Detailed analysis of the influence of an inductively coupled plasma reactive-ion etching process on the hole depth and shape of photonic crystals in InP∕InGaAsP

Abstract

The authors report on the fabrication of photonic crystals in the InP∕InGaAsP∕InP material system for applications at telecommunication wavelengths. To achieve low optical loss, the photonic crystal holes must demonstrate smooth sidewalls and should be simultaneously deep and cylindrical. The authors present the etching process of these structures based on a Cl2∕Ar∕N2 chemistry with an inductively coupled plasma reactive-ion etching system. A systematic analysis is provided on the dependency of the hole sidewall roughness, depth, and shape on the process parameters such as etching power, pressure, and chemical composition of the plasma. They found that a low plasma excitation power and a low physical etching are beneficial for achieving deep holes, whereas for the nitrogen content in the plasma, a delicate balance needs to be found. Nitrogen has a negative impact on the hole shape and surface roughness but is capable of preventing underetching below the mask by passivation of the sidewalls. With the authors’ process more than 4μm deep holes with low conicity have been demonstrated.

Comparative study of Cl2, Cl2∕O2, and Cl2∕N2 inductively coupled plasma processes for etching of high-aspect-ratio photonic-crystal holes in InP

“…[15][16][17] Very recently, a detailed study was presented on the use of N 2 as a passivation component in ICP etching of InP photonic crystals. 18 In the present article, we describe a comprehensive investigation of these processes and their conditions. Apart from the detailed report on using O 2 as the passivating component, a comparison of the use of O 2 and N 2 is also provided.…”

Limitations of Cl2/O2‐based ICP‐RIE of deep holes for planar photonic crystals in InP

“…The results presented in Ref. [12] suggest, e.g., that there is a fundamental correlation between deep holes and rough sidewall surfaces. However, the data were not consistent enough to enable a clear identification of inherent trade-offs between all relevant output parameters, such as hole depth, hole shape, and sidewall roughness.…”

“…The separate influence of various input parameters of the Cl 2 /N 2 process was analyzed in detail in Ref. [12]. The results presented in Ref.…”

Atomic scale study of InP etching by Cl2-Ar ICP plasma discharge

“…Indeed, it is now possible with plasma etching process using high density plasma reactors such as Inductive Coupled Plasma (ICP) to transfer nanometer scale patterns from the mask to the substrate [1][2][3][4][5]. The success of the high aspect ratio pattern transfer without geometrical defects [6][7][8][9] (bowing, undercut, trenching,..) is tributary of a good understanding of the physical and chemical mechanisms of the plasma discharge and the surface kinetic processes.…”