液相沈積絕緣膜之電漿處理效應

Abstract

沈積一薄層的液相沈積氧化膜在MSQ膜上，可以阻擋光阻去除時MSQ膜的被破壞，並減低水氣的吸附，以及強化MSQ膜與銅導線間的附著力。 在本研究中，為了在MSQ膜上沈積我們的液相沈積氧化膜，我們採用了氫氣電漿處理。此外，氫氣電漿處理MSQ膜可以不改變其介電常數並改善其漏電流。雖然，氫氣電漿處理MSQ膜然後覆蓋液相沈積氧化膜將稍微增加其漏電流，但是隨著氫氣電漿處理越久其不佳的效應就越小。再著，我們發現其液相沈積膜沈積在MSQ膜上的潛伏不成長的時間(incubation time)隨著氫氣電漿處理時間越久而越長，但其的沈積速率卻大致相同，為此，根據二次離子質譜儀(SIMS)與沈積厚度的相對時間表，我們試著建立其機制解釋的模型。依本研究的結論，10分鐘的氫氣電漿是最佳的處理條件。 為了再改善經過一氧化二氮(N2O)電漿處理液相沈積氧化膜後，其薄膜的電氣特性。因此，第一次，我們研究經過兩階段一氧化二氮(N2O)電漿後液相沈積氧化膜的電氣特性。由C-V圖，我們明顯地發現這些試片的平帶電壓(flat-band voltage)不是偏移至左邊就是右邊，為此，試著提出機制解釋，並發現左偏移量大於右偏移量。由J-E圖，因為氮原子結合(nitrogen incorporation)在矽基板與二氧化矽膜之交界面與再氧化的反應能夠降低其漏電流。意即，第一階段時液相沈積氧化膜厚度要薄，其漏電流將明顯地降低。 附帶地，為了沈積出高品質的液相沈積氧化膜，我們採用了來自日本的新二氧化矽粉末與新六氟矽酸溶液，它們的雜質含量更少。與我們的預期相同，採用相同的新六氟矽酸溶液的條件下，新粉末沈積出的液相沈積氧化膜比使用舊粉末有低於2個等級(order)的漏電流密度，達到2x10-9 A/cm2。此外，它的崩潰電場小幅增加，沈積厚度的均勻性佳，約2％的差距，而其介電常數3.3。

To reduce the probability of moisture uptake and to strength the adhesion between MSQ/liner-LPD and copper, the improvement of liner LPD-SiO2 deposited on MSQ is studied. In this work, to make LPD-SiO2 deposited on MSQ film, we adopted H2 plasma treatment on MSQ. In addition, H2 plasma treatment can improve MSQ leakage current but dielectric constant invariant. Although LPD deposition after H2 plasma can make leakage current slightly increase, however the increase can be reduced if the time of plasma treatment is long enough. Besides, LPD-SiO2 incubation time also increases as H2 plasma treatment time increases. However the deposition rate is almost independent of plasma treatment. We have proposed a model to explain the phenomenon about incubation time according to the results of SIMS spectra and LPD deposition-rate graph. Conclusively, 10min H2 plasma is the best condition in this work. To further improve the performance of LPD-SiO2 with N2O plasma, at the first time, we investigated two-steps N2O plasma. From the C-V curves, we obviously found that the flat-band voltage of these samples shifts to either left or right. And we have tried to introduce two mechanisms about the flat-band voltage shift. However, the amount of left-shift for the first mechanism is larger than that of right-shift for the second. From the leakage current (J-E) curves, we found the better improvement of LPD-SiO2 with two-steps N2O plasma. Nitrogen incorporation at Si/LPD-SiO2 interface and reoxidation reaction can make leakage current decrease. As the thickness of LPD-SiO2 in the first-step N2O plasma decreases, the leakage current density obviously decreases. In addition, to deposit high quality LPD oxide film, we adopted new SiO2 powder & new H2SiF6 liquids with less impurity. Under the condition of new H2SiF6 liquids, the leakage current density of LPD-SiO2 prepared with new SiO2 powder at E=2MV/cm is 2x10-9 A/cm2, and approximately two orders lower than that with old SiO2 powder. The breakdown field is also slightly high. The uniformity of deposition thickness is about ~2%, and the dielectric constant value is ~3.3.