Guan-Sik Cho

Temperature-dependent Cl2/Ar plasma etching of bulk single-crystal ZnO

The etch rate of bulk ZnO in Cl2/Ar high density plasmas was found to be thermally activated with an activation energy of ∼0.31 eV at 200 °C).

Investigation of GaAs Dry Etching in a Planar Inductively Coupled BCl3 Plasma

We investigated dry etching of GaAs in a planar inductively coupled plasma (ICP) reactor with BCl 3 gas chemistry. The process parameters included planar ICP source power, chamber pressure, reactive ion etching (RIE) chuck power, and gas flow rate. The ICP source power was varied from 0 to 500 W. Chamber pressure was changed from 5 to 20 mTorr. RIE chuck power was controlled from 0 to 150 W. The gas flow rate was varied from 10 to 40 sccm. We found that a process condition at 20 sccm BCl 3 , 300 W ICP, 100 W RIE, and 7.5 mTorr chamber pressure gave an excellent etch result. The etched GaAs feature showed extremely smooth surface (rms roughness 3000 A/min) and good selectivity to a photoresist (>3:1). X-ray photoelectron spectroscopy study on the surface of processed GaAs proved a very clean surface of the material after dry etching. We also noticed that our planar ICP source was successfully ignited both with and without RIE chuck power, which was generally not the case with a typical cylindrical ICP source, where assistance of RIE chuck power was required for turning on a plasma and maintaining it. These results indicate that the planar ICP source could be a very versatile tool for advanced dry etching of damage-sensitive compound semiconductors.

Role of inert gas additive on dry etch patterning of InGaP in planar inductively coupled BCl3 plasmas

Abstract The dry etch characteristics of InGaP in BCl3 planar inductively coupled plasmas (ICP) with additions of Ar or Ne were determined. The inert gas additive provided enhanced etch rates relative to pure BCl3 and Ne addition in particular produced much higher etch rates at low ratios of BCl3 in the mixture. The etched features tended to have sloped sidewalls and much rougher surfaces than for GaAs and AlGaAs etched under the same conditions. The practical effect of the Ar or Ne addition was the ability to operate the ICP source over a somewhat broader range of pressures and still maintain practical etch rates. The use of room temperature BCl3-based etching in a planar ICP appears feasible for base and emitter mesa applications in InGaP/GaAs heterojunction bipolar transistors.

Planar Inductively Coupled BCl3 Plasma Etching of III-V Semiconductors

Both Ga-based (GaAs, AlGaAs) and In-based (InGaP, InP, InAs, and InGaAsP) compound semiconductors were etched in a planar inductively coupled plasma (ICP) reactor in pure BCl 3 . The Ga-based materials etched at significantly higher rates, as expected from the higher volatilities of their trichloride etch products relative to InCl 3 . In contrast to the more common cylindrical geometry ICP sources, the dc self-bias which controls ion energy is not strongly dependent on source power up to ∼400 W while etch rates increase rapidly over this power range. The source tunes easily even at very low powers (<100 W) but operates inefficiently above ∼10 mTorr, with a marked decrease in both emission intensity from the discharge and in resulting etch rates of the compound semiconductors. The etched surfaces of both AlGaAs and GaAs have comparable root-mean-square roughness and similar stoichiometry to the unetched control samples, while the surfaces of In-based materials are degraded by the BCl 3 etching.

O2/N2 Plasma Etching of Acrylic in a Multi-layers Electrode RIE System

We investigated dry etching of acrylic (PMMA) in O2/N2 plasmas using a multi-layers electrode reactive ion etching (RIE) system. The multi-layers electrode RIE system had an electrode (or a chuck) consisted of 4 individual layers in a series. The diameter of the electrodes was 150 mm. The etch process parameters we studied were both applied RIE chuck power on the electrodes and % O2 composition in the N2/ O2 plasma mixtures. In details, the RIE chuck power was changed from 75 to 200 W.% O2 in the plasmas was varied from 0 to 100% at the fixed total gas flow rates of 20 sccm. The etch results of acrylic in the multi- layers electrode RIE system were characterized in terms of negatively induced dc bias on the electrode, etch rates and RMS surface roughness. Etch rate of acrylic was increased more than twice from about 0.2 µm/min to over 0.4 µm/min when RIE chuck power was changed from 75 to 200 W. 1 sigma uniformity of etch rate variation of acrylic on the 4 layers electrode was slightly increased from 2.3 to 3.2% when RIE chuck power was changed from 75 to 200 W at the fixed etch condition of 16 sccm O2/4 sccm N2 gas flow and 100 mTorr chamber pressure. Surface morphology was also investigated using both a surface profilometry and scanning electron microscopy (SEM). The RMS roughness of etched acrylic surface was strongly affected by % O2 composition in the O2/N2 plasmas. However, RIE chuck power changes hardly affected the roughness results in the range of 75-200 W. During etching experiment, Optical Emission Spectroscopy (OES) data was taken and we found both N2 peak (354.27 nm) and O2 peak (777.54 nm). The preliminarily overall results showed that the multi-layers electrode concept could be successfully utilized for high volume reactive ion etching of acrylic in the future.

Enhancement of Light Guiding Efficiency in CMOS Image Sensor by Introducing an Optical Thin Film

We consider introducing an optical thin film to the light guiding wall of a pixel in order to enhance the light guiding efficiency of a CMOS image sensor. Simulating the reflectance as a function of the incidence angle using the Essential Macleod program, we find that the range of total internal reflection is greatly increased for several materials. Particularly when air is chosen as the thin film material, the critical angle of total internal reflection could be shifted to about 50 degrees.

Dry etching of GaAs-based semiconductors in high-density planar inductively coupled BCl/sub 3/ plasmas

Summary form only given, as follows. We investigated planar ICP etching of GaAs-based semiconductors including GaAs, AlGaAs and InGaP with BCl/sub 3/ gas chemistry.

Plasma diagnosis and end-point detection with an optical emission spectroscopy during high density inductively coupled BCl/sub 3/ plasma etching

Summary form only given, as follows. Plasma diagnosis and end-point detection technology with optical emission spectroscopy is getting attention for precise control of dry etching process. Especially, optical emission spectroscopy can be a very useful tool for monitoring of dry etching of compound semiconductors. OES technology does not interfere plasma processing during monitoring.

High Density Inductively Coupled Plasma Etching of InP in BCl 3 -Based Chemistries

We studied InP etching in high density planar inductively coupled and /Ar plasmas(PICP). The investigated process parameters were PICP source power, RIE chuck power, chamber pressure and /Ar gas composition. It was found that increase of PICP source power and RIE chuck power increased etch rate of InP, while that of chamber pressure decreased etch rate. Etched InP surface was clean and smooth (RMS roughness /min) after the planar /Ar ICP etching. It may make it possible to open a new regime of InP etching with -free plasma chemistry. Some amount of Ar addition (

Dry Etching of GaAs and AlGaAs Semiconductor Materials in High Density BCl 3 and BCl 3 /Ar Inductively Coupled Plasmas

We investigated dry etching of GaAs and AiGaAs in a high density planar inductively coupled plasma system with BCland BCl/Ar gas chemistry. A detailed etch process study of GaAs and ALGaAs was peformed as functions of ICP source power, RIE chuck power and mixing ratio of and Ar. Chamber process pressure was fixed at 7.5 mTorr in this study. The ICP source power and RIE chuck power were varied from 0 to 500 W and from 0 to 150 W, respectively. GaAs etch rate increased with the increase of ICP source power and RIE chuck power. It was also found that etch rates of GaAs in /5Ar plasmas were relatively high with applied RIE chuck power compared to pure 20 sccm plasmas. The result was the same as AlGaAs. We expect that high ion-assisted effect in /Ar plasma increased etch rates of both materials. The GaAs and AlGaAs features etched at 20 sccm and /5Ar with 300 W ICP source power, 100 W RIE chuck power and 7.5 mTorr showed very smooth surfaces(RMS roughness