JP6266352B2 - Heat treatment apparatus and heat treatment method - Google Patents

Description

  The present invention relates to a heat treatment apparatus and a heat treatment method for heating a thin plate-shaped precision electronic substrate (hereinafter simply referred to as “substrate”) such as a semiconductor wafer by irradiating flash light.

  In the semiconductor device manufacturing process, impurity introduction is an indispensable step for forming a pn junction in a semiconductor wafer. Currently, impurities are generally introduced by ion implantation and subsequent annealing. The ion implantation method is a technique in which impurity elements such as boron (B), arsenic (As), and phosphorus (P) are ionized and collided with a semiconductor wafer at a high acceleration voltage to physically perform impurity implantation. The implanted impurities are activated by annealing. At this time, if the annealing time is about several seconds or more, the implanted impurities are deeply diffused by heat, and as a result, the junction depth becomes deeper than required, and there is a possibility that good device formation may be hindered.

  Therefore, in recent years, flash lamp annealing (FLA) has attracted attention as an annealing technique for heating a semiconductor wafer in an extremely short time. Flash lamp annealing is a semiconductor wafer in which impurities are implanted by irradiating the surface of the semiconductor wafer with flash light using a xenon flash lamp (hereinafter, simply referred to as “flash lamp” means xenon flash lamp). Is a heat treatment technique for raising the temperature of only the surface of the material in a very short time (several milliseconds or less).

  The radiation spectral distribution of a xenon flash lamp ranges from the ultraviolet region to the near infrared region, has a shorter wavelength than the conventional halogen lamp, and almost coincides with the fundamental absorption band of a silicon semiconductor wafer. Therefore, when the semiconductor wafer is irradiated with flash light from the xenon flash lamp, the semiconductor wafer can be rapidly heated with little transmitted light. Further, it has been found that if the flash light irradiation is performed for a very short time of several milliseconds or less, only the vicinity of the surface of the semiconductor wafer can be selectively heated. For this reason, if the temperature is raised for a very short time by the xenon flash lamp, only the impurity activation can be performed without deeply diffusing the impurities.

  In the heat treatment apparatus using such a flash lamp, the surface temperature of the semiconductor wafer is rapidly increased while the surface temperature of the semiconductor wafer is rapidly increased in order to instantaneously irradiate the surface of the semiconductor wafer with flash light having extremely high energy. It will not rise that much. For this reason, rapid thermal expansion occurs only on the surface of the semiconductor wafer, and the semiconductor wafer is deformed so as to warp with the upper surface convex. Then, at the next moment, the semiconductor wafer was deformed so as to warp with the bottom surface convex by reaction.

  When the semiconductor wafer is deformed so that the upper surface is convex, the edge of the wafer collides with the susceptor. On the contrary, when the semiconductor wafer is deformed so that the lower surface is convex, the central portion of the wafer has collided with the susceptor. As a result, there has been a problem that the semiconductor wafer is cracked by an impact that collides with the susceptor.

  When a wafer crack occurs during flash heating, it is necessary to quickly detect the crack, stop the introduction of the subsequent semiconductor wafer, and clean the chamber. Also, from the viewpoint of preventing adverse effects such as particles generated by wafer cracking scattering outside the chamber and adhering to the subsequent semiconductor wafer, the semiconductor inside the chamber is opened before opening the inlet / outlet of the chamber immediately after flash heating. It is preferable to detect cracks in the wafer.

  For this reason, for example, in Patent Document 1, a light projecting unit and a light receiving unit are connected to a support pin that supports a semiconductor wafer, and reflected light of light incident on the support pin from the light projecting unit is received by the light receiving unit. A heat treatment apparatus for detecting cracks in a semiconductor wafer by determining the above is disclosed. When the semiconductor wafer is cracked during flash heating, the light incident on the support pins is not reflected by the lower surface of the semiconductor wafer, and the wafer crack is detected by utilizing the fact that the intensity of the light received by the light receiving part is greatly reduced. -ing

JP 2009-278069 A

  However, in the apparatus disclosed in Patent Document 1, light is applied to a part of a semiconductor wafer and the reflected light is measured. For this reason, it can be detected when the semiconductor wafer is largely cracked, but when only a part of the peripheral edge of the semiconductor wafer is cracked, the crack may not be detected.

  In order to detect such a defect in only a part of the peripheral edge of the semiconductor wafer, it is conceivable to provide an imaging camera to image the entire semiconductor wafer and analyze the image data. However, since the lamps are arranged at a high density at a position where the entire semiconductor wafer can be accommodated, it has been difficult to install an imaging camera. Even if the image pickup camera is forcibly installed, the image pickup camera itself is exposed to flash light, which causes a problem of damaging the image pickup camera. Furthermore, when a halogen lamp is used for preheating, the light from the halogen lamp also enters the imaging camera, and the captured image may be significantly deteriorated.

  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 apparatus and a heat treatment method capable of reliably detecting a crack in a substrate during flash light irradiation in a chamber.

In order to solve the above-mentioned problems, a first aspect of the present invention provides a heat treatment apparatus for heating a substrate by irradiating the substrate with flash light, a chamber for accommodating the substrate, and a holding means for holding the substrate in the chamber. And a flash lamp for irradiating the substrate held by the holding means with flash light, an illuminating means for irradiating the substrate with light, and emitted from the illuminating means and reflected over the entire circumference of the peripheral edge of the substrate. It is characterized by comprising: a light receiving means for receiving light; and a detecting means for detecting cracks in the substrate based on the light received by the light receiving means.

  According to a second aspect of the present invention, in the heat treatment apparatus according to the first aspect of the invention, the detecting means is configured to apply the reflected light received by the light receiving means and the flash light before irradiating the flash light from the flash lamp. The crack of the substrate is detected from a comparison with the reflected light received by the light receiving means.

  According to a third aspect of the present invention, in the heat treatment apparatus according to the first or second aspect of the invention, the light receiving means is disposed immediately below the center of the substrate held by the holding means, A light guide unit that receives and guides reflected light from a predetermined position of the light guide unit, and a rotation unit that rotates the light guide unit around the center line of the substrate.

  According to a fourth aspect of the present invention, in the heat treatment apparatus according to the third aspect of the present invention, the light receiving means receives the reflected light guided by the light guide section, converts it into an electrical signal, and transmits it to the detection means. And a photodiode.

  The invention of claim 5 is the heat treatment apparatus according to claim 4 of the invention, in which laser light is incident on the light guide portion and emitted toward the peripheral edge of the substrate held by the holding means. A laser light irradiation unit, a light receiving mode in which reflected light from the peripheral portion of the substrate reaches the photodiode from the light guide unit, and an irradiation mode in which light emitted from the laser light irradiation unit is incident on the light guide unit And switching means for switching to any of the above.

  According to a sixth aspect of the present invention, in the heat treatment apparatus according to the fourth aspect of the present invention, laser light is incident on the light guide portion and emitted toward the peripheral portion of the substrate held by the holding means. A laser beam irradiation unit; and a branch fiber that causes reflected light from the peripheral portion of the substrate to reach the photodiode from the light guide unit, and allows light emitted from the laser beam irradiation unit to enter the light guide unit Are further provided.

  The invention of claim 7 is the heat treatment apparatus according to any one of claims 1 to 6, wherein the illuminating means is a halogen lamp for preheating the substrate before flash light irradiation. And

The invention according to claim 8 is the heat treatment method for heating the substrate by irradiating the substrate with flash light, and the light emitted from the illumination means and reflected over the entire periphery of the peripheral portion of the substrate before the flash light irradiation. A first light receiving step for receiving light, a flash heating step for irradiating the substrate with flash light from a flash lamp, and light emitted from the illumination means after being irradiated with flash light and reflected over the entire periphery of the peripheral portion of the substrate. A second light receiving step for receiving light, and a detection step for detecting cracks in the substrate from a comparison between the reflected light received in the first light receiving step and the reflected light received in the second light receiving step. It is characterized by that.

  According to a ninth aspect of the present invention, in the heat treatment method according to the eighth aspect of the present invention, in the first light receiving step and the second light receiving step, the first light receiving step and the second light receiving step are arranged immediately below the center of the substrate, A light guide unit that receives and guides reflected light from a predetermined position is rotated.

  The invention of claim 10 is the heat treatment method according to claim 9 of the invention, further comprising the step of causing the laser light to be incident on the light guide and emitting the laser light toward the peripheral edge of the substrate. Features.

According to the first to seventh aspects of the present invention, the light emitted from the illuminating means and reflected over the entire circumference of the peripheral portion of the substrate is received, and the crack of the substrate is detected based on the received light. When the substrate is cracked, the peripheral edge always has a defect. Therefore, if the crack is detected based on the reflected light over the entire periphery of the substrate, the substrate can be reliably detected in the chamber during flash light irradiation. Can do.

  In particular, according to the second aspect of the present invention, since the crack of the substrate is detected from the comparison between the reflected light received before irradiating the flash light from the flash lamp and the reflected light received after the flash light irradiation, the reflected light measurement is performed. It is possible to accurately detect a crack in the substrate by eliminating the influence of the background at the time.

  In particular, according to the third aspect of the present invention, the light guide portion that is disposed immediately below the center of the substrate and receives and guides reflected light from a predetermined position in the peripheral portion of the substrate is centered on the center line of the substrate. Since it is rotated, the reflected light can be received over the entire circumference of the peripheral edge of the substrate with a simple configuration.

  In particular, according to the invention of claim 5 and claim 6, since the laser light irradiating part for making the light beam incident on the light guide part and emitting the laser light toward the peripheral part of the substrate is provided, the in-plane temperature of the substrate The uniformity of distribution can be improved.

According to the eighth to tenth aspects of the present invention, the light emitted from the illuminating means before the flash light irradiation and reflected over the entire circumference of the peripheral portion of the substrate is received, and is emitted from the illuminating means after the flash light irradiation. Then, the light reflected over the entire periphery of the substrate is received, and cracks in the substrate are detected from a comparison of the reflected light. When the substrate is cracked, the peripheral edge always has a defect. Therefore, if the crack is detected based on the reflected light over the entire periphery of the substrate, the substrate can be reliably detected in the chamber during flash light irradiation. Can do. Further, since the reflected light before and after the flash light irradiation is compared, the influence of the background at the time of the reflected light measurement can be eliminated and the crack of the substrate can be accurately detected.

  In particular, according to the ninth aspect of the present invention, since the light guide unit that is disposed immediately below the center of the substrate and receives and guides the reflected light from a predetermined position in the peripheral portion of the substrate is rotated, the structure is simplified. Thus, the reflected light can be received over the entire circumference of the peripheral edge of the substrate.

  In particular, according to the invention of claim 10, the method further includes the step of emitting the laser light to the light guide portion and emitting the laser light toward the peripheral portion of the substrate, thereby improving the uniformity of the in-plane temperature distribution of the substrate. Can be made.

It is a longitudinal cross-sectional view which shows the structure of the heat processing apparatus which concerns on this invention. It is a perspective view of a holding part. It is a top view of a susceptor. It is the figure which expanded the support pin vicinity when a semiconductor wafer was mounted in the susceptor. It is a top view of a transfer mechanism. It is a side view of a transfer mechanism. It is a top view which shows arrangement | positioning of a some halogen lamp. It is a figure which shows the structure of a light-receiving part. It is a longitudinal cross-sectional view of a light guide rod. It is a block diagram which shows the structure of a detection part. It is a flowchart which shows the process sequence in the heat processing apparatus of FIG. It is a flowchart which shows the process sequence in the heat processing apparatus of FIG. It is a figure which shows a mode that the light reception mode is selected and the intensity | strength of the reflected light from a semiconductor wafer is measured. It is a figure which shows a mode that the irradiation mode is selected and a laser beam is irradiated to the peripheral part of a semiconductor wafer. It is a figure which shows an example of the reflected light intensity before flash light irradiation. It is a figure which shows an example of the reflected light intensity after flash light irradiation. It is a figure which shows an example of difference data. It is a figure which shows the structural example at the time of using a branch fiber.

  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 the present embodiment is a flash lamp annealing apparatus that heats a semiconductor wafer W by irradiating a disk-shaped semiconductor wafer W as a substrate with flash light irradiation. The size of the semiconductor wafer W to be processed is not particularly limited, and is, for example, φ300 mm or φ450 mm. Impurities are implanted into the semiconductor wafer W before being carried into the heat treatment apparatus 1, and an activation process of the impurities implanted by the heat treatment by the heat treatment apparatus 1 is executed. In FIG. 1 and the subsequent drawings, the size and number of each part are exaggerated or simplified as necessary for easy understanding.

  The heat treatment apparatus 1 includes a chamber 6 that accommodates a semiconductor wafer W, a flash heating unit 5 that houses a plurality of flash lamps FL, and a halogen heating unit 4 that houses a plurality of halogen lamps HL. A flash heating unit 5 is provided on the upper side of the chamber 6, and a halogen heating unit 4 is provided on the lower side. The heat treatment apparatus 1 includes a holding unit 7 that holds the semiconductor wafer W in a horizontal posture inside the chamber 6, and a transfer mechanism 10 that transfers the semiconductor wafer W between the holding unit 7 and the outside of the apparatus, Is provided. Furthermore, the heat treatment apparatus 1 includes a control unit 3 that controls the operation mechanisms provided in the halogen heating unit 4, the flash heating unit 5, and the chamber 6 to perform 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 upper and lower openings. The upper opening is closed by an upper chamber window 63 and the lower opening is closed by a lower chamber window 64. ing. 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 portion of the chamber 6 is also a disk-shaped member made of quartz and functions as a quartz window that transmits light from the halogen heating unit 4 into the chamber 6.

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

  By attaching the reflection rings 68 and 69 to the chamber side portion 61, a recess 62 is formed on the inner wall surface of the chamber 6. That is, a recess 62 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 is formed. . The recess 62 is formed in an annular shape along the horizontal direction on the inner wall surface of the chamber 6, and surrounds the holding portion 7 that holds the semiconductor wafer W.

  The chamber side portion 61 and the reflection rings 68 and 69 are formed of a metal material (for example, stainless steel) having excellent strength and heat resistance. Further, the inner peripheral surfaces of the reflection rings 68 and 69 are mirrored by electrolytic nickel plating.

  The chamber side 61 is formed with a transfer opening (furnace port) 66 for carrying the semiconductor wafer W into and out of the chamber 6. The transfer 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 recess 62. Therefore, when the gate valve 185 opens the transfer opening 66, the semiconductor wafer W is carried into the heat treatment space 65 through the recess 62 from the transfer opening 66 and the semiconductor wafer W is carried out from the heat treatment space 65. It can be performed. Further, when the gate valve 185 closes the transfer opening 66, the heat treatment space 65 in the chamber 6 becomes a sealed space.

Further, a gas supply hole 81 for supplying a processing gas (nitrogen gas (N ₂ ) in the present embodiment) to the heat treatment space 65 is formed in the upper portion of the inner wall of the chamber 6. The gas supply hole 81 is formed at a position above the recess 62 and may be provided in the reflection ring 68. The gas supply hole 81 is connected to a gas supply pipe 83 through 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 gas supply source 85. A valve 84 is inserted in the middle of the path of the gas supply pipe 83. When the valve 84 is opened, nitrogen gas is supplied from the gas supply source 85 to the buffer space 82. The nitrogen 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 hole 81 and is supplied from the gas supply hole 81 into the heat treatment space 65. Note that the processing gas is not limited to nitrogen gas, but is an inert gas such as argon (Ar) or helium (He), or oxygen (O ₂ ), hydrogen (H ₂ ), chlorine (Cl ₂ ), A reactive gas such as hydrogen chloride (HCl), ozone (O ₃ ), or ammonia (NH ₃ ) may be used.

  On the other hand, a gas exhaust hole 86 for exhausting the gas in the heat treatment space 65 is formed in the lower portion of the inner wall of the chamber 6. The gas exhaust hole 86 is formed at a position lower than the recess 62 and may be provided in the reflection 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 the exhaust unit 190. A valve 89 is inserted in the middle of the path of the gas exhaust pipe 88. When the valve 89 is opened, the gas in the heat treatment space 65 is discharged from the gas exhaust hole 86 to the gas exhaust pipe 88 through the buffer space 87. 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. Further, the gas supply source 85 and the exhaust unit 190 may be a mechanism provided in the heat treatment apparatus 1 or may be a utility of a factory where the heat treatment apparatus 1 is installed.

  A gas exhaust pipe 191 that exhausts the gas in the heat treatment space 65 is also connected to the tip of the transfer opening 66. The gas exhaust pipe 191 is connected to the exhaust unit 190 via a valve 192. By opening the valve 192, the gas in the chamber 6 is exhausted through the transfer opening 66.

  FIG. 2 is a perspective view of the holding unit 7. The holding unit 7 includes a base ring 70 and a susceptor 74. The base ring 70 is made of quartz, and is configured by a plurality of claw portions 72 (four in this embodiment) standing on an annular ring portion 71. FIG. 3 is a plan view of the susceptor 74. The susceptor 74 is a circular flat plate member made of quartz. The diameter of the susceptor 74 is larger than the diameter of the semiconductor wafer W. That is, the susceptor 74 has a larger planar size than the semiconductor wafer W. A plurality of support pins 75 are erected on the upper surface of the susceptor 74. In the present embodiment, a total of six support pins 75 are provided upright every 60 ° along a circumference that is concentric with the outer circumference of the susceptor 74. The diameter of the circle in which the six support pins 75 are arranged (the distance between the support pins 75 facing each other) is smaller than the diameter of the semiconductor wafer W. Each support pin 75 is made of quartz. The number of support pins 75 is not limited to six, and may be three or more that can stably support the semiconductor wafer W.

  Further, on the upper surface of the susceptor 74, a plurality of (five in the present embodiment) guide pins 76 are erected concentrically with the six support pins 75. The diameter of the circle in which the five guide pins 76 are arranged is slightly larger than the diameter of the semiconductor wafer W. Each guide pin 76 is made of quartz. Instead of the plurality of guide pins 76, an annular member having a tapered surface that forms a predetermined angle with the horizontal plane may be provided so as to expand upward. Further, the susceptor 74 is provided with four through holes 79 through which lift pins 12 of the transfer mechanism 10 to be described later penetrate for the delivery of the semiconductor wafer W.

  The base ring 70 is attached to the chamber 6 by placing the ring portion 71 on the bottom surface of the recess 62. The susceptor 74 is placed on the claw 72 of the base ring 70 attached to the chamber 6. The semiconductor wafer W carried into the chamber 6 is placed in a horizontal posture on the susceptor 74 held by the base ring 70.

  FIG. 4 is an enlarged view of the vicinity of the support pins 75 when the semiconductor wafer W is placed on the susceptor 74. A support rod 73 is erected on each claw portion 72 of the base ring 70. When the upper end portion of the support rod 73 is fitted into a recess formed in the lower surface of the susceptor 74, the susceptor 74 is held on the base ring 70 without being displaced.

  The support pin 75 and the guide pin 76 are also erected by being fitted into a recess formed in the upper surface of the susceptor 74. The upper ends of the support pin 75 and the guide pin 76 erected on the upper surface of the susceptor 74 protrude from the upper surface. The semiconductor wafer W is supported by point contact by a plurality of support pins 75 erected on the susceptor 74 and placed on the susceptor 74. The semiconductor wafer W is supported by a plurality of support pins 75 at a predetermined interval from the upper surface of the susceptor 74. Further, the height position of the upper end of the guide pin 76 is higher than the upper end of the support pin 75, and the horizontal displacement of the semiconductor wafer W is prevented by the plurality of guide pins 76. The support pins 75 and the guide pins 76 may be processed with quartz integrally with the susceptor 74.

  Further, when the annular member having the tapered surface is provided instead of the guide pin 76, the horizontal displacement of the semiconductor wafer W is prevented by the annular member. And the area | region which opposes the semiconductor wafer W supported by the at least some support pin 75 among the upper surfaces of the susceptor 74 becomes a plane.

  As shown in FIGS. 2 and 3, the susceptor 74 has an opening 78 and a notch 77 penetrating vertically. The notch 77 is provided to pass the probe tip of the contact thermometer 130 using a thermocouple. On the other hand, the opening 78 is provided for receiving radiation light (infrared light) emitted from the lower surface of the semiconductor wafer W held by the holding plate 74 by the radiation thermometer 120.

  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 has an arc shape that follows the generally annular recess 62. Two lift pins 12 are erected on each transfer arm 11. Each transfer arm 11 can be rotated by a horizontal movement mechanism 13. The horizontal movement mechanism 13 includes a transfer operation position (a position indicated by a solid line in FIG. 5) for transferring the pair of transfer arms 11 to the holding unit 7 and the semiconductor wafer W held by the holding unit 7. It is moved horizontally between the retracted positions (two-dot chain line positions in FIG. 5) that do not overlap in plan view. As the horizontal movement mechanism 13, each transfer arm 11 may be rotated by an individual motor, or a pair of transfer arms 11 may be interlocked by a single motor using a link mechanism. It may be moved.

  The pair of transfer arms 11 are moved up and down together with the horizontal moving mechanism 13 by the lifting mechanism 14. When the elevating mechanism 14 raises the pair of transfer arms 11 at the transfer operation position, a total of four lift pins 12 pass through through holes 79 (see FIGS. 2 and 3) formed in the susceptor 74, and the lift pins The upper end of 12 protrudes from the upper surface of the susceptor 74. On the other hand, when the elevating mechanism 14 lowers the pair of transfer arms 11 at the transfer operation position, the lift pins 12 are extracted from the through holes 79, and the horizontal movement mechanism 13 moves the pair of transfer arms 11 so as to open each of them. The transfer arm 11 moves to the retracted position. The retracted position of the pair of transfer arms 11 is directly above the ring portion 71 of the base ring 70. Since the ring portion 71 is placed on the bottom surface of the recess 62, the retracted position of the transfer arm 11 is inside the recess 62. Note that an exhaust mechanism (not shown) is also provided in the vicinity of the portion where the drive unit (the horizontal movement mechanism 13 and the lifting mechanism 14) of the transfer mechanism 10 is provided, and the atmosphere around the drive unit of the transfer mechanism 10 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 the present embodiment) xenon flash lamps FL inside the housing 51, and an upper part of the light source. And a reflector 52 provided so as to cover. A lamp light emission window 53 is mounted on the bottom of the casing 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-like quartz window made of quartz. By installing the flash heating unit 5 above the chamber 6, the lamp light emission window 53 faces the upper chamber window 63. The flash 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.

  Each of the plurality of flash lamps FL is a rod-shaped lamp having a long cylindrical shape, and the longitudinal direction of each of the flash lamps FL is along the main surface of the semiconductor wafer W supported by the susceptor 7 (that is, along the horizontal direction). They are arranged in a plane so as to be parallel. Therefore, the plane formed by the arrangement of the flash lamps FL is also a horizontal plane.

  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 capacitor at both ends thereof, and an outer peripheral surface of the glass tube. And a triggered electrode. Since xenon gas is an electrical insulator, electricity does not flow into the glass tube under normal conditions even if electric charges are accumulated in the capacitor. However, when the insulation is broken by applying a high voltage to the trigger electrode, the electricity stored in the capacitor flows instantaneously in the glass tube, and light is emitted by excitation of atoms or molecules of xenon at that time. In such a xenon flash lamp FL, the electrostatic energy previously stored in the capacitor is converted into an extremely short light pulse of 0.1 to 100 milliseconds, so that the continuous lighting such as the halogen lamp HL is possible. It has the characteristic that it can irradiate extremely strong light compared with a light source. That is, the flash lamp FL is a pulse light emitting lamp that emits light instantaneously in an extremely short time of less than 1 second. The light emission time of the flash lamp FL can be adjusted by the coil constant of the lamp power source that supplies power to the flash lamp FL.

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

  A plurality of halogen lamps HL (40 in this embodiment) are built in the halogen heating unit 4 provided below the chamber 6. The plurality of halogen lamps HL irradiate the heat treatment space 65 from below the chamber 6 through the lower chamber window 64. FIG. 7 is a plan view showing the arrangement of the plurality of halogen lamps HL. In the present embodiment, 20 halogen lamps HL are arranged in two upper and lower stages. Each halogen lamp HL is a rod-shaped lamp having a long cylindrical shape. The 20 halogen lamps HL in both the upper and lower stages are arranged so that their longitudinal directions are parallel to each other along the main surface of the semiconductor wafer W held by the holding unit 7 (that is, along the horizontal direction). Yes. Therefore, the plane formed by the arrangement of the halogen lamps HL in both the upper stage and the lower stage is a horizontal plane.

  Further, as shown in FIG. 7, the arrangement density of the halogen lamps HL in the region facing the peripheral portion is higher than the region facing the central portion of the semiconductor wafer W held by the holding portion 7 in both the upper stage and the lower stage. Yes. That is, in both the upper and lower stages, the arrangement pitch of the halogen lamps HL is shorter on the end side than on the center part 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, the lamp group composed of the upper halogen lamp HL and the lamp group composed of the lower halogen lamp HL are arranged so as to intersect in a lattice pattern. That is, a total of 40 halogen lamps HL are arranged so that the longitudinal direction of the upper halogen lamps HL and the longitudinal direction of the lower halogen lamps HL are orthogonal to each other.

  The halogen lamp HL is a filament-type light source that emits light by making the filament incandescent by energizing the filament disposed inside the glass tube. Inside the glass tube, a gas obtained by introducing a trace amount of a halogen element (iodine, bromine, etc.) into an inert gas such as nitrogen or argon is enclosed. By introducing a halogen element, it is possible to set the filament temperature to a high temperature while suppressing breakage of the filament. Therefore, the halogen lamp HL has a characteristic that it has a longer life than a normal incandescent bulb and can continuously radiate strong light. 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, and by arranging the halogen lamp HL along the horizontal direction, the radiation efficiency to the upper semiconductor wafer W becomes excellent.

  In the present embodiment, the light receiving unit 40 is provided below the holding unit 7. FIG. 8 is a diagram illustrating a configuration of the light receiving unit 40. In FIG. 8, for convenience of illustration, the configurations of the halogen heating unit 4 and the chamber 6 are simplified. The light receiving unit 40 includes a light guide rod 45, a rotation motor 44, and a photodiode 41. Further, a lens 43, a switching mirror 46, and a laser unit 48 are provided along with the light receiving unit 40. The light receiving unit 40 receives light from the lower peripheral edge of the semiconductor wafer W held by the holding unit 7 at the upper end of the light guide rod 45 and guides it to the photodiode 41.

  FIG. 9 is a longitudinal sectional view of the light guide rod 45. The light guide rod 45 is a substantially rod-shaped optical member made of quartz. The light guide rod 45 includes a light receiving head portion 45a located at the upper end and a light guide portion 45b provided below the light receiving head portion 45a along the vertical direction. The light guide portion 45b has a cylindrical shape, and in the present embodiment, the diameter is 15 mm. The light receiving head portion 45a is formed with a reflecting surface 45c and an incident surface 45d. In the present embodiment, the incident surface 45d is formed along the vertical direction, and the angle α formed by the reflecting surface 45c and the horizontal plane is 56.7 °. The light guide rod 45 may be manufactured by cutting out the reflection surface 45c and the incident surface 45d from one cylindrical quartz rod, or the light receiving head portion 45a and the light guide portion 45b are separated from each other. You may make it adhere | attach as a member.

  The light guide rod 45 is disposed immediately below the center of the semiconductor wafer W held by the holding unit 7. Specifically, the center line CX (FIG. 8) penetrating the center of the semiconductor wafer W held by the holding unit 7 in a horizontal posture in the vertical direction is aligned with the center axis of the cylindrical light guide unit 45b. An optical rod 45 is provided.

  As shown in FIG. 8, the light guide rod 45 is rotated about the central axis of the light guide part 45 b (that is, the center line CX of the semiconductor wafer W) by the rotation motor 44 provided below the halogen heating part 4. It is possible. The rotation motor 44 of the present embodiment is a hollow motor having a hollow motor shaft, and the lower end of the light guide portion 45b is inserted into the hollow portion. And the lens 43 is arrange | positioned in the position facing the lower end surface of the light guide part 45b, and the switching mirror 46 is arrange | positioned under the lens 43 further. The posture of the switching mirror 46 is changed by the posture control motor 47. The photodiode 41 is provided on the side of the switching mirror 46.

  The upper end side of the light guide part 45b of the light guide rod 45 passes through the bottom wall of the halogen heating part 4 and a reflector for the halogen lamp HL (not shown). You may make it provide a bearing in the site | part through which the light guide part 45b penetrates the bottom wall of the halogen heating part 4. FIG. The light guide portion 45b is further provided so as to pass through the gap in the arrangement of the halogen lamps HL (see FIG. 7) and to have its upper end positioned at least above the upper halogen lamp HL. A light receiving head portion 45a is connected to the upper end of the light guide portion 45b. For this reason, even when the light guide rod 45 rotates, the contact between the light guide rod 45 and the halogen lamp HL is prevented.

  When the halogen lamp HL of the halogen heating unit 4 is lit with a very weak output (for example, an output of about 1%), the halogen lamp HL functions as an illuminating means, and the semiconductor wafer held by the holding unit 7 The lower surface of W will be illuminated. Since the susceptor 74 and the support pin 75 of the holding unit 7 are made of quartz, the light from the halogen lamp HL is transmitted.

  A part of the light emitted from the halogen lamp HL and reflected at the peripheral edge of the lower surface of the semiconductor wafer W is incident on the incident surface 45d of the light guide rod 45 as shown in FIG. The reflected light from the peripheral edge of the semiconductor wafer W is slightly refracted when being incident on the incident surface 45d and is guided to the reflecting surface 45c. The light is totally reflected by the reflection surface 45c and travels toward the light guide 45b. In the present embodiment, the angle α formed by the reflecting surface 45c and the horizontal plane is 56.7 °, and in this case, the angle β formed by the horizontal plane of the light from the peripheral surface of the lower surface of the semiconductor wafer W is about 35 °. Is incident on the incident surface 45d, the light is totally reflected by the reflecting surface 45c and travels downward in the vertical direction. The angle β can be set to an appropriate value according to the arrangement configuration of the heat treatment apparatus 1 (positional relationship between the light guide rod 45 and the semiconductor wafer W, etc.), specifically, the reflection surface 45c and the horizontal plane. The angle α can be adjusted.

  Light traveling downward in the vertical direction from the light receiving head portion 45a travels straight along the longitudinal direction inside the light guide portion 45b provided along the vertical direction, that is, parallel to the central axis of the light guide portion 45b. . And the light guide | induced inside the light guide part 45b is radiate | emitted from the lower end surface of the light guide part 45b. Since the incident angle of the light traveling downward in the vertical direction with respect to the lower end surface of the light guide 45b is 0 °, no refraction occurs when the light is emitted from the lower end surface. Therefore, the light emitted from the lower end of the light guide rod 45 travels downward in the vertical direction.

  The light emitted from the lower end surface of the light guide rod 45 passes through the lens 43 and reaches the switching mirror 46. When the light receiving unit 40 receives the reflected light from the peripheral edge of the lower surface of the semiconductor wafer W, the normal line of the switching mirror 46 is set at an angle of 45 ° from the horizontal plane. Therefore, the light emitted downward from the lower end surface of the light guide rod 45 in the vertical direction is reflected by the switching mirror 46 and travels in the horizontal direction to reach the photodiode 41 (see FIG. 13).

  The light receiving unit 40 rotates the light guide rod 45 around the center line CX while irradiating the lower surface of the semiconductor wafer W with a weak output from the halogen lamp HL. Reflected light can be received over the entire periphery of the lower surface peripheral edge.

  The laser unit 48 provided along with the light receiving unit 40 is a very high-power semiconductor laser having an output of 80 W to 120 W, for example, and emits a visible light laser having a wavelength of 800 nm to 820 nm. The laser light emitted from the laser unit 48 is guided to the light receiving unit 40 by the optical fiber 49.

  The switching mirror 46 is provided between the exit end of the optical fiber 49 and the lens 43. The posture control motor 47 can change the posture of the switching mirror 46 between a posture in which the normal line is in the horizontal direction and a posture in which the normal is 45 ° from the horizontal plane. As described above, when the light receiving unit 40 receives the reflected light from the peripheral edge of the lower surface of the semiconductor wafer W, the normal line of the switching mirror 46 is set at 45 ° from the horizontal plane, and the reflected light is guided to the light guide rod 45. To the photodiode 41. On the other hand, when the normal of the switching mirror 46 is in the horizontal direction, the laser beam emitted from the emission end of the optical fiber 49 enters the lens 43 (see FIG. 14). The laser light that has passed through the lens 43 enters the lower end of the light guide rod 45 and is guided to the peripheral edge of the lower surface of the semiconductor wafer W through an optical path opposite to that described above. That is, the switching mirror 46 receives the reflected light from the peripheral portion of the semiconductor wafer W from the light guide rod 45 to the photodiode 41 and receives the light by the light receiving unit 40, and the laser light emitted from the laser unit 48. The mode is switched to one of the irradiation modes to be incident on the light guide rod 45.

  The photodiode 41 that has received the reflected light from the peripheral edge of the semiconductor wafer W in the light receiving mode generates a photocurrent corresponding to the intensity of the received light by the photovoltaic effect, and converts the reflected light into an electrical signal. . The photodiode 41 has a characteristic that the response time is extremely short. As shown in FIG. 8, the photodiode 41 is electrically connected to the detection unit 20, and transmits an electrical signal generated in response to light reception to the detection unit 20.

  FIG. 10 is a block diagram illustrating a configuration of the detection unit 20. The detection unit 20 includes a current-voltage conversion circuit 21, an amplification circuit 22, a high-speed A / D converter 23, and a determination unit 24. The current-voltage conversion circuit 21 is a circuit that converts a weak current generated in the photodiode 41 into a signal having a voltage that can be easily handled. The current-voltage conversion circuit 21 can be configured using, for example, an operational amplifier.

  The amplifier circuit 22 amplifies the voltage signal output from the current-voltage conversion circuit 21 and outputs the amplified voltage signal to the high-speed A / D converter 23. The high-speed A / D converter 23 converts the voltage signal amplified by the amplifier circuit 22 into a digital signal. The determination unit 24 is configured by a microcomputer including a CPU, a memory, and the like. The determination unit 24 samples a digital signal output from the high-speed A / D converter 25 at a predetermined interval by executing a processing program set in advance, and accumulates intensity data of reflected light received by the photodiode 41. . And the determination part 24 detects the crack of the semiconductor wafer W by comparing the intensity | strength of the reflected light before and behind flash light irradiation, but this process is further mentioned later.

  The detection unit 20 is connected to the control unit 3 via a communication line. The control unit 3 controls the various operation mechanisms 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 stores a CPU that performs various arithmetic processes, a ROM that is a read-only memory that stores basic programs, a RAM that is a readable and writable memory that stores various information, control software, data, and the like. It has a magnetic disk. The processing in the heat treatment apparatus 1 proceeds as the CPU of the control unit 3 executes a predetermined processing program.

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

  Next, a processing procedure for the semiconductor wafer W in the heat treatment apparatus 1 will be described. The semiconductor wafer W to be processed here is a semiconductor substrate to which impurities (ions) are added by an ion implantation method. The activation of the impurities is performed by flash light irradiation heat treatment (annealing) by the heat treatment apparatus 1. FIG. 11 and FIG. 12 are flowcharts showing a processing procedure in the heat treatment apparatus 1. The processing procedure of the heat treatment apparatus 1 described below proceeds by the control unit 3 controlling each operation mechanism of the heat treatment apparatus 1.

  First, prior to the processing, the air supply valve 84 is opened, and the exhaust valves 89 and 192 are opened to start supply / exhaust to the chamber 6. When the valve 84 is opened, nitrogen gas is supplied from the gas supply hole 81 to the heat treatment space 65. When the 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.

  Further, when the valve 192 is opened, the gas in the chamber 6 is also exhausted from the transfer opening 66. Further, the atmosphere around the drive unit of the transfer mechanism 10 is also exhausted by an exhaust mechanism (not shown). Note that nitrogen gas is continuously supplied to the heat treatment space 65 during the heat treatment of the semiconductor wafer W in the heat treatment apparatus 1, and the supply amount is appropriately changed according to the treatment process.

  Subsequently, the gate valve 185 is opened to open the transfer opening 66, and the semiconductor wafer W after the ion implantation is transferred into the heat treatment space 65 in the chamber 6 through the transfer opening 66 by a transfer robot outside the apparatus ( Step S1). The semiconductor wafer W carried in by the carrying robot advances to a position immediately above the susceptor 74 of the holding unit 7 and stops. Then, when the pair of transfer arms 11 of the transfer mechanism 10 moves horizontally from the retracted position to the transfer operation position and rises, the lift pins 12 protrude from the upper surface of the susceptor 74 through the through holes 79 and the semiconductor wafer W. Receive. At this time, the lift pin 12 rises above the upper end of the support pin 75 of the susceptor 74.

  After the semiconductor wafer W is placed on the lift pins 12, the transfer robot leaves the heat treatment space 65 and the transfer opening 66 is closed by the gate valve 185. Then, as the pair of transfer arms 11 are lowered, the semiconductor wafer W is mounted on the susceptor 74 from the transfer mechanism 10 and supported from below in a horizontal posture (step S2).

  The semiconductor wafer W is supported by point contact by six support pins 75 erected on the upper surface of the susceptor 74 and placed on the holding unit 7. The semiconductor wafer W is supported by six support pins 75 so that the center thereof coincides with the central axis of the circular susceptor 74 (that is, at the center of the upper surface of the susceptor 74). Further, the semiconductor wafer W is supported by the susceptor 74 with the surface on which the pattern is formed and impurities are implanted 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 support pins 75 and the top surface of the susceptor 74, and the semiconductor wafer W is connected to the top surface of the susceptor 74. Supported in parallel. The pair of transfer arms 11 lowered to below the susceptor 74 is retracted to the retracted position by the horizontal movement mechanism 13.

  After the semiconductor wafer W is supported by the holding unit 7 from below in a horizontal posture, the 40 halogen lamps HL of the halogen heating unit 4 are turned on (step S3). At this time, the halogen lamp HL is turned on with a weak output (for example, an output of about 1%) under the control of the control unit 3. Even with such a weak output, the halogen lamp HL emits light with sufficient illuminance as illumination means, and the lower surface of the semiconductor wafer W supported by the susceptor 74 is illuminated by light from the halogen lamp HL. A part of the light emitted from the halogen lamp HL and reflected at the peripheral edge of the lower surface of the semiconductor wafer W enters the light guide rod 45 of the light receiving unit 40. The reflected light is guided to the photodiode 41 by the light guide rod 45, and the detection unit 20 measures the intensity of the reflected light and acquires it as pre-flash data (step S4). At this time, a light receiving mode in which light reaches the photodiode 41 from the light guide rod 45 is selected.

  FIG. 13 is a diagram illustrating a state in which the light reception mode is selected and the intensity of reflected light from the semiconductor wafer W is measured. Of the reflected light from the lower peripheral edge of the semiconductor wafer W, the light incident on the incident surface 45d of the light guide rod 45 at a predetermined incident angle (light whose angle β in FIG. 9 is about 35 °) is totally reflected on the reflective surface 45c. Reflected and heads downward in the vertical direction. When the light receiving mode is selected, the reflected light emitted from the lower end of the light guide rod 45 passes through the lens 43 and is reflected by the switching mirror 46 to reach the photodiode 41. The lens 43 is arranged at a position where the light emitted from the light guide rod 45 is condensed on the photodiode 41.

  The photodiode 41 that has received the reflected light from the semiconductor wafer W guided by the light guide rod 45 generates a photocurrent and outputs an electrical signal to the detection unit 20. The electrical signal transmitted from the photodiode 41 is converted into a voltage signal that can be easily handled by the current-voltage conversion circuit 21, amplified by the amplifier circuit 22, and then converted into a digital signal by the high-speed A / D converter 23. Then, the digital signal output from the high-speed A / D converter 23 is sampled by the determination unit 24, so that the level of the digital signal is acquired as the intensity of the reflected light at the lower peripheral edge of the semiconductor wafer W.

  Further, when measuring the reflected light intensity at the peripheral edge of the lower surface of the semiconductor wafer W, the rotation motor 44 rotates the light guide rod 45. The rotation motor 44 rotates the light guide rod 45 once with the center line CX of the semiconductor wafer W as the rotation center. While the light guide rod 45 rotates once at a constant speed, the determination unit 24 of the detection unit 20 samples the digital signal output from the high-speed A / D converter 23 at a predetermined interval, so that the periphery of the lower surface of the semiconductor wafer W is The reflected light intensity can be measured over the entire circumference. That is, light reaching the photodiode 41 out of the light incident on the incident surface 45d of the light guide rod 45 is reflected light from a specific region on the lower peripheral edge of the semiconductor wafer W, and the light guide rod 45 rotates once. As a result, the measurement region circulates along the periphery of the lower surface of the semiconductor wafer W, and the reflected light intensity can be measured over the entire periphery of the periphery of the lower surface (step S5). The acquired reflected light intensity over the entire periphery of the lower surface periphery of the semiconductor wafer W is stored as pre-flash data 27 in a storage unit such as a memory of the determination unit 24 (see FIG. 10).

  FIG. 15 is a diagram illustrating an example of the reflected light intensity (that is, pre-flash data 27) before the flash light irradiation measured as described above. The vertical axis in FIG. 15 indicates the reflected light intensity measured by the determination unit 24 of the detection unit 20, and the horizontal axis indicates the rotation angle of the light guide rod 45. The light incident on the incident surface 45d of the light guide rod 45 at a predetermined angle includes light reflected from other than the peripheral edge of the lower surface of the semiconductor wafer W (for example, light reflected by the wall surface of the chamber 6 or the quartz susceptor 74). It is. In many cases, the light reflected by the lower peripheral edge of the semiconductor wafer W passes through the susceptor 74 of the holding unit 7 and enters the light guide rod 45. For this reason, various disturbance elements are included in the reflected light intensity measured by the detection unit 20 as the background. FIG. 15 shows data including such a background. The portion where the reflected light intensity is high is a measured value of the reflected light that has passed through the notch 77 of the susceptor 74, and the apparent reflected light intensity is high because it does not pass through the quartz susceptor 74. It is.

  After the reflected light intensity is measured over the entire periphery of the lower surface periphery of the semiconductor wafer W, the outputs of the 40 halogen lamps HL are greatly increased and preheating (assist heating) is started (step S6). The halogen light emitted from the halogen lamp HL is irradiated from the lower surface of the semiconductor wafer W through the lower chamber window 64 and the susceptor 74 made of quartz. By receiving light 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 to the retracted position inside the recess 62, there is no obstacle to heating by the halogen lamp HL.

  When preheating with the halogen lamp HL is performed, the temperature of the semiconductor wafer W is measured by the contact thermometer 130. That is, a contact thermometer 130 incorporating a thermocouple contacts the lower surface of the semiconductor wafer W held by the holding unit 7 via the notch 77 of the susceptor 74 to measure the temperature of the wafer being heated. The measured temperature of the semiconductor wafer W is transmitted to the control unit 3. The controller 3 monitors whether or not the temperature of the semiconductor wafer W that is heated by light irradiation from the halogen lamp HL has reached a predetermined preheating temperature T1. The preheating temperature T1 is set to about 200 ° C. to 800 ° C., preferably about 350 ° C. to 600 ° C. (in this embodiment, 600 ° C.) at which impurities added to the semiconductor wafer W are not likely to diffuse due to heat. . Note that when the temperature of the semiconductor wafer W is increased by light irradiation from the halogen lamp HL, temperature measurement by the radiation thermometer 120 is not performed. This is because the halogen light irradiated from the halogen lamp HL enters the radiation thermometer 120 as disturbance light, and accurate temperature measurement cannot be performed.

  After the temperature of the semiconductor wafer W reaches the preheating temperature T1, the control unit 3 maintains the semiconductor wafer W at the preheating temperature T1 for a while. Specifically, when the temperature of the semiconductor wafer W measured by the temperature sensor reaches the preheating temperature T1, the control unit 3 controls the output of the halogen lamp HL so that the temperature of the semiconductor wafer W is substantially equal to the preheating temperature. T1 is maintained for a predetermined time.

  By performing such preheating by the halogen lamp HL, the entire semiconductor wafer W is uniformly heated to the preheating temperature T1. In the preliminary heating stage with the halogen lamp HL, the temperature of the peripheral edge of the semiconductor wafer W where heat dissipation is more likely to occur tends to be lower than that in the central area, but the arrangement density of the halogen lamps HL in the halogen heating section 4 is The region facing the peripheral portion is higher than the region facing the central portion of the semiconductor wafer W (see FIG. 7). For this reason, the light quantity irradiated to the peripheral part of the semiconductor wafer W which tends to generate heat increases, and the in-plane temperature distribution of the semiconductor wafer W in the preheating stage can be made uniform. Furthermore, since the inner peripheral surface of the reflection ring 69 attached to the chamber side portion 61 is a mirror surface, the amount of light reflected toward the peripheral edge of the semiconductor wafer W by the inner peripheral surface of the reflection ring 69 increases. The in-plane temperature distribution of the semiconductor wafer W in the preheating stage can be made more uniform.

  If the temperature of the peripheral portion of the semiconductor wafer W is still lower than the central portion, the laser unit 48 and the light guide rod 45 irradiate the peripheral portion of the semiconductor wafer W with laser light to assist preheating. At this time, an irradiation mode in which the laser light emitted from the laser unit 48 is incident on the light guide rod 45 is selected.

  FIG. 14 is a diagram illustrating a state in which the irradiation mode is selected and the peripheral edge of the semiconductor wafer W is irradiated with laser light. The laser unit 48 emits a visible light laser having a wavelength of 800 nm to 820 nm at an output of 80 W to 120 W. When the irradiation mode is selected, the laser light emitted from the laser unit 48 and guided by the optical fiber 49 is incident on the lens 43 without hitting the switching mirror 46. The laser beam that has passed through the lens 43 is incident on the lower end of the light guide rod 45. Laser light is emitted from the lens 43 upward in the vertical direction, and the laser light is directly incident on the lower end surface of the light guide rod 45.

  The laser light incident perpendicularly to the lower end surface of the light guide portion 45b of the light guide rod 45 is guided to the upper light receiving head portion 45a, reflected by the reflecting surface 45c, and then held by the holding portion 7 from the incident surface 45d. The light is emitted toward the peripheral edge of the semiconductor wafer W (towards the obliquely upward direction). The laser light emitted from the light receiving head portion 45a of the light guide rod 45 reaches the lower surface peripheral portion of the semiconductor wafer W and is absorbed, and raises the temperature of the irradiated region.

  Further, the rotation motor 44 rotates the light guide rod 45 while emitting laser light from the light guide rod 45 toward the peripheral edge of the lower surface of the semiconductor wafer W. The rotation motor 44 rotates the light guide rod 45 once with the center line CX of the semiconductor wafer W as the rotation center. As a result, the irradiation area of the laser beam emitted from the light guide rod 45 turns so as to draw a circular trajectory along the peripheral edge of the lower surface of the semiconductor wafer W. Thereby, the peripheral edge of the semiconductor wafer W in which the relative temperature decrease has occurred can be irradiated with laser light, and the peripheral edge can be heated to further improve the uniformity of the in-plane temperature distribution.

  When a predetermined time elapses after the temperature of the semiconductor wafer W reaches the preheating temperature T1 due to preheating, the flash lamp FL of the flash heating unit 5 irradiates the surface of the semiconductor wafer W with flash light (step S7). At this time, a part of the flash light emitted 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. Flash heating of the semiconductor wafer W is performed by irradiation.

  Since the flash heating is performed by irradiation with 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 irradiated from the flash lamp FL is converted into a light pulse in which the electrostatic energy stored in the capacitor in advance is extremely short, and the irradiation time is extremely short, about 0.1 milliseconds to 100 milliseconds. It is a strong flash. Then, the surface temperature of the semiconductor wafer W that is flash-heated by flash light irradiation from the flash lamp FL instantaneously rises to a processing temperature T2 of 1000 ° C. or more, and the impurities injected into the semiconductor wafer W are activated. Later, the surface temperature drops rapidly. As described above, in the heat treatment apparatus 1, the surface temperature of the semiconductor wafer W can be raised and lowered in a very short time, so that the impurities are activated while suppressing diffusion of the impurities injected into the semiconductor wafer W due to heat. Can do. Since the time required for the activation of impurities is extremely short compared to the time required for the thermal diffusion, the activation is possible even in a short time in which diffusion of about 0.1 millisecond to 100 millisecond does not occur. Complete.

  After the end of the flash heat treatment, the halogen lamp HL is turned off after a predetermined time has elapsed. Further, when laser light irradiation is performed from the laser unit 48 to the peripheral portion of the semiconductor wafer W, the laser light irradiation is also stopped. Thereby, the temperature of the semiconductor wafer W is rapidly lowered from the preheating temperature T1. Then, the halogen lamp HL is turned on again with a weak output during the cooling of the semiconductor wafer W (step S8). The output of the halogen lamp HL at this time is exactly the same as the output of the halogen lamp HL (output in step S3) at the time of reflected light intensity measurement before flash light irradiation. In place of temporarily turning off the halogen lamp HL, the output of the halogen lamp HL is reduced from the output at the time of preliminary heating (the value of step S6) to the output of the halogen lamp HL at the time of measuring the reflected light intensity before flash light irradiation. You may make it let it. If the 40 halogen lamps HL have a weak output of about 1%, the temperature of the semiconductor wafer W is lowered from the preheating temperature T1 because it functions as an illuminating unit but hardly as a heating unit.

  As before the flash light irradiation, a part of the light emitted from the halogen lamp HL and reflected by the peripheral edge of the lower surface of the semiconductor wafer W enters the light guide rod 45 of the light receiving unit 40. Then, the reflected light is guided to the photodiode 41 by the light guide rod 45, and the detection unit 20 measures the intensity of the reflected light and acquires it as post-flash data (step S9). At this time, a light receiving mode in which light reaches the photodiode 41 from the light guide rod 45 is selected.

  Similarly to the above, a part of the reflected light from the lower surface periphery of the semiconductor wafer W is totally reflected by the reflecting surface 45c and travels downward in the vertical direction. When the light receiving mode is selected, the reflected light emitted from the lower end of the light guide rod 45 passes through the lens 43 and is reflected by the switching mirror 46 to reach the photodiode 41. The photodiode 41 that has received the reflected light from the semiconductor wafer W generates a photocurrent and outputs an electrical signal to the detector 20. The electrical signal transmitted from the photodiode 41 is converted into a voltage signal that can be easily handled by the current-voltage conversion circuit 21, amplified by the amplifier circuit 22, and then converted into a digital signal by the high-speed A / D converter 23. Then, the digital signal output from the high-speed A / D converter 23 is sampled by the determination unit 24, so that the level of the digital signal is acquired as the intensity of the reflected light at the lower peripheral edge of the semiconductor wafer W.

  In addition, the rotation motor 44 rotates the light guide rod 45 when measuring the reflected light intensity after the flash light irradiation. The rotation motor 44 rotates the light guide rod 45 once with the center line CX of the semiconductor wafer W as the rotation center. While the light guide rod 45 rotates once at a constant speed, the determination unit 24 of the detection unit 20 samples the digital signal output from the high-speed A / D converter 23 at a predetermined interval, so that the periphery of the lower surface of the semiconductor wafer W is The reflected light intensity can be measured over the entire circumference (step S10). The obtained reflected light intensity over the entire periphery of the lower surface periphery of the semiconductor wafer W is stored as post-flash data 28 in a storage unit such as a memory of the determination unit 24 (see FIG. 10).

  FIG. 16 is a diagram showing an example of measured reflected light intensity after flash light irradiation (that is, post-flash data 28). Similarly to FIG. 15, the vertical axis of FIG. 16 indicates the reflected light intensity measured by the determination unit 24 of the detection unit 20, and the horizontal axis indicates the rotation angle of the light guide rod 45. Similar to the measurement before the flash light irradiation, the reflected light intensity actually measured by the detection unit 20 after the flash light irradiation includes various disturbance elements as the background. However, since the factors such as the reflection on the wall surface of the chamber 6 and the shape of the susceptor 74 are the same before and after the flash light irradiation, the background data does not change.

  After the flash light irradiation, the reflected light intensity is measured over the entire periphery of the lower surface periphery of the semiconductor wafer W, and then the 40 halogen lamps HL are completely turned off (step S11). The temperature of the semiconductor wafer W after flash heating held by the holding unit 7 is continuously lowered.

  Next, the determination unit 24 of the detection unit 20 compares the reflected light intensity data before and after the flash light irradiation (step S12). Specifically, the determination unit 24 subtracts the pre-flash data 27 as shown in FIG. 15 from the post-flash data 28 as shown in FIG. 16 to obtain the difference data 29 (see FIG. 10).

  FIG. 17 is a diagram illustrating an example of the difference data 29. As described above, the actually measured reflected light intensity includes background data, but the background data does not change before and after the flash light irradiation. Therefore, by obtaining the difference between the pre-flash data 27 and the post-flash data 28, the influence of the background can be eliminated. That is, the difference data 29 is a change in the reflected light intensity of the pure semiconductor wafer W before and after the flash light irradiation.

  The determination unit 24 detects a crack in the semiconductor wafer W by determining whether or not the absolute value of the reflected light intensity included in the difference data 29 exceeds a predetermined threshold (step S13). As shown in FIG. 17, when the absolute value of the reflected light intensity included in the difference data 29 shows a large value, it means that a large abnormality has occurred in the peripheral edge of the semiconductor wafer W before and after the flash light irradiation. I mean. Specifically, it is assumed that the peripheral edge of the semiconductor wafer W was cracked by the flash light irradiation.

  For this reason, when the absolute value of the reflected light intensity included in the difference data 29 exceeds a predetermined threshold value, the determination unit 24 determines that the semiconductor wafer W is cracked during the flash light irradiation. In this case, the process proceeds to step S14, and abnormality handling processing is performed. As the abnormality handling process, for example, the control unit 3 to which the wafer crack detection signal is transmitted from the detection unit 20 issues a warning or stops the operation of the heat treatment apparatus 1.

  On the other hand, when the absolute value of the reflected light intensity included in the difference data 29 is equal to or less than the predetermined threshold, the determination unit 24 indicates that the semiconductor wafer W is not cracked and the flash light irradiation has been performed normally. judge. In this case, the process proceeds to step S15, and the semiconductor wafer W is unloaded. In the carry-out process, after the temperature of the semiconductor wafer W measured by the radiation thermometer 120 and / or the contact-type thermometer 130 is lowered to a predetermined temperature or lower, the pair of transfer arms 11 of the transfer mechanism 10 is again moved to the retracted position. As a result, the lift pins 12 protrude from the upper surface of the susceptor 74 and receive the heat-treated semiconductor wafer W from the susceptor 74. Subsequently, the transfer opening 66 closed by the gate valve 185 is opened, and the semiconductor wafer W placed on the lift pins 12 is unloaded by the transfer robot outside the apparatus, and a series of the semiconductor wafers W in the heat treatment apparatus 1 are transferred. The heat treatment is completed.

  In this embodiment, the reflected light at the peripheral edge of the semiconductor wafer W is received and its intensity is measured, and cracks in the semiconductor wafer W during flash light irradiation are detected based on the measurement results. As is well known, the semiconductor wafer W is single crystal silicon, and when it is cracked during flash light irradiation, it is cracked along a specific crystal orientation. Therefore, when the semiconductor wafer W of single crystal silicon is cracked, it cannot be broken so that only the central portion is removed, and it is always cracked so as to include any peripheral region. However, only a part of the peripheral edge of the semiconductor wafer W may be broken, but in this case also, a defect occurs in any of the peripheral areas. These mean that the crack of the semiconductor wafer W can be reliably detected by detecting an abnormality in the reflected light intensity at the peripheral edge without inspecting the entire surface of the semiconductor wafer W.

  Therefore, in the heat treatment apparatus 1 according to the present embodiment, the intensity of the reflected light from the peripheral edge of the semiconductor wafer W is measured to reliably detect cracks in the semiconductor wafer W during flash light irradiation. Even when the semiconductor wafer W is cracked so as to be largely divided into two parts from the vicinity of the center, or even when only a part of the peripheral edge is cracked small, a defect occurs in any of the peripheral edges and the reflected light intensity is increased. Since an abnormality occurs, any form of cracking can be reliably detected.

  In addition, since it is not necessary to inspect the entire surface of the semiconductor wafer W, an imaging camera or the like is unnecessary, and the reflected light from the peripheral edge of the semiconductor wafer W is received by the light receiving unit 40 having a simple configuration to detect cracks. Can do. The light receiving section 40 having the light guide rod 45 as a main element can be attached to the halogen heating section 4 having a high density and the halogen lamp HL, and even if the semiconductor wafer W is cracked during flash light irradiation. The crack can be detected in the chamber 6. If a wafer crack can be detected in the chamber 6 before opening the gate valve 185 after the flash light irradiation, particles due to the wafer crack can be prevented from scattering from the transfer opening 66.

  In the present embodiment, the reflected light intensity from the peripheral edge of the lower surface of the semiconductor wafer W is measured before and after the flash light irradiation, and is obtained as pre-flash data 27 and post-flash data 28, and the difference between them is obtained. The abnormality of reflected light intensity is detected. In this way, by taking the difference in reflected light intensity before and after flash light irradiation, it is possible to reliably detect abnormalities in the reflected light intensity by eliminating the influence of the background inevitably included when measuring the reflected light intensity. it can.

  Further, by rotating the light guide rod 45 of the light receiving unit 40 once, the reflected light is received over the entire periphery of the lower surface peripheral portion of the semiconductor wafer W and the intensity thereof is measured. Since the reflected light intensity can be measured over the entire circumference of the peripheral edge of the semiconductor wafer W with such a simple configuration, the light receiving unit 40 is attached to the halogen heating unit 4 in which the halogen lamp HL is arranged at a high density. Can do.

  While the embodiments of the present invention have been described above, the present invention can be modified in various ways other than those described above without departing from the spirit of the present invention. For example, in the above embodiment, the switching mirror 46 switches between the light receiving mode and the irradiation mode. However, both modes may be performed in parallel using a branching fiber instead. FIG. 18 is a diagram illustrating a configuration example when a branch fiber is used. A branch fiber 149 is provided instead of the switching mirror 46 of the above embodiment (FIG. 8). In FIG. 18, the same elements as those in the above embodiment are denoted by the same reference numerals.

  The distal end side of the branch fiber 149 is provided to face the lens 43. The proximal end of the branch fiber 149 is bifurcated and one is connected to the laser unit 48 and the other is provided to face the photodiode 41. The branch fiber 149 is a bundle of a plurality of optical fiber strands. A group of them is connected to the laser unit 48 on the base end side, and the rest is opposed to the photodiode 41. On the distal end side of the branch fiber 149, a group of optical fiber strands connected to the laser unit 48 and an optical fiber strand facing the photodiode 41 are mixed and bundled.

  Such a branched fiber 149 can reach the photodiode 41 from one side branched by guiding the reflected light of the peripheral edge of the semiconductor wafer W emitted from the lower end of the light guide rod 45. The branch fiber 149 can also guide the laser light emitted from the laser unit 48 from the other branched side and enter the light guide rod 45. In other words, the branch fiber 149 causes the reflected light from the peripheral edge of the semiconductor wafer W to reach the photodiode 41 from the light guide rod 45 and be received by the light receiving unit 40 and to guide the laser light emitted from the laser unit 48. The light can enter the rod 45. Even if such a branch fiber 149 is used, the same processing as in the above embodiment can be performed.

  In addition, the laser unit 48 is not necessarily indispensable when assistance by laser beam irradiation is not performed at the time of preheating. In this case, it is not necessary to provide the switching mirror 46 or the branch fiber 149. When the laser unit 48 is provided, the light guide rod 45 that receives the reflected light from the semiconductor wafer W can be used as the laser light emitting portion, which is preferable.

  In the above embodiment, when the reflected light intensity is measured, the lower surface of the semiconductor wafer W is illuminated by the halogen lamp HL for preheating. Instead, a dedicated illumination unit is provided, Thereby, the peripheral edge of the lower surface of the semiconductor wafer W may be illuminated.

  In the above embodiment, the determination unit 24 acquires the difference data 29 and detects the crack of the semiconductor wafer W. However, the control unit 3 performs the wafer processing based on the pre-flash data 27 and the post-flash data 28. You may make it detect a crack. At this time, the content of the arithmetic processing executed by the control unit 3 is the same as that of the determination unit 24 of the above embodiment.

  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, and 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, and may be an arbitrary number.

  The substrate to be processed by the heat treatment apparatus according to the present invention is not limited to a semiconductor wafer, and may be a glass substrate or a solar cell substrate used for a flat panel display such as a liquid crystal display device. Further, the technique according to the present invention may be applied to bonding of metal and silicon or crystallization of polysilicon.

DESCRIPTION OF SYMBOLS 1 Heat processing apparatus 3 Control part 4 Halogen heating part 5 Flash heating part 6 Chamber 7 Holding part 10 Transfer mechanism 20 Detection part 24 Judgment part 27 Data before flash 28 Data after flash 29 Differential data 40 Light receiving part 41 Photodiode 44 Rotating motor 45 Light guide rod 46 Switching mirror 48 Laser unit 65 Heat treatment space 74 Susceptor 75 Support pin 149 Branch fiber HL Halogen lamp FL Flash lamp W Semiconductor wafer

Claims (10)

A heat treatment apparatus for heating a substrate by irradiating the substrate with flash light,
A chamber for housing the substrate;
Holding means for holding the substrate in the chamber;
A flash lamp for irradiating flash light onto the substrate held by the holding means;
Illumination means for irradiating the substrate with light;
A light receiving means for receiving light emitted from the illumination means and reflected over the entire periphery of the peripheral edge of the substrate;
Detecting means for detecting cracks in the substrate based on light received by the light receiving means;
A heat treatment apparatus comprising: The heat treatment apparatus according to claim 1, wherein
The detection means detects cracks in the substrate from a comparison between reflected light received by the light receiving means before irradiating flash light from the flash lamp and reflected light received by the light receiving means after irradiation of flash light. A heat treatment apparatus characterized by In the heat treatment apparatus according to claim 1 or 2,
The light receiving means is
A light guide portion that is disposed immediately below the center of the substrate held by the holding means, and receives and guides reflected light from a predetermined position of the peripheral portion of the substrate;
A rotating part that rotates the light guide part around the center line of the substrate;
The heat processing apparatus characterized by including. The heat treatment apparatus according to claim 3, wherein
The heat receiving apparatus further includes a photodiode that receives reflected light guided by the light guide unit, converts the reflected light into an electric signal, and transmits the electric signal to the detecting unit. The heat treatment apparatus according to claim 4, wherein
A laser beam irradiator that emits laser beam toward the peripheral edge of the substrate held by the holding means by entering laser beam into the light guide;
Switching between a light receiving mode in which reflected light from the peripheral edge of the substrate reaches the photodiode from the light guide unit and an irradiation mode in which light emitted from the laser light irradiation unit is incident on the light guide unit Switching means;
A heat treatment apparatus further comprising: The heat treatment apparatus according to claim 4, wherein
A laser beam irradiator that emits laser beam toward the peripheral edge of the substrate held by the holding means by entering laser beam into the light guide;
A branched fiber that causes reflected light from the peripheral edge of the substrate to reach the photodiode from the light guide unit, and makes light emitted from the laser light irradiation unit enter the light guide unit,
A heat treatment apparatus further comprising: In the heat processing apparatus in any one of Claims 1-6,
The heat treatment apparatus, wherein the illumination means is a halogen lamp that preheats the substrate before flash light irradiation. A heat treatment method for heating a substrate by irradiating the substrate with flash light,
A first light receiving step for receiving light emitted from the illumination means and reflected over the entire periphery of the peripheral portion of the substrate before the flash light irradiation;
A flash heating step of irradiating the substrate with flash light from a flash lamp;
A second light receiving step for receiving light emitted from the illumination means after flash light irradiation and reflected over the entire periphery of the peripheral portion of the substrate;
A detection step of detecting cracks in the substrate from a comparison between the reflected light received in the first light receiving step and the reflected light received in the second light receiving step;
A heat treatment method comprising: The heat treatment method according to claim 8, wherein
In the first light receiving step and the second light receiving step, a light guide portion that is disposed immediately below the center of the substrate and receives and guides reflected light from a predetermined position in a peripheral portion of the substrate is rotated. A heat treatment method. The heat treatment method according to claim 9, wherein
A heat treatment method, further comprising a step of causing a laser beam to enter the light guide portion and emitting the laser beam toward a peripheral portion of the substrate.

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