氢气氛退火对硅上低温外延制备的硅锗薄膜性能的影响

doi:10.15541/jim20160247

摘要/Abstract

摘要：

采用反应型热化学气相沉积系统在硅(100)衬底上外延生长富锗硅锗薄膜。四氟化锗作为锗源, 乙硅烷作为还原性气体。通过设计表面反应, 在低温条件下(350℃)制备了高质量的富锗硅锗薄膜。研究了氢退火对低温硅锗外延薄膜微结构和电学性能的影响。结果发现退火温度高于700℃时, 外延薄膜的表面形貌随着退火温度的升高迅速恶化。当退火温度为650℃时, 获得了最佳的退火效果。在该退火条件下, 外延薄膜的螺旋位错密度从3.7×10⁶ cm^-2下降到4.3×10⁵ cm^-2, 表面粗糙度从1.27 nm下降到1.18 nm, 而外延薄膜的结晶质量也有效提高。霍尔效应测试表明, 经退火处理的样品载流子迁移率明显提高。这些结果表明, 经过氢退火处理后, 反应型热化学气相沉积制备的低温硅锗外延薄膜可以获得与高温下硅锗外延薄膜相比拟的性能。

关键词: 硅锗薄膜, 低温外延, 氢退火, 螺旋位错

Abstract:

Ge-rich SiGe thin films were epitaxially grown on Si (100) substrate by reactive thermal chemical vapor deposition. Germanium tetrafluoride (GeF₄) was selected as the Ge source material and disilane (Si₂H₆) is used as the reductant gas. By designing the surface reaction, high quality Ge-rich Si_1-_xGe_x epilayers were prepared under low temperature (350℃) conditions. Effect of hydrogen annealing on the microstructure and electrical property was studied. The results reveal that the surface morphology of SiGe epilayer deteriorates drastically if the annealing temperature is higher than 700℃. The optimal annealing temperature is found to be 650℃. Under this condition, the threading dislocation density decreases from 3.7×10⁶ cm^-2 to 4.3×10⁵ cm^-2 and the surface root mean square roughness is also slightly decreased from 1.27 nm to 1.18 nm. Simultaneously, the crystalline quality of the SiGe epilayers is effectively improved. Carrier mobility of the annealed samples, measured by Hall-effect equipment, is enhanced obviously as compared to that of the as-deposited samples. These results suggest that the properties of the annealed SiGe thin films, epitaxially grown by reactive thermal chemical vapor deposition at low-temperature, can be comparable to those of SiGe epilayers grown by high-temperature techniques.

Key words: silicon germanium, low-temperature epitaxy, hydrogen annealing, threading dislocation density

中图分类号:

TQ174

王锦, 陶科, 李国峰, 梁科, 蔡宏琨. 氢气氛退火对硅上低温外延制备的硅锗薄膜性能的影响[J]. 无机材料学报, 2017, 32(2): 191-196.

WANG Jin, TAO Ke, LI Guo-Feng, LIANG Ke, CAI Hong-Kun. Effect of Hydrogen Annealing on the Property of Low-temperature Epitaxial Growth of Sige Thin Films on Si Substrate[J]. Journal of Inorganic Materials, 2017, 32(2): 191-196.

图/表 7

图1 硅锗外延薄膜的断面透射电镜照片(a)及样品不同深度的电子衍射谱(b~d)

Fig. 1 (a) Cross-sectional TEM image of epitaxial SiGe films on silicon substrate, (b)-(d) electron diffraction patterns for Si substrate, SiGe/Si interface and SiGe epilayer (e) which extracted from (d) for calculation The red circles mark the position for measurement of electron diffraction patterns

图2 经不同温度退火后硅锗外延薄膜表面的SEM照片

Fig. 2 SEM images of SiGe epilayers annealed at different temperatures(a) 650℃; (b) 700℃; (c) 750℃

图3 经不同温度退火处理后硅锗外延薄膜由TOF-SIMS测得的离子组分深度分布

Fig. 3 Composition depth profile of ions detected by TOF-SIMS measurement from epitaxial SiGe films annealed at different temperatures

图4 未经退火处理和经退火处理的硅锗外延薄膜的Raman谱图

Fig. 4 Raman spectra of epitaxial SiGe films with or without postannealing

图5 硅锗外延薄膜经选择性湿法腐蚀后的表面扫描电镜照片

Fig. 5 SEM images of SiGe films after a selective wet etch, and pits with reversed pyramidal structure exhibited on the surface(a) As-deposited sample; (b) 650℃-annealed sample

表1 由霍尔仪测得的硅锗外延薄膜的电学性能(膜厚900 nm)

Table 1 Electrical properties of SiGe thin films by Hall-effect measurement

Si_xGe_1-_x	Resistance /(Ω·cm)	Carrier concentration/cm^-3	Mobility/ (cm²·V^-1·s^-1)
As-grown	0.402	6.35×10¹⁶	244
Annealed	1.470	1.07×10¹⁶	409

表2 文献中报道的采用低温/高温法制备的锗外延薄膜的性能参数

Table 2 Summary of the process parameters and film quality from literatures which reported the epitaxial growth of Ge by using low temperature/high temperature method

Ref.		Temp./℃	Thickness /nm	RMS roughness/nm		TDD/cm^-2		Mobility/(cm²·V^-1·s^-1)
Ref.		Temp./℃	Thickness /nm	As-grown	Annealed	As-grown	Annealed	Annealed
[21]	LT	400	1224	0.40	0.7	1.70×10⁸	1.00×10⁷	NA
[21]	HT	670	1224	0.40	0.7	1.70×10⁸	1.00×10⁷	NA
[22]	LT	350	50	0.70	NA	5.00×10⁵	NA	550
[22]	HT	600	300	0.70	NA	5.00×10⁵	NA	550
[23]	LT	335	2000	0.60	1.6	NA	2.00×10⁷	NA
[23]	HT	670	2000	0.60	1.6	NA	2.00×10⁷	NA
[24]	LT	400	2500	1.20	1.0	NA	6.00×10⁶	NA
[24]	HT	750	2500	1.20	1.0	NA	6.00×10⁶	NA
[25]	LT	400	980	3.19	0.9	NA	6.00×10⁶	NA
[25]	HT	670	980	3.19	0.9	NA	6.00×10⁶	NA

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