Radiant energy – Inspection of solids or liquids by charged particles – Positive ion probe or microscope type
Reexamination Certificate
2001-11-26
2003-12-30
Lee, John R. (Department: 2881)
Radiant energy
Inspection of solids or liquids by charged particles
Positive ion probe or microscope type
Reexamination Certificate
active
06670610
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to systems and methods for directing a miller and especially systems and methods for imaging and milling dies for defect detection and analysis.
BACKGROUND OF THE INVENTION
Scanning electron microscopes are known in the art. U.S. Pat. No. 5,659,172 of Wagner describes a method for reliable defect detection using multiple perspective Scanning Electron Microscope (SEM) images. A SEM usually includes an electron gun for generating an electron beam, a SEM lens system for focusing and converging the electron beam, a deflection coil for deflecting the electron beam, a detector for detecting electrons, such as secondary emitted electrons or reflected electrons that are emitted/reflected from an object and a processor that is operative to construct SEM images in response to detection signals provided from the detector. Usually, the electron gun, the SEM lens system and the deflection coil are located within a column, that is commonly referred to as SEM column. The resolution of a SEM and its power consumption are inversely proportional to the distance between the SEM column and the object. This distance is also referred to as a working distance. The detector can also be placed within the SEM column.
Focused ion beam (FIB) systems are known in the art. FIB systems are generally utilized to perform die milling and cross sectioning. The milled or cross sectioned die is usually analyzed by an inspection device, such as a SEM, to detect defects. FIB systems can also be utilized to generate FIB images. FIB systems usually include an ion source for generating an ion beam, a FIB lens system for focusing the ion beam to provide a focused ion beam and an ion beam deflector for deflecting the focused ion beam. A FIB system that is operative to generate a FIB image also has a detector and a processor. Usually, the ion source, the FIB lens system and the ion beam deflector are located within a column, that is commonly referred to as FIB column. The detector can also be placed within the FIB column.
SEM images are generated by irradiating an object with an electron beam, collecting signals resulting from an interaction of the electron beam with at least one portion of the object and processing the collected signals. FIB images are generated in a similar analogues manner, except that the object is irradiated with a focused ion beam.
Systems that include both FIB and SEM systems are known in the art and are referred to as FIB/SEM systems. SEM system allows to inspect a surface of an inspected object, such as a surface of a multi layered die. FIB systems allow for milling the surface and exposing inner layers to inspection. Usually, after the FIB mills the die, the SEM system is utilized to inspect the revealed layers and to further analyze the milled die for detecting defects. A prior art FIB/SEM system is the XL860 DualBeam Workstation of FEI. Such a prior art system
10
is illustrated at FIG.
1
. System
10
includes FIB column
12
and SEM column
14
. FIB column generated ion beam
15
and SEM column
14
generates electron beam
13
. System
10
further has stage
18
, detectors
26
and
28
and at least one processor (not shown) coupled to detectors
26
and
28
and being operative to generate images. Stage
18
supports the object, such a wafer
20
. Detectors
26
and
28
receive electrons, such as secondary emitted electrons and reflected electrons, emitted or reflected from wafer
20
in response to an irradiation of wafer
20
by electron beam
13
or ion beam
15
, and provide detection signals to the processor.
FIB column
12
is angularly displaced from SEM column
14
at a predefined angle and is located substantially adjacent to SEM column
14
. This arrangement forces both columns to be placed in a relatively large working distance from wafer
20
. For example, at XL860 DualBeam Workstation the working distance of the SEM column is 5 mm and the working distance of FIB column
12
is 16.5 mm.
This arrangement also limits the width of the columns and further reduces the performances of at least one of SEM column
14
and FIB column
12
.
Ideally, during use of the system for defect detection and analysis, electron beam
13
and focused ion beam
15
are aimed to the same point on an object that is evaluated. Because of the angular displacement between SEM column
14
and FIB column
12
changes in the vertical displacement, caused by changes in the object surface or mechanical inaccuracies of a stage that supports and moves the die, between the surface of wafer
20
and either one of the columns must be compensated by a calibration step. The calibration is usually done manually and is time-consuming. The need for the calibration process is illustrated at
FIGS. 2 and 3
. A change in the vertical displacement (H
1
of
FIG. 2
versus H
2
of
FIG. 3
) between surface
21
of wafer
20
and SEM column
14
(and accordingly also between surface
21
and FIB column
12
) causes ion beam
13
to irradiate point
27
on surface
20
while electron beam
15
irradiates point
17
. In order to have both beams irradiate the same point one of the beams must be slightly deflected.
There is a need to provide an efficient system and method for directing a miller. There is a need to provide a system that efficiently combines the capabilities of a scanning electron microscope and of a focused ion beam generator. There is a need to provide a system and method that allows placement of an object at a small working distance from a scanning electron microscope and at a small working distance from a focused ion beam generator.
SUMMARY OF THE INVENTION
The invention provides a method for directing a miller, the system including: a first imager, for locating a landmark on an die; a stage, for moving the die from a first location in which the object is accessible to the first imager to a second location in which the die is accessible to a miller; and a second imager, for directing a miller to mill the die at the desired location.
The second imager can be operative to locate the landmark and to direct the miller to mill at the desired location in response to landmark information and displacement information. The second imager can be operative to generate at least one image of at least one portion of the die and to locate the landmark in response to an analysis of the at least one image of the at least one portion. The second imager can also be operative to generate at least one image of at least one portion of the die and to locate the landmark in response to a comparison between a first image that includes the landmark and the at least one image of the at least one portion, the first image being generated by the first imager.
The first imager can include a scanning electron microscope. The scanning electron microscope includes a SEM column, at least one detector and at least one processor operable to generate SEM images of the die.
The second imager conveniently is also capable of milling the object. A focused ion beam miller and imager can be utilized for imaging and milling. The focused ion beam miller and imager can include a focused ion beam column, for generating and controlling a focused ion beam, at least one detector and a processor, the processor being operable to generate focused ion beam images of the die, to locate the landmark and to direct the miller.
The second imager can include a scanning electron microscope. The scanning electron microscope can include a SEM column, at least one detector and at least one processor operable to generate SEM images of the die.
Conveniently, the first imager and the second miller are spaced apart. The distance between the first imager and the miller exceeds 10 mm. The stage is operative to place the object at a small working distance from the miller and at a small working distance from the first imager. The sum of the small working distance from the miller and the small working distance from the first imager preferably does not exceed 15 mm but can also be limited to 5 mm or even less.
The invention prov
Ben-Porath Ariel
Shachal Dubi
Shemesh Dror
Stepanov Alexey
Applied Materials Inc.
Blakely & Sokoloff, Taylor & Zafman
Johnston Phillip A
Lee John R.
LandOfFree
System and method for directing a miller does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System and method for directing a miller, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System and method for directing a miller will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3145975