Heat treatment method and heat treatment apparatus

Abstract

To provide a heat treatment method and a heat treatment device, capable of appropriately creating a temperature profile.SOLUTION: A semiconductor wafer is heated by a flash light irradiation from a flash lamp after a pre-heating by a halogen lamp. In a voltage signal output when performing a front surface temperature measurement of the semiconductor wafer by an upper radiation thermometer, a termination period is set to a trigger point when a voltage difference Vp between a voltage at a start period of a determination period having a constant length and a voltage of the termination period is a constant value or larger. A temperature data acquired before a predetermined number from the temperature data acquired at the trigger point from a plurality of pieces of temperature data acquired by the upper radiation thermometer is a start point temperature data, and the temperature data at a constant number after a start point temperature data from the plurality of pieces of temperature data is extracted to create a temperature profile.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a heat treatment method and a heat treatment apparatus that heat a substrate by irradiating the substrate with flash light. Substrates to be processed include, for example, semiconductor wafers, substrates for liquid crystal display devices, substrates for flat panel displays (FPDs), substrates for optical disks, substrates for magnetic disks, and substrates for solar cells. [Background Art]

[0002] In semiconductor device manufacturing processes, flash lamp annealing (FLA), which heats a semiconductor wafer in an extremely short time, has attracted attention. Flash lamp annealing is a heat treatment technique in which flash light is irradiated onto the surface of a semiconductor wafer using a xenon flash lamp (hereinafter, when simply referred to as "flash lamp", it means a xenon flash lamp), thereby raising the temperature of only the surface of the semiconductor wafer in an extremely short time (several milliseconds or less).

[0003] The radiation spectral distribution of a xenon flash lamp ranges from the ultraviolet region to the near-infrared region, has a shorter wavelength than conventional halogen lamps, and substantially matches the fundamental absorption band of silicon semiconductor wafers. Therefore, when flash light is irradiated from a xenon flash lamp onto a semiconductor wafer, little light is transmitted, and the temperature of the semiconductor wafer can be raised rapidly. It has also been found that, in the case of flash light irradiation for an extremely short time of several milliseconds or less, only the vicinity of the surface of the semiconductor wafer can be selectively heated.

[0004] This type of flash lamp annealing is used for processes that require very short heating times, such as typically activating impurities implanted in semiconductor wafers. By irradiating the surface of a semiconductor wafer, which has been implanted with impurities by ion implantation, with flash light from a flash lamp, the surface of the semiconductor wafer can be heated to the activation temperature for a very short time, allowing for impurity activation without deep diffusion of the impurities. Generally, since it is difficult to reach the target temperature of the semiconductor wafer surface with flash light irradiation alone, the surface of the semiconductor wafer is preheated to a predetermined temperature before flash light is irradiated.

[0005] In heat treatment, including flash heating, it is crucial to properly control the temperature of the semiconductor wafer, and for this purpose, it is necessary to accurately measure the temperature of the semiconductor wafer during heat treatment. Typically, in the heat treatment of semiconductor wafers, temperature measurement is performed using a non-contact radiation thermometer. Patent Document 1 discloses a technique for measuring the surface temperature of a semiconductor wafer during flash light irradiation using a radiation thermometer and creating a temperature profile by plotting the measured temperatures over time. In the technique disclosed in Patent Document 1, a warning signal is transmitted before flash light irradiation, and a certain number of temperature data points are extracted as a trigger when the measured temperature reaches a threshold after the transmission of the warning signal, and a temperature profile is created. By extracting a certain number of temperature data points based on such trigger detection, the temperature data at the moment of flash light irradiation can be included in that certain number of temperature data points. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2020 / 003894 [Overview of the project] [Problems that the invention aims to solve]

[0007] In Patent Document 1, trigger detection is performed after the transmission of a warning signal in order to prevent false trigger detection caused by large fluctuations in the radiation thermometer reading immediately after the halogen lamp used for preheating is switched on. However, even after the transmission of the warning signal, there remains a risk of false trigger detection due to fluctuations in the output of the halogen lamp. To prevent such false detections, it is conceivable to set the trigger detection threshold to a value that exceeds the fluctuations in the output of the halogen lamp.

[0008] On the other hand, in recent years, annealing processes that reduce the amount of heat introduced into the semiconductor wafer by lowering the preheating temperature and the temperature reached by flash light irradiation have been considered. In such low-heat annealing processes, the rise in surface temperature of the semiconductor wafer during flash light irradiation (jump temperature) is small, so if the trigger detection threshold is increased as described above, the trigger detection becomes impossible.

[0009] This invention has been made in view of the above problems, and aims to provide a heat treatment method and a heat treatment apparatus that can appropriately create a temperature profile. [Means for solving the problem]

[0010] To solve the above problems, the invention of claim 1 provides a heat treatment method for heating a substrate by irradiating the substrate with flash light, comprising: a preheating step of preheating the substrate by irradiating the substrate with light from a continuously lit lamp; a flash light irradiation step of irradiating the surface of the preheated substrate with flash light from a flash lamp; a temperature measurement step of measuring the surface temperature of the substrate with a radiation thermometer at a predetermined data acquisition cycle; a trigger determination step of setting the end of the determination period as the trigger point when the voltage of the signal output from the radiation thermometer at the end of the determination period is higher than the voltage of the signal output from the radiation thermometer at the start of the determination period by a certain value or more; and a profile creation step of creating a temperature profile by extracting a certain number of temperature data from the plurality of temperature data after the starting temperature data from the temperature data obtained in the temperature measurement step, using a predetermined number of temperature data obtained earlier than the temperature data obtained at the trigger point as the starting temperature data. The start of the determination period is during the preheating process, and the end of the determination period is after the start of flash light irradiation. It is characterized by the following:

[0011] Furthermore, the invention of claim 2 is characterized in that, in the heat treatment method according to the invention of claim 1, a warning step is further provided in which a warning signal is transmitted before irradiating with flash light from the flash lamp, and the trigger determination step is started after the warning signal has been transmitted.

[0012] Furthermore, the invention of claim 3 is characterized in that, in the heat treatment method according to the invention of claim 1 or claim 2, it further comprises a filtering step of removing noise from the signal output from the radiation thermometer using a digital filter.

[0013] Furthermore, the invention of claim 4 is characterized in that, in the heat treatment method according to any one of the inventions of claims 1 to 3, the length of the determination period is 20 milliseconds or more and 100 milliseconds or less.

[0014] Furthermore, the invention of claim 5 is characterized in that, in the heat treatment method according to any one of the inventions of claims 1 to 4, it is determined that a crack has occurred in the substrate when a temperature rise occurs during the cooling stage in the temperature profile.

[0015] Furthermore, the invention of claim 6 is a heat treatment apparatus for heating a substrate by irradiating the substrate with flash light, comprising: a chamber for housing the substrate; a continuous lighting lamp for irradiating the substrate housed in the chamber with light to preheat the substrate; a flash lamp for irradiating the surface of the preheated substrate with flash light; a radiation thermometer for receiving infrared light emitted from the surface of the substrate and measuring the temperature of the surface at a predetermined data acquisition cycle; a trigger determination unit that sets the end of the determination period as a trigger point when the voltage of the signal output from the radiation thermometer at the end of the determination period is higher than the voltage of the signal output from the radiation thermometer at the start of the determination period by a certain value or more; and a profile creation unit that sets a starting point temperature data as a number of temperature data acquired earlier than the temperature data acquired at the trigger point from among a plurality of temperature data acquired by the radiation thermometer, and extracts a certain number of temperature data from the plurality of temperature data after the starting point temperature data to create a temperature profile. The start of the determination period is during the preheating, and the end of the determination period is after the start of the flash light irradiation. It is characterized by the following:

[0016] Furthermore, the invention of claim 7 is characterized in that, in the heat treatment apparatus according to the invention of claim 6, it further comprises a warning signal transmitting unit that transmits a warning signal before irradiating a flash light from the flash lamp, and the trigger determination unit starts determination after the warning signal has been transmitted.

[0017] Furthermore, the invention of claim 8 is characterized in that, in the heat treatment apparatus according to the invention of claim 6 or claim 7, noise is removed from the signal output from the radiation thermometer by a digital filter.

[0018] Furthermore, the invention of claim 9 is characterized in that, in the heat treatment apparatus according to any one of claims 6 to 8, the length of the determination period is not less than 20 milliseconds and not more than 100 milliseconds.

[0019] Furthermore, the invention of claim 10 is characterized in that, in the heat treatment apparatus according to any one of claims 6 to 9, it is determined that cracking has occurred in the substrate when a temperature rise occurs in the temperature drop step in the temperature profile.

Effect of the Invention

[0020] According to the inventions of claims 1 to 5, when the voltage of a signal output from a radiation thermometer at the end of a determination period is higher than the voltage of a signal output from the radiation thermometer at the start of the determination period by a predetermined value or more, the end is set as a trigger time point, and a predetermined number of temperature data before and after the trigger time point are extracted to create a temperature profile. Therefore, the time point immediately after the start of flash light irradiation can be reliably determined as the trigger time point, and an appropriate temperature profile can be created.

[0021] In particular, according to the invention of claim 2, trigger determination is started after a warning signal is transmitted, so that false detection of noise immediately after lighting of a continuous lighting lamp as a trigger time point can be prevented.

[0022] In particular, according to the invention of claim 3, noise is removed from a signal output from a radiation thermometer by a digital filter, so the time point immediately after the start of flash light irradiation can be more reliably determined as the trigger time point.

[0023] According to the inventions of claims 6 to 10, when the voltage of a signal output from a radiation thermometer at the end of a determination period is higher than the voltage of a signal output from the radiation thermometer at the start of the determination period by a predetermined value or more, the end is set as a trigger time point, and a predetermined number of temperature data before and after the trigger time point are extracted to create a temperature profile. Therefore, the time point immediately after the start of flash light irradiation can be reliably determined as the trigger time point, and an appropriate temperature profile can be created.

[0024] In particular, according to the invention of claim 7, since trigger determination is started after the advance notice signal is transmitted, it is possible to prevent false detection of noise immediately after lighting of a continuously lighting lamp as a trigger timing.

[0025] In particular, according to the invention of claim 8, since noise is removed from the signal output from the radiation thermometer by a digital filter, it is possible to more reliably determine the time immediately after the start of flash light irradiation as the trigger timing. [BRIEF DESCRIPTION OF THE DRAWINGS]

[0026] [Figure 1] It is a longitudinal sectional view showing the configuration of the heat treatment apparatus according to the present invention. [Figure 2] It is a perspective view showing the overall appearance of the holding portion. [Figure 3] It is a plan view of the susceptor. [Figure 4] It is a cross-sectional view of the susceptor. [Figure 5] It is a plan view of the transfer mechanism. [Figure 6] It is a side view of the transfer mechanism. [Figure 7] It is a plan view showing the arrangement of a plurality of halogen lamps. [Figure 8] It is a diagram showing a drive circuit for a flash lamp. [Figure 9] It is a block diagram showing the configuration of a high-speed radiation thermometer including a main part of an upper radiation thermometer. [Figure 10] It is a diagram showing changes in voltage signals before and after flash light irradiation. [Figure 11] It is a diagram showing changes in temperature data before and after flash light irradiation. [Figure 12] It is a diagram showing the correlation between a preheating temperature and a jump temperature. [MODE FOR CARRYING OUT THE INVENTION]

[0027] Embodiments of the present invention will be described in detail below 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.) shall, unless otherwise specified, not only strictly represent the positional relationship but also represent a state in which there is a relative displacement in terms of angle or distance within a tolerance or a range in which a similar level of function can be obtained. Similarly, expressions indicating equality (e.g., "identical," "equal," "homogeneous," etc.) shall, unless otherwise specified, not only represent a state in which there is a quantitatively strictly equal state but also represent a state in which there is a difference in which a tolerance or a similar level of function can be obtained. Furthermore, expressions indicating shape (e.g., "circular," "square," "cylindrical," etc.) shall, unless otherwise specified, not only strictly represent the geometrically precise shape but also represent a shape within a range in which a similar level of effect can be obtained, and may have, for example, irregularities or chamfers. Additionally, expressions such as "equipped," "possessing," "containing," "having," etc., for a component are not exclusive expressions that exclude the existence 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."

[0028] Figure 1 is a longitudinal cross-sectional view showing the configuration of the heat treatment apparatus 1 according to the present invention. The heat treatment apparatus 1 in Figure 1 is a flash lamp annealing apparatus that heats a disc-shaped semiconductor wafer W, which is used as a substrate, by flashing light onto the wafer. The size of the semiconductor wafer W to be processed is not particularly limited, but for example, it may be φ300 mm or φ450 mm (in this embodiment, it is φ300 mm). Impurities are injected into the semiconductor wafer W before it is brought into the heat treatment apparatus 1, and the heat treatment by the heat treatment apparatus 1 activates the injected impurities. Note that in Figure 1 and subsequent figures, the dimensions and number of parts are exaggerated or simplified as necessary for ease of understanding.

[0029] The heat treatment apparatus 1 comprises a chamber 6 for housing a semiconductor wafer W, a flash heating unit 5 incorporating multiple flash lamps FL, and a halogen heating unit 4 incorporating multiple halogen lamps HL. The flash heating unit 5 is located on the upper side of the chamber 6, while the halogen heating unit 4 is located on the lower side. The heat treatment apparatus 1 also includes a holding unit 7 inside the chamber 6 for holding the semiconductor wafer W in a horizontal position, and a transfer mechanism 10 for transferring the semiconductor wafer W between the holding unit 7 and the outside of the apparatus. Furthermore, the heat treatment apparatus 1 includes a control unit 3 that controls the operating mechanisms provided in the halogen heating unit 4, the flash heating unit 5, and the chamber 6 to perform heat treatment on the semiconductor wafer W.

[0030] Chamber 6 is constructed by mounting quartz chamber windows on the top and bottom of a cylindrical chamber side section 61. The chamber side section 61 has a roughly cylindrical shape with openings at the top and bottom. The upper opening is closed by an upper chamber window 63, and the lower opening is closed by a lower chamber window 64. The upper chamber window 63, which forms the ceiling of chamber 6, is a disc-shaped member made of quartz and functions as a quartz window that transmits flash light emitted from the flash heating section 5 into chamber 6. Similarly, the lower chamber window 64, which forms the floor of chamber 6, is also a disc-shaped member made of quartz and functions as a quartz window that transmits light from the halogen heating section 4 into chamber 6.

[0031] Furthermore, a reflective ring 68 is attached to the upper part of the inner wall surface of the chamber side portion 61, and a reflective ring 69 is attached to the lower part. Both reflective rings 68 and 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 portion 61. On the other hand, the lower reflective ring 69 is attached by fitting it from the lower side of the chamber side portion 61 and securing it with screws (not shown). In other words, both reflective rings 68 and 69 are detachably attached to the chamber side portion 61. The inner space of the chamber 6, that is, the space enclosed by the upper chamber window 63, the lower chamber window 64, the chamber side portion 61, and the reflective rings 68 and 69, is defined as the heat treatment space 65.

[0032] By attaching the reflective rings 68 and 69 to the chamber side portion 61, a recess 62 is formed on the inner wall surface of the chamber 6. Specifically, the recess 62 is formed by the central portion of the inner wall surface of the chamber side portion 61 where the reflective rings 68 and 69 are not attached, the lower end surface of the reflective ring 68, and the upper end surface of the reflective 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 holding portion 7 that holds the semiconductor wafer W. The chamber side portion 61 and the reflective rings 68 and 69 are made of a metal material (for example, stainless steel) with excellent strength and heat resistance.

[0033] Furthermore, a transport opening (furnace opening) 66 is provided on the side portion 61 of the chamber for loading and unloading semiconductor wafers W into and out of the chamber 6. The transport opening 66 can be opened and closed by a gate valve 185. The transport opening 66 is connected in communication with the outer surface of the recess 62. Therefore, when the gate valve 185 is open, semiconductor wafers W can be loaded into the heat treatment space 65 from the transport opening 66 through the recess 62 and unloaded from the heat treatment space 65. When the gate valve 185 closes the transport opening 66, the heat treatment space 65 inside the chamber 6 becomes a sealed space.

[0034] Furthermore, through-holes 61a and 61b are drilled in the side portion 61 of the chamber. Through-hole 61a is a cylindrical hole for guiding infrared light emitted from the upper surface of the semiconductor wafer W held by the susceptor 74 (described later) to the infrared sensor 29 of the upper radiation thermometer 25. On the other hand, through-hole 61b is a cylindrical hole for guiding infrared light emitted from the lower surface of the semiconductor wafer W to the lower radiation thermometer 20. Through-holes 61a and 61b are provided at an inclination with respect to the horizontal direction such that their axes in the direction of penetration intersect with the main surface of the semiconductor wafer W held by the susceptor 74. A transparent window 26 made of calcium fluoride material that transmits infrared light in the wavelength range measurable by the upper radiation thermometer 25 is attached to the end of 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 measurable by the lower radiation thermometer 20 is attached to the end of the through hole 61b facing the heat treatment space 65.

[0035] Furthermore, a gas supply hole 81 for supplying a processing gas to the heat treatment space 65 is formed in the upper part of the inner wall of the chamber 6. The gas supply hole 81 is formed in a position above the recess 62 and may be provided in the reflecting ring 68. The gas supply hole 81 is 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 also interposed in the path of 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 flows into the buffer space 82 spreads out within the buffer space 82, which has less fluid resistance than the gas supply hole 81, and is supplied from the gas supply hole 81 into the heat treatment space 65. As the processing gas, for example, an inert gas such as nitrogen (N2), or a reactive gas such as hydrogen (H2), ammonia (NH3), or a mixed gas of these can be used (in this embodiment, nitrogen gas).

[0036] On the other hand, a gas exhaust port 86 for exhausting gas from the heat treatment space 65 is formed in the lower part of the inner wall of the chamber 6. The gas exhaust port 86 is formed in a position below the recess 62 and may be provided in the reflecting ring 69. The gas exhaust port 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 the exhaust section 190. A valve 89 is interposed in the path of the gas exhaust pipe 88. When the valve 89 is opened, the gas from the heat treatment space 65 is discharged from the gas exhaust port 86 through the buffer space 87 to the gas exhaust pipe 88. Note that there may be multiple gas supply holes 81 and gas exhaust holes 86 along the circumferential direction of the chamber 6, or they may be slit-shaped. Also, the processing gas supply source 85 and the exhaust section 190 may be mechanisms provided in the heat treatment apparatus 1, or they may be utilities of the factory where the heat treatment apparatus 1 is installed.

[0037] Furthermore, a gas exhaust pipe 191 for discharging gas from the heat treatment space 65 is connected to the tip of the transport opening 66. The gas exhaust pipe 191 is connected to the exhaust section 190 via a valve 192. By opening the valve 192, the gas in the chamber 6 is exhausted through the transport opening 66.

[0038] Figure 2 is a perspective view showing the overall appearance of the holding part 7. The holding part 7 is composed of a base ring 71, a connecting part 72, and a susceptor 74. The base ring 71, the connecting part 72, and the susceptor 74 are all made of quartz. In other words, the entire holding part 7 is made of quartz.

[0039] The base ring 71 is a quartz material with an arc shape, partially missing from its annular shape. This missing portion is provided to prevent interference between the transfer arm 11 of the transfer mechanism 10 (described later) and the base ring 71. The base ring 71 is supported by the wall surface of the chamber 6 by being placed on the bottom surface of the recess 62 (see Figure 1). Multiple connecting parts 72 (four in this embodiment) are erected on the upper surface of the base ring 71 along the circumferential direction of its annular shape. The connecting parts 72 are also made of quartz material and are fixed to the base ring 71 by welding.

[0040] The susceptor 74 is supported by four connecting parts 72 provided on the base ring 71. Figure 3 is a plan view of the susceptor 74. Figure 4 is a cross-sectional view of the susceptor 74. The susceptor 74 comprises a retaining plate 75, a guide ring 76, and a plurality of substrate support pins 77. The retaining plate 75 is a substantially circular, flat member made of quartz. The diameter of the retaining plate 75 is larger than the diameter of the semiconductor wafer W. That is, the retaining plate 75 has a planar size larger than the semiconductor wafer W.

[0041] A guide ring 76 is installed on the upper peripheral edge of the retaining 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 circumference of the guide ring 76 is tapered so as to widen upward from the retaining plate 75. The guide ring 76 is made of quartz, the same material as the retaining plate 75. The guide ring 76 may be welded to the upper surface of the retaining plate 75, or it may be fixed to the retaining plate 75 by a separately processed pin or the like. Alternatively, the retaining plate 75 and the guide ring 76 may be manufactured as a single integrated member.

[0042] The area of ​​the upper surface of the retaining plate 75 that is inside the guide ring 76 is a planar retaining surface 75a for holding the semiconductor wafer W. Multiple substrate support pins 77 are erected on the retaining surface 75a of the retaining plate 75. In this embodiment, a total of 12 substrate support pins 77 are erected at 30° intervals along the circumference of the outer circumference of the retaining surface 75a (the inner circumference of the guide ring 76) concentric with the outer circumference of the retaining surface 75a. The diameter of the circle in 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, and if the diameter of the semiconductor wafer W is φ300 mm, the diameter is φ270 mm to φ280 mm (φ270 mm in this embodiment). Each substrate support pin 77 is made of quartz. Multiple substrate support pins 77 may be provided on the upper surface of the retaining plate 75 by welding, or they may be processed integrally with the retaining plate 75.

[0043] Returning to Figure 2, the four connecting parts 72 erected on the base ring 71 and the peripheral edge of the holding plate 75 of the susceptor 74 are fixed by welding. In other words, the susceptor 74 and the base ring 71 are fixedly connected by the connecting parts 72. The holding part 7 is mounted in the chamber 6 by the base ring 71 of the holding part 7 being supported by the wall surface of the chamber 6. When the holding part 7 is mounted in the chamber 6, the holding plate 75 of the susceptor 74 is in a horizontal position (a position in which the normal coincides with the vertical direction). In other words, the holding surface 75a of the holding plate 75 is a horizontal plane.

[0044] The semiconductor wafer W, once loaded into the chamber 6, is placed and held in a horizontal position on the susceptor 74 of the holding unit 7 mounted on the chamber 6. At this time, the semiconductor wafer W is supported by 12 substrate support pins 77 erected on the holding plate 75 and held by the susceptor 74. More precisely, the upper ends of the 12 substrate support pins 77 contact the lower surface of the semiconductor wafer W to support it. Since the height of the 12 substrate support pins 77 (the distance from the upper end of the substrate support pins 77 to the holding surface 75a of the holding plate 75) is uniform, the semiconductor wafer W can be supported in a horizontal position by the 12 substrate support pins 77.

[0045] 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, horizontal displacement of the semiconductor wafer W supported by the plurality of substrate support pins 77 is prevented by the guide ring 76.

[0046] Furthermore, as shown in Figures 2 and 3, the holding plate 75 of the susceptor 74 has an opening 78 that penetrates vertically. The opening 78 is provided for the lower radiation thermometer 20 to receive synchrotron radiation (infrared light) emitted from the lower surface of the semiconductor wafer W. That is, the lower radiation thermometer 20 measures the temperature of the semiconductor wafer W by receiving light emitted from the lower surface of the semiconductor wafer W through the opening 78 and a transparent window 21 fitted in a through hole 61b of the chamber side portion 61. In addition, the holding plate 75 of the susceptor 74 has four through holes 79 through which the lift pins 12 of the transfer mechanism 10, which will be described later, pass for the transfer of the semiconductor wafer W.

[0047] Figure 5 is a plan view of the transfer mechanism 10. Figure 6 is a side view of the transfer mechanism 10. The transfer mechanism 10 comprises two transfer arms 11. The transfer arms 11 are shaped like arcs that generally follow the annular recess 62. Two lift pins 12 are erected on each transfer arm 11. The transfer arms 11 and lift pins 12 are made of quartz. Each transfer arm 11 is rotatable by a horizontal movement mechanism 13. The horizontal movement mechanism 13 moves the pair of transfer arms 11 horizontally between a transfer operation position (solid line position in Figure 5) where the semiconductor wafer W is transferred to the holding part 7 and a retracted position (dotted line position in Figure 5) where the semiconductor wafer W held by the holding part 7 does not overlap in a plan view. The horizontal movement mechanism 13 may consist of individual motors that rotate each transfer arm 11, or it may consist of a linkage mechanism that uses a single motor to rotate a pair of transfer arms 11 in conjunction.

[0048] Furthermore, the pair of transfer arms 11 are moved up and down 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 Figures 2 and 3) drilled 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 and removes the lift pins 12 from the through holes 79, and the horizontal movement mechanism 13 moves the pair of transfer arms 11 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 holding part 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. Furthermore, an exhaust mechanism (not shown) is also provided near the area where the drive unit (horizontal movement mechanism 13 and lifting mechanism 14) of the transfer mechanism 10 is located, so that the atmosphere around the drive unit of the transfer mechanism 10 is discharged to the outside of the chamber 6.

[0049] Returning to Figure 1, the flash heating unit 5, located above the chamber 6, is configured with a light source consisting of multiple (30 in this embodiment) xenon flash lamps FL inside a housing 51, and a reflector 52 provided to cover the top of the light source. A lamp light emission window 53 is also attached to the bottom of the housing 51 of the flash heating unit 5. The lamp light emission window 53, which constitutes the floor of the flash heating unit 5, is a plate-shaped quartz window made of quartz. As the flash heating unit 5 is installed above the chamber 6, the lamp light emission window 53 faces the upper chamber window 63. The flash lamps FL irradiate the 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.

[0050] Each of the multiple flash lamps FL is a rod-shaped lamp with a long cylindrical shape, and they are arranged in a planar manner such that their longitudinal directions are parallel to each other along the main surface (i.e., along the horizontal direction) of the semiconductor wafer W held by the holding part 7. Therefore, the plane formed by the arrangement of the flash lamps FL is also a horizontal plane.

[0051] Figure 8 shows the 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 Figure 8, the control unit 3 includes a pulse generator 31 and a waveform setting unit 32, and is connected to the input unit 33. Various known input devices such as keyboards, mice, and touch panels can be used as the input unit 33. Based on the input content from the input unit 33, the waveform setting unit 32 sets the waveform of the pulse signal, and the pulse generator 31 generates a pulse signal according to that waveform.

[0052] The flash lamp FL comprises a rod-shaped glass tube (discharge tube) 92 containing xenon gas and having an anode and 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 the capacitor 93 by the power supply unit 95, and a charge corresponding to the applied voltage (charging voltage) is charged. A high voltage can also be applied to the trigger electrode 91 from the trigger circuit 97. The timing of the trigger circuit 97 applying voltage to the trigger electrode 91 is controlled by the control unit 3.

[0053] The IGBT96 is a bipolar transistor with a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) incorporated into its gate, making it a switching element suitable for handling high power. A pulse signal is applied to the gate of the IGBT96 from the pulse generator 31 of the control unit 3. When a voltage above a predetermined value (High voltage) is applied to the gate of the IGBT96, the IGBT96 turns on, and when a voltage below a predetermined value (Low voltage) is applied, the IGBT96 turns off. In this way, the drive circuit including the flash lamp FL is turned on and off by the IGBT96. By turning the IGBT96 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.

[0054] Even if the IGBT 96 is turned on while the capacitor 93 is charged and a high voltage is applied to both electrodes of the glass tube 92, electricity does not normally flow inside the glass tube 92 because xenon gas is an electrically insulating material. However, if the trigger circuit 97 applies a high voltage to the trigger electrode 91 and breaks down the insulation, a current flows instantaneously inside the glass tube 92 due to the discharge between the two electrodes, and light is emitted due to the excitation of xenon atoms or molecules at that time.

[0055] As shown in Figure 8, a drive circuit is provided individually for each of the multiple flash lamps FL located in the flash heating unit 5. In this embodiment, since 30 flash lamps FL are arranged in a planar configuration, 30 drive circuits like the one shown in Figure 8 are provided corresponding to them. Therefore, the current flowing through each of the 30 flash lamps FL is individually controlled on and off by the corresponding IGBT96.

[0056] Furthermore, the reflector 52 is positioned above the multiple flash lamps FL so as to cover them all. The basic function of the reflector 52 is to reflect the flash light emitted from the multiple flash lamps FL towards the heat treatment space 65. The reflector 52 is made of an aluminum alloy plate, and its surface (the side facing the flash lamps FL) is roughened by blasting.

[0057] The halogen heating unit 4, located below the chamber 6, has multiple 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 below the chamber 6 through the lower chamber window 64 into the heat treatment space 65 using multiple halogen lamps HL.

[0058] Figure 7 is a plan view showing the arrangement of multiple halogen lamps HL. The 40 halogen lamps HL are arranged in two rows, upper and lower. Twenty halogen lamps HL are arranged in the upper row, which is closer to the holding part 7, and another 20 halogen lamps HL are arranged in the lower row, which is further from the holding part 7. Each halogen lamp HL is a rod-shaped lamp with 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 holding part 7 (i.e., along the horizontal direction). Therefore, the planes formed by the arrangement of halogen lamps HL in both the upper and lower rows are horizontal planes.

[0059] Furthermore, as shown in Figure 7, in both the upper and lower sections, the arrangement density of halogen lamps HL is higher in the region facing the periphery of the semiconductor wafer W held by the holding section 7 than in the region facing the center. In other words, in both the upper and lower sections, the arrangement pitch of halogen lamps HL is shorter at the periphery than at the center of the lamp arrangement. Therefore, a greater amount of light can be irradiated to the periphery of the semiconductor wafer W, where temperature drops are more likely to occur during heating by light irradiation from the halogen heating section 4.

[0060] Furthermore, the lamp group consisting of halogen lamps HL in the upper row and the lamp group consisting of halogen lamps HL in the lower row are arranged to intersect in a grid pattern. In other words, a total of 40 halogen lamps HL are arranged such that the longitudinal directions of the 20 halogen lamps HL in the upper row and the longitudinal directions of the 20 halogen lamps HL in the lower row are perpendicular to each other.

[0061] The halogen lamp HL is a filament-type light source that emits light by passing an electric current through a filament placed inside a glass tube, causing the filament to become incandescent. Inside the glass tube is a gas containing trace amounts of halogen elements (iodine, bromine, etc.) introduced into an inert gas such as nitrogen or argon. By introducing halogen elements, it is possible to set the filament temperature to a high level while suppressing filament breakage. Therefore, the halogen lamp HL has the characteristics of having a longer lifespan and being able to continuously emit strong light compared to a normal incandescent light bulb. In other words, the halogen lamp HL is a continuous-lighting lamp that emits light continuously for at least 1 second or more. Furthermore, because the halogen lamp HL is a rod-shaped lamp, it has a long lifespan, and by arranging the halogen lamp HL horizontally, the radiation efficiency to the semiconductor wafer W above is excellent.

[0062] Furthermore, a reflector 43 is also provided inside the housing 41 of the halogen heating unit 4, below the two-tiered halogen lamps HL (Figure 1). The reflector 43 reflects the light emitted from the multiple halogen lamps HL towards the heat treatment space 65.

[0063] As shown in Figure 1, the heat treatment apparatus 1 includes an upper radiation thermometer 25 and a lower radiation thermometer 20. The upper radiation thermometer 25 is a high-speed radiation thermometer for measuring the rapid temperature change of the upper surface of the semiconductor wafer W when flash light is irradiated from a flash lamp FL.

[0064] Figure 9 is a block diagram showing the configuration of the high-speed radiation thermometer unit 101, including the main part of the upper radiation thermometer 25. The infrared sensor 29 of the upper radiation thermometer 25 is mounted on the outer wall surface of the chamber side portion 61 such that its optical axis coincides with the axis in the direction of penetration of the through hole 61a. The infrared sensor 29 receives infrared light emitted from the upper surface of the semiconductor wafer W held by the susceptor 74 through a transparent calcium fluoride window 26. The infrared sensor 29 is equipped with an InSb (indium antimony) optical element, and its measurement wavelength range is 5 μm to 6.5 μm. The transparent calcium fluoride window 26 selectively transmits infrared light in the measurement wavelength range of the infrared sensor 29. The resistance of the InSb optical element changes according to the intensity of the received infrared light. The infrared sensor 29 equipped with an InSb optical element has an extremely short response time and enables high-speed measurement with a remarkably short sampling interval (as short as approximately 20 microseconds). The infrared sensor 29 is electrically connected to the high-speed radiation thermometer unit 101 and transmits the signal generated in response to light reception to the high-speed radiation thermometer unit 101.

[0065] The high-speed radiation thermometer unit 101 includes a signal conversion circuit 102, an amplification circuit 103, an A / D converter 104, a filtering processing unit 105, a temperature conversion unit 106, and a storage unit 107. The signal conversion circuit 102 is a circuit that converts the resistance change generated by the InSb optical element of the infrared sensor 29 into a signal in the order of current change and voltage change, and finally converts it into an easily handleable voltage signal for output. The signal conversion circuit 102 is configured using, for example, an operational amplifier. The amplification circuit 103 amplifies the voltage signal output from the signal conversion circuit 102 and outputs it to the A / D converter 104. The A / D converter 104 converts the voltage signal amplified by the amplification circuit 103 into a digital signal.

[0066] The filtering processing unit 105 performs spatial filtering on the voltage signal converted to a digital signal by the A / D converter 104 using a digital filter. The digital filter used by the filtering processing unit 105 is a filter intended for noise removal, such as a median filter or a smoothing filter. The filtering processing unit 105 removes noise from the voltage signal output from the A / D converter 104.

[0067] The temperature conversion unit 106 performs predetermined calculations on the noise-removed voltage signal output from the filtering processing unit 105, that is, the signal indicating the intensity of infrared light received by the infrared sensor 29, and converts it into a temperature. The temperature determined by the temperature conversion unit 106 is the temperature of the upper surface of the semiconductor wafer W. The upper radiation thermometer 25 is composed of the infrared sensor 29, signal conversion circuit 102, amplification circuit 103, A / D converter 104, filtering processing unit 105, and temperature conversion unit 106. The lower radiation thermometer 20 has a configuration that is generally similar to the upper radiation thermometer 25, but it does not need to support high-speed measurement.

[0068] The voltage signal data, from which noise has been removed by the filtering processing unit 105, and the temperature data calculated by the temperature conversion unit 106 are stored and accumulated in the storage unit 107. The storage unit 107 is configured using, for example, a magnetic disk or an SSD (Solid State Drive).

[0069] As shown in Figure 9, the high-speed radiation thermometer unit 101 is electrically connected to the control unit 3, which is the controller of the entire heat treatment apparatus 1. The control unit 3 controls the various operating mechanisms provided in the heat treatment apparatus 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 calculations, a ROM, which is a read-only memory that stores basic programs, a RAM, which is a read-write memory that stores various information, and a storage unit 35 (for example, a magnetic disk or SSD) that stores control software and data. Processing in the heat treatment apparatus 1 proceeds when the CPU of the control unit 3 executes a predetermined processing program. The control unit 3 also includes a pulse generator 31 and a waveform setting unit 32 (Figure 8). Based on the input content from the input unit 33, the waveform setting unit 32 sets the waveform of the pulse signal, and the pulse generator 31 outputs a pulse signal to the gate of the IGBT 96 accordingly.

[0070] The control unit 3 includes a pulse generator 31 and a waveform setting unit 32 (not shown in Figure 9), as well as a trigger determination unit 36, a profile creation unit 37, and a warning signal transmission unit 38. The trigger determination unit 36, the profile creation unit 37, and the warning signal transmission unit 38 are functional processing units realized by the CPU of the control unit 3 executing a predetermined processing program. The warning signal transmission unit 38 transmits a flash warning signal a predetermined time (for example, 1 second) before the start of flash light irradiation from the flash lamp FL. The detailed processing contents of the trigger determination unit 36 ​​and the profile creation unit 37 will be described further later.

[0071] Furthermore, a display unit 34 and an input unit 33 are connected to the control unit 3. The display unit 34 and the input unit 33 function as the user interface of the heat treatment apparatus 1. The control unit 3 displays various information on the display unit 34. The operator of the heat treatment apparatus 1 can input various commands and parameters from the input unit 33 while confirming the information displayed on the display unit 34. For example, a keyboard or mouse can be used as the input unit 33. For example, a liquid crystal display can be used as the display unit 34. In this embodiment, a liquid crystal touch panel provided on the outer wall of the heat treatment apparatus 1 is used as both the display unit 34 and the input unit 33 to combine the functions of both.

[0072] 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 section 4, flash heating section 5, and chamber 6 due to thermal energy generated from the halogen lamp HL and flash lamp FL during the heat treatment of semiconductor wafers W. For example, water cooling pipes (not shown) are provided in the wall of the chamber 6. Furthermore, the halogen heating section 4 and flash heating section 5 are air-cooled structures that dissipate heat by forming a gas flow inside. 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 section 5 and the upper chamber window 63.

[0073] Next, the processing operation of the heat treatment apparatus 1 will be described. First, a typical heat treatment procedure for the semiconductor wafer W to be processed will be described. Here, the semiconductor wafer W to be processed is a semiconductor substrate to which impurities (ions) have been added by ion implantation. The activation of these impurities is performed by flash light irradiation heating treatment (annealing) by the heat treatment apparatus 1. The processing procedure of the heat treatment apparatus 1 described below proceeds as the control unit 3 controls each operating mechanism of the heat treatment apparatus 1.

[0074] First, the supply valve 84 is opened, and the exhaust valves 89 and 192 are opened, initiating the supply and exhaust of air into the chamber 6. When valve 84 is opened, nitrogen gas is supplied to the heat treatment space 65 from the gas supply port 81. When valve 89 is opened, the gas inside the chamber 6 is exhausted from the gas exhaust port 86. As a result, the nitrogen gas supplied from the top of the heat treatment space 65 inside the chamber 6 flows downward and is exhausted from the bottom of the heat treatment space 65.

[0075] Furthermore, when valve 192 is opened, the gas inside chamber 6 is also exhausted from the transport opening 66. In addition, the atmosphere around the drive unit of the transfer mechanism 10 is also exhausted by an exhaust mechanism (not shown). During the heat treatment of semiconductor wafers W in the heat treatment apparatus 1, nitrogen gas is continuously supplied to the heat treatment space 65, and the amount supplied is changed as appropriate according to the processing step.

[0076] Next, the gate valve 185 opens, the transport opening 66 is opened, and the semiconductor wafer W to be processed is transported through the transport opening 66 by a transport robot outside the apparatus into the heat treatment space 65 inside the chamber 6. At this time, there is a risk that the atmosphere outside the apparatus may be drawn in as the semiconductor wafer W is transported in, but since nitrogen gas is continuously supplied to the chamber 6, the nitrogen gas flows out from the transport opening 66, minimizing the entrainment of such external atmosphere.

[0077] The semiconductor wafer W, loaded by the transport robot, moves forward to a position directly above the holding section 7 and stops. 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 pin 12 to protrude from the upper surface of the holding plate 75 of the susceptor 74 through the through hole 79 and receive the semiconductor wafer W. At this time, the lift pin 12 rises above the upper end of the substrate support pin 77.

[0078] After the semiconductor wafer W is placed on the lift pin 12, the transport robot exits the heat treatment space 65, and the transport opening 66 is closed by the gate valve 185. Then, as the pair of transfer arms 11 descend, the semiconductor wafer W is transferred from the transfer mechanism 10 to the susceptor 74 of the holding section 7 and 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 also held in the holding section 7 with the patterned surface and impurities injected facing upwards. A predetermined gap is formed between the back surface (the main surface opposite to the front surface) of the semiconductor wafer W, which is 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.

[0079] After the semiconductor wafer W is held horizontally from below by the susceptor 74 of the holding part 7 made of silica, the 40 halogen lamps HL of the halogen heating part 4 are lit simultaneously to start preheating (assisted heating). The halogen light emitted from the halogen lamps HL passes through the lower chamber window 64 and the susceptor 74, which are made of silica, and irradiates the lower surface of the semiconductor wafer W. The semiconductor wafer W is preheated and its temperature rises due to the light irradiation from the halogen lamps HL. 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.

[0080] When preheating is performed using a halogen lamp HL, the temperature of the semiconductor wafer W is measured by a lower radiation thermometer 20. Specifically, the lower radiation thermometer 20 receives infrared light emitted from the lower surface of the semiconductor wafer W held by the susceptor 74 through an opening 78 via a 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 monitors whether the temperature of the semiconductor wafer W, which is heated by light irradiation from the halogen lamp HL, has reached a predetermined preheating temperature T1, and controls the output of the halogen lamp HL. In other words, the control unit 3 feedback-controls the output of the halogen lamp 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. Thus, the lower radiation thermometer 20 is a radiation thermometer for temperature control of the semiconductor wafer W during preheating. The preheating temperature T1 is set to approximately 200°C to 800°C, preferably 350°C to 600°C (600°C in this embodiment), so as not to cause the impurities added to the semiconductor wafer W to diffuse due to heat.

[0081] After the semiconductor wafer W reaches the preheating temperature T1, the control unit 3 temporarily maintains the semiconductor wafer W at that preheating temperature T1. Specifically, when the temperature of the semiconductor wafer W, as measured by the lower radiation thermometer 20, reaches the preheating temperature T1, the control unit 3 adjusts the output of the halogen lamp HL to maintain the temperature of the semiconductor wafer W at approximately the preheating temperature T1.

[0082] By performing preheating with halogen lamps HL in this manner, the entire semiconductor wafer W is uniformly heated to the preheating temperature T1. During the preheating stage with halogen lamps HL, the temperature of the peripheral parts of the semiconductor wafer W, where heat dissipation is more likely, tends to be lower than that of the central part. However, the density of halogen lamps HL in the halogen heating section 4 is higher in the region facing the peripheral parts of the semiconductor wafer W than in the region facing the central part. As a result, more light is irradiated to the peripheral parts of the semiconductor wafer W, where heat dissipation is more likely, making it possible to achieve a uniform in-plane temperature distribution of the semiconductor wafer W during the preheating stage.

[0083] Furthermore, the surface temperature of the semiconductor wafer W is measured by the upper radiation thermometer 25 while the semiconductor wafer W is being preheated. The surface of the heated semiconductor wafer W emits infrared light of an intensity corresponding to its temperature. The infrared light emitted from the surface of the semiconductor wafer W passes through the transparent window 26 and is received by the infrared sensor 29 of the upper radiation thermometer 25.

[0084] A resistance change occurs in the InSb optical element of the infrared sensor 29 in accordance with the intensity of the received infrared light. The resistance change in the InSb optical element of the infrared sensor 29 is converted into a voltage signal by the signal conversion circuit 102. The voltage signal output from the signal conversion circuit 102 is amplified by the amplification circuit 103 and then converted into a digital signal suitable for processing by a computer by the A / D converter 104. Then, the filtering processing unit 105 removes noise from the voltage signal converted into a digital signal by the A / D converter 104. This removes noise caused by output fluctuations of the halogen lamp HL and noise caused by the infrared sensor 29.

[0085] The voltage signal, from which noise has been removed by the filtering processing unit 105, is subjected to predetermined calculations by the temperature conversion unit 106 to convert it into temperature data. That is, the upper radiation thermometer 25 receives infrared light emitted from the surface of the heated semiconductor wafer W and measures the surface temperature of the semiconductor wafer W from the intensity of the infrared light at a predetermined data acquisition period (for example, 40 microseconds). The voltage signal data from which noise has been removed by the filtering processing unit 105 and the temperature data calculated by the temperature conversion unit 106 are sequentially stored in the storage unit 107.

[0086] When the semiconductor wafer W reaches the preheating temperature T1 and a predetermined time has elapsed, the flash lamp FL of the flash heating unit 5 irradiates the surface of the semiconductor wafer W held by the susceptor 74 with flash light. At this time, a portion of the flash light emitted from the flash lamp FL goes directly into the chamber 6, and another portion is reflected by the reflector 52 before going into the chamber 6, and the semiconductor wafer W is flash-heated by the irradiation of these flash lights.

[0087] When the flash lamp FL emits a flash of light, the power supply unit 95 pre-charges the capacitor 93 at a predetermined charging voltage. Then, with the capacitor 93 charged, the pulse generator 31 of the control unit 3 outputs a pulse signal to the IGBT 96 to drive the IGBT 96 on and off. By lowering the charging voltage to the capacitor 93, it is also possible to reduce the irradiation energy of the flash light and perform low-heat annealing.

[0088] The waveform of the pulse signal can be defined by inputting a recipe from the input unit 33, in which the pulse width time (on time) and pulse interval time (off time) are sequentially set as parameters. When an 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 repeatedly switches on and off accordingly. Then, the pulse generator 31 outputs a pulse signal according to the pulse waveform set by the waveform setting unit 32. As a result, a pulse signal with the set waveform is applied to the gate of the IGBT 96, and the on / off drive 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.

[0089] Furthermore, the control unit 3 controls the trigger circuit 97 in synchronization with the timing when the pulse signal output from the pulse generator 31 turns on, and applies a high voltage (trigger voltage) to the trigger electrode 91. When a pulse signal is input to the gate of the IGBT 96 while charge is accumulated in the capacitor 93, and a high voltage is applied to the trigger electrode 91 in synchronization with the timing when the pulse signal turns on, a current always flows between the electrodes at both ends inside the glass tube 92 when the pulse signal is on, and light is emitted by the excitation of xenon atoms or molecules at that time.

[0090] In this way, the 30 flash lamps FL of the flash heating unit 5 emit light, and the flash light is irradiated onto the surface of the semiconductor wafer W held in the holding unit 7. If the flash lamps FL were to emit light without using the IGBT 96, the charge stored in the capacitor 93 would be consumed in one flash, and the output waveform from the flash lamps FL would be a simple single pulse with a width of about 0.1 milliseconds to 10 milliseconds. In contrast, in this embodiment, an IGBT 96, which is a switching element, is connected to the circuit and a pulse signal is output to its gate, thereby intermittently switching the supply of charge from the capacitor 93 to the flash lamps FL by the IGBT 96 and controlling the on / off state of the current flowing through the flash lamps FL. As a result, the emission of light from the flash lamps FL is, so to speak, chopper controlled, the charge stored in the capacitor 93 is divided and consumed, and the flash lamps FL blink repeatedly in a very short time. Note that the next pulse is applied to the gate of the IGBT 96 and the current value increases again before the current value flowing through the circuit becomes completely "0", so the light output does not become completely "0" even while the flash lamps FL are blinking repeatedly.

[0091] By controlling the on / off state of the current flowing through the flash lamp FL using the IGBT96, the light emission pattern (time waveform of the light output) of the flash lamp FL can be freely defined, and the light emission time and intensity can be freely adjusted. The on / off drive pattern of the IGBT96 is defined by the pulse width time and pulse interval time input from the input unit 33. In other words, by incorporating the IGBT96 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 time and pulse interval time input from the input unit 33.

[0092] Specifically, for example, increasing the ratio of pulse width time to pulse interval time input from input unit 33 increases the current flowing through the flash lamp FL, resulting in stronger light emission intensity. Conversely, decreasing the ratio of pulse width time to pulse interval time input from input unit 33 decreases the current flowing through the flash lamp FL, resulting in weaker light emission intensity. Furthermore, by appropriately adjusting the ratio of pulse interval time to pulse width time input from input unit 33, the light emission intensity of the flash lamp FL can be maintained at a constant level. In addition, by increasing the total time of the combination of pulse width time and pulse interval time input from input unit 33, current will continue to flow through the flash lamp FL for a relatively long period of time, thus 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 applied 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.

[0093] In this way, flash light is irradiated from the flash lamp FL onto the surface of the semiconductor wafer W for an irradiation time of 0.1 milliseconds to 100 milliseconds, and the semiconductor wafer W is flash-heated. The surface temperature of the semiconductor wafer W, which is flash-heated by the flash light irradiation from the flash lamp FL, instantaneously rises to a processing temperature T2 of 1000°C or more, and after the impurities injected into the semiconductor wafer W are activated, the surface temperature rapidly decreases. In this way, the heat treatment apparatus 1 can raise and lower the surface temperature of the semiconductor wafer W in a very short time by irradiating with flash light for an extremely short irradiation time. As a result, it is possible to activate the impurities injected into the semiconductor wafer W while suppressing the thermal diffusion of the impurities. Since the time required for impurity activation is extremely short compared to the time required for thermal diffusion, activation can be completed even in a short time of about 0.1 milliseconds to 100 milliseconds, during which no diffusion occurs.

[0094] Even when the surface temperature of the semiconductor wafer W rapidly rises and falls due to flash light irradiation, the surface temperature is measured by the upper radiation thermometer 25. Since the upper radiation thermometer 25 measures the surface temperature of the semiconductor wafer W at an extremely short sampling interval, it is possible to track the changes even if the surface temperature of the semiconductor wafer W changes rapidly during flash light irradiation.

[0095] After the flash heating process is completed, the halogen lamp HL is turned off after a predetermined time has elapsed. This causes the semiconductor wafer W to rapidly cool down from the preheating temperature T1. The temperature of the semiconductor wafer W during the cooling process 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 cooled down to a predetermined temperature based on the measurement result of the lower radiation thermometer 20. After the temperature of the semiconductor wafer W has cooled down to below the predetermined temperature, the pair of transfer arms 11 of the transfer mechanism 10 move horizontally again from the retracted position to the transfer operation position and rise, causing the lift pin 12 to protrude from the upper surface of the susceptor 74 and receive the heat-treated semiconductor wafer W from the susceptor 74. Subsequently, the transport opening 66, which had been closed by the gate valve 185, is opened, and the semiconductor wafer W placed on the lift pin 12 is transported out by a transport robot outside the device, completing the heat treatment of the semiconductor wafer W in the heat treatment apparatus 1.

[0096] Next, the creation of a temperature profile showing the temperature change on the surface of the semiconductor wafer will be described. In the heat treatment apparatus 1 of this embodiment, the upper radiation thermometer 25 measures the surface temperature of the semiconductor wafer W from the stage when the semiconductor wafer W is preheated to a preheating temperature T1 by light irradiation from the halogen lamp HL. The upper radiation thermometer 25 also measures the surface temperature when the surface temperature of the semiconductor wafer W rises or falls rapidly due to flash light irradiation from the flash lamp FL. That is, the upper radiation thermometer 25 continuously measures the surface temperature of the semiconductor wafer W from the preheating stage by the halogen lamp HL until the flash light irradiation by the flash lamp FL is completed. The data acquisition period (sampling interval) of the upper radiation thermometer 25 is extremely short, for example, 40 microseconds, so even if the surface temperature of the semiconductor wafer W rises or falls rapidly during flash light irradiation, the change can be measured. The voltage signal data and temperature data output from the upper radiation thermometer 25 at a sampling interval of 40 microseconds are temporarily stored in the storage unit 107 of the high-speed radiation thermometer unit 101.

[0097] The profile creation unit 37 extracts a portion of the multiple temperature data stored in the storage unit 107 and plots them sequentially to create a temperature profile showing the time change of the surface temperature of the semiconductor wafer W. By analyzing the temperature profile created by the profile creation unit 37, the highest temperature reached on the surface of the semiconductor wafer W during flash light irradiation (peak temperature) and the amount of heat introduced into the semiconductor wafer W can be calculated. At this time, if the number of data points of the temperature data constituting the temperature profile is excessively large, the data analysis will take a long time. For this reason, the number of temperature data points for creating a temperature profile is set to a certain number, and in this embodiment, for example, it is set to 3000 points. Therefore, the profile creation unit 37 extracts 3000 temperature data points from multiple temperature data measured and acquired by the upper radiation thermometer 25 from the preheating stage to the flash light irradiation stage to create a temperature profile. If the sampling interval is 40 microseconds, a temperature profile with a length of 120 milliseconds will be created. Therefore, it is necessary to set the range of temperature data to be extracted so that the surface temperature of the semiconductor wafer W before and after flash light irradiation is appropriately included in the temperature profile.

[0098] Figure 10 shows the change in the voltage signal before and after flash light irradiation. The memory unit 107 of the high-speed radiation thermometer unit 101 also stores the voltage signal data output by the upper radiation thermometer 25 when it measures the surface temperature of the semiconductor wafer W at a sampling interval of 40 microseconds. The voltage signal data output from the upper radiation thermometer 25 and stored in the memory unit 107 is the signal data from which noise has been removed by the filtering processing unit 105. Figure 10 shows the voltage signal data stored in the memory unit 107 arranged in chronological order. In the example in Figure 10, flash light irradiation from the flash lamp FL starts at time t3, and as the surface temperature of the semiconductor wafer W rises rapidly, the voltage signal value also starts to rise rapidly. In this embodiment, a trigger determination for temperature data extraction is made based on the time-series change of the voltage signal shown in Figure 10.

[0099] In this embodiment, the flash warning signal emitter 38 emits a flash warning signal during the preheating process before the flash lamp FL begins to emit flash light. In the example shown in Figure 10, the flash warning signal emitter 38 emits a flash warning signal at time t1, one second before the flash lamp FL begins to emit flash light. After the flash warning signal is emitted, the trigger determination unit 36 ​​begins trigger determination.

[0100] The trigger determination unit 36 ​​sets time t4 as the trigger point when the voltage of the signal output from the upper radiation thermometer 25 at the end of the determination period (time t4) is higher than the voltage of the signal output from the upper radiation thermometer 25 at the start of the determination period (time t2) by a certain value or more. The length of the determination period is, for example, 50 milliseconds. More specifically, the trigger determination unit 36 ​​compares the voltage signal value at time t2, 50 milliseconds before a certain time t4, with the voltage signal value at time t4. The trigger determination unit 36 ​​then sets time t4 as the trigger point when the voltage difference Vp between the voltage value at time t2 and the voltage value at time t4 is greater than or equal to a certain value (for example, 100mV). Such a trigger determination is equivalent to setting the end of the determination period as the trigger point when the slope of the voltage change from the start to the end of the determination period exceeds a predetermined value.

[0101] After the trigger point is determined, the profile creation unit 37 extracts a portion of the multiple temperature data stored in the storage unit 107 to create a temperature profile. Figure 11 shows the change in temperature data before and after flash light irradiation. The storage unit 107 of the high-speed radiation thermometer unit 101 also stores temperature data of the surface temperature of the semiconductor wafer W measured by the upper radiation thermometer 25 at a sampling interval of 40 microseconds. The temperature data of the semiconductor wafer W measured by the upper radiation thermometer 25 is temperature data calculated by the temperature conversion unit 106. Figure 11 shows the temperature data stored in the storage unit 107 arranged in chronological order.

[0102] The profile creation unit 37 uses a predetermined number of temperature data points (e.g., 500 points) acquired earlier than the temperature data acquired at the trigger time t4, from among the multiple temperature data acquired by the upper radiation thermometer 25 and stored in the storage unit 107, as the starting temperature data. In the example in Figure 11, the temperature data acquired at time t5 is used as the starting temperature data. If the sampling interval is 40 microseconds, the time from time t5 to time t4 is 20 milliseconds (40 microseconds × 500).

[0103] Next, the profile creation unit 37 extracts a certain number of temperature data points (for example, 3000 points) from the multiple temperature data stored in the storage unit 107, starting from the initial temperature data, and creates a temperature profile. This certain number of points starting from the initial temperature data is greater than the predetermined number of points that can be traced back from the temperature data at the trigger time to the initial temperature data. The 3000th temperature data point after the initial temperature data is acquired at time t6. In other words, in the example in Figure 11, the profile creation unit 37 creates a temperature profile from 3000 temperature data points acquired between time t5 and time t6. If the sampling interval is 40 microseconds, the time from time t5 to time t6 is 120 milliseconds (40 microseconds × 3000). In other words, the profile creation unit 37 creates a temperature profile from temperature data from 20 milliseconds before to 100 milliseconds after time t4, which is the trigger time. Therefore, if time t4, which is the trigger time, is immediately after the start of flash light irradiation, the surface temperature of the semiconductor wafer W before and after flash light irradiation can be included within the range of the temperature profile.

[0104] As described above, the change in the surface temperature of the semiconductor wafer W from time t5 to time t6 in Figure 11 is created as a temperature profile. The profile creation unit 37 stores the created temperature profile in the storage unit 35. The created temperature profile may also be displayed on the display unit 34. The control unit 3 may also analyze the created temperature profile to calculate the highest temperature reached on the surface of the semiconductor wafer W during flash light irradiation and the amount of heat introduced into the semiconductor wafer W.

[0105] Furthermore, the control unit 3 may detect cracks in the semiconductor wafer W during flash light irradiation by analyzing the temperature profile. Specifically, the control unit 3 determines that a crack has occurred in the semiconductor wafer W if a temperature rise occurs during the cooling phase of the temperature profile (from time t7 to time t6, when the surface temperature of the semiconductor wafer W reaches its highest value). The reason for this determination is that if the semiconductor wafer W is processed normally without cracking, a temperature rise should not occur during the cooling phase of the temperature profile, and such a temperature rise is considered to be due to a temperature measurement error in the upper radiation thermometer 25 caused by a crack in the semiconductor wafer W.

[0106] In this embodiment, the end of a determination period having a certain length is determined as the trigger point when the slope of the voltage change from the start to the end of that period exceeds a predetermined value. Since the determination is made based on whether the voltage difference Vp between the voltage at the start and the voltage at the end of the determination period having a certain length is above a certain value, even if noise is included in the voltage signal due to unavoidable output fluctuations of the halogen lamp HL during the determination period, it is prevented from being mistakenly detected as the trigger point due to such noise. Therefore, the moment immediately after the start of flash light irradiation can be reliably determined as the trigger point, and the surface temperature change of the semiconductor wafer W before and after flash light irradiation can be reliably included in the temperature profile.

[0107] To reliably detect the start of flash light irradiation while preventing false detection of noise, the appropriate length of the judgment period is preferably 20 milliseconds to 100 milliseconds. If the judgment period is shorter than 20 milliseconds, the judgment will be based on the slope of the voltage signal over a very short period, which may lead to false detection of noise caused by output fluctuations of halogen lamps HL as the trigger point. Conversely, if the judgment period is longer than 100 milliseconds, the judgment period will be longer than the flash light irradiation time, which may prevent detection of the start of flash light irradiation. For this reason, the length of the judgment period is set to 20 milliseconds to 100 milliseconds. In other words, it is important that the judgment is based on the slope of the voltage change from a little before a certain point in time, rather than immediately before that point.

[0108] Furthermore, by appropriately setting the criteria for the voltage difference Vp between the voltage at the start and end of the judgment period (100mV in this embodiment), even when low-heat annealing is performed by lowering the preheating temperature and the maximum temperature reached by flash light irradiation, the time immediately after the start of flash light irradiation can be reliably determined as the trigger point. Thus, as in this embodiment, even if the voltage signal contains noise or the maximum temperature reached during flash light irradiation is low, an appropriate temperature profile can be created.

[0109] Here, it is also conceivable to make a determination based on the temperature difference measured by the upper radiation thermometer 25 (i.e., the slope of the temperature change) rather than the voltage difference between the start and end of the determination period. However, there are the following problems with making a determination based on the measured temperature difference. Figure 12 shows the correlation between the preheating temperature and the jump temperature. The preheating temperature is the temperature of the semiconductor wafer W when preheating is performed by the halogen lamp HL. The jump temperature is the temperature rise when the surface temperature of the semiconductor wafer W rises from the preheating temperature to the maximum temperature reached by flash light irradiation (i.e., maximum temperature reached - preheating temperature). Note that in Figure 12, the charging voltage to the capacitor 93 by the power supply unit 95 is constant. That is, the energy of the flash light irradiated from the flash lamp FL is constant.

[0110] As shown in Figure 12, even when irradiated with flash light of the same energy, the jump temperature decreases as the preheating temperature increases. In other words, even when irradiated with flash light of the same energy, the jump temperature is affected by the preheating temperature. Therefore, if the determination is made based on the measured temperature difference between the start and end of the determination period, the accuracy of the determination will be affected by the preheating temperature, making it impossible to make a stable determination. For this reason, in this embodiment, the trigger determination is made based on the voltage difference between the start and end of the determination period.

[0111] Furthermore, in this embodiment, trigger determination is initiated after the flash warning signal is transmitted. This prevents misidentification of large voltage signal fluctuations that occur immediately after the halogen lamp HL is switched on as the trigger point, and ensures that the moment immediately after the start of flash light irradiation is reliably determined as the trigger point.

[0112] Furthermore, in this embodiment, noise is removed from the voltage signal by a digital filter. This makes it possible to remove noise that has been included in the voltage signal due to output fluctuations of the halogen lamp HL after the warning signal has been transmitted. In addition, noise included in the voltage signal due to the infrared sensor 29 can also be removed. As a result, the moment immediately after the start of flash light irradiation can be determined as the trigger point with greater reliability.

[0113] While embodiments of the present invention have been described above, various modifications can be made to this invention without departing from its spirit. For example, in the above embodiment, the sampling interval of the upper radiation thermometer 25 was set to 40 microseconds, but it is not limited to this and can be set to an appropriate value. If the emission time of the flash lamp FL is extended by on / off control by the IGBT96, it is preferable to also extend the sampling interval of the upper radiation thermometer 25. As the sampling interval lengthens, the time range of the temperature profile also lengthens proportionally.

[0114] Furthermore, while the above embodiment uses 3000 temperature data points to create a temperature profile, it is not limited to this and can be set to any appropriate number of data points. Similarly, the number of points used to return from the temperature data acquired at the trigger point to the starting temperature data is not limited to 500, but can be set to any appropriate number.

[0115] Furthermore, in the above embodiment, the warning signal transmitting unit 38 transmitted a flash warning signal one second before the start of flash light irradiation, but it is not limited to this, and the warning signal transmitting unit 38 may transmit a flash warning signal at an appropriate timing before the start of flash light irradiation.

[0116] Furthermore, although the flash heating unit 5 is equipped with 30 flash lamps FL in the above embodiment, the number of flash lamps FL is not limited to this, and can be any number. Also, the flash lamps FL are not limited to xenon flash lamps, but may be krypton flash lamps. Similarly, the number of halogen lamps HL provided in the halogen heating unit 4 is not limited to 40, but can be any number.

[0117] Furthermore, in the above embodiment, a filament-type halogen lamp HL was used as a continuous-lighting lamp that emitted light continuously for 1 second or more to preheat the semiconductor wafer W. However, the invention is not limited to this, and a discharge-type arc lamp (for example, a xenon arc lamp) or an LED lamp may be used as a continuous-lighting lamp instead of the halogen lamp HL to perform preheating. [Explanation of symbols]

[0118] 1 Heat treatment apparatus 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 29 Infrared Sensor 33 Input section 34 Display section 36 Trigger determination unit 37 Profile Creation Section 38 Warning signal transmission unit 63 Upper chamber window 64 Lower chamber window 65 Heat treatment space 74 Susceptors 93 Capacitors 96 IGBT 101 High-speed radiation thermometer unit 105 Filtering Processing Unit 106 Temperature conversion unit 107 Storage section FL Flash Lamp HL halogen lamp W Semiconductor wafer

Claims

1. A heat treatment method for heating a substrate by irradiating it with a flash of light, A preheating step in which the substrate is preheated by irradiating it with light from a continuously lit lamp, A flash light irradiation step in which flash light is irradiated from a flash lamp onto the surface of the preheated substrate, A temperature measurement step in which the surface temperature of the substrate is measured by a radiation thermometer at a predetermined data acquisition cycle, A trigger determination step in which the end of the determination period is set as the trigger point when the voltage of the signal output from the radiation thermometer at the end of the determination period is higher than the voltage of the signal output from the radiation thermometer at the start of the determination period by a certain value or more, A profile creation step is performed to create a temperature profile by selecting a predetermined number of temperature data acquired earlier than the temperature data acquired at the trigger point from among the multiple temperature data acquired in the temperature measurement step as the starting temperature data, and extracting a certain number of temperature data from the multiple temperature data after the starting temperature data. Equipped with, A heat treatment method characterized in that the start of the determination period is during the preheating process, and the end of the determination period is after the start of irradiation with flash light.

2. In the heat treatment method according to claim 1, The process further includes a warning step of transmitting a warning signal before emitting a flash of light from the flash lamp, The heat treatment method is characterized in that the trigger determination step is started after the warning signal is transmitted.

3. In the heat treatment method according to claim 1, A heat treatment method further comprising a filtering step of removing noise from the signal output from the radiation thermometer using a digital filter.

4. In the heat treatment method according to claim 1, A heat treatment method characterized in that the length of the judgment period is 20 milliseconds or more and 100 milliseconds or less.

5. In the heat treatment method according to claim 1, A heat treatment method characterized by determining that a crack has occurred in the substrate when a temperature rise occurs during the cooling stage in the aforementioned temperature profile.

6. A heat treatment apparatus for heating a substrate by irradiating it with a flash of light, A chamber for housing the circuit board, A continuous lighting lamp that irradiates light onto the substrate housed in the chamber to preheat the substrate, A flash lamp that irradiates the surface of the preheated substrate with flash light, A radiation thermometer that receives infrared light emitted from the surface of the substrate and measures the temperature of the surface at a predetermined data acquisition cycle, A trigger determination unit that sets the end of the determination period as the trigger point when the voltage of the signal output from the radiation thermometer at the end of the determination period is higher than the voltage of the signal output from the radiation thermometer at the start of the determination period by a certain value or more, A profile creation unit creates a temperature profile by selecting a predetermined number of temperature data points acquired by the radiation thermometer from among multiple temperature data points acquired by the radiation thermometer as the starting temperature data points, and by extracting a certain number of temperature data points from the multiple temperature data points after the starting temperature data points. Equipped with, A heat treatment apparatus characterized in that the start of the determination period is during the preheating, and the end of the determination period is after the start of irradiation with flash light.

7. In the heat treatment apparatus according to claim 6, The unit further comprises a warning signal transmitting unit that transmits a warning signal before emitting a flash of light from the flash lamp, The heat treatment apparatus is characterized in that the trigger determination unit starts determining the trigger after the warning signal is transmitted.

8. In the heat treatment apparatus according to claim 6, A heat treatment apparatus characterized by removing noise from the signal output from the radiation thermometer using a digital filter.

9. In the heat treatment apparatus according to claim 6, A heat treatment apparatus characterized in that the length of the determination period is 20 milliseconds or more and 100 milliseconds or less.

10. In the heat treatment apparatus according to claim 6, A heat treatment apparatus characterized in that it determines that a crack has occurred in the substrate when a temperature rise occurs during the cooling stage in the temperature profile.

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