High-contrast grating vertical cavity surface emitting laser and preparation method thereof

Abstract

The present application discloses a high-contrast grating vertical cavity surface emitting laser and a method for manufacturing the same. The laser comprises a first reflector layer, an active layer, a second reflector layer, and a grating layer, sequentially arranged from bottom to top. A patterned first protective layer and a second protective layer are sequentially arranged on the grating layer. The grating layer is configured as a patterned film layer including grating strips. The first protective layer covers the grating strips. An etching selectivity exists between the first protective layer and the second protective layer. In the embodiments of the present application, a protective layer having an etching selectivity is provided on the grating layer, enabling selective etching of the outer protective layer. When protecting a portion of the chip structure, the etching selectivity effectively and completely maintains the integrity of the inner protective layer, thereby protecting the grating strips by the inner protective layer and improving the stability of the emitting laser.

Description

Technical Field

[0001] The present invention generally relates to the technical field of semiconductor lasers, and in particular to a high-contrast grating vertical cavity surface emitting laser and a preparation method thereof. Background Art

[0002] With the deepening of research on laser emission modules and the expansion of application needs, three-dimensional imaging has attracted widespread attention. In optical three-dimensional imaging systems, the laser emission module is the core component. Currently, the industry primarily uses vertical-cavity surface-emitting lasers (VCSELs). These are primarily used to project modulated light into the target space. A receiving camera captures the modulated light and analyzes its characteristics, ultimately forming an effective depth map.

[0003] In vertical cavity surface emitting lasers, high contrast gratings with oxide spacers are widely used due to their polarization properties and small divergence angle performance.

[0004] Currently, in the process of forming a high-contrast grating vertical-cavity surface-emitting laser, the high-contrast grating structure of the exposed oxide isolation layer, as well as other chip structures, have poor mechanical stability and are easily damaged by external factors. Summary of the Invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, it is desired to provide a high-contrast grating vertical cavity surface emitting laser and a preparation method thereof, wherein a protective layer with a selective etching ratio is provided outside the grating layer, so that when the outermost protective layer is selectively etched, the inner protective layer is completely retained, thereby stably protecting the grating strips.

[0006] In a first aspect, a high-contrast grating vertical cavity surface emitting laser is provided, comprising a first reflector layer, an active layer, a second reflector layer and a grating layer arranged in sequence from bottom to top, a patterned first protective layer and a second protective layer arranged in sequence on the grating layer, the grating layer being configured as a patterned film layer including grating strips, the first protective layer covering the grating strips, and an etching selectivity ratio existing between the first protective layer and the second protective layer.

[0007] In one or more embodiments of the present application, the thickness of the second protective layer is greater than the thickness of the first protective layer.

[0008] In one or more embodiments of the present application, the etching rate of the second protective layer is greater than the etching rate of the first protective layer.

[0009] In one or more embodiments of the present application, the second protective layer is selectively etched to expose the patterned film layer of the first protective layer on the grating strips, or is selectively etched to form a film layer with a thinner thickness.

[0010] In one or more embodiments of the present application, the first protective layer and the second protective layer are configured as single-layer or composite-layer films comprising at least any one of SiO2, SiN, TiO2, AlN, Ta2O5, AlOx and HfO2 or a mixture thereof.

[0011] In one or more embodiments of the present application, the high-contrast grating vertical cavity surface emitting laser also includes an N-type metal electrode layer, a substrate and a P-type metal electrode layer, the substrate is arranged on the N-type metal electrode layer, the first reflector layer is arranged on the substrate, and the P-type metal electrode layer is arranged on the grating layer.

[0012] In a second aspect, an embodiment of the present application provides a method for preparing the high-contrast grating vertical cavity surface emitting laser described in the first aspect, the method comprising:

[0013] forming a first reflector layer, an active layer and a second reflector layer in sequence on a substrate;

[0014] forming a patterned oxide layer and a grating layer in sequence on the upper second reflector layer;

[0015] forming a patterned first protective layer on the grating layer;

[0016] Depositing a second protective layer on the first protective layer, wherein there is an etching selectivity ratio between the first protective layer and the second protective layer;

[0017] The second protective layer is selectively etched to form a patterned second protective layer.

[0018] In one or more embodiments of the present application, the thickness of the second protective layer is greater than the thickness of the first protective layer.

[0019] In one or more embodiments of the present application, forming a patterned first protective layer and a second protective layer includes: using the first protective layer and the second protective layer to be set to form the first protective layer or the second protective layer through an atomic layer deposition process, a plasma enhanced chemical vapor deposition process, a physical vapor deposition process, a pulsed laser deposition process or a plasma enhanced atomic deposition process.

[0020] In one or more embodiments of the present application, forming a patterned second protective layer on the first protective layer includes:

[0021] The second protective layer is selectively etched to expose the first protective layer on the grating strips to form the patterned second protective layer, or the thickness of the second protective layer is reduced.

[0022] In summary, the high-contrast grating vertical cavity surface emitting laser and preparation method provided in the embodiments of the present application sequentially form a protective layer with an etching selectivity on the grating layer, and perform an etching process on the protective layer close to the grating layer to form protection for the grating strips, and then selectively etch the outer protective layer. When protecting part of the chip structure, due to the etching selectivity, the integrity of the internal protective layer can be effectively and completely maintained, thereby realizing the protection of the grating strips by the inner protective layer and improving the stability of the emitting laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Other features, objects and advantages of the present application will become more apparent upon reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0024] Figure 1 This is a schematic structural diagram of a high-contrast grating vertical cavity surface emitting laser according to an embodiment of the present application;

[0025] Figure 2 This is a schematic structural diagram of a high-contrast grating vertical cavity surface emitting laser according to another embodiment of the present application;

[0026] Figure 3 This is a schematic structural diagram of a high-contrast grating vertical cavity surface emitting laser according to another embodiment of the present application;

[0027] Figure 4 This is a flow chart of the preparation process of the high-contrast grating vertical cavity surface emitting laser according to an embodiment of the present application.

[0028] Description of reference numerals:

[0029] 1-N-type metal electrode layer; 2-substrate; 3-first reflector layer; 4-active layer, 5-oxide layer; 6-second reflector layer, 7-oxide isolation layer, 8-grating microstructure layer, 9-first protective layer, 10-second protective layer, 11-P-type metal electrode layer. DETAILED DESCRIPTION

[0030] The present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the relevant invention and are not intended to limit the invention. It should also be noted that, for ease of description, only portions relevant to the invention are shown in the accompanying drawings.

[0031] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0032] It is understood that the high-contrast grating VCSEL formed uses a high-contrast grating with an oxide spacer layer to improve light output performance. The high-contrast grating structure may include a low-refractive-index oxide spacer layer and a high-refractive-index grating microstructure layer above the spacer layer, such as an array of grating strips.

[0033] It is understandable that after the microstructure of the grating is formed, in order to prevent external chemical or mechanical damage, the grating structure needs to be protected, such as by providing a protective layer.

[0034] It is also understood that in one embodiment, the protective layer protecting the grating structure is typically a relatively thin film layer, which may not effectively protect the overall chip structure. Therefore, a thicker protective layer is required outside the protective layer to provide stable protection for the emitting laser chip.

[0035] Furthermore, in order not to affect the normal use of the emitting laser, the outer protective layer can be selectively etched according to the structural design requirements of the device to expose part of the inner protective layer, or the second protective layer can be thinned to achieve the emission and formation of polarized laser.

[0036] It is understandable that when etching the outer protective layer, over-etching and other phenomena often occur, which can easily damage the inner protective layer, exposing the grating strips and thus failing to effectively protect the grating structure. The embodiments of the present application take into account the problems caused by etching and, by adopting different deposition processes and combining different deposition materials, form a protective layer with an etching selectivity on the grating layer. Therefore, when selectively etching the outer protective layer, due to the existing etching selectivity, damage to the inner protective layer due to over-etching can be avoided, and the inner protective layer can be fully protected.

[0037] In order to better understand and illustrate the high contrast grating vertical cavity surface emitting laser and its preparation method provided by the embodiment of the present application, the following Figures 1 to 4 Elaborate in detail.

[0038] Figure 1 This is a structural diagram of a high-contrast grating vertical cavity surface emitting laser according to an embodiment of the present application. Figure 1 As shown, the structure includes:

[0039] A first reflector layer, an active layer, a second reflector layer and a grating layer are arranged in sequence from bottom to top, wherein a patterned first protective layer and a second protective layer are arranged in sequence on the grating layer, the grating layer is configured as a patterned film layer including grating strips, the first protective layer covers the grating strips, and there is an etching selectivity ratio between the first protective layer and the second protective layer.

[0040] Specifically, the high-contrast grating vertical cavity surface emitting laser of the embodiment of the present application includes, from bottom to top, an N-type metal electrode layer 1, a substrate 2, a first reflector layer 3 (in this example, the first reflector layer 3 is an N-type reflector layer, such as a bottom-distributed Bragg reflector), an active layer 4, an oxide layer 5, a second reflector layer 6 (in this example, the second reflector layer is a P-type reflector layer), an oxide isolation layer 7, a grating layer, a first protective layer 9, a P-type metal electrode layer 11 and a second protective layer 10.

[0041] It can be understood that the oxide layer is provided with an opening, and the opening is used to control the divergence angle of the laser.

[0042] It can also be understood that the grating layer may include a patterned oxide isolation layer 7 and a grating microstructure layer 8 on the oxide isolation layer, such as arranged grating strips.

[0043] In an embodiment of the present application, the first protective layer covers the grating microstructure, so that there is an etching selectivity ratio between the second protective layer and the first protective layer, so that after the patterned first protective layer is formed, the second protective layer can be selectively etched according to the chip design requirements. When the pattern is formed, due to the existing etching selectivity, damage to the first protective layer can be avoided, thereby ensuring the integrity of the first protective layer.

[0044] It is understood that the purpose of the second protective layer is to provide more stable protection for the device chip above the first protective layer. Therefore, the selective etching of the second protective layer, that is, the etched portion and the retained portion, can be determined according to the actual structural requirements and is not limited in this embodiment of the present application.

[0045] For example, Figure 1 As shown, in one embodiment, in order to ensure the normal use of the emitting laser, when the second protective layer is selectively etched, the second protective layer on the grating layer is etched away to expose the first protective layer on the grating layer, thereby forming a patterned second protective layer.

[0046] Or, as Figure 2 As shown, the second protective layer between the grating strips can be further etched according to design requirements to form a patterned second protective layer.

[0047] For example, Figure 3As shown, in one embodiment, when the second protective layer is selectively etched, the thickness of part or all of the second protective layer can be reduced according to design requirements to form a patterned second protective layer.

[0048] Optionally, in an embodiment of the present application, in order to achieve the etching selectivity ratio of the first protective layer and the second protective layer, different deposition processes and materials can be selected when forming the first protective layer and the second protective layer to form film layers with different properties such as density.

[0049] For example, the first protective layer and the second protective layer with an etching selectivity ratio can be formed by adopting different processes such as chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), physical vapor deposition (PVD), pulsed laser deposition (PLD), atomic layer deposition (ALD), and plasma enhanced atomic layer deposition (PEALD).

[0050] The material of the first protective layer or the second protective layer can be at least one of SiO2, SiN, TiO2, AlN, Ta2O5, AlOx, and HfO2, or a mixture thereof. During deposition, single-layer or composite-layer deposition can be performed, correspondingly forming a single-layer structure of at least one of SiO2, SiN, TiO2, AlN, Ta2O5, AlOx, and HfO2, or a composite-layer structure of at least two or more of the above-mentioned materials, or a single-layer structure or composite-layer structure of a mixture of the above-mentioned materials. Composite-layer structures include, but are not limited to, stacked SiO2 and SiN layers, and the composite-layer structures are not described in detail here.

[0051] It can be understood that the deposition process of the semiconductor and the selection of materials can be determined according to actual conditions, and the embodiments of the present application do not impose any restrictions on this.

[0052] It can be understood that in the embodiment of the present application, after the first protective layer and the second protective layer are formed by adopting different processes and material deposition, when the first protective layer and the second protective layer are etched, the etching rates of the first protective layer and the second protective layer can be made different, thereby further ensuring the protection of the first protective layer structure.

[0053] Optionally, in an embodiment of the present application, considering that the thickness of the first protective layer is usually set to be thin, in order to effectively protect the chip of the device, a thicker second protective layer can be set so that the thickness of the second protective layer is at least greater than the thickness of the first protective layer.

[0054] It can also be understood that the thickness settings of the first protective layer and the second protective layer can be determined according to actual device requirements, and the embodiments of the present application do not limit this.

[0055] The high-contrast grating vertical cavity surface emitting laser provided in the embodiment of the present application forms protective layers with different etching selectivities on the grating layer in sequence, and performs an etching process on the protective layer close to the grating layer to protect the grating strips. Thereafter, the outer protective layer is selectively etched. When protecting part of the chip structure, the integrity of the internal protective layer can be effectively and completely maintained due to the existing etching selectivity, thereby realizing protection of the grating strips by the inner protective layer and improving the stability of the emitting laser.

[0056] On the other hand, for the high-contrast grating vertical cavity surface emitting laser provided by the above embodiment, the embodiment of the present application also provides a preparation method thereof.

[0057] Figure 4 A schematic diagram of a process for preparing a high-contrast grating vertical cavity surface emitting laser according to an embodiment of the present application is shown in FIG. Figure 4 As shown, the method includes:

[0058] S1, forming a patterned first protective layer on the grating layer and the P-type metal electrode layer;

[0059] S2, depositing a second protective layer on the first protective layer and the P-type metal electrode layer, wherein the first protective layer and the second protective layer have an etching selectivity ratio;

[0060] S3, selectively etching the second protective layer to form a patterned second protective layer.

[0061] Specifically, in the preparation method in the embodiment of the present application, when forming the first protective layer and the second protective layer, different process methods or materials are adopted so that the first protective layer and the second protective layer have a selective etching ratio, so that the second protective layer can be selectively etched to form a pattern, and the etching of the first protective layer can be avoided, thereby achieving effective protection of the first protective layer.

[0062] Optionally, in order to further more effectively protect the first protective layer and the chip, a thicker second protective layer may be provided, such that the thickness of the second protective layer is greater than that of the first protective layer.

[0063] Optionally, as described in the above embodiments, when forming the first protective layer and the second protective layer, different processes such as chemical vapor deposition, plasma enhanced chemical vapor deposition, physical vapor deposition, pulsed laser deposition, atomic layer deposition, and plasma enhanced atomic layer deposition can be used to form the first protective layer and the second protective layer with an etching selectivity ratio.

[0064] For example, the above-mentioned different processes can be used to form a single layer structure of at least any one of SiO2, SiN, TiO2, AlN, Ta2O5, AlOx, and HfO2, or a composite layer structure of at least two or more of them, or a single layer structure or composite layer structure of a mixture of the materials described in the above embodiments.

[0065] Furthermore, when the second protective layer is selectively etched, patterned etching can be performed according to the design structure of the device.

[0066] For example, Figure 2 and Figure 3 As shown, the patterned second protective layer is formed so that the first protective layer on the grating strips is exposed, or the second protective layer is thinned.

[0067] In summary, the high-contrast grating vertical cavity surface emitting laser and its preparation method provided in the embodiments of the present application, by sequentially forming a protective layer with a selective etching ratio on the grating layer, and performing an etching process on the protective layer close to the grating layer to form protection for the grating strips, and then selectively etching the outer protective layer. When protecting part of the chip structure, due to the etching selectivity, the integrity of the internal protective layer can be effectively and completely maintained, thereby realizing the protection of the grating strips by the inner protective layer and improving the stability of the emitting laser.

[0068] It should be noted that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "left", "right", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like used herein to indicate orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings and are only used to facilitate the description of the present invention and simplify the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation to the present application.

[0069] In the description of this application, the terms "first," "second," etc. are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include at least one of such features.

[0070] Unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be interpreted broadly. For example, they can refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0071] The above description is merely a preferred embodiment of the present application and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of the invention herein is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the inventive concept. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features having similar functions disclosed in this application.

Claims

1. A high-contrast grating vertical cavity surface emitting laser, comprising a first reflector layer, an active layer, a second reflector layer and a grating layer arranged from bottom to top, characterized in that: A patterned first protective layer and a second protective layer are sequentially provided on the grating layer, the grating layer is provided as a patterned film layer including grating strips, the first protective layer covers the grating strips, an etching selectivity exists between the first protective layer and the second protective layer, and an etching rate of the second protective layer is greater than an etching rate of the first protective layer; The first protective layer and the second protective layer are configured to include SiO2, SiN, TiO2, AlN, Ta2O5, AlO x and HfO2 or a mixture thereof.

2. The high-contrast grating vertical cavity surface emitting laser according to claim 1, characterized in that: The thickness of the second protective layer is greater than that of the first protective layer.

3. The high-contrast grating vertical cavity surface emitting laser according to claim 1, characterized in that: The second protection layer is selectively etched to expose the patterned film layer of the first protection layer on the grating strips, or is selectively etched to form a film layer with a thinner thickness.

4. The high-contrast grating vertical cavity surface emitting laser according to any one of claims 1 to 3, characterized in that: Also includes: An N-type metal electrode layer, a substrate and a P-type metal electrode layer, wherein the substrate is arranged on the N-type metal electrode layer, the first reflector layer is arranged on the substrate, the P-type metal electrode layer is arranged on the grating layer, and the P-type metal electrode layer is located at a position on the grating layer different from that at which the grating strips are arranged.

5. A method for preparing a high-contrast grating vertical cavity surface emitting laser according to any one of claims 1 to 4, characterized in that: The preparation method comprises: forming a first reflector layer, an active layer and a second reflector layer in sequence on a substrate; sequentially forming a patterned grating layer on the second reflector layer; forming a patterned first protective layer on the grating layer; Depositing a second protective layer on the first protective layer, wherein there is an etching selectivity ratio between the first protective layer and the second protective layer; The second protective layer is selectively etched to form a patterned second protective layer.

6. The preparation method according to claim 5, characterized in that The thickness of the second protective layer is greater than that of the first protective layer.

7. The preparation method according to claim 6, characterized in that Forming the first protective layer and the second protective layer includes: The first protective layer or the second protective layer is formed by using an atomic layer deposition process, a plasma enhanced chemical vapor deposition process, a physical vapor deposition process, a pulsed laser deposition process or a plasma enhanced atomic deposition process.

8. The preparation method according to claim 6 or 7, characterized in that The selectively etching the second protective layer includes: The second protective layer is selectively etched to expose the first protective layer on the grating strips, or the thickness of the second protective layer is reduced.

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