Preparation method of electro-optical modulator structure
The electro-optical modulator is prepared by local oxidation, which solves the problems of unsmooth waveguide sidewalls and many lithography steps, and realizes the manufacturing of electro-optical modulators with lower losses and cost.
Patent Information
- Application Number
- CN202311803475.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-25
- Publication Date
- 2025-07-04
AI Technical Summary
When manufacturing electro-optical modulators in traditional silicon-based optoelectronics, the waveguide side walls are not smooth enough, resulting in large insertion losses, and the photolithography process is often used, which is costly.
The local oxidation method is used instead of the etching process. By forming a local oxidation region on the surface of the waveguide functional layer, a ridge waveguide with smooth boundaries is formed, and multiple doped regions are formed in the ridge waveguide region. The difference in oxidation rate of the doped material is used to save the photolithography step.
Electro-optical modulators with smoother sidewave walls and lower insertion losses are manufactured, reducing production costs.
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Figure CN120255182A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of silicon-based optoelectronic device manufacturing processes, and particularly to a manufacturing method for an electro-optic modulator structure with low optical loss. Background Art
[0002] An electro-optic modulator is an active device in silicon-based optoelectronics, which functions to change the carrier concentration in the waveguide region by varying the reverse-biased PN junction voltage. Due to the carrier dispersion effect, the carrier concentration in the silicon waveguide region affects the refractive index and absorption rate of the silicon waveguide. Therefore, by changing the reverse-biased PN junction voltage, the electro-optic modulator can modulate the refractive index of the silicon waveguide, thereby changing the phase of the light in the waveguide.
[0003] An important index of the electro-optic modulator is the insertion loss, which has two main sources: one is the carrier dispersion effect in the waveguide region, and the higher the electron and hole concentrations in the waveguide region, the greater the loss; the other is the transmission loss of the waveguide in the waveguide region, and the smoother the sidewalls of the waveguide in the waveguide region, the smaller the loss.
[0004] Traditional silicon-based optoelectronic processes generally use reactive ion etching to form the waveguide region of the electro-optic modulator, and this process will make the sidewalls of the waveguide not smooth enough, thus bringing additional insertion loss to the electro-optic modulator.
[0005] In addition, when manufacturing an electro-optic modulator using traditional silicon-based optoelectronic processes, in the previous process, as many as 7 lithographies are required, including 1 lithography for forming the ridge waveguide region by lithography etching, and 6 lithographies for subsequent lithography ion implantation to form the modulator. This also becomes an important factor in raising the cost of the device. Summary of the Invention
[0006] The purpose of the present invention is to overcome the above-mentioned defects existing in the prior art and provide a preparation method for an electro-optic modulator structure.
[0007] To achieve the above purpose, the technical solution of the present invention is as follows:
[0008] The present invention provides a preparation method for an electro-optic modulator structure, including:
[0009] Providing a substrate with a waveguide functional layer on its surface;
[0010] Forming two local material oxidation regions of the waveguide functional layer on the surface of the waveguide functional layer, separating the two oxidation regions from each other, and partially entering the waveguide functional layer to form a ridge waveguide with smooth boundaries formed by the waveguide functional layer material, including a protruding ridge portion of the ridge waveguide formed between the two oxidation regions, and a flat portion of the ridge waveguide located below the oxidation regions on both sides of the ridge portion.
[0011] Further, two phase-separated sacrificial doping regions are formed below the surface of the waveguide functional layer, and then, through a local thermal oxidation process and by utilizing the characteristic that the oxidation rate of the doped material is faster than that of the undoped material, an oxidation region is formed on the surface region of the waveguide functional layer corresponding to the sacrificial doping regions.
[0012] Further, local material oxidation regions of two waveguide functional layers are formed on the surface of the waveguide functional layer, such that the two oxidation regions are phase-separated and partially penetrate into the waveguide functional layer to form a ridge waveguide with a smooth boundary formed by the material of the waveguide functional layer, including a protruding ridge portion of the ridge waveguide formed between the two oxidation regions and a flat portion of the ridge waveguide below the oxidation regions on both sides of the ridge portion. Specifically, it includes:
[0013] Two phase-separated first injection windows are formed on the surface of the waveguide functional layer;
[0014] Through the two first injection windows, two phase-separated sacrificial doping regions of a first doping type are formed by injection below the surface of the waveguide functional layer;
[0015] Through an in-situ thermal oxidation process and by utilizing the characteristic that the oxidation rate of the doped material is faster than that of the undoped material, a material oxidation region of the waveguide functional layer is formed in the sacrificial doping regions, such that the formed oxidation regions are phase-separated and partially penetrate from the surface of the waveguide functional layer into the waveguide functional layer to form a protruding ridge portion between the two oxide regions and a flat portion below the oxidation regions on both sides of the ridge portion, thereby forming a ridge waveguide with a smooth boundary formed by the material of the waveguide functional layer.
[0016] Further, it further includes: forming a first doping region of a first doping type, a second doping region of the first doping type, and a third doping region of the first doping type that are sequentially connected on one side of the ridge portion, and forming a fourth doping region of a second doping type, a fifth doping region of the second doping type, and a sixth doping region of the second doping type that are sequentially connected on the other side opposite to the ridge portion, and making the formed first doping region and the fourth doping region connected at the ridge portion.
[0017] Further, the second doping region and the fifth doping region are respectively located in one flat portion, and the third doping region and the sixth doping region are respectively located on the waveguide functional layer outside the flat portion.
[0018] Further, the doping concentrations of the first doping region to the third doping region increase sequentially, and the doping concentrations of the fourth doping region to the sixth doping region increase sequentially.
[0019] Further, the method for forming the first doping region to the sixth doping region specifically includes:
[0020] Through the two first injection windows, two second doping regions of a first doping type are formed by injection in the flat portion below the oxidation region;
[0021] Remove the two first injection windows; then, a second injection window and a third injection window are respectively formed on both sides of one of the second doping regions, so as to form a first doping region of the first doping type and a third doping region of the first doping type on both sides of one of the second doping regions by injection, and a fourth injection window and a fifth injection window are respectively formed on both sides of the other second doping region, so as to form a fourth doping region of the second doping type and a sixth doping region of the second doping type on both sides of the other second doping region by injection, and a sixth injection window is formed on the other second doping region, and by increasing the injection dose of the second doping type during injection, the doping concentration of the first doping type existing in the other second doping region is reversely compensated, so as to adjust and form the other second doping region into a fifth doping region of the second doping type.
[0022] Further, the method for forming the first injection window specifically includes:
[0023] A first dielectric layer and a hard mask layer are sequentially formed on the surface of the waveguide functional layer;
[0024] Through photolithography and etching processes, two separated trenches with bottoms located on the surface of the waveguide functional layer are formed on the surface of the hard mask layer, and the first injection window is formed by the trenches;
[0025] The method for removing the two first injection windows specifically includes:
[0026] Fill the two first injection windows with a second dielectric layer;
[0027] Through a planarization process, the hard mask layer is removed and stopped on the first dielectric layer.
[0028] Further, the method for forming the second injection window to the sixth injection window specifically includes:
[0029] Through 5 photolithography processes, the second injection window to the sixth injection window formed by different photoresist patterns located at corresponding positions are formed on the surface of the first dielectric layer in batches, and before forming each subsequent injection window, the photoresist pattern forming the previous injection window is removed.
[0030] Further, the substrate includes a SOI substrate, which sequentially includes a bottom silicon layer, a buried oxide layer, and a top silicon layer, and the top silicon layer located on the surface of the SOI substrate forms the waveguide functional layer.
[0031] As can be seen from the above technical solutions, in the present invention, a local oxidation method is adopted to replace the traditional etching method for preparing a ridge waveguide. The smooth boundary of the oxidation region formed after local oxidation of the waveguide functional layer material can be utilized to manufacture an electro-optic modulator with smoother waveguide sidewalls and lower optical insertion loss. Further, by pre-forming a sacrificial doping region in the region where local oxidation is required and utilizing the characteristic that the oxidation rate of the doped material is faster than that of the undoped material, an oxidation region with a smooth boundary can be formed directionally, so that the ridge waveguide formed along the boundary of the oxidation region has smooth sidewalls; and, by using the first implantation window when forming the sacrificial doping region as the ion implantation mask when forming the second doping region, one lithography for ion implantation can be saved, thus effectively reducing the cost. Description of the Drawings
[0032] Figure 1 It is a flowchart of a method for preparing an electro-optic modulator structure according to a preferred embodiment of the present invention.
[0033] Figures 2 - 10 According to a preferred embodiment of the present invention Figure 1 Schematic diagram of the process steps for preparing an electro-optic modulator structure by the method. Detailed Embodiments
[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meaning as understood by those of ordinary skill in the art in the field to which the present invention belongs. The words such as "including" used herein are intended to mean that the elements or items appearing before the word cover the elements or items listed after the word and their equivalents, without excluding other elements or items.
[0035] The core idea of the present invention is to provide a method for preparing an electro-optic modulator structure, including: providing a substrate with a waveguide functional layer on its surface; forming two local material oxidation regions of the waveguide functional layer on the surface of the waveguide functional layer, separating the two oxidation regions from each other, and partially entering the waveguide functional layer to form a ridge waveguide with a smooth boundary formed by the material of the waveguide functional layer, including a protruding ridge portion of the ridge waveguide formed between the two oxidation regions, and a flat portion of the ridge waveguide located below the oxidation regions on both sides of the ridge portion.
[0036] By using the local oxidation method to replace the traditional etching method for preparing the ridge waveguide, the present invention can utilize the smooth boundary of the oxidation region formed after the local oxidation of the waveguide functional layer material to manufacture an electro-optic modulator with smoother waveguide sidewalls and lower optical insertion loss.
[0037] A method for preparing an electro-optic modulator structure of the present invention can first form two separated sacrificial doping regions in the regions that need to be locally oxidized below the surface of the waveguide functional layer, and then through the local thermal oxidation process, and by using the characteristic that the oxidation rate of the doped material is faster than that of the undoped material, the oxidation region with a smooth boundary is directionally formed on the surface region of the waveguide functional layer corresponding to the sacrificial doping region, so that the ridge waveguide formed along the boundary of the oxidation region can have smooth sidewalls.
[0038] A method for preparing an electro-optic modulator structure of the present invention can also, after preparing and forming the above-mentioned ridge waveguide, further form a plurality of doping regions with different concentrations arranged in sequence from the center to both sides in the ridge waveguide region, including forming a first doping region of the first doping type, a second doping region of the first doping type, and a third doping region of the first doping type connected in sequence on one side of the protruding ridge portion of the ridge waveguide, and forming a fourth doping region of the second doping type, a fifth doping region of the second doping type, and a sixth doping region of the second doping type connected in sequence on the other side opposite to the ridge portion. Moreover, by using the injection window when forming the sacrificial doping region as the ion implantation mask when forming the second doping region, one lithography for ion implantation can be saved, so the cost is effectively reduced.
[0039] The following further elaborates on the specific implementation manners of the present invention in conjunction with the accompanying drawings.
[0040] Reference Figure 1 A method for preparing an electro-optic modulator structure of the present invention includes the following steps:
[0041] Step S1: Provide a substrate with a waveguide functional layer on its surface.
[0042] Such as Figure 2As shown, a SOI substrate 100 is utilized to fabricate an electro-optic modulator structure of the present invention. The SOI substrate 100 sequentially includes a bottom silicon layer (not shown), a buried oxide layer 11, and a top silicon layer 12 from bottom to top. Among them, the top silicon layer 12 located on the surface of the SOI substrate 100 is used as the waveguide functional layer 121.
[0043] In some embodiments, the thickness of the top silicon layer 12, i.e., the waveguide functional layer 121, can be 100 - 500 nanometers.
[0044] Step S2: Form a ridge waveguide on the waveguide functional layer.
[0045] As Figure 3 shown, first, a first dielectric layer and a hard mask layer are sequentially formed on the surface of the waveguide functional layer 121 through a dielectric deposition process.
[0046] In some embodiments, through a chemical vapor deposition process, a first silicon dioxide dielectric layer 13 with a thickness of, for example, 5 nanometers, a silicon nitride layer 14 with a thickness of 50 nanometers, and a third silicon dioxide dielectric layer 15 with a thickness of 2 micrometers are sequentially formed on the surface of the silicon waveguide functional layer 121. Among them, the silicon nitride layer 14 and the third silicon dioxide dielectric layer 15 together form the hard mask layer 16.
[0047] As Figure 4 shown, then, through a first photolithography and etching process, two separated trenches 17 are formed on the surface of the third silicon dioxide dielectric layer 15 serving as the hard mask layer 16, and during etching, the bottoms of the two trenches 17 are located on the surface of the waveguide functional layer 121. Among them, two oxidation regions to be formed for the silicon ridge waveguide are defined by the two trenches 17, and two separated first injection windows 171 are formed by the two trenches 17.
[0048] As Figure 5 shown, then, through an ion implantation process, and through the two first injection windows 171, two separated sacrificial doping regions 18 of the first doping type are formed below the surface of the waveguide functional layer 121 corresponding to the positions of the two first injection windows 171.
[0049] The first doping type can be one of P-type or N-type. Correspondingly, the second doping type can be the other of P-type or N-type. Hereinafter, the case where the first doping type is P-type and the second doping type is N-type is taken as an example for illustration.
[0050] In some embodiments, through a P-type impurity ion implantation process, and using the hard mask formed by the third silicon dioxide dielectric layer 15 and the silicon nitride layer 14, two separated P+-type heavily doped sacrificial doping regions 18 are formed below the surface of the silicon waveguide functional layer 121.
[0051] As shown Figure 6 in the figure, then, through a local in-situ thermal oxidation process, and by utilizing the characteristic that the oxidation rate of the doped silicon material in the sacrificial doping region 18 is faster than that of the undoped silicon material outside the sacrificial doping region 18, two phase-separated oxidation regions 19 formed by the oxidation of the local silicon material of the waveguide functional layer 121 are directionally formed on the surface region of the waveguide functional layer 121 corresponding to the sacrificial doping region 18. During the oxidation process, since the silicon material on the surface of the waveguide functional layer 121 will be consumed, the bottoms of the two formed oxidation regions 19 enter into the waveguide functional layer 121, thereby forming a new surface of the waveguide functional layer 121 with a concave morphology respectively below the two oxidation regions 19, and thus forming an upward protruding silicon ridge between the two oxidation regions 19, that is, between the two concave morphologies, thereby forming a ridge waveguide 20 structure. Among them, the protruding ridge portion 21 of the ridge waveguide 20 is formed by this silicon ridge, and the flat portion 22 of the ridge waveguide 20 is formed by the concave portions of the waveguide functional layer 121 below the oxidation regions 19 on both sides of the ridge portion 21.
[0052] When the doped silicon material in the sacrificial doping region 18 is rapidly preferentially oxidized to the boundary of the sacrificial doping region 18, due to the rapid decrease in the oxidation rate, a smooth interface morphology will be generated on the surface of the silicon material at the boundary, so that the silicon ridge waveguide 20 formed corresponding to the boundary of the oxidation region 19 can have a smooth boundary (including the side walls of the ridge portion 21 and the surface of the flat portion 22).
[0053] Therefore, by using a local oxidation method to replace the traditional etching method for preparing the ridge waveguide 20, the smooth boundary of the oxidation region 19 formed after the local oxidation of the waveguide functional layer 121 material can be utilized to manufacture an electro-optic modulator with smoother waveguide side walls and lower optical insertion loss.
[0054] Step S3: Form a plurality of doping regions on the ridge waveguide.
[0055] After that, it also includes forming a plurality of doping regions 30 on the ridge waveguide 20, including forming a first doping region 31, a second doping region 32, and a third doping region 33 that are sequentially connected and doped with P-type on one side of the ridge portion 21 of the ridge waveguide 20, and forming a fourth doping region 34, a fifth doping region 35, and a sixth doping region 36 that are sequentially connected and doped with N-type on the other side opposite to the ridge portion 21 (refer to Figure 10)。And make the formed first doped region 31 and the fourth doped region 34 connected at the ridge 21 to form a PN junction region, and make the second doped region 32 and the fifth doped region 35 located on a flat portion 22 respectively, and the third doped region 33 and the sixth doped region 36 located on the waveguide functional layer 121 outside the flat portion 22 where they are located respectively. Among them, the doping concentrations of the first doped region 31 to the third doped region 33 increase in sequence, and the doping concentrations of the fourth doped region 34 to the sixth doped region 36 increase in sequence.
[0056] As Figure 7 shown, through the implantation process of P-type doping ions, and again through two first implantation windows 171, two second doped regions 32 doped with medium P-type are formed in the flat portion 22 below the oxidation region 19 corresponding to the positions of the two first implantation windows 171.
[0057] As Figure 8 shown, then, through the dielectric deposition process, the two first implantation windows 171 are filled with a second dielectric layer. For example, through the chemical vapor deposition process, a silicon dioxide second dielectric layer (not shown) is formed on the surface of the third dielectric layer 15, and the two first implantation windows 171 are filled.
[0058] As Figure 9 shown, then, through the planarization process, the hard mask layer 16 is removed and stopped on the first dielectric layer 13. That is, the two first implantation windows 171 are removed. For example, through the chemical mechanical polishing process, the silicon dioxide third dielectric layer 15 is removed and stopped on the silicon nitride layer 14, and the remaining silicon nitride layer 14 material is removed using hot phosphoric acid to expose the surface of the first dielectric layer 13. It can be understood that the surface at the position of the original first implantation window 171 may contain oxidation region 19 material and / or second dielectric layer material. And, the second doped region 32 is covered by the oxidation region 19 material.
[0059] As Figure 10 shown, then, through 5 photolithography processes, second implantation windows to sixth implantation windows formed by different photoresist patterns at corresponding positions are formed on the surface of the first dielectric layer 13 in sequence, and before each formation of the subsequent implantation window, the photoresist pattern forming the previous implantation window is removed. And through the second implantation window to the sixth implantation window, the first doped region, the third doped region 33 to the sixth doped region 36 are formed in sequence. Thus, six doped regions 30 are formed on the ridge waveguide 20.
[0060] In some embodiments, a photoresist layer may be formed on the surface of the first dielectric layer 13; then, through a second photolithography process, a third implantation window formed by a photoresist pattern at a corresponding position is formed on the surface of the first dielectric layer 13 at the defined position of the third doped region 33; and through an implantation process of P-type doping ions, a P-type heavily doped third doped region 33 is formed on the waveguide functional layer 121 outside one of the flat portions 22 on the left side below through the third implantation window.
[0061] Remove the photoresist pattern used to form the third implantation window. Then, a photoresist layer is formed again on the surface of the first dielectric layer 13; then, through a third photolithography process, a second implantation window formed by a photoresist pattern at a corresponding position is formed on the surface of the first dielectric layer 13 at the defined position of the first doped region 31; and through an implantation process of P-type doping ions, a P-type lightly doped first doped region 31 is formed on one side of the ridge 21 near the left flat portion 22 below through the second implantation window.
[0062] And so on, on both sides of the other second doped region 32 on the right side, a fourth implantation window and a fifth implantation window formed by a photoresist pattern are formed in two steps through photolithography, and through two N-type impurity implantations, an N-type lightly doped fourth doped region 34 and an N-type heavily doped sixth doped region 36 are respectively formed on both sides of the other second doped region 32 on the right side. However, different from the formation of each P-type doped region, it is also necessary to perform one more photolithography to form a sixth implantation window formed by a photoresist pattern at the defined position of the fifth doped region 35, that is, the current position of the other second doped region 32 on the right side, and through increasing the implantation dose (for example, doubling the dose), perform an N-type medium doping ion implantation on the other second doped region 32 on the right side to reversely compensate the existing P-type medium doping impurity concentration in the second doped region 32 on the right side, so that the P-type medium doped second doped region 32 on the right side can be adjusted and formed into an N-type medium doped fifth doped region 35.
[0063] It can be seen that since the P-type medium doped second doped region 32 on the left side has been formed by implantation through the first implantation window 171 in the previous step, the present invention only needs to perform 6 photolithography steps in total to complete the above steps of forming the ridge waveguide 20 and each doped region 30, which reduces one photolithography step compared with the existing method of forming an electro-optic modulator by etching to form a ridge waveguide.
[0064] In summary, by using the local oxidation method to replace the traditional etching method for preparing the ridge waveguide 20, the present invention can utilize the smooth boundary of the oxidation region 19 formed after the local oxidation of the waveguide functional layer 121 material to manufacture an electro-optic modulator with smoother waveguide sidewalls and lower optical insertion loss. Further, by pre-forming the sacrificial doping region 18 in the region of the waveguide functional layer 121 that needs to be locally oxidized, and utilizing the characteristic that the oxidation rate of doped silicon material is faster than that of undoped silicon material, the oxidation region 19 with a smooth boundary can be formed directionally, so that the ridge waveguide 20 formed along the boundary of the oxidation region 19 has smooth sidewalls; and, by using the first implantation window 171 formed when forming the sacrificial doping region 18 as the ion implantation mask for forming the second doping region 32, one lithography for ion implantation can also be saved, thus effectively reducing the cost.
[0065] Although the embodiments of the present invention have been described in detail above, it is obvious to those skilled in the art that various modifications and changes can be made to these embodiments. However, it should be understood that such modifications and changes are all within the scope and spirit of the present invention described in the claims. Moreover, the present invention described herein can have other embodiments and can be implemented or realized in various ways.
Claims
1. A method for preparing an electro-optic modulator structure, characterized in that, Including: Providing a substrate with a waveguide functional layer on its surface; Forming two local material oxidation regions of the waveguide functional layer on the surface of the waveguide functional layer, separating the two oxidation regions, and partially entering the waveguide functional layer to form a ridge waveguide with a smooth boundary formed by the material of the waveguide functional layer, including a protruding ridge portion of the ridge waveguide formed between the two oxidation regions and a flat portion of the ridge waveguide below the oxidation regions on both sides of the ridge portion.
2. The method for preparing the electro-optical modulator structure according to claim 1, wherein By first forming two separated sacrificial doping regions below the surface of the waveguide functional layer, and then through a local thermal oxidation process, and utilizing the characteristic that the oxidation rate of the doped material is faster than that of the undoped material, forming the oxidation region on the surface region of the waveguide functional layer corresponding to the sacrificial doping region.
3. The method for preparing the electro-optic modulator structure according to claim 1, characterized in that, The forming of two local material oxidation regions of the waveguide functional layer on the surface of the waveguide functional layer, separating the two oxidation regions, and partially entering the waveguide functional layer to form a ridge waveguide with a smooth boundary formed by the material of the waveguide functional layer, including a protruding ridge portion of the ridge waveguide formed between the two oxidation regions and a flat portion of the ridge waveguide below the oxidation regions on both sides of the ridge portion, specifically includes: Forming two separated first injection windows on the surface of the waveguide functional layer; Through the two first injection windows, injecting and forming two separated sacrificial doping regions of the first doping type below the surface of the waveguide functional layer; Through an in-situ thermal oxidation process, and utilizing the characteristic that the oxidation rate of the doped material is faster than that of the undoped material, forming the material oxidation region of the waveguide functional layer in the sacrificial doping region, separating the formed oxidation regions, and partially entering the waveguide functional layer from the surface of the waveguide functional layer to form a protruding ridge portion between the two oxide regions and a flat portion below the oxidation regions on both sides of the ridge portion, thereby forming a ridge waveguide with a smooth boundary formed by the material of the waveguide functional layer.
4. The method for preparing the electro-optic modulator structure according to claim 3, characterized in that, Further including: Forming a first doping region of the first doping type, a second doping region of the first doping type, and a third doping region of the first doping type connected in sequence on one side of the ridge portion, and forming a fourth doping region of the second doping type, a fifth doping region of the second doping type, and a sixth doping region of the second doping type connected in sequence on the other side opposite to the ridge portion, and making the formed first doping region connected to the fourth doping region at the ridge portion.
5. The method for preparing the electro-optical modulator structure according to claim 4, characterized in that, The second doping region and the fifth doping region are respectively located on one flat portion, and the third doping region and the sixth doping region are respectively located on the waveguide functional layer outside the flat portion.
6. The method for preparing the electro-optical modulator structure according to claim 4, characterized in that, The doping concentrations of the first doping region to the third doping region increase in sequence, and the doping concentrations of the fourth doping region to the sixth doping region increase in sequence.
7. The method for preparing the electro-optic modulator structure according to claim 4, wherein The method for forming the first doping region to the sixth doping region specifically includes: Through the two first injection windows, injecting and forming two second doping regions of the first doping type in the flat portion below the oxidation region. Remove the two first injection windows; then, form a second injection window and a third injection window on both sides of one of the second doping regions respectively, so as to form a first doping region of a first doping type and a third doping region of the first doping type on both sides of one of the second doping regions respectively by injection, and form a fourth injection window and a fifth injection window on both sides of the other second doping region respectively, so as to form a fourth doping region of a second doping type and a sixth doping region of the second doping type on both sides of the other second doping region respectively by injection, and form a sixth injection window on the other second doping region, and reverse-compensate the doping concentration of the first doping type existing in the other second doping region by increasing the injection dose of the second doping type during injection, so as to adjust and form the other second doping region into a fifth doping region of the second doping type.
8. The method for preparing the electro-optic modulator structure according to claim 7, wherein The method for forming the first injection window specifically includes: Form a first dielectric layer and a hard mask layer on the surface of the waveguide functional layer in sequence; Through a photolithography and etching process, form two separated trenches with bottoms located on the surface of the waveguide functional layer on the surface of the hard mask layer, and form the first injection window by the trenches; The method for removing the two first injection windows specifically includes: Fill the two first injection windows with a second dielectric layer; Through a planarization process, remove the hard mask layer, and stop at the first dielectric layer.
9. The method for preparing the electro-optical modulator structure according to claim 8, characterized in that, The method for forming the second injection window to the sixth injection window specifically includes: Through 5 photolithography processes, form the second injection window to the sixth injection window formed by different photoresist patterns located at corresponding positions on the surface of the first dielectric layer in batches, and remove the photoresist pattern forming the previous injection window before forming each subsequent injection window.
10. The method for preparing the electro-optical modulator structure according to claim 1, characterized in that, The substrate includes a SOI substrate, and the SOI substrate sequentially includes a bottom silicon layer, a buried oxide layer and a top silicon layer, and the top silicon layer located on the surface of the SOI substrate forms the waveguide functional layer.