High Temperature Rapid Thermal Processing Research Articles

A Study on the Formation of 2-Dimensional Tungsten Disulfide Thin Films on Sapphire Substrate by Sputtering and High Temperature Rapid Thermal Processing.

As direct formation of p-type two-dimensional transition metal dichalcogenides (TMDC) films on substrates, tungsten disulfide (WS2) thin films were deposited onto sapphire glass substrate through shadow mask patterns by radio-frequency (RF) sputtering at different sputtering powers ranging from 60 W to 150 W and annealed by rapid thermal processing (RTP) at various high temperatures ranging from 500 °C to 800 °C. Based on scanning electron microscope (SEM) images and Raman spectra, better surface roughness and mode dominant E12g and A1g peaks were found for WS2 thin films prepared at higher RF sputtering powers. It was also possible to obtain high mobilities and carrier densities for all WS2 thin films based on results of Hall measurements. Process conditions for these WS2 thin films on sapphire substrate were optimized to low RF sputtering power and high temperature annealing.

Impact of germanium co-doping on oxygen precipitation in heavily boron-doped Czochralski silicon

We have investigated the impact of germanium (Ge) co-doping on oxygen precipitation (OP) in heavily boron (B)-doped Czochralski (CZ) silicon subjected to low-high two-step anneal without or with the prior high temperature rapid thermal process (RTP). Herein, the Ge concentration is one order of magnitude higher than the B concentration. It is found that the Ge co-doping exhibits the effect of suppression or enhancement on OP in the heavily B-doped CZ silicon without or with the prior RTP. In the case without the prior RTP, the compressive stress introduced by the Ge co-doping compensates the tensile stress arising from the B-doping, which is not beneficial for the growth of oxide precipitates. While, in the case with the prior RTP, the Ge co-doping increases the amount of vacancies introduced by the RTP and, moreover, may enable to generate more heterogeneous nucleation centers of oxide precipitates, thus leading to the enhanced OP in the heavily B-doped CZ silicon.

Thermal and Hygroscopic Properties of Indoor Particulate Matter Collected on an Underground Subway Platform

In order to clarify the thermal and hygroscopic properties of indoor particulate matter (PM) in a semiclosed subway space, which is critically important for understanding of the distinctive particle formation processes as well as the assessment of their health effects, the size-resolved PMs (i.e., <TEX>$PM_{2.5}$</TEX> and <TEX>$PM_{10-2.5}$</TEX>) were intensively collected on the platform of Miasageori station on the Seoul Subway Line-4. The elemental concentrations in soluble and insoluble fractions were determined by PIXE from the bulkily pretreated <TEX>$PM_{2.5}$</TEX>. The thermal and hygroscopic characteristics of individual particles were investigated via a combination of the unique pretreatment techniques (i.e., the high-temperature rapid thermal process and the water dialysis) and SEM-EDX analysis. Iron and calcium were unequaled in insoluble and soluble <TEX>$PM_{2.5}$</TEX> fractions, respectively, with overwhelming concentration. The SEM-EDX's elemental net-counts for the pre- and post-pyrolyzed PMs newly suggest that magnesium and several elements (i.e., silica, aluminum, and calcium) may be readily involved in the newly generated subway fine PM by a high-temperature thermal processing when trains are breaking and starting. Through the water dialysis technique, it turned out that calcium has meaningful amount of water soluble fraction. Furthermore, the concentrations of the counter-ions associated with the calcium in subway <TEX>$PM_{10-2.5}$</TEX> were theoretically estimated.

Rapid thermal processing induced vacancy-oxygen complexes in Czochralski-grown Si1−xGex

Rapid thermal processing (RTP) induced vacancy-oxygen (VOm m ≥ 2) complexes can act as the precursors for oxide precipitate nucleation thus enhancing oxygen precipitation (OP) in Czochralski silicon (Cz-Si). In our preceding work, we have reported that 1020 cm−3 germanium (Ge)-doping in Cz-Si facilitates the formation of VOm complexes during the high temperature RTP. Then, how the even higher Ge-doping at 1021 cm−3 in Cz-Si affects the formation of VOm complexes during the RTP is an interesting issue to be addressed. Actually, such high Ge-doping in Cz-Si forms Cz-Si1−xGex alloys. In the present work, we have investigated the formation of VOm complexes in Cz-Si1−xGex (x = 0.035–0.038) wafers subjected to the high temperature RTP. The Cz-Si1−xGex wafers are found to exhibit much weaker OP than Cz-Si counterparts when subjected to the same two-step (nucleation-growth) anneal following the high temperature RTP, indicating that the formation of VOm complexes during the RTP is suppressed in Cz-Si1−xGex wafers. The ‘gold-marker method’ in combination with deep level spectroscopy further confirms the suppressed formation of VOm complexes in Cz-Si1−xGex wafers during the RTP. Besides, the characterization of the oxygen out-diffusion depth profiles in Cz-Si1−xGex and Cz-Si wafers annealed at different temperatures in the range 650–1000 °C indicates that the oxygen diffusivity in Cz-Si1−xGex is a little smaller. The calculations based on density functional theory reveal that in Cz-Si1−xGex the vacancies incline to locate at the first nearest neighboring sites of the Ge atoms and the capture of Oi atoms by the vacancies is less energetically favorable. The aforementioned adverse conditions are believed to be responsible for the suppressed formation of VOm complexes in Cz-Si1−xGex.

Oxygen precipitation in 1020 cm−3 germanium-doped Czochralski silicon

We have investigated the effects of germanium (Ge)-doping at the level of 1020 cm−3 on oxygen precipitation (OP) behaviors in Czochralski (CZ) silicon subjected to different low-high two-step anneals without or with prior high temperature rapid thermal processing (RTP). It is found that Ge-doping remarkably suppresses OP in CZ silicon without prior RTP. However, Ge-doping significantly enhances OP in CZ silicon with prior RTP. The suppressed OP in the case of the absence of prior RTP is primarily due to the fact that the 1020 cm−3 Ge-doping introduces compressive strain into silicon crystal lattice, which increases the critical size of oxygen precipitate nuclei for a given nucleation temperature. Moreover, it is revealed that the 1020 cm−3 Ge-doping facilitates the formation of vacancy-oxygen (V-O) complexes and may introduce Ge-V-O complexes in CZ silicon during high temperature RTP. More vacancy-related complexes in CZ silicon not only reduce the critical size of oxygen precipitate nuclei but also provide more precursors for oxygen precipitate nucleation. Therefore, the 1020 cm−3 Ge-doping enhances OP in CZ silicon subjected to the two-step anneals following high temperature RTP.

Dislocation motion during rapid thermal processing of single-crystalline silicon wafers

We have investigated the motion of dislocations originating from Vicker indentations in single-crystalline silicon wafers subjected to high temperature rapid thermal processing (RTP) under different ambients. It is found that the dislocations move very rapidly due to the release of residual stress around the indentations during the RTP. Moreover, as the RTP temperature exceeds 1100 °C, the dislocation gliding distances in the specimens subjected to the RTP in N2 atmosphere are much shorter than in Ar ambient. We believe that the nitrogen atoms injected into the indentation by the RTP under N2 ambient exhibit a pinning effect on dislocation motion. It is thus shown that the high temperature RTP in N2 ambient can improve the mechanical strength of silicon wafer.

Effects of High Temperature Rapid Thermal Processing on the Formation of Oxidation Induced Stacking Faults in 300 mm Nitrogen-Doped Czochralski Silicon Wafers

Oxidation induced stacking faults (OSFs) are more readily generated in nitrogen-doped Czochralski (NCz) silicon wafers because of possessing more grown-in oxygen precipitates (OPs). This issue is worthy to be addressed. In this work, the effects of rapid thermal processing (RTP) at high temperature in different atmospheres on the formation of OSFs in 300 mm NCz silicon wafers have been investigated. It is found that the prior RTP at 1250 °C in Ar atmosphere can effectively annihilate OSFs, while that in N2 atmosphere promotes the formation of OSFs instead. The reason for this result has been elucidated in the text.

Nitrogen Enhanced Oxygen Precipitation in Czochralski Silicon Wafers Coated with Silicon Nitride Films

Oxygen precipitation (OP) behaviors were investigated for Czochralski (Cz) silicon wafers, which were coated with silicon nitride (SiNx) films or not, subjected to two-step anneal of 800C/4 h+1000°C/16 h following rapid thermal processing (RTP) at different temperatures ranging from 1150 to 1250C for 50 s. It was found that OP in the Cz silicon wafers coated with SiNx films was stronger in each case. This was because that nitrogen atoms diffused into bulk of Cz silicon wafer from the surface coated SiNx film during the high temperature RTP. Furthermore, it was proved that the RTP lamp irradiation facilitated the in-diffusion of nitrogen atoms, which was most likely due to that the ultraviolet light enhanced the breakage of silicon-nitrogen bonds.

Effects of high temperature rapid thermal processing on oxygen precipitation in heavily arsenic-doped Czochralski silicon

Oxygen precipitation (OP) behaviors in heavily arsenic-doped Czochralski silicon wafers without and with prior rapid thermal processing at 1100–1250°C, subjected to subsequent two-step anneal of 450, 650 and 800°C/4h+1000°C/16h, have been investigated. It is found that the prior RTP at 1250°C substantially enhances OP in each two-step anneal. Such enhancement effect exhibits most significantly in the two-step anneal with the nucleation at 800°C. However, in order to form the highest density of oxygen precipitates, the most desirable nucleation temperature is 650°C in both cases without and with prior RTP. The OP nucleation mechanisms operating in the three low temperatures as mentioned above have been tentatively discussed.

High Temperature RTP Application in SOI Manufacturing

Significant performance enhancements are offered by silicon on insulator (SOI) or strained silicon, SOI being adopted for advanced devices in sustaining Moore’s law. Sub-45 nm device options are including fully depleted (FD) devices, that are stressing even more specifications for thickness uniformity. Nano-uniformity, considering thickness variation contributions from device level to wafer scale, has been introduced in substrate optimization and latest Unibond products are verifying FD requirements. Rapid Thermal Processing (RTP) based surface smoothing has been introduced in Unibond processing to combine thickness control and product quality requirements.

Impact of metal silicide precipitate dissolution during rapid thermal processing of multicrystalline silicon solar cells

Synchrotron-based analytical x-ray microprobe techniques were employed to study the dissolution of iron, copper, and nickel silicide precipitates at structural defects in cast multicrystalline silicon in response to rapid thermal processing (RTP). A direct correlation was observed between iron silicide precipitate dissolution, increased minority carrier recombination, and decreased device performance after high-temperature (1000°C) RTP. In contrast, iron precipitates comparable in size to as-grown material remained after lower-temperature RTP (860°C); in this case the material exhibited higher minority carrier diffusion length and better solar cell performance. RTP at both temperatures effectively dissolved nickel and copper silicide precipitates. It is concluded that iron dissolved from structural defect reservoirs detrimentally affects the cell performance, likely by forming distributed point defects and smaller precipitates. For cast multicrystalline silicon, higher performance can be expected by inhibiting the dissolution of these precipitates, i.e., by reducing the time and/or temperature of processing steps.

High Temperature Rapid Thermal Oxidation and Nitridation of 4H-SiC in Diluted N&lt;sub&gt;2&lt;/sub&gt;O and NO Ambient

A high temperature rapid thermal processing (HT-RTP) above 1400oC was investigated for use in the gate oxide formation of 4H-SiC by a cold-wall oxidation furnace. The gate oxide film of ~50nm can be formed for several minutes in the oxidizing atmospheres such as N2O and O2, where the oxidation rates were 8-10nm/min. After the initial oxide formation, the HT-RTPs in various ambient gases were conducted, and the dependences of their MOS interface properties on the gases were evaluated by a capacitance-voltage (CV) measurement. Based on the results, the process sequence of gate oxidation was determined as follows; the initial oxide was formed by the HT-RTO (oxidation) in N2O or in O2 with subsequent post annealing in Ar ambient, and then the HT-RTN (nitridation) in NO was conducted. The total process time becomes 20-50min. The interface trap density (Dit) of fabricated MOS capacitor shows 3-5x1011cm-2eV-1 at Ec-E~0.2eV. The field-effect channel mobility of fabricated 4H-SiC lateral MOSFETs was ~30cm2/Vs.

Effect of rapid thermal processing on high temperature oxygen precipitation behaviour inCzochralski silicon wafer

The effect of rapid thermal processing (RTP) on the oxygen precipitation occurring at1050 °C in a Czochralski (CZ) silicon wafer has been investigated. It has been proved thatthe RTP-induced vacancies only enhance the early stage oxygen precipitation at1050 °C in terms of the precipitation rate. Furthermore, it is somewhat unexpected that after a lengthy1050 °C anneal the oxygen precipitates generated in the CZ silicon wafer with prior RTP treatmenthad considerably lower density and larger sizes in comparison with those generated in theCZ silicon wafer without prior RTP treatment. The reason for this is that the prior RTPtreatment will dissolve some of the grown-in oxygen precipitates, thus making the RTP-treatedwafer possess fewer nuclei contributing to oxygen precipitation in the subsequent1050 °C anneal. Moreover, the numbers of resulting precipitated oxygen atoms due to a lengthy1050 °C anneal were nearly the same in the CZ silicon wafers with and without prior RTPtreatment. Additionally, it has been illustrated that the high temperature RTP hassuperior capability to dissolve the existing oxygen precipitates. It is worthwhile to point outthat, when addressing the effect of RTP on the oxygen precipitation behaviour duringthe subsequent anneal, two functions arising from the RTP treatment, that is,the injection of vacancies into the silicon wafer and the dissolution of grown-inoxygen precipitates existing in the silicon wafer, should be taken into account.

Thermal Behavior of Large-Diameter Silicon Wafers during High-Temperature Rapid Thermal Processing in Single Wafer Furnace

Thermal behavior of 200-mm- and 300-mm-diameter Si (100) wafers during high-temperature rapid thermal processing (RTP) in a single wafer furnace (SWF) is investigated as a function of temperature, pressure, process time, wafer handling method and speed. Significant elastic wafer shape deformation was observed during wafer temperature ramp-up. Slip generation was frequently observed in wafers processed above 1050°C. Size, shape and spatial distribution of crystal defects generated during RTP were characterized using an optical microscope and X-ray topography. The wafer handling method and speed are found to be very important in reducing defect generation during RTP at the given process conditions. Highly reproducible, slip-free RTP results were achieved in 200-mm- and 300-mm-diameter Si (100) wafers processed at 1100°C by optimizing the wafer handling method and speed.

A comprehensive study of AlGaAs/GaAs beryllium- and carbon-doped base heterojunction bipolar transistor structures subjected to rapid thermal processing

AlGaAs/GaAs single heterojunction bipolar transistor (HBT) structures with Be- and C-doped bases have been annealed at different temperatures using rapid thermal processing (RTP). Both electrical and low-temperature photoluminescence measurements were used to investigate their thermal stability. We found that the conventional AlGaAs/GaAs abrupt HBT structures could undergo significant degradation at temperatures commonly encountered in typical RTP for device fabrication. The decrease of current gain was observed in both molecular beam epitaxy-grown HBTs with a Be-doped base and metalorganic chemical vapor deposition-grown HBTs with a C-doped base after RTP at temperatures greater than 600 °C. Our studies show that high-temperature RTP could induce undesirable degradation in AlGaAs/GaAs HBTs. Different degradation mechanisms, which are similar to those for the degradation of the Be- and C-doped base HBTs under current-induced stress, are responsible for the degradation of the Be- and C-doped HBTs subjected to RTP. The degradation of Be-doped HBTs is believed to be due to the outdiffusion of Be from the highly doped base, whereas the decrease of current gain for C-doped HBTs is closely related to the unintentionally incorporated hydrogen during material growth.

Ultrahigh Si+ implant activation efficiency in GaN using a high-temperature rapid thermal process system

Si + implant activation efficiencies above 90%, even at doses of 5×1015 cm−2, have been achieved in GaN by rapid thermal processing at 1400–1500 °C for 10 s. The annealing system utilizes molybdenum intermetallic heating elements capable of operation up to 1900 °C, producing high heating and cooling rates (up to 100 °C s−1). Unencapsulated GaN shows severe surface pitting at 1300 °C and complete loss of the film by evaporation at 1400 °C. Dissociation of nitrogen from the surface is found to occur with an approximate activation energy of 3.8 eV for GaN (compared to 4.4 eV for AlN and 3.4 eV for InN). Encapsulation with either rf magnetron reactively sputtered or metal organic molecular beam epitaxy-grown AlN thin films provides protection against GaN surface degradation up to 1400 °C, where peak electron concentrations of ∼5×1020 cm−3 can be achieved in Si-implanted GaN. Secondary ion mass spectrometry profiling showed little measurable redistribution of Si, suggesting DSi⩽10−13 cm2 s−1 at 1400 °C. The implant activation efficiency decreases at higher temperatures, which may result from SiGa to SiN site switching and resultant self-compensation.

Deposition of ultra-thin oxide dielectrics for MOSFETs by a combination of low-temperature plasma-assisted oxidation, and intermediate and high-temperature rapid thermal processing

In order to match shrinking lateral dimensions in ULSI devices, there will be a need to reduce equivalent oxide thicknesses for gate dielectrics to at least 5–6 nm, and perhaps to as thin as ∼3 nm. This reduction will have to be accomplished with low thermal budget, and more-than-likely low temperature processing as well. In this paper the important processing steps required for formation of ultra-thin gate oxides by thin film deposition as contrasted with conventional thermal oxidation, or the emerging technique of rapid thermal oxidation (RTO), are identified. Several different low thermal budget/low-temperature processing alternatives are identified in which interface formation, bulk oxide deposition, and structural and chemical relaxation are performed separately and controlled independently.

The Effects of Preheatings on Axial Oxygen Precipitation Uniformity in Czochralski Silicon Crystals

The puller thermal history effect on axial oxygen precipitation depends on the subsequent heat treatment. Two approaches can improve the axial oxygen precipitation uniformity after a two‐step heat treatment . A high temperature rapid thermal process (RTP) preheating, 1200°C for 2 min in argon ambient can influence the thermal history effect by reducing the oxygen precipitation at the seed‐end of the crystal in comparison to the tang‐end. Low temperature preheat treatments, such as thermal donor annihilation heat treatment and polysilicon CVD processes, can increase the oxygen precipitation of the tang‐end wafers much more than that of the seed‐end and, therefore, also increase the uniformity of the precipitation.

Rapid Thermal Processing for Self-Aligned Silicide Technology

ABSTRACTA self-aligned titanium silicide process which combines the use of ion-beam mixing and rapid thermal processing (RTP) has been developed for CMOS VLSI applications. Shallow silicided junctions are formed by implanting dopants into silicide layers previously formed by ion-beam mixing with Si ions and low temperature annealing, and the subsequent drive-in of the implanted ions into the Si substrate during high temperature RTP. In addition, the formation of TiN on TiSi2 is achieved simultaneously during this process as a diffusion barrier for Al metallization. Short-channel MOS transistors with SALICIDE structure have been successfully fabricated and tested. Results of the impurity diffusion in silicide layer, the impurity segregation at both silicide/Si and oxide/silicide interfaces, contact stabilit of Al/TiN/TiSi2 structure, and device characteristics will be reported. Issues related to this process and its application to submicron device fabrication are discussed and foreseeable problem areas identified.