Marangoni Dryer Integrated High Performance Cleaner for Cu/Low k Post Strip Clean for 45nm Technology Node and Beyond

Abstract

To address the water mark issue from hydrophobic film drying, and the stringent particle removal requirements for the 45nm technology node and beyond, we developed a cleaner with an innovative single wafer Marangoni dryer. The single wafer Marangoni dryer design features and process characterization data are presented in this paper. The major results can be summarized as: (1) With the immersion type Marangoni dryer, as the wafer is lifted out of a DIW bath, a stable and uniform meniscus can be easily maintained, making the single-wafer Marangoni dryer ideal for drying hydrophilic, hydrophobic or hydrophobic/hydrophilic mixed patterned wafers; (2) The new Marangoni dryer leaves ~14nm [1] water film on the wafer after drying, therefore any dissolved or suspended materials contained inside the water film, and potentially left on the wafer surface after water evaporation, is less than 14nm in diameter. This feature is critical for the 45nm technology node and beyond because 23nm particle could be killer defects at these nodes [2]; (3) Because of the strong Marangoni flow effect, high aspect ratio features can be completely dried without leaving any water droplets inside the trenches; therefore copper corrosion can be prevented; (4) The Marangoni dryer uses N2 as the carrier gas, so when a wafer is lifted out of the degasified DIW bath through the N2/IPA spray zone, it is thoroughly dried in an oxygen-free environment before exposure to the ambient environment; (5) The Marangoni dryer is free of electrostatic charge and centrifugal force because of the slow (2mm/s~20mm/s) wafer linear lifting speed compared to linear speed at wafer edge during SRD.

Chemical Mechanical Planarization-Related to Contaminants: Their Sources and Characteristics

“…Such watermarks tend to cause significant degradation in device performance [15]. IPA-based Marangoni drying process was proposed and used to eliminate watermarks [55]. The addition of surfactants that can convert hydrophobic to hydrophilic of the films will prevent the formation of watermarks after drying [42].…”

Experimental Investigation of High-Performance Wafer Drying Induced by Marangoni Effect in Post-CMP Cleaning

“…Empirical understanding showed that the thinner the residual water film, the less the deposited particles and watermark defects, and thus the better the drying performance. 18 Therefore, the residual thickness of the water film on the wafer surface has a close correlation to the characterization of Marangoni drying. Numerical analysis is considered as a crucial method to investigate the Marangoni drying mechanism.…”

Evolution of entrained water film thickness and dynamics of Marangoni flow in Marangoni drying

“… 11,12 Marangoni drying can realize the drying of wafers by Marangoni-driven flow after a sequence of wet cleaning processes, and it has been widely employed in the manufacturing of integrated circuits (ICs). 13 When a wafer is withdrawn from a deionization (DI) water bath, a meniscus and an entrained water film are induced on the wafer surface, as shown in Fig. 1 .…”