Preparation method of high-perpendicularity BTO waveguide

Abstract

The invention discloses a preparation method of a high-perpendicularity BTO waveguide. The preparation method comprises the following steps: S1, growing a Si3N4 film layer; s2, coating a photoresist; s3, etching is carried out; s4, a BTO sol-gel agent is poured; step S5, annealing; s6, performing CMP (chemical mechanical polishing); and S7, growing a cladding. The invention discloses a preparation method of a high-perpendicularity BTO waveguide, which comprises the following steps of: transferring a pattern through twice etching, transferring the pattern to a quartz substrate, removing photoresist, cleaning, and removing organic matters on the surface of a wafer. And solidifying the BTO solution in the etched groove through a customized mold, and filling each corner of the groove with the solution through ultrasound. And the thickness of the BTO and the flatness of the surface are adjusted through CMP. And growing an upper cladding to prepare a BTO waveguide with high perpendicularity, thereby improving the performance of the modulator, and realizing a barium titanate waveguide structure with high aspect ratio, high absolute depth, vertical side wall angle and smooth side wall.

Description

Technical Field

[0001] The invention belongs to the technical field of waveguide preparation technology, and in particular relates to a method for preparing a high-verticality BTO waveguide. Background Art

[0002] With the development of micro-electromechanical system (MEMS) technology, silicon material has begun to emerge as a low-cost, easy-to-process structural material in the field of microelectronics. However, as a functional material, silicon material still has many deficiencies in performance. In the field of optoelectronic transmission, a new type of MEMS device, its transmission loss is large, and many various materials show better performance (quality factor Q) than silicon. Specifically, in the technical fields of optical waveguides, microwave technology, sensors, and biochips, devices based on perovskite materials such as lithium niobate and barium titanate have emerged.

[0003] Due to the chemical stability and compact crystal structure of barium titanate materials. Currently, perovskite materials face problems such as difficult etching and by-products that easily remain in the etching cavity, resulting in a low reaction rate on its surface, leading to a slow etching process. During the etching process, due to the unevenness of the barium titanate surface (such as defects, impurities, etc.) and the uneven distribution of the etchant, the etching results may be uneven. The by-products produced during the etching process may be difficult to completely remove and remain in the etching cavity or the surface of the material, causing chamber contamination. In addition, the etched barium titanate waveguide will have defects such as a low waveguide angle and rough side walls.

[0004] Therefore, further improvements are made to the above problems. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for preparing a high verticality BTO waveguide to achieve a barium titanate waveguide structure with a high aspect ratio, a high absolute depth, a vertical side wall angle and a smooth side wall.

[0006] To achieve the above objectives, the present invention provides a method for preparing a high verticality BTO waveguide, comprising the following steps:

[0007] Step S1: Using low pressure chemical vapor deposition method on a quartz substrate (SiO 2 ) is grown on a Si layer with a preset thickness (1um) 3 N 4 Thin film layer, thus obtaining a wafer, and processed by CMP process to ensure Si 3 N 4 The thickness, surface roughness and uniformity of the film layer;

[0008] Step S2: Si3 N 4 The surface of the film layer is subjected to adhesion enhancement and is coated with photoresist;

[0009] Step S3: Perform the first etching step, introduce the first etching gas into the process chamber of the etching equipment, and use the first process parameters to etch the upper Si layer. 3 N 4 The thin film layer is subjected to plasma etching; a second step of etching is performed, a second etching gas is introduced into the process chamber of the etching equipment, and a second process parameter is used to perform plasma etching on the lower quartz substrate;

[0010] Step S4: Use a degumming liquid and plasma cleaning to remove the residual photoresist, place the etched wafer in a customized mold, pour BTO (barium titanate) sol-gel, and ultrasonically heat the bottom to facilitate the BTO sol-gel to enter the etched grooves;

[0011] Step S5: After being completely solidified, the BTO sol-gel is placed in an annealing furnace for annealing, and after annealing, the BTO sol-gel is completely solidified into a layer of BTO film;

[0012] Step S6: adjusting the thickness and surface flatness of the BTO film by CMP process;

[0013] Step S7: Use PECVD (plasma enhanced chemical vapor deposition) to grow a cladding layer (boro-phospho-silicate glass (BPSG)) to prepare a BTO waveguide with high verticality, thereby improving the modulator performance.

[0014] As a further preferred technical solution of the above technical solution, for the first etching step of step S3, the first process parameter includes the lower electrode power and the upper electrode power, the upper electrode power is greater than 1500W, the lower electrode power is greater than 100W, and the etching time is determined by Si 3 N 4 The thickness of the thin film layer determines the etching process (it can be overetched by about 10% to ensure clean etching).

[0015] As a further preferred technical solution of the above technical solution, for the second etching step of step S3, the second process parameters include lower electrode power and upper electrode power, the upper electrode power is greater than 1500W, and the lower electrode power is greater than 200W.

[0016] As a further preferred technical solution of the above technical solution, the first etching gas is a first fluorine-based gas and Ar, O 2 The first fluorine-based gas is CHF 3 With CF 4, the ratio of C atoms to F atoms in the first fluorine-based gas is maintained at a preset ratio (between 1:2 and 1:4).

[0017] As a further preferred technical solution of the above technical solution, the second etching gas is a second fluorine-based gas and Ar, O 2 The second fluorine-based gas is C 4 F 8 With CF 4 , the ratio of C atoms to F atoms in the second fluorine-based gas is maintained at a preset ratio (between 1:2 and 1:4). BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the process of the present invention.

[0019] Figure 2 is a schematic diagram of a wafer of the present invention.

[0020] Figure 3 It is a schematic diagram of the pattern after photolithography of the present invention.

[0021] Figure 4 It is a schematic diagram of the first etching step of the present invention.

[0022] Figure 5 It is a schematic diagram of the second etching step of the present invention.

[0023] Figure 6 It is a schematic diagram of forming a BTO thin film according to the present invention.

[0024] Figure 7 It is a schematic diagram of removing excess BTO film according to the present invention.

[0025] Figure 8 is a schematic diagram of the growth blanket of the present invention.

[0026] Reference numerals include: 1, Si 3 N 4 1. Thin film layer; 2. Quartz substrate; 3. Photoresist; 4. BTO thin film; 5. Cladding layer. DETAILED DESCRIPTION

[0027] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are only examples, and those skilled in the art can think of other obvious variations. The basic principles of the present invention defined in the following description can be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not deviate from the spirit and scope of the present invention.

[0028] In the preferred embodiment of the present invention, those skilled in the art should note that the low pressure chemical vapor deposition method, CMP, etc. involved in the present invention can be regarded as prior art.

[0029] Preferred embodiments.

[0030] like Figure 1-8 As shown, the present invention discloses a method for preparing a high verticality BTO waveguide, comprising the following steps:

[0031] Step S1: Using low pressure chemical vapor deposition method on a quartz substrate 2 (SiO 2 ) is grown on a Si layer with a preset thickness (1um) 3 N 4 Thin film layer 1, thereby obtaining a wafer, and processed by CMP process to ensure Si 3 N 4 The thickness, surface roughness and uniformity of the film layer 1;

[0032] Step S2: Si 3 N 4 The surface of the thin film layer 1 is subjected to adhesion enhancement and coated with a photoresist 3;

[0033] Step S3: Perform the first etching step, introduce the first etching gas into the process chamber of the etching equipment, and use the first process parameters to etch the upper Si layer. 3 N 4 The thin film layer is subjected to plasma etching; a second step of etching is performed, a second etching gas is introduced into the process chamber of the etching equipment, and a second process parameter is used to perform plasma etching on the lower quartz substrate;

[0034] Step S4: Use a degumming liquid and plasma cleaning to remove residual photoresist to avoid organic pollution, place the etched wafer in a customized mold, pour BTO (barium titanate) sol-gel, and ultrasonically heat the bottom to facilitate the BTO sol-gel to enter the etched grooves;

[0035] Step S5: After being completely solidified, the BTO sol-gel is placed in an annealing furnace for annealing (placed in an annealing furnace for rapid annealing at 800° C. for 5 minutes), and after annealing, the BTO sol-gel agent is completely solidified into a layer of BTO film 4;

[0036] Step S6: Adjust the thickness and surface flatness of the BTO film 4 by CMP process (the excess BTO needs to be thinned by CMP to ensure uniformity, and the Si 3 N 4 It can also serve as a polishing stop layer to prevent the uniformity of subsequent growth of silicon oxide film);

[0037] Step S7: Use PECVD (plasma enhanced chemical vapor deposition) to grow the cladding 5 (Boro-phospho-silicate glass (BPSG)) to prepare a BTO waveguide with high verticality, thereby improving the modulator performance.

[0038] Specifically, for the first etching step of step S3, the first process parameters include the lower electrode power and the upper electrode power, the upper electrode power is greater than 1500W, the lower electrode power is greater than 100W, and the etching time is determined by Si 3 N 4 The thickness of the film layer is determined (it can be overetched by about 10% to ensure clean etching), where:

[0039] Upper electrode power: 1500~2000W;

[0040] Lower electrode power: 100~300W;

[0041] Cavity pressure: 5~10mT;

[0042] CF 4 Flow rate: 20-40 sccm;

[0043] CHF 3 Flow rate: 40~80sccm;

[0044] Ar flow rate is: 10~40sccm.

[0045] More specifically, for the second etching step of step S3, the second process parameters include the lower electrode power and the upper electrode power, the upper electrode power is greater than 1500W, and the lower electrode power is greater than 200W, wherein:

[0046] Upper electrode power: 1500~2000W;

[0047] Lower electrode power: 100~400W;

[0048] Cavity pressure: 5~10mT;

[0049] CF 4 Flow rate: 10~80sccm;

[0050] C 4 F 8 Flow rate: 40~200sccm;

[0051] O 2 The flow rate is: 10~40sccm.

[0052] Furthermore, the first etching gas is a first fluorine-based gas and Ar, O 2 Mixed gas (Ar, O 2One of them or a mixture of two of them is acceptable), the first fluorine-based gas is CHF 3 With CF 4 , the ratio of C atoms to F atoms in the first fluorine-based gas is maintained at a preset ratio (between 1:2 and 1:4).

[0053] Furthermore, the second etching gas is a second fluorine-based gas and Ar, O 2 Mixed gas (Ar, O 2 One of them or a mixture of two of them is acceptable), the second fluorine-based gas is C 4 F 8 With CF 4 , the ratio of C atoms to F atoms in the second fluorine-based gas is maintained at a preset ratio (between 1:2 and 1:4).

[0054] The present invention transfers the pattern by etching twice, firstly, a first fluorine-based gas is introduced into the process chamber of the etching equipment, and a first process parameter is used to etch the upper silicon nitride layer (Si 3 N 4 The first step is to perform plasma etching on the silicon oxide layer (thin film layer). In the second step of etching, a second fluorine-based gas is introduced into the process chamber of the etching equipment, and the silicon oxide layer (quartz substrate) is plasma etched using the second process parameters. The pattern is transferred to the silicon oxide layer. Degumming and cleaning are performed to remove organic matter on the surface of the wafer. The BTO solution is solidified in the etched grooves through a customized mold, and the solution is filled into every corner of the grooves through ultrasound. The thickness and surface flatness of the BTO are then adjusted through CMP. The upper cladding is grown to prepare a high verticality BTO waveguide, thereby improving the performance of the modulator.

[0055] For the present invention, the growth of Si 3 N 4 As a mask layer for etching quartz substrates and a polishing stop layer for subsequent CMP, Si 3 N 4 Due to its good chemical stability and mechanical strength, it is very suitable as a polishing stop layer. Through the use of photoresist (i.e., evenly applying photoresist on the surface of the wafer) and photolithography technology, the pattern to be etched is defined. Then, these patterns are used as masks to 3 N 4 The basic structure of the waveguide is formed. After applying the BTO solution, ultrasonic waves are applied to the bottom of the wafer, and a certain amount of pressure is applied above the wafer for 20 minutes. Through the combination of ultrasonic vibration and pressure from above, the BTO solution is better filled into the etched structure, and the formation of bubbles and voids is reduced, thereby improving the verticality and sidewall smoothness of the waveguide. A BTO waveguide with high verticality and low sidewall roughness is prepared.

[0056] It is worth mentioning that the technical features such as low-pressure chemical vapor deposition and CMP involved in the patent application of this invention should be regarded as prior art. The specific structure, working principle and possible control method and spatial arrangement method of these technical features can be selected according to the conventional methods in the field, and should not be regarded as the inventive point of this patent. This patent will not be further elaborated.

[0057] For those skilled in the art, it is still possible to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a high verticality BTO waveguide, characterized in that: The following steps are involved: Step S1: growing a Si3N4 thin film layer of a preset thickness on a quartz substrate using a low pressure chemical vapor deposition method to obtain a wafer, and processing the wafer using a CMP process to ensure the thickness, surface roughness and uniformity of the Si3N4 thin film layer; Step S2: increasing the adhesion of the surface of the Si3N4 thin film layer and coating it with photoresist; Step S3: performing the first etching step, introducing the first etching gas into the process chamber of the etching equipment, and performing plasma etching on the upper Si3N4 thin film layer using the first process parameters; performing the second etching step, introducing the second etching gas into the process chamber of the etching equipment, and performing plasma etching on the lower quartz substrate using the second process parameters; Step S4: Use a degumming liquid and plasma cleaning to remove the residual photoresist, place the etched wafer in a customized mold, pour BTO sol-gel, and ultrasonically heat the bottom to facilitate the BTO sol-gel to enter the etched grooves; Step S5: After being completely solidified, the BTO sol-gel is placed in an annealing furnace for annealing, and after annealing, the BTO sol-gel is completely solidified into a layer of BTO film; Step S6: adjusting the thickness and surface flatness of the BTO film by a CMP process; Step S7: Use PECVD to grow the cladding to prepare a BTO waveguide with high verticality, thereby improving the modulator performance.

2. The method for preparing a high verticality BTO waveguide according to claim 1, characterized in that: For the first etching step of step S3, the first process parameters include the lower electrode power and the upper electrode power, the upper electrode power is greater than 1500W, the lower electrode power is greater than 100W, and the etching time is determined by the thickness of the Si3N4 thin film layer.

3. The method for preparing a high verticality BTO waveguide according to claim 2, characterized in that: For the second etching in step S3, the second process parameters include the lower electrode power and the upper electrode power, the upper electrode power is greater than 1500W, and the lower electrode power is greater than 200W.

4. The method for preparing a high verticality BTO waveguide according to claim 1, characterized in that: The first etching gas is a mixed gas of a first fluorine-based gas, Ar and O2. The first fluorine-based gas is CHF3 and CF4. The ratio of C atoms to F atoms in the first fluorine-based gas is maintained at a preset ratio.

5. The method for preparing a high verticality BTO waveguide according to claim 1, characterized in that: The second etching gas is a mixed gas of a second fluorine-based gas, Ar and O2. The second fluorine-based gas is C4F8 and CF4. The ratio of C atoms to F atoms in the second fluorine-based gas is maintained at a preset ratio.

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