US4785182A — Secondary electron detector for use in a gaseous …

Claim 1

Independent Claim 363 words

A device for generating, amplifying and detecting secondary electrons from a surface of a sample which comprises: (a) a vacuum envelope having a pressure limiting aperture; (b) a charged particle beam source located within the vacuum envelope and capable of emitting a charged particle beam; (c) focusing means located within the vacuum envelope and capable of directing a charged particle beam emitted by the charged particle beam source through the pressure limiting aperture; (d) sample platform means, disposed outside the vacuum envelope, capable of maintaining a sample enveloped in gas at a pressure of at least 0.05 torr in registration with the pressure limiting aperture such that a surface of the sample may be exposed to a charged particle beam emitted from the charged particle beam source and directed through the pressure limiting aperture; (e) an electrode disposed outside of the vacuum envelope and positioned within between about 1 and about 200 mm from the sample platform means such that secondary electrons emitted from a surface of a sample located on the sample platform means and exposed to a charged particle beam emitted from the charged particle beam source may come into contact with it; (f) a voltage source, connected between the electrode and an electrical ground, capable of maintaining an electrical potential difference between the electrode and the sample platform means of greater than about 50 volts and less than about 2000 volts, the electrode potential being positive relative to the sample platform means potential so as to accelerate secondary electrons emitted from a surface of a sample located on the sample platform means with an electric field of sufficient strength so as to cause emitted secondary electrons to collide with gas molecules and produce negative charge carriers which can subsequently produce additional negative charge carriers through multiple collisions with other gas molecules resulting in a number of negative charge carriers greater than and proportional to the number of original secondary electrons, the strength of the electric field being sufficiently low so as to avoid catastrophic electrical discharging or arcing; (g) a current amplifier connected to the electrode; and (h) current detection means connected between the current amplifier and an electrical ground.

Claim 2

Independent Claim 363 words

A device for generating, amplifying and detecting secondary electrons from a surface of a sample which comprises: (a) a vacuum envelope having a pressure limiting aperture; (b) a charged particle beam source located within the vacuum envelope and capable of emitting a charged particle beam; (c) focusing means located within the vacuum envelope and capable of directing a charged particle beam emitted by the charged particle beam source through the pressure limiting aperture; (d) sample platform means, disposed outside the vacuum envelope, capable of maintaining a sample enveloped in gas at a pressure of at least 0.05 torr in registration with the pressure limiting aperture such that a surface of the sample may be exposed to a charged particle beam emitted from the charged particle beam source and directed through the pressure limiting aperture; (e) an electrode disposed outside of the vacuum envelope and positioned within between about 1 and about 200 mm from the sample platform means such that secondary electrons emitted from a surface of a sample located on the sample platform means and exposed to a charged particle beam emitted from the charged particle beam source may come into contact with it; (f) a voltage source, connected between the electrode and an electrical ground, capable of maintaining an electrical potential difference between the electrode and the sample platform means of greater than about 50 volts and less than about 2000 volts, the electrode potential being positive relative to the sample platform means potential so as to accelerate secondary electrons emitted from a surface of a sample located on the sample platform means with an electric field of sufficient strength so as to cause emitted secondary electrons to collide with gas molecules and produce negative charge carriers which can subsequently produce additional negative charge carriers through multiple collisions with other gas molecules resulting in a number of negative charge carriers greater than and proportional to the number of original secondary electrons, the strength of the electric field being sufficiently low so as to avoid catastrophic electrical discharging or arcing; (g) a current amplifier connected to the electrode; and (h) current detection means connected between the current amplifier and an electrical ground.

Claim 3

Dependent Claim 16 words

A device of claim 1 wherein the charged particle beam source is an electron beam source.

Claim 4

Dependent Claim 18 words

A device of claim 1 wherein the electrode is positioned approximately 10 mm from the sample platform means.

Claim 5

Dependent Claim 11 words

A device of claim 1 wherein the voltage source is adjustable.

Claim 6

Dependent Claim 367 words

A scanning electron microscope which comprises: (a) a vacuum envelope having a pressure limiting aperture; (b) an electron beam source located within the vacuum envelope and capable of emitting an electron beam; (c) focusing means located within the vacuum envelope and capable of directing an electron beam emitted by the electron beam source through the pressure limiting aperture; (d) electron beam scanning means located within the vacuum envelope and capable of scanning an electron beam emitted by the electron beam source across the diameter of the pressure limiting aperture; (e) sample platform means, disposed outside the vacuum envelope, capable of maintaining a sample enveloped in gas at a pressure of at least 0.05 torr in registration with the pressure limiting aperture such that a surface of the sample may be exposed to an electron beam emitted from the electron beam source and directed through the pressure limiting aperture; (f) an electrode disposed outside of the vacuum envelope and positioned within between about 1 and about 200 mm of the sample platform means such that secondary electrons emitted from a surface of a sample located on the sample platform means and exposed to an electron beam emitted from the electron beam source may come into contact with it; (g) a voltage source, connected between the electrode and an electrical ground, capable of maintaining an electrical potential difference between the electrode and the sample platform means of greater than about 50 volts and less than about 2000 volts, the electrode potential being positive relative to the sample platform means potential, so as to accelerate the secondary electrons with an electric field of sufficient strength so as to cause the secondary electrons emitted from the sample to collide with gas molecules and produce negative charge carriers which can subsequently produce additional negative charge carriers through multiple collisions with other gas molecules resulting in a number of negative charge carriers greater than and proportional to the number of original secondary electrons, the strength of the electric field being sufficiently low so as to avoid catastrophic electrical discharging or arcing; (h) a current amplifier connected to the electrode; and (i) current detection means connected between the current amplifier and an electrical ground.

Claim 7

Dependent Claim 367 words

A scanning electron microscope which comprises: (a) a vacuum envelope having a pressure limiting aperture; (b) an electron beam source located within the vacuum envelope and capable of emitting an electron beam; (c) focusing means located within the vacuum envelope and capable of directing an electron beam emitted by the electron beam source through the pressure limiting aperture; (d) electron beam scanning means located within the vacuum envelope and capable of scanning an electron beam emitted by the electron beam source across the diameter of the pressure limiting aperture; (e) sample platform means, disposed outside the vacuum envelope, capable of maintaining a sample enveloped in gas at a pressure of at least 0.05 torr in registration with the pressure limiting aperture such that a surface of the sample may be exposed to an electron beam emitted from the electron beam source and directed through the pressure limiting aperture; (f) an electrode disposed outside of the vacuum envelope and positioned within between about 1 and about 200 mm of the sample platform means such that secondary electrons emitted from a surface of a sample located on the sample platform means and exposed to an electron beam emitted from the electron beam source may come into contact with it; (g) a voltage source, connected between the electrode and an electrical ground, capable of maintaining an electrical potential difference between the electrode and the sample platform means of greater than about 50 volts and less than about 2000 volts, the electrode potential being positive relative to the sample platform means potential, so as to accelerate the secondary electrons with an electric field of sufficient strength so as to cause the secondary electrons emitted from the sample to collide with gas molecules and produce negative charge carriers which can subsequently produce additional negative charge carriers through multiple collisions with other gas molecules resulting in a number of negative charge carriers greater than and proportional to the number of original secondary electrons, the strength of the electric field being sufficiently low so as to avoid catastrophic electrical discharging or arcing; (h) a current amplifier connected to the electrode; and (i) current detection means connected between the current amplifier and an electrical ground.

Claim 8

Dependent Claim 20 words

A scanning electron microscope of claim 5 wherein the elelctrode is positioned approximately 10 mm from the sample platform means.

Claim 9

Dependent Claim 13 words

A scanning electron microscope of claim 5 wherein the voltage source is adjustable.

Claim 10

Dependent Claim 33 words

A scanning electron microscope of claim 5 wherein the electron beam source is capable of emitting an electron with energy within the range from about 1 kiloelectron volt to about 40 kiloelectron volts.

Claim 11

Independent Claim 161 words

A method for generating, amplifying and detecting secondary electrons from a surface of a sample which comprises: (a) scanning the surface of the sample under a suitable gaseous pressure with a charged particle beam having sufficient energy so as to cause secondary electrons to be emitted from the surface of the sample; (b) accelerating the secondary electrons with an electric field of sufficient strength so as to cause them to collide with gas molecules and produce negative charge carriers which can subsequently produce additional negative charge carriers through multiple collisions with other gas molecules resulting in a number of negative charge carriers greater than and proportional to the number of original secondary electrons, the strength of the electric field being sufficiently low so as to avoid catastrophic electrical discharging or arcing; and (c) detecting electrical current resulting from electrons and ionized gas molecules, thereby detecting a signal proportional to the number of secondary electrons emitted from the surface of the sample.

Claim 12

Independent Claim 161 words

A method for generating, amplifying and detecting secondary electrons from a surface of a sample which comprises: (a) scanning the surface of the sample under a suitable gaseous pressure with a charged particle beam having sufficient energy so as to cause secondary electrons to be emitted from the surface of the sample; (b) accelerating the secondary electrons with an electric field of sufficient strength so as to cause them to collide with gas molecules and produce negative charge carriers which can subsequently produce additional negative charge carriers through multiple collisions with other gas molecules resulting in a number of negative charge carriers greater than and proportional to the number of original secondary electrons, the strength of the electric field being sufficiently low so as to avoid catastrophic electrical discharging or arcing; and (c) detecting electrical current resulting from electrons and ionized gas molecules, thereby detecting a signal proportional to the number of secondary electrons emitted from the surface of the sample.

Claim 13

Dependent Claim 15 words

A sample according to claim 9, wherein the charged particle beam is an electron beam.

Claim 14

Dependent Claim 25 words

A method according to claim 1, wherein the electron beam has energy within the range from about 1 kiloelectron volt to about 40 kiloelectron volts.

Claim 15

Dependent Claim 22 words

A method according to claim 9, wherein the gaseous pressure is within the range from about 0.05 torr to about 20 torr.

Claim 16

Dependent Claim 25 words

A method according to claim 9, wherein the electric field comprises an electrical potential of at least 50 volts and less than about 2000 volts.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1991-11-15	1992-05-16	1992-11-15	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1995-11-15	1996-05-16	1996-11-15	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1999-11-15	2000-05-16	2000-11-15	$7700.00	Window Closed / Lapsed

Secondary electron detector for use in a gaseous atmosphere

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