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Boosting Ge-Epi P-Well Mobility & Crystal Quality with Si or Sn Implantation and Melt Annealing
... However, Hall Effect measurements only represent the bulk data without providing electrical properties in depth profile form. Differential Hall Effect Metrology (DHEM), developed recently by Active Layer Parametrics (ALP) Inc., provides depth profiles of critical electrical properties through semiconductor layers at nanometer-level depth resolution [20][21] [22]. DHEM is based on the Differential Hall Effect (DHE) method, which makes successive sheet resistance and mobility measurements on a layer using Hall Effect and Van der Pauw techniques as the thickness of the layer is reduced through successive processing steps, typically involving chemical or electrochemical etching or oxidation [23] [24]. ...
Electrical properties and microstructure of phosphorus (P) implanted p-type Si substrates were evaluated by four-point probe (4PP), Differential Hall Effect Metrology (DHEM), secondary ion mass spectrometry (SIMS) and transmission electron microscopy (TEM) techniques, after RTA 750–950°C and CO
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laser 120–140W annealing. When RTA temperature was increased, defect concentration at a-Si/c-Si interface gradually disappeared. For CO
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laser annealing, defects were found to aggregate at the end of range (EOR) region. Sheet resistance (Rs) values decreased significantly with increasing RTA temperature due to defects disappearing at EOR. Rs did not change appreciably for the CO
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laser annealing case. The dopant activation ratio was less than 50% below RTA temperature of 850 °C, and it increased to 70% at 950 °C. For CO
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laser annealing, the activation ratio could reach to over 80% regardless of the laser power. The highest active concentration and the lowest resistivity or mobility were found to be within the top 20 nm region of the surface. Although RTA annealing conditions influenced dopant diffusion and the resulting electrical property depth profiles significantly, depth profiles did not change much with changes in CO
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laser power level. It was demonstrated that DHEM data in conjunction with SIMS and TEM data can be successfully employed to evaluate, in detail, the electrical properties of ultra-shallow junctions for metal oxide semiconductor field effect transistor (MOSFET) applications.
Differential Hall effect metrology (DHEM) was used to accurately and effectively evaluate the carrier concentration, mobility, and resistivity depth profiles at nano-scale resolution for BF2 and P implanted poly-Si layers after RTA (750–950 °C) and CO2 laser (115–135 W) annealing. Microstructure was characterized by transmission electron microscopy (TEM), total dopant concentration was measured by secondary ion mass spectrometer (SIMS). After implantation, the amorphous-Si (a-Si) surface was found to recover fully by RTA annealing, however a residual a-Si layer remained at the surface after CO2 laser annealing. The carrier concentration and active ratio at the a-Si regrowth region was higher than deeper into the samples. The active ratio could reach ~ 100% at the regrowth region for the CO2 laser annealed samples, but the mobility values deteriorated due to impurity scattering. Away from the regrowth region near the surface, RTA could produce higher carrier concentration and active ratio compared to CO2 laser annealing. The suitable carrier concentration value was ~ E + 19 #/cm³ to obtain relatively high mobility of ~ 40 cm²/V s for the BF2 and P implanted poly-Si. The resistivity was related to the carrier concentration and to the presence of the a-Si residue at the surface. It was demonstrated that DHEM in conjunction with SIMS and TEM can be successfully employed to evaluate, in detail, the electrical properties in ultra-shallow junctions of poly-Si and to correlate these electrical properties to process conditions.
We investigated the effects of Sn, Si and cluster-C implantation into both P-well and N-well doped regions of 100nm Ge-epilayer on Si wafers after RTA annealing. For the P-well case a 7.3x increase in bulk drift mobility to 3384cm 2 /V-s with cluster-C implant and for the N-well case a 2.8x increase in bulk drift mobility to 1256cm2/V-s with Sn implant. Measuring layer mobility depth profiles shows mobility in the top 10-20nm of the surface can be up to 7Kcm2/V-s for N-well and 45Kcm2/V-s for P-well.
- J Borland
J. Borland, ECS Symposium on High Purity and High Mobility Semiconductors
14, Oct 2016, ECS Transactions, vol.75, no.4, p 199.