Nickel induced crystallization of amorphous silicon thin films

Abstract

Nickel ͑Ni͒ induced crystallization of amorphous silicon (a-Si) has been studied by selective deposition of Ni on a-Si thin films. The a-Si under and near the Ni-covered regions was found to be crystallized after heat treatment at 500°C from 1 to 90 h. Micro-Auger electron spectroscopy revealed that a large amount of Ni stayed in the region under the original Ni coverage, but no Ni was detected either in the crystallized region next to the Ni coverage or in the amorphous region beyond the front of the laterally crystallized Si. X-ray photoelectron spectroscopy revealed a nonuniform Ni distribution through the depth of the crystallized film under the original Ni coverage. In particular, a Ni concentration peak was found to exist at the interface of the crystallized Si and the buried oxide. It was found that a layer of 5-nm-thick Ni could effectively induce lateral crystallization of over 100 m of a-Si, but the lateral crystallization rate was found to decrease upon extended heat treatment. Transmission electron microscopy analysis showed that the crystallized film under the Ni coverage was composed of randomly oriented fine grains, while that outside the Ni coverage was mainly composed of large ͑110͒-oriented grains. A unified mechanism is proposed to explain the Ni induced crystallization of a-Si and possible reasons for the reduction in the lateral crystallization rate are discussed.

Metal Induced Crystallization

“…This mechanism is supported by the following experimental observations. Jin et al (Jin et al, 1998) studied the XPS depth profile of Ni (10 nm) covered a-Si films (70 nm) which was annealed at 500 C for 1 hr. Ar ions with energy of 4 keV were used for sputtering during depth profiling.…”

Characterization of the MIC/MILC interface and its effects on the performance of MILC thin-film transistors

“…This crucial but missing information might be particularly relevant to the unexpectedly high leakage current measured in conventional MILC TFT's [9], in which the edge of the MIC region is self-aligned to the edge of the transistor channel region. Furthermore, while the crystal grains are indeed larger in MILC poly-Si films [4], [6], the corresponding field effect mobility is still lower than those typically reported for poly-Si films obtained using laser crystallization [10] or SPC of Si implanted a-Si [11]. This suggests that the crystal grains in low temperature MILC films may be less ideal and may contain a significant number of intra-granular defects.…”

“…While no measurable amount of Ni has been detected within the MILC region using either transmission electron microscopy (TEM) [5], [6] or Auger electron spectroscopy (AES) [4], none of these techniques are particularly appropriate for trace element detection. Therefore, it is still not clear how Ni is distributed, from inside the MIC region, across the MIC/MILC interface, through the MILC region and finally across the MILC front to inside the a-Si region.…”

“…growth [4]. Low temperature TFT's with high field effect mobility have been fabricated [6]- [8], thus establishing MILC as a potentially enabling technology for realizing systems requiring low process temperature yet with high performance transistors-such as the active matrix liquid crystal displays with on-panel integrated driver circuits.…”

32.3: Metal‐Induced Unilaterally Crystallized Polycrystalline Silicon Thin‐Film Transistor Technology for Active‐Matrix Organic Light‐Emitting Diode Displays with Reduced Susceptibility to Cross‐Talk

“…Nickel was evaporated before heat treatment at 500 o C for metal-induced lateral crystallization [6]. Any excess nickel was removed prior to heavy source/drain boron implantation, at a dose of 4x10 15 /cm 2 .…”