Semiconductor structure and manufacturing method thereof

Abstract

This invention provides a semiconductor structure and its manufacturing method. The semiconductor structure includes a transparent substrate, an epitaxial structure, and a distributed Bragg reflector structure. The epitaxial structure is disposed on one side of the transparent substrate, and the distributed Bragg reflector structure is disposed on the back side of the transparent substrate opposite to the epitaxial structure. Visible light can substantially pass through the epitaxial structure, the transparent substrate, and the distributed Bragg reflector structure in a substantial sequence, but other light rays besides visible light can be substantially reflected back into the transparent substrate by the distributed Bragg reflector structure.

Description

Technical Field

[0001] This invention relates to a semiconductor structure and a method for manufacturing the same, and more particularly to a semiconductor structure and a method for manufacturing the same for improving optical alignment. Prior Technology

[0002] Optical alignment calibration is a crucial step in semiconductor manufacturing, particularly in the photolithography process, to ensure precise alignment of patterns on the wafer for proper stacking of multilayer structures. This technology involves using an optical system to detect alignment marks and adjusting the position of the wafer or photomask based on the location of these marks, thereby guaranteeing nanometer-level precision.

[0003] Optical alignment calibration techniques applied to transparent substrates (e.g., silicon carbide substrates, gallium nitride substrates, or other transparent materials) differ from traditional silicon-based processes. This is primarily because the physical properties of transparent substrates (such as optical transparency, refractive index, and thickness uniformity) present unique challenges to the design and implementation of optical alignment calibration systems. Specifically, existing techniques place a metal mirror on one side of the transparent substrate to significantly improve the intensity and contrast of the alignment mark reflection signal.

[0004] However, using metal mirrors presents two main problems. First, metal mirrors have limited high-temperature resistance and cannot withstand the high temperatures encountered during the manufacturing process (e.g., potentially up to 800°C). Therefore, during high-temperature processes, metal mirrors may deform or degrade in performance, affecting the stability of the process results. Second, metal mirrors generate high reflectivity in the visible light region relative to the alignment marks, thus affecting alignment calibration in subsequent exposure lithography processes and preventing effective alignment. Summary of the Invention

[0005] The main objective of this invention is to provide an innovative semiconductor structure and its manufacturing method, employing a dual-band Bragg reflector structure in a transparent substrate for optical alignment calibration during the manufacturing process. It provides high reflectivity for light in the 436 nm and 940 nm wavelength bands and high average transmittance for visible light in the 500–750 nm range. Applied to edge alignment of transparent substrates, it enhances the calibration of wafer alignment marks in photolithography and improves the accuracy and intensity of exposure in photolithography. Furthermore, the dual-band Bragg reflector structure of this invention exhibits high-temperature resistance, capable of withstanding process temperatures exceeding 800°C, ensuring the stability of the reflector structure in subsequent high-temperature thin-film deposition processes, thereby improving the accuracy and efficiency of process alignment calibration.

[0006] To achieve the above objectives, the present invention provides a semiconductor structure comprising a transparent substrate, an epitaxial structure, and a distributed Bragg reflector structure. The epitaxial structure is disposed on one side of the transparent substrate, and the distributed Bragg reflector structure is disposed on the back side of the transparent substrate opposite to the epitaxial structure. Visible light can substantially and sequentially penetrate the epitaxial structure, the transparent substrate, and the distributed Bragg reflector structure, but other light rays besides visible light can be substantially reflected back into the transparent substrate by the distributed Bragg reflector structure.

[0007] In one embodiment of the semiconductor structure of the present invention, the distributed Bragg reflector structure includes a first symmetrical film stack having a plurality of pairs of first oxide films and second oxide films stacked alternately, wherein the refractive index of one of the first oxide films is greater than the refractive index of one of the second oxide films.

[0008] In a semiconductor structure according to an embodiment of the present invention, the thicknesses of each first oxide film and each second oxide film in the first symmetrical film stack have a first front-to-back symmetry relationship.

[0009] In one embodiment of the semiconductor structure of the present invention, the distributed Bragg reflector structure further includes a second symmetric film stack having multiple pairs of first oxide films and second oxide films stacked alternately, and the thickness of each first oxide film and each second oxide film in the second symmetric film stack is greater than the thickness of each first oxide film and each second oxide film in the first symmetric film stack.

[0010] In a semiconductor structure according to an embodiment of the present invention, the thicknesses of each first oxide film and each second oxide film in the second symmetrical film stack have a second front-to-back symmetry relationship.

[0011] In a semiconductor structure according to an embodiment of the present invention, the refractive index of one of the first oxide thin film and the second oxide thin film is in the range of 1.4 to 3.0.

[0012] In one embodiment of the semiconductor structure of the present invention, the first oxide film and the second oxide film are two of silicon dioxide (SiO2), titanium dioxide (TiO2), tantalum pentoxide (Ta2O5), niobium pentoxide (Nb2O5), aluminum oxide (Al2O3), and zirconium dioxide (ZrO2).

[0013] In a semiconductor structure according to an embodiment of the present invention, the thickness range of each first oxide film and each second oxide film in the first symmetrical film stack is 20~60 nanometers (nm).

[0014] In a semiconductor structure according to an embodiment of the present invention, the thickness range of each first oxide film and each second oxide film in the second symmetric film stack is 50~220 nanometers (nm).

[0015] In one embodiment of the semiconductor structure of the present invention, the total thickness of a distributed Bragg reflector structure ranges from 800 nanometers (nm) to 3 micrometers (µm).

[0016] In one embodiment of the semiconductor structure of the present invention, the other light includes dual-band light of 436 nanometers (nm) and 940 nanometers (nm).

[0017] To achieve the above objectives, the present invention provides a semiconductor structure comprising a transparent substrate and a distributed Bragg reflector structure. The distributed Bragg reflector structure is disposed on the back side of one of the transparent substrates. The distributed Bragg reflector structure comprises a first symmetrical film stack and a second symmetrical film stack. The first symmetrical film stack has a plurality of pairs of alternating low-refractive-index oxide films and high-refractive-index oxide films, and the second symmetrical film stack has a plurality of pairs of alternating low-refractive-index oxide films and high-refractive-index oxide films. The thickness of each low-refractive-index oxide film and each high-refractive-index oxide film in the second symmetrical film stack is greater than the thickness of each low-refractive-index oxide film and each high-refractive-index oxide film in the first symmetrical film stack. Visible light can substantially and sequentially penetrate the epitaxial structure and the distributed Bragg reflector structure, but other light rays besides visible light can be substantially reflected back into the transparent substrate by the distributed Bragg reflector structure.

[0018] In another embodiment of the semiconductor structure of the present invention, the thicknesses of each low-refractive-index oxide film and each high-refractive-index oxide film in the first symmetrical film stack have a first front-to-back symmetry relationship, and the thicknesses of each low-refractive-index oxide film and each high-refractive-index oxide film in the second symmetrical film stack have a second front-to-back symmetry relationship.

[0019] In another embodiment of the semiconductor structure of the present invention, the refractive index range of one of the low refractive index oxide thin film and the high refractive index oxide thin film is 1.4 to 3.0.

[0020] In another embodiment of the semiconductor structure of the present invention, the low refractive index oxide film and the high refractive index oxide film are two of silicon dioxide (SiO2), titanium dioxide (TiO2), tantalum pentoxide (Ta2O5), niobium pentoxide (Nb2O5), aluminum oxide (Al2O3), and zirconium dioxide (ZrO2).

[0021] In another embodiment of the semiconductor structure of the present invention, the thickness range of each low-refractive-index oxide film and each high-refractive-index oxide film in the first symmetrical film stack is 20~60 nanometers (nm).

[0022] In another embodiment of the semiconductor structure of the present invention, the thickness range of each low-refractive-index oxide film and each high-refractive-index oxide film in the second symmetric film stack is 50~220 nanometers (nm).

[0023] In another embodiment of the semiconductor structure of the present invention, the total thickness of one of the distributed Bragg reflector structures ranges from 800 nanometers (nm) to 3 micrometers (µm).

[0024] In another embodiment of the semiconductor structure of the present invention, the other light includes dual-band light of 436 nanometers (nm) and 940 nanometers (nm).

[0025] To achieve the above objectives, the present invention provides a method for manufacturing a semiconductor structure, comprising the following steps: First, a transparent substrate is provided. Second, a distributed Bragg reflector structure is formed and disposed on the back side of the transparent substrate. The distributed Bragg reflector structure comprises: a first symmetrical film stack having a plurality of pairs of alternating low-refractive-index oxide films and high-refractive-index oxide films; and a second symmetrical film stack having a plurality of pairs of alternating low-refractive-index oxide films and high-refractive-index oxide films, wherein the thickness of each oxide film in the second symmetrical film stack is greater than the thickness of each oxide film in the first symmetrical film stack, such that visible light can substantially and sequentially penetrate the transparent substrate and the distributed Bragg reflector structure, but other light rays besides visible light can be substantially reflected back into the transparent substrate by the distributed Bragg reflector structure.

[0026] After referring to the drawings and the embodiments described below, those skilled in the art will understand other objects of the present invention, as well as the technical means and implementation of the present invention. Simple Explanation of the Diagram

[0027] Figure 1 shows a schematic diagram of a semiconductor structure according to an embodiment of the present invention; Figure 2 shows a schematic diagram illustrating the front-to-back symmetry relationship of two sets of symmetrical film stacks in a distributed Bragg reflector structure according to an embodiment of the present invention; Figure 3 shows a schematic diagram of the spectrum of a dual-band distributed Bragg reflector design in one embodiment of the present invention; and Figure 4 shows a schematic diagram of the manufacturing process steps of a semiconductor structure in one embodiment of the present invention. Implementation

[0028] The present invention will be explained below through embodiments. These embodiments are not intended to limit the implementation of the invention to any specific environment, application, or special method as described in the embodiments. Therefore, the descriptions of the embodiments are for illustrative purposes only and are not intended to limit the invention. It should be noted that in the following embodiments and drawings, elements not directly related to the present invention have been omitted and are not shown, and the dimensional relationships between the elements in the drawings are for ease of understanding only and are not intended to limit the actual scale.

[0029] Please refer to Figure 1, which shows a schematic diagram of a semiconductor structure according to an embodiment of the present invention. In this embodiment, the semiconductor structure 100 includes a transparent substrate 1, a distributed Bragg reflector (DBR) structure 10, and an epitaxial structure 20. The transparent substrate 1 can be, for example, but not limited to, a sapphire substrate, a silicon carbide substrate, or a gallium nitride substrate. To overcome the various problems encountered in the prior art regarding the optical alignment calibration of transparent substrates, the present invention specifically forms a distributed Bragg reflector structure 10 on one of the exposed back sides of the transparent substrate 1 before the device epitaxial process, for optical alignment calibration in the subsequent patterning process of the epitaxial structure on the transparent substrate, as detailed below.

[0030] Next, an epitaxial process is performed on the transparent substrate 1 to form an epitaxial structure 20. Then, a photoresist layer 30 and an alignment mark 32 are formed on the epitaxial structure 20. The photoresist layer 30 is the so-called zero layer, used to establish the reference coordinate system for the entire wafer and to set the alignment mark 32. A top-view magnified view of the alignment mark is shown in Figure 1, in the partially magnified area indicated by the scribed line. It should be noted that the aforementioned epitaxial structure 20 can grow different epitaxial films according to the design requirements of the device in actual applications, thereby forming different types of devices, such as Schottky diodes or high electron mobility transistors (HEMTs) applied on third-generation semiconductor transparent substrates, but not limited to these. Since this invention does not focus on the internal epitaxial structure design of the components, the epitaxial structure is only represented by an epitaxial structure 20, and the detailed technical details of the component structure are omitted here. Those skilled in the art can easily apply the optical alignment calibration technology of this invention to the epitaxial process of various components to obtain high-precision and stable alignment calibration.

[0031] Please refer to Figure 1 for a detailed description of the distributed Bragg reflector structure 10 disposed on the back side of the transparent substrate 1 and opposite to the epitaxial structure 20. As shown in the figure, in a preferred embodiment, the distributed Bragg reflector structure 10 of the present invention is a dual-band distributed Bragg reflector, allowing visible light in the 500-750 nm wavelength range to substantially and sequentially penetrate the epitaxial structure 20, the transparent substrate 1, and the distributed Bragg reflector structure 10. On the other hand, other light rays besides visible light, such as, but not limited to, ultraviolet light with a wavelength of 436 nm and / or infrared light with a wavelength of 940 nm, can be substantially reflected back into the transparent substrate 1 by the distributed Bragg reflector structure 10.

[0032] In detail, in a preferred embodiment, the distributed Bragg reflector structure 10 of the present invention has two sets of symmetrical optical thin film stacked structures, including a first symmetrical film stack S1 and a second symmetrical film stack S2. The first symmetrical film stack S1 is composed of a plurality of pairs of alternately stacked optical dielectric thin films, each pair having two types of optical dielectric thin films, including a first oxide thin film and a second oxide thin film. Similarly, the second symmetrical film stack S2 is also composed of a plurality of pairs of alternately stacked first oxide thin films and second oxide thin films. Specifically, the first oxide thin film is a high refractive index oxide thin film, and the second oxide thin film is a low refractive index oxide thin film. For example, the first oxide thin film may be, but is not limited to, titanium dioxide (TiO2) with a refractive index of approximately 2.2 to 2.7. The second oxide thin film may be, but is not limited to, silicon dioxide (SiO2) with a refractive index of approximately 1.4 to 1.5. In essence, the first oxide film and the second oxide film can be selected from oxide dielectric materials with a refractive index range of 1.4 to 3.0. For example, two high- and low-refractive-index oxide dielectric materials can be selected from silicon dioxide (SiO2), titanium dioxide (TiO2), tantalum pentoxide (Ta2O5), niobium pentoxide (Nb2O5), aluminum oxide (Al2O3), zirconium dioxide (ZrO2) and other oxide dielectric materials as two oxide films stacked alternately.

[0033] Taking titanium dioxide (TiO2) as the first oxide film and silicon dioxide (SiO2) as the second oxide film as an example, the distributed Bragg reflector structure 10 with dual-band characteristics of the present invention is composed of a first symmetrical film stack S1 and a second symmetrical film stack S2. Each symmetrical film stack has 11 layers of alternating high and low refractive index oxide films, but this is not a limitation. For example, the distributed Bragg reflector structure 10 of the present invention can be composed of two or more sets of film stacks, and the number of logarithms or layers of two alternating optical films in each symmetrical film stack can be increased or decreased according to the actual application.

[0034] Taking the distributed Bragg reflector structure 10 as an example, which consists of two sets of film stacks, a first symmetrical film stack S1 and a second symmetrical film stack S2, and each set of film stacks has 11 oxide thin films, as shown in Table 1 and Figure 1 below, the first symmetrical film stack S1 includes an oxide thin film L1, an oxide thin film L2, an oxide thin film L3...an eleventh oxide thin film L11, and the second symmetrical film stack S2 includes an oxide thin film L12...an oxide thin film L20, an oxide thin film L21, and an oxide thin film L22, and each oxide thin film is made of alternating layers of titanium dioxide (TiO2) and silicon dioxide (SiO2). Since both of these oxide dielectric materials are high-temperature resistant materials, with titanium dioxide (TiO2) having a melting point of approximately 1843°C and silicon dioxide (SiO2) having a melting point of approximately 1713°C, the distributed Bragg reflector structure 10 of the present invention has the ability to withstand process temperatures exceeding 800°C. First symmetric membrane stack S1 Second symmetric membrane stack S2 number of floors L1 L2 L3 … L11 L12 … L20 L21 L22 film TiO2 SiO2 TiO2 TiO2 SiO2 SiO2 TiO2 SiO2 Table 1

[0035] Specifically, to increase the reflection efficiency of the reflector, the present invention arranges a first front-to-back symmetry relationship and a second front-to-back symmetry relationship between the layers in the first symmetric film stack S1 and the second symmetric film stack S2 of the distributed Bragg reflector structure 10. Please refer to Figure 2, which shows a schematic diagram of the two front-to-back symmetry relationships of the two sets of symmetric film stacks in the distributed Bragg reflector structure of the present invention. In detail, taking the aforementioned embodiment as an example, the first front-to-back symmetry relationship refers to the fact that, with the central layer L6 of the first symmetric film stack S1 as the center, the thickness and oxide film material of each layer before and after this central layer are the same. Please refer to Figures 1 and 2 together with Table 1. The 5th oxide film L5 and the 7th oxide film L7, located before and after the central layer L6, have the same thickness, approximately 49.3 nanometers (nm). The oxide film material is titanium dioxide (TiO2) in both cases. Furthermore, in the first symmetrical film stack S1, the 1st oxide film L1 and the 11th oxide film L11, located at the very front and the very back of the central layer L6, have the same thickness, approximately 24.6 nanometers (nm). The oxide film material is also titanium dioxide (TiO2). Similarly, the second front-back symmetry refers to the fact that, with the central layer L17 of the second symmetrical film stack S2 as the center, the thickness and oxide film material of all layers before and after this central layer are the same. For example, the 16th oxide film L16 and the 18th oxide film L18, located before and after the central layer L17, have the same thickness, approximately 205.2 nanometers (nm), and the oxide film material is silicon dioxide (SiO2). In addition, in the second symmetric film stack S2, the 12th oxide film L12 and the 22nd oxide film L22, located at the front and back of the central layer L17, have the same thickness, approximately 102.6 nanometers (nm), and the oxide film material is silicon dioxide (SiO2).

[0036] In the specific embodiments described above, the thickness of each first oxide film and each second oxide film in the first symmetrical film stack S1 ranges from 20 to 60 nanometers (nm). On the other hand, the thickness of each first oxide film and each second oxide film in the second symmetrical film stack S2 ranges from 50 to 220 nanometers (nm). Thus, the total thickness of the distributed Bragg reflector structure 10 of the present invention, composed of these two sets of symmetrical film stacks, ranges from 800 nanometers (nm) to 3 micrometers (µm).

[0037] Furthermore, to achieve a dual-band reflection effect, preferably, the thickness of each low-refractive-index oxide film and each high-refractive-index oxide film in the second symmetrical film stack S2 (totaling 11 layers) is greater than the thickness of each low-refractive-index oxide film and each high-refractive-index oxide film in the first symmetrical film stack S1 (also totaling 11 layers). Under this film structure, the dual-band Bragg reflector structure of the present invention can achieve the following design spectrum characteristics: the optical reflection efficiency substantially achievable by the first symmetrical film stack S1 reaches a reflectance greater than 80% in the 436 nm band, with a full width at half maximum (FWHM) of 130-150 nm, and is applicable to ultraviolet light wavelengths of 370-500 nm. On the other hand, the optical reflection efficiency that its second symmetric film stack S2 can substantially achieve is a reflectance (R%) greater than 80% in the 940 nm band, a half-width at half-maximum (FWHM) of 200–400 nm, and an applicable infrared wavelength range of 750–1100 nm. Moreover, it achieves an average transmittance (T%) greater than 80% in the visible light region, and its applicable visible light wavelength range is 500–750 nm, as shown in Figure 3.

[0038] As described above, the dual-band Bragg reflector structure of this invention achieves a high reflectivity of over 80% in the 436 nm and 940 nm wavelengths outside the visible light region, and provides a high average transmittance of over 80% in the 500-750 nm visible light region. This allows for the application of 940 nm infrared light for edge alignment of the transparent substrate, overcoming the limitation of visible light's inability to align transparent substrate edges. Furthermore, the 436 nm wavelength can be used for G-line exposure in subsequent photolithography processes to enhance exposure accuracy and intensity. On the other hand, in the visible light band, the dual-band Bragg reflector structure of this invention allows visible light to substantially penetrate the transparent substrate and the reflector structure itself without causing reflection that would interfere with the calibration signal of the alignment marks, thereby enhancing the calibration signal of the alignment marks 32 on the surface of the wafer photoresist layer 30. Furthermore, the material of this reflector film is an oxide dielectric material, thus possessing high-temperature resistance, withstanding process temperatures up to 800°C. This ensures the stability of the reflector structure in subsequent high-temperature thin-film deposition processes, thereby improving process accuracy and efficiency. This heat resistance is substantially different from reflectors made using metals such as silver and aluminum, because these metals have low melting points and are unsuitable for subsequent high-temperature processes. In this way, the technology of this invention possesses characteristics such as high-temperature resistance and high reflectivity in both bands, achieving superior optical alignment calibration effects across multiple bands.

[0039] Please refer to Figure 4, which shows a schematic diagram of the manufacturing process steps of the semiconductor structure of the present invention. First, in step S01, a transparent substrate is provided. Second, in step S02, a distributed Bragg reflector structure is formed and disposed on one back side of the transparent substrate. The distributed Bragg reflector structure includes: a first symmetrical film stack having a plurality of pairs of alternating low-refractive-index oxide films and high-refractive-index oxide films; and a second symmetrical film stack having a plurality of pairs of alternating low-refractive-index oxide films and high-refractive-index oxide films. The thickness of each oxide film in the second symmetrical film stack is greater than the thickness of each oxide film in the first symmetrical film stack, such that visible light can substantially and sequentially penetrate the transparent substrate and the distributed Bragg reflector structure, but other light rays besides visible light can be substantially reflected back into the transparent substrate by the distributed Bragg reflector structure. The description of the relevant components can be found in the foregoing content and will not be repeated here.

[0040] The above embodiments are merely illustrative of the implementation of the present invention and to explain its technical features, and are not intended to limit the scope of protection of the present invention. Any changes or equivalent arrangements that can be easily made by those skilled in the art are within the scope of the present invention, and the scope of protection of the present invention shall be determined by the scope of the patent application.

[0041] 1:Transparent substrate 10: Distributed Bragg mirror structure 20: Epitaxial Structure 30: Photoresist layer 32: Alignment Mark 100: Semiconductor Structure L1: First oxide film L2: Second oxide film L3: Third oxide film L4: Fourth oxide film L6: 6th oxide film L8: 8th oxide film L9: 9th layer oxide film L10: 10th oxide film L11: 11th oxide film L12: 12th oxide film L13: 13th oxide film L14: 14th layer oxide film L15: 15th layer oxide film L17: 17th layer oxide film L19: 19th layer oxide film L20: 20th oxide film L21: 21st oxide film L22: 22nd oxide film S1: First symmetric membrane stack S2: Second symmetric membrane stack

Claims

1. A semiconductor structure comprising: a transparent substrate; an epitaxial structure disposed on one side of the transparent substrate; and a distributed Bragg reflector structure disposed on a back side of the transparent substrate opposite to the epitaxial structure, comprising: a first symmetrical film stack having a plurality of pairs of alternating stacked first oxide films and second oxide films, wherein the refractive index of one of the first oxide films is greater than the refractive index of one of the second oxide films; and a second symmetrical film stack having a plurality of pairs of alternating stacked first oxide films and second oxide films, wherein the thickness of each of the first oxide films and each of the second oxide films in the second symmetrical film stack is greater than the thickness of each of the first oxide films and each of the second oxide films in the first symmetrical film stack, wherein... Visible light can substantially pass through the epitaxial structure, the transparent substrate, and the distributed Bragg reflector structure in a substantial sequence, but other light rays besides the visible light can be substantially reflected back into the transparent substrate by the distributed Bragg reflector structure.

2. The semiconductor structure as claimed in claim 1, wherein the thicknesses of each of the first oxide films and each of the second oxide films in the second symmetrical film stack have a second front-to-back symmetry relationship.

3. The semiconductor structure as claimed in claim 1, wherein the refractive index of one of the first oxide film and the second oxide film is in the range of 1.4 to 3.

0.

4. The semiconductor structure as described in claim 1, wherein the first oxide film and the second oxide film are two of silicon dioxide (SiO2), titanium dioxide (TiO2), tantalum pentoxide (Ta2O5), niobium pentoxide (Nb2O5), aluminum oxide (Al2O3), and zirconium dioxide (ZrO2).

5. The semiconductor structure as claimed in claim 1, wherein the thickness of each of the first oxide film and each of the second oxide film in the first symmetric film stack is in the range of 20 to 60 nanometers (nm).

6. The semiconductor structure as claimed in claim 1, wherein the thickness of each of the first oxide film and each of the second oxide film in the second symmetric film stack ranges from 50 to 220 nanometers (nm).

7. The semiconductor structure as described in claim 1, wherein the total thickness of one of the distributed Bragg mirror structures ranges from 800 nanometers (nm) to 3 micrometers (µm).

8. The semiconductor structure as described in claim 1, wherein the other light includes dual-band light of 436 nanometers (nm) and 940 nanometers (nm).

9. A semiconductor structure comprising: a transparent substrate; and a distributed Bragg reflector structure disposed on a back side of the transparent substrate, comprising: a first symmetrical film stack disposed on a back side of the transparent substrate, the first symmetrical film stack having a plurality of pairs of alternately stacked low-refractive-index oxide films and high-refractive-index oxide films; and a second symmetrical film stack having a plurality of pairs of alternately stacked low-refractive-index oxide films and high-refractive-index oxide films, wherein the thickness of each low-refractive-index oxide film and each high-refractive-index oxide film in the second symmetrical film stack is greater than the thickness of each low-refractive-index oxide film and each high-refractive-index oxide film in the first symmetrical film stack, wherein... Visible light can substantially pass through the transparent substrate and the distributed Bragg reflector structure in a sequential manner, but other light rays besides the visible light can be substantially reflected back into the transparent substrate by the distributed Bragg reflector structure.

10. The semiconductor structure as claimed in claim 9, wherein the refractive index of one of the low-refractive-index oxide films and the high-refractive-index oxide films is in the range of 1.4 to 3.

0.

11. The semiconductor structure as claimed in claim 9, wherein the low-refractive-index oxide film and the high-refractive-index oxide film are two of silicon dioxide (SiO2), titanium dioxide (TiO2), tantalum pentoxide (Ta2O5), niobium pentoxide (Nb2O5), aluminum oxide (Al2O3), and zirconium dioxide (ZrO2).

12. The semiconductor structure as claimed in claim 9, wherein the thickness of each of the low-refractive-index oxide films and each of the high-refractive-index oxide films in the first symmetrical film stack ranges from 20 to 60 nanometers (nm).

13. The semiconductor structure as claimed in claim 9, wherein the thickness of each of the low-refractive-index oxide films and each of the high-refractive-index oxide films in the second symmetric film stack ranges from 50 to 220 nanometers (nm).

14. The semiconductor structure as claimed in claim 9, wherein the total thickness of one of the distributed Bragg mirror structures ranges from 800 nanometers (nm) to 3 micrometers (µm).

15. The semiconductor structure as claimed in claim 9, wherein the other light comprises dual-band light of 436 nanometers (nm) and 940 nanometers (nm).

16. A method for manufacturing a semiconductor structure, comprising: providing a transparent substrate; and forming a distributed Bragg reflector structure disposed on a back side of the transparent substrate, the distributed Bragg reflector structure comprising: a first symmetrical film stack disposed on a back side of the transparent substrate, having a plurality of pairs of alternately stacked low-refractive-index oxide films and high-refractive-index oxide films; and a second symmetrical film stack having a plurality of pairs of alternately stacked low-refractive-index oxide films and high-refractive-index oxide films, wherein the thickness of each low-refractive-index oxide film and each high-refractive-index oxide film in the second symmetrical film stack is greater than the thickness of each low-refractive-index oxide film and each high-refractive-index oxide film in the first symmetrical film stack, wherein... Visible light can substantially pass through the transparent substrate and the distributed Bragg reflector structure in a sequential manner, but other light rays besides the visible light can be substantially reflected back into the transparent substrate by the distributed Bragg reflector structure.

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