JPH04330769A - Method of connecting wiring - Google Patents

Abstract

PURPOSE:To make possible a good connection of a wiring by a method wherein a contact hole is formed in an insulating film on a base metal film by dry etching, a metal crown generated due to the formation of this contact hole is removed by wet etching and the overhang part of the insulating film is selectively etched away. CONSTITUTION:An insulating film 2, an Al film 3, which is a base conductive film, and an insulating film 4 are formed in order on a semiconductor substrate 1. A contact hole 6 is formed in the film 4 by performing an RIE of a strong ionicity on the film 4 via a resist mask 5. As this hole 6 is shallow, the base Al film 3 is sputtered and the so-called Al crown 7 is generated. Then, the film 3 is etched away by performing a wet etching. At this time, the film 4 is formed into the form of an overhang and an overhang part 4a is formed. Owing to this, the film 4 is etched into a thickness of 500Angstrom or thereabouts by performing a plasma etching having not an ionicity and the overhang part 4a is removed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring connection method in semiconductor integrated circuits such as VLSIs.

0002

[Prior Art] In the manufacturing process of semiconductor integrated circuits, especially in the VLSI manufacturing process, pattern dimensions are becoming smaller and smaller.
The processing accuracy of dry etching is also becoming more stringent than before. Even in lithography technology, there are problems such as difficulty in patterning when forming contact holes when there is a large step difference in the base, and flattening and smoothing treatments have become essential. Normally, planarization and smoothing are performed by applying a resist film on a surface having steps and etching back the resist film. Then, to connect the wiring, a resist mask is formed on the surface that has been flattened and smoothed in this way, contact holes are formed by dry etching such as RIE (reactive ion etching), and then the entire surface including the contact holes is formed. A wiring material is formed by vapor deposition or the like (for example, Al is formed, or blanket tungsten (W) is formed and etched back to form a W buried layer in the contact hole, and then Al is formed on the entire surface), and then It is patterned and connected to the underlying Al (or Al alloy) film to form wiring.

0003

[Problems to be Solved by the Invention] However, due to the above-mentioned planarization, new problems are occurring in dry etching. That is, as shown in FIG. 5A, an insulating film 2, a base Al (or Al alloy) film 3, and an insulating film 4 are sequentially formed on a semiconductor substrate 1 on which an element is formed, and after planarization, a resist mask 5 is formed. When the contact hole 6 is formed in the insulating film 4 by dry etching, the film thickness of the insulating film 4 to be processed differs, and the shallow contact hole 6 shown in the figure is often over-etched. By this over-etching, the underlying Al (or Al alloy) film 3 is sputtered, evaporated,
As a result, an Al deposit 7 called an Al crown is formed on the inner wall surface of the hole. In severe cases, this Al crown 7 remains even after the resist mask 5 is removed, as shown in FIG. 5B, and causes trouble in the subsequent wiring process. R
In forming the contact hole 6 by IE, the stronger the ionicity, the more precise the contact hole 6 can be obtained.
The above-mentioned Al crown 7 is generated due to the strong ionicity. Such a problem with the Al crown 7 essentially occurs when the thickness of the insulating film 4 to be processed by planarization or the like varies depending on the location, and a solution has been desired.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides a wiring connection method that enables good wiring connections by removing the so-called metal crown produced by dry etching.

[0005]

[Means for Solving the Problems] The present invention provides a base metal film 3
A step of forming a contact hole 6 in the upper insulating film 4 by dry etching, a step of removing the metal crown 7 generated by the dry etching by wet etching, and selectively removing the eaves portion 4a of the insulating film 4 in the contact hole 6. Etching removal process and contact hole 6
The method is characterized in that it includes a step of connecting the wiring 11A to the base metal film 3 via the base metal film 3.

[0006]

In the present invention, after the contact hole 6 is formed in the insulating film 4 by dry etching, the metal crown 7 produced by the dry etching is completely removed by performing wet etching. During this wet etching, the base metal film 3 is also isotropically etched, so that an overhang, that is, an eaves portion 4a is formed in the insulating film 4. However, by selectively etching away this eaves portion 4a after that, a good wiring connection to the contact hole 6 can be made. In addition, the base metal film 3 is etched by wet etching and becomes concave.
The contact area between the wiring 11A and the base metal film 3 increases,
Contact resistance is also reduced.

[0007]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 4.

In this example, as shown in FIG. 1A, an insulating film 2, an Al (or Al alloy) film 3 serving as a base conductive film, and an insulating film 4 are sequentially formed on a semiconductor substrate 1 on which elements are formed. . Here, in order to flatten the level difference on the surface (not shown), a resist film is formed and then etched back to flatten the insulating film 4. Then, highly precise contact holes 6 are formed in the insulating film 4 through the resist mask 5 by RIE with strong ionicity. Since this contact hole 6 is shallow, over-etching occurs frequently when forming other deep contact holes at the same time, and as a result, the underlying Al (or Al alloy) film 3 is sputtered and a so-called Al crown 7 is generated.

Next, as shown in FIG. 1B, even if the resist mask 5 is removed, the Al crown 7 remains.

Next, as shown in FIG. 2C, about 500 Å of the Al (or Al alloy) film 3 is removed by wet etching using acid or alkali. The Al crown 7 is completely removed by this wet etching process. However, since this wet etching is isotropic etching, when etching the Al (or Al alloy) film 3, side etching also progresses under the insulating film 4, causing the insulating film 4 to overhang, resulting in a so-called eaves portion 4a. It is formed.

As shown in FIG. 6, if an Al film 8, which is a wiring material, is buried in the contact hole 6 by vapor deposition or the like while the eaves part 4a is still formed, a cavity without the Al film 8 is created under the eaves part 4a. 10 is formed, which is not preferable. Note that when forming a tungsten buried layer in the contact hole 6 using the selective tungsten CVD method, tungsten is well buried even if the eaves portion 4a exists.

For this reason, in this example, after the wet etching of Al (or Al alloy), as shown in FIG. 4 to 50
Etching is performed to approximately 0 Å to remove the eaves portion 4a. In this plasma etching, for example, CF4 is used as the gas.
:O2 is supplied at a flow rate of 100SCCM:20SCCM, the pressure is set to 100 mtorr, and the power is set to 300W.

Next, as shown in FIG. 3E, a wiring material such as an Al film 11 is deposited on the entire surface including the inside of the contact hole 6 by vapor deposition, and then patterned to form an underlying Al (or Al alloy) layer as shown in FIG. 3F. ) An upper layer wiring 11A connected to the film 3 is formed.

Alternatively, after the step of FIG. 2D, the steps of FIG. 4A and FIG.
For example, blanket tungsten (W) as shown in B
12 is formed and etched back to form a tungsten buried layer 12A in the contact hole 6. After that,
An Al film is formed so as to be in contact with the tungsten buried layer 12A, and is patterned to form an Al upper layer wiring 13 connected to the base Al film 3 via the tungsten buried layer 12A.

According to the above method, after forming the contact hole 6 in the insulating film 4 on the Al (or Al alloy) film 3 by RIE, the contact hole 6 is formed by wet etching.
By removing the Al crown 7, a contact hole 6 without the Al crown 7 is formed. Moreover, Al(
or Al alloy) during wet etching, the underlying Al (
(or Al alloy) film 3 is also isotropically etched to form an eaves portion 4a on the insulating film 4, but is then selectively removed by plasma etching, so the contact hole 6 has a so-called overhang shape. This results in a contact hole with no Therefore, the subsequent wiring material, for example, the Al film 11 or the blanket tungsten film 12
The filling is also carried out in a complete state with no cavities, and the Al upper layer wiring 13 and the base layer A are connected through the contact hole 6 to the Al upper layer wiring 11A or the tungsten buried layer 12A.
Good connection with the Al (or Al alloy) film 3 is achieved. In addition, the underlying Al (or Al alloy) can be etched by wet etching.
Since the film 3 is partially etched away and becomes concave, the contact area with the wiring material increases and contact resistance is also reduced.

[0016]

According to the present invention, it is possible to form a contact hole without a metal crown, and the upper layer wiring and the underlying metal film can be well connected through the contact hole. Furthermore, since the contact portion of the base metal film becomes concave and has a large surface area, contact resistance with the upper layer wiring is also reduced. Therefore, it is suitable for application to, for example, the manufacture of ultra-LSIs that require fine contact holes.

[Brief explanation of drawings]

FIG. 1 is a manufacturing process diagram (Part 1) showing an embodiment of the wiring connection method of the present invention.

FIG. 2 is a manufacturing process diagram (part 2) showing an embodiment of the wiring connection method of the present invention.

FIG. 3 is a manufacturing process diagram (Part 3) showing an embodiment of the wiring connection method of the present invention.

FIG. 4 is a manufacturing process diagram showing another embodiment of the wiring connection method of the present invention.

FIG. 5 is a manufacturing process diagram for explaining the conventional method.

FIG. 6 is a sectional view showing a comparative example.

[Explanation of symbols]

1 Semiconductor substrate 2 Insulating film 3 Al (or Al alloy) film 4 Insulating film 5 Resist mask 6 Contact hole 7 Al crown 8 Upper layer wiring 11 Al film 11A Upper layer Al wiring 12 Blanket tungsten 12A Tungsten buried layer 13 Upper layer Al wiring

Claims (1)

[Claims] 1. A step of forming a contact hole in an insulating film on a base metal film by dry etching, a step of removing a metal crown produced by the dry etching by wet etching, and a step of forming an eaves of the insulating film in the contact hole. 1. A wiring connection method comprising the steps of: selectively etching away a portion of the contact hole; and connecting a wiring to the base metal film through the contact hole.