具吸熱性質儲氫合金元件的設計與製作在晶片散熱的應用

Abstract

電晶體的尺寸和電路設計隨著科技的發展，使得電晶體密度、總數和總消耗功率在標準大小的晶片上每年非常顯注的增加，這發展趨勢帶來一個不可避免的問題：晶片工作上的溫度持續增加。舉例來說，現今前端微處理器的電晶體數目和工作頻率以每兩年2倍的成長速度增加。因此，以微處理器功率密度增加的速率來看，在不久的未來微處理器將會和核反應爐一樣熱，而現存的積體電路散熱的科技將不能維持在正常工作溫度下。換句話說，可以想像得出在高溫的工作環境下不會有好的性能表現。因此，晶片散熱科技在下一世代的高性能微處理器發展時將會是所面臨到最重要的挑戰。為了解決這問題，一個新型的散熱設計與散熱元件將在這碩士論文中提出和製作。具有吸熱性質的儲氫合金將被用來維持晶片的工作溫度和吸收晶片上放出的熱量。氫氣從微管道充入裝滿儲氫合金的散熱器，當儲氫合金放出氫氣時，將會觸發吸熱反應，並且從儲氫合金散熱器底部帶走大量的熱。初步估計，一個完全充氫的儲氫合金，體積2公分x 5公分 x 10 公分的儲氫合金容器，在60分鐘內，至少有2.2 J/sec.cm2 的熱通量密度。散熱能力將會比同體積大小的液態二氧化碳來得高。且此散熱器的設計是直接接在氣瓶上，在吸熱過程中將不會有能量損耗，此設計將非常適合於攜帶式個人3C 電子器材，譬如筆記形電腦等。因為矽有絕佳的熱導係數且可塑性高，被動式矽基座將與冷卻裝置連結，將可帶來可觀且印象深刻的答案。

The development trend in the scaling of transistor and circuit design already made a dramatic increase of transistor density, number, and total power consumption in a standard-sized chip every year. Such a development brings on an unavoidable problem that is continuous temperature rising of a functional chip. For instance, the present transistor number and working frequency of a microprocessor double every 2 years. Accordingly, in a very near future, the increment rate of power density of the microprocessor would make itself as hot as a nuclear reactor in which the existing integrated circuit cooling techniques will not be capable of maintaining its working temperature. On the other hand, poor circuit performance can be expected while it operates at high temperature. Thus, chip cooling has become one of the most important technical challenges in the development of next generation high performance microelectronic device. In order to resolve the issue, a novel cooling scheme and device are presented and fabricated in this dissertation. An endothermic hydrogen storage alloy is utilized to absorb the heat released by the chip and maintain the working temperature of the chip. Via the flow of hydrogen gas through a micromachined silicon heat sink filled with the alloy, a triggered endothermic reaction could take away large amount of heat generated from a heated device. Based on the simulation results, a complete hydriding hydrogen storage alloy of 2cm x 5cm x 10cm, the heat sink can provide 2.2 J/sec.cm2 cooling ability for 60 minutes at least. The heat dissipation ability of hydrogen storage alloy is better than the same volume of liquid gas such like carbon dioxide. Since the heat sink is designed to directly connect a gas reservoir, no power consumption is required in the cooling process which makes itself more fascinating to portable personal 3C devices like notebook, palm pilot, tablet PC…. etc. Due to the superior heat conductivity and manufacturability of silicon, the passive silicon based heat sink combined with the present cooling apparatus could provide a cost effective solution.