A UHF-ECR Plasma Etcher for Insulation Films

OVERVIEW: In the rapid evolution of VLSI technology toward smaller geometries and increased levels of chip integration, minimum features of 0.18 μm are already being mass produced, and feature sizes of 0.13 μm are being developed. At the same time, 300-mm fab lines are being built, and this is driving a demand for new etching technologies that support smaller tolerances and larger wafer sizes. Insulation layer etching demands good selectivity between mask and substrate and high-aspect vertical processing to deal with increasing aspect ratios and thinner mask thicknesses that go along with shrinking geometries and increasing integration levels. Meanwhile, damascene processes (electroplating for chip interconnects) using a combination of low-κ (low dielectric constant) insulation materials and Cu interconnects are being investigated, and etchers capable of processing these structures will be in great demand. To address these issues, we have developed an insulation layer etcher that uses UHF-ECR (ultra high frequency electron cyclotron resonance) plasma. The unique advantages of this approach are that it enables good control over CF2/F radicals, an important etchant for selectivity and high-aspect openings, and good control over the ratio of ions to CF2, which is important in achieving vertical profiles. This etcher is capable of (1) producing stable and uniform medium-to-high density plasmas over a large area at low-to-medium pressures using UHF wave (450 MHz) ECR, and (2) increasing the doubled-near-surface effect* and good radical ratio control through control over the UHF wave flat antenna and antenna bias. Taken together, these capabilities amount to a powerful plasma process tool able to process fine features below 0.13 μm. Hironobu Kawahara Takafumi Tokunaga Masayuki Kojima Ken’etsu Yokogawa