Thin crystalline Si layers are prospective for next generation solar cells due to low cost and for thin film transistors on plastic substrate in flat panel display. To make the thin-layer crystalline Si solar cells and transistors, a film transfer process is essential. The film transfer process consists of film growth on suitable substrates, separation of film from the substrate, and transfer of the film it to another substrate.
In our work, mica and $CoSi_2$/Si substrates were used to grow Si thin film. Firstly we tested the thermal stability of mica substrates. In solid phase crystallization process, mica substrates were unstable at the annealing temperature of 600℃. So metal induced crystallization carried out at lower crystallization temperature. Amorphous Si films were deposited at 200℃ by plasma enhanced chemical vapor deposition on mica substrate. A 0.1M Ni solution was coated on the amorphous Si films by spin coater. These films were crystallized at 500℃ and for 10 hr in a furnace. These films were completely crystallized without cracks. A mica is layer structure so we could delaminate the mica substrate after transferring the film to the plastic substrate.
Secondly, the $CoSi_2$ layers were grown in situ on a Si substrate by metal organic chemical vapor deposition. For thin $CoSi_2$, the uniform epi-Si growth was possible. But the agglomeration of $CoSi_2$ was found for thick $CoSi_2$. The $CoSi_2$ layers were epitaxially grown on the Si substrates. Then an epi-Si layer was grown in coherent with $CoSi_2$/Si substrates by liquid phase epitaxy from 985℃ to 900℃ for 3hr. The $CoSi_2$ layer can be selectively etched by 1:50(HF:DI water)solution to the epi-Si layer and Si substrate after transferring the epi-Si to plastic substrate.
Thirdly, we fabricated thin-layer crystalline Si solar cells by polishing a Si wafer. The $n^+pp^+$ and $n^+$p structure pn junctions were formed by ion showering and implantation, respectively. Also we simulated the wafer thickness influence on the photovoltaic characteristics of Si solar cell using PC1D and silvaco simulation tools. We fabricate a cell with the Si thickness of 50.8㎛ and characterized the photovoltaic characteristics.
