Glass through hole high-speed etching method based on cooperative driving of laser-induced piezoelectric nano domain and chemical potential

Abstract

The invention discloses a glass through hole high-speed etching method based on laser-induced piezoelectric nano domain and chemical potential cooperative driving, which comprises the following steps: performing scanning modification on a glass substrate by adopting infrared-ultraviolet dual-band laser, and forming an oxygen vacancy concentration gradient in a modified area through time sequence regulation and control and gradient increase of power density along the thickness direction, constructing a chemical potential difference along the axial direction of the through hole; the modified glass substrate is immersed in Fe / HO composite catalytic etching liquid, an ultrasonic field is applied, the driving phase of the ultrasonic field and a pulse packet sequence of laser scanning are kept locked, the oxygen vacancy concentration gradient area generates a piezoelectric nano domain under the action of periodic stress, and the oxygen vacancy concentration gradient area generates a piezoelectric nano domain; the potential of the piezoelectric nano domain drives the active particles in the etching liquid to directionally migrate and react; and monitoring and maintaining the oxidation-reduction activity of the etching liquid in real time, and realizing anisotropic etching by utilizing the synergistic effect of the chemical potential difference and the piezoelectric potential until a through hole is formed.

Description

TECHNICAL FIELD

[0001] The application relates to a glass via high-speed etching method based on laser-induced piezoelectric nanodomain and chemical potential synergistic driving. BACKGROUND

[0002] With the slowing down of Moore's law, 2.5D / 3D integration technology based on glass interposer has become a key path to continue the performance improvement of integrated circuits due to its low cost, low dielectric constant, excellent high-frequency performance and thermal expansion matching. The preparation efficiency and quality of TGV, as a vertical interconnection structure of glass interposer, directly determine the cost and yield of advanced packaging.

[0003] The existing TGV etching technology mainly includes:

[0004] Traditional wet etching: HF-based etching solution is used to directly etch glass, but the Si-O-Si network bond energy is high, the etching rate of unmodified glass is extremely low, the deep via preparation takes too long time, and the side etching is serious, which is difficult to meet the production rhythm requirements.

[0005] Laser-assisted etching: microcracks or structural modification are induced in glass by laser to improve etching selectivity. For example, after modification by single-pulse infrared laser, the etching rate is improved but still insufficient, and the selectivity ratio of modified / unmodified area is limited. However, this scheme has two major bottlenecks: (1) the absolute etching rate of laser modification still cannot meet the efficient production requirements; (2) the modification area structure is not uniform, resulting in large etching rate fluctuation and difficult hole shape control.

[0006] Ultrasonic-assisted etching: ultrasonic field is applied in the etching solution to enhance mass transfer, but traditional ultrasonic only uses macroscopic mechanical stirring effect, which has limited effect on mass transfer enhancement in high aspect ratio micro-holes, and ultrasonic cavitation bubbles can easily damage the hole wall and introduce surface roughness.

[0007] In summary, the core problem of the existing technology is that the three bottlenecks of etching rate, deep hole mass transfer efficiency and reaction kinetics have not been systematically broken through. The specific performance is as follows:

[0008] Kinetic limitation: although the Fe³⁺ / H2O2 catalytic system can produce active free radicals, the lifetime of ·OH is extremely short, the effective action range is limited, the actual utilization rate is extremely low, and the reaction rate is limited by the catalyst regeneration efficiency.

[0009] Mass transfer limitation: there is a significant diffusion boundary layer in the high aspect ratio via, and the exchange efficiency of reactants and products is low, resulting in a significant decrease in the bottom etching rate and "V-shaped" or "bowing" defects in the hole shape.

[0010] Synergistic absence: lack of energy / material time sequence coupling mechanism among laser modification, ultrasonic assistance and chemical catalysis, each unit works independently, and fails to form multi-field synergistic enhancement effect of "structure-energy-reaction".

[0011] Therefore, there is an urgent need for a new TGV high-speed etching method that breaks through the etching kinetics and mass transfer limit by synergistic action of laser-induced structure regulation and external field coupling driving to realize the preparation of high-aspect-ratio and high-selectivity glass via holes. SUMMARY

[0012] The present application is to solve the problems existing in the prior art and provide a glass via hole high-speed etching method based on laser-induced piezoelectric nanodomain and chemical potential synergistic driving.

[0013] The technical scheme adopted by the present application is:

[0014] A glass via hole high-speed etching method based on laser-induced piezoelectric nanodomain and chemical potential synergistic driving, comprising:

[0015] Laser gradient modification step: scanning modification of glass substrate by infrared-ultraviolet dual-band laser, forming oxygen vacancy concentration gradient in the modified region by time sequence regulation and increasing power density gradient along the thickness direction, and constructing chemical potential difference along the via axial direction;

[0016] Ultrasonic coupling catalysis step: immersing the modified glass substrate into Fe³⁺ / H2O2 composite catalytic etching solution and applying ultrasonic field, the driving phase of the ultrasonic field is locked with the pulse packet sequence of laser scanning, so that the oxygen vacancy concentration gradient region generates piezoelectric nanodomain under the action of periodic stress, and the electric potential of the piezoelectric nanodomain drives the directional migration and reaction of active particles in the etching solution;

[0017] Dynamic etching step: real-time monitoring and maintaining the redox activity of the etching solution, realizing anisotropic etching by synergistic action of the chemical potential difference and piezoelectric potential, and forming a via hole.

[0018] Further, in the laser gradient modification step, the wavelength of the infrared laser is 1064 nm, the wavelength of the ultraviolet laser is 355 nm, the ultraviolet laser pulse is emitted with a delay of 20-40 ns after the infrared laser pulse triggers, and the power density gradient increasing parameter along the thickness direction is: the surface modification region power density is 5×10 6 W / cm², the power density increases by 0.5×10 6 W / cm² for every 50 μm depth, and the bottom modification region reaches 8×10 6 W / cm².

[0019] Further, the timing regulation is specifically that the laser works in a burst mode, each burst containing 5-15 laser pulses, and the time interval between the pulse bursts is 0.5-2 μs, and a quasi-polar nanodomain structure with a size of 5-10 nm is formed in the modification region through the mode.

[0020] Further, the driving phase of the ultrasonic field is locked with the pulse burst sequence of the laser scanning, that is, the driving signal of the ultrasonic transducer and the pulse burst trigger signal of the laser controller are connected to a phase-locked loop circuit, so that the phase difference between the ultrasonic phase and the laser pulse burst phase is constant within the range of π / 2±π / 6.

[0021] Further, the potential driving of the piezoelectric nanodomain is specifically that the ultrasonic stress generates a periodic potential Δφ in the oxygen vacancy concentration gradient region, and the range of the potential Δφ is 0.2 V to 0.3 V.

[0022] Further, the etching solution containing Fe³⁺ / H2O2 specifically comprises 4-10 wt% HF, 3-6 wt% H2SiF6, 0.05-0.08 mol / L FeCl3, 3-4 wt% H2O2, 0.02-0.05 wt% fluorocarbon surfactant, and the balance is deionized water.

[0023] Further, the redox activity of the etching solution is maintained by online monitoring of the H2O2 concentration and dynamic replenishment, so that the H2O2 concentration fluctuation is less than ±0.5%, the etching temperature is controlled at 35-40℃, and ultrasonic assistance with a frequency of 40-80 kHz and a power of 200-300 W is applied.

[0024] The present application has the following beneficial effects:

[0025] (1) Through infrared-ultraviolet double-pulse laser timing coupling, the thermal softening effect of infrared laser reduces the compactness of the glass network structure, and the ultraviolet laser initiates multiphoton ionization under delayed triggering, and the two synergistically improve the energy coupling efficiency and the reactivity of the modification region. The power density gradient scanning along the thickness direction forms an oxygen vacancy concentration gradient in the modification region, and the chemical potential difference generated by the concentration gradient effectively drives the directional migration of active particles in the etching solution to the deep hole, thereby alleviating the bottom etching lag caused by the limited diffusion of reactants in the traditional method. The phase locking of the ultrasonic field and the pulse burst sequence of the laser scanning makes the modification region produce piezoelectric nanodomains under the action of periodic stress, and the micro-potential of the nanodomain further enhances the directional separation efficiency of the electron-hole pair in the Fe³⁺ / H2O2 catalytic system, and improves the redox cycle rate and the utilization rate of hydroxyl radicals.

[0026] (2) The laser-induced oxygen vacancy concentration gradient and the piezoelectric nanodomain together construct the axial and radial differential reaction environment. The axial chemical potential difference preferentially accelerates longitudinal etching, while the local electric potential of the piezoelectric nanodomain inhibits the migration of active particles for lateral etching, both of which synergistically improve the etching selectivity ratio of the modified region to the unmodified region, which is conducive to the formation of a through-hole structure with steep sidewalls and controllable morphology, avoiding the problems of excessive side etching and hole shape distortion commonly existing in traditional methods.

[0027] (3) The Burst mode laser modulation method forms a quasi-polar nanodomain structure with uniform size in the modified region, providing a stable structural basis for the piezoelectric effect. The ultrasonic phase locking ensures the repeatability of the piezoelectric catalytic effect in the long etching process. At the same time, by monitoring and dynamically adding H2O2 online, the concentration of H2O2 is maintained stable, eliminating the etching rate drift caused by the decomposition of the oxidant, making the process window of the etching process wider and ensuring the batch consistency. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The flowchart of the present application. DETAILED DESCRIPTION

[0029] The present application will be further described below in conjunction with the drawings.

[0030] First, the preparation work before the experiment is carried out. Corning Pyrex® 7740 glass commonly used in the field of semiconductor packaging is selected as the substrate, and its thickness is set to 500 μm according to the high aspect ratio requirement of the target TGV through-hole (it can be adjusted to 300-800 μm according to the actual packaging requirement). The glass substrate is pretreated: ultrasonic cleaning with acetone and ethanol for 15 min to remove surface oil, then rinsing with deionized water for 3 times, and finally drying in a 80℃ vacuum drying oven for 2h to ensure that the substrate surface is free of impurities, avoiding affecting the uniformity of subsequent laser modification and etching reaction.

[0031] The equipment required for the experiment is prepared, including a pulsed laser that can output infrared-ultraviolet dual-band (infrared module wavelength 1064 nm, maximum power 10 W; ultraviolet module wavelength 355 nm, maximum power 5 W), an ultrasonic generating system with a phase-locked loop circuit (frequency adjustment range 20-100 kHz, power adjustment range 0-500 W), an H2O2 concentration online monitor (detection accuracy ±0.1%), a constant temperature water bath (temperature control accuracy ±0.5℃), and analytical pure reagents (HF, H2SiF6, FeCl3, H2O2, fluorocarbon surfactant) and deionized water for preparing etching solution.

[0032] The pretreated glass substrate is fixed on a three-dimensional moving platform, the distance between the laser focus and the surface of the substrate on the three-dimensional moving platform is adjusted to ensure that the laser energy accurately acts on the inside of the substrate. Turn on the laser and set it to Burst mode, each packet contains 10 laser pulses (adjustable within the range of 5-15 according to modification needs), the time interval between pulse packets is set to 1 μs (optimizable within the interval of 0.5-2 μs) to ensure effective superposition of pulse energy in the substrate and avoid excessive concentration of energy leading to substrate rupture.

[0033] where the infrared laser power is adjusted to 6 W (corresponding to a surface power density of 5×10 6 W / cm²), the ultraviolet laser power is adjusted to 2.5 W, and the ultraviolet laser pulse is set to be emitted 30 ns after the infrared laser pulse is triggered (the delay time can be fine-tuned within 20-40 ns) through the timing control module of the laser - the infrared laser first acts on the glass, and through the thermal effect, the temperature of the local area is raised to about 1300℃, softening the Si-O-Si network structure of the glass and reducing its bond energy; then the ultraviolet laser is incident in the form of a short pulse, which breaks the softened Si-O bond using the multi-photon ionization effect to promote the oxygen atom to form an oxygen vacancy. At the same time, the three-dimensional moving platform is controlled to move the substrate along the thickness direction, and every 50 μm depth, the infrared laser power is increased by 0.5 W (corresponding to an incremental power density of 0.5×10 6 W / cm²), until the infrared laser power at the bottom of the substrate (at a depth of 500 μm) reaches 9.5 W (corresponding to a power density of 8×10 6 W / cm²), by setting this power gradient, the glass substrate forms a gradient distribution of increasing oxygen vacancy concentration from the surface to the bottom, laying a structural foundation for subsequent construction of a chemical potential difference along the axis of the via.

[0034] During this process, the structure of the modified region can be observed by transmission electron microscopy (TEM), and it can be found that quasi-polar nanodomains with a size of about 8 nm (the size can be controlled within the range of 5-10 nm by adjusting the Burst mode parameters) are formed in the modified region, which provides a local ordered structure for the subsequent generation of piezoelectric effect.

[0035] After laser gradient modification, enter the ultrasonic coupling catalysis step, which is as follows:

[0036] First, prepare the Fe3+ / H2O2 composite catalytic etching solution according to the formula: measure deionized water, and then 4-10 wt% HF, 3-6 wt% H2SiF6, 0.05-0.08 mol / L FeCl3, 3-4 wt% H2O2, and 0.02-0.05 wt% fluorocarbon surfactant. Stir for 30 min with a magnetic stirrer to ensure uniform mixing of all components. Among them, H2SiF6 can react with etching product SiO2 to form soluble H2SiF6, avoiding the adhesion of precipitates to the via wall; the fluorocarbon surfactant can reduce the surface tension of the etching solution and improve its wettability in high aspect ratio vias.

[0037] Pour the prepared etching solution into a constant temperature water bath, set the temperature to 38°C (can be controlled within 35-40°C), and after the temperature is stable, immerse the modified glass substrate completely in the etching solution, at the same time, start the ultrasonic generating system, adjust the ultrasonic frequency to 60 kHz (can be optimized within 40-80 kHz), and adjust the power to 250 W (can be adjusted within 200-300 W), and connect the driving signal of the ultrasonic transducer and the pulse package trigger signal of the laser to the phase-locked loop circuit, adjust the circuit to make the phase difference between the ultrasonic phase and the laser pulse package phase constant at π / 2, and ensure that the periodic stress of the ultrasonic field and the quasi-polar nanodomain formation in the modified region are synchronized.

[0038] When the ultrasonic stress acts on the oxygen vacancy concentration gradient region, the quasi-polar nanodomain generates a piezoelectric effect due to stress induction, forming a periodic potential Δφ of 0.25 V (the potential range can be adjusted within 0.2-0.3 V by adjusting the ultrasonic power), which can drive the active particles such as Fe3+ and ·OH in the etching solution to migrate along the via axis direction, and accelerate the oxidation conversion of Fe2+ to Fe3+, and strengthen the catalytic cycle efficiency.

[0039] Finally, enter the dynamic etching step, which is as follows:

[0040] The probe of the H2O2 concentration on-line monitor is inserted into the etching solution to monitor the concentration change of H2O2 in real time during the etching process. Since H2O2 is gradually consumed in the catalytic reaction, when the concentration of H2O2 is monitored to decrease to 3.8wt% (i.e. deviating from the initial concentration by 0.2wt%, and the fluctuation is controlled within ±0.5%), the H2O2 solution with a concentration of 30wt% is dynamically added to the etching solution through the peristaltic pump to maintain the stable concentration of H2O2 and ensure the continuous and stable redox activity of the etching solution. In this process, the chemical potential difference is generated by the oxygen vacancy concentration gradient in the modified region of the glass substrate, which drives the active particles to diffuse to the bottom. The potential of the piezoelectric nanodomain further accelerates the particle migration and reaction, and the two synergistic effects make the etching reaction preferentially proceed along the axial direction, realizing anisotropic etching. The formation of the through-hole is observed in real time by an optical microscope. When the etching is carried out for 25min (which can be adjusted to 20-35min according to the thickness of the substrate), the glass substrate is completely penetrated to form a TGV through-hole with a diameter of 50μm and a high aspect ratio of 10:1.

[0041] After the etching is completed, the substrate is taken out of the etching solution, washed with deionized water for 5 times to remove the residual etching solution on the surface, and then subjected to subsequent metallization treatment (PVD sputtering Ti / Cu seed layer + electroplating Cu filling).

[0042] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements without departing from the principles of the present application, and these improvements should also be considered as the protection scope of the present application.

Claims

1. A high-speed etching method for glass through-holes based on the synergistic driving of laser-induced piezoelectric nanodomains and chemical potential, characterized in that: include: Laser gradient modification steps: The glass substrate is scanned and modified using infrared-ultraviolet dual-band lasers. By controlling the timing and increasing the power density gradient along the thickness direction, an oxygen vacancy concentration gradient is formed in the modified region, and a chemical potential difference is constructed along the axis of the via. Ultrasonic coupling catalysis step: The modified glass substrate is immersed in Fe³⁺ / H₂O₂ composite catalytic etching solution, and an ultrasonic field is applied. The driving phase of the ultrasonic field is locked with the pulse packet sequence of the laser scan, so that the oxygen vacancy concentration gradient region generates piezoelectric nanodomains under periodic stress. The potential of the piezoelectric nanodomains drives the directional migration and reaction of active particles in the etching solution. Dynamic etching step: The redox activity of the etching solution is monitored and maintained in real time. Anisotropic etching is achieved by utilizing the synergistic effect of the chemical potential difference and piezoelectric potential until a through hole is formed.

2. The high-speed etching method for glass through-holes based on the synergistic driving of laser-induced piezoelectric nanodomains and chemical potential as described in claim 1, characterized in that: In the laser gradient modification step, The infrared laser wavelength is 1064 nm, and the ultraviolet laser wavelength is 355 nm. The ultraviolet laser pulse is emitted with a delay of 20-40 ns after being triggered by the infrared laser pulse. The power density gradient increasing parameter along the thickness direction is: Power density of surface modified zone 5×10 6 W / cm², power density increases by 0.5 × 10⁻⁵ for every 50 μm increase in depth. 6 W / cm² reaches 8×10 in the bottom modified zone. 6 W / cm².

3. The high-speed etching method for glass through-holes based on the synergistic driving of laser-induced piezoelectric nanodomains and chemical potential as described in claim 1 or 2, characterized in that: The timing control specifically involves the laser operating in Burst mode, each containing 5-15 laser pulses with a time interval of 0.5-2 μs between pulse packets. This mode forms quasi-polar nanodomain structures with a size of 5-10 nm within the modified region.

4. The high-speed etching method for glass through-holes based on the synergistic driving of laser-induced piezoelectric nanodomains and chemical potential as described in claim 1, characterized in that: Maintaining the driving phase of the ultrasonic field locked to the pulse packet sequence of the laser scan means that the driving signal of the ultrasonic transducer and the pulse packet trigger signal of the laser controller are connected to the phase-locked loop circuit, so that the phase difference between the ultrasonic phase and the laser pulse packet is kept constant within the range of π / 2±π / 6.

5. The high-speed etching method for glass through-holes based on the synergistic driving of laser-induced piezoelectric nanodomains and chemical potential as described in claim 1 or 4, characterized in that: The potential-driven mechanism of piezoelectric nanodomains is as follows: ultrasonic stress generates a periodic potential Δφ in the oxygen vacancy concentration gradient region, and the potential Δφ ranges from 0.2 V to 0.3 V.

6. The high-speed etching method for glass through-holes based on the synergistic driving of laser-induced piezoelectric nanodomains and chemical potential as described in claim 1, characterized in that: The specific composition of the etching solution containing Fe³⁺ / H₂O₂ is as follows: 4-10 wt% HF, 3-6 wt% H₂SiF₆, 0.05-0.08 mol / L FeCl₃, 3-4 wt% H₂O₂, 0.02-0.05 wt% fluorocarbon surfactant, with the balance being deionized water.

7. The high-speed etching method for glass through-holes based on the synergistic driving of laser-induced piezoelectric nanodomains and chemical potential as described in claim 1, characterized in that: Maintaining the redox activity of the etching solution involves online monitoring of H2O2 concentration and dynamic replenishment to ensure that the H2O2 concentration fluctuation is less than ±0.5%, controlling the etching temperature at 35-40℃, and applying ultrasonic assistance at a frequency of 40-80 kHz and a power of 200-300 W.

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