Dry processes to form fine features on advanced substrates

Laser drilling and wet etching have been widely used today for processing buildup layers on semiconductor package substrate, posing challenges in reducing feature size and keeping high throughput. This work demonstrates concept of applying lithography method and dry etch on coupon level to form fine features on heterogeneous materials, paving the way for developing dual-damascene and metallization processes in advanced substrates and panel production. A heterogeneous dielectric material, Ajinomoto build-up film (ABF) layer is patterned with fine vias and trenches of dimension < 10 um. First, dry film resist (DFR) is applied on ABF surface by lamination. A novel digital lithography method is utilized to pattern the DFR with high alignment accuracy and flexibility. The patterned DFR is directly used as mask to transfer its features onto ABF by a dry etch process. The plasma etch process etches ABF of 5-10 um forming fine vias and trenches with aspect ratio (AR) of 1-2. Etch rate and selectivity of ABF/DFR are explored. This work validates the feasibility of forming straight vias and trenches on ABF down to 5 um with AR up to 2 by dry plasma etch using patterned DFR directly as mask. Further optimization on tapper angle of features and metallization processes are on-going and will be shared in our future study.