviolet rays with a wavelength of 400 nm or less are divided into several bands for each wavelength. The UV-A region is 320 nm-400 nm, and more than 98% of the sunlight reaching the earth's surface is the UV-A region. UV-A affects the skin's blackening and skin aging. The UV-B region is 280nm-320nm, and only about 2% of sunlight reaches the earth's surface. The human body has very serious effects such as skin cancer, cataracts and erythema. UV-B is mostly absorbed by the ozone layer, but recently, the amount of reaching the surface by the destruction of the ozone layer is increasing and the area is increasing, which is a serious environmental problem. UV-C is between 200nm and 280nm, and everything from sunlight is absorbed into the atmosphere and hardly reaches the earth's surface. This area is widely used for sterilization. One of the quantified effects of ultraviolet rays on the human body is the UV Index defined by the amount of UV-B incident.

Ultraviolet rays can be detected by using a photo multiplier tube (PMT) or a semiconductor device. Since semiconductor devices are cheaper and smaller than PMT, most of them use a lot of semiconductor devices in recent years. In semiconductor devices, GaN, SiC, etc., in which the energy band gap is suitable for ultraviolet detection, and the energy band gap are small, but Si is widely used. Among them, in particular, GaN-based devices, Schottky junction type, MSM (metal-semi conductor-metal) type and PIN type devices are mainly used. Schottky junction type devices are preferred because of their simple process. have.

The structure of a conventional Schottky junction ultraviolet sensing element is shown in FIGS. 1 and 2. As shown in FIG. 1 and FIG. 2, the conventional Schottky junction UV sensing device first grows a GaN and SiC layer on the substrate 10 using MOCVD or MBE. In the substrate 10 to be used, sapphire is most frequently used for GaN layer growth, Si, GaAs, SiC, etc. are used, and glass is rarely used. In the case of a sapphire substrate is grown on the (0001) surface, if the growth immediately due to the difference in the lattice constant between GaN and sapphire, cracks do not grow properly. Therefore, after growing the low temperature buffer layer 11 at a temperature of 500 ~ 600 ℃ lower than the normal growth temperature, the growth temperature is raised to grow the layer required for the device. The low temperature buffer layer mainly grows GaN or AlN and has a thickness of 0.1 μm or less. After growing the low temperature buffer layer, the high temperature buffer layer 12 is grown on it, and the GaN layer is usually grown. Generally, about 0.5 to 2 um should be grown to reduce the influence of defects caused by the substrate and the buffer layer, thereby improving the crystallinity of the layer. . The high temperature buffer layer may grow an AlGaN layer when the light absorbing layer is an AlGaN layer. The high temperature buffer layer may be artificially doped with a dopant such as Si to maintain the doping concentration of the layer as n-type. After growing the high temperature buffer layer, the GaN layer is used as the light absorbing layer to detect the UV-A region according to the wavelength of light to be absorbed. However, although the wavelength band of UV-A is 400nm to 320nm, when GaN is used as the light absorbing layer, the cut-off wavelength is 375nm, which makes it impossible to detect an accurate UV-A wavelength. In order to detect the UV-B and UV-C areas, an Al composition may be grown in the light absorbing layer differently. For example, in order to detect the UV-B area, an AlGaN layer containing about 30% of Al is grown. To detect the C region, an AlGaN layer containing about 45% Al is grown. In the case where the high temperature buffer layer is GaN and the light absorbing layer is AlGaN, if the Al composition is high, another intermediate buffer layer may be inserted between the high temperature buffer layer and the light absorbing layer because cracking occurs during or after growth due to a lattice constant difference. The intermediate buffer layer to be inserted grows an AlGaN or AlN layer to lower the growth temperature or to grow a thin layer (<0.1um) having a larger Al composition than the light absorbing layer. The doping concentration of the light absorbing layer is maintained at n-type while the doping concentration is low, so the efficiency is large. Therefore, it is maintained at 1E17cm ^{- 3} or less, but the AlGaN layer may have a doping concentration of 1E18cm. The thickness of the light absorbing layer grows in various ways depending on the structure of the device from 0.1um to 2um. After the MOCVD growth is completed, the ohmic junction layer 16 is first formed. The wafer may be formed directly on the light absorbing layer 13, or the light absorbing layer may be etched and formed in a high temperature buffer layer. In the case of forming an ohmic junction in the high temperature buffer layer, when the high temperature buffer layer has a higher doping concentration than the light absorbing layer, and the ohmic bonding characteristic is good and when the light absorbing layer is AlGaN, it is difficult to secure the ohmic bonding characteristic than the GaN or the light absorbing layer. An AlGaN layer having a low Al composition may be formed and an ohmic junction layer may be formed thereon. As the metal for forming the ohmic junction, Ti / Al and Cr / Ni / Au are mainly used. In case of Ti / Al, the thickness of Ti (<500Å) / Al (> 3000Å) is formed, and the metal is deposited and then heat treated at a temperature of> 400 ° C. for a suitable time in a mixed gas atmosphere containing nitrogen or nitrogen to form an ohmic junction layer. To form. After the ohmic junction layer is formed, the Schottky junction layer 14 is formed on the light absorbing layer. The metals mainly used are Ni, Pt, Ru, Au, and the like. In the case of the Schottky junction sensing device, ultraviolet light transmittance of the Schottky junction layer is an important item because light must pass through the Schottky junction layer and enter the light absorbing layer. Therefore, most of the metal thickness is formed by depositing less than 500Å. Also, in order to improve electrical and reliability characteristics, an oxide may be formed by heat treatment after metal deposition. That is, a lot of improved characteristics such as NiO _x and RuO _x have been reported. The heat treatment temperature is variously performed by the metal and the process, and is mainly performed at about 300 ° C.

ITO is often used to further form a light transmissive conductive layer on the Schottky junction layer to improve electrical properties. After the Schottky bonding layer is formed, Au is thickly deposited on the Schottky bonding layer for wire connection with the external electrode to form the Schottky pad layer 15. It mainly uses Ni / Au or Cr / Ni / Au and may be formed separately on the ohmic junction layer. Since the region in which the Schottky pad layer is formed does not transmit light and thus does not act as a Schottky bonding layer, the region of the Schottky pad layer should be reduced to the minimum space for the bonding wire. After the formation of the Schottky pad layer, the back side of the substrate is wrapped / polished to a total thickness of about 100 um, and then scribed / breaked to separate into individual elements. The separated individual device is mounted in a TO-CAN type package or an SMD type package to operate as a sensing device.

In the Schottky junction sensing element, a depletion layer is formed on the light absorbing layer in contact with the Schottky junction layer due to the Schottky barrier effect by the Schottky junction layer. In the depletion layer, there are no electrons or holes that can move charges, and at this time, electrons or holes generated by light move to the Schottky junction layer and the ohmic junction layer, and current flows. That is, when the sensing element is exposed to ultraviolet rays, ultraviolet rays pass through the Schottky junction layer and enter the depletion layer, and the incident ultraviolet rays generate electrons / holes, and electrons move to the Schottky junction layer and holes move to the ohmic junction layer. And the current is sensed to measure the amount of incident light of ultraviolet rays. As the doping concentration of the light absorbing layer is lower, the thickness of the depletion layer is increased and the amount of electrons / holes generated by light increases, so it is preferable to reduce the doping concentration of the possible depletion layer. In addition, since the ultraviolet light is transmitted through the Schottky bonding layer, the transmittance of the Schottky bonding layer should be good, but the thickness of the metal should be thin or a metal having good transmittance should be used. In addition, since the higher the potential barrier by the Schottky junction has a stable electrical characteristics to form a Schottky junction layer in consideration of these characteristics overall. In general, the bias is not applied externally during the operation of the device, but the bias is also applied in the reverse direction to increase the light conversion efficiency. That is, a negative bias is applied to the Schottky bonding layer and a positive bias is applied to the ohmic bonding layer. In this case, the thickness of the depletion layer is increased to increase the light change efficiency. When the sensing element is packaged in TO-can type or SMD type, a window must be made of a material that transmits ultraviolet rays, and quartz is mainly used. Or it may be composed of an encapsulant of the Si series.

In the case of a sensing device fabricated to detect a UV-A region using a conventional GaN layer as a light absorbing layer, a cut corresponding to a value of 10% UV-A reactivity (A / W) as shown in FIG. The off wavelength is 375 nm, and thus there is a problem in that pure UV-A (400 nm to 320 nm) area cannot be detected, and when GaN is used as a light absorbing layer, a wavelength longer than a cut-off wavelength of 375 nm may not be detected. On the other hand, the detection element having a wavelength shorter than the cut-off wavelength of 375 nm, the AlxGa1-xN (0≤x≤1) layer as a light absorbing layer, it is possible to vary the cut-off wavelength by changing the Al composition of the light absorbing layer. . For example, an Al0.3Ga0.7N layer containing about 30% of the Al composition is used as a light absorption layer to detect the UV-B cutoff wavelength region, and an Al composition is weak to detect the UV-C cutoff wavelength region. The AlGaN layer containing about 45% may be used as the light absorbing layer.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide an In _x Ga _{1 - x} N (0 ≦ _x ≦ 0.5) layer. Or a thinner In _y Ga _{1 - y} N (0 ≦ _y ≦ x) layer having a lower In composition than the light absorbing layer and forming a Schottky bonding layer thereon, thereby forming a conventional AlGaN or GaN layer. An object of the present invention is to provide a semiconductor device for ultraviolet sensing suitable for detecting a wavelength having a longer cut-off wavelength than a detector using a material as a light absorbing layer, that is, longer than 375 nm.

In order to achieve the above object, the present invention uses In _x as a light absorbing layer to detect an accurate UV-A (320 nm to 400 nm) wavelength instead of a GaN light absorbing layer used to detect a conventional UV-A (320 nm to 400 nm) wavelength. Capturing a structure formed using a Ga _{1 - x} N (0 ≦ _x ≦ 0.5) layer or a very thin In _y Ga _{1 - y} N (0 ≦ _y ≦ x) layer having a lower In composition than the light absorbing layer 13 thereon. A structure formed of a (capping) layer to form a transparent Schottky junction layer thereon, the ohmic junction layer is a semiconductor light-receiving element formed on the light absorbing layer, on the capping layer or on the high temperature buffer layer, accurate UV-A (320nm ~ 400nm) Provided is a semiconductor device for detecting ultraviolet rays formed with a structure for detecting a wavelength or detecting a wavelength longer than 375 nm, which is a cut-off wavelength when GaN is used as a light absorbing layer.

Hereinafter, with reference to the accompanying drawings, preferred embodiments that do not limit the present invention will be described in detail.

7, 8 and 9, 10 illustrate the ultraviolet sensing semiconductor device according to the first and second embodiments of the present invention, respectively, as shown in FIGS. A GaN layer was used as the light absorbing layer 13 to detect -A (400 nm to 320 nm). However, in the present exemplary embodiments, a thick In _x Ga _{1 - x} N (0≤x≤0.5) layer is lighted unlike the conventional structure. A structure composed of the absorbing layer 13 or an In _y Ga _{1 - y} N (0 ≦ _y ≦ x) layer having a smaller In composition than the light absorbing layer and having a very thin layer is formed of the capping layer 17.

In view of the process technology, the substrate 10 mainly uses sapphire, but SiC, Si, GaAs, glass, and the like may also be used. In the case of a 2 inch diameter sapphire substrate, the thickness is 300 to 450 um, and a (0001) plane is mainly used as a growth plane. A tilted substrate is also used to improve the surface of the light absorbing layer. As a device for growing on the substrate 10, mainly MOCVD, MBE, HVPE and the like are used. In the case of MOCVD, after the substrate 10 is mounted, the temperature is raised to 1,000 ° C. or more to perform a thermal cleaning process to remove impurities on the surface of the substrate 10, and then grow. First, the low temperature buffer layer is grown. That is, after lowering the growth temperature of the MOCVD to 500 ~ 600 ℃, to grow the low temperature buffer layer 11 to 200 ~ 500 하는데 thickness GaN or AlN is grown. The reason for growing the low temperature buffer layer is to solve this problem because the lattice constant between the substrate and the growing layer is different and crystal growth is not possible. After the low temperature buffer layer 11 is grown, the growth temperature is increased to 1,000 ° C. or more, and the high temperature buffer layer 12 is grown. The high temperature buffer layer 12 mainly grows a GaN layer, and generally has a thickness of 0.5 to 3 μm and is n-type doped, whether or not artificially doped. Doping concentration was mid. Keep E16 ~ low E18 cm ^-3 . On the high temperature buffer layer 12 grows a light absorbing layer 13 that absorbs ultraviolet light to generate a current. The light absorbing layer 13 is grown to have a low doping concentration as possible to grow an In _x Ga _{1 - x} N (0 ≦ _x ≦ 0.5) layer below 1 um thickness. The light absorption layer 13, the In _x Ga _{1 - x} N When growing (0≤x≤0.5) layer _{In x Ga 1 - x N (} 0≤x≤0.5) layer is a difference of In composition in accordance with the temperature Indicates. If the temperature is higher than 850 ° C, the temperature must be grown below 850 ° C because the In _x Ga _{1 - x} N (0≤x≤0.5) layer, which is a light absorbing layer having a large amount of In composition, cannot be obtained even though the In flow rate increases. do. In addition, when the thickness of the In _x Ga _{1 - x} N (0 ≦ _x ≦ 0.5) light absorbing layer is 0.1 μm or less, it has low light reactivity (A / W). The light absorption layer which becomes 0.1 micrometer or more is effective. After the growth of the light absorbing layer 13, the capping layer 17 is grown. An In _y Ga _{1 - y} N (0 ≦ _y ≦ x) layer of 20 nm or less may be used as the capping layer. The capping layer is a layer having a smaller In composition than the light absorbing layer, and the growth temperature of the capping layer may be grown between 600 and 1200 ° C. The thickness of the capping layer should be less than 1/10 of the thickness of the space charge region (SCR) region formed in the light absorbing layer to affect the optical reactivity of the light absorbing layer by 10% or less. In addition, the doping concentration should be equal to or lower than the light absorbing layer. After the capping layer is finished, the grown sample is taken out of the growth apparatus, washed with HF solution, and then proceeded to the chip manufacturing process. First, a pattern is formed on the capping layer 17 using a photoresist, a Ti / Al metal is deposited using an electron beam or a thermal evaporator, and then the photoresist is removed to form an ohmic junction layer 16. Metals commonly used to form ohmic junctions in N-type GaN layers include Ti / Al, Cr / Ni / Au, and the deposition thickness is about Ti (100 to 500Å) for Al (5,000 to 10,000Å). Deposition The deposited ohmic bonding layer 16 undergoes a heat treatment process to secure ohmic bonding characteristics, and is generally heat treated for several minutes in a nitrogen or general air atmosphere at a temperature of about 500 ° C.

Some metals, such as Cr / Ni / Au, can secure ohmic bonding properties even without heat treatment. The ohmic bonding layer 16 may be formed on the light absorbing layer 13 and the capping layer 17, but when it is difficult to obtain ohmic bonding characteristics from the light absorbing layer and the capping layer, the ohmic bonding layer 16 may be formed as shown in FIGS. 10 to 14. The light absorbing layer 13 may be etched and formed on the high temperature buffer layer 12. Etching mainly uses a dry etching method using an inductively coupled plasma generator (ICP). After the ohmic junction layer 16 is formed, a pattern is formed using a photoresist on the region where the Schottky junction layer 14 is to be formed, and Ni, Ru, and ITO (Indium) are formed by using an electron beam or an evaporator. -Tin-Oxide), Pt, Pd, Au is thinly deposited a conductive oxide containing any one and then the photoresist is removed to form a Schottky junction layer (14).

The thickness of the Schottky metal to be deposited is 100 kPa or less in consideration of the transmittance. After the Schottky metal is deposited, the heat treatment is performed, and the temperature is lower than the temperature at which the ohmic junction layer 16 is formed. When Ni is deposited, NiOx is formed by heat treatment in an oxygen atmosphere. Ni may also be formed as a Schottky bonding layer without heat treatment. After the Schottky bonding layer 14 is formed, a pattern is formed with a photoresist to form the Schottky pad layer 15, and Ni / Au, Pt / Au, etc. are deposited using an electron beam or a thermal evaporator, and then the photoresist is removed. The schottky pad layer 15 is formed. The deposition thickness is about Ni, Pt (<500Å), Au (> 5,000Å) and no additional heat treatment. When the schottky pad layer 15 is formed, a thickness corresponding to the wavelength may be deposited using SiO ₂ to prevent reflection of incident ultraviolet rays. Then, by inspecting the characteristics of the device in the state of the wafer to distinguish between good and bad devices by ink marks, and then grinding / lapping / polishing the back surface of the substrate 10 to form a total thickness of about 100um and then separately by scribing and breaking process The chip is separated into chips and the package process is performed. In the packaging process, the chips manufactured in the TO-CAN or SMD type package are die-bonded, and the Schottky pad layer 15 and the ohmic bonding layer 16 are wired using Au or Al wires for the anode and cathode of the package, respectively. Bond The final assembly is then encapsulant or glass to completely separate the chip from the external environment. 9, 10 and 13 and 14 show an example in which the ohmic junction layer 16 is formed on the high temperature buffer layer 12 without being formed on the capping layer 17 in the present invention. This case is formed when the band gap of the capping layer 17 is high or when it is difficult to obtain ohmic bonding characteristics for other reasons.

As in the conventional operation, the manufactured chips are separated into individual chips and packaged in a TO-CAN or SMD type to operate. When the bias is reversed or zero biased between the anode and the cathode, the incident ultraviolet rays penetrate the Schottky junction layer 14 to be absorbed in the depletion layer formed on the capped layer 17 and the light absorbing layer 13, As holes are generated and they move to the cathode and the anode, respectively, and current flows, thereby detecting the amount of incident light. By changing the In composition in the light absorption layer of In _x Ga _{1 - x} N (0≤x≤0.5), the wavelength of the detected ultraviolet rays can be adjusted. That is, as can be seen in the graph of FIG. 6, when the InGaN layer having an In composition of 15% is formed as the light absorbing layer 13, only a wavelength of 400 nm or less is absorbed by the band gap, so that an accurate UV-A region can be detected. When the In composition is formed at about 30%, it absorbs wavelengths of 450 nm or less and enables detection even at wavelengths longer than the UV-A wavelength.

In the prior art, a GaN layer having a cut-off wavelength of 375 nm was used as a light absorbing layer to detect UV-A (400 nm to 320 nm) wavelengths. When the GaN layer is used as a light absorbing layer, an accurate UV-A cut-off wavelength is not obtained, and a detection device having a cut-off wavelength longer than 375 nm cannot be made. When In _x Ga _{1 - x} N (0≤x≤0.5) layer is used as the light absorbing layer in this technology, the cut-off wavelength is 400 nm at 15% of In composition and the 450-nm cut-off wavelength at 30%. The detector element can be manufactured. In order to uniformly improve the non-uniform Schottky characteristics caused by the In composition difference, In _y Ga _1-y N (0 ≦ _y ≦) over the light absorbing layer, In _x Ga _{1 - x} N (0 ≦ _x ≦ 0.5). x) layer was used as the capping layer. Therefore, in the present invention, In _x Ga _{1 - x} N (0 ≦ _x ≦ 0.5) is used as the light absorbing layer to make an accurate UV-A (400 nm to 320 nm) wavelength detection device and a wavelength longer than 375 nm obtained by using GaN as the light absorbing layer. The detection element can be manufactured.

Claims (11)

In the semiconductor light receiving element for ultraviolet sensing having a structure consisting of a buffer layer, a light absorbing layer, a Schottky bonding layer, an ohmic bonding layer on a substrate The buffer layer is composed of an Al _x Ga _{1 - x} N (0≤x≤1) layer, and the light absorbing layer is composed of an In _x Ga _1-x N (0 <x≤0.5) layer, and the buffer layer or the light absorbing layer An ohmic junction layer is formed in a portion of the phase, and a Schottky junction layer is formed on the light absorbing layer. The method according to claim 1, The substrate is ultraviolet sensing semiconductor device, characterized in that the substrate is selected from the group consisting of sapphire, SiC, Si, GaAs, glass. The method according to claim 1, Ultraviolet-sensing semiconductor device, characterized in that the thickness of the light absorption layer made of 1um or less. The method according to claim 1, Ultraviolet-sensing semiconductor device, characterized in that the ohmic junction layer made of a metal containing Au or Al. The method according to claim 1, The Schottky bonding layer is a semiconductor device for ultraviolet sensing, characterized in that consisting of a conductive oxide containing any one or more of Au, Ru, Indium-Tin-Oxide (ITO), Ni, Pt, Pd. In the semiconductor light receiving element for ultraviolet sensing having a structure consisting of a buffer layer, a light absorbing layer, a capping layer, a Schottky bonding layer, an ohmic bonding layer on a substrate, The buffer layer is made of an Al _x Ga _{1 - x} N (0≤x≤1) layer, the light absorbing layer is made of an In _x Ga _1-x N (0 <x≤0.5) layer, and the capping layer is In _an ultraviolet layer comprising a _y Ga _{1 - y} N (0 ≦ _y ≦ x) layer, an ohmic junction layer formed in a portion of the buffer layer or the capped layer, and a Schottky junction layer formed on the capping layer Sensing Semiconductor Device. The method according to claim 6, The semiconductor device for ultraviolet sensing, characterized in that the substrate is selected from the group consisting of sapphire, SiC, Si, GaAs, glass. The method according to claim 6, Ultraviolet-sensing semiconductor device, characterized in that the thickness of the light absorption layer made of 1um or less. The method according to claim 6, Ultraviolet-sensing semiconductor device, characterized in that the thickness of the capping layer is made of 20nm or less. The method according to claim 6, Ultraviolet-sensing semiconductor device, characterized in that the ohmic junction layer made of a metal containing Au or Al. The method according to claim 6, The Schottky bonding layer is a semiconductor device for ultraviolet sensing, characterized in that consisting of a conductive oxide containing any one or more of Au, Ru, Indium-Tin-Oxide (ITO), Ni, Pt, Pd.

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