Transient enhanced diffusion after laser thermal processing of ion implanted silicon

Abstract

The effect of laser thermal processing ͑LTP͒ on implantation-induced defect evolution and transient enhanced diffusion ͑TED͒ of boron was investigated. A 270-Å-thick amorphous layer formed by 10 keV Si ϩ implantation was melted and regrown using a 20 ns ultraviolet laser pulse. Transmission electron microscopy revealed that recrystallization of the amorphous layer following LTP results in a high concentration of stacking faults and microtwins in the regrown region. Also, the end-of-range loop evolution during subsequent 750°C furnace annealing, is different in a LTP sample compared to a control sample. Secondary ion mass spectroscopy of a boron marker layer 6000 Å below the surface showed that LTP alone produced no enhanced diffusion. However, during subsequent furnace annealing, the boron layer in the LTP sample experienced just as much TED as in the control sample which was only implanted and furnace annealed. These results imply that laser melting and recrystallization of an implantation-induced amorphous layer does not measurably reduce the excess interstitials released from the end-of-range implant damage. © 1999 American Institute of Physics. ͓S0003-6951͑99͒00149-7͔Continued scaling of the transistor to sub-100 nm dimensions requires the formation of ultrashallow highly doped abrupt junctions for contact formation. A box-shaped, high dopant concentration profile could ideally meet such a requirement. 1 Ion implantation and conventional rapid thermal annealing inevitably lead to less than ideal Gaussian or exponential dopant profile. Also, the interaction between implantation induced point defects and dopant atoms during annealing can considerably broaden the profile shape through transient enhanced diffusion ͑TED͒. One proposed method for circumventing some of these problems is the use of laser annealing. 2 Various approaches proposed include: melting and regrowing crystalline silicon in the presence of a dopant ͑the PGILD process͒ or preamorphization of the surface by implantation followed by a dopant implant into the amorphous material and finally laser melting only the amorphous material ͓also called laser thermal processing ͑LTP͔͒. 2-4 The advantage of the second method is that lower temperatures can be used because amorphous Si melts at a temperature 300°C lower than crystalline Si. This is important because it allows thickness of the melted region to be controlled by the preamorphization.One question that remains is does LTP have an advantage in the transient enhanced diffusion reduced from the implant. It is well known that after implantation induced amorphization of Si, there exists a highly damaged region in the crystalline material just beyond the amorphous/ crystalline interface. 5 This layer, referred to as the end-ofrange ͑EOR͒ damage region, is known to contain a large supersaturation of interstitials. During annealing these interstitials are released and flow both toward the surface and into the bulk, resulting in TED of the common dopants ͑e.g., B, As, P͒. 6 This TED has the undesirable effe...

Varying implant dose rate for defect reduction in laser thermal processing

“…Laser thermal processing (LTP), which involves the melting and recrystallization of a preamorphized layer, has shown promising results in creating low resistance ultra shallow junctions [1]. However, as previously reported [2], there is a high density of stacking faults and microtwins after LTP processing. During LTP, the power is set such that only the amorphous layer melts and thus, the recrystallization process originates at the amorphous/crystalline (a/c) interface.…”

“…Defect densities after LTP at powers of 0.73-0.77 J/ cm 2 were investigated for all dose rates. Fig.…”

Reliability Issues Related to Laser-Annealed Implanted Back-Wafer Contacts in Bipolar Silicon-on-Glass Processes

“…Since they can travel easily in silicon, they are not confined to the actual implanted contact region. The interstitials are not directly annealed by the laser annealing, which only recrystallizes a few tens of nanometers thin region at the surface [7].…”

Role of low temperature rapid thermal annealing in post-laser-annealed p-channel metal-oxide-semiconductor field effect transistor

“…3͑a͒, the high leakage current is due to the presence of crystalline defects, such as stacking faults, microtwins, dislocation, and EOR damage, extending throughout the original PAI region that could not be removed by the single-pulse LA. [13][14][15] Fast recrystallization of the melted PAI region causes the formation of crystalline defects. [13][14][15] Even the recrystallized PAI layer is epitaxial with the Si ͑100͒ substrate, as shown by the diffraction pattern in the inset in Fig.…”

“…[13][14][15] Fast recrystallization of the melted PAI region causes the formation of crystalline defects. [13][14][15] Even the recrystallized PAI layer is epitaxial with the Si ͑100͒ substrate, as shown by the diffraction pattern in the inset in Fig. 3͑a͒; the crystalline defects lead to the highly leaky junctions shown in Fig.…”