Method of forming an optical device

Abstract

A method for forming an optical device includes: providing a substrate, the substrate including a first substrate, a buried oxide layer on the first substrate, and a second substrate on the buried oxide layer; forming an initial third waveguide and a corresponding initial third groove in the second substrate, the initial third waveguide including an initial third starting region; forming a first dielectric layer in the initial third groove and on the initial third waveguide; removing part of the first dielectric layer and part of the initial third waveguide to form a third waveguide and a corresponding third groove in the second substrate, the third waveguide including a third starting region, a projected area of the third starting region on a surface of the substrate being smaller than a projected area of the initial third starting region on the surface of the substrate. The formed optical device can effectively reduce return loss.

Description

Technical Field

[0001] This invention relates to the field of semiconductors, and more particularly to a method for forming an optical device. Background Technology

[0002] Silicon offers significant advantages as a substrate material for photonic integrated chips. For example, it is compatible with Complementary Metal Oxide Semiconductor (CMOS) processes, reducing mass production costs and facilitating optoelectronic integration with electronic chips. However, as application areas expand, the requirements for photonic devices become increasingly complex. Simply fabricating complex SOI waveguide devices on SOI (Silicon-On-Insulator) substrates is no longer sufficient to meet future development needs.

[0003] To further improve the performance of photonic integrated chips, silicon-based SiN-on-SOI hybrid integration material platforms have attracted widespread attention from researchers. Combining SOI with SiNx materials can realize complex, high-performance photonic integrated chips.

[0004] However, the current photonic integrated chips combining SOI and SiNx materials have high losses, resulting in high return loss in existing waveguide interlayer structures. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a method for forming an optical device to improve the performance of the optical device.

[0006] To address the aforementioned technical problems, the present invention provides a method for forming an optical device, comprising: providing a substrate, the substrate including a first substrate, a buried oxide layer on the first substrate, and a second substrate on the buried oxide layer; forming an initial third waveguide and an initial third groove corresponding to the initial third waveguide within the second substrate, the initial third groove exposing the surface of the buried oxide layer, the initial third waveguide including an initial third starting region; forming a first dielectric layer within the initial third groove and on the initial third waveguide; removing a portion of the first dielectric layer and a portion of the initial third waveguide, and forming a third waveguide and a third groove corresponding to the third waveguide within the second substrate, wherein the projected area of ​​the third starting region on the substrate surface is smaller than the projected area of ​​the initial third starting region on the substrate surface.

[0007] Optionally, the projection pattern of the third starting region onto the substrate surface includes a triangle or a trapezoid.

[0008] Optionally, the projection pattern of the initial third starting region on the substrate surface includes a rectangle.

[0009] Optionally, the third starting region includes a first end and a second end opposite to each other, and the third waveguide also includes a third ending region and a third surrounding region located between the third starting region and the third ending region, the third surrounding region being spirally distributed; the second end is connected to the third surrounding region.

[0010] Optionally, the substrate includes a first region, a second region, and a third region; before forming the first dielectric layer in the initial third groove and on the initial third waveguide, the substrate further includes: forming a first waveguide and a first groove located on both sides of the first waveguide in the second substrate of the first region.

[0011] Optionally, before forming the first dielectric layer in the initial third groove and on the initial third waveguide, the method further includes: forming a second waveguide and a second groove located on both sides of the second waveguide in the second substrate of the second region, wherein the depth of the second groove is greater than the depth of the first groove; the first dielectric layer is also located in the first groove, the second groove, on the first waveguide, and on the second waveguide.

[0012] Optionally, the depth of the initial third groove is greater than the depth of the second groove.

[0013] Optionally, the method for forming the first waveguide includes: forming an initial mask structure on a second substrate; forming a first photoresist layer on the initial mask structure, wherein the first photoresist layer exposes a portion of the initial mask structure surface in a first region; etching the initial mask structure using the first photoresist layer as a mask until it exposes the surface of the second substrate in the first region, thereby forming the first mask structure; and etching the second substrate using the first mask structure as a mask to form a discrete first waveguide and first grooves located on both sides of the first waveguide within the second substrate.

[0014] Optionally, the method for forming the second waveguide includes: forming a second photoresist layer on a first mask structure, the second photoresist layer exposing a portion of the surface of the first mask structure on a second region; etching the first mask structure with the second photoresist layer until the surface of a second substrate in the second region is exposed to form a second mask structure; and etching the second substrate with the second mask structure to form a discrete second waveguide and second grooves located on both sides of the second waveguide within the second substrate.

[0015] Optionally, the initial third groove is located on both sides of the initial third waveguide; the method for forming the initial third waveguide includes: forming a third photoresist layer on the second mask structure, the third photoresist layer exposing a portion of the surface of the second mask structure on the third region; etching the second mask structure with the third photoresist layer until the surface of the second substrate on the third region is exposed, forming the third mask structure; etching the second substrate with the third mask structure mask, forming the initial third waveguide and the initial third groove located on both sides of the initial third waveguide in the second substrate of the third region.

[0016] Optionally, the initial mask structure includes an anti-reflective layer and a hard mask layer located on the anti-reflective layer.

[0017] Optionally, the first waveguide includes: a first starting region, a first ending region, and a first surrounding region located between the first starting region and the first ending region, wherein the first surrounding region is spirally distributed; the second waveguide includes: a second starting region, a second ending region, and a second surrounding region located between the second starting region and the second ending region, wherein the second surrounding region is spirally distributed.

[0018] Optionally, after forming the third waveguide, the method further includes: forming a beam-splitting structure on a first dielectric layer in the first and second regions, the beam-splitting structure having a fourth groove; forming a fourth waveguide on the first dielectric layer in the third region, the fourth waveguide having fifth grooves on both sides, the fifth grooves exposing the surface of the first dielectric layer; forming a second dielectric layer on the first dielectric layer, the beam-splitting structure and the fourth waveguide being located within the second dielectric layer, the second dielectric layer also being located within the fourth groove and the fifth groove.

[0019] Optionally, the materials of the beam splitting structure and the fourth waveguide include silicon nitride. Optionally, the third groove is located on one side of the third waveguide; the method of removing part of the first dielectric layer and the initial third waveguide includes: forming a fourth mask structure on the first dielectric layer, the fourth mask structure exposing part of the surface of the first dielectric layer on the initial third starting region; etching the first dielectric layer and the initial third starting region with the fourth mask structure as a mask until the buried oxide layer surface is exposed, forming the third waveguide and the third groove on one side of the third waveguide.

[0020] Optionally, the etching process for the first dielectric layer and the initial third waveguide includes a dry etching process.

[0021] Optionally, the material of the first substrate includes silicon; the material of the buried oxide layer includes silicon oxide; and the material of the second substrate includes silicon.

[0022] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0023] The technical solution of this invention involves first forming an initial third waveguide, then removing a portion of the first dielectric layer and a portion of the initial third waveguide to form a third waveguide. The third waveguide includes a third starting region, the projected area of ​​which on the substrate surface is smaller than the projected area of ​​the initial third starting region on the substrate surface. This reduces the area of ​​the top surface of the third starting region of the third waveguide, allowing more light to couple from the third waveguide into the fourth waveguide via evanescent waves. The smaller reflection interface provided by the third waveguide effectively reduces return loss.

[0024] Furthermore, the projection shape of the third initiation region onto the substrate surface includes a triangle or a trapezoid. This gives the third waveguide a pointed tip, and the width of the third initiation region is gradually changing, allowing more light to couple from the third waveguide into the fourth waveguide via evanescent waves. The third waveguide provides a smaller reflection interface, thus effectively reducing return loss. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of an optical device in one embodiment;

[0026] Figures 2 to 15 This is a schematic diagram of the optical device formation process in one embodiment of the present invention;

[0027] Figure 16 This is a schematic diagram of the optical device formation process in another embodiment of the present invention. Detailed Implementation

[0028] As described in the background section, current photonic integrated chips combining SOI and SiNx materials suffer from high losses, resulting in significant return losses in existing waveguide interlayer structures. This will be analyzed and explained in conjunction with specific embodiments.

[0029] Figure 1 This is a schematic diagram of the structure of an optical device in one embodiment.

[0030] Please refer to Figure 1The optical device includes: a substrate, the substrate including a first substrate 100, a buried oxide layer 101 on the first substrate 100, and a second substrate 102 on the buried oxide layer 101, the substrate including a first region I, a second region II, and a third region III; a first waveguide 103 located within the second substrate 102 and first grooves (not shown) located on both sides of the first waveguide 103; a second waveguide 104 located within the second substrate 102 and second grooves (not shown) located on both sides of the second waveguide 104, the depth of the second waveguide 104 being greater than the depth of the first waveguide 103; a third waveguide 105 located within the second substrate 102 and third grooves (not shown) located on both sides of the third waveguide 105, the third grooves exposing the surface of the buried oxide layer 101. The depth of the third waveguide 105 is greater than the depth of the second waveguide 104; a first dielectric layer 106 is located within the first groove, the second groove, the third groove, and on the second substrate 102; a beam-splitting structure 108 is located on the first dielectric layer 106 in the first region I and the second region II, the beam-splitting structure 108 having a fourth groove (not shown); a fourth waveguide 109 is located on the first dielectric layer 106 in the third region III, the fourth waveguide 109 having fifth grooves (not shown) on both sides, the fifth grooves exposing the surface of the first dielectric layer 106; a second dielectric layer 107 is located on the first dielectric layer 106, the beam-splitting structure 108 and the fourth waveguide 109 are located within the second dielectric layer, the second dielectric layer 107 is also located within the fourth groove and the fifth groove.

[0031] In the optical device, light enters the fourth waveguide 109 from the third waveguide 105 and is then exited from the fourth waveguide 109 into the optical fiber system. The materials of the beam splitter 108 and the fourth waveguide 109 include silicon nitride. When light enters the fourth waveguide 109 from the third waveguide 105, it is reflected at the wide interface on the surface of the third waveguide 105, thereby causing return loss and affecting the output stability of the laser.

[0032] However, due to the limitations of the etching process, the size of the third waveguide 105 could not be further reduced.

[0033] To address the aforementioned problems, the present invention provides a method for forming an optical device. This method involves first forming an initial third waveguide, then removing a portion of the first dielectric layer and a portion of the initial third waveguide to form a third waveguide. The third waveguide includes a third starting region, the projection of which onto the substrate surface is smaller than the projection of the initial third starting region onto the substrate surface. This reduces the area of ​​the top surface of the third starting region of the third waveguide, allowing more light to couple from the third waveguide into the fourth waveguide via evanescent waves. The smaller reflection interface provided by the third waveguide effectively reduces return loss.

[0034] 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.

[0035] Figures 2 to 15 This is a schematic diagram of the optical device formation process in one embodiment of the present invention.

[0036] Please refer to Figure 2 A substrate is provided, the substrate including a first substrate 200, a buried oxide layer 201 on the first substrate 200 and a second substrate 202 on the buried oxide layer 201, the substrate including a first region I, a second region II and a third region III.

[0037] In this embodiment, the material of the first substrate 200 includes silicon; the material of the buried oxide layer 201 includes silicon oxide; and the material of the second substrate 202 includes silicon.

[0038] Next, a first waveguide and first grooves located on both sides of the first waveguide are formed within the second substrate 202. For the formation process of the first waveguide, please refer to [reference needed]. Figures 3 to 5 .

[0039] Please refer to Figure 3 An initial mask structure is formed on the second substrate 202; a first photoresist layer (not shown) is formed on the initial mask structure, the first photoresist layer exposing a portion of the initial mask structure surface on the first region I; the initial mask structure is etched with the first photoresist layer until it is exposed on the surface of the second substrate 202 in the first region I, forming a first mask structure, the first mask structure having a first opening 205.

[0040] In this embodiment, the initial mask structure includes an anti-reflection layer 203 and a hard mask layer 204 located on the anti-reflection layer 203.

[0041] The anti-reflective layer 203 is made of silicon oxide, and the hard mask layer 204 is made of silicon nitride.

[0042] Please refer to Figure 4 and Figure 5 , Figure 5 for Figure 4 Top view of the first waveguide in the middle. Figure 4 for Figure 5 A cross-sectional view along the XX1 direction shows that the second substrate 202 is etched using the first mask structure as a mask, and a first waveguide 207 and a first groove 206 located on both sides of the first waveguide 207 are formed in the second substrate 202.

[0043] The first waveguide 207 includes: a first starting region A1, a first ending region B1, and a first surrounding region C1 located between the first starting region A1 and the first ending region B1, wherein the first surrounding region C1 is spirally distributed.

[0044] The first surrounding area C1 is the region between the first starting area A1 and the first ending area B1, and the first surrounding area C1 continuously surrounds the first area I in a spiral shape.

[0045] In other embodiments, the first surrounding region C1 can also be other desired arrangement states.

[0046] In this embodiment, after forming the first waveguide 207 and the first grooves 206 located on both sides of the first waveguide 207, the method further includes forming a first filling layer 208 within the first grooves 206. The first filling layer 208 is used to protect the first grooves 206.

[0047] In this embodiment, the material of the first filling layer 208 includes amorphous carbon.

[0048] Next, a second waveguide and second grooves located on both sides of the second waveguide are formed within the second substrate 202. The depth of the second groove is greater than the depth of the first groove. Please refer to [link to documentation] for the formation process of the second waveguide. Figures 6 to 8 .

[0049] Please refer to Figure 6 A second photoresist layer (not shown) is formed on the first mask structure, the second photoresist layer exposing a portion of the surface of the first mask structure on the second region II; the first mask structure is etched with the second photoresist layer until the surface of the second substrate 202 in the second region II is exposed to form a second mask structure, the second mask structure having a second opening 209.

[0050] Please refer to Figure 7 and Figure 8 , Figure 8 for Figure 7 Top view of the second waveguide in the middle. Figure 7 for Figure 8 A cross-sectional view along the XX1 direction shows that the second substrate 202 is etched using the second mask structure mask, and a second waveguide 211 and second grooves 210 located on both sides of the second waveguide 211 are formed in the second substrate 202.

[0051] The second waveguide 211 includes: a second starting region A2, a second ending region B2, and a second surrounding region C2 located between the second starting region A2 and the second ending region B2, wherein the second surrounding region C2 is spirally distributed.

[0052] The second surrounding area C2 is the region between the second starting area A2 and the second ending area B2, and the second surrounding area C2 continuously surrounds the second area II in a spiral shape.

[0053] In other embodiments, the second surrounding region C2 can also be in other desired arrangement states.

[0054] In this embodiment, after forming the second waveguide 211 and the second grooves 210 located on both sides of the second waveguide 211, the method further includes forming a second filling layer 212 within the second grooves 210. The second filling layer 212 is used to protect the second grooves 210.

[0055] In this embodiment, the material of the second filling layer 212 includes amorphous carbon.

[0056] Next, an initial third waveguide and an initial third groove corresponding to the initial third waveguide are formed within the second substrate 202. The initial third groove exposes the surface of the buried oxide layer 201. The initial third waveguide includes an initial third initiation region. The formation process of the initial third waveguide is described in [reference needed]. Figures 9 to 11 .

[0057] In this embodiment, the initial third groove region is located on both sides of the initial third waveguide.

[0058] Please refer to Figure 9 A third photoresist layer (not shown) is formed on the second mask structure, the third photoresist layer exposing a portion of the surface of the second mask structure on the third region III; the second mask structure is etched with the third photoresist layer until it is exposed on the surface of the second substrate 202 in the third region III to form a third mask structure, the third mask structure having a third opening 213.

[0059] Please refer to Figure 10 and Figure 11 , Figure 11 for Figure 10 Top view of the initial third waveguide. Figure 10 for Figure 11 A cross-sectional view along the XX1 direction shows that the second substrate 202 is etched using the third mask structure, forming an initial third waveguide 215 and initial third grooves 214 on both sides of the initial third waveguide 215 within the second substrate 202.

[0060] In this embodiment, the depth of the initial third groove 214 is greater than the depth of the second groove 210. The initial third waveguide 215 includes: an initial third starting region A3, a third ending region B3, and a third surrounding region C3 located between the initial third starting region A3 and the third ending region B3, wherein the third surrounding region C3 is spirally distributed.

[0061] In this embodiment, the projection of the initial third starting region A3 of the initial third waveguide 215 onto the substrate surface is rectangular.

[0062] In this embodiment, after forming the initial third waveguide 215 and the initial third grooves 214 located on both sides of the initial third waveguide 215, the method further includes: removing the first filling layer 208 in the first groove 206 and the second filling layer 212 in the second groove 210.

[0063] The process for removing the first filler layer 208 and the second filler layer 212 includes an ashing process.

[0064] Please refer to Figure 12 A first dielectric layer 218 is formed in the first groove 206, the second groove 210, the initial third groove 214, on the first waveguide 207, on the second waveguide 211, and on the initial third waveguide 215.

[0065] The method for forming the first dielectric layer 218 includes: forming a dielectric material layer (not shown) in the first groove 206, the second groove 210, the initial third groove 214 and the hard mask layer 204; planarizing the dielectric material layer and the hard mask layer 204 until the surface of the anti-reflection layer 203 is exposed; and forming the first dielectric layer 218 in the first groove 206, the second groove 210, the initial third groove 214, the first waveguide 207, the second waveguide 211 and the initial third waveguide 215.

[0066] In this embodiment, the material of the first dielectric layer 218 includes silicon oxide.

[0067] Please refer to Figure 13 and Figure 14 , Figure 14 for Figure 13 The top view of the first dielectric layer 218 is omitted. Figure 13 for Figure 14 A cross-sectional view along the YY1 direction shows the removal of a portion of the first dielectric layer 218 and the initial third waveguide 215, resulting in the formation of a third waveguide 217 and a third groove 216 corresponding to the third waveguide 217 within the second substrate 202.

[0068] In this embodiment, the third groove 216 is located on one side of the third waveguide 217.

[0069] The third waveguide 217 includes: a third starting region A4, a third ending region B3, and a third surrounding region C3 located between the third starting region A4 and the third ending region B3, wherein the third surrounding region C3 is spirally distributed.

[0070] In this embodiment, the projected area of ​​the third starting region A4 on the substrate surface is smaller than the projected area of ​​the initial third starting region A3 on the substrate surface. This reduces the area of ​​the top surface of the third starting region A4 of the third waveguide 217, allowing more light to couple from the third waveguide 217 into the fourth waveguide via evanescent waves. The smaller reflection interface of the third waveguide 217 effectively reduces return loss.

[0071] The third surrounding area C3 is the region between the third starting area A4 and the third ending area B3, and the third surrounding area C3 continuously surrounds the third area III in a spiral shape.

[0072] In other embodiments, the third surrounding region C3 can also be other desired arrangement states.

[0073] In this embodiment, the projection pattern of the third starting region A4 on the substrate surface is a triangle.

[0074] The third starting region A4 includes a first end T1 and a second end T2, which are opposite each other. The first end T1 is the vertex of the triangle, and the second end T2 is connected to the third surrounding region C3.

[0075] The projection pattern of the third starting region A4 onto the substrate surface is triangular. This results in the third waveguide 217 having a tip T1, and the width of the third starting region A4 being gradually reduced. Consequently, the area of ​​the top surface of the third starting region A4 of the third waveguide 217 is reduced, allowing more light to couple from the third waveguide 217 into the fourth waveguide via evanescent waves. The reduced reflection interface provided by the third waveguide 217 effectively reduces return loss.

[0076] In this embodiment, a portion of the first dielectric layer 218 and the initial third starting region A3 are removed to form the third waveguide 217 and the third groove 216 corresponding to the third waveguide 217.

[0077] The method for removing a portion of the first dielectric layer 218 and the initial third starting region A3 includes: forming a fourth mask structure (not shown) on the first dielectric layer 218, the fourth mask structure exposing a portion of the surface of the first dielectric layer 218 on the initial third starting region A3; etching the first dielectric layer 218 and the initial third starting region A3 using the fourth mask structure as a mask until the surface of the buried oxide layer 201 is exposed, forming the third waveguide 217 and a third groove 216 located on one side of the third waveguide 217.

[0078] The etching process for the first dielectric layer 218 and the initial third starting region 215 includes a dry etching process.

[0079] Please refer to Figure 15 A beam-splitting structure 219 is formed on a first dielectric layer 218 in the first region I and the second region II. The beam-splitting structure 219 has a fourth groove (not shown). A fourth waveguide 220 is formed on the first dielectric layer 218 in the third region III. The fourth waveguide 220 has a fifth groove (not shown) on both sides. The fifth groove exposes the surface of the first dielectric layer 218. A second dielectric layer 221 is formed on the first dielectric layer 218. The beam-splitting structure 219 and the fourth waveguide 220 are located within the second dielectric layer 221. The second dielectric layer 221 is also located within the fourth groove and the fifth groove.

[0080] In this embodiment, the materials of the beam splitting structure 219 and the fourth waveguide 220 include silicon nitride.

[0081] In this embodiment, the material of the second medium 221 includes silicon oxide.

[0082] Because the projected area of ​​the third starting region A4 on the substrate surface is smaller than the projected area of ​​the initial third starting region A3 on the substrate surface, the area of ​​the top surface of the third starting region A4 of the third waveguide 217 is reduced. This allows more light to couple from the third waveguide 217 into the fourth waveguide 220 via evanescent waves. Since the reflection interface provided by the third waveguide 217 is smaller, return loss can be effectively reduced.

[0083] Figure 16 This is a schematic diagram of the optical device formation process in another embodiment of the present invention.

[0084] Please refer to Figure 16 , Figure 16 and Figure 14 The difference is that the projection pattern of the third starting region A4 on the substrate surface is trapezoidal.

[0085] The projection pattern of the third starting region A4 onto the substrate surface is trapezoidal. This makes the width of the third starting region A4 of the third waveguide 217 gradually change, thereby reducing the area of ​​the top surface of the third starting region A4 of the third waveguide 217. This allows more light to couple from the third waveguide 217 into the fourth waveguide via evanescent waves. The smaller reflection interface provided by the third waveguide 217 effectively reduces return loss.

[0086] 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 device, characterized in that, include: A substrate is provided, the substrate comprising a first substrate, a buried oxide layer on the first substrate, and a second substrate on the buried oxide layer; An initial third waveguide and an initial third groove corresponding to the initial third waveguide are formed within the second substrate. The initial third groove exposes the buried oxide layer surface. The initial third waveguide includes an initial third initiation region. A first dielectric layer is formed within the initial third groove and on the initial third waveguide; A portion of the first dielectric layer and a portion of the initial third waveguide are removed, and a third waveguide and a third groove corresponding to the third waveguide are formed in the second substrate. The third waveguide includes a third starting region, and the projected area of ​​the third starting region on the substrate surface is smaller than the projected area of ​​the initial third starting region on the substrate surface. A fourth waveguide is formed on the first dielectric layer above the third waveguide.

2. The method for forming an optical device as described in claim 1, characterized in that, The projection pattern of the third starting region onto the substrate surface includes a triangle or a trapezoid.

3. The method for forming an optical device as described in claim 2, characterized in that, The projection pattern of the initial third starting region on the substrate surface includes a rectangle.

4. The method for forming an optical device as described in claim 1, characterized in that, The third starting region includes a first end and a second end opposite to each other. The third waveguide also includes a third ending region and a third surrounding region located between the third starting region and the third ending region. The third surrounding region is spirally distributed. The second end is connected to the third surrounding region.

5. The method for forming an optical device as described in claim 1, characterized in that, The substrate includes a first region, a second region, and a third region; before forming a first dielectric layer in the initial third groove and on the initial third waveguide, it further includes: forming a first waveguide and a first groove located on both sides of the first waveguide in the second substrate of the first region.

6. The method for forming an optical device as described in claim 5, characterized in that, Before forming the first dielectric layer in the initial third groove and on the initial third waveguide, the method further includes: forming a second waveguide and a second groove located on both sides of the second waveguide in the second substrate of the second region, wherein the depth of the second groove is greater than the depth of the first groove; the first dielectric layer is also located in the first groove, the second groove, on the first waveguide and on the second waveguide.

7. The method for forming an optical device as described in claim 6, characterized in that, The depth of the initial third groove is greater than the depth of the second groove.

8. The method for forming an optical device as described in claim 6, characterized in that, The method for forming the first waveguide includes: forming an initial mask structure on a second substrate; forming a first photoresist layer on the initial mask structure, wherein the first photoresist layer exposes a portion of the initial mask structure surface in a first region; etching the initial mask structure using the first photoresist layer as a mask until it exposes the surface of the second substrate in the first region, thereby forming the first mask structure; and etching the second substrate using the first mask structure as a mask to form a discrete first waveguide and first grooves located on both sides of the first waveguide within the second substrate.

9. The method for forming an optical device as described in claim 8, characterized in that, The method for forming the second waveguide includes: forming a second photoresist layer on a first mask structure, the second photoresist layer exposing a portion of the surface of the first mask structure on a second region; etching the first mask structure with the second photoresist layer until the surface of a second substrate in the second region is exposed to form a second mask structure; and etching the second substrate with the second mask structure to form a discrete second waveguide and second grooves located on both sides of the second waveguide within the second substrate.

10. The method for forming an optical device as described in claim 9, characterized in that, The initial third groove is located on both sides of the initial third waveguide; the method for forming the initial third waveguide includes: forming a third photoresist layer on the second mask structure, the third photoresist layer exposing a portion of the surface of the second mask structure on the third region; etching the second mask structure with the third photoresist layer until it is exposed on the surface of the second substrate in the third region, forming the third mask structure; etching the second substrate with the third mask structure mask, forming the initial third waveguide and the initial third groove located on both sides of the initial third waveguide in the second substrate of the third region.

11. The method for forming an optical device as described in claim 8, characterized in that, The initial mask structure includes an anti-reflective layer and a hard mask layer located on the anti-reflective layer.

12. The method for forming an optical device as described in claim 6, characterized in that, The first waveguide includes: a first starting region, a first ending region, and a first surrounding region located between the first starting region and the first ending region, wherein the first surrounding region is spirally distributed; the second waveguide includes: a second starting region, a second ending region, and a second surrounding region located between the second starting region and the second ending region, wherein the second surrounding region is spirally distributed.

13. The method for forming an optical device as described in claim 5, characterized in that, After forming the third waveguide, the process further includes: forming a beam-splitting structure on a first dielectric layer in the first and second regions, the beam-splitting structure having a fourth groove; forming a fourth waveguide on the first dielectric layer in the third region, the fourth waveguide having fifth grooves on both sides, the fifth grooves exposing the surface of the first dielectric layer; forming a second dielectric layer on the first dielectric layer, the beam-splitting structure and the fourth waveguide being located within the second dielectric layer, the second dielectric layer also being located within the fourth groove and the fifth groove.

14. The method for forming an optical device as described in claim 13, characterized in that, The materials of the beam splitting structure and the fourth waveguide include silicon nitride.

15. The method for forming an optical device as described in claim 1, characterized in that, The third groove is located on one side of the third waveguide; the method for removing part of the first dielectric layer and the initial third waveguide includes: forming a fourth mask structure on the first dielectric layer, the fourth mask structure exposing part of the surface of the first dielectric layer on the initial third starting region; etching the first dielectric layer and the initial third starting region with the fourth mask structure as a mask until the surface of the buried oxide layer is exposed, forming the third waveguide and the third groove on one side of the third waveguide.

16. The method for forming an optical device as described in claim 1, characterized in that, The etching process for the first dielectric layer and the initial third waveguide includes a dry etching process.

17. The method for forming an optical device as described in claim 1, characterized in that, The material of the first substrate includes silicon; the material of the buried oxide layer includes silicon oxide; and the material of the second substrate includes silicon.

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