Advanced Semiconductor Manufacturing Research Articles

Recent Advances in CMP Slurries: Composition and Analysis Perspectives

Chemical Mechanical Planarization (CMP) slurries play key role during planarization process in advanced semiconductor manufacturing, serving to planarize wafer surfaces and minimize unevenness in multi-layered device scheme. This paper provides a comprehensive review of the composition of CMP slurries and the analytical methods used to evaluate their components. The primary constituents of CMP slurries―abrasive particles, chemical agents, and various additives―are examined in detail, highlighting their roles and interactions. We report the latest research trends in CMP slurry composition and analytical methods, offering insights into future research directions and providing foundational information for optimizing CMP slurry performance. This, in turn, is expected to contribute to the ongoing advancement of the semiconductor industry and the fabrication of high-performance devices.

Toray commercializes PFAS-free mold release film

On May 22, 2024, Toray Industries, Inc., announced that it recently commercialized a mold release film for advanced semiconductor applications that is free of per- and polyfluoroalkyl substances (PFAS; see Glossary note 1). The film's material reportedly does not contain the organic fluorine compounds that European and other countries are looking to regulate. The film could reportedly help improve operational rates in advanced semiconductor manufacturing by slashing problematic mold contamination by more than 80%.

(Invited) The Use of Plasmas for Isotropic Atomic Layer Etching

Atomic layer etching (ALE) is set to be a vital part of the advanced semiconductor manufacturing toolbox, known for its precise control of the film thickness and minimal damage. These benefits are possible due to the sequential self-limiting half-cycles that are employed within an ALE process. Initially, ALE was underestimated due to low etch rates, but it is now experiencing a renaissance due to the requirements imposed by further downscaling.1 The ALE community is mostly divided into two groups: plasma anisotropic and thermal isotropic etching. 2 In this work, the focus is on exploring isotropic plasma ALE, which is a relatively unexplored direction. This approach involves using plasma radicals to modify and/or etch material isotropically, while minimizing the directional ion component of the plasma. Isotropic plasma ALE can offer several benefits over strictly thermal ALE, such as higher etch rates, lower operating temperatures, and the ability to etch more resistant materials.In this talk we will first address some of the different techniques employed for plasma isotropic ALE in the literature. Subsequently, we will discuss our own work, which has focused on two isotropic plasma ALE chemistries. The first involves alternating between plasma fluorination and ligand-exchange half-cycles, this ALE chemistry has been found to be effective for etching Al2O3, HfO2, AlN, and GaN films.3,4 Surface contaminants and roughness were found to be reduced post ALE, an aspect that is particularly important for AlN and GaN films that are used in quantum, power semiconductor and LED applications. The second approach involves using diketone (e.g. acetylacetone, hexafluoroacetylacetone) doses followed by either H2 or O2 plasma exposures for ALE of Al2O3 and ZnO.5 The diketone in this process acts to etch the surface, however due to competitive adsorption of different diketone orientations an etch inhibition layer forms. The plasma step is then utilized to clean the surface, removing the self-limiting inhibitor layer, enabling etching to continue in the next cycle. This ALE chemistry diverges from the typical modification/removal ALE cycle, where a modified layer if often observed on the material post ALE. In comparison the diketone ALE chemistry does not rely on modification of the surface making it an ideal process for surface cleaning. This approach provides improved selectivity over the plasma fluorination process and also enables smoothing.Plasma isotropic ALE is a growing part of the ALE community that can help accelerate the adoption of ALE in academia and industry. The potential benefits of ALE are only just beginning to be explored, and more processes are needed to etch the ever-increasing range of materials utilized in IC manufacturing. Kanarik, K. J., Tan, S. & Gottscho, R. A. Atomic Layer Etching: Rethinking the Art of Etch. J Phys Chem Lett 9, 4814–4821 (2018).George, S. M. Mechanisms of Thermal Atomic Layer Etching. Acc Chem Res 53, 1151–1160 (2020).Chittock, N. J. et al. Isotropic plasma atomic layer etching of Al2O3 using a fluorine containing plasma and Al(CH3)3. Appl Phys Lett 117, 162107 (2020).Wang, H., Hossain, A., Catherall, D. & Minnich, A. J. Isotropic plasma-thermal atomic layer etching of aluminum nitride using SF6 plasma and Al(CH3)3. 1–14 (2022) doi:arXiv.2209.00150.Mameli, A., Verheijen, M. A., Mackus, A. J. M., Kessels, W. M. M. & Roozeboom, F. Isotropic Atomic Layer Etching of ZnO Using Acetylacetone and O2 Plasma. ACS Appl Mater Interfaces 10, 38588–38595 (2018).

Guest Editorial Special Section on the 2022 SEMI Advanced Semiconductor Manufacturing Conference

Guest Editorial Special Section on the 2022 SEMI Advanced Semiconductor Manufacturing Conference

Coherent spin–valley oscillations in silicon

Electron spins in silicon quantum dots are excellent qubits because they have long coherence times, high gate fidelities, and are compatible with advanced semiconductor manufacturing techniques. The valley degree of freedom, which results from the specific character of the Si band structure, is a unique feature of electrons in Si spin qubits. However, the small difference in energy between different valley levels often poses a challenge for quantum computing in Si. Here, we show that the spin-valley coupling in Si, which enables transitions between states with different spin and valley quantum numbers, enables coherent control of electron spins in Si. We demonstrate coherent manipulation of effective single- and two-electron spin states in a Si/SiGe double quantum dot without ac magnetic or electric fields. Our results illustrate that the valley degree of freedom, which is often regarded as an inconvenience, can itself enable quantum manipulation of electron spin states.

Japanese Semiconductor Industry’s Collaboration with Taiwan Semiconductor Manufacturing Company

On 17 December 2021, Japan granted administrative approval to Taiwan Semiconductor Manufacturing Co Ltd (TSMC) to build a US$7 billion semiconductor chip-manufacturing foundry in Japan. The collaboration between the Sony Group and the world’s No. 1 Taiwanese chipmaker is named Japan Advanced Semiconductor Manufacturing, Inc. and will provide foundry service with 22/28-nanometre capability. This joint venture has taken off due to mutual commercial interest and support from the Japanese and Taiwanese authorities.

Alliances Relation Change between Japanese Tech Firms and Taiwanese Ones: Alliances Cases of Sharp & Foxconn vs. Sony & TSMC

The Sony, Denso and TSMC plan to make a joint venture called the ‘Japan Advanced Semiconductor Manufacturing (JASM)’ as a new fab by 2024. The alliance is very significant when considering the repetitive chip shortage and the geopolitical issues like the ‘Chip 4’ alliance. This study looks into the alliances relation change between Japan and Taiwan by comparing the Sony & TSMC case with the Sharp & Foxconn one. The Sharp & Foxconn case is also meaningful because Foxconn became a major shareholder of Sharp which had been Japanese pride of consumer electronics for a long time. The comparative analysis for two cases is to be made from four aspects; the alliance type & purpose, synergy type, market segmentation and government position. As a result, the Sharp & Foxconn case takes an intra-industry nature as a forward integration. Whereas, the Sony & TSMC case has both intra-industry and inter-industry nature as a backward integration. The synergy type of Sharp & Foxconn case is a reciprocal one with few government supports. But the Sony & TSMC case can expect a sequential synergy with a strong government support.

Guest Editorial Special Section on the 2020 and 2021 SEMI Advanced Semiconductor Manufacturing Conferences

We are very pleased to introduce this Special Section covering ASMC 2020 and ASMC 2021. These two conferences were held virtually, like most other technical conferences over the last two years; fortunately, the technical community has now reverted to in-person conferences, allowing attendees more personal interaction and the ability to focus on the conference. This includes ASMC 2022 which was held in May of this year, as we hope the COVID-19 pandemic is for the most part behind us.

Effect of pH and Ion Concentration on Wetting of Nanoholes and Water Structuring

Like supervias in the back end of line, and deep contact holes with an aspect ratio higher than sixty in 3D-NAND memory, higher aspect ratio patterning is one of the important issue in advanced semiconductor manufacturing. As with the difficulty of patterning, the technique of cleaning the nanostructure so that it does not affect the next process is also considered important. In semiconductor cleaning, chemicals such as HF and NH4OH that include reactant ions are used for cleaning the semiconductor surface. Ions in bulk aqueous solutions were shown either as structure making or breaking effects in Marcus’s study (Chem. Rev., 2009). The classification of ions as structure making or breaking was confirmed using 1 M solutions in nanotrenches (Vereecke, Micro. Eng., 2021). This shows there is an ion effect, and it can change properties between solution and material surface. The addition of structure breaking ions in HF solutions was used to decrease the etch rate of oxide between fins (Vereecke, Micro. Eng., 2022). Going further from Marcus’s study, we focused on pH and ion concentration in the addition of structure making ions. In the nanostructure, it was considered necessary to study because the surface properties may vary depending on the degree of structuring and the influence of the zeta potential depending on the concentration and pH of the ions.In this work, we used an in-situ ATR-FTIR (Attenuated Total Reflection – Fourier Transformed Infra-Red) spectroscopy technique (Nicolet iS50 AEM, Thermo Fisher Scientific, USA) to characterize the wetting of nanostructures embedded in a silica matrix by UPW (Ultra-Pure Water) and electrolyte solutions, and a streaming zeta potential analyzer (SURPASS3, Anton Paar, Austria) to characterize the surface potential of flat surfaces of the same material. Wetting in the nanostructures was characterized by an analysis of the ratio of the OH stretching peak to OH bending peak (Vrancken, Langmuir, 2016). Also, dissolution of CO2 in the wetted nanostructures was monitored to compare the solubility and diffusivity in the nano-confined solutions with that in bulk solutions. In this experiment, we used dense arrays of silicon nanoholes in a PEALD SiO2 matrix (depth of about 300 nm, diameter of about 20 nm, and pitch 90 nm) that were fabricated on Si wafers using arrays of nanostructures, as described in Vereecke (2021). Crystal drying, wetting with a solution, and applying CO2 were performed in this order. HI, HBr, HCl were used for chemicals and pH 1, 2, 3, 4 was used for pH.Monitoring of the OH stretching to bending ratio showed little improvement in wetting as a function of pH between 1 to 4 as compared to UPW. Also, little difference was observed when changing the acid from HCl to HBr and HI, with anions of higher structure breaking properties according to Marcus (Chem. Rev., 2009). A higher CO2 solubility and a lower CO2 diffusivity were measured in the nanoconfined solutions as compared to bulk UPW, indicative of water structuring. A higher CO2 solubility at pHs 2-3 as opposed to pH 1 and 4 may originate from the proximity to the isoelectric point. Results will be complemented with tests performed at the isoelectric point and pH 0, with 1 M solutions where structure breaking properties of the used anions are expected to be stronger and wetting might be improved.

Effect of pH and Ion Concentration on Wetting of Nanoholes and Water Structuring

In advanced semiconductor manufacturing, with deep contact holes with an aspect ratio higher than sixty in 3D-NAND memory, higher aspect ratio patterning is one of the important issues in advanced semiconductor manufacturing. In this work, we used an in-situ ATR-FTIR spectroscopy technique to characterize the wetting of nanostructures embedded in a silica matrix by UPW and electrolyte solutions as a function of pH. There was little influence of pH on the wetting of nanoholes in the studied range of 1 to 4, but wetting seemed to be less close to the isoelectric point. Also, HCl seemed to lend a better wetting compared to HI, in opposition to their structure breaking effect according to Marcus. A correlation was observed between these observations and the CO2 solubility, indicative of the influence of water structuring.

Ice-VII-like Structure Observed By XRD in Water Confined in Silica Nanoholes

In advanced semiconductor manufacturing, deep hydrophilic nanoholes are found in various applications, which require a wet clean after patterning. However, wetting of high aspect ratio nanoholes was showed to be incomplete for non-settled reasons. In this study, X-ray diffraction (XRD) was used to characterize water confined in deep nanoholes with 20 nm diameter. Long XRD measurements were made possible by the anomalous capillary condensation occurring in these nanoholes, which was proved by Attenuated Total Reflection – Fourier Transformed Infra-Red measurements. Condensation occurred in nanoholes submitted to the clean-room air with a relative humidity (RH) of about 40%, while no condensation was observed under a N2 flow with a RH of about 30%. XRD measurements showed the presence of small peaks varying as a function of the XR incidence angle, which were not present in the Si and oxide references. These peaks gave evidence for structuring of water confined in nanoholes.

Valley Splitting in Silicon from the Interference Pattern of Quantum Oscillations.

We determine the energy splitting of the conduction-band valleys in two-dimensional electrons confined in silicon metal oxide semiconductor Hall-bar transistors. These silicon metal oxide semiconductor Hall bars are made by advanced semiconductor manufacturing on 300mm silicon wafers and support a two-dimensional electron gas of high quality with a maximum mobility of 17.6×10^{3} cm^{2}/Vs and minimum percolation density of 3.45×10^{10} cm^{-2}. Because of the low disorder, we observe beatings in the Shubnikov-de Haas oscillations that arise from the energy splitting of the two low-lying conduction band valleys. From the analysis of the oscillations beating patterns up to T=1.7 K, we estimate a maximum valley splitting of ΔE_{VS}=8.2 meV at a density of 6.8×10^{12} cm^{-2}. Furthermore, the valley splitting increases with density at a rate consistent with theoretical predictions for a near-ideal semiconductor-oxide interface.

Qubits made by advanced semiconductor manufacturing

Full-scale quantum computers require the integration of millions of qubits, and the potential of using industrial semiconductor manufacturing to meet this need has driven the development of quantum computing in silicon quantum dots. However, fabrication has so far relied on electron-beam lithography and, with a few exceptions, conventional lift-off processes that suffer from low yield and poor uniformity. Here we report quantum dots that are hosted at a 28Si/28SiO2 interface and fabricated in a 300 mm semiconductor manufacturing facility using all-optical lithography and fully industrial processing. With this approach, we achieve nanoscale gate patterns with excellent yield. In the multi-electron regime, the quantum dots allow good tunnel barrier control—a crucial feature for fault-tolerant two-qubit gates. Single-spin qubit operation using magnetic resonance in the few-electron regime reveals relaxation times of over 1 s at 1 T and coherence times of over 3 ms.

Static and dynamic interaction between polyvinyl acetal brushes and flat surfaces—Measuring near-surface brush volume ratio and nodule volume change for moving brushes

The cleaning mechanism for brush scrubbing, known as the contact-type cleaning method, utilizes the direct contact of impurities onto brushes or brush-induced fluid flow depending on the contact condition. Applying brush cleaning to nanosized defects in advanced semiconductor manufacturing requires understanding of the interaction between the brush and scrubbing surface under actual operating conditions. We observed the near-surface brush volume ratio and brush nodule deformation using high-speed photography to obtain insights into efficient nanosized cleaning. Evanescent fields on a prism and a convex lens facilitate the definition of the observation depths of several hundred nanometers. Starting rotation experiments revealed a drastic reduction in the brush volume ratio, indicating that the static contact is far from the dynamic contact. The volume change during roller brush nodule deformation depends on the surface material. Furthermore, large friction materials exhibit large deformation and rapid recovery. These nodule deformations may generate a different fluid flow near the surface owing to the brush's fluid absorption and desorption.

Dynamic white-light interferometry via multiwavelength tilt iteration and sliding local least squares.

The growing interest in microprofile measurements for advanced semiconductor manufacturing and electronic glass screens has stimulated the demand for in situ dynamic white-light interferometry (DWLI). However, it is challenging to perform vibration-insensitive measurements because of the broad-spectrum interference. In this Letter, we report a vertical scanning DWLI using multiwavelength tilt iteration and sliding local least squares. Numerical simulations and comparative experiments were conducted to verify the principle and performance of the proposed method. To the best of our knowledge, this is the first time such a DWLI has been proposed to achieve excellent vibration-resistant performance without using complex photoelectric compensation systems.

Machine learning-based virtual metrology on film thickness in amorphous carbon layer deposition process

A stringent manufacturing process control is important to achieve reliable process control in nanoscale semiconductor manufacturing processes. Based on the advanced process control mechanisms in advanced semiconductor manufacturing, virtual metrology (VM) can be used to reduce the time and cost incurred in conventional metrology. This paper proposes a VM model based on the neural network (NN) architecture for predicting film thickness in amorphous carbon layer deposition processes, which is used for etch hard mask in high-aspect-ratio etch processes. A series of deposition experiments was conducted using the Box–Behnken design. The equipment status data and in situ optical emission spectroscopy (OES) sensor data were collected. Conventional recipe-based process modeling with the equipment status data showed a reasonable correlation with the deposited film thickness, and the augmentation of in situ plasma chemistry information through OES improved the machine learning accuracy with artificial neural networks. Consequently, our model’s prediction accuracy was approximately 99.5% for R2 when both equipment status data and OES sensor data were used as training data, as compared to when only equipment status data were used to train the model. Therefore, we recommend that in situ OES sensor data, as well as equipment status data, should be used in training NN-based VM models for high prediction accuracy.

A four-qubit germanium quantum processor.

The prospect of building quantum circuits1,2 using advanced semiconductor manufacturing makes quantum dots an attractive platform for quantum information processing3,4. Extensive studies of various materials have led to demonstrations of two-qubit logic in gallium arsenide5, silicon6-12 and germanium13. However, interconnecting larger numbers of qubits in semiconductor devices has remained a challenge. Here we demonstrate a four-qubit quantum processor based on hole spins in germanium quantum dots. Furthermore, we define the quantum dots in a two-by-two array and obtain controllable coupling along both directions. Qubit logic is implemented all-electrically and the exchange interaction can be pulsed to freely program one-qubit, two-qubit, three-qubit and four-qubit operations, resulting in a compact and highly connected circuit. We execute a quantum logic circuit that generates a four-qubit Greenberger-Horne-Zeilinger state and we obtain coherent evolution by incorporating dynamical decoupling. These results are a step towards quantum error correction and quantum simulation using quantum dots.

Characterization of Wetting of Deep Silica Nanoholes by Aqueous Solutions Using ATR-FTIR

In advanced semiconductor manufacturing, deep hydrophilic nanoholes are found in various applications, which require a wet clean after patterning. In this work, we use an in-situ ATR-FTIR spectroscopy technique to characterize the wetting of nanoholes in a silica matrix by UPW and electrolyte solutions. Wetting was much slower than predicted by a numerical model, while temperature cycling evidenced the formation of unexpectedly stable gas pockets in the wetted nanoholes. Water structuring in the nanoholes was characterized by an analysis of the OH stretching peak. Besides, monitoring the dissolution of CO2 in the wetted nanoholes allowed to compare the diffusivity in the nano-confined solutions with that in bulk solutions. Our results strongly suggest that the gas pockets were stabilized by the decreased gas diffusivity resulting from water structuring.

Wetting of deep hydrophilic nanoholes by aqueous solutions

In advanced semiconductor manufacturing, deep hydrophilic nanoholes are found in various applications, which require a wet clean after patterning. In this work, we use an in-situ ATR-FTIR spectroscopy technique to characterize the wetting of nanoholes in a silica matrix by UPW and electrolyte solutions. Besides, water structuring in the nanoholes was characterized by an analysis of the OH stretching peak, while monitoring the dissolution of CO2 in the wetted nanoholes allowed characterizing the diffusivity and the permittivity in the nano-confined solutions. The formation of gas pockets or nanobubbles upon wetting of nanoholes was evidenced by heating tests showing an hysteresis in plots of the OH stretching to bending ratio when temperature was decreased. This was accompanied by water structuring that was characterized by a large fraction of the OH stretching peak showing up at frequencies higherthan that of ice. Dissolution of CO2 in confined solutions showed a solubility higher by a factor up to about 50 compared to bulk UPW, indicating a decrease in permittivity. The wetting time decreased significantly by heating the solution, while the addition of NaI or CoCl2 at 1 M concentration, respectively a structure making or breaking salt, had no significant effect at room temperature. Finally, a slower diffusion, as measured with CO2, was most likely the cause of the surprisingly long lifetime of the nanobubbles formed upon wetting of the nanoholes.

Guest Editorial Special Section on the 2019 SEMI Advanced Semiconductor Manufacturing Conference

Dear readers—We hope this editorial finds you and your family safe as we and the world battle—or, hopefully at the time of this publication, recover from—perhaps the greatest world-wide health crisis in the last century, COVID-19. Fortunately, the contributions of our semiconductor manufacturing industry over the last 40 years have put us in a much more comfortable position than those who faced past pandemics. It is likely that many of you have been working from home using your high-speed Internet connection and one of multiple computers that you and most families own. The worldwide Internet and computing infrastructure that our industry has enabled allows many engineers and others to VPN into work, communicate and share documents via e-mail, and attend video meetings. On the personal side, you can keep up with family and friends, with the latest news, and information and instructions from the government. Semiconductors allow your children to attend (or perhaps teach) school remotely. Certainly school aged children will be missing contact with their friends, but, fortunately, they can still video chat, message, or at least call friends with their mobile phones. The whole family can enjoy their favorite shows and movies via streaming services, and of course try new video games.