Silicon carbide photoelectric detector with high absorption and utilization rate and preparation method thereof

Abstract

The invention provides a silicon carbide photoelectric detector with high absorption and utilization rate and a preparation method thereof, a silicon carbide epitaxial layer in the detector is arranged on a silicon carbide substrate, a recess exists from the middle area to the edge of the silicon carbide epitaxial layer, and the recess enables the central area to be of a trapezoidal structure; the ohmic contact is arranged on the inclined surface and the edge part of the trapezoidal structure, and the metal electrode is arranged on the ohmic contact. According to the method, the inclined plane is etched through oblique angle etching, and the metal electrode is prepared on the inclined plane. Compared with a conventional ultraviolet photoelectric detector, due to the existence of the inclined plane metal electrode, ultraviolet light incident on the inclined plane is reflected to the side wall of the device base region and can enter the base region without being absorbed by a plurality of layers of silicon carbide films, so that the light intensity received by the base region is increased, the photon-generated carrier concentration is improved, and the performance of the device is improved. In the preparation process, the etching masks of the inclined plane and the vertical base region are formed at one time by utilizing different exposure morphologies of patterns with different line widths, so that the complexity of the preparation process is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor devices, and in particular relates to a high absorption utilization rate silicon carbide photoelectric detector and a preparation method thereof. Background Art

[0002] Ultraviolet photodetectors (UV PDs) are extremely important optoelectronic semiconductor devices that play an important role in fields such as fire warning, aerospace engine monitoring, and missile warning. Currently, silicon-based and gallium arsenide-based detectors have been commercialized and widely used in civil and military fields.

[0003] The working environment of ultraviolet detectors is often harsh, especially in extremely high temperature environments. Due to the material properties of high intrinsic carrier concentration and low thermal conductivity of silicon and gallium arsenide, traditional detectors based on silicon and gallium arsenide are difficult to work in high temperature environments above 200°C. In addition, the narrow band gap also requires traditional detectors based on silicon and gallium arsenide to use filters to shield light radiation in other bands to achieve ultraviolet detection functions, making the equipment larger, the process more complicated, and the cost higher. The wide band gap and high thermal conductivity of silicon carbide enable silicon carbide-based ultraviolet detectors to cope with extremely high temperature environments. The switching ratio of the photodetector is proportional to the light absorption rate. As the light incidence depth increases, the material's absorption rate of light decreases exponentially.

[0004] Conventional silicon carbide photodetector devices usually use vertical structures, and light must pass through multiple film layers and highly doped semiconductor layers before reaching the detector base, which greatly reduces the detector's light absorption and utilization rate. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a high absorption utilization rate silicon carbide photodetector and a preparation method thereof. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0006] In a first aspect, the present invention provides a high absorption utilization rate silicon carbide photodetector, comprising: a silicon carbide substrate 1, a silicon carbide epitaxial layer 2, an ohmic contact 4 and a metal electrode 5;

[0007] Among them, the silicon carbide epitaxial layer 2 is on the silicon carbide substrate 1, and there is a depression from the middle area to the edge of the silicon carbide epitaxial layer 2, which makes the central area have a trapezoidal structure; the ohmic contact 4 is on the slope and edge of the trapezoidal structure, and the metal electrode 5 is on the ohmic contact 4.

[0008] Optionally, the length of the lower base of the trapezoidal structure is greater than the length of the edge portion, and the height of the trapezoidal structure is consistent with the height of the edge portion.

[0009] Optionally, the metal of the ohmic contact 4 includes nickel, titanium, aluminum and silver.

[0010] Optionally, the metal forming the metal electrode 5 includes nickel, titanium, aluminum and silver.

[0011] In a second aspect, the present invention provides a method for preparing a silicon carbide photodetector with high absorption utilization rate, comprising:

[0012] S100, selecting a silicon carbide substrate 1, and epitaxially growing a silicon carbide epitaxial layer 2 thereon;

[0013] S200, spin coating a photoresist 3 on the epitaxially grown silicon carbide 2;

[0014] S300, designing a predetermined layout of a photoresist, and forming a predetermined pattern on the photoresist 3 using the predetermined layout;

[0015] S400, etching the silicon carbide epitaxial layer 2 using the predetermined pattern to remove the photoresist 3 and form the silicon carbide epitaxial layer 2 into a predetermined structure; wherein a depression exists from the middle region to the edge of the predetermined structure, and the depression makes the central region present a trapezoidal structure;

[0016] S500, forming an ohmic contact 4 by evaporating or sputtering metal on the silicon carbide epitaxial layer 2 having a predetermined structure, and forming a metal electrode 5 by evaporating or sputtering metal on the ohmic contact 4;

[0017] S600, by means of an etching or stripping process, the ohmic contact 4 and the metal electrode 5 between the edge portion and the inclined portion of the trapezoidal structure and the central area of ​​the upper surface of the trapezoidal structure are stripped to obtain a silicon carbide photodetector with high absorption and utilization efficiency.

[0018] Optionally, S400 includes:

[0019] The etching gas components and proportions are adjusted, and etching is performed from top to bottom at the predetermined pattern position to remove the photoresist 3 and form a predetermined structure of the silicon carbide epitaxial layer 2. The gas components include: SF6, O2, HBr, Cl2, Ar and He.

[0020] Optionally, the metal used to form the ohmic contact 4 includes nickel, titanium, aluminum and silver.

[0021] Optionally, the metal used to form the metal electrode 5 includes nickel, titanium, aluminum and silver.

[0022] Optionally, S500 includes:

[0023] By evaporating or sputtering metal on the silicon carbide epitaxial layer 2 having a predetermined structure;

[0024] Forming an ohmic contact pattern by etching or stripping according to the type of metal;

[0025] The ohmic contact pattern is subjected to rapid thermal annealing to form the ohmic contact 4 , or the ohmic contact 4 is formed by removing a portion where the ohmic contact pattern is not formed after rapid thermal annealing in a self-aligned manner.

[0026] Optionally, a light reflecting layer is prepared on the metal electrode 5 .

[0027] Beneficial effects:

[0028] The present invention provides a silicon carbide photodetector with high absorption utilization rate and a preparation method thereof, wherein the silicon carbide epitaxial layer in the detector is on the silicon carbide substrate, and there is a depression from the middle area to the edge of the silicon carbide epitaxial layer, and the depression makes the central area present a trapezoidal structure; the ohmic contact is on the inclined surface and the edge part of the trapezoidal structure, and the metal electrode is on the ohmic contact. The present invention realizes etching of the inclined surface by oblique etching, and prepares the metal electrode on the inclined surface. Compared with conventional ultraviolet photodetectors, due to the presence of the inclined metal electrode, the ultraviolet light incident on the inclined surface of the structure will be reflected to the side wall of the device base region, and can enter the base region without being absorbed by the multi-layer silicon carbide film, thereby increasing the light intensity received by the base region, increasing the concentration of photogenerated carriers, and improving the performance of the device. In the preparation process, the difference in exposure morphology of different line width patterns is utilized to form an etching mask of the inclined surface and the vertical base region at one time, which greatly reduces the complexity of the preparation process.

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of a silicon carbide photodetector with high absorption utilization rate provided by the present invention;

[0031] Figure 2-Figure 3 It is a layout of a silicon carbide photodetector with high absorption utilization rate provided by the present invention;

[0032] Figure 4-Figure 8 It is a schematic diagram of the preparation process of a high absorption utilization rate silicon carbide photoelectric detector provided by the present invention. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0034] First, refer to Figure 1 As shown, the present invention provides a high absorption utilization rate silicon carbide photodetector, comprising: a silicon carbide substrate 1, a silicon carbide epitaxial layer 2, an ohmic contact 4 and a metal electrode 5;

[0035] The silicon carbide epitaxial layer 2 is on the silicon carbide substrate 1, and there is a depression from the middle area to the edge of the silicon carbide epitaxial layer 2, which makes the central area present a trapezoidal structure; the ohmic contact 4 is on the inclined surface and edge of the trapezoidal structure, and the metal electrode 5 is on the ohmic contact 4. The length of the bottom of the trapezoidal structure is greater than the length of the edge part, and the height of the trapezoidal structure is consistent with the height of the edge part.

[0036] refer to Figure 2 and Figure 3 The high absorption utilization rate silicon carbide photodetector of the present invention can be round or square with rounded corners. From top to bottom, the center area of ​​the layout directly exposes the silicon carbide epitaxial layer 2, the closed hollow is also the exposed silicon carbide epitaxial layer 2, and the shaded part is the metal electrode 5.

[0037] The metals of the ohmic contact 4 include nickel, titanium, aluminum and silver, and the metals forming the metal electrode 5 include nickel, titanium, aluminum and silver.

[0038] In a second aspect, the present invention provides a method for preparing a silicon carbide photodetector with high absorption utilization rate, comprising:

[0039] S100, a silicon carbide substrate 1 is selected, and a silicon carbide epitaxial layer 2 is epitaxially grown thereon, such as Figure 4 shown.

[0040] S200, spin coating a photoresist 3 on the epitaxially grown silicon carbide 2, such as Figure 5 shown.

[0041] S300, designing a predetermined layout of a photoresist, and forming a predetermined pattern on the photoresist 3 using the predetermined layout;

[0042] In this step, the photoresist layout can be designed first, and the layout design makes a>>b, and the photolithography pattern is formed by one exposure. Since the line width difference is large here, the following can be achieved by adjusting the exposure, hardening and curing process conditions: Figure 6 The predetermined pattern of the photoresist is shown.

[0043] S400, etching the silicon carbide epitaxial layer 2 using a predetermined pattern to remove the photoresist 3 and form the silicon carbide epitaxial layer 2 into a predetermined structure, such as Figure 7 As shown; wherein there is a depression from the middle area to the edge of the predetermined structure, and the depression makes the central area have a trapezoidal structure;

[0044] In this step, the etching gas components and proportions can be adjusted, and etching can be performed from top to bottom at the predetermined pattern position to remove the photoresist 3 and form a predetermined structure of the silicon carbide epitaxial layer 2. The gas components include: SF6, O2, HBr, Cl2, Ar and He.

[0045] S500, forming an ohmic contact 4 by evaporating or sputtering metal on the silicon carbide epitaxial layer 2 having a predetermined structure, and forming a metal electrode 5 by evaporating or sputtering metal on the ohmic contact 4;

[0046] The metals used to form the ohmic contact 4 include nickel, titanium, aluminum and silver; the metals used to form the metal electrode 5 include nickel, titanium, aluminum and silver.

[0047] In this step, metal is evaporated or sputtered on the silicon carbide epitaxial layer 2 having a predetermined structure; an ohmic contact pattern is formed by etching or stripping according to the type of metal; the ohmic contact pattern is subjected to rapid thermal annealing to form an ohmic contact 4, or an ohmic contact 4 is formed by removing a portion where the ohmic contact pattern is not formed after rapid thermal annealing in a self-aligned manner.

[0048] S600, by etching or stripping process, the ohmic contact 4 and the metal electrode 5 between the edge portion and the inclined portion of the trapezoidal structure and the central area of ​​the upper surface of the trapezoidal structure are stripped to obtain a silicon carbide photodetector with high absorption utilization rate, such as Figure 8 shown.

[0049] The present invention can further prepare a light reflection layer on the metal electrode 5 to improve the light reflection efficiency, and can also directly use the metal electrode as the light reflection layer. The final cross-sectional schematic diagram is as follows: Figure 6 As shown:

[0050] The present invention provides a silicon carbide photodetector with high absorption utilization rate and a preparation method thereof. The silicon carbide epitaxial layer in the detector is on a silicon carbide substrate, and there is a depression from the middle area to the edge of the silicon carbide epitaxial layer, which makes the central area present a trapezoidal structure; the ohmic contact is on the inclined surface and the edge part of the trapezoidal structure, and the metal electrode is on the ohmic contact. The present invention realizes etching of the inclined surface by oblique etching, and prepares the metal electrode on the inclined surface. Compared with conventional ultraviolet photodetectors, due to the presence of the inclined metal electrode, the ultraviolet light incident on the inclined surface of the structure will be reflected to the side wall of the device base region, and can enter the base region without being absorbed by multiple layers of silicon carbide films, thereby increasing the light intensity received by the base region, increasing the concentration of photogenerated carriers, and improving the performance of the device. In the preparation process, the difference in exposure morphology of different line width patterns is utilized to form an etching mask for the inclined surface and the vertical base region at one time, which greatly reduces the complexity of the preparation process.

[0051] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the claimed application, those skilled in the art may understand and implement other variations of the disclosed embodiments by reviewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality of components or steps.

[0052] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A high absorption efficiency silicon carbide photodetector, characterized in that: include: Silicon carbide substrate (1), silicon carbide epitaxial layer (2), ohmic contact (4) and metal electrode (5); The silicon carbide epitaxial layer (2) is on the silicon carbide substrate (1), and there is a depression from the middle area to the edge of the silicon carbide epitaxial layer (2), and the depression makes the central area present a trapezoidal structure; the ohmic contact (4) is on the inclined surface and edge part of the trapezoidal structure, and the metal electrode (5) is on the ohmic contact (4).

2. The high absorption efficiency silicon carbide photodetector according to claim 1, characterized in that: The length of the lower base of the trapezoidal structure is greater than the length of the edge portion, and the height of the trapezoidal structure is consistent with the height of the edge portion.

3. The high absorption efficiency silicon carbide photodetector according to claim 1, characterized in that: The metal of the ohmic contact (4) includes nickel, titanium, aluminum and silver.

4. The high absorption efficiency silicon carbide photodetector according to claim 1, characterized in that: The metal forming the metal electrode (5) includes nickel, titanium, aluminum and silver.

5. A method for preparing a silicon carbide photodetector with high absorption efficiency, characterized in that: include: S100, selecting a silicon carbide substrate (1), and epitaxially growing a silicon carbide epitaxial layer (2) thereon; S200, spin coating a photoresist (3) on the epitaxially grown silicon carbide (2); S300, designing a predetermined layout of a photoresist, and forming a predetermined pattern on the photoresist (3) using the predetermined layout; S400, etching the silicon carbide epitaxial layer (2) using the predetermined pattern to remove the photoresist (3) and form the silicon carbide epitaxial layer (2) into a predetermined structure; wherein a depression exists from the middle region to the edge of the predetermined structure, and the depression causes the central region to have a trapezoidal structure; S500, forming an ohmic contact (4) by evaporating or sputtering a metal on the silicon carbide epitaxial layer (2) having a predetermined structure, and forming a metal electrode (5) by evaporating or sputtering a metal on the ohmic contact (4); S600, through an etching or stripping process, the ohmic contact (4) and the metal electrode (5) between the edge portion and the inclined portion of the trapezoidal structure and the central area of ​​the upper surface of the trapezoidal structure are stripped to obtain a silicon carbide photodetector with high absorption and utilization rate.

6. The method for preparing a silicon carbide photodetector with high absorption efficiency according to claim 5, characterized in that: S400 includes: The etching gas components and proportions are adjusted, and etching is performed from top to bottom at the predetermined pattern position to remove the photoresist (3) and form a predetermined structure of the silicon carbide epitaxial layer (2). The gas components include: SF6, O2, HBr, Cl2, Ar and He.

7. The method for preparing a silicon carbide photodetector with high absorption efficiency according to claim 5, characterized in that: Metals used to form the ohmic contact (4) include nickel, titanium, aluminum and silver.

8. The method for preparing a silicon carbide photodetector with high absorption efficiency according to claim 1, characterized in that: The metals used to form the metal electrode (5) include nickel, titanium, aluminum and silver.

9. The method for preparing a silicon carbide photodetector with high absorption efficiency according to claim 7, characterized in that: S500 includes: By evaporating or sputtering a metal on the silicon carbide epitaxial layer (2) having a predetermined structure; Forming an ohmic contact pattern by etching or stripping according to the type of metal; The ohmic contact pattern is subjected to rapid thermal annealing to form an ohmic contact (4), or the ohmic contact (4) is formed by removing a portion where the ohmic contact pattern is not formed after rapid thermal annealing in a self-alignment manner.

10. The method for preparing a silicon carbide photodetector with high absorption efficiency according to claim 5, characterized in that: A light reflecting layer is prepared on the metal electrode (5).

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