Improvement of Fundamental Technology of 3-D Thermal Compression Bonding With High Accuracy

Abstract

Thermal compression bonding (TCB) involves three technology themes: high-speed and high-accuracy motion, substrate–die planarity, and stability for long production runs. We will propose solutions for each of these themes. For high-speed and high-accuracy motion, we propose a nonreaction servo (NRS) system, which has an XY table with a linear motor coil and stator magnet that floats on a base. The system can separate the vibration produced by the reaction force of the linear motor from the moving component. With NRS, we can shorten the settling time from 530 to 120 ms with 1- $\mu \text{m}$ settling accuracy. TCB requires highly accurate planarity between die and substrate. We propose a leaf spring fixed-stage planarity adjustment system operated by cam that can achieve much improved planarity of $5.3~\mu \text{m}$ on a 12-in stage, compared to 47 $\mu \text{m}$ achieved by manual shim adjustment. We further propose a reference positioning system (RPS) that can compensate for bond shift due to thermal expansion during long production runs. RPS has achieved XY $\pm 2~\mu \text{m}$ (3 sigma) during continuous 200 IC production. For 3-D devices using a flip-chip bonder that incorporates our proposed subsystems, we can bond with less than $2~\mu \text{m}$ variation in gap height between die and substrate, with each layer’s height variation less than $1~\mu \text{m}$ , and with up to 43% improved productivity compared to a bonder without NRS.