AVS 61st International Symposium & Exhibition
    Plasma Science and Technology Thursday Sessions
       Session PS2+TF-ThM

Paper PS2+TF-ThM2
Highly Selective Atomic Layer Etching of Silicon Dioxide Using Fluorocarbons

Thursday, November 13, 2014, 8:20 am, Room 308

Session: Atomic Layer Etching (ALE) and Low-Damage Processing
Presenter: Eric Hudson, Lam Research Corporation
Authors: E. Hudson, Lam Research Corporation
V. Vidyarthi, Lam Research Corporation
R. Bhowmick, Lam Research Corporation
R. Bise, Lam Research Corporation
H.J. Shin, Lam Research Corporation
G. Delgadino, Lam Research Corporation
B. Jariwala, Lam Research Corporation
D. Lambert, Lam Research Corporation
S. Deshmukh, Lam Research Corporation
Correspondent: Click to Email
As microelectronics advancements require smaller device features, masking layers are becoming thinner. Additionally, there are tighter requirements on allowable loss of films during processing. This leads to exacting requirements for etch, where a target film must be removed with very high selectivity to a mask and/or substrate film. For etching of SiO2 or similar materials, this high selectivity is typically achieved using very polymerizing fluorocarbon-based combinations of gases. However this approach can introduce problems with etch rate loading, such that the oxide in features with larger critical dimension (CD) tends to etch more slowly due to excessive passivation.

A novel approach for oxide etching has been developed which addresses this tradeoff between selectivity and etch rate loading. The etch process is based on repeated cycles of fluorocarbon deposition and etch reaction activation, similar to the process described by Metzler et al [1]. In each cycle there are two different phases of plasma conditions in which (1) a thin film of fluorocarbon polymer is deposited and (2) the polymer film is bombarded by noble gas ions to activate the etch reaction. Under the right conditions, oxide films are incrementally etched in each cycle. This atomic layer etch approach is less susceptible to etch rate loading because under properly adjusted conditions, the oxide etch front remains clear of polymer buildup after each cycle. Under the same conditions, polymer can build up on the mask or substrate surface with successive cycles, protecting the film and resulting in minimal loss. The process times for the deposition and activation phases of the cycle are the primary parameters for process control. A comparison of model and experiment is presented to characterize the effect of these two time parameters upon process results.

[1] Metzler, et al JVST A 32, 020603 (2014).