Alternating Dielectric Package Substrate for Fine-Pitch Via Alignment

The patent divides the dielectric structure into alternating pairs of positive-type and negative-type photo-imageable dielectric layers. This segmentation allows each layer type to be processed independently with its own lithography parameters, enabling finer pitch control (18 micrometers) while maintaining thickness uniformity. The segmented layer structure reduces cumulative Bump Thickness Variation by preventing error propagation across the entire dielectric stack.

The patent applies different dielectric material properties locally - positive-type photo-imageable dielectric in alternating layers versus negative-type photo-imageable dielectric in alternating layers. Each material type has optimized characteristics for its specific processing requirements, allowing local optimization of via formation and trace patterning. This local quality approach reduces stress concentration at via locations while achieving the desired fine pitch interconnections.

The alternating layer structure segments the stress distribution throughout the dielectric stack. By interspersing positive-type and negative-type dielectric layers, the patent creates a segmented stress field that prevents stress concentration at single via locations. This segmentation reduces the cumulative stress effect while enabling the reduced 18 micrometer bump pitch.

The patent uses composite dielectric structures combining positive-type and negative-type photo-imageable dielectric materials in alternating layers. This composite approach allows optimization of stress characteristics - the alternating materials have different mechanical properties that collectively reduce stress at via locations while maintaining the fine pitch geometry required for 18 micrometer bump pitch interconnections.

The patent implements self-aligned via formation where the via pattern is automatically registered to the trace pattern through the alternating positive/negative dielectric layer structure. The self-service alignment mechanism eliminates the need for separate via-pads and fiducials, as the lithography process inherently aligns vias to traces through the material properties and processing sequence of the alternating dielectric layers, reducing misalignment-related device failures.

The alternating dielectric layer structure performs preliminary alignment preparation by establishing a self-registering framework before via formation. The positive-type and negative-type layers are deposited and processed in a predetermined sequence that pre-establishes the alignment relationship between vias and traces, eliminating the need for subsequent alignment adjustments and reducing misalignment issues that lead to device failures.