Semiconductor metrology and inspection based on an x-ray source with an electron emitter array

A measurement system, comprising:

• an electron emitter array based x-ray illumination source configured to illuminate an area of a specimen with an incident x-ray beam, wherein the electron emitter based x-ray illumination source includes,
• an electron emitter array including a plurality of electron emitters each fabricated on a common substrate, each of the plurality of electron emitters comprising:
• an emitter structure fabricated on the common substrate, the emitter structure terminating at a sharp tip;
• an extractor electrode fabricated around the sharp tip of the emitter structure, wherein a void separates the emitter tip and at least a portion of the extractor electrode;
• and
• a first insulating layer disposed between the emitter structure and the extractor electrode, wherein the first insulating layer electrically isolates the emitter structure from the extractor electrode, wherein a difference in electrical potential between the emitter structure and the extractor electrode stimulates an electron current flow from the sharp tip of the emitter structure;
• and
• an anode structure spatially separated from the electron emitter array, wherein a difference in electrical potential between the anode structure and the substrate accelerates the electron current flow from each of the plurality of electron emitters of the electron emitter array to the anode, wherein the incidence of the electron current flow onto the anode structure stimulates X-ray emission from the anode structure;
• an x-ray detector configured to receive radiation from the specimen in response to the incident x-ray beam and generate signals indicative of a first property of the specimen;
• an electron lens located around a path of the electron current flow from the electron emitter array to the anode structure;
• a first barrier separating a first portion of a vacuum chamber and a second portion of the vacuum chamber, wherein the electron emitter array is disposed in the first portion of the vacuum chamber and the electron lens is disposed in the second portion of the vacuum chamber, and wherein the first portion of the vacuum chamber is maintained at a lower pressure than the second portion of the vacuum chamber;
• and
• a second barrier separating a third portion of the vacuum chamber and the second portion of the vacuum chamber, wherein the anode structure is disposed in the third portion of the vacuum chamber, wherein the second portion of the vacuum chamber is maintained at a lower pressure than the third portion of the vacuum chamber.

A method comprising:

• providing a first difference in electrical potential between at least one emitter structure of an electron emitter array and at least one extractor electrode corresponding to the at least one emitter structure, the first difference in electrical potential stimulating an electron current flow from a sharp tip of the at least one emitter structure, wherein each emitter structure of the electron emitter array is fabricated on a common substrate;
• providing a second difference in electrical potential between the common substrate and an anode structure, the second difference in electrical potential accelerating the electron current flow from the electron emitter array to the anode structure;
• focusing the electron current flow onto an area of an anode structure with an electron lens disposed in a path of the electron current between the electron emitter array and the anode structure, the incidence of the electron current flow onto the anode structure stimulating X-ray emission;
• maintaining a vacuum in a first portion of a vacuum chamber, wherein the electron emitter array is disposed in the first portion of the vacuum chamber;
• maintaining a vacuum in a second portion of the vacuum chamber, wherein the electron lens is disposed in the second portion of the vacuum chamber, and wherein the vacuum maintained in the first portion of the vacuum chamber is a lower pressure than the vacuum maintained in the second portion of the vacuum chamber;
• and
• maintaining a vacuum in a third portion of the vacuum chamber, wherein the anode structure is disposed in the third portion of the vacuum chamber, and wherein the vacuum maintained in the second portion of the vacuum chamber is a lower pressure than the vacuum maintained in the third portion of the vacuum chamber.