End face coupler structure and forming method thereof

Abstract

The present application provides an end-face coupler structure and a method for forming the same. The end-face coupler structure comprises an SOI substrate comprising a bottom silicon layer, a buried oxide layer, and a top silicon layer. A silicon waveguide structure is formed in the top silicon layer, and the silicon waveguide structure is covered by a cladding layer. The cladding layer comprises a first refractive index modulation region and a second refractive index modulation region. The first refractive index modulation region comprises a plurality of first refractive index modulation structures spaced equally apart from the edges of the silicon waveguide structure. The second refractive index modulation region comprises a plurality of second refractive index modulation structures whose density gradually decreases away from the silicon waveguide structure. The refractive indices of the first and second refractive index modulation structures are greater than the refractive index of the cladding layer and less than the refractive index of the silicon waveguide structure. The present application provides an end-face coupler structure and a method for forming the same, which can improve the performance of the end-face coupler and reduce coupling loss.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to an end face coupler structure and a method for forming the same. Background Art

[0002] Electronic integrated circuits use current signals as information carriers, while optoelectronic chips use higher-frequency light waves. Compared to electronic integrated circuits, optoelectronic chips exhibit lower transmission loss, wider transmission bandwidth, smaller time delays, and stronger resistance to electromagnetic interference.

[0003] Currently, optoelectronic chips are typically formed by integrating an end coupler with an integrated photonic circuit. The end coupler receives optical signals transmitted by optical fibers and further transmits them to the integrated photonic circuit. As a key component for coupling optical signals between optical fibers and optoelectronic chips, significant optical signal loss in the end coupler can affect the quality of the optical signal received by the integrated photonic circuit in the optoelectronic chip, thereby impacting the functionality of the optoelectronic chip.

[0004] Therefore, it is necessary to provide a more effective and reliable technical solution to improve the performance of the end coupler and reduce the coupling loss. Summary of the Invention

[0005] The present application provides an end face coupler structure and a forming method thereof, which can improve the performance of the end face coupler and reduce coupling loss.

[0006] One aspect of the present application provides a method for forming an end-face coupler structure, comprising: providing an SOI substrate, the SOI substrate comprising a bottom silicon layer, a buried oxide layer, and a top silicon layer, wherein a silicon waveguide structure is formed in the top silicon layer, wherein the width of the silicon waveguide structure gradually increases from the incident end of the silicon waveguide structure toward the extension direction of the silicon waveguide structure, the silicon waveguide structure is covered by a cladding layer, the cladding layer comprising a first refractive index modulation region and a second refractive index modulation region, wherein the first refractive index modulation region extends from the incident end toward the extension direction of the silicon waveguide structure, and the second refractive index modulation region is adjacent to the first refractive index modulation region and extends in a direction opposite to the extension direction of the silicon waveguide structure; forming a plurality of first refractive index modulation structures in the first refractive index modulation region with an equal spacing to the edge of the silicon waveguide structure, and forming a plurality of second refractive index modulation structures in the second refractive index modulation region with a density gradually decreasing from the incident end toward the direction away from the incident end, wherein the refractive indexes of the first and second refractive index modulation structures are greater than the refractive index of the cladding layer and smaller than the refractive index of the silicon waveguide structure.

[0007] In some embodiments of the present application, the material of the silicon waveguide structure is silicon, and the material of the cladding layer is silicon dioxide.

[0008] In some embodiments of the present application, a method of forming the first refractive index modulation structure and the second refractive index modulation structure includes:

[0009] A patterned photoresist layer is formed on the surface of the cladding layer, and the patterned photoresist layer defines the positions of the first refractive index modulation structure and the second refractive index modulation structure; the cladding layer is etched using the patterned photoresist layer as a mask to form a plurality of grooves; and the patterned photoresist layer is removed to form the first refractive index modulation structure and the second refractive index modulation structure in the plurality of grooves.

[0010] In some embodiments of the present application, the materials of the first refractive index modulation structure and the second refractive index modulation structure include materials with a refractive index greater than that of the cladding layer and less than that of the silicon waveguide structure, and the materials of the first refractive index modulation structure and the second refractive index modulation structure include silicon nitride, silicon oxynitride, and silicon-rich silicon oxide.

[0011] In some embodiments of the present application, the method for forming the first refractive index modulation structure and the second refractive index modulation structure includes: forming a patterned photoresist layer on the surface of the cladding layer, the patterned photoresist layer defining the positions of the first refractive index modulation structure and the second refractive index modulation structure; performing an ion implantation process on the cladding layer using the patterned photoresist layer as a mask to form the first refractive index modulation structure and the second refractive index modulation structure; and removing the patterned photoresist layer.

[0012] In some embodiments of the present application, the implanted ions in the ion implantation process include ions with an ion diameter larger than that of oxygen ions, and the implanted ions in the ion implantation process include nitrogen, arsenic, phosphorus, and aluminum; the implantation concentration of the ion implantation process is 1E16atom / cm 3 to 1E19 atom / cm 3 .

[0013] In some embodiments of the present application, the length of the first refractive index modulation zone is 9 microns to 18 microns, and the width is 1.5 microns to 3 microns; the length of the second refractive index modulation zone is 1 micron to 4 microns, and the width is 3 microns to 4 microns.

[0014] In some embodiments of the present application, the width of the first refractive index modulation structure is 100 nanometers to 500 nanometers, and the distance between the first refractive index modulation structure and the silicon waveguide structure is 100 nanometers to 400 nanometers.

[0015] In some embodiments of the present application, the cross-sectional shape of the second refractive index modulation structure includes a circle, a rectangle, or a regular polygon.

[0016] In some embodiments of the present application, a size of the second refractive index modulation structure is 80 nanometers to 400 nanometers, and a spacing between the second refractive index modulation structures is 100 nanometers to 600 nanometers.

[0017] In some embodiments of the present application, the upper surfaces of the first refractive index modulation structure and the second refractive index modulation structure are coplanar with the upper surface of the silicon waveguide structure, and the lower surfaces of the first refractive index modulation structure and the second refractive index modulation structure are coplanar with the lower surface of the silicon waveguide structure.

[0018] In some embodiments of the present application, a method for forming the cladding layer and the first and second refractive index modulation structures includes: providing an SOI substrate, the SOI substrate including a bottom silicon layer, a buried oxide layer and a top silicon layer, etching the top silicon layer to form the silicon waveguide structure; forming a first partial cladding layer on the surface of the buried oxide layer, the top surface of which is flush with the top surface of the silicon waveguide structure; forming the first and second refractive index modulation structures flush with the top surface of the silicon waveguide structure in the first partial cladding layer; and forming a second partial cladding layer on the surface of the silicon waveguide structure, the surface of the first partial cladding layer, and the surfaces of the first and second refractive index modulation structures.

[0019] In some embodiments of the present application, a method for forming the cladding layer and the first and second refractive index modulation structures includes: providing an SOI substrate, the SOI substrate including a bottom silicon layer, a buried oxide layer and a top silicon layer, etching the top silicon layer to form the silicon waveguide structure; forming a first partial cladding layer on the surface of the buried oxide layer, the top surface of which is higher than the top surface of the silicon waveguide structure; forming the first and second refractive index modulation structures flush with the top surface of the first partial cladding layer in the first partial cladding layer; and forming a second partial cladding layer on the surface of the silicon waveguide structure, the surface of the first partial cladding layer, and the surfaces of the first and second refractive index modulation structures.

[0020] Another aspect of the present application provides an end-face coupler structure, comprising: an SOI substrate, the SOI substrate comprising a bottom silicon layer, a buried oxide layer, and a top silicon layer; a silicon waveguide structure formed in the top silicon layer, the width of the silicon waveguide structure gradually increasing from the incident end of the silicon waveguide structure toward the extension direction of the silicon waveguide structure; the silicon waveguide structure being covered by a cladding layer, the cladding layer comprising a first refractive index modulation region and a second refractive index modulation region, the first refractive index modulation region extending from the incident end toward the extension direction of the silicon waveguide structure, the second refractive index modulation region adjacent to the first refractive index modulation region and extending in a direction opposite to the extension direction of the silicon waveguide structure; a plurality of first refractive index modulation structures formed in the first refractive index modulation region having an equal spacing to an edge of the silicon waveguide structure; a plurality of second refractive index modulation structures having a density gradually decreasing from the incident end toward a direction away from the incident end, the refractive indexes of the first and second refractive index modulation structures being greater than the refractive index of the cladding layer and less than the refractive index of the silicon waveguide structure.

[0021] In some embodiments of the present application, the material of the silicon waveguide structure is silicon, and the material of the cladding layer is silicon dioxide.

[0022] In some embodiments of the present application, the materials of the first refractive index modulation structure and the second refractive index modulation structure include materials with a refractive index greater than that of the cladding layer and less than that of the silicon waveguide structure, and the materials of the first refractive index modulation structure and the second refractive index modulation structure include silicon nitride, silicon oxynitride, and silicon-rich silicon oxide.

[0023] In some embodiments of the present application, the first refractive index modulation structure and the second refractive index modulation structure have doping ions, and the doping ions include nitrogen, arsenic, phosphorus, and aluminum; the doping concentration of the doping ions is 1E16atom / cm 3 to 1E19 atom / cm 3 .

[0024] In some embodiments of the present application, the length of the first refractive index modulation zone is 9 microns to 18 microns, and the width is 1.5 microns to 3 microns; the length of the second refractive index modulation zone is 1 micron to 4 microns, and the width is 3 microns to 4 microns.

[0025] In some embodiments of the present application, the width of the first refractive index modulation structure is 100 nanometers to 500 nanometers, and the distance between the first refractive index modulation structure and the silicon waveguide structure is 200 nanometers to 400 nanometers.

[0026] In some embodiments of the present application, the cross-sectional shape of the second refractive index modulation structure includes a circle, a rectangle, or a regular polygon.

[0027] In some embodiments of the present application, a size of the second refractive index modulation structure is 80 nanometers to 400 nanometers, and a spacing between the second refractive index modulation structures is 100 nanometers to 600 nanometers.

[0028] In some embodiments of the present application, the upper surfaces of the first refractive index modulation structure and the second refractive index modulation structure are coplanar with the upper surface of the silicon waveguide structure, and the lower surfaces of the first refractive index modulation structure and the second refractive index modulation structure are coplanar with the lower surface of the silicon waveguide structure.

[0029] The present application provides an end face coupler structure and a method for forming the same. The first refractive index modulation structure and the second refractive index modulation structure are used to reduce the refractive index difference between the cladding layer and the silicon waveguide structure, thereby improving the performance of the end face coupler and reducing coupling loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The following figures describe in detail exemplary embodiments disclosed in this application. Identical reference numerals denote similar structures in several views of the drawings. Those skilled in the art will appreciate that these embodiments are non-limiting, exemplary embodiments, and that the drawings are for illustration and description purposes only and are not intended to limit the scope of this application. Other embodiments may also achieve the same inventive intent as described in this application. It should be understood that the drawings are not drawn to scale. Among them:

[0031] Figure 1 This is a flow chart of a method for forming an end face coupler structure according to an embodiment of the present application;

[0032] Figures 2 to 7 Schematic diagram of each step in the method for forming an end face coupler structure according to an embodiment of the present application;

[0033] Figure 8 Schematic diagram of the structure of the first refractive index modulation region in the end coupler described in some embodiments of the present application;

[0034] Figure 9 Schematic diagram of the structure of the first refractive index modulation region in the end coupler described in other embodiments of the present application;

[0035] Figure 10 Schematic diagram of the structure of the second refractive index modulation zone in the end face coupler described in some embodiments of the present application. DETAILED DESCRIPTION

[0036] The following description provides specific application scenarios and requirements of the present application, with the purpose of enabling those skilled in the art to make and use the content of this application. Various local modifications to the disclosed embodiments will be apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of this application. Therefore, this application is not limited to the embodiments shown, but is intended to be of the widest scope consistent with the claims.

[0037] The technical solution of the present invention is described in detail below with reference to the embodiments and drawings.

[0038] Since the core diameter of the optical fiber is generally 10 microns, while the width of the silicon waveguide structure in the end coupler is generally 400 nm, the two differ by two orders of magnitude. Therefore, when light enters the silicon waveguide structure from the optical fiber, there will be a large mode mismatch, resulting in low coupling efficiency and large coupling loss.

[0039] The traditional solution is to reduce the size of the silicon waveguide structure at the fiber end face and lower the effective refractive index at the end face to increase the mode spot, reduce the mode spot mismatch, and reduce coupling loss. However, this approach does not significantly improve the performance of the end face coupler. As device size decreases, technical solutions are needed to further improve end face coupler performance, reduce coupling loss, and reduce device size.

[0040] Based on this, the present application provides an end face coupler structure and a method for forming the same. The first refractive index modulation structure and the second refractive index modulation structure are used to reduce the refractive index difference between the cladding layer and the silicon waveguide structure, which can improve the performance of the end face coupler, reduce coupling loss, and reduce device size.

[0041] Figure 1 This is a flow chart of a method for forming an end face coupler structure according to an embodiment of the present application.

[0042] This application provides a method for forming an end face coupler structure, referring to Figure 1 Shown, including:

[0043] Step S1: Providing an SOI substrate, wherein the SOI substrate includes a bottom silicon layer, a buried oxide layer, and a top silicon layer, wherein a silicon waveguide structure is formed in the top silicon layer, wherein the width of the silicon waveguide structure gradually increases from an incident end of the silicon waveguide structure toward an extension direction of the silicon waveguide structure, and the silicon waveguide structure is covered by a cladding layer, wherein the cladding layer includes a first refractive index modulation region and a second refractive index modulation region, wherein the first refractive index modulation region extends from the incident end toward the extension direction of the silicon waveguide structure, and the second refractive index modulation region is adjacent to the first refractive index modulation region and extends in a direction opposite to the extension direction of the silicon waveguide structure;

[0044] Step S2: forming a plurality of first refractive index modulation structures having an equal edge spacing to the silicon waveguide structure in the first refractive index modulation region, and forming a plurality of second refractive index modulation structures having a density gradually decreasing from the incident end toward a direction away from the incident end in the second refractive index modulation region, wherein the refractive index of the first refractive index modulation structure and the second refractive index modulation structure is greater than the refractive index of the cladding layer and is less than the refractive index of the silicon waveguide structure.

[0045] Figures 2 to 7 The following is a structural diagram of each step in the method for forming the end face coupler structure according to the embodiment of the present application. The method for forming the end face coupler structure according to the embodiment of the present application is described in detail with reference to the accompanying drawings.

[0046] refer to Figure 2 、 Figure 3 、 Figure 4 As shown, Figure 2 For top view, Figure 3 For the Figure 2 The longitudinal section at the dotted line XX, Figure 4 For the Figure 2 Longitudinal section view at the dotted line YY.

[0047] refer to Figure 3 As shown, an SOI substrate is provided, which includes a bottom silicon layer 100, a buried oxide layer 110 and a top silicon layer (the top silicon layer is omitted because it is etched to form a silicon waveguide structure), and a silicon waveguide structure 120 is formed in the top silicon layer.

[0048] refer to Figure 2 As shown, the width of the silicon waveguide structure 120 gradually increases along the incident end 122 of the silicon waveguide structure 120 toward the extension direction of the silicon waveguide structure 120 (i.e., the left side in the figure). The width of the silicon waveguide structure 120 refers to the width of the silicon waveguide structure 120 at Figure 2 The vertical dimension.

[0049] The silicon waveguide structure 120 is covered by a cladding layer 150. Figure 2 It is a top view. In practice, the silicon waveguide structure 120 is completely buried and blocked by the cladding layer 150. In order to show the silicon waveguide structure 120, the present application omits the part of the cladding layer 150 that is higher than the upper surface of the silicon waveguide structure 120.

[0050] Continue to refer Figure 2As shown, the cladding layer 150 includes a first refractive index modulation zone 111 and a second refractive index modulation zone 112. The first refractive index modulation zone 111 extends from the incident end 122 toward the extension direction of the silicon waveguide structure 120. The first refractive index modulation zone 111 includes a portion of the silicon waveguide structure 120 and a portion of the cladding layer 150 on both sides of the portion of the silicon waveguide structure 120. The second refractive index modulation zone 112 is adjacent to the first refractive index modulation zone 111 and extends in the opposite direction to the extension direction of the silicon waveguide structure 120 to the boundary of the cladding layer 150.

[0051] In some embodiments of the present application, the SOI substrate is a conventional structure in the semiconductor field, and therefore its formation method and detailed structure are not described in detail herein.

[0052] In some embodiments of the present application, the material of the silicon waveguide structure 120 is, for example, silicon, and the material of the cladding layer 150 is, for example, silicon dioxide.

[0053] In some embodiments of the present application, the buried oxide layer 110 has a thickness of 2 microns to 3 microns.

[0054] In some embodiments of the present application, the thickness of the coating layer 150 is 300 nanometers to 500 nanometers, for example, 400 nanometers.

[0055] Continue to refer Figure 2 As shown, in some embodiments of the present application, the length of the first refractive index modulation region 111 is 9 microns to 18 microns, and the width is 1.5 microns to 3 microns; the length of the second refractive index modulation region 112 is 1 micron to 4 microns, and the width is 3 microns to 4 microns. The length of the first refractive index modulation region 111 accounts for 5%-15% of the length of the silicon waveguide structure 120. Wherein, the length refers to Figure 1 The horizontal dimension, the width refers to Figure 2 The vertical dimension.

[0056] In some embodiments of the present application, the upper surfaces of the first refractive index modulated region 111 and the second refractive index modulated region 112 are coplanar with the upper surface of the silicon waveguide structure 120, and the lower surfaces of the first refractive index modulated region 111 and the second refractive index modulated region 112 are coplanar with the lower surface of the silicon waveguide structure 120. However, considering the error range in actual processing and to ensure that the first refractive index modulated region 111 and the second refractive index modulated region 112 are in full contact with the silicon waveguide structure 120, the lower surfaces of the first refractive index modulated region 111 and the second refractive index modulated region 112 can be designed to be slightly lower than the lower surface of the silicon waveguide structure 120.

[0057] refer to Figure 5、 Figure 6 and Figure 7 As shown, Figure 5 For top view, Figure 6 For the Figure 5 The longitudinal section at the dotted line XX, Figure 7 For the Figure 5 Longitudinal section view at the dotted line YY.

[0058] A plurality of first refractive index modulation structures 131 are formed in the first refractive index modulation region 111, with the same spacing as the edge of the silicon waveguide structure 120 (i.e., the first refractive index modulation structures 131 are parallel to the edge of the silicon waveguide structure 120). A plurality of second refractive index modulation structures 132 are formed in the second refractive index modulation region 112, with the density gradually decreasing from the incident end 122 toward the direction away from the incident end 122 (i.e., the number of second refractive index modulation structures 132 gradually decreases from the incident end 122 toward the direction away from the incident end 122). The refractive index of the first and second refractive index modulation structures 131, 132 is greater than the refractive index of the cladding layer 150 and less than the refractive index of the silicon waveguide structure 120. The density of the second refractive index modulation structures 132 refers to the number of second refractive index modulation structures 132 in a second refractive index modulation region 112 of equal length. That is, the number of the second refractive index modulation structures 132 gradually decreases from the incident end 122 to a direction away from the incident end 122 or the spacing of the second refractive index modulation structures 132 gradually increases from the incident end 122 to a direction away from the incident end 122.

[0059] In some embodiments of the present application, the method for forming the first refractive index modulation structure 131 and the second refractive index modulation structure 132 includes: forming a patterned photoresist layer on the surface of the cladding layer 150, the patterned photoresist layer defining the positions of the first refractive index modulation structure 131 and the second refractive index modulation structure 132; etching the cladding layer 150 using the patterned photoresist layer as a mask to form a plurality of grooves; removing the patterned photoresist layer; and forming the first refractive index modulation structure 131 and the second refractive index modulation structure 132 in the plurality of grooves.

[0060] In some embodiments of the present application, the method for forming the cladding layer 150 and the first refractive index modulation structure 131 and the second refractive index modulation structure 132 includes: first forming the silicon waveguide structure 120 and a first portion of the cladding layer 150 flush with the top surface of the silicon waveguide structure 120; forming the first refractive index modulation structure 131 and the second refractive index modulation structure 132 flush with the top surface of the silicon waveguide structure 120; and then forming a second portion of the cladding layer 150 on the surface of the silicon waveguide structure 120, the surface of the first portion of the cladding layer 150, and the surface of the first refractive index modulation structure 131 and the second refractive index modulation structure 132, and finally forming a cladding layer that completely covers the silicon waveguide structure 120 and the first refractive index modulation structure 131 and the second refractive index modulation structure 132.

[0061] In some other embodiments of the present application, the method for forming the cladding layer 150 and the first refractive index modulation structure 131 and the second refractive index modulation structure 132 includes: first forming the silicon waveguide structure 120 and a first partial cladding layer 150 with a top surface slightly higher than the top surface of the silicon waveguide structure 120, and the silicon waveguide structure 120 is covered and protected by the cladding layer 150; forming the first refractive index modulation structure 131 and the second refractive index modulation structure 132 flush with the top surface of the first partial cladding layer 150; and forming a second partial cladding layer 150 on the surface of the first partial cladding layer 150 and the surface of the first refractive index modulation structure 131 and the second refractive index modulation structure 132, and finally forming a cladding layer that completely covers the silicon waveguide structure 120 and the first refractive index modulation structure 131 and the second refractive index modulation structure 132.

[0062] In some embodiments of the present application, the material of the first refractive index modulation structure 131 and the second refractive index modulation structure 132 includes a material whose refractive index is greater than the refractive index of the cladding layer 150 (silicon dioxide, a refractive index of approximately 1.44) and less than the refractive index of the silicon waveguide structure 120 (silicon, a refractive index of approximately 3.476), and the materials of the first refractive index modulation structure 131 and the second refractive index modulation structure 132 include silicon nitride, silicon oxynitride, silicon-rich silicon oxide, etc.

[0063] In some embodiments of the present application, the method for forming the first refractive index modulation structure 131 and the second refractive index modulation structure 132 includes: forming a patterned photoresist layer on the surface of the cladding layer 150, the patterned photoresist layer defining the positions of the first refractive index modulation structure 131 and the second refractive index modulation structure 132; performing an ion implantation process on the cladding layer 150 using the patterned photoresist layer as a mask to form the first refractive index modulation structure 131 and the second refractive index modulation structure 132; and removing the patterned photoresist layer.

[0064] In some embodiments of the present application, the ions implanted in the ion implantation process include ions with a diameter larger than that of oxygen ions, and the ions implanted in the ion implantation process include nitrogen, arsenic, phosphorus, and aluminum; the implantation concentration of the ion implantation process is 1E16atom / cm 3 to 1E19 atom / cm 3 Adjusting the injection concentration can also adjust the refractive index of the first refractive index modulation structure 131 and the second refractive index modulation structure 132 .

[0065] In some embodiments of the present application, the width of the first refractive index modulation structure 131 is 100 nanometers to 500 nanometers, the spacing between the first refractive index modulation structure 131 and the silicon waveguide structure 120 is 0 to 400 nanometers, and the first refractive index modulation structure 131 may be in contact with the silicon waveguide structure 120. Figure 5 The vertical dimension.

[0066] In some embodiments of the present application, the cross-sectional shape of the second refractive index modulation structure 132 includes a circle, a rectangle, or a regular polygon (only a square is used as an example in the present application).

[0067] In some embodiments of the present application, the size of the second refractive index modulation structure 132 (the diameter if it is a circle, and the side length if it is a regular polygon) is 80 nanometers to 400 nanometers, and the spacing between the second refractive index modulation structures 132 is 100 nanometers to 600 nanometers.

[0068] In some embodiments of the present application, the upper surfaces of the first refractive index modulation structure 131 and the second refractive index modulation structure 132 are coplanar with the upper surface of the silicon waveguide structure 120, and the lower surfaces of the first refractive index modulation structure 131 and the second refractive index modulation structure 132 are coplanar with the lower surface of the silicon waveguide structure 120. However, considering the tolerance range in actual processing, the lower surfaces of the first refractive index modulation structure 131 and the second refractive index modulation structure 132 can be designed to be slightly lower than the lower surface of the silicon waveguide structure 120.

[0069] In the technical solution of the present application, the first refractive index modulation structure 131 is used to adjust the equivalent refractive index of the first refractive index modulation zone 111, so that the equivalent refractive index of the first refractive index modulation zone 111 gradually decreases from the incident end 122 toward the direction extending from the silicon waveguide structure 120; the second refractive index modulation structure 132 is used to adjust the equivalent refractive index of the second refractive index modulation zone 112, so that the equivalent refractive index of the second refractive index modulation zone 112 gradually decreases from the incident end 122 toward the direction away from the incident end 122 until it decreases back to the refractive index of the optical fiber (silica material).

[0070] In the technical solution of the present application, the first refractive index modulation region 111 is used to reduce the refractive index difference between the cladding layer 150 and the silicon waveguide structure 120, increase the mode spot size, reduce the coupling loss, and thus reduce the size of the device. The second refractive index modulation region 112 is used to form a region with a smooth refractive index change between the optical fiber and the silicon waveguide structure 120 (refer to Figure 5 , the optical fiber structure is generally set up in Figure 5 The right side of the mid-end face coupling device is adjacent to the second refractive index modulation zone 112. The light in the optical fiber passes through the second refractive index modulation zone 112 and enters the incident end 122), guiding the light to better enter the silicon waveguide structure 120 from the optical fiber, reducing coupling loss, and thus reducing the size of the device.

[0071] Figure 8 Schematic diagram of the structure of the first refractive index modulation region in the end face coupler described in some embodiments of the present application. For the purpose of simplicity, only the first refractive index modulation region 111 is shown, and the second refractive index modulation region 112 is omitted.

[0072] refer to Figure 8 As shown, in some embodiments of the present application, the first refractive index modulation structure 131 is not Figure 5 The long strip shown in the Figure 5 The shapes of the second refractive index modulation structures 132 are the same, and this arrangement can facilitate the design and manufacture of the mask when the first refractive index modulation structure 131 and the second refractive index modulation structure 132 are manufactured.

[0073] Figure 9 Schematic diagram of the structure of the first refractive index modulation region in the end face coupler described in some other embodiments of the present application. For the purpose of simplicity, only the first refractive index modulation region 111 is shown, and the second refractive index modulation region 112 is omitted.

[0074] refer to Figure 9 As shown, there may be multiple first refractive index modulation structures 131 on both sides of the silicon waveguide structure 120 , and the density of the first refractive index modulation structures 131 decreases from the incident end 122 to the incident end 122 .

[0075] Figure 10 Schematic diagram of the structure of the second refractive index modulation region in the end face coupler described in some embodiments of the present application. For the purpose of simplicity, only the second refractive index modulation region 112 is shown, and the first refractive index modulation region 111 is omitted.

[0076] refer to Figure 10 As shown, the spacing between the second refractive index modulation structures 132 gradually increases from the incident end 122 to a direction away from the incident end 122 .

[0077] The present application provides a method for forming an end face coupler structure, which utilizes the first refractive index modulation structure and the second refractive index modulation structure to reduce the refractive index difference between the cladding layer and the silicon waveguide structure, thereby improving the performance of the end face coupler, reducing coupling loss, and reducing the size of the device.

[0078] The embodiment of the present application also provides an end face coupler structure, referring to Figure 5 、 Figure 6 and Figure 7 As shown, the SOI substrate includes an SOI substrate including a bottom silicon layer 100, a buried oxide layer 110 and a top silicon layer, wherein a silicon waveguide structure 120 is formed in the top silicon layer, wherein the width of the silicon waveguide structure 120 gradually increases along the incident end 122 of the silicon waveguide structure 120 toward the extension direction of the silicon waveguide structure 120, and the silicon waveguide structure 120 is covered by a cladding layer 150, wherein the cladding layer 150 includes a first refractive index modulation region 111 and a second refractive index modulation region 112, wherein the first refractive index modulation region 111 extends from the incident end 122 toward the extension direction of the silicon waveguide structure 120, and the second refractive index modulation region 112 Region 112 is adjacent to the first refractive index modulation region and extends in the opposite direction to the extension direction of the silicon waveguide structure 120; the first refractive index modulation region 111 is formed with a plurality of first refractive index modulation structures 131 with an edge spacing equal to that of the silicon waveguide structure 120, and the second refractive index modulation region 112 is formed with a plurality of second refractive index modulation structures 132 whose density gradually decreases from the incident end 122 to the direction away from the incident end 122, and the refractive index of the first refractive index modulation structure 131 and the second refractive index modulation structure 132 is greater than the refractive index of the cladding layer 150 and less than the refractive index of the silicon waveguide structure 120.

[0079] refer to Figure 6 As shown, the SOI substrate includes a bottom silicon layer 100, a buried oxide layer 110 and a top silicon layer (the top silicon layer is omitted because it is etched to form a silicon waveguide structure), and a silicon waveguide structure 120 is formed in the top silicon layer.

[0080] refer to Figure 5 As shown, the width of the silicon waveguide structure 120 gradually increases along the incident end 122 of the silicon waveguide structure 120 toward the extending direction of the silicon waveguide structure 120. The width of the silicon waveguide structure 120 refers to the width of the silicon waveguide structure 120 at Figure 5 The vertical dimension.

[0081] The silicon waveguide structure 120 is covered by a cladding layer 150. Figure 5It is a top view. In practice, the silicon waveguide structure 120 is completely buried and blocked by the cladding layer 150. In order to show the silicon waveguide structure 120, the present application omits the part of the cladding layer 150 that is higher than the upper surface of the silicon waveguide structure 120.

[0082] Continue to refer Figure 5 As shown, the cladding layer 150 includes a first refractive index modulation zone 111 and a second refractive index modulation zone 112. The first refractive index modulation zone 111 extends from the incident end 122 toward the extension direction of the silicon waveguide structure 120. The first refractive index modulation zone 111 includes a portion of the silicon waveguide structure 120 and a portion of the cladding layer 150 on both sides of the portion of the silicon waveguide structure 120. The second refractive index modulation zone 112 is adjacent to the first refractive index modulation zone 111 and extends in the opposite direction to the extension direction of the silicon waveguide structure 120 to the boundary of the cladding layer 150.

[0083] In some embodiments of the present application, the material of the bottom silicon layer 100 is, for example, silicon; the material of the silicon waveguide structure 120 is, for example, silicon; and the material of the cladding layer 150 is, for example, silicon dioxide.

[0084] In some embodiments of the present application, the buried oxide layer 110 has a thickness of 2 microns to 3 microns.

[0085] In some embodiments of the present application, the thickness of the coating layer 150 is 300 nanometers to 500 nanometers, for example, 400 nanometers.

[0086] Continue to refer Figure 5 As shown, in some embodiments of the present application, the length of the first refractive index modulation region 111 is 9 microns to 18 microns, and the width is 1.5 microns to 3 microns; the length of the second refractive index modulation region 112 is 1 micron to 4 microns, and the width is 3 microns to 4 microns. The length of the first refractive index modulation region 111 accounts for 5% to 15% of the length of the silicon waveguide structure 120. Wherein, the length refers to Figure 5 The horizontal dimension, the width refers to Figure 5 The vertical dimension.

[0087] In some embodiments of the present application, the upper surfaces of the first refractive index modulated region 111 and the second refractive index modulated region 112 are coplanar with the upper surface of the silicon waveguide structure 120, and the lower surfaces of the first refractive index modulated region 111 and the second refractive index modulated region 112 are coplanar with the lower surface of the silicon waveguide structure 120. However, considering the error range in actual processing and to ensure that the first refractive index modulated region 111 and the second refractive index modulated region 112 are in full contact with the silicon waveguide structure 120, the lower surfaces of the first refractive index modulated region 111 and the second refractive index modulated region 112 can be designed to be slightly lower than the lower surface of the silicon waveguide structure 120.

[0088] Continue to refer Figure 5 、 Figure 6 and Figure 7 As shown, a plurality of first refractive index modulation structures 131 are formed in the first refractive index modulation zone 111, and the spacing between the first refractive index modulation structures 131 and the edge of the silicon waveguide structure 120 is equal (that is, the first refractive index modulation structures 131 are parallel to the edge of the silicon waveguide structure 120). A plurality of second refractive index modulation structures 132 are formed in the second refractive index modulation zone 112, and the density gradually decreases from the incident end 122 to the direction away from the incident end 122 (that is, the number of second refractive index modulation structures 132 gradually decreases from the incident end 122 to the direction away from the incident end 122). The refractive index of the first refractive index modulation structure 131 and the second refractive index modulation structure 132 is greater than the refractive index of the cladding layer 150 and less than the refractive index of the silicon waveguide structure 120.

[0089] In some embodiments of the present application, the material of the first refractive index modulation structure 131 and the second refractive index modulation structure 132 includes a material whose refractive index is greater than the refractive index of the cladding layer 150 (silicon dioxide, a refractive index of approximately 1.44) and less than the refractive index of the silicon waveguide structure 120 (silicon, a refractive index of approximately 3.476), and the materials of the first refractive index modulation structure 131 and the second refractive index modulation structure 132 include silicon nitride, silicon oxynitride, silicon-rich silicon oxide, etc.

[0090] In some embodiments of the present application, the first refractive index modulation structure 131 and the second refractive index modulation structure 132 have doped ions (formed by ion implantation of the cladding layer 150), the doped ions include ions with an ion diameter larger than the diameter of oxygen ions (silicon dioxide contains oxygen), and the doped ions include nitrogen, arsenic, phosphorus, and aluminum; the doping concentration of the doped ions is 1E16 atom / cm 3 to 1E19 atom / cm 3 Adjusting the injection concentration can also adjust the refractive index of the first refractive index modulation structure 131 and the second refractive index modulation structure 132 .

[0091] In some embodiments of the present application, the width of the first refractive index modulation structure 131 is 100 nanometers to 500 nanometers, the spacing between the first refractive index modulation structure 131 and the silicon waveguide structure 120 is 0 to 400 nanometers, and the first refractive index modulation structure 131 may be in contact with the silicon waveguide structure 120. The width refers to Figure 5 The vertical dimension.

[0092] In some embodiments of the present application, the cross-sectional shape of the second refractive index modulation structure 132 includes a circle, a rectangle, or a regular polygon (only a square is used as an example in the present application).

[0093] In some embodiments of the present application, the size of the second refractive index modulation structure 132 (the diameter if it is a circle, and the side length if it is a regular polygon) is 80 nanometers to 400 nanometers, and the spacing between the second refractive index modulation structures 132 is 100 nanometers to 600 nanometers.

[0094] In some embodiments of the present application, the upper surfaces of the first refractive index modulation structure 131 and the second refractive index modulation structure 132 are coplanar with the upper surface of the silicon waveguide structure 120, and the lower surfaces of the first refractive index modulation structure 131 and the second refractive index modulation structure 132 are coplanar with the lower surface of the silicon waveguide structure 120. However, considering the tolerance range in actual processing, the lower surfaces of the first refractive index modulation structure 131 and the second refractive index modulation structure 132 can be designed to be slightly lower than the lower surface of the silicon waveguide structure 120.

[0095] In the technical solution of the present application, the first refractive index modulation structure 131 is used to adjust the equivalent refractive index of the first refractive index modulation zone 111, so that the equivalent refractive index of the first refractive index modulation zone 111 gradually increases from the incident end 122 toward the direction extending from the silicon waveguide structure 120; the second refractive index modulation structure 132 is used to adjust the equivalent refractive index of the second refractive index modulation zone 112, so that the equivalent refractive index of the second refractive index modulation zone 112 gradually decreases from the incident end 122 toward the direction away from the incident end 122 until it decreases back to the refractive index of the optical fiber (silica material).

[0096] In the technical solution of the present application, the first refractive index modulation region 111 is used to reduce the refractive index difference between the cladding layer 150 and the silicon waveguide structure 120, increase the mode spot size, reduce the coupling loss, and thus reduce the size of the device. The second refractive index modulation region 112 is used to form a region with a smooth refractive index change between the optical fiber and the silicon waveguide structure 120 (refer to Figure 5 , the optical fiber structure is generally set up in Figure 5The right side of the mid-end face coupling device is adjacent to the second refractive index modulation zone 112. The light in the optical fiber passes through the second refractive index modulation zone 112 and enters the incident end 122), guiding the light to better enter the silicon waveguide structure 120 from the optical fiber, reducing coupling loss, and thus reducing the size of the device.

[0097] Figure 8 Schematic diagram of the structure of the first refractive index modulation region in the end face coupler described in some embodiments of the present application. For the purpose of simplicity, only the first refractive index modulation region 111 is shown, and the second refractive index modulation region 112 is omitted.

[0098] refer to Figure 8 As shown, in some embodiments of the present application, the first refractive index modulation structure 131 is not Figure 5 The long strip shown in the Figure 5 The shapes of the second refractive index modulation structures 132 are the same, and this arrangement can facilitate the design and manufacture of the mask when the first refractive index modulation structure 131 and the second refractive index modulation structure 132 are manufactured.

[0099] Figure 9 Schematic diagram of the structure of the first refractive index modulation region in the end face coupler described in some other embodiments of the present application. For the purpose of simplicity, only the first refractive index modulation region 111 is shown, and the second refractive index modulation region 112 is omitted.

[0100] refer to Figure 9 As shown, there may be multiple first refractive index modulation structures 131 on both sides of the silicon waveguide structure 120 , and the density of the first refractive index modulation structures 131 decreases from the incident end 122 to the incident end 122 .

[0101] Figure 10 Schematic diagram of the structure of the second refractive index modulation region in the end face coupler described in some embodiments of the present application. For the purpose of simplicity, only the second refractive index modulation region 112 is shown, and the first refractive index modulation region 111 is omitted.

[0102] refer to Figure 10 As shown, the spacing between the second refractive index modulation structures 132 gradually increases from the incident end 122 to a direction away from the incident end 122 .

[0103] The present application provides an end face coupler structure and a method for forming the same. The first refractive index modulation structure and the second refractive index modulation structure are used to reduce the refractive index difference between the cladding layer and the silicon waveguide structure, thereby improving the performance of the end face coupler, reducing coupling loss, and reducing the device size.

[0104] In summary, after reading the contents of this application, those skilled in the art will understand that the foregoing contents are presented by way of example only and are not intended to be limiting. Although not expressly stated herein, those skilled in the art will understand that this application is intended to encompass various reasonable changes, improvements, and modifications to the embodiments. Such changes, improvements, and modifications are within the spirit and scope of the exemplary embodiments of this application.

[0105] It should be understood that the term "and / or" used in this embodiment includes any and all combinations of one or more of the associated listed items. In contrast, the term "directly" indicates the absence of intervening elements. It should also be understood that the terms "comprise," "comprising," "include," or "including," when used in this application document, indicate the presence of the recited features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0106] It should also be understood that although the terms first, second, third, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. Therefore, without departing from the teachings of the present application, the first element in some embodiments may be referred to as the second element in other embodiments. The same reference numerals or the same reference designators represent the same elements throughout the specification.

[0107] In addition, this specification describes exemplary embodiments by reference to idealized exemplary cross-sectional views and / or plan views and / or perspective views. Therefore, differences from the illustrated shapes due to, for example, manufacturing techniques and / or tolerances are foreseeable. Therefore, the exemplary embodiments should not be interpreted as limited to the shapes of the regions shown herein, but should include deviations in shapes due to, for example, manufacturing. Therefore, the regions shown in the figures are schematic in nature, and their shapes are not intended to illustrate the actual shapes of the regions of the device nor to limit the scope of the exemplary embodiments.

Claims

1. A method for forming an end face coupler structure, characterized in that: include: Providing an SOI substrate, the SOI substrate comprising a bottom silicon layer, a buried oxide layer, and a top silicon layer, wherein a silicon waveguide structure is formed in the top silicon layer, wherein the width of the silicon waveguide structure gradually increases from an incident end of the silicon waveguide structure toward an extension direction of the silicon waveguide structure, and the silicon waveguide structure is covered by a cladding layer, wherein the cladding layer comprises a first refractive index modulation region and a second refractive index modulation region, wherein the first refractive index modulation region extends from the incident end toward the extension direction of the silicon waveguide structure, and the second refractive index modulation region is adjacent to the first refractive index modulation region and extends in a direction opposite to the extension direction of the silicon waveguide structure; A plurality of first refractive index modulation structures having an equal edge spacing to the silicon waveguide structure are formed in the first refractive index modulation region, and a plurality of second refractive index modulation structures having a density gradually decreasing from the incident end toward a direction away from the incident end are formed in the second refractive index modulation region, wherein the refractive index of the first refractive index modulation structure and the second refractive index modulation structure is greater than the refractive index of the cladding layer and is less than the refractive index of the silicon waveguide structure.

2. The method for forming an end face coupler structure according to claim 1, wherein: The material of the silicon waveguide structure is silicon, and the material of the cladding layer is silicon dioxide.

3. The method for forming an end face coupler structure according to claim 2, wherein: A method of forming the first refractive index modulation structure and the second refractive index modulation structure includes: forming a patterned photoresist layer on the surface of the cladding layer, wherein the patterned photoresist layer defines positions of the first refractive index modulation structure and the second refractive index modulation structure; Using the patterned photoresist layer as a mask, etching the cladding layer to form a plurality of grooves; removing the patterned photoresist layer; The first refractive index modulation structure and the second refractive index modulation structure are formed in the plurality of grooves.

4. The method for forming an end face coupler structure according to claim 3, wherein: The materials of the first refractive index modulation structure and the second refractive index modulation structure include silicon nitride, silicon oxynitride, and silicon-rich silicon oxide.

5. The method for forming an end face coupler structure according to claim 2, wherein: A method of forming the first refractive index modulation structure and the second refractive index modulation structure includes: forming a patterned photoresist layer on the surface of the cladding layer, wherein the patterned photoresist layer defines positions of the first refractive index modulation structure and the second refractive index modulation structure; performing an ion implantation process on the cladding layer using the patterned photoresist layer as a mask to form the first refractive index modulation structure and the second refractive index modulation structure; The patterned photoresist layer is removed.

6. The method for forming an end face coupler structure according to claim 5, wherein: The implanted ions in the ion implantation process include ions with a diameter larger than that of oxygen ions, and the implanted ions in the ion implantation process include nitrogen, arsenic, phosphorus, and aluminum; the implantation concentration in the ion implantation process is 1E16 atom / cm 3 to 1E19 atom / cm 3 .

7. The method for forming an end face coupler structure according to claim 1, wherein: The length of the first refractive index modulation zone is 9 microns to 18 microns, and the width is 1.5 microns to 3 microns; the length of the second refractive index modulation zone is 1 micron to 4 microns, and the width is 3 microns to 4 microns.

8. The method for forming an end face coupler structure according to claim 1, wherein: The width of the first refractive index modulation structure is 100 nanometers to 500 nanometers, and the distance between the first refractive index modulation structure and the silicon waveguide structure is 100 nanometers to 400 nanometers.

9. The method for forming an end face coupler structure according to claim 1, wherein: The cross-sectional shape of the second refractive index modulation structure includes a circle, a rectangle or a regular polygon.

10. The method for forming an end face coupler structure according to claim 9, wherein: The size of the second refractive index modulation structure is 80 nanometers to 400 nanometers, and the spacing between the second refractive index modulation structures is 100 nanometers to 600 nanometers.

11. The method for forming an end face coupler structure according to claim 1, wherein: The upper surfaces of the first refractive index modulation structure and the second refractive index modulation structure are coplanar with the upper surface of the silicon waveguide structure, and the lower surfaces of the first refractive index modulation structure and the second refractive index modulation structure are coplanar with the lower surface of the silicon waveguide structure.

12. The method for forming an end face coupler structure according to claim 1, wherein: The method of forming the cladding layer and the first and second refractive index modulation structures includes: Providing an SOI substrate, wherein the SOI substrate comprises a bottom silicon layer, a buried oxide layer and a top silicon layer, and etching the top silicon layer to form the silicon waveguide structure; forming a first portion of a cladding layer on the surface of the buried oxide layer with a top surface flush with the top surface of the silicon waveguide structure; forming the first refractive index modulation structure and the second refractive index modulation structure flush with the top surface of the silicon waveguide structure in the first cladding layer; A second partial cladding layer is formed on the silicon waveguide structure, the surface of the first partial cladding layer, the surfaces of the first refractive index modulation structure, and the second refractive index modulation structure.

13. The method for forming an end face coupler structure according to claim 1, wherein: The method of forming the cladding layer and the first and second refractive index modulation structures includes: Providing an SOI substrate, wherein the SOI substrate comprises a bottom silicon layer, a buried oxide layer and a top silicon layer, and etching the top silicon layer to form the silicon waveguide structure; forming a first portion of a cladding layer on the surface of the buried oxide layer, the top surface of which is higher than the top surface of the silicon waveguide structure; forming the first refractive index modulation structure and the second refractive index modulation structure flush with the top surface of the first partial cladding layer in the first partial cladding layer; A second partial cladding layer is formed on the silicon waveguide structure, the surface of the first partial cladding layer, the surfaces of the first refractive index modulation structure, and the second refractive index modulation structure.

14. An end face coupler structure, characterized in that: include: an SOI substrate, the SOI substrate comprising a bottom silicon layer, a buried oxide layer, and a top silicon layer, a silicon waveguide structure formed in the top silicon layer, the width of the silicon waveguide structure gradually increasing from an incident end of the silicon waveguide structure toward an extension direction of the silicon waveguide structure, the silicon waveguide structure being covered by a cladding layer, the cladding layer comprising a first refractive index modulation region and a second refractive index modulation region, the first refractive index modulation region extending from the incident end toward the extension direction of the silicon waveguide structure, the second refractive index modulation region adjacent to the first refractive index modulation region and extending in a direction opposite to the extension direction of the silicon waveguide structure; Several first refractive index modulation structures having an edge spacing equal to that of the silicon waveguide structure are formed in the first refractive index modulation region, and several second refractive index modulation structures having a density gradually decreasing from the incident end toward away from the incident end are formed in the second refractive index modulation region. The refractive indexes of the first and second refractive index modulation structures are greater than the refractive index of the cladding layer and are less than the refractive index of the silicon waveguide structure.

15. The end face coupler structure according to claim 14, wherein: The material of the silicon waveguide structure is silicon, and the material of the cladding layer is silicon dioxide.

16. The end face coupler structure according to claim 15, wherein: The materials of the first refractive index modulation structure and the second refractive index modulation structure include silicon nitride, silicon oxynitride, and silicon-rich silicon oxide.

17. The end face coupler structure according to claim 15, wherein: The first refractive index modulation structure and the second refractive index modulation structure have doping ions, and the doping ions include nitrogen, arsenic, phosphorus, and aluminum; the doping concentration of the doping ions is 1E16atom / cm 3 to 1E19 atom / cm 3 .

18. The end face coupler structure according to claim 14, wherein: The length of the first refractive index modulation zone is 9 microns to 18 microns, and the width is 1.5 microns to 3 microns; the length of the second refractive index modulation zone is 1 micron to 4 microns, and the width is 3 microns to 4 microns.

19. The end face coupler structure according to claim 14, wherein: The width of the first refractive index modulation structure is 100 nanometers to 500 nanometers, and the distance between the first refractive index modulation structure and the silicon waveguide structure is 200 nanometers to 400 nanometers.

20. The end face coupler structure according to claim 14, wherein: The cross-sectional shape of the second refractive index modulation structure includes a circle, a rectangle or a regular polygon.

21. The end face coupler structure according to claim 20, wherein: The size of the second refractive index modulation structure is 80 nanometers to 400 nanometers, and the spacing between the second refractive index modulation structures is 100 nanometers to 600 nanometers.

22. The end face coupler structure according to claim 14, wherein: The upper surfaces of the first refractive index modulation structure and the second refractive index modulation structure are coplanar with the upper surface of the silicon waveguide structure, and the lower surfaces of the first refractive index modulation structure and the second refractive index modulation structure are coplanar with the lower surface of the silicon waveguide structure.

Images