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研究生：	施佳男 Shih, Jia-Nan
論文名稱：	不同退火方式對N型金氧半電容之電性及微結構影響 Effect of various annealing methods on electrical properties and microstructure for N-type metal-insulator-semiconductor capacitors
指導教授：	李文熙 Lee, Wen-Hsi
學位類別：	碩士 Master
系所名稱：	電機資訊學院 - 電機工程學系 Department of Electrical Engineering
論文出版年：	2015
畢業學年度：	103
語文別：	英文
論文頁數：	119
中文關鍵詞：	金屬閘極、高介電常數、微波退火、飛秒雷射退火
外文關鍵詞：	metal gate, high-κ, microwave annealing, femtosecond laser annealing
相關次數：	點閱：138 下載：5
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在高效能積體電路的應用上，金氧半場效電晶體扮演著舉足輕重的角色，原因是因為其本身的低製造成本、低消耗功率以及可微縮的優點。半導體元件為了滿足時代的進展，互補式金氧半電容的厚度不斷微縮，然而當傳統氧化層微縮到1.5nm以下時，穿隧漏電流將會明顯增大進而導致元件的功率消耗過大。因此，具高介電係數的氧化層材料被提出用以替換傳統的二氧化矽降低漏電流
在眾多被研究高介電材料中，二氧化鉿被認為是很有潛力的高介電材料，然而多晶矽閘極搭配高介電材料，已被發現會有熱穩定性不佳的缺點，同時介面也存在著費米能接夾止效應，因此，金屬閘極製程不僅可以克服上述的缺點也可以降低閘極電阻值以及防止多晶矽的空乏效應進而提元件效能。
然而，大多的高介電常數材料相較於傳統的二氧化矽具有更多的介面態密度以及在高溫退火後會產生更厚的界面層以及大量的平帶電壓偏移，因此，降低熱預算並且能有效修復高介電常數材料的缺陷是一個重要的課題。
根據以上所提，本實驗分別以TiN/Al/TiN/HfO2/Si substrate MOS-Cap與TiN/Ti/TiN/HfO2/Si substrate MOS-Cap分別經過不同參數的微波、飛秒雷射與RTA金屬沉積後退火的處理。並分別在物性及電性方面做分析比較。
經RTA 400˚C退火後的試片，EOT會降低進而提升閘極氧化層電容值，並且介面態密度及氧化層捕捉電荷密度能有明顯的減少，但因為鋁的擴散而導致漏電流提升、崩潰電壓降低以及大量的平帶電壓偏移。然而經過適當的飛秒雷射退火的試片，幾乎沒有擴散問題的產生，平帶電壓及EOT也幾乎不變，但介面態密度及氧化層捕捉電荷密度能有些許的降低進而些許降低漏電流與提升崩潰電壓。此外，經過微波退火 2700W的試片可以獲得最低的EOT、介面態密度以及氧化層捕捉電荷密度並且只有些許的鋁或鈦擴散因而得到高閘極氧化層電容值、高崩潰電壓以及低漏電流。

For the high performance integrated circuits applications such as microprocessors, memories and high power devices, the metal-oxide-semiconductor field effect transistors (MOSFETs) are the most important device because of its low cost, power consumption and scalable property especially. In order to meet the progress of the times, the shrinkage of equivalent oxide thickness (EOT) of semiconductor device is requested in CMOS. However, when SiO2 is scale down to 1.5nm and below, the tunneling current becomes quite significant, resulting in large gate leakage current and higher power consumption.
High-κ dielectric is proposed to replace SiO2 for reducing the gate leakage current, especially HfO2. Unfortunately, polysilicon gates have been reported to be thermodynamically unstable on many high-κ materials and lead to Fermi-level pinning effect at the polysilicon/ high-κ interface. Therefore, metal gates are expected to provide a turning point in possessing a better thermal stability and retardation of the Fermi-level pinning effect. In addition, metal gates can possess a lower gate resistance and retardation of depletion effect to increase the performance of devices.
This study investigated the analysis of electrical characteristics and physical properties of TiN/Al/TiN/HfO2/Si and TiN/Ti/TiN/HfO2/Si structures with microwave anneal (MWA), femtosecond laser anneal (FLA) and rapid thermal anneal (RTA) for post-metal annealing respectively.
The sample annealed by RTA at 400˚C could lower the EOT and get larger gate oxide capacitance. Interface states density and oxide trapped charge density could also be lowered. But the diffusion of Al or Ti into oxide films occurred evidently. These results make leakage current larger, breakdown voltage lower and shift of flat band voltage large. However, there are no phenomenon of diffusion of Al or Ti into oxides films, no change of EOT and no shift of flat band voltage for the samples annealed by FLA. But interface states density and oxide trapped charge density could be lowered slightly. These results make leakage current slightly lower and breakdown voltage slightly larger. Besides, the sample annealed by MWA at 2700W could get the lowest EOT, interface states density and oxide trapped charge density. And the diffusion of Al or Ti into oxides films is really slight. Therefore, the high gate oxide capacitance, high breakdown voltage and low leakage current can be obtained.

Chapter 1	Introduction	........1
1-1	Background	............1
1-1-1	Aggressively scaling of silicon based CMOS devices	................1
1-1-2	The requirement of high-κ materials	....3
1-1-3	The emergence of metal gate	......4
1-2	Introduction to CMOS processing	......6
1-2-1	Gate-first integration scheme	......6
1-2-2	Gate-last integration scheme	......8
1-3	Issues of high-κ material	.....10
1-3-1	Flat-band voltage shift during thermal process	...................10
1-3-2	Interfacial layer growth during thermal process	...................10
1-3-3	Crystallization during thermal process	...12
1-3-4	Higher density of interface states	...12
1-3-5	Reliability	...........12
1-4	Motivation	...........13
Chapter 2	Theory	...........15
2-1	Ideal MOS behavior	.........15
2-2	Gate oxide charge	.........21
2-2-1	Fixed Charge	...........22
2-2-2	Mobile ion charge	.........22
2-2-3	Oxide-trapped charge	.........23
2-2-4	Interface trapped charge	.....23
2-3	Novel annealing techniques	.....25
2-3-1	Fundamentals of microwave annealing	...25
2-3-2	Fundamentals of femtosecond laser technique	...................32
Chapter 3	Experimental Procedure	.....36
3-1	Fabrication process of MIS capacitor	...36
3-1-1	Clean substrate and grow sacrifical oxide	...................36
3-1-2	Grow chemical oxide layer	.....36
3-1-3	High-κ dielectric deposited by MOCVD	...36
3-1-4	Metal gate films deposited by PVD	...37
3-1-5	Lithography and etching steps	.....37
3-2	Post-metal annealing	.........40
3-2-1	Parameters of rapid thermal annealing	...41
3-2-2	Parameters of microwave annealing	...42
3-2-3	Parameters of femtosecond laser annealing	...................43
3-3	Electrical measurements	.........43
3-3-1	C-V and G-V measurement	.........44
3-3-2	I-V measurement	...........44
3-4	Physical measurements	.........44
Chapter 4	The Analysis of TiN/Al/TiN/HfO2/Si MOS Capacitors	.............45
4-1	The samples annealed by RTA	.....45
4-1-1	Variety of Cox and EOT after RTA	...45
4-1-2	Shift of flat band voltage after RTA	...50
4-1-3	Decrease of interface states after RTA	...54
4-1-4	Study of hysteresis and oxide trapped charge after RTA	.............57
4-1-5	Leakage current of the samples annealed by RTA	...................59
4-1-6	Breakdown voltage of the samples annealed by RTA	...................60
4-2	The samples annealed by FLA	.....61
4-2-1	Variety of Cox and EOT after FLA	...61
4-2-2	Shift of flat band voltage after FLA	...65
4-2-3	Decrease of interface states after FLA	...66
4-2-4	Study of hysteresis and oxide trapped charge after FLA	.............67
4-2-5	Leakage current of the samples annealed by FLA	...................68
4-2-6	Breakdown voltage of the samples annealed by FLA	...................69
4-3	The samples annealed by MWA	.....71
4-3-1	Variety of Cox and EOT after MWA	...71
4-3-2	Shift of flat band voltage after MWA	...76
4-3-3	Decrease of interface states after MWA	...79
4-3-4	Study of hysteresis and oxide trapped charge after MWA	.............80
4-3-5	Leakage current of the samples annealed by MWA	...................81
4-3-6	Breakdown voltage of the samples annealed by MWA	...................83
4-4	Summary	.............85
Chapter 5	The Analysis of TiN/Ti/TiN/HfO2/Si MOS Capacitors	.............86
5-1	The samples annealed by RTA	.....86
5-1-1	Variety of Cox after RTA	.....86
5-1-2	Shift of flat band voltage after RTA	...87
5-1-3	Decrease of interface states after RTA	...88
5-1-4	Study of hysteresis and oxide trapped charge after RTA	.............89
5-1-5	Leakage current of the samples annealed by RTA	...................90
5-1-6	Breakdown voltage of the samples annealed by RTA	...................91
5-2	The samples annealed by FLA	.....93
5-2-1	Variety of Cox after FLA	.....93
5-2-2	Shift of flat band voltage after FLA	...94
5-2-3	Decrease of interface states after FLA	...95
5-2-4	Study of hysteresis and oxide trapped charge after FLA	.............96
5-2-5	Leakage current of the samples annealed by FLA	...................97
5-2-6	Breakdown voltage of the samples annealed by FLA	...................98
5-3	The samples annealed by FLA	.....99
5-3-1	Variety of Cox after MWA	.....99
5-3-2	Shift of flat band voltage after MWA	..100
5-3-3	Decrease of interface states after MWA	..101
5-3-4	Study of hysteresis and oxide trapped charge after MWA	..............102
5-3-5	Leakage current of the samples annealed by MWA	..................104
5-3-6	Breakdown voltage of the samples annealed by MWA	..................106
5-4	Summary	..............108
Chapter 6	Conclusions	........109
6-1	Main results obtained from this study	..109
6-2	Future work	..........112
Reference	..............113
                                    

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