2019 Fiscal Year Research-status Report
Selective growth of ultra-long grain in metal thin film for microelectronic application
| Project/Area Number |
18K14139
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| Research Institution | Shimane University |
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Principal Investigator |
Pham Hoang.Anh 島根大学, 学術研究院理工学系, 助教 (60750213)
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| Project Period (FY) |
2018-04-01 – 2021-03-31
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| Keywords | Thin film / Aluminum film / Gold film / Laser annealing / Selective growth / Single crystal |
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| Outline of Annual Research Achievements |
In the FY2019, we investigated the effect of reflectivity on the laser annealing process of the sputtered Al films. The Al thin films were deposited by sputtering with thickness varied from 15 nm to 100 nm. At the laser wavelength 405 nm, the reflectivity of the thermally deposited film (50 nm thick) was 66%, while the reflectivity of the sputter-deposited films was 80-96%, which increased with film thickness. Within this range of reflectivity, stable growth of single-grain crystal could not be maintained. We have tried Al-Si3N4 and Al-Si2O sandwich structure to control the reflectivity. The reflectivity of Al (20 nm) - Si4N3 (36 nm) can be reduced to 67%. However, single-grain crystal could not be obtained. It was probably that the energy was mainly absorbed by Si4N3 layer instead of Al.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
By changing the sputtering parameters, the Al film thickness and surface roughness can be controlled, but the reflectivity still remained high (>80%). Application of Al-Si3N4 sandwich structure reduced further the reflectivity, but the energy absorption by Al film was insufficient to maintain a stable melting pool for single-grain growth.
We also investigated the laser annealing process of Au thin films 40-60 nm thick. Au film was melted easily by laser annealing, but single grain growth could not be realized. The reason could be the high vapor pressure of Au at its melting point and poor wettability of Au on SiO2 substrate. At lower laser power, we observed solid stage grain growth in Au films, leading to surface smoothening, formation of strong (111) texture with large grain sizes.
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| Strategy for Future Research Activity |
Through this study, the effect of reflectivity, vapor pressure and wettability of the metal on the single-grain crystal growth by laser annealing has been understood. A new laser annealing system is being built with the ability to adjust the laser wavelength. By this way, the wavelength corresponding to the minimum reflectivity of Al films (about 810 nm) can be used to optimize the laser annealing process of sputter-deposited Al thin films.
In the FY2020, we are also going to investigate the effect of SiO2 cap layer on the laser annealing process of Au films. The application of SiO2 cap layer is to suppress evaporation of Au melt due to its high vapor pressure. By this way, the Au melting pool is expected to be stabilized for single-grain crystal growth.
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| Causes of Carryover |
Purchase of Au thin films was delayed due to personnel changes of the providing company. We are plane to order Au sputtering target to prepare the Au films by ourselves.
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