Light inlet surface expansion type three-dimensional microarray structure

Abstract

The utility model discloses a light incident surface expansion type three-dimensional microarray structure which comprises a silicon wafer body, three-dimensional microstructures arranged in an array mode are formed on the silicon wafer body, the three-dimensional microstructures are inverted pyramid-shaped, the silicon wafer body is a Si (100) crystal face, and the side face of a cavity of the inverted pyramid-shaped three-dimensional microstructures is a Si (111) crystal face. In the three-dimensional micro-array structure formed by the utility model, the surface area of a single three-dimensional micro-structure can be increased by 73%, so that the spectral absorption efficiency is effectively improved; incident light can be internally reflected for multiple times through the inverted pyramid type three-dimensional microstructure side face (Si (111) crystal face), multiple times of absorption are formed, and the spectral absorption efficiency is further improved.

Description

Technical Field

[0001] This utility model belongs to the field of semiconductor technology and relates to a light-gathering surface extended three-dimensional microarray structure. Background Technology

[0002] Photosensitive chips are a core component of photodetectors. The high photoelectric conversion efficiency of photosensitive chips directly affects the responsivity of photodetectors. Currently, traditional photosensitive chips all employ planar structures. Limited by the inherent band structure of photoelectric materials and the surface area size of the photosensitive chip, the photoelectric conversion efficiency of photosensitive chips has become one of the bottlenecks restricting high-responsivity photodetectors. Furthermore, the field of solar cells also faces the challenge of further improving photoelectric conversion efficiency.

[0003] In recent years, the popular black silicon technology has achieved the fabrication of micro- and nano-structures on the silicon surface by using techniques such as femtosecond laser irradiation, resulting in a high aspect ratio cone structure. At the same time, combined with energy level doping technology, it effectively improves the photoelectric conversion efficiency in the near-ultraviolet to near-infrared (250nm~2500nm) band. However, there are still practical difficulties in achieving high photoelectric conversion efficiency based on black silicon technology: (1) The black silicon fabrication process is not a traditional standard semiconductor process, and there is no relevant mature equipment. It is necessary to build a dedicated platform, and the process repeatability is poor; (2) The fabrication process includes processes such as energy absorption, melting, doping, and recrystallization, which have a long cycle; (3) Black silicon has extremely high surface activity and is prone to adsorbing water and oxygen in the atmosphere, thus becoming ineffective. It is necessary to passivate the dangling bonds on the black silicon surface and internal structural defects in situ, which is technically difficult. Utility Model Content

[0004] (I) Purpose of the utility model

[0005] The purpose of this invention is to address the shortcomings of existing technologies and propose a light-gathering surface extended three-dimensional microarray structure based on the theory of anisotropic wet etching of single-crystal silicon, in response to practical needs.

[0006] (II) Technical Solution

[0007] To solve the above-mentioned technical problems, this utility model provides a light-gathering surface extended three-dimensional micro-array structure, which includes a silicon wafer body, the silicon wafer body forming an array of three-dimensional microstructures, the three-dimensional microstructures being inverted pyramid shape, the silicon wafer body being a Si(100) crystal plane, and the side of the cavity of the inverted pyramid-shaped three-dimensional microstructure being a Si(111) crystal plane.

[0008] The inverted pyramid-shaped three-dimensional microstructure cavity reflects incident light multiple times from its side, resulting in multiple absorptions.

[0009] In the three-dimensional microstructure, the angle θ between the Si(100) crystal plane and the Si(111) crystal plane is 54.74°.

[0010] The inverted pyramid-shaped three-dimensional microstructure cavity has four sides, all of which are identical triangles. The side length of the microstructure is L, and the geometric relationship between the height H of the lateral triangles and the surface area S2 of the three-dimensional microstructure is H = L / (2×cosθ) and S2 = 4×(L×H) / 2 = L. 2 / cosθ, the surface area S2 of the three-dimensional microstructure is compared to the surface area S1 of the planar structure by L. 2 The increase is ΔS = (S2 - S1) / S1 = (1 - cosθ) / cosθ.

[0011] The three-dimensional microarray structure is an M×N array structure, where M and N are both integers.

[0012] The front side of the silicon wafer body is a polished crystal surface, and a three-dimensional microstructure is formed on the front side of the silicon wafer body.

[0013] (III) Beneficial Effects

[0014] The above-mentioned technical solution provides an extended light-gathering surface three-dimensional microarray structure and its fabrication method, which have the following beneficial effects:

[0015] (1) In the three-dimensional microarray structure formed by this utility model, the surface area of ​​a single three-dimensional microstructure can be increased by 73%, which effectively improves the spectral absorption efficiency; the side surface (Si(111) crystal plane) of the inverted pyramid-shaped three-dimensional microstructure can reflect the incident light internally multiple times, forming multiple absorptions, which further improves the spectral absorption efficiency.

[0016] (2) The fabrication process of the three-dimensional microarray structure proposed in this utility model is simple and easy to realize the M×N array structure. Attached Figure Description

[0017] Figure 1 Scanning electron microscope (SEM) image of the fabrication process of the extended three-dimensional microarray structure with light-gathering surface.

[0018] Figure 2 Flowchart of the fabrication process for an extended three-dimensional microarray structure with an extended light-gathering surface. Detailed Implementation

[0019] To make the objectives, contents, and advantages of this utility model clearer, the specific embodiments of this utility model will be described in further detail below with reference to the accompanying drawings and examples.

[0020] See Figure 1 The light-gathering surface extended three-dimensional microarray structure in this embodiment includes a silicon wafer body, which forms an array of three-dimensional microstructures. The three-dimensional microstructures are inverted pyramid shapes. The silicon wafer body has a Si (100) crystal plane, and the side of the cavity of the inverted pyramid-shaped three-dimensional microstructure has a Si (111) crystal plane.

[0021] The inverted pyramid-shaped three-dimensional microstructure cavity reflects incident light multiple times from its side, resulting in multiple absorptions and further improving photoelectric conversion efficiency.

[0022] In the three-dimensional microstructure, the angle θ between the Si(100) crystal plane and the Si(111) crystal plane is 54.74°.

[0023] The inverted pyramid-shaped three-dimensional microstructure cavity has four sides, all of which are identical triangles.

[0024] The side length of the microstructure is L. The geometric relationship between the height (H) of the lateral triangle and the surface area (S2) of the three-dimensional microstructure is H = L / (2×cosθ) and S2 = 4×(L×H) / 2 = L 2 / cosθ, therefore the surface area of ​​the three-dimensional microstructure (S2) is compared with the surface area of ​​the planar structure (S1=L 2 The increase is ΔS = (S2 - S1) / S1 = (1 - cosθ) / cosθ, which is ΔS = 73.3%.

[0025] The surface area of ​​a single three-dimensional microstructure is 73.3% larger than that of a planar structure, effectively improving photoelectric conversion efficiency; the light-gathering surface extended three-dimensional microstructure can be fabricated into an M×N array.

[0026] See Figure 1 and Figure 2 The fabrication method of the extended three-dimensional microarray structure with light-gathering surface in this embodiment includes the following steps:

[0027] (a) Surface polishing: A 4-inch Si(100) crystal silicon wafer is selected as the silicon wafer body and the front side is polished.

[0028] (b) Deposition of mask layer: The mask layer deposited on the front and back sides of the silicon wafer can be a SiO2 layer, a Si3N4 layer or a metal Cr layer;

[0029] (c) Patterned mask layer: front mask layer photolithography, the pattern to be etched on the silicon wafer is made into a photomask, and chromium is etched by exposure, development and cerium ammonium nitrate solution. The pattern to be retained is protected by photoresist, and the photomask pattern is transferred to the surface of the silicon wafer. The part not protected by the mask layer is exposed to the Si surface, forming the window to be etched.

[0030] (d) Anisotropic wet etching of the Si(100) crystal plane on the front side: The patterned wafer is immersed in the etching solution, and anisotropic wet etching of the Si(100) crystal plane is performed until an inverted pyramid-shaped cavity is formed, such as Figure 1 As shown in (b);

[0031] Among them, the anisotropic etching solution for the silicon wafer body surface is selected from alkaline inorganic etchant (KOH solution), TMAH system (tetramethylamine hydroxide) or EPW system (ethylenediamine, catechol and water); when the mask layer deposited on the silicon wafer body is selected from SiO2 layer, Si3N4 layer or metal Cr layer, the corresponding mask layer removal methods are hydrofluoric acid solution (HF) etching, reactive ion etching (RIE) or cerium ammonium nitrate solution ((NH4)Ce(NO3)5) etching.

[0032] When using an alkaline inorganic etchant (KOH solution) for anisotropic etching of silicon wafers, isopropanol (IPA) needs to be added to the etchant to improve the flatness of the silicon surface after etching.

[0033] (e) Remove the mask layer:

[0034] Example

[0035] Taking KOH solution as an anisotropic etchant, a metallic Cr layer as a mask layer, and cerium ammonium nitrate solution as an etchant to remove the Cr mask layer as an example, the fabrication method of the light-advancing surface extended three-dimensional microarray structure includes the following steps:

[0036] (a) Surface polishing: A 4-inch Si(100) crystal silicon wafer is selected as the silicon wafer body and the front side is polished.

[0037] (b) Deposition of mask layer: 300 nm thick chromium (Cr) layer is deposited on both sides of the silicon wafer by magnetron sputtering;

[0038] (c) Patterned mask layer: front chromium mask layer photolithography, the pattern to be etched on the silicon wafer is made into a photomask, and chromium is etched by exposure, development and cerium ammonium nitrate solution. The pattern to be retained is protected by photoresist, and the photomask pattern is transferred to the surface of the silicon wafer. The part not protected by the chromium layer is exposed to the Si surface, forming the window to be etched.

[0039] (d) Anisotropic wet etching of the Si(100) crystal plane on the front side: The patterned wafer is immersed in KOH etchant (50℃, 30wt%, with isopropanol (IPA) added to the etchant) to perform anisotropic wet etching of the Si(100) crystal plane until an inverted pyramid cavity is formed, such as Figure 1 As shown in (b);

[0040] (e) Removal of the mask layer: The chromium mask layer was removed using a cerium ammonium nitrate solution to obtain an extended three-dimensional microarray structure with an extended light-gathering surface, such as... Figure 1 As shown in (c).

[0041] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A light-gathering surface extended three-dimensional microarray structure, characterized in that, It includes a silicon wafer body, on which an array of three-dimensional microstructures are formed. The three-dimensional microstructures are inverted pyramid shape. The silicon wafer body has a Si(100) crystal plane, and the side of the cavity of the inverted pyramid-shaped three-dimensional microstructure has a Si(111) crystal plane.

2. The light-gathering surface extended three-dimensional microarray structure as described in claim 1, characterized in that, The inverted pyramid-shaped three-dimensional microstructure cavity reflects incident light multiple times from its sides, resulting in multiple absorptions.

3. The light-gathering surface extended three-dimensional microarray structure as described in claim 2, characterized in that, In the three-dimensional microstructure, the angle θ between the Si(100) crystal plane and the Si(111) crystal plane is 54.74°.

4. The light-gathering surface extended three-dimensional microarray structure as described in claim 3, characterized in that, The inverted pyramid-shaped three-dimensional microstructure cavity has four sides, all of which are identical triangles.

5. The light-gathering surface extended three-dimensional microarray structure as described in claim 4, characterized in that, The microstructure has a side length of L. The geometric relationship between the height H of the lateral triangle and the surface area S2 of the three-dimensional microstructure is H = L / (2×cosθ), S2 = 4×(L×H) / 2 = L 2 / cosθ.

6. The light-gathering surface extended three-dimensional microarray structure as described in claim 5, characterized in that, The surface area S2 of the three-dimensional microstructure is equal to the surface area S1 of the planar structure. 2 The increase is ΔS = (S2 - S1) / S1 = (1 - cosθ) / cosθ.

7. The light-gathering surface extended three-dimensional microarray structure as described in claim 6, characterized in that, The three-dimensional microarray structure is an M×N array structure, where M and N are both integers.

8. The light-gathering surface extended three-dimensional microarray structure as described in claim 7, characterized in that, The front side of the silicon wafer is a polished crystal surface, and a three-dimensional microstructure is formed on the front side of the silicon wafer.

9. A photosensitive chip, characterized in that, The light-gathering surface extended three-dimensional microarray structure includes any one of claims 1-8.

10. A photodetector, characterized in that, Includes the photosensitive chip as described in claim 9.

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