CO₂-laser drilling of TGVs for glass interposer applications

Abstract

Glass as a substrate material for interposer application has many benefits compared to conventional packaging materials like silicon, ceramic or polymer based laminates because of its excellent dielectric and transparent properties. Furthermore, the integration potential of glass is superior because of the dimensional stability under thermal load and the coefficient of thermal expansion (CTE) matching to that of silicon ICs. A small pitch size of conductor traces, small scale through-vias and high alignment accuracy are the key requirements that will be achieved from glass based packaging. Also the transparency of glass has benefits for photonic packaging. Glass substrates are available in wafer and large scale panel formats.Very fast CO 2 -laser drilling of holes and thermal posttreatments for reducing mechanical stress are very promising for fast processing and high reliability. Holes with a diameter smaller 100 µm in different glasses with thicknesses between 145 and 500 µm have been achieved by CO 2 -laser drilling. The holes have been metallized by sputtering a seed layer and galvanic copper platting. The CO 2 -laser drilling in combination with copper metallization has high potential for through glass via forming in glass substrates for interposer applications.

Application of Through Glass Via (TGV) Technology for Sensors Manufacturing and Packaging

“…Mechanical techniques including the abrasive jet machining method make it difficult to form vias less than 100 µm in diameter. In contrast, laser ablation presents an effective means of creating low diameter and high depth-to-width ratio vias by forming micro-vias through thermal shock and ablation [ 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 ]. Lasers have widespread applications in cutting and drilling various materials, including PCB substrates.…”

Application of Through Glass Via (TGV) Technology for Sensors Manufacturing and Packaging

“…Mechanical techniques including the abrasive jet machining method make it difficult to form vias less than 100 µm in diameter. In contrast, laser ablation presents an effective means of creating low diameter and high depth-to-width ratio vias by forming microvias through thermal shock and ablation [57][58][59][60][61][62][63][64][65][66][67][68]. Lasers have widespread applications in cutting and drilling various materials, including PCB substrates.…”

Fabrication and Characterization of Through-Glass Vias by the ECDM Process

“…However, there are chances of thermally induced stresses resulting in reduced reliability. 15 Plasma etching generates relatively high temperatures (>150 °C) resulting in poor etch mask selectivity and damage to the photoresist. In case, the polymerbased etch masks are replaced by hard metal masks, micro-masking defects are observed.…”