Radiant energy – Inspection of solids or liquids by charged particles – Analyte supports
Reexamination Certificate
2003-03-25
2004-12-07
Nguyen, Kiet T. (Department: 2881)
Radiant energy
Inspection of solids or liquids by charged particles
Analyte supports
C250S307000
Reexamination Certificate
active
06828566
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and an apparatus for fabrication of a specimen. More particularly, the present invention relates to a method and an apparatus for extracting a micro-specimen including a specific small area of a semiconductor material such as a semiconductor wafer or a semiconductor device chip from the semiconductor material by separation using an ion beam and for fabricating a specimen used for carrying out an observation, an analysis and/or a measurement of the specific small area.
2. Description of the Prior Art
In recent years, efforts made to shrink geometries of semiconductor devices make progress at a very great pace. In a structure analysis of these semiconductor devices, there has been demanded an observation of a nanoscopic structure which is so small that, at a resolution of an ordinary scanning electron microscope referred to hereafter simply as an SEM, the structure can not be observed any longer. As a result, observation by means of a transmission electron microscope which is abbreviated hereafter to a TEM is indispensable in place of an SEM. Traditionally, however, fabrication of a specimen for an observation using a TEM can not help resorting to manual work which must be done by a well trained person and takes a long time. For this reason, in reality, the method for observation of a specimen using a TEM does not come into wide use as the method for observation by means of an SEM, whereby a specimen can be fabricated with ease and results of observations can be thus be obtained immediately, did.
The conventional method for fabrication of a specimen for an observation by using a TEM is explained as follows.
FIG. 2
is diagrams showing the first conventional method for fabrication of a specimen for observation using a TEM. A specimen for observation using a TEM is also referred to hereafter simply as a TEM specimen. To be more specific, FIG.
2
/(
a
) is a diagram showing a semiconductor wafer
2
on which LSIs were fabricated. The semiconductor wafer
2
is referred to hereafter simply as a wafer or a substrate. As shown in FIG.
2
/(
b
), the wafer
2
comprises an upper-layer portion
2
A and a lower-portion
2
B or a substrate. Assume that a specimen for TEM observation of a specific area on the wafer
2
is fabricated. First of all, a mark not shown in the figure is put on an area
22
subjected to the observation using a TEM. By exercising care so as not to damage the area
22
to be observed, an injury is deliberately inflicted on the wafer
2
by using a tool such as a diamond pen in order to cleave the wafer
2
or the wafer
2
is cut by means of a dicing saw in order to take out a sliber chip
21
shown in FIG.
2
/(
b
). In order to make the center of a TEM specimen being created the area
22
to be observed, the areas
22
of two chips are stuck to each other by using adhesive
23
to produce 2 specimens
24
stuck together as shown in FIG.
2
/(
c
). Then, the two stuck specimens
24
are sliced by means of a diamond cutter to produce slice specimens
25
shown in FIG.
2
/(
d
). The dimensions of each of the slice specimens
25
are about 3 mm×3 mm×0.5 mm. Then, the slice specimen
25
is put on a grinding plate to be ground by using abrasives into a thin specimen, namely, a ground specimen
25
′ with a thickness of about 20 microns. Subsequently, the ground specimen
25
′ is attached to a single-hole holder
28
mounted on a TEM stage, that is, a stage for holding a TEM specimen as shown in FIG.
2
/(
e
). Then, ion beams
27
are irradiated to the surfaces of the ground specimen
25
′ as shown in FIG.
2
/(
f
). Sputtering fabrication (or ion-milling fabrication) is then carried out on the center of the specimen
25
′ as shown in FIG.
2
/(
g
). Finally, when a hole has been bored through the center of the specimen
25
′, the irradiation of the ion beams
27
is halted as shown in FIG.
2
/(
h
). A thinned area
26
with a thickness not exceeding a value of about 100 nm fabricated as described above has been observed by a TEM. This method is described in references such as a book with a title of “High-Resolution Electron Microscope: Principle and Usage”, authored by Hisao Horiuchi and published by Kyoritsu Syuppan, Page 182, and used as prior-art reference 1.
FIG. 3
is a diagram showing the second conventional method for fabrication of a TEM specimen. This method is a method for fabrication of a specimen using a focused ion beam which is abbreviated hereafter to an FIB. As shown in the figure, first of all, a mark not shown in the figure is created by using a laser beam or an FIB in the vicinity of an area
22
to be observed on the wafer
2
and then the wafer
2
is diced as shown in FIG.
3
/(
a
). A sliver chip
21
shown in FIG.
3
/(
b
) is then taken out from the wafer
2
. The sliver chip
21
is further sliced to produce slice specimens
21
′ shown in FIG.
3
/(
c
). The dimensions of each of the slice specimens
21
′ are about 3 mm×0.1 mm×0.5 mm which is the thickness of the wafer
2
. Then, the slice chip
21
′ is ground into a thinned specimen
21
″. The thinned specimen
21
″ is then stuck to a TEM-specimen holder
31
which resembles a thin metallic disc plate and has a cut portion
31
′ as shown in FIG.
3
/(
d
). Subsequently, the area
22
to be observed on the thinned specimen
21
″ is further thinned by means of an FIB
32
so that only a slice
22
′ having a thickness of about 100 nm is left as shown in FIGS.
3
/(
e
), (
f
). The slice
22
′ is used as a specimen for an observation using a TEM. This method is described in documents such as a collection of theses with a title of “Microscopy of Semiconducting Materials 1989”, Institute of Physics Series No. 100, Pages 501 to 506, which is used as prior-art reference 2.
FIG. 4
is a diagram showing the third conventional method for fabrication of a TEM specimen. The method is disclosed in Japanese Patent Laid-open No. Hei 5-52721 which is used as prior-art reference 3. As shown in the figure, first of all, a specimen substrate
2
is held in such a posture that an FIB
32
is irradiated to the surface of the specimen substrate
2
perpendicularly. The surface of the specimen substrate
2
is then scanned by the FIB
32
along the circumference of a rectangle to form a rectangular hole
33
with a sufficient thickness on the surface as shown in FIG.
4
/(
a
). Then, the specimen substrate
2
is inclined so that the surface thereof forms a gradient of about 70 degrees with the axis of the FIB
32
and a bottom trench
34
for separation is further created on a side wall of the rectangular hole
33
as shown in FIG.
4
/(
b
). The gradient angle of the specimen substrate
2
is adjusted by using a sample stage which is not shown in the figure. Subsequently, the orientation of the specimen substrate
2
is restored to its original posture so that the FIB
32
is again irradiated to the surface of the specimen substrate
2
perpendicularly and a trench
35
is further created as shown in FIG.
4
/(
c
). Then, by driving a manipulator for holding a probe
36
, the tip of the probe
36
is brought into contact with the surface of a portion
40
of the specimen substrate
2
to be separated as shown in FIG.
4
/(
d
). It should be noted that the manipulator itself is not shown in the figure. In this state, the FIB
32
is irradiated to a local area including the tip of the probe
36
while gas
39
for deposition is being supplied from a gas nozzle
37
to create an ion-beam-assisted-deposition film
38
which is abbreviated hereafter to an IBAD film or a deposition film. In this way, the portion
40
of the specimen substrate
2
to be separated and the tip of the probe
36
which have been brought into contact with each other are firmly joined to each other by the deposition film
38
as shown in FIG.
4
/(
e
). Finally, portions left around the portion
40
of the specimen substrate
2
to be sep
Doi Yasunori
Kawanami Yoshimi
Madokoro Yuichi
Tomimatsu Satoshi
Umemura Kaoru
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