JP5951209B2 - Heat treatment method - Google Patents

Description

The present invention, thin plate-like precision electronic substrate such as a glass substrate for a semiconductor wafer or a liquid crystal display device (hereinafter, simply referred to as "substrate") relates to a heat treatment how to heat the substrate by irradiating a flash light to.

  In recent years, flash lamp annealing (FLA) has attracted attention as an annealing technique for heating a semiconductor wafer in an extremely short time. Flash lamp annealing uses a xenon flash lamp (hereinafter referred to simply as “flash lamp” to mean xenon flash lamp) to irradiate the surface of a semiconductor wafer with flash light, so that only the surface is exposed for a very short time. This is a heat treatment technology that raises the temperature to (a few milliseconds or less). Such an extremely short time heat treatment is suitable for, for example, activating the impurities implanted into the semiconductor wafer by an ion implantation method.

  On the other hand, there is a strong demand for heat treatment for a slightly longer time (several tens of milliseconds to several hundreds of milliseconds) than the above-described extremely short time heat treatment. In order to satisfy such a demand, Patent Document 1 discloses a technique for extending the light emission time by controlling the current flowing in the flash lamp using an insulated gate bipolar transistor, thereby increasing the heat treatment time to several tens of milliseconds or more. Has been proposed.

JP 2009-70948 A

  However, when the heat treatment is performed for several tens of milliseconds to several hundreds of milliseconds using a flash lamp, the surface temperature distribution of the semiconductor wafer surface becomes higher than that of the central portion, resulting in uneven surface temperature distribution. found. This is because a part of the flash light travels around the side of the semiconductor wafer and reaches the lower surface of the peripheral edge during the flash light irradiation. If the heat treatment time is an extremely short time of several milliseconds or less, the heat treatment is completed before the heat effect of the flash light reaching the lower surface of the peripheral portion is transmitted to the upper surface, but the heat time is several tens of milliseconds or more. Then, since the thermal effect is transmitted to the upper surface during the heat treatment, the temperature distribution becomes non-uniform.

  In general, a pattern is often formed on the surface of a semiconductor wafer irradiated with flash light. If the pattern is formed, the light absorptance on the surface of the semiconductor wafer becomes non-uniform, so even if the flash light is irradiated with a uniform illuminance distribution, the temperature distribution on the surface may become non-uniform. .

The present invention has been made in view of the above problems, and an object thereof is to provide a heat treatment method that can be uniformly heated by irradiating a flash light to the substrate.

To solve the above problems, a first aspect of the invention, in the heat treatment method of heating a substrate by irradiating a flash light to a substrate having a resist film formed on the surface, the substrate accommodated in a chamber, wherein The supporting step of supporting the lower surface of the peripheral portion of the substrate by the annular member placed on the cooling plate with the back surface of the substrate facing upward, and cooling the substrate by the cooling plate placing the annular member, A flash irradiation step of irradiating flash light from a flash lamp onto the back surface of the substrate supported by the annular member, and the peripheral portion of the substrate by the annular member formed of a material opaque to the flash light The flash light irradiated from the flash lamp is prevented from entering the lower surface.

According to a second aspect of the present invention, in the heat treatment method according to the first aspect of the present invention, the irradiance of the flash lamp is 1 × 10 ⁸ W / m ² or less.

According to the first and second aspects of the present invention, the lower surface of the peripheral edge of the substrate is supported by the annular member made of a material opaque to the flash light, and the flash light is irradiated from the flash lamp onto the upper surface of the substrate. In order to prevent the flash light from entering the lower surface of the peripheral edge of the substrate, the substrate can be irradiated with the flash light and heated uniformly. Moreover, since the flash light is irradiated while the substrate is cooled by the cooling plate, the temperature history can be made uniform among the plurality of substrates. In addition, since the back surface of the substrate is irradiated with flash light, it is possible to more uniformly heat the substrate while suppressing pattern dependency on the absorption of flash light.

In particular, according to the invention of claim 2, since the irradiance of the flash lamp is 1 × 10 ⁸ W / m ² or less, the jumping of the substrate can be prevented and the flash light can be surely prevented.

It is a figure which shows the principal part structure of the heat processing apparatus which concerns on this invention. It is a perspective view of a support ring. It is a figure which shows the drive circuit of a flash lamp. It is a figure which shows the state which flash-heats the semiconductor wafer hold | maintained at the holding | maintenance part. It is a figure which shows the principal part structure of the heat processing apparatus of 2nd Embodiment. It is a figure which shows the state which flash-heats the semiconductor wafer of 2nd Embodiment.

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

<First Embodiment>
FIG. 1 is a diagram showing a main configuration of a heat treatment apparatus 1 according to the present invention. The heat treatment apparatus 1 is a flash lamp annealing apparatus that performs heat treatment by irradiating a substantially circular semiconductor wafer W as a substrate with flash light. In the first embodiment, a semiconductor wafer W coated with a photoresist is irradiated with flash light to perform a baking process (post-coating baking process) of the resist film and a post-exposure heating process (post-exposure baking). In FIG. 1 and the subsequent drawings, the size and number of each part are exaggerated or simplified as necessary for easy understanding.

  The heat treatment apparatus 1 mainly includes a substantially cylindrical chamber 6 that houses a semiconductor wafer W, a holding unit 7 that holds the semiconductor wafer W in the chamber 6, and the delivery of the semiconductor wafer W to the holding unit 7. A transfer unit 4 for performing a process, a flash irradiation unit 5 for irradiating a semiconductor wafer W in the chamber 6 with flash light, a gas supply unit 8 for supplying a processing gas into the chamber 6, and an exhaust unit for exhausting the chamber 6 2 is provided. In addition, the heat treatment apparatus 1 includes a control unit 3 that controls each of these units to perform the heat treatment of the semiconductor wafer W.

  The chamber 6 is provided below the flash irradiation unit 5 and includes a chamber side portion 63 having a substantially cylindrical inner wall and a chamber bottom portion 62 that covers a lower portion of the chamber side portion 63. A space surrounded by the chamber side 63 and the chamber bottom 62 is defined as a heat treatment space 65. A chamber window 61 is attached to the upper opening of the chamber 6 to close it.

  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 flash irradiation unit 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.

  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 (not shown). That is, an O-ring is sandwiched between the lower peripheral edge portion of the chamber window 61 and the chamber side portion 63 to prevent gas from flowing in and out from the gap.

  The chamber side 63 is provided with a transfer opening 66 for carrying in and out the semiconductor wafer W. The transfer opening 66 can be opened and closed by a gate valve (not shown). When the transfer opening 66 is opened, the semiconductor wafer W can be carried into and out of the chamber 6 by a transfer robot (not shown). When the transfer opening 66 is closed, the heat treatment space 65 becomes a sealed space in which ventilation with the outside is blocked.

  In the first embodiment, the holding unit 7 provided in the chamber 6 includes a support ring 71 and a cooling plate 72. FIG. 2 is a perspective view of the support ring 71. As shown in the figure, the support ring 71 is an annular (ring-shaped) plate-like member. The outer diameter of the annular support ring 71 is larger than the diameter of the semiconductor wafer W (φ300 mm in this embodiment). That is, the outer peripheral shape of the support ring 71 is larger than the peripheral shape of the semiconductor wafer W. Further, the inner diameter of the support ring 71 is slightly smaller than the diameter of the semiconductor wafer W. Therefore, the support ring 71 can support the lower surface of the peripheral edge of the semiconductor wafer W over the entire circumference at the inner circumferential portion thereof.

  The support ring 71 is formed of a material that is opaque to the flash light emitted from the flash lamp FL of the flash irradiation unit 5, that is, a material that does not transmit the flash light. As a material opaque to such flash light, silicon (Si), silicon carbide (SiC), boron nitride (BN), or the like can be employed. In the case of a sintered body, aluminum nitride (AlN) can also be used as a material opaque to flash light.

  Returning to FIG. 1, the cooling plate 72 is a substantially disk-shaped member made of metal (for example, aluminum), and is provided in the chamber 6 to mount the support ring 71. The diameter of the cooling plate 72 is approximately equal to the outer diameter of the support ring 71. The cooling plate 72 incorporates a cooling mechanism (not shown) (for example, a water-cooled tube or a Peltier element), and the cooling plate 72 is cooled by the cooling mechanism. A temperature sensor (not shown) is also provided inside the cooling plate 72. The temperature sensor measures the temperature of the cooling plate 72 and transmits the measurement result to the control unit 3.

  A support ring 71 is placed on the peripheral edge of the upper surface of the cooling plate 72, and the semiconductor wafer W is supported by the support ring 71 in a horizontal posture (a posture in which the normal direction of the main surface is along the vertical direction). The semiconductor wafer W is supported such that its central axis coincides with the central axis of the support ring 71. Since the annular support ring 71 supports the lower surface of the peripheral edge of the semiconductor wafer W, a gap having a predetermined interval is formed between the lower surface of the inner region of the semiconductor wafer W and the upper surface of the cooling plate 72. The gap distance is equal to the thickness of the support ring 71. The inner region of the semiconductor wafer W is a region excluding the peripheral edge portion of the main surface of the semiconductor wafer W.

  The semiconductor wafer W supported by the support ring 71 placed on the cooling plate 72 is cooled to a predetermined temperature by the cooling plate 72 and maintained at that temperature. When the temperature of the semiconductor wafer W supported by the support ring 71 is adjusted, the temperature of the cooling plate 72 measured by the temperature sensor is built in the cooling plate 72 so as to be a predetermined temperature set in advance. The cooling mechanism is controlled by the control unit 3. That is, the temperature control of the cooling plate 72 by the control unit 3 is feedback control, more specifically, PID (Proportional, Integral, Derivative) control.

  The transfer unit 4 is provided below the cooling plate 72 of the holding unit 7. The transfer unit 4 includes a plurality of (three in the present embodiment) lift pins 44 and an air cylinder 45 that raises and lowers the lift pins 44. The upper end height positions of the three lift pins 44 are included in the same horizontal plane. The three lift pins 44 are moved up and down along the vertical direction by the air cylinder 45 at once. Each lift pin 44 moves up and down along the inside of an insertion hole that penetrates the cooling plate 72 vertically. When the air cylinder 45 raises the three lift pins 44, the tip of each lift pin 44 protrudes from the upper surface of the cooling plate 72 and rises to a position higher than the upper surface of the support ring 71. When the air cylinder 45 lowers the three lift pins 44, the tip of each lift pin 44 is embedded in the insertion hole of the cooling plate 72 and descends below the lower surface of the cooling plate 72.

The gas supply unit 8 supplies a processing gas to the heat treatment space 65 in the chamber 6. The gas supply unit 8 includes a processing gas supply source 81 and a valve 82, and supplies the processing gas to the heat treatment space 65 by opening the valve 82. The processing gas supplied by the gas supply unit 8 is an inert gas such as nitrogen (N ₂ ), argon (Ar), helium (He), or oxygen (O ₂ ), hydrogen (H ₂ ), chlorine (cl). ₂ ), reactive gases such as water vapor (H ₂ O), hydrogen chloride (Hcl), ozone (O ₃ ), and ammonia (NH ₃ ) can be used. The processing gas supply source 81 may be constituted by a gas tank provided in the heat treatment apparatus 1 and a feed pump, or use the power of the factory where the heat treatment apparatus 1 is installed. May be.

  The exhaust unit 2 includes an exhaust device 21 and a valve 22, and the atmosphere in the chamber 6 is exhausted from the exhaust port 23 by opening the valve 22. The exhaust port 23 is a slit formed in the chamber side portion 63 so as to surround the holding portion 7. The height position where the exhaust port 23 is formed is not more than the same height position as the semiconductor wafer W supported by the support ring 71, and is preferably slightly lower than the semiconductor wafer W. When the exhaust unit 2 exhausts air from the slit-shaped exhaust port 23 formed so as to surround the holding unit 7, gas is uniformly discharged from the periphery of the semiconductor wafer W held by the holding unit 7. Become.

  As the exhaust device 21, an exhaust utility of a factory where the vacuum pump or the heat treatment device 1 is installed can be used. When a vacuum pump is employed as the exhaust device 21 and the atmosphere of the heat treatment space 65 that is a sealed space is exhausted without supplying the processing gas from the gas supply unit 8, the inside of the chamber 6 can be decompressed to a vacuum atmosphere. Further, even when a vacuum pump is not used as the exhaust device 21, the inside of the chamber 6 is decompressed to a pressure lower than the atmospheric pressure by performing exhaust without supplying the processing gas from the gas supply unit 8. Can do.

  The flash irradiation unit 5 is provided above the chamber 6. The flash irradiating unit 5 is provided so as to cover a plurality of light sources (30 in the present embodiment, but only 11 are shown in FIG. 1 for the sake of illustration) and the upper part of the light source. And a reflector 52. The flash irradiation unit 5 irradiates the semiconductor wafer W supported by the support ring 71 in the chamber 6 with flash light from the flash lamp FL via the quartz 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 supported by the support ring 71 (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.

  FIG. 3 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 an IGBT (insulated gate bipolar transistor) 96 are connected in series. As shown in FIG. 3, the control unit 3 includes a pulse generator 31 and a waveform setting unit 32 and is connected to the input unit 33. As the input unit 33, various known input devices such as a keyboard, a mouse, and a touch panel can be employed. The waveform setting unit 32 sets the waveform of the pulse signal based on the input content from the input unit 33, and the pulse generator 31 generates the pulse signal according to the waveform.

  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 (charging voltage) is charged. A high voltage can be applied to the trigger electrode 91 from the trigger circuit 97. The timing at which the trigger circuit 97 applies a voltage to the trigger electrode 91 is controlled by the control unit 3.

  The IGBT 96 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. A pulse signal is applied from the pulse generator 31 of the control unit 3 to the gate of the IGBT 96. The IGBT 96 is turned on when a voltage higher than a predetermined value (High voltage) is applied to the gate of the IGBT 96, and the IGBT 96 is turned off when a voltage lower than the predetermined value (Low voltage) is applied. In this way, the drive circuit including the flash lamp FL is turned on / off by the IGBT 96. When the IGBT 96 is turned on / off, the connection between the flash lamp FL and the corresponding capacitor 93 is interrupted.

  Even if the IGBT 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 glass is normal in the state. No electricity flows in the tube 92. However, when the trigger circuit 97 applies a high voltage to the trigger electrode 91 to break the insulation, an electric current instantaneously flows in the glass tube 92 due to the discharge between the both end electrodes, and excitation of the xenon atoms or molecules at that time Emits 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 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 is configured with a magnetic disk. The processing in the heat treatment apparatus 1 proceeds as the CPU of the control unit 3 executes a predetermined processing program. As shown in FIG. 3, the control unit 3 includes a pulse generator 31 and a waveform setting unit 32. As described above, the waveform setting unit 32 sets the waveform of the pulse signal based on the input content from the input unit 33, and the pulse generator 31 outputs the pulse signal to the gate of the IGBT 96 in accordance therewith.

  Next, a processing procedure of the semiconductor wafer W in the heat treatment apparatus 1 having the above configuration 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, a gate valve (not shown) is opened to open the transfer opening 66, and a semiconductor wafer W to be processed is transferred into the chamber 6 through the transfer opening 66 by a transfer robot outside the apparatus. In the first embodiment, the semiconductor wafer W to be processed is a semiconductor substrate on which a photoresist is applied to form a resist film. For example, the photoresist may be applied by spin coating using a spin coater provided separately from the heat treatment apparatus 1.

  A hand of a transfer robot holding a semiconductor wafer W having a resist film formed on the surface enters the chamber 6 from the transfer opening 66 and is directly above the holding unit 7 (more precisely, the central axis of the semiconductor wafer W and the support ring) At a position where the central axis of 71 coincides). Subsequently, the three lift pins 44 rise further than the through holes of the cooling plate 72 and receive the semiconductor wafer W from the hand. Thereafter, the hand of the transfer robot moves out of the chamber 6 and the transfer opening 66 is closed, whereby the heat treatment space 65 in the chamber 6 is made a sealed space. Then, the three lift pins 44 that support the semiconductor wafer W are lowered and embedded in the insertion holes of the cooling plate 72. In the process in which the lift pins 44 are lowered, the semiconductor wafer W is transferred from the lift pins 44 to the support ring 71 and supported. The semiconductor wafer W is supported such that its central axis coincides with the central axis of the support ring 71. Therefore, the support ring 71 supports the lower surface of the peripheral edge over the entire circumference of the semiconductor wafer W.

  Here, the surface of the semiconductor wafer W is a main surface on which a device is formed, and the back surface is a surface on the opposite side. Various thin films such as a resist film are formed on the surface of the semiconductor wafer W on which the device is formed, and a pattern is also formed by an exposure process. Usually, neither film formation nor pattern formation is performed on the back surface of the semiconductor wafer W (however, as a result of film formation on the front surface, film formation is unavoidably performed on the back surface). On the other hand, the lower surface of the semiconductor wafer W is a surface facing downward in the vertical direction, and the upper surface is a surface facing upward. Therefore, the surface of the semiconductor wafer W may face the upper surface, and may face the lower surface.

  In the first embodiment, the semiconductor wafer W is loaded into the chamber 6 with the back surface of the semiconductor wafer W facing the top surface. Therefore, the semiconductor wafer W is supported by the support ring 71 in a state where the back surface of the semiconductor wafer W faces the upper surface (that is, a state where the resist film faces the lower surface). On the surface of the semiconductor wafer W on which the resist film has been formed, the peripheral edge resist film is peeled off in advance by edge portion removal processing. Therefore, the inner peripheral portion of the support ring 71 is in contact with the peripheral portion of the surface of the semiconductor wafer W from which the resist film has been removed, and is not in direct contact with the resist film. Further, in a state where the semiconductor wafer W is supported by the support ring 71, a gap with a predetermined interval is formed between the lower surface of the inner region of the semiconductor wafer W and the upper surface of the cooling plate 72. The resist film does not come into contact with the cooling plate 72. Therefore, dust generation due to contact between the resist film and any member is prevented.

  In addition, after the transfer opening 66 is closed and the heat treatment space 65 is closed, the valve 82 is opened to supply a processing gas (nitrogen gas in this embodiment) from the gas supply unit 8 to the heat treatment space 65. At the same time, the valve 22 is opened and the exhaust unit 2 exhausts from the heat treatment space 65. Thereby, an air flow of nitrogen gas is formed in the heat treatment space 65 in the chamber 6, and the periphery of the semiconductor wafer W held by the holding unit 7 is made a nitrogen atmosphere. From the viewpoint of increasing the atmosphere replacement efficiency in the chamber 6, the gas supply unit 8 is provided after the exhaust unit 2 exhausts the heat treatment space 65 without supplying the processing gas to once form a reduced-pressure atmosphere lower than the atmospheric pressure. It is preferable to supply the processing gas from.

  The cooling plate 72 is temperature-controlled in advance by the control unit 3 to a predetermined temperature. When the semiconductor wafer W is supported by the support ring 71 and held in proximity to the cooling plate 72, temperature control by the cooling plate 72 is started with respect to the semiconductor wafer W, and the temperature of the semiconductor wafer W becomes the temperature control temperature of the cooling plate 72. Get closer.

  After the semiconductor wafer W is supported by the support ring 71, it waits for a predetermined time. During this time, the entire semiconductor wafer W including the resist film formed on the surface is adjusted to the temperature of the cooling plate 72. Then, after a predetermined time has elapsed, the flash light is irradiated toward the semiconductor wafer W from the flash lamp FL of the flash irradiation unit 5 under the control of the control unit 3. When the flash lamp FL irradiates flash light, the electric power is accumulated in the capacitor 93 by the power supply unit 95 in advance. Then, in a state where charges are accumulated in the capacitor 93, a pulse signal is output from the pulse generator 31 of the control unit 3 to the IGBT 96 to drive the IGBT 96 on and off.

  The waveform of the pulse signal can be defined by inputting from the input unit 33 a recipe in which the pulse width time (on time) and the pulse interval time (off time) are sequentially set as parameters. When the operator inputs such a recipe from the input unit 33 to the control unit 3, the waveform setting unit 32 of the control unit 3 sets a pulse waveform that repeats ON / OFF accordingly. Then, the pulse generator 31 outputs a pulse signal according to the pulse waveform set by the waveform setting unit 32. As a result, a pulse signal that repeatedly turns on and off is applied to the gate of the IGBT 96, and the on / off driving of the IGBT 96 is controlled. Specifically, the IGBT 96 is turned on when the pulse signal input to the gate of the IGBT 96 is on, and the IGBT 96 is turned off when the pulse signal is off.

  Further, in synchronization with the timing when the pulse signal output from the pulse generator 31 is turned on, the control unit 3 controls the trigger circuit 97 to apply a high voltage (trigger voltage) to the trigger electrode 91. A pulse signal is input to the gate of the IGBT 96 in a state where electric charges are accumulated in the capacitor 93 and a high voltage is applied to the trigger electrode 91 in synchronization with the timing when the pulse signal is turned on. When is turned on, a current always flows between both end electrodes in the glass tube 92, and light is emitted by the excitation of atoms or molecules of xenon at that time.

  In this way, by connecting the IGBT 96 as a switching element in the circuit and outputting a pulse signal that repeatedly turns on and off to the gate, the supply of charge from the capacitor 93 to the flash lamp FL is intermittently performed by the IGBT 96 and the flash lamp FL is supplied. The flowing current is controlled. As a result, the light emission of the flash lamp FL is chopper-controlled, and the electric charge accumulated in the capacitor 93 is divided and consumed, and the flash lamp FL repeats blinking in a very short time. However, since the next pulse is applied to the gate of the IGBT 96 before the current value flowing through the flash lamp FL becomes completely “0”, the current value increases again, so that the light is emitted even while the flash lamp FL is repeatedly blinking. The output is not completely “0”. Therefore, when pulse signals with relatively short intervals are output to the IGBT 96, the flash lamp FL is continuously emitting light during that time.

The waveform of the pulse signal can be arbitrarily set by defining the time of the pulse width and the time of the pulse interval. For this reason, the on / off drive of the IGBT 96 can be arbitrarily controlled, and by setting a large number of pulse signals having a relatively short pulse interval, the flash lamp FL can be extended to 10 milliseconds to 1000 milliseconds. it can. The irradiation energy of the flash light emitted from the flash lamp FL is ^{1J / cm 2 ~100J / cm 2} .

  In the first embodiment, the light emission time of the flash lamp FL is set to several tens of milliseconds. A part of the flash light emitted from the flash lamp FL directly goes 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. The semiconductor wafer W is heated by such flash light irradiation.

  FIG. 4 is a diagram showing a state in which the semiconductor wafer W held by the holding unit 7 is flash-heated. A resist film 11 is formed on the surface of the semiconductor wafer W. The semiconductor wafer W is supported by the support ring 71 with the surface on which the resist film 11 is formed facing the lower surface. Flash light is irradiated from the flash lamp FL onto the upper surface (back surface in the first embodiment) of the semiconductor wafer W. The flash light emitted from the flash lamp FL is a flash light with a very short irradiation time and high intensity. The temperature of the back surface of the semiconductor wafer W irradiated with flash light from the flash lamp FL suddenly increases rapidly. Then, heat conduction occurs from the back surface to the surface of the semiconductor wafer W that has been rapidly heated, and the resist film 11 formed on the surface is heated.

  In this way, the flash light is irradiated from the flash lamp FL onto the back surface of the semiconductor wafer W, whereby the temperature of the surface of the semiconductor wafer W on which the resist film 11 is formed also rises rapidly and then falls rapidly. As the surface temperature of the semiconductor wafer W rises, the solvent evaporates from the resist film 11 and the baking process of the resist film 11 is executed. Note that since the thickness of the resist film 11 is as extremely thin as 100 nm or less, the baking process can be completed only by increasing the surface temperature of the semiconductor wafer W for a short time.

  In the first embodiment, the back surface of the semiconductor wafer W is irradiated with flash light. The back surface of the semiconductor wafer W is not patterned. For this reason, the light absorptance on the back surface of the semiconductor wafer W is uniform, the flash light absorption has no pattern dependence, and the semiconductor wafer W can be uniformly heated if the flash light is irradiated with a uniform illuminance distribution. it can. Since the silicon semiconductor wafer W substantially absorbs light having a wavelength shorter than 1.1 μm, the flash light from the xenon flash lamp FL is almost absorbed by the semiconductor wafer W itself. Therefore, even if a pattern is formed on the surface of the semiconductor wafer W, the absorption of the flash light is not affected thereby. Further, there is no possibility that the ultraviolet light component of the flash light passes through the semiconductor wafer W to expose the resist film 11.

  Further, the lower surface of the peripheral edge of the semiconductor wafer W is supported over the entire circumference by an annular support ring 71 that is opaque to the flash light. Accordingly, the flash light that tries to go around the side of the semiconductor wafer W is blocked by the support ring 71, and such stray light does not reach the lower surface of the peripheral edge of the semiconductor wafer W. As a result, the flash light that wraps around the side of the semiconductor wafer W and reaches the lower surface of the peripheral portion does not heat the lower surface of the peripheral portion, preventing the temperature of the peripheral portion from becoming higher than the inner region, The in-plane temperature distribution on the surface of the semiconductor wafer W can be made uniform.

  Even after the baking of the resist film 11 by flash light irradiation from the back surface of the semiconductor wafer W is completed, the semiconductor wafer W is continuously cooled by the cooling plate 72 and maintained at a predetermined temperature control temperature. Thereby, the temperature fall rate of the semiconductor wafer W after a baking process can be raised. Eventually, when a predetermined time elapses, the three lift pins 44 are raised to lift the processed semiconductor wafer W away from the support ring 71. Then, the transfer opening 66 is opened, and the hand of the transfer robot enters the chamber 6 and stops just below the semiconductor wafer W. Subsequently, the three lift pins 44 are lowered to deliver the semiconductor wafer W to the hand of the transfer robot. Thereafter, the hand of the transfer robot that has received the semiconductor wafer W is withdrawn from the chamber 6, so that the semiconductor wafer W is unloaded and the baking process of the resist film 11 in the heat treatment apparatus 1 is completed. Note that the heat treatment space 65 in the chamber 6 may be replaced with an atmospheric atmosphere before the transfer opening 66 is opened.

  In the first embodiment, the periphery of the surface of the semiconductor wafer W on which the resist film 11 is formed is supported by the support ring 71 that is opaque to the flash light, and the back surface of the semiconductor wafer W is irradiated with the flash light. Yes. By irradiating the back surface on which the pattern is not formed with flash light, the pattern dependency of flash light absorption is eliminated and the semiconductor wafer W is uniformly heated, and also the resist film 11 is prevented from being exposed to the ultraviolet light component of the flash light. doing. Further, since the peripheral edge of the surface of the semiconductor wafer W is supported by the support ring 71 over the entire periphery, the flash light irradiated from the flash lamp FL is prevented from flowing around the peripheral edge of the surface of the semiconductor wafer W. The semiconductor wafer W can be heated uniformly. Further, it is possible to prevent the resist film 11 from being exposed to the stray light that has entered the sides of the semiconductor wafer W.

  Here, when the light emission time of the flash lamp FL is about several milliseconds, even if the flash light wraps around and reaches the lower surface of the peripheral edge of the semiconductor wafer W (the surface in the first embodiment), the thermal effect is the upper surface. Since the flash heating is completed before it is transmitted to the light, the influence of stray light is small. As in the first embodiment, when the light emission time of the flash lamp FL is set to 10 milliseconds or more and 1 second or less by intermittently flowing the current flowing through the flash lamp FL by the IGBT 96, the heat generated by the flash light that has entered the lower surface of the peripheral portion Since the influence appears on the upper surface before the end of the flash heating, the technical significance of shielding light by the opaque support ring 71 is increased.

  Further, if the irradiance of the flash light emitted from the flash lamp FL is too strong, only the upper surface of the semiconductor wafer W is suddenly heated up and thermally expanded, so that the semiconductor wafer W warps so that the upper surface is convex. There is a possibility of jumping from the support ring 71. When the semiconductor wafer W jumps from the support ring 71, a gap is generated between the lower surface of the peripheral edge of the semiconductor wafer W and the support ring 71, so that flash light enters from the gap and reaches the lower surface of the peripheral edge to reach the temperature distribution. Uniformity may be impaired. Further, the semiconductor wafer W is warped so that the upper surface is convex, and then warped so that the lower surface is convex due to the recoil that the warp returns. At this time, the resist film 11 formed on the surface of the semiconductor wafer W may come into contact with the cooling plate 72 and the resist film 11 may be contaminated.

For this reason, the irradiance of the flash light emitted from the flash lamp FL is set to 1 × 10 ⁸ W / m ² or less. If the irradiance of the flash light is 1 × 10 ⁸ W / m ² or less, it is possible to prevent jumping due to the rapid thermal expansion of the upper surface of the semiconductor wafer W, thereby preventing the incidence of stray light. Thus, the semiconductor wafer W can be uniformly flash-heated, and contamination of the resist film 11 can be prevented.

  In the first embodiment, the resist film 11 formed on the surface of the semiconductor wafer W is baked by flash light irradiation from the flash lamp FL. The heat treatment time by flash light irradiation is an extremely short time of 1 second or less. The conventional post-coating bake treatment that is placed on a hot plate and heated takes at least 30 seconds or more for the semiconductor wafer W to reach the target temperature. Compared with this, the time required for the post-coating bake treatment by flash light irradiation is remarkably short, and as a result, the throughput in the heat treatment apparatus 1 can be improved.

  Furthermore, in the first embodiment, the semiconductor wafer W is supported by the support ring 71 placed on the cooling plate 72, and the temperature of the semiconductor wafer W before and after the flash light irradiation is adjusted to a predetermined temperature by the cooling plate 72. ing. That is, flash light irradiation is performed while the semiconductor wafer W is cooled by the cooling plate 72. For this reason, it is possible to make the temperature history uniform among a plurality of semiconductor wafers W processed continuously. Further, heat storage in the holding unit 7 and the chamber 6 due to flash heating can be prevented.

Second Embodiment
Next, a second embodiment of the present invention will be described. FIG. 5 is a diagram showing a main configuration of the heat treatment apparatus 1a of the second embodiment. In FIG. 5, the same elements as those in the first embodiment are denoted by the same reference numerals as those in FIG. This heat treatment apparatus 1a is also a flash lamp annealing apparatus that performs heat treatment by irradiating a substantially circular semiconductor wafer W as a substrate with flash light. In the second embodiment, the semiconductor wafer W into which impurities have been implanted by ion implantation is irradiated with flash light to activate the impurities.

  In the first embodiment, the holder 7 that holds the semiconductor wafer W is provided with the cooling plate 72, but in the second embodiment, the holder 7 is provided with a heating plate 74 that heats the semiconductor wafer W. The heating plate 74 is a substantially disk-shaped member made of metal (for example, aluminum), and is provided in the chamber 6 to place the support ring 71 thereon. The heating plate 74 incorporates a heating mechanism (not shown) (for example, a resistance heating element such as a nichrome wire), and the heating plate 74 is heated by the heating mechanism. A temperature sensor (not shown) is also provided inside the heating plate 74. The temperature sensor measures the temperature of the heating plate 74 and transmits the measurement result to the control unit 3.

  In the second embodiment, a support ring 71 is placed on the periphery of the upper surface of the heating plate 74, and the semiconductor wafer W is supported in a horizontal posture by the support ring 71. Since the annular support ring 71 supports the lower surface of the peripheral edge of the semiconductor wafer W, a gap having a predetermined interval is formed between the lower surface of the inner region of the semiconductor wafer W and the upper surface of the heating plate 74. The semiconductor wafer W supported by the support ring 71 placed on the heating plate 74 is heated to a predetermined temperature by the heating plate 74 and maintained at that temperature.

  The remaining configuration of the heat treatment apparatus 1a of the second embodiment is the same as that of the heat treatment apparatus 1 of the first embodiment. Further, the processing procedure of the semiconductor wafer W in the heat treatment apparatus 1a of the second embodiment is substantially the same as that of the first embodiment. However, in the second embodiment, the semiconductor wafer W to be processed is a semiconductor substrate in which impurities are implanted on the surface by an ion implantation method. The semiconductor wafer W in which impurities are implanted into such a surface is carried into the chamber 6.

  Further, in the second embodiment, contrary to the first embodiment, the semiconductor wafer W is loaded into the chamber 6 with the surface thereof facing the upper surface. Therefore, the semiconductor wafer W is supported by the support ring 71 in a state where the surface into which the impurities are implanted faces the upper surface. The support ring 71 contacts and supports the peripheral edge of the back surface of the semiconductor wafer W.

  The temperature of the heating plate 74 is adjusted to a predetermined temperature by the control unit 3 in advance. The semiconductor wafer W is preheated to a predetermined temperature (about 200 ° C. to about 800 ° C.) by being supported by the support ring 71 and being held in proximity to the heating plate 74. Then, after the predetermined time has elapsed, the semiconductor wafer W is heated to a predetermined temperature, and then flash light is irradiated from the flash lamp FL of the flash irradiation unit 5 toward the semiconductor wafer W under the control of the control unit 3. The flash light irradiation is the same as in the first embodiment, and the light emission time of the flash lamp FL is extended to several tens of milliseconds by intermittently supplying the electric charge to the flash lamp FL by the IGBT 96.

  FIG. 6 is a diagram illustrating a state in which the semiconductor wafer W according to the second embodiment is flash-heated. A pattern 12 is formed on the surface of the semiconductor wafer W, and impurities are implanted into, for example, a source / drain region of the pattern 12. The semiconductor wafer W is supported by the support ring 71 with the surface on which the pattern 12 is formed facing the upper surface. While the semiconductor wafer W is heated by the heating plate 74, the upper surface (the surface in the second embodiment) of the semiconductor wafer W is irradiated with flash light from the flash lamp FL. The flash light emitted from the flash lamp FL is a flash light with a very short irradiation time and high intensity. The temperature of the surface of the semiconductor wafer W irradiated with flash light from the flash lamp FL instantaneously rises rapidly to the processing temperature (1000 ° C. or higher), whereby the impurity activation processing is executed. Note that since the irradiation time of the flash light is extremely short, diffusion of impurities due to heat can be suppressed.

  In the second embodiment, the surface of the semiconductor wafer W on which the pattern 12 is formed is supported by the support ring 71 with the upper surface facing upward, and the surface of the semiconductor wafer W is irradiated with flash light. The lower surface of the peripheral edge of the semiconductor wafer W is supported over the entire circumference by an annular support ring 71 that is opaque to the flash light. Accordingly, the flash light that tries to go around the side of the semiconductor wafer W is blocked by the support ring 71, and such stray light does not reach the lower surface of the peripheral edge of the semiconductor wafer W. As a result, the flash light that wraps around the side of the semiconductor wafer W and reaches the lower surface of the peripheral portion does not heat the lower surface of the peripheral portion, preventing the temperature of the peripheral portion from becoming higher than the inner region, The in-plane temperature distribution on the surface of the semiconductor wafer W can be made uniform. Therefore, the surface of the semiconductor wafer W can be heated uniformly.

<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, the resist film 11 formed on the surface of the semiconductor wafer W is baked. Instead, a metal film is formed on the surface of the semiconductor wafer W, and silicide ( For example, nickel silicide) may be formed. In the second embodiment, the impurities implanted into the surface of the semiconductor wafer W are activated. Instead, defects introduced during ion implantation may be recovered by flash heating.

  Further, depending on the purpose of flash heating, the surface of the semiconductor wafer W may be supported with the support ring 71 placed on the cooling plate 72 facing the upper surface, or the support ring placed on the heating plate 74. 71 may support the back surface of the semiconductor wafer W toward the top surface. In any case, since the lower surface of the peripheral edge of the semiconductor wafer W is supported over the entire circumference by the annular support ring 71 that is opaque to the flash light, it is possible to prevent the flash light from flowing around and make the semiconductor wafer W uniform. Can be heated.

  However, when the processing temperature is relatively low, such as a resist film baking process or silicide formation, the back surface of the semiconductor wafer W is supported by the support ring 71 toward the top surface, and flash light is applied to the back surface of the semiconductor wafer W. Is preferably irradiated. By irradiating flash light to the back surface on which no pattern is formed, the semiconductor wafer W can be uniformly heated without the pattern dependency of flash light absorption. On the other hand, when a relatively high processing temperature is required, such as impurity activation and defect recovery, the surface of the semiconductor wafer W is supported by the support ring 71 toward the upper surface, and flashed on the surface of the semiconductor wafer W. It is necessary to irradiate light. This is because it is difficult to raise the temperature to a high temperature in the heat conduction to the surface when the back surface of the semiconductor wafer W is irradiated with the flash light as compared with the case where the front surface is directly irradiated with the flash light.

  Further, the holding unit 7 may be provided with a temperature control plate having a heating mechanism and a cooling mechanism, and the support ring 71 may be placed on the temperature control plate. The temperature control plate heats or cools the semiconductor wafer W according to the purpose of flash heating.

  Further, the support ring 71 may be formed of the same material as the cooling plate 72 or the heating plate 74. In this way, the temperature uniformity between the support ring 71 and the cooling plate 72 or the heating plate 74 can be improved, and the temperature of the semiconductor wafer W can be adjusted more uniformly. However, the support ring 71 must be made of a material that is at least opaque to flash light. When the same material is used, the support ring 71 and the cooling plate 72 or the heating plate 74 may be integrally formed, or separate members may be laminated.

  In addition, as in the first embodiment, when the back surface of the semiconductor wafer W is irradiated with flash light, the film (for example, silicon nitride film) inevitably formed on the back surface is peeled off, and then the semiconductor wafer W is removed. It may be carried into the chamber 6. By peeling off such a film, the semiconductor wafer W can be heated more uniformly.

  In the above embodiment, the flash irradiation unit 5 is provided with 30 flash lamps FL. However, the present invention is not limited to this, and the number of flash lamps FL can be any number. . The flash lamp FL is not limited to a xenon flash lamp, and may be a krypton flash lamp.

  The substrate to be processed by the heat treatment technique according to the present invention is not limited to a semiconductor wafer, and may be a glass substrate or a solar cell substrate used for a liquid crystal display device or the like. In the case of a rectangular substrate such as a glass substrate, the support ring 71 may also be a corresponding quadrangular annular member.

DESCRIPTION OF SYMBOLS 1,1a Heat processing apparatus 2 Exhaust part 3 Control part 4 Transfer part 5 Flash irradiation part 6 Chamber 7 Holding part 8 Gas supply part 11 Resist film 12 Pattern 65 Heat treatment space 71 Support ring 72 Cooling plate 74 Heating plate 96 IGBT
FL Flash lamp W Semiconductor wafer

Claims (2)

A heat treatment method for heating a substrate having a resist film formed on the surface thereof by irradiating the substrate with flash light,
A supporting step of accommodating the substrate in a chamber, with the back surface of the substrate facing the top surface, and supporting the lower surface of the peripheral edge of the substrate by an annular member placed on a cooling plate;
A flash irradiation step of irradiating flash light from a flash lamp on the back surface of the substrate supported by the annular member while cooling the substrate by the cooling plate on which the annular member is placed;
With
A heat treatment method, wherein the annular member formed of a material opaque to flash light prevents the flash light irradiated from the flash lamp from entering the lower surface of the peripheral edge of the substrate . The heat treatment method according to claim 1,
An irradiance of the flash lamp is 1 × 10 ⁸ W / m ² or less .

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