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Patterning the group-111 nitrides has been challenging due to their strong bond energies and relatively inert chemical nature as compared to other compound semiconductors. Plasma etch processes have been used almost exclusively to pattern these films. The use of high-density plasma etch systems, including inductively coupled plasmas (ICP), has resulted in relatively high etch rates (often greater than 1 .O pdmin) with anisotropic profiles and smooth etch morphologies. However, the etch mechanism is often dominated by high ion bombardment energies which can minimize etch selectivity. The use of an ICP-generated BCl,/Cl, pl%sma has yielded a highly versatile GaN etch process with rates ranging from 100 to 8000 Mmin making this plasma chemistry a prime candidate for optimization of etch selectivity. In this study, we will report ICP etch rates and selectivities for GaN, AlN, and InN as a function of BCl,/Cl, flow ratios, cathode rf-power, and ICP-source power. GaN:InN and GaN:AlN etch selectivities were typically less than 7: 1 and showed the strongest dependence on flow ratio. This trend may be attributed to faster GaN etch rates observed at higher concentrations of atomic C1 which was monitored using optical emission spectroscopy (OES).

A 1‐day‐old Appaloosa colt developed vesicles/bullae involving the skin of the lips and prepuce and multiple mucous membranes. Histopathology revealed subepidermal vesicles/bullae that were clear or contained variable numbers of neutrophils and erythrocytes. The separated epidermis appeared viable. The denuded dermal papillae were often disrupted by microabscesses or coated with fibrinosuppurative debris. Fragmented basement membrane components were attached to exposed dermal papillae. Immunoperoxidase staining of sections for deposition of IgG, IgM, IgA, and C3 were positive for IgG at the basement membrane and intercellular bridges. Complete recovery ensued. The characteristics of the subepidermal bullous lesions and clinical course of lesion resolution in this foal suggested a drug‐induced pathogenesis. The only known drug exposure of the foal or mare was topical application of 7% iodine to the umbilicus at the time of foaling. Similar reactions to iodine administration have been reported in humans.

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