Laser Damage Gettering and Its Application to Lifetime Improvement in Silicon

Abstract

Lattice defects induced by laser irradiation and their thermal stability during subsequent oxidation were studied by transmission electron microscopy, x‐ray topography, and preferential etching. High power laser pulses above 20 J/cm2 produced dislocation lines and dislocation clusters. Laser pulses of about 15 J/cm2 also generated dislocation clusters and pseudo‐swirl defects in the irradiated region. All of these defects were thermally stable. However, thermally stable defects were not observed when laser pulses of less than 15 J/cm2 were used, although unstable dislocations were generated. The suppression of defect formation by laser damage gettering was examined using Sirtl etching. It was found that thermally stable dislocations and pseudo‐swirl defects acted as sinks for point defects and prevented the formation of precipitates during a subsequent oxidation. Laser damage gettering was used to improve generation lifetime in metal‐oxide‐semiconductor (MOS) capacitors with the result that generation lifetime in the gettered area was improved by two orders of magnitude over that in the ungettered area.

Application of photoluminescence characterization to the development and manufacturing of high-efficiency silicon solar cells

“…37 With the correct use of post-ablation NaOH etching, the formation of these dislocations can be avoided. 38,39 Many solar cell structures incorporate laser ablation steps to form contacts or as an edge isolation technique or to sculpture the surface for specific cell designs.…”

An introduction to gold gettering in silicon

“…The damage is produced using a variety of techniques such as a laser, abrasion, phosphorus diffusion, etc. During subsequent thermal anneals, the damaged areas on the backside act as sinks which are thought to cause the migration of metals from the bulk and surface of the wafer to the backside (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30).…”

Getters in silicon

“…[1]. There is also a special damaged layer production method in inactive wafer regions by high-energy laser irradiation [8][9][10][11]. After irradiation the wafers are annealed with the aim to form a dislocation structure with the required in-layer defect density.…”