U.S. patent application number 12/109623 was filed with the patent office on 2008-08-21 for liquid phase etching method and liquid phase etching apparatus.
This patent application is currently assigned to MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.. Invention is credited to Hisataka Kanada, Bunji Mizuno, Ichiro Nakayama, Yuichiro Sasaki.
Application Number | 20080196834 12/109623 |
Document ID | / |
Family ID | 32905455 |
Filed Date | 2008-08-21 |
United States Patent
Application |
20080196834 |
Kind Code |
A1 |
Mizuno; Bunji ; et
al. |
August 21, 2008 |
LIQUID PHASE ETCHING METHOD AND LIQUID PHASE ETCHING APPARATUS
Abstract
A liquid phase etching method which comprises spraying a
chemically reactive liquid, with a specific speed, to a solid
article, an aggregate of solid articles or a gelatinous material to
be treated; and a liquid etching apparatus having a mechanism for
holding a processing object to be treated and a nozzle structure
for spraying a chemically reactive liquid to the processing object
to be treated which is held by the mechanism. The method and
apparatus allow the significant improvement of the etching rate
while maintaining the accuracy of etching.
Inventors: |
Mizuno; Bunji; (Ikoma-shi,
JP) ; Sasaki; Yuichiro; (Machida-shi, JP) ;
Nakayama; Ichiro; (Kadoma-shi, JP) ; Kanada;
Hisataka; (Katano-shi, JP) |
Correspondence
Address: |
RATNERPRESTIA
P.O. BOX 980
VALLEY FORGE
PA
19482
US
|
Assignee: |
MATSUSHITA ELECTRIC INDUSTRIAL CO.,
LTD.
Osaka
JP
|
Family ID: |
32905455 |
Appl. No.: |
12/109623 |
Filed: |
April 25, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10546015 |
Aug 18, 2005 |
7378031 |
|
|
PCT/JP2004/002073 |
Feb 23, 2004 |
|
|
|
12109623 |
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Current U.S.
Class: |
156/345.21 ;
257/E21.251; 257/E21.257; 257/E21.309; 257/E21.314 |
Current CPC
Class: |
H01L 21/31111 20130101;
H01L 21/32139 20130101; H01L 21/31144 20130101; H01L 21/6708
20130101; H01L 21/32134 20130101 |
Class at
Publication: |
156/345.21 |
International
Class: |
H01L 21/306 20060101
H01L021/306 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 21, 2003 |
JP |
2003-044550 |
Claims
1. A liquid phase etching apparatus comprising: a vacuum chamber;
and a nozzle mechanism provided in the vacuum chamber for spraying
a chemical reactive liquid to a processing object in vacuum
atmosphere, wherein at least the nozzle mechanism is protected by
anticorrosive treatment, the anticorrosive treatment is a process
of forming a thin film of substance having corrosion resistance to
the liquid in the exposed part of the nozzle mechanism, and the
treatment is a surface treatment by using plasma.
2. The liquid phase etching apparatus of claim 1, further
comprising: a stage for holding the processing object, a charging
mechanism provided at the exit of the nozzle mechanism, and a
voltage application mechanism for applying a voltage to the stage,
wherein the charging mechanism applies an electric charge to
particles of the sprayed liquid, and the voltage application
mechanism can accelerate the charged particles of the liquid.
3. The liquid phase etching apparatus of claim 1, further
comprising a magnetic field application mechanism, wherein the
magnetic field application mechanism controls the trajectory of
liquid particles.
4. The liquid phase etching apparatus of claim 1, further
comprising a liquid feed device, wherein the liquid feed device
feeds the liquid continuously or intermittently to the nozzle
mechanism.
5. The liquid phase etching apparatus of claim 1, further
comprising a surface active agent feed mechanism, wherein the
surface active agent feed mechanism includes: a spraying section
for spraying the surface active agent to the processing object, and
a feed device for feeding the surface active agent to the spraying
section.
6. The liquid phase etching apparatus of claim 1, wherein the
vacuum atmosphere has higher degree of vacuum than 1E-3 Torr.
Description
[0001] This application is a divisional of U.S. patent application
Ser. No. 10/546,015, filed Aug. 18, 2005, which is a National Phase
of PCT/JP2004/002073, filed on Feb. 23, 2004, all of which are
incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to a technical field of
processing the surface of solid materials or other processing
objects, in particular a field of forming fine pattern on them. The
field includes, for example, a liquid phase etching method and a
liquid phase etching apparatus for use in manufacture of
semiconductor device or MEMS (micro-electro-mechanical system)
device.
BACKGROUND ART
[0003] In processing (etching) process of semiconductor as a
typical example of fine patterning, the semiconductor surface is
irradiated with reactive gas in plasma state, and the semiconductor
is processed into desired shape.
[0004] Explaining briefly by referring to FIG. 9, a vacuum chamber
1 is coupled to a vacuum pump 2 for creating vacuum. A processing
object like silicon wafer 3 is placed in the vacuum chamber 1, and
desired gas is introduced, and plasma 4 is generated to cause
interaction with the surface of the processing object, and the
processing object is processed. In FIG. 9, the processing object is
etched.
[0005] Meanwhile, as disclosed in Japanese Patent Unexamined
Publication No. H9-27654, the conventional etching was often
processed by immersing the solid processing object in liquid.
However, etching in the liquid is sufficiently fast in etching
processing speed, but is not suited to fine patterning because
etching tends to be isotropic.
[0006] The reason of using plasma in etching is to make etching
anisotropic in order to meet the demand for higher precision in
fine patterning.
[0007] However, when plasma is used in etching, the processing
speed is sacrificed. As a result, in the semiconductor industrial
field, typically, it took about 10 minutes to process one
wafer.
DISCLOSURE OF THE INVENTION
[0008] The etching method of the invention is etching a processing
object which may be either solid, solid assembly or gel material,
by spraying a chemically reactive liquid at a specified speed.
[0009] Also, the etching method of the invention is spraying a
chemically reactive liquid to a processing object placed in a
vacuum chamber, by using a nozzle mechanism. The degree of vacuum
in the vacuum chamber while processing the processing object may be
a sufficient degree of vacuum for preventing generation of impulse
wave when surpassing the sonic speed at the time of jet injection
of liquid.
[0010] Also, the etching method of the invention is further
characterized by impinging the liquid particles charged on the
surface to the processing object, which is either solid, solid
assembly or gel material, with induced acceleration and induced
deceleration in electric field or magnetic field, by applying an
electric charge to injected liquid particles.
[0011] Also, the etching method of the invention is further
characterized by processing the solid or solid assembly selectively
by spraying chemically reactive liquid to the portion exposed from
the mask, by covering part of the surface of solid or solid
assembly with a resin material and using as mask.
[0012] Also, the etching apparatus of the invention is comprising a
mechanism for holding a processing object and a nozzle structure
for spraying chemically reactive liquid to the held processing
object.
[0013] By using the liquid phase etching method and liquid phase
etching apparatus of the invention, the etching speed can be
enhanced substantially.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic sectional view of liquid phase etching
apparatus in an embodiment of the invention.
[0015] FIGS. 2A to 2D are process charts showing other processing
process in the embodiment of the invention.
[0016] FIGS. 3A to 3C are process charts showing other processing
process in the embodiment of the invention.
[0017] FIG. 4 is a schematic sectional view of liquid phase etching
apparatus in the embodiment of the invention.
[0018] FIG. 5 is a schematic sectional view of another liquid phase
etching apparatus in the embodiment of the invention.
[0019] FIG. 6 is a schematic sectional view of another liquid phase
etching apparatus in the embodiment of the invention.
[0020] FIG. 7 is a schematic sectional view of a different liquid
phase etching apparatus in the embodiment of the invention.
[0021] FIG. 8 is a schematic sectional view of a further liquid
phase etching apparatus in the embodiment of the invention.
[0022] FIG. 9 is a schematic sectional view of plasma etching
apparatus in a prior art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] The invention is intended to realize both characteristics of
(1) high speed etching by using liquid and (2) anisotropic etching
by using plasma, simultaneously by spraying liquid to the
processing object at an extremely high speed, and hence presents a
processing technology capable of processing at high speed and
having an extremely sharp anisotropy.
[0024] The system capable of impinging liquid drops at super high
speed also has an effect of generating plasma on the top surface of
the processing object when the liquid drops impinge, so that the
features of the invention may be exhibited more outstandingly.
[0025] The invention enables to transfer the existing "etching
process" using plasma to processing in liquid, which is high in
processing capability, and hence the productivity is improved from
several times to one digit higher. The semiconductor industry
requires a tremendous investment for manufacturing equipment. It is
extremely difficult to realize the chip unit price worthy of
investment, and it is very difficult to adapt to so-called silicon
cycle. Therefore, if the etching process time can be improved by
one digit, the productivity is enhanced and it is expected to
change the industrial structure dramatically.
[0026] A preferred embodiment of the invention is described below
while referring to the accompanying drawings. In the drawings, the
components having same basic function are identified with same
reference numerals.
Preferred Embodiment
[0027] A preferred embodiment of the invention is explained by
referring to embodiment 1. FIG. 1 is an explanatory diagram of
liquid phase etching apparatus used in the preferred embodiment.
Referring now to FIG. 1, the outline of the etching apparatus of
embodiment 1 is explained. A vacuum chamber 10 is coupled to a
vacuum pump 20 for creating vacuum. A stage 40 and plural nozzles
50 are placed in the vacuum chamber 10. The stage 40 holds a
processing object 30 which is either solid, solid assembly or gel
material. The nozzles 50 are connected to a liquid feed device 60
for feeding specified liquid, and particles of chemically reactive
liquid 70 can be sprayed to the processing object 30. From a
variety of liquid 70 capable of etching the processing object 30, a
solvent suited to the processing object is selected and used.
[0028] Keeping the vacuum chamber at a higher degree of vacuum than
about 1E-3 Torr (that is, at lower pressure), the liquid 70 is
sprayed from the nozzles 50 at a speed of over 1000 km/hour. The
sprayed liquid 70 wets the processing object surface 31, which is
etched simultaneously.
[0029] If wettability of liquid 70 on the processing object surface
31 is poor, a surface active agent is sprayed to the processing
object surface from a spray outlet 81 of a surface active agent
feed device 80. The surface active agent may be sprayed before
spraying of liquid 70, simultaneously with spraying, or right after
spraying of liquid 70. By the presence of surface active agent, the
liquid 70 permeates into all parts of the processing object surface
31, and it is etched uniformly.
[0030] For example, when the liquid 70 is sprayed to the processing
object 30 by accelerating to a speed of more than 10,000 km/hour,
part of liquid components may be transformed into plasma by gaining
a high energy. The generated plasma is effective to activate the
processing object surface 31, and further accelerate the etching
process speed.
[0031] Anticorrosive processing of nozzles 50 is explained.
[0032] Nozzles are not always made of materials excellent in
corrosion resistance. If nozzles are made of materials not so high
in corrosion resistance, the nozzle basic shape is formed by using
a material suited to nozzle processing, and the surface directly
contacting with the etching liquid must be coated with an
anticorrosive substance. This coating process is either irradiation
of nozzle surface directly with plasma mainly composed of desired
anticorrosive substance, or irradiation of nozzle surface with
plasma for generating an anticorrosive substance by reacting with
the material forming the basic shape. Coating the nozzle surface
with an anticorrosive substance enables the corrosion resistance of
the nozzle to the etching liquid to improve remarkably.
[0033] Other processing process of the preferred embodiment of the
invention is explained by referring to embodiment 2. FIGS. 2A to
2D, FIGS. 3A to 3C and FIG. 4 explain embodiment 2. FIGS. 2A to 2D
are process charts of embodiment 2 showing the process in the case
of using the photo resist as mask and semiconductor as processing
object. FIGS. 3A to 3D are process charts of embodiment 2 showing
the process in the case of using the coating substance as mask and
semiconductor as processing object. And FIG. 4 is an explanatory
diagram of etching apparatus of embodiment 2 in the case of using
semiconductor as processing object.
[0034] As an example of fine patterning of processing object 30,
the latest processing of fine patterning of semiconductor device is
explained.
[0035] In 2002, generally, the semiconductor is processed more
finely than 0.25 .mu.m. Accordingly, the size of fine particles of
liquid 70 for processing it should be smaller than 0.2 .mu.m. The
size of fine particles may be small enough for the factor
determining the size of the object of processing (critical
dimension). If the required processing precision is large, the size
of a corresponding particle may be selected from sizes smaller than
the required processing precision. In embodiment 2, the etching
apparatus includes nozzles 50 for forming fine particles smaller
than 0.2 .mu.m, or supersonic nozzles 51 for forming liquid fine
particles at higher speed. In the invention, the supersonic nozzles
spray liquid fine particles at a speed of no less than 1000
km/hour, or more preferably spray liquid fine particles by
accelerating to a speed of no less than 3,000 km/hour.
[0036] Referring to FIG. 2, the semiconductor substrate to be
processed is explained. As an example of semiconductor substrate, a
silicon wafer 90 forming a thin film 100 of a substance necessary
for forming a semiconductor element thereon is used. The
semiconductor substrate to be processed is silicon substrate, or
silicon substrate forming silicon oxide film, silicon nitride film,
oxide film of rare earth elements, or metal film of aluminum or
copper, thereon.
[0037] Although there are various liquid for etching the thin film
100 of processing object material, a solvent suitable for the
material of the semiconductor substrate to be processed is selected
and used.
[0038] The degree of vacuum of vacuum chamber 10 is kept higher
than about 1E-3 Torr, and the liquid 70 is sprayed from the nozzles
50 at a speed of no less than about 1000 km/hour. When the sprayed
liquid reaches and wets the processing object surface 31, it is
etched at the same time. Depending on a relation between processing
object surface 31 and liquid 70, a surface active agent is used for
the liquid permeating into all parts of the processing object
surface 31, and for obtaining a homogeneous etching effect. If
wetting of liquid 70 on the processing object surface 31 is poor,
by spraying the surface active agent to the processing object
surface, the liquid 70 is distributed in all parts of the
processing object surface 31, so that uniform etching is
attained.
[0039] For example, if the liquid 70 reaches the processing object
at a high speed exceeding about 10,000 km/hour, part of liquid
components may be transformed into plasma by receiving high energy.
The generated plasma activates the processing object surface, and
may further accelerate the etching speed.
[0040] When manufacturing a semiconductor device, it may be
required to process in a very fine size of 0.1 .mu.m smaller than
0.25 .mu.m. In such a case, as shown in FIG. 2B, a photo resist 110
is formed on the thin film 100, using it as mask, it may be
processed in desired pattern and size by using the so-called
lithography. At this time, in order to provide the photo resist
with corrosion resistance to withstand liquid phase etching, it is
preferred to process the surface of photo resist 110 preliminarily
by plasma 120 as shown in FIG. 2B.
[0041] By plasma processing of the surface of the photo resist
composed of organic materials, polymerization reaction of organic
materials takes place on the surface. By this reaction, cross
linking of organic materials on the surface is promoted, so that an
anticorrosive photo resist 111 obtained as shown in FIG. 2C. An
appropriate plasma 120 may be determined in consideration of:
plasma of rare gases; interaction with substance for composing the
photo resist 110; interaction with etching liquid 70 such as
solvents, acid or alkali to be used.
[0042] Depending on the combination of etching liquid 70 such as
solvents, acid or alkali to be used, sufficient corrosion
resistance may not be achieved in the photo resist 110 mainly
composed of organic materials.
[0043] In such a case, as shown in FIG. 3, a coating substance 130
made of material having enough corrosion resistance is applied on
the surface of the processing object 100, and liquid phase etching
is executed by using the coating substance 130 as mask. In
embodiment 2, the processing object corresponds to the thin film
100 formed on the surface of silicon substrate 90.
[0044] At first, using the photo resist 110 as mask, the coating
substance 130 is etched by using etching liquid 70, such as
solvent, acid or alkali, capable of etching the coating substance
130.
[0045] Further, using the patterned coating substance 131 as mask,
as shown in FIG. 4, in the vacuum chamber 10, the processing object
100 is etched in liquid phase and processed as desired by spraying
the solvent and acidic or alkaline etching liquid 70 for etching
the processing object 100 from the supersonic nozzles 51. The
vacuum degree in the vacuum chamber 10 is kept at degree of vacuum
higher than 1E-3 Torr (that is, lower pressure), and the liquid 70
is sprayed from nozzles 51 at a speed of higher than 1,000 km/hour.
The degree of vacuum is thus maintained in order to prevent
generation of impulse waves or the like by surpassing the sonic
speed at the time of jet injection of the chemically reactive
liquid.
[0046] By the method explained above, the semiconductor substrate
or other thin film to be processed can be processed very finely
according to the mask pattern.
[0047] Other processing process of the preferred embodiment of the
invention is explained below by referring to embodiment 3. In
manufacture of semiconductor device in which precision processing
is required, overhang of etching groove or forming of taper may
cause to worsen the processing precision. Hence, there is a strong
demand for an etching method of digging groove in the vertical
direction from the surface of flat solid body.
[0048] Embodiment 3, by referring to FIG. 5 and FIG. 6, explains an
etching method of digging groove in the vertical direction by
making use of electric field or magnetic field at the time of
etching process.
[0049] FIG. 5 is an explanatory diagram of etching apparatus for
accelerating the liquid 70 by applying an electric field to the
processing object in embodiment 3 of the invention, and FIG. 6 is
an explanatory diagram of etching apparatus for accelerating the
liquid 70 in rotating direction by applying a magnetic field to the
vacuum chamber in embodiment 3 of the invention.
[0050] As shown in FIG. 5, a charging mechanism 140 is provided at
the outlet or near the outlet of the nozzles 50, and an electric
charge is applied to the ejecting pulverized liquid (that is,
liquid particles) 70. By making use of this electric charge, the
ejecting pulverized liquid 70 is provided with freedom in
directivity. For this purpose, a voltage application mechanism 150
is provided for applying a voltage to the stage holding the
semiconductor solid.
[0051] The liquid 70 sprayed out from the nozzles 50 is first
provided with an electric charge by the charging mechanism 140, and
is accelerated by the voltage application mechanism 150 and reaches
the processing object 30. The applicable voltage is limited by
electric discharge or leak varying with the structure of the
apparatus or electrical characteristic of the liquid to be used.
This problem will be further discussed in embodiment 5. By applying
the voltage intermittently by combining with a system of promoting
vaporization of the liquid used in the etching, effects of current
leak or the like may be prevented.
[0052] Further, as shown in FIG. 6, by using a magnetic field
application mechanism 160 for applying a magnetic field, the liquid
71 can be accelerated in the rotating direction, and the motion
trajectory can be varied, and the direction can be controlled
freely. Reference numeral 71 refers to the liquid rotated in its
trajectory.
[0053] Another processing process of the preferred embodiment of
the invention is explained below by referring to embodiment 4. Only
one nozzle 50 for injecting liquid may be used in etching process,
but when the processing object such as a solid has a certain area,
if only one nozzle is used then, the incident angle to the surface
of the pulverized liquid particles varies depending on the location
of the processing. This is the same phenomenon as a flat surface
illuminated by a spot light source varies in luminance depending on
the location. Therefore, to process uniformly on the entire surface
of the processing object, it is effective to use plural nozzles. In
embodiment 4, a case of using the plural nozzles is explained.
[0054] FIG. 7 shows an etching apparatus in embodiment 4 of the
invention, in which nozzles are provided at every individual
semiconductor chip. FIG. 8 shows an etching apparatus having
numerous fine nozzles by making use of MEMS in embodiment 4 of the
invention.
[0055] For example, in the manufacturing process of silicon
semiconductor, plural chips 170 are formed at intervals of about 1
cm. As shown in FIG. 7, nozzles 50 are installed immediately above
the individual chips 170, and the angle variation of liquid 70 may
be minimized. Besides, by installing the plural nozzles in every
chip, effects of angle changes may be minimized.
[0056] Further, as shown in FIG. 8, for example, by using micro
nozzles 52 making use of MEMS or micro machining, nozzles may be
disposed at intervals of several microns. At this time, etching may
be carried out using nozzles densely installed in an area
corresponding to the entire surface of the processing object. Or by
installing nozzles in a specific area, and by moving the nozzles or
the processing object, the entire surface of the processing object
may be etched. In FIG. 8, each nozzle is shown in magnified view
for the sake of explanation.
[0057] A further processing process of the preferred embodiment of
the invention is explained below by referring to embodiment 5.
Depending on the characteristic of the etching liquid, such as
solvent, acid or alkali, used in liquid phase etching, the time of
vaporization of the liquid used in the etching in the vacuum
chamber 10 varies.
[0058] When the vaporization speed is sufficiently fast, the
sprayed liquid is soon vaporized after a specified etching time and
there is no problem. If the vaporization speed is slow, the liquid
remains after necessary etching time, which may lead to etching
defects. Accordingly, when the vaporization speed is slow, it is
required to prevent excessive supply of liquid by controlling the
spraying amount of the etching liquid. To solve this problem, the
liquid feed device 60 includes an intermittent spray circuit or
intermittent spray device (not shown), and the liquid is sprayed
from the nozzles intermittently, and it is preferred to set a
necessary time interval for allowing the etching liquid to be
evaporated after being sprayed out.
[0059] In the foregoing preferred embodiment, it is desired to
spray the chemically reactive liquid at super high speed, but if
not so high, the speed may be enough as far as part or most of
liquid components can be transformed into plasma.
INDUSTRIAL APPLICABILITY
[0060] As explained herein, the invention presents a liquid phase
etching method capable of spraying an etching liquid to the
processing object at a high speed, and is intended to enhance the
etching speed substantially while maintaining anisotropy or other
fine patterning performance of dry etching.
* * * * *