Thermo-optical phase shifter and manufacturing method

Abstract

The invention discloses a thermo-optical phase shifter and a manufacturing method. The thermo-optical phase shifter comprises a waveguide arranged in a dielectric layer; the cavity is arranged in the dielectric layer outside the waveguide side surface; the heat conduction electrode is arranged in the cavity and comprises a first heat conduction electrode suspended in the cavity; wherein in the first state, the first heat conduction electrode is separated from the side wall of the cavity, and the waveguide is subjected to heat insulation through the cavity, so that the power required for maintaining the work of the thermo-optic phase shifter resistor is relatively low; and in the second state, the first heat conduction electrode is stressed to move to be connected with the side wall of the cavity, and the waveguide radiates heat outwards through the heat conduction electrodes, so that the opening and closing speed of the thermo-optical phase shifter can be increased, and the thermo-optical phase shifter has the advantages of low Ppi power and short temperature rising and falling time.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon-based optoelectronic devices, and particularly to a thermo-optic phase shifter and a manufacturing method thereof. Background Art

[0002] A thermo-optic phase shifter is an active device in silicon-based optoelectronics. Its function is to change the refractive index of a silicon waveguide by resistive heating, thereby changing the phase of the light propagating in the waveguide.

[0003] For a thermo-optic phase shifter, there are two relatively important performance indicators:

[0004] One is Pπ, which is the power required to change the optical phase in the thermo-optic phase shifter by π.

[0005] The other is the heating and cooling time, which is the time required for the thermo-optic phase shifter to heat up from a 0.1π phase shift to a 0.9π phase shift (or to cool down from a 0.9π phase shift to a 0.1π phase shift after stopping heating a thermo-optic phase shifter with a π phase change of the optical phase) after applying the power Pπ to an unheated thermo-optic phase shifter.

[0006] The thermo-optic phase shifter can adopt the substrate hollowing technology (which means removing the silicon substrate of silicon-on-insulator by etching) to reduce the heat dissipation efficiency, thereby greatly reducing Pπ. However, after using the substrate hollowing technology to reduce the heat dissipation efficiency, the heating and cooling time will be greatly increased. Summary of the Invention

[0007] The purpose of the present invention is to overcome the above-mentioned defects existing in the prior art, and provide a thermo-optic phase shifter and a manufacturing method thereof.

[0008] To achieve the above purpose, the technical solution of the present invention is as follows:

[0009] The present invention provides a thermo-optic phase shifter, including:

[0010] A waveguide disposed in a dielectric layer;

[0011] A cavity disposed in the dielectric layer outside the side of the waveguide;

[0012] A heat conduction electrode disposed in the cavity, and the heat conduction electrode includes a first heat conduction electrode suspended in the cavity;

[0013] Wherein, in a first state, the first heat conduction electrode is separated from the side wall of the cavity, and the waveguide is thermally insulated through the cavity; in a second state, the first heat conduction electrode is forced to move to be connected with the side wall of the cavity, and the waveguide dissipates heat outward through the heat conduction electrode.

[0014] Further, the heat conduction electrode further includes a second heat conduction electrode disposed on the side wall of the cavity near the waveguide side. In the first state, the first heat conduction electrode is separated from the second heat conduction electrode and the side wall of the cavity, and the waveguide is thermally insulated through the cavity. In the second state, the first heat conduction electrode is forced to move to be connected to the second heat conduction electrode, so as to be connected to the side wall of the cavity, and the waveguide dissipates heat outward through the second heat conduction electrode and the first heat conduction electrode.

[0015] Further, by applying opposite voltages to the first heat conduction electrode and the second heat conduction electrode, the first heat conduction electrode is attracted to move to be connected to the second heat conduction electrode, and by removing the voltage, the first heat conduction electrode is separated from the second heat conduction electrode.

[0016] Further, the dielectric layer is disposed on the SOI substrate. The SOI substrate sequentially includes a bottom silicon layer, a buried oxide layer, and a top silicon layer. The waveguide is formed by patterning the top silicon layer. The dielectric layer includes the buried oxide layer disposed on the bottom silicon layer, and a first dielectric layer, a second dielectric layer, and a third dielectric layer sequentially disposed on the buried oxide layer. The cavity forms an opening through the bottom silicon layer.

[0017] Further, a heating electrode is also disposed in the dielectric layer, and the heating electrode, the first heat conduction electrode, and the second heat conduction electrode are respectively led out from the surface of the dielectric layer through contact electrodes.

[0018] Further, the first heat conduction electrode and the second heat conduction electrode form a comb-like structure arranged relatively staggeredly, and the comb teeth of the first heat conduction electrode are connected as a whole, and the comb teeth of the second heat conduction electrode are independently disposed on the side wall of the cavity.

[0019] Further, the cavities are respectively disposed in the dielectric layers outside both sides of the waveguide, and heat conduction electrodes are respectively disposed in each of the cavities on each side.

[0020] The present invention also provides a method for manufacturing a thermo-optic phase shifter, including:

[0021] Providing a substrate;

[0022] Forming a dielectric layer on the substrate, forming a waveguide in the dielectric layer, and forming a heat conduction electrode including a first heat conduction electrode in the dielectric layer outside the side of the waveguide;

[0023] Forming a cavity in the dielectric layer corresponding to the position of the heat conduction electrode through the substrate, so that the first heat conduction electrode is suspended in the cavity.

[0024] Further, the substrate includes an SOI substrate, and the SOI substrate sequentially includes a bottom silicon layer, a buried oxide layer, and a top silicon layer; forming a dielectric layer on the substrate, forming a waveguide in the dielectric layer, and forming a heat conduction electrode including a first heat conduction electrode in the dielectric layer outside the side of the waveguide, specifically including:

[0025] Pattern the top silicon layer to form a waveguide on the buried oxide layer;

[0026] Form a first dielectric layer on the buried oxide layer to cover the waveguide;

[0027] Form a second trench and a first trench arranged in sequence on the surfaces of the first dielectric layer on both sides of the waveguide, and stop at the bottom silicon layer;

[0028] Form a first heat conduction electrode in the first trench and a second heat conduction electrode in the second trench;

[0029] Form a second dielectric layer on the first dielectric layer to cover the first heat conduction electrode and the second heat conduction electrode;

[0030] Form a third trench on the surface of the second dielectric layer above the waveguide;

[0031] Form a heating electrode in the third trench;

[0032] Form a third dielectric layer on the second dielectric layer to cover the heating electrode;

[0033] Form a contact electrode on the surface of the third dielectric layer, the bottom of which is respectively connected to the heating electrode, the first heat conduction electrode, and the second heat conduction electrode; thereby forming the dielectric layer including the buried oxide layer, the first dielectric layer to the third dielectric layer on the SOI substrate, forming the waveguide in the dielectric layer, and forming the heat conduction electrode including the first heat conduction electrode and the second heat conduction electrode in the dielectric layer outside the side of the waveguide;

[0034] Forming a cavity in the dielectric layer corresponding to the position of the heat conduction electrode through the substrate, so that the first heat conduction electrode is suspended in the cavity, specifically including:

[0035] Thin the back surface of the bottom silicon layer facing away from the buried oxide layer;

[0036] Form a fourth trench on the back surface of the bottom silicon layer, the bottom of which is located in the dielectric layer, and make the fourth trench surround the side of the first heat conduction electrode;

[0037] Through the fourth groove, the dielectric layer material around the first heat conduction electrode is removed until a cavity is formed in the dielectric layer corresponding to the position of the heat conduction electrode, so that the first heat conduction electrode is suspended in the cavity, and the second heat conduction electrode is at least exposed on the side wall of the cavity close to the waveguide side.

[0038] Further, when forming the first groove and the second groove, the first groove and the second groove are formed into a comb structure arranged relatively staggeredly, and the teeth of the first groove are connected into one body, and the teeth of the second groove are independently located between the teeth of the first groove.

[0039] It can be seen from the above technical solutions that in the present invention, by providing a cavity in the dielectric layer on the side of the waveguide and suspending the first heat conduction electrode in the cavity, in the first state (when the system is in the off working state), the first heat conduction electrode can be separated from the side wall of the cavity, so that the cavity can be used to insulate the waveguide, making the power required to maintain the resistance operation of the thermo-optic phase shifter relatively low, thereby greatly reducing the Pπ power of the thermo-optic phase shifter. In the second state (when the system is in the on working state), by applying force to move the first heat conduction electrode and connecting it to the side wall of the cavity, heat can be dissipated outward through the heat conduction electrode, so that the opening / closing speed of the thermo-optic phase shifter can be increased, and thus the heating and cooling time of the thermo-optic phase shifter can be significantly shortened. Description of the Drawings

[0040] Figure 1 It is a schematic structural diagram of a thermo-optic phase shifter according to a preferred embodiment of the present invention.

[0041] Figure 2 It is Figure 1 a top view structural schematic diagram along the A-A direction in

[0042] Figure 3 It is Figure 2 a schematic diagram of the position change state of the heat conduction electrode in the structure.

[0043] Figures 4 - 15 It is a schematic diagram of the process steps of a manufacturing method of a thermo-optic phase shifter according to a preferred embodiment of the present invention. Detailed Embodiments

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely below. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention pertains. The words such as "including" used herein mean that the elements or items appearing before this word cover the elements or items listed after this word and their equivalents, without excluding other elements or items.

[0045] The following further elaborates on the specific embodiments of the present invention with reference to the accompanying drawings.

[0046] Reference Figure 1 A thermo-optic phase shifter of the present invention includes a dielectric layer 20, a waveguide 131 disposed in the dielectric layer 20, a cavity 40 disposed in the dielectric layer 20 outside the side of the waveguide 131, and a heat-conducting electrode 30 disposed in the cavity 40. The heat-conducting electrode 30 includes a first heat-conducting electrode 31 suspended in the cavity 40.

[0047] The thermo-optic phase shifter of the present invention can be optimally integrated into, for example, a Micro Electro-Mechanical System (MEMS).

[0048] Among them, when the thermo-optic phase shifter is in the first state (i.e., the system is in the closed working state), by using the state where the first heat-conducting electrode 31 is separated from the sidewall of the cavity 40, the waveguide 131 in the dielectric layer 20 is isolated from the outside through the cavity 40, that is, the cavity 40 plays a role in heat insulation. At this time, the heat dissipation effect of the system will be poor, so that the power required to maintain the resistance operation of the thermo-optic phase shifter is low, thereby greatly reducing the Pπ power of the thermo-optic phase shifter.

[0049] When the thermo-optic phase shifter is in the second state (i.e., the system is in the open working state), by driving the first heat-conducting electrode 31 to move, the first heat-conducting electrode 31 moves to be connected to the sidewall of the cavity 40 close to the waveguide 131 after being stressed, so that the waveguide 131 can dissipate heat to the outside through the heat-conducting electrode 30 (the first heat-conducting electrode 31). Since the heat dissipation effect of the system is good at this time, the opening / closing speed of the thermo-optic phase shifter can be increased, thereby significantly shortening the heating and cooling time of the thermo-optic phase shifter. Therefore, the thermo-optic phase shifter of the present invention simultaneously has the characteristics of low Pπ and short heating and cooling time. That is, the thermo-optic phase shifter of the present invention combines the respective advantages of the thermo-optic phase shifters with and without a substrate hollowing structure in the prior art.

[0050] Reference Figures 1 - 3 。In some embodiments, the heat conduction electrode 30 further includes a second heat conduction electrode 32; the second heat conduction electrode 32 is disposed on the side wall of the cavity 40 close to the waveguide 131. When the thermo-optic phase shifter is in the first state, the first heat conduction electrode 31 is freely suspended in the cavity 40 and is separated from the second heat conduction electrode 32 and the side wall of the cavity 40, as Figure 2 shown. At this time, the waveguide 131 is effectively thermally insulated through the cavity 40. When the thermo-optic phase shifter is in the second state, when the first heat conduction electrode 31 is driven, it moves under force to be connected to the second heat conduction electrode 32, and the first heat conduction electrode 31 itself can also be directly connected to the side wall of the cavity 40, so that the entire heat conduction electrode 30 is connected to the side wall of the cavity 40, as Figure 3 shown. At this time, the waveguide 131 can rapidly dissipate heat outward through the heat conduction electrode 30 (the second heat conduction electrode 32 and the first heat conduction electrode 31) with good heat conduction performance.

[0051] In some embodiments, by applying opposite voltages to the first heat conduction electrode 31 and the second heat conduction electrode 32, the system is in the on working state, and currents in opposite directions are generated in the first heat conduction electrode 31 and the second heat conduction electrode 32, so as to generate an electrostatic attraction effect between the first heat conduction electrode 31 and the second heat conduction electrode 32. Under the action of the electrostatic attraction force, the suspended first heat conduction electrode 31 is attracted by the second heat conduction electrode 32 fixed on the side wall of the cavity 40 and moves to be connected to the second heat conduction electrode 32, so that the entire heat conduction electrode 30 is connected to the side wall of the cavity 40, and the waveguide 131 can dissipate heat outward through the heat conduction electrode 30 connected to the dielectric layer 20, realizing the rapid opening and closing of the thermo-optic phase shifter.

[0052] On the contrary, by removing the opposite voltages applied to the first heat conduction electrode 31 and the second heat conduction electrode 32 (that is, not applying any voltage to the first heat conduction electrode 31 and the second heat conduction electrode 32), the system is in the off working state, and the first heat conduction electrode 31 is in a free suspended state because it is not driven by the electrostatic attraction force, so as to be separated from the second heat conduction electrode 32. At this time, by using the isolation effect of the medium such as air in the cavity 40, the heat dissipation effect of the system becomes poor, so the operating power for maintaining the resistance of the thermo-optic phase shifter is also low, realizing a large reduction in Pπ.

[0053] Reference Figure 1 。In some embodiments, the dielectric layer 20 is disposed on the SOI substrate 10 (that is, the dielectric layer 20 is fabricated on the SOI substrate 10. Figure 1The dielectric layer 20 is shown as an inverted state between the dielectric layer 20 and the SOI substrate 10). The SOI substrate 10 includes a bottom silicon layer 11, a buried oxide layer 12 and a top silicon layer 13 in sequence; the waveguide 131 is formed by the patterned top silicon layer 13. The dielectric layer 20 includes a buried oxide layer 12 disposed on the bottom silicon layer 11 of the SOI substrate 10, and a first dielectric layer 21, a second dielectric layer 22 and a third dielectric layer 23 disposed in sequence on the buried oxide layer 12. In this way, the waveguide 131 is covered by the dielectric layer 20. The dielectric layer 20 forms the cladding of the waveguide 131 and acts as an isolation layer. Among them, the waveguide 131 is located in the first dielectric layer 21, the thermal conductive electrode 30 is located in the buried oxide layer 12 and the first dielectric layer 21, and the cavity 40 is located in the buried oxide layer 12 and the first dielectric layer 21 to the third dielectric layer 23.

[0054] It can be understood that the dielectric layer may also be a dielectric layer provided on other forms of substrates.

[0055] The cavity 40 forms an opening 41 through the bottom silicon layer 11, that is, a through hole connected to the cavity 40 is provided on the bottom silicon layer 11, and serves as a passage formed on the bottom silicon layer 11 for the cavity 40 to communicate with the outside. It can be understood that the opening 41 needs to be completely connected between the first heat-conducting electrode 31 and the second heat-conducting electrode 32, and between the first heat-conducting electrode 31 and the side wall of the cavity 40, so as to ensure that the first heat-conducting electrode 31 is in a freely suspended state in the cavity 40.

[0056] In some embodiments, the upper end of the first thermally conductive electrode 31 and the upper end of the second thermally conductive electrode 32 are connected to the bottom silicon layer 11. The portion of the bottom silicon layer 11 located on the upper end of the first thermally conductive electrode 31 is also in the same free suspension state as the first thermally conductive electrode 31 due to the separation of the opening 41.

[0057] In some embodiments, a heating electrode 50 (heating resistor) is further provided in the dielectric layer 20; specifically, the heating electrode 50 is located in the second dielectric layer 22. The waveguide 131 is spaced a certain distance from the heating electrode 50, the bottom silicon layer 11, and the heat-conducting electrode 30. The heating electrode 50 is disposed facing the waveguide 131, and may be located in the dielectric layer 20 outside the side of the waveguide 131 facing away from the bottom silicon layer 11. The projection width of the heating electrode 50 on the bottom silicon layer 11 may completely cover the waveguide 131, so as to produce a better heating effect on the waveguide 131.

[0058] In some embodiments, the heating electrode 50 is at a certain distance from the thermally conductive electrode 30. The lower end of the thermally conductive electrode 30 is at a certain distance from the bottom of the cavity 40. The distance between the heating electrode 50 and the lower surface of the bottom silicon layer 11 is not less than the distance between the lower end of the thermally conductive electrode 30 and the lower surface of the bottom silicon layer 11, and is less than the distance between the bottom of the cavity 40 and the lower surface of the bottom silicon layer 11.

[0059] In some embodiments, the heating electrode 50, the first heat conducting electrode 31, and the second heat conducting electrode 32 are respectively led out from the lower surface of the dielectric layer 20 (i.e., the surface of the dielectric layer 20 facing away from the underlying silicon layer 11) through the contact electrode 60. The contact electrode 60 can be, for example, a contact hole. A voltage is applied to the heating electrode 50 through the contact electrode 60, causing the heating electrode 50 to heat the waveguide 131. Opposite voltages are applied to the first heat conducting electrode 31 and the second heat conducting electrode 32 through the contact electrode 60 to generate an electrostatic attraction between the first heat conducting electrode 31 and the second heat conducting electrode 32. One end of the contact electrode 60 connected to the first heat conducting electrode 31 is also suspended in the cavity 40 and forms a support for the first heat conducting electrode 31 through the other end passing through the dielectric layer 20.

[0060] Reference Figures 2 - 3 And with reference to Figure 1 . In some embodiments, the first heat conducting electrode 31 and the second heat conducting electrode 32 form a comb structure arranged relatively staggeredly. Each comb tooth of the first heat conducting electrode 31 is connected as a whole, and each comb tooth of the second heat conducting electrode 32 is independently disposed on the side wall of the cavity 40. The traveling direction of the waveguide 131 in the length direction in the dielectric layer 20 ( Figures 2 - 3 the up-and-down direction shown) is consistent with the arrangement direction of each comb tooth, and the distribution length of the heat conducting electrode 30 in the direction along the side wall of the cavity 40 corresponds to the length in the traveling direction of the waveguide 131 to form a better heat dissipation effect.

[0061] Reference Figures 1 - 3 . In some embodiments, the cavities 40 are disposed in the dielectric layer 20 outside both sides of the waveguide 131, and heat conducting electrodes 30 are respectively provided in each cavity 40 on each side. Further, the cavities 40 on both sides can surround the dielectric layer 20 and communicate with each other.

[0062] In some embodiments, the material of the dielectric layer 20 can be silicon dioxide. The waveguide 131 can be a silicon waveguide 131. The material of the heat conducting electrode 30 includes gold. The material of the heating electrode 50 includes tungsten and titanium. The material of the contact electrode 60 includes copper. However, it is not limited thereto.

[0063] The following further details a method for manufacturing a thermo-optic phase shifter of the present invention through specific embodiments and in combination with the drawings.

[0064] Reference Figures 4 - 15 . A method for manufacturing a thermo-optic phase shifter of the present invention can be used to manufacture a thermo-optic phase shifter of the present invention such as Figure 1 above, and may include the following steps:

[0065] Step S1: Provide a substrate.

[0066] As Figure 4As shown in the figure, a thermo-optic phase shifter of the present invention is fabricated using a SOI substrate 10. The SOI substrate 10 sequentially includes a bottom silicon layer 11, a buried oxide layer 12, and a top silicon layer 13 from bottom to top.

[0067] Step S2: Form a dielectric layer 20 on the substrate, form a waveguide 131 in the dielectric layer 20, and form a heat-conducting electrode 30 including a first heat-conducting electrode 31 in the dielectric layer 20 outside the side of the waveguide 131.

[0068] As Figure 5 shown, first, use photolithography and etching processes to pattern the top silicon layer 13 of the SOI substrate 10 to form a waveguide 131 on the buried oxide layer 12 and expose the upper surface of the buried oxide layer 12.

[0069] As Figure 6 shown, then, use a dielectric deposition process to form, for example, a first dielectric layer 21 of silicon dioxide on the upper surface of the SOI substrate 10, that is, form the first dielectric layer 21 on the upper surface of the buried oxide layer 12, so that the first dielectric layer 21 covers the buried oxide layer 12 and the waveguide 131.

[0070] As Figure 7 shown, then, use photolithography and etching processes to form a second trench 34 and a first trench 33 arranged in sequence in the direction away from the waveguide 131 on the upper surface of the first dielectric layer 21 on both sides of the waveguide 131, and make the bottom of the second trench 34 and the bottom of the first trench 33 stop at the upper surface of the bottom silicon layer 11.

[0071] As Figure 8 shown, then, fill the first trench 33 and the second trench 34 with metal (such as gold), fill the first trench 33 and the second trench 34, and remove the excess filled metal material on the upper surface of the first dielectric layer 21 by chemical mechanical polishing, while flattening the upper surface of the first dielectric layer 21, so as to form a first heat-conducting electrode 31 in the first trench 33 and a second heat-conducting electrode 32 in the second trench 34, and form a pair of heat-conducting electrodes 30 composed of the first heat-conducting electrode 31 and the second heat-conducting electrode 32. The upper surface of the first dielectric layer 21 after flattening covers the waveguide 131 therein.

[0072] As Figure 9 shown, then, use a dielectric deposition process to form, for example, a second dielectric layer 22 of silicon dioxide on the upper surface of the first dielectric layer 21 to cover the first heat-conducting electrode 31 and the second heat-conducting electrode 32.

[0073] As Figure 10 shown, then, use photolithography and etching processes to form a third trench 51 on the upper surface of the second dielectric layer 22 corresponding to the upper part of the waveguide 131, and make the bottom of the third trench 51 be at a certain distance from the waveguide 131 below.

[0074] As Figure 11 shown, next, the third trench 51 is filled with a metal (such as tungsten, titanium) until the third trench 51 is full, and the excess filled metal material on the upper surface of the second dielectric layer 22 is removed by chemical mechanical polishing while flattening the upper surface of the second dielectric layer 22, thereby forming a heating electrode 50 in the third trench 51.

[0075] As Figure 12 shown, then, by means of a dielectric deposition process, a third dielectric layer 23 such as silicon dioxide is formed on the upper surface of the second dielectric layer 22 to cover the heating electrode 50.

[0076] Next, by means of a photolithography and etching process, contact hole trenches are formed on the surface of the third dielectric layer 23, the bottoms of which are respectively connected to the heating electrode 50, the first heat conducting electrode 31, and the second heat conducting electrode 32, and the contact hole trenches are filled with a metal (such as copper) until the contact hole trenches are full; and the excess filled metal material on the upper surface of the third dielectric layer 23 is removed by chemical mechanical polishing while flattening the upper surface of the third dielectric layer 23, thereby forming contact electrodes 60 in the contact hole trenches.

[0077] Through the above steps, a dielectric layer 20 including a buried oxide layer 12, a first dielectric layer 21, a second dielectric layer 22, and a third dielectric layer 23 is formed on the SOI substrate 10, a waveguide 131 and a heating electrode 50 are formed in the dielectric layer 20, heat conducting electrodes 30 including a first heat conducting electrode 31 and a second heat conducting electrode 32 are formed in the dielectric layer 20 outside both sides of the waveguide 131, and at the same time, contact electrodes 60 led out through the dielectric layer 20 are formed on the heating electrode 50 and the heat conducting electrodes 30.

[0078] Step S3: A cavity 40 is formed in the dielectric layer 20 at the position corresponding to the heat conducting electrode 30 through the substrate, so that the first heat conducting electrode 31 is suspended in the cavity 40.

[0079] As Figure 13 shown, after that, the SOI substrate 10 (bottom silicon layer 11) with the above device structure formed thereon is inverted so that the lower surface (back surface) of the bottom silicon layer 11 faces upward and the upper surface of the third dielectric layer 23 faces downward. And the back surface of the bottom silicon layer 11 is thinned.

[0080] As Figure 14As shown, next, a photolithography and etching process is adopted to form a fourth trench 42 on the back surface of the bottom silicon layer 11, and the bottom of the fourth trench 42 is located in the dielectric layer 20. Preferably, the bottom of the fourth trench 42 is deep enough to be below the heat conduction electrode 30, and the fourth trench 42 surrounds the side surface of the first heat conduction electrode 31, and the fourth trench 42 is located between the first heat conduction electrode 31 and the second heat conduction electrode 32 on the side close to the second heat conduction electrode 32, separating the first heat conduction electrode 31 from the second heat conduction electrode 32 (refer to Figure 2 ).

[0081] As Figure 15 shown, finally, a wet etching process is adopted, and through the opening 41 formed by the fourth trench 42 on the back surface of the bottom silicon layer 11, the material of the part of the dielectric layer 20 (including the buried oxide layer 12, the first dielectric layer 21 to the third dielectric layer 23) around the first heat conduction electrode 31 is etched and removed until a cavity 40 is formed in the dielectric layer 20 at the position corresponding to the heat conduction electrode 30, so that the material of the dielectric layer 20 on the first heat conduction electrode 31 (including the part of the contact electrode 60 connected thereto) is completely (or basically) removed, so that the first heat conduction electrode 31 can be suspended in the cavity 40, and the second heat conduction electrode 32 is at least exposed on the side wall of the cavity 40 close to the waveguide 131 side (that is, it is necessary to connect a part of the second heat conduction electrode 32 (such as Figure 2 the inner end of the second heat conduction electrode 32 shown in) to the side wall of the cavity 40). In this way, the cavity 40 communicates with the outside through the opening 41 formed by the fourth trench 42 on the back surface of the bottom silicon layer 11 of the SOI substrate 10.

[0082] When forming the first trench 33 and the second trench 34, by making the first trench 33 and the second trench 34 form a comb-like structure of relatively staggered grooves, and making each comb-shaped groove of the first trench 33 communicate as a whole, and making each comb-shaped groove of the second trench 34 independently located between each comb-shaped groove of the first trench 33, the first heat conduction electrode 31 and the second heat conduction electrode 32 formed after filling can also correspondingly have a comb-like structure of relatively staggered settings. And after the cavity 40 is formed, opposite voltages are applied to the first heat conduction electrode 31 and the second heat conduction electrode 32 through the contact electrode 60, so that each electrode comb on the first heat conduction electrode 31 is offset to form an interdigitated state with each electrode comb on the second heat conduction electrode 32 (refer to Figure 3 ), realizing the maximization of the heat dissipation area of the heat conduction electrode 30. And after canceling the voltages applied to the first heat conduction electrode 31 and the second heat conduction electrode 32 (including forming a current flowing in the same direction in the first heat conduction electrode 31 and the second heat conduction electrode 32), each electrode comb on the first heat conduction electrode 31 returns to a state separated from each electrode comb on the second heat conduction electrode 32 (refer to Figure 2) to optimize the heat insulation effect of the cavity 40.

[0083] In summary, in the present invention, by providing the cavity 40 in the dielectric layer 20 outside both sides of the waveguide 131, providing the heat conduction electrode 30 in the cavity 40, and suspending the first heat conduction electrode 31 in the heat conduction electrode 30 in the cavity 40 and fixing the second heat conduction electrode 32 in the heat conduction electrode 30 on the side wall of the cavity 40, when the system is in the off working state, the first heat conduction electrode 31 can be separated from the side wall of the cavity 40 and the second heat conduction electrode 32, so that the cavity 40 can be used to insulate the waveguide 131, resulting in a lower power required to maintain the resistance operation of the thermo-optic phase shifter, thereby greatly reducing the Pπ power of the thermo-optic phase shifter. When the system is in the on working state, by making the first heat conduction electrode 31 shift and connect to the second heat conduction electrode 32 under the action of electrostatic attraction force, and thus connect to the side wall of the cavity 40, the heat conduction electrode 30 can be used to dissipate heat outward, so that the opening / closing speed of the thermo-optic phase shifter can be accelerated, and therefore the heating and cooling time of the thermo-optic phase shifter can be significantly shortened. As a result, the thermo-optic phase shifter of the present invention simultaneously has the advantages of low Pπ power and short heating and cooling time.

[0084] Although the embodiments of the present invention have been described in detail above, it is obvious to those skilled in the art that various modifications and changes can be made to these embodiments. However, it should be understood that such modifications and changes are all within the scope and spirit of the present invention described in the claims. Moreover, the present invention described herein can have other embodiments and can be implemented or realized in various ways.

Claims

1. A thermo-optical phase shifter, characterized in that, Comprising: A waveguide disposed in a dielectric layer; A cavity disposed in the dielectric layer outside the side of the waveguide; A heat-conducting electrode disposed in the cavity, the heat-conducting electrode including a first heat-conducting electrode suspended in the cavity; Wherein, in the first state, the first heat-conducting electrode is separated from the side wall of the cavity, and the waveguide is thermally insulated by the cavity; in the second state, the first heat-conducting electrode is forced to move to be connected to the side wall of the cavity, and the waveguide dissipates heat outward through the heat-conducting electrode.

2. The thermo-optical phase shifter according to claim 1, wherein The heat-conducting electrode further includes a second heat-conducting electrode disposed on the side wall of the cavity close to the waveguide side. In the first state, the first heat-conducting electrode is separated from the second heat-conducting electrode and the side wall of the cavity, and the waveguide is thermally insulated by the cavity; In the second state, the first heat-conducting electrode is forced to move to be connected to the second heat-conducting electrode, and thus to be connected to the side wall of the cavity, and the waveguide dissipates heat outward through the second heat-conducting electrode and the first heat-conducting electrode.

3. The thermo-optical phase shifter according to claim 2, characterized in that, By applying opposite voltages to the first heat-conducting electrode and the second heat-conducting electrode, the first heat-conducting electrode is attracted to move to be connected to the second heat-conducting electrode, and by removing the voltage, the first heat-conducting electrode is separated from the second heat-conducting electrode.

4. The thermo-optic phase shifter according to claim 1, characterized in that The dielectric layer is disposed on an SOI substrate, the SOI substrate sequentially includes a bottom silicon layer, a buried oxide layer, and a top silicon layer, the waveguide is formed by patterning the top silicon layer, the dielectric layer includes the buried oxide layer disposed on the bottom silicon layer and a first dielectric layer, a second dielectric layer, and a third dielectric layer sequentially disposed on the buried oxide layer, and the cavity forms an opening through the bottom silicon layer.

5. The thermo-optic phase shifter according to claim 2, wherein A heating electrode is further disposed in the dielectric layer, and the heating electrode, the first heat-conducting electrode, and the second heat-conducting electrode are respectively led out from the surface of the dielectric layer through contact electrodes.

6. The thermo-optic phase shifter according to claim 1, wherein The first heat-conducting electrode and the second heat-conducting electrode form a comb-like structure arranged relatively staggeredly, and the comb teeth of the first heat-conducting electrode are connected as a whole, and the comb teeth of the second heat-conducting electrode are independently disposed on the side wall of the cavity.

7. The thermo-optic phase shifter according to claim 1, wherein The cavities are respectively disposed in the dielectric layer outside both sides of the waveguide, and the heat-conducting electrodes are respectively disposed in the cavities on each side.

8. A method for fabricating a thermo-optic phase shifter, characterized in that, Comprising: Providing a substrate; Forming a dielectric layer on the substrate, forming a waveguide in the dielectric layer, and forming a heat-conducting electrode including a first heat-conducting electrode in the dielectric layer outside the side of the waveguide; Forming a cavity in the dielectric layer corresponding to the position of the heat-conducting electrode through the substrate, so that the first heat-conducting electrode is suspended in the cavity.

9. The method for manufacturing a thermo-optic phase shifter according to claim 8, wherein, The substrate includes an SOI substrate, the SOI substrate sequentially includes a bottom silicon layer, a buried oxide layer, and a top silicon layer; the forming a dielectric layer on the substrate, forming a waveguide in the dielectric layer, and forming a heat-conducting electrode including a first heat-conducting electrode in the dielectric layer outside the side of the waveguide specifically includes: Patterning the top silicon layer to form a waveguide located on the buried oxide layer; Forming a first dielectric layer on the buried oxide layer to cover the waveguide; Second trenches and first trenches are formed in sequence on the surfaces of the first dielectric layers on both sides of the waveguide, and stop at the underlying silicon layer; A first heat-conducting electrode is formed in the first trench, and a second heat-conducting electrode is formed in the second trench; A second dielectric layer is formed on the first dielectric layer to cover the first heat-conducting electrode and the second heat-conducting electrode; A third trench is formed on the surface of the second dielectric layer above the waveguide; A heating electrode is formed in the third trench; A third dielectric layer is formed on the second dielectric layer to cover the heating electrode; A contact electrode is formed on the surface of the third dielectric layer, the bottom of which is connected to the heating electrode, the first heat-conducting electrode and the second heat-conducting electrode respectively; thereby, a dielectric layer including the buried oxide layer, the first dielectric layer to the third dielectric layer is formed on the SOI substrate, a waveguide is formed in the dielectric layer, and a heat-conducting electrode including the first heat-conducting electrode and the second heat-conducting electrode is formed in the dielectric layer outside the side of the waveguide; A cavity is formed in the dielectric layer corresponding to the position of the heat-conducting electrode through the substrate, so that the first heat-conducting electrode is suspended in the cavity, specifically including: Thinning the back surface of the underlying silicon layer facing away from the buried oxide layer; A fourth trench is formed on the back surface of the underlying silicon layer, the bottom of which is located in the dielectric layer, and the fourth trench surrounds the side of the first heat-conducting electrode; Through the fourth trench, the dielectric layer material around the first heat-conducting electrode is removed until a cavity is formed in the dielectric layer corresponding to the position of the heat-conducting electrode, so that the first heat-conducting electrode is suspended in the cavity, and the second heat-conducting electrode is at least exposed on the side wall of the cavity close to the waveguide side.

10. The method for manufacturing a thermo-optical phase shifter according to claim 9, wherein When forming the first trench and the second trench, the first trench and the second trench are formed into a comb structure arranged relatively staggeredly, and the teeth of the first trench are connected into one body, and the teeth of the second trench are independently located between the teeth of the first trench.

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