Method of forming optical waveguide structure
By using etching processes of planarization material layers and pattern transfer layers in the optical waveguide structure, a waveguide structure with vertical sidewalls is formed, which solves the transmission loss problem caused by non-vertical sidewalls of optical waveguides in the prior art and achieves more efficient optical signal transmission.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SEMICON MFG INT (BEIJING) CORP
- Filing Date
- 2022-06-06
- Publication Date
- 2026-05-19
AI Technical Summary
Existing etching processes are insufficient to form ridge-shaped optical waveguides with excellent sidewall perpendicularity and roughness, resulting in significant optical signal transmission loss, especially in lidar optical sensing chips where performance is inadequate.
A planarization material layer and a pattern transfer layer are formed on the substrate surface. A waveguide structure with vertical sidewalls is formed by etching, including forming a pattern transfer layer and a first patterning layer on the surface of the planarization material layer, and using a hard mask layer to improve the verticality and flatness of the sidewalls.
This improved the verticality of the optical waveguide sidewalls, reduced transmission loss, and enhanced the transmission performance of optical signals.
Smart Images
Figure CN117233887B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of optical device technology, and in particular to a method for forming an optical waveguide structure. Background Technology
[0002] Silicon-based materials offer advantages such as small size, low power consumption, CMOS process compatibility, and ease of monolithic and micro / nano-integration with existing electronic and photonic devices, making them the most commonly used material for fabricating optoelectronic integrated chips. Silicon photonic integration based on silicon waveguides has become a key technology for developing high-performance and low-cost optical communication components and photonic integrated devices.
[0003] Silicon-based optical waveguides are the medium through which light waves propagate. They are the most fundamental unit structure in optoelectronic chips and integrated circuit technology, primarily serving to confine, transmit, and couple light waves. Types of optical waveguides include rectangular waveguides and ridge waveguides. Ridge waveguides have wide applications in integrated optics, forming the basis for many optoelectronic devices such as thin-film lasers, couplers, modulators, and optical switches. Ridge waveguides are increasingly attracting attention.
[0004] The transmission loss of a ridge waveguide is a crucial parameter for evaluating its performance. It depends on the sidewall angle and roughness of the ridge waveguide, and is primarily influenced by the photolithography and etching processes used in its fabrication. Therefore, silicon-based optoelectronic integrated products have specific requirements for the morphology of ridge waveguides. Existing photolithography and etching processes are insufficient to meet these special design requirements. For example, for optical sensing chips used in LiDAR, customers desire ridge waveguides with the lowest possible transmission loss, which necessitates that the sidewall angles of the ridge waveguide be as perpendicular as possible, while simultaneously minimizing sidewall roughness.
[0005] In summary, the ridge-shaped waveguide morphology formed by existing etching processes needs further improvement. Summary of the Invention
[0006] The technical problem solved by this invention is to provide a method for forming an optical waveguide structure to improve the optical signal transmission performance.
[0007] To solve the above-mentioned technical problems, the present invention provides a method for forming an optical waveguide structure, comprising: forming a substrate having a groove in the substrate, a portion of the bottom surface of the groove having an initial waveguide layer, the initial waveguide layer including a first region and an initial second region located on the first region; forming a planarization material layer, a pattern transfer layer located on the surface of the planarization material layer, and a first patterning layer located on the surface of the pattern transfer layer on the substrate surface, the top surface of the planarization material layer being higher than the top surface of the initial waveguide layer, the first patterning layer exposing a portion of the pattern transfer layer on the initial waveguide layer, the pattern transfer layer having a harderness than the first patterning layer; using the first patterning layer as a mask, etching the pattern transfer layer, the planarization material layer, and the initial second region, such that the width of the initial second region is smaller than the width of the first region, forming a second region with the initial second region, and forming a waveguide layer with the first region and the second region.
[0008] Optionally, the initial waveguide layer may also have an initial hard mask layer on top; the method may further include: etching the initial hard mask layer to form a hard mask layer; the method of etching the initial second region may include: using the hard mask layer as a mask to etch the initial second region.
[0009] Optionally, before etching the initial second region and after forming the hard mask layer, the process further includes: removing the pattern transfer layer, the planarization material layer, and the first patterning layer.
[0010] Optionally, the process for removing the pattern transfer layer, the planarization material layer, and the first patterning layer includes an ashing process.
[0011] Optionally, the angle between the sidewall of the hard mask layer and the direction of the substrate surface ranges from 86 degrees to 90 degrees.
[0012] Optionally, the material of the hard mask layer includes one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide, silicon carbonitride, and silicon carbonitride.
[0013] Optionally, the thickness of the hard mask layer ranges from 1200 angstroms to 1500 angstroms.
[0014] Optionally, the method for forming the substrate includes: providing an initial substrate, the initial substrate including a substrate and a waveguide material layer located on the surface of the substrate; forming an initial hard mask layer on the surface of the waveguide material layer, the initial hard mask layer exposing a portion of the waveguide material layer; using the initial hard mask layer as a mask, etching the initial substrate until the substrate is exposed, thereby forming the substrate.
[0015] Optionally, the method for forming the initial hard mask layer includes: forming a hard mask material layer on the surface of the waveguide material layer; forming a second patterning layer on the surface of the hard mask material layer, wherein the second patterning layer exposes a portion of the hard mask material layer; and etching the hard mask material layer using the second patterning layer as a mask to form the initial hard mask layer.
[0016] Optionally, the substrate includes a base layer and an insulating dielectric layer located on the base layer.
[0017] Optionally, the insulating dielectric layer may be made of silicon oxide; the waveguide layer may be made of silicon.
[0018] Optionally, the pattern transfer layer may include a silicon-based anti-reflective coating material.
[0019] Optionally, the silicon content in the pattern transfer layer ranges from 30% to 40%.
[0020] Optionally, the planarization material layer may be made of organic carbon materials.
[0021] Optionally, the material of the first patterning layer may include a photoresist material.
[0022] Optionally, the depth of the groove ranges from 3,000 angstroms to 5,000 angstroms.
[0023] Optionally, the thickness of the pattern transfer layer ranges from 500 angstroms to 1000 angstroms.
[0024] Optionally, the angle between the sidewall of the second region and the substrate surface direction ranges from 86 degrees to 90 degrees.
[0025] Compared with the prior art, the technical solution of the embodiments of the present invention has the following beneficial effects:
[0026] In the method for forming an optical waveguide structure provided by the present invention, a planarization material layer is formed on the surface of a substrate. The top surface of the planarization material layer is higher than the top surface of the initial waveguide layer. The planarization material layer improves the filling ability in the groove, which is beneficial to forming a planarized surface. A pattern transfer layer and a first patterning layer located on the surface of the planarization material layer are formed on the surface of the planarization material layer. Since the planarization material layer is used to fill the groove, the thickness of the first patterning layer is reduced and the uniformity of the first patterning layer is improved. At the same time, since the hardness of the pattern transfer layer is greater than that of the first patterning layer, it is beneficial to accurately transfer the pattern of the first patterning layer onto the pattern transfer layer, improve the perpendicularity and flatness of the sidewalls after etching of the pattern transfer layer, and thus improve the perpendicularity of the second region sidewalls of the formed waveguide layer.
[0027] Furthermore, the initial waveguide layer also has an initial hard mask layer on top; the method further includes: etching the initial hard mask layer to form a hard mask layer. The pattern transfer layer transfers the pattern onto the hard mask layer, which can improve the verticality and flatness of the hard mask layer sidewalls, thereby improving the verticality of the second region sidewalls of the formed waveguide layer.
[0028] Furthermore, before etching the initial second region and after forming the hard mask layer, the process also includes removing the pattern transfer layer, the planarization material layer, and the first patterning layer. This can reduce the influence of the pattern transfer layer, the planarization material layer, and the first patterning layer on the etching process, i.e., reduce the scattering of etching ions by the planarization material layer and reduce the thickness of the mask layer on the initial waveguide layer, thereby improving the verticality and flatness of the sidewalls of the second region of the formed waveguide layer. Attached Figure Description
[0029] Figures 1 to 3 This is a schematic diagram of the cross-sectional structure corresponding to each step in a method for forming an optical waveguide structure.
[0030] Figures 4 to 10 This is a schematic cross-sectional view of each step in the optical waveguide structure formation method according to an embodiment of the present invention. Detailed Implementation
[0031] It should be noted that the terms "surface" and "on" in this specification are used to describe the relative spatial position and are not limited to whether there is direct contact.
[0032] As mentioned in the background section, the ridge-shaped optical waveguide morphology formed by existing etching processes needs further improvement, and its performance urgently needs to be enhanced. This paper will now illustrate and analyze this phenomenon using an optical waveguide structure as an example.
[0033] Figures 1 to 3 This is a schematic diagram of the cross-sectional structure corresponding to each step in a method for forming an optical waveguide structure.
[0034] Please refer to Figure 1 A substrate is provided, the substrate including a base 100, an insulating layer 101 on the base 100 and a silicon material layer (not shown) on the insulating layer 101; an initial hard mask layer 102 is formed on the surface of the substrate, the initial hard mask layer 102 exposing a portion of the substrate surface; using the initial hard mask layer 102 as a mask, the substrate is etched until the surface of the insulating layer 101 is exposed, a groove 103 is formed in the substrate, and an initial optical waveguide 104 is formed with the silicon material layer, the initial optical waveguide 104 including a first region I and an initial second region II located on the first region I.
[0035] Please refer to Figure 2 After forming the initial optical waveguide 104, a photoresist material layer (not shown in the figure) is formed on the substrate surface. The photoresist material layer fills the groove 103, and the surface of the photoresist material layer is higher than the top surface of the initial hard mask layer 102. The patterned photoresist material layer forms a photoresist layer 105, which exposes part of the surface of the initial hard mask layer 102 on the initial optical waveguide 104. Using the photoresist layer 105 as a mask, the initial hard mask layer 102 is etched to form a hard mask layer 106. After forming the hard mask layer 106, the photoresist layer 105 is removed.
[0036] Please refer to Figure 3 After removing the photoresist layer 105, the initial second region II of the initial optical waveguide 104 is etched using the hard mask layer 106 as a mask, the initial second region II is used as the second region II', and the first region I and the second region II' are used to form the optical waveguide 107.
[0037] The optical waveguide 107 formed by the above method has a ridge structure. After forming the initial optical waveguide 104, a photoresist material layer is formed on the substrate surface. Due to the small width of the groove 103, the filling ability of the photoresist material layer is poor, which may leave pits when the photoresist material layer fills the groove 103, resulting in poor surface flatness of the photoresist material layer. In order to transfer the pattern to the hard mask layer 106, a photoresist material layer pattern transfer layer with a relatively high thickness is required. However, due to the insufficient hardness of the photoresist material, under the existing photolithography conditions, the sidewalls and bottom of the formed photoresist layer 105 are not perpendicular. The greater the thickness of the photoresist layer 105, the more the sidewalls and bottom of the formed hard mask layer 106 deviate from the ideal vertical angle, thus causing the sidewalls of the second region II' of the formed optical waveguide 107 to be non-perpendicular. Specifically, in this embodiment, the angle between the sidewalls and bottom of the second region II' is approximately 75°. The morphology of the sidewalls in the second region II' results in significant transmission loss in the optical waveguide, which needs further improvement.
[0038] To address the aforementioned issues, this invention provides a method for forming an optical waveguide structure. A planarization material layer is formed on the substrate surface, with its top surface higher than the initial waveguide layer's top surface. This planarization material layer enhances the filling capability within the grooves, facilitating the formation of a planarized surface. A pattern transfer layer and a first patterning layer are formed on the surface of the planarization material layer. Because the planarization material layer fills the grooves, the thickness of the first patterning layer is reduced, and its uniformity is improved. Furthermore, since the hardness of the pattern transfer layer is greater than that of the first patterning layer, it facilitates the accurate transfer of the pattern from the first patterning layer onto the pattern transfer layer, improving the verticality and flatness of the pattern transfer layer's sidewalls, and consequently, enhancing the verticality of the second region's sidewalls of the formed waveguide layer.
[0039] To make the above-mentioned objectives, features and beneficial effects of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
[0040] Figures 4 to 10 This is a schematic cross-sectional view of each step in the optical waveguide structure formation method according to an embodiment of the present invention.
[0041] The method for forming an optical waveguide structure includes: forming a substrate, the substrate having a groove, a portion of the bottom surface of the groove having an initial waveguide layer, the initial waveguide layer including a first region and an initial second region located on the first region.
[0042] In this embodiment, an initial hard mask layer is also provided on top of the initial waveguide layer. For the substrate formation method, please refer to [reference needed]. Figures 4 to 6 .
[0043] Please refer to Figure 4 An initial substrate is provided, comprising a substrate and a waveguide material layer 202 located on the surface of the substrate.
[0044] In this embodiment, the initial substrate is a silicon-on-insulator substrate.
[0045] The substrate includes a substrate layer 200 and an insulating dielectric layer 201 located on the substrate layer 200.
[0046] The insulating dielectric layer 201 is made of silicon oxide; the waveguide material layer 202 is made of silicon. In this embodiment, the waveguide material layer 202 is used to form a silicon waveguide. In other embodiments, the waveguide material layer may be made of silicon nitride, and the waveguide material layer is used to form a silicon nitride waveguide.
[0047] In this embodiment, the substrate layer 200 is made of silicon, the insulating dielectric layer 201 is made of silicon oxide, and the waveguide material layer 202 is made of silicon. The insulating dielectric layer 201 is used to cover the waveguide layer.
[0048] In other embodiments, the substrate material includes silicon, silicon carbide, silicon germanium, a multi-element semiconductor material composed of group III-V elements, or germanium-on-insulator (GOI). The multi-element semiconductor material composed of group III-V elements includes InP, GaAs, GaP, InAs, InSb, InGaAs, or InGaAsP.
[0049] Please refer to Figure 5 An initial hard mask layer is formed on the surface of the waveguide material layer 202, exposing part of the waveguide material layer 202.
[0050] The material of the initial hard mask layer includes one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon carbon oxynitride, and silicon carbonitride.
[0051] In this embodiment, the initial hard mask layer has a two-layer structure. Specifically, the initial hard mask layer includes an oxide layer 203a and a nitride layer 203b located on the oxide layer 203a. More specifically, the material of the oxide layer 203a is silicon oxide, and the material of the nitride layer 203b is silicon nitride. In other embodiments, the initial hard mask layer can be a single-layer or multi-layer composite structure.
[0052] The initial hard mask layer has a thickness ranging from 1200 angstroms to 1500 angstroms.
[0053] The method for forming the initial hard mask layer includes: forming a hard mask material layer (not shown in the figure) on the surface of the waveguide material layer 202; forming a second patterning layer (not shown in the figure) on the surface of the hard mask material layer, wherein the second patterning layer exposes a portion of the hard mask material layer; and etching the hard mask material layer using the second patterning layer as a mask to form the initial hard mask layer. Specifically, the mask material layer includes a silicon oxide material layer and a silicon nitride material layer located on the silicon oxide material layer. The silicon oxide material layer is etched to form an oxide layer 203a, and the silicon nitride material layer is etched to form a nitride layer 203b.
[0054] The material of the second patterning layer includes photoresist. In this embodiment, the material of the second patterning layer is photoresist.
[0055] In this embodiment, after the initial hard mask layer is formed, the second patterning layer is also removed.
[0056] The process for removing the second patterning layer includes an ashing process.
[0057] Please refer to Figure 6 Using the initial hard mask layer as a mask, the initial substrate is etched until the substrate is exposed to form the substrate.
[0058] The substrate has a recess 204, and a portion of the bottom surface of the recess 204 has an initial waveguide layer 205. The initial waveguide layer 205 includes a first region I and an initial second region II located on the first region I. The initial second region II is used to form a second region of the waveguide layer, which includes the first region I and the second region.
[0059] The etching process for the initial substrate includes a dry etching process. In this embodiment, the etching process for the initial substrate is a dry etching process, which is beneficial for achieving a better morphology of the groove 204.
[0060] In this embodiment, the depth of the groove 204 ranges from 3000 angstroms to 5000 angstroms. Depth refers to the dimension along the normal direction of the substrate surface.
[0061] Please refer to Figure 7 A planarization material layer 206, a pattern transfer layer 207 on the surface of the planarization material layer 206, and a first patterning layer 208 on the surface of the pattern transfer layer 207 are formed on the substrate surface. The top surface of the planarization material layer 206 is higher than the top surface of the initial hard mask layer. The first patterning layer 208 exposes part of the pattern transfer layer 207 on the initial waveguide layer 205. The hardness of the pattern transfer layer 207 is greater than that of the first patterning layer 208.
[0062] In the above embodiments, the planarization material layer 206 improves the filling capacity within the groove 204, which is beneficial for forming a planarized surface. A pattern transfer layer 207 and a first patterning layer 208 located on the surface of the planarization material layer 206 are formed. Since the planarization material layer is used to fill the groove, the thickness of the first patterning layer 208 is reduced, and the uniformity of the first patterning layer 208 is improved. At the same time, since the hardness of the pattern transfer layer 207 is greater than that of the first patterning layer 208, it is beneficial to accurately transfer the pattern of the first patterning layer 208 onto the pattern transfer layer 207, thereby improving the verticality and flatness of the sidewall of the pattern transfer layer 207, and further improving the verticality of the second region sidewall of the formed waveguide layer.
[0063] The material of the first patterning layer 208 includes photoresist. In this embodiment, the material of the first patterning layer 208 is photoresist.
[0064] The pattern transfer layer 207 includes a silicon-containing anti-reflective coating material. In this embodiment, the pattern transfer layer 207 is a silicon-containing anti-reflective coating material.
[0065] In this embodiment, the silicon content in the pattern transfer layer 207 ranges from 30% to 40%. The reason for using this silicon content range is that a higher silicon content is beneficial for increasing the hardness of the pattern transfer layer 207, improving the sidewall morphology and smoothness after etching, thereby increasing the accuracy of subsequent pattern transfer. The silicon content range can be adjusted according to actual needs.
[0066] In this embodiment, the thickness of the pattern transfer layer 207 ranges from 500 angstroms to 1000 angstroms.
[0067] In this embodiment, the material of the planarization material layer 206 includes organic carbon material.
[0068] In this embodiment, the material of the first patterning layer 208 includes photoresist material.
[0069] Subsequently, using the first patterning layer 208 as a mask, the pattern transfer layer 207, the planarization material layer 206, and the initial second region II are etched, so that the width of the initial second region II is smaller than the width of the first region I. The etched initial second region II is used as the second region II', and the first region I and the second region II form a waveguide layer.
[0070] As mentioned earlier, the initial waveguide layer is topped with an initial hard mask layer. For details on the formation method of the mask layer, please refer to [link to documentation]. Figure 8 .
[0071] Please refer to Figure 8Using the first patterning layer 208 as a mask, the pattern transfer layer 207, the planarization material layer 206 and the initial hard mask layer are etched to obtain the etched pattern transfer layer 207, the planarization material layer 206 and the initial hard mask layer, and the etched initial hard mask layer is used as the hard mask layer 209.
[0072] In the above example, since the sidewalls of the pattern transfer layer 207 have good verticality and flatness after being etched, the pattern can be transferred to the hard mask layer 209 through the pattern transfer layer 207, which can improve the verticality and flatness of the sidewalls of the hard mask layer 209, thereby improving the verticality of the second region sidewalls of the formed waveguide layer.
[0073] In this embodiment, the material of the hard mask layer 209 includes one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon carbon oxynitride, and silicon carbon oxynitride.
[0074] In this embodiment, the thickness of the hard mask layer 209 ranges from 1200 angstroms to 1500 angstroms.
[0075] In this embodiment, the angle between the sidewall of the hard mask layer 209 and the substrate surface ranges from 86 degrees to 90 degrees.
[0076] In this embodiment, please refer to Figure 9 Before etching the initial second region II and after forming the hard mask layer 209, the pattern transfer layer 207, the planarization material layer 206, and the first patterning layer 208 are also removed.
[0077] In this embodiment, the process of removing the pattern transfer layer 207, the planarization material layer 206 and the first patterning layer 208 includes an ashing process.
[0078] In the above embodiments, by removing the pattern transfer layer 207, the planarization material layer 206, and the first patterning layer 208, the influence of the pattern transfer layer 207, the planarization material layer 206, and the first patterning layer 208 on the etching process can be reduced. That is, the scattering of etching ions by the planarization material layer 206 can be reduced, and the thickness of the mask on the initial waveguide layer 205 can be reduced, thereby improving the verticality and flatness of the sidewall of the second region of the formed waveguide layer. At the same time, removing the pattern transfer layer 207 and the planarization material layer 206 can prevent organic byproducts generated during the subsequent etching process of forming the waveguide layer (specifically the second region of the waveguide layer) from adhering to the sidewall of the waveguide layer, which is beneficial to reducing the roughness of the sidewall of the waveguide layer.
[0079] In this embodiment, please refer to Figure 10After removing the pattern transfer layer 207, the planarization material layer 206 and the first patterning layer 208, the initial second region II is etched using the hard mask layer 209 as a mask, so that the width of the initial second region II is smaller than the width of the first region I, to form the second region II', and the waveguide layer 210 is formed by the first region I and the second region II'.
[0080] In this embodiment, the waveguide layer 202 is made of silicon. In other embodiments, the waveguide layer may be made of silicon nitride.
[0081] In this embodiment, the angle between the sidewall of the second region II' and the substrate surface ranges from 86 degrees to 90 degrees. This improves the perpendicularity between the sidewall of the second region II' and the substrate surface, thereby helping to reduce the transmission loss of the optical waveguide.
[0082] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.
Claims
1. A method for forming an optical waveguide structure, characterized in that, include: A substrate is formed having a groove therein, and a portion of the bottom surface of the groove has an initial waveguide layer, the initial waveguide layer comprising a first region and an initial second region located on the first region; A planarization material layer, a pattern transfer layer located on the surface of the planarization material layer, and a first patterning layer located on the surface of the pattern transfer layer are formed on the surface of the substrate. The top surface of the planarization material layer is higher than the top surface of the initial waveguide layer. The first patterning layer exposes a portion of the pattern transfer layer on the initial waveguide layer. The hardness of the pattern transfer layer is greater than that of the first patterning layer. Using the first patterning layer as a mask, the pattern transfer layer, the planarization material layer, and the initial second region are etched, such that the width of the initial second region is smaller than the width of the first region, and a second region is formed from the initial second region, and a waveguide layer is formed from the first region and the second region.
2. The method for forming an optical waveguide structure as described in claim 1, characterized in that, The initial waveguide layer is also topped with an initial hard mask layer; the method further includes etching the initial hard mask layer to form a hard mask layer.
3. The method for forming an optical waveguide structure as described in claim 2, characterized in that, Before etching the initial second region and after forming the hard mask layer, the method further includes: removing the pattern transfer layer, the planarization material layer, and the first patterning layer; the method of etching the initial second region includes: using the hard mask layer as a mask to etch the initial second region.
4. The method for forming an optical waveguide structure as described in claim 3, characterized in that, The process for removing the pattern transfer layer, the planarization material layer, and the first patterning layer includes an ashing process.
5. The method for forming an optical waveguide structure as described in claim 2, characterized in that, The angle between the sidewall of the hard mask layer and the surface of the substrate ranges from 86 degrees to 90 degrees.
6. The method for forming an optical waveguide structure as described in claim 2, characterized in that, The material of the hard mask layer includes one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon carbon oxynitride, and silicon carbonitride.
7. The method for forming an optical waveguide structure as described in claim 2, characterized in that, The thickness of the hard mask layer ranges from 1200 angstroms to 1500 angstroms.
8. The method for forming an optical waveguide structure as described in claim 2, characterized in that, The method for forming the substrate includes: providing an initial substrate, the initial substrate including a substrate and a waveguide material layer located on the surface of the substrate; forming an initial hard mask layer on the surface of the waveguide material layer, the initial hard mask layer exposing a portion of the waveguide material layer; using the initial hard mask layer as a mask, etching the initial substrate until the substrate is exposed, thereby forming the substrate.
9. The method for forming an optical waveguide structure as described in claim 8, characterized in that, The method for forming the initial hard mask layer includes: forming a hard mask material layer on the surface of the waveguide material layer; forming a second patterned layer on the surface of the hard mask material layer, wherein the second patterned layer exposes a portion of the hard mask material layer; and etching the hard mask material layer using the second patterned layer as a mask to form the initial hard mask layer.
10. The method for forming an optical waveguide structure as described in claim 8, characterized in that, The substrate includes a base layer and an insulating dielectric layer located on the base layer.
11. The method for forming an optical waveguide structure as described in claim 10, characterized in that, The insulating dielectric layer is made of silicon oxide; the waveguide layer is made of silicon.
12. The method for forming an optical waveguide structure as described in claim 1, characterized in that, The pattern transfer layer comprises a silicon-containing anti-reflective coating material.
13. The method for forming an optical waveguide structure as described in claim 12, characterized in that, The silicon content in the pattern transfer layer ranges from 30% to 40%.
14. The method for forming an optical waveguide structure as described in claim 1, characterized in that, The material of the planarization material layer includes organic carbon materials.
15. The method for forming an optical waveguide structure as described in claim 1, characterized in that, The material of the first patterning layer includes photoresist material.
16. The method for forming an optical waveguide structure as described in claim 1, characterized in that, The depth of the groove ranges from 3,000 angstroms to 5,000 angstroms.
17. The method for forming an optical waveguide structure as described in claim 1, characterized in that, The thickness of the pattern transfer layer ranges from 500 angstroms to 1000 angstroms.
18. The method for forming an optical waveguide structure as described in claim 1, characterized in that, The angle between the sidewall of the second region and the surface of the substrate ranges from 86 degrees to 90 degrees.