TW200813267A - Crystallization furnace - Google Patents

Abstract

The present invention relates to a method and a furnace for crystallization of silicon. The furnace comprises a crucible or a plurality of crucibles for containing the silicon; a heating device for heating the crucible; a heat discharging device for discharging the heat from the crucible; stirring device comprising an electromagnetic device supplied with an alternating current for applying an alternating electromagnetic field to the crucible.

Description

200813267 IX. DESCRIPTION OF THE INVENTION: TECHNICAL FIELD The present invention relates to a furnace for crystallization of ruthenium. [Prior Art]

The most common substrate material used in photovoltaic cells is polycrystalline germanium. Industrially, such materials are generally produced in a crystallization furnace by directional solidification (DS) by various related techniques. A variant of DS is described, for example, in U.S. Patent Application Serial No. 2/7/447/7-Ai. In the prior art, the heater of the furnace is usually supplied with electric power from a three-phase alternating current. This alternating current also establishes a stirring force which is at least similar to the thermal buoyancy generated by the temperature difference in the furnace. This agitation force causes a cycle of the melt which improves the condensate of the impurities leaving the crystal and reduces the temperature gradient in the Shishi melt. However, the disturbance force depends on the heating power of the furnace. SUMMARY OF THE INVENTION An object of the present invention is to provide a bright furnace which can improve the quality of flaws produced by a furnace. Another object is to improve the control of crystallization of ruthenium. The present invention is disclosed in the first item of the patent application. Further features of the present invention are disclosed in the dependent claims. [Embodiment] Reference is now made to Figs. 1 and 2. The furnace contains an upper casing for loading and unloading. The vacuum is tight. 1 and the lower housing 10. The furnace in which the upper casing can be closed is produced by a seal 8 5 200813267 The furnace further comprises crucible 4 for containing the raw material for crystallization. The material can be, for example, produced by the Siemens process or the like. The material is placed in the crucible prior to the start of the crystallization process. In Fig. 1 and Fig. 2, a layer of solid crucible 6 and a layer of melting crucible 5 are shown. The furnace further comprises a heating device 3 for heating the crucible 4, whereby the bucket melting heating device can be arranged, for example, as one or several heating elements that are close to being attached. The heating device 3 can be, for example, based on an electric heating element, for example, powered by a direct current t "single phase "three phase $ power. The heating device can be, for example, based on a conventional heating element or an inductive heating element. The furnace may, for example, comprise a thermal insulation device 2 for the thermal insulation of the crucible. In Fig. 1, it is shown that the heat insulating device 2 surrounds the heating device 3 and also surrounds the weir 4. Furthermore, the furnace may, for example, comprise a lower insulating means 12, the lower edge of which has an opening for the guide member 13. The furnace further includes a row of heat devices for venting heat from the crucible during crystallization. There are several alternative examples of heat removal devices. In an example, the insulating device 12 is moved, for example, moved downward to increase the heat sergeant leaving the raft or 'in some instances it is possible to lower the stack relative to the heating device 3 by, for example, a guide 13埚 Supports 1 ^ and 坩埚 4. It is also possible that the electric power reaching the heating device 3 is reduced during the cold portion. Another possible solution is to actively remove heat by the circulation of the cooling gas, as disclosed in the World Patent Application No. WO 〇 2〇〇6/〇 82〇85. Furthermore, the 'solution furnace contains a gas inlet 7 and a gas outlet 9 for the atmosphere of the gas, and those skilled in the art will know the term "inert atmosphere" as used herein. , means the atmosphere in contact with the chopped metal in the 2008 200813267 material and hot zone in the furnace. 'The atmosphere is essentially chemical for the material of the furnace and the base metal phase in both solid and liquid states. It is inert. The term used herein includes any gas pressure of an inert atmosphere, including vacuum.

The furnace further comprises a stirring device 14. The agitation device 14 includes one or more electromagnetic devices that are powered by an alternating current for applying an alternating electromagnetic field to the crucible in the crucible 4. The electromagnetic device may, for example, comprise a coil or other type of conductive rail that is adapted to provide a sufficient alternating electromagnetic field when supplying alternating current. For example, an electromagnetic device includes a coil having a 1 to 50 revolution. The stirring device is connected to a power source. The power source can be, for example, a controllable power source for controlling the frequency and/or amplitude of the alternating current supplied to the coil. Alternatively, the power source is supplied at a fixed frequency and/or a fixed amplitude current. The agitation force provided by the alternating current can be described as the Lorentz force, which is provided by the following formula...

Re(Jx(B + Bs)) = -Re(JxB)+ Re(J)xBs) + -Re(JxB) v-v--/ 2 v-v-

Lorentzy force

Static part of Lorentz's force

Lorentz force has a frequency-dependent part of time

The theory of Lorentz's force with a frequency-dependent part of the time-dependent part of Lorentz's force is further described in textbooks such as PA Davidson's Cambridge textbook "An Introduction to Magnetohydrodynamics" in Cambridge University Press, 2001. , and R. Moreau at the Kluwer College Press in London in 1990 7 200813267

In this example, the stirring device 14 is placed outside the insulating device 2 to protect the stirring device from heat from the heating device 3. Further, it is possible to cool, for example, a water-cooling mechanism or the like. The mechanism provides some or all of the components of the agitation device 14. ^ In this example, the five-coil coils that are oriented horizontally are placed in a loop with a number of thermostats 2. The coils are adjustable from about 丨〇 to J Hz. _ The frequency of the alternating current supply. The amplitude of the current can be adjusted from 0 to 3. In this example, the coil is connected to a controllable power supply containing a control mechanism to control the frequency of the current delivered to the coil and Amplitude value. These values may be constant, or these values may be changed according to preset time intervals for the process. Alternatively, these values may be controlled according to one or several process parameters such as furnace temperature and the like. Here, the sensor for sensing the process parameters will be connected to the control mechanism of the power source. In the above embodiments, it has been found that at least 0.5 is generated. The centimeter/second call + current melting rate current will be appropriate. The average melting rate cannot be directly measured, but based on the model and simulation, it is possible to calculate the supply to the stirring device to achieve this average melting rate. There is a possibility that the furnace is provided with an electromagnetic control device for concentrating the electromagnetic field from the coil. The electromagnetic control device can be, for example, a magnetic focusing material, such as that provided by Fluxtrol of Auburn HiU, Michigan, USA. Fluxtrol A (trademark). In this case, the heating device is powered by direct current, while the agitating device is powered by electromechanical. The electromagnetic field from the heating device will be so static that it will not cause melting. Stirring in the mixture. In the selected example, the alternating currents of the individual coils can be displaced relative to each other. In a further example, the stirring device comprises three coils, each of which is powered by an individual phase of three-phase alternating current. In the selected example, there are several collapses in the furnace. 4. Proof of the invention According to the invention, the agitation mechanism 14 is unique The heating means 3 by the control features of the first embodiment of the release coating

Improved control of the crystallization process and material of the peaks can be achieved. The four standard crucibles used to make the polycrystalline germanium are coated with a PV grade crucible according to standard procedures. The two-loaded accident was placed on the graphite support plate in (4) and then the furnace was closed. Air: Backfilled with argon. The hanging system is added by the top and bottom resistance heaters: to all frequencies (four). The heat-dissipating device and the electromagnetic stirring device were activated, and the 1-polycrystalline ingot block was grown. After completing the Crystal Warrior, the program is cooled. The key block is cut into 16 blocks 15: 2 ^ Semilab ΓοΓ' From the -PCD instrument to measure the block piece life. The shadow of the four blocks from one of the ingots is used. The infrared image shows no precipitation of the second phase. ::: In Figure 3. The average minority carrier lifetime of the function is shown in the graph;: in the cow: the set curve). In the middle of the line (for the comparison, the same private sequence is applied in the case of the electromagnetic device without using the electromagnetic (four) device. The corresponding image from the four blocks of the mirror block is shown in Figure 4. Infrared image display Precipitation of the second phase. The average minority carrier lifetime as a function of position in the block is shown in Figure 5 (curve with a dotted line). The two quality requirements for solar grade bismuth ingots are high. The minority carrier has a service life and no precipitation. The present invention improves these properties as can be seen in Figures 4 and 5. Lu 2: by means of an electromagnetic stirrer, the second half of the device is 28x28x4 mm square copper. The 5 turns of the contour are placed around the outside of the thermal insulation in the DS furnace. The coil is 18 mm high and is placed at an upright position of the ingot at a distance of 37 cm from the (four) wall. The 2D axisymmetric finite element method (FEM) calculation for a furnace with coils indicates a coil current of 283 amps at 50 Hz, which can achieve a large melting rate of 3 ng/sec and an average melting rate of 2 7 cm/sec. .

_ A model of electromagnetically imparted JLiAii The calculation system described in Example 2 was repeated, but the current system was reduced by 20/. . The 2D axisymmetric FEM calculation of a furnace with coils indicates that a maximum melting rate of 3 〇 cm/sec and an average melting rate of 0.6 cm/sec can be obtained with a coil current of 566 amps at 5 Hz. lAJj 4: By means of an electromagnetic stirring j|_ stirring grip, the 2D axisymmetric FEM calculation of the furnace and coil of Example 2 indicates that the maximum melting of minutes/second can be obtained with a coil current of 2830 amps at 30 Hz. Rate and average melting rate of 2·8 cm/sec. 10 200813267

Heater Scrambled (Comparative) Model Count The 3D FEM calculation is made up of a DS furnace with three-phase AC heaters placed above and below the raft. Heating at a maximum capacity with a current of about 1 〇 8 amps (per phase) produces a maximum melting rate of 2·2 cm/sec and an average melting rate of 0.6 Å/min. The agitation effect during crystallization is reduced due to reduced power input. Half (the ratio of the maximum temperature difference between the center and the wall of the hanging enamel in the enamel with the melting fossils is 1〇K. The model calculation indicates that the average melting in the range of 〇1_〇5 public" Rate. It has been shown that the furnace according to the invention has been added

[Simple description of the diagram] In the figure: the dissolved matter. This result Fig. 1 illustrates an example of the invention as viewed from the (four) plane;

'Where during the crystallization period' is the use of the minority carrier of the sample shown in the crystallization period. 2008 11267 [Main component symbol description] 1 Upper casing 2 Insulation device 3 Heating device 4 坩埚5 Melting 矽6 Solid矽7 Gas inlet 8 Seal 9 Gas outlet 10 Lower housing 11 坩埚 Support 12 Lower insulation 13 Guide 14 Stirrer 12

Claims (1)

200813267 X. Patent application: A furnace for crystallization of bismuth, characterized in that the furnace comprises: one 坩埚 or a plurality of 坩埚 for accommodating 矽; a heating device for heating 坩埚; For discharging heat from the crucible; stirring l to contain an electromagnetic device powered by an alternating current for applying an alternating electromagnetic field to the crucible. The surname is 2. The furnace of the patent scope 帛1, characterized in that the tantalum "^ is connected to the S-controllable power source for controlling the frequency and/or amplitude of the alternating current supplied to the electromagnetic device. ...3. The furnace of the second item of the patent scope is characterized in that: from the mouth of the sea " X control power supply, the six Rays ^ 扪乂々丨 1 electric system early phase AC, with from 5_200 Hz, compared The best is 1 (the frequency of M00 Hertz. 4. The furnace of any one of the scope of the patent application to the third item, the strong sign is that the sandalwood device contains several electromagnetic devices, and each The electromagnetic attire is powered by an alternating current supplied to the 苴_, the phase of the current or the phase of the electromagnetic current. 5·If the scope of the patent application is the first item, the spear is the third of the three The furnace of the item, the inch sign is that the stirring device comprises two magnetic devices, and each of the electromagnetic clothes is respectively powered by the individual phases of the three-phase alternating current. 6·If the patent application scope is 1st, the 5th item is 5 The furnace of any one, /, 4 inch sign is: the electromagnetic device sentence winter 'straight 3 - has a coil of 1_5 〇 turn. 7 · If the scope of patent application 1 Jg nightmare r = u 囷乐i staff to the younger brother 6 furnaces of any of its orders, 13 200813267 characterized by: electromagnetic The device is disposed near the crucible. 8. The furnace of claim 1, wherein the agitating device comprises an electromagnetic control device for concentrating the electromagnetic field from the electromagnetic device to the hazard. The furnace of the first aspect of the invention is characterized in that the furnace further comprises a heat insulating device enclosing the crucible and the heating device. 10. The furnace according to claim 9 wherein the agitating device is located in the heat insulation. The outer surface of the device. 1 η · The furnace of claim i is characterized in that the heating device is powered by a direct current power source. 〃 12 · For example, the patent scope 帛i item _, It is characterized in that: the chopped polycrystalline stone eve. 13) (4) of claim i, wherein the feeding device provides at least (^ centimeters, the average melting rate of seconds). 14. A method for crystallization of ruthenium, characterized in that the method comprises the steps of: applying the ruthenium to a ruthenium or a plurality of ruthenium; heating the ruthenium to melt the shovel; sputum to start crystallization; The crucible discharges C-containing the mixing device of the electromagnetic device, and the molten solution is stirred by applying an alternating magnetic field to the gamma. = · The method of claim 14 is characterized in that the second step comprises the action of the hunter-controllable power supply control to control the frequency and/or amplitude of the alternating current supplied to the magnetic device. 14 200813267 ... 16 A method as claimed in claim 15 characterized in that the mixing step comprises supplying a single-phase alternating current having a frequency of from 5_2 Hz, more preferably 1 Hz. ”,, _如如The method of claim 15 is characterized in that the mixing device comprises a plurality of electromagnetic devices, and each of the electromagnetic devices is displaced in phase or phase with respect to currents of 夂, 'α to other electromagnetic devices. AC power supply. 18. The method according to any one of claims 14 to 17, wherein the (four) mixing device comprises three electromagnetic devices, and each of the magnetic devices is powered by individual phases of three-phase alternating current. . 19. The method of any one of claims 14 to 18, wherein the electromagnetic device comprises a coil having i. The method of any one of claims 14 to 19, wherein the electromagnetic device is disposed near the crucible. 21. The method of claim 14, wherein the electromagnetic field from the electromagnetic device is concentrated to 坩埚. 22. The method of claim 14, wherein the blazing furnace further comprises a thermal insulation device surrounding the hanging field and the heating device. 23. The method of claim 22, wherein the agitating device is located on an outer side of the thermal insulation device. 23. The method of claim 14, wherein the heating means supplies power by a DC power source. 24. The method of claim 14, wherein the method is: 2008. 25. The method of claim 14, wherein the method provides an average melting rate of at least 0.5 cm/sec. XI. Schema: as the next page 16