JP2014060255A - Manufacturing method of deep ultraviolet-emitting element of nitride semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a deep ultraviolet-emitting element of a nitride semiconductor which can reduce process induced damages and achieve simplification of a manufacturing process.SOLUTION: A manufacturing method of a deep ultraviolet-emitting element of a nitride semiconductor according to the present embodiment comprises: a semiconductor thin film formation process of forming a semiconductor thin film 120 on a substrate 110; a first electrode formation process of forming a first electrode 130 on the semiconductor thin film 120; a mesa structure part formation process of dry etching the semiconductor thin film 120 by using the first electrode 130 as a mask to form a mesa structure part 140 having a mesa structure on the semiconductor thin film 120 at a part covered with the first electrode 130; and a second electrode formation process of forming after the mesa structure part formation process, a second electrode 150 on the semiconductor thin film 120 at a part exposed by dry etching with the first electrode 130 being left.

Description

  The present invention relates to a method for manufacturing a nitride semiconductor deep ultraviolet light emitting device. More specifically, the present invention relates to a method for manufacturing a nitride semiconductor deep ultraviolet light-emitting device that forms a mesa structure by etching a semiconductor thin film formed of a nitride semiconductor formed on a substrate.

  In recent years, nitride semiconductors have attracted a great deal of attention as materials for light-emitting devices since the realization of high-intensity blue light-emitting diodes (LEDs). This nitride semiconductor has already been put into practical use in fields such as a light source for a traffic light, a liquid crystal backlight, and illumination.

  By the way, the band gap of the nitride semiconductor is wide from 6.2 eV of AlN to 0.75 eV of InN. For this reason, there is a possibility that an LED that covers a wide wavelength region from the deep ultraviolet light region of 210 nm to the infrared light region of 1.8 μm can be manufactured by producing a mixed crystal of nitride semiconductor. In particular, LEDs capable of emitting deep ultraviolet light (hereinafter also referred to as “deep ultraviolet LEDs”) are required to be put to practical use in various fields including medical fields such as sterilization, disinfection, and skin disease treatment. It has been. Current deep ultraviolet light sources include, for example, mercury lamps and gas lasers. However, these light sources have problems to be overcome, such as environmental problems, power consumption, and size. Under such circumstances, for example, realization of a deep ultraviolet LED that is environmentally friendly, energy-saving, and compact is expected.

In order to produce an LED having a light emission wavelength below the ultraviolet light region (in other words, a light emission wavelength shorter than light in the ultraviolet light region) using a nitride semiconductor, it is currently put into practical use, for example, as a white LED. It is necessary to use Al _x Ga _1-x N (X ≧ 0) having a relatively large band gap as the light emitting layer instead of the In _x Ga _1-x N-based (X ≧ 0) light emitting layer.
On the other hand, in order to manufacture a deep ultraviolet LED, for example, not only a thin film growth technique by epitaxial growth for forming a film structure such as a light emitting layer provided in the deep ultraviolet LED, but also a process technique for processing into a device is very important.

  In this type of technical field, it is common to process a semiconductor thin film formed on a substrate by etching in order to form an element structure. Etching includes wet etching and dry etching. For example, when etching a physically and chemically stable material such as a nitride semiconductor, dry etching is widely used because wet etching is difficult. ing. In addition, a chlorine-based gas is used as an etching gas when dry-etching a nitride semiconductor.

  The dry etching is usually performed using a RIE (Reactive Ion Etching) apparatus. In the chamber of this apparatus, first, an etching gas is made into a plasma state under reduced pressure to generate reactive ions. Thereafter, the generated reactive ions are accelerated by the potential gradient generated in the negative electrode, and the object to be etched is chemically etched by causing the reactive ions to collide vertically with the substrate installed in the chamber of the RIE apparatus. For this reason, the cross-sectional shape of etching has anisotropy, unlike isotropic wet etching.

One of the most important factors in dry etching is selection of a mask material that can increase the selectivity with respect to the object to be etched (that is, the nitride semiconductor etching rate / mask etching rate). If the mask is not resistant to the etching gas, the mask is etched simultaneously with the etching of the object to be etched. As a mask in the case of using a chlorine-based gas as an etching gas, for example, an oxide film such as SiO ₂ or a metal that is corrosion resistant to chlorine such as Ni is used. As a mask for this dry etching, Patent Document 1 describes SiO ₂ , and Patent Document 2 and Non-Patent Document 1 describe Ni.

JP 10-41584 A JP 2012-89754 A Japanese Patent Laid-Open No. 2004-119772

Chang-Chin Yu, et. al. , Jpn. J. et al. App. Phys. 41 (2002) L910

By the way, the mask itself used for the dry etching described above is a structure that is not necessary for a semiconductor device such as a light emitting element to perform its function. Therefore, it is necessary to remove this mask. If the mask material is SiO _{2 as} described above, the mask can be removed using, for example, hydrofluoric acid or a fluorine-based gas. Further, if the mask material is Ni as described above, the mask can be removed using, for example, nitric acid. However, when removing the mask by dissolving it with an acid, an acid belonging to a strong acid may be used. In this case, the device surface and crystal defects may be damaged (see Patent Document 3). Also, care must be taken when handling strong acids. Further, when the mask is removed by dry etching, plasma damage may occur in the semiconductor device and device characteristics may deteriorate.

Further, in the method for manufacturing a semiconductor device (laser diode) described in Patent Document 1, a step of opening the SiO ₂ layer 9 used as a mask for dry etching is required to form an electrode. Therefore, the required number of photomasks is as follows: (1) mesa etching mask, (2) SiO ₂ layer 9 opening mask, (3) electrode 7 formation mask, and (4) electrode 8 formation mask. It becomes 4 sheets. Further, when Ni is used as a mask for dry etching as in the method for manufacturing a semiconductor device (light emitting element) described in Patent Document 2, the required number of photomasks is (1) a mesa etching mask, (2 3) a mask for forming the p-electrode 12 and (3) a mask for forming the n-electrode 13. In the above technical field, it is desirable that the number of manufacturing steps and the number of photomasks be as small as possible from the viewpoint of throughput and cost.

  The present invention has been made in view of the above problems, and provides a method for manufacturing a nitride semiconductor deep ultraviolet light-emitting element capable of reducing process damage and simplifying the manufacturing process. It is aimed.

  In order to solve the above problems, the present inventor has intensively studied without being caught by the common general knowledge of the prior art. As a result, the semiconductor thin film is dry-etched using the first electrode as a mask and covered with the first electrode of the semiconductor thin film. The inventors have found that the above problems can be solved by a method for manufacturing a nitride semiconductor deep ultraviolet light emitting device having a step of forming a mesa structure portion in the cracked portion, and have completed the present invention.

  One embodiment of the present invention is a nitride semiconductor deep ultraviolet light-emitting element manufacturing method in which a mesa structure is formed by etching a semiconductor thin film formed of a nitride semiconductor formed on a substrate. A semiconductor thin film forming step for forming the semiconductor thin film made of a physical semiconductor, a first electrode forming step for forming a first electrode on the semiconductor thin film formed by the semiconductor thin film forming step, and the first electrode forming step Forming a mesa structure having a mesa structure in a portion covered with the first electrode of the semiconductor thin film by dry-etching the semiconductor thin film using the first electrode formed by the step as a mask After the step and the mesa structure forming step, a second electrode is formed on a part of the semiconductor thin film exposed by the dry etching with the first electrode remaining. A second electrode forming step of forming a manufacturing method of the nitride semiconductor of deep ultraviolet light-emitting device characterized by having a.

Here, the “mesa structure” refers to a plate-like structure formed on a planar substrate.
In the method for manufacturing a nitride semiconductor deep ultraviolet light-emitting device, the surface of the first electrode opposite to the surface on the semiconductor thin film side is a surface formed of Ni, and the semiconductor thin film The etching gas for dry etching may be a chlorine-based gas.
In the method for manufacturing a nitride semiconductor deep ultraviolet light emitting element, the semiconductor thin film may be a semiconductor thin film formed of AlGaN.

  In the method for manufacturing a nitride semiconductor deep ultraviolet light emitting device, the semiconductor thin film forming step includes a step of forming a buffer layer on the substrate and a step of forming a first conductivity type semiconductor layer on the buffer layer. Forming a light emitting layer on the first conductive type semiconductor layer, forming a second conductive type semiconductor layer different from the first conductive type on the light emitting layer, Forming a contact layer on the semiconductor layer of the second conductivity type, wherein the first electrode forming step includes forming the first electrode on the contact layer, and forming the mesa structure portion The step includes dry etching the contact layer, the second conductive type semiconductor layer, the light emitting layer, and the first conductive type semiconductor layer using the first electrode as the mask, The electrode forming step includes the dry etching process. It may have a step of forming the second electrode on a part of the semiconductor layer of the first conductivity type exposed by ring.

  According to the method for manufacturing a nitride semiconductor deep ultraviolet light emitting device according to the present invention, there is provided a method for manufacturing a nitride semiconductor deep ultraviolet light emitting device capable of simplifying the number of manufacturing steps and reducing process damage. It becomes possible to provide.

(A) to (d) are process cross-sectional views for explaining an embodiment of a manufacturing process of a nitride semiconductor deep ultraviolet light emitting device according to the present invention. (A) to (d) are process cross-sectional views for explaining an embodiment of a manufacturing process of a nitride semiconductor deep ultraviolet light emitting device according to the present invention. (A)-(g) is process sectional drawing for demonstrating the comparative example of the manufacturing process of the deep ultraviolet light emitting element of the nitride semiconductor which concerns on this invention. (A)-(d) is process sectional drawing for demonstrating the comparative example of the manufacturing process of the deep ultraviolet light emitting element of the nitride semiconductor which concerns on this invention. (A)-(d) is process sectional drawing for demonstrating the comparative example of the manufacturing process of the deep ultraviolet light emitting element of the nitride semiconductor which concerns on this invention. It is the figure put together in the table | surface in order to compare the manufacturing process of an Example and a comparative example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Natural Semiconductor Deep Ultraviolet Light-Emitting Device Manufacturing Method]
FIGS. 1A to 1D are process cross-sectional views for explaining an embodiment of a manufacturing process of a nitride semiconductor deep ultraviolet light emitting element according to the present invention.
The manufacturing process of a nitride semiconductor deep ultraviolet light emitting device according to the present embodiment includes a nitride semiconductor deep ultraviolet light emitting device that forms a mesa structure by etching a semiconductor thin film made of a nitride semiconductor formed on a substrate. In the manufacturing method, a semiconductor thin film forming step of forming the semiconductor thin film made of the nitride semiconductor on the substrate, and a first electrode formed on the semiconductor thin film formed by the semiconductor thin film forming step The semiconductor thin film is dry-etched using the first electrode formed in the electrode forming step and the first electrode forming step as a mask, and a mesa structure is formed on a portion of the semiconductor thin film covered with the first electrode. A mesa structure forming step for forming the mesa structure, and after the mesa structure forming step, the dry etching is performed with the first electrode remaining. Some of the semiconductor thin film that has issued a second electrode forming step of forming a second electrode.

  According to this manufacturing method, since the mask used for forming the mesa structure portion is used as the first electrode, a step of removing this mask is not required. Further, it is not necessary to newly form another electrode on the mesa structure. Therefore, the number of manufacturing steps and the number of photomasks can be reduced as compared with the prior art. Further, since a step of removing the mask is not required, process damage to the light emitting element (that is, damage due to strong acid or plasma damage) generated in the step of removing the mask can be reduced.

As described above, according to the manufacturing method according to the present embodiment, it is possible to provide a manufacturing method of a nitride semiconductor deep ultraviolet light-emitting element that can simplify the number of manufacturing steps and reduce process damage. Is possible.
Hereinafter, the detail of each above-mentioned process is demonstrated.

(Semiconductor thin film formation process)
FIG. 1A is a diagram illustrating a process of forming the semiconductor thin film 120 on the substrate 110.
First, as shown in FIG. 1A, a semiconductor thin film 120 is formed on a substrate 110 (hereinafter, this process is also referred to as “semiconductor thin film forming process”).
The substrate 110 may be any substrate that can form the semiconductor thin film 120 on the substrate 110. For this reason, the material of the substrate 110 is not particularly limited, but is preferably a material having a lattice constant close to that of the semiconductor thin film 120.

  The semiconductor thin film 120 is a semiconductor thin film made of a nitride semiconductor, and is a semiconductor thin film having a stacked structure including at least a p-type semiconductor layer and an n-type semiconductor layer. When the nitride semiconductor deep ultraviolet light emitting device 1 according to this embodiment is a deep ultraviolet light emitting device, the semiconductor thin film 120 has a structure capable of emitting deep ultraviolet light and matches the wavelength of the desired deep ultraviolet light. A nitride semiconductor composition (for example, AlGaN) may be used. Further, the light emitting layer may have a quantum well structure instead of the above-described stacked structure. Further, a buffer layer (not shown) may be provided on the substrate 110 side (that is, between the semiconductor thin film 120 and the substrate 110). This buffer layer is a layer for relaxing lattice mismatch. Further, from the viewpoint of contact resistance with each electrode described later, a layer in contact with one electrode may be a highly doped p-type semiconductor layer, and a layer in contact with the other electrode may be a highly doped n-type semiconductor layer.

(First electrode forming step)
FIG. 1B is a diagram illustrating a process of forming the first electrode 130 on the semiconductor thin film 120 formed on the substrate 110.
After the aforementioned semiconductor thin film formation step, as shown in FIG. 1B, a first electrode 130 is formed on the semiconductor thin film 120 formed on the substrate 110 (hereinafter, this step is referred to as “first electrode formation”). Also referred to as “process”.)
The material of the first electrode 130 is capable of electrical contact with the semiconductor thin film 120, and a metal having excellent corrosion resistance against dry etching in the mesa structure forming process described later is the first. There is no particular limitation as long as the outermost surface 130a of the electrode 130 is covered. Here, “a metal excellent in corrosion resistance against dry etching” refers to a metal having a good selectivity with respect to the semiconductor thin film 120 in dry etching. As a selection ratio with respect to dry etching, when the etching amount of the first electrode 130 is 1, the etching amount of the semiconductor thin film 120 is preferably 10 or more, and the etching amount of the semiconductor thin film 120 is 100 or more. Is more preferable. For example, when a chlorine-based gas is used as the etching gas, the outermost surface 130a of the first electrode 130 is preferably covered with Ni.

  When the uppermost layer 120a of the semiconductor thin film 120 is, for example, p-type AlGaN or p-type GaN, the first electrode 130 is made of, for example, Ni / Au / Ni or Ni / Au / Al / Ti / Au / Ni. A laminated structure may be used.

(Mesa structure forming process)
FIG. 1C is a diagram showing a process of forming a mesa structure portion 140 having a mesa structure in the semiconductor thin film 120 by dry etching a part of the semiconductor thin film 120 using the first electrode 130 as a mask.
After the first electrode forming step described above, as shown in FIG. 1C, a part of the semiconductor thin film 120 (specifically, the first electrode 130 is covered with the first electrode 130 as a mask). First, dry etching is performed on a region where the semiconductor thin film 120 is exposed. In this manner, a mesa structure portion 140 having a mesa structure is formed in a portion covered with the first electrode 130 of the semiconductor thin film 120 (hereinafter, this process is also referred to as a “mesa structure portion forming process”). Here, the “mesa structure portion 140” refers to a portion having a high trapezoidal structure formed in a part of the nitride semiconductor deep ultraviolet light emitting element 1. Further, the direction of current flow in the mesa structure 140 is mainly perpendicular to the surface of the substrate 110 (the vertical direction in FIG. 1).

In the case where an insulating substrate is used as the substrate 110, dry etching is preferably performed so that the lower layer portion of the region where the semiconductor thin film 120 is exposed is not covered with the first electrode 130. In other words, when an insulating substrate is used as the substrate 110, it is preferable to dry-etch the semiconductor thin film 120 so that the surface of the substrate 110 is not exposed.
As a dry etching method, a known method for etching a nitride semiconductor can be applied. As a nitride semiconductor etching gas, a chlorine-based gas is widely used, and this chlorine-based gas can be used. As an apparatus used for dry etching, any apparatus can be used as long as it can plasma a chlorine-based gas and cause a reactive species to collide with the substrate 110. Examples of the apparatus used for dry etching include CCP-RIE (Capacitive Coupled Plasma RIE), ICP-RIE (Inductive Coupled RIE), ECR-RIE (Electron Cycloton Resonance-RIE), and the like.

(Second electrode forming step)
FIG. 1D is a diagram illustrating a process of forming the second electrode 150 on a part of the portion exposed by dry etching of the semiconductor thin film 120.
After the above-described mesa structure forming step, as shown in FIG. 1D, the second electrode 150 is formed on a part of the exposed portion of the semiconductor thin film 120 by dry etching (hereinafter, this step is referred to as “second step”). Also referred to as an “electrode formation step”). At this time, the first electrode 130 remains on the mesa structure portion 140 without being removed.
The material of the second electrode 150 is not particularly limited as long as it can electrically contact the dry-etched semiconductor thin film 120 described above. Further, when the portion exposed by dry etching of the semiconductor thin film 120 is n-type AlGaN, the second electrode 150 is made of, for example, Ti, Ti / Au, Ti / Al / Ti / Au, Ti / Al / Mo / A laminated structure such as Au may be used, but is not limited thereto.

  As a method of forming the second electrode 150, a known method can be applied, and for example, a lift-off method using a resist or an etching method can be given. Note that the lift-off method is preferable as a method of forming the second electrode 150 from the viewpoint of reducing damage to the deep ultraviolet light emitting element 1 of the nitride semiconductor.

<Effect of this embodiment>
As described above, in the method of manufacturing the nitride semiconductor deep ultraviolet light emitting device 1 according to this embodiment, the first electrode 130 is used as a mask material in the mesa structure forming step. For this reason, the process of removing the mask material in the mesa structure part forming process is not required, and the process of newly forming the electrode is not required. Therefore, with the above manufacturing method, the number of manufacturing steps and the number of photomasks can be reduced as compared with the prior art. Further, since the process of removing the mask material in the mesa structure forming process is not required, there is no need to use a chemical such as a strong acid, and it is not necessary to expose to plasma. Therefore, the process damage to the deep ultraviolet light emitting element 1 of a nitride semiconductor can also be reduced.

  In the method for manufacturing the nitride semiconductor deep ultraviolet light emitting element 1 according to the present embodiment, the outermost surface 130a of the first electrode 130 (that is, the surface opposite to the surface on the semiconductor thin film 120 side) is Ni. Covered with. For this reason, when the etching gas is a chlorine-based gas, the selectivity during dry etching can be increased. Therefore, the processing accuracy at the time of dry etching can be improved.

  If the pattern area of the mesa etching and the pattern area of the electrode (p-electrode 12 in Patent Document 2) are substantially the same as in a light emitting diode or a laser diode, this electrode is made of a metal having dry etching resistance. If covered, this electrode can also be used as a mask for dry etching. Conventionally, for example, an etching mask that is not necessary for a semiconductor device has been removed. By using this electrode as a dry etching mask, a removal process for removing the etching mask and an electrode for newly forming another electrode are provided. The number of formation steps can be reduced. Therefore, the number of manufacturing steps can be reduced. Furthermore, since a dry etching mask is used as an electrode, the number of photomasks can be reduced.

An embodiment of the present invention will be described with reference to FIG. 2, taking a light emitting diode as an example of a light emitting element using a nitride semiconductor thin film. In addition, this invention is not limited to the following Example.
FIGS. 2A to 2D are process cross-sectional views for explaining an embodiment of a manufacturing process of a nitride semiconductor deep ultraviolet light emitting device according to the present invention.
First, as shown in FIG. 2A, a stacked body 220 was formed on a sapphire substrate 210. The sapphire substrate 210 corresponds to the substrate 110 in FIG. The stacked body 220 is a stacked body formed using a metal organic chemical vapor deposition method (MOCVD method), and is a stacked body made of a nitride semiconductor thin film. The stacked body 220 was formed by sequentially forming an AlN buffer layer 221, an n-type AlGaN layer 222, an AlGaN light emitting layer 223, a p-type AlGaN layer 224, and a p ⁺ -type AlGaN contact layer 225. Hereinafter, the entire substrate on which the laminated body 220 having an LED structure is formed on the substrate 210 is referred to as an LED substrate 230. Note that the above-described stacked body 220 corresponds to the semiconductor thin film 120 in FIG.

As described above, in this embodiment, sapphire is used as the substrate 210. However, for example, SiC, GaN, AlN, Si, Ga ₂ O ₃ , MgAlO ₂ , ZnO, or the like can be used.
Next, as shown in FIG. 2B, the first electrode 240 was formed on the LED substrate 230. The first electrode 240 is an electrode formed using vapor deposition and lift-off technology, and is an electrode formed by sequentially stacking a Ni layer, an Au layer, and a Ni layer. Note that the first electrode 240 corresponds to the first electrode 130 in FIG.

  Next, as shown in FIG. 2C, the LED substrate 230 was etched to form a mesa structure portion 241 having a mesa structure. In this step, etching was performed by ICP-RIE until the n-type AlGaN layer 222 was exposed using chlorine as an etching gas. Here, the outermost surface 240a of the first electrode 240 is a surface formed of Ni that is resistant to chlorine-based gas. For this reason, even if it exposes to chlorine plasma, the 1st electrode 240 is hardly etched. The mesa structure 241 described above corresponds to the mesa structure 140 in FIG.

  Thereafter, as shown in FIG. 2D, the second electrode 250 was formed in a desired region on the n-type AlGaN layer 222 of the LED substrate 230. The second electrode 250 is an electrode formed using vapor deposition and lift-off technology, and is an electrode formed by laminating a Ti layer, an Al layer, a Ti layer, and an Au layer in this order. Note that the second electrode 250 corresponds to the second electrode 150 in FIG.

Finally, annealing is performed at 750 ° C. by RTA (Rapid Thermal Annealing), and the interface of the first electrode 240 / p ⁺ type AlGaN contact layer 225 and the interface of the second electrode 250 / n type AlGaN layer 222 are respectively ohmic. Joined.
Through the above steps, the light emitting element (light emitting diode element) 2 having the mesa structure portion 241 and using the nitride semiconductor thin film was manufactured. The light emitting diode element 2 corresponds to the nitride semiconductor deep ultraviolet light emitting element 1 in FIG.

In the above process, two masks are necessary: (1) mask for forming mesa etching and first electrode 240, and (2) mask for forming second electrode 250.
Moreover, the manufacturing method of the light emitting diode element 2 according to the present embodiment does not have a step of removing the mask material for forming the mesa structure portion 241 by strong acid or plasma etching unlike the conventional technique. For this reason, the light emitting diode element 2 obtained in the present embodiment is not damaged due to strong acid or plasma etching, and good diode characteristics can be obtained.

In the present manufacturing method, the AlN buffer layer 221, the n-type AlGaN layer 222, the AlGaN light emitting layer 223, the p-type AlGaN layer 224, and the p ⁺ -type AlGaN contact layer 225 are sequentially formed on the substrate 210. Therefore, the light emitting diode element 2 can have a desired band gap value.
In this embodiment, the AlN buffer layer 221 corresponds to the “buffer layer” of the present invention, the n-type AlGaN layer 222 corresponds to the “first conductivity type semiconductor layer” of the present invention, and the AlGaN light emitting layer 223 includes The p-type AlGaN layer 224 corresponds to the “second conductivity type semiconductor layer” of the present invention, and the p ⁺ -type AlGaN contact layer 225 corresponds to the “contact layer” of the present invention. doing.

<Comparative example>
3 (a) to 3 (g), 4 (a) to 4 (d), and 5 (a) to 5 (d) are comparative examples of manufacturing steps of a nitride semiconductor deep ultraviolet light emitting device according to the present invention. It is process sectional drawing for demonstrating. The manufacturing method described in this comparative example is substantially the same as the manufacturing method according to the prior art. FIG. 3 is a diagram for comparison with the embodiment described with reference to FIG. 4 and 5 are diagrams for comparison with the embodiment described with reference to FIG.

First, as shown in FIG. 3A (specifically, as shown in FIG. 4A), an LED substrate 330 was formed. The method for producing the LED substrate 330 is the same as the method described in the above embodiment. Therefore, the description thereof is omitted here. In addition, the code | symbol 310 in Fig.4 (a) has shown the board | substrate corresponding to the board | substrate 210 shown to Fig.2 (a). Reference numeral 320 denotes a laminate corresponding to the laminate 220 shown in FIG. Reference numeral 321 denotes an AlN buffer layer corresponding to the AlN buffer layer 221 shown in FIG. Reference numeral 322 denotes an n-type AlGaN layer corresponding to the n-type AlGaN layer 222 shown in FIG. Reference numeral 323 denotes an AlGaN light emitting layer corresponding to the AlGaN light emitting layer 223 shown in FIG. Reference numeral 324 denotes a p-type AlGaN layer corresponding to the p-type AlGaN layer 224 shown in FIG. Further, reference numeral 325 denotes a ^{p +} -type AlGaN contact layer corresponding to the ^{p +} -type AlGaN contact layer 225 shown in FIG. 2 (a).

Next, as shown in FIG. 3A (specifically, as shown in FIG. 4B), a mask (hereinafter also referred to as “Ni mask”) 301 formed of Ni on the LED substrate 330 is provided. Formed. The Ni mask 301 is a mask formed using vapor deposition and lift-off technology.
Next, as shown in FIG. 3B (specifically, as shown in FIG. 4C), the LED substrate 330 was etched to form a mesa structure portion 340 having a mesa structure. In this step, etching was performed by ICP-RIE until the n-type AlGaN layer 322 was exposed using chlorine as a dry etching gas. Thereafter, as shown in FIG. 3C (specifically, as shown in FIG. 4D), the Ni mask 301 was removed. Here, the Ni mask 301 was removed using nitric acid.

Next, as shown in FIG. 3D (specifically, as shown in FIG. 5A), a resist 311 was applied to the entire surface of the LED substrate 330. Thereafter, the resist 311 was patterned so as to expose a part of the top (p ⁺ -type AlGaN contact layer 325) of the mesa structure 340 of the LED substrate 330. Thereafter, as shown in FIG. 3E (specifically, as shown in FIG. 5B), a first electrode 307 was formed on the top of the mesa structure 340 of the LED substrate 330. The first electrode 307 is an electrode formed using vapor deposition and lift-off technology, and is an electrode formed by sequentially stacking a Ni layer and an Au layer. Thereafter, as shown in FIG. 3F (specifically, as shown in FIG. 5C), the resist 311 was removed.

  Next, as shown in FIG. 3G (specifically, as shown in FIG. 5D), a second electrode 308 was formed on the n-type AlGaN layer 322 exposed by dry etching. The second electrode 308 is an electrode formed using vapor deposition and lift-off technology in the same manner as the first electrode 307, and is formed by sequentially stacking a Ti layer, an Al layer, a Ti layer, and an Au layer. Electrode.

Finally, annealing was performed at 750 ° C. by RTA to make ohmic junctions between the interface of the first electrode 307 / p ⁺ type AlGaN contact layer 325 and the interface of the second electrode 308 / n-type AlGaN layer 322, respectively.
As described above, the number of masks required in the comparative example is (1) a mesa etching mask, (2) a first electrode 307 formation mask, and (3) a second electrode 308 formation mask. is there.

  FIG. 6 is a diagram summarized in a table for comparison of manufacturing steps between the example and the comparative example. In FIG. 6, the necessary manufacturing steps and the necessity / unnecessity of the mask are compared between the example and the comparative example. In FIG. 6, “◯” means that implementation or formation is required, and “-” means that implementation or formation is not required. As shown in FIG. 6, in the example, it is understood that “removal of the dry etching mask” and “first electrode forming step” are unnecessary as compared with the comparative example. That is, in this example, it can be seen that the number of necessary masks and the number of manufacturing steps are reduced as compared with the comparative example. Further, since the dry etching mask is not removed, process damage that occurs when the mask is removed can be reduced.

  The method for manufacturing a nitride semiconductor deep ultraviolet light emitting device of the present invention is suitable as a method for manufacturing a light emitting device in which a mesa structure is formed by dry etching.

DESCRIPTION OF SYMBOLS 1 Nitride semiconductor deep ultraviolet light emitting element 2, 3 Light emitting diode 110,210,310 Substrate 120 Semiconductor thin film 120a Top layer 130,240,307 First electrode 130a, 240a Outer surface 140,241,340 Mesa structure 150, 250, 308 Second electrode 220, 320 Laminate 221, 321 AlN buffer layer 222, 322 n-type AlGaN layer 223, 323 AlGaN light emitting layer 224, 324 p-type AlGaN layer 225, 325 p ⁺ -type AlGaN contact layers 230, 330 LED substrate 301 Mask 311 Resist

Claims (4)

In a method for manufacturing a nitride semiconductor deep ultraviolet light-emitting element that forms a mesa structure by etching a semiconductor thin film made of a nitride semiconductor formed on a substrate,
A semiconductor thin film forming step of forming the semiconductor thin film made of the nitride semiconductor on the substrate;
A first electrode forming step of forming a first electrode on the semiconductor thin film formed by the semiconductor thin film forming step;
Using the first electrode formed in the first electrode forming step as a mask, the semiconductor thin film is dry-etched, and a mesa structure portion having a mesa structure is formed in a portion covered with the first electrode of the semiconductor thin film. A mesa structure forming step to be formed;
A second electrode forming step of forming a second electrode on a part of the semiconductor thin film exposed by the dry etching with the first electrode remaining after the mesa structure forming step;
A method for producing a nitride semiconductor deep ultraviolet light emitting device, comprising: The surface of the first electrode opposite to the surface on the semiconductor thin film side is a surface formed of Ni,
2. The method of manufacturing a nitride semiconductor deep ultraviolet light emitting device according to claim 1, wherein an etching gas for dry etching the semiconductor thin film is a chlorine-based gas. 3.   3. The method for manufacturing a nitride semiconductor deep ultraviolet light-emitting device according to claim 1, wherein the semiconductor thin film is a semiconductor thin film formed of AlGaN. The semiconductor thin film forming step includes a step of forming a buffer layer on the substrate, a step of forming a first conductivity type semiconductor layer on the buffer layer, and a light emitting layer on the first conductivity type semiconductor layer. Forming a semiconductor layer of a second conductivity type different from the first conductivity type on the light emitting layer, forming a contact layer on the semiconductor layer of the second conductivity type, Have
The first electrode forming step includes a step of forming the first electrode on the contact layer,
The mesa structure forming step includes a step of dry etching the contact layer, the second conductivity type semiconductor layer, the light emitting layer, and the first conductivity type semiconductor layer using the first electrode as the mask. And
4. The method according to claim 1, wherein the second electrode forming step includes a step of forming the second electrode on a part of the semiconductor layer of the first conductivity type exposed by the dry etching. 5. The manufacturing method of the deep ultraviolet light emitting element of the nitride semiconductor as described in any one of Claims.

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