JPH03196620A - Formation of copper wiring and target used therefor - Google Patents

Abstract

PURPOSE:To simply and cheaply form a copper wire by heat-treating the copper wiring part, which is formed by the use of a copper alloy target containing B at the specific rate, into the specific temperature within atmosphere containing N2 gas or NH3 so as to form a boride layer at the surface of the copper wiring layer part. CONSTITUTION:When forming a copper wiring part on the substrate by applying a sputtering method, a copper alloy target, which contains B at the rate of 0.5-5wt.%, is used as a sputtering target. And the formed copper wiring part is heat-treated to 300 deg.C or more within the atmosphere containing N2 gas or NH3 gas so as to form a boron nitride layer on 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 manufacturing LSIs, it has been common to use M or M 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, VLS I-? 'ULS
As symbolized by the advent of I, there is no end to the demand for higher integration in semiconductor devices, and as a result, ever finer wiring has become necessary.Recently, Cu has been used as the wiring material. is being considered. This is because Cu has favorable properties such as superior electron migration resistance and stress migration resistance compared to M or M alloys, less risk of disconnection, and low resistance.

However, when considering the use of Cu as the wiring material,
Since Cu diffuses into St and Si0g films, 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 with Ti arranged 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).
Volume 2 of the 49th Autumn 1988 (Showa 63) Proceedings of the 49th Academic Conference of the Japan Society of Applied Physics.

See page 434].

However, in the proposed method, the required nitriding temperature to form a TiN layer on the surface of the Cu-Ti alloy thin film layer is as high as about 800°C, so the equipment currently used for LSI manufacturing cannot be used. In addition, since the specific resistance of the Cu-Ti alloy itself is high, it is inconvenient that a sufficiently low specific resistance cannot be obtained unless most of the Ti in the Cu is exposed to the surface as TiN through nitriding treatment. Furthermore, Cu-
Since the formation of the Ti alloy thin film layer is carried out by sputtering a target material in which a Ti piece is placed on Cu, there are also problems in terms of workability and it cannot be said to be fully satisfactory industrially.

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 object, and as a result, they found that ``a copper wiring layer formed by a sputtering coating method'' by nitriding treatment. In order to prevent oxidation of the copper wiring layer by forming a nitride layer on the surface,
If a small atomic radius is included in the copper wiring layer,
It is possible to form a nitride layer that is effective in preventing oxidation at a much lower nitriding temperature than when Ti is included, and a boron nitride layer that is thick enough to exhibit oxidation resistance can be formed. Even if the amount necessary for formation is contained in Cu, the increase in specific resistance is small, so if the B content is regulated within an appropriate range, there is no risk of deterioration in the performance of copper wiring. B
The formation of the copper-containing wiring layer can be stably performed by using the "sputtering coating method using a Cu-8 alloy target", and the previously proposed method using a "mosaic target with a Ti piece placed on Cu" We were able to obtain new knowledge that this process does not cause such "deterioration in handling properties during sputtering processing."

The present invention has been made based on the above-mentioned findings and the like. ``When forming a copper wiring section on a base using a sputtering coating method, B is added in an amount of 0.5 to 5% as a sputtering target. (Hereinafter, % indicating the component ratio is weight %.
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 a % of Cu, and the remainder is substantially made of Cu.

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 B content in the Cu-8 alloy sputtering target according to the present invention is set at 0.5 to 5% is because the B content of the target is less than 0.5%. Even if the "Cu-B alloy wiring layer obtained by sputtering" is nitrided, a boron nitride layer with sufficient thickness and oxidation-resistant protection is not formed on its surface; This is because if it is included, the conductivity of the "Cu--B alloy wiring layer obtained by sputtering" will be adversely affected.

By using the above-mentioned alloy form as the sputtering target for forming the copper alloy wiring layer,
As mentioned above, difficulties in handling during sputtering can be prevented.

Further, the Cu-B alloy wiring layer formed using the Cu-8 alloy sputtering target is then nitrided to improve oxidation resistance, and the nitriding treatment is performed using N2, which is extremely easy industrially. Gas or NH.

It is carried out by heating in a gas-containing atmosphere.

In this case, the ``nitride surface layer with excellent oxidation protection'' that was not formed in the Cu-Ti alloy wiring layer unless heated to about 800°C is 300°C in the Cu-B alloy wiring layer.
Since it is formed even at a very low temperature of about 0.degree. C. or higher, it is fully possible to use equipment conventionally used for manufacturing LSIs. However, Cu-
Even with a B alloy wiring layer, if the nitriding temperature is below 300°C, it will be difficult to stably form a "boron nitride surface layer with sufficient oxidation-resistant protection," so it cannot be used in an atmosphere containing N2 gas or NH3 gas. Although the heating temperature was set at 300°C or higher, it is preferably about 400°C or higher. In addition,
It goes without saying that the higher the nitrogen pressure in the nitriding atmosphere, the better.
It may be adjusted as appropriate depending on the B content of the u-B alloy wiring layer.

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> By sputtering using a sputtering target made of Cu-2,5χB alloy, a substrate made of SiO
After forming a rts thick Cu-B thin film (B content was 2.5%), it was heated to 400 °C (substrate temperature) in a nitrogen pressure atmosphere of 100 P and 1 and held for 2 hours. did.

Next, Ar ion etching (acceleration voltage: 1 kV) was performed on the surface layer of the Cu-BFI film nitrided in this way and on the surface layer for 15 minutes, 30 minutes, 45 minutes, and 60 minutes, respectively.
XPS analysis (X-ray photoelectron spectroscopy) near the peaks of B and N was performed on the etched samples, and the results are shown in FIGS. 1 to 5 for each etching time.

As is clear from the results shown in Figures 1 to 5, C
It can be seen that in the copper thin film obtained using the U-8 alloy sputtering target, an 88 surface layer is formed even when the nitriding process 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 88 surface layer had excellent oxidation protection.

In addition, apart from this, B content is 0.6% and 1
．． The same applies to the nitrided Cu-BFil films obtained under the same conditions as above, except that sputtering targets made of 1%, 2.0%, 4.2%, and 4.9% Cu-B alloys were used. We carried out a similar investigation, and we were able to obtain almost the same good results in this case as well.

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 a low cost with good workability. .

4,

[Brief explanation of drawings]

Figures 1 to 5 show the nitrided Cu -B*Wj! obtained in the example. The results of XPS analysis on the surface are summarized by etching time and shown separately.

Claims (2)

[Claims] (1) When forming a copper wiring part on a base using a sputtering coating method, a copper alloy target containing 0.5 to 5% by weight of B is used as a sputtering target, and the formed copper A method for forming an oxidation-resistant copper wiring, comprising heating the wiring part at 300° C. or higher in an atmosphere containing N_2 gas or NH_3 gas to form a boron nitride layer on the surface of the copper wiring part. (2) A copper alloy sputtering target for forming an oxidation-resistant copper wiring, characterized in that it contains B in a proportion of 0.5 to 5% by weight, and the remainder consists essentially of Cu.