Diagnostics and Control of High-Density Etching Plasmas
- PDF / 1,915,624 Bytes
- 11 Pages / 414.72 x 648 pts Page_size
- 79 Downloads / 210 Views
1. INTRODUCTION The next generation ultra-large-scale integrated (ULSI) technologies have pushed development of high-density large-area plasmas at low pressures.
To date, various plasma sources satisfying
these requirements have been developed; electron-cyclotron-resonance (ECR) plasmas, heliconwave excited plasmas, surface-wave excited plasmas and inductively-coupled plasmas (ICPs). Such advanced etching reactors enable a high etch rate, a high etch anisotropy and low RIE lag. However, the high density sources have common problems of low etch selectivity of SiOG to Si, anomalous local side-wall etching (called notch ) and charge-up damages, along with poor reproducibility. Several advanced etching technologies for clearing such difficulties in high-density plasma etching have been proposed: The first is downstream etching to obtain high etch selectivity in fluorocarbon ICP [I], the second is pulsed plasma etching to obtain notch-free etch profile in chlorine ECR plasma [2] and in chlorine ICP [3, 4]. The pulsed plasma also enhances etch selectivities [5, 6]. The third is hot wall etching to obtain high selectivity in fluorocarbon ICPs [6, 7]. Although these proposals appear promising, the underlying mechanisms have not been fully clarified due to poor plasma diagnostics, especially on fluorocarbon plasmas. In this article, we present the space- and time-resolved measurements of neutral radicals in a chlorine ICP of pulsed etching mode and in fluorocarbon (CF 4/C4Fs) ICP of downstream etching mode and of hot wall etching mode. Several advanced diagnostic techniques are used such as electron density measurements by a plasma oscillation method (POM), negative ion density by photodetachment combined with POM, and neutral radical density by appearance mass spectrometry. The comprehensive measurements successfully disclose the underlying physics and chemistry in the high-density plasma etching. 15 Mat. Res. Soc. Symp. Proc. Vol. 406 © 1996 Materials Research Society
2. PULSED PLASMA ETCHING FOR CHARGE-UP SUPPRESSION 2.1 Experimental Figure 1 shows a schematic representation of the experimental apparatus used in this study. As shown in Fig. 1(a), a two-turn loop antenna for rf excitation is wound around a Pyrex tube 16 cm both in inner diameter and in length. A quartz tube of 12 cm in diameter is set inside the Pyrex tube to reduce the thermal load from the plasma. Square-wave amplitude-modulated 13.56 MHz power is coupled to the antenna, where typical conditions are a 100 uts period, - I [ts rise and fall times, a 50 % duty cycle and 100% modulation depth at an instantaneous power of 400
W. Chlorine gas is fed through a mass flow controller to produce a typical pressure of - 8 mTorr in the reactor. The plasma produced in the source region diffuses to a downstream region in a grounded stainless-steel cylindrical chamber 30 cm in inner diameter and 45 cm in length. The plasma parameters such as electron density ne, electron temperature T. and plasma potential VP are measured by a planar Langmuir probe of 1x3 mm 2 loc
Data Loading...
