Oral Sessions


S19:Advanced Materials, Automatic Process & Assembly

Oct. 27, 2022 15:40 PM - 17:40 PM

Room: R504c
Session chair: Dyi Chung Hu,Siplus / Fan-Yi Ouyang, Professor, NTHU

Organic Molecules Induced Adhesion Enhancement in IC Packaging  
發表編號:S19-1時間:15:40 - 16:10

Invited Speaker

Thomas Thomas, Global Product Manager Atotech Deutschland GmbH

Advancement of electronic devices has lead the IC package technology to move toward ultra-fine L/S (< 8 µm) manufacturing. To maintain a good conductive traces integrity, adhesion enhancement system by introducing adhesion promotor molecules is becoming necessary. This work demonstrates the development of a novel adhesion enhancement system which can fulfil all challenges in IC package manufacturing. Organic molecule adhesion promotor introduced in the process to serve as chemical interface bridge, improving significantly the adhesion of substrate laminates on smooth conductive traces at zero line width reduction.

Interfacial Microstructure Evolution of Indium Jointed with Different Surface Finishes after Thermal Treatments
發表編號:S19-2時間:16:10 - 16:25

Cheng-Lun Chen

High performance computing (HPC) products market is growing to meet current and future demands in business, government, engineering, and science. HPC system can process big data and perform complex calculation at high speeds, where the system also generates a lot of heat continuously. The accumulated heat needs to be managed to avoid affecting the performance and lifetime of HPC system. Therefore, a key design and development of HPC products is to achieve high thermal dissipation in electronic devices. The application of thermal interface materials (TIMs) has been a promising thermal dissipation solution for electronic devices. However, the thermal conductivities of current silicone-based TIMs have been insufficient for future products. Indium is a potential candidate for high heat dissipation needs, because the thermal conductivity of pure indium is around 86 W/mK, which is higher than most silicone-based TIMs. When indium has been applied as a metallic TIM and jointed with the metal of surface finish, there is an intermetallic compound (IMC) reaction at the interface of indium joint. The phase and microstructure of IMC depend on the conditions of thermal treatments and the type of surface finish. The interfacial condition of indium joint is the key to heat dissipation performance. Therefore, the interfacial mechanism and mechanical properties of indium joints have been investigated by applying different surface finishes and various heat treatments in this study.
In this paper, the interfacial reactions of indium jointed with different surface finishes (Au/Ni(V) and Au/Ni) have been investigated, respectively. For studying the interfacial microstructure evolution of the indium joints, they have been treated with different thermal treatments, including reflow process (with 245oC peak temperature) and high temperature storage tests (aging at 100oC, 125oC, and 150oC for 250~1000 hours). The interfacial morphologies of indium joint and the growth behaviors of IMC have been observed, and the interfacial IMC has been identified as Ni28In72 phase. For Au/Ni(V) surface finish, there is rock shaped IMC grains on the surface of Ni(V) layer, and the grain size of IMC increases with the increase of the reflow cycle. In Ni(V) layer, there is a significant In/Ni inter-diffusion reaction after different thermal treatments. For Au/Ni surface finish, the thickness of IMC increases with the increase of aging time and temperature, and the growth rate of IMC increases with the elevating storage temperature. In the results of shear tests, it indicates that increasing IMC thickness has no significant effect on the shear strength of indium joints, and moreover, the failure mode of all indium joints are ductile fracture in the bulk of indium.

Characterization and TEM analysis of electroless Ni-P plating with various P and S content
發表編號:S19-3時間:16:25 - 16:40

Ming-chun Hsieh

Electroless Ni-P plating film is known for its capability of being tuned into different chemical, mechanical, electrical and magnetic properties. Therefore, electroless Ni-P plating film, as a low-cost and facile functional surface treatment, has been popularly used in various applications. In electrical industrial field, as the trend to substitute Si chip with wide band gap materials such as SiC or GaN in order to achieve high-function, dense-current = more compact in dimension power modules, related packaging components are requested to endure high temperature environment usage. However, in the case of electroless Ni-P plating film, as phosphorous is over-saturated, IMC= intermetallic compound such as Ni3P precipitates after high temperature aging. As a result, electroless Ni-P plating film becomes fragile after high temperature aging. Fragile electroless Ni-P plating film results in cracks on substrate surface and causes discontinuity in electrical circuit and eventually module breakdown. Considering of Ni’s excellent stability in ambient atmosphere and its multi-functionality, the importance of high-temperature resistant electroless Ni-P plating film development is obvious. In this study, the authors propose an innovative electroless Ni-P plating film whose cracks do not occur after severe environment tests by suppressing phosphorous content and sulfur content.

Cyber-Physical System of laser micro processing for semiconductor package fabrication
發表編號:S19-4時間:16:40 - 16:55

Yohei Kobayashi, Hiroharu Tamaru, Kazuyuki Sakaue, Haruyuki Sakurai, Kohei Shimahara, Tsubasa Endo and Shuntaro Tani

The process rule of a semiconductor is getting smaller and smaller. Accordingly, the size of a via hole or line and space in a package is also becoming smaller. In addition, yearly evolving materials are being tested as substrate materials for the next-generation higher-frequency circuit boards or buildup substrates. The laser micro-hole drilling is a key technology for realizing these demands, and development of lasers with higher output power and shorter wavelengths is being vigorously conducted in order to drill smaller holes at higher speeds. On the other hand, significant challenges exist for drilling small holes in newly emerging materials. Depending on the parameters, drilling can damage the copper film behind the hole or chip the material due to its own brittleness. Therefore, it is necessary to optimize various processing parameters such as laser pulse width, pulse energy, repetition frequency, irradiation time, wavelength, and beam trajectory according to the required design, including hole diameter, aspect ratio, and pitch. Currently, parameter optimization is being done manually in a trial-and-error manner, which could take several months or even years for new materials and designs. The time required for feasibility testing can slow down the design process, and also forces material manufacturers to spend a great deal of time examining what kind of material composition will actually be used.
For this reason, fully automated parameter optimization is desired, which has been hindered by several factors. One of the most significant factor is that post-processing observation and evaluation cannot be done without human intervention, which is a barrier to algorithm-based optimization. To overcome this barrier, we have constructed a cyber-physical system that can perform not only processing, but also micrometer-accurate sample handling, measurements, evaluations, and parameter suggestions in a completely autonomous manner.
Figure 1 shows a picture of a fully-automated laser processing machine named Meister Data Generator (MDG). It works 24 hours, 7 days a week. There are many types of laser oscillators in the system, and laser parameters such as pulse duration or wavelength can be tested under a variety of conditions. For example, grid search to find a suitable parameter set in a 4-dimensional parameter space is an easy task for MDG. If one simply performs a grid search, the machine can test 10,000 drilling conditions in a few hours. Figure 2 shows an example of a result of a laser drilling in glass material with ten thousand different laser parameters taken with a scanning electron microscope.
One of the main features of this system is that all data on processing and measurement, obtained in the process of grid search or algorithm-based parameter optimization, are stored in a unified database. Huge amount of high precision data can be used to make a deep neural network (DNN) to make a laser processing simulator [1]. With the simulator, one can perform an intensive parameter in a cyber space, making this system what one would call a Cyber-Physical System.
Since laser processing is highly nonlinear and results can differ even under the same laser irradiation conditions, it was unclear whether the feedback would work. It is possible to have an artificial intelligence (AI) in the MDG system to perform the actual trial and error. We have found that Bayesian optimization works well for a feedback loop of the laser processing [2]. We can ask MDG to find a good parameter set with a feedback process with the help of AI. It helps to reduces a lead time of a production system.

Another important feature is that this system can be used as a cloud service via a browser. Once the sample to be tested is set in MDG, the processing-measuring cycle and parameter optimization can be performed as a web service. The user who accesses the system from anywhere in the world does not have to care about where it is located in the same way as the case for supercomputers. The user will not even need to care if MDG really executes an experiment or it uses a simulator to respond in the future when the simulators mature. This system works not only for the parameter finding for laser micro-processing but also for an experiment to figure out physics behind the laser processing phenomena, which would reveal the extremes of processing.
[1] Shuntaro Tani, and Yohei Kobayashi, "Ultrafast laser ablation simulator using deep neural networks," Sci Rep 12, 5837 (2022).
[2] Keiichi Bamoto, Haruyuki Sakurai, Shuntaro Tani, and Yohei Kobayashi, "Autonomous parameter optimization for femtosecond laser micro-drilling," Optics Express vol. 30, pp. 243-254 (2022)

Effect of Ni existence on void formation in micro-vias of high density interconnect (HDI)
發表編號:S19-5時間:16:55 - 17:10

Ming-chun Hsieh, Zheng Zhang, Jeyun Yeom, Aiji Suetake, Hiroyoshi Yoshida, Chuantong Chen, Massahiko Nishijima, Joohaeng Kang, Hidekazu Honma, Yu Shimizu, Yuhei Kitahara, Koji Kita, Takashi Matsunami, Kuniaki Otsuka, and Katsuaki Suganuma

IC chips and electrical components are electrically connected by fine-pitched conductive lines, micro-vias and PTHs (plating through hoes) among multi-layered PCBs with high density interconnect (HDI) inside of various electrical devices. Nowadays, along with requests of modules to be more dimensionally compact, lots of material and manufacturing improvement effort has been made. One of the major change is the diameter of micro-via has been dramatically decreased. In late 20th century, the diameter of micro-via was 125 μm. And now, the diameter is under 10 μm, which is approximately 1/13 of the old-time size. On the other hand, void occurrence in micro-vias has been reported for decades. As voids seldom cause fatal damages in big-diameter micro-via, the consciousness toward voids in micro-via was not high. However, recently micro-vias encounter reliability problems such as delamination and cracks. We can assume the impact of voids become more obvious in nowadays tiny-diameter micro-vias. Moreover, together with the trend to substitute IC chip material from Si to wide band gap semiconductor such as SiC and GaN, which can work at higher temperature (> 200 ℃) than conventional Si, micro-via, as an essential electrical component, is facing challenge of its reliability in severer environment. In this study, the authors investigated possible related content = nickel, whose ion is added in conventional plating solution for stress releasing purpose in electroless Cu plated layer, that may have influence on void formation. Morphological and ingredient difference between voids in conventional electroless copper plating layer with Ni ion additive and a new electroless copper plating layer called “OPC-FLET”, which is without Ni ion additive is analyzed and compared.

A Plasma Enhanced CVD Technology for Solving Issues on Sidewall Deposition in Trenches and Holes
發表編號:S19-6時間:17:10 - 17:25

Masaharu Shiratani

EUV lithography drives the miniaturization of semiconductors for higher integration, and semiconductor manufacturing is in transition from two-dimensional (2D) to three-dimensional (3D) structures [1], which plays a crucial role in supporting packaging for edge computing such as Internet-of-Things (loT). 3D power scaling enables higher integration without reducing the size of transistors by arranging them vertically instead of horizontally. One of the important processes in manufacturing 3D structured semiconductors is the formation of films on sidewalls of trenches and holes. Such films are often deposited by plasma enhanced chemical vapor deposition (PECVD) [2]. Due to the gas decomposition by plasma, PECVD method archives a high deposition rate of good quality films at low temperature, which is an advantage over other deposition methods such as atomic layer deposition (ALD) [3]. However, this does not fully meet the actual manufacturing requirements. For instance, SiO2 dielectric films deposited by PECVD usually have low coverage and poor film quality on sidewall of trenches and holes compared to films on surface. Ion impact is one of the most important factors contributing to improving step coverage and film quality in trenches and holes. One parameter that characterized ion impact is the ion energy distribution function (IEDF) and ion angular distribution (IADF) [4,5]. There are strong needs for low temperature deposition in trenches and holes. Here, we show a plasma CVD technology for solving such issues on sidewall deposition in trenches and holes, based on experimental and simulation results.
Our PECVD experiments clearly demonstrated that amplitude modulated discharge PECVD is an excellent technology for solving such issues on sidewall deposition in trenches and holes [6, 12]. Details on the experiments will be described in the proceedings paper and presented at the conference.
To reveal the mechanism leading to the excellent experimental results. We carried out particle-in-cell/Monte Carlo collision (PIC-MCC) simulation [12]. We investigated plasma parameters using 1d3v PIC-MCC simulation in the capacitively coupled discharge Ar plasma at 10 mTorr with and without amplitude modulation. AM frequency f_AM is varied from 1 kHz to 1 MHz to evaluate the AM frequency dependence on the plasma parameters. The electron density, axial electric field E_z, and IEDF vary with time in AM discharges. The variation of electron density decreases with increasing the AM frequency above 10 kHz, one of the peak energy of IEDF decreases with increasing the AM frequency above 1 MHz, and one of E_z shows no significant difference with respect to the AM frequency. In other words, our simulation shows that the amplitude modulation frequency of amplitude modulated discharge PECVD is a good tuning knob to control IEDF and IAFD. The behavior of ions inside the microstructure of substrates such as holes and trenches, and the AM frequency dependence on electron energy distribution function (EEDF) which is related to radical generation rates will be reported at the conference.
In short, we show a plasma CVD technology for solving such issues on sidewall deposition in trenches and holes, based on experimental and simulation results.

Evolution of Interfacial Voids for Nano-Twinned Cu Joint
發表編號:S19-7時間:17:25 - 17:40

Jian-Yuan Huang

In this paper, we deposited highly (111)-oriented nano-twinned Cu as the Cu joints, and the joints were bonded at 250 ℃. To study voids evolution more precisely, we developed the new characterization method by plan-view images of focused ion beam (FIB).
Furthermore, we analyzed the interfacial voids of the Cu joints after annealing. We studied the quantitative analysis of the interfacial voids distribution, and we also examined the kinetics study of voids evolution. We classified the evolution of interfacial voids during the thermal compression bonding (TCB) process into three different stages, including plastic deformation, creep deformation, and void ripening. The interface and voids evolution are impacted by grain boundary and lattice diffusion.
On the basis of our experimental data, we found that voids ripen significantly at early stage of the TCB process, which was owing to higher diffusivity of grain boundary diffusion. However, if the bonding interface was eliminated during the TCB process, the sizes of interfacial voids do not change obviously due to lower diffusivity of lattice diffusion.


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