Wafer level grating coupler and preparation method and application thereof

Abstract

The application provides a wafer-level grating coupler and a preparation method and application thereof, and belongs to the technical field of optoelectronic integration. The preparation method comprises the following steps: providing a wafer-level substrate, wherein the wafer-level substrate comprises an insulator and an active functional layer which is stacked on the insulator; sequentially preparing a non-photosensitive adhesive layer and a photosensitive adhesive layer on the active functional layer, and then performing step-by-step ultraviolet lithography processing to form a lithography area; performing developing processing to open the lithography area to form a plurality of windows, remove the main body of the non-photosensitive adhesive layer through the windows, form a groove with a cantilever structure, and expose the active functional layer at the bottom of the groove; depositing a mask pattern arranged periodically through the windows in a way of oblique incidence; removing the remaining non-photosensitive adhesive layer and photosensitive adhesive layer, and then performing selective etching on the active functional layer to form a periodically distributed strip grating structure; removing the mask pattern, depositing a passivation layer on the strip grating structure, and obtaining the grating coupler.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic integration technology, specifically relating to a wafer-level grating coupler, its fabrication method, and its application. Background Technology

[0002] With the rapid development of information technology, high-speed communication, big data transmission, and sensing technologies are no longer sufficient to meet the demands of high-capacity, high-speed information processing. Visible-ultraviolet (ViUV) band optoelectronic integration technology, as an emerging technology field, is demonstrating enormous development potential and broad application prospects. In recent years, the rapid development of ViUV band optoelectronic integration technology has led to the emergence of grating couplers, which, as key interface devices for efficient optical transmission between on-chip optoelectronic devices and external optical fibers, have become one of the core technologies in modern optical communication, sensing, and quantum technology. Grating couplers utilize the diffraction effect of periodic grating structures to convert light with larger modes in optical fibers into light with smaller modes, and then vertically transmit this light to horizontally arranged waveguides, achieving efficient off-chip to on-chip optical transmission. This offers significant advantages such as small size, ease of fabrication, flexible design, and suitability for wafer-level testing.

[0003] However, existing grating coupler technology still faces many challenges. In traditional optical communication bands (such as 1310nm and 1550nm), the coupling efficiency of grating couplers is limited by their inherent directionality and mode matching problems, resulting in significant energy coupling losses. Improved designs such as double etching or DBR mirrors are needed to achieve higher efficiency, but these improvements often require additional process steps, increasing manufacturing complexity and cost. At the same time, the length of the grating and the weakening of refractive index modulation result in a narrow reflection bandwidth, limiting its application in high-speed optical communication. More seriously, the fabrication of grating couplers in the visible-ultraviolet band faces special challenges: because the corresponding grating period is smaller (generally 100-400nm), and traditional step-lithography (light sources with wavelengths of 193nm and above) single-exposure technology cannot achieve 100nm-level structures or periodic grating structures, the coupling efficiency is difficult to improve, which seriously restricts the industrialization progress of emerging applications such as biosensing and quantum technology.

[0004] Furthermore, wafer-level large-area fabrication is crucial for the mass production of optoelectronic integrated chips. Particularly for visible-ultraviolet applications, submicron periodic grating structures need to be fabricated on materials such as III-V group lithium and / or thin-film lithium niobate. Technologies such as electron beam lithography, laser direct writing, or advanced EUV lithography suffer from time-consuming processes and high processing costs.

[0005] To address these issues, researchers have conducted several investigations. For example, patent CN102253459A discloses a silicon-on-insulator waveguide grating coupler and its fabrication method; CN104765247A discloses a method for fabricating a submicron grating; CN112782795B discloses a method for fabricating a submicron grating with halved period; and CN102368098B discloses a periodically modulated submicron diffraction grating and its fabrication method. While these existing technologies can achieve, or theoretically achieve, the fabrication of submicron-level periodic gratings, it remains difficult to simultaneously achieve high precision, cost, and timeliness, thus failing to meet the requirements for wafer-level mass production.

[0006] Therefore, how to solve the problems of difficulty in fabricating the hundred-nanometer-scale periodic structure of wafer-level gratings in the visible-ultraviolet band and high cost of large-area fabrication, so as to enable the gratings to achieve high-precision and high-stability optical signal processing in the visible-ultraviolet band and improve coupling efficiency, is an urgent technical problem to be solved. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a wafer-level grating coupler, its fabrication method, and its applications. This invention utilizes a stacked structure combining non-photosensitive and photosensitive adhesive layers, along with key processes such as traditional step-through ultraviolet lithography single-exposure technology and tilted-incident deposition masking technology, to achieve the fabrication of strip grating structures with grating periods of 120 nm and above. This method not only enables high-precision and high-stability optical signal processing in the visible-ultraviolet band but also allows for flexible control of the grating period and fill ratio, enhancing the adaptability of device design. The entire process flow is highly compatible with existing wafer manufacturing technologies, possessing good scalability and mass production stability, providing reliable technical support for the high-performance and large-scale application of visible-ultraviolet optoelectronic integrated circuits.

[0008] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for fabricating a wafer-level grating coupler, the method comprising the following steps: A wafer-level substrate is provided, the wafer-level substrate comprising an insulator and an active functional layer stacked on the insulator.

[0009] A non-photosensitive adhesive layer and a photosensitive adhesive layer are sequentially prepared on the active functional layer, and then a step-by-step ultraviolet lithography process is performed to form a photolithographic region in the photosensitive adhesive layer.

[0010] The photolithography area is opened to form several windows, and the main body of the non-photosensitive adhesive layer is removed through the windows to form a "groove" of the overhanging structure. The bottom of the groove exposes the active functional layer.

[0011] A periodically arranged mask pattern is deposited on the exposed active functional layer through the window in an oblique incidence manner.

[0012] The remaining non-photosensitive adhesive layer and photosensitive adhesive layer are removed, and then the active functional layer is selectively etched to form a periodically distributed strip grating structure.

[0013] The mask pattern is removed, and then a passivation layer is deposited on the strip grating structure to obtain the grating coupler.

[0014] This invention utilizes a stacked structure combining non-photosensitive and photosensitive adhesive layers, along with key processes such as step-through ultraviolet lithography single-exposure technology and tilted incident deposition masks, to achieve the fabrication of ultra-high line density strip grating structures with grating periods of 120 nm and above. This method not only enables high-precision and high-stability optical signal processing at short wavelengths but also allows for flexible control of the grating period and fill ratio, enhancing the adaptability of device design. The entire process is highly compatible with existing wafer manufacturing technologies, possessing excellent scalability and mass production stability, providing reliable technical support for the high-performance and large-scale application of short-wavelength photonic integrated circuits.

[0015] It should be noted that a wafer-level grating coupler refers to a grating coupler fabricated on a wafer-level substrate that is suitable for visible-ultraviolet light and communication band optical signals. It is an integrated optoelectronic device that achieves efficient coupling between optical signals and chip waveguides through a periodic strip grating structure. It has the advantages of wafer-level manufacturing and can significantly improve production efficiency and flexibility.

[0016] In this invention, step-by-step ultraviolet lithography refers to focusing the pattern on the photomask onto the photosensitive adhesive layer by distributing repeated ultraviolet exposures, thereby achieving pattern definition.

[0017] It should be noted that the "undercut groove" refers to the recessed space formed between the photosensitive adhesive layer and the active functional layer. The top edge of the groove is formed by the side edge of the photosensitive adhesive layer, and this edge extends into the groove relative to the sidewall of the groove. Its extension range exceeds the vertical projection boundary of the sidewall of the groove, so that the edge of the photosensitive adhesive layer "hangs" above the groove space, presenting a hanging shape with the top hanging upside down towards the recessed area, i.e., the "Under-Cut" structure.

[0018] It should be noted that "oblique incidence" refers to the directional transport deposition method used to form the mask unit in the mask pattern deposition process: the gaseous material is tilted at a preset angle relative to the surface normal of the photosensitive adhesive layer, that is, there is an angle between the transport direction and the vertical projection path of the window.

[0019] It should be noted that "window" refers to an opening made in the photosensitive adhesive layer to allow gaseous substances to pass through.

[0020] It should be noted that "several" refers to at least one, such as 1, 10, 20, 50, or more than 50.

[0021] Preferably, the active functional layer includes any one or a combination of at least two of the following: gallium nitride layer, aluminum nitride layer, gallium oxide layer, indium phosphide layer, lithium niobate layer, silicon nitride layer, or silicon layer.

[0022] Preferably, the thickness of the active functional layer is 50-5000nm, for example, it can be 50nm, 100nm, 200nm, 500nm, 1000nm, 1500nm, 2000nm, 2500nm, 3000nm, 3500nm, 4000nm, 4500nm or 5000nm, etc.

[0023] Preferably, the material of the non-photosensitive adhesive layer includes LOR series non-photosensitive adhesives and / or SF series non-photosensitive adhesives. For example, LOR series non-photosensitive adhesives may be LOR20A / B, LOR10A / B, LOR5A / B, or LOR3A / B, etc., and SF series non-photosensitive adhesives may be SF8, SF6, or SF2, etc.

[0024] Preferably, the material of the photosensitive adhesive layer includes any one or a combination of at least two of the following: S18 series adhesive, AR series adhesive, SPR series adhesive, ArF adhesive, or KrF adhesive. For example, the S18 series adhesive may be S1823, S1816, or S1805, and the AR series adhesive may be AR80, etc.

[0025] Preferably, the thicknesses of the non-photosensitive adhesive layer and the photosensitive adhesive layer are proportioned according to the target grating period and the angle of oblique incidence of the strip grating structure. For example, the thickness ratio of the non-photosensitive adhesive layer to the photosensitive adhesive layer can be (0.3-5.5):1, such as 0.38:1, 0.62:1, 0.8:1, 1.2:1, 2.86:1, or 5.1:1.

[0026] In this invention, adjusting the thickness ratio of the non-photosensitive adhesive layer and the photosensitive adhesive layer to meet the required grating period and tilt angle through mathematical matching helps to realize the fabrication of a grating coupler with adjustable fill ratio.

[0027] Preferably, during the step-through ultraviolet lithography process, the parameters include: the light source is ultraviolet light or deep ultraviolet light (e.g., it can be G line, I line, KrF, ArF, etc.), and the exposure linewidth is ≥0.2μm (e.g., it can be 0.2μm, 0.35μm, 0.45μm, 0.55μm, 0.65μm, 0.75μm, 0.85μm, 0.9μm, 1μm, 1.5μm or 2μm, etc.).

[0028] It should be noted that the G line is the mercury lamp spectral line with a wavelength of 436 nm; the I line is the mercury lamp spectral line with a wavelength of 365 nm; KrF is the excimer laser with a wavelength of 248 nm, which belongs to deep ultraviolet light; and ArF is the excimer laser with a wavelength of 193 nm, which belongs to deep ultraviolet light.

[0029] It should be noted that during the step-through ultraviolet lithography process, the photomask can be designed and manufactured according to a ratio of mask linewidth:actual linewidth = 5:1.

[0030] Preferably, the photolithography area includes a plurality of exposure areas for forming the window; the width of the exposure area is ≥200nm, for example, it can be 200nm, 350nm, 500nm, 700nm or 1000nm, etc.; the exposure period of the photolithography area is ≥240nm, for example, it can be 240nm, 400nm, 600nm, 800nm, 1000nm or 2000nm, etc., preferably 240-2000nm.

[0031] Preferably, the concentration of the developing solution used in the developing process is 0.15-25wt%, for example, it can be 0.15wt%, 0.26wt%, 1wt%, 2.38wt%, 5wt%, or 25wt%.

[0032] Preferably, the developer comprises any one or a combination of at least two of tetramethylammonium hydroxide aqueous solution (TMAH aqueous solution), potassium hydroxide aqueous solution (KOH aqueous solution), or n-butyl acrylate aqueous solution (nBA aqueous solution).

[0033] Preferably, the developing time is 0.5-2 min, for example, it can be 0.5 min, 1 min, 1.5 min or 2 min.

[0034] Preferably, the oblique incidence method includes: First, the first mask unit is deposited in a first tilt direction, and then the second mask unit is deposited in a second tilt direction; wherein, there is an intersection between the first tilt direction and the second tilt direction.

[0035] The present invention uses the above-mentioned oblique incidence method, which can make the mask unit period proportionally smaller than the exposure period.

[0036] Preferably, the angle between the first inclined direction and the vertical direction is denoted as α1, where α1 = 0°-90°, and can be, for example, 10°, 20°, 40°, 50° or 70°; the angle between the second inclined direction and the vertical direction is denoted as α2, where α2 = 0°-90°, and can be, for example, 10°, 20°, 40°, 50° or 70°.

[0037] In this invention, by precisely controlling the degree of tilt in the tilt direction, that is, the angle between the tilt direction and the vertical direction, the width and fill ratio of the mask unit can be precisely controlled.

[0038] Preferably, the material of the mask pattern includes any one or a combination of at least two of nickel, chromium, or tantalum.

[0039] Preferably, the thickness of the mask pattern is 20-100nm, for example, it can be 20nm, 40nm, 60nm, 80nm or 100nm.

[0040] Preferably, the arrangement period of the mask pattern is 120-2000nm, for example, it can be 120nm, 200nm, 500nm, 750nm, 1000nm, 1500nm or 2000nm, etc.

[0041] Preferably, the arrangement period of the mask pattern is half of the exposure period of the photolithography area.

[0042] Preferably, α1 = α2; both α1 and α2 satisfy the following requirement: α < arctanD / h, where D is the width of the window and h is the thickness of the photosensitive adhesive layer.

[0043] It should be noted that the width D of the window is also the width of the exposure area.

[0044] In this invention, the angle between the tilting direction and the vertical direction is defined to satisfy α < arctanD / h, in order to prevent the deposition path of the mask pattern from being completely blocked by the photosensitive adhesive layer.

[0045] Preferably, the fill ratio of the mask pattern is denoted as f, 0 < f = d / Λ ≤ 1, for example, it can be 0.2, 0.4, 0.6, 0.8 or 1, etc.; where d is the unit width of the mask pattern and Λ is the arrangement period of the mask pattern.

[0046] It should be noted that "fill ratio" refers to the proportion of the protrusions in the period of the grating. Λ is the arrangement period of the mask pattern, which is also the distribution period of the final strip grating structure.

[0047] In this invention, a suitable mask pattern fill ratio helps to achieve high-efficiency visible-ultraviolet photonic coupling.

[0048] Preferably, the preparation method includes the following steps: (1) A wafer-level substrate is provided, the wafer-level substrate comprising an insulator and an active functional layer stacked on the insulator; wherein the active functional layer comprises any one or a combination of at least two of gallium nitride, aluminum nitride, gallium oxide, indium phosphide, lithium niobate, silicon nitride or silicon; and the thickness of the active functional layer is 50-5000 nm.

[0049] (2) The wafer-level substrate is pre-cleaned, then baked or surface-adhesive treated. Subsequently, a non-photosensitive adhesive layer and a photosensitive adhesive layer are sequentially prepared on the active functional layer. Then, a stepper lithography machine is used for stepper ultraviolet lithography, and photolithographic regions are formed in the photosensitive adhesive layer through exposure. Afterward, post-baking is performed to suppress the standing wave effect. The non-photosensitive adhesive layer is made of LOR series non-photosensitive adhesive and / or SF series non-photosensitive adhesive; the photosensitive adhesive layer is made of S18 series adhesive, AR... The photolithography process utilizes any one or a combination of at least two of the following: a series of adhesives, SPR series adhesives, ArF adhesives, or KrF adhesives; the thicknesses of the non-photosensitive adhesive layer and the photosensitive adhesive layer are proportioned according to the target grating period and the angle of oblique incidence of the obtained strip grating structure; the parameters of the step-through ultraviolet lithography process include: the light source is ultraviolet or deep ultraviolet light, and the exposure linewidth is ≥0.2μm; the lithography area includes several exposure zones for forming windows; the width of the exposure zone is ≥200nm; and the exposure period of the lithography area is ≥240nm.

[0050] (3) A developing solution with a concentration of 0.15-25wt% is used for 0.5-2min of developing treatment to open the photolithography area to form several windows. The developing solution dissolves the main body of the non-photosensitive adhesive layer through the windows to form a groove with a hanging structure. The bottom of the groove exposes the active functional layer. The developing solution includes any one or a combination of at least two of tetramethylammonium hydroxide aqueous solution, potassium hydroxide aqueous solution or n-butyl acrylate aqueous solution.

[0051] (4) Using a tiltable deposition apparatus, the first mask unit is deposited through the window in a first tilt direction, and the second mask unit is deposited through the window in a second tilt direction, thereby depositing a periodically arranged mask pattern on the exposed active functional layer; wherein, the first tilt direction and the second tilt direction are mirror symmetrical; the angle between the first tilt direction and the vertical direction is denoted as α1, α1=0°-90°; the angle between the second tilt direction and the vertical direction is denoted as α2, α2=α1; both α1 and α2 satisfy The following requirements apply: α < arctanD / h, where D is the width of the window and h is the thickness of the photosensitive adhesive layer; the fill ratio of the mask pattern is denoted as f, 0 < f = d / Λ ≤ 1, where d is the unit width of the mask pattern and Λ is the arrangement period of the mask pattern; the material of the mask pattern includes any one or a combination of at least two of nickel, chromium, or tantalum; the thickness of the mask pattern is 20-100 nm; the arrangement period of the mask pattern is 120-2000 nm; and the arrangement period of the mask pattern is half the exposure period of the photolithography area.

[0052] (5) Use adhesive remover to remove the remaining non-photosensitive adhesive layer and photosensitive adhesive layer after step (4).

[0053] (6) Based on step (5), the maskless protection area of ​​the active functional layer is etched to form a periodically distributed strip grating structure; wherein, the resist remover includes acetone and / or N-methylpyrrolidone; the selective etching method includes ICP (inductively coupled plasma etching) or RIE (reactive ion etching); the distribution period of the strip grating structure is 120-2000nm (e.g., it can be 2000nm, 1000nm, 400nm, 300nm, 200nm or 120nm, etc.).

[0054] (7) Remove the mask pattern and then deposit a passivation layer on the strip grating structure to obtain the grating coupler; the material of the passivation layer includes silicon oxide, polymethyl methacrylate (PMMA) or any one of air.

[0055] In this invention, the tilting direction of the tiltable deposition apparatus can be achieved by either a rotating substrate clamp or a rotating substrate.

[0056] For example, tilting deposition can be achieved using a tilting deposition apparatus, such as electron beam evaporation, magnetron sputtering, or optical coating. The tilting deposition apparatus could be, for example, the Plassys MEB550SL3.

[0057] In a second aspect, the present invention provides a wafer-level grating coupler, wherein the grating coupler is prepared by the preparation method described in the first aspect.

[0058] The grating period of the wafer-level grating coupler is ≥120nm, for example, it can be 2000nm, 1000nm, 400nm, 300nm, 200nm or 120nm, etc.

[0059] Preferably, the grating period of the wafer-level grating coupler is 120-2000 nm.

[0060] Thirdly, the present invention provides an application of the grating coupler as described in the second aspect in an optoelectronic chip.

[0061] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0062] Compared with the prior art, the present invention has the following beneficial effects: This invention utilizes a stacked structure combining non-photosensitive and photosensitive adhesive layers, along with key processes such as step-through UV lithography single-exposure technology and tilted-incident deposition masking, to fabricate strip grating structures with grating periods of 120 nm and above. This method not only enables high-precision and high-stability optical signal processing at visible-ultraviolet wavelengths but also allows for flexible control of the grating period and fill ratio, enhancing the adaptability of device design. The entire process is highly compatible with existing wafer manufacturing technologies, possessing excellent scalability and mass production stability, providing reliable technical support for the high-performance and large-scale application of visible-ultraviolet optoelectronic chips. Attached Figure Description

[0063] Figure 1 This is a schematic diagram of the wafer-level substrate provided in step (1) of the fabrication process of Embodiment 1 of the present invention.

[0064] Figure 2 This is a schematic diagram of the structure after step (2) of the preparation process in Embodiment 1 of the present invention.

[0065] Figure 3 This is a schematic diagram of the structure after step (3) in the preparation process of Embodiment 1 of the present invention.

[0066] Figure 4 This is a schematic diagram of the structure after the deposition of the first mask unit in step (4) of the preparation process of Embodiment 1 of the present invention.

[0067] Figure 5This is a schematic diagram of the structure after the deposition of the second mask unit in step (4) of the preparation process of Embodiment 1 of the present invention.

[0068] Figure 6 This is a schematic diagram of the structure after step (5) of the preparation process in Embodiment 1 of the present invention.

[0069] Figure 7 This is a schematic diagram of the structure after step (6) in the preparation process of Embodiment 1 of the present invention.

[0070] Figure 8 This is a schematic diagram of the structure after step (7) in the preparation process of Embodiment 1 of the present invention.

[0071] Wherein, 1-wafer-level substrate; 11-bottom silicon; 12-buried oxide layer; 13-active functional layer; 2-non-photosensitive adhesive layer; 3-photosensitive adhesive layer; 4-window; 5-groove; 6-first mask unit; 7-second mask unit; 8-strip grating structure; 9-passivation layer. Detailed Implementation

[0072] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0073] It should be understood that in the description of this invention, the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0074] It should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0075] Example 1 This embodiment provides a method for fabricating a wafer-level grating coupler, the method comprising the following steps: (1) Provide wafer-level substrates, such as Figure 1 As shown, the wafer-level substrate 1 includes an insulator and an active functional layer 13 stacked on the insulator; wherein, the insulator includes a stacked bottom silicon 11 and a buried oxide layer 12, and the active functional layer 13 is stacked on the buried oxide layer 12; the active functional layer 13 is a gallium nitride layer with a thickness of 300 nm.

[0076] (2) The wafer-level substrate 1 is pre-cleaned (including organic cleaning and inorganic cleaning), then baked or surface-adhesive treated. Subsequently, a non-photosensitive adhesive layer 2 and a photosensitive adhesive layer 3 (including pre-baking) are sequentially prepared on the active functional layer 13 using a spin coating method. Then, a step-by-step ultraviolet lithography process is performed using a stepper lithography machine to form a photolithographic region in the photosensitive adhesive layer 3 through exposure. After that, a post-baking process is performed to suppress the standing wave effect. The non-photosensitive adhesive layer 2 is made of LOR series non-photosensitive adhesive, and the LOR series non-photosensitive adhesive is LOR20A / B. The photosensitive adhesive layer 3 is made of S18 series adhesive, specifically S1805; the thickness ratio of the non-photosensitive adhesive layer 2 to the photosensitive adhesive layer 3 is 0.62:1, and the thickness of the photosensitive adhesive layer is 500nm; the parameters of the step-through ultraviolet lithography process include: the light source is ultraviolet light with a wavelength of 365nm (I-line), the exposure linewidth is 0.4μm, and the minimum linewidth of the mask design is 2μm; the lithography area includes several exposure zones used to form windows; the width of the exposure zone is 400nm; and the exposure period of the lithography area is 600nm.

[0077] The structural diagram after step (2) is shown below. Figure 2 As shown.

[0078] (3) A developing solution with a concentration of 2.38wt% is used for 1 minute to open the photolithography area so that the plurality of exposure areas form a plurality of windows 4. The developing solution dissolves the main body of the non-photosensitive adhesive layer 2 through the windows 4 to form a groove 5 with a hanging structure. The bottom of the groove 5 exposes the active functional layer 13. The developing solution is a TMAH aqueous solution.

[0079] The structural diagram after step (3) is shown below. Figure 3 As shown.

[0080] (4) Using a tiltable deposition apparatus (i.e., a Plassys MEB550SL3 apparatus), the first mask unit 6 is deposited through the window 4 in a first tilt direction, and the second mask unit 7 is deposited through the window 4 in a second tilt direction, thereby depositing a periodically arranged mask pattern on the exposed active functional layer 13; wherein, the first tilt direction and the second tilt direction are mirror symmetrical; the angle between the first tilt direction and the vertical direction is denoted as α1, α1 = 15°; the angle between the second tilt direction and the vertical direction is denoted as α2, α2 = α1; both α1 and α2 satisfy The following requirements apply: α < arctanD / h, where D is the width of the window (i.e., the width of the exposure area), and h is the thickness of the photosensitive adhesive layer 3; the fill ratio of the mask pattern is denoted as f, f = d / Λ, f = 0.887, where d is the unit width of the mask pattern, d = 266 nm, Λ is the arrangement period of the mask pattern, Λ = 300 nm; the material of the mask pattern is nickel; the thickness of the mask pattern is 60 nm; the arrangement period of the mask pattern is 300 nm; and the arrangement period of the mask pattern is half the exposure period of the photolithography area.

[0081] The structural diagram after deposition of the first mask unit in step (4) is shown below. Figure 4 As shown, the structural diagram after the deposition of the second mask unit in step (4) is as follows. Figure 5 As shown.

[0082] (5) Use adhesive remover to remove the remaining non-photosensitive adhesive layer and photosensitive adhesive layer after step (4).

[0083] The structural diagram after step (5) is shown below. Figure 6 As shown.

[0084] (6) Based on step (5), the maskless protection area of ​​the active functional layer 13 is etched to form a periodically distributed strip grating structure 8; wherein the resist remover is acetone; the selective etching method is ICP method; and the distribution period of the strip grating structure 8 is 300nm.

[0085] The structural diagram after step (6) is shown below. Figure 7 As shown.

[0086] (7) Remove the mask pattern and then deposit a passivation layer 9 on the strip grating structure using PECVD (plasma-enhanced chemical vapor deposition) to obtain the grating coupler; the passivation layer 9 is made of silicon oxide and covers the strip grating structure 8.

[0087] The structural diagram after step (7) is shown below. Figure 8 As shown.

[0088] Example 2 This embodiment provides a method for fabricating a wafer-level grating coupler, the method comprising the following steps: (1) A wafer-level substrate is provided, the wafer-level substrate comprising an insulator and an active functional layer stacked on the insulator; wherein the insulator comprises a stacked bottom silicon and a buried oxide layer, and the active functional layer is stacked on the buried oxide layer; the active functional layer is an aluminum nitride layer with a thickness of 200 nm.

[0089] (2) The wafer-level substrate is pre-cleaned (including organic and inorganic cleaning), then surface adhesion is enhanced, and then a non-photosensitive adhesive layer and a photosensitive adhesive layer (including pre-baking) are sequentially prepared on the active functional layer using a spin coating method. Then, a stepper lithography machine is used for stepper ultraviolet lithography, and photolithographic regions are formed in the photosensitive adhesive layer through exposure. Afterwards, post-baking is performed to suppress the standing wave effect. The non-photosensitive adhesive layer is made of LOR series non-photosensitive adhesive, specifically LOR10A / B. The photosensitive adhesive layer is made of ArF adhesive, specifically EPIC2350; the thickness ratio of the non-photosensitive adhesive layer to the photosensitive adhesive layer is 0.38:1, and the thickness of the photosensitive adhesive layer is 250nm; the parameters of the step-through ultraviolet lithography process include: the light source is deep ultraviolet light with a wavelength of 193nm (ArF), the exposure linewidth is 0.2μm, and the minimum linewidth of the mask design is 1μm; the lithography area includes several exposure zones used to form windows; the width of the exposure zone is 200nm; and the exposure period of the lithography area is 240nm.

[0090] (3) A developing solution with a concentration of 2.38wt% is used for 1 minute to open the photolithography area so that the plurality of exposure areas form a plurality of windows. The developing solution dissolves the main body of the non-photosensitive adhesive layer through the windows to form a groove of the hanging structure. The bottom of the groove exposes the active functional layer. The developing solution is a TMAH aqueous solution.

[0091] (4) Using a tiltable deposition apparatus (i.e., a Plassys MEB550SL3 apparatus), the first mask unit is deposited through the window in a first tilt direction, and the second mask unit is deposited through the window in a second tilt direction, thereby depositing a periodically arranged mask pattern on the exposed active functional layer; wherein, the first tilt direction and the second tilt direction are mirror symmetrical; the angle between the first tilt direction and the vertical direction is denoted as α1, α1 = 30°; the angle between the second tilt direction and the vertical direction is denoted as α2, α2 = α1; the α1 and α2 satisfies the following requirements: α < arctanD / h, where D is the width of the window (i.e., the width of the exposure area), and h is the thickness of the photosensitive adhesive layer; the fill ratio of the mask pattern is denoted as f, f = d / Λ, f is 0.464, where d is the unit width of the mask pattern, and Λ is the arrangement period of the mask pattern; the material of the mask pattern is nickel; the thickness of the mask pattern is 60 nm; the arrangement period of the mask pattern is 120 nm; the arrangement period of the mask pattern is half of the exposure period of the photolithography area.

[0092] (5) Use adhesive remover to remove the remaining non-photosensitive adhesive layer and photosensitive adhesive layer after step (4).

[0093] (6) Based on step (5), the maskless protection area of ​​the active functional layer is etched to form a periodically distributed strip grating structure; wherein the resist remover is acetone; the selective etching method is ICP method; and the distribution period of the strip grating structure is 120nm.

[0094] (7) Remove the mask pattern, and then use PECVD (plasma-enhanced chemical vapor deposition) to deposit a passivation layer on the strip grating structure to obtain the grating coupler; the passivation layer is made of silicon oxide and covers the strip grating structure.

[0095] Example 3 This embodiment provides a method for fabricating a wafer-level grating coupler, the method comprising the following steps: (1) A wafer-level substrate is provided, the wafer-level substrate comprising an insulator and an active functional layer stacked on the insulator; wherein the insulator comprises a stacked bottom silicon and a buried oxide layer, and the active functional layer is stacked on the buried oxide layer; the active functional layer is a lithium niobate layer with a thickness of 600 nm.

[0096] (2) The wafer-level substrate is pre-cleaned (including organic and inorganic cleaning), then pre-baked, and then non-photosensitive and photosensitive adhesive layers are sequentially prepared on the active functional layer using a spin coating method. Then, step-by-step ultraviolet lithography is performed using a stepper lithography machine to form photolithographic regions in the photosensitive adhesive layer through exposure, followed by post-baking to suppress the standing wave effect; wherein, the non-photosensitive adhesive layer is made of LOR series non-photosensitive adhesive, and the LOR series non-photosensitive adhesive is LOR5A / B; the photosensitive... The adhesive layer is made of AR series adhesive, specifically AR80; the thickness ratio of the non-photosensitive adhesive layer to the photosensitive adhesive layer is 1:1, and the thickness of the photosensitive adhesive layer is 750nm; the parameters of the step-through ultraviolet lithography process include: the light source is ultraviolet light with a wavelength of 365nm (I-line), the exposure linewidth is 1μm, and the minimum linewidth of the mask design is 5μm; the lithography area includes several exposure zones used to form windows; the width of the exposure zone is 1000nm; and the exposure period of the lithography area is 1500nm.

[0097] (3) A developing solution with a concentration of 2.38wt% is used for 1 minute to open the photolithography area so that the plurality of exposure areas form a plurality of windows. The developing solution dissolves the main body of the non-photosensitive adhesive layer through the windows to form a groove of the hanging structure. The bottom of the groove exposes the active functional layer. The developing solution is a TMAH aqueous solution.

[0098] (4) Using a tiltable deposition apparatus (i.e., a Plassys MEB apparatus), the first mask unit is deposited through the window in a first tilt direction, and the second mask unit is deposited through the window in a second tilt direction, thereby depositing a periodically arranged mask pattern on the exposed active functional layer; wherein, the first tilt direction and the second tilt direction are mirror symmetrical; the angle between the first tilt direction and the vertical direction is denoted as α1, α1 = 45°; the angle between the second tilt direction and the vertical direction is denoted as α2, α2 = α1; both α1 and α2 are... The following requirements must be met: α < arctanD / h, where D is the width of the window (i.e., the width of the exposure area), and h is the thickness of the photosensitive adhesive layer; the fill ratio of the mask pattern is denoted as f, f = d / Λ, f is 0.333, where d is the unit width of the mask pattern, and Λ is the arrangement period of the mask pattern; the material of the mask pattern is nickel; the thickness of the mask pattern is 60 nm; the arrangement period of the mask pattern is 750 nm; and the arrangement period of the mask pattern is half of the exposure period of the photolithography area.

[0099] (5) Use adhesive remover to remove the remaining non-photosensitive adhesive layer and photosensitive adhesive layer after step (4).

[0100] (6) Based on step (5), the maskless protection area of ​​the active functional layer is etched to form a periodically distributed strip grating structure; wherein the resist remover is acetone; the selective etching method is ICP method; and the distribution period of the strip grating structure is 750nm.

[0101] (7) Remove the mask pattern, and then use PECVD (plasma-enhanced chemical vapor deposition) to deposit a passivation layer on the strip grating structure to obtain the grating coupler; the passivation layer is made of silicon oxide and covers the strip grating structure.

[0102] Example 4 The difference between this embodiment and Embodiment 1 is that the thickness ratio of the non-photosensitive adhesive layer to the photosensitive adhesive layer is 2.86:1.

[0103] The remaining preparation methods and parameters are consistent with those in Example 1.

[0104] Example 5 The difference between this embodiment and Embodiment 1 is that the thickness ratio of the non-photosensitive adhesive layer to the photosensitive adhesive layer is 5.1:1.

[0105] The remaining preparation methods and parameters are consistent with those in Example 1.

[0106] Example 6 The difference between this embodiment and Embodiment 2 is that the thickness ratio of the non-photosensitive adhesive layer to the photosensitive adhesive layer is 0.8:1.

[0107] The remaining preparation methods and parameters are consistent with those in Example 2.

[0108] Example 7 The difference between this embodiment and Embodiment 2 is that the thickness ratio of the non-photosensitive adhesive layer to the photosensitive adhesive layer is 1.2:1.

[0109] The remaining preparation methods and parameters are consistent with those in Example 2.

[0110] Example 8 The difference between this embodiment and Embodiment 3 is that the thickness ratio of the non-photosensitive adhesive layer to the photosensitive adhesive layer is 2:1.

[0111] The remaining preparation methods and parameters are consistent with those in Example 3.

[0112] Example 9 The difference between this embodiment and Embodiment 3 is that the thickness ratio of the non-photosensitive adhesive layer to the photosensitive adhesive layer is 3:1.

[0113] The remaining preparation methods and parameters are consistent with those in Example 3.

[0114] Example 10 The difference between this embodiment and Embodiment 1 is that the concentration of the alkaline developing solution is 0.13%.

[0115] The remaining preparation methods and parameters are consistent with those in Example 1.

[0116] Example 11 The difference between this embodiment and Embodiment 1 is that the concentration of the alkaline developing solution is 10%.

[0117] The remaining preparation methods and parameters are consistent with those in Example 1.

[0118] Example 12 The difference between this embodiment and Embodiment 1 is that the developing time is 15 seconds.

[0119] The remaining preparation methods and parameters are consistent with those in Example 1.

[0120] Example 13 The difference between this embodiment and Embodiment 1 is that the development process takes 190 seconds.

[0121] The remaining preparation methods and parameters are consistent with those in Example 1.

[0122] Example 14 The difference between this embodiment and Embodiment 1 is that the deposition of the second mask unit is not performed; that is, the mask pattern is deposited only through the window in the first tilt direction.

[0123] The remaining preparation methods and parameters are consistent with those in Example 1.

[0124] Comparative Example 1 The difference between this comparative example and Example 1 is that the non-photosensitive adhesive layer is not provided.

[0125] The remaining preparation methods and parameters are consistent with those in Example 1.

[0126] Comparative Example 2 The difference between this comparative example and Example 1 is that in step (4), the deposition direction of the mask pattern is replaced with a direction perpendicular to the window, without any tilt direction.

[0127] The remaining preparation methods and parameters are consistent with those in Example 1.

[0128] analyze As can be seen from Examples 1-3 and Examples 4-9, the thicknesses of the non-photosensitive adhesive layer and the photosensitive adhesive layer are matched according to the target grating period and the angle of oblique incidence of the strip grating structure, which helps to realize the fabrication of a grating coupler with adjustable fill ratio.

[0129] As can be seen from the comparison between Example 1 and Examples 10-11, if the concentration of the developer is too low, it will result in insufficient development, leaving non-photosensitive adhesive residue on the substrate, which will easily fall off after the mask is deposited; if the concentration of the developer is too high, it will result in overdevelopment, causing the photosensitive adhesive pattern to deform or collapse, affecting the masking effect.

[0130] As can be seen from the comparison between Example 1 and Examples 12-13, if the development time is too short, the development will be insufficient, resulting in rough sidewalls of the photosensitive adhesive and non-photosensitive adhesive residue on the substrate, leading to grating jaggedness or detachment; if the development time is too long, it will cause overdevelopment, deformation or collapse of the photosensitive adhesive pattern, affecting the masking effect.

[0131] A comparison between Example 1 and Example 14 shows that if the mask pattern is deposited through the window only in the first tilt direction, it will affect the fill ratio of the mask pattern, that is, the fill ratio of the strip grating structure.

[0132] As can be seen from the comparison between Example 1 and Comparative Example 1, if the non-photosensitive adhesive layer is not provided, the tilted mask pattern will stick together and cannot form a grating pattern.

[0133] As can be seen from the comparison between Example 1 and Comparative Example 2, if in step (4), the deposition direction of the mask pattern is replaced with the direction perpendicular to the window and there is no tilt direction, then the mask pattern and the photolithography pattern have the same period, and the grating period remains unchanged.

[0134] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for fabricating a wafer-level grating coupler, characterized in that, The preparation method includes the following steps: A wafer-level substrate is provided, the wafer-level substrate comprising an insulator and an active functional layer stacked on the insulator; A non-photosensitive adhesive layer and a photosensitive adhesive layer are sequentially prepared on the active functional layer, and then a step-by-step ultraviolet lithography process is performed to form a photolithographic region in the photosensitive adhesive layer; The photolithography area is opened to form several windows, and the main body of the non-photosensitive adhesive layer is removed through the windows to form a "groove" of the overhanging structure. The bottom of the groove exposes the active functional layer. A periodically arranged mask pattern is deposited on the exposed active functional layer through the window in an oblique incidence manner. The remaining non-photosensitive adhesive layer and photosensitive adhesive layer are removed, and then the active functional layer is selectively etched to form a periodically distributed strip grating structure. The mask pattern is removed, and then a passivation layer is deposited on the strip grating structure to obtain the grating coupler.

2. The preparation method according to claim 1, characterized in that, The active functional layer includes any one or a combination of at least two of the following: gallium nitride layer, aluminum nitride layer, gallium oxide layer, indium phosphide layer, lithium niobate layer, silicon nitride layer, or silicon layer; And / or, the thickness of the active functional layer is 50-5000 nm.

3. The preparation method according to claim 1 or 2, characterized in that, The materials of the non-photosensitive adhesive layer include LOR series non-photosensitive adhesives and / or SF series non-photosensitive adhesives; And / or, the photosensitive adhesive layer is made of step-type ultraviolet photoresist; The stepper UV photoresist includes any one or a combination of at least two of the following: S18 series photoresist, AR series photoresist, SPR series photoresist, ArF photoresist, or KrF photoresist. And / or, the thickness ratio of the non-photosensitive adhesive layer and the photosensitive adhesive layer is determined according to the target grating period and the angle of oblique incidence of the strip grating structure.

4. The preparation method according to claim 1, characterized in that, During the step-through ultraviolet lithography process, the parameters include: the light source is ultraviolet light or deep ultraviolet light, and the exposure linewidth is ≥0.2μm; And / or, the photolithography region includes a plurality of exposure areas for forming the window; the width of the exposure area is ≥200nm; the exposure period of the photolithography region is ≥240nm.

5. The preparation method according to claim 1, characterized in that, During the development process, the concentration of the developing solution used is 0.15-25 wt%. The developer includes any one or a combination of at least two of the following: an aqueous solution of tetramethylammonium hydroxide, an aqueous solution of potassium hydroxide, or an aqueous solution of n-butyl acrylate. And / or, the development process takes 0.5-2 minutes.

6. The preparation method according to claim 1, characterized in that, The oblique incidence method includes: First, the first mask unit is deposited in a first tilt direction, and then the second mask unit is deposited in a second tilt direction; wherein, there is an intersection between the first tilt direction and the second tilt direction; The angle between the first tilting direction and the vertical direction is denoted as α1, where α1 = 0° - 90°; the angle between the second tilting direction and the vertical direction is denoted as α2, where α2 = 0° - 90°. And / or, the material of the mask pattern includes any one or a combination of at least two of nickel, chromium, or tantalum; And / or, the thickness of the mask pattern is 20-100 nm; And / or, the arrangement period of the mask pattern is 120-2000nm.

7. The preparation method according to claim 6, characterized in that, The arrangement period of the mask pattern is half of the exposure period of the photolithography area; And / or, α1 = α2; both α1 and α2 satisfy the following requirement: α < arctanD / h, where D is the width of the window and h is the thickness of the photosensitive adhesive layer; And / or, the fill ratio of the mask pattern is denoted as f, 0 < f = d / Λ ≤ 1, where d is the unit width of the mask pattern and Λ is the arrangement period of the mask pattern.

8. The preparation method according to claim 1, characterized in that, The preparation method includes the following steps: (1) A wafer-level substrate is provided, the wafer-level substrate comprising an insulator and an active functional layer stacked on the insulator; wherein the active functional layer comprises any one or a combination of at least two of gallium nitride, aluminum nitride, gallium oxide, indium phosphide, lithium niobate, silicon nitride, or silicon; and the thickness of the active functional layer is 50-5000 nm. (2) The wafer-level substrate is pre-cleaned, then baked or surface-adhesive treated. Subsequently, a non-photosensitive adhesive layer and a photosensitive adhesive layer are sequentially prepared on the active functional layer. Then, a stepper lithography machine is used for stepper ultraviolet lithography. Photolithographic regions are formed in the photosensitive adhesive layer through exposure, followed by post-baking to suppress standing wave effects. The non-photosensitive adhesive layer is made of LOR series non-photosensitive adhesive and / or SF series non-photosensitive adhesive; the photosensitive adhesive layer is made of stepper ultraviolet photoresist. The stepper ultraviolet photoresist package... The adhesive comprises any one or a combination of at least two of the following: S18 series adhesives, AR series adhesives, SPR series adhesives, ArF adhesives, or KrF adhesives; the thicknesses of the non-photosensitive adhesive layer and the photosensitive adhesive layer are proportioned according to the target grating period and the angle of oblique incidence of the obtained strip grating structure; the parameters of the step-through ultraviolet lithography process include: the light source is ultraviolet light or deep ultraviolet light, and the exposure linewidth is ≥0.2μm; the lithography area includes several exposure zones for forming windows; the width of the exposure zone is ≥200nm; and the exposure period of the lithography area is ≥240nm. (3) A developing solution with a concentration of 0.15-25wt% is used for 0.5-2min of developing treatment to open the photolithography area to form several windows. The developing solution dissolves the main body of the non-photosensitive adhesive layer through the windows to form a groove with a hanging structure. The bottom of the groove exposes the active functional layer. The developing solution includes any one or a combination of at least two of tetramethylammonium hydroxide aqueous solution, potassium hydroxide aqueous solution or n-butyl acrylate aqueous solution. (4) Using a tiltable deposition apparatus, the first mask unit is deposited through the window in a first tilt direction, and the second mask unit is deposited through the window in a second tilt direction, thereby depositing a periodically arranged mask pattern on the exposed active functional layer; wherein, the first tilt direction and the second tilt direction are mirror symmetrical; the angle between the first tilt direction and the vertical direction is denoted as α1, α1=0°-90°; the angle between the second tilt direction and the vertical direction is denoted as α2, α2=α1; both α1 and α2 satisfy The following requirements apply: α < arctanD / h, where D is the width of the window and h is the thickness of the photosensitive adhesive layer; the fill ratio of the mask pattern is denoted as f, 0 < f = d / Λ ≤ 1, where d is the unit width of the mask pattern and Λ is the arrangement period of the mask pattern; the material of the mask pattern includes any one or a combination of at least two of nickel, chromium, or tantalum; the thickness of the mask pattern is 20-100 nm; the arrangement period of the mask pattern is 120-2000 nm; and the arrangement period of the mask pattern is half the exposure period of the photolithographic region. (5) Use adhesive remover to remove the remaining non-photosensitive adhesive layer and photosensitive adhesive layer after step (4); (6) Based on step (5), the maskless protection area of ​​the active functional layer is etched to form a periodically distributed strip grating structure; wherein, the resist remover includes acetone and / or N-methylpyrrolidone; the selective etching method includes ICP or RIE; the distribution period of the strip grating structure is 120-2000 nm; (7) Remove the mask pattern and then deposit a passivation layer on the strip grating structure to obtain the grating coupler; the material of the passivation layer includes any one of silicon oxide, polymethyl methacrylate or air.

9. A wafer-level grating coupler, characterized in that, The grating coupler is prepared using the fabrication method described in any one of claims 1-8; The grating period of the wafer-level grating coupler is ≥120nm.

10. An application of the grating coupler as described in claim 9 in an optoelectronic chip.

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