電漿製程對多孔隙低介電材料結構、電性及可靠度之影響

Effect of Plasma Treatment on Structural, Electrical, and Reliability Characteristics of Porous Low-k Dielectrics.

黃俊夫(Jun-Fu Huang)

指導教授 ： 鄭義榮

國立暨南國際大學/科技學院/電機工程學系/碩士(2013年)

https://doi.org/10.6837/NCNU.2013.00064

摘要

本論文研究探討不同氣體電漿製程對多孔隙低介電材料之影響，主要可分成三部分，第一部分主要研究低介電 ( low-k ) 材料經過H2/He電漿以及使用標準電漿製程和遙控電漿製程技術後，其對薄膜特性、電性以及可靠度之影響。實驗結果得到，經過電漿製程後，會在薄膜表面做改質動作，而標準電漿在表面改質的厚度遠比遙控電漿改質厚度大的多，這表示失去離子之轟擊，電漿製程對低介電材料之傷害減少；折射率經過標準H2/He電漿製程後上升，且隨時間越長，折射率則變得更大，但遙控H2/He電漿製程對折射率則是改變不大。同時，經過標準H2/He電漿後會使得薄膜表面容易被HF侵蝕，且疏水性質變差，致使薄膜介電常數大幅提高，薄膜機械強度和電性以及可靠度皆變得更差，且當通入標準電漿製程時間拉長，對薄膜影響更大，導致其特性、電性及可靠度也跟著變更差；另一方面，通入遙控H2/He電漿其特性則和未經過電漿處理之低介電薄膜沒有太大的改變，例如：薄膜蝕刻速率、表面疏水性質以及介電常數，而電性和可靠度方面其甚至有改善未經過電漿處理之低介電薄膜之功能。
論文第二部分為研究不同N2/NH3比例之電漿，觀察其對多孔隙低介電材料薄膜特性、電性以及可靠度之影響。實驗結果顯示，經過五種不同比例之N2/NH3電漿通入之下，其在表面造成的薄膜改質程度是很接近的，其之後影響薄膜後造成之機械強度和硬度也有相近的值。通入純N2和純NH3電漿後，其在表面改質使得其Si-N和C-N鍵結變多，其中以純N2鍵結最多，進而影響其特性，如薄膜蝕刻，純N2和純NH3電漿就容易被HF蝕刻，電性則是使得漏電流增加以及介電常數的提高；在疏水性質方面隨著NH3比例上升，呈現較低的疏水性質，進而使得電性變差，介電常數提高，可靠度也隨著變差；N2/NH3比例之電漿之中，電性與可靠度大致呈現隨著NH3比例上升而變差的趨勢。
第三部分為研究不同條件之N2/H2電漿製程以及在N2/H2電漿中加入偏壓，觀察其對多孔隙低介電材料薄膜特性、電性以及可靠度之影響。實驗結果發現，N2/H2電漿中，純H2電漿會使得低介電材料薄膜其特性變差，如HF蝕刻率上升，且因為其疏水性質差，導致容易和水氣反應，導致其電性的崩壞，如漏電流急遽上升，進而導致介電常數之提高，也使得可靠度變差，而純N2電漿則呈現有較高疏水性質，當純H2電漿混入N2後，可改善其特性如：薄膜蝕刻率、表面疏水性質、介電常數，電性方面也可以得到改善，如漏電流的下降，以及可靠度上升。另外，在電漿製程時加入正偏壓抑制正離子，使之在電漿製程中不作用，只剩下電子反應，所以離子衝擊變小，致使N2/H2電漿特性和電性以及可靠度皆得到改善。

關鍵字

低介電材料 ； 電漿 ； H2/He ； 標準電漿 ； 遙控電漿 ； 可靠度 ； N2/NH3 ； N2/H2 ； 正偏壓

並列摘要

This thesis investigates the effect of different kinds of plasma on porous low-k dielectric materials. It can be divided into three parts. The first part is about the effect of H2/He plasma for low dielectric (low-k) materials by using standard and remote plasma methods, and discusses the film properties, electrical properties and the reliability. The results show the film will be modified on surface after plasma treatment, and the modification of thickness on the surface changed by standard plasma is much thicker than the modification of thickness on surface changed by remote plasma. It means that remote plasma treatment causes lower damage for low dielectric material because of the loss of ion bombardment. The film on mechanical strength, electrical properties and the reliability are getting worse when using standard plasma treatment. When the time of standard plasma treatment gets longer, it will have a greater impact on the film, and makes properties, electrical properties and reliability much worse. On the other hand, using remote H2/He plasma treatment changes the properties of low dielectric film not much. For example: the etching rate, the hydrophobicity on surface and dielectric constant. And it can improve the low dielectric film on the electrical properties and reliability.
The second part of thesis is about the different N2/NH3 proportion of plasma, and observes the effects of porous low dielectric properties, electrical properties and the reliability. The experimental results show that all modifications of thickness on the surface are close after five different proportions of N2/NH3 plasma treatment. The mechanical strength and hardness have similar values. The Si-N and C-N bond on surface increases after using pure N2 and pure NH3 plasma, and the pure N2 plasma have most Si-N and C-N bond, thereby affecting its properties, such as the etching rate. The leakage current and dielectric constant increases on the electrical properties. The hydrophobicity decreases as the proportion of NH3 increases, thus making the electrical properties get worse, and the dielectric constant increased, also with the worse reliability. The electrical properties and reliability present worse trend as the proportion of NH3 increases among the different of N2/NH3 proportion plasma.
The third part of the thesis is about different conditions of N2/H2 plasma treatment and adds bias during plasma.It was found that pure H2 plasma would make the properties of low dielectric film worse such as the etching rate by HF, and because of its worse hydrophobic, so that leakage current increases rapidly, also leading dielectric constant to increase, even making reliability worse. While pure H2 plasma mixed with N2, it can improve its characteristics such as: the etching rate, the hydrophobic properties, dielectric constant, and it also can improve electrical properties, for example, the leakage current decreases and reliability increases. Further, when the plasma treatment adding a positive bias suppresses positive ions, so that positive ions in the plasma processes do not work, but only the electrons react in the plasma processes so that the impact by plasma becomes smaller, and resulting in the properties, electrical properties and the reliability of N2/H2 plasma are improved.

並列關鍵字

low-k ； plasma ； H2/He ； standard plasma ； remote plasma ； reliability ； N2/NH3 ； N2/H2 ； positive bias

參考文獻

參考文獻

[1] T. C. Chang, Y. J. Mei, H. S. Chang, S. J. Chang, W. F. Wu, F. M. Pan, B. T. Dai, M. S. K. Chen, A. Tnang, and C. Y. Chang, VLSI Multilevel Interconnection Conference (1997) 695.

[2] Y. J. Mei, T. C. Chang, S. J. Chang, and C. Y. Chang, Thin Solid Films 501 (1997) 308.

[3] T. C. Chang, Y. J. Mei Y. L. Lin, S. J. Chang, C. Y. Cbang, W. Lur, F. Y. Shih, and H. D. Huang, Dielectric for ULSI Multilevel Interconnection Conference (1997) 337.

[4] Web.it.nctu.edu.tw/~FMPANLAB/LowK.htm‎