CN106941205B - Waveguide and method of forming the same - Google Patents
Waveguide and method of forming the same Download PDFInfo
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- CN106941205B CN106941205B CN201610005308.4A CN201610005308A CN106941205B CN 106941205 B CN106941205 B CN 106941205B CN 201610005308 A CN201610005308 A CN 201610005308A CN 106941205 B CN106941205 B CN 106941205B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
- H01P3/00—Waveguides; Transmission lines of the waveguide type
- H01P3/18—Waveguides; Transmission lines of the waveguide type built-up from several layers to increase operating surface, i.e. alternately conductive and dielectric layers
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Abstract
The invention provides a waveguide and a forming method thereof, wherein the forming method of the waveguide comprises the following steps: providing a substrate; forming a black phosphorus layer and a graphene layer on the black phosphorus layer on the substrate; forming a patterned mask layer on the graphene layer; etching the graphene layer and the black phosphorus layer until the substrate is exposed; and removing the patterned mask layer. The formed waveguide of the present invention has low absorption and scattering losses.
Description
Technical Field
The invention relates to the technical field of guided wave optics, in particular to a waveguide and a forming method thereof.
Background
Waveguide (waveguide) is a structure used to directionally guide electromagnetic waves. Optical waveguides are an important element in integrated optics, and are a basic unit structure in planar lightwave circuits, and have been successfully applied in many fields, such as: signal processing, optical communication, optical sensing, and the like. Materials commonly used in integrated optics are silicon dioxide, group III-V compound semiconductors, lithium niobate, polymers, silicon-on-insulator (SOI), and the like. Among these materials, silicon-on-insulator materials are becoming a material with great potential for applications because they are suitable for both active and passive devices. Optical waveguides on SOI materials have been successfully implemented and used, but SOI materials have a significant impact on device design and performance due to the limited thickness of the buried silicon dioxide layer and the inability to process at the interface between the buried silicon dioxide layer and the top silicon layer.
The performance of the waveguides formed by the prior art needs to be improved.
Disclosure of Invention
The problem addressed by the present invention is that the performance of waveguides formed by the prior art is poor.
To solve the above problem, an embodiment of the present invention provides a method for forming a waveguide, including: providing a substrate; forming a black phosphorus layer and a graphene layer on the black phosphorus layer on the substrate; forming a patterned mask layer on the graphene layer; etching the graphene layer and the black phosphorus layer until the substrate is exposed; and removing the patterned mask layer.
Optionally, forming a black phosphorus layer on the substrate and a graphene layer on the black phosphorus layer comprises: forming a red phosphorus layer on the substrate; carrying out heat treatment on the red phosphorus layer to form a black phosphorus layer; forming a silicon carbide layer on the black phosphorus layer; and carrying out heat treatment on the silicon carbide layer to form a graphene layer.
Optionally, the heat treating the red phosphorus layer comprises: heating the red phosphorus to 1000 ℃ at high pressure; the red phosphorus was cooled to 600 degrees celsius at a rate of 100 degrees celsius per hour.
Optionally, the method for forming the waveguide further includes: and after the black phosphorus layer is formed, thinning the black phosphorus layer to reach a preset thickness.
Optionally, argon plasma is used for thinning the black phosphorus layer.
Optionally, the silicon carbide layer is thermally treated at a temperature greater than 1000 degrees celsius to thermally decompose the silicon carbide layer.
Optionally, forming a black phosphorus layer on the substrate and a graphene layer on the black phosphorus layer comprises: forming a red phosphorus layer on the substrate; forming a silicon coating layer on the red phosphorus layer and a carbon-containing material layer on the silicon coating layer; and carrying out heat treatment on the red phosphorus layer, the silicon coating layer and the carbon-containing material layer to enable the red phosphorus layer to form a black phosphorus layer, and the silicon coating layer and the carbon-containing material layer to form a graphene layer.
Optionally, the method for forming the waveguide further includes: and after the red phosphorus layer is formed, thinning the red phosphorus layer to reach the preset thickness.
Optionally, argon plasma is used for thinning the red phosphorus layer.
Optionally, the red phosphorus layer is formed by a chemical vapor deposition process or a molecular beam epitaxy process.
Correspondingly, the embodiment of the invention also provides a waveguide formed by adopting the method. The waveguide includes: a substrate; a black phosphorus layer on the substrate; and the graphene layer is positioned on the black phosphorus layer, and the size of the graphene layer and the size of the black phosphorus layer along the surface direction of the substrate are the same.
Compared with the prior art, the technical scheme of the embodiment of the invention has the following advantages:
in the method for forming the waveguide, after a black phosphorus layer and a graphene layer located on the black phosphorus layer are formed on a substrate, a patterned mask layer is formed on the graphene layer, and the graphene layer and the black phosphorus layer are etched by taking the patterned mask layer as a mask until the substrate is exposed, so that the waveguide with the graphene-black phosphorus composite structure is formed. Because the graphene layer and the black phosphorus layer in the waveguide are formed by the same mask layer through an etching process, the shapes of the graphene layer and the black phosphorus layer are consistent, and absorption and scattering loss can be reduced.
Furthermore, the embodiment of the invention adopts a novel photoelectric material black phosphorus, and the black phosphorus material is a direct band gap material and has an adjustable band gap width (band gap), so that the band gap width of the black phosphorus material can be adjusted by adjusting the thickness of the black phosphorus material, and the waveguide of the embodiment of the invention has a wide application range.
Correspondingly, the waveguide of the embodiment of the invention also has the advantages.
Drawings
Fig. 1 to 9 are schematic cross-sectional views of intermediate structures formed in a method of forming a waveguide according to an embodiment of the present invention.
Detailed Description
As can be seen from the background art, the prior art techniques have poor performance in forming waveguides.
The inventor of the present invention has studied the forming method of the silicon waveguide on the SOI substrate of the prior art and found that: in order to improve the performance of the silicon waveguide on the SOI substrate, a silicon oxide dielectric layer is deposited after the silicon waveguide is formed in the prior art; and after the dielectric layer is flattened, forming a graphene (graphene) layer on the silicon waveguide. It is desirable to tune and improve the performance of the silicon waveguide through the graphene layer, but additional absorption and scattering losses (absorption and scattering losses) tend to be created, resulting in reduced waveguide performance. The inventors of the present invention further studied the process of forming a graphene (graphene) layer on a silicon waveguide, and found that the graphene layer is generally transferred to the silicon waveguide by a mechanical transfer method after the silicon waveguide is formed, and it is difficult to precisely position and cover the silicon waveguide device and to form an edge-conformal (edge-conformal) graphene-silicon composite structure due to the mechanical transfer method, thereby causing an increase in absorption and scattering loss of the silicon waveguide.
Based on the above research, the embodiment of the invention provides a method for forming a waveguide, which includes forming a black phosphorus layer and a graphene layer on the black phosphorus layer on a substrate, then forming a patterned mask layer on the graphene layer, and etching the graphene layer and the black phosphorus layer by using the patterned mask layer as a mask until the substrate is exposed, so as to form the waveguide with a graphene-black phosphorus composite structure. Because the graphene layer and the black phosphorus layer in the waveguide are formed by the same mask layer through an etching process, the shapes of the graphene layer and the black phosphorus layer are consistent, and the transmission loss is favorably reduced. Furthermore, the embodiment of the invention adopts a novel photoelectric material black phosphorus, and the black phosphorus material is a direct band gap material with adjustable band gap width (band gap), so that the band gap width of the black phosphorus material can be adjusted by adjusting the thickness of the black phosphorus material, and the black phosphorus material can be used in optical paths of various wave bands, thereby enlarging the application range of the waveguide of the embodiment of the invention.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
It should be noted that these drawings are provided to facilitate understanding of the embodiments of the present invention and should not be construed as unduly limiting the invention. For greater clarity, the dimensions shown in the figures are not to scale and may be exaggerated, reduced or otherwise altered.
Referring first to fig. 1, a substrate 100 is provided, and a black phosphorus layer 110 and a graphene layer 120 on the black phosphorus layer 110 are formed on the substrate 100.
In this embodiment, the substrate 100 is a silicon wafer. A variety of electrical or optical elements may be formed within the substrate 100. In other embodiments, the substrate 100 may be other semiconductor materials or insulating materials. For example, the substrate 100 may also be a silicon germanium, III-V semiconductor material, or the like, or a multilayer structure material such as Si-SiGe, Si-SiC, silicon-on-insulator (SOI), or germanium-on-insulator (GOI); or an insulating material such as glass.
In some embodiments, referring to fig. 2 to 4 together, the method of forming the black phosphorus layer 110 and the graphene layer 120 on the black phosphorus layer 110 on the substrate 100 includes: forming a red phosphorus layer 111 on the substrate 100; performing heat treatment on the red phosphorus layer 111 to form a black phosphorus layer 110; forming a silicon carbide layer 121 on the black phosphorus layer 110; the silicon carbide layer 121 is heat-treated to form the graphene layer 120.
Specifically, as shown in fig. 2, a red phosphor layer 111 is formed on the substrate 100. The process of forming the red phosphorus layer 111 on the substrate 100 may be a chemical vapor deposition process or a molecular beam epitaxy process.
Next, as shown in fig. 3, the red phosphor layer 111 is heat-treated to form a black phosphor layer 110. Since red phosphorus and black phosphorus are allotropes, the red phosphorus layer 111 can be converted into the black phosphorus layer 110 after heat treatment. In one embodiment, the process of performing a heat treatment on the red phosphorus layer 111 to form the black phosphorus layer 110 includes: heating the red phosphorus layer 111 to 1000 degrees celsius at a constant high pressure of 10 kilobars (kbar); next, the red phosphorus layer 111 is cooled to 600 degrees celsius at a cooling rate of 100 degrees celsius per hour, thereby transforming the red phosphorus layer 111 into the black phosphorus layer 110. In order to obtain high black phosphorus quality, the temperature rising and reducing processes can be circularly executed for a plurality of times.
In some embodiments, after the black phosphorus layer 110 is formed, the black phosphorus layer 110 is further thinned, so that the thickness of the black phosphorus layer 110 reaches a preset thickness. As mentioned above, the band gap width of the two-dimensional black phosphorus material is related to its thickness, i.e., the number of layers. It was found that the band gap width decreased as the number of black phosphorus layers increased, and that the band gap width of black phosphorus in a single layer was 2.5eV and that of black phosphorus in a bulk state was 0.3 eV. Since the photoelectric properties of the black phosphorus material are related to the band gap width thereof, the thickness of the black phosphorus layer 110 needs to be controlled based on the application scenario in which the waveguide is to be formed. Specifically, in some embodiments, the black phosphorus layer 110 is thinned using an argon plasma. By controlling the technological parameters of the argon plasma etching, the thinning thickness can be accurately controlled, and even the effect of removing layer by layer can be achieved.
Next, as shown in fig. 4, a silicon carbide layer 121 is formed on the black phosphorus layer 110. Specifically, the silicon carbide layer 121 may be formed using an Atomic Layer Deposition (ALD) process, and the deposition temperature is 150 degrees celsius. After the silicon carbide layer 121 is formed, the silicon carbide layer 121 is subjected to a heat treatment to form the graphene layer 120 as shown in fig. 1. In some embodiments, the silicon carbide layer 121 is thermally treated at a temperature greater than 1000 degrees celsius to thermally decompose the silicon carbide layer 121. Specifically, the heat treatment of the silicon carbide layer 121 may be performed in an Ultra High Vacuum (UHV) environment or an argon atmosphere. For example, when the silicon carbide 121 layer is heat-treated in an ultra-high vacuum environment, the temperature of the heat treatment process is 1280 degrees celsius; when the silicon carbide layer 121 is heat-treated under an argon atmosphere, the temperature of the heat treatment process is 1650 ℃.
In still other embodiments, referring to fig. 5 to 7 simultaneously, the method of forming the black phosphorus layer 110 and the graphene layer 120 on the black phosphorus layer 110 on the substrate 100 includes: forming a red phosphorus layer 115 on the substrate 100; forming a silicon Coating layer (Si-Coating)125 on the red phosphorus layer, and a carbon-containing material layer 126 on the silicon Coating layer 125; the red phosphorus layer 115, the silicon coating layer 125 and the carbon-containing material layer 126 are subjected to heat treatment, so that the red phosphorus layer 115 forms the black phosphorus layer 110, and the silicon coating layer 125 and the carbon-containing material layer 126 form the graphene layer 120.
Specifically, as shown in fig. 5, a red phosphor layer 115 is formed on the substrate 100. The process of forming the red phosphorus layer 115 may be a chemical vapor deposition process or a molecular beam epitaxy process. Since the red phosphorus layer 115 is used to form a black phosphorus layer in a subsequent process, in order to obtain a black phosphorus layer having a predetermined thickness, the thickness of the red phosphorus layer 115 needs to be adjusted. Accordingly, in some embodiments, the red phosphor layer 115 is thinned after the red phosphor layer 115 is formed. Specifically, the red phosphorus layer 115 may be thinned by using argon plasma, and the thinned thickness may be accurately controlled by controlling the process parameters of the argon plasma etching. After thinning, the thickness of the red phosphorus layer 115 corresponds to the thickness of the black phosphorus layer to be formed, so that the purpose of regulating the band gap width of the black phosphorus layer is achieved, and meanwhile, the application range of the waveguide formed by the embodiment of the invention is enlarged.
Next, as shown in fig. 6, a silicon clad layer 125 and a carbon-containing material layer 126 on the silicon clad layer are formed on the red phosphorus layer 115. The coating layer 125 and the carbon-containing material layer 126 can be formed on the red phosphorus layer 115 by a spin coating process, which is simple. For example, Tetraethoxysilane (TEOS) may be used to form the silicon coating layer 125, and Polymethylmethacrylate (PMMA) may be used to form the carbon-containing material layer 126. Of course, the silicon coating 125 and the carbon-containing material 126 may be formed by other materials or by other processes.
Next, as shown in fig. 7, the red phosphorus layer 115, the silicon cladding layer 125 and the carbon-containing material layer 126 are subjected to a heat treatment, so that the red phosphorus layer 115 (also refer to fig. 6) forms a black phosphorus layer 110, and the silicon cladding layer 125 and the carbon-containing material layer 126 form a graphene layer 120 as shown in fig. 1. In an embodiment of the present invention, the red phosphorus layer 115, the silicon cladding layer 125, and the carbon-containing material layer 126 may be heat-treated by a laser annealing process.
The process of performing the heat treatment on the red phosphorus layer 115 to convert the red phosphorus layer 115 into the black phosphorus layer 110 may refer to the description of the foregoing embodiments, and will not be described herein again. Because red phosphorus and black phosphorus are allotropes, a high-quality black phosphorus layer can be obtained through the cyclic heating and cooling treatment processes.
Between 1200 and 1400 degrees celsius, the solid solubility of carbon in silicon is only 10-4～10-3Atomic percent (at.%); but at 1404 degrees celsius eutectic point (eutectic point), the solubility of carbon in liquid silicon reaches 0.75 atomic percent. By laser annealing, the dissolved carbon in the molten liquid silicon can precipitate during cooling, which in turn unites (collice) and nucleates (nucleate) to form graphene layers. Accordingly, embodiments of the present invention use rapid heating and cooling of the silicon coating 125 and the carbon-containing material layer 126 of a laser annealing process to form the graphene layer 120. At high temperatures, organic substances and silicon may volatilize. Of course, after the graphene layer 120 is formed, the remaining material may be cleaned. For example, after the graphene layer 120 is formed, the remaining layer of carbon-containing material 126 is removed, resulting in the structure shown in fig. 1.
It should be noted that, in the above embodiments, the method for forming the black phosphorus layer 110 and the graphene layer 120 on the black phosphorus layer 110 on the substrate 100 is only an example, and in other embodiments, other processes may be adopted, which is not limited in the present invention.
Next, referring to fig. 8, after forming a black phosphorus layer 110 and a graphene layer 120 on the substrate 100, an imaged mask layer 130 is formed on the graphene layer 120.
The shape of the patterned mask layer 130 is designed according to a specific optical path, and corresponds to the shape of the waveguide to be formed, which is not limited in the present invention. The patterned mask layer 130 may be a photoresist layer or a hard mask layer. When the patterned mask layer 130 is a photoresist layer, the patterned mask layer is formed by coating, drying, photoetching, developing and other processes on the photoresist material; when the patterned mask layer 130 is a hard mask, a hard mask material layer, such as titanium nitride or silicon nitride, is formed on the graphene layer 120, an imaged photoresist layer is formed on the hard mask material layer by using the method, the patterned photoresist layer is etched with the patterned photoresist layer as a mask, an imaged hard mask layer is formed, and then the patterned photoresist layer is removed.
Next, referring to fig. 9, the patterned mask layer 130 (also referring to fig. 8) is used as a mask to etch the graphene layer 120 and the black phosphorus layer 110 until the substrate 100 is exposed, so as to form a waveguide. After the etching process, the patterned mask layer 130 also needs to be removed.
In some embodiments, the process of etching the graphene layer 120 and the black phosphorus layer 110 is dry etching. Such as reactive ion etching. After the etching process, a groove exposing the substrate 100 is formed, and the remaining graphene layer 120 and the black phosphorus layer 110 under the mask layer 130 and the substrate 110 form a waveguide according to an embodiment of the present invention.
In the embodiment of the invention, the graphene layer and the black phosphorus layer in the waveguide are formed by etching by taking the imaged mask layer 130 as a mask, so that the graphene layer and the black phosphorus layer are consistent in shape and have the same edge, thereby being beneficial to reducing transmission loss and improving the performance of the waveguide.
Correspondingly, the embodiment of the invention also provides a waveguide formed by adopting the method. Referring to fig. 9, the waveguide includes: a substrate 100; a black phosphorus layer 110 on the substrate 100; the graphene layer 120 is located on the black phosphorus layer 110, and the size of the graphene layer 110 and the size of the black phosphorus layer 120 along the surface direction of the substrate 100 are the same, and the positions of the graphene layer and the black phosphorus layer correspond to each other. It should be noted that the above-mentioned dimension identity is not strictly identical in an exponential sense, but is consistent in dimension within an allowable error range of the etching process.
Correspondingly, the waveguide according to the embodiment of the present invention also has the advantages of the method described above, and specific reference may be made to the description of the method, which is not repeated herein.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (4)
1. A method of forming a waveguide, comprising:
providing a substrate;
forming a black phosphorus layer and a graphene layer on the black phosphorus layer on the substrate;
forming a patterned mask layer on the graphene layer;
etching the graphene layer and the black phosphorus layer until the substrate is exposed;
removing the patterned mask layer;
forming a black phosphorus layer on the substrate and a graphene layer on the black phosphorus layer includes:
forming a red phosphorus layer on the substrate;
forming a silicon coating layer on the red phosphorus layer and a carbon-containing material layer on the silicon coating layer;
and carrying out heat treatment on the red phosphorus layer, the silicon coating layer and the carbon-containing material layer to enable the red phosphorus layer to form a black phosphorus layer, and the silicon coating layer and the carbon-containing material layer to form a graphene layer.
2. The method of forming a waveguide of claim 1 further comprising: and after the red phosphorus layer is formed, thinning the red phosphorus layer to reach the preset thickness.
3. The method of claim 2, wherein said thinning of said red phosphorus layer is performed using an argon plasma.
4. The method of claim 1, wherein the red phosphor layer is formed using a chemical vapor deposition process or a molecular beam epitaxy process.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201610005308.4A CN106941205B (en) | 2016-01-05 | 2016-01-05 | Waveguide and method of forming the same |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201610005308.4A CN106941205B (en) | 2016-01-05 | 2016-01-05 | Waveguide and method of forming the same |
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| CN106941205A CN106941205A (en) | 2017-07-11 |
| CN106941205B true CN106941205B (en) | 2019-12-31 |
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Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112379480B (en) * | 2020-11-17 | 2022-05-24 | 济南晶正电子科技有限公司 | Preparation method of waveguide structure composite substrate, composite substrate and photoelectric crystal film |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104217930A (en) * | 2013-06-05 | 2014-12-17 | 中芯国际集成电路制造(上海)有限公司 | Method for forming graphene patterns |
| CN104310326A (en) * | 2014-10-29 | 2015-01-28 | 浙江大学 | Black phosphorus preparation method with high conversion rate |
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2016
- 2016-01-05 CN CN201610005308.4A patent/CN106941205B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104217930A (en) * | 2013-06-05 | 2014-12-17 | 中芯国际集成电路制造(上海)有限公司 | Method for forming graphene patterns |
| CN104310326A (en) * | 2014-10-29 | 2015-01-28 | 浙江大学 | Black phosphorus preparation method with high conversion rate |
Non-Patent Citations (1)
| Title |
|---|
| "Waveguide-integrated black phosphorus photodetector with high responsivity and low dark current";Nathan Youngblood等;《Nature Photonics》;20150502;第2-3栏，附图1 * |
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