Application of cyclic fluorocarbon/argon discharges to device patterning

Abstract

With increasing demands on device patterning to achieve smaller critical dimensions and pitches for the 5 nm node and beyond, the need for atomic layer etching (ALE) is steadily increasing. In this work, a cyclic fluorocarbon/Ar plasma is successfully used for ALE patterning in a manufacturing scale reactor. Self-limited etching of silicon oxide is observed. The impact of various process parameters on the etch performance is established. The substrate temperature has been shown to play an especially significant role, with lower temperatures leading to higher selectivity and lower etch rates, but worse pattern fidelity. The cyclic ALE approach established with this work is shown to have great potential for small scale device patterning, showing self-limited etching, improved uniformity and resist mask performance.

Mechanism of SiN etching rate fluctuation in atomic layer etching

“…Atomic layer etching (ALE) is a promising technology that is able to overcome these issues. [1][2][3] ALE has been widely developed in recent years with an emphasis on Si-based, 4 dielectric-based, [5][6][7][8][9][10][11][12][13][14][15] and metal-based [16][17][18][19] materials processing. In this paper, we focus on ALE for dielectric films, which consists of two sequential steps: the surface adsorption of a polymer and desorption steps.…”

Characterizing fluorocarbon assisted atomic layer etching of Si using cyclic Ar/C4F8 and Ar/CHF3 plasma

“…14,15 Additionally, the process has shown promise for device patterning on a manufacturing scale. 16 In this article we further characterize this process, especially with regard to process parameter impact on etch behavior, material etching selectivity, and surface chemistry. Additionally, several interesting phenomena have been observed and will be presented here.…”

Evaluation of ALE processes for patterning

“…Initial work on the impact of etch step time, substrate temperature and the effect of profile feature has been previously reported. 7 Springboarding from these initial findings, using C 4 F 8 as precursor gas, we optimized our process further by reducing the reactor volume and also the precursor chemistry. We were able to use these processes to demonstrate a successful etch stop on SiN, as shown in Figure 1.…”

“…This was first demonstrated by Metzler et al 6 and has also been evaluated for device patterning. 7 An inert plasma is maintained at all time, while alternating cycles of a precursor pulse and an etch step with increased ion energy are applied to the wafer. While this plasma-enhanced ALE (PE-ALE) approach does not offer atomic layer control in the deposition cycle, the following etch cycle offers high enough selectivity to the original substrate to show self-limiting behavior.…”