It was known that silicon nitride is a wide band-gap semiconductor emitting photoluminescence(PL)at low temperatures in the late eighties of 20

th

century .In this paper

silicon nitride film was prepared by low pressure chemical vapor deposition(LPCVD). The PL of the samples was measured at room temperature by an Nd:YAG laser spectrometer with excitation of 265nm(5.0eV).Under the laser excitation

six luminescence emission bands of LPCVD silicon nitride film were observed corresponding to photon energies of 2.97

2.77

2.55

2.32

2.10 and 1.9eV respectively. The result of X-ray photoelectron spectroscopy(XPS)shows that the N/Si ratio of the samples is 0.76. Reports on the relative gap state model of LPCVD silicon nitride film has been made previously by the same authors

[4]

. A series of LPCVD-Si

3

N

4

films was treated by rapid thermal annealing(RTA)for 5s in N

2

at 800

900

1000 and 1100℃. Another six PL peaks at 3.1

3.0

2.85

2.6

2.36 and 2.2eV were observed after RTA at 900~1100℃.The six peak positions of PL after RTA at 800℃ are much as the same as that of as-synthesized. The infrared spectra(IR)of samples annealed at 900~1100℃ show that the Si-O-Si bond-stretching bands are weaker than that for the samples as-synthesized or after RTA at 800℃. The 3.1

3.0

2.36 and 2.2eV emission bands of the annealed samples are caused by the electronic transition of ≡Si

0→

E

v

≡Si

0→

N-Si-O

≡Si

0→

N

-

and

E

c

→

≡Si

0

respectively. These emission bands are higher than the energy gap of the as-synthesized samples. The two new emission bands of 2.85 and 2.6eV may be related to the oxygen-vacancies(≡Si

0

-Si

0

≡)in the annealed samples. Based on the results of X-ray diffraction

IR and XPS

we conclude that the amount of the oxygen-vacancies plays an important role in the photoluminescence at 2.85 and 2.6eV. The origin of these emission bands is discussed.