Papers by Keyword: Particle Removal

Abstract: The EUV lithography process is increasingly employed in the advanced semiconductor process, and high-NA EUV equipment is being developed for high-volume manufacturing. Therefore, particle contamination control for EUV masks is a key success factor for the yield increase of the EUV lithography process in the future and for this, the needs of EUV pellicle will increase. Although materials for the EUV pellicle membrane are still under development, unlike ArF pellicles, its fabrication is complicated and difficult, resulting in low production yield and high production costs. To reduce EUV pellicle operating costs, it is possible to consider ways to reduce production costs by enhancing the yield of EUV pellicle or reusing particle contaminated EUV pellicle by particle removal. Both methods require damage-free particle removal technology of EUV pellicle. Pinpoint particle removal technology, a cleaning technology that satisfies these requirements, was developed, and particles bigger than 5 μm could be removed in a cleanroom environment without damaging fragile EUV pellicle. The possibility of the damage-free EUV pellicle cleaning process was verified through the process window evaluation of Pinpoint cleaning technology.

Abstract: Cleaning tests with ultrasound-superposed water jets are performed to explore the optimal injection distance from the jet nozzle to a glass plate spin-coated with small silica particles (as a cleaning sample). The cleaning performance is evaluated based on particle removal efficiency (PRE) that is calculated using the haze method. Visualization of the water jet and liquid film flow over the cleaning target shows that the jet flow with short injection distance tends to be in a steady state, while the water jet shape instability grows for long injection distance, leading to atomization of the jet. The cleaning tests with varying the injection distance suggest that there exists an optimal injection distance at which the PRE becomes maximal.

Abstract: The process of quickly removing abrasive particles of silica and ceria slurries is important in the use of CMP equipment. Megasonic cleaning of nozzle injection type is one of a variety of post-CMP cleaning methods and its performance including cleaning efficiency and erosion was explored experimentally with parametric studies. In the cleaning process, it is favorable to achieve both high efficiency and low damage. The cleaning efficiency was defined by particle removal efficiency (PRE) with a glass sample spin-coated with small silica particles; the damage was detected from mass loss of aluminum foils after the cleaning. The cleaning tests show that the performance of nozzle injection megasonic cleaning depends significantly on ultrasound frequency and water temperature. Toward more efficient and less erosive cleaning, the nozzle injection angle is also expected to play a key role.

Abstract: The removal of particle contamination is key to maximize yield. Some common particle removal techniques are not relevant anymore when complex and fragile structures are present on the surface. This led to the development of new cleaning processes based on innovative concepts to improve particle removal efficiency without any pattern damage. Some of these processes rely on a resist film lift off. One of these particle removal processes is studied in this paper. The process consists in some resist spin-coating followed by a diluted ammonia dispense to remove this film, which results in particle removal. This specific resist film is made of two immiscible organic polymers. A study was conducted to understand how the organization of these two polymers in the film is key for the film lift-off and the cleaning efficiency. This organization was shown to depend on the substrate contact angle and the resist formulation. A surface preparation is required on hydrophobic surface to reduce their water contact angle and ensure the efficiency of the process. As a result, compared to a high velocity aerosol cleaning technique, this resist peeling process requires multiple steps and a significant process time. A Particle Removal Efficiency study was then performed on blanket wafers to determine and understand how the different process parameters impacted on the cleaning efficiency. It led to the optimization of this process efficiency on blanket wafers. A comparison between an optimized process and a high velocity aerosol cleaning technique underlined the potential of such a process. Compared to high velocity aerosol cleaning, it demonstrated higher efficiency on blanket wafers, without causing any pattern damage on patterned wafers. These results lead to promising perspectives for using this process in the cleaning of fragile structure or targeting small particles with high adhesion.

Abstract: In this study, organic strip, particle removal efficiency and wettability were investigated at different mixing concentrations of diluted Sulfuric-Peroxide-HF (DSP⁺) solutions with and without the addition of IPA. Organic strip evaluation was carried out with KrF photoresist (PR), and the strip rate was increased rapidly with the increase in H₂SO₄ concentration mixed with DI water (DIW). The effects of H₂O₂ and IPA addition on diluted H₂SO₄ were observed below 30 vol% of H₂SO₄. The thickness of PR was increased with the addition of H₂O₂ to the solutions and the strip rate was increased when IPA was added. Silica particles were used to evaluate particle removal efficiency. The concentration of HF was the predominant factor of increasing PRE, and the addition of H₂SO₄ and H₂O₂ assisted in obtaining high PRE, while IPA addition reduced PRE. Decreasing of contact angle was observed with an increase of IPA addition to DSP⁺ solutions, and improved wettability of DSP⁺ solutions was expected to effectively clean particles in high-aspect-ratio (HAR) contact holes.

Abstract: Visualization experiments are performed to examine the role of acoustic cavitation bubbles that appear in 0.43-MHz ultrasonic water flow spreading over glass surfaces in the context of physical cleaning. The cleaning performance is evaluated using glass samples on which small silica particles are spin-coated. The visualization suggests that acoustic cavitation bubbles play a major role in particle removal as in the case of conventional cleaning with ultrasonic cleaning baths.

Abstract: Thin organic self-assembled monolayer films are used to promote adhesion and seal the pores of metal oxides as well as direct the deposition of layers on patterned surfaces. Defects occur as the self-assembled monolayer forms, and the number and type of defects depend on surface preparation, deposition solvent, temperature, time and other parameters. Particles commonly deposit during organosilane self-assembly on metal oxide surfaces. The particles are defects because they are prone to react in subsequent processing, which may not be desirable if the organosilane serves as a pore sealant or passivation layer. Cleaning the organosilane by solvent extraction to remove non-polar agglomerates followed by an aqueous mixture of ammonium hydroxide and hydrogen peroxide, which is Standard Clean 1, a common particle removal step for silicon surfaces, produced monolayers with few agglomerates based on atomic force microscopy without etching the layer. The combined cleaning sequence contained fewer particles than separate cleaning steps, showing that the cleans removed particles with different compositions. The thickness and contact angle of cleaned monolayers was comparable to those made using a costlier solvent.

Abstract: Wet cleaning has become challenging as the feature size of semiconductor devices decreased to sub-5 nm nodes. One of the key challenges is removing various types and sizes of particles and contamination from complex and fragile 3D structures without pattern damage and film loss. Conventional physical cleaning methods, such as dual-fluid spray or megasonic cleaning, are being used for the particle removal process. However, in advanced device nodes, these methods induce pattern damage and film loss. In this paper, we describe a novel particle removal technology called Nanolift which uses a polymer film consisting of two organic resins with different functions and achieved high particle removal efficiency on various types and sizes of particles with no pattern damage and minimum film loss.

Abstract: Sulfuric Peroxide Mixture (SPM, H₂SO₄ + H₂O₂) has been widely used in semiconductor manufacturing processes due to its high reactivity and attractive price. However, SPM releases SO₄^2- ions that can be high impact on the environmental contaminations. Therefore, the SPM process requires a high cost wastewater treatment. So, the development of alternative chemicals has been becoming an important task in the semiconductor manufacturing process. In this paper, we evaluated the feasibility of replacing SPM with dissolved ozone water (DIO₃) in the wafer cleaning process, and confirmed that the Particle removal efficiency (PRE) was improved around 68% by mixing with diluted hydrofluoric acid (DHF). And, the PRE was also increased when the concentration of ozone in dissolved ozone water increased. Additionally the PRE was improved up to 98% by combining physical cleaning after O₃ process.

Abstract: The use of highly corrosive chemicals to remove nano-particles on the surface of the wafer, results in substrate losses. This has resulted in the use of megasonics which provides acoustic cavitation to remove small particles. The megasonic wave does generate bubble cavitation which applies mechanical force to wafer structure, the violent cavitation such as transit cavitation or micro jet will damage the patterned structures [1,2]. A new megasonic technology is proposed in this paper, this technology provides stable control of bubble cavitation, without pattern damage at the different modes. The technology shows better particle performance when compared with the industry standard two-fluid nozzle cleaning technology. This Timely Energized Bubble Oscillation mode provides stable cavitation with a wide power window. It is unlike conventional megasonic which creates transit cavitation and damage when the bubble implodes. This new megasonic technology can be used to clean “sensitive” structures at 28nm and below without any pattern damage.