Contribution of atomic and molecular ions to dry-etch damage

Using ions of low energy is accepted as an essential requirement in achieving low damage when dry-etching III-V semiconductors. SiCl₄ is widely used to make GaAs electron devices. We have studied the effect of a SiCl₄ reactive ion etching environment as well as the effect of the bombardment by the separate constituent ions from a SiCl₄ discharge in a low-energy implanter. Photoluminescence intensity measurements from GaAs/AlGaAs quantum well probe structures have been used to study the damage inflicted. We find that molecular ions contribute less to deep damage than do atomic ions. Thus, low damage may be promoted by selecting reactive etch chemistries with low ion energies and small atomic to molecular ion fractions.