The development of low-k materials started with silicon dioxide that had a dielectric constant (k) of 4, then to fluorinated oxides, the addition of carbon, and now porosity. And the advances have been impressive. Today, 65 nm devices with a k value of 2.9 and as many as 11 copper layers are in production. For the 45 nm node, a k value of ～ 2.5 is targeted. Arriving at this point has required new chemistries, optimization of the dielectric stack and integration schemes that address maintaining the effective k value and minimizing failure mechanisms.
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