ROFIN, a manufacturer of industrial lasers and laser systems enters the semiconductor market with a turnkey solution for front-end-of-line (FEOL) processing. The new laser wafer processing system Waferlase 200/300/450, is a fully automated modular platform comprising a market-leading handling system for (ultra) thin semiconductor wafers and a choice of laser processing modules, depending on the type of application. The Waferlase 200/300/450 product family starts with solutions for IGBT laser annealing and debris-free wafer marking.
Leading ultra-thin wafer handling technology
ROFIN integrated top-notch wafer handling technology to provide precise, non-contact transportation of ultra-thin wafers, even with considerable warpage and bow. The system comes with two or more cassette ports for Open Cassette or FOUP wafer carrier systems. Integrated scanners detect the exact position of the wafer in its carrier. The comprehensive but easy-to-use system software controls slot allocation, wafer warpage measurement, wafer location as well as wafer ID detection, and would even change the pick-and-place sequence automatically in case of a wafer damage threat, e.g. due to extensive or opposite bowing of neighboring wafers. A high-end dual-arm robot takes care of wafer loading and unloading. The pre-aligner module centers and aligns the wafer. A “vacuum handshake” between end-effector and pre-aligner, including wafer safeguard, secures damage-free handling of the wafer back side. Thus, high-end technology and sophisticated software control integrated in ROFIN’s Waferlase 200/300/450 guarantees highest throughput at negligible wafer breakage rates.
IGBT laser annealing
The Insulated Gate Bipolar Transistor (IGBT) market is constantly growing because of significant advantages IGBTs offer compared to other transistor devices such as high voltage capability, low ON-resistance, ease of drive, fast switching speeds, robustness, etc.
One of the key factors contributing to this market growth is the increasing demand in automotive and industrial applications, including renewable energy, communications, medical, lighting and transportation.
IGBTs are manufactured on mechanically thinned wafers with a typical thickness of 100μm or less. In order to establish a field stop and/or emitter layer on the rear side of the wafer, deep-implanted doping elements (like phosphorous or boron) have to be activated through a high-temperature annealing process towards the end of the FEOL process chain. Very often, the sensitive devices on the wafer front side are protected by an attached tape. Due to low damage temperatures of the tape, the heat-sensitivity of the front side devices, as well as a non-uniform heat distribution in the processing chamber, conventional oven activation is characterized by low activation levels and rates. ROFIN’s laser annealing process has been developed to overcome these issues and to provide significantly higher process stability and yield at competitive costs/wafer levels. Laser annealing deep-activates the dopants and simultaneously prevents damage to the wafer front side and the protection tape. The laser allows for precise depth control of the field stop and/or emitter layer activation in the range of up to 2μm. With activation rates exceeding 90 percent, ROFIN’s IGBT laser annealing solution is far superior to conventional methods.
Wafer marking
ROFIN’s Waferlaser 200/300/450 systems produce traceable markings on transparent, semitransparent and opaque wafer materials. Two methods – hard and debris-free marking – are used which differ in terms of process, depth and location of the mark. Debris-free marking in clean-room environment is achieved solely by melting of the silicon wafer surface.
ROFIN’s new patent-pending marking technology allows the user to precisely control the marking depth ranging from less than 1μm to 7μm. The debris-free marking process uses a tailor-made IC–marking laser source with 532nm wavelength. This dedicated solution achieves high contrast with excellent performance at small character heights.
