Metal etch in advanced immersion tank with precision uniformity using agitation and wafer rotation

摘要

The interaction of N_2 bubbles, wafer rotation and chemistry works together to etch the metal layer in the MEI Advanced Metal Etch Tank. The fine N_2 bubble agitation provides interface mixing on chemical boundary layer constantly. This constant mixing also enhances the wetting of the wafer features ensuring a more consistent etch removal. The etch uniformity across the wafer is optimized by rotating the wafers and controlling the flow of the N_2 sparger. In addition, the agitation and constant stirring of the wafer/metal chemical interface layer ensures consistent etch rates from wafer to wafer within the cassette regardless of slot position. By utilizing this right combination of hardware and software control capabilities the MEI Advanced Etch Tank achieves < 2% uniformity (coefficient variance) on 200mm gold micro-coil patterned wafers and < 5% (NU) on 200mm copper wafers, which are comparable to the much more expensive and physically larger alternative process tools previously described.