An assessment on crystallization phenomena of Si in Al/a-Si thin films via thermal annealing and ion irradiation

Formation techniques for upper active channel in monolithic 3D integration: an overview

The concept of three-dimensional stacking of device layers has attracted significant attention with the increasing difficulty in scaling down devices. Monolithic 3D (M3D) integration provides a notable benefit in achieving a higher connection density between upper and lower device layers than through-via-silicon. Nevertheless, the practical implementation of M3D integration into commercial production faces several technological challenges. Developing an upper active channel layer for device fabrication is the primary challenge in M3D integration. The difficulty arises from the thermal budget limitation for the upper channel process because a high thermal budget process may degrade the device layers below. This paper provides an overview of the potential technologies for forming active channel layers in the upper device layers of M3D integration, particularly for complementary metal-oxide-semiconductor devices and digital circuits. Techniques are for polysilicon, single crystal silicon, and alternative channels, which can solve the temperature issue for the top layer process.

Thermokinetic Study of Aluminum-Induced Crystallization of a-Si: The Effect of Al Layer Thickness

The effect of the aluminum layer on the kinetics and mechanism of aluminum-induced crystallization (AIC) of amorphous silicon (a-Si) in (Al/a-Si)n multilayered films was studied using a complex of in situ methods (simultaneous thermal analysis, transmission electron microscopy, electron diffraction, and four-point probe resistance measurement) and ex situ methods (X-ray diffraction and optical microscopy). An increase in the thickness of the aluminum layer from 10 to 80 nm was found to result in a decrease in the value of the apparent activation energy Ea of silicon crystallization from 137 to 117 kJ/mol (as estimated by the Kissinger method) as well as an increase in the crystallization heat from 12.3 to 16.0 kJ/(mol Si). The detailed kinetic analysis showed that the change in the thickness of an individual Al layer could lead to a qualitative change in the mechanism of aluminum-induced silicon crystallization: with the thickness of Al ≤ 20 nm. The process followed two parallel routes described by the n-th order reaction equation with autocatalysis (Cn-X) and the Avrami-Erofeev equation (An): with an increase in the thickness of Al ≥ 40 nm, the process occurred in two consecutive steps. The first one can be described by the n-th order reaction equation with autocatalysis (Cn-X), and the second one can be described by the n-th order reaction equation (Fn). The change in the mechanism of amorphous silicon crystallization was assumed to be due to the influence of the degree of Al defects at the initial state on the kinetics of the crystallization process.

Perspectives on metal induced crystallization of a-Si and a-Ge thin films

In recent times, the metal induced crystallization (MIC) process in amorphous semiconductors (a-Si and a-Ge) has been extensively investigated by many researchers due to potential applications of crystalline semiconductors in high-density data storage devices, flat panel displays, and high performance solar cells. In this context, we have presented a review on different schemes of MIC in metal/a-Si and metal/a-Ge bilayer films (with stacking change) on various substrates under different annealing conditions. The parameters, which limit crystallization of a-Si and a-Ge have been analyzed and discussed extensively keeping in mind their applications in solar cells and flat panel displays. The MIC of a-Si and a-Ge films under ion beam irradiation has also been discussed in detail. At the end, some suggestions to overcome the limitations of the MIC process in producing better crystalline semiconductors have been proposed. We believe that this review article will inspire readers to perform a thorough investigation on various aspects of MIC for further development of high efficiency solar cells and high quality flat panel displays.