Apparatus and methods for optically inspecting a sample for anomalies
First Claim
1. An inspection system for detecting defects on a sample, the system comprising:
- a beam generator for directing an incident beam towards a sample surface;
a detector positioned to detect a detected beam originating from the sample surface in response to the incident beam, wherein the detector comprises;
a sensor for detecting the detected beam and generating a detected signal based on the detected beam;
a non-linear component coupled to the sensor, the non-linear component being arranged to generate a non-linear detected signal based on the detected signal; and
a first analog-to-digital converter (ADC) coupled to the non-linear component, the first ADC being arranged to digitize the non-linear detected signal into a first digitized detected signal, wherein the detector further comprises a first feed back circuit for automatically adjusting an illumination intensity of the incident beam based on the non-linear detected signal or the detected signal; and
a data processor for determining whether there is a defect present on the sample surface based on the first digitized detected signal.
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Abstract
Disclosed are methods and apparatus for detecting a relatively wide dynamic range of intensity values from a beam (e.g., scattered light, reflected light, or secondary electrons) originating from a sample, such as a semiconductor wafer. In other words, the inspection system provides detected output signals having wide dynamic ranges. The detected output signals may then be analyzed to determine whether defects are present on the sample. For example, the intensity values from a target die are compared to the intensity values from a corresponding portion of a reference die, where a significant intensity difference may be defined as a defect. In a specific embodiment, an inspection system for detecting defects on a sample is disclosed. The system includes a beam generator for directing an incident beam towards a sample surface and a detector positioned to detect a detected beam originating from the sample surface in response to the incident beam. The detector has a sensor for detecting the detected beam and generating a detected signal based on the detected beam and a non-linear component coupled to the sensor. The non-linear component is arranged to generate a non-linear detected signal based on the detected signal. The detector further includes a first analog-to-digital converter (ADC) coupled to the non-linear component. The first ADC is arranged to digitize the non-linear detected signal into a digitized detected signal.
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Citations
19 Claims
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1. An inspection system for detecting defects on a sample, the system comprising:
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a beam generator for directing an incident beam towards a sample surface;
a detector positioned to detect a detected beam originating from the sample surface in response to the incident beam, wherein the detector comprises;
a sensor for detecting the detected beam and generating a detected signal based on the detected beam;
a non-linear component coupled to the sensor, the non-linear component being arranged to generate a non-linear detected signal based on the detected signal; and
a first analog-to-digital converter (ADC) coupled to the non-linear component, the first ADC being arranged to digitize the non-linear detected signal into a first digitized detected signal, wherein the detector further comprises a first feed back circuit for automatically adjusting an illumination intensity of the incident beam based on the non-linear detected signal or the detected signal; and
a data processor for determining whether there is a defect present on the sample surface based on the first digitized detected signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 17)
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11. An inspection system as recited in claim 23, wherein the variable voltage supply component is a proportional integral differential (PID) controller.
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18. A method for detecting defects on a sample, the method comprising:
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directing an incident beam towards a first sample surface;
detecting a first detected beam and generating a first detected signal based on the first detected beam, wherein the first detected beam originates from the first sample surface in response to the incident beam;
generating a first non-linear detected signal based on the first detected signal;
digitizing the first non-linear detected signal into a first digitized detected signal;
analyzing the first digitized detected signal to determine whether it corresponds to a defect on the first sample surface; and
automatically adjusting an illumination intensity of the incident beam based on the first non-linear detected signal or the first detected signal. - View Dependent Claims (19)
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Specification