摘 要

本研究探討氮化鉭薄膜於鉻/氮化鉭/矽之系統中，其鉻/氮化鉭/矽界面微結構及反應，期望對氮化鉭薄膜於金屬鉻的阻障層作用有更進一步的了解。
研究採用12英吋Si(100)晶圓為基板，以濺鍍方式沈積鉻膜300 nm和氮化鉭薄膜30 nm，於真空壓力為5×10-5 torr的真空退火爐中，經500、600、700、800、900及1000℃持溫1小時，試片於爐中自然冷卻至室溫，再行取出；而後以XRD、TEM及HRTEM進行試片之相鑑定、結構分析及界面之反應判定；並以AFM進行薄膜表面形態觀察，另以四點探針儀對試片進行電性分析。
剛沉積的氮化鉭薄膜為非結晶結構，然而Ta2N薄膜經退火處理500℃後產生結晶現象，此時氮化鉭薄膜的阻障能力已大幅降低。隨著退火溫度升高，其試片的粗糙度、表面電阻值及氮化鉭/矽界面的a-layer有上升的趨勢。且試片經退火處理800℃持溫1小時後，於Ta2N與Si之界面產生析出物往矽基材內成長。綜合XRD、TEM EDS、晶格影像計算及繞射圖d-spacing分析等方法，判定該析出物應為鉻矽化合物(CrSi2)，而原本位於a-layer內之中間過渡產物因高溫時Ta2N的鍵結已破壞，使得氮化鉭/矽界面產生矽化反應，進而轉變為鉭矽化合物(TaSi2)。

Abstract

We studied the microstructure and interfacial reaction of tantalum nitride in the Cr/Si system. The films were deposited on a Si(100) wafer with a diameter of 12 inches by using sputtering method. The thickness of the chromium and the tantalum nitride was about 300 nm and 30 nm, respectively.
After the samples were formed, annealing processes were carried out in a tube furnace with a vacuum level of 5 × 10-5 torr. The samples were annealed at temperatures ranging from 500, 600, 800, 900, and 1000oC for one hour in the vacuum furnace and cooled by furnace cooling. We studied the properties of the Cr/Ta2N/Si system after the annealing processes through XRD, TEM, HRTEM, AFM, and four-point probe analyses.
Degradation of the Ta2N barrier layer occurs at 500oC by an entire crystallization of the amorphous Ta2N. We found that the roughness, the sheet resistance of the samples and the thickness of the amorphous layer increased as the annealing temperature increased. In the annealing process at 800oC, we observed the precipitation of a silicide with rectangular shape residing in the silicon wafer along the interface between Ta2N and Si substrate. The phase of the precipitation had been identified as CrSi2 by using XRD、TEM EDS、lattice images and d-spacing methods. The chemical reaction of Si with Ta forming TaSi2 required excess energy to break the chemical bonds between Ta and N in the compound of Ta2N.

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