High verticality InP/InGaAsP etching in Cl2/H2/Ar inductively coupled plasma for photonic integrated circuits

Abstract

High verticality and reduced sidewall deterioration of InP/InGaAsP in Cl 2 / H 2 / Ar inductively coupled plasma etching is demonstrated for a hydrogen dominant gas mixture. Selectivity Ͼ20: 1, an etch rate of 24 nm/s, and a sidewall slope angle of Ͼ89°have been measured for etch depths Ͼ7 m. The Ar flow is minimized to reduce surface etch damage while increased Cl 2 and H 2 gas flow is shown to increase etch rate and selectivity. The high chamber pressure required for plasma ignition causes isotropic etching at the start and creates an undercut beneath the masking layer. A novel ignition scheme using a hydrogen gas "flood" is suggested and results are presented.

Nanometer-Scale Vertical-Sidewall Reactive Ion Etching of InGaAs for 3-D III-V MOSFETs

“…This is partially due to the less directional ion bombardment that results from enhanced ion collisions in the plasma under higher pressure [10]. Enhanced chemical etching also contributes to the undercut since more reactive species are produced at higher pressure [4]. A similar undercut appears when the RF platen power is decreased from 160 to 50 W (substrate bias voltage reduced from 280 to 120 V) as in Fig.…”

“…This changes the profile from tapered to vertical. Without SiCl 4 we only obtain tapered sidewalls. This can be seen in Fig.…”

“…High verticality and high aspect ratio have been demonstrated in a variety of chemistries including those based on CH 4 /H 2 [7], Cl 2 [4], [5], [8], BCl 3 [9], [10], SiCl 4 [11], and HBr [6]. However, we are not aware of any demonstration of sub-20 nm features with vertical sidewalls fabricated by RIE in In-based heterostructures.…”

“…Dry etch of indiumcontaining III-V materials, mostly InP/InGaAsP, has been studied extensively for optical device applications [4]- [6]. High verticality and high aspect ratio have been demonstrated in a variety of chemistries including those based on CH 4 /H 2 [7], Cl 2 [4], [5], [8], BCl 3 [9], [10], SiCl 4 [11], and HBr [6].…”

“…Fig. 1(a) and (b) show D = 15 and 28 nm NWs with aspect ratio greater than 10 fabricated by optimized RIE conditions: 20 W ICP power, 160 W RF platen power (resulting in 280 V substrate bias voltage), 0.2 Pa chamber pressure, 250°C substrate temperature and gas flows of 7/0.55/7 SCCM for BCl 3 , SiCl 4 and Ar, respectively. The etching rate is about 1.8 nm/s (total etching time is 135 s) and the selectivity to the HSQ mask is approximately 8:1.…”