Laser annealing

Figure 5 CL spectra of uHrahigh vacuunn-cleaved CdS before and after in situ deposition of 50 A of Cu, and after in situ laser annealing using an energy density of 0.1J /cm. The electron-beam voltage is 2 kV. ...

Boron implant with laser anneal. Boron atoms are accelerated into the backside of the CCD, replacing about 1 of 10,000 silicon atoms with a boron atom. The boron atoms create a net negative charge that push photoelectrons to the front surface. However, the boron implant creates defects in the lattice structure, so a laser is used to melt a thin layer (100 nm) of the silicon. As the silicon resolidihes, the crystal structure returns with some boron atoms in place of silicon atoms. This works well, except for blue/UV photons whose penetration depth is shorter than the depth of the boron implant. Variations in implant depth cause spatial QE variations, which can be seen in narrow bandpass, blue/UV, flat fields. This process is used by E2V, MIT/LL and Samoff. 

MBE growth of very thin layer of boron and silicon. The problems associated with boron implant and laser anneal can be overcome by growing a very thin (5 nm) layer of silicon with boron atoms on the backside of the thinned CCD (1% boron, 99% silicon). The growth is applied by molecular beam epitaxy (MBE) machines. This process was developed by JPL and MIT/LL. 

A wide variety of process-induced defects in Si are passivated by reaction with atomic hydrogen. Examples of process steps in which electrically active defects may be introduced include reactive ion etching (RIE), sputter etching, laser annealing, ion implantation, thermal quenching and any form of irradiation with photons or particles wih energies above the threshold value for atomic displacement. In this section we will discuss the interaction of atomic hydrogen with the various defects introduced by these procedures. 

G.E. Jellison, Jr., Optical and Electrical Properties of Pulsed Laser-Annealed Silicon R.F. Wood and G.E. Jellison, Jr., Melting Model of Pulsed Laser Processing R.F. Wood and F.W. Young, Jr., Nonequilibrium Solidification Following Pulsed Laser Melting... 

D.M. Zehner, Surface Studies of Pulsed Laser Irradiated Semiconductors D.H. Lowndes, Pulsed Beam Processing of Gallium Arsenide R.B. James, Pulsed C02 Laser Annealing of Semiconductors R. T. Young and R.F. Wood, Applications of Pulsed Laser Processing... 

Sameshima, T. Usui, S. Sekiya, M. 1986. XeCl excimer laser annealing used in the fabrication of poly-Si TFTs. IEEE Electron Device Lett. 7 276-278. 

D. Hill, T. Jawhari, J.G. Cespedes, J.A. Garcia and E. Bertran, In-situ monitoring of laser annealing by micro-Raman spectroscopy for hydrogenated silicon nanoparticles produced in radio frequency glow discharge, Phys. Status SolidiA, 203, 1296-1300 (2006). 

Historically thermal annealing has been the method of removing implantation damage. Recently however, laser annealing has been pursued as an attractive alternative. Tsien, et al. 

White and Christie used SIMS and RBS to measure dopant profile broadening caused by pulsed laser annealing (47). They also observed the incorporation of Group III-V dopants in Si at levels exceeding previously accepted solid solubility limits. Non-substitutional species, like Fe, were not incorporated in the Si but were segregated to the surface. 

Figure 5. RBS spectra obtained from near random and aligned orientations for pulsed-laser annealed, As ion-implanted Si. (Reproduced, with permission, from Ref. 46. Copyright 1981, Journal of Applied Physics.,)...

Photo-detector regions are formed in JP-A-1205476 by laser annealing a multi-layer structure of HgTe and CdTe. Radiation which has generated charge carriers between two detector elements will be absorbed in the multi-layer structure thereby reducing cross-talk. 

In JP-A-3108371 cross-talk is reduced by introducing metal atoms by a laser annealing process at regions between photodiodes. 

Inoue, S. Utsunomiya, S. Saeki, T. and Shimoda, T. (2002) Surface-Free Technology by Laser Annealing (SUFTLA) and Its Application to Poly-Si TFT LCDs on Plastic Film With Integrated Drivers. IEEE Trans. Electron Devices, 49, 1353—1360. 

Botti, S., Asilyan, L.S., Ciardi, R., Fabbri, F., Forety, S., Santoni, A., and Orlanducci, S. Catalyst-free growth of carbon nanotubes by laser annealing of amorphous SiC films. Chem. Phys. Lett. 396, 2004 1-5. 

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