JPS61150236A - Semiconductor device - Google Patents

Abstract

PURPOSE:To contrive to improve the adhesion of a film of high melting point metal with an insulation film by preventing the quality change of the insulation film, by a method wherein an interfacial layer 2 having a specific absolute value of produced free energy is provided between the insulation film and the film of high melting point metal. CONSTITUTION:A semiconductor element is composed of a gate electrode 1 made of a film of high melting point metal, an interfacial layer 2, an SiO2 film 3, and an Si signal crystal substrate 4. The CVD and sputtering methods are used for adhesion. The CVD method uses tungsten fluoride for the raw material gas and mixes SiH4 for Si addition. To form the oxide of the interfacial layer, O2 and water present in the CVD atmosphere at the initial stage of evaporation are utilized. The sputter method uses W and Si targets and forms an oxide layer by simultaneous sputtering through introduction of a trace of O2 at the initial stage. The title device of MOS type excellent in adhesion with the SiO2 film is obtained by interposing an interfacial layer between the electrode wiring film and the lower layer SiO2 film, and the yield of the ultra-high IC improves.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a semiconductor device that uses a high melting point metal film for electrodes and wiring formed on the surface of a semiconductor substrate via an insulating film. This is aimed at preventing deterioration and improving the adhesion between the insulating film and the high melting point metal film.

[Background of the invention]

Conventionally, polycrystalline silicon has been used for the electrodes and wiring of MO8 elements. However, in order to increase the integration and speed of devices, a material with lower resistance than polycrystalline silicon is required.

Therefore, it would be ideal if pure metal could be used as the material for electrodes and wiring, but this has the following problems. That is,
During the manufacturing process, metal may peel off from the insulating S'-io (silicon dioxide) film, or during high-temperature heat treatment, metal and Sin may react, causing deterioration of device characteristics such as poor dielectric strength. There are problems such as concerns that it may cause

In particular, there has been a strong desire to solve the problem of insufficient adhesion between the high melting point metal film and the 5in2 film, since it greatly affects the reliability of the device.

[Object of the Invention] □ The object of the present invention is to prevent deterioration of the insulating film and to provide a high melting point metal film in a semiconductor device that uses a high melting point metal film as an electrode/wiring formed on a selvage film, particularly a SiO film. An object of the present invention is to provide a semiconductor device that can improve the adhesion between a metal film and an insulating film.

[Summary of the invention]

In the semiconductor device to which the present invention is applied, during the manufacturing process, the insulating film and the electrode/wiring film are heated at a high temperature of about 1000° C. while in contact with each other. When using high melting point metals for electrodes and wiring,
The free energy of formation of metal oxides is negative and larger in absolute value than that of SiO2 (i.e., the free energy of formation is S
i lower than that of O2), when metal and 5in2
I end up reacting. On the other hand, if the free energy of formation of the metal oxide is more negative than that of 5in2 and its absolute value is smaller, it should be difficult for the metal to react with Si'02. (When the free energy of formation is positive, it is unstable, so it is out of the question.) However, at high temperatures of about 1000°C, the stability of 5in2 itself also becomes a problem. That is, even if the metal and 5in2 hardly react, dissociation of 5in2 may be observed when the amount of oxygen contained in the metal decreases. Therefore, it is effective to provide an oxide layer between the metal film and the SiO2 film. However, in many cases, oxides do not have a stoichiometric composition, so if oxygen is insufficient at that time, if an oxide with a free energy of formation lower than 5iOz is used, S i O2 It is dangerous because it may be returned. For this reason, in the present invention, as shown in the cross-sectional view of the embodiment (FIG. 1) described later, between the insulating film (SiO2 film 3) and the high melting point metal film (gate electrode 1), The interface layer 2 is constructed by mixing 1 to 50% of an oxide whose absolute value of free energy of formation is smaller than that of 5 in 2 with an oxide whose absolute value of free energy of formation is the same or larger than that of 5 iOz.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of the embodiment, in which 1 is a gate electrode made of a high-melting point metal film, 2 is an interface layer, 3 is a SiO2 film, and 4 is a Si monosheath crystal substrate. M with tungsten (W) as gate electrode 1
Prototyping of O8 semiconductor devices was carried out using two types of deposition methods and two types of interfacial layers.

For adhesion, CV D (Chemical Vapor
We used the Deposition method and the Span method.

In the CV and D methods, tungsten fluoride (WF, ) was used as a raw material gas, and SiH4 was mixed to add Si.

To form an oxide in the interfacial layer, 0,2 and water (H, O) present in the CVD atmosphere at the initial stage of vapor deposition were used. In the sputtering method, W and Si targets were used, and an oxide layer was formed by initially introducing a small amount of 02 and performing temporary sputtering. The above four types of samples I and TI consist of a combination of two types of deposition methods and two types of interfacial layers.

FIG. 2 shows the results of examining the adhesion between the gate electrode 1 and the SiO2 film 3, the quality of the adhesion, and the presence or absence of deterioration of the SiO2 film 3. Note that the thickness of the boundary and the surface M (oxide layer) 2 are both 5 nm. .

As shown in Fig. 2, when using the CVD method, when the interface layer is only WO3, the high point metal film (gate electrode 1
) and S i O, film 3 had poor adhesion, but the interface layer was made of wo containing 10% S i O2 Sample ■
So, when heated to about 10007, good adhesion is achieved. Samples obtained by sputtering method■,■
As shown in FIG. 2, the adhesiveness was good regardless of the presence or absence of Sin in WO3, but the adhesiveness of sample (2) containing SiO□ in WO3 was better than that of sample (2). in the end,
Dry etching 9. Except for sample I where peeling was observed. The electrodes are formed by MO as shown in FIG.
,, an S element can be formed. There were no problems with the measured characteristics such as flat band voltage, Sin, and dielectric strength voltage of the film 3.

The effect of adding SiO□ to the interface layer 2 was observed when the amount was 1% or more. However, more than 50% S i O2
However, this does not have to be -Si'02; as Si, O, -XΣ1 will have the effect of improving adhesion, but the underlying SiO film 3 will deteriorate. There was no. Moreover, the effect of improving adhesion was observed when the thickness of the interface layer 2 was at least a monomolecular layer and at most 5'On' m. Furthermore, the composition of the W oxide in the interface layer 2 is also W
Not limited to Oa, the above effect was observed in the range of WOy=4 to 3.

The above explanation is about the case where W is used as the high melting point metal, but similar effects can be obtained when Mo (molybdenum) is used as the high melting point metal and M o O, + Si O, is used for the interface layer. It was done. In this case, using Tie instead of Sin may produce an effect, but since the free energy of formation of TiO takes a negative and larger value than that of SiO2, unless x>2, the lower layer Deterioration of the SiO□ film was observed. Note that the compound containing C (carbon) is Wo.

The effect of improving adhesion was observed even when it was added to

〔Effect of the invention〕

According to the present invention, by interposing an interface layer between the electrode/wiring film made of a high-melting point metal and the lower SiC2 film, the electrode/wiring film can be formed while preventing deterioration of the lower 5in2 film. It can be made into an MO8 type semiconductor device with good adhesion to SiO, film, and is effective in improving the yield and reliability of ultra-high integrated circuits, which are made up of a large number of MO3 elements with a thin 5in2 film. There is. In addition, in the future, the vapor deposition equipment used to form electrodes and wiring will be improved and oxidizing impurities in the atmosphere inside the equipment will be reduced, and the metal of the electrodes and wiring will become pure, making the underlying Sj, O, and films unstable. This increases the possibility that this will occur, and therefore the usefulness of the present invention increases.

[Brief explanation of the drawing]

FIG. 1 is a sectional view for explaining the present invention in detail, and FIG. 2 is a diagram showing a comparison of characteristics of specifications of four types of samples I to (2) of the example. DESCRIPTION OF SYMBOLS 1... Gate electrode (high melting point metal film), 2... Interface layer, 3... SiO, film, 4... Si single crystal substrate.

Claims (1)

[Claims] 1. In a semiconductor device having an insulating film formed on the surface of a semiconductor substrate, and an electrode/wiring made of a high melting point metal film formed on the insulating film, the insulating film and the electrode/wiring are formed on the insulating film. An oxide whose absolute value of free energy of formation is smaller than that of silicon dioxide and an oxide whose absolute value of free energy of formation is the same or larger than that of silicon dioxide are used between the wiring and the wiring.
A semiconductor device comprising a 50% mixed layer having a thickness of at least a monomolecular layer and at most 50 nm. 2. The semiconductor device according to claim 1, wherein the insulating film is a silicon dioxide film.