Electroplated metal layer of MEMS probe

Abstract

The invention relates to the technical field of probe card manufacturing, and provides an electroplated metal layer of an MEMS probe, which comprises a patterned electroplated metal layer which sequentially comprises a gold layer, a first copper layer, a nickel alloy layer and a rhodium tip layer; the metal atom permeable layer comprises a gold-nickel permeable layer, a copper-nickel permeable layer, a rhodium-nickel permeable layer, a copper-rhodium permeable layer and a gold-copper permeable layer; and after the graphical electroplating metal layer is subjected to alloying heat treatment, a metal atom permeation layer is formed between contact surfaces of all layers of the graphical electroplating metal layer. The ohmic contact performance between the patterned electroplated metal layers is improved, so that the contact resistance is reduced, the electric connection reliability between the patterned electroplated metal layers is improved, and the contact capability between the patterned electroplated metal layers is enhanced; and on the other hand, the bonding between the metal layers in the bonding process is firmer, the reduction of the yield caused by poor bonding is reduced, and the yield in the assembling and bonding process is improved.

Description

Technical Field

[0001] This invention relates to the field of probe card technology, and more specifically to an electroplated metal layer for a MEMS probe. Background Technology

[0002] As the integration of semiconductor chips continues to increase, the performance requirements for test probe cards are becoming increasingly stringent. Microelectromechanical systems (MEMS) probes, with their high precision, high density, and excellent mechanical consistency, have become a key component in the high-end testing market.

[0003] Traditional MEMS probe manufacturing processes typically involve depositing a metal release layer on a silicon substrate, electroplating to form the probe body structure, and finally removing the release layer (i.e., the "sacrificial layer") using chemical or physical methods to obtain a standalone metal probe. Current conventional processes do not perform any further heat treatment after the metal release layer treatment to optimize the metal interface performance.

[0004] This technological deficiency leads to inherent risks in the fabricated MEMS probes in the following aspects: 1. Electrical performance risks: The contact between multi-layer metal electroplated structures is mainly physical stacking. There may be micro-oxide layers or defects at the interface, which can lead to high and unstable contact resistance, affecting the fidelity of test signals.

[0005] 2. Assembly process risks: During the bonding process of the corresponding MEMS probe assembly, the unstable metal interface is difficult to withstand hot pressure, which can easily lead to interface failure and reduce the yield of the final product. Summary of the Invention

[0006] To address the problems of high and unstable contact resistance and reduced yield of final products in existing technologies, the present invention aims to provide an electroplated metal layer for MEMS probes.

[0007] To address the above problems, the present invention provides the following technical solution: An electroplated metal layer for a MEMS probe includes: a patterned electroplated metal layer, wherein the patterned electroplated metal layer sequentially comprises a gold layer, a first copper layer, a nickel alloy layer, and a rhodium tip layer; The metal atom permeation layer includes a gold-nickel permeation layer, a copper-nickel permeation layer, a rhodium-nickel permeation layer, a copper-rhodium permeation layer, and a gold-copper permeation layer; After the patterned electroplated metal layer undergoes alloying heat treatment, a metal atom penetration layer is formed between the contact surfaces of each layer of the patterned electroplated metal.

[0008] In some embodiments, the gold-nickel penetration layer is disposed between the gold layer and the nickel alloy layer; The copper-nickel penetration layer is disposed between the first copper layer and the nickel alloy layer; The rhodium-nickel infiltration layer is disposed between the rhodium needle tip layer and the nickel alloy layer; The copper-rhodium penetration layer is disposed between the first copper layer and the rhodium needle tip layer; The gold-copper permeation layer is disposed between the gold layer and the first copper layer.

[0009] In some embodiments, the thickness of the gold layer ranges from 1 μm to 10 μm, and the thickness of the first copper layer ranges from 20 μm to 40 μm.

[0010] In some embodiments, the alloying heat treatment temperature ranges from 350°C to 400°C.

[0011] In some embodiments, the alloying heat treatment employs a laser rapid thermal annealing device.

[0012] In some embodiments, the alloying heat treatment takes 30 seconds to 5 minutes.

[0013] In some embodiments, the thickness of the nickel alloy layer ranges from 70 μm to 100 μm.

[0014] In some embodiments, the nickel alloy layer is one of a nickel-cobalt alloy, a nickel-tungsten alloy, or a nickel-phosphorus alloy.

[0015] In some embodiments, the thickness of the gold-nickel permeation layer is 5 nanometers to 100 nanometers.

[0016] In some embodiments, the thickness of the rhodium needle tip layer ranges from 10 μm to 30 μm.

[0017] The beneficial effects of this invention are as follows: by adding an alloying process to the manufacturing process of the probe, a metal atom penetration layer is formed between the contact surfaces of each layer of the patterned electroplated metal, which improves the ohmic contact performance between the patterned electroplated metal layers, reduces the contact resistance, and improves the reliability of the electrical connection between them, thereby enhancing the contact capability between the patterned electroplated metal layers; on the other hand, it makes the bonding between the metal layers more solid during the bonding process, reduces the yield drop caused by poor bonding, and improves the yield during the assembly bonding process. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the fabrication process of the electroplated metal layer for the MEMS probe of this invention. Figure 2 This is a schematic diagram of the structure of a patterned electroplated metal layer according to another embodiment of the present invention.

[0019] Figure label: 1. Gold layer; 2. First copper layer; 3. Nickel alloy layer; 4. Rhodium needle tip layer; 5. Patterned electroplated metal layer. Detailed Implementation

[0020] 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.

[0021] 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.

[0022] 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.

[0023] like Figure 1-2 As shown, this embodiment provides an alloying process method for a MEMS probe, which includes the following steps: S10, preparing a patterned electroplated metal layer 5 that has completed the release layer process; S20, placing the patterned electroplated metal layer 5 in an annealing apparatus and performing alloying heat treatment on the patterned electroplated metal layer 5 in a protective gas; S30, after the alloying heat treatment is completed, the patterned electroplated metal layer 5 is cooled in situ in the process chamber of the annealing apparatus; S40, the patterned electroplated metal layer forms a metal atom penetration layer.

[0024] S10. Prepare the patterned electroplated metal layer 5 that has undergone the release process: This step aims to provide an object for alloying treatment. Specifically, it prepares a patterned electroplated metal layer 5 that has been fabricated using MEMS probe technology and has undergone sacrificial layer release. Its structure includes, from bottom to top, a gold layer 1, a first copper layer 2, a nickel alloy layer 3, and a rhodium tip layer 4, which are electroplated sequentially. First, three release layers are deposited sequentially on a silicon substrate: a titanium metal layer, a nickel metal layer, and a copper metal layer. A patterned electroplated metal layer 5 is then formed by electroplating on the copper metal layer. Finally, the independent patterned electroplated metal layer 5 is obtained after completely removing the three release layers by wet etching. At this point, the silicon substrate has been separated.

[0025] S20. Perform alloying heat treatment: The patterned electroplated metal layer 5 prepared in step S10 is transferred to the process chamber of a laser rapid thermal annealing equipment and placed stably on a temperature-controlled substrate.

[0026] Gas control: After closing the chamber, introduce high-purity nitrogen as a protective gas into the chamber, setting the gas flow rate to 3-10 SLM. Continuously introduce nitrogen to replace and remove air from the chamber, ensuring an oxygen-free protective gas environment is maintained during processing to prevent metal oxidation at high temperatures.

[0027] Heat treatment process: Start the laser heat source and temperature control system of the equipment. Control the output of the process laser energy to rapidly and uniformly heat up the patterned electroplated metal layer 5. Set and stabilize the heat treatment temperature at 400℃, which is within the range of 350℃-400℃, and maintain this temperature for 60 seconds.

[0028] S30. In-situ cooling: Once the heat treatment time is reached, the laser heat source is immediately turned off, and heating is stopped. The patterned electroplated metal layer 5 remains on the substrate in the original process chamber, undergoing natural cooling (i.e., "in-situ cooling") under continuous nitrogen protection. The chamber can only be opened and the processed patterned electroplated metal layer 5 removed once the temperature sensor in the chamber detects that the temperature of the patterned electroplated metal layer has naturally dropped below 150°C (usually requiring 10-15 minutes). This in-situ cooling method avoids the thermal shock caused by suddenly exposing the high-temperature patterned electroplated metal layer 5 to the external environment, effectively preventing thermal stress deformation or cracking of the fine structure of the patterned electroplated metal layer 5 due to rapid temperature changes.

[0029] S40. The patterned electroplated metal layer 5 forms a metal atom penetration layer.

[0030] Optionally, this embodiment may also include step S50 after step S40: plasma cleaning: the patterned electroplated metal layer 5 that has been cooled in situ is transferred to a plasma cleaning device and subjected to low-temperature plasma surface treatment under argon and / or hydrogen to remove the extremely thin surface contaminants or oxide layers that may be formed after alloying heat treatment.

[0031] Optionally, this embodiment may further include step S60 after step S50: inert environment encapsulation. This involves encapsulating the cooled patterned electroplated metal layer in a sealed enclosure filled with nitrogen or argon gas, or in a sealed container purged with inert gas. Function and effect: The clean, activated surface after alloying treatment is maintained, preventing oxidation or contamination during transportation and storage, ensuring a high degree of consistency between factory performance and final use performance, making it particularly suitable for high-reliability products.

[0032] like Figure 1-2 As shown, this embodiment provides an electroplated metal layer for a MEMS probe, which includes a patterned electroplated metal layer 5, which sequentially includes a gold layer 1, a first copper layer 2, a nickel alloy layer 3, and a rhodium tip layer 4. The patterned electroplated metal layer 5 undergoes alloying heat treatment, so that a metal atom penetration layer is formed between the contact surfaces of each layer of the patterned electroplated metal. The metal atom penetration layer includes a gold-nickel penetration layer, a copper-nickel penetration layer, a rhodium-nickel penetration layer, a copper-rhodium penetration layer, and a gold-copper penetration layer.

[0033] As shown in the above structure, the metal atom penetration layer is the result of the mutual penetration of metal atoms between the various layers of the patterned electroplated metal layer 5 after alloying heat treatment. By adding an alloying process to the manufacturing process of the probe, a metal atom penetration layer is formed between the contact surfaces of the various layers of the patterned electroplated metal, which improves the ohmic contact performance between the patterned electroplated metal layers, reduces the contact resistance, and improves the reliability of the electrical connection between them, thereby enhancing the contact ability between the patterned electroplated metal layers. On the other hand, it makes the bonding between the metal layers stronger during the bonding process, reduces the yield drop caused by poor bonding, and improves the yield during the assembly bonding process.

[0034] Optionally, in this embodiment, an electroplated metal layer for a MEMS probe is also provided. An iridium alloy layer is deposited on the surface of the rhodium tip layer 4 by electroplating. The thickness of the iridium alloy layer is 0.1μm~2μm. The patterned electroplated metal layer 5 first optimizes the internal interface through alloying heat treatment, and finally electroplats a harder and more wear-resistant material on the final contact surface for use in the tip or easily worn areas, thereby increasing the probe's wear resistance.

[0035] Optionally, in this embodiment, an electroplated metal layer for a MEMS probe is also provided. Between the first copper layer and the nickel alloy layer, a diffusion barrier layer formed by physical vapor deposition is provided. The diffusion barrier layer is made of titanium nitride or tantalum nitride, and its thickness is 10nm~100nm. Added before alloying heat treatment, this diffusion barrier layer works synergistically with the subsequent alloying heat treatment: the heat treatment optimizes other interfaces, while this diffusion barrier layer actively prevents excessive diffusion of copper, fundamentally suppressing interfacial reactions at high temperatures and improving the high-temperature operating limit of the probe.

[0036] like Figure 1-2 As shown, in this embodiment, the gold-nickel penetration layer is disposed between the gold layer 1 and the nickel alloy layer 3; A copper-nickel penetration layer is disposed between the first copper layer 2 and the nickel alloy layer 3; A rhodium-nickel penetration layer is disposed between the rhodium needle tip layer 4 and the nickel alloy layer 3; A copper-rhodium penetration layer is disposed between the first copper layer 2 and the rhodium needle tip layer 4; The gold-copper infiltration layer is disposed between the gold layer 1 and the first copper layer 2.

[0037] Working principle: The alloying process involves reacting the metal surface at high temperatures (350℃~400℃) to form a metal atom-permeated layer with low resistivity. This improves the interfacial properties between different metal layers. Because the alloying process improves the ohmic contact between the metal layers, it enhances the mechanical stress distribution and durability of the entire MEMS probe structure. The alloying process not only improves electrical performance but also enhances the adhesion and thermal stability between the metal layers. Under high-temperature conditions, the formed alloy layer exhibits better thermal conductivity and mechanical adaptability.

[0038] like Figure 1-2 As shown, in this embodiment, the thickness of the gold layer 1 ranges from 1μm to 10μm, the thickness of the first copper layer 2 ranges from 20μm to 40μm, the thickness of the nickel alloy layer 3 ranges from 70μm to 100μm, and the thickness of the rhodium needle tip layer 4 ranges from 10μm to 30μm.

[0039] The thickness of the gold layer 1 ranges from 1 μm to 10 μm, preferably 2 μm; The thickness of the first copper layer 2 ranges from 20μm to 40μm, preferably 30μm; The thickness of the nickel alloy layer 3 ranges from 70 μm to 100 μm, preferably 80 μm; The thickness of the rhodium needle tip layer 4 ranges from 10 μm to 30 μm, preferably 20 μm.

[0040] In this embodiment, the protective gas is nitrogen.

[0041] In different embodiments, the protective gas can be nitrogen, but other protective gases such as argon and helium can also be used.

[0042] Preferably, the alloying heat treatment temperature range is 350°C to 400°C, for example, 350°C or 400°C can be selected. When the heat treatment temperature is set to 350°C, it needs to be maintained for a relatively long time (the time depends on the thickness of the patterned electroplated metal layer 5), which is suitable for designs that are more sensitive to thermal shock or have a more intricate structure.

[0043] Another preferred option is to set the heat treatment temperature to 400°C and maintain it for a relatively short time (the duration depends on the thickness of the patterned electroplated metal layer 5). This approach utilizes the rapid heating characteristics of laser RTA to achieve the required stronger contact between metal layers in a very short time through higher temperatures, which is beneficial for improving efficiency.

[0044] In this embodiment, the alloying heat treatment uses a laser rapid thermal annealing device.

[0045] In this embodiment, the alloying heat treatment employs a laser rapid thermal annealing device. Laser rapid thermal annealing uses a laser beam as a heat source, which has the characteristics of strong local heating capability and small heat-affected zone, helping to avoid damage to the front of the device, and also ensuring good heating uniformity and stable, easily controllable temperature of the patterned electroplated metal layer 5.

[0046] In this embodiment, the alloying heat treatment time is 30 seconds to 5 minutes.

[0047] In this embodiment, the selectable time is 30 seconds, 1 minute, 2 minutes, 3 minutes, 4 minutes and 5 minutes. Preferably, the alloying heat treatment in this embodiment is 1 minute. Laser rapid thermal annealing of the patterned electroplated metal layer 5 by a rapid thermal annealing furnace (RTA) is beneficial to improving the annealing efficiency.

[0048] The patterned electroplated metal layer 5 includes at least two different metal or alloy layers.

[0049] like Figure 2 As shown, in this embodiment, the patterned electroplated metal layer 5 includes a gold layer 1, a first copper layer 2, a nickel alloy layer 3, and a rhodium tip layer 4. The material of the patterned electroplated metal layer 5 includes gold, nickel, rhodium, and copper. It should be noted that this application does not impose specific requirements or special 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. The nickel alloy layer 3 provides the main mechanical strength and elasticity, the rhodium tip layer 4 provides excellent wear-resistant contact characteristics, and the gold layer 1 and the first copper layer 2 provide good conductivity and interlayer bonding.

[0050] In this embodiment, the nickel alloy layer is one of nickel-cobalt alloy, nickel-tungsten alloy, or nickel-phosphorus alloy.

[0051] As shown in the above structure, preferably, the nickel alloy layer is a nickel-tungsten alloy, which has the function of resisting plastic deformation, ensuring that the shape and elastic recovery ability of the probe cantilever beam remain stable after multiple contacts.

[0052] In this embodiment, the thickness of the gold-nickel permeation layer is 5 nanometers to 100 nanometers.

[0053] As shown in the above structure, preferably, the thickness of the gold-nickel permeation layer is between 20 and 50 nanometers.

[0054] In this embodiment, the release layer process includes the following steps: S01, Provide a silicon substrate; SO2, silicon substrate is pretreated; S03. A metal release layer is sequentially formed on a silicon substrate; S04. Perform photolithography on the top of the metal release layer; S05. A patterned electroplated metal layer 5 is formed on the metal release layer; S06. By using a wet etching process, a mixed etching solution is used to remove the metal release layer, thereby separating the patterned electroplated metal layer 5 from the silicon substrate and obtaining an independent patterned electroplated metal layer 5.

[0055] As shown in the above structure, in the release layer process, an independent patterned electroplated metal layer 5 can be obtained simply by releasing the metal release layer. The metal element of the metal release layer can be any one of copper, zinc, titanium, nickel, silver, aluminum, etc. Preferably, in this embodiment, copper and titanium are selected as the elements of this metal release layer.

[0056] In this embodiment, the mixed etching solution includes an NH4OH-H2O2 solution and a ferric chloride solution used for etching the metal release layer.

[0057] Preferably, a mixed aqueous solution of NH4OH-H2O2 is used. This solution has a relatively fast etching rate for titanium, while the etching rate for metals such as nickel, copper, gold, and rhodium above it is extremely slow, showing good selectivity.

[0058] Preferably, the etching solution used for etching the copper metal layer is an aqueous solution of ferric chloride (FeCl3), which can efficiently etch copper while having almost no corrosion on the silicon substrate and the electroplated precious metal layers such as gold (Au) and rhodium (Rh).

[0059] In this embodiment, in S02, the pretreatment consists of cleaning and drying. The silicon substrate is placed in an ultrasonic cleaner for cleaning, and then placed in a spin dryer for drying.

[0060] In summary, this invention provides an electroplated metal layer for a MEMS probe. By adding an alloying process to the probe manufacturing process, a metal atom-permeable layer is formed between the contact surfaces of each layer of the patterned electroplated metal 5, improving the ohmic contact performance between the patterned electroplated metal layers 5, reducing the contact resistance, and improving the reliability of the electrical connection between them, thereby enhancing the contact capability between the patterned electroplated metal layers 5. On the other hand, it makes the bonding between the metal layers more robust during the bonding process, reducing the yield drop caused by poor bonding and improving the yield during the assembly and bonding process.

[0061] 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. An electroplated metal layer of a MEMS probe, characterized by, Comprise: A patterned electroplated metal layer, which comprises a gold layer, a first copper layer, a nickel alloy layer and a rhodium tip layer in sequence; A metal atom permeation layer, which comprises a gold-nickel permeation layer, a copper-nickel permeation layer, a rhodium-nickel permeation layer, a copper-rhodium permeation layer and a gold-copper permeation layer; After alloying heat treatment, the metal atom permeation layer is formed between the contact surfaces of each layer of the patterned electroplated metal.

2. The electroplated metal layer of the MEMS probe according to claim 1, wherein: The gold-nickel permeation layer is arranged between the gold layer and the nickel alloy layer; The copper-nickel permeation layer is arranged between the first copper layer and the nickel alloy layer; The rhodium-nickel permeation layer is arranged between the rhodium tip layer and the nickel alloy layer; The copper-rhodium permeation layer is arranged between the first copper layer and the rhodium tip layer; The gold-copper permeation layer is arranged between the gold layer and the first copper layer.

3. The electroplated metal layer of the MEMS probe according to claim 1 or 2, wherein: The thickness of the gold layer ranges from 1 μm to 10 μm, and the thickness of the first copper layer ranges from 20 μm to 40 μm.

4. The electroplated metal layer of a MEMS probe according to claim 1, wherein: The alloying heat treatment temperature ranges from 350°C to 400°C.

5. The electroplated metal layer of a MEMS probe according to claim 1, wherein: The alloying heat treatment uses a laser rapid thermal annealing device.

6. The electroplated metal layer of a MEMS probe according to claim 1, wherein: The alloying heat treatment time is 30 seconds to 5 minutes.

7. The electroplated metal layer of a MEMS probe according to claim 1, wherein: The thickness of the nickel alloy layer ranges from 70 μm to 100 μm.

8. The electroplated metal layer of a MEMS probe according to claim 1, wherein: The nickel alloy layer is one of a nickel-cobalt alloy, a nickel-tungsten alloy or a nickel-phosphorus alloy.

9. The electroplated metal layer of a MEMS probe according to claim 2, wherein: The thickness of the gold-nickel permeation layer is 5 nm to 100 nm.

10. The electroplated metal layer of a MEMS probe according to claim 1 or 2, wherein: The thickness of the rhodium tip layer ranges from 10 μm to 30 μm.

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