U.S. patent application number 10/656190 was filed with the patent office on 2004-03-11 for surface purification apparatus and surface purification method.
Invention is credited to Miki, Nobuhiro, Nitta, Takahisa.
Application Number | 20040045579 10/656190 |
Document ID | / |
Family ID | 26528536 |
Filed Date | 2004-03-11 |
United States Patent
Application |
20040045579 |
Kind Code |
A1 |
Miki, Nobuhiro ; et
al. |
March 11, 2004 |
Surface purification apparatus and surface purification method
Abstract
By a simple apparatus construction and process, it is made
possible to "clean precisely" a surface at the molecular/atomic
level, and the purification degree of the surface processed
minutely is made into 10.sup.12 molecules/cm.sup.2 or less. A
steam-spraying nozzle is disposed such that a line slit nozzle is
in a diameter direction, and mist-containing steam is sprayed onto
the surface of a substrate. Thereby, particles in the
steam-spraying surface (the particles were made to adhere by
dipping the substrate in a solution containing polystyrene
(particle diameter of 0.6 .mu.m) or alumina (particle diameter of
0.3 .mu.m to 0.5 .mu.m) particles at 10.sup.5 particles/ml.) are
removed by about 90% to 95% after ten-seconds spraying, and by 99%
or more, that is, to less than the detection limit of a wafer
inspection device, after twenty-seconds spraying.
Inventors: |
Miki, Nobuhiro; (Tokyo,
JP) ; Nitta, Takahisa; (Tokyo, JP) |
Correspondence
Address: |
CONNOLLY BOVE LODGE & HUTZ LLP
SUITE 800
1990 M STREET NW
WASHINGTON
DC
20036-3425
US
|
Family ID: |
26528536 |
Appl. No.: |
10/656190 |
Filed: |
September 8, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10656190 |
Sep 8, 2003 |
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09417009 |
Oct 12, 1999 |
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6630031 |
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Current U.S.
Class: |
134/1.3 ; 134/1;
134/102.1; 134/137; 134/2; 134/30; 134/31; 134/902 |
Current CPC
Class: |
B08B 7/0057 20130101;
B08B 2230/01 20130101; H01L 21/67051 20130101; B08B 3/00 20130101;
Y10S 134/902 20130101; Y10S 438/906 20130101 |
Class at
Publication: |
134/001.3 ;
134/001; 134/002; 134/030; 134/031; 134/902; 134/102.1;
134/137 |
International
Class: |
B08B 007/02; B08B
007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 12, 1999 |
JP |
11-228919 |
Oct 12, 1999 |
JP |
11-290344 |
Claims
What is claimed is:
1. A surface purification apparatus used in a manufacturing process
of a semiconductor device or a liquid crystal display device,
characterized by comprising means for bringing steam into contact
with and means for spraying steam onto a surface having need of
purification, wherein said surface is purified.
2. A surface purification apparatus described in claim 1,
characterized in that said surface is one selected from among
process surfaces from a substrate to a semiconductor device,
surfaces of process apparatus and process apparatus parts, and
surfaces of apparatus and apparatus parts in relation to
lithographic processes.
3. A surface purification apparatus described in claim 1,
characterized in that said surface is processed with saturated or
superheated steam at a temperature of 70.degree. C. to 200.degree.
C.
4. A surface purification apparatus described in claim 1,
characterized by comprising a steam supply apparatus comprising a
steam generation system, a steam-superheating system, a control
system for supplied ultrapure-water quantity and heat amount, and a
steam pressure control system, constructed with including a steam
inlet and steam-spraying nozzle, and arbitrarily switching and
supplying saturated or superheated steam at a temperature of
70.degree. C. to 200.degree. C.
5. A surface purification apparatus described in claim 4,
characterized in that said steam supply apparatus further includes
a switching system for a supply line for a solution containing a
purification promotion ingredient and said ultrapure water supply
line, and an injection pump, and comprises a system for switching
steam containing said purification promotion ingredient and steam
not containing it.
6. A surface purification apparatus described in claim 1,
characterized by comprising irradiation means for irradiating with
ultraviolet rays, wherein said surface is processed in combination
with processing of irradiating said surface with ultraviolet rays
in said steam processing.
7. A surface purification apparatus described in claim 6,
characterized in that said irradiation means uses an ultraviolet
lamp of a wavelength corresponding to a 50% transmissive distance
of not less than 10 mm to steam.
8. A one-by-one surface purification apparatus characterized in
that a system for introducing steam, and a drive system in which a
spraying surface is swept by a steam-spraying nozzle moving
relatively to a surface being processed, are provided in a chamber
including a substrate take in/out system and an atmosphere
discharge system, and said steam-spraying nozzle sprays steam onto
said surface.
9. A surface purification apparatus described in claim 1,
characterized in that an ultraviolet reactor comprising an
ultraviolet lamp of a wavelength corresponding to a 50%
transmissive distance of not less than 10 mm to steam, is
accompanied, said ultraviolet lamp is disposed in parallel with
said surface, and said surface in steam processing is irradiated
and processed.
10. A surface purification apparatus described in claim 8,
characterized in that said atmosphere discharge system further
comprises a suction system, and the surface being processed is
dried by discharging the atmosphere in the chamber after
superheated steam processing.
11. A surface purification method used in a manufacturing process
of a semiconductor device or a liquid crystal display device,
characterized in that, by using a process for bringing steam into
contact with a surface having need of purification, and a process
for spraying steam onto the surface having need of purification,
said surface is processed.
12. A surface purification method described in claim 11,
characterized in that said surface is one selected from among
process surfaces from a substrate to a semiconductor device,
surfaces of process apparatus and process apparatus parts, and
surfaces of apparatus and apparatus parts in relation to
lithographic processes.
13. A surface purification method described in claim 11,
characterized in that said surface is processed with saturated or
superheated steam at a temperature of 70.degree. C. to 200.degree.
C.
14. A surface purification method described in claim 11,
characterized in that said surface is processed in combination with
processing of irradiating said surface with ultraviolet rays of a
wavelength corresponding to a 50% transmissive distance of not less
than 10 mm to steam, in said steam processing.
15. A surface purification method described in claim 14,
characterized in that organic matters having adhered to said
surface are removed by said steam processing and said process of
irradiating with ultraviolet rays.
16. A surface purification method described in claim 14,
characterized in that an organic matter film formed on said surface
is removed by said steam processing and said process of irradiating
with ultraviolet rays.
17. A surface purification method described in claim 14,
characterized in that particles having adhered to said surface are
removed by said steam processing and said process of irradiating
with ultraviolet rays.
18. A surface purification method described in claim 13,
characterized in that generation of water marks is staved off by
discharging the atmosphere in the chamber after superheated steam
processing of said surface, and drying the surface being
processed.
19. A surface purification method described in claim 11,
characterized in that said surface is a silicon substrate, and said
silicon surface is made to be a hydrogen termination structure by
steam-processing silicon exposed on said silicon substrate surface.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a purification technique
for process surfaces from substrates to semiconductor devices,
surfaces of process apparatus and process apparatus parts, and
surfaces of apparatus and apparatus parts in relation to
lithographic processes, in manufacturing processes of semiconductor
devices and liquid crystal display devices, particularly to an
innovative technique for surface purification by "precise cleaning
action of steam and ultraviolet rays", and breakaway from a
resources/energy high-consumption type technique, that is, a
development of an environment-symbiosis type technique which makes
dependence upon chemical substances minimum.
[0003] 2. Description of the Related Art
[0004] A very minute process surface cleaning technique in
manufacturing a semiconductor device or a liquid crystal display
device, depends on a multi-stage process in which a large quantity
of ultrapure water and various kinds of chemicals are used in a
large-sized apparatus called wet cleaning system. As a technique
for renovating this, a cleaning technique using a one-by-one
cleaning system is also promoted.
[0005] But, these cleaning techniques have not entirely reached the
satisfactory level in breakaway from a load of cleaning process and
burdens of ultrapure water and chemicals, and following to
performance development demand.
[0006] In a cleaning technique in a general industrial field,
"fluid jet method" is a generally used method.
Cleaning.about.surface-peeling.about.- surface-polishing are
possible by a particulate fluid (ice particulates/abrasive
particulates) entrained on a jet flow of a high-pressure fluid. It
is generally used in case of a large size such as aircraft/vehicles
and requiring on-the-spot cleaning. Cleaning methods of spraying
steam are also well known, and used for cleaning not only in
industrial fields but also in medical/food fields and homes. But,
as described later, there is a great difference between the
cleaning level in these fields and a required level in a
manufacturing field of semiconductor devices or liquid crystal
display devices.
[0007] Manufacturing process of semiconductor devices/liquid
crystal display devices differs from other fields in the feature
that it is consistently surface-processing process. It has the
technical feature that a surface purification technique affects the
performance of products. It is a special field wherein purification
levels of all surfaces of not only process surfaces from substrates
to semiconductor devices, but also surfaces of process apparatus
and process apparatus parts as a matter of course, to surfaces of
apparatus and apparatus parts in relation to lithographic
processes, become severer with progress of technical
generations.
[0008] Surfaces to deal with in the present invention are as
follows: such as surfaces of silicon substrates/glass
substrates/chemical mechanical polishing (CMP)
substrates/lithographic process substrates/wiring substrates as
process surfaces from substrates to semiconductor devices; such as
surfaces of ion-implantation apparatus/plasma apparatus/CVD
apparatus and their apparatus parts as surfaces of process
apparatus and process apparatus parts; and such as surfaces of
stepper devices and mask reticles as surfaces of apparatus and
apparatus parts in relation to lithographic processes.
[0009] The present inventors perceive the principle of surface
purification by steam and ultraviolet rays. And, not "Cleaning" but
"Purification" is intended. This is because the purification degree
in a general cleaning technique and the purification required
degree in a manufacturing field of a semiconductor device or a
liquid crystal display device are quiet different in level. Table 1
shows the difference in surface purification degree level.
1TABLE 1 Difference in Surface Purification Degree Level cleaning
level {circle over (1)} 1 to 10 mg/cm.sup.2 :contaminant-molecular
layers level (10.sup.18 to 10.sup.19 on surface of surface
roughness molecules/cm.sup.2) of several .mu.m to scores .mu.m
level {circle over (2)} 1 to 10 .mu.g/cm.sup.2 :monomolecular layer
to 10 (10.sup.15 to 10.sup.16 molecular layers of contaminant
molecules/cm.sup.2) molecules cleaning level {circle over (3)} 1 to
10 ng/cm.sup.2 :10.sup.-2 to 10.sup.-3 molecular layers of level
(10.sup.12 to 10.sup.13 contaminant molecules molecules/cm.sup.2)
level {circle over (4)} 0.1 to 1 pg/cm.sup.2 :10.sup.-6 to
10.sup.-7 molecular layers of (10.sup.8 to 10.sup.9 contaminant
molecules molecules/cm.sup.2)
[0010] In general, cleaning is a technique from the level {circle
over (1)} to the level {circle over (2)}. For example, in a metal
material surface, the roughness of the mechanical polishing surface
is scores .mu.m, and mechanical processing oil is adhering at a
level of several mg/cm.sup.2. Even in case that the surface
roughness is decreased to about 10 .mu.m by chemical polishing
surface, it is adhering at a level of 1 mg/cm.sup.2. The cleaning
object is attained when the contamination is removed by about three
figures starting from this level {circle over (1)} to reach the
level {circle over (2)}. In a general industrial field, this
surface may be considered to be pure.
[0011] On the other hand, in semiconductor/liquid crystal
industries, the level {circle over (2)} is the starting point.
Present of contaminant molecules in several molecular layers means
that molecules/atoms of the substrate are not present in the
surface. It defeats its own purpose of making the surface function.
Purification is a technique in which the contamination is decreased
from the level by about three figures to reach the level {circle
over (3)}. Even in this case, a problem may yet remain in the
surface operation mechanism in accordance with the kind of
contaminant molecules. In the future ultra-LSI generation, the
level {circle over (4)} (10.sup.-6 to 10.sup.-7 molecular layers)
is required which is lower by about four figures than the level
{circle over (3)}.
SUMMARY OF THE INVENTION
[0012] It is an object of the present invention to provide a
surface purification apparatus and a surface purification method
capable of "precisely cleaning" a surface into the molecular/atomic
level and making the purification degree of the surface 10.sup.12
molecules/cm.sup.2 or less, by a new principle and apparatus. In
this specification, "Precise Cleaning" of a surface at the
molecular/atomic level is expressed by the term of
"Purification".
[0013] In order to attain the above object, a surface purification
apparatus of the present invention is an apparatus used in a
manufacturing process of a semiconductor device or a liquid crystal
display device, comprising means for bringing steam into contact
with and means for spraying steam onto a surface having need of
purification, wherein said surface is purified.
[0014] In an aspect of the surface purification apparatus of the
present invention, said surface is one selected from among process
surfaces from a substrate to a semiconductor device, surfaces of
process apparatus and process apparatus parts, and surfaces of
apparatus and apparatus parts in relation to lithographic
processes.
[0015] In an aspect of the surface purification apparatus of the
present invention, said surface is processed with saturated or
superheated steam at a temperature of 70.degree. C. to 200.degree.
C.
[0016] An aspect of the surface purification apparatus of the
present invention, comprises a steam supply apparatus comprising a
steam generation system, a steam-superheating system, a control
system for supplied ultrapure-water quantity and heat amount, and a
steam pressure control system, constructed with including a steam
inlet and steam-spraying nozzle, and arbitrarily switching and
supplying saturated or superheated steam at a temperature of
70.degree. C. to 200.degree. C.
[0017] In an aspect of the surface purification apparatus of the
present invention, said steam supply apparatus further includes a
switching system for a supply line for a solution containing a
purification promotion ingredient and said ultrapure water supply
line, and an injection pump, and comprises a system for switching
steam containing said purification promotion ingredient and steam
not containing it.
[0018] An aspect of the surface purification apparatus of the
present invention, comprises irradiation means for irradiating with
ultraviolet rays, wherein said surface is processed in combination
with processing of irradiating said surface with ultraviolet rays
in said steam processing.
[0019] In an aspect of the surface purification apparatus of the
present invention, said irradiation means uses an ultraviolet lamp
of a wavelength corresponding to a 50% transmissive distance of not
less than 10 mm to steam.
[0020] In a surface purification apparatus of the present
invention, a system for introducing steam, and a drive system in
which a spraying surface is swept by a steam-spraying nozzle moving
relatively to a surface being processed, are provided in a chamber
including a substrate take in/out system and an atmosphere
discharge system, and said steam-spraying nozzle sprays steam onto
said surface.
[0021] In an aspect of the surface purification apparatus of the
present invention, an ultraviolet reactor comprising an ultraviolet
lamp of a wavelength corresponding to a 50% transmissive distance
of not less than 10 mm to steam, is accompanied, said ultraviolet
lamp is disposed in parallel with said surface, and said surface in
steam processing is irradiated and processed.
[0022] In an aspect of the surface purification apparatus of the
present invention, said atmosphere discharge system further
comprises a suction system, and the surface being processed is
dried by discharging the atmosphere in the chamber after
superheated steam processing.
[0023] A surface purification method of the present invention is a
method used in a manufacturing process of a semiconductor device or
a liquid crystal display device, wherein, by using a process for
bringing steam into contact with a surface having need of
purification, and a process for spraying steam onto the surface
having need of purification, said surface is processed.
[0024] In an aspect of the surface purification method of the
present invention, said surface is one selected from among process
surfaces from a substrate to a semiconductor device, surfaces of
process apparatus and process apparatus parts, and surfaces of
apparatus and apparatus parts in relation to lithographic
processes.
[0025] In an aspect of the surface purification method of the
present invention, said surface is processed with saturated or
superheated steam at a temperature of 70.degree. C. to 200.degree.
C.
[0026] In an aspect of the surface purification method of the
present invention, said surface is processed in combination with
processing of irradiating said surface with ultraviolet rays of a
wavelength corresponding to a 50% transmissive distance of not less
than 10 mm to steam, in said steam processing.
[0027] In an aspect of the surface purification method of the
present invention, organic matters having adhered to said surface
are removed by said steam processing and said process of
irradiating with ultraviolet rays.
[0028] In an aspect of the surface purification method of the
present invention, an organic matter film formed on said surface is
removed by said steam processing and said process of irradiating
with ultraviolet rays.
[0029] In an aspect of the surface purification method of the
present invention, particles having adhered to said surface are
removed by said steam processing and said process of irradiating
with ultraviolet rays.
[0030] In an aspect of the surface purification method of the
present invention, generation of water marks is staved off by
discharging the atmosphere in the chamber after superheated steam
processing of said surface, and drying the surface being
processed.
[0031] In an aspect of the surface purification method of the
present invention, said surface is a silicon substrate, and said
silicon surface is made to be a hydrogen termination structure by
steam-processing silicon exposed on said silicon substrate
surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is a typical view showing the principal construction
of a steam supply apparatus of an embodiment of the present
invention; and
[0033] FIG. 2 is a typical view showing the principal construction
of a surface purification apparatus of an embodiment of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] The present invention uses new measures of "steam
processing" and "ultraviolet processing" to the new issue that a
surface is "purified" at the molecular/atomic level.
[0035] A chemical action of high-temperature steam and a physical
action of steam-spraying are used jointly. A characteristic of each
of saturated steam and superheated steam is utilized. Further, by
superimposing ultraviolet irradiation, a photochemical action at a
high temperature is utilized. That is, used is a new measure for
purification different in either of mechanism and level from a
general steam cleaning.
[0036] The present inventors have found the fact that "cleaning at
molecular/atomic level" can easily be realized by a physicochemical
action of steam at a high temperature and a photochemical action of
ultraviolet rays. Hereinafter, the actions of steam and ultraviolet
rays will be described in detail.
[0037] Besides, a purification apparatus for realizing this new
effect and details of a steam supply apparatus and an ultraviolet
irradiation apparatus used in this apparatus will be described.
[0038] 1. Purification Action and Purification Effect of Steam and
Ultraviolet Rays
[0039] Using an example of purification of a silicon substrate
surface, the mechanisms of the actions of steam and ultraviolet
rays and the discovery of the new effect will be described.
[0040] (1) Purification of Organic Matters
[0041] Table 2 shows purification test results of oleic acid
adhering to silicon wafer surfaces. After saturated steam at
120.degree. C. is sprayed for thirty seconds, oleic acid was
purified to monomolecular layer or less.
[0042] Here, in case of superimposing ultraviolet irradiation on
120.degree. C. saturated steam processing, it was removed to
monomolecular layer ten seconds after, and to less than the
detection limit of FTIR measurement twenty seconds after.
2TABLE 2 Steam Processing and Steam/Ultraviolet Rays
Superimposition Processing of Silicon Wafer Surface-Adhering Oleic
Acid steam processing [120.degree. C. saturated steam] before
processing 10 sec processing 30 sec processing oleic acid- 0.2
mg/cm.sup.2 0.5 .mu.g/cm.sup.2 0.05 .mu.g/cm.sup.2 adhering
quantity (oleic acid 4 .times. 10.sup.17/cm.sup.2 1 .times.
10.sup.15/cm.sup.2 1 .times. 10.sup.14/cm.sup.2 molecules)
thickness of about 2700 about 7 molecular monomolecular molecular
layer molecular layers layers on average layer or less on average
steam/ultraviolet before processing 10 sec processing 30 sec
processing rays superimposition processing [120.degree. C.
saturated steam] oleic acid- 0.2 mg/cm.sup.2 0.1 .mu.g/cm.sup.2
<0.005 ng/cm.sup.2 adhering quantity (oleic acid 4 .times.
10.sup.17/cm.sup.2 2 .times. 10.sup.14/cm.sup.2 <1 .times.
10.sup.10/cm.sup.2 molecules) thickness of about 2700 almost less
than molecular layer molecular layers monomolecular detection limit
on average layer on average silicon wafer: 4 inches steam-spraying
quantity: 2.55 L/sec, line slit nozzle: 50 mm .times. 1.0 mm
ultraviolet irradiation quantity: KrI excimer lamp 10 mW/cm.sup.2
(silicon wafer surface) detection limit of FTIR/ATR: 1 .times.
10.sup.12 molecules/cm.sup.2) detection limit
[0043] This purification effect is mainly by the following two
actions.
[0044] Effect of Steam:
[0045] Oleic acid is an oily matter having the melting point of
14.degree. C., the boiling point of 233.degree. C., and the
viscosity of about 2 centipoise. At 120.degree. C., the vapor
pressure of oleic acid rises, and the viscosity decreases to 1/5 or
less. A steam-spraying power can easily blow away this liquid from
a surface to purify. But, since a monomolecular adsorption layer
has an adsorption energy, it is difficult to blow away by a
steam-spraying power only.
[0046] Although water is known to hydrate in a hydrophobic manner
with hydrocarbon to form a cluster, the hydration power of water at
a high temperature of 100.degree. C. or more is remarkably great.
This hydration power increases the solvent ability remarkably. The
mist quantity brought into contact with a monomolecular adsorption
layer is about 10.sup.5 times the oleic acid monomolecular layer
every second. It is a sufficient layer for dissolving and removing
the oleic acid monomolecular adsorption layer from a surface.
[0047] Effect of Ultraviolet Rays:
[0048] Ultraviolet rays of a wavelength near 200 nm have an effect
of decomposing an organic matter by a photochemical reaction. For
example, the decomposition rate of oleic acid molecules is 0.05
.mu.g/cm.sup.2.multidot.sec at the normal temperature (when the
quantum efficiency is 100% in 10 mW/cm.sup.2). At a high
temperature of 100.degree. C. or more, this effect is further
amplified.
[0049] The effect of steam/ultraviolet rays superimposition
processing as shown in Table 2 is by this photochemical
reaction.
[0050] (2) Purification of Particles
[0051] Table 3 shows purification test results of particles
adhering to silicon wafer surfaces. Silicon wafers (diameter of 4
inches) were dipped in solutions containing 10.sup.5 particles/ml
of alumina particles (particle diameter of 0.3 .mu.m to 0.5 .mu.m)
or polystyrene particles (particle diameter of 0.6 .mu.m). Steam
processing and steam/ultraviolet rays superimposition processing
were performed to their surfaces.
[0052] Either the alumina particles/polystyrene particles were
purified by 20-second processing to less than the detection limit
of a wafer inspection device.
[0053] In case of polystyrene particles, purification was
remarkably shortened by steam/ultraviolet rays superimposition
processing. Besides, it was found that superheated steam has a
greater purification effect.
[0054] As shown in Table 3 and a comparative example, in case of
ultraviolet irradiation in air at the normal temperature, the
purification effect of polystyrene particles is low. This is
because the transmittance of ultraviolet rays of the wavelength of
191 nm in air is not sufficiently great. The 191 nm ultraviolet
rays well permeate steam. Here, an advantage of steam atmosphere
appears.
3TABLE 3 Steam Processing and Steam/Ultraviolet Rays
Superimposition Processing of Silicon Wafer Surface-Adhering
particles surface- adhering before 10 sec 20 sec particles
processing processing processing {circle over (1)} steam alumina
4200 50 particles/ <1 particle/ processing particles particles/
wafer wafer [120.degree. C. saturated wafer steam] {circle over
(2)} steam polystyrene 7000 70 particles/ <1 particle/
processing particles particles/ wafer wafer [120.degree. C.
saturated wafer steam] {circle over (3)} steam/ polystyrene 7000 5
particles/ <1 particle/ ultraviolet particles particles/ wafer
wafer rays wafer superimposition processing [120.degree. C.
saturated [120.degree. C. steam] saturated steam] {circle over (4)}
steam/ polystyrene 7000 <1 particle/ ultraviolet particles
particles/ wafer rays wafer superimposition processing [120.degree.
C. superheated steam] {circle over (5)} comparison: polystyrene
7000 2500 500 ultraviolet particles particles/ particles/
particles/ irradiation in wafer wafer wafer normal- temperature air
silicon wafer: 4 inches steam-spraying quantity: 2.55 L/sec, line
slit nozzle: 50 mm .times. 1.0 mm ultraviolet irradiation quantity:
KrI excimer lamp 10 mW/cm.sup.2 (silicon wafer surface)
[0055] Effect of Steam:
[0056] The effect by using steam is by the following three
actions.
[0057] 1) Collision Force of Mist:
[0058] The mist in steam collides against surface-adhering
particles at the steam-spraying velocity. The size of mist is about
5 .mu.m to 50 .mu.m in diameter. The collision force by the
spraying velocity of about 40 m/sec is sufficient to detach
particles of 0.1 .mu.m to several .mu.m from a wafer. Besides, the
number of mist colliding every second corresponds to 10.sup.6 to
10.sup.7 times the number of surface-adhering particles (about 50
to 100 particles/cm.sup.2).
[0059] mist quantity colliding surface: 0.015 g/1.5
L.multidot.sec
[0060] weight of one mist: 2.08.times.10.sup.-11 g (as a sphere of
the diameter of 5 .mu.m)
[0061] the number of mist colliding surface: about 10.sup.9
particles/sec
[0062] 2) Scattering Force of Mist:
[0063] A wafer surface has roughness. It has ups and downs in about
0.1 .mu.m figure on a bare silicon surface/oxide film surface, and
in several .mu.m or more on a CMP surface or a device surface in
accordance with the minute structure mode. A mist collides against
these surface ups and downs, and scatters and reflects. The
reflected mist collides against side surfaces or adhering points of
adhering particles at various angles. This scattering force is
effective to detach particles from a surface.
[0064] 3) Lift-Off Effect of High-temperature Mist:
[0065] It is well known that lift-off, that is, an action of
dissolving a particle adhering point and lifting the particle off a
surface is effective to detach the particle from the surface. It is
called slide etching, and an infinitesimal amount of solution is
enough. Water is said to be the greatest solvent because of its
great polarity. In particular, the solvent action of hot water is
great, and it produces a sufficient lift-off effect. For example,
the solubility of SiO.sub.2 to water at 100.degree. C. is about 100
times that at the normal temperature (the solubility of SiO.sub.2
to water: 0.013% (20.degree. C.), 1.4% (100.degree. C.)).
[0066] A silicon wafer surface is a natural oxide film SiO.sub.2 in
general. Besides, various surface structures are constructed on
thermal oxidation film SiO.sub.2 base. Even in a metal structure
surface, the metal surface is naturally oxidized to form an oxide
film. On these surfaces, the solvency of hot water acts.
[0067] For the above reasons, the solvency of high-temperature mist
becomes a strong lift-off effect.
[0068] Effect of Ultraviolet Rays:
[0069] The effect of ultraviolet rays is by the following
action.
[0070] Ultraviolet Decomposition of Organic Polymer Particle:
[0071] It was described before that ultraviolet rays decompose
oleic acid molecules at a rate of 0.05 .mu.g/cm.sup.2 .multidot.sec
at the normal temperature (when the quantum efficiency is 100% in
10 mW/cm.sup.2). Also in relation to polystyrene particles, the
photochemical equivalent is almost the same. Since the used
ultraviolet light quantity (10 mW/cm.sup.2) is about 10.sup.6 times
the polystyrene molecule reaction equivalent every second, it is a
light quantity enough for purification.
[0072] polystyrene particle (0.6 .mu.m) 7000 particles/4-inch
wafer=polystyrene molecule 1.times.10.sup.-5/cm.sup.2
[0073] In many cases, the particle contaminant sources in
semiconductor/liquid crystal processes are organic high-molecule
materials. This is because many organic high-molecule materials are
used in containers, pipes, structural materials, and component
parts. Cleaning process is also not exceptional. For this reason,
particle contamination of unknown origin may be pretty sure to be
considered organic high molecules. Ultraviolet processing is the
most suitable for purification of such organic matter
particles.
[0074] (3) Removal of Organic film
[0075] In semiconductor/liquid crystal-manufacturing, lithographic
process is so important that it should be considered a key process.
In lithographic process, there is a process in which an organic
high-molecule film called resist film is used, and the film is
removed after performing light irradiation, development, and
etching. In general, oxygen plasma ashing process is used. A new
technique has been looked for to replace this ashing process, which
requires a long time and produces a large amount of
contamination.
[0076] Steam/ultraviolet processing can easily remove this organic
high-molecule film. It is by the principle that an organic
high-molecule film is changed by steam, and the boundary layer
between the film and a surface is changed by ultraviolet rays.
Since it is not decomposed but peeled off, short-time processing is
possible. There is no problem of contamination attendant upon the
ashing process.
[0077] Details of this technique will be described in the below
examples.
[0078] 2. Surface Effect of Steam
[0079] Some characteristic surface effects have been found.
[0080] (1) Water Mark Effect
[0081] As a problem on the final finishing when a substrate surface
is purified, the solution of water mark is a difficult problem.
Even if cleaning is finished with ultrapure water, a waterdrop
remaining on the surface generates a water mark to be obstacle to a
minute circuit construction. It is considered that a process of
drying with the waterdrop dissolving a very small amount of the
surface is the cause of the generation. Superheated steam
processing completely settles this problem. Since superheated steam
contains no mist, there is no water mark generation source. It is
the most suitable processing for final finishing.about.drying.
[0082] (2) Hydrogen Termination Effect
[0083] A problem on the final finishing when a silicon surface is
purified, is to change terminal groups of silicon atoms arranged in
the surface into hydrogen. A surface which has become bare silicon
by hydrofluoric processing, shows a peak of Si--OH alongside Si--H
in an FTIR-ATR spectrum, for example. For making complete hydrogen
terminal groups, hydrogen annealing in a hydrogen atmosphere is
being studied. The present inventors have found that steam
processing is effective for hydrogen termination. This is supposed
to be the effect of a chemical action of hot water as exemplified
below.
[0084] reaction of water at 100.degree. C. and sulfur:
2H.sub.2O+3S=SO.sub.2+2H.sub.2S
[0085] 3. Steam supply Apparatus
[0086] FIG. 1 exemplifies a fundamental view of a steam supply
apparatus. An evaporator 1 and a heating block 2 for generating
saturated steam, and a superheater 3 and a heating block 4 for
generating superheated steam, are disposed between a constant flow
pump 5 and a pressure control needle valve 6. The internal pressure
of this steam generation system is measured with a pressure gauge
7. The temperatures of saturated and superheated steams are
measured with thermometers 8 and 9. The heating area in the
evaporator 1 is so designed as to satisfy the burnout point
condition of a boiling characteristic curve.
[0087] Switching Steam of Pure Water and Steam Containing Promotion
Ingredient:
[0088] When steam of ultrapure water is generated, a valve 10 for
an ultrapure water line is opened. When steam containing a
promotion ingredient is generated, a valve 11 for an aqueous
solution line is opened.
[0089] Switching Saturated and Superheated Steams:
[0090] When saturated steam is supplied, the heating block 4 for
superheating is not supplied with heat. At this time, the
superheater 3 merely functions as a passage for steam. When
superheated steam is supplied, the heating block 4 for superheating
is supplied with heat to perform superheating by the superheater
3.
[0091] Switching Steam-contact and Steam-spraying:
[0092] When steam is introduced into a processing chamber 15, an
introduction valve 12 is opened. When steam is sprayed onto a
surface to be processed, a steam-spraying valve 13 is opened and
steam is sprayed onto the surface 16 to be processed, through a
steam-spraying nozzle 14.
[0093] Table 4 exemplifies control conditions for steam supply.
Table 5 exemplifies conditions of the water-spraying nozzle. The
nozzle shape/steam quantity/spraying velocity are arbitrarily
designed so as to meet the purpose.
4TABLE 4 Control Condition for Steam Supply saturated steam
generation superheated steam generation water supply conditions
conditions quantity and heat internal tempera- steam internal
tempera- steam quantity pressure ture quantity pressure ture
quantity ml/sec KWH Kg/cm.sup.2 .degree. C. L/sec Kg/cm.sup.2
.degree. C. L/sec 1.5 3.9 1.0 100 2.55 -- -- -- 1.5 3.9 2.0 120
2.69 1.00 120 2.69 1.5 4.0 3.6 140 2.83 1.00 140 2.83 1.5 4.0 6.0
160 2.96 1.00 160 2.96 water supply quantity temperature:
20.degree. C.; quantity of heat: net value (except radiation loss)
saturated steam: exemplified are only cases of 100 to 160.degree.
C. superheated steam: exemplified are only cases of 100.degree. C.
saturated superheated steam generation
[0094]
5TABLE 5 Condition Example of Steam-spraying Nozzle point nozzle
line slit nozzle steam-spraying steam-spraying linear linear steam
quantity velocity velocity L/sec nozzle shape m/sec nozzle shape
m/sec 2.55 inside 120 200 mm .times. 0.5 mm 52 diameter of 5 mm
2.55 inside 32 200 mm .times. 1.0 mm 13 diameter of 10 mm 2.55 50
mm .times. 1.0 mm 52
[0095] 4. Ultraviolet Reactor
[0096] Selections of the ultraviolet wavelength and time
characteristics of a lamp used in an ultraviolet reactor are
important technical factors.
[0097] Selection of Ultraviolet Wavelength:
[0098] The shorter the ultraviolet wavelength is, the greater the
energy is and the lower the transmissivity to the irradiation
atmosphere is. The ultraviolet wavelength must be so selected as to
satisfy the transmissivity.
[0099] Table 6 shows relations between ultraviolet wavelengths and
50% transmissive distances to air, water, and steam. It is found
that ultraviolet wavelengths whose 50% transmissive distances are
10 mm or more in steam atmosphere, are 185 nm or more.
[0100] A relation between the light absorption sectional area of
molecules present in the atmosphere and the light transmissivity,
is given by expression (1). Logarithms of the transmissivity become
proportional to distances. The present inventors use 50%
transmissive distance as an index. This 50% transmissive distance
is given by expression (2). Table 1 shows relations between
ultraviolet wavelengths and 50% transmissive distances to air,
water, and steam obtained by expression (2) or actual measurements.
For example, the 50% transmissive distance of ultraviolet rays of
the wavelength of 172 nm to air is obtained as 3.1 mm from the
light absorption sectional area of oxygen (0.259.times.10.sup.-19
molecules/cm.sup.2) while the actual measurement of 2.2 mm is
obtained. Both are almost equal.
[0101] .delta.CL=1n (I.degree./I) (1)
[0102] .delta.: light absorption sectional area
(molecules/cm.sup.2), O.sub.2 . . . 0.259.times.10.sup.-19
[0103] C: molecule concentration (partial pressure of molecule)
[0104] L: transmissive distance (cm)
[0105] I.degree./I: light transmissivity=incident light
intensity/transmitted light intensity (2)
[0106] .delta.CL.sub.50=1n (100/50)
[0107] L.sub.50: 50% transmissive distance
6TABLE 6 Ultraviolet Wavelength and 50% Transmissive distances to
Air/Water/Steam 50% transmissive distance excimer wavelength energy
air water steam ultraviolet lamp nm eV mm mm mm Xe excimer lamp 172
7.21 3 ArCl excimer lamp 175 7.08 6 <10 <10 185 6.70 40 10
>1 .times. 10.sup.4 KrI excimer lamp 191 6.49 100 28 ArF excimer
lamp 193 6.42 >100 42 KrBr excimer lamp 207 5.99 >100 KrCl
excimer lamp 222 5.58 low-pressure 185 .multidot. 254 mercury lamp
i-line lamp 365 3.41
[0108] Selection of Time Response:
[0109] An ultraviolet lamp is selected in accordance with which of
a moment type and a constant type ultraviolet processing is
performed in.
[0110] An ultraviolet excimer lamp can be used in a moment-type
process. It reaches its stationary state in several seconds after
being lit.
[0111] It is suitable for a sequential process by unit time of
second in one-by-one ultraviolet processing. A low-pressure mercury
lamp, an i-line lamp, or the like can be used in a constant-type
process. Although they require scores minutes for reaching their
stationary states after being lit, they are stable after then.
[0112] 5. One-By-One Surface Purification Apparatus
[0113] A one-by-one surface purification apparatus has a drive
system in which a spraying surface is swept by a substrate surface
and a steam-spraying nozzle moving relatively, in a chamber
comprising a substrate take-in/out system/an atmosphere purge
system/a liquid discharge system, and constructed by disposing a
point nozzle or a line slit nozzle.
[0114] FIG. 2 exemplifies a one-by-one surface purification
apparatus having a spin rotation system.
[0115] This surface purification apparatus comprises a
steam-processing chamber 23 provided with a spin rotation system 22
for rotating a substrate 21, and a lamp chamber 26 including an
ultraviolet lamp 24 and having a quartz window board 25. A gas
inlet 27 to the chamber and a discharge duct 28 are
accompanied.
[0116] When steam is introduced into the processing chamber from
the steam supply apparatus apparatus shown in FIG. 1, the steam
introduction valve 12 is opened. When steam is sprayed onto a
surface to be processed, the steam-spraying valve 13 is opened and
steam is sprayed onto the surface of the substrate 21 through the
steam-spraying nozzle 14.
[0117] Shown is an example of the steam-spraying nozzle 14 in which
a line slit nozzle is disposed in a diameter direction. It may be a
system in which a spot nozzle is driven radially, or several
nozzles are moved in a proper distance or fixed. The spraying angle
and spraying distance of the nozzle and the linear velocity of
sprayed steam are optimized in various respects, such as the object
of processing/the surface structure of the substrate/protection for
damage.
[0118] The steam-processing chamber 23 is kept in temperature.
Steam is condensed little by little on the inner wall of the
chamber. It serves to clean the inner wall. In this manner, the
interior of the chamber is always kept clean.
[0119] The gas inlet 27 to the chamber is used for changing the
atmosphere when a substrate is taken in/out. It is used also for
adding an effective ingredient for processing to the atmosphere.
The discharge duct 28 preferably has a cooling structure.
[0120] Hereinafter, effects of a new purification process in which
a steam processing apparatus and an ultraviolet processing
apparatus are combined, will be described in detail with reference
to examples.
EXAMPLE 1
[0121] Silicon substrate purification was performed using a
one-by-one surface purification apparatus and an ultraviolet
processing apparatus.
[0122] In purification step 1, purification of organic
matter/particle was performed by fluoric acid/hydrogen
peroxide-containing steam processing under KrI excimer ultraviolet
irradiation. In purification step 2, fluoric acid-containing steam
processing was performed under KrI excimer ultraviolet irradiation.
In purification step 3, drying was performed by superheated steam
processing.
[0123] Table 7 shows the purification results. Organic matters,
metal, particles, and water marks were purified to less than their
detection limits.
[0124] Besides, as for silicon substrate surfaces, the peak ratios
of Si--O/Si--H, which appear in FTIR-ATR spectrum, were 0.05 or
less. In case of a conventional wet cleaning, the peak ratio of
Si--OH/Si--H is 0.1 to 0.5, and the hydrogen termination effect of
steam processing is confirmed.
7TABLE 7 Silicon Substrate Purification Result processed surface
silicon thermal processing condition silicon oxidation film steam
processing processing processing temperature time time [detail of
steam] .degree. C. sec sec step 1 steam/ 100 15 15 ultraviolet rays
superimposition processing [steam containing promotion ingredient
A] step 2 steam/ 100 15 15 ultraviolet rays superimposition
processing [steam containing promotion ingredient B] step 3 drying
120 15 15 [superheated steam] processing organic matter
molecules/cm.sup.2 less than less than result concentration
detection detection limit limit metal impurity atoms/cm.sup.2 less
than less than concentration detection detection limit limit number
of particles/ 5 or less 5 or less particles wafer water marks
marks/wafer 1 or less 1 or less substrate size: 8 inches
steam-spraying quantity: 2.55 L/sec, line slit nozzle: 100 mm
.times. 1.0 mm ultraviolet irradiation quantity: KrI excimer lamp
10 mW/cm.sup.2 (silicon wafer surface) promotion ingredient
solution A: fluoric acid/hydrogen peroxide
(HF0.5%/H.sub.2O.sub.20.5%) promotion ingredient solution B:
diluted fluoric acid (HF0.2%) detection limit of organic matters:
in FTIR/ATR (1 .times. 10.sup.12 molecules/cm.sup.2) detection
limit of metal: chemical analysis (1 .times. 10.sup.10
atoms/cm.sup.2) detection limit of particles: in wafer inspection
device (particles/water marks of 0.1 .mu.m or more)
EXAMPLE 2
[0125] Purification of surfaces of masks for semiconductor/liquid
crystal manufacturing (for lithography) was performed.
[0126] Glass Substrate Purification:
[0127] In step 1, alkali and a surface active agent were used as
purification promotion ingredients. Lift-off effect of particles by
slide etching of glass surfaces and slide etching promotion effect
by alkali were superimposed, and all the alien substances on the
glass surfaces were purified. Organic matters were purified by hot
steam.
[0128] In step 2, surface active agent adsorption layers at
monomolecular layer level on surfaces were purified.
[0129] In step 3, pure dried surfaces were obtained by
superheating.
[0130] Blanks Purification:
[0131] Because chromic oxide forming a surface layer of a chromic
oxide film has a non-stoichiometric composition, it is etched by
hot steam. Accordingly, step 1 was omitted, and surfaces were
slide-etched by pure-water steam-spraying by step 2, and all the
contamination in sputtering process could be purified.
[0132] Mask Purification:
[0133] By purification by step 2 only, adhering of etching liquid
components(e.g., ceric salt solution) in wet-etching process could
be purified. By superimposition of ultraviolet processing, resist
residue in resist-peeling step could be purified.
8TABLE 8 Photomask Purification Result processing processed surface
condition glass processing steam substrate blanks mask [detail of
temperature processing processing processing steam] .degree. C.
time time time step 1 steam processing 100 30 sec -- -- [steam
containing promotion ingredient] step 2 steam/ 100 15 sec 15 to 30
15 to 30 ultraviolet rays sec sec superimposition processing
[saturated steam] step 3 drying 120 15 to 30 15 to 30 15 to 30
[superheated sec sec sec steam] processing organic matter not not
not result detected detected detected metal impurity not not not
detected detected detected particles 1 or less 1 or less 1 or less
steam-spraying quantity: 2.55 L/sec, line slit nozzle: 50 mm
.times. 1.0 mm ultraviolet irradiation quantity: KrI excimer lamp
10 mW/cm.sup.2 (surface to be processed) promotion ingredient
solution: alkali/surface active agent
EXAMPLE 3
[0134] Purification of chemical mechanical polishing (CMP) surfaces
was performed.
[0135] Used was the one-by-one minute processing surface
purification apparatus having the spin rotation system shown in
FIG. 1. The mist-containing steam generation apparatus is a
switching type between purification promotion ingredient-containing
mist generation and pure-water mist generation, like example 1. The
line slit nozzle and mist-containing steam-spraying conditions
shown in Table 5 were used. Table 9 shows the processing steps,
processing details, and processing times.
9TABLE 9 Surface Purification Result after CMP Cu-wiring CMP
surface oxide film CMP Al-wiring CMP acid alumina surface surface
slurry alkaline acid alumina polishing processing silica slurry
slurry iron oxide step [detail of steam] polishing polishing salt
mixed step 1 steam/ultraviolet 1 min 1 min 1 min processing [steam
containing promotion ingredient] step 2 steam/ultraviolet 15 to 30
sec 15 to 30 sec 15 to 30 sec processing [saturated steam] step 3
drying processing 15 to 30 sec 15 to 30 sec 15 to 30 sec
[superheated steam] steam-spraying quantity: 2.55 L/sec, line slit
nozzle: 50 mm .times. 1.0 mm steam temperature: 100 to 140.degree.
C., selected in accordance with polishing slurry ultraviolet
irradiation quantity: low-pressure mercury lamp 10 mW/cm.sup.2
(surface to be processed) promotion ingredient solution: acid or
alkali/surface active agent, selected in accordance with polishing
slurry
[0136] Oxcide Film CMP surface:
[0137] After alkaline silica slurry polishing, steam processing of
step 1 was directly performed not through scrubber processing using
brush. For purification promotion, an HF-surface active agent was
used.
[0138] After step 1, slurry particles are not measured on surfaces.
After step 2, surface active agents are not detected on
surfaces.
[0139] Al-Wiring CMP Surface:
[0140] Performed was the same processing as the oxide film CMP
surface processing except using an alkaline-surface active agent as
a purification promotion solution. It is direct processing not
through scrubber processing. After step 1, alumina slurry particles
do not remain on surfaces. This is by the spraying power of steam,
the effect of the promotion agent, that is, slide-etching effect on
the oxide film surface, and the zeta-potential effect of oxide
film/alumina slurry particle of the surface active agent. After
step 2, surface active agents are not detected on surfaces.
[0141] Cu-Wiring CMP Surface:
[0142] Performed was quite the same processing as Al-wiring CMP
surface processing. Similarly, by the spraying power of steam, the
slide-etching effect, and the zeta-potential effect of the surface
active agent, completely pure surfaces were obtained.
EXAMPLE 4
[0143] Shown are examples of excimer ultraviolet processing
apparatus in which resist films are peeled off by steam/ultraviolet
rays superimposition processing.
[0144] Shown are examples of steam/ultraviolet rays superimposition
processing to ion-implanted resist films, which are hard to peel
off. Sample: silicon thermal oxidation film etched surface,
ion-implantation to the lower-layer silicon substrate.
[0145] Ion-implantation conditions: acceleration energy of 80 keV,
dose amount of phosphorus of 6.times.10.sup.15/cm.sup.2.
[0146] Ultraviolet lamp: KrI excimer lamp, wavelength; 191 nm.
[0147] Ultraviolet irradiation quantity: 10 mW/cm.sup.2 (surface to
be processed).
[0148] Table 10 shows the peeling-off results.
[0149] After saturated steam processing at 100.degree. C. and
ultraviolet irradiation processing for two minutes of the condition
1, the resist film could be removed by spraying process for one
minute.
[0150] After saturated steam processing at 120.degree. C. and
ultraviolet irradiation processing for thirty seconds of the
condition 2, the resist film could be removed by spraying process
for thirty seconds.
* * * * *