A Study of Flip Chip Microwave Device with Protecting Capability Submount(II)

We use the flip chip(FC) structure to solve the thermal problem of the power HEMT device, because the active layer is close to the surface of HEMT device. The proposed flip chip structure could let the active layer more close to the heat sink submount and through many connecting pillars (which connect the chip and the submount), thus form many dissipation paths to sink the excess heat to a high thermal conductivity AlN submounts. In the first year, we have accomplished several GaN power High Electron Mobility Transistor (HEMT) devices with gate width of 1 mm. We are now beginning to separate these power HEMT devices and trying to flip chip them on top of some AlN submounts. In the second year, we will add a rare earth oxide layer under the gate of HEMT device in order to form a GaN MOS structure to enhance its output performance. We will also analyze the optimal parameters (temperature, pressure, force, ultrasonic power and the bonding period of time ..etc.,) for the flip chip bonding process and increase the thickness of HEMTs pad to improve the flip chip quality. At the end of this second year project, we will deliberate a reliable GaN HEMT module with the output power above 5W. The additional advantage of flip chip structure is that it can combined with many parallel GaN HEMTs devices on a submount to form a large integrated power HEMT element. This is also our goal in the end of the whole project with a output power as high as 20W.

Project ID:PB9808-2392
External Project ID:NSC98-2221-E182-058