| 摘要 |
<p>A method of dry etching a GaAs/AlGaAs stacked system with high selectivity without employing a chlorofluorocarbon (CFC) gas. When selectively etching an n ©& -GaAs layer stacked on an n ©& -AlGaAs layer for forming e.g. a gate recess of a high electron mobility transistor (HEMT), a gas having a composition capable of yielding free sulfur (S) and fluorine radicals (F*) in a plasma under conditions of discharge dissociation is used as an etching gas. S is deposited on a pattern sidewall to form a sidewall protection film to contribute to anisotropic etching. On the other hand, F* plays the role of formation of AlFX with low vapor pressure on an exposed surface of the underlayer of n ©& -AlGaAs to stop etching, to say nothing of a role of an etchant. Although a gas system which is by far the simplest is a mixed system of S<6>F<6>/Xe, a gas system may be employed which is capable of generating Cl* or Br* for producing a reaction product having a high vapor pressure or augmenting S deposition. More concretely, mixed systems of S<6>F<6>/Cl<6>, S<6>F<6>/S<6>Cl<6> or S<6>Cl<6>/ClF<7> may be employed. <IMAGE></p> |
