JPH012323A - Manufacturing method of semiconductor device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a semiconductor device in which an insulating film covers an electrode or wiring partially formed on a semiconductor substrate, and further forms, for example, a second layer wiring. The present invention relates to a method for manufacturing a device.

[Conventional technology]

The electrodes or wiring that partially exist on the semiconductor substrate are
If it is covered with an insulating film made of J or 5iJ4, a step will be created on the surface of the insulating film. When forming the second layer wiring on this insulating film, disconnection is likely to occur at the stepped portion, so the surface needs to be flattened to prevent this. One method for flattening is to flatten the surface by coating a resist as a dummy film on the vA sewing, and then maintain flatness by selecting etching conditions that make the etching rates of the dummy film and insulating film almost equal. An etch bank method is known in which the dummy film is removed as is.

[Problem that the invention seeks to solve]

However, even if such an etch bank method is used, if the dummy film is thin, the surface after the dummy film is coated is not sufficiently flat and a step remains. In this state, when the dummy film on the surface is etched to expose the insulating film, the surface of the insulating film becomes higher than the surface of the remaining dummy film. Even if the etching is further carried out, the difference in level cannot be eliminated because the etching speed of the dummy film and the insulating film are almost the same, and there is a drawback that the surface of the insulating film cannot be sufficiently flat after the dummy film is completely removed. This drawback can be reduced to some extent by making the dummy film thicker, but it requires a large amount of material for the dummy film and requires a long processing time to remove the dummy film.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor device in which the surface of an insulating film after etching is flattened even if some steps are formed on the surface after being coated with a dummy film.

[Means for solving problems]

In order to achieve the above object, the method of the present invention covers an insulating film having a step on the surface of a semiconductor substrate with a dummy film, and then separates the dummy film. ! When etching is performed until the dummy film is removed under conditions where the etching rates of the films are approximately equal, the insulating film is exposed in the middle of the etching process, and then a step of etching only the insulating film is inserted.

[Effect]

When the dummy film on the surface is etched and a part of the insulating film is exposed, the difference in level between the insulating film and the dummy film, which occurs as described above, can be eliminated by etching only the insulating film. Therefore, a flat surface is obtained, and if the dummy film is removed by etching the dummy film and the insulating film at approximately the same etching rate, a flat surface of the insulating film is obtained.

〔Example〕

FIG. 1 shows the steps of an etch-back method according to an embodiment of the present invention.
A wiring 2 having a thickness of 1n is formed of an alloy film or the like.

A film 3 of about 1-thickness made of Sing or Si3N4 for insulation is coated on this. The surface of this insulating film 3 has a step caused by the presence of the conductive film 2.
The positive photoresist film 4 having a thickness of 1 to 2 μm is applied thinly to the high parts of the insulating film 3 and thickly to the low parts, but a step still remains on the surface. Next, as shown in FIG. 1), dry etching is performed using reactive ions 5 to the extent that the surface of the high portion 31 above the wiring 2 of the insulating film 3 is slightly etched. In this dry etching, plasma is generated in the mixed gas of the main etching gas and 02 to completely separate the photoresist film 4. ! 3
Since the etching is carried out under conditions where the etching speed is approximately equal, a step remains between the surface of the cold-color border film 31 and the surface of the photoresist film 4.Next, from this state, only the insulating film 31 exposed slightly higher than the photoresist film 4 is etched. Etching is performed so that the surface heights of the high portions of the photoresist film 4 and the insulating film 3 are made equal as shown in FIG. 1(e). At this stage, a few percent of 03 gas is added to the main etching gas.
Dry etching is performed by generating plasma in the added mixed gas, and etching conditions are determined so that only the insulation 1113 is etched and the etching selectivity with respect to the photoresist film 4 is high. Further, from this state, as in the first stage, etching was performed using the main etching gas and a mixed gas of 0 □ under conditions where the etching speed of the photoresist film 4 and the insulating film 3 were almost equal. The dry etching is stopped at the point where the photoresist film 4 is removed.The main etching gas is CF when the insulating film is Sing.

When CHF3.5iJa, CF O, SF4. Use NF2. Switching the etching stage and determining the end point
According to the above etching method, which is performed by monitoring plasma generation during etching and detecting changes in emission intensity due to changes in the material to be etched, the steps of the planarizing dummy film 4 are insulated in the middle. Since this can be alleviated by etching the film 3, a flat surface of the insulating film can be obtained even if there is some level difference on the surface of the dummy film 4. In the above embodiment, photoresist is used as the dummy film 4, but other materials may be used as well.

[Effects of the Invention] According to the present invention, the level difference on the surface of the dummy film for planarization can be alleviated by etching the exposed insulating film in the middle, so even if the dummy film is not very planarized, An insulating film having a flattened surface can be obtained. Therefore, since the dummy film can be made thinner, processing time can be shortened and semiconductor devices can be improved. ! Effective in reducing manufacturing man-hours.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view sequentially showing steps of an etchback method in an embodiment of the present invention. 1: Silicon substrate, 2: Wiring, 3: Insulating film, 4: Positive resist film, 5: Reactive ions. 1.・Guh. s1 diagram

Claims (1)

[Claims] (1) After covering an insulating film with a step on the surface of a semiconductor substrate with a dummy film, etching is performed until the dummy film is removed under conditions such that the etching rates of the dummy film and the insulating film are approximately equal. A method for manufacturing a semiconductor device, comprising inserting a step in the middle of the etching step in which the insulating film is exposed and then only the insulating film is etched.