Solid State Phenomena Vol. 314

Abstract: This paper addresses challenges and solutions of replacement metal gate of gate-all-around nanosheet devices. The unit process and integration solutions for the metal gate patterning as well as interface dipole patterning to offer multiple threshold voltage have been developed. The challenges of long channel device integration are also discussed.

Abstract: Thermally activated ozone gas (TAO) was demonstrated as an alternative technology to conventional spin-on carbon (SOC) stripping. The SOC stripping rate with ozone gas was found to be a function of substrate temperature and actual ozone amount calculated from the ozone flow rate and concentration. Furthermore, work function metal (WFM) stripping rate showed a high selectivity to SOC films, and the amount of oxidation TiN, which is a WFM metal, was also equivalent to conventional technology of SOC stripping. This TAO gas process can be used in clean tools, making it a promising integrated solution for SOC stripping followed by post clean.

Abstract: Batch SPM systems do not meet the current clean specification/requirements below 28nm. Single wafer SPM systems use a high volume of chemistry which runs to drain, while meeting the cleaning specifications below 28nm. The work in this paper describe the use of a batch SPM system and a single wafer clean in an integrated system, Ultra-C Tahoe which results in meeting the technical specification and using less that 80% of the SPM chemistry used in single wafer systems. The data collected shows this new system meet the specifications, whilst saving more than 80%of SPM chemistry.

Abstract: Efficient cleaning of contaminations in the semiconductor industry is a determining factor in ensuring the good quality of the electronics products. We present here the dynamic wetting characterization of a fluid on top of DTI structures using ultra-high frequency acoustic method. The dynamics of the fluid will be established using a PDMS micro-channel placed on top of the structures, in order to obtain conditions as close as possible to those used in the industrial process. Wetting state of the DTI structures is determined based on the measured acoustic reflection coefficient.

Abstract: 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.

Abstract: Wet etching in nanometer-sized three-dimensional spaces creates new challengesbecause of the scaling of semiconductor devices with complex 3D architecture. Wet etching withinspaces is affected by the mass transport of the etchant ions that are impacted by the hydrophobicityand surface potential of surface. However, the kinetics of chemical reactions within the spaces is stillunclear.In this paper, we studied the effect of hydrophobicity and surface potential of silicon surface on SiO2etching in nanometer-sized narrow spaces by adding various additive components to etching solutions.We found that the transport of etchant ions into narrow spaces is governed by controlling thehydrophobicity and surface potential of the confined system walls.

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: Test structure development is critical for single wafer pattern collapse evaluations. A good test vehicle not only allows optimization and benchmarking of different processes, but also facilitates understanding of the underlying mechanism. For high aspect ratio silicon nanopillar arrays, by increasing the gap distance in one direction while keeping the other direction constant, an unexpected higher collapse rate is found. This preliminary finding is contradictory to the prevalent models that are based on equilibrium force balance between capillary and mechanical interactions. It is postulated that the asymmetric arrangement of pillars facilitates the formation of liquid bridge and thus more pattern collapse. Such test structures can bring useful insights to understand the dynamic mechanism of pattern collapse.

Abstract: Damage-free drying becomes increasingly difficult with the scaling of semiconductor devices. In this work, we studied a new sublimation drying technology for 3nm node and beyond. In order to investigate the collapse factor by conventional sublimation drying, we observed the pattern with cryo-SEM and revealed that the collapse occurred when the liquid film on the substrate solidified. Based on this result, we considered that it was important to deposit a solidified film uniformly from the substrate side to suppress collapse. Two key process parameters were evaluated to achieve the uniform formation of the solidified film. One is interfacial free energy and the other is film thickness of solution just before solidification. By optimizing two key parameters, it was successfully demonstrated to suppress pattern collapse of challenging devices. In this paper, we report on a new drying method: sublimation drying by LPD (Liquid-phase deposition).

Abstract: Radical formation and detection in aqueous solutions under acoustic irradiation are important during wet cleaning processes in semiconductor industries. Oxidizing radicals such as hydroxyl and hydroperoxyl radicals have been widely studied and characterized using fluorescence and chemiluminescence methods. Hydrogen radicals, which are strongly reducing in nature, have not received much attention. In this study, the rate of hydrogen radical generation in a megasonic field (0.93 MHz) was measured using an electrochemical technique. Specifically, the method is based on the reduction of cupric ions to cuprous chloride complex by the hydrogen radicals in the presence of an excess of chloride ions. This is followed by chronoamperometric determination of the oxidation of cuprous chloride complex back to cupric ions. Hydrogen radical generation rate was measured at different megasonic power densities.