J. Hong

PLASMA ETCHING OF III-V SEMICONDUCTORS IN BCL3 CHEMISTRIES : PART I: GAAS AND RELATED COMPOUNDS

BCl3/Ar discharges provide rapid, smooth pattern transfer in GaAs, AlGaAs, GaP, and GaSb over a wide range of plasma conditions. At high BCl3-to-Ar ratio there is significant surface roughening on GaSb, which is correlated with the presence of B- and Cl-containing residues detected by Auger electron spectroscopy. BCl3/N2 discharges provide similar etch rates to BCl3/Ar, but when used with photoresist masks lead to rough morphologies on the semiconductor materials due to enhanced dissociation and redeposition of the resist. Etch rates with electron cyclotron resonance discharges are up to two orders of magnitude higher than for rf-only conditions.

Cl2/Ar plasma etching of binary, ternary, and quaternary In‐based compound semiconductors

A simple Cl2/Ar plasma chemistry can provide smooth, high‐rate etching of InP, InAs, InGaAs, A1InAs, and InGaAsP at room temperature under conditions in which there is a balance between formation and sputter desorption of the normally involatile InCl3. When the neutral/ion ratio is either too high or too low, surface roughening is apparent due either to the presence of InCl3, or to preferential loss of the group V element. The etching has been investigated as a function of microwave power (600–1000 W), rf power (0–300 W), process pressure (1.5–10 mTorr), and Cl2:Ar ratio under electron cyclotron resonance conditions. Use of N2 or H2, rather than Ar, as gas additives to the chlorine, did not produce smooth, stoichiometric etched surfaces.

Patterning of thin film NiMnSb using inductively coupled plasma etching

Several plasma chemistries based on fluorine (SF6, NF3), Cl2/Ar, BI3/Ar, or BBr3/Ar were compared for etching NiMnSb under inductively coupled plasma (ICP) conditions. ICP source power, radio frequency chuck power, and plasma composition were found to have strong effects on the etch rate. SF6/Ar discharges provided the fastest etch rates for NiMnSb (>1 μm min−1) even with small amounts of source power (100 W) addition. On the other hand, NF3/Ar showed net deposition rather than etching at source powers >100 W or at high NF3 percentages. Cl2/Ar showed a similar trend, with net deposition at low dc self-bias (−100 V), but net etching above this threshold. BBr3/Ar discharges produced deposition under all the conditions investigated while relatively high etch rates (⩾3000 A min−1) were obtained with BI3/Ar at halide percentages ⩾70%. In terms of etched surface morphology, SF6/Ar provided the best surfaces, with root-mean-square roughness of 2.5 nm and vertical etched profiles. Surfaces etched in plasma chemis...

IC1 plasma etching of III–V semiconductors

Etch rates in excess of 1.5 μm/min for InP and InSb, 1.2 μm/min for GaAs and 0.7 μm/min for GaSb at room temperature were obtained in electron cyclotron resonance IC1/Ar plasmas at low additional rf power (150 W). There was little dependence of etch rate on microwave power over the range 400–1000 W for InP, and selectivities of 6–10 over mask materials such as SiO2, SiNx, and W were typical. Smooth surface morphologies were obtained over a wide range of plasma parameters for GaAs and GaSb, while preferential loss of P led to rough morphologies for InP at high rf powers. IC1-based plasmas appear to be promising universal etchants for Ga- and In-based III–V semiconductors.

Thermal stability and etching characteristics of electron beam deposited SiO and SiO2

We have studied the thermal stability and etching characteristics of electron beam deposited SiO and SiO2. Scanning electron microscopy, Auger, atomic form microscopy, and ellipsometry were used to analyze the surface morphology, roughness, and film composition as a function of annealing temperatures. Both SiO and SiO2 showed excellent thermal stability up to 400 °C anneal and refractive index, surface morphology and pattern edge definition of both films barely changed. For higher temperature anneal, based on Auger analysis results, the ratio of Si/O of SiO2 film stayed constant after 700 °C. However, the Si/O ratio of SiO film increased from 0.54 to 0.62 due to oxygen outdiffusion. Dry etch characteristics of SiO and SiO2 were investigated using SF6 and NF3 discharges in a Plasma Therm inductively coupled plasma system. Wet etches were performed using buffered HF and HF/H2O solutions. Dry etch rates of SiO2 were comparable with that of conventional plasma enhanced chemical vapor deposition SiO2. SiO2 etc...

Plasma etching of III–V semiconductors in BCl3 chemistries: Part II: InP and related compounds

BCl3/Ar and BCl3/N2 plasma chemistries were compared for patterning of InP, InAs, InSb, InGaAs, InGaAsP, and AlInAs. Under electron cyclotron resonance conditions etch rates in excess of 1 µm/min can be achieved at room temperature with low additional rf chuck power (150 W). The etch rates are similar for both chemistries, with smoother surface morphologies for BCl3/Ar. However, the surfaces are still approximately an order of magnitude rougher (as quantified by atomic force microscopy) than those obtained under the same conditions with Cl2/Ar. InP surfaces etched at high BCl3-to-Ar ratios have measurable concentrations of boron-and chlorine-containing residues.

New plasma chemistries for dry etching of InGaAlP alloys: BI3 and BBr3

Inductively coupled plasma etching of InGaP, AlInP and AlGaP in BI3 or BBr3 discharges was investigated as a function of source power, dc chuck bias and plasma composition. InGaP etches at the fastest rates (>6000 A min−1) in both chemistries, followed by AlGaP. It is found that AlInP provides an excellent etch stop for the other two materials in both mixtures. The InGaP surface morphology improves with increasing BI3 or BBr3 content, and with increasing dc chuck bias. The etched features for this material are highly anisotropic. Etch selectivities for InGaP over SiO2 and SiNx of ⩾8 are obtained in both plasma chemistries, and there is no etch incubation time with either mixture, indicating that both can scavenge the native oxide on InGaP, AlGaP and AlInP.