Hideo Ohtsuki

Vertical and Smooth Etching of InP by Cl2/Xe Inductively Coupled Plasma

We have demonstrated anisotropic and smooth etching of InP by an inductively coupled plasma (ICP) using Cl2/Xe at high substrate temperatures. We investigated the etching characteristics by varying the substrate temperature, gas pressure, Cl2 flow rate and rf power. Vertical and smooth dry etching of InP was achieved under a low dc bias of -80 V. The ICP etching process is an effective low-damage dry-etching technique for microfabrication of InP-based optoelectronic devices.

Highly angular dependent high-contrast grating mirror and its application for transverse-mode control of VCSELs

We report on the design and fabrication of a highly angular dependent high contrast grating (HCG) mirror. The modeling and experiment on amorphous-Si/SiO2 HCG clearly show the large angular dependence of reflectivity, which enables single transverse-mode operations of large-area VCSELs. We fabricate 980 nm VCSELs with the angular dependent HCG functioning as a spatial frequency filter. We obtained the single transverse mode operation of the fabricated device in contrast to conventional VCSELs with semiconductor multilayer mirrors

Mass Effect of Etching Gases in Vertical and Smooth Dry Etching of InP

We compared several kinds of etching gases in inductively coupled plasma (ICP) and electron cyclotron resonance (ECR) plasma etching processes for investigating the etching performance. It was found that a heavy etching gas such as SiCl4 plays an important role for smooth etching of InP, which is independent of ICP and ECR plasma sources.

Plasma Diagnostics in Inductively Coupled Plasma Etching Using Cl2/Xe

We investigated the plasma characteristics in an inductively coupled plasma (ICP) etching process using Cl2/Xe by means of a quadrupole mass spectrometer equipped with an ion energy analyzer. It was found that the ion energy of Cl+ increased with decreasing etching pressure, and the quantity of Cl+ increased with decreasing Cl2 flow rate. Ions including etching products such as Si+, Cl+, Xe+ and SiClx+ were observed in the etching plasma. It is suggested from the results of this experiment that the etching profile can be controlled by the in situ monitoring of the quantity of Cl+ ions.

Emission Spectrochemical Analysis in Dry Etching Process of InP by Cl2 Inductively Coupled Plasma

We carried out a diagnostic study of the Cl2 inductively coupled plasma (ICP) etching process by means of spectrochemical analysis using a narrow-field optical fiber probe. Many elements including etching products such as Cl+, Si, In and SiClx were observed in the etching plasma. It was found that the state of the plasma is strongly dependent on the monitoring distance normal to the sample. To stabilize the dry etching process, it is important to monitor the plasma at the spot of the reaction between sample and plasma.

Smooth and Vertical Profile Dry Etching of Si Using XeF2 Plasma

We demonstrated the discharge of XeF2 plasma and investigated the dry etching process of Si using XeF2 plasma. A vertical etching profile and a smooth etched surface, which satisfy the requirements for optical device fabrication, were obtained. The etching rate of Si was 0.7 µm/min at 1 Pa and 100 W. It was found that the RF power dependences of the emission intensities of Xe, F, and XeF were similar to that of the etching rate of Si. The etching rate ratio of Si to SiO2 in the XeF2 plasma etching process was approximately 10, which was much larger than that in the CF4/O2 plasma etching process. We believe that XeF2 plasma etching is a very simple and useful process for Si-based optical devices such as photonic crystals, narrow optical waveguides, and micro-electro-mechanical systems (MEMS) device fabrication.

Iodine Solid Source Inductively Coupled Plasma Etching of InP

We have demonstrated vertical and smooth inductively coupled plasma (ICP) dry etching of InP using solid iodine as a gas source at a low process temperature of 90°C. We prepared a solid iodine crystal in the ICP etching chamber as the etching gas source. Iodine gas was supplied from the solid source at a high vapor pressure into the process chamber. Vertical and smooth etching was realized under the condition of low temperature and low power. The typical etching rate was 0.4 µm/min. We believe that solid I2-ICP etching is a very simple and useful process for InP-based device fabrication with a resist mask.

Low-Temperature Dry Etching of InP by Inductively Coupled Plasma Using HI/Cl2

We have demonstrated vertical and smooth inductively coupled plasma (ICP) dry etching of InP using HI/Cl2 gasses at a low process temperature of 90°C. We measured the etching rate by varying bias power. A small flow rate of HI was required to obtain vertical profiles. We consider that HI/Cl2-ICP etching is useful in InP-based device fabrication with a resist mask.

Solid source dry etching process for GaAs and InP

In this study, we have demonstrated vertical and smooth inductively coupled plasma (ICP) dry etching of InP and GaAs using either solid iodine or ICl3 powder as gas sources at a low process temperature of 90 °C. We prepared solid iodine crystal and ICl3 powder in the ICP etching chamber as etching gas sources in a process chamber. Iodine or chlorine gases were supplied with a high vapor pressure from the solid source into the process chamber. Vertical and smooth etching was realized under a condition of low temperature and low bias RF power. We believe that solid iodine- and ICl3 powder-ICP etching are very simple and useful processes for InP- and GaAs-based device fabrication with a resist mask.

Measurement of plasma density for control of etching profile in inductively coupled plasma etching of InP

We investigated the effect of the plasma density on the control of the etching profile in an inductively coupled plasma (ICP) etching of InP. It was found that the total ion density is not a good measure of the control of the etching profile. We have to take into account the quantity of each ion for etching profile control. We suggest that the etching profile of InP can be controlled by the in situ monitoring of the quantity of Cl+ ions.