JP2020021831A - Thermal treatment apparatus - Google Patents

Abstract

To provide a thermal treatment apparatus capable of preventing a harmful substance from being discharged to the outside with simple constitution.SOLUTION: A trap box 90 is provided halfway in a path of a gas exhaust pipe for discharging a gas in a chamber. A gas including arsenic discharged from a semiconductor wafer in a heat treatment in the chamber flows in the trap box 90 and is then cooled by a radiator 92, so that the arsenic is deposited as a solid. The gas flow having been cooled strikes on a trap plate 95 and then deposited arsenic sticks on the trap plate 95 to be caught. The harmless gas having the arsenic caught and removed is discharged to outside a device. Thus, the harmful substance can be prevented from being discharged to the outside through simple constitution such that the radiator 92 and the trap plate 95 are provided inside a housing 91.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a heat treatment apparatus for heating a thin precision electronic substrate (hereinafter, simply referred to as a “substrate”) such as a semiconductor wafer by light irradiation or the like.

  2. Description of the Related Art In a semiconductor device manufacturing process, flash lamp annealing (FLA), which heats a semiconductor wafer in a very short time, has attracted attention. Flash lamp annealing uses a xenon flash lamp (hereinafter, simply referred to as a xenon flash lamp when simply referred to as a "flash lamp") to irradiate the surface of the semiconductor wafer with flash light, thereby extremely exposing only the surface of the semiconductor wafer. This is a heat treatment technology that raises the temperature in a short time (several milliseconds or less).

  The emission spectral distribution of the xenon flash lamp is from the ultraviolet region to the near infrared region, the wavelength is shorter than that of a conventional halogen lamp, and almost coincides with the basic absorption band of a silicon semiconductor wafer. Therefore, when the semiconductor wafer is irradiated with flash light from the xenon flash lamp, the transmitted light is small and the temperature of the semiconductor wafer can be rapidly raised. In addition, it has been found that when the flash light is irradiated for a very short time of several milliseconds or less, only the vicinity of the surface of the semiconductor wafer can be selectively heated.

  Such flash lamp annealing is used for a process requiring extremely short-time heating, for example, activation of impurities typically implanted into a semiconductor wafer. By irradiating the surface of the semiconductor wafer into which impurities are implanted by the ion implantation method with flash light from a flash lamp, the surface of the semiconductor wafer can be heated to the activation temperature for a very short time, and the impurities can be diffused deeply. Only the impurity activation can be performed without causing the impurity activation.

  On the other hand, semiconductor devices are typically formed using silicon, but in recent years, which has reached the limit of miniaturization, attempts to form semiconductor devices using materials instead of silicon have been active. Semiconductors such as germanium and gallium arsenide (GaAs) have higher mobility than silicon. When a transistor is formed using these materials, a semiconductor device having higher performance than silicon can be manufactured. For example, Patent Document 1 discloses that a semiconductor thin film of gallium arsenide containing tin, germanium, lead, or the like is subjected to flash lamp annealing to obtain a semiconductor thin film with high carrier mobility and high quality. ing.

JP-A-2002-252174

  However, it has been found that when a gallium arsenide semiconductor is heated to 400 ° C. or higher, arsenic (As) is released from a semiconductor thin film by outward diffusion. Also in flash lamp annealing, the semiconductor thin film reaches a temperature range of 400 ° C. or higher for a short period of time, and there is a concern that arsenic may be released due to outward diffusion. Arsenic is known to be harmful even in trace amounts.

  For this reason, it is necessary to prevent arsenic released during heating from being discharged from the flash lamp annealing apparatus to the outside. Generally, a scrubber and an exclusion device are connected to factory exhaust as a measure to prevent harmful substances such as arsenic from being released into the atmosphere. However, incorporating such a scrubber or exclusion device into a flash lamp annealing device is not realistic from the viewpoint of cost performance and footprint.

  The present invention has been made in view of the above problems, and has as its object to provide a heat treatment apparatus that can prevent harmful substances from being discharged to the outside with a simple configuration.

  In order to solve the above problem, the invention according to claim 1 is a heat treatment apparatus for heating a substrate, wherein a chamber for accommodating the substrate, a heating source for heating the substrate accommodated in the chamber, and an atmosphere in the chamber. Exhaust path, and a trap section provided in the exhaust path and capturing a substance contained in the atmosphere, wherein the trap section cools an airflow passing through the housing inside the housing. A cooling unit is provided.

  According to a second aspect of the present invention, in the heat treatment apparatus according to the first aspect of the present invention, the trap unit further includes a trap plate in which the airflow cooled by the cooling unit collides with the inside of the housing. And

  According to a third aspect of the present invention, in the heat treatment apparatus according to the second aspect of the present invention, the trap unit accommodates a collecting substrate to which the substance deposited by the cooling unit cooling the airflow is attached. A part is further provided inside the housing.

  According to a fourth aspect of the present invention, in the heat treatment apparatus according to any one of the first to third aspects, the heating source includes a lamp for irradiating the substrate with light to heat the substrate.

  According to a fifth aspect of the present invention, in the heat treatment apparatus according to any one of the first to fourth aspects, the substance is arsenic.

  According to the first to fifth aspects of the present invention, since the trap section provided in the exhaust path is provided with a cooling section for cooling an airflow passing through the casing inside the casing, the substance contained in the atmosphere is provided. Can be deposited as a solid and captured, and the harmful substance can be prevented from being discharged to the outside with a simple configuration.

  In particular, according to the second aspect of the present invention, since the trap section includes the trap plate against which the airflow cooled by the cooling section collides, harmful substances can be more reliably captured.

  In particular, according to the third aspect of the present invention, since the trap section includes the storage section for storing the collection substrate to which the substance deposited by cooling the airflow is attached, the trap section is analyzed. The capture of harmful substances can be confirmed.

It is a longitudinal section showing the composition of the heat treatment equipment concerning the present invention. It is a perspective view showing the whole appearance of a maintenance part. It is a top view of a susceptor. It is sectional drawing of a susceptor. It is a top view of a transfer mechanism. It is a side view of a transfer mechanism. It is a top view showing arrangement of a plurality of halogen lamps. It is a perspective view which shows the structure of a trap box. It is a front view of a trap box. It is a top view of a trap box.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a longitudinal sectional view showing a configuration of a heat treatment apparatus 1 according to the present invention. The heat treatment apparatus 1 of FIG. 1 is a flash lamp annealing apparatus that heats a semiconductor wafer W having a disk shape as a substrate by irradiating the semiconductor wafer W with flash light. The size of the semiconductor wafer W to be processed is not particularly limited, but is, for example, φ300 mm or φ450 mm (φ300 mm in the present embodiment). A semiconductor thin film of gallium arsenide is formed on the semiconductor wafer W before being loaded into the heat treatment apparatus 1, and the heat treatment performed by the heat treatment apparatus 1 activates the impurities implanted into the gallium arsenide. Note that, in FIG. 1 and each of the following drawings, the dimensions and the numbers of the respective parts are exaggerated or simplified as necessary for easy understanding.

  The heat treatment apparatus 1 includes a chamber 6 accommodating a semiconductor wafer W, a flash heating unit 5 containing a plurality of flash lamps FL, and a halogen heating unit 4 containing a plurality of halogen lamps HL. A flash heating unit 5 is provided above the chamber 6, and a halogen heating unit 4 is provided below the chamber 6. The heat treatment apparatus 1 further includes a holding unit 7 that holds the semiconductor wafer W in a horizontal position inside the chamber 6, a transfer mechanism 10 that transfers the semiconductor wafer W between the holding unit 7 and the outside of the apparatus, Is provided. Further, the heat treatment apparatus 1 includes a trap box 90 for removing harmful arsenic from the gas exhausted from the chamber 6. Further, the heat treatment apparatus 1 includes a control unit 3 that controls each operation mechanism provided in the halogen heating unit 4, the flash heating unit 5, and the chamber 6 to execute the heat treatment of the semiconductor wafer W.

  The chamber 6 is configured by mounting quartz chamber windows above and below a cylindrical chamber side portion 61. The chamber side portion 61 has a substantially cylindrical shape with an open top and bottom. The upper opening is provided with an upper chamber window 63 mounted and closed, and the lower opening is provided with a lower chamber window 64 mounted and closed. ing. The upper chamber window 63 constituting the ceiling of the chamber 6 is a disk-shaped member formed of quartz, and functions as a quartz window for transmitting flash light emitted from the flash heating unit 5 into the chamber 6. Further, the lower chamber window 64 constituting the floor of the chamber 6 is also a disc-shaped member formed of quartz, and functions as a quartz window for transmitting light from the halogen heating unit 4 into the chamber 6.

  A reflection ring 68 is mounted on the upper part of the inner wall surface of the chamber side part 61, and a reflection ring 69 is mounted on the lower part. The reflection rings 68 and 69 are both formed in an annular shape. The upper reflecting ring 68 is mounted by being fitted from above the chamber side 61. On the other hand, the lower reflective ring 69 is mounted by being fitted from below the chamber side 61 and fastened with screws (not shown). That is, the reflection rings 68 and 69 are both detachably attached to the chamber side 61. The space inside the chamber 6, that is, the space surrounded by the upper chamber window 63, the lower chamber window 64, the chamber side 61 and the reflection rings 68 and 69 is defined as the heat treatment space 65.

  By attaching the reflection rings 68 and 69 to the chamber side 61, a concave portion 62 is formed on the inner wall surface of the chamber 6. That is, a concave portion 62 is formed which is surrounded by a central portion of the inner wall surface of the chamber side portion 61 where the reflection rings 68 and 69 are not mounted, a lower end surface of the reflection ring 68, and an upper end surface of the reflection ring 69. . The concave portion 62 is formed in an annular shape along the horizontal direction on the inner wall surface of the chamber 6 and surrounds the holding portion 7 that holds the semiconductor wafer W. The chamber side 61 and the reflection rings 68 and 69 are formed of a metal material (for example, stainless steel) having excellent strength and heat resistance.

  Further, a transfer opening (furnace opening) 66 for carrying the semiconductor wafer W in and out of the chamber 6 is formed in the chamber side 61. The transport opening 66 can be opened and closed by a gate valve 185. The transport opening 66 is connected to the outer peripheral surface of the concave portion 62 in communication. Therefore, when the gate valve 185 opens the transfer opening 66, the semiconductor wafer W is transferred from the transfer opening 66 through the concave portion 62 to the heat treatment space 65 and unloaded from the heat treatment space 65. It can be performed. When the gate valve 185 closes the transfer opening 66, the heat treatment space 65 in the chamber 6 becomes a closed space.

  Further, a through hole 61a is formed in the chamber side portion 61. The radiation thermometer 20 is attached to a 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 emitted from the lower surface of the semiconductor wafer W held by a susceptor 74 described later to the radiation thermometer 20. The through hole 61a is provided to be inclined 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. At the end of the through hole 61a on the side facing the heat treatment space 65, 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 mounted.

Further, a gas supply hole 81 for supplying a processing gas to the heat treatment space 65 is formed in an upper portion of an inner wall of the chamber 6. The gas supply hole 81 is formed above the concave portion 62 and may be provided on the reflection 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. An air supply valve 84 is interposed in the middle of the path of the gas supply pipe 83. When the air supply valve 84 is opened, the processing gas is supplied from the processing gas supply source 85 to the buffer space 82. The processing gas flowing into the buffer space 82 flows so as to expand in the buffer space 82 having a smaller fluid resistance than the gas supply holes 81, and is supplied from the gas supply holes 81 into the heat treatment space 65. As the processing gas, for example, an inert gas such as nitrogen (N ₂ ), a reactive gas such as hydrogen (H ₂ ), ammonia (NH ₃ ), or a mixed gas obtained by mixing them can be used. In the embodiment, nitrogen gas).

  On the other hand, a gas exhaust hole 86 for exhausting the gas in the heat treatment space 65 is formed below the inner wall of the chamber 6. The gas exhaust hole 86 is formed at a position lower than the concave portion 62, and may be provided on the reflection ring 69. The gas exhaust hole 86 is connected to a gas exhaust pipe 88 via a buffer space 87 formed in an annular shape inside the side wall of the chamber 6. The gas exhaust pipe 88 is connected to the exhaust part 190. An exhaust valve 89 and a trap box 90 are interposed in the middle of the path of the gas exhaust pipe 88. When the exhaust valve 89 is opened, the gas in the heat treatment space 65 is exhausted from the gas exhaust hole 86 to the gas exhaust pipe 88 via the buffer space 87. Note that a plurality of gas supply holes 81 and gas exhaust holes 86 may be provided along the circumferential direction of the chamber 6 or may be slit-shaped.

  As the exhaust unit 190, an exhaust utility of a factory where the vacuum pump and the heat treatment apparatus 1 are installed can be used. When a vacuum pump is adopted as the exhaust unit 190, the air supply valve 84 is closed, and the atmosphere in the heat treatment space 65, which is a closed space, is exhausted without supplying any gas from the gas supply hole 81, the inside of the chamber 6 becomes a vacuum atmosphere. The pressure can be reduced to Further, even when a vacuum pump is not used as the exhaust unit 190, the inside of the chamber 6 can be depressurized to a pressure lower than the atmospheric pressure by performing the exhaust without supplying the gas from the gas supply hole 81. .

  FIG. 8 is a perspective view showing the configuration of the trap box 90. FIG. 9 is a front view of the trap box 90, and FIG. 10 is a plan view of the trap box 90. In each of FIGS. 8 to 10, an XYZ orthogonal coordinate system in which the Z-axis direction is a vertical direction and the XY plane is a horizontal plane is shown in order to clarify the directional relationship.

  The trap box 90 is provided in the middle of the path of the gas exhaust pipe 88. The installation position of the trap box 90 is not particularly limited, but it is preferable that the trap box 90 be provided as close to the gas exhaust hole 86 of the chamber 6 as possible in the course of the gas exhaust pipe 88.

  The trap box 90 includes a radiator 92, a trap plate 95, and a wafer accommodating portion 96 as main components inside a housing 91. The housing 91 is a hollow rectangular parallelepiped box. The housing 91 is provided with an air supply port 97 for taking in gas inside and an exhaust port 98 for discharging gas inside. The supply port 97 and the exhaust port 98 are connected to a gas exhaust pipe 88 that guides the gas exhausted from the chamber 6.

  The radiator 92 is provided on the entire cross section (YZ cross section) of the housing 91 so as to separate the internal space of the housing 91. The radiator 92 includes a plurality of cooling pipes 93, a tank (not shown), and a circulation pump. The plurality of cooling pipes 93 are arranged in parallel at predetermined intervals. Each of the plurality of cooling pipes 93 is formed of a material having excellent heat conductivity, for example, aluminum. The cooling liquid (for example, cooling water) whose temperature is controlled to a predetermined temperature stored in the tank is configured to flow and circulate through the plurality of cooling pipes 93 by a circulation pump. The gas passing between the plurality of cooling pipes 93 is cooled by the cooling pipes 93 through which the cooling liquid flows. Since the radiator 92 is provided on the entire cross section of the casing 91, it cools the entire airflow passing through the casing 91. In order to increase the cooling efficiency of the radiator 92, the cooling pipe 93 may have a meandering shape with a large surface area, or a plurality of cooling pipes 93 may be arranged in a grid.

  The trap plate 95 is a plate-like member provided inside the housing 91 in parallel with the radiator 92. As shown in FIGS. 8 and 9, the trap plate 95 is provided so as to shield an upper part of a cross section (YZ cross section) of the housing 91. Therefore, the lower part of the trap plate 95 is open in the cross section of the housing 91 in which the trap plate 95 is installed. Although the material of the trap plate 95 is not particularly limited, for example, a vinyl chloride resin can be used.

  The radiator 92 and the trap plate 95 are provided detachably with respect to the housing 91. Therefore, the radiator 92 and the trap plate 95 can be exchanged as needed.

  The wafer accommodating portion 96 is provided below the trap plate 95 inside the housing 91. The wafer accommodating section 96 places the measurement wafer MW in a horizontal position below the trap plate 95. That is, the wafer accommodating portion 96 places the measurement wafer MW perpendicular to the trap plate 95. The measurement wafer MW is a silicon substrate having the same shape and size as a general semiconductor wafer W. However, no pattern formation or film formation processing has been performed on the measurement wafer MW.

  FIG. 2 is a perspective view showing the overall appearance of the holding unit 7. The holding unit 7 includes a base ring 71, a connecting unit 72, and a susceptor 74. The base ring 71, the connecting portion 72, and the susceptor 74 are all formed of quartz. That is, the entire holding section 7 is formed of quartz.

  The base ring 71 is an arc-shaped quartz member in which a part is omitted from the ring shape. The missing portion is provided to prevent interference between a transfer arm 11 of the transfer mechanism 10 described below and the base ring 71. The base ring 71 is supported on the wall surface of the chamber 6 by being placed on the bottom surface of the concave portion 62 (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 ring shape. The connecting portion 72 is also a quartz member, and is fixed to the base ring 71 by welding.

  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 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 plate-shaped member formed of quartz. The diameter of the holding plate 75 is larger than the diameter of the semiconductor wafer W. That is, the holding plate 75 has a larger planar size than the semiconductor wafer W.

  A guide ring 76 is provided on a peripheral edge 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 has a tapered surface that widens upward from the holding plate 75. The guide ring 76 is formed of the same quartz as the holding plate 75. The guide ring 76 may be welded to the upper surface of the holding plate 75, or may be fixed to the holding plate 75 by a separately processed pin or the like. Alternatively, the holding plate 75 and the guide ring 76 may be processed as an integral member.

  A region inside the guide ring 76 on the upper surface of the holding plate 75 is a flat holding surface 75a for holding the semiconductor wafer W. A plurality of substrate support pins 77 are provided upright on the holding surface 75 a of the holding plate 75. In the present embodiment, a total of 12 substrate support pins 77 are erected at every 30 ° along the outer circumference of the holding surface 75a (the inner circumference of the guide ring 76). The diameter of the circle in which the twelve 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. If the diameter of the semiconductor wafer W is φ300 mm, φ270 mm to φ280 mm (this embodiment) (Φ270 mm in the form). Each substrate support pin 77 is formed of quartz. The plurality of substrate support pins 77 may be provided on the upper surface of the holding plate 75 by welding, or may be processed integrally with the holding plate 75.

  Returning to FIG. 2, the four connecting portions 72 erected on the base ring 71 and the peripheral edge 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 portion 72. By supporting the base ring 71 of the holder 7 on the wall surface of the chamber 6, the holder 7 is mounted on the chamber 6. When the holding unit 7 is mounted on the chamber 6, the holding plate 75 of the susceptor 74 is in a horizontal posture (a posture 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.

  The semiconductor wafer W carried into the chamber 6 is placed and held in a horizontal posture on the susceptor 74 of the holding unit 7 mounted on the chamber 6. At this time, the semiconductor wafer W is supported by twelve substrate support pins 77 erected on the holding plate 75 and held by 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. Since the height of the twelve substrate support pins 77 (the distance from the upper end of the substrate support pins 77 to the holding surface 75a of the holding plate 75) is uniform, the semiconductor wafer W is placed in a horizontal posture by the twelve substrate support pins 77. Can be supported.

  The semiconductor wafer W is supported by the 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 larger than the height of the substrate support pins 77. Therefore, the horizontal displacement of the semiconductor wafer W supported by the plurality of substrate support pins 77 is prevented by the guide ring 76.

  As shown in FIGS. 2 and 3, the holding plate 75 of the susceptor 74 has an opening 78 penetrating vertically. The opening 78 is provided for the radiation thermometer 20 to receive radiation light (infrared light) radiated from the lower surface of the semiconductor wafer W. That is, the radiation thermometer 20 receives the light radiated from the lower surface of the semiconductor wafer W through the opening 78 and the transparent window 21 attached to the through hole 61a of the chamber side portion 61, and reduces the temperature of the semiconductor wafer W. Measure. Further, 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 to be described later pass for transferring the semiconductor wafer W.

  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 arm 11 is formed in a circular arc shape along the generally annular concave portion 62. Each transfer arm 11 is provided with two lift pins 12 standing upright. The transfer arm 11 and the lift pins 12 are formed of quartz. Each transfer arm 11 is rotatable by a horizontal movement mechanism 13. The horizontal movement mechanism 13 moves the pair of transfer arms 11 to a transfer operation position (solid line position in FIG. 5) where the semiconductor wafer W is transferred to the holding unit 7 and the semiconductor wafer W held by the holding unit 7. The horizontal movement is performed between a retracted position (a position indicated by a two-dot chain line in FIG. 5) that does not overlap in a plan view. The horizontal movement mechanism 13 may be configured to rotate each transfer arm 11 by an individual motor, or may be rotated by linking a pair of transfer arms 11 by a single motor using a link mechanism. It may be moved.

  Further, the pair of transfer arms 11 is moved up and down by the elevating mechanism 14 together with the horizontal moving mechanism 13. When the lifting mechanism 14 raises the pair of transfer arms 11 at 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 end of 12 protrudes from the upper surface of susceptor 74. On the other hand, when the elevating mechanism 14 lowers the pair of transfer arms 11 at the transfer operation position, pulls out the lift pins 12 from the through holes 79, and moves the horizontal movement mechanism 13 to open the pair of transfer arms 11, The transfer arm 11 moves to the retreat position. The retracted position of the pair of transfer arms 11 is immediately above the base ring 71 of the holding unit 7. Since the base ring 71 is placed on the bottom surface of the concave portion 62, the retreat position of the transfer arm 11 is inside the concave portion 62. An exhaust mechanism (not shown) is also provided near the portion where the driving unit (the horizontal moving mechanism 13 and the elevating mechanism 14) of the transfer mechanism 10 is provided, and an atmosphere around the driving unit of the transfer mechanism 10 is provided. Is discharged to the outside of the chamber 6.

  Returning to FIG. 1, the flash heating unit 5 provided above the chamber 6 includes a light source including a plurality of (30 in this embodiment) xenon flash lamps FL and a light source above the light source. And a reflector 52 provided so as to cover the reflector. A lamp light emission window 53 is mounted on the bottom of the housing 51 of the flash heating unit 5. The lamp light emission window 53 constituting the floor of the flash heating unit 5 is a plate-shaped quartz window made of quartz. When the flash heating unit 5 is installed above the chamber 6, the lamp light emission window 53 faces the upper chamber window 63. The flash 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.

  The plurality of flash lamps FL are rod-shaped lamps each having a long cylindrical shape, and each of the plurality of flash lamps FL has a longitudinal direction along the main surface of the semiconductor wafer W held by the holding unit 7 (that is, along the horizontal direction). They are arranged in a plane so as to be parallel to each other. Therefore, the plane formed by the arrangement of the flash lamps FL is also a horizontal plane. The area where the plurality of flash lamps FL are arranged is larger than the plane size of the semiconductor wafer W.

  The xenon flash lamp FL has a rod-shaped glass tube (discharge tube) in which xenon gas is sealed and an anode and a cathode connected to a condenser are disposed at both ends thereof, and is provided on the outer peripheral surface of the glass tube. And a trigger electrode. Since xenon gas is electrically an insulator, electricity does not flow in a glass tube in a normal state even if charges are stored in a capacitor. However, when a high voltage is applied to the trigger electrode to break the insulation, the electricity stored in the capacitor flows instantaneously into the glass tube, and light is emitted by the excitation of xenon atoms or molecules at that time. In such a xenon flash lamp FL, since the electrostatic energy stored in the condenser in advance is converted into an extremely short light pulse of 0.1 to 100 milliseconds, continuous lighting such as a halogen lamp HL is performed. It has a feature that it can emit extremely strong light compared to a light source. That is, the flash lamp FL is a pulsed lamp that emits light instantaneously in a very short time of less than one second. The light emission time of the flash lamp FL can be adjusted by the coil constant of a lamp power supply that supplies power to the flash lamp FL.

  The reflector 52 is provided above the plurality of flash lamps FL so as to cover the entirety. The basic function of the reflector 52 is to reflect flash light emitted from the plurality of flash lamps FL to the heat treatment space 65 side. The reflector 52 is made of an aluminum alloy plate, and its surface (the surface facing the flash lamp FL) is roughened by blasting.

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

  FIG. 7 is a plan view showing an arrangement of a plurality of halogen lamps HL. The forty halogen lamps HL are arranged in two upper and lower stages. Twenty halogen lamps HL are arranged in an upper stage near the holding unit 7 and 20 halogen lamps HL are arranged in a lower stage farther from the holding unit 7 than the upper stage. Each halogen lamp HL is a rod-shaped lamp having a long cylindrical shape. The upper and lower 20 halogen lamps HL are arranged so that their respective longitudinal directions are parallel to each other along the main surface of the semiconductor wafer W held by the holder 7 (that is, along the horizontal direction). I have. Therefore, the plane formed by the arrangement of the halogen lamps HL in both the upper and lower stages is a horizontal plane.

  Further, as shown in FIG. 7, the arrangement density of the halogen lamps HL in the region opposed to the peripheral portion is higher than the region opposed to the central portion of the semiconductor wafer W held by the holding portion 7 in both the upper and lower stages. I have. That is, in both upper and lower stages, the arrangement pitch of the halogen lamps HL is shorter at the periphery than at the center of the lamp array. For this reason, it is possible to irradiate a larger amount of light to the peripheral portion of the semiconductor wafer W where the temperature is likely to decrease during heating by light irradiation from the halogen heating unit 4.

  Further, a lamp group composed of the upper halogen lamps HL and a lamp group composed of the lower halogen lamps HL are arranged so as to intersect in a grid pattern. That is, a total of 40 halogen lamps HL are arranged such that the longitudinal direction of the 20 halogen lamps HL arranged in the upper stage and the longitudinal direction of the 20 halogen lamps HL arranged in the lower stage are orthogonal to each other. I have.

  The halogen lamp HL is a filament type light source that emits light by incandescent the filament by energizing the filament disposed inside the glass tube. A gas in which a trace amount of a halogen element (iodine, bromine, or the like) is introduced into an inert gas such as nitrogen or argon is sealed inside the glass tube. By introducing a halogen element, it is possible to set the temperature of the filament to a high temperature while suppressing breakage of the filament. Therefore, the halogen lamp HL has a characteristic that it has a longer life and can continuously emit strong light as compared with a normal incandescent lamp. That is, the halogen lamp HL is a continuous lighting lamp that emits light continuously for at least one second. Further, since the halogen lamp HL is a rod-shaped lamp, it has a long life. By arranging the halogen lamp HL along the horizontal direction, the radiation efficiency to the upper semiconductor wafer W becomes excellent.

  A reflector 43 is also provided below the two-stage halogen lamp HL in the housing 41 of the halogen heating unit 4 (FIG. 1). The reflector 43 reflects the light emitted from the plurality of halogen lamps HL to the heat treatment space 65 side.

  The control unit 3 controls the various operation mechanisms described above provided in the heat treatment apparatus 1. The configuration of the control unit 3 as hardware is the same as that of a general computer. That is, the control unit 3 includes a CPU that is a circuit for performing various arithmetic processing, a ROM that is a read-only memory that stores a basic program, a RAM that is a readable and writable memory that stores various information, and control software and data. It has a magnetic disk for storing. The processing in the heat treatment apparatus 1 proceeds when the CPU of the control unit 3 executes a predetermined processing program.

  In addition to the above-described configuration, the heat treatment apparatus 1 prevents an excessive rise in temperature of the halogen heating unit 4, the flash heating unit 5, and the chamber 6 due to heat energy generated from the halogen lamp HL and the flash lamp FL during the heat treatment of the semiconductor wafer W. Therefore, it has various cooling structures. For example, a water cooling tube (not shown) is provided on the wall of the chamber 6. Further, the halogen heating unit 4 and the flash heating unit 5 have an air cooling structure that forms a gas flow inside and discharges 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.

  Next, a processing operation in the heat treatment apparatus 1 will be described. First, the procedure of the heat treatment for the semiconductor wafer W to be processed will be described. Here, the semiconductor wafer W to be processed is a semiconductor substrate having a gallium arsenide semiconductor thin film formed on a silicon base material. The activation of the impurities implanted in the gallium arsenide semiconductor thin film is performed by flash light irradiation heat treatment (annealing) by the heat treatment apparatus 1. The processing procedure of the semiconductor wafer W described below proceeds by the control unit 3 controlling each operation mechanism of the heat treatment apparatus 1.

  First, the air supply valve 84 is opened, and the exhaust valve 89 is opened, and air supply and exhaust to the chamber 6 are started. When the air supply valve 84 is opened, nitrogen gas is supplied from the gas supply hole 81 to the heat treatment space 65. When the exhaust valve 89 is opened, the gas in the chamber 6 is exhausted from the gas exhaust hole 86. Thereby, 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.

  Subsequently, the gate valve 185 is opened to open the transfer opening 66, and the semiconductor wafer W to be processed is carried into the heat treatment space 65 in the chamber 6 via the transfer opening 66 by the transfer robot outside the apparatus. At this time, there is a possibility that the atmosphere outside the apparatus may be involved when the semiconductor wafer W is loaded, but since the nitrogen gas is continuously supplied to the chamber 6, the nitrogen gas flows out from the transfer opening 66, and Entrapment of an external atmosphere can be minimized.

  The semiconductor wafer W carried in by the transfer robot advances to a position immediately above the holding unit 7 and stops. When the pair of transfer arms 11 of the transfer mechanism 10 move horizontally from the retreat position to the transfer operation position and rise, the lift pins 12 protrude from the upper surface of the holding plate 75 of the susceptor 74 through the through holes 79. To receive the semiconductor wafer W. At this time, the lift pins 12 rise above the upper ends of the substrate support pins 77.

  After the semiconductor wafer W is placed on the lift pins 12, the transfer robot exits the heat treatment space 65, and the transfer opening 66 is closed by the gate valve 185. When the pair of transfer arms 11 is lowered, the semiconductor wafer W is transferred from the transfer mechanism 10 to the susceptor 74 of the holding unit 7 and is held from below in a horizontal posture. The semiconductor wafer W is supported by a plurality of substrate support pins 77 erected on a holding plate 75 and held by a susceptor 74. The semiconductor wafer W is held by the holder 7 with the surface on which the gallium arsenide semiconductor thin film is formed as the upper surface. A predetermined gap is formed between the back surface (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 have descended to below the susceptor 74 are retracted by the horizontal moving mechanism 13 to the retracted position, that is, to the inside of the recess 62.

  After the semiconductor wafer W is held from below in a horizontal position by the susceptor 74 of the holding unit 7 formed of quartz, the 40 halogen lamps HL of the halogen heating unit 4 are simultaneously turned on to perform preliminary heating (assist heating). ) Is started. The halogen light emitted from the halogen lamp HL passes through the lower chamber window 64 and the susceptor 74 formed of quartz and irradiates the lower surface of the semiconductor wafer W. Upon receiving the light irradiation from the halogen lamp HL, the semiconductor wafer W is preheated and the temperature rises. Since the transfer arm 11 of the transfer mechanism 10 is retracted inside the concave portion 62, there is no obstacle to heating by the halogen lamp HL.

  When performing preheating by the halogen lamp HL, the temperature of the semiconductor wafer W is measured by the radiation thermometer 20. That is, the radiation thermometer 20 receives infrared light radiated from the lower surface of the semiconductor wafer W held by the susceptor 74 through the opening 78 through the transparent window 21 and measures the temperature of the wafer being heated. The measured temperature of the semiconductor wafer W is transmitted to the control unit 3. The control unit 3 controls the output of the halogen lamp HL while monitoring whether or not the temperature of the semiconductor wafer W which is heated by the irradiation of light from the halogen lamp HL has reached a predetermined preheating temperature T1. That is, the control unit 3 performs feedback control of the output of the halogen lamp HL based on the value measured by the radiation thermometer 20 so that the temperature of the semiconductor wafer W becomes the preheating temperature T1.

  After the temperature of the semiconductor wafer W reaches the preheating temperature T1, the control unit 3 temporarily maintains the semiconductor wafer W at the preheating temperature T1. Specifically, when the temperature of the semiconductor wafer W measured by the radiation thermometer 20 reaches the preheating temperature T1, the control unit 3 adjusts the output of the halogen lamp HL to substantially reduce the temperature of the semiconductor wafer W to the preliminary temperature. The heating temperature T1 is maintained.

  By performing such preheating by the halogen lamp HL, the entire semiconductor wafer W is uniformly heated to the preheating temperature T1. At the stage of preheating by the halogen lamp HL, the temperature of the peripheral portion of the semiconductor wafer W where heat radiation tends to occur tends to be lower than that of the central portion, but the arrangement density of the halogen lamp HL in the halogen heating section 4 is: The region facing the peripheral portion is higher than the region facing the center of the substrate W. For this reason, the amount of light applied to the peripheral portion of the semiconductor wafer W where heat radiation easily occurs is increased, and the in-plane temperature distribution of the semiconductor wafer W in the preheating stage can be made uniform.

  When a predetermined time elapses after the temperature of the semiconductor wafer W reaches the preheating temperature T1, the flash lamp FL of the flash heating unit 5 irradiates the surface of the semiconductor wafer W held by the susceptor 74 with flash light. At this time, a part of the flash light radiated from the flash lamp FL goes directly into the chamber 6, and the other part is once reflected by the reflector 52 and then goes into the chamber 6. The flash heating of the semiconductor wafer W is performed by the irradiation.

  Since the flash heating is performed by irradiating flash light (flash light) from the flash lamp FL, the surface temperature of the semiconductor wafer W can be increased in a short time. That is, the flash light emitted from the flash lamp FL is converted into a light pulse in which the electrostatic energy previously stored in the condenser is extremely short, and the irradiation time is extremely short, from about 0.1 millisecond to about 100 milliseconds. It is a strong flash. Then, the surface temperature of the semiconductor wafer W, which is flash-heated by flash light irradiation from the flash lamp FL, instantaneously rises to the processing temperature T2, and after the impurities injected into the semiconductor wafer W are activated, the surface temperature becomes higher. Falls rapidly. As described above, in the heat treatment apparatus 1, since the surface temperature of the semiconductor wafer W can be raised and lowered in a very short time, it is possible to activate the impurities while suppressing diffusion of the impurities injected into the semiconductor wafer W due to heat. Can be. Since the time required for activating the impurity is extremely shorter than the time required for thermal diffusion, the activation is performed even in a short time in which diffusion of about 0.1 to 100 milliseconds does not occur. Complete.

  After the completion of the flash heating process, the halogen lamp HL is turned off after a lapse of a predetermined time. As a result, the temperature of the semiconductor wafer W rapidly drops from the preheating temperature T1. The temperature of the semiconductor wafer W during the temperature decrease is measured by the radiation thermometer 20, and the measurement result is transmitted to the control unit 3. The control unit 3 monitors whether or not the temperature of the semiconductor wafer W has dropped to a predetermined temperature based on the measurement result of the radiation thermometer 20. Then, after the temperature of the semiconductor wafer W has dropped to a predetermined value or less, the pair of transfer arms 11 of the transfer mechanism 10 move horizontally again from the retreat position to the transfer operation position and rise, so that the lift pins 12 The semiconductor wafer W protruding from the upper surface of the semiconductor wafer 74 and having undergone the heat treatment is received from the susceptor 74. Subsequently, the transfer opening 66 closed by the gate valve 185 is opened, and the semiconductor wafer W mounted on the lift pins 12 is unloaded by the transfer robot outside the apparatus, and the semiconductor wafer W is heated in the heat treatment apparatus 1 by heat treatment. Is completed.

  In the present embodiment, the semiconductor wafer W on which the gallium arsenide semiconductor thin film is formed is subjected to the heat treatment. It is known that gallium arsenide is released from a semiconductor thin film by outward diffusion when heated to 400 ° C. or higher. If the above preheating temperature T1 is 400 ° C. or higher, arsenic is released from the semiconductor wafer W during preheating by the halogen lamp HL. If the processing temperature T2 is 400 ° C. or higher, arsenic is released from the semiconductor wafer W even during flash heating by the flash lamp FL for a short time. Arsenic released from the semiconductor wafer W exists in the heat treatment space 65 in the chamber 6 as a gas. Arsenic is harmful even in a trace amount, and it is necessary to prevent arsenic released from the semiconductor wafer W from being discharged outside the heat treatment apparatus 1.

  For this reason, the heat treatment apparatus 1 is provided with a trap box 90. When the exhaust valve 89 is opened, the atmosphere in the chamber 6 containing arsenic is exhausted from the gas exhaust hole 86 to the gas exhaust pipe 88. The gas containing arsenic flows through the gas exhaust pipe 88 and flows into the trap box 90 from the air supply port 97. As shown in FIG. 9, the gas flowing into the trap box 90 from the air supply port 97 passes between the plurality of cooling pipes 93 of the radiator 92. As the gas containing arsenic passes between the plurality of cooling tubes 93, it is cooled to room temperature, whereby gaseous arsenic precipitates as a solid.

  Subsequently, the gas flow cooled by the radiator 92 collides with the trap plate 95. As shown in FIG. 9, the gas flow colliding with the trap plate 95 changes the direction of the flow downward of the open trap plate 95. At this time, the solid arsenic precipitated by cooling is attached to the trap plate 95 and captured.

  The gas flow directed to the lower side of the trap plate 95 flows to the far side of the trap box 90 beyond the open portion below the trap plate 95. At this time, the gas flow also comes into contact with the surface of the measurement wafer MW placed in the wafer accommodating section 96, and a part of the deposited solid arsenic also adheres to the surface of the measurement wafer MW. Further, a part of the arsenic captured by the trap plate 95 falls on the surface of the measurement wafer MW.

  The gas flow that has passed below the trap plate 95 flows out of the exhaust port 98 again into the gas exhaust pipe 88 and is discharged to the exhaust unit 190. Arsenic contained in the gas flowing from the air supply port 97 of the trap box 90 is precipitated as a solid by being cooled by the radiator 92, and the deposited arsenic adheres to the trap plate 95 and the measurement wafer MW to be captured. Is done. Accordingly, harmful arsenic is not contained in the gas flowing out from the exhaust port 98 of the trap box 90, and harmless gas is discharged from the exhaust unit 190 to the outside of the heat treatment apparatus 1.

  As described above, although arsenic is harmful, it has the property of being precipitated as a solid when cooled to about room temperature. The present invention has been completed by utilizing such characteristics of arsenic. By cooling the gas discharged from the chamber 6 with the radiator 92, the arsenic is deposited as a solid, and the arsenic is harmful. Has been removed. In the present embodiment, the arsenic released from the semiconductor wafer W during the heat treatment is collected and rendered harmless by the trap box 90 having a simple configuration in which the radiator 92 and the trap plate 95 are provided inside the casing 91. . Therefore, it is possible to prevent harmful arsenic from being discharged to the outside with a simple configuration without incorporating a scrubber or a special exclusion device.

  In addition, the measurement wafer MW placed in the wafer accommodating portion 96 is taken out, and particles attached to the surface of the measurement wafer MW are analyzed to confirm whether or not arsenic is deposited and captured. Can be. If arsenic is not detected from the surface of measurement wafer MW, or if the amount of arsenic detected is remarkably small, it is suspected that arsenic may not be sufficiently collected by trap box 90.

  Further, since the radiator 92 and the trap plate 95 are detachably provided, the radiator 92 and the trap plate 95 which are contaminated by the deposition of arsenic can be replaced at an appropriate timing. The radiator 92 and the trap plate 95 may be replaced periodically, or may be replaced based on the state of contamination.

  Although the embodiments of the present invention have been described above, various changes other than those described above can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the radiator 92, the trap plate 95, and the wafer accommodating portion 96 are provided inside the housing 91. However, the trap plate 95 and the wafer accommodating portion 96 are not essential elements. It is sufficient that a radiator 92 is provided in the inside. If at least the radiator 92 is provided, the gas discharged from the chamber 6 can be cooled to deposit arsenic as a solid, and the arsenic can be captured by the inner wall surface of the housing 91. Even in this case, it is possible to prevent arsenic from being discharged to the outside. However, when the trap plate 95 is provided as in the above embodiment, the deposited arsenic can be more reliably captured and recovered.

  Further, in the above embodiment, the gas flow is cooled by the radiator 92 having the plurality of cooling pipes 93. However, the present invention is not limited to this. For example, the gas flow is cooled by another cooling mechanism such as a Peltier device. You may make it cool.

  The heat treatment of the semiconductor wafer W may be performed by setting the inside of the chamber 6 to a reduced pressure atmosphere. Even in this case, the same effect as in the above embodiment can be obtained by depositing and capturing arsenic released from the semiconductor wafer W in the trap box 90. However, when the inside of the chamber 6 is set to a reduced pressure atmosphere, the inside of the trap box 90 is also set to a reduced pressure lower than the atmospheric pressure. Therefore, the material of the trap plate 95 is preferably a metal material that can be used even under reduced pressure.

  Further, in the above embodiment, the flash heating unit 5 is provided with 30 flash lamps FL. However, the present invention is not limited to this, and the number of flash lamps FL can be any number. . The flash lamp FL is not limited to a xenon flash lamp, but may be a krypton flash lamp. Further, the number of halogen lamps HL provided in the halogen heating unit 4 is not limited to 40 but may be any number.

  In the above embodiment, the preheating of the semiconductor wafer W is performed using the filament type halogen lamp HL as a continuous lighting lamp that emits light continuously for 1 second or more. However, the present invention is not limited to this. The preliminary heating may be performed using a discharge type arc lamp (for example, a xenon arc lamp) as a continuous lighting lamp instead of the halogen lamp HL.

  Further, the heating source for heating the semiconductor wafer W is not limited to the lamp. For example, the semiconductor wafer W may be heated by a hot plate having a heater.

  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 for a flat panel display such as a liquid crystal display device or a substrate for a solar cell. The film formed on the substrate is not limited to gallium arsenide, and may be any film containing arsenic. Further, the technology according to the present invention is suitable for heat treatment of a substrate that releases not only arsenic but also harmful substances that precipitate as a solid when cooled.

REFERENCE SIGNS LIST 1 heat treatment device 3 control unit 4 halogen heating unit 5 flash heating unit 6 chamber 7 holding unit 10 transfer mechanism 63 upper chamber window 64 lower chamber window 65 heat treatment space 74 susceptor 88 gas exhaust pipe 90 trap box 91 housing 92 radiator 93 Cooling tube 95 Trap plate 96 Wafer accommodating section FL Flash lamp HL Halogen lamp MW Measurement wafer W Semiconductor wafer

Claims (5)

A heat treatment apparatus for heating a substrate,
A chamber for accommodating the substrate;
A heating source for heating the substrate housed in the chamber,
An exhaust path for exhausting the atmosphere in the chamber;
A trap unit that is provided in the exhaust path and captures a substance contained in the atmosphere;
With
The heat treatment apparatus according to claim 1, wherein the trap unit includes a cooling unit that cools an airflow passing through the housing inside the housing. The heat treatment apparatus according to claim 1,
The heat treatment apparatus according to claim 1, wherein the trap unit further includes a trap plate in which the airflow cooled by the cooling unit collides with the inside of the housing. The heat treatment apparatus according to claim 2,
The heat treatment apparatus according to claim 1, wherein the trap section further includes a housing section for housing a collecting substrate to which the substance deposited by the cooling section cooling the airflow is attached. The heat treatment apparatus according to any one of claims 1 to 3,
The heat treatment apparatus according to claim 1, wherein the heating source includes a lamp that irradiates the substrate with light to heat the substrate. The heat treatment apparatus according to any one of claims 1 to 4,
The heat treatment apparatus, wherein the substance is arsenic.

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