Source: http://www.patentsencyclopedia.com/app/20120288970
Timestamp: 2018-04-27 09:55:27
Document Index: 70461824

Matched Legal Cases: ['art 5', 'art 4', 'art 5', 'art 4', 'art 4', 'art 5', 'art 5', 'art 4', 'art 5', 'art 190', 'art 190', 'art 190', 'art 150', 'art 150', 'art 150', 'art 150', 'art 150', 'art 150', 'art 150', 'art 150', 'art 5', 'art 5', 'art 5', 'art 5', 'art 4', 'art 4', 'art 4', 'art 4', 'art 4', 'art 4', 'art 160', 'art 150', 'art 160', 'art 150', 'art 150', 'art 150', 'art 160', 'art 160', 'art 160', 'art 150', 'art 150', 'art 160', 'art 150', 'art 160', 'art 150', 'art 160', 'art 35', 'art 35', 'art 35', 'art 160', 'art 32', 'art 33', 'art 32', 'art 33', 'art 160', 'art 4', 'art 5', 'art 4', 'art 5', 'art 5', 'art 4', 'art 4', 'art 4', 'art 150', 'art 150', 'art 150', 'art 150', 'art 160', 'art 160', 'art 150', 'art 150', 'art 160', 'art 150', 'art 150', 'art 150', 'art 150', 'art 150', 'art 150', 'art 150', 'art 160', 'art 160', 'art 160', 'art 160', 'art 33', 'art 33', 'art 150', 'art 160', 'art 33', 'art 33', 'art 150', 'art 160', 'art 32', 'art 32', 'art 150', 'art 160', 'art 32', 'art 32', 'art 32', 'art 35', 'art 150', 'art 150', 'art 150', 'art 150', 'art 160', 'art 33', 'art 160', 'art 33', 'art 32', 'art 33', 'art 160', 'art 32', 'art 5', 'art 4']

HEAT TREATMENT METHOD AND HEAT TREATMENT APPARATUS FOR HEATING SUBSTRATE BY IRRADIATING SUBSTRATE WITH LIGHT - Patent application
Patent application title: HEAT TREATMENT METHOD AND HEAT TREATMENT APPARATUS FOR HEATING SUBSTRATE BY IRRADIATING SUBSTRATE WITH LIGHT
Inventors: Kazuyuki Hashimoto (Kyoto-Shi, JP) Tatsufumi Kusuda (Kyoto-Shi, JP)
Patent application number: 20120288970
After flash irradiation on a semiconductor wafer is started and then the temperatures of front and back surfaces of the semiconductor wafer become equal to each other, the temperature of the back surface of the semiconductor wafer, which has a known emissivity, is measured with a radiation thermometer. The emissivity of the front surface of the semiconductor wafer is calculated based on the intensity of radiated light from a black body having an equal temperature to the temperature of the back surface thereof, and the intensity of radiated light actually radiated from the front surface of the semiconductor wafer. Then, the temperature of the front surface of the semiconductor wafer heated by the flash irradiation is calculated based on the calculated emissivity and the intensity of the radiated light from the front surface of the semiconductor wafer that has been measured after the flash irradiation is started.
1. A heat treatment apparatus for heating a substrate by irradiating a front surface of the substrate with light, the substrate including a known emissivity on a back surface thereof, the heat treatment apparatus comprising: a chamber for receiving a substrate therein; a holder for holding the substrate within said chamber; an irradiation part for irradiating the front surface of the substrate held by said holder with light; a quartz window provided in said chamber, for eliminating light having a predetermined wavelength range from light emitted from said irradiation part; a photodetector element provided on the front surface side of said substrate, for receiving radiated light radiated from said front surface; a filter for selectively allowing light having a selective wavelength range included in radiated light directed from the front surface of said substrate toward said photodetector element to pass therethrough, said selective wavelength range being included in said predetermined wavelength range; a back-surface temperature measuring part provided on the back surface side of said substrate, for measuring a temperature of said back surface; a radiated light intensity measuring part for measuring an intensity of the radiated light received by said photodetector element; an emissivity calculating part calculating an emissivity of the front surface of said substrate after irradiation by said irradiation part is started and then the temperatures of the front and back surfaces of said substrate become equal to each other, based on the temperature of the back surface of said substrate measured by said back-surface temperature measuring part and the intensity of the radiated light from the front surface of said substrate measured by said radiated light intensity measuring part; and a front-surface temperature calculating part for calculating the temperature of the front surface of said substrate heated by said irradiation, based on the emissivity of the front surface of said substrate calculated by said emissivity calculating part and the intensity of the radiated light from the front surface of said substrate measured by said radiated light intensity measuring part after said irradiation is started.
2. The heat treatment apparatus according to claim 1, wherein said radiated light intensity measuring part is configured to measure intensities of radiated light from the front surface of said substrate in chronological order after said irradiation is started, to thereby obtain a history of radiated light intensity, and said front-surface temperature calculating part is configured to calculate a history of front-surface temperature of said substrate heated by said irradiation, based on said history of radiated light intensity.
3. The heat treatment apparatus according to claim 2, wherein said front-surface temperature calculating part is configured to calculate a maximum temperature at which the front surface of said substrate has reached from said history of front-surface temperature.
4. The heat treatment apparatus according to claim 1, wherein said irradiation part comprises a flash lamp for irradiating the substrate with a flash of light.
5. The heat treatment apparatus according to claim 1, wherein said photodetector element comprises an InSb photoconductive element.
6. The heat treatment apparatus according to claim 5, wherein said filter is a long-wave pass filter for selectively allowing light having a wavelength of 5 μm or more to pass therethrough.
7. A method of heating a substrate by irradiating a front surface of the substrate with light, the substrate including a known emissivity on a back surface thereof, the method comprising the steps of: (a) eliminating light having a predetermined wavelength range from light emitted from an irradiation part and irradiating the substrate with the resultant light; (b) selectively allowing light having a selective wavelength range included in radiated light from the front surface of said substrate to pass through, and receiving the light by a photodetector element, said selective wavelength range being included in said predetermined wavelength range; (c) calculating an emissivity of the front surface of said substrate based on a temperature of the back surface of said substrate and an intensity of the radiated light from the front surface of said substrate received by said photodetector element, the temperature of the back surface being measured after the irradiation in said step (a) is started and then a temperature of the front surface of said substrate and the temperature of the back surface thereof become equal to each other; and (d) calculating the temperature of the front surface of said substrate heated by said irradiation based on the emissivity of the front surface of said substrate calculated in said step (c) and the intensity of the radiated light from the front surface of said substrate received by said photodetector element after said irradiation is started.
8. The method according to claim 7, wherein in said step (d), intensities of radiated light from the front surface of said substrate after said irradiation is started are measured in chronological order to obtain a history of radiated light intensity, and a history of front-surface temperature of said substrate heated by said irradiation is calculated based on said history of radiated light intensity.
9. The method according to claim 8, wherein in said step (d), a maximum temperature that the front surface of said substrate has reached is calculated from said history of front-surface temperature.
10. The method according to claim 7, wherein in said step (a), a flash lamp emits the substrate with a flash of light.
[0002] The present invention relates to a heat treatment method and a heat treatment apparatus for heating a thin plate-like precision electronic substrate (hereinafter referred to simply as a "substrate") having a back surface of a known emissivity such as a semiconductor wafer and a glass substrate for a liquid crystal display device by irradiating the substrate with light.
[0004] In the process of manufacturing a semiconductor device, impurity doping is an essential step for forming a pn junction in a semiconductor wafer. At present, it is common practice to perform impurity doping by an ion implantation process and a subsequent annealing process. The ion implantation process is a technique for causing ions of impurity elements such as boron (B), arsenic (As) and phosphorus (P) to collide against the semiconductor wafer with high acceleration voltage, thereby physically implanting the impurities into the semiconductor wafer. The implanted impurities are activated by the subsequent annealing process. When annealing time in this annealing process is approximately several seconds or longer, the implanted impurities are deeply diffused by heat. This results in a junction depth much greater than a required depth, which might constitute a hindrance to good device formation.
[0005] In recent years, attention has been given to flash lamp annealing (FLA) that is an annealing technique for heating a semiconductor wafer in an extremely short period of time. The flash lamp annealing is a heat treatment technique in which xenon flash lamps (the term "flash lamp" as used hereinafter refers to a "xenon flash lamp") are used to irradiate the surface of a semiconductor wafer with a flash of light, thereby raising the temperature of only the surface of the semiconductor wafer doped with impurities in an extremely short period of time (several milliseconds or less).
[0006] The xenon flash lamps have a spectral distribution of radiation ranging from ultraviolet to near-infrared regions. The wavelength of light emitted from the xenon flash lamps is shorter than that of light emitted from conventional halogen lamps, and approximately coincides with a fundamental absorption band of a silicon semiconductor wafer. Thus, when a semiconductor wafer is irradiated with a flash of light emitted from the xenon flash lamps, the temperature of the semiconductor wafer can be raised rapidly, with only a small amount of light transmitted through the semiconductor wafer. Also, it has turned out that flash irradiation, that is, the irradiation of a semiconductor wafer with a flash of light in an extremely short period of time of several milliseconds or less allows a selective temperature rise only near the surface of the semiconductor wafer. Therefore, the temperature rise in an extremely short period of time with the xenon flash lamps allows only the activation of impurities to be achieved without deep diffusion of the impurities.
[0007] U.S. Pat. No. 7,935,913 discloses the technique in which a light measuring part including a calorimeter disposed outside a chamber body, a light guide structure for guiding the light emitted to the inside of the chamber body to the calorimeter, and a calculation part that performs computations based on an output from the calorimeter is provided in a flash lamp annealer, to thereby measure the energy of the light emitted to the inside of the chamber body from a flash lamp with the calorimeter. In addition, U.S. Pat. No. 7,935,913 discloses that the surface temperature of a substrate is obtained by computations based on the energy of a flash of light measured by the calorimeter.
[0008] In the technique disclosed in U.S. Pat. No. 7,935,913, the total energy (amount of heat) of single flash irradiation is measured, to thereby obtain the maximum attained temperature of the surface of the substrate from the total energy. However, even if the total energy of flash irradiation is constant, the light energy to be absorbed differs between different emissivities of surfaces of a semiconductor wafer, which causes variations in the surface temperature to be attained. Typically, the flash lamp annealing is performed for activating impurities implanted into a source and a drain formed in the surface of a semiconductor wafer. In other words, fine device patterns including source and drain regions are formed in the surface of the semiconductor wafer on which flash lamp annealing is performed, and an emissivity frequently differs depending on patterns. This makes it extremely difficult to measure the surface temperature of the semiconductor wafer to be actually treated or processed in which impurities have been implanted.
[0009] The present invention is intended for a heat treatment apparatus that heats a substrate including a back surface a known emissivity by irradiating the substrate with light.
[0010] According to one aspect of the present invention, the heat treatment apparatus comprises: a chamber for receiving a substrate therein; a holder for holding the substrate within the chamber; an irradiation part for irradiating the front surface of the substrate held by the holder with light; a quartz window provided in the chamber, for eliminating light having a predetermined wavelength range from light emitted from the irradiation part; a photodetector element provided on the front surface side of the substrate, for receiving radiated light from the front surface; a filter for selectively allowing light having a selective wavelength range included in radiated light directed from the front surface of the substrate toward the photodetector element to pass therethrough, the selective wavelength range being included in the predetermined wavelength range; a back-surface temperature measuring part provided on the back surface side of the substrate, for measuring a temperature of the back surface; a radiated light intensity measuring part for measuring an intensity of the radiated light received by the photodetector element; an emissivity calculating part calculating an emissivity of the front surface of the substrate after irradiation by the irradiation part is started and then the temperatures of the front and back surfaces of the substrate become equal to each other, based on the temperature of the back surface of the substrate measured by the back-surface temperature measuring part and the intensity of the radiated light from the front surface of the substrate measured by the radiated light intensity measuring part; and a front-surface temperature calculating part for calculating the temperature of the front surface of the substrate heated by the irradiation, based on the emissivity of the front surface of the substrate calculated by the emissivity calculating part and the intensity of the radiated light from the front surface of the substrate measured by the radiated light intensity measuring part after the irradiation is started.
[0011] The temperature of the front surface is calculated based on the intensity of radiated light from the front surface relative to the same temperature of the back surface as the temperature of the front surface, which enables to obtain the temperature of the front surface of the substrate regardless of device patterns formed on the front surface. Further, the heat treatment apparatus includes: the quartz window for eliminating light having a predetermined wavelength range from light emitted from the irradiating part; and the filter for selectively allowing light having a selective wavelength range included in the predetermined wavelength range to pass therethrough. This enables to measure the intensity of radiated light from the front surface of the substrate without being affected by the light emitted from the irradiation part.
[0012] The present invention is also intended for a method of heating a substrate having a back surface of a known emissivity by irradiating a front surface of the substrate with light.
[0013] According to one aspect of the present invention, the heat treatment method comprises the steps of: (a) eliminating light having a predetermined wavelength range from light emitted from an irradiation part and irradiating a substrate with the resultant light; (b) selectively allowing light having a selective wavelength range included in radiated light from the front surface of the substrate to pass through, and receiving the light by a photodetector element, the selective wavelength range being included in the predetermined wavelength range; (c) calculating an emissivity of the front surface of the substrate based on a temperature of the back surface of the substrate and an intensity of the radiated light from the front surface of the substrate received by the photodetector element, the temperature of the back surface being measured after the irradiation in the step (a) is started and then a temperature of the front surface of the substrate and the temperature of the back surface thereof become equal to each other; and (d) calculating the temperature of the front surface of the substrate heated by the irradiation based on the emissivity of the front surface of the substrate calculated in the step (c) and the intensity of the radiated light from the front surface of the substrate received by the photodetector element after the irradiation is started.
[0014] The temperature of the front surface is calculated based on the intensity of radiated light from the front surface relative to the same temperature of the back surface as the temperature of the front surface, which enables to obtain the temperature of the front surface of the substrate regardless of device patterns formed on the front surface. Further, light having a predetermined wavelength range is eliminated from the light emitted from the irradiation part and the substrate is irradiated with the resultant light, and light having a selective wavelength range included in the predetermined wavelength range of radiated light from the front surface of the substrate is selectively allowed to path through and is received by the photodetector element. This enables to measure the intensity of radiated light from the front surface of the substrate without being affected by the light emitted from the irradiation part.
[0015] It is therefore an object of the present invention to obtain the temperature of the front surface of a substrate irrespective of device patterns formed on the front surface thereof.
[0017] FIG. 1 is a longitudinal sectional view showing a configuration of a heat treatment apparatus according to the present invention;
[0018] FIG. 2 is a perspective view showing the entire external appearance of a holder;
[0019] FIG. 3 is a top plan view of the holder;
[0020] FIG. 4 is a side view of the holder as seen from one side;
[0021] FIG. 5 is a plan view of a transfer mechanism;
[0022] FIG. 6 is a side view of the transfer mechanism;
[0023] FIG. 7 is a plan view showing an arrangement of halogen lamps;
[0024] FIG. 8 is a diagram showing a driving circuit for a flash lamp;
[0025] FIG. 9 is a diagram showing a configuration of a photodetector part;
[0026] FIG. 10 is a block diagram showing configurations of a sampling part and a controller;
[0027] FIG. 11 is a graph showing changes in the temperature of a front surface of a semiconductor wafer;
[0028] FIG. 12 is a graph showing the correlation between the temperature of a black body and an output from an InSb photoconductive element;
[0029] FIG. 13 is a graph showing changes in the output signal level from the InSb photoconductive element in flash irradiation; and
[0030] FIG. 14 is a graph showing changes in the temperature of a semiconductor wafer in flash irradiation.
[0031] A preferred embodiment according to the present invention will now be described in detail with reference to the drawings.
[0032] FIG. 1 is a longitudinal sectional view showing a configuration of a heat treatment apparatus 1 according to the present invention. The heat treatment apparatus 1 according to the preferred embodiment of the present invention is a flash lamp annealer for irradiating a disk-shaped semiconductor wafer W having a diameter of 300 mm and serving as a substrate with a flash of light to heat the semiconductor wafer W. The semiconductor wafer W prior to the transport into the heat treatment apparatus 1 is implanted with impurities. The heat treatment apparatus 1 performs a heating treatment on the semiconductor wafer W to thereby activate the impurities implanted in the semiconductor wafer W.
[0033] The heat treatment apparatus 1 includes a chamber 6 for receiving a semiconductor wafer W therein, a flash heating part 5 including a plurality of built-in flash lamps FL, a halogen heating part 4 including a plurality of built-in halogen lamps HL, and a shutter mechanism 2. The flash heating part 5 is provided over the chamber 6, and the halogen heating part 4 is provided under the chamber 6. The heat treatment apparatus 1 further includes a holder 7 provided inside the chamber 6 and for holding a semiconductor wafer W in a horizontal position, and a transfer mechanism 10 provided inside the chamber 6 and for transferring a semiconductor wafer W between the holder 7 and the outside of the heat treatment apparatus 1. The heat treatment apparatus 1 further includes a controller 3 for controlling operating mechanisms provided in the shutter mechanism 2, the halogen heating part 4, the flash heating part 5, and the chamber 6 to cause the operating mechanisms to heat-treat a semiconductor wafer W.
[0034] The chamber 6 is configured such that upper and lower chamber windows 63 and 64 made of quartz are mounted to the top and bottom, respectively, of a tubular chamber side portion 61. The chamber side portion 61 has a generally tubular shape having an open top and an open bottom. The upper chamber window 63 is mounted to block the top opening of the chamber side portion 61, and the lower chamber window 64 is mounted to block the bottom opening thereof. The upper chamber window 63 forming the ceiling of the chamber 6 is a disk-shaped member made of quartz, and serves as a quartz window that transmits a flash of light emitted from the flash heating part 5 therethrough into the chamber 6. The lower chamber window 64 forming the floor of the chamber 6 is also a disk-shaped member made of quartz, and serves as a quartz window that transmits light emitted from the halogen heating part 4 therethrough into the chamber 6.
[0035] Quartz (SiO2) allows light in every wavelength range from visible light to infrared radiation (near infrared radiation) having a relatively short wavelength to pass therethrough, but hardly allows infrared radiation having a long wavelength of 4 μm or more to pass therethrough. That is, the upper chamber window 63 serving as a quartz window functions as a filter that eliminates light having a wavelength range of 4 μm or more from a flash of light emitted from the flash heating part 5.
[0036] An upper reflective ring 68 is mounted to an upper portion of the inner wall surface of the chamber side portion 61, and a lower reflective ring 69 is mounted to a lower portion thereof. Both of the upper and lower reflective rings 68 and 69 are in the form of an annular ring. The upper reflective ring 68 is mounted by being inserted downwardly from the top of the chamber side portion 61. The lower reflective ring 69, on the other hand, is mounted by being inserted upwardly from the bottom of the chamber side portion 61 and fastened with screws (not shown). In other words, the upper and lower reflective rings 68 and 69 are removably mounted to the chamber side portion 61. An interior space of the chamber 6, i.e. a space surrounded by the upper chamber window 63, the lower chamber window 64, the chamber side portion 61, and the upper and lower reflective rings 68 and 69, is defined as a heat treatment space 65.
[0037] A recessed portion 62 is defined in the inner wall surface of the chamber 6 by mounting the upper and lower reflective rings 68 and 69 to the chamber side portion 61. Specifically, the recessed portion 62 is defined which is surrounded by a middle portion of the inner wall surface of the chamber side portion 61 where the reflective rings 68 and 69 are not mounted, a lower end surface of the upper reflective ring 68, and an upper end surface of the lower reflective ring 69. The recessed portion 62 is provided in the form of a horizontal annular ring in the inner wall surface of the chamber 6, and surrounds the holder 7 for holding a semiconductor wafer W.
[0038] The chamber side portion 61, and the upper and lower reflective rings 68 and 69 are made of a metal material (e.g., stainless steel) with high strength and high heat resistance. The inner peripheral surfaces of the upper and lower reflective rings 68 and 69 are provided as mirror surfaces by electrolytic nickel plating.
[0039] The chamber side portion 61 is provided with a transport opening (throat) 66 for the transport of a semiconductor wafer W therethrough into and out of the chamber 6. The transport opening 66 is openable and closable by a gate valve 185. The transport opening 66 is connected in communication with an outer peripheral surface of the recessed portion 62. Thus, when the transport opening 66 is opened by the gate valve 185, a semiconductor wafer W is allowed to be transported through the transport opening 66 and the recessed portion 62 into the heat treatment space 65 and to be transported out of the heat treatment space 65. When the transport opening 66 is closed by the gate valve 185, the heat treatment space 65 in the chamber 6 is an enclosed space.
[0040] At least one gas supply opening 81 for supplying a treatment gas (in this preferred embodiment, nitrogen (N2) gas) therethrough into the heat treatment space 65 is provided in an upper portion of the inner wall of the chamber 6. The gas supply opening 81 is provided above the recessed portion 62, and may be provided in the upper reflective ring 68. The gas supply opening 81 is connected in communication with a gas supply pipe 83 through a buffer space 82 provided in the form of an annular ring inside the side wall of the chamber 6. The gas supply pipe 83 is connected to a nitrogen gas supply source 85. A valve 84 is inserted at some midpoint in the gas supply pipe 83. When the valve 84 is opened, nitrogen gas is fed from the nitrogen gas supply source 85 to the buffer space 82. The nitrogen gas flowing in the buffer space 82 flows in a spreading manner within the buffer space 82 which is lower in fluid resistance than the gas supply opening 81, and is supplied through the gas supply opening 81 into the heat treatment space 65.
[0041] On the other hand, at least one gas exhaust opening 86 for exhausting a gas from the heat treatment space 65 is provided in a lower portion of the inner wall of the chamber 6. The gas exhaust opening 86 is provided below the recessed portion 62, and may be provided in the lower reflective ring 69. The gas exhaust opening 86 is connected in communication with a gas exhaust pipe 88 through a buffer space 87 provided in the form of an annular ring inside the side wall of the chamber 6. The gas exhaust pipe 88 is connected to an exhaust part 190. A valve 89 is inserted at some midpoint in the gas exhaust pipe 88. When the valve 89 is opened, the gas in the heat treatment space 65 is exhausted through the gas exhaust opening 86 and the buffer space 87 to the gas exhaust pipe 88. The at least one gas supply opening 81 and the at least one gas exhaust opening 86 may include a plurality of gas supply openings 81 and a plurality of gas exhaust openings 86, respectively, arranged in a circumferential direction of the chamber 6, and may be in the form of slits. The nitrogen gas supply source 85 and the exhaust part 190 may be mechanisms provided in the heat treatment apparatus 1 or be utility systems in a factory in which the heat treatment apparatus 1 is installed.
[0042] A gas exhaust pipe 191 for exhausting the gas from the heat treatment space 65 is also connected to a distal end of the transport opening 66. The gas exhaust pipe 191 is connected through a valve 192 to the exhaust part 190. By opening the valve 192, the gas in the chamber 6 is exhausted through the transport opening 66.
[0043] Further, a photodetector part 150 for receiving the radiated light from the front surface of a semiconductor wafer W is provided in the upper portion of the inner wall of the chamber 6. As shown in FIG. 1, the photodetector part 150 is provided above the holder 7, that is, on the front surface side of the semiconductor wafer W held by the holder 7. The photodetector part 150 is provided on the inner wall of the chamber 6 such that a distal end thereof is inclined toward the front surface of the semiconductor wafer W held by the holder 7, and may be provided in the upper reflective ring 68.
[0044] FIG. 9 is a diagram showing the configuration of the photodetector part 150. The photodetector part 150 includes a condenser lens 151, a long-wave pass filter 152, and an InSb (indium antimonide) photoconductive element 153 in a casing. The condenser lens 151 is a lens made of germanium (Ge) and condenses light entering the photodetector part 150 toward the InSb photoconductive element 153. Germanium hardly allows light having a relatively short wavelength of 2 μm or less but allows light having a wavelength larger than 2 μm to pass therethrough to some extent. The long-wave pass filter 152 blocks light having a wavelength less than 5 μm and allows light having a long wavelength of 5 μm or more to pass therethrough. The InSb photoconductive element 153 is a photodetector element that generates a photocurrent according to the intensity of the received light.
[0045] In the photodetector part 150, the light entering through the condenser lens 151 passes through the long-wave pass filter 152 and is received by the InSb photoconductive element 153. The InSb photoconductive element 153 shows excellent responsivity in a wavelength range of 6.5 μm or less. Meanwhile, the long-wave pass filter 152 selectively allows light having a wavelength of 5 μm or more therethrough. As a result, the detection wavelength range of the photodetector part 150 according to this preferred embodiment in which the InSb photoconductive element 153 is included is 5 μm to 6.5 μm.
[0046] FIG. 2 is a perspective view showing the entire external appearance of the holder 7. FIG. 3 is a top plan view of the holder 7. FIG. 4 is a side view of the holder 7 as seen from one side. The holder 7 includes a base ring 71, coupling portions 72, and a susceptor 74, and holds a semiconductor wafer W in the chamber 6. The base ring 71, the coupling portions 72, and the susceptor 74 are all made of quartz. In other words, the whole of the holder 7 is made of quartz.
[0047] The base ring 71 is a quartz member in the form of an annular ring. The base ring 71 is supported by the wall surface of the chamber 6 by being placed on the bottom surface of the recessed portion 62 (with reference to FIG. 1). The multiple coupling portions 72 (in this preferred embodiment, four coupling portions 72) are mounted upright on the upper surface of the base ring 71 in the form of the annular ring and arranged in a circumferential direction of the base ring 71. The coupling portions 72 are quartz members, and are rigidly secured to the base ring 71 by welding. The base ring 71 may be of an arcuate shape such that a portion is removed from the annular ring.
[0048] The planar susceptor 74 is supported by the four coupling portions 72 provided on the base ring 71. The susceptor 74 is a generally circular planar member made of quartz. The diameter of the susceptor 74 is greater than the diameter of a semiconductor wafer W. In other words, the susceptor 74 has a size, as seen in plan view, greater than that of the semiconductor wafer W. Multiple (in this preferred embodiment, five) guide pins 76 are mounted upright on the upper surface of the susceptor 74. The five guide pins 76 are disposed along the circumference of a circle concentric with the outer circumference of the susceptor 74. The diameter of a circle on which the five guide pins 76 are disposed is slightly greater than the diameter of the semiconductor wafer W. The guide pins 76 are also made of quartz. The guide pins 76 may be machined from a quartz ingot integrally with the susceptor 74. Alternatively, the guide pins 76 separately machined may be attached to the susceptor 74 by welding and the like.
[0049] The four coupling portions 72 provided upright on the base ring 71 and the lower surface of a peripheral portion of the susceptor 74 are rigidly secured to each other by welding. In other words, the susceptor 74 and the base ring 71 are fixedly coupled to each other with the coupling portions 72, and the holder 7 is an integrally formed member made of quartz. The base ring 71 of such a holder 7 is supported by the wall surface of the chamber 6, whereby the holder 7 is mounted to the chamber 6. With the holder 7 mounted to the chamber 6, the susceptor 74 of a generally disc-shaped configuration assumes a horizontal position (a position such that the normal to the susceptor 74 coincides with a vertical direction). A semiconductor wafer W transported into the chamber 6 is placed and held in a horizontal position on the susceptor 74 of the holder 7 mounted to the chamber 6. The semiconductor wafer W is placed inside the circle defined by the five guide pins 76. This prevents the horizontal misregistration of the semiconductor wafer W. The number of guide pins 76 is not limited to five, but may be determined so as to prevent the misregistration of the semiconductor wafer W.
[0050] As shown in FIGS. 2 and 3, an opening 78 and a notch 77 are provided in the susceptor 74 so as to extend vertically through the susceptor 74. The notch 77 is provided to allow a distal end portion of a probe of a contact-type thermometer 130 including a thermocouple to pass therethrough. The opening 78, on the other hand, is provided for a radiation thermometer 120 to receive radiated light (infrared light) emitted from the back surface of the semiconductor wafer W held by the susceptor 74. The radiation thermometer 120 and the contact-type thermometer 130 are each provided on the back surface side of the semiconductor wafer W held by the holder 7. The radiation thermometer 120 is formed of, for example, a pyrometer, and receives radiated light from the back surface of the semiconductor wafer W to measure the temperature of the back surface. The susceptor 74 further includes four through holes 79 bored therein and designed so that lift pins 12 of the transfer mechanism 10 to be described later pass through the through holes 79, respectively, to transfer a semiconductor wafer W.
[0051] FIG. 5 is a plan view of the transfer mechanism 10. FIG. 6 is a side view of the transfer mechanism 10. The transfer mechanism 10 includes a pair of transfer arms 11. The transfer arms 11 are of an arcuate configuration extending substantially along the annular recessed portion 62. Each of the transfer arms 11 includes the two lift pins 12 mounted upright thereon. The transfer arms 11 are pivotable by a horizontal movement mechanism 13. The horizontal movement mechanism 13 moves the pair of transfer arms 11 horizontally between a transfer operation position (a position indicated by solid lines in FIG. 5) in which a semiconductor wafer W is transferred to and from the holder 7 and a retracted position (a position indicated by dash-double-dot lines in FIG. 5) in which the transfer arms 11 do not overlap the semiconductor wafer W held by the holder 7 as seen in plan view. The horizontal movement mechanism 13 may be of the type which causes individual motors to pivot the transfer arms 11 respectively or of the type which uses a linkage mechanism to cause a single motor to pivot the pair of transfer arms 11 in cooperative relation.
[0052] The pair of transfer arms 11 is moved upwardly and downwardly together with the horizontal movement mechanism 13 by an elevating mechanism 14. As the elevating mechanism 14 moves up the pair of transfer arms 11 in their transfer operation position, the four lift pins 12 in total pass through the respective four through holes 79 (with reference to FIGS. 2 and 3) bored in the susceptor 74 so that the upper ends of the lift pins 12 protrude from the upper surface of the susceptor 74. On the other hand, as the elevating mechanism 14 moves down the pair of transfer arms 11 in their transfer operation position to take the lift pins 12 out of the respective through holes 79 and the horizontal movement mechanism 13 moves the pair of transfer arms 11 so as to open the transfer arms 11, the transfer arms 11 move to their retracted position. The retracted position of the pair of transfer arms 11 is immediately over the base ring 71 of the holder 7. The retracted position of the transfer arms 11 is inside the recessed portion 62 because the base ring 71 is placed on the bottom surface of the recessed portion 62. An exhaust mechanism (not shown) is also provided near the location where the drivers (the horizontal movement mechanism 13 and the elevating mechanism 14) of the transfer mechanism 10 are provided, and is configured to exhaust an atmosphere around the drivers of the transfer mechanism 10 to the outside of the chamber 6.
[0053] Referring again to FIG. 1, the flash heating part 5 provided over the chamber 6 includes an enclosure 51, a light source provided inside the enclosure 51 and including the multiple (in this preferred embodiment, 30) xenon flash lamps FL, and a reflector 52 provided inside the enclosure 51 so as to cover the light source from above. The flash heating part 5 further includes a lamp light radiation window 53 mounted to the bottom of the enclosure 51. The lamp light radiation window 53 forming the floor portion of the flash heating part 5 is a plate-like quartz window made of quartz. The flash heating part 5 is provided over the chamber 6, whereby the lamp light radiation window 53 is opposed to the upper chamber window 63. The flash lamps FL direct a flash of light from over the chamber 6 through the lamp light radiation window 53 and the upper chamber window 63 toward the heat treatment space 65.
[0054] The flash lamps FL, each of which is a rod-shaped lamp having an elongated cylindrical shape, are arranged in a plane so that the longitudinal directions of the respective flash lamps FL are in parallel with each other along the main surface of a semiconductor wafer W held by the holder 7 (that is, in a horizontal direction). Thus, a plane defined by the arrangement of the flash lamps FL is also a horizontal plane.
[0055] FIG. 8 is a diagram showing a driving circuit for each flash lamp FL. As illustrated in FIG. 8, a capacitor 93, a coil 94, a flash lamp FL, and an IGBT (insulated-gate bipolar transistor) 96 are connected in series. The flash lamp FL includes a rod-shaped glass tube (discharge tube) 92 containing xenon gas sealed therein and having positive and negative electrodes provided on opposite ends thereof, and a trigger electrode 91 attached to the outer peripheral surface of the glass tube 92. A power supply unit 95 applies a predetermined voltage to the capacitor 93, and the capacitor 93 is charged in accordance with the applied voltage (charging voltage). A trigger circuit 97 is capable of applying a high voltage to the trigger electrode 91. The timing of the voltage application from the trigger circuit 97 to the trigger electrode 91 is under the control of the controller 3.
[0056] The IGBT 96 is a bipolar transistor which includes a MOSFET (metal-oxide-semiconductor field-effect transistor) incorporated in the gate thereof, and is also a switching element suitable for handling a large amount of power. An IGBT controller 98 is connected to the gate of the IGBT 96. The IGBT controller 98 is a circuit for applying a signal to the gate of the IGBT 96 to drive the IGBT 96. Specifically, when the IGBT controller 98 applies a voltage ("high" voltage) not less than a predetermined level to the gate of the IGBT 96, the IGBT 96 turns on. When the IGBT controller 98 applies a voltage ("low" voltage) less than the predetermined level to the gate of the IGBT 96, the IGBT 96 turns off. In this manner, the circuit including the flash lamp FL is turned on and off by the IGBT 96. By turning the IGBT 96 on and off, the current flowing from the capacitor 93 to the flash lamp FL is interrupted. The IGBT controller 98 changes the IGBT 96 to be turned on and off under the control of the controller 3.
[0057] Even if, with the capacitor 93 in the charged state, the IGBT 96 turns on to apply a high voltage across the electrodes of the glass tube 92, no electricity will flow through the glass tube 92 in a normal state because the xenon gas is electrically insulative. However, if the trigger circuit 97 applies a high voltage to the trigger electrode 91 to produce an electrical breakdown, an electrical discharge between the electrodes causes a current to flow momentarily in the glass tube 92, so that xenon atoms or molecules are excited at this time to cause light emission.
[0058] The reflector 52 shown in FIG. 1 is provided over the plurality of flash lamps FL so as to cover all of the flash lamps FL. A fundamental function of the reflector 52 is to reflect the light emitted from the plurality of flash lamps FL toward the holder 7. The reflector 52 is a plate made of an aluminum alloy. A surface of the reflector 52 (a surface which faces the flash lamps FL) is roughened by abrasive blasting to produce a stain finish thereon.
[0059] The multiple (in this preferred embodiment, 40) halogen lamps HL are incorporated in the halogen heating part 4 provided under the chamber 6. The halogen lamps HL direct light from under the chamber 6 through the lower chamber window 64 toward the heat treatment space 65. FIG. 7 is a plan view showing an arrangement of the multiple halogen lamps HL. In this preferred embodiment, 20 halogen lamps HL are arranged in an upper tier, and 20 halogen lamps HL are arranged in a lower tier. Each of the halogen lamps HL is a rod-shaped lamp having an elongated cylindrical shape. The 20 halogen lamps HL in the upper tier and the 20 halogen lamps HL in the lower tier are arranged so that the longitudinal directions thereof are in parallel with each other along a main surface of a semiconductor wafer W held by the holder 7 (that is, in a horizontal direction). Thus, a plane defined by the arrangement of the halogen lamps HL in each of the upper and lower tiers is also a horizontal plane.
[0060] As shown in FIG. 7, the halogen lamps HL in each of the upper and lower tiers are disposed at a higher density in a region opposed to the peripheral portion of the semiconductor wafer W held by the holder 7 than in a region opposed to the central portion thereof. In other words, the halogen lamps HL in each of the upper and lower tiers are arranged at shorter intervals near the ends of the lamp arrangement than in the central portion thereof. This allows a greater amount of light to impinge upon the peripheral portion of the semiconductor wafer W where a temperature fall is prone to occur when the semiconductor wafer W is heated by the irradiation thereof with light from the halogen heating part 4.
[0061] The group of halogen lamps HL in the upper tier and the group of halogen lamps HL in the lower tier are arranged to intersect each other in a lattice pattern. In other words, the 40 halogen lamps HL in total are disposed so that the longitudinal direction of the halogen lamps HL in the upper tier and the longitudinal direction of the halogen lamps I-IL in the lower tier are orthogonal to each other.
[0062] Each of the halogen lamps HL is a filament-type light source which passes current through a filament disposed in a glass tube to make the filament incandescent, thereby emitting light. A gas prepared by introducing a halogen element (iodine, bromine and the like) in trace amounts into an inert gas such as nitrogen and argon is sealed in the glass tube. The introduction of the halogen element allows the temperature of the filament to be set at a high temperature while suppressing a break in the filament. Thus, the halogen lamps HL have the properties of having a longer life than typical incandescent lamps and being capable of continuously emitting intense light. In addition, the halogen lamps HL, which are rod-shaped lamps, have a long life. The arrangement of the halogen lamps HL in a horizontal direction provides good efficiency of radiation to the semiconductor wafer W provided over the halogen lamps HL.
[0063] Also as shown in FIG. 1, the heat treatment apparatus 1 includes the shutter mechanism 2 provided alongside the halogen heating part 4 and the chamber 6. The shutter mechanism 2 includes a shutter plate 21, and a sliding drive mechanism 22. The shutter plate 21 is a plate opaque to halogen light, and is made of, for example, titanium (Ti). The sliding drive mechanism 22 causes the shutter plate 21 to slidably move in a horizontal direction, thereby bringing the shutter plate 21 into and out of a light shielding position lying between the halogen heating part 4 and the holder 7. When the sliding drive mechanism 22 moves the shutter plate 21 forward, the shutter plate 21 is inserted into the light shielding position (a position indicated by dash-double-dot lines in FIG. 1) lying between the chamber 6 and the halogen heating part 4 to provide isolation between the lower chamber window 64 and the plurality of halogen lamps HL. Thus, light directed from the plurality of halogen lamps HL toward the holder 7 in the heat treatment space 65 is intercepted. On the other hand, when the sliding drive mechanism 22 moves the shutter plate 21 backward, the shutter plate 21 is retracted from the light shielding position lying between the chamber 6 and the halogen heating part 4 to open the space lying under the lower chamber window 64.
[0064] As shown in FIG. 8, the heat treatment apparatus 1 according to this preferred embodiment includes a sampling part 160 for sampling a signal outputted from the photodetector part 150 to transmit the sampled signal to the controller 3. FIG. 10 is a block diagram showing configurations of the sampling part 160 and the controller 3. The photodetector part 150 is installed in the upper portion of the inner wall of the chamber 6, and receives the radiated light from the front surface of the semiconductor wafer W held by the holder 7. The light having a wavelength of 5 μm or more included the radiated light that has been radiated from the front surface of the semiconductor wafer W and entered the photodetector part 150 is selectively allowed to pass through the long-wave pass filter 152 and reaches the InSb photoconductive element 153.
[0065] The InSb photoconductive element 153 generates a change in resistance in accordance with the intensity of received light. The InSb photoconductive element 153 is capable of performing high-speed measurement with an extremely short response time. The InSb photoconductive element 153 of the photodetector part 150 is electrically connected to the sampling part 160, and transmits a signal generated in response to light reception to the sampling part 160.
[0066] The sampling part 160 includes a low-pass filter 161, a differentiating circuit 162, an amplifier 163, an A/D converter 164, and a CPU 165, and measures the intensity of the radiated light received by the InSb photoconductive element 153 of the photodetector part 150. The low-pass filter (LPF) 161 removes a high-frequency noise from the signal transmitted from the photodetector part 150. The differentiating circuit 162 eliminates a DC component from the signal that has passed through the low-pass filter 161, to thereby extract a change amount of the signal. The differentiating circuit 162 may be configured using, e.g. AC coupling.
[0067] The amplifier 163 amplifies the signal outputted from the differentiating circuit 162 and transmits the amplified signal to the A/D converter 164. The A/D converter 164 converts the signal amplified by the amplifier 163 to a digital signal. The CPU 165 executes a predetermined processing program and samples the digital signals outputted from the A/D converter 164 at predetermined time intervals, to thereby sequentially store the digital signals in a memory (not shown) separately provided. In other words, the sampling part 160 measures the levels of signals transmitted from the InSb photoconductive element 153 of the photodetector part 150 in chronological order, to thereby obtain a plurality of pieces of signal level data. The CPU 165 of the sampling part 160 is tailored for sampling of the signals from the photodetector part 150, whereby the sampling interval is set to approximately several microseconds. The CPU 165, the A/D converter 164, the memory and the like may be incorporated into a single one-chip microcomputer.
[0068] The CPU 165 of the sampling part 160 is connected to the controller 3 via a communication line. The controller 3 controls the above-mentioned various operating mechanisms provided in the heat treatment apparatus 1. The controller 3 is similar in hardware configuration to a typical computer. Specifically, the controller 3 includes a CPU for performing various computation processes, a ROM or read-only memory for storing a basic program therein, a RAM or readable/writable memory for storing various pieces of information therein, and a magnetic disk 31 for storing control software, data and the like therein. The controller 3 is connected to the IGBT controller 98 and a display part 35, and is capable of controlling the operation of the IGBT controller 98 as well as causing the display part 35 to display the computation results or the like thereon. It suffices that the display part 35 is formed of, for example, a liquid crystal display or the like. Further, the controller 3 is also connected to the radiation thermometer 120 provided on the back surface side of the semiconductor wafer W, and the measurement results of the radiation thermometer 120 are transmitted to the controller 3. It should be noted that though not shown in FIG. 10, the contact-type thermometer 130 including a thermocouple is also connected to the controller 3.
[0069] The controller 3 can perform a general-purpose process but cannot perform sampling at time intervals as short as the CPU 165 of the sampling part 160. The signal level data stored in the memory by the CPU 165 is transferred to the controller 3 and stored in the magnetic disk 31. The controller 3 further includes a temperature calculating part 32 and an emmisivity calculating part 33. The temperature calculating part 32 and the emmisivity calculating part 33 are functional processors implemented by executing a predetermined processing program by the CPU of the controller 3, and the processing thereof is further described below. The communication line connecting the sampling part 160 and the controller 3 to each other may provide serial communication or parallel communication.
[0070] The heat treatment apparatus 1 further includes, in addition to the above-mentioned components, various cooling structures to prevent an excessive temperature rise in the halogen heating part 4, the flash heating part 5 and the chamber 6 because of the heat energy generated from the halogen lamps HL and the flash lamps FL during the heat treatment of a semiconductor wafer W. As an example, a water cooling tube (not shown) is provided in the walls of the chamber 6. Also, the halogen heating part 4 and the flash heating part 5 have an air cooling structure for forming a gas flow therein to exhaust heat. Air is also supplied to a gap between the upper chamber window 63 and the lamp light radiation window 53 to cool down the flash heating part 5 and the upper chamber window 63.
[0071] Next, a procedure for the treatment of a semiconductor wafer W in the heat treatment apparatus 1 having the above-mentioned configuration will be described. First, the procedure for the process of heating a semiconductor wafer W in the heat treatment apparatus 1 will be described briefly, and then, the procedure of calculating the temperature of the front surface of the semiconductor wafer W during the treatment will be described.
[0072] Device patterns of a gate, a source, a drain, and the like are formed on the front surface of a semiconductor wafer W to be treated in the heat treatment apparatus 1.
[0073] Accordingly, fine asperities are formed on the front surface of the semiconductor wafer W, and the emissivity is determined by the asperities. Therefore, a different device pattern results in different emissivity on the front surface of the semiconductor wafer W. On the other hand, device patterns are not formed on the back surface of the semiconductor wafer W. For this reason, the emissivity of the back surface of the semiconductor wafer W remains constant regardless of device patterns on the front surface thereof, and a value thereof has already been known.
[0074] The source and drain regions formed in the front surface of the semiconductor wafer W are doped with impurities (ions) by an ion implantation process. The impurities with which the semiconductor substrate W is doped are activated by the heat treatment apparatus 1 performing the process of heating (annealing) the semiconductor wafer W by irradiation. The procedure for the treatment in the heat treatment apparatus 1 which will be described below proceeds under the control of the controller 3 over the operating mechanisms of the heat treatment apparatus 1.
[0075] First, prior to the treatment, the valve 84 is opened for supply of gas, and the valves 89 and 192 for exhaust of gas are opened, so that the supply and exhaust of gas into and out of the chamber 6 start. When the valve 84 is opened, nitrogen gas is supplied through the gas supply opening 81 into the heat treatment space 65. When the valve 89 is opened, the gas within the chamber 6 is exhausted through the gas exhaust opening 86. This causes the nitrogen gas supplied from an upper portion of the heat treatment space 65 in the chamber 6 to flow downwardly and then to be exhausted from a lower portion of the heat treatment space 65.
[0076] The gas within the chamber 6 is exhausted also through the transport opening 66 by opening the valve 192. Further, the exhaust mechanism (not shown) exhausts an atmosphere near the drivers of the transfer mechanism 10. It should be noted that the nitrogen gas is continuously supplied into the heat treatment space 65 during the heat treatment of a semiconductor wafer W in the heat treatment apparatus 1. The amount of nitrogen gas supplied into the heat treatment space 65 is changed as appropriate in accordance with processing steps.
[0077] Subsequently, the gate valve 185 is opened to open the transport opening 66. A transport robot outside the heat treatment apparatus 1 transports an impurity-implanted semiconductor wafer W through the transport opening 66 into the heat treatment space 65 in the chamber 6. The semiconductor wafer W transported into the heat treatment space 65 by the transport robot is moved forward to a position lying immediately over the holder 7 and is stopped thereat. Then, the pair of transfer arms 11 of the transfer mechanism 10 is moved horizontally from the retracted position to the transfer operation position and is then moved upwardly, whereby the lift pins 12 pass through the through holes 79 and protrude from the upper surface of the susceptor 74 to receive the semiconductor wafer W.
[0078] After the semiconductor wafer W is placed on the lift pins 12, the transport robot moves out of the heat treatment space 65, and the gate valve 185 closes the transport opening 66. Then, the pair of transfer arms 11 moves downwardly to transfer the semiconductor wafer W from the transfer mechanism 10 to the susceptor 74 of the holder 7, so that the semiconductor wafer W is held in a horizontal position. The semiconductor wafer W is held on the susceptor 74 so that the impurity-implanted front surface thereof on which device patterns are formed is the upper surface. Also, the semiconductor wafer W is held inside the five guide pins 76 on the upper surface of the susceptor 74. The pair of transfer arms 11 moved downwardly below the susceptor 74 is moved back to the retracted position, i.e. to the inside of the recessed portion 62, by the horizontal movement mechanism 13.
[0079] After the semiconductor wafer W is placed and held on the susceptor 74 of the holder 7, the 40 halogen lamps HL in the halogen heating part 4 turn on simultaneously to start preheating (assist heating). Halogen light emitted from the halogen lamps HL is transmitted through the lower chamber window 64 and the susceptor 74 both made of quartz, and impinges upon the back surface of the semiconductor wafer W. The semiconductor wafer W is irradiated with the halogen light from the halogen lamps HL, so that the temperature of the semiconductor wafer W rises. It should be noted that the transfer arms 11 of the transfer mechanism 10, which are retracted to the inside of the recessed portion 62, do not become an obstacle to the heating using the halogen lamps HL.
[0080] FIG. 11 is a graph showing changes in the temperature of the front surface of the semiconductor wafer W. After the semiconductor wafer W is placed on the susceptor 74, the controller 3 turns on the 40 halogen lamps HL at time t0, so that the temperature of the semiconductor wafer W irradiated with the halogen light is raised to a preheating temperature T1. The preheating temperature T1 is 300° C. or higher and 800° C. or lower.
[0081] In preheating with the halogen lamps HL, the temperature of the semiconductor wafer W is measured with the contact-type thermometer 130. That is, the contact-type thermometer 130 including a built-in thermocouple comes into contact with the back surface of the semiconductor wafer W held by the susceptor 74 through the notch 77, to thereby measure the wafer temperature during temperature rise. The measured temperature of the semiconductor wafer W is transmitted to the controller 3. The controller 3 controls the output from the halogen lamps HL while monitoring whether or not the temperature of the semiconductor wafer W, which rises by irradiation from the halogen lamps HL, reaches the predetermined preheating temperature T1. That is, the controller 3 effects feedback control of the output from the halogen lamps HL, based on the measurement value of the contact-type thermometer 130, so that the temperature of the semiconductor wafer W is equal to the preheating temperature T1. It should be noted that in the stage of preheating, no difference is caused in temperature between the front and back surfaces of the semiconductor wafer W, and the temperature of the back surface of the semiconductor wafer W that has been measured with the contact-type thermometer 130 is equal to the temperature of the front surface thereof.
[0082] After the temperature of the semiconductor wafer W reaches the preheating temperature T1, the controller 3 maintains the temperature of the semiconductor wafer W at the preheating temperature T1 for a short time interval. Specifically, at time t1 when the temperature of the semiconductor wafer W measured with the contact-type thermometer 130 reaches the preheating temperature T1, the controller 3 controls the output from the halogen lamps HL to maintain the temperature of the semiconductor wafer W at approximately the preheating temperature T1.
[0083] By performing such preheating using the halogen lamps HL, the temperature of the entire semiconductor wafer W is uniformly raised to the preheating temperature T1. In the stage of preheating using the halogen lamps HL, the semiconductor wafer W shows a tendency to be lower in temperature in a peripheral portion thereof where heat dissipation is liable to occur than in a central portion thereof However, the halogen lamps HL in the halogen heating part 4 are disposed at a higher density in a region opposed to the peripheral portion of the semiconductor wafer W than in a region opposed to the central portion thereof. This causes a greater amount of light to impinge upon the peripheral portion of the semiconductor wafer W where heat dissipation is liable to occur, thereby providing a uniform in-plane temperature distribution of the semiconductor wafer W in the stage of preheating. Further, the inner peripheral surface of the lower reflective ring 69 mounted to the chamber side portion 61 is provided as a mirror surface. Thus, a greater amount of light is reflected from the inner peripheral surface of the lower reflective ring 69 toward the peripheral portion of the semiconductor wafer W. This provides a more uniform in-plane temperature distribution of the semiconductor wafer W in the stage of preheating.
[0084] Next, the flash lamps FL start emitting a flash of light at time t2 when a predetermined time period has elapsed since the temperature of the semiconductor wafer W reached the preheating temperature T1. It should be noted that a time interval when the temperature of the semiconductor wafer W reaches the preheating temperature T1 from the room temperature (a time interval between the time t0 and the time t1) and the time interval when the flash lamps FL emit light after reaching the preheating temperature T1 (a time interval between the time t1 and the time t2) are only on the order of several seconds. For the flash irradiation from a flash lamp FL, the capacitor 93 is charged in advance by the power supply unit 95. Then, with the capacitor 93 in the charged state, the IGBT controller 98 outputs a pulse signal to the gate of the IGBT 96 under the control of the controller 3 to drive the IGBT 96 on and off.
[0085] The waveform of the pulse signal outputted from the IGBT controller 98 is specified by inputting, to the controller 3, a recipe that is a sequence of defined parameters indicating a time interval (ON time) equivalent to the pulse width and a time interval (OFF time) equivalent to the pulse interval between pulses. After an operator inputs such a recipe, the controller 3 sets a pulse waveform having repeated ON and OFF time intervals in accordance with the recipe. Then, the IGBT controller 98 outputs the pulse signal in accordance with the pulse waveform. As a result, the pulse signal having the set waveform is applied to the gate of the IGBT 96, so that driving the IGBT 96 on and off is controlled. Specifically, the IGBT 96 turns on when the pulse signal inputted to the gate of the IGBT 96 is on, whereas the IGBT 96 turns off when the pulse signal is off.
[0086] In synchronization with the timing when the pulse signal outputted from the IGBT controller 98 turns on, the controller 3 controls the trigger circuit 97 to apply a high voltage (trigger voltage) to the trigger electrode 91. With the electrical charges stored in the capacitor 93, the pulse signal is inputted to the gate of the IGBT 96, and the high voltage is applied to the trigger electrode 91 in synchronization with the timing when the pulse signal turns on. This causes a current to flow across the electrodes of the glass tube 92 without fail when the pulse signal is on, and the resultant excitation of xenon atoms or molecules induces light emission, whereby the flash lamp FL emits light.
[0087] The waveform of the current flowing through the glass tube 92 when the flash lamp FL emits light depends on the waveform of the pulse signal inputted to the gate of the IGBT 96. That is, the value of the current flowing through the glass tube 92 of the flash lamp FL increases when the pulse signal inputted to the gate of the IGBT 96 is on, and the value of the current decreases when the pulse signal is off, which specifies the sawtooth current waveform. It should be noted that an individual current waveform corresponding to each pulse is defined by the constant of the coil 94.
[0088] The emission intensity of the flash lamp FL is roughly proportional to the current flowing through the flash lamp FL. Thus, the intensity waveform (profile) of the light emission output from the flash lamp FL is approximately similar to the waveform of the current flowing through the flash lamp FL. In this manner, the flash lamp FL emits light, whereby flash irradiation is performed on the front surface of the semiconductor wafer W held by the holder 7.
[0089] In a case where the flash lamp FL is caused to emit light without using the IGBT 96, the electrical charges stored in the capacitor 93 are consumed by single light emission, and the intensity waveform from the flash lamp FL is obtained as a single pulse having a width of approximately 0.1 milliseconds to 10 milliseconds. On the other hand, in this preferred embodiment, the IGBT 96 serving as a switching element is connected in the circuit, and a pulse signal is outputted to the gate of the IGBT 96. Accordingly, the electrical charges are intermittently supplied from the capacitor 93 to the flash lamp FL by the IGBT 96, so that the current flowing through the flash lamp FL is controlled. As a result, so to speak, light emission from the flash lamp FL is subjected to chopper control, and the electrical charges stored in the capacitor 93 are consumed in a divided manner, so that the flash lamp FL repeats blinking in an extremely short period of time. It should be noted that the current value increases again by application of the following pulse to the gate of the IGBT 96 before the value of the current flowing through the flash lamp FL becomes exactly "0", which means that the emission intensity does not become exactly "0" also while the flash lamp FL repeats blinking.
[0090] Such flash irradiation from the flash lamp FL is performed on the semiconductor wafer W, whereby the temperature of the front surface of the semiconductor wafer W is raised from the preheating temperature T1 to the treatment temperature T2. This allows activation of the implanted impurities. The treatment temperature T2 is 1,000° C. or higher and 1,400° C. or lower at which the activation of the implanted impurities is achieved. The time waveform of emission intensity of the flash lamp FL may be changed as appropriate by adjusting the waveform of the pulse signal to be applied to the gate of the IGBT 96. The time waveform of emission intensity may be determined in accordance with an object of the heat treatment (for example, activation of implanted impurities or the process of recovering crystal defects caused in the implantation of impurities). It should be noted that even if the time waveform of emission intensity of the flash lamp FL has any form, the total emission time of the flash lamp FL in single heating is one second or less. The waveform of the pulse signal applied to the gate of the IGBT 96 may be adjusted in accordance with the time interval equivalent to the pulse width and time interval equivalent to a pulse interval between pulses inputted to the controller 3.
[0091] When flash irradiation from the flash lamp FL is ended, the IGBT 96 turns off, and the light emission from the flash lamp FL is stopped. This causes the temperature of the front surface of the semiconductor wafer W to start falling rapidly from the treatment temperature T2. Then, the halogen lamps HL turn off at time t3 after a lapse of a predetermined time period since the light emission from the flash lamp FL stops. This causes the temperature of the semiconductor wafer W to start falling from the preheating temperature T1. At the same time that the halogen lamps HL turn off, the shutter mechanism 2 inserts the shutter plate 21 into the light shielding position lying between the halogen heating part 4 and the chamber 6. The temperatures of filaments and tube walls of the halogen lamps HL do not decrease immediately after the halogen lamps HL turn off, but radiant heat is continuously emitted from the filaments and the tube walls at elevated temperature for a short time interval to obstruct the temperature decrease of the semiconductor wafer W. The insertion of the shutter plate 21 interrupts the radiant heat emitted from the halogen lamps HL immediately after the turning off toward the heat treatment space 65 to increase the speed at which the temperature of the semiconductor wafer W decreases.
[0092] The controller 3 monitors whether or not the temperature of the semiconductor wafer W that is measured with the contact-type thermometer 130 has fallen to a predetermined temperature. Then, after the temperature of the semiconductor wafer W falls to be equal to or lower than a predetermined temperature, the pair of transfer arms 11 of the transfer mechanism 10 is again moved horizontally from the retracted position to the transfer operation position and moved upwardly, whereby the lift pins 12 protrude from the upper surface of the susceptor 74 to receive the semiconductor wafer W after the heat treatment from the susceptor 74. Subsequently, the transport opening 66 which has been closed is opened by the gate valve 185, and the transport robot outside the heat treatment apparatus 1 transports the semiconductor wafer W placed on the lift pins 12 to the outside. Thus, the heat treatment apparatus 1 completes the heating treatment of the semiconductor wafer W.
[0093] Next, description will be given of the procedure of calculating the temperature of the front surface of the semiconductor wafer W heated by the flash irradiation as described above. The temperature of the front surface of the semiconductor wafer W according to this preferred embodiment is calculated with the photodetector part 150 and the radiation thermometer 120. Prior to calculating the temperature, the correlation between the intensity of the radiated light received by the InSb photoconductive element 153 of the photodetector part 150 and the level (voltage) of the signal outputted from the InSb photoconductive element 153 is determined in advance. The correlation is determined by, for example, blackbody test using a blackbody furnace.
[0094] FIG. 12 is a graph showing the correlation between the temperature of a black body and the output from the InSb photoconductive element 153. The black body is assumed to be a perfect radiator (having an emissivity of 1.0), and according to the Planck's law regarding black body radiation, the intensity I' (λ, T) of the radiated light having a wavelength λ (m) from a black body with a temperature T (K) is expressed as in Expression (1) below. In Expression (1), a constant c is a speed of light 3×108 (m/s), k is a Boltzmann constant 1.3807×10-23 (J/K), and h is a Planck constant 6.626×10-34 (Js).
I ' ( λ , T ) = 2 hc 2 λ 5 1 hc λ kT - 1 ( 1 ) ##EQU00001##
[0095] In this preferred embodiment, the intensity I expressed by Expression (2) below is regarded as the intensity of radiated light measured by the InSb photoconductive element 153 in consideration of the wavelength range actually measured by the InSb photoconductive element 153. Expression (2) is provided for integrating the intensity I' (λ, T) of a black body obtained by Expression (1) by the wavelength ranges k1 to k2 actually measured by the InSb photoconductive element 153. As described above, the wavelength range that can be received by the InSb photoconductive element 153 is 6.5 μm or less, and the log-wave pass filter 152 allows light having a wavelength of 5 μm or more to pass therethrough. Therefore, the wavelength range actually measured by the InSb photoconductive element 153 is 5 μm to 6.5 μm (λ1=5 μm, λ2=6.5 μm).
I=∫.sub.λ1.sup.λ2I'(λ,T)dλ (2)
[0096] Through the integration by the wavelength ranges λ1 to λ2, the intensity I of Expression (2) is taken as a function of temperature. Accordingly, for example, the intensities I1, I2, I3, and I4 of radiated light from a black body of 400° C., 600° C., 800° C., and 1,000° C., respectively, are obtained from Expression (2). The intensity of radiated light of a black body obtained from Expression (2) is a theoretical value calculated based on the Planck's law.
[0097] Meanwhile, the photodetector part 150 receives the radiated light from a black body of 400° C., 600° C., 800° C., and 1,000° C. with a blackbody furnace, so that signal levels V1, V2, V3, and V4 outputted from the InSb photoconductive element 153 are obtained, respectively (FIG. 12). The signal levels are values measured by the photodetector part 150 and the sampling part 160. Strictly speaking, the signal levels outputted from the InSb photoconductive element 153 are levels of the signals outputted from the A/D converter 164 that are measurable by the CPU 165 of the sampling part 160.
[0098] An approximate expression indicating the correlation between the intensity I of radiated light received by the InSb photoconductive element 153 and the level V of the signal outputted from the InSb photoconductive element 153 is obtained from the theoretical value of the intensity of radiation light radiated from a black body and the measured value received by the photodetector part 150. Specifically, the least squares method is used, to thereby obtain a coefficient α so as to obtain a minimum sum of squares determined by Expression (3) below. In Expression (3) below, n=4 because measurement is performed at four points in the example above.
i = 1 n ( Vi - α Ii ) 2 ( 3 ) ##EQU00002##
[0099] α is determined in this manner, which determines Expression (4) for converting the signal level V outputted from the InSb photoconductive element 153 to the intensity I of the radiated light. It should be noted that approximation is performed at four points for obtaining the correlation between the intensity I of radiaion light and the signal level V in the above-mentioned example, which is not limited to four points. It suffices that approximation is performed at a plurality of points, and the approximation accuracy is enhanced with a larger number of measurement points.
I = V α ( 4 ) ##EQU00003##
[0100] Expression (4) and the coefficient α obtained as described above are stored in a storage part such as the magnetic disk 31 of the controller 3. With the controller 3 holding Expression (4) in advance, flash irradiation as described above is performed. When flash irradiation is performed, the photodetector part 150 and the sampling part 160 measure the intensity of radiated light from the front surface of the semiconductor wafer W.
[0101] FIG. 13 is a graph showing changes in the signal level outputted from the InSb photoconductive element 153 in flash irradiation. FIG. 14 is a graph showing changes in the temperature of a semiconductor wafer W in flash irradiation. A flash of light that reaches the heat treatment space 65 in the chamber 6 when light is emitted from the flash lamp FL is the light that has passed through the tube wall of the glass tube 92, the lamp light radiation window 53, and the upper chamber window 63. Those are each made of quartz that hardly allows light having a wavelength of 4 μm or more to pass therethrough, and thus, light having a wavelength region of 4 μm or more is eliminated from the flash of light that reaches the heat treatment space 65. Further, light having a wavelength region of 4 μm or more is eliminated from halogen light that passes from the halogen lamps HL through the lower chamber window 64 made of quartz to be emitted to the heat treatment space 65.
[0102] A part of the light that has reached the heat treatment space 65 in the chamber 6 enters the photodetector part 150 as well. The light that reaches the heat treatment space 65 and enters the photodetector part 150 has a wavelength less than 4 μm, whereas the long-wave pass filter 152 of the photodetector part 150 blocks light having a wavelength less than 5 μm. In other words, the long-wave pass filter 152 allows only light having a selective wavelength range (5 μm or more) included in the wavelength range (4 82 m or more) eliminated by the upper chamber window 63 being a quartz window. Accordingly, a flash of light that has entered the photodetector part 150 from the heat treatment space 65 is all shielded by the long-wave pass filter 152 and does not reach the InSb photoconductive element 153. Similarly, halogen light that has entered the photodetector part 150 from the heat treatment space 65 does not reach the InSb photoconductive element 153. As a result, the InSb photoconductive element 153 is capable of receiving radiated light from the front surface of the semiconductor wafer W without being affected by an extremely intense flash of light and halogen light.
[0103] Meanwhile, the temperature of the semiconductor wafer W is raised to the preheating temperature T1 by preheating with halogen lamps HL, and the temperature of the front surface thereof is raised further from the preheating temperature T1 by flash irradiation from the flash lamp FL. The radiated light having an intensity corresponding to the temperature is radiated from the front surface of the semiconductor wafer W whose temperature has been raised. The radiated light from the front surface of the semiconductor wafer W also enters the photodetector part 150. Then, the light having a wavelength of 5 μm or more that has passed through the long-wave pass filter 152 included in the radiated light that has entered the photodetector part 150 reaches the InSb photoconductive element 153. The wavelength range that can be received by the InSb photoconductive element 153 is 6.5 μm or less, and accordingly, the wavelength range actually measured by the InSb photoconductive element 153 is 5 μm to 6.5 μm.
[0104] The InSb photoconductive element 153 generates and outputs a change in resistance corresponding to the intensity of the radiated light that has been received. On this occasion, a flash of light is blocked by the upper chamber window 63 and the long-wave pass filter 152 for all wavelength ranges, and the halogen light is blocked by the lower chamber window 64 and the long-wave pass filter 152. Accordingly, light received by the InSb photoconductive element 153 is purely radiated light from the front surface of the semiconductor wafer W. The signal outputted from the InSb photoconductive element 153 passes through the low-pass filter 161, whereby a noise is removed. Subsequently, the signal is then inputted to the differentiating circuit 162, so that a DC component is eliminated. Then, the signal outputted from the differentiating circuit 162 is amplified by the amplifier 163 and is then converted by the A/D converter 164 to a digital signal suitably handled by a computer. Then, the level of the digital signal outputted from the A/D converter 164 turns into the voltage to be inputted to the CPU 165, which is obtained as the level of a signal outputted from the InSb photoconductive element 153.
[0105] The level data of the signal outputted from the InSb photoconductive element 153 that has been obtained by the CPU 165 of the sampling part 160 is transmitted to the controller 3 to be stored in a storage part such as the magnetic disk 31. The controller 3 calculates the intensity I of radiated light based on the level V of the signal outputted from the InSb photoconductive element 153 and Expression (4) stored in advance in a storage part such as the magnetic disk 31, and associates a value of the intensity I with the measurement time to store those in the magnetic disk 31.
[0106] In this manner, the sampling part 160 performs single sampling on the intensity of radiated light on the front surface of the semiconductor wafer W. Then, the sampling part 160 repeatedly measures the intensity of radiated light a plurality of times at constant intervals until a predetermined time interval determined in advance elapses. Accordingly, the sampling part 160 sequentially measures the intensities of radiated light from the front surface of the semiconductor wafer W immediately after irradiation from the flash lamp FL is started. Then, the intensities of radiated light that have been measured in chronological order are sequentially stored in the magnetic disk 31 of the controller 3, whereby a history of radiated light intensity of the front surface of the semiconductor wafer W is obtained. It should be noted that the time period when sampling is performed is at least from time ta when the flash lamp FL starts light emission to time td when the temperature of the back surface is measured with the radiation thermometer 120 described below.
[0107] In FIG. 14, a solid line and a broken line indicate the temperatures of the front and back surfaces of the semiconductor wafer W in flash irradiation, respectively. The flash lamp FL starts emitting light at the time ta, and an intense flash of light is radiated in an extremely short period of time. Accordingly, the temperature of the front surface of the semiconductor wafer W rises at high speed, whereas the temperature of the back surface thereof does not rise so high from the preheating temperature T1. After that, the flash lamp FL stops emitting light, whereby the temperature of the front surface of the semiconductor wafer W falls rapidly, and at the same time, the temperature of the back surface rises slightly due to heat conduction from the front surface to the back surface. Accordingly, the temperatures of the front and back surfaces become equal to each other at the time tc. The times shown in FIGS. 13 and 14 are all near the time t2 of FIG. 11. The graph of FIG. 11 is plotted with a time scale of seconds, whereas the graphs of FIGS. 13 and 14 are plotted with a time scale of milliseconds. Thus, the times ta to td are shown as overlaid on the time t2 in FIG. 11.
[0108] In this preferred embodiment, the temperature of the back surface of the semiconductor wafer W is measured with the radiation temperature 120 at the time td after the flash lamp FL starts irradiation with a flash of light and then the temperatures of the front and back surfaces of the semiconductor wafer W become equal to each other after. In the case of a semiconductor wafer W having a diameter of 300 mm, the time interval required between the time ta when the flash lamp FL starts emitting light and the time tc when the temperatures of the front and back surfaces thereof become equal to each other is approximately 20 milliseconds. Accordingly, the time td when the measurement of the temperature of the back surface is started with the radiation thermometer 120 is approximately 50 milliseconds after the time ta. If 50 milliseconds have elapsed since the time ta when the flash lamp FL starts emitting light, the temperatures of the front and back surfaces are precisely equal to each other irrespective of whether the treatment temperature T2 is high or low.
[0109] The radiation thermometer 120 measures the intensity of infrared light radiated from the back surface of the semiconductor wafer W through the opening 78 of the susceptor 74 to obtain the temperature of the back surface. The response speed of the radiation thermometer 120 including a pyrometer is lower compared with the InSb photoconductive element 153, a photodiode and the like. However, temperature does not change abruptly after the time td when the temperatures of the front and back surfaces of the semiconductor wafer W become equal to each other, whereby it is sufficiently possible to measure the temperature of the back surface even with the radiation thermometer 120 including a pyrometer.
[0110] In the case of measuring the temperature of the back surface with the radiation thermometer 120, the emmisivity of the back surface of the semiconductor wafer W is required. As described above, device patterns are not formed on the back surface of the semiconductor wafer W, and accordingly, the emissivity of the back surface is constant regardless of a wafer, which is a known value (emissivity of so-called bare wafer). This enables to accurately measure the temperature of the back surface of the semiconductor wafer W with the radiation thermometer 120.
[0111] The temperature of the back surface of the semiconductor wafer W that has been measured with the radiation thermometer 120 is transmitted to the controller 3. In addition, the temperature of the back surface that has been measured at the time td after the time tc when the temperatures of the front and back surfaces of the semiconductor wafer W become equal to each other is the temperature of the front surface of the semiconductor wafer W as it is. In other words, measuring the temperature of the back surface of the semiconductor wafer W after the time tc is equal to measuring the temperature of the front surface thereof.
[0112] The emissivity calculating part 33 of the controller 3 calculates the intensity of radiated light from the front surface assuming that the front surface of the semiconductor wafer W is a black body from the temperature of the back surface (=temperature of the front surface) measured with the radiation thermometer 120 (that is, assuming that the emissivity of the front surface is one). Expression (2) derived from the Planck's law may be used for this calculation. The emissivity calculating part 33 applies a back surface temperature of Td measured at the time td to Expression (2), to thereby calculate the intensity I (Td) of the radiated light from the front surface at the temperature of Td assuming that the front surface of the semiconductor wafer W is a black body.
[0113] The intensity I (Td) of radiated light is the intensity of radiated light from a black body with the measured front surface temperature of Td assuming that the front surface of the semiconductor wafer W is a black body. However, the front surface of the actual semiconductor wafer W is not a black body but has an emissivity less than one that depends on device patterns. Therefore, the intensity of radiated light actually radiated from the front surface of the semiconductor wafer W with the front surface temperature of Td is smaller than I (Td). The intensity of radiated light actually radiated from the front surface of the semiconductor wafer W is measured by the photodetector part 150 and the sampling part 160.
[0114] As shown in FIG. 13, the InSb photoconductive element 153 that has received radiated light from the front surface of the semiconductor wafer W outputs a signal of the level Vd at the time td when the temperature of the back surface of the semiconductor wafer W is measured with the radiation thermometer 120. The signal level Vd is associated with the measurement time td to be stored in the magnetic disk 31. The intensity I (td) obtained by dividing the signal level Vd outputted from the InSb photoconductive element 153 at the time td by a in accordance with Expression (4) is the intensity of radiated light actually radiated from the front surface of the semiconductor wafer W having the front surface temperature of Td.
[0115] Expression (5) below holds between the intensity I (Td) of radiated light from the black body with the temperature of Td and the intensity I (td) of radiated light actually radiated from the front surface of the semiconductor wafer W with the front surface temperature of Td. In Expression (5), ε is the emissivity of the front surface of the semiconductor wafer W.
I(td)=εI(Td) (5)
[0116] The emissivity calculating part 33 calculates the emissivity ε of the front surface of the semiconductor wafer W from Expression (5). In other words, the emissivity calculating part 33 calculates the emissivity ε of the front surface of the semiconductor wafer W based on the intensity I (Td) of radiated light from the black body with a temperature equal to the black surface temperature of Td measured with the radiation thermometer 120 after the temperatures of the front and back surfaces become equal to each other, and the intensity I (td) of radiated light actually radiated from the front surface of the semiconductor wafer W with the front surface temperature of Td measured by the photodetector part 150 and the sampling part 160. The calculated emissivity ε is stored in the magnetic disk 31.
[0117] Next, the temperature calculating part 32 of the controller 3 calculates the temperature of the front surface of the semiconductor wafer W using the emissivity ε calculated as described above. The temperature calculating part 32 calculates the temperature of the front surface of the semiconductor wafer W heated by flash irradiation, based on the emissivity ε of the front surface of the semiconductor wafer W and the intensity of radiated light from the front surface of the semiconductor wafer W measured by the photodetector part 150 and the sampling part 160.
[0118] The intensities of radiated light from the front surface of the semiconductor wafer W are obtained in chronological order as a history of radiated light intensity to be stored in the magnetic disk 31. Accordingly, the temperature calculating part 32 is capable of calculating the temperature of the front surface of the semiconductor wafer W based on the measured intensity of radiated light at an appropriate time between the time to when the flash lamp FL starts emitting light and the time td when the temperature of the back surface is measured with the radiation thermometer 120.
[0119] For example, as shown in FIG. 13, the level of the signal outputted from the InSb photoconductive element 153 has reached the maximum value Vb at the time tb. Therefore, it is conceivable that the temperature of the front surface of the semiconductor wafer W has reached the maximum value (that is, treatment temperature T2) by the time tb. The intensity I (tb) obtained by dividing the signal level Vb by a in accordance with Expression (4) is the intensity of radiated light from the front surface of the semiconductor wafer W at the time tb. The intensity I (T2) obtained by dividing the intensity I (tb) of radiated light on the front surface of the semiconductor wafer W at the time tb by the emissivity ε of the front surface is the intensity of radiated light from the black body with the treatment temperature T2 being the maximum attained temperature. If the intensity I (T2) of radiated light from a black body is determined, the temperature T2 of the black body is obtained with, for example, Expression (2) derived from the Planck's law. The temperature calculating part 32 calculates the maximum temperature (treatment temperature T2) that the front surface has reached from the history of radiated light intensity of the front surface of the semiconductor wafer W in this manner.
[0120] While the description has been given of the example in which the maximum temperature that the front surface of the semiconductor wafer W reaches at the time tb, the temperature that the front surface of the semiconductor wafer W reaches at another time can be calculated by a similar technique as well. Alternatively, a similar technique to that described above may be applied for the entire history of radiated light intensity in which the intensities of radiated light from the front surface of the semiconductor wafer W are obtained in chronological order, to thereby calculate the history of front-surface temperature of the semiconductor wafer W heated by flash radiation. Still alternatively, the temperature calculating part 32 may calculate the maximum temperature that the front surface of the semiconductor waver W reaches from the history of front-surface temperature after the history of front-surface temperature of the semiconductor wafer W is obtained. The controller 3 may cause the display part 35 to display the temperature of the front surface of the semiconductor wafer W or the history of front-surface temperature calculated as described above.
[0121] In this preferred embodiment, light having a wavelength of 4 μm or more is eliminated from a flash of light emitted from the flash lamp FL by a quartz window such as the upper chamber window 63, whereby the semiconductor wafer W is irradiated with the resultant light. Accordingly, the wavelength of a flash of light entering the photodetector part 150 from the heat treatment space 65 in the chamber 6 is less than 4 μm. Meanwhile, the long-wave pass filter 152 of the photodetector part 150 blocks light having a wavelength less than 5 μm. As a result, even while the flash lamp FL is emitting light, no flash of light reaches the InSb photoconductive element 153 of the photodetector part 150, which enables to receive radiated light from the front surface of the semiconductor wafer W without being affected by ambient light.
[0122] A part of radiation light radiated from the front surface of the semiconductor wafer W whose temperature has been raised by preheating and flash heating enters the photodetector part 150 to be condensed by the InSb photoconductive element 153. Of radiated light directed from the front surface of the semiconductor wafer W toward the InSb photoconductive element 153, light of a selective wavelength range (5 μm or more) included in the wavelength range (4 μm or more) eliminated by the quartz window, is selectively allowed to pass through the long-wave pass filter 152. Then, the intensity of radiated light received by the InSb photoconductive element 153 is measured by the sampling part 160. The intensities of radiated light from the front surface of the semiconductor wafer W are measured in chronological order to be obtained as the history of radiaion light intensity.
[0123] The emissivity calculating part 33 calculates the emissivity ε of the front surface of the semiconductor wafer W based on the intensity of radiated light from a black body having an equal temperature to the temperature of the back surface measured with the radiation thermometer 120 after flash irradiation by the flash lamp FL is started and then the temperatures of the front and back surfaces of the semiconductor wafer W become equal to each other, and the intensity of radiated light actually radiated from the front surface of the semiconductor wafer W measured by the sampling part 160. In other words, the emissivity of the back surface of the semiconductor wafer W has been known and, with the use of the accurate measurement of the temperature of the back surface with the radiation thermometer 120, the temperature of the front surface is obtained substantially by measuring the temperature of the back surface after the temperatures of the front and back surfaces of the semiconductor wafer W become equal to each other. Then, the emissivity calculating part 33 calculates the emissivity ε based on the intensity of radiated light radiated from a black body with the temperature of the front surface and the intensity of radiated light actually radiated from the front surface of the semiconductor wafer W.
[0124] The temperature calculating part 32 calculates the temperature of the front surface of the semiconductor wafer W heated by flash irradiation, based on the emissivity ε calculated by the emissivity calculating part 33, and the intensity of radiated light from the front surface of the semiconductor wafer W measured by the sampling part 160 after flash irradiation by the flash lamp FL is started. If the emissivity ε of the front surface of the semiconductor wafer W is determined, the temperature calculating part 32 is capable of calculating the temperature of the front surface based on the emissivity ε and the intensity of radiated light of the front surface of the semiconductor wafer W with the use of, for example, Expression (2) derived from the Plank's law.
[0125] To summarize the description above, the technique according to the present invention employs the fact that the temperature of the back surface of the semiconductor wafer W can be measured accurately with the radio thermometer 120. Then, with the use of the temperature of the back surface measured after the temperatures of the front and back surfaces of the semiconductor wafer W become equal to each other after flash irradiation, the temperature of the front surface is calculated by normalizing the intensity of radiaion light radiated from the front surface of the semiconductor wafer W to the intensity of radiation light of a black body. This enables to obtain the temperature of the front surface of the semiconductor wafer W regardless of device patterns formed on the front surface.
[0126] While the preferred embodiment according to the present invention has been described hereinabove, various modifications of the present invention in addition to that described above may be made without departing from the scope and spirit of the invention. For example, while heating is performed by irradiating the semiconductor wafer W with a flash of light from the flash lamp FL in the preferred embodiment above, the present invention is not limited thereto. The technique according to the present invention is preferably applicable even in a case where the semiconductor wafer W is heated by different type of irradiation. For example, the technique according to the present invention is preferably applicable in a case where the front surface of a semiconductor wafer W is heated by strong irradiation with laser light in an extremely short period of time. Further, the technique according to the present invention is preferably applicable to a rapid thermal process (RTP) apparatus for heating a semiconductor wafer W over approximately several seconds by halogen lamps or the like. Also in a case where the semiconductor wafer W is heated by different type of irradiation as described above, the temperature of the front surface can be calculated by normalizing the intensity of radiated light from the front surface of the semiconductor wafer W to the intensity of radiated light of a black body with the use of the temperature of the back surface measured after irradiation is started and then the temperatures of the front and back surfaces of the semiconductor wafer W become equal to each other after.
[0127] Also, the setting of the waveform of the pulse signal is not limited to inputting the parameters including the pulse width one by one to the controller 3. For example, the setting of the waveform may be done by an operator inputting the waveform directly in graphical form to the controller 3, by reading the waveform previously set and stored in a storage part such as a magnetic disk, or by downloading the waveform from outside the heat treatment apparatus 1.
[0128] Also, while the trigger voltage is applied to the trigger electrode 91 in synchronization with the timing when the pulse signal turns on in the preferred embodiment above, the timing when the trigger voltage is applied is not limited thereto. Alternatively, the trigger voltage may be applied at regular intervals irrespective of the waveform of a pulse signal. Still alternatively, in a case where the intervals between pulse signals are short and, a current is caused to pass through the flash lamp FL at a pulse in the state in which the current value of a current that has flowed through the flash lamp FL at a previous pulse persists for a predetermined value or more, the current keeps flowing through the flash lamp FL as it is. Accordingly, it is not required to apply the trigger voltage per pulse and, for example, the trigger voltage may be applied only in the application of the first pulse. That is, the trigger voltage may be applied at an appropriate timing as long as a current is caused to flow through the flash lamp FL when the pulse signal turns on.
[0129] Although the IGBT 96 is used as a switching element in the preferred embodiment above, another transistor capable of turning on and off the circuit in accordance with the signal level inputted to the gate thereof may be used in place of the IGBT 96. It is, however, preferable to use an IGBT and a gate turn-off (GTO) thyristor which are suitable for handling high power as a switching element because the emission of light from the flash lamps FL consumes considerably high power.
[0130] Although the 30 flash lamps FL are provided in the flash heating part 5 according to the preferred embodiment above, the present invention is not limited thereto. Any number of flash lamps FL may be provided. The flash lamps FL are not limited to the xenon flash lamps, but may be krypton flash lamps. Also, the number of halogen lamps HL provided in the halogen heating part 4 is not limited to 40. Any number of halogen lamps HL may be provided.
[0131] Also, in the preferred embodiment above, the semiconductor wafer W is preheated by irradiating the semiconductor wafer W with halogen light from the halogen lamps HL. The technique for preheating is not limited thereto, but the semiconductor wafer W may be preheated by placing the semiconductor wafer W on a hot plate.
[0132] Moreover, a substrate to be processed or treated by the heat treatment technique according to the present invention is not limited to a semiconductor wafer, but may be a glass substrate for use in a flat panel display for a liquid crystal display and the like, and a substrate for a solar cell. Also, the technique according to the present invention may be applied to the joining of metal and silicon, and to the crystallization of polysilicon.
[0133] While the invention has been described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is understood that numerous other modifications and variations can be devised without departing from the scope of the invention.
Patent applications by Tatsufumi Kusuda, Kyoto-Shi JP
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