Analysis of semiconductor surfaces by secondary ion mass spectrometry
AssigneeMicron Technology, Inc.
InventorEugene P. Marsh
Life of this patent
Estimating the term…
Abstract
An apparatus and method for mass spectrometric determination of contaminant components of a thin oxide surface layer of a semiconductor wafer use 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.
Claims51
A method for determining the concentration of a contaminant in a thin oxide surface layer having a depth, said thin oxide layer located on a semiconductor material, said method comprising:
- providing a mass spectrometer apparatus having a primary sputtering ion beam, directing apparatus, and analyzing apparatus, said directing apparatus and analyzing apparatus for directing and analyzing a secondary ion stream produced by operation of said mass spectrometer apparatus;
- predetermining a mass of surface layer required to be sampled for determining a contaminant concentration;
- supporting said semiconductor material on a movable mechanical stage within said mass spectrometer apparatus;
- moving said movable mechanical stage in a scanning motion while sputtering said thin oxide surface layer;
- directing said secondary ion stream formed during operation of said mass spectrometer apparatus for analysis, said semiconductor material sputtered to a depth not generally exceeding the depth of said thin oxide surface layer;
- and
- moving said movable mechanical stage in a rastering motion to sputter and analyze said thin oxide surface layer over an extended area.
A method for determining a concentration of a contaminant in a thin oxide surface layer having a depth, said thin oxide layer located on a semiconductor material, said method comprising:
- providing a mass spectrometer apparatus having a primary sputtering ion beam, a directing apparatus, and an analyzing apparatus, said directing apparatus and analyzing apparatus for directing and analyzing a secondary ion stream produced by the operation of said mass spectrometer apparatus;
- predetermining a mass of surface layer required to be sampled for determining a contaminant concentration at preset limits of said contaminant concentration;
- supporting said semiconductor material on a movable mechanical stage within said mass spectrometer apparatus;
- moving said movable mechanical stage while sputtering said thin oxide surface layer;
- directing said secondary ion stream to said mass spectrometer apparatus for analysis, said movable mechanical stage moved at a speed, said semiconductor material sputtered to a depth not substantially exceeding the depth of said surface layer;
- and
- moving said movable mechanical stage in a rastering motion to sputter and analyze said thin oxide surface layer over an extended area, a total sputtered analyte approximately equaling said predetermined required mass of an analyte.
An apparatus for determining quantities of conductive trace elements and compounds in a shallow surface layer having a depth, said apparatus comprising:
- a movable mechanical stage configured to move a semiconductor wafer laterally in X and Y axes;
- a primary ion beam for focusing on said shallow surface layer of said semiconductor wafer;
- a mass spectrometer detector and analyzer configured to determine a content of a secondary ion stream;
- directing apparatus configured to direct said secondary ion stream to said mass spectrometer detector for analysis;
- stage control apparatus configured to move said movable mechanical stage at a planar scanning speed in multiple scanning paths such that said 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, said 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 said secondary ion stream;
- a movable stage configured to support, scan and raster a surface layer of the semiconductor wafer to produce said secondary ion stream;
- an interferometer to determine non-planarity of said surface layer;
- and
- control apparatus for providing a uniform extraction field of surface layer depth independent of the non-planarity of said surface layer.
A method for determining the concentration of a contaminant in an oxide surface layer having a depth, said oxide layer located on a semiconductor material using a mass spectrometer apparatus having a primary sputtering ion beam, a moveable mechanical stage, directing apparatus and analyzing apparatus, said method comprising:
- supporting said semiconductor material on said moveable mechanical stage;
- moving said moveable mechanical stage while sputtering said oxide surface layer to a depth not generally exceeding the depth of said oxide surface layer, the sputtering rate in mass per unit time controlled by varying a primary ion beam strength and the sputter depth controlled by varying a scanning speed in length per unit time;
- and
- analyzing said sputtered oxide surface layer over an extended area.
A method for determining the concentration of a contaminant in an oxide surface layer having a depth, said oxide surface layer located on a semiconductor material using a mass spectrometer apparatus having a primary sputtering ion beam, a moveable mechanical stage, directing apparatus and analyzing apparatus, said method comprising:
- supporting said semiconductor material on said moveable mechanical stage;
- moving said moveable mechanical stage while sputtering said oxide surface layer to a depth not generally exceeding the depth of said oxide surface layer;
- analyzing said sputtered oxide surface layer over an extended area;
- measuring non-planarity of said oxide surface layer of said semiconductor material;
- and
- continuously correcting for the non-planarity of said surface of said semiconductor material during sputtering.
A method for determining the concentration of a contaminant in an oxide surface layer having a depth, said oxide surface layer located on a semiconductor material using a mass spectrometer apparatus having a primary sputtering ion beam, a moveable mechanical stage, directing apparatus and analyzing apparatus, said method comprising:
- supporting said semiconductor material on said moveable mechanical stage;
- moving said moveable mechanical stage while sputtering said oxide surface layer to a depth not generally exceeding the depth of said oxide surface layer;
- analyzing said sputtered oxide surface layer over an extended area;
- measuring non-planarity of said oxide surface layer of said semiconductor material, the measuring the non-planarity of said oxide surface layer of said semiconductor material comprising:
- directing one portion of an interferometer split beam to an X-Y location on said oxide surface layer of said semiconductor material being reflected back to a detector;
- directing another portion of said split beam to a mirror at a known distance being reflected back to said detector;
- and
- determining a difference in traveled distance by use of phase modulation and Fourier analysis to determine an offset of said semiconductor material surface;
- and
- continuously correcting for the non-planarity of said surface of said oxide surface layer located on said semiconductor material during sputtering.
A method for determining the concentration of a contaminant in an oxide surface layer having a depth, said oxide surface layer located on a semiconductor material using a mass spectrometer apparatus having a primary sputtering ion beam, a moveable mechanical stage, directing apparatus and analyzing apparatus, said method comprising:
- supporting said semiconductor material on said moveable mechanical stage;
- moving said moveable mechanical stage while sputtering said oxide surface layer to a depth not generally exceeding the depth of said oxide surface layer;
- analyzing said sputtered oxide surface layer over an extended area;
- measuring non-planarity of said oxide surface of said semiconductor material;
- and
- continuously correcting for the non-planarity of said oxide surface layer of said semiconductor material during sputtering, the continuously correcting for the non-planarity comprising moving said moveable mechanical stage along a Z-axis to maintain an approximately constant distance between said primary sputtering ion beam and said oxide surface layer of said semiconductor material being sputtered.
A method for determining the concentration of a contaminant in an oxide surface layer of depth Q on a semiconductor material using a mass spectrometer apparatus having a primary sputtering ion beam, a moveable mechanical stage, directing apparatus and analyzing apparatus, said method comprising:
- supporting said semiconductor material on said moveable mechanical stage;
- moving said moveable mechanical stage while sputtering said oxide surface layer to a depth not generally exceeding the depth of said oxide surface layer;
- analyzing said sputtered oxide surface layer over an extended area;
- measuring non-planarity of said oxide surface of said semiconductor material;
- and
- continuously correcting for the non-planarity of said oxide surface layer of said semiconductor material during sputtering, the continuously correcting for the non-planarity comprising changing an electrical potential of said semiconductor material relative to an extraction potential.
Dependencies are inferred from the claim text.