JP2010045093A - Thermal processing apparatus - Google Patents

Abstract

A heat treatment apparatus capable of freely setting an annealing time and a temperature profile during annealing.
A capacitor, a coil, a flash lamp, and a switching element such as an IGBT are connected in series. The analog signal output unit 10 outputs a trigger signal for applying a voltage equal to or higher than a threshold value at which the flash lamp FL starts to emit light between both end electrodes of the flash lamp FL, and then outputs an analog signal having a predetermined waveform to the switching element 96. Output to the gate. When a trigger signal is output to the gate of the switching element 96, a trigger voltage is applied to the trigger electrode 91, and the flash lamp FL starts to emit light. Thereafter, the current flowing through the flash lamp FL is controlled in accordance with the analog signal output from the analog signal output unit 10.
[Selection] Figure 6

Description

  The present invention relates to a heat treatment apparatus for heating a substrate by irradiating light onto a semiconductor wafer, a glass substrate for a liquid crystal display device or the like (hereinafter simply referred to as “substrate”).

  Conventionally, as a device capable of short-time annealing, a high-speed lamp annealing device that uses a light energy irradiated from a halogen lamp to raise the temperature of a semiconductor wafer at a speed of about several hundred degrees per second has been used (for example, Patent Document 1). Even if it is short-time annealing, it is a story compared with a resistance heating type heat treatment apparatus using a cantal heater or the like, and the annealing time was about several seconds.

  On the other hand, as a device capable of annealing in a shorter time, a xenon flash lamp (hereinafter simply referred to as “flash lamp” means xenon flash lamp) is used to irradiate the surface of a semiconductor wafer with flash light (flash). A flash lamp annealing apparatus is known (for example, Patent Document 2). The flash light irradiation time of the xenon flash lamp is an extremely short time of 10 milliseconds or less. The xenon flash lamp has a radiation spectral distribution from the ultraviolet region to the near-infrared region, which has a shorter wavelength than that of a 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 an extremely short time of 10 milliseconds or less, only the vicinity of the surface of the semiconductor wafer can be selectively heated. For this reason, the flash lamp annealing apparatus is suitable for ion activation treatment of a semiconductor wafer after ion implantation, and can form a shallow junction by performing only ion activation without causing thermal diffusion of ions.

  As an apparatus capable of annealing in a shorter time than a flash lamp annealing apparatus, there is a laser annealing apparatus. The laser annealing apparatus is an apparatus that anneals by scanning a pulse laser of several tens of nanoseconds in both X and Y directions.

JP 2000-199688 A JP 2004-055821 A

  However, conventionally, there has been no technology that can realize an annealing time in an intermediate region between a high-speed lamp annealing apparatus using a halogen lamp and a flash lamp annealing apparatus. That is, there has been no heat treatment apparatus in which the annealing time at each position on the main surface of the semiconductor wafer is about 10 milliseconds to 1 second. In recent years, such heat treatment with an intermediate annealing time has been required in various processes such as activation processing, metal processing, and wiring processing in transistor fabrication.

  If an intermediate annealing time is to be realized with a halogen lamp, the filament must be made thicker because a larger output is required. If this is done, the amount of heat increases and the temperature rise / fall rate slows down. Occurs.

  In the laser annealing apparatus, the annealing time in the intermediate region can theoretically be achieved by increasing the time during which the pulse laser stays at each position on the semiconductor wafer. However, when the time during which the pulse laser stays at a specific position becomes long, the temperature rises to an unexposed area, and the phenomenon of switching that occurs in the overlapping portion of the temperature rise becomes significant. As a larger problem, as a result of the longer time that the pulse laser stays at each position, it takes about one hour to process one semiconductor wafer, resulting in an unrealistic throughput.

  Further, there is a demand not only to rapidly raise the temperature and to rapidly lower the temperature, but also to freely change the temperature profile during annealing.

  The present invention has been made in view of the above problems, and an object thereof is to provide a heat treatment apparatus capable of freely setting an annealing time and a temperature profile during annealing.

  In order to solve the above problems, the invention of claim 1 is directed to a heat treatment apparatus that heats a substrate by irradiating the substrate with light, the holding means for holding the substrate, and the substrate held by the holding means. A flash lamp for irradiating light; a switching element connected in series with the flash lamp, a capacitor and a coil; and an analog signal output means for controlling driving of the switching element by outputting an analog signal to the switching element; It is characterized by providing.

  The invention of claim 2 is the heat treatment apparatus according to claim 1, further comprising trigger voltage applying means for applying a trigger voltage for light emission from the outside of the flash lamp, wherein the analog signal output means is After outputting a trigger signal for applying a voltage equal to or higher than a threshold at which the flash lamp starts to emit light between both end electrodes of the flash lamp when the trigger voltage applying means applies the trigger voltage, An analog signal having a predetermined waveform is output to the switching element.

  The invention according to claim 3 is the heat treatment apparatus according to claim 2, wherein the analog signal output means outputs the trigger signal for a predetermined time after the trigger voltage applying means applies the trigger voltage. The analog signal having the predetermined waveform is output to the switching element.

  According to a fourth aspect of the present invention, in the heat treatment apparatus according to the second or third aspect of the invention, the analog signal output means includes a waveform storage unit that stores a waveform level at predetermined intervals as digital data, and A D / A converter that converts the digital data stored in the waveform storage unit into an analog signal, and the waveform storage unit includes a trigger data area that stores data for generating the trigger signal; and A waveform data area for storing data for generating an analog signal having a predetermined waveform is set.

  According to a fifth aspect of the present invention, in the heat treatment apparatus according to the second or third aspect of the present invention, the analog signal output means includes a pulse signal generating means for generating a pulse signal including one or more pulses, and the pulse. A low-pass filter that generates an analog signal by subjecting the pulse signal generated by the signal generation means to low-pass filter processing, and the pulse signal generation means includes a single pulse for generating the trigger signal and A pulse group for generating an analog signal having the predetermined waveform is generated.

  According to a sixth aspect of the present invention, in the heat treatment apparatus according to any one of the first to fifth aspects of the present invention, the analog is in accordance with the amount of charge remaining in the capacitor after the flash lamp has finished emitting light. It further includes an amplifier that amplifies the analog signal output from the signal output means.

  According to a seventh aspect of the present invention, in the heat treatment apparatus according to any one of the first to sixth aspects, the switching element is a transistor, and the analog signal output means outputs an analog signal to the gate of the transistor. It is characterized by outputting.

  According to an eighth aspect of the present invention, in the heat treatment apparatus according to the seventh aspect of the present invention, the transistor is an insulated gate bipolar transistor.

  According to the first to eighth aspects of the present invention, since the driving of the switching element is controlled by outputting the analog signal to the switching element connected in series with the flash lamp, the capacitor, and the coil, the flash is generated by the waveform of the analog signal. The current flowing through the lamp and the light emission can be freely controlled, and the annealing time and temperature profile during annealing can be set freely.

  In particular, according to the invention of claim 2, the analog signal output means applies a voltage equal to or higher than a threshold value at which the flash lamp starts to emit light between both end electrodes of the flash lamp when the trigger voltage applying means applies the trigger voltage. After the trigger signal for outputting is output to the switching element, an analog signal having a predetermined waveform is output to the switching element, so that the flash lamp can be surely started to emit light.

  In particular, according to the invention of claim 3, the analog signal output means outputs an analog signal having a predetermined waveform to the switching element after a predetermined time has elapsed since the trigger voltage applying means applied the trigger voltage. Current is already flowing through the flash lamp at the time when the signal is output, and the current flowing through the flash lamp and light emission can be reliably controlled by the waveform of the analog signal.

  In particular, according to the sixth aspect of the present invention, the switching circuit further includes an amplifier that amplifies the analog signal output from the analog signal output means in accordance with the amount of charge remaining in the capacitor after the flash lamp has finished emitting light. Errors due to device differences can be corrected.

  In particular, according to the invention of claim 8, since the switching element is an insulated gate bipolar transistor, it is suitable for light emission of a flash lamp that requires high power.

  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 lamp annealing apparatus that irradiates a substantially circular semiconductor wafer W as a substrate with 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 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 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 (in this embodiment) for supporting the semiconductor wafer W from the lower surface (surface opposite to the side irradiated with light from the lamp house 5) through the holding portion 7. 3) support pins 70 are provided upright. 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. A portion of the chamber side 63 opposite to the transfer opening 66 is provided with a processing gas (for example, an inert gas such as nitrogen (N ₂ ) gas, helium (He) gas, argon (Ar) gas) in the heat treatment space 65, 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) via 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 disk-shaped holding unit 7 that holds the semiconductor wafer W in a horizontal position in the chamber 6 and performs preheating of the semiconductor wafer W held before light irradiation, and a holding unit. And a holding unit elevating mechanism 4 that elevates 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 is installed on a hot plate (heating plate) 71 that preheats the semiconductor wafer W (so-called assist heating), and an upper surface of the hot plate 71 (a surface on the side where the holding unit 7 holds the semiconductor wafer W). The susceptor 72 is provided. 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 is made of quartz (or may be aluminum nitride (AIN) or the like), and a pin 75 for preventing displacement of the semiconductor wafer W is provided on the upper surface thereof. The susceptor 72 is installed on the hot plate 71 with its lower surface in surface contact with the upper surface of the hot plate 71. Thus, the susceptor 72 diffuses the thermal energy from the hot plate 71 and transmits it to the semiconductor wafer W placed on the upper surface of the susceptor 72, and can be removed from the hot plate 71 and cleaned during maintenance.

  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 includes a light source composed of a plurality of (30 in this embodiment) xenon flash lamps FL inside the housing 51, and a reflector 52 provided so as to cover the light source, It is configured with. 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 light from the flash lamp FL through 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 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 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.

  FIG. 6 is a diagram showing a driving circuit for the flash lamp FL. As shown in the figure, a capacitor 93, a coil 94, a flash lamp FL, and a switching element 96 are connected in series. The flash lamp FL includes a rod-shaped glass tube (discharge tube) 92 in which xenon gas is sealed and an anode and a cathode are disposed at both ends thereof, and a trigger electrode provided on the outer peripheral surface of the glass tube 92. 91. A predetermined voltage is applied to the capacitor 93 by the power supply unit 95, and a charge corresponding to the applied voltage is charged. A trigger voltage can be applied from the trigger circuit 97 to the trigger electrode 91. The timing at which the trigger circuit 97 applies a voltage to the trigger electrode 91 is controlled by the control unit 3. The driving circuit for the flash lamp FL is provided with a protection diode 98 for protecting the switching element 96 from an overvoltage caused by a counter electromotive force or the like.

  In the present embodiment, an insulated gate bipolar transistor (IGBT) is used as the switching element 96. The IGBT is a bipolar transistor in which a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is incorporated in a gate portion, and is a switching element suitable for handling high power. The emitter / collector of the switching element 96 using IGBT is connected to both end electrodes of the flash lamp FL. An analog signal is output from the analog signal output unit 10 to the gate of the switching element 96. As a result, a voltage is applied between the gate and the emitter to control the driving of the IGBT.

  Even if the switching element 96 is turned on while the capacitor 93 is charged and a high voltage is applied to both end electrodes of the glass tube 92, the xenon gas is electrically an insulator, so that the normal state Then, no electricity flows in the glass tube 92. However, when the trigger circuit 97 applies a high voltage to the trigger electrode 91 to break the insulation, a current flows instantaneously between the both end electrodes in the glass tube 92, and light is generated by excitation of atoms or molecules of xenon at that time. Is released. That is, when the capacitor 93 is charged and the switching element 96 is turned on and a voltage is applied to the trigger electrode 91, the flash lamp FL starts to emit light. The current flowing through the flash lamp FL is controlled by the switching element 96.

  FIG. 7 is a block diagram showing the configuration of the drive mechanism of the switching element 96 in the first embodiment. The analog signal output unit 10 includes a waveform storage unit 101 and a D / A converter (digital-analog conversion circuit) 102. The waveform storage unit 101 is configured by a memory that can read out stored digital data, for example, every 50 microseconds. The waveform of the analog signal output from the analog signal output unit 10 is set by the control unit 3 and stored in the waveform storage unit 101 as digital data.

  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 is configured with a magnetic disk. Further, the control unit 3 is provided with an input unit (for example, a keyboard and a mouse) for an operator to input commands and data and a display unit (for example, a display) for confirming various information. The control unit 3 controls various operation mechanisms provided in the heat treatment apparatus 1 by executing control software stored in advance. The control unit 3 sets the waveform of the analog signal output from the analog signal output unit 10 as digital data, transfers the waveform data to the analog signal output unit 10, and stores it in the waveform storage unit 101.

  FIG. 8 is a diagram illustrating an example of the data structure of the waveform data stored in the waveform storage unit 101. In FIG. 8, the memory address of the waveform storage unit 101 and the data stored therein are represented in hexadecimal. In the waveform storage unit 101, the waveform data set by the control unit 3 is stored as digital data. Each memory address stores 1-byte digital data.

  In the waveform storage unit 101, a trigger data area TR and a waveform data area DR are set. In the trigger data area TR (addresses “000” to “07F” in the example of FIG. 8), the maximum value “FF (decimal number 255)” is stored in all addresses. On the other hand, any value between “00” and “FF” is stored in each waveform address DR (addresses “080” to “1FF” in the example of FIG. 8). The waveform storage unit 101 stores the waveform level of the analog signal at predetermined intervals (50 microseconds in the present embodiment) as digital data in both the trigger data region TR and the waveform data region DR.

  The digital data stored in the waveform storage unit 101 is read every 50 microseconds sequentially from the address “000”, converted into an analog signal by the D / A converter 102, and output from the analog signal output unit 10. The analog signal output from the analog signal output unit 10 is transmitted to the gates of 30 switching elements 96 through the amplifier 99. The lamp house 5 of the present embodiment is provided with 30 flash lamps FL. However, the control unit 3 that sets waveform data and the analog signal output unit 10 that outputs waveform data as analog signals are 30. One flash lamp FL is provided in common. On the other hand, one switching element 96 is provided for each drive circuit of 30 flash lamps FL, and one amplifier 99 is also provided for each of the 30 switching elements 96. One trigger circuit 97 is also provided for each of the 30 flash lamps FL.

  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 FIGS. 1 and 5). 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. 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 held on the upper surface of the susceptor 72. When the holding unit 7 is raised to the processing position, the semiconductor wafer W held 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. Further, the distance between the holding unit 7 and the chamber window 61 can be arbitrarily adjusted by controlling the rotation amount of the motor 40 of the holding unit lifting mechanism 4.

  After the preheating time of about 60 seconds elapses, light irradiation heating (annealing) of the semiconductor wafer W by the flash lamp FL is started. When irradiating light from the flash lamp FL, charges are accumulated in the capacitor 93 by the power supply unit 95 in advance. Then, in the state where electric charges are accumulated in the capacitor 93, an analog signal is output from the analog signal output unit 10 to the gate of the switching element 96 under the control of the control unit 3, and a high voltage is applied from the trigger circuit 97 to the trigger electrode 91. Applied to cause the flash lamp FL to emit light.

  FIG. 9 is a timing chart showing the correlation between the trigger voltage, the analog signal output to the gate of the switching element 96, and the current flowing through the flash lamp FL. As described above, waveform data as shown in FIG. 8 is stored in advance as digital data by the control unit 3 in the waveform storage unit 101 of the analog signal output unit 10. Of the digital data in FIG. 8, the waveform data region DR is appropriately set by the control unit 3 by the operator. On the other hand, the trigger data region TR may be set by the operator together with the waveform data region DR, or the control unit 3 may automatically add to the address before the set waveform data region DR. The setting by the operator may be manually input from the input unit to the control unit 3, read from the magnetic disk of the control unit 3, or downloaded to the control unit 3 via the network. You may make it do.

  The digital data in FIG. 8 stored in the waveform storage unit 101 is read out at predetermined intervals (50 microseconds) in order from the address “000”, converted into an analog signal by the D / A converter 102, and output as an analog signal. Output from the unit 10. The output analog signal is transmitted to the gate of the switching element 96 through the amplifier 99. As a result, the analog signal shown in FIG. 9B is output to the gate of the switching element 96. That is, “FF”, which is the maximum value, is stored in the addresses “000” to “07F” that are the trigger data region TR of the waveform storage unit 101, and the maximum and constant voltage is maintained from time t0 to time t2. A trigger signal is output to the gate of the switching element 96. As a result, the switching element 96 is turned on, and the maximum voltage is applied from the capacitor 93 between the both end electrodes of the flash lamp FL.

  In this state, a trigger voltage is applied from the trigger circuit 97 to the trigger electrode 91 at time t1, as shown in FIG. Note that time t1 is a timing at which, for example, digital data at address “070” in the trigger data area TR is read out, and the control unit 3 that has detected that the digital data at address “070” has been read out controls the trigger circuit 97. Then, the trigger voltage may be applied to the trigger electrode 91. Alternatively, the trigger signal may be applied to the trigger electrode 91 by transmitting the digital data of the address “070” directly from the analog signal output unit 10 to the trigger circuit 97.

  When a voltage is applied to the trigger electrode 91 in a state where the maximum voltage from the capacitor 93 is applied between the both end electrodes of the flash lamp FL, the insulation of the flash lamp FL is broken, and both end electrodes as shown in FIG. Current begins to flow between them. As a result, the flash lamp FL starts to emit light.

  After a voltage is applied to the trigger electrode 91 at time t1 and the flash lamp FL starts to emit light, data reading from the trigger data region TR is completed at time t2 when a predetermined time has elapsed, and data from the waveform data region DR is obtained. Move to read. That is, reading after the address “080” is executed. As a result, after time t2, an analog signal having a waveform as shown in FIG. 9B which is D / A converted in accordance with the digital data stored in the waveform data region DR is output to the gate of the switching element 96. Note that the trigger signal with the maximum and constant voltage obtained by D / A converting the digital data read from the trigger data area TR is also the switching element from time t1 to time t2 after the flash lamp FL starts to emit light. It is output to 96 gates.

  Since the resistance is low after the flash lamp FL starts to emit light at the time t1, the current continues to flow through the flash lamp FL even if the voltage between the electrodes is low. Therefore, the switching element 96 controls the current flowing through the circuit according to the analog signal output from the analog signal output unit 10, and the current as shown in FIG. 9C flows through the flash lamp FL.

  The light emission output of the flash lamp FL is substantially proportional to the current flowing through the flash lamp FL. Therefore, the output waveform of the light emission output of the flash lamp FL also has a pattern as shown in FIG. The flash lamp FL emits light with such an output waveform, and light irradiation heating of the semiconductor wafer W held by the holding portion 7 at the processing position is performed. As a result, the surface temperature of the semiconductor wafer W rises. The temperature change pattern of the semiconductor wafer W at this time depends on the waveform of the light emission output from the flash lamp FL.

  When the flash lamp FL is caused to emit light without using the switching element 96 as in the prior art, the light becomes an extremely short and strong flash with an irradiation time of about 0.1 milliseconds to 10 milliseconds, and the semiconductor wafer W The surface temperature reaches the maximum temperature in about several milliseconds. On the other hand, as in the present embodiment, the switching element 96 is connected in the circuit and the analog signal as shown in FIG. Therefore, the surface temperature of the semiconductor wafer W can reach the maximum temperature over a long time compared to the conventional flash heating. The maximum temperature that the surface temperature of the semiconductor wafer W reaches is a processing temperature T2 of about 1000 ° C. to about 1300 ° C., which is almost the same as that of the conventional flash heating.

  After the light irradiation 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 moved from the holding unit 7 to the support pins 70. Passed to. 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 the transfer robot outside the apparatus, and the light of the semiconductor wafer W in the heat treatment apparatus 1 is transferred. The irradiation annealing process 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.

  In the first embodiment, an IGBT switching element 96 is connected in series to the driving circuit of the flash lamp FL, and an analog signal is output to the gate of the switching element 96 to control the current flowing through the flash lamp FL. The light emission of the lamp FL is controlled. The waveform of the analog signal applied to the gate of the switching element 96 can be freely set by digital data stored in the waveform data region DR of the waveform storage unit 101. Then, by changing the waveform of the analog signal output to the gate of the switching element 96, the waveform of the current flowing through the flash lamp FL changes and the light emission mode also changes. As a result, the temperature profile drawn by the surface temperature of the semiconductor wafer W also changes. That is, the temperature profile of the light irradiation annealing time of the flash lamp FL and the surface temperature of the semiconductor wafer W can be freely set by changing the waveform of the analog signal output to the gate of the switching element 96.

  Incidentally, depending on the signal output to the gate of the switching element 96, a large back electromotive force may be generated in the coil 94. For example, when a pulse signal that repeatedly turns on and off is output to the gate of the switching element 96, the current flowing through the drive circuit of the flash lamp FL is also on / off controlled (chopper control), and the coil 94 is switched to the coil 94 at the moment of switching on and off. A very large counter electromotive force is generated. Although the protective diode 98 is provided to protect the switching element 96 from such a large counter electromotive force, when the counter electromotive force exceeding the withstand voltage limit is generated, the protective diode 98 and the switching element are provided. There is also a possibility that 96 may be damaged. For this reason, the current flowing through the flash lamp FL must be kept low. Further, the current waveform flowing through the flash lamp FL may be disturbed by the beat effect determined from the on / off frequency of the pulse signal and the natural vibration frequency determined from the relationship between the capacitor 93 and the coil 94.

  Therefore, in the present embodiment, driving of the switching element 96 is controlled by outputting an analog signal to the gate of the switching element 96. Analog signals have a significantly lower frequency than pulse signals that repeatedly turn on and off. For this reason, the change in the current flowing through the drive circuit of the flash lamp FL also becomes a low frequency, and the back electromotive force generated in the coil 94 can be made small. As a result, there is no possibility that a large back electromotive force acts on the protection diode 98 and the switching element 96 and breaks them, and if necessary for the annealing process, a large current can be passed through the flash lamp FL. In addition, if the signal is an analog signal, the above-described beat effect is alleviated.

  However, even if only the analog signal having a waveform as shown after time t2 in FIG. 9B is output to the gate of the switching element 96 to cause the flash lamp FL to emit light, both end electrodes of the flash lamp FL depend on the signal level. There is a possibility that no sufficient voltage is applied to the flash lamp FL even if a voltage is applied to the trigger electrode 91. For this reason, in the present embodiment, in addition to the waveform data area DR that stores digital data for generating an analog signal having a predetermined waveform, the trigger data area TR that stores digital data for generating a trigger signal has a waveform. It is set in the storage unit 101.

  When the trigger circuit 97 applies the trigger voltage to the trigger electrode 91 by outputting a trigger signal having a maximum and constant voltage obtained by D / A converting the digital data stored in the trigger data region TR to the gate of the switching element 96. At (time t1), a maximum voltage from the capacitor 93, which is a voltage equal to or higher than a threshold value at which the flash lamp FL starts to emit light, is applied between both end electrodes of the flash lamp FL. For this reason, when the trigger circuit 97 applies the trigger voltage to the trigger electrode 91 at time t1, the current surely flows between both end electrodes of the flash lamp FL, and the flash lamp FL starts to emit light.

  Then, at time t2 after a predetermined time has elapsed since the trigger circuit 97 applied the trigger voltage at time t1, an analog signal having a predetermined waveform obtained by D / A converting the digital data stored in the waveform data region DR is a switching element. It is output to 96 gates. Since the digital signal read out from the trigger data region TR is D / A converted and the trigger signal having the maximum and constant voltage is output to the gate of the switching element 96 even during the lapse of the predetermined time, the flash lamp FL The maximum voltage from the capacitor 93 continues to be applied between the two end electrodes, and a current flows stably to the flash lamp FL at time t2. For this reason, even if the signal level of the analog signal obtained by D / A converting the digital data stored in the waveform data area DR is low, current continues to flow through the flash lamp FL, and the flash lamp FL follows the waveform of the analog signal. The waveform of the flowing current can be controlled.

  As shown in FIG. 7, the heat treatment apparatus 1 of the first embodiment is provided with an amplifier 99 that amplifies the analog signal output from the analog signal output unit 10. The amplifier 99 is provided in each of the 30 switching elements 96. The amplifier 99 amplifies the analog signal output from the analog signal output unit 10 in accordance with the amount of charge remaining in the capacitor 93 after the flash lamp FL has finished emitting light. Specifically, the larger the amount of charge remaining in the capacitor 93 after the flash lamp FL has finished emitting light, the larger the amplification factor of the analog signal.

  In the heat treatment apparatus 1 of the first embodiment, the current flowing through the flash lamp FL is suppressed by outputting an analog signal having a predetermined waveform to the gate of the switching element 96 to control the driving of the switching element 96. For this reason, electric charge remains in the capacitor 93 even after the flash lamp FL has finished emitting light. The amount of charge remaining in the capacitor 93 can be measured by measuring the voltage across the capacitor 93 with a voltmeter (not shown). A large amount of charge remaining in the capacitor 93 means that the power consumed by the flash lamp FL is small. Therefore, when the amount of charge remaining in the capacitor 93 is large after the flash lamp FL has finished emitting light, the amplifier 99 corresponding to the flash lamp FL increases the analog signal amplification factor to flow into the flash lamp FL. The current is increased. In this way, the error due to the machine difference of the switching element 96 can be corrected by the amplifier 99. The control unit 3 that detects the residual charge amount of the capacitor 93 may adjust the amplification factor of the amplifier 99.

<2. Second Embodiment>
Next, a second embodiment of the present invention will be described. The overall configuration of the heat treatment apparatus of the second embodiment and the processing procedure for the semiconductor wafer W are the same as those of the heat treatment apparatus 1 of the first embodiment. The heat treatment apparatus of the second embodiment is different from the first embodiment in the configuration of the drive mechanism of the switching element 96.

  FIG. 10 is a block diagram showing the configuration of the drive mechanism of the switching element 96 in the second embodiment. The same elements as those in the first embodiment are denoted by the same reference numerals. The analog signal output unit 20 includes a waveform storage unit 201, a pulse generator 202, and a low-pass filter 203.

  The waveform storage unit 201 is configured by a memory, and stores waveform data set by the control unit 3. However, unlike the first embodiment, the waveform data of the second embodiment sequentially defines a pulse rising time (on time) and a space time between pulses (off time). That is, in the second embodiment, the control unit 3 sets the waveform data of the pulse signal and stores it in the waveform storage unit 201. The waveform data can be set manually by the operator from the input unit to the control unit 3 or read from the magnetic disk of the control unit 3 as in the first embodiment. However, it may be downloaded to the control unit 3 via a network.

  The pulse generator 202 generates and outputs a pulse signal including one or more pulses according to the waveform data stored in the waveform storage unit 201. The pulse signal output from the pulse generator 202 is subjected to low-pass filter processing by the low-pass filter 203. That is, the low-pass filter 203 takes out a low-frequency component from the pulse signal and passes it while suppressing the high-frequency component. The pulse signal subjected to the low-pass filter processing becomes an analog signal. Therefore, the analog signal output unit 20 outputs an analog signal to the 30 switching elements 96.

  Also in the second embodiment, after the preheating of the semiconductor wafer W is completed, the analog signal is transferred from the analog signal output unit 20 to the gate of the switching element 96 under the control of the control unit 3 in a state where electric charges are accumulated in the capacitor 93. And a high voltage is applied from the trigger circuit 97 to the trigger electrode 91 to cause the flash lamp FL to emit light. FIG. 11 is a timing chart showing the correlation among the pulse signal, the trigger voltage, the output signal from the low-pass filter 203, and the current flowing through the flash lamp FL. In accordance with the waveform data stored in the waveform storage unit 201, the pulse generator 202 generates a pulse signal having a waveform as shown in FIG.

  As shown in the figure, the pulse generator 202 generates a pulse signal including a single pulse PT for generating a trigger signal and a pulse group PG for generating an analog signal having a predetermined waveform. Among these, the pulse group PG is appropriately set by the operator by the control unit 3. On the other hand, the operator may set the single pulse PT together with the pulse group PG, or the control unit 3 automatically adds the pulse data of a predetermined length before the set pulse group PG. May be.

  By applying low-pass filter processing to a pulse signal having a waveform as shown in FIG. 11A, the signal output from the low-pass filter 203 becomes an analog signal having a waveform as shown in FIG. Then, an analog signal having the waveform shown in FIG. 11C is output from the analog signal output unit 20 to the gate of the switching element 96.

  By applying low-pass filter processing to a relatively long single pulse PT transmitted from the pulse generator 202 at time t10, the level of the output signal from the low-pass filter 203 gradually increases, and eventually the analog signal having the maximum voltage is reached. Is output to the gate of the switching element 96. As a result, the switching element 96 is turned on, and the maximum voltage is applied from the capacitor 93 between the both end electrodes of the flash lamp FL.

  In this state, a trigger voltage is applied from the trigger circuit 97 to the trigger electrode 91 at time t11 as shown in FIG. When the trigger voltage is applied to the trigger electrode 91 in a state where the maximum voltage from the capacitor 93 is applied between the both ends of the flash lamp FL, the insulation of the flash lamp FL is broken and both ends as shown in FIG. Current begins to flow between the electrodes. As a result, the flash lamp FL starts to emit light.

  After a voltage is applied to the trigger electrode 91 at time t11 and the flash lamp FL starts to emit light, an analog signal in which the pulse group PG is subjected to low-pass filter processing is output to the gate of the switching element 96 at time t12. Note that the single pulse PT remains on for a certain period from time t11 when the flash lamp FL starts to emit light, and the output signal from the low-pass filter 203 maintains the maximum level.

  Since the resistance is low after the flash lamp FL starts to emit light at time t11, the current continues to flow through the flash lamp FL even if the voltage between the electrodes is low. For this reason, the switching element 96 controls the current flowing through the circuit in accordance with the analog signal in which the pulse group PG is subjected to the low-pass filter processing, and the current as shown in FIG. 11D flows through the flash lamp FL.

  The light emission output of the flash lamp FL is substantially proportional to the current flowing through the flash lamp FL. Therefore, the output waveform of the light emission output of the flash lamp FL also has a pattern as shown in FIG. The flash lamp FL emits light with such an output waveform, and light irradiation heating of the semiconductor wafer W is performed. As a result, the surface temperature of the semiconductor wafer W rises. The temperature change pattern of the semiconductor wafer W at this time depends on the waveform of the light emission output from the flash lamp FL.

  Also in the second embodiment, an IGBT switching element 96 is connected in series to the driving circuit of the flash lamp FL, and an analog signal is output to the gate of the switching element 96 to control the current flowing through the flash lamp FL. The light emission of the lamp FL is controlled. The waveform of the analog signal applied to the gate of the switching element 96 can be freely set by the waveform data stored in the waveform storage unit 201. Then, by changing the waveform of the analog signal output to the gate of the switching element 96, the waveform of the current flowing through the flash lamp FL changes and the light emission mode also changes. As a result, the temperature profile drawn by the surface temperature of the semiconductor wafer W also changes. That is, as in the first embodiment, the temperature profile of the light irradiation annealing time of the flash lamp FL and the surface temperature of the semiconductor wafer W can be freely set by changing the waveform of the analog signal output to the gate of the switching element 96. can do.

  In the second embodiment, the driving of the switching element 96 is controlled by outputting an analog signal obtained by applying a low-pass filter process to the pulse signal to the gate of the switching element 96. The analog signal that has been low-pass filtered by the low-pass filter 203 has a significantly lower frequency than the pulse signal generated by the pulse generator 202. For this reason, the change in the current flowing through the drive circuit of the flash lamp FL also becomes a low frequency, and the back electromotive force generated in the coil 94 can be made small. As a result, as in the first embodiment, there is no possibility that a large back electromotive force acts on the protection diode 98 and the switching element 96 and breaks them, and a large current is passed through the flash lamp FL if necessary for the annealing process. It is also possible.

  In the second embodiment, the pulse generator 202 generates a single pulse PT for generating a trigger signal in addition to the pulse group PG for generating an analog signal having a predetermined waveform. A trigger signal having a maximum voltage obtained by applying a low-pass filter process to a relatively long single pulse PT is output to the gate of the switching element 96, whereby the trigger circuit 97 applies a trigger voltage to the trigger electrode 91 (time t11). ), A maximum voltage from the capacitor 93, which is a voltage equal to or higher than a threshold value at which the flash lamp FL starts to emit light, is applied between both end electrodes of the flash lamp FL. For this reason, when the trigger circuit 97 applies the trigger voltage to the trigger electrode 91 at time t11, the current surely flows between both end electrodes of the flash lamp FL, and the flash lamp FL starts to emit light.

  Then, at time t12 after the trigger circuit 97 applies the trigger voltage at time t11, an analog signal obtained by subjecting the pulse group PG to low-pass filter processing is output to the gate of the switching element 96. After applying the trigger voltage, the pulse PT is on for a certain period of time, and the trigger signal output from the low-pass filter 203 maintains the maximum level. For this reason, the maximum voltage from the capacitor 93 is continuously applied between the both ends of the flash lamp FL, and a current flows stably to the flash lamp FL at time t12. As a result, as in the first embodiment, even if the signal level of the analog signal obtained by subjecting the pulse group PG to the low-pass filter processing is low, current continues to flow through the flash lamp FL, and the flash lamp follows the waveform of the analog signal. The waveform of the current flowing through the FL can be controlled.

<3. Third Embodiment>
Next, a third embodiment of the present invention will be described. The overall configuration of the heat treatment apparatus of the third embodiment and the processing procedure for the semiconductor wafer W are the same as those of the heat treatment apparatus 1 of the first embodiment. The heat treatment apparatus of the third embodiment differs from the first embodiment in the configuration of the drive mechanism of the switching element 96.

  FIG. 12 is a block diagram showing the configuration of the drive mechanism of the switching element 96 in the third embodiment. The analog signal output unit 30 includes two analog switches 301 and 302 and an inverter 303.

  The analog switch 301 switches on / off of the trigger signal transmitted to the gate of the switching element 96. As in the first and second embodiments, the trigger signal is a signal having the maximum voltage at which the switching element 96 is turned on.

  The analog switch 302 switches on / off of an analog signal transmitted to the gate of the switching element 96. The analog signal is an analog signal obtained by D / A converting the digital data stored in the waveform data region DR in the first embodiment, or an analog signal obtained by performing low-pass filter processing on the pulse group PG in the second embodiment. It is a signal of a predetermined waveform similar to.

  The analog switch 301 and the analog switch 302 are on / off controlled by a switching signal. Since the switching signal input to the analog switch 302 is inverted by the inverter 303, only one of the analog switch 301 and the analog switch 302 is always on. That is, when the switching signal is on, the analog switch 301 is on and the analog switch 302 is off. Conversely, when the switching signal is off, the analog switch 301 is off and the analog switch 302 is on. It becomes. The switching signal may be output from the control unit 3.

  Also in the third embodiment, after the preheating of the semiconductor wafer W is completed, the analog signal is output from the analog signal output unit 30 to the gate of the switching element 96 under the control of the control unit 3 in a state where electric charges are accumulated in the capacitor 93. And a high voltage is applied from the trigger circuit 97 to the trigger electrode 91 to cause the flash lamp FL to emit light. FIG. 13 is a timing chart showing the correlation among the switching signal, the trigger voltage, the analog signal, the signal output to the gate of the switching element 96, and the current flowing through the flash lamp FL.

  As shown in FIG. 13A, the switching signal is on from time t20 to time t22. Therefore, the analog switch 301 is on and the analog switch 302 is off. For this reason, from time t20 to time t22, as shown in FIG. 13D, a trigger signal, which is a maximum voltage signal for turning on the switching element 96, is output to the gate of the switching element 96. . As a result, the switching element 96 is turned on, and the maximum voltage is applied from the capacitor 93 between the both end electrodes of the flash lamp FL.

  In this state, a trigger voltage is applied from the trigger circuit 97 to the trigger electrode 91 at time t21 as shown in FIG. When a voltage is applied to the trigger electrode 91 in a state where the maximum voltage from the capacitor 93 is applied between the both end electrodes of the flash lamp FL, the insulation of the flash lamp FL is broken, and both end electrodes as shown in FIG. Current begins to flow between them. As a result, the flash lamp FL starts to emit light.

  After a voltage is applied to the trigger electrode 91 at time t21 and the flash lamp FL starts to emit light, the switching signal is turned from on to off at time t22 when a certain time has elapsed, and the analog switch 301 is switched from the off state to the analog state. The switch 302 is turned on. As a result, after time t22, as shown in FIG. 13D, the analog signal of FIG. 13C is output to the gate of the switching element 96 as it is. Note that the trigger signal is output to the gate of the switching element 96 from time t21 to time t22 after the flash lamp FL starts to emit light.

  Since the resistance is low after the flash lamp FL starts to emit light at time t21, the current continues to flow through the flash lamp FL even if the voltage between the electrodes is low. Therefore, the switching element 96 controls the current flowing through the circuit in accordance with the analog signal of FIG. 13C, and the current as shown in FIG. 13E flows through the flash lamp FL.

  The light emission output of the flash lamp FL is substantially proportional to the current flowing through the flash lamp FL. Therefore, the output waveform of the light emission output of the flash lamp FL also has a pattern as shown in FIG. The flash lamp FL emits light with such an output waveform, and the semiconductor wafer W is heated by light irradiation. As a result, the surface temperature of the semiconductor wafer W rises. The temperature change pattern of the semiconductor wafer W at this time depends on the waveform of the light emission output from the flash lamp FL.

  Also in the third embodiment, an IGBT switching element 96 is connected in series to the driving circuit of the flash lamp FL, and an analog signal is output to the gate of the switching element 96 to control the current flowing through the flash lamp FL. The light emission of the lamp FL is controlled. Similar to the first and second embodiments, the waveform of the analog signal applied to the gate of the switching element 96 can be freely set. Therefore, even in the third embodiment, the temperature profile of the light irradiation annealing time of the flash lamp FL and the surface temperature of the semiconductor wafer W can be freely set.

  Further, as in the first and second embodiments, an analog signal is output to the gate of the switching element 96 to control the driving of the switching element 96, so that a large back electromotive force acts on the protection diode 98 and the switching element 96. There is no risk of damage.

  In the third embodiment, the trigger signal is output before the analog signal is output from the analog signal output unit 30, so that the trigger circuit 97 applies the trigger voltage to the trigger electrode 91 (time t21). The maximum voltage from the capacitor 93, which is a voltage equal to or higher than the threshold value at which the flash lamp FL starts to emit light, is applied between the both ends of the flash lamp FL. For this reason, when the trigger circuit 97 applies the trigger voltage to the trigger electrode 91 at time t21, the current surely flows between both end electrodes of the flash lamp FL, and the flash lamp FL starts to emit light.

  Then, an analog signal having a predetermined waveform is output to the gate of the switching element 96 at time t22 after a predetermined time has elapsed since the trigger circuit 97 applied the trigger voltage at time t21. Since the trigger signal is output to the gate of the switching element 96 even after the predetermined time has elapsed, the maximum voltage from the capacitor 93 is continuously applied between the both end electrodes of the flash lamp FL, and the flash lamp at time t22. A current flows stably through FL. As a result, as in the first and second embodiments, even if the signal level of the analog signal having a predetermined waveform is low, the current continues to flow through the flash lamp FL, and the current flowing through the flash lamp FL according to the waveform of the analog signal is reduced. The waveform can be controlled.

<4. 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 embodiment, an analog signal is generated by D / A converting digital data, and in the second embodiment, an analog signal is generated by performing low-pass filter processing on the pulse signal. The present invention is not limited to these as long as an analog signal having a predetermined waveform can be generated. That is, the present invention may be any form that controls the driving of the switching element 96 by outputting an analog signal having a predetermined waveform to the gate of the switching element 96 connected to the driving circuit of the flash lamp FL. Preferably, after a trigger signal for applying a voltage equal to or higher than a threshold value at which the flash lamp FL starts to emit light between both ends of the flash lamp FL is output to the gate of the switching element 96, the current flowing through the flash lamp FL is controlled. It is preferable to output an analog signal having a predetermined waveform to the gate.

  Further, the amplifier 99 provided in the first embodiment may be provided in the second embodiment and the third embodiment.

  In the above embodiments, 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.

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 drive circuit of a flash lamp. It is a block diagram which shows the structure of the drive mechanism of the switching element in 1st Embodiment. It is a figure which shows an example of the data structure of the waveform data memorize | stored in the waveform memory | storage part. It is a timing chart which shows the correlation of a trigger voltage, the analog signal output to the gate of a switching element, and the electric current which flows into a flash lamp. It is a block diagram which shows the structure of the drive mechanism of the switching element in 2nd Embodiment. It is a timing chart which shows the correlation of the electric current which flows into a pulse signal, a trigger voltage, the output signal from a low-pass filter, and a flash lamp. It is a block diagram which shows the structure of the drive mechanism of the switching element in 3rd Embodiment. It is a timing chart which shows the correlation of the electric current which flows into a switching signal, a trigger voltage, an analog signal, the signal output to the gate of a switching element, and a flash lamp.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heat processing apparatus 3 Control part 4 Holding part raising / lowering mechanism 5 Lamphouse 6 Chamber 7 Holding part 10,20,30 Analog signal output part 60 Upper opening 61 Chamber window 65 Heat processing space 71 Hotplate 72 Susceptor 91 Trigger electrode 92 Glass tube 93 Capacitor 94 Coil 96 Switching element 97 Trigger circuit 98 Protection diode 99 Amplifier 101, 201 Waveform storage unit 102 D / A converter 202 Pulse generator 203 Low-pass filter 301, 302 Analog switch 303 Inverter FL Flash lamp DR Waveform data area TR Trigger data area W Semiconductor wafer

Claims (8)

A heat treatment apparatus for heating a substrate by irradiating the substrate with light,
Holding means for holding the substrate;
A flash lamp for irradiating light onto the substrate held by the holding means;
A switching element connected in series with the flash lamp, capacitor and coil;
Analog signal output means for controlling driving of the switching element by outputting an analog signal to the switching element;
A heat treatment apparatus comprising: The heat treatment apparatus according to claim 1, wherein
A trigger voltage applying means for applying a trigger voltage for light emission from the outside of the flash lamp;
The analog signal output means outputs a trigger signal for applying a voltage equal to or higher than a threshold at which the flash lamp starts to emit light between both end electrodes of the flash lamp when the trigger voltage applying means applies the trigger voltage. After outputting to a switching element, the heat processing apparatus characterized by outputting the analog signal of a predetermined waveform to the said switching element. The heat treatment apparatus according to claim 2,
The analog signal output means outputs the analog signal having the predetermined waveform to the switching element after outputting the trigger signal for a predetermined time after the trigger voltage applying means applies the trigger voltage. Heat treatment equipment. In the heat treatment apparatus according to claim 2 or claim 3,
The analog signal output means includes
A waveform storage unit for storing the waveform level at predetermined intervals as digital data;
A D / A converter for converting the digital data stored in the waveform storage unit into an analog signal;
With
In the waveform storage unit, a trigger data area for storing data for generating the trigger signal and a waveform data area for storing data for generating an analog signal of the predetermined waveform are set. Heat treatment equipment. In the heat treatment apparatus according to claim 2 or claim 3,
The analog signal output means includes
Pulse signal generating means for generating a pulse signal including one or more pulses;
A low-pass filter that generates an analog signal by applying a low-pass filter process to the pulse signal generated by the pulse signal generating means;
With
The heat treatment apparatus, wherein the pulse signal generating means generates a single pulse for generating the trigger signal and a pulse group for generating an analog signal having the predetermined waveform. In the heat processing apparatus in any one of Claims 1-5,
A heat treatment apparatus, further comprising an amplifier that amplifies an analog signal output from the analog signal output means in accordance with an amount of electric charge remaining in the capacitor after light emission of the flash lamp is completed. In the heat processing apparatus in any one of Claims 1-6,
The switching element is a transistor;
The heat treatment apparatus, wherein the analog signal output means outputs an analog signal to the gate of the transistor. The heat treatment apparatus according to claim 7, wherein
The heat treatment apparatus, wherein the transistor is an insulated gate bipolar transistor.

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