JPH04256313A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a method of forming TiN of complete (111) orientation CONSTITUTION:The sputtering of TiN is performed such that positive bias is applied to the substrate in case of performing the sputtering in the mixed gas atmosphere of gas easy to be electrified in positive such as inert gas and nitrogen and that negative bias is applied to the substrate in case of performing the sputtering in the mixed gas atmosphere of gas easy to be electrified in negative such as halogen and nitrogen.

Description

[Detailed description of the invention]

[Object of the invention]

0002

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 wiring.

0003

2. Description of the Related Art Conventionally, aluminum has been widely used for wiring in semiconductor devices because it is easy to process and has low wiring resistance.

However, in recent years, as semiconductor devices have become more highly integrated, circuits have become increasingly finer, and interconnects have also become increasingly finer and multilayered, which has led to problems with the reliability of interconnects. It becomes.

[0005] Electromigration and stress migration due to aluminum diffusion are causes of deterioration in interconnect reliability. In order to prevent this problem, aluminum alloy wiring to which a shell or the like is added is being considered. This method suppresses diffusion into aluminum by precipitating a compound of the additive metal and aluminum at grain boundaries, but there are problems such as an increase in wiring resistance and a decrease in wiring workability due to the additive metal. On the other hand, titanium nitride (Ti
A wiring method with a laminated structure using a N) film as a base for an aluminum film has also been proposed. In the case of a face-centered cubic lattice such as aluminum, the {111} plane has the smallest surface energy, and to improve interconnect reliability, strengthen the (111) orientation, which can prevent lateral migration. There is a need. On the other hand, it is known that the orientation of the TiN film used as a base affects the orientation of the aluminum film, and when TiN is (111) oriented, aluminum is (111) oriented, and TiN is (200) oriented. In the case of orientation, aluminum is (200) oriented. Therefore, in order to obtain an aluminum film with (111) orientation, (11)
1) It is sufficient to form oriented TiN. As a method for forming this (111) oriented TiN, there is a method of forming it by a non-bias sputtering method in an argon (Ar) and nitrogen atmosphere.

However, in the conventional non-bias sputtering method, in addition to the (111) orientation, the (200) orientation is also included (
(see FIG. 4), there was a problem in that TiN with perfect (111) orientation could not be formed.

[0007]Also, there is a method of increasing the substrate temperature in order to improve the orientation, but according to experiments conducted by the present inventors,
In the case of a TiN film, when the temperature is increased, the (111)-oriented T
It was found that iN also reversed to (200) oriented TiN. Therefore, it has been extremely difficult to obtain (100) oriented TiN in good condition.

[0008]Furthermore, the above-mentioned problems arise when NaCl
The same was true for the case where a tungsten nitride (TaN) film having a type crystal structure was formed with the (111) orientation.

[0009]

[Problems to be Solved by the Invention] As described above, in the conventional non-bias sputtering method, Ti with perfect (111) orientation cannot be sputtered.
There was a problem that N or TaN could not be formed.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a method for forming TiN or TaN with perfect (111) orientation.

[Configuration of the invention]

0012

[Means for Solving the Problems] Accordingly, in the first aspect of the present invention, when forming a TiN or TaN thin film by sputtering, sputtering is performed in a mixed gas atmosphere of nitrogen and a gas that tends to be positively charged, such as an inert gas. for,
A positive bias should be applied to the substrate, and when sputtering is performed in a mixed gas atmosphere of nitrogen and a gas that tends to be negatively charged, such as halogen gas, it is recommended to perform sputtering while applying a negative bias to the substrate. I have to.

In the second aspect of the present invention, sputtering is performed using a target containing a constituent element of the barrier metal layer such as titanium nitride or tantalum nitride in a gas atmosphere that is easily charged either positively or negatively. The sputtering bias control described above is performed depending on the situation.

[0014]

[Operation] TiN has a face-centered cubic lattice structure, and Ti+q
-N-q, it has a structure that is easily charged, so by applying a slight electric field perpendicular to the substrate surface, TiN
become more likely to be regularly arranged so that they have orientation. The present invention has been developed with this in mind. When the gas is easily charged positively, the target side is made negative and the substrate side is made positive, so that the gas can easily assist in sputtering the target. Conversely, if the gas tends to be negatively charged, the target side is made positive and the substrate side is made negative, so that the electric field is applied to help the gas sputter the target.

[0015] This electric field causes TiN to adhere to the substrate with uniform energy and with good orientation. For example, when the substrate side is positive, TiN is deposited in order so that N is on the substrate side, and conversely, when the substrate side is negative, TiN is deposited in order so that Ti is on the substrate side. Thereby, the orientation can be controlled and TiN with perfect (111) orientation can be formed.

For example, when an inert gas is used as a carrier gas, the gas is positively charged, so a positive bias is applied, while when a halogen gas is used, the gas is negatively charged, so a negative bias is applied. put on.

Furthermore, by applying a negative bias to the substrate side, the density of nitrogen on the surface side of the nitride film increases,
Oxygen is prevented from entering the film, which improves the film quality. The above description also applies to TaN having a NaCl type crystal structure.

(Example) Examples of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is an explanatory diagram showing a method of forming a TiN film according to a first embodiment of the present invention.

[0020] In this method, the degree of vacuum is 1 x 10-8 Torr.
After that, Ar and N2 were introduced at equal flow rates, and 1×1
0-3 Torr, -150V to Ti target 1,
This is characterized in that a bias of 50V is applied to the silicon substrate 2, and 100 nm of TiN is deposited by sputtering.

Next, the manufacturing process of a semiconductor device using this will be explained.

First, as shown in FIG. 2(a), the surface orientation (
100), n-type silicon substrate 21 with a specific resistance of 4 to 5 Ωcm
A silicon oxide film 22 with a thickness of 2 μm is formed by hydrogen combustion oxidation on
The silicon oxide film 22 is patterned using reactive ion etching to form a contact hole 23 with a diameter of 1.2 μm.

Subsequently, the substrate was placed in the bias sputtering apparatus shown in FIG.
After setting it to orr, Ar and N2 were introduced at equal flow rates,
1 x 10-3 Torr, -15 to Ti target 1
A bias of 50 V is applied to the silicon substrate 2 to deposit TiN 24 to a thickness of 100 nm over the entire surface of the substrate. Here, Ar is easily charged positively, causes movement in the direction of the Ti target, and collides with it. T obtained in this way
The iN film has a complete (11
1) It has an orientation (Fig. 2(b)).

Next, the target is replaced with aluminum, and an aluminum film is formed on this upper layer by sputtering. Here, too, an aluminum film with perfect (111) orientation can be obtained (FIG. 2(c)).

Thereafter, as shown in FIG. 2(d), these TiN films and aluminum films are patterned to obtain electrodes. This serves, for example, as a pasted electrode on the surface of the source/drain region of an FET.

In the above embodiment, an n-type silicon substrate is used, but it goes without saying that a p-type silicon substrate may also be used.

Example 2 In the above example, a TiN sputtering method using a mixed gas of Ar gas and nitrogen gas was described, but here, a case will be described in which fluorine (F2) gas is used instead of Ar gas.

The difference between this method and Example 1 is that, as shown in FIG.
V, at which a bias of -50V is applied to the silicon substrate 2.

That is, even with this method, the degree of vacuum inside the container is 1×
After setting it to 10-8 Torr, F2:N2 =2:1
A mixed gas mixed at a ratio of 1×10-3 To
rr, a bias of 200 V is applied to the Ti target 1, and a bias of -50 V is applied to the silicon substrate 2, and 100 nm of TiN is deposited by sputtering. Here, fluorine tends to be negatively charged, receives a force in the direction of the Ti target 1, and collides with the target. The TiN film thus obtained also has a complete (111) orientation, as shown in the X-ray diffraction results in FIG.

[0030] In the above embodiments, the case where a contact hole is formed on a Si substrate has been explained, but when a second layer wiring is formed on a polycrystalline silicon or metal silicide wiring with an insulating film interposed therebetween. These can also be applied to via holes for connecting wiring in exactly the same way.

Further, in the above embodiment, the aluminum film was formed on the TiN film, but the same method can be implemented by using an aluminum alloy, copper, or a copper alloy instead of the aluminum film. Further, the type of gas is not limited to the above embodiments, and can be selected as appropriate, and a bias may be applied depending on the charging of the gas.

Further, in the above embodiment, only the TiN film was described, but other films such as NaCl-type face-centered cubic lattice structure films, such as TaN, can also be applied. Furthermore, TiN may be used as a sputtering target, and in this case, it is not necessary to introduce nitrogen gas. Further, it is preferable that the ratio of the constituent materials of the target be approximately equal to the composition ratio of the film to be formed.

[0033]

As explained above, according to the present invention, the bias applied to the substrate is selected depending on the type of gas used, and a TiN film is formed by bias sputtering. ) oriented Ti
An N film can be formed, and wiring formed on this film can also have a perfect (111) orientation, making it possible to obtain highly reliable wiring.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a sputtering method according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the manufacturing process of a semiconductor device using the method of the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a sputtering method according to a second embodiment of the present invention.

FIG. 4 T formed by the method of the present invention and the conventional method
A diagram showing the X-ray diffraction results of an iN film.

[Explanation of symbols]

1 Ti target 2 Board 21 Silicon substrate 22 Silicon oxide film 23 Contact hole 24 TiN film 25 Aluminum film

Claims (2)

[Claims] 1. A step of forming an element region in a semiconductor substrate, a step of forming a barrier metal layer of forming a titanium nitride thin film or a tantalum nitride thin film as a barrier metal on the semiconductor substrate, and a step of forming an element region on the barrier metal layer. In the method of manufacturing a semiconductor device, the barrier metal layer forming step includes forming a wiring layer on the semiconductor substrate in a mixed gas atmosphere of a gas that is easily charged positively or negatively and nitrogen gas. A method for manufacturing a semiconductor device, characterized in that the sputtering step is performed while applying a positive bias when the gas tends to be positively charged, and a negative bias when the gas tends to be negatively charged. 2. A step of forming an element region in a semiconductor substrate, a step of forming a barrier metal layer of forming a titanium nitride thin film or a tantalum nitride thin film as a barrier metal layer on the semiconductor substrate, and the barrier metal layer. and a wiring layer forming step of forming a wiring layer thereon, wherein the barrier metal layer forming step uses a target containing a constituent element of the barrier metal layer, and a gas that is easily charged positively or negatively. A sputtering process in which sputtering is performed in an atmosphere while applying a positive bias to the semiconductor substrate when the gas is likely to be positively charged, and a negative bias when the gas is likely to be negatively charged. Production method.