Effects of hydrogen implantation temperature on ion-cut of silicon

Abstract

We have studied the effect of ion implantation temperature on the nature of cleavage and layer transfer, and the electrical properties in hydrogen implanted p-Si. The lattice damage and the hydrogen concentration in the as-implanted Si and transferred Si films were analyzed with elastic recoil detection, respectively. Implantations performed at −140 °C [low temperature (LT)] and room temperature (RT) resulted in a variation in the thickness and surface morphology of the transferred layers. The transferred layer from room temperature hydrogen ion implantation was both thicker and atomically smoother than the transferred layer produced by −140 °C hydrogen implantation. The as-transferred layer obtained from RT-implanted p-Si wafer was n-type, but converted to p-type after annealing at 650 °C or higher. The transferred layer obtained from LT-implanted Si wafer was highly resistive even after high temperature annealing. These variations were observed to be correlated with the damage profiles measured by ion channeling; channeling data showed that the room temperature implantation provided a deeper and narrower damage distribution than that obtained from the −140 °C implantation. The nature of the implantation damage was evaluated with the aid of IR spectroscopy and was found to consist of Si–H defects. The type and population of these defects were observed to be dependent on the ion implantation temperature. In both room temperature and −140 °C implantations, the presence of the implantation damage facilitated the nucleation of Si–H defects that developed into H platelets, which were the precursor defects for the cleavage and the layer transfer.

Microwave enhanced ion-cut silicon layer transfer

“…For the given concentrations and energies of hydrogen and boron ions irradiating the sample, these results are consistent with previous papers. 9,20,22 As can be seen in Fig. 4͑b͒, after sequential anneals to repair radiation damage there is no visible damage near the surface of the transferred layer.…”

“…Because previous research efforts used conventional annealing methods, the radiation repair anneals in this work were done using conventional means in order to attain higher temperatures and to have a common reference point. 9,20,26 When viewing the data in Table I, most noteworthy is the change in conductivity type and the temperature of the anneals where this change takes place. Previous researchers have also observed this behavior, in which the surfaces of uncut samples start the fabrication process as p type, and after the cut step in Fig.…”

“…Spectra from both random and channeled orientations demonstrate that the ion-cut process was successful in using microwaves to initiate the exfoliation, and coherent layer transfer, of single crystal silicon. 19,20 Spectrum ͑c͒, obtained from an "as-cut" sample in random orientation, indicates the presence of a continuous layer of silicon on top of the insulator, while also hinting at a mild surface microroughness as is evident from the width of the low energy edge at channels 150-160. 20 RUMP simulation of the RBS spectra ͑c͒ determined the thickness of the transferred layer to be 475 nm and that of the oxide layer 500 nm.…”

“…19,20 Spectrum ͑c͒, obtained from an "as-cut" sample in random orientation, indicates the presence of a continuous layer of silicon on top of the insulator, while also hinting at a mild surface microroughness as is evident from the width of the low energy edge at channels 150-160. 20 RUMP simulation of the RBS spectra ͑c͒ determined the thickness of the transferred layer to be 475 nm and that of the oxide layer 500 nm. Spectrum ͑b͒, obtained from a ͓001͔ aligned sample of as-cut SOI, shows a dramatic decrease in yield, indicating that the transferred layers have kept most their crystallinity.…”

“…Depending on implantation parameters, incubation times, and anneal temperatures, previously published microroughness values vary between 3.4 and 10 nm over 1 m sampling distances. 20,21,26 An established method of removing the lattice damage created during the ion-cut process is through a radiation repair treatment which consists of high temperature anneals. 9,20,26 Table I demonstrates the electrical behavior of as-cut and postannealed transferred layers fabricated using the ion-cut process shown in Fig.…”