| 1. |
- Bowallius, O., et al.
(författare)
-
Evaluation of different oxidation methods for silicon for scanning capacitance microscopy
- 2001
-
Ingår i: Materials Science in Semiconductor Processing. - 1369-8001 .- 1873-4081. ; 4:03-jan, s. 81-84
-
Tidskriftsartikel (refereegranskat)abstract
- Different oxides, namely, native, thermal, and wet-chemical (H2SO4 + H2O2 based) oxides on Si are evaluated in the context of scanning capacitance microscopy (SCM). The samples investigated consisted of uniformly doped Si substrates and p-type epitaxial doping-staircase structures with concentrations ranging from 5 x 10(14) to 2 x 10(19) cm(-3) The bias for which the SCM signal (dC/dV) is maximised for the lowest doped region was used for comparing the different oxidation methods. It is shown that for a better evaluation of the surface oxide properties, it is essential to obtain dC/dV curves for a sufficiently large doping range. Best results in terms of low values of flat-band voltages (1 V), uniformity, and consistency across a large doping range were obtained for the wet-chemical oxide. For the native oxide case, the difference in the dC/dV peak bias Values obtained at regions doped to 5 x 10(14) to 10(17) cm(-3) was anomalously large and suggests appreciable distortion of the dC/dV curves. For the same oxidation procedure the full-width at half-maximum of the dC/dV curve obtained on the cleaved surface is typically 2 times larger than that on the planar (100) surface. It is most likely that interface states are responsible for the observed distortion.
|
|
| 2. |
- Bowallius, O., et al.
(författare)
-
Scanning capacitance microscopy investigations of SiC structures
- 2001
-
Ingår i: Materials Science in Semiconductor Processing. - 1369-8001 .- 1873-4081. ; 4:03-jan, s. 209-211
-
Tidskriftsartikel (refereegranskat)abstract
- We have applied scanning capacitance microscopy (SCM) to investigate SIC structures grown by vapour-phase epitaxy. The SCM technique is evaluated using n- and p-type doping staircase structures with doping concentrations ranging from 10(16) to 10(20) cm(-3). The n- and p-type doping was obtained by doping SiC with nitrogen and aluminium, respectively. The sample cross-sections for SCM were obtained by simple cleaving. For doping levels above 10(17) cm(-3) the SCM data are consistent with doping data obtained independently from secondary ion mass spectroscopy (SIMS). Treating the samples with diluted hydrofluoric acid significantly improves the SCM signal for the low-doped regions. The SCM technique has been used to investigate doping redistribution in patterned regrowth of n- and p-type SIC around dry-etched mesas. In both cases, contrast variations were seen close to the mesa walls, indicative of doping variations; lower and higher incorporation for p- and n-type, respectively. The observations are shown to be consistent with the expected trends in dopant incorporation in the SiC material.
|
|
| 3. |
- Duteil, F., et al.
(författare)
-
Luminescence and microstructure of Er/O co-doped Si structures grown by MBE using Er and SiO evaporation
- 2000
-
Ingår i: Materials Science in Semiconductor Processing. - 1369-8001 .- 1873-4081. ; 3:5-6, s. 523-528
-
Tidskriftsartikel (refereegranskat)abstract
- Er and O co-doped Si structures have been prepared using molecular-beam epitaxy (MBE) with fluxes of Er and O obtained from Er and silicon monoxide (SiO) evaporation in high-temperature cells. The incorporation of Er and O has been studied for concentrations of up to 2×1020 and 1×1021 cm-3, respectively. Surface segregation of Er can take place, but with O co-doping the segregation is suppressed and Er-doped layers without any indication of surface segregation can be prepared. Si1-xGex and Si1-yCy layers doped with Er/O during growth at different substrate temperatures show more defects than corresponding Si layers. Strong emission at 1.54µm associated with the intra-4f transition of Er3+ ions is observed in electroluminescence (EL) at room temperature in reverse-biased p-i-n-junctions. To optimize the EL intensity we have varied the Er/O ratio and the temperature during growth of the Er/O-doped layer. Using an Er-concentration of around 1×1020 cm-3 we find that Er/O ratios of 1:2 or 1:4 give higher intensity than 1:1 while the stability with respect to breakdown is reduced for the highest used O concentrations. For increasing growth temperatures in the range 400-575 °C there is an increase in the EL intensity. A positive effect of post-annealing on the photoluminescence intensity has also been observed.
|
|
| 4. |
- Grivickas, P., et al.
(författare)
-
Carrier lifetime investigation in 4H-SiC grown by CVD and sublimation epitaxy
- 2001
-
Ingår i: Materials Science in Semiconductor Processing. - 1369-8001 .- 1873-4081. ; 4:03-jan, s. 191-194, s. 191-194
-
Tidskriftsartikel (refereegranskat)abstract
- Depth-resolved carrier lifetime measurements were performed in low-doped epitaxial layers of 4H silicon carbide samples. The technique used was a pump-and-probe technique where carriers are excited by an above-bandgap laser pulse and probed by free carrier absorption. Results from chemical vapour deposition samples show that lifetimes as high as 2 mus may be observed in the mid-region of 40 mum thick epilayers. For epilayers grown by the sublimation method decay transients were characterised by a fast (few nanoseconds) initial recombination, tentatively assigned to the 'true' lifetime, whereas a slow tail of several hundred microsecond decay time was assigned to trapping centres. From the saturation of this level at increased pumping we could derive the trapping concentration and their depth distribution peaking at the epilayer/substrate interface.
|
|
| 5. |
- Jacob, AP, et al.
(författare)
-
Ultrathin oxynitridation process through ion implantation in a poly Si1-xGex gate MOS capacitor
- 2003
-
Ingår i: Materials Science in Semiconductor Processing. - : Elsevier Science B.V., Amsterdam.. - 1369-8001 .- 1873-4081. ; 6:03-Jan, s. 37-41
-
Tidskriftsartikel (refereegranskat)abstract
- Effect of temperature and time of heat treatment on the distribution of ion-implanted nitrogen in poly Si0.65Ge0.35 gate MOS samples was studied. Secondary ion mass spectrometry (SIMS) was used for the qualitative analysis of the nitrogen distribution. Rapid thermal processing was carried out for a temperature range of 950-1070degreesC for the redistribution of ions. The nitrogen implantation doses were 5 x 10(14) cm(-2), 2 x 10(15) cm(-2) and 5 x 10(15) cm(-2), all with an implantation energy of 50 keV. For a uniform distribution of nitrogen in the SiO2 region, an optimal temperature at a well calibrated time must be applied and this depends on the implantation dose. For medium and high concentrations the optimal conditions were 1050degreesC and 15s, and 1070degreesC and 15s, respectively. A uniform nitrogen distribution could be obtained throughout the SiO2 film. Prolonged heat treatment can cause degradation of the oxide layer and movement of the nitrogen and oxygen into the channel and the poly-Si0.65Ge0.35 layer.
|
|
| 6. |
- Kuznetsov, A. Y., et al.
(författare)
-
Self-interstitial migration during ion irradiation of boron delta-doped silicon
- 2000
-
Ingår i: Materials Science in Semiconductor Processing. - 1369-8001 .- 1873-4081. ; 3:4, s. 279-283
-
Tidskriftsartikel (refereegranskat)abstract
- Boron delta layers in silicon, grown by molecular beam epitaxy and characterized by the secondary ion mass spectrometry, have been employed to investigate the migration of silicon self-interstitials during irradiation with MeV protons in the 500-850 degreesC temperature range. After growth, the samples were thinned from the backside to a thickness that made them transparent for the proton energies used. As a result, the generation rate of point defects can be considered as essentially uniform throughout the samples. However: the evolution of the boron profiles is almost identical to that observed after injection of self-interstitials caused by thermal oxidation of the samples at elevated temperature. This strongly indicates that the surface acts as a reflective boundary for the migrating self-interstitials or/ and an efficient sink for mobile vacancies. Furthermore, higher value of interstitial supersaturation in the near-surface region in proton-irradiated samples is consistent with experimentally detected depth dependence for immobile fraction in boron clusters. Then, activation energy of boron mobilization, (0.9 +/- 0.4) eV, was attributed to the dissociation of boron clusters.
|
|
| 7. |
- Li, Zhicheng, et al.
(författare)
-
Direct observation of electron-beam-induced nucleation and growth in amorphous GaAs
- 2004
-
Ingår i: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 7:1-2, s. 19-25
-
Tidskriftsartikel (refereegranskat)abstract
- In situ observation of the nucleation and growth stimulated by an electron beam in amorphous GaAs was performed using a high-resolution electron microscopy. The results showed that the crystallization was closely related to the current density of the electron beam. Crystallization could not take place when the current density was 50 pA/cm(2), nanocrystals with the random orientation formed under the 74 pA/cm(2) electron beam, large grains and twining structure formed during the crystallization induced by the 93 pA/cm(2) electron beam. Ionization process and electron-beam heating were suggested to be the possible mechanisms for the irradiation-induced crystallization.
|
|
| 8. |
- Vomiero, Alberto, et al.
(författare)
-
Effects of thermal annealing on the structural properties of sputtered W-Si-N diffusion barriers
- 2004
-
Ingår i: Materials Science in Semiconductor Processing. - : Elsevier BV. - 1369-8001 .- 1873-4081. ; 7:4-6 SPEC. ISS., s. 325-330
-
Tidskriftsartikel (refereegranskat)abstract
- W-Si-N thin films were deposited via rf-magnetron sputtering from a W 5Si3 target in Ar/N2 reactive gas mixtures over a large range of compositions, obtained by varying the partial flow of nitrogen within the reaction chamber. The samples of each set were then thermally annealed in vacuum at different temperatures up to 980°C. Film composition was determined by Rutherford backscattering spectrometry (RBS), surface film morphology by scanning electron microscopy (SEM), micro-structure by transmission electron microscopy (TEM), vibrational properties by FT-IR absorption and Raman scattering spectroscopy, and electrical resistivity by four-point probe measurements. Independently of the deposition conditions, all the as-deposited films have an amorphous structure, while their composition varies, showing an increase of Si/W ratio from 0.1 up to 0.55 when the nitrogen concentration in the films increases from 0 to 60 at%. Thermal treatments in vacuum induce an important loss of nitrogen in the nitrogen-rich samples, especially at temperatures higher than 600°C. Samples with high nitrogen content preserve their amorphous structure even at the highest annealing temperature, despite the chemical bonding ordering observed by means of FTIR measurements. Raman spectroscopy of as-deposited films rich in nitrogen suggests the presence of an important amorphous silicon nitride component, but fails to detect any structural rearrangement either within the composite matrix of film or within silicon nitride component. Segregation of metallic tungsten was detected by TEM in the annealed sample with lowest nitrogen content (W 58Si21N21). Finally, the resistivity of the films increases with the N content, while the loss of nitrogen accompanies the decrease of resistivity especially of samples with high nitrogen content. © 2004 Elsevier Ltd. All rights reserved.
|
|
