Etch Loading Effect Research Articles

Highly selective etching of SiNx over SiO2 using ClF3/Cl2 remote plasma

Highly selective etching of silicon nitride over silicon oxide is one of the most important processes especially for the fabrication of vertical semiconductor devices including 3D NAND (Not And) devices. In this study, isotropic dry etching characteristics of SiN x and SiO2 using ClF3/Cl2 remote plasmas have been investigated. The increase of Cl2 percent in ClF3/Cl2 gas mixture increased etch selectivity of SiN x over SiO2 while decreasing SiN x etch rate. By addition of 15% Cl to ClF3/Cl2, the etch selectivity higher than 500 could be obtained with the SiN x etch rate of ∼8 nm min−1, and the increase of Cl percent to 20% further increased the etch selectivity to higher than 1000. It was found that SiN x can be etched through the reaction from Si–N to Si–F and Si–Cl (also from Si–Cl to Si–F) while SiO2 can be etched only through the reaction from Si–O to Si–F, and which is also in extremely low reaction at room temperature. When SiN x /SiO2 layer stack was etched using ClF3/Cl2(15%), extremely selective removal of SiN x layer in the SiN x /SiO2 layer stack could be obtained without noticeable etching of SiO2 layer in the stack and without etch loading effect.

High aspect ratio silicon etch: A review

High aspect ratio (HAR) silicon etch is reviewed, including commonly used terms, history, main applications, different technological methods, critical challenges, and main theories of the technologies. Chronologically, HAR silicon etch has been conducted using wet etch in solution, reactive ion etch (RIE) in low density plasma, single-step etch at cryogenic conditions in inductively coupled plasma (ICP) combined with RIE, time-multiplexed deep silicon etch in ICP-RIE configuration reactor, and single-step etch in high density plasma at room or near room temperature. Key specifications are HAR, high etch rate, good trench sidewall profile with smooth surface, low aspect ratio dependent etch, and low etch loading effects. Till now, time-multiplexed etch process is a popular industrial practice but the intrinsic scalloped profile of a time-multiplexed etch process, resulting from alternating between passivation and etch, poses a challenge. Previously, HAR silicon etch was an application associated primarily with microelectromechanical systems. In recent years, through-silicon-via (TSV) etch applications for three-dimensional integrated circuit stacking technology has spurred research and development of this enabling technology. This potential large scale application requires HAR etch with high and stable throughput, controllable profile and surface properties, and low costs.

Study of Mask Proximity Impact on Mask Mean-to-Target Specification

An analytic relationship of the mask mean-to-target (MTT) and the mask uniformity specifications affected by the mask proximity effect (MPE) is suggested. MPE mainly caused by e-beam proximity and the etch loading effect makes different MTTs for patterns with different pitch sizes. Γ is the parameter introduced to represent MTT differences induced by MPE. The mask MTT and uniformity (M–U) curves which define the boundary of the specification region shift along the mask MTT axis according to the sign of Γ. The mask M–U curves translate upward for a positive Γ and downward for a negative Γ. M–U specifications are calculated for 45 and 51 nm half-pitch sizes. Γ's are obtained from the experimental proximity curve and they are -0.5 and -0.8 nm for the 45 and 51 nm nodes, respectively. For the 45 nm node, the lower and upper mask MTT specifications are -5.35 and 3.91 nm, respectively. For the 51 nm node, the lower and upper MTT specifications are -9.00 and 3.90 nm, respectively. M–U curves are shown to be translated downward for negative Γ's and their amounts are -2.55 and -0.72 nm for the 45 and 51 nm nodes, respectively.

Polysilicon Etchback Plasma Process Using HBr , Cl2, and SF 6 Gas Mixtures for Deep‐Trench Isolation

Etchback of polysilicon used for refilling deep trenches isolating bipolar devices has been investigated in a magnetically enhanced reactive ion etcher using , , and gas combinations. Etch rates, uniformities, and loading effects have been studied as a function of gas mixtures. Polysilicon etchback processes with uniformity better than 2%, polysilicon etch rate larger than 5000 Aå/min, and loading factor less than 1.3 were obtained with a gas mixture consisting of less than 9 sccm flow in a predominant and mixture. It was found that the etch roughness and surface profile of the resulting trench polysilicon was a strong function of percentage in the mixture. The controllable trench polysilicon etchback profile with smooth surface and curvature was obtained by using 60 sccm and 50 sccm gas mixtures with 6 sccm gas flow.