U.S. patent application number 10/010548 was filed with the patent office on 2002-05-23 for method of etching semiconductor device using neutral beam and apparatus for etching the same.
Invention is credited to Lee, Do-Haing, Yeom, Geun-Young.
Application Number | 20020060201 10/010548 |
Document ID | / |
Family ID | 19700627 |
Filed Date | 2002-05-23 |
United States Patent
Application |
20020060201 |
Kind Code |
A1 |
Yeom, Geun-Young ; et
al. |
May 23, 2002 |
Method of etching semiconductor device using neutral beam and
apparatus for etching the same
Abstract
A method and an apparatus for etching a semiconductor device
which can perform an etching process without causing electrical and
physical damages using a neutral beam generated by a simple
apparatus. In the method, ions of an ion beam having a
predetermined polarity are extracted from an ion source and
accelerated. An accelerated ion beam is reflected by a reflector
and neutralized. A substrate to be etched positioned in the path of
the neutral beam in order to etch a special material layer on the
substrate with the neutral beam. The gradient of the reflector is
adjusted to control an angle of incidence of the ion beam incident
on the reflector, and a voltage is applied to the reflector to
control the path of an incident ion beam.
Inventors: |
Yeom, Geun-Young; (Seoul,
KR) ; Lee, Do-Haing; (Suwon-City, KR) |
Correspondence
Address: |
Daniel F. Drexler
Cantor Cloburn LLP
55 Griffin South Road
Bloomfield
CT
06002
US
|
Family ID: |
19700627 |
Appl. No.: |
10/010548 |
Filed: |
November 8, 2001 |
Current U.S.
Class: |
216/66 ;
156/345.39; 216/63; 216/75; 216/79; 257/E21.214 |
Current CPC
Class: |
H01L 21/67069 20130101;
H01L 21/302 20130101; H01J 37/3053 20130101; H01J 37/317 20130101;
H01J 2237/3174 20130101 |
Class at
Publication: |
216/66 ; 216/63;
216/75; 216/79; 156/345.39 |
International
Class: |
C23F 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 22, 2000 |
KR |
2000-69660 |
Claims
What is claimed is:
1. A method of etching a semiconductor device using a neutral beam
comprising: extracting an ion beam having a predetermined polarity
from an ion source to accelerate the ion beam; reflecting an
accelerated ion beam by a reflector to neutralize the reflected ion
beam; and positioning a substrate to be etched in the path of a
neutral beam to etch a special material layer on the substrate with
the neutral beam.
2. The method of claim 1, wherein the step of neutralizing the ion
beams is performed after adjusting the angle of incidence of the
ion beam incident on the reflector.
3. The method of claim 2, wherein the angle of incidence of the ion
beam incident on the reflector is within the range of 75-85.degree.
from the vertical line to the horizontal surface of the
reflector.
4. The method of claim 3, wherein the step of neutralizing the ion
beam is performed after adjusting the gradient of the reflector to
an incident ion beam.
5. The method of claim 3, wherein the step of neutralizing the ion
beam is performed after applying a voltage to the reflector to
adjust the path of an incident ion beam.
6. The method of claim 1, wherein the reflector is one of a
semiconductor substrate, a silicon dioxide substrate and a metal
substrate.
7. An apparatus for etching a semiconductor device using a neutral
beam, the apparatus comprising: an ion source for extracting and
accelerating an ion beam having a predetermined polarity; a
reflector positioned in the path of the ion beam accelerated from
the ion source for reflecting and neutralizing the ion beam; and a
stage for positioning a substrate to be etched in the path of the
neutral beam.
8. The apparatus of claim 7, wherein the ion source is an
inductively coupled plasma source, and a grid is formed to
accelerate the ion beam at the rear of the ion source.
9. The apparatus of claim 7, wherein the reflector is formed of a
plurality of plates which are spaced apart from each other to
reflect the ion beam.
10. The apparatus of claim 7, wherein the reflector is formed of a
plate which may be tilted to adjust the angle of incidence of an
incident ion beam to the horizontal surface of the plate.
11. The apparatus of claim 7, wherein the reflector is formed of a
plurality of cylindrical reflectors, which are overlapped, of which
adjacent reflectors have different polarities.
12. The apparatus of claim 7, wherein the position of the stage is
adjusted to the path of the neutral beams reflected by the
reflector.
13. The apparatus of claim 7, wherein the reflector is one of a
semiconductor substrate, a silicon dioxide substrate, and a metal
substrate.
14. The apparatus of claim 7, further comprising an ion beam
blocker having a slit passing only ions within a predetermined
range between the ion source and the reflector.
15. The apparatus of claim 7, further comprising a retarding grid
between the reflector and the stage.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method of etching a
semiconductor device and an apparatus for etching the same, and
more particularly, to a method of etching a nanoscale semiconductor
device and an apparatus for etching the same without damage by
using a neutral beam.
[0003] 2. Description of the Related Art
[0004] As an increase in the integration density of semiconductor
devices has been required, the design rule of integrated
semiconductor circuits has been reduced. Thus, a critical dimension
of 0.25 .mu.m or less is needed. Ion enhanced etching tools, such
as a high density plasma etcher and a reactive ion etcher are
mainly used as etching tools for realizing nanoscale semiconductor
devices. In such case, high density ions having energies of a few
hundred eV bombard a semiconductor substrate or a specific material
layer on the semiconductor substrate for anisotropic etching. The
bombardment of such ions causes physical and electrical damages to
the semiconductor substrate or the specific material layer.
[0005] Examples of physical damage are as follows. A substrate or a
specific material layer having crystallinity is transformed into an
amorphous layer. Also, a specific material layer, on which some
incident ions are adsorbed or bombarded, of which partial
components are only selectively desorbed therefrom to change
chemical composition of a surface layer to be etched. Atomic bonds
of the surface layer are changed into dangling bonds by this
bombardment. Dangling bonds may result in electrical damage as well
as physical damage. As electrical damage, there is gate dielectric
charge-up or polysilicon notching due to photoresist charging.
Besides this physical and electrical damages, there is also
possible contamination by materials of a chamber or the
contamination of a surface layer by a reactive gas such as the
generation of C-F polymers caused by the use of a CF-based gas.
[0006] Physical and electrical damages due to the bombardment of
ions reduces the reliability of nanoscale semiconductor devices and
productivity. New apparatuses and methods for etching semiconductor
devices are required to be developed in order to cope with the
trend toward further increases in the integration density of
semiconductor devices and reductions in design rule due to
increased integration density.
[0007] D. B. Oakes suggests a damage-free etching technique with a
hyperthermal atomic beam in his thesis "Selective, Anisotropic and
Damage-Free SiO.sub.2 Etching with a Hyperthermal Atomic Beam".
Japanese Takashi Yunogami suggests a silicon oxide etching
technique with a neutral beam or neutral radicals causes less
damage in his thesis "Development of neutral-beam-assisted etcher"
(J.Vac. Sci. Technol. A 13(3), May/June, 1995). M. J. Goeckner
suggests an etching technique with a hyperthermal neutral beam
having no charges instead of plasma in his thesis "Reduction of
Residual Charge in Surface-Neutralization-Based Beams" (1997
2.sup.nd International Symposium on Plasma Process-Induced Damage,
May 13-14, Monterey, Calif.).
[0008] In the damage-free etching technique by D. B. Oakes, since
ions do not exist, it is expected that physical and electrical
damages do not occur and contamination is low. However, scalability
is difficult in that it is difficult to perform anisotropic etching
on micro-devices, and etch rate is low. In the silicon etching
technique by Takashi Yunogami, scalability is easy, but it is
difficult to adjust the direction of the neutral beam and
contamination possibility is high when extracting an ion beam. In
the etching technique by M. J. Goeckner, scalability is possible
and a high neutral beam flux can be obtained, but the direction of
the neutral beam is not clear due to ion-electron recombination,
ions are mixed, and contamination possibility is high when
extracting ions.
SUMMARY OF THE INVENTION
[0009] To solve the above-described problems, it is a first object
of the present invention to provide a method of etching a
semiconductor device which can perform an etching process without
causing electrical and physical damages by the use of a neutral
beam generated by installing only a simple apparatus and an
apparatus for etching the large area by using the neutral
beams.
[0010] It is a second object of the present invention to provide a
damage-free method of etching a semiconductor device that can
adjust the direction of a neutral beam to improve anisotropic
etching by using only a simple apparatus and an apparatus for
etching the large area.
[0011] Accordingly, to achieve the first object, there is provided
a method of etching a semiconductor device using a neutral beam. An
ion beam having a predetermined polarity is extracted from an ion
source to accelerate the ion beam. An accelerated ion beam is
reflected by a reflector to neutralize the reflected ion beam. A
substrate to be etched is positioned in the path of a neutral beam
to etch a special material layer on the substrate with the neutral
beam. The step of neutralizing the ion beams is performed after
adjusting the angle of incidence of the ion beam incident on the
reflector. The angle of incidence of the ion beam incident on the
reflector is within the range of 75-85.degree. from the vertical
line to the horizontal surface of the reflector. The step of
neutralizing the ion beam is performed after adjusting the gradient
of the reflector to an incident ion beam. The step of neutralizing
the ion beam is performed after applying a voltage to the reflector
to adjust the path of an incident ion beam.
[0012] To achieve the second object, there is provided an apparatus
for etching a semiconductor device using a neutral beam. The
apparatus includes: an ion source for extracting and accelerating
an ion beam having a predetermined polarity; a reflector positioned
in the path of the ion beam accelerated from the ion source for
reflecting and neutralizing the ion beam; and a stage for
positioning a substrate to be etched in the path of the neutral
beam. The ion source is an inductively coupled plasma source, and a
grid is formed to accelerate the ion beam at the rear of the ion
source. An ion beam blocker having a slit passing only ions is
included within a predetermined range between the ion source and
the reflector.
[0013] The reflector is formed of a plate which may be tilted to
adjust the angle of incidence of an incident ion beam to the
horizontal surface of the plate. The reflector is formed of a
plurality of cylindrical reflectors, which are overlapped, of which
adjacent reflectors have different polarities. The position of the
stage is adjusted to the path of the neutral beams reflected by the
reflector. The reflector is a semiconductor substrate, a silicon
dioxide substrate, and a metal substrate.
[0014] According to the present invention, a reflector for
reflecting an ion beam at a predetermined angle of incidence is
included between an ion source generating an ion beam and a stage
in which a substrate to be etched is installed. Thus, a neutral
beam can be obtained by a simple method. An etching process can be
easily performed for a nanoscale semiconductor device without
causing electrical and physical damages to a substrate to be etched
using the neutral beam, and scalability is easy.
[0015] Also, an acceleration voltage of an ion beam may be
controlled in an ion source. Only ions within a predetermined range
may be incident on a reflector through a slit in an ion beam
blocker. The gradient of reflectors or voltages applied to the
reflectors may be controlled to adjust the direction of the neutral
beam. Thus, a more improved anisotropic etching process can be
performed.
[0016] Further, only ions having a predetermined direction are
extracted to drastically reduce contamination generated due to the
bombardment of unnecessary ions on the inner walls of a
chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The above objects and advantages of the present invention
will become more apparent by describing in detail preferred
embodiments thereof with reference to the attached drawings in
which:
[0018] FIG. 1 is a schematic diagram of an apparatus for etching a
semiconductor device using a neutral beam according to a first
embodiment of the present invention;
[0019] FIG. 2 is a cross-section of a substrate to be etched as
shown in FIG. 1;
[0020] FIG. 3 is a perspective schematic diagram of an apparatus
for etching a semiconductor device using a neutral beam according
to a second embodiment of the present invention;
[0021] FIG. 4 is a graph showing variations in etch rate with
respect to acceleration voltage resulting from an etching process
according to the first embodiment of the present invention;
[0022] FIG. 5 is a graph showing variations in etch rate with
respect to incident angle resulting from the etching process
according to the first embodiment of the present invention;
[0023] FIG. 6 is a graph showing variations in etch rate with
respect to RF power resulting from the etching process according to
the first embodiment of the present invention; and
[0024] FIG. 7 is a scanning electron microscope (SEM) micrograph of
an etch pattern resulting from the etching process according to the
first embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0025] Hereinafter, embodiments of the present invention will be
described in detail with reference to the attached drawings.
However, the embodiments of the present invention may be modified
into various other forms, and the scope of the present invention
must not be interpreted as being restricted to the embodiments. The
embodiments are provided to more completely explain the present
invention to those skilled in the art.
[0026] <First Embodiment>
[0027] FIG. 1 is a schematic diagram of an apparatus for etching a
semiconductor device according to a first embodiment of the present
invention. FIG. 1 is a simplified diagram to explain the principle
of the present invention, and elements shown in FIG. 1 are included
in a chamber under moderate vacuum.
[0028] Describing an etching method of the present invention, an
ion beam having a predetermined polarity is extracted from an ion
source and then accelerated. An accelerated ion beam is reflected
by a reflector and neutralized into a neutral beam. A substrate to
be etched is positioned in the path of the neutral beam to etch a
specific material layer on the substrate by the neutral beam.
[0029] Theoretical mechanism of the reflection of the accelerated
ion beam by the reflector and then the transformation of the
reflected ion beam into the neutral beam is based on a thesis
"Molecular dynamics simulations of Cl.sup.2+ impacts onto a
chlorinated silicon surface: Energies and angles of the reflected
Cl.sub.2 and Cl fragments" (J.Vac. Sci. Technol. A 17(5),
September/October 1999) by B. A. Helmer and D. B. Graves. According
to this thesis, when Cl.sup.2+ ions are incident on a silicon
substrate having a chloride (Cl) monolayer at an angle higher than
a critical incidence angle, the Cl.sup.2+ ions may be neutralized.
Also, the distribution of reflected neutral Cl.sub.2 molecules and
Cl atomic fragments to Cl.sub.2 molecules incident at the angle of
incidence of 85.degree. is represented as a polar angle and an
azimuthal angle, respectively. This thesis shows that nearly 90% or
more of ions that are incident at an angle within a predetermined
range are reflected as neutral atoms or neutral molecules and the
azimuthal angle of the reflected particles is close to
0.degree..
[0030] The present invention applies preferred conditions and forms
to a process of etching nanoscale semiconductor device based on the
theoretical mechanism, and an etching method.
[0031] An etching apparatus of the present invention will be
described with reference to FIG. 1. Referring to FIG. 1, an ion
source 10 generates an ion beam. The ion beam passes through a slit
having a predetermined diameter. The slit is positioned at the rear
of the ion source 10 in the path of the ion beam. The ion beam is
reflected by a reflector 18 and neutralized into a neutral beam.
The neutralized ion beam is incident on a substrate 20 to be etched
in order to etch a specific material layer on the substrate 20. The
ion source 10 may generate the ion beam from a variety of reactive
gases. An inductively coupled plasma (ICP) generator, which applies
an inductive power to an induction coil 12 to generate plasma, is
used in the present embodiment. A variety of transformed ion
sources may be used instead. A voltage is applied to the end of the
ion source 10 to accelerate the ion beam. A grid 14 having a
plurality of holes is formed so that ions of the ion beam penetrate
through the plurality of holes.
[0032] An ion beam blocker 16 with a slit having a circular or
rectangular shape of a predetermined diameter at the centre of the
ion beam blocker 16 is disposed at the rear of the ion source 10.
The ion beam blocker 16 passes ions that have a predetermined
direction and are within a predetermined range of the ion beam
accelerated by the ion source 10 and blocks other ions from
entering chamber to prevent contamination caused by the bombardment
of unnecessary ions on the inner walls of the chamber or components
of the chamber. Also, it prevents the neutral beam reflected by the
reflector 18 from bombarding unnecessary ions and then dispersing,
which would inhibit an anisotropic etching process with the neutral
beam.
[0033] A reflector 18 is slanted to the horizontal plane to reflect
ions that passed through the slit. The reflector 18 can be tilted
so that the gradient of the reflector 18 is adjusted within an
appropriate range. It is preferable that the reflector 18 is
grounded to discharge charges generated by an incident ion beam.
The reflector 18 may take various shapes, e.g., rectangular or
circular, and may be formed of a silicon semiconductor substrate, a
substrate having silicon oxide on the surface, or a metal
substrate. The reflector 18 may be a plurality of substrates spaced
apart from each other and each having a predetermined size in
consideration of the area required for passing the ion beam
extracted from the ion source 10 and in consideration of the
gradient of the reflector 18 or may be a single substrate.
[0034] The gradient and size of the reflector 18 may be adjusted
according to the size of the slit of the ion beam blocker 16. In
other words, the ion beam passed through the slit has a projected
area that is entirely within the reflector 18 so that all of the
ions of the ion beam passed through the slit are reflected by the
reflector 18. The gradient of the reflector 18 may be adjusted
within a range of at least 5-15.degree. to the horizontal plane in
the present embodiment. The gradient of the reflector 18 to the
horizontal plane is nearly equal to the angle of incidence .theta.i
or the angle of reflection .theta.r to the horizontal surface of
the reflector 18, as shown in FIG. 1. Thus, the gradient of at
least 5-15.degree. to the horizontal plane means the angle of
incidence to the vertical line is at least 75-85.degree..
[0035] A substrate 20 to be etched is disposed in the path of the
ion beam neutralized due to the reflection by the reflector 18. The
substrate 20 to be etched may be mounted on a stage (not shown) to
be disposed in a vertical direction to the path of the neutral
beam. The direction and position of substrate 20 to be etched may
be adjusted and slanted at a predetermined angle depending on the
kind of etching process. As shown in FIG. 1, length L1 from the
rear of the ion source 10 to the centre of the reflector 18 is
equal to length L2 from the substrate 20 to the centre of the
reflector 18, i.e., lengths L1 and L2 are 10 cm in this embodiment.
The length from the rear of the ion source 10 to the substrate 20
to be etched may be arbitrary.
[0036] A retarding grid (not shown) for controlling ion flux is
installed at an appropriate position between the grid 14 and the
substrate 20 to be etched, e.g., at any place between the stage (or
faraday cup) on which the substrate 20 is positioned and the
reflector 18.
[0037] An etching process for the present invention may use one of
a variety of gases, instead of one specific gas, depending on the
kind of material layer to be etched and the kind of etch masks. For
example, the reactive gas may be Cl.sub.2, Cl.sub.2/C.sub.2F.sub.6,
SiCl.sub.4, CCl.sub.4/O.sub.2, or SiCl.sub.4/O.sub.2, when silicon
is etched using a silicon oxide layer as an etch mask. The reactive
gas may be Cl.sub.2/SiCl.sub.4, Cl.sub.2/CCl.sub.4,
Cl.sub.2/CHCl.sub.3, or Cl.sub.2/BCl.sub.3 when aluminum is etched
using a silicon oxide layer, a silicon nitride layer, or a
photoresist layer as an etch mask.
[0038] FIG. 2 is a cross-section of the substrate to be etched
shown in FIG. 1 which shows variations in etch rate depending on
the conditions of the etching process of the present invention.
Referring to FIG. 2, a material layer 32 to be etched is formed on
a semiconductor substrate 30. An etch mask layer 34 having a
predetermined pattern is formed on the material layer 32 to be
etched. A silicon substrate is coated with a photoresist layer,
i.e., the material layer 32 to be etched, on which a bar-shaped
chrome layer, i.e., the etch mask layer 34, is patterned.
[0039] FIG. 4 is a graph showing variations in etch rate with
respect to acceleration voltage resulting from the etching process
according to the first embodiment of the present invention. Here,
the horizontal axis indicates an acceleration voltage applied to
the grid 14 of FIG. 1 to extract and accelerate the ion beam. The
vertical axis indicates the etch rate of the photoresist layer. An
inductive power of 250 W is applied to the induction coil 12 of the
ion source 10, the angle of incidence .theta.i to the horizontal
surface of the reflector 18 is 5.degree., and O.sub.2 as a plasma
reaction gas flows at a rate of 4 sccm. ".circle-solid." represents
etching of the photoresist layer with an ion beam unneutralized as
in the prior art, and ".box-solid." represents etching of the
photoresist layer with a neutral beam reflected by the reflector 18
as in the present invention. FIG. 4 shows that etch rate difference
varies slowly up to an acceleration voltage of 1000 V and increases
drastically for voltages greater than 1000V.
[0040] FIG. 5 is a graph showing variations in etch rate with
respect to the angle of incidence resulting from the etching
process according to the first embodiment of the present invention.
Here, the horizontal axis indicates the angle of incidence .theta.i
with respect to the horizontal surface of the reflector 18 shown in
FIG. 1, and the vertical axis indicates etch rate of the
photoresist layer. An inductive power of 300 W is applied to the
induction coil 12 of the ion source 10. Acceleration voltage is
1000V, and O.sub.2 as a plasma reaction gas flows at a rate of 4
sccm. Etch rate is at its maximum, i.e., about 75 .ANG./min, when
the angle of incidence is 10.degree..
[0041] FIG. 6 is a graph showing variations in etch rate with
respect to RF power resulting from the etching process according to
the first embodiment of the present invention. Here, the horizontal
axis indicates inductive power applied to the induction coil 12,
and the vertical axis indicates etch rate of the photoresist layer.
The angle of Incidence .theta.i with respect to the horizontal
surface of the reflector 18 is 10.degree., an acceleration voltage
of 1000V is applied to the grid 14, and O.sub.2 as a plasma
reaction gas flows at a rate of 4 sccm. FIG. 6 shows that
increasing the RF power increases the etch rate.
[0042] FIG. 7 is a scanning electron microscope (SEM) micrograph of
etch patterns resulting from the etching process according to the
first embodiment of the present invention. Here, black bar-shaped
patterns indicate photoresist layers that are inhibited from being
etched by chrome layers, which have been are removed therefrom.
Other patterns indicate photoresist layers that are etched to a
predetermined depth.
[0043] In the present embodiment, when ion currents were measured
at the faraday cup in which the substrate 20 to be etched is
placed, depending on whether the reflector 18 of FIG. 1 exists or
not, the ion currents increased drastically with increases in
acceleration voltage and RF power in the prior art having no
reflector. The ion currents were close to zero for all conditions
when the ion currents were measured with varying acceleration
voltage and RF power in the present invention. This means that the
ions of the ion beam are nearly completely neutralized by the
reflector 18 of the present invention.
[0044] The increase in ion currents was not remarkable for all
acceleration voltage and RF power conditions when the ion currents
were measured with varying length between the grid 14 and the
substrate 20 to be etched.
[0045] The increase of retarding grid potential decreased the ion
currents detected at the faraday cup and nearly zero ion current
was detected above the potential close to the acceleration voltage
when the ion currents were measured at the faraday cup with varying
the retarding grid potential.
[0046] <Second Embodiment>
[0047] FIG. 3 is a perspective schematic diagram of an apparatus
for etching a semiconductor device according to a second embodiment
of the present invention. FIG. 3 is a simplified drawing to explain
the principles of the present invention. Components of FIG. 3 are
included in a chamber under moderate vacuum as in FIG. 1. An
etching method according to the second embodiment is similar to the
first embodiment except for the shape of a reflector and a method
of reflecting the ion beam. In other words, an ion beam having a
predetermined polarity is extracted from an ion source and then
accelerated. An accelerated ion beam is reflected by a plurality of
cylindrical reflector, of which adjacent cylindrical reflectors
have different polar voltages, to be neutralized. A substrate to be
etched is positioned in the path of a neutral beam to etch a
specific material layer on the substrate to be etched by the
neutral beam. Like reference numerals in FIG. 1 denote the same
members and the detailed descriptions thereof are omitted.
[0048] Referring to FIG. 3, the ion beam is extracted from an ion
source 10. The ion beam is reflected by a plurality of cylindrical
reflectors which are positioned at the rear of the ion source 10 in
the path of the ion beam. A reflected ion beam is neutralized into
a neutral beam. The neutral beam is incident on a substrate 20 to
be etched in order to etch a specific material layer on the
substrate 20. An ion beam blocker 16 (not shown in FIG. 3)
including a slit having a predetermined diameter may be placed
between the ion source 10 and the cylindrical reflectors.
[0049] A voltage may be applied to the end of the ion source 10 to
accelerate the ion beam. A grid 14 having a plurality of holes 14a
through which ions of the ion beam pass may be provided.
[0050] A plurality of cylindrical reflectiors 40a, 40b, 40c, and
40d which overlap radially are included between the ion source 10
and the substrate 20 in the present embodiment. Adjacent reflectors
of the plurality of cylindrical reflectors 40a, 40b, 40c, and 40d
have different polar voltages. Thus, ions having a predetermined
polarity are repulsed from reflectors having the same polarity as
said ions when the ion beam passes through the plurality of
cylindrical reflectors 40a, 40b, 40c, and 40d. In contrast, the
ions are attracted to reflectors having a different polarity from
said ions, so said ions are reflected by such reflectors. The
reflected ion beam passes through the plurality of cylindrical
reflectors 40a, 40b, 40c, and 40d to perform an etching process on
the substrate 20. The lengths radii, and voltages of the plurality
of cylindrical reflectors 40a, 40b, 40c, and 40d may be adjusted
according to design. The plurality of cylindrical reflectors 40a,
40b, 40c, and 40d may be formed of the same material as the
reflector in the first embodiment, preferably, a conductive
material.
[0051] In the present embodiment, the plurality of cylindrical
reflectors may be slanted so that they are tilted within a physical
range. Preferably, the strengths of the voltages applied to the
plurality of cylindrical reflectors can be controlled. In other
words, the trajectory of the ion beam can be controlled by
controlling the mass, speed, and the angle of incidence of the
incident ion beam and the magnitude of electromagnetic fields in
the plurality of cylindrical reflectors. The incident ion beam
traveling in a parabolic path bombard the surfaces of the plurality
of cylindrical reflectors and then are transformed into neutral
beam. The neutral beam moves in a straight line. Here, the angle of
incidence of the ion beam to the longitudinal axis of the plurality
of cylindrical reflectors may be adjusted within the range of at
least 5-15.degree..
[0052] An etching process of the present embodiment may use various
reaction gases depending on the kind of material layer to be etched
and the kind of etch mask.
[0053] Although the invention has been described with reference to
the first and second embodiments, it will be apparent to one of
ordinary skill in the art that modifications to the described
embodiments may be made without departing from the spirit and scope
of the invention. For example, the shape of an ion source, the kind
of reaction gas, and the material of a reflector may be
modified.
[0054] According to the present invention, a neutral beam can be
obtained by a simple method. An etching process can be easily
performed for a nanoscale semiconductor device without causing
electrical and physical damages to a substrate to be etched using
the neutral beam, and scalability is easy.
[0055] Also, the gradient of reflectors or voltages applied to the
reflectors may be controlled to adjust the direction of the neutral
beam. Thus, a more improved anisotropic etching process can be
performed.
[0056] Further, only ions having a predetermined direction are
extracted to drastically reduce contamination generated due to the
bombardment of unnecessary ions on the inner walls of a
chamber.
* * * * *