System for directly measuring the depth of a high aspect ratio etched feature on a wafer

摘要

A system (10) for directly measuring the depth of a high aspect ratio etched feature on a wafer (80) that includes an etched surface (82) and a non-etched surface (84). The system (10) utilizes an infrared reflectometer (12) that in a preferred embodiment includes a swept laser (14), a fiber circulator (16), a photodetector (22) and a combination collimator (18) and an objective lens (20). From the objective lens (20) a focused incident light (23) is produced that is applied to the non-etched surface (84) of the wafer (80). From the wafer (80) is produced a reflected light (25) that is processed through the reflectometer (12) and applied to an ADC (24) where a corresponding digital data signal (29) is produced. The digital data signal (29) is applied to a computer (30) that, in combination with software (32), measures the depth of the etched feature that is then viewed on a display (34).