JPS6030099B2 - Etching gradient determination method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION During the manufacture of semiconductor devices, after depositing an insulating thin film, when photo-etching metal wiring, the side surface of the insulating thin film is placed at a predetermined angle of 90 degrees or less with respect to the semiconductor chip surface. Etching is carried out with a certain degree of tediousness.

This is because metal wiring is formed by metal evaporation after the side surface of the insulating thin film is etched almost perpendicular to the semiconductor substrate surface, which may cause disconnection in the metal wiring, and measures are taken to prevent this disconnection. It is a treatment. However, if the frequency is too small, the length of the inclined part in the direction parallel to the substrate, that is, the part of the inclined part, will increase, and the film thickness will become thinner in parts other than the designated parts, which will reduce the breakdown voltage in those parts. In devices where the thickness of the device is lowered or where elements are densely integrated, other elements may be etched at the same time, so the forehead must be set so as to fall within a certain predetermined range.

Currently, there are methods for applying this deep etching process, such as applying a substance with a high etching rate to the surface of the insulating thin film depending on the desired degree of etching, or applying a substance with a high etching rate to the surface of the thin film using an appropriate method. Etching is performed after the change, but this requires great precision, and with the current state of technology,
Even assuming that the film thickness is constant, it is said that it is impossible to perform an oblique etching process with a constant thickness due to factors such as the condition of the thin film surface, and it is inevitable that some error will occur. . It is also important to accurately control the thickness of the thin film when performing inclined etching.
This is somewhat influenced by the condition of the substrate surface, etc., and is 10% for wafers in one lot and 20% for each lot.
There is a variation of about 30%. The percentage of defective products due to inappropriate etching of semiconductor devices manufactured under the above-mentioned conditions is about 5%. Furthermore, measuring the frequency is not only useful for determining whether a product is defective, but also important for investigating the cause of a defective product.

Conventionally, as a typical method for measuring the above-mentioned value, first, the thickness t of the insulating thin film is determined using a beam of light, etc., and then the neck is measured.

Using a scale, I checked the mirror skin d on the real column and found the forehead degree 8 from 8=skin. According to the measurement method, the neck.

The work of actually measuring the inside of a slope using a survey has the disadvantage that it is very time-consuming and requires skill and precision. SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for determining an etching gradient, which eliminates the above-mentioned drawbacks and can easily determine whether or not the etching degree is within a predetermined degree of complexity.

The present invention will be explained based on preferred embodiments. FIG. 1 is a plan view showing that a hole is provided in a part of a resist film 1 deposited on an insulating thin film in the semiconductor device of the present invention. The holes 2 and 3 are separated by the minimum allowable slope b, and the holes 3 and 4 are separated by the minimum allowable slope b. The maximum permissible inclination a and the minimum permissible inclination b are determined from a predetermined value, for example, 15 to 20 degrees, taking into consideration the thickness of the thin film and its variation.
In order to obtain the above structure, holes 2, 3,
4 and etching process is performed, the surface of the insulating thin film 6 provided on the surface of the substrate 5 of the semiconductor device is formed into a two-layer structure, and the upper layer is made of a material such as polysilicon, which has a faster etching rate than the lower layer. Since it has two layers with silicon oxide, etching in the lateral direction is faster than etching in the vertical direction.

This allows the side surface of the insulating thin film 6 to have an angle of 90 degrees or less relative to the substrate surface. After performing inclined etching on the insulating thin film 6 as described above,
Peel off the resist film.

In this state, various cross-sectional shapes along the line 1-1' are shown in FIG. FIG. 2A shows an insulating thin film 6 on a semiconductor substrate 5.
This shows a state where the normal inclined etching process has been applied.

FIG. 2B shows that because the slope of the insulating thin film 6 was etched to a length greater than the maximum allowable slope, the cross-sectional shape 7 of the groove of the insulating thin film in a portion having twice the length of the maximum permissible slope becomes triangular. This shows that the frequency has become excessive.

In FIG. 2C, on the contrary, since the inclination of the insulating thin film 1 is less than the minimum permissible value, the cross-sectional shape 8 of the groove of the insulating thin film in the portion having twice the minimum permissible length is trapezoidal. It has become. These conditions can be easily determined by microscopic observation. In other words, when light is shined on this area, interference fringes appear on the oblique part of the forehead, so by examining the state of these interference fringes under a microscope, the states of A, B, and C in Figure 2 can be determined. can be easily distinguished. That is, if the cross-sectional shape 7 of the insulating thin film groove is trapezoidal and the etching process is performed so that the cross-sectional shape 8 of the insulating thin film groove is triangular, it is obvious that the groove has a predetermined degree. Next, another embodiment according to the present invention will be described.

FIG. 3 is a plan view showing a state in which only a predetermined portion 12 of the resist layer 11 on the surface of the semiconductor device of the present invention is removed and before etching treatment is performed. FIG. 4 shows the shape of the corresponding portion of the semiconductor element after the etching process has been applied to the etched body. A is a plan view, B is
It is a sectional view along row 0'.

FIG. 5 shows a measurement mask 15 for measuring whether the slope of the slope etching shown in FIG. 4 is within the allowable range.
shows.

Reference numeral 13 represents a line indicating the maximum allowable inclination, and 14 represents a line indicating the minimum allowable inclination.

The measurement mask is placed on the etched part of the insulating thin film 6 formed on the surface of the substrate 5 of the semiconductor element after the inclined etching process shown in FIG.
It is possible to easily determine whether or not the degree of inclination is within the permissible range by visually determining whether it is between the line 13 indicating the maximum allowable inclination and the line indicating the minimum allowable inclination. . In the above measurement, the thickness of the thin film and its variation are taken into account in advance, and the small hole 12 and the maximum allowable slope 13 are
Determine the minimum allowable slope of 14.

As shown above, according to the present invention, it is possible to easily measure whether the elasticity of a thin film is within an allowable range, and it is very useful for speeding up measurement work, distinguishing between defective products, and investigating the cause of defective products. Beneficial.

[Brief explanation of the drawing]

Figure 1 is a plan view showing the state before the insulating thin film is subjected to etching treatment, and Figures 2 A to C are various shapes of the thin film after etching treatment, cut along the lines 1-1' in Figure 1. FIG. 3 is a plan view showing the state before etching treatment, and FIGS. 4A and B are plan views showing the shape of the thin film after etching treatment and row 0'.
FIG. 5 is a plan view showing the measurement mask. 5... Semiconductor substrate, 6, 7, 8... Groove cross-sectional shape of insulating thin film. O / Figure O 2 Figure Age 3 Figure O 4 Figure Juice J Figure

Claims (1)

[Claims] 1. A resist film is deposited on an insulating thin film deposited on the surface of a semiconductor substrate, a plurality of holes are provided in the resist film, and etching is performed from the holes to form a plurality of insulating thin films with inclined side walls. In forming the groove, the holes in the resist film are formed in advance so that the distance between them is twice as large as the maximum allowable slope width of the side wall of the groove and twice as long as the minimum allowable slope width of the side wall of the groove. The etching is performed on the insulating film, and the slope of the groove is determined based on whether or not the optical interference fringes on the side walls of the plurality of grooves are continuous. Method of determining slope.