Numerical Investigation of SiO₂ Coating Deposition in Wafer Processing Reactors with SiCl₄/O₂/Ar Inductively Coupled Plasmas

Abstract

Simulations and experiments are performed to obtain a better insight in the plasma enhanced chemical vapor deposition process of SiO2 by SiCl4/O2/Ar plasmas for introducing a SiO2‐like coating in wafer processing reactors. Reaction sets describing the plasma and surface chemistry of the SiCl4/O2/Ar mixture are presented. Typical calculation results include the bulk plasma characteristics, i.e., electrical properties, species densities, and information on important production and loss processes, as well as the chemical composition of the deposited coating, and the thickness uniformity of the film on all reactor surfaces. The film deposition characteristics, and the trends for varying discharge conditions, are explained based on the plasma behavior, as calculated by the model.

Formation of a Nanoscale SiO2Capping Layer on Photoresist Lines with an Ar/SiCl4/O2Inductively Coupled Plasma: A Modeling Investigation

“…The flux of SiCl is roughly 100 times lower than the flux values for SiCl 2 and SiCl 3 , but it is still an important precursor due to its higher probability for deposition (i.e., 1.00 for SiCl vs. 0.05 for SiCl 2 and SiCl 3 ). [10] The fluxes of the other neutral depositing species (i.e., Si, SiO, and SiO 2 ) are even lower (<10 13 cm À2 Á s À1 ) and are not shown. Besides, the SiCl þ 1À3 ion fluxes are only about one order of magnitude lower than these neutral fluxes, so they will also contribute to SiCl x layer growth.…”

“…[9] The reaction set that considers the Ar/SiCl 4 /O 2 plasma chemistry has been presented and discussed in detail in another paper and thus will not be repeated here; however, a list of species included in the model is presented in Table 1. [10] Furthermore, to predict the shape of the deposited SiO 2 capping layer on a mask line as a function of time, a nanoscale Monte Carlo (MC) simulation is performed. [11][12][13][14] This two-dimensional MC model uses the calculated fluxes, energy, and angular distributions from the HPEM as input to launch MC particles toward the nanoscale features.…”

“…[24] This type of reactor has a planar coil on top of the reactor chamber, and is often referred to as a transformer coupled plasma (TCP) reactor with a centrally located gas nozzle in the top dielectric window. [10] Calculations are performed for the following operating conditions: 13.56 MHz coil operating frequency, 10 mTorr Positive ions: Figure 3a, and is compared with a transmission electron microscopy (TEM) picture of the capping layer obtained under the same operating conditions, as shown in Figure 3b, in order to validate the model. Because carrying out the deposition processes and taking successful TEM pictures can be laborious, performing simulations for different conditions is an interesting alternative for obtaining more insight in the deposition process in a shorter timescale.…”

“…However, 95% of SiCl 2 and SiCl 3 is reflected from the surface, so there is not a strong density gradient near the walls and the net flux toward the wafer based on diffusion is relatively small. [10] This is not true for the ions, as they are accelerated through the sheath, and 100% lost at the walls (by wall neutralization). Moreover, SiCl þ has an even higher flux to the wafer than SiCl.…”

“…Indeed, the density of the parent molecule, SiCl 2 , is typically maximum near the center of the wafer. [10] As it is clear from the deposited SiCl x layer is subsequently oxidized to near stoichiometric SiO 2 with minimal concentrations of trapped chlorine. [8] In the next sections, we will explain how the capping layer profile can be altered by tuning the process parameters, including chamber pressure, dilution of the gas mixture with Ar, coil power, and applied bias to the substrate electrode.…”