Chemically controlled megasonic cleaning of patterned structures using solutions with dissolved gas and surfactant

• Published in: Ultrasonics sonochemistry Vol. 82; p. 105859
• Main Authors: Sahoo, Bichitra Nanda, Han, So Young, Kim, Hyun-Tae, Ando, Keita, Kim, Tae-Gon, Kang, Bong-Kyun, Klipp, Andreas, Yerriboina, Nagendra Prasad, Park, Jin-Goo
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.01.2022; Elsevier
• Subjects: Acoustic bubble cavitation; Dissolved gas; Megasonic cleaning; Particle removal; Pattern damage; Short Communication; Surfactant; Pattern damage; Particle removal; Surfactant; Megasonic cleaning; Dissolved gas; Acoustic bubble cavitation
• ISSN: 1350-4177; 1873-2828
• DOI: 10.1016/j.ultsonch.2021.105859

[Display omitted] •Megasonic cleaning performance of Si wafer & polysilicon line pattern is evaluated.•Role of SDS surfactant in the presence of DIW and H2-DIW megasonic cleaning studied.•SDS concentration is found to be a playing key role in obtaining optimized performance.•Bubble dynamics in the megasonic standing wave field are observed using HSC.•Clustering and population density of bubbles is a key factor to enhances the PRE. Acoustic cavitation is used for megasonic cleaning in the semiconductor industry, especially of wafers with fragile pattern structures. Control of transient cavitation is necessary to achieve high particle removal efficiency (PRE) and low pattern damage (PD). In this study, the cleaning performance of solutions with different concentrations of dissolved gas (H2) and anionic surfactant (sodium dodecyl sulfate, SDS) in DIW (DI water) on silicon (Si) wafers was evaluated in terms of PRE and PD. When only DIW was used, PRE was low and PD was high. An increase in dissolved H2 gas concentration in DIW increased PRE; however, PD also increased accordingly. Thus, we investigated the megasonic cleaning performance of DIW and H2-DIW solutions with various concentrations of the anionic surfactant, SDS. At 20 ppm SDS in DIW, PRE reached a maximum value and then decreased with increasing concentration of SDS. PRE decreased slightly with increasing concentrations of SDS surfactant when dissolved in H2-DIW. Furthermore, PD decreased significantly with increasing concentrations of SDS surfactant in both DIW and H2-DIW cases. A high-speed camera setup was introduced to analyze bubble dynamics under a 0.96 MHz ultrasonic field. Coalescence, agglomeration, and the population of multi-bubbles affected the PRE and PD of silicon wafers differently in the presence of SDS surfactant. We developed a hypothesis to explain the change in bubble characteristics under different chemical environmental conditions.