Electron beam system for inspection and review of 3d devices

Patent metadata

Field	Value
Publication number	US-2021327770-A1
Application number	US-202117224407-A
Country	US
Kind code	A1
Filing date	Apr 7, 2021
Priority date	Apr 15, 2020
Publication date	Oct 21, 2021
Grant date	—

Abstract

An electron beam system for wafer inspection and review of 3D devices provides a depth of focus up to 20 microns. To inspect and review wafer surfaces or sub-micron-below surface defects with low landing energies in hundreds to thousands of electron Volts, a Wien-filter-free beam splitting optics with three magnetic deflectors can be used with an energy-boosting upper Wehnelt electrode to reduce spherical and chromatic aberration coefficients of the objective lens.

First claim

What is claimed is:

1 . A system comprising:
an electron beam source that generates an electron beam; a beam-limiting aperture disposed in a path of the electron beam; a lower Wehnelt electrode disposed in the path of the electron beam; an upper Wehnelt electrode disposed in the path of the electron beam between the lower Wehnelt electrode and the beam-limiting aperture; an annular detector disposed on a surface of the upper Wehnelt electrode facing the lower Wehnelt electrode; a magnetic condenser lens disposed in the path of the electron beam between the upper Wehnelt electrode and the beam-limiting aperture, wherein the magnetic condenser lens includes pole pieces and a condenser lens coil; a deflector disposed in the path of the electron beam between the upper Wehnelt electrode and the condenser lens; a magnetic objective lens coil disposed in the path of the electron beam between the deflector and the upper Wehnelt electrode; and a ground tube disposed in the path of the electron beam, wherein the magnetic objective lens coil is disposed around the ground tube.

2 . The system of claim 1 , further comprising an aperture disposed in the path of the electron beam between the condenser lens and the beam-limiting aperture.

3 . The system of claim 1 , wherein the electron beam source includes a tip with a radius less than 1 μm.

4 . The system of claim 1 , wherein the deflector is a magnetic deflector or a Wien filter.

5 . The system of claim 4 , wherein the deflector is the magnetic deflector, and further comprising an upper magnetic deflector and a middle magnetic deflector, the upper magnetic deflector disposed in the path of the electron beam between the deflector and the magnetic condenser lens, and the middle magnetic deflector disposed in the path of the electron beam between the upper magnetic deflector and the magnetic deflector.

6 . The system of claim 5 , wherein the upper magnetic deflector is configured to deflect the electron beam to the middle magnetic deflector, wherein the middle magnetic deflector is configured to deflect the electron beam toward the magnetic deflector in a direction opposite that of the upper magnetic deflector, and wherein the magnetic deflector is configured to deflect the electron beam and collimate the electron beam along the path into the ground tube.

7 . The system of claim 5 , wherein each of the magnetic deflector, the upper magnetic deflector, and the middle magnetic deflector have eight magnetic pole pieces that are rotationally symmetric.

8 . The system of claim 5 , further comprising a side detector disposed between the middle magnetic deflector and the magnetic deflector, wherein the side detector is configured to collect at least secondary electrons.

9 . The system of claim 8 , further comprising an electron beam bender disposed between the middle magnetic deflector and the magnetic deflector, wherein the electron beam bender is configured to filter between the secondary electrons from back scattered electrons at the side detector.

10 . A method comprising:
generating an electron beam with an electron beam source; directing the electron beam through a beam-limiting aperture; directing the electron beam through a magnetic condenser lens disposed along a path of the electron beam downstream of the beam-limiting aperture; directing the electron beam through a deflector disposed along a path of the electron beam downstream of the magnetic condenser lens; directing the electron beam through an objective lens, wherein the objective lens includes a ground tube, an upper Wehnelt electrode, and a lower Wehnelt electrode; directing the electron beam from the lower Wehnelt electrode at a surface of a wafer; and receiving back-scattered electrons from the wafer at an annular detector disposed on a surface of the upper Wehnelt electrode, wherein the surface of the upper Wehnelt electrode faces the lower Wehnelt electrode.

11 . The method of claim 10 , wherein a beam voltage of the electron beam is from 50 kV to 100 kV and has a landing energy from 50 keV to 100 keV.

12 . The method of claim 10 , wherein the magnetic condenser lens is configured to form the electron beam to have a small depth of focus mode and a large depth of focus mode, wherein a numeric aperture is smaller for the large depth of focus mode than the small depth of focus mode.

13 . The method of claim 10 , wherein the wafer includes a three-dimensional semiconductor structure.

14 . The method of claim 10 , wherein a depth of focus for the electron beam is up to 20 μm.

15 . The method of claim 10 , wherein the electron beam source includes a tip with a radius less than 1 μm.

16 . The method of claim 10 , wherein the deflector is a magnetic deflector or a Wien filter.

17 . The method of claim 16 , wherein the deflector is the magnetic deflector, and further directing the electron beam through an upper magnetic deflector and a middle magnetic deflector disposed along the path of the electron beam between the deflector and the magnetic condenser lens.

18 . The method of claim 17 , wherein the upper magnetic deflector is configured to deflect the electron beam to the middle magnetic deflector, wherein the middle magnetic deflector is configured to deflect the electron beam toward the magnetic deflector in a direction opposite that of the upper magnetic deflector, and wherein the magnetic deflector is configured to deflect the electron beam and collimate the electron beam along the path into the ground tube.

19 . The method of claim 17 , further comprising receiving secondary electrons at a side detector disposed between the middle magnetic deflector and the magnetic deflector.

20 . The method of claim 19 , further comprising bending electrons returned from the wafer between the middle magnetic deflector and the magnetic deflector thereby filtering between the secondary electrons from back scattered electrons at the side detector.

Assignees

• Kla Corp

Inventors

• Jiang Xinrong
• Sears Christopher

Classifications

• H10P74/203 Primary

  Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects · CPC title

• H01J2237/281

  Bottom of trenches or holes · CPC title

• H01J2237/24475

  Scattered electron detectors · CPC title

• H01J2237/152

  Magnetic means · CPC title

• H01J2237/141

  Coils · CPC title