Integrated electron optical/differential pumping/imaging signal system for an environmental scanning electron microscope

An environmental scanning electron microscope comprising:

• (a) an objective lens magnetic housing having two annular diaphragms attached thereto at different axial locations defining at least two interior passages of different pressure, and including means for generating and directing an electron beam toward a specimen supported within a specimen chamber;
• (b) an aperture holder releasably secured between said two diaphragms, said aperture holder comprising:
• (i) a main body having a conduit therein;
• (ii) a lower pressure limiting aperture in the lower end of said conduit sized to permit an electron beam to pass therethrough and sealed to one of said diaphragms to limit the passage of gas from the specimen chamber of the said environmental scanning electron microscope to the lower interior passage above said lower aperture;
• (iii) a port in said main body above the said lower aperture, said port providing communication from said conduit into a lower interior passage in said objective lens assembly provided between said two diaphragms;
• (iv) an upper pressure limiting aperture within said conduit positioned above said lower aperture and above the said port therein, said upper aperture being sized to permit an electron beam to pass therethrough and sealed to limit the passage of gas from the conduit to an upper interior passage within said objective lens assembly;
• and
• (v) an electron detector located at the lower end of said main body and separated therefrom by insulating means.

An environmental scanning electron microscope comprising:

• (a) a substantially cylindrical objective lens magnetic housing containing an axially disposed vacuum liner tube and containing means for magnetically focusing a beam of electrons passing through said liner tube, said housing having upper and lower pumping ports therein axially distanced from one another;
• (b) at least two annular diaphragms of nonmagnetic material and a final magnetic annular diaphragm attached to said housing at different axial locations and extending inwardly of said housing, said diaphragms defining at least two interior passages, each of which communicate with the said upper and lower pumping ports, respectively;
• and
• (c) aperture means located within the central opening of said diaphragms to permit passage of said electron beam from said vacuum liner tube into said interior passages and then into a specimen chamber and to limit passage of gas molecules from the said specimen chamber into the said interior passages.

An environmental scanning electron microscope comprising:

• (a) a substantially cylindrical objective lens magnetic housing containing an axially disposed vacuum liner tube and containing means for magnetically focusing a beam of electrons passing through said liner tube;
• (b) an annular ring comprised of magnetic material abutting said magnetic housing at the lower end thereof and containing at least two ports therein located axially with respect to one another;
• (c) at least two annular diaphragms comprised of nonmagnetic material and a final magnetic annular diaphragm attached to said annular ring at different axial locations and extending inwardly of said ring, said diaphragms defining at least two interior passages, each of which communicates with one of the said ports in said annular ring;
• and
• (d) aperture means located within the central openings of said diaphragms to permit passage of said electron beam from said vacuum liner tube into said interior passages and then into a specimen chamber nd to limit passage of gas molecules from the said specimen chamber into the said interior passages.

An environmental scanning electron microscope comprising:

• (a) a substantially cylindrical objective lens magnetic housing containing an axially disposed vacuum liner tube and containing means for magnetically focusing a beam of electrons passing through said liner tube;
• (b) an annular ring comprised of magnetic material abutting said magnetic housing at the lower end thereof and containing at least two ports therein located axially with respect to one another;
• (c) at least two annular diaphragms comprised of nonmagnetic material and a final magnetic annular diaphragm attached to said annular ring at different axial locations and extending inwardly of said ring, said diaphragms defining at least two interior passages, each of which communicates with one of the said ports in said annular ring;
• and
• (d) a combination aperture holder and electron detector releasably received and sealed within the central openings of the said annular diaphragms, said aperture holder having apertures therein for passage of the electron beam and gas into and out of the specimen chamber and the said interior passages and having electron detector means associated with the lower portion thereof, said detector means being insulated from the body of said aperture holder.

An environmental scanning electron microscope comprising:

• (a) a substantially cylindrical objective lens magnetic housing containing an axially disposed vacuum liner tube and containing means for magnetically focusing a beam of electrons passing through said liner tube, said housing having a pumping port therein;
• (b) an annular diaphragm of nonmagnetic material and a final magnetic annular diaphragm attached to said housing at different axial locations and extending inwardly of said housing, said diaphragms defining an interior passage which communicates with said pumping port;
• and
• (c) aperture means located within the central opening of said diaphragms to permit passage of said electron beam from said vacuum liner tube into said interior passage and then into a specimen chamber and to limit passage of gas molecules from the said specimen chamber into the said interior passage.

An environmental scanning electron microscope comprising:

• (a) a substantially cylindrical objective lens magnetic housing containing an axially disposed vacuum liner tube and containing means for magnetically focusing a beam of electrons passing through said liner tube;
• (b) an annular ring comprised of magnetic material abutting said magnetic housing at the lower end thereof an containing a pumping port;
• (c) an annular diaphragm of nonmagnetic material and a final magnetic annular diaphragm attached to said housing at different axial locations and extending inwardly of said housing, said diaphragms defining an interior passage which communicates with said pumping port;
• and
• (d) a combination aperture holder and electron detector releasably received and sealed within the central opening of said diaphragms said aperture holder having apertures thereon for passage of the electron beam and gas into and out of a specimen chamber and the said interior passage and having electron detector means associated with the lower portion thereof, said detector means being insulated from the body of said aperture holder.