High mechanical reliability of background GaAs LSI chips with low thermal resistance

The fracture strength of mechanically ground GaAs LSI chips was investigated in comparison to that of chemically thinned ones to confirm their appropriateness for practical use in the GaAs LSI manufacturing process. In addition, the effect of wafer-thinning on thermal resistance was evaluated quantitatively. GaAs LSI-sized 6.35-mm-square chips with mirror-ground back-surfaces (R_max=0.1 μm) have been confirmed to be almost as highly reliable as chemically thinned ones through fracture stress experiments. The 1 μm post-grinding chemical etching in the original wafer-thinning technology proved to be effective for eliminating the surface flaws due to grinding, which act as stress concentrators and reduce mechanical strength. The thermal resistance of background 5-mm-square GaAs chips was observed to be expectedly low utilizing the newly established surface temperature measurement technology based on the diode drop technique. Furthermore, the thermal resistance was judged to be independent of the back-surface treatment