KR920008400B1 - Wet etch-back method of blanket tungsten for via-filling - Google Patents

Abstract

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Description

Wet Etch-Back Method of Blanket Tungsten for Beer Filling

1 is a cross-sectional view showing a manufacturing process of the prior art.

2 is a cross-sectional view showing a manufacturing process of the present invention.

* Explanation of symbols for main parts of the drawings

1: first metal layer 2: second metal layer

3: tungsten 4: intermediate dielectric

5 substrate 6 oxide layer

7 gate 8 gate oxide layer

9: photosensitive film

FIELD OF THE INVENTION The present invention relates to a wet etch-back method of blank tungsten for via-filling, in particular blank tungsten for the connection between metal and metal wires. Via-Plug, ie, suitable for use as a contact.

In the conventional high-density MOS device fabrication process, RIE, which is one of dry etch methods having an anisotropic etching property after depositing a blank kit tungsten by CVD for effective metal-to-metal connection Tungsten plugs were formed in the via site, that is, the contact site by etching back by the Reactive Ion Etch method.

Referring to the manufacturing process of the prior art described above with reference to Figure 1 as follows.

First, the via hole, which is a connection path between the first metal layer 1 and the second metal layer 2, is defined and then the blank kit tungsten 3 is deposited by CVD. Blank kit tungsten (3) is effectively filled in the via hole.

However, as shown in FIG. 1A, since tungsten 3 is unnecessarily deposited on the interdielectric 4, tungsten remains only in the via hole to act as a plug of the first metal layer 1 and the second metal layer 2. In order to etch-back the RIE method, which is a dry etching method having anisotropic etching characteristics, the second layer is made of aluminum and silicon (A + Si) or a second layer of aluminum, silicon, and copper (Al + Si + Cu). The metal layer 20 was deposited by a sputtering technique.

However, the prior art is a photo process that proceeds after deposition of the second metal layer 2 as the surface of the dielectric dielectric 4 becomes rough due to etch-back radiation radiation damage by the dry etch-back method. Problems with reflectivity arise, and micro-loading effects such as the global-loading effect and the local-loading effect appear. As shown in the figure, the top position of the tungsten plug is lowered below the intermediate dielectric 40 and the surface thereof becomes rough so that step coverage in the subsequent deposition process of the second metal layer 20 is improved. There are problems such as poor or electrically vulnerable, such as surface leakage current and electrical material transfer (Electromigration) occurs.

The present invention has been invented to eliminate the above problems, and the isotropic etch characteristics of the tungsten etch-back to be used as a via-plug instead of the etch of the blank kit tungsten by the RIE method, which is one of the dry etch methods, are provided. The purpose of the present invention is to prevent radiation damage and various loading effects on the dielectric 4 generated by dry etching by performing a wet etch method.

The process sequence of the present invention having the above object will be described in detail with reference to Figs.

First, in order to etch the blank kittungsten (3) etched by the wet etch back method and not to etch the intermediate dielectric 40 covering the other region, only the tungsten 3 can be selectively etched. The choice of chemicals for etching is important.

In the embodiment of the present invention, a chemical agent having a ratio of HF (48%): HNO 3 (Conc): H ₂ O = 15: 35: 75 was used.

When the selection of the chemical is made, as shown in FIG. 2A, after defining the via hole, the blank kit tungsten (3) is deposited and the via mask is reused thereon, wherein the photoresist film to be used must be a negative photoresist film. After adjusting the exposure time slightly larger than the critical dimension, the photo process is performed so that only the via hole is covered with the photoresist film, and then etched back by the wet etching method. The isotropic etch characteristics of the method also etch a portion of the tungsten underneath the photosensitive film 9, leaving only tungsten 30 in the via hole region, as shown in FIG. 2B.

Here, the end point of the etch is determined by the exact time adjustment obtained through the experiment.

Subsequently, the photoresist film 9 is removed and a second metal layer 2 made of aluminum and silicon (Al + Si) or aluminum and silicon and copper (Al + Si + Cu) is deposited thereon. The process is completed in the form.

As described above, when the blank kit tungsten (3) is used as a via plug for effective connection between a metal and a metal, the wet etching method may be generated by using a wet etch method as the etch method of the tungsten (30). There is an effect that can prevent radiation damage and various micro loading effects.

Claims (1)

In the use of the etch-back of the blank kit tungsten 30 deposited by CVD as a via hole plug for connecting the first metal layer 10 and the second metal layer 2, the deposited tungsten (3 The via mask is reused, but the photoresist used is a negative photoresist, and the photoresist 9 is sufficiently covered by the photoresist 9 by adjusting the exposure time longer than the limited time of the via hole, and only the tungsten 3 can be etched back. Blanking for beer peeling, characterized in that the wet etching method isotropically etched using a chemical agent of HF (48%): HNO₃ (Conc): H₂O = 15: 35: 75 Wet etch-back method of tungsten.

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