Method for improving adhesive force and stability between glass through hole substrate and copper layer

Abstract

The invention discloses a method for improving adhesive force and stability between a glass through hole substrate and a copper layer, which is characterized in that a polytetrafluoroethylene film is deposited between the glass through hole substrate and the copper layer through magnetron sputtering, so that the thermal stress difference between copper and the glass through hole substrate is relieved, and the interface adhesive force between the copper layer and the substrate is improved. The polytetrafluoroethylene film is soft in texture, has excellent mechanical buffering capacity, can form a flexible buffering interface between copper and a glass through hole substrate, effectively disperses interface stress, and relieves the problems of warping, cracking and film layer falling caused by material rigidity difference. In addition, the film also has good physical isolation characteristics, and can inhibit the interface diffusion behavior of copper under a high temperature condition to a certain extent. According to the method, high-quality deposition of the copper layer on the glass through hole substrate is achieved, the stability of interface bonding is improved, the electromagnetic coupling effect of a device in the high-frequency signal transmission process can be restrained, and then the signal integrity and the overall electrical reliability are guaranteed.

Description

Technical Field

[0001] The present invention belongs to the field of chip packaging technology, and specifically relates to a method for constructing a flexible buffer interface by depositing a high molecular polymer barrier layer through magnetron sputtering, thereby improving the interface stability and adhesion between a through-glass substrate and a copper layer. Background Art

[0002] Through-glass-via (TGV) copper plating technology is an important packaging technology for achieving high-density integration and high-speed optoelectronic integration. Leveraging the low dielectric loss, high mechanical strength, and excellent optical properties of TGL substrates, it has shown broad application prospects in the fields of semiconductors, biology, and high-end sensors. However, the significant difference in the coefficient of thermal expansion (CTE) between glass and copper can easily lead to stress concentration at the heterogeneous interface, causing warping, microcrack propagation, and structural fatigue, seriously affecting the long-term stability of metal interconnects. Constructing a barrier layer with a controllable microstructure and thermal expansion coefficient can effectively reduce interface stress, enhance heterogeneous interface coupling, and inhibit metal diffusion at high temperatures, thereby improving the stability and reliability of interconnects. Currently, barrier layer materials used in silicon-based through-hole interconnect technology are often used, such as metals or metal nitrides such as Ti, TiN, Ta, and Cr. However, there is still a significant difference in the thermal expansion coefficient between this type of inorganic material and the glass through-hole substrate and the filled metal copper. When experiencing hot and cold cycles or long-term service conditions, the interface is prone to cumulative thermal stress, which in turn causes interface delamination and crack propagation of the metal interconnect structure, and even exacerbates electromigration behavior, ultimately weakening the structural stability and long-term reliability of the device. Summary of the Invention

[0003] This invention aims to address the interfacial stress accumulation between through-glass via (TGO) substrates and copper metal caused by differences in material properties, preventing the resulting reliability risks of interconnect delamination, crack propagation, and increased electromigration. The method provides a method for improving the adhesion and stability between TGO substrates and copper layers. This method utilizes magnetron sputtering to deposit a polymer barrier layer on the TGO substrate surface, creating a flexible buffer interface that securely bonds the copper layer to the glass, effectively improving the long-term stability and mechanical integrity of the metal interconnect structure.

[0004] To achieve the above-mentioned purpose, the present invention provides a method for improving the adhesion and stability between a through-glass via substrate and a copper layer, comprising the following steps:

[0005] Step 1: Ultrasonic cleaning of the through-glass substrate.

[0006] Step 2: The substrate cleaned in step 1 is subjected to oxygen plasma treatment to enhance the surface roughness of the through-glass substrate and improve the adhesion of the film.

[0007] Step 3: Place the polytetrafluoroethylene target material on the RF sputtering target position in the magnetron sputtering coating machine, and sputter-deposit a polytetrafluoroethylene film as a barrier layer on the substrate treated in step 2 under a vacuum environment and inert gas.

[0008] Step 4: Electrolessly copper-plating the substrate on which the polytetrafluoroethylene film is sputter-deposited.

[0009] Furthermore, in the above step 1, the through-glass substrate is ultrasonically cleaned at room temperature using ethanol and acetone, respectively, with an ultrasonic power of 50 to 100 W, a frequency of 40 to 60 Hz, and an ultrasonic time of 5 to 20 minutes; after ultrasonic cleaning, the substrate is rinsed with distilled water and finally dried.

[0010] Furthermore, in the above step 2, it is preferred that the power of the oxygen plasma treatment is 50 to 150 W, the time is 2 to 10 min, the oxygen flow rate is 30 to 60 sccm, and the treatment temperature is room temperature.

[0011] Furthermore, in the above step 3, it is preferred to use a vacuum of 3×10- 4 ~5×10- 4 The polytetrafluoroethylene film is sputter-deposited at a flow rate of 10 to 50 sccm of inert gas, a chamber pressure of 0.8 to 1.2 Pa, a substrate heating temperature of 20 to 120° C., and a radio frequency sputtering power of 20 to 100 W, and the sputtering time is 10 to 30 minutes.

[0012] Furthermore, in the above step 3, it is more preferable to -4 ~5×10 -4 The polytetrafluoroethylene film is sputter-deposited at a flow rate of 20-40 sccm of inert gas, a chamber pressure of 0.8-1 Pa, a substrate heating temperature of 40-80° C., and a radio frequency sputtering power of 20-60 W, and the sputtering time is 10-20 min.

[0013] Furthermore, in the above step 3, the thickness of the polytetrafluoroethylene film is preferably 100 to 200 nm.

[0014] Furthermore, in the above step 3, the inert gas is nitrogen or argon.

[0015] Furthermore, in the above step 4, the formula of the electroless copper plating solution is preferably as follows: per liter of copper plating solution, the solution contains 10-20 g of copper sulfate pentahydrate, 20-40 g of potassium sodium tartrate, 5-10 mL of formaldehyde, 1-5 mg of L-malic acid, 1-5 mg of nickel sulfate, 1-10 mg of 2,2'-bipyridine, and 5-20 mg of sodium dodecylbenzenesulfonate, with the remainder being deionized water. The pH of the copper plating solution is controlled at 10-13; the temperature of the electroless copper plating is controlled at 20-40°C.

[0016] In the invention, magnetron sputtering is used to deposit a polytetrafluoroethylene (PTFE) film on a through-glass (TGO) substrate. Because PTFE is an insulating material and cannot stably ignite a plasma when used directly as a target, a conductive target is provided during the sputtering process to assist in attracting dust and ensure proper TGO deposition. This conductive target, which can be selected from graphite, metal, or their alloys, does not participate in the deposition process and does not affect the chemical composition and structural properties of the final film. This configuration allows for uniform deposition of the PTFE film on the TGO substrate surface while maintaining film purity.

[0017] The beneficial effects of the present invention are as follows:

[0018] 1. The present invention deposits a polytetrafluoroethylene film as a barrier layer between the through-glass substrate and the copper layer by magnetron sputtering to alleviate the thermal stress difference between the copper and the through-glass substrate, improve the interfacial adhesion between the copper layer and the substrate, and combine it with oxygen plasma treatment to improve the surface activity of the substrate, effectively enhancing the adhesion between the barrier layer and the through-glass substrate. The polytetrafluoroethylene film is soft in texture and has excellent mechanical buffering capacity. It can form a flexible buffer interface between the copper and the through-glass substrate, effectively disperse the interfacial stress, and alleviate the warping, cracking and film shedding problems caused by the difference in material rigidity. In addition, the film also has good physical isolation properties, which can inhibit the interfacial diffusion behavior of copper under high temperature conditions to a certain extent.

[0019] 2. In the present invention, the substrate heating temperature is controlled below 200°C, which effectively avoids thermal deformation of the glass through-hole substrate and maintains the structural integrity and mechanical stability of the polytetrafluoroethylene film, so that it has good interface buffering performance in subsequent processes.

[0020] 3. This invention incorporates a polytetrafluoroethylene film as a barrier layer, effectively mitigating residual stress accumulation during the electroless copper plating process, inhibiting copper film warping and delamination, and improving interfacial stability. Polytetrafluoroethylene film possesses both a low dielectric constant and excellent electrical insulation properties, helping to suppress electromagnetic coupling interference during high-frequency signal transmission, thereby ensuring signal integrity and system electrical stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The SEM and EDS element distribution images (center) of the front side (left) and cross-sectional side (right) of the sputter-deposited polytetrafluoroethylene film on the through-glass substrate in Example 1 are shown.

[0022] Figure 2 This is a Raman spectrum of the polytetrafluoroethylene film sputter-deposited on the through-glass substrate in Example 1.

[0023] Figure 3This is an infrared spectrum of the polytetrafluoroethylene film sputter-deposited on the through-glass substrate in Example 1.

[0024] Figure 4 1 is a graph showing the effect of electroless copper plating after sputtering and depositing a polytetrafluoroethylene film on a through-glass hole substrate in Example 1 and the effect of direct electroless copper plating without depositing a polytetrafluoroethylene film.

[0025] Figure 5 These are the XRD diffraction patterns at different tilt angles of the Cu(111), Cu(200), Cu(220), and Cu(311) crystal planes on the through-glass substrate sputter-deposited with polytetrafluoroethylene film and chemically copper-plated in Example 1. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and examples, but the protection scope of the present invention is not limited to these examples.

[0027] Example 1

[0028] Step 1: The silicate glass through-hole substrate was ultrasonically cleaned at room temperature for 5 minutes using ethanol and acetone respectively, with an ultrasonic power of 100 W and a frequency of 40 Hz. After ultrasonic cleaning, the substrate was rinsed with distilled water and finally dried.

[0029] Step 2: Place the substrate cleaned in step 1 in a plasma treatment device, set the power to 100 W, the time to 8 minutes, and the oxygen flow to 40 sccm, and perform oxygen plasma treatment on the substrate at room temperature to enhance the surface roughness of the substrate and improve the adhesion of the film.

[0030] Step 3: Place the polytetrafluoroethylene (PTFE) target on the RF sputtering target in the magnetron sputtering coating machine. The target purity is 99.99%. Then place the substrate processed in step 2 into the magnetron sputtering coating machine and fix it. Vacuum it to 5×10 -4 Pa, set the substrate rotation speed to 10 rpm, the substrate heating temperature to 40 ° C, the argon flow rate to 15 sccm, the chamber pressure to 0.8 Pa, the RF sputtering power to 25 W, and the sputtering time to 10 min, and deposit a PTFE film as a barrier layer on the substrate by magnetron sputtering.

[0031] Step 4: placing the substrate on which the PTFE film was sputter-deposited in step 3 in a copper plating solution for chemical copper plating, wherein the formula of the copper plating solution is as follows: per liter of copper plating solution, 10 g of copper sulfate pentahydrate, 30 g of potassium sodium tartrate, 5 mL of formaldehyde, 3 mg of L-malic acid, 2 mg of nickel sulfate, 3 mg of 2,2'-bipyridine, and 10 mg of sodium dodecylbenzenesulfonate are contained, and the balance is deionized water. The pH of the copper plating solution is controlled at 12; the temperature of the chemical copper plating is controlled at 30° C. and the time is 25 min.

[0032] pass Figure 1 Scanning electron microscope (SEM) images and energy dispersive spectrometer (EDS) elemental distribution maps show that the deposited PTFE film has good density and morphological consistency. The PTFE film forms a continuous dense layer with a thickness of approximately 200nm on the surface of the glass through-hole substrate. Elemental analysis results further confirm the uniform distribution of fluorine-containing elements in the through-hole area, indicating that the PTFE film can completely cover the entire hole wall and substrate surface, demonstrating excellent film consistency and film quality. This provides a stable and reliable interface foundation for the subsequent deposition of the copper layer.

[0033] Depend on Figure 2 The Raman spectrum of the -1 The CF2 stretching vibration peak at the bottom is the most significant Raman characteristic peak of PTFE. Figure 3 In the infrared spectrum, 673 cm -1 The obvious CF2 stretching vibration peak also appears at . The appearance of the above characteristic peaks indicates that PTFE has been successfully sputtered and deposited on the surface of the through-glass substrate.

[0034] pass Figure 4 The morphology of the copper layer deposited on the PTFE film by electroless plating can be observed. The image shows that the copper film forms a continuous and uniform coating on the PTFE surface, with no apparent shedding, voids, or irregular accumulation, demonstrating that electroless copper plating achieves excellent film formation on the PTFE film. The tight interface between the copper layer and the PTFE film indicates that the initial surface activation treatment and barrier layer structure provide a good adhesion foundation for subsequent metal deposition, helping to improve the stability and conductivity of the overall interconnect structure.

[0035] Depend on Figure 5 It can be seen that the adhesion of the copper film on the glass through-hole substrate is significantly improved after the PTFE film is deposited by magnetron sputtering. The stress of the copper film obtained by chemical copper plating is -13.73 MPa, indicating that the presence of PTFE film can significantly reduce the stress accumulation during chemical copper plating and reduce the interface stress.

[0036] Example 2

[0037] In step 3 of this embodiment, the substrate processed in step 2 is placed in a magnetron sputtering coating machine and fixed, and vacuumed to 5×10 -4 Pa, set the substrate rotation speed to 10 rpm, the substrate heating temperature to 80 ° C, the argon flow rate to 20 sccm, the chamber pressure to 0.8 Pa, the RF sputtering power to 25 W, and the sputtering time to 20 min, and deposit the PTFE thin film barrier layer on the substrate by magnetron sputtering. The other steps and conditions are the same as those in Example 1.

[0038] Example 3

[0039] In step 3 of this embodiment, the substrate processed in step 2 is placed in a magnetron sputtering coating machine and fixed, and vacuumed to 5×10 -4 Pa, set the substrate rotation speed to 10 rpm, the substrate heating temperature to 60 ° C, the argon flow rate to 30 sccm, the chamber pressure to 0.8 Pa, the RF sputtering power to 25 W, and the sputtering time to 30 min, and magnetron sputtering was used to deposit a PTFE film as a barrier layer on the substrate. The other steps and conditions are the same as those in Example 1.

[0040] Example 4

[0041] In step 3 of this embodiment, the substrate processed in step 2 is placed in a magnetron sputtering coating machine and fixed, and vacuumed to 5×10 -4 Pa, set the substrate rotation speed to 10 rpm, the substrate heating temperature to 40 ° C, the argon flow rate to 30 sccm, the chamber pressure to 0.8 Pa, the RF sputtering power to 50 W, and the sputtering time to 20 min, and magnetron sputtering was used to deposit a PTFE film as a barrier layer on the substrate. The other steps and conditions are the same as those in Example 1.

[0042] Example 5

[0043] In step 3 of this embodiment, the substrate processed in step 2 is placed in a magnetron sputtering coating machine and fixed, and vacuumed to 5×10 -4 Pa, set the substrate rotation speed to 10 rpm, the substrate heating temperature to 60 ° C, the argon flow rate to 20 sccm, the chamber pressure to 0.8 Pa, the RF sputtering power to 50 W, and the sputtering time to 10 min, and magnetron sputtering was used to deposit a PTFE film as a barrier layer on the substrate. The other steps and conditions are the same as those in Example 1.

[0044] Example 6

[0045] In step 3 of this embodiment, the substrate processed in step 2 is placed in a magnetron sputtering coating machine and fixed, and vacuumed to 5×10 -4 Pa, set the substrate rotation speed to 10 rpm, the substrate heating temperature to 80 ° C, the argon flow rate to 30 sccm, the chamber pressure to 0.8 Pa, the RF sputtering power to 50 W, and the sputtering time to 15 min, and magnetron sputtering was used to deposit a PTFE film as a barrier layer on the substrate. The other steps and conditions are the same as those in Example 1.

Claims

1. A method for improving the adhesion and stability between a through-glass via substrate and a copper layer, characterized by: The method comprises the following steps: Step 1: Ultrasonic cleaning of the through-glass substrate; Step 2: treating the substrate cleaned in step 1 with oxygen plasma; Step 3: Place the polytetrafluoroethylene target material on the RF sputtering target position in the magnetron sputtering coating machine, and sputter-deposit a polytetrafluoroethylene film as a barrier layer on the substrate treated in step 2 under a vacuum environment and inert gas; Step 4: Electrolessly copper-plating the substrate on which the polytetrafluoroethylene film is sputter-deposited.

2. The method for improving adhesion and stability between a through-glass via substrate and a copper layer according to claim 1, wherein: In step 1, the through-glass substrate is ultrasonically cleaned at room temperature using ethanol and acetone, respectively, with an ultrasonic power of 50 to 100 W, a frequency of 40 to 60 Hz, and an ultrasonic time of 5 to 20 minutes; after ultrasonic cleaning, the substrate is rinsed with distilled water and finally dried.

3. The method for improving adhesion and stability between a through-glass via substrate and a copper layer according to claim 1, wherein: In step 2, the power of the oxygen plasma treatment is 50-150 W, the time is 2-10 min, the oxygen flow rate is 30-60 sccm, and the treatment temperature is room temperature.

4. The method for improving adhesion and stability between a through-glass via substrate and a copper layer according to claim 1, wherein: In step 3, the vacuum degree is 3×10-4~5×10- 4 The polytetrafluoroethylene film is sputter-deposited at a flow rate of 10 to 50 sccm of inert gas, a chamber pressure of 0.8 to 1.2 Pa, a substrate heating temperature of 20 to 120° C., and a radio frequency sputtering power of 20 to 100 W, and the sputtering time is 10 to 30 minutes.

5. The method for improving adhesion and stability between a through-glass via substrate and a copper layer according to claim 1, wherein: In step 3, the vacuum degree is 3×10 -4 ~5×10 -4 The polytetrafluoroethylene film is sputter-deposited at a flow rate of 20 to 40 sccm of inert gas, a chamber pressure of 0.8 to 1 Pa, a substrate heating temperature of 40 to 80° C., and a radio frequency sputtering power of 20 to 60 W, and the sputtering time is 10 to 30 minutes.

6. The method for improving adhesion and stability between a through-glass via substrate and a copper layer according to claim 1, wherein: In step 3, the thickness of the polytetrafluoroethylene film is 100 to 200 nm.

7. The method for improving adhesion and stability between a through-glass via substrate and a copper layer according to claim 1, 4 or 5, wherein: In step 3, the inert gas is nitrogen or argon.

8. The method for improving adhesion and stability between a through-glass via substrate and a copper layer according to claim 1, wherein: In step 4, the formula of the copper plating solution for chemical copper plating is as follows: per liter of copper plating solution, it contains 10-20g of copper sulfate pentahydrate, 20-40g of potassium sodium tartrate, 5-10mL of formaldehyde, 1-5mg of L-malic acid, 1-5mg of nickel sulfate, 1-10mg of 2,2'-bipyridine, and 5-20mg of sodium dodecylbenzenesulfonate, and the balance is deionized water. The pH of the copper plating solution is controlled at 10-13; the temperature of the chemical copper plating is controlled at 20-40°C.

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