Flash irradiation device

Abstract

To provide a flash irradiation device capable of further reducing a thermal history of an object to be treated.SOLUTION: A flash irradiation device includes: a flash discharge lamp for generating flash light by discharging; an inductor having a first terminal connected to an anode of the flash discharge lamp; a capacitor having a first terminal connected to a second terminal of the inductor and storing electric charge to be supplied to the flash discharge lamp; a switching element for switching conduction / non-conduction between a cathode of the flash discharge lamp and the second terminal of the capacitor; a first rectifier having a cathode terminal connected to the second terminal of the inductor and having an anode terminal connected to the cathode of the flash discharge lamp; and a second rectifier having a cathode terminal connected to a first node between the second terminal of the inductor and the first terminal of the capacitor and having an anode terminal connected to a second node between a first terminal of the inductor and the anode of the flash discharge lamp.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a flash irradiation device.

Background Art

[0002] Conventionally, a flash irradiation device has been used for heat treatment in manufacturing processes such as heat treatment of semiconductor substrates and printable electronics. In particular, in recent years, with the miniaturization of semiconductor processes, an instantaneous heat treatment method using a flash irradiation device has attracted attention as a method for activating implanted impurities while suppressing their diffusion due to long-term heating.

[0003] Therefore, the present applicant has been developing a flash irradiation device equipped with a flash discharge lamp (also referred to as a "flash lamp") suitable for a heat treatment device for semiconductor wafers, and has developed, for example, a flash irradiation device as described in Patent Document 1 below.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The flash irradiation device as described above is an indispensable device for performing short-time heat treatment of semiconductor substrates, and further improvements are being intensively studied. Recently, in particular, against the background of further miniaturization of semiconductor processes, a flash irradiation device capable of further reducing the heat history of the object to be processed is required.

[0006] In view of the above problems, an object of the present invention is to provide a flash irradiation device capable of further reducing the heat history in the object to be processed.

Means for Solving the Problems

[0007] The flash irradiation device of the present invention a flash discharge lamp that generates a flash by discharge; an inductor having a first terminal connected to the anode of the flash discharge lamp; a capacitor that accumulates charge to be supplied to the flash discharge lamp, with a first terminal connected to the second terminal of the inductor; a switching element that switches between energization and non-energization between the cathode of the flash discharge lamp and the second terminal of the capacitor; a first rectifier having a cathode terminal connected to the second terminal of the inductor and an anode terminal connected to the cathode of the flash discharge lamp; characterized by comprising a second rectifier having a cathode terminal connected to a first node between the second terminal of the inductor and the first terminal of the capacitor and an anode terminal connected to a second node between the first terminal of the inductor and the anode of the flash discharge lamp.

[0008] At the start of lighting of the flash discharge lamp, it is common to start lighting by switching the switching element from the non-energized state to the energized state, or by applying a starting pulse voltage to the trigger electrode after switching the switching element from the non-energized state to the energized state. The time from when these starting operations are executed until a flash is emitted from the flash discharge lamp is extremely short and depends on the parameters of each circuit element and the shape and size of the flash discharge lamp.

[0009] On the other hand, immediately after the flash is irradiated on the object to be processed and the switching element is switched from the energized state to the non-energized state, the power supply to the flash discharge lamp continues for a while by the energy stored in the inductor. And while the power required for the light emission of the flash discharge lamp is being supplied, the light output from the flash discharge lamp also continues.

[0010] That is, immediately after switching the switching element from the energized state to the non-energized state, promptly stopping the power supply to the flash discharge lamp by the energy stored in the inductor greatly contributes to reducing the thermal history of the object to be processed.

[0011] As a method for promptly stopping the power supply to the flash discharge lamp by the energy stored in the inductor, for example, it is conceivable to configure a mechanism for disconnecting the inductor and the flash discharge lamp immediately after or simultaneously with switching the switching element from the energized state to the non-energized state.

[0012] However, such a method requires control of the timing for disconnecting the inductor and the flash discharge lamp, requires a discharge path for discharging energy, requires a withstand voltage design for the load at the disconnection timing, etc., and the design difficulty becomes extremely high, and many problems can occur, so it cannot be said to be a practical method.

[0013] Therefore, the inventors of the present invention arrived at the above configuration through intensive studies. The flash irradiation device with the above configuration, without requiring complicated timing control or complicated circuit design, immediately after the switching element switches from the energized state to the non-energized state, the energy stored in the inductor is mainly consumed via the second rectifier.

[0014] And after the switching element switches to the non-energized state, since almost no current is supplied to the flash discharge lamp by the current flowing through the second rectifier, the time during which the light output continues in the flash discharge lamp is significantly reduced. Therefore, according to the above configuration, the thermal history of the object to be processed can be further reduced.

[0015] In the above flash irradiation device, The second rectifier may have a configuration having a plurality of diode elements connected in series.

[0016] According to the above configuration, for example, even when one of the plurality of diode elements included in the second rectifier is damaged and a short circuit occurs between both terminals, it is possible to avoid a short circuit between the first terminal of the capacitor and the anode of the flash discharge lamp.

[0017] The above flash irradiation device In the discharge operation, the peak value of the forward current flowing through the second rectifier is I fp Let, the forward voltage of the second rectifier be V f Let, the resistance value between the cathode terminal of the second rectifier and the first node be R p1 Let, the resistance value between the anode terminal of the second rectifier and the second node be R p2 When, it may be configured to satisfy the following formula (1). 100 [V] ≧ V f + (R p1 + R p2 )·I fp (1)

[0018] In a state where current is flowing through the second rectifier, it can be assumed that a voltage derived from the left - hand side formula of the above formula (1) is applied between the first node and the second node. Note that when the voltage is the voltage of the second node with respect to the first node as a reference, it becomes a positive voltage.

[0019] Then, a voltage substantially equal to the voltage is applied between the anode and the cathode of the flash discharge lamp. And if the voltage exceeds the lower limit value of the voltage required to maintain the lighting of the flash discharge lamp, current may flow through the flash discharge lamp, and in some cases, it may emit light enough to heat the object to be processed.

[0020] Here, the inventors investigated the lower limit value of the voltage required to maintain lighting for a flash discharge lamp used in a semiconductor manufacturing process, more specifically, a flash discharge lamp used as a light source for heat treatment of a semiconductor wafer. And in a flash discharge lamp used in a semiconductor manufacturing process (for example, a flash discharge lamp used for heat treatment of a 12-inch silicon wafer), immediately after switching the switching element from an energized state to a non-energized state, the voltage required to maintain lighting, that is, the voltage between the electrodes of the flash discharge lamp immediately after it goes out, was confirmed to be generally in the range of 100 V to 200 V.

[0021] Therefore, with the above configuration, the current generated by the energy stored in the inductor can be more reliably passed to the second rectifier.

Advantages of the Invention

[0022] According to the present invention, a flash irradiation device capable of further reducing the thermal history in the object to be processed is realized.

Brief Description of the Drawings

[0023]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0024] Hereinafter, the flash irradiation device of the present invention will be described with reference to the drawings. Note that each of the following drawings is schematically illustrated, and the dimensional ratios and the number of elements on the drawings do not necessarily match the actual dimensional ratios and the number of elements.

[0025] First, the configuration of the flash irradiation device 1 will be described. FIG. 1 is a side view schematically showing an embodiment of the flash irradiation device 1. As shown in FIG. 1, the flash irradiation device 1 includes a flash discharge lamp 10 and a reflection member 20, and is configured to irradiate a flash L1 onto the main surface W1a of the object to be processed W1 supported by a support 30.

[0026] As shown in FIG. 1, the flash discharge lamp 10 in the present embodiment includes a luminous tube 11, an anode 12p and a cathode 12n spaced apart from each other in the luminous tube 11, and a trigger tube 13 composed of a tube body 13a and a conductor 13b. When a voltage necessary for light emission is applied between the anode 12p and the cathode 12n via a power supply line (15, 15) and a trigger pulse voltage is applied to the conductor 13b of the trigger tube 13, a discharge occurs in the luminous tube 11 and the flash L1 is emitted.

[0027] The reflection member 20 is disposed on the side opposite to the object to be processed W1 when viewed from the flash discharge lamp 10, and has a reflection surface 21 that reflects the flash L1 emitted from the flash discharge lamp 10 and traveling toward the side opposite to the object to be processed W1 so as to travel toward the object to be processed W1 side.

[0028] Next, the configuration of the circuit for lighting the flash discharge lamp 10 will be described. FIG. 2 is a circuit diagram showing an example of the circuit for lighting the flash discharge lamp 10. The circuit for lighting the flash discharge lamp 10 includes a power supply circuit C1 connected to the anode 12p and the cathode 12n of the flash discharge lamp 10, and a trigger circuit C2 connected to the conductor 13b of the trigger tube 13 (not shown for the sake of illustration). Further, the present embodiment includes a control unit 9 for controlling the energized / non-energized state of the switching elements (4, 8) to be described later, but whether or not to include the control unit 9 is optional, and the switching elements (4, 8) may be configured to be controlled by human operation.

[0029] As shown in FIG. 2, the power supply circuit C1 includes an inductor 2 having its first terminal connected to the anode 12p of the flash discharge lamp 10, a capacitor 3 having its first terminal connected to the second terminal of the inductor 2, and a switching element 4 for switching the energization / non-energization between the cathode 12n of the flash discharge lamp 10 and the second terminal of the capacitor 3.

[0030] Furthermore, the power supply circuit C1 includes a first rectifier 5a having its cathode terminal connected to the second terminal of the inductor 2 and its anode terminal connected to the cathode 12n of the flash discharge lamp 10, and a second rectifier 5b having its cathode terminal connected to a first node n1 between the second terminal of the inductor 2 and the first terminal of the capacitor 3 and its anode terminal connected to a second node n2 between the first terminal of the inductor 2 and the anode 12p of the flash discharge lamp 10. The first node n1 is an arbitrary position between the second terminal of the inductor 2 and the first terminal of the capacitor 3, and the second node n2 is an arbitrary position between the first terminal of the inductor 2 and the anode 12p of the flash discharge lamp 10.

[0031] Although a power supply circuit (for example, a DC-DC converter or the like) for charging the capacitor 3 is connected in front of the capacitor 3, for the convenience of finally explaining the configuration of the power supply circuit C1 that contributes to the lighting operation of the flash discharge lamp 10, the description of the power supply circuit is omitted. Also, for the following description of the operation of the power supply circuit C1, the operation starting from the state where the charging of the capacitor 3 is completed is described. This also applies to the trigger capacitor 7 in the trigger circuit C2 described later.

[0032] The inductor 2 adjusts the time constant of the current supplied to the flash discharge lamp 10. That is, the inductor 2 adjusts the rising speed and falling speed of the current supplied from the capacitor 3 to the flash discharge lamp 10.

[0033] The capacitor 3 stores the charge for causing the flash discharge lamp 10 to emit light supplied from a power source or the like, and operates to discharge to the flash discharge lamp 10.

[0034] The switching element 4 is an element that switches the cathode 12n of the flash discharge lamp 10 and the second terminal of the capacitor 3 between an energized state and a non-energized state. In this embodiment, the switching element 4 switches between the energized state and the non-energized state by controlling the voltage applied to the control terminal by the control unit 9. The switching element 4 can be any element considering current capacity, breakdown voltage, switching speed, ON resistance, etc., but the switching element 4 in this embodiment is an IGBT (Insulated Gate Bipolar Transistor).

[0035] As shown in FIG. 2, the first rectifier 5a of this embodiment is composed of two diode elements (5a1, 5a2) connected in series. After switching the switching element 4 from the energized state to the non-energized state, the current flowing from the anode 12p to the cathode 12n of the flash discharge lamp 10 is regenerated to the first terminal of the capacitor 3.

[0036] In this way, the first rectifier 5a regenerates the current, thereby protecting the switching element 4 from a high-voltage load. When the first rectifier 5a is not provided, the voltage between both terminals of the switching element 4 generally exceeds 6500V, which is the breakdown voltage of a high-breakdown-voltage / high-current switching element. Protecting from such a significantly higher voltage compared to a general light-emitting device is particularly important in the flash irradiation device 1 where a high light output is required for heat-treating the object to be processed W1.

[0037] Note that the first rectifier 5a of this embodiment is composed of two diode elements (5a1, 5a2) connected in series, but the number of diode elements constituting the first rectifier 5a may be one, or may be three or more. However, the diode element may lose its rectifying action due to deterioration, wear, etc., and there is a risk that the anode terminal and the cathode terminal will short-circuit. For this reason, from the viewpoint of fail-safe, the first rectifier 5a preferably has a configuration in which a plurality of diode elements are connected in series so that a short circuit between the first terminal of the capacitor 3 and the cathode 12n of the flash discharge lamp 10 is avoided even if one diode element shorts.

[0038] Further, the diode element constituting the first rectifier 5a has a rectifying function, and as long as it can withstand the voltage and current capacity, it may be, for example, a parasitic diode element formed in a semiconductor device or the like.

[0039] As shown in FIG. 2, the second rectifier 5b of the present embodiment is composed of two diode elements (5b1, 5b2) connected in series. After switching the switching element 4 from the energized state to the non-energized state, the current flowing to the second node n2 by the energy stored in the inductor 2 is made to flow to the first terminal of the capacitor 3. As a result, the flash irradiation device 1 causes the current flowing to the anode 12p of the flash discharge lamp 10 to rapidly decrease after switching the switching element 4 from the energized state to the non-energized state, as compared with the conventional configuration.

[0040] Note that the second rectifier 5b of the present embodiment is composed of two diode elements (5b1, 5b2) connected in series, but the number of diode elements constituting the second rectifier 5b may be one or three or more. However, for the same reason as the first rectifier 5a, it is preferable that the second rectifier 5b has a configuration in which a plurality of diode elements are connected in series.

[0041] Further, the diode element constituting the second rectifier 5b, like the first rectifier 5a, has a rectifying function, and as long as it can withstand the voltage and current capacity, it may be, for example, a parasitic diode element formed in a semiconductor device or the like.

[0042] As shown in FIG. 2, the trigger circuit C2 includes a transformer 6, a trigger capacitor 7 connected in series to the primary side of the transformer 6, and a switching element 8. One terminal of the secondary side of the transformer 6 is connected to the conductor 13b of the flash discharge lamp 10, and the other terminal is connected to the second terminal of the capacitor 3.

[0043] When the switching element 8 is switched from the non-conductive state to the conductive state under the control of the control unit 9 while the trigger capacitor 7 is charged, the charge stored in the trigger capacitor 7 is discharged, and a current is generated on the primary side of the transformer 6. Due to the generation of this current, an electromotive force is generated on the secondary side of the transformer 6, and a pulse voltage is applied to the conductor 13b of the flash discharge lamp 10. At this time, if the capacitor 3 of the power supply circuit C1 is charged and the switching element 4 is controlled to be in the conductive state, a discharge occurs between the anode 12p and the cathode 12n of the flash discharge lamp 10 using the pulse voltage applied to the conductor 13b as a trigger, and the flash L1 is emitted.

[0044] Any element can be selected as the switching element 8 in consideration of current capacity, withstand voltage, switching speed, ON resistance, etc. However, the switching element 8 in the present embodiment is a thyristor.

[0045] As described above, the control unit 9 is an element that controls the conductive / non-conductive state of the switching elements (4, 8), and is, for example, an arithmetic processing device such as a CPU or an MPU.

[0046] Here, the operation from the state where the capacitor 3 and the trigger capacitor 7 are charged until the flash discharge lamp 10 finishes lighting will be described with reference to the graph shown in the drawing.

[0047] FIG. 3 is a schematic graph showing the time changes of the current I1 flowing from the second node n2 to the anode 12p of the flash discharge lamp 10 and the current I2 flowing from the second node n2 to the second rectifier 5b. Note that, for the graph of the current I1 shown in FIG. 3, the waveform in the conventional configuration without the second rectifier 5b is shown by a broken line.

[0048] First, after the charging of the capacitor 3 and the trigger capacitor 7 is completed and the control unit 9 controls the switching element 4 of the power supply circuit C1 from the non-conductive state to the conductive state, the timing at which the switching element 8 of the trigger circuit C2 is switched from the non-conductive state to the conductive state is time t1. And, in order to stop the lighting of the flash discharge lamp 10, the timing at which the control unit 9 switches the switching element 4 of the power supply circuit C1 from the conductive state to the non-conductive state is time t2.

[0049] At time t1, a pulse voltage is applied to the conductor 13b of the flash discharge lamp 10, and when the discharge is started, the current I1 flowing from the capacitor 3 to the anode 12p of the flash discharge lamp 10 via the second node n2 gradually increases. At this time, since the potential of the first node n1 is higher than that of the second node n2, no current I2 flows through the second rectifier 5b.

[0050] Then, when a certain amount of current I1 flows through the flash discharge lamp 10 and the irradiation of the flash L1 necessary for the heat treatment of the object to be processed W1 is completed (at time t2), the control unit 9 switches the switching element 4 from the conductive state to the non-conductive state. Immediately after this, due to the energy stored in the inductor 2, a current flows from the first node n1 toward the second node n2. Then, when the potential of the second node n2 becomes higher than that of the first node n1 and the potential difference becomes larger than the voltage at which the forward conduction of the second rectifier 5b is possible (hereinafter referred to as "forward voltage"), the current I2 flowing through the second rectifier 5b gradually increases.

[0051] Note that the second rectifier 5b and the anode 12p of the flash discharge lamp 10 are connected to the second node n2, but the impedance of the second rectifier 5b in the state where the current I2 flows is extremely small compared to the impedance between the anode 12p and the cathode 12n of the flash discharge lamp 10. For this reason, most of the current generated by the energy stored in the inductor 2 flows from the second node n2 toward the first node n1 through the second rectifier 5b, and the time changes of the current I1 and the current I2 have waveforms as shown in FIG. 3.

[0052] In the case of the conventional configuration without the second rectifier 5b, the current generated by the energy stored in the inductor 2 has nowhere to go except to the flash discharge lamp 10 without the generation of the current I2. Therefore, as shown by the dashed line in FIG. 3, after the time t2 has passed, the current I1 flows through the flash discharge lamp 10 for a while, and the output of the flash L1 is maintained at a relatively high intensity.

[0053] As described above, after the switching element 4 switches from the energized state to the non-energized state, the current I2 flows through the second rectifier 5b when the voltage of the second node n2 with respect to the first node n1 is greater than the forward voltage of the second rectifier 5b. Therefore, in the state where the current I2 is flowing through the second rectifier 5b, the sum of the forward voltages of the respective diode elements (5b1, 5b2) constituting the second rectifier 5b (forward voltage V f ), and the peak value of the current I2 (peak current I of the forward current of the second rectifier 5b fp ), and the sum of the resistance values (R p1 , R p2 ) of the path (for example, a wiring cable) excluding the diode elements (5b1, 5b2) from the first node n1 to the second node n2 via the second rectifier 5b. When the sum of the voltages derived by the product is applied between the first node n1 and the second node n2. At this time, if the sum value exceeds the lower limit value of the voltage required for lighting the flash discharge lamp 10, there is a possibility that discharge from the anode 12p to the cathode 12n of the flash discharge lamp 10 may occur.

[0054] And, as described above, the lower limit value of the voltage required for lighting the flash discharge lamp 10 depends on the shape and size of the lamp. However, when the present inventors investigated various flash discharge lamps used for heating semiconductor wafers, it was confirmed that it was generally in the range of 100V to 200V. Therefore, it is preferable that each of the above parameters satisfies the relationship of the above equation (1). For the sake of caution, the above equation (1) is reproduced below. 100[V] ≧ V f + (R p1 + Rp2 )·I fp (1)

[0055] Incidentally, as an example, for the peak current I fp assuming a value of 2 kA and a forward voltage V f of 5 V for the second rectifier 5b, by setting the total value of each resistance (R p1 , R p2 ) to 47.5 mΩ or less, the flash irradiation device 1 satisfying the above equation (1) can be realized. These values are set based on the value of the peak current I fp in the experimentally configured flash irradiation device 1 and the forward voltage of commercially available diode elements. Also, a resistance value of this level can be sufficiently realized by selecting a cable made of a material with a relatively low resistance value from commercially available cables and adjusting the cable length.

[0056] The condition of the above equation (1) is a preferable condition for further suppressing the maintenance of the lighting of the flash discharge lamp 10. However, when the time during which the peak current I fp flows is extremely short and is considered not to have a significant influence on the thermal history of the object to be processed W1, it does not have to be satisfied.

[0057] In the flash irradiation device 1 configured as described above, as shown in FIG. 3, after switching the switching element 4 from the energized state to the non-energized state, the current flowing through the flash discharge lamp 10 rapidly decreases. For this reason, since the lighting state of the flash discharge lamp 10 is suppressed from being maintained unnecessarily, the thermal history in the object to be processed W1 is further reduced.

[0058] The configuration provided in the above-described flash irradiation device 1 is merely an example, and the present invention is not limited to each illustrated configuration. That is, for example, in each of the power supply circuit C1 and the trigger circuit C2 shown in FIG. 2, arbitrary circuit elements (for example, high resistance elements and smoothing elements) may be connected as long as the main circuit operation is not inhibited.

Explanation of Reference Numerals

[0059] 1: Flash irradiation device 2: Inductor 3: Capacitor 4: Switching element 5a: First rectifier 5a1: Diode element 5a2: Diode element 5b: Second rectifier 5b1: Diode element 5b2: Diode element 6: Transformer 7: Trigger capacitor 8: Switching element 9: Control unit 10: Flash discharge lamp 11: Light emitting tube 12n: Cathode 12p: Anode 13: Trigger tube 13a: Tube body 13b: Conductor 20: Reflective member 21: Reflective surface 30: Support C1: Power supply circuit C2: Trigger circuit L1: Flash W1: Object to be processed W1a: Main surface

Claims

1. A flash discharge lamp that generates a flash by discharge, an inductor having a first terminal connected to the anode of the flash discharge lamp, a capacitor that accumulates charge to be supplied to the flash discharge lamp, with a first terminal connected to the second terminal of the inductor, a switching element that switches conduction / non-conduction between the cathode of the flash discharge lamp and the second terminal of the capacitor, a first rectifier having a cathode terminal connected to the second terminal of the inductor and an anode terminal connected to the cathode of the flash discharge lamp, a second rectifier having a cathode terminal connected to a first node between the second terminal of the inductor and the first terminal of the capacitor and an anode terminal connected to a second node between the first terminal of the inductor and the anode of the flash discharge lamp. A flash irradiation device characterized by comprising:

2. The flash irradiation device according to claim 1, wherein the second rectifier has a plurality of diode elements connected in series.

3. In the discharging operation, let the peak value of the forward current flowing through the second rectifier be I fp and let the forward voltage of the second rectifier be V f and let the resistance value between the cathode terminal of the second rectifier and the first node be R p1 and let the resistance value between the anode terminal of the second rectifier and the second node be R p2 When this is the case, the flash irradiation device according to claim 1 or 2, characterized in that the following formula (1) is satisfied. 100 [V] ≥ V f + (R p1 + R p2 ) · I fp (1)

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