Analysis of semiconductor surfaces by secondary ion mass spectrometry and methods
AssigneeMicron Technology, Inc.
InventorEugene P. Marsh
Life of this patent
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Abstract
An apparatus and method for mass spectrometric determination of contaminant components of a thin oxide surface layer of a semiconductor wafer using a movable mechanical stage to scan and raster a large area of the wafer in a continuous scanning motion. The mass of analyte is greatly increased, resulting in improved sensitivity to trace components in the surface layer by a factor of 10-100 or more. A light beam interferometer is used to determine non-planarity from e.g. warping of the wafer and provide a correction by maintaining a constant separation between the wafer and the extraction plate or adjusting the electrical bias of the wafer relative to the extraction bias.
Claims20
A method for determining the concentration of a contaminant in a thin oxide surface layer having a depth, the thin oxide surface layer located on a semiconductor material, the method comprising:
- providing a mass spectrometer apparatus having a primary sputtering ion beam, directing apparatus, and analyzing apparatus, the directing apparatus and analyzing apparatus for directing and analyzing a secondary ion stream produced by operation of the mass spectrometer apparatus, the mass spectrometer apparatus comprising one of a secondary ion mass spectrometer (SIMS) and a time-of-flight secondary ion mass spectrometer (TOF-SIMS);
- predetermining a mass of surface layer required to be sampled for determining a contaminant concentration;
- supporting the semiconductor material on a movable mechanical stage within the mass spectrometer apparatus;
- moving the movable mechanical stage in a scanning motion while sputtering the thin oxide surface layer;
- directing the secondary ion stream produced by operation of the mass spectrometer apparatus for analysis, the semiconductor material sputtered to a depth not generally exceeding the depth of the thin oxide surface layer;
- moving the movable mechanical stage in a rastering motion to sputter and analyze the thin oxide surface layer over an extended area;
- and
- measuring a non-planarity of the thin oxide surface layer.
A method for determining a concentration of a contaminant in a thin oxide surface layer having a depth, the thin oxide surface layer located on a semiconductor material, the method comprising:
- providing a mass spectrometer apparatus having a primary sputtering ion beam, a directing apparatus, and an analyzing apparatus, the directing apparatus and analyzing apparatus for directing and analyzing the secondary ion stream produced by operation of the mass spectrometer apparatus, the mass spectrometer apparatus comprising one of a secondary ion mass spectrometer (SIMS) and a time-of-flight secondary ion mass spectrometer (TOF-SIMS);
- predetermining a mass of surface layer required to be sampled for determining a contaminant concentration at preset limits of the contaminant concentration;
- supporting the semiconductor material on a movable mechanical stage within the mass spectrometer apparatus;
- moving the movable mechanical stage while sputtering the thin oxide surface layer;
- directing the secondary ion stream to the mass spectrometer apparatus for analysis, the movable mechanical stage moved at a speed, the semiconductor material sputtered to a depth not substantially exceeding the depth of the thin oxide surface layer;
- moving the movable mechanical stage in a rastering motion to sputter and analyze the thin oxide surface layer over an extended area, a total sputtered analyte approximately equaling the predetermined required mass of surface layer;
- and
- measuring a non-planarity of the thin oxide surface layer.
An apparatus for determining quantities of conductive trace elements and compounds in a shallow surface layer having a depth, the apparatus comprising:
- a movable mechanical stage configured to move a semiconductor wafer laterally in X and Y axes and at least one other axis;
- a primary ion beam for focusing on a shallow surface layer of the semiconductor wafer;
- a mass spectrometer detector and analyzer configured to determine a content of a secondary ion stream, the mass spectrometer detector comprising one of a SIMS and a TOF-SIMS;
- directing apparatus configured to direct the secondary ion stream to the mass spectrometer detector for analysis;
- and
- stage control apparatus configured to move the movable mechanical stage at a planar scanning speed in multiple scanning paths such that the primary ion beam is rastered over an area not confined to electrostatically rasterable area limits.
An apparatus for determining concentrations of trace components of a surface layer having a depth on a semiconductor wafer, the apparatus comprising:
- a secondary ion mass spectrometer having a primary sputtering beam for producing a secondary ion stream and a secondary ion detector to receive the secondary ion stream, the secondary ion mass spectrometer comprising one of a SIMS and a TOF-SIMS;
- a movable stage configured to support, scan and raster the surface layer of the semiconductor wafer to produce the secondary ion stream, the movable stage movable in at least two axes of direction;
- an interferometer to determine non-planarity of the surface layer;
- and
- control apparatus for providing a uniform extraction field of the surface layer depth independent of the non-planarity of the surface layer.
Dependencies are inferred from the claim text.