Effect of simultaneous source and bias pulsing in inductively coupled plasma etching

Abstract

Pulsed rf plasmas show promise to overcome challenges for plasma etching at future technological nodes. In pulsed plasmas, it is important to characterize the transient phenomena to optimize plasma processing of materials. In particular, it is important to evaluate the effect of the ion energy and angular distribution (IEAD) functions during pulsing on etching of nanoscale features. In this work, the impact of simultaneous pulsing of both source and bias in an inductively coupled plasma on plasma characteristics and feature profile evolution is discussed using results from a two-dimensional reactor scale plasma model coupled to a Monte Carlo based feature profile model. Results are discussed for an Ar∕Cl2 gas mixture which is typically used for poly-Si etching. The consequences of duty cycle, pulse shape, and the phase lag between source and bias power pulses on discharge characteristics, IEADs to the wafer, and feature profile evolution are discussed. The low plasma density during the initial period of the pulse was found to introduce a high energy tail component to the IEADs. This high energy tail component can be affected by modifying the pulse shape. The Si etching rate is found to increase with increasing duty cycle but is lower compared to continuous mode of operation due to lower time averaged power deposition. Pulsing the source and bias out of phase provides for increased ion energies and fluxes to the wafer for a given duty cycle.

Overview of atomic layer etching in the semiconductor industry

“…22 It is widely used in semiconductor industry today due to its ability to enable better uniformity, greater selectivity, and less ioninduced damage. 30,[126][127][128][129][130][131] The productivity advantage of power pulsing is that it does not involve gas exchange and so can be made faster by eliminating overhead time involved in evacuating the chamber between chemically distinct reaction steps. 5 The connection between power pulsing and ALE has been recognized, 5,7,12,22,126,131,132 as suggested by Agarwal and Kushner.…”

Developing a linear model of RF power generators with pseudo random binary signals (PRBS)

“…First, the collected input and output data, which are the PRES data (u(t)) and the RF delivered power ( Pde 1(t)), go through a stable filter, respectively. The transfer func-1160 tion of the stable filter is 1 1 A(z) z n + An_ 1 Z n-1 + ... + A 1 Z + AO ' (4) the solution of A( z) = 0 is all located inside the unit cir cle, which means that the filter dynamic is stable. Then, the output of the stable filter formulates a vector, ¢( t) .…”

“…The Bosch process requires alternately etching and pas sivating the hole, resulting in periodic plasma impedance disturbances. Finally, high aspect ratio features used in modern IC proceses such as 3D NAND Flash memory require the use of pulsed RF to neutralize trapped charge and control the chemistry of the plasma [2], [1]. These processes may require RF pulse widths as low as 5,LS, and rise/fall times of 2fLs ( Figure 2).…”

Isolation Trench Etch Process Using Pulsed RF Bias Power in HBr/CF4/O2 Plasma

“…Pulsed plasma dry etch is known to have increased selectivity to masks, enlarging windows of loading control as well. Other advantageous aspects of pulsed power process include such factors as charge pile-up reduction and negative ions utilization, plasma damage reduction at high power levels, as reported by authors [1][2][3][4][5]. Although pulsed RF power had been devised decades ago, it is rather recent to practically implement in manufacturing processes.…”