Light sensing element and manufacturing method thereof

Abstract

The invention relates to a light sensing element and a manufacturing method thereof. The light sensing element comprises a substrate, a light action area, a filtering layer and a carbonized side wall. Wherein the light action area is arranged on the substrate, the filtering layer covers the light action area, only light with a specific wavelength is selectively allowed to pass through and is received by the light action area, and light with other wavelengths is blocked from passing through. The carbonized side wall covers the side wall of the filtering layer and part of the side wall of the substrate and can prevent light rays of other wavelengths except the specific wavelength from penetrating through the side wall of the substrate and being received by the light action area.

Description

Technical Field

[0001] The present invention relates to a light sensing element and a manufacturing method thereof, and in particular to a light sensing element which selectively allows light of a specific wavelength to penetrate and a manufacturing method thereof. Background Art

[0002] A bandpass filter (BPF) is an optical component that selectively allows light of a specific wavelength range to pass through while filtering out light of other wavelengths. This filter is very useful in optical sensing devices because it can be used to separate and detect specific wavelengths or frequencies of light in a certain area, and is therefore used in technical fields such as biomedical imaging and environmental monitoring.

[0003] The working principle of optical bandpass filters is based on the interference and reflection of light. They usually consist of a transparent substrate and a multilayer thin film structure. These thin film layers are alternately stacked in different materials and have specific optical thicknesses to achieve high transmittance for specific wavelengths and high reflectivity for other wavelengths. When light hits the surface of the filter, it enters the multilayer thin film structure of the filter, and the light interferes and reflects at the material interface between the multilayer thin film structures. Since different wavelengths of light propagate at different speeds in different materials, the interference between the multilayer thin film structures will cause some wavelengths of light to be phase-added and enhanced, while other wavelengths of light will be phase-destructed and weakened. Through proper design, the multilayer thin film structure of the filter can form a resonant cavity, so that light of specific wavelengths can be enhanced, while other wavelengths of light will be reflected or absorbed, allowing light beams of specific wavelengths to pass through the filter, forming the so-called "bandpass" effect.

[0004] However, although conventional sensing devices can use bandpass filters to filter specific light wavelengths, in actual applications, some light still enters the sensing device and generates photocurrent on the photodiode interface, affecting the detection accuracy. To overcome the above problems, the industry urgently needs an innovative light sensing structure and manufacturing method to improve the above filtering problem. Summary of the invention

[0005] The main purpose of the present invention is to provide an innovative light sensing element and a manufacturing method thereof, so as to improve the problems of traditional light sensing elements such as erroneous signals caused by poor filtering and reduced sensing accuracy.

[0006] To achieve the above-mentioned purpose, the present invention provides a light sensing element, wherein the light sensing element comprises a substrate, a light action region, a filter layer and a carbonized sidewall. The light action region is arranged on the substrate, and the filter layer covers the light action region, selectively allowing only a light of a specific wavelength to pass through and be received by the light action region, while blocking light of other wavelengths from passing through. The carbonized sidewall covers the sidewall of the filter layer and a portion of the sidewall of the substrate, and can block light of other wavelengths other than the specific wavelength from passing through the sidewall of the substrate and being received by the light action region.

[0007] In one embodiment, the filter layer is a bandpass filter layer.

[0008] In one embodiment, the depth of the carbonized sidewalls is less than approximately 1 / 4 of the thickness of the substrate.

[0009] In one embodiment, the depth of the carbonized sidewalls is between 40 μm and 50 μm.

[0010] In one embodiment, the carbonized sidewalls are formed by irradiating the filter layer sidewalls and a portion of the substrate sidewalls with a high-energy laser beam.

[0011] In one embodiment, the light of a specific wavelength is ultraviolet light having a wavelength range of about 100 nm to 400 nm.

[0012] In one embodiment, the substrate is a silicon substrate.

[0013] To achieve the above-mentioned purpose, the present invention provides a method for manufacturing a light sensing element, comprising: providing a substrate; forming a light action area, which is arranged on the substrate; forming a filter layer, which covers the light action area, selectively allowing only light of a specific wavelength to pass through and be received by the light action area, while blocking light of other wavelengths from passing through; and forming a carbonized sidewall, which covers the sidewall of the filter layer and a portion of the sidewall of the substrate, wherein the carbonized sidewall can block light of other wavelengths other than the specific wavelength from passing through the sidewall of the substrate and being received by the light action area.

[0014] In one embodiment, the step of forming the carbonized sidewall is: providing a high-energy laser beam to irradiate the sidewall of the filter layer and a portion of the sidewall of the substrate.

[0015] In one embodiment, the step of forming the carbonized sidewall is: forming a carbonized sidewall having a depth less than about 1 / 4 of the thickness of the substrate.

[0016] After referring to the accompanying drawings and the embodiments described below, a person having ordinary technical knowledge in this technical field will understand other objects of the present invention, as well as the technical means and implementation schemes of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the structure of a light sensing element in one embodiment of the present invention;

[0018] Figure 2 is a schematic diagram of manufacturing a light sensing element according to an embodiment of the present invention;

[0019] Figure 3 is a schematic diagram of manufacturing a light sensing element according to an embodiment of the present invention; and

[0020] Figure 4 This is a magnified scanning electron microscope image of the carbonized sidewall in one embodiment of the present invention.

[0021] Description of Reference Numerals

[0022] 1 Light sensor

[0023] 10 substrate

[0024] 20 Light action area

[0025] 30 filter layer

[0026] 40 Upper electrode

[0027] 50 Lower electrode

[0028] 60 Carbonized sidewall

[0029] 100 Wafer

[0030] T Thickness. DETAILED DESCRIPTION

[0031] The present invention will be explained below by way of examples, and the examples of the present invention are not intended to limit the present invention to any specific environment, application or special method as described in the examples. Therefore, the description of the examples is only for the purpose of explaining the present invention, and is not intended to limit the present invention. It should be noted that in the following examples and drawings, elements that are not directly related to the present invention have been omitted and are not shown, and the dimensional relationship between the elements in the drawings is only for easy understanding, and is not intended to limit the actual proportion.

[0032] See also Figure 1, which is a schematic diagram of the structure of a light sensing element in an embodiment of the present invention. As shown in the figure, the light sensing element 1 in this embodiment includes a substrate 10, a light active area 20, a filter layer 30, an upper electrode 40, and a lower electrode 50. Among them, the substrate 10 is used as the bottom supporting material of the light sensing element 1, and is usually made of an optically transparent material to allow light to pass through. The material of the substrate 10 is usually selected from materials with good light transmittance, such as silicon, quartz, etc. In the embodiment of the present invention, a silicon substrate 10 with N-type doping is used as the substrate material. As for the thickness of the substrate 10, it can be adjusted according to specific application requirements and designs, usually in the range of hundreds of microns (μm) to several millimeters (mm). In the embodiment of the present invention, the thickness of the silicon substrate 10 is about 400 microns, and its line resistance value is about 0.008 to 0.0125 ohm-centimeters (Ω-cm).

[0033] Please continue reading Figure 1 , the light action region 20 includes a silicon diode photosensitive structure, which is arranged in the central area of ​​the substrate 10, as a part for detecting light signals, and is usually a P / N diode photosensitive structure for receiving light of a specific wavelength. Secondly, the filter layer 30 is a band pass filter layer covering the light action region 20, selectively allowing only light of a specific wavelength to pass through and be received by the light action region 20, and blocking light of other wavelengths from passing through. In one embodiment of the present invention, the filter layer 30 of the present invention only allows ultraviolet light with a specific wavelength in the range of about 100 nanometers (nm) to 400 nanometers to pass through, and blocks light of other wavelengths, such as visible light and infrared light in the wavelength range of 400 nanometers to 1100 nanometers, to avoid being absorbed by the light action region 20. The filter layer 30 is a multilayer thin film structure. In the present invention, the filter layer 30 can be a composite layer of tantalum pentoxide (Ta2O5) and silicon dioxide (SiO2), but is not limited thereto. The upper electrode 40 is disposed in the filter layer 30, and the lower electrode 50 is disposed on the back side of the substrate 10, for applying an electric field to control the optical properties of the filter layer 30. By changing the refractive index of the dielectric layer in the filter layer structure by voltage, the central wavelength or bandwidth of the filter can be adjusted.

[0034] A feature of the optical sensing element 1 of the present invention is that it further comprises a carbonized sidewall 60 disposed on the peripheral sidewall of the filter layer 30 and the peripheral sidewall of part of the substrate 10 to reduce the interference of external sidelight on the optical action area 20. Figure 1As shown, the carbonized sidewall 60 is used to block the aforementioned external light such as visible light or infrared light with a wavelength of about 400 nanometers to 1100 nanometers from entering the light sensing element 1 through the peripheral sidewalls of the substrate 10 and the filter layer 30 in the light sensing element 1 and being received by the light action area 20, thereby generating an error signal. In a preferred embodiment, the depth of the carbonized sidewall 60 is approximately less than 1 / 4 of the thickness of the substrate 10, for example, its depth is between 40 micrometers and 50 micrometers, and the width of the carbonized sidewall 60 is between 13 micrometers and 17 micrometers, but it is not limited thereto. The actual depth and width of the carbonized sidewall 60 can be adjusted accordingly according to the range of the light action area 20 in the light sensing element 1 to play the effect of substantially blocking external light from penetrating into the light action area.

[0035] Please refer to the combined Figures 2 to 3 , which shows the process steps of manufacturing a light sensing element in one embodiment of the present invention. Figure 2 The schematic diagram of a part of the structure of a wafer 100 before being divided is shown. The wafer 100 already has a part of the structure of several light sensing elements 1 before being divided, including a substrate 10, a light active area 20, a filter layer 30, an upper electrode 40 and a lower electrode 50. Please refer to the above content for the function of each component, which will not be repeated here. Before dividing the wafer 100, the area between each light sensing element is a functionally ineffective area, such as Figure 2 As shown in the dotted line range, the subsequent process will perform segmentation processing in this functional invalid area.

[0036] See also Figure 3 In this step, a high-energy laser beam is used to irradiate the functional ineffective area between each light sensing element, so that the high-energy laser beam focuses the energy on the sidewalls of the filter layer 30 and part of the sidewalls of the substrate 10, and carbonizes them, thereby forming a carbonized sidewall 60 on the sidewalls of the filter layer 30 and part of the sidewalls of the substrate 10, and the effect of blocking visible light and infrared light is achieved through the melted carbonized structure. In actual applications, a high-energy laser is used to perform secondary laser cutting on the ineffective area to form a carbonized sidewall 60 with a depth less than 1 / 4 of the thickness of the substrate, for example, between 40 microns and 50 microns, and a width between 13 microns and 17 microns on the sidewalls of the filter layer 30 and part of the sidewalls of the substrate 10. Figure 4 As shown in FIG. 1 , a scanning electron microscope magnified image of the carbonized sidewalls on the filter layer and the periphery of the substrate in the optical sensing element of the present invention is shown. The thickness T between the dotted lines in the figure is about 42 microns. After the laser processing is completed, the wafer 100 is finally cut by a wheel cutting method to form several Figure 1 The final structure of the light sensing element 1 is shown.

[0037] In summary, the optical sensing element of the present invention forms a carbonized sidewall structure on the sidewall of the optical sensing element through a high-energy laser to block external light, especially visible light and infrared light, from entering the interior through the sidewall of the element to cause erroneous signals, and only allows light in the ultraviolet wavelength range to penetrate into the interior of the element, thereby improving the detection accuracy of the optical sensing element.

[0038] The above embodiments are only used to illustrate the implementation scheme of the present invention and to explain the technical features of the present invention, and are not used to limit the protection scope of the present invention. Any changes or equivalent arrangements that can be easily completed by a person skilled in the art belong to the scope claimed by the present invention, and the scope of protection of the present invention shall be subject to the claims.

Claims

1. A light sensing element, comprising: a substrate; a light action area, disposed on the substrate; a filter layer, covering the light action area, selectively allowing only light of a specific wavelength to pass through and be received by the light action area, while blocking light of other wavelengths from passing through; and a carbonized side wall, covering the filter layer side wall and a portion of the substrate side wall, in, The carbonized sidewall can block the light of other wavelengths except the specific wavelength from passing through the substrate sidewall and being received by the light action area. 2 . The light sensing element as claimed in claim 1 , wherein the filter layer is a bandpass filter layer. 3 . The optical sensor device as claimed in claim 1 , wherein a depth of the carbonized sidewall is less than ¼ of a thickness of the substrate. 4 . The optical sensor device as claimed in claim 1 , wherein a depth of the carbonized sidewall is between 40 μm and 50 μm. 5 . The optical sensing device as claimed in claim 1 , wherein the carbonized sidewall is formed by irradiating the filter layer sidewall and a portion of the substrate sidewall with a high-energy laser beam. 6 . The light sensing element as claimed in claim 1 , wherein the light of the specific wavelength is ultraviolet light having a wavelength range of 100 nm to 400 nm. The light sensing device as claimed in claim 1 , wherein the substrate is a silicon substrate.

8. A method for manufacturing a light sensing element, comprising: providing a substrate; forming a light action area disposed on the substrate; forming a filter layer covering the light action area, selectively allowing only light of a specific wavelength to pass through and be received by the light action area, while blocking light of other wavelengths from passing through; and forming a carbonized side wall, covering the filter layer side wall and a portion of the substrate side wall, in, The carbonized sidewall can block the light of other wavelengths except the specific wavelength from passing through the substrate sidewall and being received by the light action area. 9 . The method for manufacturing a light sensing element as claimed in claim 8 , wherein the step of forming the carbonized sidewall comprises: providing a high-energy laser beam to irradiate the sidewall of the filter layer and a portion of the sidewall of the substrate. 10 . The method for manufacturing a light sensing device as claimed in claim 9 , wherein the step of forming the carbonized sidewall comprises: forming the carbonized sidewall with a depth less than 1 / 4 of the thickness of the substrate.

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