JP2545450B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] A dry etching process of a silicon oxide film, which is one process of a semiconductor device manufacturing process, relates to a dry etching process for a film to be etched containing an organic group and a base film (inorganic silicon oxide film). ), The organic silicon oxide film formed on the inorganic silicon oxide film is dry-etched with a mixed gas containing a fluorine-containing gas and oxygen. .

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching process of a silicon oxide film, which is one process of manufacturing a semiconductor device.

With the recent trend toward higher integration of semiconductor devices, a configuration in which a plurality of circuit wirings are stacked with an insulating film interposed between them has been put into practical use. In such circuit wiring, unevenness due to the circuit wiring in the lower layer is flattened by applying organic silicon, and the circuit wiring in the upper layer is patterned thereon.

[Prior Art] Conventionally, when laminating a plurality of layers of circuit wiring on a wafer, first, as shown in FIG. 1A, for example, a predetermined wiring 2 is patterned with aluminum on the wafer 1 and then Si is formed.
The first base film 3 (inorganic silicon oxide film) made of a CVD film of O ₂ is formed as an insulating film. Then, in order to flatten the unevenness of the first underlayer film 3 due to the wiring 2, an organic silicon material such as arganosilanol is applied on the first underlayer film 3 and an annealing treatment is applied to the first underlayer film 3. As shown in FIG. 2B, an organic silicon oxide film 4 having a flat surface is formed of SiO ₂ containing an organic group. Thereafter, as shown in FIG. 1 (c), the organic silicon oxide film 4 is uniformly and flatly dry-etched with a fluorine-containing gas until the convex portions of the first base film 3 are exposed. Then, as shown in FIG. 1 (d), a second base film 5 is formed as an insulating film on the thin organic silicon oxide film 4, and a predetermined circuit wiring is patterned thereon.

[Problems to be Solved by the Invention] The thinning of the thickness of the organic silicon oxide film 4 by dry etching the organic silicon oxide film 4 as described above makes the through holes for connecting the upper and lower wirings shallow. This is to shorten the time required for etching the through hole and vapor deposition of aluminum into the through hole. However, the organic silicon oxide film 4 formed by annealing the organic silicon material contains Si in addition to SiO _2.
Since there is a bond between an organic group such as a methyl group, a phenyl group or a vinyl group, the reaction between active ions or radicals and SiO ₂ which mainly constitutes the film to be etched is inhibited by this organic group during etching. As a result, there is a problem that the etching rate of the organic silicon oxide film 4 is reduced and thus the throughput is reduced, and the selection ratio between the organic silicon oxide film 4 and the first base film 3 is small.

An object of the present invention is to provide an etching method which has a high etching rate for a film to be etched containing an organic group and a large selection ratio with respect to a base film (inorganic silicon oxide film).

[Means for Solving the Problems] The above object is achieved by dry-etching an organic silicon oxide film formed on an inorganic silicon oxide film with a mixed gas containing a fluorine-containing gas and oxygen.

[Function] Oxygen added to the mixed gas decomposes the organic groups contained in the organic silicon oxide film into CO ₂ and H ₂ O during the dry etching process to sublimate, and the organic groups interfere with the etching. Prevents and improves the etching rate of the organic silicon oxide film. On the other hand, even if oxygen is added to the mixed gas used for dry etching, the etching rate of the inorganic silicon oxide film as the base film hardly changes. As a result, the selection ratio between the inorganic silicon oxide film as the base film and the organic silicon oxide film as the film to be etched is significantly improved.

[Embodiment] An embodiment of the present invention will be described below.

In this embodiment, reactive ion etching is applied to the organic silicon oxide film 4 shown in FIG. 1 (b) under the following conditions.

The reaction gas used for the etching is a mixed gas of CF ₄ + CHF ₃ + O ₂ . Then, for example, with respect to _{CF 4 · 100N 2 sccm + CHF} 3 · 100N 2 sccm, the O ₂ varied 0~100N ₂ sccm, Reactive by RIE device mixtures of these gases in the field of pressure 0.4torr and 800W FIG. 2 shows changes in etching rate and selectivity with respect to changes in the amount of added O ₂ when ion etching is performed. Then, FIG. 2 shows the etching rate A of the organic silicon oxide film 4, the etching rate B and the selection ratio C of the first base film 3 (inorganic silicon oxide film).

That is, when the flow rate of O ₂ is about 10% or more of the total flow rate of the mixed gas with respect to the organic silicon oxide film 4 containing an organic group, the etching rate A is about 8 times as compared with the case where O ₂ is not added. The flow rate of O ₂ contributes little to the etching rate B for the first underlayer 3. Therefore, a large gap occurs between the etching rate A of the organic silicon oxide film 4 and the etching rate B of the first base film 3,
As a result, the selection ratio C becomes about 6 times larger than that when O ₂ is not added.

In order to improve the etching rate of the organic silicon oxide film 4 as described above, by adding O ₂ to the mixed gas, the organic group CxHy on the surface of the organic silicon oxide film 4 reacts with O ₂ plasma.
This is because it is decomposed into CO ₂ and H ₂ O and sublimated, and as a result, SiO ₂ can react with the active ions and radicals without being blocked by the organic groups.

[Effects of the Invention] As described in detail above, the present invention has a high etching rate for an organic silicon oxide film as a film to be etched and a large selection ratio with respect to an inorganic silicon oxide film as a base film containing no organic group. An excellent effect that the etching method can be provided is exhibited.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of a semiconductor device of the present invention and a conventional semiconductor device, and FIG. 2 is a graph showing an etching rate and a selection ratio when the O ₂ flow rate is changed. In the figure, 1 is a wafer, 3 is a base film (inorganic silicon oxide film), and 4 is an organic silicon oxide film.

Claims (1)

(57) [Claims] 1. A method of manufacturing a semiconductor device, comprising a step of dry etching an organic silicon oxide film formed on an inorganic silicon oxide film with a mixed gas containing a fluorine-containing gas and oxygen.