Composite metal structure for MEMS probe, probe and probe card
By using a titanium, nickel, and copper composite metal structure as the release layer in the MEMS probe card, and combining it with a wet etching process, the problems of long processing time and high chemical consumption of silicon-based release layers have been solved, achieving efficient MEMS probe production, reducing costs and environmental pressure, and improving yield.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-26
- Publication Date
- 2026-03-31
AI Technical Summary
Existing MEMS probe cards suffer from long processing times, high chemical consumption, and poor surface quality and uniformity after release, making it difficult to meet the production requirements of high-end products.
A titanium metal underlayer, a nickel metal underlayer, and a copper seed layer are used as release layers for the silicon substrate. Combined with a wet etching release process, the metal thin film is etched and released by mixing the etching solution, thereby reducing the material removal volume.
Significantly reduce the amount of etching solution used, lower material costs and environmental impact, and improve the yield of MEMS probes.
Smart Images
Figure CN121762889A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of probe card technology, specifically to a composite metal structure for MEMS probes, a probe, and a probe card. Background Technology
[0002] Currently, silicon-based and silicon oxide-based materials are widely used as release layer materials in the fabrication of probe cards (MEMS probes) for microelectromechanical systems (MEMS). Silicon-based materials are commonly used due to their good mechanical strength and chemical stability, especially when etching release layers on 8-inch silicon substrates with a thickness of approximately 725 μm, where they can provide sufficient mechanical support. However, this silicon-based release layer process has some significant drawbacks, including long release process times, the need for large amounts of chemical solutions, and poor surface quality and uniformity after release. These drawbacks are acceptable in the manufacture of low-end products, but for the production of high-end products, these limitations require further improvement. Summary of the Invention
[0003] In view of the long processing time and large chemical consumption of existing technologies, the purpose of this invention is to provide a stable and fixed composite metal structure, probe and probe card for MEMS probes.
[0004] To address the above problems, the present invention provides the following technical solution: A composite metal structure for MEMS probes, comprising: Silicon substrate; A titanium metal underlayer is disposed on the silicon substrate; A nickel metal underlayer is disposed on the titanium metal underlayer; A copper seed layer covers the nickel metal base layer, and the top surface of the copper seed layer has a hollow space; A patterned electroplated metal layer is formed within the hollow space of the copper seed layer.
[0005] In some embodiments, the cross-sectional areas of the titanium metal underlayer, the nickel metal underlayer, and the copper seed layer are all the same.
[0006] In some embodiments, the cross-sectional shape of the hollow space can be any one of a circle, a square, or a trapezoid.
[0007] In some embodiments, the thickness of the titanium metal underlayer ranges from 0.2 μm to 10 μm; the thickness of the nickel metal underlayer ranges from 0.2 μm to 5 μm; and the thickness of the copper seed layer ranges from 0.1 μm to 10 μm.
[0008] An embodiment of the present invention also provides a MEMS probe, which is made of the above-mentioned composite metal structure by an etching process, wherein the titanium metal underlayer, the nickel metal underlayer and the copper seed layer are all etched and released by a mixed etching solution, and the patterned electroplated metal layer is separated from the silicon substrate, thereby obtaining an independent MEMS probe.
[0009] In some embodiments, the patterned electroplated metal layer includes a gold layer, a first copper layer, a nickel alloy layer, and a rhodium needle tip layer.
[0010] In some embodiments, the mixed etching solution includes an NH4OH-H2O2 solution and a ferric chloride solution.
[0011] In some embodiments, the concentration of the ferric chloride solution is 35 wt%.
[0012] In some embodiments, the thickness of the gold layer ranges from 1 μm to 10 μm, the thickness of the first copper layer ranges from 20 μm to 40 μm, the thickness of the nickel alloy layer ranges from 70 μm to 100 μm, and the thickness of the rhodium needle tip layer ranges from 10 μm to 30 μm.
[0013] An embodiment of the present invention also provides a probe card, including the MEMS probes described above.
[0014] The beneficial effects of this invention are as follows: By using titanium metal as the base layer, nickel metal as the base layer and copper seed layer as the release layer of the silicon substrate, and in conjunction with the wet etching release process, the volume of material to be removed is reduced from the cubic millimeter level of the silicon substrate to the cubic micrometer level of the metal film. This greatly reduces the amount of etching solution used, which not only directly reduces material costs, but also alleviates the environmental pressure and cost of waste liquid treatment and improves the yield of MEMS probes. Attached Figure Description
[0015] Figure 1 This is a schematic flowchart of the method for fabricating the composite metal structure for MEMS probes according to the present invention. Figure 2 A schematic diagram of the structure of the titanium metal underlayer, the nickel metal underlayer, and the copper seed layer provided by the present invention; Figure 3 This is a schematic diagram of the structure of a patterned electroplated metal layer according to another embodiment of the present invention.
[0016] Figure label: 1. Silicon substrate; 2. Titanium metal underlayer; 3. Nickel metal underlayer; 4. Copper seed layer; 5. Patterned electroplated metal layer; 6. Gold layer; 7. First copper layer; 8. Nickel alloy layer; 9. Rhodium tip layer. Detailed Implementation
[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.
[0018] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.
[0019] For ease of description of the first, second, and third directions in the embodiments of this application, the first direction is the left-right direction in the figures, the second direction is the front-back direction in the figures, and the third direction is the up-down direction in the figures. The x-axis arrow direction is referred to as the "right" direction, the y-axis arrow direction as the "up" direction, and the z-axis arrow direction as the "back" direction, but these are not the sole limitations in the actual application of this application.
[0020] Example 1 Traditional techniques employ MEMS probe fabrication processes. In their release processes, traditional techniques use silicon-based or silicon oxide-based methods for MEMS probe fabrication. The main drawbacks are that the release process (etching silicon substrate 1: 8-inch silicon substrate 1 thickness: 725μm) is time-consuming, requires a large amount of chemical solutions, and results in poor surface quality and uniformity after release. While this method can still be used for low-end products, it requires further improvement or other methods to enhance the process level for high-end products.
[0021] like Figure 1-3 As shown, this embodiment provides a method for fabricating a composite metal structure for MEMS probes, including the following steps: S10, Provide a silicon substrate 1; S20. A titanium metal underlayer 2, a nickel metal underlayer 3 and a copper seed layer 4 are sequentially formed on a silicon substrate 1. S30. A patterned electroplated metal layer 5 is formed on the copper seed layer 4; S40. The titanium metal underlayer 2, nickel metal underlayer 3 and copper seed layer 4 are removed by wet etching process, so that the patterned electroplated metal layer 5 is separated from the silicon substrate 1, thereby obtaining an independent composite metal structure for MEMS probe.
[0022] like Figure 1-3As shown, this embodiment provides a composite metal structure for MEMS probes, comprising: a silicon substrate 1; a titanium metal underlayment 2 disposed on the silicon substrate 1; a nickel metal underlayment 3 disposed on the titanium metal underlayment 2; a copper seed layer 4 covering the nickel metal underlayment 3, wherein the top surface of the copper seed layer 4 has a hollow space; and a patterned electroplated metal layer 5 formed within the hollow space of the copper seed layer 4. The hollow space is a patterned opening formed by coating the surface of the copper seed layer 4 with photoresist and then exposing and developing it, and the opening defines the area for subsequent electroplating.
[0023] By using titanium metal underlayer 2, nickel metal underlayer 3 and copper seed layer 4 as release layers for silicon substrate 1, and in conjunction with wet etching release process, the volume of material to be removed is reduced from the cubic millimeter level of silicon substrate 1 to the cubic micrometer level of metal film, thus greatly reducing the amount of etching solution used. This not only directly reduces material costs, but also alleviates the environmental pressure and cost of waste liquid treatment, and improves the yield of MEMS probes.
[0024] This embodiment 1 illustrates the basic process of the method of the present invention, the corresponding structure of which is a Ti / Ni / Cu three-layer continuous thin film, which forms a suspended patterned electroplated metal layer 5 after release.
[0025] Example 2 like Figure 1 and Figure 2 As shown, in this embodiment, in S20, the titanium metal underlayer 2, the nickel metal underlayer 3, and the copper seed layer 4 are continuously deposited in a vacuum environment. The cross-sectional areas of the titanium metal underlayer 2, the nickel metal underlayer 3, and the copper seed layer 4 are all the same.
[0026] like Figure 1-3 As shown, in this embodiment, before step S30, the copper seed layer 4 is photolithographically etched to form at least one hollow space; in step S30, a patterned electroplated metal layer 5 is formed in the hollow space.
[0027] Through the above structural design, a hollow space is formed on the top surface of the copper seed layer 4 by photolithography or etching process. The pattern of the hollow space defines the pattern of the MEMS probe body (such as cantilever beam, needle tip, etc.) formed by subsequent electroplating. The hollow space is a patterned opening formed by coating photoresist on the surface of the copper seed layer 4 and then exposing and developing it. This opening defines the area for subsequent electroplating.
[0028] In this embodiment, multiple patterned electroplated metal layers 5 are sequentially placed in the hollow space of the copper seed layer 4 using an electroplating process. Finally, a mixed etching solution is used to etch and release the titanium metal underlayment 2, the nickel metal underlayment 3, and the copper seed layer 4. After the titanium metal underlayment 2, the nickel metal underlayment 3, and the copper seed layer 4 are completely etched and released, the patterned electroplated metal layers 5 are separated from the silicon substrate 1, thereby obtaining an independent composite metal structure for MEMS probes.
[0029] Specifically, the shape of the hollow space can be a geometric cube such as a cylinder, cuboid, or frustum, and its size is not limited.
[0030] In this embodiment, the hollow space is formed by coating the surface of the copper seed layer 4 with photoresist, exposing it with a photomask, and developing the area of the groove or recess of the patterned electroplated metal layer 5 to be produced. Before release, the copper seed layer 4 forms a support structure, and the patterned electroplated metal layer 5 constructs a patterned structure in the copper seed layer 4.
[0031] In another embodiment, a mask layer is provided on the surface of the hollow space. The mask layer is used to protect the copper seed layer 4 part where the patterned electroplated metal layer 5 needs to be constructed, to prevent the patterned electroplated metal layer 5 from being etched by the mixed release liquid, and to ensure that the fabrication accuracy of the patterned electroplated metal layer 5 can reach the service level.
[0032] In another embodiment, the patterned electroplated metal layer 5 after electroplating is post-processed, which includes cleaning and drying. Specifically, the patterned electroplated metal layer 5 is cleaned with deionized water or distilled water to remove the mixed etching solution on its surface, the patterned electroplated metal layer 5 is washed with hot water, and then dried.
[0033] In another embodiment, hollow grooves are photolithographically etched in both the titanium metal underlayer 2 and the nickel metal underlayer 3. The purpose is to increase the surface area of the titanium metal underlayer 2 and the nickel metal underlayer 3, which is beneficial for contact with the mixed etching solution, and helps to accelerate the evaporation rate and efficiency of the titanium metal underlayer 2 and the nickel metal underlayer 3, and prevents the titanium metal underlayer 2 and the nickel metal underlayer 3 from leaving residues on the silicon substrate 1.
[0034] Example 3 According to Example 1 or 2, such as Figure 1-3 As shown, in this embodiment, in step S21, the silicon substrate 1 that has been pretreated in step S10 is placed in a magnetron sputtering fixture, and titanium metal underlayer 2 is sputtered by DC sputtering.
[0035] It should be noted that the silicon substrate 1, which has been pretreated in S10, is placed in the magnetron sputtering fixture, a titanium target is mounted on the target base, and the target base spacing is adjusted. Then, argon gas is introduced into the sputtering cavity for protection. The silicon substrate 1 is then transferred into the sputtering cavity, and the sputtering cavity is then evacuated to a vacuum to ensure that the silicon substrate 1 is at an angle with the direction of the magnetron sputtering magnetic field. The titanium metal underlayer 2 is obtained by sputtering using DC sputtering.
[0036] This embodiment provides specific process parameters: target-substrate distance 80mm, background vacuum better than 5.0×10⁻⁶. -4 Pa, working pressure 0.5Pa, DC power 500W, time 3 minutes, thickness 0.5μm.
[0037] like Figure 1-3 As shown, in this embodiment, the specific steps of S20 further include: S22. Continue to adjust the sputtering conditions and use an RF power supply to sputter a nickel metal underlayer on the titanium underlayer to obtain a nickel metal underlayer 3.
[0038] It should be noted that the sputtering conditions are adjusted to maintain the angle between the silicon substrate 1, which is completed by sputtering titanium metal underlayer 2 in S21, and the magnetron sputtering magnetic field. Then, a nickel target is placed on the target base, and a nickel metal underlayer 3 is obtained by sputtering on the titanium underlayer using an RF power supply.
[0039] like Figure 1-3 As shown, in this embodiment, the specific steps of S20 further include: S23. Continue to adjust the sputtering conditions and use an RF power supply to sputter a copper seed layer 4 on the nickel metal substrate 3.
[0040] It should be noted that the sputtering conditions are adjusted to maintain the angle between the titanium metal layer 2 completed by sputtering nickel metal layer 3 in S22 and the magnetron sputtering magnetic field. Then, a copper target is mounted on the target base, and a copper seed layer 4 is obtained by sputtering on the nickel metal layer 3 using an RF power supply.
[0041] Thus, through the three steps S21, S22, and S23 described above, a composite metal structure consisting of a titanium metal underlayer 2 (~0.5 μm), a nickel metal underlayer 3 (~1.0 μm), and a copper seed layer 4 (~1.0 μm) was sequentially deposited in an integrated high-vacuum multi-chamber sputtering system in an in-situ manner without atmospheric exposure. This process ensures atomic-level cleanliness and excellent adhesion at the interfaces between the layers, laying a crucial foundation for the fabrication of high-performance MEMS probes.
[0042] like Figure 3 As shown, in this example, step S30 may specifically include: The patterned electroplated metal layer 5 includes a gold layer 6, a first copper layer 7, a nickel alloy layer 8, and a rhodium needle tip layer 9.
[0043] It should be noted that the patterned electroplated metal layer 5 includes a gold layer 6, a first copper layer 7, a nickel alloy layer 8, and a rhodium needle tip layer 9. It should be noted that... Figure 3 The diagram shown is only one representative cross-section and does not fully represent the complete three-dimensional stacked structure.
[0044] In some embodiments, the patterned electroplated metal layer 5 is made of gold, nickel, rhodium, and copper. It should be noted that this application does not impose specific requirements or limitations on the material and shape of the patterned electroplated metal layer 5. Those skilled in the art can reasonably select the material and shape of the patterned electroplated metal layer 5 according to actual needs. This application is applicable to the preparation of various types of probes.
[0045] Through the above structural design, the nickel alloy layer 8 provides the main mechanical strength and elasticity, the rhodium needle tip layer 9 provides excellent wear-resistant contact characteristics, and the gold layer 6 and the first copper layer 7 provide good electrical conductivity and interlayer bonding.
[0046] like Figure 1-3 As shown, in this embodiment, the thickness of the titanium metal underlayer 2 ranges from 0.2μm to 10μm; the thickness of the nickel metal underlayer 3 ranges from 0.2μm to 5μm; and the thickness of the copper seed layer 4 ranges from 0.1μm to 10μm.
[0047] In some embodiments, the thickness of the titanium metal underlayer 2 is 0.2μm to 10μm, for example, 0.2μm, 0.5μm, 1.0μm, 1.2μm, 1.4μm, 1.6μm, 5μm or 10μm, preferably 0.5μm.
[0048] The thickness of the nickel metal underlayer 3 is 0.2μm to 5μm, for example, 0.5μm, 1.0μm, 1.2μm, 1.4μm, 1.6μm, 5μm or 10μm, preferably 1.0μm.
[0049] The thickness of the copper seed layer 4 is 0.1 μm to 10 μm, for example, 0.1 μm, 0.5 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 5 μm or 10 μm, preferably 1.0 μm.
[0050] like Figure 1 As shown, in this embodiment, step S10 further includes placing the silicon substrate 1 into an ultrasonic cleaner for cleaning, and then placing it into a spin dryer for drying. In step S10, the silicon substrate 1 is cleaned using the RCA standard cleaning method.
[0051] like Figure 1-3As shown, this embodiment also provides a MEMS probe, which is made by etching the above-mentioned composite metal structure. The titanium metal base layer 2, the nickel metal base layer 3 and the copper seed layer 4 are all etched and released by a mixed etching solution. The patterned electroplated metal layer 5 is separated from the silicon substrate 1, thereby obtaining an independent MEMS probe.
[0052] like Figure 1 As shown, in this embodiment, in S40, the titanium metal underlayer 2, the nickel metal underlayer 3, and the copper seed layer 4 are selectively etched using a mixed etching solution. The mixed etching solution used in this metal release method is: The NH4OH-H2O2 solution used for etching the titanium metal underlayer 2; Ferric chloride solution is used to etch the nickel metal underlayer 3 and the copper seed layer 4.
[0053] Preferably, the etching solution used for etching the titanium underlayer is a mixed aqueous solution of NH4OH-H2O2. A typical ratio is 28% ammonia (NH4OH): 30% hydrogen peroxide (H2O2): water (H2O) = 1:1:5 (volume ratio). This solution has a relatively fast etching rate for titanium, while the etching rate for the metals above, such as nickel, copper, gold, and rhodium, is extremely slow, showing good selectivity.
[0054] Preferably, the etching solution used for etching the nickel metal underlayer 3 and the copper seed layer 4 is an aqueous solution of ferric chloride (FeCl3). A typical formulation is a 35wt% FeCl3 aqueous solution. This solution can efficiently etch nickel and copper, while having almost no erosion on the silicon substrate 1 and the electroplated precious metal layers such as gold (Au) and rhodium (Rh).
[0055] like Figure 1 As shown, in this embodiment, the metal release of the titanium metal underlayer 2, nickel metal underlayer 3 and copper seed layer 4 of the silicon substrate 1 by the mixed etching solution is performed simultaneously.
[0056] It is understood that the above-mentioned Ti / Ni / Cu material combination is a preferred solution after in-depth research, and its design is based on the following principles: Titanium (Ti) has excellent adhesion to silicon (Si) substrates, making it an ideal first layer; Nickel (Ni) has good compatibility and adhesion to both titanium and copper, and its etching characteristics are intermediate between the two; Copper (Cu) has excellent conductivity, making it an ideal seed layer material for electroplating. The combination of these three materials, and their removal through specific etching solutions (such as NH4OH-H2O2 and FeCl3), forms the basis of the efficient release process of this invention.
[0057] In other possible implementations, those skilled in the art can make equivalent material substitutions according to actual needs, provided that process feasibility and functional similarity are guaranteed. For example, the titanium metal underlayer 2 can be replaced by chromium (Cr), tantalum (Ta), etc.; the nickel metal underlayer 3 can be replaced by cobalt (Co), etc.; the copper seed layer 4 can be replaced by silver (Ag), etc., and the corresponding etching solution also needs to be adjusted according to the chemical properties of the selected materials.
[0058] In this embodiment, the thickness of the gold layer 6 ranges from 1 μm to 10 μm, preferably 2 μm; The thickness of the first copper layer 7 ranges from 20μm to 40μm, preferably 30μm; The thickness of the nickel alloy layer 8 ranges from 70 μm to 100 μm, preferably 80 μm; The thickness of the rhodium needle tip layer 9 ranges from 10 μm to 30 μm, preferably 20 μm.
[0059] In summary, the present invention provides a probe card, including the aforementioned MEMS probe.
[0060] These probes are precisely arranged and fixed on the substrate of the probe card for high-density, high-reliability electrical testing of the tested objects such as chips.
[0061] In summary, this invention provides a composite metal structure, probe, and probe card for MEMS probes. By using a titanium metal underlayer 2, a nickel metal underlayer 3, and a copper seed layer 4 as the release layer of the silicon substrate 1, and in conjunction with a wet etching release process, the volume of material to be removed is reduced from the cubic millimeter level of the silicon substrate 1 to the cubic micrometer level of the metal thin film. This greatly reduces the amount of etching solution used, which not only directly reduces material costs but also alleviates the environmental pressure and cost of waste liquid treatment and improves the yield of MEMS probes.
[0062] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.
Claims
1. A composite metal structure for MEMS probes, characterized in that, include: Silicon substrate; A titanium metal underlayer is disposed on the silicon substrate; A nickel metal underlayer is disposed on the titanium metal underlayer; A copper seed layer covers the nickel metal base layer, and the top surface of the copper seed layer has a hollow space; A patterned electroplated metal layer is formed within the hollow space of the copper seed layer.
2. The composite metal structure for MEMS probes according to claim 1, characterized in that: The cross-sectional areas of the titanium metal underlayer, the nickel metal underlayer, and the copper seed layer are all the same.
3. The composite metal structure for MEMS probes according to claim 1, characterized in that: The cross-sectional shape of the hollow space can be any one of a circle, a square, or a trapezoid.
4. The composite metal structure for MEMS probes according to claim 1, characterized in that: The thickness of the titanium metal underlayer ranges from 0.2 μm to 10 μm; the thickness of the nickel metal underlayer ranges from 0.2 μm to 5 μm; and the thickness of the copper seed layer ranges from 0.1 μm to 10 μm.
5. A MEMS probe, characterized in that, The composite metal structure according to any one of claims 1-4 is formed by an etching process, wherein the titanium metal underlayer, the nickel metal underlayer and the copper seed layer are all etched and released by a mixed etching solution, and the patterned electroplated metal layer is separated from the silicon substrate, thereby obtaining an independent MEMS probe.
6. The MEMS probe according to claim 5, characterized in that: The patterned electroplated metal layer includes a gold layer, a first copper layer, a nickel alloy layer, and a rhodium needle tip layer.
7. The MEMS probe according to claim 5, characterized in that: The mixed etching solution includes NH4OH-H2O2 solution and ferric chloride solution.
8. The MEMS probe according to claim 7, characterized in that: The concentration of the ferric chloride solution is 35 wt%.
9. The MEMS probe according to claim 6, characterized in that, The thickness of the gold layer ranges from 1 μm to 10 μm, the thickness of the first copper layer ranges from 20 μm to 40 μm, the thickness of the nickel alloy layer ranges from 70 μm to 100 μm, and the thickness of the rhodium needle tip layer ranges from 10 μm to 30 μm.
10. A probe card, characterized in that, Includes the MEMS probe as described in any one of claims 5-9.