應用在低介電常數金屬層間介電質的旋轉式塗佈HSQ之特性研究

Abstract

隨著CMOS尺寸縮小至0.35um或是以下時，在選擇金屬層間介電質時，低介 電常數特性就變得越來越重要。在本論文中，我們將介紹一種以HSQ為基 本結構，名為流動性的氧化層(Flowable Oxide(FOx))之低介電常數旋轉 式塗佈材料，並且討論它應用在低介電常數金屬層間介電質時的一些特性 。在我們的研究中，首先提到的是FOx膜厚度的縮小問題。FOx膜厚度縮小 率小於5%，與一般的旋轉式塗佈材料(膜厚度約縮小10%)比較起來小了許 多。我們也研究FOx膜的一些熱特性。它有很好的抗裂性，可以在700度溫 度下而不產生裂隙。另外，我們也研究了電漿處理對FOx膜的效用和FOx膜 的防水性。經過電漿處理的FOx膜在歷經升溫和降溫的溫度循環時，在膜 應力的變化上比沒有經過電漿處理的FOx膜要小。氫氣的電漿處理能使FOx 膜的介電常數變得很低。另一方面，氧氣的電漿處理因產生了矽-氫氧鍵 ，使得FOx膜更易吸水。氨的電漿處理則可降低FOx膜的吸水性。矽-氫氧 鍵的形成是由於空氣中的氧原子與FOx膜的原子鍵結所致。同時，對FOx膜 熱處理的時間和溫度效應也是我們研究的範圍。我們發現，熱處理的溫度 和時間必需小心地控制，以得到能保持低介電常數特性的矽-氫鍵較多之 FOx膜。如果FOx膜結構中有較多的矽-氫鍵，而樣狀(cage-like)和網狀( network)結構的比例也能保持大一點的值，我們將可得到一個有低介電常 數特性的FOx膜。關於降低氧化層介電常數的機制，在本論文中也解釋了 離子極化密度和電子極化密度與介電常數間的關係。最後，我們也討論了 FOx膜一些如電容-電壓和電流-電壓的基本電特性。 As the CMOS geometry shrinks to 0.35um and beyond, low dielectric constant properties become increasingly important in the selection of intermetal dielectric oxide. In this thesis, we introduce a low-k SOG material that is Hydrogen Silsesquioxane (HSQ) -based flowable oxide (FOx) and study its characteristics when used for low-k IMD applications. In the present study, film shrinkage has been reported. The FOx film thickness shrinkage is smaller than 5% that exhibits less reduction than the conventional SOGs (reduce to 10 %). Thermal properties of the FOx film have also been investigated. The FOx film has good crack resistance and will not crack till 700oC. The plasma treated films show smaller variations in film stress than as spun FOx film during the thermal heating and cooling cycle. Plasma curing effects and water absorption resistance of FOx have been realized. H2 plasma curing treatment causes the lowest dielectric constant of FOx. On the other hand, O2 plasma curing treatment makes the FOx film higher moisture absorption due to the formation of Si-OH bonds and NH3 plasma curing treatment makes lower moisture absorption. The formation of Si-OH bonds is caused by the O component in the air incorporating into the film structure. In addition, curing time and temperature effects are also stated. It is found that we should carefully select the optimal curing time and temperature to get Si-H rich film for conserving low dielectric constant properties of the FOx film. If the Si-H bonds retain ata high level and the cage-like/network ratio is not too small, the low dielectric constantproperty of the film will conserve. Mechanisms of the reduction in oxide's dielectric constant have been reported to explain the relationship between ionic polarization density and electronic polarization density with dielectric constant. Finally, basic electrical characteristics such as C-V and I-V measurements are measured for each plasma curing FOx film.