Heat treatment method and heat treatment apparatus

Abstract

This invention provides a heat treatment method and apparatus for preventing cracks caused by repeated stress on a substrate during flash irradiation. The current flowing to the flash lamp is controlled by an IGBT. The IGBT repeatedly switches on and off according to the waveform of a pulse signal output from a pulse generator. Because the IGBT repeatedly switches on and off, the current flowing to the flash lamp also repeatedly increases and decreases, causing the surface temperature of the semiconductor wafer to repeatedly increase and decrease slightly while simultaneously rising. If the on / off cycle in the pulse signal is shortened and the on / off cycle of the IGBT is set to less than 200 microseconds, the magnitude of the increase and decrease in the surface temperature of the semiconductor wafer also decreases. Therefore, the stress value repeatedly acting on the semiconductor wafer becomes below the fatigue limit, preventing wafer cracks caused by repeated stress.

Description

Technical Field

[0001] This invention relates to a heat treatment method and apparatus for heating a substrate by irradiating it with light. The substrate to be processed includes, for example, semiconductor wafers, substrates for liquid crystal displays, substrates for flat panel displays (FPDs), substrates for optical discs, substrates for magnetic disks, or substrates for solar cells. Prior Technology

[0002] In the manufacturing process of semiconductor devices, flash annealing (FLA), which heats semiconductor wafers for an extremely short time, has attracted much attention. Flash annealing is a heat treatment technique that uses a xenon flash lamp (hereinafter, when referred to as "flash lamp", it means xenon flash lamp) to irradiate the surface of the semiconductor wafer, causing the surface of the semiconductor wafer to heat up for an extremely short time (less than a few milliseconds).

[0003] The radiation spectrum of a xenon flash lamp extends from the ultraviolet to the near-infrared region, with a wavelength shorter than that of previous halogen lamps, almost coinciding with the fundamental absorption band of silicon semiconductor wafers. Therefore, when a xenon flash lamp illuminates a semiconductor wafer, less light is transmitted, allowing the wafer to heat up rapidly. Furthermore, it has been demonstrated that even a very short flash of less than a few milliseconds can selectively heat only the vicinity of the semiconductor wafer's surface.

[0004] This type of flash annealing is used for processes requiring extremely short heating times, typically for activating impurities implanted into semiconductor wafers. By using ion implantation to irradiate the surface of the semiconductor wafer with implanted impurities with a flash lamp, the surface of the semiconductor wafer can be heated to the activation temperature in a very short time, enabling impurity activation without allowing the impurities to diffuse deeply.

[0005] Regarding heat treatment devices for using this type of xenon flash lamp, Patent Documents 1 and 2 disclose a method for controlling the flash lamp's emission by insulated-gate bipolar transistors (IGBTs) on the flash lamp's discharge circuit. In the devices disclosed in Patent Documents 1 and 2, by inputting a specific pulse signal to the gate of the IGBT, the IGBT repeatedly switches on and off at high speed along the waveform of the pulse signal. This allows for the determination of the waveform of the current flowing to the flash lamp, control of the lamp's emission, and free adjustment of the flash lamp's emission time and intensity. [Previous Technical Documents] [Patent Literature]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2009-070948 [Patent Document 2] Japanese Patent Application Publication No. 2011-119562 Summary of the Invention

[0007] [The problem the invention aims to solve] In flash annealing, the semiconductor wafer is subjected to an extremely high-energy flash for a very short time, resulting in a surge of stress that can sometimes cause wafer cracks. This is especially true in cases where IGBTs are used to control the current flowing to the flash lamp, as disclosed in Patent Documents 1 and 2. The repeated switching of the IGBTs on and off within a short period causes the current flowing to the circuitry containing the flash lamp to fluctuate microscopically. Consequently, the surface temperature of the semiconductor wafer also fluctuates slightly while reaching the target temperature. This rapid fluctuation in surface temperature creates repeated stress on the semiconductor wafer, leading to the problem that the semiconductor wafer becomes more susceptible to fracture due to a mechanism similar to fatigue failure.

[0008] The present invention was made in view of the above-mentioned problems, and its purpose is to provide a heat treatment method and heat treatment apparatus that can prevent cracks caused by repeated stress in the substrate during flash irradiation. [Technical means to solve the problem]

[0009] To solve the above problems, the first aspect of the present invention is a heat treatment method for heating a substrate by irradiating it with light, comprising: a preheating step, which heats the substrate to a specific preheating temperature by irradiating it with light from a continuously lit lamp; and a flash heating step, which, after the preheating step, irradiates the surface of the substrate with flashes from a plurality of flash lamps, thereby raising the surface of the substrate to a specific processing temperature; and in the flash heating step, the current flowing to the plurality of flash lamps is controlled by a switching element, and the on and off cycle of the switching element is set to 200 microseconds or less in the flash heating step.

[0010] Furthermore, in the heat treatment method of the first state sample, a voltage of 3400 V or less is applied to the plurality of flash lamps in the above-mentioned flash heating step.

[0011] Furthermore, in the heat treatment method of the third state sample, in the above-mentioned flash heating step, the difference between the maximum and minimum values ​​of the surface temperature of the substrate caused by the switching element is set to 10°C or less.

[0012] Furthermore, in the heat treatment method of any one of the first to third states, the plurality of flash lamps includes a first flash lamp and a second flash lamp. In the flash heating step, the current flowing to the first flash lamp is controlled by a first switching element, and the current flowing to 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.

[0013] Furthermore, the fifth state is a heat treatment method for heating a substrate by irradiating it with light, comprising: a preheating step, which heats the substrate to a specific preheating temperature by irradiating it with light from a continuously lit lamp; and a flash heating step, which, after the preheating step, irradiates the surface of the substrate with flashes from a plurality of flash lamps, thereby raising the surface of the substrate to a specific processing temperature; wherein the plurality of flash lamps includes a first flash lamp and a second flash lamp, and in the flash heating step, the current flowing to the first flash lamp is controlled by a first switching element, and the current flowing to 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] Furthermore, in the heat treatment method of the fifth state sample, the first and second switching elements are individually given different pulse signals for switching on and off.

[0015] Furthermore, in the heat treatment method of the 5th state sample, the first and second switching elements are given a common pulse signal for switching on and off, and the pulse signal given to the second switching element is reversed by an inverting circuit.

[0016] Furthermore, the eighth embodiment is a heat treatment apparatus for heating a substrate by irradiating it with light, comprising: a chamber for housing the substrate; a continuously lit lamp for irradiating the substrate housed in the chamber with light to heat the substrate to a specific preheating temperature; a plurality of flash lamps for irradiating the surface of the substrate heated to the preheating temperature with flashes to raise the surface of the substrate to a specific processing temperature; a plurality of switching elements for controlling the current flowing to the plurality of flash lamps; and a pulse generator for generating pulse signals that turn the plurality of switching elements on and off; and setting the on and off period of the pulse signals output by the pulse generator to the plurality of switching elements to 200 microseconds or less.

[0017] Furthermore, the ninth state sample is in the heat treatment apparatus of the eighth state sample, and further includes a capacitor that supplies power to the plurality of flash lamps, and sets the charging voltage of the capacitor to 3400 V or less.

[0018] Furthermore, in the heat treatment apparatus of the 10th state sample, the difference between the maximum and minimum surface temperature of the substrate caused by the switching on and off of the plurality of switching elements when the plurality of flash lamps irradiate the substrate is set to be 10°C or less.

[0019] Furthermore, in the heat treatment apparatus of any one of the 8th to 10th states, the plurality of flash lamps includes a first flash lamp and a second flash lamp, and the plurality of switching elements includes 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. When the flash lamps illuminate the flash, 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] Furthermore, the 12th embodiment is a heat treatment apparatus for heating a substrate by irradiating it with light, comprising: a chamber for housing the substrate; a continuously lit lamp for irradiating the substrate housed in the chamber with light to heat the substrate to a specific preheating temperature; a plurality of flash lamps for irradiating the surface of the substrate heated to the preheating temperature with flashes to raise the surface of the substrate to a specific processing temperature; a plurality of switching elements for controlling the current flowing to the plurality of flash lamps; and a pulse generator for generating pulse signals that turn the plurality of switching elements on and off; wherein the plurality of flash lamps includes a first flash lamp and a second flash lamp, and the plurality of switching elements includes a first switching element for controlling the current flowing to the first flash lamp and a second switching element for controlling the current flowing to the second flash lamp, wherein when the flash lamps irradiate the substrate with light, 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] Furthermore, in the heat treatment apparatus of the 12th state sample, the pulse generator outputs different pulse signals to the first switching element and the second switching element respectively.

[0022] Furthermore, in the heat treatment apparatus of the 12th state sample, the pulse generator outputs a common pulse signal to the first switching element and the second switching element, and the heat treatment apparatus further includes a reversing circuit that reverses the pulse signal applied to the second switching element. [Effects of the Invention]

[0023] According to the heat treatment method of the first to fourth states, the switching period of the switching element that controls the current flowing to the flash lamp is set to less than 200 microseconds. Therefore, the surface temperature change of the substrate is reduced, which can prevent cracks caused by repeated stress from forming on the substrate during flash irradiation.

[0024] According to the heat treatment method of the 5th to 7th states, in the flash heating step, the second switch element is turned off when the first switch element is turned on, and the second switch element is turned on when the first switch element is turned off. Therefore, the intensity of the emitted light from the first flash lamp and the second flash lamp cancels each other out, which can prevent cracks caused by repeated stress from being generated on the substrate during flash irradiation.

[0025] According to the heat treatment apparatus of states 8 to 11, the period for turning on and off the pulse signal output by the pulse generator to the plurality of switching elements is set to less than 200 microseconds. Therefore, the surface temperature change of the substrate is reduced, which can prevent cracks caused by repeated stress from forming on the substrate during flash irradiation.

[0026] According to the heat treatment apparatus of states 12 to 14, when the flash is irradiated by the flash lamp, the second switch element is turned off when the first switch element is turned on, and the second switch element is turned on when the first switch element is turned off. Therefore, the intensity of the emitted light from the first flash lamp and the second flash lamp cancels each other out, which can prevent cracks caused by repeated stress from being generated on the substrate during flash irradiation. Simple Explanation of the Diagram

[0027] Figure 1 is a longitudinal sectional view showing the configuration of the heat treatment apparatus of the present invention. Figure 2 is a perspective view showing the overall appearance of the retaining part. Figure 3 is a top view of the base. Figure 4 is a cross-sectional view of the base. Figure 5 is a top view of the transfer mechanism. Figure 6 is a side view of the transfer mechanism. Figure 7 is a top view showing the arrangement of a plurality of halogen lamps. Figure 8 shows the driving circuit of the flash lamp. Figure 9 shows the variation of surface temperature on a semiconductor wafer. Figure 10 shows an example of the waveform of the pulse signal input to the IGBT. Figure 11 shows the change in surface temperature of a semiconductor wafer during flash heating. Figure 12 shows the increase or decrease of the surface temperature of a semiconductor wafer during flash heating. Figure 13 is a diagram showing an example of the waveforms of the pulse signals input to the first IGBT and the second IGBT respectively in the second embodiment. Figure 14 is a diagram showing the driving circuit of the second flash lamp in the third embodiment. Implementation

[0028] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following expressions indicating relative or absolute positional relationships (e.g., "in one direction," "along one direction," "parallel," "orthogonal," "center," "concentric," "coaxial," etc.) not only strictly indicate the positional relationship unless otherwise specified, but also indicate the state of relative displacement in angle or distance within the tolerance range or to achieve the same level of function. Furthermore, expressions indicating equal states (e.g., "same," "equal," "homogeneous," etc.) not only quantitatively indicate strictly equal states unless otherwise specified, but also indicate states where there are differences in tolerance or to achieve the same level of function. Furthermore, expressions indicating shape (e.g., "circular shape," "quadrilateral shape," "cylindrical shape," etc.) not only strictly indicate the shape geometrically unless otherwise specified, but also indicate the shape within the range of achieving the same level of effect, for example, it may have concave or convex features or chamfers. Furthermore, the expressions "possessing," "including," "containing," "comprise," and "having" are not exclusive expressions that exclude other constituent elements. Also, the expression "at least one of A, B, and C" includes "only A," "only B," "only C," "any two of A, B, and C," and "all of A, B, and C."

[0029] <First Implementation> Figure 1 is a longitudinal sectional view showing the configuration of the heat treatment apparatus 1 of the present invention. The heat treatment apparatus 1 of Figure 1 is a flash lamp annealing device that heats a semiconductor wafer W, which is a circular plate-shaped substrate, by flash irradiation. The size of the semiconductor wafer W to be processed is not particularly limited; for example, it can be... 300 mm or 450 mm (in this embodiment) (300 mm). Furthermore, in Figure 1 and the following figures, for ease of understanding, the dimensions or quantities of each part are exaggerated or simplified as needed.

[0030] The heat treatment apparatus 1 includes: a chamber 6 that houses a semiconductor wafer W; a flash heating unit 5 that houses a plurality of flash lamps FL; and a halogen heating unit 4 that houses a plurality of halogen lamps HL. The flash heating unit 5 is disposed on the upper side of the chamber 6, and the halogen heating unit 4 is disposed on the lower side. Furthermore, inside the chamber 6, the heat treatment apparatus 1 includes: a holding unit 7 that holds the semiconductor wafer W in a horizontal position; and a transfer mechanism 10 that transfers the semiconductor wafer W between the holding unit 7 and the outside of the apparatus. The heat treatment apparatus 1 also includes a control unit 3 that controls the halogen heating unit 4, the flash heating unit 5, and the various operating mechanisms disposed in the chamber 6 to perform heat treatment on the semiconductor wafer W.

[0031] The chamber 6 is constructed by mounting quartz chamber windows on the upper and lower sides of a cylindrical chamber side 61. The chamber side 61 is generally cylindrical with openings at the top and bottom. The upper opening is fitted with an upper chamber window 63 and is blocked, while the lower opening is fitted with a lower chamber window 64 and is blocked. The upper chamber window 63, which forms the top wall of the chamber 6, is a circular plate-shaped component made of quartz and functions as a quartz window to allow light emitted from the flash heating unit 5 to pass into the chamber 6. Similarly, the lower chamber window 64, which forms the bottom plate of the chamber 6, is also a circular plate-shaped component made of quartz and functions as a quartz window to allow light from the halogen heating unit 4 to pass into the chamber 6.

[0032] Furthermore, a reflective ring 68 is installed on the upper part of the inner wall of the chamber side portion 61, and a reflective ring 69 is installed on the lower part. Both reflective rings 68 and 69 are formed into a circular shape. The upper reflective ring 68 is installed by inserting it from the upper side of the chamber side portion 61. On the other hand, the lower reflective ring 69 is installed by inserting it from the lower side of the chamber side portion 61 and fixing it with screws (not shown in the figure). That is, both reflective rings 68 and 69 are detachably installed on the chamber side portion 61. The space inside the chamber 6, which is surrounded 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.

[0033] By mounting reflective rings 68 and 69 on the chamber side portion 61, a recess 62 is formed on the inner wall surface of the chamber 6. Specifically, a 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 mounted, the lower end face of the reflective ring 68, and the upper end face of the reflective ring 69. The recess 62 is formed in a ring shape along the horizontal direction on the inner wall surface of the chamber 6, surrounding the holding portion 7 that holds the semiconductor wafer W. The chamber side portion 61 and the reflective rings 68 and 69 are formed of a metal material with excellent strength and heat resistance (e.g., stainless steel).

[0034] Furthermore, a transfer opening (furnace opening) 66 is formed on the side portion 61 of the chamber for transferring semiconductor wafers W into and out of the chamber 6. The transfer opening 66 is configured to be openable and closed by a gate valve 185. The transfer opening 66 is connected to the outer peripheral surface of the recess 62. Therefore, when the gate valve 185 opens the transfer opening 66, semiconductor wafers W can be transferred into and out of the heat treatment space 65 through the recess 62. Furthermore, when the gate valve 185 closes the transfer opening 66, the heat treatment space 65 inside the chamber 6 becomes a sealed space.

[0035] Furthermore, through holes 61a and 61b are provided on the side portion 61 of the chamber. Through hole 61a is a cylindrical hole used to guide infrared light emitted from the upper surface of the semiconductor wafer W held on the base 74 to the infrared sensor 29 of the upper radiation thermometer 25. On the other hand, through hole 61b is a cylindrical hole used to guide infrared light emitted from the lower surface of the semiconductor wafer W to the lower radiation thermometer 20. Through holes 61a and 61b are arranged at an angle relative to the horizontal direction such that their through-direction axes intersect with the main surface of the semiconductor wafer W held on the base 74. A transparent window 26 made of calcium fluoride material that allows infrared light in the wavelength range that the upper radiation thermometer 25 can measure is installed at the end of through hole 61a facing the heat treatment space 65. Furthermore, a transparent window 21 made of barium fluoride material that allows infrared light in the wavelength range that can be measured by the lower radiation thermometer 20 to pass through is installed at the end of the through hole 61b facing the heat treatment space 65.

[0036] Furthermore, a gas supply hole 81 for supplying processing gas to the heat treatment space 65 is formed on the upper part of the inner wall of the chamber 6. The gas supply hole 81 is formed at a position higher than the recess 62, and may also be provided in the reflective ring 68. The gas supply hole 81 is connected to the gas supply pipe 83 through a buffer space 82 formed in the annular shape inside the side wall of the chamber 6. The gas supply pipe 83 is connected to the processing gas supply source 85. Furthermore, a valve 84 is inserted in the middle of the path of the gas supply pipe 83. When the valve 84 is open, the processing gas is delivered from the processing gas supply source 85 to the buffer space 82. The processing gas flowing into the buffer space 82 flows in an expanding manner in the buffer space 82 where the fluid resistance is less than that of the gas supply hole 81, and is supplied to the heat treatment space 65 from the gas supply hole 81. 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 mixture of these can be used (nitrogen in this embodiment).

[0037] On the other hand, a gas exhaust port 86 is formed on the lower part of the inner wall of the chamber 6 to discharge the gas in the heat treatment space 65. The gas exhaust port 86 is formed at a position lower than the recess 62, or it can be provided in the reflective ring 69. The gas exhaust port 86 is connected to the gas exhaust pipe 88 through a buffer space 87 formed in the inner side wall of the chamber 6. The gas exhaust pipe 88 is connected to the exhaust section 190. Furthermore, a valve 89 is inserted in the path of the gas exhaust pipe 88. When the valve 89 is opened, the gas in the heat treatment space 65 is discharged from the gas exhaust port 86 through the buffer space 87 to the gas exhaust pipe 88. Moreover, a plurality of gas supply ports 81 and gas exhaust ports 86 can be provided along the circumference of the chamber 6, or they can be elongated. Furthermore, the processing gas supply source 85 and the exhaust section 190 can be a mechanism provided in the heat treatment apparatus 1, or they can be the physical entity of the factory where the heat treatment apparatus 1 is provided.

[0038] Furthermore, a gas exhaust pipe 191 is connected to the front end of the conveying opening 66 to discharge the gas in the heat treatment space 65. 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 discharged through the conveying opening 66.

[0039] Figure 2 is a perspective view showing the overall appearance of the retaining part 7. The retaining part 7 is composed of a base ring 71, a connecting part 72, and a base 74. The base ring 71, the connecting part 72, and the base 74 are all made of quartz. That is, the entire retaining part 7 is made of quartz.

[0040] The abutment ring 71 is a quartz component with an arc shape formed by removing a portion of a circular ring. This missing portion is provided to prevent interference between the transfer arm 11 of the transfer mechanism 10 and the abutment ring 71. The abutment ring 71 is supported on the wall of the chamber 6 by being placed on the bottom surface of the recess 62 (see Figure 1). On the upper surface of the abutment ring 71, a plurality of connecting portions 72 (four in this embodiment) are erected along the circumference of its circular shape. The connecting portions 72 are also quartz components and are fixed to the abutment ring 71 by welding.

[0041] The base 74 is supported by four connecting portions 72 disposed on the base ring 71. Figure 3 is a top view of the base 74. Figure 4 is a cross-sectional view of the base 74. The base 74 includes a retaining plate 75, a guide ring 76, and a plurality of substrate support pins 77. The retaining plate 75 is a generally circular flat plate member formed 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 larger planar dimension than the semiconductor wafer W.

[0042] A guide ring 76 is provided on the periphery of the upper surface of the holding plate 75. The guide ring 76 is a ring-shaped component with an inner diameter larger than the diameter of the semiconductor wafer W. For example, in a semiconductor wafer W with a diameter of... In the case of 300 mm, the inner diameter of the guide ring 76 is 320 mm. The inner circumference of the guide ring 76 is a tapered surface that widens upwards from the retaining plate 75. The guide ring 76 is formed of the same quartz as the retaining plate 75. The guide ring 76 can be fused to the upper surface of the retaining plate 75, or it can be fixed to the retaining plate 75 by means of separately machined pins, etc. Alternatively, the retaining plate 75 and the guide ring 76 can be machined into a single component.

[0043] The area on the upper surface of the holding plate 75 that is further inward than the guide ring 76 becomes the planar holding surface 75a for holding the semiconductor wafer W. A plurality of substrate support pins 77 are erected on the holding surface 75a of the holding plate 75. In this embodiment, a total of 12 substrate support pins 77 are erected at 30° intervals along a circle concentric with the outer circumference of the holding surface 75a (the inner circumference of the guide ring 76). The diameter of the circle with the 12 substrate support pins 77 (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, then 270 mm~ 280 mm (in this embodiment) (270 mm). Each substrate support pin 77 is formed of quartz. A plurality of substrate support pins 77 can be disposed on the upper surface of the retaining plate 75 by soldering, or can be machined integrally with the retaining plate 75.

[0044] Returning to Figure 2, the four connecting portions 72 erected on the base ring 71 are fixed to the periphery of the retaining plate 75 of the base 74 by welding. That is, the base 74 and the base ring 71 are fixedly connected by the connecting portions 72. The base ring 71 of this retaining portion 7 is supported on the wall of the chamber 6, thereby the retaining portion 7 is installed in the chamber 6. With the retaining portion 7 installed in the chamber 6, the retaining plate 75 of the base 74 is in a horizontal position (the normal is aligned with the vertical direction). That is, the retaining surface 75a of the retaining plate 75 is a horizontal surface.

[0045] The semiconductor wafer W, moved into chamber 6, is placed horizontally on the base 74 of the holding portion 7 mounted in chamber 6. At this time, the semiconductor wafer W is supported on the base 74 by 12 substrate support pins 77 erected on the holding plate 75. More precisely, the upper ends of the 12 substrate support pins 77 contact the lower surface of the semiconductor wafer W to support it. The height of the 12 substrate support pins 77 (the distance from the upper end of the substrate support pin 77 to the holding surface 75a of the holding plate 75) is uniform; therefore, the semiconductor wafer W can be supported in a horizontal position by the 12 substrate support pins 77.

[0046] Furthermore, the semiconductor wafer W is supported by a plurality of substrate support pins 77 spaced apart 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 positional deviation of the semiconductor wafer W supported by the plurality of substrate support pins 77 is prevented by the guide ring 76.

[0047] Furthermore, as shown in Figures 2 and 3, an opening 78 is formed vertically through the holding plate 75 of the base 74. The opening 78 is configured to allow the lower radiation thermometer 20 to receive radiation light (infrared light) emitted from the lower surface of the semiconductor wafer W. That is, the lower radiation thermometer 20 receives the light emitted from the lower surface of the semiconductor wafer W through the opening 78 and the transparent window 21 of the through hole 61b mounted on the side of the chamber 61 to measure the temperature of the semiconductor wafer W. Furthermore, four through holes 79 are provided in the holding plate 75 of the base 74 for the lifting pin 12 of the transfer mechanism 10 to pass through for the transfer of the semiconductor wafer W.

[0048] Figure 5 is a top view of the transfer mechanism 10. Figure 6 is a side view of the transfer mechanism 10. The transfer mechanism 10 has two transfer arms 11. The transfer arms 11 are arc-shaped, such as those along a generally annular recess 62. Two lifting pins 12 are provided on each transfer arm 11. The transfer arms 11 and the lifting pins 12 are made of quartz. Each transfer arm 11 can be rotated by a horizontal movement mechanism 13. The horizontal movement mechanism 13 moves a pair of transfer arms 11 horizontally between a transfer operation position (solid line position in Figure 5) where the semiconductor wafer W is transferred relative to the holding portion 7, and a retraction position (double-dotted line position in Figure 5) where, in top view, the transfer arms do not coincide with the semiconductor wafer W held in the holding portion 7. As a horizontal moving mechanism 13, it can be a horizontal moving mechanism 13 in which each transfer arm 11 is rotated separately by an individual motor, or it can be a horizontal moving mechanism 13 in which a linkage mechanism is used and a pair of transfer arms 11 are rotated in conjunction by a single motor.

[0049] Furthermore, the pair of transfer arms 11 move up and down together with the horizontal moving mechanism 13 via 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 lifting pins 12 pass through the through holes 79 in the base 74 (see Figures 2 and 3), with the upper ends of the lifting pins 12 protruding from the upper surface of the base 74. On the other hand, when the lifting mechanism 14 lowers the pair of transfer arms 11 to the transfer operation position, it pulls the lifting pins 12 out of the through holes 79. When the horizontal moving mechanism 13 moves the pair of transfer arms 11 to open, each transfer arm 11 moves to the retracted position. The retracted position of the pair of transfer arms 11 is directly above the base ring 71 of the holding part 7. The base ring 71 is placed on the bottom surface of the recess 62, therefore, the retracted position of the transfer arms 11 is inside the recess 62. Furthermore, an exhaust mechanism (not shown) is provided near the drive unit (horizontal movement mechanism 13 and lifting mechanism 14) of the transfer mechanism 10, configured to exhaust the gas around the drive unit of the transfer mechanism 10 to the outside of the chamber 6.

[0050] Returning to Figure 1, the flash heating unit 5, located above the chamber 6, is constructed within the housing 51 by a light source consisting of a plurality of xenon flash lamps (30 in this embodiment) and a reflector 52 positioned to cover the light source. Furthermore, a light-emitting window 53 is installed at the bottom of the housing 51 of the flash heating unit 5. The light-emitting window 53, constituting the bottom plate of the flash heating unit 5, is a plate-shaped quartz window. By positioning the flash heating unit 5 above the chamber 6, the light-emitting window 53 faces the upper chamber window 63. The flash lamps FL illuminate the heat treatment space 65 from above the chamber 6 through the light-emitting window 53 and the upper chamber window 63.

[0051] Each of the multiple flash lamps FL is a long, cylindrical rod-shaped lamp, arranged in a planar manner with their respective length directions parallel to each other along the main surface (i.e., along the horizontal direction) of the semiconductor wafer W held in the holding part 7. Therefore, the plane formed by the arrangement of the flash lamps FL is also a horizontal plane.

[0052] Figure 8 shows the driving circuit of the flash lamp FL. As shown in the figure, capacitor 93, coil 94, flash lamp FL, and 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, which are connected to the input unit 33. The input unit 33 can be any known input device such as a keyboard, mouse, or touch panel. The waveform setting unit 32 sets the waveform of the pulse signal based on the input content from the input unit 33, and the pulse generator 31 generates a pulse signal according to this waveform.

[0053] The flash unit FL includes: a rod-shaped glass tube (discharge tube) 92, which contains xenon gas and has an anode and a cathode at both ends; and a trigger electrode 91 attached to the outer circumferential surface of the glass tube 92. A specific voltage is applied to a capacitor 93 by a power supply unit 95, charging the capacitor 93 with a charge corresponding to the applied voltage (charging voltage). Furthermore, a high voltage can be applied to the trigger electrode 91 from a trigger circuit 97. The timing of the voltage application from the trigger circuit 97 to the trigger electrode 91 is controlled by a control unit 3.

[0054] The IGBT96 is a bipolar transistor with a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) mounted at its gate, making it suitable for handling high-power switching devices. 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 certain value (High voltage) is applied to the gate of the IGBT96, the IGBT96 becomes ON; when a voltage below a certain value (Low voltage) is applied, the IGBT96 becomes OFF. In this way, the drive circuit including the flash lamp FL is switched on and off according to the IGBT96. By switching the IGBT96 on and off, the connection between the flash lamp FL and the corresponding capacitor 93 is interrupted, thus controlling the on / off state of the current flowing to the flash lamp FL.

[0055] Even when the IGBT 96 is switched on while the capacitor 93 is charged, and a high voltage is applied to the two electrodes of the glass tube 92, no current flows through the glass tube 92 under normal conditions because xenon is an electrical insulator. However, when the trigger circuit 97 applies a high voltage to the trigger electrode 91, breaking the insulation, current flows instantaneously through 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 this time.

[0056] As shown in Figure 8, the drive circuits are individually disposed on a plurality of flash lamps (FLs), which are disposed on the flash heating unit 5. In this embodiment, the 30 flash lamps (FLs) are arranged in a planar shape, and therefore, 30 drive circuits, each containing an IGBT 96 as shown in Figure 8, are correspondingly disposed thereon. Thus, the current flowing to each of the 30 flash lamps (FLs) is individually controlled to be switched on and off by the corresponding IGBT 96.

[0057] Furthermore, reflector 52 is disposed above the plurality of flash units FL to cover them as a whole. The basic function of reflector 52 is to reflect the flash emitted from the plurality of flash units FL to one side of the heat treatment space 65. Reflector 52 is formed of aluminum alloy plate, and its surface (the side facing the flash unit FL) is roughened by sandblasting.

[0058] The halogen heating unit 4, located below the chamber 6, has a plurality of halogen lamps HL (40 in this embodiment) built inside the housing 41. The halogen heating unit 4 is a light irradiation unit that heats the semiconductor wafer W by irradiating light from below the chamber 6 through the lower chamber window 64 into the heat treatment space 65 using the plurality of halogen lamps HL.

[0059] Figure 7 is a top view showing the arrangement of a plurality of halogen lamps HL. The 40 halogen lamps HL are arranged in two sections, upper and lower. Twenty halogen lamps HL are arranged in the upper section near the holding part 7, and another twenty halogen lamps HL are arranged in the lower section, further away from the holding part 7. Each halogen lamp HL is a long, cylindrical rod-shaped lamp. In both the upper and lower sections, the twenty halogen lamps HL are arranged parallel to each other along the main surface (i.e., along the horizontal direction) of the semiconductor wafer W held in the holding part 7. Therefore, the plane formed by the arrangement of the halogen lamps HL in both the upper and lower sections is a horizontal plane.

[0060] Furthermore, as shown in Figure 7, the halogen lamp HL has a higher density in the upper and lower sections compared to the region facing the center of the semiconductor wafer W held in the holding section 7 and the region facing the periphery. That is, the spacing between the halogen lamps HL in the periphery is shorter in both the upper and lower sections compared to the central part of the lamp arrangement. Therefore, when heating is performed using light irradiation from the halogen heating section 4, more light can be applied to the periphery of the semiconductor wafer W, which is prone to temperature drop.

[0061] Furthermore, the lamp group consisting of the upper halogen lamps HL and the lamp group consisting of the lower halogen lamps HL are arranged in a crisscrossing grid pattern. That is, a total of 40 halogen lamps HL are arranged such that the length directions of the 20 halogen lamps HL in the upper section and the length directions of the 20 halogen lamps HL in the lower section are orthogonal to each other.

[0062] Halogen lamps (HL) are light sources that emit light by incandescently burning a filament inside a glass tube. The glass tube contains a gas containing trace amounts of halogen elements (iodine, bromine, etc.) introduced into an inert gas such as nitrogen or argon. Introducing halogen elements helps prevent filament breakage and maintains a high filament temperature. Therefore, halogen lamps (HL) have a longer lifespan and can continuously emit stronger light compared to conventional incandescent bulbs. Specifically, halogen lamps (HL) are continuously lit for at least one second. Furthermore, halogen lamps (HL) are rod-shaped, resulting in a longer lifespan. By arranging halogen lamps (HL) horizontally, the radiation efficiency towards the semiconductor wafer W is excellent.

[0063] Furthermore, a reflector 43 (Fig. 1) is also provided below the two halogen lamps HL inside the housing 41 of the halogen heating section 4. The reflector 43 reflects the light emitted from the plurality of halogen lamps HL to one side of the heat treatment space 65.

[0064] 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 positioned obliquely above the semiconductor wafer W held by the base 74, and receives infrared light emitted from the upper surface of the semiconductor wafer W to measure the temperature of the upper surface. The infrared sensor 29 of the upper radiation thermometer 25 has an InSb (indium antimonide) optical element to cope with the rapid temperature change of the upper surface of the semiconductor wafer W at the moment of being irradiated. On the other hand, the lower radiation thermometer 20 is positioned obliquely below the semiconductor wafer W held by the base 74, and receives infrared light emitted from the lower surface of the semiconductor wafer W to measure the temperature of the lower surface.

[0065] The control unit 3 controls the various operating mechanisms installed in the heat treatment apparatus 1. The hardware configuration of the control unit 3 is the same as that of a regular computer. That is, the control unit 3 includes a CPU for performing various arithmetic operations, a ROM for storing the basic program, RAM for storing various information, and a memory unit (e.g., a magnetic disk or SSD) for pre-storing control software or data. The CPU of the control unit 3 executes a specific processing program to perform the processing in the heat treatment apparatus 1. Furthermore, the control unit 3 includes a pulse generator 31 and a waveform setting unit 32 (Figure 8). Based on the input from the input unit 33, the waveform setting unit 32 sets the waveform of the pulse signal, and accordingly, the pulse generator 31 generates a pulse signal that turns the IGBT 96 on and off.

[0066] In addition to the above-described configuration, the heat treatment apparatus 1 also includes various cooling structures to prevent excessive temperature rise in the halogen heating section 4, the flash heating section 5, and the chamber 6 caused by the heat generated by the halogen lamp HL and the flash lamp FL during the heat treatment of the semiconductor wafer W. For example, a water-cooled pipe (not shown) is provided in the wall of the chamber 6. Furthermore, the halogen heating section 4 and the flash heating section 5 are air-cooled structures that form a gas flow inside to dissipate heat. In addition, air is supplied to the gap between the upper chamber window 63 and the lamp emission window 53 to cool the flash heating section 5 and the upper chamber window 63.

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

[0068] First, the gas supply valve 84 is opened, and the exhaust valves 89 and 192 are also opened to begin supplying and exhausting gas into the chamber 6. When valve 84 is open, nitrogen is supplied to the heat treatment space 65 through the gas supply port 81. Then, when valve 89 is opened, the gas in the chamber 6 is discharged through the gas exhaust port 86. Thus, the nitrogen supplied from the upper part of the heat treatment space 65 within the chamber 6 flows downwards and is discharged from the lower part of the heat treatment space 65.

[0069] Furthermore, by opening valve 192, the gas in chamber 6 is also discharged from the transfer opening 66. Additionally, by using the exhaust mechanism (not shown in the diagram), the gas around the drive section of transfer mechanism 10 is also discharged. Moreover, during the heat treatment of the semiconductor wafer W in the heat treatment apparatus 1, nitrogen is continuously supplied to the heat treatment space 65, and the supply amount is appropriately changed according to the processing steps.

[0070] Subsequently, the gate valve 185 opens, causing the transfer opening 66 to open. The semiconductor wafer W to be processed is then transferred into the heat treatment space 65 of the chamber 6 by the external transfer robot through the transfer opening 66. At this time, along with the transfer of the semiconductor wafer W, there is a possibility of entrainment of gas from outside the device. However, since nitrogen is continuously supplied to the chamber 6, nitrogen flows out from the transfer opening 66, which can suppress the entrainment of such external gas to a minimum.

[0071] The semiconductor wafer W, brought in by the transfer robot, stops at a position directly above the holding section 7. Then, one pair of transfer arms 11 of the transfer mechanism 10 moves horizontally from the retracted position to the transfer action position and rises, thereby allowing the lifting pin 12 to protrude through the through hole 79 from the upper surface of the holding plate 75 of the base 74 to receive the semiconductor wafer W. At this time, the lifting pin 12 rises to a position higher than the upper end of the substrate support pin 77.

[0072] After the semiconductor wafer W is placed on the lifting pin 12, the transfer robot exits from the heat treatment space 65, and the transfer opening 66 is closed by the gate valve 185. Then, a pair of transfer arms 11 descend, thereby transferring the semiconductor wafer W from the transfer mechanism 10 to the base 74 of the holding portion 7, where it is held horizontally from below. The semiconductor wafer W is held on the base 74 by a plurality of substrate support pins 77 erected on the holding plate 75. Furthermore, the semiconductor wafer W is held in the holding portion 7 with the surface covered with a nickel film as its upper surface. A specific gap is formed between the back side (the main surface opposite to the upper 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. One of the transfer arms 11, which has descended to below the base 74, retracts to a retraction position, i.e., inside the recess 62, by the horizontal movement mechanism 13.

[0073] After the semiconductor wafer W is held horizontally from below by the base 74 of the quartz-formed holding part 7, the 40 halogen lamps HL of the halogen heating part 4 are lit together to begin preheating (auxiliary heating). The halogen light emitted from the halogen lamps HL passes through the lower cavity window 64 formed by quartz and the base 74 and irradiates the lower surface of the semiconductor wafer W. By receiving the light irradiation from the halogen lamps HL, the semiconductor wafer W is preheated and its temperature rises. Furthermore, the transfer arm 11 of the transfer mechanism 10 is recessed inside the recess 62, so it does not become an obstacle to the heating of the halogen lamps HL.

[0074] Figure 9 shows the surface temperature change of the semiconductor wafer W. At time t1, the halogen lamp HL is lit to begin preheating of the semiconductor wafer W. During preheating using the halogen lamp HL, the temperature of the semiconductor wafer W is measured by the lower radiation thermometer 20. That is, the lower radiation thermometer 20 receives infrared light emitted from the lower surface of the semiconductor wafer W held on the base 74 through the opening 78 via the transparent window 21 to measure the temperature of the wafer 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, heated by the light from the halogen lamp HL, has reached the specific preheating temperature T1, and controls the output of the halogen lamp HL. That is, the control unit 3 performs feedback control on the output of the halogen lamp HL based on the measured value obtained by the lower radiation thermometer 20 to make the temperature of the semiconductor wafer W reach the preheating temperature T1. Thus, the lower radiation thermometer 20 is a radiation thermometer used for temperature control 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 the moment 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 lamp HL to maintain the temperature of the semiconductor wafer W almost at the preheating temperature T1.

[0076] By using halogen lamps HL for preheating, the entire semiconductor wafer W is uniformly heated to the preheating temperature T1. During the preheating stage using halogen lamps HL, the temperature of the peripheral portion of the semiconductor wafer W, which is more prone to heat dissipation, tends to be lower than that of the central portion. However, the density of halogen lamps HL in the halogen heating section 4 is higher in the area opposite the central portion of the semiconductor wafer W than in the area opposite the peripheral portion. Therefore, the amount of light irradiating the peripheral portion of the semiconductor wafer W, which is prone to heat dissipation, is increased, which makes the in-plane temperature distribution of the semiconductor wafer W more uniform during the preheating stage.

[0077] When the temperature of the semiconductor wafer W reaches the preheating temperature T1 and a specific time t3 has elapsed, the flash lamp FL of the flash heating unit 5 irradiates the surface of the semiconductor wafer W held on the base 74. At this time, part of the flash emitted from the flash lamp FL is directed directly into the cavity 6, while the other part is temporarily reflected by the reflector 52 and directed into the cavity 6. The semiconductor wafer W is flash-heated by the irradiation of these flashes.

[0078] When the flash lamp FL illuminates the scene, a charge is pre-stored in the capacitor 93 by the power supply unit 95 using a specific charging voltage. In this embodiment, the capacitor 93 is charged using a charging voltage of 3400 V or less. Subsequently, with a charge stored in the capacitor 93, a pulse signal is output from the pulse generator 31 of the control unit 3 to the gate of the IGBT 96 to drive the IGBT 96 to turn on and off.

[0079] The waveform of the pulse signal can be defined, for example, by inputting a formula from the input unit 33 that sequentially sets the pulse width time (on-time) and the pulse interval time (off-time) as parameters. When the operator inputs this formula 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 turns on and off. Then, according to the pulse waveform set by the waveform setting unit 32, the pulse generator 31 generates and outputs a pulse signal, which is input to the gate of the IGBT 96.

[0080] Figure 10 shows an example of the waveform of the pulse signal input to the IGBT96. As shown in the figure, the pulse signal in this embodiment alternately turns on and off. Furthermore, in this embodiment, the period Ts of the pulse signal's on and off, i.e., the total time of one on-time and one off-time, is less than 200 microseconds. By applying a pulse signal with the waveform shown in Figure 10 to the gate of the IGBT96, the on-off drive of the IGBT96 is controlled. Specifically, when the pulse signal input to the gate of the IGBT96 is on, the IGBT96 becomes on; when the pulse signal is off, the IGBT96 becomes off.

[0081] Furthermore, the control unit 3 synchronously controls the trigger circuit 97 to apply a high voltage (trigger voltage) to the trigger electrode 91 at the moment when the pulse signal output from the pulse generator 31 becomes on. With a charge accumulated in the capacitor 93, a pulse signal is input to the gate of the IGBT 96, and a high voltage is applied to the trigger electrode 91 synchronously at the moment the pulse signal becomes on. Thus, when the pulse signal is on, current flows between the two electrodes inside the glass tube 92, and light is emitted due to the excitation of xenon atoms or molecules at this time.

[0082] In this way, the 30 flash lamps FL in the flash heating section 5 emit light, illuminating the surface of the semiconductor wafer W held in the holding section 7. Here, when the flash lamps FL are emitted without using the IGBT 96, the charge stored in the capacitor 93 is consumed in one emission, and the output waveform from the flash lamps FL becomes a simple single pulse with a width of approximately 0.1 milliseconds to 10 milliseconds. In contrast, in this embodiment, by connecting the switching element, i.e., the IGBT 96, to the circuit and outputting a pulse signal to its gate, the IGBT 96 interrupts the supply of charge from the capacitor 93 to the flash lamps FL, thereby controlling the on / off state of the current flowing to the flash lamps FL. As a result, it can be said that the emission of the flash lamps FL is controlled by chopping, the charge stored in the capacitor 93 is divided and consumed, and the flash lamps FL repeatedly light up and turn off for a very short period of time. Furthermore, before the current flowing through the circuit completely becomes "0", the next pulse is applied to the gate of the IGBT96 and the current value increases again. Therefore, the light output will not completely become "0" during the repeated on and off of the FL flash.

[0083] By using the IGBT96 to control the on / off switching of the current flowing to the flash lamp (FL), the flash lamp's emission mode (the timing waveform of the emission output) can be freely defined, and the emission time and intensity can be freely adjusted. The on / off driving mode of the IGBT96 is defined by the pulse width and pulse interval time input from the input section 33. That is, simply by assembling the IGBT96 into the flash lamp's drive circuit and appropriately setting the pulse width and pulse interval time input from the input section 33, the flash lamp's emission mode can be freely defined.

[0084] Specifically, for example, when the ratio of the pulse width time to the pulse interval time input from input section 33 is increased, the current flowing to the flash lamp FL increases, and the light intensity becomes stronger. Conversely, when the ratio of the pulse width time to the pulse interval time input from input section 33 is decreased, the current flowing to the flash lamp FL decreases, and the light intensity becomes weaker. Furthermore, by appropriately adjusting the ratio of the pulse interval time to the pulse width time input from input section 33, the light intensity of the flash lamp FL can be maintained at a constant level. Moreover, by extending the total time of the combination of the pulse width time and the pulse interval time input from input section 33, the current will continue to flow to the flash lamp FL for a relatively longer period of time, and the light emission time of the flash lamp FL will be longer. The light emission time of the flash lamp FL is appropriately set between 0.1 milliseconds and 100 milliseconds. The maximum surface temperature of the semiconductor wafer W and the heat input to the semiconductor wafer W are determined by the charging voltage to the capacitor 93 and the waveform of the light emission mode of the flash lamp FL.

[0085] In this way, the surface of the semiconductor wafer W is flash-heated by the flash lamp FL for a duration of 0.1 ms to 100 ms (10 ms in this embodiment). Subsequently, the surface temperature of the semiconductor wafer W, heated by the flash from the flash lamp FL, rises instantaneously to the processing temperature T2. The surface of the semiconductor wafer W reaches the processing temperature T2 in approximately 10 ms, thereby causing the nickel film to react with silicon to form nickel silicon. 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 remains on, the flash lamp FL stops emitting light, and the surface temperature drops rapidly. Thus, in the heat treatment apparatus 1, by irradiating with a flash of extremely short duration, the surface temperature of the semiconductor wafer W can rise and fall in a very short time.

[0086] After the flash heating process is completed, the halogen lamp HL is also extinguished. This causes the semiconductor wafer W to rapidly cool down from the preheating temperature T1. The temperature of the semiconductor wafer W during cooling 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 decreased to a specific temperature based on the measurement result of the lower radiation thermometer 20. Then, after the temperature of the semiconductor wafer W decreases below a specific temperature, one of the transfer arms 11 of the transfer mechanism 10 moves horizontally from the retracted position to the transfer action position and rises. This causes the lifting pin 12 to protrude from the upper surface of the base 74 and receive the heat-treated semiconductor wafer W from the base 74. Then, the transfer opening 66, which was closed by the gate valve 185, opens, and the semiconductor wafer W placed on the lifting pin 12 is removed by a transfer robot outside the device. The heat treatment of the semiconductor wafer W in the heat treatment device 1 is completed.

[0087] Figure 11 shows the change in surface temperature of the semiconductor wafer W during flash heating. This figure magnifies the time interval t3 to t4 in Figure 9. The interval t3 to t4 is approximately 10 milliseconds. The IGBT 96 repeatedly switches on and off according to the waveform of the pulse signal output from the pulse generator 31, thereby causing the current flowing to the flash lamp FL to repeatedly increase and decrease. As a result, the intensity of the light emitted from the flash lamp FL also repeatedly increases and decreases. As shown in Figure 11, during the flash heating process from time t3 to t4, the surface temperature of the semiconductor wafer W repeatedly increases and decreases slightly while rising from the preheating temperature T1 to the processing temperature T2.

[0088] In this embodiment, the on / off period Ts of the pulse signal output by the pulse generator 31 is set to less than 200 microseconds. Therefore, the on / off period of the IGBT 96 during repeated on / off cycles becomes extremely short, less than 200 microseconds, resulting in a smaller amplitude of temperature fluctuations on the semiconductor wafer W. That is, the on-time of the IGBT 96 is extremely short; therefore, during the on-time of the IGBT 96, the current flowing to the flash lamp FL increases, and the temperature rise of the semiconductor wafer W is very small. Similarly, the off-time of the IGBT 96 is also extremely short; therefore, during the off-time of the IGBT 96, the current flowing to the flash lamp FL decreases, and the temperature drop of the semiconductor wafer W is also very small. As a result, the amplitude of temperature fluctuations on the semiconductor wafer W is small.

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

[0090] The switching cycle of the IGBT96 is extremely short, less than 200 microseconds. Therefore, the cycle of current increase / decrease in the flash lamp FL is also extremely short. As a result, the cycle of surface temperature increase / decrease in the semiconductor wafer W also becomes approximately less than 200 microseconds. If the charging voltage of capacitor 93 (i.e., the voltage applied to the flash lamp FL) is less than 3400 V, and the switching cycle of the IGBT96 is less than 200 microseconds, then the difference Td between the maximum and minimum values ​​of the surface temperature increase / decrease in one cycle of the semiconductor wafer W becomes less than 10°C.

[0091] When the surface temperature of semiconductor wafer W repeatedly increases or decreases due to the switching on and off of IGBT 96, repeated stress will act on semiconductor wafer W due to thermal expansion and contraction. However, if the difference Td between the maximum and minimum surface temperature of semiconductor wafer W is less than 10°C, the stress value repeatedly acting on semiconductor wafer W will fall below the fatigue limit. Therefore, even if repeated stress acts on semiconductor wafer W, it will not cause cracks in semiconductor wafer W. That is, as in the first embodiment, it is possible to prevent cracks caused by repeated stress in semiconductor wafer W during flash irradiation.

[0092] <Second Implementation Method> Next, the second embodiment of the present invention will be described. The configuration of the heat treatment apparatus and the processing sequence of the semiconductor wafer W in the second embodiment are generally the same as those in the first embodiment. In the second embodiment, the phase of the increase or decrease in intensity of light emitted from a certain flash lamp FL is reversed with the phase of the increase or decrease in intensity of light emitted from a flash lamp FL next to it.

[0093] In the second embodiment, similar to the first embodiment, 30 flash lamps (FLs) are arranged in a planar configuration, parallel to each other, along a horizontal direction. Each of the 30 flash lamps (FLs) is individually equipped with a drive circuit as shown in FIG8. That is, an IGBT 96 is individually connected in series with each of the 30 flash lamps (FLs). Therefore, a total of 30 IGBT 96s are provided in the heat treatment apparatus 1.

[0094] In the second embodiment, the control unit 3 individually controls the on / off switching of 30 IGBTs 96. Specifically, the pulse generator 31 of the control unit 3 outputs pulse signals with waveforms inherent to each of the 30 IGBTs 96.

[0095] Designate any one of the 30 flash units (FLs) arranged horizontally as the first flash unit (FL), and designate the adjacent unit as the second flash unit (FL). Designate the switching element connected to the first flash unit (FL) as the first IGBT 96, and the switching element connected to the second flash unit (FL) as the second IGBT 96. Therefore, the first IGBT 96 controls the current flowing to the first flash unit (FL), and the second IGBT 96 controls the current flowing to the second flash unit (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 respectively. Figure 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 respectively in the second embodiment. The pulse generator 31 outputs the pulse signal shown in the upper part of Figure 13 to the first IGBT 96 and the pulse signal shown in the lower part of Figure 13 to the second IGBT 96.

[0097] As shown in Figure 13, the pulse signal input to the first IGBT 96 is phase-reversed with the pulse signal input to the second IGBT 96. That is, when the pulse signal input to the first IGBT 96 is on, the pulse signal input to the second IGBT 96 becomes off. Conversely, when the pulse signal input to the first IGBT 96 is off, the pulse signal input to the second IGBT 96 becomes on.

[0098] During flash illumination, when the pulse generator 31 applies the pulse signal shown in Figure 13 to the first IGBT 96 and the second IGBT 96 respectively, the first IGBT 96 repeatedly turns on and off according to the waveform of the pulse signal in the upper part of Figure 13, and the second IGBT 96 repeatedly turns on and off according to the waveform of the pulse signal in the lower part of Figure 13. Thus, when the first IGBT 96 is on, the second IGBT 96 is off, and when the first IGBT 96 is off, the second IGBT 96 is on. As a result, the phase of the increase or decrease of the current flowing to the first flash lamp FL and the second flash lamp FL is reversed, and the phase of the increase or decrease of the intensity of the light emitted from the first flash lamp FL and the phase of the increase or decrease of the intensity of the light emitted from the second flash lamp FL are also reversed.

[0099] When the phase reversal of the increase / decrease in intensity of light emitted from adjacent first flash lamps FL and second flash lamps FL, the intensity of the emitted light from the first flash lamps FL and second flash lamps FL will cancel each other out. In this way, during flash heating, the repeated increase / decrease in intensity of light irradiating the semiconductor wafer W is suppressed, and the surface temperature of the semiconductor wafer W rises monotonically. As a result, during flash heating, repetitive stress will not act on the semiconductor wafer W, preventing cracks in the semiconductor wafer W. That is, as in the second embodiment, cracks caused by repetitive stress during flash irradiation can be prevented in the semiconductor wafer W. Furthermore, instead of one first flash lamp FL and one second flash lamp FL, there are 15 of each, and the first flash lamps FL and the second flash lamps FL are arranged alternately to form an arrangement of 30 flash lamps FL.

[0100] <Third Implementation Method> Next, the third embodiment of the present invention will be described. The configuration of the heat treatment apparatus and the processing sequence of the semiconductor wafer W in the third embodiment are generally the same as in the first embodiment. In the third embodiment, similar to the second embodiment, the phase of the increase / decrease in intensity of light emitted from a certain flash lamp FL is reversed with the phase of the increase / decrease in intensity of light emitted from a neighboring flash lamp FL. As a method of achieving this, in the second embodiment, the control unit 3 individually controls the on / off state of a plurality of IGBTs 96; in contrast, in the third embodiment, the waveform of the pulse signal is reversed by an inversion circuit.

[0101] In the third embodiment, similar to the first embodiment, the 30 flash lamps (FLs) are arranged in a planar configuration, parallel to each other, along a horizontal direction. Each of the 30 flash lamps (FLs) is individually equipped with a drive circuit as shown in FIG8. That is, an IGBT 96 is individually connected in series with each of the 30 flash lamps (FLs). Therefore, a total of 30 IGBT 96s are provided in the heat treatment apparatus 1.

[0102] Similar to the second embodiment, any one of the 30 flash lamps (FLs) arranged horizontally 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. Therefore, the first IGBT 96 controls the current flowing to the first flash lamp (FL), and the second IGBT 96 controls the current flowing to the second flash lamp (FL). Moreover, similar to the second embodiment, there are 15 first flash lamps and 15 second flash lamps, and the first and second flash lamps are alternately arranged to form an arrangement of 30 flash lamps (FLs).

[0103] Figure 14 is a diagram showing the driving circuit of the second flash lamp FL in the third embodiment. In the third embodiment, the same driving circuit as shown in Figure 8 is provided for the first flash lamp FL. On the other hand, the driving circuit shown in Figure 14 is provided for the second flash lamp FL.

[0104] In Figure 14, the same symbols are used to label the same elements as in Figure 8. The circuit shown in Figure 14 differs from that in Figure 8 in that it includes an inverting circuit 99. Specifically, an inverting circuit 99 is provided between the gate of the IGBT 96 and the pulse generator 31 of the control unit 3. The inverting circuit 99 reverses the polarity of the input signal and outputs it. The inverting circuit 99 is, for example, an operational amplifier. In the circuit of Figure 14, the remaining configuration is the same as that in Figure 8, except for the inclusion of the inverting circuit 99.

[0105] In the third embodiment, the pulse generator 31 of the control unit 3 outputs a pulse signal with a common waveform (i.e., the same waveform) to all 30 IGBTs 96. The pulse signal output from the pulse generator 31 is directly input to the first IGBT 96. Therefore, a pulse signal with 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 the inverting circuit 99 and input to the second IGBT 96. Therefore, a pulse signal with a waveform inverted from the pulse signal output from the pulse generator 31 is input to the second IGBT 96. For example, assuming that the pulse generator 31 outputs the pulse signal shown in the upper section of FIG13, the pulse signal shown in the upper section of FIG13 will be input to the first IGBT 96, and the pulse signal shown in the lower section of FIG13 will be input to the second IGBT 96.

[0106] Therefore, in the third embodiment, similar to the second embodiment, the pulse signals input to the first IGBT 96 and the pulse signals input to the second IGBT 96 are phase-reversed during flash illumination. Consequently, 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 current flowing to the first flash lamp FL and the second flash lamp FL are reversed, and the phases of the intensity of the light emitted from the first flash lamp FL and the intensity of the light emitted from the second flash lamp FL are reversed. Therefore, similar to the second embodiment, the intensity of the emitted light from the first flash lamp FL and the second flash lamp FL cancel each other out.

[0107] Even as in the third embodiment, during flash heating, the intensity of light irradiating the semiconductor wafer W is suppressed from repeatedly increasing or decreasing, and the surface temperature of the semiconductor wafer W rises monotonically. As a result, during flash heating, repetitive stress does not act on the semiconductor wafer W, thus preventing cracks in the semiconductor wafer W. That is, as in the third embodiment, it is possible to prevent cracks caused by repetitive stress from occurring in the semiconductor wafer W during flash irradiation.

[0108] <Example of Change> The embodiments of the present invention have been described above, but various modifications can be made to these embodiments without departing from their spirit. For example, the first embodiment can be combined with the second or third embodiment. That is, the on and off cycle of the IGBT96 can be set to 200 microseconds or less, and the phase reversal of the increase and decrease in intensity of light emitted from the adjacent flash lamp FL can be achieved. In this way, cracks in the semiconductor wafer W caused by repeated stress during flash irradiation can be more effectively prevented.

[0109] Furthermore, in the second and third embodiments, the phase of the increase or decrease in intensity of the light emitted from adjacent first flash lamps FL and second flash lamps FL is reversed, but this is not a limitation. The first flash lamp FL and second flash lamp FL can be any of the plurality of flash lamps FL provided in the flash heating unit 5. For example, all of the right and left halves of the arrangement of 30 flash lamps FL can be set as first flash lamps FL and second flash lamps FL. However, if the first flash lamp FL and second flash lamp FL are set as adjacent lamps as in the second and third embodiments, the effect of canceling out the intensity of the emitted light from both can be obtained with the highest efficiency.

[0110] Furthermore, while the above embodiments use IGBT96 as the switching element, it is not limited to this. For example, GTO (Gate Turn Off) thyristors or GCT (Gate Commutated Turn Off) thyristors can also be used as switching elements. GTO and GCT thyristors have a self-arc suppression function that changes from an on state to an off state by applying a negative signal to the gate. Also, as a basic function of thyristors, GTO and GCT thyristors have the function of changing from an off state to an on state when a positive signal is applied to the gate. That is, the GTO and GCT thyristor systems are switched 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 it is not limited to this. For example, the inverting circuit 99 can also be a NOT circuit.

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

[0113] Furthermore, in the above embodiment, a halogen lamp HL with a filament is used as a continuous lighting lamp for more than 1 second to preheat the semiconductor wafer W, but it is not limited to this. A discharge type arc lamp (e.g., a xenon arc lamp) or an LED lamp instead of a halogen lamp HL can also be used as a continuous lighting lamp for preheating.

[0114] 1: Heat treatment equipment 3: Control Department 4: Halogen heating element 5: Flash heating section 6: Chamber 7: Maintaining section 10: Transfer mechanism 11: Transfer Arm 12: Top-lifting pin 13: Horizontal moving mechanism 14: Lifting mechanism 20: Lower radiation thermometer 21: Transparent Window 25: Upper radiation thermometer 26: Transparent Window 29: Infrared sensor 31: Pulse Generator 32: Waveform setting section 33: Input Section 41: Shell 43: Reflector 51: Shell 52: Reflector 53: Light-emitting window 61: Side of the chamber 61a: Through hole 61b: Through hole 62: concave part 63: Superior chamber window 64: Lower chamber window 65: Heat treatment space 66:Transportation opening 68: Reflection ring 69: Reflection Ring 71: Abutment Ring 72: Connecting Part 74: Base 75: Retention Plate 75a: Maintain surface 76: Guide ring 77: Substrate support pin 78: Opening 79: Through hole 81: Gas supply port 82: Buffer space 83: Gas supply pipe 84: Valve 85: Processing gas supply source 86: Gas exhaust port 87: Buffer space 88: Gas exhaust pipe 89: Valve 91: Trigger Electrode 92: Glass tube 93: Capacitor 94: Coil 95: Power Supply Unit 96: IGBT 97: Trigger Circuit 99: Reverse Circuit 185: Gate valve 190: Exhaust section 191: Gas exhaust pipe 192: Valve FL: Flash HL: Halogen lamp T1: Preheating temperature T2: Processing temperature t1: Time t2: Time t3: Time t4: Time Td: difference Ts: Period W: Semiconductor wafer

Claims

1. A heat treatment method comprising heating a substrate by irradiating it with light, and comprising: The preheating step involves irradiating the substrate with light from a continuously lit lamp to heat the substrate to a specific preheating temperature. The flash heating step, after the preheating step, involves irradiating the surface of the substrate with flashes from a plurality of flash lamps, thereby raising the surface of the substrate to a specific processing temperature; and in the flash heating step, the current flowing to the plurality of flash lamps is controlled by a switching element, and in the flash heating step, the switching period, which is the sum of the switching time and the disconnection time of the switching element, is set to 200 microseconds or less.

2. The heat treatment method of claim 1, wherein in the above-mentioned flash heating step, a voltage of 3400 V or less is applied to the plurality of flash lamps.

3. The heat treatment method of claim 2, wherein in the above-mentioned flash heating step, the difference between the maximum and minimum values ​​of the surface temperature of the substrate caused by the switching element is set to 10°C or less.

4. The heat treatment method according to any one of claims 1 to 3, wherein the plurality of flash lamps includes a first flash lamp and a second flash lamp, in the above flash heating step, the current flowing to the first flash lamp is controlled by a first switching element, and the current flowing to the second flash lamp is controlled by a second switching element, in the above 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 comprising heating a substrate by irradiating it with light, and comprising: The preheating step involves irradiating the substrate with light from a continuously lit lamp to heat the substrate to a specific preheating temperature. The process includes a flash heating step, which, after the preheating step, involves irradiating the surface of the substrate with flashes from a plurality of flash lamps, thereby raising the surface of the substrate to a specific processing temperature. The plurality of flash lamps includes a first flash lamp and a second flash lamp. In the flash heating step, the current flowing to the first flash lamp is controlled by a first switching element, and the current flowing to 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 of claim 5, wherein the first switching element and the second switching element are respectively given different pulse signals for switching on and off.

7. The heat treatment method of claim 5, wherein the first switching element and the second switching element are given a common pulse signal for switching on and off, and the pulse signal given to the second switching element is reversed by an inverting circuit.

8. A heat treatment apparatus for heating a substrate by irradiating it with light, comprising: a chamber for housing the substrate; a continuously lit lamp for irradiating the substrate housed in the chamber with light to heat the substrate to a specific preheating temperature; a plurality of flash lamps for irradiating the surface of the substrate heated to the preheating temperature with flashes to raise the surface of the substrate to a specific processing temperature; a plurality of switching elements for controlling current flowing to the plurality of flash lamps; and a pulse generator for generating pulse signals that turn the plurality of switching elements on and off; and setting the on and off period of the pulse signals output by the pulse generator to the plurality of switching elements to a total time of one on and one off cycle of 200 microseconds or less.

9. The heat treatment apparatus of claim 8, further comprising a capacitor that supplies power to the plurality of flash lamps, wherein the charging voltage of the capacitor is set to 3400 V or less.

10. The heat treatment apparatus of claim 9, wherein the difference between the maximum and minimum surface temperature of the substrate generated by the switching on and off of the plurality of switching elements when the plurality of flash lamps irradiate the substrate is set to 10°C or less.

11. The heat treatment apparatus of any one of claims 8 to 10, wherein the plurality of flash lamps includes a first flash lamp and a second flash lamp, the plurality of switching elements includes a first switching element for controlling the current flowing to the first flash lamp and a second switching element for controlling the current flowing to the second flash lamp, wherein when a flash is emitted 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.

12. A heat treatment apparatus for heating a substrate by irradiating it with light, comprising: a chamber for housing the substrate; continuously lit lamps for irradiating the substrate housed in the chamber with light to heat the substrate to a specific preheating temperature; a plurality of flash lamps for irradiating the surface of the substrate heated to the preheating temperature with flashes to raise the surface of the substrate to a specific processing temperature; a plurality of switching elements for controlling current flowing to the plurality of flash lamps; and a pulse generator for generating pulse signals that turn the plurality of switching elements on and off; wherein the plurality of flash lamps includes a first flash lamp and a second flash lamp, and the plurality of switching elements includes a first switching element for controlling current flowing to the first flash lamp and a second switching element for controlling current flowing to the second flash lamp. When the flash is emitted by the flash lamp, the second switch element is turned off when the first switch element is turned on, and the second switch element is turned on when the first switch element is turned off.

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

14. The heat treatment apparatus of claim 12, wherein the pulse generator outputs a common pulse signal to the first switching element and the second switching element, and the heat treatment apparatus further includes a reversing circuit that reverses the pulse signal applied to the second switching element.

Images