Papers by Keyword: Dry Cleaning

Abstract: We propose an optimal strategy for cleaning 20-nm contaminants in atmospheric pressure by using CO₂ solid particles injected from a supersonic nozzle. We found that an excessively small exit diameter of the nozzle results in the shock wave, which decreases the particle removal efficiency (PRE). Based on the incompressible flow theory, we developed a supersonic nozzle that can issue CO₂ solid particles without shock wave. The shape of CO₂ beam and PRE of the developed nozzle are compared with the results of a pre-existing nozzle for vacuum condition by analyzing scanning electron microscopy (SEM) image of substrates. The results show that when we use the newly developed nozzle in atmospheric pressure, PRE is above 95 % without pattern damage. This work can pave the way for cleaning nanoscale contaminants that occur during manufacture of semiconductor chips at little cost.

Abstract: Dry cleaning process has been limited to particular field of removing native oxide because it has low etching selectivity for various oxide films. To increase etching selectivity, we added H₂O steam feeding step before NF₃ feeding step. From the experimental, we can change selectivity between oxide films from tens to hundreds.

Abstract: As the size of functional patterns in the semiconductor chips shrinks down to below 100 nm, removing nanoscale contaminant particles is an important technological challenge that the current semiconductor manufacturing industry must overcome. Several cleaning methods proposed to date, such as megasonic cleaning [1], droplet impact [2], and cryogenic aerosol cleaning [3], have difficulties in cleaning of sub-100 nm contaminant particles, let alone their tendency to induce pattern damages. Kim et al. [4] has recently developed a new method, where CO₂ solid particles nucleated from a supersonic nozzle physically attack contaminant nanoscale particles on the wafer, thus detaching them. A drawback of this novel scheme is that the cleaning must be executed in vacuum because CO₂ gas needs to sublimate into solid and be accelerated supersonically as exiting the nozzle. This has adverse effects on the cost and rate of the semiconductor manufacturing process. Here we investigate the effects of vacuum chamber pressure on the performance of the CO₂ dry cleaning system. We observe the cryogenic CO₂ beams, dents induced by CO₂ solid particles, and wafer surfaces initially contaminated with cerium oxide particles, which indicate the effects of the chamber pressure.

Abstract: HfO₂ gate stack has been one of the most popular subjects of research in recent years due to its outstanding material properties, such as high-k (20~25), wide band gap (~5.68eV), and the compatibility with Si-based semiconductor process technology. However, the interfacial layer (IL) with a reduced k-value between HfO₂ dielectric and Si channel is still a critical issue for future ultra large scale integration (ULSI) technology application of the HfO₂ gate stack. Various ways have been studied to improve the IL properties of HfO₂ gate stack and to achieve ~1nm-thick equivalent oxide thickness (EOT) of the gate stack. Recently, fluorine incorporations into the HfO₂ gate stack have been suggested for improvement of the electrical properties of the gate stack by defect passivation.^1,2 However, it was reported that the SiO_x IL grows during the fluorine treatment of HfO₂ film, which finally led to degradation of electrical characteristics.² In this paper, we present interesting findings on the IL removal effect of fluorine incorporation into the HfO₂ gate stack where a post-gate dry cleaning technique is used with the NF₃/NH₃ plasma.

Abstract: As the integration density of memory increases, a low resistivity gate electrode is essential to meet the current needs of high speed operation. It has been known that one of major limitation of low resistivity gate is dopant penetration between poly-si and metal gate. Those dopants are penetrated and segregated on the surface of poly-si when annealed, which increases interfacial resistance and causes detrimental performance on the devices. Surface oxidation, level of boron oxide or silicon oxide on the poly-si surface is also getting higher after annealing. Therefore, it is necessary to remove those dopants oxidized layers on the surface of the activated poly-si in order to obtain minimal increases of interfacial resistance.

Abstract: An ultrasonic dry cleaning system is a kind of air-blowing cleaning system, which clears away fine particles of dust adhering to a surface. This system does not require high cost consumables such as highly pure gases or chemical solvents. Moreover it removes micro contaminant particles without additional cooling or heating processes. In this paper, a numerical simulation of the ultrasonic dry cleaning system was carried out to propose an optimum ultrasonic generator. We evaluated the flow in the chamber according to the groove shape of ultrasonic generator, and system operating pressure using a commercial fluid dynamic simulation tool. And the trend of the sound pressure level (SPL) according to frequency was checked to determine whether or not the ultrasonic generator module could generate an ultrasonic wave. The particle trajectories were compared for several conditions and particle sizes. We confirmed that an ultrasonic wave of sufficient flow velocity can be generated through the ultrasonic generator module. And the changes of SPL according to the system operating pressure and the shape of the ultrasonic generator groove were confirmed respectively.