Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/6310
標題: 低介電常數高熱穩定性的氟化非晶碳薄膜之研究
Low dielectric constant and high thermal stability fluorinated amorphuos carbon films
作者: 吳貴盛
關鍵字: 氟化非晶碳薄膜;低介電常數
出版社: 電機工程學系
摘要: 
中文摘要
在邁向深次微米的領域時,必須使用介電常數更低的材料,以降低因元件尺寸縮小所產生RC時間延遲的影響。本論文以電漿輔助化學氣相沉積(PECVD)系統製作氟化非晶碳(a-C:F)薄膜,使其具有低的介電值及良好的熱穩定性,可用來做金屬內連線的介電層。
a-C:F薄膜的製作,是以CF4和CH4為反應氣體,改變不同的製程參數,包括CF4/CH4氣體流量比40%~90%、RF功率25 W~300 W、基板溫度35℃~300℃、製程壓力0.5 torr和1 torr、及以方波脈衝開關比調變射頻電漿來沉積a-C:F薄膜,以探討各參數對沉積薄膜的影響。並對薄膜作退火處理,以探討薄膜的熱穩定性。
a-C:F薄膜的特性分別以N&K analyzer、FTIR光譜儀、X光光電子能譜儀、原子力顯微鏡、C-V量測儀、及I-V測量儀分析薄膜厚度及折射率、薄膜鍵結結構、碳氟鍵的種類、薄膜表面粗糙度、介電值及漏電流。
從FTIR的分析,當C-F/C-H的比例趨近∞,位於波數範圍1000~ 1500 cm-1的特徵峰群寬度縮小,在此範圍內CF2的對稱伸張模及CHx的彎曲模的波峰位置下降,CF2的非對稱伸張模往右移動,波數位置1200 cm-1的波峰亦向右移動,且其峰值最高,CF伸張模的波峰位置上升;或從XPS的分析,當CF、CF2、及CF3的含量愈多,則a-C:F薄膜有較低的介電值。
實驗結果與分析顯示,基板溫度高於100℃有助於提昇a-C:F薄膜的熱穩定性。在較高的射頻功率(≧ 150 W)、較大的CF4/CH4氣體流量比(F ≧ 80%)、較高的脈衝頻率(1 kHz)、100℃的基板溫度、及0.5 torr等條件下可以沉積出低介電常數高熱穩定性的a-C:F薄膜。
在脈衝頻率1 kHz、RF峰值功率300 W、CF4/CH4氣體流量比85%、基板溫度100℃、及壓力0.5 torr的條件下所製作的a-C:F薄膜在1 MHz的C-V量測下具有低的介電值2.4,在0.5 MV/cm的電場量測下具有低的漏電流密度10-9 A/cm2,並且在10-5 torr的真空環境下,經過一個小時400℃的退火處理後,其薄膜厚度縮減率為零、介電值為2.5及漏電流密度為10-7 A/cm2,此薄膜具有低介電值及高熱穩定性,可用來做金屬內連線的介電層。

Abstract
In the deep sub-micron ULSI circuits, new intermetal dielectric (IMD) materials which have lower dielectric constant shall be used to reduce the RC time delay. In this thesis, fluorinated amorphous carbon (a-C:F) thin films were deposited using plasma-enhanced chemical vapor deposition. These films having low dielectric constant and good thermal stability can be used as intermetal dielectric materials.
a-C:F films were deposited using CH4 and CF4 as the reactant gases. The different process parameters, including 40 to 90% CF4/CH4 flow-rate ratio, 25 to 300 W RF plasma power, 30 to 300℃ substrate temperature, 0.5 and 1 torr process pressure and different pulse-wave modulation of RF plasma were used to study the influences of these parameters on the properties of a-C:F films. The a-C:F films were annealed at 400℃ for one hour in the vacuum environment to investigate the thermal stability of the films.
The thickness and refractive index, the bonding structure, the C-F bonding, the surface roughness, the dielectric constant and the leakage current of the films were measured using N&K analyzer, FTIR spectrometer, XPS, AFM, C-V measurement and I-V measurement, respectively.
a-C:F films exhibit low dielectric constant can be verified by the characteristics of the FTIR absorbent spectrum including the infinite peak intensity ratio of C-F/C-H modes, the reduction of the width of absorption peaks group located between 1000 to 1500 cm-1, the decrease of the peak intensity of the CF2 symmetric stretching mode and the CHx bending mode, the shift to the higher wavenumber of CF2 asymmetric stretching mode and 1200 cm-1 peak, the highest peak intensity of 1200 cm-1 peak, and the increase of the peak intensity of the CF stretching mode ; or can be verified from the XPS signals having high CF, CF2 and CF3 contents.
From the results and analysis, the substrate temperature higher than 100℃ can improve the thermal stability of a-C:F films. a-C:F films having low dielectric constant and high thermal stability can be obtained using high RF power (150 W), high CF4/CH4 flow-rate ratio (F ≧ 80%), high pulse modulation frequency (1kHz) and 100℃ substrate temperature.
The a-C:F film deposited with 1 kHz pulse modulation frequency, 300 W RF power, 85% CF4/CH4 flow-rate ratio, and 100℃ substrate temperature has lower dielectric constant about 2.4 which was analyzed from 1 MHz C-V measurement, and has lower leakage current density about 10-9 A/cm2 which was measured at 0.5 MV/cm electric field. After 400℃ for one hour annealing in 10 -5 torr vacuum environment, the shrinkage of the films thickness, the dielectric constant and the leakage current of the film was zero, 2.5 and 10-7 A/cm2, respectively. The a-C:F film deposited with 1 kHz modulation of RF power has low dielectric constant and high thermal stability. It can be used as intermetal dielectric material.
URI: http://hdl.handle.net/11455/6310
Appears in Collections:電機工程學系所

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