Effect of Hydrogen Annealing on the Property of Low-temperature Epitaxial Growth of Sige Thin Films on Si Substrate

doi:10.15541/jim20160247

Abstract

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

CLC Number:

TQ174

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.

Figures/Tables 7

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

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

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

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

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

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

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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