Suspension area device with adjustable capacitor

Abstract

The invention relates to a floating zone device configured to continuously zone via induction heating along the vertical direction of a polycrystalline rod to produce a single crystal ingot from the polycrystalline rod during a floating zone process by means of a continuous introduction of thermal power via a coil unit (5) of the floating zone device, the unit being moved along the vertical direction of the polycrystalline rod and surrounding the polycrystalline rod at a distance, wherein the current thermal power during the floating zone process results from the current effective power of an emitter unit (4) of the floating zone device, the emitter unit comprising a capacitor (1) and electrically interacting with the coil unit (5). The capacitor (3) is adjustable and configured to keep the frequency of the emitter unit (4) modulated at a prescribable and essentially constant value during the floating zone process.

Description

Technical Field

[0001] The present invention relates to a levitation region apparatus and a method for producing monocrystalline ingots (more particularly monocrystalline silicon ingots) from polycrystalline rods (more particularly polycrystalline silicon rods) through a levitation region process on the levitation region apparatus. Background Technology

[0002] In the process of suspending a single crystal ingot used to produce silicon, the frequency of the emitter unit varies greatly depending on the load.

[0003] During the general suspension process, the load is relatively low during droplet formation, and therefore, the frequency established in the emitter unit is significantly lower than, for example, the frequency established under maximum load towards, for example, the end of the single crystal ingot being produced. This frequency response between the initial (droplet conical) and the completed single crystal ingot phase often reaches approximately 150 to 200 kHz.

[0004] In the transmitter unit, what becomes even more apparent in this context is that a so-called "power hole" can be established due to the interaction between the coils and capacitors used for frequency generation. This power hole has the undesirable consequence of the dissipated power always generated by the transmitter unit being extremely significant in that frequency range. For example, for a specified group of transmitter units in a floating region device, a power hole may appear in the frequency range from 2800 kHz to 3000 kHz.

[0005] The problem with producing single crystal ingots using the suspended region process is that, during the suspended region process, the effective power obtained in the power void is too small to serve as the thermal power for the single crystal ingot, and therefore may have unpredictable effects on the single crystal ingot (e.g., freezing, dripping, dislocations, etc.).

[0006] Therefore, the objective technical problem of the present invention is to simply provide a levitation region device and a method for producing single crystal ingots by means of a levitation region process, wherein the above-mentioned disadvantages are absent or at least present to a low degree, in particular to avoid frequency response caused by load during the levitation region process, which may be in the range of, for example, from 150 kHz to 200 kHz.

[0007] The problem is solved by the levitation region apparatus according to claim 1 and the method for producing single crystal ingots by means of the levitation region process according to claim 7. Summary of the Invention

[0008] The present invention has recognized that, with regard to known requirements, in the generation of a suspended region monocrystalline ingot, the aim is to maximize the predictability and reproducibility of the effective power input to the crystal rod from the start of the suspended region process with the heating of the monocrystalline rod to the end of the production of the monocrystalline ingot, and the power provided by the transmitter unit in this frequency range must also be performed accordingly.

[0009] In this respect, the underlying technical teaching of this invention is that if the levitation region device or levitation region process is configured such that the frequency of the transmitter unit remains modulated at a specifyable and substantially constant value throughout the levitation region process (through continuous adjustment tracking via modulation over the levitation region process), substantially constant effective power can be introduced into the polycrystalline ingot in a simple manner (for producing a single crystal ingot with substantially uniform physical properties) via the transmitter unit in the form of thermal power through the coil unit. This fixed modulation of the frequency is achieved by the transmitter unit including an adjustable capacitor.

[0010] The described frequency adaptation via capacitors during the suspension process enables the complete overcoming of the aforementioned drawbacks known from the prior art; in particular, the frequency response caused by unfavorable loads, which can be, for example, in the range of 150 to 200 kHz, and its adverse consequences on the process, can thus be avoided.

[0011] According to the first aspect, the present invention relates to a levitation region apparatus configured to produce a single crystal ingot from a polycrystalline rod (more specifically, a polycrystalline silicon rod) via continuous levitation region melting by induction heating through a coil unit continuously introducing thermal power via the levitation region apparatus along the vertical direction of the polycrystalline rod during a levitation region process, the unit moving along the vertical direction of the polycrystalline rod and surrounding the polycrystalline rod at a distance.

[0012] Here, the current thermal power during the levitation process originates from the effective current power of the emitter unit of the levitation device, which includes a capacitor, and the emitter unit interacts electrically with the coil unit, particularly via the generator unit.

[0013] The capacitor is configured to be adjustable, and hereby configured to maintain the frequency modulation of the transmitter unit at a specifyable and substantially constant value during the levitation process.

[0014] Therefore, in particular, to avoid the problem scenarios known in the prior art (fluctuations in active or effective power).

[0015] By using adjustable capacitors, load-related frequency shifts can be avoided.

[0016] In a preferred variant, the adjustable capacitor can be configured as an adjustable variable capacitor.

[0017] In a preferred variant, the adjustable capacitor can be operated by means of an actuation drive via a control loop, and the setting of the capacitor can be triggered by a motor unit. Triggered by the setting of the capacitor, the motor unit preferably continuously modulates a specified value of the frequency within the suspension region, independent of the load.

[0018] In another preferred variation, the adjustable capacitor can be configured to maintain the modulated frequency substantially at a constant value during the levitation region pulling process. This constant value can be in the range of 2600 kHz to 3100 kHz, preferably in the range of 2850 kHz to 3000 kHz, and more preferably substantially corresponding to 2970 kHz. However, the levitation region device according to the invention is not limited to these frequency values, and can also be implemented for frequencies above or below these ranges.

[0019] In another preferred variant, the single crystal ingot may include a starting cone, a substantially shaped cylindrical ingot portion, and a tail cone, and the levitation region device may be configured to independently modulate the specified values ​​of the frequencies of the starting cone, the cylindrical ingot portion, and the tail cone via triggering of an adjustable capacitor.

[0020] In a further preferred variant, the adjustable capacitor can be configured to avoid load-induced frequency response, particularly in the range of 150 to 200 kHz, during the levitation process for producing single crystal ingots from polycrystalline rods.

[0021] The coil unit is configured as a particularly high-performance induction coil.

[0022] Regarding the basic operation of melting at the polycrystalline rod, this occurs in a known manner for the apparatus and method of the present invention, and therefore will not be further addressed here.

[0023] Providing the adjustable capacitor (or one or more preferred variations thereof) of the present invention on the levitation region device, and the method of the present invention using the adjustable capacitor (or one or more preferred variations thereof), provides advantages for the single crystal ingot to be produced, including the following: - The possibility of reoperating the process within the optimal frequency range of approximately 3000 kHz for melting polycrystalline rods and producing single-crystal ingots.

[0024] - Avoiding power voids leads to process instability during the levitation process. One result is that operation in levitation device components (especially high-frequency induction coils) becomes significantly easier.

[0025] - The possibility of modulating the optimal frequency modulation in different process stages during the suspended region process leads to an increase in yield.

[0026] - The effect of melting movement and the resulting reduction of dislocations within the single crystal ingot; additionally, preferably, the radial resistance (described in the form of radial resistance variation RRV) is optimized during the levitation process due to the continuous change / adaptation of frequency modulation in the ingot phase.

[0027] According to the second aspect, the present invention therefore relates to a method for producing single crystal ingots (more particularly single crystal silicon ingots) from polycrystalline rods (more particularly polycrystalline silicon rods) by means of a levitation region process (or in combination with one of its preferred variations as described above) on a levitation region apparatus of the present invention, wherein - During the levitation region process, single crystal ingots are produced from polycrystalline rods via continuous levitation region melting through induction heating, which continuously introduces thermal power via coil units, along the vertical direction of the polycrystalline rod. These units move along the vertical direction of the polycrystalline rod and surround it at a certain distance. The current thermal power during the levitation region process originates from the effective current power of the emitter unit of the levitation region device, which includes a capacitor. This emitter unit interacts electrically with the coil units, particularly via a power generator unit. -∙During the levitation process, the capacitor, which is adjustable, maintains the frequency of the transmitter unit at a specified and substantially constant value during the levitation process.

[0028] In a preferred variant, the adjustable capacitor can be operated by means of an actuation drive via a control loop, and the setting of the capacitor can be triggered by a motor unit.

[0029] In a preferred variant, the adjustable capacitor can be configured as an adjustable variable capacitor.

[0030] In another preferred variant, the motor unit can be continuously triggered via a capacitor during the suspension process, independently of the load, to modulate a specified value of the frequency.

[0031] In another preferred variant, the single crystal ingot may include a starting cone, a substantially shaped cylindrical ingot portion, and a tail cone, the frequency of which can be independently modulated by a specified value via a triggering adjustable capacitor.

[0032] In a further preferred variant, the assignable frequency value can be in the range of 2600 kHz to 3100 kHz, preferably in the range of 2850 kHz to 3000 kHz, and more preferably substantially corresponding to 2970 kHz. However, the method according to the invention is not limited to these frequency values, and can also be implemented for frequencies in ranges higher or lower than these values.

[0033] The capacitor is preferably placed in the primary circuit of the transformer of the transmitter unit. In an alternative variation, it may also be placed in the secondary circuit of the transformer of the transmitter unit.

[0034] The present invention further relates to a method for producing wafers of semiconductor material from a single crystal ingot (more specifically, a single crystal silicon ingot), said single crystal ingot being produced by a method of a levitation region process (or one or more combinations thereof) on a levitation region apparatus (or one or more advantageous variations thereof) of the present invention, wherein, starting from the end of the method for producing the single crystal ingot, at least the following steps are performed: • Cut the single crystal ingot into thin wafers. • Further chemical and / or mechanical processing of at least one thin wafer of semiconductor material, said further processing including at least one of the following further processing steps: edge rounding, grinding, cleaning, polishing, deposition of oxide layer, epitaxial growth of single crystal layer (more particularly silicon layer) or SiGe layer or GaN layer. Attached Figure Description

[0035] Figure 1 A schematic diagram showing details of a levitation region device is provided, which includes a transmitter unit 4 with an adjustable capacitor 1 of the present invention, a coil unit 5, and an ingot (indicated within the coil unit 5 and extending a certain distance relative to it) during the levitation region process.

[0036] Figure 2 Details of the electrical equivalent circuit diagram of the transmitter unit 4 with adjustable capacitor 1 in the transition region (right-hand side, open-circuit side in the equivalent circuit diagram) of the coil unit 5 are shown. Detailed Implementation

[0037] The following describes a preferred exemplary embodiment of the levitation region device of the present invention, which is configured to perform the method of the present invention for producing monocrystalline silicon ingots.

[0038] During the suspension region process, induction heating, by means of a suspension region device, continuously introduces thermal power via coil unit 5 to melt the polycrystalline rod along the vertical direction of the continuous region, and melts the polycrystalline rod on the suspension region device. Figure 1 (As shown in the diagram) the production of monocrystalline silicon ingots, wherein the unit moves along the vertical direction of the polycrystalline rod and surrounds the polycrystalline rod at a certain distance.

[0039] Here, the current thermal power during the levitation zone process originates from the effective current power of the transmitter unit 4 of the levitation zone device, including the capacitor 1, and the transmitter unit 4 interacts electrically with the coil unit 5 via the power generator unit 6.

[0040] Capacitor 1 is adjustable and configured to maintain the frequency of transmitter unit 5 during the levitation process, independent of the load, and modulated to a specifyable and substantially constant value.

[0041] The adjustable capacitor 1 is configured as an adjustable variable capacitor.

[0042] The adjustable capacitor 1 can be operated via an actuation drive through a control loop. The setting of capacitor 1 is triggered by motor unit 3, such as... Figure 1 The diagram illustrates this very illustratively. Through the setting of trigger capacitor 1, motor unit 3 continuously modulates a specified value of frequency within the suspension region, independent of the load. Motor unit 3 is then triggered via control unit 7, with frequency verification unit 2 connected therebetween.

[0043] Figure 2 The following details are shown: the transition region of the transmitter unit 4 with the adjustable capacitor 1 of the present invention to the coil unit 5 ( Figure 2 The electrical equivalent circuit diagram (right-hand side, open-circuit side) in the equivalent circuit diagram is in Figure 2 The transition from the primary circuit to the secondary circuit is indicated by a dashed line, representing a transformer. In this exemplary embodiment, capacitor 1 is located within the primary circuit and has a modulated, adjustable capacitance ranging from 100 to 1000 pF at a voltage of 20 kV. However, in various preferred variations of the invention, different modulations within different capacitance ranges and voltage ranges are also possible, and the invention is not limited to these values ​​of the adjustable capacitor.

[0044] The adjustable capacitor 1 is configured to maintain the modulated frequency substantially at a constant value during the levitation region pulling process, which substantially corresponds to 2970 kHz, and accordingly, compared with known embodiments of the levitation region device, to avoid load-induced frequency response during the levitation region process for producing single crystal ingots from polycrystalline ingots, particularly in the range of 150 kHz to 200 kHz (in other words, in the case of embodiments of the invention, the frequency response is theoretically toward 0, controlled by control characteristics, with fluctuations typically around + / - 2 kHz).

[0045] After producing single-crystal silicon ingots, the following steps are performed to produce semiconductor material wafers from the single-crystal ingots: - Cut the single crystal ingot into thin wafers. - Further chemical and mechanical processing of at least one thin wafer of semiconductor material, said further processing including edge rounding, grinding, cleaning and polishing further processing steps.

Claims

1. A levitation region device configured to produce a single crystal ingot from a polycrystalline rod via continuous levitation region melting along the vertical direction of the polycrystalline rod by induction heating through a coil unit (5) via the levitation region device, the unit moving along the vertical direction of the polycrystalline rod and surrounding the polycrystalline rod at a certain distance, wherein the current thermal power during the levitation region process originates from the effective current power of an emitter unit (4) of the levitation region device, which includes a capacitor (1), and the emitter unit, in particular via a power generator unit, electrically interacts with the coil unit (5). in The capacitor (1) is adjustable and configured to maintain the frequency of the transmitter unit (4) during the levitation process, in particular independently of the load, modulated to a specifyable and substantially constant value.

2. The suspension zone device according to claim 1, wherein, The adjustable capacitor (1) can be operated by means of an actuation drive via a control loop, and the setting of the capacitor (1) is triggered by a motor unit (3).

3. The suspension zone device according to claim 2, wherein, The motor unit (3) continuously modulates a specified value of the frequency independently of the load during the suspension process via the setting of the capacitor.

4. The suspension zone device according to any one of claims 1 to 3, wherein, The single crystal ingot includes a starting cone, a substantially shaped cylindrical ingot portion, and a tail cone. The levitation region device is configured to modulate, independently of each other, a specifiable value for the frequency of the starting cone, the cylindrical ingot portion, and the tail cone via the triggering of the adjustable capacitor (1).

5. The suspension zone device according to any one of claims 1 to 4, wherein, The adjustable capacitor (1) is configured to maintain the modulated frequency substantially at a constant value during the levitation region pulling process, the constant value being in the range of 2600 kHz to 3100 kHz, preferably in the range of 2850 kHz to 3000 kHz, and preferably substantially corresponding to 2970 kHz.

6. The suspension zone device according to any one of claims 1 to 5, wherein, The adjustable capacitor (1) is configured to avoid a frequency response caused by the load, particularly in the range of 150 to 200 kHz, during the suspended region process for producing single crystal ingots from polycrystalline rods.

7. A method for producing single-crystal ingots, more particularly single-crystal silicon ingots, from polycrystalline rods, more particularly polycrystalline silicon rods, by means of a levitation region process on a levitation region apparatus according to any one of claims 1 to 6, wherein - During the levitation process, single crystal ingots are produced from polycrystalline rods via continuous levitation melting through induction heating, which continuously introduces thermal power via coil units (5) through a levitation device, moving along the vertical direction of the polycrystalline rod and surrounding it at a certain distance. The current thermal power during the levitation process originates from the effective current power of the emitter unit (4) of the levitation device, which includes a capacitor (1). This emitter unit electrically interacts with the coil units (5), particularly via a power generator unit. - During the levitation process, the capacitor (1) is configured to adjustably maintain the frequency of the transmitter unit (4) at a specified and substantially constant value during the levitation process.

8. The method according to claim 7, wherein, The adjustable capacitor (1) can be operated by means of an actuation drive via a control loop, and the setting of the capacitor (1) is triggered by a motor unit (3).

9. The method according to claim 8, wherein, The motor unit (3) continuously modulates a specified value of the frequency independently of the load during the process in the suspended region, triggered by the setting of the capacitor (1).

10. The method according to any one of claims 7 to 9, wherein, The single crystal ingot includes a starting cone, a substantially shaped cylindrical ingot portion and a tail cone, and the frequency of the starting cone, the cylindrical ingot portion and the tail cone are independently modulated to a specified value by means of the triggering of the adjustable capacitor (1).

11. The method according to any one of claims 7 to 10, wherein, The specified value of the frequency is in the range of 2600 kHz to 3100 kHz, preferably in the range of 2850 kHz to 3000 kHz, and preferably substantially corresponds to 2970 kHz.

12. A method for producing wafers of semiconductor material from a single crystal ingot, more specifically a single crystal silicon ingot, said single crystal ingot being produced using a levitation region apparatus according to any one of claims 1 to 6, on the method for producing single crystal ingots, more specifically single crystal silicon ingots, by means of a levitation region process according to any one of claims 7 to 11, wherein... Starting from the end of the method used to produce single crystal ingots, at least the following steps shall be performed: - Cut the single crystal ingot into thin wafers. - Further chemical and / or mechanical processing of at least one thin wafer of semiconductor material, said further processing including at least one of the following further processing steps: edge rounding, grinding, cleaning, polishing, deposition of oxide layer, single crystal layer, more particularly silicon layer, or epitaxial growth of SiGe layer or GaN layer.

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