Enhancements in resizing single crystalline silicon wafers up to 450 mm by using thermal laser separation

Abstract

This paper presents improvements in resizing single crystalline Si wafers by using the dicing technology "Thermal Laser Separation" (TLS). Results of this work support the general need to resize wafers to smaller diameters and will play an important role during the transition to larger wafer diameters as currently projected in the ITRS for 450 mm: Wafers of new sizes have to be easily adapted to fit, e.g., currently available metrology tools. TLS process parameters were developed for resizing Si wafers and to produce demo wafers which were analyzed and compared with current state of the art techniques plasma etching, laser ablation and mechanical wafer sawing. For the first time, circular cuts with diameters up to 300 mm were produced out of 450 mm ( thickness: 925 mu m) single crystalline Si wafers with TLS. The TLS process results in two important benefits for resized wafers: First, the edge of the new wafer is of higher quality than the edges produced by state of the art resizing techniques. Second, the TLS process is up to 24 times faster than known resizing processes

Ultrashort pulse laser dicing of thin Si wafers: the influence of laser-induced periodic surface structures on the backside breaking strength

“…These cracks might cause chip failure under thermal load. Another dicing method is thermal laser separation [6]. This process is based on rapid laser-heating and subsequent water cooling to induce a mechanical stress field inside the Si-wafer.…”

Ultrafast-laser dicing of thin silicon wafers: strategies to improve front- and backside breaking strength

“…In both cases, wavelength, pulse duration, and focusing conditions are typically chosen such that the absorption takes place mainly inside the volume of the wafer [10,13]. In the first example, the laser acts as volume heat source that generates a stress field which causes the wafer to crack [10,11]. In the case of stealth dicing [12,13], pulsed laser light is focused tightly below the surface to generate a defect inside the volume.…”

“…The highest edge quality provide laser dicing methods based on thermal stress generation [10,11] or stealth dicing [12]. In both cases, wavelength, pulse duration, and focusing conditions are typically chosen such that the absorption takes place mainly inside the volume of the wafer [10,13].…”