Heat treatment method and heat treatment device

Abstract

To provide a heat treatment method capable of preventing a substrate from being cracked by a repeated stress during irradiation with flash light, and a heat treatment device.SOLUTION: A current flowing to a flash lamp, which emits flash light, is controlled by an IGBT. The IGBT repeats ON and OFF in accordance with a waveform of a pulse signal which is outputted from a pulse generator. The IGBT repeats ON and OFF, such that the current flowing to the flash lamp is also repeatedly increased and decreased, and a surface temperature of a semiconductor wafer rises while repeatedly rising and falling slightly. A cycle of ON and OFF at the time in which the IGBT repeats ON and OFF is made equal to or shorter than 200 microseconds by shortening an ON / OFF cycle in the pulse signal, thereby also reducing a fluctuation width in the rise and fall of the surface temperature of the semiconductor wafer. Thus, a stress value which repeatedly acts on the semiconductor wafer becomes equal to or less than a fatigue limit, thereby preventing the wafer from being cracked by the repeated stress.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a heat treatment method and a heat treatment apparatus for heating a substrate by irradiating the substrate with 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, is attracting attention in the semiconductor device manufacturing process.Flash lamp annealing is a heat treatment technology that uses a xenon flash lamp (hereinafter, simply referred to as "flash lamp" means a xenon flash lamp) to irradiate the surface of a semiconductor wafer with flash light, thereby raising the temperature of only the surface of the semiconductor wafer in an extremely short time (a few milliseconds or less).

[0003] The spectral distribution of radiation from a xenon flash lamp is in the ultraviolet to near-infrared range, with a shorter wavelength than conventional halogen lamps and a wavelength that roughly matches the fundamental absorption band of silicon semiconductor wafers. Therefore, when a semiconductor wafer is irradiated with flash light from a xenon flash lamp, little light is transmitted, making it 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 area near the surface of the semiconductor wafer.

[0004] Flash lamp annealing is used in processes that require heating for an extremely short period of time, such as activating impurities implanted in a semiconductor wafer. 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 in an extremely short period of time, allowing only the impurities to be activated without diffusing them deeply.

[0005] Patent Documents 1 and 2 disclose heat treatment apparatuses using such xenon flash lamps, 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, causing the IGBT to repeatedly turn on and off at high speed in accordance with the waveform of the pulse signal. This defines the waveform of the current flowing through the flash lamp, controlling the lamp light emission and making it possible to freely adjust the light emission time and light intensity of the flash lamp. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-070948 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-119562 Summary of the Invention [Problem to be solved by the invention]

[0007] In flash lamp annealing, a semiconductor wafer is irradiated with a flash of light with extremely high energy for an extremely short period of time, which instantaneously increases the stress acting on the semiconductor wafer and can lead to wafer cracking. In particular, as disclosed in Patent Documents 1 and 2, when an IGBT is used to control the current flowing through the flash lamp, the IGBT repeatedly turns on and off in a short period of time, which microscopically increases and decreases the current flowing through the circuit including the flash lamp. As a result, the surface temperature of the semiconductor wafer also repeatedly increases and decreases slightly until it reaches the target temperature. Repeated increases and decreases in the surface temperature of the semiconductor wafer over a short period of time result in repeated stress acting on the semiconductor wafer. As a result, a problem has arisen in which the semiconductor wafer becomes more susceptible to cracking due to a mechanism similar to fatigue fracture.

[0008] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a heat treatment method and a heat treatment apparatus that can prevent cracks from occurring in a substrate due to repeated stress when irradiated with flash light. [Means for solving the problem]

[0009] In order to solve the above problems, a first aspect of the present invention is a heat treatment method for heating a substrate by irradiating the substrate with light, comprising: a preheating step in which light is irradiated onto the substrate from a continuously lit lamp to heat the substrate to a predetermined preheating temperature; and a flash heating step in which, after the preheating step, flash light is irradiated onto the surface of the substrate from a plurality of flash lamps to raise the temperature of the surface of the substrate to a predetermined processing temperature, wherein in the flash heating step, current flowing through the plurality of flash lamps is controlled by a switching element, and in the flash heating step, the on and off cycle of the switching element is set to 200 microseconds or less.

[0010] In a second aspect, in the heat treatment method according to the first aspect, a voltage of 3400 V or less is applied to the plurality of flash lamps in the flash heating step.

[0011] In a third aspect, in the heat treatment method according to the second aspect, in the flash heating step, the difference between the maximum and minimum values of the surface temperature of the substrate caused by turning on and off the switching element is set to 10° C. or less.

[0012] In a fourth aspect, in the heat treatment method according to any one of the first to third aspects, the plurality of flash lamps include a first flash lamp and a second flash lamp, and in the flash heating step, the current flowing through the first flash lamp is controlled by a first switching element, and the current flowing through the second flash lamp is controlled by a second switching element, and in the flash heating step, the second switching element is turned off when the first switching element is turned on, and the second switching element is turned on when the first switching element is turned off.

[0013] Furthermore, a fifth aspect is a heat treatment method for heating a substrate by irradiating the substrate with light, the method comprising: a preheating step in which light is irradiated onto the substrate from a continuously lit lamp to heat the substrate to a predetermined preheating temperature; and a flash heating step in which, after the preheating step, flash light is irradiated onto the surface of the substrate from a plurality of flash lamps to raise the temperature of the surface of the substrate to a predetermined processing temperature, wherein the plurality of flash lamps include a first flash lamp and a second flash lamp; in the flash heating step, a current flowing through the first flash lamp is controlled by a first switching element, and a current flowing through the second flash lamp is controlled by a second switching element; and in the flash heating step, the second switching element is turned off when the first switching element is turned on, and the second switching element is turned on when the first switching element is turned off.

[0014] In addition, a sixth aspect is the heat treatment method according to the fifth aspect, wherein different pulse signals are applied to the first switching element and the second switching element to turn them on and off individually.

[0015] In addition, a seventh aspect is a heat treatment method according to the fifth aspect, in which a common pulse signal for turning on and off the first switching element and the second switching element is applied, and the pulse signal applied to the second switching element is inverted by an inversion circuit.

[0016] An eighth aspect is a heat treatment apparatus for heating a substrate by irradiating the substrate with light, the heat treatment apparatus comprising: a chamber for accommodating a substrate; a continuously lit lamp for irradiating the substrate accommodated in the chamber with light to heat the substrate to a predetermined preheating temperature; a plurality of flash lamps for irradiating the surface of the substrate heated to the preheating temperature with flash light to raise the temperature of the surface of the substrate to a predetermined processing temperature; a plurality of switching elements for controlling current flowing through the plurality of flash lamps; and a pulse generator for generating pulse signals for turning the plurality of switching elements on and off, wherein the on and off period of the pulse signals output by the pulse generator to the plurality of switching elements is 200 microseconds or less.

[0017] In addition, a ninth aspect is the heat treatment apparatus according to the eighth aspect, further comprising a capacitor that supplies power to the plurality of flash lamps, and a charging voltage of the capacitor is set to 3400V or less.

[0018] In addition, in a tenth aspect, in the heat treatment apparatus according to the ninth aspect, the difference between the maximum and minimum values of the surface temperature of the substrate caused by the on / off of the multiple switching elements when irradiated with flash light from the multiple flash lamps is set to 10°C or less.

[0019] In an eleventh aspect, in a heat treatment apparatus according to any one of the eighth to tenth aspects, the plurality of flash lamps include a first flash lamp and a second flash lamp, the plurality of switching elements include a first switching element that controls the current flowing to the first flash lamp and a second switching element that controls the current flowing to the second flash lamp, and when flash light is irradiated from the flash lamps, the second switching element is turned off when the first switching element is turned on, and the second switching element is turned on when the first switching element is turned off.

[0020] a plurality of flash lamps that heat the surface of the substrate, heated to the preheating temperature, by irradiating the surface with flash light; a plurality of switching elements that control current flowing through the plurality of flash lamps; and a pulse generator that generates pulse signals that turn on and off the plurality of switching elements, wherein the plurality of flash lamps include a first flash lamp and a second flash lamp, and the plurality of switching elements include a first switching element that controls the current flowing through the first flash lamp and a second switching element that controls the current flowing through the second flash lamp; and during flash light irradiation from the flash lamps, the second switching element is turned off when the first switching element is turned on, and the second switching element is turned on when the first switching element is turned off.

[0021] In a thirteenth aspect, in the heat treatment apparatus according to the twelfth aspect, the pulse generator outputs different pulse signals to the first switching element and the second switching element, respectively.

[0022] In a fourteenth aspect, in the heat treatment device according to the twelfth aspect, the pulse generator further includes an inversion circuit that outputs a pulse signal common to the first switching element and the second switching element and inverts the pulse signal applied to the second switching element. [Effects of the Invention]

[0023] According to the heat treatment methods of the first to fourth aspects, the on / off cycle of the switching element that controls the current flowing through the flash lamp is set to 200 microseconds or less, thereby reducing the fluctuation range of the substrate surface temperature and preventing cracks caused by repeated stress on the substrate when irradiated with flash light.

[0024] According to the heat treatment methods of the fifth to seventh aspects, in the flash heating process, the second switching element is turned off when the first switching element is turned on, and the second switching element is turned on when the first switching element is turned off, so that the intensity of the emitted light from the first flash lamp and the second flash lamp cancels each other out, thereby preventing cracks from occurring in the substrate due to repeated stress when irradiated with flash light.

[0025] According to the heat treatment apparatuses of the eighth to eleventh aspects, the on and off cycle of the pulse signal output by the pulse generator to the multiple switching elements is set to 200 microseconds or less, thereby reducing the fluctuation range of the substrate surface temperature and preventing cracks caused by repeated stress on the substrate when irradiated with flash light.

[0026] According to the heat treatment apparatuses of the twelfth to fourteenth aspects, when flash light is irradiated from the flash lamp, the second switching element is turned off when the first switching element is turned on, and the second switching element is turned on when the first switching element is turned off, so that the intensity of the emitted light from the first flash lamp and the second flash lamp cancels out each other, thereby preventing cracks from occurring in the substrate due to repeated stress when flash light is irradiated. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a vertical cross-sectional view showing the configuration of a heat treatment apparatus according to the present invention. [Figure 2] FIG. 2 is a perspective view showing the overall appearance of the holding portion. [Figure 3] FIG. [Figure 4] FIG. 2 is a cross-sectional view of a susceptor. [Figure 5] FIG. [Figure 6] FIG. [Figure 7] FIG. 2 is a plan view showing the arrangement of a plurality of halogen lamps. [Figure 8] FIG. 2 is a diagram showing a driving circuit for a flash lamp. [Figure 9] FIG. 10 is a diagram showing changes in the surface temperature of a semiconductor wafer. [Figure 10] FIG. 2 is a diagram showing an example of the waveform of a pulse signal input to an IGBT. [Figure 11] FIG. 10 is a diagram showing changes in the surface temperature of a semiconductor wafer during flash heating. [Figure 12] FIG. 10 is a diagram showing an increase and decrease in the surface temperature of a semiconductor wafer during flash heating. [Figure 13] 10A and 10B are diagrams showing examples of waveforms of pulse signals input to the first IGBT and the second IGBT in the second embodiment. [Figure 14] FIG. 10 is a diagram showing a drive circuit for a second flash lamp in the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Hereinafter, expressions indicating relative or absolute positional relationships (e.g., "in one direction," "along one direction," "parallel," "orthogonal," "center," "concentric," "coaxial," etc.) not only strictly represent the positional relationship but also represent a state of relative angular or distance displacement within a tolerance or a range that provides equivalent functionality, unless otherwise specified. Furthermore, expressions indicating an equal state (e.g., "identical," "equal," "homogeneous," etc.) not only represent a state of strict quantitative equality but also represent a state of difference that provides a tolerance or equivalent functionality, unless otherwise specified. Furthermore, expressions indicating a shape (e.g., "circular," "square," "cylindrical," etc.) not only represent a geometrically strict shape but also represent a shape within a range that provides equivalent functionality, such as irregularities or chamfers, unless otherwise specified. Furthermore, expressions such as "comprise," "comprise," "include," "have," etc., regarding components, are not exclusive expressions that exclude the presence of other components. Furthermore, 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."

[0029] First Embodiment 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). Note that in FIG. 1 and the subsequent figures, the dimensions and number of various parts are exaggerated or simplified as necessary for ease of understanding.

[0030] Heat treatment apparatus 1 includes a chamber 6 that accommodates a semiconductor wafer W, a flash heating unit 5 that incorporates multiple flash lamps FL, and a halogen heating unit 4 that incorporates multiple halogen lamps HL. The flash heating unit 5 is provided above chamber 6, and the halogen heating unit 4 is provided below. Heat treatment apparatus 1 also includes, inside chamber 6, a holder 7 that holds the semiconductor wafer W in a horizontal position, and a transfer mechanism 10 that transfers the semiconductor wafer W between the holder 7 and the outside of the apparatus. Heat treatment apparatus 1 also includes a control unit 3 that controls the operating mechanisms provided in the halogen heating unit 4, flash heating unit 5, and chamber 6 to perform heat treatment on the semiconductor wafer W.

[0031] The chamber 6 is constructed by attaching quartz chamber windows to 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 attached to and closing the upper opening, and a lower chamber window 64 attached to and closing the lower opening. The upper chamber window 63, which forms the ceiling of the chamber 6, is a disc-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, which forms the floor of the chamber 6, is also a disc-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.

[0032] Furthermore, a reflective ring 68 is attached to the upper part of the inner wall surface of the chamber side 61, and a reflective ring 69 is attached to the lower part. Both 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 61. On the other hand, the lower reflective ring 69 is attached by fitting it from the lower side of the chamber side 61 and fastening it with screws (not shown). In other words, both reflective rings 68, 69 are detachably attached to the chamber side 61. The internal space of the chamber 6, i.e., the space surrounded by the upper chamber window 63, the lower chamber window 64, the chamber side 61, and the reflective rings 68, 69, is defined as a heat treatment space 65.

[0033] By attaching the reflecting rings 68, 69 to 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 attached, 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 made of a metal material (e.g., stainless steel) that has excellent strength and heat resistance.

[0034] Furthermore, a transfer opening (furnace port) 66 is formed in the chamber side portion 61, through which a semiconductor wafer W is loaded into and unloaded from the chamber 6. The transfer opening 66 can be opened and closed by a gate valve 185. The transfer opening 66 is connected to the outer peripheral surface of the recessed portion 62. Therefore, when the gate valve 185 opens the transfer opening 66, the semiconductor wafer W can be loaded into and unloaded from the heat treatment space 65 through the transfer opening 66 and the recessed portion 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.

[0035] Furthermore, through-holes 61a and 61b are formed in the chamber side portion 61. The through-hole 61a is a cylindrical hole for guiding infrared light radiated from the upper surface of a semiconductor wafer W held on a susceptor 74 (described later) to the infrared sensor 29 of the upper radiation thermometer 25. 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 angle with respect to the horizontal direction so that their penetrating axes intersect with the main surface of the semiconductor wafer W held on the susceptor 74. A transparent window 26 made of calcium fluoride material that transmits infrared light in a wavelength range measurable by the upper radiation thermometer 25 is attached to the end of the through-hole 61a facing the heat treatment space 65. Furthermore, a transparent window 21 made of barium fluoride material that transmits infrared light in the wavelength range that can be measured by the lower radiation thermometer 20 is attached to the end of the through hole 61b facing the heat treatment space 65.

[0036] Gas supply holes 81 are formed in the upper part of the inner wall of the chamber 6 to supply processing gas to the heat treatment space 65. The gas supply holes 81 are formed at a position above the recess 62 and may be provided in the reflecting ring 68. The gas supply holes 81 are connected to a gas supply pipe 83 via 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 gas supply pipe 83. When the valve 84 is opened, 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 spreads within the buffer space 82, which has lower fluid resistance than the gas supply holes 81, and is supplied from the gas supply holes 81 into the heat treatment space 65. The processing gas may be, for example, an inert gas such as nitrogen (N), a reactive gas such as hydrogen (H) or ammonia (NH), or a mixture thereof (nitrogen gas in this embodiment).

[0037] Meanwhile, a gas exhaust hole 86 is formed in the lower part of the inner wall of the chamber 6 to exhaust gas from the heat treatment space 65. The gas exhaust hole 86 is formed below the recess 62 and may be provided in the reflecting ring 69. The gas exhaust hole 86 is connected to a gas exhaust pipe 88 via 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 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 multiple numbers 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 where the heat treatment apparatus 1 is installed.

[0038] A gas exhaust pipe 191 for discharging gas from 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 in the chamber 6 is exhausted through the transfer opening 66.

[0039] 2 is a perspective view showing the overall appearance of the holder 7. 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. In other words, the entire holder 7 is made of quartz.

[0040] 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.

[0041] 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. That is, the holding plate 75 has a planar size larger than that of the semiconductor wafer W.

[0042] 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, if the diameter of the semiconductor wafer W is φ300 mm, the inner diameter of the guide ring 76 is φ320 mm. The inner periphery of the guide ring 76 has a tapered surface that widens upward from the holding plate 75. The guide ring 76 is made of quartz, the same as the holding plate 75. The guide ring 76 may be welded 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.

[0043] The area of the upper surface of the holding plate 75 that is 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 opposing substrate support pins 77) is smaller than the diameter of the semiconductor wafer W. If the diameter of the semiconductor wafer W is 300 mm, the diameter is 270 mm to 280 mm (270 mm in this embodiment). Each substrate support pin 77 is made of quartz. The plurality of substrate support pins 77 may be provided on the upper surface of the holding plate 75 by welding, or may be machined integrally with the holding plate 75.

[0044] Returning to FIG. 2, four connecting portions 72 erected on the base ring 71 are fixed to the peripheral edge of the holding plate 75 of the susceptor 74 by welding. That is, the susceptor 74 and the base ring 71 are fixedly connected by the connecting portions 72. The base ring 71 of the holding portion 7 is supported on the wall surface of the chamber 6, and the holding portion 7 is thereby attached to the chamber 6. When the holding portion 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.

[0045] 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 erected 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 underside 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 the twelve substrate support pins 77 can support the semiconductor wafer W in a horizontal position.

[0046] 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.

[0047] 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 (infrared light) emitted from the underside of the semiconductor wafer W. That is, the lower radiation thermometer 20 receives the light emitted from the underside of the semiconductor wafer W through the opening 78 and a transparent window 21 attached to the through-hole 61b of the chamber side 61, thereby measuring the temperature of the semiconductor wafer W. Furthermore, the holding plate 75 of the susceptor 74 is formed 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.

[0048] 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 arc-shaped so as to fit the generally annular recess 62. Two lift pins 12 are provided 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 (position indicated by a solid line in FIG. 5) where the transfer arms 11 transfer the semiconductor wafer W to the holder 7 and a retracted position (position indicated by a two-dot chain line in FIG. 5) where the 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 one that rotates each transfer arm 11 using an individual motor, or one that uses a link mechanism to rotate a pair of transfer arms 11 in conjunction with one another using a single motor.

[0049] Furthermore, 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, a total of four lift pins 12 pass through 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 so as to open, 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. Because 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 also 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.

[0050] Returning to FIG. 1 , the flash heating unit 5, which is provided above the chamber 6, is configured with a light source made up of multiple (30 in this embodiment) xenon flash lamps FL inside a housing 51, and a reflector 52 provided to cover the light source from above. 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, which forms the floor of the flash heating unit 5, is a plate-shaped quartz window made of quartz. By installing the flash heating unit 5 above the chamber 6, the lamp light emission window 53 faces the upper chamber window 63. The flash lamps FL irradiate a heat treatment space 65 with flash light from above the chamber 6 through the lamp light emission window 53 and the upper chamber window 63.

[0051] The multiple flash lamps FL are each a rod-shaped lamp having a long cylindrical shape, and are arranged in a plane 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 flash lamps FL is also a horizontal plane.

[0052] 8 is a diagram showing a drive circuit for a flash lamp FL. As shown in the figure, a capacitor 93, a coil 94, a flash lamp FL, and an IGBT (insulated gate bipolar transistor) 96 are connected in series. Also, as shown in FIG. 8, a control unit 3 includes a pulse generator 31 and a waveform setting unit 32, and is connected to an input unit 33. Various known input devices such as a keyboard, a mouse, or a touch panel can be used as the input unit 33. The waveform setting unit 32 sets the waveform of a pulse signal based on the input content from the input unit 33, and the pulse generator 31 generates a pulse signal in accordance with that waveform.

[0053] The flash lamp FL includes a rod-shaped glass tube (discharge tube) 92 filled with xenon gas and having an anode and a cathode at both ends, and a trigger electrode 91 attached to the outer surface of the glass tube 92. A predetermined voltage is applied to a capacitor 93 by a power supply unit 95, and an electric charge corresponding to the applied voltage (charging voltage) is stored in the capacitor 93. A high voltage can be applied to the trigger electrode 91 from a trigger circuit 97. The timing at which the trigger circuit 97 applies a voltage to the trigger electrode 91 is controlled by the control unit 3.

[0054] The IGBT 96 is a bipolar transistor incorporating a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) in its gate, and is a switching element suitable for handling large amounts of power. A pulse signal is applied to the gate of the IGBT 96 from the pulse generator 31 of the control unit 3. When a voltage equal to or greater than a predetermined value (high voltage) is applied to the gate of the IGBT 96, the IGBT 96 turns on, and when a voltage less than the predetermined value (low voltage) is applied, the IGBT 96 turns off. In this way, the drive circuit including the flash lamp FL is turned on and off by the IGBT 96. By turning the IGBT 96 on and off, the connection between the flash lamp FL and the corresponding capacitor 93 is interrupted, and the current flowing through the flash lamp FL is controlled on and off.

[0055] Even if the IGBT 96 is turned on and a high voltage is applied to both electrodes of the glass tube 92 while the capacitor 93 is charged, xenon gas is an electrical insulator, so under normal conditions no electricity flows through the glass tube 92. However, if the trigger circuit 97 applies a high voltage to the trigger electrode 91, causing the insulation to break down, a discharge occurs between the electrodes, causing a current to flow instantaneously through the glass tube 92, and light is emitted due to the excitation of xenon atoms or molecules at that time.

[0056] A drive circuit such as that shown in Fig. 8 is provided individually for each of the multiple flash lamps FL provided in the flash heating unit 5. In this embodiment, 30 flash lamps FL are arranged in a plane, and therefore 30 drive circuits including IGBTs 96 such as that shown in Fig. 8 are provided corresponding to the 30 flash lamps FL. Therefore, the current flowing through each of the 30 flash lamps FL is individually on / off controlled by the corresponding IGBT 96.

[0057] Furthermore, reflector 52 is provided above the multiple flash lamps FL so as to cover them entirely. The basic function of reflector 52 is to reflect the flash light emitted from the multiple flash lamps FL toward the heat treatment space 65. Reflector 52 is made of an aluminum alloy plate, and its surface (the surface facing the flash lamps FL) is roughened by blasting.

[0058] The halogen heating unit 4, which is provided below the chamber 6, has a plurality of halogen lamps HL (40 in this embodiment) built into the inside of 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 from below the chamber 6 through a lower chamber window 64 into a heat treatment space 65.

[0059] FIG. 7 is a plan view showing the arrangement of multiple halogen lamps HL. 40 halogen lamps HL are arranged in two rows, upper and lower. 20 halogen lamps HL are arranged in the upper row, which is closer to the holder 7, and 20 halogen lamps HL are also arranged in the lower row, which is farther from the holder 7 than the upper row. Each halogen lamp HL is a rod-shaped lamp having a long cylindrical shape. In both the upper and lower rows, the 20 halogen lamps HL 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 rows is a horizontal plane.

[0060] 7, the halogen lamps HL are arranged more densely in the region facing the periphery of the semiconductor wafer W held by the holder 7 on both the upper and lower tiers than in the region facing the center of the semiconductor wafer W. That is, on both the upper and lower tiers, the halogen lamps HL are arranged at a shorter pitch in the periphery of the lamp arrangement than in the center. This allows a greater amount of light to be irradiated onto the periphery of the semiconductor wafer W, which is prone to temperature drop during heating due to light irradiation from the halogen heating unit 4.

[0061] The lamp group consisting of the halogen lamps HL on the upper row and the lamp group consisting of the halogen lamps HL on the lower row are arranged so as to intersect in a grid pattern. That is, a total of 40 halogen lamps HL are arranged so that the longitudinal direction of the 20 halogen lamps HL arranged on the upper row and the longitudinal direction of the 20 halogen lamps HL arranged on the lower row are perpendicular to each other.

[0062] A halogen lamp HL is a filament-type light source that emits light by passing electricity through a filament placed inside a glass tube, causing it to incandescent. The glass tube is filled with an inert gas, such as nitrogen or argon, containing trace amounts of halogen elements (iodine, bromine, etc.). The introduction of halogen elements makes it possible to set the filament temperature at a high temperature while preventing filament breakage. Therefore, compared to standard incandescent light bulbs, halogen lamps HL have the characteristics of a longer lifespan and the ability to continuously emit strong light. In other words, halogen lamps HL are continuous lamps that emit light continuously for at least one second. Furthermore, because halogen lamps HL are rod-shaped, they have a long lifespan, and by arranging them horizontally, they achieve excellent radiation efficiency toward the semiconductor wafer W above.

[0063] Also, a reflector 43 is provided below the two-tiered halogen lamps HL inside 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.

[0064] As shown in FIG. 1, the heat treatment apparatus 1 includes 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 top surface of the semiconductor wafer W to measure the temperature of the top surface. The infrared sensor 29 of the upper radiation thermometer 25 includes an InSb (indium antimonide) optical element to respond to the sudden temperature change on the top 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 bottom surface of the semiconductor wafer W to measure the temperature of the bottom surface.

[0065] The control unit 3 controls the various operating mechanisms provided in the heat treatment device 1. 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 (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, thereby causing the heat treatment device 1 to perform processing. The control unit 3 also includes a pulse generator 31 and a waveform setting unit 32 (FIG. 8). The waveform setting unit 32 sets the waveform of a pulse signal based on input from the input unit 33, and the pulse generator 31 generates a pulse signal that turns the IGBT 96 on and off accordingly.

[0066] In addition to the above configuration, the heat treatment apparatus 1 is equipped with various cooling structures to prevent excessive temperature rise in the halogen heating unit 4, flash heating unit 5, and chamber 6 due to the thermal energy generated by the halogen lamps HL and flash lamps FL during heat treatment of the semiconductor wafer W. For example, a water-cooled pipe (not shown) is provided in the wall of the chamber 6. The halogen heating unit 4 and flash heating unit 5 also have an air-cooled structure that creates 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 upper chamber window 63.

[0067] Next, the processing operations in the heat treatment apparatus 1 will be described. First, a typical heat treatment procedure for a semiconductor wafer W to be processed will be described. The semiconductor wafer W to be processed here is a silicon semiconductor substrate with a thin film of nickel formed on the source and drain regions. Nickel silicide is formed by flash light irradiation heat treatment (annealing) in the heat treatment apparatus 1. The processing procedure of the heat treatment apparatus 1, which will be described below, proceeds as the control unit 3 controls each operating mechanism of the heat treatment apparatus 1.

[0068] First, the air supply valve 84 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 through the gas supply hole 81. When the valve 89 is opened, the gas inside the chamber 6 is exhausted through the gas exhaust hole 86. As a result, the nitrogen gas supplied from the upper part of the heat treatment space 65 inside the chamber 6 flows downward and is exhausted from the lower part of the heat treatment space 65.

[0069] Furthermore, by opening the valve 192, the gas inside 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 changed as appropriate depending on the treatment process.

[0070] Next, gate valve 185 is opened to open transfer opening 66, and a semiconductor wafer W to be processed is carried into heat treatment space 65 in chamber 6 through transfer opening 66 by a transfer robot outside the apparatus. At this time, there is a risk that the atmosphere outside the apparatus may be drawn in as the semiconductor wafer W is carried in, but since nitrogen gas is continuously supplied to chamber 6, the nitrogen gas flows out from transfer opening 66, making it possible to minimize the drawing in of such external atmosphere.

[0071] The semiconductor wafer W carried in by the transfer 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 retracted 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 higher than the upper ends of the substrate support pins 77.

[0072] After the semiconductor wafer W is placed on the lift pins 12, the transfer robot exits the heat treatment space 65, and the transfer opening 66 is closed by the gate valve 185. Then, the pair of transfer arms 11 descend, transferring the semiconductor wafer W from the transfer mechanism 10 to the susceptor 74 of the holder 7, where it is held horizontally from below. The semiconductor wafer W is supported by a plurality of substrate support pins 77 erected on the holding plate 75 and held on the susceptor 74. The semiconductor wafer W is held on the holder 7 with the front surface on which the nickel film is formed facing up. 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, which have descended to below the susceptor 74, are retracted to a retracted position, i.e., inside the recess 62, by the horizontal movement mechanism 13.

[0073] After the semiconductor wafer W is held from below in a horizontal position by the susceptor 74 of the holder 7, which is made of quartz, the 40 halogen lamps HL of the halogen heating unit 4 are turned on all at once to begin preheating (assisted heating). The halogen light emitted from the halogen lamps HL passes through the lower chamber window 64 and the susceptor 74, both of which are 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, so it does not interfere with heating by the halogen lamps HL.

[0074] FIG. 9 shows changes in the surface temperature of a semiconductor wafer W. At time t1, the halogen lamps HL are turned on to start preheating the semiconductor wafer W. During preheating using the halogen lamps HL, the temperature of the semiconductor wafer W is measured by the lower radiation thermometer 20. Specifically, the lower radiation thermometer 20 receives infrared light radiated from the underside of the semiconductor wafer W held on the susceptor 74 through the openings 78 and measures 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. Specifically, the control unit 3 performs feedback control of the output of the halogen lamps HL based on the measurement value from the lower radiation thermometer 20 so that the temperature of the semiconductor wafer W reaches 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, for example, 850°C.

[0075] 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, at time t2 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.

[0076] By performing preheating using the halogen lamps HL in this manner, the temperature of the entire semiconductor wafer W is uniformly raised to the preheating temperature T1. During preheating using the halogen lamps HL, the temperature of the peripheral portion of the semiconductor wafer W, where heat dissipation is more likely, 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 of the semiconductor wafer W than in the region facing the central portion. As a result, a greater amount of light is irradiated onto the peripheral portion of the semiconductor wafer W, where heat dissipation is more likely, and the in-plane temperature distribution of the semiconductor wafer W during the preheating stage can be made uniform.

[0077] At time t3, when a predetermined time has elapsed since the temperature of the semiconductor wafer W reached the preheating temperature T1, the flash lamps FL of the flash heating unit 5 irradiate the surface of the semiconductor wafer W held on the susceptor 74 with flash 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 is reflected by the reflector 52 before heading into the chamber 6, and the semiconductor wafer W is flash-heated by the irradiation of these flash lights.

[0078] When the flash lamp FL emits a flash of light, the power supply unit 95 stores electric charge in the capacitor 93 at a predetermined charging voltage. In this embodiment, the capacitor 93 is charged at a charging voltage of 3400 V or less. Then, with electric charge stored in the capacitor 93, the pulse generator 31 of the control unit 3 outputs a pulse signal to the gate of the IGBT 96 to turn the IGBT 96 on and off.

[0079] The waveform of the pulse signal can be specified by inputting a recipe in which, for example, the pulse width time (on time) and the pulse interval time (off time) are set sequentially as parameters from the input unit 33. When the operator inputs such a recipe from the input unit 33 to the control unit 3, the waveform setting unit 32 of the control unit 3 sets a pulse waveform that repeats on and off in accordance with the recipe. Then, the pulse generator 31 generates and outputs a pulse signal in accordance with the pulse waveform set by the waveform setting unit 32, and the pulse signal is input to the gate of the IGBT 96.

[0080] FIG. 10 is a diagram showing an example of the waveform of a pulse signal input to the IGBT 96. As shown in the diagram, the pulse signal of this embodiment alternates between on and off states. In this embodiment, the on-off period Ts of the pulse signal, i.e., the total time of one on-state and one off-state, is 200 microseconds or less. By applying a pulse signal having a waveform as shown in FIG. 10 to the gate of the IGBT 96, the on-off driving of the IGBT 96 is controlled. Specifically, when the pulse signal input to the gate of the IGBT 96 is on, the IGBT 96 is in the on state, and when the pulse signal is off, the IGBT 96 is in the off state.

[0081] Furthermore, in synchronization with the timing at which the pulse signal output from the pulse generator 31 turns on, the control unit 3 controls the trigger circuit 97 to apply a high voltage (trigger voltage) to the trigger electrode 91. When charge is accumulated in the capacitor 93, a pulse signal is input to the gate of the IGBT 96, and in synchronization with the timing at which the pulse signal turns on, a high voltage is applied to the trigger electrode 91. When the pulse signal is on, a current flows between the electrodes at both ends in the glass tube 92, and light is emitted due to the excitation of xenon atoms or molecules at that time.

[0082] In this way, the 30 flash lamps FL of the flash heating unit 5 emit light, irradiating the surface of the semiconductor wafer W held in the holder 7 with a flash of light. If the flash lamps FL were driven without the IGBT 96, the charge stored in the capacitor 93 would be consumed with each flash, resulting in a simple single-pulse output waveform with a width of approximately 0.1 to 10 milliseconds. In contrast, in this embodiment, the IGBT 96, which functions as a switching element, is connected to the circuit and a pulse signal is output to its gate. This allows the IGBT 96 to intermittently control the supply of charge from the capacitor 93 to the flash lamp FL, thereby controlling the on / off of the current flowing through the flash lamp FL. As a result, the light emission of the flash lamp FL is essentially chopper-controlled, with the charge stored in the capacitor 93 being consumed in parts, causing the flash lamp FL to repeatedly blink for an extremely short period of time. Note that before the current flowing through the circuit reaches zero, the next pulse is applied to the gate of the IGBT 96, causing the current to increase again. Therefore, the light emission output of the flash lamp FL does not become completely zero even while the flash lamp FL is repeatedly blinking.

[0083] By controlling the on / off of the current flowing through the flash lamp FL using the IGBT 96, the light emission pattern (time waveform of the light emission output) of the flash lamp FL can be freely defined, and the light emission time and light intensity can be freely adjusted. The on / off drive pattern of the IGBT 96 is defined by the pulse width and pulse interval time input from the input unit 33. In other words, by incorporating the IGBT 96 into the drive circuit of the flash lamp FL, the light emission pattern of the flash lamp FL can be freely defined simply by appropriately setting the pulse width and pulse interval time input from the input unit 33.

[0084] Specifically, for example, increasing the ratio of the pulse width time to the pulse interval time input from the input unit 33 increases the current flowing through the flash lamp FL, thereby increasing the light emission intensity. Conversely, decreasing the ratio of the pulse width time to the pulse interval time input from the input unit 33 decreases the current flowing through the flash lamp FL, thereby decreasing the light emission intensity. Furthermore, by appropriately adjusting the ratio of the pulse interval time to the pulse width time input from the input unit 33, the light emission intensity of the flash lamp FL can be maintained constant. Furthermore, by lengthening the total combined time of the pulse width time and pulse interval time input from the input unit 33, current continues to flow through the flash lamp FL for a relatively long period of time, thereby extending the light emission time of the flash lamp FL. The light emission time of the flash lamp FL is appropriately set between 0.1 milliseconds and 100 milliseconds. The maximum temperature reached on the surface of the semiconductor wafer W and the amount of heat input to the semiconductor wafer W are determined by the charging voltage to the capacitor 93 and the waveform of the light emission pattern of the flash lamp FL.

[0085] In this manner, the flash lamps FL irradiate the surface of the semiconductor wafer W with a flash of light for an irradiation time of 0.1 milliseconds to 100 milliseconds (10 milliseconds in this embodiment), thereby flash-heating the semiconductor wafer W. The surface temperature of the semiconductor wafer W, which is flash-heated by the irradiation of the flash of light from the flash lamps FL, instantaneously rises to a processing temperature T2. As the surface of the semiconductor wafer W is heated to the processing temperature T2 over approximately 10 milliseconds, the nickel thin film reacts with silicon to form nickel silicide. The processing temperature T2 is, for example, 1250°C. After the surface temperature of the semiconductor wafer W reaches the processing temperature T2 at time t4, the pulse signal is not turned on, the flash lamps FL stop emitting light, and the surface temperature drops rapidly. In this manner, in the heat treatment apparatus 1, the surface temperature of the semiconductor wafer W can be raised or lowered in an extremely short time by irradiating the surface with a flash of light with an extremely short irradiation time.

[0086] After the flash heating process is completed, the halogen lamps HL are also turned off. This causes the temperature of the semiconductor wafer W to rapidly decrease from the preheating temperature T1. The temperature of the semiconductor wafer W during this decrease is measured by the lower radiation thermometer 20, and the measurement result is transmitted to the control unit 3. The control unit 3 monitors, based on the measurement result of the lower radiation thermometer 20, whether the temperature of the semiconductor wafer W has decreased to a predetermined temperature. After the temperature of the semiconductor wafer W has decreased to or below the predetermined temperature, the pair of transfer arms 11 of the transfer mechanism 10 again move horizontally from the retracted position to the transfer operation position and rise, causing the lift pins 12 to protrude from the upper surface of the susceptor 74 and receive the heat-treated semiconductor wafer W from the susceptor 74. Next, the transfer opening 66, which had been closed by the gate valve 185, is opened, and the semiconductor wafer W placed on the lift pins 12 is removed by a transfer robot external to the apparatus, completing the heat treatment of the semiconductor wafer W in the heat treatment apparatus 1.

[0087] FIG. 11 shows the change in the surface temperature of the semiconductor wafer W during flash heating. This figure is an enlarged view of the period from time t3 to time t4 in FIG. 9. The period from time t3 to time t4 is approximately 10 milliseconds. As the IGBT 96 repeatedly turns on and off in accordance with the waveform of the pulse signal output from the pulse generator 31, the current flowing through the flash lamps FL also repeatedly increases and decreases. As a result, the intensity of the light emitted from the flash lamps FL also repeatedly increases and decreases. As shown in FIG. 11, during the flash heating process from time t3 to time t4, the surface temperature of the semiconductor wafer W increases from the preheating temperature T1 to the processing temperature T2 while repeatedly increasing and decreasing slightly.

[0088] In this embodiment, the on-off period Ts of the pulse signal output by the pulse generator 31 is set to 200 microseconds or less. Therefore, the on-off period when the IGBT 96 repeatedly turns on and off is also extremely short, at 200 microseconds or less, and the fluctuation range of the increase and decrease in the surface temperature of the semiconductor wafer W is also small. That is, because the on-time of the IGBT 96 is extremely short, the current flowing through the flash lamps FL increases while the IGBT 96 is on, and the temperature range by which the surface temperature of the semiconductor wafer W increases is very small. Furthermore, because the off-time of the IGBT 96 is also extremely short, the current flowing through the flash lamps FL decreases while the IGBT 96 is off, and the temperature range by which the surface temperature of the semiconductor wafer W decreases is also very small. As a result, the fluctuation range of the surface temperature of the semiconductor wafer W is small.

[0089] FIG. 12 is a diagram showing the increase and decrease in the surface temperature of the semiconductor wafer W during flash heating. This figure is a further enlargement of a portion of FIG. 11. During flash heating, the surface temperature of the semiconductor wafer W increases and decreases repeatedly microscopically, but gradually increases macroscopically. FIG. 12 shows approximately one cycle of increase and decrease in the surface temperature of the semiconductor wafer W.

[0090] Because the on / off cycle of the IGBT 96 is extremely short at 200 microseconds or less, the cycle of increase and decrease of the current flowing through the flash lamp FL is also extremely short, and as a result, the cycle of increase and decrease of the surface temperature of the semiconductor wafer W is also approximately 200 microseconds or less. If the on / off cycle of the IGBT 96 is 200 microseconds or less under the condition that the charging voltage of the capacitor 93 (i.e., the voltage applied to the flash lamp FL) is 3400 V or less, the difference Td between the maximum value and the minimum value in one cycle of increase and decrease of the surface temperature of the semiconductor wafer W will be 10°C or less.

[0091] When the surface temperature of the semiconductor wafer W repeatedly increases and decreases due to the on / off switching of the IGBT 96, thermal expansion and contraction causes repeated stress to act on the semiconductor wafer W. However, if the difference Td between the maximum and minimum surface temperature values of the semiconductor wafer W at this time is 10°C or less, the value of the repeated stress acting on the semiconductor wafer W will be below the fatigue limit. Therefore, even if repeated stress acts on the semiconductor wafer W, it will not result in cracking of the semiconductor wafer W. In other words, by following the first embodiment, it is possible to prevent cracks from occurring in the semiconductor wafer W due to repeated stress when irradiated with flash light.

[0092] Second Embodiment Next, a second embodiment of the present invention will be described. The configuration of the heat treatment apparatus and the processing procedure for semiconductor wafers W in the second embodiment are generally the same as those in the first embodiment. In the second embodiment, the phase of increase and decrease in the intensity of light emitted from a certain flash lamp FL is reversed to the phase of increase and decrease in the intensity of light emitted from the adjacent flash lamp FL.

[0093] In the second embodiment, as in the first embodiment, 30 flash lamps FL are arranged in a plane parallel to one another along the horizontal direction. A drive circuit such as that shown in FIG. 8 is provided for each of the 30 flash lamps FL. That is, an IGBT 96 is individually connected in series to each of the 30 flash lamps FL. Therefore, a total of 30 IGBTs 96 are provided in the heat treatment apparatus 1.

[0094] In the second embodiment, the control unit 3 individually controls the on / off of the 30 IGBTs 96. Specifically, the pulse generator 31 of the control unit 3 outputs a pulse signal with a waveform unique to each of the 30 IGBTs 96.

[0095] An arbitrary lamp among the 30 flash lamps FL arranged side by side in the horizontal direction is designated as the first flash lamp FL, and the lamp next to it is designated as the second flash lamp FL. Furthermore, the switching element connected to the first flash lamp FL is designated as the first IGBT 96, and the switching element connected to the second flash lamp FL is designated as the second IGBT 96. Thus, the first IGBT 96 controls the current flowing through the first flash lamp FL, and the second IGBT 96 controls the current flowing through the second flash lamp FL.

[0096] In the second embodiment, the pulse generator 31 outputs pulse signals of different waveforms to the first IGBT 96 and the second IGBT 96. Fig. 13 is a diagram showing an example of the waveforms of the pulse signals input to the first IGBT 96 and the second IGBT 96 in the second embodiment. The pulse generator 31 outputs the pulse signal shown in the upper part of Fig. 13 to the first IGBT 96, and outputs the pulse signal shown in the lower part of Fig. 13 to the second IGBT 96.

[0097] 13, the phases of the pulse signal input to the first IGBT 96 and the pulse signal input to the second IGBT 96 are inverted. That is, when the pulse signal input to the first IGBT 96 is on, the pulse signal input to the second IGBT 96 is off. Conversely, when the pulse signal input to the first IGBT 96 is off, the pulse signal input to the second IGBT 96 is on.

[0098] When the pulse generator 31 applies a pulse signal as shown in Fig. 13 to each of the first and second IGBTs 96 during flash light irradiation, the first IGBT 96 repeatedly turns on and off in accordance with the waveform of the pulse signal in the upper part of Fig. 13, and the second IGBT 96 repeatedly turns on and off in accordance with the waveform of the pulse signal in the lower part of Fig. 13. As a result, when the first IGBT 96 turns on, the second IGBT 96 turns off, and when the first IGBT 96 turns off, the second IGBT 96 turns on. As a result, the phases of increase and decrease in the current flowing through the first and second flash lamps FL are reversed, and the phases of increase and decrease in the intensity of the light emitted from the first and second flash lamps FL are also reversed.

[0099] When the phases of the increase and decrease in the intensity of light emitted from adjacent first and second flash lamps FL are reversed, the intensity of the light emitted by the first and second flash lamps FL cancel each other out. This suppresses repeated increases and decreases in the intensity of light irradiated onto the semiconductor wafer W during flash heat treatment, resulting in a monotonous increase in the surface temperature of the semiconductor wafer W. As a result, repeated stress is not applied to the semiconductor wafer W during flash heat treatment, preventing cracks in the semiconductor wafer W. In other words, the second embodiment prevents cracks in the semiconductor wafer W due to repeated stress during flash light irradiation. Note that there are 15 first and second flash lamps FL instead of just one, and the first and second flash lamps FL are alternately arranged to form an array of 30 flash lamps FL.

[0100] <Third embodiment> Next, a third embodiment of the present invention will be described. The configuration of the heat treatment apparatus and the processing procedure for semiconductor wafers W in the third embodiment are generally the same as those in the first embodiment. In the third embodiment, as in the second embodiment, the phase of increase and decrease in the intensity of light emitted from a certain flash lamp FL is reversed to the phase of increase and decrease in the intensity of light emitted from the adjacent flash lamp FL. To achieve this, in the second embodiment, the control unit 3 individually controls the on / off of multiple IGBTs 96, but in the third embodiment, the waveform of the pulse signal is reversed by an inversion circuit.

[0101] In the third embodiment, as in the first embodiment, 30 flash lamps FL are arranged in a plane parallel to one another along the horizontal direction. A drive circuit such as that shown in FIG. 8 is provided for each of the 30 flash lamps FL. That is, an IGBT 96 is individually connected in series to each of the 30 flash lamps FL. Therefore, a total of 30 IGBTs 96 are provided in the heat treatment apparatus 1.

[0102] As in the second embodiment, any one of the 30 flash lamps FL arranged side by side in the horizontal direction is designated the first flash lamp FL, and the lamp next to it is designated the second flash lamp FL. The switching element connected to the first flash lamp FL is designated the first IGBT 96, and the switching element connected to the second flash lamp FL is designated the second IGBT 96. Thus, the first IGBT 96 controls the current flowing through the first flash lamp FL, and the second IGBT 96 controls the current flowing through the second flash lamp FL. As in the second embodiment, there are 15 each of the first flash lamps FL and second flash lamps FL, and the array of 30 flash lamps FL is formed by alternately arranging the first flash lamps FL and the second flash lamps FL.

[0103] Fig. 14 is a diagram showing a drive circuit for the second flash lamps FL in the third embodiment. In the third embodiment, the first flash lamps FL are provided with a drive circuit similar to that shown in Fig. 8. On the other hand, the second flash lamps FL are provided with a drive circuit as shown in Fig. 14.

[0104] In FIG. 14, the same elements as those in FIG. 8 are denoted by the same reference numerals. The circuit shown in FIG. 14 differs from that in FIG. 8 in that an inversion circuit 99 is provided. Specifically, the inversion circuit 99 is provided between the gate of the IGBT 96 and the pulse generator 31 of the control unit 3. The inversion circuit 99 inverts the polarity of the input signal and outputs it. The inversion circuit 99 is, for example, an operational amplifier. The remaining configuration of the circuit in FIG. 14 is the same as that in FIG. 8, except for the inversion circuit 99.

[0105] In the third embodiment, the pulse generator 31 of the control unit 3 outputs pulse signals of a common waveform (i.e., the same waveform) to all 30 IGBTs 96. The pulse signal output from the pulse generator 31 is input directly to the first IGBT 96. Therefore, a pulse signal having the same waveform as the pulse signal output from the pulse generator 31 is input to the first IGBT 96. On the other hand, the pulse signal output from the pulse generator 31 is inverted by an inverter circuit 99 and input to the second IGBT 96. Therefore, a pulse signal whose waveform is the inverse of the pulse signal output from the pulse generator 31 is input to the second IGBT 96. For example, if the pulse generator 31 outputs a pulse signal as shown in the upper part of FIG. 13, the pulse signal as shown in the upper part of FIG. 13 will be input to the first IGBT 96, and the pulse signal as shown in the lower part of FIG. 13 will be input to the second IGBT 96.

[0106] In this manner, in the third embodiment, as in the second embodiment, the phases of the pulse signals input to the first IGBT 96 and the second IGBT 96 are reversed during flash light irradiation. As a result, when the first IGBT 96 is turned on, the second IGBT 96 is turned off, and when the first IGBT 96 is turned off, the second IGBT 96 is turned on. As a result, the phases of the increase and decrease in the current flowing through the first flash lamp FL and the second flash lamp FL are reversed, and the phases of the increase and decrease in the intensity of the light emitted from the first flash lamp FL and the second flash lamp FL are reversed. Therefore, as in the second embodiment, the intensity of the light emitted from the first flash lamp FL and the second flash lamp FL cancel each other out.

[0107] Even in the third embodiment, the intensity of light irradiated onto the semiconductor wafer W is prevented from repeatedly increasing and decreasing during flash heat treatment, and the surface temperature of the semiconductor wafer W rises monotonically. As a result, repeated stress is not applied to the semiconductor wafer W even during flash heat treatment, and cracks in the semiconductor wafer W can be prevented. In other words, by adopting the third embodiment, it is possible to prevent cracks from occurring in the semiconductor wafer W due to repeated stresses during flash light irradiation.

[0108] <Modification> Although the embodiments of the present invention have been described above, various modifications can be made to the present invention without departing from the spirit of the invention. For example, the first embodiment may be combined with the second or third embodiment. That is, the on / off cycle of the IGBT 96 may be set to 200 microseconds or less, and the phases of the increase and decrease in the intensity of light emitted from adjacent flash lamps FL may be reversed. This more reliably prevents cracking of the semiconductor wafer W due to repeated stress during flash light irradiation.

[0109] Furthermore, in the second and third embodiments, the phases of increase and decrease in the intensity of light emitted from the adjacent first flash lamp FL and second flash lamp FL are reversed, but this is not limited to this, and the first flash lamp FL and second flash lamp FL may be any of the multiple flash lamps FL provided in the flash heating unit 5. For example, all of the right half and all of the left half of an array of 30 flash lamps FL may be first flash lamps FL and second flash lamps FL. However, if the first flash lamp FL and the second flash lamp FL are adjacent lamps as in the second and third embodiments, the effect of canceling out the intensity of the light emitted from the two lamps can be most efficiently obtained.

[0110] Furthermore, in the above-described embodiments, IGBTs 96 are used as switching elements, but this is not limiting. For example, GTO (Gate Turn Off) thyristors or GCT (Gate Commutated Turn Off) thyristors may be used as switching elements. GTO thyristors and GCT thyristors have a self-extinguishing function that transitions from an ON state to an OFF state when a negative signal is applied to the gate. Furthermore, GTO thyristors and GCT thyristors have a basic function of transitioning from an OFF state to an ON state when a positive signal is applied to the gate. In other words, GTO thyristors and GCT thyristors are turned on and off by a signal applied to the gate.

[0111] Furthermore, in the third embodiment, an operational amplifier is used as the inverting circuit 99, but the present invention is not limited to this, and the inverting circuit 99 may be, for example, a NOT circuit.

[0112] Furthermore, in the above embodiment, the flash heating unit 5 is provided with 30 flash lamps FL, but this is not limited to this and the number of flash lamps FL can be any number. Furthermore, the flash lamps FL are not limited to xenon flash lamps and may be krypton flash lamps. Furthermore, the number of halogen lamps HL provided in the halogen heating unit 4 is not limited to 40 and can be any number.

[0113] Furthermore, 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, but this is not limited to this, and preheating may be performed using a discharge arc lamp (e.g., a xenon arc lamp) or an LED lamp as a continuously lit lamp instead of the halogen lamp HL. [Explanation of symbols]

[0114] 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 31 Pulse Generator 32 Waveform setting section 33 Input section 63 Upper chamber window 64 Lower chamber window 65 Heat Treatment Space 74 Susceptor 93 Capacitor 96 IGBT 99 Inverter Circuit FL flash lamp HL halogen lamp W Semiconductor wafer

Claims

1. A heat treatment method for heating a substrate by irradiating the substrate with light, comprising: a preheating step of irradiating the substrate with light from a continuously lit lamp to heat the substrate to a predetermined preheating temperature; a flash heating step of irradiating the surface of the substrate with flash light from a plurality of flash lamps to raise the temperature of the surface of the substrate to a predetermined processing temperature after the preheating step; Equipped with In the flash heating step, currents flowing through the plurality of flash lamps are controlled by switching elements; In the flash heating step, the on / off cycle of the switching element is set to 200 microseconds or less.

2. The heat treatment method according to claim 1, In the flash heating step, a voltage of 3400 V or less is applied to the plurality of flash lamps.

3. The heat treatment method according to claim 2, In the flash heating step, the difference between the maximum and minimum values of the surface temperature of the substrate caused by turning on and off the switching element is set to 10° C. or less.

4. The heat treatment method according to any one of claims 1 to 3, the plurality of flash lamps include a first flash lamp and a second flash lamp; In the flash heating step, a current flowing through the first flash lamp is controlled by a first switching element, and a current flowing through the second flash lamp is controlled by a second switching element; In the flash heating step, the second switching element is turned off when the first switching element is turned on, and the second switching element is turned on when the first switching element is turned off.

5. A heat treatment method for heating a substrate by irradiating the substrate with light, comprising: a preheating step of irradiating the substrate with light from a continuously lit lamp to heat the substrate to a predetermined preheating temperature; a flash heating step of irradiating the surface of the substrate with flash light from a plurality of flash lamps to raise the temperature of the surface of the substrate to a predetermined processing temperature after the preheating step; Equipped with the plurality of flash lamps include a first flash lamp and a second flash lamp; In the flash heating step, a current flowing through the first flash lamp is controlled by a first switching element, and a current flowing through the second flash lamp is controlled by a second switching element; In the flash heating step, the second switching element is turned off when the first switching element is turned on, and the second switching element is turned on when the first switching element is turned off.

6. The heat treatment method according to claim 5, A heat treatment method in which different pulse signals are applied to the first switching element and the second switching element to turn them on and off individually.

7. The heat treatment method according to claim 5, A heat treatment method comprising: applying a common pulse signal for turning on and off the first switching element and the second switching element; and inverting the pulse signal applied to the second switching element by an inverter circuit.

8. A heat treatment apparatus that heats a substrate by irradiating the substrate with light, a chamber for housing the substrate; a continuously lit lamp that irradiates light onto the substrate accommodated in the chamber to heat the substrate to a predetermined preheating temperature; a plurality of flash lamps that irradiate a surface of the substrate heated to the preheating temperature with flash light to raise the temperature of the surface of the substrate to a predetermined processing temperature; a plurality of switching elements for controlling currents flowing through the plurality of flash lamps; a pulse generator that generates pulse signals that turn on and off the plurality of switching elements; Equipped with The heat treatment apparatus has an on / off cycle of 200 microseconds or less in the pulse signal output from the pulse generator to the plurality of switching elements.

9. 9. The heat treatment apparatus according to claim 8, a capacitor for supplying power to the plurality of flash lamps; The heat treatment device is configured so that the charging voltage of the capacitor is 3400V or less.

10. 10. The heat treatment apparatus according to claim 9, A heat treatment apparatus in which the difference between the maximum and minimum surface temperatures of the substrate caused by the on / off of the plurality of switching elements during irradiation of flash light from the plurality of flash lamps is 10° C. or less.

11. 11. The heat treatment apparatus according to claim 8, the plurality of flash lamps include a first flash lamp and a second flash lamp; the plurality of switching elements include a first switching element that controls a current flowing through the first flash lamp and a second switching element that controls a current flowing through the second flash lamp; During irradiation of flash light from the flash lamp, the heat treatment apparatus turns off the second switching element when the first switching element is turned on, and turns on the second switching element when the first switching element is turned off.

12. A heat treatment apparatus that heats a substrate by irradiating the substrate with light, a chamber for housing the substrate; a continuously lit lamp that irradiates light onto the substrate accommodated in the chamber to heat the substrate to a predetermined preheating temperature; a plurality of flash lamps that irradiate a surface of the substrate heated to the preheating temperature with flash light to raise the temperature of the surface of the substrate to a predetermined processing temperature; a plurality of switching elements for controlling currents flowing through the plurality of flash lamps; a pulse generator that generates pulse signals that turn on and off the plurality of switching elements; Equipped with the plurality of flash lamps include a first flash lamp and a second flash lamp; the plurality of switching elements include a first switching element that controls a current flowing through the first flash lamp and a second switching element that controls a current flowing through the second flash lamp; During irradiation of flash light from the flash lamp, the heat treatment apparatus turns off the second switching element when the first switching element is turned on, and turns on the second switching element when the first switching element is turned off.

13. 13. The heat treatment apparatus according to claim 12, The heat treatment apparatus, wherein the pulse generator outputs different pulse signals to the first switching element and the second switching element, respectively.

14. 13. The heat treatment apparatus according to claim 12, the pulse generator outputs a common pulse signal to the first switching element and the second switching element; The heat treatment apparatus further comprises an inversion circuit that inverts the pulse signal applied to the second switching element.

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