Heat Treatment Method

Abstract

To provide a heat treatment method that can heat a substrate efficiently.SOLUTION: A plurality of flash lamps FL is disposed over a chamber 6 that houses a semiconductor wafer W and a plurality of LED lamps 45 is disposed below the chamber. A surface of the semiconductor wafer W, which has been preliminarily heated by light from the LED lamps 45, is irradiated with flash light from the flash lamps FL. By the irradiation with the light with a wavelength of 900 nm or less from the LED lamps 45, the temperature of the semiconductor wafer W is increased to a preliminary heating temperature at a temperature rising speed of 30°C / s or more. Since the light with a wavelength of 900 nm or less emitted from the LED lamps 45 is also well absorbed in the semiconductor wafer W in a low-temperature range of 500°C or less, the semiconductor wafer W can be heated efficiently. After the irradiation with the flash light, the LED lamps 45 are turned off and the temperature of the semiconductor wafer W is decreased at a temperature drop rate of more than 10°C / s.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a heat treatment method for heating a thin precision electronic substrate such as a semiconductor wafer (hereinafter simply referred to as "substrate") by irradiating the substrate with light. [Background technology]

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

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

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

[0005] A heat treatment apparatus that typically performs such flash lamp annealing has a flash lamp above a chamber that contains a semiconductor wafer and a halogen lamp below it (for example, Patent Document 1). In the apparatus disclosed in Patent Document 1, the semiconductor wafer is preheated by light irradiation from a halogen lamp, and then the surface of the semiconductor wafer is irradiated with flash light from the flash lamp. Preheating is performed with a halogen lamp because it is difficult for the surface of the semiconductor wafer to reach the target temperature by flash light irradiation alone. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2011-159713 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, halogen lamps mainly radiate infrared light with a relatively long wavelength. In terms of the spectral absorptance of silicon semiconductor wafers, the absorptance of infrared light with a long wavelength of 1 μm or more is low in the low temperature range below 500°C. In other words, semiconductor wafers below 500°C do not absorb much infrared light irradiated from halogen lamps, so preheating with a halogen lamp results in inefficient heating in the initial stage of preheating.

[0008] In addition, the light emitted from the halogen lamp passes through a quartz window installed in the chamber before being irradiated onto the semiconductor wafer. Quartz has a low spectral transmittance for light in a relatively long wavelength range. In other words, part of the light emitted from the halogen lamp is absorbed by the quartz window, further reducing the efficiency of preheating by the halogen lamp.

[0009] The present invention has been made in view of the above problems, and an object of the present invention is to provide a heat treatment method capable of heating a substrate efficiently. [Means for solving the problem]

[0010] In order to solve the above problem, the invention of claim 1 is as follows: Silicon semiconductor substrate By shining light on The semiconductor substrate In the heat treatment method, Silicon semiconductor substrate The LED lamp installed on one side of the chamber is used to irradiate the sample with light having a wavelength of 900 nm or less. Semiconductor Substrate a first heating step of heating the substrate to a predetermined preheating temperature at a heating rate of 30° C. / sec or more; Semiconductor Substrate A flash lamp provided on the other side of the chamber is irradiated with a flash light to the Semiconductor Substrate and a second heating step of further heating the mixture.

[0011] The invention of claim 2 is the heat treatment method according to the invention of claim 1, further comprising turning off the LED lamps after the second heating step. Semiconductor Substrate The method further comprises a temperature decreasing step of decreasing the temperature at a temperature decreasing rate of more than 10° C. / sec. Effect of the Invention

[0012] According to the invention of claims 1 and 2, the LED lamp emits light with a wavelength of 900 nm or less. Semiconductor Substrate The temperature is raised to a specified preheating temperature at a heating rate of 30°C / sec or more, and the light emitted from the LED lamp is in the low temperature range. Silicon semiconductor substrate It is also well absorbed by Semiconductor Substrate can be heated efficiently. [Brief description of the drawings]

[0013] [Figure 1] 1 is a vertical cross-sectional view showing a configuration of a heat treatment apparatus for performing a heat treatment method according to the present invention; [Diagram 2] FIG. 2 is a perspective view showing the overall appearance of a holding portion. [Diagram 3] FIG. [Figure 4] FIG. 2 is a cross-sectional view of a susceptor. [Diagram 5] FIG. [Figure 6] FIG. [Figure 7] FIG. 2 is a plan view showing a plurality of LED lamps arranged on a circular substrate. [Figure 8] 2 is a diagram showing a change in the surface temperature of a semiconductor wafer during heat treatment in the heat treatment apparatus of FIG. 1. [Figure 9] FIG. 1 is a diagram showing temperature changes during heating of a semiconductor wafer. [Figure 10] FIG. 1 is a diagram showing a temperature change when a semiconductor wafer is cooled. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0015] Fig. 1 is a vertical cross-sectional view showing the configuration of a heat treatment apparatus 1 for carrying out a heat treatment method according to the present invention. The heat treatment apparatus 1 in Fig. 1 is a flash lamp annealing apparatus that heats a disk-shaped semiconductor wafer W as a substrate by irradiating the semiconductor wafer W with flash light. The size of the semiconductor wafer W to be treated is not particularly limited, but is, for example, φ300 mm or φ450 mm. In Fig. 1 and the subsequent figures, the dimensions and number of each part are exaggerated or simplified as necessary for ease of understanding.

[0016] The heat treatment apparatus 1 includes a chamber 6 that accommodates a semiconductor wafer W, a flash heating unit 5 that incorporates a plurality of flash lamps FL, and an LED heating unit 4 that incorporates a plurality of LED (Light Emitting Diode) lamps 45. The flash heating unit 5 is provided on the upper side of the chamber 6, and the LED heating unit 4 is provided on the lower side. The heat treatment apparatus 1 also includes, inside the chamber 6, a holding unit 7 that holds the semiconductor wafer W in a horizontal position, and a transfer mechanism 10 that transfers the semiconductor wafer W between the holding unit 7 and the outside of the apparatus. The heat treatment apparatus 1 also includes a control unit 3 that controls the LED heating unit 4, the flash heating unit 5, and each operating mechanism provided in the chamber 6 to perform heat treatment of the semiconductor wafer W.

[0017] The chamber 6 is configured by mounting quartz chamber windows on the top and bottom of a cylindrical chamber side portion 61. The chamber side portion 61 has a roughly cylindrical shape with openings at the top and bottom, with an upper chamber window 63 mounted and closed at the upper opening, and a lower chamber window 64 mounted and closed at the lower opening. The upper chamber window 63 constituting the ceiling of the chamber 6 is a disk-shaped member made of quartz, and functions as a quartz window that transmits the flash light emitted from the flash heating unit 5 into the chamber 6. The lower chamber window 64 constituting the floor of the chamber 6 is also a disk-shaped member made of quartz, and functions as a quartz window that transmits the light from the LED heating unit 4 into the chamber 6.

[0018] In addition, a reflective ring 68 is attached to the upper part of the inner wall surface of the chamber side part 61, and a reflective ring 69 is attached to the lower part. Both of the reflective rings 68, 69 are formed in an annular shape. The upper reflective ring 68 is attached by fitting it from the upper side of the chamber side part 61. On the other hand, the lower reflective ring 69 is attached by fitting it from the lower side of the chamber side part 61 and fastening it with screws (not shown). In other words, both of the reflective rings 68, 69 are detachably attached to the chamber side part 61. The inner space of the chamber 6, i.e., the space surrounded by the upper chamber window 63, the lower chamber window 64, the chamber side part 61, and the reflective rings 68, 69, is defined as a heat treatment space 65.

[0019] By mounting the reflecting rings 68, 69 on the chamber side portion 61, a recess 62 is formed on the inner wall surface of the chamber 6. That is, the recess 62 is formed by a central portion of the inner wall surface of the chamber side portion 61 where the reflecting rings 68, 69 are not mounted, the lower end surface of the reflecting ring 68, and the upper end surface of the reflecting ring 69. The recess 62 is formed in an annular shape along the horizontal direction on the inner wall surface of the chamber 6, and surrounds the holder 7 that holds the semiconductor wafer W. The chamber side portion 61 and the reflecting rings 68, 69 are formed from a metal material (e.g., stainless steel) that has excellent strength and heat resistance.

[0020] Further, a transfer opening (furnace port) 66 for carrying a semiconductor wafer W into and out of the chamber 6 is formed in the chamber side portion 61. The transfer opening 66 can be opened and closed by a gate valve 185. The transfer opening 66 is connected in communication with the outer circumferential surface of the recess 62. Therefore, when the gate valve 185 opens the transfer opening 66, the semiconductor wafer W can be carried into and out of the heat treatment space 65 through the transfer opening 66 and the recess 62. Furthermore, when the gate valve 185 closes the transfer opening 66, the heat treatment space 65 in the chamber 6 becomes an airtight space.

[0021] Further, a through hole 61a is formed in the chamber side 61. A radiation thermometer 20 is attached to the portion of the outer wall surface of the chamber side 61 where the through hole 61a is provided. The through hole 61a is a cylindrical hole for guiding infrared light radiated from the lower surface of a semiconductor wafer W held by a susceptor 74 described later to the radiation thermometer 20. The through hole 61a is provided at an incline with respect to the horizontal direction so that the axis of the through hole 61a intersects with the main surface of the semiconductor wafer W held by the susceptor 74. Thus, the radiation thermometer 20 is provided obliquely below the susceptor 74. A transparent window 21 made of a barium fluoride material that transmits infrared light in a wavelength range that can be measured by the radiation thermometer 20 is attached to the end of the through hole 61a facing the heat treatment space 65.

[0022] Further, a gas supply hole 81 is formed in the upper part of the inner wall of the chamber 6 to supply a processing gas to the heat treatment space 65. The gas supply hole 81 is formed at a position above the 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. Further, a valve 84 is inserted in the middle of the gas supply pipe 83. When the valve 84 is opened, the processing gas is supplied from the processing gas supply source 85 to the buffer space 82. The processing gas that has flowed into the buffer space 82 flows in a spreading manner in the buffer space 82, which has a smaller fluid resistance than the gas supply hole 81, and is supplied from the gas supply hole 81 into the heat treatment space 65. The processing gas may be, for example, nitrogen (N 2 ) or hydrogen (H 2 ), ammonia (NH 3 ) or a mixed gas of these gases (nitrogen gas in this embodiment) can be used.

[0023] On the other hand, a gas exhaust hole 86 is formed in the lower part of the inner wall of the chamber 6 to exhaust the gas in the heat treatment space 65. The gas exhaust hole 86 is formed at a position lower than the recessed portion 62, and may be provided in the reflecting ring 69. The gas exhaust hole 86 is connected to a gas exhaust pipe 88 through a buffer space 87 formed in an annular shape inside the side wall of the chamber 6. The gas exhaust pipe 88 is connected to an exhaust unit 190. A valve 89 is inserted in the middle of the gas exhaust pipe 88. When the valve 89 is opened, the gas in the heat treatment space 65 is exhausted from the gas exhaust hole 86 through the buffer space 87 to the gas exhaust pipe 88. The gas supply hole 81 and the gas exhaust hole 86 may be provided in a plurality of holes along the circumferential direction of the chamber 6, or may be slit-shaped. The process gas supply source 85 and the exhaust unit 190 may be mechanisms provided in the heat treatment apparatus 1, or may be utilities of a factory in which the heat treatment apparatus 1 is installed.

[0024] 2 is a perspective view showing the overall appearance of the holder 7. The holder 7 is configured to include a base ring 71, a connecting portion 72, and a susceptor 74. The base ring 71, the connecting portion 72, and the susceptor 74 are all made of quartz. That is, the entire holder 7 is made of quartz.

[0025] The base ring 71 is an arc-shaped quartz member with a portion missing from the annular shape. This missing portion is provided to prevent interference between the base ring 71 and a transfer arm 11 of the transfer mechanism 10, which will be described later. The base ring 71 is placed on the bottom surface of the recess 62, and is supported by the wall surface of the chamber 6 (see FIG. 1). A plurality of connecting portions 72 (four in this embodiment) are erected on the upper surface of the base ring 71 along the circumferential direction of the annular shape. The connecting portions 72 are also quartz members, and are fixed to the base ring 71 by welding.

[0026] The susceptor 74 is supported by four connecting portions 72 provided on the base ring 71. FIG. 3 is a plan view of the susceptor 74. FIG. 4 is a cross-sectional view of the susceptor 74. The susceptor 74 includes a holding plate 75, a guide ring 76, and a plurality of substrate support pins 77. The holding plate 75 is a substantially circular flat member made of quartz. The diameter of the holding plate 75 is larger than the diameter of the semiconductor wafer W. In other words, the holding plate 75 has a larger planar size than the semiconductor wafer W.

[0027] A guide ring 76 is installed on the periphery of the upper surface of the holding plate 75. The guide ring 76 is an annular member having an inner diameter larger than the diameter of the semiconductor wafer W. For example, when the diameter of the semiconductor wafer W is φ300 mm, the inner diameter of the guide ring 76 is φ320 mm. The inner circumference of the guide ring 76 is a tapered surface that widens from the holding plate 75 upward. The guide ring 76 is made of quartz, similar to the holding plate 75. The guide ring 76 may be fused to the upper surface of the holding plate 75, or may be fixed to the holding plate 75 by a separately processed pin or the like. Alternatively, the holding plate 75 and the guide ring 76 may be processed as an integrated member.

[0028] The area of ​​the upper surface of the holding plate 75 inside the guide ring 76 is a flat holding surface 75a that holds the semiconductor wafer W. A plurality of substrate support pins 77 are provided on the holding surface 75a of the holding plate 75. In this embodiment, a total of 12 substrate support pins 77 are provided at 30° intervals along a circumference concentric with the outer circumferential circle of the holding surface 75a (the inner circumferential circle of the guide ring 76). The diameter of the circle on which the 12 substrate support pins 77 are arranged (the distance between the opposing substrate support pins 77) is smaller than the diameter of the semiconductor wafer W, and is φ270 mm to φ280 mm (φ270 mm in this embodiment) if the diameter of the semiconductor wafer W is φ300 mm. Each substrate support pin 77 is made of quartz. The substrate support pins 77 may be provided on the upper surface of the holding plate 75 by welding, or may be processed integrally with the holding plate 75.

[0029] Returning to FIG. 2, four connecting parts 72 erected on the base ring 71 and the peripheral part of the holding plate 75 of the susceptor 74 are fixed by welding. That is, the susceptor 74 and the base ring 71 are fixedly connected by the connecting parts 72. The base ring 71 of the holding part 7 is supported on the wall surface of the chamber 6, and the holding part 7 is attached to the chamber 6. When the holding part 7 is attached to the chamber 6, the holding plate 75 of the susceptor 74 is in a horizontal position (a position in which the normal line coincides with the vertical direction). That is, the holding surface 75a of the holding plate 75 is a horizontal plane.

[0030] The semiconductor wafer W carried into the chamber 6 is placed and held in a horizontal position on the susceptor 74 of the holder 7 attached to the chamber 6. At this time, the semiconductor wafer W is supported by twelve substrate support pins 77 standing on a holding plate 75 and held on the susceptor 74. More precisely, the upper ends of the twelve substrate support pins 77 contact the lower surface of the semiconductor wafer W to support the semiconductor wafer W. The heights of the twelve substrate support pins 77 (the distance from the upper ends of the substrate support pins 77 to the holding surface 75a of the holding plate 75) are uniform, so that the twelve substrate support pins 77 can support the semiconductor wafer W in a horizontal position.

[0031] Furthermore, the semiconductor wafer W is supported by a plurality of substrate support pins 77 at a predetermined distance from the holding surface 75a of the holding plate 75. The thickness of the guide ring 76 is greater than the height of the substrate support pins 77. Therefore, the guide ring 76 prevents the semiconductor wafer W supported by the plurality of substrate support pins 77 from shifting in the horizontal direction.

[0032] 2 and 3, an opening 78 is formed in the holding plate 75 of the susceptor 74, penetrating vertically. The opening 78 is provided so that the radiation thermometer 20 can receive radiation light (infrared light) emitted from the underside of the semiconductor wafer W. That is, the radiation thermometer 20 receives the light emitted from the underside of the semiconductor wafer W through the opening 78 and a transparent window 21 attached to the through hole 61a of the chamber side part 61, and measures the temperature of the semiconductor wafer W. Furthermore, the holding plate 75 of the susceptor 74 is provided with four through holes 79 through which the lift pins 12 of the transfer mechanism 10, which will be described later, pass to transfer the semiconductor wafer W.

[0033] FIG. 5 is a plan view of the transfer mechanism 10. FIG. 6 is a side view of the transfer mechanism 10. The transfer mechanism 10 includes two transfer arms 11. The transfer arms 11 are formed in an arc shape that is aligned with the generally annular recess 62. Two lift pins 12 are provided upright on each of the transfer arms 11. The transfer arms 11 and the lift pins 12 are made of quartz. Each transfer arm 11 is rotatable by a horizontal movement mechanism 13. The horizontal movement mechanism 13 horizontally moves the pair of transfer arms 11 between a transfer operation position (solid line position in FIG. 5) where the semiconductor wafer W is transferred to the holder 7 and a retracted position (double-dashed line position in FIG. 5) where the pair of transfer arms 11 do not overlap the semiconductor wafer W held by the holder 7 in a plan view. The horizontal movement mechanism 13 may be a mechanism that rotates each transfer arm 11 using an individual motor, or a mechanism that uses a link mechanism to rotate a pair of transfer arms 11 in unison using a single motor.

[0034] Also, a 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 the through holes 79 (see FIGS. 2 and 3) formed in the susceptor 74, and the upper ends of the lift pins 12 protrude from the upper surface of the susceptor 74. On the other hand, when the lifting mechanism 14 lowers the pair of transfer arms 11 to the transfer operation position to extract 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 the retracted position. The retracted position of the pair of transfer arms 11 is directly above the base ring 71 of the holding portion 7. Since the base ring 71 is placed on the bottom surface of the recess 62, the retracted position of the transfer arm 11 is inside the recess 62. In addition, an exhaust mechanism (not shown) is provided in the vicinity of the portion where the drive units (horizontal movement mechanism 13 and lifting mechanism 14) of the transfer mechanism 10 are provided, and the atmosphere around the drive units of the transfer mechanism 10 is configured to be discharged to the outside of the chamber 6.

[0035] Returning to FIG. 1, the flash heating unit 5 provided above the chamber 6 includes a light source composed of a plurality of (30 in this embodiment) xenon flash lamps FL inside the housing 51, and a reflector 52 provided so as to cover the upper part of the light source. Further, a lamp light emission window 53 is attached to the bottom of the housing 51 of the flash heating unit 5. The lamp light emission window 53 constituting the floor of the flash heating unit 5 is a plate-shaped quartz window formed of quartz. By installing the flash heating unit 5 above the chamber 6, the lamp light emission window 53 faces the upper chamber window 63. The flash lamp FL irradiates 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.

[0036] The multiple flash lamps FL are each a rod-shaped lamp having a long cylindrical shape, and are arranged in a plane such that their respective longitudinal directions are parallel to each other along the main surface of the semiconductor wafer W held by the holder 7 (i.e., along the horizontal direction). Therefore, the plane formed by the arrangement of the flash lamps FL is also a horizontal plane. The area in which the multiple flash lamps FL are arranged is larger than the planar size of the semiconductor wafer W.

[0037] The xenon flash lamp FL comprises a cylindrical glass tube (discharge tube) filled with xenon gas and having an anode and a cathode connected to a capacitor at both ends, and a trigger electrode attached to the outer periphery of the glass tube. Since xenon gas is an electrical insulator, electricity does not flow through the glass tube under normal conditions even if an electric charge is stored in the capacitor. However, when a high voltage is applied to the trigger electrode to break down the insulation, the electricity stored in the capacitor flows instantly through the glass tube, and light is emitted by the excitation of the xenon atoms or molecules at that time. In such a xenon flash lamp FL, the electrostatic energy stored in the capacitor in advance is converted into an extremely short light pulse of 0.1 to 100 milliseconds, so that it has the characteristic of being able to irradiate extremely strong light compared to a light source that is continuously lit such as a halogen lamp. In other words, the flash lamp FL is a pulsed light emitting lamp that emits light instantaneously for an extremely short time of less than one second. The light emission time of the flash lamps FL can be adjusted by the coil constant of the lamp power supply that supplies power to the flash lamps FL.

[0038] Moreover, the reflector 52 is provided above the multiple flash lamps FL so as to cover them entirely. The basic function of the reflector 52 is to reflect the flash light emitted from the multiple flash lamps FL toward the heat treatment space 65. The reflector 52 is made of an aluminum alloy plate, and its surface (the surface facing the flash lamps FL) is roughened by blasting.

[0039] The LED heating unit 4 provided below the chamber 6 has multiple LED lamps 45 built in the inside of the housing 41. The LED heating unit 4 heats the semiconductor wafer W by irradiating light from the multiple LED lamps 45 into the heat treatment space 65 from below the chamber 6 through a lower chamber window 64.

[0040] FIG. 7 is a plan view showing a plurality of LED lamps 45 arranged on an annular substrate 44. Although several thousand LED lamps 45 are arranged in the LED heating unit 4, the number is simplified in FIG. 7 for convenience of illustration. While conventional halogen lamps are rod-shaped lamps, each LED lamp 45 is a point light source lamp. The annular substrate 44 on which the plurality of LED lamps 45 are arranged is installed parallel to (i.e., horizontally) the main surface of the semiconductor wafer W held by the holder 7. Therefore, the plane formed by the arrangement of the plurality of LED lamps 45 is a horizontal plane.

[0041] 7, the LED lamps 45 are arranged in a concentric pattern. More specifically, the LED lamps 45 are arranged in a concentric pattern coaxial with the central axis CX of the semiconductor wafer W held by the holder 7. In each concentric circle, the LED lamps 45 are arranged at equal intervals. For example, in the example shown in FIG. 7, eight LED lamps 45 are arranged at equal intervals of 45° in the second concentric circle from the inside.

[0042] The LED lamp 45 includes a light-emitting diode. A light-emitting diode is a type of diode that emits light by electroluminescence when a forward voltage is applied. The LED lamp 45 of this embodiment emits light with a wavelength of 900 nm or less. The LED lamp 45 is a continuous lighting lamp that emits light continuously for at least one second.

[0043] A voltage is applied to each of the multiple LED lamps 45 from a power supply unit 49 (FIG. 1), causing the LED lamp 45 to emit light. The power supply unit 49 individually adjusts the power supplied to each of the multiple LED lamps 45 under the control of the control unit 3. That is, the power supply unit 49 can individually adjust the emission intensity and emission time of each of the multiple LED lamps 45 arranged in the LED heating unit 4.

[0044] The control unit 3 controls the various operating mechanisms provided in the heat treatment device 1. The hardware configuration of the control unit 3 is similar to that of a general computer. That is, the control unit 3 includes a CPU, which is a circuit that performs various arithmetic processing, a ROM, which is a read-only memory that stores basic programs, a RAM, which is a readable and writable memory that stores various information, and a magnetic disk that stores control software, data, and the like. The CPU of the control unit 3 executes a predetermined processing program, and thereby the processing in the heat treatment device 1 proceeds.

[0045] In addition to the above configuration, the heat treatment apparatus 1 is provided with various cooling structures to prevent excessive temperature rise in the LED heating unit 4, the flash heating unit 5, and the chamber 6 due to thermal energy generated from the LED lamps 45 and the flash lamps FL during heat treatment of the semiconductor wafer W. For example, a water-cooling pipe (not shown) is provided on the wall of the chamber 6. The LED heating unit 4 and the flash heating unit 5 are also of an air-cooled structure that forms a gas flow inside to exhaust heat. Air is also supplied to the gap between the upper chamber window 63 and the lamp light emission window 53 to cool the flash heating unit 5 and the upper chamber window 63.

[0046] Next, the processing operation in the heat treatment apparatus 1 will be described. The semiconductor wafer W to be processed is a silicon (Si) semiconductor substrate into which impurities have been implanted by ion implantation as a previous process. The impurities are activated by an annealing process performed by the heat treatment apparatus 1. The processing procedure for the semiconductor wafer W described below progresses as a result of the control unit 3 controlling each operating mechanism of the heat treatment apparatus 1.

[0047] First, prior to processing of the semiconductor wafer W, the valve 84 for supplying air is opened, and the exhaust valve 89 is also opened to start supplying and exhausting air to and from the chamber 6. When the valve 84 is opened, nitrogen gas is supplied to the heat treatment space 65 from the gas supply hole 81. When the valve 89 is opened, the gas in the chamber 6 is exhausted from the gas exhaust hole 86. As a result, the nitrogen gas supplied from the upper part of the heat treatment space 65 in the chamber 6 flows downward and is exhausted from the lower part of the heat treatment space 65.

[0048] Next, the gate valve 185 is opened to open the transport opening 66, and the semiconductor wafer W to be treated is carried into the heat treatment space 65 in the chamber 6 through the transport opening 66 by a transport robot outside the apparatus. At this time, there is a risk that the atmosphere outside the apparatus may be drawn in with the carrying in of the semiconductor wafer W, but since nitrogen gas is continuously supplied to the chamber 6, the nitrogen gas flows out from the transport opening 66, making it possible to minimize the entrainment of such external atmosphere.

[0049] The semiconductor wafer W carried in by the transport robot advances to a position directly above the holder 7 and stops there. Then, the pair of transfer arms 11 of the transfer mechanism 10 move horizontally from the retreated position to the transfer operation position and rise, causing the lift pins 12 to pass through the through holes 79 and protrude from the upper surface of the holding plate 75 of the susceptor 74 to receive the semiconductor wafer W. At this time, the lift pins 12 rise to a position above the upper ends of the substrate support pins 77.

[0050] After the semiconductor wafer W is placed on the lift pins 12, the transport robot leaves the heat treatment space 65, and the transport opening 66 is closed by the gate valve 185. Then, the pair of transfer arms 11 descend, and the semiconductor wafer W is transferred from the transfer mechanism 10 to the susceptor 74 of the holder 7, where it is held from below in a horizontal position. The semiconductor wafer W is supported by a plurality of substrate support pins 77 erected on the holding plate 75 and held by the susceptor 74. The semiconductor wafer W is held by the holder 7 with the surface on which the pattern has been formed and the impurities have been implanted as the upper surface. A predetermined gap is formed between the back surface (the main surface opposite to the front surface) of the semiconductor wafer W supported by the plurality of substrate support pins 77 and the holding surface 75a of the holding plate 75. The pair of transfer arms 11 that descend to below the susceptor 74 are retreated to a retreat position, that is, inside the recess 62, by the horizontal movement mechanism 13.

[0051] After the semiconductor wafer W is held from below in a horizontal position by the susceptor 74 of the holder 7 made of quartz, the multiple LED lamps 45 of the LED heating unit 4 are turned on to start preheating (assisted heating). Light emitted from the multiple LED lamps 45 passes through the lower chamber window 64 and the susceptor 74, both made of quartz, and is irradiated onto the underside of the semiconductor wafer W. The semiconductor wafer W is preheated by being irradiated with light from the LED lamps 45, and its temperature increases. Note that the transfer arm 11 of the transfer mechanism 10 is retracted inside the recess 62, and does not interfere with heating by the LED lamps 45.

[0052] FIG. 8 is a diagram showing the change in the surface temperature of the semiconductor wafer W during heat treatment in the heat treatment apparatus 1. At time t1, the LED lamps 45 are turned on and the temperature of the semiconductor wafer W starts to rise. The temperature of the semiconductor wafer W, which rises due to the light irradiation from the LED lamps 45, is measured by the radiation thermometer 20. The measured temperature of the semiconductor wafer W is transmitted to the control unit 3. The control unit 3 controls the power supply unit 49 to adjust the output of the LED lamps 45 while monitoring whether the temperature of the semiconductor wafer W, which rises due to the light irradiation from the LED lamps 45, has reached a predetermined preheating temperature T1. That is, the control unit 3 feedback-controls the output of the LED lamps 45 based on the measured value by the radiation thermometer 20 so that the temperature of the semiconductor wafer W becomes the preheating temperature T1. The preheating temperature T1 is set to about 200° C. to 800° C., preferably about 350° C. to 600° C. (600° C. in this embodiment) at which there is no risk of impurities added to the semiconductor wafer W being diffused by heat.

[0053] The temperature of the semiconductor wafer W, which is raised by irradiation with light from the LED lamps 45, reaches the preheating temperature T1 at time t2. Fig. 9 is a diagram showing temperature changes during heating of the semiconductor wafer W. The solid line in Fig. 9 shows the temperature change of the semiconductor wafer W of this embodiment, which is raised by irradiation with light from the LED lamps 45. The dotted line in Fig. 9 shows, as a comparative example, the temperature change of the semiconductor wafer W, which is raised by irradiation with light from a conventional halogen lamp.

[0054] In this embodiment, the LED lamps 45 irradiate the semiconductor wafer W with light having a wavelength of 900 nm or less. In terms of the spectral absorptance of the silicon semiconductor wafer W, the absorptance of infrared light having a wavelength of 1 μm or more is low in the low temperature range of 500° C. or less, but the absorptance of light having a wavelength of 900 nm or less is relatively high. That is, even in the low temperature range of 500° C. or less, the semiconductor wafer W absorbs the light irradiated from the LED lamps 45 well. Therefore, even when the temperature of the semiconductor wafer W is 500° C. or less in the initial stage of preheating, the semiconductor wafer W can be efficiently heated by the LED lamps 45.

[0055] On the other hand, the halogen lamp mainly irradiates the semiconductor wafer with infrared light having a wavelength of 1 μm or more. Therefore, especially when the temperature of the semiconductor wafer is relatively low, such as 500° C. or less, the semiconductor wafer hardly absorbs the infrared light irradiated from the halogen lamp, and the heating efficiency of the semiconductor wafer is low. As a result, as shown in FIG. 9, the temperature rise rate of the semiconductor wafer W irradiated with light from the LED lamp 45 is significantly higher than the temperature rise rate of the semiconductor wafer irradiated with light from the halogen lamp. While the temperature rise rate of the semiconductor wafer irradiated with light from the halogen lamp is about 7° C. / sec, the temperature rise rate of the semiconductor wafer W heated by the light irradiation from the LED lamp 45 is 30° C. / sec or more. That is, in this embodiment, the semiconductor wafer W is irradiated with light having a wavelength of 900 nm or less from the LED lamp 45, thereby raising the temperature of the semiconductor wafer W to the preheating temperature T1 at a temperature rise rate of 30° C. / sec or more.

[0056] In addition, a quartz lower chamber window 64 is present between the multiple LED lamps 45 and the holder 7. Therefore, the light emitted from the LED lamps 45 passes through the quartz lower chamber window 64 before being irradiated onto the semiconductor wafer W. The spectral transmittance of quartz is low for light in a relatively long wavelength range, but is high for light with a wavelength of 900 nm or less. Therefore, the light emitted from the LED lamps 45 is hardly absorbed by the lower chamber window 64. This allows the LED lamps 45 to heat the semiconductor wafer W more efficiently.

[0057] After the temperature of the semiconductor wafer W reaches the preheating temperature T1, the control unit 3 temporarily maintains the semiconductor wafer W at the preheating temperature T1. Specifically, at time t2 when the temperature of the semiconductor wafer W measured by the radiation thermometer 20 reaches the preheating temperature T1, the control unit 3 adjusts the output of the LED lamps 45 to maintain the temperature of the semiconductor wafer W at approximately the preheating temperature T1.

[0058] At time t3, when a predetermined time has elapsed since the temperature of the semiconductor wafer W reached the preheating temperature T1, the flash lamps FL of the flash heating unit 5 irradiate the surface of the semiconductor wafer W held on the susceptor 74 with flash light. At this time, part of the flash light emitted from the flash lamps FL heads directly into the chamber 6, and the other part is reflected by the reflector 52 and then heads into the chamber 6, and the semiconductor wafer W is flash-heated by the irradiation of these flash lights.

[0059] Since flash heating is performed by irradiating a flash light (light flash) from the flash lamp FL, the surface temperature of the semiconductor wafer W can be raised in a short time. That is, the flash light irradiated from the flash lamp FL is an extremely short and strong flash with an irradiation time of about 0.1 milliseconds to 100 milliseconds, in which electrostatic energy previously stored in a capacitor is converted into an extremely short light pulse. The surface temperature of the semiconductor wafer W flash-heated by the irradiation of the flash light from the flash lamp FL instantaneously rises to a processing temperature T2 of 1000°C or more, and the impurities implanted in the semiconductor wafer W are activated, and then the surface temperature drops rapidly. In this way, the heat treatment device 1 can raise and lower the surface temperature of the semiconductor wafer W in an extremely short time, so that the impurities can be activated while suppressing the diffusion of the impurities implanted in the semiconductor wafer W due to heat. The time required for activating the impurities is extremely short compared to the time required for their thermal diffusion, so that the activation is completed even in a short time of about 0.1 milliseconds to 100 milliseconds in which diffusion does not occur.

[0060] After the flash heating process is completed, the LED lamps 45 are turned off at time t4 after a predetermined time has elapsed. This causes the temperature of the semiconductor wafer W to rapidly drop from the preheating temperature T1. The temperature of the semiconductor wafer W during the drop is measured by the radiation thermometer 20, and the measurement result is transmitted to the control unit 3. The control unit 3 monitors whether the temperature of the semiconductor wafer W has dropped to a predetermined temperature based on the measurement result of the radiation thermometer 20.

[0061] Fig. 10 is a diagram showing temperature changes during cooling of the semiconductor wafer W after time t4. The solid line in Fig. 10 shows the temperature change of the semiconductor wafer W in this embodiment when the LED lamps 45 are turned off. The dotted line in Fig. 10 shows, as a comparative example, the temperature change of the semiconductor wafer W when the conventional halogen lamp is turned off.

[0062] The LED lamp 45 has a faster rise and fall in output than a conventional halogen lamp. That is, the LED lamp 45 reaches the target output almost immediately after it is turned on, and does not emit any heat after it is turned off. Therefore, after the LED lamp 45 is turned off, no light is irradiated onto the semiconductor wafer W, and the temperature of the semiconductor wafer W drops rapidly.

[0063] On the other hand, the halogen lamp continues to emit light for a while even after it is turned off because the temperature of the filament does not drop immediately after the halogen lamp is turned off. Therefore, some light continues to be irradiated onto the semiconductor wafer for a while after the halogen lamp is turned off, which prevents the semiconductor wafer from rapidly decreasing in temperature. As a result, as shown in FIG. 10, the temperature drop rate of the semiconductor wafer W when the LED lamp 45 is turned off is greater than the temperature drop rate of the semiconductor wafer when the halogen lamp is turned off. The temperature drop rate of the semiconductor wafer W when the LED lamp 45 is turned off is greater than 10° C. / sec. That is, in this embodiment, after the LED lamp 45 is turned off at time t4, the temperature of the semiconductor wafer W drops at a rate greater than 10° C. / sec.

[0064] After the temperature of the semiconductor wafer W drops to a predetermined temperature or lower, the pair of transfer arms 11 of the transfer mechanism 10 again move horizontally from the retracted position to the transfer operation position and rise, causing the lift pins 12 to protrude from the upper surface of the susceptor 74 and receive the heat-treated semiconductor wafer W from the susceptor 74. Then, the transfer opening 66 that had been closed by the gate valve 185 is opened, and the semiconductor wafer W placed on the lift pins 12 is transferred out of the chamber 6 by a transfer robot outside the apparatus, completing the heat treatment of the semiconductor wafer W.

[0065] In this embodiment, the semiconductor wafer W is preheated to a preheating temperature T1 by light irradiation from the LED lamps 45, and then the surface of the semiconductor wafer W is irradiated with flash light from the flash lamps FL to heat the surface to a processing temperature T2. The energy consumed when preheating the semiconductor wafer W with the LED lamps 45 is less than half the energy consumed when preheating with conventional halogen lamps. In other words, by preheating the semiconductor wafer W with the LED lamps 45, it is possible to reduce energy consumption and reduce the environmental load.

[0066] Furthermore, by preheating the semiconductor wafer W with the LED lamps 45, both the temperature increase rate and the temperature decrease rate of the semiconductor wafer W are higher than in the case of conventional halogen lamps. Therefore, both the temperature increase time and the temperature decrease time of the semiconductor wafer W are shorter. As a result, the processing time of the semiconductor wafer W can be shortened by the LED lamps 45, and the throughput can be improved.

[0067] Furthermore, by preheating the semiconductor wafer W with the LED lamps 45, the temperature rise rate of the semiconductor wafer W can be increased, shortening the temperature rise time and suppressing unnecessary diffusion of the impurities implanted in the semiconductor wafer W. As a result, when flash heating is performed following the preheating, the impurities can be activated while suppressing diffusion of the impurities, making it possible to realize shallow junctions.

[0068] Furthermore, in this embodiment, the temperature drop rate of the semiconductor wafer W when the LED lamps 45 are turned off after the flash light irradiation is also large. If the temperature drop rate of the semiconductor wafer W after the flash light irradiation is small, there is a risk that the impurities activated by the flash heating will become inactive (inactivated). In this embodiment, since the temperature drop rate of the semiconductor wafer W after the flash light irradiation is also large, it is possible to prevent the impurities activated by the flash heating from becoming inactive.

[0069] Although the embodiment of the present invention has been described above, this invention can be modified in various ways without departing from the spirit of the invention. For example, in the above embodiment, the LED lamps 45 are arranged in a concentric circle shape, but this is not limited to this. For example, the LED lamps 45 may be arranged in a lattice shape at equal intervals.

[0070] In the above embodiment, the flash heating unit 5 is provided with 30 flash lamps FL, but the number of flash lamps FL is not limited to this and may be any number. In addition, the flash lamps FL are not limited to xenon flash lamps and may be krypton flash lamps.

[0071] Furthermore, the substrate to be processed by the heat treatment apparatus 1 is not limited to a semiconductor wafer, but may be a glass substrate used in a flat panel display such as a liquid crystal display device, or a substrate for a solar cell. [Explanation of symbols]

[0072] 1 Heat treatment equipment 3. Control Unit 4 LED heating section 5 Flash heating section 6 Chambers 7 Holding part 20 Radiation thermometer 45 LED lamps 49 Power supply section 65 Heat Treatment Space 74 Susceptor 75 Retaining Plate 77 Board support pin FL Flash lamp W Semiconductor wafer

Claims

1. A heat treatment method for heating a silicon semiconductor substrate by irradiating the semiconductor substrate with light, comprising: a first heating step of irradiating a silicon semiconductor substrate held by a holder in a chamber with light having a wavelength of 900 nm or less from an LED lamp provided on one side of the chamber to heat the semiconductor substrate to a predetermined preheating temperature at a heating rate of 30° C. / sec or more; a second heating step of irradiating the semiconductor substrate heated to the preheating temperature with a flash light from a flash lamp provided on the other side of the chamber to further heat the semiconductor substrate; A heat treatment method comprising:

2. The heat treatment method according to claim 1, The heat treatment method further comprises, after the second heating step, a temperature decreasing step of turning off the LED lamps and decreasing the temperature of the semiconductor substrate at a temperature decreasing rate of more than 10° C. / second.

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