鉬金屬閘極金氧半元件之電性研究

Investigation of electrical characteristics for MOS devices with Molybdenum metal gate

簡伯諺(Po-Yen Chien)

指導教授 ： 張廖貴術

國立清華大學/原子科學院/工程與系統科學系/碩士(2007年)

摘要

傳統電晶體製程使用多晶矽當作閘極材料已經行之多年。然而，由於通道長度跟閘極界電層的厚度快速的微縮，多晶矽的使用已經面臨了許多問題。例如:閘極空乏區的產生，較高的閘極片電阻，較大的閘極穿遂電流以及在製作時，硼離子穿透到通道的可能性大增。因此，使用金屬閘極與高介電常數的介電層取代多晶矽與矽氧化層已經成為不可避免的趨勢。
在這篇論文裡頭，我們製作了一個具有高功函數且可接受的電性的金屬閘極，在考慮到所有電性之下，我們發現氮化鉬(2.4)擁有較好的電性與較高的功函數，例如在遲滯現象，電應力引起的漏電流上升，電應力引起的平帶電壓偏移都有較佳的表現。
除此之外，氮化鈦插入氮化鉬的上層與下層組成不同的金屬閘極堆疊也被拿來討論。而我們發現，將氮化鈦插入氮化鉬的下層能夠有效的改善所有的電性能力，即使這樣子堆疊之後，功函數有下降一點的趨勢。這結果代表的是，將氮化鈦插入氮化鉬的下面比插入上面要來的好，並且可以當作一個讓P型金氧半電晶體使用的金屬閘極。
最後，金屬閘極與高介電常數介電層的組合也被拿來討論。我們採用氮化鈦插入氮化鉬下面的金屬堆疊當作金屬閘極，常見的氮氧化鉿當作高介電常數介電層，一起組合起來探討其電性與熱穩定性的好壞。而實驗結果發現，這樣的搭配擁有小的等效氧化層厚度與可接受的電性能力，除此之外，也能達到可接受的熱穩定性。

關鍵字

鉬 ； 金屬閘極

並列摘要

Traditional transistor processes use poly-Si as gate material for decades. However, aggressive scaling of channel length and gate oxide thickness in a conventional transistor aggravates the problems of poly-silicon (poly-Si) gate depletion, high gate resistance, high gate tunneling leakage current, and boron penetration into the channel region. As a result, there is immense interest in metal gates and alternative gate dielectrics with higher permittivity.
In this work we developed a good metal gate with high work function and acceptable electrical characteristics. By considering all the electrical characteristics, we find that Mo0.9N0.1 (=MoN(2.4)) shows higher work function and better electrical characteristics such as hysteresis, SILC, stress induced charge trapping.
Moreover, the differences of MoN metal gate inserting TiN layer in different position were compared. Metal gate with MoN/TiN film exhibits better performance for all the electrical characteristics despite a little lower WF. The results show that MoN/TiN metal gate electrode is better than TiN/MoN metal one and it can be a promising candidate for MOS device applications.
Finally, the integration of metal gate and high-k dielectric was investigated. MoN/TiN and HfOxNy were selected as the metal gate and gate dielectric candidates to study the electrical characteristics and thermal stability. The experimental results show that thin EOT and acceptable electrical characteristics are observed in MoN/TiN/HfOxNy MOS device. Furthermore, acceptable thermal stability is also achieved.

參考文獻

[2] You-Seok Suh et al., Electrical Characteristics of TaSixNy Gate Electrodes For Dual Gate Si-CMOS Devices 2001, Symposium on VLSl Technology Digest of Technical Papers p.47

[3] L. Chang et al., 2000, “Gate length scaling and threshold voltage control of double-gate MOSFETs,” in IEDM Tech. Dig., pp. 719–722

[8] P. Ranade et al., 2002, “Tunable work function molybdenum gate technology for FDSOI-CMOS,” in IEDM Tech. Dig., pp. 363–366

[9] Tzung-Lin Li et al., June, 2005, Continuous and Precise Work Function Adjustment for Integratable Dual Metal Gate CMOS Technology Using Hf–Mo Binary Alloys IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 52, NO. 6

[10] You-Seok Suh et al., JULY 2003, “Effect of the Composition on the Electrical Properties of TaSixNy Metal Gate Electrodes” IEEE ELECTRON DEVICE LETTERS, VOL. 24, NO. 7