Apparatus and method for non-contact surface voltage probing by scanning photoelectron emission

• US 5,150,043 A
• Filed: 02/11/1991
• Issued: 09/22/1992
• Est. Priority Date: 02/11/1991
• Status: Expired due to Fees

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Flesner, Larry D.
• Primary Examiner(s): Karlsen, Ernest F.
• Assistant Examiner(s): BURNS, WILLIAM
• Application Number:
  US07/653,829
• Time in Patent Office: 589 Days
• Field of Search: 324/158 R, 324/158 D, 324/96, 356/389, 356/237
• US Class Current: 324/750.14
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• CPC Class Codes: G01R 31/308 using non-ionising electromagnetic radiation, e.g. optical radiation investigating or analysing materials by the use of optical means G01N21/00; image analysis G06T7/00

Abstract

An apparatus and method for non-contact sensing electrical potentials of selected regions on the surface of a sample are provided. A typical sample is an integrated circuit, electronic device, or semiconductor material. The sample is positioned within a vacuum chamber and irradiated with an ultraviolet light beam so that the material emits electrons by the photoelectric effect. The electrons have kinetic energies which are variable according to the electrical potential of the surface of the material. Emitted electrons having kinetic energies within a predetermined range are selected by an electron energy analyzer. An electron detector receives the selected electrons and produces electrical signals corresponding to the energies of said selected electrons. In another embodiment of the invention, a modulated light beam other than the ultraviolet light probe beam irradiates the material in order to produce time varying modulation of the photoelectron energy spectrum.

Claims

1. An apparatus for sensing the electrical potential on the surface of a material, comprising:

a vacuum chamber in which the material is positioned;

an ultraviolet light source for irradiating a first surface of the material with an ultraviolet beam so that the material emits electrons having kinetic energies which are variable according to the electrical potential of said first surface of the material;

first means positioned to irradiate a second surface of the material, different than said first surface, with a modulated light beam for producing photovoltaic effects in the material; and

second means positioned to receive said emitted electrons for displaying data corresponding to said emitted electrons having kinetic energies within a predetermined range.

2. The apparatus of claim 1, wherein said first means includes:

a Nd-YAG laser for generating said modulated light beam.

3. The apparatus of claim 2, wherein said first means further includes:

an optical fiber positioned to receive said modulated light beam from said Nd-YAG laser and emit said modulated light beam so as to illuminate selected regions of said material.

4. A non-contact method for sensing photovoltaic effects on the surface of a material, comprising the steps of:

irradiating a selected first region of the material with an ultraviolet light beam so that the material emits electrons having kinetic energies which are variable according to the electrical potential of the sample surface, said sample surface being positioned within a vacuum chamber;

irradiating a selected second region of the material with a modulated light beam to produce photovoltaic effects in the material while simultaneously irradiating the material with said ultraviolet light beam, said modulated beam having a wavelength longer than the wavelength of said ultraviolet light beam;

selecting electrons having kinetic energies within a predetermined range; and

producing electrical signals corresponding to the energies of said selected electrons.

5. The method of claim 4 wherein:

said first region of said material is on a first surface of said material; and

said second region of said material is on a second surface of said material, said second surface being different than said first surface.

6. The method of claim 5 further including:

propagating said modulated beam through an optical light guide.