Thomson-Csf

Jean Vatus

Jean Chevrier

The invention pertains to a method for the selective etching of a surface layer which is automatically stopped at a subjacent layer. According to the invention, a first layer of a material containing gallium is selectively etched with respect to a second layer containing aluminium by reactive ion etching in the presence of a pure freon plasma C Cl.sub.2 F.sub.2. At low pressures (0.5 to 2.5 pascals), the etching is anisotropic and makes it possible to etch the gate recess of a field effect transistor. At a higher pressure (6 to 10 pascals), the etching is isotropic and makes it possible to sub-etch the first layer. Application to the manufacture of field effect transistors made of group III-V materials, with low access resistances.

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Verrieres le Bouisson, France

Jean Vatus