Via Pillar Substrates for Ultra Fine Pitch Flip Chip Interconnects

The patent replaces the mechanical laser drilling process with an electrochemical etching process using ferric chloride solution. This chemical etching method produces smooth, non-tapered via walls by uniformly removing dielectric material through electrochemical reactions, eliminating the roughness and tapering problems inherent in mechanical laser drilling while maintaining ease of manufacture for high-density via arrays.

The patent changes the fundamental parameter of via formation from mechanical removal (laser drilling) to electrochemical removal (ferric chloride etching). This parameter change transforms the via wall characteristics from rough and tapered to smooth and cylindrical, directly resolving the manufacturing precision issue while preserving the ability to efficiently create high-density via patterns.

The patent applies preliminary action by creating a precise copper seed layer pattern through photolithography and electroplating before the via filling process. This pre-formed seed layer acts as a controlled template that guides subsequent copper deposition, ensuring uniform via filling without dimpling or overfill. The preliminary seed layer pattern prevents the electroplating process from creating surface irregularities that would interfere with subsequent via stacking operations.

The patent introduces a copper seed layer as an intermediary between the dielectric substrate and the final via fill. This intermediate layer serves as a controlled foundation that regulates copper deposition during electroplating, preventing direct uncontrolled growth that causes dimpling and overfill. The seed layer mediates the filling process to achieve uniform via structures suitable for high-density stacking.

The patent merges multiple separate via drilling operations into a single batch chemical etching process. Instead of drilling each via individually with a laser (sequential operation), the ferric chloride etching solution simultaneously processes entire arrays of vias across the substrate in parallel (batch operation). This merging of operations dramatically increases productivity while maintaining precise control over via density and geometry through the uniform chemical etching process.

The patent replaces the mechanical sequential laser drilling system with a chemical batch etching system using ferric chloride. This substitution transforms the production methodology from a time-consuming sequential mechanical process to an efficient parallel chemical process, dramatically improving throughput while maintaining the ability to create high-density via patterns with precise geometric control.

The patent applies local quality by creating spatially varying copper seed layer thicknesses or compositions tailored to specific via locations and sizes. Different regions of the substrate receive customized seed layer characteristics that are optimized for their local via geometry requirements. This localized customization of the seed layer ensures that subsequent electroplating fills via of different sizes at appropriate rates, preventing dimpling in smaller vias and overfill in larger vias, thereby achieving consistent fill quality across varied via geometries.

The patent changes parameters of the seed layer (such as thickness, composition, or deposition conditions) locally across the substrate to match the specific requirements of different via sizes. By adjusting seed layer parameters rather than via fill parameters, the process achieves uniform filling across varied via geometries, as the seed layer acts as a pre-configured template that guides appropriate copper deposition rates for each local via configuration.