Measuring and testing – Sampler – sample handling – etc.
Reexamination Certificate
2002-06-19
2004-08-24
Raevis, Robert (Department: 2856)
Measuring and testing
Sampler, sample handling, etc.
Reexamination Certificate
active
06779410
ABSTRACT:
This invention claims priority from Korean Patent Application No. 2001-35111, filed Jun. 20, 2001, the contents of which are incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vertical scanning electronic microscope (SEM) used to conduct a surface analysis of a sample. More particularly, this invention relates to a sample holder used in the vertical SEM. The present invention further relates to an auxiliary apparatus for holding a sample in the sample holder and to a method of loading a sample in the sample holder using the same.
2. Description of the Related Art
To manufacture a semiconductor integrated circuit, a semiconductor layer pattern multi-layer, an insulating layer pattern, and a conductive layer pattern are formed on a wafer where the integrated circuit will be implemented. A scanning electronic microscope (SEM) is generally used to inspect and analyze the patterns formed during each process. To analyze a wafer, the wafer is first cut to a proper size to produce a sample. The surface and cut section of the wafer are then analyzed in the SEM. A sample holder is used to mount the sample in a predetermined position in the SEM.
FIG. 1
is a schematic diagram illustrating the configuration of a conventional vertical scanning electronic microscope (SEM)
100
. An SEM
100
uses various electronic lenses to focus an electron beam light source onto the sample. Using the focused electron beam, the SEM
100
scans a desired portion of a sample and detects various signals, such as secondary electrons, back scattering electrons, or X-rays, that are emitted from the sample. The SEM
100
then image-processes the signals to generate a magnified image of the desired area.
Referring to
FIG. 1
, the SEM
100
includes a sample chamber
104
, which receives a sample
10
held in a sample holder
200
. An electron gun
108
generates an electron beam
132
, which is directed through a column portion
102
into the sample chamber
104
. An electron beam guide
110
, formed in the column portion
102
, guides the electron beam
132
in the desired direction. Anodes
112
, focusing lenses
114
, deflection coils
116
, and objective lenses
118
are sequentially formed below the electron beam guide
110
. An end of the electron gun
108
includes a filament tip for generating the electron beam
132
.
A shutter (not shown) is positioned in a lower end of the objective lens
118
to control the supply of the electron beam
132
. The electron beam
132
generated in the electron gun
108
is accelerated and focused. The depth of focus is adjusted using an objective iris (not shown) in the objective lens
118
. The electron beam
132
scans the sample
10
mounted on a sample holder
200
. Secondary electrons
134
generated by the sample
10
are detected by a detector
120
.
The detected electronic signals are amplified using an amplifier
122
and displayed as an image on a display screen. The signals are transferred, for instance, to a cathode-ray tube
126
and scanned onto an inner fluorescent screen thereof. A surface image of the sample
10
is thereby displayed. A deflection angle is controlled by a deflection coil (not shown) in the cathode-ray tube
126
.
In the SEM
100
, a scanning plane of the sample
10
is decomposed into delicate pixels, and electronic signals corresponding to the pixels are transmitted clockwise to generate a screen image. The electronic signals that are passed through the amplifier
122
are transmitted into a scanning circuit
124
. A deflection angle of the electron beam
132
is controlled in the deflection coil
116
of the column portion
102
. In addition, the electron signals that are passed through the amplifier
122
are transmitted into an image transmission portion
128
to display the image.
A turbo pump
130
is installed in a lower end of the sample chamber
104
to maintain the sample chamber
104
in a vacuum state. A preliminary chamber
106
is installed on the side of the sample chamber
104
to maintain the vacuum state when the sample holder
200
is loaded or unloaded into the sample chamber
104
.
FIG. 2
is a schematic plan view of a conventional sample holder
200
(e.g., model S-5000 manufactured in Japan by Hitachi).
FIG. 3
is a cross-sectional view of the sample holder
200
taken along line III-III′ of FIG.
2
. Referring to
FIGS. 2 and 3
, the body of the sample holder
200
has a generally circular, rod-like shape. A sample holding portion
203
, formed in a forward portion of the sample holder
200
, is configured to receive and hold a sample
10
.
A sapphire tip
210
is formed at the forward end of the sample holder
200
. A handle
206
is formed at a rearward end of the sample holder
200
. The body of the sample holder
200
has a first body portion
202
, which includes a sample holding portion, and a second body portion
204
. The second body portion
204
is larger in diameter than the first body portion
202
. The first and the second body portions
202
,
204
can be attached to and separated from each other.
The sample holding portion
203
is typically formed by horizontally removing an upper portion of the first body portion
202
. A ridge
213
, having a predetermined height, may be formed around the edge of the sample holding portion
203
. A sample insertion groove
212
is formed to a predetermined depth in the sample holding portion
203
to receive and hold the sample. Sample insertion auxiliary grooves
214
are provided on both sides of the sample insertion groove
212
. The auxiliary grooves
214
facilitate the insertion and removal of a sample
10
using forceps. Screw holes
220
are formed through a sidewall of the sample insertion groove
212
.
In the conventional sample holder
200
, the sample
10
is inserted along one side of the sample insertion groove
212
. An aluminum spacer
216
is also inserted into the sample insertion groove
212
, and contacts a side of the sample
10
. Two copper set screws
218
are inserted through the holes
220
into contact with a sidewall of the spacer
226
. The screws
218
are advanced through the holes
220
to force the spacer
216
into close contact with the sample
10
, thereby holding the sample
10
in place.
To use the conventional sample holder
200
, a wafer is first cut at a desired location to produce a sample having a size of around 5-10 mm×4-6 mm. The sample
10
is positioned vertically in the center of the sample insertion groove
212
using forceps. The spacer
216
is then inserted into the insertion groove
212
along a side of the sample
10
, in the same manner. The screws
218
are then advanced through the screw holes
220
to force the spacer
216
into close contact with the sample
10
. The sample
10
is thereby held in place between a sidewall of the sample insertion groove
212
and the spacer
216
. A driver (e.g., a flathead screwdriver) is used to drive the screws
218
into the holes
220
.
Unfortunately however, because the conventional sample holder
200
uses the screws
218
to hold the sample
10
in place, several problems occur. Among other things, a tightening force applied to the screw
218
by the screwdriver is transferred to the sample
10
through the spacer
216
. The tightening force can cause the sample
10
to be broken. Broken sample particles can cause leaks in the various O-rings in the sample chamber
104
(see FIG.
1
). Because the sample chamber
104
is maintained in a high vacuum state, breaches in the O-ring seals permit external air to flow into the sample chamber
104
and reduce the vacuum state of the sample chamber
104
. The performance of the turbo pump
130
is also lowered as a result of breeches in the O-ring seals.
In addition, external gas molecules that flow into the sample chamber
104
move into the column portion
102
and are adsorbed to the filament tip of the electron gun
108
. The filament tip must then be heated and flashed to remove the adsorbed gas molecules. Flashing cu
Jung Ho-Hyung
Kim Dae-Jung
Koo Bon-Se
Marger Johnson & McCollo, P.C.
Raevis Robert
Samsung Electronics Co,. Ltd.
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