The present invention provides a method for evaluating a vitreous silica crucible which can measure a three-dimensional shape of the inner surface of the crucible in a non-destructive manner. According to the present invention, A method for evaluating a vitreous silica crucible, including the steps of: moving an internal ranging section along an inner surface of the vitreous silica crucible in a contactless manner; measuring a distance between the internal ranging section and the inner surface as a distance from the inner surface, by subjecting the inner surface of the crucible to irradiation with laser light and then detecting a reflected light from the inner surface, the laser light being emitted from the internal ranging section in an oblique direction with respect to the inner surface, and the measurement being conducted at a plurality of measuring points along a course of a movement of the internal ranging section; and obtaining a three-dimensional shape of the inner surface of the crucible, by associating three-dimensional coordinates of each of the measuring points with the distance from the inner surface, is provided.

Method for evaluating silica glass crucible, method for producing silicon single crystals

More than 90% of all Photovoltaic (PV) installations are based on crystalline silicon, several hundred thousand tons of which are processed by the solar industry each year. During the last few years, we have seen a huge price reduction in the polysilicon market. But still, the raw material contributes significantly to the total costs and further price reductions might be expected. Today, most polysilicon is produced by the Siemens process, but alternative routes like fluidized-bed reactors or upgraded metallurgical silicon might provide a better cost structure and thus might gain market shares. The majority of solar silicon is crystallized by the directional solidification method (also called vertical gradient freeze method). This technique is quite robust, easy to handle, and easily scalable. Block sizes between 500 kg and 1 ton are the actual standard. The latest development is the small-grain, high-performance multi. Compared to quasi-mono (mono-like) silicon, the better cost structure and the lower process complexity of the high-performance multi are a clear advantage. Some 40% of the silicon is crystallized as mono ingots. Right now, Czochralski (Cz) is the standard technology: 8″ or 9″ ingots of cylindrical shape and a length of 1.5–2 m are grown. Since Cz is hardly scalable to larger ingots, the challenge is to reduce cost by accelerating the process, by reducing downtime, and by making a better use of the consumables. Actual trends are multipulling, feeding, continuous pulling, or active crystal cooling to mention just some of them. In particular, for high-efficiency cell technologies like Interdigitated Back Contact (IBC) or Heterojunction with Intrinsic Thin layer (HIT), high-quality n-type material is required. Finally, the Float-Zone (FZ) technique will be discussed. FZ ingots have at least two orders of magnitude lower oxygen levels compared to Cz material and the corresponding minority carrier lifetimes are very high. Right now, the process suffers by its complexity and the lack of affordable feed rods. Overcoming these limitations, FZ might be an interesting alternative for high-efficiency applications.

Silicon Crystallization Technologies

Techniques for the formation of a silicon ingot using a low-grade silicon feedstock include forming within a crucible device a molten silicon from a low-grade silicon feedstock and performing a directional solidification of the molten silicon to form a silicon ingot within the crucible device. The directional solidification forms a generally solidified quantity of silicon and a generally molten quantity of silicon. The method and system include removing from the crucible device at least a portion of the generally molten quantity of silicon while retaining within the crucible device the generally solidified quantity of silicon. Controlling the directional solidification of the generally solidified quantity of silicon, while removing the more contaminated molten silicon, results in a silicon ingot possessing a generally higher grade of silicon than the low-grade silicon feedstock.

Method and system for forming a silicon ingot using a low-grade silicon feedstock

A system for growing a crystal ingot from a melt includes a first crucible, a second crucible, and a weir. The first crucible has a first base with a top surface and a first sidewall that form a first cavity. The second crucible is located within the first cavity of the first crucible, and has a second base and a second sidewall that form a second cavity. The second base has a bottom surface that is shaped to allow the second base to rest against the top surface of the first base. The second crucible includes a crucible passageway to allow movement of the melt therethrough. The weir is located inward from the second sidewall to inhibit movement of the melt from a location outward of the weir to a location inward of the weir.

Crucible for controlling oxygen and related methods

An apparatus for growing ingots by the Czochralski method is described. The ingots are drawn from a melt/crystal interface in a quantity of molten silicon replenished by crystalline feedstock. The apparatus includes a crucible configured to hold the molten silicon and a weir supported in the crucible. The weir is configured to separate the molten silicon into an inner growth region from an outer region configured to receive the crystalline feedstock. The weir includes a sidewall extending vertically and a top wall. An annular heat shield is disposed on the top wall of the weir that covers at least about 70% of the outer region.

Heat Shield For Improved Continuous Czochralski Process

A weir is extended vertically to define an optimal annular gap between the top of the weir and the underside of a super-adjacent heat shield. The annular gap provides a high velocity stream of argon gas to be directed from the growth region to the melt region to substantially eliminate the transport of airborne particles from the melt region to the growth region. The tall weir may be configured as a modular, reusable weir extension supportably engaged with an outer (and/or inner) weir.

Weir design providing optimal purge gas flow, melt control, and temperature stabilization for improved single crystal growth in a continuous Czochralski process

A method is disclosed for continuous CZ crystal growing wherein one or more crystal ingots are pulled into a growth chamber from a crystal/melt interface defined in a crucible containing molten crystalline material that is continuously replenished by crystalline feedstock. The method includes separating the molten crystalline material, controlling the flow of the molten crystalline material and defining an annular space with respect to sidewalls of a heat shield in the chamber.

Weir method for improved single crystal growth in a continuous czochralski process

In a Czochralski process for growing single crystal silicon ingots, a system is provided for adding solid material to the liquid silicon during crystal growth for the purpose of directly controlling the latent heat of fusion with respect to a crystal melt interface. In contrast to the standard method for controlling power to the crucible heater, the present system has been found to be much more effective for controlling melt temperature in the crucible, especially in heavily insulated systems. The system provides the advantage of reducing the electric power required to operate a Czochralski grower, while increasing the speed with which the melt temperature can be raised or lowered in a controlled manner.

Methods for controlling melt temperature in a czochralski grower

A weighing system is provided for a continuous Czochralski process that accurately measures the weight of the crucible and melt during crystal growth to control the introduction of feedstock in order to keep the weight approximately constant. The system can measure the weight of the crucible while the crucible is rotating, and is insensitive to vibrations of the melt surface as well as variable torques on the crucible shaft induced by the rotation. The system also measures the weight of the crucible and its contents in order to control the amount of feedstock recharged after an ingot is withdrawn.

Crucible weight measurement system for controlling feedstock introduction in Czochralski crystal growth

In a Czochralski process for growing single crystal silicon ingots, a system is provided for adding solid material to the liquid silicon during crystal growth for the purpose of directly controlling the latent heat of fusion with respect to a crystal melt interface. In contrast to the standard method for controlling power to the crucible heaters, the present system has been found to be much more effective for controlling melt temperature in the crucible, especially in heavily insulated systems. The system provides the advantages of reducing the electric power required to operate a Czochralski grower, while increasing the speed with which the melt temperature can be raised or lowered in a controlled manner.

Method and apparatus for controlling melt temperature in a Czochralski grower

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