Which variables (such as pull speed, melt temperature, annealing temperature/duration, cooling rate, etc.) affect the grain size of czochralski-grown polycrystalline silicon? In what direction does increasing/decreasing these variables influence grain size? What other controllable variables increase/decrease grain size?
Kalainathan et al. have reported that annealing at higher temperatures, and for longer durations, increases the grain size. After annealing, Sabatino et al. report that high cooling rates lead to larger grain sizes. Has there been success with these methods?
Dear@Aaron,
welcome!
Czochralski method is used normally to grow single crystal by pulling the crystal out of the silicon melt. One starts with single crystal seed in form of slim rod which is immersed in the melt at the beginning and then one starts to pull the rod slowly
to form a much larger single crystal rod. The parameters of the growth resulting in single crystal is published in literature.
Perhaps the most suitable method for polycrystal is the directional solidification to get columnar structure.
From the theoretical point of view the formation of polycrystalline structure starts with the nucleation phase and ends with the growth phase. Both phases contribute to the grain size. If one increases the number of nucleus in the first phase then one gets smaller grains that can be further grown by further deposition.
By annealing at elevated temperature one increase some grains on the cost of their neighbors.
Polycrystals can be obtained spontaneously by depositing silicon with high rate at low temperature substrate. This is called the supersaturation condition.
Best wishes
Dear@Aaron,
welcome!
Czochralski method is used normally to grow single crystal by pulling the crystal out of the silicon melt. One starts with single crystal seed in form of slim rod which is immersed in the melt at the beginning and then one starts to pull the rod slowly
to form a much larger single crystal rod. The parameters of the growth resulting in single crystal is published in literature.
Perhaps the most suitable method for polycrystal is the directional solidification to get columnar structure.
From the theoretical point of view the formation of polycrystalline structure starts with the nucleation phase and ends with the growth phase. Both phases contribute to the grain size. If one increases the number of nucleus in the first phase then one gets smaller grains that can be further grown by further deposition.
By annealing at elevated temperature one increase some grains on the cost of their neighbors.
Polycrystals can be obtained spontaneously by depositing silicon with high rate at low temperature substrate. This is called the supersaturation condition.
Best wishes
I think annealing between 1050-1100deg C for 30 minutes, will increase the grain size.
Temperature of the melt and pulling speed are most important to obtain a mono crystal. If you obtain a crystal with a dislocation, reverse the pulling direction until the crystal re-melts.
Hi,
In my case, the grain size, crystallinity and roughness of the thin film are increasing with increasing annealing time, temperature and deposition time which directly affect the formation of the crystals.
Aaron B. Christian
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