CN112269223B - Silicon-based wedge-shaped waveguide micro-ring cavity and preparation method thereof - Google Patents
Silicon-based wedge-shaped waveguide micro-ring cavity and preparation method thereof Download PDFInfo
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Abstract
The invention provides a silicon-based wedge-shaped waveguide micro-ring cavity which comprises a straight waveguide (a) and a waveguide micro-ring cavity (b), wherein the cross section of the waveguide micro-ring cavity (b) is isosceles trapezoid, a circular micro disc (c) with a wedge-shaped edge is arranged at the center of the waveguide micro-ring cavity (b), an annular window (d) is arranged between the waveguide micro-ring cavity (b) and the circular micro disc (c), a cavity (e) is arranged below the waveguide micro-ring cavity (b), the waveguide micro-ring cavity (b) is in a suspended state by the cavity (e), and the circular micro disc (c) is in a partially suspended state; the straight waveguide (a) is an embedded strip waveguide, and the straight waveguide (a) and the waveguide micro-ring cavity (b) are mutually laterally coupled. The section of the micro-ring cavity of the silicon-based wedge-shaped waveguide micro-ring cavity is trapezoidal, and the scattering loss of the side wall is low.
Description
Technical Field
The invention relates to the technical field of on-chip micro-nano optoelectronic device preparation, in particular to a silicon-based wedge-shaped waveguide micro-ring cavity and a preparation method thereof.
Background
Optical microcavity refers to a micro-optical resonator of comparable size to an optical wavelength. Typical optical microcavities have three main structures: Fabry-Perot (F-P) microcavities, Whispering Gallery Mode (WGM) microcavities, and photonic crystal microcavities. The whispering gallery mode micro-cavity utilizes the total reflection principle to locally form a closed loop in the cavity by the light waves, the intrinsic Q value of the structure is high, the preparation process is simple, the coupling with other devices is convenient, and the whispering gallery mode micro-cavity has a huge application prospect in the research fields of photonic devices such as an optical integrated gyroscope, an integrated stimulated Brillouin laser and an integrated optical frequency comb which are researched at present.
At present, the whispering gallery mode microcavity mainly comprises structures such as a microsphere cavity, a microdisk cavity, a microring core cavity, a waveguide microring cavity and the like. The preparation process of the microsphere cavity and the micro-ring core cavity both needs to use a laser heat treatment process, and the compatibility with the micro-nano process is poor. The integration of the microdisk cavities with other on-chip waveguide devices is poor. The waveguide micro-ring cavity has the advantages of good process compatibility and on-chip integration, but the Q value of the waveguide micro-ring cavity obtained by the current manufacturing method is generally 106It is not high enough, and the main reasons are two points: (1) the traditional waveguide micro-ring cavity is usually prepared in a photoetching mode, so that the residual stress in the material is large, the surface roughness is high, and the light scattering and diffraction loss are increased; (2) the section of the prepared waveguide micro-ring cavity is square, the distance between the mode field in the cavity and the rough side wall of the cavity is very close, and the scattering loss of the side wall is high.
Disclosure of Invention
Based on this, there is a need for a high-Q waveguide micro-ring cavity and a method for making the same. The technical scheme for solving the technical problems is as follows:
the invention provides a silicon-based wedge-shaped waveguide micro-ring cavity which comprises a straight waveguide and a waveguide micro-ring cavity, wherein the cross section of the waveguide micro-ring cavity is isosceles trapezoid, a circular micro-disc with a wedge-shaped edge is arranged at the center of the waveguide micro-ring cavity, an annular window is arranged between the waveguide micro-ring cavity and the circular micro-disc, a cavity is arranged below the waveguide micro-ring cavity, the waveguide micro-ring cavity is in a suspended state, the circular micro-disc is in a partially suspended state, the straight waveguide is an embedded strip-shaped waveguide, and the straight waveguide and the waveguide micro-ring cavity are mutually laterally coupled.
Further, the diameter L1 of the circular microdisk is 1mm-40mm, the angle of the wedge shape of the edge of the circular microdisk is 30-75 degrees, and the annular width L2 of the annular window is 6 μm-8 μm; the length of the lower base of the isosceles trapezoid is 5 mu m +/-10 percent, the height of the lower base of the isosceles trapezoid is 5 mu m-8 mu m, and the included angle between the waist of the isosceles trapezoid and the lower base is 30-50 degrees; the width of the straight waveguide is 900nm +/-10%. The height of the isosceles trapezoid is the distance from the top of the waveguide micro-ring cavity to the upper surface of the silicon substrate.
The waveguide micro-ring structure comprises a silicon substrate, a first silicon dioxide layer and a second silicon dioxide layer, wherein the first silicon dioxide layer and the second silicon dioxide layer are arranged on the silicon substrate, the second silicon dioxide layer is arranged in a circular area in the center of the silicon substrate, the first silicon dioxide layer is arranged in an area outside the circular area, third silicon dioxide is further arranged on the surfaces of the first silicon dioxide layer and the second silicon dioxide layer, and the waveguide micro-ring cavity and the circular micro-disk are arranged on the first silicon dioxide layer; the straight waveguide comprises a waveguide dielectric layer and a cladding layer, the waveguide dielectric layer is buried in the third silicon dioxide layer, and the cavity is arranged on the silicon substrate.
Further, the waveguide medium layer is silicon nitride.
Further, the roughness of the side wall of the waveguide micro-ring cavity is +/-120 nm.
The invention also provides a preparation method of the silicon-based wedge-shaped waveguide micro-ring cavity, which comprises the following steps:
s1, performing first thermal oxidation;
generating a first silicon dioxide layer with the thickness of 5-7 mu m on a silicon substrate by utilizing a silicon-based thermal oxidation process;
s2, carrying out first isotropic wet etching;
s21, sequentially coating an adhesive and a photoresist on the surface of the first silicon dioxide layer prepared in the step S1 to prepare a circular mask;
s22, etching a disc with a wedge-shaped edge on the first silicon dioxide layer by using a hydrofluoric acid buffer solution;
s23, removing the photoresist;
s3, performing second thermal oxidation;
performing second thermal oxidation process treatment on the silicon substrate treated in the step S2, and growing a second silicon dioxide layer on the surface of the silicon substrate, wherein the thickness of the second silicon dioxide layer is 2-3 μm;
s4, depositing a silicon nitride layer on the surfaces of the first silicon dioxide layer and the second silicon dioxide layer by a plasma enhanced chemical vapor deposition method;
s5, etching the silicon nitride straight waveguide by the reactive ions;
s51, preparing a mask of the straight waveguide to be etched by coating a positive photoresist;
s52, etching a silicon nitride straight waveguide by using a reactive ion etching machine;
s53, removing residual silicon nitride by using a phosphoric acid wet etching process;
s54, removing the positive photoresist;
s55, growing a third silicon dioxide layer with the thickness of 200nm on the surfaces of the first silicon dioxide layer and the second silicon dioxide layer processed in the step S54 through atomic deposition to serve as a straight waveguide coating layer;
s6, performing second isotropic wet etching;
s61, manufacturing an annular window mask on the disc;
s62, etching an annular window on the disc by using a hydrofluoric acid buffer solution;
s63, removing the photoresist to prepare a light-emitting waveguide micro-ring cavity and a circular micro-disc;
s7, gas phase etching is carried out on the silicon layer below the annular window, and a cavity is prepared;
and etching the silicon layer below the annular window by using xenon fluoride gas phase, forming a cavity below the second silicon dioxide layer of the first silicon dioxide layer, and obtaining the wedge-shaped optical waveguide micro-ring cavity of the circular micro-disc and the air cladding after etching.
Further, the process parameters of the first isotropic wet etching in step S2 are as follows: the hydrofluoric acid buffer solution consists of 49% of HF and 40% of NH4F and deionized water, wherein the etching time is 10min-15min, and the etching temperature is 25-35 ℃; the process parameters of the second isotropic wet etching in the step S6 are as follows: the hydrofluoric acid buffer solution consists of 49% of HF and 40% of NH4F and deionized water, wherein the etching time is 5-15 min, and the etching temperature is 15-25 ℃.
Further, in the step S4, a silicon nitride layer is deposited by plasma enhanced chemical vapor deposition as a waveguide dielectric layer, the reaction temperature is 315 ℃ to 385 ℃, the deposition is completed, and then the annealing is performed for 2.7h to 3.3h, and the annealing temperature is 900 ℃ to 1100 ℃.
Further, the process for removing the photoresist comprises the following steps: firstly, putting a silicon substrate into an acetone solution for ultrasonic cleaning for 5min, then putting an isopropanol solution for ultrasonic cleaning for 5min, then repeating the cleaning step for 1-2 times until the surface photoresist is completely removed, putting the silicon substrate into deionized water for soaking for 5min, and drying the silicon substrate by a nitrogen gun.
The invention has the beneficial effects that:
(1) the section of the micro-ring cavity of the silicon-based wedge-shaped waveguide micro-ring cavity is trapezoidal, and the scattering loss of the side wall is low.
(2) A cavity is formed below the waveguide micro-ring cavity, the waveguide micro-ring cavity is in a suspended state, and the circular micro-disc is in a partially suspended state, so that the resonant cavity is wrapped by gas atmosphere, and interface light reflection is enhanced.
(3) The surface of the waveguide micro-ring cavity is treated by a chemical etching method, the material internal stress is small, the surface is smooth, and the surface roughness can reach +/-120 nm.
(4) The preparation method can be suitable for preparing silicon-based wedge-shaped waveguide micro ring cavities with different sizes, in particular to the silicon-based wedge-shaped waveguide micro ring cavities with small sizes.
(5) The silicon-based wedge-shaped waveguide micro ring cavity on the two side walls of the waveguide micro ring cavity takes silicon-based materials as substrates, can utilize a mature microelectronic CMOS (complementary metal oxide semiconductor) processing technology, is easy for large-scale batch production and is beneficial to reducing the cost of devices.
Drawings
FIG. 1 is a top view of a silicon-based wedge waveguide micro-ring cavity of the present invention;
FIG. 2 is a schematic cross-sectional view of a silicon-based wedge waveguide micro-ring cavity of the present invention;
FIG. 3 is a flow chart of the present invention for preparing a silica-based wedge waveguide micro-ring cavity.
Description of reference numerals:
a straight waveguide, b waveguide micro-ring cavity, c round micro-disc, d ring window and e cavity.
1 silicon substrate, 2 first silicon dioxide layer, 3 second silicon dioxide layer, 4 silicon nitride layer, 5 third silicon dioxide layer.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.
The silicon-based wedge-shaped waveguide micro-ring cavity provided by the invention is shown in figure 1 and comprises a straight waveguide a and a waveguide micro-ring cavity b, wherein the cross section of the waveguide micro-ring cavity b is in an isosceles trapezoid shape, a circular micro-disc c with a wedge-shaped edge is arranged at the center of the waveguide micro-ring cavity b, an annular window d is arranged between the waveguide micro-ring cavity b and the circular micro-disc c, a cavity e is arranged below the waveguide micro-ring cavity b, so that the waveguide micro-ring cavity b is in a suspended state, the circular micro-disc c is in a partially suspended state, the straight waveguide a is an embedded strip waveguide, and the straight waveguide a and the waveguide micro-ring cavity b are laterally coupled with each other. The diameter L1 of the circular micro disc c is 1mm-40mm, the angle of the wedge shape of the edge of the circular micro disc c is 30-75 degrees, and the annular width L2 of the annular window d is 6 μm-8 μm; the length of the upper base of the isosceles trapezoid is 3 mu m +/-10 percent, the length of the lower base is 5 mu m +/-10 percent, the height of the isosceles trapezoid is 5 mu m-8 mu m, and the included angle between the waist and the lower base of the isosceles trapezoid is 30-50 degrees. The width of the straight waveguide a is 900nm +/-10%. The size of the silicon-based wedge-shaped waveguide micro-ring cavity can be specifically adjusted according to the use requirement.
Fig. 2 is a schematic cross-sectional view of a silicon-based wedge-shaped waveguide micro ring cavity of the present invention, and it can be seen from the figure that the silicon-based wedge-shaped waveguide micro ring cavity includes a silicon substrate 1, the first silicon dioxide layer 2 is disposed in a circular region at the center of the silicon substrate 1, the second silicon dioxide layer 3 is disposed in a region outside the circular region, the surfaces of the first silicon dioxide layer 2 and the second silicon dioxide layer 3 are further provided with a third silicon dioxide layer 5, and the waveguide micro ring cavity b and a circular microdisk c are disposed in the first silicon dioxide layer 2; the straight waveguide a comprises a waveguide dielectric layer and a cladding layer, the waveguide dielectric layer is buried in the third silicon dioxide layer 5, and the cavity e is arranged on the silicon substrate 1. The width of the straight waveguide a refers to the width of the dielectric layer.
The steps which are not particularly described in the invention are all prepared by adopting the prior art in the technical field. A silicon substrate having dimensions of 3mm by 4mm by 1mm was used as the silicon substrate 1.
The equipment such as a contact ultraviolet exposure machine and a reaction ion machine in the invention are conventional equipment in the field.
Example 1
The embodiment provides a preparation method of a silicon-based wedge-shaped waveguide micro-ring cavity, which comprises the following steps:
s1, performing first thermal oxidation;
the silicon substrate 1 is firstly oxidized by wet oxygen to form a silicon dioxide layer, and then is oxidized by dry oxygen at the temperature of 1000 ℃ for 24 hours to form a first silicon dioxide layer 2 with the thickness of 5 mu m on the silicon substrate 1.
S2, performing first isotropic wet etching;
s21, cleaning the silicon substrate 1 processed in the step S1 by adopting a standard RCA process, drying by using a nitrogen gun, and baking for 1h at 120 ℃ in a baking oven; sequentially evaporating and coating an adhesive Hexamethyldisilane (HDMS) adhesive on the surface of the first silicon dioxide layer 2, and spin-coating AZ6310 photoresist; finally, photoetching is carried out by using a contact type ultraviolet exposure machine, and a circular mask is prepared after development is finished;
s22, etching a disc with a wedge-shaped edge on the first silicon oxide layer 2 by using a hydrofluoric acid buffer solution; the hydrofluoric acid buffer solution consists of 49% of HF and 40% of NH4F and deionized water. The etching time is 15min, and the etching temperature is 35 ℃.
S23, cleaning the photoresist; firstly, the silicon substrate 1 is placed into an acetone solution for ultrasonic cleaning for 5min, and then placed into an isopropanol solution for ultrasonic cleaning for 5 min. The cleaning was repeated until the surface was completely cleaned of AZ6310 photoresist. Soaking in deionized water for 5min, and blowing with nitrogen gas.
S3, performing second thermal oxidation;
performing a second thermal oxidation process on the silicon substrate 1 processed in step S2 to form a second silicon dioxide layer 3 with a thickness of 3 μm on the surface of the silicon substrate 1;
s4, depositing a waveguide dielectric layer silicon nitride layer 4 on the first silicon dioxide layer 2 and the second silicon dioxide layer 3 by using a Plasma Enhanced Chemical Vapor Deposition (PECVD) method, wherein the thickness is 250nm, the deposition reaction temperature is 315 ℃, and annealing is carried out for 2.7h after the deposition is finished, and the annealing temperature is 900 ℃.
S5, etching a strip-shaped silicon nitride straight waveguide dielectric layer by using a reactive ion machine;
s51, photoetching a silicon nitride straight waveguide mask by using a contact ultraviolet alignment exposure machine, wherein the photoresist uses AZ5214 positive photoresist, the width of a silicon nitride straight waveguide medium is about 900nm, single TE mode transmission is ensured, and the phase of the silicon nitride straight waveguide mask is matched with the phase of a waveguide micro-ring cavity b;
s52, etching the silicon nitride straight waveguide dielectric layer by using a reactive ion etching machine;
s53, removing residual silicon nitride by using a phosphoric acid wet etching process, wherein the concentration of phosphoric acid is 15%.
S54, removing the photoresist; the process is the same as step S23.
S55, growing a third silicon dioxide layer 5 on the surfaces of the first silicon dioxide layer 2 and the second silicon dioxide layer 3 processed in the step S54 through atomic deposition to serve as a silicon nitride straight waveguide medium layer coating layer, wherein the thickness of the third silicon dioxide layer is 200nm, and a straight waveguide a is prepared;
s6, performing second isotropic wet etching;
s61, photoetching and manufacturing a mask of an annular window d on the disc by adopting a contact type ultraviolet alignment exposure machine, wherein the photoresist uses AZ5214 positive photoresist, and the width of the annular window is 6 mu m;
s62, corroding an annular window d on the disc by using a hydrofluoric acid buffer solution; the hydrofluoric acid buffer solution consists of 49% of HF and 40% of NH4F and deionized water. The etching time is 10min, and the etching temperature is 15 ℃.
S63, removing the AZ5214 photoresist.
S7, gas phase etching is conducted on the silicon layer 1 below the annular window d;
and etching the silicon layer 1 below the annular window d by the xenon fluoride phase etching system to form a cavity e, and obtaining a silicon dioxide circular microdisk c and a wedge-shaped waveguide micro-ring cavity b of the air cladding after etching.
Example 2
The embodiment provides a preparation method of a silicon-based wedge-shaped waveguide micro-ring cavity, which comprises the following steps:
s1, performing first thermal oxidation;
the silicon substrate 1 is firstly oxidized into silicon dioxide by wet oxygen, and then is oxidized by dry oxygen at the temperature of 1000 ℃ for 24 hours, and a first silicon dioxide layer 2 with the thickness of 7 mu m is formed on the silicon substrate 1.
S2, performing first isotropic wet etching;
s21, cleaning the silicon substrate 1 processed in the step S1 by adopting a standard RCA process, drying by using a nitrogen gun, and baking for 1h at 120 ℃ in a baking oven; sequentially evaporating and coating an adhesive Hexamethyldisilane (HDMS) adhesive on the surface of the first silicon dioxide layer 2, and spin-coating AZ6310 photoresist; finally, photoetching is carried out by using a contact type ultraviolet exposure machine, and a circular mask is prepared after development is finished;
s22, etching a disc with a wedge-shaped edge on the first silicon dioxide layer 2 by using a hydrofluoric acid buffer solution; the hydrofluoric acid buffer solution consists of 49% of HF and 40% of NH4F and deionized water. The etching time is 10min, and the etching temperature is 25 ℃.
S23, cleaning the photoresist; firstly, the silicon substrate 1 is placed into an acetone solution for ultrasonic cleaning for 5min, and then placed into an isopropanol solution for ultrasonic cleaning for 5 min. The cleaning was repeated until the surface was completely cleaned of AZ6310 photoresist. Soaking in deionized water for 5min, and blowing with nitrogen gas.
S3, performing second thermal oxidation;
performing a second thermal oxidation process on the silicon substrate 1 processed in the step S2 to form a second silicon dioxide layer 3 with a thickness of 2 μm on the surface of the silicon substrate 1;
s4, depositing a silicon nitride layer 4 on the first silicon dioxide layer 2 and the second silicon dioxide layer 3 by using a Plasma Enhanced Chemical Vapor Deposition (PECVD) method, wherein the thickness is 250nm, the deposition reaction temperature is 385 ℃, and annealing is carried out for 3.3h after the deposition is finished, wherein the annealing temperature is 1100 ℃.
S5, etching a strip-shaped silicon nitride straight waveguide dielectric layer by using a reactive ion machine;
s51, photoetching a silicon nitride straight waveguide mask by using a contact ultraviolet alignment exposure machine, wherein the photoresist uses AZ5214 positive photoresist, the width of a silicon nitride straight waveguide medium is about 900nm, single TE mode transmission is ensured, and the phase of the silicon nitride straight waveguide mask is matched with the phase of a waveguide micro-ring cavity b;
s52, etching the silicon nitride straight waveguide dielectric layer by using a reactive ion etching machine;
s53, removing residual silicon nitride by using a phosphoric acid wet etching process, wherein the concentration of phosphoric acid is 15%.
S54, removing the photoresist; the process is the same as step S23.
S55, growing a third silicon dioxide layer 5 on the surfaces of the first silicon dioxide layer 2 and the second silicon dioxide layer 3 processed in the step S54 through atomic deposition, wherein the third silicon dioxide layer is used as a coating layer of a silicon nitride straight waveguide medium layer, the thickness of the third silicon dioxide layer is 200nm, and a straight waveguide a is prepared;
s6, performing second isotropic wet etching;
s61, photoetching and manufacturing a mask of an annular window d on the disc by adopting a contact type ultraviolet alignment exposure machine, wherein the photoresist uses AZ5214 positive photoresist, and the width of the annular window d is 8 mu m;
s62, corroding an annular window d on the disc by using a hydrofluoric acid buffer solution; the hydrofluoric acid buffer solution consists of 49% of HF and 40% of NH4F and deionized water. The etching time is 15min, and the etching temperature is 25 ℃.
S63, removing the AZ5214 photoresist.
S7, gas phase etching is carried out on the silicon substrate 1 under the annular window d;
and etching the silicon substrate 1 below the annular window d by the xenon fluoride phase etching system, forming a cavity e below the first silicon dioxide layer 2 and the second silicon dioxide layer 3, and obtaining a silicon dioxide circular microdisk c and a wedge-shaped waveguide micro-ring cavity b of the air cladding after etching.
Example 3
The embodiment provides a preparation method of a silicon-based wedge-shaped waveguide micro-ring cavity, which comprises the following steps:
s1, performing first thermal oxidation;
the silicon substrate 1 is firstly oxidized into silicon dioxide by wet oxygen, and then is oxidized by dry oxygen at the temperature of 1000 ℃ for 24h to form a first silicon dioxide layer 2 with the thickness of 6 mu m on the silicon substrate 1.
S2, performing first isotropic wet etching;
s21, cleaning the silicon substrate 1 processed in the step S1 by adopting a standard RCA process, drying by using a nitrogen gun, and baking for 1h at 120 ℃ in a baking oven; sequentially evaporating and coating an adhesive Hexamethyldisilane (HDMS) adhesive on the surface of the first silicon dioxide layer 2, and spin-coating AZ6310 photoresist; finally, photoetching is carried out by using a contact type ultraviolet exposure machine, and a circular mask is prepared after development is finished;
s22, etching a disc with a wedge-shaped edge on the first silicon dioxide layer 2 by using a hydrofluoric acid buffer solution; the hydrofluoric acid buffer solution consists of 49% of HF and 40% of NH4F and deionized water. The etching time is 15min, and the etching temperature is 25 ℃.
S23, cleaning the photoresist; firstly, the silicon substrate 1 is placed into an acetone solution for ultrasonic cleaning for 5min, and then placed into an isopropanol solution for ultrasonic cleaning for 5 min. The cleaning was repeated until the surface was completely cleaned of AZ6310 photoresist. Soaking in deionized water for 5min, and blowing with nitrogen gas.
S3, performing second thermal oxidation;
performing a second thermal oxidation process on the silicon substrate 1 processed in step S2 to form a second silicon dioxide layer 3 with a thickness of 3 μm on the surface of the silicon substrate 1;
s4, depositing a silicon nitride layer 4 on the first silicon dioxide layer 2 and the second silicon dioxide layer 3 by using a Plasma Enhanced Chemical Vapor Deposition (PECVD) method, wherein the thickness is 250nm, the deposition reaction temperature is 350 ℃, and annealing is carried out for 3 hours after the deposition is finished, wherein the annealing temperature is 1000 ℃.
S5, etching a strip-shaped silicon nitride straight waveguide dielectric layer by using a reactive ion machine;
s51, photoetching a silicon nitride straight waveguide mask by using a contact ultraviolet alignment exposure machine, wherein the photoresist uses AZ5214 positive photoresist, the width of a silicon nitride straight waveguide medium is about 900nm, single TE mode transmission is ensured, and the phase of the silicon nitride straight waveguide mask is matched with the phase of a waveguide micro-ring cavity b;
s52, etching the silicon nitride straight waveguide dielectric layer by using a reactive ion etching machine;
s53, removing residual silicon nitride by using a phosphoric acid wet etching process, wherein the concentration of phosphoric acid is 15%.
S54, removing the photoresist; the process is the same as step S23.
S55, growing a third silicon dioxide layer 5 on the surfaces of the first silicon dioxide layer 2 and the second silicon dioxide layer 3 processed in the step S45 through atomic deposition to serve as a silicon nitride straight waveguide coating layer, wherein the thickness of the third silicon dioxide layer is 200nm, and a straight waveguide a is prepared;
s6, performing second isotropic wet etching;
s61, photoetching and manufacturing a mask of an annular window d on the disc by adopting a contact type ultraviolet alignment exposure machine, wherein the photoresist uses AZ5214 positive photoresist, and the width of the annular window d is 7 mu m;
s62, corroding an annular window d on the disc by using a hydrofluoric acid buffer solution; the hydrofluoric acid buffer solution consists of 49% of HF and 40% of NH4F and deionized water. The etching time is 5min, and the etching temperature is 25 ℃.
S63, removing the AZ5214 photoresist.
S7, gas phase etching is conducted on the silicon layer 1 below the annular window d;
and etching the silicon layer 1 below the annular window d by the xenon fluoride phase etching system, forming a cavity e below the first dioxide layer 2 and the second silicon dioxide layer 3, and obtaining a silicon dioxide circular microdisk c and a wedge-shaped waveguide micro-annular cavity b of the air cladding after etching.
The silicon-based wedge waveguide micro-ring cavities prepared in examples 1-3 were subjected to dimensional testing and Q-value testing, and the results are shown in Table 1.
Table 1 results of testing silicon-based wedge waveguide micro-ring cavities prepared in examples 1-3
As can be seen from Table 1, the roughness of the side wall of the waveguide micro-ring cavity b of the silicon-based wedge-shaped waveguide micro-ring cavity prepared by the method can reach +/-120 nm, and the Q value can reach 108。
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (9)
1. A silicon-based wedge-shaped waveguide micro-ring cavity is characterized by comprising a straight waveguide (a) and a waveguide micro-ring cavity (b), wherein the cross section of the waveguide micro-ring cavity (b) is isosceles trapezoid, a circular micro disc (c) with a wedge-shaped edge is arranged at the center of the waveguide micro-ring cavity (b), an annular window (d) is arranged between the waveguide micro-ring cavity (b) and the circular micro disc (c), a cavity (e) is formed below the waveguide micro-ring cavity (b), the waveguide micro-ring cavity (b) is in a suspended state by the cavity (e), and the circular micro disc (c) is in a partially suspended state; the straight waveguide (a) is an embedded strip waveguide, and the straight waveguide (a) and the waveguide micro-ring cavity (b) are mutually laterally coupled.
2. The silicon-based wedge waveguide micro ring cavity of claim 1, wherein the diameter L1 of the circular micro disk (c) is 1mm-40mm, the angle of the edge wedge of the circular micro disk (c) is 30 ° -75 °, and the annular width L2 of the annular window (d) is 6 μm-8 μm; the length of the lower base of the isosceles trapezoid is 5 mu m +/-10 percent, the height of the lower base of the isosceles trapezoid is 5 mu m-8 mu m, and the included angle between the waist of the isosceles trapezoid and the lower base is 30-50 degrees; the width of the straight waveguide (a) is 900nm +/-10%.
3. The silicon-based wedge waveguide micro ring cavity according to any one of claims 1-2, comprising a silicon substrate (1), a first silicon dioxide layer (2) and a second silicon dioxide layer (3) which are arranged on the silicon substrate (1), wherein the first silicon dioxide layer (2) is arranged in a circular area at the center of the silicon substrate (1), the second silicon dioxide layer (3) is arranged in an area outside the circular area, a third silicon dioxide layer (5) is further arranged on the surfaces of the first silicon dioxide layer (2) and the second silicon dioxide layer (3), and the waveguide micro ring cavity (b) and the circular micro disc (c) are arranged on the first silicon dioxide layer (2); the straight waveguide (a) comprises a waveguide dielectric layer and a cladding layer, the waveguide dielectric layer is buried in the third silicon dioxide layer (5), and the cavity (e) is arranged on the silicon substrate (1).
4. The silicon-based wedge waveguide micro-ring cavity of any of claims 1-2, wherein the waveguide dielectric layer is silicon nitride.
5. The silicon-based wedge waveguide micro-ring cavity according to any of claims 1-2, wherein the roughness of the side wall of the waveguide micro-ring cavity (b) is ± 120 nm.
6. The preparation method of the silicon-based wedge-shaped waveguide micro-ring cavity as claimed in any one of claims 1 to 5, characterized by comprising the following steps:
s1, performing first thermal oxidation;
generating a first silicon dioxide layer (2) with the thickness of 5-7 mu m on a silicon substrate (1) by utilizing a silicon-based thermal oxidation process;
s2, performing first isotropic wet etching;
s21, coating an adhesive and a photoresist on the surface of the first silicon dioxide layer (2) prepared in the step S1 in sequence to prepare a circular mask;
s22, etching a disc with a wedge-shaped edge on the first silicon dioxide layer (2) by using a hydrofluoric acid buffer solution;
s23, removing the photoresist;
s3, performing second thermal oxidation;
performing second thermal oxidation process treatment on the silicon substrate (1) treated in the step S2, and growing a second silicon dioxide layer (3) on the surface of the silicon substrate (1), wherein the thickness of the second silicon dioxide layer (3) is 2-3 μm;
s4, depositing a silicon nitride layer (4) on the surfaces of the first silicon dioxide layer (2) and the second silicon dioxide layer (3) by a plasma enhanced chemical vapor deposition method;
s5, etching the silicon nitride straight waveguide (a) by reactive ions;
s51, preparing a mask of the straight waveguide (a) to be etched by coating a positive photoresist;
s52, etching the silicon nitride straight waveguide dielectric layer by using a reactive ion etching machine;
s53, removing residual silicon nitride by using a phosphoric acid wet etching process;
s54, removing the positive photoresist;
s55, growing a third silicon dioxide layer (5) with the thickness of 200nm on the surfaces of the first silicon dioxide layer (2) and the second silicon dioxide layer (3) processed in the step S54 through atomic deposition to serve as a cladding layer of the straight waveguide (a);
s6, performing second isotropic wet etching;
s61, manufacturing a mask of an annular window (d) on the disc;
s62, etching an annular window (d) on the disc by using a hydrofluoric acid buffer solution;
s63, removing the photoresist to prepare a waveguide micro-ring cavity (b) and a circular micro-disc (c);
s7, gas phase etching the silicon layer below the annular window (d) to prepare a cavity (e);
and (3) etching the silicon layer below the annular window (d) by using xenon fluoride, forming a cavity (e) below the first silicon dioxide layer (2) and the second silicon dioxide layer (3), and obtaining a circular microdisk (c) and a wedge-shaped waveguide micro-annular cavity (b) of the air cladding after etching.
7. The method for preparing the silicon-based wedge waveguide micro ring cavity according to claim 6, wherein the process parameters of the first isotropic wet etching of the step S2 are as follows: the hydrofluoric acid buffer solution consists of 49% of HF and 40% of NH4F and deionized water, wherein the etching time is 10min-15min, and the etching temperature is 25-35 ℃; the process parameters of the second isotropic wet etching in the step S6 are as follows: the hydrofluoric acid buffer solution consists of 49% of HF and 40% of NH4F and deionized water, wherein the etching time is 5-15 min, and the etching temperature is 15-25 ℃.
8. The method for preparing the silicon-based wedge-shaped waveguide micro ring cavity according to claim 6, wherein in the step S4, a silicon nitride layer (4) is deposited by utilizing plasma enhanced chemical vapor deposition to serve as a straight waveguide dielectric layer, the reaction temperature is 315-385 ℃, the deposition is finished, and the annealing is carried out, wherein the annealing temperature is 900-1100 ℃, and the annealing time is 2.7h-3.3 h.
9. The method for preparing the silicon-based wedge waveguide micro-ring cavity according to claim 6, wherein the process for removing the photoresist comprises: firstly, putting a silicon substrate (1) into an acetone solution for ultrasonic cleaning for 5min, then putting an isopropanol solution for ultrasonic cleaning for 5min, repeating the cleaning step for 1-2 times until the surface photoresist is completely removed, putting the silicon substrate into deionized water for soaking for 5min, and drying the silicon substrate by a nitrogen gun.
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