Simulation and Characterization of IPVD System with External ICP Antenna

Abstract

The experimental ionized physical vapor deposition (IPVD) system with an external antenna is described, and experimental characterization of the plasma was performed: plasma density was up to 5 × 1012 cm−3, the argon ionization ratio was ∼0.2–0.4%, and copper ionization ratio was ∼28% in bulk plasma, corresponding to ionized Cu+ flux ratio in range the 73–95%. To aid further development and IPVD technology extendibility to the future nanoscale fabrication, the 2D plasma fluid model for IPVD system was developed. The model comprised the Cu + Ar collisional mechanism including charge exchange and Penning ionization, considering gas rarefaction effect, variable ion mobility approach, and analytical approach in description of the thermalization of sputtered Cu. The simulation results were validated through experimental measurements of the plasma characteristics by electrical probe and provided reasonable results in 2 to 15 Pa pressure range. The implementation of the model for optimized design of scaled‐up IPVD system was demonstrated.

Coupling and Shielding Properties of the Baffle in ICP System

“…This generates strong induced currents in the plasma and produces a high density of the charged species. Probe measurements [7] in such a system determined an electron density up to ∼5 × 10 12 cm −3 within much larger bulk plasma volume than in typical PVD systems. We want to mention that such density is achieved without exposure of the external magnetic field to the core plasma.…”

“…The plots from top to bottom in column (a) represent simulation results at various bulk plasma densities: 1 × 10 9 cm −3 , 5 × 10 9 cm −3 , 1 × 10 10 cm −3 , 5 × 10 10 cm −3 , and 1 × 10 11 cm −3 . Although the ICP core plasma density may be as high as 5 × 10 12 cm −3 [7], the plasma density close to deposition baffle applicable for use in the sheath model is lower. It follows from the sheath model that sheath thickness is smaller at increased bulk plasma density.…”

“…All slots under investigation have comparable transparency to RF magnetic fields, however, more compact slot structures are preferable due to increased efficiency per unit area and higher-dimensional variability in design. The E-H transition occurs in the 200-600 W interval, achieving similar plasma density values for all slot types saturating up to 4-5 × 10 12 cm −3 [7]. The DB implementation affected the E-H transition (a hysteresis shape).…”

“…Nevertheless, of high opacity to deposition, this type of slot structure had tendency to fail (see Section 3.4 below) due to the disproportional heat load on individual slots as we found out later by heat transfer simulation and experimental observation. The investigations of more specific slots configurations were discussed yet in [6,7].…”

“…The fundamentals of IPVD technology have been described in publications elsewhere, for instance [1][2][3][4][5]. In this paper, we will focus on the physics and engineering aspects of an RF transparent baffle but opaque to deposition in experimental IPVD system [6,7] with an external ICP antenna. In Section 2, we will describe basic properties of the ICP with deposition baffle (DB).…”