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Timestamp: 2013-06-20 01:59:02
Document Index: 598639465

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Heat-treating apparatus Abstract: A processing gas is prevented from entering into a space below a placement table. A supporting surface 62 for supporting the lower face of a placement table 58 is provided at an inner circumferential portion of the upper end of a support 56. A circumferentially extending purge gas groove 64 is formed outside the supporting surface 62, in an intermediate circumferential portion of the upper end of the support 56. A narrow flow path 68 is provided outside the purge gas groove 64, at a position corresponding to an outer circumferential portion of the upper end of the support 56. A purge gas fed from purge gas-feeding means 66 into the purge gas groove diffuses in the circumferential direction in the purge gas groove 64 and flows out to the outside from the narrow flow path 68. Such a flow of the purge gas prevents a processing gas from entering into the purge gas groove 64 and a space S1 below the placement table. ...
Agent: Oblon, Spivak, Mcclelland Maier & Neustadt, P.C. - Alexandria, VA, USInventors: Sumi TANAKA, Takayuki Kamaishi, Kouki SuzukiUSPTO Applicaton #: #20080011734 - Class: 219390000 (USPTO) - 01/17/08 - Class 219 Related Patent Categories: Electric Heating, Heating Devices, Combined With Container, Enclosure, Or Support For Material To Be Heated, Muffle-type EnclosureThe Patent Description & Claims data below is from USPTO Patent Application 20080011734, Heat-treating apparatus.
[0001] This application is a Continuation Application of PCT International
Application No. PCT/JP2004/011551 filed on Aug. 11, 2004, which
designated the United States.
[0002] The present invention relates to a heat-treating apparatus for
performing a specified heat treatment on an object to be processed such
as a semiconductor wafer.
[0003] Generally, various processes, e.g., a film forming process, an
etching process, an oxidation/diffusion process, an annealing process and
a modification process, are performed on a semiconductor wafer serving as
an object to be processed in a manufacturing process of a semiconductor
integrated circuit. For example, in the film forming process, a
polysilicon film, a SiO.sub.2 film, a W (tungsten) film, a WSi (tungsten
silicide) film, a Ti (titanium) film, a TiN (titanium nitride) film, a
TiSi (titanium silicide) film and the like are deposited on a surface of
the wafer. A heat-treating apparatus performing such a film forming
process is disclosed in, for example, Japanese Patent Laid-open
Application Nos. H9-237763 and 2001-23966.
[0004] Here, a conventional general single-wafer heat-treating apparatus
will be described with reference to FIG. 7. FIG. 7 shows a configuration
of a conventional general single-wafer heat-treating apparatus. The
heat-treating apparatus includes an evacuatable processing chamber 2,
wherein a shower head 4 for introducing various necessary gases into the
processing chamber 2 is installed in a ceiling portion thereof. Further,
inside the processing chamber 2, a placement table 8 of a thin plate
shape is supported on a cylindrical support column 6 which is extended
upward from a bottom portion of the chamber, and a semiconductor wafer W
is mounted on an upper surface of the placement table 8. A plurality of
heating lamps 10 is installed under the processing chamber 2. Heat rays
emitted from the heating lamps 10 are introduced into the chamber through
a transmission window 12 provided in the bottom portion of the chamber,
whereby the wafer W as well as the placement table 8 is heated.
[0005] A N.sub.2 gas serving as a purge gas is supplied into a space under
the placement table 8 by a purge gas feeding unit 14 to thereby prevent a
processing gas from entering into the space under the placement table 8.
Accordingly, an unnecessary film is prevented from being adhered to an
upper surface of the transmission window 12 or a lower surface of the
placement table 8. If an unnecessary film is adhered to the transmission
window 12, a transmittance of the heat rays becomes decreased to thereby
deteriorate a heating efficiency. Further, if an unnecessary film is
unevenly adhered to the lower surface of the placement table 8, a light
absorptance becomes nonuniform and a temperature distribution is
developed on the placement table 8 to thereby decrease an in-surface
uniformity of the wafer's temperature. In order to overcome such a
drawback, it is very important to supply the above-mentioned purge gas.
[0006] For example, in the aforementioned film forming process, if a
diffusion rate of a processing gas used for film forming is not so high,
the processing gas can be sufficiently prevented from entering into the
space under the placement table 8. However, in case of using a processing
gas having a very high diffusion rate, e.g., a silane gas, even though
the purge gas is supplied into the space under the placement table 8, the
processing gas enters into the space under the placement table 8 from a
small gap, whereby an unnecessary film can be adhered to the lower
surface of the placement table 8 or the upper surface of the transmission
[0007] In order to avoid such a phenomenon, it can be considered to
substantially increase a flow rate of the purge gas. But, if so, a
pressure inside the space under the placement table 8 is also increased.
Since the increased pressure is exerted on the whole lower surface of the
placement table 8, it is possible that the placement table 8 is raised to
thereby generate a misalignment of the placement table. Further, in case
that the placement table 8 is strongly fixed to the support column 6, the
placement table 8 itself can be destroyed. Besides, since a flow speed of
the purge gas jetting outwardly through the gap between the upper surface
of the support column 6 and the lower surface of the placement table 8
becomes considerably greater, a circumferential portion of the placement
table 8 is partially cooled to thereby deteriorate the in-surface
uniformity of the temperature of the wafer W. Accordingly, it is not
allowable to sharply increase the flow rate of the purge gas.
[0008] The present invention has been conceived to effectively resolve the
above drawbacks; and it is, therefore, an object of the present invention
to provide a heat-treating apparatus capable of definitely preventing a
processing gas from entering into a space under a placement table for
mounting an object to be processed thereon.
[0009] The above-mentioned object is achieved by the present invention
disclosed in claims. In accordance with the present invention, there is
provided a heat-treating apparatus, including an evacuatable processing
chamber; a cylindrical support column extending upward from a bottom
portion of the processing chamber; a placement table of a plate shape,
supported on a top end of the support column, for mounting an object to
be processed thereon; a heating lamp for heating the object mounted on
the placement table; and a gas feeding unit for supplying a processing
gas in the processing chamber, wherein a supporting surface is formed in
a circumferential direction at an inner circumferential portion of a top
portion of the cylindrical support column to support a lower surface of a
circumferential portion of the placement table in contact therewith, a
purge gas groove for flowing a purge gas therein is formed in a
circumferential direction at an intermediate circumferential portion of
the top portion of the cylindrical support column, a narrow flow path for
discharging the purge gas flowing in the purge gas groove while
preventing the processing gas from entering into the purge gas groove is
formed around at an outer circumferential portion of the top portion of
the cylindrical support column, and a purge gas feeding unit for
supplying the purge gas in the purge gas groove is installed.
[0010] Consequently, the purge gas supplied into the purge gas groove is
distributed approximately uniformly in the purge gas groove, and
discharged outside through the narrow flow path. The purge gas is
discharged from the narrow flow path with a flow speed increased due to a
throttling effect in the narrow flow path. Thus, even though the
processing gas has a high diffusion rate, it is possible to prevent the
processing gas from entering into the purge gas groove and the space
under the placement table through the narrow flow path.
[0011] A labyrinth groove may be disposed on a surface of a member for
defining the narrow flow path to definitely prevent the processing gas
narrow flow path is a gap between an upper surface of the outer
circumferential portion of the cylindrical support column and a lower
surface of the placement table facing to the upper surface, and the purge
gas groove formed at the intermediate circumferential portion of the top
portion of the cylindrical support column is a gap between the outer
circumferential portion and the inner circumferential portion of the top
portion of the cylindrical support column. In this case, the labyrinth
groove may be disposed in a circumferential direction on the upper
surface of the outer circumferential portion of the cylindrical support
[0013] A cylindrical pressing member having a pressing portion for
pressing an upper surface of the circumferential portion of the placement
table may be disposed in a radial direction outside the cylindrical
support column at a specified interval, whereby a purge gas discharge
flow path may be formed between an inner circumferential surface of the
pressing member and an outer circumferential surface of the support
column and the purge gas discharged from the narrow flow path flows down
therethrough. As described above, the purge gas discharge flow path
prevents the processing gas from reaching the narrow flow path.
Preferably, the pressing member is made of a low heat conductive
[0014] Preferably, a lower portion of the pressing member is fixed at the
bottom portion of the processing chamber via a resilient member, whereby
the placement table is movable upward by resiliently deforming the
resilient member when an upward force is applied to the placement table.
By such a fixed structure, even though a pressure in the space under the
placement table is higher than that in the processing space above the
placement table, the placement table is temporarily displaced to reduce
the pressure in the space under the placement table, whereby the
placement table can be prevented from being damaged.
[0015] Preferably, both the supporting surface and the lower surface of
the circumferential portion of the placement table in contact with the
supporting surface are mirror finished. Accordingly, both surfaces become
to have a close contact and it is possible to prevent the processing gas
from entering into the space under the placement table even if the
processing gas enters into the purge gas groove.
[0016] A light blocking member may be installed at the support column to
prevent light emitted from the heating lamp from leaking outward in a
radial direction of the support column. The light blocking member may be
formed of a light reflective member.
[0017] Preferably, the heat-treating apparatus is provided with a purge
gas feeding unit for supplying a purge gas in a space under the placement
table inside the support column. Consequently, it is possible to
effectively prevent the processing gas from entering into the space. In
this case, preferably, a cylindrical flow path forming member is disposed
inward in a radial direction of the cylindrical support column at a
specified interval, and formed between an inner circumferential surface
of the support column and an outer circumferential surface of the flow
path forming member is a purge gas outlet passage through which the purge
gas supplied in the space under a lower surface of the placement table
flows down, having a lower portion connected to a vacuum exhaust system
for exhausting the processing chamber to vacuum via a purge gas passage.
[0018] FIG. 1 provides a cross sectional view showing a configuration of a
heat-treating apparatus in accordance with a first preferred embodiment
[0019] FIG. 2 illustrates a magnified sectional view showing a support
column and its neighboring members depicted in FIG. 1;
[0020] FIG. 3 describes a magnified plan view showing the support column
[0021] FIG. 4 offers a magnified sectional view showing a support column
and its neighboring members in accordance with a second preferred
[0022] FIG. 5 presents a magnified plan view showing the support column in
accordance with the second preferred embodiment of the present invention;
[0023] FIGS. 6A and 6B represent explanatory diagrams for explaining
related arts of the present invention; and
[0024] FIG. 7 sets forth a schematic view showing a configuration of a
conventional general single-wafer heat-treating apparatus.
[0025] Hereinafter, there will be described heat-treating apparatus in
accordance with preferred embodiments of the present invention with
[0026] First, there will be a first preferred embodiment of the present
invention with reference to FIGS. 1 to 3. FIG. 1 provides a cross
sectional view showing a configuration of a heat-treating apparatus in
FIG. 2 illustrates a magnified sectional view showing a support column
and its neighboring members depicted in FIG. 1; and FIG. 3 describes a
magnified plan view showing the support column depicted in FIG. 1.
Herein, a case of forming a polysilicon film by using a CVD method
exemplifies a heat treatment.
[0027] A heat-treating apparatus 20 has an evacuatable cylindrical
processing chamber 22 which is made of, e.g., aluminum. A shower head 24
serving as a gas feeding unit for introducing a necessary processing gas
into the processing chamber 22, e.g., a shower head 24, is airtightly
installed via a sealing member 26 such as an O-ring in a ceiling portion
of the processing chamber 22. A plurality of gas injection holes 28 is
provided on a lower surface of the shower head 24, and a processing gas
is supplied into a processing space S through the gas injection holes 28.
In an illustrated embodiment, a silane gas (SiH.sub.4), a H.sub.2 gas and
a N.sub.2 gas (a carrier gas) are used as a processing gas.
[0028] Further, referring to FIG. 1 in which the shower head 24 is
simplified, it may look like as if all processing gases are mixed in the
shower head 24 and then supplied into the processing space S. However,
the shower head 24 may be configured to be suitable for a gas feeding
method called as a so-called post-mix method. In this case, a plurality
of divided rooms is provided in the shower head 24, so that different
gases are introduced into respective rooms and those gases are mixed for
the first time when injected into the processing space S from the shower
head 24. In this embodiment, practically, a silane gas, which is supplied
into the shower head 24 together with a carrier gas, is diffused
separately from a H.sub.2 gas in the shower head 24, and the silane gas
and the H.sub.2 gas are mingled after being injected into the processing
[0029] Disposed on a sidewall of the processing chamber 22 is a gate valve
30 to be opened and closed when a semiconductor wafer W serving as an
object to be processed is loaded or unloaded into or from the processing
chamber 22. A plurality of gas exhaust ports 34 is formed in a
circumferential portion of a bottom wall 32 of the processing chamber 22.
Plural lines 36, each having a relatively large-diameter, are connected
to the gas exhaust ports 34, respectively, and those lines 36 constitute
parts of a vacuum exhaust system 38 in which a vacuum pump 22 is
installed. Consequently, an atmosphere in the processing chamber 22 can
be exhausted to vacuum approximately uniformly. An opening 40 of a large
diameter is formed in a central portion of the bottom wall 32 of the
processing chamber 22, and a transmission window 42 having a sufficient
pressure resistance to withstand against inside pressure is airtightly
installed at the opening 40 via a sealing member 44 such as an O-ring.
The transmission window 42 is made of transparent quartz, for example.
[0030] A lamp housing 46 provided underneath the transmission window 42 is
installed to cover the transmission window 42. A heating lamp unit 48 for
heating the wafer W is installed in the lamp housing 46. In the
illustrated embodiment, the heating lamp unit 48 includes a lamp mount 50
serving as a reflective plate and a plurality of heating lamps 52 mounted
on the lamp mount 50. The lamp mount 50 is connected to a rotation axis
of a motor 54 and the heating lamps 52 irradiate heat rays toward the
[0031] A cylindrical support column 56 is installed on the bottom wall 32
of the processing chamber 22 and extended upward therefrom. A placement
table 58 of a thin plate shape is supported on a top portion of the
support column 56 and the semiconductor wafer W is mounted on an upper
surface of the placement table 58. In the illustrated embodiment, the
placement table 58 is a circular plate made of black graphite, on which a
gray SiC coating is performed. In particular, as specifically shown in
FIG. 2, an annular base plate 60 is mounted on an upper surface of the
bottom wall 32 of the processing chamber 22 to surround the opening 40
and the cylindrical support column 56 is made to stand up on the base
plate 60. In the illustrated embodiment, the base plate 60 is made of
aluminum and the support column 56 is made of transparent quartz.
[0032] The cylindrical support column 56 has a specified thickness, e.g.,
about 9.5 mm. A top portion of the support column 56 has an inner
circumferential portion, an outer circumferential portion and an
intermediate circumferential portion interposed therebetween. The inner
circumferential portion of the top portion of the support column 56 is
formed to have a higher height than the outer and the intermediate
circumferential portion, whereby an upper surface of the inner
circumferential portion serves as an annular supporting surface 62, which
is in contact with a lower surface of a circumferential portion of the
placement table 58 to support the placement table 58. Both the supporting
surface 62 and the lower surface of the circumferential portion of the
placement table 58 are mirror finished to thereby provide an airtight,
uniform contact with each other. A width of the supporting surface 62 is
about 2.7 mm, for example.
[0033] The intermediate circumferential portion of the top portion of the
support column 56 is formed to have a lower height than the inner and the
outer circumferential portion, whereby an annular purge gas groove 64
surrounded by the inner and the outer circumferential portion is provided
in the intermediate circumferential portion. The purge gas groove 64 has
a width of about 2.2 mm and a depth of about 2.0 mm. On a lower surface
of the purge gas groove 64, i.e., an upper surface of the intermediate
circumferential portion, a plurality of gas holes 64A are formed at
specified intervals in a circumferential direction. Connected to the gas
holes 64A are purge gas introduction passages 66 serving as a first purge
gas feeding unit, respectively. The purge gas introduction passages 66
are extended vertically inside the support column 56, respectively, and
lower portions thereof pass through the base plate 60 and the bottom wall
32. A purge gas whose flow rate is controlled is supplied from a gas
source (not shown) thereto. A N.sub.2 gas or a nonreactive gas such as an
Ar gas can be used as the purge gas, and a N.sub.2 gas is used in the
[0034] Further, an upper surface of the outer circumferential portion of
the support column 56 is lower than the upper surface of the inner
circumferential portion, i.e., the supporting surface 62, whereby a very
narrow gap 68 is formed between an upper surface 70 of the outer
circumferential portion of the support column 56 and a lower surface of
the circumferential portion of the placement table 58. The gap 68 has a
width L1 of, e.g., a few to several tens of .mu.m and a depth L2 of,
e.g., about 4.6 mm in a diametrical direction. The gap 68 provides a
narrow flow path (hereinafter, referred to as "narrow flow path 68") for
discharging the purge gas supplied into the purge gas groove 64 to the
outside. The narrow flow path 68 is extended in a ring shape along a
periphery of the support column 56. The narrow flow path 68 can be formed
such that the upper surface 70 is a few to several tens of .mu.m lower
than the supporting surface 62 by performing a cutting off or a blast
processing on the upper surface 70 of the outer circumferential portion
of the support column 56.
[0035] A light blocking member 72 is installed all over an outer
circumferential surface of the support column 56. The light blocking
member 72 blocks the heat rays emitted from heating lamps 52 to prevent
the heat rays from leaking out. Thus, parts disposed outside the light
blocking member 72 are protected from heat. The light blocking member 72
can be formed of a light absorptive material made of black or gray
ceramic. Additionally, a light reflective material such as aluminum can
be used for the light blocking member 72 to improve a heating efficiency
[0036] A cylindrical pressing member 74 for pressing the placement table
58 toward the support column 56 is installed outside the support column
56 at a specified interval. The pressing member 74 is formed of a low
thermal conductive material, e.g., quartz, and an annular pressing
portion 74A is installed at a top end thereof. A lower surface of an
inner circumferential portion of the pressing portion 74A is in contact
with an upper surface of the circumferential portion of the placement
table 58, whereby the placement table 58 is pressurized and fixed on the
support column 56.
[0037] An annular stepped portion 76 is provided on an upper surface of
the circumferential portion of the placement table 58 to accommodate the
pressing portion 74A. Thus, a central upper surface of the placement
table 58 and an upper surface of the pressing portion 74A are positioned
on a same horizontal plane, whereby no turbulent flow is generated in a
flow of the processing gas.
[0038] An annular flange portion 74B is formed in a lower portion of the
pressing member 74. The flange portion 74B is attached to the base plate
60 via plural bolts 78 provided at equal intervals along a periphery of
flange portion 74B and resilient members, e.g., coil springs 80,
respectively stuck on the bolts 78 such that it can move upward while
being pressured downward by the coil springs 80. The bolts 78 and coil
springs 80 are made of high corrosion resistant material, e.g., Inconel
(a registered trademark).
[0039] There is a small gap between a lower surface of the flange portion
74B and an upper surface of the base plate 60. Accordingly, a cylindrical
gap (having a width L3 of, e.g., about 0.3 mm) formed between an outer
circumferential surface of the cylindrical support column 56 and an inner
circumferential surface of the cylindrical pressing member 74 can be used
as a purge gas discharge flow path 82. A purge gas discharged from the
above-mentioned narrow flow path 68 flows downward along the purge gas
discharge flow path 82, and then it is discharged out through the gap
between a lower surface of the flange portion 74B and an upper surface of
the base plate 60.
[0040] Further, a purge gas introduction passage 84 serving as a second
purge gas feeding unit is formed such that it passes through the bottom
wall 32 of the processing chamber 22 and the base plate 60. The purge gas
whose flow rate is controlled can be introduced into a space S1 under the
placement table 58 inside the cylindrical support column 56 from a gas
source (not shown) through the purge gas introduction passage 84. For
example, a N.sub.2 gas or a nonreactive gas such as an Ar gas can be used
as the purge gas, and a N.sub.2 gas is used in the present embodiment.
[0041] A cylindrical flow path forming member 86 is disposed on the base
plate 60 and separated inwardly by a gap of a specified width from the
support column 56, whereby a cylindrical purge gas outlet passage 88 is
formed between an outer circumferential surface of the flow path forming
member 86 and an inner circumferential surface of the support column 56
disposed at an outside thereof. A top end of the flow path forming member
86 is separated slightly from the placement table 58, and the purge gas
supplied in the space S1 under the placement table 58 flows into the
purge gas outlet passage 88 from a top end thereof and flows down
therethrough. The flow path forming member 86 is formed of a heat
resistant material, e.g., transparent quartz. A width L4 of the purge gas
outlet passage 88 is about 1.0 mm, for example.
[0042] A plurality of, e.g., four (see FIG. 3), gas holes 90 are formed at
approximately equal intervals in a bottom portion of the purge gas outlet
passage 88, i.e., on an upper surface of the base plate 60 in a
circumferential direction thereof. Connected to the gas holes 90 are
purge gas passages 92 passing through the bottom wall 32 of the
processing chamber 22 and the base plate 60 and communicating with the
lines 36 of the vacuum exhaust system 38. The purge gas passages 92
respectively include through holes (through paths) 94 which penetrate the
base plate 60 and the bottom wall 32; outlets 94A of the through holes
94; and outer attached lines 96 which are, for example, stainless lines
connected to openings 36A disposed on sidewalls of the lines 36. The
outer attached line 96 is set to have a length equal to or longer than,
e.g., about 30 cm, that is long enough to prevent an unreacted processing
gas flowing in the line 36 from entering into the space S1 under the
placement table 58 even if the unreacted processing gas is diffused in
the outer attached line 96 in a reverse direction to the purge gas flow.
Further, a proper length of the outer attached line 96 depends on an
inner diameter of the outer attached line 96.
[0043] Disposed in a circumferential portion of the base plate 60 is a
cooling jacket 98 for cooling the base plate 60 by circulating a coolant
such as cooling water along a periphery of the base plate 60. Further,
installed in an outer periphery of the pressing member 74 is a lifting
mechanism (not shown) for elevating the wafer W while supporting the
lower surface of the circumferential portion of the wafer W when
transferring the wafer W or mounting it on the placement table 58.
[0044] Hereinafter, there will be explained an operation of the
heat-treating apparatus.
[0045] First, an unprocessed semiconductor wafer W is introduced into the
processing chamber 22 through an opened gate valve 30 and mounted on the
placement table 58. Then, after sealing the processing chamber 22, the
heat rays are irradiated on the lower surface of the placement table 58
by turning on the heating lamps 52 of the heating lamp unit 48, whereby a
temperature of the wafer W mounted on the upper surface of the placement
table 58 is raised to a specified processing temperature, e.g.,
700.degree. C., and the specified temperature is maintained.
[0046] At the same time, a SiH.sub.4 gas, a H.sub.2 gas and a N.sub.2 gas
serving as a processing gas are supplied into the processing space S in
the processing chamber 22 from the shower head 24. The SiH.sub.4 gas and
the H.sub.2 gas have a pyrolysis reaction to thereby deposit a
polysilicon film on the surface of the wafer W. Since the processing
chamber 22 is exhausted to vacuum, various unreacted gases and a reaction
by-product gas flow down from the periphery of the placement table 58
approximately uniformly, and then flow into the lines 36 of the vacuum
exhaust system 38 through the gas exhaust port 34 to be discharged
outside. Under such a condition, if there is a small gap, the SiH.sub.4
gas and the H.sub.2 gas having a very large diffusion coefficient enter
into the space S1 under the placement table 58 through the gap, whereby
an unnecessary film may be deposited on the lower surface of the
placement table 58 or the upper surface of the transmission window 42.
[0047] However, in the present embodiment, a N.sub.2 gas serving as a
purge gas is supplied into the space S1 through the purge gas
introduction passage 84 and, further, into the top portion of the support
column 56 through the purge gas introduction passages 66. Therefore, the
SiH.sub.4 gas and the H.sub.2 gas can be prevented from entering into the
space S1. As shown in FIG. 2, the purge gas supplied in the space S1 from
the purge gas introduction passage 84 moves up in the space S1 and
changes its direction in proximity to the lower surface of the placement
table 58 as indicated by an arrow 100 to flow down in the purge gas
outlet passage 88. Further, the purge gas passes through the purge gas
passages 92 including the through paths 94 and the outer attached lines
96 and flows into vacuum exhausted lines 36. Thereafter, the purge gas
and gases issued from the processing space S flow together in the lines
36 to be discharged outside the system.
[0048] At this time, an unreacted SiH.sub.4 gas or an unreacted H.sub.2
gas flowing in the lines 36 may enter into the space S1 by diffusing in
the outer attached lines 96, the through paths 94 and the purge gas
outlet passages 88 in a reverse direction to the purge gas. However, the
lines 36 are strongly exhausted to vacuum by a vacuum pump (not shown).
Accordingly, the SiH.sub.4 gas or the H.sub.2 gas hardly enters into the
purge gas passages 92. Further, the length of the outer attached lines 96
is, e.g., about 30 cm that is sufficiently long. Furthermore, since the
flow path forming member 86 is shaped as a cylinder with the
approximately same height as the support column 56, the vertical length
of the purge gas outlet passage 88 formed outside the flow path forming
member 86 is also long. Consequently, even if the SiH.sub.4 gas or the
H.sub.2 gas can enter into the purge gas passages 92, it cannot reach the
space S1. Further, a flow rate of the purge gas supplied through the
purge gas introduction passage 84 is, e.g., about 1000 sccm, but it is
[0049] Further, the SiH.sub.4 gas and the H.sub.2 gas in the processing
space S may diffuse into the purge gas discharge flow path 82 in the
reverse direction to the purge gas flow to thereby enter into the space
S1 under the placement table 58 through the gap between the supporting
surface 62 and the lower surface of the placement table 58. But, the
purge gas made of N.sub.2 gas is supplied into the purge gas groove 64
formed at the top portion of the support column 56 through the purge gas
introduction passages 66 and diffuses in the purge gas groove 64 in a
circumferential direction. After passing through the narrow flow path 68,
the purge gas is issued into the purge gas discharge flow path 82 and
flows down therein. At a lower portion of the purge gas discharge flow
path 82, the purge gas arrives at the gas exhaust port 34 through a gap
between the base plate 60 and the flange portion 74B of the pressing
member 74 and then is discharged outside the system via the lines 36 of
the vacuum exhaust system 38. At this time, since a vertical width L1 of
the narrow flow path 68 is very small, i.e., a few to several tens of
.mu.m, a flow speed of the purge gas flowing outward in the narrow flow
path 68 becomes very high. Accordingly, the SiH.sub.4 gas and the H.sub.2
gas are certainly prevented from diffusing in the reverse direction to
the purge gas flow and entering into the space S1. Further, since the
pressing member 74 is shaped as a cylinder with the approximately same
height as the support column 56, the vertical length of the purge gas
discharge flow path 82 formed inside the pressing member 74 is also long.
Consequently, it is possible to prevent the SiH.sub.4 gas and the H.sub.2
gas from diffusing up to the top portion of the purge gas discharge flow
path 82.
[0050] Further, both the supporting surface 62 of the support column 56
and the lower surface of the placement table 58 in contact therewith are
mirror finished, so that they are in a surface contact approximately
uniformly in a circumferential direction without a gap. Therefore, even
if the SiH.sub.4 gas and the H.sub.2 gas enter into the purge gas groove
64 through the narrow flow path 68, it is possible to prevent them from
entering into the space S1 under the placement table 58. Further, the
purge gas supplied into the space S1 can be prevented from locally
leaking from a gap between the supporting surface 62 of the support
column 56 and the lower surface of the placement table 58 in contact
therewith. Thus, a local cooling of the placement table 58 caused by a
local leakage of the purge gas does not occur to thereby increase
in-surface uniformity of temperature in the placement table 58 and the
wafer W. Further, the flow rate of the purge gas supplied through the
purge gas introduction passages 66 is, e.g., about 500 to 1000 sccm, but
it is not limited thereto. Furthermore, even if the SiH.sub.4 gas and the
H.sub.2 gas enter the space S1 through the gap between the supporting
surface 62 of the support column 56 and the lower surface of the
placement table 58 in contact therewith, since there exists an air flow
100 of the purge gas flowing along the purge gas outlet passage 88 in
proximity of the supporting surface 62, the gases are immediately
discharged along with the air flow 100.
[0051] In the conventional heat-treating apparatus, when a pressure in the
space under the placement table is increased by supplying purge gas
thereto at a high flow rate, a high pressure is applied to the whole
placement table to thereby make it possible to damage the placement
table. However, in the present embodiment, even though a purge gas flows
at a high flow rate through the purge gas introduction passages 66, a
high pressure is exerted only to a small-area portion defining the narrow
flow path 68 and there is no possibility of damaging the placement table
58. Therefore, as long as there is no problem in temperature distribution
of the placement table 58, a flow rate of purge gas supplied from the
purge gas introduction passages 66 can be increased, whereby the
SiH.sub.4 gas and the H.sub.2 gas can be definitely prevented from
entering into the space S1 under the placement table 58.
[0052] Further, the circumferential portion of the placement table 58 is
maintained by the pressing portion 74A of the pressing member 74 which is
made of a low heat conductive material such as quartz to thereby reduce
an amount of heat lost through the pressing portion 74A from the
circumferential portion of the placement table 58. Thus, there is no bad
influence on the in-surface uniformity of temperature of the wafer W.
[0053] Additionally, when a large upward force is applied to the placement
table 58 by a pressure unexpectedly abnormally decreased in the
processing space S or a pressure accidentally increased in the space S1
under the placement table 58, the placement table 58 and the pressing
member 74 for fastening the placement table 58 temporarily rise against a
spring force of the coil springs 80 for fixing the lower portion of the
pressing member 74. Accordingly, a pressure difference between the space
S1 and the processing space S can be reduced to thereby prevent the
placement table 58 from being damaged.
[0054] Hereinafter, there will be described a second preferred embodiment
of the present invention with reference to FIGS. 4 and 5. FIG. 4 offers a
magnified sectional view showing a support column and neighboring members
invention; and FIG. 5 presents a plan view showing the support column in
accordance with the second preferred embodiment. In FIGS. 4 and 5, parts
having the same functions as the parts shown in FIGS. 1 to 3 will be
assigned like reference numerals, and description thereof will be
[0055] The upper surface 70 of the outer circumferential portion of the
support column 56, for defining the narrow flow path 68, is flat in the
above-mentioned first preferred embodiment (see FIG. 2), whereas an
annular labyrinth groove 110 extending in a circumferential direction is
formed at an approximately central portion of an upper surface 70 in the
[0056] A depth and a width of the labyrinth groove 110 are about 2.0 mm
and 1.0 mm, respectively. Only one labyrinth groove 110 is provided in
the illustrated embodiment, but a plurality of labyrinth grooves may be
provided in a concentric circular shape. Even if a SiH.sub.4 gas and a
H.sub.2 gas enter into the narrow flow path 68 by diffusing in the purge
gas discharge flow path 82 outside the narrow flow path 68 in a reverse
direction to the purge gas flow, the labyrinth groove 110 disposed in the
narrow flow path 68 allows the SiH.sub.4 gas and the H.sub.2 gas to stay
in the labyrinth groove 110 to thereby prevent them from diffusing into
the purge gas groove 64. Thus, such a configuration can certainly prevent
the gases from entering the space S1 under the lower surface.
[0057] Further, though there is described an exemplary case of forming the
polysilicon film as a heat treatment in the above-mentioned preferred
embodiments, the present invention can be applied to heat-treating
apparatuses for performing another heat treatment, for example, a heat
treatment for forming another kind of film and a heat treatment such as
an oxidation/diffusion process and a modification process in addition to
a film forming process, without being limited thereto. Further, an object
to be processed by the heat-treating apparatus is not limited to a
semiconductor wafer and may be an LCD substrate, a glass substrate, and
[0058] Hereinafter, there will be described related arts of the present
invention with reference to FIGS. 6A and 6B.
[0059] FIG. 6A depicts a conventional arrangement of the medium passage
122, provided in a part 120 such that the heat-treating apparatus cools
or heats the part 120. An exit side end portion of the medium passage 122
is linearly extended outwardly from a central portion of the part 120 in
a radial direction. Meanwhile, the medium passage 122 starts from an
entrance side end portion of a circumferential portion of the part 120;
is extended counter-clockwise in a circumferential direction; after
changing a direction thereof near to an exit side end portion, is
extended inwardly in a radial direction; is extended clockwise in a
circumferential direction; after changing a direction thereof near to the
exit side end portion, is extended inwardly in a radial direction; is
extended counter-clockwise in a circumferential direction; and is
repeatedly extended likewise to thereby reach the central portion of the
part 120. A heat medium flows around in the medium passage 122 starting
from the circumferential portion of the part 120 and gradually approaches
the central portion. After reaching the central portion, the heat medium
is discharged outwardly in a radial direction. Further, there is a part
in which the heat medium flows in a reverse direction.
[0060] In such a manner of heat medium flow, there is generated heat
distribution due to a large temperature difference between portions where
the heat medium flows at the beginning and afterwards, that is, the
circumferential portion and the central portion of the part 120 in this
case. Consequently, the part 120 cannot be heated or cooled with a
sufficiently uniform in-surface temperature.
[0061] A medium passage improved to overcome such a drawback, is
represented in FIG. 6B. A medium passage 126 provided in a part 124
starts from an entrance side end portion of a circumferential portion of
the part 124; is spirally extended counter-clockwise to a central portion
thereof; is inverted after reaching the central portion; and is spirally
extended clockwise to the circumferential portion.
[0062] In the medium passage 126 thus formed, a heat medium (a cooling
medium or a heating medium) flows spirally from the circumferential
portion to the central portion. Then, reversely, the heat medium flows
spirally from the central portion to the circumferential portion.
Therefore, the part 124 can be cooled or heated with a sufficiently
uniform in-surface temperature.
[0063] The part 124 can become a part that needs to be cooled or heated as
one used in a semiconductor wafer heat-treating apparatus, a plasma
processing apparatus or the like, for example, a shower head or a bottom
portion of a processing chamber.
[0064] While the invention has been shown and described with respect to
art that various changes and modifications may be without departing from
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