U.S. patent application number 10/949341 was filed with the patent office on 2005-04-28 for specimen cooling system of focused ion beam apparatus.
This patent application is currently assigned to Samsung Electronics Co., Ltd.. Invention is credited to Choi, Chel-jong, Song, In-yong.
Application Number | 20050086946 10/949341 |
Document ID | / |
Family ID | 34511145 |
Filed Date | 2005-04-28 |
United States Patent
Application |
20050086946 |
Kind Code |
A1 |
Song, In-yong ; et
al. |
April 28, 2005 |
Specimen cooling system of focused ion beam apparatus
Abstract
Provided is a specimen cooling system of a focused ion beam
apparatus. The specimen cooling system includes: a reaction
chamber; a stage which is installed in the reaction chamber; a
specimen holder which is installed over the stage and on which a
specimen is placed; a heat transmission part which is attached to
the specimen holder and extends from the interior of the reaction
chamber to the outside so as to transmit heat, which is generated
in the specimen during a process, outside the reaction chamber; and
a heat sink which is connected to an end of the heat transmission
part that extends from the interior of the reaction chamber to the
outside and which absorbs the heat transmitted by the heat
transmission part.
Inventors: |
Song, In-yong; (Gyeonggi-do,
KR) ; Choi, Chel-jong; (Gyeonggi-do, KR) |
Correspondence
Address: |
BURNS DOANE SWECKER & MATHIS L L P
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
Samsung Electronics Co.,
Ltd.
Gyeonggi-do
KR
|
Family ID: |
34511145 |
Appl. No.: |
10/949341 |
Filed: |
September 27, 2004 |
Current U.S.
Class: |
62/3.2 ;
62/201 |
Current CPC
Class: |
H01J 37/3056 20130101;
G01N 1/32 20130101; F25B 21/02 20130101; C23C 14/541 20130101; G01N
1/42 20130101; H01J 2237/2001 20130101; F25D 3/10 20130101 |
Class at
Publication: |
062/003.2 ;
062/201 |
International
Class: |
F25B 021/02; F25B
019/00; F25D 017/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 28, 2003 |
KR |
10-2003-0075629 |
Claims
What is claimed is:
1. A specimen cooling system of a focused ion beam apparatus,
comprising: a reaction chamber; a stage which is installed in the
reaction chamber; a specimen holder which is installed on the stage
and on which a specimen is placed; a heat transmission part which
is attached to the specimen holder and extends from the interior of
the reaction chamber to the outside so as to transmit heat, which
is generated in the specimen during a process, outside the reaction
chamber; and a heat sink which is connected to an end of the heat
transmission part that extends from the interior of the reaction
chamber to the outside and which absorbs the heat transmitted by
the heat transmission part.
2. The specimen cooling system of claim 1, wherein a trench is
formed in a surface of the specimen holder so that the specimen can
be placed on the specimen holder.
3. The specimen cooling system of claim 1, wherein the specimen
holder is formed of at least one of Cu, Fe, Au, and Ag.
4. The specimen cooling system of claim 1, further comprising a
specimen placing part between the stage and the specimen
holder.
5. The specimen cooling system of claim 4, wherein the specimen
placing part is made of a stainless material.
6. The specimen cooling system of claim 1, wherein the reaction
chamber comprises a cooling port which is provided at a portion of
the reaction chamber through which the heat transmission part
penetrates.
7. The specimen cooling system of claim 6, wherein the cooling port
is formed of at least one of Cu, Fe, Au, and Ag.
8. The specimen cooling system of claim 1, wherein the heat
transmission part comprises a portion which is formed in the shape
of a wire and is attached to the specimen holder and a portion
which is formed in the shape of a bar to extend from the interior
of the reaction chamber to the outside through the cooling
port.
9. The specimen cooling system of claim 1, wherein the shape of the
heat transmission part is one of a wire, a bar, and a tube.
10. The specimen cooling system of claim 1, wherein the heat
transmission part is formed of at least one of Cu, Fe, Au, and
Ag.
11. The specimen cooling system of claim 1, wherein the heat sink
is a cooling vessel comprising a cooling medium.
12. The specimen cooling system of claim 11, wherein the heat
transmission part extends into the interior of the cooling vessel
so that an end of the heat transmission part dips into the cooling
medium.
13. The specimen cooling system of claim 12, wherein the cooling
medium is one of liquid nitrogen and liquid helium.
14. The specimen cooling system of claim 12, wherein the cooling
vessel is a Dewar vessel.
15. The specimen cooling system of claim 1, wherein the heat sink
is a peltier element.
Description
BACKGROUND OF THE INVENTION
[0001] This application claims the priority of Korean Patent
Application No. 2003-75629, filed on Oct. 28, 2003, in the Korean
Intellectual Property Office, the disclosure of which is
incorporated herein in its entirety by reference.
[0002] 1. Field of the Invention
[0003] The present invention relates to a specimen cooling system,
and more particularly, to a specimen cooling system of a focused
ion beam apparatus for preventing thermal damage to a device caused
by high temperature heat during the micromachining of the device
using a focused ion beam.
[0004] 2. Description of the Related Art
[0005] Focused ion beam (FIB) apparatuses irradiate a focused ion
beam on a specific micro-part of a specimen to be micromachined so
as to achieve desired micromachining. The FIB is adopted in various
fields such as micromachining of devices, estimation and analysis
of semiconductor processes, ion implantation processes, in-situ
processes, secondary ion mass spectrometry (SIMS), and the
like.
[0006] When a transmission electron microscopy (TEM) specimen is
manufactured using an FIB, the FIB considerably contributes to a
high-resolution analysis in a specific location of the TEM
specimen. However, the FIB causes thermal damage to the TEM
specimen compared to a specimen that is manufactured using a
conventional ion miller. Also, it is difficult to observe in
high-resolution such problems as a crystal defect, due to the thick
thickness of the TEM specimen. In other words, when the TEM
specimen is formed of silicon or the materials that are stable with
respect to heat using the FIB, the structure of the TEM specimen is
hardly affected by heat, i.e., varies only slightly. However, in a
case where materials that unstable with respect to heat, for
example, semiconductor materials such as high thermal conductive
metal materials, InGaAs, InGaP, or the like, are micromachined
using the FIB, heat is locally generated in the semiconductor
materials. When the semiconductor materials are observed with a
TEM, the structures of the semiconductor materials are seen to be
varying due to thermal damage.
[0007] It is reported that thermal damage to a specimen
manufactured with an FIB having a substantial acceleration voltage
of 30 keV is about 20 nm deep.
[0008] FIG. 1 shows a conventional a temperature control apparatus.
Namely, FIG. 1 is a cross-sectional view of a reactive ion etching
(RIE) unit adopting a temperature control apparatus disclosed in
U.S. Pat. No. 5,892,207. A temperature control apparatus 10
includes a liquid nitrogen supply device 13 which supplies liquid
nitrogen into a temperature control space 12 formed in a support
11, a heating device 14 which heats the support 11, and temperature
sensors 15 and 16 which detect the temperature of the support 11.
When the temperature sensors 15 and 16 detect the temperature of
the support 1 1 on which a wafer is mounted, a controller 18
controls the liquid nitrogen supply device 13 and the heating
device 14 to cool or heat the support 11 so as to control the
temperature which is set by a temperature setting device 17.
[0009] The temperature control apparatus 10 directly carries low
temperature liquid nitrogen or high temperature gaseous nitrogen
thereinto. Thus, the temperature control apparatus 10 must withdraw
the low temperature liquid nitrogen or the high temperature gaseous
nitrogen therefrom. As a result, the temperature control apparatus
10 has a complicated structure, and a vacuum in the temperature
control apparatus 10 is difficult to control due to leakage of the
nitrogen from the temperature control apparatus 10.
SUMMARY OF THE INVENTION
[0010] The present invention provides a specimen cooling system
having a simple structure to improve high cooling efficiency so as
to considerably reduce thermal damage to a target specimen during a
process using an FIB.
[0011] According to an aspect of the present invention, there is
provided a specimen cooling system of a focused ion beam apparatus.
The specimen cooling system includes: a reaction chamber; a stage
which is installed in the reaction chamber; a specimen holder which
is installed over the stage and on which a specimen is placed; a
heat transmission part which is attached to the specimen holder and
extends from the interior of the reaction chamber to the outside so
as to transmit heat, which is generated in the specimen during a
process, outside the reaction chamber; and a heat sink which is
connected to an end of the heat transmission part that extends from
the interior of the reaction chamber to the outside and which
absorbs the heat transmitted by the heat transmission part.
[0012] A trench is formed in a surface of the specimen holder to
place the specimen on the specimen holder.
[0013] The specimen holder is formed of Cu, Fe, Au, or Ag.
[0014] The specimen placing part between the stage and the specimen
holder
[0015] The reaction chamber includes a cooling port which is
provided at a portion of the reaction chamber through which the
heat transmission part penetrates.
[0016] The shape of the heat transmission part is that of a wire, a
bar, or a tube.
[0017] The heat transmission part includes a portion which is
formed in the shape of a wire to be attached to the specimen holder
and a portion which is formed in the shape of a bar to extend from
the interior of the reaction chamber to the outside through the
cooling port.
[0018] The heat transmission part and the cooling port are formed
of Cu, Fe, Au, or Ag.
[0019] The heat sink is a cooling vessel including a cooling
medium.
[0020] The heat transmission part extends into the interior of the
cooling vessel so that an end of the heat transmission part dips
into the cooling medium.
[0021] The cooling medium is liquid nitrogen or liquid helium.
[0022] The heat sink is a peltier element.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The above and other features and advantages of the present
invention will become more apparent by describing in detail
exemplary embodiments thereof with reference to the attached
drawings in which:
[0024] FIG. 1 is a schematic cross-sectional view of a conventional
temperature control apparatus for controlling the temperature of
wafer;
[0025] FIG. 2 is a schematic cross-sectional view of an FIB
apparatus adopting a specimen cooling system according to an
embodiment of the present invention;
[0026] FIGS. 3A through 3C are cross-sectional views showing main
members of the specimen cooling system of the FIB apparatus of FIG.
2;
[0027] FIG. 4A is a diagram and a photo showing a specimen
manufactured using the FIB apparatus of FIG. 2;
[0028] FIG. 4B is a photo for comparing a specimen manufactured
according to the present invention with a specimen manufactured
according to the prior art;
[0029] FIGS. 5A through 5C are photos of the surface of a film
between trench structures formed in a specimen, according to the
prior art; and
[0030] FIGS. 6A through 6C are photos of the surface of a film
between trench structures formed in a specimen, according to the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0031] Hereinafter, an embodiment of a specimen cooling system of
an FIB apparatus according to the present invention will be
described in detail with reference to the attached drawings. FIG. 2
is a schematic cross-sectional view of an FIB apparatus adopting a
specimen cooling system, according to an embodiment of the present
invention.
[0032] Referring to FIG. 2, the FIB apparatus includes a reaction
chamber 21 in which a predetermined process is performed on a
specimen 25, a stage 22 which is installed inside the reaction
chamber 21 and over which the specimen 25 is mounted, and a
specimen placing part 23. A specimen holder 24 is further provided
on the specimen placing part 23 to hold the specimen 25 thereon.
The specimen holder 24 is connected to a heat transmission part 26
which transmits heat of the specimen 25 to the outside during the
predetermined process. The heat transmission part 26 penetrates
through the reaction chamber 21 to extend to the outside and
includes a cooling port 27 that is formed at a portion of the
chamber 21 through which the heat transmission part 26 penetrates
and that shuts the interior of the chamber 21 off from the outside.
The heat transmission part 26 extends from the interior of the
reaction chamber 21 to the outside and is connected to a heat sink
28. Here, the heat sink 28 absorbs heat transmitted by the heat
transmission part 26 so as to cool the specimen 25.
[0033] As shown in FIG. 3C, the heat sink 28 may be a cooling
vessel 30 containing a cooling medium 29 or a peltier element. When
the heat sink 28 is the cooling vessel 30 containing the cooling
medium 29, the heat transmission part 26 is connected to the
interior of the cooling vessel 30 and dips into the cooling medium
29. The cooling vessel 30 may be a Dewar vessel. As shown in FIG.
3B, the heat transmission part 26 may be formed of flexible heat
transmission wires 26a and a fixed heat transmission bar 26b (refer
to FIG. 4) or a cooling tube.
[0034] Referring to FIG. 2, it is preferable that the specimen
placing part 23 is formed by micromachining a stainless material so
as not to disperse the cooling efficiency of the specimen holder
24. The specimen holder 24 serves to hold the specimen 25 thereon
and transmits heat, which is locally generated in the specimen 25
during a process using an FIB, to the heat transmission part
26.
[0035] FIG. 3A is a perspective view of the specimen holder 24 used
in the specimen cooling system of the FIB apparatus, according to
an embodiment of the present invention. Referring to FIG. 3A, a
trench structure 24a, to which the specimen 25 is attached, is
formed in the upper surface of the specimen holder 24. The specimen
holder 24 may be formed to have various sizes according to an
adopted process. As described above, the specimen holder 24
contacts the specimen 25 to transmit heat, which is generated in
the specimen 25 during the process using the FIB, to the heat
transmission part 26. Thus, it is preferable that the specimen
holder 24 is formed of a material having high thermal conductivity.
In otherwords, the specimen holder 24 may be formed of copper (Cu),
iron (Fe), gold (Au), silver (Ag), or an alloy of Cu, Fe, Au, and
Ag.
[0036] Only an adjacent portion 24b to the trench structure 24a
contacting the specimen 25 needs to be formed of a material having
high thermal conductivity so as to rapidly transmit heat, which is
generated in the specimen 25 placed in the trench structure 24a of
the specimen holder 24, to the heat transmission part 26. In this
case, a remaining portion 24c of the specimen holder 24 can be
formed of a material having lower thermal conductivity than the
material of which the adjacent portion 24b is formed, for example,
stainless steel. The heat transmission part 26 may be attached to a
side or a lower portion of the specimen holder 24. However, in a
case where the heat transmission part 26 is attached to the lower
portion of the specimen holder 24, the heat transmission part 26
has a relatively complicated structure.
[0037] The heat transmission part 26 is attached to a portion of
the specimen holder 24 to transmit heat of the specimen holder 24
outside the reaction chamber 21. The entire heat transmission part
26 may be formed in the shape of a thin wire, tube, or bar. In view
of thermal conductivity, it is preferable that the heat
transmission part 26 is formed in a bar shape. However, a portion
of the heat transmission part 26 may be formed in the shape of a
flexible wire so that the specimen holder 24 holding the specimen
25 can move inside the reaction chamber 21 during the process.
Therefore, as shown in FIG. 3B, it is preferable that the heat
transmission part 26 is formed of the flexible heat transmission
wires 26a, which contact the specimen holder 24, and the fixed heat
transmission bar 26b. It is preferable that the heat transmission
part 26 is formed of a material having high thermal conductivity
like the specimen holder 24. In other words, the heat transmission
part 26 may be formed of the same material as the specimen holder
24 or a material having high thermal conductivity. In order to
improve cooling efficiency for the specimen 25, it is preferable
that the heat transmission part 26 is short in length yet
relatively thick.
[0038] The cooling port 27 is formed at the portion of the reaction
chamber 21 through which the heat transmission part 26 penetrates
to the outside. According to the present invention, the cooling
port 27 may be formed of the same material as the specimen holder
24 or the heat transmission part 26 so that the heat transmission
part 26 easily transmits heat from the interior of the reaction
chamber 21 to the outside. The cooling port 27 may be formed of a
material different from the specimen holder 24 or the heat
transmission part 26 but one having high thermal conductivity. The
cooling port 27 may be formed of aluminum (Al) but may be formed of
Cu, Fe, Au, Ag, or the like. Preferably, a portion of the heat
transmission part 26 that is formed inside the reaction chamber 21
and a portion of the heat transmission part 26 that extends outside
the reaction chamber 21 form a single body, so as to prevent a gas
from leaking from the interior of the reaction chamber 21 to the
outside.
[0039] FIG. 3C is a sectional view of the heat sink 28 according to
an embodiment of the present invention. Referring to FIG. 3C, the
heat sink 28 may be the cooling vessel 30 containing the cooling
medium 29. The heat transmission part 26 that goes through the
cooling port 27 of the reaction chamber 21 is connected to the
cooling vessel 30. The heat transmission part 26 extends into the
cooling vessel 30 containing the cooling medium 29 so that an end
thereof dips into the cooling medium 29. The cooling medium 29 is
preferably at a low temperature and in a stable state and may be
liquid nitrogen or liquid helium. In a case where the cooling
vessel 30 contains low temperature liquid nitrogen, the temperature
inside the cooling vessel 30 is about -179.degree. C. Thus, the
cooling vessel 30 is manufactured in consideration of the
temperature of the cooling agent. The cooling vessel 30 may also be
a vessel that contains general liquid nitrogen or liquid helium.
The specimen cooling system of the FIB apparatus according to the
present invention may use a peltier element or the cooling vessel
30 containing the cooling medium 29 as the heat sink 28.
[0040] FIG. 4A is a diagram and a photo showing a specimen
manufactured adopting a process using the specimen cooling system
of the FIB apparatus according to the present invention. Referring
to FIG. 4A, a portion of a specimen 25 is micromachined to form a
film 25b having a thickness of about 50 to 100 nm between trench
structures 25a. The micromachining using the specimen cooling
system of the FIB apparatus according to the present invention
hardly causes thermal damage to the specimen 25. This will be
explained in detail with reference to FIG. 4B.
[0041] FIG. 4B is a photo for comparing a specimen manufactured
according to the present invention with a specimen manufactured
according to the prior art. Referring to FIG. 4B, A denotes a
border between trench structures 25a and a specimen which are
manufactured according to the prior art. The structure of the
border A is broken and melted due to thermal damage caused during a
process using an FIB. B denotes a border between trench structures
25a and a planarized portion of a specimen which are manufactured
according to the present invention. Cooling is performed during
micromachining so as to hardly cause thermal damage to the border
B. Thus, the border B is very clearly formed.
[0042] In the specimens manufactured according to the present
invention and the prior art, the surfaces of the films 25b between
the trench structures 25 were observed separately from the
specimens. This will be explained with reference to FIGS. 5A
through 5C and FIGS. 6A through 6C.
[0043] FIGS. 5A through 5C are photos of the surface of a film
between trench structures formed in a specimen, according to the
prior art, and FIGS. 6A through 6C are photos of the surface of a
film between trench structures formed in a specimen, according to
the present invention. Referring to the photos of FIGS. 5A and 5B,
thermal damage C, which has been caused during micromachining using
the FIB, is found in the surface of the film. As shown in FIG. 5C,
the film is not uniform. In contrast, as shown in FIGS. 6A through
6C, the surface of the film, which has been manufactured according
to the present invention, is very clearly. In other words, when a
process is performed using the specimen cooling system of the FIB
apparatus according to the present invention, the film is hardly
damaged by heat.
[0044] As described above, a specimen cooling system of an FIB
apparatus according to the present invention can have a very simple
structure to improve cooling efficiency. Thus, thermal damage to a
target specimen can be considerably reduced during a process using
an FIB.
[0045] While the present invention has been particularly shown and
described with reference to exemplary embodiments thereof, it will
be understood by those of ordinary skill in the art that various
changes in form and details may be made therein without departing
from the spirit and scope of the present invention as defined by
the following claims.
* * * * *