Semiconductor structure and method of forming the same

Abstract

The method includes: forming a waveguide comprising a substrate layer and a protrusion; forming a first metal film and a second metal film on opposite sides of the protrusion; and depositing an insulating layer over the first metal film and the second metal film. The insulating layer is etched to form a first opening and a second opening on opposite sides of the protrusion. The first metal film and the second metal film are also exposed to the first opening and the second opening, respectively. A first electrode and a second electrode are formed in the first opening and the second opening, respectively. The first metal film includes a first portion located between the first electrode and the protrusion. The second metal film includes a second portion located between the second electrode and the protrusion. The first electrode and the second electrode are configured to apply an electric field to the protrusion. Embodiments of this application also relate to semiconductor structures and methods of forming the same.

Description

Technical Field

[0001] Embodiments of this application relate to semiconductor structures and methods of forming the same. Background Technology

[0002] Electrical signal transmission and processing is one of the technologies used for signal transmission and processing. In recent years, optical signal transmission and processing has been used in an increasing number of applications, especially due to the use of fiber optics for signal transmission.

[0003] To achieve optical signal transmission, electrical signals need to be converted into optical signals, and vice versa. Therefore, electro-optic modulators have been developed, and efforts are underway to improve their efficiency. Summary of the Invention

[0004] Some embodiments of this application provide a method for forming a semiconductor structure, comprising: forming a waveguide including a substrate layer and a protrusion located above the substrate layer and bonded to the substrate layer; forming a first metal film and a second metal film on opposite sides of the protrusion; depositing an insulating layer over the first metal film and the second metal film; etching the insulating layer to form a first opening and a second opening in the insulating layer, wherein the first opening and the second opening are located on opposite sides of the protrusion, and wherein the first metal film and the second metal film are respectively exposed to the first opening and the second opening; forming a first electrode in the first opening, wherein the first metal film includes a first portion located between the first electrode and the protrusion; and forming a second electrode in the second opening, wherein the second metal film includes a second portion located between the second electrode and the protrusion, and wherein the first electrode and the second electrode are configured to apply an electric field to the protrusion.

[0005] Other embodiments of this application provide a method for forming a semiconductor structure, comprising: forming a waveguide including a substrate layer and a protrusion located above the substrate layer; depositing an insulating layer on the waveguide; performing a deposition process and a patterning process to form a first metal film and a second metal film, wherein the first metal film and the second metal film are above the substrate layer and below the top of the protrusion, and wherein the first metal film is located on the side of the protrusion opposite to the second metal film and spaced apart from the second metal film by a first interval; depositing an additional insulating layer above the first metal film and the second metal film; and forming a ground electrode and a signal electrode respectively connected to the first metal film and the second metal film in the additional insulating layer, wherein the ground electrode and the signal electrode are spaced apart by a second interval greater than the first interval, and wherein the first metal film, the second metal film, the ground electrode, the signal electrode and the waveguide together form an electro-optic modulator.

[0006] Further embodiments of this application provide a semiconductor structure including: an insulating layer; a waveguide located above the insulating layer, wherein the waveguide includes a substrate layer and a protrusion located above the substrate layer and bonded to the substrate layer; a first electrode and a second electrode located on opposite sides of the protrusion; a first metal film electrically connected to the first electrode; and a second metal film electrically connected to the second electrode. Attached Figure Description

[0007] Various aspects of the embodiments of this disclosure will be best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be noted that, in accordance with standard industry practice, the various components are not drawn to scale. In fact, for clarity of discussion, the dimensions of the various components may be arbitrarily increased or decreased.

[0008] Figure 1A and Figures 1B to 6A , Figure 6B and Figure 6C A view showing an intermediate stage in the formation of an electro-optic modulator according to some embodiments is shown.

[0009] Figures 7 to 10A , Figure 10B , Figure 10C , Figure 11A , Figure 11B , Figure 11C , Figure 12A , Figure 12B , Figure 12C , Figure 12D and Figures 13 to 16 A view of an electro-optic modulator according to an alternative embodiment is shown.

[0010] Figure 17A process flow for forming an electro-optic modulator according to some embodiments is shown. Detailed Implementation

[0011] The following disclosure provides numerous different embodiments or instances for implementing various features of the embodiments of this disclosure. Specific examples of components and arrangements are described below to simplify the embodiments of this disclosure. Of course, these are merely examples and are not intended to be limiting. For example, in the following description, forming a first component on or over a second component may include embodiments where the first and second components are in direct contact, and may also include embodiments where an additional component may be formed between the first and second components, thereby allowing the first and second components to not be in direct contact. Furthermore, reference numerals and / or characters may be repeated in various instances of the embodiments of this disclosure. This repetition is for simplicity and clarity and does not in itself indicate a relationship between the various embodiments and / or configurations discussed.

[0012] Furthermore, for ease of description, this document uses spatial relative terms such as “below,” “under,” “lower,” “above,” and “upper” to describe the relationship between one element or component and another (or other elements or components) as shown in the figures. In addition to the orientations depicted in the figures, spatial relative terms are intended to include different orientations of the device during use or operation. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatial relative descriptors used herein can be interpreted accordingly.

[0013] An electro-optic modulator and a method for forming the same are provided. According to some embodiments of this disclosure, the electro-optic modulator includes a waveguide with protrusions. The waveguide may include lithium niobate. Signal and ground electrodes are formed on opposite sides of the protrusions to apply a voltage, such that an electric field is applied to the protrusions. The electric field can change the refractive index of the protrusions, and thus modulate an optical signal in the waveguide. A metal film is formed extending from the signal and ground electrodes toward the protrusions. Because the metal film is closer to the protrusions than the signal and ground electrodes, the electric field applied to the protrusions can be increased without increasing the voltage, and the modulation efficiency can be improved.

[0014] The embodiments discussed herein are intended to provide examples of how the subject matter of the embodiments of this disclosure can be made or used, and modifications that can be made while remaining within the scope of consideration of the different embodiments will be readily understood by those skilled in the art. Throughout the various views and illustrative embodiments, the same reference numerals are used to denote the same elements. While method embodiments may be discussed as being implemented in a particular order, other method embodiments may be implemented in any logical order.

[0015] Figure 1A and Figures 1B to 6A , Figure 6B and Figure 6C A cross-sectional view is shown illustrating an intermediate stage in the formation of an electro-optic modulator according to some embodiments of the present disclosure. The corresponding process is also schematically reflected in, for example... Figure 17 The process flow 200 shown is as follows.

[0016] refer to Figure 1A A wafer 20 is formed. The wafer 20 may include a plurality of identical device dies 20', which may be formed as optical integrated circuit (PIC) dies. The wafer 20 includes a substrate 22 and an insulating layer 24 above the substrate 22. According to some embodiments, the substrate 22 may be formed of or include a silicon substrate, a dielectric substrate, etc. The insulating layer 24 may be formed of a low-refractive-index material such as silicon oxide.

[0017] A waveguide 26 is formed above the insulating layer 24. The corresponding process is shown as follows. Figure 17 Process 202 in the process flow 200 shown. According to some embodiments, waveguide 26 comprises a material having a high refractive index. For example, waveguide 26 may comprise lithium niobate. Waveguide 26 includes a substrate layer (substrate portion) 26B and protrusions 26P that protrude above the substrate layer 26B. The substrate layer 26B and the protrusions 26P are continuously bonded to each other, wherein there is no distinguishable interface between them.

[0018] According to some embodiments, the formation of waveguide 26 may include: depositing a blanket layer, such as a lithium niobate layer; recessing some portions of the blanket layer such that protrusions 26P are formed above an underlying portion that forms a substrate layer 26B. Additional etching processes may be performed to remove some portions of the underlying portion, thereby forming a waveguide 26 isolated from the surrounding environment.

[0019] Figure 1B A top view of an exemplary waveguide 26 according to some embodiments is shown. Waveguide 26 has a longitudinal direction in the X direction, wherein optical signals are also propagated in the X direction. Protrusions 26P merge at opposite ends and separate at locations between opposite ends. Figure 1A The structure shown can be derived from Figure 1B The section 1A-1A is obtained.

[0020] Figure 2 The formation of insulating layer 28 is shown. The corresponding process is shown as follows. Figure 17 Process 204 in the process flow 200 shown. According to some embodiments, the insulating layer 28 comprises a material having a refractive index lower than that of the waveguide 26. For example, the insulating layer 28 may be formed of or comprise silicon oxide.

[0021] According to some embodiments, the formation of the insulating layer 28 includes a blanket deposition process, which may include conformal deposition processes such as atomic layer deposition (ALD), chemical vapor deposition (CVD), etc. The portion of the insulating layer 28 offset from the protrusion 26P may have a flat top surface, and the portion of the insulating layer 28 overlapping and adjacent to the protrusion 26P may have a top surface and sidewalls parallel to the corresponding top surface and sidewalls of the protrusion 26P.

[0022] According to an alternative embodiment, the formation of the insulating layer 28 includes: depositing an insulating material to a level above the top surface of the protrusion 26P; performing a planarization process, such as a chemical mechanical polishing (CMP) process or a mechanical polishing process, to make the top surface of the insulating material flush with the surface; and then etching back the insulating material. According to these embodiments, the protrusion 26P is exposed.

[0023] Next, a conductive film 30 is formed over the insulating layer 28. The corresponding process is shown as follows. Figure 17 Process 206 in the process flow 200 shown. The conductive film 30 includes a portion located above and near the protrusion 26P. The portions of the conductive film 30 located on opposite sides of the protrusion 26P can be formed in pairs, with these pairs located on opposite sides of the corresponding protrusion 26P.

[0024] According to some embodiments, the conductive film 30 is formed below or flush with the top surface of the protrusion 26P, and above or flush with the bottom end of the protrusion 26P. In other words, the bottom surface of the conductive film 30 can be flush with the bottom end of the protrusion 26P (see reference). Figure 16 (Example in the text). The top surface of the conductive film 30 may be flush with or lower than the top surface of the protrusion 26P.

[0025] The conductive film 30 may include a metal and is therefore optionally referred to as a metal film, but other conductive materials such as doped silicon may also be used. According to some embodiments, the formation of the conductive film 30 may include deposition processes such as physical vapor deposition (PVD), CVD, plating, etc., and subsequent patterning processes by etching to define a pattern for the conductive film 30. The conductive film 30 may include Ta, TaN, Ti, TiN, W, Co, Cu, indium tin oxide (ITO), alloys thereof, and / or multilayers thereof.

[0026] The conductive film 30 can be formed from the homogeneous material discussed above. Alternatively, the conductive film 30 can have a composite structure including a barrier layer and a metal layer above the barrier layer, which is similar to the structure of the electrode 44. Figure 5 Except that the height (thickness) of the conductive film 30 is less than the height of the electrode 44 (e.g. Figure 6A Thickness T2 in the middle).

[0027] refer to Figure 3 An insulating layer 32 is formed. The corresponding process is shown as follows. Figure 17 Process 208 in the process flow 200 shown. Forming the insulating layer 32 may include: depositing an insulating material to a level above the top surface of the protrusion 26; and performing a planarization process such as a CMP process or a mechanical polishing process to make the top surface of the insulating material flush with the surface. The insulating material may include silicon oxide or other materials with a low refractive index, for example, a refractive index lower than that of the waveguide 26.

[0028] Next, a conductive film 34 is formed over the insulating layer 28. The corresponding process is shown as follows. Figure 17 Process 210 in the process flow 200 shown. The conductive film 34 includes portions that overlap with the metal film 30, and may include portions that overlap with the protrusions 26P. Some portions of the conductive film 34 are also vertically offset from the protrusions 26P. The portions of the conductive film 34 may be formed in pairs, with each pair overlapping the metal film pair and possibly overlapping one of the protrusions 26P. The midpoint of the closely positioned conductive film 34 may be vertically aligned (flush) with the center of the corresponding underlying protrusion 26P.

[0029] According to some embodiments, the spacing S1 between the conductive films 34 in the same pair can be smaller than the spacing S2 between the underlying metal films 30. The spacing S1 can also be less than, equal to, or greater than the width W1 of the protrusion 26P. Forming conductive films 34 with smaller spacing can improve the effect of confining the electric field, as shown in the reference... Figure 6A , Figure 6B and Figure 6C The discussion.

[0030] The conductive film 34 may comprise a metal or metal alloy and is therefore optionally referred to as a metal film, while other conductive materials such as silicon-doped materials may also be used. According to some embodiments, the formation of the conductive film 34 may include PVD, CVD, etc. The conductive film 34 may comprise Ta, TaN, Ti, TiN, W, Co, Cu, indium tin oxide (ITO), alloys thereof, and / or multilayers thereof. The material of the conductive film 34 may be the same as or different from the material of the metal film 30.

[0031] The conductive film 34 can be formed of the same homogeneous material as discussed above. Alternatively, the conductive film 34 can have a composite structure including a barrier layer and a metal layer above the barrier layer, which is similar to the structure of the electrode 44. Figure 5 ), except that the height (thickness) of the conductive film 34 is smaller than the height of the electrode 44 (e.g. Figure 6A Thickness T2 in the middle).

[0032] According to some embodiments, such as Figure 3As shown, metal films 30 and 34 are formed. According to an alternative embodiment, metal film 30 is formed, but metal film 34 is not formed. According to still some alternative embodiments, metal film 34 is formed instead of metal film 30.

[0033] Further reference Figure 3 An insulating layer 36 is formed. The corresponding process is shown as follows. Figure 17 Process 212 in process flow 200 shown. Formation of insulating layer 36 may include: depositing insulating material to a level above the top surface of metal film 34; and performing a planarization process such as CMP or mechanical polishing to make the top surface of the insulating material flush. The insulating material may include silicon oxide or other materials with a low refractive index. The materials of insulating layers 36, 32, and 28 may be the same as each other or different from each other in any combination. When insulating layers 36, 32, and 28 are formed of the same material, the interfaces between them may be distinguishable or may not be distinguishable.

[0034] refer to Figure 4 A patterning process is performed to form the opening 38. The corresponding process is shown as follows. Figure 17 Process 214 in the process flow 200 shown. According to some embodiments, the patterning process is performed by an anisotropic etching process to etch insulating layers 36, 32, and 28. After the patterning process, at least some portions of the metal film 30 are exposed, and the edges of the conductive film 34 are also exposed through the opening 38.

[0035] According to some embodiments, insulating layers 36 and 32 are formed of the same material, such as silicon oxide. Therefore, insulating layers 36 and 32 are shown merged together in the following figures, although they can also be formed of different materials. The interface between insulating layers 36 and 32 may or may not be distinguishable.

[0036] According to some embodiments, the exposed portion of the metal film 30 may be the edge of the metal film 30. In these embodiments, the metal film 30 is also etched during the etching process. According to an alternative embodiment, the exposed portion of the metal film 30 is not etched, and therefore both the top surface and the edges of the metal film 30 are exposed. The corresponding structure can be derived from... Figure 7 This is achieved. Furthermore, in the etching process, the metal film 34 is etched, exposing the edges of the metal film 34, while the top surface of the remaining portion of the metal film 34 is covered by the insulating layer 36.

[0037] The etching process can be stopped at the top surface of the insulating layer 28 (e.g.) Figure 4 As shown), or stop at the mid-level between the top and bottom surfaces of the insulating layer 28 (as can be seen from). Figure 9(Implementation). The etching process can also be stopped at the top surface of the conductive film 30 using the conductive film 30 as an etching stop layer. In these embodiments, the insulating layer 28 is exposed at the bottom surface of the opening 38, and the top surface of the conductive film 30 is exposed. The etching process can also be stopped at the top surface of the waveguide 26, and therefore, the top surface of the substrate layer 26P of the waveguide 26 is exposed.

[0038] refer to Figure 5 Electrodes 44S and 44G are formed in opening 38. The corresponding process is shown as follows. Figure 17 Process 216 in process flow 200 shown. Electrode 44G can be used as an electrical ground node. Electrode 44S is a signal node, on which a varying voltage is applied to apply an electrical signal. Electrodes 44S and 44G are also individually and collectively referred to as electrode 44. It should be understood that although signal nodes 44S are located between ground nodes 44G, according to an alternative embodiment, electrical ground nodes 44G may be located between signal nodes 44S.

[0039] According to some embodiments, electrode 44 may include a conductive pad 40, such as a diffusion barrier layer, an adhesive layer, etc. In some embodiments, forming electrode 44 includes: performing a blanket deposition process to form conductive pad 40; depositing a thin seed layer of copper or a copper alloy; and filling the remainder of opening 38 with a metallic material (this forms metallic region 42). The deposition process used to form conductive pad 40 and seed layer may include PVD, CVD, ALD, etc. Conductive pad 40 may include titanium, titanium nitride, tantalum, tantalum nitride, or other optional materials.

[0040] The filling process used to form the metal region 42 may include, for example, electroplating, electroless plating, deposition, etc. A CMP process may be performed to flush the surfaces of the conductive pad 40 and the filler material, and to remove excess material from the surface of the insulating layer 36.

[0041] Therefore, the electro-optic modulator 46 is formed to include waveguide 26, conductive films 30 and 34, and electrodes 44S and 44G. Throughout the description, electrode 44S, the metal film 30 electrically connected to electrode 44S, and the conductive film 34 are collectively referred to as (composite signal) electrode 44S'. Each of electrode 44G and the metal film 30 and metal film 34 electrically connected to the corresponding electrode 44G are collectively referred to as (composite ground) electrode 44G'.

[0042] In the operation of the electro-optic modulator 46, electrode 44S (and corresponding electrode 44S') can be used as a signal node, on which an electrical signal is applied. The electrical signal is modulated into an optical signal by the electro-optic modulator 46. Electrode 44G (and corresponding electrode 44G') can be used as a ground node, which is electrically grounded and / or may have a voltage VSS.

[0043] refer to Figure 6A The above structure is formed above the electro-optic modulator 46 to continue the formation of wafer 20. The corresponding process is shown as follows. Figure 17 Process 218 in the process flow 200 shown. The above structure may include a dielectric layer 48, optical components 50, and electrical connections (not shown) for conducting electrical signals to signal node 44S' and ground node 44G'.

[0044] The dielectric layer 48 may include silicon oxide, silicon oxynitride, etc. Optical devices 50 may include waveguides (such as nitride waveguides or silicon waveguides), grating couplers, edge couplers, etc. Electrical connections to the electro-optic modulator 46 may include contact plugs, metal wires, vias, etc., which can connect to signal node 44S' and ground node 44G'.

[0045] The next step can be to remove, such as Figure 5 The substrate 22 is shown in the figure. The corresponding process is shown as follows. Figure 17 Process 220 in the process flow 200 shown. The removal process may include: attaching a carrier (not shown) to the front side of the wafer 20; and performing a polishing process on the substrate 20. An implantation process may also be performed to form a layer (e.g., which may include hydrogen) in the substrate 20, followed by an annealing process, such that a bulk portion of the substrate 20 can be detached from the remaining layers of the substrate 20.

[0046] A polishing process can then be performed to remove the remaining layers of substrate 20, exposing insulating layer 24. Alternatively, the remaining layers of substrate 20 can be patterned to form optical devices, such as silicon waveguides, grating couplers, etc.

[0047] like Figure 6A As shown, the following structure is formed below the electro-optic modulator 46. The corresponding process is shown as follows. Figure 17 Process 222 is shown in process flow 200. The following structure may include a dielectric layer 54 and an optical device 56. The dielectric layer 54 may include silicon oxide, silicon oxynitride, etc. The optical device 54 may include waveguides (such as nitride waveguides or silicon waveguides), grating couplers, edge couplers, etc. The optical device 56 may also represent an optical device formed using the remainder of substrate 20.

[0048] After the upper and lower structures of wafer 20 are formed to complete the formation of wafer 20, wafer 20 can be sawn into individual device dies 20', which can be PIC dies.

[0049] Figure 6C A top view of an electro-optic modulator 46 according to some embodiments is shown. Figure 6CAs shown, the signal electrode 44S' is located on the side of each of the protrusions 26P opposite to one of the ground electrodes 44G'. Therefore, the signal electrode 44S' and the ground electrode 44G' can apply an electric field to both protrusions 26P. When the magnitude of the electric field changes due to the changing electrical signal, the refractive index of the protrusions 26P changes, and therefore the optical signal in the protrusions 26P changes (modulates) to reflect the electrical signal. The electrical signal is thus converted into an optical signal by the electro-optic modulator 46.

[0050] The magnitude of the optical signal modulation is related to the magnitude of the electric field. The electric field is directly proportional to the voltage difference between the signal electrode 44S' and the ground electrode 44G', and inversely proportional to the distance between them. (Reference) Figure 6A The electric field is applied by a pair of metal films 30 located on opposite sides of the protrusion 26P.

[0051] If a metal film 30 is not formed, the spacing between adjacent electrodes 44G and 44S will be S3 ( Figure 6A The formation of the metal film 30 reduces the spacing from S3 to S2, and thus increases the electric field without requiring a larger voltage. This improves the modulation efficiency. According to some embodiments, the spacing ratio S2 / S3 can be less than about 0.8, and can be in the range between about 0.3 and about 0.8.

[0052] Furthermore, the metal film 34 has the function of confining the electric field to the corresponding lower region and can be used as a reflector to reflect energy that may be scattered in the upward direction. Therefore, the metal film 34 also has the function of increasing the electric field applied to the waveguide 26 without the need to increase the voltage.

[0053] According to some embodiments, the thickness T1 of the metal film 30 is significantly smaller than the thickness T2 (height) of the electrodes 44S and 44G. The thickness ratio T1 / T2 can be less than about 0.1, and can be in the range between about 0.05 and 0.1. Therefore, although the metal film 30 has the function of reducing the spacing between the signal electrode and the ground electrode, because the metal film 30 is much thinner than the electrodes 44S and 44G, the metal film 30 has lower interference to the optical signal than the electrodes 44S and 44G.

[0054] Figure 6A It shows Figure 6C Section 6A-6A in the middle. Figure 6B It shows Figure 6C Section 6B-6B in the middle. In, for example... Figure 6B In the cross-section shown, a terminating resistor 60 is formed to electrically connect the ground electrode 44G' to the signal electrode 44S'. The terminating resistor 60 functions to adjust the impedance of the electro-optic modulator 46. Figure 6BAs shown, the terminating resistor 60 can be formed using the same material as the metal film 30 and in the same forming process as the metal film 30. The resistance of the terminating resistor 60 can be adjusted by changing the width W2 ( Figure 6C Adjustments are made according to these embodiments. Figure 6B As shown, the terminating resistor 60 is formed at a position above the metal film 30.

[0055] By forming the metal film 30, the size of the electro-optic modulator 46 can be reduced without adversely reducing its bandwidth. For example, with the formation of the metal film 30, the length L of the electro-optic modulator 46 ( Figure 6C The length of the electro-optic modulator can be reduced to about 60% to about 80% (even without forming the metal film 34), while still maintaining the bandwidth of the electro-optic modulator 46 without decreasing, or even increasing.

[0056] By forming metal films 30 and 34, the size of the electro-optic modulator 46 can be further reduced without adversely reducing its bandwidth. For example, with the formation of metal films 30 and 34, the length L ( Figure 6C The length of the electro-optic modulator can be reduced to about 25% and about 40% of that of the electro-optic modulators without metal films 30 and 34, while still maintaining the bandwidth of the electro-optic modulator 46 without reduction, or even increasing.

[0057] Figures 7 to 16 A view of an electro-optic modulator 46 according to an alternative embodiment is shown. Unless otherwise stated, the materials, structures, and fabrication processes of the components in these embodiments are substantially the same as those of the same components indicated by the same reference numerals in the foregoing embodiments. Throughout the description, the details regarding materials, structures, and fabrication processes provided in each embodiment can be applied to any other embodiments where applicable.

[0058] It should be understood that this approach can be adopted. Figures 7 to 16 Different structures are used to help match the optical characteristics of waveguide 26 with the electrical characteristics of electrodes 44G' and 44S'. Therefore, the performance of the electro-optic modulator can be optimized.

[0059] In addition, in such Figures 7 to 16 In some of the embodiments shown, the metal film 34 is shown as a dashed line to indicate that in each of these embodiments, the metal film 34 may or may not be formed.

[0060] Figure 7 An electro-optic modulator 46 according to an optional embodiment is shown. These embodiments are similar to, for example... Figure 6A , Figure 6B and Figure 6CIn the embodiments shown, the metal film 30 is partially located below and overlaps with the electrode 44. Furthermore, the metal film 34 is not formed. According to these embodiments, in the process of forming the opening 38 ( Figure 4 In the process, instead of etching the metal film 30, the metal film 30 serves as an etch stop layer and is not etched. The top surface of the exposed portion of the metal film 30 is exposed through the opening 38. The remaining processes for forming the wafer 20 and the PIC die 20' are essentially the same as discussed above and will not be repeated here.

[0061] Therefore, in the subsequent formation of electrode 44, conductive pad 40 can be conformally formed on the exposed top surface and sidewalls of metal film 30. Furthermore, since metal film 30 is partially exposed and electrode 44 is formed on the exposed portion, metal film 30 can also be considered as a portion of the seed layer used to form electrodes 44G' and 40S'.

[0062] Figure 8 An electro-optic modulator 46 according to an optional embodiment is shown. These embodiments are similar to, for example... Figure 6A , Figure 6B and Figure 6C In the embodiment shown, the metal film 30 is located entirely beneath the electrode 44. Furthermore, the metal film 30 extends laterally beyond the edges of electrodes 44S and 44G in the direction toward the protrusion 26P. In the direction away from the protrusion 26P, the metal film 30 may extend beyond the edge of electrode 44G, which faces away from the protrusion 26P. Alternatively, the metal film 30 may have an edge perpendicularly flush with the edge of the upper electrode 44G, which faces away from the protrusion 26P.

[0063] According to these embodiments, in the process of forming opening 38 ( Figure 4 In the process, instead of etching the metal film 30, the metal film 30 serves as an etch stop layer and is not etched. The top surface of the exposed portion of the metal film 30 is exposed through the opening 38. In other words, the opening 38 is limited to the area directly above the metal film 30. The remaining processes for forming the wafer 20 and the PIC die 20' are essentially the same as discussed above and will not be repeated here.

[0064] Therefore, in the subsequent formation of electrode 44, conductive pad 40 can be conformally formed on the exposed top surface of metal film 30. Furthermore, since electrode 44 is formed on the exposed portion of metal film 30, metal film 30 can also be considered as a seed layer for forming electrodes 44G' and 40S'.

[0065] According to some embodiments, because the opening 38 overlaps entirely with the metal film 30, the metal film 30 can be used as a seed layer for plating the metal region 42 without the need to form an additional barrier layer and seed layer. For example, when the metal region 42 is formed of or includes tungsten, cobalt, etc., the conductive pad 40 can be omitted, and the conductive pad 40 can also be used as a diffusion barrier. Furthermore, the metal material of the metal region 42 can be directly plated from the metal film 30 without the need to form an additional seed layer. The resulting electro-optic modulator 46 can be used with… Figure 8 The electro-optic modulator 46 shown is essentially the same, except that it does not form a conductive pad 40, and the entire metal region 42 can be formed using a homogeneous material, which can be a metallic material.

[0066] Figure 9 An electro-optic modulator 46 according to an optional embodiment is shown. These embodiments are similar to, for example... Figure 6A , Figure 6B and Figure 6C In the embodiment shown, the metal film 30 is formed at a level higher than the bottom of the electrode 44. The metal film 30 is correspondingly bonded to the electrode 44 via edge contacts.

[0067] According to these embodiments, in the process of forming opening 38 ( Figure 8 In the process, the metal film 30 can be etched, or alternatively, the metal film 30 can be left unetched, and the opening 38 is precisely aligned with the edge of the metal film 30. After the etching process that exposes the top surface of the insulating layer 28, an over-etching process can be performed, and the resulting opening 38 extends into the insulating layer 28.

[0068] According to some embodiments, the bottom end of the opening 38 may be horizontal between the top and bottom surfaces of the insulating layer 28. According to an alternative embodiment, etching may be performed through the insulating layer 28, exposing the top surface of the substrate layer 26B of the waveguide 26. The remaining processes for forming the wafer 20 and the PIC die 20' can be substantially the same as discussed above and will not be repeated herein.

[0069] Therefore, in the subsequent formation of electrode 44, electrode 44 extends to a level below the bottom surface of metal film 30. Electrode 44 can be separated from waveguide 26 by the remainder of insulating layer 28, or it can be in physical contact with substrate layer 26B of waveguide 26.

[0070] Figure 10A , Figure 10B and Figure 10C An electro-optic modulator 46 according to an optional embodiment is shown. Figure 10C A top view of the electro-optic modulator 46 according to these embodiments is shown. Figure 10A It shows Figure 10C The section 10A-10A in the middle, and Figure 10BIt shows Figure 10C Section 10B-10B in the example. These embodiments are similar to those shown below. Figure 6A , Figure 6B and Figure 6C In the embodiments shown, the metal film 30 is partially located below the electrode 44 and partially offset (vertically) from the electrode 44. These embodiments can also be combined with... Figure 7 The embodiments are essentially the same. Top views and additional cross-sectional views are also shown.

[0071] like Figure 10A The structure shown is similar to Figure 7 The structures shown are basically the same (except in Figure 10A A conductive film 34 can be formed in it, and details will not be repeated here. Figure 10B The cross-section shown illustrates the terminating resistor 60. The portion of the terminating resistor 60 and the portion of the metal film 30 extending directly below the electrode 44 are portions of a continuous metal film, and are made of the same material and formed in the same process.

[0072] Figure 11A , Figure 11B and Figure 11C An electro-optic modulator 46 according to an optional embodiment is shown. Figure 11C A top view of the electro-optic modulator 46 according to these embodiments is shown. Figure 11A It shows Figure 11C Section 11A-11A in the middle, and Figure 11B It shows Figure 11C Sections 11B-11B in the example. These embodiments are similar to those shown below. Figure 6A , Figure 6B and Figure 6C In the embodiment shown, the end portions of electrodes 44G and 44S have a longitudinal direction that turns from the X direction to the Y direction, and are therefore no longer directly above the protrusion 26P.

[0073] like Figure 11A The structure shown is similar to Figure 6A The structure is basically the same as that in other texts, and the details will not be repeated here. In other texts... Figure 11B In the cross-section shown, a terminating resistor 60 is formed. The terminating resistor 60 and the portion of the metal film 30 extending directly below the electrode 44 are discrete portions of the same metal film and are formed as part of the same planar film.

[0074] Figure 12A , Figure 12B , Figure 12C and Figure 12D An electro-optic modulator 46 according to an optional embodiment is shown. Figure 12A A cross-sectional view is shown, and Figure 12B , Figure 12Cand Figure 12D A top view of electrode 44 (and electrodes 44G' and 44S') according to various embodiments is shown. These embodiments are similar to those shown below. Figure 6A , Figure 6B and Figure 6C The embodiment shown, in addition to further patterning the metal film 30 to form openings therein, should be understood that... Figure 12B , Figure 12C and Figure 12D Some exemplary patterns are shown, and all other applicable patterns are also within the scope of embodiments of this disclosure.

[0075] Patterning of the metal film 30 can help reduce the pattern loading effect during the formation of the metal film 30 (e.g., Figure 3 (The process shown in the diagram). This structure helps to adjust the electric field between electrodes 44 and helps to match the optical characteristics of the electro-optic modulator 46. Therefore, the performance of the electro-optic modulator 46 is improved.

[0076] Figure 13 An electro-optic modulator 46 according to an optional embodiment is shown. These embodiments are similar to, for example... Figure 6A , Figure 6B and Figure 6C In the embodiment shown, the substrate layer 26B of waveguide 26 can be divided into two discrete portions, instead of being formed as a continuous layer extending from the left edge of the left ground electrode 44G to the right edge of the right ground electrode 44G. Each of the two discrete portions can be located directly beneath the corresponding protrusion 26P and extend laterally beyond the edge of the corresponding protrusion 26P. This structure helps to match the optical characteristics of waveguide 26 with the electrical characteristics of electrodes 44G' and 44S'. Therefore, the performance of electro-optic modulator 46 is improved.

[0077] Figure 14 An electro-optic modulator 46 according to an optional embodiment is shown. These embodiments are similar to, for example... Figure 6A , Figure 6B and Figure 6C In the embodiment shown, the substrate 26B of waveguide 26 can be divided into two discrete parts. Furthermore, the edges of the protrusion 26P and the substrate 26B can be vertically flush. This structure helps to match the optical characteristics of waveguide 26 with the electrical characteristics of electrodes 44G' and 44S'. Therefore, the performance of the electro-optic modulator 46 is improved.

[0078] Figure 15 An electro-optic modulator 46 according to an optional embodiment is shown. These embodiments are similar to, for example... Figure 6A , Figure 6B and Figure 6CThe embodiment shown, in addition to forming a slot 62 in the waveguide 26 by etching, for example, allows for perpendicular alignment with the metal film 30 and / or the electrode 44. The formation of the slot 62 facilitates matching the optical characteristics of the waveguide 26 with the electrical characteristics of the electrodes 44G' and 44S'. This improves the performance of the electro-optic modulator 46.

[0079] Figure 16 An electro-optic modulator 46 according to an optional embodiment is shown. These embodiments are similar to, for example... Figure 6A , Figure 6B and Figure 6C The embodiment shown in the figure has the metal film 30 in physical contact with the waveguide 26 to simplify the manufacturing process.

[0080] The embodiments of this disclosure have several advantageous features. By forming a metal film to reduce the spacing between the signal electrode and the ground electrode, the electric field applied to the waveguide can be increased. This improves the electro-optic modulation efficiency.

[0081] According to some embodiments of this disclosure, the method includes: forming a waveguide including a substrate layer and a protrusion located above the substrate layer and bonded to the substrate layer; forming a first metal film and a second metal film on opposite sides of the protrusion; forming an insulating layer above the first metal film and the second metal film; forming a first electrode electrically coupled to the first metal film next to the protrusion, wherein the first electrode is located in the insulating layer, and wherein the first metal film includes a first portion located between the first electrode and the protrusion; and forming a second electrode electrically coupled to the second metal film next to the protrusion, wherein the second electrode is located in the insulating layer, wherein the second metal film includes a second portion located between the second electrode and the protrusion, and wherein the first electrode and the second electrode are configured to apply an electric field to the protrusion.

[0082] In one embodiment, after etching the insulating layer, the portion of the first metal film directly below the first opening is also etched. In another embodiment, forming the first electrode includes: depositing a diffusion barrier; depositing a metal material; and performing a planarization process to remove the portions of the diffusion barrier and the metal material located above the insulating layer.

[0083] In an embodiment, the method further includes: forming a first conductive film and a second conductive film that overlap with the first metal film and the second metal film respectively, wherein, after forming the first electrode and the second electrode, the first electrode and the second electrode are electrically connected to the first conductive film and the second conductive film respectively.

[0084] In one embodiment, the first metal film and the second metal film are spaced apart by a first lateral distance, and the first conductive film and the second conductive film are spaced apart by a second lateral distance smaller than the first lateral distance. In another embodiment, the first metal film overlaps with a first portion of the protrusion, and the second metal film overlaps with a second portion of the protrusion. In yet another embodiment, the waveguide is formed over a substrate, and the method further includes: removing the substrate; and forming an optical device on the side of the waveguide opposite to the insulating layer.

[0085] In one embodiment, the method further includes forming a terminating resistor, wherein the terminating resistor is formed using a common process shared with the first and second metal films. In another embodiment, the terminating resistor is formed directly over and across the protrusion. In yet another embodiment, the terminating resistor is formed as a planar resistor coplanar with the first and second metal films. In a third embodiment, a first portion of the first metal film is patterned.

[0086] According to some embodiments of this disclosure, the method includes: forming a waveguide including a substrate layer and a protrusion located above the substrate layer; forming a first metal film and a second metal film above the substrate layer and below the top of the protrusion, wherein the first metal film is located on the side of the protrusion opposite to the second metal film and is spaced apart from the second metal film by a first interval; and forming a ground electrode and a signal electrode respectively connected to the first metal film and the second metal film, wherein the ground electrode and the signal electrode are spaced apart by a second interval greater than the first interval, and wherein the first metal film, the second metal film, the ground electrode, the signal electrode and the waveguide together form an electro-optic modulator.

[0087] In this embodiment, the first metal film and the second metal film are formed in a first forming process, and the ground electrode and the signal electrode are formed in a second forming process independent of the first forming process. In this embodiment, the first metal film and the second metal film have a height smaller than that of the ground electrode and the signal electrode.

[0088] In one embodiment, the method further includes forming a first conductive film and a second conductive film over a first metal film and a second metal film, wherein the first conductive film and the second conductive film are electrically connected to a ground electrode and a signal electrode, respectively. In another embodiment, the first metal film physically contacts the top surface of the substrate layer of the waveguide.

[0089] According to some embodiments of this disclosure, the structure includes: an insulating layer; a waveguide located above the insulating layer, wherein the waveguide includes a substrate layer and a protrusion located above the substrate layer and bonded to the substrate layer; a first electrode and a second electrode located on opposite sides of the protrusion; a first metal film electrically connected to the first electrode, wherein a first portion of the first metal film is laterally located between the first electrode and the protrusion; and a second metal film electrically connected to the second electrode, wherein a second portion of the second metal film is laterally located between the second electrode and the protrusion. In embodiments, the first electrode is electrically grounded, and the second electrode is connected to a signal node. In embodiments, the first metal film has a smaller height than the first electrode.

[0090] Some embodiments of this application provide a method for forming a semiconductor structure, comprising: forming a waveguide including a substrate layer and a protrusion located above the substrate layer and bonded to the substrate layer; forming a first metal film and a second metal film on opposite sides of the protrusion; depositing an insulating layer over the first metal film and the second metal film; etching the insulating layer to form a first opening and a second opening in the insulating layer, wherein the first opening and the second opening are located on opposite sides of the protrusion, and wherein the first metal film and the second metal film are respectively exposed to the first opening and the second opening; forming a first electrode in the first opening, wherein the first metal film includes a first portion located between the first electrode and the protrusion; and forming a second electrode in the second opening, wherein the second metal film includes a second portion located between the second electrode and the protrusion, and wherein the first electrode and the second electrode are configured to apply an electric field to the protrusion.

[0091] In some embodiments, the first metal film and the second metal film are exposed to the first opening and the second opening, respectively, and the method further includes filling the first opening and the second opening with a conductive material to form the first electrode and the second electrode. In some embodiments, after etching the insulating layer, the portion of the first metal film directly below the first opening is also etched. In some embodiments, forming the first electrode includes: depositing a diffusion barrier; depositing a metal material; and performing a planarization process to remove the portions of the diffusion barrier and the metal material above the insulating layer. In some embodiments, the method further includes: forming a first conductive film and a second conductive film that overlap the first metal film and the second metal film, respectively, wherein after forming the first electrode and the second electrode, the first electrode and the second electrode are electrically connected to the first conductive film and the second conductive film, respectively. In some embodiments, the first metal film and the second metal film are spaced apart by a first lateral distance, and the first conductive film and the second conductive film are spaced apart by a second lateral distance smaller than the first lateral distance. In some embodiments, the first metal film overlaps with a first portion of the protrusion, and the second metal film overlaps with a second portion of the protrusion. In some embodiments, the waveguide is formed above a substrate, and the method further includes: removing the substrate; and forming an optical device on the side of the waveguide opposite to the insulating layer. In some embodiments, the method further includes forming a terminating resistor, wherein the terminating resistor is formed using a common process shared with the first metal film and the second metal film. In some embodiments, the terminating resistor is formed directly over the protrusion and spans over the protrusion. In some embodiments, the terminating resistor is formed as a planar resistor in the same plane as the first metal film and the second metal film. In some embodiments, the first portion of the first metal film is patterned.

[0092] Other embodiments of this application provide a method for forming a semiconductor structure, comprising: forming a waveguide including a substrate layer and a protrusion located above the substrate layer; depositing an insulating layer on the waveguide; performing a deposition process and a patterning process to form a first metal film and a second metal film, wherein the first metal film and the second metal film are above the substrate layer and below the top of the protrusion, and wherein the first metal film is located on the side of the protrusion opposite to the second metal film and spaced apart from the second metal film by a first interval; depositing an additional insulating layer above the first metal film and the second metal film; and forming a ground electrode and a signal electrode respectively connected to the first metal film and the second metal film in the additional insulating layer, wherein the ground electrode and the signal electrode are spaced apart by a second interval greater than the first interval, and wherein the first metal film, the second metal film, the ground electrode, the signal electrode and the waveguide together form an electro-optic modulator.

[0093] In some embodiments, the first metal film and the second metal film are formed in a first forming process, and the ground electrode and the signal electrode are formed in a second forming process independent of the first forming process. In some embodiments, the first metal film and the second metal film have a height smaller than that of the ground electrode and the signal electrode. In some embodiments, the method further includes forming a first conductive film and a second conductive film over the first metal film and the second metal film, wherein the first conductive film and the second conductive film are electrically connected to the ground electrode and the signal electrode, respectively. In some embodiments, the first metal film physically contacts the top surface of the substrate layer of the waveguide.

[0094] Further embodiments of this application provide a semiconductor structure including: an insulating layer; a waveguide located above the insulating layer, wherein the waveguide includes a substrate layer and a protrusion located above the substrate layer and bonded to the substrate layer; a first electrode and a second electrode located on opposite sides of the protrusion; a first metal film electrically connected to the first electrode; and a second metal film electrically connected to the second electrode.

[0095] In some embodiments, the first electrode is electrically grounded, and the second electrode is connected to a signal node. In some embodiments, the first metal film includes a first portion laterally located between the first electrode and the protrusion, and the second metal film includes a second portion laterally located between the second electrode and the protrusion.

[0096] The foregoing outlines features of several embodiments to enable those skilled in the art to better understand various aspects of the embodiments of this disclosure. Those skilled in the art should understand that they can readily use the embodiments of this disclosure as a basis to design or modify other processes and structures for performing the same purposes and / or achieving the same advantages as the embodiments described herein. Those skilled in the art should also recognize that such equivalent constructions do not depart from the spirit and scope of the embodiments of this disclosure, and that various changes, substitutions, and alterations can be made herein without departing from the spirit and scope of the embodiments of this disclosure.

Claims

1. A method for forming a semiconductor structure, comprising: A waveguide is formed, the waveguide including a substrate layer and a protrusion located above the substrate layer and coupled to the substrate layer; A first metal film and a second metal film are formed on opposite sides of the protrusion; An insulating layer is deposited over the first metal film and the second metal film; The insulating layer is etched to form a first opening and a second opening in the insulating layer, wherein the first opening and the second opening are located on opposite sides of the protrusion, and wherein the first metal film and the second metal film are exposed to the first opening and the second opening, respectively; A first electrode is formed in the first opening, wherein the first metal film includes a first portion located between the first electrode and the protrusion; and A second electrode is formed in the second opening, wherein the second metal film includes a second portion located between the second electrode and the protrusion, and wherein the first electrode and the second electrode are configured to apply an electric field to the protrusion.

2. The method according to claim 1, wherein, The first metal film and the second metal film are exposed to the first opening and the second opening, respectively, and the method further includes filling the first opening and the second opening with a conductive material to form the first electrode and the second electrode.

3. The method according to claim 2, wherein, After etching the insulating layer, the portion of the first metal film directly below the first opening is also etched.

4. The method according to claim 1, wherein, Forming the first electrode includes: Deposition diffusion barrier; Deposited metallic materials; and A planarization process is performed to remove the portion of the diffusion barrier and the metal material located above the insulating layer.

5. The method according to claim 1, further comprising: A first conductive film and a second conductive film are formed, which overlap with the first metal film and the second metal film, respectively. After the first electrode and the second electrode are formed, the first electrode and the second electrode are electrically connected to the first conductive film and the second conductive film, respectively.

6. The method according to claim 5, wherein, The first metal film and the second metal film are spaced apart by a first lateral distance, and the first conductive film and the second conductive film are spaced apart by a second lateral distance smaller than the first lateral distance.

7. The method according to claim 5, wherein, The first metal film overlaps with a first portion of the protrusion, and the second metal film overlaps with a second portion of the protrusion.

8. The method according to claim 1, wherein, The waveguide is formed above the substrate, and the method further includes: Remove the substrate; and An optical device is formed on the side of the waveguide opposite to the insulating layer.

9. A method for forming a semiconductor structure, comprising: A waveguide is formed, the waveguide including a substrate layer and a protrusion located above the substrate layer; An insulating layer is deposited on the waveguide; A deposition process and a patterning process are performed to form a first metal film and a second metal film, wherein the first metal film and the second metal film are above the substrate layer and below the top of the protrusion, and wherein the first metal film is located on the side of the protrusion opposite to the second metal film and is spaced apart from the second metal film by a first gap; An additional insulating layer is deposited over the first metal film and the second metal film; and A ground electrode and a signal electrode are formed in the additional insulating layer, respectively connected to the first metal film and the second metal film, wherein the ground electrode and the signal electrode are spaced apart by a second interval greater than the first interval, and wherein the first metal film, the second metal film, the ground electrode, the signal electrode and the waveguide together form an electro-optic modulator.

10. A semiconductor structure, comprising: Insulating layer; A waveguide, located above the insulating layer, wherein the waveguide includes a substrate layer and a protrusion located above the substrate layer and bonded to the substrate layer; The first electrode and the second electrode are located on opposite sides of the protrusion; A first metal film, electrically connected to the first electrode; and The second metal film is electrically connected to the second electrode.

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