JPH0765885B2 - Thin film thickness measurement method - Google Patents

Description

The present invention relates to a method for measuring the thickness of an insulating thin film on the surface of a conductive substance.

[Conventional technology]

FIG. 4 is an explanatory diagram of an electric capacitance method which is an example of a conventional method. In the figure, 1 is a conductive thin film, 2 is an insulating film which is an object to be measured, 3 is an electrode layer, and 4 is an electric system for measuring capacitance.

Further, FIG. 5 is a graph showing the measurement results by the electric system 4.

The conventional method mentioned here is merely an example, and there are various other conventional methods. For details, refer to, for example, the literature (Kanehara, A., “Basic Technology of Thin Films”, Physical Engineering Experiment 5, The University of Tokyo Press, 74 Pp.-77).

Next, the capacitance method will be described. In order to measure the film thickness of the insulating film 2 formed on the conductive material 1, the insulating film 2
In the so-called sandwich structure of the electrode layer 3 formed above, the capacitance between both electrodes is measured by the electric system 4 using the upper and lower conductive layers 1 and 3 as electrode layers, and the insulating film 2 of the known dielectric constant is measured. The film thickness can be calculated. This is a method called the capacitance method.

In this measurement method, the thickness of the insulating film 2 is 100Å
It is generally known that a tunnel current flows between both electrodes in the case of (Angstrom) or less. FIG. 5 shows the tunnel current flowing through the aluminum oxide film, and the tunnel current flowing between the electrodes and the thickness of the insulating film 2 have a proportional relationship. That is,
Very thin ultrathin films below 100Å are possible by monitoring this tunnel current. Note that FIG. 5 is a graph described on page 80 of the document (Takei Sakai, “Electronic Properties”, Standard Electrical Engineering Course, Corona Publishing Co.).

[Problems to be Solved by the Invention]

The conventional thin film thickness measuring method is as described above,
It is impossible to perform some processing (for example, non-destructive measurement) on the DUT, or it is not possible to measure the thin film in the local or microscopic area of the DUT. There was a problem.

The present invention has been made in view of such a point, and its purpose is to enable non-destructive measurement and local area measurement, and particularly high-precision thin film thickness of 100 Å or less. To obtain a measuring method.

[Means for Solving the Problems]

In order to solve such a problem, the present invention measures the thickness of the insulating thin film by measuring the current flowing when the sharp conductive tip has been brought close to the surface of the insulating thin film in a non-contact manner. It was done like this.

[Action]

The thin film thickness measuring method according to the present invention enables non-contact, non-destructive measurement of an extremely thin film in an extremely local region.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram of an embodiment of a method for measuring the thickness of a thin film according to the present invention. In the figure, 1 is a conductive substance as a conductive thin film, 2 is an insulating film as an object to be measured, and 5 is a conductive tip having a sharp tip.

When measuring the film thickness of the insulating film 2 that is the object to be measured on the conductive substance 1, the conductive tip 5 having a sharp tip is brought close to the surface of the insulating film 2 using a piezo element or the like. When the distance between the tip of the conductive chip 5 and the surface of the insulating film 2 approaches about 10Å, a tunnel current flows between the conductive chip 5 and the conductive substance 1.

Since the magnitude of this tunnel current varies depending on the thickness of the insulating film 2 as described above with reference to FIG. 5, it is possible to measure the thickness of the insulating film 2 by monitoring this current value. Become.

In addition, although the crystallinity of the conductive tip 5 is not particularly specified in the above-mentioned embodiment, a polycrystal may be used, and if a single crystal tip is used, a tip having a finer tip can be manufactured.

Further, as shown in FIG. 2, by performing the same measurement using another chip 6, more accurate measurement can be performed.

Furthermore, if single crystal chips having different crystal axes are used as the two chips shown in FIG. 2, the emission current from each single crystal chip is unique to the crystal axis as shown in FIG. Therefore, more accurate measurement can be performed. Fig. 3 is a graph described on page 79 of the literature (Takao Sakai, "Electronic Properties", Standard Electrical Engineering Course, Corona Publishing Co., Ltd.) (11
1), (211) and (011) indicate crystal axes.

Furthermore, in this embodiment, the environment between the chip 5 and the insulating film 2 is not specified, but it is possible in vacuum or in the atmosphere. However, noise and contamination are reduced in a vacuum.

〔The invention's effect〕

As described above, according to the present invention, non-contact, non-destructive, local film thickness measurement is performed by utilizing a tunnel current from a sharp conductive tip for thin film thickness measurement. By using a plurality of conductive chips, it is possible to accurately measure the film thickness of an extremely thin film of 100 Å or less.

[Brief description of drawings]

1 and 2 are explanatory views of first and second embodiments of the method for measuring the thickness of a thin film according to the present invention, FIG. 3 is a graph showing the relationship between a tungsten crystal and a surface field emission current, and FIG. Is an explanatory view of a conventional method for measuring the film thickness of a thin film, and FIG. 5 is a graph showing the relationship between tunnel current and the thickness of an insulating film.

Claims (1)

[Claims] 1. A film thickness measuring method for measuring a thickness of an insulating thin film on a surface of a conductive substance, wherein a current flowing when a conductive tip having a sharp tip is brought into contact with the surface of the insulating thin film in a non-contact manner. A method for measuring the thickness of a thin film, which comprises measuring the thickness of the insulating thin film by measuring.