Light inlet surface expansion type three-dimensional microarray structure and preparation method thereof

Abstract

The invention 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 in an inverted pyramid shape, the silicon wafer body is a Si (100) crystal face, and the side face of a cavity of the inverted pyramid type three-dimensional microstructures is a Si (111) crystal face. In the formed three-dimensional micro-array structure, the surface area of a single three-dimensional micro-structure can be increased by 73%, and 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] The invention belongs to the technical field of semiconductors and relates to a light-incoming surface-expanded three-dimensional microarray structure and a preparation method thereof. Background Art

[0002] Photosensitive chips are the core components of photoelectric detection devices. High photoelectric conversion efficiency photosensitive chips directly affect the responsiveness of photoelectric detection devices. At present, the surface of traditional photosensitive chips adopts a planar structure. Limited by the inherent band structure of photoelectric materials and the surface area size of photosensitive chips, the photoelectric conversion efficiency of photosensitive chips has become one of the bottlenecks restricting high-responsiveness photoelectric detection devices. In addition, there is also the problem of further improving the photoelectric conversion efficiency in the field of solar cells.

[0003] In recent years, the popular black silicon technology uses femtosecond laser irradiation and other technologies to achieve the processing and preparation of micro-nano structures on the silicon surface, obtaining a sharp cone structure with a large aspect ratio, and at the same time combines energy level doping technology to effectively improve 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 preparation process is not a traditional standard semiconductor process, and there is no relevant mature equipment. It is necessary to build a dedicated platform by ourselves, and the process repeatability is poor; (2) The preparation process includes processes such as energy absorption, melting, doping, and recrystallization, and the cycle is long; (3) Black silicon has extremely high surface activity and is easily degraded by absorbing water and oxygen in the atmosphere. It is necessary to passivate the dangling bonds on the black silicon surface and the internal structural defects in situ, which is technically difficult. Summary of the invention

[0004] (I) Purpose of the invention

[0005] The purpose of the present invention is to propose a three-dimensional microarray structure with extended light-inlet surface and a preparation method thereof based on the theory of anisotropic wet etching of single-crystal silicon in response to actual needs and deficiencies in the prior art.

[0006] (II) Technical solution

[0007] In order to solve the above technical problems, the present invention provides a three-dimensional microarray structure with an expanded light-incoming surface, which includes a silicon wafer body, the silicon wafer body is formed with a three-dimensional microstructure arranged in an array, the three-dimensional microstructure is an inverted pyramid, the silicon wafer body is a Si(100) crystal plane, and the side of the inverted pyramid-shaped three-dimensional microstructure cavity is a Si(111) crystal plane.

[0008] Among them, the side of the inverted pyramid-shaped three-dimensional microstructure cavity reflects the incident light internally multiple times, forming multiple absorptions.

[0009] Among them, 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, which are identical triangles. The side length of the microstructure is L, and the geometric relationship between the side triangle height H and the three-dimensional microstructure surface area S2 is H = L / (2×cosθ), S2 = 4×(L×H) / 2 = L 2 / cosθ, the surface area of ​​the three-dimensional microstructure S2 is compared to the surface area of ​​the planar structure S1 = L 2 Increase value ΔS = (S2 - S1) / S1 = (1 - cosθ) / cosθ.

[0011] The present invention also provides a method for preparing a light-incoming surface-expanded three-dimensional microarray structure, comprising the following steps:

[0012] (a) Surface polishing: A 4-inch Si (100) silicon wafer was selected as the silicon wafer body and the front side was polished;

[0013] (b) Deposition of mask layer: The mask layer deposited on the front and back sides of the silicon wafer body can be SiO2 layer, Si3N4 layer or metal Cr layer;

[0014] (c) Patterned mask layer: front mask layer photolithography, the pattern to be etched on the silicon wafer is made into a photomask, and the chromium is corroded 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 body. The part not protected by the mask layer exposes the Si surface to form a window to be etched;

[0015] (d) Anisotropic wet etching of the Si (100) crystal plane on the front side: The patterned wafer is immersed in an etching solution and anisotropic wet etching of the Si (100) crystal plane is performed until an inverted pyramid-shaped cavity is formed. Figure 1 (b)

[0016] Among them, the anisotropic etching solution for the surface of the silicon wafer body is an alkaline inorganic etchant (KOH solution), TMAH system (tetramethylammonium hydroxide) or EPW system (ethylenediamine, catechol and water); when the mask layer deposited on the body is a SiO2 layer, a Si3N4 layer or a metal Cr layer, the corresponding mask layer removal methods are hydrofluoric acid solution (HF) corrosion, reactive ion etching (RIE) or cerium ammonium nitrate solution ((NH4)Ce(NO3)5) corrosion.

[0017] When an alkaline inorganic etchant (KOH solution) is selected as an anisotropic etchant for the surface of the silicon wafer, isopropyl alcohol (IPA) needs to be added to the etchant to improve the flatness of the silicon surface after etching.

[0018] (e) Removing the mask layer:

[0019] (III) Beneficial effects

[0020] The three-dimensional microarray structure with extended light-incoming surface and the preparation method thereof provided by the above technical solution have the following beneficial effects:

[0021] (1) In the three-dimensional microarray structure formed by the present invention, the surface area of ​​a single three-dimensional microstructure can be increased by 73%, effectively improving the spectral absorption efficiency; the side surface of the inverted pyramid-shaped three-dimensional microstructure (Si (111) crystal surface) can perform multiple internal reflections on the incident light, forming multiple absorptions, further improving the spectral absorption efficiency.

[0022] (2) The three-dimensional microarray structure preparation process proposed in the present invention is simple and easy to realize an M×N array structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a scanning electron microscope (SEM) image of the preparation process of the light-incoming surface extended three-dimensional microarray structure.

[0024] Figure 2 This is a process flow chart for preparing a three-dimensional microarray structure with extended light-incoming surface. DETAILED DESCRIPTION

[0025] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below in conjunction with the drawings and examples.

[0026] See also Figure 1 In this embodiment, the light-incoming surface-expanded three-dimensional microarray structure includes a silicon wafer body, which forms a three-dimensional microstructure arranged in an array. The three-dimensional microstructure is an inverted pyramid. The silicon wafer body is a Si(100) crystal plane, and the side of the inverted pyramid-shaped three-dimensional microstructure cavity is a Si(111) crystal plane.

[0027] The side of the inverted pyramid-shaped three-dimensional microstructure cavity reflects the incident light multiple times internally, forming multiple absorptions, further improving the photoelectric conversion efficiency.

[0028] In the three-dimensional microstructure, the angle θ between the Si(100) crystal plane and the Si(111) crystal plane is 54.74°.

[0029] The inverted pyramid-shaped three-dimensional microstructure cavity has four sides, and the four sides are identical triangles.

[0030] The side length of the microstructure is L, and the geometric relationship between the side triangle height (H) and the three-dimensional microstructure surface area (S2) is H = L / (2×cosθ), S2 = 4×(L×H) / 2 = L 2 / cosθ, so the surface area of ​​the three-dimensional microstructure (S2) is smaller than the surface area of ​​the planar structure (S1 = L 2)Increase value ΔS = (S2-S1) / S1 = (1-cosθ) / cosθ, that is, ΔS = 73.3%.

[0031] The surface area of ​​a single three-dimensional microstructure is 73.3% larger than that of a planar structure, effectively improving the photoelectric conversion efficiency; the light-incoming surface extended three-dimensional microstructure can be manufactured into an M×N array scale.

[0032] See also Figure 1 and Figure 2 The method for preparing the light-incoming surface extended three-dimensional microarray structure of this embodiment comprises the following steps:

[0033] (a) Surface polishing: A 4-inch Si (100) silicon wafer was selected as the silicon wafer body and the front side was polished;

[0034] (b) Deposition of mask layer: The mask layer deposited on the front and back sides of the silicon wafer body can be SiO2 layer, Si3N4 layer or metal Cr layer;

[0035] (c) Patterned mask layer: front mask layer photolithography, the pattern to be etched on the silicon wafer is made into a photomask, and the chromium is corroded 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 body. The part not protected by the mask layer exposes the Si surface to form a window to be etched;

[0036] (d) Anisotropic wet etching of the Si (100) crystal plane on the front side: The patterned wafer is immersed in an etching solution and anisotropic wet etching of the Si (100) crystal plane is performed until an inverted pyramid-shaped cavity is formed. Figure 1 (b)

[0037] Among them, the anisotropic etching solution for the surface of the silicon wafer body is an alkaline inorganic etchant (KOH solution), TMAH system (tetramethylammonium hydroxide) or EPW system (ethylenediamine, catechol and water); when the mask layer deposited on the silicon wafer body is a SiO2 layer, a Si3N4 layer or a metal Cr layer, the corresponding mask layer removal methods are hydrofluoric acid solution (HF) corrosion, reactive ion etching (RIE) or cerium ammonium nitrate solution ((NH4)Ce(NO3)5) corrosion.

[0038] When an alkaline inorganic etchant (KOH solution) is selected as an anisotropic etchant for the surface of the silicon wafer, isopropyl alcohol (IPA) needs to be added to the etchant to improve the flatness of the silicon surface after etching.

[0039] (e) Removing the mask layer:

[0040] Example

[0041] Taking KOH solution as an anisotropic etchant, a metal Cr layer as a mask layer and ammonium cerium nitrate solution as an etching solution for removing the Cr mask layer as an example, the method for preparing a light-incoming surface extended three-dimensional microarray structure includes the following steps:

[0042] (a) Surface polishing: A 4-inch Si (100) silicon wafer was selected as the silicon wafer body and the front side was polished;

[0043] (b) Deposition of mask layer: 300 nm thick chromium (Cr) is deposited on both sides of the silicon wafer by magnetron sputtering;

[0044] (c) Patterned mask layer: The front chromium mask layer is photolithographically processed to make a photomask with the pattern to be etched on the silicon wafer. The chromium is corroded by exposure, development and cerium ammonium nitrate solution. The pattern to be retained is protected by photoresist. The photomask pattern is transferred to the surface of the silicon wafer body. The part not protected by the chromium layer is exposed on the Si surface to form a window to be etched.

[0045] (d) Anisotropic wet etching of the front Si (100) crystal surface: The patterned wafer is immersed in a KOH etchant (50°C, 30 wt%, isopropyl alcohol (IPA) added to the etchant) to perform anisotropic wet etching of the Si (100) crystal surface until an inverted pyramid-shaped cavity is formed. Figure 1 (b)

[0046] (e) Removing the mask layer: Using cerium ammonium nitrate solution to remove the chromium mask layer, a three-dimensional microarray structure with an extended light-incoming surface is obtained, such as Figure 1 (c) as shown.

[0047] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A three-dimensional microarray structure with an extended light-incoming surface, characterized in that: The invention comprises a silicon wafer body, which forms a three-dimensional microstructure arranged in an array. The three-dimensional microstructure is an inverted pyramid. The silicon wafer body is a Si (100) crystal plane, and the side of the inverted pyramid three-dimensional microstructure cavity is a Si (111) crystal plane.

2. The light-incoming surface-extended three-dimensional microarray structure according to claim 1, characterized in that: The side of the inverted pyramid-shaped three-dimensional microstructure cavity reflects the incident light multiple times internally, forming multiple absorptions.

3. The light-incoming surface-extended three-dimensional microarray structure according to 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-incoming surface-extended three-dimensional microarray structure according to claim 3, characterized in that: The inverted pyramid-shaped three-dimensional microstructure cavity has four sides, which are identical triangles. The side length of the microstructure is L, and the geometric relationship between the side triangle height H and the three-dimensional microstructure surface area S2 is H = L / (2×cosθ), S2 = 4×(L×H) / 2 = L 2 / cosθ, the surface area of ​​the three-dimensional microstructure S2 is compared to the surface area of ​​the planar structure S1 = L 2 Increase value ΔS = (S2 - S1) / S1 = (1 - cosθ) / cosθ.

5. A method for preparing the light-incoming surface extended three-dimensional microarray structure according to claim 4, characterized in that: The following steps are involved: (a) Surface polishing: Si(100) crystal silicon wafer is selected as the silicon wafer body and the front side is polished; (b) Deposition of mask layer: The mask layer deposited on the front and back sides of the silicon wafer body can be SiO2 layer, Si3N4 layer or metal Cr layer; (c) Patterned mask layer: front mask layer photolithography, the pattern to be etched on the silicon wafer is made into a photomask, and the chromium is corroded 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 body. The part not protected by the mask layer exposes the Si surface to form a window to be etched; (d) Anisotropic wet etching of the Si (100) crystal plane on the front side: immersing the patterned wafer in an etching solution and performing anisotropic wet etching of the Si (100) crystal plane until an inverted pyramid-shaped cavity is formed; (e) Removing the mask layer.

6. The method for preparing a three-dimensional microarray structure with an extended light-incoming surface according to claim 5, characterized in that: In step (d), the anisotropic etching solution for the surface of the silicon wafer body is an alkaline inorganic etchant, a TMAH system or an EPW system; the alkaline inorganic etchant is a KOH solution, the TMAH system is tetramethylammonium hydroxide, and the EPW system is ethylenediamine, catechol and water.

7. The method for preparing a three-dimensional microarray structure with an extended light-incoming surface according to claim 6, characterized in that: In step (d), when an alkaline inorganic etchant is selected as the anisotropic etchant for the surface of the silicon wafer body, isopropyl alcohol is added to the etchant.

8. The method for preparing a three-dimensional microarray structure with an extended light-incoming surface according to claim 7, characterized in that: In step (e), when the mask layer deposited on the silicon wafer body is selected from SiO2 layer, Si3N4 layer or metal Cr layer, the corresponding methods for removing the mask layer are hydrofluoric acid solution HF etching, reactive ion etching RIE or ammonium cerium nitrate solution (NH4)Ce(NO3)5 etching.

9. The method for preparing a three-dimensional microarray structure with an extended light-incoming surface according to claim 8, characterized in that: In step (b), when Cr is selected as the mask layer, 300 nm thick chromium is magnetron sputtered on the front and back surfaces of the silicon wafer body.

10. The method for preparing a three-dimensional microarray structure with an extended light-incoming surface according to claim 9, characterized in that: When Cr is selected as the mask layer, in step (d), the patterned wafer is immersed in a KOH etchant at a temperature of 50° C. and 30 wt %, and isopropanol is added to the etchant to perform anisotropic wet etching of the Si (100) crystal surface; in step (e), the chromium mask layer is removed using a cerium ammonium nitrate solution.

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