JP5084069B2 - Induction heating apparatus and induction heating method - Google Patents

Description

  The present invention relates to an induction heating apparatus and method, and more particularly to an apparatus and method for semiconductor substrate heat treatment suitable for controlling the temperature of an object to be heated when a substrate such as a large-diameter wafer is processed.

  As an apparatus for heat-treating a substrate such as a semiconductor wafer using induction heating, those disclosed in Patent Document 1 and Patent Document 2 are known. As shown in FIG. 5, the heat treatment apparatus disclosed in Patent Document 1 is a batch-type heat treatment apparatus, in which wafers 2 stacked in multiple stages are placed in a quartz process tube 3, and graphite or the like is placed on the outer periphery of the process tube 3. The heating tower 4 formed of the conductive member is disposed, and the solenoid-like induction heating coil 5 is disposed on the outer periphery thereof. According to the heat treatment apparatus 1 having such a configuration, the heating tower 4 is heated by the influence of the magnetic flux generated by the induction heating coil 5, and the wafer 2 disposed in the process tube 3 is heated by the radiant heat from the heating tower 4. The

  Further, as shown in FIG. 6, the heat treatment apparatus disclosed in Patent Document 2 is a single-wafer type heat treatment apparatus, in which a susceptor 7 divided into concentric circles is formed of graphite or the like, and the upper surface of the susceptor 7 is A wafer 8 is placed on the side, and a plurality of annular induction heating coils 9 are arranged concentrically on the lower surface side to enable individual power control for the plurality of induction heating coils 9. According to the heat treatment apparatus 6 having such a configuration, since heat transfer between the susceptor 7 positioned in the heating range by each induction heating coil 9 and the other susceptor 7 is suppressed, power control for the induction heating coil 9 is performed. This improves the temperature distribution controllability of the wafer 8.

  In Patent Document 2, it is described that the distribution of heat generation is favorably controlled by dividing the susceptor 7 on which the wafer 8 is placed. However, in Patent Document 3, the cross-sectional shape of the susceptor is devised. It is disclosed to improve the heat generation distribution. The heat treatment apparatus disclosed in Patent Document 3 pays attention to the fact that the heat generation amount is reduced on the inner side where the diameter of the induction heating coil formed in an annular shape is small, and by increasing the thickness of the inner part of the susceptor, The inner part is closer to the induction heating coil than the part, and the amount of heat generation and the heat capacity are increased.

JP 2004-71596 A JP 2009-87703 A JP 2006-100067 A

  However, in any of the heat treatment apparatuses configured as described above, the magnetic flux acts perpendicularly to the graphite. For this reason, when a metal film or the like is formed on the surface of the wafer as an object to be heated, the wafer may be directly heated, and temperature distribution control may be disturbed.

  On the other hand, when heating is promoted by applying a horizontal magnetic flux to graphite (susceptor), it becomes difficult to heat a large number of susceptors in a stacked arrangement. In order to solve this problem, when a plurality of induction heating coils are arranged close to each other in the stacking direction (vertical direction), there arises a problem that heating control becomes unstable due to the influence of mutual induction between the induction heating coils.

  Therefore, in the present invention, the above problems are solved, and even when a plurality of induction heating coils are arranged in the vertical direction while applying a horizontal magnetic flux to the susceptor, the influence of mutual induction between the induction heating coils is suppressed, An object of the present invention is to provide an induction heating apparatus and method capable of enabling good heating control.

  In order to achieve the above object, an induction heating apparatus according to the present invention includes three sets of induction heating coils having a core, which are induction-heated by a magnetic flux emitted from an end surface of the core, and 3 connected to each of the induction heating coils. The three sets of induction heating coils are laminated with the end surfaces of the cores aligned, and the middle stage is defined as the main heating coil, the upper stage as the upper subordinate heating coil, and the lower stage as the lower subordinate heating coil. The upper subordinate heating coil core is provided with another coil magnetically coupled to the upper subordinate heating coil, and the lower subordinate heating coil core is magnetically coupled to the lower subordinate heating coil. Another coil is provided, and among the three inverters, the first inverter and the upper subordinate heating coil are connected, and the third inverter and the lower subordinate heating coil are connected to each other. Subsequently, another coil provided in the core of the upper subordinate heating coil, another coil provided in the core of the lower subordinate heating coil, and the main heating coil are connected in series to the second inverter. It is characterized by that.

  In addition, an induction heating method for achieving the above object includes three sets of induction heating coils having a core and three inverters connected to each of the induction heating coils, which are induction heated by a magnetic flux emitted from an end face of the core. The three sets of induction heating coils are arranged so that the end faces of the core are aligned, and the middle stage is defined as the main heating coil, the upper stage as the upper subordinate heating coil, and the lower stage as the lower subordinate heating coil. An induction heating method using an induction heating device, wherein the upper stage dependent heating is performed such that a reverse coupling inductance is generated with respect to a coupling inductance of the main heating coil, the upper stage dependent heating coil, and the lower stage dependent heating coil. Connect another coil provided in the coil core and another coil provided in the lower subordinate heating coil core to operate the inverter. The features.

  Furthermore, in the induction heating method as described above, it is desirable to synchronize the current supplied to the heating coils from the first inverter, the second inverter, and the third inverter.

  According to the induction heating method having such characteristics, it is possible to perform power control (zone control control) while avoiding the influence of mutual induction between the adjacently arranged main heating coil, upper subordinate heating coil, and lower subordinate heating coil. It becomes possible.

  According to the induction heating apparatus and method having the above-described features, even when a plurality of induction heating coils are arranged in the vertical direction while applying a horizontal magnetic flux to the susceptor, mutual induction between the induction heating coils is achieved. The influence can be suppressed, and good heating control is possible.

It is a block diagram which shows the structure of the heat processing apparatus which concerns on 1st Embodiment. It is a block diagram for demonstrating the structure of the power supply part in the heat processing apparatus which concerns on 1st Embodiment. It is a block diagram for demonstrating the mode of cancellation of the magnetic flux between the stacked induction heating coils. It is a block diagram which shows the structure of the heat processing apparatus which concerns on 2nd Embodiment. It is a figure which shows the structure of the conventional batch type induction heating apparatus. It is a figure which shows the structure of the conventional single wafer type induction heating apparatus.

  Hereinafter, embodiments of the induction heating apparatus and the induction heating method of the present invention will be described in detail with reference to the drawings. First, a schematic configuration of an induction heating apparatus (hereinafter simply referred to as a heat treatment apparatus) according to the first embodiment will be described with reference to FIGS. 1A is a block diagram illustrating a planar configuration of the heat treatment apparatus, and FIG. 1B is a block diagram illustrating a side configuration of the heat treatment apparatus. FIG. 2 is a diagram for explaining the configuration of the power supply unit.

The heat treatment apparatus 10 according to the present embodiment is of a batch type in which heat treatment is performed by stacking a wafer 54 as an object to be heated and a susceptor 52 as a heating element in multiple stages.
The heat treatment apparatus 10 includes a boat 50 in which wafers 54 and horizontally arranged susceptors 52 are stacked in multiple stages in the vertical direction, and an induction heating coil that heats the susceptor 52 (the main heating coil 30, the subordinate heating coil 32, which will be described in detail later) 34, the reverse coupling coils 36 and 38), and the power source 12 that supplies power to the induction heating coil.

  The susceptor 52 may be made of a conductive member, and may be made of, for example, graphite, SiC, SiC-coated graphite, refractory metal, or the like. The susceptor 52 in the present embodiment has a circular planar shape.

  The susceptors 52 constituting the boat 50 are stacked and arranged via support members 56, respectively. The support member 56 is preferably made of quartz or the like that is not affected by heating by electromagnetic induction.

  Further, the boat 50 in this embodiment is placed on a turntable 58 having a motor (not shown), and can rotate the susceptor 52 and the wafer 54 during the heat treatment process. By adopting such a configuration, it is possible to suppress an uneven distribution of heat generation when the susceptor 52 is heated. Further, as will be described in detail later, even when the arrangement of the induction heating coil as a heating source is biased from the center of the susceptor 52, the susceptor 52 can be uniformly heated.

  The induction heating coil according to the embodiment includes one main heating coil 30 and two subordinate heating coils 32 and 34 arranged adjacent to each other so as to be electromagnetically coupled to the main heating coil 30. It is arrange | positioned on the periphery in the outer peripheral side. The main heating coil 30 and the subordinate heating coils 32 and 34 are stacked adjacent to each other in the same direction as the stacking direction of the susceptor 52. In addition, the main heating coil 30 according to the embodiment includes reverse coupling coils 36 and 38 that electromagnetically reversely couple the two subordinate heating coils 32 and 34. Here, the electromagnetic coupling causes, for example, an induced electromotive force in a direction to cancel the magnetic flux generated by the main heating coil 30 to the subordinate heating coils 32 and 34 based on a change in current supplied to the main heating coil 30. Such a state that is in a mutual induction relationship, that is, a state that causes mutual inductance. Electromagnetic reverse coupling refers to the main heating coil 30 when the main heating coil 30 is viewed as a primary winding (primary coil) and the subordinate heating coils 32 and 34 are viewed as secondary windings (secondary coils). And the sub-heating coils 32 and 34 are coupled to each other to generate a mutual inductance having a polarity opposite to that of the mutual inductance.

  Each induction heating coil (the main heating coil 30 and the subordinate heating coils 32 and 34) is configured by winding a copper wire around a core 40 disposed on the outer peripheral side of the boat 50. The core 40 may be made of a ferrite ceramic or the like, and may be formed by firing after forming a clay-like raw material. This is because it is possible to freely form a shape by using such a member. Further, by using the core 40, the diffusion of magnetic flux can be prevented compared to the case of the induction heating coil alone, and highly efficient induction heating with concentrated magnetic flux can be realized.

  In this embodiment, the winding directions of the main heating coil 30 and the subordinate heating coils 32 and 34 around the core 40 are the same. The reverse coupling coils 36 and 38 have the winding direction opposite to that of the subordinate heating coils 32 and 34 on the rear end side of the core 40 where the subordinate heating coils 32 and 34 are arranged on the front end side (susceptor 52 arrangement side). Arranged in a state. By adopting such a configuration, the mutual inductance generated between the main heating coil 30 and the subordinate heating coils 32, 34 by matching the directions of the currents supplied to the main heating coil 30 and the subordinate heating coils 32, 34. Then, the mutual inductance generated between the reverse coupling coils 36 and 38 and the subordinate heating coils 32 and 34 has a reverse polarity, and the influence of the mutual induction power cancels each other. For this reason, the influence of the mutual induction produced between the main heating coil 30 and the subordinate heating coils 32 and 34 arranged adjacent to each other is reduced, and individual power controllability can be improved. The winding ratio between the subordinate heating coils 32 and 34 and the reverse coupling coils 36 and 38 is preferably about 7: 1. In this case, the number of turns of the main heating coil 30 is preferably matched with the number of turns of the subordinate heating coils 32 and 34.

For example, in the case of the configuration shown in FIG. 2, the current input to the subordinate heating coil 32 is I ₁ , the current voltage is V ₁ , the current input to the main heating coil 30 is I ₂ , and the current voltage is V _2. And the mutual inductance + M ₁₂ (+ M ₂₁ ) generated between the reverse coupling coil 36 and the subordinate heating coil 32 and the subordinate heating when the current input to the subordinate heating coil 34 is I ₃ and the voltage of the current is V _3. The mutual inductance −M ₁₂ (−M ₂₁ ) generated between the coil 32 and the main heating coil 30 is equal, and the mutual inductance + M ₂₃ (+ M ₃₂ ) generated between the reverse coupling coil 38 and the subordinate heating coil 34, When the mutual inductance −M ₂₃ (−M ₃₂ ) generated between the subordinate heating coil 34 and the main heating coil 30 is equal, Expressions 1 to 3 are established. The

Here, L ₁ is the self-inductance of the subordinate heating coil 32, L ₂ is the self-inductance of the main heating coil 30, and L ₃ is the self-inductance of the subordinate heating coil 34.

  The mutual inductance M is

(L1 and L2 are self-inductances in the primary and secondary windings). Note that the self-inductance L can be obtained by Equation 5.

  Here, N represents the number of coil turns, φ represents the magnetic flux (wb), and I represents the current value. As described above, the number of turns of the coil differs between the main heating coil 30 and the reverse coupling coils 36 and 38. For this reason, even if the magnetic flux (dφ) per unit current (dI) is equal, the value of the self-inductance L will be different. Therefore, in order to make the mutual inductance M generated between the subordinate heating coils 32 and 34 the same (the polarities are opposite), it is necessary to adjust the coupling coefficient k. The coupling coefficient k can be changed according to the distance between the coils and the arrangement form. Therefore, based on the mutual inductance −M between the main heating coil 30 and the subordinate heating coils 32 and 34, the coupling coefficient k for obtaining the mutual inductance + M having the reverse polarity is calculated. In order to obtain the calculated coupling coefficient k, the reverse coupling coils 36 and 38 are arranged after adjusting the arrangement form and the distance between the coils.

  By satisfying such a relationship, the term including the mutual inductance due to mutual induction between the main heating coil 30 and the subordinate heating coils 32 and 34 is canceled, and mutual induction between the adjacent induction heating coils is cancelled. The influence of induction can be avoided.

  The core 40 around which the main heating coil 30 and the subordinate heating coils 32 and 34 are wound has a central axis parallel to the mounting surface of the wafer 54 in the susceptor 52 (a direction perpendicular to the central axis in the mounting state). Be placed. The leading end surface of the core 40 serving as the magnetic pole surface is opposed to the susceptor 52. With such a configuration, an alternating magnetic flux is generated in a direction parallel to the wafer 54 mounting surface of the susceptor 52 from the magnetic pole surface around which the main heating coil 30 and the subordinate heating coils 32 and 34 are wound.

  As described above, when the main heating coil 30 is regarded as a primary winding and the subordinate heating coils 32 and 34 are regarded as secondary windings, the details will be described later so that the directions of the currents applied to both are the same. Inverters 14a to 14c are connected. For this reason, the main heating coil 30 and the subordinate heating coils 32 and 34 stacked in the vertical direction are depolarized from each other.

  As shown in FIG. 3, the main heating coil 30 and the subordinate heating coils 32, 34 having such an arrangement relationship have the direction of the magnetic flux radiated so as to intersect perpendicularly to the mounting surface of the susceptor 52. , They are reversed and cancel each other. Therefore, even when a metal film or the like is formed on the surface of the wafer 54 placed on the susceptor 52, there is no possibility that the wafer 54 is directly heated by the influence of the magnetic flux in the vertical direction, and the temperature of the wafer 54 is increased. There is no risk of variations in distribution.

  Further, the main heating coil 30, the subordinate heating coils 32 and 34, and the reverse coupling coils 36 and 38 are preferably tubular members (for example, copper pipes) having a hollow inside. By inserting a cooling member (for example, cooling water) into the copper tube during the heat treatment, it becomes possible to suppress heating of the main heating coil 30, the subordinate heating coils 32 and 34, and the reverse coupling coils 36 and 38 themselves. Because.

  As described above, the main heating coil 30 and the subordinate heating coils 32 and 34 are arranged adjacent to each other in the vertical direction along the boat 50 in which the susceptors 52 on which the wafers 54 are stacked are stacked in the vertical direction. . By adopting such a configuration, it becomes possible to heat more susceptors 52 and wafers 54 at a time, and heat treatment of the wafers 54 can be performed efficiently. Further, if power control is performed individually on the stacked induction heating coils, the temperature distribution in the vertical direction in the plurality of susceptors 52 stacked in the boat 50 can be controlled. It is also possible to suppress temperature variations.

  The main heating coil 30 and the subordinate heating coils 32 and 34 configured as described above are connected to a single power supply unit 12. The power supply unit 12 is provided with inverters 14a to 14c, choppers 16a to 16c, a converter 18, a three-phase AC power source 20, and zone control means 22, and each induction heating coil (main heating coil 30 and subordinate heating coil 32). , 34) can be adjusted so that the current, voltage, frequency, and the like to be supplied can be adjusted. In the case of the embodiment shown in FIG. 2, inverters 14a to 14c employ series resonance type inverters. Therefore, as a configuration for easily switching the frequency, it is preferable to connect the resonance capacitor 26 in parallel and increase or decrease the capacitance by the switch 28 in accordance with the resonance frequency.

  Moreover, the heat processing apparatus 10 which concerns on embodiment has arrange | positioned the transformer 24 between each induction heating coil (the main heating coil 30 and the subordinate heating coil 32) and each inverter 14a-14c.

  The zone control means 22 performs power control on the main heating coil 30 and each of the subordinate heating coils 32 and 34 while avoiding the influence of mutual induction generated between the adjacent main heating coil 30 and the subordinate heating coils 32 and 34. Take a role.

  Since the main heating coil 30 and the subordinate heating coils 32, 34 arranged adjacent to each other are operated individually, the main heating coil 30 and the subordinate heating coil 32, or the main heating coil 30 and the subordinate heating coil 34 are arranged. Mutual induction may occur in, which may adversely affect individual power control. For this reason, the zone control means 22 matches the frequency of the current applied to the adjacent main heating coil 30 and the subordinate heating coils 32 and 34 based on the detected current frequency and waveform (current waveform), and The main heating coil 30 and the subordinate heating coils 32 and 34 arranged adjacent to each other are controlled by synchronizing the phase of the current waveform (the phase difference is 0 or the phase difference is approximated to 0), or by controlling to maintain a predetermined phase difference. It enables power control (zone control control) that avoids the influence of mutual induction between them.

  Such control includes, for example, detecting the current value, the frequency of the current, the voltage value, and the like applied to each induction heating coil (the main heating coil 30 and the subordinate heating coils 32 and 34), and this is detected by the zone control means 22. To enter. The zone control means 22 detects the phase between the current waveform input to the main heating coil 30 and the current waveform input to the subordinate heating coils 32 and 34, and synchronizes them or maintains a predetermined phase difference. For this control, the inverter 14b or the inverter 14c is configured to output a signal that instantaneously changes the frequency of the current applied to the subordinate heating coil 32 or the subordinate heating coil 34.

  Regarding power control, a signal to be changed in units of elapsed time from the start of the heat treatment based on a control map (vertical temperature distribution control map) stored in a storage means (memory) (not shown) provided in the power supply unit 12. Power control for obtaining a desired vertical temperature distribution may be performed based on the temperature of the susceptor 52 that is output to the inverters 14a to 14c and the choppers 16a to 16c or fed back from temperature measurement means (not shown). . The control map corrects the temperature change between the stacked susceptors 52 from the start of the heat treatment to the end of the heat treatment, and obtains an arbitrary temperature distribution (for example, a uniform temperature distribution). What is necessary is just to have recorded the electric power value given to the heating coils 32 and 34 with the elapsed time from the heat processing start.

  In this way, the power supply unit 12 instantaneously adjusts the frequency of the current to be applied to the subordinate heating coils 32 and 34 based on the signal from the zone control means 22 and performs phase control of the current waveform, and each induction. By performing power control between the heating coils, the temperature distribution in the vertical direction in the boat 50 can be controlled.

  Further, in the heat treatment apparatus 10 according to the embodiment, by providing the reverse coupling coils 36 and 38 that are magnetically reversely coupled to the subordinate heating coils 32 and 34, the main heating coil 30 and the subordinate heating coils 32 and 34 are arranged. The influence of mutual induction in can be suppressed in advance. For this reason, the influence of mutual induction avoided by the zone control means 22 is reduced, and the controllability of power control for the main heating coil 30 and the subordinate heating coils 32 and 34 can be improved.

  Further, according to the heat treatment apparatus 10 configured as described above, even when a conductive member such as a metal film is formed on the surface of the wafer 54, the metal film generates heat, and the temperature distribution of the wafer 54. There is no danger of being disturbed.

  Next, a second embodiment according to the heat treatment apparatus of the present invention will be described with reference to FIG. Most of the configuration of the heat treatment apparatus according to this embodiment is the same as that of the heat treatment apparatus according to the first embodiment described above. Therefore, portions having the same configuration are denoted by reference numerals obtained by adding 100 to the drawings, and detailed description thereof will be omitted.

  FIG. 4A is a block diagram illustrating a planar configuration of the heat treatment apparatus 110 according to the second embodiment, and FIG. 4B illustrates a planar configuration of a core used in the heat treatment apparatus 110 according to the present embodiment. FIG. In addition, in the same figure, although the description of a power supply part is abbreviate | omitted, the power supply part with the structure similar to the said embodiment shall be connected.

  The heat treatment apparatus 110 according to the present embodiment is characterized in that a plurality of induction heating coils corresponding to the subordinate heating coil 32, the main heating coil 30, and the subordinate heating coil 34 according to the first embodiment are provided. (In FIG. 4, only the subordinate heating coils 132a and 132b are displayed. Hereinafter, in order to simplify the description, they are simply referred to as induction heating coils 132a and 132b).

  By arranging a plurality of induction heating coils 132a and 132b in the direction along the circumferential direction of the susceptor 152, the horizontal heatable range is increased, and the temperature distribution in the surface of the wafer 154 can be stabilized. Become.

  Further, in the heat treatment apparatus 110 according to the embodiment, the core 140 around which a plurality of (two in the form shown in FIG. 4) induction heating coils 132 a and 132 b are wound is a single core, and the magnetic poles 141 a and 141 b protrude from the yoke 141. Further, the induction heating coils 132a and 132b are wound respectively. In addition, in the heat treatment apparatus 110 according to the present embodiment, the induction heating coils 132a and 132b arranged in the circumferential direction (horizontal direction) of the susceptor 152 are connected in parallel to the power supply unit (actually an inverter in the power supply unit). It is configured to do. This is because such an arrangement eliminates the need to consider the influence of mutual induction between the induction heating coils 132a and 132b arranged in parallel.

  In addition, each induction heating coil 132a, 132b is configured such that the magnetic flux generated by both the winding directions of the core 140 with respect to the magnetic poles 141a, 141b becomes an additional polarity. In such a configuration, the generated magnetic flux is generated along a locus as indicated by broken lines a to c, and the center side of the susceptor 152 can be heated more than the magnetic flux generated by one induction heating coil. Become.

  The two induction heating coils 132a and 132b may be selectable between single operation and mutual operation by a changeover switch (not shown). In such a configuration, since the heating range of the susceptor 152 changes depending on the combination of the induction heating coils to be operated, it becomes possible to control the temperature distribution in the wafer 154 plane.

DESCRIPTION OF SYMBOLS 10 ......... Semiconductor substrate heat processing apparatus (heat processing apparatus), 12 ......... Power supply part, 14a-14c ......... Inverter, 16a-16c ......... Chopper, 18 ......... Converter, 20 ......... Three-phase AC power supply 22 ......... Zone control means, 24 ......... Transformer, 26 ......... Resonance capacitor, 28 ......... Switch, 30 ......... Main heating coil, 32, 34 ......... Subordinate heating coil, 36,38 ... ...... Reverse coupling coil, 40... Core, 50... Boat, 52... Susceptor 54... Wafer 56.

Claims (3)

The induction heating coil includes three sets of induction heating coils having a core that is induction-heated by magnetic flux emitted from the end face of the core, and three inverters connected to each of the induction heating coils. The induction heating device is configured by arranging the end faces of the cores in a stacked manner, and defining the middle stage as a main heating coil, the upper stage as an upper subordinate heating coil, and the lower stage as a lower subordinate heating coil,
In the core of the upper subordinate heating coil, another coil magnetically coupled to the upper subordinate heating coil is provided,
The core of the lower dependent heating coil is provided with another coil that is magnetically coupled to the lower dependent heating coil,
Of the three inverters, a first inverter and the upper subordinate heating coil are connected, a third inverter and the lower subordinate heating coil are connected, and the second inverter is connected to the upper subordinate heating coil. An induction heating apparatus, wherein another coil provided in a core, another coil provided in a core of the lower subordinate heating coil, and the main heating coil are connected in series. The induction heating coil includes three sets of induction heating coils having a core that is induction-heated by magnetic flux emitted from the end face of the core, and three inverters connected to each of the induction heating coils. It is an induction heating method using an induction heating device in which the end surfaces of the cores are aligned and arranged, the middle stage is defined as a main heating coil, the upper stage is defined as an upper subordinate heating coil, and the lower stage is defined as a lower subordinate heating coil,
In order to generate a reverse coupling inductance with respect to the coupling inductance of the main heating coil and the upper subordinate heating coil and the lower subordinate heating coil,
An induction heating method characterized by connecting another coil provided in the upper subordinate heating coil core and another coil provided in the lower subordinate heating coil core and operating the inverter. 3. The induction heating method according to claim 2, wherein currents supplied to the heating coils from the first inverter, the second inverter, and the third inverter are synchronized. 4.