Laser Drilling of High-Density Through Glass Vias (TGVs) for 2.5D and 3D Packaging

Abstract

Thin glass (< 100 microns) is a promising material from which advanced interposers for high density electrical interconnects for 2.5D chip packaging can be produced. But thin glass is extremely brittle, so mechanical micromachining to create through glass vias (TGVs) is particularly challenging. In this article we show how laser processing using deep UV excimer lasers at a wavelength of 193 nm provides a viable solution capable of drilling dense patterns of TGVs with high hole counts. Based on mask illumination, this method supports parallel drilling of up over 1,000 through vias in 30 to 100 µm thin glass sheets. (We also briefly discuss that ultrafast lasers are an excellent alternative for laser drilling of TGVs at lower pattern densities.) We present data showing that this process can deliver the requisite hole quality and can readily achieve future-proof TGV diameters as small 10 µm together with a corresponding reduction in pitch size.

Advanced laser scanning for highly-efficient ablation and ultrafast surface structuring: experiment and model

“…The sigmoid functions primitive is the softplus function 61 . The function coincides with scientific works, where constant ablation depth per pulse has been observed experimentally for an initial pulse number 64 , 70 .…”

Micro-drilling of alkali-silicate glass with ultraviolet picosecond laser

“…power or shortening the laser wavelength, like other authors did [1][2][3][4][5][6][7][8][13][14][15][16][17][18]. Preliminary irradiation of glass with 60 Co generates intensive coloration and removes luminescence centers thereby increase the efficiency of UV-laser beam absorption for drillingholes 5−25 µm without cracking.…”

“…UV fs-lasers are used also for extruding glass fibers of nano-and submicron diameters [14]. Excimer laser (193 nm) illumination through a mask allows parallel drilling of 1000 through holes in 30−100 µm thin glass interposers for 2.5D and 3D packaging small consumer electronics [15]. Multilayer dielectric gratings were made with picosecond laser in vacuum [16].…”

Micro-Hole Drilling on Glass Substrates—A Review

“…Recently, drilling high density through glass vias (TGVs) became more important for the development of thin (~100 μm) glass interposers in new 2.5D and 3D chip package strategies, due to the demand for higher functionality in small consumer electronics [ 4 , 5 ]. These, often metalized, TGVs (diameters: 10 to 50 μm, depths: up to 100 μm) are used to connect traces and pads on the top and bottom surfaces of the glass interposers [ 4 , 5 , 13 , 14 ].…”