Thermal treatment device

Abstract

To provide a thermal treatment device capable of reducing the number of elements set to a device.SOLUTION: An element set containing a capacitor 93, a coil 94, a thyristor 96, and a regenerative diode 97 one by one, respectively to three flush lamps FL that are parallely connected. One thyristor 96 integrally controls an ON / an OFF of a current flowing in the three flush lamps FL corresponded that are parallely connected. By the thyristor 96, a tail current flowing in each flush lamp FL can be suppressed at a flash light irradiation. Also, since the element set that is smaller number of the flush lamps FL that are parallely connected is provided, the number of elements provided to the thermal treatment device can be reduced as compared with the case where the element set is individually set to each flush lamp FL. Thus, an increase of a device cost can be suppressed, and an installation space of each element can be reduced.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a heat treatment apparatus for heating a substrate by irradiating the substrate with a flash light, for example, a semiconductor wafer, a substrate for a liquid crystal display device, a substrate for a flat panel display (FPD), a substrate for an optical disk, a substrate for a magnetic disk, or a substrate for a solar cell. [Background technology]

[0002] Flash lamp annealing (FLA), which heats semiconductor wafers in an extremely short time, has been attracting attention in the semiconductor device manufacturing process. Flash lamp annealing is a heat treatment technique that uses a xenon flash lamp (hereinafter, simply "flash lamp" means a xenon flash lamp) 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 in an extremely short time (several milliseconds or less).

[0003] The spectral distribution of radiation from a xenon flash lamp is in the ultraviolet to near infrared range, and has a shorter wavelength than conventional halogen lamps, which almost matches the fundamental absorption band of silicon semiconductor wafers. Therefore, when a semiconductor wafer is irradiated with flash light from a xenon flash lamp, there is little transmitted light, and it is possible to rapidly heat the semiconductor wafer. It has also been found that if the flash light is irradiated for an extremely short period of time, less than a few milliseconds, it is possible to selectively heat only the vicinity of the surface of the semiconductor wafer.

[0004] Such flash lamp annealing is used in processes that require heating for an extremely short time, such as activating impurities typically implanted in semiconductor wafers. By irradiating the surface of a semiconductor wafer into which impurities have been implanted by ion implantation with a flash light from a flash lamp, the surface of the semiconductor wafer can be heated to the activation temperature for an extremely short time, and only the impurity activation can be performed without deep diffusion of the impurities.

[0005] As heat treatment apparatuses using such xenon flash lamps, Patent Documents 1 and 2 disclose an apparatus in which an insulated gate bipolar transistor (IGBT) is provided in the discharge circuit of the flash lamp to control the light emission of the flash lamp. In the apparatuses disclosed in Patent Documents 1 and 2, a predetermined pulse signal is input to the gate of the IGBT to regulate the waveform of the current flowing through the flash lamp, thereby controlling the lamp light emission, and the light emission time and light emission intensity of the flash lamp can be freely adjusted. In the apparatuses disclosed in Patent Documents 1 and 2, the flash lamp and the IGBT are connected in series in a one-to-one relationship. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2009-070948 A [Patent Document 2] JP 2011-119562 A Summary of the Invention [Problem to be solved by the invention]

[0007] In recent cutting-edge semiconductor manufacturing processes, annealing technology that can achieve low thermal history while heating to high temperatures is required to accommodate changes in materials and structures. Low thermal history annealing is a heat treatment in which the total amount of heat input to the semiconductor wafer is small. Flash lamp annealing is required to rapidly raise the surface temperature of the semiconductor wafer to a high temperature in a short period of time. To achieve this, a strong flash of light must be irradiated for a shorter exposure time. For example, it is required to raise the surface temperature of the semiconductor wafer to 600°C or more by irradiating it with a flash of light for an exposure time of 0.1 milliseconds.

[0008] However, in order to significantly raise the temperature of the surface of a semiconductor wafer by irradiating a flash light with an extremely short irradiation time, it is necessary to use a considerable number of flash lamps. This requires the installation of a large number of elements such as IGBTs according to the number of flash lamps. The installation of a large number of elements such as IGBTs increases the cost of the equipment and also necessitates a large installation space.

[0009] The present invention has been made in view of the above problems, and has an object to provide a heat treatment apparatus capable of reducing the number of elements provided in the apparatus. [Means for solving the problem]

[0010] In order to solve the above problems, a first aspect of the present invention provides a heat treatment apparatus for heating a substrate by irradiating the substrate with a flash light, the heat treatment apparatus comprising: a chamber for accommodating a substrate; a holder for holding the substrate in the chamber; a plurality of flash lamps for irradiating flash light to the substrate held in the holder; a discharge circuit for passing current through the plurality of flash lamps to cause the plurality of flash lamps to emit light; and a control unit for controlling the discharge circuit, wherein the discharge circuit comprises M element sets (M is an integer smaller than N) for N flash lamps (N is an integer greater than or equal to 2) connected in parallel.

[0011] In a second aspect, in the heat treatment apparatus according to the first aspect, one element set is provided for the N flash lamps connected in parallel.

[0012] In addition, a third aspect is the heat treatment apparatus according to the second aspect, wherein the element set includes one switching element that controls a current flowing through the N flash lamps.

[0013] In addition, a fourth aspect is the heat treatment apparatus according to the third aspect, wherein the element set further includes one each of a coil, a capacitor, and a diode.

[0014] In a fifth aspect, in the heat treatment apparatus according to the third or fourth aspect, the switching element is a thyristor.

[0015] A sixth aspect is the heat treatment apparatus according to the fifth aspect, wherein the thyristor is a GTO thyristor or a GCT thyristor.

[0016] In a seventh aspect, in the heat treatment device according to the third or fourth aspect, the switching element is an IGBT. Effect of the Invention

[0017] According to the heat treatment apparatus of the first to seventh aspects, M (M is an integer smaller than N) element sets are provided for N (N is an integer greater than or equal to 2) flash lamps connected in parallel, so that the number of elements provided in the heat treatment apparatus can be reduced compared to the case where an element set is provided individually for each flash lamp. [Brief description of the drawings]

[0018] [Figure 1] 1 is a vertical cross-sectional view showing a configuration of a heat treatment apparatus according to the present invention. [Diagram 2] FIG. 2 is a perspective view showing the overall appearance of a holding portion. [Diagram 3] FIG. [Figure 4] FIG. 2 is a cross-sectional view of a susceptor. [Diagram 5] FIG. [Figure 6] FIG. [Figure 7] FIG. 2 is a plan view showing an arrangement of a plurality of halogen lamps. [Figure 8] FIG. 2 is a diagram showing a discharge circuit of a flash lamp. [Figure 9] FIG. 2 is a block diagram showing a configuration of a control unit. [Figure 10] FIG. 4 is a diagram showing changes in current flowing through a flash lamp. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. In the following, expressions indicating relative or absolute positional relationships (e.g., "in one direction," "along one direction," "parallel," "orthogonal," "center," "concentric," "coaxial," etc.) not only strictly indicate the positional relationship, but also indicate a state in which the relative angle or distance is displaced within a range in which a tolerance or similar function is obtained, unless otherwise specified. Furthermore, expressions indicating an equal state (e.g., "same," "equal," "homogeneous," etc.) not only indicate a state in which the relative position is strictly equal quantitatively, but also indicate a state in which there is a difference in which a tolerance or similar function is obtained, unless otherwise specified. Furthermore, expressions indicating a shape (e.g., "circular," "square," "cylindrical," etc.) not only indicate a geometrically strict shape, but also indicate a shape within a range in which a similar effect is obtained, and may have, for example, unevenness or chamfering. Furthermore, each expression such as "comprises," "includes," "has," "includes," and "has" for a component is not an exclusive expression that excludes the presence of other components. In addition, the expression "at least one of A, B, and C" includes "A only," "B only," "C only," "any two of A, B, and C," and "all of A, B, and C."

[0020] FIG. 1 is a vertical cross-sectional view showing the configuration of a heat treatment apparatus 1 according to the present invention. The heat treatment apparatus 1 in FIG. 1 is a flash lamp annealing apparatus that heats a disk-shaped semiconductor wafer W as a substrate by irradiating the semiconductor wafer W with flash light. The size of the semiconductor wafer W to be treated is not particularly limited, but is, for example, φ300 mm or φ450 mm (φ300 mm in this embodiment). Impurities are implanted into the semiconductor wafer W before it is carried into the heat treatment apparatus 1, and activation processing of the implanted impurities is performed by the heat treatment by the heat treatment apparatus 1. Note that in FIG. 1 and the subsequent figures, the dimensions and numbers of each part are exaggerated or simplified as necessary for easy understanding.

[0021] The heat treatment apparatus 1 includes a chamber 6 that accommodates a semiconductor wafer W, a flash heating unit 5 that incorporates a plurality of flash lamps FL, and a halogen heating unit 4 that incorporates a plurality of halogen lamps HL. The flash heating unit 5 is provided on the upper side of the chamber 6, and the halogen heating unit 4 is provided on the lower side. The heat treatment apparatus 1 also includes, inside the chamber 6, a holding unit 7 that holds the semiconductor wafer W in a horizontal position, and a transfer mechanism 10 that transfers the semiconductor wafer W between the holding unit 7 and the outside of the apparatus. The heat treatment apparatus 1 also includes a control unit 3 that controls the respective operating mechanisms provided in the halogen heating unit 4, the flash heating unit 5, and the chamber 6 to perform heat treatment of the semiconductor wafer W.

[0022] The chamber 6 is configured by mounting quartz chamber windows on the top and bottom of a cylindrical chamber side portion 61. The chamber side portion 61 has a roughly cylindrical shape with openings at the top and bottom, with an upper chamber window 63 mounted and closed at the upper opening, and a lower chamber window 64 mounted and closed at the lower opening. The upper chamber window 63 constituting the ceiling of the chamber 6 is a disk-shaped member made of quartz, and functions as a quartz window that transmits the flash light emitted from the flash heating unit 5 into the chamber 6. The lower chamber window 64 constituting the floor of the chamber 6 is also a disk-shaped member made of quartz, and functions as a quartz window that transmits the light from the halogen heating unit 4 into the chamber 6.

[0023] In addition, a reflective ring 68 is attached to the upper part of the inner wall surface of the chamber side part 61, and a reflective ring 69 is attached to the lower part. Both of the reflective rings 68, 69 are formed in an annular shape. The upper reflective ring 68 is attached by fitting it from the upper side of the chamber side part 61. On the other hand, the lower reflective ring 69 is attached by fitting it from the lower side of the chamber side part 61 and fastening it with screws (not shown). In other words, both of the reflective rings 68, 69 are detachably attached to the chamber side part 61. The inner space of the chamber 6, i.e., the space surrounded by the upper chamber window 63, the lower chamber window 64, the chamber side part 61, and the reflective rings 68, 69, is defined as a heat treatment space 65.

[0024] By mounting the reflecting rings 68, 69 on the chamber side portion 61, a recess 62 is formed on the inner wall surface of the chamber 6. That is, the recess 62 is formed by a central portion of the inner wall surface of the chamber side portion 61 where the reflecting rings 68, 69 are not mounted, the lower end surface of the reflecting ring 68, and the upper end surface of the reflecting ring 69. The recess 62 is formed in an annular shape along the horizontal direction on the inner wall surface of the chamber 6, and surrounds the holder 7 that holds the semiconductor wafer W. The chamber side portion 61 and the reflecting rings 68, 69 are formed from a metal material (e.g., stainless steel) that has excellent strength and heat resistance.

[0025] Further, a transfer opening (furnace port) 66 for carrying a semiconductor wafer W into and out of the chamber 6 is formed in the chamber side portion 61. The transfer opening 66 can be opened and closed by a gate valve 185. The transfer opening 66 is connected in communication with the outer circumferential surface of the recess 62. Therefore, when the gate valve 185 opens the transfer opening 66, the semiconductor wafer W can be carried into and out of the heat treatment space 65 through the transfer opening 66 and the recess 62. Furthermore, when the gate valve 185 closes the transfer opening 66, the heat treatment space 65 in the chamber 6 becomes an airtight space.

[0026] Further, through holes 61a and 61b are formed in the chamber side 61. The through hole 61a is a cylindrical hole for guiding infrared light radiated from the upper surface of the semiconductor wafer W held on the susceptor 74 to the infrared sensor 29 of the upper radiation thermometer 25, which will be described later. On the other hand, the through hole 61b is a cylindrical hole for guiding infrared light radiated from the lower surface of the semiconductor wafer W to the lower radiation thermometer 20. The through holes 61a and 61b are provided at an incline with respect to the horizontal direction so that the axis of the through hole 61a intersects with the main surface of the semiconductor wafer W held on the susceptor 74. A transparent window 26 made of a calcium fluoride material that transmits infrared light in a wavelength range that can be measured by the upper radiation thermometer 25 is attached to the end of the through hole 61a facing the heat treatment space 65. Further, at the end of the through hole 61b facing the heat treatment space 65, a transparent window 21 made of a barium fluoride material that transmits infrared light in the wavelength range that the lower radiation thermometer 20 can measure is attached.

[0027] Further, a gas supply hole 81 is formed in the upper part of the inner wall of the chamber 6 to supply a processing gas to the heat treatment space 65. The gas supply hole 81 is formed at a position above the recessed portion 62, and may be provided in the reflecting ring 68. The gas supply hole 81 is connected to a gas supply pipe 83 through a buffer space 82 formed in an annular shape inside the side wall of the chamber 6. The gas supply pipe 83 is connected to a processing gas supply source 85. A valve 84 is inserted in the middle of the gas supply pipe 83. When the valve 84 is opened, the processing gas is supplied from the processing gas supply source 85 to the buffer space 82. The processing gas that has flowed into the buffer space 82 flows in a spreading manner in the buffer space 82, which has a smaller fluid resistance than the gas supply hole 81, and is supplied from the gas supply hole 81 to the heat treatment space 65. As the processing gas, for example, an inert gas such as nitrogen (N2), a reactive gas such as hydrogen (H2) or ammonia (NH3), or a mixed gas of these gases can be used (nitrogen gas in this embodiment).

[0028] On the other hand, a gas exhaust hole 86 is formed in the lower part of the inner wall of the chamber 6 to exhaust the gas in the heat treatment space 65. The gas exhaust hole 86 is formed at a position lower than the recessed portion 62, and may be provided in the reflecting ring 69. The gas exhaust hole 86 is connected to a gas exhaust pipe 88 through a buffer space 87 formed in an annular shape inside the side wall of the chamber 6. The gas exhaust pipe 88 is connected to an exhaust unit 190. A valve 89 is inserted in the middle of the gas exhaust pipe 88. When the valve 89 is opened, the gas in the heat treatment space 65 is exhausted from the gas exhaust hole 86 through the buffer space 87 to the gas exhaust pipe 88. The gas supply hole 81 and the gas exhaust hole 86 may be provided in a plurality of holes along the circumferential direction of the chamber 6, or may be slit-shaped. The process gas supply source 85 and the exhaust unit 190 may be mechanisms provided in the heat treatment apparatus 1, or may be utilities of a factory in which the heat treatment apparatus 1 is installed.

[0029] A gas exhaust pipe 191 for discharging gas from within the heat treatment space 65 is also connected to the tip of the transfer opening 66. The gas exhaust pipe 191 is connected to an exhaust unit 190 via a valve 192. By opening the valve 192, the gas from within the chamber 6 is exhausted via the transfer opening 66.

[0030] 2 is a perspective view showing the overall appearance of the holder 7. The holder 7 holds a semiconductor wafer W in the chamber 6. The holder 7 is configured to include a base ring 71, a connecting portion 72, and a susceptor 74. The base ring 71, the connecting portion 72, and the susceptor 74 are all made of quartz. That is, the entire holder 7 is made of quartz.

[0031] The base ring 71 is an arc-shaped quartz member with a portion missing from the annular shape. This missing portion is provided to prevent interference between the base ring 71 and a transfer arm 11 of the transfer mechanism 10, which will be described later. The base ring 71 is placed on the bottom surface of the recess 62, and is supported by the wall surface of the chamber 6 (see FIG. 1). A plurality of connecting portions 72 (four in this embodiment) are erected on the upper surface of the base ring 71 along the circumferential direction of the annular shape. The connecting portions 72 are also quartz members, and are fixed to the base ring 71 by welding.

[0032] The susceptor 74 is supported by four connecting portions 72 provided on the base ring 71. FIG. 3 is a plan view of the susceptor 74. FIG. 4 is a cross-sectional view of the susceptor 74. The susceptor 74 includes a holding plate 75, a guide ring 76, and a plurality of substrate support pins 77. The holding plate 75 is a substantially circular flat member made of quartz. The diameter of the holding plate 75 is larger than the diameter of the semiconductor wafer W. In other words, the holding plate 75 has a larger planar size than the semiconductor wafer W.

[0033] A guide ring 76 is installed on the periphery of the upper surface of the holding plate 75. The guide ring 76 is an annular member having an inner diameter larger than the diameter of the semiconductor wafer W. For example, when the diameter of the semiconductor wafer W is φ300 mm, the inner diameter of the guide ring 76 is φ320 mm. The inner circumference of the guide ring 76 is a tapered surface that widens from the holding plate 75 upward. The guide ring 76 is made of quartz, similar to the holding plate 75. The guide ring 76 may be fused to the upper surface of the holding plate 75, or may be fixed to the holding plate 75 by a separately processed pin or the like. Alternatively, the holding plate 75 and the guide ring 76 may be processed as an integrated member.

[0034] The area of ​​the upper surface of the holding plate 75 inside the guide ring 76 is a flat holding surface 75a that holds the semiconductor wafer W. A plurality of substrate support pins 77 are provided on the holding surface 75a of the holding plate 75. In this embodiment, a total of 12 substrate support pins 77 are provided at 30° intervals along a circumference concentric with the outer circumferential circle of the holding surface 75a (the inner circumferential circle of the guide ring 76). The diameter of the circle on which the 12 substrate support pins 77 are arranged (the distance between the opposing substrate support pins 77) is smaller than the diameter of the semiconductor wafer W, and is φ270 mm to φ280 mm (φ270 mm in this embodiment) if the diameter of the semiconductor wafer W is φ300 mm. Each substrate support pin 77 is made of quartz. The substrate support pins 77 may be provided on the upper surface of the holding plate 75 by welding, or may be processed integrally with the holding plate 75.

[0035] Returning to FIG. 2, four connecting parts 72 erected on the base ring 71 and the peripheral part of the holding plate 75 of the susceptor 74 are fixed by welding. That is, the susceptor 74 and the base ring 71 are fixedly connected by the connecting parts 72. The base ring 71 of the holding part 7 is supported on the wall surface of the chamber 6, and the holding part 7 is attached to the chamber 6. When the holding part 7 is attached to the chamber 6, the holding plate 75 of the susceptor 74 is in a horizontal position (a position in which the normal line coincides with the vertical direction). That is, the holding surface 75a of the holding plate 75 is a horizontal plane.

[0036] The semiconductor wafer W carried into the chamber 6 is placed and held in a horizontal position on the susceptor 74 of the holder 7 attached to the chamber 6. At this time, the semiconductor wafer W is supported by twelve substrate support pins 77 standing on a holding plate 75 and held on the susceptor 74. More precisely, the upper ends of the twelve substrate support pins 77 contact the lower surface of the semiconductor wafer W to support the semiconductor wafer W. The heights of the twelve substrate support pins 77 (the distance from the upper ends of the substrate support pins 77 to the holding surface 75a of the holding plate 75) are uniform, so that the twelve substrate support pins 77 can support the semiconductor wafer W in a horizontal position.

[0037] Furthermore, the semiconductor wafer W is supported by a plurality of substrate support pins 77 at a predetermined distance from the holding surface 75a of the holding plate 75. The thickness of the guide ring 76 is greater than the height of the substrate support pins 77. Therefore, the guide ring 76 prevents the semiconductor wafer W supported by the plurality of substrate support pins 77 from shifting in the horizontal direction.

[0038] 2 and 3, an opening 78 is formed in the holding plate 75 of the susceptor 74, penetrating vertically. The opening 78 is provided so that the lower radiation thermometer 20 can receive radiation light (infrared light) emitted from the lower surface of the semiconductor wafer W. That is, the lower radiation thermometer 20 receives light emitted from the lower surface of the semiconductor wafer W through the opening 78 and a transparent window 21 attached to the through hole 61b of the chamber side part 61, and measures the temperature of the semiconductor wafer W. Furthermore, the holding plate 75 of the susceptor 74 is provided with four through holes 79 through which lift pins 12 of the transfer mechanism 10, which will be described later, pass to transfer the semiconductor wafer W.

[0039] 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 two transfer arms 11. The transfer arms 11 are formed in an arc shape that is aligned with the generally annular recess 62. Two lift pins 12 are provided upright on each of the transfer arms 11. The transfer arms 11 and the lift pins 12 are made of quartz. Each transfer arm 11 is rotatable by a horizontal movement mechanism 13. The horizontal movement mechanism 13 horizontally moves the pair of transfer arms 11 between a transfer operation position (solid line position in FIG. 5) where the semiconductor wafer W is transferred to the holder 7 and a retracted position (double-dashed line position in FIG. 5) where the pair of transfer arms 11 do not overlap the semiconductor wafer W held by the holder 7 in a plan view. The horizontal movement mechanism 13 may be a mechanism that rotates each transfer arm 11 using an individual motor, or a mechanism that uses a link mechanism to rotate a pair of transfer arms 11 in unison using a single motor.

[0040] The pair of transfer arms 11 are raised and lowered together with the horizontal movement mechanism 13 by the lifting mechanism 14. When the lifting mechanism 14 raises the pair of transfer arms 11 to the transfer operation position, the total of four lift pins 12 pass through the through holes 79 (see FIGS. 2 and 3) formed in the susceptor 74, and the upper ends of the lift pins 12 protrude from the upper surface of the susceptor 74. On the other hand, when the lifting mechanism 14 lowers the pair of transfer arms 11 to the transfer operation position to remove the lift pins 12 from the through holes 79, and the horizontal movement mechanism 13 moves the pair of transfer arms 11 to open them, each transfer arm 11 moves to a retracted position. The retracted position of the pair of transfer arms 11 is directly above the base ring 71 of the holder 7. Since the base ring 71 is placed on the bottom surface of the recess 62, the retracted position of the transfer arms 11 is inside the recess 62. In addition, an exhaust mechanism (not shown) is provided near the location where the drive part of the transfer mechanism 10 (horizontal movement mechanism 13 and lifting mechanism 14) is located, and is configured to exhaust the atmosphere around the drive part of the transfer mechanism 10 to the outside of the chamber 6.

[0041] Returning to FIG. 1, the chamber 6 is provided with two radiation thermometers (pyrometers in this embodiment), an upper radiation thermometer 25 and a lower radiation thermometer 20. The upper radiation thermometer 25 is installed diagonally above the semiconductor wafer W held on the susceptor 74, and receives infrared light radiated from the upper surface of the semiconductor wafer W to measure the temperature of the upper surface. The infrared sensor 29 of the upper radiation thermometer 25 is equipped with an InSb (indium antimony) optical element so as to be able to respond to a sudden temperature change of the upper surface of the semiconductor wafer W at the moment when the flash light is irradiated. On the other hand, the lower radiation thermometer 20 is installed diagonally below the semiconductor wafer W held on the susceptor 74, and receives infrared light radiated from the lower surface of the semiconductor wafer W to measure the temperature of the lower surface.

[0042] The flash heating unit 5 provided above the chamber 6 is configured to include a light source consisting of multiple (63 in this embodiment) xenon flash lamps FL inside a housing 51, and a reflector 52 provided to cover the light source from above. The flash lamps FL irradiate flash light to the semiconductor wafer W held by the holder 7. A lamp light emission window 53 is attached to the bottom of the housing 51 of the flash heating unit 5. The lamp light emission window 53 constituting the floor of the flash heating unit 5 is a plate-shaped quartz window made of quartz. The flash heating unit 5 is installed above the chamber 6, so that the lamp light emission window 53 faces the upper chamber window 63. The flash lamps FL irradiate flash light from above the chamber 6 through the lamp light emission window 53 and the upper chamber window 63 into the heat treatment space 65.

[0043] The multiple flash lamps FL are rod-shaped lamps each having a long cylindrical shape, and are arranged in a plane such that their longitudinal directions are parallel to each other along the main surface of the semiconductor wafer W held by the holder 7 (i.e., along the horizontal direction). Therefore, the plane formed by the arrangement of the flash lamps FL is also a horizontal plane. Note that the multiple flash lamps FL may be arranged in two or more stages.

[0044] Fig. 8 is a diagram showing a discharge circuit of the flash lamps FL. This discharge circuit passes a current through the flash lamps FL to cause the flash lamps FL to emit light. As shown in Fig. 8, a plurality of flash lamps FL (three in this embodiment) are connected in parallel. A capacitor 93, a coil 94, and a thyristor 96 are connected in series to the three flash lamps FL. In other words, one element set including the capacitor 93, the coil 94, and the thyristor 96 is provided for the three flash lamps FL.

[0045] Each flash lamp FL includes a rod-shaped glass tube (discharge tube) 92 filled with xenon gas and having an anode and a cathode disposed at both ends, and a trigger electrode 91 provided on the outer circumferential surface of the glass tube 92. A high voltage can be applied to the trigger electrode 91 from a trigger circuit (not shown). The timing at which the trigger circuit applies a voltage to the trigger electrode 91 is controlled by the control unit 3.

[0046] The capacitor 93 is a passive element that accumulates electric charge to cause the flash lamp FL to discharge. A predetermined voltage is applied to the capacitor 93 by the power supply unit 95, and an electric charge corresponding to the applied voltage (charging voltage) is stored in the capacitor 93. The coil 94 is a passive element that resists a sudden change in current when the change occurs in the discharge circuit. Note that in the circuit of Fig. 8, a floating resistor 98 is provided in series with the flash lamp FL, but this is not provided as an element, but is a resistance that inevitably occurs in the circuit.

[0047] The thyristor 96 is an active element that controls the current flowing through the three flash lamps FL. The thyristor 96 in this embodiment is, for example, a GCT (Gate Commutated Turn off) thyristor. The GCT thyristor is an improved version of the gate of a GTO (Gate Turn Off) thyristor. Thus, like the GTO thyristor, the GCT thyristor has a self-extinguishing function that transitions from an on state to an off state by applying a negative signal to the gate. In addition, the GCT thyristor has a basic function of transitioning from an off state to an on state by applying a positive signal to the gate. That is, the thyristor 96 is a switching element that has a switching function that is turned on and off by a signal applied to the gate. The current flowing through the flash lamp FL is turned on and off by turning the thyristor 96 on and off.

[0048] Even if the thyristor 96 is turned on and a high voltage is applied to both ends of the glass tube 92 while the capacitor 93 is charged, xenon gas is an electrical insulator and so under normal conditions no electricity flows through the glass tube 92. However, when a high voltage is applied to the trigger electrode 91 and the insulation is broken down, a discharge occurs between the two ends of the electrodes causing a current to flow instantaneously through the glass tube 92, and light is emitted due to the excitation of the xenon atoms or molecules at that time. The light emitted from the glass tube 92 by this instantaneous discharge is the flash light.

[0049] In this embodiment, since the thyristor 96 is connected in series to the flash lamp FL, when the thyristor 96 is turned off, a coil surge occurs in which a large voltage is momentarily generated in the reverse direction in the coil 94 due to a sudden change in current. Since the high voltage caused by such a coil surge may destroy other circuit elements, a regenerative diode 97 is provided in the discharge circuit to absorb the high voltage caused by the coil surge, as shown in Fig. 8. This regenerative diode 97 protects the elements in the discharge circuit from the coil surge.

[0050] As shown in FIG. 8, in this embodiment, one element set is provided for three flash lamps FL connected in parallel. One element set includes one each of a capacitor 93, a coil 94, a thyristor 96, and a regenerative diode 97. In addition, in this embodiment, 63 flash lamps FL are provided in the flash heating unit 5. Therefore, 21 (=63 / 3) element sets are provided in the heat treatment device 1, and 21 each of the capacitors 93, coils 94, thyristors 96, and regenerative diodes 97 are provided for the 63 flash lamps FL. One thyristor 96 collectively controls the on / off of the current flowing through the corresponding three flash lamps FL connected in parallel. That is, the current flowing through the 63 flash lamps FL is individually turned on and off by the corresponding thyristor 96.

[0051] 1, the reflector 52 is provided above the multiple flash lamps FL so as to cover them entirely. The basic function of the reflector 52 is to reflect the flash light emitted from the multiple flash lamps FL toward the heat treatment space 65. The reflector 52 is made of an aluminum alloy plate, and its surface (the surface facing the flash lamps FL) is roughened by blasting.

[0052] The halogen heating unit 4 provided below the chamber 6 has a plurality of halogen lamps HL (40 in this embodiment) built inside the housing 41. The halogen heating unit 4 is a light irradiation unit that heats the semiconductor wafer W by irradiating light from the plurality of halogen lamps HL into a heat treatment space 65 from below the chamber 6 through a lower chamber window 64.

[0053] FIG. 7 is a plan view showing the arrangement of a plurality of halogen lamps HL. 40 halogen lamps HL are arranged in two tiers, upper and lower. 20 halogen lamps HL are arranged in the upper tier close to the holder 7, and 20 halogen lamps HL are also arranged in the lower tier farther from the holder 7 than the upper tier. Each halogen lamp HL is a rod-shaped lamp having a long cylindrical shape. The 20 halogen lamps HL in both the upper and lower tiers are arranged so that their longitudinal directions are parallel to each other along the main surface of the semiconductor wafer W held by the holder 7 (i.e., along the horizontal direction). Therefore, the plane formed by the arrangement of the halogen lamps HL in both the upper and lower tiers is a horizontal plane.

[0054] 7, the halogen lamps HL are arranged at a higher density in the region facing the periphery of the semiconductor wafer W held by the holder 7 in both the upper and lower tiers than in the region facing the center of the semiconductor wafer W. That is, in both the upper and lower tiers, the arrangement pitch of the halogen lamps HL is shorter in the periphery of the lamp arrangement than in the center. This makes it possible to irradiate a greater amount of light to the periphery of the semiconductor wafer W, which is prone to temperature drop during heating by light irradiation from the halogen heating unit 4.

[0055] The lamp group consisting of the halogen lamps HL in the upper row and the lamp group consisting of the halogen lamps HL in the lower row are arranged to intersect in a lattice pattern. That is, a total of 40 halogen lamps HL are arranged so that the longitudinal direction of the 20 halogen lamps HL arranged in the upper row and the longitudinal direction of the 20 halogen lamps HL arranged in the lower row are perpendicular to each other.

[0056] The halogen lamp HL is a filament type light source that emits light by passing electricity through a filament disposed inside a glass tube, which becomes incandescent. A gas consisting of an inert gas such as nitrogen or argon with a small amount of halogen elements (iodine, bromine, etc.) is sealed inside the glass tube. By introducing halogen elements, it is possible to set the temperature of the filament at a high temperature while suppressing filament breakage. Therefore, the halogen lamp HL has the characteristics of having a longer life than a normal incandescent light bulb and being able to continuously irradiate strong light. In other words, the halogen lamp HL is a continuous lighting lamp that emits light continuously for at least one second or more. In addition, since the halogen lamp HL is a rod-shaped lamp, it has a long life, and by arranging the halogen lamp HL along the horizontal direction, the radiation efficiency to the semiconductor wafer W above is excellent.

[0057] Also, a reflector 43 is provided below the two-tiered halogen lamps HL within the housing 41 of the halogen heating unit 4 (FIG. 1). The reflector 43 reflects the light emitted from the multiple halogen lamps HL toward the heat treatment space 65.

[0058] The control unit 3 controls the above-mentioned various operating mechanisms provided in the heat treatment device 1. FIG. 9 is a block diagram showing the configuration of the control unit 3. The hardware configuration of the control unit 3 is similar to that of a general computer. That is, the control unit 3 includes a CPU, which is a circuit that performs various arithmetic processing, a ROM, which is a read-only memory that stores basic programs, a RAM, which is a readable and writable memory that stores various information, and a storage unit 34 (e.g., a magnetic disk or SSD) that stores control software, data, and the like. The CPU of the control unit 3 executes a predetermined processing program, and thereby the processing in the heat treatment device 1 proceeds.

[0059] A processing recipe 35 that defines the procedure and conditions for processing the semiconductor wafer W is stored in the memory unit 34 of the control unit 3. The processing recipe 35 is acquired by the heat processing apparatus 1, for example, by an operator of the apparatus inputting the processing recipe 35 via an input unit 32 (described later) and storing the processing recipe in the memory unit 34. Alternatively, the processing recipe 35 may be transferred by communication from a host computer that manages a plurality of heat processing apparatuses 1 to the heat processing apparatus 1 and stored in the memory unit 34.

[0060] Elements such as the thyristor 96 are electrically connected to the control unit 3. The control unit 3 controls the discharge circuit of the flash lamp FL in accordance with, for example, the contents of the process recipe 35. Specifically, the control unit 3 controls a signal applied to the gate of the thyristor 96 to switch the thyristor 96 between an on state (conducting state) and an off state (cutting state).

[0061] The control unit 3 is also connected to a display unit 33 and an input unit 32. The display unit 33 and the input unit 32 function as a user interface for the heat treatment device 1. The control unit 3 displays various information on the display unit 33. An operator of the heat treatment device 1 can input various commands and parameters from the input unit 32 while checking the information displayed on the display unit 33. For example, a keyboard or a mouse can be used as the input unit 32. For example, a liquid crystal display can be used as the display unit 33. In this embodiment, a liquid crystal touch panel provided on the outer wall of the heat treatment device 1 is used as the display unit 33 and the input unit 32 to combine the functions of both.

[0062] In addition to the above configuration, the heat treatment apparatus 1 is provided with various cooling structures to prevent an excessive temperature rise in the halogen heating unit 4, the flash heating unit 5, and the chamber 6 due to the thermal energy generated from the halogen lamps HL and the flash lamps FL during the heat treatment of the semiconductor wafer W. For example, a water-cooling pipe (not shown) is provided in the wall of the chamber 6. The halogen heating unit 4 and the flash heating unit 5 are also of an air-cooled structure that forms a gas flow inside to remove heat. Air is also supplied to the gap between the upper chamber window 63 and the lamp light emission window 53 to cool the flash heating unit 5 and the upper chamber window 63.

[0063] Next, the processing operation in the heat treatment apparatus 1 will be described. The semiconductor wafer W to be processed is a semiconductor substrate to which impurities (ions) have been added by ion implantation. The impurities are activated by a flash light irradiation heat treatment (annealing) performed by the heat treatment apparatus 1. The processing procedure of the heat treatment apparatus 1 described below progresses as the control unit 3 controls each operating mechanism of the heat treatment apparatus 1.

[0064] First, the valve 84 for supplying air is opened, and the exhaust valves 89, 192 are also opened to start supplying and exhausting air to and from the chamber 6. When the valve 84 is opened, nitrogen gas is supplied to the heat treatment space 65 from the gas supply hole 81. When the valve 89 is opened, the gas in the chamber 6 is exhausted from the gas exhaust hole 86. As a result, the nitrogen gas supplied from the upper part of the heat treatment space 65 in the chamber 6 flows downward and is exhausted from the lower part of the heat treatment space 65.

[0065] Furthermore, by opening the valve 192, the gas in the chamber 6 is also exhausted from the transfer opening 66. Furthermore, the atmosphere around the drive unit of the transfer mechanism 10 is also exhausted by an exhaust mechanism (not shown). Note that, during the heat treatment of the semiconductor wafer W in the heat treatment apparatus 1, nitrogen gas is continuously supplied to the heat treatment space 65, and the supply amount is appropriately changed depending on the treatment process.

[0066] Next, the gate valve 185 is opened to open the transport opening 66, and the semiconductor wafer W to be treated is carried into the heat treatment space 65 in the chamber 6 through the transport opening 66 by a transport robot outside the apparatus. At this time, there is a risk that the atmosphere outside the apparatus may be drawn in with the carrying in of the semiconductor wafer W, but since nitrogen gas is continuously supplied to the chamber 6, the nitrogen gas flows out from the transport opening 66, making it possible to minimize the entrainment of such external atmosphere.

[0067] The semiconductor wafer W carried in by the transport robot advances to a position directly above the holder 7 and stops there. Then, the pair of transfer arms 11 of the transfer mechanism 10 move horizontally from the retreated position to the transfer operation position and rise, causing the lift pins 12 to pass through the through holes 79 and protrude from the upper surface of the holding plate 75 of the susceptor 74 to receive the semiconductor wafer W. At this time, the lift pins 12 rise to a position above the upper ends of the substrate support pins 77.

[0068] After the semiconductor wafer W is placed on the lift pins 12, the transport robot leaves the heat treatment space 65, and the transport opening 66 is closed by the gate valve 185. Then, the pair of transfer arms 11 descend, and the semiconductor wafer W is transferred from the transfer mechanism 10 to the susceptor 74 of the holder 7, where it is held from below in a horizontal position. The semiconductor wafer W is supported by a plurality of substrate support pins 77 erected on the holding plate 75 and held by the susceptor 74. The semiconductor wafer W is held by the holder 7 with the surface on which the pattern has been formed and the impurities have been implanted as the upper surface. A predetermined gap is formed between the back surface (the main surface opposite to the front surface) of the semiconductor wafer W supported by the plurality of substrate support pins 77 and the holding surface 75a of the holding plate 75. The pair of transfer arms 11 that descend to below the susceptor 74 are retreated to a retreat position, that is, inside the recess 62, by the horizontal movement mechanism 13.

[0069] After the semiconductor wafer W is held from below in a horizontal position by the susceptor 74 of the holder 7 made of quartz, the 40 halogen lamps HL of the halogen heating unit 4 are turned on all at once to start preheating (assisted heating). Halogen light emitted from the halogen lamps HL passes through the lower chamber window 64 and the susceptor 74, both made of quartz, and is irradiated onto the underside of the semiconductor wafer W. The semiconductor wafer W is preheated by being irradiated with light from the halogen lamps HL, and its temperature rises. Note that the transfer arm 11 of the transfer mechanism 10 is retracted inside the recess 62, and does not interfere with heating by the halogen lamps HL.

[0070] When preheating is performed by the halogen lamps HL, the temperature of the semiconductor wafer W is measured by the lower radiation thermometer 20. That is, the lower radiation thermometer 20 receives infrared light radiated from the lower surface of the semiconductor wafer W held on the susceptor 74 through the openings 78 through the transparent window 21 to measure the wafer temperature during heating. The measured temperature of the semiconductor wafer W is transmitted to the control unit 3. The control unit 3 controls the output of the halogen lamps HL while monitoring whether the temperature of the semiconductor wafer W, which is heated by the light irradiation from the halogen lamps HL, has reached a predetermined preheating temperature T1. That is, the control unit 3 feedback-controls the output of the halogen lamps HL based on the measurement value by the lower radiation thermometer 20 so that the temperature of the semiconductor wafer W becomes the preheating temperature T1. In this way, the lower radiation thermometer 20 is a radiation thermometer for controlling the temperature of the semiconductor wafer W during preheating. The preheating temperature T1 is set to about 200° C. to 800° C., preferably about 350° C. to 600° C. (400° C. in this embodiment), at which the impurities added to the semiconductor wafer W will not diffuse due to heat.

[0071] After the temperature of the semiconductor wafer W reaches the preheating temperature T1, the control unit 3 temporarily maintains the semiconductor wafer W at the preheating temperature T1. Specifically, when the temperature of the semiconductor wafer W measured by the lower radiation thermometer 20 reaches the preheating temperature T1, the control unit 3 adjusts the output of the halogen lamps HL to maintain the temperature of the semiconductor wafer W at approximately the preheating temperature T1.

[0072] By performing such preheating with the halogen lamps HL, the temperature of the entire semiconductor wafer W is uniformly raised to the preheating temperature T1. During the preheating stage with the halogen lamps HL, the temperature of the peripheral portion of the semiconductor wafer W, where heat dissipation is more likely to occur, tends to be lower than that of the central portion, but the arrangement density of the halogen lamps HL in the halogen heating unit 4 is higher in the region facing the peripheral portion than in the region facing the central portion of the semiconductor wafer W. As a result, a greater amount of light is irradiated to the peripheral portion of the semiconductor wafer W, where heat dissipation is more likely to occur, and the in-plane temperature distribution of the semiconductor wafer W during the preheating stage can be made uniform.

[0073] When a predetermined time has elapsed since the temperature of the semiconductor wafer W reached the preheating temperature T1, the flash lamps FL irradiate the surface of the semiconductor wafer W with a flash of light. At this time, part of the flash light emitted from the flash lamps FL heads directly into the chamber 6, and the other part heads into the chamber 6 after being reflected by the reflector 52, and the semiconductor wafer W is flash-heated by the irradiation of these flash lights.

[0074] Before the flash lamp FL emits a flash of light, the power supply unit 95 applies a predetermined charging voltage to the capacitor 93 to store electric charge in the capacitor 93. The amount of electric charge stored in the capacitor 93 is determined by the product of the capacitance C of the capacitor 93 and the charging voltage V of the power supply unit 95.

[0075] With the charge stored in the capacitor 93, a positive signal is given to the gate of the thyristor 96 under the control of the control unit 3, and the thyristor 96 is turned on. In addition, in synchronization with the timing when the thyristor 96 is turned on, a high voltage (trigger voltage) is applied to the trigger electrode 91 under the control of the control unit 3. With the charge stored in the capacitor 93, the thyristor 96 is turned on, and a high voltage is applied to the trigger electrode 91 in synchronization with the timing when the thyristor 96 is turned on, so that a current flows between the electrodes at both ends in the glass tube 92, and light is emitted by the excitation of xenon atoms or molecules at that time, and the flash lamps FL emit flash light. In this way, the 63 flash lamps FL of the flash heating unit 5 emit light, and the flash light is irradiated on the surface of the semiconductor wafer W held by the holding unit 7, and the surface of the semiconductor wafer W is heated. In this embodiment, 21 thyristors 96 are turned on simultaneously, and a high voltage is applied to the trigger electrodes 91 of the 63 flash lamps FL simultaneously.

[0076] 10 is a diagram showing changes in the current flowing through the flash lamp FL. A current starts to flow through the flash lamp FL at the same time that the thyristor 96 is turned on. The waveform of the current flowing through the flash lamp FL while the thyristor 96 is turned on is determined by the capacitance C of the capacitor 93, the inductance L of the coil 94, the charging voltage V, etc. In this embodiment, the maximum value I of the current flowing through the flash lamp FL is MAX reaches about 4000A.

[0077] At time t1, 0.1 milliseconds after the thyristor 96 turns on and current begins to flow through the flash lamp FL, a negative signal is applied to the gate of the thyristor 96 under the control of the control unit 3, turning the thyristor 96 off. By turning the thyristor 96 off, the discharge current flowing through the flash lamp FL is forcibly cut off, and the light emission of the flash lamp FL is stopped.

[0078] The dotted line in Fig. 10 after time t1 shows the waveform of the current flowing through the flash lamp FL when the flash lamp FL is made to emit light without providing the thyristor 96. As shown by the dotted line in Fig. 10, when the thyristor 96 is not provided, the current flowing through the flash lamp FL is not forcibly shut off, so the tail current continues to flow for a relatively long period of time. For this reason, the surface of the semiconductor wafer W continues to be heated even after time t1, which reduces the rate at which the temperature of the semiconductor wafer W drops after irradiation with the flash light, thereby hindering the reduction in thermal history.

[0079] The solid line in Fig. 10 shows the current change in this embodiment when the thyristor 96 is turned off. When the thyristor 96 is turned off and the current flowing through the flash lamp FL is forcibly cut off, the tail current can be significantly suppressed compared to the dotted line in Fig. 10. As a result, the semiconductor wafer W is hardly heated after time t1 when the thyristor 96 is turned off, and the total amount of heat input to the semiconductor wafer W can be reduced to achieve annealing with a low thermal history. It is also possible to increase the rate at which the temperature of the semiconductor wafer W is lowered after time t1.

[0080] However, when the thyristor 96 is turned off, there is a risk of a coil surge occurring, in which a large voltage is momentarily generated in the reverse direction in the coil 94 due to a sudden change in current. For this reason, a regenerative diode 97 is provided in the discharge circuit to absorb the high voltage caused by the coil surge (Fig. 8). Although the provision of the regenerative diode 97 can protect the elements in the discharge circuit from the coil surge, a small amount of tail current remains, as shown in Fig. 10, because the current caused by the voltage generated in the coil 94 continues to flow through the regenerative diode 97 and the flash lamp FL even after the thyristor 96 is turned off.

[0081] 10 flows and the flash lamps FL emit light, so that the 63 flash lamps FL irradiate the surface of the semiconductor wafer W with a flash light having an irradiation time of about 0.1 milliseconds, and the surface is instantaneously heated to a processing temperature T2 and then rapidly cooled. In this embodiment, the processing temperature T2 is 1000°C. That is, in this embodiment, a large current of up to 4000A is instantaneously passed through the 63 flash lamps FL, so that the surface of the semiconductor wafer W is heated to about 600°C by flash light irradiation having an irradiation time of about 0.1 milliseconds. This makes it possible to activate the impurities implanted in the semiconductor wafer W while suppressing their diffusion due to heat.

[0082] The halogen lamps HL are turned off after a predetermined time has elapsed since the current supply to the flash lamps FL was stopped. This causes the temperature of the semiconductor wafer W to rapidly drop from the preheating temperature T1. The temperature of the semiconductor wafer W during the drop is measured by the lower radiation thermometer 20, and the measurement result is transmitted to the control unit 3. The control unit 3 monitors whether the temperature of the semiconductor wafer W has dropped to a predetermined temperature based on the measurement result of the lower radiation thermometer 20. Then, after the temperature of the semiconductor wafer W has dropped to a predetermined temperature or lower, the pair of transfer arms 11 of the transfer mechanism 10 again move horizontally from the retreat position to the transfer operation position and rise, so that the lift pins 12 protrude from the upper surface of the susceptor 74 and receive the semiconductor wafer W after the heat treatment from the susceptor 74. Next, the transfer opening 66 that had been closed by the gate valve 185 is opened, and the semiconductor wafer W placed on the lift pins 12 is carried out by a transfer robot outside the apparatus, and the heat treatment of the semiconductor wafer W in the heat treatment apparatus 1 is completed.

[0083] In this embodiment, by adjusting the capacitance C of the capacitor 93, the inductance L of the coil 94, the charging voltage V to the capacitor 93, etc., the flash lamps FL are instantaneously discharged with a large current of up to 4000 A, and the irradiation time of the flash lamps FL is set to an extremely short time of about 0.1 milliseconds. Even if the irradiation time is an extremely short flash light irradiation of about 0.1 milliseconds, the surface temperature of the semiconductor wafer W can be raised from the preheating temperature T1 to about 600° C. by passing a large current of up to 4000 A through the 63 flash lamps FL. Therefore, the surface temperature of the semiconductor wafer W can be instantaneously raised to a high temperature while keeping the amount of heat input to the semiconductor wafer W low (low thermal history), and the impurities implanted in the wafer surface can be highly activated and prevented from diffusing.

[0084] In other words, in order to raise the surface temperature of the semiconductor wafer W to 600° C. by irradiating it with a flash light having an irradiation time of about 0.1 millisecond, it is necessary to provide 63 flash lamps FL that discharge a large current of up to 4000 A. If an element set is provided for each of the 63 flash lamps FL, it is necessary to provide at least 63 thyristors 96, capacitors 93, etc. This would significantly increase the cost of the device and would also require a large installation space for the elements.

[0085] In this embodiment, one capacitor 93, one coil 94, one thyristor 96, and one regenerative diode 97 are provided for each of the three flash lamps FL connected in parallel. That is, 21 element sets are provided for the 63 flash lamps FL. This allows the number of elements provided in the heat treatment device 1 to be reduced compared to the case where an element set is provided for each flash lamp FL, suppressing increases in device costs and allowing the installation space for the elements to be compact.

[0086] 8, when one thyristor 96 or the like is connected to three flash lamps FL arranged in parallel, all of the currents flowing through the three flash lamps FL will flow through the single thyristor 96. For example, as in the above example, when a maximum current of 4000 A flows through each flash lamp FL, a large current of 12000 A will flow through the thyristor 96.

[0087] The thyristor 96 in this embodiment is a GCT thyristor, and the on-current of a typical GCT thyristor is 6000 A. In other words, according to the on-current standard, it is impossible to connect two flash lamps FL, through which a maximum current of 4000 A flows, in parallel to one thyristor 96. However, the rated surge on-current (I TSM ) is, for example, 50000A. The rated surge current is the peak value of a non-repetitive 60Hz sine half-wave on-current that can be passed within the rated junction temperature range. Since the 60Hz sine half-wave is about 8 milliseconds, the time during which a current flows through the flash lamp FL during flash light irradiation with an irradiation time of about 0.1 milliseconds in this embodiment is shorter than that. In addition, the flash light irradiation from the flash lamp FL is also non-repetitive. Therefore, with regard to flash light irradiation, if the rated junction temperature can be maintained, it is possible to pass a current up to the rated surge current of the thyristor 96. Then, the thyristor 96, which is a GCT thyristor with a rated surge current of 50000A, can be connected in parallel to 12 flash lamps FL through which a current of up to 4000A flows, based on a simple calculation of the current alone. Therefore, it is quite possible to provide one thyristor 96 for three flash lamps FL connected in parallel, and to switch the three flash lamps FL collectively using the thyristor 96.

[0088] Although the embodiment of the present invention has been described above, this invention can be modified in various ways without departing from the spirit of the invention. For example, the thyristor 96 is not limited to a GCT thyristor, but may be a GTO thyristor. A GTO thyristor also has the function of being turned off by applying a reverse signal to the gate.

[0089] Also, an IGBT (Insulated Gate Bipolar Transistor) may be used instead of the thyristor 96. The IGBT is a semiconductor element that switches between an on state and an off state according to a signal input to the gate. The IGBT has a lower rated current than the GCT thyristor or the GTO thyristor, but can switch between an on state and an off state at high speed. The GCT thyristor, the GTO thyristor, and the IGBT are all switching elements that turn on and off the current flowing through the connected flash lamps FL. That is, it is sufficient that one switching element is connected to three flash lamps FL connected in parallel, and the current flowing through the three flash lamps FL is collectively controlled by the switching element.

[0090] In the above embodiment, one element set is provided for three flash lamps FL connected in parallel, but the present invention is not limited to this. For example, two element sets may be provided for three flash lamps FL. Alternatively, one element set may be provided for two or four or more flash lamps FL connected in parallel. In short, it is sufficient to provide fewer element sets than the number of flash lamps FL connected in parallel, and more precisely, it is sufficient to provide M element sets (M is an integer smaller than N) for N flash lamps FL connected in parallel (N is an integer equal to or greater than 2). In this way, the number of elements provided in the heat treatment device 1 can be reduced compared to the case where an element set is provided for each flash lamp FL.

[0091] There is also a technique called simmer discharge as a measure to prevent the flash lamp FL from going out before its lifespan expires. This is a technique in which, rather than immediately transitioning to a main discharge after a trigger discharge, a weak discharge (simmer discharge) state is maintained in the glass tube 92 for a while after the trigger discharge occurs, and then a main discharge is generated. The simmer discharge moves in the opposite direction to gravity over time due to the influence of convection of the xenon gas sealed in the glass tube 92, so damage to the glass tube 92 can be reduced by generating a main discharge at a timing when the discharge path has moved to the vicinity of the central axis of the glass tube 92.

[0092] To generate such a simmer discharge, it is necessary to connect a resistor in parallel with the thyristor 96 in the discharge circuit of Fig. 8. Also, to transition from the simmer discharge to the main discharge, a switching element such as an IGBT or a thyristor is required. Even in this case, the same effect as in the above embodiment can be obtained by providing a number of switching elements that is less than the number of flash lamps FL connected in parallel. Note that the switching element for transitioning from the simmer discharge to the main discharge may be a thyristor that does not have a turn-off function and can only be turned on.

[0093] In the above embodiment, the flash heating unit 5 is provided with 63 flash lamps FL, but the number of flash lamps FL is not limited to this and may be any number. The flash lamps FL are not limited to xenon flash lamps and may be krypton flash lamps. The number of halogen lamps HL provided in the halogen heating unit 4 is not limited to 40 and may be any number.

[0094] In the above embodiment, the semiconductor wafer W is preheated using a filament-type halogen lamp HL as a continuously lit lamp that emits light continuously for one second or more. However, this is not limited to this, and preheating may be performed using a discharge-type arc lamp (e.g., a xenon arc lamp) or an LED lamp as a continuously lit lamp instead of the halogen lamp HL.

[0095] Furthermore, the heat treatment apparatus 1 is not limited to heat treatment for activating impurities, and may also perform heat treatment of a high dielectric constant gate insulating film (High-k film), bonding of metal and silicon, or crystallization of polysilicon. [Explanation of symbols]

[0096] 1 Heat treatment equipment 3. Control Unit 4 Halogen heating section 5 Flash heating section 6 Chambers 7 Holding part 10 Transfer mechanism 20 Lower radiation thermometer 25 Upper radiation thermometer 32 Input section 33 Display section 34 Storage section 63 Upper chamber window 64 Lower chamber window 65 Heat Treatment Space 74 Susceptor 91 Trigger Electrode 92 Glass Tube 93 Capacitor 94 Coil 96 Thyristor 97 Regenerative diode FL Flash lamp HL Halogen Lamp W Semiconductor wafer

Claims

1. A heat treatment apparatus for heating a substrate by irradiating the substrate with a flash light, comprising: a chamber for housing a substrate; a holder that holds the substrate in the chamber; a plurality of flash lamps for irradiating the substrate held by the holder with flash light; a discharge circuit that causes a current to flow through the plurality of flash lamps to emit light; A control unit that controls the discharge circuit; Equipped with The heat treatment apparatus includes a discharge circuit having M element sets (M is an integer smaller than N) for N flash lamps (N is an integer equal to or greater than 2) connected in parallel.

2. 2. The heat treatment apparatus according to claim 1, A heat treatment apparatus including one element set for the N flash lamps connected in parallel.

3. 3. The heat treatment apparatus according to claim 2, The element set includes one switching element that controls current flowing through the N flash lamps.

4. 4. The heat treatment apparatus according to claim 3, The element set further includes one each of a coil, a capacitor, and a diode.

5. 4. The heat treatment apparatus according to claim 3, The heat treatment device, wherein the switching element is a thyristor.

6. 6. The heat treatment apparatus according to claim 5, The heat treatment device, wherein the thyristor is a GTO thyristor or a GCT thyristor.

7. 4. The heat treatment apparatus according to claim 3, The heat treatment device, wherein the switching element is an IGBT.

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