Lifetime degradation of n-type Czochralski silicon after hydrogenation

Abstract

Hydrogen plays an important role in the passivation of interface states in silicon-based metal-oxide semiconductor technologies and passivation of surface and interface states in solar silicon. We have shown recently [Vaqueiro-Contreras et al., Phys. Status Solidi RRL 11, 1700133 (2017)] that hydrogenation of n-type silicon slices containing relatively large concentrations of carbon and oxygen impurity atoms {[C s ] ! 1 Â 10 16 cm À3 and [O i ] ! 10 17 cm À3 } can produce a family of C-O-H defects, which act as powerful recombination centres reducing the minority carrier lifetime. In this work, evidence of the silicon's lifetime deterioration after hydrogen injection from SiN x coating, which is widely used in solar cell manufacturing, has been obtained from microwave photoconductance decay measurements. We have characterised the hydrogenation induced deep level defects in n-type Czochralski-grown Si samples through a series of deep level transient spectroscopy (DLTS), minority carrier transient spectroscopy (MCTS), and high-resolution Laplace DLTS/MCTS measurements. It has been found that along with the hydrogen-related hole traps, H 1 and H 2 , in the lower half of the gap reported by us previously, hydrogenation gives rise to two electron traps, E 1 and E 2 , in the upper half of the gap. The activation energies for electron emission from the E 1 and E 2 trap levels have been determined as 0.12, and 0.14 eV, respectively. We argue that the E 1 /H 1 and E 2 /H 2 pairs of electron/hole traps are related to two energy levels of two complexes, each incorporating carbon, oxygen, and hydrogen atoms. Our results show that the detrimental effect of the C-O-H defects on the minority carrier lifetime in n-type Si:O þ C materials can be very significant, and the carbon concentration in Czochralski-grown silicon is a key parameter in the formation of the recombination centers. V

Correlated annealing and formation of vacancy-hydrogen related complexes in silicon

“…The DLTS spectrum of the as-implanted sample shows signals of several defects: E1, E2, VO, V 2 (−/0), double acceptor state of trivacancy (V 3 (=/−)) [11], VOH, E4, E5 * and E5. The E1 and E2 peaks in figure 1 are observed together only in H-containing samples, and their energy positions are close to those attributed to carbon-oxygen-hydrogen complexes in [12,13] and labeled there E1 and E2 as well. The E4 peak consists of overlapping contributions from V 2 (−/0) and, presumably, V 2 H(−/0) [8,14,15].…”

Electronic Properties and Structure of Boron–Hydrogen Complexes in Crystalline Silicon

“…These peaks can be related to oxygen-related thermal double donors, carbonhydrogen, and carbon-oxygen-hydrogen complexes. [32,33,[41][42][43][44] Annealing at 100 C under reverse bias has resulted in the appearance of a strong electron emission signal with its maximum at about 87 K in the DLTS spectrum. It can be seen from Figure 2b that the average concentration of the RBA-induced trap is about 2.5 Â 10 13 cm À3 .…”

“…Three dominant electron emission signals with their maxima at about 69, 78, and 90 K are observed in the DLTS spectrum of the plasma‐hydrogenated sample. A comparison of DLTS signatures of the observed traps with those, which are available in the literature for silicon samples subjected to similar treatments, allows us to suggest that the peaks with their maxima at 69 and 78 K are related to acceptor levels of the COH complexes, [ 43,44 ] and the peak with its maximum at 90 K to two CH complexes. [ 32 ] The RBA treatment has resulted in some tiny changes in the magnitudes of the peaks due to the COH complexes, and in a small increase in the magnitude of the peak due to the CH complexes.…”