Hydrogel-mediated semiconductor wafer bonding

Abstract

The concept of hydrogel-mediated semiconductor wafer bonding was proposed and demonstrated in this work. The unique property of hydrogels was utilized to simultaneously realize high mechanical stability, electrical conductivity, and optical transparency in semiconductor interfaces. The high applicability of this method for rough surfaces to be bonded was also demonstrated, owing to the soft, deformable interfacial contact agent to be solidified in the bonding process. Furthermore, the bonding experiments were carried out in ambient air at room temperature, which, therefore, provides cost and throughput advantages in device production. In addition, the developed bonding technique was used for demonstrating the fabrication and operation of solar cell devices, with current paths across the bonded interfaces, which verified the method's practical applicability. Our semiconductor bonding and interfacial engineering scheme are expected to open up a pathway for simple, handy, and low-cost, but flexible and high-performance optoelectronic material integration.

III–V Light-Emitting Diodes on Silicon by Hydrogel-Mediated Wafer Bonding

“…The detachment normal stress of the bonded interface was measured as 43 kPa. The employment of the hydrogel PAM enables bond formation at room temperature [35]. The hydrogen bonds stemming from PAM may cause the adhesion to the semiconductor surfaces [45,46].…”

“…Therefore, wafer bonding is a promising scheme for high-performance semiconductor optoelectronics, and has been employed in the fabrication of a variety of devices such as light-emitting diodes [1,2,4,5,24], lasers [7,8,[25][26][27], photodetectors [28,29], and solar cells [25,[30][31][32][33][34]. Hydrogel-mediated semiconductor wafer bonding is an emerging technique for heterogeneous materials integration, simultaneously forming interfaces with high mechanical stability, electrical conductivity, optical transparency, and surface-roughness tolerance [35]. This hydrogel-mediated bonding technique has been applied to introduce wavelength-converting materials [36] and graphene quantum dots [37] into semiconductor interfaces, towards the realization of ultrahigh-performance optoelectronic devices.…”

“…This hydrogel-mediated bonding technique has been applied to introduce wavelength-converting materials [36] and graphene quantum dots [37] into semiconductor interfaces, towards the realization of ultrahigh-performance optoelectronic devices. However, so far, the semiconductor material combination and device demonstration for hydrogel-mediated bonding have been limited to homogeneous Si-to-Si and a solar cell, respectively [35]. Therefore, the demonstration of a hydrogel-bonded light-emitting device would be an important technical milestone to verify the versatility of the hydrogel-mediated semiconductor bonding scheme for applications in optoelectronics.…”

Graphene-Quantum-Dot-Mediated Semiconductor Bonding: A Route to Optoelectronic Double Heterostructures and Wavelength-Converting Interfaces

“…Figure 6 shows the dependence of the interfacial mechanical bonding strength and electrical resistivity on the PAM concentration for the samples with HF surface pretreatment bonded at room temperature. It is noted that the employment of hydrogel can enable mechanically stable bond formation at room temperature [40][41][42], which was conversely difficult in the case of the bonding approach (1). The hydrogen bonds stemming from PAM presumably causes adhesion to semiconductor surfaces [43,44].…”

“…In addition, the PAM matrix holds the GQDs and suppresses their sedimentation owing to its viscosity induced by the entanglement of PAM polymer chains. Other hydrogel materials, such as agarose and polyvinyl alcohol, may also be used as bonding agents [42]. The interfacial bonding mechanical strength was observed to gradually decrease when the PAM concentration increases, which is potentially attributed to the spatial non-uniformity of the PAM at the bonded interface due to the increased viscosity of the PAM solution, as shown in Figure 6.…”