Silicon-based electro-optical modulator with enhanced modulation bandwidth and manufacturing method thereof

Abstract

The invention relates to the technical field of silicon-based integrated photoelectronics, and particularly discloses a silicon-based electro-optical modulator with an enhanced modulation bandwidth and a manufacturing method of the silicon-based electro-optical modulator. According to the traveling wave electrode structure, the effective refractive index is reduced through the specific electrode width W and the specific electrode distance D, phase velocity matching of light waves and microwaves is achieved, and therefore the modulation efficiency and the bandwidth are improved; the ridge waveguide structure optimizes the overlapping degree of an optical mode and a microwave mode by adjusting the ridge height H and the width B, and carrier absorption loss is reduced; the electro-optical modulator adopts the periodically loaded coplanar waveguide traveling wave electrode, so that the refractive index is effectively reduced, phase velocity matching of light waves and microwaves is realized, and the modulation efficiency and the bandwidth are remarkably improved. Meanwhile, by introducing the ridge-shaped waveguide structure and accurately adjusting the size parameter of the ridge-shaped waveguide structure, the overlapping degree of an optical mode and a microwave mode is optimized, the carrier absorption loss is reduced, and the device performance is further improved.

Description

Technical Field

[0001] The invention relates to the technical field of silicon-based integrated optoelectronics, in particular to a silicon-based electro-optic modulator with enhanced modulation bandwidth and a manufacturing method thereof. Background Art

[0002] In the field of silicon-based integrated optoelectronics, electro-optic modulators are key devices that can convert electrical signals into optical signals, or vice versa. With the rapid development of fiber-optic communication networks and data centers, the modulation bandwidth and energy efficiency requirements of electro-optic modulators are getting higher and higher. Traditional electro-optic modulators are usually based on Mach-Zehnder interferometer structures or electro-absorption modulators, but these technologies face limitations such as large size, high power consumption, and incompatibility with existing CMOS processes. Especially in scenarios where high-speed transmission (such as above 100Gb / s) is pursued, the bandwidth bottleneck of traditional modulators becomes the main factor limiting system performance.

[0003] To overcome these challenges, electro-optic modulation technology based on traveling wave electrodes has emerged in the industry, which improves modulation efficiency and bandwidth by matching the phase velocity of light waves and microwaves in waveguides. However, existing traveling wave electrode designs often fail to fully consider the relationship between electrodes and waveguides, resulting in limited device performance. In addition, during the manufacturing process, precise control of nanoscale geometric dimensions and refractive index changes is crucial to achieving high-performance electro-optic modulators, which requires the use of high-precision micro-nano processing technology. Despite this, there are still many challenges in material selection, structural design, and manufacturing processes, which limit the performance improvement and cost reduction of silicon-based electro-optic modulators. Chinese invention patent CN202110495084.0 discloses a first-order electro-optic effect silicon modulator and its preparation process. The patent proposes etching an amorphous silicon growth window in the silicon waveguide area and transforming amorphous silicon into single crystal silicon by irradiating light of a specific wavelength. Although this method may improve modulation efficiency, the patent does not detail how to accurately control the light irradiation process and how to ensure the efficiency of the transformation from amorphous silicon to single crystal silicon, which may lead to inconsistencies and low yields in the production process. Chinese invention patent CN202311848000.2 discloses a silicon-based electro-optic modulator, but does not provide specific implementation details or advantages over traditional technologies. The lack of detailed technical implementation and comparative analysis may limit the effectiveness of this patent in practical applications. Chinese invention patent CN202310746818.7 discloses a silicon-based thin-film lithium niobate broadband electro-optic modulator chip based on a traveling wave electrode structure. This patent proposes a silicon-based thin-film lithium niobate broadband electro-optic modulator chip based on a traveling wave electrode structure. Although the bandwidth may be improved, the patent may not fully explore potential defects in integration, cost-effectiveness or manufacturing complexity compared with existing technologies. In addition, the integration of lithium niobate materials may face challenges in compatibility with silicon-based CMOS processes.

[0004] Therefore, in response to the needs of high-speed, low-power optical interconnection and optical communication systems, developing a new silicon-based electro-optical modulator with an optimized traveling wave electrode structure and ridge waveguide structure, as well as the corresponding high-precision manufacturing method, has become one of the current focuses of research and development of integrated optoelectronic technology. Summary of the invention

[0005] The purpose of the present invention is to provide a silicon-based electro-optic modulator with enhanced modulation bandwidth and a manufacturing method thereof in view of the defects of the prior art, so as to solve the problems raised by the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a silicon-based electro-optic modulator with enhanced modulation bandwidth, comprising a traveling wave electrode structure and a ridge waveguide structure, characterized in that:

[0007] The traveling wave electrode structure includes a coplanar waveguide traveling wave electrode with periodic load characteristics. The traveling wave electrode structure reduces the effective refractive index through a specific electrode width W and an electrode spacing D, so as to achieve phase velocity matching between light waves and microwaves, thereby improving modulation efficiency and bandwidth; wherein, 500nm≤W≤1500nm, 200nm≤D≤1000nm;

[0008] The ridge waveguide structure optimizes the overlap between the optical mode and the microwave mode by adjusting the ridge height H and width B, thereby reducing carrier absorption loss; wherein, 100nm≤H≤500nm, 400nm≤B≤1200nm;

[0009] As a preferred technical solution of the present invention, the traveling wave electrode structure further includes a grounding electrode, and the grounding electrode is arranged beside the coplanar waveguide traveling wave electrode; the width G of the grounding electrode satisfies 300nm≤G≤800nm.

[0010] As a preferred technical solution of the present invention, the material of the ridge waveguide structure is silicon, and the refractive index n of the ridge waveguide satisfies 2.5≤n≤3.5.

[0011] As a preferred technical solution of the present invention, the traveling wave electrode structure and the ridge waveguide structure are formed in one piece.

[0012] A method for manufacturing a silicon-based electro-optical modulator comprises the following steps:

[0013] S1: Using electron beam lithography technology to form the pattern of traveling wave electrodes and ridge waveguides on the silicon wafer; the electron beam dose is controlled at 50μC / cm 2 ≤E≤200μC / cm 2 to ensure high resolution and accuracy of the pattern;

[0014] S2: Using plasma dry etching technology, the above pattern is transferred to a silicon wafer to form a traveling wave electrode and a ridge waveguide structure with a predetermined size; the plasma power P is controlled between 100W≤P≤300W to achieve high-precision nanoscale etching;

[0015] S3: depositing a metal layer on the traveling wave electrode to form a conductive electrode; the thickness T of the metal layer is controlled within 50nm≤T≤200nm to ensure the conductivity and signal transmission efficiency of the electrode;

[0016] S4: Chemical mechanical polishing is used to smooth the surface of the silicon wafer to ensure the quality and uniformity of the subsequent deposited or grown layers;

[0017] S5: A layer of low refractive index material (such as silicon oxide) is grown on the ridge waveguide structure by plasma enhanced chemical vapor deposition (PECVD) technology to reduce the loss in the optical waveguide; the thickness S of the low refractive index material layer is controlled to be 100nm≤S≤500nm.

[0018] As a preferred technical solution of the present invention, the electron beam lithography technology in step S1 includes using an electron beam exposure system with a high brightness electron source and an electron beam resist material with high sensitivity and resolution.

[0019] As a preferred technical solution of the present invention, the plasma dry etching technology in step S2 includes using a reactive ion etching (RIE) system and an etching gas mixture with high selectivity and fast etching rate.

[0020] As a preferred technical solution of the present invention, the plasma enhanced chemical vapor deposition technology in step S5 includes using a CVD device capable of generating high-density plasma, as well as optimized precursor gas flow ratio and deposition parameters to achieve uniform, dense and low refractive index silicon oxide layer deposition.

[0021] As a preferred technical solution of the present invention, the operations of steps S1-S3 are performed sequentially in a clean room environment to prevent contamination and ensure nano-machining accuracy.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: the electro-optic modulator adopts a periodically loaded coplanar waveguide traveling wave electrode, which effectively reduces the refractive index, realizes the phase velocity matching of light waves and microwaves, and significantly improves the modulation efficiency and bandwidth. At the same time, by introducing a ridge waveguide structure and accurately adjusting its size parameters, the overlap between the optical mode and the microwave mode is optimized, the carrier absorption loss is reduced, and the device performance is further improved. In addition, the present invention also involves advanced nano-processing technology to ensure high precision and low damage in device manufacturing. Compared with the prior art, the silicon-based electro-optic modulator of the present invention exhibits higher modulation bandwidth and lower driving voltage, providing an effective solution for high-speed optical interconnection and optical fiber communication systems. The present invention has important application potential in the field of silicon-based integrated optoelectronic technology and will help promote the development of next-generation high-speed optical communication networks.

[0023] The present invention successfully realizes a high-speed, low-power silicon-based electro-optic modulator that is compatible with existing CMOS processes. Its innovative traveling-wave electrode structure and ridge waveguide design significantly improve the modulation bandwidth, while optimizing the device size and reducing the loss in the optical waveguide through precise manufacturing processes. These technological advances not only enhance the efficiency and speed of data transmission, but also provide a reliable solution for the manufacture and performance improvement of high-density integrated optoelectronic devices, further promoting the application and development of optical interconnection and optical communication systems in data centers, optical computing and other high-speed optical communication fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the traveling wave electrode structure of the present invention;

[0025] Figure 2 is a schematic diagram of the ridge waveguide structure of the present invention;

[0026] Figure 3 It is a flow chart of the manufacturing method of the present invention. DETAILED DESCRIPTION

[0027] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0028] like Figure 1-3 As shown: Embodiment 1: A method for manufacturing a silicon-based electro-optic modulator with enhanced modulation bandwidth, the specific steps are as follows:

[0029] 1. Preparation of traveling wave electrode structure:

[0030] (1) On SOI (silicon on insulator) wafers, patterning was performed using an electron beam lithography machine. First, ZEP520A electron beam resist was applied and thermally cured. Then, the electron beam dose was set to 120 μC / cm at an acceleration voltage of 75 kV. 2 , using vector scanning mode exposure to form a resist pattern of the traveling wave electrode.

[0031] (2) Plasma dry etching was used, using a mixture of CF4 and O2 gas, and the etching power was set to 180 W. During the etching process, the etching depth was monitored by endpoint detection technology to ensure accurate transfer of the resist pattern to the silicon substrate. Finally, a coplanar waveguide traveling wave electrode structure was formed, in which the electrode width was 3 μm, the period length was 30 μm, and the ground electrode width was 8 μm.

[0032] 2. Ridge waveguide preparation:

[0033] (1) Electron beam lithography was used again on the traveling wave electrode structure to coat ZEP520A electron beam resist and perform thermal curing. Then, the electron beam dose was set to 150 μC / cm at an acceleration voltage of 75 kV. 2 , using vector scanning mode exposure to form a ridge waveguide resist pattern.

[0034] (2) Plasma dry etching was performed using a mixture of SF6 and O2 with an etching power of 220 W. Similarly, endpoint detection technology was used to monitor the etching process and the resist pattern was accurately transferred to the silicon substrate to form a ridge waveguide structure with a ridge height of 1.5 μm and a ridge width of 2 μm.

[0035] 3.Metal layer deposition and polishing:

[0036] (1) Using evaporation deposition technology, a 300nm thick aluminum metal layer is formed on the traveling wave electrode. During the deposition process, the deposition rate and thickness are controlled in real time by a film thickness monitor to ensure the uniformity and conductivity of the metal layer.

[0037] (2) Use chemical mechanical polishing (CMP) technology to planarize the metal layer. During the polishing process, select appropriate polishing liquid and polishing pad, and adjust the polishing pressure and polishing time to make the surface flatness reach less than 5nm.

[0038] 4. Silicon oxide layer deposition:

[0039] A 300nm thick layer of low-refractive-index silicon oxide material is grown on the ridge waveguide using plasma enhanced chemical vapor deposition (PECVD) technology. During the deposition process, the growth rate and refractive index of silicon oxide are controlled by adjusting the power of the RF power supply, the gas flow ratio and the cavity pressure to reduce the loss in the optical waveguide.

[0040] The completed electro-optic modulator was tested for performance. The S parameters of the modulator were measured using a network analyzer to determine the 3dB bandwidth. At the same time, the driving voltage of the modulator was measured using a voltage-current characteristic analyzer. The test results showed that the 3dB bandwidth of the modulator reached 50GHz, the driving voltage was lower than 1.5V, the insertion loss was less than 2dB, the return loss was better than 30dB, and the crosstalk was less than -35dB. This shows that the manufactured electro-optic modulator has superior high-speed transmission performance and low power consumption characteristics, and is very suitable for application in high-speed optical communication systems.

[0041] Embodiment 2: A method for manufacturing a silicon-based electro-optic modulator with enhanced modulation bandwidth, the specific steps are as follows:

[0042] 1. Preparation of traveling wave electrode structure:

[0043] (1) Patterning is performed on a high-resistance silicon wafer using ultraviolet lithography technology. First, AZ5214E ​​photoresist is applied, and a resist pattern of a traveling wave electrode is formed through steps such as soft baking, exposure, and development.

[0044] (2) Reactive ion etching (RIE) was used, using SF6 gas, and the etching power was set to 200 W. During the etching process, the etching endpoint was monitored by optical emission spectroscopy (OES), and the resist pattern was transferred to the silicon substrate to form a coplanar waveguide traveling wave electrode structure with an electrode width of 3 μm, a period length of 30 μm, and a ground electrode width of 8 μm.

[0045] 2. Ridge waveguide preparation:

[0046] On the traveling wave electrode structure, ultraviolet lithography technology is used to coat AZ5214E ​​photoresist, and a ridge waveguide resist pattern is formed through steps such as soft baking, exposure, and development.

[0047] Through reactive ion etching, CHF3 gas was used, and the etching power was set to 240 W. Similarly, the etching process was monitored using OES technology, and the resist pattern was accurately transferred to the silicon substrate to form a ridge waveguide structure with a ridge height of 1.5 μm and a ridge width of 2 μm.

[0048] 3.Metal layer deposition and polishing:

[0049] (1) Sputtering deposition technology is used to form a 300nm thick copper metal layer on the traveling wave electrode. During the deposition process, the deposition rate and thickness are controlled in real time by a film thickness monitor to ensure the uniformity and conductivity of the metal layer.

[0050] (2) Use chemical mechanical polishing (CMP) technology to planarize the metal layer. During the polishing process, select appropriate polishing liquid and polishing pad, and adjust the polishing pressure and polishing time to make the surface flatness reach less than 5nm.

[0051] 4. Silicon oxide layer deposition:

[0052] A 300nm thick layer of low-refractive-index silicon oxide material is grown on the ridge waveguide using plasma enhanced chemical vapor deposition (PECVD) technology. During the deposition process, the growth rate and refractive index of silicon oxide are controlled by adjusting the power of the RF power supply, the gas flow ratio and the cavity pressure to reduce the loss in the optical waveguide.

[0053] The performance of the completed electro-optic modulator was tested. The S parameters of the modulator were measured using a network analyzer to determine the 3dB bandwidth. At the same time, the driving voltage of the modulator was measured using a voltage-current characteristic analyzer. The test results showed that the 3dB bandwidth of the modulator reached 48GHz, the driving voltage was 1.6V, the insertion loss was less than 2.5dB, the return loss was better than 28dB, and the crosstalk was less than -32dB. The results show that the electro-optic modulator has good high-speed data transmission performance while achieving low power consumption, and can meet the speed and efficiency requirements of modern communication systems.

[0054] Embodiment 3: A method for manufacturing a silicon-based electro-optic modulator with enhanced modulation bandwidth, the specific steps are as follows:

[0055] 1. Preparation of traveling wave electrode structure:

[0056] On silicon-on-insulator (SOI) wafers, extreme ultraviolet (EUV) lithography technology is used for patterning. First, a high-resolution EUV-specific resist is applied, and the resist pattern of the traveling wave electrode is formed through soft baking, exposure, development and other steps. Using EUV lithography technology, smaller feature sizes can be obtained, thereby achieving a more compact device design.

[0057] 2. Ridge waveguide preparation:

[0058] On the traveling wave electrode structure, ZEP520A electron beam resist was coated using electron beam lithography (EBL) technology and thermally cured. Then, the electron beam dose was set to 200 μC / cm under the condition of accelerating voltage of 100 kV. 2 , using vector scanning mode exposure to form a ridge waveguide resist pattern. Through plasma dry etching, using CF4 and Ar mixed gas, the etching power is set to 250W to form a ridge waveguide structure with a ridge height of 1μm and a ridge width of 1.8μm.

[0059] 3.Metal layer deposition and polishing:

[0060] Atomic layer deposition (ALD) technology is used to form a 100nm thick highly conductive metal layer on the traveling wave electrode. The material is gold (Au) to provide lower resistance and higher signal transmission efficiency.

[0061] 4. Silicon oxide layer deposition:

[0062] Plasma-enhanced chemical vapor deposition (PECVD) technology is used to grow a 200nm thick layer of low-refractive-index silicon oxide material on the ridge waveguide. During the deposition process, the growth rate and refractive index of silicon oxide are precisely controlled by precisely controlling the power of the RF power supply, the gas flow ratio, and the cavity pressure.

[0063] 5.Performance testing and optimization:

[0064] The completed electro-optic modulator was tested for performance, including the measurement of modulation bandwidth, insertion loss, return loss, and crosstalk. The S parameters of the modulator were measured using a network analyzer to determine the 3dB bandwidth. The test results showed that the 3dB bandwidth of the modulator reached 52GHz, the driving voltage was lower than 1.2V, the insertion loss was less than 1.5dB, the return loss was better than 35dB, and the crosstalk was less than -40dB. The performance of the electro-optic modulator was further improved by optimizing the back-end process, such as optimizing the deposition conditions and thickness of the metal layer, and adjusting the refractive index of the silicon oxide layer.

[0065] Embodiment 4: A method for manufacturing a silicon-based electro-optic modulator with enhanced modulation bandwidth, the specific steps are as follows:

[0066] 1. Preparation of traveling wave electrode structure:

[0067] On silicon-on-insulator (SOI) wafers, laser direct writing (LDW) technology is used for patterning to achieve more sophisticated electrode design. First, the pattern of the traveling wave electrode is directly written on the silicon wafer using a laser direct writing system, and then the resist pattern is cured through a heat treatment process.

[0068] 2. Ridge waveguide preparation:

[0069] Electron beam lithography (EBL) was used to coat high-resolution electron beam resist on the traveling wave electrode structure and thermally cured. Then, the electron beam dose was set to 150 μC / cm under an acceleration voltage of 100 kV. 2 , using vector scanning mode exposure to form a ridge waveguide resist pattern.

[0070] 3.Metal layer deposition and polishing:

[0071] Atomic layer deposition (ALD) technology is used to form a 50nm thick tantalum (Ta) layer on the traveling wave electrode as a barrier layer to prevent the metal layer from reacting with the silicon substrate. Subsequently, a 150nm thick platinum (Pt) metal layer is deposited by magnetron sputtering technology to ensure excellent conductivity and corrosion resistance.

[0072] 4. Silicon oxide layer deposition:

[0073] Plasma-enhanced chemical vapor deposition (PECVD) technology is used to grow a 200nm thick layer of low-refractive-index silicon oxide material on the ridge waveguide. During the deposition process, the growth rate and refractive index of silicon oxide are precisely controlled by precisely controlling the power of the RF power supply, the gas flow ratio, and the cavity pressure.

[0074] 5.Performance testing and optimization:

[0075] The completed electro-optic modulator was subjected to performance tests, including the measurement of modulation bandwidth, insertion loss, return loss, crosstalk and other parameters. The test results showed that the 3dB bandwidth of the modulator reached 60GHz, the driving voltage was lower than 0.8V, the insertion loss was less than 0.5dB, the return loss was better than 45dB, and the crosstalk was less than -50dB. By adopting different manufacturing processes and materials, the electro-optic modulator of the present invention significantly reduces power consumption and improves overall performance while maintaining high-speed transmission performance.

[0076] The above embodiments only express the implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Claims

1. A silicon-based electro-optic modulator with enhanced modulation bandwidth, comprising a traveling wave electrode structure and a ridge waveguide structure, characterized in that: The traveling wave electrode structure includes a coplanar waveguide traveling wave electrode with periodic load characteristics. The traveling wave electrode structure reduces the effective refractive index through a specific electrode width W and an electrode spacing D, so as to achieve phase velocity matching between light waves and microwaves, thereby improving modulation efficiency and bandwidth; wherein, 500nm≤W≤1500nm, 200nm≤D≤1000nm; The ridge waveguide structure optimizes the overlap between the optical mode and the microwave mode and reduces carrier absorption loss by adjusting the ridge height H and width B; wherein, 100nm≤H≤500nm, 400nm≤B≤1200nm.

2. A silicon-based electro-optic modulator with enhanced modulation bandwidth according to claim 1, characterized in that: The traveling wave electrode structure further includes a grounding electrode, which is arranged beside the coplanar waveguide traveling wave electrode; a width G of the grounding electrode satisfies 300nm≤G≤800nm.

3. The silicon-based electro-optic modulator with enhanced modulation bandwidth according to claim 1, characterized in that: The material of the ridge waveguide structure is silicon, and the refractive index n of the ridge waveguide satisfies 2.5≤n≤3.

5.

4. The silicon-based electro-optic modulator with enhanced modulation bandwidth according to claim 1, characterized in that: The traveling wave electrode structure and the ridge waveguide structure are integrally formed.

5. A method for manufacturing a silicon-based electro-optic modulator according to any one of claims 1 to 4, characterized in that: The specific steps include: S1: Using electron beam lithography technology to form the pattern of traveling wave electrodes and ridge waveguides on the silicon wafer; the electron beam dose is controlled at 50μC / cm 2 ≤E≤200μC / cm 2 to ensure high resolution and accuracy of the pattern; S2: Using plasma dry etching technology, the above pattern is transferred to a silicon wafer to form a traveling wave electrode and a ridge waveguide structure with a predetermined size; the plasma power P is controlled between 100W≤P≤300W to achieve high-precision nanoscale etching; S3: depositing a metal layer on the traveling wave electrode to form a conductive electrode; the thickness T of the metal layer is controlled within 50nm≤T≤200nm to ensure the conductivity and signal transmission efficiency of the electrode; S4: Chemical mechanical polishing is used to smooth the surface of the silicon wafer to ensure the quality and uniformity of the subsequent deposited or grown layers; S5: A layer of low refractive index material is grown on the ridge waveguide structure by plasma enhanced chemical vapor deposition technology to reduce the loss in the optical waveguide; the thickness S of the low refractive index material layer is controlled to be 100nm≤S≤500nm.

6. The method for manufacturing a silicon-based electro-optic modulator according to claim 1, characterized in that: The electron beam lithography technology in step S1 includes using an electron beam exposure system with a high brightness electron source and an electron beam resist material with high sensitivity and resolution.

7. The method for manufacturing a silicon-based electro-optic modulator according to claim 6, characterized in that: The plasma dry etching technology in step S2 includes using a reactive ion etching system and an etching gas mixture with high selectivity and fast etching rate.

8. The method for manufacturing a silicon-based electro-optic modulator according to claim 7, characterized in that: The plasma enhanced chemical vapor deposition technology in step S5 includes using a CVD device capable of generating high-density plasma, as well as optimized precursor gas flow ratios and deposition parameters to achieve uniform, dense and low-refractive-index silicon oxide layer deposition.

9. The method for manufacturing a silicon-based electro-optic modulator according to claim 5, characterized in that: The operations of steps S1-S3 are carried out in a clean room environment to prevent contamination and ensure nano-machining accuracy.

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