End point detection method for physical etching process
AssigneeVarian Associates, Inc.
InventorsDaniel F. Downey, George T. Lecouras
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Abstract
A method for determining the end point for a physical etching process step measures the current at the target being etched and detects changes in the current. Changes in the current measured at the target are indicative of transitions between dissimilar materials or of depth of penetration in a particular material. Momentary changes in the etching flux of the physical etching process are factored out by measuring the current on a mask placed in the vicinity of the target and by subtracting mask current from current measured at the target.
Claims7
A method for determining the end point of a physical etching process step, comprising the steps of:
- measuring the current through a semiconductor layer having at least one overlying layer thereon being etched;
- measuring the current through a mask positioned in the vicinity of said layer;
- subtracting said current through said mask from said current measured through said semiconductor layer to produce a layer-dependent current component;
- and
- detecting changes in said layer-dependent current component as the physical etching step progresses with end point being indicated by detection of a change greater than a preselected amount.
Dependencies are inferred from the claim text.