JPH0722395A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enhance a metal wiring material in step coverage by a method wherein a tapered contact hole is provided in an interlayer insulating film only by reactive ion etching. CONSTITUTION:A photoresist film 3 high in development solubility and a photoresist film 31 lower in solubility than the film 3 are successively laminated on an interlayer insulating film 2 by spin coating, exposed to light, and developed. As the photoresist film 3 is more dissolved than the photoresist 31 tat development, a photomask pattern of large overhang structure is formed. When the interlayer insulating film 2 is removed through a reactive ion etching method using this photomask as a mask, ions not only vertical but also oblique take part enough in etching, and a sputtering phenomenon caused by oblique ions is restrained from occurring on a resist film, so that a forward tapered contact hole can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to the formation of fine contact holes.

[0002]

2. Description of the Related Art In the manufacture of semiconductor integrated circuits, a semiconductor device having a half micron rule is currently being manufactured by an ultrafine processing technique. The process that becomes the most problematic as miniaturization progresses is the process of forming contact holes. In order to reduce the chip area of the semiconductor integrated circuit as much as possible, the miniaturization in the plane direction has been rapidly advanced, but the miniaturization in the vertical direction has been delayed as compared with the case of the plane direction. For example, the aspect ratio of the contact hole (ratio of the depth of the contact hole divided by the diameter of the contact hole) is increased. When the aspect ratio of the contact hole is increased, the step coverage of the metal wiring material in the contact hole portion is deteriorated, and the contact resistance is increased and the reliability is decreased. Fig.3 (a)-
(D) shows a process cross-sectional flow of contact hole formation using conventional reactive ion etching. Figure 3 (d)
As is clear from the above, when the aspect ratio is increased, the step coverage of the metal wiring material 4 is extremely deteriorated. In order to improve the step coverage of the metal wiring material in the contact hole portion, it is most effective to form the contact hole in a forward tapered shape.

However, when the silicon oxide film is etched by the commonly used reactive ion etching, in order to obtain a practical etching rate, it is necessary to increase the ionicity, which is anisotropic etching. Isotropic dry etching using a radical component has a low etching rate and is not practical. In addition, there is an example in which taper etching is realized by setting a low selection ratio to the photoresist (ratio of the etching rate of the silicon oxide film divided by the etching rate of the photoresist film) and retreating the forwardly tapered photoresist mask by etching. is there. However, even in this case, it is difficult to form a forward tapered photoresist pattern with a fine pattern, and a forward tapered contact hole can be obtained only with a relatively large pattern.

[0004]

According to the present invention, a contact hole having a forward taper in a silicon oxide film can be realized only by a reactive ion etching process without performing a wet process which is an isotropic etching. The step coverage of the metal wiring material in the contact hole portion can be improved.

[0005]

In order to solve the above problems, a method of manufacturing a semiconductor device according to the present invention is characterized in that a reactive ion etching is performed on an interlayer insulating film with a photoresist film having an overhang shape, A forward tapered contact hole is formed in the interlayer insulating film.

Further, the photoresist film is formed with an upper layer having higher solubility in a developing solution as an upper layer.

[0007]

By using the present invention, it is possible to form an ideal tapered contact hole by a relatively simple method, which contributes to improving the step coverage of the metal wiring material and improving the reliability of the device. It is a thing.

[0008]

Embodiment An embodiment of the present invention will be described with reference to the drawings. 1A to 1E show process cross-sectional flows in a method for manufacturing a semiconductor device using the present invention. In the drawings,
The steps of separation and gate formation are omitted. FIG. 1A shows a place where an insulating film 2 is deposited after forming isolations, gates, diffusions, etc. on a semiconductor substrate 1. Figure 1 (b)
Has a photoresist film 3 of 1.5 μm on the interlayer insulating film 2.
The photoresist film 31 is applied by spin coating, and the photoresist film 31 having a dissolution rate lower than that of the photoresist film 3 at the time of development is applied by 0.5 μm.

Next, exposure and development are performed using a predetermined mask (reticle). At this time, the photoresist film 3 has a higher developing dissolution rate than the photoresist film 31 and thus is largely dissolved during development, and a large overhanging photoresist pattern as shown in FIG. 1C is formed. When reactive ion etching is performed using such a large overhang-shaped resist pattern, not only vertical component ions but also oblique component ions are likely to enter during the reactive ion etching, and the interlayer insulating film 2 is etched into a tapered shape. To be done. Further, since the photoresist pattern has an overhang shape, diagonal ions are less likely to collide with the photoresist film, and sputtering from the photoresist film is reduced. Therefore, the amount of polymer generated is reduced, and the etching rate in the oblique direction is less likely to decrease. For these reasons, a forward tapered contact hole is formed (FIG. 1D). Finally, Figure 1
(E) is the figure which vapor-deposited the metal wiring material 4 by the sputtering method.

As described above, in order to form a contact hole having a forward taper by using reactive ion etching, when forming a photomask pattern, a photoresist film having a different dissolution rate during development is formed into a laminated structure, or a photoresist film is formed. By hardening the film surface and decreasing the dissolution rate in the vicinity of the photoresist film surface during development, a large reverse taper overhang can be formed in the photoresist pattern. When the silicon oxide film is processed by reactive ion etching using this photomask pattern, there is a large space because the photomask pattern has an inverse taper overhang, and not only the vertical component ions but also the diagonal component ions. This makes it possible to perform positive taper etching processing (Fig. 2). Further, in the overhang-shaped photomask pattern, the occurrence of the sputtering phenomenon of the photomask material during etching is suppressed and the polymer adhesion is suppressed, so that the etching rate of the horizontal component is less likely to decrease.

[0011]

As described above, by using the tapered contact hole forming method of the present invention, the step coverage in the contact hole portion of the metal wiring is improved and the reliability is improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view in order of the steps in a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a state of reactive ion etching using a photomask having an overhang shape.

3A to 3C are cross-sectional views in order of steps of a method for manufacturing a semiconductor device according to a conventional technique.

[Explanation of symbols]

 1 Silicon Substrate 2 Interlayer Insulation Film 3 Photoresist Film 4 Metal Wiring Material 31 Photoresist Film

Claims (2)

[Claims] 1. A method of manufacturing a semiconductor device, comprising: forming a forward tapered contact hole in the interlayer insulating film by performing reactive ion etching with a photoresist film having an overhang shape on the interlayer insulating film. Method. 2. The photoresist film is formed by laminating a plurality of photoresist films having different solubilities in a developing solution, and the solubility of the lower photoresist film in the developing solution is the solubility of the upper photoresist film in the developing solution. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the semiconductor device has high conductivity.