JP5543123B2 - Heat treatment susceptor and heat treatment apparatus - Google Patents

Description

  The present invention is a heat treatment apparatus for heating a substrate by irradiating flash light (flash) to a semiconductor wafer, a glass substrate for a liquid crystal display device or the like (hereinafter simply referred to as “substrate”), and a treatment target thereof. The present invention relates to a susceptor for heat treatment that holds a substrate.

  Conventionally, a lamp annealing apparatus using a halogen lamp has been generally used in an ion activation process of a semiconductor wafer after ion implantation. In such a lamp annealing apparatus, ion activation of a semiconductor wafer is performed by heating (annealing) the semiconductor wafer to a temperature of about 1000 ° C. to 1100 ° C., for example. In such a heat treatment apparatus, the temperature of the substrate is raised at a rate of several hundred degrees per second by using the energy of light irradiated from the halogen lamp.

  On the other hand, in recent years, as semiconductor devices have been highly integrated, it is desired to reduce the junction depth as the gate length becomes shorter. However, even when ion activation of a semiconductor wafer is performed using the above-described lamp annealing apparatus that raises the temperature of the semiconductor wafer at a speed of several hundred degrees per second, ions such as boron and phosphorus implanted in the semiconductor wafer are heated. It was found that the phenomenon of deep diffusion occurs. When such a phenomenon occurs, there is a concern that the junction depth becomes deeper than required, which hinders good device formation.

  For this reason, only the surface of the semiconductor wafer into which ions have been implanted by irradiating the surface of the semiconductor wafer with flash light using a xenon flash lamp (hereinafter simply referred to as “xenon flash lamp”). There has been proposed a technique for raising the temperature of the material in an extremely 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. It has also been found that if the flash 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 a xenon flash lamp, only the ion activation can be performed without diffusing ions deeply.

  In heat treatment equipment that uses a xenon flash lamp, the semiconductor wafer is irradiated with extremely high energy light instantaneously, so the surface temperature of the semiconductor wafer rises rapidly and abrupt thermal expansion occurs on the wafer surface. The semiconductor wafer was broken with high probability. In order to solve the cracks peculiar to the heat treatment using such a xenon flash lamp, for example, Patent Documents 1 and 2 disclose a technique for forming a taper at the peripheral portion of a wafer pocket of a susceptor holding a semiconductor wafer. .

JP 2004-179510 A JP 2004-247339 A

  By using techniques such as those disclosed in Patent Documents 1 and 2, the semiconductor wafer can be prevented from cracking to some extent when a xenon flash lamp is used, but the type of semiconductor wafer and heat treatment conditions (preliminary) Cracks still occurred with considerable frequency depending on the heating temperature and irradiation energy.

  In addition, when the surface of the semiconductor wafer suddenly thermally expands, the susceptor is damaged and particles are generated.

  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 susceptor and a heat treatment apparatus capable of preventing the substrate from being cracked when irradiated with flash light from a flash lamp.

  In order to solve the above-mentioned problems, the invention of claim 1 is a heat treatment apparatus for heating a substrate by irradiating the substrate with flash light, and a substrate support portion for placing and supporting the substrate in a horizontal posture; A flash lamp for irradiating the substrate supported by the substrate with flash light, wherein the substrate support is formed of pyrolytic boron nitride (PBN).

  The invention according to claim 2 is the heat treatment apparatus according to claim 1, further comprising a hot plate for preheating the substrate before irradiating flash light from the flash lamp, wherein the substrate support portion is the hot plate. It is characterized by being a susceptor mounted on.

  According to a third aspect of the present invention, in the heat treatment apparatus according to the first aspect of the present invention, there is provided a hot plate for preheating the substrate before irradiating flash light from the flash lamp, and a quartz plate mounted on the hot plate. And a susceptor, wherein the substrate support part is a sheet member placed on the susceptor.

  According to a fourth aspect of the present invention, in the heat treatment apparatus according to the third aspect of the present invention, the heat treatment apparatus further includes a guide portion that regulates a position of the edge portion of the substrate, and the guide portion is formed of pyrolytic boron nitride. It is characterized by.

  According to a fifth aspect of the present invention, in the heat treatment susceptor for holding the substrate when the substrate is heat-treated by irradiating the substrate with flash light from a flash lamp, the heat treatment susceptor is made of pyrolytic boron nitride. It is characterized by forming.

  According to the first to fourth aspects of the present invention, the substrate support portion for supporting the substrate irradiated with the flash light from the flash lamp in a horizontal posture is formed of pyrolytic boron nitride which is relatively flexible. Therefore, even if the substrate vibrates vigorously during flash light irradiation, the impact applied to the substrate can be mitigated, and cracking of the substrate can be prevented.

  In particular, according to the invention of claim 2, the susceptor formed of pyrolytic boron nitride having a relatively high thermal conductivity is placed on the hot plate, and the substrate can be preheated quickly. .

  In particular, according to the invention of claim 4, since the guide portion for regulating the position of the edge portion of the substrate is formed of pyrolytic boron nitride, even if the substrate is in contact with the guide portion during flash light irradiation. It is possible to prevent the substrate from cracking.

  According to the invention of claim 5, since the susceptor for heat treatment that holds the substrate when the flash light is irradiated to the substrate from the flash lamp is formed of pyrolytic boron nitride, the substrate is Even if it vibrates violently, the impact applied to the substrate can be mitigated, and cracking of the substrate can be prevented.

It is a longitudinal cross-sectional view which shows the structure of the heat processing apparatus which concerns on this invention. It is sectional drawing which shows the gas path of the heat processing apparatus of FIG. It is sectional drawing which shows the structure of a holding | maintenance part. It is a top view which shows a hot plate. It is a longitudinal cross-sectional view which shows the structure of the heat processing apparatus of FIG. It is a figure which shows the holding | maintenance part which mounted the semiconductor wafer. It is a figure which shows the structure of the holding | maintenance part of 2nd Embodiment. It is a figure which shows the structure of the holding | maintenance part of 3rd Embodiment. It is a figure which shows the structure of the holding | maintenance part of 4th Embodiment. It is a figure which shows the other example of a structure of a holding | maintenance part.

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

<1. First Embodiment>
First, the overall configuration of the heat treatment apparatus according to the present invention will be outlined. 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 is a flash lamp annealing apparatus that irradiates a substantially circular semiconductor wafer W as a substrate with flash light and heats the semiconductor wafer W.

  The heat treatment apparatus 1 includes a substantially cylindrical chamber 6 that accommodates a semiconductor wafer W, and a lamp house 5 that houses a plurality of flash lamps FL. Further, the heat treatment apparatus 1 includes a control unit 3 that controls each operation mechanism provided in the chamber 6 and the lamp house 5 to execute the heat treatment of the semiconductor wafer W.

  The chamber 6 is provided below the lamp house 5 and includes a chamber side 63 having a substantially cylindrical inner wall and a chamber bottom 62 covering the lower part of the chamber side 63. A space surrounded by the chamber side 63 and the chamber bottom 62 is defined as a heat treatment space 65. An upper opening 60 is formed above the heat treatment space 65, and a chamber window 61 is attached to the upper opening 60 to be closed.

  The chamber window 61 constituting the ceiling portion 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 lamp house 5 to the heat treatment space 65. The chamber bottom 62 and the chamber side 63 constituting the main body of the chamber 6 are formed of, for example, a metal material having excellent strength and heat resistance such as stainless steel, and a ring on the upper side of the inner side surface of the chamber side 63. 631 is formed of an aluminum (Al) alloy or the like having durability superior to stainless steel against deterioration due to flash light irradiation.

  Further, in order to maintain the airtightness of the heat treatment space 65, the chamber window 61 and the chamber side portion 63 are sealed by an O-ring. That is, the O-ring is sandwiched between the lower surface peripheral portion of the chamber window 61 and the chamber side portion 63, the clamp ring 90 is brought into contact with the upper peripheral portion of the chamber window 61, and the clamp ring 90 is attached to the chamber side portion 63. The chamber window 61 is pressed against the O-ring by screwing.

  The chamber bottom 62 has a plurality of (this embodiment) for supporting the semiconductor wafer W from the lower surface (surface opposite to the side irradiated with the flash light from the lamp house 5) through the holding portion 7. Then, three support pins 70 are erected. The support pin 70 is made of, for example, quartz and is fixed from the outside of the chamber 6 and can be easily replaced.

The chamber side 63 has a transfer opening 66 for carrying in and out the semiconductor wafer W, and the transfer opening 66 can be opened and closed by a gate valve 185 that rotates about a shaft 662. In a portion of the chamber side 63 opposite to the transfer opening 66, an inert gas such as nitrogen (N ₂ ) gas, helium (He) gas, argon (Ar) gas, etc. Alternatively, an introduction path 81 for introducing oxygen (0 ₂ ) gas or the like is formed, one end of which is connected to an air supply mechanism (not shown) via a valve 82, and the other end is formed inside the chamber side portion 63. Connected to the gas introduction buffer 83. A discharge passage 86 for discharging the gas in the heat treatment space 65 is formed in the transfer opening 66 and is connected to an exhaust mechanism (not shown) through a valve 87.

  FIG. 2 is a cross-sectional view of the chamber 6 cut along a horizontal plane at the position of the gas introduction buffer 83. As shown in FIG. 2, the gas introduction buffer 83 is formed over about ３ of the inner periphery of the chamber side 63 on the opposite side of the transfer opening 66 shown in FIG. Then, the processing gas guided to the gas introduction buffer 83 is supplied into the heat treatment space 65 from the plurality of gas supply holes 84.

  The heat treatment apparatus 1 also includes a substantially disc-shaped holding unit 7 that holds the semiconductor wafer W in a horizontal position inside the chamber 6 and performs preheating of the held semiconductor wafer W before irradiation with flash light. And a holding unit elevating mechanism 4 that elevates the unit 7 with respect to the chamber bottom 62 which is the bottom surface of the chamber 6. 1 includes a substantially cylindrical shaft 41, a moving plate 42, guide members 43 (three arranged around the shaft 41 in the present embodiment), a fixed plate 44, a ball screw 45, It has a nut 46 and a motor 40. A substantially circular lower opening 64 having a smaller diameter than the holding portion 7 is formed in the chamber bottom 62 which is the lower portion of the chamber 6, and the stainless steel shaft 41 is inserted through the lower opening 64 to hold the holding portion. 7 (strictly speaking, the hot plate 71 of the holding unit 7) is connected to the lower surface of the holding unit 7 to support it.

  A nut 46 that is screwed into the ball screw 45 is fixed to the moving plate 42. The moving plate 42 is slidably guided by a guide member 43 that is fixed to the chamber bottom 62 and extends downward, and is movable in the vertical direction. Further, the moving plate 42 is connected to the holding unit 7 via the shaft 41.

  The motor 40 is installed on a fixed plate 44 attached to the lower end of the guide member 43, and is connected to the ball screw 45 via the timing belt 401. When the holding part 7 is raised and lowered by the holding part raising / lowering mechanism 4, the motor 40 as the driving part rotates the ball screw 45 under the control of the control part 3, and the moving plate 42 to which the nut 46 is fixed follows the guide member 43. Move vertically. As a result, the shaft 41 fixed to the moving plate 42 moves along the vertical direction, and the holding unit 7 connected to the shaft 41 moves between the delivery position of the semiconductor wafer W shown in FIG. 1 and the semiconductor wafer W shown in FIG. Move up and down smoothly between the processing positions.

  On the upper surface of the moving plate 42, a mechanical stopper 451 having a substantially semi-cylindrical shape (a shape obtained by cutting the cylinder in half along the longitudinal direction) is provided so as to extend along the ball screw 45. If the upper limit of the mechanical stopper 451 is struck against the end plate 452 provided at the end of the ball screw 45, the moving plate 42 is prevented from rising abnormally. Thereby, the holding part 7 does not rise above a predetermined position below the chamber window 61, and the collision between the holding part 7 and the chamber window 61 is prevented.

  The holding unit lifting mechanism 4 has a manual lifting unit 49 that manually lifts and lowers the holding unit 7 when performing maintenance inside the chamber 6. The manual elevating part 49 has a handle 491 and a rotating shaft 492. By rotating the rotating shaft 492 via the handle 491, the ball screw 45 connected to the rotating shaft 492 is rotated via the timing belt 495 to hold the holding part. 7 can be moved up and down.

  A telescopic bellows 47 that surrounds the shaft 41 and extends downward is provided below the chamber bottom 62, and its upper end is connected to the lower surface of the chamber bottom 62. On the other hand, the lower end of the bellows 47 is attached to the bellows lower end plate 471. The bellows lower end plate 471 is attached by being screwed to the shaft 41 by a flange-shaped member 411. The bellows 47 is contracted when the holding portion 7 is raised with respect to the chamber bottom 62 by the holding portion lifting mechanism 4, and the bellows 47 is expanded when the holding portion 7 is lowered. When the holding unit 7 moves up and down, the airtight state in the heat treatment space 65 is maintained by the expansion and contraction of the bellows 47.

  FIG. 3 is a cross-sectional view showing the configuration of the holding unit 7. The holding unit 7 includes a hot plate (heating plate) 71 for preheating (so-called assist heating) the semiconductor wafer W before flash light irradiation, and an upper surface of the hot plate 71 (on the side where the holding unit 7 holds the semiconductor wafer W). A susceptor 72 placed on the surface. As described above, the shaft 41 that moves up and down the holding unit 7 is connected to the lower surface of the holding unit 7.

  The susceptor 72 of the first embodiment is formed of pyrolytic boron nitride (PBN). Pyrolytic boron nitride is precisely a ceramic of a compound of nitrogen and boron called hexagonal structure boron nitride (Hexagonal Structure Pyrolytic Boron Nitride). Pyrolytic boron nitride has a structure in which nitrogen and boron are alternately positioned at the vertices of a regular hexagon and are formed in a multi-layered plane. By stacking such surfaces in a two-layer cycle (that is, nitrogen and boron are alternately positioned along the stacking direction), hexagonal boron nitride, that is, the pyrolytic boron nitride of the present embodiment can be obtained. It is formed. Bonds in the planes of the laminated surfaces are covalent bonds, and bonds between the planes are van der Waals bonds.

  The Young's modulus of pyrolytic boron nitride is about 22 GPa. Compared with the Young's modulus of iron being about 200 GPa and that of aluminum alloy being about 70 GPa, it can be said that pyrolytic boron nitride is a material that is more flexible than a general metal material despite being a ceramic.

The thermal conductivity of pyrolytic boron nitride is about 20 to 120 W · m ⁻¹ · K ⁻¹ . Considering that the thermal conductivity of alumina (Al ₂ O ₃ ) is about 20 W · m ⁻¹ · K ⁻¹ , and the thermal conductivity of general glass is about 1 W · m ⁻¹ · K ^−1. It can be said that pyrolytic boron nitride has a relatively large thermal conductivity. In addition, pyrolytic boron nitride, which is ceramic, has high heat resistance.

  The susceptor 72 formed of pyrolytic boron nitride is placed on the hot plate 71 with its lower surface in surface contact with the upper surface of the hot plate 71. Further, a recess 176 having a tapered periphery is formed on the upper surface of the susceptor 72, and the semiconductor wafer W is placed in the recess 176 (the bottom surface of the recess 176). Further, a pin 75 that prevents the semiconductor wafer W from being displaced is provided on the upper surface of the susceptor 72 and outside the recess 176. The pin 75 may be formed of pyrolytic boron nitride or may be formed of quartz.

  The hot plate 71 includes an upper plate 73 and a lower plate 74 made of stainless steel. A resistance heating wire 76 such as a nichrome wire for heating the hot plate 71 is disposed between the upper plate 73 and the lower plate 74, and is filled with a conductive nickel (Ni) solder and sealed. The end portions of the upper plate 73 and the lower plate 74 are bonded by brazing.

  FIG. 4 is a plan view showing the hot plate 71. As shown in FIG. 4, the hot plate 71 includes a disc-shaped zone 711 and an annular zone 712 that are concentrically arranged in a central portion of a region facing the held semiconductor wafer W, and a zone 712. There are four zones 713 to 716 obtained by equally dividing a peripheral substantially annular region into four equal parts in the circumferential direction, and a slight gap is formed between the zones. The hot plate 71 is provided with three through holes 77 through which the support pins 70 are inserted, every 120 ° on the circumference of the gap between the zone 711 and the zone 712.

  In each of the six zones 711 to 716, heaters are individually formed so that mutually independent resistance heating wires 76 circulate, and each zone is individually formed by a heater built in each zone. Heated. The semiconductor wafer W held by the holding unit 7 is heated by heaters built in the six zones 711 to 716. Each of the zones 711 to 716 is provided with a sensor 710 that measures the temperature of each zone using a thermocouple. Each sensor 710 passes through the inside of a substantially cylindrical shaft 41 and is connected to the control unit 3.

  When the hot plate 71 is heated, the resistance heating wire disposed in each zone is set so that the temperature of each of the six zones 711 to 716 measured by the sensor 710 becomes a predetermined temperature. The amount of power supplied to 76 is controlled by the control unit 3. The temperature control of each zone by the control unit 3 is performed by PID (Proportional, Integral, Derivative) control. In the hot plate 71, the temperature of each of the zones 711 to 716 is continuously measured until the heat treatment of the semiconductor wafer W (when plural semiconductor wafers W are continuously processed, the heat treatment of all the semiconductor wafers W) is completed. Then, the power supply amount to the resistance heating wire 76 disposed in each zone is individually controlled, that is, the temperature of the heater built in each zone is individually controlled, and the temperature of each zone becomes the set temperature. Maintained. The set temperature of each zone can be changed by an offset value set individually from the reference temperature.

  The resistance heating wires 76 respectively disposed in the six zones 711 to 716 are connected to a power supply source (not shown) via a power line passing through the inside of the shaft 41. On the way from the power supply source to each zone, the power lines from the power supply source are arranged so as to be electrically insulated from each other inside a stainless tube filled with an insulator such as magnesia (magnesium oxide). The The interior of the shaft 41 is open to the atmosphere.

  Next, the lamp house 5 is provided above the holding part 7 in the chamber 6. The lamp house 5 includes a flash light source including a plurality of (30 in this embodiment) xenon flash lamps FL and a reflector 52 provided so as to cover the light source inside the housing 51. Configured. A lamp light emission window 53 is attached to the bottom of the casing 51 of the lamp house 5. The lamp light radiation window 53 constituting the floor of the lamp house 5 is a plate-like member made of quartz. By installing the lamp house 5 above the chamber 6, the lamp light emission window 53 faces the chamber window 61. The lamp house 5 heats the semiconductor wafer W by irradiating the semiconductor wafer W held by the holding unit 7 in the chamber 6 with flash light from the flash lamp FL via the lamp light emission window 53 and the chamber window 61. .

  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 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 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 instantaneously flows into the glass tube due to the discharge between the electrodes at both ends, and the excitation of the xenon atoms or molecules at that time Light is emitted. In such a xenon flash lamp FL, the electrostatic energy stored in the condenser in advance is converted into an extremely short light pulse of 0.1 to 10 milliseconds, which is extremely in comparison with a continuous light source. It has the feature that it can irradiate strong light.

  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 flash light emitted from the plurality of flash lamps FL toward the holding unit 7. The reflector 52 is formed of an aluminum alloy plate, and the surface (the surface facing the flash lamp FL) is roughened by blasting to exhibit a satin pattern. The roughening process is performed when the surface of the reflector 52 is a perfect mirror surface, and a regular pattern is generated in the intensity of the reflected light from the plurality of flash lamps FL, so that the surface temperature distribution of the semiconductor wafer W is obtained. This is because the uniformity of the is reduced.

  Further, 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.

  In addition to the above configuration, the heat treatment apparatus 1 is used for various cooling purposes in order to prevent excessive temperature rise of the chamber 6 and the lamp house 5 due to the heat energy generated from the flash lamp FL and the hot plate 71 during the heat treatment of the semiconductor wafer W. It has the structure of For example, water-cooled tubes (not shown) are provided on the chamber side 63 and the chamber bottom 62 of the chamber 6. The lamp house 5 has an air cooling structure provided with a gas supply pipe 55 and an exhaust pipe 56 for exhausting heat by forming a gas flow therein (see FIG. 1). Air is also supplied to the gap between the chamber window 61 and the lamp light emission window 53 to cool the lamp house 5 and the chamber window 61.

  Next, a processing procedure for the semiconductor wafer W in the heat treatment apparatus 1 will be described. Here, the semiconductor wafer W to be processed is a semiconductor substrate to which impurities (ions) are added by an ion implantation method, and activation of the added impurities is executed by light irradiation heating processing (annealing) by 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, the holding unit 7 is lowered from the processing position shown in FIG. 5 to the delivery position shown in FIG. The “processing position” is the position of the holding unit 7 when the semiconductor wafer W is irradiated with light from the flash lamp FL, and is the position in the chamber 6 of the holding unit 7 shown in FIG. Further, the “delivery position” is the position of the holding unit 7 when the semiconductor wafer W is carried in and out of the chamber 6, and is the position of the holding unit 7 shown in FIG. The reference position of the holding unit 7 in the heat treatment apparatus 1 is the processing position. Before the processing, the holding unit 7 is located at the processing position, and this is lowered to the delivery position at the start of processing. As shown in FIG. 1, when the holding portion 7 is lowered to the delivery position, the holding portion 7 comes close to the chamber bottom portion 62, and the tip of the support pin 70 penetrates the holding portion 7 and protrudes above the holding portion 7.

  Next, when the holding unit 7 is lowered to the delivery position, the valve 82 and the valve 87 are opened, and normal temperature nitrogen gas is introduced into the heat treatment space 65 of the chamber 6. Subsequently, the gate valve 185 is opened to open the transfer opening 66, and the semiconductor wafer W is loaded into the chamber 6 through the transfer opening 66 by the transfer robot outside the apparatus and placed on the plurality of support pins 70. Is done.

  The purge amount of nitrogen gas into the chamber 6 when the semiconductor wafer W is loaded is about 40 liters / minute, and the supplied nitrogen gas is moved from the gas introduction buffer 83 in the direction of the arrow AR4 shown in FIG. Then, the exhaust gas is exhausted by utility exhaust via the discharge path 86 and the valve 87 shown in FIG. A part of the nitrogen gas supplied to the chamber 6 is also discharged from an outlet (not shown) provided inside the bellows 47. In each step described below, nitrogen gas is continuously supplied to and exhausted from the chamber 6, and the supply amount of the nitrogen gas is variously changed according to the processing process of the semiconductor wafer W.

  When the semiconductor wafer W is loaded into the chamber 6, the transfer opening 66 is closed by the gate valve 185. The holding unit lifting mechanism 4 raises the holding unit 7 from the delivery position to a processing position close to the chamber window 61. In the process in which the holding unit 7 is lifted from the delivery position, the semiconductor wafer W is transferred from the support pins 70 to the susceptor 72 of the holding unit 7, and is placed and supported in a horizontal posture on the recess 176 of the susceptor 72. FIG. 6 is a view showing the holding unit 7 on which the semiconductor wafer W is placed. In the figure, the semiconductor wafer W is placed in the center of the recess 176 of the susceptor 72, but the semiconductor wafer W may be slightly slid and its end may be in contact with the tapered surface of the recess 176. When the holding unit 7 moves up to the processing position, the semiconductor wafer W supported by the susceptor 72 is also held at the processing position.

  Each of the six zones 711 to 716 of the hot plate 71 is heated to a predetermined temperature by a heater (resistive heating wire 76) individually incorporated in each zone (between the upper plate 73 and the lower plate 74). ing. When the holding unit 7 rises to the processing position and the semiconductor wafer W comes into contact with the holding unit 7, the semiconductor wafer W is preheated by the heater built in the hot plate 71 and the temperature gradually rises.

  Preheating for about 60 seconds is performed at this processing position, and the temperature of the semiconductor wafer W rises to a preset preheating temperature T1. The preheating temperature T1 is set to about 200 ° C. to 800 ° C., preferably about 350 ° C. to 550 ° C., in which impurities added to the semiconductor wafer W are not likely to diffuse due to heat.

  After the preheating time of about 60 seconds elapses, flash light is irradiated from the flash lamp FL of the lamp house 5 toward the semiconductor wafer W under the control of the control unit 3 while the holding unit 7 is positioned at the processing position. At this time, a part of the flash light emitted from the flash lamp FL goes directly to the holding part 7 in 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 of the flash light. Since flash heating is performed by flash light irradiation from the flash lamp FL, the surface temperature of the semiconductor wafer W can be increased in a short time.

  In other words, the flash light emitted from the flash lamp FL of the lamp house 5 is converted to a light pulse whose electrostatic energy stored in advance is extremely short, and the irradiation time is about 0.1 to 10 milliseconds. A short and strong flash. The surface temperature of the semiconductor wafer W flash-heated by flash light irradiation from the flash lamp FL instantaneously rises to a processing temperature T2 of about 1000 ° C. to 1100 ° C., and the impurities added to the semiconductor wafer W are activated. After being converted, the surface temperature rapidly decreases. 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 impurities added to the semiconductor wafer W due to heat. Can do. Since the time required for activation of the added impurity is extremely short compared to the time required for thermal diffusion, activation is possible even for a short time when no diffusion of about 0.1 millisecond to 10 millisecond occurs. Is completed.

  Further, by preheating the semiconductor wafer W by the holding unit 7 before the flash heating, the surface temperature of the semiconductor wafer W can be quickly raised to the processing temperature T2 by the flash light irradiation from the flash lamp FL. .

  After the flash heating is finished and the standby for about 10 seconds at the processing position, the holding unit 7 is lowered again to the delivery position shown in FIG. 1 by the holding unit lifting mechanism 4, and the semiconductor wafer W is transferred from the holding unit 7 to the support pins 70. Is passed. Subsequently, the transfer opening 66 closed by the gate valve 185 is opened, and the semiconductor wafer W placed on the support pins 70 is unloaded by a transfer robot outside the apparatus, and the semiconductor wafer W is flushed in the heat treatment apparatus 1. The heat treatment is completed.

  As described above, nitrogen gas is continuously supplied to the chamber 6 during the heat treatment of the semiconductor wafer W in the heat treatment apparatus 1, and the supply amount is about 30 liters / minute when the holding unit 7 is located at the processing position. When the holding unit 7 is located at a position other than the processing position, the rate is about 40 liters / minute.

  By the way, the surface temperature of the semiconductor wafer W that is flash-heated by flash irradiation of several milliseconds from the flash lamp FL instantaneously increases to a processing temperature T2 of about 1000 ° C. to 1100 ° C., while the back surface temperature at that moment is The temperature does not increase so much from the preheating temperature T1 of about 350 ° C. to 550 ° C. For this reason, rapid thermal expansion occurs only on the wafer surface side, and the semiconductor wafer W warps so that the upper surface is convex. Then, at the next moment, the surface temperature of the semiconductor wafer W rapidly decreases, while the back surface temperature also slightly increases due to heat conduction from the front surface to the back surface, so that the semiconductor wafer W is warped in the opposite direction. Stress to act. As a result, the semiconductor wafer W vibrates violently on the susceptor 72, and the semiconductor wafer W may be cracked by an impact at that time.

  In the first embodiment, flash light is irradiated from a flash lamp FL onto a semiconductor wafer W mounted and supported in a horizontal posture on a susceptor 72 formed of pyrolytic boron nitride. Pyrolytic boron nitride is a relatively flexible material with a Young's modulus of about 22 GPa, and even if the semiconductor wafer W vibrates vigorously during flash light irradiation, the impact on the wafer can be reduced. As a result, it is possible to prevent cracking of the semiconductor wafer W during flash light irradiation, and to improve the yield of flash heating accordingly. Further, if the frequency of wafer cracking is reduced, flash light irradiation can be performed from the flash lamp FL with a larger energy than before, so that a better activation process can be promoted.

  Further, pyrolytic boron nitride has a relatively smooth surface property, and even if the semiconductor wafer W vibrates violently, the susceptor 72 is hardly damaged, and as a result, generation of particles can be suppressed.

  The susceptor 72 that supports the semiconductor wafer W is placed on a hot plate 71 having a heater that preheats the semiconductor wafer W before irradiating flash light from the flash lamp FL. That is, the semiconductor wafer W is preheated from the hot plate 71 via the susceptor 72. Since pyrolytic boron nitride has a relatively high thermal conductivity, good heat transfer from the hot plate 71 to the semiconductor wafer W during preheating is performed, and the semiconductor wafer W can be quickly heated to the preheating temperature T1. it can.

<2. Second Embodiment>
Next, a second embodiment of the present invention will be described. The overall configuration of the heat treatment apparatus and the processing procedure for the semiconductor wafer W in the second embodiment are the same as those in the first embodiment. The second embodiment differs from the first embodiment in the configuration of a holding unit that holds the semiconductor wafer W in a horizontal posture and performs preheating.

  FIG. 7 is a diagram illustrating a configuration of the holding unit 7a according to the second embodiment. In the figure, the same elements as those in the first embodiment are denoted by the same reference numerals. The holding unit 7 a is configured by placing a quartz susceptor 172 on the upper surface of the hot plate 71 and further placing a buffer sheet 173 on the upper surface of the susceptor 172. The susceptor 172 is the same as the susceptor 72 of the first embodiment except that the material is quartz, and includes a recess 176 and a pin 75 on the upper surface.

  The buffer sheet 173 is a sheet member formed of pyrolytic boron nitride, and is placed in the recess 176 of the susceptor 172. The buffer sheet 173 has a planar size equal to or greater than that of the semiconductor wafer W, and the semiconductor wafer W is placed on the buffer sheet 173.

  In the second embodiment, flash light is irradiated from a flash lamp FL onto a semiconductor wafer W placed and supported in a horizontal posture on a buffer sheet 173 formed of pyrolytic boron nitride. Even in this case, since the pyrolytic boron nitride is a relatively flexible material, even if the semiconductor wafer W vibrates violently during flash light irradiation, the impact applied to the wafer can be reduced. As a result, it is possible to prevent the semiconductor wafer W from being cracked during flash light irradiation. Moreover, since pyrolytic boron nitride has a relatively smooth surface property, even if the semiconductor wafer W vibrates violently, the buffer sheet 173 is hardly damaged, and the generation of particles can be suppressed. Furthermore, since pyrolytic boron nitride has a relatively high thermal conductivity, the semiconductor wafer W can be quickly heated to the preheating temperature T1 during the preheating.

<3. Third Embodiment>
Next, a third embodiment of the present invention will be described. The overall configuration of the heat treatment apparatus and the processing procedure for the semiconductor wafer W in the third embodiment are the same as those in the first embodiment. The third embodiment differs from the first embodiment in the configuration of a holding unit that holds the semiconductor wafer W in a horizontal posture and performs preheating.

  FIG. 8 is a diagram illustrating a configuration of the holding unit 7b according to the third embodiment. In the figure, the same elements as those in the first embodiment and the second embodiment are denoted by the same reference numerals. The holding portion 7 b is configured by placing a quartz susceptor 272 on the upper surface of the hot plate 71, placing a buffer sheet 173 on the upper surface of the susceptor 272, and installing a wafer guide 174. The susceptor 272 of the third embodiment is a flat plate member made of quartz. The buffer sheet 173 is the same as that of the second embodiment.

  Since the susceptor 272 of the third embodiment is not provided with a recess or a pin, a wafer guide 174 for regulating the position of the edge of the semiconductor wafer W is provided around the buffer sheet 173. Wafer guide 174 is formed of pyrolytic boron nitride. The shape of the wafer guide 174 may be a pin shape, or may be formed with a tapered portion as shown in FIG.

  When the holding unit 7b is raised from the delivery position to the processing position and receives the semiconductor wafer W from the support pins 70, the semiconductor wafer W may slide sideways, but the wafer guide 174 causes the semiconductor wafer W to move more than the buffer sheet 173. It is prevented from slipping out. At this time, flash heating may be performed while the end portion of the semiconductor wafer W is in contact with the wafer guide 174.

  In the third embodiment, flash light is irradiated from a flash lamp FL onto a semiconductor wafer W mounted and supported in a horizontal posture on a buffer sheet 173 formed of pyrolytic boron nitride. If it does in this way, the same effect as a 1st embodiment and a 2nd embodiment can be acquired. Further, since the wafer guide 174 for regulating the position of the edge of the semiconductor wafer W is also formed by pyrolytic boron nitride, the flash lamp FL is kept in a state where the edge of the semiconductor wafer W is in contact with the wafer guide 174. Even if flash light is irradiated from above, cracking of the semiconductor wafer W and generation of particles can be prevented.

<4. Fourth Embodiment>
Next, a fourth embodiment of the present invention will be described. The overall configuration of the heat treatment apparatus and the processing procedure for the semiconductor wafer W in the fourth embodiment are the same as those in the first embodiment. The fourth embodiment differs from the first embodiment in the configuration of a holding unit that holds the semiconductor wafer W in a horizontal posture and performs preheating.

  FIG. 9 is a diagram illustrating a configuration of the holding unit 7c according to the fourth embodiment. In the figure, the same elements as those in the first to third embodiments are denoted by the same reference numerals. The holding portion 7 c is configured by placing a susceptor 372 having a concave concave portion 376 formed on the upper surface of the hot plate 71. The susceptor 372 is formed with a concave recess 376 having an outer diameter larger than the diameter of the semiconductor wafer W in plan view. That is, when the susceptor 372 is viewed from above, the concave shape of the concave portion 376 is larger than the planar size of the semiconductor wafer W. The concave shape defining the concave portion 376 has a predetermined radius of curvature. The susceptor 372 of the fourth embodiment is formed of pyrolytic boron nitride.

  When the holding part 7c rises from the delivery position to the processing position and receives the semiconductor wafer W from the support pins 70, the peripheral end of the semiconductor wafer W is supported by the inner wall surface of the recess 376, as shown in FIG. Become. As a result, a gap is formed in which a gas layer is sandwiched between the lower surface of the semiconductor wafer W and the surface of the susceptor 372.

  In the fourth embodiment, flash light is irradiated from a flash lamp FL onto a semiconductor wafer W placed and supported in a horizontal posture on a susceptor 372 formed of pyrolytic boron nitride. Even in this case, since the susceptor 372 is formed of pyrolytic boron nitride, even if the semiconductor wafer W vibrates vigorously at the time of flash light irradiation, the crack can be prevented and the susceptor 372 can be damaged. It is also possible to suppress the generation of particles.

  In addition, since a gas layer gap is formed between the surface of the susceptor 372 and the lower surface of the semiconductor wafer W, the lower surface of the semiconductor wafer W remains on the surface of the susceptor 372 even if the semiconductor wafer W vibrates violently during flash light irradiation. The semiconductor wafer W can be more reliably prevented from cracking.

<5. Modification>
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 first and fourth embodiments, the semiconductor wafer W is placed on the susceptors 72 and 372 formed of pyrolytic boron nitride, and in the second and third embodiments, the pyrolytic boron nitride is used. Although the semiconductor wafer W was mounted on the formed buffer sheet 173, the member for mounting the semiconductor wafer W is not limited to these. In other words, any form may be used as long as the substrate support portion for supporting the semiconductor wafer W irradiated with flash light from the flash lamp FL in a horizontal posture is formed by pyrolytic boron nitride.

  Further, a holding unit that holds the semiconductor wafer W in a horizontal posture and performs preheating may be as shown in FIG. The holding part 7d shown in FIG. 10 is obtained by removing the buffer sheet 173 from the holding part 7b of the third embodiment, and the same elements as those of the third embodiment are denoted by the same reference numerals. In the holding unit 7d shown in FIG. 10, the semiconductor wafer W is directly mounted on the quartz susceptor 272, but the holding unit 7d has moved from the delivery position to the processing position and received the semiconductor wafer W. Occasionally, the flash light is emitted from the flash lamp FL while the semiconductor wafer W slides sideways and is in contact with the wafer guide 174. In such a case, if the end of the semiconductor wafer W is in contact with the wafer guide 174 formed of pyrolytic boron nitride, wafer cracking can be reduced.

  Further, instead of pyrolytic boron nitride, the substrate support portion for placing and supporting the semiconductor wafer W in a horizontal posture is formed of, for example, silicon (Si), aluminum (Al), or lead (Pb). Anyway. All of these materials are relatively flexible and have high thermal conductivity. However, while pyrolytic boron nitride and silicon, which have excellent heat resistance, can be used for heat treatment in a high temperature range of 400 ° C. or higher, aluminum and lead have a low melting point, so that the intermediate temperature is 200 ° C. to 400 ° C. It is desirable to use in the heat treatment of the area. If the heat treatment is 200 ° C. or less, the substrate support portion may be formed of a resin material such as polytetrafluoroethylene, vinyl chloride, polyether ether ketone, polypropylene, or polyethylene.

  In the above embodiment, the lamp house 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.

  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 used for a liquid crystal display device or the like.

DESCRIPTION OF SYMBOLS 1 Heat processing apparatus 3 Control part 4 Holding part raising / lowering mechanism 5 Lamphouse 6 Chamber 7,7a, 7b, 7c, 7d Holding part 60 Upper opening 61 Chamber window 65 Heat processing space 71 Hotplate 72,172,272,372 Susceptor 75 Pin 76 Resistance heating wire 173 Buffer sheet 174 Wafer guide FL Flash lamp W Semiconductor wafer

Claims (5)

A heat treatment apparatus for heating a substrate by irradiating the substrate with flash light,
A substrate support unit for placing and supporting the substrate in a horizontal position;
A flash lamp for irradiating flash light to the substrate supported by the substrate support;
With
A heat treatment apparatus, wherein the substrate support portion is formed of pyrolytic boron nitride (PBN). The heat treatment apparatus according to claim 1, wherein
A hot plate for preheating the substrate before irradiating flash light from the flash lamp;
The heat treatment apparatus, wherein the substrate support part is a susceptor placed on the hot plate. The heat treatment apparatus according to claim 1, wherein
A hot plate for preheating the substrate before irradiating flash light from the flash lamp;
A quartz susceptor placed on the hot plate;
Further comprising
The heat treatment apparatus, wherein the substrate support portion is a sheet member placed on the susceptor. The heat treatment apparatus according to claim 3, wherein
A guide part for regulating the position of the edge part of the substrate;
A heat treatment apparatus, wherein the guide portion is formed of pyrolytic boron nitride. A susceptor for heat treatment that holds the substrate when the substrate is subjected to heat treatment by irradiating the substrate with flash light from a flash lamp,
A heat treatment susceptor, wherein the heat treatment susceptor is formed of pyrolytic boron nitride.

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