Use of optical photomasks will extend to the 22-nm node and beyond. Mask minimum resolution and critical dimension
(CD) requirements for this node are very challenging to the mask industry. Optimization of resist materials and resist
thickness are key factors for improving CD performance. In general, thinner resists result in better minimum resolution
performance. The minimum useable resist thickness is often linked to the chrome hard mask dry etching performance.
More specifically, improvement of chrome etch rate selectivity to resist while simultaneously maintaining good CD
performance is difficult. In order to use a very thin e-beam resist, the underlying chrome hard mask material thickness
needs to be thin or it needs to be comprised of a material that has a fast etch rate and good dry etch selectivity to resist.
Use of thin and/or fast etch rate hard mask materials that are capable of reducing dry etch induced CD error such as etch
bias, etch bias uniformity, etch bias linearity, and etch global loading effect is required for meeting 22-nm mask
requirements. In this paper, the dry etching effect dependence on hard mask thickness, hard mask material composition
and resist thickness for building advanced binary masks for 22-nm node is studied. The results from this work will show
that dry etch induced CD error such as etch bias, etch bias uniformity, etch bias linearity, and etch global loading effect
are significantly improved by use of an ultra thin or high etch rate hard mask material.