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WO2011113338A1 - 一种提纯硅的方法 - Google Patents

一种提纯硅的方法 Download PDF

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Publication number
WO2011113338A1
WO2011113338A1 PCT/CN2011/071767 CN2011071767W WO2011113338A1 WO 2011113338 A1 WO2011113338 A1 WO 2011113338A1 CN 2011071767 W CN2011071767 W CN 2011071767W WO 2011113338 A1 WO2011113338 A1 WO 2011113338A1
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Prior art keywords
silicon
aluminum
purified
temperature
melt
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French (fr)
Inventor
姜学昭
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INTIRAYMI SILICON TECHNOLOGIES Ltd
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INTIRAYMI SILICON TECHNOLOGIES Ltd
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Priority to CA2793292A priority Critical patent/CA2793292A1/en
Priority to US13/635,875 priority patent/US20130008372A1/en
Priority to EP11755655A priority patent/EP2548844A1/en
Priority to JP2013500314A priority patent/JP2013522160A/ja
Publication of WO2011113338A1 publication Critical patent/WO2011113338A1/zh
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • C01B33/037—Purification

Definitions

  • the present invention relates to a method of producing high purity silicon for use in a solar cell. Background technique
  • Photovoltaic power generation is a technology that directly converts light energy into electrical energy by utilizing the photovoltaic effect of the semiconductor interface.
  • a key component of this technology is solar cells, and one of the key aspects in the preparation of solar cells is the preparation of high purity silicon.
  • the current metallurgical process (physical method), which has yielded some results, is generally a combination of two types of purification methods.
  • the first type is a directional solidification and a zone melting method that removes most of the impurities in the silicon and improves the overall purity of the silicon. This is the basic method in physics.
  • the second type is a special purification method for boron and phosphorus, which are electroactive impurities in silicon, which are difficult to remove by the first type of method.
  • Two types of methods have been complemented and combined to produce high purity silicon capable of producing solar cells.
  • the solar cell produced has the defects of insufficient photoelectric conversion efficiency and rapid decay, which indicates that the impurity content in the high-purity silicon prepared by the prior art is not stable, and the purity of silicon needs further improve. Therefore, the current metallurgical method cannot meet the needs of solar cells.
  • the existing methods for removing boron and phosphorus can be divided into: pickling method, oxidation method, high temperature vacuum evaporation method (above 150 CTC), and direction solidification method.
  • the pickling method, the oxidation method, and the evaporation method are limited to the surface of solid silicon and molten silicon, and the reaction is continued by the concentration of boron and phosphorus atoms in a very low concentration (parts per million) in the silicon. Diffusion is maintained, and the effect of a single operation is limited.
  • the high temperature evaporation process also brings environmental pollution to silicon. Since the partial condensation coefficient of boron and phosphorus is relatively large, the purification effect of single directional solidification is not good. Furthermore, there is no conventional method for removing boron and phosphorus from both boron and phosphorus. Summary of the invention
  • the main object of the present invention is to provide a new method for purifying silicon, which can simultaneously effectively remove harmful impurities such as boron and phosphorus in silicon, and simultaneously reduce the content of other impurities in silicon, and the 4N level (ie, the purity is 99.99%,
  • the purity of silicon in the same or 5N grade ie, purity of 99.999%, the same below is further higher, which better meets the requirements of solar cells for high-purity silicon.
  • the present invention adopts the following technical solutions:
  • a method of purifying silicon the steps of which are as follows:
  • the heating device is moved in synchronization with the growth rate of the precipitated silicon to maintain the temperature at both ends of the aluminum silicon melt;
  • a method of removing impurities from the silicon to be purified is characterized in that the difference in precipitation temperature of silicon and impurities in the aluminum silicon melt is such that boron, phosphorus and other impurities are concentrated together until the final condensed portion is removed.
  • the silicon to be purified is dissolved in the aluminum melt to form a homogeneous system at a temperature lower than the melting point of silicon, to obtain an aluminum-silicon melt; and silicon atoms are precipitated at a certain temperature, at this time, boron is obtained. Phosphorus and other impurities are still dissolved in the aluminum-silicon melt to purify the silicon.
  • the high-purity aluminum is a high-purity aluminum of 4N or 5N grade; the silicon to be purified is a 4N or 5N grade of silicon to be purified.
  • Another method of purifying silicon is as follows:
  • a solution of 4N or 5N grade aluminum and silicon to be purified is placed in close contact with an enclosed environment vacuum, when the air pressure is lower than 10- 2 Pa start of heating, the temperature remains constant when aluminum and silicon are up 80CTC, so Part of the silicon is dissolved in aluminum to form an aluminum-silicon melt;
  • the heating device is controlled to maintain the temperature of the left side of the aluminum-silicon melt to 800 ° C, and the undissolved silicon When the temperature rises, when the interface temperature between the aluminum silicon melt and the silicon reaches 900 °C, the solute silicon begins to diffuse to the right side of the aluminum silicon melt, and the purified silicon is precipitated;
  • the heating device is moved in synchronization with the growth rate of the precipitated silicon to maintain the temperature at both ends of the aluminum silicon melt;
  • a method for purifying silicon as described above, wherein a weight ratio of the weight of the silicon to be purified to the aluminum is from 106% to 146%: 74%.
  • a method for purifying silicon characterized in that the steps are as follows:
  • the heating device is moved in synchronization with the growth rate of the precipitated purified silicon to maintain the temperature at both ends of the aluminum silicon melt;
  • the solvent is selected from 4N or 5N aluminum
  • the mass of the aluminum silicon melt can be high, which ensures the precipitation of pure silicon.
  • the Al-Si binary phase diagram of Figure 1 shows that the precipitate is pure silicon free of aluminum.
  • Figure 3 and Figure 4 show the binary phase diagrams of A1-P and A1-B, respectively. It is seen from the figure that A1 has binding forces with impurities P and B and both compounds A1P, A1B 2 and the like are formed. Since the content of phosphorus and boron in the aluminum is in the ppm level, the precipitation temperature is very close to the melting point of aluminum of 660 ° C, and away from the temperature range of 800 ° C to 900 ° C in which the pure silicon is dissolved and precipitated in the purification process of the present invention. The apparent difference in precipitation temperature determines that impurities in the silicon to be purified will remain in the aluminum-silicon melt during the purification process and be removed from the silicon.
  • the present invention utilizes the difference in precipitation temperature in the aluminum-silicon melt so that boron, phosphorus and other impurities are enriched together to the final condensed portion.
  • Figure 1 shows the Al-Si binary phase diagram.
  • FIG. 2 is a schematic view of a device, a use state, and a temperature distribution of the method for purifying silicon according to the present invention.
  • Figure 3 shows the A1-P binary phase diagram.
  • Figure 4 is a binary phase diagram of A1-B. detailed description
  • the basic principle of the method of the invention is: selecting a suitable solvent high-purity aluminum (4N or 5N grade), and dissolving 4N or 5N grade silicon to be purified in an aluminum melt to form a homogeneous system at a temperature far below the melting point of silicon. .
  • the silicon atoms are precipitated at a certain temperature, at which time boron, phosphorus and other impurities are still dissolved in the aluminum silicon melt, thereby achieving the purpose of purifying silicon.
  • the Al-Si binary phase diagram of Fig. 1 shows that in a hypereutectic melt having a silicon content exceeding 12.1%, pure silicon precipitates when it is cooled to a liquidus line corresponding to a certain component.
  • concentration of silicon in the aluminum-silicon melt is lower than this concentration, silicon can be dissolved in the aluminum-silicon melt.
  • a purification device as shown in FIG. 2 is designed, and the silicon body 1 to be purified (4N or 5N grade) is placed on the right side of the high purity (4N grade or higher) graphite boat 2, which is combined with the aluminum silicon melt 5
  • the solid-liquid interface temperature is controlled at 900 °C.
  • the interface temperature between the aluminum silicon melt 5 and the precipitated pure silicon 6 interface is controlled at 80 CTC.
  • the graphite boat 2 was placed in a quartz tube 3, connected to a vacuum unit, and placed in a vacuum atmosphere having a gas pressure of less than 10 - 2 Pa.
  • the quartz tube 3 was placed in a heating furnace 4, and the ends of the aluminum silicon melt were maintained at constant temperature gradients of 900 ° C and 800 ° C, respectively.
  • the silicon to be purified 1 is dissolved in the aluminum silicon melt 5, and when the silicon concentration in the aluminum silicon melt 5 at the solid-liquid interface rises to 37%, solid-liquid two phases appear. balance. Since the silicon concentration in the aluminum silicon melt 5 at a low temperature is low, the high concentration silicon on the right side will diffuse to the left side of the aluminum silicon melt 5 . As the silicon to be purified 1 continues to dissolve, as the silicon concentration at the left end of the aluminum silicon melt 5 rises to 28%, precipitated pure silicon 6 will appear at the left end.
  • the result of the dissolution-diffusion-precipitation dynamic balance of the silicon to be purified is that the amount of precipitated pure silicon on the left side is increasing, which causes the solid-liquid interface to continue to shift to the right.
  • the furnace 4 is moved to the right by means of the hob moving device 7 (which may be a hob moving the cart as shown) to maintain the relative stability of the above dynamic balance conditions to ensure the quality of the precipitated silicon crystal.
  • the silicon seed crystals are placed at the left end of the graphite boat to help grow a square single crystal silicon ingot with a defined size of the graphite container.
  • the temperature is lowered at °C/min. When the temperature drops to 700 ⁇ 800°C, the power is turned off. After free cooling to room temperature, the vacuum system is deflated, the quartz tube 3 is opened, the graphite boat 2 is taken out, and all the materials in the boat are poured out. Cut the pure silicon 6 on the left side.
  • the silicon solute diffusion process and the furnace temperature distribution diagram, the steps of purifying silicon are as follows:
  • 4N or 5N grade aluminum and silicon (1) take the level of 4N or 5N, 26% by weight of silicon to the total weight of the alumina-silica ratio for the high-purity alumina graphite boat mixture below 10- 2 Pa gas pressure in 2 melted.
  • the quartz tube 3 is quickly removed from the heating furnace 4, and the square aluminum-silicon alloy ingot is obtained after the material is cooled.
  • the aluminum silicon alloy ingot is cooled to room temperature and taken out, and the surface is polished and dried for use.
  • the 4N or 5N grade high-purity silicon is cleaned and cleaned for use.
  • a quartz tube 3 is closed and the vacuum system is turned on, when the air pressure is lower than 10- 2 Pa to start heating.
  • the aluminum silicon alloy ingot begins to melt.
  • the temperature is further increased until the right end of the aluminum silicon melt reaches 900 ° C, and the left end is kept at a constant temperature of 800 ° C.
  • the concentration of solute silicon at the right end of the aluminum silicon melt is gradually increased to 37%. The difference in concentration causes the solute silicon to diffuse to the left, causing pure silicon to precipitate at the left end interface.
  • the heating furnace 4 controls the graphite boat 2 to be located in the temperature range of 80 CTC, and maintains the constant temperature. After the dissolved concentration of silicon in the aluminum is uniform, the heating furnace is adjusted to keep the left end of the graphite boat at 80 CTC while raising the temperature on the right side. When the solid-liquid interface temperature between the undissolved silicon and aluminum-silicon melt on the right side reaches 900 ° C, the solute silicon begins to diffuse from right to left to the left side of the graphite boat, and pure silicon is precipitated.
  • Example 1 Thereafter, the steps (4), (5), and (6) in Example 1 were carried out to obtain purified high-purity silicon.
  • Precipitating pure silicon at the left end of high-purity graphite boat 2 Place a silicon seed crystal with a square section that fits the inner wall of the boat, and place the aluminum-silicon alloy ingot prepared in the above step at 5 locations of the aluminum-silicon melt.
  • the silicon to be purified is placed at one place of the silicon to be purified.
  • the temperature-increasing temperature control process thereafter needs to prevent over-temperature callback.
  • the left side interface between the seed crystal and the aluminum silicon alloy is observed, and when the seed crystal starts to grow stably, the furnace moving device 7 is started to move the heating furnace 4 to the right in synchronization with the growth speed. 4) According to the above steps, the high-purity silicon and high-purity single crystals with large grain structure can be deposited along the seed crystal interface.
  • the silicon to be purified 1 is continuously dissolved in the aluminum-silicon melt 5, and the length is continuously shortened.
  • the length of pure silicon ingots connected to the seed crystals continues to grow.
  • the temperature is gradually lowered.

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  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
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Abstract

本发明涉及一种提纯硅的方法，该方法步骤为：将由高纯铝和待提纯硅制备的铝硅合金和待提纯硅紧密接触地置于封闭环境后在真空条件下加热，铝硅合金锭熔化形成铝硅熔体；当铝硅熔体和待提纯硅的界面处和自由端的温度分别达到900℃和800℃时保持恒温，使左端界面处析出提纯硅；当提纯硅开始析出后，与析出硅的生长速度同步向待提纯硅的方向移动加热装置，以保持铝硅熔体两端的温度；当待提纯硅溶解完毕时，降温、恢复气压后切下析出的提纯硅。经过本发明的提纯过程，可同时有效去除4N或5N级硅中的硼、磷及其他杂质，使硅的纯度得到进一步的提高，更稳定地满足太阳能电池对高纯硅的要求。

Description

一种提纯硅的方法
技术领域
本发明涉及一种制取高纯硅的方法， 所制高纯硅用于太阳能电池。 背景技术
光伏发电是利用半导体界面的光生伏特效应而将光能直接转变为电能的一种技术。 这 种技术的关键元件是太阳能电池， 而制备太阳能电池的关键环节之一在于制备高纯硅。
避开现有技术中高成本、 高能耗、 环保负担重的改良西门子法， 寻求用于太阳能电池 的低成本、 低能耗、 环境友好型的制取高纯硅的新提纯方法， 是降低光伏发电成本， 促进 光伏发电向主体能源转化的一项战略举措。
已略见成效的现行的冶金法 （物理法） 大体上是两类提纯方法的组合。 第一类是可以 除去硅中绝大多数杂质， 提高硅整体纯度的定向凝固和区域熔化法。 这是物理法中的基础 方法。 第二类是针对第一类方法难以除掉的硅中电活性杂质硼、 磷的专项提纯方法。 两类 方法互补加合已制备出能制造出太阳能电池的高纯硅。 从实际效果看， 所制出的太阳能电 池存在光电转换效率不够高和出现快衰退现象的缺陷， 这表明现有技术制得的高纯硅中的 杂质含量尚不稳定， 硅的纯度还需进一步提高。 因此， 现行的冶金法尚不能满足太阳能电 池的需要。
现有除硼、 磷的方法可分为： 酸洗法、 氧化法、 高温真空蒸发法 （150CTC以上） 和定 向凝固法。 酸洗法、 氧化法和蒸发法只限于在固体硅和熔融体硅的表面上进行， 反应的持 续进行是依靠在硅体内浓度很低 （百万分之几） 的硼、 磷原子的浓差扩散维持， 单次操作 的效果有限。 高温蒸发过程还会带来环境对硅的污染。 由于硼、 磷的分凝系数比较大， 单 次定向凝固的提纯效果也不好。 再者， 现有去除硼和磷的方法中还没有一种能同时去除硼 和磷两种杂质的方法。 发明内容
本发明的主要目的是提供一种新的提纯硅的方法， 可以同时有效去除硅中的有害杂质 硼和磷， 并能同时降低硅中其他杂质的含量， 将 4N级（即纯度为 99.99%， 下同）或 5N级 (即纯度为 99.999%，下同）硅的纯度进一步更高，更好地满足太阳能电池对高纯硅的要求。
为实现上述目的， 本发明采用以下技术方案：
一种提纯硅的方法， 其步骤如下：
( 1 ) 将由 4N或 5N级铝和 4N或 5N级硅制备的铝硅合金和待提纯硅紧密接触地置于 封闭环境后抽真空， 当气压低于 10—2Pa时加热， 铝硅合金熔化形成铝硅熔体；
(2) 控制加热装置， 使铝硅熔体和待提纯硅的界面温度达到 900°C， 且铝硅熔体的自 由端温度达到 800°C， 此后保持恒温， 使铝硅熔体的自由端析出提纯硅；
(3)提纯硅的结晶开始析出后， 与析出硅的生长速度同步地移动加热装置， 保持铝硅 熔体两端的温度；
(4) 当待提纯硅溶解完毕时， 降温至室温， 恢复气压后取出炉料， 将析出的提纯硅切 下。
如上所述的提纯硅的方法， 其中， 所述铝硅合金制备方法如下：
取 4N或 5N级铝和 4N或 5N级硅， 按照硅为 26%、 铝为 74%的重量百分比混合， 将 铝硅混合物在气压低于 10—2Pa的条件下熔化， 当铝硅混合均匀后， 迅速停止加热， 冷却后 得到铝硅合金。
如上所述的提纯硅的方法，其中， 所述待提纯硅的重量为所述铝硅合金的重量的 80%〜 120%。
如上所述的提纯硅的方法，其中， 铝硅熔体和待提纯硅的界面温度进一步达到 103CTC ; 铝硅熔体的自由端温度进一步达到 930°C。 从待提纯硅中除掉杂质的方法， 其特征在于， 利用铝硅熔体中硅与杂质的析出温度差 使得硼、 磷和其它杂质一起被富集到最后冷凝部分被除掉。
选取适宜的溶剂高纯铝， 在低于硅熔点温度下， 将待提纯硅溶于铝熔体中形成均相体 系， 得到铝硅熔体； 在一定温度下再将硅原子析出， 此时硼、 磷及其他杂质仍溶解在铝硅 熔体中， 从而提纯硅。
所述高纯铝为 4N或 5N级的高纯铝； 所述待提纯硅为 4N或 5N级的待提纯硅。 另一种提纯硅的方法， 其步骤如下：
( 1 )将 4N或 5N级铝和待提纯硅紧密接触地置于封闭环境后抽真空，当气压低于 10—2Pa 时开始加热，当铝和硅的温度均达到 80CTC时保持恒温，使部分硅溶解在铝中形成铝硅熔体； (2) 待溶解在铝中的部分硅溶解均匀后， 控制加热装置， 保持铝硅熔体左侧温度达到 800°C， 而将未溶解硅的温度提升， 当铝硅熔体和硅的界面温度达到 900 °C时， 溶质硅开始 向铝硅熔体右侧扩散， 并析出提纯硅；
(3)提纯硅的结晶开始析出后， 与析出硅的生长速度同步地移动加热装置， 保持铝硅 熔体两端的温度；
(4) 当待提纯硅溶解完毕时， 降温至室温， 恢复气压后取出炉料， 将析出的提纯硅切 下。
如上述的提纯硅的方法， 其中， 所述待提纯硅的重量与所述铝的重量比为 106%-146% ： 74%。 一种提纯硅的方法， 其特征在于， 包括步骤如下：
1 ) 将硅籽晶、 由 4N或 5N级铝和 4N或 5N级硅制备的按重量百分比含硅 38%的铝 硅合金和待提纯硅从左至右置于石墨舟中； 密闭抽真空， 气压低于 10—2Pa时加热， 铝硅合 金熔化成铝硅熔体；
2)控制加热装置， 使铝硅熔体和待提纯硅的界面温度达到 1030°C， 铝硅熔体与硅籽晶 界面温度达到 930°C， 恒温， 铝硅熔体沿硅籽晶析出提纯硅；
3)提纯硅析出后， 与析出提纯硅的生长速度同步地移动加热装置， 保持铝硅熔体两端 的温度；
4)当待提纯硅溶解完毕时， 降温至室温， 恢复气压后取出炉料， 将析出的提纯硅切下。 本发明的有益效果为：
由于溶剂选用 4N或 5N级铝，铝硅熔体中可容杂质量较大，从而保证了纯硅的析出量。 图 1的 Al-Si二元相图显示析出物为不含铝的纯硅。
图 3、 图 4分别为 A1-P和 A1-B二元相图。 从图中看出 A1与杂质 P和 B具有结合力且 都有化合物 A1P、 A1B2等生成。 由于磷和硼在铝中的含量处在 ppm级， 其析出温度很接近 铝的熔点 660°C， 而远离本发明提纯过程中溶解、 析出纯硅的 800°C〜900°C温度区间。 析 出温度的明显差别决定了待提纯硅中的杂质在提纯过程中将留在铝硅熔体中， 而从硅中去 除。 对于其他杂质， 同样会因析出温度差而被留在熔体内。 本发明利用铝硅熔体中的析出 温度差使得硼、 磷和其它杂质一起被富集到最后冷凝部分被除掉。
经过本发明的提纯过程， 可同时有效去除 4N或 5N级硅中的硼、 磷及其他杂质， 使硅 的纯度得到进一步的提高， 更稳定地满足太阳能电池对高纯硅的要求。 附图说明
图 1为 Al-Si二元相图。
图 2为本发明提纯硅方法所用装置、 使用状态及温度分布示意图。
图 3为 A1-P二元相图。
图 4为 A1-B二元相图。 具体实施方式
本发明方法的基本原理是： 选取适宜的溶剂高纯铝（4N或 5N级）， 在远低于硅熔点温 度下， 将 4N或 5N级的待提纯硅溶于铝熔体中形成均相体系。 在一定温度下再将硅原子析 出， 此时硼、 磷及其他杂质仍溶解在铝硅熔体中， 从而达到提纯硅的目的。
图 1的 Al-Si二元相图显示出： 在硅含量超过 12.1%的过共晶熔体中， 降温到与某组分 对应的液相线相交时便有纯硅析出。 当铝硅熔体中硅浓度低于此浓度时， 硅可溶进铝硅熔 体中。 以此设计出如图 2所示的提纯装置， 将待提纯硅体 1 (4N或 5N级） 置于高纯 （4N 级或更高） 石墨舟 2的右侧， 其与铝硅熔体 5的固 -液界面温度控制在 900°C。 铝硅熔体 5 与析出纯硅 6界面交接处温度控制在 80CTC。将石墨舟 2置于石英管 3中，与真空机组相连， 置于气压低于 10—2Pa的真空气氛中。 将石英管 3置于加热炉 4中， 保持铝硅熔体两端分别 处在 900°C和 800°C的恒定温度梯度中。
在 900°C固 -液界面处， 待提纯硅 1溶入铝硅熔体 5中， 当固 -液界面处铝硅熔体 5中的 硅浓度上升至 37%时， 出现固-液两相平衡。 由于低温处铝硅熔体 5中硅浓度较低， 右侧的 高浓度硅将向铝硅熔体 5左侧扩散。 随着待提纯硅 1继续溶解， 当铝硅熔体 5左端的硅浓 度随之上升至 28%时， 在左端将出现析出的纯硅 6。 待提纯硅的溶解-扩散-析出动平衡的结 果是左侧纯硅的析出量不断增多， 这将引起固 -液界面持续右移。 为此， 借助炉架移动装置 7 (可以是如图所示的炉架移动小车）令加热炉 4也同步向右移动， 以保持上述动平衡条件 的相对稳定， 才能保证析出硅晶体的质量。 此外， 在生长条件适宜时， 石墨舟左端设置硅 籽晶有助于生长出与石墨容器确定外形尺寸的方形的单晶硅锭。
当铝硅熔体右侧的待提纯硅全部溶入熔体后， 结束提纯操作。 恒温 1 小时后， 以约 -2
°C/min的速度降温， 当温度下降至 700〜800°C时断电， 自由冷却至室温后， 令真空系统放 气， 打开石英管 3， 取出石墨舟 2， 倒出舟内全部物料， 切下左侧的纯硅 6。
实施例 1
如图 2所示的硅溶质扩散过程及加热炉温度分布示意图， 提纯硅步骤如下：
( 1 )取 4N或 5N级的铝和 4N或 5N级的硅，按硅重量占铝硅总重量的 26%进行配比， 将硅铝混合物在气压低于 10—2Pa的高纯石墨舟 2中熔化。 在成分混合均匀后， 将石英管 3 迅速移出加热炉 4， 待物料冷却后得到方型铝硅合金锭。 将铝硅合金锭冷却至室温后取出， 打磨清洗表面后烘干备用。 另将 4N或 5N级的高纯硅清洁表面后一并烘干备用。
(2) 按照含硅 26%的铝硅合金锭重量的 80%称量 4N或 5N级硅， 将铝硅合金锭与待 提纯硅装入石墨舟 2 中， 合金锭置于石墨舟左侧， 待提纯硅置于石墨舟右侧 （尺寸不限， 以顺利装进石墨舟为准）。
( 3 ) 封闭石英管 3并开启真空系统， 当气压低于 10—2Pa时开始加热。 随着温度升高， 铝硅合金锭开始熔化。 继续升温， 至铝硅熔体右端达到 900°C， 左端为 800°C时保持恒温， 铝硅熔体右端的溶质硅浓度逐步升高至 37%。 浓度差促使溶质硅向左侧扩散， 致使左端界 面处析出纯硅。
(4) 当左端出现纯硅结晶析出后， 启动炉架移动装置 7， 与析出硅的生长速度同步向 右移动加热炉 4。
( 5 ) 透过石英管 3观察， 当右侧的待提纯硅溶解完毕即停止生长时， 开始降温。
( 6) 当温度降至室温时， 停止真空泵， 令真空系统放气， 气压恢复后取出石墨舟 2倒 出炉料。 将左侧经提纯过的高纯硅切下， 余料用于配置工业用高纯铝硅合金。
实施例 2
( 1 ) 取 4N或 5N级铝和 4N或 5N级硅原料， 按照重量比铝： 硅 =74%： 146%进行配 比， 并一同放入石墨舟 2中。 将铝置于石墨舟左侧， 硅置于舟右侧。
(2)封闭石英管 3并开启真空系统， 当气压低于 10—2Pa时开始加热。 加热炉 4控制石 墨舟 2全部位于 80CTC温度区间， 保持恒温， 待硅在铝中的溶解浓度均匀后， 调整加热炉， 令石墨舟左端保持 80CTC同时将右侧温度提升。当右侧尚未溶解的硅和铝硅熔体之间的固液 界面温度达到 900°C时， 溶质硅开始从右向左扩散至石墨舟左侧， 并析出纯硅。
此后按照实施例 1中的步骤 （4)、 （5)、 ( 6) 进行操作， 得到提纯过的高纯硅。
实施例 3
按图 2所示装置进行， 包括步骤如下：
1 )取 4N或 5N级铝和 4N或 5N级硅， 按重量百分比含硅 38%的铝硅合金成分配料， 装入高纯石墨舟 2中。 在气压低于 10—2Pa气氛下加热熔化， 成分均匀后， 将石英管 3移出 加热炉 4。 物料冷却后得到含硅 38%的四方型断面的铝硅合金锭。 经打磨清洗表面后烘干 备用。
2)在高纯石墨舟 2左端析出纯硅部位 6处放置与舟内壁吻合的方型断面的硅籽晶，将上 步骤配制的铝硅合金锭置于铝硅熔体部位 5处。 待提纯硅置于待提纯硅部位 1处。
3 ) 封闭石英管 3， 开启真空系统。 当气压低于 10— 2Pa后， 开始加热。 待提纯硅 1和铝 硅熔体 5交界处温度值升到低于该铝硅合金熔点 50°C时减慢升温速度。 注意观察。 俟铝硅 合金熔化时， 温控由手控转自动控制。 自控小幅缓慢升温。 当籽晶与铝硅合金熔体左侧界 面温度达到 930°C、 待提纯硅与铝硅合金熔体右侧界面温度达到 1030°C。 从铝硅合金熔化 开始， 此后的升温控温过程需防止超温回调。 观测籽晶与铝硅合金左侧界面， 当籽晶开始 稳定生长后启动炉架移动装置 7与生长速度同步向右移动加热炉 4。 4)按上列步骤平稳操作， 可沿籽晶界面沉积析出大晶粒结构的高纯硅以及高纯度单晶 。
5) 随着加热炉向右移动， 待提纯硅 1不断溶入铝硅熔体 5中， 长度不断縮短。 另一侧 与籽晶相连的纯硅锭长不断增长。 在待提纯硅， 全部溶入铝硅熔体 5(长度减到零)后， 徐徐 降温。
6) 温度降至室温时， 关停真空系统。 放气后取出石墨舟 2， 取出炉料。 将左侧带有硅 籽晶的高纯硅锭切下。 余料为含硅 38%的铝硅过共晶高硅合金。

Claims

权利要求书
1. 一种提纯硅的方法， 其特征在于， 步骤如下：
( 1 ) 将由 4N或 5N级铝和 4N或 5N级硅制备的铝硅合金和待提纯硅紧密 接触地置于封闭环境后抽真空， 当气压低于 10— 2Pa时加热，铝硅合金熔化形成铝 硅熔体；
(2) 控制加热装置， 使铝硅熔体和待提纯硅的界面温度达到 900°C， 且铝 硅熔体的自由端温度达到 800°C， 此后保持恒温， 使铝硅熔体的自由端析出提纯
(3)提纯硅的结晶开始析出后， 与析出硅的生长速度同步地移动加热装置， 保持铝硅熔体两端的温度；
(4) 当待提纯硅溶解完毕时， 降温至室温， 恢复气压后取出炉料， 将析出 的提纯硅切下。
2. 如权利要求 1所述的提纯硅的方法， 其特征在于， 所述铝硅合金制备方 法为： 取 4N或 5N级铝和待提纯硅， 按照硅为 26%、 铝为 74%的重量百分比混 合， 将铝硅混合物在气压低于 10—2Pa的条件下熔化， 当铝硅混合均匀后， 迅速停 止加热， 冷却后得到铝硅合金。
3. 如权利要求 1或 2所述的提纯硅的方法， 其特征在于， 所述待提纯硅的 重量为所述铝硅合金的重量的 80%〜120%。
4. 如权利要求 1所述的提纯硅的方法， 其中， 铝硅熔体和待提纯硅的界面 温度进一步达到 103CTC； 铝硅熔体的自由端温度进一步达到 930°C。
5. 从待提纯硅中除掉杂质的方法， 其特征在于， 利用铝硅熔体中硅与杂质 的析出温度差使得硼、 磷和其它杂质一起被富集到最后冷凝部分被除掉。
6. 如权利要求 5所述的从待提纯硅中除掉杂质的方法， 其特征在于， 选取 适宜的溶剂高纯铝，在低于硅熔点温度下， 将待提纯硅溶于铝熔体中形成均相体 系， 得到铝硅熔体； 在一定温度下再将硅原子析出， 此时硼、 磷及其他杂质仍溶 解在铝硅熔体中， 从而提纯硅。
7. 如权利要求 6所述的从待提纯硅中除掉杂质的方法， 其特征在于， 所述 高纯铝为 4N或 5N级的高纯铝； 所述待提纯硅为 4N或 5N级的待提纯硅。
8. 一种提纯硅的方法， 其特征在于， 步骤如下： ( 1 )将 4N或 5N级铝和待提纯硅紧密接触地置于封闭环境后抽真空， 当气 压低于 10—2Pa时开始加热， 当铝和硅的温度均达到 80CTC时保持恒温， 使部分硅 溶解在铝中形成铝硅熔体；
(2) 待溶解在铝中的部分硅溶解均匀后， 控制加热装置， 保持铝硅熔体左 侧温度达到 800°C， 而将未溶解硅的温度提升， 当铝硅熔体和硅的界面温度达到 900°C时， 溶质硅开始向铝硅熔体右侧扩散， 并析出提纯硅；
(3)提纯硅的结晶开始析出后， 与析出硅的生长速度同步地移动加热装置， 保持铝硅熔体两端的温度；
(4) 当待提纯硅溶解完毕时， 降温至室温， 恢复气压后取出炉料， 将析出 的提纯硅切下。
9. 如权利要求 4所述的提纯硅的方法， 其特征在于， 所述待提纯硅的重量 与所述铝的重量比为 106%-146%： 74%。
10. 一种提纯硅的方法， 其特征在于， 包括步骤如下：
1 ) 将硅籽晶、 由 4N或 5N级铝和 4N或 5N级硅制备的按重量百分比含硅 38%的铝硅合金和待提纯硅从左至右置于石墨舟中； 密闭抽真空， 气压低于 10—2Pa时加热， 铝硅合金熔化成铝硅熔体；
2)控制加热装置， 使铝硅熔体和待提纯硅的界面温度达到 1030°C， 铝硅熔 体与硅籽晶界面温度达到 930°C， 恒温， 铝硅熔体沿硅籽晶析出提纯硅；
3) 提纯硅析出后， 与析出提纯硅的生长速度同步地移动加热装置， 保持铝 硅熔体两端的温度；
4) 当待提纯硅溶解完毕时， 降温至室温， 恢复气压后取出炉料， 将析出的 提纯硅切下。
PCT/CN2011/071767 2010-03-19 2011-03-14 一种提纯硅的方法 Ceased WO2011113338A1 (zh)

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