CN117233892A - Preparation method of optical waveguide and optical waveguide - Google Patents
Preparation method of optical waveguide and optical waveguide Download PDFInfo
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- CN117233892A CN117233892A CN202311153505.7A CN202311153505A CN117233892A CN 117233892 A CN117233892 A CN 117233892A CN 202311153505 A CN202311153505 A CN 202311153505A CN 117233892 A CN117233892 A CN 117233892A
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- 229910052581 Si3N4 Inorganic materials 0.000 claims abstract description 59
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims abstract description 59
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Abstract
The application provides a preparation method of an optical waveguide, the optical waveguide, relating to the technical field of optical fiber communication, wherein the optical waveguide comprises a substrate; forming a lower cladding layer on a substrate; forming a deposition layer on the lower cladding layer in a mode of multiple deposition and doping, wherein each deposition layer comprises an undoped region and a doped region for reducing film stress of the deposition layer, and the undoped regions of each layer are overlapped with each other; forming a waveguide core in the non-doped regions overlapped with each other by patterning the deposition layer; an upper cladding layer is formed over the waveguide core and the lower cladding layer. According to the preparation method of the optical waveguide, the deposition layer used for forming the waveguide core is optimized, and is divided into the doped region used for reducing the tensile stress and the undoped region used for forming the waveguide core, so that the influence of the tensile stress on the substrate in the process of forming the waveguide core is reduced, the probability of substrate warpage and silicon nitride waveguide core crack generation is reduced, and the optical waveguide is facilitated to have good optical performance.
Description
Technical Field
The present application relates to the field of optical fiber communications technologies, and in particular, to a method for manufacturing an optical waveguide and an optical waveguide.
Background
Chemical Vapor Deposition (LPCVD) processStoichiometric silicon nitride (Si 3 N 4 ) Film/waveguide core (hereinafter abbreviated as Si 3 N 4 Thin film/waveguide core) has the advantages of wide wavelength range (400-2350 nm) transparency, high optical power, low optical propagation loss, wafer level fabrication process, si 3 N 4 Waveguide core and silicon (Si) substrate, silicon dioxide (SiO) 2 ) Planar waveguide platforms of cladding layers enable a wide range of planar integrated devices and chip-scale solutions. However, stoichiometric Si prepared by LPCVD 3 N 4 The film has larger tensile stress, and can lead the substrate to warp seriously in the process, thereby having adverse effect on the subsequent photoetching and etching processes and the accuracy of the waveguide dimension, when Si 3 N 4 When the thickness of the film (waveguide) is more than 300nm, cracks are likely to occur during deposition or after high-temperature annealing, and thicker Si is required 3 N 4 The use of a waveguide core creates a barrier.
The existing technical methods for manufacturing thicker silicon nitride films/waveguide cores mainly comprise the following steps:
(1) multi-step spin-deposition: in SiO 2 Depositing Si with a certain thickness on the lower cladding layer by LPCVD 3 N 4 Thin film, then rotating the substrate by 45 DEG, and depositing Si with a certain thickness by LPCVD 3 N 4 A film. The technical proposal disperses Si by rotating the substrate by 45 degrees 3 N 4 Uniaxial stress of the film;
(2) photon Damascus process: in SiO 2 On the lower cladding, a groove structure is formed by photoetching and etching processes, and then Si is deposited by LPCVD 3 N 4 Removing Si outside the groove by the film and the CMP process 3 N 4 A film. Si in some grooves 3 N 4 Used as waveguide core, the rest groove structure is used for dispersing Si 3 N 4 Stress of the film;
(3) non-stoichiometric silicon nitride film: adjusting the film composition of the silicon nitride film (e.g., a silicon-rich silicon nitride film) can reduce film stress and achieve thicker silicon nitride films/waveguide cores.
Multi-step spin-on deposition, lightThe sub-Damascus process is implemented by conducting a process on Si 3 N 4 The stress of the film is dispersed, thicker Si can be realized 3 N 4 Film/waveguide core, but when Si is desired 3 N 4 When the film is thicker, the stress is still large, the substrate warpage is serious, and Si 3 N 4 The problem of film cracks is also easy to occur; the non-stoichiometric silicon nitride film solves the problem of serious substrate warpage and Si from the viewpoint of reducing the stress of the silicon nitride film 3 N 4 The problem of film cracking, but non-stoichiometric silicon nitride, significantly increases the optical propagation loss of the silicon nitride waveguide.
Disclosure of Invention
The application aims to provide a preparation method of an optical waveguide and the optical waveguide, which are used for solving the problem that a substrate is easy to warp and break in the existing preparation process of a thicker optical waveguide.
A first aspect of an embodiment of the present application provides a method for manufacturing an optical waveguide, including:
providing a substrate;
forming a lower cladding layer on the substrate;
forming a deposition layer on the lower cladding layer in a mode of multiple deposition and doping, wherein each deposition layer comprises an undoped region and a doped region for reducing film stress of the deposition layer, and the undoped regions of each layer are overlapped with each other;
forming a waveguide core in the non-doped regions overlapped with each other by patterning the deposition layer;
an upper cladding layer is formed over the waveguide core and the lower cladding layer.
In some alternative embodiments of the application, a stoichiometric silicon nitride film is deposited;
and doping a partial region of the silicon nitride film to form a deposition layer comprising a doped region and an undoped region, wherein the undoped region has tensile stress, and the tensile stress of the doped region is smaller than that of the undoped region or the doped region exhibits compressive stress.
In some optional embodiments of the present application, an ion implantation masking layer is fabricated on a corresponding position of the silicon nitride film, and a width of the ion implantation masking layer fabricated each time is not smaller than a width of a waveguide core to be fabricated and formed;
performing ion implantation on the silicon nitride film with the ion implantation masking layer, forming an undoped region in a region covered by the ion implantation masking layer, and forming a doped region in a region not covered by the ion implantation masking layer;
the ion implantation masking layer is selectively removed.
In some alternative embodiments of the present application, after removing the last-fabricated ion implantation masking layer, the deposited layer is patterned and a waveguide core is formed, specifically: manufacturing an etching masking layer on the last deposition layer and in the overlapped non-doped region lamination range; etching by taking the etching masking layer as a mask to form a waveguide core, and removing the etching masking layer;
or,
after removing the ion implantation masking layer manufactured for the last time, continuing to deposit a layer of silicon nitride film with stoichiometric ratio, and then patterning the deposited layer and forming a waveguide core specifically comprises the following steps: manufacturing an etching masking layer on the silicon nitride film which is continuously deposited and in the overlapped non-doped region lamination range; etching by taking the etching masking layer as a mask to form a waveguide core, and removing the etching masking layer;
or,
the ion implantation masking layer manufactured for the last time is reserved, and the steps of patterning the deposition layer and forming the waveguide core are as follows: and etching by taking the ion implantation masking layer manufactured at the last time as a mask to form a waveguide core, and removing the ion implantation masking layer.
In some optional embodiments of the present application, the material of the ion implantation masking layer is photoresist, metal or polysilicon;
the etching masking layer is made of photoresist, amorphous silicon, amorphous carbon, metal, polysilicon or a lamination of the above materials;
the substrate is made of silicon;
the material of the lower cladding is silicon dioxide, the silicon dioxide lower cladding grows on a silicon substrate through thermal oxidation, and the thickness of the silicon dioxide lower cladding is 4-20 um;
the thickness of each deposition layer is 100-300 nm;
the upper cladding layer is made of silicon dioxide, and the silicon dioxide upper cladding layer with a flat surface is formed through planarization.
In some optional embodiments of the present application, the conditions for performing the ion implantation are specifically:
the implanted ions are any one of the following: B. p, si;
the injection energy is 10-500 keV;
the implantation dose is 10 12 ～10 17 /cm 2 。
In some optional embodiments of the application, removing the ion implantation masking layer comprises:
removing the ion implantation masking layer by a wet method;
the wet removal selection ratio of the ion implantation masking layer to the waveguide core is larger than a preset selection ratio.
In some alternative embodiments of the present application, forming a waveguide core in undoped regions overlapping each other by patterning the deposited layer includes:
the waveguide core is formed by dry etching the deposited layer.
A second aspect of the embodiments of the present application provides an optical waveguide, which is prepared by using the preparation method of an optical waveguide according to any one of the embodiments, including:
a substrate;
a lower cladding layer formed on the substrate;
a waveguide core composed of a multi-deposited undoped stack of partially undoped regions of deposited film that has undergone stress relief;
and the upper cladding layer is used for cladding the waveguide core.
In some alternative embodiments of the application, the material of the substrate is silicon;
the lower cladding is made of silicon dioxide, and the thickness of the silicon dioxide lower cladding is 4-20 um;
the waveguide core is made of silicon nitride with stoichiometric ratio, and the thickness of the waveguide core is more than 300nm;
the number of the laminated layers is more than or equal to 2, and the thickness of each laminated layer is 100-300 nm.
The technical scheme of the application has the following beneficial technical effects:
according to the preparation method of the optical waveguide, the deposition layer for forming the waveguide core is optimized, and the deposition layer is divided into the doped region for reducing the tensile stress and the undoped region for forming the waveguide core, so that the influence of the tensile stress on the substrate in the process of forming the waveguide core is reduced, the probability of thoroughly warping and generating cracks of the silicon nitride waveguide core is reduced, and the optical waveguide is facilitated to have good optical performance.
Drawings
FIG. 1 is a schematic flow chart of a method for manufacturing an optical waveguide according to the present application.
Fig. 2 is a schematic diagram of a preparation method according to an embodiment of the present application.
Fig. 3 is a schematic diagram of a preparation method according to a second embodiment of the present application.
Fig. 4 is a schematic diagram of a preparation method according to a third embodiment of the present application.
In the drawing the view of the figure,
a substrate 1;
a lower cladding layer (2);
a deposition layer 3; ion implantation masking layer, 30; doped regions 31; undoped regions, 32; etching the masking layer 33;
a waveguide core 4;
upper cladding, 5.
Detailed Description
The objects, technical solutions and advantages of the present application will become more apparent by the following detailed description of the present application with reference to the accompanying drawings. It should be understood that the description is only illustrative and is not intended to limit the scope of the application. In addition, in the following description, descriptions of well-known structures and techniques are omitted so as not to unnecessarily obscure the present application.
The terminology used in the one or more embodiments of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the one or more embodiments of the application. As used in one or more embodiments of the application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used in one or more embodiments of the present application refers to and encompasses any or all possible combinations of one or more of the associated listed items.
It should be understood that, although the terms first, second, etc. may be used in one or more embodiments of the application to describe various information, these information should not be limited by these terms. These terms are only used to distinguish one type of information from another. For example, a first may also be referred to as a second, and similarly, a second may also be referred to as a first, without departing from the scope of one or more embodiments of the application. The word "if" as used herein may be interpreted as "responsive to a determination" depending on the context.
The existing method for manufacturing the thicker silicon nitride film/waveguide core has the following defects: existing multi-step spin-on deposition and photonic Damascus processes on Si 3 N 4 When the film is thicker, the stress is still large, the substrate warpage is serious, si 3 N 4 The film is easy to crack; the non-stoichiometric silicon nitride film significantly increases the optical propagation loss of the silicon nitride waveguide.
In order to solve the problems, the application provides the preparation method of the optical waveguide, which obviously reduces the influence of tensile stress on the substrate in the process of forming the waveguide core in two ways, reduces the probability of warping and cracking of the substrate, and simultaneously ensures that the optical waveguide has good optical performance.
First, the thicker film required is divided into a plurality of depositions. For example, for an optical waveguide composed of a stoichiometric silicon nitride film, the film thickness per deposition is no greater than 300nm.
Secondly, by means of doping, the deposited layer (film layer) deposited each time is provided with an undoped region for forming the waveguide core and a doped region for reducing the film stress of the deposited layer. For example, for an optical waveguide composed of a silicon nitride film with a stoichiometric ratio, when the undoped region has a larger tensile stress, adjusting the ion implantation process parameters of the doped region causes the doped region to exhibit a tensile stress that is reduced or even reduced, thereby reducing the tensile stress exhibited by the deposited layer as a whole, or causing the tensile stress exhibited by the deposited layer as a whole to be zero or even to exhibit a slight compressive stress. Similarly, for optical waveguides constructed of other waveguide materials, when the undoped region has a tensile stress, the stress exhibited by each deposited layer may also be adjusted based on the same principle.
In summary, by the two modes, the film stress presented by each deposition layer is in a state of mutual balance, and the film thickness is further increased by depositing the deposition layer with the stress balance for a plurality of times, particularly for the optical waveguide formed by the silicon nitride film with stoichiometric ratio, a thicker silicon nitride waveguide core can be manufactured, the stress problem is obviously solved, and adverse effects such as substrate warpage, film cracking and the like are effectively avoided; on the other hand, the optical waveguide prepared by the same application principle can be applied to silicon-based photonic chips and devices to optimize the device performance.
[ embodiment one ]
As shown in fig. 1, a first embodiment of the present application provides a method for manufacturing an optical waveguide, including:
step S101: providing a substrate 1;
step S102: forming a lower cladding layer 2 on a substrate 1;
step S103: forming a deposition layer 3 on the lower cladding layer 2 through a mode of multiple deposition and doping, wherein each deposition layer 3 comprises an undoped region 32 and a doped region 31 for reducing the film stress of the deposition layer 3, and the undoped regions 32 of each layer are overlapped with each other;
step S104: forming a waveguide core 4 in undoped regions 32 overlapping each other by patterning the deposition layer 3;
step S105: an upper cladding layer 5 is formed on the waveguide core 4 and the lower cladding layer 2.
In this embodiment, the substrate 1 may be, but is not limited to, a silicon substrate 1, and the material of the lower cladding layer 2 is SiO 2 The lower cladding layer 2 is formed by thermal oxidation growth on the silicon substrate 1. The waveguide core 4 is formed in the undoped region 32. The deposition layer 3 includes first deposition layer 3 to n-th deposition layer 3 stacked in order from bottom to top. The thickness of the lower cladding layer 2 is 4-20 um. The thickness of the first to nth deposition layers 3 to 3 is preferably 100 to 300nm. The thicknesses of the first to nth deposition layers 3 to 3 may be the same.
Step S103 may include: depositing a stoichiometric silicon nitride film; and doping partial regions of the silicon nitride film to form a deposition layer 3 comprising a doped region 31 and an undoped region 32, wherein the undoped region 32 has a tensile stress, and the doped region 31 has a tensile stress smaller than that of the undoped region 32 or the doped region 31 exhibits a compressive stress.
In this embodiment, the deposition and doping to form the deposition layer 3 includes: depositing a stoichiometric silicon nitride film; and doping partial regions of the silicon nitride film to form a deposition layer 3 comprising a doped region 31 and an undoped region 32, wherein the undoped region 32 has a tensile stress, and the doped region 31 has a tensile stress smaller than that of the undoped region 32 or the doped region 31 exhibits a compressive stress. Doping a partial region of the silicon nitride film, comprising: manufacturing an ion implantation masking layer 30 on the corresponding position of the silicon nitride film, wherein the width of the ion implantation masking layer 30 manufactured each time is not smaller than the width of the waveguide core 4 to be manufactured and formed; performing ion implantation on the silicon nitride film with the ion implantation masking layer 30, forming an undoped region 32 in a region covered by the ion implantation masking layer 30, and forming a doped region 31 in a region not covered by the ion implantation masking layer 30; the ion implantation masking layer 30 is selectively removed.
Specifically, as shown in FIG. 2 (a), a lower cladding layer 2 is formed on a substrate 1, and then Si is deposited in stoichiometric ratio by LPCVD over the lower cladding layer 2 3 N 4 Film as the first Si 3 N 4 Waveguide core layer. As shown in FIG. 2 (b), at the firstOne Si 3 N 4 The ion implantation masking layer 30 is fabricated on the waveguide core layer, and the material of the ion implantation masking layer 30 may be patterned photoresist, polysilicon, etc. The ion implantation masking layer 30 can be removed by a wet process and is specific to Si 3 N 4 Has high wet removal selectivity to Si 3 N 4 The damage of the film is small. The position corresponding to the ion implantation masking layer 30 is used for forming the waveguide core 4 subsequently, so that the ion implantation masking layer 30 can completely cover the area where the waveguide core 4 is located, the width of the ion implantation masking layer 30 is larger than the width of the waveguide core 4, and the thickness of the ion implantation masking layer 30 is enough to prevent the first ion from being implanted into the first Si below 3 N 4 In the waveguide core layer. As shown in fig. 2 (c), the first Si is masked by the ion implantation masking layer 30 3 N 4 The waveguide core layer is injected with first ions, and the first Si 3 N 4 Doped regions 31 (also denoted as ion implanted regions) and undoped regions 32 (also denoted as non-ion implanted regions) are formed in the waveguide core layer, resulting in a first deposited layer 3. The implantation conditions of the first ions are as follows: the first ion can be B, P, si ion with implantation energy of 10-500 keV and implantation dosage of 10 12 ～10 17 /cm 2 The method comprises the steps of carrying out a first treatment on the surface of the Si of the first ion implantation region 3 N 4 The tensile stress of the film may decrease with increasing implant dose and even translate into lower compressive stress. As shown in fig. 2 (d), the ion implantation masking layer 30 is wet-removed. As shown in fig. 2 (e), stoichiometric Si is deposited on the first deposition layer 3 by LPCVD 3 N 4 Film as second Si 3 N 4 The waveguide core layer, like the above steps, continues on the second Si 3 N 4 An ion implantation masking layer 30 is fabricated over the waveguide core layer. As shown in fig. 2 (f), the second Si is masked by the ion implantation masking layer 30 3 N 4 The waveguide core layer is injected with first ions, and is formed of second Si 3 N 4 Doped regions 31 and undoped regions 32 are formed in the waveguide core layer resulting in a second deposited layer 3. Wherein the first ion implantation conditions, energy and metrology are the same as the above steps. As shown in fig. 2 (g), the ion implantation masking layer 30 is wet-removed. As shown in FIG. 2 (h), the above steps are repeated until an nth deposition layer is formed3, n is Si 3 N 4 Number of thin film depositions. n is more than or equal to 2; n times deposited Si 3 N 4 The total thickness of the film is greater than or equal to the required Si 3 N 4 The thickness of the waveguide core 4; n Si 3 N 4 Each Si in the film 3 N 4 The thickness of the film, the range of ion implantation conditions may be the same; the first n-1 ion implantation masking layers 30 of the n ion implantation masking layers 30 completely cover Si 3 N 4 The first n-1 ion implantation masking layers 30 have a width greater than Si in the region of the waveguide core 4 3 N 4 Waveguide core 4 width, n ion implantation masking layer 30 width equal to Si 3 N 4 The width of the waveguide core 4, the thickness of each ion implantation masking layer 30 needs to be sufficient to prevent ion implantation of Si thereunder 3 N 4 In the film.
Patterning the deposited layer 3 and forming the waveguide core 4 may include: and etching by taking the ion implantation masking layer 30 manufactured at the last time as a mask to form the waveguide core 4, and removing the ion implantation masking layer 30.
Specifically, as shown in fig. 2 (i), the n-th ion implantation masking layer 30 is used as a mask for the Si 3 N 4 The deposited layer 3 is dry etched to form Si 3 N 4 A waveguide core 4; through material selection and dry etching process adjustment of the n-th ion implantation masking layer 30, si is enabled to be in a state of 3 N 4 The n-th ion implantation masking layer 30 has a high dry etching selectivity.
As shown in fig. 2 (j), step S105 includes: wet removing the n-th ion implantation masking layer 30, depositing SiO 2 The film was used as an upper cladding layer 5 to obtain Si 3 N 4 A waveguide; alternatively to SiO 2 The upper cladding layer 5 is subjected to a planarization process. The preparation method of the optical waveguide provided by the embodiment is to obtain thicker Si 3 N 4 The film is divided into a plurality of depositions, and Si deposited each time 3 N 4 The film thickness is not more than 300nm, si deposited at a time 3 N 4 Ion implantation masking layer 30 is formed on the film to cover the region of optical waveguide core 4, ion implantation is performed, and Si is implanted with ions 3 N 4 The film region forms a doped region 31, and tensile stress is reducedSmall or even low compressive stress, while the undoped region 32 in which the waveguide core 4 is located is not affected by the optical properties of the implanted ions, si 3 N 4 Patterning and depositing SiO after the film reaches the required thickness 2 Upper cladding layer 5 forms Si 3 N 4 An optical waveguide. The technical proposal reduces thicker Si 3 N 4 The tensile stress of the film and the probability of crack generation are prevented at the same time 3 N 4 Damaged by implanted ions or implanted ion pairs Si 3 N 4 Producing optical influence and ensuring Si 3 N 4 The waveguide core 4 has good optical properties.
It has been found that the n-th ion implantation masking layer 30 is Si 3 N 4 The etched masking layer of the optical waveguide core 4 may be present with implanted ion pairs Si 3 N 4 Damage to the side wall of the optical waveguide core 4 and increased roughness of the side wall (Si is changed by ion implantation) 3 N 4 Etching characteristics of (c) implantation of ions into Si 3 N 4 The optical waveguide core 4 affects optical performance and the like.
In order to solve the above problems, the present application also provides a method for manufacturing an optical waveguide, which reduces the etching to Si by manufacturing an etching masking layer 3 N 4 Damage to the surface.
[ example two ]
The second embodiment of the application provides a preparation method of an optical waveguide, which comprises the following steps: providing a substrate 1; forming a lower cladding layer 2 on a substrate 1; forming a deposition layer 3 on the lower cladding layer 2 through a mode of multiple deposition and doping, wherein each deposition layer 3 comprises an undoped region 32 and a doped region 31 for reducing the film stress of the deposition layer 3, and the undoped regions 32 of each layer are overlapped with each other; forming a waveguide core 4 in undoped regions 32 overlapping each other by patterning the deposition layer 3; an upper cladding layer 5 is formed on the waveguide core 4 and the lower cladding layer 2.
In the present embodiment, forming the deposition layer 3 includes: depositing a stoichiometric silicon nitride film; and doping partial regions of the silicon nitride film to form a deposition layer 3 comprising a doped region 31 and an undoped region 32, wherein the undoped region 32 has a tensile stress, and the doped region 31 has a tensile stress smaller than that of the undoped region 32 or the doped region 31 exhibits a compressive stress. Depositing and doping to form a deposition layer 3, comprising: depositing a stoichiometric silicon nitride film; and doping partial regions of the silicon nitride film to form a deposition layer 3 comprising a doped region 31 and an undoped region 32, wherein the undoped region 32 has a tensile stress, and the doped region 31 has a tensile stress smaller than that of the undoped region 32 or the doped region 31 exhibits a compressive stress. Doping a partial region of the silicon nitride film, comprising: manufacturing an ion implantation masking layer 30 on the corresponding position of the silicon nitride film, wherein the width of the ion implantation masking layer 30 manufactured each time is not smaller than the width of the waveguide core 4 to be manufactured and formed; performing ion implantation on the silicon nitride film with the ion implantation masking layer 30, forming an undoped region 32 in a region covered by the ion implantation masking layer 30, and forming a doped region 31 in a region not covered by the ion implantation masking layer 30; the ion implantation masking layer 30 is selectively removed.
Specifically, with reference to the embodiment one corresponding step, a substrate 1 is provided; forming a lower cladding layer 2 on a substrate 1; depositing stoichiometric Si by LPCVD over the lower cladding layer 2 3 N 4 Film as the first Si 3 N 4 Waveguide core layer. At the first Si 3 N 4 An ion implantation masking layer 30 is manufactured on the waveguide core layer, and under the masking effect of the ion implantation masking layer 30, the first Si is formed 3 N 4 The waveguide core layer is injected with first ions, and the first Si 3 N 4 Doped regions 31 and undoped regions 32 are formed in the waveguide core layer, resulting in a first deposited layer 3. The ion implantation masking layer 30 is removed by a wet process. Stoichiometric Si deposition by LPCVD on the first deposited layer 3 3 N 4 Film as second Si 3 N 4 Waveguide core layer. At the second Si 3 N 4 An ion implantation masking layer 30 is manufactured on the waveguide core layer, and the second Si is masked by the ion implantation masking layer 30 3 N 4 The waveguide core layer is injected with first ions, and is formed of second Si 3 N 4 Doped regions 31 and undoped regions 32 are formed in the waveguide core layer resulting in a second deposited layer 3. The ion implantation masking layer 30 is removed by a wet process. Repeating the above steps to form an n-th depositionLamination 3. The n-th ion implantation masking layer 30 is removed by a wet process.
Patterning the deposited layer 3 and forming the waveguide core 4 may include: as shown in fig. 3 (a), an etching mask layer 33 is formed on the last deposition layer 3 within the overlapping undoped region 32; as shown in fig. 3 (b), etching is performed with the etching mask layer 33 as a mask, forming the waveguide core 4, and the etching mask layer 33 is removed.
Patterning the etch mask layer 33; the etching mask layer 33 may be made of photoresist, amorphous silicon, amorphous carbon, metal, or their laminated layers, si 3 N 4 Should have a high etch selectivity to etch masking layer 33 and the process of removing etch masking layer 33 should be specific to Si 3 N 4 The surface damage is small; the width of the etching masking layer 33 is smaller than that of all the ion implantation masking layers 30, and the lower part of the etching masking layer 33 corresponds to all Si 3 N 4 The waveguide core 4 region of layer 3 is deposited. Dry etching Si with the patterned etching mask layer 33 as a mask 3 N 4 Depositing layer 3 to form Si 3 N 4 A waveguide core 4. Removing the etching mask layer 33; as shown in FIG. 3 (c), siO is deposited 2 Upper cladding 5 to form Si 3 N 4 A waveguide; alternatively to SiO 2 The upper cladding layer 5 is planarized.
The method for manufacturing the optical waveguide provided in this embodiment is helpful for reducing the etching to Si by using the etching masking layer 33 instead of the n-th ion implantation masking layer 30 as the etching mask 3 N 4 Damage to the surface.
[ example III ]
The third embodiment of the application provides a preparation method of an optical waveguide, which comprises the following steps: providing a substrate 1; forming a lower cladding layer 2 on a substrate 1; forming a deposition layer 3 on the lower cladding layer 2 through a mode of multiple deposition and doping, wherein each deposition layer 3 comprises an undoped region 32 and a doped region 31 for reducing the film stress of the deposition layer 3, and the undoped regions 32 of each layer are overlapped with each other; forming a waveguide core 4 in undoped regions 32 overlapping each other by patterning the deposition layer 3; an upper cladding layer 5 is formed on the waveguide core 4 and the lower cladding layer 2.
In the present embodiment, forming the deposition layer 3 includes: depositing a stoichiometric silicon nitride film; and doping partial regions of the silicon nitride film to form a deposition layer 3 comprising a doped region 31 and an undoped region 32, wherein the undoped region 32 has a tensile stress, and the doped region 31 has a tensile stress smaller than that of the undoped region 32 or the doped region 31 exhibits a compressive stress. Depositing and doping to form a deposition layer 3, comprising: depositing a stoichiometric silicon nitride film; and doping partial regions of the silicon nitride film to form a deposition layer 3 comprising a doped region 31 and an undoped region 32, wherein the undoped region 32 has a tensile stress, and the doped region 31 has a tensile stress smaller than that of the undoped region 32 or the doped region 31 exhibits a compressive stress. Doping a partial region of the silicon nitride film, comprising: manufacturing an ion implantation masking layer 30 on the corresponding position of the silicon nitride film, wherein the width of the ion implantation masking layer 30 manufactured each time is not smaller than the width of the waveguide core 4 to be manufactured and formed; performing ion implantation on the silicon nitride film with the ion implantation masking layer 30, forming an undoped region 32 in a region covered by the ion implantation masking layer 30, and forming a doped region 31 in a region not covered by the ion implantation masking layer 30; the ion implantation masking layer 30 is selectively removed.
Specifically, a substrate 1 is provided; forming a lower cladding layer 2 on a substrate 1; depositing stoichiometric Si by LPCVD over the lower cladding layer 2 3 N 4 Film as the first Si 3 N 4 Waveguide core layer. At the first Si 3 N 4 An ion implantation masking layer 30 is manufactured on the waveguide core layer, and under the masking effect of the ion implantation masking layer 30, the first Si is formed 3 N 4 The waveguide core layer is injected with first ions, and the first Si 3 N 4 Doped regions 31 and undoped regions 32 are formed in the waveguide core layer, resulting in a first deposited layer 3. The ion implantation masking layer 30 is removed by a wet process. Stoichiometric Si deposition by LPCVD on the first deposited layer 3 3 N 4 Film as second Si 3 N 4 Waveguide core layer. At the second Si 3 N 4 An ion implantation masking layer 30 is manufactured on the waveguide core layer, and the second Si is masked by the ion implantation masking layer 30 3 N 4 Waveguide core injectionOne ion at the second Si 3 N 4 Doped regions 31 and undoped regions 32 are formed in the waveguide core layer resulting in a second deposited layer 3. The ion implantation masking layer 30 is removed by a wet process. Repeating the above steps until the n-1 deposition layer 3 is formed.
As shown in FIG. 4 (a), stoichiometric Si is deposited by LPCVD on the n-1 th deposition layer 3 3 N 4 The film serves as an n-th deposited layer 3. A patterned etch masking layer 33 is made over the n-th deposition layer 3.
Patterning the deposited layer 3 and forming the waveguide core 4 may include: after removing the ion implantation masking layer 30 manufactured for the last time, continuing to deposit a layer of silicon nitride film with stoichiometric ratio, and patterning the deposited layer 3 and forming the waveguide core 4 specifically comprises: an etching masking layer 33 is manufactured on the silicon nitride film which is continuously deposited and within the overlapped non-doped region 32 lamination range; etching is performed with the etching masking layer 33 as a mask, the waveguide core 4 is formed, and the etching masking layer 33 is removed. Deposit layer 3 etch masking layer 33
As shown in fig. 4 (b), the patterned etching mask layer 33 is used as a mask to dry etch Si 3 N 4 Depositing layer 3 to form Si 3 N 4 A waveguide core 4.
As shown in fig. 4 (c), the etching mask layer 33 is removed; deposition of SiO 2 Upper cladding 5 to form Si 3 N 4 A waveguide; alternatively to SiO 2 The upper cladding layer 5 is planarized.
In summary, the method for manufacturing an optical waveguide according to the present embodiment provides a method for manufacturing an optical waveguide by using Si having a relatively thick stoichiometric ratio 3 N 4 The film is divided into a plurality of depositions, and Si deposited each time 3 N 4 The film masks the ion implantation to make Si with large area 3 N 4 The film is reduced in tensile stress and even converted into low compressive stress due to ion implantation, and is used for forming Si 3 N 4 The undoped region 32 of the waveguide core 4 is masked by the ion implantation masking layer 30 to avoid material damage and degradation of optical properties due to the implanted ions. By dispersing Si with multi-step spin-deposition, photon Damascus process 3 N 4 Film stress to achieve thicker Si 3 N 4 Film and method for producing the sameCompared with the waveguide core 4, the scheme reduces Si from the prior scheme 3 N 4 Realization of thicker Si from the angle of film stress 3 N 4 Thin film/waveguide core 4, useful for thicker Si 3 N 4 Fabrication of the film/waveguide core 4. The present solution results in a stoichiometric Si compared to the non-stoichiometric silicon nitride waveguide core 4 3 N 4 The waveguide core 4 has a lower optical propagation loss. The preparation method of the optical waveguide provided by the embodiment not only reduces the thicker stoichiometric Si 3 N 4 The probability of serious warping and crack generation of the substrate 1 caused by the tensile stress of the film also ensures Si 3 N 4 Has good optical performance.
Based on the same inventive concept, the application also provides an optical waveguide, which is prepared by adopting the preparation method of the optical waveguide provided by any embodiment, and comprises the following steps:
a substrate; a lower cladding layer formed on the substrate; a waveguide core composed of a plurality of deposited undoped stacks, the stacks being partially undoped regions of the deposited film that have undergone stress reduction; and the upper cladding layer is used for cladding the waveguide core.
Specifically, the material of the substrate is silicon; the lower cladding is made of silicon dioxide, and the thickness of the silicon dioxide lower cladding is 4-20 um; the material of the waveguide core is silicon nitride with stoichiometric ratio, and the thickness of the waveguide core is more than 300nm; the number of the laminated layers is more than or equal to 2, and the thickness of each laminated layer is 100-300 nm.
It is to be understood that the above-described embodiments of the present application are merely illustrative of or explanation of the principles of the present application and are in no way limiting of the application. Accordingly, any modification, equivalent replacement, improvement, etc. made without departing from the spirit and scope of the present application should be included in the scope of the present application. Furthermore, the appended claims are intended to cover all such changes and modifications that fall within the scope and boundary of the appended claims, or equivalents of such scope and boundary.
It should be noted that, for the sake of simplicity of description, the foregoing method embodiments are all expressed as a series of combinations of actions, but it should be understood by those skilled in the art that the present application is not limited by the order of actions described, as some steps may be performed in other order or simultaneously in accordance with the present application. Further, those skilled in the art will appreciate that the embodiments described in the specification are all preferred embodiments, and that the acts and modules referred to are not necessarily all required for the present application.
In the foregoing embodiments, the descriptions of the embodiments are emphasized, and for parts of one embodiment that are not described in detail, reference may be made to the related descriptions of other embodiments.
The preferred embodiments of the application disclosed above are intended only to assist in the explanation of the application. Alternative embodiments are not intended to be exhaustive or to limit the application to the precise forms disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the application and the practical application, to thereby enable others skilled in the art to best understand and utilize the application. The application is limited only by the claims and the full scope and equivalents thereof.
Claims (10)
1. A method of making an optical waveguide comprising:
providing a substrate;
forming a lower cladding layer on the substrate;
forming a deposition layer on the lower cladding layer in a mode of multiple deposition and doping, wherein each deposition layer comprises an undoped region and a doped region for reducing film stress of the deposition layer, and the undoped regions of each layer are overlapped with each other;
forming a waveguide core in the non-doped regions overlapped with each other by patterning the deposition layer;
an upper cladding layer is formed over the waveguide core and the lower cladding layer.
2. A method of fabricating an optical waveguide according to claim 1, wherein the depositing and doping to form a deposited layer comprises:
depositing a stoichiometric silicon nitride film;
and doping a partial region of the silicon nitride film to form a deposition layer comprising a doped region and an undoped region, wherein the undoped region has tensile stress, and the tensile stress of the doped region is smaller than that of the undoped region or the doped region exhibits compressive stress.
3. The method for manufacturing an optical waveguide according to claim 2, wherein doping the partial region of the silicon nitride film comprises:
manufacturing an ion implantation masking layer on the corresponding position of the silicon nitride film, wherein the width of the ion implantation masking layer manufactured each time is not smaller than the width of the waveguide core to be manufactured and formed;
performing ion implantation on the silicon nitride film with the ion implantation masking layer, forming an undoped region in a region covered by the ion implantation masking layer, and forming a doped region in a region not covered by the ion implantation masking layer;
the ion implantation masking layer is selectively removed.
4. A method of fabricating an optical waveguide according to claim 3, wherein after removing the last ion implantation masking layer, the deposited layer is patterned and a waveguide core is formed, specifically: manufacturing an etching masking layer on the last deposition layer and in the overlapped non-doped region lamination range; etching by taking the etching masking layer as a mask to form a waveguide core, and removing the etching masking layer;
or,
after removing the ion implantation masking layer manufactured for the last time, continuing to deposit a layer of silicon nitride film with stoichiometric ratio, and then patterning the deposited layer and forming a waveguide core specifically comprises the following steps: manufacturing an etching masking layer on the silicon nitride film which is continuously deposited and in the overlapped non-doped region lamination range; etching by taking the etching masking layer as a mask to form a waveguide core, and removing the etching masking layer;
or,
the ion implantation masking layer manufactured for the last time is reserved, and the steps of patterning the deposition layer and forming the waveguide core are as follows: and etching by taking the ion implantation masking layer manufactured at the last time as a mask to form a waveguide core, and removing the ion implantation masking layer.
5. A method of manufacturing an optical waveguide according to claim 4,
the ion implantation masking layer is made of photoresist, metal or polysilicon;
the etching masking layer is made of photoresist, amorphous silicon, amorphous carbon, metal, polysilicon or a lamination of the above materials;
the substrate is made of silicon;
the material of the lower cladding is silicon dioxide, the silicon dioxide lower cladding grows on a silicon substrate through thermal oxidation, and the thickness of the silicon dioxide lower cladding is 4-20 um;
the thickness of each deposition layer is 100-300 nm;
the upper cladding layer is made of silicon dioxide, and the silicon dioxide upper cladding layer with a flat surface is formed through planarization.
6. The method for manufacturing an optical waveguide according to claim 3 or 4, wherein the ion implantation conditions are specifically:
the implanted ions are any one of the following: B. p, si;
the injection energy is 10-500 keV;
the implantation dose is 10 12 ～10 17 /cm 2 。
7. A method of fabricating an optical waveguide according to claim 3, wherein removing the ion implantation masking layer comprises:
removing the ion implantation masking layer by a wet method;
the wet removal selection ratio of the ion implantation masking layer to the waveguide core is larger than a preset selection ratio.
8. A method of fabricating an optical waveguide according to claim 1, wherein forming the waveguide core in the undoped region overlapping each other by patterning the deposited layer comprises:
the waveguide core is formed by dry etching the deposited layer.
9. An optical waveguide prepared by the method of any one of claims 1-8, comprising:
a substrate;
a lower cladding layer formed on the substrate;
a waveguide core composed of a multi-deposited undoped stack of partially undoped regions of deposited film that has undergone stress relief;
and the upper cladding layer is used for cladding the waveguide core.
10. An optical waveguide as claimed in claim 9, wherein,
the substrate is made of silicon;
the lower cladding is made of silicon dioxide, and the thickness of the silicon dioxide lower cladding is 4-20 um;
the waveguide core is made of silicon nitride with stoichiometric ratio, and the thickness of the waveguide core is more than 300nm;
the number of the laminated layers is more than or equal to 2, and the thickness of each laminated layer is 100-300 nm.
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