Cheng-Guo Jin

Activated boron and its concentration profiles in heavily doped Si studied by soft x-ray photoelectron spectroscopy and Hall measurements

The chemical bonding states of boron (B) in shallow P+/N junctions on Si substrates were studied by soft x-ray photoelectron spectroscopy (SXPES). This study revealed three chemical bonding states of B embedded in bulk Si. The concentration profiles of B were successfully determined by combining SXPES with step-by-step etching of Si substrates. The concentration profiles of B thus determined were in good agreement with those determined by secondary ion mass spectroscopy. The concentration profiles of holes were also determined by combining Hall measurements with the step-by-step etching of Si substrates. The concentration profiles of B having the lowest binding energy were found to agree well with the concentration profiles of holes. Therefore, B with the lowest binding energy can be assigned as activated B and those having the middle and highest binding energies can be attributed to deactivated B having chemical bonding states different from that of activated B.

Estimation of ultra-shallow plasma doping (PD) layer's optical absorption properties by spectroscopic ellipsometry (SE)

We evaluated the optical absorption properties of ultra-shallow (<10 nm) plasma doping (PD) layers by spectroscopic ellipsometry (SE). The optical absorption coefficients of PD layers are much larger than that of crystalline Si (c-Si) substrate by one figure at maximum in the wavelength range from 400 nm to 800 nm. We also found that higher DC bias during PD resulted in higher optical absorption coefficient for the same PD time of 60 seconds.

Hard X-ray Photoelectron spectroscopy (HX-PES) study on chemical binding states of ultra shallow plasma-doped silicon layer for the application of advanced ULSI devices

We took HX-PES measurement (Si 1s) on silicon samples doped by plasma doping (PD) for the first time before and after annealing using either spike RTA or flash lamp anneal (FLA) in SPring-8. After PD, the carrier density of n-Si substrate decreased to intrinsic Si level due to defect induced carrier traps. After annealing, the results revealed that the chemical binding states of the doped samples were well recovered showing high impurity activation

The difference of chemical binding states between ultra shallow plasma doping (PD) and ion implantation (I/I) samples studied by hard X-ray photoelectron spectroscopy (HX-PES)

We measured HX-PES (Si 1s) of low energy ion implanted silicon substrate before and after spike RTA, and compared it with that of plasma doped (PD) samples. As-doped I/I sample showed higher hole density compared to as-doped PD sample due to lower defect induced carrier trap. After spike RTA, PD sample showed superior impurity activation than that of I/I sample. Both I/I sample and PD sample showed excellent recrystallization after spike RTA. HX-PES can be very useful for optimizing the semiconductor doping and thermal activation processes for advanced micro-devices that have the junction depth shallower than 10 nm.

Ultra-shallow junction and high-k dielectric for Nano CMOS

In this work, combination of the plasma doping method with flush lamp annealing (FLA) or solid-state laser annealing (ASLA) is shown to be very promising technique to form ultra-shallow and low-resistive junctions for future nano CMOS. Amorphisation by He plasma (He-PA process) is shown to be effective for obtaining shallow junction depth (Xj) and low sheet resistance (Rs). The He-PA process is found to contribute to the increase of sheet charier concentration, which governs the sheet resistances as revealed by Hall measurements. However, even if these techniques are used, activation rate under the annealing conditions to keep shallow Xj is still low, thus, further investigation to improve the carrier activation is necessary. The junction leakage for the ultra-shallow Si P/N junction diodes formed by plasma doping of boron is examined, and it was shown to be as low as that formed by the low energy ion implantation. Feasibility study of La2O3 gate oxide of MOS capacitors and MOSFET is presented. The effect of annealing temperature on the effective mobility is investigated been obtained and shows strong correlation of the mobility and interface states. Insertion of Y2O3 or Sc2O3 at La2O3/Si interface suppresses the increase of EOT after the annealing.

Comparison of chemical binding states between ultra shallow plasma doping (PD) and ion implantation (I/I) combined with Ge pre-amorphizaiton ion implantation (Ge-PAI) by using hard X-ray photoelectron spectroscopy (HX-PES)

We measured HX-PES (Si 1s) of ultra low energy ion implantation (I/I) samples combined with Ge pre-amorphizaiton ion implantation (Ge-PAI) before and after spike RTA, and compared it with that of plasma doping (PD) samples. As-doped I/I sample showed higher hole density compared to as-doped PD sample due to lower defect induced carrier trap. Ge-PAI+I/I sample showed strong asymmetric in lower binding energy region due to Si-Ge bonding. After spike RTA, PD sample showed superior impurity activation than that of Ge-PAI+I/I sample. Both Ge-PAI+I/I and PD sample showed excellent recrystallization after spike RTA.bonding.

Profiling of carrier properties for shallow junctions using a new sub-nanometer step-by-step etching technique

A new step-by-step etching technique which is combined with electrical and/or physical analyses for in depth profiling of shallow junctions is proposed. The etching process is composed of scarified oxidation by using ozone and removal of the oxide formed. Combining the etching technique and Hall measurements, concentration profiles and mobility profiles of activated carriers were successfully obtained for the samples doped with boron (B) or arsenic (As) by the plasma doping (PD) method.