JPH0247101B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for dry etching an insulating film, such as an oxide film or a nitride film formed on a semiconductor substrate.

Manufacturing a semiconductor device includes a step of forming an insulating film such as an oxide film or a nitride film on a semiconductor substrate, and then selectively etching this insulating film to shape it into a desired pattern. There are wet etching methods and dry etching methods for etching this insulating film, but the dry etching method is suitable for forming fine patterns and is generally being widely adopted.

The inventors discovered the following phenomenon while investigating the plasma etching characteristics of insulating films used in semiconductor devices.

In other words, the nitride film formed on the semiconductor substrate is
Plasma etching can be performed using an etching gas containing _CF4 as a main component. At this time, when we investigated the distribution of etching rates in the center and periphery of the semiconductor substrate, we found that the nitride film immediately after being formed on the substrate had a uniform distribution over the entire surface of the substrate, as shown by A in the attached figure. However, after forming the nitride film, while rotating the semiconductor substrate at a speed of 100 to 5000 rpm,
In the case of a nitride film obtained by spraying butyl acetate onto the nitride film and drying it, the distribution of the etching rate between the center and the periphery is not uniform, as shown in (b) of the same figure. It was found that the speed is about 5 times faster in the center and about 3 times faster in the periphery than in case (a) above. Although the detailed mechanism of such accelerated etching is not yet clear, it is clear from the above fact that the etching rate is increased by at least the butyl acetate remaining on the nitride film. . The difference in etching rate between the center and peripheral areas is thought to be due to the fact that the amount of butyl acetate remaining on the nitride film becomes uneven due to centrifugal force during rotation, and this uneven etching rate is due to When viewed from the other side, this is not preferable in terms of obtaining a uniform semiconductor device.

This invention makes use of the above phenomenon to increase the etching speed of insulating films such as oxide films and nitride films, thereby shortening the etching work time, and at the same time reducing the uneven etching speed between the center and the periphery. It is an attempt to improve sexuality.

An embodiment of the dry etching method according to the present invention will be described below.

In this example method, butyl acetate vapor is mixed in advance with an etching gas, in this case an etching gas that uses CF ₄ gas as the main component gas, and this etching gas is used to plasma-etch the nitride film. be. Specifically, an anode coupling type parallel plate reactor was used, and CF ₄ was used as the etching gas as the main component gas.
The etching gas was mixed with 5% oxygen (O ₂ ) gas and 25% butyl acetate vapor, the wafer stage temperature during etching was 120°C, the etching pressure was 0.6 mTorr, and the applied RF power was 1.5 W/. When plasma etching a nitride film under the conditions of cm ² and examining the etching rate distribution between the center and peripheral areas of the nitride film, we found that the etching rate increased and increased as shown in c in the figure. A uniform distribution of etching rates was obtained.

Note that each parameter has an optimum value determined by the etching apparatus and a value determined by the quality of the nitride film (Si ₃ N ₄ ) that is the film to be etched, and is not uniquely determined. A similar tendency to that shown by C in the figure in the above-mentioned specific example was possible within the following condition range.

Etching gas: CF ₄ + O ₂ + butyl acetate
(Butyl acetate is a few to 70%) Etching temperature: 5 to 130°C Etching pressure: 0.05 to 0.6 mTorr Applied RF power density: 0.1 to 3 W/cm ² In addition, as another example, instead of the butyl acetate, Similar to butyl acetate, we also investigated isopropyl alcohol and ethyl alcohol, which have weak -OH group bonds and are easy to remove in plasma, but in this case, the results were similar to the previous example, that is, in the case of C in the figure. It was confirmed that similar trends to those shown were obtained.

Furthermore, although plasma etching was explained in the above embodiments, it is of course applicable to reactive ion etching as well, and is applicable not only to semiconductor devices but also to all types of dry etching of insulating films. be.

As described above, the present invention provides a method for etching insulating films such as oxide films and nitride films.
By increasing the etching speed, it is possible to shorten the working time, and the non-uniformity of the etching speed between the center and the periphery of the insulating film can be corrected, resulting in an insulating film with a uniform thickness. It is something that you have.

[Brief explanation of the drawing]

The drawings are diagrams showing etching characteristics of dry etching methods according to a conventional example and an embodiment of the present invention. A: Etching characteristics of a conventional example; C: Etching characteristics of an embodiment of the present invention.

Claims (1)

[Claims] 1. When etching an insulating film such as an oxide film or a nitride film by dry etching such as plasma etching or reactive ion etching,
A method for dry etching an insulating film, characterized in that etching is performed using an etching gas containing CF ₄ gas as a main component gas mixed with at least one of butyl acetate, isopropyl alcohol, or ethyl alcohol.