JPH0758728B2 - Pattern length measurement method in semiconductor device manufacturing - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern length measuring method in manufacturing a semiconductor device, and more particularly to a length measuring method of a metal pattern body formed under an insulating film.

(Prior Art) Conventionally, an optical microscope or a scanning electron microscope has been used for measuring the length of a metal pattern body in the manufacture of a semiconductor element.

In the optical microscope, it was possible to observe the metal pattern through the SiO ₂ or SiN insulating film of several μm or less. Therefore, the pattern length has been measured in an arbitrary process after forming the metal pattern body to be measured and ending the production of the integrated circuit (IC). The magnification of the microscope is mainly about
2000 times.

On the other hand, in the scanning electron microscope, it was difficult to observe the metal pattern through the insulating film.
Therefore, usually, immediately after forming the metal pattern body,
As shown in FIG. 2, the length was measured with the substrate 1 and the metal pattern body 2 exposed. In addition, after forming an insulating film on the metal pattern body, a predetermined region of the insulating film is removed to expose the metal pattern body for length measurement. In both cases, the microscope magnification has been increased from several thousand times to 20,000 times.

(Problems to be Solved by the Invention) However, in the former optical microscope observation, it was difficult to obtain a high-magnification image, and there was a problem that the accuracy of length measurement was low.

On the other hand, although a high-magnification image can be obtained by the latter scanning electron microscope observation, in the observation method before forming the insulating film, dust in the measurement atmosphere and contamination of the element formation region of the substrate due to contamination of the support stand There is a problem that the performance or yield of IC is reduced. On the other hand, in the scanning electron microscope observation method in which a predetermined region of the insulating film is removed after forming the insulating film, the problem due to contamination of the substrate does not occur, but the insulating film in the predetermined region on the measurement metal pattern body However, since the metal pattern body to be measured is also etched at the same time, there is a problem that the metal pattern body disappears or the resolution decreases. Further, an etching method for selectively removing only the insulating film can be used for removing the insulating film, but wet etching is used for this selective etching, which causes penetration of an etching solution.
Sometimes caused a wiring failure.

The present invention eliminates the problems of low accuracy, substrate contamination, disappearance of measurement metal pattern body or resolution degradation and wiring failure described above, and highly accurate measurement of metal pattern body without adversely affecting IC fabrication. Moreover, it is an object of the present invention to provide a method that is simple and easy.

(Means for Solving the Problems) In the present invention, after forming a metal pattern body made of a first metal on a substrate, a protective film made of a second metal having a large etching selectivity with respect to an insulating film is used. After covering the metal pattern body and forming an insulating film on the entire surface of the substrate including the metal pattern body, the insulating film is selectively removed in a predetermined region including the protective film to expose the protective film, Then, the length of the metal pattern body is measured through the exposed protective film.

(Operation) In the above method, since the length of the metal pattern body is measured after the substrate is covered with the insulating film, the substrate is not contaminated. Further, since the length measurement is performed after removing the insulating film on the metal pattern body, the measurement can be performed using a scanning electron microscope. At this time, the metal pattern body is covered with the protective film, but since the protective film is made of metal, the length of the metal pattern body can be measured through the protective film. Further, the protective film is formed of a metal having a large etching selection ratio with respect to the insulating film. When the metal pattern body is covered with such a protective film, when the insulating film is removed, for example, an insulating film etching method is used. As a result, even if an etching method that may also etch the metal pattern body is used, the metal pattern body is not etched. As the etching method, there is a dry etching method such as a reactive ion etching method, and unlike the case of wet etching, penetration of an etching solution does not occur.

(Embodiment) An embodiment of the present invention will be described below with reference to FIG.
In one embodiment, when a field effect transistor is formed, a length-measuring metal pattern body having the same pattern as that of the gate electrode of the transistor is formed, and the formation of the gate electrode of the field effect transistor is observed from the metal pattern body. This is the case. In each of FIGS. 1A to 1D, a cross-sectional view is shown on the left side and a plan view is shown on the right side. The plan view is a plan view of only the metal pattern body portion for length measurement in the right half of the sectional view.

First, as shown in FIG. 1A, a gate electrode 12 of a field effect transistor is formed on a semiconductor substrate 11 by using a tungsten (W) -based metal, and at the same time, the same metal and the same pattern as the gate electrode 12 are measured. A long metal pattern body 13 is formed on the substrate 11.

Next, as shown in FIG. 1 (b), after forming the source / drain regions 14 of the field effect transistor in the substrate 11, an ohmic electrode 15 is formed thereon by using AuGe / Ni / Au metal. However, at the same time, a protective film 16 made of the same metal is formed on the length measuring metal pattern body 13 side, and the protective film 16 covers the length measuring metal pattern body 13.

After that, an insulating film 17 is formed on the substrate 11 so as to cover the entire surface of the protective film 16 and the electrodes 12 and 15 as shown in FIG.

After that, a predetermined region of the insulating film 17 is removed by reactive ion etching using a fluorine-based gas, an opening 18 is formed, and the protective film 16 is exposed. The removal of the insulating film 17 is carried out at the same time as the step of forming a through hole 19 for forming a wiring in the insulating film 16 on the electrodes 12 and 15 of the field effect transistor. Of course, they may be separate. At the time of removing the insulating film 17, the gate electrode metal (metal for measuring length pattern metal) is etched by the reactive ion etching with the fluorine gas, but the ohmic electrode metal (metal for protective film) is not etched. The metal pattern body for length measurement 13 covered with the protective film 16 is not etched and retains its original shape.

After that, the length of the length-measuring metal pattern body 13 is measured by the scanning electron microscope through the exposed protective film 16 (the length-measuring direction is the direction of arrow A in FIG. 1 (d)). The formation condition and the formation length of the gate electrode 12 are judged.

Although the reactive ion etching using fluorine gas is used as the etching method in the above-described embodiment, other dry etching methods can be used as long as the etching rate of the protective film is sufficiently low.

Although the ohmic electrode metal is used as the protective film, other metals may be used as long as they have a large etching selection ratio to the insulating film and can observe the pattern body formed thereunder by a scanning electron microscope. Good.

Further, in the above-mentioned one embodiment, in order to determine the formation condition of the gate electrode of the field effect transistor, the same metal pattern body for length measurement as the gate electrode is formed, but the present invention is also applicable to other cases. Of course it can be applied.

(Effect of the Invention) As described in detail above, according to the method of the present invention, since the length of the metal pattern body is measured after the substrate is covered with the insulating film, contamination of the substrate can be prevented, and Since the insulating film is removed from the metal pattern body, a scanning electron microscope can be used, and highly accurate length measurement is possible. Further, since the metal pattern body is covered with the protective film, it is possible to prevent the metal pattern body from being etched even when using an etching method that may also etch the metal pattern body when removing the insulating film, such as reactive ion etching. It is possible to prevent disappearance of the metal pattern body or reduction of resolution. Further, as a result, since dry etching such as the above-described reactive ion etching can be used as an insulating film etching method, there is a problem when wet etching is used, that is, penetration of an etching solution and occurrence of wiring failure due to it. Solvable. As described above, according to the method of the present invention, it is possible to easily and accurately measure the length of the metal pattern body without adversely affecting the IC fabrication, and it can be expected that the performance and yield of the IC will be improved.

[Brief description of drawings]

FIG. 1 is a sectional view and a plan view showing an embodiment of a pattern length measuring method in the production of a semiconductor device of the present invention, and FIG. 2 is a sectional view showing an example of a conventional metal pattern body length measuring method. 11 ... Semiconductor substrate, 13 ... Metal pattern body for length measurement, 16 ... Protective film, 17 ... Insulating film, 18 ... Opening part.

Claims (1)

[Claims] 1. (a) After forming a metal pattern body made of a first metal on a substrate, the metal pattern body is covered with a protective film made of a second metal having a large etching selectivity with respect to an insulating film. And (b) after forming an insulating film over the entire surface of the substrate including the insulating film, (c) selectively removing the insulating film in a predetermined region including the protective film to expose the protective film. Then, (d) a pattern length measuring method in manufacturing a semiconductor device, wherein the length of the metal pattern body is measured through the exposed protective film.