Radiant energy – Irradiation of objects or material – Irradiation of semiconductor devices
Reexamination Certificate
2003-11-04
2004-09-21
Wells, Nikita (Department: 2881)
Radiant energy
Irradiation of objects or material
Irradiation of semiconductor devices
C250S307000
Reexamination Certificate
active
06794663
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to method and apparatus specimen fabrication for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer or a device or preparing the micro sample to be separated by using a focused ion beam.
Electronic parts such as a semiconductor memory typified by a dynamic random access memory, a microprocessor, a semiconductor device such as a semiconductor laser, and a magnetic head are required to be manufactured in a high yield since decrease in the manufacturing yield due to occurrence of a defect causes profit deterioration. Consequently, early detection/measure of/against a defect, a foreign matter, and poor processing as causes of a failure are big tasks. For example, at a site of manufacturing a semiconductor device, energies are put into finding a failure by a careful test and analyzing the cause of the failure. In an actual electronic part manufacturing process using a wafer, a wafer being processed is tested, the cause of an abnormal portion such as a defect in a circuit pattern or a foreign matter is tracked down, and a measurement to be taken is examined.
Usually, to observe a fine structure of a sample, a scanning electron microscope (hereinbelow, abbreviated as SEM) with high resolution is used. However, as the packing density of a semiconductor device is becoming higher, an object cannot be observed with the resolution of the SEM. Therefore, in place of the SEM, a transmission electron microscope (hereinbelow, abbreviated as TEM) having higher observation resolution is used.
Conventional TEM sample fabrication is accompanied by a work of making a sample into small pieces by cleaving, cutting, or the like. When the sample is a wafer, in most cases, the wafer has to be cut.
Recently, there is a micro area processing method of irradiating a sample with an ion beam and applying an action that particles constructing the sample are released from the sample by sputtering, that is, a method of using a process with a focused ion beam (hereinbelow, abbreviated as FIB). According to the method, first, a strip pellet having a thickness of sub millimeters including an area to be observed is cut from a sample such as a wafer by using a dicer or the like. A part of the strip pellet is processed with an FIB into a thin film state to thereby prepare a TEM sample. The feature of the sample for TEM observation processed with the FIB is that a part of a specimen is processed to a thin film having a thickness of about 100 nm for the TEM observation. Although the method enables a requested observation area to be positioned with accuracy of a micrometer level and to be observed, still, the wafer has to be cut.
Although monitoring a result of a process during fabrication of a semiconductor device or the like has an big advantage from the viewpoint of managing the yield, a wafer is cut for preparation of a sample as described above and a piece of the wafer is not subjected to a following process but is discarded. In recent years, particularly, the diameter of a wafer is increasing to reduce the price of manufacturing a semiconductor device. Specifically, the number of semiconductor devices which can be manufactured from a single wafer is increased to reduce a unit price. However, it increases the price of the wafer itself, an added value increases as the manufacturing process advances and, further, the number of semiconductor devices lost by discarding a wafer increases. Therefore, the conventional test method accompanying cutting of the wafer is very uneconomical.
To deal with the problem, there is a method of preparing a sample without cutting a wafer. The method is disclosed in Japanese Patent Application No. H05-52721, “Method of separating sample and method of analyzing sample separated by the separating method” (known technique 1). According to the method, as shown in FIGS.
2
(
a
) to
2
(
g
), first, the posture of a sample
2
is maintained so that the surface of the sample
2
is irradiated with an FIB
1
at the right angle and scanned with the FIB
1
in a rectangular shape, and a rectangular hole
7
having a required depth is formed in the surface of the sample (FIG.
2
(
a
)). Subsequently, the sample
2
is tilted and a bottom hole
8
is formed. The tilt angle of the sample
2
is changed by a specimen stage (not shown) (FIG.
2
(
b
)). The posture of the sample
2
is changed, the sample
2
is disposed so that the surface of the sample
2
becomes perpendicular to the FIB
1
again, and a trench
9
is formed (FIG.
2
(
c
)). By driving a manipulator (not shown), the tip of a probe
3
at the end of the manipulator is made come into contact with a portion to be separated in the sample
2
(FIG.
2
(
d
)). A deposition gas
5
is supplied from a gas nozzle
10
, and an area including the tip of the probe
3
is locally irradiated with the FIB
1
to form an ion beam assist deposition film (hereinbelow, simply called deposition film
4
). The separation portion in the sample
2
and the tip of the probe
3
which are in contact with each other are connected to each other by the deposition film
4
(FIG.
2
(
e
)). The peripheral portion is trenched with the FIB
1
(FIG.
2
(
f
)), and a micro sample
6
as a sample separated from the sample
2
is cut. The cut separated sample
6
is supported by the connected probe
3
(FIG.
2
(
g
)). The micro sample
6
is processed with the FIB
1
and the area to be observed is walled, thereby obtaining a TEM sample (not shown). According to the method, a micro sample including a requested analysis area is separated from a sample such as a wafer by using a process with an FIB and means for carrying the micro sample. The micro sample separated by the method is introduced to any of various analyzers and can be analyzed.
A similar sample fabricating method is disclosed in Japanese Patent Application Laid-Open No. H09-196213, “Apparatus and method for preparing micro sample” (known technique 2). According to the method, as shown in FIGS.
9
(
a
) to
9
(
j
), first, the FIB
1
is emitted to form marks
403
and
404
for identifying a target position and, after that, rectangular holes
401
and
402
are formed on both outer sides of the marks
403
and
404
in the sample
2
(FIG.
9
(
a
)). Subsequently, a trench
406
is formed with the FIB
1
(FIG.
9
(
b
)). The specimen stage is tilted and the surface of the sample is obliquely irradiated with the FIB
1
, thereby forming a tapered trench
408
, and an extraction sample
407
which is connected to the sample
4
only via a residual area
405
is formed (FIG.
9
(
c
)). The tilted specimen stage is returned to the original position and the probe
3
is controlled by a probe controller so as to come into contact with a part of the extraction sample
407
. The residual area
405
of the extraction sample
407
will be cut with an FIB later. In consideration of a probe drift or the like, it is desirable to cut the residual area
405
in short time, so that the volume of the residual area
405
has to be low. Consequently, due to a fear that the residual area
405
is destroyed by the contact of the probe
3
, the probe
3
is made contact while preventing a damage as much as possible by using the probe controlling method. The probe
3
and the extraction sample
407
which are in contact with each other are fixed by using a deposition film
409
(FIG.
9
(
d
)). Subsequently, the residual area
405
is cut with the FIB
1
(FIG.
9
(
e
)). In such a manner, the extraction sample
407
is cut out, and the probe
3
is lifted by the probe driving apparatus to extract the extraction sample
407
(FIG.
9
(
f
)). Subsequently, the cut extraction sample
407
is allowed to come into contact with a trench
411
formed in an extracted sample holder (FIG.
9
(
g
)). At this time, the extraction sample
407
has to come into contact at a sufficiently low speed so that the extraction sample
407
is not destroyed or is
Fukuda Muneyuki
Ishitani Tohru
Kashima Hideo
Koike Hidemi
Seya Eiichi
A. Marquez, Esq. Juan Carlos
Fisher Esq. Stanley P.
Kalivoda Christopher M.
Reed Smith LLP
Wells Nikita
LandOfFree
Method and apparatus for specimen fabrication does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for specimen fabrication, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for specimen fabrication will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3217278