Optical phase shifter and method for manufacturing the same

Abstract

An optical phase shifter is provided. The optical phase shifter includes a substrate, a first waveguide layer, a second waveguide layer, a metal layer and a third waveguide layer. The first waveguide layer is located on the substrate. The second waveguide layer is located on the first waveguide layer. The metal layer is located on the second waveguide layer and is configured to receive a control voltage. The third waveguide layer is located on the metal layer. A waveguide structure formed by the second waveguide layer and the third waveguide layer receives light coupled out from the first waveguide layer. The light forms an optical field confinement in the third waveguide layer. The third waveguide layer has a refractive index that changes with the control voltage to modulate the phase of the light.

Description

Technical Field

[0001] The present disclosure relates to the technical field of integrated photonics, in particular to the technical field of optical phased arrays, and specifically to an optical phase shifter and a method for manufacturing the same. Background Art

[0002] Optical phase shifters are the core components of optical phased arrays. With the vigorous development of silicon-based integrated optical phased array technology, the array size of high-performance optical phased arrays has expanded to hundreds to thousands of channels. Ultra-low insertion loss and low power consumption optical phase shifters can greatly increase the output light power of optical phased arrays and reduce the total driving power consumption, and therefore have become the core technology for the industrialization of silicon-based integrated optical phased arrays.

[0003] At present, the commonly used phase shifters on silicon-based platforms can be divided into two types: thermally tunable phase shifters based on thermo-optical effect and PN anti-shift phase shifters based on carrier dispersion. Thermally tunable phase shifters achieve phase modulation by heating silicon waveguides, and their insertion loss is negligible, but the power consumption of the phase shifter is relatively large. Although the power consumption of the PN anti-shift phase shifter is very low, the light field will introduce a large insertion loss when passing through the area where the carriers are distributed. These two phase shifters may be difficult to apply to ultra-large-scale integration due to their respective shortcomings in power consumption or insertion loss, and thus may be difficult to meet the demand for high-performance silicon-based integrated optical phased arrays. Research on optical phase shifters that can provide ultra-low insertion loss, low power consumption and high integration is still one of the current hot topics. Summary of the invention

[0004] The present disclosure provides an optical phase shifter and a method for manufacturing the same.

[0005] According to one aspect of the present disclosure, an optical phase shifter is provided. The optical phase shifter includes a substrate, a first waveguide layer, a second waveguide layer, a metal layer, and a third waveguide layer. The first waveguide layer is located on the substrate. The second waveguide layer is located on the first waveguide layer. The metal layer is located on the second waveguide layer and is configured to receive a control voltage. The third waveguide layer is located on the metal layer. The waveguide structure formed by the second waveguide layer and the third waveguide layer receives light coupled out from the first waveguide layer. The light forms an optical field confinement in the third waveguide layer. The third waveguide layer has a refractive index that changes with the control voltage to modulate the phase of the light.

[0006] According to another aspect of the present disclosure, a method for manufacturing an optical phase shifter is provided. The method includes: forming a first waveguide layer on a substrate; forming a second waveguide layer on the first waveguide layer; forming a metal layer on the second waveguide layer, the metal layer being configured to receive a control voltage; and forming a third waveguide layer on the metal layer. The waveguide structure formed by the second waveguide layer and the third waveguide layer receives the light coupled out from the first waveguide layer. The light forms an optical field confinement in the third waveguide layer. The third waveguide layer has a refractive index that changes with the control voltage to modulate the phase of the light.

[0007] According to one or more embodiments of the present disclosure, an optical phase shifter that is compatible with a CMOS process and has low insertion loss may be provided.

[0008] These and other aspects of the disclosure will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Further details, features and advantages of the present disclosure are disclosed in the following description of exemplary embodiments in conjunction with the accompanying drawings, in which:

[0010] Figure 1 A cross-sectional view along a first direction of an optical phase shifter according to an exemplary embodiment of the present disclosure is shown.

[0011] Figure 2A and Figure 2B sectional views of the optical phase shifter along the second direction according to exemplary embodiments are respectively shown, wherein Figure 2A Shown along Figure 1 A cross-sectional view taken along line AA', and Figure 2B Shown along Figure 1 A cross-sectional view taken along line BB'.

[0012] Figures 3A to 3D A method of manufacturing an optical phase shifter according to an exemplary embodiment of the present disclosure is shown.

[0013] Figures 4A to 4C A cross-sectional view and a top view of an optical phase shifter according to another exemplary embodiment along a first direction and a second direction are respectively shown, wherein a mode field distribution diagram is shown in conjunction with the top view.

[0014] Figure 5 A graph illustrating insertion loss simulation results according to an exemplary embodiment. DETAILED DESCRIPTION

[0015] It will be understood that, although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and / or parts in this article, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish an element, component, region, layer or part from another element, component, region, layer or part. Therefore, the first element, component, region, layer or part discussed below may be referred to as the second element, component, region, layer or part without departing from the teaching of the present disclosure.

[0016] Spatially relative terms such as "below," "beneath," "lower," "below," "above," "upper," and the like may be used herein for ease of description to describe the relationship of one element or feature to another element or feature as illustrated in the figure. It will be understood that these spatially relative terms are intended to cover different orientations of the device in use or operation in addition to the orientation depicted in the figure. For example, if the device in the figure is flipped, the element described as "below other elements or features" or "below other elements or features" or "below other elements or features" will be oriented to "above other elements or features." Therefore, the exemplary terms "below" and "below" can cover both orientations above and below. Terms such as "before" or "before" and "after" or "followed by" can be similarly used, for example, to indicate the order in which light passes through the elements. The device can be oriented in other ways (rotated 90 degrees or in other orientations) and the spatially relative descriptors used in this article are interpreted accordingly. In addition, it will also be understood that when a layer is referred to as being “between two layers,” it can be the only layer between the two layers, or one or more intervening layers may also be present.

[0017] The terms used herein are only for the purpose of describing a specific embodiment and are not intended to limit the present disclosure. As used herein, the singular forms "one", "one" and "the" are intended to also include plural forms, unless the context clearly indicates otherwise. It will be further understood that the terms "include" and / or "comprise" specify the existence of the features, integral bodies, steps, operations, elements and / or parts when used in this specification, but do not exclude the existence of one or more other features, integral bodies, steps, operations, elements, parts and / or their groups or add one or more other features, integral bodies, steps, operations, elements, parts and / or their groups. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items, and the phrase "at least one of A and B" refers to only A, only B, or both A and B.

[0018] It will be understood that when an element or layer is referred to as being "on another element or layer," "connected to another element or layer," "coupled to another element or layer," or "adjacent to another element or layer," it may be directly on another element or layer, directly connected to another element or layer, directly coupled to another element or layer, or directly adjacent to another element or layer, or there may be intermediate elements or layers. Conversely, when an element is referred to as being "directly on another element or layer," "directly connected to another element or layer," "directly coupled to another element or layer," or "directly adjacent to another element or layer," there are no intermediate elements or layers. However, in no case should "on..." or "directly on..." be interpreted as requiring that one layer completely cover the layer below.

[0019] Embodiments of the present disclosure are described herein with reference to schematic illustrations (and intermediate structures) of idealized embodiments of the present disclosure. As such, variations in the illustrated shapes, for example as a result of manufacturing techniques and / or tolerances, should be expected. Therefore, embodiments of the present disclosure should not be interpreted as being limited to the specific shapes of the zones illustrated herein, but should include shape deviations, for example, due to manufacturing. Therefore, the zones illustrated in the figures are schematic in nature, and their shapes are not intended to illustrate the actual shapes of the zones of the device and are not intended to limit the scope of the present disclosure.

[0020] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present disclosure belongs. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the relevant art and / or the context of this specification, and will not be interpreted in an idealized or overly formal sense, unless explicitly defined as such herein.

[0021] As used herein, the term "substrate" may refer to the substrate of a cut wafer, or may indicate the substrate of an uncut wafer. Similarly, the terms chip and die may be used interchangeably unless such interchange would cause a conflict. It should be understood that the term "layer" includes a thin film and should not be interpreted as indicating vertical or horizontal thickness unless otherwise specified.

[0022] In the related art, crystals with electro-optical effect (such as lithium niobate, etc.) have been used as waveguides to achieve phase modulation of light based on electro-optical modulation. However, for silicon-based platforms, integrating such heterogeneous waveguides on silicon-based waveguides such as silicon may have problems with process compatibility and complexity. For example, the etching, bonding process of such heterogeneous waveguides and the subsequent process for manufacturing metal electrodes are not compatible with the CMOS (complementary metal oxide semiconductor) process used in silicon-based platforms, and the etching process of such heterogeneous waveguides is also difficult. In addition, when considering germanium silicon photodetectors (which can be used in conjunction with optical phased arrays to convert optical signals into electrical signals), how to make them compatible with the production of germanium silicon photodetectors is also an issue that needs to be considered urgently.

[0023] In view of at least one of the above technical problems, according to one aspect of an embodiment of the present disclosure, an optical phase shifter and a manufacturing method thereof are proposed. The embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0024] Figure 1 A cross-sectional view of an optical phase shifter 100 along a first direction according to an exemplary embodiment of the present disclosure is shown.

[0025] exist Figure 1 In the figure, the first direction refers to the x-axis direction in the three-dimensional coordinate system composed of the x-axis, the y-axis and the z-axis, which may also be referred to as the "lateral direction" hereinafter. The z-axis direction perpendicular to the x-axis direction may also be referred to as the "vertical direction" hereinafter.

[0026] like Figure 1 As shown, the optical phase shifter 100 includes a substrate 110 , a first waveguide layer 130 , a second waveguide layer 140 , a metal layer 150 , and a third waveguide layer 160 .

[0027] The first waveguide layer 130 is located on the substrate 110. The second waveguide layer 140 is located on the first waveguide layer 130. The metal layer 150 is located on the second waveguide layer 140 and is configured to receive a control voltage. The third waveguide layer 160 is located on the metal layer 150. The waveguide structure formed by the second waveguide layer 140 and the third waveguide layer 160 receives the light coupled out from the first waveguide layer 130. The light forms an optical field confinement in the third waveguide layer 160.

[0028] The third waveguide layer 160 has a refractive index that varies with a control voltage to modulate the phase of light.

[0029] According to the optical phase shifter of the embodiment of the present disclosure, on the one hand, a three-layer waveguide structure can be designed to provide sufficient device spacing to be compatible with the production of germanium silicon photodetectors, while ensuring that the three-layer waveguide structure only causes low insertion loss. On the other hand, the positions of the third waveguide layer and the metal layer in the optical phase shifter can be designed to ensure that the overall manufacturing process of the optical phase shifter is compatible with the CMOS process, and reduce the process complexity caused by the third waveguide layer and the metal layer.

[0030] Various aspects of the optical phase shifter 100 according to an embodiment of the present disclosure are described in detail below.

[0031] The substrate 110 may include a silicon substrate. In an example, the optical phase shifter 100 may be entirely formed on a SOI (silicon-on-insulator) wafer, which may include the substrate 110 and a buried oxide layer 120 located on the substrate 110. The buried oxide layer 120 may include silicon dioxide (SiO2).

[0032] The first waveguide layer 130 may be located on the buried oxide layer 120 .

[0033] According to some embodiments, the first waveguide layer 130 may include silicon (Si). In an example, the first waveguide layer 130 may be formed using the top silicon layer of the SOI wafer. Therefore, the first waveguide layer 130 using silicon may be fabricated in a manner compatible with the SOI chip, thereby facilitating the fabrication of the optical phase shifter 100 to be compatible with the CMOS process.

[0034] The first waveguide layer 130 may be configured as a light input port of the optical phase shifter 100. Light from a light emitting device such as a laser may be input through the first waveguide layer 130 and transmitted in the first waveguide layer 130 so that the light can enter the optical phase shifter 100 for phase modulation. Figure 1 A transmission area 101a for light input is schematically shown.

[0035] Similarly, the first waveguide layer 130 may also be configured as a light output port of the optical phase shifter 100. The light processed by the optical phase shifter 100 may be transmitted in the first waveguide layer 130 and output from the first waveguide layer 130 to a subsequent device such as a germanium silicon photodetector. Figure 1 A transmission region 101b for light output is schematically shown.

[0036] Understandably, due to Figure 1 The cross-sectional view of the optical phase shifter 100 is shown in a symmetrical manner, so the roles of the transmission region 101a and the transmission region 101b can be interchanged, that is, the transmission region 101b can be used for light input, and the transmission region 101a can be used for light output.

[0037] According to some embodiments, the first waveguide layer 130 may include a first coupling region 102 a via which light transmitted in the first waveguide layer 130 may be coupled out of the first waveguide layer 130 .

[0038] Specifically, the light transmitted in the transmission region 101 a of the first waveguide layer 130 may be coupled out of the first waveguide layer 130 via the first coupling region 102 a to be coupled to the waveguide structure jointly constituted by the second waveguide layer 140 and the third waveguide layer 160 .

[0039] As described above, the first waveguide layer 130 can couple input light into the optical phase shifter 100 to be phase modulated by the optical phase shifter 100. Therefore, by providing a coupling region for light coupling in the first waveguide layer 130, good light coupling efficiency can be provided between the first waveguide layer 130 and the waveguide structure formed by the second waveguide layer 140 and the third waveguide layer 160 located thereon, thereby facilitating light coupling into the optical phase shifter 100.

[0040] Similarly, the first waveguide layer 130 may further include a third coupling region 102b, through which light from the waveguide structure jointly constituted by the second waveguide layer 140 and the third waveguide layer 160 may be coupled into the first waveguide layer 130. Specifically, light from the waveguide structure jointly constituted by the second waveguide layer 140 and the third waveguide layer 160 may be coupled into the first waveguide layer 130 via the first coupling region 102b, so as to be output to a subsequent device, such as a germanium silicon photodetector, via the transmission region 101b.

[0041] In an example, each of the first coupling region 102a and the third coupling region 102b may be located below the waveguide structure jointly constituted by the second waveguide layer 140 and the third waveguide layer 160 in the vertical direction to provide coupling of light between the first waveguide layer 130 and the waveguide structure. In other words, the waveguide structure jointly constituted by the second waveguide layer 140 and the third waveguide layer 160 may at least partially cover each of the first coupling region 102a and the third coupling region 102b in the vertical direction. It should be noted that the term "covering" used herein is intended to indicate an overlapping relationship between two layers in the vertical direction, and does not limit whether the two layers are in direct contact or whether there are other layers between them.

[0042] In an example, an interlayer dielectric layer for isolation may be provided between the first coupling region 102a and the third coupling region 102b. The interlayer dielectric layer may include silicon dioxide (SiO2). Figure 1 For simplicity of illustration, the interlayer dielectric layer and the buried oxide layer 120 are shown as a whole, but those skilled in the art will appreciate that the interlayer dielectric layer may be an independent layer.

[0043] According to some embodiments, the length of the first coupling region 102a may be in the range of 50 um to 1000 um along the direction in which the light is transmitted, and the width may gradually decrease along the length direction. In this way, it may be helpful to couple the light transmitted in the first waveguide layer 130 to the waveguide structure formed by the second waveguide layer 140 and the third waveguide layer 160 via the first coupling region 102a with a higher coupling efficiency.

[0044] In an example, the first coupling region 102a may be patterned into a cone, the length of which is along the direction in which light is transmitted, and the width of which gradually decreases along the length direction (also referred to as an inverted cone, which will be referred to hereinafter). Figure 4C The top view of FIG. 1 shows the inverted cone shape). Here, as Figure 1 As shown in FIG. 1 , the length may be relative to the x-axis direction, and the width may be relative to the y-axis direction which is perpendicular to the x-axis direction on a horizontal plane. That is, the width of the first coupling region 102a may be along Figure 1 The width of the tapered first coupling region 102a of the first waveguide layer 130 decreases at the coupling end, and the mode field limiting capability is weakened. When the width of the waveguide structure formed by the second waveguide layer 140 and the third waveguide layer 160 located on the first waveguide layer 130 is relatively large, the light coupled out of the first waveguide layer 130 can be coupled into the waveguide structure.

[0045] In an example, the first coupling region 102 a may be a portion of the first waveguide layer 130 that is covered by a waveguide structure formed by the second waveguide layer 140 and the third waveguide layer 160 .

[0046] According to some embodiments, the second waveguide layer 140 may include at least one of silicon nitride (Si3N4) or polysilicon (poly-Si). The refractive index of silicon nitride is about 1.9, and the refractive index of polysilicon is about 3.4. In the case where the cladding of the second waveguide layer 140 (i.e., the interlayer dielectric layer located above and below the second waveguide layer 140) is silicon dioxide (refractive index is about 1.4), the second waveguide layer 140 has a higher refractive index relative to the cladding, and thus helps to play a role in light field confinement. This is because the light field can be confined in a medium with a higher refractive index, and the medium with a higher refractive index than the surrounding environment is the "optical waveguide" that confines the light field.

[0047] In an example, a germanium-silicon photodetector to be used later may be formed at a position corresponding to the height of the second waveguide layer 140. Therefore, the optical phase shifter 100 is compatible with the fabrication of the germanium-silicon photodetector.

[0048] In an example, an interlayer dielectric layer for isolation may also be provided between the second waveguide layer 140 and the first waveguide layer 130. The interlayer dielectric layer may include silicon dioxide (SiO2). Figure 1 For simplicity of illustration, the interlayer dielectric layer is shown as a whole with the buried oxide layer 120 and the interlayer dielectric layer between the first coupling region 102a and the third coupling region 102b, but those skilled in the art will appreciate that the interlayer dielectric layer may be an independent layer.

[0049] According to some embodiments, the thickness of the second waveguide layer 140 may be in the range of 50 nm to 1000 nm, which may help the waveguide structure formed by the second waveguide layer 140 and the third waveguide layer 160 to support light field transmission, thereby helping the overall waveguide structure to cause only low insertion loss.

[0050] According to some embodiments, the second waveguide layer 140 may include a second coupling region 103 a , and the light coupled out from the first waveguide layer 130 may be coupled into the waveguide structure formed by the second waveguide layer 140 and the third waveguide layer 160 via the second coupling region 103 a .

[0051] As described above, the light transmitted in the first waveguide layer 130 can be coupled out of the first waveguide layer 130 via the first coupling region 102a to be coupled to the waveguide structure jointly constituted by the second waveguide layer 140 and the third waveguide layer 160. Therefore, by providing a coupling region for light coupling in the second waveguide layer 140, good light coupling efficiency can be provided between the first waveguide layer 130 and the waveguide structure jointly constituted by the second waveguide layer 140 and the third waveguide layer 160, thereby facilitating light coupling into the optical phase shifter 100.

[0052] Similarly, the second waveguide layer 140 may further include a fourth coupling region 103 b , and light coupled out of the waveguide structure formed by the second waveguide layer 140 and the third waveguide layer 160 may be coupled into the first waveguide layer 130 via the fourth coupling region 103 b .

[0053] According to some embodiments, the metal layer 150 may include at least one of aluminum (Al), copper (Cu), or gold (Au). By using a metal having good electrical contact performance as the metal layer for receiving the control voltage, the operational stability of the optical phase shifter 100 may be ensured.

[0054] In an example, considering the manufacturing process of the metal layer, aluminum or copper may be selected to be compatible with the CMOS process.

[0055] Figure 1 A groove 104 for the metal layer 150 is also schematically shown. In an example, the control voltage can be provided by an electrical connection such as a lead or a wire that is electrically connected to the metal layer 150 via the groove 104 ( Figure 1 (not shown) is applied to the metal layer 150.

[0056] Here, since the metal layer is disposed under the third waveguide layer, it can help separate the process of manufacturing the third waveguide layer from the CMOS process used in the optical phase shifter, so that the third waveguide layer can be additionally formed after the bottom structure is formed by the CMOS process, thereby helping the overall manufacturing process of the optical phase shifter to be compatible with the CMOS process and reducing the process complexity caused by the third waveguide layer.

[0057] According to some embodiments, the thickness of the metal layer 150 may be in the range of 50 nm to 300 nm, which may help the second waveguide layer 140 and the third waveguide layer 160 to jointly form a waveguide structure to support light field transmission, thereby helping the overall waveguide structure to cause only low insertion loss.

[0058] According to some embodiments, the third waveguide layer 160 may include a lithium niobate (LiNbO3) thin film. In this way, a waveguide layer having a good electro-optical effect may be provided to achieve phase modulation.

[0059] Since the third waveguide layer can be formed on the bottom structure by additionally using a bonding process after the bottom structure is formed by a CMOS process, it can help make the overall manufacturing process of the optical phase shifter compatible with the CMOS process and reduce the process complexity caused by the third waveguide layer.

[0060] In addition, as mentioned above, the light field can be confined in a medium with a higher refractive index, and the medium with a higher refractive index than the surrounding environment is the "optical waveguide" that confines the light field. The second waveguide layer 140 and the third waveguide layer 160 can be high refractive index regions relative to the surrounding environment, so the light field can be confined in the high refractive index region. The third waveguide layer 160 can be, for example, a planar thin film waveguide, so there is a refractive index difference in the z-axis direction, but there is no refractive index restriction in the y-axis direction. By arranging the second waveguide layer 140 with restrictions in both the z-axis direction and the y-axis direction below the third waveguide layer 160, the waveguide structure jointly formed by the second waveguide layer 140 and the third waveguide layer 160 can be similar to a ridge waveguide, and light field restriction is also formed in the y-axis direction.

[0061] According to some embodiments, the optical phase shifter 100 may further include: a first interlayer dielectric layer 145 located between the second waveguide layer 140 and the metal layer 150 ; and a second interlayer dielectric layer 155 located between the metal layer 150 and the third waveguide layer 160 .

[0062] In this way, a space can be provided between the two waveguide layers 140, 160 and the metal layer 150 to help adjust the distance between the three, so that the waveguide structure jointly constituted by the second waveguide layer 140 and the third waveguide layer 160 can support light field transmission and help the overall waveguide structure only cause low insertion loss.

[0063] In an example, the first interlayer dielectric layer 145 and the second interlayer dielectric layer 155 may each include silicon dioxide (SiO2). Figure 1 For simplicity of illustration, the first interlayer dielectric layer 145 and the second interlayer dielectric layer 155 are shown as a whole with other interlayer dielectric layers for isolation, but those skilled in the art will appreciate that the first interlayer dielectric layer 145 and the second interlayer dielectric layer 155 may each be an independent layer.

[0064] According to some embodiments, the thickness of at least one of the first interlayer dielectric layer 145 or the second interlayer dielectric layer 155 may be less than or equal to 500 nm. This thickness may help provide an appropriate distance between the two waveguide layers 140, 160 and the metal layer 150, so that the waveguide structure formed by the second waveguide layer 140 and the third waveguide layer 160 can support light field transmission, and help the overall waveguide structure cause only low insertion loss.

[0065] As described above, according to the optical phase shifter of the embodiment of the present disclosure, on the one hand, a three-layer waveguide structure can be designed to provide sufficient device spacing to be compatible with the production of germanium silicon photodetectors, while ensuring that the three-layer waveguide structure only causes low insertion loss. On the other hand, the positions of the third waveguide layer and the metal layer in the optical phase shifter can be designed to ensure that the overall manufacturing process of the optical phase shifter is compatible with the CMOS process, and reduce the process complexity caused by the third waveguide layer and the metal layer.

[0066] Figure 2A and Figure 2B The cross-sectional views of the optical phase shifter 100 along the second direction are shown respectively, wherein Figure 2A Shown along Figure 1 A cross-sectional view taken along line AA', and Figure 2B Shown along Figure 1 A cross-sectional view taken along line BB'.

[0067] exist Figure 2A and Figure 2B In the figure, the second direction may represent the y-axis direction in a three-dimensional coordinate system composed of an x-axis, a y-axis, and a z-axis, which is perpendicular to the first direction along the x-axis direction in a horizontal plane.

[0068] like Figure 2A and Figure 2BAs shown, the optical phase shifter 100 includes a substrate 110, a first waveguide layer 130, a second waveguide layer 140, a metal layer 150, and a third waveguide layer 160. The first waveguide layer 130 is located on the substrate 110. The second waveguide layer 140 is located on the first waveguide layer 130. The metal layer 150 is located on the second waveguide layer 140. The third waveguide layer 160 is located on the metal layer 150. The waveguide structure formed by the second waveguide layer 140 and the third waveguide layer 160 receives the light coupled out from the first waveguide layer 130.

[0069] because Figure 2A It is along Figure 1 The cross-sectional view is taken along the line AA', so Figure 2A The first waveguide layer 130 and the second waveguide layer 140 shown may respectively represent the first coupling region (at Figure 1 The first coupling region 102a is shown in FIG. 1 and the second coupling region 102b in the second waveguide layer 140 is shown in FIG. Figure 1 103a). Through the first coupling region, light transmitted in the first waveguide layer 130 can be coupled out of the first waveguide layer 130. Through the second coupling region, light coupled out of the first waveguide layer 130 can be coupled into the waveguide structure jointly constituted by the second waveguide layer 140 and the third waveguide layer 160. That is, light can be transmitted in the first waveguide layer 130, coupled toward the third waveguide layer 160 through the first coupling region of the first waveguide layer 130 and the second coupling region of the second waveguide layer 140, so as to perform phase modulation on the light in the phase shifter part jointly constituted by the second waveguide layer 140, the metal layer 150 and the third waveguide layer 160 for realizing the phase shifter operation.

[0070] like Figure 2B Shown along Figure 1 The cross-sectional view taken along line BB′ therefore shows the phase shifter portion composed of the second waveguide layer 140, the metal layer 150 and the third waveguide layer 160. That is, after light is coupled into the phase shifter portion through the first waveguide layer 130, phase modulation of the light is achieved by applying a control voltage through the metal layer 150.

[0071] This unique three-layer waveguide structure of the optical phase shifter according to the embodiment of the present disclosure can only cause low insertion loss, and can make the overall manufacturing process of the optical phase shifter compatible with the CMOS process and reduce the process complexity.

[0072] Figures 3A to 3D A method of manufacturing an optical phase shifter according to an exemplary embodiment of the present disclosure is shown.

[0073] exist Figures 3A to 3D, steps S301 to S304 of the method for manufacturing an optical phase shifter according to an embodiment of the present disclosure are respectively shown. In step S301, a first waveguide layer 330 is formed on a substrate 310. In step S302, a second waveguide layer 340 is formed on the first waveguide layer 330. In step S303, a metal layer 350 is formed on the second waveguide layer 340, and the metal layer 350 is configured to receive a control voltage. In step S304, a third waveguide layer 360 is formed on the metal layer 350. The waveguide structure formed by the second waveguide layer 340 and the third waveguide layer 360 receives the light coupled out from the first waveguide layer 330. The light forms an optical field confinement in the third waveguide layer 360. The third waveguide layer 360 has a refractive index that changes with the control voltage to modulate the phase of the light.

[0074] According to the method for manufacturing an optical phase shifter in an embodiment of the present disclosure, on the one hand, a unique three-layer waveguide structure can be used to provide sufficient device spacing to be compatible with the manufacture of germanium silicon photodetectors, and on the other hand, the overall manufacturing process of the optical phase shifter can be guaranteed to be compatible with the CMOS process and the process complexity can be reduced.

[0075] The following describes in detail various aspects of steps S301 to S304 of the method for manufacturing an optical phase shifter according to an embodiment of the present disclosure.

[0076] like Figure 3A As shown, in step S301, the substrate 310 may include a silicon substrate. In an example, an SOI wafer may be used, which may include a substrate 310 and a buried oxide layer 320 located on the substrate 310. The buried oxide layer 320 may include silicon dioxide (SiO2). A first waveguide layer 330 may be formed on the buried oxide layer 320.

[0077] The first waveguide layer 330 may include silicon (Si). In an example, the top silicon layer of the SOI wafer may be used as the first waveguide layer 330. The first waveguide layer 330 may also be additionally formed using a deposition process.

[0078] As described above, since the first waveguide layer 330 can be configured as the optical input port and the optical output port of the optical phase shifter, the first waveguide layer 330 can be etched to form two parts 330-1 and 330-2 corresponding to the optical input port and the optical output port, respectively. Figure 3A shown.

[0079] In an example, an interlayer dielectric layer may be formed between the two parts 330 - 1 and 330 - 2 in a subsequent step (eg, step S302 ) for isolation. The interlayer dielectric layer may include silicon dioxide (SiO 2 ).

[0080] According to some embodiments, forming the first waveguide layer 330 may include forming a first coupling region 302 a via which light transmitted in the first waveguide layer 330 is coupled out of the first waveguide layer 330 .

[0081] Since the first waveguide layer 330 can couple the input light into the optical phase shifter to be phase-modulated by the optical phase shifter, by providing a coupling region for light coupling in the first waveguide layer 330, the first waveguide layer 330 and the second waveguide layer 340 (in the first waveguide layer 340) located thereon can be phase-modulated. Figure 3B ) and the third waveguide layer 360 (shown in Figure 3D The waveguide structure formed by the optical phase shifter (as shown in the figure) provides good optical coupling efficiency, thereby facilitating the light to enter the optical phase shifter.

[0082] Similar to the first coupling region 302a formed at the portion 330-1 of the optical input port, a third coupling region 302b may be formed at the portion 330-2 of the optical output port. Figure 3B ) and the third waveguide layer 360 (shown in Figure 3D The light of the waveguide structure formed by the first waveguide layer 330 can be coupled into the first waveguide layer 330 to be output to a subsequent device, such as a germanium silicon photodetector.

[0083] In an example, the first coupling region 302a may be patterned into an inverted tapered shape (hereinafter referred to as Figure 4C The top view of FIG. 1 shows the inverted cone shape). That is, the width of the first coupling region 302a can be along Figure 3B The length of the first coupling region 302a may be in the range of 50 um to 1000 um.

[0084] like Figure 3B As shown, in step S302, the second waveguide layer 340 may include at least one of silicon nitride (Si3N4) or polycrystalline silicon (poly-Si). The second waveguide layer 340 may be formed using a deposition process.

[0085] In an example, the second waveguide layer 340 and the third waveguide layer 360 (in Figure 3D The waveguide structure jointly constituted by the first coupling region 302a and the third coupling region 302b is formed to at least partially cover each of the first coupling region 302a and the third coupling region 302b in the vertical direction.

[0086] In an example, the thickness of the second waveguide layer 340 may be formed in the range of 50 nm to 1000 nm. In addition, the second coupling region 303a and the fourth coupling region 303b in the second waveguide layer 340 may be formed corresponding to the first coupling region 302a and the third coupling region 302b in the first waveguide layer 330.

[0087] In an example, the SiGe photodetector may be formed at a position comparable to the height of the second waveguide layer 140. Therefore, the optical phase shifter may be compatible with the fabrication of the SiGe photodetector.

[0088] In an example, an interlayer dielectric layer covering the bottom structure may be formed for isolation before forming the second waveguide layer 340. The interlayer dielectric layer may include silicon dioxide (SiO2). Figure 3B For simplicity of illustration, the interlayer dielectric layer is shown as a whole with the buried oxide layer 320 and the interlayer dielectric layer between the first coupling region 302a and the third coupling region 302b, but those skilled in the art will appreciate that the interlayer dielectric layer may be an independent layer.

[0089] like Figure 3C As shown, in step S303, the metal layer 350 may include at least one of aluminum (Al), copper (Cu) or gold (Au). The metal layer 350 may be formed using a metal process compatible with a CMOS process (such as a sputtering process). In this case, aluminum or copper may be preferably used.

[0090] In an example, the metal layer 350 may be formed to have a thickness in the range of 50 nm to 300 nm.

[0091] As mentioned above, since the metal layer 350 is formed in the third waveguide layer 360 (in Figure 3D The third waveguide layer 360 is formed before the bottom structure (shown in FIG. 1 ), which can help separate the process of manufacturing the third waveguide layer 360 from the CMOS process used by the optical phase shifter, so that the third waveguide layer 360 is additionally formed after the bottom structure is formed by the CMOS process, thereby helping the overall manufacturing process of the optical phase shifter to be compatible with the CMOS process and reducing the process complexity caused by the third waveguide layer 360.

[0092] like Figure 3D As shown, in step S304, the third waveguide layer 360 may include a lithium niobate (LiNbO3) film. After the bottom structure is formed by the CMOS process, a bonding process may be used to form the prepared lithium niobate film (for example, produced by an additional lithium niobate film manufacturing process) on the bottom structure. Therefore, the overall manufacturing process of the optical phase shifter may be compatible with the CMOS process, and the process complexity caused by the third waveguide layer may be reduced.

[0093] According to some embodiments, the method for manufacturing an optical phase shifter may further include: forming a first interlayer dielectric layer 345 between the second waveguide layer 340 and the metal layer 350 (in Figure 3C and forming a second interlayer dielectric layer 355 (in Figure 3D ).

[0094] In an example, the first interlayer dielectric layer 345 and the second interlayer dielectric layer 355 may each include silicon dioxide (SiO2). Figure 3C , 3D For simplicity of illustration, the first interlayer dielectric layer 345 and the second interlayer dielectric layer 355 are shown as a whole with other interlayer dielectric layers for isolation, but those skilled in the art will appreciate that the first interlayer dielectric layer 345 and the second interlayer dielectric layer 355 may each be an independent layer.

[0095] In an example, a thickness of at least one of the first interlayer dielectric layer 345 or the second interlayer dielectric layer 355 may be less than or equal to 500 nm.

[0096] In the example, Figure 3D As shown, the second interlayer dielectric layer 355 can be etched to form a groove 304 for the metal layer 350. In an example, the control voltage can be supplied through an electrical connection member (such as a lead or a wire) electrically connected to the metal layer 350 via the groove 304. Figure 3D ) and is applied to the metal layer 350.

[0097] According to the method for manufacturing an optical phase shifter in an embodiment of the present disclosure, on the one hand, a unique three-layer waveguide structure can be used to provide sufficient device spacing to be compatible with the manufacture of germanium silicon photodetectors, and on the other hand, the overall manufacturing process of the optical phase shifter can be guaranteed to be compatible with the CMOS process and the process complexity can be reduced.

[0098] Figures 4A to 4C A cross-sectional view and a top view of an optical phase shifter 400 along a first direction and a second direction according to another exemplary embodiment are respectively shown, wherein the optical phase shifter 400 according to another exemplary embodiment Figure 4C The top view shows the mode field distribution diagram. It can be understood that Figures 4A to 4C The various elements shown in the drawings are not necessarily drawn to scale and, for illustrative purposes, may be exaggerated in scale in some cases.

[0099] like Figure 4A As shown, from a cross-sectional view along a first direction (ie, the x-axis direction), the optical phase shifter 400 includes, from bottom to top, a substrate 410 , a first waveguide layer 430 , a second waveguide layer 440 , a metal layer 450 , and a third waveguide layer 460 .

[0100] In addition, the optical phase shifter 400 may further include a first interlayer dielectric layer 445 located between the second waveguide layer 440 and the metal layer 450 , and a second interlayer dielectric layer 455 located between the metal layer 450 and the third waveguide layer 460 .

[0101] Since various aspects of the above layers have been combined Figure 1 , Figure 2A and Figure 2B , Figures 3A to 3D In order to simplify the description, different from Figure 1 The complete device shown, Figure 4A Only a symmetrical half of the complete device is shown schematically, which corresponds to Figure 1 The left half of the complete device is shown.

[0102] Figure 4B FIG. 4 shows a cross-sectional view of the optical phase shifter 400 along the second direction (ie, the y-axis direction). Figure 4B The thicknesses of the first waveguide layer 430, the second waveguide layer 440, the metal layer 450, and the third waveguide layer 460 are marked. Figure 4B As shown, the thickness H1 of the first waveguide layer 430 may be 220 nm, the thickness H2 of the second waveguide layer 440 may be 300 nm, and the thickness H2 of the metal layer 450 may be 220 nm. metal The thickness H2 of the third waveguide layer 460 may be 100 nm, and the thickness H2 of the third waveguide layer 460 may be 300 nm. In addition, the thickness H2 of the interlayer dielectric layer between the first waveguide layer 430 and the second waveguide layer 440 may be 100 nm. gap1 The thickness H of each of the first interlayer dielectric layer 445 and the second interlayer dielectric layer 455 may be 180 nm. gap2 It can be 30nm.

[0103] Figure 4C 4 shows a top view of the optical phase shifter 400. Figure 4C As shown, the first waveguide layer 430 may have a length extending along the first direction (ie, the x-axis direction). The width W of the first end portion 430-1 of the first waveguide layer 430 11 The width W of the second end portion 430 - 2 may be 500 nm. 12 It can be 200nm. Figure 4C From the top view shown in the figure, the coupling region 430-3 where the first waveguide layer 430 is covered by the waveguide structure formed by the second waveguide layer 440 and the third waveguide layer 460 can be formed into an inverted cone shape. taper It can be 300μm.

[0104] The waveguide structure formed by the second waveguide layer 440 and the third waveguide layer 460 may partially cover the first waveguide layer 430 to form the coupling region 430-3 in the first waveguide layer 430. The width W2 of the second waveguide layer 440 may be 1000 nm.

[0105] Figure 4C The mode field distribution in the first waveguide layer 430 when light enters the first waveguide layer 430 and the mode field distribution in the third waveguide layer 460 when light is coupled to the third waveguide layer 460 are shown above and below, respectively. Figure 4C It can be seen from the mode field distribution diagram that when light enters the first waveguide layer 430, the mode field formed in the first waveguide layer 430 is small and low in height, while when light is coupled to the third waveguide layer 460, the mode field formed in the third waveguide layer 460 is large and high in height. The insertion loss of the optical phase shifter 400 can be simulated by the two mode field distributions.

[0106] Figure 5 A graph showing insertion loss simulation results according to an exemplary embodiment. The insertion loss simulation results may be based on Figures 4A to 4C The device parameters of the optical phase shifter 400 are obtained.

[0107] like Figure 5 , which shows a curve showing the coupling efficiency as the length of the coupling region 430-3 of the first waveguide layer 430 varies. Figure 5 It can be seen that when the length of the coupling region 430 - 3 is 300-350 μm, a coupling efficiency of approximately 1 can be achieved, corresponding to an insertion loss of 0.04 dB. It can be seen that the optical phase shifter 400 according to the embodiment of the present disclosure can provide a relatively low insertion loss.

[0108] The above description is only an illustration of the illustrative embodiments and application technical principles of the present disclosure. Those skilled in the art should understand that the scope of the present disclosure to which the embodiments of the present disclosure relate is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, and should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the above-mentioned inventive concept. For example, the technical solutions formed by replacing the above-mentioned features with technical features (but not limited to) having similar functions to the technical features disclosed in the embodiments of the present disclosure also fall within the scope of protection of the present disclosure.

[0109] Although the present disclosure has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description should be considered illustrative and schematic, not restrictive; the present disclosure is not limited to the disclosed embodiments. By studying the drawings, the disclosure and the appended claims, those skilled in the art will be able to understand and implement variations to the disclosed embodiments when practicing the claimed subject matter. In the claims, the word "comprising" does not exclude other elements or steps that are not listed, the indefinite article "a" or "an" does not exclude a plurality, the term "plurality" means two or more, and the term "based on" should be interpreted as "based at least in part on". The mere fact that certain measures are recorded in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. An optical phase shifter, comprising: substrate; A first waveguide layer, located on the substrate; a second waveguide layer, located on the first waveguide layer; a metal layer, located on the second waveguide layer, configured to receive a control voltage; as well as A third waveguide layer is located on the metal layer, wherein the waveguide structure formed by the second waveguide layer and the third waveguide layer receives the light coupled out from the first waveguide layer. wherein the light forms a light field confinement in the third waveguide layer, and wherein the third waveguide layer has a refractive index that varies with the control voltage to modulate the phase of the light, The first waveguide layer includes a first coupling region, which is a portion of the first waveguide layer covered by a waveguide structure formed by the second waveguide layer and the third waveguide layer, and a width of the first coupling region gradually decreases along a length direction in which light is transmitted to form a cone.

2. The optical phase shifter according to claim 1, wherein: The first waveguide layer includes silicon.

3. The optical phase shifter according to claim 1 or 2, wherein: Via the first coupling region, light transmitted in the first waveguide layer is coupled out of the first waveguide layer.

4. The optical phase shifter according to claim 3, wherein: The length of the first coupling region is along the direction in which the light is transmitted and is in a range of 50 um to 1000 um.

5. The optical phase shifter according to claim 1 or 2, wherein: The second waveguide layer includes at least one of silicon nitride or polysilicon.

6. The optical phase shifter according to claim 5, wherein: The thickness of the second waveguide layer is in the range of 50 nm to 1000 nm.

7. The optical phase shifter according to claim 1 or 2, wherein: The second waveguide layer includes a second coupling region, through which the light coupled out of the first waveguide layer is coupled into the waveguide structure formed by the second waveguide layer and the third waveguide layer.

8. The optical phase shifter according to claim 1 or 2, wherein: The metal layer includes at least one of aluminum, copper or gold.

9. The optical phase shifter according to claim 8, wherein: The thickness of the metal layer is in the range of 50 nm to 300 nm.

10. The optical phase shifter according to claim 1 or 2, wherein: The third waveguide layer includes a lithium niobate thin film.

11. The optical phase shifter according to claim 1 or 2, further comprising: A first interlayer dielectric layer, located between the second waveguide layer and the metal layer; as well as The second interlayer dielectric layer is located between the metal layer and the third waveguide layer.

12. The optical phase shifter according to claim 11, wherein: A thickness of at least one of the first interlayer dielectric layer or the second interlayer dielectric layer is less than or equal to 500 nm.

13. A method for manufacturing an optical phase shifter, comprising: forming a first waveguide layer over the substrate; forming a second waveguide layer on the first waveguide layer; forming a metal layer over the second waveguide layer, the metal layer being configured to receive a control voltage; as well as forming a third waveguide layer on the metal layer, wherein the waveguide structure formed by the second waveguide layer and the third waveguide layer receives the light coupled out from the first waveguide layer, wherein the light forms a light field confinement in the third waveguide layer, and wherein the third waveguide layer has a refractive index that varies with the control voltage to modulate the phase of the light, The forming of the first waveguide layer includes: forming a first coupling region, the first coupling region being a portion of the first waveguide layer covered by a waveguide structure formed by the second waveguide layer and the third waveguide layer, and a width of the first coupling region gradually decreases along a length direction in which light is transmitted to form a cone. 14 . The method of claim 13 , light transmitted in the first waveguide layer being coupled out of the first waveguide layer via the first coupling region.

15. The method according to claim 13 or 14, further comprising: forming a first interlayer dielectric layer between the second waveguide layer and the metal layer; as well as A second interlayer dielectric layer is formed between the metal layer and the third waveguide layer.

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