U.S. patent application number 10/267127 was filed with the patent office on 2003-05-01 for heat treating apparatus and method.
This patent application is currently assigned to Dainippon Screen Mfg. Co., Ltd.. Invention is credited to Kusuda, Tatsufumi.
Application Number | 20030081945 10/267127 |
Document ID | / |
Family ID | 19145982 |
Filed Date | 2003-05-01 |
United States Patent
Application |
20030081945 |
Kind Code |
A1 |
Kusuda, Tatsufumi |
May 1, 2003 |
Heat treating apparatus and method
Abstract
A heat treating apparatus for heat treating a substrate by
irradiating the substrate with light includes a heat treating
chamber for receiving the substrate, a heating plate for preheating
the substrate through a thermal diffuser plate, xenon flashlamps
for heating the substrate preheated by the heating plate, to a
treating temperature by irradiating the substrate with flashes of
light, and a decompression mechanism for decompressing the heat
treating chamber when the xenon flashlamps heat the substrate.
Inventors: |
Kusuda, Tatsufumi; (Kyoto,
JP) |
Correspondence
Address: |
OSTROLENK FABER GERB & SOFFEN
1180 AVENUE OF THE AMERICAS
NEW YORK
NY
100368403
|
Assignee: |
Dainippon Screen Mfg. Co.,
Ltd.
|
Family ID: |
19145982 |
Appl. No.: |
10/267127 |
Filed: |
October 7, 2002 |
Current U.S.
Class: |
392/416 ;
257/E21.324 |
Current CPC
Class: |
C30B 31/12 20130101;
H01L 21/67115 20130101; H01L 21/324 20130101 |
Class at
Publication: |
392/416 |
International
Class: |
A21B 002/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 29, 2001 |
JP |
2001-330230 |
Claims
What is claimed is:
1. A heat treating apparatus for heat treating a substrate by
irradiating the substrate with light, comprising: a heat treating
chamber for receiving the substrate; assist heating means for
preheating the substrate; flash heating means for heating the
substrate preheated by said assist heating means, to a treating
temperature by irradiating the substrate with flashes of light; and
decompression means for decompressing said heat treating chamber
when said flash heating means heats the substrate.
2. A heat treating apparatus as defined in claim 1, wherein said
flash heating means comprises xenon flashlamps.
3. A heat treating apparatus as defined in claim 1, wherein said
decompression means is arranged to decompress said heat treating
chamber to {fraction (1/10)} to {fraction (1/1000)} atmospheric
pressure.
4. A heat treating apparatus as defined in claim 3, wherein said
assist heating means is arranged to preheat the substrate to 200 to
600 degrees centigrade.
5. A heat treating apparatus as defined in claim 3, wherein said
flash heating means is arranged to heat the substrate to 1,000 to
1,100 degrees centigrade.
6. A heat treating apparatus as defined in claim 3, wherein said
flash heating means is arranged to heat the substrate to the
treating temperature in 0.1 to 10 milliseconds.
7. A heat treating method for heat treating a substrate by
irradiating the substrate with light, comprising: a substrate
loading step for loading the substrate into a heat treating
chamber; a preheating step for preheating the substrate loaded into
said heat treating chamber; a decompressing step for decompressing
said heat treating chamber; a flash heating step for heating the
substrate to a treating temperature by irradiating the substrate
with flashes of light after the substrate in said heat treating
chamber is preheated to a predetermined preheat temperature; an
opening step for opening said heat treating chamber to atmosphere;
and a substrate unloading step for unloading the substrate from
said heat treating chamber.
8. A heat treating method as defined in claim 7, wherein said flash
heating step is executed to heat the substrate to the treating
temperature by irradiating the substrate with flashes of light
immediately after the substrate in said heat treating chamber is
preheated to the predetermined preheat temperature.
9. A heat treating method as defined in claim 8, wherein said
decompressing step is executed to decompress said heat treating
chamber to {fraction (1/10)} to {fraction (1/1000)} atmospheric
pressure.
10. A heat treating method as defined in claim 9, wherein said
preheating step is executed to preheat the substrate to 200 to 600
degrees centigrade.
11. A heat treating method as defined in claim 9, wherein said
flash heating step is executed to heat the substrate to 1,000 to
1,100 degrees centigrade.
12. A heat treating method as defined in claim 9, wherein said
flash heating step is executed to heat the substrate to the
treating temperature in 0.1 to 10 milliseconds.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a heat treating apparatus
and method for heat treating substrates such as semiconductor
wafers by irradiating the substrates with light.
[0003] 2. Description of the Related Art
[0004] A heat treating apparatus such as a lamp annealing apparatus
with halogen lamps is used to execute a step of activating ions
implanted in a semiconductor wafer. Such a heat treating apparatus
activates ions in the semiconductor wafer by heating the wafer to a
temperature of about 1,000 to 1,100 deg C., for example. Then, the
heat treating apparatus heats the wafer at a rate of some several
hundred degrees per second by using the energy of light emitted
from the halogen lamps.
[0005] However, it has been found that, even when ions in the
semiconductor wafer are activated by using the heat treating
apparatus that heats the wafer at the rate of several hundred
degrees per second, the ions implanted in the semiconductor wafer
present a blunt profile, that is the ions become dispersed. When
such a phenomenon occurs, the ions become dispersed even though
implanted in high concentration into the surface of the
semiconductor wafer, and hence a problem of having to implant the
ions in a larger amount than is necessary.
[0006] To solve the above problem, it is conceivable to use xenon
flashlamps, for example, to irradiate the surface of the
semiconductor wafer with flashes, thereby to heat, within an
extremely short time, only the surface of the semiconductor wafer
implanted with ions. However, although the surface of the
semiconductor wafer may be heated very quickly by using xenon
flashlamps, the wafer is heated only to 500 degrees or thereabouts.
It is impossible to heat the semiconductor wafer to the temperature
of about 1,000 to 1,100 deg C. necessary for activating the ions in
the wafer.
[0007] On the other hand, Japanese Patent Publication (Unexamined)
No. 2001-237195, by way of addressing the above problem, discloses
a heat treating apparatus having a preheating device for preheating
a substrate before heating the substrate by xenon flashlamps.
[0008] With such a heat treating apparatus, flashes from the xenon
flashlamps may cause a reaction of the gas in the heat treating
chamber storing the semiconductor wafer. Where, for example, oxygen
is present in the gas, ozone is momentarily generated from the
oxygen to lower the pressure in the heat treating chamber in an
instant. Such a sudden pressure drop produces a relatively loud
sound, i.e. vibration. This vibration scatters particles in the
heat treating chamber, and hence a problem of the particles
adhering to the semiconductor wafer under heat treatment. In an
extreme case, the vibration could move the semiconductor wafer.
[0009] The gas in the heat treating chamber circulates therein by
convection. It is therefore difficult to heat the surface of the
semiconductor wafer uniformly in time of preheating by the
preheating device or flash heating by the xenon flashlamps.
[0010] Further, the above heat treating apparatus has numerous
materials for sealing the heat treating chamber or maintaining the
chamber at a high temperature. Where oxygen is present in the heat
treating chamber, these materials are oxidized in time of flash
heating by the xenon flashlamps, thereby shortening the service
life of the heat treating chamber. Where the gas in the heat
treating chamber contains organic substances, these substances
become melanized and adhere to a translucent plate forming the heat
treating chamber, to reduce the life of the heat treating
chamber.
SUMMARY OF THE INVENTION
[0011] The object of the present invention, therefore, is to
provide a heat treating apparatus and method for treating
semiconductor wafers uniformly and cleanly without reducing the
life of the apparatus.
[0012] The above object is fulfilled, according to the present
invention, by a heat treating apparatus for heat treating a
substrate by irradiating the substrate with light, comprising a
heat treating chamber for receiving the substrate, an assist
heating device for preheating the substrate, a flash heating device
for heating the substrate preheated by the assist heating device,
to a treating temperature by irradiating the substrate with flashes
of light, and a decompression device for decompressing the heat
treating chamber when the flash heating device heats the
substrate.
[0013] This heat treating apparatus is free from a reaction of the
gas in the heat treating chamber which could scatter particles and
move the substrate. By decompressing the heat treating chamber, no
convection occurs in the heat treating chamber. Consequently, the
surface of the substrate may be heated uniformly. Further, the
decompression of the heat treating chamber is effective to avoid a
reduction in the life of the heat treating apparatus due to
oxidation of the materials forming the heat treating chamber or
melanization of organic substances.
[0014] In another aspect of the invention, there is provided a heat
treating method for heat treating a substrate by irradiating the
substrate with light. This method comprises a substrate loading
step for loading the substrate into a heat treating chamber, a
preheating step for preheating the substrate loaded into the heat
treating chamber, a decompressing step for decompressing the heat
treating chamber, a flash heating step for heating the substrate to
a treating temperature by irradiating the substrate with flashes of
light after the substrate in the heat treating chamber is preheated
to a predetermined preheat temperature, an opening step for opening
the heat treating chamber to atmosphere, and a substrate unloading
step for unloading the substrate from the heat treating
chamber.
[0015] Preferably, the flash heating step is executed to heat the
substrate to the treating temperature by irradiating the substrate
with flashes of light immediately after the substrate in the heat
treating chamber is preheated to the predetermined preheat
temperature. With this method, even when the heat treating chamber
is in a decompressed state, the flash heating step may be executed
for the substrate having reached the preheat temperature.
[0016] Other features and advantages of the present invention will
be apparent from the following detailed description of the
embodiment of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] For the purpose of illustrating the invention, there are
shown in the drawings several forms which are presently preferred,
it being understood, however, that the invention is not limited to
the precise arrangement and instrumentalities shown.
[0018] FIG. 1 is a sectional side view of a heat treating apparatus
according to the invention;
[0019] FIG. 2 is a sectional side view of the heat treating
apparatus;
[0020] FIG. 3 is a schematic plan view of the heat treating
apparatus;
[0021] FIG. 4 is an enlarged side view of a portion of a thermal
diffuser plate;
[0022] FIG. 5 is a flow chart showing a semiconductor wafer heat
treating operation of the heat treating apparatus according to the
invention; and
[0023] FIG. 6 is a graph showing changes in the temperature of the
semiconductor wafer.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] An embodiment of the present invention will be described
hereinafter with reference to the drawings. FIGS. 1 and 2 are
sectional side views of a heat treating apparatus according to the
invention. FIG. 3 is a schematic plan view of the apparatus.
[0025] This heat treating apparatus includes a heat treating
chamber 65 having a translucent plate 61, a bottom plate 62 and a
pair of side plates 63 and 64 for receiving and heat treating a
semiconductor wafer W. The translucent plate 61 acting as part of
the heat treating chamber 65 is formed of an infrared transmitting
material such as quartz. The bottom plate 62 acting as part of the
heat treating chamber 65 has support pins 70 erected thereon and
extending through a thermal diffuser plate 73 and a heating plate
74 to be described hereinafter, for supporting the semiconductor
wafer W at the lower surface thereof.
[0026] The side plate 64 acting as part of the heat treating
chamber 65 defines an opening 66 for loading and unloading the
semiconductor wafer W. The opening 66 is closable by a gate valve
68 pivotable about an axis 67. With the opening 66 opened, the
semiconductor wafer W is loaded into the heat treating chamber 65
by a transport robot not shown.
[0027] A plurality of (21 in this embodiment) cylindrical xenon
flashlamps 69 are arranged parallel to one another above the heat
treating chamber 65. A reflector 71 is disposed above the xenon
flashlamps 69.
[0028] Each xenon flashlamp 69 includes a glass tube filled with
xenon gas and having an anode and a cathode disposed at opposite
ends thereof and connected to a capacitor, and a trigger electrode
wound around the glass tube. Since xenon gas is an electrical
insulator, electricity does not flow through the glass tube in a
normal state. However, when the insulation is broken by applying a
high voltage to the trigger electrode, electricity stored in the
capacitor flows through the glass tube. This generates Joule heat
which heats the xenon gas, thereby emitting light. In the xenon
flashlamps 69, electrostatic energy stored is converted into
extremely short light pulses of 0.1 to 10 milliseconds. Thus, the
xenon flashlamps 69 are characterized by their capability of
emitting extremely strong light compared with continuously lit
light sources.
[0029] A light diffuser plate 72 is disposed between the xenon
flashlamps 69 and translucent plate 61. The light diffuser plate 72
is formed of quartz glass which is an infrared transmitting
material with surfaces thereof given light diffusion treatment.
[0030] The heat treating chamber 65 has the thermal diffuser plate
73 and heating plate 74 arranged in the stated order therein. The
thermal diffuser plate 73 has pins 75 provided on the upper surface
thereof for holding the semiconductor wafer W against
displacement.
[0031] The heating plate 74 is provided for preheating the
semiconductor wafer W. This heating plate 74 is formed of white
aluminum nitride. The heating plate 74 contains a heater and a
sensor for controlling the heater. The heating plate 74 need not be
formed entirely of white aluminum nitride, but only the surface
thereof opposed to the thermal diffuser plate 73 may be formed of
white aluminum nitride.
[0032] With white aluminum nitride used for forming the surface of
the heating plate 74 opposed to the thermal diffuser plate 73 as
noted above, the heating plate 74 is prevented from burning in time
of flash exposure described hereinafter. However, the heating plate
74 may be formed of non-white aluminum nitride or silicon carbide
(SiC).
[0033] The thermal diffuser plate 73 is provided for diffusing
thermal energy from the heating plate 74 to heat the semiconductor
wafer W uniformly. The thermal diffuser plate 73 is formed of a
material having a smaller coefficient of thermal conductivity than
the heating plate 74.
[0034] Specifically, the thermal diffuser plate 73 may be formed of
quartz which has a moderate coefficient of thermal conductivity and
which never contaminates the semiconductor wafer W. Instead of
quartz, sapphire which is an aluminum oxide may be used.
[0035] FIG. 4 is an enlarged side view of a portion of the thermal
diffuser plate 73.
[0036] As shown in FIG. 4, the thermal diffuser plate 73 has a
recess 90 formed in the surface thereof to have a shape
corresponding to the outside diameter of semiconductor wafer W. The
recess 90 has a depth substantially corresponding to the thickness
of wafer W, and this depth is not depicted in FIGS. 1 through 3.
The wafer W is positioned in the recess 90 and held against
displacement by the positioning pins 75 noted hereinbefore. The
recess 90 and positioning pins 75 constitute a positioning device
for the wafer W. It is possible to omit either the recess 90 or
positioning pins 75.
[0037] Referring again to FIGS. 1 through 3, the thermal diffuser
plate 73 and heating plate 74 are driven by an air cylinder 76 to
move vertically between a position shown in FIG. 1 for loading and
unloading the semiconductor wafer W, and a position shown in FIG. 2
for heat treating the wafer W.
[0038] The thermal diffuser plate 73 and heating plate 74 are
lowered to the position shown in FIG. 1 for loading and unloading
the semiconductor wafer W. In this position, the transport robot
not shown is used to carry the semiconductor wafer W in through the
opening 66 and place the wafer W on the support pins 70, or to
remove the wafer W from the support pins 70 and carry the wafer W
out through the opening 66. In this state, upper ends of the
support pins 70 extend through bores formed in the thermal diffuser
plate 73 and heating plate 74, and project upward from the surface
of thermal diffuser plate 73. For expediency of description, FIG. 1
shows the bores in the thermal diffuser plate 73 and heating plate
74 which actually are invisible in side view.
[0039] The thermal diffuser plate 73 and heating plate 74 are
raised to the position shown in FIG. 2, in which the two plates 73
and 74 are above the upper ends of support pins 70, for heat
treating the semiconductor wafer W. In this state, the
semiconductor wafer W is raised, with the lower surface thereof
supported by the upper surface of thermal diffuser plate 73, to the
position close to the translucent plate 61.
[0040] Particles may be generated when the thermal diffuser plate
73 and heating plate 74 are moved up and down between the loading
and unloading position and the heat treating position. In order to
prevent such particles from adhering to the semiconductor wafer W,
a bellows 77 is disposed to extend between a support member 80
supporting the heating plate 74 and the bottom plate 62 of heat
treating chamber 65.
[0041] An intake passage 78 is formed in the side wall 63 remote
from the opening 66 of the heat treating chamber 65. This intake
passage 78 is provided to introduce air in time of opening the
chamber 65 to the atmosphere to be described hereinafter. Instead
of air, nitrogen gas or other gas may be introduced.
[0042] The bottom plate 62 of heat treating chamber 65 defines an
exhaust port 79. This exhaust port 79 is connected to a
decompression mechanism such as a vacuum pump through a switch
valve 81. The exhaust port 79 and switch valve 81 constitute the
decompression device of the present invention.
[0043] An operation of the heat treating apparatus for heat
treating the semiconductor wafer W according to the invention will
be described next. FIG. 5 is a flow chart showing the operation for
heat treating the semiconductor wafer W by the heat treating
apparatus according to the invention. FIG. 6 is a graph showing
changes in the temperature of the semiconductor wafer W.
[0044] In this heat treating apparatus, with the thermal diffuser
plate 73 and heating plate 74 lowered to the position shown in FIG.
1 for loading and unloading the semiconductor wafer W, the
transport robot not shown carries the semiconductor wafer W in
through the opening 66 and places the wafer W on the support pins
70. Upon completion of the wafer loading operation, the opening 66
is closed by the gate valve 68 (step S1). Subsequently, the thermal
diffuser plate 73 and heating plate 74 are raised by the air
cylinder 76 to the position shown in FIG. 2 for heat treating the
semiconductor wafer W.
[0045] The thermal diffuser plate 73 and heating plate 74 have been
heated by the heater mounted in the heating plate 74. Thus, with
the thermal diffuser plate 73 and heating plate 74 raised to the
heat treating position shown in FIG. 2, the semiconductor wafer W
is preheated by through contact with the hot thermal diffuser plate
73. The temperature of wafer W gradually increases as shown in FIG.
6 (step S2).
[0046] In this preheating step, the wafer W receives thermal energy
from the heating plate 74 through the thermal diffuser plate 73.
Consequently, the wafer W may be heated uniformly even when the
heating plate 74 has a temperature distribution not entirely
uniform.
[0047] In parallel with the preheating step, the heat treating
chamber 65 is decompressed (step S3). That is, the switch valve 81
is opened to connect the intake passage 78 to the decompression
mechanism not shown, thereby purging and decompressing the heat
treating chamber 65. Preferably, the heat treating chamber 65 is
decompressed to {fraction (1/10)} to {fraction (1/100)} atmospheric
pressure to produce various advantageous effects to be described
hereinafter.
[0048] In this state, the semiconductor wafer W continues to be
heated through the thermal diffuser plate 73. In time of
temperature increase, the surface temperature of semiconductor
wafer W is constantly monitored by a temperature sensor not shown,
to determine whether the surface has reached a preheat temperature
T1 (step S4).
[0049] The preheat temperature T1 is in a range of about 200 to 600
deg C. Even if the semiconductor wafer W is heated to such preheat
temperature T1, the ions implanted in the wafer W remain unchanged,
i.e. are never dispersed.
[0050] Immediately after the surface temperature of semiconductor
wafer W reaches the preheat temperature T1 in FIG. 6, the xenon
flashlamps 69 are lit for flash heating (step S5). The lighting
time of the xenon flashlamps 69 in this flash heating step is about
0.1 to 10 milliseconds. In this way, the electrostatic energy
prestored in the xenon flashlamps 69 is converted into such an
extremely short light pulse. This results in very strong flashes
being emitted.
[0051] In this state, the surface temperature of semiconductor
wafer W reaches temperature T2 in FIG. 6. This temperature T2 is
about 1,000 to 1,100 deg C., i.e. a temperature necessary for
treating the semiconductor wafer W. When the surface of
semiconductor wafer W is heated to this treating temperature T2,
the ions in the wafer W are activated.
[0052] The surface of semiconductor wafer W is heated to the
treating temperature T2 in the extremely short time of about 0.1 to
10 milliseconds. Consequently, the activation of the ions in the
semiconductor wafer W is completed in a short time. This prevents
the ions implanted in the semiconductor wafer W from becoming
dispersed to present a blunt profile.
[0053] As noted above, before lighting the xenon flashlamps 69 to
heat the semiconductor wafer W, the heating plate 74 is used to
raise the surface temperature of semiconductor wafer W to the
preheat temperature T1 of about 200 to 600 deg C. The semiconductor
wafer W may therefore be heated by the xenon flashlamps 21 quickly
to the treating temperature T2 of about 1,000 to 1,100 deg C.
[0054] In this flash heating step, the heating plate 74 is
subjected to rays transmitted through the thermal diffuser plate 73
formed of quartz. However, the heating plate 74 formed of white
aluminum nitride is never burnt.
[0055] The above flash heating step is executed under the
decompressed condition. This step therefore is executed free from a
reaction of the gas in the heat treating chamber 65 which could
scatter particles and move the semiconductor wafer W, as in the
prior art.
[0056] Similarly, by decompressing the heat treating chamber 65, no
convection occurs in the heat treating chamber. Consequently, the
surface of semiconductor wafer W may be heated uniformly in the
preheating step and flash heating step.
[0057] Further, by decompressing the heat treating chamber 65,
oxygen and organic substances may be excluded from the heat
treating chamber 65. This avoids a reduction in the life of the
heat treating apparatus due to oxidation of the materials forming
the heat treating chamber 65 or melanization of organic
substances.
[0058] After the flash heating step, the switch valve 81 is closed
and air is introduced through the intake passage 78 to open the
heat treating chamber 65 to the atmosphere (step S6). The
semiconductor wafer W stops being heated by the heating plate 74
(step S7).
[0059] As noted above, flash heating is carried out immediately
after the surface temperature of semiconductor wafer W reaches the
preheat temperature T1. Upon completion of the flash heating step,
the heat treating chamber 65 is opened to the atmosphere. These
steps are taken for the following reason.
[0060] In the heat treating apparatus according to the invention,
the heating plate 74 is installed in the decompressed heat treating
chamber 65. It is therefore difficult to cool the heating plate 74
and to maintain the heating plate 74 at a desired temperature.
Where this problem is addressed by using a cooling device such as
Peltier elements, the semiconductor wafer W will have reduced
temperature uniformity.
[0061] The heat treating apparatus according to the invention,
therefore, carries out flash heating immediately after the surface
temperature of semiconductor wafer W reaches the preheat
temperature T1, avoiding the flash heating being carried out when
the semiconductor wafer W becomes heated above the preheat
temperature T1. After the flash heating step, the heat treating
chamber 65 is opened to the atmosphere to cool its interior.
Consequently, as shown in FIG. 6, the temperature of semiconductor
wafer W lowers quickly after slightly overshooting (as at H) the
preheat temperature T1.
[0062] After completion of the opening to the atmosphere of the
heat treating chamber 65, the air cylinder 76 lowers the thermal
diffuser plate 73 and heating plate 74 to the position shown in
FIG. 1 for loading and unloading the semiconductor wafer W. The
opening 66 that has been closed by the gate valve 68 is opened. The
transport robot not shown removes the semiconductor wafer W resting
on the support pins 70 and carries the wafer W out of the apparatus
(step S8).
[0063] The above embodiment uses the heating plate 74 as the
preheating device. Instead, lamps such as halogen lamps may be used
as the preheating device.
[0064] The present invention may be embodied in other specific
forms without departing from the spirit or essential attributes
thereof and, accordingly, reference should be made to the appended
claims, rather than to the foregoing specification, as indicating
the scope of the invention.
[0065] This application claims priority benefit under 35 U.S.C.
Section 119 of Japanese Patent Application No. 2001-330230 filed in
the Japanese Patent Office on Oct. 29, 2001, the entire disclosure
of which is incorporated herein by reference.
* * * * *