Project description and objectives:
Smart systems work best when built with the highest performing components, i.e. those built from the most suitable materials using the best processes. As these processes are generally not compatible with a universal platform, heterogeneous integration of the components is needed to realise the best system performance. Semiconductor based components (electronics, sensors, lasers) have their essential functionality in thin layers (< 10 m thick) near the surface of the processed wafers. This opens up the opportunity for integration onto a new platform using only thin coupons of the material. After printing, wafer scale processing can be used to connect the coupons with metal tracks, thereby forming arrays of integrated modules on the target wafer surface. The “Transfer-print OPerations for Heterogeneous InTegration” (TOP-HIT) project set out to develop micro-transfer-print as a versatile, scalable, and reliable technology for the compact heterogeneous integration of thin functional materials and devices.
Figure 1 shows a schematic overview of the printing process, while figure 2 shows semiconductor device coupons ready for pick up from a source wafer. The transfer process relies on the ability to release the components from their initial substrate – generally through undercut etching - together with a patterned stamp and an associated tool to pick and place arrays of components in a parallel process. The accuracy of the printing is better than ±1.5 microns across 200mm diameter wafers. The use of array printing means that, depending on the application, ten of thousands of devices can be printed per minute.
In TOP-HIT we sought to advance the micro-transfer-print technology for compact, heterogeneous integration by exploring different materials and device structures. We validated the device integration on two different technology platforms: one in the photonics, the other in the electronics domain.
The consortium consisted of two research performing organizations (UCC/Tyndall and imec), an SME – X-Celeprint, a foundry (X-FAB), and two end users namely Huawei (Caliopa and CIP divisions) and Seagate who are leaders in the silicon photonics and magnetic read-write head industries respectively. The strong collaboration between the partners contributed to the achievements of the project. Figure 3 illustrates the roles of the different partners within TOP-HIT.
