Engineering topics

Lane, R. L.

Publications and source records attributed to Lane, R. L..

8 records

NASA NTRS1984

Cold-Crucible Premelter for Silicon

System allows replenishment of silicon melt in crystal puller. Cold crucible consists of water-cooled, silver plated boat in 500kHz field. Induced secondary currents cause preheated chunks of silicon to melt. Magnetic repulsion between current in silicon and in boat prevents silicon from touching boat. Used for crystal growth of other materials sufficiently conductive and difficult to keep free of contamination by container walls at temmperature of operation.

Lane, R. L.↗

NASA NTRS1984

Shield Boosts Silicon-Growth Rate

Radiation shield permits faster growth--by 20 percent--of singlecrystal silicon from molten silicon by producting sharper thermal gradients near growth front.

Lane, R. L.↗

NASA NTRS1983

Modified Silicon Furnace Lowers Crystal Cost

Modified Czochralski setup grows several large crystals in succession from one crucible. Modified apparatus is expected to reduce cost per crystal by about 50 percent. Key features are: isolation valve between growth and pulling chamber, and recharging mechanism. Functional changes reduce cycle time and prolong crucible life.

Lane, R. L.↗

NASA NTRS1982

Recharging the Silicon Crucible in a Hot Furnace

"Melt recharger" adds raw silicon to crucible in crystal-growing furnace without disturbing inert-gas atmosphere or significantly lowering temperature of melt. Crucible-refill hopper is lowered into hot zone of crystal-pulling chamber through an isolation valve. Cable that supports hopper is fastened to cone-shaped stopper in bottom of hopper. Stopper moves out of opening in hopper, allowing part of polysilicon charge to drop into crucible.

Lane, R. L.↗

NASA NTRS1982

Advanced Czohcralski ingot growth

A summary of advanced Cz ingot-growth activities is presented. Five ingots (totalling 150 kg) were grown from one crucible by use of chunk silicon replenishment between ingot pulls. The cost of the ingot growth was reduced from $80/kg (conventional Cz growth) to $20/kg. Further improvements can be made by achieving a better understanding of crystalline silicon growth and the influence on growth of contaminants from the atmosphere and/or the crucible. This should lead to a higher percentage of monocrystalline growth and possible increased growth rates.

Lane, R. L.↗

NASA NTRS1981

Development of advanced Czochralski growth process to produce low cost 150 kg silicon ingots from a single crucible for technology readiness

Six growth runs used the Kayex-Hameo Automatic Games Logic (AGILE) computer based system for growth from larger melts in the Mod CG2000. The implementation of the melt pyrometer sensor allowed for dip temperature monitoring and usage by the operator/AGILE system. Use of AGILE during recharge operations was successfully evaluated. The tendency of crystals to lose cylindrical shape (spiraling) continued to be a problem. The hygrometer was added to the Furnace Gas Analysis System and used on several growth runs. The gas chromatograph, including the integrator, was also used for more accurate carbon monoxide concentration measurements. Efforts continued for completing the automation of the total Gas Analysis System. An economic analysis, based on revised achievable straight growth rate, is presented.

Lane, R. L.↗

NASA NTRS1980

Performance of silicon solar cells fabricated from multiple Czochralski ingots grown by using a single crucible

Results on the performance of solar cells fabricated on wafers from multiple silicon ingots of large diameter, grown by using a single crucible and a sequential melt replenishment Czochralski (CZO) technique are presented. Samples were analyzed for resistivity, dislocation density and impurity content. Solar cells were fabricated from the seed, center and tang end of each ingot to evaluate the growth reproducibility and material quality. The cell efficiency within a given wafer varies by no more than plus or minus 5% of the average value. A small but consistent decrease in the cell efficiency is observed from the first to the fourth ingot grown from a single crucible. This decrease may be related to an increase in impurity content or dislocation density or a combination of both. The efficiency of the cells fabricated from the tang end of the fourth ingot is about 10% lower than that of the control cell. An impurity effects model is employed to correlate this decrease in efficiency with the impurity build-up in the residual melt.

Kachare, A. H.↗

NASA NTRS1980

Mutiple Czochralski growth of silicon crystals from a single crucible

An apparatus for the Czochralski growth of silicon crystals is presented which is capable of producing multiple ingots from a single crucible. The growth chamber features a refillable crucible with a water-cooled, vacuum-tight isolation valve located between the pull chamber and the growth furnace tank which allows the melt crucible to always be at vacuum or low argon pressure when retrieving crystal or introducing recharge polysilicon feed stock. The grower can thus be recharged to obtain 100 kg of silicon crystal ingots from one crucible, and may accommodate crucibles up to 35 cm in diameter. Evaluation of the impurity contents and I-V characteristics of solar cells fabricated from seven ingots grown from two crucibles reveals a small but consistent decrease in cell efficiency from 10.4% to 9.6% from the first to the fourth ingot made in a single run, which is explained by impurity build-up in the residual melt. The crystal grower thus may offer economic benefits through the extension of crucible lifetime and the reduction of furnace downtime.

Lane, R. L.↗