Photocathode including silicon substrate with boron layer
AssigneeKLA-Tencor Corporation
InventorsYung-Ho Alex Chuang, John Fielden
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Abstract
A photocathode is formed on a monocrystalline silicon substrate having opposing illuminated (top) and output (bottom) surfaces. To prevent oxidation of the silicon, a thin (e.g., 1-5 nm) boron layer is disposed directly on the output surface using a process that minimizes oxidation and defects. An optional second boron layer is formed on the illuminated (top) surface, and an optional anti-reflective material layer is formed on the second boron layer to enhance entry of photons into the silicon substrate. An optional external potential is generated between the opposing illuminated (top) and output (bottom) surfaces. The photocathode forms part of novel electron-bombarded charge-coupled device (EBCCD) sensors and inspection systems.
Claims19
A sensor for generating an electric signal in response to photons directed onto a receiving surface, the sensor comprising:
- a photocathode disposed adjacent to the receiving surface and configured to emit photoelectrons in response to said photons, the photocathode including:
- a silicon substrate having a first surface facing the receiving surface, and a second surface facing away from the receiving surface, and
- a first layer consisting essentially of boron disposed directly on the second surface of the silicon substrate;
- a detection device positioned to collect electrons emitted from the photocathode having a detecting surface facing the second layer, said detection device configured to detect said photoelectrons emitted by said photocathode, and configured to generate said electric signal in response to said detected photoelectrons;
- and
- a housing operably connected between the photocathode and the detection device such that the detecting surface of the detection device is separated from the first layer of the photocathode by an intervening gap region,
- wherein when an electric field is generated between the photocathode and the detection device, electrons emitted from the photocathode into the gap region are accelerated toward the detection device by the electric field.
An inspection system comprising:
- an illumination source configured to transmit photons onto a sample;
- a sensor configured to detect photons from the sample;
- and
- an optical system configured to guide the photons from the illumination source to the sample, and from the sample to a receiving surface of the sensor,
- wherein the sensor comprises:
- a photocathode disposed adjacent to the receiving surface and configured to emit photoelectrons in response to said photons, the photocathode including:
- a monocrystalline silicon substrate having a first surface directed toward the optical system, and a second surface facing away from the optical system, and
- a first layer consisting essentially of boron disposed directly on the second surface of the silicon substrate;
- a detection device having a detecting surface facing the second layer, said detection device being configured to detect said photoelectrons emitted by said photocathode, and being configured to generate said electric signal in response to said detected photoelectrons;
- a housing operably connecting the photocathode and the detection device such that the detecting surface of the detection device is separated from the second layer of the photocathode by an intervening gap region;
- and
- conductive structures configured to generate an electric field between the photocathode and the detection device such that electrons emitted from the photocathode into the gap region are accelerated toward the detection device by the electric field.
An electron-bombarded charge-coupled device (EBCCD) sensor for generating an electric signal in response to photons directed onto a receiving surface, the EBCCD sensor comprising:
- a photocathode disposed adjacent to the receiving surface and configured to emit photoelectrons in response to said photons, the photocathode including:
- a silicon substrate having a first surface facing the receiving surface, and a second surface facing away from the receiving surface, and
- a first layer consisting essentially of boron disposed directly on the second surface of the silicon substrate;
- a charge coupled device (CCD) positioned to collect electrons emitted from the photocathode having a detecting surface facing the second layer, said CCD configured to detect said photoelectrons emitted by said photocathode, and configured to generate said electric signal in response to said detected photoelectrons;
- and
- a housing operably connected between the photocathode and the CCD such that the detecting surface of the detection device is separated from the first layer of the photocathode by an intervening gap region,
- wherein when an electric field is generated between the photocathode and the CCD, electrons emitted from the photocathode into the gap region are accelerated toward the CCD by the electric field.
Dependencies are inferred from the claim text.