Chapter 3 - Silicon wafer manufacturing process

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Si wafers constitute 52% of the total price of solar cells. The silicon wafer manufacturing process has evolved from slurry-based wafering to diamond wire sawing. The process of cutting with a diamond wire saw is discussed in detail, including its advantages over earlier sawing processes. There has been a complete change to the diamond wire sawing method for both mono Si and mc-Si wafers since 2018. The change has been supported by the quick introduction of chemical texturing methods. Monocrystalline silicon wafers are made with 93% polysilicon used by their counterparts, polysilicon wafers. The elaboration of improvements using diamond wire sawing is made in terms of wafering process stability and cost reductions. Also, discussion is held on the market share of the wafer type, which is dominated by p-type material, while the casted multi-Si wafer share has been reduced to less than 50% during 2019. Also, discussion is held on the quicker gain of both the n- and p-type mono wafers to reach 60% by 2019. In addition, the p-type high-performance (HP) multicrystalline silicon dominance is discussed. Discussion is held on the trend of wafer thickness for p-type mono driven by PERx from 170μm in 2019 to 140μm over the next years while that of the n-type from 150μm in 2019 to 115μm (lead by HJT) and that of mc-Si wafer are still awaited. Also, details are given on polysilicon utilization, which is 16.5g for 156.75×156.75mm2 multicrystalline wafers and 15.5g for mono wafers. In addition, the kerf loss is now 80μm in 2019 and is going to be reduced further to 60μm over the next few years. The total thickness variation is likely to improve to 10μm. Alternate wafering processes such as the direct wafer process and the new method of epitaxy are elaborated upon, stating their current status as well as expected improvements so that they can compete with the present wafering process.