Annealing Chamber Research Articles

Selective Area Mass Transport Regrowth of Gallium Nitride

Selective area mass transport regrowth of GaN was performed on wafers with etched wells and SiO2 mask. The samples were annealed in NH3 and H2 flow, with no gallium precursor. At 1060°C, only little mass transport occured, but the sidewall morphology changed, depending on crystallographic orientation. At 1160°C, the sidewalls grew out about 1 µm in 1 min, independent of orientation. The technique can potentially be performed in an annealing chamber, providing a low cost regrowth process. A promising application is ohmic contact regrowth to high composition AlGaN/GaN high electron mobility transistors.

Structural reordering and electrical activation of ion-implanted GaAs and InP due to laser annealing in a controlled atmosphere

The effects of the ambient atmosphere in the annealing chamber on the electrical and structural characteristics of Zn-implanted III-V compound semiconductors, processed by low-power pulsed-laser annealing are presented. The samples were analyzed using several complementary experimental techniques: Reflection high-energy electron diffraction, Rutherford backscattering spectroscopy, Raman spectroscopy, secondary ion mass spectroscopy, and electrical measurements. During the laser beam irradiation in the presence of gas inlet into the annealing chamber the ambient gas atoms diffused well into the target changing the stoichiometry and the electrical parameters. Redistribution of the implanted impurity was also observed. By varying the type of gas used and its pressure, it was possible to achieve electrical activation of up to 80%. It seems all structure and electrical parameters achieve their best values at the same ambient atmosphere and density of the deposited laser power P, e.g., 1.5 atm of ${\mathrm{N}}_{2}$ and $P=6.5 {\mathrm{M}\mathrm{W}/\mathrm{c}\mathrm{m}}^{2}$ for InP.

Synthesis of high quality CdTe films by graphite box annealing

CdTe films were prepared by graphite box annealing of an evaporated CdTe precursor in different ambient conditions in the quartz annealing chamber. Large grain growth was observed for films synthesized at 710 K in argon atmosphere. The films thus produced were characterized by measuring the optical, microstructural and electrical properties.

Properties of multilayered thin films for thermal ink-jet printing devices

The material properties of sputtered HfB 2, Al alloy, and Ta thin films have been studied to understand their behavior in the thin film heater stack used in ink-jet printing devices. The electrical resistivity of the HfB 2 heater film was found to increase with increasing working pressure, reflecting the dominant effect of grain boundary scattering on the conduction electrons. Also the stress variations in the HfB 2 and Ta samples are described during the thermal cycling, respectively. The HfB 2 (∼ 0.1 μm) stress can be repeatedly controlled from tension (+3 × 10 9 dyn/cm 2, 100°C) to compression (−3.5 × 10 9 dyn/cm 2, 400°C). However, the compressive stress of the sputtered Ta film (∼0.6 μm) was observed to increase after each thermal cycle until film cracking. Auger examinations indicate that the stress-temperature behavior of Ta is due to the incorporation of oxygen impurities resulting from the poor atmosphere seal of the quartz annealing chamber.

Development of a Cluster Tool and Analysis of Deposition of Silicon Oxide by TEOSO2 PECVD

AbstractA single wafer cluster tool was developed. It is composed of a central robot arm wafer handler and three processing chambers: a RF PECVD chamber, a microwave after glow RPECVD chamber and a rapid thermal annealing chamber. The tool is designed to allow high flexibility, with in-situ multi-sequential processing capability. An in depth study of the deposition of silicon oxide by PECVD was performed. As unique features, it handles TEOS vapor without a carrier gas and it includes a double stage gas distribution system. The films were characterized by means of: ellipsometry, FTIRS, RBS, AES, SIMS, stress and etch rate in diluted (1:100) HF solution. Good uniformity (>98 %) was obtained. The results show that the quality of the films is most influenced by the wafer temperature and flux of oxygen. For the best condition, the following results were obtained: deposition rate of 370 nm/min., refraction index of 1.46, stoichiometry of 2.0, intrinsic stress of 1.3×109 dyn/cm2, carbon content below the AES and SIMS detection limit and low OH content. We also propose a model that fits our results.

Minimal Glass Deformations with Rapid Thermal Annealing Control

A critical step in the fabrication of polycrystalline silicon thin-film transistors (TFT's) is to crystallize the amorphous silicon layer deposited on glass. This paper describes a complete rapid thermal annealing (RTA) process applied to the crystallization of the amorphous layer. The RTA heating and cooling rates have been optimized to minimize thermal gradients and to improve glass substrate stability. Numerical simulations taking into account the lamp characteristics, the annealing chamber configuration and the sample properties have been developed and allow elucidation of thermal nonuniformities in the sample during the RTA process. Although the transition point of a glass (T g) is often considered as an upper limit in usual polysilicon TFT's processes, this paper shows that if the cooling rate is accurately controlled, annealing temperatures can be above T g without thermal damage to the glass.

Repeated compressive stress increase with 400 °C thermal cycling in tantalum thin films due to increases in the oxygen content

Stresses which build up in thin films such as tantalum, during thermal processing, can cause major reliability problems in electronic and x-ray optics applications. We demonstrate that 50–200 nm thick sputtered β-Ta thin films undergo repeated compressive stress increases when thermally cycled to 400 °C (at a rate of 10 °C/min) and back in a purified He ambient because of small amounts of oxygen gettered by the tantalum. The oxygen contamination results from the poor quality of the atmospheric seal on the quartz annealing chamber. As-deposited Ta thin films have a compressive stress ranging from −1 to −4 GPa. The compressive stress buildup was monitored in situ and was shown to increase −0.5 GPa on average after each thermal cycle for a final value from −6 to −7 GPa after seven cycles. After being cycled thermally seven times any perturbation of the film such as a four-point probe resistivity measurement can cause the film to instantaneously crack in a serpentine pattern, relieving the large compressive stress. Auger electron spectroscopy depth profiling analysis was used to determine that the as-deposited film contained 1 at. % oxygen which increased to 8%–12% after seven thermal cycles with an approximate doubling in resistivity. The −0.5 GPa average compressive stress increase in Ta thin films when cycled to 400 °C is attributed to a 1.3% increase in oxygen concentration leading to a Ta unit cell expansion of 0.6%.

Compressive Stress Increase With Repeated Thermal Cycling in Tantalum(Oxygen) Thin Films

ABSTRACTStresses which build up in thin films, such as tantalum, during thermal processing, can cause major reliability problems in x-ray optics and electronic applications. We have demonstrated that 50 nm to 200 nm thick sputtered beta tantalum thin films undergo repeated compressive stress increases when thermally cycled from room temperature to 400°C (at 10°C/min) and back in a purified He ambient because of low levels of oxygen gettered by the tantalum. The oxygen contamination is a result of the poor quality of the quartz annealing chamber atmospheric seal. As-deposited stress in the sputter deposited tantalum films ranges from -1 to -4 GPa. The compressive stress build up was monitored in situ and was shown to increase -0.5 GPa on average after each thermal cycle for a final value of -6 to -7 GPa after seven cycles. After being cycled thermally seven times any perturbation of the film such as a four point probe resistivity measurement can cause the film to instantaneously crack in a serpentine pattern relieving the large compressive stress. Auger electron spectroscopy depth profiling analysis indicated that the as-deposited films contained one atomic percent oxygen which increased to eight to twelve percent after seven thermal cycles accompanied by an approximate doubling in resistivity. In conclusion, the increase in oxygen concentration in tantalum thin films which occurs upon thermal cycling leads to a repetitive increase in compressive stress which could be detrimental when the films are used in x-ray or electronic applications.