A method for patterning a multilayer film artificial conductor based on a lift-off process
Patent Information
- Application Number
- CN202310277159.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-03-21
- Publication Date
- 2026-10-27
- Estimated Expiration
- 2043-03-21
AI Technical Summary
[0004]M.Yamaguchi团队的研究均采用了溅射镀膜的方式来制备互连线、天线等无源器件，但其由于铁磁金属和非磁金属层本身的应力作用，无法获得较厚的多层膜，其厚度通常在10个微米以内
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of radio frequency devices and integrated circuit technology, and specifically relates to a method for fabricating multilayer film artificial conductors based on lift-off process. Background Technology
[0002] With the continuous increase in the operating frequency of next-generation microelectronic and integrated circuit devices, the eddy current loss of traditional radio frequency passive devices (such as waveguides, interconnects, inductors, and antennas) at high frequencies has become a significant drawback that cannot be ignored. To suppress this drawback, artificial conductors start by improving the skin effect, introducing a negative permeability metal layer to compensate for the positive permeability of traditional conductor materials (copper, aluminum, silver, etc.), and using a multilayer film structure to make the permeability of the target device approach zero and the skin depth approach infinity.
[0003] Since 2008, several research teams have used multilayer film structures composed of alternating ferromagnetic and nonmagnetic metals as carriers to fabricate passive devices such as microwave transmission lines, coplanar waveguides, and helical inductors. For example, in 2010, M. Yamaguchi's team studied coplanar waveguides fabricated from Al / NiFe and Cu / CoZrNb multilayer film structures. When the real part of the permeability became negative, the transmission resistance of the coplanar waveguide decreased significantly [1]. In 2011, they further utilized Cu / Co... 85 Zr3Nb 12 The interconnects of the spiral inductor were fabricated using a multilayer film structure, which reduced the resistance by about 8.7% compared to pure copper material, while keeping the inductance value unchanged [2]. In 2018, S. Dai's team used electrochemical deposition to design and fabricate a coplanar waveguide that could suppress radio frequency eddy current loss by alternately depositing Cu and CoCu layers. Its resistance value at 10 GHz was reduced by 82%, and the skin effect was suppressed in the 7-13 GHz band [3].
[0004] M. Yamaguchi's team's research has consistently employed sputtering deposition to fabricate passive devices such as interconnects and antennas. However, due to the stress inherent in the ferromagnetic and non-magnetic metal layers, it's impossible to obtain thick multilayer films, typically with a thickness of less than 10 micrometers. Furthermore, device size and film thickness are limited by traditional photolithography techniques. When patterning large devices like antennas, three significant problems arise: first, large-area patterning requires specific types of photoresist, making it prohibitively expensive; second, the lift-off process is extremely complex and time-consuming, hindering large-scale deployment; and third, the poor orientation of films obtained through sputtering can cause the film to encapsulate the photoresist cross-sections, potentially resulting in rough edges and burrs after lift-off, or even making lift-off impossible.
[0005] S. Dai's team used electrochemical deposition to prepare thin films with good adhesion and thicknesses reaching tens of micrometers. Compared to sputtering, electrochemical deposition has a shorter preparation cycle and can produce a wider variety of thin films, attracting widespread attention in industry. Thin films obtained through electrochemical deposition are generally patterned using etching. The choice of etching process typically depends on factors such as the material to be etched, the required structural shape and precision, the etching rate, production volume, and cost. Different materials have different etching properties; therefore, only materials with certain chemical reactivity can be etched. For example, the M-Cu (M being one or two of Ni, Fe, and Co) and its alloys used in this study show poor etching performance with conventional etchants (such as ferric chloride, hydrofluoric acid, and sodium hydroxide) due to limitations in substrate and alloy materials. Furthermore, because the etching rate is difficult to control precisely, the etching depth is also difficult to control accurately, requiring subsequent etching steps to adjust the depth. Additionally, the etching process can cause damage to the material surface, such as creating surface roughness and altering surface chemical properties, which may affect device performance. Summary of the Invention
[0006] To address the above problems, this invention comprehensively considers the disadvantages of the two processing techniques mentioned above and combines their advantages; it designs a novel lift-off method based on patterned hot pressing transfer, which can be used for patterning large-size devices; at the same time, it can also utilize multilayer film artificial conductors to prepare high-precision, high-quality, and low-cost devices.
[0007] The technical solution of this invention is:
[0008] A method for fabricating patterned multilayer artificial conductors based on lift-off process includes the following steps:
[0009] S1, Process the substrate;
[0010] S2. Preparation of hot-press transfer material: The radio frequency passive device is patterned and the pattern is transferred onto the hot-press transfer material;
[0011] S3. Use a hot press transfer machine to transfer the pattern on the hot press transfer material onto the substrate to obtain a substrate with the initial pattern;
[0012] S4. Sputter a Ti seed layer and a Cu seed layer sequentially onto the substrate;
[0013] S5. Electroplating a periodic multilayer film structure [M-Cu / Cu] on a substrate. n This yields an initial passive device based on multilayer film artificial conductor materials;
[0014] S6. Place the substrate in an organic solvent and vibrate it with an ultrasonic generator until the thermal transfer material on the substrate is completely dissolved in acetone to obtain a radio frequency passive device.
[0015] Furthermore, the specific method of S1 is as follows:
[0016] A ceramic or glass substrate with a thickness of 1.01 mm was used as the substrate. The substrate was ultrasonically cleaned in sequence with deionized water, acetone and anhydrous ethanol to remove impurities from the ceramic substrate. Finally, it was dried with nitrogen.
[0017] Furthermore, in S3, the working temperature of the heat transfer machine is set to 200 degrees Celsius, and it is preheated for 5 minutes. The substrate and the heat transfer material are placed into the heat transfer machine together and repeated 6-8 times. After obtaining the substrate with the initial pattern, it is left to stand for 5 minutes.
[0018] Furthermore, the specific method of S4 is as follows:
[0019] The substrate obtained in S3 was placed into the magnetron sputtering equipment, and the Ti and Cu targets were installed in place. The vacuum chamber pressure was then evacuated to 10. -4 Below Pa; then, inert argon gas was introduced to adjust the pressure to 0.6 Pa, and the sputtering power of the RF sputtering source was set to 80 W to form a 50 nm thick Ti buffer layer; on the Ti buffer layer, a 200 nm thick Cu layer was formed using the same RF sputtering method, with a sputtering pressure of 0.5 Pa and a sputtering power of 65 W.
[0020] Furthermore, the organic solvent used in S6 is acetone solution.
[0021] The beneficial effects of this invention are: compared with traditional lift-off and etching processes, such as... Figure 1 , Figure 2 As shown; the innovation of this invention is that: the hot-press transfer material is used to pattern the substrate, which provides a basis for the one-time lift-off process of subsequent film formation. The significant advantages of this invention are: (1) Compared with the traditional lift-off process, this invention is applicable to multilayer film artificial conductors obtained by electrochemical deposition process, and can be used for patterning most passive devices, and can process devices with a size of 10 micrometers and above; (2) Compared with the traditional etching process, this invention can be used for superlattice materials M-Cu and their alloys, and the lift-off process avoids excessive etching of the device structure; at the same time, this invention has lower requirements for substrate materials and can be applied to ceramics, glass, low-resistivity silicon, high-resistivity silicon and PCB boards. Attached Figure Description
[0022] Figure 1 The flowcharts are for the traditional lift-off process and the traditional etching process.
[0023] Figure 2 A schematic diagram of a multilayer film artificial conductor material;
[0024] Figure 3 This is a flowchart of the etching process used in multilayer film artificial conductor interconnects;
[0025] Figure 4 This is a schematic diagram of the microstrip line designed in the embodiment;
[0026] Figure 5 The image shows a physical image of the microstrip line prepared for the example. Detailed Implementation
[0027] The invention will now be further described with reference to the accompanying drawings.
[0028] The purpose of this invention is to provide a method for fabricating multilayer artificial conductors based on a lift-off process, specifically for non-traditional multilayer artificial conductor materials M-Cu (where M is one or two of Ni, Fe, and Co) and their alloys, such as... Figure 3 As shown, based on the lift-off process in the photolithography process and combined with the advantages of wet etching, the radio frequency passive devices (such as microstrip lines, coplanar waveguides, etc.) are patterned.
[0029] Example
[0030] This example includes the following steps:
[0031] Step 1: Use a ceramic substrate with a thickness of 1.01 mm as the substrate. Use deionized water, acetone and anhydrous ethanol to ultrasonically clean the substrate in sequence to remove impurities. Finally, dry it with nitrogen.
[0032] Step 2: Use Altium Designer software to design the microstrip line pattern. The microstrip line length is 1.8682mm. Figure 5 As shown, thermal transfer material is printed onto a polymer substrate layer such as polyester film or polyimide film using a laser printer with a resolution of 2400*2400dpi.
[0033] Step 3: Turn on the heat transfer machine, set the operating temperature to 200 degrees Celsius, and preheat for 5 minutes. After the temperature reaches the preset temperature, align the cleaned substrate and the printed substrate, and place them together into the heat transfer machine. Repeat this operation 6-8 times. Afterward, let the substrate sit for 5 minutes to cool to room temperature before proceeding to the next step.
[0034] Step 4: Sequentially sputter Ti and Cu seed layers onto the substrate: Place the substrate processed in Step 3 into the magnetron sputtering equipment, and install the Ti and Cu targets in place. Evacuate the vacuum chamber to 10...-4 Below Pa; then, inert argon gas was introduced to adjust the pressure to 0.6 Pa, and the RF sputtering source was set to a sputtering power of 80 W to form a 50 nm thick Ti buffer layer; on the Ti buffer layer, a 200 nm thick Cu layer was formed using the same RF sputtering method, with a sputtering pressure of 0.5 Pa and a sputtering power of 65 W. Ti, as a buffer layer, can effectively improve adhesion and prevent interdiffusion between Cu and the substrate Si.
[0035] Step 5: Using a mature electroplating process, a periodic multilayer film structure [CoCu / Cu]n is grown on the substrate through electrochemical deposition. After electrochemical deposition, the substrate is removed and treated sequentially with deionized water and nitrogen. At this point, the substrate contains a Ti attachment layer, a Cu seed layer, and a [ferromagnetic layer-conductor layer] multilayer film structure to suppress the skin effect, with a thickness of approximately 20 micrometers.
[0036] Step 6: Place the substrate and acetone solution in the same beaker, and then place the beaker in a cleaning tank. Place an ultrasonic generator at the bottom of the tank, select an oscillation frequency of 28 kHz, and an oscillation time of 5 minutes. The high-frequency sound waves generated by the ultrasonic generator cause tiny bubbles to form in the acetone solution and burst instantly, generating an impact force that completely dissolves the thermal transfer material on the substrate in the acetone. Due to the disappearance of the underlying support layer and the vibration of the solution, the film formed on the upper layer of the thermal transfer material will break away from the thin film layer of the specified pattern, resulting in a microstrip line structure of the specified width.
Claims
1. A method for fabricating patterned multilayer artificial conductors based on a lift-off process, characterized in that, Includes the following steps: S1, Substrate processing; S2. Preparation of hot-press transfer material: The radio frequency passive device is patterned and the pattern is transferred onto the hot-press transfer material; S3. Use a hot press transfer machine to transfer the pattern on the hot press transfer material onto the substrate to obtain a substrate with the initial pattern; S4. Sputter a Ti seed layer and a Cu seed layer sequentially onto the substrate; S5. Electroplating a periodic multilayer film structure [M-Cu / Cu] on a substrate. n M is one or two of Ni, Fe, and Co, to obtain an initial passive device based on a multilayer film artificial conductor material; S6. Place the substrate in an organic solvent and vibrate it with an ultrasonic generator until the thermal transfer material on the substrate is completely dissolved in acetone to obtain a radio frequency passive device.
2. The method for fabricating patterned multilayer artificial conductors based on lift-off process according to claim 1, characterized in that, The specific method for S1 is: A ceramic or glass substrate with a thickness of 1.01 mm was used as the substrate. The substrate was ultrasonically cleaned in sequence with deionized water, acetone and anhydrous ethanol to remove impurities from the ceramic substrate. Finally, it was dried with nitrogen.
3. The method for fabricating patterned multilayer artificial conductors based on lift-off process according to claim 1, characterized in that, In S3, set the heat transfer machine operating temperature to 200 degrees Celsius, preheat for 5 minutes, put the substrate and heat transfer material into the heat transfer machine together, and repeat 6-8 times to obtain a substrate with an initial pattern, then let it stand for 5 minutes.
4. The method for fabricating patterned multilayer artificial conductors based on lift-off process according to claim 1, characterized in that, The specific method for S4 is: The substrate obtained in S3 was placed into the magnetron sputtering equipment, and the Ti and Cu targets were installed in place. The vacuum chamber pressure was then evacuated to 10. - 4 Below Pa; then, inert argon gas was introduced to adjust the pressure to 0.6 Pa, and the sputtering power of the RF sputtering source was set to 80 W to form a 50 nm thick Ti buffer layer; on the Ti buffer layer, a 200 nm thick Cu layer was formed using the same RF sputtering method, with a sputtering pressure of 0.5 Pa and a sputtering power of 65 W.
5. The method for fabricating patterned multilayer artificial conductors based on lift-off process according to claim 1, characterized in that, The organic solvent used in S6 is acetone solution.
Citation Information
Patent Citations
Method of forming through-wafer interconnects for vertical wafer level packaging
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