Method for metal thin filmization of high aspect ratio tgv semiconductor 3d package substrate

Abstract

The application relates to the technical field of flip-chip packaging, and discloses a high-aspect-ratio TGV semiconductor 3D packaging substrate metal thin filmization method.The method constructs a multi-physical field environment coupling a focused acoustic field, a temperature gradient from bottom to top and an electrochemical reaction, uses acoustic streaming effect to strengthen hole bottom mass transfer, combines a thermal gradient to improve the bottom reaction rate, and based on in-situ alternating current impedance real-time regulation of the acoustic field focus and the current density, realizes defect-free bottom-up filling.The system comprises an electrolyte tank, a heat control module, a phased acoustic transducer array, an electrochemical workstation, an impedance monitoring unit and a central control unit.The application significantly improves filling compactness and process repeatability, is suitable for extreme structures with a depth-width ratio of more than 20:1, and provides key technical support for high-performance chip 3D packaging.

Description

Technical Field

[0001] This invention belongs to the field of flip-chip packaging technology, specifically relating to a method for metal thin film formation on high aspect ratio TGV semiconductor 3D packaging substrates. Background Technology

[0002] With the rapid development of 3D integrated packaging technology in high-performance computing, artificial intelligence chips, and advanced sensors, through-silicon via (TSV) substrates have become key carriers for high-density interconnect structures due to their excellent electrical insulation, thermal stability, and high-frequency characteristics. Among them, the high aspect ratio (TGV) structure can significantly improve the interconnect density and signal transmission efficiency per unit area, and is a core process step for realizing vertical chip stacking and heterogeneous integration. This structure is typically formed by etching deep holes in a glass substrate and depositing a conductive metal layer on its inner wall to create electrical pathways.

[0003] In existing technologies, electroplating is commonly used to fill TGV vias with metal to form a reliable conductive path. However, under high aspect ratio conditions, due to the limitations of the via geometry, the electrolyte cannot diffuse sufficiently to the bottom of the via, and the current lines are highly concentrated at the via opening, resulting in a much higher metal deposition rate at the opening than at the bottom. This uneven current distribution causes the via opening to quickly "close," forming a closed cavity or hole defect inside the via. Such defects not only severely weaken the conductivity and thermal conductivity of the interconnect structure, but also trigger crack propagation under subsequent thermal cycling or mechanical stress, significantly reducing package reliability and device lifespan.

[0004] Therefore, there is an urgent need for a thin-film method that can achieve uniform, void-free metal filling in high aspect ratio TGV structures to overcome the sealing and void problems caused by uneven current distribution in existing electroplating processes, thereby meeting the stringent requirements of advanced 3D packaging for high-reliability interconnects. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method and system for metal thin-film deposition on high aspect ratio TGV semiconductor three-dimensional packaging substrates. This invention achieves precise spatiotemporal reconstruction of the metal ion transport process and electrode reaction kinetics within high aspect ratio micropores by constructing a multiphysics environment coupled with a spatially tunable acoustic field, a precisely controlled thermal gradient field, and an electrochemical feedback loop.

[0006] This invention utilizes a phased-array acoustic transducer to generate a high-intensity focused sound beam at the bottom of micropores. Through the acoustic flow effect, it forcibly overcomes the diffusion boundary layer limitation, significantly improving the mass transfer efficiency in the micropore bottom region. Simultaneously, by applying heat to the bottom of the substrate and cooling it in the electrolyte bulk, a stable bottom-up temperature gradient is established. Leveraging the exponential dependence of the chemical reaction rate on temperature, the deposition advantage at the micropore bottom is further enhanced. The entire deposition process is controlled by a closed-loop control system based on in-situ AC impedance spectroscopy analysis. This system monitors the metal filling height in real time and dynamically adjusts the acoustic field focus position and applied current density simultaneously, ensuring that the metal layer fills from bottom to top in a defect-free plunger flow mode. This fundamentally eliminates preferential sealing and the formation of internal voids caused by the current congestion effect at the micropore opening.

[0007] This invention provides a method for metallization of high aspect ratio TGV semiconductor three-dimensional packaging substrates, comprising:

[0008] A semiconductor packaging substrate with through-glass vias is provided to be processed, wherein a conductive seed layer is pre-deposited on the inner wall of the through-glass via;

[0009] The semiconductor packaging substrate is placed in an electrolyte tank, with the conductive seed layer of the substrate serving as the cathode, and the bottom of the substrate in contact with a heat source. At the same time, the electrolyte in the electrolyte tank is cooled, thereby establishing a positive temperature gradient from bottom to top in the depth direction of the penetrating glass via.

[0010] A focused sound field is generated in the bottom region of the through-hole in the glass by means of a phased acoustic transducer array deployed under the substrate.

[0011] A preset electrochemical deposition process is applied between the cathode and the anode deployed in the electrolyte, while the temperature gradient is continuously maintained and the focused acoustic field is driven to initiate preferential deposition of metal at the bottom of the through-hole in the glass.

[0012] During the deposition process, the AC impedance characteristic value of the through-hole in the glass is obtained in real time through the impedance monitoring unit, and the real-time height of the metal filling layer is calculated based on the AC impedance characteristic value.

[0013] Based on the real-time height, the focus position of the focused sound field is synchronously adjusted upward by the control unit, and the current density parameter of the electrochemical deposition process is adjusted until the through-glass via is completely filled with metal.

[0014] This invention provides a high aspect ratio TGV semiconductor three-dimensional packaging substrate metallization thin film system for implementing the method, comprising:

[0015] Electrolyte tank, used to contain electrolyte and anode;

[0016] The substrate fixing and thermal control module is used to clamp the semiconductor packaging substrate and make its conductive seed layer serve as the cathode. The substrate fixing and thermal control module integrates a bottom heating unit and an electrolyte cooling circuit to establish a preset temperature gradient in the through-glass via of the substrate.

[0017] A phased acoustic transducer array module is deployed below the substrate fixing and thermal control module to generate a spatially adjustable focused sound field.

[0018] An electrochemical workstation, connected to the cathode and anode, is used to apply an electrochemical deposition process;

[0019] An impedance monitoring unit, connected to the cathode and anode, is used to measure the AC impedance of the through-hole in the glass in real time.

[0020] The central control unit is signal-connected to the substrate fixing and thermal control module, the phased acoustic transducer array module, the electrochemical workstation, and the impedance monitoring unit. The central control unit is configured to coordinately regulate the operating parameters of each module based on the feedback data from the impedance monitoring unit.

[0021] In one embodiment of the present invention, in the step of providing the semiconductor packaging substrate to be processed, the conductive seed layer is prepared by physical vapor deposition. Specifically, firstly, a titanium or chromium layer with a thickness of 20 to 50 nanometers is deposited as an adhesion layer by magnetron sputtering. Then, a copper layer with a thickness of 200 to 500 nanometers is deposited on the adhesion layer by magnetron sputtering as a conductive layer to ensure that the entire through-hole has a uniform and low-resistance initial conductive path.

[0022] Furthermore, in the step of establishing a bottom-up positive temperature gradient, the bottom heating unit of the substrate fixing and thermal control module is a planar thin-film resistance heater or a Peltier effect thermoelectric cooler array. The bottom heating unit precisely controls the bottom temperature of the substrate between 40°C and 70°C, with a temperature control accuracy of ±0.1°C. The electrolyte cooling circuit consists of a coil heat exchanger and an external circulating cooler, constantly controlling the temperature of the main electrolyte between 20°C and 30°C. Thus, a stable linear temperature gradient with a value of 0.2°C to 1°C per millimeter is formed along the depth direction of the penetrating glass via.

[0023] In one embodiment of the present invention, the phased acoustic transducer array module is composed of piezoelectric ceramic transducer units arranged in a two-dimensional matrix, the material of which is lead zirconate titanate. The overall operating frequency of the array is set in the range of 5 MHz to 20 MHz to ensure that the wavelength of the sound wave is smaller than the diameter of the through-hole in the glass, thereby achieving precise sound beam focusing. The central control unit integrates a beamforming algorithm module, which calculates an independent excitation signal phase delay value for each transducer unit in the array based on the target focal coordinates. The calculation of the phase delay value follows the principle of sound path difference compensation, ensuring that the sound waves emitted by each unit are superimposed in phase at the target focal position, forming a maximum sound pressure. The sound intensity of the sound field is controlled below the threshold for inducing cavitation effect. Its main mechanism is the acoustic flow effect, that is, generating strong microscale vortices in the focal region, forcing convection to significantly thin the concentration polarization boundary layer thickness of metal ions on the cathode surface, compressing it from the conventional tens of micrometers to less than 1 micrometer.

[0024] Furthermore, in the step of applying the electrochemical deposition process, the electrolyte composition includes copper sulfate as the main salt, with a concentration of 200 g / L to 250 g / L; sulfuric acid as the supporting electrolyte, with a concentration of 50 g / L to 70 g / L; chloride ions as a leveling agent, with a concentration of 50 mg / L to 80 mg / L; and a polyether inhibitor, which forms an adsorption layer on the top and sidewall regions of the via, inhibiting the electrodeposition reaction in these regions. The core of this invention lies in the fact that the focused acoustic field exerts a strong mechanical stripping and disturbance effect on the inhibitor molecular layer adsorbed at the bottom of the via, thereby forming an "active window" at the bottom of the via with a significantly lower inhibitor concentration than in other regions. This, combined with the temperature gradient effect, creates a strong bottom growth advantage.

[0025] As one embodiment of the present invention, the steps of impedance monitoring, height calculation, and closed-loop control are specifically implemented as follows:

[0026] The impedance monitoring unit applies a small sinusoidal AC voltage disturbance at a fixed frequency, such as 10 kHz, to the through-hole in the glass and measures its current response to calculate the complex impedance value. The central control unit stores a pre-calibrated impedance-height mapping model. This model was established through impedance measurements and scanning electron microscopy cross-sectional analysis of a series of through-hole samples with different fill heights, uniquely correlating the magnitude and phase angle of the complex impedance to the geometric height of the metal filler layer.

[0027] During real-time deposition, the central control unit executes the following closed-loop control logic at a frequency of 10 to 50 times per second: querying the current impedance value and resolving the current fill height through the mapping model. The target focal position of the phased acoustic transducer array. Set as A fixed offset is added to ensure that the acoustic field focus is always directly in front of the growth interface; simultaneously, the current density output by the electrochemical workstation is adjusted. The current density employs a programmed current boosting strategy, and its functional relationship is as follows: ,in The initial deposition current density, The gain coefficient is positive. This current regulation strategy ensures that a low current is used in the early stages of filling to obtain a dense initial nucleation layer, and the current is increased linearly as the cross-sectional area of ​​the filling channel decreases to maintain a constant volumetric filling rate.

[0028] Furthermore, after the through-hole in the glass is completely filled with metal, the method further includes a planarization step. Specifically, after the central control unit detects that the filling height has reached or exceeded the height of the substrate surface, it releases the focused sound field and replaces it with a uniform low-intensity diffuse sound field covering the entire substrate surface. At the same time, a planarization electroplating current is applied to deposit a uniformly thick metal overplating layer on the substrate surface for subsequent chemical mechanical polishing processes.

[0029] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0030] 1. This invention reconstructs the mass transfer and reaction dynamics environment within micropores from a physical perspective by introducing a spatially adjustable focused sound field and a controlled thermal gradient field. This achieves a "super conformal" filling mode that preferentially nucleates from the bottom and grows upwards. It fundamentally solves the technical problem of preferential closure of the orifice and formation of internal voids caused by uneven current density distribution in traditional electroplating methods, ensuring the density and integrity of the metal filling.

[0031] 2. The closed-loop feedback control system based on in-situ AC impedance monitoring proposed in this invention achieves real-time, precise monitoring and dynamic control of the filling process. This system can autonomously track the metal growth interface and simultaneously optimize the acoustic field focus and current density, making the entire filling process highly automated, deterministic, and highly repeatable. It overcomes the limitations of traditional methods, such as sensitivity to complex organic additive systems and narrow process windows.

[0032] 3. This method can be successfully applied to extreme structures with aspect ratios exceeding 20:1 and even higher, greatly expanding the development space of 3D packaging technology in terms of vertical interconnect density and performance. The obtained void-free metal-filled structure has excellent electrical and thermal conductivity, as well as superior mechanical reliability and resistance to electron migration, providing key technical support for advanced packaging needs in fields such as high-performance computing, artificial intelligence chips, and RF modules. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the overall technical solution architecture of the high aspect ratio TGV semiconductor 3D packaging substrate metal thin film method proposed in this invention;

[0034] Figure 2 This is a schematic diagram of the core principle framework of multi-physics field synergistic regulation of coupled acoustic field-thermal gradient-electrochemical feedback in this invention;

[0035] Figure 3 This is a logical flow diagram of the defect-free filling process of metal from bottom to top through the glass through hole in this invention;

[0036] Figure 4 This is a logic framework diagram of closed-loop control and dynamic parameter adjustment based on in-situ AC impedance feedback in this invention.

[0037] Figure 5 This is a schematic diagram of the multi-level interaction relationship and data flow of the phased acoustic transducer array and the temperature gradient field working together in the micropore in this invention.

[0038] Figure 6 This is a breakdown framework diagram of the entire process from initial seed layer preparation to final planarization in this invention. Detailed Implementation

[0039] Please refer to Figures 1 to 6 This invention provides a method for metal thin-film deposition on high aspect ratio TGV semiconductor three-dimensional packaging substrates. Its core lies in constructing a multi-physics synergistic environment that couples a spatially tunable acoustic field, a precisely controlled thermal gradient field, and an electrochemical feedback loop. This allows for the spatiotemporal reconstruction of the metal ion transport process and electrode reaction kinetics within the through-holes of the glass. This method ensures that metal deposition fills from bottom to top in a defect-free plunger flow pattern, completely eliminating preferential sealing and internal void defects caused by excessively high orifice current density.

[0040] The method includes the following steps:

[0041] S1, a semiconductor packaging substrate with a through-glass via is provided to be processed, wherein a conductive seed layer is pre-deposited on the inner wall of the through-glass via;

[0042] S2, the semiconductor packaging substrate is placed in an electrolyte tank, the conductive seed layer of the substrate is used as the cathode, and the bottom of the substrate is in contact with the heat source. At the same time, the electrolyte in the electrolyte tank is cooled, thereby establishing a positive temperature gradient from bottom to top in the depth direction of the through-hole in the glass.

[0043] S3, a focused sound field is generated in the bottom region of the through-hole in the glass by means of a phased acoustic transducer array deployed under the substrate;

[0044] S4, a preset electrochemical deposition process is applied between the cathode and the anode deployed in the electrolyte, while the temperature gradient is maintained and the focused acoustic field is driven to initiate the preferential deposition of metal at the bottom of the through-hole in the glass.

[0045] S5. During the deposition process, the AC impedance characteristic value of the through-hole in the glass is obtained in real time through the impedance monitoring unit, and the real-time height of the metal filling layer is calculated based on the AC impedance characteristic value.

[0046] S6, based on the real-time height, the focus position of the focused sound field is synchronously adjusted upward by the control unit, and the current density parameter of the electrochemical deposition process is adjusted until the through-glass via is completely filled with metal.

[0047] In step S1, the semiconductor packaging substrate is a borosilicate glass substrate with a thickness between 300 micrometers and 800 micrometers, on which multiple through-holes are formed by laser drilling or dry etching. The diameter of the through-holes ranges from 10 micrometers to 50 micrometers, and the depth ranges from 200 micrometers to 1000 micrometers, with a corresponding aspect ratio of not less than 20:1. The conductive seed layer is prepared using physical vapor deposition. First, a titanium adhesion layer with a thickness of 20 nanometers to 50 nanometers is deposited in a vacuum chamber by magnetron sputtering. This adhesion layer is used to enhance the interfacial bonding strength between the subsequent copper layer and the inner wall of the glass. Then, a copper conductive layer with a thickness of 200 nanometers to 500 nanometers is deposited in the same chamber.

[0048] The entire deposition process was carried out in an argon atmosphere, with sputtering power set between 300 and 600 watts, and the substrate temperature controlled below 100 degrees Celsius to avoid thermal deformation of the glass substrate. After deposition, the sheet resistance of the inner wall of the via was measured using the four-probe method to ensure it was below 0.5 ohms per square meter, thus providing a uniform and low-resistance initial conductive path for subsequent electrochemical deposition.

[0049] In step S2, the semiconductor packaging substrate is clamped in a substrate fixing and thermal control module, which consists of two parts. The upper part is an insulating clamp used to fix the edge of the substrate and lead out electrical connections; the lower part integrates a planar thin-film resistance heater, which is in direct contact with the bottom of the substrate. The planar thin-film resistance heater is composed of nickel-chromium alloy resistance wire printed on an alumina ceramic substrate, with a maximum heating power of 50 watts and a temperature control accuracy of ±0.1 degrees Celsius. The electrolyte tank is a rectangular container made of polytetrafluoroethylene, which contains enough electrolyte to completely immerse the substrate.

[0050] The electrolyte cooling circuit consists of a stainless steel coil wound around the outer wall of the tank and an external circulating cooler. The cooling medium is a mixture of deionized water and ethylene glycol, with a constant flow rate of two liters per minute. By independently controlling the bottom heater and the cooling circuit, the temperature at the bottom of the substrate is stably maintained between 40°C and 70°C, while the temperature of the main electrolyte is controlled between 20°C and 30°C. This creates a stable linear positive temperature gradient along the axial direction of the glass via, with a gradient value of 0.2°C to 1°C per millimeter. The existence of this temperature gradient results in a significantly higher electrochemical reaction rate at the bottom of the via than at the opening, because the metal deposition rate follows Arrhenius's law, exhibiting an exponential dependence on temperature.

[0051] In step S3, the phased-array acoustic transducer module is deployed directly below the substrate fixing and thermal control module, and the two are acoustically matched through a 0.5 mm thick deionized water coupling layer. The array consists of 64 piezoelectric ceramic transducer units arranged in an 8×8 matrix, each unit measuring 1.5 mm × 1.5 mm, made of lead zirconate titanate (PZT-5H). The overall operating frequency of the array is set in the range of 5 MHz to 20 MHz, corresponding to wavelengths of 75 μm to 18.75 μm, which is smaller than the minimum aperture diameter, meeting the Rayleigh diffraction limit and ensuring that the sound beam can be focused at the sub-micron level within the aperture. The central control unit incorporates a beamforming algorithm module, which uses the target focal coordinates... Calculate an independent excitation signal phase delay value for each transducer unit. The formula for calculating the phase delay value is:

[0052] ;

[0053] in, For operating frequency, The speed at which sound waves propagate in the coupling medium. For the first The geometric distance from each transducer unit to the target focus. The reference distance is used. Through this phase compensation mechanism, the sound waves emitted by all units are superimposed in phase at the target focal point, forming a maximum sound pressure level. The sound intensity of the focused sound field is strictly controlled below the cavitation threshold, typically ranging from 10 watts per square centimeter to 30 watts per square centimeter. At this intensity, the main mechanism is the acoustic flow effect, which induces strong microscale vortex flow in the focal region, forcing convection to significantly thin the concentration polarization boundary layer on the cathode surface, compressing its thickness from 30 micrometers under conventional electroplating conditions to less than 1 micrometer, thereby greatly improving the metal ion mass transfer rate in the bottom region of the aperture.

[0054] In step S4, the electrochemical deposition process is performed by an electrochemical workstation. The electrolyte composition includes: 200 g / L to 250 g / L copper sulfate as the main salt, providing a copper ion source; 50 g / L to 70 g / L sulfuric acid as a supporting electrolyte to improve solution conductivity and suppress hydrogen evolution side reactions; 50 mg / L to 80 mg / L chloride ions as a leveling agent to promote grain refinement; and a polyethylene oxide-polypropylene oxide block copolymer inhibitor at a concentration of 10 mg / L to 30 mg / L. This inhibitor molecules preferentially adsorb at the top and sidewall regions of the via, forming a hydrophobic protective film that significantly inhibits the copper deposition rate in this region. However, at the bottom of the via, the high-intensity shear force and microturbulence generated by the focused acoustic field continuously peel off and disturb the adsorption layer, causing the desorption rate of the inhibitor molecules to be much higher than the adsorption rate, thus forming an "active window" with a significantly low inhibitor concentration at the bottom of the via. This active window works synergistically with the aforementioned temperature gradient effect to create a strong bottom growth advantage, ensuring that metal deposition strictly starts from the bottom of the hole.

[0055] In step S5, the impedance monitoring unit applies a sinusoidal AC voltage disturbance with an amplitude of 10 millivolts to the through-hole of the glass at a fixed frequency of 10 kHz, and simultaneously acquires the current response signal. The complex impedance is calculated using lock-in amplification technology. ,in For the real part, This is the imaginary part. The central control unit internally stores an impedance-height mapping model, which is obtained through offline calibration: a series of through-hole samples with fill heights of 0%, 20%, 40%, 60%, 80%, and 100% are prepared, their complex impedance at 10 kHz is measured, and the corresponding actual fill height is accurately determined using scanning electron microscopy cross-sectional images. By using polynomial regression fitting, the complex impedance modulus is established. With phase angle A unique mapping relationship to the filling height h. During real-time deposition, the central control unit performs impedance sampling and height resolution 30 times per second to obtain the current filling height. .

[0056] In step S6, the central control unit is based on Execute closed-loop control logic. First, position the target focal point of the phased acoustic transducer array. Set as:

[0057] ;

[0058] in To maintain a fixed offset, a value ranging from 5 to 10 micrometers was used to ensure that the acoustic field focus remained directly in front of the metal growth interface, continuously enhancing the mass transfer capability in that region. Secondly, the current density output by the electrochemical workstation was dynamically adjusted. The functional relationship is as follows:

[0059] ;

[0060] in The initial deposition current density is taken as 1.5 mA / cm² to 3.0 mA / cm². The gain factor ranges from 0.01 mA / cm² / µm to 0.03 mA / cm² / µm. This upcurrent strategy ensures a low current is used in the initial filling stage to obtain a dense, dendrite-free initial nucleation layer; as the filling height increases, the effective cross-sectional area of ​​the via decreases, and linearly increasing the current density maintains a constant volumetric filling rate, avoiding local over-deposition or roughness deterioration caused by excessively high current density. When the height reaches or exceeds the surface height of the substrate, the filling is considered complete.

[0061] After filling is complete, the method also includes a planarization step. The central control unit immediately shuts down the focused sound field mode and switches to the diffuse sound field mode: all transducer units are excited with the same phase, generating a uniform low-intensity sound field covering the entire substrate surface, with the sound intensity reduced to below 1 watt per square centimeter. Simultaneously, the electrochemical workstation switches to constant current mode, applying a planarization current of 1.0 mA per square centimeter for 60 to 120 seconds, depositing a uniform copper overplating layer with a thickness of 5 to 10 micrometers on the substrate surface. This overplating layer provides sufficient material allowance for subsequent chemical mechanical polishing processes, ensuring a final surface flatness better than a peak-to-valence value of 0.5 micrometers.

[0062] The high aspect ratio TGV semiconductor three-dimensional packaging substrate metallization thin film system includes: an electrolyte tank for containing electrolyte and an anode; a substrate fixing and thermal control module for clamping the semiconductor packaging substrate and using its conductive seed layer as a cathode, the substrate fixing and thermal control module integrating a bottom heating unit and an electrolyte cooling circuit for establishing a preset temperature gradient within the through-glass via of the substrate; a phased-array acoustic transducer module deployed below the substrate fixing and thermal control module for generating a spatially adjustable focused sound field; an electrochemical workstation connected to the cathode and anode for applying an electrochemical deposition process; an impedance monitoring unit connected to the cathode and anode for real-time measurement of the AC impedance of the through-glass via; and a central control unit whose signals are connected to the substrate fixing and thermal control module, the phased-array acoustic transducer module, the electrochemical workstation, and the impedance monitoring unit, the central control unit being configured to coordinately regulate the operating parameters of each module based on feedback data from the impedance monitoring unit.

[0063] The electrolyte tank is made of corrosion-resistant polytetrafluoroethylene (PTFE) and contains a titanium mesh anode. The anode area is more than twice the area of ​​the substrate cathode to ensure uniform current distribution. The bottom heating unit of the substrate fixing and thermal control module is a planar thin-film resistance heater, with a platinum resistance thermometer (PT100) embedded between the heater and the substrate contact surface to achieve closed-loop temperature control. The coil-type heat exchanger of the electrolyte cooling circuit is closely attached to the outer wall of the tank, and flow meters and temperature sensors are installed at the inlet and outlet of the cooling medium to ensure cooling stability.

[0064] Each piezoelectric unit of the phased-array acoustic transducer module is equipped with an independent power amplifier and phase controller, which are uniformly scheduled by the central control unit through a digital signal processor. The electrochemical workstation has multiple modes including constant potential, constant current, and pulse electroplating, with a current resolution better than 0.1 microamps and a potential resolution better than 0.1 millivolts. The impedance monitoring unit is integrated inside the electrochemical workstation and adopts a dual-channel phase-locked amplification architecture, enabling in-situ measurements without interference during the deposition process. The central control unit is an industrial-grade embedded computer running a real-time operating system, internally containing beamforming algorithms, impedance-height mapping models, and closed-loop control logic, with the execution delay of all control commands not exceeding 10 milliseconds.

[0065] Through the synergistic operation of the above methods and systems, this invention achieves void-free, crack-free, and high-density metal filling of high aspect ratio through-glass vias. The filling structure was verified by X-ray tomography, showing no internal porosity or delamination defects; its resistivity, measured using the four-probe method, is close to the theoretical value of bulk copper; after 500 thermal cycling tests, the interconnect structure showed no signs of failure, demonstrating excellent mechanical reliability and thermal stability.

Claims

1. A method of thinning a metal film of a high aspect ratio TGV semiconductor three-dimensional package substrate, characterized by, The application relates to a method for filling a through-glass via (TGV) in a semiconductor package substrate with metal, comprising the following steps: providing a semiconductor package substrate to be processed, which has a through-glass via with a previously deposited conductive seed layer on the inner wall of the through-glass via; placing the semiconductor package substrate in an electrolyte tank, with the conductive seed layer of the substrate as a cathode, and contacting the bottom of the substrate with a heat source, while cooling the electrolyte in the electrolyte tank, so as to establish a positive temperature gradient from bottom to top in the depth direction of the through-glass via; generating a focused acoustic field in the bottom region of the through-glass via by means of a phased acoustic transducer array arranged below the substrate; applying a preset electrochemical deposition program between the cathode and an anode arranged in the electrolyte, while continuously maintaining the temperature gradient and driving the focused acoustic field, so as to initiate preferential deposition of metal at the bottom of the through-glass via; during the deposition process, acquiring real-time AC impedance characteristic values of the through-glass via by means of an impedance monitoring unit, and calculating a real-time height of the metal filling layer based on the AC impedance characteristic values; and according to the real-time height, synchronously adjusting the focal point position of the focused acoustic field upward by means of a control unit, and adjusting the current density parameter of the electrochemical deposition program, until the through-glass via is completely filled with metal. The preparation of the conductive seed layer adopts a physical vapor deposition method, comprising the following steps: depositing a titanium or chromium adhesion layer with a thickness of 20-50 nm on the inner wall of the through-glass via by means of magnetron sputtering; and continuously depositing a copper conductive layer with a thickness of 200-500 nm on the adhesion layer by means of magnetron sputtering, so as to form an initial conductive path which is uniform and has low resistance. The establishment of the positive temperature gradient from bottom to top in the depth direction of the through-glass via comprises the following steps: controlling the temperature of the bottom of the substrate to be between 40-70 DEG C by means of a bottom heating unit, with a temperature control accuracy of plus or minus 0.1 DEG C; constantly controlling the temperature of the main electrolyte to be between 20-30 DEG C by means of an electrolyte cooling loop; and forming a stable linear temperature gradient in the axial direction of the through-glass via, with a value of 0.2 DEG C per mm to 1 DEG C per mm. The bottom heating unit is a planar thin-film resistance heater or a Peltier effect thermoelectric cooler array; and the electrolyte cooling loop is composed of a coil pipe heat exchanger and an external circulating cooling machine. The phased acoustic transducer array arranged below the substrate generates a focused acoustic field in the bottom region of the through-glass via, comprising the following steps: the phased acoustic transducer array is composed of two-dimensional matrix arranged piezoelectric ceramic transducer units, and the material is lead zirconate titanate; the working frequency of the array is set to be in the range of 5-20 MHz, so as to ensure that the wavelength of the acoustic wave is smaller than the diameter of the through-glass via; a beam forming algorithm module is used to calculate independent excitation signal phase delay values for each transducer unit, so that the acoustic waves of the units are in phase at the target focal point to form an acoustic pressure maximum value; the sound intensity of the focused acoustic field is controlled to be lower than the cavitation threshold, and micro-scale vortices are generated in the focal point region by means of acoustic streaming effect to thin the concentration polarization boundary layer to below 1 micron. ​ ​ 2. The high aspect ratio TGV semiconductor three-dimensional package substrate metal thinning method of claim 1, wherein, ​ ​ ​ 3. The high aspect ratio TGV semiconductor three-dimensional package substrate metal thinning method of claim 1, wherein, ​ ​ ​ ​ 4. The high aspect ratio TGV semiconductor three-dimensional package substrate metal thinning method of claim 3, wherein, ​ 5. The high aspect ratio TGV semiconductor three-dimensional package substrate metal thinning method of claim 1, wherein, ​ ​ ​ ​ ​ 6. The high aspect ratio TGV semiconductor three-dimensional package substrate metal thinning method of claim 5, wherein, The phase delay value is calculated according to the principle of sound path difference compensation, and the expression is: ； wherein, is the operating frequency, is the speed of sound in the coupling medium, is the geometric distance of the th transducer element to the target focal point, is the reference distance.

7. The high aspect ratio TGV semiconductor three-dimensional package substrate metal thinning method of claim 1, wherein, The electrolyte composition used in the electrochemical deposition process includes: Copper sulfate 200 grams per liter to 250 grams per liter as the main salt; Sulfuric acid 50 grams per liter to 70 grams per liter as the supporting electrolyte; Chloride ion 50 milligrams per liter to 80 milligrams per liter as the leveling agent; Polyether type inhibitor 10 milligrams per liter to 30 milligrams per liter for forming an adsorbed inhibition layer on the top and sidewall of the via hole; The focused acoustic field produces mechanical peeling and disturbance effects on the adsorbed inhibitor molecular layer at the bottom of the via hole, forming an active window with significantly lower inhibitor concentration at the bottom of the via hole.

8. The high aspect ratio TGV semiconductor three-dimensional package substrate metal thinning method of claim 1, wherein, The real-time height of the metal filling layer is calculated based on the characteristic values of the alternating current impedance, including: A sinusoidal alternating voltage disturbance with a fixed frequency of 10 kilohertz and an amplitude of 10 millivolts is applied, and the current response is measured to calculate the complex impedance; Through a pre-calibrated impedance-height mapping model, the modulus and phase angle of the complex impedance are uniquely associated with the geometric height value of the metal filling layer; The impedance-height mapping model is established by impedance measurement and scanning electron microscope cross-section analysis of via hole samples with different filling heights.

9. The high aspect ratio TGV semiconductor three-dimensional package substrate metal thinning method of claim 1, wherein, The current density parameter is adjusted according to the real-time height, including: A programmed upflow strategy is employed, with a current density function relationship of wherein is an initial deposition current density, having a value of 1.5 milliampere per square centimeter to 3.0 milliampere per square centimeter, is a gain coefficient, having a value of 0.01 milliampere per square centimeter per micrometer to 0.03 milliampere per square centimeter per micrometer, is a current fill height.

10. The high aspect ratio TGV semiconductor three-dimensional package substrate metal thinning method of claim 8, wherein, The focal point position of the focused acoustic field is adjusted according to the real-time height, including: The target focal position is set to be wherein a fixed offset of 5 microns to 10 microns, ensuring the sound field focal point is always located directly in front of the metal growth interface.​

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