JPH0418691B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for manufacturing a semiconductor device using polycrystalline silicon in a multilayer wiring structure.

[Conventional technology]

Conventionally, semiconductor devices with a multilayer wiring structure have been proposed that use polycrystalline silicon for the lower layer wiring, and after forming the polycrystalline silicon wiring into a desired pattern, the surface is oxidized to form an insulating film made of an oxide film. A structure is adopted in which the upper layer wiring is formed on the upper layer wiring.

For example, as shown in FIG. 2, a polycrystalline silicon film is formed on the insulating film 12 of the semiconductor substrate 11, and then formed into a predetermined pattern shape by a photoresist process to form the polycrystalline silicon wiring 13. .
Then, this polycrystalline silicon wiring 13 is thermally oxidized to form an oxide film 14 on its surface, and an upper layer wiring 15 is formed thereon in a desired pattern to form a multilayer wiring structure.

[Problem that the invention seeks to solve]

In the conventional semiconductor device manufacturing method described above, when the surface of the polycrystalline silicon wiring 13 is oxidized, non-uniform oxidation reaction tends to occur at the contact area between the polycrystalline silicon wiring 13 and the underlying insulating film 12 (portion A in the figure). , the oxide film 14 in this portion will not grow sufficiently. Therefore, in this part, the oxide film 14
can no longer reliably cover the surface of the polycrystalline silicon wiring 13, leaving a portion of the polycrystalline silicon wiring 13 exposed.

For this reason, when the upper layer wiring 15 is formed as shown in the figure, the polycrystalline silicon wiring 13 and the upper layer wiring 15 come into contact with each other at the exposed portion of the polycrystalline silicon wiring 13, resulting in an electrical short circuit, resulting in reliability of the semiconductor device. This causes a decrease in performance and a decrease in manufacturing yield.

[Means for Solving the Problems] The method for manufacturing a semiconductor device of the present invention forms an oxide film with a sufficient thickness as an insulating film on a polycrystalline silicon wiring, and eliminates the problem caused by non-uniformity of the oxide film. This is intended to improve quality and yield by preventing short circuits with upper layer wiring.

The method for manufacturing a semiconductor device of the present invention includes the steps of stopping pattern etching midway through forming a polycrystalline silicon wiring and performing oxidation in this state;
After that, anisotropic etching is performed to leave an oxide film on the side surfaces of the polycrystalline silicon wiring, and then oxidation is performed again to form a second layer on the polycrystalline silicon wiring.
The method includes a step of forming an oxide film.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIGS. 1A to 1E are cross-sectional views showing an embodiment of the present invention in the order of its manufacturing steps, and the steps will be explained below.

First, as shown in FIG.
After growing a polycrystalline silicon film 3 thereon, a photoresist film 4 is formed in the shape of a wiring pattern, and using this as a mask, the polycrystalline silicon film 3 is etched. Then, as shown in Figure b, when the polycrystalline silicon film 3 has been etched by approximately 3/4 to 5/6 of its total thickness, that is, the unmasked portion is 1/3
Etching is stopped when only 4 to 1/6 of the thickness remains, and polycrystalline silicon wiring 5 is formed.

Next, as shown in FIG. 3C, after removing the photoresist film 4, the polycrystalline silicon film 3 is thermally oxidized to form an oxide film 6 on the surface. At this time, the conditions of the oxidation treatment are controlled so that the unmasked portion of the polycrystalline silicon film 3 is oxidized over its entire thickness to form an oxide film 6a.

Next, anisotropic etching is performed on the entire surface as shown in FIG. . At this time, the oxide film 6 on the upper surface of the polycrystalline silicon wiring 5 is almost completely removed, but a relatively thick oxide film 6 is left on the side surfaces of the polycrystalline silicon wiring 5.

Thereafter, the polycrystalline silicon interconnection 5 is thermally oxidized again as shown in FIG. As a result, the polycrystalline silicon wiring 5 is reliably covered with the oxide film 6 and the oxide film 7, and especially the side surfaces are sufficiently covered with the thick oxide film 6 and this second oxide film 7. It turns out.
Note that due to this second oxidation, the second oxide film 7 is slightly grown in areas other than the polycrystalline silicon wiring 5.

Thereafter, a multilayer wiring structure can be constructed by forming through holes etc. on the oxide film 6 and the second oxide film 7, forming the upper layer wiring 8 of a desired pattern, and forming a protective film etc. (not shown). .

According to the wiring structure formed in this way, the polycrystalline silicon wiring 5 is oxidized while leaving a part of the polycrystalline silicon film 3 in areas other than the polycrystalline silicon wiring 5. Since there is no contact portion with the insulating film, a uniform oxide film can be grown on the polycrystalline silicon film. Furthermore, by anisotropically etching the once grown oxide film, a thick oxide film 6 is left on the side surface of the polycrystalline silicon wiring 5, and then oxidation is performed again to grow a second oxide film 7. Therefore, polycrystalline silicon wiring 5
By making the thickness of the oxide film sufficiently large on the side surfaces of the polycrystalline silicon wiring, it is possible to improve the coverage on the side surfaces of the polycrystalline silicon wiring where coverage defects are likely to occur.

Therefore, a part of the polycrystalline silicon wiring 5 is never exposed through the oxide films 6 and 7.
A short circuit with the upper layer wiring 8 can be reliably prevented.

Here, anisotropic etching may be performed so as to completely remove the oxide film 6a grown on the polycrystalline silicon film 3 other than the polycrystalline silicon wiring 5.

〔Effect of the invention〕

As explained above, in the present invention, when forming a polycrystalline silicon wiring, pattern etching is stopped midway and oxidation is performed, and then anisotropic etching is performed to form an oxide film on the side surface of the polycrystalline silicon wiring. Since a second oxide film is formed over the polycrystalline silicon wiring by oxidizing it again after that, uneven parts of the oxide film will not occur in some parts of the polycrystalline silicon wiring. Therefore, polycrystalline silicon wiring can be reliably covered with an oxide film. This prevents a portion of the polycrystalline silicon wiring from being exposed and prevents short circuits with upper layer wiring, thereby improving the reliability and manufacturing yield of the semiconductor device.

[Brief explanation of drawings]

1A to 1E are sectional views showing an embodiment of the present invention in the order of steps, and FIG. 2 is a sectional view illustrating problems of the conventional method. 1, 11... Semiconductor substrate, 2, 12... Insulating film, 3... Polycrystalline silicon film, 4... Photoresist, 5... Polycrystalline silicon wiring, 6, 6a...
Oxide film, 7, 7a... second oxide film, 8... upper layer interconnection, 13... polycrystalline silicon interconnection, 14... oxide film, 15... upper layer interconnection.

Claims (1)

[Claims] 1. Growing a polycrystalline silicon film on the insulating film of the substrate, selectively etching it to form a polycrystalline silicon wiring, and oxidizing the polycrystalline silicon wiring to form an insulating film with the upper layer wiring. In a method for manufacturing a semiconductor device, selective etching when forming the polycrystalline silicon wiring is stopped midway, and oxidation is performed with the polycrystalline silicon film remaining in areas other than the polycrystalline silicon wiring. , performing anisotropic etching on the oxide film to leave an oxide film on the side surface of the polycrystalline silicon interconnect, and then performing oxidation again to form a second oxide film overlapping at least the polycrystalline silicon interconnect. A method for manufacturing a semiconductor device, comprising the steps of: