METHOD OF FORMING SPACERS FOR A GATE OF A TRANSISTOR

摘要

A method for forming spacers of a field effect transistor gate, comprising forming a nitride layer covering the gate, modifying the nitride layer by contacting the nitride layer with plasma comprising ions heavier than hydrogen and CxHy so as to form a nitride-based modified layer and a carbon film; with the modifying being so executed that plasma creates an anisotropic bombardment with hydrogen (H)-based ions from CxHy in a favorite direction parallel to flanks of the gate and so as to modify an upper portion of the thickness of the nitride-based layer at the level of the flanks of the gate only, with the anisotropic bombardment with ions heavier than hydrogen enabling the carbon in CxHy to form a carbon film, and removing the nitride-based modified layer, using etching of the nitride-based modified layer to said carbon film and to the non-modified portions which the spacers are made of.

主权项

1. A method for forming spacers of a field effect transistor gate, with the gate being located above an active layer made of a semiconductor material, comprising a step of forming a nitride-based layer overlying the gate of said transistor, wherein after the step of forming the nitride-based layer:
at least a step of modifying the nitride-based layer by contacting the nitride-based layer with plasma wherein CxHy is introduced where x is the proportion of carbon and y is the proportion of hydrogen ions (H), and comprising ions heavier than hydrogen; with the conditions of plasma, more particularly the concentration of CxHy, the ion energy and the main implantation direction being so chosen that:
plasma creates an anisotropic bombardment with hydrogen-based ions (H, H+, H2+, H3+ etc.) from CxHy, with the bombardment being anisotropic in a direction parallel to flanks of the gate and so as to modify an upper portion of the thickness of the nitride-based layer at the level of the flanks of the gate only, while keeping non-modified portions of the nitride-based layer covering the flanks of the gate;plasma chemical species containing carbon from CxHy form a carbon film specifically on surfaces parallel to the direction of the bombardment;plasma creates a bombardment with the ions heavier than hydrogen which prevents said carbon-containing plasma chemical species from CxHy from forming a carbon film, more particularly on the surfaces of the nitride-based layer which are perpendicular to the direction of the bombardment; at least a step of removing the nitride-based modified layer using a selective etching of the nitride-based modified layer relative to non-modified portions of the nitride-based layer.