Transmission Laser Welding of Similar and Dissimilar Semiconductor Materials

Abstract

Laser micro-welding is an advanced manufacturing method today applied in various domains. However, important physical limitations have prevented so far to demonstrate its applicability in silicon (Si) and other technology-essential semiconductors. Concentrating on circumventing the optical limits on the deliverable energy density at interfaces between narrow-gap materials with intense infrared light, the first feasibility demonstration of transmission laser welding between Si workpieces using nanosecond laser pulses is made. A shear joining strength of 32 ± 10 MPa which compares very favorably to the complex process alternatives is obtained. Supported by experiments repeated on different material combinations including gallium arsenide, it is confirmed that this remarkable performance level is achievable for similar and dissimilar semiconductors. The demonstrations rely on a small footprint fiber laser, an aspect that holds great promises for the advent of a high-efficiency flexible process beneficial for important technology developments including lab-on-a-chip and hybrid semiconductor systems.

Ultrafast Laser Welding of Silicon

“…In order to devise a procedure for performing ultrafast laser welding of silicon, let us develop in this Section our reasoning based on the existing state of the art. First, let us recall that the only demonstrations of laser‐joined silicon samples have been realized with nanosecond pulses [ 14 ] and continuous light. [ 15 ] This is consistent with the fact that this long‐interaction regime is adapted to the production of repeatable modifications inside silicon.…”

“…In order to devise a procedure for performing ultrafast laser welding of silicon, let us develop in this Section our reasoning based on the existing state of the art. First, let us recall that the only demonstrations of laser-joined silicon samples have been realized with nanosecond pulses [14] and continuous light. [15] This is consistent with the fact that this long-interaction regime DOI: 10.1002/adpr.202200300 While ultrafast laser welding is an appealing technique for bonding transparent workpieces, it is not applicable for joining silicon samples due to nonlinear propagation effects which dramatically diminish the possible energy deposition at the interface.…”

“…However, silicon–silicon ultrafast laser welding is still an open issue, as the absorption is necessarily nonlinear (multiphoton ionization)—and thus, the energy deposition at the interface between two silicon samples is less efficient than in the silicon–metal configuration. While it was shown that nanosecond pulses [ 14 ] or continuous light [ 15 ] can be employed for joining silicon samples, thermal effects in such regimes are expected to decrease the degree of control on the energy deposition. The demonstration of an ultrafast laser‐based technique for joining stacked semiconductors such as silicon would have direct applications in microelectronics, and even beyond.…”

Silicon–metal and silicon–silicon ultrafast laser welding with domesticated filaments

“…However, siliconsilicon ultrafast laser welding is still an open issue, as the absorption is necessarily nonlinear (multi-photon ionization)-and thus, the energy deposition at the interface between two silicon samples is less efficient than in the silicon-metal configuration. It was shown that nanosecond pulses 25 or continuous light 26 can be employed for joining silicon samples. This is consistent with the fact that this long-interaction regime is adapted to the production of repeatable modifications inside silicon.…”

Bonding of PMMA to silicon by femtosecond laser pulses

“…Shear joining strength measurements reveal 2.2 MPa between the samples, thus holding a high potential for applications. The potential of nanosecond-laser welding of silicon to other semiconductors has been also studied, revealing a shear joining strengths of > 10 MPa for all processed configurations 15 .…”