U.S. patent application number 11/964754 was filed with the patent office on 2008-08-14 for apparatus having vacuum vessel.
Invention is credited to Masayuki Kobayashi, Tomohiro Kudo, Hiroaki Mito, Tomonori Saeki, Yasuo Yahagi.
Application Number | 20080190928 11/964754 |
Document ID | / |
Family ID | 39684957 |
Filed Date | 2008-08-14 |
United States Patent
Application |
20080190928 |
Kind Code |
A1 |
Yahagi; Yasuo ; et
al. |
August 14, 2008 |
APPARATUS HAVING VACUUM VESSEL
Abstract
An apparatus having a vacuum vessel that has a mechanism using a
lubricant therein and not causing defects and faults to samples
introduced into the vacuum vessel even it is an apparatus where
lubricating oil or grease is applied is provided. An apparatus
having a vacuum vessel that has a mechanism using a lubricant
therein such as CD-SEM, in which a lubricant (oil, grease) whose
adsorption amount per minute to a surface of a material introduced
into the vacuum vessel of an apparatus for evaluating a lubricant
after the start of vacuum evacuation and after reaches a
quasi-equilibrium state is below 0.09 ng/cm.sup.2 is employed.
Inventors: |
Yahagi; Yasuo; (Tokyo,
JP) ; Kobayashi; Masayuki; (Fujisawa, JP) ;
Mito; Hiroaki; (Tokyo, JP) ; Kudo; Tomohiro;
(Hitachinaka, JP) ; Saeki; Tomonori; (Yokosuka,
JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET, SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
39684957 |
Appl. No.: |
11/964754 |
Filed: |
December 27, 2007 |
Current U.S.
Class: |
220/228 |
Current CPC
Class: |
H01J 37/16 20130101;
H01J 37/28 20130101; H01J 2237/022 20130101; H01J 2237/16 20130101;
H01J 2237/2817 20130101; H01J 2237/182 20130101; G01N 33/00
20130101 |
Class at
Publication: |
220/228 |
International
Class: |
B65D 53/06 20060101
B65D053/06 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 27, 2006 |
JP |
2006-352761 |
Claims
1. An apparatus having a vacuum vessel that includes a mechanism
using a lubricant therein, wherein, to the mechanism in the vacuum
vessel, a lubricant whose adsorption amount per minute to a surface
of a material introduced into the vacuum vessel after starting
vacuum evacuation and after reaching a quasi-equilibrium state is
less than 0.09 ng/cm.sup.2 is used.
2. The apparatus having the vacuum vessel according to claim 1,
wherein the lubricant is oil.
3. The apparatus having the vacuum vessel according to claim 1,
wherein the lubricant is grease.
4. The apparatus having the vacuum vessel according to claim 1,
wherein the surface of the material is an element surface of a
crystal oscillator.
5. An apparatus having a vacuum vessel that includes a mechanism
using a lubricant therein, wherein, in the mechanism of the vacuum
vessel, a lubricant whose adsorption amount per minute to a surface
of a material introduced into the vacuum vessel after starting
vacuum evacuation and after reaching nearly a quasi-equilibrium
state is less than 0.09 ng/cm.sup.2 is used.
6. The apparatus having the vacuum vessel according to claim 5,
wherein the lubricant is oil.
7. The apparatus having the vacuum vessel according to claim 5,
wherein the lubricant is grease.
8. The apparatus having the vacuum vessel according to claim 5,
wherein the surface of the material is an element surface of a
crystal oscillator.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority from Japanese Patent
Application No. JP 2006-352761 filed on Dec. 27, 2006, the content
of which is hereby incorporated by reference into this
application.
TECHNICAL FIELD OF THE INVENTION
[0002] The present invention relates to an apparatus having a
vacuum vessel. More particularly, the present invention relates to
a technique effectively applied to a vacuum apparatus such as a
semiconductor manufacturing apparatus having a vacuum vessel.
BACKGROUND OF THE INVENTION
[0003] In recent years, miniaturization and highly integrated
configurations of semiconductor devices have been remarkably
progressed, and in particular, CMOS (Complementary MOS)
semiconductor devices combining n-type and p-type MOSs are superior
to bipolar type devices in view of their power consumption and
ultrafine and highly integrated configuration, and have been
developed day after day. At the most advanced research and
development level made public in the IEDM (International Electron
Devices Meeting) in December, 2004, the gate length of the planar
type CMOS has reached to 5 nm, i.e., the size of about 18 Si atoms
(H. Wakabayashi, T. Ezaki, M. Hane, T. Ikezawa, T. Sakamoto, H.
Kawaura, S. Yamagami, N. Ikarashi, K. Takeuchi, T. Yamamoto, and T.
Mogami, "Transport properties of sub-10-nm planar-bulk-CMOS
devices," in International Electron Device Meeting Tech. Dig., San
Francisco, Calif., Dec. 13-15, 2004, pp. 429-432, (2004)
(Non-Patent Document 1)).
[0004] At mass production level, the production of 90-nm process
generation has started in 2004, and at the moment of the present
application, 65-nm process generation is about to begin. In order
to shift to the mass production in a short period while securing
ensuring reliability from the product development, it is
indispensable to shorten and optimize conditions of mass production
process. To gain high reliability, it is primarily required to
limit the designed geometric structure certainly in an acceptable
dimension range. For this purpose, the dimension measurement of
ultrafine patterns formed by lithography technology is
indispensable. For this measurement, as an inline inspecting
apparatus, electron microscope CD-SEM (Critical-Dimension Scanning
Electron Microscope) designed and manufactured exclusively for
dimension measurement, that is, a length measuring SEM is employed,
and from the viewpoints of securement of semiconductor device
reliability and the semiconductor manufacturing period, a highly
precise and high throughput measurement is required.
[0005] Further, on the other hand, for improving the mass
production efficiency, the Si wafer size has been made larger to 8
inches, 12 inches in diameter (so-called 300 mm wafer) Therefore,
in addition to the large size of a sample chamber as the vacuum
vessel for CD-SEM, high precision and high speed drive of the
sample stage are indispensable. Since the mechanical drive system
where the sample stage is put on a guide rail and driven at a high
speed by a ball screw is employed, lubricating oil is applied to
the guide rail and the ball screw. As the lubricating oil, oil of
low vapor pressure used widely as vacuum oil is used. Further,
lubricating oil and grease are applied to other moving parts in the
vacuum vessel in the same manner. Meanwhile, recently, conspicuous
defects and faults considered to be caused by the lubricating oil
where components included in oil attach onto the wafer surface and
pose contamination to the wafer have become obvious in the
lithography process of semiconductors.
[0006] For example, as suggested in the paragraphs [0122] to [0125]
in Japanese Patent Application Laid-Open Publication No.
2002-250707 (Patent Document 1), some problems such as organic
contamination supposed to arise from oil and the like have
occurred. And, it is considered that according to the present
invention, such contamination is solved by removing it by
plasma.
[0007] In the vacuum apparatus having moving parts in the vacuum
vessel, lubricating oil and grease are applied in the same manner
as in the above CD-SEM, and in the case when such an apparatus is
used, conspicuous defects and faults considered to arise from
components included in oil have occurred to samples.
SUMMARY OF THE INVENTION
[0008] Meanwhile, in the above-said technology of semiconductor
device, as well as the ultrafine and highly integrated
configuration of semiconductor devices, the development cycle of
products has become shorter and the prices of mass production
products have become lower. In order to secure reliability from the
product development and shift to the mass production in a short
period, it is indispensable to shorten and optimize conditions of
mass production process. The mask and wafer for lithography used in
the manufacturing process must not have any defect. In order to
obtain highly reliable products, it is primarily required to
contain a designed geometric structure precisely in an allowable
dimension range. For this purpose, the dimension measurement of
ultrafine patterns formed by lithography technology is
indispensable. For this measurement, as an inline inspecting
apparatus, an electron microscope CD-SEM designed and manufactured
exclusively for dimension measurement is used, and from the
viewpoints of securement of semiconductor device reliability and
the semiconductor manufacturing period, a high-precision and
high-throughput measurement is required.
[0009] Therefore, in addition to enlarging the size of a sample
chamber as a vacuum vessel for CD-SEM, high-precision and
high-speed drive of a sample stage is indispensable. Since a
mechanical drive system where the sample stage is put on a guide
rail and driven at a high speed by a ball screw is employed,
lubricating oil is applied to the guide rail and the ball screw. As
the lubricating oil, a lubricating oil of low vapor pressure used
widely as vacuum oil is used. On the other hand, the manufacturing
processes of products are complicated, and despite that the oil
having a low vapor pressure used widely in the vacuum vessel is
used, conspicuous defects and faults considered to be caused by
contamination of the lubricating oil components, more particularly,
components included in the lubricating oil attaching onto the wafer
surface pose contamination of the wafer surface and it has become
apparent in the lithography process of semiconductor.
[0010] With regard to the contamination attaching to the wafer
surface, the inventors of the present invention have conducted
various physical and chemical analyses, and as the result of
detailed examination of the measurement results, it has been found
that the contamination is caused by the components of lubricating
oil attaching onto the wafer surface. The lubricating oil used in
the vacuum vessel is lubricating oil of low vapor pressure, but
even in vacuum, an extremely small amount of lubricating oil
components will be vaporized, and then attach on the wafer surface
as contamination. And as a consequence, the problems where it
causes conspicuous defects and faults in the semiconductor process
have become apparent.
[0011] Accordingly, an object of the present invention is to
provide an apparatus that has a vacuum vessel including a mechanism
using a lubricant inside and does not cause defects and faults to
samples introduced into the vacuum vessel even in an apparatus
where lubricating oil and grease are applied.
[0012] The above and other objects and novel characteristics of the
present invention will be apparent from the description of this
specification and the accompanying drawings.
[0013] The typical ones of the inventions disclosed in this
application will be briefly described as follows.
[0014] In order to achieve the above object, the present invention
is an apparatus having a vacuum vessel that includes a mechanism
using a lubricant therein, in which a lubricant whose adsorption
amount per minute to a surface of a material introduced into the
vacuum vessel of an apparatus for evaluating a lubricant is less
than 0.09 ng/cm.sup.2 after reaching a quasi-equilibrium state
after starting vacuum evacuation is employed in the mechanism of
the vacuum vessel.
[0015] The effects obtained by typical aspects of the present
invention will be briefly described below.
[0016] According to the present invention, in the apparatus having
a vacuum vessel that includes a mechanism using a lubricant
therein, even it is an apparatus in which lubricants are applied,
it is possible to control the occurrence of defects and faults
including contamination to samples in processes after introduction
into the vacuum vessel.
BRIEF DESCRIPTIONS OF THE DRAWINGS
[0017] FIG. 1 is a diagram showing an example of a CD-SEM having a
mechanism using lubricants in a vacuum vessel thereof according to
an embodiment of the present invention;
[0018] FIG. 2 is a diagram showing an example of a stage system in
the CD-SEM according to the embodiment of the present
invention;
[0019] FIG. 3A is a diagram showing an example of an apparatus for
evaluating a lubricant and it is a top view of the vacuum vessel
unit thereof according to the embodiment of the present
invention;
[0020] FIG. 3B is a diagram showing an example of an apparatus for
evaluating a lubricant and it is a front view of the vacuum vessel
unit thereof according to the embodiment of the present
invention;
[0021] FIG. 4 is a diagram showing an example of a temperature
profile for performing a thermal cleaning of the vacuum vessel of
the apparatus for evaluating a lubricant according to the
embodiment of the present invention;
[0022] FIG. 5A is a front view showing an example of the shape of a
stainless steel plate for applying lubricating oil used in the
apparatus for evaluating a lubricant according to the embodiment of
the present invention;
[0023] FIG. 5B is a side view showing an example of the shape of
the stainless steel plate for applying lubricating oil used in the
apparatus for evaluating a lubricant according to the embodiment of
the present invention;
[0024] FIG. 6 is a diagram showing an example of a measurement
result by a quadrupole mass spectrometer in the case when
lubricating oil is not used evaluated by use of the apparatus for
evaluating a lubricant according to the embodiment of the present
invention;
[0025] FIG. 7 is a diagram showing an example of a measurement
result by a crystal oscillator in the case when lubricating oil is
not used evaluated by use of the apparatus for evaluating a
lubricant according to the embodiment of the present invention;
[0026] FIG. 8 is a diagram showing an example of measurement
results by a quadrupole mass spectrometer in the case when three
kinds of lubricating oils and the case when lubricating oil is not
used evaluated by use of the apparatus for evaluating a lubricant
according to the embodiment of the present invention;
[0027] FIG. 9 is a diagram showing an example of measurement
results by a crystal oscillator in the case when three kinds of
lubricating oils and the case when a lubricating oil is not used
evaluated by use of the apparatus for evaluating a lubricant
according to the embodiment of the present invention; and
[0028] FIG. 10 is a diagram showing examples of: an average
adsorption amount per minute obtained by linearly fitting the
measurement results by the crystal oscillator in the cases when
three kinds of lubricating oils are used and in the case when
lubricating oil is not used by use of the apparatus for evaluating
a lubricant according to the embodiment of the present invention;
the number of defects and faults in a lithography process; and
measurement results of contact angle of purified water.
DESCRIPTIONS OF THE PREFERRED EMBODIMENTS
[0029] Hereinafter, embodiments of the present invention will be
described in detail with reference to the accompanying drawings.
Note that components having the same function are denoted by the
same reference symbols throughout the drawings for describing the
embodiment, and the repetitive description thereof will be
omitted.
[0030] (Outline of the Embodiments)
[0031] In order to shift to the mass production of semiconductor
devices in a short period while securing reliability from the
product development, it is indispensable to shorten and optimize
conditions of mass production process. To obtain high reliability,
it is primarily required to contain a designed geometric structure
precisely in an allowable dimension range. For this purpose, a
dimension measurement of ultrafine patterns formed by lithography
technology is indispensable. As an inline inspecting apparatus of
the semiconductor process, an electron microscope CD-SEM designed
and manufactured exclusively for dimension measurement is employed,
and from the viewpoints of securement of semiconductor device
reliability and the semiconductor manufacturing period, a
high-precision and high-throughput measurement is required.
[0032] Therefore, in addition to enlarging the size of a sample
chamber as a vacuum vessel for CD-SEM, high-precision and
high-speed drive of a sample stage is indispensable. Since a
mechanical drive system where the sample stage is put on a guide
rail and driven at a high speed by a ball screw is employed,
lubricating oil is applied to the guide rail and the ball screw. As
the lubricating oil, a lubricating oil of low vapor pressure used
widely as vacuum oil is used. On the other hand, the manufacturing
processes of products are complicated, and despite that the oil
having a low vapor pressure used widely in the vacuum vessel is
used, conspicuous defects and faults considered to be caused by
contamination of the lubricating oil components, more particularly,
components included in the lubricating oil attaching onto the
surface of a wafer (also described as "sample") pose contamination
of the wafer surface and it has become apparent in the lithography
process of semiconductors.
[0033] The contamination by lubricating oil components to a wafer
inspected by CD-SEM occurs when the vacuum vessel is
pressure-reduced in a situation where the wafer and the lubricating
oil coexist in the vacuum vessel of CD-SEM. Therefore, the
inventors of the present invention have devised a method for
preliminarily investigating vaporization/adsorption behaviors in
vacuum of the lubricating oil to be used in the vacuum vessel. A
feature of the present invention is an apparatus for evaluating a
lubricant for performing the measurement evaluation of
vaporization/adsorption behaviors of the lubricating oil for
realizing the method.
[0034] Hereinafter, first, CD-SEM as an inline inspecting apparatus
of semiconductor process is described, and further, the apparatus
for evaluating a lubricant for performing the measurement
evaluation of vaporization/adsorption behaviors of the lubricating
oil is described.
[0035] (CD-SEM)
[0036] With reference to FIG. 1, an example of a CD-SEM according
to an embodiment of the present invention is described. The CD-SEM
comprises a controller 1, an electron-optical system controller 2
that is controlled by the controller 1, a stage controller 3, a
sample transfer controller 4, and a sample exchange chamber
controller 5, and further an electron optical system, a stage
system, a sample transfer system, and a sample exchange chamber
that are controlled by these controllers 2, 3, 4 and 5.
[0037] In this CD-SEM, the controller 1 controls the
electron-optical system controller 2, the stage controller 3, the
sample transfer controller 4, and the sample exchange chamber
controller 5 on the basis of acceleration voltage, sample
information, measurement position information, wafer cassette
information and the like inputted by an operator via user interface
that is not shown.
[0038] The sample transfer controller 4 received a command from the
controller 1 controls a transfer robot 8 so that an arbitral wafer
7 is moved from a wafer cassette 6 to a predefined position in a
sample exchange chamber 9. The sample exchange chamber controller
5, in sync with the movement of the wafer 7 in and out of the
sample exchange chamber 9, performs control so as to open and close
gate valves 10 and 11. Further, the sample exchange chamber
controller 5 controls a vacuum pump (not shown) that evacuates the
inside of the sample exchange chamber 9 to vacuum, and when the
gate valve 11 opens, it forms a similar vacuum as that of a sample
chamber 12 in the inside of the sample exchange chamber 9. The
wafer 7 that enters in the sample exchange chamber 9 is sent to the
sample chamber 12 via the gate valve 11 and fixed onto a sample
stage 13.
[0039] The electron-optical system controller 2 controls a high
voltage controller 14, a condenser lens controller 15, an amplifier
16, a deflection signal controller 17, and an objective lens
controller 18 in accordance with the command from the controller
1.
[0040] By an extraction electrode 19, an electron beam 21 extracted
from an electron source 20 is focused by a condenser lens 22 and an
objective lens 23 and radiated onto the wafer arranged on the
sample stage 13. The electron beam 21 is made to scan on the wafer
7 one-dimensionally or two-dimensionally by a deflector 24 that
received signals from the deflection signal controller 17.
[0041] Due to the radiation of the electron beam 21 onto the wafer
7, a secondary charged particle 25 discharged from the wafer 7 is
converted into secondary electrons 29 by a secondary electron
conversion electrode 27, and the secondary electrons 29 are trapped
by a secondary charged particle detector 30, and used as a
luminance signal of a display screen of a display device 26 via the
amplifier 16.
[0042] Further, by synchronizing deflection signals of the display
device 26 and deflection signals of the deflector 24, it is
possible to reproduce a pattern shape on the wafer on the display
device 26.
[0043] Next, with reference to FIG. 2, an example of the stage
system is described. On a guide rail 34 and its base 33, a guide
rail 32 and its base 31 are arranged, and further thereon, the
sample stage 13 is arranged. The wafer 7 is fixed onto the sample
stage 13. The rotation movement of a ball screw 35 is converted
into linear movement and the guide rail 32 and its base 31, the
sample stage 13, and the wafer 7 can move on the guide rail 34
linearly (in X direction). In the same manner, the rotation
movement of a ball screw (not shown) is converted into linear
movement, and the sample stage 13 can move on the guide rail 34
linearly (in Y direction).
[0044] In such a CD-SEM, as mechanisms to use a lubricant in the
sample chamber 12 as a vacuum vessel, there are the guide rails 32
and 34, the ball screw 35 and the like, and lubricating oil is
applied to these guide rails 32 and 34, the ball screw 35 and the
like.
[0045] (Apparatus for Evaluating a Lubricant)
[0046] With reference to FIG. 3A (top view of vacuum vessel
portion) and FIG. 3B (front view of vacuum vessel portion), an
example of the apparatus for evaluating a lubricant is described.
The apparatus for evaluating a lubricant comprises a
stainless-steel vacuum vessel 101, a quadrupole mass spectrometer
102 connected to one side of the stainless-steel vacuum vessel 101,
an angle type valve 103 connected to the other side of
stainless-steel vacuum vessel (also simply referred to as vacuum
vessel) 101, a turbo-molecular pump 104 connected to the angle type
valve 103, a dry scroll pump 105 connected to the turbo-molecular
pump 104, a counter 106 of the apparatus for evaluating a lubricant
and the like.
[0047] This apparatus for evaluating a lubricant is an apparatus
where a stainless steel plate for lubricant application 107 is put
in the stainless steel vacuum vessel 101, and the measurement of
vaporized/adsorbed components from the lubricant can be carried out
by a crystal oscillator element 108 attached to one of flanges of
the vacuum vessel 101.
[0048] The size of the main portion of the stainless-steel vacuum
vessel 101 is approximately 25 cm in diameter and 30 cm in height.
To this, via a copper gasket of ICF152 standard flange and the
angle type valve 103, the vacuum vessel 101 can be evacuated by use
of the turbo-molecular pump 104 whose throughput is 150 L per
minute, and the dry scroll pump 105 whose throughput is 250 L per
minute as auxiliary evacuation. Further, although not shown in FIG.
3A and FIG. 3B, a B-A gauge and a Pirani gauge are attached as
vacuum gauges. Furthermore, although not shown in FIG. 3A and FIG.
3B either, high purity nitrogen gas can be introduced into the
vacuum vessel 101 when the vacuum is released.
[0049] The crystal oscillator element 108 and the quadrupole mass
spectrometer 102 were respectively attached beforehand to ports
having flanges of ICF70 standard of the stainless steel vacuum
vessel 101 via the copper gasket and a nipple having a length of
about 20 cm. As the crystal oscillator element 108, TM-400 made by
MAXTEK Inc. was employed, and as the quadrupole mass spectrometer
102, SPECTPA (Trademark) made by MICROVISION was employed. While
the vacuum vessel 101 was evacuated, the entire vacuum vessel 101
was heated up by, for example, a temperature profile as shown in
FIG. 4, and heated up to 130.degree. C. for 24 hours. In this
manner, the vacuum vessel 101 was cleaned.
[0050] While the vacuum vessel 101 was evacuated, when the
temperature of the vacuum vessel 101 was lowered to around
70.degree. C., degassing operation of a head of the quadrupole mass
spectrometer 102 was carried out for about 5 minutes, and
thereafter, the vacuum vessel 101 was continued to be evacuated
until the temperature of the vacuum vessel 101 reached around the
room temperature. At this moment, the vacuum pressure reached
nearly 5.times.10.sup.5 Pa. Thereafter, water at about 25.degree.
C. was made to flow via a temperature adjuster to a water-cooling
pipe of the crystal oscillator element 108, and this operation was
carried out over 2 hours. A basic resonance frequency of the
crystal oscillator element 108 was 6.04 MHz, and about 20 nm of
chrome (Cr) and about 155 nm of gold (Au) formed in a pattern on an
AT-cut quartz (crystal) crystal plate and are made into electrodes.
The stainless steel plate for lubricant application 107 was made of
a plate of size 31 cm.times.16 cm, thickness 1.5 mm bent and
processed so as to comprise 3 parts as shown in FIG. 5A (front
view) and FIG. 5B (side view).
[0051] By making the shape of the plate to which the lubricant is
applied constant, it is possible to make the application amount of
the lubricant nearly constant, and it is possible to quantitatively
compare characteristics of different lubricating oils. At the
longer fold-back side, that is, at the side of 301 in FIG. 5, two
circular holes having a diameter of 2 cm are made for easily
operating application of the lubricating oil to the plate and
arranging the plate into the vacuum vessel. Hereinafter, this
stainless-steel plate for lubricant application 107 is referred to
as test plate for lubricant application.
[0052] Meanwhile, the vacuum vessel and the turbo pump in the above
evaluation apparatus are simply examples, and they are not limited
by the size of the vacuum vessel and the throughput of the pump as
long as the same vacuum performance can be obtained.
[0053] By use of the above-described apparatus for evaluating a
lubricant for performing the measurement evaluation of
vaporization/adsorption components of the lubricant, evaluation of
the lubricant was carried out. As an example, three kinds of
fluorinated lubricants, namely, a lubricating oil A, a lubricating
oil B, and a lubricating oil C processed for lowering the vapor
pressure were evaluated. The procedures are described
hereinafter.
[0054] First, the vacuum vessel 101 and the measuring instruments
were cleaned and the measuring instruments were stabilized. While
the vacuum vessel 101 was evacuated, the entire vacuum vessel 101
was heated up by the temperature profile as shown in FIG. 4, and
heated at 130.degree. C. for 24 hours. Accordingly, the vacuum
vessel 101 was cleaned. While the vacuum vessel 101 was evacuated,
when the temperature of the vacuum vessel 101 lowered to around
70.degree. C., degassing operation of the head of the quadrupole
mass spectrometer 102 was carried out for about 5 minutes.
Thereafter, the vacuum vessel 101 was continued to be evacuated
until the temperature of the vacuum vessel 101 reached around the
room temperature. According to the foregoing, the measuring
instruments were cleaned. Further thereafter, water at about
25.degree. C. was made to flow via the temperature adjuster to the
water cooling pipe of the crystal oscillator element 108, and this
operation was carried out over 2 hours. According to the foregoing,
the cleaning of the vacuum vessel 101 and the measuring instruments
and the stabilization of the measuring instruments were
completed.
[0055] Next, in order to acquire background data of the apparatus
system, while lubricating oil was not applied to the test plate for
lubricant application (107) shown in FIG. 5, the stainless-steel
plate was placed in the vacuum vessel 101, and after the vacuum
vessel 101 was closed with a lid, the vacuum vessel 101 was
evacuated by vacuum pumps (the turbo-molecular pump 104, the dry
scroll pump 105). From when 2 to 3 minutes has elapsed after the
evacuation started, the time changes of partial pressure were
acquired by the quadrupole mass spectrometer 102. As an example,
the time changes concerning a ratio of a mass number m and the
number of charges z, which is m/z=69 is shown in FIG. 6.
[0056] In the case when lubricating oil is not applied to the test
plate for lubricant application, although the partial pressure
slightly decreases with lapse of the evacuation time, it may be
regarded as nearly constant.
[0057] Next, the lubricating oil A was applied to the test plate
for lubricant application, and in the same manner, the time changes
of partial pressure were acquired by the quadrupole mass
spectrometer 102, and the result is shown in FIG. 7.
[0058] And further, the cleaning of the vacuum vessel 101 was
carried out, and another lubricating oil B was applied to the
cleaned test plate for lubricant application, and the plate was
placed in the vacuum vessel 101. And after the vacuum vessel 101
was closed with the lid, the vacuum vessel 101 was evacuated by the
vacuum pumps. After the time change of partial pressure was
acquired by the quadrupole mass spectrometer 102, the cleaning and
the like of the vacuum vessel 101 were carried out in the same
manner, and further, with regard to the other lubricating oil C,
the time change of partial pressure were acquired by the quadrupole
mass spectrometer 102 in the same manner. These results are shown
in FIG. 8. In FIG. 8, 601 shows the time change of partial pressure
concerning m/z=69 of the lubricating oil B, and 602 shows that of
the lubricating oil C.
[0059] Referring to the time changes of partial pressure acquired
by the quadrupole mass spectrometer 102 shown in FIG. 7 and FIG. 8,
it is found that, in the respective cases, the partial pressure
decreases rapidly until about 20 minutes have elapsed after the
evacuation started, then, the decrease amount per unit time, i.e.,
the decrease ratio declines gradually, and it becomes nearly
constant after about 30 minutes from the evacuation started. The
system state where the ratio of the partial pressure decrease
observed by use of the quadrupole mass spectrometer 102 becomes
extremely low and the partial pressure decrease can be regarded to
be substantially constant as seen in the time period of about
several hours is defined as "quasi-equilibrium state" herein. After
reaching to the quasi-equilibrium state judged by the time changes
of partial pressure measured by the quadrupole mass spectrometer
102, the time changes of the resonance frequency of the crystal
oscillator element 108 were observed. Here, it is shown that the
changes of the resonance frequency of the crystal oscillator
element 108 can be converted into the weight area density of
materials that attached onto the surface of the crystal oscillator
element, according to the following Equation 1 taught in Sauerbrey
(G. Sauerbrey, "Verwendung von Schwingquarzen zur Wagung dunner
Schichten und zur Mikrowagung," Zeitschrift fur Physik, 155, pp.
206-222 (1959) (Non-Patent Document 2)--p 208).
.DELTA.m/F=-.rho..sub.Qd.DELTA.f/f Equation 1
[0060] Here, .DELTA.m means the amount of weight increase of
materials attaching onto the surface of the crystal oscillator
element, F means an area of the surface of the crystal oscillator
element where the materials attach thereon, .rho..sub.Q means a
density of the crystal oscillator crystal, d means an thickness of
the crystal oscillator crystal, .DELTA.F means an change of the
resonance frequency of the crystal oscillator corresponding to the
amount of weight increase of the material attaching onto the
surface, and f means a basic resonance frequency of the crystal
oscillator. Results of the observation on the time changes of the
resonance frequency of the crystal oscillator in four cases that
lubricating oils A, B and C are applied to the test plate for
lubricant applications respectively and nothing is applied to the
test plate for lubricant application are shown in FIG. 9. In FIG.
9, 701 shows the result of the time changes in the case when
nothing is applied, 702 shows the result in the case when the
lubricating oil A is applied, 703 shows the result in the case when
the lubricating oil B is applied, and 704 shows the result in the
case when the lubricating oil C is applied.
[0061] From this data, in order to obtain an average adsorption
ratio of the adsorbed materials in the period concerned, the actual
measurement data in FIG. 9 is further fitted so as to be linear,
and a graph obtained as a result and an equation are shown. The
average adsorption ratios of the respective lubricating oils are
collectively shown in the second row in the table of FIG. 10.
[0062] In order to show the effectiveness of this measurement, the
lubricating oil A, the lubricating oil B and the lubricating oil C
were used respectively as lubricating oils to the operating
mechanism parts in the CD-SEM vacuum vessel, and it was checked
whether defects and faults arising from the contamination of
lubricating oil components in the lithography process occurred or
not, and the number of defects was measured by an apparatus using
the optical scattering principle (generally sold commercially as a
foreign matter inspecting apparatus). As a result, the lubricating
oil A and the lubricating oil B caused defects and faults arising
from the contamination of lubricating oil components in the
lithography process, and the number of defects exceeded the max
countable limit, so that it was described that the number of
defects and faults in the lithography process was more than 30000
in the third row of the table shown in FIG. 10. On the other hand,
the lubricating oil C showed the same level as that in the case
where oil was not used, that is, it is the background level of the
measurement apparatus, and it may be said that it did not cause
defects and faults arising from the contamination of lubricating
oil components in the lithography process.
[0063] In order to further confirm the above, the surface
adsorption, the number of defects and faults, and the static
contact angle of purified water on a surface exposed to oil
(hereinafter, simply referred to as contact angle of purified) were
measured. The measurement of the contact angle of purified water is
used to grasp a wettability of purified water to a certain surface,
that is, a change of surface energy. Its measurement principle is
quite simple and it only requires just to drop purified water onto
a wafer exposed to contamination in vacuum and to measure the
geometric contact angle of purified water. As the apparatus to
measure the contact angle of purified water, Drop Master 500 made
by Kyowa Interface Science Co., Ltd., was employed. The dropping
amount of the purified water for one time is about 1 .mu.l, and an
image can be obtained after 2 seconds after dropping. The result is
shown in the fourth row of the table shown in FIG. 10. In the case
of the lubricating oil C, the measurement result of the contact
angle of purified water was 5.5.degree. which is almost same as
5.degree. in the case without oil within the margin of error. On
the contrary, in the cases of the lubricating oils A and B, the
contact angle of purified water was 12.degree., and so the contact
angle of purified water was twice of that in the case without
oil.
[0064] Generally, as it is known that fluorine coating has a water
repellant effect, when fluorinated lubricant is adsorbed to the
surface, the contact angle of purified water increases. The contact
angle of purified water in the case of the lubricating oil C which
was thought to cause a small number of defects and faults in the
lithography process and not cause the contamination of lubricating
oil components is almost same as that in the case without oil, and
it is thought that there is no contamination on the surface due to
the fluorinated lubricant. On the other hand, in the cases of the
lubricating oils A and B, the contact angle of purified water
increases over twice in comparison with the case without oil,
therefore it is thought that the fluorinated lubrican is attached
to the surface and the surface is contaminated.
[0065] According to the foregoing, the lubricating oil whose
adsorption amount per minute is less than 0.09 ng/cm.sup.2 after
the start of vacuum evacuation and after reaching the
quasi-equilibrium state in the observation by the crystal
oscillator by use of the apparatus for evaluating a lubricant for
performing a measurement evaluation of vaporized/adsorbed
components of the lubricating oil shown in FIG. 3 shows preferable
results. Also as to grease in which such oil is used as its base
oil, since the vapor pressure is regulated by the base oil, the
present invention is also effective to grease.
[0066] In this manner, by using lubricating oil and grease
classified by the adsorption amount per unit time observed by the
crystal oscillator by use of the apparatus for evaluating a
lubricant for performing a measurement evaluation of
vaporized/adsorbed components of lubricating oil shown in FIG. 3 to
the mechanism using lubricant in the vacuum vessel in the CD-SEM
shown in FIG. 1, it is possible not to cause defects and faults to
samples due to the contamination by lubricating oil components in
the vacuum vessel. As a result, even for an apparatus where
lubricating oil and grease are applied, it is possible to control
the occurrence of defects and faults including contamination to
samples in the process after introducing it into a vacuum
vessel.
[0067] In the foregoing, the invention made by the inventors of the
present invention has been concretely described based on the
embodiments. However, it is needless to say that the present
invention is not limited to the foregoing embodiments and various
modifications and alterations can be made within the scope of the
present invention.
[0068] For example, the present invention is applicable to, not
merely a CD-SEM, but also widely to general apparatuses which have
mechanisms using lubricants such as oil, grease and the like in a
vacuum vessel thereof.
[0069] The apparatus having a vacuum vessel according to the
present invention is applicable to vacuum apparatuses such as
semiconductor manufacture apparatuses having vacuum vessels and
general apparatuses having mechanisms using lubricants in vacuum
vessels thereof.
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