MICROELECTRONICS PROCESSING: 'Zero-overlap' laser system speeds ultrathin wafer dicing

摘要

Solid-state, fiber-based, and ultrafast lasers continue to make inroads in microelectronics processing applications, specifically for silicon wafer dicing in the semiconductor industry and in a variety of laser-based cutting and texturizing applications in the photovoltaics industry. While most of these laser-based cutting methods rely on linear movement of the laser beam along a substrate, Electro Scientific Industries (ESI; Portland, OR) has developed a production-ready system that incorporates 355 nm commercially available UV laser (with approximate 8 (mu)m spot size) to spatially separated points along the desired scribe line of a wafer. Pulsing at around 240 kHz, the laser energy is delivered in multiple passes in spatially separate pulses that avoid the debris, heat buildup, and plume interactions of linear laser-based scribing methods. The spatial separation allows the use of higher laser-fluence values for higher wafer-cutting speeds (a few meters per second) than would be possible using linear movement of the laser beam. In addition, the laser pattern can be selectively optimized to control material removal rates for different semiconductor layers (see figure).