Microwave heating apparatus and processing method

In the microwave heating apparatus, four microwave introduction ports are arranged at positions spaced apart from each other at an angle of about 90° in a ceiling portion of a processing chamber in such a way that the long sides and the short sides thereof are in parallel to inner surfaces of four sidewalls. The microwave introduction port are disposed in such a way that each of the microwave introduction ports are not overlapped with another microwave introduction port whose long sides are in parallel to the long sides of the corresponding microwave introduction port when the corresponding microwave introduction port is moved in translation in a direction perpendicular to the long sides thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application Nos. 2011-289024 and 2012-179802 filed on Dec. 28, 2011 and Aug. 14, 2012, respectively, the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a microwave heating apparatus for performing a predetermined process by introducing microwaves into a processing chamber and a processing method for heating a target object to be processed by using the microwave heating apparatus.

BACKGROUND OF THE INVENTION

As an LSI device or a memory device is miniaturized, a depth of a diffusion layer in a transistor manufacturing process is decreased. Conventionally, doping atoms implanted into the diffusion layer are activated by a high-speed heating process referred to as an RTA (Rapid Thermal Annealing) using a lamp heater. However, in the RTA process, as the diffusion of the doping atoms progresses, the depth of the diffusion layer exceeds a tolerable range, and this makes the miniaturized design difficult. Since the depth of the diffusion layer is incompletely controlled, the electrical characteristics of devices deteriorate. For example, a problem such as occurrence of leakage current or the like is generated.

Recently, an apparatus using microwaves has been suggested as an apparatus for heating a semiconductor wafer. When doping atoms are activated by microwave heating, a microwave directly acts on the doping atoms. Hence, excessive heating does not occur, and the diffusion of the diffusion layer can be suppressed.

As for the heating apparatus using microwaves, a microwave heating apparatus in which a specimen is heated by introducing microwaves into a pyramid-shaped horn through a rectangular waveguide is suggested in, e.g., Japanese Patent Application Publication No. S62-268086. In this reference, the rectangular waveguide and the pyramid-shaped horn are arranged at an angle of about 45° in an axial direction, so that two orthogonally polarized microwaves in a TE10mode can be radiated to the specimen at the same phase.

In Japanese Utility Model Application Publication No. H6-17190, a microwave heating apparatus including a heating chamber having a square cross section whose size is set to about λ/2 to λ of a free space wavelength of the introduced microwaves is suggested as a heating apparatus for bending a heating target object.

When doping atoms are activated by microwave heating, it is required to supply a power larger than a certain level. Accordingly, microwaves may efficiently be introduced into a processing chamber by providing a plurality of microwave introduction ports. When a plurality of microwave introduction ports is provided, microwaves introduced from one of the microwave introduction ports may enter another microwave introduction port, thereby deteriorating power usage efficiency and heating efficiency

In the case of microwave heating, the microwaves are directly irradiated to a semiconductor wafer disposed immediately below the microwave introduction ports, so that the surface of the semiconductor wafer is not uniformly heated.

SUMMARY OF THE INVENTION

In view of the above, the present invention provides a microwave heating apparatus and a processing method which are capable of uniformly processing a target object while improving power use efficiency and heating efficiency.

In accordance with an aspect of the present invention, there is provided a microwave heating apparatus including a processing chamber configured to accommodate a target object to be processed, the processing chamber having therein a microwave irradiation space; and a microwave introducing unit configured to introduce microwaves for heating the target object into the processing chamber.

The processing chamber includes a top wall, a bottom wall and four sidewalls connected to one another; the microwave introducing unit includes a first to a fourth microwave source; the top wall has a first to a fourth microwave introduction port through which the microwaves generated by the first to the fourth microwave source are introduced into the processing chamber; each of the first to the fourth microwave introduction port is of a substantially rectangular shape having long sides and short sides in a plan view, and the microwave introduction ports are arranged in such a way that the long sides and the short sides thereof are in parallel to inner surfaces of the four sidewalls; and the microwave introduction port are disposed at positions spaced apart from each other at an angle of about 90° in such a way that each of the microwave introduction ports are not overlapped with another microwave introduction port whose long sides are in parallel to the long sides of the corresponding microwave introduction port when the corresponding microwave introduction port is moved in translation in a direction perpendicular to the long sides thereof.

A ratio L1/L2between a long side L1and a short side L2of each of the microwave introduction ports may be set to about 4 or more.

The first to the fourth microwave introduction port may be arranged such that central axes thereof parallel to the long sides of adjacent two of the microwave introduction ports are perpendicular to each other and central axes of two of the microwave introduction ports which are not adjacent to each other is not overlapped with each other on a same straight line.

The microwave radiation space may be defined by the top wall, the four sidewalls and a partition provided between the top wall and the bottom wall, and an inclined portion for reflecting the microwaves toward the target object is provided at the partition.

The inclined portion may have an inclined surface having a position higher than a reference position corresponding to the height of the target object and a position lower than the reference position, and may be disposed to surround the target object.

The microwave introducing unit may include one or more waveguides through which microwaves are transmitted toward the processing chamber; and one or more adaptor members attached to an outer side of the top wall of the processing chamber, each of the adaptor members being formed of a plurality of metallic block bodies, wherein each of the adaptor members includes therein a substantially S-shaped waveguide path through which the microwaves are transmitted. In this case, the waveguide paths may have one ends connected to the waveguides and the other ends connected to the microwave introduction ports such that the waveguides are not vertically overlapped with all or some of the microwave introduction ports.

In accordance with another aspect of the present invention, there is provided a processing method for heating a target object to be processed by using a microwave heating apparatus including: a processing chamber configured to accommodate the target object, the processing chamber having therein a microwave irradiation space; and a microwave introducing unit configured to introduce microwaves for heating the target object into the processing chamber.

The processing chamber includes a top wall, a bottom wall and four sidewalls connected to one another; the microwave introducing unit includes a first to a fourth microwave source; the top wall has a first to a fourth microwave introduction port through which the microwaves generated by the first to the fourth microwave source are introduced into the processing chamber; each of the first to the fourth microwave introduction port is of a substantially rectangular shape having long sides and short sides in a plan view, and the microwave introduction ports are disposed in such a way that the long sides and the short sides thereof are in parallel to inner surfaces of the four sidewalls; and the microwave introduction port are disposed at positions spaced apart from each other at an angle of about 90° in such a way that each of the microwave introduction ports are not overlapped with another microwave introduction port whose long sides are in parallel to the long sides of the corresponding microwave introduction port when the corresponding microwave introduction port is moved in translation in a direction perpendicular to the long sides thereof.

In the microwave heating apparatus and the processing method in accordance with the aspects of the present invention, the loss of the microwaves radiated into the processing chamber is reduced, so that the power use efficiency and the heating efficiency can be improved. Further, the target object can be uniformly heated.

DETAILED DESCRIPTION OF THE EMBODIMENTS

First Embodiment

First, a schematic configuration of a microwave heating apparatus in accordance with a first embodiment of the present invention will be described with reference toFIG. 1.FIG. 1is a cross sectional view showing a schematic configuration of the microwave heating apparatus in accordance with the present embodiment. The microwave heating apparatus1of the present embodiment performs an annealing process by irradiating microwaves to, e.g., a semiconductor wafer (hereinafter, simply referred to as “wafer”) for manufacturing semiconductor devices through a series of consecutive operations.

The microwave heating apparatus1includes: a processing chamber2accommodating a wafer W as a target object to be processed; a microwave introducing unit3for introducing microwaves into the processing chamber2; a supporting unit4for supporting a wafer W in the processing chamber2; a gas supply mechanism5for supplying a gas into the processing chamber2; a gas exhaust unit6for vacuum-exhausting the processing chamber2; and a control unit8for controlling the respective components of the microwave heating apparatus1.

The processing chamber2is made of a metal material, such as aluminum, aluminum alloy, stainless steel or the like, for example. The microwave introducing unit3is provided above the processing chamber2to introduce electromagnetic waves (microwaves) into the processing chamber2. The configuration of the microwave introducing unit3will be described in detail later.

The processing chamber2has a hollow inside and includes a plate-shaped ceiling portion11serving as a top wall; a bottom portion13serving as a bottom wall; four sidewall portions12serving as sidewalls for connecting the ceiling portion11and the bottom portion13; a plurality of microwave introduction ports10vertically extending through the ceiling portion11; a loading/unloading port12aprovided at a corresponding sidewall portion12; and a gas exhaust port13aprovided at the bottom portion13. Here, the four sidewall portions12form a square column shape having horizontal cross sections that are connected to one another at a right angle. Therefore, the processing chamber2has a cubical shape including a space therein. The inner surfaces of the sidewall portions12are preferably flat and serve as reflective surfaces for reflecting microwaves.

The processing chamber2may be fabricated by machining. In that case, it is practically difficult to form the angled parts, i.e., the parts where one of the sidewall portions12are brought into contact with another sidewall portion or the parts where the sidewall portions12and the bottom portion13are brought into contact with each other, at a right angle. Thus, the corner parts may be rounded. A simulation result shows that, when the rounding process is performed, it is preferable to set the radius of curvature “Rc” within the range from about 15 mm to 16 mm in order to suppress reflection by the microwave introduction ports10(seeFIGS. 9D and 9E). The loading/unloading port12ais used for loading and unloading the wafer W with respect to a transfer chamber (not shown) adjacent to the processing chamber2.

A gate valve “GV” is provided between the processing chamber2and the transfer chamber. The gate valve GV serves to open and close the loading/unloading port12a. When the gate valve GV is closed, the processing chamber2is airtightly sealed. When the gate valve GV is opened, the wafer W can be transferred between the processing chamber2and the transfer chamber.

The supporting unit4includes a plate-shaped hollow lift plate15provided in the processing chamber2; a plurality of tube-shaped supporting pins14extending upward from a top surface of the lift plate15; and a tube-shaped shaft16extending from a bottom surface of the lift plate15to the outside of the processing chamber2through the bottom portion13. The shaft16is fixed to an actuator (not shown) outside of the processing chamber2.

The supporting pins14serves to contact with the wafer W and support the wafer W in the processing chamber2. The upper portions of the supporting pins14are arranged along the circumferential direction of the wafer W. Further, the supporting pins14, the lift plate15and the shaft16are configured such that the wafer W can be vertically displaced by the actuator.

The supporting pins14, the lift plate15and the shaft16are configured such that the wafer W can be attracted onto the supporting pins14by the gas exhaust unit6. Specifically, each of the supporting pins14and the shaft16has a tube shape communicating with the inner space of the lift plate15. Further, suction holes for sucking the bottom surface of the wafer W are formed at the upper portions of the supporting pins14.

The supporting pins14and the lift plate15are made of a dielectric material, e.g., quartz, ceramic or the like.

The microwave heating apparatus1further includes a gas exhaust line17for connecting a gas exhaust port13aand the gas exhaust unit6; a gas exhaust line18for connecting the shaft16and the gas exhaust line17; a pressure control valve19disposed on the gas exhaust line17, and an opening/closing valve20and a pressure gauge21which are disposed on the gas exhaust line18. The gas exhaust line18is directly or indirectly connected to the shaft16so as to communicate with the inner space of the shaft16. The pressure control vale19is provided between the gas exhaust port13aand the connection node of the gas exhaust lines17and18.

The gas exhaust unit6has a vacuum pump such as a dry pump or the like. By operating the vacuum pump of the gas exhaust unit6, the inner space of the processing chamber2is vacuum-exhausted. At this time, by opening the opening/closing valve20, the bottom surface of the wafer W is sucked, so that the wafer W is attracted and fixed to the supporting pins14. Further, a gas exhaust equipment provided at a facility where the microwave heating apparatus1is installed may be used instead of the vacuum pump of the gas exhaust unit6.

As described above, the microwave heating apparatus1includes the gas supply mechanism5for supplying a gas into the processing chamber2. The gas supply mechanism5includes a gas supply unit5aprovided with a gas supply source (not shown); a shower head22provided below a position where the wafer W is to be disposed in the processing chamber2; a substantially quadrilateral frame-like rectifying plate23arranged between the shower head22and the sidewall portions12; a line24for connecting the shower head22and the gas supply unit5a; and a plurality of lines25, connected to the gas supply unit5a, for introducing a processing gas into the processing chamber2. The shower head22and the rectifying plate23are made of a metal material, e.g., aluminum, aluminum alloy, stainless steel or the like.

The shower head22serves to cool the wafer W by using a cooling gas in the case of performing a relatively low temperature process on the wafer W. The shower head22includes a gas channel22acommunicating with the line24; and a plurality of gas injection holes22bcommunicating with the gas channel22ato inject a cooling gas toward the wafer W. In the example shown inFIG. 1, the gas injection holes22bare formed at the top surface of the shower head22. The shower head22is not a necessary component of the microwave heating apparatus1and thus may not be provided.

The rectifying plate23has a plurality of rectifying openings23avertically extending through the rectifying plate23. The rectifying plate23serves to allow a gas to flow toward the gas exhaust port13awhile rectifying an atmosphere at a location where the wafer W is to be disposed in the processing chamber2. The rectifying plate23is not a necessary component of the microwave heating apparatus1and thus may not be provided.

The gas supply unit5ais configured to supply a processing gas or a cooling gas, e.g., N2, Ar, He, Ne, O2, H2or the like. Further, as for a unit for supplying a gas into the processing chamber2, an external gas supply unit that is not included in the configuration of the microwave heating apparatus1may be used instead of the gas supply unit5a.

The microwave heating apparatus1includes mass flow controllers (not shown) and opening/closing valves (not shown) disposed on the lines24and25. Types of gases to be supplied into the shower head22and the processing chamber2, and the flow rates thereof are controlled by the mass flow controllers and the opening/closing valves.

In the microwave heating apparatus1of the present embodiment, a microwave radiation space “S” is formed of a space defined by the ceiling portion11, the four sidewall portions12, the shower head22and the rectifying plate23in the processing chamber2. Microwaves are radiated into the microwave radiation space S through a plurality of microwave introduction ports10provided at the ceiling portion11. Here, the shower head22and the rectifying plate23also serve as partitioning portions for defining the lower side of the microwave radiation space S in the processing chamber2. Since each of the ceiling portion11, the four sidewall portions12, the shower head22and the rectifying plate23of the processing chamber2is made of a metal material, the microwaves are reflected and scattered into the microwave radiation space S.

The microwave heating apparatus1still further includes a plurality of radiation thermometers26for measuring a surface temperature of the wafer W; and a temperature measurement unit27connected to the radiation thermometers26. InFIG. 1, only the radiation thermometer for measuring a surface temperature of the central portion of the wafer W is illustrated and the other radiation thermometers26are not shown. The radiation thermometers26are extended from the bottom portion13toward a location where the wafer W will be disposed in such a way that the upper portions of the radiation thermometers26approach the bottom surface of the wafer W.

Next, the configuration of the microwave introducing unit3will be described with reference toFIGS. 1 and 2.FIG. 2explains a schematic configuration of a high voltage power supply unit40of the microwave introducing unit3.

As described above, the microwave introducing unit3is provided above the processing chamber2to introduce electromagnetic waves (microwaves) into the processing chamber2. As shown inFIG. 1, the microwave introducing unit3includes a plurality of microwave units30for introducing microwaves into the processing chamber2; and the high voltage power supply unit40connected to the microwave units30.

In the present embodiment, the microwave units30have the same configuration. Each of the microwave units30includes a magnetron31for generating microwaves for processing the wafer W; a waveguide32through which the microwaves generated by the magnetron31are transmitted to the processing chamber2; and a transmitting window33that is fixed to the ceiling portion11so as to cover the microwave introduction ports10. The magnetron31corresponds to a microwave source in the present invention.

The magnetron31has an anode and a cathode (both not shown) to which a high voltage supplied by the high voltage power supply unit40is applied. As for the magnetron31, a device capable of oscillating microwaves of various frequencies may be used. The frequency of the microwaves generated by the magnetron31is adjusted to an optimal level in accordance with process types for a target object. For example, in an annealing process, the microwaves preferably have a high frequency of about 2.45 GHz, 5.8 GHz or the like. Especially, a frequency of about 5.8 GHz is more preferably used.

The waveguide32is of a tubular shape having a rectangular cross section and extends upward from the top surface of the ceiling portion11of the processing chamber2. The magnetron31is connected to a substantially upper end portion of the waveguide32. A lower end portion of the waveguide32comes into contact with a top surface of the transmitting window33. The microwaves generated by the magnetron31are introduced into the processing chamber2through the waveguide32and the transmitting window33.

The transmitting window33is made of a dielectric material, e.g., quartz, ceramic or the like. The space between the transmitting window33and the ceiling portion11is airtightly sealed by a sealing member (not shown). A distance (gap G) from a bottom surface of the transmitting window33to a height level corresponding to the surface of the wafer W supported by the supporting pins14is preferably to set to, e.g., about 25 mm or more and more preferably set in a range from about 25 mm to 50 mm, in order to prevent the microwaves from being directly radiated onto the wafer W.

The microwave unit30further includes a circulator34, a detector35and a tuner36which are provided on the waveguide32; and a dummy load37connected to the circulator34. The circulator34, the detector35and the tuner36are provided in that order from the upper end portion of the waveguide32. The circulator34and the dummy load37serve as an isolator for isolating reflected waves from the processing chamber2. In other words, the circulator34transmits the reflected waves from the processing chamber2to the dummy load37, and the dummy load37converts the reflected waves transmitted by the circulator34into heat.

The detector35serves to detect the reflected waves from the processing chamber2in the waveguide32. The detector35includes, e.g., an impedance monitor, specifically a standing wave monitor for detecting an electric field in the waveguide32. The standing wave monitor may be formed of, e.g., three pins protruding into the inner space of the waveguide32. The reflected waves from the processing chamber2can be detected by detecting a location, a phase and an intensity of an electric field of standing waves by the standing wave monitor. Further, the detector35may be formed of a directional coupler capable of detecting traveling waves and reflected waves.

The tuner36serves to adjust an impedance between the magnetron31and the processing chamber2. The impedance matching by the tuner36is performed based on the detection result of the reflected waves by the detector35. The tuner36may be formed of, e.g., a conductor plate (not shown) capable of projecting into and retracting from the inner space of the waveguide32. In that case, by adjusting the projecting amount of the conductor plate into the inner space of the waveguide32, it is possible to control the power amount of the reflected waves at the conductor plate to thereby adjust the impedance between the magnetron31and the processing chamber2.

(High Voltage Power Supply Unit)

The high voltage power supply unit40supplies a high voltage for generating microwaves to the magnetron31. As shown inFIG. 2, the high voltage power supply unit40includes an AC-DC conversion circuit41connected to a commercial power source; a switching circuit42connected to the AC-DC conversion circuit41; a switching controller43for controlling an operation of the switching circuit42; a step-up transformer44connected to the switching circuit42; and a rectifier circuit45connected to the step-up transformer44. The magnetron31is connected to the step-up transformer44via the rectifier circuit45.

The AC-DC conversion circuit41serves to convert alternating currents (AC) (e.g., three-phase 200V) from the commercial power source into direct currents (DC) of a predetermined waveform by rectification. The switching circuit42controls on and off of the DC converted by the AC-DC conversion circuit41. In the switching circuit42, phase-shift type PWM (Pulse Width Modulation) control or PAM (Pulse Amplitude Modulation) control is performed by the switching controller23to generate a pulse-shaped voltage waveform. The step-up transformer44serves to boost the voltage waveform outputted from the switching circuit to a predetermined level. The rectifier circuit45serves to rectify the voltage boosted by the step-up transformer44and supply the rectified voltage to the magnetron31.

<Arrangement of Microwave Introduction Ports>

Next, the arrangement of the microwave introduction ports10of the present embodiment will be described in detail with reference toFIGS. 1,3and4.FIG. 3shows a state in which the bottom surface of the ceiling portion11of the processing chamber2shown inFIG. 1is seen from the inside of the processing chamber2. InFIG. 3, the size and the position of the wafer W are indicated by a double dotted line on the ceiling portion11. A notation “O” indicates the center of the wafer W. In the present embodiment, the notation O also indicates the center of the ceiling portion11. Accordingly, two lines passing through the notation O indicate central lines M connecting central points of facing sides among four sides forming boundaries between the ceiling portion11and the sidewall portions12.

Further, the center of the wafer W and the center of the ceiling portion11need not coincide with each other. InFIG. 3, for the convenience of explanation, reference numerals12A to12D are used to indicate contact portions between the ceiling portion11and the inner surfaces of the four sidewall portions12of the processing chamber2to distinguish the four sidewalls12.FIG. 4is an enlarged plan view showing one microwave introduction port10.

As shown inFIG. 3, in the present embodiment, four microwave introduction ports10are equidistantly arranged in a substantially cross shape in the ceiling portion11. Hereinafter, when the four microwave introduction ports10need to be distinguished, reference numerals10A to10D will be assigned thereto. In the present embodiment, the microwave introduction ports10are respectively connected to the microwave units30. In other words, the four microwave units30are provided.

The microwave introduction ports10are of a rectangular shape having long sides and short side when viewed from the plane. A ratio L1/L2of the long side L1to the short side L2of the microwave introduction ports10is set to be greater than or equal to about 2 and smaller than or equal to about 100. It is preferably set to about 4 or above and more preferably set in a range from about 5 to 20. The reason that the ratio L1/L2is set to about 2 or above and more preferably about 4 or above is to improve the directivity of the microwaves radiated into the processing chamber2from the microwave introduction ports10in the direction perpendicular to the long side of the microwave introduction ports10(direction parallel to the short side).

When the ratio L1/L2is smaller than about 2, the microwaves radiated from the microwave introduction ports10into the processing chamber2are easily directed toward the direction parallel to the long side of the microwave introduction ports10(direction perpendicular to the short side). Further, when the ratio L1/L2is smaller than about 2, the directivity of the microwaves immediately below the microwave introduction ports10is enhanced. Accordingly, the microwaves are directly radiated to the wafer W, so that the wafer W is locally heated.

On the other hand, when the ratio L1/L2is greater than about 20, the directivity of the microwaves immediately below the microwave introduction ports10or the microwaves directed toward the direction parallel to the long side of the microwave introduction ports10(direction perpendicular to the short side) is excessively decreased, so that the heating efficiency of the wafer W may deteriorate.

Preferably, the long side L1of the microwave introduction ports10satisfies the equation L1=n×λg/2 (here, n indicates an integer), wherein λg indicates a guide wavelength of the waveguide32. More preferably, n is set to 2. The microwave introduction ports10may have different sizes or ratios L1/L2. However, it is preferable that the four microwave introduction ports10have the same size and shape in order to improve the uniformity and the controllability of the heating process for the wafer W.

In the present embodiment, the four microwave introduction ports10are arranged immediately above the wafer W to vertically overlap the wafer W. Here, in order to obtain uniform distribution of the electric field on the wafer W, it is preferable that the microwave introduction ports10are arranged in the ceiling portion11in a diametrical direction of the wafer W to vertically overlap the wafer W within a distance ranging from about ⅕ to ⅗ of the radius of the wafer W in a diametrical direction from the center of the wafer W. If the uniform heating can be realized in the surface of the wafer W, the position of the wafer W may not be overlapped with the positions of the microwave introduction ports10.

In the present embodiment, the four microwave introduction ports10are arranged in such a way that the long sides and the short sides thereof are in parallel with the inner surfaces of the corresponding four sidewall portions12A to12D. For example, inFIG. 3, the long sides of the microwave introduction ports10A are in parallel to the sidewall portions12B and12D, and the short sides of the microwave introduction ports10A are in parallel with the sidewall portions12A to12C. InFIG. 3, electromagnetic vectors100showing the dominant directivity of the microwaves radiated from the microwave introduction ports10A are indicated by solid-line arrows, and electromagnetic vectors101showing the directivity of the microwaves reflected by the sidewall portions12B and12D are indicated by dotted-line arrows. Most of the microwaves radiated from the microwave introduction ports10A propagate in a direction perpendicular to the long sides thereof (direction parallel to the short sides).

Moreover, the microwaves radiated from the microwave introduction ports10A are reflected by the two sidewall portions12B and12D. Since the sidewall portions12B and12D are disposed in parallel to the long sides of the microwave introduction ports10A, the reflected waves (the electromagnetic vectors101) have directivity reversed by about 180° from the directivity of the traveling waves (the electromagnetic vectors100) and are hardly scattered toward the other microwave introduction ports10B to10D. By arranging the four microwave introduction ports10having the ratio L1/L2of about 2 or above in such a way that the long sides and the short sides thereof are in parallel with the inner surfaces of the four sidewall portions12A to12D, it is possible to control the directions of the microwaves radiated from the microwave introduction ports10and the reflected waves thereof.

In the present embodiment, the four microwave introduction ports10having the ratio L1/L2of, e.g., about to above, are circumferentially arranged at positions spaced apart from each other at an angle of about 90°. In other words, the four microwave introduction ports10are rotationally symmetrically arranged about the center O of the ceiling portion11, and the rotation angle is about 90°. Further, the microwave introduction ports10are arranged in such a way that each one of the microwave introduction ports is not overlapped with another microwave introduction port10whose long sides are in parallel with the long sides of the corresponding microwave introduction port10when the corresponding microwave introduction port10is moved in translation in a direction perpendicular to the long sides thereof.

InFIG. 3, the microwave introduction ports10A to10D are arranged in a cross shape, for example. In other words, two adjacent microwave introduction ports10are spaced apart from each other at an angel of about 90° such that the central axes AC thereof parallel to the long sides of the adjacent microwave introduction ports10are perpendicular to each other. Moreover, even when the microwave introduction port10A is moved in translation in a direction perpendicular to the long side thereof, the microwave introduction ports10A is not overlapped with the microwave introduction port100whose long side is in parallel to the long side of the microwave introduction port10A. In other words, the microwave introduction port10(the microwave introduction port100) having the same longitudinal direction as that of the microwave introduction port10A are not disposed between the two sidewall portions12B and12D parallel to the long side of the microwave introduction port10A within the length of the long side of the microwave introduction port10A.

With such arrangement, it is possible to efficiently prevent the microwaves radiated from the microwave introduction port10A with the directivity perpendicular to the long side of the microwave introduction port10A and the reflected waves thereof from entering other microwave introduction ports10. In other words, if other microwave introduction ports10having the same direction are interposed between the two sidewall portions12B and12D parallel to the microwave introduction port10A within the length of the long side of the microwave introduction port10A, the microwaves are excited in the same direction. Therefore, the microwaves and the reflected waves easily enter the microwave introduction ports10of the same direction, and this leads to an increase of power loss. On the other hand, if no microwave introduction port10having the same direction as that of the microwave introduction port10A is interposed between the two parallel sidewall portions12B and12D within the length of the long side of the microwave introduction port10A, it is possible to reduce the power loss caused when the microwaves radiated from the microwave introduction port10A and the reflected waves thereof enter other microwave introduction ports10.

InFIG. 3, the microwaves radiated from the microwave introduction ports10A and the reflected waves thereof hardly enter the microwave introduction ports10B and10D because they are excited in a different direction from those radiated from the microwave introduction ports10B and10D that are arranged adjacent to the microwave introduction port10A by an interval of about 90°. Therefore, when the microwave introduction port10A is moved in translation in a direction perpendicular to the long side thereof, it may be overlapped with the microwave introduction ports10B and10D having different longitudinal directions.

In the present embodiment, two microwave introduction ports10that are not adjacent to each other among the four microwave introduction ports10forming a cross shape are arranged such that the central axes AC thereof are not overlapped with each other on the same straight line. For example, inFIG. 3, the microwave introduction port10A and the microwave introduction port10C that is not adjacent thereto are arranged so as not to be overlapped with each other although the central axes thereof are disposed in the same direction. As such, by arranging two microwave introduction ports10that are not adjacent to each other among the four microwave introduction ports10forming a cross shape in such a way that the central axes AC thereof are not overlapped with each other on the same straight line, it is possible to reduce power loss caused when the microwaves radiated in a direction perpendicular to the short sides thereof from one of the two microwave introduction ports10having the same direction of the central axes AC enter the other microwave introduction port.

In such arrangement, the central axis AC of each of the microwave introduction ports10need not coincide with the central line M. Therefore, the microwave introduction ports10may be located at positions significantly deviated from the central line M. For example, the long sides of the microwave introduction ports10may be disposed at positions adjacent to the sidewall portions12. However, it is preferable that the microwave introduction ports10are disposed near the central line M in order to uniformly introduce the microwaves into the processing chamber2. As shown inFIG. 3, it is preferable that at least some of the microwave introduction ports10coincides with the central line M. In another embodiment, two microwave introduction ports10that are not adjacent to each other among the four microwave introduction ports10forming a cross shape may be arranged such that the central axes AC thereof coincide with each other. In that case, the central axes AC may coincide with the central line M.

Although the microwave introduction port10A has been described as an example, the other microwave introduction ports10B to10D are also arranged such that the above-described relationship is satisfied between the corresponding microwave introduction ports10and the corresponding sidewall portions12.

Various components of the microwave heating apparatus1are connected to the control unit8and controlled by the control unit8. The control unit8is typically a computer.FIG. 5explains a configuration of the control unit8shown inFIG. 1. In the example shown inFIG. 5, the control unit8includes a process controller81having a CPU; and a user interface82and a storage unit83which are connected to the process controller81.

The process controller81serves to control the components (e.g., the microwave introducing unit3, the supporting unit4, the gas supply unit5a, the gas exhaust unit6, the temperature measurement unit27and the like) of the microwave heating apparatus1which are related to the processing conditions such as a temperature, a pressure, a gas flow rate, a microwave output and the like.

The user interface82includes a keyboard or a touch panel on which a process operator inputs commands to operate the microwave heating apparatus1; a display for visually displaying the operation status of the microwave heating apparatus1and the like.

The storage unit83stores therein control programs (software) or recipes including processing condition data to be used in realizing various processes that are performed by the microwave heating apparatus1under the control of the process controller51. If necessary, the process controller81retrieves a control program or recipe from the storage unit83in accordance with an instruction from the user interface82and executes the control program or recipe. As a consequence, a desired process in the processing chamber2of the microwave heating apparatus1is performed under the control of the process controller81.

The control programs or the recipes may be stored in a computer-readable storage medium, e.g., a CD-ROM, a hard disk, a flexible disk, a flash memory, a DVD, a Blu-ray disc or the like. Further, the recipes may be transmitted on-line from another device through, e.g., a dedicated line, when necessary.

Hereinafter, a processing sequence for annealing a wafer W in the microwave heating apparatus1will be described. First, a command for performing annealing in the microwave heating apparatus1is inputted from the user interface82to the process controller81. Second, the process controller81receives the command and reads out the recipes that have been stored in the storage unit83or the computer-readable storage medium. Then, control signals are transmitted from the process controller81to the end devices (e.g., the microwave introducing unit3, the supporting unit4, the gas supply unit5a, the gas exhaust unit6and the like) of the microwave heating apparatus1such that the annealing process is performed under the conditions based on the recipes.

Thereafter, the gate valve GV is opened, and the wafer W is loaded into the processing chamber2through the gate valve GV and the loading/unloading port12aby a transfer unit (not shown). The wafer W is mounted on the supporting pins14. Then, the gate valve GV is closed, and the processing chamber2is vacuum-evacuated by the gas exhaust unit6. At this time, the opening/closing valve20is opened, so that the bottom surface of the wafer W is sucked and the wafer W is fixed by suction to the supporting pins14. Next, a processing gas and a cooling gas of predetermined flow rates are introduced into the processing chamber2by the gas supply unit5a. The inner space of the processing chamber2is controlled to a predetermined pressure by adjusting a gas exhaust amount and a gas supply amount.

Thereafter, microwaves are generated by applying a voltage from the high voltage power supply unit40to the magnetron31. The microwaves generated by the magnetron31transmit the waveguide32and the transmitting window33and then are introduced into a space above the wafer W in the processing chamber2. In the present embodiment, microwaves are sequentially generated by the magnetrons31and introduced into the processing chamber2through the microwave introduction ports10. The magnetrons may be simultaneously generated by the magnetrons31and introduced into the processing chamber2from the microwave introduction ports10.

The microwaves introduced into the processing chamber2are radiated to the surface of the wafer W, so that the wafer W is rapidly heated by electromagnetic wave heat such as Joule heat, magnetic heat, induction heat or the like. As a result, the wafer W is annealed

When a control signal for completing the annealing process is transmitted from the process controller81to the end devices of the microwave heating apparatus1, the generation of the microwaves is stopped and the supply of the processing gas and the cooling gas is stopped. In this manner, the annealing for the wafer W is completed. Next, the gate valve is opened, and the wafer W is unloaded by a transfer unit (not shown).

The microwave heating apparatus1is preferably used for an annealing process for activating doping atoms injected into the diffusion layer in the manufacturing process of semiconductor devices, for example.

Hereinafter, the functional effects of the microwave heating apparatus1and the method for processing a wafer W by using the microwave heating apparatus1in accordance with the embodiment of the present invention will be described with reference toFIGS. 3,6A,6B,7A and7B. In the present embodiment, with the combination of the shape and arrangement of the microwave introduction ports10and the shapes of the sidewall portions12of the processing chamber2, the microwaves radiated from the microwave introduction ports10into the processing chamber2are efficiently radiated to the wafer W while the microwaves radiated from one of the microwave introduction ports10is suppressed from entering the other microwave introduction ports10. This principal will be described below.

FIGS. 6A and 6Bschematically show the radiation directivity of the microwaves in the microwave introduction port10in which the ratio L1/L2between the lengths of the long side L1and the short side L2is about 4 or above.FIGS. 7A and 7Bschematically show the radiation directivity of the microwaves in the microwave introduction port10having the ratio L1/L2smaller than about 2.FIGS. 6A and 7Ashow the microwave introduction port10viewed from a lower portion of the ceiling portion11that is not shown therein.FIGS. 6B and 7Bare partial enlarged cross sectional views ofFIG. 1to show cross sections of the microwave introduction port10and the ceiling portion11.

InFIGS. 6A,6B,7A and7B, arrows indicate the electromagnetic vectors100radiated from the microwave introduction port10. Longer arrows indicate stronger directivity of the microwaves. InFIGS. 6A,6B,7A and7B, the X-axis and the Y-axis are in parallel to the bottom surface of the ceiling portion11; the X-axis is perpendicular to the long sides of the microwave introduction ports10; the Y-axis is in parallel to the long sides of the microwave introduction ports10; and the Z-axis is perpendicular to the bottom surface of the ceiling portion11.

In the present embodiment, as described above, the four microwave introduction ports10formed in a rectangular shape having long sides and short sides when seen from above are arranged at the ceiling portion11. Further, the microwave introduction ports10used in the present embodiment preferably have the ratio L1/L2of, e.g., about 2 or above, and more preferably about 4 or above. Thus, as shown inFIG. 6A, the radiation directivity of the microwaves is increased and dominant in a direction perpendicular to the long side (direction parallel to the short side) along the X-axis. Accordingly, the microwaves radiated from any of the microwave introduction ports10mainly propagate along the ceiling portion11of the processing chamber2and then are reflected by the reflective surfaces, i.e., the inner surfaces of the sidewall portions12parallel to the long sides thereof.

In the present embodiment, the four sidewall portions12of the processing chamber2are orthogonally connected to one another, and the four microwave introduction ports10are disposed in such a way that the long sides and the short sides thereof are in parallel to the inner surfaces of the four sidewall portions12A to12D. Therefore, the reflected waves of the microwaves radiated from one of the microwave introduction ports10are directed substantially in a 180° reversed direction and thus hardly enter the other microwave introduction ports10.

In the present embodiment, as shown inFIG. 3, the four microwave introduction ports10having the ratio L1/L2of, e.g., about 2 or above, are arranged at locations spaced apart from each other at an angle of about 90°. In other words, the four microwave introduction ports10are arranged at an interval of about 90° such that they substantially form an a cross shape and the central axes AC thereof parallel to the long sides of the two adjacent microwave introduction ports10are perpendicular to each other.

Further, the microwave introduction ports10are arranged in such a way that each one of the microwave introduction ports10is not overlapped with another microwave introduction port10whose long sides are in parallel to the long sides of the corresponding microwave introduction port10when the corresponding microwave introduction port10is moved in translation in a direction perpendicular to the long sides thereof. Hence, it is possible to prevent the microwaves radiated from one of the microwave introduction ports10having the same excitation direction of the microwaves and the reflected waves thereof from entering the other microwave introduction port10in a direction perpendicular to the long sides of the microwave introduction port10.

Furthermore, by arranging the two microwave introduction ports10that are not adjacent to each other among the four microwave introduction ports10are arranged such that the central axes AC thereof are not overlapped with each other on the same straight line, the microwaves radiated from one of the microwave introduction ports10having the same excitation direction of the microwaves and the reflected waves thereof hardly enter the other microwave introduction port10in a direction perpendicular to the short sides of the microwave introduction port10.

As such, in the present embodiment, the microwave introduction ports10are arranged in consideration of the shape of the microwave introduction ports10, especially the ratio L1/L2, the radiation directivity of the microwaves which depends on the shape of the microwave introduction ports10, and the shape of the sidewall portions12. Therefore, it is possible to prevent the microwaves introduced from one of the microwave introduction ports10from entering the other microwave introduction ports10, thereby minimizing the power loss.

In the microwave heating apparatus1of the present embodiment, by employing the combination of the shape and arrangement of the microwave introduction ports10and the shape of the sidewall portions12, it is possible to prevent the microwaves having the radiation directivity shown inFIGS. 6A and 6Bradiated from one of the microwave introduction ports10and/or the reflected waves propagating in the reverse direction thereof from entering the other microwave introduction port10to thereby improve the use efficiency of supplied power.

In the present embodiment, by setting the ratio L1/L2to about 2 or above and preferably about 4 or above, as shown inFIG. 6B, the directivity of the microwaves radiated from the microwave introduction ports10is increased in the horizontal direction (X-axis direction) and widened mainly in the horizontal direction along the bottom surface of the ceiling portion11. Further, in the present embodiment, the distance (gap G) from the bottom surface of the transmitting window33to the surface of the wafer W supported by the supporting pins14is set to about 25 mm or above. As such, by ensuring the sufficient gap G in consideration of the radiation directivity of the microwaves, few microwaves are directly radiated to the wafer W positioned immediately below the microwave introduction ports10and, thus, the heating is uniformly carried out. As a result, in the microwave heating apparatus1of the present embodiment, the wafer W can be uniformly processed.

Meanwhile, in the case of the microwave introduction ports10having the ratio L1/L2smaller than 2, as shown inFIG. 7A, the directivity of the microwaves is increased in a direction parallel to the long sides (direction perpendicular to the short sides) along the Y-axis. Hence, the directivity thereof is relatively decreased in a direction perpendicular to the long sides (direction parallel to the short sides), and thus the difference in the radiation directivities of the microwaves is eliminated. Accordingly, when the microwave introduction ports10having the ratio L1/L2smaller than 2 (e.g., long side:short side=1:1) are arranged as shown inFIG. 3, the microwaves radiated from the microwave introduction port10A propagate in a direction parallel to the long sides of the microwave introduction ports10A. Then, the microwave may enter the microwave introduction port10C.

Further, the directivity of the microwaves radiated from the microwave introduction ports10having the ratio L1/L2smaller than 2 is increased in a downward direction (i.e., in a direction toward the wafer W along the Z-axis) as shown inFIG. 7B, so that the ratio in which the microwaves are directly radiated to the wafer W immediately below the microwave introduction ports10is increased. As a consequence, the wafer W is locally heated.

Hereinafter, the result of simulation on the radiation directivity of the microwave introduction ports10on which the present invention is based will be explained with reference toFIGS. 8A and 8B.FIG. 8Ashows the result of simulation on the radiation directivity of the microwave introduction ports10having the ratio L1/L2of about 6.FIG. 8Bshows the result of simulation on the radiation directivity of the microwave introduction ports10having the ratio L1/L2smaller than 2. The X-axis, the Y-axis and the Z-axis inFIGS. 8A and 8Bare the same as those inFIGS. 6A,6B,7A and7B.

Although the radiation directivity is not explicitly expressed because it is indicated by black and white inFIGS. 8A and 8B, the darker (black) indicates the higher radiation directivity.

Referring toFIG. 8A, the microwave introduction port10having the ratio L1/L2of about 6 has a higher radiation directivity in the X-axis direction and a lower radiation directivity in the Y-axis direction and the Z-axis direction. On the other hand, referring toFIG. 8B, the microwave introduction port10having the ratio L1/L2smaller than about 2 has a higher radiation directivity in the Z-axis direction (in a downward direction). This indicates that the microwaves tend to be radiated from the microwave introduction ports10in the same moving direction as that in the waveguide32and then directly radiated toward the wafer W. Therefore, by setting the ratio L1/L2to, e.g., about 2 or above, preferably about 4 or above, the radiated microwaves can be efficiently propagated in a direction perpendicular to the long sides of the microwave introduction ports10and in a horizontal direction along the bottom surface of the ceiling portion11.

Next, a result of simulation on the power absorption efficiency of the wafer W in the case of varying the shape of the processing chamber and the shape and the arrangement of the microwave introduction ports10will be described with reference toFIGS. 9A to 9C. The upper images shown inFIGS. 9A to 9Cexplain the shape and arrangement of the microwave introduction ports10and the sidewall portions12of the microwave heating apparatus1as the simulation target which are projected with respect to the arrangement of the wafer W. The intermediate images shown therein are simulation result maps showing the volume loss density distribution of the microwave power in the surface of the wafer

The lower images show a scattering parameter, a wafer absorption power (Pw), and a ratio (Aw) of a wafer area to an entire area (wafer area+inner area of the processing chamber) which can be obtained from the simulation. In this simulation, the examination was performed by introducing the microwaves of about 3000 W from one microwave introduction port indicated by the black box in the upper images ofFIGS. 9A to 9C. The dielectric loss tangent (tans) of the wafer W was set to about 0.1.

FIG. 9Ashows the result simulation on a configuration of a comparative example in which four microwave introduction ports10are provided in a processing chamber having a cylindrical sidewall portion12.FIG. 9Bshows a result of simulation on a configuration example in which four microwave introduction ports10are provided at a processing chamber having a square column shaped sidewall portion12. InFIGS. 9A and 9B, the ratio L1/L2between the lengths of the long side L1and the short side L2of the microwave introduction ports10is set to about 2. Further, inFIGS. 9A and 9B, the microwave introduction ports10are arranged immediately above an outer peripheral portion of the circular wafer W such that the tangential direction of the peripheral portion of the wafer W is in parallel to the longitudinal direction of the microwave introduction ports10. Moreover, inFIG. 9B, the microwave introduction ports10are arranged in such a way that each one of the microwave introduction ports10overlapped with another microwave introduction port10whose long sides are in parallel to the long sides of the corresponding microwave introduction port10when the corresponding microwave introduction port10is moved in translation in a direction perpendicular to the long sides thereof.

Meanwhile,FIG. 9Cshows the simulation result on a configuration same as that of the present embodiment in which four microwave introduction ports10are disposed at rotation positions of about 90° in the processing chamber having a square column shaped sidewall portion12. InFIG. 9C, long sides and short sides of the four microwave introduction ports10are in parallel with the inner surfaces of the four sidewall portions12, and the ratio L1/L2between the lengths of the long side L1and the short side L2of the microwave introduction ports10is set to about 4. Moreover, inFIG. 9C, the microwave introduction ports10are arranged in such a way that each one of the microwave introduction ports10is not overlapped with another microwave introduction port10whose long sides are in parallel with the long sides of the corresponding microwave introduction port10when the corresponding microwave introduction port10is moved in translation in a direction perpendicular to the long sides thereof.

Here, the absorption power of the wafer W may be calculated by using scattering parameters (S parameters). On the assumption that an input power is Pin, and an entire power absorbed by the wafer W is Pw, the entire power Pw may be calculated by the following Eq. 1. Notations “S11,” “S21,” “S31” and “S41” denote S parameters of the four microwave introduction ports10. The microwave introduction port10indicated by the black shaded box corresponds to PORT10.
Pw=Pin(1−|S11|2−|S21|2−|S31|2−|S41|2)  Eq. 1

In order to increase the power absorption efficiency of the wafer W, it is preferable to increase a ratio of an area of the wafer W to the inner area of the processing chamber which defines the microwave radiation space S and also preferable to increase “Aw” shown in the following Eq. 2. Awrepresents a ratio of the wafer area to the entire area (the wafer area+the inner area of the processing chamber).
Aw=[wafer area/(wafer area+inner area of processing chamber)]×100  Eq. 2

The distribution of the power absorption in the surface of the wafer W was obtained by calculating an electromagnetic wave volume loss density by using pointing vectors in the surface of the wafer W. Further, the entire power Pwabsorbed by the wafer W and the power pwabsorbed by the wafer W per unit volume may be calculated by the following Eqs. 3 and 4, respectively. The maps in the intermediate images ofFIGS. 9A to 9Cwere created by calculating such values by using an electromagnetic field simulator and plotting same on the wafer W. Although the electromagnetic wave volume loss density is not explicitly expressed because the maps are indicated by black and white, the lighter black (white) indicates the higher electromagnetic wave volume loss density in the surface of the wafer W.

where, {right arrow over (S)}, {right arrow over (J)}, {right arrow over (E)} and {right arrow over (H)} respectively indicate pointing vector, current density, electric field and magnetic field.

In the case of using the wafer W as a target object to be processed, Joule loss mainly occurs in the Eqs. 3 and 4. Therefore, the relationship between the power pw absorbed by the wafer W per unit volume and the electric field may be expressed by using the following Eq. 5 modified from the Eq. 4. The power pwabsorbed by the wafer W per unit volume is substantially in proportion to a square of the electric field.

The comparison betweenFIGS. 9A and 9Band9C reveals that the case shown in theFIG. 9Cwhich employs the combination of the shape and arrangement of the microwave introduction ports10and the shape of the sidewall portions12of the processing chamber2in accordance with the present embodiment ensures a small difference in the electric field, an increased entire power Pw absorbed by the wafer W and an excellent power absorption efficiency. Moreover, the ratio Awof the area of the wafer W to the inner area of the processing chamber which defines the microwave radiation space S is higher in the case shown inFIG. 9Cthan the cases shown inFIGS. 9A and 9B.

Next, a simulation result on the effects of rounding of angled inner portions of connecting parts between adjacent sidewall portions12of the processing chamber2on the reflection of microwaves will be explained with reference toFIGS. 9D and 9E.FIG. 9Dschematically shows a configuration of a microwave heating apparatus used in the simulation. Specifically,FIG. 9Dschematically shows the shape of the sidewall portion12(only the position of the inner surfaces are shown) in the case of performing rounding of the connecting parts between the adjacent sidewall portions12, and the positional relationship of the wafer W.

FIG. 9Dalso shows the positions of the four microwave introduction ports10A to10D provided in the ceiling portion11(not shown) which are projected above the wafer W. As can be seen fromFIG. 9D, the angled inner portions C between the sidewall portions12A and12B, the sidewall portions12B and12C, the sidewall portions12C and12D, and the sidewall portions12D and12A are rounded with a curvature of radius Rc. Other configurations are the same as those of the microwave heating apparatus1shown inFIG. 1.

In the simulation, scattering parameters S11and S31were analyzed by varying the curvature of radius Rc of the rounding processing of the angled inner portions C in the unit of 1 mm in a range from 0 mm (right angle) to 18 mm. Here, the scattering parameters S11and S31were analyzed on the assumption that the microwaves were introduced through the microwave introduction port10A. S11is a scattering parameter of the microwaves radiated from the microwave introduction port10A and the reflected waves thereof. S31is a scattering parameter of the microwaves radiated from the microwave introduction port10A and reflected to the microwave introduction port10C.

FIG. 9Eshows the simulation result. As can be seen fromFIG. 9E, when the radius of curvature Rc is within the range from about 15 mm to 16 mm, S11and S31have little variation and have relatively low values. Accordingly, in order to prevent the reflected waves from entering the microwave introduction ports10and increase the use efficiency of the microwave power, it is preferable to perform rounding of the angled inner portions C of the connecting parts between adjacent sidewall portions12of the processing chamber2by setting the curvature of radius Rc within the range from about 15 mm to 16 mm. Although this simulation has been performed on the rounding of the angled inner portions C of the connecting parts between adjacent sidewall portions12of the processing chamber2, the curvature of radius Rc may be preferably applied to the rounding of the angled inner portions of the connecting parts between the sidewall portions12and the bottom portion13.

As can be seen from the above simulation results, the microwave heating apparatus1of the present embodiment provides excellent power use efficiency and heating efficiency by reducing the loss of the microwaves radiated into the processing chamber2. Besides, it is found that the wafer W can be uniformly heated by using the microwave heating apparatus1of the present embodiment.

Second Embodiment

Next, a microwave heating apparatus in accordance with a second embodiment of the present invention will be described with reference toFIGS. 10 and 11.FIG. 10is a cross sectional view showing a schematic configuration of a microwave heating apparatus1A of the present embodiment.FIG. 11explains a rectifying plate23A of the microwave heating apparatus1A of the present embodiment which serves as a microwave reflection mechanism.

The microwave heating apparatus1A of the present embodiment includes a processing chamber2for accommodating a wafer W as a target object to be processed; a microwave introducing unit3for introducing microwaves into the processing chamber2; a supporting unit4for supporting the wafer W in the processing chamber2; a gas supply mechanism5A for supplying a gas into the processing chamber2; a gas exhaust unit6for vacuum-evacuating the processing chamber2; and a control unit8for controlling the respective components of the microwave heating apparatus1A. The microwave heating apparatus1A of the present embodiment is different from the microwave heating apparatus1of the first embodiment in the shape of the rectifying plate23A of a gas supply mechanism5A. Thus, inFIG. 10, components having substantially the same configuration and function as those inFIG. 1are denoted by like reference characters, and thus the description thereof will be omitted. InFIG. 10, the loading/unloading port12aand the gate valve GV are not illustrated.

In the present embodiment as well, the shower head22and the rectifying plate23A of the gas supply mechanism5A serve as partitioning portions for defining the bottom portion of the microwave radiation space S. Further, the microwave heating apparatus1A includes the rectifying plate23A having an inclined portion for reflecting microwaves toward the wafer W. In other words, the top surface of the rectifying plate23A which surrounds the periphery of the wafer W is inclined so as to be widened from the wafer W side (inner side) toward the sidewall portions12side (outer side). The angle and the width of the inclined portion are uniform along the inner surfaces of the sidewall portions12. The shower head22and the rectifying plat23A are made of a metal, e.g., aluminum, aluminum alloy, stainless steel or the like.

In the present embodiment, in order to efficiently focus the microwaves on the center of the wafer W, the inclined portion of the rectifying plate23A is provided to have a position P1higher than a reference position P0corresponding to the height of the wafer W and a position P2lower than the reference position P0. Specifically, as shown inFIG. 11, the upper end of the inclined upper surface (the inclined portion) of the rectifying plate23A is located at a position (the upper position P1) upper than the wafer W supported by the supporting pins14. Further, the lower end of the inclined upper surface (the inclined portion) of the rectifying plate23A is located at a position (the lower position P2) lower the wafer W supported by the supporting pins14.

InFIG. 11, the directions of the microwaves reflected by the inclined portion of the rectifying plate23A are schematically indicated by electromagnetic vectors100and101. The microwaves that have been scattered in the microwave radiation space S and moved downward, i.e., from the ceiling portion11of the processing chamber2toward the rectifying plate23, can be reflected by the inclined portion and transmitted toward the center of the wafer W. Hence, the microwaves can be focused on the center of the wafer W. As a consequence, the heating efficiency can be increased by the reflected waves, and the entire surface of the wafer W can be uniformly heated.

The angle of the upper surface (the inclined portion) of the rectifying plate23A may be randomly set as long as the microwaves radiated from the microwave introduction ports10can be effectively reflected toward the wafer W. Specifically, it may be properly set in consideration of the arrangement and the shape (e.g., the ratio L1/L2), the gap G and the like of the microwave introduction ports10.

In the microwave heating apparatus1A of the present embodiment, the inclined portion is provided at the rectifying plate23A, so that the number of components can be reduced thereby simplifying the apparatus configuration compared to the case of providing the inclined portion as a separate member.

The other configurations and the effects of the microwave heating apparatus1A of the present embodiment are the same as those of the microwave heating apparatus1of the first embodiment. Specifically, in the present embodiment, the four sidewall portions12of the processing chamber2are orthogonally connected to one another, and the four microwave introduction ports10are arranged in such a way that the long sides and the short sides thereof are in parallel to the inner surfaces of the four sidewall portions12A to12D. The four microwave introduction ports10are circumferentially located at positions spaced apart from each other at an interval of about 90° and arranged in such a way that each one of the microwave introduction ports10is not overlapped with another microwave introduction port10whose long sides are in parallel to the long sides of the long sides of the corresponding microwave introduction port10when the corresponding microwave introduction port10is moved in translation in a direction perpendicular to the long sides thereof. Further, two microwave introduction ports10that are not adjacent to each other among the four microwave introduction ports10are disposed such that the central axes AC thereof do not coincide with each other on the same straight line. Hence, the microwaves introduced from one of the microwave introduction ports10are prevented from entering the other microwave introduction ports10.

In the present embodiment, in addition to such arrangement of the microwave introduction ports10, an inclined portion is formed in the rectifying plate23A in order to effectively focus the microwaves on the center of the wafer W. Accordingly, it is possible to focus the microwaves on the center of the wafer W while minimizing the loss of the microwaves radiated from the microwave introduction ports10. As a result, the heating efficiency of the wafer W can be increased.

In the above embodiment, since the bottom of the microwave radiation space S is defined by the shower head22and the rectifying plate23A of the gas supply mechanism5A, the top surface of the rectifying plate23serves as the inclined portion. However, in the case of a microwave heating apparatus that does not have the shower head22and the rectifying plate23A, an inclined portion may be provided at the bottom portion13of the processing chamber2. In that case, a part of the inner wall of the bottom portion13may be inclined at a predetermined angle, or a separate member having an inclined portion may be provided on the bottom portion13.

The inclined portion for reflecting microwaves is not necessarily provided at the lower portion of the microwave radiation space S and may be provided at the upper portion of the microwave radiation space S. For example, although it is not shown, the inclined portion may be formed by an angle between the ceiling portion11and the sidewall portions12.

Third Embodiment

Hereinafter, a microwave heating apparatus in accordance with a third embodiment of the present invention will be described with reference toFIGS. 12 to 14.FIG. 12is a cross sectional view showing a schematic configuration of a microwave heating apparatus1B of the present embodiment.FIG. 13explains a state in which a microwave introducing adaptor50serving as an adaptor member having a waveguide for transmitting microwaves is installed at the ceiling portion11.FIG. 14explains grooves formed at the microwave introducing adaptor50.

The microwave heating apparatus1B of the present embodiment performs annealing by radiating microwaves to the wafer W for manufacturing semiconductor devices through a plurality of consecutive operations. In the following description, the difference between the microwave heating apparatus1B of the present embodiment and the microwave heating apparatus1of the first embodiment will be described. In the microwave heating apparatus1B shown inFIGS. 12 to 14, components having substantially the same configuration and function as those in the microwave heating apparatus1of the first embodiment are denoted by like reference characters, and thus the description thereof will be omitted.

The microwave heating apparatus1B includes a processing chamber2for accommodating a wafer W serving as a target object to be processed; a microwave introducing unit3A for introducing the microwaves into the processing chamber2; a supporting unit4for supporting the wafer W in the processing chamber2; a gas supply mechanism5for supplying a gas into the processing chamber2; a gas exhaust unit6for vacuum-evacuating the processing chamber2, and a control unit8for controlling the respective components of the microwave heating apparatus1B.

The microwave introducing unit3A is provided above the processing chamber2to introduce electromagnetic waves (microwaves) into the processing chamber2. As shown inFIG. 12, the microwave introducing unit3A includes a plurality of microwave units30for introducing the microwaves into the processing chamber2; a high voltage power supply unit connected to the microwave units30; and a microwave introducing adaptor50connected between the waveguide32and the microwave introduction ports10to transmit the microwaves therebetween.

In the present embodiment, the microwave units30have the same configuration. Each of the microwave units30includes a magnetron31for generating microwaves for processing the wafer W; a waveguide32through which the microwaves generated by the magnetron31is transmitted to the processing chamber2; and a transmitting window33fixed to the ceiling portion11so as to cover the microwave introduction ports10. Each of the microwave units30further includes a circulator34; a detector35and a tuner36which are provided on the waveguide32; and a dummy load37connected to the circulator34.

As shown inFIG. 13, the microwave introducing adaptor50is formed of a plurality of metallic block bodies. In other words, the microwave introducing adaptor50includes a single large central block51disposed at the center; and four auxiliary blocks52A to52D disposed around the central block51. The block bodies are fixed to the ceiling portion11by a fixing unit, e.g., bolts or the like.

As shown inFIG. 14, the central block51has a plurality of grooves51aformed at a side surface thereof. At the side surface of the central block51, the grooves51aare arranged from the top surface to the bottom surface of the central block51while forming a substantially S shape. The number of the grooves51acorresponds to the number of the microwave units30. In the present embodiment, four grooves51aare formed.

The auxiliary blocks52A to52D are combined with the central block51, thereby forming the microwave introducing adaptors50. The auxiliary blocks52A to52D are arranged to correspond to the grooves51aof the central block51. In other words, each of the auxiliary blocks52A to52D is fixed to the side surface where the groves51aof the central block51are formed. Further, an approximately S-shaped waveguide path53capable of transmitting microwaves therethrough is formed by blocking the openings of the grooves51aat the side surface of the central block51by the auxiliary blocks52A to52D. In other words, the waveguide path53is formed by three walls in the grooves51aand one wall of each of the auxiliary blocks52A to52D. The waveguide path53is a through hole extending from the top surface to the bottom surface of the microwave introducing adaptor50.

The upper end of the waveguide path53is fixed to the lower end of the waveguide32, and the lower end of the waveguide path53is connected to the transmitting window33for blocking the microwave introduction ports10. The waveguide32is position-aligned with the waveguide path53and fixed to the microwave introducing adaptors50by a fixing unit, e.g., bolts or the like. The waveguide path53is formed in an S shape in order to reduce transmission loss of the microwaves and misalign positions of the waveguide32with the microwave introduction ports10in the horizontal direction. By combining a plurality of block bodies, the waveguide path53capable of minimizing transmission loss can be formed by a simple metal process.

In the microwave heating apparatus1B of the present embodiment, the degree of freedom in the arrangement of the microwave units30and the microwave introduction ports10can be considerably increased by using the microwave introducing adaptors50. In the microwave heating apparatus1B, it is required to provide the components of the four microwave units50on the processing chamber2. However, an installation space on the processing chamber2is limited. Thus, in the configuration in which the waveguide32is directly connected to the microwave introduction ports10, the arrangement of the microwave introduction ports10may be limited by interference between the adjacent microwave units30.

The configuration of the microwave introducing adaptors50used in the present embodiment may be flexibly selected by the S-shaped waveguide path53among the fixed arrangement in which the relative positions between the waveguide32and the microwave introduction ports10are overlapped with each other vertically, the arrangement in which they are not overlapped with each other vertically, and the arrangement in which they are partially not overlapped with each other (i.e., the arrangement in which they are misaligned horizontally). Therefore, by using the microwave introducing adaptors50, the microwave introduction ports10can be provided at any portion of the ceiling portion11without being restricted to the installation space on the microwave unit30. For example, when the four microwave introduction ports11are provided near the center of the ceiling portion11, the interference between the microwave units30can be avoided by using the microwave introducing adaptors50.

As described above, in the microwave heating apparatus1B, the degree of freedom in the arrangement of the microwave introduction ports50is considerably increased by using the microwave introducing adaptors50. Hence, in accordance with the microwave heating apparatus1B of the present embodiment, the uniformity of the heating in the surface of the wafer W can be improved, thereby heating the wafer W uniformly.

The other configurations and the effects of the microwave heating apparatus1B of the present embodiment are the same as those of the microwave heating apparatus1of the first embodiment, and thus the description thereof will be omitted. Further, the block body used in the microwave introducing adaptor50may have various shapes and sizes in accordance with the arrangement or the number of the microwave introduction ports10. For example, the waveguide path may be formed by combining small block bodies such as the auxiliary blocks52A to52D without providing the central block51.

In the present embodiment, the microwave introducing adaptor50is commonly used for each of the microwave units30. However, a plurality of microwave introducing adaptors50may be provided for the microwave units30, respectively. Further, the microwave introducing adaptor50may be included in the microwave units30as one of the components thereof. The microwave introducing adaptor50may be applied to the microwave heating apparatus1A of the second embodiment.

The present invention may be variously modified without being limited to the above embodiments. For example, the microwave heating apparatus of the present invention is not limited to the case of using a semiconductor wafer as a target object to be processed and may also be applied to a microwave heating apparatus which uses as the target object a substrate for a solar cell panel or a substrate for a flat panel display, for example.

The number of the microwave units30(the magnetrons31), the number of the microwave introduction ports10, and the number of microwaves simultaneously introduced into the processing chamber2are not limited to those described in the above embodiments. For example, the microwave heating apparatus may include two or three microwave introduction ports10, or may include five or more microwave introduction ports10.

While the invention has been shown and described with respect to the embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined in the following claims.