High quality and high speed cutting of 4H-SiC JFET wafers including PCM structures by using Thermal Laser Separation

Abstract

The silicon carbide (SiC) market is gaining momentum hence productivity in device manufacturing has to be improved. The current transition from 100 mm SiC-wafers to 150 mm SiC-wafers requires novel processes in the front-end as well as the back-end of SiC-chip production. Dicing of fully processed SiC-wafers is becoming a bottleneck process since current state-of-the-art mechanical blade dicing faces heavy tool wear and achieves low throughput due to low feed rates in the range of only a few mm/s. This paper presents latest results of the novel dicing technology Thermal Laser Separation (TLS) applied for separating SiC-JFETs. We demonstrate for the first time that TLS is capable of dicing fully processed 4H-SiC wafers, including back side metal layer stacks, process control monitoring (PCM), and metal structures inside the dicing streets with feed rates up to 200 mm/s. TLS thus paves the way to efficient dicing of 150 mm SiC-wafers.

Thermal Laser Separation – A Novel Dicing Technology Fulfilling the Demands of Volume Manufacturing of 4H-SiC Devices

“…Electrical characteristics: TLS diced JFET devices were assembled using direct copper bonding substrates and were afterwards electrical characterized by measuring the on state and the blocking characteristic. It could be shown that the TLS process does not influence the electrical characteristics of these SiC devices [4]. Fig.…”

Comparison of Different Novel Chip Separation Methods for 4H-SiC

“…The TLS technology is a two-step process [3]. A first short pulsed laser scribe initiates a crack along the dicing street and cuts through the metal of the PCM structures.…”

“…The back side metallization of the SiC chip is also separated without damages, delamination (Fig. 8) [3] and negative effects on the sawing foil. TEM analysis shows no damage at the chip side walls [4].…”

Investigation on the Processing Quality of Nanosecond Laser Stealth Dicing for 4H-SiC Wafer

“…Thermal Laser Separation (TLS) defines the starting point through the initial scratch, using tensile stress generated by the heating area and cooling area to break the material apart. 6 However, irregular propagation of microcracks can affect chips performance. Stealth Dicing (SD) 7 focuses a laser beam inside the material to form modified layers and separates the chip by splitting or film expansion, which solves the problem of the method mentioned above.…”