Power and Growth Speed

For example, the hot-zone of a Kayex CG6000 puller, as shown in Fig. 2.2a has the crystal diameter of 5.5in. and quartz crucible of 16in.. The hot-zone could be divided into six major components (1) radiation shield (or cone) (2) top side insulation (3) additional side insulation (4) bottom insulation (5) top-wall insulation and (6) argon venting. The default hot-zone from Kayex did not include the cone and the top-wall insulation. The room for the bottom and side-wall insulations was still large. The temperature distribution calculated by STHAMAS is also shown on the left hand side of Fig. 2.2a, 

The main purpose of using the cone is to block the thermal radiation from the melt to crystal, so that the crystal can be cooler and pulled faster. Such an idea can be easily understood from the energy balance at the growth interface  

However, the cost for equipments and parts increases rapidly with the size. Therefore, without increasing the diameter for an economic ingot production, a continuous process should be considered seriously in the near future. In fact, among the available crystal growth techniques for PV applications, 

Similar to oxygen, carbon is also detrimental. In Cz silicon growth, carbon is released mainly from the graphite heater and susceptor, as well as raw polysilicon. Therefore, the control of argon flow path is important to reduce carbon contamination. In fact, after redirecting the argon flow, even with a flow rate of 15slpm, our hot-zone always keeps the carbon content below 0.03 ppma. 

Maycock (ed.), in PV News, PV Energy Systems (Warrenton, VA, March 2004) 

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