JPS5853859B2 - Pinhole measurement method for thin films - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring pinholes in thin films, and in particular to detecting pinholes in thin films of metal or insulators deposited on a substrate by vapor growth, sputtering, vapor deposition, etc. , regarding how to measure.

For example, in the manufacturing process of semiconductor devices, the presence of pinholes in an insulating thin film deposited on a semiconductor substrate causes problems, so it is necessary to inspect the insulating thin film for the presence of pinholes.

However, pinholes are difficult to detect with the naked eye, so
Conventionally, an insulating thin film was deposited on the surface of a semiconductor substrate for testing, and then electricity was applied to the film in water to observe whether hydrogen bubbles were generated from pinholes using water electrolysis. Alternatively, the presence or absence of pinholes has been inspected by immersing a semiconductor substrate with a thin film formed on the surface in a plating solution and observing whether metal is deposited through the pinholes.

However, among the conventional methods mentioned above, accurate inspection cannot be expected with the former because it is difficult for hydrogen gas to be generated from minute pinholes, and with the latter, inspection equipment may be seriously damaged. However, it has the disadvantage that it lacks the simplicity of inspection.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for measuring pinholes in a thin film that can easily and accurately measure the presence or absence of pinholes generated in a thin film of metal or insulator deposited on the surface of a &L substrate.

Therefore, in the thin film pinhole measuring method according to the present invention which achieves the above object, a base thin film is formed on a substrate, and the etching rate with respect to a specific etching solution is faster than that of the thin film to be measured. Thin films to be measured with pinholes are layered and then etched to enlarge and transfer the pinholes in the thin film to be measured onto the underlying thin film to measure the number and position of the pinholes. It is characterized by the fact that it is made to do so.

The method for measuring pinholes in thin films according to the present invention will be described below with reference to the drawings, taking the manufacture of semiconductor devices as an example.

First, a case where the thin film to be measured is a silicon nitride film will be described as an example.

a) An oxide film 2 is deposited on the surface of a silicon wafer 1 as a base thin film.

This oxide film 2 can be formed by heating the silicon wafer 1 in an oxidizing atmosphere to thermally oxidize its surface.

b) A silicon nitride film 3 as a thin film to be measured is deposited on the oxide film 2.

It is assumed that this silicon nitride film 3 has a pinhole, and this pinhole is indicated by reference numeral 4 in the figure.

C) Perform etching treatment by immersing silicon wafer 1 in a hydrofluoric acid buffer solution.

At this time, since pinholes 4 are formed in the silicon nitride film 3, the hydrofluoric acid buffer solution enters the surface of the underlying thin film 2 through the pinholes 4.

Then, since the etching rate of the hydrofluoric acid buffer solution on the underlying thin film is very high, the portion immediately below the pinhole 4 is eroded as shown in Figure C.

d) Next, the thin film to be measured is removed using phosphoric acid, and the number and position of pinholes transferred onto the oxide film 2 are measured.

Next, an example will be explained in which the thin film to be measured is a gold thin film.In this case, an aqueous hydrochloric acid solution is used as the etching liquid.

A chromium film can be considered as a base thin film whose etching rate for this hydrochloric acid aqueous solution is faster than that for a gold thin film.

Therefore, in this embodiment, a chromium film is deposited as a base thin film on a silicon wafer, and a gold thin film to be measured is superimposed thereon.

Then, as in C) above, the silicon wafer may be immersed in an aqueous hydrochloric acid solution to perform the etching process.

In this case too, if a pinhole exists in the gold thin film,
The hydrochloric acid aqueous solution passes through the pinhole and erodes the chromium film directly below the pinhole.

Therefore, the thin gold film to be measured is removed using a mixture of potassium iodide and iodine, and the dimensions of the pinholes transferred onto the chromium film are measured.

As described above, according to the present invention, a base thin film is formed on a substrate such that the etching speed of a specific etching solution is faster than that of the thin film to be measured, and the thin film to be measured is deposited on top of the base thin film. However, when etching is performed using a specified etching solution, the etching solution reaches the base thin film through pinholes in the thin film to be measured, and the etching solution transfers and forms large holes on the base thin film. .

As a result, pinholes in the thin film to be measured can be enlarged and transferred onto the underlying thin film, making it extremely easy to detect pinholes in the film to be measured, and accurately determining the number and location of pinholes. You can grab it.

Therefore, based on this measurement result, it becomes possible to establish a technique for forming a pinhole-free metal or insulator thin film.

[Brief explanation of drawings]

In the figure, a to d are process diagrams showing a method for measuring pinholes in a thin film to be measured according to the present invention. 1... Silicon wafer, 2... Oxide film, 3... Thin film to be measured, 4... Pinhole.

Claims (1)

[Claims] Form a base thin film on the substrate whose etching rate with a constant 1% etching solution is faster than that of the thin film to be measured, and then place a thin film of the metal or insulator to be measured for pinholes on top of it. 1. A method for measuring pinholes in a thin film, characterized in that the pinholes in the thin film to be measured are enlarged and transferred onto a base thin film by forming overlapping layers and then performing an etching process to measure the pinholes.