JPH11200032A5 - - Google Patents

Description

Next, to investigate the effect of residual _H2O partial pressure on the insulating properties of _{the Al2O3} film, the vacuum chamber 1 was baked, evacuated, and plasma cleaned, then leaked with air, exposing the inside of the vacuum chamber 1 to the air to absorb moisture. Then, without baking, the chamber was evacuated to five predetermined vacuum levels: ^1x10-6 Pa, ^5x10-6 Pa, ^1x10-5 Pa, ^5x10-5 Pa, and ^1x10-4 Pa. _{An Al2O3} film approximately 100 Å thick was immediately fabricated using the procedure shown in Figure 2. To adjust the residual _H2O partial pressure, a small amount of _H2O was introduced into the vacuum chamber 1 through a _micro -leak valve as needed to fabricate the _Al2O3 film. The residual _H2O partial pressure was measured using a quadrupole mass spectrometer during Ar gas discharge. The V-I characteristics of the film thus obtained are shown in Figure 3, along with the previous results. In the figure, curve B represents the V-I characteristics when the ultimate vacuum is 1× ^10-6 Pa, curve C represents 5× ^10-6 Pa, curve D represents 1× ^10-5 Pa, curve E represents 5× ^10-5 Pa, and curve F represents 1× ^10-4 Pa. The parenthesized values in the figure indicate the residual _H2O partial pressure during Ar gas discharge at each ultimate pressure. This indicates that when the residual _H2O partial pressure exceeds 1× ^10-6 Pa, the leakage current of the insulating film increases, and the deterioration of the insulating properties becomes noticeable (see curves E and F). This residual _H2O partial pressure of 1× ^10-6 Pa corresponds to the reason why large Al crystal grains cannot be obtained in the high vacuum described above. From this perspective, the deterioration of the insulating properties of the _Al2O3 film is thought to be due to the small _crystal grain size of the _Al film to be plasma oxidized, which results in a small crystal grain size in the _Al2O3 film after plasma oxidation, resulting in an increase in the leakage current via the numerous crystal grains present.