疊形複晶矽結構在閘極氧化層與金屬矽化物之可靠度研究

Abstract

本論文中，首先我們探討影響金屬矽化物在複晶矽薄膜上熱穩定性的原因。我們量測不同高溫快速退火溫度下金屬矽化物之片電阻以探討其熱穩定性，同時也輔以X射線繞射圖來分辨所形成金屬矽化物的相。實驗結果顯示，金屬矽化物底下的複晶矽薄膜之厚度、微結構、疊形結構和植入離子的種類對其熱穩定性有很大的影響。當金屬矽化物長在比較厚的複晶矽薄膜時，它發生聚合的溫度會比較早，而對金屬矽化物底下的矽基底快速高溫退火亦能有較佳的熱穩定性，此外，疊形複晶矽結構可以抑制二矽化鎳的聚合。 其次我們把金屬矽化物的物性分析上所得到的結果應用在電性分析，所以我們將N型與P型的金氧半電容的閘極用矽烷、二矽烷的複晶矽與矽烷的非晶矽來組成。實驗結果顯示．雖然長在矽烷複晶矽上的二矽化鈷之熱穩定性會比較差，可是具矽烷複晶矽閘極與二矽化鈷電極之金氧半電容卻有比較好的電性；此外，對於長在P型非晶矽的矽化鎳，它的熱穩定性比較差，而在電性上我們發現具非晶矽閘極與矽化鎳電極之P型金氧半電容有比較差的電性。最後我們將疊形複晶矽結構應用在電容的閘極，來探討其對氧化層的可靠度之影響，我們發現使用疊形複晶矽閘極的鋁電極電容比一般矽烷成長的複晶矽閘極電容有更大的崩潰電場、更小的電子補抓率、與更大的崩潰電荷，而對於使用疊形複晶矽閘極的二矽化鈷與矽化鎳電極之電容，即使分別經過30秒950℃ 與 800℃的金屬矽化過程，其氧化層仍保有良好的可靠度，不若傳統的閘極氧化層有極嚴重的劣化現象。

In this thesis, we have first presented a systematic study of the physics characteristics of Ni- and Co-silicides formed on different Si substrates to recognize the effects on the thermal stability. The four point probe was used to measure the sheet resistance of Ni- and Co-silicides with various silicidation temperatures. The X-ray diffraction (XRD) was carried out for phase identification. We have found that the thermal stability of the silicide is affected by thickness, microstructure, and dopant type of the underlying poly-Si film. Additionally, the stacked poly-Si film structures are found to have better thermal stability. NiSi and CoSi2 formed on a thinner poly-Si film can improve the thermal stability. The thermal annealing also has influences on the thermal stability and the morphological changes of the Ni-silicide regardless the dopant type in the underlying poly-Si film. Moreover, the stacked poly-Si sample can suppress the agglomeration of NiSi2 formed on undoped Si substrates with 950℃ recrystallization. The transmission electron microscopy (TEM) micrographs reveal that the bottom poly-Si film is still in good shape, but the Ni-silicide layer is discontinuous and broken up into isolated islands at the top poly-Si film. Secondly, we proposed disilane-silane (DS), and disilane-amorphous (DA) stacked poly-Si gate to improve the gate oxide reliability. For capacitors with Al gate electrode, capacitors with the stacked poly-Si gate have better electrical characteristics, such as higher dielectric breakdown field (Ebd), smaller electron trapping rate, and higher charge to breakdown (Qbd). For capacitors with the gate electrode of CoSi2 and NiSi, even though after 950℃ and 800℃ silicidation for 30s respectively, the capacitors with the stacked poly-Si gate were still highly reliable while the conventional one was degraded seriously. Abstract (in English)………………………………………………iii Acknowledgement……………………………………………………………v Contents……………………………………………………………………vi Table Captions ……………………………………………………………x Figure Captions………………………………………………………… xi Chapter1 Introduction 1-1 Motivation…………………………………………………………… 1 1-2 Thesis Outline……………………………………………………… 2 1-3 Mechanism of Silicidation on the Polycrystalline Silicon (Poly-Si)……………………………………………………………………3 Chapter2 Effects of Thickness of the Underlying Poly-Si Film on the Thermal Stability of Ni- and Co-Silicides 2-1 Introduction………………………………………………………… 6 2-2 Experimental Procedures……………………………………………7 2-3 Results and Discussions……………………………………………8 2-3-1 Thermal Stability of Ni-Silicide…………………………… 8 2-3-1-1 Sheet Resistance Versus RTA Temperature…………………8 2-3-1-2 X-Ray Diffraction (XRD) Spectra……………………………9 2-3-2 Thermal Stability of Co-Silicide…………………………… 9 2-3-2-1 Sheet Resistance Versus RTA Temperature…………………9 2-3-2-2 X-Ray Diffraction (XRD) Spectra……………………………10 2-4 Conclusions……………………………………………………………10 Chapter3 Effects of Microstructure of the Underlying Si Substrates on the Thermal Stability of Ni- and Co-Silicides 3-1 Introduction………………………………………………………… 17 3-2 Thermal Stability of Ni-Silicide……………………………… 18 3-2-1 Experimental Procedures…………………………………………18 3-2-2 Results and Discussions…………………………………………19 3-2-2-1 Effects on the Thermal Annealing………………………… 19 3-2-2-2 X-Ray Diffraction (XRD) Spectra……………………………21 3-2-3 Summary………………………………………………………………21 3-3 Thermal Stability of Co-Silicide ………………………………22 3-3-1 Experimental Procedures…………………………………………22 3-3-2 Results and Discussions…………………………………………23 3-3-2-1 Sheet Resistance Versus RTA Temperature…………………23 3-3-2-2 X-Ray Diffraction (XRD) Spectra……………………………25 3-3-3 Summary………………………………………………………………26 3-4 Conclusions……………………………………………………………27 Chpater4 Effects of Stacked Structure of the Underlying Poly-Si Films on the Thermal Stability of Ni- and Co-Silicides 4-1 Introduction………………………………………………………… 39 4-2 Thermal Stability of Ni-Silicide……………………………… 39 4-2-1 Experimental Procedures…………………………………………39 4-2-2 Results and Discussions…………………………………………40 4-2-2-1 Sheet Resistance Versus RTA Temperature…………………40 4-2-2-2 Transmission Electron Microscopy (TEM) Micrographs… 42 4-2-2-3 Secondary Ion Mass Spectroscopy (SIMS) Profiles………42 4-2-3 Summary………………………………………………………………43 4-3 Thermal Stability of Co-Silicide……………………………… 43 4-3-1 Experimental Procedures…………………………………………43 4-3-2 Results and Discussions…………………………………………44 4-3-3 Summary………………………………………………………………45 4-4 Conclusions……………………………………………………………45 Chapter5 Electrical Characteristics of the MOS Capacitors Using Different Stacked Structures of Poly-Si Gate with Al as Gate Electrode 5-1 Introduction………………………………………………………… 56 5-2 Experimental Procedures……………………………………………56 5-3 Results and Discussions……………………………………………57 5-3-1 C-V Characteristics………………………………………………57 5-3-2 J-E Characteristics………………………………………………59 5-3-3 Gate Voltage Shift……………………………………………… 59 5-3-4 Charge to Breakdown………………………………………………60 5-3-5 Measurement of Thin Film Stress………………………………60 5-4 Conclusions……………………………………………………………60 Chapter6 Electrical Characteristics of the MOS Capacitors Using Different Stacked Structures of Poly-Si Gate with Co-Silicide as Gate Electrode 6-1 Introduction………………………………………………………… 70 6-2 Experimental Procedures……………………………………………71 6-3 Results and Discussions……………………………………………72 6-3-1 C-V Characteristics………………………………………………72 6-3-2 J-E Characteristics………………………………………………74 6-3-3 Gate Voltage Shift……………………………………………… 75 6-3-4 Charge to Breakdown………………………………………………76 6-4 Conclusions……………………………………………………………78 Chapter7 Electrical Characteristics of the MOS Capacitors Using Different Stacked Structures of Poly-Si Gate with Ni-Silicide as Gate Electrode 7-1 Introduction…………………………………………………………121 7-2 Experimental Procedures………………………………………… 122 7-3 Results and Discussions………………………………………… 123 7-3-1 C-V Characteristics…………………………………………… 123 7-3-2 J-E Characteristics…………………………………………… 124 7-3-3 Gate Voltage Shift………………………………………………125 7-3-4 Charge to Breakdown…………………………………………… 126 7-4 Conclusions………………………………………………………… 127 Chapter8 Conclusions……………………………………………………………… 167 References…………………………………………………………………170 Vita…………………………………………………………………………174