JPH03196619A - Formation of copper wire and target used therefor - Google Patents

Abstract

PURPOSE:To simply and cheaply form a copper wire by heat-treating a copper wiring part, which is formed by the use of a copper alloy target containing Zr at the specific rate, into specific temperature within atmosphere containing N2 gas or NH3 so as to form a zirconium nitride layer at the surface of the copper wiring part. CONSTITUTION:When forming a copper wiring part on the substrate by applying a sputter coating method, a copper alloy target, which contains Zr at the rate of 5-20wt.%, is used as a sputtering target. And the formed copper wiring part is heat-treated to 300 deg.C or more in atmosphere containing N2 gas or NH3 gas so as to form a zirconium nitride layer at the surface of the copper wiring part. Hereby, the fine copper wiring excellent in performance can be mass-produced excellently in work efficiency and at low cost.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for forming copper wiring in an LSI, etc.
The present invention also relates to a copper alloy sputtering target used at that time.

<Prior art and its problems> Conventionally, in the manufacture of LSIs, it has been common to use M or A2 alloy as a wiring material and to form wiring in a desired pattern on a substrate by sputtering coating method and ion etching method. However, as symbolized by the advent of VLSI and ULSI, there is no end to the demand for higher integration in semiconductor devices, and as a result, even finer interconnections are required, so recently, interconnection materials have been The use of Cu as a material is being considered. This is because Cu has favorable properties such as superior electron migration resistance and stress migration resistance compared to Af or A1 alloys, so there is less risk of wire breakage, and it also has low resistance. .

However, when considering the application of Cu as the wiring material,
Since Cu is easily diffused into St and Si OJ, P-N
It has been pointed out that the problem is that it easily causes leakage current in the junction, and furthermore, since the oxidation resistance is not sufficient, there is also the problem that heat treatment will cause an increase in wiring resistance due to oxidation of the Cu, so it is difficult to put it into practical use now. -Ayumu was hesitant. just,
Recently, TiN films, W films, Mo films, and Ta films have been added between the copper wiring layer and the silicon substrate.

Some proposals have been made to prevent mutual diffusion of the two by providing a barrier layer such as a Cr film (for example, Japanese Patent Laid-Open No. 63-1
56341, Japanese Patent Laid-Open No. 63-174336, etc.), it is becoming clear that there is a way to prevent the leakage current in the P-N junction caused by the above-mentioned diffusion, but copper wiring No sufficient measures have been found to prevent oxidation of the copper wiring layer during the heat treatment required in the process of forming the copper wiring layer.

However, under these circumstances, the C for wiring on the ground surface
The u layer is formed by sputtering using a "mosaic target in which Ti is placed on Cu," and then the formed Cu-Ti alloy thin film wiring layer is annealed in a nitrogen atmosphere to deposit TiN on the surface of the wiring layer. A proposal was made to improve oxidation resistance by forming a layer (19B).
2nd volume of the proceedings of the 49th Autumn 1988 Academic Conference of the Japan Society of Applied Physics.

See page 434].

However, although it was thought that the proposed method could be an effective means for forming copper wiring with good performance, the required nitriding temperature to form a TiN layer on the surface of the Cu-Ti alloy thin film layer was Because the temperature is around 800℃, L
The equipment currently used for manufacturing SI cannot be used, and the formation of the Cu-Ti alloy thin film layer is performed by sputtering a "target with a Ti piece placed on Cu," resulting in poor workability. However, there were problems and it could not be said to be fully satisfactory from an industrial standpoint.

Therefore, the purpose of the present invention is to ``develop fine copper wiring that exhibits excellent oxidation resistance and sufficient conductivity easily and inexpensively on an industrial scale without the need for particularly new equipment.'' The aim is to establish a means by which the government can

<Means for Solving the Problems> Therefore, the present inventors conducted research through numerous experiments in order to achieve the above-mentioned objective. In order to prevent oxidation of the copper wiring layer by forming a nitride layer on the surface,
If Zr, which has a lower standard free energy of nitride formation than Ti, is included in the copper wiring layer, a nitride layer that is effective in preventing oxidation can be formed at a much lower nitriding temperature than when Ti is included. In addition, if the Zr content is regulated, there is no risk of deterioration in the performance of copper wiring.
The formation of the copper-containing wiring layer can be stably performed by applying the "sputtering coating method using a Cu-Zr alloy target", and the previously proposed method using a "mosaic target with a Ti piece placed on Cu". It does not cause "deterioration in handling properties during sputtering" as described above.
” I was able to gain new knowledge.

The present invention has been made based on the above-mentioned findings, etc. [When forming a copper wiring part on a base by applying a sputtering coating method, Zr is used as a sputtering target by 5 to 20% (hereinafter referred to as , % representing component ratio is weight %
A zirconium nitride layer is formed on the surface of the copper wiring by using a copper alloy target containing a ratio of It is characterized by the fact that its oxidation resistance can be significantly improved by forming Zr. It is also characterized by the fact that it is made of a copper alloy containing copper and the remainder substantially consisting of copper.

Hereinafter, the reason why the chemical composition and processing conditions of the sputtering target are limited as described above in the present invention will be explained in detail together with their functions and effects.

<Functions and Effects> First, the reason why the Zr content in the Cu-Zr alloy sputtering target according to the present invention is set at 5 to 20% is because if the Zr content of the target is less than 5%, Even if the Cu-Zr alloy wiring layer is nitrided, a zirconium nitride layer with sufficient oxidation-resistant protection cannot be formed on its surface.On the other hand, if Zr is contained in an amount exceeding 20%, C
This is because the conductivity of the "u-Zr alloy wiring layer" will be adversely affected.The sputtering target for forming the copper alloy wiring layer has the above alloy form, making handling during sputtering easier. As mentioned earlier, it is possible to prevent sexual difficulties.

Further, the Cu-Zr alloy wiring layer formed using the above-mentioned Cu-Zr alloy sputtering target is then nitrided to improve oxidation resistance. It is carried out by heating in an atmosphere containing NH3 gas.

In this case, the "nitride surface layer with excellent oxidation resistance" that was not formed in the Cu-Ti alloy wiring layer unless heated to about 800°C is 3% in the Cu-Zr alloy wiring layer.
Since it is formed even at a very low temperature of about 00° C. or higher, it is fully possible to use equipment that has been conventionally used for manufacturing LSIs. However, C according to the present invention
Even in the u-Zr alloy wiring layer, the nitriding temperature is 30°C.
If it is below 0°C, it will be difficult to stably form a "zirconium nitride surface layer with sufficient oxidation-resistant protection," so the heating temperature in an atmosphere containing N2 gas or NH gas should be 300°C.
The temperature is set to be at least .degree. C., but it is preferably about 400.degree. C. or higher. It goes without saying that the higher the nitrogen pressure in the nitriding atmosphere, the better. The heating holding time may be adjusted as appropriate depending on the heating temperature, the Zr content of the Cu--Zr alloy wiring layer, etc.

Furthermore, even if copper wiring manufactured through the above-mentioned process is subsequently subjected to heat treatment, performance deterioration due to oxidation (reduction in conductivity and occurrence of wire breakage) may occur. Therefore, it can greatly contribute to maintaining the reliability of semiconductor devices and the like.

Next, the present invention will be explained in more detail with reference to Examples.

<Example> A 7 am thick Cu-Zr thin film (Zr content is 14.5%) was formed on a SiO□ substrate by sputtering using a sputtering target made of Cu-4,5χZr alloy.
After forming a substrate, this was heated to 400° C. (substrate temperature) in a nitrogen pressure atmosphere of 100 Pa and held for 2 hours.

Next, XPS analysis (X-ray photoelectron spectroscopy) was performed on the surface layer of the Cu--Zr thin film nitrided in this way, and the results are shown in FIG.

As is clear from the results shown in Figure 1, Cu −
It can be seen that in a copper thin film obtained using a Zr alloy sputtering target, a ZrN surface layer is formed even when nitriding is performed at a relatively low temperature of 400°C.

The copper thin film after the nitriding process was held for 60 minutes in an oxidizing state expected for copper wiring (at 450 degrees Celsius in the atmosphere), and then its conductivity was measured; even in this case, it was sufficiently satisfied as an LSI wiring. It was confirmed that the ZrN surface layer had excellent oxidation protection.

In addition, apart from this, Zr content is 5.2%,
A similar investigation was conducted on nitrided Cu-Zri films obtained under the same conditions as above except that sputtering targets made of 9.8% and 19.5% Cu-Zr alloys were used. Almost the same good results were obtained in both cases.

Summary of Effects> As explained above, the present invention brings about extremely useful effects industrially, such as making it possible to mass-produce fine copper wiring with excellent performance at low cost with good workability.

[Brief explanation of drawings]

FIG. 1 shows the results of XPS analysis on the surface of the nitrided Cu--Zr thin film obtained in the example.

Claims (2)

[Claims] (1) When forming a copper wiring part on a base by applying a sputtering coating method, a copper alloy target containing 5 to 20% by weight of Zr is used as a sputtering target, and the formed copper wiring part A method for forming an oxidation-resistant copper wiring, the method comprising forming a zirconium nitride layer on the surface of the copper wiring by heat-treating the copper at 300° C. or higher in an atmosphere containing N_2 gas or NH_3 gas. (2) A copper alloy sputtering target for forming an oxidation-resistant copper wiring, characterized in that it contains Zr in a proportion of 5 to 20% by weight, and the remainder consists essentially of Cu.