JPH0786209A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a via hole small in wiring resistance, concerning the method of forming a via hole which has a barrier layer only on the bottom and does not have a barrier layer on the side. CONSTITUTION:This manufacture comprises a process of opening a hole 5 in the insulating layer 3 covering a conductive region 2 and stacking a high melting point film 4 consisting of a high melting metal or high melting point metal compound by sputtering, a process of removing the high melting point metallic film 4 stacked on the sidewall of the hole 5, leaving the high melting point metallic film 4 stacked on the surface of the conductive region 2 and the surface of the insulating layer 3, as a barrier layer 4a, and a process of stopping the hole (5) in the insulating layer 3 and stacking a conductor layer and patterning it so as to form an upper wiring 7.

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 via holes having a small wiring resistance.

The miniaturization of via holes in semiconductor devices, for example, the miniaturization of holes for connecting multi-layered wiring or contact holes for connecting semiconductor regions and wiring, increases the aspect ratio of these via holes and increases wiring resistance. This causes electromigration and deteriorates the reliability of the semiconductor device.

Therefore, in fine wiring, it is necessary to reduce the aspect ratio of the via hole and reduce the wiring resistance of the via hole.

[0004]

2. Description of the Related Art Via holes used in semiconductor devices are
For the purpose of preventing migration, upper and lower wirings to be connected are usually sandwiched by a refractory metal thin film made of a refractory metal or a compound thereof as a diffusion barrier layer and connected by a plug made of a conductor.

A process of forming such a via hole will be described with reference to FIG. FIG. 2 is a cross-sectional process diagram of a conventional example, showing a process of forming a via hole in a semiconductor device. In forming a conventional via hole, first, as shown in FIG.
Referring to, a lower layer wiring 2a of aluminum is formed as a conductive region 2 on the semiconductor substrate 1 whose surface is insulated.
Next, an insulating layer 3 made of, for example, phosphorous glass (PSG), which covers the lower layer wiring 2a, is deposited on the entire surface of the substrate.

Next, a hole 5 penetrating the insulating layer 3 is formed on the lower wiring 2a. Then, referring to FIG.
A refractory metal thin film 4 covering the upper surface of the insulating layer 3 and the inner surface of the hole 5 is deposited.

Next, referring to FIG. 2C, an aluminum layer is deposited on the refractory metal thin film 4 by filling the holes 5, and the aluminum layer is patterned to form the upper wiring 7.
To form. At this time, the hole 5 filled with aluminum constitutes a via hole that connects the lower layer wiring 2a and the upper layer wiring 7.

In the via hole formed in this step, the refractory metal thin film 4 is formed not only on the surface of the lower layer wiring 2a but also on the outer peripheral surface of the via hole. Since the refractory metal thin film 4 is formed on the outer peripheral surface of the via hole, the aluminum plug filling the hole 5 becomes thin. As a result, the effective via hole diameter is small and the aspect ratio is large, so that the wiring resistance of the via hole increases. For this reason, migration tends to occur as the current density increases.

[0009]

As described above, in the conventional method of manufacturing a semiconductor device, since the refractory metal thin film is formed on the outer periphery of the via hole, the diameter of the aluminum plug is reduced and the wiring resistance and the current density are increased. Therefore, there is a problem that migration easily occurs.

The present invention utilizes the fact that the refractory metal thin film deposited on the side wall surface of the hole forming the via hole has a different etching rate from the refractory metal thin film deposited on the plane orthogonal to the side wall of the hole. And selectively remove it,
An object of the present invention is to provide a method for manufacturing a semiconductor device, in which a via hole having no high melting point metal thin film is formed on the outer circumference, and a via hole having a large plug diameter serving as a conductor and having a small wiring resistance is formed.

[0011]

FIG. 1 is a sectional process view of an embodiment of the present invention, showing a via hole of a semiconductor device.

In order to solve the above-mentioned problems, referring to FIG. 1, the first structure of the present invention is that a conductive region 2 formed of a lower layer wiring or a semiconductor region formed on a substrate 1 and the conductive region 2 are formed. In a method of manufacturing a semiconductor device having a via hole 8 penetrating through an insulating layer 3 provided above and electrically connecting an upper wiring 7 provided on the insulating layer 3 to the conductive region 2, A step of depositing the insulating layer 3 covering the conductive region 2 on the insulating layer 3, a step of forming a hole 5 defining the via hole 8 in the insulating layer 3, and a step of exposing the bottom of the hole 5; A step of depositing a refractory metal thin film 4 made of a refractory metal or a refractory metal compound covering the exposed surface of the conductive region 2, the side wall surface of the hole 5 and the upper surface of the insulating layer 3 by sputtering; Isotropic etching of the refractory metal or the refractory metal compound The refractory metal thin film 4 for using
Of the high melting point metal thin film 4 deposited on the exposed surface of the conductive region 2 and the surface of the insulating layer 3 as a barrier layer 4a, and the high melting point deposited on the side wall surface of the hole 5. The step of removing the metal thin film 4 is performed, and then the conductor layer in which the holes 5 are filled and deposited on the insulating layer 3 is patterned to form the upper layer wiring 7, and the upper layer wiring 7 and the conductive region 2 are formed. And a step of forming the via hole 8 that sandwiches the barrier layer 4a and connects through the hole 5, and the second configuration is a method for manufacturing a semiconductor device having the first configuration. The upper wiring 7 is made of aluminum or an aluminum alloy, and the refractory metal thin film 4 is a thin film of titanium, tungsten, titanium nitride or titanium tungsten, or a titanium thin film and the titanium thin film. The third structure is characterized by comprising a titanium nitride thin film, and the third structure is the method for manufacturing a semiconductor device having the first or second structure, and after the step of removing the refractory metal thin film 4, the via hole 8 is formed. The step of depositing a resist 6 for filling the hole 5 on the insulating layer 3 before the step of forming a step, and then etching back the resist 6 to leave the resist 6 for filling the hole 5; Insulation layer 3
And a step of removing the resist 6 above.

[0013]

In the structure of the present invention, referring to FIG. 1A, first, similarly to the formation of the conventional via hole described above, the conductive layer 2 is formed on the insulating layer 3 covering the conductive region 2 and the conductive region 2 is formed on the bottom. The exposed hole 5 is opened, and the refractory metal thin film 4 covering the entire inner wall surface of the hole 5 and the upper surface of the insulating layer 3 is deposited by sputtering.

In the structure of the present invention, the refractory metal thin film on the inner surface of the hole is then etched by means for isotropically etching the refractory metal or its compound, for example, isotropic chemical etching.

Since the refractory metal thin film 4 deposited by sputtering has a columnar structure perpendicular to the surface of the substrate 1, the refractory metal thin film 4 deposited on the side wall surface of the hole 5 perpendicular to the surface of the substrate 1 is better. However, the etching rate is higher than that of the refractory metal thin film 4 deposited on the surface of the conductive region 2 parallel to the surface of the substrate 1 and the upper surface of the insulating film 3.

Therefore, referring to FIG. 1B, by applying a normal isotropic etching to the refractory metal thin film 4 deposited in the hole 5, the high-melting point metal deposited on the side wall surface of the hole 5 is etched. Only the melting point metal thin film 4 can be removed. on the other hand,
The refractory metal thin film 4 deposited on the surface of the conductive region 2 exposed on the bottom surface of the hole 5 and on the upper surface of the insulating layer 3 remains as a thin film although it is thinner than the film thickness at the time of deposition, and becomes the barrier layer 4a. The remaining film thickness is determined by the difference between the etching rates of the refractory metal thin films deposited on the surface perpendicular to the surface of the substrate 1 and the film thickness at the time of deposition. The difference between the etching rates and the film thickness at the beginning of deposition are usually clearly determined and can be easily controlled, so that the remaining film thickness, that is, the film thickness of the barrier layer 4a is easily and precisely controlled.

In this structure, referring to FIG. 1 (e), the hole 5 formed by the above process and having the barrier layer 4a on the bottom surface and the refractory metal thin film on the side wall surface is removed is formed in the upper layer. A via hole 8 is formed by embedding the material of the wiring 7. Unlike the conventional via hole described above, the via hole 8 has no refractory metal thin film on the outer periphery of the via hole.
The diameter of the conductor serving as the plug of the via hole 8 is the same as the diameter of the hole 5. Therefore, the diameter of the via hole can be prevented from being substantially reduced due to the high melting point metal thin film, so that the via hole having a small wiring resistance and a small aspect ratio can be formed, and the wiring excellent in migration resistance can be realized.

The second structure of the present invention relates to the formation of a via hole when aluminum or its alloy is used as a wiring material, and titanium, tungsten,
A thin film of titanium nitride or titanium tungsten is used. Further, the barrier layer may have a two-layer structure in which a titanium nitride thin film is provided on the titanium thin film (hereinafter referred to as "titanium nitride / titanium thin film"). Here, the isotropic etching of the titanium nitride / titanium thin film and titanium nitride can be performed by wet etching using an etchant of a mixed solution of ammonium and nitric acid. In addition, isotropic etching of tungsten and titanium tungsten can be performed using potassium ferricyanide as an etchant.

In the third structure, the refractory metal thin film deposited on the side wall surface is removed by the first or second structure, and the holes in which the refractory metal thin film remains as a barrier layer only on the bottom surface are filled with a resist, The resist is used to protect the inner surface of the hole, and the refractory metal thin film deposited on the outer side of the hole, that is, on the upper surface of the insulating layer is removed by etching. In this configuration, since the barrier layer does not exist under the wiring provided on the insulating layer, the wiring resistance is smaller than that of the wiring having the same height.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the embodiments used for forming via holes for connecting multi-layer wirings of a semiconductor device.

First, silicon oxide is formed on the surface of a semiconductor wafer on which a semiconductor element is formed to form a semiconductor substrate whose surface is insulated. Next, referring to FIG. 1A, a lower layer wiring 2a made of aluminum or its alloy is formed as a conductive region 2 on the semiconductor substrate 1. This lower layer wiring 2a can be formed by a normal wiring manufacturing process of a semiconductor device, for example, by patterning a sputtered wiring material. In this embodiment, the lower layer wiring 2
If the impurity region formed in the semiconductor substrate 1 is used as the conductive region 2 instead of a, the following steps are performed in the same manner.

Then, the conductive region 2 is covered with, for example, a thickness 70.
An insulating layer 3 is formed by depositing 0 nm silicon oxide on the entire surface of the substrate. After that, a hole 5 having a diameter of, for example, 600 nm is formed on the conductive region 2 of the insulating layer 3.

Next, as the refractory metal thin film 4, for example, titanium nitride is sputtered to cover the inner wall surface of the hole 5 and the substrate 1
Deposit so as to extend over the entire upper surface. Next, the substrate 1 is dipped in a mixed solution of ammonium and nitric acid to etch the refractory metal thin film 4. This etching is shown in Figure 1.
Referring to (b), the process ends when the refractory metal thin film 4 deposited on the side wall surface of the hole is substantially removed. Of course, by preliminarily depositing a high film thickness of the high melting point metal thin film 4,
It can also be over-etched. As a result of this etching, a barrier layer 4a made of, for example, titanium nitride having a thickness of 100 nm is formed on the conductive region 2 exposed on the bottom surface of the hole 5, while the side wall of the hole 5 has the refractory metal thin film 4 removed to form an insulating layer. 3 appears.

Next, referring to FIG. 1C, a resist 6 is deposited on the substrate 1 by, for example, spin coating. Next, the entire surface of the resist 1 is etched to remove the resist 6 in parallel with the surface of the substrate 1 until the barrier layer 4a on the upper surface of the insulating layer 3 is exposed. At this time, the resist 6 still fills the hole 5 and remains.

Next, referring to FIG. 1D, the insulating layer 3
The barrier layer 4a on the upper surface is etched and removed. Then, after removing the resist in the holes 5, referring to FIG. 1E, the holes 5 are buried and an aluminum wiring material is deposited on the entire surface of the substrate 1 and patterned to form upper layer wirings 7.

As a result, a via hole 8 connecting the conductive region 2 and the upper layer wiring 7 is completed by using the aluminum wiring material as the plug 7a and sandwiching the barrier layer 4a between the plug 7a and the conductive region 2. .

The via hole formed by this embodiment is
The diameter of the aluminum plug is 600 nm. This plug has a cross-sectional area slightly more than twice that of a conventional aluminum plug having a via hole having a barrier layer having a thickness of 100 nm at the peripheral portion, which is 400 nm. Therefore, the aspect ratio of the aluminum plug that mainly contributes to electrical connection, that is, the effective aspect ratio of the via hole can be reduced. Therefore, a via hole with a low wiring resistance is formed.

[0028]

As described above, according to the present invention, the refractory metal thin film on the side wall of the hole can be selectively removed by isotropic etching. Therefore, the diameter of the conductor serving as the plug of the via hole is defined as the via hole diameter. Since they can be made the same, the diameter of the plug can be increased, the wiring resistance can be reduced, and a method of manufacturing a semiconductor device that can easily form a via hole with less migration can be provided, which greatly contributes to the performance improvement of the semiconductor device.

[Brief description of drawings]

FIG. 1 is a sectional process drawing of an embodiment of the present invention.

FIG. 2 is a sectional process diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Conductive region 2a Lower layer wiring 3 Insulating layer 4 High melting point metal thin film 4a Barrier layer 5 Hole 6 Resist 7 Upper layer wiring 8 Via hole

Claims (3)

[Claims] 1. A conductive region (2) formed of a lower layer wiring or a semiconductor region formed on a substrate (1) and an insulating layer (3) provided on the conductive region (2) are penetrated, In a method of manufacturing a semiconductor device having a via hole (8) for electrically connecting an upper wiring (7) provided on an insulating layer (3) and the conductive region (2), the semiconductor device is provided on the substrate (1) with a via hole (8). Depositing the insulating layer (3) covering the conductive region (2),
Next, a step of forming a hole (5) that defines the via hole (8) in the insulating layer (3), and then, an exposed surface of the conductive region (2) exposed at the bottom of the hole (5), A step of depositing a refractory metal thin film (4) made of a refractory metal or a refractory metal compound covering the side wall surface of the hole (5) and the upper surface of the insulating layer (3) by sputtering; Deposition on the exposed surface of the conductive region (2) and the surface on the insulating layer (3) by etching the refractory metal thin film (4) using isotropic etching of metal or the refractory metal compound. Leaving the refractory metal thin film (4) as a barrier layer (4a) and removing the refractory metal thin film (4) deposited on the side wall surface of the hole (5), and then the insulating layer (3) patterning the deposited conductor layer by embedding the hole (5) above Forming a layer wiring (7) and forming the via hole (8) connecting the upper layer wiring (7) and the conductive region (2) through the hole (5) with the barrier layer (4a) sandwiched therebetween; A method of manufacturing a semiconductor device, comprising: 2. The method of manufacturing a semiconductor device according to claim 1, wherein the upper wiring (7) is made of aluminum or an aluminum alloy, and the refractory metal thin film (4) is made of titanium, tungsten, titanium nitride or titanium. A method for manufacturing a semiconductor device, comprising a tungsten thin film, or a titanium thin film, and a titanium nitride thin film provided on the titanium thin film. 3. The method of manufacturing a semiconductor device according to claim 1, wherein after the step of removing the refractory metal thin film (4) and before the step of forming the via hole (8),
A resist (6) for filling the hole (5) on the insulating layer (3).
And then etching back the resist (6) to leave the resist (6) filling the holes (5) and removing the resist (6) on the insulating layer (3). A method of manufacturing a semiconductor device, comprising: