Aspect ratio dependent plasma-induced charging damage in rf precleaning of a metal contact

Abstract

As the packing density increases in the fabrication of semiconductor chips, the aspect ratio and the critical dimension (CD) of a metal contact are exponentially aggravated in dry etch processing. The aspect ratio dependency of plasma-induced charging damage during the rf precleaning of a metal contact has been evaluated with a two-dimensional Monte Carlo simulation and with related experiments. From the simulation of a metal contact opened on a gate metal, it is found that the potential on a metal contact bottom, which is directly related to plasma-induced charging damage, is saturated near an aspect ratio of 4 after initially linearly increasing with the aspect ratio. However, the linear decrease of CD of a metal contact exponentially increases the potential stress on the gate oxide. These simulation results are confirmed with the two different experiments, an in situ charge-up monitoring and the electrical test of fully fabricated complementary metal–oxide–semiconductor wafers. A phase controlled inductively coupled plasma is newly proposed to suppress the plasma-induced charging damage. With this system, the plasma-induced damage is strongly suppressed when the phase delay of the bias power to the source power is near 180°.

Synchronous Pulse Plasma Operation upon Source and Bias Radio Frequencys for Inductively Coupled Plasma for Highly Reliable Gate Etching Technology

“…Historically, studies of synchronous operation of pulse plasma have been conducted and been reported. 26,36,37,39) Hashimoto et al, had reported that an RF bias with low frequency, 66.7 kHz, was forced to synchronize with a very fast pulse cycle of 66.7 kHz with 13.56 MHz source RF. 26) P2ID was suppressed at 0 degree of phase only where electron temperature of Ar plasma had a minimum value and RF bias voltage got peak.…”

Effect of time-modulation bias on polysilicon gate etching

“…24) To address this issue, several studies have been conducted in recent years on systems that synchronize source pulsing and bias pulsing. [24][25][26][27][28][29][30][31] For example, it was reported that synchronized pulsing for both source power and bias power improved the profile difference between dense and isolated patterns because the pulsed plasma provided less dissociation due to lower electron temperature and plasma density. 32) Although the etching characteristics of the pulsing technique have been investigated in these studies, optimization of the parameters and their respective roles have not yet been fully clarified.…”

Study on processing step uniformity tuning during FET fabrication and sensor wafer response as a function of chuck temperature adjustment

“…The microscopic uniformity issues have been intensively studied over the last few decades and the main contributing effects identified. Among them are aspect ratio dependent etching (ARDE), [1][2][3] depth loading between isolate (ISO) and dense structures, 1,4) and a differential charging of high aspect ratio features, 1,[5][6][7][8] all of which are often taking place in dry etch processing that can be revealed by means of discovering various profile distortions (trenching, bowing or twisting), [9][10][11] potato-shaped cross sections (in case of high aspect ratio contact holes), 12) etch stop phenomena, 3,13) etc. Discussions on what options are efficient to deal with such problems can also be found in Refs.…”