Low-k material damage during photoresist ashing process

The change of –OH and –CH3 component ratios in Fourier transform-infrared analysis of low-k materials during photoresist (PR) ashing processes were compared to assess the differences in the damages to low-k materials in a reactive ion etch (RIE) chamber and a magnetized-inductively coupled plasma (M-ICP) chamber. In M-ICP, the PR ashing rate was 28.1% higher than that of RIE, but the low-k material damage in M-ICP decreased when typical ashing conditions were used in each machine. The dependences of low-k material damage and PR ashing rate on the pressure, source power, and bias power in the M-ICP chamber were studied. We measured the ion energy distributions using an ion energy analyzer from which the flux could be also obtained. We found that the PR ashing rate increased as the ion flux increased, while the low-k material damage also increased as the ion flux and the incident ion energy increased. However, as the pressure decreased, the ion flux increased dramatically and the ion energy decreased. As a result, the PR ashing rate could be high and the low-k material damage low.