晶体生长中的缺陷消除_图文

1、State Key Lab of Silicon Material Science Crystal Growth Selected topics in silicon crystal growth 李东升 硅材料国家重点实验室 Tel:87951667-8202 Email: mselds 2008-3-19 Dr. D.S. Li State Key Lab of Silicon Material Science Selected topics in silicon crystal growth Topic 6 Elimination Of Grown-in Defects in CZ Si

2、licon Crystal 2008-3-19 Dr. D.S. Li 1 State Key Lab of Silicon Material Science 6.1 Effect of Impurities on Intrinsic Point Defect Aggregation Nitrogen Suppress interstitial- and FZ vacancy-related defects Aswirls and D-defects/voids CZ oxidation-induced stacking faults (OSF the higher the nitrogen

3、concentration the lower the defect size Variation in void morphology as a function of nitrogen concentration and cooling rate of the growing crystal. 2008-3-19 enhances the formation of Dr. D.S. Li State Key Lab of Silicon Material Science Changes the void morphology octahedron platelet rods or even

4、 rod clusters 2008-3-19 Dr. D.S. Li 2 State Key Lab of Silicon Material Science the NN dimer can form stable N2V and N2V2 complexes N2V2 complexes stable a larger enthalpy of formation Suppress vacancy aggregation prevent interstitial agglomerates N incorporate in interstitial (NI and substitutional

5、 sites (Ns at the growth interface Behind the growth interface NI+ NI N2 NI+ Ns N2V 2008-3-19 Radial vacancy and Si interstitial distributions a derived from a FZ crystal grown with an axially varying nitrogen concentration. CV0 = 8.8×1012 at/cm 3 and CI0 = 7.7×1012 at/cm 3. The solid and

6、dashed lines refer to simulation results. In FZ Silicon Dr. D.S. Li State Key Lab of Silicon Material Science In CZ silicon the effect of nitrogen on defect aggregation is strongly diminished. the formation of NxOy complexes Close to the growth interface Ns +Oi NO + V at high temperatures temperatur

7、e decreases voids of smaller size but higher density 2008-3-19 Simulated variations in the vacancy concentration as a function of temperature for a nitrogen-doped and an undoped crystal Dr. D.S. Li 3 State Key Lab of Silicon Material Science 杂质影响原生缺陷形成的模型 CZ 1015 VOID nucleation V 1014 1013 1012 45o

8、 1011 10 快冷 O2 V Super-saturation 1150o C，N2 -V2 -O、 Ge-V-O、B2 O3 促进 大尺寸原生氧沉淀 吸收空位 空位CV浓度降低 形核驱动 力降低 VOID形成温度降低 慢冷 10 Doped CZ 1015 1014 1013 1012 1011 1010 Cv or C N-N (cm-3 700 800 900 1000 1100 1200 1300 1400 T (oC N2 O (GeVO, B2O 3 N-N 密度CV -1/2 尺寸CV 1/2 高密度、小尺寸VOID 45o 晶 体 冷 却 N2 V2 O 形核温度 降低！

9、N2 O、 GeO、B2 O3 促 进小尺寸原生氧沉淀 2008-3-19 Dr. D.S. Li State Key Lab of Silicon Material Science Boron affects the intrinsic point defect aggregation in a similar way to nitrogen doping, but much higher concentrations are required 5×1018 at/cm3 In contrast with nitrogen, OSF formation is not enhance

10、d and the width of the OSF ring remains unchanged with increasing boron concentration. 1019 at/cm 3, the COPs and the OSF ring disappear in the center of the crystal. the defect-free quality of pp+ epi wafers L-pits suppressed by the high boron level V/G 2008-3-19 Variation in the OSF ring diameter

11、as a function of the boron concentration. BI and B2 I complexes Dr. D.S. Li 4 State Key Lab of Silicon Material Science Carbon the void region in the crystal center disappears while the region of Si interstitial aggregates is widened shift of tr for carbon doping and, an enlargement of the interstit

12、ial-rich region reduces the grown-in defect size higher concentrations (1×1017 at/cm3 2008-3-19 Dr. D.S. Li State Key Lab of Silicon Material Science 6.2 Formation of OSF Ring OSFs oxygen precipitates with platelet shapes suppress OSFs: increase cooling rate decrease oxygen content The peculiar

13、 ring-like distribution is a consequence of the strong enhancement of oxygen precipitation by vacancies 2008-3-19 Schematic evolution of the radial vacancy profile and accompanying void and large OI-precipitate formation at decreasing temperatures Dr. D.S. Li 5 State Key Lab of Silicon Material Scie

14、nce increasing nitrogen content, the outer and inner OSF ring boundaries are shifted towards the crystal center N2V complexes vacancy supersaturation lower void nucleation temperature the void and the OSF region overlap carbon tends to suppress OSF formation heterogeneous nucleation 2008-3-19 Variat

15、ions of the outer and inner OSF homogeneous nucleation ring boundaries as a function of the nitrogen concentration. Dr. D.S. Li State Key Lab of Silicon Material Science Variations in the OSF ring width and its radial location in comparison to the variations of the COP and LLS boundaries along the c

16、rystal axis. The LLS defects were detected on the as-polished wafer surface, which detects only the larger voids, while the COP boundary was determined by LLS measurements after repeated SC1 cleaning, which enlarges the voids to above the LLS detection limit 2008-3-19 Dr. D.S. Li 6 State Key Lab of

17、Silicon Material Science 在晶锭不同位置处不同半径的氧化诱生层错 2008-3-19 Dr. D.S. Li State Key Lab of Silicon Material Science 6.3 Elimination of Intrinsic Point Defect Aggregation How to achieve silicon with no harmful intrinsic point defect aggregates? 1. To grow “Perfect” or “Pure” silicon silicon crystals in a re

18、gime where Si interstitials and vacancies are incorporated in equal concentrations, resulting in almost complete mutual annihilation of point defects lower throughput and higher costs 2. the growth of nitrogen doped crystals with very fast pull rates (high cooling rates and subsequent high-temperature ( 1200 C wafer annealing defect engineering 3. sacrificial oxidation, hydrogen annealing 4. epi wafer approach 2008-3-19 Dr. D.S. Li 7 State Key Lab of Silicon Material Science TEM micrographs of a void defect shrinking during annealing. (a before anneali