JPH02238621A - Formation of alloy wiring - Google Patents

Abstract

PURPOSE:To eliminate a displacement of a composition with the passage of time among a plurality of elements constituting an aluminum alloy wiring and to enhance reproducibility of a characteristic by a method wherein a heat treatment is executed in a state that a metal nitride layer and an aluminum wiring layer have been applied one after another to a substratum and this metal nitride layer is utilized as a diffusion source used to form an alloy. CONSTITUTION:A metal nitride layer 21 is applied to substrata 11, 13; an aluminum wiring layer 23 is applied to the surface of the metal nitride layer 21; the substrata 11, 13, the metal nitride layer 21 and the aluminum wiring layer 23 are heat-treated; an aluminum alloy wiring layer is formed. Accordingly, at this heat treatment, the metal nitride layer 21 acts as a diffusion source when an aluminum alloy is formed between itself and the aluminum wiring layer 23; as a result, a metal wiring part can be formed without using a source to be applied. Thereby, an aluminum alloy wiring part which can suppress an electromigration can be realized with high reproducibility.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to technology for forming interconnects arranged in various semiconductor elements, particularly electromigration (
The present invention relates to a method for forming an alloy wiring which is capable of suppressing the irradiation (electromic+ration) and has excellent reproducibility.

(Prior Art) In recent years, in order to achieve higher speed, smaller size, lower power consumption, and other requirements for electronic equipment, the wiring provided inside the semiconductor elements that make up the equipment has also been miniaturized. It is being Aluminum (
A9) has been widely used, but when the line width of the wiring is made smaller due to the above-mentioned miniaturization, when using A9 alone, the wiring life is significantly reduced due to electromigration. Therefore, AQ. Instead of a simple substance, aluminum alloy wiring is constructed from an alloy of A9 and various metals (elements),
Various techniques have been proposed to suppress electromigration.

Conventionally, as an example of a technique for suppressing electromigration, an A9-Cu alloy in which a trace amount of copper (Cu) of up to 4 (wt%), preferably 1 (wt%) or less is added to A9 is deposited. Wiring has been formed. This AQ-Cu
The mechanism of electromigration resistance caused by Alloy 1 is that Cu precipitates at the grain boundaries of m, and the precipitated C
It is thought that this is to prevent grain boundary diffusion where utJ<A9. In addition, in the following explanation, the unit indicating the alloy composition is
It will be explained simply as "(%)" instead of "(% by weight)".

However, the above-mentioned m-Cu alloy has a drawback in that it is difficult to pattern it by dry etching, which is essential for image fine processing of wiring. This is because the vapor pressure of the etching product produced by the etching gas and Cu constituting the above-mentioned alloy is low, making it difficult to obtain a sufficient etching rate.

Instead of such a t,;A'n-Cu alloy, a technique has been proposed in which an aluminum alloy wiring is formed using aluminum and an element whose etching product vapor pressure is higher than that of Cu. For example, literature: “24th I.E.E.E.In
International Reliability
Physics Symposium (24th
International Reliability Physics Symposium)” (
7. P. 7-I+, +986) disclose the characteristics of aluminum alloys containing titanium, such as aluminum-titanium (/Iu-Ti) alloys and aluminum-silicon-titanium (ALI-Si-Ti) alloys.

As an example of the above-mentioned characteristics, each aluminum alloy wiring was deposited on a substrate and used as a sample, and the median-timeto-
An accelerated test called failure (MTF) is used to evaluate the relationship between the time until wire breakage and temperature conditions.

As a result, compared to the lifespan of wiring made of single A9, the binary A9-Ti alloy has /lu-0.35(%)Ti
In the case of aluminum alloy wiring made of alloy (approximately 20 times, /I
In the case of aluminum alloy wiring made of 11-0.8 (%)1 alloy, it is possible to extend the life by about 6 times.

In addition, if a similar comparison is made, the ternary system AQ--Si-
For Ti alloys, A-1 (%) Si-0.55 (%)
In the case of aluminum alloy wiring made of Ti alloy, it is about 5 times as large. Roughly speaking, the above-mentioned ternary aluminum alloy wiring including A-1
(%)Si-0.9C%)Ti alloy aluminum alloy wiring and flu-1(%)Si-1.1(%)Ti
In the case of alloy wiring made of alloy, the degree of longevity varies depending on the temperature conditions of the accelerated test, and in the temperature range of 225 ('C) or higher, the lifespan is more than 5 times longer than that of wiring made of A9 alone. You can get longevity.

As can be understood from the above explanation, aluminum alloy wiring containing various metal elements is formed instead of wiring made of A9 alone, and even when the line width is made small, sufficient longevity ( It is possible to realize highly reliable semiconductor devices by suppressing electronic migration. In addition, as is well known (in order to deposit such an aluminum alloy wiring on a substrate, a sputtering method using a target prepared in advance to have the composition of the desired aluminum alloy wiring, or a similar preparation method is used. Techniques such as vacuum evaporation using a vacuum evaporation source are used.

(Problem to be solved by the invention) However, the above-mentioned conventional method for forming alloy wiring is
This process is carried out by preparing a source to be evaporated, such as a target or an evaporation source, in advance to have the desired composition of the aluminum alloy wiring. For this reason, as the aluminum alloy wiring is subjected to heating, the composition of the plurality of elements constituting the aluminum alloy wiring changes over time. Therefore, there was a problem in that the reproducibility of the characteristics of the wiring was reduced.

To explain this point in detail, for example, if an aluminum alloy wiring is formed using deposition sources with a predetermined alloy composition immediately after preparation, the composition of these deposition sources and the aluminum alloy wiring will substantially change. Match.

However, when paying attention to the deposition source after repeatedly forming such alloy wiring, it is found that the differences in the splatter rate or evaporation rate occur between the multiple elements dispersed in the deposition source. Therefore, only the predetermined elemental composition increases. For this reason, a difference in composition occurs between the deposition source immediately after preparation and the deposition source after repeated formation of alloy wiring, and as a result, the composition of the aluminum alloy wiring obtained using each deposition source differs. This results in non-uniformity, which reduces the reproducibility of forming alloy wiring.

In view of the above-mentioned conventional problems, an object of the present invention is to provide a method for forming an aluminum alloy wiring that can suppress electromigration with high reproducibility. .

(Means for Solving the Problems) In order to achieve this object, according to the method for forming alloy wiring according to the present invention, a metal nitride layer is deposited on a base, and the surface of the metal nitride layer is The step of depositing an aluminum wiring layer on the substrate and the above-mentioned base,
The method is characterized in that it includes a step of heat-treating the metal nitride layer and the aluminum wiring layer to form an aluminum alloy wiring layer.

Further, in carrying out the present invention, it is preferable to use zirconium nitride as the metal nitride layer described above.

(Function) According to the structure of the method for forming alloy wiring of the present invention, heat treatment is performed with the metal nitride layer and the aluminum wiring layer sequentially deposited on the base. During this heat treatment, the metal nitride layer acts as a diffusion source when forming an aluminum alloy with the aluminum wiring layer, so it is possible to form alloy wiring without using a deposition source as in the conventional technology. It is possible to do this.

Furthermore, by coating the metal nitride layer described above with an excessive thickness as a diffusion source, it is also possible to function as a barrier metal at a predetermined portion between the alloy wiring formed by the heat treatment described above and the base layer. It is.

(Example) Hereinafter, an example of the method for forming an alloy wiring according to the present invention will be described with reference to the drawings. In the following description, specific conditions will be exemplified and explained in order to facilitate understanding of the present invention, but it should be understood that the present invention is not limited only to these conditions. Furthermore, except for the constituent components that characterize this embodiment, the film thickness and other numerical conditions regarding some constituent components may be omitted.

BRIEF DESCRIPTION OF THE DRAWINGS First, preferred embodiments of the present invention will be described with reference to the drawings.

FIGS. 1(A) and 1(B) are diagrams schematically showing main manufacturing process steps in cross sections to explain an example. In the figure, hatching and the like representing cross sections are partially omitted.

First, the manufacturing process steps before heat treatment will be explained with reference to FIG. 1(A).

First, a substrate 11 made of silicon is provided with any suitable insulating material for forming an interlayer insulating film, such as silicon oxide. Thereafter, the silicon oxide in a predetermined area according to the design is removed by well-known photolithography, and an interlayer insulating film 13 and a contact hole 15 are formed to expose a predetermined area of the substrate 11.
Open. Subsequently, as conventionally done, impurity diffusion regions 17'18 are formed for the purpose of electrically connecting the substrate 11 and alloy wiring to be described later. In this way, a base 19 consisting of the substrate 11, interlayer isolation film 13, contact hole 15, and impurity diffusion region 17 is obtained.

Next, for example, by a sputtering method, zirconium nitride (ZrN) % as an example of a metal nitride and the above-mentioned base 19
A metal compound layer 21 is formed by depositing a film thickness of 1,000 mm over the entire upper surface of the substrate.

Subsequently, on the surface of the metal nitride layer 21 described above, AL;
A single aluminum wiring layer 23 is formed by depositing the aluminum wiring layer 23 to a thickness of 8,000 C by sputtering.

Next, under predetermined time and temperature conditions (described in detail later) in an atmosphere of nitrogen, hydrogen, argon, or any other suitable inert gas, the above-mentioned base 19, metal nitride layer 21, and aluminum wiring are removed. Heat treatment is performed on layer 23.

By the heat treatment described above, zirconium contained in the metal nitride layer 21 is diffused into the aluminum wiring layer 23.

In this way, as shown in FIG. 1 CB), after the zirconium diffusion, a metal nitride layer 25 including a barrier metal function is formed in a predetermined portion of the substrate 11 where the contact hole 15 has been formed. At the same time, an aluminum alloy wiring layer 27 alloyed by the above-mentioned zirconium diffusion is formed. Although not shown in the drawings, at least in any process step after the aluminum wiring layer 23 is deposited, the base 1
By patterning the constituent components formed on 9 into a desired shape, an alloy wiring is completed.

4 to 6. Next, with reference to the drawings, alloy wiring was formed as a sample in the same manner as in the process of the preferred embodiment described above, and the results of investigating alloying will be explained.

In this example, as an index of alloying, Rutherford backscattering (RBS) was used before and after the heat treatment described above.
erford Back Scatterinc+)
We will explain the results of investigating the diffusion state of zirconium using the method.

This sample was manufactured using the steps of the preferred embodiment described above in which the thickness of the aluminum wiring layer 23 was set to 14,000 mm in order to facilitate understanding of the state of zirconium diffusion. In addition, the heat treatment related to sample preparation was performed in a nitrogen atmosphere for 50 minutes.
The test was carried out at a temperature of 50 (°C) for 1 hour.

FIG. 2 is a characteristic curve diagram showing the results measured by the RBS method before and after the heat treatment described above.

In the same figure, the vertical axis shows the backscattering intensity (arbitrary unit) and the horizontal axis shows the energy (MeV).Furthermore, the curve ■ shown by the dotted line is the result obtained for the sample before heat treatment, and the solid line shows the backscattering intensity (arbitrary unit). Curve II shows the results obtained with the sample after heat treatment,
Each is an expression.

To briefly explain the outline of these characteristic curves,
In the R8S measurement conducted in this example, al8
Parts mainly derived from silicon, as shown in the appendix.
The aluminum-derived portion indicated by bi and the zirconium-derived portion indicated by c% are detected. Furthermore, in the above-mentioned part a, a part a1 derived from nitrogen and a part a2 derived from oxygen are respectively recognized.

Below, among the RBS measurement results, we will explain the results regarding the diffusion state of zirconium.
As such, a predetermined peak originating from zirconium can be seen in the energy node of approximately 1.8 to 1.9 (MeV).

On the other hand, in the state of the sample after the heat treatment shown by curve (2), the above-mentioned peak tends to tail, and the energy range of part C is approximately 1.7 to 2. It is understandable that it is I (MeV). Among these, the spread toward the high energy side is more remarkable than the spread toward the low energy side, so the zirconium contained in the metal nitride layer 21
It can be seen that more diffusion occurs on the aluminum wiring layer 23 side than on the base 19 side. Therefore, it can be understood that the heat treatment described above causes the zirconium contained in the metal nitride layer 21 to become a diffusion source and form an AQ--lr alloy with aluminum contained in the aluminum wiring layer 23.

Here, as a result of experiments by omitting detailed data or by unifying the same atmosphere and time conditions as above and varying only the temperature conditions, it was found that zirconium The diffusion (alloying) of
), but not under the temperature condition of 400CG). Roughly speaking, the melting point of A9 alone deposited as the aluminum wiring layer 23 is 660 ('C).
Taking this into consideration, the suitable temperature conditions for heat treatment when using the material structure of this example are 500 to 66
It is considered to be in the range of 0 ('C).

Furthermore, from FIG. 2, by leaving the aforementioned gold R nitride layer 25 that can function as a barrier metal remaining after the heat treatment, the shift of the portion a derived from silicon to the high energy side is suppressed. It is recognized that

In the preferred embodiment described above, in order to facilitate RBS measurement, the aluminum wiring layer 23 has a thickness of 4,000 (layers) and the thickness +,
The case where the alloy wiring is formed under the conditions of the gold R nitride layer 21 of OOOC is exemplified. However, the ratio of the film thickness of the metal nitride layer 21 and the aluminum wiring layer 23 can be changed depending on the design, and in addition, by setting the heat treatment conditions arbitrarily, each element in the alloy can be changed. It is possible to control the ratio, elemental distribution, etc. More specifically, after the heat treatment {the resulting aluminum alloy wiring layer 27
Even if the surface of the layer 27 is not completely alloyed, an effect of suppressing electromigration can be expected.

In addition, depending on the design of the alloy wiring, if it is desired to sufficiently alloy aluminum and zirconium to the surface of the alloy wiring, other embodiments as described below may be used with reference to the drawings. It may also be used as a configuration.

FIGS. 2(A) and CB) are diagrams shown similarly to FIGS. 1(A) and (B) for explaining other embodiments, and have the same functions as the constituent components already explained. The same reference numerals are shown for .

In this embodiment, after the formation of the various constituent components described with reference to FIG. ) with a film thickness of about
Obtain the state shown in .

Thereafter, a heat treatment similar to that of the previous example is performed. As a result, an aluminum alloy wiring layer 31 as shown in FIG. 2 is formed, which is a feature of this embodiment. In addition, in the same figure, in order to make the explanation easier to understand, the aluminum wiring layer 23 is
The portion that was the interface between the metal layer 29 and the metal layer 29 is shown by a dotted line. Even with the configuration of such other embodiments, the same effects as those of the above-described preferred embodiment can be obtained.

Although the embodiments of the method of the present invention have been described in detail above, it is clear that the present invention is not limited only to these embodiments.

For example, the material constituting the metal nitride layer that functions as a barrier metal may be any metal silicide having a resistivity of about 1 (mΩ cm) or less, and instead of the above-mentioned zirconium nitride, for example, titanium nitride may be used. It is also possible to use objects.

Furthermore, in the above-mentioned embodiments, a specific configuration as a base was illustrated and explained, but various electrodes and wirings may be used instead of the above-mentioned substrate 11 as components connected by alloy wiring. good.

It is clear that these materials, dimensions, arrangement relationships, numerical conditions, and other specific conditions may be modified and modified in any suitable manner within the scope of the purpose of the present invention.

(Effects of the Invention) As is clear from the above description, according to the method for forming an alloy wiring of the present invention, a metal nitride layer and an aluminum wiring layer are sequentially formed on a base (heating them in the deposited state). The metal nitride layer is then used as a diffusion source for alloy formation.Therefore, alloy interconnects are formed without using a deposition source made of a pre-prepared alloy as in the past. It is possible to eliminate compositional deviations over time between multiple elements constituting the wiring, and improve the reproducibility of the characteristics of the wiring.In addition, the metal nitride layer described above can be used as an excessive diffusion source. By coating the metal with a certain thickness, it is possible to function as a barrier metal.

In this way, it is possible to provide a method for forming an alloy interconnect that can realize an aluminum alloy interconnect that can suppress electromigration with high reproducibility.

[Brief explanation of drawings]

1(A) and (B) are explanatory diagrams showing the main manufacturing process steps in a schematic cross section to explain a preferred embodiment of the method of the present invention; FIG. In order to explain the state of alloying in the sample, a characteristic curve diagram showing the results measured by laser photo backscattering, with relative intensity (arbitrary unit) on the vertical axis and energy (MeV) on the horizontal axis, is shown. FIGS. 3(A) and CB) are explanatory views similar to FIGS. 1(A) and CB) for explaining another embodiment. 11...Substrate, 13...Interlayer insulating film 15...
・Contact hole, 17... Impurity diffusion region 19
... Base, 21 ... Metal nitride layer 23 ...
Aluminum wiring layer 25...Metal nitride layer (barrier metal) 27.31
...Aluminum alloy wiring layer, 29...Metal layer. 1.4') toe

Claims (2)

[Claims] (1) A step of depositing a metal nitride layer on a base, and depositing an aluminum wiring layer on the surface of the metal nitride layer;
A method for forming an alloy wiring, comprising the step of heat-treating the metal nitride layer and the aluminum wiring layer to form an aluminum alloy wiring layer. (2) A method for forming an alloy wiring, characterized in that the metal nitride layer according to claim 1 is made of zirconium nitride.