Apparatus and methods for determining defect depths in vertical stack memory

Patent metadata

Field	Value
Publication number	US-9696264-B2
Application number	US-201414226745-A
Country	US
Kind code	B2
Filing date	Mar 26, 2014
Priority date	Apr 3, 2013
Publication date	Jul 4, 2017
Grant date	Jul 4, 2017

Abstract

Disclosed are methods and apparatus for inspecting a vertical semiconductor stack of a plurality of layers is disclosed. The method includes (a) on a confocal tool, repeatedly focusing an illumination beam at a plurality of focus planes at a plurality of different depths of a first vertical stack, wherein a defect is located at an unknown one of the different depths and the illumination beam has a wavelength range between about 700 nm and about 950 nm, (b) generating a plurality of in-focus images for the different depths based on in-focus output light detected from the first vertical stack at the different depths, wherein out-of-focus output light is inhibited from reaching the detector of the confocal system and inhibited from contributing to generation of the in-focus images, and (c) determining which one of the different depths at which the defect is located in the first vertical stack based on the in-focus images.

First claim

What is claimed is:

1. A method for inspecting a vertical stack structure, comprising:
(a) on a confocal tool, repeatedly focusing an illumination beam at a same particular xy location and a plurality of focus planes at a plurality of different depths of a first vertical stack structure having a plurality of patterned layers, wherein the different depths correspond to incremental z positions from a top surface of the first vertical stack structure, through the plurality of patterned layers of the first vertical stack structure, and to a bottom of the first vertical stack structure, and wherein a defect is located at an unknown one of the different depths and the illumination beam has a wavelength range between about 700 nm and about 950 nm;
(b) generating a plurality of in-focus images for the different depths based on in-focus output light detected from the first vertical stack structure at the different depths, wherein out-of-focus output light is inhibited from reaching the detector of the confocal system and inhibited from contributing to generation of the in-focus images; and
(c) determining which one of the different depths at which the defect is located in the first vertical stack structure based on the in-focus images.

2. The method of claim 1 , wherein the out-of-focus light is inhibited from reaching the detector of the confocal tool by an output aperture module that is positioned and dimensioned so as to block the out-of-focus output light at the wavelength range between about 700 nm and about 950 nm from reaching the detector.

3. The method of claim 1 , wherein the defect was detected in the first vertical stack structure using another inspection tool that differs from the confocal tool, wherein such defect was detected without determining a depth of such defect with respect to the first vertical stack structure.

4. The method of claim 1 , further comprising detecting the defect based on the in-focus images prior to determining which one of the different depths at which the defect is located in the first vertical stack structure based on the in-focus images.

5. The method of claim 1 , wherein determining which one of the different depths at which the defect is located in the first vertical stack structure includes determining that a particular one of the in-focus images has a sharpest contrast and defining the particular in-focus image's corresponding depth as the depth of the defect.

6. The method of claim 1 , further comprising determining a classification of the defect or discriminating a material of the defect based on the in-focus images.

7. The method of claim 1 , further comprises:
on the confocal tool, repeatedly focusing one or more illumination beams at a second plurality of focus planes at a second plurality of different depths of each of a second plurality of vertical stack structures;
generating a second plurality of in-focus images for the second different depths based on in-focus output light detected from the second vertical stack structures at the second different depths, wherein out-of-focus output light is inhibited from reaching the detector of the confocal system and inhibited from contributing to generation of the second in-focus images; and
detecting one or more second defects in the second vertical stack structures; and
for each detected second defect, determining which one of the different depths at which the second defect is located based on the second in-focus images.

8. The method of claim 7 , wherein a plurality of illumination beams are simultaneously focused at the second focus planes of the second vertical stack structures.

9. The method of claim 1 , wherein the first vertical stack structure is a three-dimensional memory structure having a plurality of alternating patterned layers formed from an oxide material and either a nitride or polysilicon material.

10. A system for detecting defects or reviewing defects in a vertical semiconductor structure, the system comprising:
an illumination optics module for repeatedly focusing an illumination beam at a same particular xy location and a plurality of focus planes at a plurality of different depths of a first vertical stack structure having a plurality of patterned layers, wherein the different depths correspond to incremental z positions from a top surface of the first vertical stack structure, through the plurality of patterned layers of the first vertical stack structure, and to a bottom of the first vertical stack structure, and wherein a defect is located at an unknown one of the different depths and the illumination beam has a wavelength range between about 700 nm and about 950 nm;
a collection optics module for collecting in-focus output light from the plurality of different depths in response to the focused illumination beam that is focused at such different depths;
a detector for detecting the in-focus output light collected from the plurality of different depths, wherein the collection optics module is further arranged to inhibit out-of-focus output light from reaching the detector so as to inhibit such out-of-focus output light from contributing to generation of the in-focus images; and
a controller operable to perform the following operations:
generating a plurality of in-focus images for the different depths based on in-focus output light detected from the first vertical stack structure at the different depths; and
determining which one of the different depths at which the defect is located in the first vertical stack structure based on the in-focus images.

11. The system of claim 10 , wherein the illumination optics module includes an illumination aperture module and the collection optics module includes an output aperture module.

12. The system of claim 11 , wherein each of the illumination and output aperture modules is in the form of a fixed pinhole or slit array.

13. The system of claim 11 , wherein each of the illumination and output aperture modules is in the form of a rotating Nipkow disk for scanning the focused illumination beam across a focal plane area of the sample.

14. The system of claim 11 , wherein each of the illumination and output aperture modules is in the form of a programmable spatial modulator for scanning the focused illumination beam across a focal plane area of the sample.

15. The system of claim 11 , wherein the illumination aperture module is positioned and dimensioned so as to block the out-of-focus output light at the wavelength range between about 700 nm and about 950 nm from reaching the detector.

16. The system of claim 10 , wherein the illumination optics module includes one or more galvanic mirrors for scanning the focused illumination beam across a focal plane area of the sample.

17. The system of claim 10 , wherein the defect was detected in the first vertical stack structure using another inspection tool that differs from the confocal tool, wherein such defect was detected without determining a depth of such defect with respect to the first vertical stack structure.

18. The system of claim 10 , wherein the controller is further operable to detect the defect based on the in-focus images prior to determining which one of the different depths at which the defect is located in the first vertical stack structure based on the in-focus images.

19. The system of claim 10 , wherein determining which one of the different depths at which the defect is located in the first vertical stack structure includes determining that a particular one of the in-focus images has a sharpest contrast and defining the parti

Assignees

• Kla Tencor Corp

Inventors

• Lange Steven R
• Danen Robert M
• Palomba Stefano

Classifications

• G01N21/9501 Primary

  Semiconductor wafers (manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20) · CPC title

• G01N2021/1785

  Three dimensional · CPC title

• G01N21/8806

  Specially adapted optical and illumination features · CPC title