Multi-scale modeling of chemical vapor deposition processes for thin film technology

An integrated framework for the neutral flux calculation inside trenches and holes during plasma etching is described, and a comparison between the two types of structure in a number of applications is presented. First, a detailed and functional set of equations for the neutral and ion flux calculations inside long trenches and holes with cylindrical symmetry is explicitly formulated. This set is based on early works [T. S. Cale and G. B. Raupp, J. Vac. Sci. Technol. B 8, 1242 (1990); V. K. Singh et al., J. Vac. Sci. Technol. B 10, 1091 (1992)], and includes new equations for the case of holes with cylindrical symmetry. Second, a method for the solution of the respective numerical task, i.e., one or a set of linear or nonlinear integral equations, is described. This method includes a coupling algorithm with a surface chemistry model and resolves the singularity problem of the integral equations. Third, the fluxes inside trenches and holes are compared. The flux from reemission is the major portion of the ...

Integrated framework for the flux calculation of neutral species inside trenches and holes during plasma etching

A molecular layer deposition approach is reported that produces a new class of hybrid organic–inorganic thin films. These films have very low densities, and display typical atomic layer deposition characteristics: controllable linear growth, conformality, low roughness, and uniform composition. Because of their aluminum content, the alucone films cannot be dry etched with oxygen plasma. In accordance with their molecular structure, the new materials are completely removed in hydrochloric acid solutions. Since they can be etched with accurate control in acidic solutions, these hybrid materials are promising for the fabrication of MEMS/NEMS (Micro/Nano Electro Mechanical Systems) devices. Doubly supported structures with 120 nm air gaps are demonstrated using alucone materials as sacrificial layers.

Sacrificial layers for air gaps in NEMS using alucone molecular layer deposition

In this paper, homogeneous and dense silicon-based coatings have been deposited from hexamethyldisiloxane (HMDSO: Si2O(CH3)6) on patterned silicium in a Townsend dielectric barrier discharge operating at atmospheric pressure. A brief description of the physical mechanisms ruling the step coverage is first described, followed by a description of the atmospheric pressure plasma process used. The step coverage is discussed with regard to the aspect ratio of the patterned wafers. Coatings deposited in and after the discharge region have also been characterized to understand the influence of plasma activation. In order to understand the experimental results, numerical simulations have been performed using a simplified reactive transport model. These results provide information and first general insight on the physical mechanisms ruling the conformity of silicon-based films deposited with this technique.

Conformity of Silica-like Thin Films Deposited by Atmospheric Pressure Townsend Discharge and Transport Mechanisms

A two dimensional feature scale model has been developed to predict film profile evolution during pulsed plasma enhanced chemical vapor deposition (PECVD). The model employs a diffusion reaction framework with a spatially variable Knudsen diffusion coefficient to account for molecular transport in evolving feature geometries. The transient model accounts for the alternating atomic layer deposition (ALD) and PECVD growth modes that contribute to deposition. A scaling analysis is used to account for diffusion limitations that affect the ALD component in high aspect ratios due to insufficient precursor exposure. The model predictions have been validated using cross section micrographs of nanostructures produced by pulsed PECVD of aluminum oxide on patterned substrates. The model provides a tool to design the fabrication of nanostructures with digital precision. By varying the relative contributions of the two modes pulsed PECVD provides an opportunity engineer the degree of conformality to produce unique morphologies that are distinct from either steady state vapor deposition processes or conventional ALD.

Feature scale modeling of pulsed plasma-enhanced chemical vapor deposition

The surface micromachining processes used to manufacture MEMS devices and integrated circuits transpire at such small length scales and are sufficiently complex that a theoretical analysis of them is particularly inviting. Under development at Sandia National Laboratories (SNL) is Chemically Induced Surface Evolution with Level Sets (ChISELS), a level-set based feature-scale modeler of such processes. The theoretical models used, a description of the software and some example results are presented here. The focus to date has been of low-pressure and plasma enhanced chemical vapor deposition (low-pressure chemical vapor deposition, LPCVD and PECVD) processes. Both are employed in SNLs SUMMiT V technology. Examples of step coverage of SiO{sub 2} into a trench by each of the LPCVD and PECVD process are presented.

Feature length-scale modeling of LPCVD & PECVD MEMS fabrication processes.

The surface micromachining processes used to manufacture MEMS devices and integrated circuits transpire at such small length scales and are sufficiently complex that a theoretical analysis of them is particularly inviting. Under development at Sandia National Laboratories (SNL) is Chemically Induced Surface Evolution with Level Sets (ChISELS), a level-set based feature-scale modeler of such processes. The theoretical models used, a description of the software and some example results are presented here. The focus to date has been of low-pressure and plasma enhanced chemical vapor deposition (low-pressure chemical vapor deposition, LPCVD and PECVD) processes. Both are employed in SNLs SUMMiT V technology. Examples of step coverage of SiO2 into a trench by each of the LPCVD and PECVD process are presented.

http://www.sandia.gov/~sjplimp/papers/jmt05.pdf

Pauline Ho

Papers

Feature length-scale modeling of LPCVD & PECVD MEMS fabrication processes.

Feature length-scale modeling of LPCVD and PECVD MEMS fabrication processes