Flexible precision thin film resistor and method of manufacturing the same

Abstract

The application relates to the field of thin-film resistors, and discloses a flexible precision thin-film resistor and a manufacturing method thereof. The manufacturing method of the flexible precision thin-film resistor comprises the following steps: performing oxidation treatment on a silicon substrate to form an insulating layer on the surface of the silicon substrate; forming a resistor layer and an electrode layer on the insulating layer; performing pattern treatment on the resistor layer to form a resistor pattern; performing laser resistance adjustment on the resistor pattern to adjust the resistance value of the resistor pattern; forming a flexible protective layer on the resistor pattern after the resistance adjustment; and performing thinning treatment on the silicon substrate. The silicon substrate is used as a resistor substrate, the substrate is thinned to 15 microns after the resistor layer and the protective layer are formed, the product has excellent flexibility, and is suitable for flexible circuits; the nickel-chromium alloy is selected as the resistor layer, vacuum sputtering and heat treatment are combined, the temperature coefficient is less than or equal to 10 ppm / DEG C in the range of -40 DEG C to 70 DEG C; the polyimide flexible protective layer is adopted, protection is achieved, and the bending performance is not affected; the resistance value precision is less than or equal to 0.02% through laser resistance adjustment, and the high-precision requirement is met.

Description

Technical Field

[0001] This invention relates to the field of thin-film resistor technology, and more specifically, to a flexible precision thin-film resistor and its manufacturing method. Background Technology

[0002] With the development of technology, flexible sensors, thanks to their flexible substrates and multimodal sensing capabilities, have been widely used in fields such as medical health, wearable devices, robotics, and aerospace. The development of these fields relies heavily on the information processing capabilities of circuit sensors, and the electronics industry continues to advance towards miniaturization, lightweighting, and high precision. Existing ultra-thin pressure sensors are typically used in robotic tactile systems. Foldable screens are made of organic flexible materials, and the market prospects for flexible circuits in curved and foldable screens are vast. To meet the miniaturization requirements of products and the need to match flexible circuits, a resistor compatible with flexible circuits is urgently needed.

[0003] Currently, the thinnest precision chip resistors on the market are 0.1mm, and they are usually made of ceramic substrate, which makes them unsuitable for flexible circuits. Ceramic substrate materials have high rigidity and poor bending performance, making it difficult to meet the flexibility requirements of flexible circuits. Summary of the Invention

[0004] This invention provides a flexible precision thin-film resistor and its manufacturing method, solving the technical problem in related technologies that ceramic substrate materials have high rigidity and poor bending performance, making it difficult to meet the flexibility requirements of flexible circuit components.

[0005] This invention provides a method for manufacturing a flexible precision thin-film resistor, comprising: The silicon substrate is oxidized to form an insulating layer on its surface. A resistive layer and an electrode layer are formed on the insulating layer; The resistive layer is patterned to form a resistive pattern; Laser trimming is applied to the resistivity pattern to adjust its resistance value. A flexible protective layer is formed on the resistor pattern after resistance adjustment; The silicon substrate is thinned to a flexible, bendable thickness.

[0006] As a further optimization of the present invention, in the step of thinning the silicon substrate, the silicon substrate is thinned to within 15 micrometers.

[0007] As a further optimization of the present invention, the flexible protective layer is a polyimide material layer.

[0008] As a further optimization of the present invention, the resistive layer is formed of a nickel-chromium alloy material (or a high-entropy alloy is used as the resistive layer).

[0009] As a further optimization of the present invention, in the laser trimming step, the accuracy of the resistance value is adjusted to within ±0.02%.

[0010] As a further optimization of the present invention, after the laser trimming step and before the flexible protective layer formation step, a heat treatment step is also included: the laser trimmed resistor is placed in a vacuum environment at 250°C to 400°C for 2 to 6 hours for heat treatment.

[0011] A flexible precision thin-film resistor, manufactured using the above-described method for manufacturing flexible precision thin-film resistors, includes: Silicon substrate, with a thickness of less than 15 micrometers; (or ultrathin microcrystalline glass substrate, with a thickness of 20-100 micrometers).

[0012] An insulating layer is formed on a silicon substrate; The resistive layer is formed on the insulating layer; The electrode layer is formed on the resistive layer; A flexible protective layer covers the resistive layer and the electrode layer.

[0013] As a further optimization of the present invention, the flexible protective layer is a polyimide material layer.

[0014] As a further optimization of the present invention, the resistance value of the resistive layer is in the range of 5Ω to 50kΩ, the resistance value accuracy is within ±0.02%, and the temperature coefficient in the range of -40℃ to 70℃ is within ±10ppm / ℃.

[0015] The resistive layer 30 is sputtered using a nickel-chromium alloy target. Nickel-chromium alloys (such as NiCr, NiCrAl, NiCrSi, etc.) have advantages such as high resistivity, low temperature coefficient, and good stability, making them suitable for the fabrication of precision resistors. (Alternatively, a high-entropy alloy can be used as the resistive layer, which has advantages such as high strength and high toughness, high temperature resistance / creep resistance, corrosion resistance / oxidation resistance, radiation resistance, fatigue resistance, and good low-temperature performance.) As a further optimization of the present invention, the thickness of the flexible protective layer does not exceed 3 micrometers.

[0016] The beneficial effects of this invention are as follows: 1. This invention uses a silicon substrate as the resistor substrate and performs a thinning process after the resistor layer and protective layer are formed, reducing the thickness of the silicon substrate to less than 15 micrometers. This enables the resistor product to obtain excellent flexibility, which can meet the needs of flexible circuits and solves the problem that existing ceramic substrate resistors cannot be bent.

[0017] 2. This invention, through laser trimming technology, employs a two-stage trimming method combining coarse and fine trimming, which can adjust the resistance value accuracy to within ±0.02%, thereby realizing the fabrication of high-precision resistors and meeting the application requirements of precision electronic components.

[0018] 3. This invention uses a nickel-chromium alloy as the resistive layer material, combined with vacuum sputtering coating and heat treatment processes, to enable the resistor product to maintain a low temperature coefficient within ±10ppm / ℃ in a temperature range of -40℃ to 70℃, thus exhibiting good temperature stability.

[0019] 4. The present invention forms a flexible polyimide protective layer on the resistor pattern, which not only protects the resistor film from the influence of the external environment, but also does not affect the overall bending performance of the resistor due to its excellent flexibility.

[0020] 5. This invention achieves product miniaturization by optimizing the parameters and sequence of each process step, with a minimum size of 0.5mm×0.25mm×0.015mm, meeting the development needs of miniaturization and lightweight electronic devices. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of a flexible precision thin-film resistor proposed in this invention.

[0022] Figure 2 This is a flowchart of a method for manufacturing a flexible precision thin-film resistor proposed in this invention.

[0023] In the picture: 10. Silicon substrate; 20. Insulation layer; 30. Resistive layer; 40. Electrode layer; 50. Flexible protective layer. Detailed Implementation

[0024] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, features described in some examples may be combined in other examples.

[0025] Example 1 like Figure 1 and Figure 2As shown, this embodiment provides a method for manufacturing a flexible precision thin-film resistor. This method involves silicon substrate oxidation, sputtering deposition, photolithography patterning, laser trimming, passivation protection, and substrate thinning to prepare a thin-film resistor product with high precision, low temperature coefficient, and good flexibility. Specifically, it includes the following steps: Step 1: Substrate oxidation treatment: First, a single-crystal silicon wafer with a thickness of 0.1 mm or more is selected as the substrate 10. The silicon substrate 10 has good mechanical strength and processing performance, and excellent flexibility can be obtained through subsequent thinning treatment (or ultra-thin microcrystalline glass, which does not require oxidation treatment).

[0026] The silicon substrate 10 is oxidized to form an insulating layer 20 on its surface. In this embodiment, a high-temperature thermal oxidation process is used: the silicon substrate 10 is placed in a high-temperature oxidation furnace and heat-treated at 1200°C for 3 to 5 hours, with oxygen or water vapor introduced, to grow a dense silicon dioxide insulating layer 20 on the surface of the silicon substrate 10. By controlling the oxidation time, the thickness of the insulating layer 20 is ensured to be greater than 1 micrometer. This insulating layer 20 is used to isolate the subsequently formed resistive layer 30 from the silicon substrate 10, preventing the silicon substrate 10 from adversely affecting the resistance value, while providing good electrical insulation performance.

[0027] In other alternatives, the insulating layer 20 can also be formed by chemical vapor deposition (CVD) or physical vapor deposition (PVD). The material of the insulating layer 20 is not limited to silicon dioxide, but can also be other insulating materials such as silicon nitride and silicon oxynitride.

[0028] Step 2: Sputtering the resistive layer and electrode layer: After the insulating layer 20 is formed, the silicon substrate 10 is cleaned to remove surface impurities and contaminants, ensuring film adhesion.

[0029] Then, a resistive layer 30 and an electrode layer 40 are sequentially formed on the insulating layer 20 using a fully automated vacuum sputtering coating equipment.

[0030] The resistive layer 30 is sputtered using a nickel-chromium alloy target. Nickel-chromium alloys (such as NiCr, NiCrAl, NiCrSi, etc.) have advantages such as high resistivity, low temperature coefficient, and good stability, making them suitable for the fabrication of precision resistors. In this embodiment, the thickness of the resistive layer 30 is controlled between 0.05 micrometers and 0.5 micrometers, and the specific thickness can be adjusted according to the target resistance value.

[0031] In other alternatives, the resistive layer 30 can also be made of other resistive materials (or high-entropy alloys) such as chromium silicon (CrSi) or tantalum nitride (TaN).

[0032] Step 3: Photolithography patterning: After sputtering the resistor layer 30 and the electrode layer 40, the resistor layer 30 is patterned using photolithography to form the required resistor pattern.

[0033] The specific steps are as follows: Photoresist coating: A layer of photoresist is coated on the surface of the silicon substrate 10 after the film has been sputtered, and the photoresist is uniformly covered by spin coating.

[0034] Exposure: Select the appropriate mask according to the product design, and use ultraviolet light exposure equipment to selectively expose the photoresist, transferring the resistance pattern on the mask to the photoresist layer.

[0035] Development: The exposed silicon substrate 10 is developed to remove unexposed or exposed photoresist (depending on the type of photoresist) and form a photoresist protection pattern.

[0036] Dry etching: Using dry etching processes, such as reactive ion etching (RIE) or inductively coupled plasma etching (ICP), the resistive layer 30 and electrode layer 40 materials in areas not protected by photoresist are removed to form a resistor pattern. Dry etching has the advantages of good anisotropy and high linewidth control precision, which can ensure the dimensional accuracy of the resistor pattern.

[0037] After the photolithography patterning is completed, the remaining photoresist is removed through a stripping process to expose the formed resistor pattern.

[0038] In other alternatives, wet etching can also be used for patterning, but dry etching is the preferred method of this invention because it can achieve higher pattern accuracy and better process repeatability.

[0039] Step 4: Laser trimming: Laser trimming is applied to the resulting resistance pattern to adjust the resistance value to the target accuracy.

[0040] In this embodiment, laser trimming is performed using a dedicated laser trimming device. By scanning a specific area of ​​the resistive layer 30 with a laser beam, the physical properties or geometric dimensions of the resistive material are locally changed, thereby precisely adjusting the resistance value.

[0041] Laser trimming is divided into two stages: Coarse adjustment stage: Using laser parameters with higher power or faster scanning speed, quickly adjust the resistance value to a first accuracy range close to the target value, for example, adjust the resistance value to within ±1% of the target value.

[0042] Fine-tuning stage: Using laser parameters with lower power or slower scanning speed, the resistance value is finely adjusted to the final target accuracy. In this embodiment, the accuracy of the resistance value can be adjusted to within ±0.02%, preferably within ±0.01%.

[0043] By using a two-stage resistance adjustment process, both resistance adjustment efficiency and high precision requirements can be guaranteed.

[0044] During laser trimming, a real-time resistance detection feedback system dynamically monitors changes in resistance value. When the resistance value reaches the target accuracy range, trimming automatically stops to ensure trimming accuracy and consistency.

[0045] In other alternatives, a single-stage resistance adjustment process can be used, or the resistance adjustment parameters and accuracy range can be adjusted according to the product accuracy requirements.

[0046] Step 5, Heat Treatment: After the laser trimming step, a heat treatment step is performed to eliminate the thermal stress and lattice defects generated during the laser trimming process, stabilize the resistive film layer, and improve the long-term stability and reliability of the resistor.

[0047] In this embodiment, the laser-trimmed resistor sheet is placed in a vacuum oven and heat-treated for 2 to 6 hours at a temperature range of 250°C to 400°C. The heat treatment temperature and time can be optimized according to the characteristics of the resistor material and product requirements. For example, for nickel-chromium resistor materials, heat treatment at 300°C for 4 hours is preferred.

[0048] The heat treatment process is carried out in a vacuum environment to prevent the resistance layer 30 from oxidizing at high temperatures and to ensure the stability of the resistance value.

[0049] Step Six: Inspection: The resistance accuracy and appearance of the heat-treated resistors are verified. Each resistor is tested using automated testing equipment to screen out defective products with resistance values ​​that are out of tolerance. The appearance of the resistors is inspected using AOI (Automated Optical Inspection) vision equipment to identify appearance defects such as scratches, defects, and contamination.

[0050] For any unqualified resistors discovered during inspection, they are removed by breaking them or marking them to prevent unqualified products from leaving the factory.

[0051] Step 7: Passivation treatment: After passing the inspection, a flexible protective layer 50 is formed on the resistor pattern.

[0052] In this embodiment, polyimide is used as the material for the flexible protective layer 50. Polyimide is a high-performance polymer material with good flexibility, high temperature resistance, insulation, and chemical stability. A polyimide solution is coated onto the resistive layer 30 and the electrode layer 40 using a mask coating process, and after curing, a flexible protective layer 50 with a thickness not exceeding 3 micrometers is formed.

[0053] The flexible protective layer 50 provides physical protection and insulation for the resistor layer 30 and electrode layer 40, preventing damage to the resistor from the external environment (moisture, dust, mechanical contact, etc.). On the other hand, the flexibility of the polyimide material itself allows the protective layer 50 to bend along with the substrate without affecting the overall flexibility of the resistor.

[0054] In other alternatives, the flexible protective layer 50 can also be made of other flexible polymer materials, such as parylene, polyurethane (PU), silicone rubber, etc.

[0055] Step 8: Substrate thinning: After the resistive film layer is protected, the silicon substrate 10 is thinned to reduce its thickness to a flexible, bendable thickness.

[0056] In this embodiment, chemical mechanical polishing (CMP) or back-side lamination is used to thin the silicon substrate 10. By controlling the equipment and process parameters, the thickness of the silicon substrate 10 is reduced from an initial thickness of more than 0.1 mm to less than 15 micrometers. Preferably, the thickness of the thinned silicon substrate 10 is controlled between 10 micrometers and 15 micrometers.

[0057] The thinned silicon substrate 10 has excellent flexibility, allowing it to be bent and folded without breaking, enabling the entire resistor product to meet the needs of flexible circuit applications.

[0058] Other alternatives include wet etching, plasma etching, and other methods for thinning.

[0059] Step 9: Cutting and separating the particles The thinned resistor sheet is attached to a UV film (ultraviolet photopolymer film) and then granulated using a resin cutter. In the mask design, a 30-micron cutting space is reserved between the resistors. A 15-micron-wide resin cutter is used to granulate the product, achieving a cutting accuracy of 1 micron.

[0060] The UV film loses its adhesiveness under ultraviolet light, making it easier to pick up individual resistors later.

[0061] Step 10, Packaging: After being separated into individual resistors, the resistors undergo UV film debonding using a UV debonding machine. Individual resistors are then removed from the UV film using a vacuum pen or automatic pick-up device. After passing visual inspection, they are placed in an anti-static packaging box and delivered to the customer.

[0062] Example 2 Structure of flexible precision thin-film resistors: This embodiment provides a flexible precision thin-film resistor, which is manufactured using the method described in Embodiment 1 above. Figure 1 As shown, the resistor includes: The silicon substrate 10 has a thickness of less than 15 micrometers. The thinned silicon substrate 10 has good flexibility and can be bent and deformed with flexible circuits without breaking. The thickness of the silicon substrate 10 is preferably between 10 and 15 micrometers.

[0063] An insulating layer 20 is formed on the silicon substrate 10. The insulating layer 20 is a silicon dioxide layer with a thickness of more than 1 micrometer, which is used to isolate the silicon substrate 10 from the resistive layer 30 and provide electrical insulation properties.

[0064] A resistive layer 30 is formed on the insulating layer 20. The resistive layer 30 is formed of a nickel-chromium alloy material (such as NiCr, NiCrAl, NiCrSi, etc.) and has a thickness of approximately 0.05 micrometers to 0.5 micrometers. The resistive layer 30 is patterned using photolithography to form the desired resistive pattern.

[0065] An electrode layer 40 is formed on the resistor layer 30. The electrode layer 40 is used for the electrical connection between the resistor and an external circuit.

[0066] A flexible protective layer 50 covers the resistive layer 30 and the electrode layer 40. The flexible protective layer 50 is a polyimide material layer with a thickness of no more than 3 micrometers, and has excellent flexibility and protective properties.

[0067] Resistor performance parameters: The performance parameters of the flexible precision thin-film resistor prepared by the above process are as follows: Resistance range: 5Ω to 50kΩ, different resistance values ​​can be customized according to customer needs.

[0068] Resistance value accuracy: within ±0.02%, preferably within ±0.01%.

[0069] Temperature coefficient: Within the operating temperature range of -40℃ to 70℃, the temperature coefficient is within ±10ppm / ℃.

[0070] Size range: Maximum size is 1mm×0.5mm×0.015mm, minimum size is 0.5mm×0.25mm×0.015mm. (When using ultra-thin microcrystalline glass, the size is 0.25mm×0.12mm×0.02mm).

[0071] Flexibility: It can achieve 45° bending without breakage or detachment on a 5cm length flexible circuit, meeting the application requirements of flexible circuits.

[0072] Example 3 The difference from Example 2 is that ultra-thin microcrystalline glass is used, which has its own advantages (flexibility, ultra-high insulation, thermal stability, flatness; no oxidation required, thinning operation). The microcrystalline glass layer is directly used as the substrate. It is flexible and bendable: the thickness is 20-100 micrometers, the bending radius is less than 3 millimeters, and it can be bent repeatedly 100,000-1.4 million times without cracking; it has extremely strong thermal stability: low thermal expansion (near zero), temperature resistance of 500-800°, thermal shock resistance, and no deformation after bending and heating; it has excellent insulation: volume resistivity >1014Ω.nm, high voltage insulation, no leakage; it has an ultra-flat surface: Ra<0.5nm, suitable for printing ultra-thin resistive films (<1 micrometer); it has good barrier properties: airtight, water and oxygen blocked, protecting the long-term stability of the resistive film.

[0073] The embodiments of the present invention have been described above, but the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the embodiments described above, all of which are within the protection scope of the embodiments described above.

Claims

1. A method for manufacturing a flexible precision thin-film resistor, characterized in that, include: The silicon substrate (10) is oxidized to form an insulating layer (20) on its surface. A resistive layer (30) and an electrode layer (40) are formed on the insulating layer (20); The resistive layer (30) is patterned to form a resistive pattern; Laser trimming is applied to the resistivity pattern to adjust its resistance value. A flexible protective layer (50) is formed on the resistor pattern after the resistance is adjusted. The silicon substrate (10) is thinned to reduce its thickness to a flexible, bendable thickness.

2. The method for manufacturing a flexible precision thin-film resistor according to claim 1, characterized in that: In the step of thinning the silicon substrate (10), the silicon substrate (10) is thinned to within 15 micrometers.

3. The method for manufacturing a flexible precision thin-film resistor according to claim 1, characterized in that: The flexible protective layer (50) is a polyimide material layer.

4. The method for manufacturing a flexible precision thin-film resistor according to claim 1, characterized in that: The resistive layer (30) is formed of a nickel-chromium alloy material.

5. The method for manufacturing a flexible precision thin-film resistor according to claim 1, characterized in that: In the laser trimming step, the resistance value is adjusted to within ±0.02%.

6. The method for manufacturing a flexible precision thin-film resistor according to claim 1, characterized in that: After the laser trimming step and before the formation of the flexible protective layer (50), a heat treatment step is also included: the laser trimmed resistor is placed in a vacuum environment of 250°C to 400°C for 2 to 6 hours for heat treatment.

7. A flexible precision thin-film resistor, manufactured using the method for manufacturing a flexible precision thin-film resistor as described in any one of claims 1 to 6, characterized in that, include: A silicon substrate (10) with a thickness of less than 15 micrometers; An insulating layer (20) is formed on a silicon substrate (10); A resistive layer (30) is formed on an insulating layer (20); An electrode layer (40) is formed on the resistive layer (30); A flexible protective layer (50) covers the resistive layer (30) and the electrode layer (40).

8. A flexible precision thin-film resistor according to claim 7, characterized in that: The flexible protective layer (50) is a polyimide material layer.

9. A flexible precision thin-film resistor according to claim 8, characterized in that: The resistance of the resistive layer (30) ranges from 5Ω to 50kΩ, with a resistance accuracy of ±0.02%, and a temperature coefficient of ±10ppm / ℃ in the range of -40℃ to 70℃.

10. A flexible precision thin-film resistor according to claim 9, characterized in that: The thickness of the flexible protective layer (50) does not exceed 3 micrometers.

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