High-k堆疊MOSFETs於不同氮濃度和退火溫度下之BTI可靠度研究

近年來，退火製程中將氮(N)與二氧化鉿(HfO2)閘極介電層結合，也大量的被應用在新世代的MOSFET上，因為其可減少等效氧化層厚度、改善崩潰特性和增加熱穩定性。但卻鮮少有探討去耦合電漿氮化(DPN)退火對閘極介電層之基本電性及負偏壓溫度不穩定性(NBTI)的影響，因此，這也就是本論文要研究的重點。實驗元件是聯華電子所提供28奈米製程的p型電晶體（pMOSFET），氧化鋯鉿(HfZrOx)介電層的製作方式是由原子層沉積技術(ALD)完成。實驗考慮的製程參數為不同退火溫度和氮的含量。量測時使用不同的溫度和電壓來做對比，再依據所得資料，進行統計、分析實驗結果與電壓的關係，且探討不同退火溫度與含氮量之間的差異。研究結果顯示，退火溫度最高(900℃)8%含氮量的電晶體，由於高溫修補了介電層中的缺陷，使得汲極電流是最高的。而在NBTI的加壓測試條件下，高溫的環境使其劣化程度明顯比低溫時嚴重。此外，不論在高溫或低溫，或是不同大小的負偏壓之下，8%含氮量、700℃退火的電晶體，其劣化程度是最小的。而上述起始特性最好的8%含氮量、900℃退火之電晶體，其可靠度明顯較差。

關鍵字

二氧化鉿(HfO2) ；去耦合電漿氮化(DPN) ；負偏壓溫度不穩定性(NBTI) ；氧化鋯鉿(HfZrOx) ；原子層沉積技術(ALD)

並列摘要

Recently, the incorporation of nitrogen (N) in HfO2 gate dielectrics in the annealing process has heavily applied in the advanced MOSFETs because of decreasing equivalent oxide thickness (EOT), improving the breakdown characteristics, and increasing thermal stability. However, only few literatures concerned about negative BTI with decoupled plasma nitridation (DPN) process. Hence, this study is focused on this subject. The experimental devices were fabricated from 28nm node high performance logic technology of United Micro-electronics Corporation (UMC). The process of HfZrOx dielectric layer was deposited by atomic layer deposition (ALD). The wafers were then annealed with different annealing temperatures and nitrogen concentrations after ALD. In this research, the different experimental temperatures and stress voltages are included in the experiment. Consequently experimental data are used to figure out the dependence of degradation on stress voltage, and to determine the difference of four kinds of wafers. The experimental results of this work indicated that the pMOSFETs under the highest annealing temperatures (900℃) have the largest drain current because of the high annealing temperatures may repair defects in the gate dielectrics. After the NBTI stress, the degradation at those high experimental temperatures reveal larger than that at low experimental temperatures. Moreover, no matter what in high or low temperature, or under different negative bias is, the pMOSFETs with 8% nitrogen 700℃ annealed conditions exhibit the minimal degradation. However, even if the pMOSFETs with 8% nitrogen 900℃ have the best initial performance, but they have worse reliability than other devices.

並列關鍵字

HfO2 ； Decoupled plasma nitridation (DPN) ； Negative bias temperature instability (NBTI) ； HfZrOx ； ALD

參考文獻

[1] J. Robertson, “Electronic structure and band offsets of high-dielectric-constant gate oxides,” Mater. Research Soc., vol. 27, pp. 217-221, 2002.

[2] D. G. Schlom and J. H. Haeni, “A thermodynamic approach to selecting alternative gate dielectrics,” Mater. Research Soc., vol. 27, pp. 198, 2002.

[3] J. Robertson, “Band offsets of wide-band-gap oxides and implications for future electronic devices,” J. Vac. Sci. Technol. B, vol. 18, pp. 1785-1791, 2000.

[4] M. Jo, H. Park, J.-M. Lee et al., “Effect of oxygen postdeposition annealing on bias temperature instability of hafnium silicate MOSFET,” IEEE Electron Device Lett., vol. 29, no. 4, pp. 399-401, 2008.

[5] A. Kerber, E. Cartier, L. Pantisano et al., “Characterization of the Vt -instability in SiO2/HfO2 gate dielectrics,” Proc. IRPS, pp.41-45, 2003.

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High-k堆疊MOSFETs於不同氮濃度和退火溫度下之BTI可靠度研究

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