Transient-enhanced diffusion in shallow-junction formation

Shallow junctions are formed in crystalline Si by low-energy ion implantation of B⁺, P⁺, or As⁺ species accompanied by electrical activation of dopants by rapid thermal annealing and the special case of spike annealing. Diffusion depths were determined by secondary ion-mass spectroscopy (SIMS). Electrical activation was characterized by sheet resistance, Hall coefficient, and reverse-bias diode-leakage measurements. The B⁺ and P⁺ species exhibit transient-enhanced diffusion (TED) caused by transient excess populations of Si interstitials. The electrically activated fraction of implanted dopants depends mainly on the temperature for B⁺ species, while for P⁺ species, it depends on both temperature and P⁺ dose. The relatively small amount of diffusion associated with As⁺ implants is favorable for shallow-junction formation with spike annealing.     

High mobility strained Si0.5Ge0.5/SSOI short channel field effect transistors with TiN/GdScO3 gate stack

Short channel p-type metal-oxide-semiconductor field effect transistors (MOSFETs) with GdScO₃ gate dielectric were fabricated on a quantum well strained Si/strained Si_0.5Ge_0.5/strained Si heterostructure on insulator. Amorphous GdScO₃ layers with a dielectric constant of 24 show small hysteresis and low density of interface states. All devices show good performance with a threshold voltage of 0.585 V, commonly used for the present technology nodes, and high I_on/I_off current ratios. We confirm experimentally the theoretical predictions that the drive current and the transconductance of the biaxially strained (1 0 0) devices are weakly dependent on the channel orientation. The transistor’s hole mobility, extracted using split C-V method on long channel devices, indicates an enhancement of 90% (compared to SiO₂/SOI transistors) at low effective field, with a peak value of 265 cm²/V s. The enhancement is however, only 40% at high electrical fields. We demonstrate that the combination of GdScO₃ dielectric and strained SiGe layer is a promising solution for gate-first high mobility short channel p-MOSFETs.     

Evolution of precipitates in lead-implanted aluminum: A backscattering and channeling study

BACKGROUND: Thirty-six mutations that cause Gaucher disease, the most common glycolipid storage disorder, are known. Although both alleles of most patients with the disease contain one of these mutations, in a few patients one or both disease-producing alleles have remained unidentified. Identification of mutations in these patients is useful for genetic counseling. MATERIALS AND METHODS: The DNA from 23 Gaucher disease patients in whom at least one glucocerebrosidase allele did not contain any of the 36 previously described mutations has been examined by single strand conformation polymorphism (SSCP) analysis, followed by sequencing of regions in which abnormalities were detected. RESULTS: Eight previously undescribed mutations were detected. In exon 3, a deletion of a cytosine at cDNA nt 203 was found. In exon 6, three missense mutations were identified: a C-->A transversion at cDNA nt 644 (Ala176-->Asp), a C-->A transversion at cDNA nt 661 that resulted in a (Pro182-->Thr), and a G-->A transition at cDNA nt 721 (Gly202-->Arg). Two missense mutations were found in exon 7: a G-->A transition at cDNA nt 887 (Arg257-->Gln) and a C-->T at cDNA nt 970 (Arg285-->Cys). Two missense mutations were found in exon 9: a T-->G at cDNA nt 1249 (Trp378-->Gly) and a G-->A at cDNA nt 1255 (Asp380-->Asn). In addition to these disease-producing mutations, a silent C-->G transversion at cDNA nt 1431, occurring in a gene that already contained the 1226G mutation, was found in one family. CONCLUSIONS: The mutations described here and previously known can be classified as mild, severe, or lethal, on the basis of their effect on enzyme production and on clinical phenotype, and as polymorphic or sporadic, on the basis of the haplotype in which they are found. Rare mutations such as the new ones described here are sporadic in nature.     

LaScO3 as a higher-κ dielectric for p-MOSFETs

The electrical properties of MOS capacitors with LaScO₃ thin films grown by molecular beam deposition (MBD) have been studied with and without post deposition annealing (PDA) in O₂ environment followed by forming gas. An EOT of 0.65 nm could be achieved for samples without PDA. However, the films suffer from large hysteresis and interface trap density. Applying PDA reduces the hysteresis, the D_it (down to the mid of 10¹¹ (eV cm²)⁻¹) and the leakage current by two orders of magnitude (down to the range of 10⁻⁴A/cm²) for an EOT of 1.1 nm. Furthermore we have successfully integrated LaScO₃ into FD MOSFETs on SOI substrates. The p-FETs with LaScO₃ show excellent characteristics with a steep subthreshold slope down to 65 mV/dec and hole mobilities comparable to HfO₂ and HfSiON.     

High mobility compressive strained Si0.5Ge0.5 quantum well p-MOSFETs with higher-k/metal-gate

Strained SiGe quantum well p-MOSFETs with LaLuO₃ higher-k dielectric were fabricated and characterized. The strained Si/strained Si_0.5Ge_0.5/strained SOI heterostructure transistors showed good output and transfer characteristics with an I_on/I_off ratio of 10⁵. The extracted hole mobility shows an enhancement of about 2.5 times over Si universal hole mobility and no degradation compared to HfO₂ or even SiO₂ gate dielectric devices.     

The effect of fluorine from BF2 source/drain extensionimplants on performance of PMOS transistors with thin gate oxides

Boron penetration from the gate electrode into the Si substrate presents a significant problem in advanced PMOS device fabrication. Boron penetration, which causes a degradation of many transistor parameters, is further enhanced when BF₂ is used to dope the gate electrode. It is known that pile-up of fluorine from the BR gate implant at the polysilicon/gate oxide interface is responsible for the enhanced boron penetration. However, no reports have been made that address enhanced boron penetration due to fluorine from the source/drain (S/D) implants. It is shown here that fluorine from the S/D extension implants is also a significant problem, degrading transistor performance for gate oxide thickness less than 27 Å and gate lengths less than 0.5 μm     

Improved GeOI substrates for pMOSFET off-state leakage control

The origin of parasitic leakage that occurs in some GeOI pMOSFETs has been investigated and located at the Ge-buried oxide (BOX) interface. Silicon passivation of that interface was found to be effective in reducing this current. An optimum thickness of the buried silicon capping is required to reduce the parasitic leakage current while preserving Ge-like back channel transport properties.     

Thermal activation of shallow boron-ion implants

Boron implanted into n-type Si at 10¹⁵ cm⁻² dose and energies from 500 eV to 1 keV was activated by annealing in nominally pure N₂ and in N₂ with small admixtures of O₂. Effective process times and temperatures were derived by thermal activation analysis of various heating cycles. The lowest thermal budgets used “spike anneals” with heating rates up to 150°C/sec, cooling rates up to 80°C/sec, and minimal dwell time at the maximum temperature. Dopant activation was determined by sheet electrical transport measurements. Surface oxidation was characterized by film thickness ellipsometry. P-n junction depths were inferred from analysis of sheet electrical transport measurements and secondary ion mass spectroscopy profiles. Boron activation increases with boron diffusion from the implanted region. Electrical activation has a thermal activation energy near 5 eV, while boron diffusion has an activation energy near 4 eV. Surface oxide can retard boron diffusion into the ambient for high-temperature anneals.