Glass Interposer Research Articles

Glass interposer for heterogeneous integration of flip-chipped photonic and electronic integrated circuits

Glass interposer for heterogeneous integration of flip-chipped photonic and electronic integrated circuits

A comprehensive numerical analysis for preventing cracks in 2.5D glass interposer

A comprehensive numerical analysis for preventing cracks in 2.5D glass interposer

Ultra‐high Aspect Ratio TGV Perforation Utilizing Selective Laser‐induced Etching with Nanochannels

At present, perforation of high aspect ratio through glass vias (TGVs) is one of the primary factors limiting the development of glass interposers. This study is based on a large number of experiments, combined with mechanistic analysis, to realize the perforation of ultra‐high/high aspect ratio fused silica TGVs using selective laser‐induced etching (SLE). Firstly, the effect of the number of pulses as well as other laser parameters on the etching selectivity is systematically investigated. It is found that the formation of nanochannels in fused silica is crucial in determining the high selectivity. Subsequently, a model based on diffusion theory is proposed to mathematically explain the reasons for the high selectivity generation. Finally, the perforations of TGVs with diameters of 5.4 µm ‐ 26.4 µm, aspect ratios of 11.7 ‐ 61.3 and vertical sidewalls are achieved, at a laser treatment speed of approximately 10,000 TGVs per minute. This research can serve as an essential reference for the manufacturing of TGVs with high aspect ratios and glass interposers with high interconnection density.This article is protected by copyright. All rights reserved.

High Speed Transmission Characteristics on Glass Based Interposers

Interposers for system in package will became more and more important for advanced electronic systems. As the industry moves toward HPC (High Performance Computing) for huge data transmission with low power consumption. The major engineering requirements for HPC application are highdensity, high speed data transmission, low loss, precision manufacturing and low cost. On the 2.5D heterogenous package structure, key technology is fine wiring connected with CPU chip and HBM chips. The fine wires needed high speed transmission. This paper presents the demonstration of Glass-based twin type interposers, Glass interposer with fine pitch metalized through via and RDL interposer with low loss dielectrics on Glass carrier. We compare twin types of Interposes fabrication process capability with panel size format 300x400mm. Finally, we compare the transmission characteristics using eye diagram for heterogenous integration application. Glass Interposer has low loss glass via, it is effective vertical interconnection. RDL interposer has low loss dielectric layers, excellent transmission characteristics obtained on fine pitch trace area.

The Effects of Etchant on via Hole Taper Angle and Selectivity in Selective Laser Etching.

This research focuses on the manufacturing of a glass interposer that has gone through glass via (TGV) connection holes. Glass has unique properties that make it suitable for 3D integrated circuit (IC) interposers, which include low permittivity, high transparency, and adjustable thermal expansion coefficient. To date, various studies have suggested numerous techniques to generate holes in glass. In this study, we adopt the selective laser etching (SLE) technique. SLE consists of two processes: local modification via an ultrashort pulsed laser and chemical etching. In our previous study, we found that the process speed can be enhanced by changing the local modification method. For further enhancement in the process speed, in this study, we focus on the chemical etching process. In particular, we try to find a proper etchant for TGV formation. Here, four different etchants (HF, KOH, NaOH, and NH4F) are compared in order to improve the etching speed. For a quantitative comparison, we adopt the concept of selectivity. The results show that NH4F has the highest selectivity; therefore, we can tentatively claim that it is a promising candidate etchant for generating TGV. In addition, we also observe a taper angle variation according to the etchant used. The results show that the taper angle of the hole is dependent on the concentration of the etchant as well as the etchant itself. These results may be applicable to various industrial fields that aim to adjust the taper angle of holes.

Thermal Isolation Performance of Polyimide Aerogel within a Die-Embedded Glass Interposer

Thermal Isolation Performance of Polyimide Aerogel within a Die-Embedded Glass Interposer

Compact OWC Receiver: Micro-Lens and PD Array on Glass Interposer

In this paper, we propose a compact optical wireless receiver based on micro-lens and photodiode array flip-chipped on a glass interposer. With simulation models and experiments, we verify the performance of two optical wireless communication receivers assembled based on this structure with gigabit and high-speed photodiodes. First, co-integrated gigabit photodiodes and micro-lenses indicate that micro-lenses can deliver a 3.5 dB gain of light collection efficiency to the gigabit photodiode array while keeping the field of view larger than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 18 degrees. Besides, a 5.5 Gbps maximum throughput has been verified by this optical wireless communication receiver with discrete multitone modulation. Moreover, co-integrated high-speed photodiodes and micro-lenses prove that micro-lenses realize a 26.6 dB improvement in light collection efficiency, enabling a 10 Gbps error-free connection using as little as -0.5 dBm transmission power. Those results conclude that the co-integration of micro-lenses on the photodiode array can enhance the light collection efficiency of the photodiode array while keeping a larger field of view, providing a high-performance, low-cost solution for the receiver of optical wireless links.

High -yield Fabrication of Thin Glass Interposers

Thin glass substrates with through vias (TGV) have excellent properties for a new generation of interposers. Glass has a large bulk resistance and low loss at high frequency (RF, mmWave). Physically, it is moisture insensitive, highly dimensionally stable, and has a thermal expansion coefficient that can be tailored to match silicon. The surface of as-received glass has roughness below 1 nm, like silicon wafers, and thus supports fine line/space patterning and advanced processes like damascene. A key focus of our current work involves metallizing thin glass interposers with TGVs, including both copper electroplating of TGVs and patterning of redistribution layers. We demonstrate void-free fill for vias ranging from in aspect ratio from 2:1 to 8:1, in a bottoms-up process like that used for through silicon vias. The vias are hermetic by helium leak detection, even after annealing in some cases to 450C. Since thin (≤ 200 micron) free-standing glass substrates are difficult to handle in current fabs, we discuss an advanced temporary bond approach using silicon or glass handles which enables high-yield processing. The bond is robust to temperatures exceeding 400 °C, and creates handle/glass stacks with total thickness variation (TTV) similar to that of a silicon wafer. The end result is a bonded pair that can be processed like a silicon wafer, with a simple mechanical debond to yield the processed thin glass. We discuss the bond and debond processes, showing the ability to control the bond strength. Data on the bonded glass stack resistance to various processing steps will also be shown.

Electrical Performance Analysis of High-Speed Interconnection and Power Delivery Network (PDN) in Low-Loss Glass Substrate-Based Interposers.

In this article, electrical performance analysis of high-speed interconnection and power delivery network (PDN) in low-loss glass substrate-based interposers is conducted considering signal integrity (SI) and power integrity (PI). The low-loss glass substrate is a superior alternative to silicon substrate in terms of high-speed signaling and fabrication yield. However, the low-loss of the substrate is vulnerable to power/ground noise in the PDN since the low-loss property of the substrate cannot suppress the noise naturally. In this article, an in-depth electrical performance analysis is conducted based on various measurements and simulations to fully benefit the advantages of the low-loss glass substrate. First, the fabrication process and test vehicles for the analysis are explained. Using the test vehicles, the electrical performance of the glass interposer's high-speed interconnection is compared with those of silicon and organic interposers. The insertion loss, eye-diagrams, and signal bandwidths of three interposer channels are compared and analyzed based on electromagnetic (EM) and circuit simulations. Also, the electrical performance of the through glass via (TGV) channel is measured and compared with through silicon via (TSV) channel. The high-speed interconnection of the glass interposer showed better performance for most of the parameters which is more suitable for maintaining the SI. Even though the low-loss of the glass substrate ensured the SI, power/ground noise issues in the PDN must be analyzed and solved. In this article, various cases inducing the power/ground noise in the PDN are considered, simulated, and measured. To solve the issues, ground TGV design and electromagnetic bandgap (EBG) design are proposed for an efficient broadband suppression of the noise generated in the glass interposer PDN.

Frequency response and transient analysis of through glass packaging vias using matrix-rational approximation (MRA) technique for three-dimensional ICs

In this paper, a computationally efficient matrix rational approximation (MRA) technique is developed to analyze the electrical behaviour of through packaging vias in glass interposer (TGVs). Using MRA technique, the electrical behaviour of TGVs utilizing differential multi-bit configuration, filled with composite copper-mixed carbon nanotube bundle (Cu-mCNTB), is investigated. A temperature-dependent π-type equivalent circuit of such differential multi-bit (DM) composite TGVs is developed using partial-element equivalent-circuit technique. The effective complex conductivity of Cu-mCNTB is also derived by appropriately considering the effects of temperature-dependent mean free path in CNTs. The frequency dependent differential- and common-mode impedances are obtained up to 100 GHz through PEEC technique. It is analyzed that composite DM-TGVs outperform silicon via counterparts in terms of reduced insertion loss using proposed MRA technique and verified through high-frequency structure simulator (HFSS). The transient analysis including crosstalk-induced propagation delay, peak crosstalk, and peak timing of coupled Cu-mCNTB/composite DM-TGVs is determined through the proposed MRA model, which exhibits error within 1% compared to the SPICE. The robustness of proposed model is examined under a wide variety of test cases including the proposed 5-Cu-mCNTB composite TGV array. For the transient analysis, the CPU runtime using the MRA model is 18.57 × faster than the SPICE. To the best of the authors’ knowledge, it is for the first time that temperature-dependent modeling and crosstalk analysis of coupled TGV structures is reported using MRA technique.

Study of Through Glass Via (TGV) Using Bessel Beam, Ultrashort Two-Pulses of Laser and Selective Chemical Etching.

Selective laser etching is a promising candidate for the mass production of glass interposers. It comprises two steps: local modification by an ultrashort-pulsed laser and chemical etching of the modified volume. According to previous studies, when an ultrashort-pulsed laser beam is irradiated on the sample, electron excitation occurs, followed by phonon vibration. In general, the electron excitation occurs for less than a few tens of picoseconds and phonon vibration occurs for more than 100 picoseconds. Thus, in order to compare the electric absorption and thermal absorption of photons in the commercial glass, we attempt to implement an additional laser pulse of 213 ps and 10 ns after the first pulse. The modified glass sample is etched with 8 mol/L KOH solution with 110 °C to verify the effect. Here, we found that the electric absorption of photons is more effective than the thermal absorption of them. We can claim that this result helps to enhance the process speed of TGV generation.

Development of high performance 2.5D packaging using glass interposer with through glass vias

Development of high performance 2.5D packaging using glass interposer with through glass vias

Characterization of Microstrip Line and SIW on ABF in Glass Interposers for mmWave Applications

Characterization of Microstrip Line and SIW on ABF in Glass Interposers for mmWave Applications

Layout Dependence Stress Investigation in through Glass via Interposer Architecture Using a Submodeling Simulation Technique and a Factorial Design Approach.

The multi-chiplet technique is expected to be a promising solution to achieve high-density system integration with low power consumption and high usage ratio. This technique can be integrated with a glass interposer to accomplish a competitive low fabrication cost compared with the silicon-based interposer architecture. In this study, process-oriented stress simulation is performed by the element activation and deactivation technique in finite element analysis architecture. The submodeling technique is also utilized to mostly conquer the scale mismatch and difficulty in mesh gridding design. It is also used to analyze the thermomechanical responses of glass interposers with chiplet arrangements and capped epoxy molding compounds (EMC) during curing. A three-factor, three-level full factorial design is applied using the analysis of variance method to explore the significance of various structural design parameters for stress generation. Analytic results reveal that the maximum first principal stresses of 130.75 and 17.18 MPa are introduced on the sidewall of Cu-filled via and the bottom of the glass interposer, respectively. Moreover, the EMC thickness and through glass via pitch are the dominant factors in the adopted vehicle. They significantly influence the stress magnitude during heating and cooling.

D-Band Integrated and Miniaturized Quasi-Yagi Antenna Array in Glass Interposer

An integrated and miniaturized D-band quasi Yagi antenna in glass interposer is presented. Single element, 1×2 and 1×4 test coupons are fabricated on 100-μm glass substrate with low-loss polymer buildup films and the return loss, gain and radiation pattern of the antennas are characterized. The proposed antenna utilizes a monopole radiator to achieve a higher bandwidth. Advantages of the glass substrate for beyond 5G communications in terms of enabling fine features and compact integration of other active and passive devices through chip embedding is discussed. An analysis of the substrate modes to ensure proper mode propagation in the selected stack-up is presented. Furthermore, the paper discusses the challenges in planar antenna measurements in sub-THz frequencies and it presents two measurement setups to overcome these challenges. The first is a low-cost probe-station-based measurement setup to characterize the return loss and boresight gain, and the second is a diode-detector-based setup to measure the normalized radiation pattern. The proposed antennas achieve high bandwidth covering the frequency range of 110-170 GHz, and 4.78 dBi, 8.41 dBi, and 11.04 dBi gain for the single element, 1×2 and 1×4 array, respectively.

Fabrication of Panel-Level Glass Substrates with Complete Design Freedom using LIDE

In this work, we present examples of highly reproducible, accurate and extremely cost-effective wafer- and panel-level fabrication of glass interposers, free of any process-dependent design limitations where any distribution and density of Through-Glass Vias (TGV) with any cross-section geometries and aspect-ratios, is possible. Glass has recently garnered significant interest for its many applications in the semiconductor packaging industry, particularly as a core substrate material for interposer applications. Glass has a unique set of material properties with great relevance for this industry, such as very high electrical resistivity, low loss tangent and low dielectric constant. Glass also exhibits low warpage due to its relatively low Young‘s Modulus while still being compatible with Silicon in terms of CTE and, when processed using a technology that doesn’t induce the generation of any defects such as microcracks or thermally-induced stress, it is highly reliable during processing and operation. Laser Induced Deep Etching (LIDE®) technology is a 2.5D glass processing technology with complete design freedom purposedly developed for cost-effective, high-volume fabrication of defect-free glass components. Despite its many advantages as an interposer material in relation to Si, its application has been hindered by the lack of reliable, precise, and cost-effective processing technologies. LIDE® consists of a two-step process: i) a very fast maskless and direct-write laser process induces subtle and very localized modification in the glass substrate, requiring a single laser pulse to modify the whole glass thickness; and ii) a wet-etching process done in batch, where the whole glass substrate is subjected to the action of an etchant and where the removal of glass occurs at an accelerated rate in the laser-modified regions. This process flow allows LIDE to fabricate several thousands of TGV per second, completely free of any defects, with a sub-micron point-to-point accuracy and ± 5 µm accuracy (cumulative) across a 510 mm x 515 mm glass panel (Cp &gt; 1.33), in any glass type, with aspect-ratios from 1:10 to 1:50 (diameter:depth).

On the optimization of molding warpage for wafer-level glass interposer packaging

On the optimization of molding warpage for wafer-level glass interposer packaging

Antenna With Embedded Die in Glass Interposer for 6G Wireless Applications

This paper presents the antenna-integrated glass interposer for D-band 6G wireless applications using die embedding technology. We implement the die-embedded package on glass substrates and characterize the electrical performance in D-band. The electrical characterization employs embedded test dies with 50 Ω Ground-Signal-Ground (GSG) ports and coplanar waveguides. We achieve low-loss die-to-package transitions by using staggered dielectric vias, which are compared with the transitions of wire-bonding and flip-chip assembly. The paper provides detailed information on the design, modeling, fabrication, and characterization of the die-to-package interconnects. This paper also demonstrates the integration of microstrip patch antenna array and embedded dies in D-band. The results show superior electrical performance provided by the die-embedded glass interposer. The die-to-package interconnect exhibits good matching (less than -10 dB S11) and low loss (0.2 dB loss) in D-band. The integrated 1 × 8 patch antenna array shows 11.6 dB broadside gain and good matching with the embedded die. Additionally, by using a temporary carrier, the antenna-integrated glass interposer also has great potential for further heterogeneous integration and thermal management.

Antenna Array on Glass Interposer for 6G Wireless Communications

This paper demonstrates integrated packaging solutions for antenna components in D-band by using glass-based package. We design sub-terahertz patch antennas at 140 GHz frequency band using HFSS simulation, and form arrays of patch antennas for 6G (sub-THz) wireless communication applications. The patch antennas and feeding networks are implemented using microstrip structures on the top of the interposer, with ground planes beneath. Build-up layers of polymer dry films are laminated on a glass core for multi-layer copper metallization, and copper structures are patterned on the polymer layers. For precise fabrication of the antenna and feeding structures in package, we implement the semi-additive patterning process to deposit the copper structures. Adequate measurement methods are applied to address difficulties in D-band antenna measurements. By forming patch antenna arrays, we obtain 10 dBi gain using a 4-element linear array and 14 dBi gain using a 4-by-4 2-D array. The bandwidths achieved for these arrays are 7% (10 GHz) and 5% (7 GHz), respectively, based on return loss measurements. Overall, the measurement results present good match to simulation. Antenna structures on glass substrates demonstrated in this paper represent the basic building block for heterogeneous integration of D-band front-end module in glass-based packages.

Wideband Analysis and Prolongation of Surrounding TGVs Shielding Structure in 3-D ICs

Through glass vias (TGVs) with low substrate loss are subjected to signal distortion issues. This letter proposes a wideband scalable model for assessing signal reliability and rationalizing 3-D integrated design in glass interposers. The established equivalent circuit model is derived for extracting the parasitic parameters of the signal transmission unit, and the relevant variables stem from the geometric dimension parameters. The result of comparative analysis uncovers that the simulation results are in excellent accordance with the analytical model. Furthermore, seven crosstalk shielding topologies are proposed, and their noise suppression ability is analyzed. Such the shielding structures can not only reach the insertion loss (IL) performance below 0.15 dB but also achieve the crosstalk suppression capability exceeding 60 dB even at 40 GHz. Feasible strategies are proposed to trade off IL, noise isolation (NI), and occupied area in order to match suitable application scenarios, which can provide a reference for layout design.