JPH04237130A - Manufacture of integrated circuit device - Google Patents

Abstract

PURPOSE:To make the ohmic contact stable and excellent by a method wherein a metallic thin film comprising the same material as that of a wiring film is formed by sputtering step to be removed by the second time sputtering step and then the wiring film is formed by the sputtering step. CONSTITUTION:A through hole 17 is made in an interlayer insulating film and then a wiring metallic film to be an upper layer wiring is sputtered on the interlayer insulating film. At this time, after the first time sputter etching step, a metallic thin film 20 comprising the same material as that of the upper layer wiring is formed by the sputtering step so as to previously cover the surface of the interlayer insulating film and the surface of the through hole 17. During the second time sputtering step, the effect of readhering matters 19 by the sputter etching step giving a trouble in making an ohmic contact of the through hole 17 can almost perfectly be averted. Through these procedures, the ohmic contact of the through hole 17 can be made stable and excellent.

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 integrated circuit device, and more particularly to a method of manufacturing a multilayer wiring.

0002

2. Description of the Related Art In manufacturing large-scale integrated circuits (LSI), multilayer wiring is frequently used due to the demand for higher density and higher speed. That is, an interlayer insulating film is formed on the first layer of wiring,
After forming an opening in a portion thereof for electrical connection, a second layer wiring film is formed on the interlayer insulating film. Thereafter, if necessary, interlayer insulating films and wiring metal films are alternately formed to form a multilayer wiring structure.

Aluminum, aluminum alloys, etc. are often used for wiring metal films, and silicon oxide, silicon nitride, etc. are often used for interlayer insulating films. In particular, insulating films containing oxygen, such as silicon oxide and silicon oxynitride produced by plasma CVD, give lower stress to the wiring metal film than silicon nitride, are effective in stress migration of the wiring metal film, and further reduce the insulation capacitance. It has become mainstream as an interlayer insulating film because it improves signal transmission speed. Also,
In the case of multilayer wiring, it is common to sandwich an organic silicon compound such as silica film between these insulating films for flattening, or to use an organic silicon compound such as silicon polyimide in combination. . These organic silicon compounds also contain oxygen. The opening in the interlayer insulating film is called a through hole, and is a part where electrical connection is established between the wiring metal films of the upper layer and the lower layer.

Generally, after forming an interlayer insulating film on the nth wiring and opening a through hole, when forming the (n+1)th wiring metal film, the following steps are taken to improve ohmic contact between the wiring metal films. method is used.

[0005] In the through-hole opening step, the interlayer insulating film is usually etched using a photoresist as a mask material to open the hole, and then the photoresist is peeled off by wet and dry processing. After that, first, sputter etching is performed in a vacuum to remove the oxide (formed by the reaction between the metal film and oxygen in the atmosphere) on the surface of the n-th wiring metal film in the through-hole portion, and the through-hole opening process. After removing the reaction products that adhered to the hole area (those that adhered during the through-hole etching process and could not be removed during the subsequent photoresist removal process), the n+1th wiring metal film was sputtered in the same vacuum. There is a method of forming it by When an organic silicon compound is sandwiched between other insulating films or used in combination with other insulating films, the substrate must be heated in the same vacuum as the sputtering process to sufficiently release gases such as moisture from the organic silicon compound in advance. There is.

By continuously performing sputter etching and sputtering in the same vacuum as described above,
Provides electrical connections between multilayer wiring films.

[0007]

[Problems to be Solved by the Invention] However, according to the experiments conducted by the present inventor, the above-mentioned conventional technology does not allow multilayer wiring even if the etching conditions for through-hole opening and the sputter etching conditions before sputtering are optimized. It has been found that there is a problem in that the ohmic contact between them becomes unstable, or that ohmic contact cannot be established at all depending on the temperature history etc.

The reason why the ohmic contact becomes unstable is considered to be as follows. During sputter etching, molecules of the insulating film dissociated from the surface of the interlayer insulating film and the side wall of the through hole re-deposit on the wiring metal film in the through hole. Alternatively, in the case of an interlayer insulating film containing oxygen such as silicon oxide or silicon oxynitride, the dissociated oxygen recombines with the wiring metal film exposed in the through-hole area to form an oxide, resulting in the formation of oxides in the through-hole area. The upper layer wiring and the lower layer wiring become partially discontinuous at the interface. Furthermore, stress migration and electromigration occur at the interface due to later temperature history and energization, resulting in complete discontinuity between the upper layer wiring and the lower layer wiring, leading to disconnection.

[0009]

[Means for Solving the Problems] In the method for manufacturing an integrated circuit device of the present invention, in forming a multilayer wiring, an nth wiring is formed, an interlayer insulating film is formed on the nth wiring, and an interlayer insulating film is formed on the nth wiring. A process of forming an opening in a part of the insulating film to reach the surface of the n-th wiring, and in the same vacuum, removing the surface of the n-th wiring exposed in the opening by sputter etching to form the (n+1)th wiring. The method includes the steps of forming a metal thin film of the same material as the film for use by sputtering, removing the metal thin film by sputter etching, and forming a film for the (n+1)th wiring by sputtering.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings. 1 to 5 are cross-sectional views in order of steps for explaining a first embodiment of the present invention. This example is an example in which a laminated film in which an organic silicon compound such as a silica film is sandwiched between silicon oxide and silicon oxide is used as an interlayer insulating film. For ease of understanding, a case of a two-layer wiring structure (n=1) will be described.

Silicon oxide 12 is formed by thermally oxidizing the surface of silicon substrate 11, for example. A first layer aluminum wiring 13 is formed on the surface of the silicon oxide 12 as a first layer wiring. On top of these, first CV
A low-temperature silicon oxide 14 is formed by the D method, plasma CVD method, or bias sputtering method, and an organic silicon compound 15 such as a silica film is coated and flattened by heat treatment (etchback is also performed in this example). , forming low-temperature silicon oxide 16 again thereon,
It is used as an interlayer insulating film [Figure 1]. Here, instead of the low-temperature silicon oxides 14 and 16, low-temperature silicon oxynitride formed by plasma CVD, low-temperature silicon nitride, or the like may be used.

Next, a through hole 17 is opened in the interlayer insulating film through a photolithography process. Here, an example in which openings are formed by isotropic etching and anisotropic etching is shown. At this time, the surface of the first layer aluminum wiring 13 reacts with oxygen in the atmosphere and becomes aluminum oxide 18 (FIG. 2). The anisotropic etching for opening the through-holes 17 must be performed under conditions where there are few reaction products (for example, fluorinated polymer) between the photoresist and the etching gas. This reaction product is almost completely removed during the photoresist stripping process using wet and dry processing.

Next, before sputtering the second layer metal wiring film, sputter etching is performed by high-frequency discharge of an inert gas such as argon at a pressure of several mTorr, and the aluminum oxide 18 in the through hole 17 is etched. etc. to be removed. However, at this time, the molecules of the insulating film dissociate from the surface layer of the interlayer insulating film and the side wall of the through hole and re-deposit on the first layer aluminum wiring 13 in the through hole 17, and oxygen If it contains, the dissociated oxygen recombines with the first layer aluminum wiring 13 in the through hole 17 portion to generate aluminum oxide again. This phenomenon is essential to sputter etching and cannot be avoided even if sputtering conditions are optimized. Next, an inert gas such as argon is discharged under a pressure of several mTorr, and an aluminum thin film 20 made of the same material as the second layer wiring metal film (aluminum film in this example) is sputtered to approximately 4 mTorr.
Approximately 0 nm is deposited. At this time, an aluminum thin film 20 of about 5 nm to 20 nm is deposited on the side wall of the through hole. In addition, some redeposit 19 such as aluminum oxide and silicon oxide remains at the interface with the first layer aluminum wiring 13 in the through hole 17 area [Fig. 3
].

Next, the aluminum thin film 20 once deposited is removed over the entire surface of the substrate by sputter etching again. Here, since the sputter etching is anisotropic etching, the aluminum thin film 20 on the side wall of the through hole is not etched much, but the aluminum on the interlayer insulating film and the first layer aluminum wiring 13 in the through hole 17 portion is not etched very much. Thin film 20 is etched. Sputter etching is terminated when the etching reaches the interface of the first layer aluminum wiring 13 in the through hole 17 portion and the re-deposition 19 is completely removed [FIG. 4]
. During sputter etching, since the object to be etched is aluminum, the above-mentioned redeposition of aluminum due to sputter etching does not pose a problem with ohmic contact. Furthermore, even in the case of an interlayer insulating film containing oxygen, since the object to be etched is aluminum, there is no recombination of aluminum with oxygen at all.

After the above-described sputter etching is completed, an aluminum film as a second layer metal wiring film is deposited to a predetermined thickness by sputtering. The above series of sputter etching and sputtering are all performed continuously in the same vacuum without exposing the substrate to the atmosphere. Also,
In order to release gas such as moisture from the organic silicon compound 15, it is preferable to perform appropriate substrate heating. In this way, the re-deposition 19 that is inevitably formed on the first layer aluminum wiring 13 in the through hole 17 portion during sputter etching can be almost completely removed. As a result, stable ohmic contact can be obtained at the through hole 17 portion. After that, through a photolithography process, the second layer aluminum wiring 2
1 [Figure 5].

[0016] In addition, multilayer wiring of three or more layers (n≧2)
In this case, the steps of forming an interlayer insulating film, opening a through hole, a series of sputter etching and wiring metal film sputtering, and forming a wiring may be repeated.

FIGS. 6 to 10 are cross-sectional views of the process order for explaining a second embodiment of the present invention. In this example, a two-layer laminated film of an organic silicon compound such as silicon polyimide and silicon oxynitride is used as an interlayer insulating film, and is applied to a three-layer wiring structure (n=2).

In exactly the same way as the first embodiment of the present invention,
After forming the second layer aluminum wiring 21, first, low-temperature silicon oxynitride 22 is formed by plasma CVD method,
An organic silicon compound 23 that can be made thick, such as silicon polyimide, is coated and planarized by heat treatment to form an interlayer insulating film consisting of a two-layer laminated film (FIG. 6). Here, the low-temperature silicon oxynitride 22 may be low-temperature silicon nitride formed by plasma CVD, or low-temperature silicon oxide formed by plasma CVD or bias sputtering.

Next, a through hole 24 is opened in the interlayer insulating film through a photolithography process. Here, an example in which openings are formed by isotropic etching and anisotropic etching is shown. At this time, the surface of the second layer aluminum wiring 21 reacts with oxygen in the atmosphere and becomes aluminum oxide 25 (FIG. 7).

Next, heat treatment is performed to release gas such as moisture contained in the organic silicon compound 23 such as silicon polyimide. Thereafter, in the same manner as in the first embodiment, sputter etching is first performed to remove the aluminum oxide 25 and the like in the through hole 24 portion. At this time, redeposit 26 (aluminum oxide or silicon oxide) is newly generated due to sputter etching. After that, the third layer wiring metal film (in this example, a laminated film of titanium and platinum films)
A titanium thin film 27 made of the same material as (in the case of a laminated film, the same material as the lower layer film) is sputtered to a thickness of approximately 40 nm.
It adheres to some extent. At this time, 5n is attached to the side wall of the through hole.
A thin titanium film 27 of about m-20 nm is deposited. In addition, the first layer aluminum wiring 2 in the through hole 24 portion
Redeposited matter 26 remains at the interface with 1 [FIG. 8].

Next, the once deposited titanium thin film 27 is removed over the entire surface of the substrate by sputter etching again. The titanium thin film 27 on the side wall of the through hole remains without being etched, but the titanium thin film 27 on the interlayer insulating film and on the second layer aluminum wiring 21 in the through hole 24 portion remains.
In addition, the redeposited matter 26 is etched away (FIG. 9). During sputter etching, since the object to be etched is titanium, the above-mentioned redeposition of titanium due to sputter etching does not pose a problem with ohmic contact. Furthermore, even in the case of an interlayer insulating film containing oxygen, since the object to be etched is titanium, there is no recombination of aluminum with oxygen at all.

Subsequently, a titanium/platinum film 28 as a third wiring metal film is deposited to a predetermined thickness by sputtering. The sputter etching and sputtering series are all performed in the same vacuum. Further, in this case, it is desirable to heat the substrate in the same vacuum before the first sputter etching to sufficiently release gas such as moisture from the organic silicon compound 23.

The reason why sputter etching is performed twice using the above method is to remove reaction products on the side wall of the through hole (those that adhered during the etching process of the through hole 24 and could not be removed during the subsequent photoresist removal process). This is because if it is not removed in the second sputter etching, it cannot be removed in the second sputter etching. Further, when the diameter of the through hole is small and the aspect ratio is large, it is necessary to take measures such as performing the first sputtering by bias sputtering so that the wiring metal film is deposited on the side wall of the through hole. However, there is a limit to this, so in such a case, it is necessary to improve the aspect ratio of the through hole in advance.

Subsequently, heat treatment is performed to stabilize the ohmic contact at the through hole 24 portion. Then, for example, plated gold 29 is formed on the titanium/platinum film 28 by a plating method, and reactive etching or ion milling is performed using this as a mask to form the third titanium/platinum film 28.
A platinum/gold film 30 is formed (FIG. 10).

As described above, it is possible to essentially completely remove the redeposited matter 26 on the through-hole 24 portion during sputter etching, and the ohmic contact at the through-hole 24 portion is good and reliable. High multilayer wiring can be formed.

[0026]

Effects of the Invention As explained above, in the present invention, when a through hole is opened in an interlayer insulating film and a wiring metal film to be an upper layer wiring is sputtered on the interlayer insulating film, the upper layer wiring is removed after the first sputter etching. By sputtering a metal thin film made of the same material as 2 and covering the surface of the interlayer insulating film and the surface of the through hole in advance,
The influence of re-deposition due to sputter etching, which is a problem when establishing ohmic contact in the through-hole portion during the second sputter etching, can be almost completely eliminated. As a result, we are able to provide multilayer wiring that has stable and good ohmic contact in the through-hole area and is also resistant to stress migration and electromigration at the interconnect metal film interface in the through-hole area, improving product yield and reliability. It has the effect of improving sex.

[Brief explanation of the drawing]

FIG. 1 is a sectional view at an intermediate step for explaining a first embodiment of the present invention.

FIG. 2 is a sectional view at an intermediate step for explaining the first embodiment of the present invention.

FIG. 3 is a sectional view at an intermediate step for explaining the first embodiment of the present invention.

FIG. 4 is a sectional view at an intermediate step for explaining the first embodiment of the present invention.

FIG. 5 is a sectional view at the final step for explaining the first embodiment of the present invention.

FIG. 6 is a sectional view at an intermediate step for explaining a second embodiment of the present invention.

FIG. 7 is a sectional view at an intermediate step for explaining a second embodiment of the present invention.

FIG. 8 is a sectional view at an intermediate step for explaining a second embodiment of the present invention.

FIG. 9 is a sectional view at an intermediate step for explaining the second embodiment of the present invention.

FIG. 10 is a sectional view at the final step for explaining the second embodiment of the present invention.

[Explanation of symbols]

11 Silicon substrate 12 Silicon oxide film 13 First layer aluminum wiring 14, 16 Low temperature silicon oxide 15, 23 Organic silicon compound 17, 24
Through holes 18, 25 Aluminum oxide 19, 26
Redeposit 20 Aluminum thin film 21 Second layer aluminum wiring 22 Low-temperature silicon oxynitride 27 Titanium thin film 28 Titanium/platinum film 29 Gold plating

Claims (4)

[Claims] 1. In forming a multilayer wiring of a semiconductor integrated circuit device, an nth wiring is formed, an interlayer insulating film is formed on the nth wiring, and a part of the interlayer insulating film is covered with the third wiring. The step of forming an opening that reaches the nth wiring surface and the step of forming the opening that reaches the nth wiring surface in the same vacuum,
The surface of the th wiring is removed by sputter etching, a metal thin film of the same material as the film for the n+1th wiring is formed by sputtering, the metal thin film is removed by sputter etching, and the film for the n+1th wiring is removed by sputter etching. A method of manufacturing an integrated circuit device, comprising the steps of: forming by sputtering. 2. The method of manufacturing an integrated circuit device according to claim 1, wherein a constituent of the interlayer insulating film includes oxygen. 3. The method of manufacturing an integrated circuit device according to claim 1, wherein the nth wiring is formed from an aluminum film, and the metal thin film is formed from an aluminum film. 4. The method of manufacturing an integrated circuit device according to claim 1, wherein the nth wiring is formed from an aluminum film, and the metal thin film is formed from a titanium film.