High performance lithium niobate electro-optic modulator and method of making the same
Patent Information
- Application Number
- CN202611269544.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-20
- Publication Date
- 2026-10-27
AI Technical Summary
[0005]基于上述问题，本申请提供了一种高性能铌酸锂电光调制器及其制备方法，通过在薄膜铌酸锂晶圆背面制作光学开槽结构并以热氧硅层作为停止层、正面仅制备切割道，解决了正面开槽造成的光刻胶缺陷与刻蚀冲突问题，从而在保证器件电光调制性能的同时，有效提升了晶圆批量加工良率与图形尺寸精度
[0016]从以上技术方案可以看出，相较于现有技术，本申请具有以下优点：
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Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor technology, and in particular to a high-performance lithium niobate electro-optic modulator and its fabrication method. Background Technology
[0002] Thin-film lithium niobate electro-optic modulators have become core optoelectronic devices in optical communication and quantum optical systems due to their advantages such as strong Pockels effect, high modulation bandwidth, and low driving power consumption. To reduce optical loss and improve electro-optic modulation efficiency, the device needs to be fabricated with an optical slotted structure to isolate the high-refractive-index silicon substrate, thereby optimizing the optical field confinement and electro-optic coupling effect.
[0003] The current mainstream manufacturing process involves sequentially etching optical slots and dicing paths on the front side of a thin-film lithium niobate wafer. However, the cavities formed by the optical slots on the front side can cause bulging and cracking during photoresist coating, interfering with subsequent deep silicon etching of the dicing paths and leading to defects such as rough waveguide edges and morphological distortion. Furthermore, the coexistence of multiple etching patterns on the front side can generate an etching load effect, resulting in decreased pattern dimensional accuracy and reduced wafer processing yield. Existing processes cannot fundamentally avoid these process conflicts.
[0004] Therefore, how to improve wafer batch processing yield and pattern size accuracy while ensuring the electro-optic modulation performance of the device is an urgent problem to be solved by those skilled in the art. Summary of the Invention
[0005] To address the aforementioned issues, this application provides a high-performance lithium niobate electro-optic modulator and its fabrication method. By fabricating an optical grooving structure on the back side of a thin-film lithium niobate wafer and using a thermo-oxygen silicon layer as a stop layer, while only fabricating dicing paths on the front side, the problem of photoresist defects and etching conflicts caused by front-side grooving is solved. This effectively improves wafer batch processing yield and pattern dimensional accuracy while ensuring the electro-optic modulation performance of the device.
[0006] In a first aspect, embodiments of this application provide a method for fabricating a high-performance lithium niobate electro-optic modulator, comprising: An optical waveguide, a modulation electrode, and an oxygen-silicon cladding are sequentially formed on the front side of a thin-film lithium niobate wafer; the thin-film lithium niobate wafer includes, from bottom to top, a silicon substrate, a thermal oxygen-silicon layer, and a single-crystal lithium niobate thin film layer. A dicing channel is etched on the front side of the thin-film lithium niobate wafer, and no optical slotting structure is formed on the front side of the thin-film lithium niobate wafer. An optical grooving structure is etched on the back side of the thin-film lithium niobate wafer; the etching of the optical grooving structure stops at the thermo-oxidative silicon layer.
[0007] Optionally, before etching the optical groove structure on the back side of the thin-film lithium niobate wafer to form the optical groove structure, the fabrication method further includes: A blue film is attached to the front side of the thin-film lithium niobate wafer.
[0008] Optionally, the etching of dicing channels on the front side of the thin-film lithium niobate wafer includes: Deep silicon etching was performed on the target area on the front side of the thin-film lithium niobate wafer using C4F8 and SF6 gases to form cleaving paths; The total etching depth of the cutting path on the silicon oxide cladding and the thermal silicon oxide layer is 7μm-10μm; The etch depth of the dicing channel on the silicon substrate is 150μm-300μm.
[0009] Optionally, the etching of the optical groove structure on the back side of the thin-film lithium niobate wafer includes: The silicon substrate is thinned from the back side; The target pattern is defined on the back side of the thinned silicon substrate using front-side marking overlay. The silicon substrate is etched based on the target pattern to form an optical groove structure.
[0010] Optionally, the thinning of the silicon substrate from the back side of the silicon substrate includes: The silicon substrate is subjected to grinding and chemical mechanical polishing processes sequentially from the back side to remove 200μm-300μm of silicon material.
[0011] Optionally, an optical waveguide is formed on the front side of the thin-film lithium niobate wafer, including: Optical waveguide patterns are defined on the front side of a thin-film lithium niobate wafer using electron beam lithography or deep ultraviolet lithography. The optical waveguide pattern is transferred to the front side of the thin-film lithium niobate wafer using a pure physical etching method with argon gas to form an optical waveguide; the etching depth is 50nm-600nm.
[0012] Optionally, a modulation electrode is formed on the front side of the thin-film lithium niobate wafer, including: Electrode patterns are defined on the front side of a thin-film lithium niobate wafer using photolithography. Based on the electrode pattern, Ti / Au or Cr / Au metal stacks are deposited on the front side of the thin-film lithium niobate wafer using electron beam evaporation or magnetron sputtering processes; Excess metal is removed through a stripping process to form a modulation electrode.
[0013] Optionally, after etching the optical groove structure on the back side of the thin-film lithium niobate wafer to form the optical groove structure, the fabrication method further includes: Remove the blue film and clean the thin-film lithium niobate wafer.
[0014] Secondly, embodiments of this application provide a high-performance lithium niobate electro-optic modulator, comprising: a thin-film lithium niobate wafer; The front side of the thin-film lithium niobate wafer is sequentially provided with an optical waveguide, a modulation electrode, and an oxygen-silicon cladding layer. The thin-film lithium niobate wafer comprises, from bottom to top, a silicon substrate, a thermally oxidized silicon layer, and a single-crystal lithium niobate thin film layer. The front side of the thin-film lithium niobate wafer has a dicing channel, but the front side of the thin-film lithium niobate wafer does not have an optical slotting structure. The back side of the thin-film lithium niobate wafer is provided with an optical slotting structure; the bottom of the optical slotting structure ends at the thermo-oxidative silicon layer.
[0015] Optionally, the depth of the dicing channel within the silicon substrate is 150μm-300μm.
[0016] As can be seen from the above technical solutions, compared with the prior art, this application has the following advantages: This application provides a method for fabricating a high-performance lithium niobate electro-optic modulator. First, an optical waveguide, a modulation electrode, and a silicon oxide cladding are sequentially formed on the front side of a thin-film lithium niobate wafer. Then, dicing paths are etched on the front side of the thin-film lithium niobate wafer, without forming an optical slotting structure. Finally, an optical slotting structure is etched on the back side of the thin-film lithium niobate wafer. The thin-film lithium niobate wafer, from bottom to top, comprises a silicon substrate, a thermally oxidized silicon layer, and a single-crystal lithium niobate thin film layer. The etching of the optical slotting structure stops at the thermally oxidized silicon layer. Thus, by fabricating an optical slotting structure on the back side of the thin-film lithium niobate wafer and using the thermally oxidized silicon layer as a stop layer, while only dicing paths are formed on the front side, the problems of photoresist defects and etching conflicts caused by front-side slotting are solved. This effectively improves wafer batch processing yield and pattern dimensional accuracy while ensuring the electro-optic modulation performance of the device. Attached Figure Description
[0017] Figure 1 A flowchart illustrating a method for fabricating a high-performance lithium niobate electro-optic modulator provided in this application embodiment; Figure 2 A side cross-sectional view of a standard thin-film lithium niobate wafer provided for an embodiment of this application; Figure 3 A side cross-sectional view of an optical waveguide provided in an embodiment of this application; Figure 4 A side sectional view of a modulation electrode provided in an embodiment of this application; Figure 5 A side sectional view of a cutting channel provided in an embodiment of this application; Figure 6 A side cross-sectional view of a blue film provided in an embodiment of this application; Figure 7 This is a schematic diagram of silicon substrate thinning provided in an embodiment of this application; Figure 8 A schematic diagram illustrating the definition of a target pattern provided in an embodiment of this application; Figure 9 This is a schematic diagram of an optical slotted structure provided in an embodiment of this application; Figure 10 This is a schematic diagram of the structure of a high-performance lithium niobate electro-optic modulator provided in an embodiment of this application. Detailed Implementation
[0018] As mentioned earlier, existing fabrication processes for lithium niobate electro-optic modulators cannot guarantee both the device's electro-optic modulation performance and wafer batch processing yield and pattern dimensional accuracy. Specifically, the current mainstream fabrication process involves sequentially etching optical slots and dicing paths on the front side of the thin-film lithium niobate wafer. However, the cavities formed by the front-side optical slots can cause bulging and cracking during photoresist coating, interfering with subsequent deep silicon etching of the dicing paths and leading to defects such as waveguide edge roughness and morphological distortion. Simultaneously, the coexistence of multiple etching patterns on the front side can generate an etching load effect, resulting in decreased pattern dimensional accuracy and reduced wafer processing yield. Existing processes cannot fundamentally avoid these process conflict issues.
[0019] To address the aforementioned problems, this application provides a method for fabricating a high-performance lithium niobate electro-optic modulator, comprising: firstly, sequentially forming an optical waveguide, a modulation electrode, and a silicon oxide cladding layer on the front side of a thin-film lithium niobate wafer; then, etching dicing paths on the front side of the thin-film lithium niobate wafer, without forming an optical grooving structure on the front side; and finally, etching an optical grooving structure on the back side of the thin-film lithium niobate wafer. The thin-film lithium niobate wafer, from bottom to top, comprises a silicon substrate, a thermally oxidized silicon layer, and a single-crystal lithium niobate thin film layer, with the etching of the optical grooving structure stopping at the thermally oxidized silicon layer.
[0020] Thus, by fabricating an optical grooving structure on the back of the thin-film lithium niobate wafer and using a thermally oxidized silicon layer as a stop layer, while only fabricating dicing paths on the front, the problems of photoresist defects and etching conflicts caused by front grooving are solved. This effectively improves wafer batch processing yield and pattern size accuracy while ensuring the electro-optic modulation performance of the device.
[0021] It should be noted that the high-performance lithium niobate electro-optic modulator and its fabrication method provided in this application can be applied to the field of semiconductor technology. The above are merely examples and do not limit the application field of the high-performance lithium niobate electro-optic modulator and its fabrication method provided in this application.
[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.
[0023] Figure 1 A flowchart illustrating a method for fabricating a high-performance lithium niobate electro-optic modulator provided in this application embodiment. (Combined with...) Figure 1 As shown in the embodiments of this application, a method for fabricating a high-performance lithium niobate electro-optic modulator may include: S101: An optical waveguide, a modulation electrode, and an oxygen-silicon cladding are sequentially formed on the front side of a thin-film lithium niobate wafer; the thin-film lithium niobate wafer includes, from bottom to top, a silicon substrate, a thermal oxygen-silicon layer, and a single-crystal lithium niobate thin film layer.
[0024] Figure 2 This is a side cross-sectional view of a standard thin-film lithium niobate wafer provided for an embodiment of this application. (In conjunction with...) Figure 2 As shown, this scheme selects a standard thin-film lithium niobate wafer as the substrate. From bottom to top (along the Z-axis), the thin-film lithium niobate wafer is sequentially configured with a silicon substrate 110, a thermo-oxygen silicon layer 120, and a single-crystal lithium niobate thin film layer 130. The silicon substrate 110 serves as a support for the entire wafer; the intermediate thermo-oxygen silicon layer 120 not only separates the silicon substrate 110, reducing optical loss caused by silicon, but also acts as a stop layer during subsequent back-side grooving etching, preventing etching penetration and damage to the upper lithium niobate optical waveguide; the uppermost single-crystal lithium niobate thin film is the core functional layer for electro-optic modulation. During processing, the optical waveguide and modulation electrode are first sequentially fabricated on the surface of the single-crystal lithium niobate thin film layer 130, and finally, a silicon oxide cladding layer is deposited. The optical waveguide is responsible for transmitting optical signals, and the modulation electrode changes the optical signal by applying an external voltage. The surface silicon oxide cladding can completely wrap the internal optical waveguide and modulation electrode, preventing dust and moisture from damaging the structure of the precision device, and also keeping the front side of the thin-film lithium niobate wafer flat and smooth.
[0025] Furthermore, since there are different ways to form optical waveguides, the embodiments of this application can be described in terms of one possible formation method.
[0026] In one embodiment, an optical waveguide is formed on the front side of the thin-film lithium niobate wafer, comprising: Optical waveguide patterns are defined on the front side of a thin-film lithium niobate wafer using electron beam lithography or deep ultraviolet lithography. The optical waveguide pattern is transferred to the front side of the thin-film lithium niobate wafer using a pure physical etching method with argon gas to form an optical waveguide; the etching depth is 50nm-600nm.
[0027] Figure 3 This is a side cross-sectional view of an optical waveguide provided in an embodiment of this application. (In conjunction with...) Figure 3 As shown, when fabricating the optical waveguide 210, electron beam lithography or deep ultraviolet lithography is first used to expose and develop the monocrystalline lithium niobate film on the surface of the thin-film lithium niobate wafer, etching out the preset pattern (optical waveguide pattern) of the optical waveguide 210. Then, an inductively coupled plasma dry etching machine is used, introducing argon gas for pure physical dry etching. Excess lithium niobate material is removed by argon ion bombardment, completely replicating the optical waveguide pattern on the photoresist into the monocrystalline lithium niobate film, forming a usable ridge or strip optical waveguide. Furthermore, the etching depth (h1) is controlled within 50nm-600nm during this process. After etching, the photoresist and etching byproducts need to be removed by cleaning. Thus, in fabricating the optical waveguide, the optical waveguide pattern is first defined on the monocrystalline lithium niobate film using electron beam lithography or deep ultraviolet lithography, and then the pattern is transferred using pure physical etching with argon gas, with the etching depth controlled within 50nm-600nm. The two photolithography methods used are compatible with both R&D and mass production. Argon etching can produce smooth, low-loss waveguide sidewalls, and the appropriate etching depth can stabilize modulation performance. The flat, groove-free front structure can also prevent subsequent photoresist bulging and cracking, thus improving processing yield.
[0028] Furthermore, since the methods of forming modulation electrodes are not entirely the same, the embodiments of this application can be described in terms of one possible formation method.
[0029] In one case, a modulation electrode is formed on the front side of a thin-film lithium niobate wafer, comprising: Electrode patterns are defined on the front side of a thin-film lithium niobate wafer using photolithography. Based on the electrode pattern, Ti / Au or Cr / Au metal stacks are deposited on the front side of the thin-film lithium niobate wafer using electron beam evaporation or magnetron sputtering processes; Excess metal is removed through a stripping process to form a modulation electrode.
[0030] Figure 4 This is a side sectional view of a modulation electrode provided in an embodiment of this application. (In conjunction with...) Figure 4As shown, when fabricating the modulation electrode 310, the required electrode pattern is first defined on the front side of the thin-film lithium niobate wafer using photolithography. Then, Ti / Au or Cr / Au metal stacks are deposited in the patterned area using electron beam evaporation or magnetron sputtering. Finally, excess metal material is removed using a lift-off process to obtain a regular coplanar waveguide modulation electrode or traveling wave modulation electrode. In this way, using Ti or Cr as the base metal ensures a firm bond with the underlying film, preventing electrode detachment; the surface Au layer has strong conductivity, reducing signal loss. Electron beam evaporation produces a high-purity metal film, while magnetron sputtering results in a uniform and dense coating; both methods can be selected as needed. The electrode edges processed by the lift-off process are neat and smooth, and no recesses or cavities are left on the front side of the wafer throughout the process. This avoids photoresist bulging and cracking problems during subsequent silicon oxide cladding deposition and dicing, improving mass production yield while stabilizing device modulation performance.
[0031] S102: A dicing channel is etched on the front side of the thin-film lithium niobate wafer, and no optical slotting structure is formed on the front side of the thin-film lithium niobate wafer.
[0032] In practical applications, an oxygen-silicon cladding layer is deposited on the fabricated modulation electrode. During the fabrication of the dicing path, etching is performed only on the front side of the thin-film lithium niobate wafer, starting from the oxygen-silicon cladding layer and proceeding downwards to form the dicing path. It is important to note that no optical grooving structures are fabricated on the front side of the thin-film lithium niobate wafer throughout the entire process; the wafer front side remains completely flat and intact. This eliminates cavities caused by grooving on the front side of the thin-film lithium niobate wafer, allowing for uniform photoresist deposition, preventing bulging and damage of the photoresist layer, eliminating process conflicts between optical grooving and the dicing path, ensuring the morphology and dimensional accuracy of the dicing path, improving wafer dicing performance, and increasing mass production yield.
[0033] Furthermore, since the methods of forming the cutting channel are not entirely the same, the embodiments of this application can be described in terms of one possible formation method.
[0034] In one case, the etching of a dicing channel on the front side of the thin-film lithium niobate wafer includes: Deep silicon etching was performed on the target area on the front side of the thin-film lithium niobate wafer using C4F8 and SF6 gases to form cleaving paths; The total etching depth of the cutting path on the silicon oxide cladding and the thermal silicon oxide layer is 7μm-10μm; The etch depth of the dicing channel on the silicon substrate is 150μm-300μm.
[0035] Figure 5 This is a side sectional view of a cutting channel provided in an embodiment of this application. (In conjunction with...) Figure 5As shown, when processing the dicing channel 410, the target area on the front side of the thin-film lithium niobate wafer is first selected. This target area is the preset chip dicing position on the thin-film lithium niobate wafer, that is, the dicing channel position between chips. Then, a deep reactive ion etching process is used, employing C4F8 and SF6 gases to perform high aspect ratio deep silicon etching on the target area on the front side of the thin-film lithium niobate wafer to complete the dicing channel opening. In addition, this process controls the total etching depth (h2) of the dicing channel 410 on the silicon oxide cladding 510 and the thermal silicon oxide layer 120 to be 7μm-10μm, and the etching depth (h3) on the silicon substrate 110 to be 150μm-300μm. Understandably, C4F8 gas forms a passivation protective film on the trench sidewalls, while SF6 gas is used to etch and remove silicon material. The alternating action of these two gases achieves deep silicon etching, resulting in dicing channels 410 with steep sidewalls and well-preserved morphology. An etching depth of 7μm-10μm can completely penetrate the silicon oxide cladding layer 510 and the thermal silicon oxide layer 120, allowing the trench to be continuous. An etching depth of 150μm-300μm on the silicon substrate 110 can create sufficiently deep trenches, facilitating subsequent wafer dicing into individual chips. This set of parameters ensures smooth dicing along the dicing channels 410 while maintaining sufficient mechanical strength in the wafer, reducing chip edge breakage and optical waveguide damage during dicing, and effectively improving chip yield.
[0036] Furthermore, since the methods of protecting the cutting track are not entirely the same, the embodiments of this application can be used to describe one possible protection method.
[0037] In one embodiment, prior to etching the optical groove structure on the back side of the thin-film lithium niobate wafer, the fabrication method further includes: A blue film is attached to the front side of the thin-film lithium niobate wafer.
[0038] Figure 6 This is a side cross-sectional view of a blue film provided in an embodiment of this application. (In conjunction with...) Figure 6 As shown, before etching the optical grooving structure on the back of the thin-film lithium niobate wafer, a blue film 610 needs to be applied to the front of the wafer. The blue film 610 provides physical protection for the precision device structure on the front, preventing damage and contamination from subsequent processes. Specifically, the blue film 610 can block the erosion and impact damage to the front of the wafer caused by particles and process solutions generated by subsequent processes, preventing damage to core functional structures such as the optical waveguide 210 and modulation electrode 310. At the same time, the blue film 610 can also provide a certain degree of mechanical support for the wafer, mitigating the risk of brittleness caused by wafer thinning, reducing the probability of fragmentation during thin wafer processing, ensuring the integrity of the front devices, and improving the overall chip yield.
[0039] S103: An optical grooving structure is formed on the back side of the thin-film lithium niobate wafer; the etching of the optical grooving structure stops at the thermally oxidized silicon layer.
[0040] In practical applications, etching is performed on the back side of the thin-film lithium niobate wafer (on the side of the silicon substrate 110) to create an optical grooving structure. The etching operation stops at the thermo-oxidative silicon layer 120 and does not extend beyond this layer upwards (in the Z-axis direction). It is understood that the thermo-oxidative silicon layer 120 has a high etch selectivity with silicon, acting as a natural etch barrier to prevent further upward etching and damage to the upper single-crystal lithium niobate film, as well as precision devices such as the optical waveguide 210 and modulation electrode 310 already fabricated on the front side of the wafer. This optical grooving structure is created from the silicon substrate 110 side, eliminating the need for grooving on the front side of the wafer. This avoids the process problems caused by traditional front-side grooving, such as photoresist bulging and etching load effects. It also isolates the light absorption loss caused by the silicon substrate 110, enhances the light field confinement effect of the optical waveguide 210, improves the optical performance of the modulator, and increases the device fabrication yield.
[0041] Furthermore, since there are different ways to form optical slotted structures, this application embodiment can describe one possible formation method.
[0042] In one embodiment, the etching of the optical groove structure on the back side of the thin-film lithium niobate wafer includes: The silicon substrate is thinned from the back side; The target pattern is defined on the back side of the thinned silicon substrate using front-side marking overlay. The silicon substrate is etched based on the target pattern to form an optical groove structure.
[0043] Furthermore, the thinning of the silicon substrate from its back side includes: The silicon substrate is subjected to grinding and chemical mechanical polishing processes sequentially from the back side to remove 200μm-300μm of silicon material.
[0044] Figure 7 This is a schematic diagram of silicon substrate thinning provided in an embodiment of this application. Figure 8 This is a schematic diagram illustrating the definition of a target pattern provided in an embodiment of this application. Figure 9 This is a schematic diagram illustrating the formation of an optical slotting structure, provided as an embodiment of this application. (In conjunction with...) Figure 7 , Figure 8 as well as Figure 9As shown, when fabricating the optical grooving structure on the back side of the wafer, the silicon substrate 110 is first thinned. Specifically, the back side of the silicon substrate 110 is sequentially thinned by grinding and then chemically mechanically polished to remove a 200μm-300μm thick layer of silicon material, denoted as t1. Grinding can quickly remove most of the silicon material, and chemical mechanical polishing can eliminate surface damage caused by grinding. The combination of these two methods results in a flat, uniform, and undamaged wafer back side. After thinning, a double-sided alignment lithography machine is used to complete the double-sided photolithography alignment on the back side. Using front-side marking overlay, the target pattern for the optical grooving is defined on the back side of the thinned silicon substrate 110 using photoresist 710. Finally, using photoresist 710 as a mask, deep reactive ion etching is performed on the back side of the thinned silicon substrate 110 based on the target pattern. Endpoint detection is used with the thermally oxidized silicon layer 120 as an automatic stop layer to precisely form the back optical grooving structure 810. Thus, using front-side marking overlay enables precise alignment between the back-side optical slots and the front-side waveguide 210 device, avoiding misalignment that could degrade the device's optical performance. Completing the thinning process before etching also reduces the subsequent trench etching depth, lowering the processing difficulty of deep silicon etching. The polished wafer has fewer surface defects on the back side, and the etched optical slots have a uniform and regular morphology, effectively isolating light absorption losses from the silicon substrate 110, stabilizing the modulator's optical performance, reducing process anomalies during back-side etching, and further improving chip processing yield.
[0045] Furthermore, since the processing methods after forming the optical slotted structure are not entirely the same, the embodiments of this application can describe one possible processing method.
[0046] In one embodiment, after etching the optical groove structure on the back side of the thin-film lithium niobate wafer to form the optical groove structure, the fabrication method further includes: Remove the blue film 610 and clean the thin-film lithium niobate wafer.
[0047] In practical applications, after forming the back optical slotting structure 810, NMP and IPA solutions can be used to remove the residual photoresist mask on the back side, then the blue film 610 on the front side of the wafer can be peeled off, and finally the wafer is thoroughly cleaned to obtain a high-performance lithium niobate electro-optic modulator. This modulator does not have an optical slotting structure 810 on the front side of the wafer, and the deep silicon etching of the dicing track 410 is not affected by the photoresist. The devices on the front side of the wafer are effectively protected by the blue film 610, avoiding processing damage. The back optical slotting is precisely shaped through deep silicon etching, with the etching stopping at the thermo-oxygen silicon layer 120. The entire fabrication process has good stability, and the device exhibits excellent electro-optic performance, meeting the requirements for wafer-level large-scale manufacturing.
[0048] In summary, the fabrication method of a high-performance lithium niobate electro-optic modulator provided in this application firstly forms an optical waveguide, a modulation electrode, and a silicon oxide cladding layer sequentially on the front side of a thin-film lithium niobate wafer. Then, dicing paths are etched on the front side of the thin-film lithium niobate wafer, without forming an optical grooving structure. Finally, an optical grooving structure is etched on the back side of the thin-film lithium niobate wafer. The thin-film lithium niobate wafer, from bottom to top, includes a silicon substrate, a thermo-oxygen silicon layer, and a single-crystal lithium niobate thin film layer; the etching of the optical grooving structure stops at the thermo-oxygen silicon layer. Thus, by fabricating an optical grooving structure on the back side of the thin-film lithium niobate wafer and using the thermo-oxygen silicon layer as a stop layer, while only dicing paths are fabricated on the front side, the problems of photoresist defects and etching conflicts caused by front-side grooving are solved. This effectively improves wafer batch processing yield and pattern dimensional accuracy while ensuring the electro-optic modulation performance of the device.
[0049] Figure 10 This is a schematic diagram of a high-performance lithium niobate electro-optic modulator provided in an embodiment of this application. (Combined with...) Figure 10 As shown, the high-performance lithium niobate electro-optic modulator includes: a thin-film lithium niobate wafer; The front side of the thin-film lithium niobate wafer is provided with an optical waveguide 210, a modulation electrode 310, and an oxygen-silicon cladding layer 510 in sequence. The thin-film lithium niobate wafer comprises, from bottom to top, a silicon substrate 110, a thermally oxidized silicon layer 120, and a single-crystal lithium niobate thin film layer 130. The front side of the thin-film lithium niobate wafer is provided with a dicing channel, and the front side of the thin-film lithium niobate wafer is not provided with an optical slotting structure 810. The back side of the thin-film lithium niobate wafer is provided with an optical grooving structure 810; the bottom of the optical grooving structure ends at the thermo-oxidative silicon layer 120.
[0050] Furthermore, the total etching depth of the dicing path on the silicon oxide cladding 510 and the thermal silicon oxide layer 120 is 7μm-10μm, and the depth within the silicon substrate 110 is 150μm-300μm.
[0051] In summary, this application provides a high-performance lithium niobate electro-optic modulator, comprising: a thin-film lithium niobate wafer. The front side of the thin-film lithium niobate wafer sequentially comprises an optical waveguide, a modulation electrode, and a silicon oxide cladding layer; the thin-film lithium niobate wafer, from bottom to top, comprises a silicon substrate, a thermally oxidized silicon layer, and a single-crystal lithium niobate thin film layer; the front side of the thin-film lithium niobate wafer has a dicing channel, and the front side of the thin-film lithium niobate wafer does not have an optical slotting structure; the back side of the thin-film lithium niobate wafer has an optical slotting structure; the bottom of the optical slotting structure terminates at the thermally oxidized silicon layer. Thus, by fabricating an optical slotting structure on the back side of the thin-film lithium niobate wafer and using the thermally oxidized silicon layer as a stop layer, while only fabricating dicing channels on the front side, the problems of photoresist defects and etching conflicts caused by front-side slotting are solved, thereby effectively improving wafer batch processing yield and pattern dimensional accuracy while ensuring the electro-optic modulation performance of the device.
[0052] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for fabricating a high-performance lithium niobate electro-optic modulator, characterized in that, The preparation method includes: An optical waveguide, a modulation electrode, and an oxygen-silicon cladding are sequentially formed on the front side of a thin-film lithium niobate wafer; the thin-film lithium niobate wafer includes, from bottom to top, a silicon substrate, a thermal oxygen-silicon layer, and a single-crystal lithium niobate thin film layer. A dicing channel is etched on the front side of the thin-film lithium niobate wafer, and no optical slotting structure is formed on the front side of the thin-film lithium niobate wafer. An optical grooving structure is etched on the back side of the thin-film lithium niobate wafer; the etching of the optical grooving structure stops at the thermo-oxidative silicon layer.
2. The preparation method according to claim 1, characterized in that, Before etching the optical grooving structure on the back side of the thin-film lithium niobate wafer, the fabrication method further includes: A blue film is attached to the front side of the thin-film lithium niobate wafer.
3. The preparation method according to claim 1, characterized in that, The etching process to form cleavage paths on the front side of the thin-film lithium niobate wafer includes: Deep silicon etching was performed on the target area on the front side of the thin-film lithium niobate wafer using C4F8 and SF6 gases to form cleaving paths; The total etching depth of the cutting path on the silicon oxide cladding and the thermal silicon oxide layer is 7μm-10μm; The etch depth of the dicing channel on the silicon substrate is 150μm-300μm.
4. The preparation method according to claim 1, characterized in that, The process of etching an optical groove structure on the back side of the thin-film lithium niobate wafer includes: The silicon substrate is thinned from the back side; The target pattern is defined on the back side of the thinned silicon substrate using front-side marking overlay. The silicon substrate is etched based on the target pattern to form an optical groove structure.
5. The preparation method according to claim 4, characterized in that, The thinning of the silicon substrate from its back side includes: The silicon substrate is subjected to grinding and chemical mechanical polishing processes sequentially from the back side to remove 200μm-300μm of silicon material.
6. The preparation method according to claim 1, characterized in that, An optical waveguide is formed on the front side of the thin-film lithium niobate wafer, comprising: Optical waveguide patterns are defined on the front side of a thin-film lithium niobate wafer using electron beam lithography or deep ultraviolet lithography. The optical waveguide pattern is transferred to the front side of the thin-film lithium niobate wafer using a pure physical etching method with argon gas to form an optical waveguide; the etching depth is 50nm-600nm.
7. The preparation method according to claim 1, characterized in that, A modulation electrode is formed on the front side of a thin-film lithium niobate wafer, including: Electrode patterns are defined on the front side of a thin-film lithium niobate wafer using photolithography. Based on the electrode pattern, Ti / Au or Cr / Au metal stacks are deposited on the front side of the thin-film lithium niobate wafer using electron beam evaporation or magnetron sputtering processes; Excess metal is removed through a stripping process to form a modulation electrode.
8. The preparation method according to claim 2, characterized in that, After etching the optical groove structure on the back side of the thin-film lithium niobate wafer, the fabrication method further includes: Remove the blue film and clean the thin-film lithium niobate wafer.
9. A high-performance lithium niobate electro-optic modulator, characterized in that, include: Thin-film lithium niobate wafers; The front side of the thin-film lithium niobate wafer is sequentially provided with an optical waveguide, a modulation electrode, and an oxygen-silicon cladding layer. The thin-film lithium niobate wafer comprises, from bottom to top, a silicon substrate, a thermally oxidized silicon layer, and a single-crystal lithium niobate thin film layer. The front side of the thin-film lithium niobate wafer has a dicing channel, but the front side of the thin-film lithium niobate wafer does not have an optical slotting structure. The back side of the thin-film lithium niobate wafer is provided with an optical slotting structure; the bottom of the optical slotting structure ends at the thermo-oxidative silicon layer.
10. The high-performance lithium niobate electro-optic modulator according to claim 9, characterized in that, The depth of the dicing channel within the silicon substrate is 150μm-300μm.