Micro/nano combined structure, manufacturing method of micro/nano combined structure, and manufacturing method of an optical device having a micro/nano combined structure integrated therewith

TECHNICAL FIELD

0001The present invention disclosed herein relates to a micro/nano combined structure, a manufacturing method of the micro/nano combined structure, and a manufacturing method of an optical device having the micro/nano combined structure integrated therewith, and more particularly, to a micro/nano combined structure able to minimize Fresnel reflection and total reflection generated due to a difference between refractive indices of air and a semiconductor material by forming a sharp wedge-shaped or parabolic anti-reflective nanostructure with a subwavelength period on a microstructure through deposition of a metal thin film, heat treatment, and blanket etching after forming the microstructure on a substrate, a method of manufacturing the micro/nano combined structure, and a method of manufacturing an optical device integrated with the micro/nano combined structure.

BACKGROUND ART

0002In general, reduction of an amount of reflection of light between two media having different refractive indices is very important issue to be addressed in optical devices such as solar cells, photodetectors, light emitting diodes, and transparent glass.

0003Such reflection of light may become a main cause of decreasing efficiency of an optical device and higher efficiency may be obtained as the reflection of light is minimized. Methods generally used to reduce the reflection of light may be broadly classified as two types.

0004The first is a method of reducing the possibility of generating total reflection by forming a micro-scale structure, and this corresponds to texturing, a microlens, or a micro grating pattern.

0005<figref idref="DRAWINGS">FIG. 1</figref> is a conceptual view illustrating reflection and transmission of light incident on a structure having a micropattern formed thereon according to an embodiment of related art, in which there may be advantages in that the possibility of the light escaping to the outside through a structure <b>1</b> having a micropattern <b>1</b><i>a </i>formed thereon according to the embodiment of related art (solid line) may be increased, but there may be disadvantages in that Fresnel reflection due to a difference between refractive indices of a medium and air may not be overcome (dotted line).

0006The second is a method of gradually changing an effective refractive index between two media through a grating or non-periodic structure having a size shorter than a wavelength, in order to fundamentally reduce a loss caused by the difference between refractive indices thereof.

0007This is referred to as a “Moth eye” structure due to the resemblance to the shape of a moth's eye.

0008<figref idref="DRAWINGS">FIG. 2</figref> is a conceptual view illustrating reflection and transmission of light incident on a structure <b>2</b> having a nanopattern <b>2</b><i>a </i>formed thereon according to another embodiment of related art, in which nearly 0% reflectance may be obtained with respect to a vertical incident angle because Fresnel reflection may rarely occur at an interface between a medium and air, but there may be disadvantages in that total reflection generated when the incident angle increases may not be removed.

0009As described above, in the case that a typical microstructure is used, total reflection may be reduced, but Fresnel reflection may be difficult to be reduced, and in the case in which a subwavelength nanostructure is used, Fresnel reflection may be reduced, but total reflection may not be reduced.

DISCLOSURE

Technical Problem

0010The present invention provides a micro/nano combined structure able to minimize Fresnel reflection and total reflection generated due to a difference between refractive indices of air and a semiconductor material by forming a sharp wedge-shaped or parabolic anti-reflective nanostructure with a subwavelength period on a microstructure through deposition of a metal thin film, heat treatment, and blanket etching after forming the microstructure on a substrate, a method of manufacturing the micro/nano combined structure, and a method of manufacturing an optical device integrated with the micro/nano combined structure.

Technical Solution

0011In accordance with an exemplary embodiment of the present invention, a micro/nano combined nanostructure includes a microstructure formed on a substrate, wherein a sharp wedge-shaped anti-reflective nanostructure with a subwavelength period is formed on a top surface of the substrate having the microstructure formed thereon.

0012Herein, the anti-reflective nanostructure may be formed by heat treating a metal thin film deposited on the substrate having the microstructure formed thereon to transform into metal particles and etching an entire surface of the substrate having the microstructure formed thereon by using the metal particles as a mask.

0013The anti-reflective nanostructure may be formed by heat treating a buffer layer and a metal thin film sequentially deposited on the substrate having the microstructure formed thereon to transform into metal particles, blanket etching the buffer layer by using the metal particles as a mask to form a nanostructured buffer layer, and etching an entire surface of the substrate having the microstructure formed thereon by using the nanostructured buffer layer as a mask.

0014In accordance with another exemplary embodiment of the present invention, a method of manufacturing a micro/nano combined nanostructure includes: forming a microstructure on a substrate; depositing a metal thin film on the substrate having the microstructure formed thereon; heat treating the metal thin film to transform into metal particles; and etching an entire surface of the substrate having the microstructure formed thereon by using the metal particles as a mask to form a sharp wedge-shaped anti-reflective nanostructure with a subwavelength period on a top surface of the substrate having the microstructure formed thereon.

0015In accordance with another exemplary embodiment of the present invention, a method of manufacturing a micro/nano combined nanostructure includes: forming a microstructure on a substrate; sequentially depositing a buffer layer and a metal thin film on the substrate having the microstructure formed thereon; heat treating the metal thin film to transform into metal particles; blanket etching the buffer layer by using the metal particles as a mask to form a nanostructured buffer layer; and etching an entire surface of the substrate having the microstructure formed thereon by using the nanostructured buffer layer as a mask to form a sharp wedge-shaped anti-reflective nanostructure with a subwavelength period on a top surface of the substrate having the microstructure formed thereon.

0016Herein, the microstructure may include surface texturing, a microlens, or a micro grating pattern, and the surface texturing may denote forming random roughness on the surface thereof by using a wet or dry etching method.

0017The microlens may denote forming the shape of a lens having a diameter ranging from a few micrometers to a few tens of micrometers, and a manufacturing method thereof may generally include a method, in which the shape of a lens is formed by heat treating a patterned photoresist and then pattern transferred to the substrate, and additionally, may include various methods such as a method of selective oxidation of aluminum.

0018The micro grating pattern may be formed through etching the substrate by using a photoresist pattern having a size ranging from a few micrometers to a few tens of micrometers as a mask.

0019The buffer layer may be formed of silicon oxide (SiO₂) or silicon nitride (SiN_x).

0020The metal thin film may be deposited with any one of silver (Ag), gold (Au), or nickel (Ni), or may be deposited by selecting metal to be transformed into metal particles with a subwavelength period after the heat treatment in consideration of surface tension with respect to the substrate.

0021The metal thin film may be deposited to have a thickness ranging from about 5 nm to about 100 nm or may be deposited by selecting a thickness at which the metal thin film is transformed into metal particles with a subwavelength period after the heat treatment.

0022The heat treatment may be performed at a temperature ranging from about 200° C. to about 900° C. or may be performed by selecting a temperature at which the metal thin film is transformed into metal particles with a subwavelength period after the heat treatment.

0023The anti-reflective nanostructure may be formed by plasma dry etching.

0024A desired aspect ratio may be obtained through adjusting a height and an angle of inclination of the anti-reflective nanostructure by controlling at least any one condition of gas flow, pressure, and driving voltage during the dry etching.

0025In accordance with another exemplary embodiment of the present invention, a method of manufacturing an optical device integrated with a micro/nano combined structure includes: sequentially stacking an n-type doping layer, an active layer, and a p-type doping layer, and then forming a microstructure on a top surface of a light-emitting part of the p-type doping layer excluding positions of p-type upper electrodes; stacking the p-type upper electrodes on a top surface of the p-type doping layer and stacking an n-type lower electrode on a bottom surface of the n-type doping layer; depositing a metal thin film on the top surface of the light-emitting part having the microstructure of the p-type doping layer formed thereon; heat treating the metal thin film to transform into metal particles; and etching an entire surface of the light-emitting part having the microstructure of the p-type doping layer formed thereon by using the metal particles as a mask to form a sharp wedge-shaped anti-reflective nanostructure with a subwavelength period on the top surface of the light-emitting part having the microstructure of the p-type doping layer formed thereon.

0026In accordance with another exemplary embodiment of the present invention, a method of manufacturing an optical device integrated with a micro/nano combined structure includes: sequentially stacking an n-type doping layer, an active layer, and a p-type doping layer, and then forming a microstructure on a top surface of a light-emitting part of the p-type doping layer; depositing a metal thin film on the top surface of the light-emitting part having the microstructure of the p-type doping layer formed thereon; heat treating the metal thin film to transform into metal particles; etching an entire surface of the light-emitting part having the microstructure of the p-type doping layer formed thereon by using the metal particles as a mask to form a sharp wedge-shaped anti-reflective nanostructure with a subwavelength period on the top surface of the light-emitting part having the microstructure of the p-type doping layer formed thereon; and stacking a transparent electrode on an entire surface of the p-type doping layer including the anti-reflective nanostructure, and then stacking a contact pad on a top surface of the transparent electrode excluding the light-emitting part and stacking an n-type lower electrode on a bottom surface of the n-type doping layer.

0027In accordance with another exemplary embodiment of the present invention, a method of manufacturing an optical device integrated with a micro/nano combined structure includes: sequentially stacking a bottom cell, a middle cell, and a top cell, and then stacking a p-type upper electrode on a top surface of one side of the top cell and stacking an n-type lower electrode on a bottom surface of the bottom cell; forming a microstructure on a top surface of the top cell excluding a region of the p-type upper electrode; depositing a metal thin film on the top surface of the top cell having the microstructure formed thereon; heat treating the metal thin film to transform into metal particles; and etching an entire surface of the top cell excluding the region of the p-type upper electrode by using the metal particles as a mask to form a sharp wedge-shaped anti-reflective nanostructure with a subwavelength period on the top surface of the top cell having the microstructure formed thereon excluding the region of the p-type upper electrode.

0028Herein, the bottom cell and the middle cell may be connected through a first tunnel junction, and the middle cell and the top cell may be connected through a second tunnel junction.

0029A buffer layer may be further included between the first tunnel junction and the middle cell.

0030In accordance with another exemplary embodiment of the present invention, a method of manufacturing an optical device integrated with a micro/nano combined structure includes: sequentially stacking an n-type doping layer, an optical absorption layer, and a p-type doping layer, and then stacking p-type upper electrodes on a top surface of the p-type doping layer excluding an optical absorption part and stacking an n-type lower electrode on a bottom surface of the n-type doping layer; forming a microstructure on a top surface of the optical absorption part of the p-type doping layer; depositing a metal thin film on the top surface of the optical absorption part of the p-type doping layer having the microstructure formed thereon; heat treating the metal thin film to transform into metal particles; and etching an entire surface of the optical absorption part of the p-type doping layer having the microstructure formed thereon by using the metal particles as a mask to form a sharp wedge-shaped anti-reflective nanostructure with a subwavelength period on the top surface of the optical absorption part of the p-type doping layer having the microstructure formed thereon.

0031In accordance with another exemplary embodiment of the present invention, a method of manufacturing an optical device integrated with a micro/nano combined structure includes: sequentially stacking an n-type doping layer, a distributed Bragg reflector layer, an active layer, and a p-type doping layer, and then forming a microstructure on a top surface of a light-emitting part of the p-type doping layer excluding a position of a p-type upper electrode; depositing a metal thin film on the top surface of the light-emitting part having the microstructure formed thereon; heat treating the metal thin film to transform into metal particles; and etching an entire surface of the light-emitting part of the p-type doping layer having the microstructure formed thereon by using the metal particles as a mask to form a sharp wedge-shaped anti-reflective nanostructure with a subwavelength period on the top surface of the light-emitting part of the p-type doping layer having the microstructure formed thereon.

0032Herein, the method may further include forming an n-type lower electrode on a bottom surface of the n-type doping layer, after forming the p-type upper electrode on one side of the p-type doping layer.

Advantageous Effects

0033According to the foregoing micro/nano combined structure of the present invention, a method of manufacturing the micro/nano combined structure, and a method of manufacturing an optical device integrated with the micro/nano combined structure, since a sharp wedge-shaped or parabolic anti-reflective nanostructure with a subwavelength period may be formed on a microstructure through deposition of a metal thin film, heat treatment, and blanket etching after forming the microstructure on a substrate, a manufacturing process may be simplified, and an amount of reflection of light generated due to a difference between refractive indices of air and a semiconductor material may not only be minimized, but an anti-reflective grating structure with a subwavelength period may also be prepared at a low cost, and efficiency may be maximized when the micro/nano combined structure is integrated with an optical device such as solar cells, photodetectors, light emitting diodes, and transparent glass.

0034Also, according to the present invention, processing may be possible when a substrate has a step height, wafer-scale processing may be possible, and since a metal mask is used, masking function may be sufficiently performed regardless of a substrate material.

DESCRIPTION OF DRAWINGS

0035<figref idref="DRAWINGS">FIG. 1</figref> is a conceptual view illustrating reflection and transmission of light incident on a structure having a micropattern formed thereon according to an embodiment of related art;

0036<figref idref="DRAWINGS">FIG. 2</figref> is a conceptual view illustrating reflection and transmission of light incident on a structure having a nanopattern formed thereon according to another embodiment of related art;

0037<figref idref="DRAWINGS">FIG. 3</figref> is a sectional view illustrating a method of manufacturing a micro/nano combined structure according to a first embodiment of the present invention;

0038<figref idref="DRAWINGS">FIG. 4</figref> is a conceptual view illustrating reflection and transmission of light incident on the micro/nano combined structure according to the first embodiment of the present invention;

0039<figref idref="DRAWINGS">FIG. 5</figref> is scanning electron microscope (SEM) micrographs showing typical micro- and nano-patterned structures, and the micro/nano combined structure according to the first embodiment of the present invention;

0040<figref idref="DRAWINGS">FIG. 6</figref> is a sectional view illustrating a method of manufacturing a micro/nano combined structure according to a second embodiment of the present invention;

0041<figref idref="DRAWINGS">FIG. 7</figref> is a sectional view illustrating a method of manufacturing an optical device integrated with a micro/nano combined structure according to a third embodiment of the present invention;

0042<figref idref="DRAWINGS">FIG. 8</figref> is a sectional view illustrating a method of manufacturing an optical device integrated with a micro/nano combined structure according to a fourth embodiment of the present invention;

0043<figref idref="DRAWINGS">FIG. 9</figref> is a sectional view illustrating an optical device integrated with a micro/nano combined structure according to a fifth embodiment of the present invention;

0044<figref idref="DRAWINGS">FIG. 10</figref> is a sectional view illustrating an optical device integrated with a micro/nano combined structure according to a sixth embodiment of the present invention;

0045<figref idref="DRAWINGS">FIG. 11</figref> is a sectional view illustrating an optical device integrated with a micro/nano combined structure according to a seventh embodiment of the present invention;

0046<figref idref="DRAWINGS">FIG. 12</figref> is a sectional view illustrating a method of manufacturing an optical device integrated with a micro/nano combined structure according to an eighth embodiment of the present invention;

0047<figref idref="DRAWINGS">FIG. 13</figref> is a graph illustrating optical power of the optical device integrated with the micro/nano combined structure according to the eighth embodiment of the present invention; and

0048<figref idref="DRAWINGS">FIG. 14</figref> is a sectional view illustrating a method of manufacturing an optical device integrated with a micro/nano combined structure according to a ninth embodiment of the present invention.

BEST MODE

0049Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be constructed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art.

First Embodiment

0050<figref idref="DRAWINGS">FIG. 3</figref> is a sectional view illustrating a method of manufacturing a micro/nano combined structure according to a first embodiment of the present invention.

0051Referring to <figref idref="DRAWINGS">FIG. 3(</figref><i>a</i>), a microstructure <b>105</b> is formed on a substrate <b>100</b> prepared in advance. Herein, the substrate <b>100</b>, for example, may be formed of a semiconductor substrate (e.g., GaAs substrate or InP substrate), but the substrate <b>100</b> is not limited thereto, and any substrate may be used so long as a metal thin film <b>110</b> to be later described may be deposited on the substrate <b>100</b> including the microstructure <b>105</b>, even in the case that the substrate is not the semiconductor substrate.

0052For example, the microstructure <b>105</b> may include surface texturing, a microlens, or a micro grating pattern.

0053The surface texturing, for example, denotes forming random roughness on the surface thereof by using a wet or dry etching method.

0054The microlens denotes forming the shape of a lens having a diameter ranging from a few micrometers to a few tens of micrometers, and a manufacturing method thereof may generally include a method, in which the shape of a lens is formed by heat treating a patterned photoresist and then pattern transferred to the substrate, and additionally, may include various methods such as a method of selective oxidation of aluminum.

0055The micro grating pattern may be formed through etching the substrate by using a photoresist pattern having a size ranging from a few micrometers to a few tens of micrometers as a mask.

0056Referring to <figref idref="DRAWINGS">FIG. 3(</figref><i>b</i>), the metal thin film <b>110</b> is deposited on a top surface of the substrate <b>100</b> having the microstructure <b>105</b> formed thereon by using, for example, an E-beam evaporator or a thermal evaporator.

0057Herein, various metals, such as silver (Ag), gold (Au), and nickel (Ni), may be deposited as the metal thin film <b>110</b>, and the metal thin film <b>110</b> may be deposited by selecting metal able to be transformed into metal particles (or metal granules) <b>120</b> (see <figref idref="DRAWINGS">FIG. 3(</figref><i>c</i>)) with a subwavelength period after being subjected to a subsequent heat treatment process in consideration of surface tension with respect to the substrate <b>100</b>.

0058Also, the metal thin film <b>110</b> may be deposited to have a thickness ranging from about 5 nm to about 100 nm and may be deposited by selecting a thickness at which the metal thin film <b>110</b> may be transformed into the metal particles <b>120</b> with a subwavelength period after the heat treatment.

0059Meanwhile, the deposition of the metal thin film <b>110</b>, for example, is not limited to E-beam evaporation or thermal evaporation, and any apparatus, such as a sputtering machine, able to deposit metal in a thickness ranging from about 5 nm to about 100 nm may be used.

0060Referring to <figref idref="DRAWINGS">FIG. 3(</figref><i>c</i>), the metal thin film <b>110</b>, for example, is transformed into the metal particles <b>120</b> through a heat treatment by using a rapid thermal annealing (RTA) method.

0061At this time, the heat treatment may be performed at a temperature ranging from about 200° C. to about 900° C., and the heat treatment may be performed by selecting a temperature at which the metal thin film <b>110</b> may be transformed into the metal particles <b>120</b> with a subwavelength period after the heat treatment.

0062Referring to <figref idref="DRAWINGS">FIG. 3(</figref><i>d</i>), an anti-reflective nanostructure <b>130</b> with a predetermined period (for example, about 100 nm to about 1000 nm) and a depth (for example, about 50 nm to about 600 nm), i.e., a subwavelength period, may be formed on the top surface of the substrate <b>100</b> itself including the microstructure <b>105</b> by performing, for example, a dry etching process on an entire surface of the substrate <b>100</b> including the metal particles <b>120</b>.

0063The anti-reflective nanostructure <b>130</b> may be periodically and constantly arranged on the surface of the substrate <b>100</b> including the microstructure <b>105</b> and may be formed as a sharp wedge shape, e.g., a cone shape, in which a cross-sectional area decreases from the surface of the substrate <b>100</b> toward an air layer on an upper side thereof. However, the anti-reflective nanostructure <b>130</b> is not limited thereto, and for example, may be formed as a parabola, triangular pyramid, quadrangular pyramid, or polypyramid shape.

0064Meanwhile, the dry etching method, for example, may use plasma dry etching, but the dry etching method is not limited thereto, and a dry etching method that improves anisotropic etching characteristics and an etching rate by simultaneously using reactive gas and plasma, for example, a reactive ion etching (RIE) method or an inductively coupled plasma (ICP) etching method, in which plasma is generated by radio frequency (RF) power, may be used.

0065A desired aspect ratio may be easily obtained through adjusting a height and an angle of inclination of the anti-reflective nanostructure <b>130</b> by controlling at least any one condition of gas flow, pressure, and driving voltage during the dry etching.

0066<figref idref="DRAWINGS">FIG. 4</figref> is a conceptual view illustrating reflection and transmission of light incident on the micro/nano combined structure according to the first embodiment of the present invention, in which Fresnel reflection and total reflection generated due to a difference between refractive indices of air and a semiconductor material may be minimized by the micro/nano combined structure of the present invention.

0067<figref idref="DRAWINGS">FIG. 5</figref> is scanning electron microscope (SEM) micrographs showing (a) typical micro-patterned structure and (b) nano-patterned structure, and (c) the micro/nano combined structure prepared according to the first embodiment of the present invention, in which GaAs is used as the substrate <b>100</b> (see <figref idref="DRAWINGS">FIG. 3(</figref><i>a</i>)) and it may be confirmed that a sharp wedge-shaped anti-reflective nanostructure may be formed on the substrate <b>100</b> having the microstructure <b>105</b> (see <figref idref="DRAWINGS">FIG. 3(</figref><i>a</i>)) formed thereon.

Second Embodiment

0068<figref idref="DRAWINGS">FIG. 6</figref> is a sectional view illustrating a method of manufacturing a micro/nano combined structure according to a second embodiment of the present invention.

0069Referring to <figref idref="DRAWINGS">FIG. 6(</figref><i>a</i>), a microstructure <b>105</b> is formed on a substrate <b>100</b> prepared in advance. Herein, the substrate <b>100</b>, for example, may be formed of a semiconductor substrate (e.g., GaAs substrate or InP substrate), but the substrate <b>100</b> is not limited thereto, and any substrate may be used so long as a buffer layer <b>107</b> to be later described may be deposited on a top surface of the substrate <b>100</b> including the microstructure <b>105</b>, even in the case that the substrate is not the semiconductor substrate.

0070Referring to <figref idref="DRAWINGS">FIG. 6(</figref><i>b</i>), the buffer layer <b>107</b>, for example, formed of silicon oxide (SiO₂) or silicon nitride (SiN_x) is deposited on the top surface of the substrate <b>100</b> having the microstructure <b>105</b> formed thereon by, for example, plasma enhanced chemical vapor deposition (PECVD), thermal chemical vapor deposition (Thermal-CVD), or sputtering, and a metal thin film <b>110</b> is sequentially deposited by using, for example, an E-beam evaporator or a thermal evaporator.

0071Herein, the buffer layer <b>107</b>, for example, is not limited to silicon oxide (SiO₂) or silicon nitride (SiN_x), and any material may be used so long as the metal thin film <b>110</b> may be transformed into metal particles (or metal granules) <b>120</b> (see <figref idref="DRAWINGS">FIG. 6(</figref><i>c</i>)) with a subwavelength period after a heat treatment by surface tension between the buffer layer <b>107</b> and the metal thin film <b>110</b>.

0072Also, the buffer layer <b>107</b> may be deposited to have a thickness ranging from about 5 nm to about 500 nm, and the thickness of the buffer layer <b>107</b> must satisfy conditions, in which, first, the metal film <b>110</b> may be transformed into the metal particles <b>120</b> with a subwavelength period after the heat treatment, and second, the buffer layer <b>107</b> may become a nanostructured buffer layer <b>107</b>′ (see <figref idref="DRAWINGS">FIG. 6(</figref><i>d</i>)) allowing predetermined portions of the top surface of the substrate <b>100</b> including the microstructure <b>105</b> to be exposed through blanket etching by using the metal particles <b>120</b>.

0073In general, in the case that the metal thin film <b>110</b> is heat treated to be transformed into the metal particles <b>120</b>, a period and a size of the metal particles <b>120</b> may be changed by surface tension between the substrate <b>100</b> and the metal thin film <b>110</b>. Therefore, in the case that a material of the substrate <b>100</b> is changed according to the purpose thereof, a thickness and a heat treatment temperature of the metal must be changed accordingly, and this may be difficult to be applied to actual applications.

0074Meanwhile, when the buffer layer <b>107</b> formed of silicon oxide (SiO₂) or silicon nitride (SiN_x) is used, the surface tension between the buffer layer <b>107</b> and the metal thin film <b>110</b> does not change even in the case that the material of the substrate <b>100</b> is changed, and thus, the metal particles <b>120</b> may be reproducibly formed with no changes in the thickness and the heat treatment temperature of the metal.

0075Various metals, such as Ag, Au, and Ni, may be deposited as the metal thin film <b>110</b>, and the metal thin film <b>110</b> may be deposited by selecting metal able to be transformed into metal particles <b>120</b> with a subwavelength period after being subjected to a subsequent heat treatment process in consideration of surface tension with respect to the substrate <b>100</b>.

0076Also, the metal thin film <b>110</b> may be deposited to have a thickness ranging from about 5 nm to about 100 nm and may be deposited by selecting a thickness at which the metal thin film <b>110</b> may be transformed into the metal particles <b>120</b> with a subwavelength period after the heat treatment.

0077Meanwhile, the deposition of the metal thin film <b>110</b>, for example, is not limited to E-beam evaporation or thermal evaporation, and any apparatus, such as a sputtering machine, able to deposit metal in a thickness ranging from about 5 nm to about 100 nm may be used.

0078Referring to <figref idref="DRAWINGS">FIG. 6(</figref><i>c</i>), the metal thin film <b>110</b>, for example, is transformed into the metal particles <b>120</b> through a heat treatment by rapid thermal annealing (RTA). At this time, the heat treatment may be performed at a temperature ranging from about 200° C. to about 900° C., and may be performed by selecting a temperature at which the metal thin film <b>110</b> may be transformed into the metal particles <b>120</b> with a subwavelength period after the heat treatment.

0079Referring to <figref idref="DRAWINGS">FIG. 6(</figref><i>d</i>), the nanostructured buffer layer <b>107</b>′ with a predetermined period (for example, about 100 nm to about 1000 nm) and a depth (for example, about 50 nm to about 600 nm), i.e., a subwavelength period, may be formed on the top surface of the substrate <b>100</b> including the microstructure <b>105</b> by performing, for example, a dry etching process on an entire surface of the substrate <b>100</b> including the buffer layer <b>107</b> and the metal particles <b>120</b>.

0080The nanostructured buffer layer <b>107</b>′ may not be aligned, but may be formed with a predetermined spacing.

0081Referring to <figref idref="DRAWINGS">FIG. 6(</figref><i>e</i>), an anti-reflective nanostructure <b>130</b> with a subwavelength period is formed on the top surface of the substrate <b>100</b> including the microstructure <b>105</b> through blanket etching by using the nanostructured buffer layer <b>107</b>′ as a mask. Thereafter, a residual buffer layer and the metal particles <b>120</b> are removed through wet etching.

0082The anti-reflective nanostructure <b>130</b> may be formed as a sharp wedge shape, e.g., a cone shape, in which a cross-sectional area decreases from the surface of the substrate <b>100</b> toward an air layer on an upper side thereof. However, the anti-reflective nanostructure <b>130</b> is not limited thereto, and for example, may be formed as a parabola, triangular pyramid, quadrangular pyramid, or polypyramid shape. In some cases, the anti-reflective nanostructure <b>130</b> may be formed as a truncated cone shape.

0083Meanwhile, the dry etching method may use plasma dry etching, but the dry etching method is not limited thereto, and a dry etching method that improves anisotropic etching characteristics and an etching rate by simultaneously using reactive gas and plasma, for example, a reactive ion etching (RIE) method or a inductively coupled plasma (ICP) etching method, in which plasma is generated by RF power, may be used.

0084A height and an angle of inclination of the anti-reflective nanostructure may be adjusted by controlling at least any one condition of gas flow, pressure, and driving voltage during the dry etching, and in particular, a desired aspect ratio may be easily obtained by controlling RF power.

0085In addition, a transparent electrode (not shown) may be further disposed between the substrate <b>100</b> and the buffer layer <b>107</b>, and the transparent electrode, for example, may be deposited by using an E-beam evaporator, a thermal evaporator, or a sputter.

0086For example, any one of indium tin oxide (ITO), tin oxide (TO), indium tin zinc oxide (IZO), and indium zinc oxide (IZO) may be selected as a material of the transparent electrode.

0087Meanwhile, since all manufacturing processes other than a process of disposing the transparent electrode are the same as those of the foregoing second embodiment, the detailed description related thereto will be referred to the foregoing second embodiment. However, in the case that the transparent electrode is disposed between the substrate <b>100</b> and the buffer layer <b>107</b>, the nanostructured buffer layer <b>107</b>′ is formed on a top surface of the transparent electrode in the foregoing <figref idref="DRAWINGS">FIG. 6(</figref><i>d</i>), a nanostructured transparent electrode is formed through blanket etching by using the nanostructured buffer layer <b>107</b>′ as a mask in <figref idref="DRAWINGS">FIG. 6(</figref><i>e</i>), and an anti-reflective nanostructure, in which a predetermined portion of the substrate also has a subwavelength period, is formed. Thereafter, a transparent electrode may be again deposited on the entire surface of the substrate <b>100</b> to connect the nanostructured transparent electrodes each other and thus, current may be allowed to be flown therebetween.

Third Embodiment

0088<figref idref="DRAWINGS">FIG. 7</figref> is a sectional view illustrating a method of manufacturing an optical device integrated with a micro/nano combined structure according to a third embodiment of the present invention.

0089Referring to <figref idref="DRAWINGS">FIG. 7(</figref><i>a</i>), the optical device has a structure of a general light-emitting device, and for example, the optical device may be formed by sequentially stacking an n-type doping layer <b>200</b>, an active layer <b>210</b>, and a p-type doping layer <b>220</b>, and then stacking p-type upper electrodes <b>230</b> on a top surface of the p-type doping layer <b>220</b> excluding a light-emitting part and stacking an n-type lower electrode <b>240</b> on a bottom surface of the n-type doping layer <b>200</b>. However, the optical device is not limited thereto.

0090Referring to <figref idref="DRAWINGS">FIG. 7(</figref><i>b</i>), the anti-reflective nanostructure <b>130</b> formed according to the first or second embodiment of the present invention is integrated on a top surface of the light-emitting part of the p-type doping layer <b>220</b>, and thus, the method of manufacturing an optical device integrated with an anti-reflective micro/nano combined structure according to the third embodiment of the present invention may be completed.

0091At this time, since the detailed description related to the method of forming the anti-reflective nanostructure <b>130</b> is the same as that of the foregoing first or second embodiment of the present invention, the detailed description related thereto will be omitted.

Fourth Embodiment

0092<figref idref="DRAWINGS">FIG. 8</figref> is a sectional view illustrating a method of manufacturing an optical device integrated with a micro/nano combined structure according to a fourth embodiment of the present invention.

0093Referring to <figref idref="DRAWINGS">FIG. 8(</figref><i>a</i>), the optical device has a structure of a general light-emitting device, and for example, the optical device may be formed by sequentially stacking an n-type doping layer <b>300</b>, an active layer <b>310</b>, and a p-type doping layer <b>320</b>, and then sequentially stacking a transparent electrode <b>330</b> and a contact pad <b>340</b> on a top surface of the p-type doping layer <b>320</b> and stacking an n-type lower electrode <b>350</b> on a bottom surface of the n-type doping layer <b>300</b>. However, the optical device is not limited thereto.

0094Referring to <figref idref="DRAWINGS">FIG. 8(</figref><i>b</i>), before stacking the transparent electrode <b>330</b>, the anti-reflective nanostructure <b>130</b> formed according to the first or second embodiment of the present invention is integrated on a top surface of the light-emitting part of the p-type doping layer <b>320</b>, and thus, the method of manufacturing an optical device integrated with a micro/nano combined structure according to the fourth embodiment of the present invention may be completed.

0095At this time, since the detailed description related to the method of forming the anti-reflective nanostructure <b>130</b> is the same as that of the foregoing first or second embodiment of the present invention, the detailed description related thereto will be omitted.

0096Meanwhile, the transparent electrode <b>330</b> is stacked on an entire surface of the p-type doping layer <b>320</b> including the anti-reflective nanostructure <b>130</b> and the contact pad <b>340</b> is then stacked on a top surface of the transparent electrode <b>330</b> excluding the light-emitting part. At this time, since the transparent electrode <b>330</b> is deposited on the anti-reflective nanostructure <b>130</b>, the shape thereof may be formed to be the same as that of the anti-reflective nanostructure <b>130</b>.

Fifth Embodiment

0097<figref idref="DRAWINGS">FIG. 9</figref> is a sectional view illustrating an optical device integrated with a micro/nano combined structure according to a fifth embodiment of the present invention.

0098Referring to <figref idref="DRAWINGS">FIG. 9</figref>, the optical device is a general triple junction solar cell and has a structure in which germanium (Ge) having a bandgap of about 0.65 eV is used as a bottom cell <b>400</b>, In_0.08Ga_0.92As having a bandgap near 1.4 eV is disposed thereon as a middle cell <b>430</b>, and In_0.56Ga_0.44P having a bandgap of about 1.9 eV is disposed thereon as a top cell <b>450</b>.

0099Each cells <b>410</b>, <b>430</b>, and <b>450</b> are electrically connected through first and second tunnel junctions <b>410</b> and <b>440</b>, a p-type upper electrode <b>460</b> is formed on a top surface of one side of the top cell <b>450</b>, and an n-type lower electrode <b>470</b> is formed on a bottom surface of the bottom cell <b>400</b>.

0100In particular, the anti-reflective nanostructure <b>130</b> formed according to the first or second embodiment of the present invention is integrated on a top surface of the top cell <b>450</b> excluding a region of the p-type upper electrode <b>460</b>, and thus, the method of manufacturing a triple junction solar cell, the optical device integrated with a micro/nano combined structure according to the fifth embodiment of the present invention, may be completed.

0101At this time, since the detailed description related to the method of forming the anti-reflective nanostructure <b>130</b> is the same as that of the foregoing first or second embodiment of the present invention, the detailed description related thereto will be omitted.

0102For example, a buffer layer <b>420</b> formed of InGaAs may be further included between the first tunnel junction <b>410</b> and the middle cell <b>430</b>.

0103That is, in view of the absorption spectrum of sunlight, the top cell <b>450</b> absorbs up to the wavelength of about 650 nm, the middle cell <b>430</b> absorbs up to the wavelength of about 900 nm, and the bottom cell <b>400</b> absorbs up to the wavelength of about 1900 nm, and thus, the solar cell may have a structure able to absorb light over a wide bandwidth.

0104Herein, the method of manufacturing the anti-reflective nanostructure <b>130</b> is applied to the surface of the top cell <b>450</b> and thus, reflection of the incident light may be minimized and as a result, efficiency of the solar cell may be increased.

Sixth Embodiment

0105<figref idref="DRAWINGS">FIG. 10</figref> is a sectional view illustrating an optical device integrated with a micro/nano combined structure according to a sixth embodiment of the present invention.

0106Referring to <figref idref="DRAWINGS">FIG. 10</figref>, the optical device has a structure of a general photodetector, and for example, the optical device may be formed by sequentially stacking an n-type doping layer <b>500</b>, an optical absorption layer <b>510</b>, and a p-type doping layer <b>520</b>, and then stacking p-type upper electrodes <b>530</b> on a top surface of the p-type doping layer <b>520</b> excluding an optical absorption part and stacking an n-type lower electrode <b>540</b> on a bottom surface of the n-type doping layer <b>500</b>. However, the optical device is not limited thereto.

0107In particular, the anti-reflective nanostructure <b>130</b> formed according to the first or second embodiment of the present invention is integrated on a top surface of the optical absorption part of the p-type doping layer <b>520</b>, and thus, the method of manufacturing an optical device integrated with a micro/nano combined structure according to the sixth embodiment of the present invention may be completed.

0108At this time, since the detailed description related to the method of forming the anti-reflective nanostructure <b>130</b> is the same as that of the foregoing first or second embodiment of the present invention, the detailed description related thereto will be omitted.

0109Herein, the method of manufacturing the anti-reflective nanostructure <b>130</b> is applied to a surface of the p-type doping layer <b>520</b> and thus, reflection of the incident light may be minimized and as a result, efficiency of the photodetector may be increased.

Seventh Embodiment

0110<figref idref="DRAWINGS">FIG. 11</figref> is a sectional view illustrating an optical device integrated with a micro/nano combined structure according to a seventh embodiment of the present invention.

0111Referring to <figref idref="DRAWINGS">FIG. 11</figref>, the optical device is general transparent glass <b>600</b>, and has a refractive index of about 1.5 and exhibits a transmittance of about 95% or more in a specific wavelength band. However, with respect to some applications such as solar cells, about 99% or more of transmittance may be required over a wide bandwidth and for this purpose, the method of manufacturing the anti-reflective nanostructure <b>130</b> formed according to the foregoing first or second embodiment of the present invention may be used.

0112That is, the anti-reflective nanostructure <b>130</b> formed according to the foregoing first or the second embodiment of the present invention is integrated on a top surface of the transparent glass <b>600</b>, and thus, high transmittance may be obtained over a wider bandwidth. Also, the anti-reflective nanostructure <b>130</b> may be integrated under as well as on the transparent glass <b>600</b> and thus, high transmittance may be obtained over a wider bandwidth.

Eighth Embodiment

0113<figref idref="DRAWINGS">FIG. 12</figref> is a sectional view illustrating a method of manufacturing an optical device integrated with a micro/nano combined structure according to an eighth embodiment of the present invention.

0114Referring to <figref idref="DRAWINGS">FIG. 12</figref>, the optical device has a structure of a general light-emitting device, i.e., a light-emitting diode (LED), and for example, the optical device may be formed by sequentially stacking an n-type doping layer (n-GaAs) <b>700</b>, a distributed Bragg reflector (DBR) layer (AlAs/AlGaAs) <b>710</b>, an active layer <b>720</b>, and a p-type doping layer <b>730</b>, and then stacking a p-type upper electrode <b>740</b> on a top surface of the p-type doping layer <b>730</b> excluding a light-emitting part and stacking an n-type lower electrode <b>750</b> on a bottom surface of the n-type doping layer <b>700</b>. However, the optical device is not limited thereto.

0115In particular, the anti-reflective nanostructure <b>130</b> formed according to the foregoing first or the second embodiment of the present invention is integrated on a top surface of the light-emitting part of the p-type doping layer <b>730</b>, and thus, the method of manufacturing an optical device integrated with a micro/nano combined structure according to the eighth embodiment of the present invention may be completed.

0116At this time, since the detailed description related to the method of forming the anti-reflective nanostructure <b>130</b> is the same as that of the foregoing first or second embodiment of the present invention, the detailed description related thereto will be omitted.

0117<figref idref="DRAWINGS">FIG. 13</figref> is a graph illustrating optical power of the optical device integrated with the micro/nano combined structure according to the eighth embodiment of the present invention, in which <figref idref="DRAWINGS">FIG. 13(</figref><i>a</i>) illustrates a typical optical device without an anti-reflective nanostructure, <figref idref="DRAWINGS">FIG. 13(</figref><i>b</i>) illustrates a typical optical device only with an anti-reflective nanopattern, <figref idref="DRAWINGS">FIG. 13(</figref><i>c</i>) illustrates a typical optical device only with an anti-reflective micropattern, and <figref idref="DRAWINGS">FIG. 13(</figref><i>d</i>) illustrates the optical device having a micro/nano combined structure according to the eighth embodiment of the present invention, and it may be confirmed that the power thereof is increased to about 35% to about 72.4% in comparison to those of typical optical devices and the output wavelength thereof is almost not changed.

Ninth Embodiment

0118<figref idref="DRAWINGS">FIG. 14</figref> is a sectional view illustrating a method of manufacturing an optical device integrated with a micro/nano combined structure according to a ninth embodiment of the present invention.

0119Referring to <figref idref="DRAWINGS">FIG. 14</figref>, the optical device has a structure of a flip-chip bonding type GaN-based light-emitting diode (LED), in which a buffer layer formed of gallium nitride (GaN) and a n-type gallium nitride (n-GaN) layer <b>810</b> are formed on a sapphire substrate <b>800</b> formed of an Al₂O₃-based component.

0120Metal organic chemical vapor deposition (MOCVD) is generally used in order to grow thin films of group 3 elements on the sapphire substrate <b>800</b> and layers are formed while growth pressure is maintained in a range of about 200 torr to about 650 torr.

0121Thereafter, the n-type gallium nitride layer <b>810</b> is grown and an active layer <b>820</b> is then grown on the n-type gallium nitride layer <b>810</b>. The active layer <b>820</b> is a light-emitting region that is a semiconductor layer having a quantum well formed of InGaN, for example, a multi-quantum well (MQW) layer. The active layer <b>820</b> is grown and then a p-type gallium nitride (p-GaN) layer <b>830</b> is subsequently grown. The p-type gallium nitride layer <b>830</b>, for example, is formed of an AlGaN or InGaN component.

0122The p-type gallium nitride layer <b>830</b> is a layer in contrast with the n-type gallium nitride layer <b>810</b>, in which the n-type gallium nitride layer <b>810</b> provides electrons to the active layer <b>820</b> by the voltage applied from the outside. In contrast, the p-type gallium nitride layer <b>830</b> provides holes to the active layer <b>820</b> by the voltage applied from the outside and thus, holes and electrons are combined in the active layer <b>820</b> to generate light.

0123Metal having high reflectivity is formed on the p-type gallium nitride layer <b>830</b> to form a p-type electrode <b>840</b> including the function of a reflecting plate. Herein, an electrode pad may be further formed on the p-type electrode <b>840</b>.

0124Thereafter, etching is performed up to the n-type gallium nitride layer <b>810</b> to open and an n-type electrode <b>850</b> is then formed on the n-type gallium nitride layer <b>810</b>.

0125The LED having the foregoing configuration is mounted on a silicon (Si) submount <b>900</b> in the form of a flip chip, in which metal bumps <b>920</b> (e.g., Au bumps) are used between the p-type and n-type electrodes <b>840</b> and <b>850</b> on the submount <b>900</b> and reflective layers <b>910</b> formed at corresponding positions to electrically bond them.

0126When the power is applied to the LED through the submount <b>900</b>, electrons and holes are combined in the active layer <b>820</b> of the flip-chip bonded LED having the foregoing structure to generate light.

0127A portion of the light generated from the active layer <b>820</b> is emitted to the outside through the sapphire substrate <b>800</b> and another portion of the light is reflected from the p-type gallium nitride layer <b>830</b>, the p-type electrode <b>840</b>, and the reflective layer <b>910</b> formed on the submount <b>900</b> and then emitted to the outside.

0128In particular, in the case that the LED is flip-chip bonded, since the light generated from the active layer <b>820</b> is emitted to the outside through the sapphire substrate <b>800</b> directly or after the reflection, luminous efficiency may increase in comparison to a light-emitting diode generating light from a top surface of a semiconductor.

0129In addition, the anti-reflective nanostructure <b>130</b> formed according to the foregoing first or the second embodiment of the present invention is integrated on an externally exposed surface of the sapphire substrate <b>800</b> so as to minimize an amount of reflection of the light generated due to the difference between refractive indices of air and a semiconductor material during the emission of the light to the outside through the sapphire substrate <b>800</b>, and thus, the method of manufacturing an optical device integrated with a micro/nano combined structure according to the ninth embodiment of the present invention may be completed.

0130At this time, since the detailed description related to the method of forming the anti-reflective nanostructure <b>130</b> is the same as that of the foregoing first or second embodiment of the present invention, the detailed description related thereto will be omitted.

0131While the present invention has been particularly shown and described with reference to exemplary embodiments related to the foregoing method of manufacturing a micro/nano combined structure and method of manufacturing an optical device integrated with a micro/nano combined structure according to the present invention, it will be understood that the present invention is not limited thereto and various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.