U.S. patent application number 10/628727 was filed with the patent office on 2004-01-29 for glow discharge emission spectroscopic analysis apparatus.
Invention is credited to Matsumoto, Susumu, Nelis, Thomas, Shimidzu, Ryosuke.
Application Number | 20040017565 10/628727 |
Document ID | / |
Family ID | 18483753 |
Filed Date | 2004-01-29 |
United States Patent
Application |
20040017565 |
Kind Code |
A1 |
Shimidzu, Ryosuke ; et
al. |
January 29, 2004 |
Glow discharge emission spectroscopic analysis apparatus
Abstract
This invention provides a glow discharge emission spectroscopic
analysis apparatus which is capable of making a desired chemical
analysis with excellent reproducibility. A glow discharge emission
spectroscopic analysis apparatus of this invention is constituted
so that the sample is held by a first electrical conductor provided
on one side of a glow discharge tube and a second electrical
conductor is movable by a cylinder rod to secure the sample in
contact with the first electrical conductor. The electrical
conductors can be electrically connected with each other. when the
sample is secured, and a negative electric potential is applied to
the electrical conductors.
Inventors: |
Shimidzu, Ryosuke; (Tokyo,
JP) ; Nelis, Thomas; (Paris, FR) ; Matsumoto,
Susumu; (Tokyo, JP) |
Correspondence
Address: |
SNELL & WILMER LLP
Suite 1200
1920 Main Street
Irvine
CA
92614
US
|
Family ID: |
18483753 |
Appl. No.: |
10/628727 |
Filed: |
July 28, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10628727 |
Jul 28, 2003 |
|
|
|
09376164 |
Aug 17, 1999 |
|
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|
6643013 |
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Current U.S.
Class: |
356/311 ;
356/316 |
Current CPC
Class: |
G01N 21/67 20130101 |
Class at
Publication: |
356/311 ;
356/316 |
International
Class: |
G01J 003/30 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 1998 |
JP |
10-365229 |
Claims
In the claims:
17. (New) An apparatus for determining the elements in a
semiconductor wafer, comprising: a conductor member having an
aperture, the conductor member has a size to extend across the
semiconductor wafer and contact one surface of the semiconductor
wafer to enable an application of uniform potential to be applied
to the entire surface of the semiconductor wafer to be sampled;
means for mounting the semiconductor wafer on the conductor member;
a glow discharge chamber unit having an anode and an opening
adjacent the aperture of the conductor member; means for exerting a
force on the semiconductor wafer to seal at least a portion of the
surface to be sampled to the glow discharge chamber unit opening
when mounted on the conductor member; means for providing a
sputtering gas to the glow discharge chamber unit; means for
providing an electrical charge of sufficient power to the conductor
member to uniformly charge the surface of the semiconductor wafer
as a cathode to the anode, whereby a glow discharge emission is
created as the semiconductor wafer is sputtered; and means for
providing a spectroscopic analysis of the light from the glow
discharge emission to determine the elements in the semiconductor
wafer.
18. (New) The apparatus of claim 17 wherein the conductor member is
larger in size than the semiconductor wafer.
19. (New) The apparatus of claim 17, wherein the conductor member
is resiliently mounted to permit adjustable movement between the
conductor member and the semiconductor wafer when the semiconductor
wafer is mounted on the conductor member.
20. (New) A system for determining the elements in a semiconductor
sample, comprising: a semiconductor wafer; a conductor member, the
conductor member has a size to extend across a first surface of the
semiconductor wafer to enable an application of uniform potential
to be applied to a surface of the semiconductor wafer to be
sampled; means for mounting the first surface of the semiconductor
wafer on the conductor member; a glow discharge chamber unit having
an anode and an opening adjacent the conductor member; means for
exerting a force on the semiconductor wafer to seal at least a
portion of a second surface of the semiconductor wafer to be
sampled to the glow discharge chamber unit opening when mounted on
the conductor member; means for providing a sputtering gas to the
glow discharge chamber unit; means for providing an electrical
charge of sufficient power to the conductor member to uniformly
change the first surface of the semiconductor wafer as a cathode to
the anode, whereby a glow discharge emission is created as the
semiconductor wafer is sputtered; and means for providing a
spectroscopic analysis of the light from the glow discharge
emission to determine the elements in the semiconductor wafer.
Description
[0001] This is a divisional application of U.S. patent application
Ser. No. 09/376,164 filed on Aug. 17, 1999.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a glow discharge emission
spectroscopic analysis apparatus, wherein a sample is arranged so
as to face an anode of a glow discharge tube, an inert gas is
supplied to the sample surface under low pressure and a glow
discharge is emitted by applying a high-frequency voltage or a DC
voltage between the sample and the anode so that a discharge
emission can be analyzed and more specifically to an improvement in
mounting and applying a potential voltage to a sample, such as a
large semiconductor wafer.
[0004] 2. Description of Related Art
[0005] One example of a glow discharge emission spectroscopic
analysis apparatus is a high-frequency glow discharge emission
spectroscopic analysis apparatus which can be utilized for chemical
analysis of conductor, non-conductor and a semiconductor materials.
With such an apparatus, sputtering and atomic emissions are
combined for analyzing bulk solids and depth profiling surfaces and
coatings.
[0006] According to recent developments in semiconductor
techniques, the diameter of a semiconductor wafers such as silicon
wafers used in manufacturing semiconductor circuit chips have
become larger and the spacing between circuit paths have decreased
so that minute impurities can impair the production of such
products.
[0007] Thus, the prior art is seeking to find apparatus and
procedures to precisely measure the properties of large
semiconductor wafers.
SUMMARY OF THE INVENTION
[0008] The present invention provides a glow discharge emission
spectroscopic analysis apparatus which is capable of making a
desired chemical analysis with excellent reproducibility.
[0009] In order to achieve the above object, according to the
present invention, in a glow discharge emission spectroscopic
analysis apparatus, where a sample is arranged so as to face an
anode of a glow discharge tube provided in a Faraday cage, and an
inert gas is supplied to the sample surface under a low pressure,
and a glow discharge is emitted by applying a high-frequency
voltage or a DC voltage between the sample and anode so that the
discharge emission can be analyzed, the sample is maintained at the
same potential as that of a negative electrode of the high
frequency voltage or DC voltage provided on one of a front surface
and a back surface of the sample excluding the sputtered
position.
[0010] In the glow discharge emission spectroscopic analysis
apparatus having the above structure, a voltage is applied to the
sample uniformly, and intensity of the discharge emission becomes
stable, and thus desired and stable analyzed results can be
obtained.
[0011] In one embodiment, the sample can be held by a first
electrical conductor provided on one side of the glow discharge
tube and second electrical conductor which is capable of being
close to or separated from the first electrical conductor, and both
the electrical conductors are electrically connected with each
other when the sample is mounted so that a negative electric
potential is provided to both of the electrical conductors.
[0012] In the glow discharge emission spectroscopic analysis
apparatus having the above structure, the sample is sandwiched
between the first electrical conductor and the second electrical
conductors. As a result, a voltage is applied to the sample
uniformly, and the intensity of the discharge emission becomes
stable, and thus desired and stable analyzed results can be
obtained.
[0013] Further, in the glow discharge emission spectroscopic
analysis apparatus, the first electrical conductor is provided to
one end of the glow discharge tube, whereas the second electrical
conductor is movable by a cylinder rod so that the sample can be
held between both the electrical conductors. As a result, the
sample can be held simply and securely in a predetermined
posture.
[0014] The present invention can be provided to measure the
properties of semiconductor wafers of a large size and the first
and second electrical conductors can be designed to carefully hold
the semiconductor wafer without exerting undue stress, while also
providing a uniform application of voltage to both sides of the
semiconductor wafer. An electrical conducting wiper can be provided
to interconnect the first and second electrical conductors when
they are closed on the semiconductor wafer for positioning the
semiconductor wafer in a sealing relationship as a cathode in the
glow discharge apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The objects and features of the present invention, which are
believed to be novel, are set forth with particularity in the
appended claims. The present invention, both as to its organization
and manner of operation, together with further objects and
advantages, may best be understood by reference to the following
description, taken in connection with the accompanying
drawings.
[0016] FIG. 1 is a drawing schematically showing a schematic
structure of a glow discharge emission spectroscopic analysis
apparatus of the present invention related to a first
embodiment;
[0017] FIG. 2 is a cross-sectional view showing a main section of
the above glow discharge emission spectroscopic analysis
apparatus;
[0018] FIG. 3 is a perspective schematic view showing a the
structure of a glow discharge emission spectroscopic analysis
apparatus of the present invention related to the second embodiment
for measuring semiconductor wafers, and more specifically a
perspective view showing a Faraday cage;
[0019] FIG. 4 is a cross-sectional schematic view showing a
structure of a Faraday cage and the movable electrical conducting
and holding members;
[0020] FIG. 5 is a sectional view showing a structure of a vicinity
of a glow discharge tube related to a second embodiment of the
present invention;
[0021] FIG. 6 is an enlarged perspective view showing a main
section of a mechanism for holding a sample for the glow discharge
tube in the second embodiment; and
[0022] FIGS. 7A, 7B, and 7C are schematic drawings for explaining
the problem found by the present inventors
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] The following description is provided to enable any person
skilled in the art to make and use the invention and sets forth the
best modes contemplated by the inventors of carrying out their
invention. Various modifications, however, will remain readily
apparent to those skilled in the art, since the general principles
of the present invention have been defined herein specifically to
provide a glow discharge emission spectroscopic analysis apparatus
for measuring the properties of samples, such as semiconductor
wafers.
[0024] The inventors of the present invention conceived of using a
glow discharge emission spectroscope analysis to large size
semiconductor wafers in a production environment and initially
arranged for a sample of a semiconductor wafer to face an anode of
a glow discharge tube. An inert gas was applied to the sample
surface under a low pressure and a glow discharge was emitted by
applying a high-frequency voltage between semiconductor wafer and
the anode so as to analyze the discharge emission. However,
scattering of analyzed data between a center portion and an outer
peripheral portion of the semiconductor wafer surface surpassed the
expected estimate of the inventors to create a problem. Moreover,
scattering of the analyzed data according to various forms of other
semiconductor wafers was also found to surpass the expected result,
thereby indicating that the glow discharge analysis may not be
dependable.
[0025] The inventors then examined their experimental results and
came to a conclusion that the scattering was mainly caused by a
state of coupling to a Faraday cage in portions other than the
portion to which a high-frequency voltage was applied even if the
same semiconductor wafer was used. This point will be described
below with reference to FIG. 7.
[0026] FIG. 7(A) shows a state wherein a voltage is applied to a
semiconductor wafer, and more specifically shows a semiconductor
wafer W adjacent to an anode A side of a glow discharge tube L
provided in a Faraday cage F so that the center of the
semiconductor wafer W coincides with the center of the anode A. A
cathode K is brought into contact with the semiconductor wafer W so
as to coincide with the center of the semiconductor wafer W, and a
high-frequency power source HF is connected between the anode A and
the cathode K. FIG. 7(B) is a drawing showing a planar relationship
between the semiconductor wafer W and the cathode K in the state of
FIG. 7(A). Moreover, FIG. 7(C) is a drawing showing another planar
relationship between the semiconductor wafer W and the cathode K,
when K is off center.
[0027] As shown in FIG. 7(B), when the cathode K is brought into
contact with the semiconductor wafer W so as to coincide with the
center of the semiconductor wafer W, the semiconductor wafer W is
composed of ring bands Z.sub.1, Z.sub.2 and Z.sub.3, and the
impedances of the ring bands are respectively Z.sub.1, Z.sub.2 and
Z.sub.3. In this case, the impedance Z.sub.t viewed from the
cathode K is represented by the following equation (1).
Z.sub.t=Z1, Z.sub.2 and Z.sub.3 (1)
[0028] In addition, as shown in FIG. 7(C), when the cathode K is
brought into contact with a peripheral portion of the semiconductor
wafer W, the semiconductor wafer W is composed of ring bands
Z.sub.1', Z.sub.2'Z.sub.3', Z.sub.4' and Z.sub.5'. In this case,
the impedance Z.sub.t' viewed from the cathode K is represented by
the following equation (2).
Z.sub.t'=Z.sub.1'+Z.sub.2'+Z.sub.3'+Z.sub.4'+Z.sub.5' (2)
[0029] The impedance Z.sub.t of an arbitrary ring band is
represented by the following equation (3).
Z.sub.i=a.sub.i+1/jb.sub.i (3)
[0030] Here, a.sub.i is a resistance component for generating a
voltage due to an electric current in an emission direction in the
ring band, and 1/jb.sub.i is a value relating to a capacitance
coupling with the Faraday cage F of the ring band. In general, the
impedance of the semiconductor wafer W is represented by
.SIGMA.Z.sub.1.
[0031] According to the above equations (1) through (3), it is
clear that the Z.sub.t is different from Z.sub.t', and even if
equal electric power is supplied to the semiconductor wafer W via
the cathode K, the intensity of the discharge emission generated at
this time varies, and thus analyzed results are different from each
other.
[0032] The operation of a spectroscope, such as polychromator and
monochromator systems, are known, see Glow Discharge Optical
Emission Spectrometry by Payling et al., pages 20-23, pages
130-137, Wiley & Sons, Ltd. 1997.
[0033] The inventors consider that the above-mentioned problem is
caused not only in the semiconductor wafer but also in a conductor,
non-conductor and the like.
[0034] FIGS. 1 and 2 show a first embodiment of the present
invention to resolve the above problem. At first, in FIG. 1, 1 is a
metallic Faraday cage, and a glow discharge tube 2 is provided in
the Faraday cage 1. There will be described below the structure of
the glow discharge tube 2 and its periphery with reference to FIG.
2. 3 is a lamp body, and a discharge emission chamber 4 which
broadens towards it bottom opening is formed therein. Vacuum ports
5 and 6 are formed in the lamp body 3, and they are connected with
a vacuum pump, not shown. Moreover, 7 is a port for introducing an
inert gas, appropriate for a sputtering plasma, such as argon
gas.
[0035] An end on the broaden opening side of the discharge emission
chamber 4 is sealed by a window 8 made of magnesium fluoride or the
like, and light 9 which is generated due to a discharge, to be
mentioned later, is introduced in a direction of a spectroscope.
Moreover, an anode 11 having a cylindrical open portion 10 at its
center is attached to the other end of the lamp body 3 which faces
the window 8 by an anode holder 12 and a supporting body 13 made
of, for example, ceramics so as to render airtight the lamp body 3.
A through hole 14 into which the cylinder section 10 is inserted is
formed in the anode holder 12, and a cylinder section 15 where the
through hole 14 is formed is slightly projected from an upper
surface of the supporting body 13 so that its peripheral portion is
held by the supporting body 13. As mentioned above, the discharge
emission chamber 4 on the anode 11 side is opened, but this opening
is sealed by a surface of the semiconductor wafer 18 to be
sputtered. As will be described later, the two conductors 16, 17
can mount and hold the wafer 18. Here, 19, 20 and 21 are sealing
members, such as O-rings.
[0036] The conductors 16, 17, comprising copper plates of proper
thickness, are conductors (hereinafter first conductor 16 and
second conductor 17) for grasping the semiconductors wafer 18 and
have an outer size larger than the semiconductor wafer 18. The
first conductor 16 which is closer to the anode 11 has a hole 22
into which the anode holder or pressing member 12 can fit. As can
be determined later, the first conductor 16 can be connected
electrically with a second conductor 17 so that they become
mutually the same in electrical potential.
[0037] Reference number 23 is a pressing member such as piston
block or the like, which presses the rear face of the second
conductor 17 when it cooperates with the first conductor 16 and
grasps the semiconductor wafer 18. The pressing member 23 is
connected with a negative pole if a high frequency power 24 is
provided externally of the Faraday cage 1 through a conductor
25.
[0038] Referring to FIG. 1, reference numeral 26 is, for example, a
plane copper plate which acts as an earth conductor when positioned
close to the semiconductor wafer 18 and is also positioned so as to
be parallel to it.
[0039] In order to conduct a material analysis of the semiconductor
wafer 18 by using the glow discharge emission spectroscopic
analysis apparatus, the wafer 18 is grasped by the two conductors
16 and 17 as shown in FIG. 1 and FIG. 2. The semiconductor wafer 18
is positioned to face the anode of the glow discharge tube 2, by
pressing the second conductor 17 in the glow discharge tube 2
direction with the pressing member 23.
[0040] When a negative voltage is applied from a high-frequency
power source 24 to the pressing member 23 in a state that the
discharge emission chamber 4 provided in the glow discharge tube 2
is in an atmosphere of argon gas, a predetermined voltage is
applied to the entire face of the semiconductor wafer 18 via the
first electrical conductor 16 and the second electrical conductor
17. As a result, a discharge is generated, and argon ions are
created based on the discharge, and the argon ions are accelerated
by a high electric field so as to collide against the surface of
the semiconductor wafer 18 which is the cathode, and is thereby
subject to a predetermined sputtering process. The sputtered
particles (atom, molecule and ion) are excited in the plasma, and
when the particles return to a ground state, a light emission which
is peculiar to the particular elements in the wafer is executed.
This emitted light is introduced in the direction of the
spectroscope as a light represented by a reference numeral 9 in
FIG. 1 and FIG. 2.
[0041] In the glow discharge emission spectroscopic analysis
apparatus, since the semiconductor wafer 18 as the sample to be
analyzed is held by the first electrical conductor 16 and the
second electrical conductor 17, the semiconductor wafer 18 can be
held securely in a predetermined state. In the held state, the
first electrical conductor 16 and the second electrical conductor
17 have equal or almost equal voltages, and both the electrical
conductors 16 and 17 come close to the entire surface of the
semiconductor wafer 18 on both faces. As a result, only by applying
a high-frequency voltage to the first electrical conductor 16, a
predetermined voltage can be applied to the whole surface of the
semiconductor wafer 18, and the applying of a voltage to the
semiconductor wafer 18 can be executed very simply and stably.
[0042] When the semiconductor wafer 18 was analyzed by using a glow
discharge emission spectroscopic analysis apparatus, intensity of
specified silicon wavelengths of 251 nm (secondary light), 288 nm
(primary light) and 288 nm (secondary light) were examined. The
results shown in the following TABLE 1 were obtained. In this
measurement, a frequency of the high-frequency voltage was 13.56
MHz, an electric power was 50 W, and a pressure in the glow
discharge tube 2 was maintained within 4 to 5 mhPa.
[0043] Changing parameters are:
[0044] a. size of the semiconductor wafer 18 (6 in or 8 in);
[0045] b. position of the semiconductor wafer 18;
[0046] c. existence/non-existence of the two electrical conductors
16 and 17; and
[0047] d. distance from the semiconductor 18 to the earth conductor
26.
1 TABLE 1 Existence/ Dis- 251 288 288 Size non-existence of tance
(2nd) (1st) (2nd) (inch) Position electrical conductors (cm) 1 806
800 33 6 Center Non-exist 21 2 578 570 28 8 Center Non-exist 21 3
234 232 11 8 Edge No-exist 21 4 1152 1130 45 8 Center Exist 21 5
1168 1157 46 8 Edge Exist 21 6 1154 1152 46 6 8 Edge 21 7 1089 1070
42 8 Edge Exist 11 8 851 835 33 8 Edge Exist 5
[0048] The following is understood from TABLE 1. At first, in
measurement 1 through measurement 3, a voltage was applied to the
semiconductor wafer 18 as shown in FIG. 7(A) without using the
first electrical conductor 16 and the second electrical conductor
17. In measurement 1 and 2, only the size of the semiconductor
wafer 18 differed from each other, and as the size of the
semiconductor wafer 18 was smaller, the emission intensity was
stronger.
[0049] In measurement 2 and measurement 3, the sizes of the
semiconductor wafer 18 were equal to each other, but the center of
the semiconductor wafer 18 was measured in measurement 2, and a
portion close to the edge of the semiconductor wafer 18 was
measured in measurement 3. The emission intensity was stronger in
the center of the semiconductor wafer 18.
[0050] Next, in measurement 4 through measurement 8, the
semiconductor wafer 18 was sandwiched between the first electrical
conductor 16 and the second electrical conductor 17 and in this
state a voltage was applied to the semiconductor wafer 18.
Measurement 4 and measurement 5 are different from each other only
in that the measuring position of the semiconductor wafer 18 is its
center or edge, and the other conditions were not different from
each other. A difference in the intensity between respective
wavelengths was hardly recognized.
[0051] In measurement 5 and measurement 6, the centers of the
semiconductor wafers 18 with different sizes were measured, and the
other conditions were not different from each other. A difference
in the intensity between respective wavelengths was also hardly
recognized.
[0052] In measurement 5, 7 and 8, the distances from the
semiconductor wafer 18 to the earth conductor 26 differed from each
other. Even if the first electrical conductor 17 held the
semiconductor wafer 18 so as to cover it, as the distance between
the semiconductor wafer 18 and the earth conductor 26 becomes
shorter, the emission intensity is reduced. It is considered that
this result occurs because the earth condition of the earth
conductor 26 is incomplete at a high frequency and an electric
power loss occurs, and thus the loss depends on the distance
between the earth conductor 26 and the semiconductor wafer 18 so
that the emission intensity changes. Moreover, it is also
considered that when capacitive coupling between the first
electrical conductor 16 and the second electrical conductor 17 and
the earth conductor 26 exceeds a fixed amount, an energy for
emission is reduced.
[0053] Although the same measurement was conducted in a condition
where a conductor was adhered on either face of the semiconductor
wafer 18 continuous to the above described measurement, no
difference was recognized between the measurement results in either
case. Namely, when the first conductor 16 is adhered only on the
sputter face side of the semiconductor 18, and when the reverse
face of the semiconductor wafer 18 is covered with the conductor 17
in a condition that the sputtered front face is exposed the same
result is obtained as when the semiconductor wafer 18 is covered
with the two conductors 16 and 17. Namely, when one front face of
the semiconductor wafer 18 is retained at the same potential, the
load is almost retained constant and it is not affected by the size
of the semiconductor wafer 18 and the location of the voltage
application.
[0054] There will be described below a second embodiment of this
invention with reference to FIGS. 3 through 6. At first, in FIG. 3,
31 is an apparatus main body containing a spectroscope, such as a
polychrometer and monochrometer for analyzing a discharge emission
generated in a glow discharge tube (mentioned later), and a power
source section and the like. This structure has been designed to
accommodate thin flat discs, such as semiconductor wafers. A
Faraday cage 32 is provided on the front side of the apparatus main
body 31.
[0055] As shown in FIG. 4, the Faraday cage 32 is made of a
metallic cylinder fixed to a bracket member 33 connected with the
apparatus main body 31. The Faraday cage 32 is composed of a
cylindrical first cage section 35 which is provided with a flange
34 and is made of metal, and a second cage section 37, which is
provided so as to contact with or be separate from the first cage
section 35, has a flange 36 at its one end, and is made of a
metallic cylinder in which the other end is closed. 38 is an air
cylinder whose one end is fixed to a side surface of the closed
side of the second cage section 37, and a forward end of a piston
rod 39 is coupled to a stanchion 40 which stands in a vertical
direction in FIG. 4. The second cage section 37 slides in the
direction of an arrow U or V by expansion and contraction of the
piston rod 39 so that the flange 23 of the first cage section 35
and the flange 36 of the second cage section 37 closely contact
with each other or are separated from each other by a predetermined
gap. Here, 41 is a guide member. Accordingly, the housing structure
of components 37 and 36 can be opened and closed to provide access
for loading semiconductor wafers.
[0056] In the Faraday cage 32, a glow discharge tube 42, and a
sample holding mechanism 44, which holds a sample 43 to be analyzed
(for example, semiconductor wafer) to one end of the glow discharge
tube 42 and applies a predetermined voltage to the sample 43, are
provided.
[0057] At first, a description will be given as to the structure of
the glow discharge tube 42. In FIG. 5, 45 is a lamp body, and a
discharge emission chamber 46 which broadens towards its bottom
opening is formed therein. Vacuum ports 47 and 48 are formed in the
lamp body 45, and they are connected with a vacuum pump, not shown.
Moreover, 49 is a port for introducing an inert gas such as argon
gas.
[0058] One end, on the broaden opening side of the discharge
emission chamber 46, is sealed by a window 50 made of magnesium
fluoride or the like, and any light 51 generated due to a discharge
effect, mentioned later, is introduced in the direction of a
spectroscope (not shown) in the apparatus main body 31. Moreover,
an anode 53 having a cylindrical portion 52 at its center is
attached to the other end which faces the window 50 by an anode
holder 54 and a supporting body 55 made of, for example, ceramics
so as to make airtight the lamp body 45. A through hole 56 into
which the cylinder section 57, where the through hole 56 is formed,
is slightly projected from an upper surface of the supporting body
55 so that its peripheral portion is held by the supporting body
55. As mentioned above, the discharge emission chamber 46 on the
anode 53 is opened, but this opening is sealed by a surface of the
semiconductor wafer 43 to be sputtered and held by the sample
holding mechanism 44, mentioned later. Here 58, 59 and 60 are
sealing members, such as O-rings.
[0059] There will be described below the structure of the mechanism
44 for holding the semiconductor wafer 43 in a predetermined site
also with reference to FIG. 6. The sample holding mechanism 44 is
provided to the anode 53 side of the glow discharge tube 42. First,
61 is a first electrical conductor provided fixedly to the
discharge tube 42, and it will sandwich the semiconductor wafer 43
with the cooperation on a second electrical conductor 41, mentioned
later, so as to cover its whole surface, and it can apply a
predetermined voltage to the semiconductor wafer 43. The first
electrical conductor 61 as well as the second electrical conductor
41 wil serve as a cathode for the discharge tube 42. The first
electrical conductor 61 is made of a copper plate having a
thickness of about 3mm, for example, and is composed of a
rectangular main body section 62 whose four corners are chamfered
and two mounting sections 63. The main body section 62 and the
mounting sections 63 whose size is at least larger than a maximum
size of the semiconductor wafer 43 are coupled to each other by an
elastic connecting plate 64 so that their rear faces (glow
discharge tube 42 side) are flush with each other (there is no
stepped portion) and will have an elastic structure to accommodate
variances in the dimensions of the wafer 43.
[0060] A hole 65 which can house the supporting body 55 on the glow
discharge tube 42 side is formed in the main body section 62, and
an elastic and electrically conductive section 66, such as a wiper
member, is provided for setting the voltages of the second
electrical conductor 71 and the first electrical conductor 61 to be
equal with each other. The wiper member 66 is projected from a
suitable position of one side surface (surface opposite to the
second electrical conductor 71, sandwich surface) 62a of the main
body section 62, and a voltage apply section 68, connected with the
high-frequency power source (not shown) via a cable 67, is provided
on the other side surface.
[0061] In addition, the mounting sections 63 are held by insulating
holding sections 70 (see FIG. 4) provided in midways of stanchions
69 which are held to the bracket member 33 (see FIG. 4) in a
horizontal direction, and thus the first electrical conductor 61 is
fixedly provided to the anode 53 of the glow discharge tube 42 so
that its plane, particularly a sandwich surface represented by a
reference symbol 62a (see FIGS. 4 and 6) is parallel with a
vertical direction.
[0062] Here, the edge portions of the main body section 62 and the
mounting sections 63 are subject to a curve face process and
chamfering process so that an edge portion, which could score the
wafer 43, is not generated.
[0063] 71 is the second electrical conductor which is made of a
copper plate of about 3 mm, for example, and it is provided so as
to move linearly with respect to the fixed first electrical
conductor 61. The second electrical conductor 71 has the same form
and size as those of the main body section 62 of the first
electrical conductor 61, but as shown in FIG. 5, it is composed of
a small rectangular pressurizing section 72 which matches with the
through hole 56 of the anode holder 54 (an area of the
semiconductor wafer 43 to be analyzed is positioned here), and a
main body section 73 of the pressurizing section 72. The
pressurizing section 72 is coupled to the main body section 73 by
an elastic coupling plate 74 so that they are flush with each other
(a stepped portion is not generated). Here, the edge portion of the
main body section 73 undergoes the curved face process and
chamfering process so that an edge portion is not generated.
[0064] There will be described below holding and moving mechanisms
of the second electrical conductor 71 with reference to FIGS. 4 and
6. In these drawings, 75 and 76 are air cylinders for moving the
second electrical conductor 71 linearly, and their cylinder
sections 75a and 76a are mounted to a mounting base 79 via spacers
78 which are held to a base member 77 mounted on the stanchions 69.
Moreover, their piston rods 75b and 76b are constituted so as to be
capable of expanding and contracting on the first electrical
conductor 61 side through holes 80 opened in the base member 77.
The ends of the piston rods 75b and 76b are mechanically coupled to
connection blocks 81 and 82 provided on a side 71b (mounted face
side) of the second electrical conductor 71 opposite to a surface
71a (see FIG. 4) for nipping or holding the pressurizing section 72
and the main body section 73.
[0065] 83, 84, and 85 are guide rods provided in the same direction
as a direction where the air cylinders 75 and 76 are provided
laterally. As for the guide rod 83, its base portion is fixed to
the connection block 81, which matches for the pressurizing section
72 of the second electrical conductor 71, and is inserted through a
guide section 86 provided to the mounting base 79. As for the other
two guide rods 84 and 85, their base portions are fixed to the main
body section 72 of the second electrical conductor 71, and are
inserted through a guide section 87 and a guide section, not shown,
provided to the mounting base 79.
[0066] As mentioned above, the second electrical conductor 71 is
held by the piston rods 75b and 76b of the two air cylinders 75 and
76 and the three guide rods 83 through 85 so as to be close to or
separated from the first electrical conductor 61, and the
contacting face 71a shield so as to be parallel with the contact
face 62a of the first electrical conductor 61. Moreover, the second
electrical conductor 71 holds the semiconductor wafer 43 in a
vertical state by cooperation with the first electrical conductor
71.
[0067] Here, in FIG. 4, a plate-shaped earth conductor 88 is
provided in the Faraday cage 32, and its voltage is maintained so
as to be equal with the voltage of the Faraday cage 32.
[0068] In the case where the material of the semiconductor wafer 43
is to be analyzed by using the glow discharge emission
spectroscopic analysis apparatus having the above structure, as
shown in FIG. 4, the semiconductor wafer 43 to be analyzed is held
between the electrical conductors 61 and 71 by a support loader or
magic hand, not shown, in the state where the second electrical
conductor 71 is separated from the first electrical conductor 61.
When the two air cylinders 75 and 76 are operated, the piston rods
75b and 76b are extended in the direction of the arrow U. As a
result, the semiconductor wafer 43 is pushed towards the direction
of the first electrical conductor 61 so as to be nipped or securely
held by the first electrical conductor 61 and the second electrical
conductor 71. In this case, since the desired position of the
semiconductor wafer 43 is previously known, the magic hand or
loader positions the semiconductor wafer 43 so that the
pressurizing section 72 in the second electrical conductor 71
matches with the through hole 56 where the anode 53 is
provided.
[0069] As mentioned above, the semiconductor wafer 43 which is
nipped by the first electrical conductor 61 and the second
electrical conductor 71 is pressed against the anode holder 54 of
the glow discharge tube 42, and since the sealing member 60 is
provided on the pressed face side of the anode holder 54, the
discharge emission chamber 46 of the glow discharge tube 42 is
accordingly sealed by the surface of the semiconductor wafer 43 in
an airtight manner. The area of the semiconductor wafer 43 to be
analyzed (area to be sputtered) faces the cylinder section 52 of
the anode 53 which is positioned in the through hole 56 of the
anode holder 54.
[0070] In the above state, the main body section 73 of the second
electrical conductor 71 contacts with the electrically conductive
section 66 provided on the contact face 62a side of the main body
section 62 of the first electrical conductor 61. Then, the voltage
of the second electrical conductor 71 is made equal with the
voltage of the first electrical conductor 61 so that the supporting
contact area for the semiconductor wafer 43 is held at the same
potential voltage.
[0071] When a high-frequency voltage is applied from a
high-frequency power source (not shown) to the first electrical
conductor 61 in a state that the discharge emission chamber 46 is
in atmosphere of argon gas, a predetermined voltage is applied to
the entire front and back face of the semiconductor wafer 43 via
the first electrical conductor 61 and the second electrical
conductor 71 which will have an equal voltage level. As a result, a
discharge is generated, and an argon ion is created based on the
discharge, and the argon ion is accelerated by a high electric
field so as to collide against the surface of the semiconductor
wafer 43 which acts as the cathode, and is thereby subject to a
predetermined sputtering process. The sputtered particles (atom,
molecule and ion) that are released from the semiconductor wafer 43
are then excited in the plasma field, and when the particles again
return to a ground state, their characteristic wavelength emission
is peculiar to the elements in the wafer 43. This emitted light is
introduced in the direction of the spectroscope in the apparatus
main body 31 as a light represented by a reference numeral 43 in
FIG. 5.
[0072] As can be appreciated by determining the depth of etch or
sputtering a profile as the elements in the wafer can be determined
for not only the surface, but for controlled distances into the
body of the wafer.
[0073] In the glow discharge emission spectroscopic analysis
apparatus, since the semiconductor wafer 43 is nipped by the first
electrical conductor 61 and the second electrical conductor 71, the
semiconductor wafer 43 can be held securely in a predetermined
state. In the nipped state, the first electrical conductor 61 and
the second electrical conductor 71 have equal voltages, and both
the electrical conductors 61 and 71 come close to each surface of
the semiconductor wafer 43. As a result, only by applying a
high-frequency voltage to the first electrical conductor 61, a
predetermined voltage can be applied to the entire surface of the
semiconductor wafer 43, and the applying of a voltage to the
semiconductor wafer 43 can be executed very simply and stably.
Particularly since a voltage from the high-frequency power source
is applied to the fixed first electrical conductor 61, it is not
necessary to install a power source cable, and thus installation of
other components can be designed easily.
[0074] In addition, in the glow discharge emission spectroscopic
analysis apparatus, the fixed first electrical conductor 61 is
composed of the main body section 62 and the mounting sections 63,
they are coupled with each other by the elastic coupling plate 64
so as to be flush with each other (no stepped portion is obtained),
and thus the first electrical conductor 61 has an elastic
structure. As a result, even if the semiconductor wafer 43 is
slightly distorted or warped, the first electrical conductor 61 can
absorb or adjust for the distortion and warpage, and can still hold
the semiconductor wafer 43 in the desired position in cooperation
with the second electrical conductor 71.
[0075] Furthermore, the movable second electrical conductor 71 is
composed of the pressurizing section 72 for pressurizing the area
of the semiconductor wafer 43 to be analyzed and the main body
section 73, has an elastic structure, and the pressing section 72
and the main body section 73 are pressurized respectively by
individual piston rods 75b and 76b. As a result, when a
pressurizing force of the piston rods 75b to the pressurizing
section 72 is set to be larger than a pressurizing force of the
piston rod 76b to the main body section 73, the portion of the
semiconductor wafer 43 including the area to be analyzed can be
pressed strongly against the anode holder 54, and thus a
predetermined airtightness can be maintained.
[0076] Even when an analysis of the semiconductor wafer 43 was
conducted by the use of the above described glow discharge emission
spectroscopic analysis apparatus, the same result as that of the
glow discharge emission spectroscopic analysis apparatus of the
first embodiment has been obtained.
[0077] In the above embodiment, the second electrical conductor 71
is driven by the two air cylinders 75 and 76, but the present
invention is not limited to this structure, and thus it may be
driven by one air cylinder or by other hydraulic and electrical
motive forces.
[0078] In addition, in the above embodiment, the semiconductor
wafer 43 is used as a sample, but the present invention is not
limited to this, and thus, conductors such as metal, non-conductors
and semiconductors such as various insulating material including
ceramics can be used for analysis. Further, when the sample is a
conductor, it is needless to say that a DC voltage may be applied
thereto instead of a high-frequency voltage.
[0079] Since the second embodiment of the glow discharge emission
spectroscopic analysis apparatus is arranged so that the sample 43
is sandwiched between the first electrical conductor 61 s and the
second electrical conductor 71 and a negative electric potential is
given to one of them, a voltage is applied to the sample 43
uniformly, and the intensity of the discharge emission becomes
stable. As a result, a desired and stable analyzed result can be
obtained. Therefore, the desired chemical analysis may be made with
excellent reproducibility.
[0080] It is not intended to limit this invention to the particular
embodiments disclosed but, on the contrary, the invention is to
cover all modifications and alternative constructions all within
the spirit and scope of the invention as expressed in the appended
claims and as known by those skilled in the field as equivalents to
the elements set forth in the claims.
* * * * *