# US 9,518,930 B2 · Scattered light measurement system

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- Number: US 9,518,930 B2
- Document ID: US9518930B2
- Status: Granted
- Kind: B2
- Application number: 13/964,399
- Filed: 2013-08-12
- Published: 2013-12-26
- Granted: 2016-12-13
- Earliest claimed: 2004-12-19
- Assignees: KLA-Tencor Corporation
- Applicants: KLA-Tencor Corporation
- Inventors: Neil Judell; Ian T. Kohl; Songping Gao; Richard E. Bills
- Web page: https://patentgrep.com/patent/US9518930B2

## CPC

- G01N 21/9501: {Semiconductor wafers (manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)}
- G01N 21/21: Polarisation-affecting properties (G01N21/19 takes precedence)
- G01N 21/47: Scattering, i.e. diffuse reflection (G01N21/25, G01N21/41 take precedence {G01N21/55 takes precedence})
- G01N 21/4738: {Diffuse reflection (precedence is given to G01N21/55 - G01N21/57 if specular component is taken into consideration), e.g. also for testing fluids, fibrous materials}
- G01N 21/474: {Details of optical heads therefor, e.g. using optical fibres}
- G01N 21/55: Specular reflectivity
- G01N 21/88: Investigating the presence of flaws or contamination
- G01N 21/8806: {Specially adapted optical and illumination features}
- G01N 21/95: characterised by the material or shape of the object to be examined (G01N21/89 - G01N21/91, G01N21/94 take precedence)
- G01N 21/956: Inspecting patterns on the surface of objects {(contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)}
- G06T 7/0004: {Industrial image inspection}
- G01N 2021/4707: {Forward scatter; Low angle scatter}
- G01N 2021/4711: {Multiangle measurement}
- G01N 2021/4792: {Polarisation of scatter light}
- G01N 2021/556: {Measuring separately scattering and specular}
- G01N 2021/8809: {Adjustment for highlighting flaws}
- G01N 2021/8848: {Polarisation of light}
- G01N 2021/8864: {Mapping zones of defects}
- G01N 2021/8877: {Proximity analysis, local statistics}
- G01N 2021/8896: {Circuits specially adapted for system specific signal conditioning}
- G01N 2201/0612: Laser diodes
- G01N 2201/105: Purely optical scan
- G06T 2207/30148: Semiconductor; IC; Wafer
- Y10T 29/49826: Assembling or joining
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

An optical collection and detection system for use in a surface inspection system for inspecting a surface of a workpiece. The surface inspection system has an incident beam projected through a back quartersphere and toward a desired location on the surface, which is a scanned spot having a known scanned spot size. The incident beam impinges on the surface to create scattered light that is collected by a collector module. The collector module includes collection optics for collecting and focusing the scattered light to form focused scattered light. A collector output slit is positioned at an output of the collector module, through which the collection optics focus the scattered light. The scattered light that is associated with the scanned spot forms an imaged spot at the collector output slit. The collector output slit has a width that is selected to be proportional to the scanned spot size, so as to allow passage of the focused scattered light associated with the scanned spot, and exclude the focused scattered light associated with the workpiece regions other than the desired spot. A collector output varying subsystem varies the collector output slit so as to at least one of minimize passage of Rayleigh light scatter through the collector output slit or optimize a signal to air-scatter-noise ratio.

## Claims

### Claim 1

An optical collection and detection system for use in a surface inspection system for inspecting a surface of a workpiece, the surface inspection system having an incident beam projected through a back quartersphere and toward a desired location on the surface comprising an scanned spot having a known scanned spot size, the incident beam impinging on the surface to create scattered light that is collected by a collector module, the collector module comprising:
collection optics for collecting and focusing the scattered light to form focused scattered light;
a collector output slit positioned at an output of the collector module and through which the collection optics focus the scattered light, with scattered light associated with the scanned spot forming an imaged spot at the collector output slit; the collector output slit having a width that is selected to be proportional to the scanned spot size to allow passage of the focused scattered light associated with the scanned spot but to exclude the focused scattered light associated with the workpiece regions other than the desired spot;
at least one of the collector output slit width and side-to-side position disposed so as to minimize passage of Rayleigh light scatter through the collector output slit.

### Claim 2

An optical collection and detection system for use in a surface inspection system for inspecting a surface of a workpiece, the surface inspection system having an incident beam projected through a back quartersphere and toward a desired location on the surface comprising an scanned spot having a known scanned spot size, the incident beam impinging on the surface to create scattered light that is collected by a collector module, the collector module comprising:
collection optics for collecting and focusing the scattered light to form focused scattered light;
a collector output slit positioned at an output of the collector module and through which the collection optics focus the scattered light, with scattered light associated with the scanned spot forming an imaged spot at the collector output slit; the collector output slit having a width that is selected to be proportional to the scanned spot size to allow passage of the focused scattered light associated with the scanned spot but to exclude the focused scattered light associated with the workpiece regions other than the desired spot;
at least one of the collector output slit width and side-to-side position disposed so as to optimize a signal to air-scatter-noise ratio.

### Claim 3

A method of inspecting a surface of a workpiece, comprising the steps of:
projecting an incident beam through a back quartersphere and toward a desired location on the surface comprising a scanned spot having a known scanned spot size,
the incident beam impinging on the surface thereby creating scattered light,
collecting and focusing the scattered light with collection optics to form focused scattered light,
focusing the scattered light through a collector output slit,
forming an imaged spot at the collector output slit with scattered light associated with the scanned spot,
selecting the collector output slit width to be proportional to the scanned spot size,
allowing passage of the focused scattered light associated with the scanned spot through the collector output slit,
excluding passage of the focused scattered light associated with the workpiece regions other than the desired spot through the collector output slit, and
varying the collector output slit to minimize passage of Rayleigh light scatter through the collector output slit.