TRANSIENT-RESPONSE CHARACTERISTICS OF VAPOR-DEPOSITED MICRO HEAT-PIPEARRAYS

The transient thermal response of vapor deposited micro heat pipe arra ys fabricated as an integral part of silicon wafers was measured to de termine if these arrays could be used to reduce the local temperature gradients and improve the reliability of semiconductor devices. Wafers with arrays of 34 and 66 micro heat pipes were evaluated using an IR thermal imaging system in conjunction with a VHS video recorder. These arrays occupied 0.75 and 1.45 percent, of the wafer cross-sectional a rea, respectively. The wafers with micro heat pipe arrays demonstrated a 30 to 45 percent reduction in the thermal time constant when compar ed to that obtained for plain silicon wafers. This reduction in respon se time was shown to lead to a significant reduction in the maximum wa fer temperature, due to the increased effective thermal conductivity c aused by the vaporization and condensation occurring in the individual micro heat pipes. The experimental results were then used to validate a transient numerical model, capable of accurately predicting the tra nsient temperature profile and thermal time constant of the wafer/heat pipe combinations.