Surface inspecting apparatus and method for calibrating same
View Patent ↗While an illumination optical system is irradiating the surface of a contaminated standard wafer with illumination light, this illumination light is scanned over the surface of the contaminated standard wafer, then detectors of a detection optical system each detect the light scattered from the surface of the contaminated standard wafer, next a predefined reference value in addition to detection results on the scattered light is used to calculate a compensation parameter “Comp” for detection sensitivity correction of photomultiplier tubes of the detectors, and the compensation parameter “Comp” is separated into a time-varying deterioration parameter “P”, an optical characteristics parameter “Opt”, and a sensor characteristics parameter “Lr”, and correspondingly managed. This makes is easy to calibrate the detection sensitivity.
1. A surface inspecting apparatus comprising:
a light unit that irradiates with illumination light a surface of a body to be inspected;
a scanner that scans the light irradiated from the light unit over the surface of the to-be-inspected body;
at least one light detector that detects the light scattered from the surface of the body to be inspected;
a processor configured to:
use a predefined reference value, as well as a detection result on measuring light incident upon the light detector from a measuring-light generator that generates the measuring light that serves as a reference for measuring detection sensitivity of the light detector, to compute a sensitivity correction value for correcting the detection sensitivity of the light detector;
separate the sensitivity correction value into element parameters corresponding to a plurality of factors influential upon detection sensitivity of the surface inspecting apparatus; and
memory, associated with the processor, for storing the element parameters obtained from the separation by the processor.
2. The surface inspecting apparatus according to claim 1 , wherein:
the measuring-light generator includes a reference body to be inspected, the reference body being formed to generate measuring light that serves as a reference for the illumination light from the light unit.
3. The surface inspecting apparatus according to claim 1 , wherein:
the measuring-light generator includes a light source that emits measuring light serving as a reference into the light detector.
4. The surface inspecting apparatus according to claim 1 , wherein:
the plurality of element parameters include an element parameter relating to a time-varying deterioration state of the light detector.
5. The surface inspecting apparatus according to claim 1 , wherein:
the plurality of element parameters include an element parameter relating to optical characteristics of the light detector.
6. The surface inspecting apparatus according to claim 1 , wherein:
the plurality of element parameters include an element parameter relating to linearity characteristics of the light detector.
7. The surface inspecting apparatus according to claim 1 , further comprising:
a display that displays the element parameters in a chronological fashion.
8. The surface inspecting apparatus according to claim 1 , further comprising:
a display that displays either a difference of the detection result with respect to a reference value, or a ratio of the detection result to the reference value.
9. The surface inspecting apparatus according to claim 1 , further comprising:
a display that display a warning for an operator if at least one of the element parameters oversteps a predefined range.
10. The surface inspecting apparatus according to claim 1 , wherein:
if at least one of the element parameters oversteps a predefined range, the processor determines whether the overstepping state has been caused by time-varying deterioration or optical conditions.
11. A method for calibrating a surface inspecting apparatus that includes a light unit that irradiates with illumination light a surface of a body to be inspected, a scanner that scans the light irradiated from the light unit over the surface of the to-be-inspected body, and at least one detector that detects the light scattered from the surface of the body to be inspected, the method comprising the steps of:
using a predefined reference value, as well as a detection result on measuring light incident upon the light detector from a measuring-light generator that generates the measuring light that serves as a reference for measuring detection sensitivity of the light detector;
computing, by a processor, a sensitivity correction value for correcting the detection sensitivity of the light detector;
separating, by the processor, the sensitivity correction value into element parameters corresponding to a plurality of factors influential upon detection sensitivity of the surface inspecting apparatus; and
storing, in memory associated with the processor, the element parameters obtained from the separation.