SolarWorld has developed a new entrant in the field of crystal growth for silicon photovoltaic substrates. The NeoGrowth technique is a contactless bulk crystal growth method for producing single crystal ingots. NeoGrowth material can be produced at a throughput on par with G5 multicrystalline silicon, but with p‐type as‐grown minority carrier lifetimes exceeding 600 microseconds for a 1.5‐ohm cm resistivity. The silicon has low oxygen, and light‐induced degradation is measured at 0.5% to 0.7% in passivated emitter rear contact–based modules. In the first report of results from this technique, p‐type resistivity can be managed within a range of 1.5 to 2.0 ohm cm over the entire ingot. Dislocation density is shown to be typically in the 10 4 to 10 5 /cm 2 range but can be managed down to even lower levels. After cell processing steps, minority carrier lifetime can exceed 1.5 milliseconds for p‐type material and cell efficiencies on industrial cells range up to 20.9%.

The aggregation of instrinsic point defects (vacancies and Si interstitials) in monocrystalline silicon has a major impact on the functioning of electronic devices. While agglomeration of vacancies results in the formation of tiny holes (so-called voids, around 100nm in size, which have almost no stress field), the aggregation of Si interstitials exerts considerable stress on the Si matrix, which, beyond a critical size, generates a network of dislocation loops around the original defect. These dislocation loops are typically microns in size. Consequently, they are much more harmful to device functioning than vacancy clusters. However, the feature size in electronic devices has now shrunk below the 100nm scale, meaning that vacancy aggregates are also no longer acceptable to many device manufacturers. This chapter is intended to give an introduction to the properties of intrinsic point defects in silicon and the nucleation and growth of their aggregates. Knowledge in this field has grown further over the last decade. It is now possible to accurately simulate the aggregation process so that the defect behavior of semiconductor silicon can be precisely tailored to the needs of the device manufacturer. Additionally, the impact of various impurities on the aggregation process is elucidated.

The Czochralski technique is the most important crystal growth method for the industrial production of silicon with the highest perfection and fabrication rate of all crystal materials. This chapter describes the equipment and processing details of the highly developed Czochralski crystal pulling method (Cz). The importance of heat and species transport phenomena, including the role of convection in the Cz process and the properties of the silicon crystals, will be discussed. Furthermore, the incorporation of oxygen during the Cz process and its influence on mechanical and electronic crystal properties will be treated, as well as the generation and behavior of intrinsic point defects (silicon vacancies and interstitials) and aggregates (voids and stacking faults) with regard to fundamental Cz growth parameters. The article concludes with a consideration of economic aspects.

In the field of monosilicon crystal growth, the Czochralski (CZ) as well as the floating zone (FZ) method have grown to a mature technology over the last 60 years and, until today, the costs have been continuously reduced. The cost driving factors for CZ and FZ are reviewed with respect to further potential improvements. Generally, the cost for the feedstock material is still dominanting the cost of ownership for both methods despite the dramtic decrease of the poly silicon price over the last years. This is particularly true for FZ where notably more than 50% of the production costs are related to the polysilicon feed rods which are much more expensive as compared to the chunk polysilicon as used for CZ. As a consequence, the FZ method is only used for applications where silicon crystals with very low oxygen concentration are required. Due to the strong influence of the feedstock material on cost, the main focus of the development work has been on the increase of crystal yield and the identification of factors impacting the yield. However, for most electronic and, in particular, for solar application, the crystal yield has reached a level where significant improvements cannot be expected anymore. With the potential change from p- to n-type silicon in the solar industry, previously developed techniques, like continuously recharged CZ, which were finally stopped for electronic applications, are reconsidered and will be discussed with respect to their future potential. Special attention will be given to the advantages and disadvantages of the FZ method. It will be shown that most of the current drawbacks of FZ can be remedied by a new technique which avoids the use of expensive polysilicon feed rods and enables the FZ method to grow dislocation free crystals with inexpensive silicon granules.

The results of highly sensitive FTIR investigation, ab initio calculations and rate equation modeling of the early stages of oxide precipitation are compared. The attachment of interstitial oxygen to VOn is energetically more favorable than the attachment to On for n  6. For higher n the energy gain is comparable. The point defect species which were detected by highly sensitive FTIR in high oxygen Czochralski silicon wafers are O1, O2, O3, and VO4. Rate equation modeling for I, V, On and VOn with n = (1..4) also yields O1, O2, O3 to appear with decreasing concentration and VO4 as that one of the VOn species which would appear in the highest concentration after RTA.

The influence of vacancy supersaturation installed by RTA pre-treatments in CZ silicon wafers on oxide precipitate nucleation was investigated in the temperature range 700-1000 {degree sign}C. Precipitation is enhanced at 800 {degree sign}C and increases with increasing vacancy concentration. Getter efficiency tests for Cu and Ni have shown that the threshold value of the normalized inner surface is shifting to higher values for increasing RTA temperature. This can be explained by a morphological change of the oxide precipitates with increasing vacancy concentration from plate-like to spherical shape.