U.S. patent application number 14/077065 was filed with the patent office on 2014-08-28 for ion beam irradiation apparatus and method for substrate cooling.
This patent application is currently assigned to NISSIN ION EQUIPMENT CO., LTD.. The applicant listed for this patent is NISSIN ION EQUIPMENT CO., LTD.. Invention is credited to Kohei TANAKA.
Application Number | 20140238637 14/077065 |
Document ID | / |
Family ID | 51386947 |
Filed Date | 2014-08-28 |
United States Patent
Application |
20140238637 |
Kind Code |
A1 |
TANAKA; Kohei |
August 28, 2014 |
ION BEAM IRRADIATION APPARATUS AND METHOD FOR SUBSTRATE COOLING
Abstract
A first cooling mechanism is equipped with a heat exchange unit,
in which heat exchange between a substrate and a cooling medium
takes place, and flexible plastic tubing for channeling the cooling
medium to the heat exchange unit; a second cooling mechanism for
cooling the substrate by heat transfer; and a cooling mechanism
control unit which, at least when the target substrate cooling
temperature of the substrate is not higher than the critical cold
resistance temperature of the plastic tubing, cools the substrate
using the second cooling mechanism while channeling the cooling
medium at a temperature higher than the critical cold resistance
temperature through the plastic tubing. In addition, comprises
temperature sensors are provided that measure the temperature of
the substrate and a cooling mechanism control unit which, with
controlling the temperature of the cooling medium in the first
cooling mechanism, is configured to control the second cooling
mechanism.
Inventors: |
TANAKA; Kohei; (Kyoto,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NISSIN ION EQUIPMENT CO., LTD. |
Kyoto-shi |
|
JP |
|
|
Assignee: |
NISSIN ION EQUIPMENT CO.,
LTD.
Kyoto-shi
JP
|
Family ID: |
51386947 |
Appl. No.: |
14/077065 |
Filed: |
November 11, 2013 |
Current U.S.
Class: |
165/47 |
Current CPC
Class: |
F25B 21/02 20130101;
H01J 37/3171 20130101; H01J 2237/2001 20130101; H01L 21/26593
20130101; H01J 37/20 20130101; F28F 3/12 20130101 |
Class at
Publication: |
165/47 |
International
Class: |
F28F 9/00 20060101
F28F009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 22, 2013 |
JP |
2013-033797 |
Feb 22, 2013 |
JP |
2013-033798 |
Claims
1. An ion beam irradiation apparatus configured to cool a substrate
supported by a substrate holding unit of a substrate transport
mechanism, the apparatus comprising: a first cooling mechanism
equipped with a heat exchange unit, in which heat exchange between
a substrate and a cooling medium takes place, and flexible plastic
tubing configured to channel the cooling medium to the heat
exchange unit; a second cooling mechanism that cools the substrate
by heat transfer; and a cooling mechanism control unit which, at
least when the target substrate cooling temperature of the
substrate is not higher than the critical cold resistance
temperature of the plastic tubing, cools the substrate using the
second cooling mechanism while channeling the cooling medium at a
temperature higher than the critical cold resistance temperature
through the plastic tubing.
2. The ion beam irradiation apparatus according to claim 1, wherein
the target substrate cooling temperature is -60.degree. C. or
lower.
3. The ion beam irradiation apparatus according to claim 1, wherein
the second cooling mechanism comprises a Peltier device having a
heat absorbing surface in contact with the substrate holding unit
and having a heat radiating surface in contact with the heat
exchange unit.
4. The ion beam irradiation apparatus according to claim 1, wherein
the heat exchange unit comprises: a gas reservoir comprising a
space between the substrate holding unit and the supported
substrate, where gas is stored during substrate cooling; a gas
pathway that supplies gas to the gas reservoir or discharges gas
from the gas reservoir; and a cooling medium channeling unit that
is in contact with at least a portion of the gas pathway and has a
cooling medium channeled therethrough.
5. The ion beam irradiation apparatus according to claim 3, wherein
the heat exchange unit comprises: a gas reservoir comprising a
space between the substrate holding unit and the supported
substrate where gas is stored during substrate cooling; a gas
pathway that supplies gas to the gas reservoir or discharges gas
from the gas reservoir; and a cooling medium channeling unit that
is in contact with at least a portion of the gas pathway and has a
cooling medium channeled therethrough.
6. The ion beam irradiation apparatus according to claim 5, wherein
the heat radiating surface of the Peltier device is in contact with
the cooling medium channeling unit.
7. The ion beam irradiation apparatus according to claim 1,
wherein: the apparatus further comprises contact-type temperature
sensors that are in contact with the substrate supported by the
substrate holding unit and measure the temperature of the
substrate, and the cooling mechanism control unit, which is
configured to control the temperature of the cooling medium in the
first cooling mechanism that keeps the temperature constant at a
target cooling medium temperature, is further configured to control
the second cooling mechanism to reduce the deviation of a measured
substrate temperature sensed by the contact-type temperature
sensors from a target substrate cooling temperature.
8. A method for substrate cooling employed in an ion beam
irradiation apparatus that comprises: first cooling, via a first
cooling mechanism equipped with a heat exchange unit, in which heat
exchange between a substrate and a cooling medium takes place, and
flexible plastic tubing for channeling the cooling medium to the
heat exchange unit, and second cooling, via a second cooling
mechanism that cools the substrate by heat transfer, and that is
configured to cool a substrate supported by a substrate holding
unit of a substrate transport mechanism, wherein: at least when the
target substrate cooling temperature of the substrate is not higher
than the critical cold resistance temperature of the plastic
tubing, the substrate is cooled by the second cooling, while the
cooling medium at a temperature higher than the critical cold
resistance temperature is channeled through the plastic tubing.
9. An ion beam irradiation apparatus configured to cool a substrate
supported by a substrate holding unit of a substrate transport
mechanism, the apparatus comprising: a first cooling mechanism
equipped with a heat exchange unit in which heat exchange between a
substrate and a cooling medium takes place; a second cooling
mechanism that cools the substrate by heat transfer; temperature
sensors that measure the temperature of the substrate; and a
cooling mechanism control unit which, along with controlling the
temperature of the cooling medium in the first cooling mechanism to
keep the temperature constant at a target cooling medium
temperature, is configured to control the second cooling mechanism
to reduce the deviation of a measured substrate temperature sensed
by the temperature sensors from a target substrate cooling
temperature of the substrate.
10. The ion beam irradiation apparatus according to claim 9,
wherein the second cooling mechanism comprises a Peltier device
having a heat absorbing surface in contact with the substrate
holding unit and a heat radiating surface in contact with the heat
exchange unit.
11. The ion beam irradiation apparatus according to claim 9,
wherein the heat exchange unit comprises: a gas reservoir
comprising a space between the substrate holding unit and the
supported substrate where gas is stored during substrate cooling; a
gas pathway configured to supply gas to the gas reservoir or
discharge gas from the gas reservoir; and a cooling medium
channeling unit that is in contact with at least a portion of the
gas pathway and has a cooling medium channeled therethrough.
12. The ion beam irradiation apparatus according to claim 10,
wherein the heat exchange unit comprises: a gas reservoir
comprising a space between the substrate holding unit and the
supported substrate where gas is stored during substrate cooling; a
gas pathway configured to supply gas to the gas reservoir or
discharge gas from the gas reservoir; and a cooling medium
channeling unit that is in contact with at least a portion of the
gas pathway and has a cooling medium channeled therethrough.
13. The ion beam irradiation apparatus according to claim 12,
wherein the heat radiating surface of the Peltier device is in
contact with the cooling medium channeling unit.
14. The ion beam irradiation apparatus according to claim 9,
wherein the temperature sensors are contact-type temperature
sensors that are in contact with the substrate supported by the
substrate holding unit and measure the temperature of the
substrate.
15. A method for substrate cooling employed in an ion beam
irradiation apparatus that comprises: first cooling, via a first
cooling mechanism equipped with a heat exchange unit, in which heat
exchange between a substrate and a cooling medium takes place,
second cooling, via a second cooling mechanism, that cools the
substrate by heat transfer, and measuring, via temperature sensors,
the temperature of the substrate, wherein cooling a substrate is
supported by a substrate holding unit of a substrate transport
mechanism, and further wherein: along with controlling the
temperature of the cooling medium in the first cooling so as to
keep it constant at a target cooling medium temperature, the second
cooling is controlled so as to reduce the deviation of a measured
substrate temperature sensed in the measuring by the temperature
sensors from a target substrate cooling temperature of the
substrate.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims foreign priority under 35 USC 119 to
Japanese Patent Application No. 2013-033797 and No. 2013-033798,
the content of which is incorporated herein by reference in its
entirety.
BACKGROUND
[0002] 1. Technical Field
[0003] Aspects of the example implementations relate to an ion beam
irradiation apparatus that irradiates a cooled substrate with an
ion beam.
[0004] 2. Related Art
[0005] When an abrupt ultra-shallow junction is created in a
silicon substrate by ion implantation, it is desirable to amorphize
the surface of the substrate. In addition, to amorphize a silicon
substrate, the substrate needs to be maintained at a low
temperature during ion implantation.
[0006] Patent Citation 1 shows an example of an ion implanter 100A
equipped with a substrate cooling mechanism. Specifically, this
implanter is an apparatus, in which ion implantation is carried out
by scanning an ion beam across a substrate W secured in a
predetermined position and, as shown in FIG. 6, the implanter has a
cooling element 9A, which is provided by securing the element to a
side wall of a vacuum chamber VR such that the element protrudes
into the vacuum chamber VR, and which has a cooling medium supplied
from outside for circulation therein; a heat radiating plate 9B
secured to the cooling element 9A; and a Peltier device 9C, whose
heat radiating surface is secured to the heat radiating plate 9B
and whose heat absorbing surface is secured to the backside of an
electrostatic chuck 9D used for chucking the substrate W. In
addition, the apparatus is configured to cool the substrate W down
to a few tens of degrees Centigrade below zero by using the Peltier
device 9C to create a temperature difference between the heat
radiating surface and the heat absorbing surface and move the heat
of the substrate W sequentially through the electrostatic chuck 9D,
the Peltier device 9C, and the heat radiating plate 9B to the
cooling element 9A.
[0007] Further, there are implanters which, conversely, are
configured such that the irradiation location of the ion beam is
fixed and the ion beam is scanned across a substrate surface by
moving the substrate using a substrate transport mechanism. Such
implanters are adapted to cool a substrate by providing flexible
plastic tubing between walls forming a vacuum chamber and an
electrostatic chuck that chucks the substrate in a substrate
transport mechanism within the vacuum chamber and supplying a
refrigerant cooling medium to the electrostatic chuck through the
plastic tubing. The purpose of using such flexible plastic tubing
is to permit tubing deformation or movement depending on the
position of the substrate as it is moved by the substrate transport
mechanism, and thereby prevent the cooling medium tubing from being
damaged as the substrate moves.
[0008] Incidentally, when amorphizing the surface of a substrate
during ion implantation as described in Patent Citation 2, it is
required that the substrate be cooled to a cryogenic temperature
such as, for example, a temperature of -40.degree. C. to
-100.degree. C.
[0009] However, cooling a substrate to such a cryogenic temperature
using the above-described prior-art substrate cooling mechanism is
difficult. For example, if a high current is directed through the
Peltier device of the ion implanter described in Patent Citation 1
in an attempt to create a temperature difference from room
temperature to a cryogenic temperature between the heat radiating
surface and heat absorbing surface thereof, the amount of Joule
heat generated as a result will also be increased and the substrate
cooling efficiency will be considerably decreased. In addition, if
the electric current directed through the Peltier device becomes
excessively high, the temperature of the substrate reaches a point
at which it cannot be decreased any more, which is why using
Peltier devices alone permits cooling only to about -20.degree. C.
or -30.degree. C., as described in Patent Citation 1.
[0010] On the other hand, it has also been contemplated to cool
substrates to cryogenic temperatures not by using Peltier devices,
but by supplying a cooling medium cooled to a cryogenic temperature
to an electrostatic chuck, to which substrates are chucked.
[0011] However, when such a cooling medium cooled to a cryogenic
temperature is directed through the plastic tubing, its temperature
drops below the critical cold resistance temperature of the
plastics and the plastic tubing becomes brittle and loses
flexibility. Consequently, if the substrate is moved by the
substrate transport mechanism while the cryogenic-temperature
cooling medium is channeled therethrough, the plastic tubing
becomes damaged. On the other hand, when using metal tubing, whose
characteristics remain practically unchanged even with a
cryogenic-temperature cooling medium, the position of the substrate
must be fixed to avoid damaging the tubing because the tubing has
almost no flexibility or degrees of freedom. Additionally, if the
position of the substrate is fixed, the degree of freedom during
ion implantation is impaired, inter alia, as a result of
limitations imposed on the region of the substrate surface where
ion beam irradiation is possible.
[0012] Further, in the ion implanter described in Patent Citation
2, a substrate is pre-chilled to a predetermined temperature in a
substrate load lock chamber provided in proximity to an ion
implantation chamber. In addition, the apparatus is adapted to load
the pre-chilled substrate into the ion implantation chamber and
carry out ion implantation without cooling the substrate while it
is being irradiated by an ion beam.
[0013] However, in methods for substrate cooling such as the one
set forth in Patent Citation 2, no consideration is given to the
temperature change occurring in a substrate while it is irradiated
by an ion beam as described above, and there is a chance that the
temperature of the substrate during ion beam irradiation may
deviate from temperatures suitable for amorphization. Consequently,
there is a risk that substrate characteristics after ion
implantation may differ from the desired characteristics.
[0014] In other words, heretofore, no substrate temperature control
has been practiced in the related art in order to monitor
temperature increase due to heat transferred to a substrate as a
result irradiation by the ion beam, minimize such temperature
increase during ion implantation as much as possible, and continue
maintaining a constant substrate temperature. Furthermore, due to
the fact that such technical problems have never been rigorously
investigated in the past, there are no known specific
configurations and methods for substrate cooling suitable for
quickly cooling a substrate to a target temperature and constantly
maintaining it at this temperature in the event of substrate
temperature changes.
RELATED ART LITERATURE
Patent Citations
[Patent Citation 1]
[0015] Japanese Patent Application Publication No. 2001-68427.
[Patent Citation 2]
[0015] [0016] US Publication 7935942
SUMMARY
Problems to be Addressed
[0017] It is an object of the example implementation to provide an
ion beam irradiation apparatus and a method for substrate cooling
that allow for a substrate to be cooled to a cryogenic temperature
of, for example, -60.degree. C. to -100.degree. C. even when
substrate cooling is performed using a cooling medium, permit free
movement of the substrate during ion beam irradiation without
impairing the flexibility of the plastic tubing through which the
cooling medium is channeled, as well as make it possible to
minimize temperature increase of the substrate while the substrate
is irradiated by an ion beam and allow for substrate temperature to
be maintained constant at a temperature (e.g., predetermined) at
all times, even during ion beam irradiation.
Means for Addressing the Problems
[0018] Namely, the ion beam irradiation apparatus of the example
implementation is an ion beam irradiation apparatus configured to
cool a substrate supported by a substrate holding unit of a
substrate transport mechanism, wherein the apparatus comprises a
first cooling mechanism equipped with a heat exchange unit, in
which heat exchange between a substrate and a cooling medium takes
place, and flexible plastic tubing for channeling the cooling
medium to the heat exchange unit; a second cooling mechanism that
cools the substrate by heat transfer; and a cooling mechanism
control unit which, at least when the target substrate cooling
temperature of the substrate is not higher than the critical cold
resistance temperature of the plastic tubing, cools the substrate
using the second cooling mechanism while channeling the cooling
medium at a temperature higher than the critical cold resistance
temperature through the plastic tubing.
[0019] Further, the method for substrate cooling of the present
example implementation is a method for substrate cooling employed
in an ion beam irradiation apparatus that is provided with a first
cooling mechanism equipped with a heat exchange unit, in which heat
exchange between a substrate and a cooling medium takes place, and
flexible plastic tubing for channeling the cooling medium to the
heat exchange unit, and a second cooling mechanism that cools the
substrate by heat transfer, and that is configured to cool a
substrate supported by a substrate holding unit of a substrate
transport mechanism, wherein, at least when the target substrate
cooling temperature of the substrate is not higher than the
critical cold resistance temperature of the plastic tubing, the
substrate is cooled by the second cooling mechanism while
channeling the cooling medium at a temperature higher than the
critical cold resistance temperature through the plastic
tubing.
[0020] In such a case, when the target substrate cooling
temperature of the substrate is not higher than the critical cold
resistance temperature of the plastic tubing, primary substrate
cooling is accomplished by directing the cooling medium at a
temperature higher than the critical cold resistance temperature to
the heat exchange unit of the first cooling mechanism, and the
remaining portion of cooling down to the target substrate cooling
temperature that could not be accomplished by the first cooling
mechanism is accomplished using heat transfer-based secondary
cooling provided by the second cooling mechanism, as a result of
which the temperature of the substrate can be reduced to the target
substrate cooling temperature.
[0021] Due to the fact that only a cooling medium at a temperature
higher than the critical cold resistance temperature is channeled
through the plastic tubing at such time, the flexibility of the
plastic tubing is never impaired and the plastic tubing is never
damaged even if the position of the substrate is changed by the
substrate transport mechanism while cooling the substrate to a
cryogenic temperature. Therefore, the substrate can be freely moved
by the substrate transport mechanism while the substrate is cooled,
and the surface of the substrate can be irradiated by the ion beam
in a variety of ways.
[0022] Moreover, since the temperature of the substrate has already
been reduced to a certain extent by the primary substrate cooling
provided by the first cooling mechanism, the substrate can be
cooled to the target substrate cooling temperature even though the
second cooling mechanism does not remove a very large amount of
heat from the substrate by heat transfer. In other words, due to
the fact that the second cooling mechanism does not have to perform
a large amount of heat transfer work and an excessively strong
cooling capability is not required, the substrate can be cooled to
the target substrate cooling temperature using, for instance,
currently available Peltier devices and the like.
[0023] For example, during ion implantation and the like, a target
substrate temperature of -60.degree. C. or lower is sufficient to
enable high-quality ion implantation by amorphizing a substrate
surface and creating ultra-shallow junctions.
[0024] As a specific configuration for enabling adequate substrate
cooling by efficiently discharging heat transferred from the
substrate by the second cooling mechanism to the environment, a
configuration is proposed, in which the second cooling mechanism is
a Peltier device whose heat absorbing surface is in contact with
the substrate holding unit and whose heat radiating surface is in
contact with the heat exchange unit.
[0025] To enhance the substrate cooling capability of the first
cooling mechanism by further increasing the area of direct or
indirect contact between the heat exchange unit and the substrate
supported by the substrate holding unit in order for the heat
exchange between the cooling medium and the substrate to be carried
out in an efficient manner, it is sufficient for the heat exchange
unit to be composed of a gas reservoir, which is a space between
the substrate holding unit and the supported substrate where gas is
stored during substrate cooling, a gas pathway for supplying gas to
the gas reservoir or discharging gas from the gas reservoir, and a
cooling medium channeling unit that is in contact with at least a
portion of the gas pathway and has a cooling medium channeled
therethrough. In such a case, the cooling medium can effect heat
exchange with the substrate not only through the substrate holding
unit, but also through the gas in the gas reservoir and the gas
pathway, as a result of which the substrate can be cooled more
efficiently, even when using the first cooling mechanism alone.
[0026] To be able to efficiently discharge the heat removed from
the substrate to the environment using heat transfer provided by
the Peltier device and maintain the cooling efficiency of the
Peltier device at a high level, it is sufficient to bring the heat
radiating surface of the Peltier device into contact with the
cooling medium channeling unit.
[0027] For example, in order to ensure that feedback-control is
exercised immediately so as to bring the temperature of a substrate
to a target substrate cooling temperature if the temperature rises
above the target substrate cooling temperature when the substrate
is irradiated by an ion beam and heat is driven into the substrate,
and to maintain the substrate constantly at this temperature, the
apparatus is further provided with contact-type temperature sensors
that are in contact with the substrate supported by the substrate
holding unit and measure the temperature of the substrate, and the
cooling mechanism control unit, along with controlling the
temperature of the cooling medium in the first cooling mechanism so
as to keep it constant at a target cooling medium temperature, is
configured to control the second cooling mechanism so as to reduce
the deviation of a measured substrate temperature sensed by the
contact-type temperature sensors from the target substrate cooling
temperature.
[0028] Further, the ion beam irradiation apparatus of the example
implementation is an ion beam irradiation apparatus configured to
cool a substrate supported by a substrate holding unit of a
substrate transport mechanism, wherein the apparatus comprises a
first cooling mechanism equipped with a heat exchange unit in which
heat exchange between a substrate and a cooling medium takes place,
a second cooling mechanism that cools the substrate by heat
transfer, temperature sensors that measure the temperature of the
substrate, and a cooling mechanism control unit which, along with
controlling the temperature of the cooling medium in the first
cooling mechanism so as to keep it constant at a target cooling
medium temperature, is configured to control the second cooling
mechanism so as to reduce the deviation of a measured substrate
temperature sensed by the contact-type temperature sensors from a
target substrate cooling temperature of the substrate.
[0029] Further, the method for substrate cooling of the example
implementation is a method for substrate cooling employed in an ion
beam irradiation apparatus that is provided with a first cooling
mechanism equipped with a heat exchange unit in which heat exchange
between a substrate and a cooling medium takes place, a second
cooling mechanism that cools the substrate by heat transfer, and
temperature sensors that measure the temperature of the substrate,
and that is configured to cool a substrate supported by a substrate
holding unit of a substrate transport mechanism, wherein along with
controlling the temperature of the cooling medium in the first
cooling mechanism so as to keep it constant at a target cooling
medium temperature, the second cooling mechanism is controlled so
as to reduce the deviation of a measured substrate temperature
sensed by the temperature sensors from a target substrate cooling
temperature of the substrate.
[0030] In such a case, by providing primary substrate cooling, the
first cooling mechanism cools the substrate to a target cooling
medium temperature and keeps it constant at a temperature in the
vicinity of the target substrate cooling temperature. For this
reason, the second cooling mechanism uses secondary cooling only
for the purpose of controlling variation from the substrate
temperature maintained by the first cooling mechanism.
[0031] Therefore, it is easy to set a high level of responsiveness
because it is sufficient for the second cooling mechanism to
control only small changes in temperature and there is no need for
a large temperature control range. For this reason, for example,
even if an increase in the temperature of the substrate due to
substrate irradiation by the ion beam does occur, the second
cooling mechanism can operate to immediately minimize the
temperature increase and can keep the temperature of the substrate
constant at all times.
[0032] Furthermore, the fact that the temperature of the substrate
can be kept constant at all times makes maintaining the surface of
the substrate during ion beam irradiation in the desired condition
easier than in the past and allows for substrates with more
favorable properties to be obtained.
[0033] To ensure instant response to substrate temperature changes,
it is sufficient for the second cooling mechanism to be a Peltier
device whose heat absorbing surface is in contact with the
substrate holding unit and whose heat radiating surface is in
contact with the heat exchange unit.
[0034] To enable a further increase in the magnitude of the
reduction in the temperature of the substrate provided by the first
cooling mechanism by increasing the area of direct or indirect
contact between the heat exchange unit and the substrate supported
by the substrate holding unit in order for the heat exchange
between the cooling medium and the substrate to be carried out in
an efficient manner, it is sufficient for the heat exchange unit to
be composed of a gas reservoir, which is a space between the
substrate holding unit and the supported substrate where gas is
stored during substrate cooling, a gas pathway for supplying gas to
the gas reservoir or discharging gas from the gas reservoir, and a
cooling medium channeling unit that is in contact with at least a
portion of the gas pathway and has a cooling medium channeled
therethrough.
[0035] As a specific configuration for enabling adequate substrate
cooling by efficiently discharging heat transferred from the
substrate by the second cooling mechanism to the environment, a
configuration is suggested, in which the heat radiating surface of
the Peltier device is in contact with the cooling medium channeling
unit.
[0036] For example, to ensure that feedback-control is exercised
immediately so as to bring the temperature of a substrate to a
target substrate cooling temperature if its temperature rises above
the target substrate cooling temperature when the substrate is
irradiated by an ion beam and heat is driven into the substrate,
and to maintain the substrate constantly at this temperature, the
temperature sensors are optionally contact-type temperature sensors
that are in contact with the substrate supported by the substrate
holding unit and measure the temperature of the substrate.
Effects
[0037] Thus, the ion beam irradiation apparatus and method for
substrate cooling of the present example implementation are
configured such that when a substrate is cooled to a cryogenic
temperature, primary substrate cooling is provided by the first
cooling mechanism by directing a cooling medium having a
temperature higher than the critical cold resistance temperature
through the plastic tubing and the remainder of substrate cooling
is accomplished using the heat transfer provided by the second
cooling mechanism, as a result of which it becomes possible to cool
the substrate to the target substrate cooling temperature while
preventing the embrittlement of the plastic tubing through which
the cooling medium is channeled. Furthermore, because the apparatus
is configured according to feedback-control variations in the
measured substrate temperature using the second cooling mechanism
while keeping it at a constant temperature in the vicinity of the
target substrate cooling temperature using the first cooling
mechanism, the range of control of the second cooling mechanism can
be narrowed down and temperature control responsiveness can be
readily increased. Consequently, even if the temperature of a
substrate rises when the substrate is irradiated by an ion beam,
the substrate can be instantly cooled to the target substrate
cooling temperature and constantly maintained at this
temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 A schematic oblique view illustrating the
configuration of an ion implantation chamber used in an ion
implanter according to an example embodiment.
[0039] FIG. 2 A schematic enlarged cross-sectional view
illustrating structure adjacent to an electrostatic chuck of a
substrate transport mechanism used in the same example
embodiment.
[0040] FIG. 3 A schematic enlarged cross-sectional view
illustrating the attachment structure of a contact-type sensor used
in the same example embodiment.
[0041] FIG. 4 A functional block diagram illustrating the
configuration of substrate cooling mechanism control units and
other units used in the same example embodiment.
[0042] FIG. 5 A schematic graph illustrating the concept of
substrate temperature control in the same example embodiment.
[0043] FIG. 6 A schematic diagram illustrating a related-art ion
implanter equipped with a substrate cooling mechanism.
DETAILED DESCRIPTION OF EXAMPLE IMPLEMENTATIONS
[0044] An example embodiment will be described with reference to
FIGS. 1 through 5.
[0045] The ion beam irradiation apparatus of this example
embodiment is an ion implanter 100 that irradiates a semiconductor
substrate with an ion beam comprising, for example, arsenic,
phosphorus, boron, and other ion species in order to implant these
ion species therein. In addition, this ion implanter 100 is
configured to be capable of low-temperature ion implantation in a
state, wherein a substrate W is cooled to a predetermined cryogenic
temperature in order to amorphize the surface of the substrate
during ion implantation and create ultra-shallow junctions therein.
Furthermore, it is configured to be capable of handling
normal-temperature ion implantation as well, which involves cooling
to a temperature at which heat-induced deformation of the
photoresist on the surface of the substrate does not occur during
ion implantation.
[0046] As shown in FIG. 1, in the ion implanter 100, the vacuum
chamber VR, the inside of which is maintained under a vacuum, is
partitioned by a partition 4. In addition, the upper structure 3U
and bottom structure 3B of the substrate transport mechanism 3 are
coupled through a connecting slit 41 formed in the partition 4,
arranged so as to be in communication with the respective
compartments of the upper structure 3U and bottom structure 3B.
[0047] More specifically, the ion implanter 100 is provided with: a
substrate transport mechanism 3 that supports a substrate W using a
substrate holding unit 31 and suitably changes the position and
attitude of the substrate W relative to the ion beam; an ion
implantation chamber 1, which is the upper compartment of the
vacuum chamber VR that houses the upper structure 3U of the
substrate transport mechanism 3 where the substrate W is irradiated
by the ion beam; a linear motion mechanism housing chamber 2, which
is the lower compartment of the vacuum chamber VR that houses the
bottom structure 3B of the substrate transport mechanism 3 as well
as various power supply cords and part of the plastic tubing 5B
used for supplying the cooling medium; and a cooling system FS used
for cooling the substrate W supported by the substrate holding unit
31.
[0048] A description of each unit will now be provided.
[0049] In the substrate transport mechanism 3, the upper structure
3U is a unit that mainly provides attitude control for the
supported substrate W, whereas the bottom structure 3B is a unit
that moves the supported substrate W in the horizontal direction so
that it moves through the ion beam. Namely, the upper structure 3U
is composed of a vertical-axis tilting mechanism 3R used for
rotation about a vertical axis, and the substrate holding unit 31
that supports the substrate W in a detachable manner. The substrate
holding unit 31 is an electrostatic chuck adapted for rotation
about a vertical axis perpendicular to the surface of the supported
substrate W. Part of the cooling system FS is provided in proximity
to the substrate holding unit 31 for cooling the supported
substrate W.
[0050] The bottom structure 3B, which is a linear motion mechanism
made up of a motor 32, a ball screw 33, a nut 34, and a guide (not
shown), moves the upper structure 3U perpendicular to the
short-side direction of the ion beam.
[0051] The upper structure 3U and the bottom structure 3B are
coupled by a coupling member through the connecting slit 41 formed
in the partition 4, and the entire upper structure 3U is moved as a
single unit as a result of the linear motion of the bottom
structure 3B in the horizontal direction, thereby moving the
substrate W supported by the substrate holding unit 31. In
addition, the coupling member effects coupling such that the upper
structure 3U can perform rotary motion independently from the
bottom structure 3B.
[0052] The ion implantation chamber 1, which is a compartment
shaped generally as a hollow rectangular parallelepiped, has an ion
beam inlet 11 used for ion beam introduction formed in the center
of a side face thereof, and a ribbon-shaped ion beam extending in a
vertical direction is introduced therethrough. An adjacent
substrate load lock chamber (not shown) is provided in this ion
implantation chamber 1. The substrate transport mechanism 3
receives a substrate W from the substrate load lock chamber and
transports the substrate W to an ion beam irradiation location,
where ion implantation into the surface of the substrate takes
place. Upon completion of ion implantation, the substrate W is
transported to a substrate unloading chamber (not shown) provided
in proximity to the ion implantation chamber 1.
[0053] The linear motion mechanism housing chamber 2 houses part of
the bottom structure 3B of the substrate transport mechanism 3.
More specifically, the motor 32 is provided on the outside, in
other words on the atmospheric side, of the linear motion mechanism
housing chamber 2, while the ball screw 33, nut 34, and the guide
are housed inside the linear motion mechanism housing chamber 2.
Furthermore, the linear motion mechanism housing chamber 2 is
configured to have a higher degree of vacuum than in the ion
implantation chamber 1.
[0054] The cooling system FS is made up of a first cooling
mechanism 5, which cools the substrate W using heat exchange
between the cooling medium and the supported substrate W; Peltier
devices 6 serving as a second cooling mechanism that cools the
substrate W by heat transfer from the substrate W; and a cooling
mechanism control unit 7, which controls the operation of the first
cooling mechanism 5 and the second cooling mechanism. In the
discussion below, explanations will be given with reference to the
oblique view of FIG. 1 and the enlarged cross-sectional view of
FIG. 2 illustrating the vicinity of the substrate holding unit
31.
[0055] The first cooling mechanism 5, which executes a so-called
refrigeration cycle, has a refrigerant circuit formed therein in
such a manner that a cooling medium circulates between a chiller 54
(not shown in FIG. 1), which is disposed outside the vacuum chamber
VR, and a heat exchange unit 5A, which is provided in the substrate
holding unit 31 within the vacuum chamber VR, in which heat
exchange between the substrate W and the cooling medium takes
place. Furthermore, as shown in FIG. 1, in the tubing that connects
the chiller 54 with the heat exchange unit 5A, the first cooling
mechanism 5 uses plastic tubing 5B at least for the tubing that
extends up to the heat exchange unit 5A within the vacuum chamber
VR. Even if the position of the heat exchange unit 5A shifts as a
result of motion of the substrate transport mechanism 3, this
plastic tubing 5B, which is flexible, is configured to follow its
motion to some extent without impeding the motion of the substrate
transport mechanism 3. More specifically, the plastic tubing 5B
that passes through the linear motion mechanism housing chamber 2,
which is housed in a bellow-like cable guide 35 along with control
signal lines (not shown) and electric power cables (not shown) used
to supply electric power from outside to the substrate transport
mechanism 3, is adapted to be movable throughout a predetermined
range in concert with the movement of the substrate transport
mechanism 3. In addition, due to the properties of the plastics,
this plastic tubing 5B becomes brittle and loses flexibility when
the temperature drops below the critical cold resistance
temperature, and there is a risk that it may be damaged when
following the motion of the substrate transport mechanism 3. For
this reason, in the present embodiment, only a cooling medium
having a temperature higher than the critical cold resistance
temperature is adapted to be channeled therethrough. It should be
noted that, as used herein, the term "critical cold resistance
temperature" includes, for example, a manufacturer-recommended
service temperature, or a temperature at which there is a risk of
reduced flexibility and damage to the plastic tubing 5B due to the
movement of the substrate transport mechanism 3, and in the present
example embodiment, the critical cold resistance temperature is set
to -60.degree. C.
[0056] As shown in FIG. 2, the heat exchange unit 5A, if described
functionally, is composed of a gas reservoir 51, which is a space
between the substrate holding unit 31 and the supported substrate W
where gas is stored when the substrate W is cooled, a gas pathway
52 used for supplying gas to the gas reservoir 51 or discharging
gas from the gas reservoir 51, and a cooling medium channeling unit
53, which is in contact with at least a portion of the gas pathway
52 and has a cooling medium channeled therethrough. As far as the
arrangement of the various members is concerned, the following
order is used: substrate W, gas reservoir 51, substrate holding
unit 31, second cooling mechanism, and cooling medium channeling
unit 53.
[0057] More specifically, the distal surface of the substrate
holding unit 31 has a thin generally-annular ridge 311, with the
flat surface of the ridge 311 configured to electrostatically chuck
the backside of the substrate W. Therefore, when holding the
substrate W, the radially innermost side of the ridge 311 forms a
space used as a gas reservoir 51, where gas is stored when the
substrate W is cooled.
[0058] In this example embodiment, the gas pathway 52 is made up of
a gas supply tube, which supplies gas to the gas reservoir 51, and
a gas discharge tube, which is used for discharging the gas from
the gas reservoir 51. The gas supply tube and the gas discharge
tube are adapted to pass through the cooling medium channeling unit
53 and allow for heat exchange between the gas and the cooling
medium to take place.
[0059] The cooling medium channeling unit 53, which is formed in
the general shape of a hollow flat cylinder, is configured so that
the cooling medium, which is cooled by the chiller 54, enters
through the plastic tubing 5B, is temporarily accumulated inside
the unit, and, once the heat exchange with the gas has taken place,
again returns to the chiller 54 through the plastic tubing 5B.
[0060] The cooling action of such a first cooling mechanism 5 will
be described next. When gas is stored in the gas reservoir 51
during the cooling of the substrate W, the efficiency of heat
transfer from the substrate W can be improved by placing a heat
conductor against the substrate W maintained under a vacuum
atmosphere, such that the conductor is in gapless contact with the
minute irregularities formed on the backside thereof. Therefore,
the cooling medium in the cooling medium channeling unit 53 can
exchange heat directly with the substrate W through the gas pathway
52, as a result of which heat conduction takes place and the
substrate W can be cooled even if there was no second cooling
mechanism. In other words, it is configured such that heat exchange
with the substrate W can occur even when using the first cooling
mechanism 5 alone. It should be noted that, since in this example
embodiment the cooling medium channeling unit 53 is also in contact
with the substrate holding unit 3 through the medium of the Peltier
devices 6, which are excellent heat conductors, the substrate W can
also be cooled by heat exchange via that thermal pathway.
[0061] The second cooling mechanism is described below.
[0062] Unlike the first cooling mechanism, the second cooling
mechanism does not provide cooling for the substrate W by heat
exchange. Instead, it is configured to cool the substrate W by heat
transfer from the substrate W to the environment outside of the
substrate W. As used herein, the term "heat transfer-based cooling"
includes cooling methods in which no cooling medium is used and
heat is transferred from an object on the low-temperature side to
an object on a high-temperature side, thereby enabling a further
reduction in the temperature of the object on the low-temperature
side. It should be noted that during heat exchange-based cooling,
such as in the first cooling mechanism 5, the substrate W is cooled
only if the temperature of the cooling medium is lower than that of
the substrate W and, therefore, the temperature of the substrate W
never becomes lower than the temperature of the cooling medium.
[0063] More specifically, the second cooling mechanism, which is
the Peltier devices 6 provided such that their heat absorbing
surfaces 61 are in contact with the substrate holding unit 31 and
their heat radiating surfaces 62 are in contact with cooling medium
channeling unit 53, is configured to remove heat from the substrate
W through the substrate holding unit 31 by an electron flux and
release the removed heat into the cooling medium channeling unit
53.
[0064] The functionality of the cooling mechanism control unit 7 is
realized by running a software program stored in the memory of what
is commonly called a "computer", which is equipped with a CPU, a
memory, an AC/DC converter, input/output structures, and the like.
For example, the software program may include, but is not limited
to, machine-readable instructions executed by a non-transitory
computer readable medium. In addition, at least when the target
substrate cooling temperature of the substrate W is not higher than
the critical cold resistance temperature of the plastic tubing 5B,
this cooling mechanism control unit 7 is configured to cool the
substrate W using the second cooling mechanism while channeling the
cooling medium at a temperature higher than the critical cold
resistance temperature through the plastic tubing 5B.
[0065] In addition, as shown in FIG. 3, there are provided
contact-type temperature sensors TS that are placed in direct
contact with the backside of the substrate W supported by the
substrate holding unit 31 and measure the temperature of the
substrate W. As shown in FIG. 2, there are several contact-type
temperature sensors TS provided for measuring temperature in
several locations on the substrate W, the sensors being located on
the substrate holding unit 31 in contact with the backside of the
substrate W across the gas reservoir 51. The cooling mechanism
control unit 7 controls the first cooling mechanism 5 and second
cooling mechanism using the measured substrate temperature obtained
from these contact-type temperature sensors TS.
[0066] More specifically, in this example embodiment, as shown in
the functional block diagram of FIG. 4, the cooling mechanism
control unit 7 comprises a first cooling mechanism control unit 71,
which controls the first cooling mechanism 5, and a second cooling
mechanism control unit 72, which controls the cooling capability of
the second cooling mechanism. In addition, in the process of
cooling medium temperature control by the first cooling mechanism
control unit 71, the measured substrate temperature sensed by the
contact-type temperature sensors TS is used to determine the target
.degree. C. value, to which the target cooling medium temperature
should be set at a temperature higher than the critical cold
resistance temperature of the plastic tubing 5B. On the other hand,
in the second cooling mechanism control unit 72, the measured
substrate temperature obtained from the contact-type temperature
sensors TS is subject to continuous feedback, with the unit
configured to perform feedback-control of the voltage applied to
the Peltier devices 6 so as to reduce the deviation of a measured
substrate temperature from a target substrate cooling
temperature.
[0067] Each control unit will be now described in detail. The first
cooling mechanism control unit 71 is provided with a cooling medium
temperature control unit 73, which controls the temperature of the
cooling medium supplied to the cooling medium channeling unit 53 so
as to match a target cooling medium temperature, and a gas control
unit 74, which controls the supply and discharge of the gas to/from
the gas reservoir 51.
[0068] The cooling medium temperature control unit 73, whose
operation is configured to be switched depending on the target
substrate cooling temperature, is configured to set the target
cooling medium temperature to a temperature higher than the
critical cold resistance temperature by a predetermined amount when
the target substrate cooling temperature is not higher than the
critical cold resistance temperature of the plastic tubing 5B, and
set the target cooling medium temperature to the same temperature
as the target substrate cooling temperature when the target
substrate cooling temperature is higher than the critical cold
resistance temperature of the plastic tubing 5B. In addition, the
cooling medium temperature control unit 73 controls each piece of
equipment in the refrigeration cycle such that, for example, the
cooling medium temperature measured by the temperature sensors
provided in the refrigeration cycle comprising the chiller 54 and
other units is maintained at a target cooling medium temperature
(e.g., preset).
[0069] The gas control unit 74 supplies a fixed amount (e.g.,
predetermined) of gas to the gas reservoir 51 through the gas
pathway 52 when the substrate W is supported by the substrate
holding unit 31 and exercises control aimed at preventing the
substrate W from falling into the vacuum chamber VR due to a
pressure difference when the electrostatic chuck is disengaged by
discharging the gas from the gas reservoir 51 and producing
practically the same pressure as the pressure within the vacuum
chamber VR prior to removing the substrate W from the substrate
holding unit 31, in other words, prior to deactivating the voltage
applied to the electrostatic chuck.
[0070] The second cooling mechanism control unit 72 controls the
voltage applied to the Peltier devices 6 based on the deviation of
the measured substrate temperature sensed by the contact-type
temperature sensors TS from a target substrate cooling temperature.
Here, the cooling medium temperature control unit 73 exercises
control such that the temperature of the cooling medium is
maintained constant at the target cooling medium temperature. As a
result, the second cooling mechanism control unit 72 controls the
voltage applied to the Peltier devices 6 such that heat
corresponding to the difference between the target substrate
cooling temperature and the target cooling medium temperature as
well as heat generated by the irradiation of the substrate W by the
ion beam are transferred from the substrate W to the cooling medium
channeling unit 53.
[0071] Referring now to the temperature variation graphs of FIG. 5,
the operation of the thus configured ion implanter 100 during
substrate cooling will be described with reference to a case in
which the target substrate cooling temperature is lower than the
critical cold resistance temperature of the plastic tubing 5B, and
a case in which the target substrate cooling temperature is higher
than the critical cold resistance temperature of the plastic tubing
5B.
[0072] If the target substrate cooling temperature is set to
-100.degree. C., which is lower than -60.degree. C., i.e. the
critical cold resistance temperature of the plastic tubing 5B, the
cooling medium temperature control unit 73 controls the chiller 54
and other units such that the target cooling medium temperature is
set to a temperature higher than the critical cold resistance
temperature, for example, to -55.degree. C., and the temperature of
the cooling medium is constantly maintained at this temperature. In
addition, the second cooling mechanism control unit 72 applies a
voltage to the Peltier devices 6 such that the heat corresponding
to the temperature differential between -100.degree. C., i.e. the
target substrate cooling temperature, and -55.degree. C., i.e. the
target cooling medium temperature, is transferred from the
substrate W by the Peltier devices 6. For example, the voltage
applied by the second cooling mechanism control unit 72 to the
Peltier devices 6 is proportionate to, or correlated with, the
temperature difference to be set between the heat absorbing surface
61 and the heat radiating surface 62.
[0073] As shown in FIG. 5(a), during the ion beam non-irradiation
period, when the substrate W is not irradiated by the ion beam, the
operation of the first cooling mechanism 5 and second cooling
mechanism maintains the temperature of the substrate W at about
-100.degree. C., but when the substrate W is irradiated by the ion
beam, a corresponding amount of heat is imparted to the substrate W
and, as a result, as illustrated in the ion beam irradiation period
of FIG. 5(a), the measured substrate temperature sensed by the
contact-type temperature sensors TS rises above -100.degree. C. In
that case, the magnitude of the deviation of the measured substrate
temperature from the target substrate cooling temperature
fluctuates and, as a result, the second cooling mechanism control
unit 72 uses feedback such that the voltage applied to the Peltier
devices 6 is adjusted in accordance with the fluctuation of the
deviation so as to maintain the temperature at -100.degree. C.
[0074] Namely, while during the ion beam non-irradiation period of
FIG. 5(a) the Peltier devices 6 continue cooling aimed at the
preset temperature differential between the target cooling medium
temperature and the target substrate cooling temperature, during
the ion beam irradiation period the Peltier devices 6 operate to
maintain the substrate W at the target substrate cooling
temperature by performing cooling aimed not only at the temperature
differential (e.g., preset) mentioned above, but also at variation
due to the temperature increase. In addition, during the ion beam
irradiation period the first cooling mechanism 5 acts to constantly
maintain the same temperature as during the ion beam
non-irradiation period without adjusting the target cooling medium
temperature, with only the Peltier devices 6, which are provided in
proximity to the substrate W and are capable of instantly adjusting
the amount of cooling if the applied voltage changes, being subject
to feedback based on the measured substrate temperature. As a
result, even if temperature changes occur, the temperature of the
substrate W can be maintained essentially constant at -100.degree.
C. practically without any time delay.
[0075] Operation in situations in which the target substrate
cooling temperature is a temperature higher than the critical cold
resistance temperature of the plastic tubing 5B, will be described
next with reference to FIG. 5(b). Here, a case in which the target
substrate cooling temperature is -40.degree. C. and the critical
cold resistance temperature is -60.degree. C., will be considered
as a specific example.
[0076] In this case, the cooling medium temperature control unit 73
sets the target cooling medium temperature to -40.degree. C., i.e.
the same temperature as the target substrate cooling temperature.
Here, during the ion beam non-irradiation period of FIG. 5(b),
there is almost no heat flowing from the outside to the substrate
W, which is maintained in a vacuum. As a result, the temperature of
the substrate W is maintained at -40.degree. C. substantially by
the operation of the first cooling mechanism 5 alone. On the other
hand, during the ion beam irradiation period, the substrate
temperature rises when the ion beam irradiates the substrate W, as
a result of which a deviation develops between the measured
substrate temperature sensed by the contact-type temperature
sensors TS and the target substrate cooling temperature. Therefore,
during the ion beam irradiation period of FIG. 5(b), the operation
of cooling is carried out by applying a voltage corresponding to
the deviation to the Peltier devices 6. Namely, whereas the first
cooling mechanism 5 continues cooling the substrate W using the
cooling medium at -40.degree. C. regardless of the measured
substrate temperature, the Peltier devices 6 perform practically no
cooling during the ion beam non-irradiation period and operate only
when the measured substrate temperature deviates from -40.degree.
C. during the ion beam irradiation period.
[0077] In this manner, the Peltier devices 6, which are provided in
the vicinity of the substrate W, perform cooling aimed only at
temperature differentials produced by deviations from the target
substrate cooling temperature, as a result of which, even when
there are fluctuations, the temperature of the substrate W can be
maintained constant at the cryogenic temperature with very high
responsiveness. More specifically, an attempt to use the first
cooling mechanism 5 to apply feedback-control to cooling aimed at a
temperature increase due to irradiation of the substrate W by the
ion beam changes the operation of the chiller 54, which is located
outside the vacuum chamber VR, far from the substrate W, and thus
produces a considerable time delay before any results become
apparent. For this reason, it is difficult to instantly cancel
temperature increases by controlling the temperature of the
substrate W using the first cooling mechanism 5 alone. By contrast,
as a result of providing temperature control of temperature
increases with the help of the Peltier devices 6 located within the
vacuum chamber VR in the vicinity of the substrate W, the substrate
can immediately, practically without any time delay, be cooled to
the target substrate cooling temperature and constantly maintained
at this temperature.
[0078] In accordance with the ion implanter 100 of the present
example embodiment described in detail above, when the target
substrate cooling temperature of the substrate W is not higher than
the critical cold resistance temperature of the plastic tubing 5B,
along with subjecting the substrate W to primary substrate cooling
by setting the target cooling medium temperature to a temperature
higher than the critical cold resistance temperature and directing
a cooling medium at a temperature higher than the critical cold
resistance temperature into the heat exchange unit 5A of the first
cooling mechanism 5, the amount of heat in the substrate W that is
not removed by the first cooling mechanism 5 by cooling down to the
target substrate cooling temperature is removed by the heat
transfer-based secondary cooling provided by the Peltier devices 6,
as a result of which the temperature of the substrate W can be
reduced to the target substrate cooling temperature.
[0079] Because only a cooling medium at a temperature higher than
the critical cold resistance temperature is channeled through the
plastic tubing 5B at such time, the flexibility of the plastic
tubing 5B is never impaired and the plastic tubing 5B is not
damaged even if the position of the substrate W is changed by the
substrate transport mechanism 3 while cooling the substrate W to a
cryogenic temperature. Therefore, the substrate W can be freely
moved by the substrate transport mechanism 3 while the substrate W
is cooled to a temperature lower than the critical cold resistance
temperature, and the surface of the substrate can be irradiated by
the ion beam in a variety of ways.
[0080] Furthermore, since the temperature of the substrate W has
already been reduced to a certain extent by the primary substrate
cooling provided by the first cooling mechanism 5, the substrate W
can be cooled to the target substrate cooling temperature even
though the Peltier devices 6 do not remove a very large amount of
heat from the substrate W by heat transfer, and the Peltier devices
6 are not required to have an excessively large capacity.
[0081] In addition, since the apparatus is configured to monitor
the temperature of the substrate W in real time using the
contact-type temperature sensors TS even during ion beam
irradiation and feedback-control of the Peltier devices 6 in
accordance with the deviation of the measured substrate temperature
from the target substrate cooling temperature, the temperature can
be maintained essentially constant at the target substrate cooling
temperature even during ion beam irradiation.
[0082] Therefore, since temperature control accuracy during
low-temperature ion implantation may be improved in comparison with
the prior art, the properties of substrates W obtained by
low-temperature ion implantation may also be superior to the
related art.
[0083] A description of other example embodiments will now be
given.
[0084] The ion beam irradiation apparatus of this example
implementation is a concept that includes not only the ion
implanter 100, but also e.g. ion doping machines, ion beam
deposition machines, ion beam etching machine, and the like. In
addition, it can be used in applications involving ion beam
irradiation in combination with temperature management not only on
substrates W such as silicon wafers, but also on glass substrates,
semiconductor substrates, and the like. In addition, when the glass
substrates and the like are irradiated with an ion beam, the
substrates may be chucked using chucking methods other than
electrostatic chucking such that the substrates are supported on
the substrate holding unit of the substrate transport
mechanism.
[0085] Although in the above-described embodiment the second
cooling mechanism used Peltier devices 6, devices capable of
cooling the substrate W using other kinds of heat transfer may also
be used. For example, these may be devices made not of
semiconductors, like the Peltier devices 6, but devices adapted to
produce the Peltier effect using dissimilar metals.
[0086] When the target substrate cooling temperature was higher
than the critical cold resistance temperature, the cooling
mechanism control unit 7 brought the target cooling medium
temperature in agreement with the target substrate cooling
temperature. However, it is also possible to set the target cooling
medium temperature to a temperature higher than the target
substrate cooling temperature. Namely, even in cases in which
temperature control of the substrate W is possible only by the
operation of the first cooling mechanism 7, the apparatus may also
be configured to act on the fluctuations, along with providing
cooling for the substrate W using the second cooling mechanism when
no fluctuations from the target substrate cooling temperature have
occurred, as shown in FIG. 5(a).
[0087] The Peltier devices 6 may be used not only for cooling the
substrate W, but also for heating if for some reason the substrate
W is overcooled by the first cooling mechanism 5. Namely, the
second cooling mechanism control unit 72 may also be configured to
permit controlling not only the magnitude of the voltage applied to
the Peltier devices 6, but also its direction. In this case, the
temperature of the substrate W can also be controlled using the
control rule shown in the above-described example embodiment if
there is a deviation of the measured substrate temperature from the
target substrate cooling temperature.
[0088] If the target substrate cooling temperature is set to a
temperature higher than the critical cold resistance temperature of
the plastic tubing 5B and responsiveness requirements are not
particularly stringent, it is possible to use feedback-control
based on the deviation of the measured substrate temperature from
the target substrate cooling temperature in the first cooling
mechanism 5 without operating the second cooling mechanism.
[0089] Although in the above-described example embodiment the
temperature of the substrate W was constantly monitored using
contact-type temperature sensors TS, it is also possible to
exercise temperature control by measuring the temperature of the
substrate W using non-contact temperature sensors.
[0090] In addition, various modifications and combinations of
embodiments are also possible where consistent with the gist of the
present inventive concept.
* * * * *