ABRUPT AND ARBITRARY PROFILE FORMATION IN SILICON USING A LOW-KINETIC-ENERGY ION-BOMBARDMENT PROCESS

We have discovered that the carrier concentration in an epitaxial sili con film formed by the low-energy ion bombardment process is easily co ntrolled by changing the ion bombardment energy during the film growth . While maintaining the perfect crystallinity of an epitaxial silicon layer grown at a temperature as low as 350 degrees C an arbitrary-shap ed carrier concentration profile has been created in the film. Formati on of box-shaped profiles as well as staircase-shaped profiles having very abrupt transitions is demonstrated. Formation of such arbitrary-s haped carrier profiles in an epitaxial layer is quite essential in the design of ultrasmall-dimension devices. The stability of carrier prof iles against heat treatments also has been investigated.