Advanced Packaging Research Articles

Revitalizing U.S. Semiconductor Manufacturing: The Strategic Impact of the CHIPS Act on Advanced Packaging and Fabrication Technologies

Revitalizing U.S. Semiconductor Manufacturing: The Strategic Impact of the CHIPS Act on Advanced Packaging and Fabrication Technologies

A strategy for the preparation of low dielectric FGQD/PSPI composite films in wafer-level packaging

Advancement of wafer-level packaging (WLP) has heightened the requirements for photosensitive polyimide (PSPI) materials, where the low dielectric property is a key element to realize high frequency communication. Herein, a poly(amidate) (PAE) was prepared using Pyromellitic Dianhydride, 4,4’-diaminodiphenyl ether, and hydroxyethyl methacrylate as the photosensitive group. Specifically, the fluorinated graphene quantum dots (FGQD) was introduced into the PAE resin by in situ polymerization, and the prepared composite films of photosensitive polyimide-fluorinated graphene quantum dots (PSPI-FGQD) showed excellent dielectric constants and other comprehensive properties. Compared with pure PSPI, the dielectric constant of PSPI-FGQD decreases from 3.8 to 3.0 at 1 MHz; the tensile strength increases from 84.5 to 110.1 MPa, the elongation at break raises from 5.24 % to 17.3 %, and the Young's modulus increases from 2.68 GPa to 2.88 GPa. The glass transition temperature (Tg) is also increased to 420 °C with the introduction of FGQD. Apart of these, the fine patterning ability was observed for the FGQD/PSPI composite film, achieving a high photolithography resolution of 10 μm (L/S). To conclude, the preparation method of low dielectric FGQD/PSPI materials has promising potential applications in advanced packaging.

Development of a new type of highly effective etchant solution for glue residue in wafer-level packaging process

We synthesize an etchant solution designed to remove polydimethylsiloxane (PDMS) residues from semiconductor wafers during wafer-to-wafer processing in advanced semiconductor packaging (AVP). The etchant solution is produced by combining hexane, a nonpolar swelling solvent, with tetrabutylammonium fluoride (TBAF), a fluorine-based compound, to enhance PDMS etching. We evaluate the etching rate of PDMS using various solvent mixtures, including 1-vinyl-2-pyrrolidone, 1-methyl-2-pyrrolidone, 1-ethyl-2-pyrrolidone, and 1-octyl-2-pyrrolidone (NOP), with different concentrations of TBAF (1.0–5.0 wt%). Notably, NOP, which contains octyl groups, demonstrates the highest PDMS etching rate, particularly when combined with 70.0 wt% hexane. The optimized solution, F3-NOP/H70, achieves an etching rate of 85.7 μm/min. Further testing confirms that the F3-NOP/H70 solution effectively removes PDMS residues from wafer surfaces without damaging dielectric layers, such as the photosolder resist and photosensitive polyimide. These results indicate that the F3-NOP/H70 solution efficiently dissolves and removes PDMS residues and preserves the integrity of adjacent wafer components, making it a promising candidate for AVP applications. This study emphasizes the importance of selecting appropriate solvent systems for residue removal in semiconductor manufacturing and offers a practical solution to enhance device quality and reliability. This approach can potentially be applied at various stages of semiconductor processing, where residue management is essential.

Reliability Simulation Analysis of TSV Structure in Silicon Interposer under Temperature Cycling.

As semiconductor integration scales expand and chip sizes shrink, Through Silicon Via (TSV) technology advances towards smaller diameters and higher aspect ratios, posing significant challenges in thermo-mechanical reliability, particularly within interposer substrates where mismatched coefficients of thermal expansion exacerbate issues. This study conducts a thermo-mechanical analysis of TSV structures within multi-layered complex interposers, and analyzes the thermal stress behavior and reliability under variable temperature conditions (-55 °C to 85 °C), taking into account the typical electroplating defects within the copper pillars in TSVs. Initially, an overall model is established to determine the critical TSV locations. Sub-model analysis is then employed to investigate the stress and deformation of the most critical TSV, enabling the calculation of the temperature cycle life accordingly. Results indicate that the most critical TSV resides centrally within the model, exhibiting the highest equivalent stress. During the temperature cycling process, the maximum deformation experiences approximately periodic variations, while the maximum equivalent stress undergoes continuous accumulation and gradually diminishes. Its peak occurs at the contact interface corner between the TSV and Redistribution Layer (RDL). The estimated life of the critical point is 3.1708 × 105 cycles. Furthermore, it is observed that electroplating defect b alleviates thermal stress within TSVs during temperature cycling. This study provides insights into TSV thermal behavior and reliability, which are crucial for optimizing the design and manufacturing processes of advanced semiconductor packaging.

Isothermal aging and electromigration reliability of Cu pillar bumps interconnections in advanced packages monitored by in-situ dynamic resistance testing

Cu pillar bump (CPB) technology as the representative advanced packaging technology possesses the characteristics of miniaturization and high density, thus playing an important role in the reliability of electronic devices. However, the brittle intermetallic compound (IMC) layer in the joints evidently affects the service performance and reliability of CPB joints. Thus, the influence of IMC layer thickness and microstructure needs to be carefully evaluated. In this study, the reliability of CPB joints with different IMC layer thickness under the condition of isothermal storage and room-temperature electromigration was tested, and the effect of initial IMC thickness of joints on the reliability was revealed. The full-IMC joints have the best isothermal storage reliability while the half-IMC joints perform the worst. Meanwhile, the thin-IMC joints own the best electromigration reliability but the full-IMC joints show the worst because that the initial voids in full-IMC joints accelerate the failure caused by electromigration.

A Review of Mechanism and Technology of Hybrid Bonding

Abstract With the development of semiconductor technology, traditional flip-chip bonding has been difficult to meet the high-density, high-reliability requirements of advanced packaging technology. As an advanced three-dimensional stacked packaging technology, Cu-SiO2 hybrid bonding technology can achieve high-density electrical interconnection without bumps, which expands the transmission performance and interconnection density of chips greatly. However, the investigation on Cu-SiO2 bonding is far from mature, and many researchers are studying Cu-SiO2 bonding passionately. There are many technologies that use different bonding mechanisms to achieve Cu-SiO2 bonding, which will affect the bonding strength directly. We review the mechanism and research progress of Cu-Cu bonding, SiO2-SiO2 bonding. What is more, we summarize the comparison of bonding conditions and bonding strength of various methods furtherly. According to the bonding mechanism, we propose some economical solutions for low-temperature Cu-SiO2 hybrid bonding, with the aim of providing certain references for the further development of advanced semiconductor packaging.

Enhanced photocatalytic degradation of polylactide (PLA) through TiO2-based up-conversion nanoparticles

As a degradable polymer material, the regulation of the degradation rate of polylactide (PLA) under an actual light exposure environment is of significant importance for realizing its multifaceted applications. This study aims to enhance the photodegradation of PLA under irradiation with lower-energy wavelengths by using TiO2-based up-conversion nanoparticles (UCNPs). Two modification methods were employed: doping TiO2 with Yb3+/Er3+/Tm3+ ions integrated within the TiO2 lattice, and creating a composite photocatalyst by adhering Y2O3: Yb3+/Er3+/Tm3+ to the exterior of TiO2 grains. The study investigated the impact of these two different TiO2-based UCNPs on the photocatalytic degradation rate and mechanism of PLA under simulated sunlight irradiation. Research has found that the doped TiO2, due to its narrower bandgap and higher photon utilization efficiency during the up-conversion process, exhibited superior catalytic efficiency in catalyzing the photodegradation reactions of PLA compared to unmodified TiO2 and composite TiO2. This work proposes a novel strategy for preparing PLA composites with enhanced photodegradation speed provided by modified TiO2, efficient light energy utilization offered by the up-conversion process, and potential applications in more advanced packaging and agricultural fields.

Brittle Fracture Behavior of Sn-Ag-Cu Solder Joints with Ni-Less Surface Finish via Laser-Assisted Bonding.

In this study, we investigated the brittle fracture behavior of Sn-3.0Ag-0.5Cu (SAC305) solder joints with a Direct Electroless Gold (DEG) surface finish, formed using laser-assisted bonding (LAB) and mass reflow (MR) techniques. Commercial SAC305 solder balls were used to ensure consistency. LAB increases void fractions and coarsens the primary β-Sn phase with higher laser power, resulting in a larger eutectic network area fraction. In contrast, MR produces solder joints with minimal voids and a thicker intermetallic compound (IMC) layer. LAB-formed joints exhibit higher high-speed shear strength and lower brittle fracture rates compared to MR. The key factor in the reduced brittle fracture in LAB joints is the thinner IMC layer at the joint interface. This study highlights the potential of LAB in enhancing the mechanical reliability of solder joints in advanced electronic packaging applications.

Reliability Risk Mitigation in Advanced Packages by Aging-Induced Precipitation of Bi in Water-Quenched Sn-Ag-Cu-Bi Solder.

Bi-doped Sn-Ag-Cu (SAC) microelectronic solder is gaining attention for its utility as a material for solder joints that connect substrates to printed circuit boards (PCB) in future advanced packages, as Bi-doped SAC is reported to have a lower melting temperature, higher strength, higher wettability on conducting pads, and lower intermetallic compound (IMC) formation at the solder-pad interface. As solder joints are subjected to aging during their service life, an investigation of aging-induced changes in the microstructure and mechanical properties of the solder alloy is needed before its wider acceptance in advanced packages. This study focuses on the effects of 1 to 3 wt.% Bi doping in an Sn-3.0Ag-0.5Cu (SAC305) solder alloy on aging-induced changes in hardness and creep resistance for samples prepared by high cooling rates (>5 °C/s). The specimens were aged at ambient and elevated temperatures for up to 90 days and subjected to quasistatic nanoindentation to determine hardness and nanoscale dynamic nanoindentation to determine creep behavior. The microstructural evolution was investigated with a scanning electron microscope in tandem with energy-dispersive spectroscopy to correlate with aging-induced property changes. The hardness and creep strength of the samples were found to increase as the Bi content increased. Moreover, the hardness and creep strength of the 0-1 wt.% Bi-doped SAC305 was significantly reduced with aging, while that of the 2-3 wt.% Bi-doped SAC305 increased with aging. The changes in these properties with aging were correlated to the interplay of multiple hardening and softening mechanisms. In particular, for 2-3 wt.% Bi, the enhanced performance was attributed to the potential formation of additional Ag3Sn IMCs with aging due to non-equilibrium solidification and the more uniform distribution of Bi precipitates. The observations that 2-3 wt.% Bi enhances the hardness and creep strength of the SAC305 alloy with isothermal aging to mitigate reliability risks is relevant for solder samples prepared using high cooling rates.

Short failure localization in advanced package using optoelectronic sampling terahertz time domain reflectometry and deconvolution method

Failure localization in advanced packaging is a challenging task. Optoelectronic sampling Terahertz time-domain reflectometry (OES THz TDR) employs ultrafast lasers to generate high-frequency THz pulse. The THz pulse is coupled into advanced package trace using radio frequency probe. When there is an open or short failure in the circuit, TDR signal could be captured. Deconvolution processing method was introduced to remove noise from multiple reflections of the remaining circuit. A short failure model with remaining circuit was studied. After deconvolution, the TDR localization accuracy improves from 573 μm to 12 μm, and the correlation coefficient improved from 99.612 % to 99.955 %. Advanced package sample including substrate, C4 bump, interposer, and micro bump was analyzed. By comparing the TDR waveform of short failure sample and references, the short failure is localized inside of the die. By destroying the failure sample and measuring the current-voltage curve, the short failure location is verified.

Molecular dynamics simulation study of Zr interposer promoting Cu-Cu low-temperature hybrid bonding

With the development of the microelectronics industry, microelectronics packaging technology continues to develop towards higher integration and smaller size. To overcome the problem that the micro-bump size of solder cannot meet the fine pitch bonding, Cu-Cu direct bonding has become one of the most promising methods in advanced packaging technology. However, since the temperature required for Cu-Cu direct bonding is approximately 400 °C, currently Cu-Cu direct bonding is mostly achieved through a hot-pressing process. Such high temperatures will lead to reduced alignment accuracy, damage to device performance, and increased equipment requirements. In order to overcome these problems, this study proposed to use active metal Zr as the interposer material to improve the Cu-Cu atomic diffusion ability and reduce the Cu-Cu direct bonding temperature. The research results indicated that the interposer structure of Zr with (111), (11-2), and (1-10) surfaces contribute to promote Cu-Cu diffusion and bonding at low temperatures. Among them, the Zr (11-2) structure had the strongest promoting effect. Due to the tight arrangement of atoms in the densely packed crystal plane, the diffusion ability of atoms is significantly weakened during the bonding process of the densely packed crystal plane. Therefore, the Zr (001) structure can only promote bonding process under specific crystalline surface of Cu, and the bonding ability was very weak. The application of this research result will have a beneficial effect on the reliability and manufacturability of three-dimensional integrated packaging.

Incomplete dissolved behavior and mechanical analysis of SnAgCu-SnBi composite solder structures for high-reliable package-on-package techniques

Due to the development of advanced packaging technology such as Package on Package (POP), traditional Sn-Ag-Cu (SAC) solder can no longer meet the demand. Utilizing the differences in temperature and performance of various solder materials to create composite structures for soldering is an effective method to achieve PoP interconnection. In this research, the microstructure of the interface between SAC305 and liquid in the incomplete dissolved solider ball was observed, and the grain orientation after solidification was analyzed. In addition, the effect of SnBi ratios on the microstructure and mechanical properties of SAC305-SnBi composite solder balls, and the fracture mechanism was analyzed according to the fracture morphology. The results show that according to Electron Backscatter Diffraction (EBSD) analysis, the grain size of Sn-Ag-Cu-Bi is small, and the orientation tends to be the same. With the rise in SnBi content, the eutectic structure in the solder ball exhibited a progressive increase and the IMC at the interface gradually changed from uneven rod-like structure to more uniform scallop-like structure. When the weight fraction of SnBi is 66.7%, the shear strength researches a maximum value of 62.2 MPa. As the SnBi content increases, there is an observable shift in the fracture location from the IMC to the solder.

Compact low-loss diplexer with stacked 2D and 3D structures using 3D glass-based advanced packaging technology

A compact low loss wideband diplexer is introduced by using stacked 2D and 3D structures through 3D advanced packaging and through glass vias (TGV). An inductor is designed by using stacked 2D and 3D structures to reduce the coupling effect between adjacent 2D inductors located in the same layer. It can greatly improve the Q factor yet minimize the chip size. This low loss, small size diplexer is developed by virtue of a modified topology and the proposed stacked 2D and 3D structures. The designed diplexer with a compact size of 1.6 mm × 0.8 mm × 0.25 mm is fabricated using 3D glass-based advanced packaging technology and measured by on-wafer probing. The measured results indicate that it achieves an insertion loss less than 0.8 dB and 0.9 dB and an isolation better than 20 dB and 17.5 dB in the bands of 0.699 GHz-0.960 GHz and 1.71 GHz-2.69 GHz, respectively. In comparison with the previously reported designs, the proposed diplexer shows the superior advantages of smaller size and lower insertion loss.

Organic nanoparticles incorporated starch/carboxymethylcellulose multifunctional coating film for efficient preservation of perishable products

Most of postharvest agricultural produces are perishable due to microorganisms infections and physiological change. Herein, one kind of multifunctional coating film of SC-ECCNPs was developed by incorporating organic nanoparticles of ECCNPs into starch/carboxymethylcellulose (SC) to prolong shelf life of food with excellent performances. The SC-ECCNPs coating was prepared with starch and sodium carboxymethylcellulose as film substrate (SC) to incorporate with organic nanoparticles of ECCNPs formed by integrating epigallocatechin-3-gallate (EGCG), cysteine (Cys), and cinnamaldehyde (CA). The incorporation of ECCNPs improves the UV-resistance and physical properties of SC-ECCNPs coating and also endows it with excellent antioxidative and broad-spectrum antibacterial activity. The application possibilities of SC-ECCNPs coating were explored with strawberries and oranges as samples, validating that the SC-ECCNPs coating can prolong the shelf life of fruits at room temperature. The biosafety of the coating was further confirmed with hemolysis and MTT experiments. The SC-ECCNPs coating film was prepared with natural substrates via a simple and green method. The investigation provides an instructive way for developing advanced packaging materials with high performances.

Investigation of lemon peel extract as a natural additive in polyvinyl alcohol/chitosan blend for advanced bioactive food packaging

Investigation of lemon peel extract as a natural additive in polyvinyl alcohol/chitosan blend for advanced bioactive food packaging

Modelling and simulation for the investigation on the ultrasonic propagation mechanism in advanced microelectronic packages

The miniaturisation, ultra-thinness and high-density multi-layer structure of advanced microelectronic packages complicate the propagation mechanism of ultrasonic waves. In this paper, a finite element model is used to simulate ultrasonic wave propagation in flip chip packages, investigating the laws of transmission and reflection at the lamination boundaries. The acoustic field of ultrasonic transducers is simulated using MATLAB and Abaqus software. The angular spectrum method (ASM) based on the Fourier transform is adopted to more precisely reveal the distribution characteristics and attenuation relationship of near‐field ultrasonic waves. The influence of the frequency and size of the ultrasonic transducer on the propagation characteristics of ultrasonic waves is analysed. Based on an acoustic field map generated by the detection model, the waveform conversions of acoustic waves in a multi-layer structure are analysed. The results show that ultrasonic waves are mainly presented in the form of reflected and transmitted waves at the layered interface and the model with a perfectly matched layer (PML) has higher accuracy. Therefore, this method is applied to ultrasonic testing in a flip chip package, which cannot only effectively exclude interference from boundary reflection but also greatly improve the reliability of waveform conversions analysis.

Combined effect of Ag element and temperature gradient on the formation of highly orientated Sn grains in micro solder joints

Sn–Ag solders are widely used for advanced electronic packaging. The combined effect of Ag element and temperature gradient (TG) on the formation of Sn grains in Cu/Sn-xAg/Cu micro solder joints was elucidated systematically. Numerous small-sized β-Sn grains were formed in both Cu/Sn/Cu and Cu/Sn-0.5Ag/Cu micro solder joints after reflow with or without TG. The Cu/Sn-0.5Ag/Cu joint was found to have more twinning β-Sn structures. The formation of the multiple β-Sn grains in these two joints was attributed to the presence of multiple tetrahedral metastable short-range order (SRO) structures which acted as nuclei for the nucleation and growth of β-Sn. The existence of TG slightly enhanced the preferred orientation characteristics of Sn grains. For the joints with Ag content was or higher than 2 wt%, several Sn grains were formed without TG, while a single or highly oriented Sn grains were observed with TG. The number and orientation of Sn grains were affected by the combined effect of Ag element and TG significantly. The β-Sn grains formed without TG were based on the {101} type cyclic twinning configuration clusters that stabilized by Ag atoms and acted as nuclei. The formation of a single or highly preferred β-Sn grains was benefit from the combined effect of Ag element and TG. The results provide theoretical guidance for optimizing the composition of Sn–Ag solders and controlling the microstructure of the joints, thereby contributing to the advancement of electronic packaging technologies.

Advanced packaging of chiplets for future computing needs

Advanced packaging of chiplets for future computing needs

Meeting Challenges of Advanced Packaging Designs with a Preimidized Polymer as Dielectric Material

Meeting Challenges of Advanced Packaging Designs with a Preimidized Polymer as Dielectric Material

Highly Functional Materials for Advanced Package

Highly Functional Materials for Advanced Package