Title: Method and apparatus for processing a micro sample
Abstract: An object of the invention is to realize a method and an apparatus for processing and observing a minute sample which can observe a section of a wafer in horizontal to vertical directions with high resolution, high accuracy and high throughput without splitting any wafer which is a sample. In an apparatus of the invention, there are included a focused ion beam optical system and an electron optical system in one vacuum container, and a minute sample containing a desired area of the sample is separated by forming processing with a charged particle beam, and there are included a manipulator for extracting the separated minute sample, and a manipulator controller for driving the manipulator independently of a wafer sample stage.
Patent Number: 6,927,391 Issued on 08/09/2005 to Tokuda, et al.
| Inventors:
|
Tokuda; Mitsuo (Tachikawa, JP);
Fukuda; Muneyuki (Kokubunji, JP);
Mitsui; Yasuhiro (Fuchu, JP);
Koike; Hidemi (Hitachinaka, JP);
Tomimatsu; Satoshi (Kokubunji, JP);
Shichi; Hiroyasu (Nishitokyo, JP);
Kashima; Hideo (Tokyo, JP);
Umemura; Kaoru (Tokyo, JP)
|
| Assignee:
|
Hitachi, Ltd. (Tokyo, JP)
|
| Appl. No.:
|
878528 |
| Filed:
|
June 29, 2004 |
Foreign Application Priority Data
| Nov 02, 2000[JP] | 2000-340387 |
| Nov 07, 2000[JP] | 2000-344226 |
| Current U.S. Class: |
250/310; 250/307 |
| Intern'l Class: |
H01J 037/25.6; G01N 023//22.5 |
| Field of Search: |
250/310,311,492.2,307,440.11
|
References Cited [Referenced By]
U.S. Patent Documents
| 4476386 | Oct., 1984 | Reid et al.
| |
| 4679976 | Jul., 1987 | Narishige et al.
| |
| 5093572 | Mar., 1992 | Hosono.
| |
| 5270552 | Dec., 1993 | Ohnishi et al.
| |
| 5525806 | Jun., 1996 | Iwasaki et al.
| |
| 5633502 | May., 1997 | Fischione.
| |
| 5727915 | Mar., 1998 | Suzuki.
| |
| 5852298 | Dec., 1998 | Hatakeyama et al.
| |
| 6039000 | Mar., 2000 | Libby et al.
| |
| 6300631 | Oct., 2001 | Shofner.
| |
| 6420722 | Jul., 2002 | Moore et al.
| |
| 6538254 | Mar., 2003 | Tomimatsu et al.
| |
| 6717156 | Apr., 2004 | Koike et al.
| |
| 6734687 | May., 2004 | Ishitani et al.
| |
| 6777674 | Aug., 2004 | Moore et al.
| |
| 2002/0166976 | Nov., 2002 | Sugaya et al.
| |
| 2003/0183776 | Oct., 2003 | Tomimatsu et al.
| |
| 2004/0129897 | Jul., 2004 | Adachi et al.
| |
| 2004/0246465 | Dec., 2004 | Iwasaki et al.
| |
| 2005/0012936 | Jan., 2005 | Murayama et al.
| |
| 2005/0035302 | Feb., 2005 | Morrison.
| |
| Foreign Patent Documents |
| 0 927 880 | Jul., 1998 | EP.
| |
| 09-326425 | Dec., 1997 | JP.
| |
| 11-108813 | Apr., 1999 | JP.
| |
| 10-013945 | Aug., 1999 | JP.
| |
| 11-260307 | Sep., 1999 | JP.
| |
| 2000/-146780 | May., 2000 | JP.
| |
| 2000/-251820 | Sep., 2000 | JP.
| |
| WO99/05506 | Feb., 1999 | WO.
| |
| WO99/17103 | Apr., 1999 | WO.
| |
Other References
Ohnishi, T., et al.: A new focused-ion-beam microsampling technique for TEM
observation of site-specific areas. ISTFA '99. Proceedings of the 25TH
International Symposium for Testing and Failure Analysis. ASM Int. 1999,
pp. 449-453 (Nov. 14-18, 1999) Materials Parks, OH, USA.
Pawley, James B.,: A Dual Needle Piezoelectric Micromanipulator for the Scanning
Electron Microscope. The Review of Scientific Instruments, vol. 43, No. 4,
Apr. 1972.
R. Weiland et al.: Wafer Conserving Full Range Construction Analysis for IC
Fabrication and process Development Based on FIB/Dual Beam Inline Application,
Proceedings from the 26th International Symposium for Testing and Failure
Analysis, Nov. 12-16, 2000, Bellevue, WA, pp. 393-396.
Japanese Office Action 2000-344226.
|
Primary Examiner: Wells; Nikita
Assistant Examiner: Hughes; James P.
Attorney, Agent or Firm: Kenyon & Kenyon
Parent Case Text
This is a continuation of application Ser. No. 09/960,479 filed 24 Sep. 2001,
now U.S. Pat. No. 6,781,125 which claims priority to Japanese Patent Application
No. 2000-340387 filed 2 Nov. 2000, the contents of which are incorporated herein
by reference in their entirety.
Claims
1. A minute sample processing apparatus comprising:
a focused ion beam system provided with an ion source, a lens for focusing an
ion beam emitted from the ion source and a scanning deflector for scanning the
ion beam emitted from the ion source; a detector for detecting secondary particles
emitted from a sample; a sample stage adapted for supporting a sample; and a vacuum
chamber on which the focus ion beam system is mounted,
wherein the probe holder is attached to the vacuum chamber with an inclination
to a surface of the sample, the probe holder including a drive shaft inserted therein
to rotate the probe holding the minute sample, the probe supported by a shaft bearing
defining a rotation axis inclined with respect to the drive shaft.
2. The minute sample processing apparatus according to claim 1, wherein the rotation
axis of the shaft bearing is parallel to the surface of the sample.
3. The minute sample processing apparatus according to claim 1, further, comprising
an electron beam system provided with an electron source, a lens for focusing an
electron beam and an electron beam scanning deflector.
4. A minute sample processing method for observing a section of a sample using
a minute sample processing apparatus which comprises a focused ion beam system
provided with an ion source, a lens for focusing an ion beam emitted from the ion
source and a scanning deflector for scanning with the ion beam emitted from the
ion source; an electron beam system provided with an electron source and a scanning
deflector for scanning with the electron beam emitted from the electron source;
and a vacuum chamber in which the focused ion beam system and the electron beam
system are mounted, wherein the method comprises:
cutting out a minute sample from the sample by applying the focused ion beam
to the sample as the minute sample;
lifting the cut-out minute sample from the sample using a probe;
changing the axis of rotation of the probe so as to be parallel to the sample
surface; and
changing the attitude of the minute sample by rotating the probe about changed axis.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus system used as observation, analysis
and evaluation means in research and development and manufacturing of an electronic
device such as a semiconductor device, liquid crystal device and a magnetic head,
a micro-electronic device or the like which require observation and analysis of
not only a surface of an object to be observed but also an inner section near the surface.
In manufacturing of a semiconductor device such as a semiconductor memory typified
by a dynamic random access memory, a microprocessor and a semiconductor laser,
and electronic parts such as a magnetic head, a product property is inspected for
quality control of a product during a manufacturing process or at completion of
the process. In the inspection, measurement of manufacturing dimension, defect
inspection of a circuit pattern, or analysis of foreign materials are carried out.
For that purpose, various means are prepared and used.
Particularly, when there is a wrong portion within the product, a minute
processing and observation apparatus is increasingly used which comprises a combination
of a focused ion beam (FIB) apparatus and an electron microscope. This apparatus
is disclosed in JP-A-11-260307 specification. In the specification, disclosed is
a technique of carrying out section processing of a sample by an FIB apparatus
and observing an exposed section by an electron microscope disposed slantingly
above the sample.
As another technique of observing the sample section, invented and used is a
method
of taking out of a processing and observation apparatus a minute sample, which
is a cut-out minute area of micron orders including an observation region, and
moving the minute sample to a separately prepared apparatus to be reprocessed into
an optimum shape and observed and analyzed. This method is disclosed in JP-A-5-52721
specification. This is a method of cutting out part of a sample and observing its
section, where a tip of a probe driven by a manipulator is positioned on a minute
sample cut by an FIB, the probe and minute sample are connected by a deposition
gas, and the minute sample is transferred in the connected condition.
SUMMARY OF THE INVENTION
The above described conventional methods have the following problems.
First, to observe a section of a hole or groove of the sample formed by FIB
processing, a sample stage is inclined to thereby observe a section of an inner
wall of the hole or groove in a slanting direction. In that case, an adjustment
range of inclination of the sample stage is limited by constraints in structure
due to a working distance of an FIB apparatus, presence of an objective lens, or
size of a sample stage, and larger inclination cannot be allowed. Thus, vertical
observation of the section of the inner wall of the hole or groove is impossible.
The vertical observation of the section is indispensable in confirmation of processing
properties such as dry etching, planarization, thin film forming, or the like in
process development or the like of semiconductor device manufacturing, but the
above described known apparatuses cannot cope with the vertical observation.
Second, a reduction in resolution resulting from the slant observation becomes
a serious problem. When slantingly emitting an electron beam to a wafer surface
from above and to observe a section of an inner wall of a hole or groove, observation
resolution in a direction perpendicular to the wafer surface, that is, of the section
of the inner wall of the hole or groove is reduced. A reduction rate reaches approximately
15% at an angle of 30°, and 30% at an angle of around 45°, which is most
frequently used. Miniaturization of recent semiconductor devices has reached the
limit, and measurement of the dimension or shape with accuracy below a few nano
meters is required. Required observation resolution is less than 3 nm, which falls
a technical limit area of a scanning electron microscope. In addition, with high
resolution of such degree, depth of focus is extremely shallow and focusing is
achieved only in a range below some ten percent of 1 μm, so that an appropriate
observation range of a vertical section of the device at the time of slant observation
is often less than half of a required area. This problem can be solved by vertical
observation. The vertical observation enables superior observation in focus on
the whole observation area.
Third, the observation section exists on a wall surface of a minute hole or
groove formed in the wafer, so that numeral density of secondary electrons coming
out of the hole are reduced in comparison with those on the surface of the wafer.
Thus, secondary electron detecting efficiency is reduced and it causes a reduction
in S/N of a secondary electron image, inevitably resulting in a reduction in accuracy
of the section observation.
Miniaturization of LSI patterns progresses at a rate of 30% reduction
every a few years without stop, and higher resolution is increasingly required
in the observation apparatus. Moreover, even if surface distribution of an atomic
property X-ray excited by emitting an electron beam is measured by an X-ray detector
to carry out elementary analysis (EDX analysis), enlargement of an X-ray generation
area due to the electron beam entering into the sample causes surface resolution
of analysis to be approximately 1 μm though the electron beam has a diameter
equal or less than 0.1 μm, which is insufficient for analysis of the LSI
element section having a minute structure.
Fourth, cases where the vertical observation of the section is indispensable
include evaluation of workmanship of etching, implantation of grooves or holes,
planarization or the like in wafer process. In order to accurately measure a dimension
and shape of a processed section, a sample of a chip size including a section to
be observed has been determined and observed by a scanning electron microscope
for general purpose in the past. However, accompanying with miniaturization progress
of devices and enlargement of diameter of the wafer, sometimes failure is resulted
since it is considerably difficult to accurately break an element circuit pattern
at a position to be observed. However, failure in creating an evaluation sample
is not allowed because of poor supply capacity or increased price of the wafer
for evaluation.
Fifth, with the technique disclosed in JP-A-5-52721 specification, it is possible
to obtain sufficient level of observation and analysis accuracy such as resolution,
but the sample has to be manufactured in the conventional apparatus, taken out
of the apparatus, and introduced into the separately prepared observation and analysis
apparatus, thus there is a problem of requiring hours of time for taking out the
minute sample, processing, observation and analysis. Further, in a case where the
sample exposed to the air is degraded by oxidation or moisture adsorption, it is
difficult to avoid the degradation. Section observation of the semiconductor device
has been recently considered to be important as an advantageous inspection technique
in manufacturing the semiconductor, and a desirable throughput in that case at
present is observation and analysis of more than a few positions per hour, and
processing at much higher speed will be desired in the future. Contrary to the
desire, the problem of extremely low throughput of the conventional method has
not been solved.
In view of the above problems, the present invention has its object to provide
a method and apparatus for processing and observing a minute sample, which can
vertically observe an inner section of the sample to be observed, and can carry
out observation and analysis with high resolution, high accuracy and high throughput
without degradation resulting from exposure to the air and without failure.
Another object of the present invention is to provide a minute sample processing
apparatus which requires minimum capacity of a vacuum container and a reduced occupying
area and has high operability even when the apparatus is intended for a large sample.
Still another object of the present invention will be described in embodiments
described hereinafter.
In order to attain the above object, there is provided a minute sample processing
apparatus, including: a focused ion beam optical system comprising an ion source,
a lens for focusing an ion beam and an ion beam scanning deflector; an electron
beam optical system comprising an electron source, a lens for focusing an electron
beam and an electron beam scanning deflector; a detector for detecting a secondary
particle emitted from the sample; and a sample stage on which the sample is placed,
wherein the apparatus further comprises a probe for supporting a minute sample
cut out by emitting the ion beam to the sample, and a mechanism for operating the probe.
Further, in order to attain another object, there is provided a charged
particle beam apparatus, including: a sample stage for placing a sample in a vacuum
container; a charged particle source; a irradiation optical system for irradiating
a charged particle beam from the charged particle source to the sample; a secondary
particle detector for detecting a secondary particle generated from the sample
by applying the charged particle beam to the sample; a needle member whose tip
is capable of coming into contact with the sample; a probe holder for holding the
needle member; an introduction mechanism capable of introducing and extracting
the probe holder into and from the vacuum container; and a moving mechanism having
a mechanism of slanting the probe holder to a surface of the sample stage.
Structure and technical effects for achieving other objects of the present
invention will be described in embodiments described hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of a first embodiment of an apparatus according to the
present invention, showing a whole structure thereof;
FIG. 2 is a plan view of the first embodiment of the apparatus according to
the present invention, showing the whole structure thereof;
FIG. 3 is a view showing a detailed structure of the first embodiment of the
apparatus according to the present invention;
FIG. 4 is a view showing an example of a minute sample processing method of
the present invention;
FIG. 5 is views showing an example of a minute sample observation method of
the present invention;
FIG. 6 is a side view of a second embodiment of the apparatus according to the
present invention, showing a whole structure thereof;
FIG. 7 is a plan view of the second embodiment of the apparatus according to
the present invention, showing the whole structure thereof;
FIG. 8 is a side view of a third embodiment of the apparatus according to the
present invention, showing a whole structure thereof;
FIG. 9 is a plan view of the third embodiment of the apparatus according to
the present invention, showing the whole structure thereof;
FIG. 10 is a view showing a detailed structure of the fourth embodiment of the
apparatus according to the present invention;
FIG. 11 is a view showing an example of a minute sample fixed to a second sample
stage in the fourth embodiment of the present invention;
FIG. 12 is a view showing details of essential portions of the fourth embodiment
of the present invention;
FIG. 13 is a view showing details of essential portions of the fourth embodiment
of the present invention;
FIG. 14 is a view showing an example of a minute sample observation method;
FIG. 15 is a view showing an example of a minute sample processing method;
FIG. 16 is a sectional view of a sample creating apparatus of a fifth embodiment
of the present invention;
FIG. 17 is a sectional view of a probe moving mechanism for the sample creating
apparatus of the fifth embodiment of the present invention;
FIG. 18 is a plan view of the probe moving mechanism for the sample creating
apparatus of the fifth embodiment of the present invention;
FIG. 19 is a sectional view of a sample creating apparatus of a sixth embodiment
of the present invention;
FIG. 20 is an enlarged view of essential portions of the sample creating apparatus
of the sixth embodiment of the present invention;
FIG. 21A is a vertical sectional view of a sample stage of the sixth embodiment
of the present invention;
FIG. 21B is a horizontal sectional view of the sample stage of the sixth embodiment;
FIG. 22 is a sectional view of a sample creating apparatus of a seventh embodiment
of the present invention;
FIG. 23A is a sectional view of a probe holder of the seventh embodiment, showing
a condition in which the probe is projected;
FIG. 23B is a sectional view of the probe holder of the seventh embodiment,
showing a condition in which the probe is received;
FIG. 24 is a sectional view of a sample stage fine moving mechanism of the seventh embodiment;
FIG. 25 is views showing processing steps to process a minute sample with the
sample creating apparatus of the seventh embodiment;
FIG. 26 is a sectional view of a failure inspection apparatus of an eighth embodiment
of the present invention; and
FIG. 27 is a sectional view of a sample observation apparatus of a ninth embodiment
of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A structure and an operation of a minute sample processing and observation apparatus
according to the present invention will be described.
(Embodiment 1)
A structure and an operation of a first embodiment of an apparatus of the invention
will be described with reference to FIGS. 1,
2 and
3. FIGS. 1 and
2 show a whole structure of the apparatus and FIG. 3 shows structures of a focused
ion beam optical system, scanning electron microscope optical system and around
a sample stage in detail. Shown in this embodiment is a wafer corresponding apparatus
in the minute sample processing and observation apparatus of the present invention.
FIG. 3 shows a schematic bird's eye section of FIG. 1, and there are some differences
between the figures, though not essential, in orientations or details of apparatuses
for convenience in description. In FIG. 1, around a center of an apparatus system
are appropriately located a focused ion beam optical system
31 and an electron
beam optical system
41 above a vacuum sample chamber
60. A sample
stage
24 on which a wafer
21 to be a sample is placed is located
inside the vacuum sample chamber
60. Two optical systems
31 and
41
are adjusted in such a manner that their respective central axes intersect at a
point on a surface or near the surface of the wafer
21. A mechanism for
moving the wafer
21 backward and forward, and right and left with high accuracy
is provided in the sample stage
24, and is controlled in such a manner that
a designated position on the wafer
21 falls immediately below the focused
ion beam optical system
31. The sample stage
24 has functions of
rotational, vertical and slanting movements. An exhaust apparatus (not shown) is
connected to the vacuum sample chamber
60 and the chamber
60 is controlled
so as to have an appropriate pressure. The optical systems
31,
41
also individually comprise respective exhaust systems (not shown) and they are
maintained at appropriate pressures. A wafer introducing device
61 and wafer
conveying device
62 are provided within the vacuum sample chamber
60.
A wafer transferring robot
82 and a cassette introducing device
81
are disposed adjacent to the vacuum sample chamber
60. Provided on the left
side of the vacuum sample chamber
60 is an operation controller
100
for controlling the whole apparatus and a series of processing of sample processing,
observation and evaluation.
Next, an outline of an operation of introducing the wafer in this embodiment
will be described. When a wafer cassette
23 is placed on a table of the
cassette introducing device
81 and an operation start command is issued
from the operation controller
100, the wafer transferring robot
82
pulls out a wafer to be a sample from a designated slot in the cassette, and an
orientation adjustment device
83 shown in FIG. 2 adjusts an orientation
of the wafer
21 to a predetermined position. Then, the wafer transferring
robot
82 places the wafer
21 on a placement stage
63 when
a hatch on an upper portion of the wafer introducing device
61 is opened.
When the hatch is closed, a narrow space is formed around the wafer to be a load
lock chamber, and after air is exhausted by a vacuum exhaust device (not shown),
the placement stage
63 is lowered. Next, the wafer conveying device
62
takes up the wafer
21 on the placement stage
63 and places it on
the sample stage
24 at a center of the vacuum sample chamber
60.
The sample stage
24 is provided with means for chucking the wafer
21
according to need in order to correct a warp or prevent vibration of the wafer
21. A coordinate value of an observation and analysis position on the wafer
21 is input from the operation controller
100, and the sample stage
24 is moved and stopped when the observation and analysis position of the
wafer
21 falls immediately below the focused ion beam optical system
31.
Next, a process of sample processing, observation and evaluation will be described
with reference to FIG.
3. In the minute sample processing and observation
apparatus of the present invention, the focused ion beam optical system
31
comprises an ion source
1, a lens
2 for focusing an ion beam emitted
from the ion source
1, an ion beam scanning deflector
3 or the like,
and the electron beam optical system
41 comprises an electron gun
7,
electron lens
9 for focusing an electron beam
8 emitted from the
electron gun
7, an electron beam scanning deflector
10 or the like.
The apparatus is further provided with a secondary particle detector
6 for
detecting a secondary particle from the wafer by applying a focused ion beam (FIB)
4 or the electron beam
8 to the wafer
21, the movable sample
stage
24 on which the wafer
21 is placed, a sample stage controller
25 for controlling a position of the sample stage for determining a desired
sample position, a manipulator controller
15 for moving a tip of a probe
72 to an extracting position of a minute sample, extracting the minute sample
and controlling a position or direction optimum for observation and evaluation
of a determined position of the minute sample by applying the focused ion beam
4 (FIB) or electron beam
8 to the minute sample, an X-ray detector
16 for detecting an atomic property X-ray excited at the time of applying
the electron beam
8, and a deposition gas supplying device
17.
Next, an outline of the process of sample processing, observation and evaluation
after introducing the wafer in this embodiment will be described. The sample stage
is first lowered and the probe
72 is horizontally (in X and Y directions)
moved relative to the sample stage
24 with the tip of the probe
72
separated from the wafer
21, and the tip of the probe
72 is set in
a scanning area of the FIB
4. The manipulator controller
15 which
is a mechanism for operating the probe stores a positional coordinate and then
evacuates the probe
72.
The focused ion beam optical system
31 apples the FIB
4 to the
wafer
21 to form a rectangular U-shaped groove across an observation and
analysis position p
2 as shown in FIG. 4. A processing area has a length
of about 5 μm, width of about 1 μm and depth of about 3 μm, and
is connected to the wafer
21 at its one side surface. Then, the sample stage
24 is inclined, and an inclined surface of a triangular prism is formed
by the FIB.
4. In this condition, however, the minute sample
22 is
connected with the wafer
21 by a support portion S
2.
Then, the inclination of the sample stage
24 is returned, and thereafter,
the probe
72 at the tip of the manipulator
70 is brought into contact
with an end portion of the minute sample
22. Then, the deposition gas is
deposited on a contact point
75 by application of the FIB.
4, and
the probe
72 is joined to and made integral with the minute sample
22.
Further, the support portion S
2 is cut by the FIB.
4 to cut out the
minute sample
22. The minute sample
22 is brought into a condition
of being supported by the probe
72, and ready is completed that a surface
and an inner section of the minute sample
22 for the purpose of observation
and analysis is taken out as an observation and analysis surface p
3.
Next, as shown in FIG.
5(
b), the manipulator
70 is operated
to lift the minute sample
22 up to a level apart from the surface of the
wafer
21. If necessary, the observation section p
3 of the minute
sample
22 may be additionally processed to a desired shape by appropriately
adjusting the application angle of the FIB
4 with rotating operation of
the manipulator. As an example of the additional processing, there is a finishing
processing for forming an observation section p
2 slantingly formed by tapering
of the beam of the FIB
4 to be a real vertical section. In section processing/observation
having been performed hitherto, an observation surface has to be a side wall of
a hole dug by the FIB, while in the apparatus of this embodiment, the sample can
be additionally processed after being lifted, with the observation surface thereof
appropriately moved. Therefore, it becomes possible to form a desired section appropriately.
Then, the minute sample
22 is rotated, and the manipulator
70
is moved in such a manner that the electron beam
8 of the electron beam
optical system
41 substantially vertically enters into the observation section
p
3 to control attitude of the minute sample
22, and then stopped.
Thus, even in case of observing a section of the sample, detection efficiency of
a secondary electron by the secondary particle detector
6 is increased as
much as in the case of observing an outermost surface of the wafer. Observation
condition of the observation and analysis surface p
3 of the minute sample
22 is greatly improved. A reduction in resolution which has been a problem
in the conventional method can be avoided. The angles of the observation and analysis
surfaces p
2, p
3 can be adjusted to desirable angles, and therefore,
it becomes possible to perform more exact observation and analysis. With this,
direction of observation of the inner section of an object sample can be freely
selected. Consequently, there can be provided a minute sample processing and observation
apparatus which permits observing a shape and dimension of etching or planarization,
an implanting condition, coating thickness or the like with high resolution by
substantially vertically observing the section, and achieving measurement and evaluation
with high accuracy.
In this embodiment, the resolution can be improved by transferring a minute sample
by movement of the manipulator
70 immediately below the electron beam optical
system
41 to reduce a working distance. In an apparatus, like this embodiment,
in which an ion beam optical system and an electron beam optical system are disposed
in one vacuum container, a space in the vacuum container is limited, and it is
difficult to bring a large sample close to the electron beam optical system. However,
by positioning a cut-out minute sample below the electron beam optical system as
is in this embodiment, such a problem can be solved.
Further, the minute sample
22 is observed and analyzed while being
placed in the sample chamber of a vacuum atmosphere without taken out of the apparatus,
so that observation and analysis of the inner section of the sample to be observed
and analyzed can be achieved with high resolution, high accuracy and an optimum
angle without contamination or deposition of foreign materials resulting from exposure
to the outside atmosphere. In addition, observation and analysis can be achieved
with high throughput of processing more than a few positions per hour. This method
also allows observation to be carried out simply by lifting and appropriately positioning
the minute sample, which permits facilitating operation and reduction in operation time.
In this embodiment, the section of the semiconductor sample cut by FIB application
is moved substantially perpendicularly to the optical axis of the scanning electron
microscope to be observed. Thus, an extremely meritorious effect is exerted in
such a case of observing a thin film layer formed in the semiconductor sample.
For example, wiring formed in the semiconductor wafer has been often formed from
copper or the like these days. Metal such as copper tends to be diffused in the
semiconductor wafer to degrade the property of the semiconductor, so that it is
necessary to form a barrier metal around the wiring to prevent diffusion. The barrier
metal is an extremely thin film with a thickness on the order of 0.01 μm
to 0.02 μm when the wiring has a thickness of 0.1 μm to 0.2 μm,
and is formed from metal such as tantalum. In an inspection process of the semiconductor
wafer, whether a barrier metal is formed appropriately or not is an important inspection item.
When the electron beam is slantingly emitted with respect to the observation
section as in the conventional section processing and observation, a distance that
the electron beam interferes in the sample is increased to reduce the resolution
of the scanning electron microscope and to sometimes make it difficult to observe
the barrier metal. Further, since the barrier metal is the thin film as described
above, the electron beam entering into the barrier metal sometimes interferes adjacent
other material areas. In such a case, there is a possibility of detecting information
on other materials from a position where materials constituting the barrier metal
only should exist. Thus, information on the copper of the adjacent wiring is detected
regardless of the barrier metal being appropriately formed, which leads to a possibility
of obtaining an inspection result that function as the barrier metal is not effected.
This presents a problem especially in an EDX analysis for analyzing composition
of a sample by detecting a property X-ray specific to material which is resulted
from the electron beam application.
The metal which forms the wiring or barrier metal is sometimes corroded or oxidized
at its surface when made in contact with the air, thus making it difficult to observe
the section.
In this embodiment, for solving the above two problems together, observation
by
the scanning electron microscope capable of non-destructive observation with high
resolution can be achieved in a vacuum atmosphere where the sample is cut out,
and the electron beam application perpendicularly to the sample section is permitted.
With this structure, it become possible to carry out section processing and observation
of the semiconductor element which is becoming increasingly more minute with high
resolution and accuracy.
Further, also in a case an additional processing is effected after observation
by the scanning electron microscope, the minute sample can be positioned below
the optical axis of the FIB without being exposed to the air. Therefore, there
is no possibility that a position to be additionally processed is hidden by the
oxide film and alignment of processing positions becomes impossible.
Further, in this embodiment, the minute sample
22 having the observation
and analysis surface p
3 can be inclined or moved in various ways by the
manipulator
70. Thus, it becomes possible, for example, to provide a hole
in the observation section p
2 and to also confirm three-dimensional fault
forming condition in the sample.
In the example shown in FIG. 3, the manipulator
70 and the electron beam
optical system
41 are provided opposite to each other with respect to the
FIB
4. However, in order to reduce the number of operation of the manipulator
70 or the like to minimize processing/observation time, it is preferable
that a relative angle between the manipulator
70 and the electron beam optical
system
41 is set close to 90° in a surface perpendicular to the application
direction of the FIB
4. The reason is that by setting so, it is sufficient
that the manipulator
70 simply carries out an operation of lifting the minute
sample
22 from the wafer
21, operation of rotating the probe
72
in such a manner that the observation section p
2 is perpendicular to the
electron beam
8, and other fine adjustment operations.
Used in the above description is an example of lifting the minute sample
22
from the wafer
21 by the manipulator
70, but not limited to this.
The wafer
21 may be lowered to thereby consequently lift the minute sample
22. In this case, the sample stage
24 is provided with a Z-axis moving
mechanism for moving the wafer
21 in a Z direction (an optical axis direction
of the FIB
4). With this structure, it becomes possible to perform cutting
out and lifting of the minute sample
22 in a condition where the optical
axis of the electron beam optical system
41 is located in the portion of
the wafer
21 to be the minute sample
22. In this case, the process
from cutting out the minute sample
22 by the FIB
4 to observing the
observation section p
2 can occur with confirmation by the electron microscope
without frequent changes of electron beam application positions during the process.
By the electron beam optical system
41, an electron microscope image of
the surface of the wafer
21 slantingly viewed can be obtained. A section
to be processed or processing arrival position by the FIB
4 is superposed
on the electron microscope image to be model displayed, then the section processing
condition by the FIB
4 can be easily confirmed. In order to display the
section to be processed in a superposed manner on the electron microscope image,
animation showing a portion to be a section is displayed on the electron microscope
image in the superposed manner based on a processing depth to be set and a dimension
in the electron microscope image calculated from magnification.
If the processing depth is calculated in real time based on current and acceleration
voltage of the FIB, material of the sample and the like, and an animation showing
the present processing depth are displayed in an interposed manner on the electron
microscope image, it becomes easy to confirm progress of the processing. The electron
beam optical system
41 of this embodiment is disposed in a bird's eye position
with respect to the wafer
21, and the electron micro-scope image becomes
a bird's eye image. Therefore, by displaying also the above-described animation
into three-dimensional display together with the electron microscope image, it
is possible to confirm the processing condition more clearly.
Further, this embodiment has a function of setting a position of the section
processing on a scanning ion microscope image (SIM image) formed on the basis of
the secondary electron obtained by scanning the wafer
21 with the FIB. However,
it is possible to provide also a sequence where other setting and operation of
the apparatus (driving of the sample stage and determination of the processing
position by the ion beam) are automatically carried out based on inputs of the
section position and the processing depth. In this case, a portion to be an upside
of the observation section p
3 is first designated on the SIM image, and
the processing depth (a dimension in the depth direction of the observation section
p
3) is set. Based on these two settings, the forming angle of the inclined
portion of the minute sample
22 and the observation and analysis surface
p
3 are automatically determined, and the subsequent processing is automatically
carried out by the settings. It is also possible to provide a sequence where the
subsequent processing is automatically carried out by setting the observation and
analysis surface p
3 (rectangular area) on the SIM image and setting the
processing depth.
In this embodiment, after the minute sample
22 is lifted, the probe
72
is operated so that the observation section p
3 is appropriately positioned
with respect to the electron beam
8. In FIG. 4, for example, when simply
rotating the probe
72, the minute sample
22 is rotated around an
attachment point to the probe
72. Therefore, the observation section p
3
includes components of not only a rotation around a longitudinal axis of the minute
sample
22 but also a rotation around an axis in the application direction
of the FIB
4. Imparting a mechanism for removing the rotational components
to the manipulator or manipulator controller, and operating the manipulator in
timing compliant with the rotation of the probe
72 or timing different from
the rotational operation allow the observation section p
3 to be accurately
positioned in a surface perpendicular to the optical axis of the electron beam
8.
The same effect can be obtained by disposing the probe
72 to have an angle
slightly larger than 90° to the electron beam optical system
41 in
the surface perpendicular to the optical axis of the FIB
4. In this case,
the effect is achieved by disposing the probe
72 to a rotational component
around the axis in the application direction of the focused ion beam plus 90°
with respect to the electron beam optical system
41.
Including the rotational component around the axis in the application direction
of the FIB
4 is resulted from the rotation axis of the probe
72 being
inclined with respect to the observation and analysis surface p
2 and the
observation section p
3. That is, the above problem can be solved by forming
the probe
72 such that the rotation axis becomes parallel to the observation
and analysis surface p
2 and observation section p
3. Therefore, in
a case of the apparatus having a mirror structure as shown in FIG. 3, the rotation
axis of the probe
72 is preferably formed in parallel with the surface of
the wafer
21 (perpendicular to the optical axis of the FIB
4). By
curve the tip of the probe
72, even a probe having the rotation axis parallel
to the surface of the wafer
21 can support the minute sample
22.
Further, it is preferable to form the rotation axis of the probe
72 so as
to be perpendicular to the electron beam optical system
41 so that the sample
can be moved below the optical axis of the electron beam
8 by rotation and
parallel movement of the probe. Specific examples of the structure of the probe
will be further described in detail in a description on a subsequent embodiment.
If a mechanism to transfer a driving power from the manipulator controller
15
to a probe having a rotation axis with a different height from a probe holder
71
and parallel to the wafer
21 is provided, alignment of the observation section
p
3 with the electron beam
8 can be carried out without moving the
minute sample
22 on a large scale.
The minute sample
22 in a suspended condition by the probe
72 is
susceptible to vibration, thus in observation and analysis with high magnification
and in a locating environment of much vibration, the minute sample
22 may
be grounded on a safe position on the wafer
21 or grounded on a minute sample
port provided on a space around the wafer on the sample stage to thereby substantially
restrain the vibration of the minute sample, permitting superior observation and
analysis. FIG. 18 shows an example thereof such that earthquake resistance is improved
by grounding the cutout minute sample
22 on the wafer
21. In adopting
such a method, it is preferable to make a sequence in advance such that the grounding
position of the minute sample matches the optical axis of the electron beam
8.
In creating the minute sample
22 shown in FIG. 4, the minute sample
22
is processed into pentahedron. This achieves creating of the minute sample especially
with reduced waste in processing and in a reduced period of time for separation
of the minute sample. It is needless to say that the same effect of the present
invention can be obtained by forming the minute sample
22 into tetrahedron
(not shown) or a shape close to tetrahedron which can minimize processing time
because of the least processing surface.
In the EDX analysis in which the electron beam
8 is scanned on the minute
sample
22, elementary analysis accuracy is improved by forming the minute
sample
22 thinner in the electron beam application direction than an entry
distance of about 1 μm by the electron beam application. The EDX analysis
is carried out using a detector of an X-ray generated from the minute sample resulting
from the electron beam application. Forming the minute sample to be a thinner film
permits avoiding enlargement of an X-ray generation area resulting from entry of
a charged particle beam, thus enabling the elementary analysis with high resolution.
By applying the analysis thus far described to the semiconductor wafer with or
without pattern, the analysis can be used in an inspection of a semiconductor manufacturing
process to contribute to improvement of manufacturing yield by early detection
of failure and quality control in a short period of time.
(Embodiment 2)
A structure and an operation of a minute sample processing and observation apparatus
according to a second embodiment of the present invention will be described with
reference to FIGS. 6 and 7. FIG. 7 is a plan view of FIG. 6, and there are some
differences between the figures in orientations or details of apparatuses for convenience
in description but they are not essential differences. In this apparatus, a focused
ion beam optical system
31 is vertically disposed and a second focused ion
beam optical system
32 is located at an angle of approximately 40°
at the upper part of a vacuum sample chamber
60 disposed in the central
part of the apparatus system. An electron beam optical system
41 is slantingly
located at an angle of approximately 45°. Three optical systems
31,
32,
41 are adjusted in such a manner that their respective central
axes intersect at a point around a surface of a wafer
21. Similarly to the
apparatus of the first embodiment, inside the vacuum sample chamber
60 is
located a sample stage
24 on which the wafer
21 to be a sample is
placed. The sample stage
24 in this embodiment has functions of horizontal
(X-Y), rotational and vertical movements, but a slanting function is not necessarily required.
Next, a sample creating operation by this apparatus will be described with
reference to FIG.
4. An FIB
4 is applied from the focused ion beam
optical system
31 to the wafer
21 to form a rectangular U-shaped
groove across an observation and analysis position p
2 as shown in FIG.
4.
This is identical to the first embodiment. Then, an inclined surface of a triangular
prism is formed by processing with the FIB
4 from another focused ion beam
optical system
32. In this condition, however, the minute sample
22
and wafer
21 are connected with each other by a support portion. Then, a
minute sample is cut out using the FIB
4 from the focused ion beam optical
system
31 similarly to the first embodiment. That is, a probe
72
at a tip of a probe holder
71 of a manipulator
70 is brought into
contact with an end portion of a minute sample
22, and then deposition gas
is deposited on a contact point
75 by application of the FIB
4, where
the probe
72 is joined to and made integral with the minute sample
22,
and the support portion is cut by the FIB
4 to cut out the minute sample
22. Subsequent steps of observation and analysis of the minute sample
22
are identical to the first embodiment.
As described above, also in this embodiment, high speed observation and analysis
with high resolution can be achieved similarly to the first embodiment. In this
embodiment, slanting of the sample stage can be eliminated especially by using
two focused ion beam optical systems. Omitting the slanting mechanism of the sample
stage can improve positioning accuracy of the sample stage more than a few to ten
times. In a manufacturing site of LSI devices, it has come into practice in recent
years that various wafer inspection and evaluation apparatus carry out a foreign
material inspection and defect inspection, that a property and coordinate data
of a wrong portion on the wafer are recorded, and that subsequent apparatus for
a further detail inspection receives the coordinate data to determine a designated
coordinate position and to carry out observation and analysis. High positioning
accuracy permits automation of determining the observation position of the wafer
21 and simplification of its algorithm. This can substantially reduce required
time, which permits obtaining high throughput. Further, the sample stage having
no slanting mechanism is compact and lightweight and can easily obtain high rigidity
to increase reliability, thus permitting superior observation and analysis and
miniaturization or a reduction in cost of the apparatus.
Imparting a swinging function to the focused ion beam optical system
31
to be appropriately moved between the vertical and inclined positions permits processing
identical to the second embodiment without slanting the sample stage
24,
and thus the effect of the present invention can be obtained.
(Embodiment 3)
A structure and an operation of a minute sample processing and observation apparatus
according to a third embodiment of the present invention will be described with
reference to FIGS. 8 and 9. FIG. 9 is a plan view of FIG. 8, and there are some
differences between the figures in orientations or details of apparatuses for convenience
in description but they are not essential difference. In the apparatus of this
embodiment, a focused ion beam optical system
33 is slantingly located at
an angle of approximately 45° at an upper portion of a vacuum sample chamber
60 disposed at the central part of the apparatus system. An electron beam
optical system
42 is also slantingly located at an angle of approximately
45°. Two optical systems
33,
42 are adjusted in such a manner
that their respective central axes intersect at a point around a surface of a wafer
21. Similarly to the apparatus of the first embodiment, inside the vacuum
sample chamber
60 is located a sample stage
24. Further, similarly
to the second embodiment, the sample stage
24 has no slanting function.
Next, processes of sample processing, observation and evaluation after introducing
the wafer will be described with reference to FIG. 19 also. The sample stage is
first lowered to move a probe
72 horizontally (in X and Y directions) relative
to the sample stage
24 with the tip of the probe
72 separated from
the wafer
21, and the tip of the probe
72 is set in a scanning area
of the FIB
4. The manipulator controller
15 stores a positional coordinate
and then evacuates the probe
72.
The sample stage is oriented in such a manner that an intersection line of a
vertical plane containing an optical axis of a focused ion beam optical system
33 and a top surface of the wafer is superposed on an observation section
of a sample to be formed. Then, an FIB
4 is applied to the wafer
21
for scanning to form a vertical section C
1 having a length and depth required
for the observation. Then, an inclined cut section C
2 which intersects a
formed section is formed. When forming the inclined cut section C
2, the
sample stage is rotated around a horizontal axis up to a position where an inclination
angle of an inclined surface is obtained to determine the orientation. Next, an
inclined groove is formed by the FIB
4 in parallel with a vertical cut line.
Further, an end C
3 is cut orthogonal to the groove. A processing area has
a length of about 5 μm, width of about 1 μm and depth of about 3 μm,
and is connected to the wafer
21 in a cantilevered condition of a length
of about 5 μm. Then, the probe
72 at the tip of a manipulator
70
is brought into contact with an end portion of a minute sample
22, and then
deposition gas is deposited on a contact point
75 by application of the
FIB
4, where the probe
72 is joined to and made integral with the
minute sample
22. Then, the other end C
4 supporting the minute sample
is cut by the FIB
4 to cut out the minute sample
22. The minute sample
22 is brought into a condition of being supported by the probe
72,
and ready to be taken out with a surface and an inner section for the purpose of
observation and analysis as an observation and analysis surface p
3 is completed.
Processing thereafter is substantially identical to the first embodiment except
that an orientation of the sample stage
24 is also required to be appropriately
adjusted when setting the optimum orientation of the minute sample for processing
and observation by the focused ion beam optical system or observation by electron
beam optical system, and thus description thereof will be omitted.
As described above, also in this embodiment, high speed observation and analysis
with high resolution can be achieved similarly to the first embodiment. This embodiment
has a feature that one focused ion beam optical system is inclined with respect
to the sample stage to thereby cut out and extract the minute sample from the wafer
without imparting a slanting function to the sample stage. Generally, a large number
of devices are required to be mounted around the optical system, causing lack of
spaces, and a large total mass of the devices makes difficult design of a mounting
substrate including ensuring rigidity. Maintenance thereof is also a matter of
concern. This embodiment eliminates the need for a slanting mechanism of the sample
stage, and requires only one focused ion beam optical system, which can provide
a simple, compact and lightweight structure and reduced cost.
(Embodiment 4)
An outline of structure of a minute sample processing and observation apparatus
according to a fourth embodiment of the present invention will be described with
reference to FIG.
10. In this embodiment, a second sample stage
18
and second sample stage controller
19 for controlling an angle, a height
and the like of the second sample stage are added to a basic structure of the minute
sample processing and observation apparatus shown in FIG.
3. The process
from applying an ion beam from the focused ion beam optical system
31 to
a wafer to extracting a minute sample from the wafer is identical to the first
embodiment. In this embodiment, the extracted minute sample is fixed to the second
sample stage for observation and analysis instead o
