CHEMICAL VAPOR DEPOSITION OF THIN FILM MATERIALS FOR ...

Table 3. Chemical composition change with depth of analysis.
Atomic concentration (at%)
Hf N C O
Surface 30.0 35.8 25.7 8.4
Intermediate 36.5 36.5 19.2 7.9
Bulk 49.3 31.7 14.3 4.6
In the spectra and table above, ‘surface’ means XPS analysis without any etching,
‘intermediate’ represents a very thin layer (2~3nm) measured immediately after surface etching
and before the constant bulk properties, and ‘bulk’ means most of the thin film thickness where
no (or very small) qualitative or quantitative chemical changes can be detected. Fig.34(c) shows
a large C 1s peak from thin film surface analysis, which indicates more than 20 at% C. The
position of this C 1s peak is at 286.1 ev, which is different from the C 1s signal of adventitious
hydrocarbon (284.8ev). This result further rules out the possibility of air contamination. This
carbon signal probably comes from the N-C bonds, which exist in complexes of TDMAH
incomplete decomposition products. This assignment was supported by the existence of the left
shoulder on N 1s peak in Fig.34(b), which represents N in an organic matrix. With Ar + ion
etching, the chemical state change of C 1s peak shows a clear trend from organic carbon (N-C,
286.1ev) to metal carbide (Hf-C, 282.3ev). Meanwhile, the peak shoulder on N 1s disappeared
gradually. Although the existence of hafnium carbide phase was reported as a natural phase
produced by PEALD reaction in the bulk, the possibility of chemical state change due to ion
sputtering could not be ruled out. Apart from the disappearance of N-C groups due to ion etching,
another obvious change is the shape and position of Hf 4f peak. The height ratio between the two
spin orbit splitting peaks of Hf 4f5/2 and Hf4f7/2 increases with sputtering time until the bulk
properties are obtained. It has been reported in certain XPS studies of hafnium nitride thin film
that Hf4f5/2 has relatively stronger intensity than Hf4f7/2 due to the enhancement effect of N 2s.
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