Method of forming optical devices

Abstract

A method for forming an optical device, comprising: providing a substrate, the substrate comprising a coupling region; forming a first dielectric layer on the substrate; forming an initial waveguide trench in the first dielectric layer on the coupling region; forming a patterned layer on the surface of the first dielectric layer and in the initial waveguide trench, the patterned layer exposing at least a portion of the bottom of the initial waveguide trench; etching the first dielectric layer using the patterned layer as a mask to form a waveguide structure on the substrate, the waveguide structure comprising a waveguide end structure on the coupling region. The method for forming the semiconductor structure improves the process stability of small-size waveguides, reduces the coupling loss during light propagation, and improves the light propagation efficiency.

Description

Technical Field

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

[0002] Silicon-based optical devices are information functional devices that use light as an information carrier. Due to their advantages such as low cost, small size, and low power consumption, they are widely used in sensors, communication products, and network products.

[0003] Light propagates through optical fibers into optical devices, and propagation loss mainly occurs at the coupling point between the fiber and the waveguide. By using waveguides with gradually decreasing dimensions, the waveguide tip becomes smaller, which helps improve evanescent wave coupling during light propagation, thereby reducing coupling loss and increasing light propagation efficiency.

[0004] However, in the existing technology, due to process limitations, it is difficult to form small-sized waveguide ends, which increases the coupling loss during light propagation and reduces the light propagation efficiency. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a method for forming an optical device, which improves the stability of the fabrication process of small-sized waveguides, reduces coupling loss during light propagation, and improves light propagation efficiency.

[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 coupling region; forming a first dielectric layer on the substrate; forming an initial waveguide trench within the first dielectric layer on the coupling region; forming a patterned layer on the surface of the first dielectric layer and within the initial waveguide trench, the patterned layer exposing at least a portion of the bottom of the initial waveguide trench; and etching the first dielectric layer using the patterned layer as a mask to form a waveguide structure located on the substrate, the waveguide structure including a waveguide end structure located on the coupling region.

[0007] Optionally, the ratio of the depth of the initial waveguide trench to the thickness of the first dielectric layer is in the range of 1:2 to 1:100.

[0008] Optionally, the depth of the initial waveguide trench ranges from 50 nanometers to 200 nanometers.

[0009] Optionally, the waveguide end structure has a first end and a second end opposite to each other, wherein the width of the second end is smaller than the width of the first end.

[0010] Optionally, the width of the second end ranges from 100 nanometers to 150 nanometers.

[0011] Optionally, the method for forming the patterned layer includes: forming an initial patterned layer on the surface of the first dielectric layer and within the initial waveguide trench, and an upper mask layer located on the initial patterned layer, wherein the upper mask layer exposes a portion of the initial patterned layer within the initial waveguide trench; and etching the initial patterned layer using the upper mask layer as a mask to form the patterned layer.

[0012] Optionally, the material of the patterning layer includes a carbon-containing material; the material of the upper mask layer includes photoresist.

[0013] Optionally, the substrate further includes a beam-splitting region and a body region; the waveguide structure further includes a beam-splitting structure located on the beam-splitting region and a waveguide body structure located on the body region.

[0014] Optionally, the method for forming the optical device further includes: forming a beam splitting trench in a first dielectric layer on the beam splitting region while forming the initial waveguide trench; the patterning layer is also located in the beam splitting trench; etching the first dielectric layer using the patterning layer as a mask to form a beam splitting structure located on the beam splitting region, wherein the surface of the beam splitting structure is flush with the surface of the waveguide end structure.

[0015] Optionally, the patterned layer is also located on the first dielectric layer on the body region; the first dielectric layer is etched using the patterned layer as a mask to form the waveguide end structure and simultaneously form the waveguide body structure located on the body region. The waveguide body structure has a third end and a fourth end, and the fourth end is connected to the first end of the waveguide end structure.

[0016] Optionally, the top surface of the waveguide body structure is higher than the top surface of the waveguide end structure.

[0017] Optionally, the width of the waveguide body structure is greater than the width of the waveguide end structure.

[0018] Optionally, the width of the waveguide body structure ranges from 600 nanometers to 1000 nanometers.

[0019] Optionally, before forming the first dielectric layer, the method for forming the optical device further includes: forming a coupling waveguide layer on the substrate, the coupling waveguide layer including a second dielectric layer on the substrate, a coupling waveguide structure within the second dielectric layer, and a third dielectric layer on the second dielectric layer and the coupling waveguide structure.

[0020] Optionally, the material of the first dielectric layer includes silicon nitride.

[0021] Compared with the prior art, the technical solution of the embodiments of the present invention has the following beneficial effects:

[0022] In the optical device formation method provided by the technical solution of the present invention, since an initial waveguide trench is first formed on the coupling region, the patterned layer formed on the coupling region is at least partially located within the initial waveguide trench. Therefore, the initial waveguide trench protects the patterned layer on the coupling region, reduces the possibility of the patterned layer on the coupling region peeling off due to the influence of other processes, and improves the stability of the patterned layer on the coupling region. Subsequently, the first dielectric layer can be etched using the patterned layer in the initial waveguide trench as a mask, thereby stably forming the waveguide end structure. The waveguide end structure reduces the coupling loss during light propagation and improves the light propagation efficiency.

[0023] Furthermore, since the patterned layer formed on the coupling region is at least partially located within the initial waveguide trench, and the initial waveguide trench protects the patterned layer, the possibility of the patterned layer within the initial waveguide trench peeling off is small. This allows for the stable formation of a small-sized patterned layer on the coupling region, thereby stably forming a small-sized waveguide end structure. The width of the second end of the waveguide end structure can reach 100 nanometers to 150 nanometers, reducing coupling loss during light propagation and improving light propagation efficiency. Attached Figure Description

[0024] Figure 1 This is a top view of an optical device;

[0025] Figures 2 to 7 This is a schematic diagram of the formation process of the optical device according to an embodiment of the present invention. Detailed Implementation

[0026] As described in the background section, in the prior art, due to process limitations, it is difficult to form small-sized waveguide ends, which increases the coupling loss during light propagation and reduces the light propagation efficiency.

[0027] Figure 1 This is a top view of an optical device.

[0028] The optical device includes: a substrate 100; a beam splitting structure 101 located on the substrate 100; and a waveguide structure (not shown) located on the substrate 100. The waveguide structure includes a waveguide body structure 102 and a waveguide end structure 103. The width of the waveguide end structure 103 is smaller than the width of the waveguide body structure 102. The waveguide body structure 102 is connected to the waveguide end structure 103. The height of the waveguide structure is greater than the height of the beam splitting structure 101.

[0029] The method for forming the waveguide structure includes: forming a first dielectric layer (not shown) on the substrate 100; forming a patterned layer (not shown) on the first dielectric layer; and etching the first dielectric layer using the patterned layer as a mask to form the waveguide structure, the waveguide structure including a waveguide end structure 103.

[0030] Because the width of the waveguide end structure 103 is small, the size of the patterned layer required to form the waveguide end structure 103 is also small. However, the small-sized patterned layer is prone to peeling off from the surface of the first dielectric layer, thereby damaging the integrity of the patterned layer and making it impossible to form the waveguide end structure 103 subsequently. As a result, the overall width of the waveguide structure is large, which increases the coupling loss in the light propagation process and reduces the light propagation efficiency.

[0031] To address the aforementioned technical problems, the present invention provides a method for forming an optical device. This method involves first forming an initial waveguide trench within a first dielectric layer on the coupling region, and then forming a patterned layer on the surface of the first dielectric layer and within the initial waveguide trench. This ensures that the patterned layer on the coupling region is at least partially located within the initial waveguide trench, thereby reducing the likelihood of the patterned layer peeling off. Furthermore, the patterned layer can be used as a mask to stably form the waveguide end structure, thereby reducing coupling loss during light propagation and improving light propagation efficiency.

[0032] 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.

[0033] Figures 2 to 7 This is a schematic diagram of the formation process of the optical device according to an embodiment of the present invention.

[0034] Please refer to Figure 2 A substrate 200 is provided; a coupling waveguide layer (not shown) is formed on the substrate 200.

[0035] The substrate 200 is made of materials including silicon, silicon-germanium, silicon carbide, silicon-on-insulator (SOI), and germanium-on-insulator (GOI). Specifically, in this embodiment, the substrate 200 is made of silicon.

[0036] The substrate 200 includes a coupling region I, a beam-splitting region II, and a body region.

[0037] The coupling region I provides a platform for the formation of the subsequent waveguide end structure; the body region provides a platform for the formation of the subsequent waveguide body structure; and the beam splitting region II provides a platform for the formation of the subsequent beam splitting structure.

[0038] The coupled waveguide layer includes a second dielectric layer 201 located on the substrate 200, a coupled waveguide structure 202 located within the second dielectric layer 201, and a third dielectric layer 203 located on the second dielectric layer 201 and the coupled waveguide structure 202.

[0039] The coupled waveguide structure 202 is used to receive optical signal transmission from the waveguide structure above the coupled waveguide layer, thereby enabling the optical signal to propagate within the optical device.

[0040] In this embodiment, the material of the second dielectric layer 201 includes silicon oxide; the material of the coupled waveguide structure 202 includes silicon; and the material of the third dielectric layer 203 includes silicon oxide.

[0041] The method for forming the coupled waveguide layer includes: forming a first initial material layer (not shown) on the substrate 200; forming a coupled waveguide material layer (not shown) on the first initial material layer; etching the coupled waveguide material layer to form a coupled waveguide structure 202; forming a second initial material layer (not shown) surrounding the coupled waveguide structure 202, wherein the first initial material layer and the second initial material layer constitute a second dielectric layer 201; and forming a third dielectric layer 203 located on the second dielectric layer 201 and the coupled waveguide structure 202.

[0042] Please refer to Figure 3 A first dielectric layer 204 is formed on the third dielectric layer 203; an initial waveguide trench 211 is formed in the first dielectric layer 204 on the coupling region I.

[0043] The first dielectric layer 204 provides raw materials for the waveguide structure that is subsequently formed.

[0044] In this embodiment, the material of the first dielectric layer 204 includes silicon nitride.

[0045] The purpose of forming an initial waveguide trench 211 on the coupling region I is to ensure that the patterned layer subsequently formed on the coupling region I is at least partially located within the initial waveguide trench 211, thereby protecting the patterned layer on the coupling region I and improving the process stability of the patterned layer formation process.

[0046] In this embodiment, the ratio of the depth of the initial waveguide trench 211 to the thickness of the first dielectric layer 204 ranges from 1:2 to 1:100. A deeper initial waveguide trench 211 provides better protection for the patterned layer subsequently formed on the coupling region I. However, a smaller thickness of the first dielectric layer 204 below the initial waveguide trench 211 results in some loss in the height of the waveguide end structure subsequently formed on the coupling region I. Preferably, the depth of the initial waveguide trench 211 ranges from 50 nanometers to 200 nanometers.

[0047] In this embodiment, while forming the initial waveguide trench 211, a beam splitting trench 210 is formed in the first dielectric layer 204 on the beam splitting region II.

[0048] Because a beam splitting trench 210 is formed on the beam splitting region II, the height of the first dielectric layer 204 on the beam splitting region II is reduced to a certain extent. Therefore, after the beam splitting structure and the waveguide body structure are subsequently formed, the top surface of the beam splitting structure is lower than the top surface of the waveguide body structure.

[0049] In this embodiment, the beam splitting trench 210 and the initial waveguide trench 211 are formed simultaneously, and the depth of the beam splitting trench 210 is the same as the depth of the initial waveguide trench 211.

[0050] Specifically, the method for forming the beam splitting trench 210 and the initial waveguide trench 211 includes: forming a mask structure (not shown) on the surface of a first dielectric layer 204 located on the coupling region I and the beam splitting region II, the mask structure exposing a portion of the surface of the first dielectric layer 204 on the coupling region I and the beam splitting region II; using the mask structure as a mask, etching the first dielectric layer 204 to form the initial waveguide trench 211 located on the coupling region I and the beam splitting trench 210 located on the beam splitting region II.

[0051] Since the beam splitting trench 210 and the initial waveguide trench 211 are formed simultaneously and their formation processes are the same, the process steps are simple and the process cost is low.

[0052] Next, a patterned layer is formed on the surface of the first dielectric layer 204 and within the initial waveguide trench 211, the patterned layer exposing at least a portion of the bottom of the initial waveguide trench 211.

[0053] Specifically, the process of forming the graphical layer is as follows: Figures 4 to 5 As shown.

[0054] Please refer to Figure 4An initial patterned layer 205 and an upper mask layer 206 are formed on the surface of the first dielectric layer 204 and within the initial waveguide trench 211, the upper mask layer 206 exposing a portion of the initial patterned layer 205 within the initial waveguide trench 211.

[0055] The initial patterning layer 205 is also located within the beam-splitting trench 210 and on the surface of the first dielectric layer 204 on the body region.

[0056] The upper mask layer 206 is also located on the surface of the initial patterned layer 205 on the beam-splitting region II and the body region. The upper mask layer 206 exposes a portion of the initial patterned layer 205 on the surface of the beam-splitting region II, thereby covering the surface of the initial patterned layer 205 on the beam-splitting trench 210 with the upper mask layer 206. The upper mask layer 206 is also located on the surface of the initial patterned layer 205 on the body region, and the upper mask layer 206 exposes a portion of the initial patterned layer 205 on the body region.

[0057] In this embodiment, the initial patterning layer 205 is made of a carbon-containing material; the upper mask layer 206 is made of photoresist.

[0058] Because the initial patterned layer 205 located on the first dielectric layer 204 has higher material hardness and density, resulting in better stability, the process window is larger during the subsequent etching of the first dielectric layer 204.

[0059] Please refer to Figure 5 The initial patterned layer 205 is etched using the upper mask layer 206 as a mask to form the patterned layer 207.

[0060] The patterned layer 207 exposes at least a portion of the bottom of the initial waveguide trench 211. Specifically, in this embodiment, the patterned layer 207 on the coupling region I is located within the initial waveguide trench 211.

[0061] Since the patterned layer 207 on coupling region I is used to subsequently form a small-sized waveguide end structure, the size of the patterned layer 207 on coupling region I is relatively small. Furthermore, the patterned layer 207 on coupling region I is located within the initial waveguide trench 211. Therefore, the initial waveguide trench 211 protects the patterned layer 207 on coupling region I, reducing the possibility of the patterned layer 207 peeling off due to other process influences, thus improving the stability of the patterned layer 207 on coupling region I. Consequently, the first dielectric layer 204 can be etched subsequently using the patterned layer 207 within the initial waveguide trench 211 as a mask, thereby stably forming a small-sized waveguide end structure and reducing coupling loss during light propagation.

[0062] In this embodiment, the patterning layer 207 is also located within the beam splitting trench 210 and on the first dielectric layer 204 located on the body region, for subsequent formation of the beam splitting structure located on the beam splitting region II and the waveguide body structure located on the body region.

[0063] Please refer to Figure 6 and Figure 7 , Figure 6 for Figure 7 A schematic diagram of the cross-section along the BB' direction. Figure 7 for Figure 6 In a top view along the Q direction, using the patterned layer 207 as a mask, the first dielectric layer 204 is etched to form a waveguide structure 223 located on the third dielectric layer 203, the waveguide structure 223 including a waveguide end structure 220 located on the coupling region I.

[0064] The waveguide structure 223 serves as a medium for optical signal propagation. After the optical signal enters the waveguide structure 223, due to evanescent wave coupling, the optical signal is displaced into the coupling waveguide structure 202 below the waveguide structure 223 to continue propagating.

[0065] The waveguide end structure 220 has a first end (not shown) and a second end (not shown) opposite each other, and the width H2 of the second end is smaller than the width H1 of the first end.

[0066] It should be noted that the width is the dimension of the waveguide end structure 220 in the direction parallel to the surface of the substrate 200 and perpendicular to the extension direction of the waveguide end structure 220.

[0067] Specifically, the width H1 of the first end ranges from 600 nanometers to 1000 nanometers; the width H2 of the second end ranges from 100 nanometers to 150 nanometers.

[0068] Since the patterned layer 207 formed on the coupling region I is located within the initial waveguide trench 211, and the initial waveguide trench 211 protects the patterned layer 207, the possibility of the patterned layer 207 within the initial waveguide trench 211 peeling off is small. Therefore, the small-sized patterned layer 207 formed on the coupling region I has high stability in subsequent processes. Thus, after etching the first dielectric layer 204 using the patterned layer 207 as a mask, a small-sized waveguide end structure 220 located on the coupling region I can be stably formed.

[0069] Because the waveguide end structure 220 is small in size, the coupling loss is small when the optical signal is displaced from the waveguide end structure 220 to continue propagating in the coupled waveguide structure 202, thereby improving the optical propagation efficiency and the performance of the optical device.

[0070] The width of the waveguide end structure 220 gradually decreases from the first end to the second end. Because the width of the waveguide end structure 220 decreases gradually, the stability of the waveguide end structure 220 is better.

[0071] In this embodiment, the waveguide structure 223 further includes a beam splitting structure 221 located on the beam splitting region II and a waveguide body structure 222 located on the body region III.

[0072] Specifically, the method for forming the beam-splitting structure 221 and the waveguide body structure 222 includes: etching the first dielectric layer 204 using the patterned layer 207 as a mask to form the beam-splitting structure 221 located on the beam-splitting region II and the waveguide body structure 222 located on the body region III. The beam-splitting structure 221, the waveguide body structure 222, and the waveguide end structure 220 are formed simultaneously.

[0073] The beam splitting structure 221 connects to an external optical fiber and the waveguide body structure 222. The surface of the beam splitting structure 221 is flush with the surface of the waveguide end structure 220; the top surface of the waveguide body structure 222 is higher than the top surface of the beam splitting structure 221.

[0074] The waveguide body structure 222 has a third end (not shown) and a fourth end (not shown) opposite each other. The fourth end is connected to the first end of the waveguide end structure 220, and the third end is connected to the beam splitting structure 221. The top surface of the waveguide body structure 222 is higher than the top surface of the waveguide end structure 220.

[0075] In this embodiment, the width H3 of the waveguide body structure 222 is greater than the width of the waveguide end structure 220. The width H3 of the waveguide body structure 222 ranges from 600 nanometers to 1000 nanometers.

[0076] During the propagation of the optical signal, the light enters the beam splitting structure 221 from the external optical fiber for splitting, then enters the waveguide body structure 222 for propagation, and finally passes through the small-sized waveguide end structure 220, and is efficiently and with low loss displaced into the coupling waveguide structure 202 below the waveguide structure 223 to continue propagating.

[0077] After the beam splitting structure 221, waveguide body structure 222, and waveguide end structure 220 are formed, a fourth dielectric layer (not shown) is formed surrounding the beam splitting structure 221, waveguide body structure 222, and waveguide end structure 220.

[0078] The material of the fourth dielectric layer includes silicon oxide.

[0079] 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 of forming an optical device, characterized by, include: A substrate is provided, the substrate including a coupling region; A first dielectric layer is formed on the substrate; An initial waveguide trench is formed within the first dielectric layer on the coupling region; A patterned layer is formed on the surface of the first dielectric layer and within the initial waveguide trench, the patterned layer exposing at least a portion of the bottom of the initial waveguide trench; Using the patterned layer as a mask, the first dielectric layer is etched to form a waveguide structure on the substrate, the waveguide structure including a waveguide end structure located on the coupling region.

2. The method of forming an optical device according to claim 1, wherein, The ratio of the depth of the initial waveguide trench to the thickness of the first dielectric layer is in the range of 1:2 to 1:

100.

3. The method of forming an optical device of claim 2, wherein, The depth range of the initial waveguide trench is 50 nanometers to 200 nanometers.

4. The method for forming an optical device as described in claim 1, characterized in that, The waveguide end structure has a first end and a second end, the width of the second end being smaller than the width of the first end.

5. The method of forming an optical device of claim 4, wherein, The width of the second end ranges from 100 nanometers to 150 nanometers.

6. The method for forming an optical device according to claim 1, wherein The method for forming the patterned layer includes: forming an initial patterned layer on the surface of the first dielectric layer and within the initial waveguide trench, and an upper mask layer located on the initial patterned layer, wherein the upper mask layer exposes a portion of the initial patterned layer within the initial waveguide trench; and etching the initial patterned layer using the upper mask layer as a mask to form the patterned layer.

7. The method for forming an optical device as described in claim 6, characterized in that, The material of the patterning layer includes a carbon-containing material; the material of the upper mask layer includes photoresist.

8. The method for forming an optical device according to claim 1, wherein The substrate further includes a beam-splitting region and a body region; the waveguide structure further includes a beam-splitting structure located on the beam-splitting region and a waveguide body structure located on the body region.

9. The method of forming an optical device according to claim 8, wherein, Also includes: While forming the initial waveguide trench, a beam splitting trench is formed in the first dielectric layer on the beam splitting region. The patterned layer is also located within the beam-splitting trench; the first dielectric layer is etched using the patterned layer as a mask to form a beam-splitting structure located on the beam-splitting region, and the surface of the beam-splitting structure is flush with the surface of the waveguide end structure.

10. The method of forming an optical device of claim 8, wherein, The patterned layer is also located on the first dielectric layer on the body region; the first dielectric layer is etched using the patterned layer as a mask to form the waveguide end structure and simultaneously form the waveguide body structure located on the body region. The waveguide body structure has a third end and a fourth end, and the fourth end is connected to the first end of the waveguide end structure.

11. The method of forming an optical device of claim 8, wherein, The top surface of the waveguide body structure is higher than the top surface of the waveguide end structure.

12. The method for forming an optical device as described in claim 8, characterized in that, The width of the waveguide body structure is greater than the width of the waveguide end structure.

13. The method for forming an optical device according to claim 8, wherein The width of the waveguide body structure ranges from 600 nanometers to 1000 nanometers.

14. The method for forming an optical device according to claim 1, wherein Before forming the first dielectric layer, the method further includes forming a coupling waveguide layer on the substrate, the coupling waveguide layer including a second dielectric layer on the substrate, a coupling waveguide structure within the second dielectric layer, and a third dielectric layer on the second dielectric layer and the coupling waveguide structure.

15. The method for forming an optical device according to claim 1, wherein The material of the first dielectric layer includes silicon nitride.

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